State-of-the-art snapshot spectral imaging (SI) systems introduce color-coded apertures (CCAs) into their setups to obtain a flexible spatial-spectral modulation, allowing spectral information to be reconstructed from a set of coded measurements. Besides the CCA, other optical elements, such as lenses, prisms, or beam splitters, are usually employed, making systems large and impractical. Recently, diffractive optical elements (DOEs) have partially replaced refractive lenses to drastically reduce the size of the SI devices. The sensing model of these systems is represented as a projection modeled by a spatially shift-invariant convolution between the unknown scene and a point spread function (PSF) at each spectral band. However, the height maps of the DOE are the only free parameters that offer changes in the spectral modulation, which causes the ill-posedness of the reconstruction to increase significantly. To overcome this challenge, our work explores the advantages of the spectral modulation of an optical setup composed of a DOE and a CCA. Specifically, the light is diffracted by the DOE and then filtered by the CCA, located close to the sensor. A shift-variant property of the proposed system is clearly evidenced, resulting in a different PSF for each pixel, where a symmetric structure constraint is imposed on the CCA to reduce the high number of resulting PSFs. Additionally, we jointly design the DOE and the CCA parameters with a fully differentiable image formation model using an end-to-end approach to minimize the deviation between the true and reconstructed image over a large set of images. Simulation shows that the proposed system improves the spectral reconstruction quality in up to 4 dB compared with current state-of-the-art systems. Finally, experimental results with a fabricated prototype in indoor and outdoor scenes validate the proposed system, where it can recover up to 49 high-fidelity spectral bands in the 420–660 nm.

中文翻译：

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移变彩色编码衍射光谱成像系统

最先进的快照光谱成像 (SI) 系统在其设置中引入了彩色编码孔径 (CCA)，以获得灵活的空间光谱调制，从而允许从一组编码测量中重建光谱信息。除了 CCA 之外，通常还会使用其他光学元件，例如透镜、棱镜或分束器，这使得系统变得庞大且不切实际。最近，衍射光学元件 (DOE) 已部分取代折射透镜，以大幅减小 SI 器件的尺寸。这些系统的传感模型表示为由未知场景和每个光谱带的点扩散函数 (PSF) 之间的空间位移不变卷积建模的投影。然而，DOE 的高度图是唯一提供光谱调制变化的自由参数，这导致重建的不适定性显着增加。为了克服这一挑战，我们的工作探索了由 DOE 和 CCA 组成的光学装置的光谱调制的优势。具体来说，光被 DOE 衍射，然后被靠近传感器的 CCA 过滤。所提出的系统的移位变量特性得到了明显的证明，导致每个像素的 PSF 不同，其中对 CCA 施加了对称结构约束以减少产生的大量 PSF。此外，我们使用端到端方法联合设计具有完全可微分图像形成模型的 DOE 和 CCA 参数，以最大程度地减少大量图像上真实图像和重建图像之间的偏差。仿真表明，与当前最先进的系统相比，所提出的系统将频谱重建质量提高了 4 dB。最后，在室内和室外场景中制造原型的实验结果验证了所提出的系统，它可以在 420-660 nm 范围内恢复多达 49 个高保真光谱带。