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Schlieren effect in Amici prisms.

It is shown that a system consisting of a polarizer, an Amici prism, and an analyzer may act like a phase and amplitude spatial filter capable of producing four fully distinct images. Two of these are complementary Schlieren or Foucault testlike images, another one is like a phase-edge test pattern, and the fourth is similar to a bright field image. An analysis is made of how the system works when the incident beam is collimated. The formation of the observed images can be explained by assuming that this analysis remains valid for incident beams of small covergence. Some experimental results are presented.