• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 Ⅳ
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• pp.2403-2406
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• 2003

When viewing images, the relative luminance of the surround has a profound impact on the apparent contrast of the image. The dark surround causes the image elements to appear lighter than those viewed in an illuminated surround. For this reason, it is worthwhile to briefly review the general results of brightness sealing under a various viewing condition. Two of the most often cited parers on the topic of brightness scaling are Stevens-stevens and Bartleson-Breneman's function. There are, however, significant differences between the perceptual functions for simple-field and complex-field viewing. In this paper, we research the relationship between Steven's power law and Bartleson-Breneman's function. We present an appropriate brightness perception function due to TV system viewing conditions. Highlight luminance peak and absolute brightness threshold value in various adaptation levels are obtained from the proposed brightness function . Also, the luminance value of black level to produce the same contrast ratio with variety of display highlight luminance peak is obtained from the proposed brightness function.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.1291-1296
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• 2005

In this paper, we prevent a display quality drop for image of characteristics brightness ununiformity depend on LED use to LED vision. It is about that method also a control system development equipped with brightness compensation function of LED vision which is done easily for LED set up of LED vision. Generally, It is calculate driving current value is attended by each brightness to brightness characteristics mathematical function establish by "Y=aX+b", When is doing brightness value for "Y", driving current value for "X", brightness compensation value by using time for "b", characteristics value for "a" ground with characteristics curve of LED. So much, First It is create brightness data of each pixel take a photograph red, green and blue of LED vision. Second It is get average error about each pixel which get average brightness value of entire. Last, It is handle a complicated for about gradationally regulation to color and brightness of image send to LED vision. Also It raise the whole average brightness value of vision adjust for "b" value to solve brightness drop problem of LED using the long time.

• 방송공학회논문지
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• 제23권2호
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• pp.283-292
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• 2018

LDR (low dynamic range) 영상에 비해서 밝기 범위가 크게 늘어난 HDR (high dynamic range) 영상을 촬영할 수 있는 장비와 디스플레이할 수 있는 기기들이 개발되고 있고 영상의 밝기 범위를 효율적으로 변환하는 방법에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 LDR 영상을 HDR 영상으로 효율적으로 변환하기 위해서 guided filter를 사용한 reverse tone mapping 기법을 제안한다. Guided filter를 사용하여 한 장의 LDR 영상으로부터 BEF(brightness enhancement function)을 구한 후에 LDR 영상에서 밝기가 포화된 부분을 효율적으로 복원하여 HDR 영상을 생성하는 기법을 제안한다. 또한 영상이 지나치게 밝거나 어두운 경우 영상 촬영시의 노출 값을 추정하여 보정한 후에 밝기 범위를 변환하는 방법을 이용하여 생성되는 HDR 영상의 화질을 극대화하는 방법을 연구하고 모의 실험 결과로부터 제안하는 기법은 기존의 방법에 비해서 우수한 화질의 HDR 영상을 생성하는 것을 입증한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.787-789
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• 2017

에지 검출은 이미지 분석, 패턴 인식 및 컴퓨터 비전과 같은 많은 응용분야에서 사용되고 있다. 기존의 에지 검출 방법들에는 Sobel, Prewitt, Roberts, LoG(Laplacian of Gaussian)등이 존재한다. 기존 에지 검출 방법은 원영상이 저조도일 경우 화소 휘도의 변화가 적기 때문에 에지 검출이 미흡하다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해 저조도 영상의 화소 휘도를 변환하는 함수를 제안하였다. 그리고 화소 휘도 변환 함수의 성능을 확인하기 위해 기존의 방법 Sobel, Prewitt, Roberts, LoG(Laplacian of Gaussian)에 적용하여 비교 분석하였다.

• 한국정보통신학회논문지
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• 제19권7호
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• pp.1680-1686
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• 2015

에지 검출은 대부분의 영상 처리 응용에서 필수적인 전처리 과정으로서 여러 분야에서 널리 사용되고 있으며, 기존의 에지 검출 방법에는 Sobel, Roberts, Laplacian, LoG(Laplacian of Gaussian) 등이 있다. 기존의 에지 검출 방법들은 저조도 환경에서 화소의 휘도 변화가 적기 때문에 에지 검출 특성이 미흡하게 나타난다. 따라서 본 연구에서는 이러한 문제점을 해결하기 위해, 전처리 과정에서 휘도 변환 함수를 사용한 알고리즘과 국부 마스크의 평균 및 표준편 차에 따른 가중치를 적용하여 에지를 검출하는 알고리즘을 제안하였다. 그리고 제안한 알고리즘의 성능을 평가하기 위해, 기존의 Sobel, Roberts, Prewitt, Laplacian, LoG 에지 검출 방법들과 비교하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.836-841
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• 2004

This paper describes ASIC design for brightness revision control, A LED Pixel Matrix (LPM) design and LPM in natural color LED vision. A designed chip has 256 levels of gradation correspond to each Red, Green, Blue LED pixel respectively, which have received 8bit image data. In order to maintain color uniformity by reducing the original rank error of LED, we adjusted the specific character value 'a' and brightness revision value 'b' to pixel unit, module unit and LED vision respectively by brightness characteristic function with 'Y=aX+b'. In this paper, if designed custom chip and brightness revision control method are applied to manufacturing of natural color LED vision, we can obtain good quality of image. Furthermore, it may decrease the cost for manufacturing LED vision or installing the plants.

• ETRI Journal
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• 제39권1호
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• pp.76-86
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• 2017

In this study, we propose an automatic contrast enhancement method based on transfer function modification (TFM) by histogram equalization. Previous histogram-based global contrast enhancement techniques employ histogram modification, whereas we propose a direct TFM technique that considers the mean brightness of an image during contrast enhancement. The mean point shifting method using a transfer function is proposed to preserve the mean brightness of an image. In addition, the linearization of transfer function technique, which has a histogram flattening effect, is designed to reduce visual artifacts. An attenuation factor is automatically determined using the maximum value of the probability density function in an image to control its rate of contrast. A new quantitative measurement method called sparsity of a histogram is proposed to obtain a better objective comparison relative to previous global contrast enhancement methods. According to our experimental results, we demonstrated the performance of our proposed method based on generalized measures and the newly proposed measurement.

• 제어로봇시스템학회논문지
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• 제22권5호
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• pp.382-388
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• 2016

When Flat Panel Display (FPD) is made with backlight module, such as LED TV, it inherently suffers from the non-uniform backlight luminance problem that results in un-even brightness distribution throughout the TV screen. If the luminance of each pixel location of a TV screen as a function of the driving voltage can be measured, it can be used to compensate the non-uniformity of the backlight module. We use a carefully calibrated imaging system to take pictures of a TV screen at different levels of brightness and generate the compensation functions for the driving circuitry to correct the luminance level at each pixel location. Making use of the fact that the luminance of the screen is normally brightest at around the center of the screen and gradually decreases toward the border of the screen, the luminance of the whole TV screen is approximated by a mathematical function of the pixel locations. The parameters of the function are computed in the least square sense by the values of both the pixel luminance sent from the driving circuit and the grayscale value measured from the image taken by the imaging system. To justify the correction system, a simple second order polynomial function is used to approximate the luminance across the screen. When the driving circuit voltage is corrected according to the measured function, the variance of the screen luminance is reduced to one tenth of the one measured from the un-corrected TV screen.

• 전자공학회논문지 IE
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• 제46권3호
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• pp.12-18
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• 2009

본 논문은 LED 디스플레이 시스템에서 균일하고 부드러운 영상표출을 위하여 각각의 Red, Green, Blue LED의 휘도를 조절하여 흰색보정을 유지할 수 있는 프로세서를 설계하였다. 이 프로세서는 일반적인 LED소자의 특성곡선을 근거로 "a"를 고유특성 값, "b"를 사용시간에 따른 휘도보정 값, "X"를 구동전류 값, "Y"를 휘도 값이라 할 때, "Y=aX+b"로 설정되는 휘도 특성함수에 의하여 각 픽셀의 휘도에 따른 구동 전류 값을 산출하여 휘도를 보정하고, 또한 장시간 사용 시 LED소자의 휘도 저하 문제를 해결하기 위하여 "b"값을 조절하여 LED 디스플레이 시스템의 전체 평균 휘도 값을 상향시킬 수 있도록 구현하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.243-246
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• 2004

In this paper, we have proposed the contrast control method using brightness preserving on the FPD(Flat Panel Display). The proposed algorithms consist of three blocks: the contrast enhancement, the white-level-expander, and the black-level-expander. The proposed method has employed probability density function in order to control the brightness of the image changed extremely. In order for real-time processing, we have calculated cumulative density function using the linear approximation method. The image histogram and image quality were compared with the conventional image enhancement algorithms. The proposed methods have been used in display devices that need image enhancement such as LCD TV, PDP, and FPD.