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 method of producing a curved holographic optical element (“HOE”) that comprises at least one hologram recorded in a holographic film, the method comprising:
positioning and orienting the holographic film in a planar geometry;
optically recording a hologram in the holographic film with a first laser having a first wavelength while the holographic film is in the planar geometry, the first wavelength different from a playback wavelength of the curved HOE; and
applying a curvature to the holographic film.
2 . The method of claim 1 wherein applying a curvature to the holographic film includes stretching the holographic film, and wherein optically recording the hologram in the holographic film with a first laser having a first wavelength while the holographic film is in the planar geometry includes optically recording the hologram in the holographic film with the first laser having a first wavelength that is less than the playback wavelength of the curved HOE.
3 . The method of claim 1 wherein applying a curvature to the holographic film includes compressing the holographic film, and wherein optically recording the hologram in the holographic film with a first laser having a first wavelength while the holographic film is in the planar geometry includes optically recording the hologram in the holographic film with the first laser having a first wavelength that is greater than the playback wavelength of the curved HOE.
4 . The method of claim 1 wherein:
optically recording a hologram in the holographic film while the holographic film is in the planar geometry includes optically recording the hologram with a holographic optical power P H that is less than a total optical power P T of the curved HOE while the holographic film is in the planar geometry; and
applying a curvature to the holographic film includes applying a geometric optical power P G that is less than the total optical power P T of the curved HOE to the holographic film, and wherein the total optical power P T of the curved HOE includes an additive combination of the holographic optical power P H and the geometric optical power P G given, at least approximately, by P T =P H +P G .
5 . The method of claim 1 wherein:
positioning and orienting the holographic film in a planar geometry includes mounting the holographic film on a planar surface; and
optically recording a hologram in the holographic film with a first laser having a first wavelength while the holographic film is in the planar geometry includes optically recording the hologram in the holographic film with the first laser having the first wavelength while the holographic film is mounted on the planar surface, and wherein the method further comprises:
removing the holographic film from the planar surface before applying the curvature to the holographic film.
6 . The method of claim 1 wherein applying a curvature to the holographic film includes at least one of: mounting the holographic film on a curved surface or embedding the holographic film within a curved volume.