A phase modulating homodyne interferometer with tilting error compensation by use of an integrated four-photodetector.

The tilting error of the measuring reflector moving with the measured object influences the accuracy of displacement measurement in laser interferometers. To solve this problem, a phase modulating homodyne interferometer with tilting error compensation is proposed for precision displacement measurement. In this interferometer, the displacement and tilting angle of the measured object are obtained simultaneously by differentially processing the phase changes of four interference signals detected with an integrated four-photodetector, and the obtained tilting angle is used to compensate its influence on the displacement result. The optical configuration of this interferometer is designed, and the displacement measurement with tilting error compensation is presented. An experimental setup is constructed, and the feasibility and effectiveness of the proposed interferometer are demonstrated.