Method of imaging a coding pattern and determining translation of imaged cells relative to tags

• US 7,905,406 B2
• Filed: 02/05/2008
• Issued: 03/15/2011
• Est. Priority Date: 02/08/2007
• Status: Expired due to Fees

• Current Assignee: Silverbrook Research Pty Limited
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Lapstun, Paul
• Primary Examiner(s): Frech; Karl D.
• Application Number:
  US12/025,761
• Publication Number:
  US 20080191020A1
• Time in Patent Office: 1,134 Days
• Field of Search: 235/454, 235/462.08, 235/462.09, 235/462.1, 235/487
• US Class Current: 235/454
• CPC Class Codes: G06F 2203/0337 Status LEDs integrated in the mouse to provide visual feedback to the user about the status of the input device, the PC, or the user
• CPC Class Codes: G06F 2203/0384 Wireless input, i.e. hardware and software details of wireless interface arrangements for pointing devices
• 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 19/06 characterised by the kind of the digital marking, e.g. shape, nature, code
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06T 7/32 using correlation-based methods

Abstract

A method of imaging a coding pattern disposed on a surface of a substrate. The method comprises the steps of: (a) operatively positioning an optical reader relative to the surface and capturing an image of a portion of the coding pattern; (b) sampling and decoding one or more translation symbols contained in the imaged portion; (c) determining a translation of one or more cells of the coding pattern relative to a tag containing the cells; and (d) using the determined translation to sample and decode tag data contained in the imaged portion.

Claims

1. A method of imaging a coding pattern disposed on a surface of a substrate, said method comprising the steps of:

(a) operatively positioning an optical reader relative to said surface and capturing an image of a portion of said coding pattern, said coding pattern comprising;

a plurality of target elements defining a target grid, said target grid comprising a plurality of cells, wherein neighboring cells share target elements;

a plurality of data elements contained in each cell; and

a plurality of tags, each tag being defined by a plurality of contiguous cells, each tag comprising respective tag data encoded by a respective set of said data elements,

wherein each cell comprises one or more translation symbols encoded by a respective set of said data elements, said one or more translation symbols identifying a translation of said cell relative to a tag containing said cell;

(b) sampling and decoding one or more translation symbols contained in said imaged portion;

(c) determining a translation of one or more cells relative to a tag containing said one or more cells; and

(d) using said determined translation to sample and decode said tag data.

2. The method of claim 1, wherein said determined translation is a maximum likelihood translation.

3. The method of claim 1, wherein step (c) comprises:

aligning said tag with said target grid.

4. The method of claim 1, wherein each cell comprises a pair of orthogonal translation symbols, each orthogonal translation symbol identifying a respective orthogonal translation of said cell relative to a tag containing said cell.

5. The method of claim 1, wherein each tag is square and comprises M² contiguous square cells, wherein M is an integer having a value of at least 2.

6. The method of claim 5, wherein M translation symbols in a row of M cells define a cyclic position code having minimum distance M, said code being defined by a first codeword, and wherein step (b) comprises decoding said first codeword.

7. The method of claim 5, wherein M translation symbols in a column of M cells define a cyclic position code having minimum distance M, said code being defined by a second codeword, and wherein step (b) comprises decoding said second codeword.

8. The method of claim 1, wherein each tag comprises N cells, and at least N translation symbols form a third codeword with minimum distance N, wherein N is an integer having a value of at least 4, and wherein step (b) comprises decoding said third codeword.

9. The method of claim 8, wherein said captured image contains a tag-sized portion of said coding pattern, and said tag-sized portion contains at least N translation symbols.

10. The method of claim 1, wherein each cell comprises at least one orientation symbol encoded by at least one data element, such that any tag-sized portion of said coding pattern is guaranteed to contain a plurality of said orientation symbols, each orientation symbol identifying an orientation of a layout of said tag data with respect to said target grid.

11. The method of claim 1, wherein said data elements are macrodots.

12. The method of claim 1, wherein a portion of data is represented by a macrodot occupying one of a plurality of possible positions within a cell, each position representing one of a plurality of possible data values.

13. The method of claim 1, wherein each cell defines a symbol group, each symbol group comprising a plurality of Reed-Solomon symbols encoded by a plurality of said data elements.

14. The method of claim 13, wherein each symbol comprises two halves, each half comprising 2 bits of data represented by a macrodot occupying one of 4 possible positions within said half.

15. The method of claim 13, wherein said method comprises the further step of:

using said determined translation to sample and decode said Reed-Solomon symbols.

16. A system for imaging a coding pattern disposed on a surface of a substrate, said system comprising:

(A) said substrate, wherein said coding pattern comprises;

a plurality of target elements defining a target grid, said target grid comprising a plurality of cells, wherein neighboring cells share target elements;

a plurality of data elements contained in each cell; and

a plurality of tags, each tag being defined by a plurality of contiguous cells, each tag comprising respective tag data encoded by a respective set of said data elements,

wherein each cell comprises one or more translation symbols encoded by a respective set of said data elements, said one or more translation symbols identifying a translation of said cell relative to a tag containing said cell;

(B) an optical reader comprising;

an image sensor for capturing an image of a portion of said coding pattern, said image sensor having a field-of-view of at least one tag diameter and less than two tag diameters; and

a processor configured for performing the steps of;

(i) sampling and decoding one or more translation symbols;

(ii) determining a translation of one or more cells relative to a tag containing said one or more cells; and

(iii) using said determined translation to sample and decode said tag data.

17. The system of claim 16, wherein each cell comprises a pair of orthogonal translation symbols, each orthogonal translation symbol identifying a respective orthogonal translation of said cell relative to a tag containing said cell.

18. The system of claim 16, wherein each tag is square and comprises M² contiguous square cells, wherein M is an integer having a value of at least 2.

19. The system of claim 16, wherein each tag comprises N cells, and at least N translation symbols form a third codeword with minimum distance N, wherein N is an integer having a value of at least 4.

20. The system of claim 16, wherein said reader is an optically imaging pen having a nib.