Fingerprint sensor with gain control features and associated methods
DCFirst Claim
1. 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;
analog-to-digital (A/D) conversion means having a controllable range and for converting analog signals from said array of fingerprint sensing elements to digital signals based upon the range;
scanning means responsive to said array of fingerprint sensing elements and positioned in communication with said A/D conversion means for operating said A/D conversion means and said array of fingerprint sensing elements to perform sequential A/D conversions of predetermined ones of said array of fingerprint sensing elements; and
range determining and setting means responsive to each said A/D conversion means for controlling the range of said A/D conversion means 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.
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Abstract
A fingerprint sensor includes an array of fingerprint sensing elements; analog-to-digital (A/D) converters having a controllable range; a scanner to perform sequential A/D conversions of predetermined ones of the array of fingerprint sensing elements; and a range determining and setting circuit for controlling the range of the A/D converters based upon prior A/D conversions to thereby provide enhanced conversion resolution. A plurality of A/D converters are preferably used for simultaneously converting analog signals from a corresponding plurality of fingerprint sensing elements. The A/D converters may include at least one reference voltage input for permitting setting of first and second points of the range. The range scale determining and setting circuit may generate a histogram based upon prior A/D conversions. In addition, the range scale determining and setting circuit may set a default range for initial ones of the fingerprint sensing elements.
173 Citations
26 Claims
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1. A fingerprint sensor to enhance conversion resolution of ridges and valleys of sensed fingerprints, the fingerprint sensor comprising:
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an array of fingerprint sensing elements, each element comprising an electric field sensing electrode and an amplifier associated therewith;
analog-to-digital (A/D) conversion means having a controllable range and for converting analog signals from said array of fingerprint sensing elements to digital signals based upon the range;
scanning means responsive to said array of fingerprint sensing elements and positioned in communication with said A/D conversion means for operating said A/D conversion means and said array of fingerprint sensing elements to perform sequential A/D conversions of predetermined ones of said array of fingerprint sensing elements; and
range determining and setting means responsive to each said A/D conversion means for controlling the range of said A/D conversion means 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A fingerprint sensor to enhance conversion resolution of ridges and valleys of sensed fingerprints, the fingerprint sensor comprising:
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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. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A fingerprint sensor to enhance conversion resolution of ridges and valleys of sensed fingerprints, the fingerprint sensor comprising:
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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. - View Dependent Claims (18, 19, 20, 21)
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22. A method for sensing fingerprints using an array of fingerprint sensing elements, each element comprising an electric field sensing electrode and an amplifier associated therewith, to enhance conversion resolution of ridges and valleys of the sensed fingerprints, the method comprising the steps of:
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sequentially converting analog signals from predetermined ones of the array of fingerprint sensing elements to digital signals using at least one A/D converter having a controllable range; and
determining and controlling the range of the at least one A/D converter based upon a plurality of the performed sequential A/D conversions performed by the at least one A/D converter to thereby provide enhanced conversion resolution of ridges and valleys of sensed fingerprints. - View Dependent Claims (23, 24, 25, 26)
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Specification