为了提高复杂产品内部结构在线检测的速度，针对复杂产品内部结构射线图像的特点，提出了一种基于方向投影的特征压缩与识别方法。首先对图像进行投影，变换为一维投影特征，然后在此基础上利用差分量化法将投影特征量化为0,1字符串特征，并以此作为最终识别的特征,采用KMP算法和NC匹配法相结合的方法，对待检复杂产品进行识别。实验表明，该方法具有识别速度快、效率高的特点，在复杂产品的检测识别中是一种新的尝试。

To improve the on-line measurement speed of complex products' inner structure, according to its features this paper puts forward a method of feature compression and identification on the basis of direction projection. Firstly the image is projected and transformed into one-dimension projection. Then through differencing quantization, they are qualified into zero and one alphabetic string, which is looked as final identification features. Finally the products will be tested through KMP algorithm and NC matching method. The experiments prove that this method can characterize quickly with high efficiency, which is a new try in test and identification of complex products.