使用彩色影像感測器之多重輸入輸出之攝影機通訊系統

Abstract

本論文實作了一個新型態的可見光攝影機通訊系統。 可見光通訊是最新的無線傳輸技術之一，藉由對發光二極體對於發 光強度的調變以感光元件來接收訊號。可見光通訊具有低干擾、高空 間辨識度、封包安全性高等優點，其中利用發光二極體為傳送端、攝 影機為接收端的可見光攝影機通訊系統更有低成本的優點。然而，可 見光攝影機通訊仍有相當多挑戰需要克服，首先是傳輸距離受到限制， 第二是受限於相機拍攝速度而傳輸速度偏低。 我們提出了可以改善以上兩項挑戰的多輸入多輸出可見光通訊系 統，將傳送端由以往常見的單顆發光二極體更改為三顆發光二極體， 並利用彩色影像感測器有紅、藍、綠三個頻道的特型構成多個接收端。 三個發光二極體藉由通過偏振片與色散片會合併成一串偏振方向不同 的光束，使得攝影機拍攝到三種不同顏色訊號的強度變化，藉此同時 接收三顆燈的訊息，因而提高了資料傳輸速度。 另外，本系統是以多組強度持續變化的偏振光進行傳輸，由於合成 的光束亮度保持不變，因此可以自由切換傳輸速度，即使在長距離的 情境下，也能藉由長曝光進行傳輸，形成一個傳輸距離很有彈性的系 統。目前我們是利用軟體無線電來實作傳送端訊號，並採用實驗用相 機進行訊號接收，未來將以實作到更普遍的設備中為目標，希望設計 一套演算機制讓接收端能據環境調整至最佳的設定，以融入日常生活 情境。 關鍵字：無線通訊、攝影機通訊、可見光、多重輸入輸出

The thesis presents a new type of visible light camera communication. Visible light communication(VLC) is one of the latest techniques in wireless communication. Unlike common RF communication, the receiver of VLC receives optical signals from the LED light. VLC has several advantages including low interference, high spatial discrimination ability and secure. Besides, camera communication (CamCom), a kind of VLC, is low cost since the devices in CamCom (LED and camera) is ubiquitous in our daily life. However, there are challenges for CamCom to overcome. First, the effective distance is constrained. Second, the throughput is low due to low frame rate. We present multiple input multiple output VLC that can improve the challenges above. By using e LED lights as Tx and RGB image sensor as Rx and the technique of polarization, we achieve higher throughput than before. Furthermore, our system transmits data by multiple polarized light beams with changing intensity of each. However, the intensity of combined beam remains the same so that we can flexibly tune the symbol rate without being detected by human eye. This improvement make it possible to transmit at a long distance. We are now using software defined radio to implement the Tx while utilizing experimental camera as Rx. In the future, it is our goal to implement the system on more general devices in our daily life. Also, we will try to design a computational mechanism for Rx to change the setting automatically in order to feat the environment. Keywords: Wireless Network, Camera Communications, VLC, MIMO