Patent ID: 7239153
Filing Date: 2007-07-03
Classification: G06K,H01L

Abstract:
1. Sensor module for measuring structures in a surface, especially in a finger surface being moved over the sensor module, comprising a number of sensor elements and an outer electrode located aside the sensor elements, said sensor elements constituting an essentially linear array, and said outer electrode having larger dimensions than each of said sensor elements and extending along a substantial part of said array of sensor elements, the sensor elements also being coupled to an electronic circuit positioned on a substrate, said substrate comprising conductor leads coupling the sensor elements to the electronic circuit, and said electronic circuit being adapted to measure a magnitude of a capacitance or AC impedance between each of said number of sensor elements and the outer electrode, and that said array of sensor elements is adapted to measure a movement between the sensor and the surface, the electronic circuit being adapted to measure the magnitude of the capacitance or impedance between each sensor element and the outer electrode at chosen points of time, and to combine the measured values to generate a representation of a surface pattern, wherein the sensor elements are coupled to at least one drive circuit providing a varying current or voltage, thus coupling a signal through the sensor elements to the outer electrode, said outer electrode being powered by an AC signal being inverted with respect to the signal coupled to the sensor, so that said electronic circuit measures the magnitude of the capacitance or AC impedance between each of said number of sensor elements being provided with said signal and said outer electrode being provided with the inverted AC signal, wherein the magnitude of the capacitance or AC impedance between each of said number of sensor elements and the outer electrode is measured through a single signal path.