Dynamic shield electrode of a stylus

• US 8,878,823 B1
• Filed: 03/27/2012
• Issued: 11/04/2014
• 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
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): RITCHIE, DARLENE M
• Application Number:
  US13/431,425
• Time in Patent Office: 952 Days
• Field of Search: 345156-179, 178 1801- 2004, 361/816, 382/187
• US Class Current: 345/179
• 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.

Claims

1. An apparatus comprising:

a 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 the object;

a tip shield coupled with the stylus housing and extending from the end, wherein the tip shield is configured to receive a transmit (TX) potential;

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, wherein the first mode and the second mode are not performed concurrently; and

a processor configured to instruct the switch to electrically couple the tip shield to the conductive tip in the first mode if the force sensor detects that the conductive tip is not in contact with the object, and configured to instruct the switch to electrically isolate the tip shield from the conductive tip in the second mode if the force sensor detects that the conductive tip is in contact with the object.

2. The apparatus of claim 1, 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.

3. The apparatus of claim 1, further comprising a transmit (TX) drive circuit coupled to the processor.

4. The apparatus of claim 3, wherein the TX drive circuit is configured to transmit a TX potential in the first mode to the tip shield and to the conductive tip if the force sensor detects that the conductive tip is not in contact with the object.

5. The apparatus of claim 3, wherein the TX drive circuit is configured to transmit a TX potential in the second mode to the conductive tip if the force sensor detects that the conductive tip is in contact with the object.

6. A method comprising:

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

electrically coupling a tip shield to the conductive tip in a first mode, wherein the tip shield is configured to receive a transmit (TX) potential;

electrically isolating the tip shield from the conductive tip in a second mode;

instructing a switch which is coupled to the tip shield and the conductive tip to electrically couple the tip shield to the conductive tip in the first mode if a force sensor detects that the conductive tip is not in contact with the object;

instructing the switch to electrically isolate the tip shield from the conductive tip in the second mode if the force sensor detects that the conductive tip is in contact with the object; and

wherein the first mode and the second mode are not performed concurrently.

7. The method of claim 6, 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.

8. 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 force sensor coupled to the conductive tip and configured to detect proximity of the conductive tip with an object;

a tip shield coupled with the stylus housing and extending from the end;

a switch electrically coupled to the tip shield and the processing device; and

a processing device configured to transmit a transmit (TX) potential to the conductive tip and the tip shield in a first mode and to electrically isolate the tip shield from the conductive tip in a second mode, wherein the processor is further configured to transmit the TX potential in the first mode to the tip shield and to the conductive tip if the force sensor detects that the conductive tip is not in contact with the object, and configured to electrically isolate the tip shield from the conductive tip in the second mode if the force sensor detects that the conductive tip is in contact with the object, wherein the first mode and the second mode are not performed concurrently.

9. The system of claim 8, wherein the processing device comprises a selection circuit configured to transmit the TX potential in the first mode over first and second outputs to the tip shield and the conductive tip, respectively, and in the second mode to transmit the TX potential over the second output to the conductive tip.

10. The system of claim 8, 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.