New Capacitive Fingerprint Image Acquisition System

Abstract

The invention provides a novel capacitance type fingerprint image acquisition system which comprises a sensing element array, a sensing element array driving circuit, an insulating surface, a comparator array, a programmable reference voltage source and a self-adaptive process algorithm logic circuit, wherein the sensing element array comprises a plurality of sensing elements; the sensing element array driving circuit is used for inputting voltage signals to the sensing element array; the insulating surface covers on the sensing element array and is used as a contact surface of fingers; the comparator array is configured beside the sensing element array and output of the sensing element array is used as the input of the comparator array; the programmable reference voltage source is used as input reference voltage of the comparator array; the self-adaptive process algorithm logic circuit is used for adjusting the programmable reference voltage source in a self-adaptive manner. By adopting the system provided by the invention, the sensitivity of a capacitance sensor can be improved, so that clear fingerprint images of dry, wet, oily and normal fingers can be acquired, and the system is applicable to acquisition of special fingerprint.

Description

technical field [0001] The invention relates to the field of integrated circuit design, in particular to a novel capacitive fingerprint image collection system suitable for special finger collection. Background technique [0002] With the rapid development of electronic automation design, living biometric authentication and identity recognition are more and more used in people's lives. Fingerprint authentication has the highest reliability and cost-effectiveness in biometric authentication, and has become the current biometric authentication. mainstream. At the same time, fingerprint collection technology is also developing rapidly, and a sensor with lower cost and smaller size will occupy a huge market, so sensors with the above advantages have become the focus of current research. Among them, the capacitive sensor has become one of the current mainstream products. [0003] With the gradual maturity of fingerprint technology and the lower and lower costs, it is believed t...

AI Technical Summary

Problems solved by technology

The sensing element structure of this existing capacitive sensor cannot eliminate the background capacitance (the parasitic capacitance from the sensing electrode to its electrode, including the parasitic capacitance from the sensing electrode to the reference electrode, from the sensing electrode to the substrate, etc., and each sensor There may be inconsistencies in the parasitic capacitance of the measuring element), the output signal of the sensing element passes through a comparator or A / D converter to obtain binary or grayscale image information, only by changing the reference capacitance value of the sensing element or changing The size of the shielding capacitor and the connected potential are used to roughly adjust the quality of the fingerprint image. This method has blurred images for fingers that are too wet or too oily. For dry and broken fingers, the collected images are too shallow or The fingerprint pattern cannot be distinguished at all, which limits the application of special fingers. At the same time, if an unclear fingerprint image is collected, it will have a certain impact on subsequent fingerprint processing and recognition.

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