Computation of optic flow from the motion of edge features in image sequences

摘要

Three-dimensional scene information relating to the depth and orientations of the visible surfaces may be obtained from the optic flow field in time varying imagery. The computation of optic flow is therefore an important step in computer vision. We review our work on calculating optic flow from the motion of edge features in an image sequence. The method is based on a spatiotemporal extension of the Marr-Hildreth edge detection scheme that smooths the data over time as well as over the spatial, image, coordinates. Edge features are defined as the zero crossings of the resultant convolution signal and their motion obtained to subpixel accuracy by a leastsquares interpolation. The details of the method are described and some computational examples are given, including a brief description of how the algorithms may be implemented on a single-instruction multiple-data machine. Some novel effects associated with the choice of metric in the spatiotemporal convolution operator that may be useful for obtaining the time to contact (depth) of objects in the periphery of the field of view are discussed.