> you own HMD optics, you have to hit the books and the websites
> explaining such
> things like chromatic aberration and astigmatism. If you're aiming
Uh, chromatic aberration should not be a problem. LASER sources
are, by definition, monochromatic. This is why in my original posts,
I mentioned that even a cheap "simple lens" could easily serve in
this function.
Now, if we're talking about a full color system, that's a different
story.
Of course, mirrors don't exhibit chromatic aberrations at all...only
refractive optics have that problem.
> available items (optical quality nonparabolic mirrors of high
> curvature are not
> something you'd be able to grind in your garage or get at Edmund
> Scientific), and
I always forget...when viewed from within its focus, do we need a
spherical or a parabolic mirror?
My thoughts were leaning towards an off-axis mirror, but talk
about something hard to grind! And good luck with finding it
off the shelf.
> You might talk
> to your friendly hobby astronomer. They've been known of using
> lenses and mirrors, sometimes.
And making them...it's not a difficult process, just very exacting.
Hobbyist grinders can often achieve results within 1/10 wavelength
(What is the ASCII code for lambda?) on 6" and smaller mirrors,
but that is with a very long focal length. Short FL mirrors are much
harder to grind accurately.
A good source for decent mirrors, is old but high quality projectors.
I've been known to rip a few out of equipment, and find the quality
is remarkable.
I have a front surfaced f/1 spherical mirror, 1" in diameter. Totally
useless for anything, so of course it got thrown in a drawer and
"forgotten" until this thread came up...and it needs resilvering now.
:-(
-- Chuck Knight
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