SYSTEMS, DEVICES, AND METHODS FOR CURVED HOLOGRAPHIC OPTICAL ELEMENTS
Systems, devices, and methods for making, replicating, and using curved holographic optical elements (“HOEs”) are described. A hologram may be optically recorded into a planar layer of holographic film with various measures in place to compensate for changes (e.g., in optical power and/or playback wavelength and/or angular bandwidth) that may result when a curvature is subsequently applied thereto. A hologram may be optically recorded into a curved layer of holographic film with various measures in place to compensate for optical effects of a curved transparent substrate upon which the holographic film is mounted. A curved HOE may be returned to a planar configuration to undergo holographic replication or holographic replication may be performed using a curved master HOE and curved “recipient” film. The curved HOEs described herein are particularly well-suited for use when integrated with a curved eyeglass lens to form the transparent combiner of a virtual retina display.
1 . A curved holographic optical element (“HOE”) having a total optical power P T , comprising:
at least one curved layer of holographic film that includes at least one hologram, wherein:
the at least one hologram has a holographic optical power P H that is less than the total optical power P T of the curved HOE; and
the at least one curved layer of holographic film has a geometric optical power P G that is less than the total optical power P T of the curved HOE, and wherein the total optical power P T of the curved HOE includes an additive combination of the holographic optical power P H of the at least one hologram and the geometric optical power P G of the at least one curved layer of holographic film given, at least approximately, by P T =P H +P G .
2 . The curved HOE of claim 1 wherein:
the total optical power P T of the curved HOE is positive and includes a total focal length f T ;
the holographic optical power P H of the at least one hologram is positive and has a first focal length f H that is greater than the total focal length f T of the curved HOE; and
the geometric optical power P G of the at least one curved layer of holographic film is positive and has a second focal length f G that is greater than the total focal length f T of the curved HOE, and wherein the total focal length f T of the curved HOE includes an additive reciprocal combination of the first focal length f H and the second focal length f G given, at least approximately, by 1/f T =1/f H +1/f G .