Title: Detecting Unknown Objects via Energy-based Separation for Open World Object Detection
Primary area: unsupervised, self-supervised, semi-supervised, and supervised representation learning
Keywords: Open World Object Detection

Abstract: In this work, we tackle the problem of Open World Object Detection (OWOD). This challenging scenario requires the detector to incrementally learn to classify given known objects without forgetting while identifying unknown objects without supervision.
Previous OWOD methods have enhanced the unknown discovery process and employed memory replay to mitigate catastrophic forgetting. 
However, since existing methods heavily rely on the detector's known class prediction information for detecting unknown objects, they struggle to effectively learn and recognize unknown object representations.
Moreover, while memory replay mitigates forgetting of old classes, it often sacrifices the knowledge of newly learned classes. To resolve these limitations, we propose DEUS (\textbf{De}tecting \textbf{U}nknowns via energy-based \textbf{S}eparation), a novel framework that addresses the challenges of Open World Object Detection. DEUS consists of ETF-Subspace Unknown Separation (EUS) and an Energy-based Known Distinction (EKD) loss.
EUS leverages ETF-based geometric properties to create orthogonal subspaces, enabling cleaner separation between known and unknown object representations  and leverages energies from both spaces to better capture distinct patterns of unknown objects, in contrast to prior energy-based approaches that consider only the energy within the known space.
Furthermore, EKD loss enforces the separation between previous and current classifiers, thus minimizing knowledge interference between previous and newly learned classes during memory replay.
We thoroughly validate DEUS on OWOD benchmarks, demonstrating outstanding performance improvements in unknown detection while maintaining competitive known class performance.