Review of the US Patent Literature on Retroreflectors

Publication Details

Abstract

Users of electronic distance measurement (EDM) instruments, such as laser trackers, total stations, and interferometers are familiar with commercially available spherically mounted retroreflectors (SMRs); spherical, or cats eye, retroreflectors; and glass prism, or corner cube, retroreflectors. However, the US patent literature discloses nearly 200 retroreflector inventions of various designs–but few are commercially available, and thus may not be fully exploited. Invention disclosures range from mechanical mountings to solutions to specific measurement problems– such as hidden points, spindle centers, and edges; methods of manufacture, such as optical replication and testing; optical coatings; minimized polarization rotation; variable attenuation; geometrical designs; optical materials; wide angle of operation; multi directional; multi instrumental, such as combination retroreflector and theodolite targets; four to six degree of freedom measurement; arrays; reduced Abb´e errors; lateral transfer; etc. This presentation will cover some representative designs with an appendix including a table of the results of a US patent search. Many of the patent terms have expired, and unexpired patents may be available for license. Users may find insight into solutions to unique problems in their applications, and manufacturers of EDM accessories may want to conduct marketing research into new products, or file additional patents on improvements thereof.