Multichannel Grating Phase-Shift Interferometers

Abstract

When a beam is focused into grating elements, it is diffracted and phase-shifted. These fundamental characteristics of gratings have been found very useful for converting conventional interferometers into real-time wavefront sensors for digital computer control and data analysis. The principle of phase-shifting interferometry has been combined with above characteristics of the gratings to produce instantaneous multichannel interferograms. Attempts have been made successfully to apply these principles to three well-known interferometers, (1) the point-diffraction interferometer, (2) the radial-shear interferometer, and (3) the double-frequency crossed-grating lateral-shear interferometer. The advantages of these new approaches are simplicity and versatility, in particular, these wavefront sensors can measure wavefronts from both continuous and pulsed sources. Optical principles and the laboratory results will be shown.