Biometric image sensing
An novel sensor is provided having a plurality of substantially parallel drive lines configured to transmit a signal into a surface of a proximally located object, and also a plurality of substantially parallel pickup lines oriented proximate the drive lines and electrically separated from the pickup lines to form intrinsic electrode pairs that are impedance sensitive at each of the drive and pickup proximal locations.
1. An impedance sensor, comprising:
a plurality of substantially parallel drive lines configured to transmit a signal to a proximally located object; and
a plurality of substantially parallel pickup lines configured to receive a resultant signal and oriented substantially perpendicular to the drive lines and separated from the drive lines on a different layer by a dielectric to form a two dimensional array of intrinsic electrode pairs that are impedance sensitive to a proximally located finger about each drive line and pickup crossover location;
wherein the dielectric is a single flexible substrate having both the drive and pickup lines located thereon.
2. The impedance sensor of claim 1 , wherein the drive and the pickup lines are located on different sections of the flexible substrate, and the flexible substrate is configured to be folded onto itself to form a dual layer configuration.
3. An impedance sensor, comprising:
a plurality of substantially parallel drive lines configured to transmit a signal to a proximally located object;
a plurality of substantially parallel pickup lines configured to receive a resultant signal and oriented substantially perpendicular to the drive lines and separated from the drive lines on a different layer by a dielectric to form a two dimensional array of intrinsic electrode pairs that are impedance sensitive to a proximally located finger about each drive line and pickup crossover location;
a signal generator configured to generate an AC signal at and AC driving frequency communicated to a drive line, and a signal processor configured to process a resultant signal from a pickup line, wherein said drive and pickup crossover locations form individual pixels configured to capture a plurality of pixels of image information; and
a signal processor including a narrow band receiver tuned to the AC driving frequency.
4. An impedance sensor, comprising:
a plurality of substantially parallel drive lines configured to transmit a signal to a proximally located object;
a plurality of substantially parallel pickup lines configured to receive a resultant signal and oriented substantially perpendicular to the drive lines and separated from the drive lines on a different layer by a dielectric to form a two dimensional array of intrinsic electrode pairs that are impedance sensitive to a proximally located finger about each drive line and pickup crossover location; and
a detection system configured to subtract the signal on a pickup plate in contact with the object being sensed from the signal on a pickup plate that is isolated from the object being sensed prior to further processing.
5. The impedance sensor of claim 4 , wherein the detection system comprises a differential amplifier for subtracting the signal on a pickup plate in contact with the object being sensed from the signal on a pickup plate that is isolated from the object.
6. The impedance sensor of claim 5 , wherein the detection system further comprises a pickup switch associated with each pickup plate for selectively connecting each pickup plate with the differential amplifier.
7. The impedance sensor of claim 4 , wherein the pickup plate that is isolated from the object is separated from the other pickup plates by a first gap that is larger than a second gap separating the other pickup plates.
8. The impedance sensor of claim 4 , wherein the signal processor includes a cascaded integrator comb filter.