Holographic diffusion screen and methods for the production thereof

Claim 1

A diffusing screen usable in bringing an image passing through an image-forming optical element or system to focus thereon, comprising an optically-generated or computer-generated holographic element which, upon reconstruction, displays an image comprising a relatively transmittant pattern on a substantially opaque background, wherein the outer periphery of said relatively transmittant pattern substantially defines a circle, said circle having a diameter approximating the diameter of the exit pupil of the optical element or system through which the image to be focused passes when in use, and wherein a substantial area of said image surrounding the center of said circle is part of said substantially opaque background, whereby a substantially annular relatively transmittant pattern is formed around the center of said circle to thereby provide a focusing screen with increased blur of out-of-focus images without substantial loss of brightness.

Claim 12

A method for producing a holographic diffusing screen, comprising: applying coherent light along first and second intersecting light paths; causing the beams of light passed along said first and second light paths to become expanded; arranging a holographic recording plate at the intersection of the two light beams such as to be perpendicular to one of said beams, said plate being rotatable about an axis that is perpendicular to the plane of said recording plate and which contains a point at substantially the center of the intersection of said two beams; exposing said holographic recording plate to said first and second light paths for a predetermined time; after completion of said exposure, rotating said holographic recording plate a predetermined amount about said axis; repeating said exposing and rotating steps until a predetermined number of exposures has been completed; and developing said plate.

Claim 13

A method for producing a holographic diffusing screen, comprising: applying coherent light along first and second intersecting light paths; causing the beams of light passed along said first and second light paths to become expanded; arranging a holographic recording plate at the intersection of the two light beams such as to be perpendicular to one of said beams, said plate being rotatable about an axis that is perpendicular to the plane of said recording plate and which contains a point at substantially the center of the intersection of said two beams; exposing said holographic recording plate to said first and second light paths for a predetermined time; after completion of said exposure, rotating said holographic recording plate a predetermined amount about said axis; repeating said exposing and rotating steps until a predetermined number of exposures has been completed; and developing said plate.

Claim 15

A method for producing a holographic diffusing screen usable in bringing an image to focus after the image has passed through an image-forming optical element or system, comprising: applying coherent light along first and second light paths; diffusing the coherent light passed along said first light path; placing a mask in the path of the diffused light, said mask being substantially opaque with a relatively transmittant portion therein substantially in the form of an annulus with outer diameter D and annulus radial width d; arranging a holographic recording plate for exposure simultaneously to said diffused light passed through said mask along said first light path and said light passed along said second light path in such a manner as to record a hologram on said holographic recording plate reproducing the pattern of said mask; and developing said plate so as to produce a holographic diffusing screen, wherein said outer diameter D of the relatively transmittant annular pattern of said mask is chosen so as to approximate the diameter of the exit pupil of an optical element or system through which the image to be focused passes when in use, and said annulus width d is chosen so as to leave a substantial area within said outer diameter D which is substantially opaque.

Claim 16

A method for producing a holographic diffusing screen usable in bringing an image to focus after the image has passed through an image-forming optical element or system, comprising: applying coherent light along first and second light paths; diffusing the coherent light passed along said first light path; placing a mask in the path of the diffused light, said mask being substantially opaque with a relatively transmittant portion therein substantially in the form of an annulus with outer diameter D and annulus radial width d; arranging a holographic recording plate for exposure simultaneously to said diffused light passed through said mask along said first light path and said light passed along said second light path in such a manner as to record a hologram on said holographic recording plate reproducing the pattern of said mask; and developing said plate so as to produce a holographic diffusing screen, wherein said outer diameter D of the relatively transmittant annular pattern of said mask is chosen so as to approximate the diameter of the exit pupil of an optical element or system through which the image to be focused passes when in use, and said annulus width d is chosen so as to leave a substantial area within said outer diameter D which is substantially opaque.