Biometric Sensing

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 physically separated from the pickup lines on a different layer by a substantially incompressible dielectric located between the drive lines and pickup lines to form a two dimensional array of intrinsic electrode pairs that are impedance sensitive to detect ridge and valley features of a proximally located finger when driven by circuitry located outside the sensing area which is connected to each drive and pickup line of the array in order to activate one or more junctions formed at individual dive and pickup line crossovers where the circuitry compromises a driver or drive multiplexor connected to each drive line, and buffer, switch or input multiplexor attached to each pickup line, and at least one differencing amplifier configured to receive it's inputs from the input buffers or input multiplexor where a signal proportional to impedance about each drive line and pickup crossover location can be differenced with a signal proportional to impedance about another drive line and pickup crossover location to differentiate impedance values in order to determine relative object proximity.