Bridging the gap: Active learning for efficient domain adaptation in object detection

In practical object detection computer vision applications, training commonly incorporates multiple data sources. Domain adaptation enhances the models' capacity to generalize across different source and target domain data. Active learning, which serves as a bridge between unsupervised and supervised domain adaptation, is an area that has been underexplored for object detection. Our methods are specifically designed to tackle the challenges of selecting target domain images for annotation, complementing the existing source domain images. First, this paper formally describes active learning in domain adaptation for object detection. We propose three new selection strategies for active learning in domain adaptation for object detection. We utilize multiple machine learning models when selecting target domain data for annotation. In particular, our best-performing selection method utilizes a domain discriminator to predict the target domain likelihood of each sample. Additionally, we introduce an evaluation framework that evaluates per -box and per -image labeling efforts in the unique object detection application. Through extensive experiments we could show that our best-performing method could improve the active learning object detection performance over random selection by about 2.4% while requiring about 13% less annotated bounding boxes on the target domain.