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Physical principles

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The recording procedure of reflective volumetric holograms is another. The idea of making of such holograms belongs to Uri N. Denisyuk.Reflection hologram recording Therefore holograms of this type are known under the name of their founder.

The reference and object light beams are formed with the help of a semi-transparent mirror and directed by a mirror on a plate from two opposite sides. The object wave shines a photographic plate on the part of an emulsion layer, reference wave - on the part of a glass substrate. The Bragg's planes in such requirements of recording scheme almost parallel planes of a photoplate. Thus, the thickness of a photolayer may be rather small.

On the recording scheme the object wave is formed from the transmission hologram. I.e. in the beginning usual transmission holograms are made by the technology, described above, and then make in a copying mode the Denisyuk's holograms from these holograms (which are termed the master holograms) .

The basic property of the reflective holograms is an opportunity of reconstruction of the image with the help of a source of white light, for example, incandescent bulb or the Sun. The important property is the colour selectivity of such hologram. It means, that at the image reconstruction by a white light, it will be restored in colour, that was used during hologram recording. For example, if ruby laser (red light) was used for recording procedure, the restored image of the object will be red.

According to property of colour selectivity it is possible to manufacture colour hologram of the object, exactly reproducing its natural colour. For this purpose it is necessary to mix three colours at the hologram recording: red, green and blue or to shine consistently a photoplate by these colours. But, technology of the colour holograms manufacturing is in an experimental stage and some more efforts and experiments will be required. It is remarkable, that a lot of people, visitors of exhibitions of the holograms, usually say, that they can see the colour volumetric images!

Additional information about physical principles of holography you can read in articles of our "Technology" and "Files" sections.