• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.3
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• pp.125-130
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• 2018

Arc lamps are now widely utilized as illumination sources for a large number of investigations in wide-field fluorescence microscopy. Among many power converters for the lamp, the PSFB (Phase-Shift Full-Bridge) converter with the ZVS (Zero Voltage Switching) is the most widely used soft switched circuit in high-power applications. Also, in the most luminaries, the power factor has to be more and more important. Thus, the power factor correction(PFC) must be included in the power system. A new igniter module using the switching power device and the transformer is proposed instead of the conventional igniter using the mechanical contactor. The proposed converter with the high power factor and high efficiency is verified through the experimental works.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2006.06a
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• pp.25-28
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• 2006

In this paper, we say the shading correction system supporting multi-resolution for camera. The shading effect is caused by non-uniform illumination, non-uniform camera sensitivity, or even dirt and dust on glass (lens) surfaces. In general this shading effect is undesirable [1]. Eliminating it is frequently necessary for subsequent processing and especially when quantitative microscopy is the fine goal. The proposed system is available on thirty nine kinds of image resolutions scanned by interlaced and progressive type. Moreover, the system is using various continuous quadratic equations instead of using the piece-wise linear curve which is composed of multiple line segments. Finally, the system could correct the correct effect without discontinuity in any image resolution. The proposed system is also experimentally demonstrated with Xilinx Virtex FPGA XCV2000E- 6BG5560 and the TV set.

• The Journal of the Korea Contents Association
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• v.9 no.8
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• pp.9-17
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• 2009

License plate recognition is an active research area. but few comparative studies on license plate binarization have been conducted. Many related researchers have experienced similar trial and error for finding an effective binarization method. To reduce this trial and error, this study implemented some binarization methods and quantitatively compared the performance of the methods. The performance evaluation consists of a low level measure and a high level measure, so it can evaluate not only the quality of binarized image itself but also the usefulness of the result. The performance evaluation was separately performed with three groups of images so as to understand the properties of the binarization methods. Experimental results show that the quality of binarization is more dependent on the evenness of illumination than the intensity of illumination. The Otsu's method has acquired the most effective performance in the group of even illumination images and the Niblack's method with parameter correction has shown the best quality in the group of uneven illumination images.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.190-199
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• 2001

In this paper, we have researched the depth of focus (DOF) and cutoff intensity of the $0.1{\mu}m$rule dense line'||'&'||'space pattern according to the various off-axis illumination (OAl) conditions in the optical system of 0.65 NA using ArF excimer laser (193 nm). We have also studied the variation of the DOF and cutoff intensity according to the sub-resolution pattern (hammer head type) size for optical proximity correction (OPC) applied to the capacitor pattern and the various OAl conditions in the same optical system. As a result, it is revealed that the cross type quadrupole or annular illumination is preferred to the conventional X type quadrupole for printing the $0.1{\mu}m$ rule dense pattern. Also, we can investigate the optimal illumination condition and the size of ope sub-resolution pattern to keep a consistent DGF and cutoff intensity trends.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.6 s.312
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• pp.65-84
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• 2006

In this paper, we present an improved image formation model and propose a color image enhancement based on the model. In the presented image formation model, an input image is represented as a product of global illumination, local illumination, and reflectance. In the proposed color image enhancement, an input RGB color image is converted into an HSV color image. Under the assumption of white-light illumination, the H and S component images are remained as they are and the V component image only is enhanced based on the image formation model. The global illumination is estimated by applying a linear LPF with wide support region to the input V component image and the local illumination by applying a JND (just noticeable difference)-based nonlinear LPF with narrow support region to the processed image, where the estimated global illumination is eliminated from the input V component image. The reflectance is estimated by dividing the input V component image by the estimated global and local illuminations. After performing the gamma correction on the three estimated components, the output V component image is obtained from their product. Histogram modeling is next executed such that the final output V component image is obtained. Finally an output RGB color image is obtained from the H and S component images of the input color image and the final output V component image. Experimental results for the test image DB built with color images downloaded from NASA homepage and MPEG-7 CCD color images show that the proposed method gives output color images of very well-increased global and local contrast without halo effect and color shift.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.29-33
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• 2007

All pixels of image sensor do not react uniformly even if the light of same radiance enters into the camera. This non-uniformity comes from the sensor pixel non-uniformity and non-uniformity induced by the changing transmission of the telescope over the field. The first contribution to the non-uniformity has high spatial frequency nature and has an influence on the result and quality of the data compression. The second source of non-uniformity has low frequency nature and has no influence of the compression result. As the contribution resulting from the sensor PRNU(Photo Response Non-Uniformity) is corrected inside the camera electronics, the effect of the remaining non-uniformity to the compression result will be negligible. The non-uniformity correction result shall have big difference according to the sensor modeling and the calculation method to get correction coefficient. Usually, the sensor can be modeled with one dimensional coefficients which are a gain and a offset for each pixel. Only two measurements are necessary theoretically to get coefficients. However, these are not the optimized value over the whole illumination level. This paper proposes the algorithm to calculate the optimized non-uniformity correction coefficients over whole illumination radiance. The proposed algorithm uses several measurements and the least square method to get the optimum coefficients. The proposed algorithm is verified using the own camera electronics including sensor, electrical test equipment and optical test equipment such as the integrating sphere.

• Journal of Korea Multimedia Society
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• v.18 no.12
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• pp.1439-1444
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• 2015

Measuring spectral reflectance can be regarded as obtaining inherent color parameters, and spectral reflectance has been used in image processing. Model-based spectrum recovering, one of the method for obtaining spectral reflectance, uses ordinary camera with multiple illuminations. Conventional model-based methods allow to recover spectral reflectance efficiently by using only a few parameters, however it requires some parameters such as power spectrum of illuminations and spectrum sensitivity of camera. In this paper, we propose an enhanced model-based spectrum recovering method without pre-measured parameters: power spectrum of illuminations and spectrum sensitivity of camera. Instead of measuring each parameters, spectral reflectance can be efficiently recovered by estimating and using the spectrum characteristic matrix which contains spectrum parameters: basis function, power spectrum of illumination, and spectrum sensitivity of camera. The spectrum characteristic matrix can be easily estimated using captured images from scenes with color checker under multiple illuminations. Additionally, we suggest fast recovering method preserving positive constraint of spectrum by nonnegative basis function of spectral reflectance. Results of our method showed accurately reconstructed spectral reflectance and fast constrained estimation with unmeasured camera and illumination. As our method could be conducted conveniently, measuring spectral reflectance is expected to be widely used.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12C
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• pp.1225-1238
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• 2003

We present an efficient algorithm for skew correction of business card images obtained by a PDA (personal digital assistant) camera. The proposed method is composed of four parts: block adaptive binarization (BAB), stripe generation, skew angle calculation, and image rotation. In the BAB, an input image is binarized block by block so as to lessen the effect of irregular illumination and shadow over the input image. In the stripe generation, character string clusters are generated merging adjacent characters and their strings, and then only clusters useful for skew angle calculation are output as stripes. In the skew angle calculation, the direction angles of the stripes are calculated using their central moments and then the skew angle of the input image is determined averaging the direction angles. In the image rotation, the input image is rotated by the skew angle. Experimental results shows that the proposed method yields skew correction rates of about 93% for test images of several types of business cards acquired by a PDA under various surrounding conditions.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.6_1
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• pp.519-528
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• 2012

It was pointed out that the terrain distortion of SAR image is even worse than that of optical image although SAR imagery has the advantages of being independent of solar illumination and weather conditions. It is thus necessary to correct terrain distortion in SAR image for various application areas to integrate SAR and optical image information. There has to be a clear evaluation of terrain correction of high resolution SAR image according to the quality of DEM because the DEM of study site is generally used in the process of terrain correction. To achieve this issue, this paper compared the effects of quality of Digital Elevation Model(DEM) in the process of terrain correction of high resolution SAR images, using the DEM produced from 1:5000 topographic contour maps, LiDAR DEM, ASTER GDEM, SRTM DEM. We used TerraSAR-X and Cosmo-SkyMed, as the test data set, which are constructed on the same X-band SAR system as KOMPSAT-5. In order to evaluate quantitatively the correction results, we conducted comparative evaluation with the KOMPSAT-2 ortho image of the same region. The evaluation results showed that the DEM produced from 1:5000 topographic contour maps achieved successful results in the terrain correction of SAR image compared with the other DEM data, and the widely used SRTM DEM data in various applications was not suitable for the terrain correction of high resolution SAR images.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1201-1207
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• 2006

In this paper, we say the adaptive shading correction system supporting multi-resolution for mobile camera. The shading effect is caused by non-uniform illumination, non-uniform camera sensitivity, or even dirt and dust on glass (lens) surfaces. In general this shading effect is undesirable [1-3]. Eliminating it is frequently necessary for subsequent processing and especially when quantitative microscopy is the fine goal. The proposed system is available on thirty nine kinds of image resolutions scanned by interlaced and progressive type. Moreover, the system is using forty kinds of continuous quadratic equations instead of using the piece-wise linear curve which is composed of multiple line segments. Finally, the system could correct the shading effect without discontinuity in any image resolution. The proposed system is implemented in VLSI with cell library based on Hynix $0.25{\mu}m$ CMOS technology.