PROCESS FOR THE PRODUCTION OF ZONE PLATES

1,207,902. Zone plates. D. RUDOLPH and G. SCHMAHL. Feb. 28, 1968 [March 14, 1967; Jan. 19, 1968], No. 9560/68. Heading G2J. [Also in Division H5] A zone plate is produced by placing a layer of photo-sensitive material 5 in the image area of an interference figure 6 formed by the superposition of a planar wave and one or two spherical waves. After development, a supported or self-supported zone plate may be produced. In the former case, embodiments are described wherein the photosensitive material is supported on a radiation transparent base of synthetic material or metal, Fig. 4 (not shown) an intermediate metal layer 9 is provided which is etched using the developed image as a mask as shown in Fig.5; metal is vapourized or sprayed on to the developed image and a developer which loosens the image layer is used, Fig. 6 (not shown) the photo-sensitive material has metal included in the layer, Fig. 8 (not shown) the developed image is used as a mask in an electron microscope to bombard a supporting layer which is subsequently subjected to metal vapour, e.g. cadmium, which adheres to the bombarded areas , Figs. 10, 11 (not shown); an impression material is applied over the developed image which may either contain metal and thus form the final zone plate by subsequently applying a supporting film and removing the developed image, or the developed image may be removed, metal vapourized over the impression material, the elevated areas of the metal layer removed by cutting and a supporting layer applied; in a final embodiment, the initial supporting layer is a metal, and a metal is deposited over the developed image galvanically. In the production of selfsupported zone plate, Fig. 3, radially extending webs 8 are applied prior to the etching step. The resulting zone plate is used in image forming systems which use short-wave radiation, e.g. X-rays.