A 600-dpi capacitive fingerprint sensor chip and image-synthesis technique

This paper examines the possibility of a low-cost, high-resolution fingerprint sensor chip. The test chip is composed of 64 x 256 sensing cells (chip size: 2.7 x 10.8 mm(2)), A new detection circuit of charge sharing is proposed, which eliminates the influences of internal parasitic capacitances. Thus, the reduced sensing-capacitor size enables a high resolution of 600 dpi, even using a conventional 0.6-mu m CMOS process. The partial fingerprint images captured are synthesized into a full fingerprint image with an image-synthesis algorithm. The problems and possibilities of this image-synthesis technique are also analyzed and discussed.