• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.11a
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• pp.179-181
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• 2016

조명이 객체에 균일하지 않은 세기의 빛을 제공하는 문제는 조명의 하드웨어 설계에서 해결해야 할 문제 중 하나였다. 본 논문에서는 객체가 받는 특정 조명의 세기가 균일하지 않은 영상을 균일한 밝기의 영상으로 보정하는 방법을 제안한다. 제안하는 방법은 밝기가 균일하지 않은 특정 조명에서 획득한 영상과 밝기가 균일한 일반 조명에서 획득한 영상을 이용한다. 우선 균일하지 않은 특정 조명에서 컬러필터나 다른 광원을 이용해서 특정 조명의 밝기를 기준으로 객체의 반사 스펙트럼을 복원한다. 복원한 반사 스펙트럼을 균일한 조명의 스펙트럼 특성으로 스펙트럴 재조명을 하여 두 영상간 밝기의 차이를 비교한다. 이 비교를 통해 특정 조명에서 획득한 영상의 밝기를 보정하고 보정 결과 비교를 통해 보정이 잘 되었음을 확인할 수 있다. 이 결과를 통해 특정 조명의 하드웨어 설계의 어려움을 줄일 수 있을 것으로 기대 된다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.3
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• pp.1-9
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• 2009

Using the projected 2-dimensional tilted images obtained from the transmission electron microscopy, we can reconstruct the 3-dimensional structures of objects, such as cells. As a preprocessing procedure, the tilted images should be registered and compensated in terms of the spatial position and the intensity difference, respectively. In this paper, we employ the fiducial marker-based approach to perform a registration, and introduce a simple intensity compensation scheme. Based on the transmissivity image formation model, we propose an algorithm that can compensate the components of the illumination and transmissivity of each image according to the tilted angle. Numerical analysis using real images obtained from the transmission electron microscopy are shown in this paper to show the performance of the proposed algorithm.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.117-126
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• 2010

In the case of failure images with controlling lighting like backlighting and excessive frontlinghting, the compensation scheme for a specific area in an image is required. The interested region is first selected by user in our method to compensate the first frame. Then we define the matching function of brightness and energy function is proposed with weight of matching function and the relationship among the neighbors. Finally, the energy is minimized by the graph-cut algorithm to compensate the brightness of the first frame. Other frames are straightforwardly compensated using the results of the first frame. The brightness variations of the previous frame is transmitted to the next frame via motion vectors. The reliability of the brightness variation is calculated based on the motion vector reliability. Video compensation result is achieved by the process of the image case. Simulation show that the proposed algorithm provides more natural results than the conventional algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5C
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• pp.512-518
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• 2006

Very large-area multi-projector display systems have wide applications since they provide immersible environments. The brightness of projectors in the system is different due to the design and aging of the bulbs, and optical properties of the projectors. Therefore it is imperative to match the brightness characteristics of projectors in the system. This issue has been addressed by many researchers. The state of the art solution considers characteristic of projector's brightness only. In this paper, we propose a method that takes into account brightness of projector as well as the dynamic range of the input image. We increase the dynamic range of the input image to utilize the maximum possible brightness of a projector while satisfying the spatial smoothness constraint. This achieves a seamless multi-display with dramatic brightness improvement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.36-45
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• 2006

In this paper, multiview calibration system for an effective 3D display is proposed. This system can be obtain 4-view image from multiview camera system. Also it can be rectify lens and camera distortion, error of bright and color, and it can be calibrate distortion of geometry. In this paper, we proposed the signal processing skill to calibrate the camera distortions which are able to take place from the acquisited multiview images. The discordance of the brightness and the colors are calibrated the color transform by extracting the feature point, correspondence point. And the difference of brightness is calibrated by using the differential map of brightness from each camera image. A spherical lens distortion is corrected by extracting the pattern of the multiview camera images. Finally the camera error and size among the multiview cameras is calibrated by removing the distortion. Accordingly, this proposed rectification & calibration system enable to effective 3D display and acquire natural multiview 3D image.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.213-224
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• 2010

In this paper, we propose an algorithm both geometric correction using a grid point image and radiometric adaptive projection that dependent upon the luminance of the input image and that of the background. This method projects and captures the grid point image then calculates the geometrically corrected position by difference between the two images. Next, to compensate color, a corrected image is calculated by the ratio divided luminance of an input image by luminance of arbitrary surface. In addition, we found the scaling factor which controls the contrast to avoid clipping error. At this time, the scaling factor is dependent on mean image lightness when background is determined. Experimental results show that the proposed method achieves good performance and is able to reduce the perceived color clipping and artifacts, better approximating the projection on a white screen.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.55-62
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• 2011

In this paper, a temporal color and luminance variation suppression algorithm for a digital video sequence is proposed by considering time-varying light source. When a video sequence is sampled with the periodically emitting illuminant and with a short exposure time, the color rolling phenomenon occurs, where the color and the luminance of the image periodically change from field to field. In conventional signal processing techniques, the luminance variation remaining in the resultant video sequence degrades the constancy of the image sequence. In the proposed method, we obtain video sequences with constant luminance and color by compensating for the inter-field luminance variation. Based on a motion detection technique, the amount of the luminance variation for each channel is estimated on the background of the sequence without the effects of moving objects. The experimental results clearly show that our strategy efficiently estimated the illuminant change without being affected by moving objects, and the variations were efficiently reduced.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.644-647
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• 2010

본 논문에서는 영역분할을 이용한 3D입체영상의 밝기 보정방법을 제안한다. 제안된 방법은 입력된 좌우 3D입체영상 중 우 영상을 이진화를 통한 영역분할을 하고 크기가 작은 영역들은 제거한다. 영역단위의 매칭을 할 때 영역경계에서 발생하는 불연속성을 제거하기 위해서 모폴로지 필터로 영역경계지역(contour region)을 일정부분 제거한다. 우 영상의 각 영역들에 대해 대응되는 좌 영상내의 영역을 상관계수(correlation coefficient)를 이용한 정합을 통해 추출한다. 좌우 영상의 영역 간 히스토그램 명세화를 수행함으로써 우 영상의 밝기 보정을 한다. 실험에서 좌 영상으로부터 블록단위 움직임보상으로 우 영상을 생성했을 때 제안한 방법이 블록평균 정합오차가 가장 작은 것을 확인 할 수 있었다.

• Journal of the Korea Computer Graphics Society
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• v.17 no.4
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• pp.31-40
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• 2011

Projector-based visual systems are widely used for VR and experience display applications. But the illumination irregularity on the screen surface due to the screen material and its light reflection properties sometimes deteriorates the user experience. This phenomenon is particularly troublesome when the participants of the head tracking VR system such as CAVE or the motion generation experience system continually move around the system. One of reason to illumination irregularity is projector-screen specular reflection component to participant's eye's position and it's analysis needs high computation complexity. Similar to calculate specular lighting term using GPU's programmable shader, Our research adjusts every pixel's brightness in runtime with given 3D screen space model to reduce illumination irregularity. For doing that, Angle-based brightness compensate function are considered for specific screen installation and modified it for GPU-friendly compute and access. Two aspects are implemented, One is function access transformation from angular form to product and the other is piecewise linear interpolate approximation.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1071-1081
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• 2021

Remote Sensing using unmanned aerial vehicles(UAV) can acquire images with higher time resolution and spatial resolution than aerial and satellite remote sensing. However, UAV images are photographed at low altitude and the area covered by one image isrelatively narrow. Therefore multiple images must be processed to monitor large area. Since UAV images are photographed under different exposure conditions, there is difference in brightness values between adjacent images. When images are mosaicked, unnatural seamlines are generated because of the brightness difference. Therefore, in order to generate seamless mosaic image, a radiometric processing for correcting difference in brightness value between images is essential. This paper proposes a relative radiometric calibration and image blending technique. In order to analyze performance of the proposed method, mosaic images of UAV images in agricultural and mountainous areas were generated. As a result, mosaic images with mean brightness difference of 5 and root mean square difference of 7 were avchieved.