We discuss two classes of motion detection algorithms. The first broad class is based on optical flow, more properly called gradient-based methods, and the second class is based on block matching. What we will show is that for the special case of subpixel motions that these two classes of algorithms are equivalent .
Equivalence is very powerful and can lead to improved insight.
This equivalence only holds for subpixel motions which has application, for example, in computer microvision. In computer microvision, we use a microscope and a CCD camera to acquire images. Computer vision algorithms are then used to quantify very small motions of very small things. In this realm, the computer vision problem has many special properties that are best illustrated by example. Our lab has two applications of computer microvision.