A new sensing and digital-conversion scheme with adaptive image-quality adjustment for a fingerprint sensor chip

A new fingerprint sensing and digital-conversion scheme is proposed. In this scheme, transforming the sensed signal to a time axis widens the dynamic range of the signal, and the transformed signal is converted to the digital signal with variable range and offset. These features make it possible to sense various fingerprints clearly. We also propose a flow that adjusts the quality of the fingerprint image adaptively. The effectiveness of the scheme on sensing fingerprints clearly was confirmed by a test chip fabricated using 0.5-/spl mu/m CMOS/sensor process. This scheme assists in precise user identification for a safe and comfortable networked world.