• 한국기계가공학회지
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• 제7권2호
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• pp.3-7
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• 2008

A polishing machine adopting a new unique structural mechanism has been developed, named as a swing-arm type polishing machine. The mechanism is such that the tool path tracks on a spherical surface, of which the diameter is adjusted by setting up the machine mechanism properly. It has a strong benefit especially for polishing axis-symmetric concave mirror surfaces. The swing-arm type polishing machine with 5-axes has been designed in order to polish a concave mirror surface lip to diameter of 2 meters. The drawings are made using 3D CAD and strain-stress analysis has been done by finite element method. AC servo-motor has been used to move the swing arm and a operating software has been developed using a LapVIEW tool. Result of the test run was satisfactory which convinces the usefulness of the swing-arm type polishing machine.

• 대한수학회지
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• 제52권2호
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• pp.389-402
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• 2015

A symmetric union is a diagram of a knot, obtained from diagrams of a knot in the 3-space and its mirror image, which are symmetric with respect to an axis in the 2-plane, by connecting them with 2-tangles with twists along the axis and 2-tangles with no twists. This paper presents an invariant of knots with symmetric union presentations, which is called the minimal twisting number, and the minimal twisting number of $10_{42}$ is shown to be two. This paper also presents a sufficient condition for non-amphicheirality of a knot with a certain symmetric union presentation.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.604-613
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• 2015

An unobstructed off-axis two-mirror system is presented in this paper. First a suitable initial configuration is established based on third-order aberration theory. In order to achieve a wide field of view (FOV) with high image quality , the diffractive mirror is adopted in the two-mirror system to increase the optimization freedom and the aberration relationship between diffractive phase coefficients and Zernike coefficients is derived. Furthermore, a complete comparison design example with a focal length of 1200 mm, F-number of 12, and FOV of 40° × 2° is given to verify the aberration correction ability of the diffractive mirror. The system average wavefront error is 0.007 λ (λ=0.6328 μm) developed from 0.061 λ when the system didn’t adopt the diffractive mirror. In this system the phase modulation function of the diffractive mirror is established as an even function of x, so we could obtain a symmetrical imaging quality about the tangential plane, and the symmetric aberration performance also brings considerable convenience to alignment and testing for the system.

• Current Optics and Photonics
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• 제1권4호
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• pp.364-371
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• 2017

Compared to one made of glass, an aluminum mirror features light weight, compact design, low cost, and quick manufacturing. Reflective mirrors and supporting structures can be made from the same material, to improve the athermal performance of the system. With the rapid development of ultraprecise machining technologies, the field of applications for aluminum mirrors has been developed rapidly. However, most of them are rotationally symmetric in shape, and are used for infrared applications. In this paper, the design and manufacture of an off-axis aluminum mirror used for a three-mirror-anastigmat (TMA) optical system at visible wavelengths is presented. An optimized, lightweight design provides a weight reduction of more than 40%, while the surface deformation caused by earth's gravity can meet the required tolerance. The two pieces of an off-axis mirror can be diamond-turned simultaneously in one setup. The centrifugal deformation of the off-axis mirror during single-point diamond turning (SPDT) is simulated through the finite-element method (FEM). The techniques used to overcome centrifugal deformation are thoroughly described in this paper, and the surface error is reduced to about 1% of the original value. After post-polishing, the form error is $1/30{\lambda}$ RMS and the surface roughness is better than 5 nm Ra, which can meet the requirements for visible-light imaging.

• 한국광학회지
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• 제28권6호
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• pp.263-272
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• 2017

넓은 시야를 가지는 광학계에서는 전반부는 음의 굴절능, 후반부는 양의 굴절능을 가지는 inverted telephoto 구조가 일반적으로 사용되고 있고, 2반사광학계에서는 inverse Cassegrain system이 inverted telephoto 구조에 해당한다. 하지만 통상적인 회전대칭 구성의 inverse Cassegrain system에서는 시야가 가려지고 광선의 차폐가 심한 문제점이 있다. 이 연구에서는 이점을 고려하여 inverse Cassegrain system의 제2면에 조리개를 두어 시야를 넓히고, 광선의 차폐가 없는 비축시야만을 사용하는 광시야 비축 2반사광학계를 설계하였다.

• Journal of Magnetics
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• 제19권2호
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• pp.130-139
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• 2014

This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator's linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.

• 한국광학회지
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• 제4권4호
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• pp.420-427
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• 1993

융착 접속 기술을 이용하여 다중모우드 광섬유와 단일 모우드 광섬유내에 유전체 박막 거울을 제작하였다. $45{\circ}$ 유전체 거울이 내장된 광섬유는 극소형이며, 광학적인 손실이 매우 작고(1.3 ${\mu}m$에서, 다중 모우드 광섬유의 경우 0.2dB, 단일 모우드 광섬유의 경우 0.5dB), 기계적 강도가 우수한 결합기로 사용될 수 있다. 반사율은 파장에 따라 변화하며, 편광에 매우 민감하였다. 백색광을 사용하여 유전체 거울로부터 반사되는 출력 파워를 원거리 스캔하며 측정하였을 때 출력 빔의 모양은 거의 원형 대칭으로써 최대 파워의 5%에서 측정된 종횡비는 1.09이었다. 다이오우드 레이저 광원을 사용하여 측정한 다중모우드 광섬유 결합기의 광분파율은 종래의 FBT(Fused Biconical Taper) 결합기보다 입력 광신호의 결합 조건에 따른 변화가 훨씬 적어서 사용하는 광통신 시스템의 모우드 잡음에 덜 민감하다. 광섬유 축에 수직하게 증착된 다층 유전체 거울들의 반사율 스펙트럼 특성을 측정하였으며, 행렬 해석법을 사용하여 실험 결과를 분석, 고찰하였다.