Depth from stereo flow

The interpretation is presented of image flow (optical flow) and its relationship with object structure. Depth extraction is described from stereo image flow when the stereo cameras have parallel optical axes or nonparallel optical axes. Using epipolar geometry, the relationship between the optical flow fields on the image planes (stereo) is derived and applied for matching the images to extract the depth information. Three methods are considered, of which the first two assume parallel optical axes: (1) spatial approach which is the same as the traditional stereo method except that binocular difference flow is used as primitives for matching; (2) spatial-temporal approach which extends previous formulation to incorporate temporal variations of image flow; and (3) under nonparallel optical axes assumption from which the model of the stereo cameras is generalized so that they are arbitrarily separated in space. Then two measures are used to evaluate how well the epipolar constraint is satisfied