Touch fingerprint sensor based on sensor cell isolation technique with pseudo direct signaling

This paper presents a 96 × 96 fingerprint sensor implemented with 0.25 μm standard CMOS technology. The implemented fingerprint sensor is based on a pseudo-direct signaling scheme that does not require an electrode for signal transmission. And the pseudo-direct signaling was combined with sensor cell isolation scheme which controls the unwanted influx of the electric fields effectively. And a pipelined scan technique was applied for fast fingerprint image capture while maintaining SNR performance. It was fabricated with 0.25 μm standard CMOS technology and was molded with 80 μm-thick epoxy after fabrication. The fingerprint sensor was tested with ARM board combined with PC applications. The obtained fingerprint images from the fingerprint sensor were enhanced to reduce the noise of the obtained images by using filtering technique, such as Wiener, 2D Gaussian, and 2D FIR filtering. From the test results, it was concluded that the implemented fingerprint sensor with the isolation scheme worked well without bezel electrode and can be used in biometric authentication systems effectively.