I. Introduction
In recent years, deep learning has made significant breakthroughs in the field of image recognition with the introduction of various neural networks, and more and more scholars have started to study crack detection techniques based on various convolutional neural networks. in 2015, makantasis [1] constructed cnn convolutional networks to achieve the detection of tunnel cracks. in 2017, zhao [2] used the zhalexnet model as the basis for developing a detection method for scratches and cracks on the surface of steel materials. In 2019, Song et al. [3] employed a lightweight neural network model called SegNet to perform segmentation extraction of crack contours with a maximum IoU of 0.782. in 2020, Chen, FC [4] proposed a rotation-invariant fully convolutional neural network (Fcn) called ARF-Crack for crack segmentation. Choi et a1. [5] constructed SDDNet for crack extraction. The model consists of a standard convolution, a densely connected separable convolution module, a modified void space pyramidal pooling module and a decoder module. Nowadays, various methods of deep learning have become mature in the recognition of cracks, but there is still a deficiency in the extraction of crack contours, which cannot extract the edge detail information of cracks well.