
Drawing Holograms by Hand (2003) - dcminter
http://amasci.com/amateur/hand1.html
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wbeaty
Scratch holograms may have led to the invention of stereo photography.

Someone recently found that Charles Wheatstone wrote about this phenomenon
first, after noticing it in lathe-turned flat surfaces. Wheatstone looked at
it a bit, then taking inspiration from the obvious 3D images, went on to
invent stereo drawings, photography, and the stereopticon.

But, Wheatstone never got it. He never realized that we can make our own
scratches, and therefore draw any 3D object. "Steampunk holography" remained
lost for about 150 years.

"It is curious, than an effect like this, which must have been seen thousands
of times, should never have attracted sufficient attention to have been made
the subject of [scientific] observation. It was one of the earliest facts
which drew my attention to the subject I am now treating." From Wheatstone,
Philosophical Transactions of the Royal Society, 128, (June 1838) "On some
remarkable, and hitherto unobserved, Phenomena of Binocular Vision" p371-

The same thing happened again in 1992. Two scientists at Polaroid corp.
accidentally made some scratch-patterns producing flat images floating in 3D.
They analyzed the scratch geometry. But they missed the secret trick, and
never attempted drawing their "holograms" using individual scratches. doi:
10.1364/AO.31.006585

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femto
I love this article. My first reaction is "no way!", but when you think about
it it's obvious that it must be so.

The hologram of a single point of light is a "zone plate": concentric rings.
Move a sharp point in concentric circles on a surface and the scratches will
form a zone plate which focuses light to a point. An abrading object is just
an array of sharp points, so the scratches formed by moving the object in
concentric circles will focus light to an array of points, corresponding to
the shape of the object: an image of the object. Simple! (but not initially
obvious.)

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dTal
Sorry to burst your balloon, but this has nothing to do with zone plates, or
even "holography" in the strict sense; no wave interference is taking place.
The mechanism is purely geometric: a gleaming scintillation of reflected light
in a scratch from a point source will exhibit apparent parallax if the scratch
is horizontal and curved. The greater the curvature, the less the
scintillation moves, and the less the apparent parallax.

~~~
wbeaty
...and that's how we prove that white-light holograms aren't holograms.
(Credit-card holograms function just like scratch-holograms, and their 3D
image is not created via diffraction.)

[Are these REALLY
holograms?]([http://amasci.com/amateur/holo3.html](http://amasci.com/amateur/holo3.html))

~~~
dTal
Interesting. I never quite grokked rainbow holograms, so perhaps there's
something in that.

But it's unfair to say all white-light holograms aren't holograms. A normal
Denisyuk reflection hologram made with lasers and everything will replay
perfectly well under a halogen lamp.

~~~
wbeaty
> I never quite grokked rainbow holograms,

If you made a scratch hologram, but your compass-point had a small cluster of
fifty tiny needles instead of a single big needle, that comes close to the
fringe-structure of Benton white-light holograms.

:)

> But it's unfair to say all white-light holograms aren't holograms

True. By "white light" I was referring to Rainbow / credit-card / Benton
holograms.

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jcl
It might be better to use the "Scratch Holograms" link at the top of that
paper, as it has better exposition and a video. :)

[http://amasci.com/amateur/holo1.html](http://amasci.com/amateur/holo1.html)

~~~
wbeaty
Latest trick: LP albums, rotating scratch-hologram animations:

[https://www.youtube.com/watch?v=DLuvkcV2oi4&t=0m26s](https://www.youtube.com/watch?v=DLuvkcV2oi4&t=0m26s)

[https://www.youtube.com/watch?v=jqNF9IWmFQE&list=PL60100E8F3...](https://www.youtube.com/watch?v=jqNF9IWmFQE&list=PL60100E8F3572CEB1&index=11)

[https://www.youtube.com/watch?v=H9gRPtkSOn0](https://www.youtube.com/watch?v=H9gRPtkSOn0)

Also gallery artists:

[https://www.youtube.com/watch?v=dQ_sjQRYhX4](https://www.youtube.com/watch?v=dQ_sjQRYhX4)

[https://www.youtube.com/watch?v=G36kP8g6SrI](https://www.youtube.com/watch?v=G36kP8g6SrI)

[https://www.youtube.com/watch?v=reM6XhbkQXM](https://www.youtube.com/watch?v=reM6XhbkQXM)

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pfedak
The Museum of Math in NYC has a wall with several intricate examples.

[http://momath.org/wp-content/gallery/main-
gallery/img_2757.j...](http://momath.org/wp-content/gallery/main-
gallery/img_2757.jpg)

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scentoni
I've played with this a bit, it was fun.

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VMG
The lazy nerd in me wonders if he can abuse sth like a dot-matrix printer to
automate this.

~~~
captainmuon
This is actually something I did as a university project. We calculated
computer generated holograms (CGH). To print them out, we found a ultra-high-
DPI fotographic slide printer and got special small-grain film to print on.
Then we printed the holograms, shone coherent light through the slides, and...
nothing. I think we never found out why it didn't work, probably the contrast
was not high enough. However, as a last effort, we used a simple 600dpi inkjet
printer on overhead slides, and it actually worked! It seems there is actually
enough information in the low-frequency part of the hologram to reconstruct an
image.

A couple of things we printed were simple geometric objects, 3d models of
ants, and the USS enterprise :-). It was pretty cool, unfortunately I don't
have the material any more.

One thing I'm wondering is why nobody is trying to create a 3D holographic
display (the Microsoft HoloLens isn't holographic AFAIK). TFT displays are
getting in the dpi range where it should be possible. You could easily render
the holograms with modern GPUs. (We actually investigated this back then
(~2005) and it was then possible by abusing textures and doing things like
putting two complex numbers in one ARGB texture. However we did not have more
time for the project, and there was no benefit over just running on our
cluser. This was before shaders, so it should be even easier now.)

~~~
VMG
The inkjet method sounds like it has reasonable cost. Maybe there is a way to
use a laser printer. Thanks!

~~~
wbeaty
Back in the old "Circuit Cellar" magazine era, they made a printer-hologram by
photographing it onto film transparency.

I recall that it was a "binary hologram" 300dpi covering a full 11" page, then
reduced to a few-mms-wide patch on monochrome slide film. Obviously the main
challenge would be in getting the darned thing in focus, so the fine pattern
doesn't blur out into gray.

Then, print out a feet-wide paper copy, so the pattern ends up as a few-cm
hologram on your slide film.

