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Yang Y, Miao Y, Liu X, Pedrini G, Tang Q, Osten W, Peng X. Intrinsic parameter-free calibration of FPP using a ray phase mapping model. Opt Lett 2022; 47:3564-3567. [PMID: 35838731 DOI: 10.1364/ol.462504] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 06/25/2022] [Indexed: 06/15/2023]
Abstract
This Letter presents a ray phase mapping model (RPM) for fringe projection profilometry (FPP) that avoids calibrating intrinsic parameters. The novelty of the RPM, to the best of our knowledge, is the ability to characterize the imaging system with independent rays for each pixel, and to associate the rays with the projected phase in the illumination field for efficient 3D mapping, which avoids complex imaging-specific modeling about lens layout and distortion. Two loss functions are constructed to flexibly optimize camera ray parameters and mapping coefficients, respectively. As a universal approach, it has the potential to calibrate different types of FPP systems with high accuracy. Experiments on wide-angle lens FPP, telecentric lens FPP, and micro-electromechanical system (MEMS)-based FPP are carried out to verify the feasibility of the proposed method.
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2
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Ohta M, Kodama S, Miyamoto Y, Osten W, Takeda M, Watanabe E. 3D imaging through a highly heterogeneous double-composite random medium by common-path phase-shift digital holography. Opt Lett 2022; 47:1170-1173. [PMID: 35230319 DOI: 10.1364/ol.451167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
A method is proposed for 3D imaging through a highly heterogeneous double-composite random medium made of a thick mildly inhomogeneous medium followed by a thin strongly scattering layer. To realize the immunity to the heterogeneous random medium, a system of common-path phase-shift digital holography is designed in such a manner that the wavefront distortion caused by the first inhomogeneous medium is canceled out by the common-path geometry, and the influence of the random phase introduced by the second scattering layer is removed by the intensity-based recording of the digital hologram on the thin scattering layer. The validity of the method was confirmed by experiments.
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3
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Zepp A, Gladysz S, Stein K, Osten W. Optimization of the holographic wavefront sensor for open-loop adaptive optics under realistic turbulence. Part I: simulations. Appl Opt 2021; 60:F88-F98. [PMID: 34612865 DOI: 10.1364/ao.425397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 07/06/2021] [Indexed: 06/13/2023]
Abstract
The modal holographic wavefront sensor enables fast measurement of individual aberration modes without the need for time-consuming calculations. However, the measurement accuracy suffers greatly from intermodal crosstalk, caused when the wavefront contains more aberrations than the one to be measured. In this paper, we present sensor optimization to minimize this effect and show the improvement when using Karhunen-Lòeve instead of Zernike modes as the basis. Finally, we show in simulation that an open-loop adaptive optics system based on the optimized sensor can be used to correct the effect of realistic, dynamic atmospheric turbulence on a wavefront and increase its Strehl ratio significantly.
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4
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Ludwig S, Pedrini G, Peng X, Osten W. Single-pixel scatter-plate microscopy. Opt Lett 2021; 46:2473-2476. [PMID: 33988613 DOI: 10.1364/ol.420593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 04/27/2021] [Indexed: 06/12/2023]
Abstract
Based on the optical memory effect of scattered light, we developed a new single-pixel camera concept. The retrieved images contain both 3D and spectral information about the sample. A spatial light modulator (SLM) generates a random intensity modulation. The signal recorded by the single-pixel detector is cross correlated by the calculated point spread function (PSF) signals of the SLM to retrieve the image. In this publication, both simulations and experimental results are presented.
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5
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Ludwig S, Ruchka P, Pedrini G, Peng X, Osten W. Scatter-plate microscopy with spatially coherent illumination and temporal scatter modulation. Opt Express 2021; 29:4530-4546. [PMID: 33771029 DOI: 10.1364/oe.412047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 12/19/2020] [Indexed: 06/12/2023]
Abstract
Scatter-plate microscopy (SPM) is a lensless imaging technique for high-resolution imaging through scattering media. So far, the method was demonstrated for spatially incoherent illumination and static scattering media. In this publication, we demonstrate that these restrictions are not necessary. We realized imaging with spatially coherent and spatially incoherent illumination. We further demonstrate that SPM is still a valid imaging method for scatter-plates, which change their scattering behaviour (i.e. the phase-shift) at each position on the plate continuously but independently from other positions. Especially we realized imaging through rotating ground glass diffusers.
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6
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Cai Z, Chen J, Pedrini G, Osten W, Liu X, Peng X. Lensless light-field imaging through diffuser encoding. Light Sci Appl 2020; 9:143. [PMID: 32864118 PMCID: PMC7438505 DOI: 10.1038/s41377-020-00380-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 07/24/2020] [Accepted: 08/02/2020] [Indexed: 05/12/2023]
Abstract
Microlens array-based light-field imaging has been one of the most commonly used and effective technologies to record high-dimensional optical signals for developing various potential high-performance applications in many fields. However, the use of a microlens array generally suffers from an intrinsic trade-off between the spatial and angular resolutions. In this paper, we concentrate on exploiting a diffuser to explore a novel modality for light-field imaging. We demonstrate that the diffuser can efficiently angularly couple incident light rays into a detected image without needing any lens. To characterize and analyse this phenomenon, we establish a diffuser-encoding light-field transmission model, in which four-dimensional light fields are mapped into two-dimensional images via a transmission matrix describing the light propagation through the diffuser. Correspondingly, a calibration strategy is designed to flexibly determine the transmission matrix, so that light rays can be computationally decoupled from a detected image with adjustable spatio-angular resolutions, which are unshackled from the resolution limitation of the sensor. The proof-of-concept approach indicates the possibility of using scattering media for lensless four-dimensional light-field recording and processing, not just for two- or three-dimensional imaging.
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Affiliation(s)
- Zewei Cai
- Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
- College of Physics and Optoelectronic Engineering, Shenzhen University, 518060 Guangdong, Shenzhen China
| | - Jiawei Chen
- College of Physics and Optoelectronic Engineering, Shenzhen University, 518060 Guangdong, Shenzhen China
| | - Giancarlo Pedrini
- Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Wolfgang Osten
- Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Xiaoli Liu
- College of Physics and Optoelectronic Engineering, Shenzhen University, 518060 Guangdong, Shenzhen China
| | - Xiang Peng
- College of Physics and Optoelectronic Engineering, Shenzhen University, 518060 Guangdong, Shenzhen China
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7
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Cai Z, Pedrini G, Osten W, Liu X, Peng X. Single-shot structured-light-field three-dimensional imaging. Opt Lett 2020; 45:3256-3259. [PMID: 32538956 DOI: 10.1364/ol.393911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 05/06/2020] [Indexed: 06/11/2023]
Abstract
This Letter reports an approach to single-shot three-dimensional (3D) imaging that is combining structured illumination and light-field imaging. The sinusoidal distribution of the radiance in the structured-light field can be processed and transformed to compute the angular variance of the local radiance difference. The angular variance across the depth range exhibits a single-peak distribution trend that can be used to obtain the unambiguous depth. The phase computation that generally requires the acquisition of multi-frame phase-shifting images is no longer mandatory, thus enabling single-shot structured-light-field 3D imaging. The proposed approach was experimentally demonstrated through a dynamic scene.
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8
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Wang F, Bian Y, Wang H, Lyu M, Pedrini G, Osten W, Barbastathis G, Situ G. Phase imaging with an untrained neural network. Light Sci Appl 2020; 9:77. [PMID: 32411362 PMCID: PMC7200792 DOI: 10.1038/s41377-020-0302-3] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/17/2020] [Accepted: 03/23/2020] [Indexed: 05/11/2023]
Abstract
Most of the neural networks proposed so far for computational imaging (CI) in optics employ a supervised training strategy, and thus need a large training set to optimize their weights and biases. Setting aside the requirements of environmental and system stability during many hours of data acquisition, in many practical applications, it is unlikely to be possible to obtain sufficient numbers of ground-truth images for training. Here, we propose to overcome this limitation by incorporating into a conventional deep neural network a complete physical model that represents the process of image formation. The most significant advantage of the resulting physics-enhanced deep neural network (PhysenNet) is that it can be used without training beforehand, thus eliminating the need for tens of thousands of labeled data. We take single-beam phase imaging as an example for demonstration. We experimentally show that one needs only to feed PhysenNet a single diffraction pattern of a phase object, and it can automatically optimize the network and eventually produce the object phase through the interplay between the neural network and the physical model. This opens up a new paradigm of neural network design, in which the concept of incorporating a physical model into a neural network can be generalized to solve many other CI problems.
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Affiliation(s)
- Fei Wang
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 201800 Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Yaoming Bian
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 201800 Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Haichao Wang
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 201800 Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Meng Lyu
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 201800 Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Giancarlo Pedrini
- Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Wolfgang Osten
- Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - George Barbastathis
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4301 USA
| | - Guohai Situ
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 201800 Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100049 Beijing, China
- Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 310024 Hangzhou, China
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9
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Guerra F, Haist T, Warsewa A, Hartlieb S, Osten W, Tarín C. Precise building deformation measurement using holographic multipoint replication. Appl Opt 2020; 59:2746-2753. [PMID: 32225826 DOI: 10.1364/ao.385594] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/10/2020] [Indexed: 06/10/2023]
Abstract
For the active control of large-scale structures, especially high-rise buildings and bridges, fast and accurate measurement of local deformations is required. We present a highly accurate and fast vision-based measurement technique and, to the best of our knowledge, first experimental results for the control of an adaptive-structures prototype frame, equipped with hydraulic actuators. Deformations are detected at multiple discrete points, based on a photogrammetric approach with additional holographic spot replication. The replication leads to effective averaging of most error contributions, especially discretization and photon noise. Measurements over a distance of 11.4 m result in a measurement uncertainty of 0.0077 pixel (corresponding to 0.055 mm in object space).
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10
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Cai Z, Liu X, Pedrini G, Osten W, Peng X. Light-field depth estimation considering plenoptic imaging distortion. Opt Express 2020; 28:4156-4168. [PMID: 32122073 DOI: 10.1364/oe.385285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
Light-field imaging can simultaneously record spatio-angular information of light rays to carry out depth estimation via depth cues which reflect a coupling of the angular information and the scene depth. However, the unavoidable imaging distortion in a light-field imaging system has a side effect on the spatio-angular coordinate computation, leading to incorrectly estimated depth maps. Based on the previously established unfocused plenoptic metric model, this paper reports a study on the effect of the plenoptic imaging distortion on the light-field depth estimation. A method of light-field depth estimation considering the plenoptic imaging distortion is proposed. Besides, the accuracy analysis of the light-field depth estimation was performed by using standard components. Experimental results demonstrate that efficiently compensating the plenoptic imaging distortion results in a six-fold improvement in measuring accuracy and more consistency across the measuring depth range. Consequently, the proposed method is proved to be suitable for light-field depth estimation and three-dimensional measurement with high quality, enabling unfocused plenoptic cameras to be metrological tools in the potential application scenarios such as industry, biomedicine, entertainment, and many others.
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11
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Kodama S, Ohta M, Ikeda K, Kano Y, Miyamoto Y, Osten W, Takeda M, Watanabe E. Three-dimensional microscopic imaging through scattering media based on in-line phase-shift digital holography. Appl Opt 2019; 58:G345-G350. [PMID: 31873519 DOI: 10.1364/ao.58.00g345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 10/15/2019] [Indexed: 06/10/2023]
Abstract
Microscopic three-dimensional imaging and phase quantification for objects hidden behind a scattering medium by using in-line phase-shift digital holography are proposed. A spatial resolution of 1.81 µm and highly accurate quantitative phase imaging are demonstrated for objects behind a scatter plate. Three-dimensional imaging was confirmed using objects with a depth difference of 1.32 mm. Further, imaging was performed using rat skin as a demonstration for imaging through a complex multilayer scattering medium, where a spatial resolution close to the theoretically predicted value was achieved by experiment.
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12
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Ludwig S, Le Teurnier B, Pedrini G, Peng X, Osten W. Image reconstruction and enhancement by deconvolution in scatter-plate microscopy. Opt Express 2019; 27:23049-23058. [PMID: 31510587 DOI: 10.1364/oe.27.023049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/17/2019] [Indexed: 06/10/2023]
Abstract
We investigated the capabilities of deconvolution for image enhancement in scatter-plate microscopy. This lensless imaging technique enables the investigation of microstructures through scattering media by cross-correlating the scattered light intensity with a previously recorded point spread function (PSF) of the scattering medium. The autocorrelation function of the PSF appears as the transfer function of the imaging process. Deconvolution methods use the knowledge of this transfer function to enhance the image quality by reducing the blur and strengthening the contrast with the objective to achieve diffraction-limited resolution. We obtained significant image enhancement both with means of inverse filtering and by applying iterative deconvolution algorithms.
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13
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Cai Z, Liu X, Pedrini G, Osten W, Peng X. Unfocused plenoptic metric modeling and calibration. Opt Express 2019; 27:20177-20198. [PMID: 31510117 DOI: 10.1364/oe.27.020177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 06/26/2019] [Indexed: 06/10/2023]
Abstract
For unfocused plenoptic imaging systems, metric calibration is generally mandatory to achieve high-quality imaging and metrology. In this paper, we present an explicit derivation of an unfocused plenoptic metric model associating a measured light field in the object space with a recorded light field in the image space to conform physically to the imaging properties of unfocused plenoptic cameras. In addition, the impact of unfocused plenoptic imaging distortion on depth computation was experimentally explored, revealing that radial distortion parameters contain depth-dependent common factors, which were then modeled as depth distortions. Consequently, a complete unfocused plenoptic metric model was established by combining the explicit metric model with the imaging distortion model. A three-step unfocused plenoptic metric calibration strategy, in which the Levenberg-Marquardt algorithm is used for parameter optimization, is correspondingly proposed to determine 12 internal parameters for each microlens unit. Based on the proposed modeling and calibration, the depth measurement precision can be increased to 0.25 mm in a depth range of 300 mm, ensuring the potential applicability of consumer unfocused plenoptic cameras in high-accuracy three-dimensional measurement.
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14
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Cai Z, Liu X, Pedrini G, Osten W, Peng X. Accurate depth estimation in structured light fields. Opt Express 2019; 27:13532-13546. [PMID: 31052874 DOI: 10.1364/oe.27.013532] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 04/12/2019] [Indexed: 06/09/2023]
Abstract
Passive light field imaging generally uses depth cues that depend on the image structure to perform depth estimation, causing robustness and accuracy problems in complex scenes. In this study, the commonly used depth cues, defocus and correspondence, were analyzed by using phase encoding instead of the image structure. The defocus cue obtained by spatial variance is insensitive to the global spatial monotonicity of the phase-encoded field. In contrast, the correspondence cue is sensitive to the angular variance of the phase-encoded field, and the correspondence responses across the depth range have single-peak distributions. Based on this analysis, a novel active light field depth estimation method is proposed by directly using the correspondence cue in the structured light field to search for non-ambiguous depths, and thus no optimization is required. Furthermore, the angular variance can be weighted to reduce the depth estimation uncertainty according to the phase encoding information. The depth estimation of an experimental scene with rich colors demonstrated that the proposed method could distinguish different depth regions in each color segment more clearly, and was substantially improved in terms of phase consistency compared to the passive method, thus verifying its robustness and accuracy.
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15
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Gorecki C, Lullin J, Perrin S, Bargiel S, Albero J, Gaiffe O, Rutkowski J, Cote JM, Krauter J, Osten W, Wang WS, Weimer M, Froemel J. Micromachined phase-shifted array-type Mirau interferometer for swept-source OCT imaging: design, microfabrication and experimental validation. Biomed Opt Express 2019; 10:1111-1125. [PMID: 30891333 PMCID: PMC6420266 DOI: 10.1364/boe.10.001111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 01/24/2019] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
OCT instruments permit fast and non-invasive 3D optical biopsies of biological tissues. However, they are bulky and expensive, making them only affordable at the hospital and thus, not sufficiently used as an early diagnostic tool. Significant reduction of system cost and size is achieved by implementation of MOEMS technologies. We propose an active array of 4x4 Mirau microinterferometers where the reference micro-mirrors are carried by a vertical comb-drive microactuator, enabling the implementation of the phase-shifting technique that improves the sensitivity and eliminates unwanted interferometric terms. We focus on the design of the imaging system, the microfabrication and the assembly of the Mirau microinterferometer, and the swept-source OCT imaging.
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Affiliation(s)
- C. Gorecki
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - J. Lullin
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - S. Perrin
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - S. Bargiel
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - J. Albero
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - O. Gaiffe
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - J. Rutkowski
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - J. M. Cote
- FEMTO-ST Institute (UMR CNRS 6174, UBFC), 15B avenue des Montboucons, 25030 Besançon, France
| | - J. Krauter
- Institut für Technische Optik, Universiät Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - W. Osten
- Institut für Technische Optik, Universiät Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - W.-S. Wang
- Fraunhofer Institute for Electronic Nanosystems, Technologie Campus 3, 09126 Chemnitz, Germany
| | - M. Weimer
- Fraunhofer Institute for Electronic Nanosystems, Technologie Campus 3, 09126 Chemnitz, Germany
| | - J. Froemel
- Fraunhofer Institute for Electronic Nanosystems, Technologie Campus 3, 09126 Chemnitz, Germany
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Pedrini G, Alekseenko I, Jagannathan G, Kempenaars M, Vayakis G, Osten W. Feasibility study of digital holography for erosion measurements under extreme environmental conditions inside the International Thermonuclear Experimental Reactor tokamak [invited]. Appl Opt 2019; 58:A147-A155. [PMID: 30873972 DOI: 10.1364/ao.58.00a147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 11/26/2018] [Indexed: 06/09/2023]
Abstract
In the International Thermonuclear Experimental Reactor under construction in southern France, there will be a need for continuous measuring of the erosion at the wall, after the reactor starts operating. A two-wavelength interferometric technique based on digital holography is proposed for the erosion measurement. This technique has the ability to tackle the challenging environmental conditions within the reactor by a long-distance measurement, where a relay optic will be used for imaging the investigated surface on the detector. We will show that the shape measurements of objects located at a distance of more than 20 m from the measuring head can be carried out in a short time (100 μs) by the two-wavelength interferometric technique. A depth accuracy of ±10 μm is achieved.
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17
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Liao M, Lu D, He W, Pedrini G, Osten W, Peng X. Improving reconstruction of speckle correlation imaging by using a modified phase retrieval algorithm with the number of nonzero-pixels constraint. Appl Opt 2019; 58:473-478. [PMID: 30645330 DOI: 10.1364/ao.58.000473] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/04/2018] [Indexed: 06/09/2023]
Abstract
Speckle correlation imaging (SCI) has been considered one of the most promising techniques for computational imaging through a scattering medium. However, the image quality is not always acceptable in conventional SCI, especially when a complex object is involved. In this work, a modified phase retrieval algorithm is introduced to significantly improve the imaging quality of SCI. In the proposed scheme, nonzero-pixel constraints, rather than the real and nonnegative constraints, are employed as the object domain constraints of the iterative algorithm in the image reconstruction process. Experimental results are presented to show the performance enhancement of this scheme, inclusive of less iterations, better image quality, and higher reliability, in comparison with the conventional SCI method.
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18
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Cai Z, Liu X, Chen Z, Tang Q, Gao BZ, Pedrini G, Osten W, Peng X. Light-field-based absolute phase unwrapping. Opt Lett 2018; 43:5717-5720. [PMID: 30499976 DOI: 10.1364/ol.43.005717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 10/24/2018] [Indexed: 06/09/2023]
Abstract
Ambiguity caused by a wrapped phase is an intrinsic problem in fringe projection-based 3D shape measurement. Among traditional methods for avoiding phase ambiguity, spatial phase unwrapping is sensitive to sensor noise and depth discontinuity, and temporal phase unwrapping requires additional encoding information that leads to an increase of image sequence acquisition time or a reduction of fringe contrast. Here, to the best of our knowledge, we report a novel method of absolute phase unwrapping based on light field imaging. In a recorded light field under structured illumination, i.e., a structured light field, a wrapped phase-encoded field can be retrieved and resampled in diverse image planes associated with several possible fringe orders in a measurement volume. Then, by leveraging phase consistency constraint in the resampled wrapped phase-encoded field, correct fringe orders can be determined to unwrap the wrapped phase without any additional encoding information. Experimental results demonstrated that the proposed method was suitable for accurate and robust absolute phase unwrapping.
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19
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Buchta D, Serbes H, Claus D, Pedrini G, Osten W. Soft tissue elastography via shearing interferometry. J Med Imaging (Bellingham) 2018; 5:046001. [PMID: 30840733 DOI: 10.1117/1.jmi.5.4.046001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 10/10/2018] [Indexed: 11/14/2022] Open
Abstract
Early detection of cancer can significantly increase the survival chances of patients. Palpation is a traditional method in order to detect cancer; however, in minimally invasive surgery the surgeon is deprived of the sense of touch. We demonstrate how shearing elastography can recover elastic parameters and furthermore can be used to localize stiffness imhomogenities even if hidden underneath the surface. Furthermore, the influence of size and depth of the stiffness imhomogenities on the detection accuracy and localization is investigated.
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Affiliation(s)
- Dominic Buchta
- University of Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Hüseyin Serbes
- University of Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Daniel Claus
- University of Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Giancarlo Pedrini
- University of Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Wolfgang Osten
- University of Stuttgart, Institut für Technische Optik, Stuttgart, Germany
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Schaal F, Rutloh M, Weidenfeld S, Stumpe J, Michler P, Pruss C, Osten W. Optically addressed modulator for tunable spatial polarization control. Opt Express 2018; 26:28119-28130. [PMID: 30469867 DOI: 10.1364/oe.26.028119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 08/17/2018] [Indexed: 06/09/2023]
Abstract
We present an optically addressed non-pixelated spatial light modulator. The system is based on reversible photoalignment of a LC cell using a red light sensitive novel azobenzene photoalignment layer. It is an electrode-free device that manipulates the liquid crystal orientation and consequently the polarization via light without artifacts caused by electrodes. The capability to miniaturize the spatial light modulator allows the integration into a microscope objective. This includes a miniaturized 200 channel optical addressing system based on a VCSEL array and hybrid refractive-diffractive beam shapers. As an application example, the utilization as a microscope objective integrated analog phase contrast modulator is shown.
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21
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Li H, Fu L, Frenner K, Osten W. Cascaded DBR plasmonic cavity lens for far-field subwavelength imaging at a visible wavelength. Opt Express 2018; 26:19574-19582. [PMID: 30114128 DOI: 10.1364/oe.26.019574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 07/13/2018] [Indexed: 06/08/2023]
Abstract
We experimentally demonstrate a novel cascaded plasmonic superlens, which can directly image subwavelength objects with magnification in the far field at a wavelength of 640nm. The lens consists of two plasmonic slabs. One is a plasmonic cavity lens used for near-field coupling, and the other one is a planar plasmonic lens for phase compensation and thus, image magnification. To tune the performance wavelength to visible and to enhance the near-field transmission, distributed Bragg reflectors are integrated to the plasmonic cavity lens around the lens center, forming additional lateral cavities for surface waves. In this article, we first show numerical results about the working principle and the performance of the lens. Then, we demonstrate the imaging performance of a fabricated superlens experimentally. The fabricated superlens exhibits a lateral resolution down to 200 nm at the wavelength of 640 nm observed in the far field. Compared to our earlier design, shift invariance is achieved with the current approach. Our results could open a way for designing and fabricating novel miniaturized plasmonic superlenses in the future.
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22
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Li H, Fu L, Frenner K, Osten W. Cascaded plasmonic superlens for far-field imaging with magnification at visible wavelength. Opt Express 2018; 26:10888-10897. [PMID: 29716019 DOI: 10.1364/oe.26.010888] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 04/09/2018] [Indexed: 06/08/2023]
Abstract
We experimentally demonstrate a novel design of a cascaded plasmonic superlens, which can directly image subwavelength objects with magnification in the far field at visible wavelengths. The lens consists of two cascaded plasmonic slabs. One is a plasmonic metasurface used for near field coupling, and the other one is a planar plasmonic lens used for phase compensation and thus image magnification. First, we show numerical calculations about the performance of the lens. Based on these results we then describe the fabrication of both sub-structures and their combination. Finally, we demonstrate imaging performance of the lens for a subwavelength double-slit object as an example. The fabricated superlens exhibits a lateral resolution down to 180 nm at a wavelength of 640 nm, as predicted by numerical calculations. This might be the first experimental demonstration in which a planar plasmonic lens is employed for near-field image magnification. Our results could open a way for designing and fabricating novel miniaturized plasmonic superlenses in the future.
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23
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Claus D, Pedrini G, Buchta D, Osten W. Accuracy enhanced and synthetic wavelength adjustable optical metrology via spectrally resolved digital holography. J Opt Soc Am A Opt Image Sci Vis 2018; 35:546-552. [PMID: 29603983 DOI: 10.1364/josaa.35.000546] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 02/05/2018] [Indexed: 06/08/2023]
Abstract
This paper demonstrates the usefulness of spectrally resolved digital holography for dual-wavelength optical metrology. Based on the large degree of phase information available, multiple de-correlated dual-wavelength phase maps can be generated, which, when averaged, result in a signal-to-noise-ratio improvement. Compared with single-wavelength averaging, no further post-processing of the reconstructed dual-wavelength phase map is required. Moreover, the constraint imposed on the wavelength stability, as experienced in the conventional dual-wavelength method, can be relaxed, and the corresponding synthetic wavelength is adapted to the object under investigation. In addition, the possibility of optical sectioning based on the narrow-width coherence envelope is also demonstrated in transmission mode.
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Singh AK, Pedrini G, Takeda M, Osten W. Scatter-plate microscope for lensless microscopy with diffraction limited resolution. Sci Rep 2017; 7:10687. [PMID: 28878361 PMCID: PMC5587816 DOI: 10.1038/s41598-017-10767-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 08/14/2017] [Indexed: 11/22/2022] Open
Abstract
Scattering media have always been looked upon as an obstacle in imaging. Various methods, ranging from holography to phase compensation as well as to correlation techniques, have been proposed to cope with this obstacle. We, on the other hand, have a different understanding about the role of the diffusing media. In this paper we propose and demonstrate a ‘scatter-plate microscope’ that utilizes the diffusing property of the random medium for imaging micro structures with diffraction-limited resolution. The ubiquitous property of the speckle patterns permits to exploit the scattering medium as an ultra-thin lensless microscope objective with a variable focal length and a large working distance. The method provides a light, flexible and cost effective imaging device as an alternative to conventional microscope objectives. In principle, the technique is also applicable to lensless imaging in UV and X-ray microscopy. Experiments were performed with visible light to demonstrate the microscopic imaging of USAF resolution test target and a biological sample with varying numerical aperture (NA) and magnifications.
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Affiliation(s)
- Alok Kumar Singh
- Institut für Technische Optik and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569, Stuttgart, Germany.
| | - Giancarlo Pedrini
- Institut für Technische Optik and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569, Stuttgart, Germany
| | - Mitsuo Takeda
- Institut für Technische Optik and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569, Stuttgart, Germany.,Center for Optical Research and Education (CORE), Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi, 321-8585, Japan
| | - Wolfgang Osten
- Institut für Technische Optik and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569, Stuttgart, Germany
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25
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Gharbi S, Pang H, Lingel C, Haist T, Osten W. Reduction of chromatic dispersion using multiple carrier frequency patterns in SLM-based microscopy. Appl Opt 2017; 56:6688-6693. [PMID: 29047963 DOI: 10.1364/ao.56.006688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/17/2017] [Indexed: 05/28/2023]
Abstract
Typically, spatial light modulator (SLM)-based microscopy is implemented using a carrier frequency in order to avoid disturbances due to the non-ideal modulation behavior of most SLMs. However, in combination with polychromatic light, this leads to strong chromatic aberrations due to the dispersion at the grating formed by the carrier frequency. In this contribution, we introduce a method based on the evaluation of multiple images obtained with different carrier frequency orientations. This way, chromatic aberrations and the limitation concerning the object field can be strongly reduced.
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26
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Claus D, Mlikota M, Geibel J, Reichenbach T, Pedrini G, Mischinger J, Schmauder S, Osten W. Large-field-of-view optical elastography using digital image correlation for biological soft tissue investigation (erratum). J Med Imaging (Bellingham) 2017; 4:029801. [DOI: 10.1117/1.jmi.4.2.029801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Daniel Claus
- Universität Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Marijo Mlikota
- Universität Stuttgart, Institut für Materialprüfung, Werkstoffkunde und Festigkeitslehre, Stuttgart, Germany
| | - Jonathan Geibel
- Universität Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Thomas Reichenbach
- Universität Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Giancarlo Pedrini
- Universität Stuttgart, Institut für Technische Optik, Stuttgart, Germany
| | - Johannes Mischinger
- Eberhard Karls Universität Tübingen, Klinik für Urologie, Universitätsklinikum Tübingen, Tübingen, Germany
| | - Siegfried Schmauder
- Universität Stuttgart, Institut für Materialprüfung, Werkstoffkunde und Festigkeitslehre, Stuttgart, Germany
| | - Wolfgang Osten
- Universität Stuttgart, Institut für Technische Optik, Stuttgart, Germany
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Abstract
A new technique using digital holography to study the photoelastic isochromatic and isopachic fringes and their respective phases is reported. Our detailed theoretical and experimental analysis shows the possibility of whole-field analysis of every section of stressed photoelastic materials.
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Banerjee PP, Osten W, Picart P, Cao L, Nehmetallah G. Digital Holography and 3D Imaging: introduction to the joint feature issue in Applied Optics and Journal of the Optical Society of America B. Appl Opt 2017; 56:DH1-DH4. [PMID: 28463290 DOI: 10.1364/ao.56.000dh1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The OSA Topical Meeting on Digital Holography and 3D Imaging (DH) was held 25-28 July 2016 in Heidelberg, Germany, as part of the Imaging Congress. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. This year, AO and the Journal of the Optical Society of America B (JOSA B) jointly decided to have one such feature issue in each journal. This feature issue includes 31 papers in AO and 11 in JOSA B, and covers a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The upcoming DH meeting (DH 2017) will be held from 29 May to 1 June in Jeju Island, South Korea.
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Boettcher T, Gronle M, Osten W. Multi-layer topography measurement using a new hybrid single-shot technique: Chromatic Confocal Coherence Tomography (CCCT). Opt Express 2017; 25:10204-10213. [PMID: 28468394 DOI: 10.1364/oe.25.010204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Often measurement tasks occur, where specimens consist of multiple layers or topography shall be examined through contaminations. Especially for unknown layer materials, it is important to measure the layer's refractive index to compensate for the errors induced on the measurement of underlying surfaces. Chromatic Confocal Coherence Tomography is proposed as a new hybrid single-shot scheme for a simultaneous measurement of thickness and refractive index of semitransparent layers, combining chromatic confocal and interferometric information. As a proof of concept, first measurements are presented along with a short discussion about their uncertainties, where minimal layer thickness and resolution are dominated by the confocal part of the signal, that is mainly influenced by the chosen microscope objective.
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Abstract
In this Letter, we demonstrate the application of light field imaging to endoscopy. By introducing a microlens array into the image plane of a conventional endoscope, the 4D light field can be captured in one snapshot. This information can be used to obtain perspective images and to digitally refocus to different planes. These features allow for the recovery of 3D information in minimally invasive surgery. Important optical setup and performance parameters are derived to enable task specific engineering of the light field imaging system.
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31
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Abstract
An alternative phase retrieval technique is discussed in this paper, which offers some advantages for the obtained resolution and reconstruction procedure. In contrast to commonly applied iterative phase retrieval routines, diffraction patterns with varying distance between the illumination source and the object are recorded. This has the same effect as changing the object sensor distance, albeit offering the advantage of preserving the resolution. Moreover, it is possible to employ the direct Fresnel propagation method without having to worry about different pixel sizes in the reconstruction plane. In addition, the influence of speckle decorrelation has carefully been studied and considered for the experimental implementation.
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32
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Claus D, Mlikota M, Geibel J, Reichenbach T, Pedrini G, Mischinger J, Schmauder S, Osten W. Large-field-of-view optical elastography using digital image correlation for biological soft tissue investigation. J Med Imaging (Bellingham) 2017; 4:014505. [PMID: 28386578 PMCID: PMC5352912 DOI: 10.1117/1.jmi.4.1.014505] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 02/17/2017] [Indexed: 11/14/2022] Open
Abstract
In minimally invasive surgery the haptic feedback, which represents an important tool for the localization of abnormalities, is no longer available. Elastography is an imaging technique that results in quantitative elastic parameters. It can hence be used to replace the lost sense of touch, as to enable tissue localization and discrimination. Digital image correlation is the chosen elastographic imaging technique. The implementation discussed here is clinically sound, based on a spectrally engineered illumination source that enables imaging of biological surface markers (blood vessels) with high contrast. Mechanical loading and deformation of the sample is performed using a rolling indenter, which enables the investigation of large organs (size of kidney) with reduced measurement time compared to a scanning approach. Furthermore, the rolling indentation results in strain contrast improvement and an increase in detection accuracy. The successful application of digital image correlation is first demonstrated on a silicone phantom and later on biological samples. Elasticity parameters and their corresponding four-dimensional distribution are generated via solving the inverse problem (only two-dimensional displacement field and strain map experimentally available) using a well-matched hyperelastic finite element model.
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Affiliation(s)
- Daniel Claus
- Universität Stuttgart , Institut für Technische Optik, Stuttgart, Germany
| | - Marijo Mlikota
- Universität Stuttgart , Institut für Materialprüfung, Werkstoffkunde und Festigkeitslehre, Stuttgart, Germany
| | - Jonathan Geibel
- Universität Stuttgart , Institut für Technische Optik, Stuttgart, Germany
| | - Thomas Reichenbach
- Universität Stuttgart , Institut für Technische Optik, Stuttgart, Germany
| | - Giancarlo Pedrini
- Universität Stuttgart , Institut für Technische Optik, Stuttgart, Germany
| | - Johannes Mischinger
- Eberhard Karls Universität Tübingen , Klinik für Urologie, Universitätsklinikum Tübingen, Tübingen, Germany
| | - Siegfried Schmauder
- Universität Stuttgart , Institut für Materialprüfung, Werkstoffkunde und Festigkeitslehre, Stuttgart, Germany
| | - Wolfgang Osten
- Universität Stuttgart , Institut für Technische Optik, Stuttgart, Germany
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Singh AK, Naik DN, Pedrini G, Takeda M, Osten W. Exploiting scattering media for exploring 3D objects. Light Sci Appl 2017; 6:e16219. [PMID: 30167232 PMCID: PMC6062180 DOI: 10.1038/lsa.2016.219] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 08/22/2016] [Accepted: 09/04/2016] [Indexed: 05/20/2023]
Abstract
Scattering media, such as diffused glass and biological tissue, are usually treated as obstacles in imaging. To cope with the random phase introduced by a turbid medium, most existing imaging techniques recourse to either phase compensation by optical means or phase recovery using iterative algorithms, and their applications are often limited to two-dimensional imaging. In contrast, we utilize the scattering medium as an unconventional imaging lens and exploit its lens-like properties for lensless three-dimensional (3D) imaging with diffraction-limited resolution. Our spatially incoherent lensless imaging technique is simple and capable of variable focusing with adjustable depths of focus that enables depth sensing of 3D objects that are concealed by the diffusing medium. Wide-field imaging with diffraction-limited resolution is verified experimentally by a single-shot recording of the 1951 USAF resolution test chart, and 3D imaging and depth sensing are demonstrated by shifting focus over axially separated objects.
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Affiliation(s)
- Alok Kumar Singh
- Institut für Technische Optik (ITO) and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Dinesh N Naik
- Institut für Technische Optik (ITO) and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
- School of Physics, University of Hyderabad, Hyderabad 500 046, India
| | - Giancarlo Pedrini
- Institut für Technische Optik (ITO) and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Mitsuo Takeda
- Institut für Technische Optik (ITO) and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
- Center for Optical Research and Education (CORE), Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi, 321- 8585, Japan
| | - Wolfgang Osten
- Institut für Technische Optik (ITO) and Stuttgart Research Center of Photonic Engineering (SCoPE), University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
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34
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Lingel C, Haist T, Osten W. Spatial-light-modulator-based adaptive optical system for the use of multiple phase retrieval methods. Appl Opt 2016; 55:10329-10334. [PMID: 28059267 DOI: 10.1364/ao.55.010329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We propose an adaptive optical setup using a spatial light modulator (SLM), which is suitable to perform different phase retrieval methods with varying optical features and without mechanical movement. By this approach, it is possible to test many different phase retrieval methods and their parameters (optical and algorithmic) using one stable setup and without hardware adaption. We show exemplary results for the well-known transport of intensity equation (TIE) method and a new iterative adaptive phase retrieval method, where the object phase is canceled by an inverse phase written into part of the SLM. The measurement results are compared to white light interferometric measurements.
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35
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Schindler J, Schau P, Brodhag N, Frenner K, Osten W. Retrieving the axial position of fluorescent light emitting spots by shearing interferometry. J Biomed Opt 2016; 21:125009. [PMID: 28030743 DOI: 10.1117/1.jbo.21.12.125009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/07/2016] [Indexed: 06/06/2023]
Abstract
A method for the depth-resolved detection of fluorescent radiation based on imaging of an interference pattern of two intersecting beams and shearing interferometry is presented. The illumination setup provides the local addressing of the excitation of fluorescence and a coarse confinement of the excitation volume in axial and lateral directions. The reconstruction of the depth relies on the measurement of the phase of the fluorescent wave fronts. Their curvature is directly related to the distance of a source to the focus of the imaging system. Access to the phase information is enabled by a lateral shearing interferometer based on a Michelson setup. This allows the evaluation of interference signals even for spatially and temporally incoherent light such as emitted by fluorophors. An analytical signal model is presented and the relations for obtaining the depth information are derived. Measurements of reference samples with different concentrations and spatial distributions of fluorophors and scatterers prove the experimental feasibility of the method. In a setup optimized for flexibility and operating in the visible range, sufficiently large interference signals are recorded for scatterers placed in depths in the range of hundred micrometers below the surface in a material with scattering properties comparable to dental enamel.
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Affiliation(s)
- Johannes Schindler
- University of Stuttgart, Institut für Technische Optik, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Philipp Schau
- University of Stuttgart, Institut für Technische Optik, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | - Nicole Brodhag
- University of Stuttgart, Institut für Technische Optik, Pfaffenwaldring 9, 70569 Stuttgart, Germany
| | | | - Wolfgang Osten
- University of Stuttgart, Institut für Technische Optik, Pfaffenwaldring 9, 70569 Stuttgart, Germany
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36
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Fu L, Berrier A, Li H, Schau P, Frenner K, Dressel M, Osten W. Depolarization of a randomly distributed plasmonic meander metasurface characterized by Mueller matrix spectroscopic ellipsometry. Opt Express 2016; 24:28056-28064. [PMID: 27906371 DOI: 10.1364/oe.24.028056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Metallic nanostructures offer efficient solutions in polarization control with a very low thickness. In this report, we investigate the optical properties of a nano-fabricated plasmonic pseudo-depolarizer using Mueller matrix spectroscopic ellipsometry in transmission configuration. The depolarizer is composed of 256 square cells, each containing a periodically corrugated metallic film with random orientation. The full Mueller matrix was analyzed as a function of incident angle in a range between 0 and 20° and over the whole rotation angle range. Depolarization could be achieved in two visible wavelength regions around the short-range and long-range surface plasmon polariton frequencies, respectively. Furthermore, depolarization for circularly polarized light was 2.5 times stronger than that for linearly polarized light. Our results could work as a guidance for realizing a broadband high efficiency dielectric metasurface depolarizers.
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37
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Eckerle M, Dietrich T, Schaal F, Pruss C, Osten W, Ahmed MA, Graf T. Novel thin-disk oscillator concept for the generation of radially polarized femtosecond laser pulses. Opt Lett 2016; 41:1680-1683. [PMID: 27192317 DOI: 10.1364/ol.41.001680] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report on the first demonstration of a radially polarized passively mode-locked thin-disk oscillator. Radial polarization was achieved by the use of a novel circular grating waveguide output coupler. We showed mode-locked operation up to a maximum average output power of 13.3 W with an optical efficiency of 21.8%. The degree of radial polarization of the emitted beam was measured to be 97±1%. The laser system generated pulses with a duration of 907 fs and an energy of 316 nJ corresponding to a peak power of 0.35 MW. To the best of our knowledge, these values exceed the performance of previously reported radially polarized mode-locked oscillator systems.
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38
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Fortmeier I, Stavridis M, Wiegmann A, Schulz M, Osten W, Elster C. Evaluation of absolute form measurements using a tilted-wave interferometer. Opt Express 2016; 24:3393-3404. [PMID: 26906998 DOI: 10.1364/oe.24.003393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Tilted-wave interferometry is a promising measurement technique for the highly accurate measurement of aspheres and freeform surfaces. However, the interferometric fringe evaluation of the sub-apertures causes unknown patch offsets, which currently prevent this measurement technique from providing absolute measurements. Simple strategies, such as constructing differences of optical path length differences (OPDs) or ignoring the piston parameter, can diminish the accuracy resulting from the absolute form measurement. Additional information is needed instead; in this paper, the required accuracy of such information is explored in virtual experiments. Our simulation study reveals that, when one absolute OPD is known within a range of 500 nm, the accuracy of the final measurement result is significantly enhanced.
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39
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Albero J, Perrin S, Passilly N, Krauter J, Gauthier-Manuel L, Froehly L, Lullin J, Bargiel S, Osten W, Gorecki C. Wafer-level fabrication of multi-element glass lenses: lens doublet with improved optical performances. Opt Lett 2016; 41:96-99. [PMID: 26696167 DOI: 10.1364/ol.41.000096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This Letter reports on the fabrication of glass lens doublets arranged in arrays and realized at wafer level by means of micro-fabrication. The technique is based on the accurate vertical assembly of separately fabricated glass lens arrays. Since each one of these arrays is obtained by glass melting in silicon cavities, silicon is employed as a spacer in order to build a well-aligned and robust optical module. It is shown that optical performance achieved by the lens doublet is better than for a single lens of equivalent numerical aperture, thanks to lower optical aberrations. The technique has good potential to match the optical requirements of miniature imaging systems.
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40
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Peterhänsel S, Gödecke ML, Paz VF, Frenner K, Osten W. Detection of overlay error in double patterning gratings using phase-structured illumination. Opt Express 2015; 23:24246-24256. [PMID: 26406630 DOI: 10.1364/oe.23.024246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
With the help of simulations we study the benefits of using coherent, phase-structured illumination to detect the overlay error in resist gratings fabricated by double patterning. Evaluating the intensity and phase distribution along the focused spot of a high numerical aperture microscope, the capability of detecting magnitude and direction of overlay errors in the range of a few nanometers is investigated for a wide range of gratings. Furthermore, two measurement approaches are presented and tested for their reliability in the presence of white Gaussian noise.
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41
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Albero J, Perrin S, Bargiel S, Passilly N, Baranski M, Gauthier-Manuel L, Bernard F, Lullin J, Froehly L, Krauter J, Osten W, Gorecki C. Dense arrays of millimeter-sized glass lenses fabricated at wafer-level. Opt Express 2015; 23:11702-11712. [PMID: 25969261 DOI: 10.1364/oe.23.011702] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This paper presents the study of a fabrication technique of lenses arrays based on the reflow of glass inside cylindrical silicon cavities. Lenses whose sizes are out of the microfabrication standards are considered. In particular, the case of high fill factor arrays is discussed in detail since the proximity between lenses generates undesired effects. These effects, not experienced when lenses are sufficiently separated so that they can be considered as single items, are corrected by properly designing the silicon cavities. Complete topographic as well as optical characterizations are reported. The compatibility of materials with Micro-Opto-Electromechanical Systems (MOEMS) integration processes makes this technology attractive for the miniaturization of inspection systems, especially those devoted to imaging.
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42
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Abstract
We present an algorithm for the computation of computer-generated holograms projecting arbitrary patterns through optical reconstruction systems with strong field-dependent aberrations. The algorithm is based on a modification of the iterative Fourier transform algorithm. Aberrations are specified using Zernike polynomials. The trade-off between reconstruction error and diffraction efficiency can be altered using a simple constant within the algorithm. We show first experimental results for the correction of the reconstruction through a strongly aberrated Fourier system.
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Gilbergs H, Fang H, Frenner K, Osten W. Adaptive state observer and PD control for dynamic perturbations in optical systems. Opt Express 2015; 23:4002-4011. [PMID: 25836439 DOI: 10.1364/oe.23.004002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
High-performance objectives pose strict limitations on residual errors present in the system. External mechanical influences can induce structural vibrations in the optical system which causes a displacement of the lenses present in the system. This will influence the imaging performance, causing degraded images or broadened structures in a lithographic processes. In this paper an adaptive state observer for the detection of structural vibrations of the optical elements of an imaging system based on a series of wavefront tilt measurements is introduced. The observer output is used as an input for a closed-loop PD control to mitigate the lens displacements directly.
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Baer G, Schindler J, Pruss C, Siepmann J, Osten W. Calibration of a non-null test interferometer for the measurement of aspheres and free-form surfaces. Opt Express 2014; 22:31200-31211. [PMID: 25607069 DOI: 10.1364/oe.22.031200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The measurement of aspheric and free-form surfaces in a non-null test configuration has the advantage that no compensation optics is required. However, if a surface is measured in a non-null test configuration, retrace errors are introduced to the measurement. We describe a method to calibrate the test space of an interferometer, enabling to compensate retrace errors. The method is effective even for strong deviations from null test configuration up to several 100 waves, enabling the fast and flexible measurement of aspheres and free-form surfaces. In this paper we present the application of the method to the calibration of the Tilted Wave Interferometer. Furthermore, the method can be generalized to the calibration of other setups.
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Georges MP, Vandenrijt JF, Thizy C, Alexeenko I, Pedrini G, Vollheim B, Lopez I, Jorge I, Rochet J, Osten W. Combined holography and thermography in a single sensor through image-plane holography at thermal infrared wavelengths. Opt Express 2014; 22:25517-25529. [PMID: 25401585 DOI: 10.1364/oe.22.025517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Holographic interferometry in the thermal wavelengths range, combining a CO(2) laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and surface shape information about objects. This is due to the fact that the holograms are affected by the thermal background emitted by objects at room temperature. We explain the setup and the processing of data which allows decoupling the two types of information. This natural data fusion can be advantageously used in a variety of nondestructive testing applications.
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Osten W, Faridian A, Gao P, Körner K, Naik D, Pedrini G, Singh AK, Takeda M, Wilke M. Recent advances in digital holography [invited]. Appl Opt 2014; 53:G44-63. [PMID: 25322137 DOI: 10.1364/ao.53.000g44] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 06/05/2014] [Indexed: 05/25/2023]
Abstract
This article presents an overview of recent advances in the field of digital holography, ranging from holographic techniques designed to increase the resolution of microscopic images, holographic imaging using incoherent illumination, phase retrieval with incoherent illumination, imaging of occluded objects, and the holographic recording of depth-extended objects using a frequency-comb laser, to the design of an infrastructure for remote laboratories for digital-holographic microscopy and metrology. The paper refers to current trends in digital holography and explains them using new results that were recently achieved at the Institute for Applied Optics of the University Stuttgart.
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Fortmeier I, Stavridis M, Wiegmann A, Schulz M, Osten W, Elster C. Analytical Jacobian and its application to tilted-wave interferometry. Opt Express 2014; 22:21313-21325. [PMID: 25321510 DOI: 10.1364/oe.22.021313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Tilted-wave interferometry (TWI) is a novel optical measurement principle for the measurement of aspherical surfaces. For the reconstruction of the wavefront and the surface under test, respectively, perturbation methods are applied, which require the calculation of the Jacobian matrix. For the practical use of the instrument, a fast and exact calculation of the Jacobian matrices is crucial, since this strongly influences the calculation times of the TWI. By applying appropriate approaches in optical perturbation methods we are able to calculate the required Jacobian matrices analytically when the nominal optical path through the system is given. As a result, calculation times for the TWI can be considerably reduced. We finally illustrate the improved TWI procedure and apply methods of optimal design to determine optimal positions of the surface under test. For such applications the fast calculation of the Jacobian matrices is essential.
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Fu L, Frenner K, Osten W. Rigorous speckle simulation using surface integral equations and higher order boundary element method. Opt Lett 2014; 39:4104-4107. [PMID: 25121662 DOI: 10.1364/ol.39.004104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The scattering of electromagnetic waves from rough surfaces has been actively studied for more than a century now because of its involvement in vast application areas. In the past two decades, great advances have been made by incorporating multiple scattering effects into analytical approaches. However, no model can yet be applied to surfaces with arbitrary roughness. It is also very difficult to study the cross-polarization, shadowing, or multiple scattering effects. In order to study more fundamentally the interaction of polarized light with more general rough surfaces of general media, we have developed a rigorous numerical simulator to calculate the resulting speckle fields. The full Maxwell equations were solved using surface integral equations combined with a boundary element method. The rough surface was discretized by higher order quadrilateral edge elements. The effective tangential electric and magnetic fields in each element in terms of 10 edges were first solved. The scattered electric and magnetic fields everywhere in space were then calculated correspondingly. One of the great advantages of such a simulator is that both the near and far fields can be calculated directly. Preliminary results of different kinds of metallic structures are presented, by which the advantages of the method are demonstrated.
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Peterhänsel S, Pruss C, Osten W. Limits of diffractometric reconstruction of line gratings when using scalar diffraction theory. Opt Lett 2014; 39:3764-3766. [PMID: 24978731 DOI: 10.1364/ol.39.003764] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study errors that occur in geometry and phase reconstruction when using scalar diffraction theory in line gratings with periods below 10 μm. The application of those gratings in so-called computer-generated holograms in high-precision interferometric testing of aspheres and free-form surfaces imposes high demands on the generated phase, leading to error budgets in the range of λ/100. Using rigorous simulations as references, we identify the limits where scalar diffraction theory fails to accurately describe grating geometries and identify the significant error mechanisms.
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Abstract
The exact measurement of positions is of fundamental importance in a multitude of image-sensor based optical measurement systems. We propose a new method for enhancing the accuracy of image-sensor based optical measurement systems by using a computer-generated hologram in front of the imaging system. Thereby, the measurement spot is replicated to a predefined pattern. Given enough light to correctly expose the sensor, the position detection accuracy can be considerably improved compared to the conventional one-spot approach. For the evaluation of the spot position we used center-of-gravity based averaging. We present simulated as well as experimental results showing an improvement by a factor of 3.6 to a positioning accuracy of better than three thousandths of a pixel for a standard industrial CCD sensor.
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