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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Subject: search.filters.subject.light-emitting diode (LED)

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Now showing 1 - 10 of 41
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    Visible Light Communication Using Receivers of Camera Image Sensor and Solar Cell
    (2016-02-01)
    Liu, Yang
    ;
    Chen, Hung-Yu
    ;
    Liang, Kevin
    ;
    Hsu, Chin-Wei
    ;
    Chow, Chi-Wai
    We propose an electronic label and sensor system using visible light communication (VLC). The downlink signal is transmitted by a white-light light-emitting diode (LED) lamp that can provide lighting, VLC, and energy harvesting for mobile devices. The downlink is received by a solar cell. The uplink can be captured by a surveillance camera image sensor. However, using the camera image sensor as a VLC receiver (Rx) is challenging since the data rate is limited by the frame rate and due to uneven light exposure. The rolling shutter effect of the image sensor can be used to increase the data rate. In this paper, we propose and demonstrate how to demodulate the obtained rolling shutter pattern using a second-order polynomial (SOP) extinction ratio (ER) enhancement scheme, together with iterative and modified quick adaptive thresholding schemes. The ER enhancement scheme can significantly reduce the large ER fluctuation. Experimental results show that by using the proposed SOP ER enhancement scheme, the bit error rate (BER) improvement can be up to two orders of magnitude. We also believe that the proposed electronic label and sensor system may be applicable to Internet-of-Things sensing networks for connecting a number of mobile devices.
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    Light Encryption Scheme Using Light-Emitting Diode and Camera Image Sensor
    (2016-02-01)
    Liu, Yang
    ;
    Liang, Kevin
    ;
    Chen, Hung-Yu
    ;
    Wei, Liang-Yu
    ;
    Hsu, Chin-Wei
    Visible light communication (VLC) is regarded as relatively secure communication when compared with other wireless communications using radio frequency (RF). However, due to the visual nature, the VLC signals are still subject to eavesdropping when they are emitted by the light source. Here, we propose a light encryption scheme using devices having light-emitting diode (LED) and a camera image sensor, such as a mobile phone. The original visible signal sending from the lamp can be first received by the proposed light encrypter. The information can be encrypted and then emitted. The light encrypter acts as an encryption gateway for signals in optical domain. The rolling shutter effect of the complementary metal-oxide semiconductor (CMOS) camera in the mobile phone can be used. By demodulating the rolling shutter pattern, the data information can be obtained. We also propose and demonstrate using the Otsu thresholding scheme to define the data logic in the rolling shutter pattern. We show that the Otsu scheme is effective for estimating the bit error rate (BER). The optimum number of intervals (segmentations) and the process time of the Otsu method are also studied.
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    Network Architecture of Bidirectional Visible Light Communication and Passive Optical Network
    (2016-06-01)
    Chow, Chi-Wai
    ;
    Yeh, Chien-Hung
    ;
    Liu, Yang
    ;
    Hsu, Chin-Wei
    ;
    Sung, Jiun-Yu
    Network architectures to combine the fiber network outside the building and the visible light communication (VLC) access network inside the building are important for effectively distributing the high-capacity data to different users. In this paper, we propose a bidirectional network combining the VLC access network and the time-wavelength-division-multiplexed passive optical network (TWDM-PON). Orthogonal frequency division multiplexed modulation is used since it offers high spectral efficiency for both the TWDM-PON and the VLC access network. Low-cost phosphor-based white-light light-emitting diodes are (LEDs) used; hence, the VLC access network can combine with the lighting systems.
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    Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
    (2014-12-01)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    光電工程研究所
    ;
    Department of Photonics
    Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
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    Enhancement of Signal Performance in LED Visible Light Communications Using Mobile Phone Camera
    (2015-10-01)
    Chow, Chi-Wai
    ;
    Chen, Chung-Yen
    ;
    Chen, Shih-Hao
    ;
    光電工程學系
    ;
    光電工程研究所
    Visible light communication (VLC) is attractive as a supplementary method for future fifth-generation (5G) wireless communication owing to the shortage of radio-frequency bandwidth in conventional wireless communications. The VLC systems reported in the literature are mainly based on PIN receivers (Rxs). It is highly desirable if these VLC signals can be detected by using built-in complementary metal-oxide-semiconductor (CMOS) cameras as Rxs to provide flexible and low-cost wireless communications. However, using the CMOS camera is challenging. In this paper, we propose and demonstrate a VLC link using a CMOS mobile phone camera as Rx. By using the rolling shutter effect of the CMOS sensor, the VLC data rate can be significantly enhanced. We first use a second-order polynomial fitting to mitigate the "blooming effect" (saturation of pixels) of the CMOS sensor. In order to extend the VLC transmission distance and mitigate the influence of the background noise, we also propose and demonstrate using histogram equalization and Sobel filter to enhance VLC signal performance. Finally, a third-order polynomial fitting is used to define the threshold. The experimental results show that significant improvement of bit error rate (BER) for about an order of magnitude under different illuminances can be achieved.
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    Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
    (2014-12)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    Department of Photonics
    Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
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    Purely Sidewall InGaN/GaN Core-Shell Nanorod Green Light-Emitting Diodes
    (2015)
    Lin, Da-Wei
    ;
    Wu, Yung-Chi
    ;
    Kuo, Hao-Chung
    ;
    Chi, Gou-Chung
    ;
    Hsu, Lung-Hsing
    A novel purely sidewall InGaN/GaN core-shell nanorod green light-emitting diode (LED) has been demonstrated by 3D dielectric passivation and selective epitaxial growth technologies. The LED device exhibits unprecedented stable emission wavelength and low efficiency droop.
  • Thumbnail Image
    Item type:Item,
    Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
    (2014-12-01)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    Department of Photonics
    Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
  • Thumbnail Image
    Item type:Item,
    Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
    (2014-12-01)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    Department of Photonics
    Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
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    Item type:Item,
    Enabling High-Injection Current Light-Emitting Diodes Prepared on 10-mu m-Thick GaN Films Grown by Hydride Vapor Phase Epitaxy
    (2015-09-01)
    Chen, Yu-An
    ;
    Chang, Chia-Wei
    ;
    Kuo, Cheng-Huang
    ;
    照明與能源光電研究所
    ;
    Institute of Lighting and Energy Photonics
    In this paper, we successfully introduced the sputtered AlN/patterned sapphire substrate template into hydride vapor phase epitaxy (HVPE) using a two-step growth method. This method simplified the procedure, realized uninterrupted growth, and improved the crystal quality of GaN films. The effects of light-emitting diodes (LEDs) grown on a 10-mu m-thick GaN film through HVPE were also compared with those of the LEDs grown on a 2.4-mu m-thick GaN film through metal organic chemical vapor deposition (MOCVD). Compared with the LEDs grown on the 2.4-mu m-thick GaN film through MOCVD, the LEDs grown on the 10-mu m-thick GaN film through HVPE had significantly enhanced light output power (3.24-4.79 mW) and extended saturation current (300-355 mA). These improvements of the LEDs were attributed to the better thermal conductivities and better crystal quality of the 10-mu m-thick GaN film through HVPE than those of the 2.4-mu m-thick GaN film through MOCVD.