Measuring patterns in biological tissues, such as, for example, the ridge and valley patterns in fingerprints has been performed using a variety of forms of energy ranging from optical energy to ultrasonic energy to electric field energy.  Each of these methods may have advantages and disadvantages.  For example, such methods may include the use of optical measurements, electrical capacitance measurements, pressure measurements, thermal measurements, ultrasonic measurements, and electric field measurements
The structure of human skin includes several layers, the outermost layer of which is an electrical insulator or a dielectric layer called the stratum corneum.  Underneath the insulating layer is an electrically conductive layer.  A fingerprint sensor, for example, an electric field based fingerprint sensor, uses electric fields to capture the shape of the electrically conductive layer.  Images of the fingerprint ridge pattern are generated based upon the captured shape of the electrically conductive layer.