Talbot holographic illumination nonscanning (THIN) fluorescence microscopy

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens

SIGNIFICANCE

Parallel phase-shifting digital holographic microscope (PPSDHM) is powerful for three-dimensional (3D) measurements of dynamic specimens. However, the PPSDHM reported previously was directly fixed on the optical bench and imposed difficulties case, thus it is required to modify the specification of the microscope or transport the microscope to another location.

AIM

We present a modularized PPSDHM. We construct the proposed PPSDHM and demonstrate the 3D measurement capability of the PPSDHM.

APPROACH

The PPSDHM was designed as an inverted microscope to record transparent objects and modularized by integrating the optical elements of the PPSDHM on an optical breadboard. To demonstrate the effectiveness of the PPSDHM, we recorded a 3D motion-picture of moving Volvoxes at 1000  frames  /  s and carried out 3D tracking of the Volvoxes.

RESULTS

The PPSDHM was practically realized and 3D images of objects were successfully reconstructed from holograms recorded with a single-shot exposure. The 3D trajectories of Volvoxes were obtained from the reconstructed images.

CONCLUSIONS

We established a modularized PPSDHM that is capable of 3D image acquisition by integrating the optical elements of the PPSDHM on an optical breadboard. The recording capability of 3D motion-pictures of dynamic specimens was experimentally demonstrated by the PPSDHM.

Single-shot stereo-polarimetric compressed ultrafast photography for light-speed observation of high-dimensional optical transients with picosecond resolution

Simultaneous and efficient ultrafast recording of multiple photon tags contributes to high-dimensional optical imaging and characterization in numerous fields. Existing high-dimensional optical imaging techniques that record space and polarization cannot detect the photon's time of arrival owing to the limited speeds of the state-of-the-art electronic sensors. Here, we overcome this long-standing limitation by implementing stereo-polarimetric compressed ultrafast photography (SP-CUP) to record light-speed high-dimensional events in a single exposure. Synergizing compressed sensing and streak imaging with stereoscopy and polarimetry, SP-CUP enables video-recording of five photon tags (x, y, z: space; t: time of arrival; and ψ: angle of linear polarization) at 100 billion frames per second with a picosecond temporal resolution. We applied SP-CUP to the spatiotemporal characterization of linear polarization dynamics in early-stage plasma emission from laser-induced breakdown. This system also allowed three-dimensional ultrafast imaging of the linear polarization properties of a single ultrashort laser pulse propagating in a scattering medium.

3-Dimensional Imaging of Cutaneous Nerve Endings

Cutaneous nerve endings are assumed to change due to dermatological pathologies, such as psoriasis. Tan et al. (2019) present a method to assess changes in nerve architecture more precisely by using 3-dimensional histology. This commentary discusses the advantages of 3-dimensional histology, as well as some limitations of the presented method. Future work should focus on intravital applications.

Volume holographic spatial-spectral imaging systems [Invited]

In this paper, we present an overview of the recent developments in applications of volume holographic imaging techniques in microscopy. In these techniques, three-dimensional imaging incorporates multiplexed volume holographic gratings, which are formed in phenanthrenequinone poly(methyl methacrylate) (PQ-PMMA) photopolymer and act as spatial-spectral filters, to obtain multiplane images from a volumetric object without scanning. We introduce recent major roles of volume holography in different imaging modalities, including large-capacity spatial-spectral multiplane microscopy, digital holographic microscopy, and structured Talbot (or speckle) illumination fluorescence imaging. Among various imaging applications of volume holography, simultaneous multiplane fluorescence microscopy for collecting spatial-spectral information is distinct and has great potential for hyperspectral imaging. Depth selective spatial-spectral information from an object is particularly useful for designing a high-resolution microscope in real-time operation. We further discuss volume holography in particle trapping and beam shaping. In addition, we investigate future prospects of volume holography in microscopy as well as endoscopy.

Speckle illumination holographic non-scanning fluorescence endoscopy

Optical sectioning endoscopy such as confocal endoscopy offers capabilities to obtain three-dimensional (3D) information from various biological samples by discriminating between the desired in-focus signals and out-of-focus background. However, in general confocal images are formed through point-by-point scanning and the scanning time is proportional to the 3D space-bandwidth product. Recently, structured illumination endoscopy has been utilized for optically sectioned wide-field imaging, but it still needs axial scanning to acquire images from different depths of focal plane. Here, we report wide-field, multiplane, optical sectioning endoscopic imaging, incorporating 3D active speckle-based illumination and multiplexed volume holographic gratings, to simultaneously obtain images of fluorescently labeled tissue structures from different depths, without the need of scanning. We present the design, and implementation, as well as experimental data, demonstrating this endoscopic system's ability to obtain optically sectioned multiplane fluorescent images of tissue samples, with cellular level resolution in wide-field fashion, and no need for mechanical or optical axial scanning.(A) Schematic drawing of the SIHN endoscopy to simultaneously acquire multiplane images from different depths. (B) Uniform, and (C) SIHN illuminated images of standard fluorescence beads (25 μm in diameter) for the two axial planes. (D) Intensity profile on fluorescently labeled signal (ie, in-focus) and background (ie, out-of-focus) of microspheres.

Spatial mode multiplexing using volume holographic gratings

We experimentally demonstrate spatial mode multiplexing of optical beams using multiplexed volume holographic gratings (MVGHs) formed in phenanthrenquinone-poly (methyl methacrylate) (PQ-PMMA) photopolymer. Multiple spatial modes of Laguerre-Gaussian (LG) beams are recorded at the same pupil area of a volume hologram resulting in MVHGs, for simultaneous reconstruction of spatial modes. In addition, a helical phase beam, a non-diffracting beam with conical phase profile, and a parabolic non-diffracting beam with cubic phase profile have also been simultaneously recorded and reconstructed from MVHGs. Utilizing Bragg wavelength degeneracy property of volume hologram these multiplexed modes are reconstructed at multiple wavelengths ranging from blue (450nm) to red (635). Due to combined effect of three-dimensional pupil, Bragg wavelength degeneracy, angular selectivity, together with spatial mode properties these, MVHGs can act as spatial mode filter with spectral filtering property. Advantages of volume holography in beam shaping are discussed. Multiple first diffraction orders with desired beam shapes obtained from the single optical element (i.e. a volume hologram with MVHGs) may find important applications in optical communication experiments, and in volume holographic imaging and microscopy. Experimental results show solid evidence that MVGHs in beam shaping provide a simple, compact, single element, and direct way to multiplex spatial modes.

Non-axial-scanning multifocal confocal microscopy with multiplexed volume holographic gratings

Confocal imaging techniques offer an optical sectioning capability to acquire three-dimensional information from various volumetric samples by discriminating the desired in-focus signals from the out-of-focus background. However, confocal, in general, requires a point-by-point scan in both the lateral and axial directions to reconstruct three-dimensional images. In addition, axial scanning in confocal is slower than scanning in lateral directions. In this Letter, a non-axial-scanning multifocal confocal microscope incorporating multiplexed holographic gratings in illumination and dual detection for depth discrimination is presented. Further, we demonstrate the ability of the proposed confocal microscopy to image ex vivo tissue structures simultaneously at different focal depths without mechanical or electro-optic axial scanning.

In vivo volumetric fluorescence sectioning microscopy with mechanical-scan-free hybrid illumination imaging

Optical sectioning microscopy in wide-field fashion has been widely used to obtain three-dimensional images of biological samples; however, it requires scanning in depth and considerable time to acquire multiple depth information of a volumetric sample. In this paper, in vivo optical sectioning microscopy with volumetric hybrid illumination, with no mechanical moving parts, is presented. The proposed system is configured such that the optical sectioning is provided by hybrid illumination using a digital micro-mirror device (DMD) for uniform and non-uniform pattern projection, while the depth of imaging planes is varied by using an electrically tunable-focus lens with invariant magnification and resolution. We present and characterize the design, implementation, and experimentally demonstrate the proposed system's ability through 3D imaging of in vivo Canenorhabditis elegans' growth cones.

A review of snapshot multidimensional optical imaging: measuring photon tags in parallel

Multidimensional optical imaging has seen remarkable growth in the past decade. Rather than measuring only the two-dimensional spatial distribution of light, as in conventional photography, multidimensional optical imaging captures light in up to nine dimensions, providing unprecedented information about incident photons' spatial coordinates, emittance angles, wavelength, time, and polarization. Multidimensional optical imaging can be accomplished either by scanning or parallel acquisition. Compared with scanning-based imagers, parallel acquisition-also dubbed snapshot imaging-has a prominent advantage in maximizing optical throughput, particularly when measuring a datacube of high dimensions. Here, we first categorize snapshot multidimensional imagers based on their acquisition and image reconstruction strategies, then highlight the snapshot advantage in the context of optical throughput, and finally we discuss their state-of-the-art implementations and applications.

Talbot multi-focal holographic fluorescence endoscopy for optically sectioned imaging

A wide-field multi-plane endoscopic system incorporating multiplexed volume holographic gratings and Talbot illumination to simultaneously acquire optically sectioned fluorescence images of tissue structures from different depths is presented. The proposed endoscopic system is configured such that multiple Talbot-illumination planes occur inside a volumetric sample and serve as the input focal planes for the subsequent multiplexed volume holographic imaging gratings. We describe the design, implementation, and experimental data demonstrating this endoscopic system's ability to obtain optically sectioned multi-plane fluorescent images of tissue samples in wide-field fashion without scanning in lateral and axial directions.

Speckle-based volume holographic microscopy for optically sectioned multi-plane fluorescent imaging

Structured illumination microscopy has been widely used to reconstruct optically sectioned fluorescence images in wide-field fashion; however, it still requires axial scanning to obtain multiple depth information of a volumetric sample. In this paper, a new imaging scheme, called speckle-based volume holographic microscopy system, is presented. The proposed system incorporates volumetric speckle illumination and multiplexed volume holographic gratings to acquire multi-plane images with optical sectioning capability, without any axial scanning. We present the design, implementation, and experimental image data demonstrating the proposed system's ability to simultaneously obtain wide-field, optically sectioned, and multi-depth resolved images of fluorescently labeled microspheres and tissue structures.

Wigner analysis of three dimensional pupil with finite lateral aperture

A three dimensional (3D) pupil is an optical element, most commonly implemented on a volume hologram, that processes the incident optical field on a 3D fashion. Here we analyze the diffraction properties of a 3D pupil with finite lateral aperture in the 4-f imaging system configuration, using the Wigner Distribution Function (WDF) formulation. Since 3D imaging pupil is finite in both lateral and longitudinal directions, the WDF of the volume holographic 4-f imager theoretically predicts distinct Bragg diffraction patterns in phase space. These result in asymmetric profiles of diffracted coherent point spread function between degenerate diffraction and Bragg diffraction, elucidating the fundamental performance of volume holographic imaging. Experimental measurements are also presented, confirming the theoretical predictions.