Patent Document ID: 5471435
Application ID: 08242555
Patent Flag: 1

Claim One:
1. A process for modelling an acoustic or electromagnetic field at a given wave number in an inhomogeneous medium comprising: setting a grid of locations within the medium, x, determining a medium model set of data points corresponding to the wave field, G.sub.0 (x), and the wave velocity in a homogeneous medium at each said location; forming sequentially a fixed number of perturbed data sets .alpha..sub.1 (x)G.sub.0 (x),. .. ,.alpha..sub.n (x)G.sub.n-1 (x), each intermediate a set of data points corresponding to the homogeneous medium and the n-th medium model of data points, for each said perturbed data set, the data corresponding to a location sequentially changing from the data for a homogeneous medium to the data in the n-th medium model; said perturbed data sets being the product of a step-wise increasing perturbation function, .alpha.(x), and the initial homogeneous medium model and iteratively successively produced approximate models; forming the Fast Fourier Transform {.alpha..sub.m (x)G.sub.m-1 (x)} of said product; forming the transformed product ##EQU11## where k.sub.0.sup.2 is the constant part of the wave number squared and .OMEGA. is the transformed space coordinates; forming the Inverse Fast Fourier Transform of the transformed product to produce a new approximate model; repeating the procedure n times; and: outputting the resulting n-th model against the chosen location grid, x, as the wave field model of the acoustic or electromagnetic field.