vision languige models

Vision-language models (VLMs) are AI systems capable of understanding and interpreting both images and text. They bridge the gap between visual input, which is represented as grids of numbers with no inherent meaning, and text input, which is a sequence of symbols lacking any visual context. To achieve this, VLMs must "ground" words in images and vice versa.

Two primary architectures for VLMs exist: matching images and text, and incorporating image tokens within a language model. CLIP (Contrastive Language-Image Pre-training), developed by OpenAI, is a notable example of the first category. It consists of two encoders - one for images (a Vision Transformer) and another for text (a Transformer model).

These encoders map the input into a shared vector space, allowing the model to compare images and captions effectively. Trained on 400 million image-caption pairs, CLIP learns to associate high similarity scores with correct image-caption pairs and low scores with incorrect ones.

Zero-shot classification is a powerful feature of CLIP, enabling classification of images without training on specific labels. By providing textual labels (e.g., "a photo of a glass bottle"), the model can classify images based on similarity to these descriptions.

The second category of VLMs involves integrating visual tokens into a language model. This architecture comprises a vision encoder, a connector, and a large language model. The vision encoder converts images into a set of patch vectors, while the connector translates these vectors into a language model's embedding space. The language model then generates responses based on the combined picture and textual input.

VLMs can perform various tasks, such as image captioning, visual question answering, understanding text in photos, classifying images based on text prompts, and searching images using textual queries. However, they are not infallible. VLMs can hallucinate information, struggle with counting, understanding spatial relationships, and processing small details. Additionally, word order can sometimes lead to confusion.

Despite these limitations, VLMs have proven to be remarkably adept at interpreting and generating both visual and textual information. They are accessible through user-friendly interfaces, allowing anyone to experiment with their capabilities using photos and text descriptions.