• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.290-294
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• 2017

The Cassegrain telescope consists of a primary concave mirror and a secondary convex mirror. In the case of a secondary mirror, it is more difficult to test wavefront error than for a primary mirror, because it reflects the entire testing beam, as it is convex in shape. In this paper we tested the wavefront error of a complex aspheric convex secondary mirror by using the Simpson-Oland-Meckel Hindle test. To separate the systematic errors, such as fabrication error and alignment error of a meniscus lens, we adopted the QN absolute test (pixel-based absolute test using the quasi-Newton method) as well. Finally, we compared the measured result with that of an ASI (Aspheric Stitching Interferometer) made by the QED company, which resulted in an rms difference of only 2.5 nm, showing a similar shape of astigmatism aberration.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.1
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• pp.63-67
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• 2002

In this paper we analyzed the optical property after we chose the lens system to cover a wide angular field which is designed to use a established designed meniscus negative outer element. The special quality of the system is to offer a wide angular field by getting only one outer negative element and to be a compacted optical system to utilize the good point of miniaturization and light-weighturization by using two aspheric surfaces. Also, we observed the aberration correction of a aspheric as we investigated two aspheric's forms to use for a aberration correction.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.83-88
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• 2008

Purpose: To design an anamorphic aspherical prism lens for the HMD optical system. Methods: First, we get the initial data, needed in design, which are distances between each surface etc., by analyzing user's demended specifications and by drawing geometrically the shape of prism lens by using CAD. Based on these data and using 'ode V' which is an optical design software, we could progress the optimization in which we treat the coefficients of the anamorphic aspherical surface as the principal variables. To reduce the cost in DTM manufacturing, we would optimize the optical system with the transmitting surface, existed in the direction of video device among 3 surfaces of the prism lens, remaining as a plane. Results: we could design one anamorphic aspherical prism lens which has the finite ray aberration of 15 ${\mu}m$, the distortion of 0.5%, and the MTF value of 0.3 over at 36 lp/mm for the video device of 12 mm ${\times}$ 9 mm size. Conclusions: We designed a prism lens used for HMD. This prism lens has the optical capacities of 15 ${\mu}m$ finite ray aberration and 0.5% distortion for the video device of 12 mm ${\times}$ 9 mm size, and become the optical system having the MTF value of 0.3 over at 36 lp/mm.

• Korean Journal of Optics and Photonics
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• v.24 no.4
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• pp.189-195
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• 2013

An F/1.2 infrared optical system that involves two aspheric BD-2 lenses and an aspheric diffractive surface was designed over $8-14{\mu}m$ with a field angle of $15.2^{\circ}$. The system may be used in uncooled cameras and is analyzed using beam synthesis propagation (BSP). The diffractive surface is modeled as a physical surface with a given thickness, and results are compared with those obtained by conventional methods, such as the exit-pupil method and a method which superposes diffraction orders.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.194-195
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• 2004

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.189-193
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• 1997

Aspheric pick-up lenses are increasingly used in consumer products such as computer and multimedia, as their mass production has become possible owing to the injection molding process. However still much work needs to be done for more effective manufacture of aspheric lenses, one area of which is the in-line inspection of produced lenses. In this paper, we present a lateral-shearing interferometer that has specially been designed to have a high immunity to external vibration and atmospheric disturbance. The interferometer comprises four prisms. They are directly attached to each other using an immersion oil so that relative sliding motions between the prisms are allowed. Their relative displacement can readily generate necessary lateral-shearing and phase-shifting to determine the wavefront of the beam collimated by the lens under inspection. A special phase-measuring algorithm of arbitrary-bucket is adopted to compensate the phase-shifting error caused by the thickness reduction in the immersion oil. Zernike polynomial fitting has done for determinating quantitative aberration of aspheric pick-up lenses. The interferometer built in this work is robust to external mechanical vibration and atmospheric disturbance so that experimental results show that it has a repeatability of less than λ/100.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.79-85
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• 2021

In this paper, a study is conducted on the design of an optical system of a time-of-flight (TOF) laser distance sensor that can measure long distances by minimizing beam divergence. When measuring a long distance, the amount of light on the object's surface decreases as the distance increases, due to the diffusion angle of the laser beam, and thus the beam at the sensor also decreases, causing measurement errors. In general, a cylindrical lens is used to reduce the divergence beam angle. However, an optical system using a cylindrical lens has the problem of degraded performance due to the difficulty with assembly tolerance, as well as the problem of the increased size of the optical system, and thus the use of aspherical lenses has been increasing recently. Therefore, in this study, the optical efficiencies and assembly tolerances of optical systems using respectively a cylindrical lens and an aspherical lens are compared and analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.290-296
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• 2019

Head-up displays for vehicles play an important role in displaying various information about the safety and convenience of driving on the windshield of the vehicle. In this study, ultra-precision machining was performed and evaluated as a method for machining a large-area aspheric free-form mirror that is applicable to augmented reality technology. Precision diamond cutting is highly accurate and suitable for the production of advanced parts with excellent surface integrity, low surface roughness, and low residual stress. By using an aspheric free-form mold, it is possible to improve the optical transfer function, reduce the distortion path, and realize a special image field curvature. To make such a mold, the diamond cutting method was used, and the result was evaluated using an aspherical shape-measuring machine. As a result, it was possible to the mold with shape accuracy (PV) below $1{\mu}m$ and surface roughness (Ra) below $0.02{\mu}m$.

• The Optical Journal
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• s.102
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• pp.18-21
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• 2006

최근에는 난이도가 높은 다양한 초정밀 광학 소자, 비구면 광학 소자나 마이크로 광학 소자 등 대부분의 가공 공정이 초정밀이면서 초미세한 연삭 가공에 의해 이루어지게 되었다. 그리고 일반적으로 초정밀 및 미세 가공 기술로서 자주 예로 드는 반도체 공정 기술에서는 제조가 어려운 다양한 광학 재료, 광학 부품 가공에 자유롭게 접근할 수 있는 초정밀 및 초미세 기계 가공으로서의 연삭 가공 기술의 진보가 새롭게 인식되기 시작했다고 할 수 있다.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.149-150
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• 2008