HOLOGRAPHY

There are many different ways to create photos. Some of these ways include digital, flash, polaroid and even painting. One of the most interesting ways though is by using holograms...or holography. By definition, holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that it appears as if the object is in the same position relative to the recording medium as it was when recorded. So, in easier terms...basically it's the process of making a picture, but the result is 3D! Pretty sweet, right?

Holography was invented in 1947 by Hungarian physicist Dennis Gabon for which he received the Nobel Prize in physics in 1971. The discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston Company in Rugby, England. This was a huge step in the world and works of physics in the early centuries because this opened up a whole world of new possibilities.

Several types of holograms can be made. Transmission holograms, such as those produced by Leith and Upatnieks, are viewed by shining laser light through them and looking at the reconstructed image from the side of the hologram opposite the source. A later refinement, the "rainbow transmission" hologram allows more convenient illumination by white light rather than by lasers or other monochromatic sources. Rainbow holograms are commonly seen today on credit cards as a security feature and on product packaging. These versions of the rainbow transmission hologram are commonly formed as surface relief patterns in a plastic film, and they incorporate a reflective aluminium coating which provides the light from "behind" to reconstruct their imagery. Another kind of common hologram, the reflection or Denisyuk hologram, is capable of multicolour image reproduction using a white light illumination source on the same side of the hologram as the viewer.

One of the most promising recent advances in the short history of holography has been the mass production of low-cost solid-state lasers—typically used by the millions in DVD recorders and other applications, but which are sometimes also useful for holography. These cheap, compact, solid-state lasers can under some circumstances compete well with the large, expensive gas lasers previously required to make holograms, and are already helping to make holography much more accessible to low-budget researchers, artists, and dedicated hobbyists.

Though holography is often referred to as 3D photography, this is a misconception. A better analogy is sound recording where the sound field is encoded in such a way that it can later be reproduced. In holography, some of the light scattered from an object or a set of objects falls on the recording medium. A second light beam, known as the reference beam, also illuminates the recording medium, so that interference occurs between the the two beams. The resulting light field is an apparently random pattern of varying intensity which is the hologram. It can be shown that if the hologram is illuminated by the original reference beam, a light field is diffracted by the reference beam which is identical to the light field which was scattered by the object or objects. Thus, someone looking into the hologram 'sees' the objects even though they may no longer be present. There are a variety of recording materials which can be used, including photographic film - these are listed below.

These three images of the same hologram were taken by positioning the camera at three positions, moving from left to right. Note that the pawn appears on the left side of the king in the left photo, but transitions to the right of the king as you sweep your eye across the hologram. This is real parallax, which tells you that the image is truly 3-dimensional. Each perspective corresponds to looking through the hologram at a particular point.

Holograms are extremely interesting and fun to work with. Perhaps in the future, holograms will be used for advertisements and even in everyday life. Maybe instead of having pictures hanging on the wall, we will have holograms sitting around! You never know!!