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Sui X, He Z, Chu D, Cao L. Non-convex optimization for inverse problem solving in computer-generated holography. LIGHT, SCIENCE & APPLICATIONS 2024; 13:158. [PMID: 38982035 PMCID: PMC11233576 DOI: 10.1038/s41377-024-01446-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 03/27/2024] [Accepted: 04/07/2024] [Indexed: 07/11/2024]
Abstract
Computer-generated holography is a promising technique that modulates user-defined wavefronts with digital holograms. Computing appropriate holograms with faithful reconstructions is not only a problem closely related to the fundamental basis of holography but also a long-standing challenge for researchers in general fields of optics. Finding the exact solution of a desired hologram to reconstruct an accurate target object constitutes an ill-posed inverse problem. The general practice of single-diffraction computation for synthesizing holograms can only provide an approximate answer, which is subject to limitations in numerical implementation. Various non-convex optimization algorithms are thus designed to seek an optimal solution by introducing different constraints, frameworks, and initializations. Herein, we overview the optimization algorithms applied to computer-generated holography, incorporating principles of hologram synthesis based on alternative projections and gradient descent methods. This is aimed to provide an underlying basis for optimized hologram generation, as well as insights into the cutting-edge developments of this rapidly evolving field for potential applications in virtual reality, augmented reality, head-up display, data encryption, laser fabrication, and metasurface design.
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Affiliation(s)
- Xiaomeng Sui
- Department of Precision Instruments, Tsinghua University, Beijing, 100084, China
- Department of Engineering, Centre for Photonic Devices and Sensors, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Zehao He
- Department of Precision Instruments, Tsinghua University, Beijing, 100084, China
| | - Daping Chu
- Department of Engineering, Centre for Photonic Devices and Sensors, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK.
- Cambridge University Nanjing Centre of Technology and Innovation, 23 Rongyue Road, Jiangbei New Area, Nanjing, 210000, China.
| | - Liangcai Cao
- Department of Precision Instruments, Tsinghua University, Beijing, 100084, China.
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Min K, Min D, Hong J, Park JH. Speckle reduction for single sideband-encoded computer-generated holograms by using an optimized carrier wave. OPTICS EXPRESS 2024; 32:13508-13526. [PMID: 38859319 DOI: 10.1364/oe.518427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 03/17/2024] [Indexed: 06/12/2024]
Abstract
Computer-generated hologram (CGH) is an evolving field that facilitates three-dimensional displays, with speckle noise reduction being a pivotal challenge. In hologram synthesis, complex data with random phase distributions are typically employed as carrier waves for wide viewing angles and a shallow depth of focus (DOF). However, these carrier waves are a source of speckle noise, which can significantly degrade image quality. In this paper, we propose a novel technique for speckle reduction for single sideband (SSB)-encoded holograms, applicable to any arbitrary 3D object. The proposed method focuses on optimizing the random carrier wave used in the hologram synthesis to achieve a uniform amplitude distribution at the object's location. This optimization results in a carrier wave that consistently exhibits uniform amplitude at specific depth planes, leading to a significant reduction of the speckle occurring from the carrier wave. The proposed method has been validated through simulations and optical experiments.
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Shiomi H, Blinder D, Birnbaum T, Inoue Y, Wang F, Ito T, Kakue T, Schelkens P, Shimobaba T. Deep hologram converter from low-precision to middle-precision holograms. APPLIED OPTICS 2023; 62:1723-1729. [PMID: 37132918 DOI: 10.1364/ao.482434] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We propose a deep hologram converter based on deep learning to convert low-precision holograms into middle-precision holograms. The low-precision holograms were calculated using a shorter bit width. It can increase the amount of data packing for single instruction/multiple data in the software approach and the number of calculation circuits in the hardware approach. One small and one large deep neural network (DNN) are investigated. The large DNN exhibited better image quality, whereas the smaller DNN exhibited a faster inference time. Although the study demonstrated the effectiveness of point-cloud hologram calculations, this scheme could be extended to various other hologram calculation algorithms.
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Xiao J, Zhang W, Zhang H. Inverse diffraction in phase space. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2023; 40:175-184. [PMID: 36607088 DOI: 10.1364/josaa.473386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Inverse diffraction refers to recovering the input field in the plane z=0 from the knowledge of the field in some plane z>0 of the free half-space to which the input field propagates. With the rapid development of computational optics, inverse diffraction is increasingly used in optimization and imaging simulations involving round-trip wave propagation. This increasing usage makes it necessary and valuable to revisit this old, important problem and clarify some existing ambiguities. In this study, an exhaustive inverse diffraction analysis is presented from the perspective of phase space. With the help of the Wigner distribution function, it is shown that the forward and inverse diffraction processes in phase space are geometrically equivalent to the deformation and recovery of the phase space diagram (PSD). The symmetries of PSD transformations corresponding to different inverse diffraction forms are revealed. The ambiguities between the conjugation of diffraction kernels and the negative diffraction distance are clarified. The physical pictures of inverse diffraction are further given. This phase space analysis provides an intuitive view on problems involving inverse diffraction and a more concise approach for understanding propagation behaviors of three-dimensional wave fields, including the phase conjugation in holography.
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Min D, Min K, Choi HJ, Lee H, Park JH. Non-hogel-based computer generated hologram with occlusion processing between the foreground light field and background hologram. OPTICS EXPRESS 2022; 30:38339-38356. [PMID: 36258402 DOI: 10.1364/oe.468748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
A novel technique is proposed to process the occlusion of a background hologram when synthesizing a front scene hologram from its light field. Unlike conventional techniques which process the occlusion in the light field domain after converting the background hologram to its light field, the proposed technique directly processes the occlusion between different domains, i.e., the background hologram and foreground light field. The key idea is to consider the background hologram as a carrier wave illuminating the front scene when synthesizing the front scene hologram from its light field. The proposed technique is not only computationally efficient as it does not require conversion between the light field and hologram domains but also accurate because all angular information of the background hologram and foreground light field is naturally considered in the occlusion processing. The proposed technique was verified by numerical synthesis and reconstruction.
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Chang C, Zhu D, Li J, Wang D, Xia J, Zhang X. Three-dimensional computer holography enabled from a single 2D image. OPTICS LETTERS 2022; 47:2202-2205. [PMID: 35486760 DOI: 10.1364/ol.452488] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 03/19/2022] [Indexed: 06/14/2023]
Abstract
To compute a high-quality computer-generated hologram (CGH) for true 3D real scenes, a huge amount of 3D data must be physically acquired and provided depending on specific devices or 3D rendering techniques. Here, we propose a computational framework for generating a CGH from a single image based on the idea of 2D-to-3D wavefront conversion. We devise a deep view synthesis neural network to synthesize light-field contents from a single image and convert the light-field data to the diffractive wavefront of the hologram using a ray-wave algorithm. The method is able to achieve extremely straightforward 3D CGH generation from hand-accessible 2D image content and outperforms existing real-world-based CGH computation, which inevitably relies on a high-cost depth camera and cumbersome 3D data rendering. We experimentally demonstrate 3D reconstructions of indoor and outdoor scenes from a single image enabled phase-only CGH.
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Kim Y, Hong K, Yeom HJ, Choi K, Park J, Min SW. Wide-viewing holographic stereogram based on self-interference incoherent digital holography. OPTICS EXPRESS 2022; 30:12760-12774. [PMID: 35472906 DOI: 10.1364/oe.454835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 03/21/2022] [Indexed: 06/14/2023]
Abstract
We propose a holographic stereogram synthesis method which uses holograms that are optically captured by self-interference incoherent digital holography (SIDH) based on a geometric phase lens. SIDH is a promising solution for hologram acquisition under low-coherence lighting condition. A mechanical scanning system is constructed to acquire multiple perspective holograms. Numerical simulations and experimental analyses conducted using high-resolution diffractive optical element demonstrate that the proposed method can produce a wide-viewing hologram which can realize realistic 3D scenarios with depth cues such as accommodation and motion parallax. The future objectives include the implementation of a multiple-camera system for holographic videos.
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Chang C, Bang K, Wetzstein G, Lee B, Gao L. Toward the next-generation VR/AR optics: a review of holographic near-eye displays from a human-centric perspective. OPTICA 2020; 7:1563-1578. [PMID: 34141829 PMCID: PMC8208705 DOI: 10.1364/optica.406004] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 09/23/2020] [Indexed: 05/19/2023]
Abstract
Wearable near-eye displays for virtual and augmented reality (VR/AR) have seen enormous growth in recent years. While researchers are exploiting a plethora of techniques to create life-like three-dimensional (3D) objects, there is a lack of awareness of the role of human perception in guiding the hardware development. An ultimate VR/AR headset must integrate the display, sensors, and processors in a compact enclosure that people can comfortably wear for a long time while allowing a superior immersion experience and user-friendly human-computer interaction. Compared with other 3D displays, the holographic display has unique advantages in providing natural depth cues and correcting eye aberrations. Therefore, it holds great promise to be the enabling technology for next-generation VR/AR devices. In this review, we survey the recent progress in holographic near-eye displays from the human-centric perspective.
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Affiliation(s)
- Chenliang Chang
- Department of Bioengineering, University of California, Los Angeles, 410 Westwood Plaza, Los Angeles, California 90095, USA
| | - Kiseung Bang
- School of Electrical and Computer Engineering, Seoul National University, Gwanak-Gu Gwanakro 1, Seoul 08826, Republic of Korea
| | - Gordon Wetzstein
- Department of Electrical Engineering, Stanford University, 350 Jane Stanford Way, Stanford, California 94305, USA
| | - Byoungho Lee
- School of Electrical and Computer Engineering, Seoul National University, Gwanak-Gu Gwanakro 1, Seoul 08826, Republic of Korea
| | - Liang Gao
- Department of Bioengineering, University of California, Los Angeles, 410 Westwood Plaza, Los Angeles, California 90095, USA
- Corresponding author:
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Efficient Hogel-Based Hologram Synthesis Method for Holographic Stereogram Printing. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10228088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
With the development of the holographic printer, printing synthetic hologram requires smaller holographic element (hogel) size to improve spatial resolution of the reconstruction. On the contrary, a larger hogel size affords higher angular resolution, but it leads to a lower lateral resolution and there exists a trade-off problem. In this paper, a hologram synthesis method based on three-dimensional (3D) rendering of computer-generated holographic stereogram (HS) is proposed to limit the spatial-angular trade-off problem. The perspectives of the 3D scene are captured by re-centering the camera method and transformed into parallax-related images by a proposed pixel re-arrangement algorithm for holographic printing. Unlike the conventional approaches, the proposed algorithm not only improves the angular resolution of the reconstruction while maintaining the hogel size fixed, but also keeps the spatial resolution without degradation. The effectiveness of the proposed method is verified by numerical simulation and an optical experiment.
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Park JH. Efficient calculation scheme for high pixel resolution non-hogel-based computer generated hologram from light field. OPTICS EXPRESS 2020; 28:6663-6683. [PMID: 32225909 DOI: 10.1364/oe.386632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 02/13/2020] [Indexed: 06/10/2023]
Abstract
We propose a method that reduces the computation time and memory requirement in non-hogel-based hologram synthesis from light field data. The non-hogel-based technique synthesizes coherent complex field for a three-dimensional scene from its light field. Unlike conventional holographic stereogram, the non-hogel-based technique reconstructs continuous parabolic wavefront for individual three-dimensional object point by globally processing the light field. However, the global processing increases the computational load significantly, making it hard to synthesize holograms with high pixel resolution. The proposed technique reduces the computational burden by processing each two-dimensional angular frequency slice of the four-dimensional light field independently. Hologram tiling technique is also proposed to make the hologram synthesis process scalable. Using the hologram tiling and the angular-frequency-slice-based processing, 25K×25 K pixel resolution hologram was synthesized successfully.
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Park DY, Park JH. Hologram conversion for speckle free reconstruction using light field extraction and deep learning. OPTICS EXPRESS 2020; 28:5393-5409. [PMID: 32121761 DOI: 10.1364/oe.384888] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 02/01/2020] [Indexed: 06/10/2023]
Abstract
A novel hologram conversion technique for speckle-less reconstruction is proposed. Many speckle-less reconstruction methods require holograms specially created for those techniques, limiting their applications to general pre-existing holograms. The proposed technique transforms an existing hologram with random phase distribution to new holograms for the application of the speckle-less reconstruction methods. The proposed technique first extracts a set of orthographic views from the existing hologram, then the extracted orthographic views are processed for the speckle noise removal using convolutional neural network. The processed orthographic views are finally used to synthesize new holograms with desired carrier waves by using non-hogel based computer generated hologram technique. The selection of the carrier wave is determined by the desired speckle-less reconstruction method. In this paper, we demonstrate the proposed technique with two speckle-less reconstruction methods; i.e. temporal speckle averaging of different random phase distributions and time-multiplexing of interleaved angular spectrums.
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