• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.5
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• pp.415-425
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• 2007

In this study, we generated an orthophoto with both LIDAR data and aerial images and compared it with that generated from only the images. For the accuracy assessment of these orthophotos, we performed not only qualitative analysis based on visual inspection but also quantitative analysis by measuring horizontal inconsistency, boundary coordinates and similarity measures on buildings. Based on the visual inspection and horizontal inconsistency, the orthophoto based on LIDAR DSM appeared to be more closer to a true-orthophoto. However, the analysis on measurements of boundary coordinates and similarity measures indicates that the orthophoto based on LIDAR DSM is more vulnerable to double mapping on occluded areas. Accordingly, if we apply an effective solution on double mapping or use only the central areas of the aerial images where occluded areas are rarely founded, we can generate automatically true-orthophotos based on a LIDAR DSM.

• The KIPS Transactions:PartB
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• v.11B no.3
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• pp.309-316
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• 2004

In this paper, we proposed the TDS(T-shape Diamond Search) based on the directions of above, below, left and right points to estimate the motion vector fast and more correctly in this method, we exploit the facts that most motion vectors are enclosed in a circular region with a radius of 2 fixels around search center(0,0). At first, the 4 points in the above, below, left and right around the search center is calculated to decide the point of the MBD(Minimum Block Distortion). And then w. above point of the MBD is checked to calculate the SAD. If the SAD of the above point is less than the previous MBD, this process is repeated. Otherwise, the right and left points of MBD are calculated to decide The points that have the MBD between right point and left point. Above processes are repeated to the predicted direction for motion estimation. Especially, if the motions of image are concentrated in the crossing directions, the points of other directions are omitted. As a result, we can estimate motion vectors fast. Experiments show that the speedup improvement of the proposed algorithm over Diamond Search algorithm(DS) and HEXgon Based Search(HEXBS) can be up to 38∼50％ while maintaining similar image Quality.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.204-210
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• 1999

We propose an optical fingerprint identification system using volume hologram for database of matched filter. Matched filters in VanderLugt correlator are recorded into a volume hologram that can store data with high density, transfer them with high speed, and select a randomly chosen data element. The multiple reference fingerprint photographs of database are prerecorded in a photorefractive material in the form of Fourier transform images, simply by passing the image displayed in a spatial light modulator through a Fourier transform lens. The angular multiplexing method for multiple holograms of database is achieved by controlling the reference directions with a step motor. Experimental results show that the proposed system can be used for secure entry systems to identify individuals for access to a restricted area, security verification of credit cards, passports, and other IDs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2146-2152
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• 2008

In In this paper, we proposed a new JPEG2000 codec using multiresolution-based rendering (MRBR) technique for video compression of 3-dimensional digital cinema. We introduced discrete wavelet transform (DWT) for stereoscopic image and stereo matching technique in the wavelet domain. The disparity was extracted using stereo matching and transmitted with the reference (left) image. Since the generated right image was degraded by the occlusion lesion, the residual image which is generated from difference between the original right image and the generated one was transmitted at the same tine. The disparity data was extracted using the dynamic programming method in the disparity domain. There is high correlation between the higher and lower subbands. Therefore we decreased the calculation amount and enhanced accuracy by restricting the search window and applying the disparity information generated from higher subband.

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.73-77
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• 1999

In this paper. wavelet transform coding for image conference is studied. Original video frames are transformed into hierarchical pyramidal images with multiresolution using the band property of wavelet transform coefficients. Moving information between neighboring frames is obtained from the low-resolution band. Also, to control the video coding procedure. a new picture set filter is proposed. This filter controls the compression ratio of each frame depending on the correlation to the reference frame by selectively eliminating less important high-resolution areas. Consequently. video quality can be preserved and bit rate can be controlled adaptively In the simulation, to test the performance of the proposed coding method, comparisons with the full search block matching algorithm and the differential image coding algorithm are made. Consequently. the proposed method shows a reasonably good performance over existing ones.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.215-224
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• 2013

An efficient homography estimation method for large sized images is proposed. Estimating an accurate homography is one of the most important parts in image stitching processes. Since hardwares have been advanced, it has been passible to take higher resolution images. However, computational cost for estimating homography has been also increased. Specifically, when too many features exist in the images, it requires lots of computations to estimate a correct homography. Furthermore, there is a high probability of obtaining an incorrect homography. Therefore, we propose a numerical method to extract the appropriate correspondences from several down-scaled images to estimate and compensate the homography numerically for restoring an original homography. Also, if there is an unbalance in color tone between the reference and the target images, we make them balanced by using local information of the overlapped regions. Experimental results show that proposed method is three times faster in 3.2 mega pixel images, five times faster in 8mega pixel images than the conventional approach. Therefore, we believe that the proposed method can be a useful tool to efficiently estimate a homography.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.5
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• pp.56-65
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• 2009

Stereoscopic images consist of the left image and the right image. Thus, stereoscopic images have much amounts of data than single image. Then an efficient image compression technique is needed, the DPCM-based predicted coding compression technique is used in most video coding standards. Motion and disparity estimation are needed to realize the predicted coding compression technique. Their performing algorithm is block matching algorithm used in most video coding standards. Full search algorithm is a base algorithm of block matching algorithm which finds an optimal block to compare the base block with every other block in the search area. This algorithm presents the best efficiency for finding optimal blocks, but it has very large computational loads. In this paper, we have proposed fast disparity estimation algorithm using motion and disparity vector information of the prior frame in stereo image coding. We can realize fast disparity vector estimation in order to reduce search area by taking advantage of global disparity vector and to decrease computational loads by limiting search points using motion vectors and disparity vectors of prior frame. Experimental results show that the proposed algorithm has better performance in the simple image sequence than complex image sequence. We conclude that the fast disparity vector estimation is possible in simple image sequences by reducing computational complexities.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.3
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• pp.70-80
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• 2010

This study proposes the algorithm to automate image alignment and detect marginal bone destructions, based on subtraction radiography for dental radiographic images necessary for dental PACS, which hasn't been covered by related literatures. The proposed algorithm enables a quick and precise detection of marginal bone destructions around teeth including implant through the knowlege-based multi-template matching in reference to ROI(Region Of Interest) obtained from applicable teeth using information about their geometric forms to solve problems single-template matching is exposed to. Actually, the test showed that it was possible not only to quickly and precisely detect marginal bone destructions around teeth, but also to get more objective and quantitative results through the algorithm.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.225-228
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• 2011

동영상을 고효율로 압축할 수 있는 중요한 기술 중의 하나가 움직임 추정 기술이다. 움직임 추정 기술에서 가장 널리 사용되는 탐색 방식과 정합오차를 판단하는 기준은 각각 전역 탐색(FS: Full Search)알고리듬과 Sum of Absolute Differences(SAD)이다. 하지만, FS와 SAD를 사용한 움직임 추정기술은 인코더 전체 계산량의 50%이상을 차지하게 된다. 무선 통신 및 인터넷 환경에서 사용되는 응용프로그램에 대해서는 많은 계산량이 실시간 전송을 어렵게 만든다. 이러한 이유로, 동영상 압축 기술에서 계산량을 줄이는 방법이 중요하게 되었다. 그 결과로, SAD대신 다른 정합 오차 기준을 사용하여 움직임 추정기술의 계산량을 줄이는 알고리듬들이 제안되었다. 본 논문에서는 계산량을 줄이면서 하드웨어 구현 시 많은 이점을 가진 1비트 변환 (One-bit Transform, 1BT)알고리듬과 1비트 변환의 성능을 향상시킨 제한된 1비트 변환(Constrained one-bit transform, C-1BT)을 소개하고 C-1BT방법에 있어서 기존 방식의 빠른 인코딩속도를 유지하면서 PSNR을 증가시키는 알고리듬을 제안한다. 제안하는 알고리듬에서는 기존 C-1BT에서 고정해서 사용한 파라미터 D값을 대신에 현재블록과 동일한 위치에 있는 참조영역의 블록과 그 주변블록의 움직임벡터 정보를 이용해서 블록의 움직임 정도를 판단하고, 블록단위로 D값을 적응적으로 결정한다. 실험결과는 제안하는 알고리듬이 기존의 알고리듬과 비교하여 평균 0.11dB PSNR 증가를 보여 준다.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.431-447
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• 2021

Recently, the use of high-resolution satellites is increasing in many areas. In order to supply useful satellite images stably, it is necessary to establish automatic precision geometric correction technic. Geometric correction is the process that corrected geometric errors of satellite imagery based on the GCP (Ground Control Point), which is correspondence point between accurate ground coordinates and image coordinates. Therefore, in the automatic geometric correction process, it is the key to acquire high-quality GCPs automatically. In this paper, we proposed iterative precision geometry correction method. we constructed an image pyramid and repeatedly performed GCP chip matching, outlier detection, and precision sensor modeling in each layer of the image pyramid. Through this method, we were able to acquire high-quality GCPs automatically. we then improved the performance of geometric correction of high-resolution satellite images. To analyze the performance of the proposed method, we used KOMPSAT-3 and 3A Level 1R 8 scenes. As a result of the experiment, the proposed method showed the geometric correction accuracy of 1.5 pixels on average and a maximum of 2 pixels.