1. A method for dynamically setting a scale for performing a cross-correlation check between a reference image and a comparison image of a mouse, the method comprising: setting a plurality of scale sizes fora cross-correlation check, the plurality of scale sizes corresponding to a plurality of predicted locations for cross-correlation, respectively; determining a velocity of motion of the mouse, and using the determined velocity to generate a predicted location for performing cross-correlation; selecting a scale size according to the predicted location; and performing the cross-correlation check according to the scale size.