Field etching enhances image sharpness in augmented reality waveguide combiners.

Abstract

This disclosure provides a waveguide and a method for forming the same. The waveguide includes a plurality of grids. The plurality of grids include a grid structure disposed on a waveguide substrate. The grid structure has a grid depth. A waveguide layer is disposed on the waveguide substrate between each of the plurality of grids and the edge of the waveguide substrate. The waveguide layer has an etching depth. The etching depth is shallower than the grid depth.

Description

Technical Field

[0001]

[0001] Embodiments of the present disclosure generally relate to waveguide combiners. More specifically, embodiments described herein provide a waveguide combiner having field etching in a waveguide layer.

Background Art

[0002]

[0002] Virtual reality 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 viewed on a head-mounted display (HMD) such as glasses or other wearable display devices having a near-eye display panel that generates a virtual reality environment in 3D and replaces the actual environment.

[0003]

[0003] Augmented reality enables an experience where a user can view an image of a virtual object that appears as part of an environment generated for display while viewing the surrounding environment through the display lens of glasses or other HMD device. Diffractive waveguide combiners are used in some augmented reality applications to transmit virtual images, graphics, and videos that enhance or augment the environment experienced by the user. Wavefront aberration in the pupil of an image, graphic, and video can cause a loss of image sharpness. Therefore, it is desirable to develop a waveguide combiner that reduces wavefront aberration.

Summary of the Invention

[0004]

[0001] The present disclosure generally relates to a waveguide combiner including a waveguide combiner having field etching in a waveguide layer.

[0005]

[0002] In one embodiment, the present disclosure provides a waveguide. The waveguide includes a plurality of gratings. The plurality of gratings include a grating structure disposed on a waveguide substrate. The grating structure has a grating depth. A waveguide layer is disposed on the waveguide substrate between each of the plurality of gratings and the edge of the waveguide substrate. The waveguide layer has an etching depth. The etching depth is shallower than the grating depth.

[0006]

[0003] In another embodiment, the present disclosure provides a waveguide. The waveguide includes a plurality of grids. The plurality of grids include a grid structure disposed on a waveguide substrate. The grid structure has a grid depth. A waveguide layer is disposed on the waveguide substrate between each of the plurality of grids and the edge of the waveguide substrate. The waveguide layer has a first sublayer disposed on the waveguide substrate. A second sublayer is disposed on the first sublayer. The waveguide layer has an etching depth from the top surface of the second sublayer to the top surface of the grid structure.

[0007]

[0004] In another embodiment, the present disclosure provides a method for forming a waveguide. The method includes determining an etching depth for etching a waveguide layer of the waveguide. The waveguide layer includes a first sublayer and a second sublayer. The etching depth is less than the grid depth of a plurality of grids of the waveguide. The second sublayer is etched to the etching depth.

[0008]

[0004] To enable a detailed understanding of the features of the Disclosure listed above, a more detailed description of the Disclosure, which has been briefly summarized above, can be obtained by referring to embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings only illustrate exemplary embodiments of the Disclosure and should not be considered limiting in scope, and the Disclosure may permit other equally effective embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic top view of a waveguide combiner according to an embodiment described herein. [Figure 2]This is a schematic side view of a portion of a waveguide according to an embodiment described herein. [Figure 3] This is a schematic side view of a portion of a waveguide according to an embodiment described herein. [Figure 4] This is a flowchart of the method for forming a waveguide. [Modes for carrying out the invention]

[0010]

[0009] For ease of understanding, the same reference numerals were used where possible to indicate the same elements common to multiple figures. It is assumed that elements and features of one embodiment may be usefully incorporated into other embodiments without further description.

[0011]

[0010] Embodiments of the present disclosure generally relate to waveguide combiners. More specifically, embodiments described herein provide waveguide combiners having field etching in the waveguide layer.

[0012]

[0011] Diffraction waveguide combiners (also referred to herein as waveguide combiners and waveguides) used in augmented reality applications tend to use gratings to redirect light from the optical engine to the user's eye. This optical direction can be achieved using an in-coupler grating to couple the incident pupil to total internal reflection (TIR), followed by a pupil expander grating and an out-coupler grating to replicate the pupil and couple the out-coupler grating, respectively. The sharpness of the image seen by the user depends on the waveguide's ability to minimize wavefront aberration in the pupil as it is guided from the optical engine to the user's eye.

[0013]

[0012] Loss of image sharpness in waveguide combiners due to pupil wavefront aberration can be caused by discontinuities in the TIR phase at the lattice boundary of the waveguide combiner. When a pupil corresponding to a certain wavelength and field of view (FOV) is TIR reflected at the boundary between the lattice region and the non-lattice region, the amplitudes and phases of the two parts of the pupil interacting with the two different regions are usually not the same. Discontinuous amplitudes and phases across the pupil correspond to a point spread function where diffraction is no longer constrained, resulting in a degradation of image sharpness as measured by the modulation transfer function (MTF). Depending on the substrate thickness and the size of the pupil, the pupil may encounter the same lattice boundary multiple times, further degrading the MTF.

[0014]

[0013] In embodiments of the present disclosure, in order to reduce this phase discontinuity at the boundary between the grid region and the non-grid region, the waveguide layer in the non-grid region may have a depth determined to more closely match the phase of the pupils reflected in the grid region with the phase of the pupils reflected in the non-grid region. The depth of the waveguide layer may be determined based on the depth and duty cycle of one or more (e.g., all) grids in the waveguide combiner. The determined depth of the waveguide layer may be shallower than at least one of the grid depths of the waveguide. By providing a waveguide layer with a determined depth on the waveguide, the waveguide may have a higher MTF than a waveguide without a waveguide layer.

[0015]

[0014] Etching the waveguide layer to a determined depth as described in this disclosure can be independently implemented in a wide range of waveguides without altering the design or structure of the grid and non-grid regions of these waveguides. The architecture described in this disclosure uses only one additional global etching step compared to the aforementioned techniques, but the enhanced image sharpness or MTF enabled by the described architecture can significantly improve the user experience and value of waveguide displays.

[0016]

[0015] Figure 1 is a schematic top view of a waveguide combiner 100 according to an embodiment described herein. The waveguide combiner 100 described later should be understood as an exemplary waveguide combiner. The waveguide combiner 100 has at least one of an in-coupler grid 102, a pupil-extension grid 104, an out-coupler grid 106, and a waveguide layer 108, which are arranged on a waveguide substrate 128. The waveguide substrate 128 has an edge 120. The waveguide layer 108 is arranged on the waveguide substrate 128 between each of the one or more grids (e.g., the in-coupler grid 102, the pupil-extension grid 104, or the out-coupler grid 106) and the edge 120. The in-coupler grid 102 receives an incident beam of light (virtual image) with intensity from a microdisplay. The incident light beam undergoes total internal reflection (TIR) ​​and propagates within the waveguide combiner 100, directing the virtual image towards the pupil-extended grating 104. The incident light beam continues under TIR and propagates within the waveguide combiner 100 to direct the virtual image towards the outcoupler grating 106, which is outcoupled to the user. As the incident light beam propagates within the TIR of the waveguide combiner 100, a portion of the light beam is incident on the incoupler grating 102, the pupil-extended grating 104, and the outcoupler grating 106, while a portion of the light beam is incident on adjacent regions of the waveguide layer 108.

[0017]

[0016] The waveguide layer 108 includes a first blanket region 122. The first blanket region 122 includes a region surrounding the in-coupler grid 102. The first blanket region 122 includes a first blanket depth 130, as shown in Figure 1B. The first blanket depth 130 is based on the depth and duty cycle of the in-coupler grid 102. For example, the first blanket depth 130 may be about 40% to about 60% of the height of the in-coupler grid 102, e.g., about 40% to about 55%, about 45% to about 55%, or about 48% to about 52%. Although not bound by theory, the first blanket region 122 may be about 40% to about 60% of the in-coupler grid 102 compared to a conventional waveguide combiner.

[0018]

[0017] The waveguide layer 108 includes a second blanket region 124. The second blanket region 124 includes a region surrounding the pupil-extended grating 104. The second blanket region 124 includes a second blanket depth 132, as shown in Figure 1B. The first blanket depth 130 and the second blanket depth 132 may be different and / or similar. The second blanket depth 132 is based on the depth and duty cycle of the pupil-extended grating 104. For example, the second blanket depth 132 may be about 40% to about 60% of the height of the pupil-extended grating 104, e.g., about 40% to about 55%, about 45% to about 55%, or about 48% to about 52%. While not strictly theoretical, the second blanket region 124 is approximately 40% to 60% of the height of the Pupil extended grating 104, which can enable improved image sharpness compared to conventional waveguide combiners.

[0019]

[0018] The waveguide layer 108 includes a third blanket region 126. The third blanket region 126 includes a region surrounding the outcoupler grid 106. The third blanket region 126 includes a third blanket depth 134, as shown in Figure 1B. The first blanket depth 130, the second blanket depth 132, and the third blanket depth 134 may be different and / or similar. The third blanket depth 134 is based on the depth and duty cycle of the outcoupler grid 106. For example, the third blanket depth 134 may be about 40% to about 60% of the height of the outcoupler grid 106, e.g., about 40% to about 55%, about 45% to about 55%, or about 48% to about 52%. While not strictly theoretical, the third blanket region 126 is approximately 40% to 60% of the height of the outcoupler grid 106, which could enable improved image sharpness compared to conventional waveguide combiners.

[0020]

[0019] Figure 2 is a schematic side view of a portion 200 of a waveguide combiner that does not include the waveguide layer 108. The portion 200 includes a diffraction grating 206 disposed on the waveguide substrate 250. The diffraction grating 206 may be an in-coupler grating 102, a pupil-extended grating 104, or an out-coupler grating 106.

[0021]

[0020] A TIR pupil 230 is shown within the substrate 250. Part 232 of the pupil 230 is undergoing TIR within the diffraction grating 206. Another part 234 of the pupil 230 is undergoing TIR in the non-lattice region 208. As shown in Figure 2, when a pupil corresponding to a certain wavelength and FOV is TIR reflected at the boundary between the diffraction grating 206 and the non-lattice region 208, the amplitudes and phases of the two parts 232 and 234 of the pupil 230 interacting with the diffraction grating 206 and the non-lattice region 208 are usually not the same. The discontinuous amplitudes and phases across the pupil 230 correspond to a point spread function where diffraction is no longer limited, resulting in a degradation of image sharpness as measured by the MTF. Depending on the substrate thickness and the size of the pupil, the pupil may encounter the same lattice boundary multiple times, further degrading the MTF.

[0022]

[0021] Figure 3 is a schematic side view of a portion 300 of a waveguide combiner 100 according to an embodiment described herein. The portion 300 includes a diffraction grating 306. The diffraction grating 306 includes a grating structure 316 disposed on a waveguide substrate 128. The diffraction grating 306 has a pitch 360. The pitch 360 is determined by the distance between the first edges 346 of the grating structure 316. The diffraction grating 306 may include a portion of one of the in-coupler grating 102, the pupil-extended grating 104, or the out-coupler grating 106. The grating structure 316 has a depth 310 and a line width 326. The diffraction grating 306 has a duty cycle determined by dividing the line width 326 by the pitch 360. The waveguide substrate 128 has an edge 120 (shown in Figure 1).

[0023]

[0022] Part 300 also includes a waveguide layer 108 disposed on the waveguide substrate 128. The waveguide layer 108 is disposed on the waveguide substrate 128 between each of one or more grids (e.g., an in-coupler grid 102, a pupil-extended grid 104, or an out-coupler grid 106) and the edge 120. The waveguide layer 108 has a depth of 318. The waveguide layer 108 includes titanium oxide (TiO), niobium oxide (NbO), or a combination thereof. Optionally, the waveguide layer 108 may include a first sublayer 352. The first sublayer 352 includes niobium oxide (NbO). The first sublayer 352 may comprise about 50% to about 100% of the height of the waveguide layer 108. Optionally, the waveguide layer 108 may include a second sublayer 354. The second sublayer 354 contains titanium oxide (NbO). The second sublayer 354 may comprise approximately 1% to 50% of the height of the waveguide layer 108. While not theoretically bound, the second sublayer 354, being titanium oxide, reduces manufacturing costs and allows for the formation of a precise waveguide layer height, thereby improving image sharpness compared to conventional waveguide combiners.

[0024]

[0023] The waveguide substrate 128 can be formed from any suitable material, on the premise that it can appropriately transmit light of a desired wavelength or wavelength range and can function as a suitable support for gratings (e.g., the input coupler grating 102, the pupil expansion grating 104, or the output coupler grating 106) and the waveguide layer 108. The material of the waveguide substrate 128 has a refractive index lower than that of the material of the grating structure 316 described herein. The selection of the substrate can include substrates of any suitable material, including but not limited to amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon-containing materials, polymers, and combinations thereof. In one embodiment that can be combined with other embodiments described herein, the waveguide substrate 128 consists of one or more of silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, or quartz materials. In another embodiment that can be combined with other embodiments described herein, the waveguide substrate 128 consists of one or more of nitrogen, titanium, niobium, lanthanum, zirconium, or yttrium-containing materials. The waveguide substrate 128 can include an optical material having a refractive index of about 2, for example, about 1.7 to 2.3, about 1.8 to 2.2, about 1.9 to 2.1, or about 2.0 to 2.1.

[0025]

[0024] The lattice structure 316 may be a nanostructure having submicron dimensions, for example, nanosize dimensions. The nanostructure may include a blazed lattice structure, a stepped lattice structure, a vertical lattice structure, or a combination thereof. The lattice structure includes one or more of silicon carbide (SiC), silicon oxycarbide (SiOC), titanium dioxide (TiO2), SiO2, vanadium (IV) oxide (VOx), aluminum oxide (Al2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (TaO5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium pentoxide (Nb2O5), cadmium stannate (Cd2SnO4), silicon nitride (SiN), silicon oxynitride (SiON), barium titanate (BaTiO3), diamond-like carbon (DLC), hafnium (IV) oxide (HfO2), lithium niobate (LiNbO3), or a SiCN-containing material.

[0026]

[0025] The lattice structure 316 may include an optical material having a refractive index of 2.0 or more, that is, a high refractive index. For example, the optical material has a refractive index in the range of about 2.0 to 2.7. In one embodiment, the optical material has a refractive index of 2.4. The optical material having a high refractive index may include a nitride or carbide of the material of the waveguide substrate 128.

[0027]

[0026] In embodiments of the present disclosure, in order to reduce phase discontinuity at the boundary between the diffraction grating 306 and the waveguide layer 108, the waveguide layer 108 may be etched to a depth of 318 so as to better match the phase of the pupils reflected by the diffraction grating 306 with the phase of the pupils reflected by the waveguide layer 108. For example, a second sublayer 354 may be etched to a depth of 318 so as to better match the phase of the pupils reflected by the diffraction grating 306 with the phase of the pupils reflected by the waveguide layer 108. The depth 318 of the waveguide layer 108 (e.g., etching depth) may be determined based on the depth and duty cycle of one or more (e.g., all) of the gratings (e.g., in-coupler grating 102, pupil extension grating 104, or out-coupler grating 106) in the waveguide combiner 100. The depth 318 of the waveguide layer 108 can be determined based on the MTF of waveguide 100, thereby ensuring that waveguide 100 has a higher MTF than other waveguides.

[0028]

[0027] Optionally, an anti-reflective layer 356 may be placed on the waveguide combiner 100. The anti-reflective layer 356 may include a material having a refractive index of less than 1.99, for example, a material with a refractive index of about 1.0 to about 1.99, about 1.0 to about 1.5, or about 1.0 to about 1.2. The anti-reflective layer may include silica oxide. The anti-reflective layer may have a depth of about 50 nm to about 150 nm, for example, about 50 nm to about 140 nm, about 60 nm to about 120 nm, about 80 nm to about 120 nm, or about 90 nm to about 110 nm. Although not theoretically bound, the anti-reflective layer 356 can improve image sharpness by preventing light from leaving the waveguide substrate outside of the out-coupler grating.

[0029]

[0028] Figure 4 is a flowchart of a method for forming a waveguide according to an embodiment described herein. In step 402, an etching depth is determined for etching the waveguide layer of the waveguide, and the etching depth is less than the grid depth of one or more grids of the waveguide. Referring to Figure 3, for example, a depth 318 (e.g., etching depth) for etching the waveguide layer 108 of waveguide 100 may be determined, and the depth 318 is less than the depth 310 of one or more grids of waveguide 100 (e.g., in-coupler grid 102, pupil-extended grid 104, or out-coupler grid 106). For example, the etching depth may have a depth of about 40% to about 60% of the grid depth.

[0030]

[0029] Optionally, the etching depth is determined based on the first depth and duty cycle of one or more grids. Optionally, the etching depth is determined based on one or more phase breaks at one or more boundaries between the waveguide layer and one or more grids. Optionally, the etching depth is determined based on the modulation transfer function (MTF) of the waveguide.

[0031]

[0030] In step 404, the waveguide layer 108 is etched to the etching depth. Continuing the example from above, the waveguide layer 108 is etched to a depth of 318. Optionally, the second sublayer 354 may be etched, thereby improving the etching accuracy compared to the first sublayer 352. Optionally, the second sublayer 354 may be etched to remove it, exposing the first sublayer 352 within the waveguide layer 108.

[0032]

[0031] Overall, the disclosure provides a waveguide combiner having a waveguide layer that is etched to a depth to improve image sharpness compared to conventional waveguide combiners. Etching the waveguide layer to a determined depth as described in the disclosure can be independently implemented in a wide range of waveguides without changing the design or structure of the grid and non-grid regions of these waveguides.

[0033]

[0032] The above description applies to embodiments of the present disclosure, but other embodiments and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the following claims.

Claims

1. Waveguide, A plurality of grids including a grid structure arranged on a waveguide substrate, wherein the grid structure has a grid depth, A waveguide layer disposed on the waveguide substrate between each of the plurality of grids and the edge of the waveguide substrate, wherein the waveguide layer has an etching depth, and the etching depth is less than the grid depth. Waveguide equipped with

2. The aforementioned plurality of grids, Incapura lattice, Pupil expanded grid, or Outcoupler lattice A waveguide according to claim 1, comprising at least one of the following.

3. The waveguide according to claim 2, further comprising a first blanket region surrounding the incoupler grid, wherein the first blanket region has a first blanket depth.

4. The waveguide according to claim 2, further comprising a second blanket region surrounding the pupil-extended grid, wherein the second blanket region has a second blanket depth.

5. The waveguide according to claim 2, further comprising a third blanket region surrounding the incoupler grid, wherein the third blanket region has a third blanket depth.

6. The waveguide according to claim 1, wherein the grid structure includes a duty cycle.

7. The waveguide according to claim 1, further comprising the plurality of grids and an anti-reflection layer disposed on the waveguide layer.

8. The waveguide layer is A first sublayer disposed on the waveguide substrate, A second sublayer disposed on top of the first sublayer and A waveguide according to claim 1, including the following:

9. The waveguide according to claim 8, wherein the first sublayer contains niobium oxide and the second sublayer contains titanium oxide.

10. The waveguide according to claim 8, wherein the first sublayer has a waveguide layer depth of about 50% to about 100%, and the second sublayer has a waveguide layer depth of about 1% to about 50%.

11. Waveguide, A plurality of grids including a grid structure arranged on a waveguide substrate, wherein the grid structure has a grid depth, A waveguide layer disposed on the waveguide substrate between each of the plurality of grids and the edge of the waveguide substrate, A first sublayer disposed on the waveguide substrate, and A second sublayer disposed on the first sublayer, wherein the waveguide layer has an etching depth from the upper surface of the second sublayer to the upper surface of the grid structure. Waveguide layer including Waveguide equipped with

12. A first blanket region surrounding the incoupler grid, comprising a first blanket region having a first blanket depth, A second blanket region surrounding the Pupil extended lattice, comprising a second blanket region having a second blanket depth, A third blanket region surrounding the outcoupler grid, the third blanket region having a third blanket depth and The waveguide according to claim 11, further comprising:

13. The waveguide according to claim 11, further comprising the plurality of grids and an anti-reflective layer disposed on the waveguide layer.

14. The waveguide according to claim 11, wherein the first sublayer contains niobium oxide and the second sublayer contains titanium oxide.

15. The waveguide according to claim 11, wherein the first sublayer has a waveguide layer depth of about 50% to about 100%, and the second sublayer has a waveguide layer depth of about 1% to about 50%.

16. A method for forming a waveguide, Determining an etching depth for etching the waveguide layer of a waveguide, wherein the waveguide layer includes a first sublayer and a second sublayer, and the etching depth is less than the grid depth of the plurality of grids of the waveguide. Etching the second sublayer to the etching depth and A method that includes this.

17. The aforementioned plurality of grids, Incapura lattice, Pupil expanded grid, or Outcoupler lattice The method according to claim 16, comprising at least one of the following.

18. The method according to claim 16, wherein determining the etching depth includes determining the etching depth based on the grid depth and the duty cycle of the plurality of grids.

19. The method according to claim 16, wherein determining the etching depth includes determining the etching depth based on one or more phase breaks at one or more boundaries between the waveguide layer and the plurality of grids.

20. The method according to claim 16, wherein determining the etching depth further includes determining the etching depth based on the modulation transfer function (MTF) of the waveguide.

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