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

Efficient High-Refractive-Index Azobenzene Dendrimers Based on a Hierarchical Supramolecular Approach

Author(s):

Fusco, Sandra; Oscurato, Stefano Luigi; Salvatore, Marcella; Reda, Francesco; Moujdi, Sara; Oliveira, Michael De; Ambrosio, Antonio; Centore, Roberto & Borbone, Fabio

Abstract:

“Real-time manipulation of light in a diffractive optical element made with an azomaterial, through the light-induced reconfiguration of its surface based on mass transport, is an ambitious goal that may enable new applications and technologies. The speed and the control over photopatterning/reconfiguration of such devices are critically dependent on the photoresponsiveness of the material to the structuring light pattern and on the required extent of mass transport. In this regard, the higher the refractive index (RI) of the optical medium, the lower the total thickness and inscription time can be. In this work, we explore a flexible design of photopatternable azomaterials based on hierarchically ordered supramolecular interactions, used to construct dendrimer-like structures by mixing specially designed sulfur-rich, high-refractive-index photoactive and photopassive components in solution. We demonstrate that thioglycolic-type carboxylic acid groups can be selectively used as part of a supramolecular synthon based on hydrogen bonding or readily converted to carboxylate and participate in a Zn(II)–carboxylate interaction to modify the structure of the material and fine-tune the quality and efficiency of photoinduced mass transport. Compared with a conventional azopolymer, we demonstrate that it is possible to fabricate high-quality, thinner flat diffractive optical elements to reach the desired diffraction efficiency by increasing the RI of the material, achieved by maximizing the content of high molar refraction groups in the chemical structure of the monomers.”

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Publication: Chemistry of Materials
Issue/Year: Chemistry of Materials, 2023
DOI: 10.1021/acs.chemmater.3c00550

Color optimization of a full-color holographic stereogram printing system using a single SLM based on iterative exposure control

Author(s):

Khuderchuluun, Anar; Dashdavaa, Erkhembaatar; Rupali, Shindae; Kwon, Ki-Chul; Kang, Hoonjong; Lee, Kwon-Yeon & Kim, Nam

Abstract:

“In this paper, color optimization of a full-color holographic stereogram printing system using a single SLM based on iterative exposure is proposed. First, an array of sub-holograms (hogels) is generated effectively within fast computergenerated integral imaging, and fully analyzed phase-modulation for red, green, and blue (RGB) channels of hogel. Then, the generated hogels are recorded into holographic material sequentially where SLM displays the R, G, and B channels of a single hogel via effectual exposure under synchronized control with three electrical shutters for RGB laser illumination to obtain verified color optimization. Numerical simulation and optical reconstructions are implemented.”

Link to Publications Page

Publication: Proc. SPIE
Issue/Year: Proc. SPIE 12445, Practical Holography XXXVII: Displays, Materials, and Applications, 124450A (8 March 2023)
DOI: 10.1117/12.2651038

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.”

Link to Publications Page

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

Coupled two-core integrated waveguides modal analysis

Author(s):

Benedicto, David; Collados, M. Victoria; Martín, Juan C.; Jesú s Atencia & Vallés, Juan A.

Abstract:

“We present a modal analysis of coupled two-core integrated waveguides fabricated by femtosecond laser writing as a function of the core-to-core distance, illuminating position and input light wavelength. In order to do that we use the correlation filter method, implementing the computer generated holograms in a phase-only spatial light modulator. Due to the two-core waveguide symmetry, we prove it is not necessary to encode the complex amplitude in a phase-only device as long as the cores are not strongly coupled. A comparison between experimental and numerical modal weights is presented, showing that simple phase-only match filters allow the modal decomposition of two-core waveguides output beams”

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Publication: Journal of Physics: Conference Series
Issue/Year: Journal of Physics: Conference Series, Volume 2407; Number 1; Pages 012016; 2022
DOI: 10.1088/1742-6596/2407/1/012016

Functional pixels: a pathway towards true holographic displays using today’s display technology

Author(s):

Falldorf, Claas; Rukin, Ilja; Müller, André F.; Kroker, Stefanie & Bergmann, Ralf. B.

Abstract:

“Today’s 3D dynamic holographic display techniques suffer from severe limitations due to an available number of pixels that is several orders of magnitude lower than required by conventional approaches. We introduce a solution to this problem by introducing the concept of functional pixels. This concept is based on pixels that individually spatially modulate the amplitude and phase of incident light with a polynomial function, rather than just a constant phase or amplitude. We show that even in the simple case of a linear modulation of the phase, the pixel count can be drastically reduced up to 3 orders of magnitude while preserving most of the image details. This scheme can be easily implemented with already existing technology, such as micro mirror arrays that provide tip, tilt and piston movement. Even though the individual pixels need to be technologically more advanced, the comparably small number of such pixels required to form a display may pave the way towards true holographic dynamic 3D displays.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 26; Pages 47528; 2022
DOI: 10.1364/oe.474589

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.”

Link to Publications Page

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

Contribution to the Improvement of the Correlation Filter Method for Modal Analysis with a Spatial Light Modulator

Author(s):

Benedicto, David; Collados, María Victoria; Martín, Juan C.; Jesus Atencia; Mendoza-Yero, Omel & Vallés, Juan A.

Abstract:

“Modal decomposition of light is essential to study its propagation properties in waveguides and photonic devices. Modal analysis can be carried out by implementing a computer-generated hologram acting as a match filter in a spatial light modulator. In this work, a series of aspects to be taken into account in order to get the most out of this method are presented, aiming to provide useful operational procedures. First of all, a method for filter size adjustment based on the standard fiber LP-mode symmetry is presented. The influence of the mode normalization in the complex amplitude encoding-inherent noise is then investigated. Finally, a robust method to measure the phase difference between modes is proposed. These procedures are tested by wavefront reconstruction in a conventional few-mode fiber.”

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Publication: Micromachines
Issue/Year: Micromachines, Volume 13; Number 11; Pages 2004; 2022
DOI: 10.3390/mi13112004

Diffraction model-informed neural network for unsupervised layer-based computer-generated holography

Author(s):

Shui, Xinghua; Zheng, Huadong; Xia, Xinxing; Yang, Furong; Wang, Weisen & Yu, Yingjie

Abstract:

“Learning-based computer-generated holography (CGH) has shown remarkable promise to enable real-time holographic displays. Supervised CGH requires creating a large-scale dataset with target images and corresponding holograms. We propose a diffraction model-informed neural network framework (self-holo) for 3D phase-only hologram generation. Due to the angular spectrum propagation being incorporated into the neural network, the self-holo can be trained in an unsupervised manner without the need of a labeled dataset. Utilizing the various representations of a 3D object and randomly reconstructing the hologram to one layer of a 3D object keeps the complexity of the self-holo independent of the number of depth layers. The self-holo takes amplitude and depth map images as input and synthesizes a 3D hologram or a 2D hologram. We demonstrate 3D reconstructions with a good 3D effect and the generalizability of self-holo in numerical and optical experiments.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 25; Pages 44814; 2022
DOI: 10.1364/oe.474137

Color Holographic Visualization of an Abnormal Retina: A Training Guide

Author(s):

Abdelazeem, Rania M. & Agour, Mostafa

Abstract:

“Holographic projection is one of the efficient tools to provide accurate three-dimensional (3D) representation of the medical data. Here, the aim of the current study is the construction of color holographic projection system to visualize an abnormal retina. The structures of the retina (blood vessels, optic disk, and ocular toxoplasmosis) are segmented using an in-house developed matlab code. The computer-generated holograms (CGHs) of the segmented structures are calculated using iterative Fourier transform algorithm (IFTA) and projected using a phase-only spatial light modulator (SLM). During the calculation process, a speckle noise reduction algorithm was applied to decrease the speckle noise of the optically reconstructed images. This is achieved by calculating an extended CGH and dividing it into a set of 16 equal holograms. The temporal-multiplexing of the 16 hologram yields a speckle-free reconstructed image. High quality Colored optical reconstruction images of an abnormal retinal structure were obtained using the proposed holographic projection system. Therefore, the proposed system can be used in corporation with the fundus photography as a significant tool for improving diagnosis and treatment of ocular toxoplasmosis.”

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Publication: 4th Novel Intelligent and Leading Emerging Sciences Conference (NILES)
Issue/Year: 4th Novel Intelligent and Leading Emerging Sciences Conference (NILES), Giza, Egypt, 2022
DOI: 10.1109/niles56402.2022.9942403
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