It has been shown previously that two overlapping circular zone plates will create the image of two separate zone plates, two circular dots of light, with the closeness of the dots proportional to the degree of overlap of the zone plates. It is shown here that more complicated patterns can be produced by superpositioning of zone plate sections if the zone plates are cut so that the same number of sections overlap in each area.
R. L. Conger, L. T. Long, and J. A. Parks, "Synthesis of Fresnel Diffraction Patterns by Overlapping Zone Plates," Appl. Opt. 7, 623-624 (1968)