• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.14-19
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• 2007

Angle sensors based on the principle of autocollimation, which are usually called autocollimators, can accurately measure small tilt angles of a light-reflecting flat surface. This paper describes a prototype micro-angle sensor that is based on the laser autocollimation technique. The new angle sensor is compact and consists of a laser diode as the light source and a quadrant photodiode as a position-sensing device. Because of its concise design, the microangle sensor facilitates dynamic measurements of the angular error motions of a precision stage without influencing the original dynamic properties of the stage. This is because the sensor only requires a small extra target mirror to be mounted on the stage. The sensitivity of the angle detection is independent of the focal length of the objective lens; therefore, an objective lens with a relatively short focal length is employed to reduce the size of the device. The micro-angle sensor uses a single lens for the both the laser collimation and focusing, which distinguishes it from the conventional laser autocollimation method that has separate collimate and objective lenses. The new micro-angle sensor has dimensions of $15.1\times22.0\times14.0mm$ and its resolution is better than 0.1 arc-second The optical design and performance of this micro-angle sensor were verified by experimental results.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.64-70
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• 2003

A measurement of spacecraft alignment is an important process of spacecraft assembly, integration and test because it is necessary that a ground station controls the precise positions of on-orbit spacecraft by using the alignment data of attitude orbit control sensors(AOCS) on spacecraft. In addition, accuracy of spacecraft alignment requirement is about $0.1^{\circ}$~$0.7^{\circ}$. The spacecraft alignment is measured by autocollimation of theodolite. This paper describes the measurement principle and method of spacecraft alignment. The result shows that all of the AOCS on the spacecraft are aligned within the tolerance required through the alignment measurement.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.537-542
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• 2002

Null tests using two different kinds of null corrector have been discussed. A parabolic mirror was used as a surface under test. After designing, encoding, and fabricating the CGH (computer generated hologram), the null CGH test was performed. An autocollimation test was also performed using a flat mirror. The reliability of the null CGH test has been discussed by comparing the result obtained by both null tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.105-111
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• 2003

A measurement of spacecraft alignment is an important process of spacecraft assembly, integration and test. Because, it is necessary that a operator of a ground station controls the precise positions of on-orbit spacecraft by using the alignment data of attitude orbit control sensors(AOCS) on spacecraft. And, an accuracy of spacecraft alignment requirement is about $0.1^{\circ}{\sim}0.7^{\circ}$. A spacecraft alignment is measured by autocollimation of theodolite. This paper describes the measurement principle and method of spacecraft alignment. The result shows that all the AOCS on the spacecraft are aligned within the tolerance required through the alignment measurement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.537-540
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• 2005

The attitude control, sensors and camera installed on the spacecraft should be located according to the system alignment requirement. The alignment measurement requirement accuracy for the sensors should be below $\pm$0.1. Therefore, Alignment Measurement System which is combined theodolite, Rotating table and digital inclinometer etc., should be used. As the measurement accuracy is required very precise, the appropriate measurement procedure and alignment angle measurement, calculation and shimming work should is accomplished. Consequently, this paper is accomplished the works to align the measurement requirement accuracy throughout alignment measurement and shimming work of installed module and sensor

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1793-1796
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• 2005

The auto-collimation by using theodolite has been accomplished for the straight measurement and the horizontality adjustment. But according to the procedure of auto-collimation or composition of the measurement equipment, an error of the measurement can be occurred. Therefore, this paper accomplished the research for enhancement of measurement accuracy according to measurement procedure of auto-collimation. For that, it has been compared the study of the combination of several precise measurement equipment with using of several theodolite.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.431-436
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• 1994

An automatic spectrorefractometer with a Littrow spectrometer arrangement has been designed and fabricated to measure the refractive indices of solids and liquids from the visible to the near IR. The achievable accuracy is numericaly analyzed by varying the measuring parameters and the electromechanical system for measuring the prism angle with a rotary encoder and a position sensitive detector is fabricated. The performance of the instrument is discussed in detail and the results of measurements are given. given.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.33.1-33.1
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• 2009

GMT(Giant Magellan Telescope)는 그레고리안(Gregorian) 방식 망원경이다. 일반적으로 그레고리안 방식은 포물면인 주경과 타원면인 부경으로 구성되어 있으나, GMT의 주경은 비구면계수가 -0.99829인 타원면이다. 부경은 지름 1.063m 7장의 반사경이 3.2m의 부경을 이루며 곡률반경은 4.2058m, 비구면계수는 -0.71087이다. 주경과 부경은 모두 1장의 중앙 반사경과 6장의 비축 반사경으로 이루어져 있다. 따라서 GMT 광학계에서 대구경 비축 비구면 반사경의 가공 및 테스트는 매우 중요하다. 이 발표에서는 GMT 부경을 테스트하기 위하여, 타원면의 기본적인 광학적 특성을 이용한 테스트 방법과 이 방법의 단점을 보완하기 위해 Reference 반사경을 이용하는 방법, 그리고 Null compensator를 이용한 방법 등을 제시한다. Null compensator를 이용한 방법에는 일반적으로 Autostigmatic 방식과 Autocollimation 방식이 있으며 이 발표에서는 이 두 방식을 상호 비교한 연구 결과에 대하여 논의한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.98-104
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• 2004

A spacecraft alignment measurement requires highly precise measurement accuracy which is less than ${\pm}0.5^{\circ}$. In general, such an alignment measurement has been performed by using three or more theodolites. However, it contains the latent accuracy error because of a position stability of spacecraft, etc. The new alignment measurement system which consists of a theodoilte, a rotating table and a digital inclinometer has been developed to possibly to possibly reduce the error. This paper describes the concept and methodology of methodology of measurement system. It was found that new measurement system can provide more accurate results than the conventional system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.2
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• pp.173-180
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• 2012

The most recent, 80 mega pixels digital camera appeared through the development of digital technology, and nonmetric digital cameras have been using in various field of photogrammetry. In this study, we experimented lens calibration using aerial photographs and ground control points. The aerial photographs were taken a non-metric digital camera which is CMOS(Complementary Metal Oxide Semiconductor) 21.1 mega pixels sensor and 35mm lens at a helicopter. And the ground control points were selected on the 1:1,000 plotting origin data. As a result, we calculated focal length, PPA(Principal Point of Autocollimation) and symmetric radial distortion coefficients from the lens. Also, RMSE(root mean square error) and maximum residual of the ground control points from the aerial triangulation were compared before and after calibration. And we found that the accuracy of the after calibration was improved very significantly.