Block patterns as two-dimensional ruler

- 51 BLOCK PATTERNS AS TWO-DIMENSIONAL RULER Disclosed is a two-dimensional pattern comprising a plurality of R-planes. Each R-plane comprises a tiling of a corresponding R-ary block, being a block of radix R integer values, 5 such that for each dimension of the pattern, the least common multiple of each of the sizes of the corresponding tiled R-ary blocks in that dimension is greater than the size of the pattern in the same dimension, and such that any R-ary sub-block of a predetermined size less than the tiled R-ary blocks occurs only on a regular grid with the same periodicity as the tiled R-ary block for that R-plane. Typically the radix of the R-planes is 2, by which 10 the pattern is formed by bit-planes and binary blocks. The pattern may be used in method of determining a two-dimensional position (xy) of a location (110) captured in an image (2000) by projecting (250) the two-dimensional pattern onto a three-dimensional scene. An image of the scene (260) including the projected two-dimensional pattern is captured. The method determines (280) from the captured image a sub-block associated with the 15 location and constructs, from a R-ary representation of the sub-block, a unique integer value for each R-plane, being a representation of the pattern in the R-plane of the sub-block associated with the location. The method uses the unique integer values from each R-plane to determine the location in the image. 3219905_1 958410_speci_02 Start Capture image of 3D Generate 2D object illuminated by 204 ruler pattern 2D ruler pattern Process Project 2D ruler captured image 201 pattern to get captured onto 3D scene image coordinate mapping 202 Finish Fig. 2A