Super-resolution imaging by optical incoherent synthetic aperture with one channel at a time

Author(s):

Bulbul, Angika & Rosen, Joseph

Abstract:

“Imaging with an optical incoherent synthetic aperture (SA) means that the incoherent light from observed objects is processed over time from various points of view to obtain a resolution equivalent to single-shot imaging by the SA larger than the actual physical aperture. The operation of such systems has always been based on two-wave interference where the beams propagate through two separate channels. This limitation of two channels at a time is removed in the present study with the proposed SA where the two beams pass through the same single channel at any given time. The system is based on a newly developed self-interference technique named coded aperture correlation holography. At any given time, the recorded intensity is obtained from interference between two waves co-propagating through the same physical channel. One wave oriented in a particular polarization is modulated by a pseudorandom coded phase mask and the other one oriented orthogonally passes through an open subaperture. Both subapertures are multiplexed at the same physical window. The system is calibrated by a point spread hologram synthesized from the responses of a guide star. All the measurements are digitally processed to achieve a final image with a resolution higher than that obtained by the limited physical aperture. This unique configuration can offer alternatives for the current cumbersome systems composed of far apart optical channels in the large optical astronomical interferometers. Furthermore, the proposed concept paves the way to an SA system with a single less-expensive compact light collector in an incoherent optical regime that may be utilized for future ground-based or space telescopes.”

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Publication: Photonics Research
Issue/Year: Photonics Research, Volume 9; Number 7; Pages 1172; 2021
DOI: 10.1364/prj.422381

Single-shot digital multiplexed holography for the measurement of deep shapes

Author(s):

Kozacki, Tomasz; Mikuła-Zdańkowska, Marta; Martinez-Carranza, Juan & Idicula, Moncy Sajeev

Abstract:

“This work develops a single-shot holographic profilometer that enables shape characterization of discontinuous deep surfaces. This is achieved by combining hologram frequency multiplexing and an illumination technique of complex amplitude in multi-incidence angle profilometer. Object illumination is carried out from seven directions simultaneously, where the radial angular coordinates of illumination plane waves obey the geometric series. It is shown that: (i) the illumination pattern provides the required frequency separation of all object wavefronts in transverse frequency space, which is necessary for hologram demultiplexing, and (ii) numerical generation of longitudinal scanning function (LSF) is possible, which has large measurement range, high axial resolution, and small side lobes. Low side lobes of LSF and the developed multiplexed field dependent aberration compensation method are essential to minimize the negative influence of speckle noise of single-shot capture on the measurement result. The utility of the proposed method is demonstrated with experimental measurement of heights of two step-like objects.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 14; Pages 21965; 2021
DOI: 10.1364/oe.428419

DL-SI-DHM: a deep network generating the high-resolution phase and amplitude images from wide-field images

Author(s):

Meng, Zhang; Pedrini, Giancarlo; Lv, Xiaoxu; Ma, Jun; Nie, Shouping & Yuan, Caojin

Abstract:

“Structured illumination digital holographic microscopy (SI-DHM) is a high-resolution, label-free technique enabling us to image unstained biological samples. SI-DHM has high re- quirements on the stability of the experimental setup and needs long exposure time. Furthermore, image synthesizing and phase correcting in the reconstruction process are both challenging tasks. We propose a deep-learning-based method called DL-SI-DHM to improve the recording, the reconstruction efficiency and the accuracy of SI-DHM and to provide high-resolution phase imaging. In the training process, high-resolution amplitude and phase images obtained by phase-shifting SI-DHM together with wide-field amplitudes are used as inputs of DL-SI-DHM. The well-trained network can reconstruct both the high-resolution amplitude and phase images from a single wide-field amplitude image. Compared with the traditional SI-DHM, this method significantly shortens the recording time and simplifies the reconstruction process and complex phase correction, and frequency synthesizing are not required anymore. By comparsion, with other learning-based reconstruction schemes, the proposed network has better response to high frequencies. The possibility of using the proposed method for the investigation of different biological samples has been experimentally verified, and the low-noise characteristics were also proved.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 13; Pages 19247; 2021
DOI: 10.1364/oe.424718

Real-time sub-wavelength imaging of surface waves with nonlinear near-field optical microscopy

Author(s):

Frischwasser, Kobi; Cohen, Kobi; Kher-Alden, Jakob; Dolev, Shimon; Tsesses, Shai & Bartal, Guy

Abstract:

“Imaging evanescent waves is of crucial importance for sub-wavelength-scale investigation of various phenomena. However, frequently used techniques for near-field imaging require either a strong perturbation of the field, long acquisition times or complex electron-based tools. Here, we introduce nonlinear near-field optical microscopy (NNOM), which is capable of real-time evanescent wave imaging by nonlinear wave mixing while using only standard optical components. As a proof-of-concept, we present non-perturbative, single-shot mapping of evanescent plasmonic patterns, utilizing the nonlinearity of the host metal, and monitor in real time the externally controlled changes to the patterns. We further demonstrate the ability to extract the full field information—the amplitude and phase of all electric-field components—in a polarization-sensitive, spin-selective manner. This simple and highly tunable technique could be extended to deep sub-wavelength imaging of polaritons in two-dimensional materials or other nanophotonic guided modes, for swift photonic device characterization and optimized light−matter interactions.”

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Publication: Nature Photonics
Issue/Year: Nature Photonics, Volume 15; Number 6; Pages 442–448; 2021
DOI: 10.1038/s41566-021-00782-2

Aberration-free digital holographic phase imaging using the derivative-based principal component analysis

Author(s):

Lai, Xiaomin; Xiao, Sheng; Xu, Chen; Fan, Shanhui & Wei, Kaihua

Abstract:

“Significance: Digital holographic microscopy is widely used to get the quantitative phase information of transparent cells.

Aim: However, the sample phase is superimposed with aberrations. To quantify the phase information, aberrations need to be fully compensated.

Approach: We propose a technique to obtain aberration-free phase imaging, using the derivative-based principal component analysis (dPCA).

Results: With dPCA, almost all aberrations can be extracted and compensated without requirements on background segmentation, making it efficient and convenient.

Conclusions: It solves the problem that the conventional principal component analysis (PCA) algorithm cannot compensate the common but intricate higher order cross-term aberrations, such as astigmatism and coma. Moreover, the dPCA strategy proposed here is not only suitable for aberration compensation but also applicable for other cases where there exist cross-terms that cannot be analyzed with the PCA algorithm.”

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Publication: Journal of Biomedical Optics
Issue/Year: Journal of Biomedical Optics, Volume 26; Number 04; 2021
DOI: 10.1117/1.jbo.26.4.046501

Comparative study on resolution enhancements in fluorescence-structured illumination Fresnel incoherent correlation holography

Author(s):

Jeon, Philjun; Kim, Jongwu; Lee, Heejung; Kwon, Hyuk-Sang & young Kim, Dug

Abstract:

“Fresnel incoherent correlation holography (FINCH) is a new approach for incoherent holography, which also has enhancement in the transverse resolution. Structured illumination microscopy (SIM) is another promising super-resolution technique. SI-FINCH, the combination of SIM and FINCH, has been demonstrated lately for scattering objects. In this study, we extended the application of SI-FINCH toward fluorescent microscopy. We have built a versatile multimodal microscopy system that can obtain images of four different imaging schemes: conventional fluorescence microscopy, FINCH, SIM, and SI-FINCH. Resolution enhancements were demonstrated by comparing the point spread functions (PSFs) of the four different imaging systems by using fluorescence beads of 1-μm diameter.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 6; Pages 9231; 2021
DOI: 10.1364/oe.417206

2.5D Microscopy: Fast, High-Throughput Imaging via Volumetric Projection for Quantitative Subcellular Analysis

Author(s):

Ren, Jinhan & Han, Kyu Young

Abstract:

“Imaging-based single-cell analysis is essential to study the expression level and functions of biomolecules at subcellular resolution. However, its low throughput has prevented the measurement of numerous cellular features from multiples cells in a rapid and efficient manner. Here we report 2.5D microscopy that significantly improves the throughput of fluorescence imaging systems while maintaining high-resolution and single-molecule sensitivity. Instead of sequential z-scanning, volumetric information is projected onto a 2D image plane in a single shot by engineering the emitted fluorescence light. Our approach provides an improved imaging speed and uniform focal response within a specific imaging depth, which enabled us to perform quantitative single-molecule RNA measurements over a 2 × 2 mm² region within an imaging depth of ∼5 μm for mammalian cells in <10 min and immunofluorescence imaging at a >30 Hz volumetric frame rate with reduced photobleaching. Our microscope also offers the ability of multicolor imaging, depth control, and super-resolution imaging.”

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Publication: ACS Photonics
Issue/Year: ACS Photonics, Volume 8; Number 3; Pages 933-942; 2021
DOI: 10.1021/acsphotonics.1c00012

3D reconstruction of weakly scattering objects from 2D intensity-only measurements using the Wolf transform

Author(s):

Ayoub, Ahmed B.; Lim, Joowon; Antoine, Elizabeth E. & Psaltis, Demetri

Abstract:

“A new approach to optical diffraction tomography (ODT) based on intensity measurements is presented. By applying the Wolf transform directly to intensity measurements, we observed unexpected behavior in the 3D reconstruction of the sample. Such a reconstruction does not explicitly represent a quantitative measure of the refractive index of the sample; however, it contains interesting qualitative information. This 3D reconstruction exhibits edge enhancement and contrast enhancement for nanostructures compared with the conventional 3D refractive index reconstruction and thus could be used to localize nanoparticles such as lipids inside a biological sample.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 3; Pages 3976; 2021
DOI: 10.1364/oe.414543

Giant Helical Dichroism of Single Chiral Nanostructures with Photonic Orbital Angular Momentum

Author(s):

Ni, Jincheng; Liu, Shunli; Hu, Guangwei; Hu, Yanlei; Lao, Zhaoxin; Li, Jiawen; Zhang, Qing; Wu, Dong; Dong, Shaohua; Chu, Jiaru & Qiu, Cheng-Wei

Abstract:

“Optical activity, demonstrating the chiral light-matter interaction, has attracted tremendous attention in both fundamental theoretical research and advanced applications of high-efficiency enantioselective sensing and next-generation chiroptical spectroscopic techniques. However, conventional chiroptical responses are normally limited in large assemblies of chiral materials by circularly polarized light, exhibiting extremely weak chiroptical signals in a single chiral nanostructure. Here, we demonstrate that an alternative chiral freedom of light—orbital angular momentum—can be utilized for generating strong helical dichroism in single chiral nanostructures. The helical dichroism by monochromatic vortex beams can unambiguously distinguish the intrinsic chirality of nanostructures, in an excellent agreement with theoretical predictions. The single planar-chiral nanostructure can exhibit giant helical dichroism of ∼20% at the visible wavelength. The vortex-dependent helical dichroism, expanding to single nanostructures and two-dimensional space, has implications for high-efficiency chiroptical detection of planar-chiral nanostructures in chiral optics and nanophotonic systems.”

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Publication: ACS Nano
Issue/Year: ACS Nano, Volume 15; Number 2; Pages 2893-2900; 2021
DOI: 10.1021/acsnano.0c08941

Velocity measurements with structured light transmitted through a multimode optical fiber using digital optical phase conjugation

Author(s):

Lars Büttner and Martin Thümmler and Jürgen Czarske

Abstract:

“Lensless fiber microendoscopes enable optical diagnostics and therapy with minimal
invasiveness. Because of their small diameters, multimode fibers are ideal candidates, but mode
scrambling hinders the transmission of structured light fields. We present the generation of a
localized fringe system at variable distances from the distal fiber end by exploiting digital optical
phase conjugation. The replayed fringe system was used for quantitative metrology. Velocity
measurements of a microchannel flow in the immediate proximity of the fiber end without the
use of any imaging lenses are shown. Lensless multimode fiber systems are of interest especially
for biomedical imaging and stimulation as well as technical inspection and flow measurements. ”

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Publication: Optics Express
Issue/Year: Vol. 28, Issue 6, pp. 8064-8075
DOI: 10.1364/OE.386047
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