SYSTEMS, DEVICES, AND METHODS FOR OPTICAL WAVEGUIDES
Systems, devices, and methods for optical waveguides that are well-suited for use in wearable heads-up displays (WHUDs) are described. An optical waveguide includes a volume of optically transparent material, a first holographic optical element (HOE) and a second holographic optical element, wherein the first HOE and the second HOE are carried by the volume of optically transparent material, and the first HOE is positioned across a width of the volume of optically transparent material from the second HOE. Light enters the optical waveguide and is propagated down a length of the waveguide by reflection between the first HOE and the second HOE. Propagation of the light within the optical waveguide does not require total internal reflection. The optical waveguide may include means to in-couple the light into the waveguide and means to out-couple the light from the waveguide. WHUDs that employ such optical waveguides are also described.
1 . An optical waveguide to receive, guide, and output light signals, the optical waveguide comprising:
a volume of optically transparent material having a first longitudinal surface and a second longitudinal surface, the second longitudinal surface opposite the first longitudinal surface across a width of the volume of optically transparent material;
a first holographic optical element (“HOE”) carried by the volume of optically transparent material at or adjacent the first longitudinal surface;
a second HOE carried by the volume of optically transparent material at or adjacent the second longitudinal surface, wherein the light signals that enter the volume of optically transparent material are sequentially reflected by and between the first HOE and the second HOE to propagate along a length of the optical waveguide;
an in-coupling region; and
an out-coupling region.
2 . The optical waveguide of claim 1 wherein the volume of optically transparent material is curved, the first HOE is curved, and the second HOE is curved.
3 . The optical waveguide of claim 1 wherein the first HOE covers at least 50% of the first longitudinal surface and the second HOE covers at least 50% of the second longitudinal surface.
4 . The optical waveguide of claim 1 wherein the in-coupling region includes at least a portion of an element selected from a group consisting of: the first HOE, the second HOE, and a dedicated in-coupling element.
5 . The optical waveguide of claim 4 wherein the in-coupling region includes a dedicated in-coupling element selected from a group consisting of: a hologram, a holographic optical element, a volume diffraction grating, a surface relief diffraction grating, a transmission grating, and a reflection grating.
6 . The optical waveguide of claim 4 wherein light signals are in-coupled by the in-coupling region according to at least one property selected from a group consisting of: a wavelength of a light signal, an angle of incidence of a light signal on the in-coupling region, and a location of incidence of a light signal on the in-coupling region.
7 . The optical waveguide of claim 1 wherein the out-coupling region includes at least a portion of an element selected from a group consisting of: the first HOE, the second HOE, and a dedicated out-coupling element.
8 . The optical waveguide of claim 7 wherein the out-coupling region includes a dedicated out-coupling element selected from a group consisting of: a hologram, a holographic optical element, a volume diffraction grating, a surface relief diffraction grating, a transmission grating, and a reflection grating.
9 . The optical waveguide of claim 7 wherein light signals are out-coupled by the out-coupling region according to at least one property selected from a group consisting of: a wavelength of a light signal, an angle of incidence of a light signal on the out-coupling region, and a location of incidence of a light signal on the out-coupling region.
10 . The optical waveguide of claim 1 wherein:
the first HOE comprises N holograms, where N is an integer greater than 1 and wherein each of the N holograms in the first HOE is responsive to light in a respective one of N distinct wavebands; and
the second HOE comprises N holograms, wherein each of the N holograms in the second HOE is responsive to light in a respective one of the N distinct wavebands.
11 . The optical waveguide of claim 10 wherein:
the first HOE comprises:
a first hologram responsive to light in a first waveband and unresponsive to light outside the first waveband;
a second hologram responsive to light in a second waveband and unresponsive to light outside the second waveband; and
a third hologram responsive to light in a third waveband and unresponsive to light outside the third waveband, wherein the first waveband, the second waveband, and the third waveband are all distinct and non-overlapping; and
the second HOE comprises:
a fourth hologram responsive to light in the first waveband and unresponsive to light outside the first waveband;
a fifth hologram responsive to light in the second waveband and unresponsive to light outside the second waveband; and
a sixth hologram responsive to light in the third waveband and unresponsive to light outside the third waveband.