• Korean Journal of Computational Design and Engineering
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• v.16 no.6
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• pp.397-406
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• 2011

Since tolerance allocation in a mobile phone camera manufacturing process greatly affects production cost and reliability of optical performance, a systematic design methodology for allocating optimal tolerances is required. In this study, we proposed the tolerance optimization procedure for determining tolerances that minimize production cost while satisfying the reliability constraints on important optical performance indices. We employed Latin hypercube sampling for evaluating the reliabilities of optical performance and a function-based sequential approximate optimization technique that can reduce computational burden and well handle numerical noise in the tolerance optimization process. Using the suggested tolerance optimization approach, the optimal production cost was decreased by 30.3 % compared to the initial cost while satisfying the two constraints on the reliabilities of optical performance.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.168-173
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• 2006

This paper proposes an auto-focusing method for production of compact camera module (CCM). The CCM test handlers are mainly used in the final CCM production stage to test and adjust the lens focus of CCMs. To improve the productivity of CCM test handlers, we propose the auto-focusing method adjusting the lens focus efficiently. The max-min-difference (MMD) method is newly developed to compute the focus value efficiently, and two-stage searching method is also developed to find the best focus position quickly. Experimental results are presented to verify the usefulness of proposed method.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.994-999
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• 2007

전방향(omnidirectional) 카메라 시스템은 보다 적은 수의 영상으로부터 주변 장면(scene)에 대한 많은 정보를 취득할 수 있는 장점이 있기 때문에 전방향 영상을 이용한 자동교정(self-calibration)과 3차원 재구성 등의 연구가 활발히 진행되고 있다. 본 논문에서는 기존에 제안된 교정 방법들을 이용하여 추정된 사영모델(projection model)의 정확성을 검증하기 위한 새로운 방법이 제안된다. 실 세계에서 다양하게 존재하는 직선 성분들은 전방향 영상에 컨투어(contour)의 형태로 사영되며, 사영모델과 컨투어의 양 끝점 좌표 값을 이용하여 그 궤적을 추정할 수 있다. 추정된 컨투어의 궤적과 영상에 존재하는 컨투어와의 거리 오차(distance error)로부터 전방향 카메라의 사영모델의 정확성을 검증할 수 있다. 제안된 방법의 성능을 평가하기 위해서 구 맵핑(spherical mapping)된 합성(synthetic) 영상과 어안렌즈(fisheye lens)로 취득한 실제 영상에 대해 제안된 알고리즘을 적용하여 사영모델의 정확성을 판단하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.557-560
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• 2015

자동초점이란 영상을 획득하는 시스템에서 고정된 촬상면에 자동으로 초점이 맺히도록 렌즈를 구동시키는 방식으로 컴퓨터비전과 카메라 등에서 매우 중요하게 사용된다. 소형 카메라의 경우 자동초점에서 렌즈구동부인 actuator의 기술은 대량생산이 이용이하고, 위치센서가 불필요하며, 회로구성이 용이한 VCM방식이 널리 사용되고 있으며, 구동의 안정성에 비해 크기와 소음이 큰 스테핑모터 방식, 크기는 가장 작지만 납 함유문제 및 습도 취약성을 갖는 피에조 방식이 있다. 그 외에 액체렌즈방식이 있는데, 소형 구조에 저전력의 장점이 있지만 화질 및 신뢰성 검증 그리고 고압이 필요한 특징을 가지는 구조도 있다. 본 논문에서 5Mpixel급 이미지 센서를 통해 획득한 영상의 선예도를 이용하여 VCM의 actuator처럼 액체렌지를 제어하여 자동으로 초점을 맞추는 제어방식을 구현하고 검증하였다.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.394-398
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• 1992

The measurable speed range of the self-mixing type semiconductor laser range finder has been greatly improved by employing a new processing circuit. Using this range finder as an external finder of a single lens reflex (SLR) autofocus (AF) camera, some clear photographs of an object moving at a medium speed of 20 mm/s is obtained.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.123-137
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• 2001

PIV (particle image velocimetry) systems use a camera to take snapshots of particles carried by a fluid at some precise instants. Signal processing methods are then used to compute the flow velocity field. In this paper, the design of the camera objective (optics) is addressed. The optimization is done in order to maximize the signal-to-noise ratio of in-focus particles. Four different kinds of noise are considered: photon shot noise, thermal and read noise, background glow shot noise, and noise made by the other particles. A semi-empirical model for the lens aberrations of a two-doublet objective is first addressed, since further, it is shown that lens aberrations (low f-value $f_{\#}$) should be used instead of the Fraunhofer diffraction (high f-value) for the fitting of the particle image size with the pixel size. Other important conclusions of the paper include the expression of optimum values for the magnification M, for the exposure period $\tau$ and for the pixel size $\xi$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.490-495
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• 1996

Though the increment of using computer vision system in modern industry, there are lots of difficulties to measure precisely because of measurement error distortion phenomenon. Among these reasons, the distortion of edge is dominant reason which is occurred by the blurred image. The blurred image is happened when camera can not discriminate its precise focus. To calibrate and generalize distortion phenomenon is important. Thus, we must fix the discrimination criteria which is collected by image recognition of precise focus. Also, radial distortion causes an inward or outward displacement of a given image point from its ideal location. This type of distortion is mainly caused by flawed radial curvature curve of the elements. Thus, we were analyzed the distortion in terms of the changed with lens magnification.

• Transactions on Electrical and Electronic Materials
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• v.9 no.6
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• pp.237-242
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• 2008

The effects of the process parameters in the molding of aspheric glass lenses for camera phone modules have been investigated experimentally. The molding conditions were optimized with respect to the form accuracy (PV) (the response variable) of the molded lens. The experimental conditions were obtained by employing a factorial design method. From the analysis of variance (ANOVA) and P-value (significance level), the slow cooling rate was found to affect the response variable most significantly. The lens molded under the optimum molding condition showed a transcription ratio of 93.4%.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.1
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• pp.82-95
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• 1992

There is the high interest for sensing of tool wear with the aim of controlling machine tools productivity from the point of view of qualitity. Difficulties in this measurement are also known. This study is on the development of measurement setup for crater wear by CCD image inturning. In this study, the crater wear measurement system consists of the He-Ne gas laser, diffraction grating. CCD camera, noise filter, slit, microcomputer, diverging lens, converging lens and so on. He-Ne laser beam passes through a diverging lens and a diffraction grating is positioned properly. A converging lens focuses so that the interference fringes can be obtained on the crater wear. Performance test revealed that the developed image technique provides precise, absolute tool-wear quantification and reduces human measurement errors. The results obtained are as follows 1. The digitizing of one image requires less than 2ses. 2. It can give detailed information on crater wear with limited times and errors 3. All parameters required by specification are easily obtained for several points of the cutting edge.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.231-235
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• 2013

Lens distortions have a significant impact on captured or projected image geometry. This paper proposes a lens distortion correction with gradient components for wide-angle lenses. In most cases, distortion coefficients are estimated using a distortion model by point correspondences. Corrected images using only point correspondences can be compensated excessively, therefore, producing bended lines into the opposite direction near the corners. To curtail these phenomena, we propose to adopt the gradient components in addition to positions to obtain the distortion coefficients. We verified the improved accuracy and the straightness of the proposed method through experimentation.