A generalized brightness change model for computing optical flow

The authors propose an image motion constraint equation based on a model which allows the brightness of a scene point to vary with time, unlike the case in the brightness constancy model. Using this model, they describe a method for the computation of optical flow and investigate its performance in a variety of conditions involving brightness variations of scene points, due to illumination nonuniformity, light source motion, specular reflection, and/or interreflection. It is shown that in the application of this method, care must be taken in the estimation of image derivatives using finite difference methods to prevent biases in the solution. A simple modification is suggested to overcome the problem. A comparison is made with two other models, including the classical brightness constancy model, through results from experiments with real images