提出可插拔的高光谱射电成像算法,提升宽频段图像重建精度。
HyperAIRI: a plug-and-play algorithm for precise hyperspectral image reconstruction in radio interferometry
- 采用带谱模型的可插拔框架,用学习化去噪器联合处理多频通道。
- 在模拟与真实数据上优于现有优化算法和单色成像方法。
- 支持动态范围自适应、图像分块处理,适合大规模射电数据。
下一代射电干涉仪需要能从大体积宽频数据中生成高分辨率、高动态范围图像的成像算法。最近,基于前向-后向结构(FB)的可插拔方法AIRI,在单色射电成像中表现出色,通过交替数据保真与正则化步骤实现。本文提出其高光谱扩展——HyperAIRI,引入学习型高光谱去噪器,并强制满足幂律谱模型。每个波段的去噪器接收当前估计图像及其两个邻近波段估计值与谱指数图,输出去噪后的图像。为保证收敛,训练时加入雅可比正则化以确保非扩张性。针对不同动态范围,构建预训练去噪器集合,按需匹配使用;每轮迭代并行更新所有波段图像。去噪器还具备空间分块功能,支持不同图像尺寸。此外,提出超谱版优化算法Hyper-uSARA,通过ℓ₂,₁范数促进跨波段联合稀疏性,同样采用FB结构。在模拟与真实观测数据上的评估表明,HyperAIRI性能显著优于对比方法,包括Hyper-uSARA、WSClean的高光谱版本,以及单色算法AIRI和uSARA。
原文摘要 · Abstract (English)
The next-generation radio-interferometric (RI) telescopes require imaging algorithms capable of forming high-resolution high-dynamic-range images from large data volumes spanning wide frequency bands. Recently, AIRI, a plug-and-play (PnP) approach taking the forward-backward algorithmic structure (FB), has demonstrated state-of-the-art performance in monochromatic RI imaging by alternating a data-fidelity step with a regularization step via learned denoisers. In this work, we introduce HyperAIRI, its hyperspectral extension, underpinned by learned hyperspectral denoisers enforcing a power-law spectral model. For each spectral channel, the HyperAIRI denoiser takes as input its current image estimate, alongside estimates of its two immediate neighboring channels and the spectral index map, and provides as output its associated denoised image. To ensure convergence of HyperAIRI, the denoisers are trained with a Jacobian regularization enforcing non-expansiveness. To accommodate varying dynamic ranges, we assemble a shelf of pre-trained denoisers, each tailored to a specific dynamic range. At each HyperAIRI iteration, the spectral channels of the target image cube are updated in parallel using dynamic-range-matched denoisers from the pre-trained shelf. The denoisers are also endowed with a spatial image faceting functionality, enabling scalability to varied image sizes. Additionally, we formally introduce Hyper-uSARA, a variant of the optimization-based algorithm HyperSARA, promoting joint sparsity across spectral channels via the $\ell_{2,1}$-norm, also adopting FB. We evaluate HyperAIRI's performance on simulated and real observations. We showcase its superior performance compared to its optimization-based counterpart Hyper-uSARA, CLEAN's hyperspectral variant in WSClean, and the monochromatic imaging algorithms AIRI and uSARA.
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