FAQs
What are holograms?
Holography is the recording of the phase and amplitude of the light waves that bounce off an object. Holograms are made using laser light and optical components in a special type of camera. The camera is nothing like a normal camera but a table made to hold the laser, mirrors and lenses which make the hologram. The process is complicated and takes many years to master. That said, there are some basic points about making holograms, that give some idea of the process. The following is a very simplified description of the process and is not meant to be a 'how to'.
Holography was invented in 1947 by Hungarian physicist Dennis Gabor (Hungarian name: G·bor DÈnes) (1900 -1979), work for which he received the Nobel Prize in Physics in 1971. It was made possible by pioneering work in the field of physics by other scientists like Mieczys Baw Wolfke who resolved technical issues that previously made advancements impossible. The discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston Company in Rugby, England. The British Thomson-Houston company filed a patent in December 1947 (patent GB685286), but the field did not really advance until the development of the laser in 1960.
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.
