Patent ID: 8013841

Claim:
A method for detecting lift from a surface portion of an optical pointing device, wherein the optical pointing device comprises (a) a coherent light source; (b) a photodetector device including an array of pixels; and (c) means for extracting motion features, wherein the means for extracting motion features includes comparators provided with an adjustable offset value, wherein the method comprises the steps of: (i) illuminating the surface portion with radiation by means of the coherent light source; (ii) detecting radiation patterns reflected from the illuminated surface portion by means of the photodetector device; (iii) comparing light intensity between neighbouring pixels in the detected radiation patterns; (iv) extracting motion features as a function of the result of the comparison of light intensity; (v) counting a total number of motion features extracted; (vi) increasing the adjustable offset value of the comparators when the total number of motion features increases, and decreasing the adjustable offset value of the comparators when the total number of motion features decreases; (vii) comparing the adjustable offset value with an offset threshold using the comparators of the means for extracting motion features; and (viii) enabling detection of a lift condition when the adjustable offset value is lower than the offset threshold.