Determining forces of contacts between styluses and objects

• US 9,218,073 B1
• Filed: 12/03/2013
• Issued: 12/22/2015
• Est. Priority Date: 07/27/2011
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Kremin, Viktor, Ryshtun, Andriy, Wright, David G.
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): Ritchie, Darlene M
• Application Number:
  US14/095,930
• Time in Patent Office: 749 Days
• Field of Search: 345173-179, 178 1801- 2004
• US Class Current: 1/1
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• 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 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04114 Touch screens adapted for alternating or simultaneous interaction with active pens and passive pointing devices like fingers or passive pens
• CPC Class Codes: G06F 3/033 Pointing devices displaced or positioned by the user , e.g. mice, trackballs, pens or joysticks; Accessories therefor digitisers characterised by the transducing means G06F3/041
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0414 using force sensing means to determine a position
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• 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

An apparatus comprising a stylus with a dynamically switch tip shield is provided. The apparatus includes an elongated stylus housing having an end, a conductive tip disposed at least partially inside the stylus housing and extending from the end, a force sensor coupled to the conductive tip and configured to detect contact between the conductive tip and an object, a tip shield coupled with the stylus housing and extending from the end, and a switch coupled to the tip shield and the conductive tip. The force sensor may be an inductive sensor, a capacitive sensor, a piezo sensor, a force sensing resistor sensor, or an optical sensor.

Claims

1. An apparatus comprising:

a stylus housing having an end;

a transmit (TX) drive circuit disposed at least partially inside the stylus housing;

a tip shield configured to be coupled to the TX drive circuit to receive a TX potential from the TX drive circuit;

a conductive tip disposed at least partially inside the stylus housing and extending from the end, the conductive tip configured to receive the TX potential from the TX drive circuit and capacitively couple a transmit signal to a sense array when the tip shield is coupled to the TX drive circuit, when the tip shield is not coupled to the TX drive circuit, and without a change in contact between the conductive tip and a touch surface;

a force sensor coupled to the conductive tip and configured to measure a force of a contact between the conductive tip and the touch surface; and

a switch configured to electrically couple the tip shield to the conductive tip when the measured force of contact indicates that the conductive tip is not in contact with the touch surface.

2. The apparatus of claim 1, wherein the force sensor comprises an inductive sensor and wherein the inductive sensor is configured to measure the force of the contact by measuring a change of an impedance of a sensing coil in the inductive sensor.

3. The apparatus of claim 1, wherein the force sensor comprises a capacitive sensor and wherein the capacitance sensor is configured to measure the force of the contact by measuring a change in a capacitance of a capacitor in the capacitive sensor.

4. The apparatus of claim 1, wherein the force sensor comprises a piezo sensor and wherein the piezo sensor is configured to measure the force of the contact by measuring a voltage generated by a piezoelectric material in the piezo sensor.

5. The apparatus of claim 1, wherein the force sensor comprises a force sensing resistor sensor and wherein the force sensing resistor sensor is configured to measure the force of the contact by measuring a change in resistance of a resistor in the force sensing resistor sensor.

6. The apparatus of claim 1, wherein the force sensor comprises an optical sensor, and wherein the optical sensor is configured to measure the force of the contact by measuring an amount of light from a light source in the optical sensor.

7. The apparatus of claim 1, wherein the tip shield is coupled with the stylus housing and extends from the end and further comprising a switch coupled to the tip shield and the conductive tip, wherein the switch is configured to electrically couple the tip shield to the conductive tip in a first mode and to electrically isolate the tip shield from the conductive tip in a second mode.

8. The apparatus of claim 7, further comprising:

a processing device configured to;

instruct the switch to electrically couple the tip shield to the conductive tip when the force sensor detects that the conductive tip is not in contact with the touch surface; and

instruct the switch to electrically isolate the tip shield from the conductive tip when the force sensor detects that the conductive tip is in contact with the touch surface.

9. The apparatus of claim 8, comprising the transmit (TX) drive circuit coupled to the processing device, wherein the TX drive circuit is configured to transmit the TX potential in the first mode to the tip shield and to the conductive tip when the force sensor detects that the conductive tip is not in contact with the touch surface and wherein the TX drive circuit is configured to transmit the TX potential in the second mode to the conductive tip when the force sensor detects that the conductive tip is in contact with the touch surface.

10. A method comprising:

detecting contact between a conductive tip of a stylus and an object;

determining a force of the contact between the conductive tip of the stylus and the object;

providing, by a transmit (TX) circuit of the stylus, a TX potential to a tip shield of the stylus and the conductive tip;

capacitively coupling a transmit signal, which is responsive to the TX potential, from the tip shield and the conductive tip to a sense array; and

instructing a switch to electrically couple the tip shield to the conductive tip when a force sensor detects that the conductive tip is not in contact with the object.

11. The method of claim 10, further comprising instructing the switch to electrically isolate the tip shield from the conductive tip when the force sensor detects that the conductive tip is in contact with the object.

12. The method of claim 10, wherein the force sensor is selected from the group consisting of an inductive sensor, a capacitive sensor, a piezo sensor, a force sensing resistor sensor, and an optical sensor.

13. A system comprising:

a stylus housing having an end;

a conductive tip disposed at least partially inside the stylus housing and extending from the end;

a tip shield;

a force sensor coupled to the conductive tip and configured to measure a force of a contact between the conductive tip and a touchscreen;

a processing device within the stylus housing, the processing device configured to provide a transmit (TX) potential to the conductive tip and to the tip shield through the conductive tip, the processing device configured to electrically couple the tip shield to the conductive tip when the measured force of contact indicates that the conductive tip is not in contact with the touchscreen, wherein the TX potential is to be capacitively coupled to a sense array of the touchscreen.

14. The system of claim 13, wherein the force sensor comprises an inductive sensor and wherein the inductive sensor is configured to measure the force of the contact by measuring a change of an impedance of a sensing coil in the inductive sensor.

15. The system of claim 13, wherein the force sensor comprises a capacitive sensor and wherein the capacitance sensor is configured to measure the force of the contact by measuring a change in a capacitance of a capacitor in the capacitive sensor.

16. The system of claim 13, wherein the force sensor comprises a piezo sensor and wherein the piezo sensor is configured to measure the force of the contact by measuring a voltage generated by a piezoelectric material in the piezo sensor.

17. The system of claim 13, wherein the force sensor comprises a force sensing resistor sensor and wherein the force sensing resistor sensor is configured to measure the force of the contact by measuring a change in resistance of a resistor in the force sensing resistor sensor.

18. The system of claim 13, wherein the force sensor comprises an optical sensor, and wherein the optical sensor is configured to measure the force of the contact by measuring an amount of light from a light source in the optical sensor.

19. The system of claim 13, wherein the processing device is further configured to transmit the TX potential in a first mode to the tip shield and to the conductive tip when the force sensor detects that the conductive tip is not in contact with the object and wherein the processing device is further configured to transmit the TX potential in a second mode to the conductive tip when the force sensor detects that the conductive tip is in contact with the object.