Patent ID: 7298460

Claim:
A method for detecting movement of a surface relative to an optical sensor having an array of photosensitive elements, the method comprising steps of: generating at least one set of quasi-sinusoidal signals responsive to motion of light received on the array in at least a first direction; combining said at least one set of quasi-sinusoidal signals to generate a phase angle value for said first direction at a first time; combining said at least one set of quasi-sinusoidal signals at a second time to generate a phase angle value for said first direction at the second time; computing wrapped phase angle changes for said first direction; computing the unwrapped phase angle changes for said first direction; and determining a value of distance moved in the first direction; and wherein the step of computing the unwrapped phase angle changes for said first direction comprises the step of computing velocity predictors for said first direction using average velocity values from a number, K, of preceding successive frames, where K is a whole number greater than or equal to two.