This paper discusses the autocorrelation obtained from a photon correlation laser Doppler anemometer when the scattering volume formed by the intersection of two laser beams is viewed through a finite width slit. It is shown that the apparent beam profile is non-Gaussian in shape and the variation of this profile as a function of slit width is discussed in some detail. The consequences of the non-Gaussian "pedestal" in the interpretation of the autocorrelograms obtained in low intensity turbulent flows are then discussed. Although the results obtained apply quantitatively only to a slit, similar effects will occur with other types of viewing optics.
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L. J. S. Bradbury (1979) studied this question.