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: A display device may include first and second display modules that provide image light to first and second waveguides. The waveguides may direct the image light to first and second eye boxes. Each display module may include optics mounted to a housing and mechanical alignment structures that mechanically adjust the position of an optical axis of the optics. The alignment structures may rotate the entire housing, may mechanically translate the optics, may adjust the position of a spatial light modulator within the module, and/or control circuitry may change a subset of pixels used by the modulator to compensate for optical misalignment between the first and second eye boxes. The device may include optical misalignment sensors that detect the optical misalignment. The control circuitry may compensate for the optical misalignment as detected by the optical misalignment sensors.

Abstract: A display system may include a waveguide with an output coupler that couples image light out of the waveguide and towards an eye box. The output coupler may also transmit world light from real-world objects towards the eye box. A bias lens may pass the world light to the output coupler. An adjustable tint layer having multiple states that involve transmission of different amounts of the world light may be disposed between the bias lens and the output coupler. Different states may impart different colors and/or may impart a gradient transmission characteristic to the world light. The bias lens itself may form the adjustable tint layer. The adjustable tint layer may have a transparent electrode layer that is provided with one or more AC voltages that heat the adjustable tint layer. The adjustable tint layer may be a self-switching electrochromic device that includes a transparent solar cell.

Abstract: An electronic device may have a spatial light modulator. Control circuitry in the electronic device may use the spatial light modulator to generate images. A light source may be used to produce illumination for the spatial light modulator. An optical system may direct the illumination onto the spatial light modulator and may direct corresponding reflected image light towards eye boxes for viewing by a user. Head-mounted support structures may be used to support the spatial light modulator, light source, and optical system. The light source may include light-emitting elements such as light-emitting diodes or lasers. Multiple light-emitting elements may be provided in the light source in a one-dimensional or two-dimensional array. During operation, the control circuitry can individually adjust the light-emitting elements.

Abstract: A display having a reflective display panel may provide image light to an eye box. The panel may include mirrors rotatable between first and second angles. The mirrors may take a non-zero time period to transition between the first and second angles. During the non-zero time period, the light source may emit pulses of illumination. The mirrors may reflect the pulses of illumination as offset pupils of image light. The mirrors may be at respective intermediate angles while reflecting each of the pulses of illumination. The mirrors may toggle between the first and second angles at a sufficiently fast rate such that the offset pupils form an effective pupil that is expanded in at least one dimension. If desired, the offset pupils may be used to display virtual objects in different focal planes at the eye box.

Abstract: A head-mounted device may have projector, a first waveguide, a second waveguide, and an optical bridge sensor coupled between the first and second waveguides. An input coupler may couple light with a calibration pattern into the first waveguide. The calibration pattern may be included in visible or infrared light produced by the projector or may be included in infrared light produced by infrared emitters mounted to the first waveguide. An output coupler may couple the light having the calibration pattern out of the first waveguide. An additional output coupler may be used to couple visible light from the projector out of the waveguide and towards an eye box. An image sensor may generate image sensor data based on the light having the calibration pattern. Control circuitry may process the calibration pattern in the image sensor data to detect deformation or warping of the first waveguide.

Abstract: An electronic device may include a display module that generates light and an optical system that redirects the light towards an eye box. The system may include an input coupler on a waveguide and a lens that directs the light towards the input coupler. The input coupler may include a prism having a reflective surface that reflects the light into the waveguide. The reflective surface may be curved to provide the light with an optical power. The prism may be configured to expand a field of view of the light. A birefringent beam displacer may expand the effective pupil size of the light. The lens may include lens elements that converge the light at a location between the lens elements and the waveguide. A switchable panel may be placed at the location and toggled between first and second orientations to increase the effective resolution of the light.

Abstract: An electronic device may provide foveated images at an eye box. The device may have a first display module that produces a low resolution portion of the image and a second display module that produces a high resolution portion of the image. A reflective input coupling prism may be mounted to a waveguide. A steering mirror may overlap the prism. The mirror may receive the high resolution portion through the waveguide and the prism. The mirror may reflect the high resolution portion back into the waveguide and may be adjusted to shift a location of the high resolution portion within the image. For example, the steering mirror may adjust the position of the high resolution portion to align with the gaze direction at the eye box. A reflective surface of the prism may reflect the low resolution portion of the image into the waveguide.

Abstract: A display may include a waveguide that directs image light towards an eye box within a field of view (FOV). A first lens may transmit world light to the waveguide and a second lens may transmit the world light and the image light to the eye box. One or more surfaces of the first and second lenses may collectively have a first region with a first optical power, a second region with a second optical power, a corridor with gradient optical power and constant astigmatism, and blending regions with variable astigmatism. The second region may be shifted downwards in elevation angle, the corridor may be elongated, and/or the blending regions may be disposed away from the FOV to prevent the blending regions from introducing astigmatism to the image light at the eye box.

Abstract: A display system may include a waveguide, an input coupler with a first surface relief grating (SRG), and an output coupler with a second SRG. A display module may produce image light that is coupled into the waveguide by the first SRG. The first SRG may have an input vector non-parallel with respect to a normal axis of the waveguide. The display module may have an optical axis tilted with respect to the input vector by a non-zero angle. A prism may redirect the image light from the module to the first SRG in a direction parallel to the input vector. The module may include lens elements with an optical axis offset with respect to the center of the field of the image light. This may cause the lens elements to output the image light in a direction parallel to the input vector of the first SRG.

Abstract: An electronic device may have a display system with a module that produces image light and a waveguide that directs the image light towards an eye box. The module may include a light source, spatial light modulator, and collimating lens between the lens and modulator. The lens may direct illumination from the light source to the modulator, which modulates the illumination to produce the image light. The lens may have a geometry that illuminates the modulator with a non-uniform illumination pattern to mitigate subsequent brightness non-uniformity introduced by the waveguide. The light source may include one or more LEDs that are independently driven by control circuitry over one or more drive lines to help mitigate the non-uniformity introduced by the waveguide and/or to operate the display in a heads-up display mode.

Abstract: An electronic device may include a display module that generates light and an optical system that redirects the light towards an eye box. The system may include an input coupler on a waveguide and a lens that directs the light towards the input coupler. The input coupler may include a prism having a reflective surface that reflects the light into the waveguide. The reflective surface may be curved to provide the light with an optical power. The prism may be configured to expand a field of view of the light. A birefringent beam displacer may expand the effective pupil size of the light. The lens may include lens elements that converge the light at a location between the lens elements and the waveguide. A switchable panel may be placed at the location and toggled between first and second orientations to increase the effective resolution of the light.

Abstract: An electronic device may include a first bias lens that transmits world light to an output coupler on a waveguide. The output coupler may transmit the world light while coupling image light out of the waveguide. A second bias lens may transmit the world light and the image light to an eye box. A tint layer may transmit the world light towards the output coupler. The tint layer may be planar and layered onto a planar surface of the first bias lens or another lens, may be separated from the first bias lens by an air gap, may be non-parallel relative to the waveguide, and/or may be curved and separated from the first bias lens and the waveguide by air gaps. When planar, the tint layer may be provided with spacers between substrates or between the tint layer and the waveguide to maximize parallelism.

Abstract: Systems and methods of dispersion compensation in an optical device are disclosed. A holographic optical element may include a set of different holograms in a grating medium. Each hologram in the set may have a corresponding grating vector with a grating frequency and direction. The directions of the grating vectors may vary as a function of the grating frequency. Different holograms in the set may diffract light in a particular direction so that the light emerges from a boundary of the grating medium in a single given direction regardless of wavelength. A prism may be used to couple light into the grating medium. The prism may be formed using materials having dispersion properties that are similar to the dispersion properties of the grating material. The prism may have an input face that receives perpendicular input light. The prism may include multiple portions having different refractive indices.

Abstract: A display may include illumination optics (36), a spatial modulator (40) and a waveguide (26). The illumination optics may produce illumination that is modulated by the spatial modulator to produce image light. The waveguide may direct the image light towards an eye box. The illumination optics may include light sources (58) an X-plate (44), and at least one Fresnel lens (60) interposed between the light sources and the X-plate. The Fresnel lenses may minimize the size of the illumination optics while still exhibiting satisfactory optical performance. The spatial light modulator may include a reflective display panel (50) and a powered prism (48) with a reflective coating on a curved reflective surface. The powered prism may optimize f-number while minimizing the volume of the spatial light modulator. The collimating optics may include a diffractive optical element (56) that compensates for thermal effects and chromatic dispersion in the display.

Abstract: A display may include a waveguide having an output coupler that couples image light out of the waveguide and towards a lens, which imparts a first power to the image light. A cover layer may have an outer surface with a three-dimensional curvature and an inner surface. A portion of the inner surface overlapping the output coupler may have a different three-dimensional curvature that forms an additional lens in the cover layer that transmits world light to the output coupler. The output coupler may transmit the world light to the lens, which transmits the world and image light to the eye box. The curvature of the portion of the inner surface may impart power to the world light that reverses the first power and/or a power imparted to the world light by the outer surface of the cover layer.

Abstract: A display may include a reflective display panel, an infrared image sensor and a waveguide. The panel may be operated in a first operating mode in which the panel reflects image light towards the waveguide and a second operating mode in which the panel reflects infrared light from the waveguide towards the infrared image sensor. The panel may also reflect infrared light from an infrared emitter towards the waveguide. If desired, the infrared image sensor may be mounted adjacent a reflective surface of a reflective input coupling prism on the waveguide. The infrared image sensor may receive the infrared light through the reflective surface. If desired, a world-facing camera may receive world light through the waveguide. The display module and the world-facing camera may be operated using a time multiplexing scheme to prevent the image light from interfering with images captured by the world-facing camera.

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: A head-mounted device may have a housing with a frame that supports lenses. Each lens may have a positive bias lens element and a negative bias lens element. A waveguide may overlap the lens. During operation, images from the waveguide may be provided to an eye box through the negative bias lens element. An eye sensor such as a gaze tracking camera may operate through the negative bias lens element. The negative bias lens element may have a protruding portion through which the sensor operates, may have a surface facing the sensor that has a curved surface to provide a desired lens characteristic, may have a prism for helping to couple light from the eye box to the eye sensor, and/or may have other features to facilitate use of the eye sensor to monitor the eye of a user in the eye box.

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.