• Title/Summary/Keyword: Null lens

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Null lens design for testing of elliptical surface (타원면경 측정 Null 렌즈 설계)

  • 김연수
    • Korean Journal of Optics and Photonics
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    • v.11 no.4
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    • pp.246-249
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    • 2000
  • The null lens is designed for testing the elliptical (conic constant>O) mirror which is the third mirror of the off-axis Three Mirror Anastigmat (TMA) designed as a high resolution camera for remote sensing. The mixed type design is proposed as a new design type which has a small annular flat mirror, but has as twice sensitivity as the autostigmatic type design. It is also shown that the null lens of the Mixed type is better than that of the autostigmatic type in terms of the sensitivity of the wavefront distortion which is given as the magnitude of optical path difference with respect to the change of each surface parameters such as the radius of curvature, thickness of lenses and tested mirror.

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Design of null lens for Alignment of the Unstable Laser Resonator (불안정형 레이저 공진기 정렬을 위한 null 렌즈 설계)

  • Kim, Hyun-Sook;Kim, Yeon-Soo
    • Korean Journal of Optics and Photonics
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    • v.17 no.2
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    • pp.186-190
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    • 2006
  • The use of null optics is proposed as a new concept for the precise alignment of a confocal unstable resonator. The characteristics of the proposed null optics are investigated and analysed with the designed null lens for a real confocal unstable resonator of which the length is 3.5 m. As a result of the analysis, the pupil map data are shown about the despace error of 1.0 mm and tilt error of 1.0 mrad.

Evaluation of a Aluminum Hyperbolic Mirror with the Diameter of 300 mm(f/1.98) by Using the Autostigmatic Null Lens System Assembled in a Fixed Tube Mount (경통고정식 자동무수차점 널 렌즈 테스트법을 이용한 직경 300 mm(f/1.98) 알루미늄 쌍곡면 거울의 형상측정)

  • Lee, Young-Hun;Jo, Jae-Heung;Rim, Cheon-Seog;Yang, Sun-Choel;Kim, Geon-Hee;Won, Jong-Ho;Jeong, Youn-Hong
    • Korean Journal of Optics and Photonics
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    • v.17 no.5
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    • pp.412-419
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    • 2006
  • We design and fabricate an autostigmatic null lens system assembled in a fixed tube mount in order to evaluate the shape of an aluminum hyperbolic mirror with the diameter of 300 mm and the f-number of 1.98, which is fabricated by a high precision aspherical DTM (diamond turning machine). Also, we evaluate the degree of shape of the aspherical mirror by this autostigmatic null lens testing method. The autostigmatic null lens system assembling in a fixed tube mount has several advantages of light weight, good mechanical stability, etc. The permissible fabricating limits of null lenses and a mount are determined by considering various tolerances to assure the measurement reliability.

KNOTS IN HOMOLOGY LENS SPACES DETERMINED BY THEIR COMPLEMENTS

  • Ichihara, Kazuhiro;Saito, Toshio
    • Bulletin of the Korean Mathematical Society
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    • v.59 no.4
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    • pp.869-877
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    • 2022
  • In this paper, we consider the knot complement problem for not null-homologous knots in homology lens spaces. Let M be a homology lens space with H1(M; ℤ) ≅ ℤp and K a not null-homologous knot in M. We show that, K is determined by its complement if M is non-hyperbolic, K is hyperbolic, and p is a prime greater than 7, or, if M is actually a lens space L(p, q) and K represents a generator of H1(L(p, q)).

A Study for the Limitation of Measurement Accuracy and Reliability of Autostigmatic Null lens System by Adjustment and Fixing Process (조정방식과 경통고정방식에 대한 자동무수차점 널 렌즈 광학계의 측정 정밀도 한계 및 신뢰도)

  • Lee, Young-Hun;Rim, Cheon-Seog
    • Korean Journal of Optics and Photonics
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    • v.16 no.5
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    • pp.440-445
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    • 2005
  • The limitation of measurement accuracy and reliability of autostigmatic null lens system are studied for the cases of using inter-distance of null lenses as the adjustment factor of alignment and fixing the distance by mounting. If we investigate the first case, the wavefront aberration of null lens system is compensated by the adjustment process even though the shape of aspherical surface is not properly fabricated. As the result, it brings about the problem of measurement reliability. However, for the fixing process by mounting null lenses, it doesn't cause the reliability problem because the wavefront aberration of null lens system is not compensated. Further, the fixing process shows nearly same result in measurement accuracy to the adjustment process, that is, $0.0316{\lambda}$ vs. $0.0326{\lambda}$. So, we can conclude the setup for autostigmatic null lens system must be constituted by means of the fixing process. Meanwhile, we introduce and define the alignment aperture on aspheircal mirror, which can be approximated as spherical zone for alignment of null lens system, and besides, we calculate the required fabrication accuracy of the zone for the necessary measurement accuracy.

Design of null lenses for testing of hyperbolic surfaces (쌍곡면 측정 null 렌즈 설계)

  • 김연수;김병윤;이윤우
    • Korean Journal of Optics and Photonics
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    • v.12 no.5
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    • pp.352-355
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    • 2001
  • A null lens is designed for testing the hyperbolic mirror which is the first mirror of the off-axis three mirror anastigmat(TMA) designed as a high resolution camera for remote sensing. To choose a better null lens system for the hyperbolic surface under test, both autostigmatic and mixed type null lenses are designed and analysed for sensitivity with respect to change of each surface parameter such as the radius of curvature and the thickness.

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Wavefront Measurement of Aspheric Lens with Null CGH (반사형 Null CGH를 이용한 비구면 사출 렌즈의 파면 측정)

  • Lee, Ho-Yeol;Kim, Dae-Chan;Jang, Hyeon-Jun;Lee, Uk-Hui;Song, Jong-Seop;O, Beom-Hwan;Park, Se-Geun;Lee, Il-Hang;Lee, Seung-Geol
    • Proceedings of the Optical Society of Korea Conference
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    • 2009.10a
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    • pp.129-130
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    • 2009
  • In order to determine the aberration coefficients of an aspheric lens with a small diameter, its transmitted wavefront was compensated with a null CGH and an auxiliary convex lens. The configuration of the measuring system and the fabrication step of CGHs could be simplified by using a reflective amplitude-type CGH as null optics. The compensated waterfronts of several sample lenses were measured and analyzed, and consequently the performance of the CGH was evaluated.

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A study for null lens design of autostigmatic type and the limitation of measurement accuracy for ultra precision manufacturing of large aspherical surface (대형 비구면의 초정밀 가공을 위한 자동무수차점 방식의 널 렌즈 설계 및 측정 정밀도의 한계에 관한 연구)

  • Kim, Kil-Seon;Rim, Cheon-Seog
    • Korean Journal of Optics and Photonics
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    • v.16 no.1
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    • pp.71-78
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    • 2005
  • A null lens system of autostigmatic type, consisting of two mirrors, is designed for testing a large aspherical mirror. The system is theoretically analyzed to determine the limitation of measurement accuracy according to the manufacturing and alignment errors. We confirmed that irregularity of the null lens surface is the principal factor among tolerances in limiting measurement accuracy. Consequently, we can predict that measurement accuracy will be from 5λ/100 to 4λ/1000 according to the amount of this irregularity. That is, we can present the limitation of possible measurement accuracy with actual alignment and manufacturing errors.

Analysis of the Optical Measurement Error Induced by Vibration of the Optical Measurement Tower for Large Mirrors (대구경 반사경 광학측정용 타워의 진동에 의한 광학측정오차 분석)

  • Kang, Pilseong;Kim, Ohgan;Ahn, Hee Kyung;Yang, Ho-Soon
    • Korean Journal of Optics and Photonics
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    • v.28 no.6
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    • pp.281-289
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    • 2017
  • In the present research, the optical measurement error induced by vibration of the optical measurement tower for large mirrors at KRISS (Korea Research Institute of Standards and Science) is investigated. The vibrations of the tower structure, the interferometer, and the null lens are measured while the surface errors of the 600-mm-diameter on-axis aspheric mirror are measuring, under various environmental conditions. The increase of surface error induced by alignment error with respect to vibration is analyzed. As a result, the interferometer and the null lens, which are located on the top of the tower, are highly sensitive to vibration. Additionally, the surface error of the mirror is strongly increased when the vibration directions of the interferometer and the null lens are different. To reduce the alignment error and the surface error induced by vibration, the tower structure should be improved, to be insensitive to low-frequency vibration. Alternatively, optical measuring under stable conditions by vibration monitoring can improve the reliability of the surface error measurement.

Fabrication Measurement and Evaluation of a Parabolic Mirror with the Diameter of 450 mm(f/2.7) by Autostigmatic Null Lens System (자동무수차점 방식 널 렌즈 광학계를 이용한 직경 450 mm(f/2.7) 포물면경의 제작 및 측정 평가)

  • Lee, Young-Hun;Jo, Jae-Heung;Rim, Cheon-Seog;Lee, Yun-Woo;Yang, Ho-Soon;Lee, Jae-Hyeob;Lee, In-Won
    • Korean Journal of Optics and Photonics
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    • v.17 no.2
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    • pp.165-174
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    • 2006
  • The autotstigmatic null lens system is designed and constructed for the fabrication of a parabolic mirror with the diameter of 450 mm(f/2.7). And the measurement reliability is also analyzed theoretically by means of the tolerancing technique using lens design software(CODE V). From this analysis, we can precisely fabricate a parabolic mirror with the large diameter of 450 mm(f/2.7). Meanwhile, in order to confirm the fabrication results by the autostigmatic method, the mirror surface is tested again by an autocollimating method that uses only a plane mirror without any null lens.