Patent ID: 8405613
Filing Date: 2013-03-26
Classification: G06F

Abstract:
1. A method for measuring relative motion between a surface and an optical sensing device, wherein the optical sensing device comprises: (i) a coherent light source; (ii) a photodetector device; and (iii) a motion detection processing circuit, wherein the photodetector device comprises: (1) an array of pixels; and (2) a plurality of comparators for extracting edge direction data, wherein the method comprises the steps of: (A) illuminating a portion of the surface at a determined flash rate using the coherent light source to produce light at the determined flash rate; (B) detecting a speckled light intensity pattern of the illuminated portion of the surface for each flash using the array of pixels; (C) extracting edge direction data of two different types from the detected speckled light intensity patterns by comparing light intensity between pixels for each light intensity pattern, wherein the two different types of extracted edge direction data include first edge direction data and second edge direction data; (D) determining a measurement of the relative motion between the optical sensing device and the surface based on the extracted edge direction data; wherein step (C) comprises adding, in the light intensity comparison between pixels, an offset in the comparison of light intensity for at least one region of light intensity patterns that promotes, for each region among the at least one region of the light intensity patterns, detection of the first edge direction data rather than detection of the second edge direction data.