1. An apparatus for estimating the distance of an object from a video image comprising an array of pixels, said apparatus comprising: imaging means having an image plane for acquiring in said image plane at a plurality of successive imaging positions, greater than two, a respective plurality of video images of a region of the object having a distance component in a given direction from said image plane, which distance component is to be determined, each image of said plurality of images having at least one pixel corresponding to a point on said object within said region; means for automatically, without any action by an operator, predicting the location of a pixel window of a predetermined size in which said at least one pixel will be located in a next succeeding one of said plurality of video images; means for estimating the value of the disparity of said at least one pixel in each pixel window, said disparity corresponding to the difference in position of said at least one pixel in a current image as compared to the position of said at least one pixel in an immediately preceding one of said plurality of images; and means for determining the value of said distance component from the value of a last estimated disparity.