• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.194-198
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• 1997

We realized CGH display of moving objects with an optical addressed spatial light modulator. CGH was calculated by the horizontal parallex method for saving a calculating time, and calculation speed was improved by making a lookup table of trigonometric function and root calculation. This lookup table was applied to a low resolution SLM, and succeeded in a simultaneous display of the three hologram images by the scanning method.

• Current Optics and Photonics
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• v.5 no.2
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• pp.134-140
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• 2021

In this paper, I introduce a novel design method of a high performance nanophotonic beam deflector providing broadband operation, large active tunability, and signal efficiency, simultaneously. By combining thermo-optically tunable vanadium dioxide nano-ridges and a metallic mirror, reconfigurable local optical phase of reflected diffraction beams can be engineered in a desired manner over broad bandwidth. The active metagrating deflectors are systematically designed for tunable deflection of reflection beams according to the thermal phase-change of vanadium dioxide nano-ridges. Moreover, by multiplexing the phase-change supercells, a robust design of actively tunable beam splitter is also verified numerically. It is expected that the proposed intuitive and simple design method would contribute to development of next-generation optical interconnects and spatial light modulators with high performances. The author also envisions that this study would be fruitful for modern holographic displays and three-dimensional depth sensing technologies.

• Electronics and Telecommunications Trends
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• v.37 no.4
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• pp.81-88
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• 2022

In this study, we investigate the trends and prospects of spatial light modulation (SLM) technology that enables full complex modulation as a next-generation SLM. Current SLM technology, which is used as a key element in holography, augmented reality (AR), XR, and realistic displays, has performance limits that modulate only amplitude or phase. Notably, SLM capable of full complex modulation does not produce diffraction noise, unlike DC and twin image, and thus has a high-efficiency performance. In the future, the application field of next-generation SLM, which can be full-complex modulated, is expected to cover a wide range of holography-AR and-XR devices, optical artificial intelligence, and 6G free space optics communications, which will greatly contribute to the development of a super-realistic metaverse platform and service.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.7-14
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• 2008

In this paper, a new high resolution XGA-SLM is implemented through modification of a commercial TFT-LCD beam projector and its optical modulation characteristics as a spatial light modulator(SLM) is also analyzed. That is, the optics module, projection lamp and fans are removed from a commercial beam projector and instead, some electric circuits to compensate their removal are manufactured and then, by inserting them into the beam projector, a new XGA-SLM is finally implemented. From some characteristic experimental results of the implemented high resolution TFT-LCD SLM, the proposed TFT-SLM is found to have an good optical linearity in amplitude and phase modulation characteristics as a function of the input gray levels. Especially, through implementation of the suggested TFT-LCD panel, the implemented SLM is proposed as a new relatively low-cost and high resolution SLM for optical information processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5C
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• pp.716-725
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• 2004

In this paper, a new multiview stereoscopic 3D display system using a VHLS(volume holographic lenticular sheet) is suggested. The VHLS, which acts just like an optical direction modulator, can be implemented by recording the diffraction gratings corresponding each directional vector of the multiview stereoscopic images in the holographic recording material by using the angularly multiplexed recording property of the conventional volume hologram. Then, this fabricated VHLS is attached to the panel of a LCD spatial light modulator and used to diffract each of the multiview image loaded in a SLM to the corresponding spatial direction for making a 3D stereo view-zone. Accordingly, in this paper, the operational principle and characteristics of the VHLS are analyzed and an optimized 4-view VHLS is fabricated by using a commercial photopolymer. Then, a new VHLS-based 4-view stereoscopic 3D display system is implemented. Through some experimental results using a 4-view image synthesized with adaptive disparity estimation algorithm, it is suggested that implementation of a new VHLS-based multiview stereoscopic 3D display system can be possible.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.12
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• pp.43-52
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• 1999

We propose a new method for tuning of center wavelength in photorefractive filter using $LiNbO_3$ crystal doped with 0.015Wt.% Fe. through the filter bandwidth property analysis using the geometrical method, a new wavelength selectivity theory was presented. In this scheme, the tuning of the center wavelength can be achieved by the real time incident angle control of the received heam, which was gotten by the spatial light modulator. So, tuning time depend on the response time of the SLM and results in the high speed turing. Because the use of thermally fixed grating in our filter, it has uniform diffraction property to the all filtering wavelength. Designed tunable filter has 4nm bandwidth and composed of the three channel with 10nm space. From the optical experiment, we get the 4.5nm, 4.25nm, 4nm bandwidth and 1530.5nm, 1540.5nm, 1549.5nm center wavelength respectively.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.29-37
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• 2015

The wavefront printer records a volume-reflection hologram as a two-dimensional array of elemental holograms from computer-generated holograms (CGHs) displayed on a spatial light modulator (SLM). The wavefront coming from the object is extracted by filtering in the spatial-frequency domain. This paper presents a method to improve color reproduction in a wavefront printer with spatial division of exposures at primary colors, by adaptive partitioning of the SLM in accordance with the color content encoded in the input CGHs, and by the controllable change of exposure times for the recording of primary colors. The method is verified with a color wavefront printer with demagnification of the object beam. The quality of reconstruction achieved by the proposed method proves its efficiency in eliminating the stripe artifacts that are superimposed on reconstructed images in conventional mosaic recording.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.955-963
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• 2008

In this paper, we propose an improved practical encryption and fault-tolerance decryption method using a non-negative value key and random function obtained with a white noise by using iterative phase wrapping method. A phase wrapping operating key, which is generated by the product of arbitrary random phase images and an original phase image. is zero-padded and Fourier transformed. Fourier operating key is then obtained by taking the real-valued data from this Fourier transformed image. Also the random phase wrapping operating key is made from these arbitrary random phase images and the same iterative phase wrapping method. We obtain a Fourier random operating key through the same method in the encryption process. For practical transmission of encryption and decryption keys via Internet, these keys should be intensity maps with non-negative values. The encryption key and the decryption key to meet this requirement are generated by the addition of the absolute of its minimum value to each of Fourier keys, respectively. The decryption based on 2-f setup with spatial filter is simply performed by the inverse Fourier transform of the multiplication between the encryption key and the decryption key and also can be used as a current spatial light modulator technology by phase encoding of the non-negative values. Computer simulations show the validity of the encryption method and the robust decryption system in the proposed technique.

• Electronics and Telecommunications Trends
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• v.31 no.6
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• pp.48-56
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• 2016

디지털 홀로그래피가 아날로그 홀로그래피와 비슷한 품질을 나타내기 위해서는 $1{\mu}m$의 픽셀피치를 가지고 있는 대면적 SLM 개발이 필수적이다. 이러한 대면적 초고해상도 SLM을 구현하기 위해서는 최근 미세 픽셀 기술이 급격히 발전하고 있는 대면적 지향의 평판디스플레이 기술을 기반으로 개발되어야 할 것으로 생각된다. 디스플레이 기술을 기반으로 스티칭 기술 등의 포토리소그래피 기술과 수직채널 TFT등의 구동 소자 기술, 고굴절율 이방성을 가지는 액정 소재 기술, 모듈 기반의 구동 기술 등을 집약하여 $1{\mu}m$급의 픽셀 피치를 가지는 대면적 초고해상도 SLM을 개발 중이다. 이렇게 개발된 초고해상도 대면적 SLM은 홀로그램 영상 재현 이외에도 다양한 광학 소자로 응용이 기대된다.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.102-111
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• 1990

In this thesis, an optical bidirectional inner-product associative memory model using liquid crystal television is proposed and analyzed theoretically and realized experimentally. The LCTV is used as a SLM(spatial light modulator), which is more practical than conventional SLMs, to produce image vector in terms of computer and CCD camera. Memory and input vectors are recorded into each LCTV through the video input connectors of it by using the image board. Two multi-focus hololenses are constructed in order to perform optical inner-product process. In forward process, the analog values of inner-products are measured by photodetectors and are converted to digital values which are enable to control the weighting values of the stored vectors by changing the gray levels of the pixels of the LCTV. In backward process, changed stored vectors are used to produce output image vector which is used again for input vector after thresholding. After some iterations, one of the stored vectors is retrieved which is most similar to input vector in other words, has the nearest hamming distance. The experimental results show that the proposed inner-product associative memory model can be realized optically and coincide well with the computer simulation.