提出结构化分布鲁棒框架,提升逆问题重建对噪声分布变化的稳定性。
A Distributionally Robust Framework for Learned Reconstructions in Inverse Problems

- 基于测量物理过程设计结构化扰动,避免传统方法过度保守。
- 在去模糊和CT重建中显著提升鲁棒性与稳定性,优于标准DRO和MSE基线。
- 适用于噪声模型复杂或未知场景,适合医学成像等高可靠性需求领域。
逆问题中的学习重建算子通常在固定噪声模型下训练,当测试时分布与训练假设不一致时泛化能力差。分布鲁棒优化(DRO)通过优化最坏情况分布来缓解此问题,但标准Wasserstein DRO对联合分布均匀扰动,过于保守且忽略测量物理过程。本文提出一种结构化DRO框架,将不确定性集限制在与数据采集过程对齐的结构化扰动上,更真实地建模前向算子和噪声模型的不确定性,支持任意可表示为随机前向算子的噪声模型。建立了该通用形式的强对偶性,并推导了联合、边缘与条件分布扰动的显式有限维对偶表示。核心结果为显式最坏情况风险界,诱导重建算子的Lipschitz常数受Tikhonov正则化约束,对适定问题较标准DRO更不保守。在线性情形下,学习到的算子实际为低秩,其秩等于数据内在维度,恢复出数据驱动的截断SVD正则化。数值实验在去模糊与投影图到CT重建任务中均验证了更强的鲁棒性、稳定性和可解释性。
原文摘要 · Abstract (English)
Learned reconstruction operators for inverse problems are typically trained under a fixed noise model, and generalize poorly when the distribution during testing differs from the one assumed during training. Distributionally robust optimization (DRO) addresses this by optimizing against the worst-case distribution within a prescribed ambiguity set, but standard Wasserstein DRO perturbs the full joint distribution uniformly, which can be overly conservative and ignores the physics of the measurement process. We develop a structured DRO framework in which the ambiguity set is restricted to structured perturbations aligned with the data-acquisition process. This allows us to learn data-driven reconstruction operators that remain robust to distributional shifts. By constraining perturbations to subsets such as $P(Y|X)$, our framework models uncertainty in the forward operator and noise model more faithfully, accommodating any noise model expressible as a stochastic forward operator. We establish strong duality for this general formulation and derive explicit finite-dimensional dual representations for perturbations in the joint, marginal, and conditional distributions. A central result is an explicit worst-case risk bound that induces Tikhonov regularization on the Lipschitz constant of the reconstruction operator, and is less conservative relative to standard DRO for well-posed problems. Numerical experiments on deblurring and sinogram-to-CT reconstruction demonstrate improved robustness, stability, and interpretability over standard DRO and MSE baselines. In the linear setting, the learned operator becomes effectively low-rank, truncating at the intrinsic dimension of the data and recovering a data-driven analogue of truncated-SVD regularization.
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