Patent ID: 8922644

Claim:
A marker device for enabling the tracking of an object by a camera, comprising: a first marker having means for changing color as it is rotated with respect to an observer, the first marker having a first means for refracting or reflecting a first predetermined color from a location on the marker when viewed from a corresponding first predetermined angle and refracting or reflecting a second predetermined color from the location on the marker when viewed from a corresponding second predetermined angle, the first and second predetermined colors being different from one another, wherein the means for refracting or reflecting includes a lenticular lens, a material having metamerism, or prisms; a second marker; means for supporting the first and second markers at a fixed distance from one another; and means for coupling the first and second markers to an object, whereby a distance to the object can be determined from an angular distance between the first and second markers and observed color of the first marker.