Calibrating a Digital Stylus

• US 20110291998A1
• Filed: 05/27/2010
• Published: 12/01/2011
• Est. Priority Date: 05/27/2010
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Mackenzie, Andrew, Adams, Guy
• Granted Patent: US 9,563,287 B2
• Time in Patent Office: Days
• US Class Current: 345/179
• CPC Class Codes: G06F 3/0321 by optically sensing the absolute position with respect to a regularly patterned surface forming a passive digitiser, e.g. pen optically detecting position indicative tags printed on a paper sheet constructional details of pen-shaped pointing devices G06F3/03545, G06F3/03542, G06F3/037
• CPC Class Codes: G06F 3/03545 Pens or stylus

Abstract

A method for calibrating a digital stylus comprising imaging a portion of a calibration pattern area of a data encoding pattern using an imaging module of the stylus in order to generate calibration data representing an error in alignment for the stylus, and using the calibration data to adjust subsequent measurements from the stylus in order to compensate for the error.

Claims

1. A method for calibrating a digital stylus comprising:

imaging a portion of a calibration pattern area of a data encoding pattern using an imaging module of the stylus in order to generate calibration data representing an error in physical alignment of the stylus; and

using the calibration data to adjust subsequent measurements from the stylus in order to compensate for the error.

2. A method as claimed in claim 1, wherein the data encoding pattern is a pattern of dots embodied on a transparent layer and responsive to illumination under infra-red light, and wherein imaging the calibration pattern area further comprises:

using an infra-red light source of the stylus, illuminating the calibration pattern area; and

imaging reflected light from the illuminated pattern area using a sensor of the stylus in order to generate pattern data representing the pattern of dots embodied by at least a portion of the calibration pattern area.

3. A method as claimed in claim 1, where the data encoding pattern is formed from a plurality of optically reflective elements.

4. A method as claimed in claim 1, wherein the calibration pattern area is a reserved portion of the data encoding pattern.

5. A method as claimed in claim 4, wherein the reserved portion is a portion from a calibration domain of the data encoding pattern, which domain defines a region of the pattern which can be used for the purpose of digital stylus calibration.

6. A method as claimed in claim 1, wherein imaging a portion of the calibration pattern area further comprises:

engaging at least a writing tip of the stylus with a corresponding receptacle of a dock in order to releasably fix the stylus in a calibration position.

7. A method as claimed in claim 6, wherein the calibration pattern area is accommodated within or adjacent to the dock such that the stylus images the area when engaged therewith.

8. A method as claimed in claim 6, further comprising:

using the calibration data, correcting an error in alignment of a tip of the stylus by providing an offset value for shifting a measurement of position determined by the stylus using the data encoding pattern.

9. A method as claimed in claim 1, wherein the calibration pattern area comprises a plurality of regions at respective different angular orientations relative to the imaging module and arranged to provide a variable calibration offset for the stylus for determining a change in the length of a writing tip of the stylus.

10. A method as claimed in claim 1, further comprising:

using the data encoding pattern to determine the type of surface on which the pattern is provided; and

on the basis of the determination, adjusting a calibration setting of the stylus to accommodate its use on that surface.

11. Apparatus comprising a data encoding pattern embodied within or on a region of a display surface of the apparatus, the data encoding pattern comprising a calibration portion reserved from a calibration domain of the pattern for correcting an error in physical alignment of a digital stylus for use with the apparatus.

12. Apparatus as claimed in claim 11, wherein the stylus is operable to generate calibration data representing an offset to be applied to measurements of position of the stylus made using the data encoding pattern.

13. Apparatus as claimed in claim 11, further comprising a dock suitable for receiving a portion of the stylus, wherein the calibration portion of the pattern is adjacent to or within the dock such that an imaging element of the stylus images the portion when engaged with the dock portion.

14. Apparatus as claimed in claim 13, wherein the portion of the stylus comprises at least a tip of the stylus.

15. Apparatus as claimed in claim 14, wherein the dock comprises an indent suitable for receiving the tip of the stylus.

16. Apparatus as claimed in claim 12, wherein the calibration data is provided by the stylus to the apparatus using a wired or wireless data communication link.

17. Apparatus as claimed in claim 13, wherein the calibration portion is imaged automatically upon engagement of the stylus with the dock.

18. A digital stylus suitable for use with a display apparatus comprising a data encoding pattern and a dock for receiving at least a tip of the stylus, wherein engagement with the dock causes the stylus to image a portion of the data encoding pattern and generate corresponding data representing an error in physical alignment of a component of the stylus.

19. A digital stylus as claimed in claim 18, wherein the generated data represents an offset value to be applied in measurements of position of the stylus on the display made using the data encoding pattern.