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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.
이혁교(Hyug-Gyo Rhee),김영식(Young-Sik Ghim),이주형(Joohyong Lee),양호순(Ho-Soon Yang),이윤우(Yun Woo Lee) Korean Society for Precision Engineering 2014 한국정밀공학회지 Vol.31 No.3
We propose a new variant of lateral shearing interferometer with a tunable laser source that enables 3D surface profile measurements of freeform optics with high speed, high vertical resolution, large departure, and large field-of-view. We have verified the proposed technique by comparing our measurement result with that of an existing technique and measuring a representative sample of freeform optics. Moreover, we propose a new algorithm that is able to compensate the rotational inaccuracy.
적응광학계용 37채널 SiC 변형거울을 이용한 파면 보상
안교훈,이혁교,이호재,이준호,양호순,김학용,Ahn, Kyohoon,Rhee, Hyug-Gyo,Lee, Ho-Jae,Lee, Jun-Ho,Yang, Ho-Soon,Kihm, Hagyong 한국광학회 2016 한국광학회지 Vol.27 No.3
본 논문에서는 37채널을 갖는 적응광학계용 SiC(Silicon Carbide) 변형거울의 파면 보상 성능 검증에 관한 내용을 다룬다. 컴퓨터 시뮬레이션을 통해 SiC 변형거울의 파면 보상 성능을 예측하였고, 실제 closed-loop 적응광학계를 구성하여 파면 보상 성능을 확인 하였다. Closed-loop 적응광학계는 광원, 위상판, SiC 변형거울, 고속 샥-하트만 센서 그리고 제어용 컴퓨터로 구성되어있다. 회전하는 위상판에 의해 왜곡된 파면을 샥-하트만 센서로 측정하고, SiC 변형거울을 이용하여 왜곡된 파면을 보상해주는 시스템이다. 결과적으로 closed-loop 적응광학계에서 500 Hz의 속도로 PV(Peak-to-Valley) $0.3{\mu}m{\sim}0.9{\mu}m$, RMS(Root-Mean-Square) $0.06{\mu}m{\sim}0.25{\mu}m$의 왜곡된 파면을 PV $0.1{\mu}m$, RMS $0.03{\mu}m$이하로 보상시킬 수 있었다. In this paper, we deal with the wavefront compensation capability of a silicon carbide (SiC) deformable mirror (DM) with 37 actuators for adaptive optics. The wavefront compensation capability of the SiC DM is predicted by computer simulation and examined by actual experiments with a closed-loop adaptive optics system consistsing of a light source, a phase plate, a SiC DM, a high speed Shack-Hartmann sensor, and a control computer. Distortion of wavefront is caused by the phase plate in the closed-loop adaptive optics system. The distorted wavefront has a peak-to-valley (PV) wavefront error of $0.3{\mu}m{\sim}0.9{\mu}m$ and root-mean-square (RMS) error of $0.06{\mu}m{\sim}0.25{\mu}m$. The high-speed Shack-Hartmann sensor measures the wavefront error of the distortion caused by the phase plate, and the SiC DM compensates for the distorted wavefront. The compensated wavefront has residual errors lower than $0.1{\mu}m$ PV and $0.03{\mu}m$ RMS. Consequently, we conclude that we can compensate for the distorted wavefront using the SiC DM in the closed-loop adaptive optics system with an operating frequency speed of 500 Hz.
Parametric Study for a Diffraction Optics Fabrication by Using a Direct Laser Lithographic System
김영광(Young-Gwang Kim),이혁교(Hyug-Gyo Rhee),김영식(Young-Sik Ghim),이윤우(Yun-Woo Lee) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.10
A direct laser lithography system is widely used to fabricate various types of DOEs (Diffractive Optical Elements) including lenses made as CGH (Computer Generated Hologram). However, a parametric study that uniformly and precisely fabricates the diffractive patterns on a large area (up to 200 mm X 200 mm) has not yet been reported. In this paper, four parameters (Focal Position Error, Intensity Variation of the Lithographic Beam, Patterning Speed, and Etching Time) were considered for stabilization of the direct laser lithography system, and the experimental results were presented.
자유 곡면 형상 측정을 위한 백색광 주사 간섭계의 정확도 향상 및 시스템 오차 분석
김영식(Young-Sik Ghim),Angela Davies,이혁교(Hyug-Gyo Rhee) Korean Society for Precision Engineering 2014 한국정밀공학회지 Vol.31 No.7
Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.
Fabrication of Dual-Line by Using a Laser Ablation Phenomenon in Direct Laser Lithographic System
김영광(Young-Gwang Kim),안누호앙(Nguyen Nu Hoang Anh),이혁교(Hyug-Gyo Rhee),김영식(Young-Sik Ghim) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.11
Diffractive Optical Element (DOE) composed of repetitive patterns is necessary for 3D measurement, or for converting a laser beam into several spots. In this study, DOEs were fabricated through a direct laser lithographic system of which it is easy to fabricate a pattern on the specimen at low cost and under relatively simple process conditions. A commonly used method in laser direct laser lithography is the thermochemical technique. In this way, a single-line can be produced. At this time, when the high power of the laser is used, the laser ablation phenomenon occurs, so that a dual-line can be produced. As a result, it is possible to fabricate a pattern quickly with the proposed process method. And especially, it can increase the effect in repetitive patterns production. To fabricate repetitive fine patterns using dual-line, hexagonal and tripleshaped patterns were fabricated, by using the writing speed and laser intensity appropriately. Optical performance evaluation was performed by comparing the diffracted image of the fabricated hexagonal repetitive patterns with the simulation result.
김기철(Gi-Chul Kim),서용범(Yongbum Seo),김영식(Young-Sik Ghim),이혁교(Hyug-Gyo Rhee) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.7
Tunable lasers have played an important role in a variety of industrial fields, by supplying stable output over a wide range of wavelengths. The external-cavity diode laser (ECDL) is widely used, because it provides a relatively broad tuning range, compact configuration, and easy control. In this paper, a new design is proposed for the Littman ECDL. The new design possesses a mode-hop-free single mode which is capable of tuning over a wide range of 17 nm, as a result of reconfiguring the pivot point location. Simulation and experimental studies were performed to verify our proposed method.
Modeling of Various Tool Influence Functions in Computer Controlled Optical Surfacing
김기철(Gi-Chul Kim),김영식(Young-Sik Ghim),이혁교(Hyug-Gyo Rhee),김학성(Hak-Sung Kim),양호순(Ho-Soon Yang),이윤우(Yun-Woo Lee) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.3
The computer controlled optical surfacing (CCOS) technique provides superior fabrication performance for optical mirrors when compared to the conventional method, which relies heavily on the skill of the optician. The CCOS technique provides improvements in terms of mass production, low cost, and short polishing time, and are achieved by estimating and controlling the moving speed of the tool and toolpath through a numerical analysis of the tool influence function (TIF). Hence, the exact estimation of various TIFs is critical for high convergence rates and high form accuracy in the CCOS process. In this paper, we suggest a new model for TIFs, which can be applied for various tool shapes, different velocity distributions, and non-uniform tool pressure distributions. Our proposed TIFs were also verified by comparisons with experimental results. We anticipate that these new TIFs will have a major role in improving the form accuracy and shortening the polishing time by increasing the accuracy of the material removal rate.