Highly Sensitive Mutual-Capacitive Fingerprint Sensor With Reference Electrode

Abstract

The sensitivity of existing fingerprint sensors (FPSs) can decrease considerably owing to environmental factors and parasitic capacitance. In order to overcome this limitation, this paper proposes a highly-sensitive 300 dpi mutual-capacitive transparent fingerprint sensor (FPS) with uniquely designed reference lines for device security. Specifically, the reference lines of the FPS induce capacitance cancellation. Images of fingertips under dry, wet, and oily surface conditions were obtained in the presence and absence of the reference lines. The results showed that the fingerprints were significantly distorted in anomalous surface environments when the reference lines were not used. However, when the reference lines were used, the sensitivity improved irrespective of the environmental conditions. With the edge-detection processing, the proposed FPS exhibited 9.25 %, 61.49 %, and 8.60 % increase in the ridge sensing improvement (RSI) of dry, oil, and wet condition, respectively, thus significantly enhancing the sensing capability. Therefore, we believe the proposed FPS can increase device security owing to its excellent performance.