Abstract: An optical reflective device referred to as a skew mirror, having a reflective axis that need not be constrained to surface normal, is described. Examples of skew mirrors are configured to reflect light about a constant reflective axis across a relatively wide range of wavelengths. In some examples, a skew mirror has a constant reflective axis across a relatively wide range of angles of incidence. Exemplary methods for making and using skew minors are also disclosed. Skew mirrors include a grating structure, which in some examples comprises a hologram.

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 light coupling device operatively coupled to the waveguide. The first light coupling device may include a first duct structure and a second duct structure oriented to reflect in-coupled light. Each of the first duct structure and the second duct structure may includes a first planar region and a second planar region parallel to the first planar region and a first surface and a second surface parallel to the first surface. The device may also include a second light coupling device disposed between the first waveguide surface and the second waveguide surface. The second light coupling device may be to positioned to receive reflected in-coupled light from the first light coupling device.

Abstract: Systems and methods for performing coherent diffraction in an optical device are disclosed. An optical device may include a grating medium with a first hologram having a first grating frequency. A second hologram at least partially overlapping the first hologram may be provided in the grating medium. The second hologram may have a second grating frequency that is different from the first grating frequency. The first and second holograms may be pair-wise coherent with each other. A manufacturing system may be provided that writes the pair-wise coherent holograms in a grating medium using a signal beam and a reference beam. Periscopes may redirect portions of the signal and reference beams towards a partial reflector, which combines the beams and provides the combined beam to a detector. A controller may adjust an effective path length difference between the signal and reference beams based on a measured interference pattern.

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 light coupling device operatively coupled to the waveguide. The first light coupling device may include a first duct structure and a second duct structure oriented to reflect in-coupled light. Each of the first duct structure and the second duct structure may includes a first planar region and a second planar region parallel to the first planar region and a first surface and a second surface parallel to the first surface. The device may also include a second light coupling device disposed between the first waveguide surface and the second waveguide surface. The second light coupling device may be to positioned to receive reflected in-coupled light from the first light coupling device.

Abstract: An optical reflective device referred to as a skew mirror, having a reflective axis that need not be constrained to surface normal, is described. Examples of skew mirrors are configured to reflect light about a constant reflective axis across a relatively wide range of wavelengths. In some examples, a skew mirror has a constant reflective axis across a relatively wide range of angles of incidence. Exemplary methods for making and using skew mirrors are also disclosed. Skew mirrors include a grating structure, which in some examples comprises a hologram.

Abstract: A method of dispersion compensation in an optical device is disclosed. The method may include identifying a first hologram grating vector of a grating medium of the optical device. The first hologram grating vector may correspond to a first wavelength of light. The method may include determining a probe hologram grating vector corresponding to a second wavelength of light different from the first wavelength of light. The method may also include determining a dispersion-compensated second hologram grating vector based at least in part on the probe hologram grating vector and the first hologram grating vector. A device for reflecting light is disclosed. The device may include a grating medium and a grating structure within the grating medium. The grating medium may include a dispersion compensated hologram.

Abstract: A method of dispersion compensation in an optical device is disclosed. The method may include identifying a first hologram grating vector of a grating medium of the optical device. The first hologram grating vector may correspond to a first wavelength of light. The method may include determining a probe hologram grating vector corresponding to a second wavelength of light different from the first wavelength of light. The method may also include determining a dispersion-compensated second hologram grating vector based at least in part on the probe hologram grating vector and the first hologram grating vector. A device for reflecting light is disclosed. The device may include a grating medium and a grating structure within the grating medium. The grating medium may include a dispersion compensated hologram.

Abstract: An optical reflective device for homogenizing light including a waveguide having a first and second waveguide surface and a partially reflective element is disclosed. The partially reflective element may be located between the first waveguide surface and the second waveguide surface. The partially reflective element may have a reflective axis parallel to a waveguide surface normal. The partially reflective element may be configured to reflect light incident on the partially reflective element at a first reflectivity for a first set of incidence angles and reflect light incident on the partially reflective element at a second reflectivity for a second set of incident angles.

Abstract: Optical systems having comb-shifted sets of holograms across different regions of a grating medium are disclosed. A first set of holograms may be formed in a first region of the grating medium and a second set of holograms may be formed in a second region of the grating medium. Each of the holograms in the first set may have a different respective grating frequency from a first set of grating frequencies. Each of the holograms in the second set may have a different respective grating frequency from a second set of grating frequencies. The second set of grating frequencies may be located within adjacent frequency gaps between the grating frequencies in the first set of grating frequencies. Comb-shifted sets of holograms may be used to perform pupil equalization, output coupling, input coupling, cross coupling, or other operations.

Abstract: An optical reflective device including a waveguide and longitudinal light homogenizing structures mounted to a surface of the waveguide are disclosed. The light homogenizing structures may receive input light and produce longitudinally homogenized light by homogenizing the input light along a longitudinal dimension of the waveguide. A cross-coupler in the waveguide may receive the longitudinally homogenized light from the light homogenizing structures and may produce two-dimensionally homogenized light by redirecting the longitudinally homogenized light along a lateral dimension of the waveguide. The light homogenizing structures may include partially reflective layers, stacked substrate layers with refractive index mismatches, and/or a combination of partially and fully reflective layers. The cross coupler and/or partially reflective layer may be formed using sets of holograms. A prism or a slanted substrate surface may couple the input light into the substrate.

Abstract: An optical device for polarizing light including a polarization altering element operatively coupled to a light path associated with the first light coupling device and the second light coupling device is described. The optical device may further include a first waveguide portion including a first layer having parallel plane surfaces with the first waveguide portion having a first light coupling device. The optical device may also include a second waveguide portion including a second layer having parallel plane surfaces with the second waveguide portion having a second light coupling device.

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: Optical systems for performing gaze tracking and imaging an external scene are disclosed. An example optical system may include light sources for emitting visible and non-visible light. The optical system may include a waveguide that is operatively coupled to the light sources. A volume holographic light coupling element may be disposed between the surfaces of the waveguide. The volume holographic light coupling element may include a grating medium and a first volume holographic grating structure within the grating medium. In some examples, the first volume holographic grating structure may be configured to reflect non-visible light of a first wavelength about a first reflective axis offset from a surface normal of the grating medium at a first incidence angle. The optical system may also include an optical filter. Another example optical system may include an imaging device that is configured to receive the light external to the optical system.

Abstract: An optical device for polarizing light including a polarization altering element operatively coupled to a light path associated with the first light coupling device and the second light coupling device is described. The optical device may further include a first waveguide portion including a first layer having parallel plane surfaces with the first waveguide portion having a first light coupling device. The optical device may also include a second waveguide portion including a second layer having parallel plane surfaces with the second waveguide portion having a second light coupling device.

Abstract: An optical reflective device for homogenizing light including a waveguide having a first and second waveguide surface and a partially reflective element is disclosed. The partially reflective element may be located between the first waveguide surface and the second waveguide surface. The partially reflective element may have a reflective axis parallel to a waveguide surface normal. The partially reflective element may be configured to reflect light incident on the partially reflective element at a first reflectivity for a first set of incidence angles and reflect light incident on the partially reflective element at a second reflectivity for a second set of incident angles.

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: An optical device including a first layer of a total internal reflection (TIR) waveguide and a second layer of the TIR waveguide is disclosed. The second layer of the TIR waveguide may be coupled to the first layer. The second layer may include an output coupling device configured to reflect light toward an exit face of the TIR waveguide. The output coupling device may include one or more diffractive gratings. The optical device may also include an input coupling face disposed on a non-diffractive edge portion the first layer or the second layer or both the first and second layer. The input coupling face may be configured to receive image light. Another optical device may include an input coupling face disposed on a non-diffractive input coupling element. The non-diffractive input coupling element may be positioned in an optical path for directing the image light to the TIR waveguide.

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 (704). Each hologram in the set may have a corresponding grating vector (708, 710, 712) 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 (722) is used to couple light into the grating medium. The prism is formed using materials having dispersion properties that are similar to the dispersion properties of the grating material but not indentical. The prism may have an input face that receives perpendicular input light. The prism may include multiple portions having different refractive indices.

Abstract: An optical reflective device for reflecting light including a grating medium having a first and second grating structure is disclosed. The first grating structure may be configured to reflect light of a wavelength about a first reflective axis offset from a surface normal of the grating medium at a first incidence angle. The second grating structure may be configured to reflect light of the wavelength about a second reflective axis offset from the surface normal of the grating medium at a second incidence angle different from the first incidence angle. The second reflective axis may be different from the first reflective axis.

Abstract: An optical device including a first layer of a total internal reflection (TIR) waveguide and a second layer of the TIR waveguide is disclosed. The second layer of the TIR waveguide may be coupled to the first layer. The second layer may include an output coupling device configured to reflect light toward an exit face of the TIR waveguide. The output coupling device may include one or more diffractive gratings. The optical device may also include an input coupling face disposed on a non-diffractive edge portion the first layer or the second layer or both the first and second layer. The input coupling face may be configured to receive image light. Another optical device may include an input coupling face disposed on a non-diffractive input coupling element. The non-diffractive input coupling element may be positioned in an optical path for directing the image light to the TIR waveguide.