Elliptical and hyperbolic zone plates

Elliptical and hyperbolic zone plates have been constructed by optical methods recording on a photosensitive material the model produced by coherent superposition of two wave fronts, one spherical and the other cylindrical. When the foci of the wave fronts coincide, we have linear zone plates. In the reconstruction, the effects of linear and nonlinear recording produce the appearance of linear foci situated symmetrically on both sides of the zone plates. Experimental results are presented.