• Current Optics and Photonics
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• v.3 no.2
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• pp.119-127
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• 2019

A new secret-key-sharing cryptosystem using optical phase-shifting digital holography is proposed. The proposed secret-key-sharing algorithm is based on the Diffie-Hellman key-exchange protocol, which is modified to an optical cipher system implemented by a two-step quadrature phase-shifting digital holographic encryption method using orthogonal polarization. Two unknown users' private keys are encrypted by two-step phase-shifting digital holography and are changed into three digital-hologram ciphers, which are stored by computer and are opened to a public communication network for secret-key-sharing. Two-step phase-shifting digital holograms are acquired by applying a phase step of 0 or ${\pi}/2$ in the reference beam's path. The encrypted digital hologram in the optical setup is a Fourier-transform hologram, and is recorded on CCDs with 256 quantized gray-level intensities. The digital hologram shows an analog-type noise-like randomized cipher with a two-dimensional array, which has a stronger security level than conventional electronic cryptography, due to the complexity of optical encryption, and protects against the possibility of a replay attack. Decryption with three encrypted digital holograms generates the same shared secret key for each user. Schematically, the proposed optical configuration has the advantage of producing a kind of double-key encryption, which can enhance security strength compared to the conventional Diffie-Hellman key-exchange protocol. Another advantage of the proposed secret-key-sharing cryptosystem is that it is free to change each user's private key in generating the public keys at any time. The proposed method is very effective cryptography when applied to a secret-key-exchange cryptosystem with high security strength.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.820-828
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• 2017

Service of digital hologram that has been recognized as a visual system for next generation requires various signal processing technologies. A transform is the most frequently used tool among signal processing techniques for 2-dimensional(D) and 3-D natural picture. A digital hologram has totally different property with a natural picture, so it is rarely efficient to apply transform tools used in 2-D image processing to a digital hologram. To overcome this a Fresnelet transform for a digital hologram has been proposed. We derive a Fresnelet transform by using the Daubechie's filter after applying an unitary Fresnel transform to a wavelet basis function. We also implement the transform as types of device and kernel code to improve operational performance. In consideration of the average time that is required for a pixel we can have observed the performance is improved up to 242 and 30 times for using the (9,7) and (5,3) filters in case of using device code.

• Current Optics and Photonics
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• v.5 no.6
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• pp.680-685
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• 2021

We propose a technique that reconstructs a hologram whose pixel number is greater than the pixel numbers of a conventional image sensor. The pixel numbers of the hologram recorded by optical scanning holography (OSH) increases as the scan area becomes larger. The reconstruction time also increases drastically as the size of the hologram increases. The holographic information of a three-dimensional (3D) scene is distributed throughout the recorded hologram; this makes the simple divide-and-stitch approach fail. We propose a technique that reconstructs the hologram without loss of holographic information. First, we record the hologram of a 3D scene using OSH. Second, we segment the hologram into sub-holograms that contain complete holographic information. Third, we reconstruct the sub-holograms simultaneously. Finally, we rearrange the reconstructions of the sub-holograms.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.92-103
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• 2012

In this paper, we discuss and propose a new algorithm of coding technique for scalably servicing holographic video in various decoding environment. The proposed algorithm consists of the hologram-based resolution scalable coding (HRS) and the light source-based SNR scalable coding (LSS). They are classified by the method generating and capturing hologram. HRS is a scalable coding technique for the optically captured hologram and LSS is one for the light source before generating hologram. HRS can provide the scalable service of 8 steps with the compression ratio from 1:1 to 100:1 for a $1,024{\times}1,024$ hologram. LSS can also provide the various service depending on the number of the light source division using lossless compression. The proposed techniques showed the scalable holographic video service according to the display with the various resolutions, computational power of the receiving equipment, and the network bandwidth.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.415-416
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• 2006

In this paper, we proposed a new coding technique of digital hologram video using 3D scanning method and video compression technique. The proposed coding consists of capturing a digital hologram to separate into RGB color space components, localization by segmenting the fringe pattern, frequency transform using $M{\tiems}N$ (segment size) 2D DCT (2 Dimensional Discrete Cosine Transform) for extracting redundancy, 3D scan of segment to form a video sequence, motion compensated temporal filtering (MCTF) and modified video coding which uses H.264/AVC.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.347-348
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• 2019

In this paper, we propose a method to increase the resolution of a digital hologram by using deep learning. We reduced the size of holograms for training super-resolution algorithm and created a dataset using a subset of them. We trained the network model with the generated dataset and confirmed the PSNR over 31dB.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.31-37
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• 2006

We propose a digital watermarking technique using a computer generated hologram. The proposed method uses two random patterns separated from the computer generated hologram (CGH). One of those is embedded into the original image as hidden watermark information and then the reconstructed image can be obtained by an optical decoding algorithm with the other one as a decoding key. We analyze an occlusion of the watermarked image that is the original image containing the hidden pattern. The embedding process is performed digitally and reconstruction optically Computer simulation and an optical experiment are shown in support of the proposed technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.10
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• pp.1390-1393
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• 2020

Recently, a hologram-like system and a virtual human to provide a realistic experience has been serviced in various places such as musical performance and museum exhibition. Also, the realistically responded virtual human in the hologram-like system need to be expressed in a way that matches the users' interaction. In this paper, to improve the feeling of being in the same space with a virtual human in the hologram-like system, user's gesture based interactive contents were presented, and the effectiveness of interaction was evaluated. Our approach was found that the gesture based interaction was provided a higher sense of co-presence for immersion with the virtual human.

• Journal of Broadcast Engineering
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• v.20 no.5
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• pp.706-717
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• 2015

The computer generated hologram (CGH) method is the technology which can generate a hologram by using only a personal computer (PC) commonly used. However, the CGH method requires a huge amount of calculational time for the 3D object with a super multi-light source or a high-definition hologram. Hence, some solutions are obviously necessary for reducing the computational complexity of a CGH algorithm or increasing the computing performance of hardware. In this paper, we propose a method which can generate a digital hologram of the 3D object with a super multi-light source using parallel distributed computing. The traditional methods has the limitation of improving CGH performance by using a single PC. However, the proposed method where a server PC efficiently uses the computing power of client PCs can quickly calculate the CGH method for 3D object with super multi-light source. In the experimental result, we verified that the proposed method can generate the digital hologram with 1,5361,536 resolution size of 3D object with 157,771 light source in 121 ms. In addition, in the proposed method, we verify that the proposed method can reduce generation time of a digital hologram in proportion to the number of client PCs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1177-1186
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• 2014

Computer-generated hologram (CGH) is to mathematically model optical phenomenon with digital computer. Because it requires huge amount of computational power, a fast and high performance technique is needed. In this paper, we proposed two parallelizations for CGH calculation. The first is to parallelize CGH algorithm in a GPU (general processing unit) and the second is to parallelize multiple GPUs. The proposed algorithm was implemented in GTX780 Ti GPU. It calculates a $1,024{\times}1,024$ hologram with 10K object points for about 24ms.