Semi-Supervised Few-Shot Object Detection via Adaptive Pseudo Labeling

Few-shot object detection (FSOD) aims to detect novel objects with limited annotated examples. Mainstream methods suffer from the data scarcity of novel classes with insufficient intra-class variations, which makes the trained model biased to base classes. Actually, there are massive unlabeled novel instances in the base dataset and their adequate utilization will enhance the discriminability of model to novel classes. This paper proposes a semi-supervised few-shot object detection method, which utilizes a teacher model and a pre-trained few-shot object detector to guide the learning of a student model through adaptive pseudo labeling. In particular, a class-adaptive threshold filtering (CATF) strategy is designed to deal with the class-imbalance problem of pseudo labels. And for each novel class, the threshold to select valuable pseudo labels is determined by quantile statistics of the confidence score distribution of pseudo labels. Furthermore, the pre-trained detector and the teacher model are associated with the preliminary CATF and in-depth CATF, respectively, and then the pseudo labels from the two-stream CATF are fused to provide supervisions. In this way, the knowledge of these two models is exploited, which improves the quality of pseudo labels. Under these supervisions, the student model is trained and the teacher model is correspondingly updated through parameters sharing, thus forming a positive feedback to improve the performance of both models. Besides, an attention module is integrated to the teacher and student models to enhance the feature representation of novel instances. The validations on PASCAL VOC and MS COCO show the effectiveness of the proposed method.