利用可攜式鏡頭輔助視障者即時辨識公車車號

Abstract

視障者搭乘公車時面臨許多困難，其中無法辨識車號是最關鍵的問題。目前解決此問題的方法是請求路人協助，或手持自製車號牌引起公車駕駛注意，但上述方法皆屬被動性，可變因素較大。有鑑於數位影像處理技術的日漸成熟及攝影機硬體成本的降低，本研究基於數位影像處理技術，利用數位相機的鏡頭模擬，輔助視障者即時辨識公車車號，並以其他感官方式發出提示訊息。本研究以主動搜尋、辨識為目標，並提升系統執行速度，即時擷取的車號資訊，以語音或震動等其他感官方式輸出。實驗中以一般大眾普遍使用鏡頭取得影像資訊，克服以往利用固定鏡頭做處理的方式利用，使用數位相機來模擬可攜式鏡頭，在非固定位置及角度的情況下進行公車區域的分割，利用階段式的處理方法提升系統速度，首先以相鄰相減法，快速擷取前景公車畫面，經過公車幾何分析判定車號所在位置，再利用Sobel測邊定位原理後搭配形態學遮罩，將框取的車號圖片做字元切割及辨識，最後藉由OCR辨識系統搭配MS SAPI 5.1做語音播放系統輸出，在公車停靠前辨識其車號並輸出，實驗畫面為停靠區前約70公尺至公車停靠，實驗中停靠影像時間約為5秒，實驗結果顯示在100張連續測試畫面中約有70張可正確框選出公車區域，其中30張可正確抓取公車車號位置做定位及辨識，且系統每秒可處理31張畫面，可達即時，未來可使用多平台執行，實現方便可攜的輔助性工具來幫助視障者。The visually impaired persons may encounter many difficulties when taking a bus. Among them, recognizing the bus number can be the most challenging task for them. Up to now, the ways to solve this problem are to ask for other passengers' help or make use of a self-made board on which shows the bus number to cause the bus driver’s attention. However, both methods are passive and not reliable. This research applies digital image processing technology, through the medium of the camera of up-to-date 3C products such as mobile phone, PDA etc, to help the visually impaired persons to recognize the bus number by senses other than sight. The study aims to delivering in-time bus information with proactive (automatic) identification, fast response without the harm to the accuracy and other sensible outputs such as vibration and sounds. In this experiment, the algorithms solve the problem of fixed lent and are able to segment the bus image with unfixed positions and angles, and speed up the system by a proposed method. First, the system catches the bus image by Frame difference, and identifies the position of bus number through geometry analysis. Then, uses Sobel mask and a location algorithm to segment the bus numbers and recognizes them by using the Optical Character Recognition (OCR). Finally, the system outputs the correct bus number phonetically through Microsoft Speech Application Interface 5.1 (MS SAPI 5.1) before the bus stops. In the experiment, the video was set to film about 70 meters from the bus station. The length of each film was around 5 seconds. Among 100 frames, about 70 ones could segment the bus images correctly, and over 30 bus numbers could be located correctly. The system processing speed is 31 images per second. In the future, this technology can be applied to multiple media and bring the realization of a more convenient and helpful tool for the visually impaired persons.