Infrared point diffraction interferometer.

The point-diffraction interferometer (PDI) is a simple common-path interferometer capable of measuring optical-path differences (OPD) directly. This interferometer, first described by Smartt in 1972,1,2 has since become available commercially for use in the visible spectrum. Currently activity in laser-fusion and high-energy-laser systems has stimulated interest in extending PDI principles to the infrared. Thus an infrared point-diffraction interferometer has been developed that provides a simple, stable, self-referencing wavefront sensor requiring no high-quality optical components.