US Patent 7818889 Target object used for retroreflexion of optical radiation

A target object (1a) used for retroflexion of optical radiation comprises at least six triple prisms (p1, p2), combined to give a 360 degree reflector which can be arranged on a geodetic measuring pole (6). The triple prisms (p1, p2) forming the 360 degree reflector are arranged in such a manner as to leave a clearance in the center of the 360 degree reflector for accommodating a section (6a) of the measuring pole (6). The prisms are also arranged in such a manner that the virtual images of the triple prism tips lie substantially in one plane perpendicular to a reference axis (10) that runs through the center of the 360 degree reflector and in parallel to the longitudinal direction of the measuring pole (6).