Vol. 10, issue 03, article # 5

pdf Barun V. V. Comparison of the visibility of lambertian and retroreflecting objects. // Atmospheric and oceanic optics. 1997. V. 10. No. 03. P. 165-170.
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Image contrast and ultimate visibility range for Lambertian and retroreflecting objects observed through a light scattering medium are compared based on the small–angle approximation of the radiation transfer theory. The cases of an isolated object and an object against the background of an underlying surface are considered. It is shown, that the account for the signal coming from the shadow region of the isolated object can, under certain conditions, cause the maximum contrast at increasing optical thickness of the medium between an observer and Lambertian or retroreflecting object. The second case can also provide the maximum contrast for a retroreflector associated with its reflecting pattern and increase it efficient albedo. This peculiarity could be considered as one of the hypotheses explaining enhanced visibility of Earth’s objects from the space. It is also shown that the dependence of the ultimate visibility range on the object albedo has a deep dip. When the Lambertian object albedo falls within a narrow range depending on the optical parameters of the medium, the small object becomes invisible over the whole scattering layer of a finite thickness because the object image contrast is below the threshold value.