Denis Gabor made the first hologram while working on electron microscopes in England in the late 1940s. He used a mercury arc lamp and produced a hologram of a small transparency containing the names of famous scientists. His main problem was the lack of a coherent light source.
The invention of the laser in the 1960s gave holography the coherent light source needed to give the size, brightness and depth of image which have intrigued and delighted viewers ever since. At first lasers were only available in universities and research laboratories, but now they are much cheaper, making them available to individuals. Further development introduced pulsed lasers which give a very powerful flash of only a few nanoseconds, enabling holograms to be made of living subjects.
Yuri Denisyuk, a Russian, devised an elegant method of using a single beam to act as both reference and object beam. Placing the film between the laser and the object allows the beam to pass through the film and be reflected off the object, so that the reference beam impinges on the film from one side, and the object beam from the other.
Transmission holograms illuminated by white light give a "rainbow smear" effect. In 1968 Stephen Benton discovered a way of eliminating this effect. He made a transfer hologram masking off the master hologram through a narrow horizontal slit; when the second hologram is flipped, the image of the slit appears in front of the hologram close to the viewpoint, and only light of one colour is seen. This gives rise to the "rainbow" effect; as the viewpoint is moved vertically, the colour of the hologram changes.
The invention of an embossing technique meant that holograms could be mass-produced for use as security devices and to enhance magazine covers.