Quasi-Cylindrical Digital Hologram by Superposition of Digital Holograms Recorded on Concyclic Positions

Compression of Digital Hologram Based on Binary Holographic Interference

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.760-762.497 ◽

2013 ◽

Vol 760-762 ◽

pp. 497-501

Author(s):

Yan Gao ◽

Hao Zhou ◽

Ji Hua Gu ◽

Tao Yang

Keyword(s):

Diffraction Efficiency ◽

Fresnel Diffraction ◽

Phase Information ◽

High Quality ◽

Digital Hologram ◽

Digital Holograms

Since the resolution of digital micro-mirror device (DMD) which is used to reconstruct the digital holograms captured in experiments is relatively low, only a part of the digital hologram can be effectively reproduced in the experiment. For the hologram has the feature of high redundancy, in this paper, we propose that compress holograms based on Binary holographic interference. First, only the amplitude of the digital hologram is retained after Fresnel diffraction, recover the phase information from the amplitude, then generate a new compressed digital hologram with the phase and amplitude, and then process the new hologram according to the principle of binary holographic interference to improve the diffraction efficiency and to obtain a high-quality reconstruction.

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A Content Hiding Method for Digital Hologram Using Multiple Fresnel Diffraction

Applied Sciences ◽

10.3390/app10144897 ◽

2020 ◽

Vol 10 (14) ◽

pp. 4897

Author(s):

Young-Ho Seo ◽

Yoon-Hyuk Lee ◽

Dong-Wook Kim

Keyword(s):

Small Region ◽

Fresnel Diffraction ◽

Encrypted Data ◽

Diffraction Plane ◽

Digital Hologram ◽

Visual Distortion ◽

Digital Holograms ◽

Fresnel Transform ◽

Processing Techniques ◽

Signal Processing Techniques

A digital hologram (DH) is so highly valued that it needs to be protected from exposure to an unpermitted person, which could be done by a content encryption. We propose an encryption scheme for digital holograms, whose goal is to hide their information with maximal visual distortion and minimal ration of the encrypted data. It uses the characteristics of the Fresnel transform and signal processing techniques. As the diffraction distance increases the region containing the object information relative to the whole diffraction plane becomes smaller. Therefore our scheme diffracts a given digital hologram twice: the first transform for reconstructing the image contained by the hologram and the second transform for concentrating the energy of the object into a small region. Then only the energy-concentrated region is encrypted to reduce the amount of data to be encrypted. Experimental results show that when the diffraction distance of the second transform is about 20 m, the encryption ratio is only 0.0058% of the hologram data, which is enough to hide the object information unrecognizably.

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Digital Hologram Watermarking Based on Multiple Deep Neural Networks Training Reconstruction and Attack

Sensors ◽

10.3390/s21154977 ◽

2021 ◽

Vol 21 (15) ◽

pp. 4977

Author(s):

Ji-Won Kang ◽

Jae-Eun Lee ◽

Jang-Hwan Choi ◽

Woosuk Kim ◽

Jin-Kyum Kim ◽

...

Keyword(s):

Neural Network ◽

Neural Networks ◽

Deep Neural Network ◽

Deep Neural Networks ◽

Training Method ◽

Digital Hologram ◽

Network Training ◽

Digital Holograms ◽

Holographic Reconstruction

This paper proposes a method to embed and extract a watermark on a digital hologram using a deep neural network. The entire algorithm for watermarking digital holograms consists of three sub-networks. For the robustness of watermarking, an attack simulation is inserted inside the deep neural network. By including attack simulation and holographic reconstruction in the network, the deep neural network for watermarking can simultaneously train invisibility and robustness. We propose a network training method using hologram and reconstruction. After training the proposed network, we analyze the robustness of each attack and perform re-training according to this result to propose a method to improve the robustness. We quantitatively evaluate the results of robustness against various attacks and show the reliability of the proposed technique.

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