Making a Monolithic Telescope Part 1: Optical Design and Aspherics.

[@HuygensOptics]

Even though this is my longest video so far, it was still only possible to discuss a tiny fraction of the aspects of optical design. Things like MTF, PSF and wavefront errors were kept outside the scope. However, I hope I can make up for some of this in the follow-up video. Also, If you have specific aspects that you want me to dive in a bit deeper, please comment to this post and maybe I can discuss these as well. By the way, sorry about my pronunciation of the word "radii". I used the Dutch way of pronouncing it and not the correct English / American way. Also the "Z" symbol allows for multiple pronunciations, the one I used might not be the one of your personal preference.

[@christopherleveck6835]

I have been fascinated by this subject and looking everywhere for more information and even started working on my own process to make a mold for using liquid optical acrylic.... I'm using a cnc lathe with a single point cutter to create the mold halves. I can make the lens any shape that can be created in a computer.... I can also cnc grind a lens out of solid glass....

[@superchromat]

When I was watching I tried really hard not to move my mouse so I wouldn't get a sense of how much time was remaining. I didn't want it to stop. Really fantastic stuff. Glad to see you back at it!

[@janzkrs8006]

I would love to watch a video about MTF, PSF and wavefront errors if you decide to make it!

[@adrianpip2000]

I have little knowledge of optics, so I'd love more in-depth explanations of the other specifics you mention, but I'm also looking forward to the practical aspects!

[@theunknown4834]

slight error on 12:40 a_6 instead of 2 a_4, nothing much :P

[@Pidrittel]

I studied physics at university, and I am always shocked how little we (physicists) know about optics when in comes to practical design considerations. I love this video(s), looking forward to similar videos in the future!

[@chatch15117]

The difference between scientist and engineer. We lean on scientist for the absolute truth/theory. But we have to bargain with reality about what's possible to manufacture and make profitable

[@kylebowles9820]

Complexity theory; must be much easier to find the equation than find a state of the equation with properties you want

[@JinKee]

There's no difference between theory and practice, **in theory**.

[@tsraikage]

as a physics major myself, I can't agree more. this videos are like alchemy for me at first and then somehow make sense after second thought and gotcha points

[@David_Hogue]

As an engineer trying to learn physics I am surprised to find myself getting into optics through physics, but it seems like a next logical step.

[@adamgt531415926]

As a lens designer, this is a fantastic introduction into the crazy world of optical design! I'm excited to see this project be manufactured.

[@iancarr8623]

Lens designers for the win!

[@romyaz1713]

how do you become a lens designer? what degree is required?

[@VoidHalo]

As a hobbyist level engineer and a person who is deeply passionate and appreciative of all things engineering, I just want to say I have a great deal of respect for you knowing what your profession is. I have a great deal of respect for anyone involved in the sciences in any capacity.

[@henryD9363]

Oh my goodness, this is so excellent! I have an ancient degree in physics had been interested in optics for a long long time. I knew "about" many of these designs and some of the math. But for the first time you put it together in full and comprehensible explanations. My goodness you tackle the subject so well. I've learned so much from this video. Thanks more than I can express. I think your video, How big is a photon?, is groundbreaking. I'll take an easy guess and say that only a tiny fraction of physics PhDs would get the right answer to your single-photon unequal-optical path interference experiment. The video should be mandatory for all physics students.

[@cncshrops]

Thank you. It's a genuine privilege to have access to a presentation like this.

[@BreakingTaps]

Fantastic information, thanks for sharing it! Really helpful to see an expert walk through the optimization process and explain different details, pros/cons of choices, etc. Looking forward to the fabrication video!

[@HuygensOptics]

Yeah, first I wanted to put it all in one video, but that was just too much information at once. I hope that I will be able to finish the follow-up in a few weeks time.

[@a.g.vianello5881]

Can’t wait for the next part. In university I learned about the theoretical process of designing an optical system but I never learnt the practical ways of making lenses or curved surfaces for mirrors. Especially aspherical ones.

[@peetiegonzalez1845]

Fascinating. Can't wait to see the practical aspects in follow-up videos.

[@wwjjss33]

Thank You for your detailed yet broad treatment of this project! Your narration is clear (the Dutch accent is just icing on the cake!) and your pace is perfect-keeping my attention without blurring past the subtleties *or* dragging things out. Fantastic! This re-kindles the love of optics that started for me when my father first showed me the moons of Jupiter through a 60mm spotting scope when I was 6 or 7 years old. Thank You for this quality content 🙏🏽

[@marcin_szczurowski]

Being a physicist with major optics, I can only say I admire what you did here. Great teaching skills.

[@StonyRC]

Hells Bells ... I thought I knew a little about lenses, but you utterly blew my mind within six minutes!!! Fascinating project - I'm going to savour each and every one of the videos in this series.

[@landspide]

your approach to explaining the theory is on point for the laymen (me), perfect 😀👍

[@leavoa]

Your systematic approach to the project, the design, and the explanations, is at least as educational as the the optical design knowledge you are sharing. I find myself feeling like an apprentice in the workshop of a wise master. Thank you.

[@bekanav]

In my 20's I tried to make a Schmidt plate with the original vacuum method, pretty much manually like he did back in the day. It was very hard work because I was afraid of losing some vacuum during fine grinding and polishing (like he was also). So I had to work for a long day. I made the pan from concrete, ground lip flat, installed the valve and sealed the pan carefully etc.. To decrease amount of deflection I did both sides of the plate. Unfortunately I indeed lost - for some reason - some vacuum when working on second side and started to have difficulties with the contact etc. and finally gave it up having become too tired of it. However first side looked visually correct on the flat, so it wasn't a complete failure. And at least I got quite a lot experience from that technique which certainly has some challenges and limitations. I remember solid telescopes were presented in one of the ATM 1-3 books which were my "bible" in those days. Perhaps a bit outdated even then but full of enthusiasm about optics and telescope making. Thank you very much for the interesting videos. One of my favorite YT channels

[@xelaxander]

Omg, I am so exited for this series. I love tinkering and getting the absolute maximum out of a design (although in my case, that’s algorithms). That reminds me how I used GDC recently myself for designing a real item. I had to measure a weird corner of my apartment for some shelves, totally not rectangular. Parametrized a quadrilateral, defined an error function to my measurements and used GDC to minimize it. The CNC cut plywood shelves fit perfectly.

[@mars5train601]

Hey, what is gdc

[@xelaxander]

@@mars5train601 Gradient Descent.

[@Edwinthebreadwin]

As always a video which conveys information to a very wide audience. One optics topic which I've never understood but always found interesting is Semiconductor lithography masks and the magic which is done to improve resolution with them.

[@GoughCustom]

Very enjoyable video, thank you!

[@christopherleveck6835]

I can't wait for the next one.... I'm going to try this. So please don't leave us hanging too long...

[@nicholaswilliams4507]

Great stuff as usual. Looking forward to the rest of this project.

[@souzzzzza]

I loved the video and the level of detail you provided. Can't wait to see your manufacturing techniques and testing methods.

[@ssssssssssss885]

Sir, your videos are the best advanced DIY ones around, your builds compete with professional scientific instrumentation. Not sure I'll ever use this, but I learn a lot. Respect and thanks!

[@janerikjakstein]

Your explanations were very easy to understand, good video.

[@mikaeljonsson99]

I only have a shallow understanding of mathematical formulas, but your videos is by far the most interesting on YT. Amazing experiments!!

[@iestynne]

Unbelievable. What a gift. An expert yet easy to follow explanation. Thank you so much.

[@Julian_Kulenkampff]

I have never done an optics project, and your videos are a great guide on how to do things. Thanks!

[@pvnerd]

Hi Jeroen, thank you for taking the time to share your expertise! Your videos are a truly unique contribution to KZbin. I’m a materials science PhD student, and I love watching your videos after a long day in the lab. Greetings from california!

[@James-wb1iq]

Thanks - that was great! Looking forward to part 2.

[@zagaberoo]

As a CS grad I was excited to see numerical optimization popping up. I almost jumped the gun and mentioned getting stuck at a local minimum after your first discussion; good thing I waited lol.

[@kieranpat]

I watched this in multiple sessions, absolutely amazing!

[@violentdesire7325]

I just want to say, I love you. This is wonderful. Apart from making me understand how a polynomial works, you really opened my eyes to the world of optics. Keep doing what you do, and please do so with the knowledge that the world is better off because of you. you are wonderful.

[@alanwardrop1777]

Wow. I have only just stumbled on your videos. I am honestly in awe at the quality of this work. In terms both of what you have DONE, and of how you have explained both the optics and the optical engineering. Fascinating and so well presented. An absolute treat.

Optics has always fascinated me, but honestly, I know little about optical design beyond what I know from high school. This introduction is a WOW for me! Thank you for this.

[@lukephillips3751]

He’s back

[@gtranquilla]

Very interesting………we were provided with a basic re-iterative computer program to refine a simple optical lens design way back in the late 70’s. I was grinding my own Newtonian mirror at the time as a personal hobby and using a homebuilt Foucault tester. This material helps me to know how much further the designs can be taken.

[@YuriyKrivosheyev]

Thank you! Very interesting. Looking forward for continuation

[@StormBurnX]

Absolutely wonderful to watch. I'd wondered what's been keeping you so busy and this is well worth the wait. Scratching a deep itch that I've had since dropping out of optical engineering / lasers & photonics studies in college.

[@n1352-m1i]

fascinating practical case study (very synthetic, too), thank you ! can't wait to see the characterization procedure and result presentation...

[@Nobe_Oddy]

WOW!!!! I'm going STRAIGHT TO PART 2 NOW!!! This is SOOOO INTERESTYING!!! I LOVE IT!!!

[@pamdemonia]

Your explanations are always so incredibly clear and easy to follow! Optics is fascinating. Thank you!

[@computer-love]

just wanted to say i really appreciate the captions, thank you for taking the time to add them

[@adrianpip2000]

Really looking forward to the next videos! You explained everything super well, even for a simple chemist like myself

[@HuygensOptics]

Thanks. Maybe that is because I'm a chemist by education too!

[@joshhyyym]

I am very much looking forward to the rest of this series. What was your reasoning behind requiring the front surface to be plano? I would have thought that allowing a spherical front surface might allow for a Bouwers-like correction.

[@HuygensOptics]

Well, it is not like it is a real requirement,. And of course in the case of the Schmidt version it is not really flat but there will be like a 30um deep ditch in the surface around the secondary. The problem is that if you make this surface too concave, you need a larger primary mirror (like with a maksutov / Bouwers) than the front window. So effectively you'd have to make the entrance window smaller. Also, you want to keep the light entering the front as perpendicular as possible with respect to the surface, to limit chromatic aberration originating from this surface. So ideally, it should also not be convex.

[@jordanwesley18]

I would imagine that the space application of a monolithic telescope having a Plano front surface would also result in the outer surface being the only surface that could not be protected from space dust, but if the surface were scratched, a Plano surface could be most easily buffed out by a robotic cleaning apparatus. Also would be helpful for an AI in any manufacturing robotics to be able to decide to polish it’s eyes at night, leaving the rest of the eye able to be encased and better protected from exposure to the manufacturing environment.

[@joshhyyym]

@@jordanwesley18 There's not much dust in space. That's the point :P No one has cleaned the mirrors on Hubble

[@jordanwesley18]

@@joshhyyym the monolithic telescope would be too heavy to compete with the aperture of the Hubble, but this could be an option for something like an explorer on the very dusty lunar surface, or for studying the debris in the Jupiter Lagrange 3 and 4. Or for manufacturing.

[@joshhyyym]

@@jordanwesley18 I think you massively over estimate the amount of dust in space, even L3/4 points. I'm sure there are some uses. But is is often much easier to have a plano window with a wiper arm in front if it. At low NA and low magnification a plano window will not add additional spherical aberration and is cheap to replace. I think trying to clean a replaceable window is a much better solution than cleaning an optical element with several complex ground and coated surfaces in an industrial environment.

[@gems34]

Brilliantly articulated I was able to follow your explanations of the theory and have a just a rudimentary understanding of the subject. You gave a lovely overview with just the right amount of detail without me getting lost. Much appreciated :)

[@CrazyNerdInventor]

We are currently doing polynomials and conical graphs in school. My mathematics teach will love this video!

[@MarionMakarewicz]

When I watch videos from content creators who are experts in their field, I have a comparison metric that I call the Leibowitz Factor. That is how likely the content creator would be recognized as a saint who preserved technical knowledge in the dark ages of ignorance. You are definitely a candidate for technological sainthood.

[@KallePihlajasaari]

Nice, that was a twisted tale, I want to find a copy of the sequel with the Wild Horse Woman. Heh heh, took it out on 14 day loan from the Internet Archive lending library.

[@czoknorris]

Cool. Very nice. Learning about optics and this is very helpful. Looking forward to all the follow ups.

[@Brunoscaramuzzi]

Can't wait to see the next video!!

[@kilimnik1983]

Truly appreciate your explanation. You helped to connect a couple of concepts in my mind.

[@TavishMcEwen]

I barely know anything about this subject but have been waiting for this video for a long time :)

[@jasperdegrood]

What a great video! I learned so much! Wat een fenomenale uitleg! dank u zeer.

[@seanmcmunn88]

This is such a great video, thanks for making this. A ton of key details packed into a 20 minute video and I cant wait to share with my technicians who love to learn about the optical assemblies we build (satellite earth imaging telescopes)

[@cylosgarage]

This is the greatest channel

[@Dudas314]

As always with your videos it was pure joy to watch and learn!

[@ghlscitel6714]

My jaw dropped. Congrats for this very informative video tutorial. So inspiring.

[@andrewnambudripad762]

Edit: You answered all of my questions as the video progressed haha. Adding additional degrees to the polynomial was going to be my question. Radius of curvature appears all over the place in math. Differential geometry and analytic number theory are what I've seen but probably algebraic topology too Edit2: Great material for a trig class for highschoolers. Also pot 'holes' are the method of machine learning people used for gradient descent (now everyone uses "DeepMind", but it has GD has 50 years of usage behind it)

[@frollard]

That swiss cheese example definitely hits it home on how a 2d plane is difficult to find a minima...the search space for these nth degree polynomials just grows to absurd levels.

[@Alexander_Sannikov]

it's really interesting to know that in general case optimal surfaces are messy and instead of deriving them analytically (which is something i'd expect in this case), people just approximate them with polynomes and optimize. I had no idea.

[@chopper3lw]

That was a lot of insight in a tiny package. Thanks!

[@richspillman4191]

I am spellbound, looking forward to the next chapter.

[@tokiomitohsaka7770]

Highly informative and well communicated as usual! Thank you.

[@markdresser8592]

I'm very glad to have found your site. I'm not sure I'll ever get beyond optical design and manufacturing as black magic but I'm learning a lot. Thanks!

[@lohikarhu734]

Always an interesting, and CHALLENGING presentation!!

[@yotacoil]

Absolutely fantastic information always! Everyone always says there is a tradeoff between ease of manufacture of sphere-shaped lenses vs image quality of aspheres, but this video finally starts to get into it, including starting to quantify how big the tradeoffs are in both quality and difficulty. I'm super excited!

[@afterSt0rm]

Sometimes the algorithm blesses us with god-llike content like this. Thank you for the amazing video, waiting anxiously for the new ones!

[@HelpBuildABetterFuture]

Another magnificent imaginative illuminating clear and focused video. Thankyou.

[@juelznavi5646]

hello, i really love your channel with the right mix between physics / engineering / practical things / theoretical things / ... you mentioned that thats your longest video so far, but i think this style (20 minutes) that you make fits really good for the viewer (attention span / depth of details) ... thanks a lot for your work

[@Xiaotian_Guan]

I'm really curious which configuration you eventually went with. I know commercial SCTs use precision ground vacuum backing plates to bend a thin piece of glass out of shape, grind the upper surface, and the correct shape resulted when vacuum is removed. A technique doesn't seem possible here. You seemed to have used a small handheld grinding tool on the second surface, suggesting you chosed the first configuration? Anyway, this is a fascinating project, and really looking forward to your next video.

[@HuygensOptics]

Very sharp observation! Yes indeed, the Classical Cassegrain is the one shown in the clips. By the way, both versions are about equally difficult and require a lot of tweaking and measurement.

[@ghlscitel6714]

@@HuygensOptics How can one measure Lambda/20 (~25 nm) deviations of an aspherical surface against the ideal geometry?

[@poobertop]

Wonderful video Huygen, very keen for subsequent episodes.

[@therealzilch]

Another wonderful video, thanks. My experience with aspherics is limited to the 6" f7 parabolic mirror I ground and figured about fifty years ago. Keep up the good work. Groeten uit Wenen, Scott

[@Coloneljesus]

Fantastically interesting video! Thank you!

[@alimqave6732]

долго ждал продолжения. спасибо, великолепная работа!

[@jamesmauer7398]

I always learn a lot from your videos - looking forward to the next part in this series!

[@multidao]

Really happy about that series!

[@patnutoris4054]

Thanks, very interesting. Looking forward for the manufacturing process.

[@salmiakki5638]

Thanks for clarifying optics for the masses

[@BorderKeeper]

Awesome video I learned a lot. Made me dream of a microchip made of glass where all logic gates are just assymterical edges inside the glass.

[@dante7228]

Well...since I do not plan to build my own optical systems I didn't find any "usefull" information. What I found instead was a lot of very interesting information! Thanks for sharing all this knowledge and insights in this topic!

[@Scrogan]

That’s really neat looking. With that numeric iterative simulation, it’s evident that there are a few degrees of freedom yet. If you allowed for 3 or even 4 aspherical surfaces, I wonder if you could eliminate chromatic aberration? Or even thermally-driven aberrations like how some BJT circuits cancel out their own temperature coefficient? I’d also wonder what it would take to make a CNC optical surface grinder of sufficient precision. Might even be able to do it with analogue mechanics by using multiplier wheels and such to generate the polynomial expressions, if you’re into retro tech.

[@HuygensOptics]

Chromatic aberration does not play a big role in this design, because most of the strongly curved surfaces in this design (apart from R4) are reflective. The difficulty in cnc-polishing is not so much the polishing action itself but converting measurements of the actual shape and the desired shape into the right toolpath.

[@yiyou6529]

Sir, I sincerely appreciate your video. I am looking forward to the follow-up part II.

[@hussainali9999]

Thank you, you really know what is going with optics.

[@alandoak5146]

I'm an RF/analog electrical engineer that recently started working on systems with a lot of laser optics (quantum computers at ColdQuanta), and these videos are interesting and helpful for a general treatment of optics. If you ever got into the specifics of laser optics (focusing, laser tweezers, EOD's, cooling traps, polarization, etc) I would watch with keen interest.

[@plcogren9404]

Excellent work, excellent style, love to listen your speech. Never mind about the length of the video. Your videos are not for tik tok followers.

[@lcsantos777]

Very interesting. I look foward to the next video!

[@stevelevesque939]

Hi . Very good video. There was a prototype lens made by Minolta for the Apollo program that appear on eBay. I didn't have enough money back then as a student to buy this unique piece of optics. It was a monolithic design with a very aggressive thickness to diameter ratio. It was a ~500mm focal length with a ~60mm diameter and a thickness of only about ~35mm !!! This was protected inside a metallic casing with Minolta branding on it. Nasa mostly selected Zeiss for their camera. Now I can't find any information anymore on this lens... I wish I could lend myself some money to me back then...

[@ilkersar7083]

The part you showed about the polynomial coefficients of the aspherical lens was very revealing.

[@esepecesito]

Amazing. Can't wait for next video.

[@MiguelJuanez]

Fascinating!!!!!!!! 👍🏽 😎 I learned a lot but still have a lot of questions. I'm ok with that and I love it! Gracias!

[@Saka_Mulia]

This is such a fascinating look at optics. Thank you.

[@mceajc]

Excellent! I am envious of your knowledge and passion.

[@williamogilvie6909]

Very interesting and clearly explained. Any university would be fortunate to gave you on their faculty..

[@nikonov-al-s]

Brilliant! Waiting for the next episode !

[@elluisito000]

Am thankful u took the time to focus on this topic.

[@babysnaykes]

I'm so happy I found this channel

[@AppliedCryogenics]

Yes! This subject really captures my imagination. Also glad to see a video, I was starting to worry.

[@franciscojoseruedazaragoza4629]

I know it is a very broad field but I wonder if it would be possible for you to make a series of videos explaining all these optics concepts from the most basic such as Fermat's principle to advanced concepts of optical system design, based in practical examples or just theoretical ones if it's needed. If there are people who have reached this type of channel, I don't think they are afraid of mathematics and, frankly, it is a bit frustrating not to find sources of information on these or similar topics that are not either extremely simple or extremely complex. Thank you very much in advance

[@Alexander_Sannikov]

> this is where some of you might say : "i'm out of here" this is where I said internally : "it's genius that they have just chosen some random even powers of a polynome plus something that looks like another common term in nonspherical optics and call it good enough"

[@carlbrenninkmeijer8925]

So clear, thank you. Funnie that the simplest shape does a good job. I mean that the lens formula is simple. We dread the idea that that would not have worked! zSailors would have seen blurred ship images..anyway, it is a mysterie to me how they used the eyeglasses on their wobbly oak boats..

[@HuygensOptics]

By making them long and heavy, the inertia could serve as a crude from of image stabilization.

[@KallePihlajasaari]

@@HuygensOptics The opposite of what one would intuitively seek when making a hand supported and guided everyday tool. In a way a design difference between nautical and terrestrial telescopes that no-one has heard of but would be a perfect micro plot twist in a story about a Victorian spy or Sherlock who gains a clue by simply hefting a telescope and knowing it was not a genuine one for the stated purpose.

[@MrBhujbalgv]

I never seen such detailed information about design optics, thanks for sharing, eger to watch next part of vedio .

[@mvadu]

I had to cross check if I am watching a royal science society channel.. Amazing explanation of light physics involved..

[@hypock1]

Absolutely awesome content - all the time and effort you put into this is greatly appreciated

[@RajasPoorna]

Thank you so much. Very excited for the next video!!