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 device comprises an optical waveguide including a volume of optically transparent material having a first longitudinal surface positioned opposite a second longitudinal surface across a width of the volume, a liquid crystal in-coupler, a controller to modulate a refractive index of the liquid crystal in-coupler, and an out-coupler. Light is in-coupled into the waveguide on a path that is dependent on the modulated refractive index of the liquid crystal in-coupler and is propagated along a length of the waveguide by total internal reflection between the longitudinal surfaces before being out-coupled by the out-coupler. In this way, light signals can be steered to create an image and/or to move an exit pupil of an image. WHUDs that employ such optical waveguides are also described.
1 . A method of operating a wearable heads-up display (WHUD) comprising a support structure that in use is worn on the head of a user, a projector with at least one light source, an optical waveguide including a volume of optically transparent material having a first longitudinal surface opposite a second longitudinal surface across a width of the volume of optically transparent material, a liquid crystal in-coupler, an out-coupler, and a controller communicatively coupled to the liquid crystal in-coupler, the method comprising:
generating a first set of light signals by the at least one light source of the projector;
modulating a refractive index of the liquid, crystal in-coupler to a first refractive index by the controller;
in-coupling the first set of light signals into the optical waveguide by the liquid crystal in-coupler, wherein the first set of light signals travel on a path within the volume of optically transparent material that is dependent on the refractive index of the liquid crystal in-coupler;
propagating the first set of light signals down a length of the volume of optically transparent material by total internal reflection between the first longitudinal surface and the second longitudinal surface; and
out-coupling the first set of light signals from the volume of optically transparent material towards an eye of the user by the out-coupler.
2 . The method of claim 1 further comprising:
generating a second set of light signals by the at least one light source of the projector;
modulating a refractive index of the liquid crystal in-coupler a second refractive index by the controller;
in-coupling the second set of light signals into the optical waveguide by the liquid crystal in-coupler, wherein the second set of light signals travel on a path within the volume of optically transparent material that is dependent on the refractive index of the liquid crystal in-coupler;
propagating the second set of light signals down a length of the volume of optically transparent material by total internal reflection between the first longitudinal surface and the second longitudinal surface; and
out-coupling the second set of light signals from the volume of optically transparent material towards and eye of the user by the out-coupler.
3 . The method of claim 1 wherein the out-coupler is a liquid crystal out-coupler communicatively coupled to the controller and the method further includes:
modulating a refractive index of the liquid crystal out-coupler to a third refractive index by the controller; and
out-coupling a first set of light signals by the liquid crystal out-coupler, wherein an output path of the first set of light signals that is dependent on the refractive index of the liquid crystal out-coupler.