Signal processing method for use with an optical navigation system

A signal processor for processing signals from an optical sensor having an array of a plurality of photosensitive elements to detect movement of a surface relative to the optical sensor, the signal processor comprising:

• sampling means for sampling each of a number (M) of phase signals from the plurality of photosensitive elements, each of the M signals having a magnitude (Ai) and including a tracking signal at a frequency being tracked and a background signal at other frequencies, which offsets the tracking signal, where i, an index of the signals, is a whole number between 0 and M-1;
• offset elimination means for eliminating the offset to the tracking signal due to the background signal to generate M non-offset phase signals having a magnitude (A′i);
• phase angle adjusting means for adjusting phase angles (θi) of the non-offset phase signals to generate M weighted phase signals (A′iθ′i);
• and
• combining means for combining each of the M weighted phase signals (A′iθ′i) to generate an average weighted phase having a phase angle (θ), that when tracked over time indicates the direction and velocity of the movement of an image of the surface mapped to the array.