Abstract

One practical method for obtaining the point spread function (PSF) of an imaging system is to measure the response of the system to a line source of illumination extending across the entire image field. If the system is rotationally symmetric, the well-known Abel inversion then enables the computation of the PSF from the line spread function. Some systems, notable x-ray image intensifiers, are space-variant, and the line source must be restricted to an isoplanatic patch. Correspondingly, the formula for computing the PSF from this finite-length line spread function (FLSF) is different from the Abel inversion. Such a formula has previously been derived by transform methods. A simple space-domain approach yields an inverse FLSF transform kernel in the form of a finite series of corrections to the Abel inversion. For a sufficiently long line source, the kernel reduces to just the Abel inversion, and as the source becomes vanishingly small (so that the FLSF is identical to the PSF), the kernel approaches an identity operation, as expected.

© 1988 Optical Society of America