What are the different types of fingerprint sensors/readers?
Capacitive Sensors Capacitive sensors use an array capacitor plates to image the fingerprint. Skin is conductive enough to provide a capacitive coupling with an individual capacitive element on the array. Ridges, being closer to the detector, have a higher capacitance and valleys have a lower capacitance. Some capacitive sensors apply a small voltage to the finger to enhance the signal and create better image contrast. Capacitive sensors can be sensitive to electrostatic discharge (shock) but they are insensitive to ambient lighting and are more resist contamination issues than some optical designs. Optical Sensors Optical sensors use arrays of photodiode or phototransistor detectors to convert the energy in light incident on the detector into electrical charge. The sensor package usually includes a light-emitting-diode (LED) to illuminate the finger. There are two detector types used by optical sensors, charge-coupled-devices (CCD) and CMOS based optical imagers. CCD detectors are sen
