Well, I have Japanese, Swiss, Czechoslovakian, Soviet, Taiwanese and of coarse Chinese, measuring instruments. And I continue to choose the sovietic, even if it is used!!!
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.
I've used Neon indicator bulbs successfully for this application. This is quite a small light source and 3 or more bulbs can be used in parallel with the right resistor in series. I didn't have an optical flat for my work at that time (30 or so years ago) and used a small piece of float glass instead. Worked quire well for my application: checking the flatness of mechanical seal surfaces. This was a custom made seal for a small shaft on a pressurized hot air engine.
Russia is a country of contrasts. Where the greatest accomplishments drown in the swamp of poverty and madness of leaders. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-AguQ8NHywDI.html
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).
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.
" 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.
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.
Led's are never as precisely monochromatic as gas discharge tubes - they have a variable electron gap, so they can produce a band of wavelengths instead of a single.
Still, they have to be a lot better than 'daylight' florescent bulbs, no? I guess there's not that much price advantage over LPS. I seem to recall that years ago sodium was the lamp of choice for optical flats. When did helium take over?
do we/ can we check this? that would be so much cheaper that and we could put those cheap lights in the lab so flats can just be used without turning on a separate source.
Kind of shocking. The P&W flat looks like crudd while the more visibly polished one, well, I would have put my money on that one. All that glitters is not gold ladies and gents.
Indeed. I am a novice surface grinder hand, and have already learned well that flat does not mean shiny and shiny does not mean flat. I am happy to achieve either, but never both so far... Not that I ever expect to get the level of flatness in those optical flats, fat chance of that...
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).
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)
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.
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.
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.
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
Doesnt the frequency mean how quickly the gap changes over the surface? If the two surfaces were absolutely perfect and exactly parallel the frequency would be 0, ie no bands at all.
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.
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.
Yes. It is by far not as clean as He-lamp, but it works in a pinch and is a lot cheaper. Also one could use a laser pointer, as that is also very monochromatic, but lighting a table with laser pointer gets difficult fast :)
Raido Enn Low pressure is the key. I'm not sure if you have ever tried the laser or not. I tested with the He-Ne laser we have, expecting to see some chrisp fringe, but result was quite disappointing. The fringe is quite fuzzy.... even with all the other lights turned off
We have some optical lab work (practical course) in university and use Soviet era mercury lamps for the same reason. You would have to have a very powerful laser and diverge the beam to get some well visible fringing, but a lab He-Ne is usually not intensive enough (although being very monochromatic). So for all practical purposes, some atomic emission lamp is your best bet.
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?
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
I have one of the "top" plates. It has a large, angled surface (1/3 the surface) on the side that has the cross lines scribed on it. What is the use case for this special flat?
huh the helium lamp works better because of the narrow bandwidth of emission is there an led equivalent there usually pretty narrow you can grow some pretty good plants under them ge daylights. That google translate is f-ing wow drink your ovaltine cool. awesome Halloween show tom thanks for filling my mind with wonder
I've heard that regular LEDs are too wide spectrum to be effective but I was wondering about a laser diode where the lens is defocused enough to make it a wider field instead of a narrow beam, then it can be pointed downwards so there's no possibility of getting a dangerius laser in your eyes. I have a 2 watt blue laser I used as the light source on a homemade optical comparator using the lenses from an old overhead projector.
ya ive seen led's (blue in particular) that you can't discern red from black. that comparator sound pretty dam handy if you can use the standard reticle from the pocket comparator you've probably already figured out that some of the most important things are measured like that that's why I like tom he's got as good of questions as he dose answers
When using white light, discernable contrast fringes only appear for a distance of a few wavelengths and fade away as the gap gets larger. So with white light, high spots will have higher contrast fringes.
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?
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
The russians were the force of subjugation behind the USSR. russians = soviets. None of their victim countries' populations ever considered themselves soviets.
@@AlexLTDLX Come on. What if you were born in the USSR and are a mixture of Poles, Russians, Kazakhs and Koreans? Before the beginning of the collapse, all were indifferent to nationality.
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.
Bill De La Vega in my laser technician classes we placed a new sheet of lens paper on the lens surface and wet it with acetone just to the point that the entire surface was wetted. Then you slowly pull the paper off in the same plane as the surface. Repeat as necessary.
Years ago we used to clean the flat in a laminar flow clean room with 190% ethanol (we also had great Christmas parties in that division of our company.
Yes when I was a graduate researcher we had optics that were part of a laser diode velocimetry rig and used ethanol (which was not denatured) to clean them. One of my lab mates got a little buzzed by the vapors after she cleaned a bunch of mirrors and lenses.
Hmm I thought that acetone would damage some optics which were coated? But I guess in this case that's not a problem. I'm wondering if hardware store variety is pure enough?
ETOH or Acetone. Would depend on the coatings. The etoh we used was Graves fine distilled. 190-200 proof. A few livers suffered greatly. (Available at select, exclusive "Spirits" vendors.
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.
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.
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...
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.
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?
Soviet precision instruments and especially the optics were considered top notch at the time. One anecdote to attest to this is about Japaneses smugglers buying lots of soviet camera lenses from Vladivostok because of their quality and dirt cheap price.
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 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!!
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.
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?
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.
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.
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.
Google is really tearing down the language barriers with technology. They just released a pair of headphones that can translate someone speaking in real time.
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?
