• 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.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.485-490
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• 2014

The purpose of this Study investigated corneal power, corneal astigmatism and corneal axis according to spherical equivalent of refractive error. We measured spherical equivalent, corneal power and corneal astigmatism in 100 subjects from January 2014 to July 2014. Measured spherical equivalent of refractive error were $-3.01{\pm}3.79D$, corneal power of $43.79{\pm}1.60D$ and corneal astigmatism of $-1.17{\pm}0.79D$ respectively. Prevalence of spherical equivalent of refractive error were as follows : myopes (61%), emmetropes (22%), hyperopes(17%). Corneal astigmatism of refractive error greater than +0.75D was 63% and prevalence of corneal astigmatism were as follows : with-the-rlue astigmatism (84.13%), against-the-rule astigmatism(9.52%) respectively. Corneal power by spherical equivalent increased from hyperopia to myopia. Between spherical equivalent of refractive error and the mean corneal power was significant correlation(r=-0.25, p=0.01). A correlation were found between corneal power and spherical equivalent of refractive error in adults. They have the highest distribution of prevalence myopia among the refractive error. When the refractive error was increased, we found that corneal power was steeper. It is recognized that this can be refractive error factor and correct visual function is considered.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.349-354
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• 2015

Purpose: To investigate the changes of corrective values of astigmatism caused by the position of circle of least confusion on retina in refining astigmatic test using cross cylinder. Methods: 62 subjects (115 eyes) aged $22.24{\pm}2.48$ years participated for this study. After astigmatic test using a radial chart, refining test was performed using a cross cylinder in a condition of maximum plus to maximum visual acuity (MPMVA). Astigmatic refining test was repeatedly performed in each condition of which S+0.75 D, S+0.50 D, S+0.25 D, S-0.25 D, S-0.50 D, and S-0.75 D are added to spherical lenses of MPMVA. The measured values were compared with the values in MPMVA condition. Results: As compared with values in condition of MPMVA, change of astigmatic axis was increased with add the power of (+) spherical lenses and (-) spherical lenses. In same spherical condition, change of astigmatic axis was decreased with increment of astigmatic power (p<0.05). The corrective power of astigmatism was reduced with increment of (+) spherical lenses (p<0.05), and was raised with increment of (-) spherical lenses compared with the power in MPMVA condition. In case of adding (+) spherical lenses, difference of astigmatic power increased with increment of corrective astigmatism power in same test condition. Conclusions: In order to obtain a proper values for corrective astigmatism, position of circle of least confusion should be accurately adjusted before the performing an astigmatism's refining test.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.1
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• pp.55-62
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• 2006

Clinical evaluation of the Closed-view autorefractor and Open-view autorefractor was performed to examine validity and repeatability compared with subjective refraction. Measurements of refractive error were performed on 126 eyes of 65 subjects (aged $26{\pm}7.5$ years) subjectively noncycloplegic. Intersession repeatability of the Closed-view and Open-view were also assessed on all 65 subjects together with Intersession repeatability on 7 to 14 days intervals. Spherical powers and spherical equivalent values of subjective refraction and autorefractions by Closed-view and Open-view were analyzed by paired T-test. The mean spherical powers of subjective refraction, Closed-view and Open-view were determined to be $-2.125{\pm}2.155D$, $-2.146{\pm}1.907D$, $-2.117{\pm}2.121D$, respectively. The mean spherical equivalent values of subjective refraction, Closed-view and Open-view were determined to be $-2.362{\pm}2.204D$, $-2.391{\pm}1.967D$, $-2.366{\pm}2.162D$, respectively. The results showed that the refractive errors as measured by the Closed-view and Open-view were found to be similar to the subjective refraction in all components.

• Proceedings of the KGS Conference
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• 2003.05a
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• pp.46-50
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• 2003

하안단구면을 이루는 퇴적층에 포함되어 있는 퇴적물들은 하안단구가 형성된 시기부터 현재까지 풍화를 받게 된다. 즉, 하안단구 퇴적층의 풍화 기간은 바로 하안단구면의 형성시기부터 현재까지가 되는 것이다 외국의 선행 연구들을 통해 볼 때, 암석의 풍화는 초기에 빠르게 진행되지만, 어느 정도 풍화가 진전되면 풍화의 속도가 점차 늦어진다고 제시되고 있으며, 암석과 토양을 구성하고 있는 풍화에 약한 몇 가지 광물들의 존재 유무와 원소 함량의 변화는 풍화 시간과 매우 긍정적인 상관 관계가 있는 것으로 나타난다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.270-271
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• 2003

lens를 통과하는 두 광선(paraxial ray, marginal ray)이 lens의 축이나 focal plane과 만나는 지점이 서로 일치하지 않을 때, 두 개의 서로 다른 교차점 사이의 거리나 높이를 종, 횡 구면수차 (Lateral, Longitudinal Spherical aberration)이라 한다. 수차의 크기는 lens의 굽어짐 (bending)형태에 따라 달라지는데 3차 근사 lens 공식으로 유도한 식은 다음과 같으며, 그 결과의 그래프는 그림.1 과 같다. (중략)

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.175-180
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• 2007

In this paper, an aberration free aspherical lens is designed and machined by new design method and the spherical aberration measuring system is developed. It confirmed the propriety of new design method by measuring optical characteristics of machined lens with the new measuring system. The system could measure a spherical aberration quantitatively by using CCD camera, laser, collimator and so on.

• Journal for History of Mathematics
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• v.18 no.1
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• pp.85-92
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• 2005

We review the well known analogizes between variations and harmonic maps. Second section contains rapid summary of the harmonic maps. In the third section we establish some basic properties of the Laplacian on Sphere. In particular we compute its spectrum and eigenfunctions.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.50-51
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• 2000

최근에 결상광학계는 광학유리를 사용한 전통적인 단순 구면형에서 플라스틱, 금속 등의 소재와 비구면 혹은 홀로그래피 광학소자를 이용한 복합적 기능형으로 발전하고 있다. 또한 엑스선에서 적외선까지 매우 넓은 분광영역에서 현미경으로 관찰할 수 있는 미소광학소자부터 구경 10 m 정도의 대구경 망원경까지 다양한 크기의 초정밀 결상광학계가 계속 개발되고 있다. 즉 구경 100 mm 정도의 구면 광학계에서 광대역 분광영역의 대구경 비구면 광학계로 발전하고 있다.$^{(1)}$ (표 1 참조) (중략)

• Journal for History of Mathematics
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• v.36 no.2
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• pp.21-34
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• 2023

Spherical trigonometry refers to the geometry related to spherical triangles. It has been an important tool for studying astronomy since ancient times. In trigonometry, concepts such as trigonometric functions naturally emerge from the relationship between arcs and chords of a circle. In this paper, we briefly examine the origin of spherical trigonometry. To introduce the basics of spherical trigonometry, we present fundamental and important theorems such as Menelaus's theorem, the law of sines and the law of cosines on a sphere, along with their proofs. Furthermore, we discuss the educational value and potential applications of spherical trigonometry.