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Extended Depth of Focus 알고리듬 파라메타 초기설정에 관한 연구
유경무(Kyungmoo Yoo),주효남(Hyonam Joo),김준식(Joonseek Kim),박덕천(Duckchun Park),최인호(Inho Choi) 한국방송·미디어공학회 2012 방송공학회논문지 Vol.17 No.4
Extended Depth of Focus (EDF) algorithms for extracting three-dimensional (3D) information from a set of optical image slices are studied by many researches recently. Due to the limited depth of focus of the microscope, only a small portion of the image slices are in focus. Most of the EDF algorithms try to find the in-focus area to generate a single focused image and a 3D depth image. Inherent to most image processing algorithms, the EDF algorithms need parameters to be properly initialized to perform successfully. In this paper, we select three popular transform-based EDF algorithms which are each based on pyramid, wavelet transform, and complex wavelet transform, and study the performance of the algorithms according to the initialization of its parameters. The parameters we considered consist of the number of levels used in the transform, the selection of the lowest level image, the window size used in high frequency filter, the noise reduction method, etc. Through extended simulation, we find a good relationship between the initialization of the parameters and the properties of both the texture and 3D ground truth images. Typically, we find that a proper initialization of the parameters improve the algorithm performance 3㏈ ~ 19㏈ over a default initialization in recovering the 3D information.
반도체 패키지의 마크문자 회전량 측정을 위한 고속 라돈 변환에 관한 연구
신균섭 ( Gyunseob Shin ),주효남 ( Hyonam Joo ),김상민 ( Sangmin Kim ),이정섭 ( Jung-seob Lee ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.1
반도체 패키지 제조공정 중에는 제품에 일련번호를 인쇄하는 마킹공정이 있다. 마킹 공정에서 새겨진 문자는 해당 관리기준에 따라 관리되고 있는데 최근 반도체 패키지의 소형화에 따라 인쇄된 마크문자의 틀어짐 정도가 관리기준에 미달되는 문제가 발생되고 있다. 본 논문에서는 마크문자의 검사 항목 중 tilted mark(angle mark) 검사를 위한 회전량 측정방법으로 golden section searching 방법을 적용한 고속 라돈 변환(radon transform)방법을 제안한다. 실험에서는 제안한 방법이 일반적인 라돈 변환에 비해 최대 약 21 배의 회전량 측정속도가 향상되는 것을 확인하였다.
Fast Detection of Mura Defects Based on Modified Watershed Algorithm
Ye Jian Zhang(장엽검),Hyonam Joo(주효남),Joon Seek Kim(김준식) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.6
Many kinds of defects show up during the process of manufacturing display panels. However, mura defects are the most difficult to detect using the conventional image processing algorithms. Many factors cause mura defects to appear in display panels. When images are taken using cameras, mura defects normally show up as relatively dark or bright regions with no definite shape, no clear contours, and very low contrast against their surrounding background. When an imaged mura defect is relatively dark compared to its background, it can be considered a water catchment basin when the whole image is visualized in three dimensions (i.e., is topographically interpreted), and such catchment basins can be detected by watershed algorithms. In this paper, for the accurate segmentation of the mura region, the flooding step of the original watershed algorithm is carefully redesigned to detect the mura defect that exists both inside and at the boundary of an image. The depth of the catchment basins is recorded iteratively and then is used to segment the mura defects. The just noticeable difference (JND) technique is used to quantify the level of the mura defects. It is shown, by extensive experiments, that the proposed algorithm performs well, detecting very low-contrast mura defects, and quickly detects defects located anywhere in the image.
Low Contrast 특성을 갖는 LCD 편광필름 결함의 크기 자동 검출
박덕천(Duckchun Park),주효남(Hyonam Joo),류근호(Keun-Ho Rew) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.5
In this paper, segmenting and classifying low contrast defects on flat panel display is one of the key problems for automatic inspection system in practice. Problems become more complicated when the quality of acquired image is degraded by the illumination irregularity. Many algorithms are developed and implemented successfully for the defects segmentation. However, vision algorithms are inherently prone to be dependent on parameters to be set manually. In this paper, one morphological segmentation algorithm is chosen and a technique using frequency domain analysis of input images is developed for automatically selection the morphological parameter. An extensive statistical performance analysis is performed to compare the developed algorithms.
QFN 패키지의 Resin Bleed와 Melting 검출 알고리즘
왕명걸(Mingjie Wang),박덕천(Duckchun Park),주효남(Hyonam Joo),김준식(Joon-Seek Kim) 제어로봇시스템학회 2009 제어·로봇·시스템학회 논문지 Vol.15 No.9
There are many different types of surface defects on semiconductor Integrated Chips (IC’s) caused by various factors during manufacturing process, such as Scratch, Flash, Resin bleed, and Melting. These defects must be detected and classified by an inspection system for productivity improvement and effective process control. Among defects, in particular, Resin bleed and Melting are the most difficult ones to classify accurately. The brightness value and the shape of Resin bleed and Melting defects are so similar that normally it is difficult to classify the Resin bleed and Melting. In this paper, we propose a segmenting method and a set of features for detecting and classifying the Resin bleed and Melting defects.
반도체 부품 마크 미세 결함 검사를 위한 패턴 영역 분할 및 인식 방법
장유정(Yuting Zhang),이정섭(Jung-Seob Lee),주효남(Hyonam Joo),김준식(Joon-seek Kim) 제어로봇시스템학회 2010 제어·로봇·시스템학회 논문지 Vol.16 No.9
To inspect the defects of printed markings on the surface of IC package, the OCV (Optical Character Verification) method based on NCC (Normalized Correlation Coefficient) pattern matching is widely used. In order to detect the micro pattern defects appearing on the small portion of the markings, a Partitioned NCC pattern matching method was proposed to overcome the limitation of the NCC pattern matching. In this method, the reference pattern is first partitioned into several blocks and the NCC values are computed and are combined in these small partitioned blocks, rather than just using the NCC value for the whole reference pattern. In this paper, we proposed a method to decide the proper number of partition blocks and a method to inspect and combine the NCC values of each partitioned block to identify the defective markings.
확장된 피사계 심도 알고리즘에서 엣지 정보 분석에 의한 3차원 깊이 정보 추출 방법
강선우(Sunwoo Kang),김준식(Joon Seek Kim),주효남(Hyonam Joo) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.2
Recently, popularity of 3D technology has been growing significantly and it has many application parts in the various fields of industry. In order to overcome the limitations of 2D machine vision technologies based on 2D image, we need the 3D measurement technologies. There are many 3D measurement methods as such scanning probe microscope, phase shifting interferometry, confocal scanning microscope, white-light scanning interferometry, and so on. In this paper, we have used the extended depth of focus (EDF) algorithm among 3D measurement methods. The EDF algorithm is the method which extracts the 3D information from 2D images acquired by short range depth camera. In this paper, we propose the EDF algorithm using the edge informations of images and the average values of all pixel on z-axis to improve the performance of conventional method. To verify the performance of the proposed method, we use the various synthetic images made by point spread function(PSF) algorithm. We can correctly make a comparison between the performance of proposed method and conventional one because the depth information of these synthetic images was known. Through the experimental results, the PSNR of the proposed algorithm was improved about 1 ~ 30 dB than conventional method.
반동체 웨이퍼 고속 검사를 위한 GPU 기반 병열처리 알고리즘
박영대(Youngdae Park),김준식(Joon Seek Kim),주효남(Hyonam Joo) 제어로봇시스템학회 2013 제어·로봇·시스템학회 논문지 Vol.19 No.12
In a the present day, many vision inspection techniques are used in productive industrial areas. In particular, in the semiconductor industry the vision inspection system for wafers is a very important system. Also, inspection techniques for semiconductor wafer production are required to ensure high precision and fast inspection. In order to achieve these objectives, parallel processing of the inspection algorithm is essentially needed. In this paper, we propose the GPU (Graphical Processing Unit)-based parallel processing algorithm for the fast inspection of semiconductor wafers. The proposed algorithm is implemented on GPU boards made by NVIDIA Company. The defect detection performance of the proposed algorithm implemented on the GPU is the same as if by a single CPU, but the execution time of the proposed method is about 210 times faster than the one with a single CPU.
임영신(Young-Shin Lim),김준식(Joon-Seek Kim),주효남(Hyonam Joo) 제어로봇시스템학회 2009 제어·로봇·시스템학회 논문지 Vol.15 No.8
In this paper, a real-time eye tracking method using fast face detection is proposed. Most of the current eye tracking systems have operational limitations due to sensors, complicated backgrounds, and uneven lighting condition. It also suffers from slow response time which is not proper for a real-time application. The tracking performance is low under complicated background and uneven lighting condition. The proposed algorithm detects face region from acquired image using elliptic Hough transform followed by eye detection within the detected face region using Haar-like features. In order to reduce the computation time in tracking eyes, the algorithm predicts next frame search region from the information obtained in the current frame. Experiments through simulation show good performance of the proposed method under various environments.
PMP 방식을 이용한 BGA 볼의 3차원 형상측정 시스템
김효준(Hyo Jun Kim),김준식(Joon Seek Kim),주효남(Hyonam Joo) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.1
As modern electronic devices get smaller and smaller, high-resolution, large Field-Of-View (FOV), fast, and cost-effective 3-dimensional (3-D) measurement is requested more and more. In particular, defect inspection machines using machine-vision technology nowadays require 3-D inspection as well as the conventional 2-D inspection. Phase Measuring Profilometry (PMP) is one of the fast non-contact 3-D shape measuring methods currently being extensively investigated in the electronic component manufacturing industry. The PMP system is well known and is successfully applied to measuring complex surface profiles with varying reflectance properties. However, for highly reflective surfaces, such as Ball Grid Arrays (BGAs), it has difficulty accurately measuring 3-D shapes. In this paper, we propose a new fast optical system that can eliminate the highly reflective saturated regions in BGA ball images. This is achieved by utilizing four Low Intensity Grating (LIG) images together with the conventional High Intensity Grating (HIG) images. Extensive experiments using BGA samples show a repeatability of under ±20um in standard deviation, which is suitable for most 3-D shape measurements of BGAs.