• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.46-47
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• 2000

본 논문에서는 적응광학시스템$^{(1)}$ 의 성능 향상에 필수적인 파면왜곡의 기울기 정보를 고속으로 측정하기 위한 중심점 추출 알고리즘을 제안하였다. 본 논문에서는 컴퓨터 내부의 영상처리전용보드와 CCD카메라를 이용하여 하트만 센싱 점 영상을 획득하였고, 획득한 하트만 센싱 점 영상에 대해 제안한 중심점 추출 알고리즘을 적용하여 서브픽셀 분해능으로 X축과 Y축의 기울기 정보를 고속으로 추출하였다. CCD센서에 촬상되는 하트만 센싱 점영상에서 각각의 점 영상은 중심점으로부터 대칭형으로 강도가 분포되어 있다고 가정할 수 있으나 전체 점영상의 각 점을 분석한 결과 비대칭적으로 예외적인 강도 분포를 갖는 점영상도 일부 발견되었다. 파면 왜곡이 없는 하트만 센싱 점영상으로부터 X, Y축 파면 왜곡 기울기 값을 추출한 결과 CCD 센서 픽셀의 기저 노이즈가 큰 불안정한 영역에서 기울기 값이 반복적으로 크게 추출되어 파면왜곡보정 시스템의 보정 성능을 떨어뜨리는 효과가 나타났다. (중략)

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.4
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• pp.793-799
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• 2007

Generally, a semiconductor chip measured with a few micro units is captured by line scan camera for higher inspection accuracy. However, the faulty inspection requires an exact boundary detection algorithm, because it is very sensitive to scan speed and lighting conditions. In this paper we propose boundary detection with subpixel edge detection in order to increase the accuracy of bump faulty detection on chips. The bump edge is detected by first derivative to four directions from bump center point and the exact edge positions are searched by the subpixel method. Also, the exact bump boundary to calculate the actual bump size is computed by LSM(Least Squares Method) to minimize errors since the bump size is varied such as bump protrusion, bump bridge, and bump discoloration. Experimental results exhibit that the proposed algorithm shows large improvement comparable to the other conventional boundary detection algorithms.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.182-184
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• 2015

We have developed a novel LED display architecture with RGGB 4sub-pixels rendering. LED light control filter algorithm is proposed in order to reduce color fringes by sub-pixel rendering which is a method of perceptual enhancement. The results show that it has 2 times higher perceptual resolution without artifacts.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1141-1144
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• 2005

In this paper, we propose an automatic displacement system for testing stability of structure. Photogrammetry is a method which can measure accurate 3D data from 2D images taken from different locations and which is suitable for analyzing and measuring the displacement of structure. This paper consists of camera calibration, feature extraction using coded target & retro-reflective circle, 3D reconstruction and analyzing accuracy. Multi-view camera which is used for measuring displacement of structure is placed with different location respectively. Camera calibration calculates trifocal tensor from corresponding points in images, from which Euclidean camera is calculated. Especially, in a step of feature extraction, we utilize sub-pixel method and pattern recognition in order to measure the accurate 3D locations. Scale bar is used as reference to measure. the accurate value of world coordinate..

• Journal of the Korean Society for Precision Engineering
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• v.32 no.12
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• pp.1039-1047
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• 2015

Contact type sensors (e.g., displacement sensor and strain gauge) were typically used to evaluate the safety and mechanical properties in machines and construction. However, those contact type sensors have been constrained because of measurement problems such as surface roughness, temperature, humidity, and shape. The Digital Image Correlation (DIC) measurement system is a vision measurement system. This measurement system uses the taken image using a CCD camera and calculates the image correlation between the reference image and the deformed image under external force to measure the displacement and strain rates. In this paper, we discuss methods to improve the measurement precision of the digital image correlation measurement system. A tensile test was conducted to compare the precision improvement effects, by using the universal test machine and the DIC measurement system, with the use of subpixel algorithms, i.e., the Coarse Fine Search (CFS) algorithm and the Peak Finding (PF) algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.185-191
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• 2022

In this study, we propose a novel super-resolution neural network based on U-Net, residual neural network, and sub-pixel convolution. To prevent the loss of detailed information due to the max pooling of U-Net, we propose down-sampling and connection using sub-pixel convolution. This uses all pixels in the filter, unlike the max pooling that creates a new feature map with only the max value in the filter. As a 2×2 size filter passes, it creates a feature map consisting only of pixels in the upper left, upper right, lower left, and lower right. This makes it half the size and quadruple the number of feature maps. And we propose two methods to reduce the computation. The first uses sub-pixel convolution, which has no computation, and has better performance, instead of up-convolution. The second uses a layer that adds two feature maps instead of the connection layer of the U-Net. Experiments with a banchmark dataset show better PSNR values on all scale and benchmark datasets except for set5 data on scale 2, and well represent local area patterns.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.3
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• pp.141-148
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• 2023

Accurate overlay metrology is essential to achieve high yields of semiconductor products. Overlay metrology performance is greatly affected by overlay target design and measurement method. Therefore, in order to improve the performance of the overlay target, measurement methods applicable to various targets are required. In this study, we propose a new algorithm that can measure image-based overlay. The proposed measurement algorithm can estimate the sub-pixel position by using a motion vector. The motion vector may estimate the position of the sub-pixel unit by applying a quadratic equation model through polynomial expansion using pixels in the selected region. The measurement method using the motion vector can calculate the stacking error in all directions at once, unlike the existing correlation coefficient-based measurement method that calculates the stacking error on the X-axis and the Y-axis, respectively. Therefore, more accurate overlay measurement is possible by reflecting the relationship between the X-axis and the Y-axis. However, since the amount of computation is increased compared to the existing correlation coefficient-based algorithm, more computation time may be required. The purpose of this study is not to present an algorithm improved over the existing method, but to suggest a direction for a new measurement method. Through the experimental results, it was confirmed that measurement results similar to those of the existing method could be obtained.

• Journal of KIISE:Software and Applications
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• v.26 no.6
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• pp.791-803
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• 1999

본 논문은 두 장의 스테레요 영상으로부터 자동적으로 특징점 정합을 수행하도록 하는 새로운 절차의 효율적인 정합방법을 제안한다. 이를 위해 초기정합의 결과로 얻을 수 있는 유일 정합쌍을 이용한다. 즉, 본 논문에서는 초기정합의 결과로 얻어낸 유일 정합쌍의 정보를 이용하여 바로 outlier들을 제거시키므로써 초기정합의 결과가 갖는 애매성까지도 동반하여 상당량을 줄이도록 한다. 결국 애매성 제거에 대한 부담이 줄어들게 되므로 애매성 제거과정에서는 이완화 방법을 사용하지 않고 빠르게 애매성을 제거시킨다. 아울러 정합의 정확도를 높이기 위해 초기정합 후 바로 서브픽셀 정확도의 정합을 수행하며 정합의 마지막 단계에서는 추가정합을 수행하므로써 정합의 성능을 향상시킨다. 실내, 실회 스테레요 영상에 대한 다양한 실험결과는 본 논문에서 제안하는 방법의 특징점 정합기법이 빠르고 효율적임을 보여준다.

• IE interfaces
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• v.11 no.3
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• pp.15-22
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• 1998

A new improved algorithm in edge location to subpixel accuracy using decent-based weight to spatial information is proposed in this paper and applied to automated visual inspection(AVI) system. An application of the new edge operator as an edge detector is also provided and compared with Tabatabai and Lyvers edge detectors. The existing algorithms located edger to subpixel accuracy using least-square or moment-based methods. The algorithms also use only spatial information or grey-level values to locate edges. However, the proposed algorithm consider the weighted sum of grey-levels values of each edge pattern. The results show that the proposed algorithm is relatively less biased and has smaller standard deviation than the edge operations developed by Tabatabai and Lyvers in the presence of noise.

• Journal of Korea Multimedia Society
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• v.20 no.12
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• pp.2009-2015
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• 2017

A two-dimensional lens is required to reproduce both the horizontal and vertical parallax through an autostereoscopic 3D display. Among the two-dimensional lenses, a hexagonal micro lens array (MLA) having good optical efficiency is mainly used. However, the hexagonal MLA has complex geometric features. The first feature is that the lens cells are zigzagged in the vertical direction, which should be reflected in the view number calculation for each sub-pixel. The second feature is that the four sides of a hexagonal lens cell are tilted, requiring a more careful view index assignment to the lens cell. In this paper, we propose a sub-pixel multiplexing scheme suitable for the features of the hexagonal MLA. We also propose a view-overlay algorithm based on a two-dimensional lens and compare subjective image quality with existing view-selection through autostereoscopic 3D display implementation.