Scattering from a thin random fluid layer

The problem of a plane wave obliquely incident from a homogeneous ideal fluid upon a random fluid layer is considered and expressions are derived for the diffusely backscattered intensity. The thin layer is taken to have properties that vary only in the two in-plane directions. A first Born approximation is used and the average intensity of the incoherent part of the backscattered wave is found to be proportional to the two-dimensional spatial Fourier transform of the auto- and cross-covariance functions of the layer. Within the confines of the validity of the first Born approximation, therefore, the inverse scattering problem may be straightforward, provided the necessary experimental data of the incoherent wave can be obtained. A sufficient condition to estimate the range in which the second-order term in the Born series can be neglected is also given.