Novel roll angular displacement amplifier

A novel compact roll angular displacement measurement system based on the use of wave retarder is presented. It utilizes the technique of common-path, heterodyne interferometry to detect the phase shift caused by roll angular displacement of a wave retarder fixed on a moving system. This novel system is set up and verified both theoretically and experimentally. Demonstrated by experiments, it can measure the roll angular displacement of a moving system down to microradian over the range of a half-degree.