US Patent 7326909 Angle-error correction algorithm

There is described a method for measuring relative motion between an illuminated portion of a surface and an optical sensing device comprising a photodetector array, which includes a plurality of rows and columns of pixels respectively aligned along first and second axes, the method allowing to determine a measurement of the relative motion between the optical sensing device and the illuminated portion of the surface based on a comparison of motion features extracted from light intensity patterns obtained with the photodetector array, wherein said method includes a checking process between two light intensity patterns for discarding erroneous motion features due to the surface design.