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고에너지 레이저용 고밀집 다채널 실리콘-카바이드 변형거울의 정밀 조립 방법
이혁교,조선호,김시현,이재현,강필성 한국광학회 2024 한국광학회지 Vol.35 No.4
대기 중 레이저 빔 전파 시 대기 난류에 의한 악영향을 해소하고 빔품질을 향상시키기 위해서 적응광학을 사용한다. 본 논문에서는 장거리 레이저 전송을 위한 적응광학계의 핵심 부품인 변형거울의 정밀 조립 방법을 제안한다. 변형거울은 거울판과 구동기, 플렉셔(flexure)로 구성되며 이 부품들을 정밀하게 조립하는 것이 성능을 좌우한다. 본 논문에서는 지그의 설계/제작을 통해 고밀집 다채널 실리콘-카바이드 변형거울을 완성했으며, 변형거울 성능 확인을 통해 제안한 방법의 유효성을 검증했다. A laser beam propagated in free space might be negatively affected by atmospheric turbulence. To overcome this and correct the wavefront errorof the laser beam itself, a deformable mirror (DM), which is a key component of adaptive optics, is widely used. In this paper, a novel precision assembling method is suggested for a multi-channel high-density DM. The material of the mirror sheet of the DM is silicon carbide (SiC), and the actuator is a stacked-type lead-magnesium-niobate (Pb(Mg 1/3 Nb 2/3 )O 3 ; PMN). To connect the mirror sheet and each actuator, a flexure is inserted. The flexure can make the DM operate with full strokes without the failure of adhesive. A series of jigs were designed and applied in order to assemble these three parts (the mirror sheet, actuators, and flexures) precisely. After assembly, the performance of the DM was also checked.
Eight-axis-polishing Machine for Large Off-axis Aspheric Optics
이혁교,양호순,문일권,Hagyong Kihm,Jae-Hyub Lee,Yun Woo Lee 한국광학회 2011 Current Optics and Photonics Vol.15 No.4
For the purpose of fabricating off-axis aspheric optics, we propose an 8-axis-polishing machine combined with a testing tower whose height is up to 9 m. The proposed polishing machine was designed and analyzed by using a well-known finite element method. The eight axes of the machine have a synchronized motion generated by a computer, and each axis was calibrated by a heterodyne laser interferometer or an optical encoder. After calibration, the maximum positioning error of the machine was less than 2 μm within a whole 2 m × 2 m area. A typical fabrication result of a φ1.5 m concave mirror was also described in this manuscript.
Pixel-based Absolute Test of a 1-m Lightweight Mirror for a Space Telescope
이혁교,김학용,양호순,김영식,Yun-Woo Lee,이주형 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.9
Large mirrors for spaceborne instruments require high-accuracy interferometry to measure theirsurface shapes. The mirrors often should be tested and fabricated more accurately than the referenceoptics against which they are compared. Furthermore, the mirrors require precise measurement tonanometer accuracy in weightless conditions. In order to address these requirements, an absolutetest scheme should be adopted to separate the surface shape of the target mirror from the errors inthe interferometer and the errors due to the gravity effect. In this manuscript, we propose a newpixel-based absolute test method that can extract the surface shape of the mirror without the errorscaused by both the interferometer and the gravity effect. The proposed method is demonstratedwith actual data from a lightweight primary mirror with a diameter of 1 m that has partially closedpockets at the back side and three bosses at the rim for flexure mounting.
Contrast 향상 필름 평가를 위한 실시간 검사장치 개발
이혁교,전병혁,이회윤,이윤우,Rhee, Hyug-Gyo,Jeon, Byeong-Hyug,Lee, Hoi-Yun,Lee, Yun-Woo 한국광학회 2008 한국광학회지 Vol.19 No.4
PDP(plasma display panel)를 비롯한 대형 디스플레이는 외부의 광이 디스플레이 내부로 입사될 경우 화질 및 명암이 저하된다. 이 문제를 해결하기 위해서 최근 관련 산업체에서는 $1\;m^2$급의 대형 투명필름 위에 수십${\sim}$수백 ${\mu}m$ 수준의 미세 패턴을 새겨서 외부 광을 차단하는 contrast 향상 필름을 개발 중이다. 이 필름이 디스플레이에 적용되려면 가장 중요한 것이 패턴의 균일도 및 이물 여부이다. 하지만 기존의 검사장비로는 $1\;m^2$급의 대형 광학 필름을 $100\;{\mu}m$ 수준의 분해능으로 짧은 시간 내에 측정할 수 없다. 본 연구에 서는 이것이 가능한 검사장비를 제안, 구축하며 실험을 통해 평가한다. The light from the exterior considerably deteriorates the performance of displays including PDP (plasma display panel). Thus semi-conductor industries have developed a special optical film that can block or absorb the exterior light. In this paper, we propose a new inspection system for tracing the defects of the film. Our system is able to inspect a $1.5\;m\;{\times}\;1\;m$ area for 10 sec with $127\;{\mu}m\;{\times}\;50{\mu}m$ spatial resolution.
Two-dimensional Linewidth Enhancement by Interference in Direct Laser Beam Lithography
이혁교,이윤우 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.5
We propose a novel direct laser beam lithographic technique with enhanced resolution by employing interference. An interference generator is introduced in our system to separate an input beam into two orthogonally polarized beams. After going through an exposure lens, these two beams meet again on the focal point and generate a small interferogram that sharpens the shape of the focused beam spot. The direction of the interference fringe can be adjusted to fabricate two-dimensional patterns.
삼차원 좌표 측정을 위한 부피 간섭계의 오차분석 및 성능평가
이혁교,주지영,김승우 한국광학회 2002 한국광학회지 Vol.13 No.6
본 연구에서는 삼차원 공간상에서 절대 좌표를 측정하기 위한 부피 간섭계의 오차원인을 분석하고 각 오차원인이 최종 결과에 미치는 영향을 계산했다. 계산결과 광검출기 배열의 비선형성, 압전소자의 비선형성, 광섬유 내부의 온도변화 둥이 오차의 주요 원인임을 알 수 있다. 제안된 간섭계의 성능을 실험적으로 검증하기 위해 분해능 측정 및 이차원 광학식 스케일과의 비교를 수행했다. 또한 간섭계의 성능을 좀 더 엄밀하게 검증하기 위해 자가보정법을 적용해서 공간상에서 간섭계가 갖는 계통오차를 추출했으며 60mm$\times$60mm$\times$20mm공간에서 최대오차 1 $\mu\textrm{m}$ 이하를 얻었다. We have recently proposed the new concept of a phase-measuring volumetric interferometer that enables us to accurately measure the xyz-coordinates of the probe without metrology frames. The interferometer is composed of a movable target and a fixed photo-detector array. The target is made of point diffraction sources to emit two spherical wavefronts, whose interference is monitored by an array of photo-detectors. Phase shifting is applied to obtain the precise phase values of the photo-detectors. Then the measured phases are fitted to a geometric model of multilateration so as to determine the xyz-location of the target by minimizing least square errors. The proposed interferometer has been designed and built with a volumetric uncertainty of less than 1.0 $\mu\textrm{m}$ within a cubic working volume of side 120 mm. Here, in this paper, we also present error sources, an evaluated uncertainty, and test results from the prototype system. The self-calibration of two-dimensional precision metrology stages is applied to test the performance of the interferometer.