Piezoelectric force sensing array

• US 9,262,003 B2
• Filed: 11/04/2013
• Issued: 02/16/2016
• Est. Priority Date: 11/04/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kitchens, Jack C., Schneider, John K., Gojevic, Stephen M.
• Primary Examiner(s): PATEL, PREMAL R
• Application Number:
  US14/071,320
• Publication Number:
  US 20150123931A1
• Time in Patent Office: 834 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 3/04144 using an array of force sensing means position sensing using the local deformation of sensor cells G06F3/0447
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: H04W 52/0254 detecting a user operation or a tactile contact or a motion of the device
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A touch sensing system may include a pressure and force sensing device capable of sensing dynamic pressure or dynamic force applied to a piezoelectric sensing array. In such implementations, an applied force may be detected (and optionally recorded) during a period of time that the force is applied and changing. The force-sensing device may have a sufficiently high resolution to function as a fingerprint sensor. The touch sensing system may include one or more additional components capable of fingerprint sensing, such as an ultrasonic transmitter that allows the device to become an ultrasonic transducer capable of imaging a finger (or another object) in detail. The force-sensing device also may be capable of functioning as an ultrasonic receiver.

Claims

1. A touch sensing system including a force-sensing device, the force-sensing device comprising:

a substrate;

an array of sensor pixel circuits disposed on the substrate;

discrete elements of a piezoelectric film layer, each discrete element corresponding with an individual sensor pixel circuit;

a plurality of pixel input electrodes, each pixel input electrode configured for making an electrical connection between a first side of a discrete element of the piezoelectric layer and one of the sensor pixel circuits;

a receiver bias electrode configured for making an electrical connection with a second side of discrete elements of the piezoelectric layer; and

a control system capable of;

receiving a signal from one or more of the sensor pixel circuits, the signal corresponding to a force applied to one or more discrete elements of the piezoelectric film layer; and

determining a location of an object exerting the force.

2. The touch sensing system of claim 1, wherein each sensor pixel circuit further comprises:

a charge amplifier capable of amplifying charges received from the pixel input electrode.

3. The touch sensing system of claim 1, wherein each sensor pixel circuit further comprises:

a peak detection circuit capable of registering a maximum amount of charge produced by the applied force.

4. The touch sensing system of claim 3, wherein each sensor pixel circuit further comprises:

a reset device capable of removing accumulated charge from the peak detection circuit.

5. The touch sensing system of claim 1, wherein the force-sensing device has a sufficiently high resolution to function as a fingerprint sensor.

6. The touch sensing system of claim 1, further comprising:

an ultrasonic transmitter, wherein the control system is capable of operating the touch sensing system in an ultrasonic imaging mode or a force-sensing mode.

7. The touch sensing system of claim 6, wherein the control system is capable of maintaining the ultrasonic transmitter in an “

off”

state when operating the touch sensing system in a force-sensing mode.

8. The touch sensing system of claim 7, further including a memory system, wherein the control system is capable of capturing a fingerprint image and storing fingerprint image data in the memory system while maintaining the ultrasonic transmitter in the “

off”

state.

9. The touch sensing system of claim 8, wherein the control system is capable of controlling access to one or more devices based, at least in part, on the fingerprint image data.

10. The touch sensing system of claim 6, wherein the force-sensing device is capable of functioning as an ultrasonic receiver when the touch sensing system is operating in the ultrasonic imaging mode.

11. The touch sensing system of claim 6, wherein the control system is capable of detecting a touch or tap received via the force-sensing device and switching on the ultrasonic transmitter in response to the touch or tap.

12. The touch sensing system of claim 1, wherein the substrate is a thin film transistor (TFT) substrate and wherein the sensor pixel circuits include TFT sensor pixel circuits.

13. A mobile display device that includes the touch sensing system of claim 1.

14. The mobile display device of claim 13, wherein the control system is capable of detecting a touch or tap received via the force-sensing device and activating at least one feature of the mobile display device in response to the touch or tap.

15. The mobile display device of claim 14, wherein the control system is capable of:

operating the mobile display device in a sleep mode during periods of inactivity;

detecting a touch or tap received via the force-sensing device; and

waking the mobile display device from the sleep mode in response to the touch or tap.

16. A touch sensing system, comprising:

an ultrasonic receiver including a piezoelectric film layer and an array of sensor pixel circuits;

an ultrasonic transmitter; and

a control system capable of;

receiving, while the ultrasonic transmitter is switched off, a signal from one or more of the sensor pixel circuits of the ultrasonic receiver, the signal corresponding to a force applied to the piezoelectric film layer; and

switching on the ultrasonic transmitter in response to the signal.

17. The touch sensing system of claim 16, wherein the control system is capable of determining a position or a motion of one or more objects corresponding to a plurality of signals received by the control system.

18. A mobile display device including the touch sensing system of claim 16, wherein the control system is capable of:

operating the mobile display device in a sleep mode during periods of inactivity; and

waking the mobile display device from the sleep mode in response to the signal.