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Fresnel Telescope

Started by wpaolini, 06/19/2006 01:53PM
Posted 06/19/2006 01:53PM Opening Post
Just curious, has anyone here ever tinkered with using a quality fresnel lens to construct a large apeture refractor?? Looks like a diffraction-limited one is feasible:


Posted 06/19/2006 03:01PM #1

What they are basically talking about (but don't know if they realize) is a Diffractive Optical Element (DOE). The Fresnel is simply an early example of a DOE. Diffractive Optics have gotten pretty common these last few years, finding widespread use in the disposable camera industry and also in the infrared where the wavelengths are longer and the tolerances aren't as critical. The primary use is for additional color correction, but that isn't to say it could be used by itself as an objective.

The main issue with DOE is light scatter off of the diffractive surface. The other problem is that they must be diamond turned, which can be costly for one-off systems (or even for production systems).