Semi-Supervised Dim and Small Infrared Ship Detection Network Based on Haar Wavelet

Traditional deep learning detection network has poor effect on the detection of infrared dim and small targets on the sea in the case of interference or bad weather. In this paper, an improved dim and small infrared ship detection network based on Haar wavelet is proposed. The HaarConv module is designed based on the high-frequency features obtained by Haar wavelet decomposition, which further increases the feature extraction ability of the backbone network for small targets. Meanwhile, the HaarUp-HaarDown module is designed by using Haar forward and inverse transform, replacing the up-sampling layer of the feature pyramid network and the down-sampling layer of backbone network to retain smaller target features. Furthermore, the pseudo-label-based method enables the network to conduct semi-supervised learning, which reduces the labeling cost and improves detection accuracy while expanding the amount of training data. The above method is applied to the YOLOv5-s lightweight network and 11278 infrared images (3352 labeled) of dim and small ships are collected as a dataset. The results show that the introduction of semi-supervised training method effectively expands the training dataset, and the mAP@.5:.95 increases by 23.5%. The proposed Haar wavelet improvement method can effectively improve the detection accuracy of dim and small infrared ship targets by more than 2%, and the number of parameters increases by only about 0.02M. Compared with existing methods, the proposed method reaches the state-of-the-art result and has good generalization performance.