Patent ID: 7502515

Claim:
A method for detecting sub-pixel motion of an optical mouse, comprising: moving the optical mouse; capturing a first image frame, wherein the first image frame comprises a plurality of image pixels; selecting one or more of the plurality of image pixels as reference pixels; capturing a second image frame after a period of time has elapsed since the first image frame was captured; and determining a displacement of the reference pixels in the second image frame relative to the first image frame using one or more brightness curve equations represented as a function of positional coordinates x and y; wherein the reference pixels satisfy the following equations: ( Ir ( x +1, y )− Ir ( x,y ))·( Ir ( x,y )− Ir ( x −1, y ))>0, | Ir ( x+ 1, y )− Ir ( x,y )|> Ith, | Ir ( x,y )− Ir ( x −1, y )|> Ith, ( Ir ( x,y +1)− Ir ( x,y ))·( Ir ( x,y )− Ir ( x,y −1))>0, | Ir ( x,y +1)− Ir ( x,y )|> Ith, and | Ir ( x,y )− Ir ( x,y −1)|> Ith, where Ir represents the brightness value of reference image coordinate (x, y), and Ith is a threshold which has a value of plural frame rates.