• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.525-532
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• 2013

Contrary to the academic interests of other existing studies elsewhere, this study deals with how the alignment algorithms such as sensitivity or Differential Wavefront Sampling (DWS) can be better used under effects from field, compensator positioning and environmental errors unavoidable from the shop-floor alignment work. First, the influences of aforementioned errors to the alignment state estimation was investigated with the algorithms. The environmental error was then found to be the dominant factor influencing the alignment state prediction accuracy. Having understood such relationship between the distorted system wavefront caused by the error sources and the alignment state prediction, we used it for simulated and experimental alignment runs for Infrared Optical System (IROS). The difference between trial alignment runs and experiment was quite close, independent of alignment methods; 6 nm rms for sensitivity method and 13 nm rms for DWS. This demonstrates the practical usefulness and importance of the prior error analysis using the alignment algorithms before the actual alignment runs begin. The error analysis methodology, its application to the actual alignment of IROS and their results are described together with their implications.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.31.1-31.1
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• 2011

In this study, we investigated alignment state estimation performances of the three methods i.e. merit function regression (MFR), differential wavefront sampling (DWS) and Multiple Design Configuration Optimization (MDCO). The three target optical systems are 1) a two-mirror Cassegrain system for deep space Earth observation, 2) intermediate size three-mirror anastigmat for Earth ocean monitoring, and 3) extremely large segmented optical system for astronomical observation. We ran alignment state estimation simulation for several alignment perturbation cases including 1mm to 10mm in decenter and from 0.1 to 1 degree in tilt perturbation error for the two-mirror Cassegrain system. In general, we note that MDCO shows more competitive estimation performance than MFR and DWS. The computational concept, case definition and the simulation results are discussed with implications to future works.

• 천문학논총
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• 제21권2호
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• pp.43-49
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• 2006

The KASINICS (KASI Near Infrared Camera System) is a ground-based Near-Infrared (NIR) imaging instrument developed by the Korea Astronomy and Space Science Institute (KASI). In this paper, we report the test results of the KASINICS camera optics system which is comprised of a 1-1 Offner relay. We measure that the surface RMS fluctuations of the Offner mirrors are at the level of $10^{-1}-10^{-2}$ of the target wavelengths, showing that the mirrors are sufficiently smooth for NIR observations. The alignment of the Offner optics system has been checked too. Our ray-tracing simulations find that the image quality should not degrade more than the pixel size of the KASINICS ($40{\mu}m$), if a de-centering or a tilt of the Offner mirrors are within 5mm, or $2.5^{\circ}$. Our measurement shows that the de-centering or the tilt of the Offner mirrors are less than 1 mm or $0.5^{\circ}$, assuring that the KASINICS image quality are not affected by the alignment errors. We have also measured that the optics resolution is $20{\mu}m$ and it does not degrade more than 10% over the detector surface area of 14.3 mm ${/times}$ 14.3mm. Overall, we conclude that the KASINICS optics system satisfies the design requirements for NIR imaging observations.

• 한국광학회지
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• 제18권1호
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• pp.31-36
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• 2007

직경과 초점거리가 수 mm인 카메라폰 렌즈의 성능을 평가하는 변조전달함수(Modulation Transfer Function: MTF) 측정장치를 개발 하였다. 전체 측정장치는 물체부, 상분석부, 렌즈 마운터로 구성되며, 물체부는 비축상 측정을 위하여 회전한다. 렌즈의 정밀한 정렬을 위하여 정밀한 수평형 거치대를 제작하였으며 광축 조정과 렌즈의 기울어짐 등의 문제를 매우 효과적으로 개선하였다. 시험렌즈의 초기정렬이 끝나면 자동으로 MTF를 측정하며 측정시간은 10초 이내이다.

• 한국항공우주학회지
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• 제32권10호
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• pp.142-146
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• 2004

인공위성용 지구관측 카메라나 천문관측 망원경에는 무게와 부피의 제약 때문에 Cassegrain 방식 망원경이 많이 쓰인다. 이와 같은 위성용 광학계의 성공적인 임무 수행을 위해서는 광학계의 정밀 정렬이 필수적이다. 본 논문에서는 인공위생용 지구관측 카메라인 MAC (Medium-sized Aperture Camera)의 조립 과정에 적용된 컴퓨터를 이용한 광학정렬 방법의 모사와 정렬실험 결과를 정리한다.

• Journal of Astronomy and Space Sciences
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• 제30권1호
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• pp.49-58
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• 2013

ARGO-M is a satellite laser ranging (SLR) system developed by the Korea Astronomy and Space Science Institute with the consideration of mobility and daytime and nighttime satellite observation. The ARGO-M optical system consists of 40 cm receiving telescope, 10 cm transmitting telescope, and detecting optics. For the development of ARGO-M optical system, the structural analysis was performed with regard to the optics and optomechanics design and the optical components. To ensure the optical performance, the quality was tested at the level of parts using the laser interferometer and ultra-high-precision measuring instruments. The assembly and alignment of ARGO-M optical system were conducted at an auto-collimation facility. As the transmission and reception are separated in the ARGO-M optical system, the pointing alignment between the transmitting telescope and receiving telescope is critical for precise target pointing. Thus, the alignment using the ground target and the radiant point observation of transmitting laser beam was carried out, and the lines of sight for the two telescopes were aligned within the required pointing precision. This paper describes the design, structural analysis, manufacture and assembly of parts, and entire process related with the alignment for the ARGO-M optical system.

• Journal of Astronomy and Space Sciences
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• 제23권4호
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• pp.327-336
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• 2006

In this paper, gain loss of KVN (Korean VLBI Network) 21-m shaped Cassegrain antenna due to misalignment of antenna optics is calculated using ray-tracing method. It enables us to estimate alignment tolerances of feed and sub-reflector positioning. According to numerical results, KVN 21-m shaped Cassegrain antenna's gain loss is more sensitive to positions of feed and sub-reflector than in case of the equivalent classical Cassegrain antenna. The result of calculation is believed to be utilized as a possible guideline when checking the performance of the antenna system.

• Journal of Astronomy and Space Sciences
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• 제31권3호
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• pp.241-246
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• 2014

The Amon-Ra instrument is the main optical payload of the proposed EARTHSHINE satellite. It consists of a visible wavelength instrument and an IR energy channel instrument to measure a global Earth albedo. We report a new sensitivity technique for efficient alignment of the visible channel instrument. Whilst the sensitivity table method has been widely used in the alignment process, the straightforward application of the method tends to produce slow process convergence because of shop floor alignment practice uncertainties. We investigated the error sources commonly associated with alignment practices and used them when estimating the Zernike polynomial coefficients. Aided with single center field wavefront error (WFE) measurements and their corresponding Zernike polynomial coefficients, the method involves the construction and use of an experimental, instead of simulated, sensitivity table to be used for alignment state estimations. A trial alignment experiment for the Amon Ra optical system was performed and the results show that 71.28 nm in rms WFE was achieved only after two alignment iterations. This tends to demonstrate its superior performance to the conventional method.

• 한국광학회지
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• 제28권4호
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• pp.146-152
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• 2017

우주용 인공위성 카메라를 구성하는 반사경의 정렬은 광학계의 고분해능, 고성능을 얻기 위한 중요한 과정 중 하나이다. 반사경들의 상호정렬에는 큐브미러(cube mirror)가 대신 사용되기 때문에, 각 반사경과 해당 큐브미러 간의 상호위치관계 정보가 우선 필요하다. 따라서 우주용 카메라 반사경들의 정렬을 위해 각 반사경의 정점과 해당 큐브미러의 상대 좌표값을 정확하게 측정해야하며, 본 논문에서는 컴퓨터 제작 홀로그램(computer-generated hologram, CGH)의 정렬용 세그먼트와 광섬유를 이용하는 새로운 측정 시스템을 제안함으로써 우주용 카메라를 구성하는 반사경의 정점을 요구조건 이내로 측정할 수 있었다. 측정 시스템은 광학계 평가용 간섭계, CGH, 광섬유, 반사경으로 구성되어 있으며, 최종적으로 데오도라이트를 이용해 큐브미러를 기준으로 주 반사경의 정점에 위치한 광섬유 끝단의 3차원 상대 좌표값을 $25{\mu}m$ 이하의 정밀도로 측정할 수 있었다.

• 한국광학회지
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• 제15권4호
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• pp.391-396
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• 2004

인공위성용 지구관측 카메라나 우주관측 망원경에는 크기와 무게의 제약 때문에 Cassegrain 방식의 망원경이 많이 쓰인다. 이와 같은 우주광학계의 성공적인 임무수행을 위해서는 망원경부의 정밀한 광학정렬이 매우 중요하다. 본 논문에서는 정렬 정밀도에 따른 Cassegrain 방식 망원경부의 광학정렬 방법 중, 간섭무늬를 이용한 방법, 파면오차를 이용한 방법, 역최적화 광학정렬 방법 등을 모사를 통해 제시하고, 현재 개발 중인 구경 300 mm급 소형 위성용 카메라에 적용한 광학정렬 실험 결과를 정리한다.