In recent years, several unsupervised, "contrastive" learning algorithms in vision have been shown to learn representations that perform remarkably well on transfer tasks. We show that this family of algorithms maximizes a lower bound on the mutual information between two or more "views" of an image; typical views come from a composition of image augmentations. Our bound generalizes the InfoNCE objective to support negative sampling from a restricted region of "difficult" contrasts. We find that the choice of (1) negative samples and (2) "views" are critical to the success of contrastive learning, the former of which is largely unexplored. The mutual information reformulation also simplifies and stabilizes previous learning objectives. In practice, our new objectives yield representations that outperform those learned with previous approaches for transfer to classification, bounding box detection, instance segmentation, and keypoint detection. The mutual information framework provides a unifying and rigorous comparison of approaches to contrastive learning and uncovers the choices that impact representation learning.

本论文探讨了基于对比学习的图像表示学习方法，提出了一种最大化互信息的下界的目标函数，并在实验中发现选择难度更大的负样本以及视角可以提高算法性能。通过比较多种学习方法，研究结果表明，基于互信息的目标函数可以使得算法在分类、边界框检测、实例分割和关键点检测等任务上获得更好的表现。

对比学习中的互信息在视觉表征中的应用