In order to provide a means to uniquely estimate the attitude in a wider range of angles to thereby realize a more accurate attitude estimate, a planar marker is provided. The planar marker includes a planar visual marker having a two-dimensional pattern code and at least two attitude inversion detection patterns Fx and Fy each consisting of a transparent cylindrical body having a pattern on the side face within the range of 180 degrees around the central axis ra and being provided so as to be orthogonal to each other on the same plane as that of planar visual marker. A marker is provided that includes at least one attitude inversion detection pattern. The attitude inversion detection pattern consists of the planar visual marker and a transparent spherical body having a pattern on a hemispherical surface and is provided on the same plane as that of the planar visual marker.
1. A marker comprising: a two-dimensional pattern code; and at least two attitude inversion detection patterns each of which consisting of a transparent cylindrical body having a pattern on a side face in a range of 180 degrees around a central axis of the cylindrical body, the attitude inversion detection patterns being provided so as to be orthogonal to each other, wherein the two-dimensional pattern code and the attitude inversion detection patterns are provided on a same plane.
2. The marker according to claim 1 , wherein the two-dimensional pattern code has a rectangular shape, a first one of the attitude inversion detection patterns is provided to be parallel to a first side constituting the rectangular shape, and a second one of the attitude inversion detection patterns is provided to be parallel to a second side that constitutes the rectangular shape, wherein the second side is adjacent to the first side.
3. The marker according to claim 1 , wherein the pattern includes:
a first colored section having at least two color sections in the central axis direction within a range of 90 degrees around the central axis of the side face; and a second colored section having at least two color sections in the central axis direction within the range of 90 degrees around the central axis of the side face adjacent to the first colored section so that the second colored section is different from the first colored section.
4. The marker according to claim 3 , wherein
the first colored section and the second colored section are each divided to two white and black sections.
5. The marker according to claim 1 , wherein
the pattern is divided to two color sections so that the two color sections have different proportions in the central axis direction depending on the direction around the central axis.
6. The marker according to claim 1 , wherein
the pattern is colored at a different position in the central axis direction depending on the direction around the central axis.
7. The marker according to claim 1 , wherein
the pattern has a different pattern or color depending on the direction around the central axis.
8. The marker according to claim 1 , wherein
the attitude inversion detection pattern has a plurality of the transparent cylindrical bodies so that the transparent cylindrical bodies have parallel central axes and the side faces are adjacent to one another.