Huygens Optics - 2022-03-26
Video Contents: 00:00 General Intro 00:56 Spherical is easy 01:32 Aspherical is hard 01:59 Ideal lens vs. spherical surface lens 03:17 The concept of the light ray 04:47 A little optics quizz 06:21 Optimum spot size using iterative numercal analysis 07:56 Use of optical design software (Zemax) 09:45 Theory of aspherics 10:54 Conical aspherics 12:02 Polynomial aspherics and even aspheres 14:24 Numerical optimization in aspherics 15:30 Effect of introducing an aspherical surface 16:55 Optical design of monolithinc telescopes 18:23 Material choice and CTE 20:52 Classical Cassegrain configuration 22:10 Schmidt Cassegrain configuration If you want to support the production of these videos, you can now become a Patron of the channel. You can find more information on : https://www.patreon.com/huygens_optics Reference to my original video on tiny monolithic telescopes: https://www.youtube.com/watch?v=HxwhCmO90UQ LInk to my video on conics: https://www.youtube.com/watch?v=WIl6FlUCHQg For the record, I do not have any commercial ties to any of the companies or individuals that are linked below. Zemax page for requesting a trial license of Optic Studio: https://www.zemax.com/pages/try-opticstudio-for-free If you want to know more about the workflow in Zemax, the great tutorial videos by Scott Sparrold of OpticsRealm are a good start: https://www.youtube.com/user/opticsrealm/videos Youtube video discussing the optical design of the James Webb telescope: https://www.youtube.com/watch?v=OE3ZowuvAJY The Thorlabs page with aspheric lenses and the formula: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3835 I used a few short clips from the following Youtube videos, assuming this use is covered under the fair use policy by placing references to the channels and links to the corresponding videos in the description. Clip from Yuri Petrunins "polishing 210mm lens": https://www.youtube.com/watch?v=ipwnK45_Kf4 Clip from Edmund Optics "How an Aspheric Lens is Made": https://www.youtube.com/watch?v=CVDT3u1La6w Clip from Learn n hv fun "Refraction of Light Through a Glass Slab[...]: https://www.youtube.com/watch?v=el8AUeZaljw Did I forget to mention you here? Let me know and I will set things straight.
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!
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
Complexity theory; must be much easier to find the equation than find a state of the equation with properties you want
There's no difference between theory and practice, **in theory**.
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.
Lens designers for the win!
how do you become a lens designer? what degree is required?
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.
Thank you. It's a genuine privilege to have access to a presentation like this.
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.
Optics is a truly fascinating science. I'm a software engineer, but lately I also have re-discovered my love for mathematics while learning cryptography, and optics also seems really fascinating the way you describe it in your videos. Your video on optical logic gates is also amazing, and it really made me think if optical computers can be made. Thank You for making all of this content fore free. Regards
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 🙏🏽
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.
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!
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.
Really looking forward to the next videos! You explained everything super well, even for a simple chemist like myself
Thanks. Maybe that is because I'm a chemist by education too!
Fascinating. Can't wait to see the practical aspects in follow-up videos.
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.
I loved the video and the level of detail you provided.
Can't wait to see your manufacturing techniques and testing methods.
Hi Jeroen, thank you for taking the time to share your expertise! Your videos are a truly unique contribution to YouTube. I’m a materials science PhD student, and I love watching your videos after a long day in the lab. Greetings from california!
I love how dense your videos are while still being really easy to understand. Probably the most I've learned in 25 minutes. Thanks for the great introduction to this stuff
your approach to explaining the theory is on point for the laymen (me), perfect 😀👍
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.
Hey, what is gdc
@Mars5 train Gradient Descent.
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.
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.
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.
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.
@Jordan Anderson There's not much dust in space. That's the point :P No one has cleaned the mirrors on Hubble
@Joshua Mcateer 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.
@Jordan Anderson 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.
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.
fascinating practical case study (very synthetic, too), thank you ! can't wait to see the characterization procedure and result presentation...
I watched this in multiple sessions, absolutely amazing!
Thanks - that was great! Looking forward to part 2.
I have never done an optics project, and your videos are a great guide on how to do things.
Thanks!
Absolutely awesome content - all the time and effort you put into this is greatly appreciated
Your explanations were very easy to understand, good video.
Great stuff as usual. Looking forward to the rest of this project.
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.
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.
So interesting. I have a physics degree and even studied astronomy, but never learned much about optics. Learning a lot here, and thinking about experimenting a bit with some code! Would be interesting to find good solutions to aspherical lenses by gradient descent, might read up on that and try myself. Your mastery is inspiring.
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.
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!
As always with your videos it was pure joy to watch and learn!
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.
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
Your explanations are always so incredibly clear and easy to follow! Optics is fascinating. Thank you!
Very interesting video! On another note, I remember in one of your previous videos about wave effects on boundaries you mentioned that you were surprised by Webb's design, since it uses many separate mirrors and that they use some clever engineering to account for that. I was really trying to find more information about this since it sounds super interesting but came up with nothing. Would you mind explaining how they do it? Or perhaps even make a video!
Awesome video, TY for this level of detail!! I love the Dremel powered sub-diameter lap at 23:17 very clever! I once tried to fabricate an F/3.2 Schwarzschild Reflector based on the work of R. Sinnott. I thought the secondary would be the challenge, a 150mm diameter F/5 with κ = 1.8 (oblate), however that was easy compared to the Primary, A 300mm diameter F/8 with κ = -13.7 (hyperboloid insanity). I could never get the primary past κ = -6 without turning it into some circular Aztec pyramid looking monstrosity, but I never thought to attack it with a sub-diameter lap attached to a power tool and I may need to re-visit this decade old project again! :-)
What a great video! I learned so much! Wat een fenomenale uitleg! dank u zeer.
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!
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)
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.
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
I only have a shallow understanding of mathematical formulas, but your videos is by far the most interesting on YT. Amazing experiments!!
This is a great explanation of the design and decision points on making this telescope. You had diffraction limited in a couple of your analyses. It might be helpful to show the the diffracted limited spot size to show how well the raytrace needs to be so that any further reduction in raytrace error doesn't improve the telescope performance.
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)
I always learn a lot from your videos - looking forward to the next part in this series!
Very enjoyable video, thank you!
Super 😄👍🏻👍🏻. Chciałbym mieć taki super teleskop ❤️. Cassegrain z jednego kawałka szkła 👁️🔭🌈👌 super sprawa.
Pozdrawiam serdecznie 😄🤚.
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
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
Huygens Optics - 2022-03-26
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.
Christopher Leveck - 2022-03-26
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 - 2022-03-26
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!
janz krs - 2022-03-26
I would love to watch a video about MTF, PSF and wavefront errors if you decide to make it!
adrianpip2000 - 2022-03-26
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!
The unknown - 2022-03-27
slight error on 12:40
a_6 instead of 2 a_4, nothing much :P