Bichromatic Interferometry Applied To Precise Adjusting The Wollaston Prism Of A Birefringent Microinterferometer

Some double refracting microinterferorneters available commercially suffer from a variable interfringe spacing across the image plane. This defect is especially produced by typical birefringent Wollaston prisms and is responsible for some errors in the measurement of optical path differences or related quantities. In particular, the errors arise when the interfringe spacing is directly measured in the image plane of the microinterferometer or determined from an interferogram recorded on a photographic material. To overcome this defect, the Wollaston prism must be adjusted so to obtain a uniform distribution of interference fringes in the image plane. It has been stated that bichromatic interferometry is a useful tool for precise adjusting the Wollaston prism of double refracting microinterferometers.