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Making IR optics.

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S. Heslop:
This is somewhat silly but i've been thinking lately about how possible it would be to make a relatively cheap FTIR spectrometer (or several) at home. I'm still at the phase where i'm trying to figure out if it'd be even possible though, but i've got a few ideas. This thread is sort of a sanity check since I'm sure there's people that know more about this stuff on here than the crap i've been able to find through google.

The things i'd like to make myself are off-axis parabolic mirrors, IR windows, and a beam splitter.

For the IR windows i've been thinking about using zinc selinide co2 laser cutter lenses and grinding them flat-enough. The most i've found about grinding lenses, flats, and mirrors at home is from the amateur astronomy world where they're grinding large chunks of glass. I'm not sure of the same techniques would translate as easily to a single 20mm diameter blank, but I'm thinking it might be possible to stick/ clamp them all to a surface and grind a whole bunch of them at once. But i'm not so sure on a good method for sticking them that would be easy to remove once the job is done.

For the beam splitter i'm thinking it might be possible to sputter a half mirror onto one of those flat-enoughs. There's alot of stuff online about sputtering at home. But I think I might need to find more info on other optical coatings to reduce internal reflections or the mirror from corroding. Not been able to find much on stuff in the mid IR region though.

I feel sort of half confident about the windows and the beam splitter, but where i'm really stuck is on the off-axis parabolic mirrors. From what i've seen (t=2m37s) they're made with fancy CNC machines. I'm not sure if there's a way to make one (or several) at home to a high standard, but I've been wondering if it'd be possible to cast or press one if I was able to get a die made. I don't think regular resins would retain their shape to a high degree, nor would anything that needed to be heated up. And then assuming i'm sputtering the mirror surface onto it then it'd need to be able to survive some temperature.

Any information or advise would be appreciated.

PK:
A tiny CNC lathe (like a taig) and a diamond tool.  You get your off axis bit with a fixture on a faceplate...
????

S. Heslop:
It'd need a fairly large swing for that I feel. Although i'm beginning to think it might not need to be a super fine surface finish since with acrylic I could try that vapour polishing thing to smooth the result out.

I might've jumped the gun a bit with this thread since i'm still trying to learn stuff about optics. The main purpose of the off axis mirrors is to gain a collimated beam from the IR source, and then to focus that beam back down to a point on the detector at the end. It seems like something that aught to be fairly accurate, but accurate is a relative term!

S. Heslop:
Are there any good websites/ forums for CNC stuff out there? Most of what i've found googling about has been absolute crap.

PK:
www.cnczone.com is good. Big, but good

Here's one I prepared earlier http://www.caswa.com/cncathome/lathe.html
Ignore all the bits about the electronics. The advent of low cost stepper drives has changed everything and it's all COTS now.
PK

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