一种基于高光谱激光雷达技术的涂改车牌识别方法

A recognition method for altered license plate based on hyperspectral lidar technology

利用高光谱激光雷达系统采集涂改车牌空间-光谱域信息,根据车牌逆反射特性,设计基于光谱特征的两次阈值法实现涂改车牌识别。首先计算光谱特征波长,利用一次阈值法分离车牌部分和涂改部分;其次,计算特征波段内车牌部分各点的光谱反射率曲线的梯度值,利用二次阈值法判别涂改类型(背景转字符涂改和字符转背景涂改);最后,根据涂改类型重建正确车牌字符,将重建信息与二维平面数据融合得到正确的二维车牌图像,送给车牌识别系统进行识别。实验结果表明该方法可实现多种涂改材料以及多种涂改类型的涂改车牌识别。

Using the spatial-spectral information of the altered license plates collected by hyperspectral lidar system,a twice-threshold method based on spectral feature is designed to recognize the altered license plates according to their retroreflection characteristics.Firstly,the characteristic wavelength of the spectra is selected,then the plate part and the altered material part are separated using the first threshold method according to the reflectance at the wavelength.Secondly,calculate the gradient value of the spectral reflectance curve at each point of the license plate part in the characteristic band,and the second threshold method is used to distinguish the alteration types,such as background to character alteration and character to background alteration.Finally,the correct license plate characters are reconstructed based on the type of the alteration,and the correct license plate image is reconstructed with the fusion of two dimensional data and the corrected license plate characters,which is sent to the license plate recognition system.Experimental results show that this method can recognize altered license plates correctly regardless of different altered materials or different altered types.