• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.5
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• pp.45-45
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• 2001

본 논문에서는 높은 회절 효율과 균일도를 갖는 컴퓨터 생성 홀로그래픽 디퓨저를 수정된 반복 푸리에 변환 알고리즘으로 설계하였다. 컴퓨터 생성 홀로그래픽 디퓨저를 설계하기 위한 새로운 방법으로 위상형 홀로 그램들을 대칭, 결합시킴으로서 계산시간을 감소시켰고 재생되는 신호 영역을 확장하였다. 설계한 16 위상형 홀로그래픽 디퓨저는 85.20%의 높은 회절 효율과 2.43%의 균일도, 18.97［㏈］의 평균 신호대 잡음비를 나타내었다. 또한, 컴퓨터 생성 홀로그래픽 디퓨저와 128 단계를 갖는 유사 랜덤 위상 디퓨저를 회절 효율과 균일도 측면에서 비교하였고, 홀로그래픽 디퓨저와 차세대 디스플레이용 소자로서 유용하게 이용될 수 있음을 제시하였다.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.17-24
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• 2001

Two-dimensional binary-phase diffraction gratings which can be employed to fabricate two- and three-dimensional periodic structures are designed and analyzed using rigorous coupled-wave analysis. These gratings serve as phase-masks which generate several diffracted waves from a normally incident beam and thus can produce a periodic interference pattern in space via nearfield holography. The properties of the diffracted beams can be controlled by varying the polarization and wavelength of the incident beam, surface-profile, groove depth and duty cycle of the mask. For the two-dimensional structure, optimum results can be obtained when the diffraction efficiency of the zero-order beam is minimized while that of the first-order maximized. On the other hand, when the diffraction efficiency of the zero-order is appreciable or even greater than other orders, we can obtain a variety of three-dimensional interference patterns which may be used to fabricate photonic crystals of tetragonal-body-centered and hexagonal structures in a submicron scale. scale.

• Korean Journal of Optics and Photonics
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• v.31 no.4
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• pp.169-175
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• 2020

We design a polarization-independent dielectric multilayer thin-film diffraction grating for a spectral-beam-combining (SBC) system with a simple grating structure and low aspect ratio. To maintain the high quality of the SBC beam, we propose a multilayer mirror structure in which the wavefront distortion due to stress accumulation is minimized. Moreover, to prevent light absorption from contamination, an optimized design to minimize the grating thickness was performed. The optimally designed diffraction grating has 99.36% diffraction efficiency for -1st-order polarization-independent light, for incidence at the Littrow angle and 1055-nm wavelength. It is confirmed that the designed diffraction grating has sufficient process margin to secure a polarization-independent diffraction efficiency of 96% or greater.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.331-336
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• 1995

The steady-state absorption saturation of the photodarkend SDG was investigated. The absorption saturation intensity was observed to increase for the photodarkened sample. The diffraction efficiency of the permanent grating due to photodarkening was also measured using the backward DFWM technique. For the low backward pump intensity, the diffraction efficiency was proportional to the intensity of the pump beam. The origin of increasing diffraction efficiency is attributed to the difference in absorption between the permanent gratings created by photodarkening. ening.

• Korean Journal of Optics and Photonics
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• v.28 no.5
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• pp.241-249
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• 2017

This paper presents the design and evaluation of the optical system for an uncooled thermal-imaging camera. The operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through optimization, we have obtained a LWIR (Long Wave Infrared) optical system with a focal length of 5.44 mm, which consists of four aspheric surfaces and two diffractive surfaces. The f-number of the optical system is F/1.2, and its field of view is $90^{\circ}{\times}67.5^{\circ}$. The hybrid lens was used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We calculated the polychromatic integrated diffraction efficiency, and the MTF drop generated by background noise. We have evaluated the thermal compensation of a LWIR fixed optical system, which is optically passively athermalized to maintain MTF performance in the focal depth. In conclusion, these design results are useful for an uncooled thermal-imaging camera.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.435-436
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• 2018

In this paper, diffraction efficiency for computer-generated hologram (CGH) generated under various conditions was measured. This paper discusses the generation conditions that should be considered in hologram reconstruction. We compared each condition by measuring the intensity of the 1st order diffraction pattern of the fringe generated under the Fresnel condition for the phase and complex hologram.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1637-1642
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• 2010

In this paper, we present the fabrication of a high-quality diffractive-lens mold having submicron patterns, which is suitable for an ultra-slim optical system. In order to fabricate high-quality diffractive lens with a variety of submicron patterns, the multi-alignment method was used; high-resolution electron-beam lithography and FAB plasma etching were carried out to obtain the patterns. The most important key technology in the multi-alignment method is to reduce alignment error, lithography error, and etching error. In this paper, these major fabrication errors were minimized, and a high-quality diffractive lens with a diameter of $267\;{\mu}m$ (NA = 0.25), minimum pattern width of 226 nm, and thickness of 819 nm was successfully fabricated.

• Korean Journal of Optics and Photonics
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• v.31 no.4
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• pp.176-182
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• 2020

The possibility of replacing the condensing-prism film used in conventional backlight units with a light-guide plate engraved with a submicrometer-periodic diffraction grating was investigated. The optimal period for the diffraction grating was determined through simulation and experiment, and the transmission-mode efficiency of the diffraction grating was calculated in terms of the polar angle and azimuthal angle of the incident light. In addition, the effects of the two methods of optimizing the polar angle and the directional angle were compared by simulation, by suggesting the shape and configuration of the light-guide plate, so that more light could be extracted by diffraction. By using a ray-tracing program, the luminance angular distribution of the light-guide plate engraved with the diffraction grating was calculated and compared to the luminance angular distribution for each actual prototype.

• Journal of KSNVE
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• v.8 no.1
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• pp.29-35
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• 1998

본 원고에서는 여러 소음 규명론에서 간과하기 쉬운 회절현상(diffraction phenomena)에 대해 알아보고, 이러한 회절현상을 이용한 소음원 규명을 제안하고자 한다. 즉 소음원 규명론의 일반적인 개념으로 생각하면 회절현상을 하나의 전달함수로 보고, 이를 바탕으로 역전달 함수인 역회절현상(inverse diffraction phenomena)을 수치적으로 모델링한다. 이 방법은 실제 실험에서 계측된 음압과 역회절 모델을 이용하여 소음원을 규명하는 방법이다. 소음원 탐지의 문제점 가운데 하나는 소음원의 가시화 일것이다. 이 논문에서는 3차원 공간에서 사용자가 쉽게 인식할 수 있는 두가지 소음원 가시화 방법을 소개한다. 간단한 실험을 통하여 이 방법의 효율성을 검증해 보고, 이를 바탕으로 TGV객실내에서의 소음원 규명을 수행한다.

• Korean Journal of Optics and Photonics
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• v.6 no.2
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• pp.108-114
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• 1995

규칙적인 간격이 $M\timesN$ 이차원패턴과 임의 모양 빔 스폿을 발생시키기 위해 일반적인 이차원 Dammann 격자보다 재구성 에러가 작고, 높은 효율을 보이는 줄무늬형 격자를 설계하였다. 회절효율은 일반적인 이차원 Dammann 격자의 효율보다 평균 15-20% 정도 높은 60% 이상을 얻었다. 설계된 격자는 컴퓨터 시뮬레이션을 통해 회절특성을 확인하였으며 우수한 패턴 발생 결과가 확인되었다. $3\times3에서 11\times11$까지의 규칙적인 스폿 배열과 문자열에 대한 효율, 계산 시간 및 표준편차를 비교분석하였다.