• 제어로봇시스템학회논문지
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• 제16권5호
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• pp.411-414
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• 2010

As high quality image is required for digital cameras in recent use, the image stabilization technique has drawn much attention to prevent image degradation from shaky disturbance by users. In this paper, the optical image stabilization (OIS) system for DSLR (Digital Single Lens Reflex) camera is considered. First, the analytic model of an OIS system is presented to demonstrate the mechanism of image destabilization due to unknown disturbance that causes blurry images on CCD sensor. Then, to enhance the stabilization performance, a sliding mode control based on the min-max nonlinear control is introduced. Through the experiments and simulations, the effectiveness of the proposed method will be verified.

• 한국소음진동공학회논문집
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• 제21권2호
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• pp.178-185
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• 2011

Optical image stabilization is a device to compensate the camera movement in the exposure time. The compensation is implemented by movable lens or image sensor that adjusts the optical path to the camera movement. Generally, the camera is moved by a handshake, thus the handshake is considered as an external disturbance. However, there are many other vibrations such as car and train vibration. In this paper, the optical image stabilization system in high frequency region is presented. Notch filter and lead compensator are designed and applied to improve the stability without changing the actuator. To verify the performance of the optical image stabilization system in high frequency region, the experiment equipment with moving object is established. It is confirmed that the opticalimage stabilization system does not diverge at the resonance frequency.

• 로봇학회논문지
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• 제5권2호
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• pp.85-92
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• 2010

In this paper, we propose a digital image stabilization technique using edge detection and Lucas-Kanade optical flow in order to minimize the motion of the shaken image. The accuracy of motion estimation based on block matching technique depends on the size of search window, which results in long calculation time. Therefore it is not applicable to real-time system. In addition, since the size of vector depends on that of block, it is difficult to estimate the motion which is bigger than the block size. The proposed method extracts the trust region using edge detection, to estimate the motion of some critical points in trust region based on Lucas-Kanade optical flow algorithm. The experimental results show that the proposed method stabilizes the shaking of motion image effectively in real time.

• 정보저장시스템학회논문집
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• 제7권2호
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• pp.75-79
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• 2011

Recently mobile phone camera become generally spread, it is required to develop high resolution, multi-functional camera module for obtaining high image quality. To satisfy this demand, number of pixels has been increased and pixel size decreased in small mobile phone cameras. As a result, image quality is seriously dropped by blur phenomena. Especially when hand tremble is occurred, image quality is dropped by camera shake. Therefore, to obtain high quality image, it is necessary to compensate user's hand tremble. In this paper, we propose voice coil actuator for compensating hand tremble, which can apply optical image stabilization (OIS) system. Sensitivity analysis and size optimization are performed to obtain high driving force. Finally, it is confirmed that the optimized electromagnetic circuit can be applied in OIS system.

• 제어로봇시스템학회논문지
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• 제17권2호
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• pp.157-163
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• 2011

This paper proposes a hybrid image stabilizing system which uses both optical image stabilizing system based on EKF (Extended Kalman Filter) and digital image stabilization based on SURF (Speeded Up Robust Feature). Though image information is one of the most efficient data for object recognition, it is susceptible to noise which results from internal vibration as well as external factors. The blurred image obtained by the camera mounted on a robot makes it difficult for the robot to recognize its environment. The proposed system estimates shaking angle through EKF based on the information from inclinometer and gyro sensor to stabilize the image. In addition, extracting the feature points around rotation axis using SURF which is robust to change in scale or rotation enhances processing speed by removing unnecessary operations using Hessian matrix. The experimental results using the proposed hybrid system shows its effectiveness in extended frequency range.

• 한국소음진동공학회논문집
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• 제20권4호
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• pp.361-372
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• 2010

Optical image stabilization is a technique to compensate the image blurring caused by some vibrations of camera at the exposure time. Pitching and yawing of camera are sensitive to the image quality so they are usually compensated by optical image stabilization. Corresponding pitching and yawing of a camera, a lens or the image sensor is translated in two-axis direction and then the optical path of camera is adjusted. In this paper, two-axis OIS actuator for mobile camera module is suggested and designed. The actuator is a voice-coil actuator that uses the electromagnetic force of voice-coil to make compensation motions. And ball bearing is used to reduce friction force. Magnetic attractive force between magnets and yokes acts as a preload and magnet springs. Prototype actuator is fabricated to measure the friction force and to verify the feasibility of the OIS actuator with ball bearing. At last, the actuator is improved in consideration of driving force and friction force. Design of experiments is used for designing the actuator.

• 한국생산제조학회지
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• 제23권3호
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• pp.266-272
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• 2014

This study proposes a closed-loop shaping control method with $H_{\infty}$ optimization for optical image stabilization (OIS) in mobile phone cameras. The image stabilizer is composed of a horizontal stage constrained by ball bearings and actuated by the magnetic force from voice coil motors. The displacement of the stage is measured by Hall effect sensors. From the OIS frequency response experiment, the transfer function models of the stage and Hall effect sensor were identified. The weight functions were determined considering the tracking performance, noise attenuation, and stability with considerable margins. The $H_{\infty}$ optimal controller was executed using closed-loop shaping and limiting the controller order, which should be less than 6 for real-time implementation. The control algorithm was verified experimentally and proved to operate as designed.

• 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.

• 항공우주시스템공학회지
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• 제10권4호
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• pp.17-25
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• 2016

본 연구에서는 초점면부 영상안정화 기법 중 렌즈 시프팅 영상안정화 기법에 적용될 광학설계를 수행하였다. 렌즈 시프팅 기법은 광학탑재체로 전달되는 미세진동외란을 보상하기 위해 광 경로를 바꿔주는 영상 안정화 기법이다. 실제 위성카메라의 제원을 참고하여 렌즈 시프팅 기법이 적용될 광학계의 요구도를 수립하였으며, 광학설계 프로그램인 Code-V를 이용해 광학계를 설계하였다. 설계된 광학계가 요구 조건을 충족하였는지 검증하기 위해 시야에 따른 광선 수차분석, 스팟 다이어그램 분석, MTF 선도분석을 수행하였다. 최종적으로 설계된 광학계는 슈미트 카세그라인 타입에 필드 플래트너와 진동보상 렌즈가 삽입된 형태이며, 주반사경 직경은 200 mm, GSD 2.87m, 나이퀴스트 주파수에서 MTF 33%으로 광학계 성능요구도를 만족하였다. 본 연구에서 설계된 진동보상렌즈의 입사광선에 대한 진동계수는 0.95~1.00 으로 성능 요구도를 만족하였다.

• 한국멀티미디어학회논문지
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• 제20권8호
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• pp.1236-1247
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• 2017

In this paper, we propose a method for evaluating the uncomfortable shaking in the video. When you shoot a video using a handheld device, such as a smartphone, most of the video contains unwanted shake. Most of these fluctuations are caused by hand tremors that occurred during shooting, and many methods for correcting them automatically have been proposed. It is necessary to evaluate the shake correction performance in order to compare the proposed shake correction methods. However, since there is no standardized performance evaluation method, a correction performance evaluation method is proposed for each shake correction method. Therefore, it is difficult to make objective comparison of shake correction method. In this paper, we propose a method for objectively evaluating video shake. Automatically analyze the video to find out how much tremors are included in the video and how much the tremors are concentrated at a specific time. In order to measure the shaking index, we proposed jitter modeling. We applied the algorithm implemented by Optical Flow to the real video to automatically measure shaking frequency. Finally, we analyzed how the shaking indices appeared after applying three different image stabilization methods to nine sample videos.