Abstract: A display may include a waveguide. An input coupler may couple image light into the waveguide and an output coupler may couple the image light out of the waveguide. A surface relief grating on the waveguide may couple infrared light into the waveguide and may couple the infrared light out of the waveguide. The surface relief grating may additionally or alternatively couple reflected infrared light into the waveguide and out of the waveguide and towards an infrared sensor. The surface relief grating may also form a cross-coupler for the image light. The infrared sensor may gather infrared sensor data based on the reflected infrared light. Control circuitry may perform gaze tracking operations based on the infrared sensor data. The input and output couplers may also be formed from surface relief gratings or may include other optical components.

Abstract: An electronic device may include a display module that produces light having an image, a lens that directs the light to a waveguide, and a waveguide that directs the light to an eye box. The lens may produce a foveated image in the light by applying a non-uniform magnification to the image in the light. The non-uniform magnification may vary as a function of angle within a field of view of the lens. This may allow the foveated image to have higher resolution within the central region than in the peripheral region. Performing foveation using the lens maximizes the resolution of images at the eye box without increasing the size of the display module. Control circuitry on the device may apply a pre-distortion to the image that is an inverse of distortion introduced by the lens in producing the foveated image.

Abstract: An electronic device may include a display module that produces light having an image, a lens that directs the light to a waveguide, and a waveguide that directs the light to an eye box. The lens may produce a foveated image in the light by applying a non-uniform magnification to the image in the light. The non-uniform magnification may vary as a function of angle within a field of view of the lens. This may allow the foveated image to have higher resolution within the central region than in the peripheral region. Performing foveation using the lens maximizes the resolution of images at the eye box without increasing the size of the display module. Control circuitry on the device may apply a pre-distortion to the image that is an inverse of distortion introduced by the lens in producing the foveated image.

Abstract: The display may include a waveguide that directs light towards an eye box. The waveguide may include first and second media layers that are edge-coupled at an interface. The first media layer may include a louvered mirror cross-coupler that redirects the light towards the second media layer. The second media layer may include a volume hologram output coupler that couples the light out of the waveguide. Additional layers may be interposed between the first media layer and waveguide substrates. The additional layers may help confine the light within the first media layer as the light propagates such that all of the light enters the second media layer through the interface. This may configure the waveguide to occupy a minimal amount of space within the display while also providing the eye box with as bright and uniform an image as possible.

Abstract: An electronic device may have a display system that produces images. The display system may have one or more pixel arrays such as liquid-crystal-on-silicon pixel arrays. Images from the display system may be coupled into a waveguide by an input coupler and may be coupled out of the waveguide using an output coupler. The input and output couplers may be formed from volume phase holographic gratings. An additional grating may be used to shift light that would otherwise pass above or below the user's field of view towards the viewer. Holographic gratings in the waveguide may have fringes with constant pitch and variable period. The period at a given portion of the grating may be Bragg-matched to maximize diffraction efficiency for light of a given incident angle.

Abstract: An electronic device may include a display module that produces light having an image, a lens that directs the light to a waveguide, and a waveguide that directs the light to an eye box. The lens may produce a foveated image in the light by applying a non-uniform magnification to the image in the light. The non-uniform magnification may vary as a function of angle within a field of view of the lens. This may allow the foveated image to have higher resolution within the central region than in the peripheral region. Performing foveation using the lens maximizes the resolution of images at the eye box without increasing the size of the display module. Control circuitry on the device may apply a pre-distortion to the image that is an inverse of distortion introduced by the lens in producing the foveated image.

Abstract: An electronic device may include an optical system that redirects light from a display module towards an eye box along an optical path. The optical path may include a holographic coupler and a resolution-enhancing holographic element. The holographic element may include a first set of holograms and the coupler may include a second set of holograms. The first set of holograms may be characterized by a first set of selectivity curves having first primary lobes. The second set of holograms may be characterized by a second set of selectivity curves having second primary lobes that overlap the first primary lobes. This may configure the holographic element to narrow the second selectivity curves by diffracting some of the light out of the optical path, thereby optimizing the resolution of images in the light provided to the eye box.

Abstract: An electronic device may include an emissive display panel that emits light. The light may propagate along an optical path extending to an eye box. A waveguide with an input coupler and an output coupler may be interposed on the optical path. An angle-selective transmission filter (ASTF) may be interposed on the optical path and may filter the emitted light as a function of angle to remove high-angle light from the optical path before the light is provided to the output coupler. The ASTF may include diffractive grating structures such as thin-film holograms, volume holograms, or surface relief gratings, louvered mirrors, multi-layer coatings, or a pinhole array. This ASTF may serve to minimize stray light within the display, thereby optimizing the contrast and the modulation transfer function (MTF) of the display.

Abstract: An electronic device may have a light source such as a laser light source. The light source may emit light into a waveguide. A phase grating may diffract the light that is emitted into the waveguide to produce diffracted light. The diffracted light may be oriented parallel to a surface normal of an angled edge of the waveguide and parallel to a surface normal of a microelectromechanical systems mirror element in a two-dimensional scanning microelectromechanical systems mirror that is coupled to the edge of the waveguide. A wave plate may be interposed between the mirror and the edge of the waveguide to change the polarization state of light reflected from the mirror element relative to incoming diffracted light from the phase grating. The phase grating may be configured so that the reflected light is not diffracted by the phase grating.

Abstract: A device including a waveguide having a first waveguide surface and a second waveguide surface parallel to the first waveguide surface is disclosed. The device may include a first volume holographic light coupling element disposed between the first waveguide surface and the second waveguide surface. The first volume holographic light coupling element may be structured to reflect at least a portion of incident light as reflected light. Incident light for which the first volume holographic light coupling element is structured to reflect may have a first angle of incidence within a total internal reflection (TIR) range with respect a first axis corresponding to a surface normal of the waveguide. Incident light for which the first volume holographic light coupling element is structured to reflect may have a second angle of incidence with respect to a second axis different from the first axis.

Abstract: An electronic device may have a display system that produces images. The display system may have one or more pixel arrays such as liquid-crystal-on-silicon pixel arrays. Images from the display system may be coupled into a waveguide by an input coupler and may be coupled out of the waveguide using an output coupler. The input and output couplers may be formed from volume phase holographic gratings. An additional grating may be used to shift light that would otherwise pass above or below the user's field of view towards the viewer. Holographic gratings in the waveguide may have fringes with constant pitch and variable period. The period at a given portion of the grating may be Bragg-matched to maximize diffraction efficiency for light of a given incident angle.

Abstract: An electronic device may include a display that produce images. The display may generate light for an optical system that redirects the light towards an eye box. The optical system may include a waveguide that propagates the light in a first direction towards the output coupler. The output coupler may couple the light out of the waveguide towards the eye box while inverting a parity of the light about the first direction. The coupler may include a first element such as a set of partial mirrors or diffractive gratings that redirects a first portion of the light in a second direction. The coupler may include a second element that redirects a second portion of the light in a third direction opposite the second direction. The first element may redirect the second portion and the second element may redirect the first portion towards the eye box.

Abstract: An electronic device may have a light source such as a laser light source. The light source may emit light into a waveguide. A phase grating may diffract the light that is emitted into the waveguide to produce diffracted light. The diffracted light may be oriented parallel to a surface normal of an angled edge of the waveguide and parallel to a surface normal of a microelectromechanical systems mirror element in a two-dimensional scanning microelectromechanical systems mirror that is coupled to the edge of the waveguide. A wave plate may be interposed between the mirror and the edge of the waveguide to change the polarization state of light reflected from the mirror element relative to incoming diffracted light from the phase grating. The phase grating may be configured so that the reflected light is not diffracted by the phase grating.