Holography Panel

As seen on Hackaday!

Bring to the con some interesting object about the size of your fist, and we'll try to make a hologram of it.

There are of course some limits to the process... the image will be life-size and the film is 4x5 inches, hence the "about the size of your fist" thing. Also, nothing can move more than 1/10 of a wavelength. And finally, the whole process must be done in a darkroom; stray light will fog the film.

I set up this panel to take to HOPE, the Hackers on Planet Earth conference. Then I did it again at FA:United, and FurtheMore and it went over pretty well.

Be sure to check the con schedule for the actual time and location, as it is subject to change.

Try not to shed, and no nose-prints on the optics.

The Darkroom

We're going to close the doors, turn off and/or cover up the lights, and string a bunch of festive red holiday safelights around the room. Visibility will be poor; I would not recommend this panel for fursuiters or young children. Please be careful with light sources (don't turn on mobile devices) as that will fog the film (it's expensive).

There will also be chemistry... this is good old-fashioned silver-halide wet photo-chemistry. The process looks like processing black and white prints. The chemistry will be in a series of open trays with tongs. Put the film in the first one, then move it to the next when the time is up. It's not especially toxic, but don't drink it, and wash it off ASAP if you get it on you. The bigger hazard is that it will stain when you least expect it (for example, the front of the only pair of pants I had when I was at HOPE). The developer looks like water, but after a few hours, it turns purple.

And finally, there will be a laser, controlled by a Tandy 200 laptop. That was THE machine to have in 1985.

What makes a good subject

The biggest challenge of holography is that nothing can move more than 1/10 of a wavelength during the exposure. The wavelength of my laser is 532 nanometers, so one gets 53 nanometers. It's Really Easy to move 53 nanometers. In a 1 second exposure, plants grow too fast. One can bend 1.5 inch bars of aluminum hundreds of nanometers by blowing at them.

The more reflective the object, the brighter the image. But not too reflective; you don't want it mirror-like. Specular reflections will make extra reference beams, forming extra images.

So, the best subject is solid, like a rock, and matte reflective. Things like dice, skulls (bones in general), chess pieces, and shells work well. Which is why there are so many holograms of those objects, to the point that it's a joke among holographers. The traditional test object is a porcelain cat. (seriously... see "Practical Holography" by Graham Saxby.)

I have had good luck with a particular stuffed hamster; at least at home, where I have very few air currents. I also have a shell which works very well.

Fleece or short-pile fur is okay - look at the hamster in the examples. Wispy or long-pile fur won't work - the lion more or less lost his mane.

The worst object is a fake flower. The thin petals move too easily in air currents.


The tarantula was done at FA United; the rest of the examples were done during the dress rehearsal.

The Handouts

Read through outline.pdf before the panel... We'll go through everything there too, but familiarity will make everything run smoothly.

~ Protius