Interference fringe detection system for distance measuring interferometer

A novel photodetection system for a homodyne distance measuring interferometer by means of fringe counting method is presented. The system is based on applying compact size integrated photodetector operating with fringe pattern having fixed, finite period. 13-element integrated photodiode arranged in novel signal processing scheme receives interference fringes movement. Additional lens is used to adjust the fringe period to photoelements’ distances. Due to the proposed configuration of the photoelement's signal processing and the applied lens the system has reduced sensitivity to interference fringe period errors caused by the angular misalignment of interfering beams. The theoretical analysis and experimental verification of the system metrological feasibilities are presented. Comparison of performance of examples of standard and novel detection systems is shown finally.

► The system operates based on fringe counting method.
► 13-element integrated photodiode is operating with fringe pattern having fixed, finite period.
► Photodetector receives interference fringes movement.
► The system has reduced sensitivity to interference fringe period errors.
► The errors are caused by the angular misalignment of interfering beams.