Using Latent Diffusion Models for Inverse Problems
There are two main approaches to solving inverse problems: supervised techniques and unsupervised methods. Supervised techniques involve training a restoration model to complete the task, while unsupervised methods use a generative model to guide the restoration process using learned priors.
One significant advancement in generative modeling is the emergence of diffusion models. These models have shown promise in resolving inverse problems, but addressing linear and non-linear inverse problems with diffusion models is challenging. To overcome this, approximation algorithms have been developed that use pre-trained diffusion models as flexible priors for tasks like inpainting, deblurring, and superresolution.
The Significance of Latent Diffusion Models
Latent Diffusion Models (LDMs) are the foundation for state-of-the-art models like Stable Diffusion. LDMs have been applied to various data modalities, including images, videos, audio, and medical domain distributions. However, existing inverse problem-solving algorithms are not compatible with LDMs. To use a base model like Stable Diffusion for an inverse problem, fine-tuning is required for each specific task.
Introducing Posterior Sampling with Latent Diffusion
A recent study by the University of Texas at Austin proposes the first framework for using pre-trained LDMs to address generic inverse problems. The researchers introduce a new algorithm called Posterior Sampling with Latent Diffusion (PSLD), which incorporates an additional gradient update step to guide the diffusion process. By leveraging the power of accessible foundation models, PSLD outperforms prior approaches without the need for fine-tuning.
Evaluating PSLD Performance
The researchers evaluated the performance of PSLD against the state-of-the-art DPS algorithm on various image restoration and enhancement tasks, including inpainting, denoising, deblur, masking, and superresolution. They used Stable Diffusion trained with the LAION dataset for their analysis and found that PSLD achieved state-of-the-art results.
However, the researchers also noticed that PSLD was influenced by the biases inherent in the dataset and underlying model. They suggest that these issues can be addressed by training new foundation models on improved datasets. They also highlight the potential of applying latent-based foundation models to resolve non-linear inverse problems, a direction that has not been explored yet.
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