System for real time finger surface pattern measurement

A system for measuring patterns in a surface, especially in finger surfaces, the system comprising a number of sensor electrodes being provided with an electrically insulating material over which the surface is to be moved, and at least one stimulation electrode for providing a varying current or voltage between the stimulation electrode and the number of sensors through the surface,

• characterized in that the sensor electrodes constitutes an essentially linear array,
• that the stimulation electrode is positioned separately from the array of sensor electrodes,
• that the system comprises a generator coupled to the stimulation electrode for applying a current or voltage with a varying amplitude or phase to the surface, and
• that the system comprises a measuring unit coupled to the sensor electrodes for, during the application of the current or voltage, measuring the impedance at the sensor electrodes in a time sequence and calculating values of predetermined characteristics of the surface and combining the calculated values for the sensor electrodes over the time sequence for generating a representation of the surface pattern.