• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.322-324
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• 2011

컴퓨터-생성 홀로그램(computer-generated hologram, CGH) 기법은 실사객체 혹은 가상의 객체로부터 계산에 의해 디지털 홀로그램을 생성해 낼 수 있다. 하지만 HD급 해상도의 디지털 홀로그램 한 프레임을 일반적인 PC를 이용해 계산하기 위해서는 약 10분 정도가 소요된다. 이는 실시간 홀로그래픽 비디오 서비스를 어렵게 하는 문제점 중에 하나이다. 본 논문에서는 CGH 기법의 과도한 연산량을 줄이기 위해 깊이정보(depth-map) 비디오 프레임간의 공간적인 중복성을 이용하는 방법을 제안한다. 이 방법은 인접한 깊이정보 프레임간의 차이를 구해 동일한 깊이값을 갖는 좌표들의 CGH 계산을 생략하는 것이다. 제안한 방법을 적용한 결과 연산속도가 52%정도 향상되는 것을 확인할 수 있었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.83-84
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• 2013

홀로그래픽 스테레오그램은, 양안 스테레오스코픽 영상들을 레이저 기준파와 간섭시켜 생성된 홀로그래픽 패턴을 감광매질인 홀로그래픽 필름에 기록한 후, 이를 다시 광학적 회절을 이용하여 3차원 영상으로 재현하는 3차원 디스플레이의 한 방법이다. 본 논문에서는 다시점의 full-color, full-parallax 영상을 디지털 방식의 스테레오그램으로 제작하여 3차원 입체 영상으로 재현하기 위한 기록 시스템에서, 기록 매질인 홀로그래픽 필름 면에서의 영상을 고해상도 영상 센서를 이용하여 직접 획득하고, 이 영상 정보를 분석하여 광축을 제어함으로써, 왜곡없는 최적의 호겔을 형성하여 높은 회절 효율을 갖는 스테레오그램을 제작하기 위한 방법 및 장치에 대한 연구개발 결과를 기술하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.108-110
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• 2013

본 논문에서는 3차원 입체 비디오 기술의 최종목표인 디지털 홀로그램 영상의 소유권 보호를 위한 디지털 워터마킹 알고리즘을 제안한다. 제안한 워터마킹 알고리즘은 디지털 홀로그램의 Fresnelet 변환 영역에서 악의적인 공격들에 대해 강한 내성을 가지는 계수 정보들을 이용하여 워터마킹 정보를 추출하여 사용한다. 제안한 알고리즘으로 압축 등의 공격을 수행하여 본 워터마킹 알고리즘의 강인성을 검증하였다. 실험 결과 제안한 디지털 홀로그램 워터마킹 알고리즘은 대부분의 공격들에 대해 매우 강한 내성을 보였다.

• International Journal of Contents
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• v.11 no.1
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• pp.15-20
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• 2015

The purpose of this research is to study methods for performing transition that have visual representation of corresponding animations with no bounce in subsequently recognized user information when attempting to interact with a virtual 3D character in real-time using user motion. If the transitions of the animation are needed owing to a variety of external environments, continuous recognition of user information is required to correspond to the motion. The proposed method includes linear interpolation of the transition using cross-fades and blending techniques. The normalized playing time of the source animation was utilized for automatically calculating the transition interpolation length of the target animation and also as the criteria in selecting the crossfades and blending techniques. In particular, in the case of blending, the weighting value based on the degree of similarity between two animations is used as a blending parameter. Accordingly, transitions for visually excellent animation are performed on interactive holographic projection systems.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.25-26
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• 2006

Azobenzene functionalized polymers have been extensively investigated due to the potential applications in the areas of optical switching, optical elements, optical information storage, and nonlinear optics. These applications are mainly achievable due to photoinduced properties of azobenzene groups with photoisomerization and photoinduced anisotropy. We report applications to the optoelectronic devices using inscribed one-(1D) and two-dimensional (2D) SRGs on azo polymer films. The inscribed holographic SRGs patterns were useful to control or enhance optoelectronic properties such as transparent electrode patterning, hybrid solar cell and ultraviolet GaN-based LED.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.169-169
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• 2006

Novel liquid crystalline malonic ester monomers were synthesized from malonyl dichloride and mesogenic alcohols as a photoresponsive group. The monomers were polymerized with aliphatic or aromatic dibromides in the presence of sodium hydride to give 8 kinds of novel poly(malonic esters) with two symmetrical azobenzene groups. We found that the resulting polymer films could be used as rewritable optical data storage (or holographic image) media through a photoisomerization of azobenzene group by Ar laser irradiation. The sensitivity of data recording was dependent not only on the thickness of the polymeric thin film but also on the intensity of laser beam.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.164-164
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• 2006

Polymeric photorefractive materials exhibit two attractive features, the large refractive index modulation (up to the order of $10^{-2}$) and the optical erasabilility of recorded holographic information. These advantages make the organic photorefractive materials to become candidates for optical data processing, e.g., pattern recognition and fingerprint verification. In this work, we demonstrate optically controlled SLMs using photorefractive composite. An incoherent image imposed in Xe-lamp light was converted into a coherent image.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.698-705
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• 2014

We propose a new development for calculating a computer-generated hologram (CGH) through the use of multiple general-purpose graphics processing units (GPGPUs). For optimization of the implementation, CGH parallelization, object point tiling, memory selection for object point, hologram tiling, CGMA (compute to global memory access) ratio by block size, and memory mapping were considered. The proposed CGH was equipped with a digital holographic video system consisting of a camera system for capturing images (object points) and CPU/GPGPU software (S/W) for various image processing activities. The proposed system can generate about 37 full HD holograms per second using about 6K object points.

• Current Optics and Photonics
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• v.4 no.2
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• pp.103-114
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• 2020

A new optical asymmetric cryptosystem is proposed by modifying the asymmetric RSA public-key protocol required in a cryptosystem. The proposed asymmetric public-key algorithm can be optically implemented by combining a two-step quadrature phase-shifting digital holographic encryption method with the modified RSA public-key algorithm; then two pairs of public-private keys are used to encrypt and decrypt the plaintext. Public keys and ciphertexts are digital holograms that are Fourier-transform holograms, and are recorded on CCDs with 256-gray-level quantized intensities in the optical architecture. The plaintext can only be decrypted by the private keys, which are acquired by the corresponding asymmetric public-key-generation algorithm. Schematically, the proposed optical architecture has the advantage of producing a complicated, asymmetric public-key cryptosystem that can enhance security strength compared to the conventional electronic RSA public-key cryptosystem. Numerical simulations are carried out to demonstrate the validity and effectiveness of the proposed method, by evaluating decryption performance and analysis. The proposed method shows feasibility for application to an asymmetric public-key cryptosystem.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.10
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• pp.1576-1583
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• 1989

In this paper, we describe real-time optical implementation of the Hopfield neural network model for two-dimensional associative memory by using commercial LCTV and Multifocus For real-time processing capability, we use LCTV as a memory mask and a input spatial light modulator. Inner product between input pattern and memory matrix is processed by the multifocus holographic lens. The output signal is then electrically thresholded fed back to the system input by 2-D CCD camera. From the good experimental results, the proposed system can be applied to pattern recognition and machine vision in future.