Autocollimators 3: Optical Design

In this episode of the Machine Tech Video Blog, I break down the optical system in an autocollimator piece-by-piece - from the light source to the eyepiece.
Here's the list:
- Light Source (almost any will do; LED is preferable)
- Target Reticle (crosshair markings are conventional)
- Objective Lens (achromatic doublet with long focal length and wide aperture; irregularity precision 1/4 wave or better; anti-reflection coating is preferable)
- Target Mirror (first surface mirror approximately same size as objective lens; flatness precision 1/10 wave or better)
- Beamsplitter (50T/50R non-polarizing cube-type; precision flatness 1/4 wave or better; anti-reflection coating is preferable)
- Scale Reticle (finer graduations = higher autocollimator resolution)
- Eyepiece (should be well-corrected for aberration and must be able to focus on external reticle; higher magnification = higher autocollimator resolution)
I discuss the selection and arrangement of each one of these components, as well as many relevant concepts in optics which were not covered in the preceding two videos in the series. By the end of this video, you'll have all the knowledge you need to go out and build your own working autocollimator. In fact, that's exactly what I'm going to do in the next video. Stay tuned!
To purchase the optics kit I used in the video, do an eBay search for "Optical Concave Convex Lens Prism Set Physical Optical Kit Laboratory Equipment".
For further reading on this topic, check out "Metrology with Autocollimators" by K. J. Hume. It's a fantastic book, albeit hard to find.
Juicy jams by Sun Hop Fat - "Yègellé Tezeta": www.sunhopfat.com/
For daily posts on related content, check us out on Instagram @laneymachinetech
For more about Laney College, check out the website: laney.edu/machine_technology/​
AND BE SURE TO SMASH THAT "LIKE" BUTTON!

[@sighpsycho]

Please list the next video, we'd all love to see the build

[@31k3csgo]

Thank you for doing this! The only thing I am more anxious to see than the autocollimator build is the continuation of the air bearing series. Your channel is gold.

[@ebrewste]

You are really doing great. You can see all the comments about what a great teacher you are. To me the thing that really takes this to the next level is that you are doing topics that aren't covered over and over on KZbin. Not only are you bringing great teaching and production values, but you are genuinely adding to the topics out there for everyone to learn from, like when scraping videos became a thing.

[@LaneyMachineTech]

Thank you! 🙏 I’m having an absolute blast making these videos! Ultraprecision is such a fascinating topic, and optics always comes up along side it. I’ve been trying to beef up my knowledge and I’m excited to share what I’ve learned.

[@tomaszkluska6419]

@@LaneyMachineTech Hello! Autocollimators 4? PLEASE!

[@VastCNC]

I went from an interest in machining, to an interest in photography, and you just explained so much of both when it comes to light and lenses.

[@LaneyMachineTech]

There’s such a rich cross-pollination between the subjects of metalworking and optics. I wonder why it’s not explored very much?

[@VastCNC]

@@LaneyMachineTech I've seen chromatic aberration "color fringing" and spherical abberation "barrel distortion" in lens reviews in images, but never an explanation this good as to how and why they occur, and how the lens elements interact and effect the resultant light waves. I kinda want one of those lens kits now.

[@piratepartyftw]

I would love to see the build video if you ever get back to this series :)

[@Leedramor]

Dude, I was learning mechanical engineering in S.Korea, and saw this "autocollimator" on a table of angle measuring devices for the first time. I had no idea what this thing was, so I came to youtube just to see how it looks like and found this amazing series. Man, I love internet. And now I love optics too, thanks to you.

[@LaneyMachineTech]

You have no idea how happy I am to hear that! Thanks! 🙌

[@mojaveri]

Wow, this video was one of the best ones on autocollimators, explaining how optical systems work and why they appear the way they do. Well done!

[@michaelbabatunde3915]

Indeed, you are down to earth a great instructor. I stay glue on your video. Many thanks

[@harshavardhanpv7099]

My professor included this video in our learning thread, I think it's the best thing that he did in our course.

[@MrEmbedded]

Would love to see the next part of this video series

[@Steve_Just_Steve]

That was AWESOME. Just the right amount of depth explained in a concise manner. So hard to find this kind of info on YT without it being dumbed down to the point of being uninformative and boring. Thank you!

[@LaneyMachineTech]

So glad you enjoyed it! I targeted this video to people like me who know something about mechanics and manufacturing but don’t have a background in optics. I tried to offer simple explanations using geometric ray optics theory which would allow me to cover some hard-hitting concepts while still being accessible. Ultimately, the idea is to build intuition so that people can have the confidence to make their own optical instruments.

[@Steve_Just_Steve]

@@LaneyMachineTech You did an excellent job, as always, can't wait for the build. There's a reason you're a teacher. Then... Lets see your dogmeat scraper on YT! ; )

[@LaneyMachineTech]

@@Steve_Just_Steve OK lol it’s on the list 😂

[@purpleduckboy]

This is a great series, easily the best explanation of how autocollimators work I've seen.

[@christoph4340]

I can't wait for the next Video. Autocollimator 4. 👏

[@harshavardhanpv7099]

No words, simply awesome✌️ Waiting for the next video

[@rodfrey]

"But this video is way too long already". Yeah, if you don't mind, we'll be the judge of that. :) Thanks for some incredible, off-the-beaten-track content. Can't wait for your build.

[@LaneyMachineTech]

Thanks! I’ll keep ‘em coming 👍

[@mulholla]

This is a great series, thanks for taking the time to make it!

[@LaneyMachineTech]

You bet!

[@maxkotlarchyk4242]

Thanks a lot for this video series. I appreciate how you broke down and built everything up from basic principles. Been working in building optical systems for a while, but just started getting into some of the more manufacturing/metrology side of things and using autocollimators in my job. This run through was great in getting a perfect understanding of what I'm working with. Keep making the awesome quality videos!

[@jonludwig8233]

Awesome work, keep em coming! Super interested to see the build process as well 🤘

[@kevinrblodgett]

Terrific! Also I'm blown away by Robin Renzetti having spindles with less runout than the wavelength of light you were talking about 🤯

[@LaneyMachineTech]

What’s more amazing to me is that those kinds of tolerances are just a matter of course in the semiconductor industry.

[@shaunmucalo6683]

I hope you do eventually find time to do a deep dive video on the more complex designs. I am hooked on this series. Love it

[@LaneyMachineTech]

Great to hear! I will definitely come back to discuss those designs.

[@DK-vx1zc]

Excellent! Very clearly explained.. Things I didnt understand before.. Looking forward to the build! Thanks for taking the time to create this series.

[@LaneyMachineTech]

Glad to hear it! 🙌

[@reiniertl]

I would like to see the continuation of this series. Maybe in 2024 we get another autocollimator month?

[@treverkirk8110]

Incredible, thank you so much for taking the time!

[@LaneyMachineTech]

I had a blast doing it!

[@das250250]

Perfect tutorial , Ty for all the effort and skill

[@mattym8]

This is an exceptional video. And I’m only halfway through.

[@LaneyMachineTech]

Thanks!

[@mattym8]

@@LaneyMachineTech ok I’m ready for the next video now. 😎

[@user-gq5pj5by7m]

Очень интересно и занимательно. Огромная благодарность!

[@adf360]

I love your videos and you are clearly a brilliant person so I'm just providing this as food for thought; LED's are a "no-no" in most inspection optics like aircraft bore-scopes because the wavelength of the light hides defects/blemishes. Same goes for inspecting aircraft wiring, USAF banned the use of LED lighting for inspections because they found it failed to cast shadows to illuminate the defects. The formal explanation was a bit more in depth/complicated but I'm retired and don't have it handy anymore.

[@LaneyMachineTech]

Weird! I never would have thought of that. If you find an article which discusses the reason behind this, I’d love to see it.

[@adf360]

@@LaneyMachineTech If you or anyone reading this can get their hands on a copy of NAVAIR 01-1A-505−1 (the bible of aircraft wire maintenance), that's where you'll find it, the change was 2014-16 time frame. From anecdotal/personal experience the difference in a sea of white aircraft wiring is 100% night/day. What you can see w/an incandescent is surprisingly imperceptible w/a comparable LED. As I understand it, the wavelength of incandescent casts a shadow across a crack/void where the LED (being more effective and of a differing wavelength) illuminates the void, making it invisible to the naked eye. Keep in mind too, aircraft wiring is typically pristine/clean even when it's cracking/crazing from old age. If the cracks were dirty, perhaps the LED would fair better.

[@vitortavares2739]

Thank you for this great work/series. Very well done.

[@LaneyMachineTech]

Thanks! 🙌

[@remoores]

Love your work, Hope you are well, cause i am hanging out for your next video

[@yagwaw]

I’m looking forward to the build a lot!

[@LaneyMachineTech]

Alright! I’m working on it now 😁

[@WoLpH]

I was kind of worried that you would start going into quantum wave interference, but this was extremely easy to understand for such a complex subject. Absolutely amazing work!

[@LaneyMachineTech]

I really tried to keep my explanations confined to simple geometric ray optics. There were some places where I had to mention the wave nature of light, but I decided to just tap dance around those topics 😅

[@aldemaria2872]

I just finished making one a few days ago! Thanks for the inspiration!

[@LaneyMachineTech]

Awesome! I’d love to see it!

[@EatRawGarlic]

Thanks for the video! Although at some point in time, most of the basics was ready knowledge for me, I noticed I could definitely use some freshening up. And seeing it applied in a practical way is always more fun than just knowing the theory.

[@LaneyMachineTech]

Glad you found value in it!

[@YagoFernades]

Dude, you are a terrific teacher. Thx for sharing

[@LaneyMachineTech]

Thank you for your kind words!

[@ctprjcstv3998]

This may be irrelevant. But for measuring small angle changes we may be able to build an electronic level which is based on TV gun. It shoots electrons to a detector receiver and the receiver shows the angle.

[@MT_T991]

Been awaiting this, as ive been playing with this idea for a couple years just haven't committed after buying an autocollimator

[@LaneyMachineTech]

Hope this got you excited about it again!

[@mardu1541]

Awesome! Can't wait for the next one. I built a real crappy collimator in uni years ago using an old soviet microscope and couple of old mouldy photo lenses. Luckily didn't have to milk a spider, but lost some hair over it :) It worked.... horrible :) This just might be a kick to revisit that project!

[@LaneyMachineTech]

Thanks! I really do hope this video series convinces you to revisit that project! Autocollimators are surprisingly easy to make and IMHO way under-utilized.

[@danielepatane3841]

Your channel is really interesting thanks for sharing

[@ShopperPlug]

Your explanation of optics is just above and beyond. I have huge interests with optics due to building laser engravers for PCBs and need a CNC frame with extreme flatness. It would be great if you made course in just optics from beginner to advance. I could not find any courses, like really well explained courses about optics, would pay for course course to understand optics. This is great it's all we need to make a perfect precision guide rail which uses your air bearings.

[@epotis]

Thank you. Fantastic video.

[@LaneyMachineTech]

Thank you!

[@francescocatalano6751]

Grazie per il video. Fatto molto bene e la traduzione in italiano è molto utile ...aspetto con MOLTO interesse il prossimo video sulla costruzione dell'autocollimatore.👍

[@bretcannon3826]

Most incandescent lights are filled with the inert gas argon rather than having the the filament in vacuum. In vacuum, the metal in the filament evaporates and deposits on the glass envelope. Argon greatly reduces this darkening of the glass.

[@LaneyMachineTech]

Good point!

[@danielepatane3841]

Since I have seen all three videos on the autocollimator subject I am looking forward to see video n4 maybe with some machining of a new autocollimator 🤔great teacher and great job anyway. Greetings

[@das250250]

Adam I was hoping to see the next installation of this collimator .. where did you go. I was contemplating a different way to solve this but with the same resolution .

[@WobblycogsUk]

More, more! Many years ago I studied physics and we covered a lot of this. Unfortunately I didn't pay much attention then and I've kicked myself for it ever since. It feels great to be learning it now. Have you seen the Oxtools series where he makes optically flat surfaces?

[@andrewphillip8432]

Another awesomely informative video! The discussion of aberrations and also eyepieces were particularly helpful to me. Now its all starting to make since to me why the old eBay autocollimators are still so expensive...

[@LaneyMachineTech]

Thank you! Personally, I don’t think they need to be so expensive. I ran the numbers and my DIY autocollimator cost less than $100. Granted it doesn’t have as fine of a resolution, but it could be made so with some additional components.

[@craigs5212]

Thanks for the video. very nice explanation. Been thinking about one for years to calibrate my surface plate but figured it was just going to be too complicated and expensive for little use. The only part I have is the eye piece from my B&L microscope used for SMT work, even have one with the reticle.

[@LaneyMachineTech]

I calculated how much it cost me to build my prototype. It was less than $100 including all the glass and the stock metal. To me, the price is worth it just for the knowledge I gained.

[@garychaplin9861]

I would really like to see the promised conclusion to this series. Also I found the air bearing series very informative.

[@ronnetgrazer362]

Clear LED bulbs aren't exclusively used for "white" or "warm white" LEDs, both pure LED colors and fosfor type LEDs tend to have a clear housing, except maybe for IR LEDs that are sometimes opaque in the visible spectrum. If they are fosfor LEDs, you can usually spot a patch of color in there. Filtering by encasing the whole thing in colored plastic is usually not needed - I've only seen it in older LEDs and I suspect that they emitted a broader part of the spectrum.

[@LaneyMachineTech]

Great point! Thanks for clarifying this detail!

[@gary6411]

Hey Adam, When can look forward to your DIY autocollimator video? I've really enjoyed this series and just didn't win one on eBay so am eager to see your design and make one. Thanks!

[@LaneyMachineTech]

I got backed up with stuff to do at the end of the semester and I wanted to get my home shop set up to make working and recording easier. I’m going to start back up on this video series this week!

[@gary6411]

@@LaneyMachineTech Please let me know if I can help in any way. While I was hoping to win the autocollimator on eBay, I began obsessing about a reflector that would be perfectly square to the surface to be measured. Also, what IS perfectly square in an autocollimator context? I had bought some 1-2-3 blocks from Cheapistan for another project ($10/pair) and was excited to find that, set on end (the 1x2 footprint), the 1x3 faces were within 1 micron of square, measured just below the top edge. The 2x3 faces were about 5 microns out of square, measured at the top edge. So my plan was to lap one 1x3 face to a mirror finish to use as an autocollimator target. Anyway, I can't wait to see your design. Many thanks!

[@sebaschtl9710]

thanks a lot for the autocollimator series. I miss the part 4 of building. Where is it? Thanks a lot.

[@rizalardiansyah4486]

Super quality!

[@LaneyMachineTech]

Thank you!

[@DennisDijkman]

Yep, this was awesome!

[@YippieKayYa33]

really love that 3 laser device you have for demonstration, do you know what something like that is called or where i could find it, same thing with the "2d" lenses? very approachable and well done video!

[@mitchwright1558]

Great series, can you list more references? Maybe an interferometer next?

[@LaneyMachineTech]

The next video series I’m planning deals entirely with DIY interferometry, including how to make your own inexpensive monochromatic light sources, source cheap optical flats and hopefully build a Fizeau-style interferometer.

[@NourMuhammad]

Man, I hope you did not forget that you own a KZbin channel!

[@Posredstvennyye_Proyekty]

this was quite interesting

[@LaneyMachineTech]

Glad to hear it!

[@reiniertl]

Just waiting to reassemble my machines, this project goes quite high on my list.

[@LaneyMachineTech]

Great! The next video will demonstrate the prototype I built. The video after that will show how to calibrate it.

[@reiniertl]

@@LaneyMachineTech This is going to be useful for all sorts of alignments and calibrations around the shop. Including measuring machine surfaces. And these instruments are expensive and difficult to source, so this is an incredible useful series. Thanks for the hard work and all the explanations. Demonstrations on how to use it will be the cherry on the pie.

[@TrekDreamer11]

@@LaneyMachineTech Looking forward to the upcoming uTubes, I am on the journey and have most of the items for a diy ccd based autocollimator. I really appreciate your work and time that you have taken to share the detail.

[@michaelennen3432]

Do you know how the scale reticules are made? I am very interested. Thanks so much for your video.

[@bobwilson7684]

amazing channel, is incredible all the bullshit that can fit into a human mind !! dude, keep it up!

[@bdgackle]

These videos are all amazing. Has anyone seen anything from the creator recently? Did he move to a new channel, or has he simply paused/stopped uploading?

[@wesbiglin4845]

is there a company or lab, that can check an autocollimator, like checking gage blocks?? there are some autocollimators for sale, but who know if they are correct and operable and accurate? thanks for 3 great videos, I learn a great deal but will have to watch several more times to get it all. thanks

[@ba208]

i'm repairing an old Hilger Watts autocollimator, which is missing the plate beamsplitter. So I am looking at 50% reflective beamsplitter specs. In the video, you said that it was important that the beamsplitter be very flat (lambda/4). Could you please explain why? I ask, because it t looks as if the HW beamsplitter (which is missing) was a 1mm or 2mm thick half-silvered mirror, held in place with a couple of spring clips. It doesn't look like the type of mount that would maintain a lambda/4 degree of flatness.

[@chuvvyyk]

Adam is the best!

[@LaneyMachineTech]

🙌

[@Bakafish]

I love this series. What's happening with the air bearing project?

[@LaneyMachineTech]

Thanks! I'm back to editing that series too, but I want to get this one done first because I've got good momentum on it. They're both part of the same overarching air bearing lathe project.

[@reiniertl]

@@LaneyMachineTech And what about the power scraper the sick AF? That would be a great addition to my first shop! I got some Chinese machines in need of scraping, need the power scraper and hand scrapers to practice and making your own is very tempting due to cost constrains.

[@LaneyMachineTech]

@@reiniertl LOL it’s on the list. Check out our Instagram account though (@laneymachinetech). There’s detailed build information for the power scraper in there, including process pictures and mechanical drawings.

[@absolute___zero]

if you could tell us where can we find cheap helium-neon lasers that would be a huge help

[@mattym8]

So will your autocollimator perform better/differently than a commercially available one or is it just a fun project because you can build something capable of resolving minute dimensions?

[@LaneyMachineTech]

The simple autocollimator prototype I’m building here will be capable of resolving about 30 arcseconds per division (about 8 arcseconds if you interpolate to 1/4 of a division). That’s actually pretty darned decent for less than $100 total investment. And it’s a very useable sensitivity and measuring range. With some simple upgrades I think I can eventually get it an order of magnitude better than that (equivalent to about 3 arc seconds per div). And with a redesign and some more expensive/complex components, I can probably get it another order of magnitude better (maybe between .1 and .5 arcseconds). Many commercial autocollimators with designs similar to mine are capable of resolving .1 arcseconds, and some more complex versions with sophisticated electronics and sensors go as low as .01 arcseconds. For me, the value in this project is multi-fold. It’s a way for me to understand the technology better and also solidify in my head several parts of optics theory. It’s also a fun challenge to see how sensitive of an instrument I can build with a DIY approach. I plan on using an autocollimator to inspect the granite guide ways on the air bearing lathe I want to eventually build. I have several commercial autocollimators already, but part of the fun of this overarching project is to take a first principles approach and see how far I can get without relying on commercially-available precision products. I’d also like to make a few autocollimators for my students to use in a granite surface plate reconditioning workshop I intend to hold when we’re allowed to do stuff like that again. So, yeah, there were many motivations for this project.

[@mattym8]

@@LaneyMachineTech That's excellent. It's like Ben Krasnow building an electron microscope because he could. I assume you've seen Dan Gelbart's air bearing lathe in his YT videos.

[@LaneyMachineTech]

@@mattym8 Yes 😂 That’s the whole reason I got into this mess.

[@Michel-Uphoff]

Will there be a build video? Please?

[@otaviocoelho]

Dude, here's the deal, I need part 4 asap. I'm holding on a Nikon collimator buy, and I know the second I make the purchase you'll post your video. Just please, spare me this purchase.

[@Elad6k]

Can't wait for the build!@#@$%$#^ DO IT!

[@LaneyMachineTech]

You’ll get it 👍

[@Elad6k]

😬

[@Elad6k]

Well?

[@LaneyMachineTech]

@@Elad6k Yep, working on it! Had to get my home shop in order. It was not fun filming in there lol

[@Elad6k]

@@LaneyMachineTech hoping everything is well🙏

[@chrisj4570g]

Love it my friend. 👊 Except, Im maybe just a little scared of ....ABERRATIONS!😳

[@LaneyMachineTech]

Did I make it too scary? 😂

[@chrisj4570g]

@@LaneyMachineTech maybe.

[@12345NoNamesLeft]

I have a shitty milling machine like that. Love to see your modifications detailed.

[@LaneyMachineTech]

So far no modifications. I just got it and I haven’t run it through its paces yet. But so far I’m actually quite happy with it. It’s a real knee mill, just miniaturized. If you don’t push it too hard, it is capable of precise work.

[@12345NoNamesLeft]

@@LaneyMachineTech John has a couple videos on it. kzbin.info/www/bejne/l6i3o5Wcd7WBZpY I miss the movable ram of a BP. The head is not spaced out far enough to cover the of the table. I cut out some of the casting to allow the full possible X and Y travel. Cast large and then machined to size - they cut corners and skipped some machining which prevents table movement. Search 6 x 26 mill modifications.

[@12345NoNamesLeft]

@@LaneyMachineTech If you mount power feeds on it, show order links and how you did it. Stefan Gotteswinter did a really nice spindle power feed. Looks like OEM, very well done.

[@LaneyMachineTech]

@@12345NoNamesLeft Great resources! I’ll check those out.

[@zachaliles]

I'm quite familiar with the price of glass going up the larger it gets from dabbling in long range precision shooting.

[@LaneyMachineTech]

Yup! The glass is by far and away the most expensive part of this system.

[@zachaliles]

@@LaneyMachineTech and higher quality glass, being more expensive, really does make a difference. I've shot rifles with very high end optics (Nightforce and U.S Optics) and they were fantastic. Crystal clear and crisp image. I just wish I could afford them for my own rifles.

[@damndeer503]

It has been a while since you posted. I hope everything is alright.

[@enotdetcelfer]

I was gonna call Darkfield Reticle as a band name but there's already a few Darkfields xD of course

[@LaneyMachineTech]

😂

[@NourMuhammad]

Still waiting !

[@yograjput5205]

Vvvv nice

[@alainfelger93]

please make the next part

[@ctprjcstv3998]

How are tiny texts made??

[@slavarecall8105]

you are best!

[@LaneyMachineTech]

💪💪💪

[@graealex]

Pretty sure your viewership knows how a light bulb works. Also, it's not really a vacuum inside, rather an inert gas below atmospheric pressure, as it's far easier to manufacture and maintain.

[@XLmoby]

Part 4 ?