Reference beam deflecting element for recording a hologram

DETAILED DESCRIPTION In accordance with teachings of the present invention, a system and method are provided to prevent at least a portion of a reference beam from intersecting with an associated diffuser.
A holographic deflector incorporating teaching of the present invention may be placed between a diffuser and a holographic film or emulsion, similar to the placement of louver screen film.
However, the holographic deflector preferably has a much thinner profile, requiring approximately 100-200 microns, as compared to the 1 mm needed to accommodate the louver film.
The holographic deflector is designed to deflect only light impinging on it from the particular angle that the reference beam strikes the holographic emulsion, and transmits nearly all other light strking it.
These deflection characteristics are due to the Bragg selectivity of the holographic structure and its recording geometry.
A holographic deflector incorporating teaching of the present invention may have nearly 100% diffraction efficiency, ensuring the passage of little or no reference beam light to the diffuser.
The holographic deflector allows the diffuser to be placed close to the holographic emulsion, enabling a closer approach to the ideal case of coincident vertical diffusion and hologram planes.
Close placement of the diffuser to the emulsion also reduces another image artifact that is produced when rays from different but neighboring points in the object beam intersect prior to propagation through the holographic emulsion.
Such a situation gives rise to a coarse fringe pattern, which manifests itself as dark horizontal lines in the image.
Finally, the holographic deflector does not impart any visible artifacts of its own into the fine structure of the image as does louver film.
This advantage is due to the microscopic nature of the fringes in a holographic optical element, as compared to the macroscopic structure of the louver film.
Accordingly, one aspect of the present invention provides a system for recording a hologram in a holographic recording material