Stylus for operating a digitizer system

• US 9,874,951 B2
• Filed: 11/03/2015
• Issued: 01/23/2018
• Est. Priority Date: 11/03/2014
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Stern, Yuval
• Primary Examiner(s): Taylor, Jr., Duane N
• Application Number:
  US14/930,815
• Publication Number:
  US 20160124530A1
• Time in Patent Office: 812 Days
• Field of Search: None
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• 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 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

An apparatus includes a housing, a tip configured to move with respect to the housing based on contact pressure applied the tip, and a circuit. The circuit detects pressure applied on the tip based on movement of the tip. The circuit includes a variable current source configured to drive a sensor, a transimpedance amplifier (TIA) configured to receive current from the sensor and an analog to digital converter configured to sample output from the TIA.

Claims

1. An apparatus comprising:

a housing;

a tip configured to move with respect to the housing based on contact pressure applied the tip;

a capacitive based sensor configured to vary capacitance based on movement of the tip, wherein the capacitive based sensor is associated with a sub-circuit including;

a current mirror configured to invert a pulse polarity of the current source; and

a resistor configured to detect current drained from the current mirror; and

a circuit configured to detect pressure applied on the tip based on movement of the tip, wherein the circuit includes;

a current source configured to drive the sensor, wherein the current source is variable;

a transimpedance amplifier (TIA) configured to receive current from the sensor; and

an analog to digital converter configured to sample output from the TIA.

2. The apparatus of claim 1, wherein amplitude of the output decreases with increase contact pressure applied on the tip.

3. The apparatus of claim 1, wherein the capacitive based sensor includes a first electrode of the capacitor that moves with respect to a second electrode based on the movement of the tip.

4. The apparatus of claim 1, wherein the capacitive based sensor includes a deformable electrode that deforms based on the contact pressure applied on the tip.

5. The apparatus of claim 4, wherein the deformable electrode is an elastomer formed with a protrusion.

6. The apparatus of claim 5, wherein the deformable electrode is formed with at least one protrusion.

7. The apparatus of claim 1, wherein the capacitive based sensor comprises:

a first electrode coated with solid dielectric layer, wherein a portion of the dielectric layer is patterned with a conductive pad that is exposed;

a second electrode formed at least in part with elastic material, wherein the second electrode contacts the conductive pad patterned on the dielectric layer; and

a support element that moves together with the tip of the apparatus and presses against the second electrode in response to pressure applied on the tip.

8. The apparatus of claim 7, wherein the first electrode is embedded in a printed circuit board assembly (PCBA) and the conductive pad is patterned on a surface of the PCBA.

9. The apparatus of claim 8, wherein the first electrode is patterned on a first layer of the PCBA and the dielectric layer is a second layer of the PCBA, which coats the first layer of the PCBA.

10. The apparatus of claim 8, wherein the PCBA is fixed to the housing.

11. The apparatus of claim 7, wherein the second electrode is supported by the support element that that moves together with the tip.

12. The apparatus of claim 1, wherein the sub-circuit comprises a capacitor and resistor configured to match input impedance to the TIA.

13. The apparatus of claim 1, wherein the circuit includes a variable gain and voltage offset for the TIA.

14. The apparatus of claim 1, wherein the variable gain and voltage offset is adjusted based on the sensor.

15. The apparatus of claim 1, wherein the output based on the movement of the tip is non-linear.

16. The apparatus of claim 1, wherein both the housing and the tip include a conductive portion and wherein the tip is configured to be electrically connected to the conductive portion of the housing based on contact pressure being below a defined threshold.

17. The apparatus of claim 16, wherein the tip is configured to be electrically disconnected to the conductive portion of the housing based on contact pressure being above the defined threshold.