• 제목/요약/키워드: aberrations

검색결과 383건 처리시간 0.019초

Optics of the light-weight and foldable telescope based on the Fresnel lens

  • Yu, Hyungjoon;Park, Yong-Sun;Chung, Haeun
    • 천문학회보
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    • 제41권1호
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    • pp.57.3-58
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    • 2016
  • We analyze an optical system of a telescope based on Fresnel type objective lens as suggested by Hyde (1999). The Fresnel objective lens can be thin, light-weight and foldable, and therefore it is possible to develop a space telescope with an aperture larger than that of traditional telescopes. Moreover a lens, whatever it is either Fresnel type or conventional, allows much larger fabrication tolerances. We design a medium-sized telescope adopting Fresnel lens as an objective lens for use in space and possibly on the ground. The well-known chromatic aberration of the Fresnel primary lens is corrected by a field lens and another Fresnel lens using Schupmann method. An additional lens is used for forming images. We analyze the chromatic and off-axis aberrations of the proposed system analytically and suggest methods for the minimization of off-axis aberrations and for the operation in wider spectral range. We also conduct ray tracing and optimize the whole optical system with commercial software. Finally we present the design parameters of a telescope with an aperture of 0.5 to 1 meters, enabling diffraction limited operation for a moderate field of view about 10 arc-minutes.

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Deep UV 마이크로 리소그라피를 위한 새로운 4-반사경 광학계에 관한 수차해석

  • 김종태;이상수
    • 한국광학회지
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    • 제4권1호
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    • pp.1-8
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    • 1993
  • 축소배율(5$\times$)을 갖고, Seidel 1차 수차중 4개의 비축수차인 코마(coma), 비점수차(astigmatism), 상면만곡(field curvature) 그리고 왜곡수차(distortion)가 제거된 마이크로 리소그라피를 위한 4-구면 반사경 광학계를 해석적으로 구하였다. 이때, $t=d_1+d_2+d_3$<0, (di는 반사거울 $c_i$$c_{i+1}$ 사이의 거리)이고, 축상 수차인 구면수차와 잔류고차수차는 반사거울 $c_3$$c_4$를 비구면화 하므로서 제거하였다. 이렇게 설계된 4-반사경 광학계의 N.A.는 0.4로서 Rayleigh분해능은 0.38 $\mu\textrm{m}$이다.

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Interplay between Epigenetics and Genetics in Cancer

  • Choi, Jae Duk;Lee, Jong-Soo
    • Genomics & Informatics
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    • 제11권4호
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    • pp.164-173
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    • 2013
  • Genomic instability, which occurs through both genetic mechanisms (underlying inheritable phenotypic variations caused by DNA sequence-dependent alterations, such as mutation, deletion, insertion, inversion, translocation, and chromosomal aneuploidy) and epigenomic aberrations (underlying inheritable phenotypic variations caused by DNA sequence-independent alterations caused by a change of chromatin structure, such as DNA methylation and histone modifications), is known to promote tumorigenesis and tumor progression. Mechanisms involve both genomic instability and epigenomic aberrations that lose or gain the function of genes that impinge on tumor suppression/prevention or oncogenesis. Growing evidence points to an epigenome-wide disruption that involves large-scale DNA hypomethylation but specific hyper-methylation of tumor suppressor genes, large blocks of aberrant histone modifications, and abnormal miRNA expression profile. Emerging molecular details regarding the modulation of these epigenetic events in cancer are used to illustrate the alterations of epigenetic molecules, and their consequent malfunctions could contribute to cancer biology. More recently, intriguing evidence supporting that genetic and epigenetic mechanisms are not separate events in cancer has been emerging; they intertwine and take advantage of each other during tumorigenesis. In addition, we discuss the collusion between epigenetics and genetics mediated by heterochromatin protein 1, a major component of heterochromatin, in order to maintain genome integrity.

Lack of Mutagenicity Potential of Periploca sepium Bge. in Bacterial Reverse Mutation (Ames) Test, Chromosomal Aberration and Micronucleus Test in Mice

  • Zhang, Mei-Shu;Bang, In-Seok;Park, Cheol-Beom
    • Environmental Analysis Health and Toxicology
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    • 제27권
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    • pp.14.1-14.6
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    • 2012
  • Objectives: The root barks of Periploca sepium Bge. (P. sepium) has been used in traditional Chinese medicine for healing wounds and treating rheumatoid arthritis. However, toxicity in high-doses was often diagnosed by the presence of many glycosides. The potential mutagenicity of P. sepium was investigated both in vitro and in vivo. Methods: This was examined by the bacterial reverse mutation (Ames) test using Escherichia coli WP2uvrA and Salmonella typhimurium strains, such as TA98, TA100, TA1535, and TA1537. Chromosomal aberrations were investigated using Chinese hamster lung cells, and the micronucleus test using mice. Results: P. sepium did not induce mutagenicity in the bacterial test or chromosomal aberrations in Chinese hamster lung cells, although metabolic activation and micronucleated polychromatic erythrocytes were seen in the mice bone marrow cells. Conclusions: Considering these results, it is suggested that P. sepium does not have mutagenic potential under the conditions examined in each study.

Preventive Effect of Ecklonia Stolonifera on the Frequency of Benzo(a)pyrene-Induced Chromosomal Aberrations

  • Lee, Ji-Hyeon;Hye- Young Oh;Park, Jae-Sue
    • Preventive Nutrition and Food Science
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    • 제1권1호
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    • pp.64-68
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    • 1996
  • Chromosomal aberration tests in vitro using Chinese hamster lung(CHL) cells were carried out to evaluate the possible role of the MeOH extract of Ecklonia stolonifera in modulating the chromosomal damage induced by Mitomycin C(MMC) and Benzo(a)pyrene(B(a)P), respectively. The MeOH extract of Ecklonia stolonifera(260$\mu\textrm{g}$/ml) reduced significantly the incidence of chromosomal aberration induced by treatment with B(a)P by 80%. The suppressive effect was much stronger than that of $\beta$-carotene, which is well known antimu-tagen. However, there was no marked decrease in the chromosomal aberration induced by MMC. In the tests involving chromosomal aberration induced by the treatment of the MeOH extract of Exklonia stlolnifera alone, there was no significant increase in comparison with the negative control. The results would seem to indicate that. at least under the conditions examined, the MeOH extract of Ecklonis stolonifera decreased the chromosomal aberrations induced by B(a)P in the CHL cells, but had little effect on the chromosomal aberration induced by MMC.

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위상변조가 회전대칭적 수차를 갖는 쌍안경 결상력에 미치는 효과 (Phase Modulation effects on the imamging performance of the binocular objective having rotationally symmetrical aberrations)

  • 홍경희;오병완;정창섭
    • 한국광학회지
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    • 제3권3호
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    • pp.143-147
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    • 1992
  • 개구상에서 위상변조를 실시하였을 때에 line spread function과 MTF에 미치는 효과를 실험적 측정에 의한 고찰을 실시하였다. 국산 쌍안경 대물렌즈를 시험렌즈로 하였다. 위상변조를 위한 위상판을 제작하고 렌즈앞에 밀착하여 MTF를 축정하였다. 위상변조는 개구상에서 일정한 범위를 $\pi$만큼 지연시켰다. 실험결과 수차가 큰 쌍안경 대물경계에 위상변조 효과는 공간주파수 여과특성은 매우 약하고 수차보정효과가 크게 나타났다. 결과적으로 적절하게 위상변조를 실시하면, 광에너지 손실이 거의없이 광학계의 결상능력을 향상시킬 수가 있음을 확증하였다.

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Karyological Variation of Callus-derived Regenerants in Allium victorialis var. platyphyllum

  • Seo, Bong-Bo;Lee, Seon-Hee;Park, Jae-Hong;Kim, In-Sun;Song, Seung-Dal
    • Journal of Plant Biology
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    • 제39권4호
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    • pp.231-235
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    • 1996
  • The calli obtained from the bulbs of A. victorialis var. platyphyllum on MS based medium containing 2 mg/L 2, 4-D and 1mg/L BA. Plants from calli were regenerated on MS basal media supplemented with combinations of NAA and four kinds of cytokinin, BA, zeatin, kinetin and 2iP, and with only each cytokinin. The good response of shoot regeneration was observed in the media with combinations of NAA and BA or zeatin, and with only BA or zeatin. Shoot regenerating response in the medium with combinations of NAA and BA or zeatin, and with only BA or zeatin. Shoot regerating response in the medium with combinations of NAA and BA or zeatin was about two times higher than that in the mediuim with only BA or zeatin. From the karyotypic analysis of the regenerated plants, abnormal diploids, aneuploids and mixoploid with structural aberrations were investigated. The somaclonal variants (AV 16-04, AV 13-03) were shown the considerable differences from normal diploid regenerant (AV 18-03) in the external morphology.

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Full-color Non-hogel-based Computer-generated Hologram from Light Field without Color Aberration

  • Min, Dabin;Min, Kyosik;Park, Jae-Hyeung
    • Current Optics and Photonics
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    • 제5권4호
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    • pp.409-420
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    • 2021
  • We propose a method to synthesize a color non-hogel-based computer-generated-hologram (CGH) from light field data of a three-dimensional scene with a hologram pixel pitch shared for all color channels. The non-hogel-based CGH technique generates a continuous wavefront with arbitrary carrier wave from given light field data by interpreting the ray angle in the light field to the spatial frequency of the plane wavefront. The relation between ray angle and spatial frequency is, however, dependent on the wavelength, which leads to different spatial frequency sampling grid in the light field data, resulting in color aberrations in the hologram reconstruction. The proposed method sets a hologram pixel pitch common to all color channels such that the smallest blue diffraction angle covers the field of view of the light field. Then a spatial frequency sampling grid common to all color channels is established by interpolating the light field with the spatial frequency range of the blue wavelength and the sampling interval of the red wavelength. The common hologram pixel pitch and light field spatial frequency sampling grid ensure the synthesis of a color hologram without any color aberrations in the hologram reconstructions, or any loss of information contained in the light field. The proposed method is successfully verified using color light field data of various test or natural 3D scenes.

Surface Error Generation of Freeform Mirror Based on Zernike Polynomial for Optical Performance Prediction

  • Lee, Sunwoo;Park, Woojin;Han, Jimin;Ahn, Hojae;Kim, Yunjong;Lee, Dae-Hee;Kim, Geon Hee;Pak, Soojong
    • 천문학회보
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    • 제45권1호
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    • pp.67.2-67.2
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    • 2020
  • Not only the magnitude of the mirror surface error, the pattern matters as it produces certain aberrations. In particular, the surface error of the freeform mirrors, which are optimized to eliminate specific aberrations, might show much higher sensitivity in optical performance. Therefore, we analyze the mirror surface error with Zernike polynomials with the goal of generating a realistic error surface. We investigate the surface error of the freeform mirror fabricated by diamond turning machine to analyze the realistic tendency of the error. The surface error with 0.22 ㎛ root-mean-square value is fitted to the Zernike terms using the incremental fitting method, which increases the number of the fitting coefficients through steps. Furthermore, optical performance via surface error pattern based on Zernike terms is studied to see the influences of each term. With this study, realistic error surface generation may allow higher accuracy not only for the feasibility test but also for all tests and predictions using optical simulations.

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라섹 수술 전과 후의 고위수차에 영향을 미치는 결정변수 (Determination Factors Affecting the High Order Aberrations in Preoperative and Postoperative LASEK)

  • 김태흥;이현;이강오;이태용
    • 한국산학기술학회논문지
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    • 제15권9호
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    • pp.5621-5627
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    • 2014
  • 라섹 수술 방법을 결정하기 위한 기준을 상세화하고자 고식적인 라섹 수술 전과 후의 고위수차에 영향을 미치는 결정변수들을 분석하였다. 2011년 11월부터 2012년 7월까지 고식적 라섹 수술을 한 대상자 중 수술한지 2개월 후 고위수차검사가 가능한 51명(102안)을 대상으로 하였다. 고위수차는 수술 전 $0.341{\mu}m$에서 수술 후 $0.538{\mu}m$로 증가하였다. 선형회귀분석에서 수술 후의 고위수차 변동에 영향을 미치는 수술 전의 굴절성분은 설명력 크기순으로 각막난시 $J_0$ 성분이 0.400, 굴절성난시 $J_0$ 성분이 0.389, 각막난시량이 0.282, 구면렌즈대응치가 0.239, 굴절성난시량이 0.213, 동공크기가 0.194였다. 다중회귀분석에서 수술 후의 고위수차와 통계적으로 의미가 있는 변수는 각막난시 $J_0$ 성분, 동공크기, 구면렌즈대응치였다. 따라서 개인에게 적합한 수술 방법 결정을 위해서는 고위수차와 더불어 파워벡터분석에 의한 각막난시도 함께 고려하는 것이 필요하다.