Multiple-beam interferometric device with common optical path and independence of the tilt angle

A multiple-beam interferometric device that consists of a light source, an interferometer and a signal process module possess the characteristics of common optical path and independence of the tilt angle. The light beam is incident to interferometer. In the interferometer, there are a coated glass plate and a corner cube where transmission and reflection beams from glass plate can be received. In the signal process module, there are a beam splitter, a position sensitive detector (PSD) and a photodiode. The interference beam that results from beams superposition between the glass plate and the corner cube is divided into two beams by the beam splitter. One of the two beams will be detected by PSD and the other by the photodiode. With the two detectors, the interference signals can be detected. By the multiple-beam interferometric device, a precision displacement measurement can be realized under conditions of common optical path and independence of the tilt angle.