Stylus tip shape

• US 9,298,285 B2
• Filed: 03/27/2014
• Issued: 03/29/2016
• Est. Priority Date: 12/05/2013
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Mohindra, Rishi, Hoshtanar, Oleksandr, Klein, Hans
• Primary Examiner(s): EURICE, MICHAEL
• Application Number:
  US14/227,021
• Publication Number:
  US 20150160744A1
• Time in Patent Office: 733 Days
• Field of Search: 345/179, 178/18.06, 178/19.03
• 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 coupled to a second conductive element and collectively configured to resemble an umbrella shape, wherein;

the first conductive element is disposed substantially at a point of contact between the stylus tip and a capacitive sensing surface, wherein the first conductive element includes a convex surface facing the capacitive sensing surface and a concave surface facing away from the capacitive sensing surface, and 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

the second conductive element is configured to couple the first conductive element at the concave surface of the first conductive element to a body of the stylus, wherein the second conductive element is elongated and is 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 second conductive element is a wire.

3. The stylus tip of claim 1, wherein the second conductive element includes an arc.

4. The stylus tip of claim 1, wherein a shape of a cross section of the first conductive element perpendicular to the axis of the stylus is an ellipse or a circle.

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

6. 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.

7. The stylus tip of claim 1, wherein the dielectric material is disposed at least within a volume contained within the concave surface of the first conductive element the and in direct contact with the concave surface.

8. 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.

9. The stylus tip of claim 8, 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.

10. The stylus tip of claim 8, wherein the second conductive element has a length equal to at least three times a width of the first conductive element.

11. A stylus tip of a passive stylus comprising:

a first conductor coupled to a second conductor and collectively configured to resemble an umbrella shape, wherein;

the first conductor is configured to capacitively couple to a plurality of mutual capacitance sensing electrodes disposed on a sensing surface, wherein the first conductor includes a convex surface facing the sensing surface and a concave surface facing away from the sensing surface and 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;

the second conductor coupled to the first conductor at the concave surface of the first conductor and to the body of the stylus, wherein the second conductor is 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 around and in direct contact with the second conductor, the dielectric material configured to provide a pen shape to the stylus tip.

12. The stylus tip of claim 11, 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.

13. The stylus tip of claim 11, 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.

14. The stylus tip of claim 11, 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.

15. The stylus tip of claim 11, wherein the second conductor includes an elongated shape and the dielectric material is disposed directly around an entire length of the second conductor.

16. The stylus tip of claim 11, wherein the LC filter includes a capacitor and an inductor coupled in series between the second conductor and the body of the stylus.

17. A method comprising:

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

a first portion coupled to a second portion and collectively configured to resemble an umbrella shape, wherein;

the first portion has a first width, includes a convex surface facing a capacitive sensing surface and a concave surface which facing away from the capacitive sensing surface, and 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

the second portion has a second width substantially smaller than the first width, is coupled to the first portion at the concave surface of the first portion, and is coupled to a body element of the stylus; and

forming a dielectric material around and in direct contact with the second portion of the conductive element, the dielectric material configured to prove a pen shape to the stylus tip.

18. The method of claim 17, 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.

19. The method of claim 17, 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.