Processing methods for speckle-based motion sensing

A method of tracking motion relative to a surface using a speckle-based motion sensor, the method comprising:

• creating on the surface a plurality of speckle patterns based on movement of the surface along at least two nonparallel axes relative to a plurality of optical detectors;
• detecting said plurality of speckle patterns with said plurality of optical detectors;
• creating a set of electrical signals emitted from said optical detectors, such that said electrical signals based on the detected speckle patterns and vary quasi periodically with the distance moved along the at least two non-parallel axes;
• sampling said electrical signals at a plurality of discrete times extending over a time interval, creating a plurality of sampled electrical signals;
• and
• processing said plurality of sampled electrical signals to determine a distance moved during said time interval,
• wherein the creating a set of electrical signals includes creating one or more sets of phase signals based on the electrical signals, the phase signals responsive to relative phases of the speckle patterns, and the phase signals are quasi-periodic with the distance moved, and
• wherein said processing of said plurality of sampled electrical signals includes multiplying the values of signals from one time interval by the values of signals from an adjacent interval to form signal products, and adding or subtracting pairs of said signal products to form at least one b-vector.