Degradation Estimation Recurrent Neural Network with Local and Non-Local Priors for Compressive Spectral Imaging

In coded aperture snapshot spectral imaging (CASSI) systems, a core problem is to recover the 3D hyperspectral image (HSI) from the 2D measurement. Current deep unfolding networks (DUNs) for the HSI reconstruction mainly suffered from three issues. Firstly, in previous DUNs, the DNNs across different stages were unable to share the feature representations learned from different stages, leading to parameter sparsity, which in turn limited their reconstruction potential. Secondly, previous DUNs fail to estimate degradation-related parameters within a unified framework, including the degradation matrix in the data subproblem and the noise level in the prior subproblem. Consequently, either the accuracy of solving the data or the prior subproblem is compromised. Thirdly, exploiting both local and non-local priors for the HSI reconstruction is crucial, and it remains a key issue to be addressed. In this paper, we first transform the DUN into a Recurrent Neural Network (RNN) by sharing parameters across stages, which allows the DNN in each stage could learn feature representation from different stages, enhancing the representativeness of the DUN. Secondly, we incorporate the Degradation Estimation Network into the RNN (DERNN), which simultaneously estimates the degradation matrix and the noise level by residual learning with reference to the sensing matrix. Thirdly, we propose a Local and Non-Local Transformer (LNLT) to effectively exploit both local and non-local priors in HSIs. By integrating the LNLT into the DERNN for solving the prior subproblem, we propose the DERNN-LNLT, which achieves state-of-the-art performance.