Spatial light modulator device and a conoscopic holography system of large dynamic range including such a modulator device
AssigneeFrance Telecom
InventorsAharon Agranat, Gabriel Sirat
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Abstract
The invention relates to a spatial light modulator device comprising a photo-refractive crystal addressed by means of a write light beam and a read light beam. The crystal is placed in the cavity of an interferometer system having a transmittivity-optical path length characteristic of steep slope so as to give rise to a dynamic range of maximum transmittivity variation for minimum variation in the refractive index or optical path length of the photo-refractive crystal. The device is applicable to conoscopic holography systems of large dynamic range and to pattern recognition in real time.
Claims17
A spatial light modulator comprising:
- an interferometer system having an optical cavity;
- a photorefractive crystal, having a transmittivity which changes rapidly with a change in refractive index, positioned in said optical cavity;
- means for directing a write beam containing analog information onto said crystal, said write beam comprising a wavelength at which said crystal absorbs, resulting in modification of the refractive index of said crystal, thus altering the optical path length of said interferometer system, resulting in a transmittivity-optical path length characteristic curve having a steep slope;
- and
- means for directing a read beam onto said crystal, said read beam comprising a wavelength at which optical characteristics of said crystal after modification vary in accordance with said analog information, said spatial light modulator having a dynamic range of amplitude variation of said analog information due to said modification of said crystal which corresponds to said slope of said transmittivity-optical path length characteristic curve.
A conoscopic holography system of large dynamic range comprising:
- a conoscope delivering a conoscopic image in the form of a first light beam representative of said conoscopic image;
- and
- a spatial light modulator device including a photo-refractive crystal placed in the cavity of an interferometer system having a transmittivity-optical path length characteristic curve having a steep slope so as to induce a dynamic range of maximum variation in said transmittivity for minimum variation in the refractive index of said crystal, said spatial light modulator device receiving both a read light beam and said first light beam representative of the conoscopic image, said first light beam constituting a write beam for said spatial light modulator device, and the two light beams being combined on the modulator device by means of an optical system for combining said light beams.
Dependencies are inferred from the claim text.