Holography

History of Holography

Dennis Gábor (1900–1979), a physicist born in Hungary, received the Nobel Prize in Physics in 1971 for his work on holography. Gábor was limited by the light sources available at the time, which consisted of mercury arc lamps that lacked the coherence necessary to produce high-quality holograms. Holography was given a significant boost by the development of the laser in the 1960s, which was the enabling technology to allow high-quality, three-dimensional holograms to be made. Significant advances in the field of holography were made by Yuri Denisyuk in the Soviet Union (who developed a technique for making reflection holograms) and by Emmett Leith and Juris Upatnieks in the United States (who worked on a technique for making transmission holograms); all created three-dimensional holograms that are similar to those we are familiar with today.

How Holography Works

In a conventional photograph, the film medium or digital sensor captures a focused image, recording for each point a value for the intensity of the light—and in color photography, its color. This results in a static, two-dimensional image. By contrast, in holography, the image that is formed on the plate is an unfocused image. The thing that differentiates this unfocused image is that it is recorded using coherent monochromatic light such as that produced from a laser. First, a reference beam is shone on the plate, which creates a pattern according to the phase of the light at any one point. Then a second beam, known as the object beam, is reflected off the object to be recorded, again onto the plate. As the light is monochromatic, interference occurs between the two light beams. This interference is recorded on a very finely grained photographic emulsion as patterns of light and dark. The plate is then processed to fix the image. To reconstruct the hologram, a light source is used to re-create the reference beam, and light is diffracted from the reference beam in a manner that reconstructs the light field originally created by the objects—thus, the user can see a representation of the original image in three dimensions.

Use in Science Communication

Holograms provide a very visual way for science communicators to advance concepts where three-dimensional representations are especially important; in addition, the technology presents an exciting vehicle for communicating a range of physics concepts. Holography also has the potential to be used in science communication to present a three-dimensional visualization of a three-dimensional object, where the original object is not available for exhibition. The Soviet Union made particularly effective use of holography in cataloguing and preserving its treasures and artifacts as three-dimensional holograms. A particularly notable exhibition of these took place in 1985, titled “Holography, Treasures of the USSR.” Holograms are particularly suitable for static displays in museums and science centers where users can view holograms at their leisure; however, careful attention should be paid to illuminating the hologram so that it is presented at optimum quality to viewers. This will depend on the technique used to produce the original hologram. For lectures or larger audiences, small holograms may present a challenge to display—small copies can be passed around for inspection. Larger holograms that could be viewed by a whole audience are likely to be prohibitively expensive. Fortunately, a range of other technologies is available that can potentially be used, as described below.

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