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컴퓨터 홀로그래피와 프레넬 회절을 이용한 위상 영상 광 암호화 시스템
윤경효,신창목,조규보,김수중,김철수,서동환 대한전자공학회 2004 電子工學會論文誌-SD (Semiconductor and devices) Vol.41 No.11
In this paper, we propose a high-level optical encryption system, which is tolerant with noises and cropping, by encrypting the phase-encoded CGH pattern of original image with the phase-encoded Fresnel diffraction pattern of random key images. For encryption, the phase-encoded CGH pattern of original image is multiplied by conjugate components which are the phase-encoded Fresnel diffraction patterns of random key images. The original information can be reconstructed by multiplying encrypted image by phase-encoded Fresnel diffraction pattern of random key images and performing Fourier transform of the multiplication result. The proposed system is robust to noises and cropping due to characteristics of CGH pattern and can guarantee high-level encryption by using Fresnel diffraction information. We verified the validity of proposed system by computer simulations, numerical analysis of noises and cropping effect and optical experiment. 본 논문에서는 원 영상의 컴퓨터 생성 홀로그램(computer generated hologram; CGH) 패턴을 위상 변조한 후, 위상 부호화한 무작위 키 영상들의 프레넬 회절(Fresnel difftaction) 위상 패턴과 곱하여 암호화함으로써 외부 교란이나 절단에 강하고, 암호화 수준이 높은 광 암호화 방법을 제안하였다. 암호화시 원 영상의 이진 CGH패턴을 위상 변조한 후, 이를 위상 키 영상들의 프레넬 회절 공액 위상정보와 곱하며, 복호화시 암호화 영상에 위상 키 영상들의 프레넬 회절 위상 정보를 다시 곱한 후 푸리에 변화시켜 원 영상 정보를 얻는다. 암호화 영상은 CGH 패턴 특성을 가지므로, 절단이나 외부 잡음에 강하며 프레넬 회절 정보를 이용하여 암호화함으로 높은 암호화 수준을 가진다. 컴퓨터 모의 실험을 통해 제안한 방법의 타당성을 확인하였으며 절단과 잡음에 대한 영향을 분석하였고, 위상 변조 특성이 있는 LCD를 사용하여 광학적으로 구현하였다.
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강혁,이근호,kang, Hyeok,Lee, Keun-Ho 한국사물인터넷학회 2016 한국사물인터넷학회 논문지 Vol.2 No.1
빛의 물리적 성질 중의 하나인 파동의 회절 현상을 설명하는 프레넬 회절과 간섭에 의해 생성되는 무아레 무늬가 있다. 본 논문에서는 무아레 무늬에서 생성되어지는 값들을 암호 시스템에서 사용되는 키로, 의사 난수 발생기에서 생성한 난수가 아닌 참난수로 만들어 사용할 수 있음을 제안한다. There is Generated Moire fringe by fresnel diffraction that explains one of light's physical phenomenon and interference. In this paper, we propose to generate true random numbers by Moire fringe should be used by not pseudo-random number in cryptosystem.
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Fresnel 영역에서의 SDTA 방법을 이용한 전산묘사에 의한 Surface Relief Hologram Mask 기록 조건 최적화
Lee, Sung-Jin,Dominguez-Caballero, Jose,Barbastathis, George 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.8
In this paper, the simulation and optimization of SRH (Surface Relief Hologram) masks for printing LCD gate patterns using TIR (Total Internal Reflection) holographic lithography was investigated. A simulation and optimization algorithm based on SDTA (Scalar Diffraction Theory Analysis) method was developed. The accuracy of the algorithm was compared to that of the RCWA (Rigorous Coupled Wave Analysis) method for estimating the Fresnel diffraction pattern of Cr amplitude masks for the given system geometry. In addition, the results from the optimization algorithm were validated experimentally. It was found that one to the most important conditions for the fabrication of SRH masks is to avoid nonlinear shape distortions of the resulting grating. These distortions can be avoided by designing SRH masks with recorded gratings having small aspect ratios of width versus depth. The optimum gap size between the Cr and SRH masks was found using the optimization algorithm. A printed LCD gate pattern with a minimum line width of $1.5{\mu}m$ exposed using the optimized SRH mask was experimentally demonstrated.
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Seok-Tae Park(박석태) 한국소음진동공학회 2024 한국소음진동공학회 논문집 Vol.34 No.2
The sound pressure measured at the near field exhibits significant fluctuation depending on the size and frequency of the sound source. Therefore, it is necessary to use the sound pressure measured or numerically calculated at a sufficient distance from a radiator to estimate the actual sound power of the source. In this study, we investigated the appropriate distance for measuring or numerically calculating the sound pressure to validly estimate the sound power of a radiator, which depends on the frequency. A theoretical estimation of the starting position of the far-field acoustic characteristics for rigid disk vibrations was conducted, and the results were numerically compared and reviewed using the Rayleigh integral method (RIM) and lumped parameter method (LPM). The analysis using these methods, with modeling based on the 1/3 wavelength rule, demonstrated accurate predictions of the near-field acoustic characteristics. It was shown that the near sound field could be accurately predicted by modeling and analyzing under the condition of the 1/3 wavelength rule using the RIM and LPM. It was found that even when elements were modeled at a larger size than the 1/3 wavelength rule, the far-field sound pressure result could effectively depict the theoretical far-field sound pressure in the case of the RIM. It was also shown that the sound pressure due to the vibration of a flexible circular disk modeled with an element size based on the 1/3 wavelength rule was well predicted by both the LPM and RIM.
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렌즈 수차에 의한 타일형 빔 결합 출력 감쇠와 왜곡 현상 분석
김병호,나정균,정윤찬 한국광학회 2020 한국광학회지 Vol.31 No.6
In this paper, we quantitatively analyze the effect of lens aberration on the degradation of beam-coupling efficiency of a tiled coherent-beam combining system. The Zernike polynomial is used to quantify the aberration of the lens, and Fresnel diffraction is applied to numerically simulate the change in the peak light intensity when combined at a distance. The results of this paper will be useful for quantitative prediction of the beam-combining efficiency that is degraded by aberration of the lens, and it is expected to be helpful for the optimal design of a practical tiled coherent beam-combining system.
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Fresnel 영역에서의 SDTA 방법을 이용한 전산묘사에 의한 Surface Relief Hologram Mask 기록 조건 최적화
이성진(SungJin LEE),Jose Dominguez-Caballero,George Barbastathis 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.8
In this paper, the simulation and optimization of SRH (Surface Relief Hologram) masks for printing LCD gate patterns using TIR (Total Internal Reflection) holographic lithography was investigated. A simulation and optimization algorithm based on SDTA (Scalar Diffraction Theory Analysis) method was developed. The accuracy of the algorithm was compared to that of the RCWA (Rigorous Coupled Wave Analysis) method for estimating the Fresnel diffraction pattern of Cr amplitude masks for the given system geometry. In addition, the results from the optimization algorithm were validated experimentally. It was found that one to the most important conditions for the fabrication of SRH masks is to avoid nonlinear shape distortions of the resulting grating. These distortions can be avoided by designing SRH masks with recorded gratings having small aspect ratios of width versus depth. The optimum gap size between the Cr and SRH masks was found using the optimization algorithm. A printed LCD gate pattern with a minimum line width of 1.5㎛ exposed using the optimized SRH mask was experimentally demonstrated.
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