• 대한기계학회논문집B
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• 제24권4호
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• pp.599-607
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• 2000

In this study, experiments have been performed to examine the effects of background gray-level on the depth-of-field and on the in-focus criteria. The normalized value of contrast(VC) and the gradient indicator(GI) were used as the in-focus criteria for the small and the large size-ranges of particles, respectively. The slightly larger number of pixels were detected with the brighter background. The maximum of the normalized value of contrast(VCmax) is decreased with the brighter background and its deviation from that with the background gray-level of 160 turned out to be about $pm$15% when the background gray-level changes from 100 to 200. However, the maximum gradient indicator(GImax) changes with the background gray-level within only $pm$5%. The depth-of-field for the VC-applicable particle-size range is largely dependent on the background gray-level. On the other hand, the depth-of-field for the GI-applicable particle-size range changes only slightly with the background gray-level. To keep the normalized standard deviation of the particle size within 0.1, the background gray-level should be set 160$pm$20 for both the VC-applicable and GI-applicable ranges which cover the particle size between $10{\mu}m$ and $300{\mu}m$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.152-154
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• 2005

This paper proposes the new subfield method to erase reverse gray levels and low gray level contour in AC plasma display panel(PDP). In the conventional method, it is supposed that output luminance levels of a PDP increase regularly. But actual output luminance levels of a PDP increase irregularly. Therefore, conventional methods are unable to effectively reduce low gray-level contours and reverse gray levels. Accordingly, a new subfield method is applied to improve the low gray-level expression in PDP. Conclusively this paper clear proof that a new subfield method can suppress low gray-level contours and reverse gray levels more effectively than conventional methods.

• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.640-646
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• 2003

We presents an edge-based point correlation algorithm for fast and stable visual inspection system. Conventional algorithms based on NGC(normalized gray-level correlation) have to overcome some difficulties in applying automated inspection systems to real factory environment. First of all, NGC algorithms involve highly complex computation and thus require high performance hardware for realtime process. In addition, lighting condition in realistic factory environments is not stable and therefore intensity variation from uncontrolled lights gives many troubles for applying NGC directly as pattern matching algorithm. We propose an algorithm to solve these problems, using thinned and binarized edge data, which are obtained from the original image. A point correlation algorithm with the thinned edges is introduced with image pyramid technique to reduce the computational complexity. Matching edges instead of using original gray-level image pixels overcomes problems in NGC method and pyramid of edges also provides fast and stable processing. All proposed methods are proved by the experiments using real images.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.327-331
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• 2005

본 논문에서는 영상에 대한 선명도를 측정하기 위한 또 다른 방법을 제시하였으며 기존의 필터링을 통한 이미지 선명화 측정과 달리 간단한 히스토그램을 가지고 수식으로 유도해 보았다. 히스토그램의 많은 정보 중에 다이나믹 레인지와 gray level, 각 level의 정도 곡선이 사용 되었으며 log scale로 그 범위를 한정 시켜 주었다. 그 결과 어느 정도 타당한 결과 값이 나왔으며, 이 결과를 토대로 HP, LP에 의한 필터링 방법 외에 또 다른 방법의 가능성을 제시한다.Q

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.327-328
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• 2007

A contour shape matching based pixel motion estimation is proposed. The pixel motion information is very useful to compensate the motion artifact generated at the specific gray level contours in the moving image for subfield gray-scale display devices. In this motion estimation method, the gray level boundary contours are extracted from the input image. Then using contour shape matching, the most similar contour in next frame is found, and the contour is divided into segment unit. The pixel motion vector is estimated from the displacement of the each segment in the contour by segment matching. From this method, more precise motion vector can be estimated and this method is more robust to image motion with rotation or from illumination variations.

• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.48-57
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• 1999

Applications of thresholding technique are based on the assumption that object and background pixels in a digital image can be distinguished by their gray level values. For the segmentation of more complex images, it is necessary to resort to multiple threshold selection techniques. This paper describes a new method for multiple threshold selection of gray level images which are not clearly distinguishable from the background. The proposed method consists of three main stages. In the first stage, a probability distribution function for a gray level histogram of an image is derived. Cluster points are defined according to the probability distribution function. In the second stage, fuzzy partition matrix of the probability distribution function is generated through the fuzzy clustering process. Finally, elements of the fuzzy partition matrix are classified as clusters according to gray level values by using max-membership method. Boundary values of classified clusters are selected as multiple threshold. In order to verify the performance of the developed algorithm, automatic inspection process of ball grid array is presented.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권1호
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• pp.46-54
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• 2002

Plasma Display Panel (PDP) is required to be both the determination of white point of each gray level and the inverse gamma correction since no-balanced RGB cell and linear property of PDP, respectively. However, these two methods cause degradation of grey level representation and undesirable false contour in the dark areas on PDP. In this paper, we implemented real time image processor of the proposed error diffusion algorithm and unsharp masking operation to protect the blurring image caused by the error diffusion. Experimental results showed drastic improvements of gray level representation and reduction of undesirable false contour.

• 한국멀티미디어학회논문지
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• 제8권10호
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• pp.1347-1359
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• 2005

본 논문에서는 공간 명암도 의존 행렬을 이용하여 문서영상의 다양한 블록들을 상세하게 분류해 낼 수 있는 방법을 제안하였다. 제안한 블록분류 방법에서는 먼저 명암도 문서영상을 이진화하여 평활화 기법을 적용함으로써 명암도 영상의 질감특징을 이용하여 분할하는 것보다 신속하게 블록을 분할하고 동시에 그 위치정보도 구할 수 있도록 하였다. 분할된 각 블록들의 공간 명암도 의존 행렬로부터 문서블록들의 7가지 질감특징을 구하고, 이를 정규화한 다음 역전파 신경회로망를 이용하여 문서블록들을 분류하였다. 문서블록들을 큰 문자, 중간 문자, 작은 문자, 표, 그래픽 및 사진 등 여섯 가지 유형으로 상세 분류하였다. 또한 명암도 문서영상의 2차 통계 질감특징을 얻기 위해 공간 명암도 의존 행렬을 구할 때, 기존의 사진과 같은 일반 영상분할에서와는 달리, 문서블록 고유의 특징이 잘 반영되도록 하였다. 즉, 분할된 각 블록을 하나의 마스크로 정하여 수평 한 방향의 공간 명암도 의존 행렬을 구함으로써 고속의 질감특징추출과 상세 블록분류가 가능하도록 하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.359-362
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• 2003

In PDP(Plasma Display Panel), sub-field method is used to implement gray scale. Each sub-field has different periods. And Every gray level has information of which sub-field has to be displayed. This is called sub-field mapping. There are several sub-field mapping values in some gray levels. So, it is possible to select best choice in this paper, we propose new sub field mapping method using a fuzzy inference system to select best sub-field mapping values in accordance with input image and environment temperature. In order to implement fuzzy system, we used MATLAB fuzzy inference editor.

• 치과방사선
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• 제22권2호
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• pp.273-282
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• 1992

The purpose of this study was to propose the utility which was evaluated the digital image processing and clinical application of the videodensitomery. The experiments were performed with IBM-PC/16bit-AT compatible, video camera(CCdtr55, Sony Co., Japan), an color monitor(MultiSync 3D, NEC, Japan) providing the resolution of 512×480 and 64 levels of gray. Sylvia Image Capture Board for the ADC(analog to digital converter) was used, composed of digitized image from digital signal and the radiographic density was measured by 256 level of gray. The periapical radiograph(Ektaspeed EP-21, Kodak Co., U. S. A) which was radiographed dried human mandible by exposure condition of 70 kVp and 48 impulses, was used for primary X-ray detector. And them evaluated for digitzed image by low and high pass filtering, correlations between aluminum equivalent values and the thickness of aluminum step wedge, aluminum equivalent values of sound enamel, dentin, and alveolar bone, the range of diffuse density for gray level ranging from 0 to 255. The obtained results were as follows: 1. The edge between aluminum steps of digitized image were somewhat blurred by low pass filtering, but edge enhancement could be resulted by high pass filtering. Expecially, edge enhancement between distal root of lower left 2nd molar and alveolar lamina dura was observed. 2. The correlation between aluminum equivalent values and the thickness of aluminum step wedge was intimated, yielding the coefficient of correlation r=0.9997(p<0.00l), the regression line was described by Y=0.9699X+0.456, and coefficient of variation amounting to 1.5%. 3. The aluminum equivalent values of sound enamel, dentin, and alvolar bone were 15.41㎜, 12.48㎜, 10.35㎜, respectively. 4. The range of diffuse density for gray level ranging from 0 to 255 was wider enough than that of photodenstiometer to be within the range of 1-4.9.