Re: [ATM] grin optics for telescopes

["Bob May" <bobmay@nethere.com>]

Gradient Refractive Index lenses are a bit difficult to build as they are
done in the melting period of making the glass.  As such, you just don't
pick up a piece of glass and grind on it for a while and have a lens to work
with.  The small size of these lenses is due to the process of making the
glass itself.  You probably could do a much larger lens but you will have to
control the refractive index of the glass very closely to obtain a good
wavefront when the light comes out of the lens.  It is a lot easier to
control the refractive index in small lenses than big ones.
After you have made such a lens, you then have to deal with the chromatic
errors of such a piece of glass as making a negative lens to compensate for
the color error of the positive lens will be a bit more odd as nobody that I
know of does such a lens.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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