Russian Optical Flat Testing

[Music] welcome back doc stools I'm Tom so I got kind of an interesting check out here that's that you guys might like what we have is we have an optical flat that was sent to me by a friend of mine in Southern California Rick piranha Mae and we got to talking at the bash and I mentioned you know he was talking about buying an optical flat off eBay and how you know it's kind of a tricky thing to find one that's in good condition right so I suggested some Russian surplus ones that I'd been looking at and and this is one of them actually it's 80 millimeter diameter and it's actually turns out that it's a really really nice optical flat anyway they sell for pretty cheap on on eBay and there's quite a few of them around anyway kind of on spec he bought one and then was having trouble having it produce fringes that he could look at so that's what we're gonna help Rick with and see if we can see some fringes and look at this cool Russian optical flat alright what I got here is I have the optical flat that Rick sent me and I have a couple I have three surfaces that we're gonna take a look at but first before we get into that I want to show you a magic trick it's kind of neat and it's it's interesting because I took this little piece of paper to work and this is a basically a certificate of accuracy from the manufacturer and we have a couple of native Russian speakers a scientists that I work with at work and I had both of them look at this and it was actually kind of entertaining to to have them translate this so but like I said I want to show you a magic trick first so let's let's do that and I think you guys will like this and it's something that you guys can do yourself with oops excuse me similar similar kinds of articles okay so here's the calibration certificate that came with the optical flat and some of you guys out there may be native speakers and can actually read this already and you know just kind of glancing at it it's got some numbers on it and dates and things like that and serial numbers that we can identify even though we can't speak Russian but oh but wait we can so on your phone google translate if you hit this little picture icon here okay let's see if we can get this thing to happen here yeah let's do that so how do you like that so we are reading Russian even though we can't somebody showed me this the other day and I was just kind of blown away and that that this could this could actually happen so we are truly living in the future and like I said I had a couple of native speakers look at this and they were actually amazed at the translation and you know they said they had some comments and said it was all wrong but this is the sign of very very high quality in the USSR so to get this stamp it was a big deal this is like the I don't know ASTM you know validation or whatever kind of stamp for the USSR and what we see here is a deviation from flatness is point zero seven and this is says mkm which is kind of a weird abbreviation for micrometers otherwise known as microns okay and so from this we can kind of derive some information about this about this optical flat here and it's got the it's gonna be really hard to see the serial number on it there as well anyway I thought you guys you get a kick out of that magic trick and so let's take a look at this optical flat and see if we can get it to to make some fringes alright so first up is our gauge block and we're pretty sure that that's flat nicely so let's wipe this off with a kimwipe gonna give the optical flat a little wipe too and then what I like to do is is Blom off as I'm putting them together let's see what we got here okay now I can I can see them from where I am here and look at the viewfinder there and you can see them but they're pretty faint and you can see them swishing around a little bit they rotate this we can get a better orientation okay there's there we go they're going across that way so this is pretty faint stuff in this particular light so this is just a fluorescent lights third are in my shop which happened to be daylight temperature so we're showing some fringes there okay and you can see they're swinging around depending on how I tipped this here alright so the optical flat does work alright and it's working on daylight fluorescence right now so one of the keys when you're doing this is everything's got to be like scrupulously clean so when I got the optical flat it had some sched on it that I took off and cleaned it real carefully and and anyway it produced fringes right out of the box no problem and we're going to look at it under a special light I have a helium light source here too which is a special wavelength so that we can actually interpret these bands and their curvatures for measurement so let's look at something else what do you think let me let me set up the next one and we'll take a look at the the next surface and see if we can see some money this is this Pratt & Whitney toolmakers flat here so we're gonna we're gonna try a different technique here we're gonna put a kimwipe down first and then we'll and these have been cleaned ahead of time and then what we're gonna do is we're just gonna slide the kimwipe out and then and hopefully we can see some okay you see that little shimmer yeah it was actually so you can see a little shimmer this is this one's harder to see this surface is not great I mean it's actually pretty flat but it's pitted so and it doesn't have a lot of a lot of I see it's it's floating on a cushion of air right now and actually it's almost running to the plate now I'm picking it up set it down and yeah this is just so hard to photograph case but we're gonna we're gonna get it under the helium light and it's a heck of a lot easier to see that it is producing fringes I can see them from here but it's the camera's having a tough time picking those up let's take a look at this other kooky surface here that's more reflective but if I can tell you that it's not very flat yeah oh let's do this see we can see in this one yeah okay and you see that weirdness so it's giving us a contour map of this screwed it around oh it's non flat condition and I think this one depending on the temperature it has a couple of humps in it that I thought you guys would get a kick out well you can sorta see him you can sort of see him all right so she up here and get some curvature then there's a contact point right there and then as I push on it it moves it around alright so let's get this fungus some healy let's get these things under some helium light and you guys can really get a good a good shot of this okay alright so we got the helium light on it's warmed up and you can see it's kind of get a and kind of a yellowish orange tint to it and once again you know it's always you can almost never be too clean with this stuff so we should get some Goodman's the helium produces a really sharp crisp interference bands there you go that's pretty good there so you can see that so the straighter those lines are the better your surface is okay when they're perfectly straight the surface is as flat as the optical flat so there's proper fringes there and so you don't read the spacing of the fringes okay what you're reading is you're reading their curvature so if they're bowed you know they have a curvature to them that's it's like reading a topo map so you know I can lean on this a little bit and you can see that the spacing changes and all that means is the little wedge of air that's between the gauge block and the optical flat is changing thicknesses okay so there's more as it gets thicker it shows more more more lines because the wedge is thicker and the spacing between the line stays the same okay and that's in this case about what is that 11 millions of an inch something like that okay so this is 600 and excuse me it's 587 point 6 nanometer wavelength light so from that we can derive the the spacing of those lines and it's a integer value of of the wavelength and we're half wavelength so okay so that's the optical flat let's look at the Pratt & Whitney flat which is about the same thickness so my focal length should be pretty good let's see if we can get some fringe ease off of this I'm just gonna sit that down there you go okay so now you can see them and you see they're nice and straight right so what that means is this this Pratt this old beater Pratt & Whitney toolmakers flight is still pretty flat even though it has some kind of corrosion spots on it now the more let's look at this other one because it's really interesting let me get it set up and we'll take a look at that one too yeah you guys you ready for this one this one's pretty cool clean it good flat a little spritz very carefully now this one's got some some interesting topology here which we can look at so just this weird little corrosion spot in the middle there and then there's a there's a little high spot over there actually there's two high spots there looks like over here and as I push on it you know the plates tilting a little bit in relation to those high spots so it's shifting things around but those are fringes and our our Russian optical flat seems to function as advertised and so if you guys are interested in playing around with this kind of interferometry stuff which is pretty neat stuff and it's accessible these are like 60 or 70 bucks on eBay the light I would suggest this going with these daylight fluorescents initially because these the helium lights can be kind of expensive so you can actually do some do some stuff with just florescent lights you know there you go so it's so as it sits there the air kind of bleeds out and it settles down even even more and you can see we have a couple distinctive high spots there so pretty neat stuff though so Rick I'm gonna send your optical flat back and it seems to it seems to function as advertised so play around with it and see if you can get it to produce some fringes now you need some flat surfaces so use the gauging surfaces of gauge blocks or other things that you're pretty sure are pretty darn flat okay thanks for watching guys [Music] you [Music]

Channel: oxtoolco

Views: 73,397

Rating: 4.9229083 out of 5

Keywords: Optical flat, Russian optics, USSR, Metrology, Translate, Interferometry, Fringes, Pratt Whitney Toolmakers flat, Gage Block, Lapping, Flatness testing

Id: 8I5P-r4ogm4

Length: 14min 38sec (878 seconds)

Published: Mon Oct 30 2017

Reddit Comments

[u/bvillebill]

As someone who makes telescope mirrors, most people use little neon lamps that cost very little and work great. And, you have to let the two pieces settle for a while to let the air out to do real testing.

[u/soaponaropebob]

What are some classic uses for an optical flat? Who would have made up the market for these 80mm Russian flats in their day?

[u/plazmatyk]

Sweet. I wonder if LED or diffused laser pointer light would work well. Neither gives a nice single spectral line, but they’re fairly monochromatic. Like a couple nm wide.