• 항공우주시스템공학회지
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• 제10권1호
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• pp.86-94
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• 2016

In this paper, position control of focal plane compensation device using piezoelectric actuator is conducted. The forcal plane compensation device installed on earth observation satellite camera compensates micro-vibration from reaction wheels. In this study, four experimental models of the open-loop compensation device are derived using MATLAB system identification toolbox in the input range of 0~50Hz. Subsequently, the PID controller for each model is designed and the performance test of each controller is conducted through MATLAB/Simulink. According to frequency response analysis of the closed-loop compensation device system, the PID controller designed for 38~50Hz input range has enough tracking performance for the whole 0~50Hz input range. The maximum output error is about $1{\mu}m$ for the input range. The simulation results has been verified by the experimental method.

• 항공우주시스템공학회지
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• 제9권4호
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• pp.23-30
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• 2015

The focal plane image stabilization for a camera is one of the most effective method that can increases the digital camera's image quality by compensating the vibration disturbance. The optical image stabilization can be implemented by making the focal plane to trace the path of incident light. To control the position of focal plane motion compensating stage precisely, a nonlinear control algorithm has been applied by considering coulomb friction which is nonlinear behavior of the compensator system. In our study, we have analyzed the hand shaking vibration using the gyro sensor, and made a mathematical model of compensating stage containing optical sensor and piezo-actuator. Then the nonlinear control algorithm has been designed and its performance has been verified by experiment. In this study, a friction driven peizo-electric actuator with $1{\mu}m$ resolution and 10mm/s speed has been used for stage movement.

• 한국멀티미디어학회논문지
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• 제12권4호
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• pp.502-511
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• 2009

컴퓨터그래픽스에서 실세계의 피사계 심도를 표현하기 위해 많은 연구가 진행되어왔다. 피사계 심도는 초점이 맺히는 초점평면을 기준으로 초점거리보다 가깝거나 멀 경우 렌즈와 조리개의 특성에 따라 해당부분이 흐리게 표현되는 현상이다. 이것을 이용하면 사람의 눈처럼 수정체에 의한 아웃 포커스 현상을 표현할 수 있기 때문에 현실감 있는 영상 표현이 가능하다. 본 논문에서는 eye-tracking 기술을 이용하여 사용자의 착안점을 계산하고 이를 바탕으로 GPU기반의 피사계 심도 조절방법을 구현함으로써 입체영상을 볼 때 발생하는 부작용을 줄이는 방법을 제안한다. 일반적으로 입체영상은 사용자의 초점을 강제로 조정하기 때문에 장시간 입체영상을 보면 어지럼증 등 부작용이 나타난다. 제안하는 기법은 눈동자의 움직임을 실시간으로 추적하여 입체영상의 피사계 심도를 자동으로 조절할 수 있기 때문에 부작용 저감이 가능하며 몰입감을 향상시킬 수 있다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권1호
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• pp.87-92
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• 2002

We present a simple experimental method for determination of limiting intrinsic fixed-pattern non-uniformity (NU) due to fabrication process in two-dimensional CCD multiplexers (MUXs) that are used for hybrid focal plane arrays. Here, this is done by determining separately the two NUs viz. that are $V_T$ dependent and $V_T$ independent. From these measurements, process dependent NU can be extracted. It is argued that $V_T$ dependent NU can be eliminated by designing novel input circuits whereas $V_T$ independent NU, primarily, dependent on process control and material variations may be reduced but cannot be eliminated completely and hence limits the FPA performance eventually.

• 제어로봇시스템학회논문지
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• 제7권12호
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• pp.1001-1008
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• 2001

This paper presents a new camera calibration algorithm for ill-conditioned cases in which the camera plane is nearly parallel to a set of non-coplanar calibration boards. for the ill-conditioned case, most of existing calibration approaches such as Tsais radial-alignment-constraint method cannot be applied. Recently, for the ill-conditioned coplanar calibration Lee&Lee[16] proposed an iterative algorithm based on the least square method. The non-coplanar calibration algorithm presented in this paper is an iterative two-stage procedure with extends the previous coplanar calibration algorithm. Through the first stage, camera, position and orientation parameters as well as one radial distortion factor are determined optimally for a given data of the scale factor and the focal length. In the second stage, the scale factor and the focal length are locally optimized. This process is repeated until any improvement cannot be expected any more Computational results are provided to show the performance of the algorithm developed.

• 한국항공우주학회지
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• 제43권5호
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• pp.472-478
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• 2015

본 논문에서는 소형 위성 카메라의 영상안정화를 위해 진동외란 보상 및 궤도상 광학정렬이 가능한 능동형 광학 보정장치의 설계에 대해 연구하였다. 능동형 광학 보정장치는 초점면부 보정장치와 부경 보정장치로 이루어져 있다. 초점면부 보정장치는 영상센서에 유입되는 진동 외란을 초점면부에서 직접 보상하는 장치이다. 또한 부경 보정장치는 초점면부 보정장치와 협력하여 궤도상에서 능동적으로 광학정렬을 수행할 수 있는 장치이다. 본 논문에서는 해상도 1 m급 소형 위성에 적용 가능한 능동형 광학 보정장치 설계를 위해 소형 고해상도 위성 카메라의 요구도를 분석하고, 진동 외란 보상과 궤도상 광학정렬이 능동적으로 가능하도록 초점면부 보정장치와 부경 보정장치의 요구도를 선정하였다. 선정된 요구도를 기준으로 본 연구에서 설계된 능동형 광학 보정장치는 초점면부에서 진동외란 보상 및 초점조절, 부경에서 틸트 및 디스페이싱 보상이 가능하므로 독립적으로 5축 제어가 가능한 시스템이다.

• 한국분무공학회지
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• 제12권4호
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• pp.191-197
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• 2007

This study presents in-line digital particle holography and its application to spray droplets to measure the characteristics of spray droplets. Several important parameters at the time of hologram recording such as the object distance and the region of laser beam used were verified. The correlation coefficient method with important parameters such as the reconstruction interval and the correlation interval was used for determination of the focal planes of particles. The optimal values of all these parameters are obtained by either numerical simulation of holograms or experiments. Using these optimal parameters, double pulse digital spray holograms in a short time interval were recorded with the synchronization system for the time control. The spatial positions of droplets that are used for the evaluation of the three dimensional droplet velocities can be easily located, which proves the feasibility of the digital holographic technology for measurements of several important features of spray droplets.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.100.5-100
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• 2002

A core technology for implementation of Augmented Reality is to develop a merging algorithm between interesting 3-D objects and real images. In this paper, we present a 3-D object recognition method to decide viewing direction toward the object from camera. This process is the starting point to merge with real image and 3-D objects. Perspective projection between a camera and 3-dimentional objects defines a plane in 3-D space that is from a line in an image and the focal point of the camera. If no errors with perfect 3-D models were introduced in during image feature extraction, then model lines in 3-D space projecting onto this line in the image would exactly lie in this plane. This observa...

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.572-576
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• 1997

X-ray laminography and DT(digital tomosynthesis) that can form a cross-sectional image of 3-D objects promise to be good solutions for inspecting interior defects of industrial products. The major factors of the digital tomosynthesis that influence on the quality of x-ray cross-sectional images are also discussed. The quality of images acquired from the DT system varies according to image synthesizing methods, the number of images used in image synthesizing, and X-ray projection angles. In this paper, a new image synthesizing method named 'log-root method' is proposed to get clear and accurate cross-sectional images, which can reduce both artifact and blurring generated by materials out of focal plane. To evaluate the quality of cross-sectional images, two evaluating criteria: (1) shape accuracy and (2) clearness in the cross-sectional image are defined. Based on this criteria, a series of simulations were performed, and the results show the superiority of the new synthesizing method over the existing ones such as averaging and minimum method.

• 전자공학회논문지B
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• 제29B권2호
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• pp.40-49
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• 1992

In this paper,a new approach-using the linear movement of the lens location in a camera and focal distance in each location for the measurement of the depth of the 3-D object from several 2-D images-is proposed. The sharply focused edges are extracted from the images obtained by moving the lens of the camera, that is, the distance between the lens and the image plane, in the range allowed by the camera lens system. Then the depthin formation of the edges are obtained by the lens location. In our method, the accurate and complicated control system of the camera and a special algorithm for tracing the accurate focus point are not necessary, and the method has some advantage that the depth of all objects in a scene are measured by only the linear movement of the lens location of the camera. The accuracy of the extracted depth information is approximately 5% of object distances between 1 and 2m. We can see the possibility of application of the method in the depth measurement of the 3-D objects.