A new wavefront-shearing interferometer has been developed in which the interference fringes produce a direct plot of the refractive index gradient in Cartesian coordinates. The simple and versatile instrument works with two separate beam splitters: the first, situated in parallel light, introduces a lateral shear, and the second, in convergent light, a shear angle in a perpendicular direction with respect to the first shear. The fringe system appears within a sharp image of the object, each fringe representing the refractive index gradient curve for that part of the object through which the fringe passes. Two alternatives are given together with a detailed description of the theory of the optical method. The method is very easy to set up and to adjust, since the precise position of the components of the optical setup is not critical. The instrument may be used to study phenomena giving rise to refractive index gradients. A direct record of the refractive index gradient curve is often the kind of information which is wanted in diffusion, electrophoresis, ultra-centrifugation, sedimentation, heat conduction, and heat flow.
© 1963 Optical Society of AmericaFull Article | PDF Article
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