Fingerprint sensor with gain control features and associated methods

A fingerprint sensor to enhance conversion resolution of ridges and valleys of sensed fingerprints, the fingerprint sensor comprising:

• an array of fingerprint sensing elements, each element comprising an electric field sensing electrode and an amplifier associated therewith;
• at least one analog-to-digital (A/D) converter having at least one reference voltage input and for converting an analog signal from at least one fingerprint sensing element to a digital signal based upon the at least one reference voltage;
• scanning means responsive to said array of fingerprint sensing elements and positioned in communication with said at least one A/D converter for operating said at least one A/D converter and said array of fingerprint sensing elements to perform sequential A/D conversions of predetermined ones of said array of fingerprint sensing elements;
• and
• reference voltage determining and setting means responsive to said at least one A/D converter for controlling the at least one reference voltage of said at least one A/D converter based upon a plurality of the sequential A/D conversions performed by said A/D conversion means to thereby provide enhanced conversion resolution of ridges and valleys of sensed fingerprints.

A fingerprint sensor to enhance conversion resolution of ridges and valleys of sensed fingerprints, the fingerprint sensor comprising:

• an array of fingerprint sensing elements, each element comprising an electric field sensing electrode and an amplifier associated therewith;
• a plurality of analog-to-digital (A/D) converters each having at least one reference voltage input and for converting an analog signal from at least one fingerprint sensing element to a digital signal based upon the at least one reference voltage;
• scanning means responsive to said array of fingerprint sensing elements and in communication with said plurality of A/D converters for operating said plurality of A/D converters and said array of fingerprint sensing elements to perform sequential A/D conversions of predetermined ones of said array of fingerprint sensing elements;
• and
• reference voltage determining and setting means responsive to said plurality of A/D converters for controlling the at least one reference voltage of each of said plurality of A/D converters based upon a plurality of the sequential A/D conversions performed by said plurality of A/D converters to thereby provide enhanced conversion resolution of ridges and valleys of sensed fingerprints, said reference voltage determining and setting means comprising histogram generating means for generating a histogram based upon the plurality of the sequential A/D conversions.