The technique of holography can also be used to optically store, retrieve, and process information. While holography is commonly used to display static 3-D pictures, it is not yet possible to generate arbitrary scenes by a holographic volumetric display.

Overview

The first holograms that recorded 3D objects were made in 1962 by Yuri Denisyuk in the Soviet Union and by Emmett Leith and Juris Upatnieks at University of Michigan, USA. Advances in photochemical processing techniques to produce high-quality display holograms were achieved by Nicholas J. Phillips.

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 that 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.

Reflection Hologram Metaphor:

Consider a tennis ball cannon and a wall with unknown characteristics. If you fire the cannon at the wall, you can obtain information about the wall based on how the tennis ball is fired and how the tennis ball bounces off the wall. Essentially, this is what a hologram does with a light beam and an object.

Instead of a tennis ball cannon, holograms use lasers. In order to record information about how the light bounces of the object, a hologram uses a photographic glass plate. The beauty of holography is that the information about how the light bounces off the object, and how the light is ‘fired' at the object gets recorded on the same plate.