CAPACITIVE SENSOR, DEVICE AND METHOD

• US 20120105081A1
• Filed: 11/02/2010
• Published: 05/03/2012
• Est. Priority Date: 11/02/2010
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated), QRG Limited
• Inventors: Yilmaz, Esat, SHAIKH, Jalil
• Granted Patent: US 8,564,314 B2
• Time in Patent Office: Days
• US Class Current: 324/686
• CPC Class Codes: G06F 2203/0338 Fingerprint track pad, i.e. fingerprint sensor used as pointing device tracking the fingertip image
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: Y10T 29/49105 Switch making
• CPC Class Codes: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.

Abstract

Exemplary capacitive sensors may be capable of determining presence and location of a touch and capable of determining a fingerprint pattern.

Claims

1. A capacitive sensor comprising:

a touch sensing area and a fingerprint sensing area;

at least one substrate;

a capacitive touch position sensor, included on the at least one substrate and in the touch sensing area, comprising a plurality of electrodes configured to enable detection of the presence and position of a touch in the touch sensing area; and

a capacitive fingerprint sensor, included on at least one substrate and in the fingerprint sensing area, comprising a plurality of electrodes configured to enable identification of the fingerprint of a finger placed in the fingerprint sensing area.

2. The capacitive sensor according to claim 1, wherein the fingerprint sensing area is outside the touch sensing area.

3. The capacitive sensor according to claim 1, wherein the fingerprint sensing area is within the touch sensing area.

4. The capacitive sensor according to claim 3, wherein electrodes within the fingerprint sensing area may be switched between a fingerprint recognition mode and a touch sensing mode.

5. The capacitive sensor according to claim 4, wherein at least two channels of the fingerprint sensor are combined in operation in the touch sensing mode.

6. The capacitive sensor according to claim 1, wherein:

at least a plurality of the electrodes of the capacitive touch position sensor is included on a surface of the substrate, and

at least a plurality of the electrodes of the capacitive fingerprint sensor is included on the surface of the substrate.

7. The capacitive sensor according to claim 1, wherein a first density of the plurality of electrodes of the capacitive fingerprint sensor is greater than a second density of the plurality of electrodes of the capacitive touch position sensor.

8. The capacitive sensor according to claim 1, wherein a conductive material of the electrodes of the touch position sensor is common to a conductive material of the electrodes of the fingerprint sensor.

9. The capacitive sensor according to claim 8, wherein the common conductive material comprises an opaque conductive material.

10. The capacitive sensor according to claim 8, wherein the common conductive material comprises a transparent conductive material.

11. A sensing device, comprising:

a capacitive sensor comprising;

first electrodes extending in a first direction in a sensing area of the capacitive sensor;

an insulator; and

second electrodes, separated from the first electrodes by the insulator, and extending in the sensing area of the capacitive sensor in a second direction different from the first direction, the first and second electrodes crossing over each other to form capacitive sensing channels in the sensing area of the capacitive sensor,

the first and second electrodes being configured to provide capacitive sensing channels in the sensing area of the capacitive sensor sufficient to enable identification of the fingerprint of a finger placed in the sensing area of the capacitive sensor; and

a control unit coupled to the first and second electrodes of the capacitive sensor and configured to;

process a first number of signals obtained from the capacitive sensing channels in a fingerprint sensing mode to identify the fingerprint of the finger placed in the sensing area of the capacitive sensor, and process a second number of signals obtained from the capacitive sensing channels to detect a touch and determine a position of the detected touch in the sensing area of the capacitive sensor in a touch position sensing mode.

12. The device of claim 11, wherein the control unit is configured such that the second number of signals processed in the touch position sensing mode is smaller than the number of signals processed in the fingerprint sensing mode.

13. The device of claim 12, wherein the control unit is configured to process signals obtained from all of the capacitive sensing channels in the fingerprint sensing mode and to process signals formed by combining signals from groups of the capacitive sensing channels in the touch position sensing mode.

14. A method of forming a capacitive sensor, the method comprising steps of:

forming a first conductive layer, comprising a plurality of first electrodes of a capacitive touch position sensor on at least one substrate in a touch sensing area and a plurality of first electrodes of a capacitive fingerprint sensor on the at least one substrate in a fingerprint sensing area; and

forming a second conductive layer, comprising a plurality of second electrodes of the capacitive touch position sensor on the at least one substrate in the touch sensing area and a plurality of second electrodes of the capacitive fingerprint sensor in the fingerprint sensing area on the at least one substrate;

wherein at least the first and second electrodes of the capacitive fingerprint sensor are formed in such a manner as to provide a density of capacitive sensing channels sufficient for sensing of a fingerprint of a finger touching the fingerprint sensing area.

15. The method of claim 14, wherein:

the substrate is an insulating substrate,

the step of forming the first conductive layer forms the first conductive layer, including both the first electrodes of the capacitive touch position sensor and the first electrodes of the capacitive fingerprint sensor, on a first surface of the insulating substrate,

the step of forming the second conductive layer forms the second conductive layer, including both the second electrodes of the capacitive touch position sensor and the second electrodes of the capacitive fingerprint sensor, on a second surface of the insulating substrate, and

the second surface is different from the first surface so that the substrate provides electrical isolation between electrodes formed by the first conductive layer and electrodes formed by the second conductive layer.

16. The method of claim 14, wherein:

the step of forming the first conductive layer forms the first conductive layer, including both the first electrodes of the capacitive touch position sensor and the first electrodes of the capacitive fingerprint sensor, on a surface of a first substrate, and

the step of forming the second conductive layer forms said second conductive layer, including both the second electrodes of the capacitive touch position sensor and the second electrodes of the capacitive fingerprint sensor, on a second substrate separate from the first substrate.