Fresnel Lens
The sample file "Fresnel Zone Plate Lens" illustrates the focusing power of an aperture consisting of concentric rings. The spacing of the rings is selected to block light from every other Fresnel zone, so that at a distance of
200.0 mm the light diffracted from all the zones interferes constructively. The constructive interference creates a bright focused spot on axis; an effect not predicted by ray tracing. This file also illustrates the intensity of the beam at several planes between the Fresnel zone plate and focus; note the concentric ripples caused by interference from the edges of the zone plate.
Since OpticStudio does not have a multiple-zoned circular aperture, the zone plate was created by placing one annular obscuration on each of several surfaces; all located at the same plane. The option to "Use Rays To Propagate To Next Surface" is used to speed the computation through all the aperture surfaces.
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