可攜式紅外線條碼辨識器

Abstract

本論文之重點在於研發一套可攜式紅外線條碼辨識器的系統，其主要特點有：體積小、成本低廉、辨識率高等。 本系統在操作方式與成本的考量下，從紅外線光學模組所得到的是一組帶有許多雜訊的類比訊號。為了使這類比訊號能被正確地解碼，首先，我們分析這能反映出條碼編碼訊息的波形。藉由觀察在示波器上光電晶體經放大後的訊號，來找出條碼架構與波形變化的關係。接著應用峰值檢出器、分壓器與比較器等由OP放大器所組合的轉換電路，來將此訊號轉換成隨著條碼寬度不同而產生不同時間寬度的脈衝訊號。 經訊號轉換過程完成後的脈衝訊號，便可以使得解碼流程已程式化的微處理器系統來讀取及計算。從實驗的數據與結果顯示，條碼辨識率成功率可以達到九成，我們證明了此條碼辨識系統的可行性。

The research and development of the portable infrared bar code reader has been developed in this thesis. The feature of the portable infrared bar code reader consists of compact in size, low cost and high recognition rate. Due to the limitation of the operation and cost of the system, the analog signal from the infrared optical module has possessed many noises. In order to decoding the analog signal correctly, firstly we analyzed the disorderly signal, which represented the message encoding in the bar code. By observing the signal from the phototransistor that is transmitted to the scope via an OP amplifier, we found out the relationship between the structure of the bar code and the variation of the signal. Secondly we transferred the signal to a series of pulse width signal that is in proportion to the width of the bar code by using peak detector, voltage divider and comparator etc., which composed of several OP amplifiers. After the transferred process has completed, the pulse signal can be further read out and calculated by the micro controller system with pre-programmed decoding procedures. Experiments indicated that the successful recognition rate has reached 90%, which proved the feasibility of the proposed hardware structure.