Improving Multiphoton Microscopy by Combining Spherical Aberration Patterns and Variable Axicons

Author(s):

Bueno, J.M.; Hernández, G.; Skorsetz, M.; Artal, P.

Abstract:

“Multiphoton (MP) microscopy is a well-established method for the non-invasive imaging of biological tissues. However, its optical sectioning capabilities are reduced due to specimen-induced aberrations. Both the manipulation of spherical aberration (SA) and the use of axicons have been reported to be useful techniques to bypass this limitation. We propose the combination of SA patterns and variable axicons to further improve the quality of MP microscopy images. This approach provides enhanced images at different depth locations whose quality is better than those corresponding to the use of SA or axicons separately. Thus, the procedure proposed herein facilitates the visualization of details and increases the depth observable at high resolution.”

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Publication: Photonics
Issue/Year: Photonics, Volume 8; Number 12; Pages 573; 2021
DOI: 10.3390/photonics8120573

Neural 3D holography

Author(s):

Choi, Suyeon; Gopakumar, Manu; Peng, Yifan; Kim, Jonghyun & Wetzstein, Gordon

Abstract:

“Holographic near-eye displays promise unprecedented capabilities for virtual and augmented reality (VR/AR) systems. The image quality achieved by current holographic displays, however, is limited by the wave propagation models used to simulate the physical optics. We propose a neural network-parameterized plane-to-multiplane wave propagation model that closes the gap between physics and simulation. Our model is automatically trained using camera feedback and it outperforms related techniques in 2D plane-to-plane settings by a large margin. Moreover, it is the first network-parameterized model to naturally extend to 3D settings, enabling high-quality 3D computer-generated holography using a novel phase regularization strategy of the complex-valued wave field. The efficacy of our approach is demonstrated through extensive experimental evaluation with both VR and optical see-through AR display prototypes.”

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Publication: ACM Transactions on Graphics
Issue/Year: ACM Transactions on Graphics, Volume 40; Number 6; Pages 1–12; 2021
DOI: 10.1145/3478513.3480542

Focal beam structuring by triple mixing of optical vortex lattices

Author(s):

Stoyanov, Lyubomir; Maleshkov, Georgi; Stefanov, Ivan; Paulus, Gerhard G. & Dreischuh, Alexander

Abstract:

“On-demand generation and reshaping of arrays of focused laser beams is highly desired in many areas of science and technology. In this work, we present a versatile approach for laser beam structuring in the focal plane of a lens by triple mixing of square and/or hexagonal optical vortex lattices (OVLs). In the artificial far field the input Gaussian beam is reshaped into ordered arrays of bright beams with flat phase profiles. This is remarkable, since the bright focal peaks are surrounded by hundreds of OVs with their dark cores and two-dimensional phase dislocations. Numerical simulations and experimental evidences for this are shown, including a broad discussion of some of the possible scenarios for such mixing: triple mixing of square-shaped OVLs, triple mixing of hexagonal OVLs, as well as the two combined cases of mixing square-hexagonal-hexagonal and square-square-hexagonal OVLs. The particular ordering of the input phase distributions of the OV lattices on the used spatial light modulators is found to affect the orientation of the structures ruled by the hexagonal OVL. Reliable control parameters for the creation of the desired focal beam structures are the respective lattice node spacings. The presented approach is flexible, easily realizable by using a single spatial light modulator, and thus accessible in many laboratories.”

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Publication: Optical and Quantum Electronics
Issue/Year: Optical and Quantum Electronics, Volume 54; Number 1; 2021
DOI: 10.1007/s11082-021-03399-5

Coded aperture correlation holography (COACH) with a superior lateral resolution of FINCH and axial resolution of conventional direct imaging systems

Author(s):

Bulbul, Angika; Hai, Nathaniel & Rosen, Joseph

Abstract:

“Fresnel incoherent correlation holography (FINCH) is a self-interference incoherent digital holography technique. It possesses a higher lateral resolution than an equivalent incoherent imaging system. However, FINCH has lower axial resolution than the direct imaging systems with the same numerical aperture. A decade after the FINCH invention, a different incoherent holographic method named coded aperture correlation holography (COACH) was developed with improved axial resolution but with the same lateral resolution as direct imaging. In this study, we propose and demonstrate a variant of COACH called coded aperture with FINCH intensity responses (CAFIR) with an improved lateral resolution that is similar to the FINCH system while maintaining its high axial resolution similar to the direct imaging system. CAFIR is implemented with coded phase masks to generate an ensemble of quasi-randomly distributed FINCH-like responses. Point spread holograms and object holograms are recorded under identical conditions, and they are cross-correlated to obtain the image reconstruction. Imaging of a multiplane object is studied to compare the axial resolution of CAFIR with FINCH and direct imaging systems.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 25; Pages 42106; 2021
DOI: 10.1364/oe.446945

Faster generation of holographic video of 3-D scenes with a Fourier spectrum-based NLUT method

Author(s):

Cao, Hongkun; Jin, Xin; Ai, Lingyu & Kim, Eun-Soo

Abstract:

“In this article, a new type of Fourier spectrum-based novel look-up table (FS-NLUT) method is proposed for the faster generation of holographic video of three-dimensional (3-D) scenes. This proposed FS-NLUT method consists of principal frequency spectrums (PFSs) which are much smaller in size than the principal fringe patterns (PFPs) found in the conventional NLUT-based methods. This difference in size allows for the number of basic algebraic operations in the hologram generation process to be reduced significantly. In addition, the fully one-dimensional (1-D) calculation framework of the proposed method also allows for a significant reduction of overall hologram calculation time. In the experiments, the total number of basic algebraic operations needed for the proposed FS-NLUT method were found to be reduced by 81.23% when compared with that of the conventional 1-D NLUT method. In addition, the hologram calculation times of the proposed method, when implemented in the CPU and the GPU, were also found to be 60% and 66% faster than that of the conventional 1-D NLUT method, respectively. It was also confirmed that the proposed method implemented with two GPUs can generate a holographic video of a test 3-D scene in real-time (>24f/s).”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 24; Pages 39738; 2021
DOI: 10.1364/oe.442267

Vector optical field with the polarization varying along an arbitrary circular trajectory on the Poincar’e sphere

Author(s):

Lü, Jia-Qi; Wang, Wen-Yue; Cheng, Tian-Yu; Lu, Zhi-Wei & Liu, Shuo

Abstract:

“As an inherent feature of vector optical field, the spatial distribution of polarization brings additional degrees of freedom to engineer the optical field and control the interaction between light and matters. Here we focus on the variation of polarization in single vector optical field, which can be defined by the trajectory on the Poincaré sphere. Based on the amplitude-phase-polarization joint modulation method we propose, vector optical field, whose variation of polarization follows arbitrary circular trajectory on the Poincaré sphere, can be generated. Moreover, the tightly focusing behaviors of the vector optical fields with the polarization varying along parallel circles on the Poincaré sphere are compared. Relations between the circular trajectory and the central intensity of the hollow focal field are concluded.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 24; Pages 39718; 2021
DOI: 10.1364/oe.441809

Realization and measurement of Airy transform of Gaussian vortex beams

Author(s):

Zhou, Lu; Zhou, Tong; Wang, Fei; Li, Xia; Chen, Ruipin; Zhou, Yimin & Zhou, Guoquan

Abstract:

“Airy transformation is a useful technique to modulate amplitude and phase of a light beam, which has important applications in particle trapping/manipulation, optical communications and optical imaging. However, most of the studies only focused on the Airy transform of Gaussian beams and other vortex-free beams in the past. In this paper, the Airy transform of Gaussian vortex beams, which are the most common vortex beams, is investigated. A universal analytical expression of the Gaussian vortex beams with topological charge (TC) m passing through an Airy transform optical system is derived. We carry out a detailed study on the output beams’ characteristics after the Airy transform of the Gaussian vortex beams with m = ± 1 and ± 2. The analytical expressions for the centroid, the beam spot size, the divergence angle and the beam propagation factor of the output beams are derived. The effects of the Airy control parameters and the TC on the normalized intensity distribution, the phase distribution, the centroid, the beam spot size and the beam propagation factor of the output beams are investigated both theoretically and experimentally. The experimental results agree reasonably well with the theoretical results which illustrate the properties of Airy transform of the Gaussian vortex beams.”

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Publication: Optics and Laser Technology
Issue/Year: Optics and Laser Technology, Volume 143; Pages 107334; 2021
DOI: 10.1016/j.optlastec.2021.107334

Clustering-based CLEAN algorithm in ghost imaging with sparse spatial frequencies

Author(s):

Chang, Chen; Wu, Guohua; Yang, Dongyue; Yin, Longfei & Luo, Bin

Abstract:

“When insufficient samples in the spatial frequency domain could be effectively compensated by the modified CLEAN algorithm, a novel aperture-synthetic scheme of ghost imaging takes advantage of a superior speed of modulation and an enhancement on the spatial resolution. However, there still exist some imperfections in the modified CLEAN reconstructions, such as the fact that some omitted scatter noise still remains or the object contour may be incomplete. Therefore, we optimize the modified CLEAN algorithm by proposing a density clustering algorithm to overcome these drawbacks and improve the visual quality.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 23; Pages 38841; 2021
DOI: 10.1364/oe.440497

Axial resolution enhancement for planar Airy beam light-sheet microscopy via the complementary beam subtraction method

Author(s):

Liu, Chao; Yu, Xianghua; Bai, Chen; Li, Xing; Zhou, Yuan; Yan, Shaohui; Min, Junwei; Dan, Dan; Li, Runze; Gu, Shuangyu & Yao, Baoli

Abstract:

“Airy beam light-sheet illumination can extend the field of view (FOV) of light-sheet fluorescence microscopy due to the unique propagation properties of non-diffraction and self-acceleration. However, the side lobes create undesirable out-of-focus background, leading to poor axial resolution and low image contrast. Here, we propose an Airy complementary beam subtraction (ACBS) method to improve the axial resolution while keeping the extended FOV. By scanning the optimized designed complementary beam that has two main lobes (TML), the generated complementary light-sheet has almost identical intensity distribution to that of the planar Airy light-sheet except for the central lobe. Subtraction of the two images acquired by double exposure respectively using the planar Airy light-sheet and the planar TML light-sheet can effectively suppress the influence of the out-of-focus background. The axial resolution improves from ∼4µm to 1.2 µm. The imaging performance was demonstrated by imaging specimens of aspergillus conidiophores and GFP labeled mouse brain section. The results show that the ACBS method enables the Airy beam light-sheet fluorescence microscopy to obtain better imaging quality.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Volume 60; Number 32; Pages 10239; 2021
DOI: 10.1364/ao.441070

Towards non-blind optical tweezing by finding 3D refractive index changes through off-focus interferometric tracking

Author(s):

Landenberger, Benjamin; Yatish & Rohrbach, Alexander

Abstract:

“In modern 3D microscopy, holding and orienting arbitrary biological objects with optical forces instead of using coverslips and gel cylinders is still a vision. Although optical trapping forces are strong enough and related photodamage is acceptable, the precise (re-) orientation of large specimen with multiple optical traps is difficult, since they grab blindly at the object and often slip off. Here, we present an approach to localize and track regions with increased refractive index using several holographic optical traps with a single camera in an off-focus position. We estimate the 3D grabbing positions around several trapping foci in parallel through analysis of the beam deformations, which are continuously measured by defocused camera images of cellular structures inside cell clusters. Although non-blind optical trapping is still a vision, this is an important step towards fully computer-controlled orientation and feature-optimized laser scanning of sub-mm sized biological specimen for future 3D light microscopy.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 12; Number 1; 2021
DOI: 10.1038/s41467-021-27262-z