Visual inspection of surface defects of extreme size based on an advanced FCOS

Surface defects of industrial products are generally detected through anchor-based object detection methods during manufacturing. However, these methods are prone to missed and false detection for ultra-elongated and ultra-fine defects. An advanced fully convolutional one-stage object detector (FCOS) is proposed. This method is based on an anchor-free FCOS network model. First, a novel type of center-ness is proposed to reduce the suppression of off-centered positions of defects of extreme size. In addition, to eliminate background interference, a self-adaptive center sampling method is proposed as a replacement for the conventional center sampling method. The regularization method and the loss function are also improved according to the defect characteristics. Experimental results show that this advanced-FCOS-based method outperforms anchor-based methodson the surface defect dataset. The proposed method effectively detects defects of extreme size without affecting the detection of normal defects. The performance of the proposed method meets the requirements of real industrial applications.