Optical blurring filter which is resistant to digital image restoration
AssigneeNorthrop Grumman Corporation
InventorWalter Dennis Clark
Life of this patent
Estimating the term…
Abstract
An optical filter for intentionally blurring camera images has a generally transparent material and a plurality of optical distortions formed in the transparent material. Placement of the transparent material longitudinally in the optical path of a camera in front of the aperture stop allows contouring the blur across the image plane. That contour is preferably random, so as to defeat digital methods for image restorations. Additionally, a linear gradient is utilized to even-out the ground resolution on oblique cameras or localized to even-out resolution on cameras that have areas of unwanted high resolution.
Claims15
A method for forming a lenticular filter, the method comprising the steps of:
- a) depositing photoresist on a transparent material;
- b) exposing the photoresist to laser speckle to effect formation of a pattern of random blobs;
- c) developing the photoresist so as to form a three dimensional structure;
- and
- d) etching the transparent material to form a plurality of protrusions and depressions thereupon, the protrusions and depressions defining a plurality of lenslets.
A method forming a lenticular filter, the method comprising the steps of:
- a) placing a mask having a plurality of apertures formed therein proximate the transparent material;
- and
- b) directing an ion beam toward the mask such that a portion of the ion beam is transmitted through the apertures and is incident upon the transparent material and such that the ion beam etches the transparent material so has to form generally elliptical recesses in the transparent material, the generally elliptical recesses defining lenslets.
A method for forming a phase filter, the method comprising the steps of:
- a) providing a transparent material having a thickness;
- and
- b) changing the thickness of the transparent material to form a plurality of protrusions and depressions at selected locations with a movable mask thereof so as to provide a plurality of different random thicknesses of the transparent material;
- c) wherein the plurality of different random thicknesses of the transparent material effect random changes in longitudinal phase of light transmitted therethrough.
Dependencies are inferred from the claim text.