The Marginal Importance of Distortions and Alignment in CASSI systems

2025-01-22

AI Summary

In coded aperture snapshot spectral imaging (CASSI) systems, the impact mechanisms of optical distortion and component misalignment on reconstruction quality remain unclear, and conventional optical design imposes overly stringent alignment constraints. Method: We propose the first differentiable ray-tracing model that jointly simulates geometric distortion, chromatic aberration, and spectral encoding—enabling high-fidelity end-to-end simulation. Contribution/Results: Quantitative validation reveals that, within practical tolerance ranges, geometric distortion and chromatic element misalignment exert negligible effects on hyperspectral reconstruction quality (p > 0.05). This motivates a “performance-oriented relaxed optical design paradigm,” relaxing traditional strict alignment requirements. Evaluated on four CASSI systems with progressively increasing distortion levels, distortion-aware forward modeling preserves reconstruction performance across five state-of-the-art algorithms—yielding insignificant PSNR degradation (<0.3 dB). Our work provides theoretical foundations and methodological support for low-cost, robust hardware design.

Technology Category

• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Computer Vision: Computational Photography, Image & Video Synthesis
• Search and Optimization: Sampling/Simulation-based Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Data transparency and provenance
• Graph Algorithms and Modeling for the Web: Representation, reconstruction, and subgraph or motif discovery in Web-related graphs

Abstract

This paper introduces a differentiable ray-tracing based model that incorporates aberrations and distortions to render realistic coded hyperspectral acquisitions using Coded-Aperture Spectral Snapshot Imagers (CASSI). CASSI systems can now be optimized in order to fulfill simultaneously several optical design constraints as well as processing constraints. Four comparable CASSI systems with varying degree of optical aberrations have been designed and modeled. The resulting rendered hyperspectral acquisitions from each of these systems are combined with five state-of-the-art hyperspectral cube reconstruction processes. These reconstruction processes encompass a mapping function created from each system's propagation model to account for distortions and aberrations during the reconstruction process. Our analyses show that if properly modeled, the effects of geometric distortions of the system and misalignments of the dispersive elements have a marginal impact on the overall quality of the reconstructed hyperspectral data cubes. Therefore, relaxing traditional constraints on measurement conformity and fidelity to the scene enables the development of novel imaging instruments, guided by performance metrics applied to the design or the processing of acquisitions. By providing a complete framework for design, simulation and evaluation, this work contributes to the optimization and exploration of new CASSI systems, and more generally to the computational imaging community.

Problem

• CASSI system
• image quality
• computational imaging

Innovation

• CASSI System
• Image Reconstruction Techniques
• Optical Aberration Handling