arXiv:2508.02923cs.CV2025-08被引 1

用莫尔斯-博特定理分析盲反问题,发现MAP虽局部稳定但难逃模糊陷阱。

A Morse-Bott Framework for Blind Inverse Problems: Local Recovery Guarantees and the Failure of the MAP

  • 将图像先验建模为莫尔斯-博特函数,揭示自然图像在流形上的平坦性与法向凸性。
  • 证明在真实解附近,后验分布存在对初始化和数据扰动均稳定的局部极小值。
  • 指出即使使用先进学习先验,仍会陷入模糊陷阱,恢复成败取决于初始位置。

最大后验估计(MAP)是盲反问题的核心框架,用于联合估计图像与前向算子。本文采用莫尔斯-博特定理分析其恢复保证:将图像势能建模为莫尔斯-博特函数,即自然图像位于流形的临界子流形上,沿流形方向局部平坦,法向严格凸。该假设与当前先进学习先验的结构特性一致,通过势能景观与海森谱实验验证。理论表明,在真实图像与算子邻域内,后验存在对初始化和数据微小扰动均稳定的局部极小值,可能解释梯度优化的实证成功。然而,这种稳定性仅为局部性质,‘模糊陷阱’——盲去卷积中稀疏先验已知的病态现象——在先进学习先验下依然存在。结果表明,MAP在盲去卷积中的失败并非先验质量不足,而是景观固有特性。因此,成功恢复依赖于围绕有利局部极小值的策略性初始化。

原文摘要 · Abstract (English)

Maximum A Posteriori (MAP) estimation is a cornerstone framework for blind inverse problems, where an image and a forward operator are jointly estimated as the maximizers of a posterior distribution. In applications such as blind deblurring, this principle is used to recover sharp images from degraded observations. In this paper, we analyze the recovery guarantees of MAP-based methods by adopting a \emph{Morse--Bott framework}. We model the image potential as a Morse--Bott function, where natural images are modeled as residing locally on a critical submanifold. This means that while the potential is locally flat along the ``natural'' directions of the image manifold, it is strictly convex in the directions normal to it. We demonstrate that this Morse--Bott hypothesis aligns with the structural properties of state-of-the-art learned priors, a finding we validate through an experimental analysis of the potential landscape and its Hessian spectrum. Our theoretical results show that, in a neighborhood of the ground-truth image and operator, the posterior admits local minimizers that are stable both with respect to initialization (gradient descents converge to the same minimizer) and to small perturbations of the data (solutions vary smoothly with the observations). This local stability potentially provides a theoretical justification for the empirical success of well designed gradient-based optimization in these settings. However, we also demonstrate that this local stability is a \textbf{local} property: the ``blurry trap'', well-known for sparse priors in blind deconvolution, persists even with state-of-the-art learned priors. Our findings demonstrate that the failure of MAP in blind deconvolution is not a limitation of prior quality, but an intrinsic characteristic of the landscape. We conclude that successful recovery depends on strategic initialization around favorable local minima.

盲反问题莫尔斯-博特图像恢复优化陷阱

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