Method of determining coordinate values of a position on a printed document with respect to a plurality of patterns printed on the document

• US 8,028,220 B2
• Filed: 05/04/2008
• Issued: 09/27/2011
• Est. Priority Date: 04/12/2001
• 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): Torres; Joseph D
• Application Number:
  US12/114,803
• Publication Number:
  US 20080236903A1
• Time in Patent Office: 1,241 Days
• Field of Search: 714/758, 714/781
• US Class Current: 714/781
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
• 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: H03M 13/15 Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] codes H03M13/17 takes precedence

Abstract

A method is disclosed of determining a coordinate value of a position on a printed document having patterns printed thereon. Each pattern represents a sequence having a repeating codeword of a cyclic position code. The method includes sensing the patterns printed on the document, obtaining from each sensed pattern a sub-sequence, mapping each of the sub-sequences to a respective mapped codeword of the cyclic position code, and determining an offset indicative of the position, in the corresponding sequence, between each mapped codeword and the codeword. Also included are the steps of deriving, for each pair of the sequences, a difference between the corresponding pair of offsets, as well as deriving the coordinate value by interpreting the differences as a digit of the coordinate value, and by interpreting the differences as a marker separating the coordinate value from an adjacent coordinate value.

Claims

1. A method of determining a first coordinate value of a position on a printed document with respect to a plurality of first patterns printed on the document, each first pattern respectively representing a first sequence h₁, with each of the first sequences having a repeating first codeword of a first cyclic position code with length n₁ and minimum distance d_min1, said method comprising the steps of:

sensing the document, via a sensing device, to sense h₁ of the first patterns, where h₁≧

2;

obtaining from each sensed first pattern a respective first sub-sequence of length w₁ symbols, where w₁≧

n₁−

d_min1+1;

mapping each of the first sub-sequences to a respective mapped codeword of the first cyclic position code;

determining a first offset indicative of the position, in the corresponding first sequence, between each mapped codeword and the first codeword;

deriving, for each of h₁−

1 pairs of the first sequences, a difference between the corresponding pair of first offsets, and thereby deriving a respective one of a plurality of first differences; and

deriving the first coordinate value by interpreting at least one of the first differences as a digit of the first coordinate value, and by interpreting at least one of the first differences as a marker separating the first coordinate value from an adjacent coordinate value.

2. The method of claim 1, the document further including a plurality of second patterns printed thereon, each second pattern representing a second sequence, each of the second sequences consisting of a repeating second codeword of a second cyclic position code, the second cyclic position code having length n₂ and minimum distance d_min2, the method including the steps of:

sensing the document, via the sensing device, to sense h₂ of the second patterns, where h₂≧

2;

obtaining from each second patterns a respective second sub-sequence of length w₂ symbols, where w₂≧

n₂−

d_min2+1;

mapping each of the second sub-sequences to a respective second mapped codeword of the second cyclic position code;

determining a second offset indicative of the position, in the corresponding second sequence, of each second mapped codeword and the first codewords; and

deriving a second coordinate value by interpreting at least one of the second offsets as a digit of the second coordinate value, and by interpreting at least one of the second offsets as a marker separating the second coordinate value from an adjacent coordinate value.

3. The method of claim 2, wherein the first and second coordinate values together define a two-dimensional coordinate.

4. The method of claim 2, wherein the first and second cyclic position codes are not the same.

5. The method of claim 2, wherein the first and second cyclic position codes are simplex codes.

6. The method of claim 1, wherein w₁≧

n₁−

d_min1+2 and w₂≧

n₂−

d_min2+2.

7. The method of claim 1, wherein w₁≧

n₁ and w₂≧

n₂.