An adaptive image binarization method for laser direct marking data matrix symbols on metal surface

The image binarization of laser direct marking Data Matrix symbols on metal surface is a key procedure during recognition. Contrast and light uniformity of the symbols is greatly affected by the uneven illumination and reflection of the parts. To avoid the limitation of present binarized methods, an adaptive binarization method composed of Otsu method and Nearest neighbor pixels contributing threshold method is proposed. It takes global and local gray information into consideration, as well as the distribution of gray gradient. Experimental results show that the proposed method has a higher recognition rate and reliability.