Capacitance detection device used for fingerprint identification and fingerprint identification device provided with same

Abstract

The invention discloses a capacitance detection device used for fingerprint identification, comprising a detection screen, a conductor frame and a detection device. The detection screen comprises a plurality of detection units, and each detection unit comprises a first conductor layer, a second conductor layer, a third conductor layer, and a fourth conductor layer. The induction capacitance can be generated by the first conductor layer and a finger touching the detection screen. The feedback capacitance can be generated between the first conductor layer and the second conductor layer, and the integral capacitance can be generated between the third conductor layer and the fourth conductor layer. When the finger contacts the detection screen, the finger is electrically connected with the conductor frame. The detection device is used to charge the induction capacitance and the feedback capacitance in the sampling phase, and can be used to measure and control the transfer of the charges of the induction capacitance and the feedback capacitance to the integral capacitance in the integral phase, and at the same time, can be used to measure the voltage variable quantity of the integral capacitance in the integral phase, and can be used to calculate the induction capacitance according to the voltage variable quantity. The capacitance detection device is advantageous in that the fingerprint detection accuracy can be improved, and at the same time, the circuit noises can be effectively reduced, and the power consumption and the area of the circuit can be reduced. The invention also discloses a fingerprint identification device.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a capacitance detection device for fingerprint identification and a fingerprint identification device with the capacitance detection device for fingerprint identification. Background technique [0002] At present, in the process of fingerprint identification, the fingerprint sensor and the finger contact part of capacitive sensor technology are mainly used, that is, the detection panel. The detection panel is composed of a plurality of tiny detection units, and a detection unit can be called a pixel. The detection pixels may be two-dimensionally distributed. When fingerprint identification is performed, the finger is placed on the detection panel. Due to the fingerprint path, the crests directly touch the detection panel, while the valleys have a short distance from the detection panel. This distance corresponds to the depth of the valleys. By identifying this distance, the ...

AI Technical Summary

Problems solved by technology

[0004] In the current fingerprint sensor implemented with semiconductor sensing capacitors, the upper layer structure facing the finger usually includes multiple conductor layers made of metal, and there are corresponding isolation layers between these conductor layers. The uppermost conductor layer is corresponding to the finger. The fingerprint detection plate, the capacitance formed between each conductor layer or as a capacitance used to process the fingerprint signal detected by the top layer detection capacitance, such as integral capacitance or as a parasitic capacitance, but if it is a parasitic capacitance, it will affect the fingerprint detection accuracy

[0005] However, the parasitic capacitance not only exists between each conductor layer, but also exists between each adjacent top detection electrode, each conductor layer and the ground.

The influence of parasitic capacitance on the detection accuracy mainly comes from two aspects: On the one hand, these parasitic capacitances are usually connected in parallel with the detection capacitance. For example, due to the existence of parasitic capacitance Cp, the input signal changes from Vin to Vin*Cf / (Cf +Cp), the parasitic capacitance Cp is usually greater than the capacitance Cf formed by the fingerprint, which will significantly reduce the accuracy of fingerprint detection; on the other hand, the parasitic capacitance usually couples the noise from the substrate to the detection capacitance, reducing the accuracy of fingerprint detection

Images