1. A method of optical tracking sensing comprising the following steps: a. illuminating a work surface with a light source for a preset exposure time, b. capturing a surface image with a two-dimensional imaging array, c. digitizing the outputs of said imaging array, d. compensating for non-uniformity of illumination by a one-time calibration, wherein an output of each pixel is measured over a perfectly uniform surface, with correction values being calculated for each element of said imaging array, said correction values then being used to correct each output value of each said element of said imaging array when each said element is read, so that corrected outputs are uniform in their response in both dark and light conditions, e. block matching said outputs to a reference frame, and f. calculating and outputting displacement vectors.