US 12,125,307 B2
Biometric skin contact sensor and methods of operating a biometric skin contact sensor
Henricus Derckx, St Asaph (GB); Michael Cowin, St Asaph (GB); Wilhelmus Van Lier, St Asaph (GB); and Toru Sakai, St Asaph (GB)
Assigned to TOUCH BIOMETRIX LIMITED, St. Asaph (GB)
Appl. No. 18/024,864
Filed by TOUCH BIOMETRIX LIMITED, St Asaph (GB)
PCT Filed Sep. 7, 2021, PCT No. PCT/GB2021/052300
§ 371(c)(1), (2) Date Mar. 6, 2023,
PCT Pub. No. WO2022/049400, PCT Pub. Date Mar. 10, 2022.
Claims priority of application No. 2014049 (GB), filed on Sep. 7, 2020; and application No. 2015391 (GB), filed on Sep. 29, 2020.
Prior Publication US 2023/0326231 A1, Oct. 12, 2023
Int. Cl. G06V 40/13 (2022.01); G06F 3/041 (2006.01); G06F 3/044 (2006.01); G06V 40/12 (2022.01)
CPC G06V 40/1306 (2022.01) [G06F 3/041661 (2019.05); G06F 3/0446 (2019.05); G06V 40/1359 (2022.01)] 15 Claims
OG exemplary drawing
 
1. A capacitive biometric skin contact sensor configured to resolve the contours of skin in contact with the sensor, wherein the sensor comprises:
a contact sensing area comprising an array of sensor pixels, wherein each sensor pixel comprises a thin film transistor and a capacitive sensing electrode connected to the thin film transistor;
a plurality of gate drive channels, wherein each gate drive channel is arranged to provide a gate drive signal to one or more of the sensor pixels;
a plurality of read-out channels, wherein each read-out channel is arranged to receive a read-out current from one or more of the sensor pixels, each read-out current being indicative of a proximity to a respective capacitive sensing electrode of a conductive object to be sensed;
a current multiplexer connected to a plurality of the read-out channels to receive read-out currents therefrom; and
an analog to digital converter configured to provide a digital signal based on said read-out currents;
wherein the sensor is configured to control at least one of the current multiplexer and the ADC to switch between operation in a first sensing mode and a second sensing mode;
wherein the sensor comprises a current mirror assembly connected to the multiplexer to receive an input current therefrom and to provide a selected gain to the input current to provide the output current,
wherein the sensor is configured to switch between operation in the first sensing mode and operation in the second sensing mode by controlling operation of at least one of: (i) the multiplexer, (ii) the current mirror assembly, and (iii) the ADC, and
wherein the analog to digital converter comprises a dual slope integrator arranged to receive, as its input, either an output current or a reference voltage, wherein said output current is based on a current from the multiplexer and is applied as the input to the dual slope integrator for a charging time period, and wherein controlling operation of the ADC to switch between operation in the first sensing mode and the second sensing mode comprises controlling operation of the dual slope integrator.