• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.119-128
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• 2014

This paper presents a new method for improving the quality of images corrupted by an external source that generates an attenuation and scattering of light like dust, water droplets and fog. Conventional defog methods typically encounter a distortion such that the restored image has low contrast and oversaturation of color in some regions because of the mis-estimated airlight and wrong media transmission. Therefore, in order to mitigate these problems, we propose a robust airlight selection method and local saturation evaluation method for estimating media transmission. The proposed method addresses the wrong media transmission and over-saturation problems caused by the mis-estimated airlight and thereby improves the restored image quality. The results of relevant experiments of the proposed method against conventional ones confirm the improved accuracy of atmospheric light estimation and the quality of restored images with regard to objective and subjective performance measures.

• Journal of Information Display
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• v.13 no.2
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• pp.91-95
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• 2012

Indium phosphide (InP) quantum dots (QDs) are considered alternatives to Cd-containing QDs for application in light-emitting devices. The multishell coating with ZnSe/ZnS was shown to improve the photoluminescence quantum yield (QY) of InP QDs more strongly than the conventional ZnS shell coating. Structural proof for this system was provided by X-ray diffraction and transmission electron microscopy. QY values in the range of 50-70% along with peak widths of 45-50 nm can be routinely achieved, making the optical performance of InP/ZnSe/ZnS QDs comparable to that of Cd-based QDs. The fabrication of a working electroluminescent light-emitting device employing the reported material demonstrated the feasibility of the desired application.

• Journal of Broadcast Engineering
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• v.24 no.7
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• pp.1246-1258
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• 2019

Since light field (LF) image has huge data volume, it requires high-performance compression technique for efficient transmission and storage of its data. Camera users may like to represent parts of image at different levels of focus at their choice anytime. To address this refocusing functionality, in this paper, we first render a focal stack consisting of multi-focus images, then compress it instead of original LF data. The proposed method has advantage of minimizing the amount of LF data to realize the targeted refocusing applications. Our experiment results show that the proposed method outperforms the state-of-the-art for LF image compression method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.114-120
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• 2009

In outdoor visible light communication channels and LED road illumination communications for the intelligent transport systems (ITS), inter symbol interference (ISI) due to multipath propagation prevents high data rate transmission. Indoor wireless optical communication systems utilizing white LED lights and on the road illumination have been studying about it. Generally, plural lights are installed in room and considered to the traffic information system using existing LED traffic lights. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses on-off keying, return-to-zero (OOK-RZ) coding and the other uses optical orthogonal frequency division multiplexing(OFDM).

• Journal of IKEEE
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• v.21 no.2
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• pp.115-122
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• 2017

In vehicular safety service, every vehicle broadcasts Basic Safety Message (BSM) periodically to inform neighbor vehicles of host vehicle information. However, this can cause network congestion in a region that is crowded with vehicles resulting in a reduction in the message delivery ratio and an increase in the end-to-end delay. Therefore, it could destabilize the vehicular safety service system. In this paper, in order to improve the congestion control and to consider the hidden node problem, we propose a congestion control scheme using entire network congestion level estimation combined with transmission power control, data rate control and time slot based transmission control algorithm. The performance of this scheme is evaluated using a Qualnet network simulator. The simulation result shows that our scheme mitigates network congestion in heavy traffic cases and enhances network capacity in light traffic cases, so that packet error rate is perfectly within 10% and entire network load level is maintained within 60~70%. Thus, it can be concluded that the proposed congestion control scheme has quite good performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.181-187
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• 2012

LED is just a semiconductor which can produce light. Currently, there are active research works on LED lighting technologies according to the growth of energy-saving environmental industry. Especially, LED communication is one of the active research works in these fields. In this paper, we design a LED communication-based PC-PC transmission system. A transmission circuit system(transmitter) using LED and a receiving circuit system(receiver) using PD(photo detector) and Op-amp are designed, respectively. The experiments for the designed system are performed as follows. One computer is connected at the end of transmitter and receiver, respectively, and text files are transmitted by using text transmission programming. In this experiment, we test the performance with various baud rates, LED colors, transmission ranges.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.11-12
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• 2012

In this paper, efficient visible light communication technology LED (Light Emitting Diode) lighting through the existing infrared sensor used for performance analysis of transmitting and receiving is possible. LED utilizes lighting by changing light into electricity. Lighting features while maintaining the basic principles of flashing LED and PD (Photo Diode) to send and receive communications from LED lighting communication convergence principle be realized simultaneously enabling. Multiple IT applications under the basic structure of LED technology development, and the current was encountered in real life. LED lighting anywhere with wireless communication technology that can, in order to ~ 1m above the initial value by taking advantage of the system H/W and infrared sensors(PD) are widely used in the entire system that can improve the speed of visible light data transmission system is finished. LED module that is used to communicate whether the performance analysis, For forecasting and communication distance on the LED and infrared sensor configuration of the implementation of the research is to study about the possibility of application methods and indicates.

• Journal of Convergence for Information Technology
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• v.8 no.5
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• pp.153-158
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• 2018

In this paper, we have studied a dimming level control method to satisfy both lighting and communication performance in visible light communication system. In the case of the most commonly used OOK and RZ-OOK modulation schemes, continuous Burst Zero Duration will seriously degrade the lighting function. This causes not only the illumination but also the performance of the entire system to deteriorate. Through this study, we analyzed the dimming level characteristics of the existing system and proposed the Illegal Pulse Insertion (IPI) algorithm as a technique to increase the dimming level. Through this, it is possible to effectively control the dimming level and improve the QoS of both lighting and communication by resolving the flicker phenomenon and dimming level reduction in the existing modulation and demodulation system.

• Journal of Ocean Engineering and Technology
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• v.34 no.6
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• pp.442-453
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• 2020

Underwater color images suffer from low visibility and color cast effects caused by light attenuation by water and floating particles. This study applied single image enhancement techniques to enhance the quality of underwater images and compared their performance with real underwater images taken in Korean waters. Dark channel prior (DCP), gradient transform, image fusion, and generative adversarial networks (GAN), such as cycleGAN and underwater GAN (UGAN), were considered for single image enhancement. Their performance was evaluated in terms of underwater image quality measure, underwater color image quality evaluation, gray-world assumption, and blur metric. The DCP saturated the underwater images to a specific greenish or bluish color tone and reduced the brightness of the background signal. The gradient transform method with two transmission maps were sensitive to the light source and highlighted the region exposed to light. Although image fusion enabled reasonable color correction, the object details were lost due to the last fusion step. CycleGAN corrected overall color tone relatively well but generated artifacts in the background. UGAN showed good visual quality and obtained the highest scores against all figures of merit (FOMs) by compensating for the colors and visibility compared to the other single enhancement methods.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.853-858
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• 2022

In this paper, we show a simultaneous transmission of underwater optical wireless power transfer and underwater optical wireless communication. A laser diode is used for electric-to-optic conversion at the transmitter and a solar cell is used for optic-to-electric conversion at the receiver. We optimized the transmitter and receiver for the best performance. The laser diode is a 100-mW laser diode and showed a conversion efficiency of 18.5%. The experimental results showed a 0.33-% DC-to-DC underwater power transfer efficiency at 5 m and a data rate of 100 kbps at 1 m.