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Reducing Noise in Holograms

IP.com Disclosure Number: IPCOM000093858D
Original Publication Date: 1966-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Nassimbene, EG: AUTHOR [+2]

Abstract

This method improves a hologram by removing the noise factor due to cross-polarization. In making holograms, a reference beam 10, usually from a laser, is directed to interfere with diffused, nonpolarized light 12 from object 13. The result is captured upon film 14. An image of the original object can be seen by looking through the film to a virtual image. The latter is formed behind the film plane by wavefront reconstruction. If the hologram is dark, it is difficult to see the image behind it. That is, it is as though an object were viewed through a grey filter. The darker the filter the more difficult it is to see the object through it.

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Reducing Noise in Holograms

This method improves a hologram by removing the noise factor due to cross- polarization. In making holograms, a reference beam 10, usually from a laser, is directed to interfere with diffused, nonpolarized light 12 from object 13. The result is captured upon film 14. An image of the original object can be seen by looking through the film to a virtual image. The latter is formed behind the film plane by wavefront reconstruction. If the hologram is dark, it is difficult to see the image behind it. That is, it is as though an object were viewed through a grey filter. The darker the filter the more difficult it is to see the object through it.

If beam 10 is produced by a gas laser using Brewster angle windows, it is polarized. However, the light which strikes film 14 from object 13 is scattered and depolarized. When polarized light is used to cause interference patterns, only light polarized in the same plane causes interference with beam 10. Light perpendicularly polarized does not. The only part of the light from object 13 which produces information is that component of beam 12 which is polarized in the same direction as beam 10. The remaining cross-polarized light does not add information. It does, however, expose film 14 thus introducing noise.

Polarizing plate 16, oriented in the same plane as beam 10, is placed over film 14. Beam 10 goes through plate 16 and light reflected from object 13 which is properly oriented passes through, bu...