1. Introduction
Performance of object detection methods has improved substantially in the recent years [7]. As the number of detectable object classes increases, so does the need for scalable methods for detection. However, scaling multi-class object detection remains a challenging task. Object categories can have a very large intra-class variability in appearance and shape. In a multi-class setup, this poses a challenge since the detection method should be discriminant to inter-class and clutter variations and invariant to intra-class variations.