Interface surface for user interaction with a computer system via a sensing device

1. An interface surface for user interaction with a computer system via a sensing device, the interface comprising:

visible graphical information; and,

substantially invisible coded data readable by the sensing device, the coded data comprising a plurality of substantially undifferentiated marks positioned relative to a predetermined pattern with a target structure extending radially outwardly from a centre of the pattern for allowing relative rotation of the predetermined pattern to be determined; wherein,

the visible graphical information indicates an operation that the user can select and transmit to the computer system by reading the coded data with the sensing device.

2. The interface surface according to claim 1 wherein each mark is circular and has a minimum radius and a maximum radius, the minimum radius being more than 40% of the maximum radius.

3. The interface surface according to claim 2 , wherein the graphical information is adjacent, or substantially coincident with, coded data.

4. The interface surface according to claim 3 , wherein the graphical information takes the form of any combination of:

text;

graphics;

images;

buttons;

icons; and

hypertext links.

5. The interface surface according to claim 2 , wherein any 10 millimeter diameter area of the coded data indicative of the operation includes sufficient information to identify the operation.

6. The interface surface according to claim 1 , wherein each mark has a plurality of possible values.

7. The interface surface according to claim 6 , wherein the value of a mark is at least partially determined by the mark's position relative to the predetermined pattern.

8. The interface surface according to claim 1 , wherein the predetermined pattern includes a plurality of lines.

9. The interface surface according to claim 8 wherein the lines are not visible.

10. The interface surface according to claim 1 , wherein the marks have centers and wherein the relative spacing of the centers of at least one pair of adjacent marks is less than 12 mm.

11. The interface surface according to claim 1 , wherein the coded data identifies remotely stored information defining a position of the coded data relative to the interface surface.

12. The interface surface according to claim 1 , wherein the coded data includes region identification information that identifies the region within which the respective coded data is disposed.

13. The interface surface according to claim 12 , wherein the region encompasses substantially the entire surface.

14. The interface surface according to claim 1 , wherein the coded data includes data identification information that identifies data associated with the region within which the respective coded data is disposed.

15. The interface surface according to claim 1 , wherein the predetermined pattern defines a plurality of symbol regions, the coded data defining at least one codeword formed from marks disposed in different symbol regions.

16. The interface surface according to claim 1 , wherein the predetermined pattern includes a plurality of circumferentially spaced target structures for allowing perspective distortion the predetermined pattern to be determined.

17. The interface surface according to claim 1 , wherein the predetermined pattern includes:

a ring target structure for allowing the predetermined pattern to be located; and,

a target structure for allowing relative rotation of the predetermined pattern to be determined, the target structure being positioned radially inwardly of the detection ring.

18. The interface surface according to claim 1 , wherein the predetermined pattern includes:

a ring target structure for allowing the predetermined pattern to be located; and,

a plurality of circumferentially spaced target structures for allowing perspective distortion of the predetermined pattern to be determined, the circumferentially spaced target structures being positioned radially outwardly of the detection ring.

19. The interface surface according to claim 1 , wherein the marks within each predetermined pattern define a plurality of codewords, the marks of different codewords being interleaved.

20. The interface surface according to claim 1 , wherein the marks are disposed in a plurality of symbol rings, the marks defining a plurality of codewords, and the marks of different codewords being interleaved within at least one symbol ring.

21. The interface surface according to claim 1 , wherein the coded data includes a plurality of symbols, each symbol being formed from a plurality of marks.

22. The interface surface according to claim 1 , wherein each mark is formed from an area bounded by two radial lines and two concentric circular arcs.

23. The interface surface according to claim 22 , wherein each radial line defines a minimum dimension, a shorter one of the two concentric arcs being at least equal to the minimum dimension.

24. The interface surface according to claim 22 , wherein each area includes at least 8 dots when the coded data is printed at a resolution of 1600 dpi.