Method for determining motion using a velocity predictor

A signal processing circuit for detecting movement of a surface relative to an optical sensor having an array of photosensitive elements, the circuit comprising:

• means for generating at least one set of quasi-sinusoidal signals responsive to motion of light received on the array in at least a first direction;
• means for combining said at least one set of quasi-sinusoidal signals to generate a phase angle value for said first direction at a first time, and combining said at least one set of quasi-sinusoidal signals at a second time to generate a phase angle value for said first direction at the second time;
• means for computing wrapped phase angle changes for said first direction from the phase angle values generated at said first and second times;
• means for computing the unwrapped phase angle changes for said first direction;
• and
• means for determining a value of distance moved in the first direction.

A method for detecting movement of a surface relative to an optical sensor having an array of photosensitive elements, the method comprising steps of:

• generating at least two sets of quasi-sinusoidal signals responsive to motion of light received on the array, the first set of quasi-sinusoidal signals related to motion in a first direction and the second set of quasi-sinusoidal signals related to motion in a second direction;
• at a first time combining said first set of quasi-sinusoidal signals to generate a wrapped phase angle value for said first direction at the first time, and combining said second set of quasi-sinusoidal signals to generate a wrapped phase angle value for said second direction at the first time;
• at a second time combining said first set of quasi-sinusoidal signals to generate a wrapped phase angle value for said first direction at the second time, and combining said second set of quasi-sinusoidal signals to generate a wrapped phase angle value for said second direction at the second time;
• computing wrapped phase angle changes between the first time and the second time for said first and second directions;
• computing the unwrapped phase angle changes for said first and second directions using velocity predictors computed for said first and second directions;
• and
• determining a value of distance moved in the first and the second directions.