• Annual Conference of KIPS
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• 2019.10a
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• pp.1053-1055
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• 2019

최근 사용자에게 단순히 체험을 제공하는 것을 넘어서 같은 내용의 체험을 제공하더라도 더욱 실감있는 체험을 제공하기 위한 연구가 이루어지고 있다. 사용자에게 시각적으로 현존감 있는 체험을 제공하기 위한 유사 홀로그램(hologram-like)시스템은 고전적인 디스플레이 방식에 빛의 간섭현상을 더해 투영되는 물체가 실제 현장에 존재하는 것과 같은 효과를 준다. 이러한 유사홀로그램 시스템은 공연, 전시, 교육 등 다양한 서비스 분야에 널리 확대가 가능한 차세대 디스플레이 시스템이다. 유사홀로그램 시스템을 구성하는 방법은 피라미드, 반투명 대형 단일 스크린 등 다양한 형태의 H/W 구성 특성에 따라 다양한 형태로 제작이 가능하지만 시스템 내부에 콘텐츠를 표현할 때 마다 H/W 구성 특성에 맞춰 콘텐츠를 매번 재구성해야 하는 번거로움이 존재한다. 본 논문에서는 다양한 형태의 H/W 구성을 가질 수 있는 유사홀로그램 시스템에 표현되는 콘텐츠 구성을 자동적으로 보정하여 다양한 종류의 유사홀로그램 시스템 H/W 를 사용하여도 콘텐츠를 변형없이 적용할 수 있는 저작도구 설계를 제안한다.

• Electronics and Telecommunications Trends
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• v.38 no.2
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• pp.66-74
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• 2023

Holography is the most promising 3D imaging technology to faithfully record and reproduce light information. In addition, it is widely explored in metrology for applications such as microscopy and tomography because it can accurately measure 3D shapes. However, the data size of a digital hologram is very large, and the data characteristics are notably different from those of conventional 2D images. The Joint Photographic Experts Group (JPEG) is a group of experts from the International Organization for Standardization/International Electrotechnical Commission. This group develops and maintains standards for still image compression. In 2014, the JPEG released a new standard for 3D image compression called JPEG Pleno to represent light fields, point clouds, and holograms. Among them, JPEG Pleno Holography is the first international standard for hologram compression. We review recent advances in JPEG Pleno Holography standardization and discuss future directions of development.

• Journal of Digital Convergence
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• v.15 no.6
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• pp.369-376
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• 2017

In a digital multimedia environment with various experiences and communication, We live in an age where it is possible to experience from imagination to reality realizable by imagination. The remarkable technology based on ICT has been attracting attention as next generation video service technology from 3DTV, UHD TV, and hologram. These media, combined with space design, are able to offer us amazing and diverse experiences. In addition, now, there is a demand for more differentiated contents using human five senses recognition technology. We analyzed the application of realistic contents to space design. As a result, we have come to the conclusion that creative production which can express more fun and convenient will be an important issue.

• ETRI Journal
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• v.41 no.1
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• pp.23-31
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• 2019

Since the late 20th century, there has been rapid development in the display industry. Only 30 years ago, we used big cathode ray tube displays with poor resolution, but now most people use televisions or smartphones with very high-quality displays. People now want images that are more realistic, beyond the two-dimensional images that exist on the flat screen, and digital holography-one of the next-generation displaysis expected to meet that need. The most important parameter that determines the performance of a digital hologram is the pixel pitch. The smaller the pixel pitch, the higher the level of hologram implementation possible. In this study, we fabricated the world-smallest $3-{\mu}m$-pixel-pitch holographic backplane based on the spatial light modulator technology. This panel could display images with a viewing angle of more than $10^{\circ}$. Furthermore, a comparative study was conducted on the fabrication processes and the corresponding holographic results from the large to the small pixel-pitch panels.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.191-197
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• 2007

This study presents in-line digital particle holography and its application to spray droplets to measure the characteristics of spray droplets. Several important parameters at the time of hologram recording such as the object distance and the region of laser beam used were verified. The correlation coefficient method with important parameters such as the reconstruction interval and the correlation interval was used for determination of the focal planes of particles. The optimal values of all these parameters are obtained by either numerical simulation of holograms or experiments. Using these optimal parameters, double pulse digital spray holograms in a short time interval were recorded with the synchronization system for the time control. The spatial positions of droplets that are used for the evaluation of the three dimensional droplet velocities can be easily located, which proves the feasibility of the digital holographic technology for measurements of several important features of spray droplets.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.22-28
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• 2015

We propose a new method for improving the phase contrast of a multiphase digital holographic microscope using a spatial light modulator (SLM). Using the SLM as the annulus, our method improves the light contrast of the object edge to achieve higher accuracy. We demonstrate a digital holographic microscopy technique that provides a 30% improvement in the phase contrast compared to conventional microscopy, which utilizes a mechanical annulus. The phase-contrast improvement allows the 3D reconstructed hologram to be determined more precisely.

• Journal of Broadcast Engineering
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• v.28 no.1
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• pp.31-41
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• 2023

Directly converting the focal depth and image size of computer-generated-hologram (CGH), which is obtained by calculating the interference pattern of light from the 3D image, is known to be quite difficult because of the less similarity between the CGH and the original image. This paper proposes a method for separately converting the each of focal length of the given CGH, which is composed of multi-depth images. Firstly, the proposed technique converts the 3D image reproduced from the CGH into a Light-Field (LF) image composed of a set of 2D images observed from various angles, and the positions of the moving objects for each observed views are checked using an object detection algorithm YOLOv5 (You-Only-Look-Once-version-5). After that, by adjusting the positions of objects, the depth-transformed LF image and CGH are generated. Numerical simulations and experimental results show that the proposed technique can change the focal length within a range of about 3 cm without significant loss of the image quality when applied to the image which have original depth of 10 cm, with a spatial light modulator which has a pixel size of 3.6 ㎛ and a resolution of 3840⨯2160.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.146-151
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• 2011

We describe, throughout a Mach-Zehnder interferometric configuration, a new test sieves calibration method based on off-axis digital holography. The experiment is conducted on a test sieve of square openings. The nominal sieve opening is 1.00 mm with maximum individual opening of 1.14 mm in size. The recorded off-axis hologram is numerically processed using Fresnel transforms to obtain an object wave (amplitude and phase). From the reconstructed phase, the average size of the illuminated openings has been measured precisely. The proposed method can provide a real time solution for calibrating test sieves very precisely and with moderate accuracy.

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.136-146
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• 2008

We proposed an adaptive steganography of an optical image using bit-planes and multichannel characteristics. The experiment's purpose was to compare the most popular methods used in optical steganography and to examine their advantages and disadvantages. In this paper we describe two digital methods: the first uses less significant bits(LSB) to encode hidden data, and in the other all blocks of $n{\times}n$ pixels are coded by using DCT(Digital Cosine Transformation), and two optical methods: double phase encoding and digital hologram watermarking with double binary phase encoding by using IFTA(Iterative Fourier Transform Algorithm) with phase quantization. Therefore, we investigated the complexity on bit plane and data, similarity insert information into bit planes. As a result, the proposed method increased the insertion capacity and improved the optical image quality as compared to fixing threshold and variable length method.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.722-732
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• 2016

A new optical one-time password (OTP) authentication method using digital holography is proposed, which enhances security strength in the authentication system. A challenge-response optical OTP algorithm based on two-factor authentication is presented using two-step phase-shifting digital holography, and two-way authentication is also performed using challenge-response handshake in both directions. Identification (ID), password (PW), and OTP are encrypted with a shared key by applying phase-shifting digital holography, and these encrypted pieces of information are verified by each party by means of the shared key. The encrypted digital holograms are obtained by Fourier-transform holography and are recorded on a CCD with 256 quantized gray-level intensities. Because the intensity pattern of such an encrypted digital hologram is distributed randomly, it guards against a replay attack and results in higher security level. The proposed method has advantages, in that it does not require a time-synchronized OTP, and can be applied to various authentication applications. Computer experiments show that the proposed method is feasible for high-security OTP authentication.