# On the Impact of Distortions in Coded Hyperspectral Systems

Léo Paillet, Antoine Rouxel, Hervé Carfantan, Simon Lacroix, Antoine Monmayrant

► To cite this version:

Léo Paillet, Antoine Rouxel, Hervé Carfantan, Simon Lacroix, Antoine Monmayrant. On the Impact of Distortions in Coded Hyperspectral Systems. 2025 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), Jun 2025, Munich, Germany. IEEE, pp.1-1, 10.1109/CLEO/Europe-EQEC65582.2025.11109355. hal-05272200

HAL Id: hal-05272200

https://hal.science/hal-05272200v1

Submitted on 22 Sep 2025

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# On The Impact of Distortions in Coded Hyperspectral Systems

Léo Paillet¹,², Antoine Rouxel¹, Hervé Carfantan², Simon Lacroix¹, Antoine Monmayrant¹
¹: LAAS-CNRS, Toulouse ; ²: IRAP, Toulouse

leo.paillet@laas.fr

## Abstract

We made a CASSI (Coded Aperture Snapshot Spectral Imager) optical simulator which allows to consider a realistic optical model. We then designed several CASSI systems in the simulator. Through our simulator, we render CASSI acquisitions and use the optical model to perform reconstruction of hyperspectral cubes from coded acquisitions. We show that single-prism systems are in fact as performant as double-Amici prism systems despite the induced distortions, as long as we model them accurately. Single-prism systems can hence be a cheaper, more compact, easier-to-fabricate option without sizable difference on the reconstruction quality.

## Introduction

**Context:** Reconstruction of coded hyperspectral acquisitions.

**Goal:** Simulate realistic CASSI systems [1] and compare reconstruction quality from different CASSI configurations.

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* Differentiable CASSI ray-tracing renderer [2] based on dO [3].
* Programmable 2D pattern resulting in a spatio-spectral data arrangement.
* Unrolling reconstruction algorithm adapted with optical models of each system.

## Optical Model

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* Infer optical model by forwardly tracing chief-rays from each pixel.
* Will be used as the inverse operator in reconstruction algorithms

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[1] Wagadarikar et al., Video rate spectral imaging using a coded aperture snapshot spectral imager, Opt. Express, 2009
[2] Paillet et al., The marginal importance of distortions and alignment in CASSI systems, Submitted, 2025
[3] Wang et al., dO: A Differentiable Engine for Deep Lens Design of Computational Imaging Systems, IEEE TCI, 2022
[4] Li et al., Pixel Adaptive Deep Unfolding Transformer for Hyperspectral Image Reconstruction, ICCV, 2023

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## Rendering

* Rendering of the system is performed through backward ray-tracing.

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## CASSI Reconstruction

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* 4 CASSI configurations and 5 state-of-the-art algorithms

## Results on SotA algorithm [4]

<table><thead><tr><th></th><th>(AP)</th><th>(SP)</th><th>(mAP)</th><th>(mSP)</th></tr></thead><tbody><tr><td>PSNR</td><td>34.1</td><td><strong>34.7</strong></td><td>34.0</td><td>33.8</td></tr><tr><td>SSIM</td><td>0.937</td><td><strong>0.943</strong></td><td>0.936</td><td>0.935</td></tr><tr><td>SAM [0-1]</td><td><strong>0.048</strong></td><td>0.048</td><td>0.049</td><td><strong>0.048</strong></td></tr></tbody></table>

Table: Results averaged over 10 scenes
Best results depend on algorithm and metric, and not on the system

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* Same quality across any misalignment, as long as they are correctly modeled.

## Conclusion

* Differentiable CASSI ray-tracing renderer.
* Distortions and misalignment have a marginal importance on reconstruction quality as long as they are correctly modeled.

* Paves the way for cheaper and simpler systems, may be extended to other fields.