• Journal of the Korean institute of surface engineering
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• v.38 no.2
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• pp.83-87
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• 2005

We enhanced the color of blue sapphires and rubies successfully by using a oxygen-propane torch flame annealing, which had not been employed so far. We confirmed that about 1 mm-thick de-coloring of the corundum samples were available with 60 minutes flame annealing through eye evaluation, color coordination characterization, and methylene iodide immersion observation. We also suggest that the color centers such as $[Fe_{Al}^{\cdot}]$ may transform into transparent $[Fe_{Al}^{x}],\;[Cr_{A1}^{x}]$ sites with $[V_o^']$ generation at the elevated temperature in oxygen-rich atmosphere by diffusion mechanism. Our results implied that the longer diffusion time and the higher oxygen partial pressure might lead to the better de-coloring enhancement in corundum gem stones.

• Korean Journal of Cognitive Science
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• v.25 no.1
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• pp.51-71
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• 2014

This paper presents an image enhancement method in real road traffic scenes. The images captured by the camera on the car cannot keep the color constancy as illumination or weather changes. In the real environment, these problems are more worse at back light conditions and at night that make more difficult to the applications of the vision-based intelligent vehicles. Using the existing image enhancement methods without considering the position and intensity of the light source and their geometric relations the image quality can even be deteriorated. Thus, this paper presents a fast and effective method for image enhancement resembling human cognitive system which consists of 1) image preprocessing, 2) color-contrast evaluation, 3) alpha blending of over/under estimated image and preprocessed image. An input image is first preprocessed by gamma correction, and then enhanced by an Automatic Color Enhancement(ACE) method. Finally, the preprocessed image and the ACE image are blended to improve image visibility. The proposed method shows drastically enhanced results visually, and improves the performance in traffic sign detection of the vision based intelligent vehicle applications.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.19-22
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• 2003

This paper proposes the method of visual resolution enhancement to render a color image on a delta-structured display. The proposed method adopted a subpixel rendering method to reduce a color fringe error caused by delta- structured display and to improve visual resolution

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1139-1142
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• 2007

In this paper, an image enhancement method by saturation and contrast improvement is proposed. Histogram equalization with color difference makes higher contrast. By generating saturation amplification ratio with color difference, the saturation improves effectively. The experimental results show that the proposed algorithm has higher contrast and more natural - look than the conventional methods.

• Journal of Korea Multimedia Society
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• v.16 no.2
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• pp.119-130
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• 2013

In this paper, we propose a new color image enhancement method to improve the color saturation as well as luminance contrast in the YCbCr color space. The proposed method uses the maximum color difference table to compensate the perceived saturation changes due to luminance contrast changes. To improve the color saturation, the method first calculates the weighting factor by using the maximum color difference table and then multiplies the weighting factor to the input color difference signals. In this step, it maps color difference signals to proper color region to prevent the color distortion by considering the correlation of color saturations depending on the luminance and hue. The experimental results show that our method effectively improves color saturation compared to the conventional methods.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.2
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• pp.90-94
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• 2013

In this paper, we propose a new algorithm to improve the contrast ratio, to preserve information of bright regions and to maintain the color of backlight image that appears with a great relative contrast. Backlight images of the natural environment have characteristics for difference of local brightness; the overall image contrast improvement is not easy. To improve the contrast of the backlight images, MSR (Multi-Scale Retinex) algorithm using the existing multi-scale Gaussian filter is applied. However, existing multi-scale Gaussian filter involves color distortion and information loss of bright regions due to excessive contrast enhancement and noise because of the brightness improvement of dark regions. Moreover, it also increases computational complexity due to the use of multi-scale Gaussian filter. In order to solve these problems, a linear MSR is performed that reduces the amount of computation from the HSV color space preventing the color distortion and information loss due to excessive contrast enhancement. It can also remove the noise of the dark regions which is occurred due to the improved contrast through edge preserving filter. Through experimental evaluation of the average color difference comparison of CIELAB color space and the visual assessment, we have confirmed excellent performance of the proposed algorithm compared to conventional MSR algorithm.

• Journal of Korea Multimedia Society
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• v.16 no.1
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• pp.29-41
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• 2013

The digital camera is impossible to preserve the appearance of a scene containing high dynamic range due to a limitations of the sensing hardware. The Retinex was proposed on the purpose to solve these problems. While the Retinex enhances visibility and color constancy, it sometimes suffers from color distortion, halo effect and reduced global contrast. This paper presents an advanced Retinex algorithm working on the YCbCr color coordinate to reduce the processing time and to improve the global contrast and color. Simulation results show that our algorithm significantly reduces the total processing time, and provide the superior result image by improving the global contrast and color consistency as well as by reducing the halo effect around the boundaries.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.5
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• pp.645-652
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• 2015

In underwater, such as fish farm and sea, turbidity is increased by water droplets and various suspended, therefore light attenuation occurs depending on the depth also caused by the scattering effect of light float. In this paper, in order to improve the visibility of underwater images obtained from these aquatic environment, we propose a visibility enhancement method using a haze removal method based on dark channel prior and a trained color transform model. In order to train a color transform model, we used underwater pattern images captured from Pohang and Yeosu, and to measure the performance of the proposed method, we carried out experiment of visibility enhancement using underwater images collected from Yeosu, Geomundo and Philippines. The results show that the proposed method can improve the visibility of underwater images of various locations.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.2
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• pp.73-77
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• 2004

The color enhancement for natural Zambian amethyst of low quality was carried out by the hydrothermal treatment method. The hydrothermal treatment conditions were as follows: reaction temperature; $300^{\circ}C$, duration; 30 hrs, filling; 40%, solvent; 6 M-HCI solution. The reddish purple amethyst of high quality was obtained under these conditions. From the result of ICP/AES, it was known that color enhancement was affected by a Fe elemental content to exist in the inside of natural Zambian amethyst. Also, from the result of UY-VIS-NIR, it was shown that the absorption peak at 550 nm after hydrothermal treatment is slightly lower than those of non-treated natural Zambian amethyst. In this study, it was known that hydrothermal treatment method was a way to suitable for increase of commercial value of natural Zambian amethyst.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.145-151
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• 2005

Color enhancement of African rubies with dark red was carried out by the heat treatment and the hydrothermal treatment method respectively. The heat treatment method brought about an adverse effect causing the color to be deteriorated. However, the hydrothermal treatment method enhanced its color and clarity. The hydrothermal treatment conditions for color enhancement of them were as follows: solvent: 0.9M $Na_2CO_3-1M\;K_2CO_3$, temperature: $450^{\circ}C$, duration: 48 hrs, filling: $30\%$, pressure: 375 atm. As the results of characteristics for African rubies obtained under these conditions, it was known that the amount of $Cr^{3+},\;Fe^{3+},\;Ti^{4+}$ was reduced after the hydrothermal treatment from the ICP/MS and XRF analyses. Also, it was found that the red color from the colorimeter analyses was getting lighter. These results were consistent with the PL analysis showing that the intensity of the luminescence peak generated by the electron transition of $Cr^{3+}$ ion became lower after the hydrothermal treatment compared with the non-treated rubies.