Pseudo-holography using scattered X rays

Abstract

A MAJOR obstacle to the formation of images with scattered X rays is the lack of a suitable X-ray lens. Radiation at such short wavelengths is not appreciably refracted by matter, which means that a lens, in the optical sense of the word, cannot exist. To overcome this difficulty, a concept can be applied which has previously been used to form an image of sources which emit their own radiation rather than scattering radiation from another source. Basically, the concept consists of a two-step process in which the radiation is used to cast shadows of a coded aperture which are recorded on film. The encoded image is then decoded by one of several possible methods, depending on the type of aperture used. This technique was first proposed for use in X-ray astronomy¹ and has been applied to imaging distribution of γ emitters (refs 2–5, and H. H. Barrett, and F. A. Horrigan, not yet published). We have used a Fresnel zone plate as a coded aperture. This is by no means the only possible aperture, but it does offer some advantages over other types. The advantages involve primarily the ease with which decoding can be accomplished.