Fresnel Zone Plates on Chalcogenide Glass Without Chromatical Aberrations

This paper proposes two systems of Fresnel Zone Plates (FZP) which can focus two parallel monochromatic and coherent beams (with different wavelenghts), eliminating the wellknown chromatical aberrations of the classical construction. FZP is one of the most important means of forming images, especially, in the spectral region of IR, x-rays, gamma rays. When a plane wave upon a FZP whose transmission is T(r) [1], the transmitted light is focused to a point. Having in view a technological “simplification”, and a mathematical determination of the radii which describe the pattern, it is necessary to find the radii values for T=0.5. The same FZP functions like a lens with focal distance f for two beams with different wavelengths (λ1, λ2) only if λ1f - λ2f, for every k. Of course, this equality can not be satisfied and the element has an important chromatical aberration.