FINGERPRINT OR PALMPRINT SENSOR

• US 20170293791A1
• Filed: 09/30/2015
• Published: 10/12/2017
• Est. Priority Date: 10/03/2014
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation), Safran Identity & Security
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation), Safran SA
• Inventors: MAINGUET, Jean-Franois, FOURRE, Joel Yann, SEGURA PUCHADES, Josep
• Granted Patent: US 10,176,357 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1318 using electro-optical elements or layers, e.g. electroluminescent sensing
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger
• CPC Class Codes: G06V 40/1365 Matching; Classification
• CPC Class Codes: G06V 40/1394 using acquisition arrangements
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

The invention relates to a print sensor (160) comprising, on a transparent support substrate, a plurality of elementary acquisition cells (161), each cell comprising a photodetector (PS), a pyroelectric conversion element (PYR), and at least one TFT transistor (RT, SF) connected to both the photodetector (PS) and the pyroelectric conversion element (PYR).

Claims

1. A fingerprint or palmprint sensor comprising:

on a support substrate, a plurality of elementary acquisition cells, each cell comprising a photodetector, a pyroelectric conversion element, and at least one TFT;

an illumination light source; and

a heat source distinct from the light source.

2. The sensor of claim 1, wherein the support substrate is transparent.

3. The sensor of claim 1, wherein the photodetector and the pyroelectric conversion element are connected in parallel.

4. The sensor of claim 1, comprising a circuit capable of controlling the acquisition of a thermal image and the acquisition of an optical image by the sensor cells, the circuit being capable, during the entire optical image acquisition phase, of turning on the light source and of keeping the heat source off and, during the entire thermal image acquisition phase, of keeping the light source off.

5. The sensor of claim 1, comprising a circuit capable of controlling the acquisition of a thermal image and the acquisition of an optical image by the sensor cells, the circuit being capable of implementing the acquisition of the thermal image during part of an integration period of the optical image acquisition phase during which the light source is on.

6. The sensor of claim 1, wherein, in each cell, the photodetector and the pyroelectric conversion element are connected to a capacitive sense node of the cell.

7. The sensor of claim 1, wherein, in each cell, the photodetector and the pyroelectric conversion element are connected to an intermediate node of the cell, the intermediate node being coupled to a capacitive sense node of the cell by a selection transistor, and each cell further comprising:

a reference capacitor connected between the capacitive sense node and a node of application of a control signal; and

an electrode connected to the capacitive sense node, the electrode being coated with a dielectric layer and being intended to form a capacitance with a user'"'"'s skin for a capacitive acquisition of a print image.

8. The sensor of claim 1, wherein the photodetector and the pyroelectric conversion element are connected to a same selection transistor enabling, in the off state, to isolate the photodetector from the pyroelectric element.

9. The sensor of claim 1, wherein the cells are arranged in an array of claim rows and columns, and wherein the heat source is controllable to heat the cells row by row.

10. The sensor of claim 1, wherein the cells are voltage readout cells, each cell comprising:

a capacitive sense node having the photodetector and the pyroelectric conversion element coupled thereto;

a reset transistor coupling the capacitive sense node to a of application of a reset potential; and

a readout circuit comprising a transistor assembled as a follower source, having its gate connected to the sense node, and having its source coupled to an output track of the cell via a readout transistor.

11. The sensor of claim 1, wherein the cells are charge readout cells, each cell comprising:

a capacitive sense node having the photodetector and the pyroelectric conversion element coupled thereto; and

a readout transistor coupling the sense node to an output track of the cell.