Method and system for estimating finger movement

A finger navigation system for estimating a finger movement of a finger, said finger navigation system comprising:

• a fingerprint sensor comprising an array of sensing elements;
• and
• processing circuitry including:
• fingerprint image acquisition circuitry for acquiring fingerprint images;
• fingerprint image matching circuitry for determining a match parameter value indicative of a correlation between acquired fingerprint images;
• a memory;
• and
• estimation circuitry for estimating said finger movement based on match parameter values,
• wherein, when said finger moves across said sensing area of the fingerprint sensor:
• said fingerprint image acquisition circuitry acquires a reference fingerprint image at a reference fingerprint image acquisition time, and at least one candidate fingerprint image at each candidate fingerprint image acquisition time in a time sequence of candidate fingerprint image acquisition times;
• said fingerprint image matching circuitry determines, for each of said candidate fingerprint image acquisition times, a match parameter value for each of a plurality of candidate finger movement directions, said match parameter value being indicative of a correlation between a reference fingerprint image portion corresponding to a reference area of said fingerprint sensor and a candidate fingerprint image portion corresponding to a candidate area of said fingerprint sensor, said candidate area being displaced a given displacement distance in said candidate finger movement direction in relation to said reference area, said given displacement distance in said candidate finger movement direction being the same for each of said candidate fingerprint image acquisition times;
• said fingerprint image matching circuitry stores in said memory, for each of said candidate finger movement directions, at least a local extremum match parameter value indicating a maximum correlation for said time sequence of candidate fingerprint image acquisition times;
• and
• said estimation circuitry estimates said finger movement based on an evaluation of the local extremum for each of said candidate finger movement directions.