Electronic imager using an impedance sensor grid array and method of making

1. An fingerprint impedance sensor, comprising:

a plurality of substantially parallel drive lines;

a plurality of substantially parallel pickup lines oriented substantially perpendicular to the drive lines and physically separated from the drive lines by a substantially incompressible dielectric located between the drive lines and pickup lines to form a plurality of impedance sensitive crossover locations where a pickup line crosses a drive line; and

circuitry that includes a signal generator connected to the drive lines, and configured to:

sequentially activate each of the drive lines by transmitting a signal to each of the drive lines, one at a time, and grounding the remaining drive lines while the signal is being transmitted to the one activated drive line to thereby cause an electric field to radiate from the one activated drive line toward the pickup line at each of the impedance sensitive crossover locations formed by the activated drive line,

for each drive line that is activated, sequentially measure an amount of the electric field on each of the pickup lines at each of the impedance sensitive crossover locations and ground the remaining pickup lines while the electric field is being measured at the one pickup line, and

distinguish between different surface features of a proximally located finger at each of one or more of the impedance sensitive crossover locations based on the amount of the electric field measured at the crossover location.

2. The fingerprint impedance sensor according to claim 1 , wherein the dielectric includes at least one of a rigid substrate, glass, ceramic, and a rigid board.

3. The fingerprint impedance sensor according to claim 1 , wherein the circuitry is configured to distinguish between a fingerprint valley and a fingerprint ridge at one or more of the crossover locations based on the amount of the electric field measured at the crossover location.

4. The fingerprint impedance sensor according to claim 1 , wherein the circuitry further comprises scanning logic configured to sequentially scan a plurality of crossover locations formed by the plurality of pickup lines.

5. The fingerprint impedance sensor according to claim 4 , wherein each of the crossover locations corresponds to a pixel of image information, and the scanning logic is configured to capture a plurality of pixels corresponding to a plurality of crossover locations.

6. The fingerprint impedance sensor according to claim 1 , wherein the signal generator is configured to generate a signal having multiple frequencies.

7. The fingerprint impedance sensor according to claim 1 , wherein the crossover locations form a finger contact area, the sensor further comprising:

a reference line located outside the finger contact area; and

a differential amplifier configured to subtract a signal on at least one of the plurality of pickup lines against a signal on the reference line.

8. The fingerprint impedance sensor according to claim 7 , wherein the distance between the reference line and a closest one of the plurality of pickup lines is greater than the distance between adjacent lines of the plurality of pickup lines.

9. The fingerprint impedance sensor according to claim 7 , wherein the reference line is positioned under a component that prevents finger contact with the reference line.

10. The fingerprint impedance sensor according to claim 9 , wherein the component comprises plastic material of a bezel.

11. The fingerprint impedance sensor according to claim 1 , wherein the dielectric is a folded rigid substrate having a top layer and a bottom layer, wherein each of the top layer and the bottom layer has the plurality of drive lines or the plurality of pickup lines located on the layer.

12. The fingerprint impedance sensor according to claim 1 , wherein the dielectric is a folded substrate that has the plurality of drive lines and the plurality of pickup lines located on the substrate, and wherein the plurality of drive lines is divided into a first bundle of drive lines and a second bundle of drive lines that are separated by at least one of the plurality of pickup lines.

13. The fingerprint impedance sensor according to claim 1 , wherein the dielectric has a dielectric constant that is greater than 1.

14. The fingerprint impedance sensor according to claim 1 , wherein the circuitry is configured to both detect a fingerprint of a proximally located finger and to track motion of the finger.