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22nd July 2014, 10:01 PM #16SENIOR MEMBER
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Michael I'm curious as to what you mean by interference in unwanted places? While I'm aware of the process, I've never used my flat for anything other than surface condition (ie "flat"/concave/convex, depending on the fringe pattern), and assume you're talking about absolute measurement circumstances?
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22nd July 2014, 10:44 PM #17Philomath in training
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Not a very precise comment on my part really - but if the spectrum bands are separated by too much distance or there are too many of them they could interfere with the other light frequencies so that clear well defined fringes are not as easy to get. Sodium is the common (cheap) solution.
Michael
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23rd July 2014, 01:58 AM #18
Peter,
have a look at
interferometer | eBay
and see what goodies you might find there.....Cheers,
Joe
9"thicknesser/planer, 12" bench saw, 2Hp Dusty, 5/8" Drill press, 10" Makita drop saw, 2Hp Makita outer, the usual power tools and carpentry hand tools...
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23rd July 2014, 11:19 AM #19SENIOR MEMBER
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- Oct 2007
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Nothing there Joe. These are the mirrors used fir autocollimation
Nikon | Instruments Products | Industrial : Autocollimator Accessories
My original intention was to scrape a cube and attach a first surface mirror to that. By flipping the cube and autocollimating on it I could auto-generate a precise 90 degree surface. However I'm also considering instead making it an adjustable 3 point stand, with one if the points a very sensitive micrometer arrangement so I can take my angular readings at the mirror end instead of the autocollimator end as is normally done. I have a very good reason for wanting that, but need to rush to work so can't explain now.
pete
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26th July 2014, 12:46 AM #20SENIOR MEMBER
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- Oct 2007
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Sorry for the delayed response, I was just heading off to bed and realised I hadn't checked this as promised so raced down and had a look.
My little Mitutoyo plate is filthy as I use that all the time and I didn't think I'd get much to work off that, so wasn't exactly surprised when I couldn't get fringes. Instead I whipped the cover of the bigger Chinese delight but also couldn't get any fringes. I grabbed a mic and that works just fine without fail, so there wasn't anything lighting wise etc to spoil the party.
While flatness may be an issue, I think a bigger problem may be that the colour and texture of a granite plate means the light isn't reflected very well, and that's something that's essential for the whole interference caper to work. So while floating the optical flat around isn't a problem, seeing anything meaningful with it is.
No great surprises there, but I thought I'd just confirm what we all suspected.