Image Perturbations and Optical Flow in Time-dependent Refraction

Abstract

The ray formulation for light propagation is applied to the problem of image perturbations (‘shimmering’) resulting from perturbations in the refractive index profile of the medium between an object and an observer. Expressions are derived relating the image diagram perturbation and the instantaneous image motion (optical flow) to the change in the refractive index profile, in the paraxial ray approximation. In special circumstances the image perturbation and optical flow can be estimated directly. These results are applied to two simple examples.