Pressure sensing display device

• US 10,496,210 B2
• Filed: 01/21/2018
• Issued: 12/03/2019
• Est. Priority Date: 04/07/2012
• Status: Active Grant

• Current Assignee: Cambridge Touch Technologies, Ltd.
• Original Assignee: Cambridge Touch Technologies, Ltd.
• Inventors: Nathan, Arokia, Lai, Jackson Chi-Sun, Cha, Suk-Bae, Church, Corbin
• Primary Examiner(s): Zheng, Xuemei
• Application Number:
  US15/876,172
• Publication Number:
  US 20180143725A1
• Time in Patent Office: 681 Days
• 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 3/0412 Digitisers structurally integrated in a display
• 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 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• 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

Abstract

A pressure sensing architecture for use with liquid crystal (LC), organic light emitting diode (OLED), electrophoretic, or other similarly fabricated displays. The described architecture includes a bottom TFT structure and a top structure with color filter material, and with liquid crystal, electrophoretic or OLED material provided in between. A piezoelectric or equivalent material is provided within the display assembly. Transmitting and receiving electrodes can be used to electrically bias the piezoelectric or equivalent material, which provides an analog electrical signal in response to incident touch pressure.

Claims

1. A pressure sensing display device, comprising:

a cover layer;

a base layer;

a plurality of display pixels provided above the base layer and below the cover layer;

a plurality of pressure sensing elements provided above the base layer, wherein each of the pressure sensing elements comprises an electrode and at least a portion of a layer of piezoelectric material; and

at least one detection circuit comprising;

an integrator having an integrator input coupled to the electrode of at least one of the plurality of pressure sensing elements and an integrator output, wherein the integrator provides an integrated value of a sensed output of the at least one of the plurality of pressure sensing elements on the integrator output;

and,

a controller, wherein the controller detects a blanking interval of the display pixels, and wherein each pressure sensing element is addressed during the blanking interval.

2. The device of claim 1, wherein an integrated circuit layer is provided above the base layer, and the at least one detection circuit comprises one or more thin film transistors of the integrated circuit layer.

3. The device of claim 1, wherein the integrator output is coupled to an input of at least one amplifier.

4. The device of claim 1, further comprising at least one amplifier which is a charge amplifier, and wherein charge at the integrator output is coupled to an input of the at least one amplifier by an addressing transistor.

5. The device of claim 1, wherein an electrode of a pressure sensing portion of the pressure sensing element is resettable by a reset transistor.

6. The device of claim 1, further comprising an insulating layer provided between the pressure sensing elements and the base layer.

7. The device of claim 1, further comprising an insulating layer provided between multiple layers of pressure sensing elements and the base layer.

8. The device of claim 1, wherein the pressure sensing elements are provided in a layer above the display pixels.

9. The device of claim 1, wherein the pressure sensing elements are provided in a layer below the display pixels.

10. The device of claim 1, wherein the pressure sensing elements are substantially co-planar with the display pixels.

11. The device of claim 1, wherein the display pixels are arranged in a grid, and wherein the pressure sensing elements replace display pixels in the grid at selected intervals.

12. The device of claim 1, wherein the display pixels are arranged in a first grid, and wherein the pressure sensing elements are arranged in a second grid.

13. The device of claim 1, wherein the layer of piezoelectric material is monolithic and common to each of the pressure sensing elements.

14. The device of claim 1, wherein each of the pressure sensing elements is configured to convert a pressure of a force applied to the pressure sensing element into a sensed output at the electrode based on the force applied to the pressure sensing element, wherein the sensed output is generated at least in part by a piezoelectric effect from deformation of the layer of piezoelectric material.

15. The device of claim 1, further comprising an addressing switch having a switch input coupled to the integrator output and a switch output coupled to a charge amplifier, wherein the addressing switch is addressable to be switched off to disconnect the integrator output from the charge amplifier and cause the integrator to store a charge generated by the sensed output of the at least one of the plurality of pressure sensing elements as the integrated value, and addressable to be switched on and provide the integrated value on the integrator output to the switch output, wherein the stored charge is proportional to the pressure of a force applied to the at least one of the plurality of pressure sensing elements.

16. The device of claim 15, further comprising a charge amplifier having an amplifier output and, an amplifier input coupled to the switch output, the switch output providing a current to the charge amplifier input, wherein when the addressing switch is in the on state, the integrator output is connected to the amplifier input and an increase in the current at the input of the charge amplifier caused by the integrated value causes a change in the voltage on the amplifier output indicative of the force causing the sensed output on the at least one of the plurality of pressure sensing elements.

17. A method of pressure sensing in a display device including a plurality of display pixels provided above a base layer and below a cover layer of the display device and a plurality of pressure sensing elements above the base layer, wherein each of the pressure sensing elements comprises an electrode and at least a portion of a layer of piezoelectric material, the method comprising:

converting a pressure of a force applied to at least one pressure sensing element of the plurality of pressure sensing elements into a sensed force output at the electrode of the at least one pressure sensing element, wherein the sensed force output is generated by a piezoelectric effect from deformation of the layer of piezoelectric material;

integrating the sensed force output of the at least one pressure sensing element using an integrator to provide an integrated value of the sensed force output on an output of the integrator;

detecting a blanking interval of the display pixels using a controller; and

,

addressing each pressure sensing element during the blanking interval.

18. A method according to claim 17, further comprising providing the sensed force output by turning off an addressing switch to disconnect the output of the integrator from an output of the addressing switch and cause the integrator to store a charge generated by the sensed force output of the at least one pressure sensing element as the integrated value, and wherein the addressing comprises turning on the addressing switch to provide the integrated value on the output of the integrator to the output of the addressing switch, wherein the stored charge is proportional to the pressure of a force applied to the at least one of the plurality of pressure sensing elements.

19. A method according to claim 18, further comprising providing a current on the output of the addressing switch to an input of a charge amplifier that is coupled to the output of the addressing switch, wherein when the addressing switch is in the on state, the integrator output is connected to the input of the charge amplifier and an increase in the current at the input of the charge amplifier caused by the integrated value causes a change in the voltage on the charge amplifier output indicative of the force causing the sensed output on the at least one of the plurality of pressure sensing elements.