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Gabor, Dennis

waves phase coherent object

(1900–79) Hungarian–British physicist: invented holography.

The son of a businessman, Gabor studied electrical engineering in Budapest and Berlin. He worked as a research engineer with the firm of Siemens and Halske but in 1933 he had to flee from the Nazis and spent the rest of his life in Britain. He was initially with the British Thomson–Houston Co at Rugby and from 1948 at Imperial College, London.

In 1947–8 Gabor conceived the idea of using the phase (or position in the wave’s cycle) as well as the intensity of received waves to build up a fuller image of the object in an electron microscope. In this way he hoped to extract better electron images so that atoms in a solid might be resolved, but soon he developed the method for use in an optical microscope also. The phase of the electron or light waves was obtained by mixing them with coherent waves directly from the wave source, and the waves then form a standing wave that is larger or smaller according to whether the two are in phase or out of phase. This interference pattern is recorded on a photographic plate. The waves from different parts of the object travel a varying number of wavelengths to the plate, and so the interference pattern and phase of the waves give information on the three-dimensional shape of the object.

When the plate (hologram, from the Greek holos , whole) is placed in a beam of coherent waves, a three-dimensional image of the object is seen and as the observer moves a different perspective appears. (A coherent wave is one in which the wave train consists of waves exactly in phase, not several waves with different phases and intensities.) For light Gabor achieved this crudely, using a pinhole in a screen in front of a mercury lamp. In 1960 lasers were invented and these powerful coherent sources allowed high quality holograms to be made by E Leith and J Upatnieks (1961). Gabor was awarded a Nobel Prize in 1971.

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