• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.67.2-67.2
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• 2011

Schwarzschild-Chang 망원경은 두 개의 반사경을 사용한 비축 망원경이다. 이 망원경에 사용된 비축 광학 이론을 이용하면 선형 비점수차를 완전히 제거할 수 있으며 3차 이상의 고차수차들도 동축 광학계와 동일한 정도로 최소화 시킬 수 있다. 이 망원경 디자인을 응용하면 단일 광학계 망원경을 제작할 수 있을뿐만 아니라 2개의 망원경 시스템을 조합할 경우 색수차나 중앙차폐 없이 대형 망원경의 focal reducer 또는 분광기의 내부 광학 장치로도 사용할 수 있다. 본 연구팀은 현재 구경 50 mm, 유효초점거리 100 mm, 시야각 $8{\times}8^{\circ}$ 인 Schwarzschild-Chang 망원경 시험 모델을 완성했다. 본 발표에서는 적외선 관측을 직접 할 수 있는 Schwarzschild-Chang 망원경의 개발 진행과정에 대하여 설명한다.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.9-12
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• 2008

Purpose: Current gas-mask is very uncomfortable structure for spectacles wearer. Improving this problem can aid military men and firemen to protect themselves and rescue other person. Methods: we changed the structure from dual type of outward lens and inward lens into a single type structure. we attached acrylic frame to gas-mask instead of outward lens and protected the gas inflow by shutting the gab of lens and frame using silicon shield, and made the frame "S" style for removing astigmatism and maintaining of vertex distance. Results: It was possible to correct visual acuity and gas shield, and could changed the lens like a common spectacles. The new type of gas-mask spectacles could remove 0.53D~1.78D astigmatism occurred from the slant of eyesight and lens surface, 0.07D~0.66D overcorrection occurred from short vertex distance, and 0.1D~0.3D astigmatism occurred from pantoscopic angle. Conclusion: Because new type of gas-mask spectacles had clear visual field, it was expected to improve fighting power and rescue ability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.961-964
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• 2012

This paper presents a sensing system to measure the deflection of a microcantilever in an atomic force microscope. In general, the optical lever method and interferometry are used for the sensing system; however, their size and cost leaves considerable room for improvement. Therefore, we used an optical pickup head whose operating principle is based on the astigmatism of the commercial optical disk drives. The developed sensing system was applied to a laboratory atomic force microscope, and satisfactory results were obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.781-782
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• 2010

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.278-279
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• 2009

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.405-410
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• 2005

In this paper, the front radiuses of curvature of spherical spectacle lenses in the cosmetic and optical point of view are investigated and are calculated using Zinken-Sommer condition. The optical power of all spherical spectacle lens shows good quality at the test using autometic lensmeter. However the front radiuses of curvature of spherical spectacle lenses are quite different depending on the lens companies. The front radius of curvature of those lenses is larger than that calculated using Zinken-Sommer condition. We know that the front radius of curvature of commercial spectacle lens is emphasized more cosmetic aspect than optical point of view.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.257-258
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• 2006

This paper presents the displacement sensor based on astigmatic method that has a small measurement range. The sensor has the characteristic that the measuring range is changed easily by exchanging a objective lens or distance between a objective lens and a collimator lens. The measuring range and resolution is evaluated by a laser interferometer.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.87-94
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• 2008

The displacement sensor using optical pickup head is presented. The measuring principle of optical pickup head in focusing direction is adopted to measure displacement. The preliminary tests were carried out to verify the feasibility of the optical pickup head as a displacement sensor and optical pickup head showed about $8\;{\mu}m$ measuring range and 10nm resolution. The methodology to expand measuring range is proposed and proved its validity. The proposed displacement sensors are applied to AFM(Atomic Force Microscope) probe head to measure the deflection of micro-cantilever.

• Korean Journal of Optics and Photonics
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• v.34 no.6
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• pp.248-260
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• 2023

A 0.5-numerical-aperture (NA) refractive-reflective objective, composed of a low-NA refractive and a reflective focal reducer, is designed. A 0.25-NA Lister objective is used for the refractive. A two-spherical-mirror system, corrected for spherical aberration, coma, and astigmatism is used for the reflective focal reducer. In spite of high NA, the refractive-reflective objective has an 18-mm working distance and improved imaging performance, compared to the 0.25-NA Lister objective.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.73-79
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• 1997

We analyzed the variation of the focus error signal with the effect of land and groove, wavefront error, and optical system parameter variation for the knife-edge and astigmatism methods on the Land/Groove recordable optical disc, using a numerical simulation method. We verified causes of the zero-cross-shift that took place by the effect of land and groove by analyzing the diffraction beam including defocus wavefront errors. We also found that the sensitivty of the focus error signal was reduced by the effect of land and groove in the astigmatism method, as in the analysis of the focus error signal with the each order of the diffraction beam.