Fizeau interferometry with automated fringe pattern analysis using temporal and spatial phase shifting

The paper presents a novel approach to measure the parameters of quasi-parallel plates in a Fizeau interferometer. The beams reflected from the front and rear surfaces lead to a complicated interferogram intensity distribution. The phase shifting techniques (temporal and spatial) are proposed to process the interferograms and obtain a two-beam-like fringe pattern encoding the plate thickness variations. Further pattern processing is conducted using the Vortex transform.