Valve patent proposes polarization multiplexing optical elements for AR/VR headsets

CheckCitation/SourcePlease click:XR Navigation Network

(XR Navigation Network December 11, 2023）很难设计一个在头显显示系统的整个视场范围内或所需波长提供可接受校正的衍射光学元件。所以在名为“Polarization-multiplexed optics for head-mounted display systems”的专利中，Valve提出了一种用于头显的偏振多路复用光学元件。

by combiningeye tracking，所述光学元件可以根据整体视场的视场部分对来自光源的光进行偏振，或者通过根据颜色对来自光源的光进行偏振，第一和第二偏振敏感衍射光学元件中的每一个都可以针对较小的视场进行优化或者第一和第二偏振敏感衍射光学元件和中的每一个都可以优化为更窄的波长范围，从而允许更大的设计自由度并最终通过整体光学组合器902进行更好的校正。

FIG. 5 is a schematic block diagram of a display system 500. Display system 500 includes a display light source 502 optically coupled to a pupil relay system 504 . Pupil relay system 504 is positioned to relay a first pupil from the display light source 502 to a second pupil located at the user's eye 506 .

Pupil relay system 504 includes polarization sensitive optics 508 . Polarization sensitive optics 508 can be very sensitive to the polarization of light passing through it. In other words, different polarizations will significantly change the intensity and stray light.

In order to optimize the polarization of the light provided to the polarization sensitive optic 508, the pupil relay system 504 of the display system 500 also includes a spatially varying polarizer 510 with a polarization that varies spatially with position, which functions to compensate for changes in polarization. to provide uniform polarized light.

For example, polarization sensitive optics 508 may be configured to compensate for any polarization produced from composite angles by one or more mirrors or other optics. The spatially varying polarizer 510 may be selectively adjusted in real time to provide optimized performance in an area or field of view based on the user's gaze location.

Spatially varying polarizer 510 may include a wave barrier formed from a birefringent material. Birefringence is a property of a material whose refractive index depends on the polarization and direction of propagation of light. A moderator changes the polarization state or phase of light passing through the moderator. Retarder can have slow axis and fast axis. When polarized light passes through a wave retarder, the light travels faster along the fast axis than along the slow axis.

As discussed above, the spatially varying polarizer 510 can provide a phase retardation that changes as a function of position to allow a more even and efficient distribution of light from the display light source 502 to the polarization sensitive optic 508 . The specific manner in which the retardation of spatially varying polarizer 510 varies may depend on the specific configuration and materials of the optical system of display system 500, such as the polarization state of the incident light, angle of incidence, materials, geometry of the various components, etc.

As an example, spatially varying polarizer 510 may provide no retardation in a first position, and may linearly increase the retardation to provide a retardation of λ/4 in a second position of the spatially varying polarizer. In general, spatially varying polarizer 510 can provide retardation that varies in any manner as a function of position, and the amount of retardation can be any value, such as λ/20, λ/10, λ/4, λ, 2λ.

In at least one embodiment, spatially varying polarizer 510 may be formed from MTR. MTR consists of two or more twisted liquid crystal LC layers on a single substrate. Subsequent LC layers are directly aligned by the previous layer, which allows simple fabrication, enables automatic layer registration, and produces monolithic films with continuously varying optical axes.

Figure 7 is a schematic diagram of a scanning beam display system or projector 700. Post-scan optics 702 may include waveguide-based optics, Pancake optics, and the like. The post-scan optics may include more than one element. The efficiency of post-scan optics 702 may be very sensitive to the polarization of the light passing through it.

Display system 700 also includes polarization compensation optics in the form of spatially varying polarizer 706 . Polarization compensation optics are located between scan mirror 608 and post-scan optics 702 to provide polarization compensation for post-scan optics 702 .

In at least one embodiment, the controller 612 is operatively coupled to the spatially varying polarizer 706 to selectively change the spatially dependent phase delay of the spatially varying polarizer to any desired configuration.

In such implementations, one or more thin film transistor layers may be provided, allowing the spatially dependent phase delay of the spatially varying polarizer 706 to be selectively controlled by the controller 612. Controller 612 may control the phase delay at any desired rate, such as only once, periodically, at a rate equal to the frame rate of display system 700 or a portion thereof, etc.

In at least one embodiment, the controller 612 may be operable to receive eye tracking information 708 for selectively adjusting the spatially dependent phase delay of the spatially varying polarizer 706 to optimize in the optimization area where the user is currently looking.

Optimizing the spatial variation of the polarizer 706 over a relatively small area or field of view is advantageous and can provide significantly better performance than optimizing over the entire field of view. Using eye-tracking information, the system can optimize various characteristics of an area (such as intensity) while configuring areas outside of a specific area to have lower performance, such as lower intensity and more stray light. Since the user's vision is less acute in the peripheral area, the user may not even notice it. This can reduce overall system performance.

In Figure 8, a display system 800 includes a waveguide-based optical system and a polarization compensation optical system in the form of a spatially varying polarizer.

A spatially varying polarizer 812 is located adjacent the coupler 806 to provide polarization compensation for light entering the waveguide 804 . For example, spatially varying polarizer 812 may be located on, adjacent to, or within waveguide 804.

In at least one embodiment, spatially varying polarizers 812 are located on adjacent sides of coupler 806 or outcoupler 808 , for example. In other embodiments, spatially varying polarizer 812 is located elsewhere in the light path between the display light source and the user's eyes to provide polarization compensation.

The display system 900 of the augmented reality system of Figure 9 can utilize polarization multiplexing to provide a waveguide structure that is optimized over wavelength.

To enable coupling of light into the optical combiner 902, the display system 900 includes a coupler 806 physically coupled to a first portion of the optical combiner 902, and a second portion of the optical combiner physically coupled to the first portion. of coupler 808.

In the embodiment shown, optical engine 908 includes a selective polarizer optical element 912 located in front of light source 910 . Selective polarizer optical element 912 may be formed from a liquid crystal material. Selective polarizer optics 912 receive light 916 that includes multiple wavelengths or colors Cl, C2, C3 (eg, red, green, blue).

The selective polarizer optics 912 can be used to receive light 916 from the display light source 910 and can be used to output first color (1) light 918 in a first polarization state (P1) and a second polarization state P2. At least a second color (C2 or C3) light, wherein the second polarization state is orthogonal to the first polarization state.

The light combiner 902 includes a first polarization sensitive diffractive optical element 904 and a second polarization sensitive diffractive optical element 906 . Each of the first and second polarization sensitive diffractive optical elements may be formed from a liquid crystal material.

The first polarization sensitive diffractive optical element 904 includes a first diffraction pattern that diffracts light of a first polarization state (P1) and passes light of a second polarization state (P2) without diffracting. Similarly, the second polarization sensitive diffractive optical element 906 includes a second diffraction pattern that diffracts light of the second polarization state (P2) and passes light of the first polarization state (P1) without diffracting. The first diffraction pattern is designed to provide optimized correction for a first color (C1) and the second diffraction pattern is designed to provide optimized correction for at least a second color (C2 and or C3).

As mentioned above, it is difficult to design diffractive optical elements that provide acceptable correction at all desired wavelengths. By polarizing the light from the light source 910 according to color, each of the first and second polarization sensitive diffractive optical elements 904 and 906 can be optimized for a narrower wavelength range, allowing greater design freedom and ultimately passing The integral optical combiner 902 performs better correction.

Continuing with the above example, the first polarization sensitive diffractive optical element 904 can be optimized only for red light (C1) in the first polarization state (P1) because the first polarization sensitive diffractive optical element will not see the second polarization state (P2 ) green or blue light. Likewise, the second polarization sensitive diffractive optical element 906 may be optimized only for green light (C2) and blue light (C3) in the second polarization state (P2), since the second polarization sensitive diffractive optical element 906 will not be visible in the first polarization state (P2). Red light (C1) in polarization state (P1).

11A illustrates an example total field of view 1100 for a head-mounted display system, including a first field of view portion 1102 having a narrow angular range surrounded by a second field of view portion 1104.

The light combiner 1002 includes a first polarization sensitive diffractive optical element 1004 and a second polarization sensitive diffractive optical element 1006. Each of the first and second polarization sensitive diffractive optical elements may be formed from a liquid crystal material.

The first polarization sensitive diffractive optical element 1004 includes a first diffraction pattern that diffracts light of a first polarization state (P1) and passes light of a second polarization state (P2) without diffracting. Similarly, the second polarization-sensitive diffractive optical element 1009 includes a second diffraction pattern that diffracts light of the second polarization state (P2) and passes light of the first polarization state (P1) without diffracting. The first diffraction pattern is designed to provide optimal correction for a first portion of the field of view, and the second diffraction pattern is designed to provide optimal correction for a second portion of the field of view.

As mentioned above, it is difficult to design a diffractive optical element that provides acceptable correction over the entire field of view of the display system. By polarizing light from the light source 1010 according to a portion of the overall field of view, each of the first and second polarization sensitive diffractive optical elements 1004 and 1006 can be optimized for smaller fields of view, allowing for more design freedom and ultimately better correction through the integral optical combiner 1002.

Valve points out that by utilizing the spatially varying polarizers discussed above, optical designers will have significantly more freedom to produce optical systems with improved performance and efficiency.

Valve's patent application titled "Polarization-multiplexed optics for head-mounted display systems" was originally submitted in July 2023 and was recently published by the United States Patent and Trademark Office.

Generally speaking, after a U.S. patent application is examined, it will be automatically published 18 months from the filing date or priority date, or it will be published within 18 months from the filing date at the request of the applicant. Note that publication of a patent application does not mean that the patent is approved. After a patent application is filed, the USPTO requires actual review, which can take anywhere from 1 to 3 years.