- This is a hologram that I made by hand.
This is also a handmade hologram,
but as you can see, it was made by someone
who actually knows what they're doing.
Both holograms were made using the same technique,
and this one and this one,
the technique is deceptively simple.
You just make scratches in a shiny surface.
I made my holograms
on sheets of black acrylic using a divider,
basically a compass where both ends are pointy.
These aren't like traditional holograms like this one,
but these types of holograms you get on credit cards
are the same as these handmade ones.
It's just that the etching is much smaller.
One thing that's hard to appreciate
on video is that this thing is 3D.
It appears to hover below the acrylic plate.
I can give you a sense of that by tilting the thing
in front of the camera or moving the camera side to side,
but to really appreciate it.
Here's a cross view stereogram.
If you're able to go cross eyed until the two images overlap
with each other, it should pop out as a 3D image.
You know, while we're doing the crossview stereogram thing
why don't I show you this traditional hologram as well?
It's pretty cool, isn't it?
And here are those other etch holograms.
To show you how etch holograms work and how to make them.
We'll start with a really simple
just a floating point of light
and then we'll work up to something as complex as this.
To create a floating point of light
all you have to do is gently score an arc
into the acrylic sheet.
Now, if I put the camera here and a light source here
then you can see that the light glint off the etched line.
But what decides the position of the glint?
Because look, as the camera moves, the glint moves as well.
Well, the simplest way to think
about it is that the etched groove is
like a curved trough shaped mirror.
I was gonna try and figure out how to build a large one
of those so that you could see what was going on.
But actually it pretty much acts the same
as a shiny tube like this one.
And this has the added benefit
of being able to change how bent it is.
See when the tube is straight, the glint is always directly
in front of the light source, wherever I put the camera.
But when the tube is curved
the glint doesn't travel as far
and the same thing happens with the etch on the arc.
And that's really the key to the whole thing
because your left eye sees this image
and your right eye sees this image.
And if your brain makes the assumption
that the glint is in fact an object
then your eyes will move so as to converge on that object.
Just like how if you hold your finger in front of your face
you'll see two fingers until your eyes move inwards
they converge on your finger.
Then you see one finger and two backgrounds
and the same thing is happening
with the glint except in the opposite direction.
Your eyes have to move apart to get the glint to overlap.
And of course, your brain uses the position
of your eyes to figure out how far away objects are.
So if your eyes have to move apart
to bring the two glints together
then that tells your brain the glint is further away
than the surface of the acrylic.
The opposite happens
when you turn the arc upside down actually
and the glint appears to be hovering above the acrylic.
If you want to make a more complex object
then you simply draw out your shape and then create lots
and lots of points around your drawing,
creating an etch for each point.
You'll notice that the image is distorted
compared to the original.
And the distortion of the image actually depends
on the location of the light source and the camera.
From what I can tell,
if it was possible to have the light source exactly parallel
with the mirror, you might get a proper rendition
of the image, but at that angle
you get basically no glint at all.
So there's a trade off, and if I was gonna do this properly
I would pre warp the image in the opposite direction
so that when the image became warped
by the viewing experience,
it would undo the pre-applied warp
and the image would look normal.
This is all well and good, but you might be thinking,
"Hold on a second, this thing is flat."
Yes, it's floating below the acrylic,
but it's all at the same depth
and the drawing itself is two dimensional.
So how can we make this hologram more interesting
by creating lines at different depths
and maybe even lines that plunge in and out of the acrylic?
Well, one clue is to be found in accidental etch holograms
that you may have witnessed in your own life
like when you've run out of wiper fluid
but you use the windscreen wiper anyway,
the top of that bright line appears to be further away
than the bottom of the bright line.
Similarly, if a metal surface has been worked
in a circular motion like this source panel
then you'll have a glint line
that appears to be touching the metal surface
at the center of the circular work pattern
and move away as the light glint moves outwards.
And that's because, well, it turns out
that the tighter the arc,
the closer the glint appears to be,
and the straighter the arc, the further away
the glint appears to be.
And that makes sense because
if the arc was perfectly straight at one extreme
well that's analogous
to the straight tube that I was holding
in front of the lights.
And in that situation
the glint is always directly in front of the light source.
So when your eyes move to line
up the glint in that scenario, they will converge
at the same depth as the light source itself.
And then at the opposite end,
if the arc was so tight that it was basically just a dot,
well the glint wouldn't move at all relative
to the surface of the acrylic.
So it should appear to be at the surface of the acrylic.
And so curvatures in between those two extremes
will give you depths in between.
Here, for example
I've created a tilted square where the top edge
of the square is further away.
So the top edge is created with straighter arcs.
The sides of the square were much trickier
because each point along the line was at a different depth.
So I had to adjust the divider
and change the position of the pivot point
as I went down the line.
By specifying where the arcs start and stop.
You can have objects that appear and disappear, depending
on the viewing angle, and if you get it just right,
that means you can create opaque objects with other objects
behind that you can only see by looking around the corner.
Because the opaque square in this hologram is quite close
to the surface of the acrylic.
In other words, I was using quite short arcs.
You can actually see the pivot points that I used
for the divider,
because it's created all these little dots in the surface
and there are various techniques you can use to prevent that
from happening, but it makes the whole process a lot slower.
The final thing I wanted to try was a hologram
of the corner of a cube sticking out.
This is a lot harder,
because all the lines are changing death along their length
and it was really mind bending to try
and work out pivot position
and divider adjustment for every single point.
I also wanted to see if I could have the actual tip
of the cube poking out from the surface of the acrylic,
which meant having some arcs that were upside down.
In the end, I made a bunch
of mistakes and it was so hard to get
to this point that I just rage quit
on this particular hologram.
So this is as much as you get of this one.
This is actually my attempt to copy William J Beaty.
He discovered the divider method independently.
Though he does mention
that he found some prior literature on this subject.
Actually, he has some great advice
on things like etching technique and stuff like that.
I'll leave a link to his website.
Actually, his YouTube channel is brilliant too.
There's a link to that in the description as well.
But anyway, as you can see, I got part of the way there.
The bits that stick out from the acrylic behave weirdly
and the glints are quite long.
I think that's an artifact of the arcs being upside down.
I thought it would be really cool to have a way
for people to be able to share their own creations
like if you end up making your own etch hologram.
So on my Discord server,
I've created a channel specifically for that.
I've called it Science Fair Project.
So if you do end up making an edge hologram
do hop over to my Discord server.
The link is in the description.
Now here's the question.
How do you get from this to this?
Well, this one was created by Matthew Brand.
He really helped me to understand what's going on,
linked to all his stuff in the description.
Some of his creations are for sale, in fact.
So one issue you may have realized with these holograms
that you don't get with this hologram,
is the image warps and bends
in weird ways as you change your viewing angle.
Matthew explained that that's
because actually an arc is the wrong shape.
In fact, most people creating etch holograms
aren't using the right shape.
They're all approximations to the correct curve.
Matthew figured out what that curve should be.
I won't go into the equations or anything like that
but look, he kindly sent me this animation
of how you might create the correct curve.
So it's possible to do it mechanically
with the right linkages.
But actually what Matthew did was create a CNC process.
So he defines the 3D shape that he wants in software,
and then his code converts
that into the appropriate etching.
The etching is then carried out by the computer.
It's really interesting
to just look at the etches themselves
because there would be no way of knowing
just looking at this mess here, that this would pop out
into a 3D shape with an appropriate light source.
This is a depiction of Borromean rings, by the way.
So here's a quick tangent about that,
because they're really cool.
It's possible to link three closed loops together
in such a way that no two loops are linked together
meaning if you break any one of the three loops
the other two come apart, and that's Borromean rings.
What about those vinyl records?
Well, earlier I said that the arc
of a circle is not the right shape
for the etch because it causes warping and distortion,
except under very specific circumstances where the arc
of a circle is the right shape for the edge line.
And that specific circumstance is when the etch goes
in a full circle
and the image rotates once for every rotation of the circle.
And that fact has been used beautifully
in these commemorative Star Wars vinyl records.
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