Gabor , Dennis

(1900–1979) Hungarian–British physicist

Gabor, the son of a businessman, was born in the Hungarian capital of Budapest; he was educated at the technological university there and in Berlin, where he obtained a doctorate in engineering in 1927. He worked initially as a research engineer for Siemens and Halske from 1927 until 1933 when, with the rise of Hitler, he decided to leave Germany and took a post with the British Thomson–Houston Company, Rugby. In 1948 he joined the staff of Imperial College, London, later serving as professor of applied electron physics from 1958 until his retirement in 1967.

Gabor is credited with the invention of the technique of holography – a method of photographically recording and reproducing three-dimensional images. The modern technique uses lasers to form such images, but the invention came out of work by Gabor on improving the resolution of the electron microscope – work done in 1948, twelve years before the introduction of the laser.

The electron microscope has theoretically much higher resolution than the optical microscope because of the shorter wavelength of electrons (resolution is limited by diffraction effects). One method of improving the resolution of the electron microscope is to improve the electron lenses used to deflect and focus the beam of electrons. Gabor was interested in increasing the resolution to the point at which atoms in a lattice could be ‘seen’. Rather than work on the electron optics of the system he had the idea of extracting more information from the electron micrographs produced by existing instruments, and to do this he proposed forming a diffraction pattern between the incident beam of electrons and a background beam that was coherent with it (i.e., one with the same wavelength and phase). The principle was that the image produced would have information on the phase of the electrons as well as the intensity and that it would be possible to reconstruct a true image from the resulting electron micrograph.

Gabor began experiments with light to investigate the technique (which he named holography from the Greek holos meaning whole – the record contained the whole information about the specimen). He used a mercury lamp and pinhole to form the first, imperfect, holograms. Subsequently, in 1961, E. Leith and J. Upatnieks produced holograms using laser light. The technique is to illuminate a specimen with light from a laser and form an interference pattern between light reflected from the specimen and direct light from the source, the pattern being recorded on a photographic plate. If the photographic record is then illuminated with the laser light, a three-dimensional image of the specimen is generated.

Gabor received the Nobel Prize for physics for his work in 1971.