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19 pages, 9326 KiB

Open AccessArticle

U-Net Driven High-Resolution Complex Field Information Prediction in Single-Shot Four-Step Phase-Shifted Digital Holography Using Polarization Camera

by Askari Mehdi, Yongjun Lim, Kwan-Jung Oh and Jae-Hyeung Park

Photonics 2024, 11(12), 1172; https://doi.org/10.3390/photonics11121172 - 12 Dec 2024

Viewed by 442

Abstract

We present a novel high-resolution complex field extraction technique utilizing U-Net-based architecture to effectively overcome the inherent resolution limitations of polarization cameras with micro-polarized arrays. Our method extracts high-resolution complex field information, achieving a resolution comparable to that of the original polarization camera. [...] Read more.

We present a novel high-resolution complex field extraction technique utilizing U-Net-based architecture to effectively overcome the inherent resolution limitations of polarization cameras with micro-polarized arrays. Our method extracts high-resolution complex field information, achieving a resolution comparable to that of the original polarization camera. Utilizing the parallel phase-shifting digital holography technique, we extracted high-resolution complex field information from four high-resolution phase-shifted interference patterns predicted by our network directly at the hologram plane. Extracting the object’s complex field directly at the hologram plane rather than the object’s plane, our method eliminates the dependency on numerical propagation during dataset acquisition, enabling reconstruction of objects at various depths without DC and conjugate noise. By training the network with real-valued interference patterns and using only a single pair of low- and high-resolution input and ground truth interference patterns, we simplify computational complexity and improve efficiency. Our simulations demonstrate the network’s robustness to variations in random phase distributions and transverse shifts in the input patterns. The effectiveness of the proposed method is demonstrated through numerical simulations, showing an average improvement of over 4 dB in peak-signal-to-noise ratio and 25% in intensity normalized cross-correlation metrics for object reconstruction quality. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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20 pages, 9956 KiB

Open AccessArticle

Object Recognition in Foggy and Hazy Conditions Using Dark Channel Prior-Based Fringe-Adjusted Joint Transform Correlator

by Jyoti Bikash Mohapatra, Naveen K. Nishchal and Jyothish Monikantan

Photonics 2024, 11(12), 1142; https://doi.org/10.3390/photonics11121142 - 4 Dec 2024

Viewed by 924

Abstract

Extreme weather conditions like fog and haze present substantial challenges to object recognition systems. Reduced visibility and contrast degradation significantly affect the auto-correlation process, often leading to failure in object recognition. To address this critical issue and to make object recognition accurate and [...] Read more.

Extreme weather conditions like fog and haze present substantial challenges to object recognition systems. Reduced visibility and contrast degradation significantly affect the auto-correlation process, often leading to failure in object recognition. To address this critical issue and to make object recognition accurate and invincible, we propose a hybrid digital–optical correlator specifically designed to perform under adverse weather conditions. This approach integrates the dark channel prior (DCP) with the fringe-adjusted joint transform correlator (FJTC), promising significant potential to enhance the robustness of the object recognition process under challenging environmental conditions. The proposed scheme presents a unique and alternative approach for object recognition under bad weather conditions. The incoming input scenes are processed with the DCP, enabling the FJTC to perform optical correlation on the refined images. The effectiveness of the proposed method is evaluated using several performance metrics like the structural similarity index measure (SSIM), peak signal-to-noise ratio (PSNR), correlation peak intensity (CPI), processing time, and recognition accuracy. To validate the performance of the proposed study, numerical simulation along with hybrid digital–optical demonstrations have been conducted. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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16 pages, 7263 KiB

Open AccessArticle

Asymmetric Optical Scanning Holography Encryption with Elgamal Algorithm

by Chunying Wu, Yinggang Ding, Aimin Yan, Ting-Chung Poon and Peter Wai Ming Tsang

Photonics 2024, 11(9), 878; https://doi.org/10.3390/photonics11090878 - 19 Sep 2024

Viewed by 878

Abstract

This paper proposes an asymmetric scanning holography cryptosystem based on the Elgamal algorithm. The method encodes images with sine and cosine holograms. Subsequently, each hologram is divided into a signed bit matrix and an unsigned hologram matrix, both encrypted using the sender’s private [...] Read more.

This paper proposes an asymmetric scanning holography cryptosystem based on the Elgamal algorithm. The method encodes images with sine and cosine holograms. Subsequently, each hologram is divided into a signed bit matrix and an unsigned hologram matrix, both encrypted using the sender’s private key and the receiver’s public key. The resulting ciphertext matrices are then transmitted to the receiver. Upon receipt, the receiver decrypts the ciphertext matrices using their private key and the sender’s public key. We employ an asymmetric single-image encryption method for key management and dispatch for securing imaging and transmission. Furthermore, we conducted a sensitivity analysis of the encryption system. The image encryption metrics, including histograms of holograms, adjacent pixel correlation, image correlation, the peak signal-to-noise ratio, and the structural similarity index, were also examined. The results demonstrate the security and stability of the proposed method. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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10 pages, 4716 KiB

Open AccessArticle

Digital Holographic Interferometry for Micro-Deformation Analysis of Morpho Butterfly Wing

by Ali Mardan Dezfouli, Nazif Demoli, Denis Abramović, Mario Rakić and Hrvoje Skenderović

Photonics 2024, 11(9), 851; https://doi.org/10.3390/photonics11090851 - 9 Sep 2024

Viewed by 671

Abstract

In this study, we present an analysis of deflections in a Morpho butterfly wing using digital holographic interferometry (DHI). Our methodology revolves around an off-axis lensless Fourier holographic setup, using laser excitation to induce deflections in the object. The implementation of a DHI [...] Read more.

In this study, we present an analysis of deflections in a Morpho butterfly wing using digital holographic interferometry (DHI). Our methodology revolves around an off-axis lensless Fourier holographic setup, using laser excitation to induce deflections in the object. The implementation of a DHI setup, tailored for rapid monitoring of micro-deformation, is a central aspect of our research. We offer an overview of the theoretical foundations of this technique, complemented by both experimental and numerical results aimed at validating our findings. We designed an optical setup that enhanced both laser illumination and hologram reconstruction for the sample. The experimental findings decisively show that the proposed method is effective for rapid deformation analysis. The deformation of the wing can be measured with micro-meter accuracy thanks to numerical analysis. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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14 pages, 8770 KiB

Open AccessArticle

The Designed Phase Mask for Suppressing the Inter-Pixel Crosstalk Noise in Intensity-Modulated Multilevel Holographic Data Storage Systems

by Takuya Nonaka, Soki Hirayama, Tsutomu Shimura and Ryushi Fujimura

Photonics 2024, 11(6), 507; https://doi.org/10.3390/photonics11060507 - 26 May 2024

Viewed by 1221

Abstract

Intensity-modulated signals have the advantage of being directly detectable by the image sensor but have the drawback that the signal quality is easily deteriorated by crosstalk noise, in contrast to phase-modulated signals. In order to suppress the crosstalk noise, we propose a new [...] Read more.

Intensity-modulated signals have the advantage of being directly detectable by the image sensor but have the drawback that the signal quality is easily deteriorated by crosstalk noise, in contrast to phase-modulated signals. In order to suppress the crosstalk noise, we propose a new signal arrangement for multilevel intensity-modulated signals. The concept of our method is to reduce the number of adjacent pixels that are a source of inter-pixel crosstalk noise and to minimize intensity modulation owing to interference with crosstalk noise. We have numerically and experimentally demonstrated that our method can reduce the error rate and improve the recording density compared to the conventional signal arrangement. Our proposed method offers a promising solution for achieving higher recording densities in intensity-modulated holographic data storage systems. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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9 pages, 4388 KiB

Open AccessArticle

Diffractive Deep-Neural-Network-Based Classifier for Holographic Memory

by Toshihiro Sakurai, Tomoyoshi Ito and Tomoyoshi Shimobaba

Photonics 2024, 11(2), 145; https://doi.org/10.3390/photonics11020145 - 4 Feb 2024

Cited by 1 | Viewed by 1471

Abstract

Holographic memory offers high-capacity optical storage with rapid data readout and long-term durability. Recently, read data pages have been classified using digital deep neural networks (DNNs). This approach is highly accurate, but the prediction time hinders the data readout throughput. This study presents [...] Read more.

Holographic memory offers high-capacity optical storage with rapid data readout and long-term durability. Recently, read data pages have been classified using digital deep neural networks (DNNs). This approach is highly accurate, but the prediction time hinders the data readout throughput. This study presents a diffractive DNN (D2NN)-based classifier for holographic memory. D2NNs have so far attracted a great deal of attention for object identification and image transformation at the speed of light. A D2NN, consisting of trainable diffractive layers and devoid of electronic devices, facilitates high-speed data readout. Furthermore, we numerically investigated the classification performance of a D2NN-based classifier. The classification accuracy of the D2NN was 99.7% on 4-bit symbols, exceeding that of the hard decision method. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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12 pages, 3776 KiB

Open AccessArticle

Reducing the Crosstalk in Collinear Holographic Data Storage Systems Based on Random Position Orthogonal Phase-Coding Reference

by Haiyang Song, Jianan Li, Dakui Lin, Hongjie Liu, Yongkun Lin, Jianying Hao, Kun Wang, Xiao Lin and Xiaodi Tan

Photonics 2023, 10(10), 1160; https://doi.org/10.3390/photonics10101160 - 16 Oct 2023

Viewed by 1382

Abstract

Previous studies have shown that orthogonal phase-coding multiplexing performs well with low crosstalk in conventional off-axis systems. However, noticeable crosstalk occurs when applying the orthogonal phase-coding multiplexing to collinear holographic data storage systems. This paper demonstrates the crosstalk generation mechanism, features, and elimination [...] Read more.

Previous studies have shown that orthogonal phase-coding multiplexing performs well with low crosstalk in conventional off-axis systems. However, noticeable crosstalk occurs when applying the orthogonal phase-coding multiplexing to collinear holographic data storage systems. This paper demonstrates the crosstalk generation mechanism, features, and elimination methods. The crosstalk is caused by an inconsistency in the intensity reconstruction from the orthogonal phase-coded reference wave. The intensity fluctuation range was approximately 40%. Moreover, the more concentrated the distribution of pixels with the same phase key, the more pronounced the crosstalk. We propose an effective random orthogonal phase-coding reference wave method to reduce the crosstalk. The orthogonal phase-coded reference wave is randomly distributed over the entire reference wave. These disordered orthogonal phase-coded reference waves achieve consistent reconstruction intensities exhibiting the desired low-crosstalk storage effect. The average correlation coefficient between pages decreased by 73%, and the similarity decreased by 85%. This orthogonal phase-coding multiplexing method can be applied to encrypted holographic data storage. The low-crosstalk nature of this technique will make the encryption system more secure. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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13 pages, 15322 KiB

Open AccessArticle

Robust Holographic Reconstruction by Deep Learning with One Frame

by Xianfeng Xu, Weilong Luo, Hao Wang and Xinwei Wang

Photonics 2023, 10(10), 1155; https://doi.org/10.3390/photonics10101155 - 15 Oct 2023

Cited by 3 | Viewed by 1536

Abstract

A robust method is proposed to reconstruct images with only one hologram in digital holography by introducing a deep learning (DL) network. The U-net neural network is designed according to DL principles and trained by the image data set collected using phase-shifting digital [...] Read more.

A robust method is proposed to reconstruct images with only one hologram in digital holography by introducing a deep learning (DL) network. The U-net neural network is designed according to DL principles and trained by the image data set collected using phase-shifting digital holography (PSDH). The training data set was established by collecting thousands of reconstructed images using PSDH. The proposed method can complete the holography reconstruction with only a single hologram and then benefits the space bandwidth product and relaxes the storage loads of PSDH. Compared with the results of PSDH, the results of deep learning are immune to most disturbances, including reference tilt, phase-shift errors, and speckle noise. Assisted by a GPU processor, the proposed reconstruction method can reduce the consumption time to almost one percent of the time needed by two-step PSDH. This method is expected to be capable of holography imaging with a single hologram, with high capacity, efficiently in the digital holography applications. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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9 pages, 3074 KiB

Open AccessCommunication

Isotropic Two-Dimensional Differentiation Based on Dual Dynamic Volume Holograms

by Pin Wang, Houxin Fan, Yaping Zhang, Yongwei Yao, Bing Zhang, Wenlong Qin and Ting-Chung Poon

Photonics 2023, 10(7), 828; https://doi.org/10.3390/photonics10070828 - 17 Jul 2023

Cited by 1 | Viewed by 1058

Abstract

We study the use of two dynamic thick holograms to realize isotropic two-dimensional (2D) differentiation under Bragg diffraction. Acousto-optic modulators (AOMs) are used as dynamic volume holograms. Using a single volume hologram, we can accomplish a first-order derivative operation, corresponding to selective edge [...] Read more.

We study the use of two dynamic thick holograms to realize isotropic two-dimensional (2D) differentiation under Bragg diffraction. Acousto-optic modulators (AOMs) are used as dynamic volume holograms. Using a single volume hologram, we can accomplish a first-order derivative operation, corresponding to selective edge extraction of an image. Since the AOM is a 1D spatial light modulator, filtering of the image only occurs along the direction of the sound propagation. To achieve 2D image processing, two AOMs are used within a Mach–Zehnder interferometer (MZI). By aligning one AOM along the x-direction on the upper arm of the interferometer and another AOM along the y-direction on the lower arm, we accomplish the sum of two first-derivative operations, leading to isotropic edge extraction. We have performed both computer simulations and optical experiments to verify the proposed idea. The system provides additional operations in optical computing using AOMs as dynamic holograms. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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Review

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19 pages, 12947 KiB

Open AccessReview

Computational Optical Scanning Holography

by Naru Yoneda, Jung-Ping Liu, Osamu Matoba, Yusuke Saita and Takanori Nomura

Photonics 2024, 11(4), 347; https://doi.org/10.3390/photonics11040347 - 10 Apr 2024

Viewed by 1662

Abstract

Holographic techniques are indispensable tools for modern optical engineering. Over the past two decades, research about incoherent digital holography has continued to attract attention. Optical scanning holography (OSH) can obtain incoherent holograms using single-pixel detection and structured illumination with Fresnel zone patterns (FZPs). [...] Read more.

Holographic techniques are indispensable tools for modern optical engineering. Over the past two decades, research about incoherent digital holography has continued to attract attention. Optical scanning holography (OSH) can obtain incoherent holograms using single-pixel detection and structured illumination with Fresnel zone patterns (FZPs). Particularly by changing the size of a detector, OSH can also obtain holograms under coherently illuminated conditions. Since 1979, OSH has continuously evolved. According to the evolution of semiconductor technology, spatial light modulators (SLMs) come to be useful for various imaging fields. By using SLM techniques for OSH, the practicality of OSH is improved. These SLM-based OSH methods are termed computational OSH (COSH). In this review, the configurations, recording and reconstruction methods, and proposed applications of COSH are reviewed. Full article

(This article belongs to the Special Issue Holographic Information Processing)

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