Patent ID: 8179369

Claim:
An optical navigation device comprising: an image input unit for emitting light, receiving light reflected from a working surface to generate an analog image signal for respective pixels, converting the analog image signals into digital image signals, and outputting the digital image signals; a delta image generator for receiving the digital image signals, generating a cumulative average for the digital image signals received for a predetermined period of time with respect to each pixel, and subtracting the cumulative average from the digital image signal in the respective pixels to generate a delta image signal for the respective pixels; and a motion value calculator for calculating a motion value using the delta image signals, wherein the delta image generator comprises: an average operation unit for calculating the cumulative average of the digital image signals applied for the predetermined period of time with respect to each pixel to output the cumulative average; an average storage unit for storing the cumulative average output from the average operation unit to output the cumulative average to the average operation unit when a next digital image signal is applied to the average storage unit; and a delta image operation unit for subtracting the cumulative average from the digital image signal in the respective pixels to generate the delta image signal for the respective pixels, wherein the average operation unit generates a new cumulative average using only edge elements of the digital image signal and the cumulative average that are arranged in an m×n matrix.