Focussed image hologram projector using a long narrow light source

Claim 1

In a projector for displaying a color picture derived from a focussed image hologram situated in a given plane, said hologram being of the type comprising a plurality of plane parallel diffraction gratings each of said gratings having grating lines of a different constant spatial frequency being modulated in accordance with a different color component of said color picture to form a spatial carrier for that color component; said projector including first means for illuminating said hologram with an incident non-coherent light beam inclined at a predetermined angle with respect to the normal to said given plane, said non-coherent light beam having a spectrum which includes a spectral wavelength portion corresponding to each respective one of said different color components, and second means responsive only to first diffraction-order output light from said respective gratings for projecting said color picture on a viewing screen; the improvement therein: a. wherein the lines of at least one of said gratings in said given plane is oriented substantially parallel to a given longitudinal axis none of said gratings in said given plane is oriented substantially perpendicular to said longitudinal axis, b. wherein said first means includes a filamentary light source having a relatively long length dimension oriented substantially parallel to said longitudinal axis and relatively small cross-section dimensions oriented substantially normal to said longitudinal axis, and optical means responsive to light from said light source for deriving said non-coherent light beam with said predetermined angle lying in a plane substantially normal to said longitudinal axis, c. wherein said second means includes a spatial filter having a narrow, longitudinal slit therein with the length of said slit being oriented along said longitudinal axis, and d. wherein said different predetermined spatial frequencies of each of said respective gratings is such as to direct through said slit only the spectral wavelength portion of first diffraction-order output light from that grating which corresponds to the color component of said picture carried by that grating.