Energy-Efficient Adaptive 3D Sensing

Author(s):

Tilmon, Brevin; Sun, Zhanghao; Koppal, Sanjeev; Wu, Yicheng; Evangelidis, Georgios; Zahreddine, Ramzi; Krishnan, Guru; Ma, Sizhuo & Wang, Jian

Abstract:

“Active depth sensing achieves robust depth estimation but is usually limited by the sensing range. Naively increasing the optical power can improve sensing range but induces eye-safety concerns for many applications, including autonomous robots and augmented reality. In this paper, we propose an adaptive active depth sensor that jointly optimizes range, power consumption, and eye-safety. The main observation is that we need not project light patterns to the entire scene but only to small regions of interest where depth is necessary for the application and passive stereo depth estimation fails. We theoretically compare this adaptive sensing scheme with other sensing strategies, such as full-frame projection, line scanning, and point scanning. We show that, to achieve the same maximum sensing distance, the proposed method consumes the least power while having the shortest (best) eye-safety distance. We implement this adaptive sensing scheme with two hardware prototypes, one with a phase-only spatial light modulator (SLM) and the other with a micro-electro-mechanical (MEMS) mirror and diffractive optical elements (DOE). Experimental results validate the advantage of our method and demonstrate its capability of acquiring higher quality geometry adaptively.”

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Publication: Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)
Issue/Year: 2023
Link: https://btilmon.github.io/e3d.html

Highly transparent wave front printed volume holograms realized by amplitude-modulated incoherent pre-illumination

Author(s):

Wilm, Tobias; Wieland, Max; Fiess, Reinhold & Stork, Wilhelm

Abstract:

“We present highly transparent, wave front printed volume holographic optical elements (vHOEs), realized with a new recording method based on the pre-illumination of incoherent light patterns. The introduced amplitudemodulated pattern illuminates a distinct area on the unexposed, photopolymer-based holographic recording material prior to the hologram recording sequence. The incoherent pre-illumination scheme enables a precise tuning of the material’s local photosensitivity without the formation of a holographic volume diraction grating. As a consequence, the pre-illumination exposure signicantly suppresses the formation of transparency diminishing structures in the material that are formed concurrently with the volume diraction grating during the hologram recording sequence. The pre-illumination component is integrated in an extended immersion-based wave front printing setup, which realizes vHOEs by sequentially recording single holographic elements in an array-like structure. A wide range of dierent recording congurations is enabled by our recording setup due to independent modulation of both wave fronts and the possibility to realize large o-axis recording angles. We introduce two hologram characterization methods, based on a diraction eciency and a slanted-edge method analysis, which are used to evaluate the implemented pre-illumination method and demonstrate signicant improvements to the see-through quality of the presented wave front recorded vHOEs.”

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Publication: Proc. SPIE 12445
Issue/Year: Proc. SPIE 12445, Practical Holography XXXVII: Displays, Materials, and Applications, 124450S, 2023
DOI: 10.1117/12.2647361

Fourier-inspired neural module for real-time and high-fidelity computer-generated holography

Author(s):

Dong, Zhenxing; Xu, Chao; Ling, Yuye; Li, Yan & Su, Yikai

Abstract:

“Learning-based computer-generated holography (CGH) algorithms appear as novel alternatives to generate phase-only holograms. However, most existing learning-based approaches underperform their iterative peers regarding display quality. Here, we recognize that current convolutional neural networks have difficulty learning cross-domain tasks due to the limited receptive field. In order to overcome this limitation, we propose a Fourier-inspired neural module, which can be easily integrated into various CGH frameworks and significantly enhance the quality of reconstructed images. By explicitly leveraging Fourier transforms within the neural network architecture, the mesoscopic information within the phase-only hologram can be more handily extracted. Both simulation and experiment were performed to showcase its capability. By incorporating it into U-Net and HoloNet, the peak signal-to-noise ratio of reconstructed images is measured at 29.16 dB and 33.50 dB during the simulation, which is 4.97 dB and 1.52 dB higher than those by the baseline U-Net and HoloNet, respectively. Similar trends are observed in the experimental results. We also experimentally demonstrated that U-Net and HoloNet with the proposed module can generate a monochromatic 1080p hologram in 0.015 s and 0.020 s, respectively.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Volume 48; Number 3; Pages 759; 2023
DOI: 10.1364/ol.477630

Pixel super-resolution quantitative phase imaging based on modulation diversity

Author(s):

Gao, Yunhui & Cao, Liangcai

Abstract:

“Quantitative phase imaging with high resolution remains a long-term pursuit of many biomedical applications. However, the performance of coherent imaging systems is challenged by the intensity-only measurement mechanism and the sampling limit of the pixels. In this work, we introduce an imaging system that achieves pixel super-resolution quantitative phase imaging based on modulation diversity. A programmable phase-only spatial light modulator is used to generate various phase modulation patterns to the wavefront, providing data diversity for phase recovery at subpixel resolution. The system requires no mechanical displacements, enabling high-speed image acquisition, providing a competitive approach to high-throughput quantitative phase imaging applications.”

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Publication: Proc. SPIE 12318
Issue/Year: Proc. SPIE 12318, Holography, Diffractive Optics, and Applications XII, 123180Q, 2022
DOI: 10.1117/12.2642054

Pixel Super-Resolution Phase Retrieval for Lensless On-Chip Microscopy via Accelerated Wirtinger Flow

Author(s):

Gao, Yunhui; Yang, Feng & Cao, Liangcai

Abstract:

“Empowered by pixel super-resolution (PSR) and phase retrieval techniques, lensless onchip microscopy opens up new possibilities for high-throughput biomedical imaging. However, the current PSR phase retrieval approaches are time consuming in terms of both the measurement and reconstruction procedures. In this work, we present a novel computational framework for PSR phase retrieval to address these concerns. Specifically, a sparsity-promoting regularizer is introduced to enhance the well posedness of the nonconvex problem under limited measurements, and Nesterov’s momentum is used to accelerate the iterations. The resulting algorithm, termed accelerated Wirtinger flow (AWF), achieves at least an order of magnitude faster rate of convergence and allows a twofold reduction in the measurement number while maintaining competitive reconstruction quality. Furthermore, we provide general guidance for step size selection based on theoretical analyses, facilitating simple implementation without the need for complicated parameter tuning. The proposed AWF algorithm is compatible with most of the existing lensless on-chip microscopes and could help achieve label-free rapid whole slide imaging of dynamic biological activities at subpixel resolution.”

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Publication: Cells
Issue/Year: Cells, Volume 11; Number 13; Pages 1999; 2022
DOI: 10.3390/cells11131999

Large depth-of-field fluorescence microscopy based on deep learning supported by Fresnel incoherent correlation holography

Author(s):

Wu, Peng; Zhang, Dejie; Yuan, Jing; Zeng, Shaoqun; Gong, Hui; Luo, Qingming & Yang, Xiaoquan

Abstract:

“Fluorescence microscopy plays an irreplaceable role in biomedicine. However, limited depth of field (DoF) of fluorescence microscopy is always an obstacle of image quality, especially when the sample is with an uneven surface or distributed in different depths. In this manuscript, we combine deep learning with Fresnel incoherent correlation holography to describe a method to obtain significant large DoF fluorescence microscopy. Firstly, the hologram is restored by the Auto-ASP method from out-of-focus to in-focus in double-spherical wave Fresnel incoherent correlation holography. Then, we use a generative adversarial network to eliminate the artifacts introduced by Auto-ASP and output the high-quality image as a result. We use fluorescent beads, USAF target and mouse brain as samples to demonstrate the large DoF of more than 400µm, which is 13 times better than that of traditional wide-field microscopy. Moreover, our method is with a simple structure, which can be easily combined with many existing fluorescence microscopic imaging technology”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 4; Pages 5177; 2022
DOI: 10.1364/oe.451409

Scalability of all-optical neural networks based on spatial light modulators

Author(s):

Ying Zuo, Zhao Yujun, You-Chiuan Chen, Shengwang Du & Liu, Junwei

Abstract:

“Optical implementation of artificial neural networks has been attracting great attention due to its potential in parallel computation at speed of light. Although all-optical deep neural networks (AODNNs) with a few neurons have been experimentally demonstrated with acceptable errors re- cently, the feasibility of large scale AODNNs remains unknown because error might accumulate inevitably with increasing number of neurons and connections. Here, we demonstrate a scalable AODNN with programmable linear operations and tunable nonlinear activation functions. We ver- ify its scalability by measuring and analyzing errors propagating from a single neuron to the entire network. The feasibility of AODNNs is further confirmed by recognizing handwritten digits and fashions respectively.”

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Publication: Physical Review Applied
Issue/Year: Physical Review Applied, 2021
DOI: https://doi.org/10.1103/PhysRevApplied.15.054034

High-Flexibility Control of Structured Light with Combined Adaptive Optical Systems

Author(s):

Grunwald, Rüdiger; Jurke, Mathias; Bock, Martin; Liebmann, Max; Bruno, Binal Poyyathuruthy; Gowda, Hitesh & Wallrabe, Ulrike

Abstract:

“Combining the specific advantages of high-resolution liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs) and reflective or refractive micro-electro-mechanical systems (MEMS) presents new prospects for the generation of structured light fields. In particular, adaptive self-apodization schemes can significantly reduce diffraction by low-loss spatial filtering. The concept enables one to realize low-dispersion shaping of nondiffracting femtosecond wavepackets and to temporally switch, modulate or deflect spatially structured beams. Adaptive diffraction management by structured illumination is demonstrated for piezo-based and thermally actuated axicons, spiral phase plates (SPPs) and Fresnel bi-mirrors. Improved non-collinear autocorrelation with angular-tunable Fresnel-bi-mirrors via self-apodized illumination and phase contrast of an SLM is proposed. An extension of the recently introduced nondiffractive Talbot effect to a tunable configuration by combining an SLM and a fluid lens is reported. Experimental results for hexagonal as well as orthogonal array beams are presented.”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 1; Pages 42; 2022
DOI: 10.3390/photonics9010042

Electro-Optic Modulation of Higher-Order Poincar’e Beam Based on Nonlinear Optical Crystal

Author(s):

Han, Lu; Li, Zhan; Chen, Chao; Sun, Xin; Zhang, Junyong & Liu, Dean

Abstract:

“Vector beams (VBs) have spatially inhomogeneous polarization states distribution and have been widely used in many fields. In this paper, we proposed a method to modulate polarization states of higher-order Poincaré (HOP) beams and designed a system based on Mach-Zehnder interferometers, in which polarization state (include azimuth and ellipticity) of generated HOP beams were modulated by linear electro-optic (EO) effect of nonlinear optical crystals. Using this method, the polarization state of generated HOP beams could be controlled by voltage signal applied on EO crystals, which makes the process of the polarization state change with no optical element moving and mechanical vibrations. Besides, due to the flexibility of the voltage signal, the polarization state could be switched directly and immediately.”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 1; Pages 41; 2022
DOI: 10.3390/photonics9010041

Lensless Optical Encryption of Multilevel Digital Data Containers Using Spatially Incoherent Illumination

Author(s):

Cheremkhin, Pavel; Evtikhiev, Nikolay; Krasnov, Vitaly; Ryabcev, Ilya; Shifrina, Anna & Starikov, Rostislav

Abstract:

“The necessity of the correction of errors emerging during the optical encryption process ledto the extensive use of data containers such as QR codes. However, due to specifics of optical encryp-tion, QR codes are not very well suited for the task, which results in low error correction capabilitiesin optical experiments mainly due to easily breakable QR code’s service elements and byte datastructure. In this paper, we present optical implementation of information optical encryption systemutilizing new multilevel customizable digital data containers with high data density. The results ofoptical experiments demonstrate efficient error correction capabilities of the new data container.”

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Publication: Applied Sciences
Issue/Year: Applied Sciences, Volume 12; Number 1; Pages 406; 2021
DOI: 10.3390/app12010406
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