• Journal of the Optical Society of Korea
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• 제20권2호
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• pp.251-256
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• 2016

The prediction of thermal effects in lithography projection objective plays a significant role in the real-time dynamic compensation of thermal aberrations. For the illuminated lithography projection objective, this paper applies finite element analysis to get the temperature distribution, surface deformation and stress data. To improve the efficiency, a temperature distribution function model is proposed to use for the simulation of thermal aberrations with the help of optical analysis software CODE V. SigFit is approved integrated optomechanical analysis software with the feature of calculating OPD effects due to temperature change, and it is utilized to prove the validation of the temperature distribution function. Results show that the impact of surface deformation and stress is negligible compared with the refractive index change; astigmatisms and 4-foil aberrations dominate in the thermal aberration, about 1.7 λ and 0.45 λ. The system takes about one hour to reach thermal equilibrium and the contrast of the imaging of dense lines get worse as time goes on.

• 진공이야기
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• 제2권2호
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• pp.24-28
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• 2015

The brightness of an electron source, along with the aberrations of an objective lens, determines the image resolution and beam current on samples, which are two important parameters for evaluating the performance of an electron microscope. Here we introduce thermal electron source, Schottky emitter and cold field electron emitter. Thermal electron source is the cheapest and stable electron source but it has the lowest brightness. Schottky emitter is 10000 times brighter than tungsten thermal electron source, but requires ultrahigh vacuum operating condition. Cold field electron emitter is 10 times brighter than Schottky emitters, but it is rather unstable and its operation requires most stringent vacuum condition, hindering its widespread use.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2001년도 Proceedings of 2001 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.123-137
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• 2001

PIV (particle image velocimetry) systems use a camera to take snapshots of particles carried by a fluid at some precise instants. Signal processing methods are then used to compute the flow velocity field. In this paper, the design of the camera objective (optics) is addressed. The optimization is done in order to maximize the signal-to-noise ratio of in-focus particles. Four different kinds of noise are considered: photon shot noise, thermal and read noise, background glow shot noise, and noise made by the other particles. A semi-empirical model for the lens aberrations of a two-doublet objective is first addressed, since further, it is shown that lens aberrations (low f-value $f_{\#}$) should be used instead of the Fraunhofer diffraction (high f-value) for the fitting of the particle image size with the pixel size. Other important conclusions of the paper include the expression of optimum values for the magnification M, for the exposure period $\tau$ and for the pixel size $\xi$.

• 한국광학회지
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• 제28권5호
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• pp.241-249
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• 2017

본 논문에서는 $7.7{\mu}m$에서 $12.8{\mu}m$ 파장 대역에 적용 가능한 비냉각 열상장비 광학계를 설계 및 분석 하였다. 최적화 과정을 통하여 설계된 원적외선 광학계의 유효초점거리는 5.44 mm를 가지며, 4면의 비구면과 2면의 회절면을 포함하였다. 광학계의 F/수는 F/1.2로 설정하였고, 시야각은 $90^{\circ}{\times}67.5^{\circ}$가 되도록 하였다. 회절면이 적용된 hybrid 렌즈를 이용하여 보다 효율적으로 고차 수차가 보정되도록 하였고, 이때 발생되는 회절 특성은 scalar 회절 효율을 이용하여 평가하였다. 또한 hybrid 렌즈에서 발생되는 회절 현상에 의한 통합 회절효율을 예측하고 배경잡음에 의한 MTF 저하를 고려하였다. 원적외선 광학계의 온도 변화에 따른 보상은 광학식 비열화를 이용하여 광학계의 MTF 성능이 초점 심도 내에서 유지되도록 하였다. 결론적으로 비냉각 열상장비에 효율적으로 적용 가능한 광학설계 결과를 얻었다.

• Current Optics and Photonics
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• 제7권3호
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• pp.273-282
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• 2023

This paper presents a new method for redistributing effectively the first orders of each lens element to achromatize and athermalize an optical system, by introducing a novel method for adjusting the slope of an achromatic and athermal line. This line is specified by connecting the housing, equivalent single lens, and aberration-corrected point on a glass map composed of available plastic and glass materials for molding. Thus, if a specific lens is replaced with the material characterized by the chromatic and thermal powers of an aberration-corrected point, we obtain an achromatic and athermal system. First, we identify two materials that yield the minimum and maximum slopes of the line from a housing coordinate, which specifies the slope range of the line spanning the available materials on a glass map. Next, redistributing the optical first orders (optical powers and paraxial ray heights) of lens elements by moving the achromatic and athermal line into the available slope range of materials yields a good achromatic and athermal design. Applying this concept to design a mobile-phone camera lens, we efficiently obtain an achromatic and athermal system with cost-effective material selection, over the specified temperature and waveband ranges.

• Current Optics and Photonics
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• 제7권2호
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• pp.213-221
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• 2023

The optical window, as a part of the collimator system, is the connector between the outside light source and the optical system inside a vacuum tank. The temperature and pressure difference between the two sides of the optical window cause not only thermoelastic deformation, but also refractive-index irregularities. To suppress the influence of these two changes on the performance of the collimator system, thermo-optical analysis is employed. Coefficients that characterize the deformations and refractive-index distributions are derived through finite-element analysis, and then imported into the collimator system using a user-defined surface in ZEMAX. The temperature and pressure difference imposed on the window seriously degrade the system performance of the collimator. A decentered and tilted lens group is designed to correct both field aberrations and the thermal effects of the window. Through lens-interval adjustment of the lens group, the diffraction-limited performance of the collimator can be maintained with a vacuum level of 10^-5 Pa and inside temperature ranging from -100 ℃ to 20 ℃.

• 한국광학회지
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• 제21권5호
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• pp.214-223
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• 2010

30 cm 급 항공용 반사 망원경계에서 외부 환경 및 내부 진동에 의해 발생하는 주 반사경의 광학적인 성능 저하를 최소화하기 위하여 주 반사경의 광기계 설계를 수행 하였다. 플렉셔를 포함한 주 반사경의 해석을 위한 경계조건으로는 광학면의 수직과 수평 방향의 중력에 의한 변형과 온도 변화 ${\pm}1^{\circ}C$에 의한 열 변형을 고려하였다. 반사경의 기계적인 변형은 NX 5 I-DEAS를 사용하여 해석 하였다. 최적화된 경량화 반사경과 플렉셔의 중력에 의한 광학면의 형상 변형은 RMS surface error 16 nm 이하로 초기 설계 목표값을 만족하였다. 온도 변화 ${\pm}1^{\circ}C$에 의한 광학면의 형상 변형과 assembly load에 의한 광학면의 형상 변형은 매우 작은 값으로 주 반사경의 변형에 영향을 주지 않음을 확인하였다.

• Toxicological Research
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• 제24권4호
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• pp.321-328
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• 2008

Smoke flavors based on the thermal decomposition of wood have been applied to a variety of food products as an alternative for traditional smoking. Despite its increasing use, the available genotoxicity data on wood smoke flavors (WSF) are still controversial. Thus, potential genotoxic effects of WSF in four short-term in vitro genotoxicity assays were investigated, which included the Ames assay, chromosomal aberration assay, micronucleus test and the alkaline comet assay. WSF did not cause any mutation in the Ames assay using five tester strains at six concentrations of 0.16, 0.31, 0.63, 1.25, 2.5 and 5 ${\mu}l/plate$. To assess clastogenic effect, the in vitro chromosomal aberration assay was performed using Chinese hamster lung cells. No statistically significant increase in the number of metaphases with structural aberrations was observed at the concentrations of 1.25, 2.5, and 5 ${\mu}l/ml$. The in vitro comet assay and micronucleus test results obtained on L5178Y cells also revealed that WSF has no genotoxicity potential, although there was a marginal increase in micronuclei frequencies and DNA damage in the respective micronucleus and comet assays. Taken together, based on the results obtained from these four in vitro studies, it is concluded that WSF is not a mutagenic agent in bacterial cells and causes no chromosomal and DNA damage in mammalian cells in vitro.

• 한국광학회지
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• 제29권3호
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• pp.110-118
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• 2018

항공용 전자 광학 타겟팅 시스템을 위한 중적외선 광학계를 설계하였다. 본 광학계는 이중 시야를 갖도록 설계되었으며, 빔 축소 전단 광학계, 줌 렌즈 그룹, 릴레이 렌즈 그룹, 콜드스탑 공액 광학계 및 냉각 적외선 검출기로 구성된다. 적외선 검출기는 단일 화소의 크기가 $15{\times}15{\mu}m$ 인 $1280{\times}1024$ 화소 배열을 가지며 잡음을 최소화하기 위하여, f/5.3의 냉각 콜드스탑이 적용된 제품으로 선정하였다. 이중 시야 ($1.50^{\circ}{\times}1.20^{\circ}$, $5.40^{\circ}{\times}4.23^{\circ}$)는 두 개의 렌즈를 삽입하는 방식으로 구현했으며, 줌 배율 변경 시 모든 시야에 걸쳐 f/5.3의 콜드스탑의 효율을 유지하도록 설계하였다. 열 효과가 이미지에 미치는 영향을 조사하기 위해 비열화 및 나르시서스 분석을 수행하였으며, 비열화 분석은 $-55{\sim}50^{\circ}C$의 작동 온도를 기준으로 초점 이동과 잔여 고차 파면 수차에 조사하였고 제르니케 다항식을 이용한 민감도 분석을 수행하여 최적의 보상자를 선정하였다. 선정된 보상자의 최적 이동을 고려한 MTF 해상력을 확인한 결과, 작동 온도 전 구간에 걸쳐 요구조건인 33 lp/mm에서 축상 10% 이상의 성능을 유지하는 것을 확인하였으며, 나르시서스 분석 결과, NITD (Narcissus Induced Temperature Difference) 값이 $1.5^{\circ}C$ 이하가 되도록 설계 된 것을 확인하였다.