基於Mask R-CNN之傾斜角度車牌識別系統

Abstract

在過去幾年中，車牌辨識系統已經廣泛用於停車場。為了容易識別車牌，停車場中使用的傳統車牌識別系統具有固定的光源和拍攝角度。對於特別傾斜的角度，例如使用超廣角鏡頭或魚眼鏡頭拍攝的車牌影像，車牌特徵變形可能特別嚴重，以致於使用傳統車牌辨識系統的辨識效果不良。本論文中，我們提出了一種基於Mask R-CNN的三階段車牌辨識系統，可用於各種拍攝角度和更傾斜的影像。實驗結果表明，該架構可識別水平傾斜角度超過0~60度的車牌，mAP可達91％。與使用YOLOv2模型的方法相比，本論文提出使用Mask R-CNN的方法在辨識傾斜45度以上的字元方面取得了重大進展。

In the past few years, license plate recognition systems have been widely used in parking lots. In order to identify license plates easily, traditional license plate recognition systems used in the parking lot have a fixed light source and a shooting angle. For particularly tilting angles, such as license plate images taken with super wide-angle lenses or fisheye lenses, the deformation of the license plate can be particularly severe, resulting in poor recognition of traditional license plate recognition systems. In this paper, we propose a three-stage license plate recognition system based on Mask R-CNN that can be used for various shooting angles and more oblique images. Experimental results show that the proposed architecture can identify license plates with bevel angles over 0~60 degrees and achieve mAP rates of up to 91%. Compared with the approach using YOLOv2 model, the proposed method with Mask R-CNN has made significant progress in identifying characters that are inclined above 45 degrees.