• 정보저장시스템학회논문집
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• 제1권2호
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• pp.143-149
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• 2005

In this paper we propose a novel volume hologram encryption system with binary amplitude masks rather than phase masks, in which volume holograms can be securely recorded against the attacks by a third party. In our system, the encryption is done by multiplexing two volume holograms in such a way that an original binary data page is first stored as a volume hologram by interference with a binary amplitude mask and then the complementary data page is stored as another volume hologram by interference with the complementary binary amplitude mask over the first hologram. The operation principle of our system is explained with the well-known theory of recording and reading a volume hologram in a photorefractive material and the experimental results are presented. Experimental data show that our encryption system is protected from blind decryptions by randomly-generated incorrect amplitude masks.

• 전자공학회논문지D
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• 제34D권11호
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• pp.48-53
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• 1997

Volume hologram was recorded using reference beam form optical fiber taper. A singel mode fiber was chemically etced to make a taper structure, and we showed experimentally that the referencing by the irregular beam pattern from this taper structure could increase the storage density of photorefractive volume hologram. The spatial selectivity of the volume hologram with this method was increased by two times compared to the normal single mode fiber referencing case. A theoretical analysis with randomly phased plane model also confirmed the results.

• 한국광학회지
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• 제8권3호
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• pp.241-244
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• 1997

체적 홀로그램을 저장하고 재생하는데 있어서 광섬유에서 유도되는 스페클 패턴을 이용하는 것을 제안하고, 이를 이론 및 실험적으로 연구하였다. 기준빔으로 광섬유에서 회절되는 스페클 패턴을 이용한 홀로그램 위치 다중화 구조는, 스페클 패턴의 상대적 위치 차이에 따라 상관 관계가 없어지는 특징을 이용하기 때문에 좋은 횡방향 위치 선택도를 가지게 하며 축방향 움직임에 대해서는 둔감한 안정성을 보여준다. 따라서 이러한 구조를 광 정보 저장 장치에 적용하면 저장 밀도를 높일 수 있으며 홀로그램 재생시의 안정도를 증가시킬 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.203-206
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• 2003

This study is focused on proposing a creative system that can display 3D hologram on the real-time basis. This method applies 3D display on volume hologram based on CGH. The process of implementing the system consists of two stages of fringe pattern recording for passive component that includes information on hologram, and irradiating object beam. Distinguished from an existing electronic holographic display system, this system is free from the process of a huge calculation that is necessary to compose CGH for a real-time 3D display.

• International Journal of Advanced Culture Technology
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• 제10권4호
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• pp.460-469
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• 2022

Increasing interest in the metaverse world these days, interest in realistic content such as 3D displays is growing. In particular, hologram images seen in movies provide viewers with an immersive display that cannot be seen in conventional 2D images. Since the first discovery of holography by Dennis Gabor in 1948, this technology has developed rapidly. Spatially, this beginning of technology like Optical hologram called analog hologram and Digital hologram such as computer-generated hologram (CGH). In analog and digital holograms, a recording angle and a recording wavelength are having important role when reproducing and display hologram. In the hologram, diffraction of light causes by unexpected formed by the synthesis from interference with object and reference light. When recording, the incident light information and mismatched reproduction light reconstruct the hologram in an undesirable direction. Reproduction light that is out of sync with incident light information with initial condition of recording will cause reconstructed image in an undesirable direction. Therefore, we analyze the holographic interference pattern generated by hologram recording in volume holograms using photopolymer and analyze the characteristics that vary depending on the angle of the reproduced light. This is expected to be used as a basic research on various holographic application that may cause as holograms are applied to industries in the future.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.1005-1008
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• 2002

The authors introduce 3D display systems developed in our laboratories for recent ten years. Those are mainly realized by several technologies in holography: electro-holography. holographic stereogram, holographic optical elements (HOE) and hologram screen. We are currently focusing the development of 3D projection screen without glasses. Powerful directionality of the light beam is required for 3D projection screen unlike 2D type. We succeeded in achieving the superior diffractive efficiency of hologram screen that is based on the advanced volume holography. This technology is extensively useful to retrieve the Bragg condition of volume hologram in the three-dimensional space. Owing to this technology we could establish the principle of multi-view projection screen and have confirmed the case of 4 viewing points.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.365-367
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• 1993

The wavelength dependence of the diffracted light in volume hologram is important in application of volume hologram, because the wavelength dependence of the diffracted light can be used to select a certain wavelength from white-light which is composed of a lot of wavelengths. Some experiments are done to analyze the wavelength dependence of diffracted lights. The coupled wave theory is used to make a theoretical approach to this model. Compared with the theoretical result, the experimental result makes a good agreement with it.

• 한국컴퓨터산업학회논문지
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• 제2권12호
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• pp.1609-1616
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• 2001

본 논문에서는 체적 홀로그램을 이용한 무안경 3차원 디스플레이 시스템을 제안하였다. 디스플레이 평면에서 다시점 스테레오 영상을 관찰할 수 있도록 각 다중화된 기준파와 물체파를 간섭시킨 후 격자 패턴을 체적홀로그램에 기록하였다. 디스플레이 하고자 하는 다안식 영상으로 구성된 물체파가 시분할적으로 update 되며 광굴절 매질에 입사될 때 브래그 조건을 만족시키면, 출력 평면에서는 회절된 영상으로부터 다안식 3차원 영상을 관찰할 수 있다. 본 시스템을 이용함으로써 시점의 증가에 따른 해상도의 저하가 없는 고해상 다시점 3차원 디스플레이를 구성할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.379-381
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• 1994

Volume holograms recorded in photorefractive materials can find important applications in optical memories and optical computing systems. One problem with a photorefractive hologram is that it gets erased by the readout light. Nondestructive readout can be achieved by hologram fixing, and several fixing methods have been reported. Fixing is accomplished by thermally activated motion of an unknown ionic defect, which neutralizes the electronic space-charge patterns. At room temperature the ionic patterns are stabilized. When the electrons are partially redistributed by light, a net space-charge pattern appears, and tile fixed hologram can be read out. In this paper, theoretical modeling and some experimental results are presented for thermal fixing of volume phase holograms in photorefractive $LiNbO_3$:Fe. Thermal fixing can be done during or after recording and depends on fixing temperature ($100{\sim}200^{\circ}C$ range) and grating length. Fixed Slating can be erased completely at the temperature over $300^{\circ}C$. Theoretical modeling shows weil the compensation of electronic Slating by ionic grating and is in good agreement with experimental results. In experiments the dependence of thermal fixing on temperatures and grating lengths is investigated.

• 디지털산업정보학회논문지
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• 제5권2호
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• pp.51-76
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• 2009

In this paper, a new hybrid opto-digital multiple information hiding and real-time extracting system was suggested and implemented using a volume holographic optical correlator. The multiple information hiding system in which the multiple information can be hided in an arbitrary cover image was digitally implemented by using the combination of pseudo random sequence and Hadamard matrix. In addition, a real-time optical extraction system in which the hided multiple information in a cover image can be extracted in real-time was implemented by using a volume holographic optical correlator. In the VanderLugt-type holographic optical correlator used in this experiment, the multiful matched spatial filters corresponding each of the hided informations were recorded in a photorefractive crystal by using the moving window-based angular multiplexing scheme.