• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.11
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• pp.49-54
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• 2005

This paper proposes the low power MDCT algorithm for precise FV with minimum size of sub-window in mobile phone. Proposed algerian uses the coefficient at the middle of whole result process requiring the least number of calculations, since it has a good characteristic when used as standard of the FV and needs minimum amount of operation. In addition, using the DCT result related to the middle frequency makes the characteristic of FV more superior because it suppresses the impulsive noise and difference of focus values is larger than any others. The proposed algorithm is implemented using Verilog HDL and verified using Excalibur-ARM board.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.435-437
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• 2010

렌즈의 피사계심도 (Depth of Field)가 낮은 카메라로 영상을 획득 했을 때, 한 영상 내에도 in-focus 영역과 out of-focus 영역이 동시에 존재하게 된다. 따라서 영상을 복원하기 위해 in-focus 영역과 out-of-focus 영역을 구분하는 focus measure가 필요하게 된다. 기존 focus measure 알고리즘은 획득된 영상의 intensity 값의 절대적인 변화나 고주파수 성분 값에 따라 in-focus와 out-of-focus를 결정하기 때문에 out-of-focus 영역이 smooth 하지 않을 경우에는 in-focus 영역이라 잘못 판단할 수 있을 뿐만 아니라 잡음에 민감한 단점을 가진다. 본 논문에서는 기존 알고리즘의 한계점을 보완하는 연구 방향을 제시한다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.8-14
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• 2006

This paper proposed noise insensitive 4*4 mid frequency-OCT (MF-DCT) focus measure operator. Proposed operator enhanced low power 8*8 MDCT operator to have 4*4 rotationally same form for Gaussian noise. MF-DCT operator acting like band-pass filter suppresses both low-frequency signal useless for focus measure and high-frequency signal affected by impulsive noise. Also it is proved to be linear because it uses the energy of band-pass filtered signal as focus measure. Experimental result shows its superiority by comparing AUM with traditional operators.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.39-45
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• 2022

In this paper, we propose methods to improve image-based auto-focus that can compensate for drawbacks of traditional auto-focus control. When adjusting the focus, there is a problem that the focus window cannot be set to the same position if the camera's LOS is not directed at the same location and flow or shake. To address this issue, we applied image tracking techniques to improve optimal focus localization accuracy. And also, although the same focus value should be calculated at the same focus step, but different values can be calculated by camera's fine shaking or image disturbance due to atmospheric scattering. To tackle this problem a SAFS (Stable Adjacency Frame Selection) has been proposed. As a result of this study, our proposed methodology shows more accurate than traditional methods in terms of finding best focus position.

• The Journal of the Korea Contents Association
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• v.10 no.6
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• pp.307-311
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• 2010

The aim of this study is to investigate PAE, as the result of the test of kVp accuracy, according to detector measurement method. Based on the indicated value of 70kVp, each distance between a focus and a kVp meter was 100cm, 80cm and 60cm and the angle of X-ray tube was set on $5^{\circ},\;10^{\circ},\;15^{\circ},\;20^{\circ},\;25^{\circ},\;30^{\circ}$. Each indicated value, 60kVp, 70kVp, 80kVp, 90kVp and 100 kVp, was used compare Small focus with Large focus. As a result, PAE on the side of cathode was higher than it on the side of anode in the case of 100cm and PAE on the side of anode was higher in the case of 80cm and 60cm. The coefficient rate was stable both the side of cathode and anode in the case of 100cm and it was fluctuated in the case of 80cm and 60cm. PAE in the case of Small focus was higher than Large focus and it was disproportionate to an indicated value. Error rate was in inverse proportion to the indicated value.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.935-938
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• 1998

In this paper, we propose a new auto focus algorithm using variance which estimate spread characteristic of image. In the proposed algorithm, the focus value is calculated via variance of difference between two adjacent pixels. This algorithm, we propose, show much more sharp focus curve than any other algorithms. It is shown experimentally that the proposed auto focus algorithm can be a efficient alternative to existing Tenengrad-based auto focusing algorithms.

• Journal of Korea Multimedia Society
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• v.16 no.1
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• pp.11-18
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• 2013

This paper presents a SFF(shape from focus) algorithm using a new focus measure based on higher order statistics for the exact depth estimation. Since conventional SFF-based 3D depth reconstruction algorithms used SML(sum of modified Laplacian) as the focus measure, their performance is strongly depended on the image characteristics. These are efficient only for the rich texture and well focused images. Therefore, this paper adopts a new focus measure using HOS(higher order statistics), in order to extract the focus value for relatively poor texture and focused images. The initial best focus area map is generated by the measure. Thereafter, the area refinement, thinning, and corner detection methods are successively applied for the extraction of the locally best focus points. Finally, a 3D model from the carefully selected points is reconstructed by Delaunay triangulation.

• Korean Journal of Digital Imaging in Medicine
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• v.9 no.1
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• pp.7-15
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• 2007

This study aim to investigate image characteristics due to focus-grid and head phantom decentering from the armorphos silicon thin film transistor detector the fixed focus-grid is applied, wish to propose right use method of digital medical equipment. Acquired image according to focus-grid and head phantom position decentering using head phantom on armorphos silicon thin film transistor detector the fixed focus-grid is applied. acquired image evaluate pixel value, histogram, plot profile, surface plot using NIB (Image J) image analysis program and compared decentering image with standard image. Mean value and standard deviation value of focus-grid lateral decentering and duplex decentering of focus-grid and head phantom decreased by ratio, consequently increase of horizontality, diagonal decentering. also, deteriorated contrast of image because frequency of high pixel value decreases fairly. according increases decentering, image distortion phenomenon was increase, by next time, pixel mean value of head phantom decentering was no big change but horizontality, diagonal, mean value and standard deviation value of pixel decreased by ratio. Even if increase pixel noise of image because wide latitude and post processing ability of digital detector, radiotechnologist can not recognize. Therefore, radiotechnologist must recognize correctly the photographing factors which increases pixel noise on the grid system installation digital detector and should exam.

• Journal of the Korea Computer Graphics Society
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• v.23 no.4
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• pp.31-40
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• 2017

As 3D cell culture has recently become possible, it has been able to observe a 3D shape of cell and volume. Generally, 3D information of a cell should be observed with a special microscope such as a confocal microscope or an electron microscope. However, a confocal microscope is more expensive than a conventional microscope and takes longer time to capture images. Therefore, there is a need for a method that can reconstruct the 3D shape of cells using a common microscope. In this paper, we propose a method of reconstructing 3D cells using the focus estimator value from multi-focal fluorescence images of cells. Initially, 3D cultured cells are captured with an optical microscope by changing the focus. Then the approximate position of the cells is assigned as ROI (Region Of Interest) using the circular Hough transform in the images. The MSBF (Modified Sliding Band Filter) is applied to the obtained ROI to extract the outlines of the cell clusters, and the focus estimator values are computed based on the extracted outlines. Using the computed focus estimator values and the numerical aperture (NA) of the microscope, we extract the outline of the cell cluster considering the depth and reconstruct the cells into 3D based on the extracted outline. The reconstruction results are examined by comparing with the combined in-focus portions of the cell images.

• Journal of the Korea Computer Industry Society
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• v.9 no.2
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• pp.69-76
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• 2008

This paper implement an Camcorder NTSC camera autofocus control system on the DSP Board. The information of camera lens control obtain the only brightness simple image processing from the NTSC camcoder camera image. The exact focus makes the exact boundaries. The camera lens control that the increase sum of the useful ingredient values. Useful value obtained experiment value. Also noise is except because a big value of the ingredients so that obtained focus more accurate value.