论文标题
关于成像中反向问题的归一流流量的鲁棒性
On the Robustness of Normalizing Flows for Inverse Problems in Imaging
论文作者
论文摘要
有条件的归一化流可以生成各种图像样本以解决反问题。成像中反向问题的最正常的流动使用有条件的仿射耦合层，该耦合耦合层可以快速产生多种图像。但是，偶尔在其产出中观察到意外的严重伪影。在这项工作中，我们通过研究这些文物的起源并提出避免它们的条件来解决这个关键问题。首先，我们从经验和理论上揭示了这些问题是由于条件仿射耦合层中的某些分布（OOD）条件输入而引起的。然后，我们进一步验证了引起像素中错误伪影的可能性与成像中的逆问题的基于马哈拉诺省距离的OOD得分高度相关。最后，根据我们的研究，我们提出了一条言论，以避免爆炸，然后基于它，我们建议一种简单的补救措施，将仿射耦合层用改良的合理二次样条耦合层替代归一化流中的流量，以鼓励生成图像样品的鲁棒性。我们的实验结果表明，我们建议的方法有效地抑制了在高分辨率空间产生和低光图像增强的归一化流中发生的关键伪影。
Conditional normalizing flows can generate diverse image samples for solving inverse problems. Most normalizing flows for inverse problems in imaging employ the conditional affine coupling layer that can generate diverse images quickly. However, unintended severe artifacts are occasionally observed in the output of them. In this work, we address this critical issue by investigating the origins of these artifacts and proposing the conditions to avoid them. First of all, we empirically and theoretically reveal that these problems are caused by "exploding inverse" in the conditional affine coupling layer for certain out-of-distribution (OOD) conditional inputs. Then, we further validated that the probability of causing erroneous artifacts in pixels is highly correlated with a Mahalanobis distance-based OOD score for inverse problems in imaging. Lastly, based on our investigations, we propose a remark to avoid exploding inverse and then based on it, we suggest a simple remedy that substitutes the affine coupling layers with the modified rational quadratic spline coupling layers in normalizing flows, to encourage the robustness of generated image samples. Our experimental results demonstrated that our suggested methods effectively suppressed critical artifacts occurring in normalizing flows for super-resolution space generation and low-light image enhancement.
