  The goal of contrastive learning based pre-training is to leverage large
quantities of unlabeled data to produce a model that can be readily adapted
downstream. Current approaches revolve around solving an image discrimination
task: given an anchor image, an augmented counterpart of that image, and some
other images, the model must produce representations such that the distance
between the anchor and its counterpart is small, and the distances between the
anchor and the other images are large. There are two significant problems with
this approach: (i) by contrasting representations at the image-level, it is
hard to generate detailed object-sensitive features that are beneficial to
downstream object-level tasks such as instance segmentation; (ii) the
augmentation strategy of producing an augmented counterpart is fixed, making
learning less effective at the later stages of pre-training. In this work, we
introduce Curricular Contrastive Object-level Pre-training (CCOP) to tackle
these problems: (i) we use selective search to find rough object regions and
use them to build an inter-image object-level contrastive loss and an
intra-image object-level discrimination loss into our pre-training objective;
(ii) we present a curriculum learning mechanism that adaptively augments the
generated regions, which allows the model to consistently acquire a useful
learning signal, even in the later stages of pre-training. Our experiments show
that our approach improves on the MoCo v2 baseline by a large margin on
multiple object-level tasks when pre-training on multi-object scene image
datasets. Code is available at https://github.com/ChenhongyiYang/CCOP.

Computer Vision and Pattern Recognition