Improved image contrast of waveguide combiners by engineering internal loss

Abstract

Embodiments disclosed herein include a waveguide combiner and method of forming a waveguide combiner. The waveguide combiner includes a substrate comprising a modified region, a plurality of optical devices disposed on the substrate, and a film layer disposed over the substrate. The modified region is treated to form a discoloration gradient. The waveguide combiner is modified using by treating the waveguide combiner to form a substrate modified region in the substrate to form a discoloration gradient.

Description

PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001IMPROVED IMAGE CONTRAST OF WAVEGUIDE COMBINERS BY ENGINEERING INTERNAL LOSSBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to optical waveguides. More specifically, embodiments described herein relate to forming optical waveguides having increased image contrast.Description of the Related Art

[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 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, 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. Augmented reality can include any type of input, such as audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the environment that the user experiences. As an emerging technology, there are many challenges and design constraints with augmented reality.

[0004] A contributor to the degradation of image contrast of waveguide combiners is the back-scattering of light in total-internal-reflection (TIR) from the substrate boundaries. To reduce the back-scattering, the substrate edges may be painted with a black paint to absorb light at the edges. However, this technique may not completely absorb the incident light and therefore only partially improves the image contrast. This back-scattering is particularly prominent for blue wavelengths, which contributes to lower blue contrast in waveguide combiners.

[0005] Accordingly, there is a need for improved systems and methods of forming optical waveguides.PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001SUMMARY

[0006] In one embodiment, a waveguide combiner is disclosed. The waveguide combiner includes a substrate, a plurality of optical devices disposed on the substrate, and a film layer disposed over the substrate. The substrate includes a modified region. The modified region is treated to form a discoloration gradient.

[0007] In another embodiment, a method of forming a waveguide combiner is disclosed. The method includes forming a waveguide combiner. The waveguide combiner includes a substrate, a plurality of optical devices disposed on the substrate; and a film layer disposed over the substrate. The waveguide combiner is treated to form a substrate modified region in the substrate to form a discoloration gradient.

[0008] In one embodiment, a waveguide combiner is disclosed. The waveguide combiner includes a substrate, a plurality of optical devices disposed on the substrate, a modified film layer disposed over the substrate, and an edge blackening region at an edge of the waveguide combiner. The modified film layer includes a film layer modified region, wherein the film layer modified region is formed using a treatment configured to increase an internal light loss of the waveguide combiner.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 is a schematic, frontal view of a waveguide, according to embodiments.

[0011] Figure 2A is a schematic view of a modified substrate waveguide combiner at cut-line A-A, according to embodiments.

[0012] Figure 2B is a schematic view of a modified film waveguide combiner at cutline A-A, according to embodiments.PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001

[0013] Figure 2C is a schematic view of a modified waveguide combiner at cut-line A-A, according to embodiments.

[0014] Figure 3A is a schematic, top view of a first waveguide combiner, according to embodiments.

[0015] Figure 3B is a schematic, top view of a second waveguide combiner, according to embodiments.

[0016] Figure 4 is a method of forming a waveguide combiner, according to embodiments.

[0017] Figure 5A is a schematic view of the waveguide combiner, according to embodiments.

[0018] Figure 5B and Figure 5C are schematic, cross-sectional views of the waveguide during the method of forming the waveguide combiner, according to embodiments.

[0019] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0020] Embodiments of the present disclosure generally relate to optical waveguides. More specifically, embodiments described herein provide for forming optical waveguides with increased image contrast.

[0021] Figure 1 is a front view of a waveguide combiner 100. It is to be understood that the waveguide combiner 100 described below is an exemplary waveguide combiner. The waveguide combiner 100 includes a substrate 101 and a plurality of optical devices 104. The plurality of optical devices 104 include an input coupling region 104A defined by a plurality of gratings 106, a waveguide region 104B, and an output coupling region 104C.PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001

[0022] The input coupling region 104A receives incident beams of light (e.g., a light image) having an intensity from a display (e.g., a micro-display). Each grating of the plurality of gratings 106 splits the incident beams into a plurality of modes. Zero-order mode (To) beams are refracted back or lost in the waveguide combiner 100. Positive first order mode (Ti) beams undergo total-internal-reflection (TIR) through the waveguide combiner 100 across the waveguide region 104B to the output coupling region 104C and output for display. Negative first-order mode (T-i) beams propagate in the waveguide combiner 100 a direction opposite the Ti beams. Among the diffracted orders, only the Ti beams output for display through output coupling region 104C, while other modes are lost due to different directionality. Therefore, it is beneficial to increase Ti beam internal loss (e.g., increase Ti absorption) within the substrate in order to increase image contrast.

[0023] Figure 2A is a schematic view of a modified substrate waveguide combiner 200A at cut-line A-A having a modified substrate 201A. In some embodiments, the waveguide combiner 100 may be the modified substrate waveguide combiner 200A. The modified substrate waveguide combiner 200A includes a modified substrate 201 A and a film layer 202A. The film layer 202A includes silicon oxide (SiOx), silicon nitride (SiN), titanium oxide (TiOx), niobium oxide (NbOx), aluminum oxide (AIOx), or other suitable materials.

[0024] The modified substrate 201 A is formed by treating the edges of the modified substrate waveguide combiner 200A. In some embodiments, the treatment includes exposing the modified substrate waveguide combiner 200A to UV-light, such as UV- light having a wavelength in the range of about 300 nm to about 400 nm. The UV- light exposure forms a modified region 210A in the modified substrate 201 A at the edge of the modified substrate waveguide combiner 200A. For example, in various embodiments, exposure to UV-light may cause the edges of the modified substrate waveguide combiner 200A to appear yellow. In the same or other embodiments, the treatment may include ion-implantation treatment, a thermal treatment, or an electron beam treatment. The modified region 210A may include a discoloration gradient from the center of the modified substrate waveguide combiner 200A, for example, to increase the aesthetic appearance of the modified substrate waveguide combiner 200A. The discoloration gradient includes adding color or removing color from a substrate. The discoloration gradient is formed by increasing the amount of UV-lightPCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001 exposure as the process moves from the center of the modified substrate waveguide combiner 200A to the edges of the modified substrate waveguide combiner 200A. The treatment increases the internal loss of the substrate, thus increasing the light absorption and reducing backscattering, thereby contributing to improvements in the virtual image contrast.

[0025] In some embodiments, the modified substrate waveguide combiner 200A includes an edge blackening region 208A. The edge blackening region 208A absorbs light at the edges of the modified substrate waveguide combiner 200A to improve the image contrast of the modified substrate waveguide combiner 200A.

[0026] Figure 2B is a schematic view of a modified film waveguide combiner 200B at cut-line A-A having a modified film layer 202B. In some embodiments, the waveguide combiner 100 may be the modified film waveguide combiner 200B. The modified film waveguide combiner 200B includes a substrate 201 B and a modified film layer 202B.

[0027] The modified film layer 202B is formed by treating the modified film waveguide combiner 200B. In some embodiments, the treatment includes exposing the modified film waveguide combiner 200B to UV-light, such as UV-light in the wavelength range of about 300 nm to about 400 nm. The UV-light exposure forms a modified region 210B in the modified film layer 202B at the edge of the modified film waveguide combiner 200B (e.g., the modified film waveguide 200B edges appear yellow). In the same or other embodiments, the treatment may include ionimplantation treatment, a thermal treatment, or an electron beam treatment. The modified region 210B may include a discoloration gradient from the center of the modified film waveguide combiner 200B. The discoloration gradient is formed by increasing the amount of treatment as the process moves from the center of the modified film waveguide combiner 200B to the edges of the modified film waveguide combiner 200B. The treatment improves image contrast of the modified film waveguide combiner 200B by reducing the internal loss of the light within the modified film layer 202B.

[0028] In some embodiments, the modified film waveguide combiner 200B includes an edge blackening region 208B. The edge blackening region 208B absorbsPCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001 light at the edges of the modified film waveguide combiner 200B to improve the image contrast of the modified film waveguide combiner 200B.

[0029] Figure 2C is a schematic view of a modified waveguide combiner 200C at cut-line A-A having a modified substrate 201 C and a modified film layer 202C. In some embodiments, the waveguide combiner 100 may be the modified waveguide combiner 200C. The modified waveguide combiner 200C includes the modified substrate 201C and the modified film layer 202C.

[0030] In some embodiments, the modified substrate 201C and the modified film layer 2020 are formed by treating the modified waveguide combiner 2000. The treatment forms a modified region 210C in the modified substrate 201 C and the modified film layer 202C, respectively, at the edge of the modified waveguide combiner 200C. In some embodiments, the treatment includes exposing the modified waveguide combiner 200C to UV-light, such as UV-light in the wavelength range of about 300 nm to about 400 nm. In the same or other embodiments, the treatment may include ion-implantation treatment, a thermal treatment, or an electron beam treatment. The modified region 21 OB may include a discoloration gradient (e.g., a yellow gradient) from the center of the modified waveguide combiner 200C. The discoloration gradient is formed by increasing the amount of treatment as the process moves from the center of the modified waveguide combiner 200C to the edges of the modified waveguide combiner 2000.

[0031] In some embodiments, the modified waveguide combiner 2000 includes an edge blackening region 208C. The edge blackening region 208C absorbs light at the edges of the modified waveguide combiner 200C to improve the image contrast of the modified waveguide combiner 2000.

[0032] Figure 3A is a schematic, top view of a first waveguide combiner 300A. Figure 3B is a schematic, top view of a second waveguide combiner 300B. As shown, the modified regions of the first waveguide combiner 300A are different than the modified regions of the second waveguide combiner 300B. For example, the first waveguide combiner 300A includes a modified region 31 OA at a left edge and a right edge of the first waveguide combiner 300A. The second waveguide combiner 300B includes modified region 31 OB at a right edge of the second waveguide combiner 300B. Accordingly, as shown in various embodiments, the modified regions of thePCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001 waveguide combiners do not need to be uniformly distributed around the edge of the waveguide combiner. Other regions of a waveguide combiner may be similarly treated to form modified regions as desired by the user of the waveguide combiner.

[0033] Figure 4 illustrates a method 400 of forming a waveguide combiner 500. Figure 5A is a schematic view of the waveguide combiner 500. Figure 5B and Figure 5C are schematic, cross-sectional views of the waveguide combiner 500 during the method 400 of forming the waveguide combiner 500.

[0034] At operation 402, as shown in Figures 5A and 5B, a waveguide combiner 500 is formed or obtained. The waveguide combiner 500 includes a substrate 501 , a plurality of optical devices 104, and a film layer 502. The plurality of optical devices 104 include an input coupling region 104A defined by a plurality of gratings 106, a waveguide region 104B, and an output coupling region 104C. The film layer 502 is formed using a chemical vapor deposition (CVD) process, a plasma enhanced CVD (PECVD) process, an atomic layer deposition (ALD) process, a physical vapor deposition (PVD) process, a spin coating process, or other suitable deposition process. The film layer 502 includes silicon oxide (SiOx), silicon nitride (Si N) , titanium oxide (TiOx), niobium oxide (NbOx), aluminum oxide (AIOx), or other suitable materials.

[0035] At optional operation 404, an edge blackened region 508 is formed at the edge of the waveguide combiner 500. The edge blackening region 508 absorbs light at the edges of the waveguide combiner 500 to improve the image contrast of the waveguide combiner 500.

[0036] At operation 406, the waveguide combiner 500 is treated to form a modified region in a modified waveguide combiner. In some embodiments, as shown in Figure 2A, the substrate 501 is treated to form the modified substrate 201A. In other embodiments, as shown in Figure 2B, the film layer 502 is treated to form the modified film layer 202B. In still other embodiments, as shown in Figure 2C, the substrate 501 and the film layer 502 are treated to form the modified substrate 201 C and the modified film layer 202C, respectively.

[0037] In some embodiments, the treatment is a UV-light treatment. The UV-light treatment includes exposing the substrate 501 and / or the film layer 502 to UV-light, for example, having a wavelength in the range of about 300 nm to about 400 nm. InPCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001 the same or other embodiments, the treatment includes an ion-implantation treatment, a thermal treatment, or an electron beam treatment. A discoloration gradient may be formed by increasing the amount of treatment as the treatment moves from the center of the waveguide combiner 500 to the edges of the waveguide combiner 500.

[0038] At optional operation 408, the modified waveguide is coated with a protective coating. The protective coating reduces the rate or likelihood of reversion of the modified waveguide combiner back to the waveguide combiner 500 without the modified region. The protective coating may include a polymer film, an optical film (e.g., silicon oxide (SiOx) or aluminum oxide (AIOx)), or a plastic cover. The protective coating reduces the exposure to air which can degrade the effects of the treatment from operation 406.

[0039] In summary, a modified waveguide combiner is provided. The modified waveguide combiner includes a modified substrate, a modified film layer disposed over a substrate, or both a modified substrate and a modified film layer. The modified waveguide combiner is treated using a UV-light treatment, an ion-implantation treatment, a thermal treatment, or an electron beam treatment. In some embodiments, a discoloration gradient may be formed by increasing the amount of treatment as the treatment moves from the center of the waveguide combiner to the edges of the waveguide combiner. The treatment increases the internal loss of the substrate, thus increasing the light absorption and reducing backscattering, thereby contributing to improvements in the virtual image contrast.

[0040] 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

PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001What is claimed is:

1. A waveguide combiner, comprising: a substrate comprising a modified region, wherein the modified region is treated to form a discoloration gradient; a plurality of optical devices disposed on the substrate; and a film layer disposed over the substrate.

2. The waveguide combiner of claim 1 , wherein the modified region is treated with a UV-light exposure treatment.

3. The waveguide combiner of claim 2, wherein the UV-light exposure treatment comprises exposing the waveguide combiner to UV-light having a wavelength of about 300 nm to about 400 nm.

4. The waveguide combiner of claim 1 , wherein the modified region is treated using an ion-implantation treatment, a thermal treatment, or an electron beam treatment.

5. The waveguide combiner of claim 1 , further comprising an edge blackening region at an edge of the waveguide combiner.

6. The waveguide combiner of claim 1 , wherein the film layer comprises a film layer modified region that is treated to form a film layer discoloration gradient.

7. The waveguide combiner of claim 1 , wherein the plurality of optical devices comprise: an input coupling region; a waveguide region; and an output coupling region.

8. A method of forming waveguide combiner, comprising: forming a waveguide combiner, the waveguide combiner comprising: a substrate;PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W001 a plurality of optical devices disposed on the substrate; and a film layer disposed over the substrate; and treating the waveguide combiner to form a substrate modified region in the substrate to form a discoloration gradient.

9. The method of claim 8, wherein treating the waveguide combiner comprises exposing the waveguide combiner to UV-light.

10. The method of claim 9, wherein the UV-light has a wavelength of about 300 nm to about 400 nm.11 . The method of claim 8, wherein treating the waveguide combiner comprises performing an ion-implantation treatment, a thermal treatment, or an electron beam treatment.

12. The method of claim 8, further comprising forming an edge blackening region at an edge of the waveguide combiner.

13. The method of claim 8, further comprising treating the waveguide combiner to form a film layer modified region in the film layer.

14. The method of claim 8, wherein the plurality of optical devices comprise: an input coupling region; a waveguide region; and an output coupling region.

15. A waveguide combiner, comprising: a substrate; a plurality of optical devices disposed on the substrate; a modified film layer disposed over the substrate, the modified film layer comprising a film layer modified region, wherein the film layer modified region is formed using a treatment configured to increase an internal light loss of the waveguide combiner; and an edge blackening region at an edge of the waveguide combiner.PCT / US25 / 46508 16 September 2025 (16.09.2025)44024809W00116. The waveguide combiner of claim 15, wherein the film layer modified region is treated with a UV-light exposure treatment.

17. The waveguide combiner of claim 16, wherein the UV-light exposure treatment comprises exposing the waveguide combiner to UV-light having a wavelength of about 300 nm to about 400 nm.

18. The waveguide combiner of claim 15, wherein the film layer modified region is treated using an ion-implantation treatment, a thermal treatment, or an electron beam treatment.

19. The waveguide combiner of claim 15, wherein the film layer modified region is treated to form a discoloration gradient.

20. The waveguide combiner of claim 15, wherein the substrate comprises a substrate modified region that is treated to form a substrate discoloration gradient.

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