  Open-vocabulary instance segmentation aims at segmenting novel classes
without mask annotations. It is an important step toward reducing laborious
human supervision. Most existing works first pretrain a model on captioned
images covering many novel classes and then finetune it on limited base classes
with mask annotations. However, the high-level textual information learned from
caption pretraining alone cannot effectively encode the details required for
pixel-wise segmentation. To address this, we propose a cross-modal
pseudo-labeling framework, which generates training pseudo masks by aligning
word semantics in captions with visual features of object masks in images.
Thus, our framework is capable of labeling novel classes in captions via their
word semantics to self-train a student model. To account for noises in pseudo
masks, we design a robust student model that selectively distills mask
knowledge by estimating the mask noise levels, hence mitigating the adverse
impact of noisy pseudo masks. By extensive experiments, we show the
effectiveness of our framework, where we significantly improve mAP score by
4.5% on MS-COCO and 5.1% on the large-scale Open Images & Conceptual Captions
datasets compared to the state-of-the-art.
