  We present RON, an efficient and effective framework for generic object
detection. Our motivation is to smartly associate the best of the region-based
(e.g., Faster R-CNN) and region-free (e.g., SSD) methodologies. Under fully
convolutional architecture, RON mainly focuses on two fundamental problems: (a)
multi-scale object localization and (b) negative sample mining. To address (a),
we design the reverse connection, which enables the network to detect objects
on multi-levels of CNNs. To deal with (b), we propose the objectness prior to
significantly reduce the searching space of objects. We optimize the reverse
connection, objectness prior and object detector jointly by a multi-task loss
function, thus RON can directly predict final detection results from all
locations of various feature maps. Extensive experiments on the challenging
PASCAL VOC 2007, PASCAL VOC 2012 and MS COCO benchmarks demonstrate the
competitive performance of RON. Specifically, with VGG-16 and low resolution
384X384 input size, the network gets 81.3% mAP on PASCAL VOC 2007, 80.7% mAP on
PASCAL VOC 2012 datasets. Its superiority increases when datasets become larger
and more difficult, as demonstrated by the results on the MS COCO dataset. With
1.5G GPU memory at test phase, the speed of the network is 15 FPS, 3X faster
than the Faster R-CNN counterpart.
