Stylus Tip Shape

• US 20150160744A1
• Filed: 03/27/2014
• Published: 06/11/2015
• Est. Priority Date: 12/05/2013
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Mohindra, Rishi, Hoshtanar, Oleksandr, Klein, Hans
• Granted Patent: US 9,298,285 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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

Abstract

Stylus tip configurations may reduce shadow effect of the stylus tip on capacitance measurements by reducing capacitive coupling between undesired portions of the stylus tip and the capacitive sensing surface. Additionally signal-to-noise ratio (SNR) of a stylus on a plurality of capacitance sensing electrodes may be improved by reducing the self capacitance between the stylus tip and the receive electrodes of a mutual capacitance touch screen.

Claims

1. A stylus tip of a stylus comprising:

a first conductive element disposed substantially at a point of contact between the stylus tip and a capacitive sensing surface, wherein the first conductive element is configured to produce a field distribution having a greater density at locations substantially opposite a tilt direction of the stylus and independent of the axial rotation of the stylus;

an elongated second conductive element configured to couple the first conductive element to a body of the stylus, the second conductive element substantially narrower than the first conductive element; and

a dielectric material disposed directly around the second conductive element, the dielectric material configured to provide a pen shape to the stylus tip.

2. The stylus tip of claim 1, wherein the first conductive element is a spheroid.

3. The stylus tip of claim 1, wherein the second conductive element is a wire.

4. The stylus tip of claim 1, wherein the second conductive element includes an arc in a region between the first conductive element and a shaft of the body of the stylus.

5. The stylus tip of claim 1, wherein the first conductive element is an ellipsoid cap.

7. The stylus tip of claim 1, wherein the first conductive element comprises:

a rigid conductor coupled to the second conductive element; and

a flexible conductor disposed substantially surrounding the rigid conductor, the flexible conductor configured to deform against the capacitive sensing surface by an application of pressure.

8. The stylus tip of claim 7, wherein the flexible conductor is configured to form a contact circle on the capacitive sensing surface, the contact circle having a diameter proportional to a force applied to the stylus tip.

9. The stylus tip of claim 7, wherein the second conductive element has a length equal to at least three times a width of the first conductive element.

10. The stylus tip of claim 1, wherein the second conductive element is electrically connected to the first conductive element.

11. The stylus tip of claim 1, further comprising a conductive float, and wherein the dielectric material is a liquid disposed within a vessel, the vessel having a shape to provide a pen shape to the stylus tip.

21. The stylus tip of claim 1, wherein the dielectric material is disposed directly around an entire length of the second conductive element.

6. (canceled)

12. A stylus tip of a passive stylus comprising:

a first conductor configured to capacitively couple to a plurality of mutual capacitance sensing electrodes disposed on a sensing surface, wherein the first conductor is configured to produce a field distribution having a greater density at locations substantially opposite a tilt direction of the stylus and independent of the axial rotation of the stylus;

a second conductor coupled to the first conductor and to the body of the stylus, the second conductor substantially narrower than the first conductor;

an LC filter coupled between the second conductor and the body of the stylus; and

a dielectric material disposed directly around the second conductor, the dielectric material configured to provide a pen shape to the stylus tip.

13. The stylus tip of claim 12, wherein the LC filter has a resonance frequency substantially equal to a transmit frequency of a transmit (TX) signal of the mutual capacitance sensing electrodes.

14. The stylus tip of claim 12, wherein the LC filter is configured to have a high impedance for frequencies substantially not equal to a transmit frequency of a transmit (TX) signal of the mutual capacitance sensing electrodes.

15. The stylus tip of claim 12, further comprising a conductive float, and wherein the dielectric material is a liquid disposed within a vessel, the vessel having a shape to provide a pen shape to the stylus tip.

22. The stylus tip of claim 12, wherein the second conductor includes an elongated shape and the dielectric material is disposed directly around an entire length of the second conductor.

16. A method comprising:

forming a conductive element of a stylus tip, the conductive element comprising;

a first portion having a first width, wherein the first portion is configured to produce a field distribution having a greater density at locations substantially opposite a tilt direction of the stylus and independent of the axial rotation of the stylus, and

a second portion having a second width substantially smaller than the first width and coupled to a body element of the stylus; and

forming a dielectric material directly around the second portion of the conductive element, the dielectric material configured to prove a pen shape to the stylus tip.

17. The method of claim 16, wherein forming the first conductive element comprises;

forming a rigid conductor coupled as the first portion of the conductive element; and

forming a flexible conductor around the rigid conductor, the flexible conductor configured to deform against a capacitive sensing surface with the application of pressure to the flexible conductor.

18. The method of claim 16, wherein forming the dielectric material comprises:

forming a vessel around the second portion of the conductive element, the vessel having a shape substantially similar to the shape of a pen and hollow;

disposing a float within the vessel, the float having a first density; and

filling the vessel with a dielectric liquid having a second density, such that the float is configure to move through the dielectric liquid and within the vessel with a change in orientation of the stylus tip.

19. The method of claim 16, wherein forming the first portion of the conductive element comprises forming a ellipsoid cap, a concave portion of which faces the second portion of the conductive element and a convex portion of which faces a capacitive sensing surface.

20. (canceled)