The shower curtain effect paradoxes

Gregoire Tremblay; Robert Bernier; Gilles Roy

doi:10.1117/12.2194837

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8 October 2015 The shower curtain effect paradoxes

Gregoire Tremblay, Robert Bernier, Gilles Roy

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Proceedings Volume 9641, Optics in Atmospheric Propagation and Adaptive Systems XVIII; 964107 (2015) https://doi.org/10.1117/12.2194837
Event: SPIE Remote Sensing, 2015, Toulouse, France

Abstract

It is generally admitted that the relative location of an aerosol between an observation device and the observed scene will have an influence on the detected image quality. These effects are usually classified under the label “shower curtain effect” (SCE). The usual formulation describing it is as follows: an observer standing away from a shower curtain can detect the presence of a person standing just behind it whereas the opposite is not true. Starting from a discussion of experimental results which seemed to invalidate the SCE, we show that it is not the only mechanism at work and that thorough analysis of the measurement setup is required before reaching such conclusion. We base our discussion on four cases, two of them of the passive detection type, the two others being of the active type. We also show that the ratio of scattered to unscattered light at the detector is of utmost importance. We show this by further developing our model [10] of the point spread function (PSF) of the receiver. This model allows the discussion of the SCE in the frequency domain in terms of the cuton and cutoff frequencies of the receiver. In the end, we show that the apparent paradoxical results we had found cannot actually be placed under the “shower curtain effect” denomination because: 1-) the amount of unscattered light captured is higher than the amount of scattered light, and 2-) the receiver cuton frequency is much higher than the aerosol cutoff frequency rendering most mechanisms of the shower curtain effect ineffective.

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Gregoire Tremblay, Robert Bernier, and Gilles Roy "The shower curtain effect paradoxes", Proc. SPIE 9641, Optics in Atmospheric Propagation and Adaptive Systems XVIII, 964107 (8 October 2015); https://doi.org/10.1117/12.2194837

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