Light engine polarization switching for birefringent waveguide substrates

Abstract

Embodiments of the present disclosure generally relate to near-eye display systems. More specifically, embodiments described herein provide a near-eye display system with a waveguide display assembly having a light engine with polarized light output and a polarization switch for projecting image light toward an input coupling grating of a waveguide combiner.

Description

44025720W001LIGHT ENGINE POLARIZATION SWITCHING FOR BIREFRINGENT WAVEGUIDE SUBSTRATES BACKGROUNDField

[0001] Embodiments described herein generally relate to near-eye display systems, and more specifically to near-eye display systems with waveguide display assemblies having light engines with polarized output light and a polarization switch.Description of the Related Art

[0002] Virtual reality (VR) is generally considered to be a computer generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display devices that have near-eye display panels as lenses to display a virtual reality environment that replaces an actual environment.

[0003] Augmented reality (AR), however, enables an experience in which a user can still see through the display lenses of the glasses or other HMD device to view the surrounding environment, yet also see images of virtual objects that are generated for display and appear as part of the environment. AR can include any type of input, such as audio and haptic inputs, as well as virtual images, graphics, and video that enhance or augment the environment that the user experiences. As an emerging technology, there are many challenges and design constraints with augmented reality.

[0004] In near-eye display systems, a light engine (or microdisplay) generates and outputs image content for display in the field of view of the user. Display light from the light engine is coupled into the waveguide combiner, which may be configured to distribute the incoming light across the waveguide combiner for output toward the eye of the user. Currently, the major competing microdisplay technologies include liquid-crystal-on-silicon (LCoS), digital light processing (DLP), organic light-emitting diode (OLED)-on-silicon, micro-LED (pLED), and laser beam scanning (LBS). As such, some of the microdisplays designed for AR output polarized light. For example, LCoS projectors or light engines are one of the microdisplays that produce polarized light. However, when polarized light is coupled into waveguide combiners formed on transparent birefringent crystalline substrates in near-eye displays, undesireable44025720W001Maltese Cross Interference artifacts may be outputted in the user’s field of view. As such, interference artifacts are an unwanted distraction to the user and it can be challenging to design the waveguide combiners to compensate for such artifacts thereby limiting the adoptability of light engines with polarized light output.

[0005] Accordingly, there is a need for improved near-eye display systems that eliminates or reduces artifacts displayed due to polarized light output by the light engine.SUMMARY

[0006] In an embodiment, a waveguide display assembly is provided. The waveguide display assembly includes a light engine, a waveguide combiner, and a polarization switch. The light engine is configured to project polarized light, and the polarization switch is configured to change a polarization state of polarized light transmitted therethrough between two or more polarization states. The waveguide display assembly also includes an input coupling grating for coupling light into the waveguide combiner in which polarized light from the light engine is coupled into the waveguide combinerafter having been transmitted through the polarization switch.

[0007] In another embodiment, a waveguide display assembly is provided. The waveguide display assembly includes a light engine to project polarized light; a Pi cell, and a waveguide combiner. The Pi cell is configured to change a polarization state of polarized light from the light engine based on a voltage state of the Pi cell. The waveguide display assembly also includes an input coupling grating for coupling polarized light transmitted through the Pi cell into the waveguide combiner. The polarized state of the polarized light transmitted through the Pi cell switches between two or more polarization states at a drive frequency greater than about 120 Hz.

[0008] In a further embodiment, a near-eye display system is provided. The near-eye display system includes a frame, a light engine to project polarized light, a polarization switch for changing a polarization state of polarized light transmitted therethrough, and a waveguide display. The waveguide display includes a waveguide combiner configured to extend across a user’s eye, an input coupling grating for coupling polarized light transmitted through the polarization switch into the waveguide combiner, and an output coupling grating for coupling light out of the waveguide44025720W001combiner to output an image within the field of view (FoV) of the user’s eye. The image output from the waveguide combiner is free of interference artifacts.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0010] Figure 1 illustrates a perspective view of a near-eye display system, according to certain embodiments of the present disclosure;

[0011] Figure 2 illustrates a cross-sectional view of the near-eye display system of Figure 1, according to certain embodiments of the present disclosure;

[0012] Figure 3 illustrates a schematic cross-sectional view of an exemplary waveguide display assembly, according to certain embodiments of the present disclosure;

[0013] Figure 4 illustrates a schematic cross-sectional view of an exemplary waveguide display assembly, according to certain embodiments;

[0014] Figures 5A and 5B illustrate schematic views of an exemplary Pi cell that may be used in a polarization switch for a waveguide display assembly, according to certain embodiments;

[0015] Figures 6A-6C illustrates changes in the image output by a waveguide combiner in a waveguide display assembly, according to certain embodiments; and

[0016] Figure 7 illustrates an exemplary driving signal for controlling a polarization switch used in a waveguide display assembly, according to certain embodiments.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is44025720W001contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.BRIEF DESCRIPTION OF THE APPENDIX

[0018] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appendix. It is to be noted, however, that the appendix illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.DETAILED DESCRIPTION

[0019] The embodiments of the present disclosure generally relate to waveguide display assemblies for near-eye display systems. More specifically, embodiments described herein relate to waveguide display assemblies with polarized light engines and polarization switches for projecting light towards waveguide combiners formed on transparent birefringent crystalline substrates. However, as discussed above, when polarized input light is coupled into a waveguide combiner formed with transparent birefringent crystalline substrates, undesirable Maltese interference artifacts can be output by the waveguide combiner in the field of view of the user. Accordingly, techniques of the present disclosure include implementation of a polarization switch to change the polarization state of the polarized input light projected by the polarized light engine. For example, a polarization switch may be used to change the polarization state of the polarized input light, effectively depolarizing the light so as to eliminate any Maltese interference artifacts perceived or registered by the user.

[0020] FIG. 1 illustrates a perspective view of a near-eye display system 100 according to certain embodiments of the present disclosure. The near-eye display system 100 can present media to a user. Examples of media presented by the near-eye display system 100 can include one or more images, video, and / or audio. In one embodiment, which can be combined with other embodiments, audio may be presented via an external device (e.g., speakers and / or headphones) that receives audio information from the near-eye display system 100, a console, or both, and presents audio data based on the audio information. The near-eye display system44025720W001100 is generally configured to operate as an artificial reality display. In one embodiment, which can be combined with other embodiments, the near-eye display system 100 can operate as an augmented reality (AR) display. The near-eye display system 100 includes optical components arranged to transport light of the desired media generated on the waveguide display to the user's eye to make the media visible to the user. The waveguide display of the near-eye display system 100 on which the image is generated can form part of a light engine, such that the image itself generates collimated lights beams, which can be guided by the optical components of the waveguide display to provide an image visible to the user.

[0021] In some embodiments, the optical components used to convey the image from the display to the user include optical waveguides and grating architectures. Such waveguide-based display systems typically transport light from a light engine to the eye via total internal reflection in a waveguide combiner. Such systems can also incorporate diffraction gratings, which cause effective beam expansion to output expanded versions of the beams provided by the light engine. This causes the image to be visible to the user over a wider area when looking at the waveguide's output than when looking at the light engine directly. In such near-eye display systems, the area or spatial volume within which the eye of the user would need to be in to receive some light from substantially most or all of the expanded beams such that the whole image is visible to the user is referred to as the “eyebox.” The eyebox may be thought of as a volume in space positioned near the optical device. When the eye of the user (and more particularly, the pupil of the eye of the user) is positioned inside this volume and facing the device, the user is able to see all of the content / imagery provided by the device. When the eye of the user is positioned outside of this volume, the user is not able to see at least some of the content / imagery provided by the device.

[0022] The near-eye display system 100 can include a frame 110, a left display system 120L, and a right display system 120R. The left display system 120L may be supported in a left portion 130L of the frame 110. The right display system 120R may be supported in a right portion 130R of the frame 110. The frame 110 may include any suitable type of mounting structures to mount the right display system 120R and the left display system 120L adjacent a user's eyes. The right display system 120R and the left display system 120L may be configured to enable the user to view content presented by the near-eye display system 100. The left and right portions 130L, 130R44025720W001of the frame 110 connect at a central portion 150. The central portion 150 of the frame 110 is intended to fit over the nose bridge of a user. The frame 110 also includes a left temporal extension 160L and a right temporal extension 160R configured to fit over the user’s ears. The frame 110 can be coupled to one or more optical components. In some embodiments, the right display system 120R and the left display system 120L may include any suitable display assembly (not shown) configured to generate a virtual image or an image light of the virtual image and to direct the image light to an eye of the user.

[0023] FIG. 2 illustrates a schematic cross-sectional view of the near-eye display system 100 of FIG. 1, according to certain embodiments of the present disclosure. FIG. 2 shows the cross-sectional portion of the near-eye display system 100 associated with the left display system 120L. In some embodiments, the left display system 120L may include a waveguide display assembly 210. The waveguide display assembly 210 is configured to direct image light, for example display light, to an eyebox plane 220 defining an eyebox and then to a user’s eye 230. The waveguide display assembly 210 can include one or more materials with one or more refractive indices. In one embodiment, which can be combined with other embodiments, the near-eye display system 100 can include one or more optical elements between the waveguide display assembly 210 and the user’s eye 230. The waveguide display assembly 210 may effectively minimize the weight and widen the field of view (“FoV”) of the near-eye display system 100. In one embodiment, which can be combined with other embodiments, the near-eye display system 100 can include one or more optical elements between the waveguide display assembly 210 and the user’s eye 230. Examples of the one or more optical elements may include an aperture, a Fresnel lens, a convex lens, a concave lens, a filter, or any other suitable optical element that affects an image light. In some embodiments, the waveguide display assembly 210 may include a stack of waveguide displays.

[0024] FIG. 2 shows the left display system 120L associated with an eye 230 and a waveguide display assembly 210. As shown, the waveguide display assembly 210 may be for one eye 230 of the user. The waveguide display assembly 210 for one eye, such as the one eye 230, may be separated or partially separated from the waveguide display assembly 210 for the other eye of the user. In certain embodiments, a single waveguide display assembly may be used for both eyes of the44025720W001user. In some embodiments, another display assembly that is separate from the waveguide display assembly 210 shown in FIG. 2 may provide the image light to an eye-box for the other eye of the user.

[0025] FIG. 3 illustrates a schematic cross-sectional view of a waveguide display assembly 300 according to one or more embodiments of the present disclosure. The waveguide display assembly 300 may be used as the waveguide display assembly 210 in FIG. 2. In some embodiments, the waveguide display assembly 300 includes a polarized light engine, such as a projector 310. The waveguide display assembly 300 also includes a polarization switch 320 and a waveguide combiner 330. The projector 310 may function as a source of light for the waveguide combiner 330 and may be utilized to inject image information into the waveguide combiner 330. In an embodiment, the projector 310 may output such image information to the waveguide combiner 330 as polarized display light. The waveguide combiner 330 in turn may be configured to distribute the incoming light from the projector 310 across the waveguide combiner 330, for output toward an eye 230.

[0026] Display light from the projector 310 is directed through the polarization switch 320 and coupled into the waveguide combiner 330 by the input coupling grating 340. The polarization switch 320 may be integrated with the projector 310 ora distinct (i.e., separate) device disposed in front of the projector 310 between the projector 310 and the waveguide combiner 330. The polarization switch 320 may be configured to switch the polarization state of the light transmitted from the projector 310 (if integrated with the projector 310) or the light to be incoupled by the waveguide combiner 330 (if external to the projector 310) between two or more polarization states. Examples of polarization switches include Pi cells, ECB nematic mode cells, VA mode cells, Blue Phase cells, or a tunable retardation birefringent material. In an embodiment, the polarization switch 320 is implemented using Pi cells.

[0027] The waveguide combiner 330 may be configured to propagate light from the projector 310 within the waveguide combiner 330 by total internal reflection (TIR). In some embodiments, the waveguide combiner 330 further includes an input coupling grating 340 and an output coupling grating 350. Polarized display light from the projector 310 can be coupled into the waveguide combiner 330 by an input coupling optical element, such as the input coupling grating 340. Once coupled into the44025720W001waveguide combiner 330, the display light can be partially coupled out of the waveguide combiner 330 at different locations by the output coupling grating 350 to reach the user’s eye 230. In some embodiments, the projector 310, or one or more components thereof, may be attached to the frame 110. For example, the projector 310 may be part of the left and right temporal extensions 160L, 160R of the frame 110 or disposed at an edge of the waveguide display assemblies 210.

[0028] In some embodiments, the output coupling grating 350 may be configured to extract light out of the waveguide combiner 330 by redirecting the light propagating within out of the waveguide combiner 330 to output image information to the eye 230. Extracted light may also be referred to as out-coupled light and the output coupling grating 350 may be referred to as light extracting optical elements. An extracted beam of light may be output by the waveguide combiner 330 at locations at which the light propagating in the waveguide combiner 330 strikes a light extracting optical element of the output coupling grating 350. The output coupling grating 350 may be disposed at the left and / or right major surfaces (e.g., the output coupling grating 350 is disposed on the right major surface as shown in FIG. 3), and / or may be disposed directly in the volume of the waveguide combiner 330.

[0029] In some embodiments, the output coupling grating 350 may be formed in a layer of material that is attached to a transparent substrate to form the waveguide combiner 330. The waveguide combiner 330 may each be planar or have another shape (e.g., curved). In some embodiments, the waveguide combiner 330 may be a surface relief grating (SRG) waveguide fabricated using transparent birefringent crystalline substrates (Ex: SiC, LiNbO3). In some other embodiments, the waveguide combiner 330 may be a monolithic piece of material and the output coupling grating 350 may be formed on a surface and / or in the interior of that piece of material.

[0030] FIG. 4 illustrates a schematic cross-sectional view of a waveguide display assembly 410 according to one or more embodiments of the present disclosure. In an embodiment, waveguide display assembly 410 includes a polarization switch 420 having a Pi cell 430 connected to a voltage source 440, according to certain embodiments. Polarized light from the projector 310 is transmitted through the polarization switch 420 prior to being coupled into the waveguide combiner 330. The Pi cell 430 of the polarization switch 420 include a voltage-reactive liquid crystal layer44025720W001(further shown and described in FIG. 5) disposed between two electrode layers. In an embodiment, the voltage source 440 may be driven by a driving signal provided by a function generator (not shown) so as to control the voltage applied to the Pi cell 430 by the voltage source 440. When a voltage is applied to the polarization switch 420, the electrodes deliver an electric field across the liquid crystal layer and cause the liquid crystal molecules to react and change orientations. The liquid crystal molecules of the liquid crystal layer near the electrode layers react and respond differently from the liquid crystals near the center of the liquid crystal layer, resulting in two boundary-controlled regions with a distinct central switching region. Specifically, the liquid crystals in the central switching region respond with a rotation angle different from the liquid crystals in the boundary-controlled regions near the electrodes. These voltage-reactive spatial regions of the liquid crystal layer enable the fast and precise electrooptic responses of Pi cells. The switching in orientation of the liquid crystals in the Pi cell in turn operate as shutters / light modulators to change the polarization of the polarized input light transmitted through the polarization switch 420. Pi cells are widely-available, small, low cost, require minimal power, and can switch the polarization states of transmitted light faster than the human eye can perceive (i.e. >120 Hz).

[0031] FIGs. 5A and 5B show cross-sectional views of a Pi cell 500 that may be used in the polarization switch 420, according to certain embodiments. In an embodiment, the Pi cell 500 includes a first and second glass layer 502 each coupled to a first and second electrode layer 504, and a liquid crystal layer 508 having a plurality of liquid crystals 506 disposed between the first and second electrode layers 504. In an embodiment, the first and second electrode layers 504 may each comprise an indium tin oxide (ITO) layer.

[0032] FIG. 5A shows the orientation of the liquid crystals 506 when a high voltage is applied by the voltage source 440 to the Pi cell 500, according to certain embodiments. As the voltage applied to the Pi cell 500 is changed, the resulting change in the electric field across the liquid crystal layer 508 causes the liquid crystals 506 to react and change orientation. FIG. 5B shows the orientation of the liquid crystals 506 when the voltage source 440 switches to applying a low voltage to the Pi cell 500, according to certain embodiments. As shown, the change in voltage causes44025720W001the orientation of the liquid crystals 506 to change from a vertical state in FIG. 5A to a horizontal state in FIG. 5B.

[0033] In an embodiment, the Pi cell 500 used for the polarization switch 420 may be larger than the pupil size of the input light transmitted between the output of the projector 310 and the input coupling grating 340 of the waveguide combiner 330. In an embodiment, as input light is being transmitted through the Pi cell 500, the change in orientation of the liquid crystals 506 depolarizes or causes a change in the polarization state of the polarized light transmitted therethrough. As implemented in the waveguide display assembly 410, the changing in the orientation of the liquid crystals 506 in the Pi cell 500 by the Pi cell 500 can in turn cause the polarization state of the transmitted light to change accordingly . For example, the switching of the orientation of the liquid crystals 506 in response to the change in the applied voltage (e.g., -30 V to 30V) can change the polarization state of the transmitted input light from the projector 310 between 0°and 90° rotations, or between 0°, 45°, and 90° rotations. In an embodiment, the time-varying voltage state of the Pi cell 500 may be controlled by the voltage source 440 according to a driving signal having a carrier frequency. The carrier frequency of the driving signal may in turn control and enable the polarization switch 420 to change the polarization state of light transmitted therethrough at a corresponding driving frequency. In an embodiment, the driving signal may have a signal (modulating) frequency of about 1kHz and a carrier frequency of about 120 Hz. In such an embodiment, the carrier frequency of the driving signal provides for a switching of the polarization state of light transmitted therethrough at a corresponding driving frequency of 120 Hz. In an embodiment, the driving signal may have a carrier frequency higher than the liquid crystal relaxation rate, such as being greater than about 250 Hz.

[0034] FIGs. 6A-6C show examples of image output 600 from the waveguide combiner within the field of view (FoV) of the user, according to certain embodiments. As the polarization state of the input light is changed by the polarization switch 420, Maltese cross interference artifacts 602 visible to the user in the corresponding outputted image 600 from the transmitted input light may also correspondingly change. For example, FIGs. 6A - 6C show each of the image output resulting from input light coupled into and out of the waveguide combiner 330 with polarization states of 0°, 45°, and 90° rotations, respectively. In each of the images shown, the visible44025720W001interference artifacts 602 in the image output within the FoV of the user is in a different position. In an embodiment, the image output may therefore change at the same rate as the change in the polarization state of the input light by the polarization switch 420 (e.g., the driving frequency). The change in the position of the visible interference artifacts 602 between the different image outputs 600 correspondingly also provides for different uninhibited regions 604 of the image output 600 free of the interference artifacts 602 to be visible to the user. In an embodiment, between all of the uninhibited regions 604 of the three image outputs 600 shown, the uninhibited regions 604 of each of the three different image outputs 600, when combined is sufficient to cover the entirety of the image output 600.

[0035] Without being bound by theory, as the human eye is unable to perceive changes occurring at >120 Hz, it is believed that when the polarization state of the input light from the projector 310 and coupled into the waveguide combiner 330 is switched at a high enough rate (i.e. driving frequency > than about 120 Hz), the corresponding switching of the resulting image output 600 causes the uninhibited regions 604 of each of the changing image outputs 600 to average over the interference artifacts 602. In an emboidment, the changing of the image outputs 600 at a rate > than about 120 smooths the resulting displayed image output actually perceived and registered by the user. Accordingly, the switching of the different corresponding image outputs 600 results in the display of an image output that is perceived by the user as being free of any interference artifact 602.

[0036] FIG. 7 is a graph of an exemplary driving signal for controlling a polarization switch in the waveguide display assembly, according to certain embodiments. In an embodiment, the phase switching between crystal orientation states in the Pi cell 500 may be controlled by a driving signal delivered to the voltage source 440. In some embodiments, the driving signal may be a sinusoidal signal as shown in FIG. 7. In other embodiments, the driving signal may be a square signal and the like for controlling and switching the voltage applied by the voltage source to the Pi cell 500. As such, the driving signal provides for manipulating and switching the voltage state of the Pi cell. In some embodiments, the driving signal provides for manipulating the output voltage applied to the Pi cell 500, for example, the driving signal may provide for switching the voltage state of the Pi cell 500 between about -30 V and about 30 V.44025720W001

[0037] The switching of the voltage state of the Pi cells by the driving signal provides for rapid changing of the distinct molecular orientations of the liquid crystals 506 in the Pi cell 500 corresponding to the frequency of the driving signal. The change in molecular orientation of the liquid crystals 506 results in a change in the polarization state of light projected by the projector 310 and transmitted through the Pi cell 500 of the polarization switch 420 towards the waveguide combiner 330. The corresponding switching in polarization state of the transmitted light through the Pi cell 500 according to the changing in the orientation of the liquid crystals 506 (driven by the frequency of the driving signal) in turn also provide for switching the resulting output images at the same frequency.

[0038] In summation, the embodiments of the present disclosure described herein relate to waveguide display assemblies, namely waveguide display assemblies with light engines having polarized light output and polarization switches for eliminating interference artifacts output by a waveguide combiner fabricated using transparent birefringent crystalline substrates. The present disclosure provides the benefit of effectively allowing light engines with polarized light output to be used with transparent birefringent crystalline substrate waveguides.

[0039] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

44025720W001What is claimed is:

1. A waveguide display assembly, comprising:a light engine to project polarized light;a waveguide combiner;a polarization switch configured to change a polarization state of polarized light transmitted therethrough between two or more polarization states; andan input coupling grating for coupling light into the waveguide combiner, wherein polarized light from the light engine is coupled into the waveguide combiner after having been transmitted through the polarization switch.

2. The waveguide display assembly of claim 1 , further comprising an output coupling grating for coupling light out of the waveguide combiner and displaying an image output within a field of view (FoV) of a user, wherein the change of the polarization state of polarized light coupled into the waveguide combiner causes viewable interference artifacts in the image output to correspondingly also change.

3. The waveguide display assembly of claim 1 , wherein polarized light transmitted through the polarization switch is coupled into the waveguide combiner in one of two or more polarization states.

4. The waveguide display assembly of claim 1 , wherein the polarization switch comprises a Pi cell connected to a voltage source, and the Pi cell changes the polarization state of polarized light transmitted therethrough based on a voltage state of the Pi cell.

5. The waveguide display assembly of claim 4, wherein the voltage state of the Pi cell is controlled by a driving signal delivered to the voltage source.

6. The waveguide display assembly of claim 1 , wherein the polarization switch changes the polarization state of polarized light transmitted therethrough at a driving frequency of about 120 Hz or greater.

7. The waveguide display assembly of claim 1 , wherein the polarization switch changes the polarization state of polarized light transmitted therethrough between 0°and 90° rotations.

8. The waveguide display assembly of claim 1 , wherein the polarization switch changes the polarization state of polarized light transmitted therethrough between 0°, 45°, and 90° rotations.44025720W0019. The waveguide display assembly of claim 2, wherein the change in the polarization state of polarized light coupled into and transmitted through the waveguide combiner correspondingly causes the image output within the field of view (FoV) of the user to be free of viewable interference artifacts.

10. The waveguide display assembly of claim 2, wherein the change of the image output by the output coupling grating at a driving frequency greater than about 120 Hz causes the image output within the field of view (FoV) of the user by the output coupling grating to be free of viewable interference artifacts.

11. The waveguide display assembly of claim 1 , wherein the polarization switch comprises Pi cells, ECB nematic mode cells, VA mode cells, Blue Phase cells, or a tunable retardation birefringent material.

12. A waveguide display assembly, comprising:a light engine to project polarized light;a Pi cell configured to change a polarization state of polarized light from the light engine based on a voltage state of the Pi cell;a waveguide combiner; andan input coupling grating for coupling polarized light transmitted from the light engine and through the Pi cell into the waveguide combiner, wherein the polarized state of the polarized light transmitted through the Pi cell switches between two or more polarization states at a drive frequency greater than about 120 Hz.

13. The waveguide display assembly of claim 12, further comprising a voltage source connected to the Pi cell, wherein the voltage state of the Pi cell is controlled by a driving signal delivered to the voltage source.

14. The waveguide display assembly of claim 13, wherein the driving signal comprises a drive frequency greater than about 250 Hz.

15. The waveguide display assembly of claim 13, wherein the driving signal comprises a drive frequency greater than about 120 Hz and a signal frequency of about 1 kHz.

16. The waveguide display assembly of claim 12, wherein the Pi cell switches the polarization state of polarized light transmitted therethrough between 0°and 90° rotations.44025720W00117. The waveguide display assembly of claim 12, wherein the Pi cell switches the polarization state of polarized light transmitted therethrough between 0°, 45°, and 90° rotations.

18. A near-eye display system, comprising:a frame;a light engine to project polarized light;a polarization switch for changing a polarization state of polarized light transmitted therethrough; anda waveguide display comprising:a waveguide combiner configured to extend across a user’s eye; an input coupling grating for coupling polarized light transmitted through the polarization switch into the waveguide combiner; andan output coupling grating for coupling light out of the waveguide combiner to output an image within a field of view (FoV) of the user’s eye that is free of interference artifacts.

19. The near-eye display system of claim 18, wherein the polarization switch is integrated with the light engineer and configured to change the polarization state of polarized light transmitted from the light engine.

20. The near-eye display system of claim 18, wherein the polarization switch is configured to change the polarization state of polarized light to be coupled into the waveguide combiner by the input coupling grating.

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