Fingerprint sensor technology - sensor structure/chip, sensing scheme, and system

This paper describes sensor structure, circuit and system techniques for a capacitive fingerprint sensor LSI and a user authentication system. The LSI must be reliable, sensitive, and tolerant to changes in the sensor surface conditions for capturing clear fingerprint image over long-term use. The LSI features a sensor structure, sensing circuit, calibration circuit and adjustable A/D convener. The system has to provide the controllability of captured fingerprint images to be suitable for identification under various conditions. The system features an adaptive fingerprint-sensing scheme. The fingerprint sensor LSI was fabricated using the 0.5-/spl mu/m CMOS process/sensor process and the fingerprint identification system was developed with the above techniques. The sufficient performance was achieved for a practical user authentication system and the effectiveness of the fingerprint sensor technology was confirmed.