A modification of the equation of one-dimensional space-variant imaging is considered in which the output image is known both as a function of an image-plane coordinate and an object-position coordinate. Under this condition, the Fourier transform of the image intensity with respect to both variables equals the product of the object Fourier transform and a transfer function. A similar relation also occurs for observation of either the integrated image intensity or the intensity at a point versus an object-scan coordinate. Consequently, for the special situation considered, the transfer-function concept may be extended to the space-variant case. The implications of factorization of the transfer function are also considered.
L. Sica, "Fourier space separability in space-variant imaging," J. Opt. Soc. Am. 71, 493-495 (1981)