This month the U.S. Patent and Trademark Office officially published a granted patent for Meta that relates to possible future smartglasses. The patent covers methods and apparatuses for efficient light propagation within waveguides for artificial reality displays and smartglasses.

In Meta's patent background they note that some standard artificial reality systems may have a waveguide display that may typically need an in-coupler to couple the light from a projector to a waveguide. Laser scanning projectors may have very high brightness; however, its optical pupil (e.g., a virtual image of an aperture of a mirror, lens, etc.) may be on a scanning mirror. The positioning of the optical pupil in laser scanning projectors may eventually cause a beam walk-off on the waveguide, thus reducing in-coupling efficiency and reducing the contrast ratio of an eye image.

In view of the foregoing drawbacks, it may be beneficial to provide an efficient and reliable mechanism for improving waveguide structures to in-couple light from light sources such that the light i-achieves total internal reflection within the waveguide as the light propagates within the waveguide.

Meta's granted patent covers an input grating assembly which may be associated with artificial reality applications. The input grating assembly system may include a Volume Bragg Grating (VBG) and/or a Surface Relief Grating (SRG).

In an example embodiment, a system may include a waveguide having a front and rear surface. The waveguide may be associated with a display and may be arranged to guide light into an eye of a user to make an image visible to the user. The light may be guided through a SRG, and/or a VBG, and may be propagated through a waveguide that causes light in-coupling.

The smartglasses may include at least one light source configured to generate light. The device may further include at least one mirror configured to direct the light into one or more rays of light. The device may further include a Surface Relief Grating disposed on a Volume Bragg Grating.

The Surface Relief Grating may be configured to receive the one or more rays of light and diffract the one or more rays of light onto one or more gratings of the Volume Bragg Grating.

The device may further include at least one waveguide disposed beneath the Volume Bragg Grating. The at least one waveguide may be configured to receive the one or more rays of light from the Volume Bragg Grating and propagate the one or more rays of light throughout the at least one waveguide such that an off-Bragg condition is exhibited by the one or more rays of light propagating through the at least one waveguide.

In another example embodiment, a method for propagating light into a waveguide is provided. The method may include directing light from a light source to at least one mirror. The method may further include receiving, via the at least one mirror, the light and emitting one or more rays of light based on the light. The method may further include receiving, at a Surface Relief Grating disposed on a Volume Bragg Grating, the one or more rays of light and diffracting, by the Surface Relief Grating, the one or more rays of light. The method may further include reflecting, by the Volume Bragg Grating, the one or more rays of light causing the one or more rays of light to propagate throughout at least one waveguide of a device such that an off-Bragg condition is exhibited by the one or more rays of light propagating through the at least one waveguide.

Meta's patent FIG. 1 below illustrates an example of future AR glasses smartglasses with new Light Projectors and waveguide  configured to direct images from the light projector 106 to a user's eye. Shown below are light projector that may include three sub-projectors 106A, 106B, and 106C that are configured to project light of different wavelengths (e.g., colors such as red, green, and/or blue);   FIG. 2 illustrates an exploded view of the light projector #106 on the smartglasses in the dashed circle A of FIG. 1.

Meta's patent FIG. 4 below is a cross-sectional view of a head-mounted display with alignment cameras; FIG. 7A is a diagram illustrating a device having an exemplary waveguide and light projector of the smartglasses in the dashed circle B of FIG. 4. 

Meta's Optical Scientist Jian Xu was the inventor of this patent that was published in November.