Space-Time Images

Abstract

So far, we have analyzed motion from only two consecutive images of a sequence, but did not consider the whole sequence. This stemmed from a limited capacity to handle image sequence data. Nowadays, video and computer hardware can record, store, and evaluate long image sequences (see section 1.2.2 and appendix B). It is much more important, however, to recognize that there is no principal reason to limit image sequence processing to an image pair. On the contrary, it seems to be an unjustified restriction. That is certainly true for the concepts developed so far. In the differential approach (section 15.2) temporal derivatives play an essential role (see (15.5), (15.12), and (15.27)). With only two consecutive images of a sequence, we can approximate the temporal derivative just by the difference between the two images. This may be the simplest approximation, but not necessarily the best (see section 6.3.5).