Bongsoon Kang

A Space-Variant Luminance Map based Color Image Enhancement

Improvement of image quality has been highly demanding for users in digital imaging systems. A variety of image enhancement algorithms has been developed to control image enhancement factors. This paper presents a color image enhancement method that makes use of a space-variant luminance map (SVLM) for the local brightness characterization. Two-dimensional gamma correction combined with the SVLM is developed to increase the intensity at the dark region and vice versa at the bright region in the luminance domain. The enhanced luminance information is applied to the adaptive contrast enhancing process and the linear color restoration. The proposed algorithm reveals details of the input image as well as minimizes loss of the edge sharpness in the non-uniform and low illumination conditions. The developed enhancement process resulted in the lowest absolute mean brightness error (AMBE) in a low-complexity fashion. A series of experimental results are discussed in terms of visual quality, the enhancement performance, and the complexity.

One dimensional conversion of color temperature in perceived illumination

This paper proposes a one-dimensional conversion method of color temperature in perceived illumination. It also presents the design and implementation of the method. The proposed method is verified using the Xilinx Virtex FPGA XCV 2000-6BG560. This method is demonstrated experimentally for color temperatures in the range of 3000 K to 25000 K. This can be applied into special effect for multimedia applications.

Edge Adaptive Color Interpolation for Ultra-Small HD-Grade CMOS Video Sensor in Camera Phones

This paper proposes an edge adaptive color interpolation for an ultra-small HD-grade complementary metal-oxide semiconductor (CMOS) video sensor in camera phones that can process 720-p/30-fps videos. Recently, proposed methods with great image quality perceptually reconstruct the green component and then estimate the red/blue component using the reconstructed green and neighbor red and blue pixels. However, these methods require the bulky memory line buffers in order to temporally store the reconstructed green components. The edge adaptive color interpolation method uses seven or nine patterns to calculate the six edge directions. At the same time, the threshold values are adaptively adjusted by the sum of the color values of the selected pixels. This method selects the suitable one among the patterns using two flowcharts proposed in this paper, and then interpolates the missing color values. For verification, we calculated the peak-signal-to-noise-ratio (PSNR) in the test images, which were processed by the proposed algorithm, and compared the calculated PSNR of the existing methods. The proposed color interpolation is also fabricated with the 0.18-㎛ CMOS flash memory process.

Color Image Enhancement Based on Adaptive Nonlinear Curves of Luminance Features

This paper proposes an image-dependent color image enhancement method that uses adaptive luminance enhancement and color emphasis. It effectively enhances details of low-light regions while maintaining well-balanced luminance and color information. To compare the structure similarity and naturalness, we used the tone mapped image quality index (TMQI). The proposed method maintained better structure similarity in the enhanced image than did the space-variant luminance map (SVLM) method or the adaptive and integrated neighborhood dependent approach for nonlinear enhancement (AINDANE). The proposed method required the smallest computation time among the three algorithms. The proposed method can be easily implemented using the field-programmable gate array (FPGA), with low hardware resources and with better performance in terms of similarity.

New video enhancement preprocessor using the region-of-interest for the videoconferencing

The development of audio/video compression systems has made feasible digital multimedia applications. Under limited bandwidth environments, the human visual attention using region-of-interest (ROI) has been reported to improve the performance in the video coding. In this paper, we propose a ROI based video preprocessor method that deals with the perceptual quality in a low-bit rate communication environment. Three separated processes of the ROI detection, the image enhancement, and the boundary reduction are proposed to deliver better video quality at the videoconferencing application for use in a fixed camera and to be compatible as a preprocessor with the conventional video coding standards. A series of the simulation results and the subjective quality comparison assessment are discussed to show the quality improvement.

Performance Analysis of PO-THMA UWB System Using Mutually Orthogonal MHP Pulses

In this paper, we propose a pulse ordered time hopping multiple access (PO-THMA) ultra-wideband (UWB) system using modified Hermite polynomial (MHP) pulses. The MHP pulses have a mutually orthogonal property between different ordered pulses and that property makes simultaneous transmission at the same time slot without collision in the THMA UWB system, and this result in increasing transmission capacity or improving bit error rate (BER). We analyze BER of the proposed system and show that the BER performance and the transmission capacity are improved dramatically when compared with those of conventional THMA UWB system.

A high transmittance color liquid crystal display mode with controllable color gamut and transparency

In this paper, we propose a color transparent liquid crystal (LC) mode that can control the properties of the color gamut and transparency in a single panel. To achieve high transmittance in the transparent LC mode, a reactive mesogen (RM) with embedded color dichroic dyes was applied instead of a color filter. Basically, the LC mode applied a 3-terminal electrode structure to switch between the transparent LC mode and the conventional color LC mode. Depending on the direction of the applied voltage, we can operate both the color mode and the transparent mode in a single panel, and modulate the transparency and color purity of the cell through appropriate voltage control. In the experiments, we confirmed that the transmittance and the color gamut of the cell were 39.4% and 2% in the transparent LC mode and 14.9% and 34% in the color LC mode, respectively. Modulation of the color gamut and transparency between each LC mode are also demonstrated in the paper.

A 2.4 GHz Current-Reused CMOS Balun-Mixer

A 0.13 mum CMOS 2.4 GHz balun-mixer is proposed, where a current-reused noise-canceling topology is adopted as the transconductance stage to reduce dc power consumption. After frequency conversion, noise-cancellation is achieved only when a specified condition is satisfied, but single-to-differential signal conversion is inherently obtained by the mixer operation. The fabricated chip shows a conversion gain of 13.5 dB, a single-side-band (SSB) noise figure of 8 dB, and an input-referred IP3 of - 6 dBm, while consuming only 3.5 mA from a 1.5 V supply voltage.

A 10-bit 80 MHz 3.0 V CMOS D/A converter for video applications

A low-voltage, high-speed, and high-resolution CMOS D/A converter is implemented using an improved unique switching sequence to reduce integral linearity error (ILE) in the output of current cells, and a novel segmented layout technique to minimize both current asymmetry due to drain current directions and voltage drop due to power line resistance. The D/A converter has been fabricated by using 0.65 /spl mu/m CMOS process. The differential linearity error (DLE) is 0.37 LSB and the ILE is 0.87 LSB. It occupies a die area of 700/spl times/800 /spl mu/m/sup 2/ and operates up to 80 MHz with 3.O V.

Image quality enhancement by real-time gamma correction for a CMOS image sensor in mobile phones

Real-time gamma correction is an essential function in display devices such as CRTs, plasma TVs, and TFT LCDs. In this paper, we present the image quality enhancement by real-time gamma correction for a CMOS image sensor in mobile phones. The proposed algorithm and system operate with a block structure and the bit width of input and output of the proposed system is 12-bit. The proposed gamma system is reduced the error range and enhanced the image quality compared with conventional system that has 10-bit input and 8-bit output. The proposed system was implemented experimentally by using Xilinx Virtex4 FPGA and was successfully demonstrated with a CMOS image sensor for mobile application.