Holography

You've seen it on movies, I'm sure. But just to clarify a few points.... Holograms are 3D images of real objects. 3D means that you are able to see different sides of an object when you tilt/rotate/pan your head around.

This is in contrast to normal photographs, where you see the same thing no matter how the hell you look at it.

To the right is a hologram I recently made in my 'lab'. By the way, this is of course a photo of a hologram, which means that what you see there is NOT 3D. To see the real hologram, well you just need to have the hologram I suppose.

So how do holograms work, and what are the concepts?

I found an awesome explanation from Wikipedia that I cannot match, so I'll hand you over to Wiki:

"The light which makes up a real scene is not only specified by its amplitude and wavelength, but also by its phase. In a photograph, the phase of the light from the original scene is lost. In a hologram, both the amplitude and the phase of the light (usually at one particular wavelength) are recorded....

Image courtesy of Wikipedia org

Image courtesy of Wikipedia org

Once the film is processed, if illuminated once again with the reference beam, diffraction from the fringe pattern on the film reconstructs the original object beam in both intensity and phase (except for rainbow holograms where the depth information is encoded entirely in the zoneplate angle). Because both the phase and intensity are reproduced, the image appears three-dimensional; the viewer can move her viewpoint and see the image rotate exactly as the original object would." (Wikipedia org. 2006)

So! I hope you understood all that. A laser, by the way, is used for holography, due to its coherent and monochromatic (single frequency) output.

For the creation of my holograms, the green DPSS laser was used. A specialized room was set up with room for exposure and development. Usually holography is carried out on an optical table, which has special vibration reduction systems, since vibrations of as little as a few micrometers (that means air currents, footsteps, loud music, temperature changes) can completely wreck a hologram.

Luckily though, the floor is concrete and the room can be completely sealed from the house environment. Vibrations were also tested for using a Michelson Interferometer setup (bottom right). This involves splitting the laser beam using a prism onto mirrors, then recombining these beams and spreading the beam with a diverging lens, so that minute interference patterns are visible (top right).

Preparing the chemical solutions....

I use the following solutions for development of the holographic film:

Developer:

Bleach:

Holographic film was supplied by Integraf. I used VRP-M film, which is sensitive to green light.

I needed a holder to securely clamp the film during exposure. This was made using two sheets of glass, some super glue, some binder peg things, and 5 minutes of work.

Inspecting a newly made hologram (my thumbnail is NOT usually that dirty... that is the result of contact with the bleaching solution... not pleasant).

A typical exposure of mine involves the following processes:

So, lets see some results... I am still only starting to get reasonably adept with the basic skills, so spare me please.

To the right is a (single beam transmission) hologram of a glass angel figurine, borrowed from Aidan.

Here is a reflection hologram made quite recently. Pretty self explanatory, bunch of coins. Didn't turn out perfect, presumably due to vibration problems.

Reflection holograms are exposed in a slightly different way to transmission holograms (all those above). They are, however, slightly more prone to vibrations, and do not offer much depth of field. An advantage of reflections holos is that you don't need to bring a laser along to view them, all that's needed is a bright source of white light (eg. halogen lamp, or normal incandescent).