車牌偵測是車牌辨識中的關鍵步驟，本論文探討以最新深度學習方法解決開放 環境下的車牌偵測問題。本研究為極少數運用最新的深度學習方法應用於車牌偵測， 包含在各種挑戰的情境下，如惡劣天氣環境、照明與交通等。本研究探討目前最新 的即時物件檢測架構，包括 SSD (Single Shot MultiBox Detector) [1]和 YOLO (You- Only-Look-Once) [2]，並針對在開放環境下之車牌偵測做了一些改善。主要修改包括 以下內容:1)在 YOLO 上調整全連接層;2)在 SSD 上調整多尺度特徵圖，錨點與 寬高比;3)建置更完整和嚴格的 AOLPE (Application-Oriented License Plate Extended) 影像資料。AOLPE 影像資料庫是 AOLP (Application-Oriented License Plate) [3]資料庫 的延伸版，加入了許多在挑戰性場景下拍攝的影像樣本。原始的 YOLO 和 SSD 不是 針對車牌進行偵測，所以本論文提出 YOLO 和 SSD 的車牌偵測版本，在 AOLPE 影 像資料庫上進行評估。本論文的主要貢獻是將車牌偵測從實驗室向應用推進了一大 步，不僅實現了實時的車牌偵測方法，而且還釋放了更接近真實場景的 AOLPE 影像資料庫，並取得了良好的測試效果。

License Plate Detection (LPD) is the pivotal step for License Plate Recognition. In this work, we explore and customize state-of-the-art detection approaches for exclusively handling the LPD in the wild. In-the-wild LPD considers license plates captured in challenging conditions caused by bad weathers, lighting, traffics, and other factors. As conventional methods failed to handle these inevitable conditions, we explore the latest real- time deep learning based detectors, namely YOLO (You- Only-Look-Once) and SSD (Single Shot Multi-Box Detector), and customize them for effectively handling the LPD. The prime modifications include the following: 1) Modifying of fully connected layer on YOLO, 2) Tuning of multi-scale feature maps, anchor boxes, and aspect ratios on SSD, and 3) Creation of a more complete and rigorous AOLPE (Application-Oriented License Plate Extended) database for robust performance evaluation. The AOLPE database is an extended version of the AOLP (Application-Oriented License Plate) database with additional images taken under extreme but realistic conditions. As the original YOLO and SSD are not intended for LPD and they failed miserably as LPDs, the performances of the proposed customized versions of both YOLO and SSD are directly evaluated on the AOLPE database. The contributions made in this study is not only a pioneering customized exploration of state-of- the-art real- time deep learning approaches for handling in-the-wild LPD, but also involves the release of the AOLPE database and evaluation protocol to define a novel and practical benchmark for LPD.

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