A 390 dpi live fingerprint imager based on feedback capacitive sensing scheme

A single-chip, 200/spl times/200 element sensor array grabs a fingerprint pattern without any optical or mechanical adaptors. Using this integrated sensor the fingerprint is captured at a rate ofl0/Frame/s by pressing the finger skin onto the chip surface. The fingerprint pattern is sampled by capacitive sensors that detect the electric field variation induced by the skin surface. The architecture is integrated in standard 2-metal 0.7 /spl mu/m digital CMOS technology. The idea of using a capacitive sensor array for detecting fingerprints has been suggested, but not implemented. The sensor described here uses a scheme, substantially different from previous approaches, based on feedback capacitance sensing.