Correlation analysis of gray scale and geometric features of femtosecond laser spot

During the processing of femtosecond laser ablation of monocrystalline silicon, the effective gray area in the spot image collected by the charge coupled-device (CCD) camera was difficult to distinguish with the background. In order to solve this problem, a method combining the principal component analysis with the adaptive histogram equalization of limited contrast was proposed to enhance the spot image, and then a detrending cross-correlation analysis method was proposed, which analyzed the long-range correlation of gray features and geometric features for the spot sequence images. The results show that the gray features of the spot sequence images have a strong long-range correlation with the spot texture contrast and the spot area, and they show a strong inverse correlation with the texture homogeneity. The correlation relationships are used to predict the gray features in the subsequent micro-groove processing.