Position determination

• US 6,570,104 B1
• Filed: 05/26/2000
• Issued: 05/27/2003
• Est. Priority Date: 05/28/1999
• Status: Expired due to Term

• Current Assignee: Anoto Group AB
• Original Assignee: Anoto Group AB
• Inventors: Ericson, Petter, Hugosson, Ola
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): Jorgensen, Leland R.
• Application Number:
  US09/580,338
• Time in Patent Office: 1,096 Days
• Field of Search: 345/179, 345/166, 345/175, 178/18.09, 178/18.01, 178/19.015, 382/306, 382/232, 382/313, 382/317, 382/321, 235/462.1, 235/454, 235/456, 235/487, 235/494, 235/472.01, 358/403, 358/471, 250/237.G, 250/231.14, 341/13, 341/143, 341/9, 356/617, D14/406
• US Class Current: 178/18.09
• 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

Abstract

A position-coding pattern (3) which extends across a surface and codes a plurality of positions (7a, 7b) on the surface is described. The coding in a first dimension is based on the use of a first and a second string of symbols, each containing a predetermined number of symbols and each having the characteristic that if a specific number of symbols is taken from the first string of symbols, the location of these symbols in the string of symbols is unambiguously determined. By means of displacements between these strings of symbols, a large number of positions can be coded in the first dimension. A third string of symbols of the same type is used for the coding in a second dimension.

Claims

1. A product for position determination, which product has a surface and a position-coding pattern applied to the surface and codes a plurality of positions on the surface, each position being coded by a specific part of the position-coding pattern and each such specific part of the position-coding pattern also contributing to the coding of adjoining positions, said position-coding pattern being based on a first string of symbols including a first predetermined number of symbols and which has the characteristic that if a group of symbols comprising a specific number of symbols less than said first number is taken from the first string of symbols, the location of said group of symbols in the first string of symbols is unambiguously defined, wherein said position-coding pattern comprises a first row of symbols comprising said first string of symbols repeated several times, and at least a second row of symbols comprising a second string of symbols repeated several times and having said characteristic of said first string of symbols, said second string of symbols including a second predetermined number of symbols which is different from said first number of symbols of said first string of symbols in order to obtain a displacement between the first and the second string of symbols along the first and the second row when the first and the second string of symbols are repeated.

2. A product as claimed claim 1, wherein the second string of symbols is a subset of the first string of symbols.

3. A product as claimed in claim 2, wherein the second string of symbols is equal to the first string of symbols except that the last symbol of the first string of symbols has been cancelled.

4. A product as claimed in claim 1, wherein the position-coding pattern comprises a plurality of first rows and a plurality of second rows, a start position of each row being predefined to define a position in a second dimension.

5. A product as claimed in claim 1, wherein the position-coding pattern further is based on a third string of symbols having said characteristic of the first string of symbols, the third string of symbols being used to determine the position in a second dimension on the surface.

6. A product as claimed in claim 5, wherein the third string of symbols is a number series consisting of numbers, each of which represents a position in a second dimension on the surface.

7. A product as claimed in claim 5, wherein the first string of symbols is a series of binary numbers and the third string of symbols is a number series with a different base.

8. A product as claimed in claim 1, wherein the first and the second rows begin in predefined positions in the first and the second strings of symbols.

9. A product as claimed in claim 1, wherein the symbols comprise a first symbol of a first type and a second symbol of a second type, said first and second symbols having the same form but different size.

10. A storage medium for a computer, on which a computer program is stored with instructions for decoding of the position-coding pattern on a product as claimed in claim 1.

11. A storage medium for a computer, on which a computer program is stored with instructions for generating the position-coding pattern on a product as claimed in claim 1.

12. A device for position determination, comprising a sensor for imaging a partial surface of a plurality of partial surfaces on a surface and image-processing means adapted to decode a position-coding pattern on a product as claimed in claim 1.

13. A device as claimed in claim 12, further comprising a pen point for writing on the surface.

14. A device as claimed in claim 12, further comprising means for wireless transfer of position information.

15. A method of generating a position-coding pattern, which position-coding pattern is arranged for coding a plurality of positions on a surface, comprising:

arranging symbols on a first row in accordance with a first string of symbols, repeated several times and which comprises a first predetermined number of symbols and which has the characteristic that if a group of symbols comprising a specific number of symbols less than said first number is taken from the first string of symbols, the location of the group of symbols in the string of symbols is unambiguously determined, and

arranging symbols on a second row in accordance with a second string of symbols, repeated several times and having the same characteristic as the first string of symbols, said second string of symbols including a second predetermined number of symbols which is different from said first number of symbols of said first string of symbols in order to obtain a displacement between the first and the second string of symbols along the first and the second row when the first and the second string of symbols are repeated.

16. A method as claimed in claim 15, further comprising the step of generating a plurality of first rows and a plurality of second rows with symbols arranged according to the first and the second string of symbols, respectively, in such a manner that a start position of each row being predefined to define a position in a second dimension.

17. A method as claimed in claim 15, further comprising the step of beginning the first and the second rows in such positions in the first and the second string of symbols, respectively, that a difference between the first and the second string of symbols is reproducible on a number series having said characteristic of the first string of symbols.

18. A storage medium for a computer, on which a computer program is stored for determining a position of a partial surface on a surface which is provided with a position-coding pattern which comprises a plurality of symbols, on the basis of an input signal representing the partial surface, said computer program comprising instructions for:

identifying a plurality of symbols in the input signal, which symbols are arranged in a predetermined number of groups of symbols;

determining the location of each group of symbols in a first predetermined string of symbols;

determining a difference number which is based on the relative positions of the groups of symbols in said first predetermined string of symbols;

determining the location of said difference number in a second predetermined number series;

determining a first coordinate for the position of the partial surface on the surface on the basis of the location of said difference number in the second predetermined number series; and

determining a second coordinate for the position of the partial surface on the surface on the basis of the relative positions of two adjoining groups of symbols in said first predetermined string of symbols.

19. A storage medium as claimed in claim 18, wherein the symbols in the position-coding pattern are arranged in rows so that each group of symbols is identified from one row, and instructions for determining a second coordinate comprises instructions for determining, for two groups of symbols from adjoining rows, in which position the string of symbols begins on the row, and, starting from these two starting positions and the relative positions of the two groups of symbols in the first string of symbols, determining the second coordinate.

20. Use of a position-coding pattern for determining a position, which position-coding pattern is based on a first string of symbols including a first predetermined number of symbols and which has the characteristic that if a group of symbols comprising a specific number of symbols less than said first number is taken from the first string of symbols, the location of said group of symbols in the string of symbols is unambiguously defined, and which position-coding pattern comprises said symbols in the first string of symbols, the symbols being arranged in a first row in accordance with the first string of symbols, repeated several times, and a second row in accordance with a second string of symbols, repeated several times and having said characteristic of the first string of symbols, said second string of symbols including a second predetermined number of symbols which is different from said first number of symbols of said first string of symbols in order to obtain a displacement between the first and the second string of symbols along the first and the second row when the first and the second string of symbols are repeated.

21. Use as claimed in claim 20, wherein the second series of symbols is a subset of the first series of symbols.

22. Use as claimed in claim 20 or 21, wherein the position-coding pattern comprises a plurality of first rows and a plurality of second rows and further is based on a third string of symbols which is a number series and which has said characteristic of the first string of symbols, the symbols being arranged in said rows such that a difference is obtained between the strings of symbols on adjacent rows so that the difference between the rows is arranged in accordance with the third string of symbols.

23. Use as claimed in claim 21, wherein the second string of symbols is equal to the first string of symbols except that the last symbol of the first string of symbols has been cancelled.