DoDo: Double DOE Optical System for Multishot Spectral Imaging

Snapshot Compressive Spectral Imaging Systems (SCSI) compress the scenes by capturing 2D projections of the encoded underlying signals. A decoder, trained with pre-acquired datasets, reconstructs the spectral images. SCSI systems based on diffractive optical elements (DOE) provide a small form factor and the single DOE can be optimized in an end-to-end manner. Since the spectral image is highly compressed in a SCSI system based on a single DOE, the quality of image reconstruction can be insufficient for diverse spectral imaging applications. This work proposes a multishot spectral imaging system employing a double-phase encoding with a double DOE architecture (DoDo), to improve the spectral reconstruction performance. The first DOE is fixed and provides the benefits of the diffractive optical systems. The second DOE provides the variable encoding of the multishot architectures. The work presents a differentiable mathematical model for the multishot DoDo system and optimizes the parameters of the DoDo architecture in an end-to-end manner. The proposed system was tested using simulations and a hardware prototype. To obtain a low-cost system, the implementation uses a deformable mirror for the variable DOE. The proposed DoDo system shows an improvement of up to 4 dB in PSNR in the reconstructed spectral images compared with the single DOE system.