Making Real Holograms!

when i say hologram this is probably what you think about right princess leia asking obi-wan for help or maybe if you're not a star wars fan maybe you think about that tupac thing a while back well i hate to be the bearer of bad news but neither of those are actually holograms the former is what's called a volumetric display and the second is known as the pepper's ghost illusion this on the other hand is a real hologram and they are frankly way cooler today we're going to be talking about holograms how they work how we make them and some things we can do with them that i think are going to amaze you let's start by just looking at some holograms these are some of the many that i've made over the last little while and i think they are excellent examples of the amazing properties of holograms you can see that as i move them and the light source around different perspectives of the object can be seen unlike a traditional photo that captures a 3d scene by flattening it into a 2d image holograms retain the 3d information of the scene this allows you to see objects as you would if they were actually in front of you they also come in different colors here's a red one a green one and even a rainbow one what's really cool is that every part of a hologram contains the entire image so a hologram of dice for example can be purposely split apart and you can see past what would be the edge of the image and see dice that you'd think should be on the other half of the plate but to understand how these are made we first need to understand some properties of light quick disclaimer this whole video will be using lasers so laser safety precautions should always be used don't look into the beam wear safety glasses do not attempt to eat the laser and definitely do not use the laser to carve a dick butt into the moon got all that good moving on let's start simple what is light this is the part where the physicists collectively panic because that answer is surprisingly complex but we're going to stick with the basics light is composed of particles called photons the bit where it gets weird and the physicists start sweating is that even though photons are particles they behave like waves that probably sounds convoluted so let's do a quick experiment to see what this looks like if you've spent any time in a physics class you've almost definitely heard of the double slit experiment the idea is pretty simple you've got a light source in this case i'll be using this little red laser pointer and a slide with a pair of very fine slits cut into it we shine the laser through the slits and project the result onto a board and depending on what it does we know photons behave like particles or like waves particles would simply project a pair of lines while waves would make many lines think of this like the difference between shooting a bb gun and ripples on a pond bbs would follow straight lines and if they bump into something they stop but ripples can bounce off of things make new ripples and go around things in the context of double slits if you shot enough bbs you would end up with two lines of impacts on the screen whereas with the ripples right after the slits two new sets of waves form and where parts of those waves overlap they'll either add together or subtract depending on if it's the peaks or troughs of the waves that are lining up when the ripples hit the screen certain areas would be struck by combined peaks and others by troughs in the context of light troughs would look darker and peaks would look brighter so when we actually do the experiment what do we get well we get many lines and a pattern known as an interference pattern meaning light is wave-like the reason i say photons or particles is because we'd actually get the same result if we only fired one photon at a time each individual photon would hit a specific spot on the screen but as you fired more of them eventually the net result would be that same interference pattern this is what i meant by things get complicated i think the best way to think about this is sort of like waves of water even though water is made of individual molecules you can still make waves with it it's definitely not a perfect analogy light is way weirder than that but i think it helps visualize it because light has wave-like properties that means it also has a wave length and for visible light this is measured in nanometers to our eyes different wavelengths of light look different colors longer wavelengths look red while shorter wavelengths look more blue now one of the many properties of waves is something called phase basically when you've got two identical waves if the peaks and troughs line up perfectly they're said to be in phase and will simply add together perfectly but if they don't quite line up they're what's called out of phase and different parts will add or subtract less evenly we measure the phase difference in degrees this is just how shifted one is relative to the other looking at the simple example of two identical sine waves if you shift one of them so that the peaks perfectly line up with the troughs of the other they're said to be 180 degrees out of phase and would actually completely cancel out the same thing applies to non-identical waves but the simplistic case makes it easier to understand now let's see how this works in the real world and do another experiment to see how phase can affect light and don't worry this is the last one and then we can make some holograms we're going to be setting up what's called a michelson interferometer it's quite simple but has a few more pieces than the double slit experiment again we're going to be using a little laser pointer as our light source and we'll talk about why that's important in a moment then we've got what's called a beam splitter basically this is just a mirror but when they applied the silver coating to it they only made the metal layer thick enough that about 50 percent of the light is actually reflected the rest goes right through as if it was an ordinary piece of glass this takes our single input laser beam and splits it into two new beams these two new beams are then each bounced off of a mirror back to the beam splitter and it's very important that the two mirrors are exactly the same distance from the beam splitter again this splits each beam in two two of them will be heading vaguely towards the laser pointer and two will be heading towards the screen which we'll be using as an output if we line everything up just right these four output beams can actually be combined simply into two overlapping ones one is heading towards the screen and one towards the laser we can ignore the one that's heading towards the laser it's hard to see the result of what happens when the laser beam is tightly focused on the screen so a simple magnifier lens is used to expand the beam so we can see what's going on and what we see is an interference pattern like before so what's happening here well laser light has two properties that make this possible first most of the light from the laser is the same color i.e the same wavelength this makes it resemble that idealized example before of identical sine waves and second the light is what's called coherent which means that when the photons leave the laser they all start off in phase with each other when the beam hit the beam splitter the two sets of photons each had to travel to a mirror and back before being recombined on the output but my setup is far from perfect so each beam had to travel a different distance relative to the other and the alignment of the beams isn't perfect either so they don't perfectly overlap as such one of them is slightly delayed and offset relative to the other so the phase of the two beams is now slightly mismatched and when the phase is mismatched the waves don't add together perfectly so some areas look dark while others look lighter in a professional grade setup where the alignment is much better you would actually see rings and the number of rings corresponds directly to the difference in path length between those two mirrors if you get everything absolutely perfect the output would either look like one solid bright spot or complete darkness which does look very odd when you can clearly see the laser beam hitting that spot but i'm doing this with cobble together garbage so you can just see sets of lines also one last note is that the pattern is extremely sensitive to vibration because any motion moves the mirrors and thus changes the pattern this will be important in a moment okay finally we can look at holograms there's actually a few different kinds of hologram but they all work on basically the same principle the basic idea is very similar to the interferometer but with a few key changes first instead of a screen we're going to be using a special type of film that can capture the interference pattern that forms so that we can look at it later we'll talk about how that film actually records the pattern in a bit again we split one starting beam in two but instead of bouncing the two beams off of two identical mirrors one beam is sent directly to the film usually by bouncing it off a mirror while the other is reflected off of an object instead also instead of only expanding the beam at the very end in this case we expand each beam so that once it's been reflected off the object or mirror it covers the whole area of the film just like how small differences in the mirror position change the phase of the light each point on the object is going to be a different distance from the film so each point on the object will change the phase of the light that hits it and when it strikes the film it'll interfere with the other beam and create a pattern we call the beam that bounces off the mirror the reference beam and the beam that bounces off the object the object beam if we think back to the interferometer and specifically the professional version where you get rings the pattern is simple because only one dimension is really being measured the difference in distance of the two mirrors but with a hologram we're measuring three dimensions so the pattern is much much more complicated but the end result is that all of that 3d information of the object gets encoded in that pattern so when we view the film on its own we can see the object as if it was in front of us now the method i just described of splitting a laser into two beams and using a mirror and lenses is all fine and well but it's quite challenging to actually do without a very expensive setup and is quite fiddly to get right but like a good scientist i prefer methods which are easy and cheap whenever possible and thankfully such a method exists the theoretical version i described is what's called a two beam hologram for fairly obvious reasons but what we'll be doing is called single beam holograms basically we're sort of cheating and making one beam act like two by setting things up in just the right way before i go further i actually need to take a moment to talk about an amazing company called litty hollow which was kind enough to supply many of the materials you're about to see me use originally their company made kits for making holograms at home and they were actually kind enough to send me not only their original kit but two of their upgrade kits and a pile of extra hologram film for me to use in this video and i should say that the film they sell and will continue to sell is by far the easiest hologram making material i've come across and is quite cheap unfortunately they're discontinuing their kits but are actually working on something even more amazing instead which is a hologram printer the idea being that you can just give the printer a 3d file you want made into a hologram and it'll spit out a hologram just like how a regular printer works it's really a very cool idea and i hope one day i can show it off on the channel links to all of their stuff can be found below and fear not as long as they continue to sell the film you can make holograms using the method i'll show even without the kit okay back to making holograms like i said we're going to be making single beam holograms but we still need to decide on the precise setup we'll be using you see holograms can really be divided into two types reflection and transmission holograms and this has to do with where the light source needs to come from in order to see the finished hologram in a transmission hologram the image needs to be backlit with laser light in order to see the final hologram whereas reflection holograms can be lit and viewed from the front personally i prefer the latter but we'll be making both types so you can see the difference and once we're used to the fundamentals we can look at other colors and the rainbow holograms i showed at the beginning as well as other recording media and how they all work but let's start simple i'm going to be using the original kit set up exactly as it was intended and this means making a transmission hologram the kit comes with some beautifully laser-cut acrylic pieces that just snap together a red laser diode and battery pack this diode has no lens on it so the beam automatically spreads out into a nice vaguely rectangular beam that will cover both the object and the film plate the kit is divided into two parts the laser mount and then the object film holder there's a spot marked on the base plate of the film holder where you can place an object and a slot for the film when i was first planning this project before i reached out to liddy hollow i was under the impression that you need super high quality lasers and equipment for doing this so i picked up an old school helium neon laser tube and even made a video about making a magnetically levitated laser table which you saw me use for the interferometer but as you'll see none of that is actually required in the end all the lasers you're going to see me use were purchased for a few dollars on amazon and my kitchen table was more than sufficient i don't know if other hologram methods require better materials they almost definitely do but this is why i'm such a fan of the liddy hollow film it simplifies everything so much and is why i'm so happy they were willing to sponsor this video and send me some materials now since this is a photographic method this will all need to be done in the dark also unlike a regular photo as we saw with the interferometer holograms are quite sensitive to vibration so you need to set this up on as large and heavy of a table as possible and turn off any sources of vibration in the room for best results for me this meant turning off all of my fans unplugging my fridge and unplugging or turning off any lights in the room just to be extra safe i also did this late at night so my neighbors aren't banging around and there's less cars going by but you don't need any special laser table or anything fancy just some basic precautions first i'm going to turn on the laser and give it a few minutes to warm up and stabilize then i use a blank glass plate and a piece of white paper in the film slot to line up the beam you want the beam to completely cover both the plate and the object you're going to image making sure the object doesn't get in the way of the plate and make a shadow obviously this means your object should already be in place at this point the glass plate is then removed and a black piece of cardstock is used to block the beam then in the dark i'll remove a film plate from its protective bag place it into the film slot and then it's time to wait i'd highly recommend sitting comfortably for this bit as you're going to need to sit perfectly still and make sure there's no noise in the room for a couple of minutes this gives everything a chance to settle and all the vibrations to go away before the exposure then being very careful not to shake everything in one smooth motion the black card is picked up and the beam is allowed to strike the setup if you move slowly you can place the card on your lap so you're comfortable now again hold perfectly still and try not to make any noise or breathe on the setup the nice thing with this film is it's basically impossible to overexpose so the longer you can sit still the better your image will be but three to five minutes is usually enough to get a good image you can go up to 20 if you've got the patience of a monk but i can't sit still that long after the exposure is done place the card so it again blocks the beam then remove your object from the stage and lift the card again you don't need to be delicate about this bit the exposure is already over now you can just view your newly created hologram the best part of this film is there's no post-processing so the hologram is viewable immediately sort of like an old polaroid film in my case i now have a lovely view of a necron from warhammer 40k which i'd borrowed from a friend okay so that's a transmission hologram and i made a few of them but like i said it requires laser light from behind view which isn't ideal for display purposes so let's spin things around and make a reflection hologram the setup is basically the same but we spin the stage around so the object is now behind the film and the beam will hit the film first i find these much easier to set up as well and the angle of the object is nicer since you're looking at it head on rather than tilted to one side liddy hollow actually sent me their reflection kit which comes with an extra stand to mount the laser on but i found it easier to keep things the way they were and not bother with it and this will be important later when we make rainbow holograms as i'm not able to mount all the other lasers on the stand one note though is if you use the setup this way the final holograms need to be lit from a low angle because of how the plates are tipped and that was how i made most of my holograms a really easy fix to this if you want to light them from above is to just spin the base around and raise the object up a bit so it's still level with the base plate the actual recording process is exactly the same as last time first we kill the lights and any sources of noise or vibration and then we block the beam in the dark place a fresh film plate in the slot wait for vibrations to subside and then do the exposure just like before the result though is much different than the transmission holograms now no laser light is required to view them and a simple flashlight from the front allows the hologram to be seen clearly another quick note about lighting a hologram for display is that for best results you want a point source of light something like a light bulb or a flashlight rather than the long tubular lights i normally use for illuminating my work area if you try and use the long lights the hologram is often obscured this is why the holograms look nice if i'm recording with my phone or a little led flashlight but is basically impossible to see under the normal work lights okay before we talk about using different colored lasers or making the rainbow holograms i want to talk about the film i'm using you see there's actually many different recording media options to choose from i just happen to like this film because it's so much easier to use traditionally though making holograms normally takes a lot more work that's because most of the other options need to be treated like old school photographs where after the exposure they need to be developed and bleached in a dark room to reveal the hologram however each recording media also comes with various pros and cons and changes what the end hologram will look like and what it can be used for the film i'm using is a photopolymer so areas where the interference pattern make a spot brighter will react more than areas where it's darker in this case the bright areas polymerize which means that they chemically link together and get denser than the dark areas as the exposure proceeds the chemicals in the film get depleted so once the hologram is made there's no more reactants left so the dark areas can't polymerize and ruin the pattern this is why there's no developer needed with these materials there's no need to wash away unreacted areas to make the hologram be visible what makes this particular film great is that the chemical reaction isn't that picky about the color of light that's used it prefers red and reacts most strongly with that but can also work with green or blue just more slowly however the color used does change the exact nature of the reaction and make the hologram that gets recorded look like the same color that was used to make it so red lasers make red holograms green make green and blue make blue and if you use all three at once it'll look whitish if you balance things properly this is because the wavelength of each color is longer or shorter and the interference pattern will be larger or smaller accordingly a more classic material is silver halide suspended in gelatin these are exactly what a regular photograph uses it's tiny grains it's usually silver chloride that are only a few nanometers wide suspended in gelatin and then spread onto a glass plate when light hits the mixture known as an emulsion the silver salt actually sheds the chlorine atoms and turns into pure silver metal the development process will wash away any unreacted salts and permanently fix the silver metal in place the difference between this and a regular photograph though is the size of those silver grains is much much smaller so the interference pattern can be recorded in the pattern of the silver metal one benefit of this though is often the end result is a much brighter hologram and only the hologram itself is visible with no colored backdrop and finally there's photoresist this is very similar to the photopolymer in that it's a chemical that's spread on plates if you've ever made a circuit board from scratch you may have used photoresist before the idea is you shine a blue or uv light on it and areas that are struck by the light chemically react and polymerize whereas dark areas don't just like the photopolymer but unlike the photopolymer the final step uses a solvent to wash away any unreacted photoresist this method is special because unlike the silver halides or photopolymer instead of the pattern being recorded as darker or denser areas the hologram gets recorded as a physical pattern of bumps on the plate this is useful because you can make a physical cast of those bumps and then transfer that pattern to other things very easily if your cast is made of metal you can heat that metal up and press it into plastic to instantly transfer the hologram pattern to that plastic this allows rapid mass production of holograms very easily if you've ever seen these products with a rainbowy sheen or these bright rainbow patterns that's actually how they're made a metal hologram mold is created and then hot stamped onto plastic to make it holographic these types of holograms are known as embossed holograms ben over at applied science actually showed that the same thing can be done with chocolate and made chocolate holograms by using commercially made embossed holograms and transferring their pattern to some chocolate i've been working on the same thing for quite some time and i'll be making a video building on his method and showing some improvements i've been tinkering with soon but i wanted to make this video first so you understand how holograms work so i can focus on the mechanics of the embossing method in that video okay so now that we know how the film works let's make some rainbow holograms my first thought was to get three different lasers a red green and blue and just shine them from far away onto the film so they overlap and seem like they're all coming from the same direction the red laser is the one from liddy hollow but the green and blue ones came from amazon the blue was by far the trickiest to find since most blue lasers are actually violet and entirely useless for this what i ended up finding that worked was this blue laser star decoration thing it projects a pattern of dots on the ceiling when you plug it in but importantly it contains a proper blue laser so this was gutted to reveal the perfect blue laser you can see that when all three lasers are aimed at a white piece of paper the colors all mix and appear whitish themselves unfortunately my original plan of just aiming them all at the film didn't quite work you can see that the two lasers on either side are tilted at a slight angle and this slight angle gets recorded in the hologram so the final hologram it looks as if there's three separate objects one in each color that don't quite overlap if i put something in the path of the beam you can see this as three very distinct separate shadows so what i need to do is make it so that all the lasers come out in a straight line and go directly to the film but i can't just aim the lasers in the same direction or only one of them would actually hit it so i need to combine all three beams into one that can just be aimed at the film liddy hollow actually sells a kit to do this and their kit uses dichroic mirrors that each allow some colors to go through while reflecting others but getting those special mirrors can be annoying and expensive so i wanted a cheaper and easier solution i ended up picking up some of these beam splitter cubes which can be purchased on amazon for a few dollars these are neat because normally you can shine a white light through them and get three colors coming out the other sides so i simply did this in reverse i shine three colors in the sides and get white light out the front rather than any kind of delicate setup i just kind of piled things up that i had on hand and took some time to line up all the lasers and within a couple of minutes i had a nice white beam i could use for the exposures since the film is less sensitive to different colors to get the best results you either need to adjust the laser power of each beam so that they're all even or change how long you leave each exposure open for i can't change the power of these lasers so instead i would just unblock each color successively first i'd let the blue laser work for a couple of minutes then i'd add red and then finally i'd add green since my green laser is actually more powerful than the other two i took a bit of practice and experimenting to get the timing right but when everything is perfect you get beautiful rainbow holograms after i'd made a few of these and i'd gotten my timing down i wanted to see if using white light gives you any color information about the object you're capturing so i picked up a pack of smarties which are basically like canadian m ms and glued some to a piece of cardstock so they all sit flat relative to the film plate after the exposure you can see that some of them really do look their proper color which i think is amazing but for now that's where i'm going to leave it like i said we're going to be coming back to holograms in a future video because these are just too cool not to want to play with more and i want to see if i can transfer some of these homemade holograms to chocolate and use them as my go-to cake decorations so be sure to subscribe to see when that video is released as always i need to say a special thank you to my amazing patrons channel members and supporters on kofi that make these videos possible your support is the main thing that lets me make these videos and i am so grateful patrons and members also get access to the discord so if that's something you're interested in or just want to help keep the flow of science videos coming there's some links below if you enjoyed this video you know the drill hit that like button subscribe and ring the bell to see when i post new videos and to see these projects long before they make it into videos head over to my other social media pages like instagram i've been posting snapshots of this project for months on instagram and twitter so people that follow me there know what i'm working on that's all for now and i'll see you next time

Channel: The Thought Emporium

Views: 315,990

Rating: 4.9547458 out of 5

Keywords: laser, hologram, holography, photopolymer, beam splitter cube, laser beam, rainbow, full color, physics, double slit, interferometer, science, nobel prize, combiner cube, litiholo, silver halid, photoresist, light, interference pattern, wave particle duality, photons, wavelength, experiment, experiments

Id: aTB2ryoWIFU

Length: 24min 40sec (1480 seconds)

Published: Thu Nov 19 2020

Reddit Comments

[u/pkrprince]

this video enlightened me on how holograms works.

[u/ch00f]

Thank god. A hologram post that isn’t just Pepper’s Ghost and an iPad.

[u/ch00f]

Could you actually align the beam splitter well enough to see complete darkness? Where would the laser energy end up in that scenario?

[u/TheBardKing]

Hey thanks for this, I'm gonna try sometime

[u/Supermonkeyjam]

Pretty common when I was a kid. You’d get them free in some cornflake boxes

[u/Slim_Lim_Boi]

I got a free silver award so ima put it on this i guess idfk here

[u/Abject_Entrepreneur1]

Didn’t Hillary use one in SC in 2016 when she wasn’t actually there?🤔

[u/esPhys]

I think the best way to think about this is sort of like waves of water. Even though water is made of individual molecules you cans still make waves with it

PICKS UP PHYSICS PITCHFORK

It's definitely not a perfect analogy, light is way weirder than that

Puts down physics pitchfork

[u/Suprcow_one]

Play 24 holograms per second, profit!