Abstract: A three-dimensional reflector for object attitude detection responds to illumination from a radiating source to produce a discrete array of light points aligned along a locus on the reflector. The array is characteristic of the reflector position with respect to the radiating source. The reflector has a corrugated surface formed with plural, parallel and spatially periodic, adjacent undulations, each having a crest and a trough. The undulations are arranged such that the locus runs through the reflector center of symmetry and the foot point of a perpendicular dropped by a detector for the array onto the surface. The foot point is a determinate point of the locus.