Patent attributes
Methods and devices for angle determination, and retroreflecting foils are presented. A retroreflecting foil (1) is arranged at a surface, an angle of which is going to be determined. The retroreflecting foil has a lens surface with a plurality of spherical microlenses (4) and a reflecting surface with a plurality of spherical mirrors (5) of a second main radius of curvature. The lens surface of the retroreflecting foil is illuminated, and transitions between darkness and light in radiation reflected from the retroreflecting foil, either upon changing a relative angle between the retroreflecting foil and the illuminating light or spatial transitions over the surface of the retroreflecting foil, are observed. An angle measure associated with the transitions is determined. The spherical mirrors present preferably at least one inner point (22) of a spherical mirror surface at which reflection according to the second main radius of curvature is prohibited.
