Force sensing in a touch display
Embodiments described herein include a display device that includes a display substrate coupled to a frame. A stiffener substrate is also coupled to the frame. A first force sensing element is disposed on the stiffener substrate, and the stiffener substrate is disposed between the first force sensing element and the display substrate. The display device also includes a second force sensing element, where a distance between the first force sensing element and the second force sensing element decreases when the display substrate is deflected.
1. A display device, comprising:
a display substrate;
a frame disposed below and secured to the display substrate, the frame being configured to deflect when a force is applied to the display substrate;
a force sensor layer disposed below the frame, the force sensor layer comprising at least one first force sensing element;
a stiffener substrate disposed below the frame and above the force sensor layer, wherein the stiffener substrate is stiffer than the force sensor layer to cause the force sensor layer to move in sync with the display substrate and the frame when the force is applied to the display substrate;
one or more intervening layers having edges secured to the frame, wherein the one or more intervening layers are disposed between the display substrate and the stiffener substrate and contact the stiffener substrate along an interface, the one or more intervening layers being configured to bend or compress under the application of force to transmit the force to the stiffener substrate along the interface; and
a second force sensing element, wherein a distance between the first force sensing element and the second force sensing element changes relative to a size of the force applied to the display substrate.
2. The display device of claim 1 , wherein the stiffener substrate is a metal material.
3. The display device of claim 1 , wherein the stiffener substrate comprises a concave, convex, or flat shape.
4. The display device of claim 1 , wherein the one or more intervening layers comprises one or more optical layers.
5. The display device of claim 1 further comprising:
a processing system configured to drive the first force sensing element for absolute capacitance sensing to detect changes in absolute capacitive coupling between the first force sensing element and the second force sensing element.
6. The display device of claim 1 further comprising:
a processing system configured to drive the second force sensing element for absolute capacitance sensing to detect changes in absolute capacitive coupling between the first force sensing element and the second force sensing element.
7. The display device of claim 1 further comprising:
a processing system configured to drive the first force sensing element for transcapacitive sensing to detect changes in capacitive coupling between a transmitter electrode of the first force sensing element and a receiver electrode of the second force sensing element.
8. The display device of claim 1 further comprising:
a processing system configured to drive the first force sensing element for transcapacitive sensing to detect changes in capacitive coupling between a receiver electrode of the first force sensing element and a transmitter electrode of the second force sensing element.
9. The display device of claim 1 further comprising:
a processing system configured to drive the first force sensing element for transcapacitive sensing to detect changes in capacitive coupling between a transmitter electrode of the first force sensing element and a receiver electrode of the first force sensing element.
10. The display device of claim 1 further comprising:
a processing system configured to drive the first force sensing element for transcapacitive sensing to detect changes in capacitive coupling between a transmitter electrode of the second force sensing element and a receiver electrode of the second force sensing element.
11. The display device of claim 1 , wherein the second force sensing element is coupled to a mid-frame of an input device.
12. An input device, comprising:
a plurality of capacitive sensing electrodes configured to receive a signal; and
a display device coupled to the plurality of capacitive sensing electrodes, the display device comprising:
a display substrate;
a frame disposed below and secured to the display substrate, the frame being configured to deflect when a force is applied to the display substrate;
a force sensor layer disposed below the frame, the force sensor layer comprising at least one first force sensing element;
a stiffener substrate disposed below the frame and above the force sensor layer, wherein the stiffener substrate is stiffer than the force sensor layer to cause the force sensor layer to move in sync with the display substrate and the frame when the force is applied to the display substrate;
one or more intervening layers having edges secured to the frame, wherein the one or more intervening layers are disposed between the display substrate and the stiffener substrate and contact the stiffener substrate along an interface, the one or more intervening layers being configured to bend or compress under the application of force to transmit the force to the stiffener substrate along the interface; and
a second force sensing element, wherein a distance between the first force sensing element and the second force sensing element changes relative to a size of the force applied to the display substrate.
13. The input device of claim 12 , wherein the one or more intervening layers comprises one or more optical layers.
14. The input device of claim 12 , wherein the display substrate is a thin film transistor (TFT) substrate.
15. The input device of claim 12 , wherein the first force sensing element comprises at least one transmitter electrode and the second force sensing element comprises at least one receiver electrode.
16. The input device of claim 12 , wherein the first force sensing element comprises at least one receiver electrode and the second force sensing element comprises at least one transmitter electrode.
17. The input device of claim 12 , wherein the first force sensing element comprises at least one transmitter electrode and at least one receiver electrode.
18. The input device of claim 12 , wherein the second force sensing element comprises at least one transmitter electrode and at least one receiver electrode.
19. The input device of claim 12 further comprising:
a processing system configured to drive the first force sensing element for absolute capacitance sensing to detect changes in absolute capacitive coupling between the first force sensing element and the second force sensing element.
20. The input device of claim 12 further comprising:
a processing system configured to drive the second force sensing element for absolute capacitance sensing to detect changes in absolute capacitive coupling between the first force sensing element and the second force sensing element.
21. An input device for force sensing, comprising:
a display substrate;
a frame disposed below and secured to the display substrate, the frame being configured to deflect when a force is applied to the display substrate;
a force sensor layer disposed below the frame, the force sensor layer comprising at least one first force sensing element;
a stiffener substrate disposed below the frame and above the force sensor layer, wherein the stiffener substrate is stiffer than the force sensor layer to cause the force sensor layer to move in sync with the display substrate and the frame when the force is applied to the display substrate;
one or more intervening layers having edges secured to the frame, wherein the one or more intervening layers are disposed between the display substrate and the stiffener substrate and contact the stiffener substrate along an interface, the one or more intervening layer being configured to bend or compress under the application of force to transmit the force to the stiffener substrate along the interface;
one or more processors; and
a memory storing instructions that, when executed by the one or more processors, cause a processing system to:
drive first voltages to the display substrate;
drive second voltages to the first force sensing element of the force sensor layer; and
receive signals from a second force sensing element, wherein a distance between the first force sensing element and the second force sensing element changes relative to a size of the force applied to the display substrate.
22. The input device of claim 21 , wherein the one or more intervening layers comprises one or more optical layers.