I can translate better than GL. The first value of 0.07 means exactly: " The total maximum deviation from absolute flatness of working surface is not more than 0.07 of micron at any place" Another value of 0.02 means: " The local deviation from flattness of working surface is not more than 0.02 of micron" The soviet industry was making two types of flattness measuring glass plates: PI (shown at your video and PM. The difference is that fist one have one working surface and second one have both sides with very very high grade of parallelism. Fist is designed to observe defraction lines pattern of air gape betveen tested surface and etalone glass surface fitted on it. Second can do the same, but also you can invesigate difference of opical way to front surface in monochrome light to obtaine absolute values of flatness deviation. This really very precise instrument to control flattness with acuracy exceeding most needs of tooling purpose.

" you can take the boy out of Russia but you can't take Russia out of the boy". I quickly sketched that symbol on a piece of paper and showed it to a colleague who used to work in Russia, he was on a conference call and couldn't talk, and the message in his eyes was priceless :) Cool measurement system. Thanks.

Tom, every time I watch one of your videos, it costs me money. I didn't know what an optical flat WAS, never mind that I NEEDED one until I watched your video! Well done OM, thanks for the info.

Good to see you posting again! You do come up with some really interesting things.

Thanks Tom, you never cease to pique my interest.

Tom Lipton: Collimating with the Russians to influence the refractions!!

Glad to see you back.. thanks for the video.

"In Soviet Russia, optics flatten you!"

Thanks a bunch for this video! I just took over our lapping area at work and have really no clue about what is all involved with it, but your video helped explain a lot without over complicating it.

One if the coolest things I've seen recently. Thanks for sharing it

Very interesting and informative. I have always found it very difficult to see interference fringes, but the He light made a huge difference. Your magic trick was mind-blowing. Translation of languages is one of the most difficult of all problems.

thanks for another interesting and informative post!

Super super cool video ! Thankyou for posting !

Thanks professor Ox. Learned something today.

Thanks for the video.

that was awesome, thank you

One can use an inexpensive low pressure sodium (LPS) lamp from the local big box store. The wavelength is very nearly 589 nanometers. This will provide far better fringes than daylight fluorescent fixtures and is nearly an order of magnitude less expensive than a new helium light source with power supply. I get better results when I remove the plastic diffusser from the LPS fixture. Your mileage may vary.

That toolmakers flat is begging to be lapped! Nice one Tom. ATB, Robin

great video. as usual.

The fact that the optical flat floats on air is awesome.

Great video Tom, I've only ever used fluorescent lights with mine, and at times they can be hard to read. I've wondered if a diffused laser or even standard LED could be used, but haven't had a chance to try. Other light sources could make a good follow up video suggestion as this has come up before.

The translator app was made possible by everyone's authentication on captchas. It's a similar tech with ReadIRIS's OCR but in this particular case, the app has a library of words that have been already transplanted from image to actual text. Which from there it's far easier to translate. And, yes, it's much faster than letter to letter translation. The app grabs a word vs letters. For example, if a word has never been put in to text-from-image, like say, some WW2 German word of notable length, the app will have trouble with it (tho, i suspect that it might also have some point to point or at least half word function based on some of the half grabs i've seen).

You can also use sodium lamps, they're commonly used to grow 'plants' so should be fairly easy to get hold of, and the wavelength is very close to that of helium. Some LEDs might also give better results than 'daylight' tubes. I'll be getting an optical flat sometime soon so I'll try a few out.

Very interesting stuff. I think that LPS lights should also work for that purpose as they put out monochromatic light. They are pretty affordable.

In the realm of the minuscule things get very interesting Tom.

That was interesting!

That’s very cool.

That's some interesting stuff.

Thanks Tom, The translator is amazing. Makes me wonder how much is "out there" that I don't have a clue how to access. Thanks for the share.

Cool stuff.

About the Soviet quality mark from Wikipedia: The sign is a pentagonal shield with a rotated letter К (from Russian word качество, kachestvo - quality) stylized as scales below the Cyrillic abbreviation СССР, SSSR (USSR).

I'll admit that I have not made careful drawings, but I am pretty certain that I know what causes those regular interference patterns. The thickness of the optical flat, measured perpendicularly, is some value T+-70 nanometers anywhere over the flat. The perpendicular thickness varies by about 1/8 wavelength. In other words, this is standard 1/8 wave optics. However, the light you see is a reflection from the shiny reference surface. It goes through the flat (plus any air gap) twice at an angle theta. Theta varies from point to point in your image, just like with any mirror. If G is the air gap, then the effective "thickness" of the plate is (T+G)/cos(theta). It's the cos(theta) term that determines the spacing. Cool stuff! Thanks for showing us all this.

Cool, thanks!

i believe the ПИ-80 is a bottom optical flat, so the working surface is the top one (marked). the bottom face is not guaranteed to be flat

1st: Whole degree of deviation from the working surface flat is: -0.07 micrometers. 2nd: Local degree of deviation from the working surface flat is: 0.02 micrometers. It's a second-class quality of accuracy so it's cheap but extremely useful. And yep! It's USSR made. Not in Russia. May be this stuff is 30 years old.

Cool, as usual

That’s brilliant. The google translate I mean. Also insights into optics. V good!

Hi Tom, How much do surface scratches on the glass affect usability? Great video! Thanks for sharing all your tips on metrology (and magic too).

That Google translator is trippy.

A darkroom light seems to work pretty well, as well. I picked up and old one for €30 and get some good fringes on gage blocks.

Neon light will work well. A flouroescent light with a green filter works, as does viewing thru green transparent film..or green glasses. Any curvature of the bands is easier to see with fewer fringes, so adjust the number of fringest 3-4 for the greatest accuracy.

thankyou. I have a very similar one.

Really loving these high accuracy based videos you and @robrens make. Is it actually a measurable means of flatness or just a representation of how flat something is or isnt and where high spots are?

Interesting...(grasshopper thought) curious what a piece ground from your surface grinder would have shown or would it even work

Great tips Tom - and a timely posting -I just dug out my (ebay) optical flats earlier today to look at deformation under clamping pressure (I'm trying to machine an aluminium heatsink to an acceptable flatness and need to play with clamping pressure) , my flats work kind of ok by eye with fluroescent lighting, but I can't get my camera to see the rainbow fringes, I tried our external low pressure sodium floodlight (a light source suggested by Gottfried Schuss in an earlier comment) once it got dark enough outside , and it looks much more promising :)

Ah those Russians. This was flat out interesting though.

amazing

Having principles is a good thing

so with a lot of time and effort you might get some pretty interesting results on your surface plate I would say ;-)

my eyes my eyes!!! the babel fish is in my eyes!

That Translate also blew me away. As a guy about your age who remembers needing quarters for a pay phone....You're right, we're living in the future.

Off the subject but, is the building in the opening scene of your videos, as well as on the covers of your books part of the Mare Island Navel shipyard?

I had no idea Google Lens could do that. Thanks.

Very Nice Sir, please dwell upon the measurement/distance of optical bands in relation to the (given) lambda of the helium light. Thanks

Wow. I'd like to live in an optical flat.

I think you can use a sodium lamp also (as in street lights). They also have a sharp spectral line, which will surely produce better fringing than luminecent lamp.

All best from Ussr

Я носитель русского языка,ромбик с знаком СССР,это клеймо знак качества,это очень высокое качество ,100% гарантия соответствия.

Great video as always. Out of curiosity, I looked on eBay, and there's still a bunch of these available. Had a question though: they are labeled as "bottom" and "top". Any idea what that means in practical terms? Does it matter which kind is used for this sort of analysis? In one of the lapping videos, you mentioned concave vs convex flats, wonder if that's what this refers to...

Will this work on a granite plate? Or does it need tone somewhat reflective? Thanks Tom. Really enjoy your videos

Is nice!

Can you use a laser-pointer with a light-diffuser to look at fringes? I am thinking that laser-pointers might be an inexpensive monochromatic light source? Not sure how to make or set-up a light-diffuser to spread out the laser light. But might be worth a try? Maybe this: small lens to spread out the light onto a piece of paper which then diffuses/reflects the light?

"Theres couple humps I thought you'd get a kick out of." Yup, if we've gotten that far, we probably would. :-D

How would this work with first surface aluminum and sliver mirrors? We are having issues with some at work and I wonder if this could help us see if the issue is the glass or surface coatings it's kind of a niche task we use them for.

Hey Tom, kind of off topic but, you did a video a while back in which you made a template and followed it with an indicator keeping it as close to zero as possible as the lathe fed in. Ive been trying to find it as I have to do something similar for a job at work coming up and want to see how you did the job to refresh my memory. Could you tell me the name of the video if its still up?

How about looking at fringes on one of your collumater mirrors?? That would be cool!

Would a red laser pointer with the lens removed, work for a light source?

Have you tried using a white LED light to see the fringes? They are typically a blue LED with some phosphors to balance out the color to white, but the spectrum typically still has a very strong blue peak compared to the much weaker and broader red peak. I'm curious if you get better results compared to a fluorescent.

If you get circles it can be hard to decide wether the part is concave or convex(high or low spot). By pressing with your finger, if the pattern moves towards your finger the part is convex, if it moves away from your finger its concave. Carbon parts can be tricky, they must be polished to a shine to be able to read. Getting both the shine and the correct shape i.e concave/convex (no you don't always want flat parts) is hard

Tom, would a sodium light make for better contrast in your interference lines? Or is Helium also a pure color

Helium discharge lamps are pretty expensive. Much cheaper to use a laser pointer with a beam spreader or diffuser. A green, blue or purple laser would provide more accurate measurements than the yellow peak of helium emission, by virtue of their shorter wavelengths (typically 532nm, 447nm, and 405nm respectively for green, blue and purple, compared with the 588nm line of helium)

So what I'm hearing is that you want to use a single wavelength light source to maximize the interference. I'd try a low pressure sodium vapor lamp (The kind used in cities, and the cheaper the better.) because they're common and have one dominant wavelength.

I've got a lot of good things from the USSR. Many Camera lenses and scintillation detectors.

Tom, I've just bought myself a Russian Optical flat off ebay. I think it would very interesting to test the sole flatness of my Record 5 1/2 hand plane. Also testing the difference in flatness before and after closing the lever cap is a very useful experiment. Many thanks for sharing your knowledge and experience. I now follow you on Instagram. Best wishes from London!!

What about a blue laser diode, is the light a narrow enough frequency band to make an effective light for viewing fringes when defocused? I have a 2 watt laser diode I was originally using for etching, but when I realized how little I used it I recycled it with an old overhead projector and some frosted glass to make a rudimentary optical comparator, so I'd be happy to keep reusing this little diode until I find it a permanent home where I find it's most useful.

Good info Tom. The translator app reminds me of the sun glasses in the movie "They Live". Any special tricks on cleaning optical flats?

Are there different coatings on optical flats for different purposes? Seems like I see different types for sale. Is there a certain one for metrology? Thanks to anyone willing to answer.

Good LED in different colors can do the job because they emit mostly in a single wavelength, a LASER can also do the work very well, I suppose it should be scattered, but what matters here is that it is a monochromatic light. For sure any of these is cheaper than a Helium bulb and much better than fluorescent. And the best thing is to turn off other light sources while testing.

So how good are your diy flats?

i thought you had another video on optical flats. i cant find it right now.

I have used my pocket laser pointer as a light source; try it.

Will any wavelength of light work? For example, a sodium "D" lamp produces a single wavelength of light; would that work?

With the polished sample under normal florescent light what color of the fringes are actually in contact with it optical flat? The purple, green or yellow?

Would LED light source be good for this? Usually the different colors are rated in their nanometer wavelengths. It was interesting that I had a 650nm laser and a 670 nm laser, to they eyes, 650 looked brighter, but to a camera with IR filter removed, the 670 was brighter.

what is the model of the He lamp? all i have are tube sources for He light and it is very pink compared to your orange

I just found a optic flat cylindrical test plate made by The VanKeuren Co. Watertown Mass. At a garage sale last weekend and they gave it to me with a few other stuff that didn’t sell at the end . I new it was a testing / calibration tool of sort. Thought it would make a good paper weight or ? As I watched your clip and the pitted flat needs a backup . ? Honestly I just stumbled across your channel and watched a few of the videos and realized that it wood be a shame to let it sit in my shot as a beer coaster ! So up fo grabs just take care of shipping cost , it feels like 10 lbs + and has nice case it stores in . 6” x 1” + /- surfaced both sides. OBTW. I did ask how they got it , they purchased the home a few years back from a elderly man that was a engineer for Hanford DOE site for over 40 years. I can send you pics and let me know if you or someone can use it . Allen S near Hanford Wa USA

Darn, I just loaned out my helium therapy light.

Magic trick? What more magic do you need than being able to wring two flat things together? Pretty spectacular with that helium neon source though.

Does the surface to have to be reflective to check with an optical flat?

Just FYI: On that paper part of that text was written by hand (2nd line). It means "bottom" or "lower", so this flat glass plate is bottom/lower. Lower plates were 60, 80, 100, 120mm , when top one was 60mm only. Plates were produced in two types: lower and upper. The lower (supporting) plates are used to check the lapping and flatness of the measuring surfaces of the end measures of length, calibers, measuring instruments and tools. The upper plates are used to measure the plane-parallel end measures of length by a technical interference method. I've get this text from Internet and translate it for you. I neverI'm not sure how work with these plates. @Tom could you explain more about them? some pics of upper plate: images.ua.prom.st/14435431_w800_h640_dc120709008.jpg images.ua.prom.st/14435433_w800_h640_dc120709010.jpg

2:45 wow ........... just wow

Hi Tom, Interesting video. Can you share a link to where you can buy them? I searched at eBay and could not find this same one. Thanks

If you like to buy on ebay, just buy a vintage tanning bulb for $25 and aim it a white ceiling. Who needs helium or sodium light ? Also I was waiting to see you put it on something that would show us only 5 fringes.

Hi Tom, do you think I could build a light source using LED's of the correct wavelength?

I find it interesting,you can acquire a precision device from the source stated,which would seem to be necessary for the former residents of the area indicated,to reproduce precision machining for their industries.Makes one consider why it becomes useless to them now? have they no need for such devices? when most government entities would highly covet them!!

Some colored LED's are rated in nanometer spectra. Red for example is commonly rated 620 Nm. An array might make a nice monochronomatic light source. There are over 6000 eBay hits for red colored LED flashlights and many are less than $10. The distance represented by fringe deviation will have to be figured in based on the actual color wavelength. Anyway monochromatic light can be affordable

just wondering how do you know that the high spot is a high spot and not a low spot ?

The smallest strong wavelength wavelength from a Helium atom is at about 447nm. You can buy LEDs with their maxima at this wavelength (royal blue). Just google 447nm LED, cost you a fiver or so for a 2W one. That will be plenty.

Hello friend, your video is very interesting. I have a flat Russian optician. I need to get the monochromatic light. Can you tell me where to get it? Thank you very much for your help. Regards, Luis

After your videos, Tom, ebay gets emptier , and it gets harder to find good stuf. остановись товарищ! Привет from russian speaking viewers!