Research on Underwater Object Detection Based on Improved YOLOv4

The complex underwater environment and lighting conditions make underwater images suffer from texture distortion and color variations. In this paper, we propose an improved YOLOv4 detection method to detect four underwater organisms: holothurian, echinus, scallop, starfish and waterweeds. Firstly, we modified the network structure, added a deep separable convolution to the backbone network, and added a 152×152 feature map, which is conducive to the detection of small targets. Secondly, k-means clustering algorithm is used to cluster the bounding box in the data set, and the size of the bounding box is improved according to the clustering results. Thirdly, we propose a new module (EASPP, Spatial Pyramid Pooling), which increases slightly the model complexity, but the improvement effect is significant. Finally, when training the model, we use multi-scale training to better train targets with different scales. The experimental results show that on our test set, the improved method in the underwater object detection method is 4.8% higher than the original YOLOv4 model in accuracy (AP), the F1-score is 5.1% higher than that of the original method, and for mAP@0.5 it reaches 81.5%, which is 5.6% higher than that of the original method, which can be concluded that our method is effective.