  Contrastive pre-training on image-text pairs, exemplified by CLIP, becomes a
standard technique for learning multi-modal visual-language representations.
Although CLIP has demonstrated remarkable performance, training it from scratch
on noisy web-scale datasets is computationally demanding. On the other hand,
mask-then-predict pre-training approaches, like Masked Image Modeling (MIM),
offer efficient self-supervised learning for single-modal representations. This
paper introduces Unmasked Token Alignment (UTA), a method that leverages
existing CLIP models to further enhance its vision-language representations.
UTA trains a Vision Transformer (ViT) by aligning unmasked visual tokens to the
corresponding image tokens from a frozen CLIP vision encoder, which
automatically aligns the ViT model with the CLIP text encoder. The pre-trained
ViT can be directly applied for zero-shot evaluation even without training on
image-text pairs. Compared to MIM approaches, UTA does not suffer from
training-finetuning inconsistency and is much more training-efficient by
avoiding using the extra [MASK] tokens. Extensive experimental results
demonstrate that UTA can enhance CLIP models and outperform existing MIM
methods on various uni- and multi-modal benchmarks. Code and models are
available at https://github.com/jihaonew/UTA.
