Bidirectional alignment for domain adaptive detection with transformers

We propose a Bidirectional Alignment for domain adaptive Detection with Transformers (BiADT) to improve cross domain object detection performance. Existing adversarial learning based methods use gradient reverse layer (GRL) to reduce the domain gap between the source and target domains in feature representations. Since different image parts and objects may exhibit various degrees of domain-specific characteristics, directly applying GRL on a global image or object representation may not be suitable. Our proposed BiADT explicitly estimates token-wise domain-invariant and domain-specific features in the image and object token sequences. BiADT has a novel deformable attention and self-attention, aimed at bi-directional domain alignment and mutual information minimization. These two objectives reduce the domain gap in domain-invariant representations, and simultaneously increase the distinctiveness of domain-specific features. Our experiments show that BiADT achieves very competitive performance to SOTA consistently on Cityscapes-to-FoggyCityscapes, Sim10K-toCitiscapes and Cityscapes-to-BDD100K, outperforming the strong baseline, AQT, by 1.9, 2.1, and 2.4 in mAP₅₀, respectively