A corner cube retroreflector having a coating including one or more layers at each reflecting surface. The coating causes the retroreflector to have polarization eigenstates that are substantially linear and to have the properties of a half-wave plate. The coated retroreflector can be used in interferometry...http://www.google.se/patents/US20030223080?utm_source=gb-gplus-sharePatent US20030223080 - Retroreflector coating for an interferometer
