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 holographic optical element (“HOE”) that comprises at least one hologram recorded in a holographic film, the method comprising:
providing a first layer of holographic film in a planar geometry;
stretching the first layer of holographic film;
optically recording a hologram in the first layer of holographic film while the first layer of holographic film is stretched; and
returning the first layer of holographic film to an unstretched state.
2 . The method of claim 1 wherein stretching the first layer of holographic film includes mounting the first layer of holographic film onto a curved surface.
3 . The method of claim 1 , further comprising at least one of:
mounting the first layer of holographic film on a curved surface for playback; or
embedding the first layer of holographic film within a curved volume for playback.
4 . The method of claim 3 wherein mounting the first layer of holographic film on a curved surface for playback includes stretching the first layer of holographic film in the direction normal to a plane of the first layer of holographic film onto the curved surface.
5 . The method of claim 1 , further comprising:
providing a second layer of holographic film in a planar geometry;
replicating the hologram from the first layer of holographic film in the second layer of holographic film while both the first layer of holographic film and the second layer of holographic film are each in respective unstretched states; and
at least one of: mounting the second layer of holographic film on a curved surface for playback or embedding the second layer of holographic film within a curved volume for playback.
6 . The method of claim 5 wherein mounting the second layer of holographic film on a curved surface for playback includes stretching the second layer of holographic film in a direction normal to a plane of the second layer of holographic film onto the curved surface.