The Design of Two Shearing Interferometers for Studying Refractive Index Distributions near Opaque Boundaries

Two wave-front shearing interferometers for the measurement of optical path distributions close to opaque obstacles are described. The introduction of a new beam splitter in one of the interferometers produces an interferogram from which the path differences in the test region can be obtained with higher accuracy. The other interferometer is designed for the investigation of refractive index distributions, where the sensitivity can be greatly enhanced by optimizing the shear of the wave-fronts.