Common-path point-diffraction phase-shifting interferometer

A method of characterizing an optical wavefront with an interferometric device comprising:

• transmitting a wavefront through a test system;
• splitting said wavefront into an object wavefront and a reference wavefront traveling along a common axis so that said object wavefront has a first intensity and first polarization and said reference wavefront has a second intensity and a second polarization;
• shifting the phase of said object wavefront relative to the phase of said reference wavefront;
• and adjusting said first intensity of said object wavefront relative to said second intensity of said reference wavefront to be in substantially the same polarization state to generate an interferogram that provides information about said wavefront.

An interferometric measurement method for characterizing the shape of an input wavefront comprising the following steps:

• passing the input wavefront through a polarizing point-diffraction plate that includes two regions, one of the regions including a first polarizing element adapted to spilt the input wavefront into a reference wavefront and a test wavefront having a common optical path and mutually orthogonal polarizations;
• passing the reference and test wavefronts through a phase-shining interferometer maintaining said common optical path;
• imaging an interferogram produced by the interferometer onto a detector;
• and analyzing the interferogram to characterize the shape of the input wavefront wherein the other of said two regions includes a second polarizing element perpendicular to the first polarizing element.

An interferometric measurement method for characterizing the shape of an input wavefront comprising the following steps:

• passing the input wavefront through a polarizing point-diffraction plate that includes two regions, one of the regions including a first polarizing element adapted to split the input wavefront into a reference wavefront and a test wavefront having a common optical path and mutually orthogonal polarizations;
• passing the reference and test wavefronts through a phase-shifting interferometer maintaining said common optical path;
• imaging an interferogram produced by the interferometer onto a detector;
• and analyzing the interferogram to characterize the shape of the input wavefront;
• wherein said one region is circumscribed by the other of said two regions of the plate.