Method, apparatus, computer program and sotrage medium for recording a movement of a user unit

• US 20070115152A1
• Filed: 12/16/2004
• Published: 05/24/2007
• Est. Priority Date: 12/16/2003
• Status: Active Grant

• Current Assignee: Anoto Group AB
• Original Assignee: Anoto Group AB
• Inventors: Edso, Tomas, Bjorklund, Andreas, Gardenfors, Torbjorn
• Granted Patent: US 7,865,043 B2
• Time in Patent Office: Days
• US Class Current: 341/51
• 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
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06V 10/17 using hand-held instruments
• CPC Class Codes: G06V 10/19 by sensing codes defining pattern positions

Abstract

A position code is recorded by capturing a sequence of images while writing on the base with a user unit. The position code may be decoded to a sequence of absolute positions reflecting the movement of the user unit over the base. If the position code in any image is not sufficiently recorded, e.g. because it is obscured by other graphics on the base, the spatial relationship of the image to another image in the sequence is determined. If the position code in this other image in the image sequence is decodable to an absolute position, the absolute position of the image in which the position code is not decodable could nevertheless be determined by using the spatial relationship. In this way the movement of the user unit can be recorded even though the position code is obscured, which could be the case when the same printing ink is used for both the position code and other graphics on the base.

Claims

1. A method of recording a movement of a user unit over a base, which is provided with a position code, comprising

determining an absolute position of the user unit on the basis of the position code in at least one image in a sequence of images of the position code obtained during the movement of the user unit over the base;

determining a spatial relationship between a first and a second image in the sequence; and

determining another absolute position of the user unit on the basis of the first-mentioned absolute position and the spatial relationship between the first image and the second image.

2. The method as claimed in claim 1, wherein determining the first-mentioned absolute position of the user unit comprises decoding the position code in said at least one image.

3. The method as claimed in claim 1, wherein determining the first-mentioned absolute position of the user unit comprises decoding position code from at least two images in the sequence.

4. The method as claimed in claim 1, wherein the determining of the spatial relationship comprises correlating content of the first and second images.

5. The method as claimed in claim 1, wherein the determining of the spatial relationship comprises correlating features of the first and second images.

6. The method as claimed in claim 1, wherein the determining of the spatial relationship comprises correlating position code information in the first and second images.

7. The method as claimed in claim 6, wherein the position code on the base comprises a plurality of symbols, each of which represents a symbol value, and wherein the determining of the spatial relationship comprises determining and correlating symbol values in the first and second images.

8. The method as claimed in claim 6, wherein the position code on the base comprises at least one group of symbols, which codes a group symbol value, and wherein the determining of the spatial relationship comprises determing and correlating group symbol values in at least the first and second images.

9. The method as claimed in claim 1, wherein the base, in addition to the position code, is provided with graphical information, which partly obscures the position code.

10. The method as claimed in claim 1, wherein the position code comprises a plurality of symbols, each of which is displaced in relation to a nominal position defined by an intersection of raster lines in a regular raster.

11. The method as claimed in claim 1, wherein the sequence of images comprises images with overlapping content.

12. An apparatus for recording a movement of a user unit over a base, which id provided with a position code, comprising a control unit which is adapted to perform the method according to claim 1.

14. A computer-readable storage medium on which is stored a computer program which, when executed in a computer, causes the computer to carry out a method according to claim 1.

13. (canceled)