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Roy D, Michalet X, Miller EW, Weiss S. Towards optical measurements of membrane potential values in Bacillus subtilis using fluorescence lifetime. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.13.598880. [PMID: 38915670 PMCID: PMC11195253 DOI: 10.1101/2024.06.13.598880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Membrane potential (MP) changes can provide a simple readout of bacterial functional and metabolic state or stress levels. While several optical methods exist for measuring fast changes in MP in excitable cells, there is a dearth of such methods for absolute and precise measurements of steady-state membrane potentials (MPs) in bacterial cells. Conventional electrode-based methods for the measurement of MP are not suitable for calibrating optical methods in small bacterial cells. While optical measurement based on Nernstian indicators have been successfully used, they do not provide absolute or precise quantification of MP or its changes. We present a novel, calibrated MP recording approach to address this gap. In this study, we used a fluorescence lifetime-based approach to obtain a single-cell resolved distribution of the membrane potential and its changes upon extracellular chemical perturbation in a population of bacterial cells for the first time. Our method is based on (i) a unique VoltageFluor (VF) optical transducer, whose fluorescence lifetime varies as a function of MP via photoinduced electron transfer (PeT) and (ii) a quantitative phasor-FLIM analysis for high-throughput readout. This method allows MP changes to be easily visualized, recorded and quantified. By artificially modulating potassium concentration gradients across the membrane using an ionophore, we have obtained a Bacillus subtilis-specific MP versus VF lifetime calibration and estimated the MP for unperturbed B. subtilis cells to be -65 mV and that for chemically depolarized cells as -14 mV. We observed a population level MP heterogeneity of ~6-10 mV indicating a considerable degree of diversity of physiological and metabolic states among individual cells. Our work paves the way for deeper insights into bacterial electrophysiology and bioelectricity research.
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Affiliation(s)
- Debjit Roy
- UCLA-DOE Institute for Genomics and Proteomics, Department of Biological Chemistry, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Xavier Michalet
- Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, CA 90095, USA
- California Nano Systems Institute, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Evan W. Miller
- Departments of Chemistry, Molecular and Cell Biology, Helen Wills Neuroscience Institute, University of California at Berkeley, CA 94720, USA
| | - Shimon Weiss
- UCLA-DOE Institute for Genomics and Proteomics, Department of Biological Chemistry, University of California at Los Angeles, Los Angeles, CA 90095, USA
- Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, CA 90095, USA
- Department of Physiology, University of California at Los Angeles, Los Angeles, CA 90095, USA
- California Nano Systems Institute, University of California at Los Angeles, Los Angeles, CA 90095, USA
- Department of Physics, Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
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2
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Wang H, Qiu S, Lu T, Kuang Y, Jin W. Underwater Single-Photon 3D Reconstruction Algorithm Based on K-Nearest Neighbor. SENSORS (BASEL, SWITZERLAND) 2024; 24:4401. [PMID: 39001180 PMCID: PMC11244583 DOI: 10.3390/s24134401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Revised: 07/04/2024] [Accepted: 07/05/2024] [Indexed: 07/16/2024]
Abstract
The high sensitivity and picosecond time resolution of single-photon avalanche diodes (SPADs) can improve the operational range and imaging accuracy of underwater detection systems. When an underwater SPAD imaging system is used to detect targets, backward-scattering caused by particles in water often results in the poor quality of the reconstructed underwater image. Although methods such as simple pixel accumulation have been proven to be effective for time-photon histogram reconstruction, they perform unsatisfactorily in a highly scattering environment. Therefore, new reconstruction methods are necessary for underwater SPAD detection to obtain high-resolution images. In this paper, we propose an algorithm that reconstructs high-resolution depth profiles of underwater targets from a time-photon histogram by employing the K-nearest neighbor (KNN) to classify multiple targets and the background. The results contribute to the performance of pixel accumulation and depth estimation algorithms such as pixel cross-correlation and ManiPoP. We use public experimental data sets and underwater simulation data to verify the effectiveness of the proposed algorithm. The results of our algorithm show that the root mean square errors (RMSEs) of land targets and simulated underwater targets are reduced by 57.12% and 23.45%, respectively, achieving high-resolution single-photon depth profile reconstruction.
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Affiliation(s)
- Hui Wang
- MOE Key Laboratory of Photoelectronic Imaging Technology and System, Beijing Institute of Technology, Beijing 100081, China
| | - Su Qiu
- MOE Key Laboratory of Photoelectronic Imaging Technology and System, Beijing Institute of Technology, Beijing 100081, China
| | - Taoran Lu
- MOE Key Laboratory of Photoelectronic Imaging Technology and System, Beijing Institute of Technology, Beijing 100081, China
| | - Yanjin Kuang
- MOE Key Laboratory of Photoelectronic Imaging Technology and System, Beijing Institute of Technology, Beijing 100081, China
| | - Weiqi Jin
- MOE Key Laboratory of Photoelectronic Imaging Technology and System, Beijing Institute of Technology, Beijing 100081, China
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Wang Z, Yang X, Tian N, Liu M, Cai Z, Feng P, Dou R, Yu S, Wu N, Liu J, Liu L. A 64 × 128 3D-Stacked SPAD Image Sensor for Low-Light Imaging. SENSORS (BASEL, SWITZERLAND) 2024; 24:4358. [PMID: 39001137 PMCID: PMC11244227 DOI: 10.3390/s24134358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 07/01/2024] [Accepted: 07/02/2024] [Indexed: 07/16/2024]
Abstract
Low-light imaging capabilities are in urgent demand in many fields, such as security surveillance, night-time autonomous driving, wilderness rescue, and environmental monitoring. The excellent performance of SPAD devices gives them significant potential for applications in low-light imaging. This article presents a 64 (rows) × 128 (columns) SPAD image sensor designed for low-light imaging. The chip utilizes a three-dimensional stacking architecture and microlens technology, combined with compact gated pixel circuits designed with thick-gate MOS transistors, which further enhance the SPAD's photosensitivity. The configurable digital control circuit allows for the adjustment of exposure time, enabling the sensor to adapt to different lighting conditions. The chip exhibits very low dark noise levels, with an average DCR of 41.5 cps at 2.4 V excess bias voltage. Additionally, it employs a denoising algorithm specifically developed for the SPAD image sensor, achieving two-dimensional grayscale imaging under 6 × 10-4 lux illumination conditions, demonstrating excellent low-light imaging capabilities. The chip designed in this paper fully leverages the performance advantages of SPAD image sensors and holds promise for applications in various fields requiring low-light imaging capabilities.
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Affiliation(s)
- Zhe Wang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xu Yang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Na Tian
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Min Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ziteng Cai
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Peng Feng
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Runjiang Dou
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuangming Yu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Nanjian Wu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jian Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Opto-Electronics Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liyuan Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
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Franks M, Dieminger T, Kaneyasu K, Sgalaberna D, Bruschini C, Charbon E, Kose U, Li B, Mos P, Wayne M, Weber T, Wu J. Demonstration of particle tracking with scintillating fibres read out by a SPAD array sensor and application as a neutrino active target. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2024; 84:202. [PMID: 39050377 PMCID: PMC11266435 DOI: 10.1140/epjc/s10052-024-12509-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 01/23/2024] [Indexed: 07/27/2024]
Abstract
Scintillating fibre detectors combine sub-mm resolution particle tracking, precise measurements of the particle stopping power and sub-ns time resolution. Typically, fibres are read out with silicon photomultipliers (SiPM). Hence, if fibres with a few hundred μ m diameter are used, either they are grouped together and coupled with a single SiPM, losing spatial resolution, or a very large number of electronic channels is required. In this article we propose and provide a first demonstration of a novel configuration which allows each individual scintillating fibre to be read out regardless of the size of its diameter, by imaging them with Single-Photon Avalanche Diode (SPAD) array sensors. Differently from SiPMs, SPAD array sensors provide single-photon detection with single-pixel spatial resolution. In addition, O(us) or faster coincidence of detected photons allows to obtain noise-free images. Such a concept can be particularly advantageous if adopted as a neutrino active target, where scintillating fibres alternated along orthogonal directions can provide isotropic, high-resolution tracking in a dense material and reconstruct the kinematics of low-momentum protons (down to 150 MeV/c), crucial for an accurate characterisation of the neutrino-nucleus cross section. In this work the tracking capabilities of a bundle of scintillating fibres coupled to SwissSPAD2 is demonstrated. The impact of such detector configuration in GeV-neutrino experiments is studied with simulations and reported. Finally, future plans, including the development of a new SPAD array sensor optimised for neutrino detection, are discussed.
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Affiliation(s)
- Matthew Franks
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
| | - Till Dieminger
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
| | - Kodai Kaneyasu
- Advanced Quantum Architecture Lab (AQUA), EPFL, Rue de la Maladière, 2000 Neuchâtel, Switzerland
| | - Davide Sgalaberna
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
| | - Claudio Bruschini
- Advanced Quantum Architecture Lab (AQUA), EPFL, Rue de la Maladière, 2000 Neuchâtel, Switzerland
| | - Edoardo Charbon
- Advanced Quantum Architecture Lab (AQUA), EPFL, Rue de la Maladière, 2000 Neuchâtel, Switzerland
| | - Umut Kose
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
| | - Botao Li
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
| | - Paul Mos
- Advanced Quantum Architecture Lab (AQUA), EPFL, Rue de la Maladière, 2000 Neuchâtel, Switzerland
| | - Michael Wayne
- Advanced Quantum Architecture Lab (AQUA), EPFL, Rue de la Maladière, 2000 Neuchâtel, Switzerland
| | - Tim Weber
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
| | - Jialin Wu
- Institute for Particle Physics and Astrophysics (IPA), ETH Zürich, Ramistrasse, 8093 Zürich, Switzerland
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Harel M, Arbiv U, Ankri R. Multiplexed near infrared fluorescence lifetime imaging in turbid media. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:026004. [PMID: 38425720 PMCID: PMC10902792 DOI: 10.1117/1.jbo.29.2.026004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/23/2024] [Accepted: 02/12/2024] [Indexed: 03/02/2024]
Abstract
Significance Fluorescence lifetime imaging (FLI) plays a pivotal role in enhancing our understanding of biological systems, providing a valuable tool for non-invasive exploration of biomolecular and cellular dynamics, both in vitro and in vivo. Its ability to selectively target and multiplex various entities, alongside heightened sensitivity and specificity, offers rapid and cost-effective insights. Aim Our aim is to investigate the multiplexing capabilities of near-infrared (NIR) FLI within a scattering medium that mimics biological tissues. We strive to develop a comprehensive understanding of FLI's potential for multiplexing diverse targets within a complex, tissue-like environment. Approach We introduce an innovative Monte Carlo (MC) simulation approach that accurately describes the scattering behavior of fluorescent photons within turbid media. Applying phasor analyses, we enable the multiplexing of distinct targets within a single FLI image. Leveraging the state-of-the-art single-photon avalanche diode (SPAD) time-gated camera, SPAD512S, we conduct experimental wide-field FLI in the NIR regime. Results Our study demonstrates the successful multiplexing of dual targets within a single FLI image, reaching a depth of 1 cm within tissue-like phantoms. Through our novel MC simulation approach and phasor analyses, we showcase the effectiveness of our methodology in overcoming the challenges posed by scattering media. Conclusions This research underscores the potential of NIR FLI for multiplexing applications in complex biological environments. By combining advanced simulation techniques with cutting-edge experimental tools, we introduce significant results in the non-invasive exploration of biomolecular dynamics, to advance the field of FLI research.
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Affiliation(s)
- Meital Harel
- Ariel University, Department of Physics, Faculty of Natural Science, Ariel, Israel
| | - Uri Arbiv
- Ariel University, Department of Physics, Faculty of Natural Science, Ariel, Israel
| | - Rinat Ankri
- Ariel University, Department of Physics, Faculty of Natural Science, Ariel, Israel
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6
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Petusseau AF, Streeter SS, Ulku A, Feng Y, Samkoe KS, Bruschini C, Charbon E, Pogue BW, Bruza P. Subsurface fluorescence time-of-flight imaging using a large-format single-photon avalanche diode sensor for tumor depth assessment. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:016004. [PMID: 38235320 PMCID: PMC10794045 DOI: 10.1117/1.jbo.29.1.016004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 12/06/2023] [Accepted: 12/20/2023] [Indexed: 01/19/2024]
Abstract
Significance Fluorescence guidance is used clinically by surgeons to visualize anatomical and/or physiological phenomena in the surgical field that are difficult or impossible to detect by the naked eye. Such phenomena include tissue perfusion or molecular phenotypic information about the disease being resected. Conventional fluorescence-guided surgery relies on long, microsecond scale laser pulses to excite fluorescent probes. However, this technique only provides two-dimensional information; crucial depth information, such as the location of malignancy below the tissue surface, is not provided. Aim We developed a depth sensing imaging technique using light detection and ranging (LiDAR) time-of-flight (TOF) technology to sense the depth of target tissue while overcoming the influence of tissue optical properties and fluorescent probe concentration. Approach The technology is based on a large-format (512 × 512 pixel ), binary, gated, single-photon avalanche diode (SPAD) sensor with an 18 ps time-gate step, synchronized with a picosecond pulsed laser. The fast response of the sensor was developed and tested for its ability to quantify fluorescent inclusions at depth and optical properties in tissue-like phantoms through analytical model fitting of the fast temporal remission data. Results After calibration and algorithmic extraction of the data, the SPAD LiDAR technique allowed for sub-mm resolution depth sensing of fluorescent inclusions embedded in tissue-like phantoms, up to a maximum of 5 mm in depth. The approach provides robust depth sensing even in the presence of variable tissue optical properties and separates the effects of fluorescence depth from absorption and scattering variations. Conclusions LiDAR TOF fluorescence imaging using an SPAD camera provides both fluorescence intensity images and the temporal profile of fluorescence, which can be used to determine the depth at which the signal is emitted over a wide field of view. The proposed tool enables fluorescence imaging at a higher depth in tissue and with higher spatial precision than standard, steady-state fluorescence imaging tools, such as intensity-based near-infrared fluorescence imaging, optical coherence tomography, Raman spectroscopy, or confocal microscopy. Integration of this technique into a standard surgical tool could enable rapid, more accurate estimation of resection boundaries, thereby improving the surgeon's efficacy and efficiency, and ultimately improving patient outcomes.
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Affiliation(s)
- Arthur F Petusseau
- Dartmouth College, Thayer School of Engineering and Dartmouth Cancer Center, Hanover, New Hampshire, United States
| | - Samuel S Streeter
- Geisel School of Medicine at Dartmouth, Department of Orthopaedics, Hanover, New Hampshire, United States
| | - Arin Ulku
- Ecole polytechnique fédérale de Lausanne, Advanced Quantum Architecture Laboratory, Neuchâtel, Switzerland
| | - Yichen Feng
- Geisel School of Medicine at Dartmouth, Department of Surgery, Hanover, New Hampshire, United States
| | - Kimberley S Samkoe
- Geisel School of Medicine at Dartmouth, Department of Surgery, Hanover, New Hampshire, United States
| | - Claudio Bruschini
- Ecole polytechnique fédérale de Lausanne, Advanced Quantum Architecture Laboratory, Neuchâtel, Switzerland
| | - Edoardo Charbon
- Ecole polytechnique fédérale de Lausanne, Advanced Quantum Architecture Laboratory, Neuchâtel, Switzerland
| | - Brian W Pogue
- Dartmouth College, Thayer School of Engineering and Dartmouth Cancer Center, Hanover, New Hampshire, United States
- University of Wisconsin-Madison, Department of Medical Physics, Madison, Wisconsin, United States
| | - Petr Bruza
- Dartmouth College, Thayer School of Engineering and Dartmouth Cancer Center, Hanover, New Hampshire, United States
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Batelić M, Stipčević M. Stochastic Adder Circuits with Improved Entropy Output. ENTROPY (BASEL, SWITZERLAND) 2023; 25:1592. [PMID: 38136472 PMCID: PMC10742554 DOI: 10.3390/e25121592] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/20/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023]
Abstract
Random pulse computing (RPC), the third paradigm along with digital and quantum computing, draws inspiration from biology, particularly the functioning of neurons. Here, we study information processing in random pulse computing circuits intended for the summation of numbers. Based on the information-theoretic merits of entropy budget and relative Kolmogorov-Sinai entropy, we investigate the prior art and propose new circuits: three deterministic adders with significantly improved output entropy and one exact nondeterministic adder that requires much less additional entropy than the previous art. All circuits are realized and tested experimentally, using quantum entropy sources and reconfigurable logic devices. Not only the proposed circuits yield a precise mathematical result and have output entropy near maximum, which satisfies the need for building a programmable random pulse computer, but also they provide affordable hardware options for generating additional entropy.
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Affiliation(s)
- Mateja Batelić
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička Cesta 32, 10000 Zagreb, Croatia
| | - Mario Stipčević
- Photonics and Quantum Optics Unit, Center of Excellence for Advanced Materials and Sensing Devices, Ruđer Bošković Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia
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Scattarella F, Diacono D, Monaco A, Amoroso N, Bellantuono L, Massaro G, Pepe FV, Tangaro S, Bellotti R, D'Angelo M. Deep learning approach for denoising low-SNR correlation plenoptic images. Sci Rep 2023; 13:19645. [PMID: 37950034 PMCID: PMC10638444 DOI: 10.1038/s41598-023-46765-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 11/04/2023] [Indexed: 11/12/2023] Open
Abstract
Correlation Plenoptic Imaging (CPI) is a novel volumetric imaging technique that uses two sensors and the spatio-temporal correlations of light to detect both the spatial distribution and the direction of light. This novel approach to plenoptic imaging enables refocusing and 3D imaging with significant enhancement of both resolution and depth of field. However, CPI is generally slower than conventional approaches due to the need to acquire sufficient statistics for measuring correlations with an acceptable signal-to-noise ratio (SNR). We address this issue by implementing a Deep Learning application to improve image quality with undersampled frame statistics. We employ a set of experimental images reconstructed by a standard CPI architecture, at three different sampling ratios, and use it to feed a CNN model pre-trained through the transfer learning paradigm U-Net architecture with VGG-19 net for the encoding part. We find that our model reaches a Structural Similarity (SSIM) index value close to 1 both for the test sample (SSIM = [Formula: see text]) and in 5-fold cross validation (SSIM = [Formula: see text]); the results are also shown to outperform classic denoising methods, in particular for images with lower SNR. The proposed work represents the first application of Artificial Intelligence in the field of CPI and demonstrates its high potential: speeding-up the acquisition by a factor 20 over the fastest CPI so far demonstrated, enabling recording potentially 200 volumetric images per second. The presented results open the way to scanning-free real-time volumetric imaging at video rate, which is expected to achieve a substantial influence in various applications scenarios, from monitoring neuronal activity to machine vision and security.
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Affiliation(s)
- Francesco Scattarella
- Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
| | - Domenico Diacono
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
| | - Alfonso Monaco
- Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy.
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy.
| | - Nicola Amoroso
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
- Dipartimento di Farmacia - Scienze del Farmaco, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
| | - Loredana Bellantuono
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
- Dipartimento di Biomedicina Traslazionale e Neuroscienze (DiBraiN), Università degli Studi di Bari Aldo Moro, 70124, Bari, Italy
| | - Gianlorenzo Massaro
- Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
| | - Francesco V Pepe
- Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
| | - Sabina Tangaro
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
- Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
| | - Roberto Bellotti
- Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
| | - Milena D'Angelo
- Dipartimento Interateneo di Fisica M. Merlin, Università degli Studi di Bari Aldo Moro, 70125, Bari, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, 70125, Bari, Italy
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9
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Massaro G, Mos P, Vasiukov S, Di Lena F, Scattarella F, Pepe FV, Ulku A, Giannella D, Charbon E, Bruschini C, D'Angelo M. Correlated-photon imaging at 10 volumetric images per second. Sci Rep 2023; 13:12813. [PMID: 37550319 PMCID: PMC10406932 DOI: 10.1038/s41598-023-39416-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023] Open
Abstract
The correlation properties of light provide an outstanding tool to overcome the limitations of traditional imaging techniques. A relevant case is represented by correlation plenoptic imaging (CPI), a quantum-inspired volumetric imaging protocol employing spatio-temporally correlated photons from either entangled or chaotic sources to address the main limitations of conventional light-field imaging, namely, the poor spatial resolution and the reduced change of perspective for 3D imaging. However, the application potential of high-resolution imaging modalities relying on photon correlations is limited, in practice, by the need to collect a large number of frames. This creates a gap, unacceptable for many relevant tasks, between the time performance of correlated-light imaging and that of traditional imaging methods. In this article, we address this issue by exploiting the photon number correlations intrinsic in chaotic light, combined with a cutting-edge ultrafast sensor made of a large array of single-photon avalanche diodes (SPADs). This combination of source and sensor is embedded within a novel single-lens CPI scheme enabling to acquire 10 volumetric images per second. Our results place correlated-photon imaging at a competitive edge and prove its potential in practical applications.
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Affiliation(s)
- Gianlorenzo Massaro
- Dipartimento Interuniversitario di Fisica, Università degli studi di Bari, 70126, Bari, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy
| | - Paul Mos
- Ecole polytechnique fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Sergii Vasiukov
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy
| | - Francesco Di Lena
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy
| | - Francesco Scattarella
- Dipartimento Interuniversitario di Fisica, Università degli studi di Bari, 70126, Bari, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy
| | - Francesco V Pepe
- Dipartimento Interuniversitario di Fisica, Università degli studi di Bari, 70126, Bari, Italy.
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy.
| | - Arin Ulku
- Ecole polytechnique fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Davide Giannella
- Dipartimento Interuniversitario di Fisica, Università degli studi di Bari, 70126, Bari, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy
| | - Edoardo Charbon
- Ecole polytechnique fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Claudio Bruschini
- Ecole polytechnique fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Milena D'Angelo
- Dipartimento Interuniversitario di Fisica, Università degli studi di Bari, 70126, Bari, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70125, Bari, Italy
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10
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Wang J, Li J, Wu Y, Yu H, Cui L, Sun M, Chiang PY. A 256 × 256 LiDAR Imaging System Based on a 200 mW SPAD-Based SoC with Microlens Array and Lightweight RGB-Guided Depth Completion Neural Network. SENSORS (BASEL, SWITZERLAND) 2023; 23:6927. [PMID: 37571709 PMCID: PMC10422305 DOI: 10.3390/s23156927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 07/30/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023]
Abstract
Light detection and ranging (LiDAR) technology, a cutting-edge advancement in mobile applications, presents a myriad of compelling use cases, including enhancing low-light photography, capturing and sharing 3D images of fascinating objects, and elevating the overall augmented reality (AR) experience. However, its widespread adoption has been hindered by the prohibitive costs and substantial power consumption associated with its implementation in mobile devices. To surmount these obstacles, this paper proposes a low-power, low-cost, single-photon avalanche detector (SPAD)-based system-on-chip (SoC) which packages the microlens arrays (MLAs) and a lightweight RGB-guided sparse depth imaging completion neural network for 3D LiDAR imaging. The proposed SoC integrates an 8 × 8 SPAD macropixel array with time-to-digital converters (TDCs) and a charge pump, fabricated using a 180 nm bipolar-CMOS-DMOS (BCD) process. Initially, the primary function of this SoC was limited to serving as a ranging sensor. A random MLA-based homogenizing diffuser efficiently transforms Gaussian beams into flat-topped beams with a 45° field of view (FOV), enabling flash projection at the transmitter. To further enhance resolution and broaden application possibilities, a lightweight neural network employing RGB-guided sparse depth complementation is proposed, enabling a substantial expansion of image resolution from 8 × 8 to quarter video graphics array level (QVGA; 256 × 256). Experimental results demonstrate the effectiveness and stability of the hardware encompassing the SoC and optical system, as well as the lightweight features and accuracy of the algorithmic neural network. The state-of-the-art SoC-neural network solution offers a promising and inspiring foundation for developing consumer-level 3D imaging applications on mobile devices.
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Affiliation(s)
- Jier Wang
- State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203, China; (J.W.); (M.S.)
| | - Jie Li
- State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203, China; (J.W.); (M.S.)
| | - Yifan Wu
- College of Electronics and Information Engineering, Tongji University, Shanghai 201804, China
| | - Hengwei Yu
- State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203, China; (J.W.); (M.S.)
| | - Lebei Cui
- State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203, China; (J.W.); (M.S.)
| | - Miao Sun
- State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203, China; (J.W.); (M.S.)
| | - Patrick Yin Chiang
- State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203, China; (J.W.); (M.S.)
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11
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Bruschini C, Antolovic IM, Zanella F, Ulku AC, Lindner S, Kalyanov A, Milanese T, Bernasconi E, Pešić V, Charbon E. Challenges and prospects for multi-chip microlens imprints on front-side illuminated SPAD imagers. OPTICS EXPRESS 2023; 31:21935-21953. [PMID: 37381279 DOI: 10.1364/oe.488177] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 06/01/2023] [Indexed: 06/30/2023]
Abstract
The overall sensitivity of frontside-illuminated, silicon single-photon avalanche diode (SPAD) arrays has often suffered from fill factor limitations. The fill factor loss can however be recovered by employing microlenses, whereby the challenges specific to SPAD arrays are represented by large pixel pitch (> 10 µm), low native fill factor (as low as ∼10%), and large size (up to 10 mm). In this work we report on the implementation of refractive microlenses by means of photoresist masters, used to fabricate molds for imprints of UV curable hybrid polymers deposited on SPAD arrays. Replications were successfully carried out for the first time, to the best of our knowledge, at wafer reticle level on different designs in the same technology and on single large SPAD arrays with very thin residual layers (∼10 µm), as needed for better efficiency at higher numerical aperture (NA > 0.25). In general, concentration factors within 15-20% of the simulation results were obtained for the smaller arrays (32×32 and 512×1), achieving for example an effective fill factor of 75.6-83.2% for a 28.5 µm pixel pitch with a native fill factor of 28%. A concentration factor up to 4.2 was measured on large 512×512 arrays with a pixel pitch of 16.38 µm and a native fill factor of 10.5%, whereas improved simulation tools could give a better estimate of the actual concentration factor. Spectral measurements were also carried out, resulting in good and uniform transmission in the visible and NIR.
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12
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Wilda CB, Burnstock A, Suhling K, Mattioli Della Rocca F, Henderson RK, Nedbal J. Visualising varnish removal for conservation of paintings by fluorescence lifetime imaging (FLIM). HERITAGE SCIENCE 2023; 11:127. [PMID: 37333623 PMCID: PMC10276100 DOI: 10.1186/s40494-023-00957-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 05/17/2023] [Indexed: 06/20/2023]
Abstract
The removal of varnish from the surface is a key step in painting conservation. Varnish removal is traditionally monitored by examining the painting surface under ultraviolet illumination. We show here that by imaging the fluorescence lifetime instead, much better contrast, sensitivity, and specificity can be achieved. For this purpose, we developed a lightweight (4.8 kg) portable instrument for macroscopic fluorescence lifetime imaging (FLIM). It is based on a time-correlated single-photon avalanche diode (SPAD) camera to acquire the FLIM images and a pulsed 440 nm diode laser to excite the varnish fluorescence. A historical model painting was examined to demonstrate the capabilities of the system. We found that the FLIM images provided information on the distribution of the varnish on the painting surface with greater sensitivity, specificity, and contrast compared to the traditional ultraviolet illumination photography. The distribution of the varnish and other painting materials was assessed using FLIM during and after varnish removal with different solvent application methods. Monitoring of the varnish removal process between successive solvent applications by a swab revealed an evolving image contrast as a function of the cleaning progress. FLIM of dammar and mastic resin varnishes identified characteristic changes to their fluorescence lifetimes depending on their ageing conditions. Thus, FLIM has a potential to become a powerful and versatile tool to visualise varnish removal from paintings. Graphical Abstract
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Affiliation(s)
- Christine B. Wilda
- Department of Physics, King’s College London, Strand, London, WC2R 2LS United Kingdom
- The Courtauld, Somerset House, Strand, London, WC1X 0RN United Kingdom
- ConservArt, 6620 E Rogers Cir, Boca Raton, FL 33487 United States
| | - Aviva Burnstock
- The Courtauld, Somerset House, Strand, London, WC1X 0RN United Kingdom
| | - Klaus Suhling
- Department of Physics, King’s College London, Strand, London, WC2R 2LS United Kingdom
| | - Francesco Mattioli Della Rocca
- School of Engineering, University of Edinburgh, King’s Buildings, Edinburgh, EH9 3JL United Kingdom
- Europe Technology Development Centre, Sony Semiconductor Solutions - Sony Europe B.V., Trento, Italy
| | - Robert K. Henderson
- School of Engineering, University of Edinburgh, King’s Buildings, Edinburgh, EH9 3JL United Kingdom
| | - Jakub Nedbal
- Department of Physics, King’s College London, Strand, London, WC2R 2LS United Kingdom
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13
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Samimi K, Desa DE, Lin W, Weiss K, Li J, Huisken J, Miskolci V, Huttenlocher A, Chacko JV, Velten A, Rogers JD, Eliceiri KW, Skala MC. Light-sheet autofluorescence lifetime imaging with a single-photon avalanche diode array. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:066502. [PMID: 37351197 PMCID: PMC10284079 DOI: 10.1117/1.jbo.28.6.066502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/02/2023] [Accepted: 06/06/2023] [Indexed: 06/24/2023]
Abstract
Significance Fluorescence lifetime imaging microscopy (FLIM) of the metabolic co-enzyme nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] is a popular method to monitor single-cell metabolism within unperturbed, living 3D systems. However, FLIM of NAD(P)H has not been performed in a light-sheet geometry, which is advantageous for rapid imaging of cells within live 3D samples. Aim We aim to design, validate, and demonstrate a proof-of-concept light-sheet system for NAD(P)H FLIM. Approach A single-photon avalanche diode camera was integrated into a light-sheet microscope to achieve optical sectioning and limit out-of-focus contributions for NAD(P)H FLIM of single cells. Results An NAD(P)H light-sheet FLIM system was built and validated with fluorescence lifetime standards and with time-course imaging of metabolic perturbations in pancreas cancer cells with 10 s integration times. NAD(P)H light-sheet FLIM in vivo was demonstrated with live neutrophil imaging in a larval zebrafish tail wound also with 10 s integration times. Finally, the theoretical and practical imaging speeds for NAD(P)H FLIM were compared across laser scanning and light-sheet geometries, indicating a 30 × to 6 × acquisition speed advantage for the light sheet compared to the laser scanning geometry. Conclusions FLIM of NAD(P)H is feasible in a light-sheet geometry and is attractive for 3D live cell imaging applications, such as monitoring immune cell metabolism and migration within an organism.
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Affiliation(s)
- Kayvan Samimi
- Morgridge Institute for Research, Madison, Wisconsin, United States
| | - Danielle E. Desa
- Morgridge Institute for Research, Madison, Wisconsin, United States
| | - Wei Lin
- University of Wisconsin, Department of Electrical and Computer Engineering, Madison, Wisconsin, United States
| | - Kurt Weiss
- Morgridge Institute for Research, Madison, Wisconsin, United States
- University of Wisconsin, Department of Biochemistry, Madison, Wisconsin, United States
| | - Joe Li
- Morgridge Institute for Research, Madison, Wisconsin, United States
| | - Jan Huisken
- Morgridge Institute for Research, Madison, Wisconsin, United States
- Georg-August-University Göttingen, Department of Biology and Psychology, Göttingen, Germany
| | - Veronika Miskolci
- University of Wisconsin, Department of Medical Microbiology and Immunology, Madison, Wisconsin, United States
- Rutgers New Jersey Medical School, Center for Cell Signaling, Newark, New Jersey, United States
- Rutgers New Jersey Medical School, Department of Microbiology, Biochemistry and Molecular Genetics, Newark, New Jersey, United States
| | - Anna Huttenlocher
- University of Wisconsin, Department of Medical Microbiology and Immunology, Madison, Wisconsin, United States
- University of Wisconsin, Department of Pediatrics, Madison, Wisconsin, United States
| | - Jenu V. Chacko
- University of Wisconsin, Laboratory for Optical and Computational Instrumentation, Madison, Wisconsin, United States
| | - Andreas Velten
- Morgridge Institute for Research, Madison, Wisconsin, United States
- University of Wisconsin, Department of Electrical and Computer Engineering, Madison, Wisconsin, United States
- University of Wisconsin, Department of Biostatistics and Medical Informatics, Madison, Wisconsin, United States
- University of Wisconsin, McPherson Eye Research Institute, Madison, Wisconsin, United States
| | - Jeremy D. Rogers
- Morgridge Institute for Research, Madison, Wisconsin, United States
- University of Wisconsin, McPherson Eye Research Institute, Madison, Wisconsin, United States
- University of Wisconsin, Department of Ophthalmology and Visual Sciences, Madison, Wisconsin, United States
| | - Kevin W. Eliceiri
- Morgridge Institute for Research, Madison, Wisconsin, United States
- University of Wisconsin, Laboratory for Optical and Computational Instrumentation, Madison, Wisconsin, United States
- University of Wisconsin, Department of Biostatistics and Medical Informatics, Madison, Wisconsin, United States
- University of Wisconsin, McPherson Eye Research Institute, Madison, Wisconsin, United States
- University of Wisconsin, Department of Biomedical Engineering, Madison, Wisconsin, United States
| | - Melissa C. Skala
- Morgridge Institute for Research, Madison, Wisconsin, United States
- University of Wisconsin, McPherson Eye Research Institute, Madison, Wisconsin, United States
- University of Wisconsin, Department of Biomedical Engineering, Madison, Wisconsin, United States
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14
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The BrightEyes-TTM as an open-source time-tagging module for democratising single-photon microscopy. Nat Commun 2022; 13:7406. [PMID: 36456575 PMCID: PMC9715684 DOI: 10.1038/s41467-022-35064-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 11/09/2022] [Indexed: 12/03/2022] Open
Abstract
Fluorescence laser-scanning microscopy (LSM) is experiencing a revolution thanks to new single-photon (SP) array detectors, which give access to an entirely new set of single-photon information. Together with the blooming of new SP LSM techniques and the development of tailored SP array detectors, there is a growing need for (i) DAQ systems capable of handling the high-throughput and high-resolution photon information generated by these detectors, and (ii) incorporating these DAQ protocols in existing fluorescence LSMs. We developed an open-source, low-cost, multi-channel time-tagging module (TTM) based on a field-programmable gate array that can tag in parallel multiple single-photon events, with 30 ps precision, and multiple synchronisation events, with 4 ns precision. We use the TTM to demonstrate live-cell super-resolved fluorescence lifetime image scanning microscopy and fluorescence lifetime fluctuation spectroscopy. We expect that our BrightEyes-TTM will support the microscopy community in spreading SP-LSM in many life science laboratories.
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15
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Ji C, Wang X, He K, Xue Y, Li Y, Xin L, Zhao W, Tian J, Sheng L. Compressed fluorescence lifetime imaging via combined TV-based and deep priors. PLoS One 2022; 17:e0271441. [PMID: 35960754 PMCID: PMC9374265 DOI: 10.1371/journal.pone.0271441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 06/30/2022] [Indexed: 11/19/2022] Open
Abstract
Compressed fluorescence lifetime imaging (Compressed-FLIM) is a novel Snapshot compressive imaging (SCI) method for single-shot widefield FLIM. This approach has the advantages of high temporal resolution and deep frame sequences, allowing for the analysis of FLIM signals that follow complex decay models. However, the precision of Compressed-FLIM is limited by reconstruction algorithms. To improve the reconstruction accuracy of Compressed-FLIM in dealing with large-scale FLIM problem, we developed a more effective combined prior model 3DTGp V_net, based on the Plug and Play (PnP) framework. Extensive numerical simulations indicate the proposed method eliminates reconstruction artifacts caused by the Deep denoiser networks. Moreover, it improves the reconstructed accuracy by around 4dB (peak signal-to-noise ratio; PSNR) over the state-of-the-art TV+FFDNet in test data sets. We conducted the single-shot FLIM experiment with different Rhodamine reagents and the results show that in practice, the proposed algorithm has promising reconstruction performance and more negligible lifetime bias.
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Affiliation(s)
- Chao Ji
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xing Wang
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Kai He
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
| | - Yanhua Xue
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
| | - Yahui Li
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
| | - Liwei Xin
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
| | - Wei Zhao
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an, Shaanxi, China
| | - Jinshou Tian
- Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an, Shaanxi, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Liang Sheng
- The Northwest Institute of Nuclear Technology, Xi’an, China
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16
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Taher J, Hakala T, Jaakkola A, Hyyti H, Kukko A, Manninen P, Maanpää J, Hyyppä J. Feasibility of Hyperspectral Single Photon Lidar for Robust Autonomous Vehicle Perception. SENSORS (BASEL, SWITZERLAND) 2022; 22:5759. [PMID: 35957316 PMCID: PMC9371088 DOI: 10.3390/s22155759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 06/15/2023]
Abstract
Autonomous vehicle perception systems typically rely on single-wavelength lidar sensors to obtain three-dimensional information about the road environment. In contrast to cameras, lidars are unaffected by challenging illumination conditions, such as low light during night-time and various bidirectional effects changing the return reflectance. However, as many commercial lidars operate on a monochromatic basis, the ability to distinguish objects based on material spectral properties is limited. In this work, we describe the prototype hardware for a hyperspectral single photon lidar and demonstrate the feasibility of its use in an autonomous-driving-related object classification task. We also introduce a simple statistical model for estimating the reflectance measurement accuracy of single photon sensitive lidar devices. The single photon receiver frame was used to receive 30 12.3 nm spectral channels in the spectral band 1200-1570 nm, with a maximum channel-wise intensity of 32 photons. A varying number of frames were used to accumulate the signal photon count. Multiple objects covering 10 different categories of road environment, such as car, dry asphalt, gravel road, snowy asphalt, wet asphalt, wall, granite, grass, moss, and spruce tree, were included in the experiments. We test the influence of the number of spectral channels and the number of frames on the classification accuracy with random forest classifier and find that the spectral information increases the classification accuracy in the high-photon flux regime from 50% to 94% with 2 channels and 30 channels, respectively. In the low-photon flux regime, the classification accuracy increases from 30% to 38% with 2 channels and 6 channels, respectively. Additionally, we visualize the data with the t-SNE algorithm and show that the photon shot noise in the single photon sensitive hyperspectral data contributes the most to the separability of material specific spectral signatures. The results of this study provide support for the use of hyperspectral single photon lidar data on more advanced object detection and classification methods, and motivates the development of advanced single photon sensitive hyperspectral lidar devices for use in autonomous vehicles and in robotics.
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Affiliation(s)
- Josef Taher
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
- Department of Computer Science, Aalto University School of Science, 02150 Espoo, Finland
| | - Teemu Hakala
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
| | - Anttoni Jaakkola
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
| | - Heikki Hyyti
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
| | - Antero Kukko
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
| | - Petri Manninen
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
| | - Jyri Maanpää
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
- Department of Computer Science, Aalto University School of Science, 02150 Espoo, Finland
| | - Juha Hyyppä
- Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute FGI, National Land Survey of Finland, 02150 Espoo, Finland; (T.H.); (A.J.); (H.H.); (A.K.); (P.M.); (J.M.); (J.H.)
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17
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Xiao D, Zang Z, Wang Q, Jiao Z, Rocca FMD, Chen Y, Li DDU. Smart Wide-field Fluorescence Lifetime Imaging System with CMOS Single-photon Avalanche Diode Arrays. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:1887-1890. [PMID: 36086288 DOI: 10.1109/embc48229.2022.9870996] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Wide-field fluorescence lifetime imaging (FLIM) is a promising technique for biomedical and clinic applications. Integrating with CMOS single-photon avalanche diode (SPAD) sensor arrays can lead to cheaper and portable real-time FLIM systems. However, the FLIM data obtained by such sensor systems often have sophisticated noise features. There is still a lack of fast tools to recover lifetime parameters from highly noise-corrupted fluorescence signals efficiently. This paper proposes a smart wide-field FLIM system containing a 192×128 COMS SPAD sensor and a field-programmable gate array (FPGA) embedded deep learning (DL) FLIM processor. The processor adopts a hardware-friendly and light-weighted neural network for fluorescence lifetime analysis, showing the advantages of high accuracy against noise, fast speed, and low power consumption. Experimental results demonstrate the proposed system's superior and robust performances, promising for many FLIM applications such as FLIM-guided clinical surgeries, cancer diagnosis, and biomedical imaging.
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18
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A Multi-Time-Gated SPAD Array with Integrated Coarse TDCs. ELECTRONICS 2022. [DOI: 10.3390/electronics11132015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Time-gating of single-photon avalanche diodes (SPADs) was commonly used as a method to reduce dark noise in biomedical imaging applications where photon events are correlated with a reference clock. Time-gating was also used to obtain timing information of photon events by shifting the gate windows applied to a SPAD array. However, in this approach, fine timing resolution comes at the cost of a lengthened measurement time due to the large number of counts required for each shift. As a solution, we present a multi-time-gated SPAD array that simultaneously applies shifted gate windows to an array of SPADs, which has the potential to reduce the measurement time compared to a single time gate window. Compared to similar works, this design has fully integrated the multi-gate generation using shared circuitry which also functions as a coarse time-to-digital converter. The proposed array, fabricated in the TSMC 65 nm standard CMOS process, achieved a median dark count rate (DCR) of 37 kHz, 4.37 ns gate widths, 550 ps timing resolution, and a peak photon detection probability (PDP) of 42.9% at 420 nm, all at a 0.8 V excess bias.
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19
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Netaev A, Schierbaum N, Seidl K. Advantages and Limitations of Fluorescence Lifetime Measurements Using Single-Photon Avalanche Diode (SPAD) Array Detector: A Comprehensive Theoretical and Experimental Study. SENSORS (BASEL, SWITZERLAND) 2022; 22:3822. [PMID: 35632231 PMCID: PMC9144122 DOI: 10.3390/s22103822] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 05/15/2022] [Accepted: 05/16/2022] [Indexed: 02/01/2023]
Abstract
Fast fluorescence lifetime (FL) determination is a major factor for studying dynamic processes. To achieve a required precision and accuracy a certain number of photon counts must be detected. FL methods based on single-photon counting have strongly limited count rates because of the detector's pile-up issue and are suffering from long measurement times in the order of tens of seconds. Here, we present an experimental and Monte Carlo simulation-based study of how this limitation can be overcome using array detectors based on single-photon avalanche diodes (SPADs). We investigated the maximum count rate per pixel to determine FL with a certain precision and accuracy before pile-up occurs. Based on that, we derived an analytical expression to calculate the total measurement time which is proportional to the FL and inversely proportional to the number of pixels. However, a higher number of pixels drastically increases data rate. This can be counteracted by lowering the time resolution. We found that even with a time resolution of four times the FL, an accuracy of 10% can be achieved. Taken all together, FLs between 10 ns and 3 ns can be determined with a 300-pixel SPAD array detector with a measurement time and data rate less than 1 µs and 700 Mbit/s, respectively. This shows the enormous potential of SPAD array detector for high-speed applications requiring continuous data read out.
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Affiliation(s)
- Alexander Netaev
- Fraunhofer Institute for Microelectronic Circuits and Systems, 47057 Duisburg, Germany; (N.S.); (K.S.)
| | - Nicolas Schierbaum
- Fraunhofer Institute for Microelectronic Circuits and Systems, 47057 Duisburg, Germany; (N.S.); (K.S.)
| | - Karsten Seidl
- Fraunhofer Institute for Microelectronic Circuits and Systems, 47057 Duisburg, Germany; (N.S.); (K.S.)
- Department of Electronic Components and Circuits, University of Duisburg-Essen, 47057 Duisburg, Germany
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20
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Smith JT, Rudkouskaya A, Gao S, Gupta JM, Ulku A, Bruschini C, Charbon E, Weiss S, Barroso M, Intes X, Michalet X. In vitro and in vivo NIR fluorescence lifetime imaging with a time-gated SPAD camera. OPTICA 2022; 9:532-544. [PMID: 35968259 PMCID: PMC9368735 DOI: 10.1364/optica.454790] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/27/2022] [Indexed: 05/20/2023]
Abstract
Near-infrared (NIR) fluorescence lifetime imaging (FLI) provides a unique contrast mechanism to monitor biological parameters and molecular events in vivo. Single-photon avalanche diode (SPAD) cameras have been recently demonstrated in FLI microscopy (FLIM) applications, but their suitability for in vivo macroscopic FLI (MFLI) in deep tissues remains to be demonstrated. Herein, we report in vivo NIR MFLI measurement with SwissSPAD2, a large time-gated SPAD camera. We first benchmark its performance in well-controlled in vitro experiments, ranging from monitoring environmental effects on fluorescence lifetime, to quantifying Förster resonant energy transfer (FRET) between dyes. Next, we use it for in vivo studies of target-drug engagement in live and intact tumor xenografts using FRET. Information obtained with SwissSPAD2 was successfully compared to that obtained with a gated intensified charge-coupled device (ICCD) camera, using two different approaches. Our results demonstrate that SPAD cameras offer a powerful technology for in vivo preclinical applications in the NIR window.
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Affiliation(s)
- Jason T. Smith
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Alena Rudkouskaya
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York 12208, USA
| | - Shan Gao
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Juhi M. Gupta
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Arin Ulku
- AQUA Lab, Ecole Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel, Switzerland
| | - Claudio Bruschini
- AQUA Lab, Ecole Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel, Switzerland
| | - Edoardo Charbon
- AQUA Lab, Ecole Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel, Switzerland
| | - Shimon Weiss
- Department of Chemistry & Biochemistry, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Margarida Barroso
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York 12208, USA
| | - Xavier Intes
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Xavier Michalet
- Department of Chemistry & Biochemistry, University of California at Los Angeles, Los Angeles, California 90095, USA
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21
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Wu ML, Ripiccini E, Kizilkan E, Gramuglia F, Keshavarzian P, Fenoglio CA, Morimoto K, Charbon E. Radiation Hardness Study of Single-Photon Avalanche Diode for Space and High Energy Physics Applications. SENSORS 2022; 22:s22082919. [PMID: 35458904 PMCID: PMC9025377 DOI: 10.3390/s22082919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/07/2022] [Accepted: 04/08/2022] [Indexed: 02/04/2023]
Abstract
The radiation hardness of 180 nm complementary metal-oxide-semiconductor (CMOS) and 55 nm bipolar-CMOS-double-diffused MOS single-photon avalanche diodes (SPADs) is studied using 10 MeV and 100 MeV protons up to a displacement damage dose of 1 PeV/g. It is found that the dark count rate (DCR) levels are dependent on the number and the type of defects created. A new stepwise increase in the DCR is presented. Afterpulsing was found to be a significant contributor to the observed DCR increase. A new model for DCR increase prediction is proposed considering afterpulsing. Most of the samples under test retain reasonable DCR levels after irradiation, showing high tolerance to ionizing and displacement damage caused by protons. Following irradiation, self-healing was observed at room temperature. Furthermore, high-temperature annealing shows potential for accelerating recovery. Overall, the results show the suitability of SPADs as optical detectors for long-term space missions or as detectors for high-energy particles.
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Affiliation(s)
- Ming-Lo Wu
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
- Correspondence: (M.-L.W.); (E.C.)
| | - Emanuele Ripiccini
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
| | - Ekin Kizilkan
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
| | - Francesco Gramuglia
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
| | - Pouyan Keshavarzian
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
| | - Carlo Alberto Fenoglio
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
| | | | - Edoardo Charbon
- AQUA Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002 Neuchâtel, Switzerland; (E.R.); (E.K.); (F.G.); (P.K.); (C.A.F.)
- Correspondence: (M.-L.W.); (E.C.)
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22
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Liu P. Resolution enhancement in random illumination microscopy using photon correlations. APPLIED OPTICS 2022; 61:2910-2914. [PMID: 35471369 DOI: 10.1364/ao.452709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 03/10/2022] [Indexed: 06/14/2023]
Abstract
Random illumination microscopy (RIM) could surpass the diffraction barrier in fluorescence microscopy by illuminating an object with unknown speckle patterns. It has been demonstrated that the resolution in RIM using second-order statistics is as good as that of conventional structured illumination microscopy (SIM) from the asymptotic point of view. Compared to classical SIM, RIM is more robust to optical aberrations and scattering introduced by thick samples. In this work, I show that the quantum correlations could further improve the resolution in random illumination microscopy due to the photon antibunching property of fluorophore emitters. In theory, the super-resolution capacity of this quantum-enhanced version of RIM corresponds to the fourth power of the point spread function under the general epi-illumination geometry.
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23
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Giudici A, Acconcia G, Labanca I, Ghioni M, Rech I. 4 ns dead time with a fully integrated active quenching circuit driving a custom single photon avalanche diode. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:043103. [PMID: 35489934 DOI: 10.1063/5.0087341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 03/30/2022] [Indexed: 06/14/2023]
Abstract
At the present time, Single Photon Avalanche Diodes (SPADs) are the enabling devices in many applications, ranging from medical imaging to laser ranging and from remote sensing to quantum key distribution. Even though they belong to different scientific domains, these applications share the need for a detector capable of attaining high count rates possibly without trading it off with other key detector's features, such as afterpulsing probability, photon detection efficiency, and dark counts. In this work, we present the characterization of a fast integrated active quenching circuit capable of driving high-performance external custom-technology SPADs for single photon detection in the visible wavelength range. Combining the prompt intervention of the electronic circuitry and the performance of a custom-technology SPAD, we attained count rates up to 250 MCps while keeping the afterpulsing probability within 2%.
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Affiliation(s)
- Andrea Giudici
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Giulia Acconcia
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Ivan Labanca
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Massimo Ghioni
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Ivan Rech
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
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24
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Fazel M, Jazani S, Scipioni L, Vallmitjana A, Gratton E, Digman MA, Pressé S. High Resolution Fluorescence Lifetime Maps from Minimal Photon Counts. ACS PHOTONICS 2022; 9:1015-1025. [PMID: 35847830 PMCID: PMC9278809 DOI: 10.1021/acsphotonics.1c01936] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Fluorescence lifetime imaging microscopy (FLIM) may reveal subcellular spatial lifetime maps of key molecular species. Yet, such a quantitative picture of life necessarily demands high photon budgets at every pixel under the current analysis paradigm, thereby increasing acquisition time and photodamage to the sample. Motivated by recent developments in computational statistics, we provide a direct means to update our knowledge of the lifetime maps of species of different lifetimes from direct photon arrivals, while accounting for experimental features such as arbitrary forms of the instrument response function (IRF) and exploiting information from empty laser pulses not resulting in photon detection. Our ability to construct lifetime maps holds for arbitrary lifetimes, from short lifetimes (comparable to the IRF) to lifetimes exceeding interpulse times. As our method is highly data efficient, for the same amount of data normally used to determine lifetimes and photon ratios, working within the Bayesian paradigm, we report direct blind unmixing of lifetimes with subnanosecond resolution and subpixel spatial resolution using standard raster scan FLIM images. We demonstrate our method using a wide range of simulated and experimental data.
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Affiliation(s)
- Mohamadreza Fazel
- Center
for Biological Physics, Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | - Sina Jazani
- Center
for Biological Physics, Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | - Lorenzo Scipioni
- Department
of Biomedical Engineering, University of
California Irvine, Irvine, California 92697, United States
- Laboratory
of Fluorescence Dynamics, The Henry Samueli School of Engineering, University of California, Irvine, California 92697, United States
| | - Alexander Vallmitjana
- Department
of Biomedical Engineering, University of
California Irvine, Irvine, California 92697, United States
- Laboratory
of Fluorescence Dynamics, The Henry Samueli School of Engineering, University of California, Irvine, California 92697, United States
| | - Enrico Gratton
- Department
of Biomedical Engineering, University of
California Irvine, Irvine, California 92697, United States
- Laboratory
of Fluorescence Dynamics, The Henry Samueli School of Engineering, University of California, Irvine, California 92697, United States
| | - Michelle A. Digman
- Department
of Biomedical Engineering, University of
California Irvine, Irvine, California 92697, United States
- Laboratory
of Fluorescence Dynamics, The Henry Samueli School of Engineering, University of California, Irvine, California 92697, United States
| | - Steve Pressé
- Center
for Biological Physics, Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
- School
of Molecular Science, Arizona State University, Tempe, Arizona 85287, United States
- E-mail:
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25
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Zhao J, Lyons A, Ulku AC, Defienne H, Faccio D, Charbon E. Light detection and ranging with entangled photons. OPTICS EXPRESS 2022; 30:3675-3683. [PMID: 35209621 DOI: 10.1364/oe.435898] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 01/08/2022] [Indexed: 06/14/2023]
Abstract
Single-photon light detection and ranging (LiDAR) is a key technology for depth imaging through complex environments. Despite recent advances, an open challenge is the ability to isolate the LiDAR signal from other spurious sources including background light and jamming signals. Here we show that a time-resolved coincidence scheme can address these challenges by exploiting spatio-temporal correlations between entangled photon pairs. We demonstrate that a photon-pair-based LiDAR can distill desired depth information in the presence of both synchronous and asynchronous spurious signals without prior knowledge of the scene and the target object. This result enables the development of robust and secure quantum LiDAR systems and paves the way to time-resolved quantum imaging applications.
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26
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Liu R, Tian X, He F, Ma J. Multi-depth photon-counting imaging based on polarisation modulation. OPTICS EXPRESS 2021; 29:39362-39375. [PMID: 34809302 DOI: 10.1364/oe.442272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 10/31/2021] [Indexed: 06/13/2023]
Abstract
We present a method for multi-depth imaging that uses polarisation modulation to reconstruct multiple depths from photon-counting observations. The echo photon signals of the scene with multiple targets are modelled under the low-flux condition based on a confocal scanning system. We establish a computational method by constructing the relationship between the received photon rate after polarisation modulation and several variables described for multi-echo signals: the detected average number of photons before polarisation modulation and the flight time corresponding to phase shift based on polarisation modulation. The photon rate is directly calculated from the photon-counting value received by a photon-counting detector based on the Poisson negative log-likelihood function. We suggest solving the abovementioned relationship by changing the waveform of the operating voltage applied to the modulator to derive analytic forms of the detected average number of photons and the flight time. We experimentally demonstrate that the proposed method can accurately reconstruct the reflectivity and depth images of two targets in a 3D scene with a significant improvement beyond what the polarisation modulation imaging method for single-depth can achieve. Moreover, we demonstrate the effectiveness of the proposed method by varying the reflection properties of the targets, the number of echo photons (e.g. less than one photon in a pulse) and the background noise. We exhibit a fast imaging capability with the imaging frequency of one pixel at 8 kHz and the root mean-square error of depth smaller than 6 cm.
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27
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Houwink Q, Kalisvaart D, Hung ST, Cnossen J, Fan D, Mos P, Can Ülkü A, Bruschini C, Charbon E, Smith CS. Theoretical minimum uncertainty of single-molecule localizations using a single-photon avalanche diode array. OPTICS EXPRESS 2021; 29:39920-39929. [PMID: 34809346 DOI: 10.1364/oe.439340] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 10/12/2021] [Indexed: 06/13/2023]
Abstract
Single-photon avalanche diode (SPAD) arrays can be used for single-molecule localization microscopy (SMLM) because of their high frame rate and lack of readout noise. SPAD arrays have a binary frame output, which means photon arrivals should be described as a binomial process rather than a Poissonian process. Consequentially, the theoretical minimum uncertainty of the localizations is not accurately predicted by the Poissonian Cramér-Rao lower bound (CRLB). Here, we derive a binomial CRLB and benchmark it using simulated and experimental data. We show that if the expected photon count is larger than one for all pixels within one standard deviation of a Gaussian point spread function, the binomial CRLB gives a 46% higher theoretical uncertainty than the Poissonian CRLB. For typical SMLM photon fluxes, where no saturation occurs, the binomial CRLB predicts the same uncertainty as the Poissonian CRLB. Therefore, the binomial CRLB can be used to predict and benchmark localization uncertainty for SMLM with SPAD arrays for all practical emitter intensities.
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28
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Thiele JC, Nevskyi O, Helmerich DA, Sauer M, Enderlein J. Advanced Data Analysis for Fluorescence-Lifetime Single-Molecule Localization Microscopy. FRONTIERS IN BIOINFORMATICS 2021; 1:740281. [PMID: 36303750 PMCID: PMC9581058 DOI: 10.3389/fbinf.2021.740281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 10/04/2021] [Indexed: 11/25/2022] Open
Abstract
Fluorescence-lifetime single molecule localization microscopy (FL-SMLM) adds the lifetime dimension to the spatial super-resolution provided by SMLM. Independent of intensity and spectrum, this lifetime information can be used, for example, to quantify the energy transfer efficiency in Förster Resonance Energy Transfer (FRET) imaging, to probe the local environment with dyes that change their lifetime in an environment-sensitive manner, or to achieve image multiplexing by using dyes with different lifetimes. We present a thorough theoretical analysis of fluorescence-lifetime determination in the context of FL-SMLM and compare different lifetime-fitting approaches. In particular, we investigate the impact of background and noise, and give clear guidelines for procedures that are optimized for FL-SMLM. We do also present and discuss our public-domain software package “Fluorescence-Lifetime TrackNTrace,” which converts recorded fluorescence microscopy movies into super-resolved FL-SMLM images.
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Affiliation(s)
- Jan Christoph Thiele
- Third Institute of Physics—Biophysics, Georg August University, Göttingen, Germany
- *Correspondence: Jan Christoph Thiele, ; Jörg Enderlein,
| | - Oleksii Nevskyi
- Third Institute of Physics—Biophysics, Georg August University, Göttingen, Germany
| | - Dominic A. Helmerich
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Jörg Enderlein
- Third Institute of Physics—Biophysics, Georg August University, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Georg August University, Göttingen, Germany
- *Correspondence: Jan Christoph Thiele, ; Jörg Enderlein,
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29
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Bowman AJ, Kasevich MA. Resonant Electro-Optic Imaging for Microscopy at Nanosecond Resolution. ACS NANO 2021; 15:16043-16054. [PMID: 34546704 DOI: 10.1021/acsnano.1c04470] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We demonstrate an electro-optic wide-field method to enable fluorescence lifetime microscopy (FLIM) with high throughput and single-molecule sensitivity. Resonantly driven Pockels cells are used to efficiently gate images at 39 MHz, allowing fluorescence lifetime to be captured on standard camera sensors. Lifetime imaging of single molecules is enabled in wide field with exposure times of less than 100 ms. This capability allows combination of wide-field FLIM with single-molecule super-resolution localization microscopy. Fast single-molecule dynamics such as FRET and molecular binding events are captured from wide-field images without prior spatial knowledge. A lifetime sensitivity of 1.9 times the photon shot-noise limit is achieved, and high throughput is shown by acquiring wide-field FLIM images with millisecond exposure and >108 photons per frame. Resonant electro-optic FLIM allows lifetime contrast in any wide-field microscopy method.
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Affiliation(s)
- Adam J Bowman
- Physics Department, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, United States
| | - Mark A Kasevich
- Physics Department, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, United States
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30
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Custom-Technology Single-Photon Avalanche Diode Linear Detector Array for Underwater Depth Imaging. SENSORS 2021; 21:s21144850. [PMID: 34300590 PMCID: PMC8309917 DOI: 10.3390/s21144850] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/07/2021] [Accepted: 07/08/2021] [Indexed: 11/19/2022]
Abstract
We present an optical depth imaging system suitable for highly scattering underwater environments. The system used the time-correlated single-photon counting (TCSPC) technique and the time-of-flight approach to obtain depth profiles. The single-photon detection was provided by a linear array of single-photon avalanche diode (SPAD) detectors fabricated in a customized silicon fabrication technology for optimized efficiency, dark count rate, and jitter performance. The bi-static transceiver comprised a pulsed laser diode source with central wavelength 670 nm, a linear array of 16 × 1 Si-SPAD detectors, with a dedicated TCSPC acquisition module. Cylindrical lenses were used to collect the light scattered by the target and image it onto the sensor. These laboratory-based experiments demonstrated single-photon depth imaging at a range of 1.65 m in highly scattering conditions, equivalent up to 8.3 attenuation lengths between the system and the target, using average optical powers of up to 15 mW. The depth and spatial resolution of this sensor were investigated in different scattering conditions.
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Abstract
We review the advancement of the research toward the design and implementation of quantum plenoptic cameras, radically novel 3D imaging devices that exploit both momentum–position entanglement and photon–number correlations to provide the typical refocusing and ultra-fast, scanning-free, 3D imaging capability of plenoptic devices, along with dramatically enhanced performances, unattainable in standard plenoptic cameras: diffraction-limited resolution, large depth of focus, and ultra-low noise. To further increase the volumetric resolution beyond the Rayleigh diffraction limit, and achieve the quantum limit, we are also developing dedicated protocols based on quantum Fisher information. However, for the quantum advantages of the proposed devices to be effective and appealing to end-users, two main challenges need to be tackled. First, due to the large number of frames required for correlation measurements to provide an acceptable signal-to-noise ratio, quantum plenoptic imaging (QPI) would require, if implemented with commercially available high-resolution cameras, acquisition times ranging from tens of seconds to a few minutes. Second, the elaboration of this large amount of data, in order to retrieve 3D images or refocusing 2D images, requires high-performance and time-consuming computation. To address these challenges, we are developing high-resolution single-photon avalanche photodiode (SPAD) arrays and high-performance low-level programming of ultra-fast electronics, combined with compressive sensing and quantum tomography algorithms, with the aim to reduce both the acquisition and the elaboration time by two orders of magnitude. Routes toward exploitation of the QPI devices will also be discussed.
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32
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Villa F, Severini F, Madonini F, Zappa F. SPADs and SiPMs Arrays for Long-Range High-Speed Light Detection and Ranging (LiDAR). SENSORS (BASEL, SWITZERLAND) 2021; 21:3839. [PMID: 34206130 PMCID: PMC8199503 DOI: 10.3390/s21113839] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/26/2021] [Accepted: 05/28/2021] [Indexed: 01/14/2023]
Abstract
Light Detection and Ranging (LiDAR) is a 3D imaging technique, widely used in many applications such as augmented reality, automotive, machine vision, spacecraft navigation and landing. Achieving long-ranges and high-speed, most of all in outdoor applications with strong solar background illumination, are challenging requirements. In the introduction we review different 3D-ranging techniques (stereo-vision, projection with structured light, pulsed-LiDAR, amplitude-modulated continuous-wave LiDAR, frequency-modulated continuous-wave interferometry), illumination schemes (single point and blade scanning, flash-LiDAR) and time-resolved detectors for LiDAR (EM-CCD, I-CCD, APD, SPAD, SiPM). Then, we provide an extensive review of silicon- single photon avalanche diode (SPAD)-based LiDAR detectors (both commercial products and research prototypes) analyzing how each architecture faces the main challenges of LiDAR (i.e., long ranges, centimeter resolution, large field-of-view and high angular resolution, high operation speed, background immunity, eye-safety and multi-camera operation). Recent progresses in 3D stacking technologies provided an important step forward in SPAD array development, allowing to reach smaller pitch, higher pixel count and more complex processing electronics. In the conclusions, we provide some guidelines for the design of next generation SPAD-LiDAR detectors.
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Affiliation(s)
- Federica Villa
- Dipartimento di Elettronica, Informazione e Bioingegneria—Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy; (F.S.); (F.M.); (F.Z.)
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33
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Xiao D, Zang Z, Sapermsap N, Wang Q, Xie W, Chen Y, Uei Li DD. Dynamic fluorescence lifetime sensing with CMOS single-photon avalanche diode arrays and deep learning processors. BIOMEDICAL OPTICS EXPRESS 2021; 12:3450-3462. [PMID: 34221671 PMCID: PMC8221960 DOI: 10.1364/boe.425663] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 05/07/2021] [Accepted: 05/10/2021] [Indexed: 06/13/2023]
Abstract
Measuring fluorescence lifetimes of fast-moving cells or particles have broad applications in biomedical sciences. This paper presents a dynamic fluorescence lifetime sensing (DFLS) system based on the time-correlated single-photon counting (TCSPC) principle. It integrates a CMOS 192 × 128 single-photon avalanche diode (SPAD) array, offering an enormous photon-counting throughput without pile-up effects. We also proposed a quantized convolutional neural network (QCNN) algorithm and designed a field-programmable gate array embedded processor for fluorescence lifetime determinations. The processor uses a simple architecture, showing unparallel advantages in accuracy, analysis speed, and power consumption. It can resolve fluorescence lifetimes against disturbing noise. We evaluated the DFLS system using fluorescence dyes and fluorophore-tagged microspheres. The system can effectively measure fluorescence lifetimes within a single exposure period of the SPAD sensor, paving the way for portable time-resolved devices and shows potential in various applications.
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Affiliation(s)
- Dong Xiao
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland, UK
- Department of Biomedical Engineering, University of Strathclyde, Glasgow G1 1XQ, Scotland, UK
| | - Zhenya Zang
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland, UK
- Department of Biomedical Engineering, University of Strathclyde, Glasgow G1 1XQ, Scotland, UK
| | - Natakorn Sapermsap
- Department of Physics, University of Strathclyde, Glasgow, G4 0RE, Scotland, UK
| | - Quan Wang
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland, UK
- Department of Biomedical Engineering, University of Strathclyde, Glasgow G1 1XQ, Scotland, UK
| | - Wujun Xie
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland, UK
- Department of Biomedical Engineering, University of Strathclyde, Glasgow G1 1XQ, Scotland, UK
| | - Yu Chen
- Department of Physics, University of Strathclyde, Glasgow, G4 0RE, Scotland, UK
| | - David Day Uei Li
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland, UK
- Department of Biomedical Engineering, University of Strathclyde, Glasgow G1 1XQ, Scotland, UK
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34
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Fast Gating for Raman Spectroscopy. SENSORS 2021; 21:s21082579. [PMID: 33916972 PMCID: PMC8067580 DOI: 10.3390/s21082579] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/02/2021] [Accepted: 04/02/2021] [Indexed: 11/16/2022]
Abstract
Fast gating in Raman spectroscopy is used to reject the fluorescence contribution from the sample and/or the substrate. Several techniques have been set up in the last few decades aiming either to enhance the Raman signal (CARS, SERS or Resonant Raman scattering) or to cancel out the fluorescence contribution (SERDS), and a number of reviews have already been published on these sub-topics. However, for many reasons it is sometimes necessary to reject fluorescence in traditional Raman spectroscopy, and in the last few decades a variety of papers dealt with this issue, which is still challenging due to the time scales at stake (down to picoseconds). Fast gating (<1 ns) in the time domain allows one to cut off part of the fluorescence signal and retrieve the best Raman signal, depending on the fluorescence lifetime of the sample and laser pulse duration. In particular, three different techniques have been developed to accomplish this task: optical Kerr cells, intensified Charge Coupling Devices and systems based on Single Photon Avalanche Photodiodes. The utility of time domain fast gating will be discussed, and In this work, the utility of time domain fast gating is discussed, as well as the performances of the mentioned techniques as reported in literature.
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35
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Michalet X. Continuous and discrete phasor analysis of binned or time-gated periodic decays. AIP ADVANCES 2021; 11:035331. [PMID: 33786208 PMCID: PMC7990508 DOI: 10.1063/5.0027834] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 01/22/2021] [Indexed: 05/29/2023]
Abstract
The time-resolved analysis of periodically excited luminescence decays by the phasor method in the presence of time-gating or binning is revisited. Analytical expressions for discrete configurations of square gates are derived, and the locus of the phasors of such modified periodic single-exponential decays is compared to the canonical universal semicircle. The effects of instrument response function offset, decay truncation, and gate shape are also discussed. Finally, modified expressions for the phase and modulus lifetimes are provided for some simple cases. A discussion of a modified phasor calibration approach is presented, and an illustration of the new concepts with examples from the literature concludes this work.
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Affiliation(s)
- Xavier Michalet
- Department of Chemistry and Biochemistry, 607 Charles E. Young Drive E., Los Angeles, California 90095, USA
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36
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Wagner F, Schiffers F, Willomitzer F, Cossairt O, Velten A. Intensity interferometry-based 3D imaging. OPTICS EXPRESS 2021; 29:4733-4745. [PMID: 33726023 DOI: 10.1364/oe.412688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/23/2021] [Indexed: 06/12/2023]
Abstract
The development of single-photon counting detectors and arrays has made tremendous steps in recent years, not the least because of various new applications, e.g., LIDAR devices. In this work, a 3D imaging device based on real thermal light intensity interferometry is presented. By using gated SPAD technology, a basic 3D scene is imaged in reasonable measurement time. Compared to conventional approaches, the proposed synchronized photon counting allows the use of more light modes to enhance 3D ranging performance. Advantages like robustness to atmospheric scattering or autonomy by exploiting external light sources can make this ranging approach interesting for future applications.
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37
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Slenders E, Castello M, Buttafava M, Villa F, Tosi A, Lanzanò L, Koho SV, Vicidomini G. Confocal-based fluorescence fluctuation spectroscopy with a SPAD array detector. LIGHT, SCIENCE & APPLICATIONS 2021; 10:31. [PMID: 33542179 PMCID: PMC7862647 DOI: 10.1038/s41377-021-00475-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 12/17/2020] [Accepted: 01/14/2021] [Indexed: 05/13/2023]
Abstract
The combination of confocal laser-scanning microscopy (CLSM) and fluorescence fluctuation spectroscopy (FFS) is a powerful tool in studying fast, sub-resolution biomolecular processes in living cells. A detector array can further enhance CLSM-based FFS techniques, as it allows the simultaneous acquisition of several samples-essentially images-of the CLSM detection volume. However, the detector arrays that have previously been proposed for this purpose require tedious data corrections and preclude the combination of FFS with single-photon techniques, such as fluorescence lifetime imaging. Here, we solve these limitations by integrating a novel single-photon-avalanche-diode (SPAD) array detector in a CLSM system. We validate this new implementation on a series of FFS analyses: spot-variation fluorescence correlation spectroscopy, pair-correlation function analysis, and image-derived mean squared displacement analysis. We predict that the unique combination of spatial and temporal information provided by our detector will make the proposed architecture the method of choice for CLSM-based FFS.
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Affiliation(s)
- Eli Slenders
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Marco Castello
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Mauro Buttafava
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Federica Villa
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Alberto Tosi
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Luca Lanzanò
- Nanoscopy and NIC@IIT, Istituto Italiano di Tecnologia, Genoa, Italy
- Dipartimento di Fisica e Astronomia, Università di Catania, Catania, Italy
| | - Sami Valtteri Koho
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy.
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38
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Gulinatti A, Ceccarelli F, Ghioni M, Rech I. Custom silicon technology for SPAD-arrays with red-enhanced sensitivity and low timing jitter. OPTICS EXPRESS 2021; 29:4559-4581. [PMID: 33771031 PMCID: PMC7920522 DOI: 10.1364/oe.413821] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/16/2020] [Accepted: 12/21/2020] [Indexed: 06/12/2023]
Abstract
Single-photon detection is an invaluable tool for many applications ranging from basic research to consumer electronics. In this respect, the Single Photon Avalanche Diode (SPAD) plays a key role in enabling a broad diffusion of these techniques thanks to its remarkable performance, room-temperature operation, and scalability. In this paper we present a silicon technology that allows the fabrication of SPAD-arrays with an unprecedented combination of low timing jitter (95 ps FWHM) and high detection efficiency at red and near infrared wavelengths (peak of 70% at 650 nm, 45% at 800 nm). We discuss the device structure, the fabrication process, and we present a thorough experimental characterization of the fabricated detectors. We think that these results can pave the way to new exciting developments in many fields, ranging from quantum optics to single molecule spectroscopy.
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Affiliation(s)
- Angelo Gulinatti
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Francesco Ceccarelli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy
- Currently with Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR) and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Massimo Ghioni
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Ivan Rech
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy
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39
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Zickus V, Wu ML, Morimoto K, Kapitany V, Fatima A, Turpin A, Insall R, Whitelaw J, Machesky L, Bruschini C, Faccio D, Charbon E. Fluorescence lifetime imaging with a megapixel SPAD camera and neural network lifetime estimation. Sci Rep 2020; 10:20986. [PMID: 33268900 PMCID: PMC7710711 DOI: 10.1038/s41598-020-77737-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 11/06/2020] [Indexed: 01/07/2023] Open
Abstract
Fluorescence lifetime imaging microscopy (FLIM) is a key technology that provides direct insight into cell metabolism, cell dynamics and protein activity. However, determining the lifetimes of different fluorescent proteins requires the detection of a relatively large number of photons, hence slowing down total acquisition times. Moreover, there are many cases, for example in studies of cell collectives, where wide-field imaging is desired. We report scan-less wide-field FLIM based on a 0.5 MP resolution, time-gated Single Photon Avalanche Diode (SPAD) camera, with acquisition rates up to 1 Hz. Fluorescence lifetime estimation is performed via a pre-trained artificial neural network with 1000-fold improvement in processing times compared to standard least squares fitting techniques. We utilised our system to image HT1080-human fibrosarcoma cell line as well as Convallaria. The results show promise for real-time FLIM and a viable route towards multi-megapixel fluorescence lifetime images, with a proof-of-principle mosaic image shown with 3.6 MP.
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Affiliation(s)
- Vytautas Zickus
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Ming-Lo Wu
- Advanced Quantum Architecture Laboratory, Ecole Polytechnique Fédérale de Lausanne, 2002, Neuchâtel, Switzerland
| | - Kazuhiro Morimoto
- Advanced Quantum Architecture Laboratory, Ecole Polytechnique Fédérale de Lausanne, 2002, Neuchâtel, Switzerland
| | - Valentin Kapitany
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Areeba Fatima
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Alex Turpin
- School of Computing Science, University of Glasgow, Glasgow, G12 8LT, UK
| | - Robert Insall
- University of Glasgow Institute of Cancer Sciences, Glasgow, UK.,Cancer Research UK, Beatson Institute, Glasgow, UK
| | - Jamie Whitelaw
- University of Glasgow Institute of Cancer Sciences, Glasgow, UK.,Cancer Research UK, Beatson Institute, Glasgow, UK
| | - Laura Machesky
- University of Glasgow Institute of Cancer Sciences, Glasgow, UK.,Cancer Research UK, Beatson Institute, Glasgow, UK
| | - Claudio Bruschini
- Advanced Quantum Architecture Laboratory, Ecole Polytechnique Fédérale de Lausanne, 2002, Neuchâtel, Switzerland
| | - Daniele Faccio
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK.
| | - Edoardo Charbon
- Advanced Quantum Architecture Laboratory, Ecole Polytechnique Fédérale de Lausanne, 2002, Neuchâtel, Switzerland.
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40
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Moreaux LC, Yatsenko D, Sacher WD, Choi J, Lee C, Kubat NJ, Cotton RJ, Boyden ES, Lin MZ, Tian L, Tolias AS, Poon JKS, Shepard KL, Roukes ML. Integrated Neurophotonics: Toward Dense Volumetric Interrogation of Brain Circuit Activity-at Depth and in Real Time. Neuron 2020; 108:66-92. [PMID: 33058767 PMCID: PMC8061790 DOI: 10.1016/j.neuron.2020.09.043] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/18/2020] [Accepted: 09/28/2020] [Indexed: 12/17/2022]
Abstract
We propose a new paradigm for dense functional imaging of brain activity to surmount the limitations of present methodologies. We term this approach "integrated neurophotonics"; it combines recent advances in microchip-based integrated photonic and electronic circuitry with those from optogenetics. This approach has the potential to enable lens-less functional imaging from within the brain itself to achieve dense, large-scale stimulation and recording of brain activity with cellular resolution at arbitrary depths. We perform a computational study of several prototype 3D architectures for implantable probe-array modules that are designed to provide fast and dense single-cell resolution (e.g., within a 1-mm3 volume of mouse cortex comprising ∼100,000 neurons). We describe progress toward realizing integrated neurophotonic imaging modules, which can be produced en masse with current semiconductor foundry protocols for chip manufacturing. Implantation of multiple modules can cover extended brain regions.
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Affiliation(s)
- Laurent C Moreaux
- Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Dimitri Yatsenko
- Vathes LLC, Houston, TX 77030, USA; Center for Neuroscience and Artificial Intelligence and Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Wesley D Sacher
- Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA; Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA; Max Planck Institute for Microstructure Physics, Halle, Germany
| | - Jaebin Choi
- Departments of Electrical Engineering and Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Changhyuk Lee
- Departments of Electrical Engineering and Biomedical Engineering, Columbia University, New York, NY 10027, USA; Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology, Korea
| | - Nicole J Kubat
- Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
| | - R James Cotton
- Shirley Ryan AbilityLab, Northwestern University, Chicago, IL 60611, USA; Center for Neuroscience and Artificial Intelligence and Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Edward S Boyden
- Howard Hughes Medical Institute, Cambridge, MA, USA; McGovern Institute, MIT, Cambridge, USA; Koch Institute, MIT, Cambridge, USA; Departments of Brain and Cognitive Sciences, Media Arts and Sciences, and Biological Engineering, MIT, Cambridge, USA
| | - Michael Z Lin
- Departments of Neurobiology and Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA 95616, USA
| | - Andreas S Tolias
- Vathes LLC, Houston, TX 77030, USA; Center for Neuroscience and Artificial Intelligence and Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA
| | - Joyce K S Poon
- Max Planck Institute for Microstructure Physics, Halle, Germany; Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Rd., Toronto, ON M5S 3G4, Canada
| | - Kenneth L Shepard
- Departments of Electrical Engineering and Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Michael L Roukes
- Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA; Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA; Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA; Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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41
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Time-Gated Single-Photon Detection in Time-Domain Diffuse Optics: A Review. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10031101] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This work reviews physical concepts, technologies and applications of time-domain diffuse optics based on time-gated single-photon detection. This particular photon detection strategy is of the utmost importance in the diffuse optics field as it unleashes the full power of the time-domain approach by maximizing performances in terms of contrast produced by a localized perturbation inside the scattering medium, signal-to-noise ratio, measurement time and dynamic range, penetration depth and spatial resolution. The review covers 15 years of theoretical studies, technological progresses, proof of concepts and design of laboratory systems based on time-gated single-photon detection with also few hints on other fields where the time-gated detection strategy produced and will produce further impact.
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42
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Ulku A, Ardelean A, Antolovic M, Weiss S, Charbon E, Bruschini C, Michalet X. Wide-field time-gated SPAD imager for phasor-based FLIM applications. Methods Appl Fluoresc 2020; 8:024002. [PMID: 31968310 PMCID: PMC8827132 DOI: 10.1088/2050-6120/ab6ed7] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We describe the performance of a new wide area time-gated single-photon avalanche diode (SPAD) array for phasor-FLIM, exploring the effect of gate length, gate number and signal intensity on the measured lifetime accuracy and precision. We conclude that the detector functions essentially as an ideal shot noise limited sensor and is capable of video rate FLIM measurement. The phasor approach used in this work appears ideally suited to handle the large amount of data generated by this type of very large sensor (512 × 512 pixels), even in the case of small number of gates and limited photon budget.
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Affiliation(s)
- Arin Ulku
- AQUA Lab, Ecole Polytechnique Fédérale de
Lausanne (EPFL), Neuchâtel, Switzerland
| | - Andrei Ardelean
- AQUA Lab, Ecole Polytechnique Fédérale de
Lausanne (EPFL), Neuchâtel, Switzerland
| | - Michel Antolovic
- AQUA Lab, Ecole Polytechnique Fédérale de
Lausanne (EPFL), Neuchâtel, Switzerland
| | - Shimon Weiss
- Department of Chemistry & Biochemistry, University of
California at Los Angeles (UCLA), Los Angeles, California, United States of
America
| | - Edoardo Charbon
- AQUA Lab, Ecole Polytechnique Fédérale de
Lausanne (EPFL), Neuchâtel, Switzerland
| | - Claudio Bruschini
- AQUA Lab, Ecole Polytechnique Fédérale de
Lausanne (EPFL), Neuchâtel, Switzerland
| | - Xavier Michalet
- Department of Chemistry & Biochemistry, University of
California at Los Angeles (UCLA), Los Angeles, California, United States of
America
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43
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Ankri R, Basu A, Ulku AC, Bruschini C, Charbon E, Weiss S, Michalet X. Single-Photon, Time-Gated, Phasor-Based Fluorescence Lifetime Imaging through Highly Scattering Medium. ACS PHOTONICS 2020; 7:68-79. [PMID: 35936550 PMCID: PMC9355389 DOI: 10.1021/acsphotonics.9b00874] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Fluorescence lifetime imaging (FLI) is increasingly recognized as a powerful tool for biochemical and cellular investigations, including in vivo applications. Fluorescence lifetime is an intrinsic characteristic of any fluorescent dye which, to a large extent, does not depend on excitation intensity and signal level. In particular, it allows distinguishing dyes with similar emission spectra, offering additional multiplexing capabilities. However, in vivo FLI in the visible range is complicated by the contamination by (i) tissue autofluorescence, which decreases contrast, and by (ii) light scattering and absorption in tissues, which significantly reduce fluorescence intensity and modify the temporal profile of the signal. Here, we demonstrate how these issues can be accounted for and overcome, using a new time-gated single-photon avalanche diode array camera, SwissSPAD2, combined with phasor analysis to provide a simple and fast visual method for lifetime imaging. In particular, we show how phasor dispersion increases with increasing scattering and/or decreasing fluorescence intensity. Next, we show that as long as the fluorescence signal of interest is larger than the phantom autofluorescence, the presence of a distinct lifetime can be clearly identified with appropriate background correction. We use these results to demonstrate the detection of A459 cells expressing the fluorescent protein mCyRFP1 through highly scattering and autofluorescent phantom layers. These results showcase the possibility to perform FLI in challenging conditions, using standard, bright, visible fluorophore or fluorescence proteins.
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Affiliation(s)
- Rinat Ankri
- Department of Chemistry & Biochemistry, UCLA, Los Angeles, California 90095, United States
- Corresponding Authors:.
| | - Arkaprabha Basu
- Department of Chemistry & Biochemistry, UCLA, Los Angeles, California 90095, United States
| | - Arin Can Ulku
- School of Engineering, École Polytechnique Fédérale de Lausanne, Neuchâtel 1015, Switzerland
| | - Claudio Bruschini
- School of Engineering, École Polytechnique Fédérale de Lausanne, Neuchâtel 1015, Switzerland
| | - Edoardo Charbon
- School of Engineering, École Polytechnique Fédérale de Lausanne, Neuchâtel 1015, Switzerland
| | - Shimon Weiss
- Department of Chemistry & Biochemistry, UCLA, Los Angeles, California 90095, United States
| | - Xavier Michalet
- Department of Chemistry & Biochemistry, UCLA, Los Angeles, California 90095, United States
- Corresponding Authors:.
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44
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Griffiths AD, Chen H, Li DDU, Henderson RK, Herrnsdorf J, Dawson MD, Strain MJ. Multispectral time-of-flight imaging using light-emitting diodes. OPTICS EXPRESS 2019; 27:35485-35498. [PMID: 31878719 DOI: 10.1364/oe.27.035485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 10/18/2019] [Indexed: 06/10/2023]
Abstract
Multispectral and 3-D imaging are useful for a wide variety of applications, adding valuable spectral and depth information for image analysis. Single-photon avalanche diode (SPAD) based imaging systems provide photon time-of-arrival information, and can be used for imaging with time-correlated single photon counting techniques. Here we demonstrate an LED based synchronised illumination system, where temporally structured light can be used to relate time-of-arrival to specific wavelengths, thus recovering reflectance information. Cross-correlation of the received multi-peak histogram with a reference measurement yields a time delay, allowing depth information to be determined with cm-scale resolution despite the long sequence of relatively wide (∼10 ns) pulses. Using commercial LEDs and a SPAD imaging array, multispectral 3-D imaging is demonstrated across 9 visible wavelength bands.
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45
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Lubin G, Tenne R, Michel Antolovic I, Charbon E, Bruschini C, Oron D. Quantum correlation measurement with single photon avalanche diode arrays. OPTICS EXPRESS 2019; 27:32863-32882. [PMID: 31878363 DOI: 10.1364/oe.27.032863] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 10/03/2019] [Indexed: 05/20/2023]
Abstract
Temporal photon correlation measurement, instrumental to probing the quantum properties of light, typically requires multiple single photon detectors. Progress in single photon avalanche diode (SPAD) array technology highlights their potential as high-performance detector arrays for quantum imaging and photon number-resolving (PNR) experiments. Here, we demonstrate this potential by incorporating a novel on-chip SPAD array with 42% peak photon detection efficiency, low dark count rate and crosstalk probability of 0.14% per detection in a confocal microscope. This enables reliable measurements of second and third order photon correlations from a single quantum dot emitter. Our analysis overcomes the inter-detector optical crosstalk background even though it is over an order of magnitude larger than our faint signal. To showcase the vast application space of such an approach, we implement a recently introduced super-resolution imaging method, quantum image scanning microscopy (Q-ISM).
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46
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Bowman AJ, Klopfer BB, Juffmann T, Kasevich MA. Electro-optic imaging enables efficient wide-field fluorescence lifetime microscopy. Nat Commun 2019; 10:4561. [PMID: 31594938 PMCID: PMC6783475 DOI: 10.1038/s41467-019-12535-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 09/17/2019] [Indexed: 12/12/2022] Open
Abstract
Nanosecond temporal resolution enables new methods for wide-field imaging like time-of-flight, gated detection, and fluorescence lifetime. The optical efficiency of existing approaches, however, presents challenges for low-light applications common to fluorescence microscopy and single-molecule imaging. We demonstrate the use of Pockels cells for wide-field image gating with nanosecond temporal resolution and high photon collection efficiency. Two temporal frames are obtained by combining a Pockels cell with a pair of polarizing beam-splitters. We show multi-label fluorescence lifetime imaging microscopy (FLIM), single-molecule lifetime spectroscopy, and fast single-frame FLIM at the camera frame rate with 103-105 times higher throughput than single photon counting. Finally, we demonstrate a space-to-time image multiplexer using a re-imaging optical cavity with a tilted mirror to extend the Pockels cell technique to multiple temporal frames. These methods enable nanosecond imaging with standard optical systems and sensors, opening a new temporal dimension for wide-field low-light microscopy.
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Affiliation(s)
- Adam J Bowman
- Physics Department, Stanford University, 382 Via Pueblo Mall, Stanford, CA, 94305, USA.
| | - Brannon B Klopfer
- Physics Department, Stanford University, 382 Via Pueblo Mall, Stanford, CA, 94305, USA
| | - Thomas Juffmann
- Faculty of Physics, University of Vienna, A-1090, Vienna, Austria
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, A-1030, Vienna, Austria
| | - Mark A Kasevich
- Physics Department, Stanford University, 382 Via Pueblo Mall, Stanford, CA, 94305, USA
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47
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Bruschini C, Homulle H, Antolovic IM, Burri S, Charbon E. Single-photon avalanche diode imagers in biophotonics: review and outlook. LIGHT, SCIENCE & APPLICATIONS 2019; 8:87. [PMID: 31645931 PMCID: PMC6804596 DOI: 10.1038/s41377-019-0191-5] [Citation(s) in RCA: 129] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 07/30/2019] [Accepted: 08/07/2019] [Indexed: 05/08/2023]
Abstract
Single-photon avalanche diode (SPAD) arrays are solid-state detectors that offer imaging capabilities at the level of individual photons, with unparalleled photon counting and time-resolved performance. This fascinating technology has progressed at a very fast pace in the past 15 years, since its inception in standard CMOS technology in 2003. A host of architectures have been investigated, ranging from simpler implementations, based solely on off-chip data processing, to progressively "smarter" sensors including on-chip, or even pixel level, time-stamping and processing capabilities. As the technology has matured, a range of biophotonics applications have been explored, including (endoscopic) FLIM, (multibeam multiphoton) FLIM-FRET, SPIM-FCS, super-resolution microscopy, time-resolved Raman spectroscopy, NIROT and PET. We will review some representative sensors and their corresponding applications, including the most relevant challenges faced by chip designers and end-users. Finally, we will provide an outlook on the future of this fascinating technology.
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48
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High-throughput smFRET analysis of freely diffusing nucleic acid molecules and associated proteins. Methods 2019; 169:21-45. [PMID: 31356875 DOI: 10.1016/j.ymeth.2019.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 06/24/2019] [Accepted: 07/22/2019] [Indexed: 11/21/2022] Open
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is a powerful technique for nanometer-scale studies of single molecules. Solution-based smFRET, in particular, can be used to study equilibrium intra- and intermolecular conformations, binding/unbinding events and conformational changes under biologically relevant conditions without ensemble averaging. However, single-spot smFRET measurements in solution are slow. Here, we detail a high-throughput smFRET approach that extends the traditional single-spot confocal geometry to a multispot one. The excitation spots are optically conjugated to two custom silicon single photon avalanche diode (SPAD) arrays. Two-color excitation is implemented using a periodic acceptor excitation (PAX), allowing distinguishing between singly- and doubly-labeled molecules. We demonstrate the ability of this setup to rapidly and accurately determine FRET efficiencies and population stoichiometries by pooling the data collected independently from the multiple spots. We also show how the high throughput of this approach can be used o increase the temporal resolution of single-molecule FRET population characterization from minutes to seconds. Combined with microfluidics, this high-throughput approach will enable simple real-time kinetic studies as well as powerful molecular screening applications.
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Dieguez A, Canals J, Franch N, Dieguez J, Alonso O, Vila A. A Compact Analog Histogramming SPAD-Based CMOS Chip for Time-Resolved Fluorescence. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2019; 13:343-351. [PMID: 30640628 DOI: 10.1109/tbcas.2019.2892825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Time-resolved fluorescence measurement is extraordinarily powerful in the analysis of substances due to its effectiveness in eliminating measurement artifacts. Some fluorescence measurements are still conducted on CMOS chips with the decay times determined after reading the data off the chip and fitting the fluorescence decay histogram. We present a novel approach in which an analog CMOS chip divides the fluorescence decay time into slices and classifies the photons according to their arrival times at a CMOS SPAD sensor. The chip was fabricated in a 1P6M 0.18 μm HV-CMOS process. The slice timings can be tailored from 168 ps to 4.9 ns, covering most fluorescence decay times. 9 timing windows are generated per pixel that count up to 13 b each, with a resolution of 0.16 mV/photon, for a maximum output voltage of 1.3 V, in an area of 150 μm × 50 μm. Here, we report on the first practical application of this circuit, which integrates an array of 5 pixels in a single chip and has an excitation light and a microfluidic chip of up to 3 channels. This system could determine the decay time of quantum dots in 20 nl of solution. Thus, this paper could help in the development of a point-of-care device based on time-resolved fluorescence.
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Ulku AC, Bruschini C, Antolovic IM, Weiss S, Michalet X, Charbon E. Phasor-based widefield FLIM using a gated 512×512 single-photon SPAD imager. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2019; 10882. [PMID: 33859449 DOI: 10.1117/12.2511148] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Single-photon avalanche diode (SPAD) imagers can perform fast time-resolved imaging in a compact form factor, by exploiting the processing capability and speed of integrated CMOS electronics. Developments in SPAD imagers have recently made them compatible with widefield microscopy, thanks to array formats approaching one megapixel and sensitivity and noise levels approaching those of established technologies. In this paper, phasor-based FLIM is demonstrated with a gated binary 512×512 SPAD imager, which can operate with a gate length as short as 5.75 ns, a minimum gate step of 17.9 ps, and up to 98 kfps readout rate (1-bit frames). Lifetimes of ATTO 550 and Rhodamine 6G (R6G) solutions were measured across a 472×256 sub-array using phasor analysis, acquiring data by shifting a 13.1 ns gate window across the 50 ns laser period. The measurement accuracy obtained when employing such a scheme based on long, overlapping gates was validated by comparison with TCSPC measurements and fitting analysis results based on a standard Levenberg-Marquardt algorithm (>90% accuracy for the lifetime of R6G and ATTO 550). This demonstrates the ability of the proposed method to measure short lifetimes without minimum gate length requirements. The FLIM frame rate of the overall system can be increased up to a few fps for phasor-based widefield FLIM (moving closer to real-time operation) by FPGA-based parallel computation with continuous acquisition at the full speed of 98 kfps.
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Affiliation(s)
| | | | | | - Shimon Weiss
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA USA
| | - Xavier Michalet
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA USA
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