Progressive Refinement Network for Occluded Pedestrian Detection
We present Progressive Refinement Network (PRNet), a novel single-stage detector that tackles occluded pedestrian detection. Motivated by human's progressive process on annotating occluded pedestrians, PRNet achieves sequential refinement by three phases: Finding high-confident anchors of visible parts, calibrating such anchors to a full-body template derived from occlusion statistics, and then adjusting the calibrated anchors to final full-body regions. Unlike conventional methods that exploit predefined anchors, the confidence-aware calibration offers adaptive anchor initialization for detection with occlusions, and helps reduce the gap between visible-part and full-body detection. In addition, we introduce an occlusion loss to up-weigh hard examples, and a Receptive Field Backfeed (RFB) module to diversify receptive fields in early layers that commonly fire only on visible parts or small-size full-body regions. Experiments were performed within and across CityPersons, ETH, and Caltech datasets. Results show that PRNet can match the speed of existing single-stage detectors, consistently outperforms alternatives in terms of overall miss rate, and offers significantly better cross-dataset generalization. Code is available."