Bi-lateral shearing interferometer with beam convergence/divergence indication

摘要

Opposite wedge plates having identical non-parallel surfaces are joined to provide an optical element which will receive a portion (e. g. one-half) of an input light beam, and project the side-by-side interference patterns directly onto a viewing screen to check for collimation of the beam. The instrument incorporates a rectangular housing having an input window in one side of the housing for admission of the beam being investigated, and a viewing window in another side located at right angles to the input window. A viewing screen is fitted into or supported in the viewing window. The optical element comprises a matched pair of optical wedge plates having the same wedge angle and being supported side-by-side with their wedge directions opposite, and is supported in and across the housing extending at forty-five degrees to the input window, from a corner adjacent the viewing window to an opposite corner. A telescope including a pair of lenses, at least one of which is adjustable with respect to the other, extends from the input window and acts to focus the interference fringe patterns onto the viewing screen. A scale on the telescope indicates the convergence and/or divergence of the beam from its source to the instrument when the patterns are visually equal and in focus.