Advanced simultaneous phase-shifting Fizeau interferometer

This study proposes an advanced simultaneous phase-shifting Fizeau interferometer. The proposed interferometer introduces a beam expander into the simultaneous phase-shifting Fizeau interferometer which employs four point sources to produce four phase shifting interferograms on a detector simutaneously. The beam expander is used to increase the aperture of the lens array and to decrease the inclination of the beam incident on the test surface such that the imaging resolution and the measurement accuracy of the interferometer can be improved. In addition, the optical zoom can be achieved by changing the magnification of the beam expander. A step plate was experimentally measured using the proposed interferometer. The phase step is clearly imaged in the detector, and the measured results are in good agreement with those obtained by the temporal phase-shifting Fizeau interferometer, which indicates that the proposed interferometer is suitable for normal apertures.