• 반도체디스플레이기술학회지
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• 제9권1호
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• pp.17-21
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• 2010

Currently miniaturized electron-optical columns find their way into electron beam lithography systems. For better lithography process, it is required to make smaller spot size and longer working distance. But, the micro-columns of the multi-beam lithography system suffer from chromatic and spherical aberration, even when the electron beam is exactly on the symmetric axis of the micro-column. The off-axis error of the electron emitting source is expected to become worse with increasing off-axis distance of the focusing spot. Especially the electron beams far from the system optical axis have a non-negligible asymmetric intensity distribution in the micro-column. In this paper, the effect of the off-axis e-beam source is analyzed. To analyze this effect is to introduce a micro-column model of which the e-beam emitting source is aligned with the center of the electron beam by shifting them perpendicular to the system optical axis. The presented solution can be used to analysis the performance of the multi-electron-beam system. The performance parameters, such as the working distances and the focusing position are obtained by the computational simulations as a function of the off-axis distance of the emitting source.

• 한국광학회지
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• 제25권2호
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• pp.85-89
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• 2014

본 논문에서는 광 스캐닝 홀로그래피 기술을 이용하여 실제 반사형 물체의 복소 홀로그램을 스펙클 잡음 없이 촬영하고 데이터양을 줄이면서 동시에 일반적인 진폭 유일 공간 광 변조기를 이용해 광학적인 방법으로 복원할 수 있도록 탈축 수평 시차 홀로그램으로 변환하였다. 변환된 탈축 수평 시차 홀로그램이 공간상에 복원되어 디스플레이가 될 수 있음을 보이기 위하여 수치적인 방법을 이용하여 홀로그램을 복원하였다.

• 한국광학회지
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• 제26권3호
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• pp.155-161
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• 2015

본 논문에서는 연안 지역 저고도 원격측정을 위한 소형 무인항공기 용 초분광센서 개발의 일환으로 비축 삼반사경 전단광학계의 설계와 성능분석 결과를 제시하였다. 이 광학계는 수 cm의 공간해상도(4cm@500m 운영고도)와 $4^{\circ}$의 시야각, 그리고 신호대 잡음비 100(@660 nm) 이상의 요구사항을 만족시키기 위하여, 70 mm의 입사동 크기와 개구수 5.0으로 설계 사양을 가지는 비구면의 주경과 부경이 포함된 비축 삼반사경 형태로 설계되었다. 본 설계의 광학성능은 $1/15{\lambda}$ 이하 RMS 파면오차 성능과 0.75이상의 MTF 성능(@660 nm)이 기대된다. 제작과 조립 단계를 고려하여 민감도 분석을 통해 3 반사경을 정렬 보상자로 선정하였으며, 경사 공차범위는 요소별로 0.17 mrad 으로 결정되었다. 이 비축 삼반사경 광학설계는 기존 초분광센서의 전단광학계에 비해 높은 광학성능을 보이고, 소형 무인항공기에 맞추어 경량화가 가능하도록 제작 기반을 설정하여, 향후 연안 원격탐사 연구에 활용될 예정이다.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.604-613
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• 2015

An unobstructed off-axis two-mirror system is presented in this paper. First a suitable initial configuration is established based on third-order aberration theory. In order to achieve a wide field of view (FOV) with high image quality , the diffractive mirror is adopted in the two-mirror system to increase the optimization freedom and the aberration relationship between diffractive phase coefficients and Zernike coefficients is derived. Furthermore, a complete comparison design example with a focal length of 1200 mm, F-number of 12, and FOV of 40° × 2° is given to verify the aberration correction ability of the diffractive mirror. The system average wavefront error is 0.007 λ (λ=0.6328 μm) developed from 0.061 λ when the system didn’t adopt the diffractive mirror. In this system the phase modulation function of the diffractive mirror is established as an even function of x, so we could obtain a symmetrical imaging quality about the tangential plane, and the symmetric aberration performance also brings considerable convenience to alignment and testing for the system.

• 한국광학회지
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• 제2권3호
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• pp.121-126
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• 1991

칼날주사형 OTF 측정장치를 개선하여 비축상 OTF 측정 정확도를 향상시켰으며 SIRA 연구팀이 개발한 50mm 평면-볼록형 표준렌즈를 사용하여 OTF 측정장치의 성능을 평가하였다. 공간 주파수 0~100 cm / mm 영역에서 표준렌즈의 MTF 측정값은 극소수의 공간 주파수를 제외하고 축상에서 $\pm$0.02, 비축상에서 $\pm$0.03 이내에서 SIRA 측정값과 일치하였으며 PTF 측정값은 SIRA 측정값과 $\pm$$5^{\circ}$이내에서 일치하였다.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.94-100
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• 2016

A novel optical design for high resolution, large field of view (FOV) and multispectral remote sensing is presented. An f/7.3 Korsch and two f/17.9 Cook three-mirror optical systems are integrated by sharing the primary and secondary mirrors, bias of the FOV, decentering of the apertures and reasonable structure arrangement. The aperture stop of the Korsch system is located on the primary mirror, while those of the Cook systems are on the exit pupils. High resolution image with spectral coverage from visible to near-infrared (NIR) can be acquired through the Korsch system with a focal length of 14 m, while wide-field imaging is accomplished by the two Cook systems whose focal lengths are both 13.24 m. The full FOV is 4°×0.13°, a coverage width of 34.9 km at the altitude of 500 km can then be acquired by push-broom imaging. To facilitate controlling the stray light, the intermediate images and the real exit pupils are spatially available. After optimization, a near diffraction-limited performance and a compact optical package are achieved. The sharing of the on-axis primary and secondary mirrors reduces the cost of fabrication, test, and manufacture effectively. Besides, the two tertiary mirrors of the Cook systems possess the same parameters, further cutting down the cost.

• 한국광학회지
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• 제13권2호
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• pp.92-97
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• 2002

초측정 할 수 있는 nodal slide식 실시간 OTF 측정 장치를 제작하였다. 비축 물체를 측정하기 위하여 nodal slide와 T-bar를 사용하고, 실시간 측정을 위하여 화소 간격이 가로 9.9$\mu\textrm{m}$와 세로 9.6$\mu\textrm{m}$인 2차원 CCD(charge coupled device)를 사용하며, 초점 길이 300mm의 시준 렌즈를 사용하여 장치를 소형화하였다. 그리고 F/8, 초점 길이 50 mm인 SIRA사의 표준 렌즈를 이용하여 측정 장치의 정확도를 평가하고 보정하였다. 본 장치의 신뢰도를 위하여 시야각이 10.6$^{\circ}$이고, 초점 길이가 25.0mm인 CCTV & VIDEO 렌즈(JAPAN, AVENIR-SE 2514)의 MTF를 측정하여 카메라 벤취(bench)형 OTF측정 장치로부터 구한 MTF 값들과 상호 비교한 결과 대부분의 공간주파수에서 4% 이내로 일치하였다.

• Current Optics and Photonics
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• 제6권1호
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• pp.44-50
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• 2022

An off-axis zone plate is able to focus on a single order while neglecting the zeroth order in a visible imaging system. This allows one to enhance the contrast quality in diffractive images, which is the major advantage of this type of zone plate. However, most previous reflection zone plates are used in focusing X-rays with a small grazing incident angle and are intricately designed with the use of a local grating period. In this study, we suggest the design of an off-axis elliptical zone plate (EZP) that is used to focus a monochromatic light beam with separation between the first and unfocused orders under a large grazing incident angle of 45°. An assumption using the total grating period, which depends on the average and constant grating period, is proposed to calculate the desired distance between the first and zeroth order and to simplify the construction of a novel model off-center EZP. Four diffractive optical elements (DOEs) with different parameters were subsequently fabricated by direct laser lithography and then verified using a performance evaluation system to compare the results from the assumption with the experimental results.

• 한국기계가공학회지
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• 제11권2호
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• pp.13-19
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• 2012

Ultra Precision Machining Techniques, such as manufacturing Micro Lens Array(MLA), off-axis mirror, $F-{\theta}$ lens for laser printer, are achieved, based on technologies in consequence of development of modern high-precision machining mechanism. Above all, FTS(Fast Tool Servo) and STS(Slow Tool Servo) are more innovative technologies for reducing time and development costs. In this paper, it is described that MLA machining technique by FTS, off-axis mirror machining technique by STS, optics for observing space, and development of infrared aspheric lens for a thermal imaging microscope.

• Current Optics and Photonics
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• 제5권6호
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• pp.660-671
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• 2021

We present a novel optical system for an augmented reality head-up display (AR HUD) with two virtual images at different conjugates by employing a confocal off-axis two-mirror and introducing the horopter circle. For a far virtual image with large asymmetrical aberrations, we initially obtain an off-axis two-mirror system corrected for these aberrations and compensated for the down angle by configuring its parameters to satisfy the confocal and Scheimpflug conditions, respectively. In addition, this system is designed to reduce the biocular parallax by matching Petzval surface into the longitudinal horopter circle in a near virtual image. This design approach enables us to easily balance the residual aberrations and biocular parallax when configuring the optical system with two different conjugates, which results in an AR HUD available for near and far virtual images together.