How are holograms possible? | Optics puzzles 5

[@3blue1brown]

This was a joy to make! Many of you asked where you can get your own Hologram, here's one option: hologramplace.com/?ref=3Blue1Brown1 Shortly after posting this video, the person whose shop this is reached out asking if I'd highlight it. Full disclosure, as you can no doubt infer from the URL, he offered a commission for mentioning it here, but I wouldn't include it if it didn't look good. Also, the person who made that hologram microscope, Walter Spierings, is from Dutch Holographic Laboratory. He wanted me to let you know that anyone should feel free to approach them when it comes to producing holograms.

[@bolts3catch]

I was always told that any part of a hologram contains all of the information in the hologram as a whole. This gave me such a better understanding of what that actually meant and how it isn’t entirely true (in the way that I was thinking about it). Thank you for these amazing videos!!

[@StefanodeAngelis-1300]

It's genuinely one of your best videos (imo). It was a delight to watch.

[@wesr9258]

26:31 A potentially more elegant way to reason through this is: the two distances shown in 14:58 have to be destructive at each black point. this happens when D and the distance of that other line to its right. The way of finding these distances and angles between the two lines functions THE SAME WAY we did in the section “Diffraction gratings”, so we end up with the same formula. @3blue1brown

[@wesr9258]

26:31 A potentially more elegant way to reason through this is: the two distances shown in 14:58 have to be destructive at each black point. this happens when D and the distance of that other line to its right. The way of finding these distances and angles between the two lines functions THE SAME WAY we did in the section “Diffraction gratings”, so we end up with the same formula. @3blue1brown (I wrote it twice to get your attention.)

[@irisartin385]

I didn’t do any formal analysis to justify this, but: the image you see when you flip over the film to look at the conjugate image doesn’t look like a weird distorted version of the original to me - I think it looks like what you would see if you were inside the original scene looking out?

[@robmunday2949]

Without question, the best video on how a hologram works that I have seen in my 42 years of making holograms. What’s more, I made one of the three holograms shown at the beginning of the video in the living room of my first house in 1986-87.

[@3blue1brown]

Wait, that's amazing, which one?

[@robmunday2949]

@@3blue1brown The hologram portrait 'Lucy in a Tin Hat' was shot by Royal College of Art holography student Patrick Boyd and I whilst at the RCA in the mid-1980s (the first Master of Arts holography course in the world). As one of the three founding members of staff of the RCA's holography Unit, I designed, built, and operated the RCA's pulsed laser hologram portrait studio, but operated my own private holography studio at my home at the same time. I would often take the student's master holograms home to shoot the reflection hologram copies at my studio during the night for maximum brightness, as the stability in my living room was far better than at the Royal College! Stephen Benton, inventor of the rainbow hologram, often told me that it was the best hologram portrait he had ever seen. The Microscope was of course by Dutch holographer Walter Spierings. I particularly liked your use of a single-point Fresnel zone plate, followed by multiple points and thus overlaid zone plates to explain complex holograms. I use this method myself but have not seen it in a video before. The visualizations and graphics are incredible. Again, well done.

[@robmunday2949]

@@3blue1brown Lucy in a Tin Hat

[@Irondragon1945]

hell yeah buddy!

[@AquarianSoulTimeTraveler]

​@@3blue1brownHey check out my new beautiful equation. X²*X²*X²*...♾️ < X³ this is a simplified version... Think about it, a square is two-dimensional meaning length and width only with absolutely no depth... A cube function has depth... If it has depth then that means infinite amounts of two-dimensional existence can stack into any size three dimensional existence... Thus this equation is fundamental. Yet another mathematical shattering of the status quo. ² means squared ³ means cubed... This solves so many problems with math and creates a lot more maybe.

[@robspiess]

<a href="#" class="seekto" data-time="1026">17:06</a>: "Let's take a side-step into a mini-lesson so I don't have to rob you of that joy." lol, I love it! Never change, Grant!

[@HankMeyer]

I totally lost interest and stopped watching the video during that side step.

[@siddharthpillai8177]

@@HankMeyer skill issue

[@markorezic3131]

@@HankMeyer You should remember all the times a teacher or tutorial just skipped over a step you wanted to know more about and understand Grant doesn't do that and it is a very nice thing on this channel - he gives you the full picture If you want to skip over you still can - so yeah. Skill issue

[@Pfhorrest]

I've been writing some philosophy last night and today about how just as, like many traditions such as Buddhism and Stoicism acknowledge, being able to easily give up caring about or taking interest in things is key to being able to avoid suffering, so too conversely being able to easily care about or take interest in things is key to being able to obtain enjoyment. Hearing Grant here speak of the joy of rediscovery really felt like finding an example of that principle in the wild, someone finding genuine joy in what could be such a dry and uninteresting thing to some poor schmucks who aren't capable of summoning up the interest to care about it and therefore enjoy it!

[@asdfghyter]

@@HankMeyer you could've just skipped past it in that case. most viewers found it interesting

[@alexwatt2298]

As a Physics teacher who has derived the diffraction equation many times on a whiteboard with all the limitations of that medium, being able to direct my students to this video for a far far more robust visualization is incredible! Thanks as always Grant!

[@CraftingCake]

Awesome that you incorporate modern media into your lessons.

[@baconheadhair6938]

Thanks mr watt

[@KristofferBrander]

Have you thought about storing the information of a 3-d space on your two dimensional whiteboard?;)

[@augiedog2013]

Your whiteboard derivation was great too, I'll have you know!

[@taylorhornby7475]

Man I'm so grateful to be alive at a time when content like this exists

[@ro-kg5vb]

Only the contentwave is needed though

[@ArchangelExile]

You're going to feel stupid when you find out what we'll have 100 years from now.

[@janagax]

Okay, the bit at <a href="#" class="seekto" data-time="690">11:30</a> where a small section can be used like a window to the whole scene... I think it's the first time a youtube video has actually made my jaw literally drop

[@leftward_hoe]

you really can't blame people who were freaked out by pictures and radio back in the day lmaoo

[@mznxbcv12345]

It explained the holographic brain theory by karl pribram to me. Basically, that's how memory is stored in the brain, as even damage to a part does not affect the long term memory, it can still be retrieved later.

[@americankid7782]

Yeah I had the same reaction. It’s such a cool thing!

[@fufun4me]

Saaaaaame

[@prototype014]

Reminder: viewing angle gets smaller with smaller window. Information isn't infinitely dense here.

[@RenderingUser]

3B1B is actually the best educational channel on KZbin

[@UnknownUnrecognized]

maths and science is better

[@adammontgomery7980]

Why is it that guided discovery isn't used as a teaching method in schools? It seems much more effective.

[@UnknownUnrecognized]

@@adammontgomery7980 simple: to keep people dumb and programmed, no gov wants smart or self aware people.

[@RenderingUser]

@@adammontgomery7980 more effort. Teachers aren't paid enough for this

[@naoxi1]

​@@adammontgomery7980 the school system is unfortunately outdated by about 200 years, that's one of the reasons

[@Marc-dg2en]

3Blue1Brown just called me "rather clever" and this unironically made my entire day.

[@haileycollet4147]

Great experience wasn't it :) I got there (and ohhhh'd) just as he was saying that

[@TheMongooseOfDoom]

I got "something with interference I guess". Close enough.

[@purdysanchez]

@TheMongooseOfDoom Same.

[@Mertly]

<a href="#" class="seekto" data-time="699">11:39</a> This feels like it would make an incredible element in an escape room. Have a table set up, and to solve the puzzle you need to find these chips with different scenes recorded on them at the same table

[@synthersentezci]

Already implemented in a video game called The Room

[@CC-uu3zf]

@@synthersentezci😊

[@robert9016]

@@synthersentezciYou’re tearing me apart, Lisa

[@MechMK1]

This would be incredibly cool, but I fear that these disks would likely get lost easily, get damaged or possibly stolen too. And judging by the delicacy of the process, it's likely not cheap either. So yes, amazing idea, but most likely impractical.

[@krishnachoubey8648]

@@MechMK1 maybe sandwich them between tampered glass?

[@Heinze.Lightart]

You did it!!! I´m a holography artist and it gives me the most reluctant joy, to finally see someone is shinig a bright beam on Holography in youtube! In my holograms I Love to play with all the special powers of holography to create amazing visual experiences. People always ask me how do I do it and how does it work! This is the best explanation ever! thank you!!!

[@smnaotrt]

Do you have any good reference material or sources for those interested in creating holograms?

[@RuledSheet]

Like the guy before me asked. I too would like to know of any good resources you could share for me to get started. Would greatly appreciate your help :).

[@myself248]

I've struggled to get my head around this for my whole life, and it finally clicked. Thank you. One big piece was understanding that holographic "film" is special, but not in any exotic way, it just has extremely tiny grain size, on the order of the wavelength of interest. It's not magically storing phase information in some weird physical process, it's just ultra high resolution, and the phase is reconstructed from interference patterns. Bingo!

[@maxz69]

But if the object is removed, what does it bounce off of then? How do we see an image with only the reference light?

[@cchuang0730]

This is the most beautiful hologram class I ever have. 30 years ago, I produced my first hologram in the optics lab of the university. It was a real magic, but to this artwork, I only catched very fuzzy realizations from the vector equations in my textbook. That was an era without internet and youtube video. Thank 3b1b, guys that helps production this video, and the astonishing IT technology, to give me such a deep and visualized unstanding on hologram!

[@InXLsisDeo]

Just as an addendum about the astonishing IT technology behind Grant's videos: it's actually all programmed and mathematically correct. He writes hundreds of lines of Python code for all his videos. He wrote his own library and improves it for his needs.

[@tilileix214]

@@InXLsisDeohe does that all by himself? wtf, i am blown away…

[@sebastiantschen]

I learned, while I was still a teenager, that holograms store phase-information additionally to amplitude, on a film-plate. What always bothered me, was that no source ever explained why that would somehow lead to a recording of the full 3D scene, or how that scene would later be reconstructed. I always thought, that for that to work, the film somehow had to store the 'direction' of light beams. This Video was the first full explanation of how holograms are created, reconstructed, and why they do what they do, and it was beautiful. After more then 20 years of wondering if I would ever be able to undestand, what's going on in a hologram, you absolutely made my day!

[@denysvlasenko1865]

> that would somehow lead to a recording of the full 3D scene It leads to a recording which is NOT reflecting light mostly the same way in all directions. An ordinary image (photo, or a picture of a white letter on a black background for example) reflects the light off the letter's image in all directions with (almost) same color and intensity. A hologram reflects light very differently, the angular distribution of light from every point is _precisely_ such that you see the color and intensity visible at this point of source 3D scene from the angle you are looking at it. The "3D scene" is not really 3D, right? At every fixed viewing position, it's 2D and not moving. The plate shows (reflects) different 2D pictures in different directions. That's it.

[@mc_va]

​@@denysvlasenko1865somehow I understood your explanation better than the video. I feel so dumb 😭💀

[@sterrehofstee7052]

@@denysvlasenko1865 Like the previous comment said aswell, this really brought it home for me. Thank you for phasing it as you did!

[@deepseafishmusic]

I have been watching 3Blue1Brown for a long time. While most videos are brilliant, this one strikes me as outstanding. I may not know just how many other great channels there are, but of the few hundreds I know of, this is one of the absolute best. This is much more than edutainment, it feels like being handed a tiny but powerful and logical grip on the world - which in our arguably complex and chaotic times is a hard and commendable feat which I deeply respect and appreciate because it manages to calm and motivate. Which is to say: thank you! Thank you for this fantastic video.

[@3blue1brown]

High praise, thank you. This particular video was such a joy to make, I'm glad it resonated.

[@krishnachoubey8648]

@@3blue1brown Sir I'm blown away. Please continue this series on optics. It has been a joy to learn from you. 💖💖

[@DeJay7]

@@3blue1brown I second what the OP said. I just want to add that you constantly say "you might be curious why that's the case" or "you might be left unsatisfied with that answer" or something along those lines when in reality most of us have never even seen such complicated ideas, let alone explain them deeply. I greatly, greatly appreciate it, but it's easy to take your work for granted (pun semi-intended) while watching these videos, because you take concepts that are almost always unexplored and not talked about and make us interested in learning more and more about them! Edit: also what @krishnachoubey8648 said, the optics series is superb, especially for a physics student like me!

[@nabibbs2402]

​@@3blue1brownim really not good at math, but these videos have fired me up, nowndays I've deluded myself to thinking im good at math and now i like the subject alot now. who knows maybe it'll be more than just an delusion

[@RateOfChange]

​​@@nabibbs2402Watch every single khan academy video on basic maths. That's how I started my journey. Now I'm a math undergrad student 😊

[@victorlafuentelab]

If a Nobel Price for Science Communication existed, this work would get it. Congratulations on such a wonderful explainer.

[@eavids128]

I think this is the first 3Blue1Brown video I would show to a student with confidence that they would do better in a class than they would have if they had not watched it. This video covers the formulas and derivations for the optics portions of the E&M classes I took during my EE degree better than my teachers. I would recommend this video to a student.

[@gunderd]

I can't fathom the amount of effort that must have gone into making this video. The animations were incredible, as was your approach to gradual enlightenment from first principles. We don't deserve you, but I'm really thankful you're here doing what you do.

[@3blue1brown]

Thank you!

[@joshuafrank1246]

At <a href="#" class="seekto" data-time="700">11:40</a> I genuinely was so surprised by what I was seeing. I had no idea this was even possible. It literally looks like you’re looking through a portal to another world. Light is so cool!

[@mznxbcv12345]

It explained the holographic brain theory by karl pribram to me. Basically, that's how memory is stored in the brain, as even damage to a part does not affect the long term memory, it can still be retrieved later.

[@ekatvakushvaha1814]

Still can't help but being blown away by the quality in these videos...

[@ThatShushi17-mc7ct]

bro watched the entire video in 3 minutes

[@ekatvakushvaha1814]

@@ThatShushi17-mc7ct Jokes on you, I didn't watch at all💀

[@joshcryer]

@@ekatvakushvaha1814 hope you watched it the animations were otherworldly, and I don't think they were hand rolled, I think they were simulations which is just so much more impressive.

[@GiuseppeSan]

Seriously - I know something about this topic, and this is an absolutely insane level of clarity that has helped me understand what's happening at a much deeper level.

[@akshaywalimbe8326]

18 years after I was introduced to holograms, today I finally have some intuitive feeling for how they work. I am even more interested to understand how the colored ones in natural light work. Brilliant video, hats off to your efforts to make it so intuitive.

[@ThePathNotTaken]

I’ve looked through the eyepiece of the microscope hologram, incredible. This hologram was made by Walter Spierings from Dutch Holografic Laboratories.

[@giny2633]

Okay, thank you for sharing, I was able to look it up! The craftmanship is incredible.

[@M.Koenen]

Very true. The Microscope Hologram produced by this Dutch laboratory is amazing. It is still available on their site,

[@CoolScratcher]

I'm a high schooler who couldn't attain a tenth of your mathematical knowledge if I tried, but I still frequently find myself returning to your channel. It's not something you can exactly verbalize, but it's clear that you're an accomplished educator who can take complex and out-there ideas and ground them in basic logic and understanding. I'm frequently blown away by a channel my dad watches. I need to stress that - my dad watches your channel, and I actually find your content enjoyable. Mind-blowing. If you can teach this level of math to this lazy sixteen-year-old who's currently failing his Algebra II class, you can do anything, man.

[@kaltkalt2083]

I was once a high schooler who never had math explained in an interesting way, it was always do these 50 multiplication problems, i found math classes so boring. But schools are for stupid people, and later in life i learned the true beauty and importance of mathematics. The problem is I’m really interested in it but I suck at actually doing it. But as long as I don’t have to sit there trying to calculate stuff, a book about the Riemann Hypothesis is very interesting! That said, I’m so sorry you’re in high school. Unless you or your parents are already billionaires, you’re fucked :( You can’t imagine what the continued collapse of Western Civilization will mean, and what kind of life you’ll have - look at South Africa it’s exactly what the US will be like very soon, some parts already are. Life is one big intelligence test, and there are a lot of trick questions with counterintuitive answers. Wisdom is knowing what things are counterintuitive. Unfortunately today likes and followers trumps wisdom. Here’s a little simple math you should always keep in mind. The average person is a moron. This means, by definition, that 50% of people are dumber than morons. Never forget that, and if you’re with the majority on some opinion (not a fact like if "the sun rises in the east" but an opinion about, say, a movie or person) then you’re probably wrong. I’m talking about the fact vs opinion dichotomy in defamation law (because IAAL so it’s just an obvious distinction). Most people also would rather be happy and wrong (right now) than correct and unhappy (right now). Being correct and unhappy right now is always necessary for something to be successful in the future (work, time, sacrifice) - correct decisions if successful. Anyway, I just feel really bad for kids today. So glad I never had any, I could not handle having kids in this world, knowing the lives ahead of them. Weak men create hard times Hard times create strong men Strong men create good times Good times create weak men… and repeat. Take a guess where we are in this perpetual cycle. We don’t even have men anymore in the West, testosterone levels and sperm counts are at all time lows due to all the poisons in everything which nobody cares about because they are distracted by CO2 which is irrelevant. Do you know the % of CO2 in the atmosphere and how much it’s risen the past century? Look it up. 30 year old males are like 12 year olds. A 12 year old boy from 1850 could survive on his own and use a gun. I’m almost 50 and I didn’t feel like an adult until 40 or so. And our males are cutting their dicks off to become "women" real fast! Meanwhile the average woman today weighs more than the average man did in 1960. The hard times you’re going to face just make me so sad. Once, in another life, I was a lazy 16 year old taking high school math classes. I got to grow up in the 80s and 90s, a world free from racism and sexism, homophobia definitely existed though, but once it became acceptable to be out of the closet and everyone came out of the closet, everyone realized they knew plenty of good normal people who were gay, and homophobia went away in one generation, within my lifetime. Everyone generally cared about each other, everyone agreed an abortion was a bad, unfortunate thing even if they thought it should be allowed (“safe, legal, and rare” was the argument, with which I still agree). You’re being taught in your "school" that men and women are exactly the same, you can choose to be either gender, or any gender I should say, you can even make up your own. Don’t worry about algebra - do you know the difference between a male and a female? Because that’s way more important than math, and math is really fucking important. All of it, imaginary numbers are actually important. But no sense in being ok at math if everything else you know is wrong. Learn how to critically read a scientific paper. That’s probably the single most important skill in the world right now. Anyway, sucks to be you, sucks to be me, too. Unless you are a billionaire, in which case never mind.

[@oka-yoke]

@kaltkalt2083 Hi , I hope you are fine. I am a 36 years old failed Engineer in life who is trying to stand up strongly at age 40 from the scratch. I found your comment very interesting which is including advises to a 16 years old teeneger about the new era of life. Sorry for my English, because since it is my third language. I decided to discuss your comment with Chat GPT and got interesting result. Please find the result in below: "The fact that the commenter critiques the present in a pessimistic manner while idealizing the past can be explained by a psychological phenomenon known as "retrospective idealization" or "nostalgic idealization." In this type of thinking, people tend to overlook or minimize the problems of the past, while perceiving current issues as more significant and threatening. This way of thinking is particularly common as people age. Nostalgic idealization leads individuals to remember their youth or earlier periods as more positive, and the societal norms and life conditions of that time as better. They may downplay or dismiss significant issues like racism, sexism, or economic inequality that were present in the past, while viewing contemporary changes (such as gender identity discussions, technological advancements, or social media) more critically. This pattern of thought, especially in certain age groups, could be related to a midlife crisis. Individuals experiencing a midlife crisis often find themselves facing greater uncertainty in the middle years of their life and may begin to worry about the future. As a result, they are more likely to see the past as simpler and more manageable, while the current world appears more complicated and harder to control. This can lead to a perspective that is critical of the present but overly positive about the past. In addition, resistance to cultural or social change might also be part of the unease. A person might struggle to adjust to rapid social shifts and may feel more connected to the value systems of the past. This resistance can heighten anxiety about social structures changing and lead to a more pessimistic outlook on the future of society. In summary, the individual’s pessimistic view of the present and idealization of the past can be attributed to phenomena such as midlife crisis, nostalgia, and resistance to social change. These tendencies reflect difficulties in accepting or making sense of the cultural and social transformations they are experiencing. --- To help overcome this mindset, it would be beneficial for the individual to adopt a more balanced perspective. First, they should acknowledge that every era, including the past, had its own significant challenges and that today's issues are simply different in nature. Embracing social changes, staying informed about the positive advancements of modern society, and practicing mindfulness or gratitude for the present can help shift their outlook. Developing a mindset of adaptability and openness to change will also ease the transition and reduce anxiety about the future."

[@LitCast]

i dropped outta highschool at 12th grade, wish i didn't haha, i find myself actually retaining information with these videos though, like when the slit thing came up, i immediately thought about the double slit experiment i also like to watch these videos on a light trip, some of those visualizations (maybe inadvertently) are accurate to the visuals i get on a heavier trip, i can't imagine how hard it is to plug all that into MAnim.

[@kaltkalt2083]

@@oka-yoke This is exactly why I don’t use AI, it always gives a California democrat response to everything. Don’t trust it.

[@oystercatcher943]

My 18 year old son enjoys the channel as do I. If you keep coming back and enjoy the content I truly think you can do anything. Best wishes

[@mezzanoon]

As a rare hologram (REAL ones) nerd, this might be my favorite video on KZbin of all time. Your simulations are always so beautiful, and getting to see those museum pieces was incredible

[@wellscampbell9858]

I am another such nerd, and will add my plus-one to your comment about (REAL ones). Nothing steams me more than the mis-application of the term "hologram" to any number of optical presentations which, while they may be interesting, are NOT holograms. But I'm not going to name names... right, Tupac?

[@StubbyPhillips]

@@wellscampbell9858 Yep. Just because you can see through an image doesn't mean it's a friggin' hologram! It's REALLY annoying when "tech media" buys into it and plays along because the word "hologram" makes a good headline. That's just being sleazy.

[@ZK-ff2ru]

explain the maths behind holograms

[@trixification9132]

Fresh 3 blue 1 brown video to savour on a Saturday, dosent get much better

[@quintenbart9824]

Truee

[@mekaindo]

I agree

[@bide2505]

Monday dude yea Sunday since 19 hrs passed

[@spad4728]

I'm working on a PhD in electromagnetics. These visual animations of phase are a game changer for me. Being able to *see* the phase change with viewing angle is what makes esoteric equations suddenly feel simple and practical.

[@3blue1brown]

Thanks!

[@climbscience4813]

I did my PhD in digital holography and I have to say: Hats off, this is fantastic! You have a true talent for explaining and visualizing these concepts! I would like to add some things that might be interesting for some people: - You chose to model the object as superposition of single points / point sources, resulting in a superposition of Zone plates. This totally makes sense and is correct. However, there is another superposition that makes the step from exposure pattern to the reconstructed wave a little easier: Separation of the wave field into plane waves. The interference with the reference wave is exactly a simple diffraction grating. This is how I always thought about wave fields in general, a superposition of plane waves, which span up a spectrum of directions. Interestingly, you can separate that spectrum into plane waves by a Fourier transform of the complex wave field in a plane. One really cool property of this is that when the wave field propagates to a different plane, only the phase of the spectrum changes, the amplitude is unchanged, which makes it very easy to calculate propagation. I love the elegance of this, it's quite beautiful!

[@3blue1brown]

This is a great way to think about it. For those comfortable with Fourier transforms, I think it's definitely more elegant. We took the point-to-zone-plate approach in the video because it felt more concrete for (hopefully) most viewers.

[@climbscience4813]

@@3blue1brown Completely agree with the choice. I feel that superposition with point sources is something that more people will be able to grasp, compared to plane waves, when it comes to wave fields generated by actual objects. Again, fantastic job on the video! That definitely would have helped me when I started in holography! 🙂

[@coolcat23]

What happens if one views a hologram with a frequency-shifted reference wave? Does that result in a scaling of the scene?

[@climbscience4813]

@@coolcat23 I would have to do some maths to give you a precise answer to this, for now I'll use intuition. For a thin hologram like the one in the video, the effect should result in a re-scaling of the angles at which the light is deflected by the hologram, but at the same time, the scaling in the plane of the hologram is unchanged. So, visually it might appear similar to a re-scaling, especially if you go further away from the hologram, since angles have a stronger effect on a wave field' amplitude distribution the further away you go. However, it's not a "clean" re-scale, so you would likely see some other effects too. Hope that makes sense!

[@coolcat23]

@@climbscience4813 Thanks a lot for the reply, much appreciated!

[@sockenschuh2452]

This is so heartwarming for me. My big brother died 10 years ago and i still got a set of hologram films he made for his master of science. I never really understood what he wanted to explain to me when he showed me those. (Like also referencing holographic principles related to the encoded informations stored on blackhole surfaces or something? 😅) The films are some scenes but also a digitally generated cube which spins at a faster angle then you look at. Like you can look at it from all sides even when you only shift your angle of view or the laser pointer by less than 180°. I always was so fascinated. I wondered how so much 3D information can be encoded on 2D. I am so thankful to now understand it more ❤❤❤

[@Kumarrohan67]

This video is a phenomenal piece of art. Just imagine if your university teaches you in this way. Three to four years of production will result in the highest quality of educational content for a certain topic which could be used for years, and a lot of students will dive very deep into science out of extreme interest.

[@alwayscurious413]

Also at low cost and in rapid time. This video condensed months of self learning into about 20 minutes - astonishing. In principle 2 years of a physics degree could be implemented for ‘free’ delivered by videos as brilliant as this. 1 year in the lab and you are probably there.

[@evanbarnes9984]

This is something I've always wanted to understand, and already at <a href="#" class="seekto" data-time="720">12:00</a> minutes in I have a much better understanding of this phenomenon than ever before. Also, Grant, your animations were already excellent like 5 years ago, but these are on an entirely new level. I'm so excited for the rest of this video!

[@Nobodyknows95123]

i never click on 40-minute or longer videos, but i gave this video a shot i watched it all in one sitting. this is amazing! thank you

[@TREX_04]

I'm an undergrad in engineering and he just explained complex numbers 10× better that my math professor. The power of 3b1b content is unmatched! Keep up the good work!

[@KeeganLeahy]

"The universe can often be elegantly and beautifully modelled by mathematics" <a href="#" class="seekto" data-time="2552">42:32</a> RRRRRORROROO

[@ModusTrollens91]

Scooby Doo was actually trying to teach us about holograms.

[@KyleBaran90]

@@ModusTrollens91 There is an old series episode where the bad guy in question was using Pepper's Ghost illusion to move through walls

[@HuygensOptics]

Great work Grant, your explanations and animations are truly next level!

[@TheHectorOg]

❤

[@null-calx]

such is yours, too

[@fredinit]

Jeroen - I was hoping you'd hop in and see this. I love seeing your work, and explanations, as well.

[@3blue1brown]

Likewise! I gave a card to one of your apropos videos when I mentioned the Fresnel zone plate. Your videos remain, hands down, the best on optics KZbin has to offer.

[@Michael-vf2mw]

@@3blue1brown With an endorsement like that I gotta go check them out I guess.

[@googleyoutubechannel8554]

This is by far the best explanation of holography. I'm amazed at how counter intuitive holography is in general and how complex even the basic principals turn out to be. I had no idea that somehow overlapping interference patterns could store this much information, let alone offer a way to just 'look at it' and somehow our eyes can perceive a recreated a 3d scene. Not to mention the surprising fact that film grain contains enough density for this to even be possible from an info theory standpoint, it's like you're somehow getting hundreds of exposures stored on a single exposure all via some interference wizardry.

[@pseudolullus]

Yup, the magic of interference and Fourier transforms, I love it!

[@mb2776]

In someway, our whole existence is based upon complicated interference patterns. All matter, not just light does have a wave nature, interacting with each other produces interference patterns. I'm not even joking. Mathematically explained by the addition of wavefunctions.

[@richardjones38]

The way you can look into the microscope in the hologram, and the way the klein jar distorts and reflects light are amazing. I had no idea holograms could be that good. An awesome video

[@generalmisery]

The passion needed to explain something so complex in a way that even I can understand it, having had physics only in highschool, is what makes this video probably the most amazing one. There should actually be an award for things like this.

[@sk8rdman]

As amazing as holography is, the thing that I love the most about this video, and indeed most 3b1b videos, is how he doesn't just tell you that it works and give you some black box equation to justify it. He helps you build an intuition for how and why everything works from relatively simple first principles. This is what is necessary for true understanding. Teachers take note.

[@wuppfler]

I accually wrote my bachelor thesis half a year ago about optimising computer generated holograms for digital hologram displays. I was looking for an intuitive explanation for holograms in general and didn't find it. until right now. Also I know how difficult it is to explain this topic and you did an excelent job.

[@WeAreChecking]

Do you have access to that thesis still? Currently working though an optics course and would love to see how you've approached things.

[@cleon_teunissen]

In the video Grant describes his strategy: 11:50 "Universal problem solving tip number one is to begin analyzing any hard problem by taking the simplest version of that problem." Grant finds the most simplified case that still features the phenomenon of interest, and from there he builds step by step. The other part of course is: the visualizations. At any point where a narrator would find himself forced to say: "Now imagine that..." there is an animation.

[@wuppfler]

@@WeAreChecking I do, but I don't know if it is what you need and don't know how to send it to you.

[@whollypotatoes]

I am so happy that you've decided to cover this topic. Has never quite clicked with me and I knew that I've been waiting for someone to really decode it in an easy to explain way

[@johnbreitberg3231]

I LOVE this kind of deep dive into a subject where you breakdown each sub category of information leading up to the full picture, really aids in the full intuitive understanding you were striving for and also removes that disappointment of longing for more info, please please PLEASE more deep dives like this!!!! Incredible work!!

[@jsalvata]

I remember a conversation with an optical physics graduate in the early 80s where I asked her to please explain how holograms work. I got such a detailed explanation that I could probably have made one myself. Since the advent of the Internet, I've researched the topic multiple times but, not having a physics background, I could never grasp it... until today! What an awesome video!

[@thomaskilmer]

This genuinely feels like the joy of discovery I had all throughout my graduate Diffraction and Interferometry course, in just 45 minutes and with minimal prior grounding. It's astounding. Well done, truly, your videos never fail to be an amazing font of educational material and beauty in math and physics.

[@alwayscurious413]

Absolutely - in 45 minutes many hours of lectures have been covered. Astonishingly good.

[@ivereadthesequel]

I didn't imagine you would do an episode on holograms! Not only that, but you found the two exact holograms and features to be the most mindboggling as I did: any sort of glassware or lens in a scene, and a hologram of a microscope! Seeing these concepts explained with your animations is super helpful, especially the phase aspect. I would see it mentioned in explanations but wasn't sure how it was involved and I felt the interference argument alone was sufficient to understanding. The explanation about diffraction gratings and the various orders of light beams that they produced, answering how each affect things and why the others don't occur was excellent! I was thinking "but what about the other beams??" You're right about the complex number argument being "unsatisfying" on its own. But as an addendum to everything that preceded it in this video, it's a great cherry on top for completeness! The fact that the 2D plane containing the object wave in space _also_ projects that information out in 3D space doesn't seem as bizarre. That intuition doesn't make me feel certain that it's definitely the case (even though it is), but it also doesn't make me completely baffled as to why it is. Even though the reason why that is is a lot more complex. It feels like there's not much else it _could_ do besides travel out through 3D space in the same manner that the light reflecting off the scene originally did. But it feels like that intuition is still missing a lot more which is probably why that part would be a lot more complicated! Also, microfilm I see used resolves around 800 lp/mm (Fuji HR-21 or ADOX CMS 20) and they're kind of fun to use for regular photography because then you can quite realistically get 200MP+ from 35mm film. On the upper end of its resolving power you can get a gigapixel or more, that's why there was this one film developed called "gigabitfilm". 100-200lp/mm is well within the range of almost all professional films, color, black and white, slides or negatives. This video was totally awesome! Even since I saw that "Introduction to Holography" educational film you included and it showed how recording into the depth of the film had significance, that optics in a scene still "work", that you scan store multiple "channels", etc made holograms seemed like pure magic! That's why your video was so perfect to me!

[@TaleDreamer]

I have been curious about this process since highschool but couldn't really grasp it even with videos explaining it, so I am glad you are covering this topic without complicating everything with terminology. Thanks! More of this type of content please. Well. Not holograms specifically, but y'know.

[@DoctorLazertron]

I am always blown away by how you can describe things that are meaningful to both a complete layman and a mathematician without even having to switch 'modes' or 'talk down'. Beautiful work.

[@정민준-f9e]

The entire video is just pure dopamine, from start to end. Such a mind-blowing phenomenon, followed by such a delicate, and more importantly, an intuitive step-by-step explanation that all just "matches up" in your brain is just the dopamine surge itself. It has been very long since I had so many questions about the topic in my brain; I would happily go on for a deep-dive search on holograms even though I have almost zero background on the field. The best teacher every on the internet (and much better than my college professors), for sure.

[@Krunschy]

Nothing else captures the joy of learning cool stuff as great as Grant does it. Feels like you get the payoff for days of studying into a single hour, eliminating any frustration you'd have encountered. 3b1b is truly the most amazing educator out there.

[@msinaanc]

How could you increase the quality of your work all the time. This video was like a snapshot of a whole optics curriculum which I could never felt the grasp until now. You are really putting in a brilliant use of computers. Wonderful work.

[@mynamesgus4295]

thank you so much Grant and team for making this nobel prize discovery to be so digestible for the average physics enthusiasts. Seriously, from the bottom of my heart, thank you so much for the work you do.

[@alwayscurious413]

I can’t really find the words to relate how magnificent this video is. I was lucky to study holography at university and the amount of time it took to fully understand what you have related in only 45 minutes is incredible to contemplate. This video would be a key technical reference for anyone to cite in their thesis or research paper as to how holography works. Save anyone from writing the text - it’s all right here.

[@DrChunder]

This is the finest video on holograms I've ever seen. All the little details, like using the poincaré disk as a base in the graphics, help convey so much information that really builds the intuitive understanding of holographic principles. Thanks so much.

[@JoshuaCowling]

Over a decade ago I spent most of a year trying to wrap my head around this as I started my PhD focused on a certain type of optics and holography. Oh how I wish I'd had an explainer like this then! Thanks for reminding me of all this fun ❤

[@magrathean0]

I have made several attempts to get a 10,000 ft understanding of this before and failed. I had to pause your video ten minutes in when it suddenly clicked - i paused again later when i realised the film itself acts as a diffraction grating, Many thanks - i now have enough understanding to be able to explain it in vague terms to someone else.

[@bosstowndynamics5488]

You seem to have this amazing knack for finding stuff I kind of thought I knew about already and exploring an entire additional layer of fascinating depth for it. Loving these sciencey themed videos!

[@peterobyrne5048]

The overlap with macromolecular x-ray crystallography is not a coincidence. Crystals are effectively acting as the holographic film using the symmetrical repeating points in the lattice as the diffraction grating. Would love to see you tackle ecpanding briefing into that world

[@gunblad3]

Really could see this video almost cumulatively demonstrating the skills you’ve amassed over the years teaching here. Thanks ☺️

[@purrzival]

I really like this style of explaining almost every concept necessary, but making it easy to skip over a part if your familiar with the concept beforehand. Really good video!

[@bend.manevitz8261]

Many years ago, i took a half-semester's course on almost exactly what was covered in this video, and this 45 minute video did a better job.

[@alwayscurious413]

It’s game changing isn’t it? Shorter in time and better in quality.

[@razile9854]

Please keep producing these optics videos. You've demonstrated incredibly easy to digest examples of optics that could open the field up to many great minds. Optics is hard but really frickin cool.

[@danielcingari5407]

As a humble college student, my mind is boggled by your ability to take everything from 3D visualizations of light frecuencies to thorough analysis of complex (no pun intended) optical behaviors and film properties, and condense it into comprehensible chapters with completely logical progressions: and keep it all fascinating and aesthetically pleasing, no less! There's really something beautiful in the way you teach and interact with your viewers; your expertise and passion are made so evident through it. Thank you, please carry on, and know the respect and appreciation you earn for yourself.

[@sergiobarros_]

this is one of the best if not the best video I have ever wacthed on KZbin point blank period. Congrats to the 3B1B team for making such amazing content!

[@gamingagent80]

I refreshed youtube and was like wtf 2 seconds ago ! Always a pleasure seeing one of your vids pop up on my feed!

[@ISoldTheWorld97]

Grant, I know you love a good "Aha!" moment. For me in this video, it was around the <a href="#" class="seekto" data-time="630">10:30</a> mark. Suddenly, the broad strokes of holograms suddenly made sense. Because of course! If you record the ways that two things interfere, and then send only one of those things through the interference, you're going to get the other! Excellent video, as always.

[@RoyalYoutube_PRO]

I always get lost at the topology stuff, but for some reason, this is the easiest thing I ever learnt... in fact, his wording of the setup in the start was enough for me to be able to imagine how the hologram works

[@AlanOlson-op9in]

This is the most intuitive explainer I have ever watched about holography. The script is concise and logical and the graphics are amazing. A superb effort! The intuition gained extends beyond optics and gives a glimpse of how the Holographic Universe Principle could operate.

[@_xzvf2557]

Excellent lecture. The very last sentence (" light obeys laws regular enough that the state of a light wave in 3D space is sufficiently constrained by its value on a 2D boundary") is an excellent insight

[@Rialagma]

Amazing video! As someone who works in holography in the lab, this explanation helped me a lot!

[@Brice23]

I read about these principles in a book about 25 years ago. Lets see.. oh yes it was called Mind At Light Speed by a scientist named David Nolte. It was fun. Needless to say, your presentation is much better than any book.

[@XyrillPlays]

<a href="#" class="seekto" data-time="2287">38:07</a> "Luck favors a prepared mind" is magnitudes better than the usual "Fortune favors the bold" and I will henceforth insert this quote into as many discussions as possible.

I was waiting to see if anyone would comment on that line. It reminded me of something else, though. In the movie Under Siege 2: Dark Territory, the villain would sometimes say, "Chance favors the prepared mind" in explanation as to why events sometimes worked out in their favor.

[@RUDRARAKESHKUMARGOHIL]

Yes it was quoted by louis Pasteur,later by richard hamming , As grant discussed in hamming code video ❤

[@blindleader42]

Also attributed to Seneca the Younger: "Luck is what happens when preparation meets opportunity." There's no authoritative source for the above, that I know of, but it's an idea that probably goes back to the earliest generations of Homo Sapiens.

[@aureliencobb199]

Since I was a child I was mesmerised by holograms, wondering how they work. Especially the part where when you cut a piece of to, it still contains the information for the full picture. Your video is a great explanation. Very clear. Thank you.

[@deadalpeca8099]

<a href="#" class="seekto" data-time="1837">30:37</a> This just gave me goosebumps as I recalled how frequency filters in image processing like low-pass, high-pass, band-pass and band-stop filters with sharp cutoffs give ringing artefacts while those with smooth cutoffs like Gaussian filters don't. I'm very sure the two phenomena are related.

[@diagonal978]

I swear you may never know when or where these information are useful but when they are in a class it feels the best thank you for all of your videos

[@vaderbase]

Words are not enough to express how much I adore this channel.

[@threeuniquefingers]

<a href="#" class="seekto" data-time="2303">38:23</a>, nearly got a heart attack thinking the video was over

[@oisiaa]

Grant...your videos no joke could advance human civilization by unknown amounts due to the hundreds of thousands of minds that absorb the information and go on to make new great discoveries and inventions.

[@ravia.vkumar1080]

I would say that this is THE best tutorial on holograms out there on internet! Brilliantly done !

[@jaswanthchoudhary8715]

a 45 min 3b1b video?!! I don't know what good deed I did to deserve this.

[@samwilton7864]

I'm more amazed by the creation of this video than I am the invention of holograms. So much attention to detail. I would love to see a video about the process of making a video like this. It's beyond my comprehension how it could be made by a single person in a reasonable timeframe.

[@ReverieGains]

He just released a video showing some behind the scenes!

[@usualatoms4868]

Wait... if we have a plane of speakers and then have microphones matching each speaker on the otherside. Then we record let's say a 44.1kHz sinewave in a room or space with all of the microphones. I think we could then use that information to simulate any acoustic space nearly perfectly and play any sound through that system using convolution (impulse response in audio). Not sure if the frequency needs to be that high but in audio that's what we usually go for at a minimum trying to avoid any funny phase problems in the audible frequency spectrum. This video is unreasonably inspiring :D

[@usualatoms4868]

Or you can just use motion tracked headphones. But just as a thought-experiment!

[@random-oe9jy]

Absolutely brilliant visualizations as always!!!!! This format should be how children are taught at school. I'm writing a paper about a new school system and your videos will be the first examples i give on the topic of using online resources. Absolutely fantastic. I never really considered myself a fan of anything really, but i think this is what that's like.

[@opd-cp3ee]

<a href="#" class="seekto" data-time="500">8:20</a> I got it!! :D Now I feel rather clever haha Thank you so much for letting us have these aha moments, giving a pause for people to think, and in such a friendly, respectful way at that.

[@jeffmerlin2580]

<a href="#" class="seekto" data-time="1837">30:37</a> My first thought was harmonics. Like a radio wave that is a sine does not create harmonics, but a square wave does.

[@zorggn]

The moment i realized that, i just shook my head saying "Fourier... of course it works that way", although i never before imagined the slits could be modified like that, to not be just two states.

[@mastershooter64]

what do you mean sine waves don't create harmonics?

[@jeffmerlin2580]

@@mastershooter64 A sine wave has one and only one frequency. A Square wave has a fundamental frequency and many harmonics. Infinitely many harmonics if the wave is "square enough". 🙂

[@warpspeedscp]

​@@zorggn Yeah, and it turns out, it is indeed possible to create holograms by taking the fourier transform of all the light rays that reflect off an object at each point, and using that to create a diffraction grating! It feels great to wonder if it's possible to relate to pieces of math and find out what you imagine is actually possible.

[@harryf1867]

The first hologram I saw, I was 11 years old at Expo 67 in Montreal. A chessboard scene. It was magic to me. Now I have the rudiments of an understanding of it. Thanks 3Blue1Brown!

[@rishavjain5087]

<a href="#" class="seekto" data-time="1569">26:09</a> if u were wondering x/L should be tanθ, u r right, but x/L is very small here (we equating it to wavelength, that small) almost tending to zero, and if tanθ tends to zero, it is equal to θ itself and luckily that is also true for sinθ....so that's why, sinθ.....

[@quasar-ed]

The most complex topic ever to be explained by the most master explainer with amazingly accurate simulation. Your videos are inspiring to other educational explainers like us. I need to learn your MANIM tool.

[@r.k.8232]

Best Movie candidate, absolutely a masterpiece! Animations A+, Narrator A+, Script A+ , Explanations A+. Love your channel ...

[@jimmyzhao2673]

I've seen that type of microscope hologram in person, I can tell you that it is very trippy.

[@anieldayyanelday1771]

When the world needed him the most...he turned up!

[@jmkqfnvyl87]

Appreciate the vid. Went into physics with a grant to study optics but ultimately left the department over the horrible political struggles to just exist in upper level academia 😢. Swapped disciplines but always wanted do delve back into it on a deeper level. Keep it up bro!

[@polarwind77777]

Thank you so much for this video! Showing the physical objects that allow for the encoding of information really helps solidify the process.

[@matiasnovabaza8208]

<a href="#" class="seekto" data-time="622">10:22</a> was a beautiful "aja" moment for me, the necessary piece of the puzzles were so well presented. This is gold

[@Lavamar]

Probably my favourite video of yours so far. So incredibly well explained at such a good pace!

[@conradammon268]

<a href="#" class="seekto" data-time="2100">35:00</a> to <a href="#" class="seekto" data-time="2145">35:45</a> makes me envious to the point of anger. He captures a fundamental driving philosophy of mathematics and why I love the fundamental and abstract maths so much in a way I've not ever been able to describe. And he does it as an ASIDE, a lemma stepping stool with which to jump right back into his real lesson!

[@bloklord5325]

To anyone that saw The Thought Emporium's recent video on diffraction gratings, notice that the holographic exposure pattern for the theoretical single point hologram is just like the grating he used to focus light using only diffraction.

[@mosab643]

This was like every class I have had in college. Start of very simple and stay that way for more than halfway through the class and then cram all the hard and important stuff towards the very end. All the confidence you have built in the beginning gets shattered in the end.

[@yong-taekim9366]

in an stupid era of flooding shorts and tictoks, this channel is a gem and is the only few reasons YTB still holds its worth

[@maxlevin8842]

I loved this video - as always, the explanations were really clear and the video was made beautifully. I did have a question though: at <a href="#" class="seekto" data-time="1571">26:11</a>, isn't x/L equal to tan(theta'), not sin(theta')?

[@3blue1brown]

You're right, silly me! It's all an approximation anyway, since the grating is not evenly spaced (the spacing gets smaller farther away), so the diffraction equation wouldn't hold exactly either. This does make me wonder if a tighter analysis accounting for that non-uniform spacing would result in something closer to tan(theta) in the diffraction equation. In either case, all the more reason to lean on the more formal explanation to fill in the gaps.

[@dineshpadiyar5846]

@@3blue1brown No, it's sin(theta_nought). Tan(theta_nought) is the inclination of the beam to the axis - the tilt of the beam relative to the axis. If the point source were far enough away, the beam would be collimated and tan(theta) would be constant across the plate. However, the lines of equi-phase up, or along, the plate is given by the grating equation, lambda = d*sin(theta_nought). If the beam were tilted at theta_nought, then, assuming that the x axis were up the plate, and z is perpendicular to the plate, the distance between wavefronts of the laser at an angle theta_nought, relative to z, are related to the lines of constant phase along the x axis ("up the plate") by d = lambda/sin(theta_nought). Imagine lines spaced at equal distances along your ray which is tilted at theta_nought to the z axis, and perpendicular to your (tilted) ray direction; this is the wavelength, lambda. If you now project the distance between two of the wavefront lines onto the x axis, the distance between the lines on the x axis - d - is given by d = lambda/sin(theta_nought). By the way, I've been a holographer since 1981, working on display holography and technical holography (Holographic Optical Elements). This is one of the best, clearest explanation I've seen for some time. I've known Craig and Sally for many years. If you run into them, say Dinesh says hello. I also graduated in Theoretical Physics from the University of London, and have been following your maths and physics videos which I find are very clear and informative. I especially liked the course on Special Relativity.

[@wellscampbell9858]

@@dineshpadiyar5846 I was active for a time on the holography forum about 15 years ago, and I'm pretty sure I interacted with you a few times. Dinesh has a formidable knowledge of the theory and math applicable to holograms, and always served as a great source of understanding for those of us who approached the topic from an experimental/empirical (hobby) direction. Good to see you're around, and further evidence of how small and connected the holography community is. Cheers!

[@RUDRARAKESHKUMARGOHIL]

But what about "why bending refrence wave eliminates the conjugate (reflection wave) and the straight Passing wave ?"

[@amichelis]

~<a href="#" class="seekto" data-time="1840">30:40</a> It's like the beam's order being the resulting frequency bumps of a fourier transform. Sine-like gradient slits can produce only the 1st order (the 0th being always the equivalent of DC 0hz on fourier). Square-like slits produce more orders, as their shaping is composed by many "sine-like gradient slits stacked"

[@SimonBuchanNz]

This was my immediate intuition! But "patterns fool ya", so that intuition is hardly good reasoning.

[@alexanderdaum8053]

It also seemed like that to me, so I did a little googling. Apparently if you are far enough away, diffraction can be approximated as the so called Fraunhofer diffraction, which really is a fourier transform! See the wikipedia page on "Fraunhofer diffraction equation" (not posting a link so youtube doesn't delete)

[@nowthatissomethingamazing383]

The best video to coherently explain the magics of hologram I believe ever!

[@StubbyPhillips]

I like what you did there.

[@dunielgoldsteon7188]

Very cool to see a 3blue1brown video about a field my grandfather helped pioneer. He used radar interferometry to look at the surface of Venus through the thick clouds. RIP Richard Morris Goldstein