Waveguide for display panel

Abstract

Aspects of the present disclosure provide an apparatus for improving performance of an output coupler of a waveguide display panel, such as reducing eye glare. An example waveguide includes an anti-reflective coating. The waveguide further includes a substrate disposed over the anti-reflective coating, wherein the substrate includes a refractive index of from 1.5 to 2.7. The waveguide further comprises a grating layer disposed over the substrate, the grating layer comprising: an output coupler grating, the output coupler grating comprising a refractive index of 2.1 to 2.5; and a coating layer covering the output coupler grating, where the coating layer includes a refractive index of from 1.5 to 1.9.

Description

Technical Field

[0001] This disclosure generally relates to an optical device. More specifically, the embodiments described herein provide a waveguide with an improved output coupler for a display panel. Background Technology

[0002] Virtual reality is generally considered to be a computer-generated simulation environment in which the user has an apparent physical presence. Virtual reality experiences can be generated in three dimensions and viewed using head-mounted displays (HMDs), such as glasses or other wearable display devices, which have near-eye display panels as lenses to display a virtual environment that substitutes for the real environment.

[0003] However, augmented reality enables experiences where users can still see their surroundings through the display lenses of glasses or other HMD devices, and also see images of virtual objects generated for display and appearing as part of the environment. Augmented reality can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and videos of the environment that enhance or amplify the user experience. As an emerging technology, augmented reality faces many challenges and design constraints.

[0004] One such challenge is displaying a virtual image superimposed on the surrounding environment. Optical devices, including waveguide combiners (such as augmented reality waveguide combiners) and planar optical devices (such as metasurfaces), are used to aid in this image superposition. The generated light is propagated through the optical device until it exits and superimposes onto the surrounding environment. The optical device can use a diffractive waveguide with a surface-embossed grating as an output coupler to couple the light output to the user's eye. In some cases, the surface-embossed grating may cause some light to leak from the near-eye display away from the user. This leakage is often referred to as eye glow. In some cases, the surface-embossed grating can provide different diffraction efficiencies for certain color bands, resulting in varying color intensities.

[0005] Therefore, there is a need in the art for improved output couplers for waveguide display panels. Summary of the Invention

[0006] Some aspects provide a waveguide. The waveguide includes an anti-reflective coating. The waveguide further includes a substrate disposed above the anti-reflective coating, wherein the substrate has a refractive index of 1.5 to 2.7. The waveguide further includes a grating layer disposed above the substrate, the grating layer including: an output coupler grating having a refractive index of 2.1 to 2.5; and a coating covering the output coupler grating, wherein the coating has a refractive index of 1.5 to 1.9.

[0007] Some aspects provide a display device. The display device includes a waveguide and an optical emitter. The waveguide includes an anti-reflective coating and a substrate disposed above the anti-reflective coating, wherein the substrate has a refractive index of 1.5 to 2.7. The waveguide further includes a grating layer disposed above the substrate, the grating layer including: an output coupler grating having a refractive index of 2.1 to 2.5; and a coating covering the output coupler grating, wherein the coating has a refractive index of 1.5 to 1.9. The optical emitter is optically coupled to the waveguide. Attached Figure Description

[0008] To gain a more detailed understanding of the features described above in this disclosure, a more specific description of the disclosure, which has been briefly summarized above, can be obtained with reference to the embodiments illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate exemplary embodiments only and should not be construed as limiting the scope of this disclosure, and other equally effective embodiments are appreciated.

[0009] Figure 1 This is a diagram illustrating an example display device using a single waveguide.

[0010] Figure 2 This is a diagram illustrating an example waveguide with an improved output coupler structure.

[0011] Figure 3 It is a description of the article about Figure 2 A graph showing the diffraction efficiency versus grating thickness associated with the described example waveguide structure.

[0012] Figure 4A and Figure 4B It is a description of the article about Figure 2 The example waveguide structure is associated with a user-to-world ratio chart.

[0013] Figure 5 This is a graph illustrating the diffraction efficiency of example gratings with and without coatings for different grating thicknesses.

[0014] Figure 6 This is a graph showing the diffraction efficiency of an example waveguide for blue, green, and red beams, respectively.

[0015] Figure 7A and Figure 7B This is a cross-sectional view illustrating example waveguides with angular etched gratings and blaze gratings, respectively.

[0016] Figure 8 This is a cross-sectional view illustrating an example waveguide with a confocal coating.

[0017] Figure 9A and Figure 9B These are cross-sectional views illustrating example waveguides with variable thicknesses and refractive gradient layers.

[0018] For ease of understanding, common elements in the figures have been designated using the same element symbols where possible. It is envisioned that elements and features of one embodiment may be beneficially incorporated into other embodiments without further description. Detailed Implementation

[0019] This disclosure provides an apparatus for improving the performance of the output coupler of a waveguide display panel.

[0020] For example, surface relief grating (SRG) on waveguide display panels used in augmented reality devices can produce eye glow, which can be expressed as the ratio of light traveling from the user's eyes to the outside world to the light traveling into the user's eyes. As an example, some commercially available augmented reality devices use double-sided binary (symmetric) gratings, while others use double-sided imprinted tilted (asymmetric) gratings for their output couplers to produce approximately 40% to 60% eye glow. Light leakage associated with eye glow can cause some of the light energy from the optical emitter to be wasted, and therefore, light leakage can affect the power consumption of portable headphones or glasses. In some cases, light leakage can affect a user's ability to engage in social communication via eye contact, as it prevents others from making eye contact with a user who is not making eye contact. In some situations, light leakage can make the content being displayed to the user less private, as others can see the content through the leakage. To reduce the effects of eye glow, some commercially available waveguides deflect eye glow to different angles by tilting the eyeglass frame. However, in addition to the inability to guarantee content privacy, frame tilt may also result in non-overlapping binocular field of view (FOV).

[0021] This disclosure provides an output coupler for a waveguide display panel that reduces eye glare and improves color uniformity. A single or multiple anti-reflective coating can be arranged to cover a substrate having an asymmetric grating to promote enhanced user-to-world ratio. In some cases, one or more layers can be arranged between the substrate and the asymmetric grating to improve color uniformity and / or reduce eye glare. As an example, a single-layer waveguide can have a substrate disposed between an anti-reflective layer and a refractive gradient layer having a refractive index greater than that of the substrate. An asymmetric grating can be disposed above the refractive gradient layer, and a coating can be arranged to cover the grating. This coating can be designed to reduce diffraction efficiency and improve the color uniformity of the output coupler.

[0022] The waveguide structures described herein offer various advantages. For example, they can reduce light leakage (e.g., eye glare) emanating from the waveguide. In some cases, eye glare from the waveguide structure can be reduced to, for example, only 0.05% to 10%. Reduced light leakage improves the performance of the display device by effectively utilizing the light emitted from the optical emitter. In some cases, reduced light leakage can improve the user experience by facilitating social interaction via eye contact. Reduced light leakage ensures user privacy when viewing content through the display panel. The waveguide structures described herein provide improved color uniformity across multiple color bands (e.g., blue, green, and red bands). This color uniformity of the waveguide structure promotes improved performance of a single-layer waveguide (e.g., a waveguide configured to guide multiple color bands, such as red, blue, and green bands) across multiple color bands.

[0023] Figure 1 This is an illustration of an example display device 100 using a single-layer waveguide. In this example, display device 100 may include an optical emitter 102 and a waveguide 104. Display device 100 may be included in an augmented reality device, such as augmented reality headphones, glasses, or a display. Optical emitter 102 may be optically coupled to waveguide 104. As an example, optical emitter 102 may include any suitable device capable of emitting electromagnetic waves in the spectrum, such as a light-emitting diode (LED) and / or a laser. Optical emitter 102 may output light in one or more spectral bands, including, for example, a blue band, a green band, and / or a red band.

[0024] Waveguide 104 may include an output coupler section 106 that diffracts light guided via waveguide 104 toward the user's eye 108. As further described herein, waveguide 104 may be configured to reduce light leakage away from the user's eye 108 (e.g., reduce eye glare) and / or improve color uniformity (e.g., reduce rainbow effect).

[0025] Figure 2 This is a cross-sectional view of an example waveguide 200 illustrating an improved output coupler structure. In this example, waveguide 200 can represent, for example... Figure 1 This depicts a portion of the output coupler segment 106. In some aspects, waveguide 200 may include a single-layer waveguide configured to guide multiple optical bands, including, for example, a blue band, a green band, a red band, or a combination thereof. In some cases, waveguide 200 may include multiple waveguide layers (not illustrated), such as a first waveguide for the blue band, a second waveguide for the green band, and a third waveguide for the red band. As shown, waveguide 200 includes an anti-reflective coating 202, a substrate 204, and a grating layer 206. In some cases, waveguide 200 may further include one or more refractive gradient layers 212a, 212b (collectively referred to as refractive gradient layer 212).

[0026] The anti-reflective coating 202 has a refractive index (n) ar1 The refractive index (n) can be less than that of substrate 204. sub The anti-reflective coating 202 allows light to be guided through the waveguide 200 via the substrate 204. For example, the anti-reflective coating 202 may cause reflected light to... Figure 1 The image depicts the object traveling through the substrate 204 and eventually through the grating layer 206 to reach the user's eye 108.

[0027] Substrate 204 may be disposed above antireflective coating 202. In some aspects, substrate 204 may be or comprise any suitable substrate material, such as silicon oxide (SiO2). x ), silicon carbide (SiC), lithium niobate (LiNbO) x ) or any combination thereof. As an example, substrate 204 may comprise a waveguide core material, such as glass (including quartz glass). The refractive index (n) of substrate 204 is... sub The value can be, for example, 1.5 to 2.7. In some aspects, the substrate 204 may include one or more sheets or layers of waveguide material (not shown).

[0028] A refractive gradient layer 212 can provide a refractive gradient between the substrate 204 and the grating layer 206. The refractive gradient layer 212 can be disposed between the substrate 204 and the grating layer 206. The refractive index (n) of the refractive gradient layer 212 is... ul1 nul2 The refractive index (n) can be greater than that of substrate 204. sub In some cases, the refractive index of the refractive gradient layer 212 may be, for example, 2.1 to 2.5. The refractive gradient layer 212 may have a thickness 226 of 1 nm to 200 nm. In some cases, the thickness of the refractive gradient layer 212 may be constant or variable, as referenced herein. Figure 8 A and Figure 8 B further elaborates.

[0029] A grating layer 206 may be disposed above a substrate 204. In this example, the grating layer 206 is disposed above a refractive gradient layer 212. The grating layer 206 may include an output coupler grating 208 and a coating 210. The output coupler grating 208 may be or include an asymmetric grating, such as a grating with a flat bottom tilt (e.g., as shown in the image). Figure 2 The depicted), shimmering grating (e.g., as Figure 7B (as depicted), a tilted grating with a tilted bottom (e.g., as shown) Figure 7A (as shown) or combinations thereof.

[0030] The grating 208 may have at least one tilt angle 214 of 40 to 80 degrees and at least one duty cycle of 20% to 80% or at least one duty cycle of 40% to 70%. The tilt angle 214 may be the angle between a plane 218 extending vertically from the substrate 204 and / or the refractive gradient layer 212 and the fins 222 of the grating 208. In some cases, the grating 208 may have fins 222 with varying tilt angles (e.g., in the range of 0 to 80 degrees) or uniform tilt angles. The duty cycle may represent the ratio of the width 216 of the fins 222 to the width 220 of the period of the grating 208. In some cases, the grating 208 may have fins 222 with different or uniform duty cycles. The grating 208 may have a height (or depth) 224 of at least 20 nm to 300 nm. In some respects, the height 224 may vary or be uniform among the fins 222.

[0031] The output coupler grating 208 may include, for example, noble metals, non-noble metals, oxides, ceramics, phase change materials, semiconductors, or any combination thereof. The output coupler grating 208 may comprise amorphous silicon (aSi), silicon oxide (SiO2), etc. x ), silicon nitride (SiNx), titanium oxide (TiO2) x ), tantalum oxide (TaO) x ), niobium oxide (NbO) x ), aluminum oxide (AlO) x ), chromium oxide (CrO) x ), magnesium oxide (MgO) x), lithium niobate (LiNbO) x (or combinations thereof). As shown, coating 210 covers output coupler grating 208 to enhance user-to-world ratio and / or improve color uniformity. In some cases, coating 210 may include one or more coatings (paint layers). As an example, coating 210 may contain photoresist material or deposited thin film material. Coating 210 can reduce diffraction efficiency and improve the color uniformity of waveguide 200. The refractive index (n) of output coupler grating 208 is... g The refractive index (n) can be greater than that of coating 210. c As an example, the refractive index (n) of the output coupler grating g The refractive index (n) can be between 2.1 and 2.5, and the coating has a refractive index (n) c The transmittance can be between 1.5 and 1.9. In some cases, using coating 210, the transmittance / reflectance ratio can be increased to about 99:1, and the potential user to world ratio can be significantly improved to about 50:1 or higher. Coating 210 can be arranged to have a continuous flat surface above grating 208.

[0032] Figure 3 Chart 300 depicts the diffraction efficiency versus grating thickness, and Figure 4A and Figure 4B It is a description of the article about Figure 2 Charts 400A and 400B show the user-to-world ratio associated with the described waveguide structure. In these examples, the grating tilt angle is -60 degrees. Regarding... Figure 3 The refractive gradient layer has varying refractive index and thickness as depicted in Figure 300. Figure 3 As shown, curves 302, 304, and 306 represent the diffraction efficiencies associated with the blue, green, and red beams, respectively. It should be understood that Figure 300 indicates that the waveguide structure described herein provides the desired diffraction efficiencies. For example, curves 302 and 304 have intersecting diffraction efficiencies across varying thicknesses, and there is an efficiency separation of less than approximately 10% between curve 306 and curves 302 and 304.

[0033] about Figure 4A Chart 400A depicts the user-to-world ratio associated with different thicknesses (e.g., thickness 226) of the refractive gradient layer 212 (labeled "bottom layer"), for blue, green, and red beams. About Figure 4B Chart 400B depicts the user-to-world ratio associated with different thicknesses of the grating (e.g., height 224), for blue, green, and red beams. Figure 4A and Figure 4BIt has been demonstrated that the user-to-world ratio can be adjusted based on the thickness of the refractive gradient layer 212 and / or the grating. In some cases, the waveguide structure described herein enables user-to-world ratios exceeding fifty, and the waveguide structure described herein facilitates beams with consistent user-to-world ratios (e.g., green and red beams or blue and green beams).

[0034] Figure 5 This is a graph 500 illustrating the diffraction efficiencies of example gratings with and without coatings for different grating thicknesses. As shown, the diffraction efficiency of the example grating with coating is lower compared to the example grating without coating. This reduced diffraction efficiency can improve color uniformity associated with the waveguide.

[0035] Figure 6 Figures 600A, 600B, and 600C illustrate the diffraction efficiencies of an example waveguide for blue, green, and red light beams, respectively. In this example, the waveguide has a refractive gradient layer comprising a first refractive gradient layer 212a and a second refractive gradient layer 212b, for example, as shown below. Figure 2 The figures are depicted. The x-axis corresponds to the thickness of the first refractive gradient layer 212a (e.g., a refractive index of 2.2 at 450 nm, 2.1 at 520 nm, and 2.1 at 620 nm), and the y-axis corresponds to the thickness of the second refractive gradient layer 212b (e.g., a refractive index of 2.7 at 450 nm, 2.6 at 520 nm, and 2.5 at 620 nm). Figures 600A, 600B, and 600C demonstrate that the diffraction efficiency can be adjusted based on the thickness of the respective refractive gradient layer.

[0036] Figure 7A and Figure 7B These are cross-sectional views of example waveguides 700A and 700B, respectively, illustrating angle-etched gratings and blazed gratings. Figure 7A As shown, grating layer 206 includes an output coupler grating 708A, which is a tilted grating with a sloping bottom. Grating 708A can actually be a tilted grating with a shoulder left from the etching process. Figure 8 As depicted in B, grating layer 206 includes output coupler grating 708B, which is a blazed grating.

[0037] Figure 8This is a cross-sectional view illustrating an example waveguide 800 with a confocal coating 810. In this example, the grating layer 206 may include a confocal coating 810 covering the output coupler grating 208. The coating 810 may be arranged to cover the output coupler grating 208 so as to have the same or similar profile as the output coupler grating 208.

[0038] Figure 9A and Figure 9B These are cross-sectional views of example waveguides 900A and 900B, which have variable thicknesses and exemplify refractive gradient layers, respectively. Figure 9A As shown, the refractive gradient layer 912A can have a varying thickness. Regarding... Figure 9B The refractive gradient layer 912B can have a gradually increasing thickness.

[0039] While the foregoing describes embodiments of the present disclosure, other and further embodiments of the present disclosure may be conceived without departing from the basic scope of the present disclosure, the scope of which is defined by the appended claims.

Claims

1. A waveguide, comprising: an anti -reflective coating; a substrate disposed above the anti -reflective coating, wherein the substrate comprises an index of refraction of 1.5 to 2.7; and a grating layer disposed above the substrate, the grating layer comprising: an output coupler grating comprising an index of refraction of 2.1 to 2.5, and one or more coatings covering the output coupler grating, wherein the one or more coatings comprise an index of refraction of 1.5 to 1.

9.

2. The waveguide of claim 1, further comprising one or more layers disposed between the substrate and the grating layer, wherein the layers have an index of refraction greater than the index of refraction of the substrate.

3. The waveguide of claim 2, wherein the one or more layers comprise a layer having an index of refraction of 2.1 to 2.

5.

4. The waveguide of claim 1, wherein the output coupler grating has an index of refraction greater than the index of refraction of the one or more coatings.

5. The waveguide of claim 1, wherein the output coupler grating comprises a flat bottomed blazed grating, a blazed grating, a tilted grating with a tilted bottom, or a combination thereof.

6. The waveguide of claim 1, wherein: the output coupler grating comprises amorphous titanium oxide (aTiOx), lithium niobate (LiNbOx), or a combination thereof; the one or more coatings comprise a photoresist material; and the substrate comprises glass, silicon oxide (SiOx), silicon carbide (SiC), lithium niobate (LiNbOx), or a combination thereof.

7. The waveguide of claim 1, wherein the output coupler grating comprises a tilted grating having at least one tilt angle of 0 degrees to 80 degrees, having at least one duty cycle of 20% to 80%, and having at least one height of 20 nm to 300 nm.

8. The waveguide of claim 1, wherein the waveguide comprises a single layer waveguide configured to guide a plurality of optical bands.

9. A display device, comprising: a waveguide, the waveguide comprising: an anti -reflective coating, a substrate disposed above the anti -reflective coating, wherein the substrate comprises an index of refraction of 1.5 to 2.7; a grating layer disposed above the substrate, the grating layer comprising: an output coupler grating comprising an index of refraction of 2.1 to 2.5, and one or more coatings covering the output coupler grating, wherein the one or more coatings comprise an index of refraction of 1.5 to 1.9; and an optical emitter optically coupled with the waveguide.

10. The display device of claim 9, wherein the waveguide further comprises one or more layers disposed between the substrate and the grating layer, wherein the one or more layers have an index of refraction greater than the index of refraction of the substrate.

11. The display device of claim 9, wherein the output coupler grating has an index of refraction greater than the index of refraction of the one or more coatings.

12. The display device of claim 9, wherein the output coupler grating comprises a slanted grating, a blazed grating, or a combination thereof.

13. The display device of claim 9, wherein: the output coupler grating comprises amorphous titanium oxide (aTiOx), lithium niobate (LiNbOx), or a combination thereof; the one or more coatings comprise a photoresist material; and the substrate comprises glass, silicon oxide (SiOx), silicon carbide (SiC), lithium niobate (LiNbOx), or any combination thereof.

14. The display device of claim 9, wherein the output coupler grating comprises a slanted grating having at least one slant angle of 0 degrees to 80 degrees, having at least one duty cycle of 20% to 80%, and having at least one height of 20 nm to 300 nm.

15. The display device of claim 9, wherein the waveguide comprises a single layer waveguide configured to guide a plurality of light bands.

16. A waveguide comprising: an anti -reflective coating; a substrate disposed above the anti -reflective coating, wherein the substrate comprises a refractive index of 1.5 to 2.7; a grating layer disposed above the substrate, the grating layer comprising: an output coupler grating comprising a refractive index of 2.1 to 2.5, and a refractive gradient layer arranged between the substrate and the grating layer.

17. The waveguide of claim 16, wherein the refractive gradient layer has a varying thickness.

18. The waveguide of claim 17, wherein the refractive gradient layer has a refractive index greater than a refractive index of the substrate.

19. The waveguide of claim 17, wherein the output coupler grating has a refractive index greater than a refractive index of the refractive gradient layer.

20. The waveguide of claim 17, wherein the output coupler grating comprises a slanted grating having at least one slant angle of 0 degrees to 80 degrees, having at least one duty cycle of 20% to 80%, and having at least one height of 20 nm to 300 nm.

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