Virtual and augmented reality systems and methods having improved diffractive grating structures
Disclosed is an improved diffraction structure for 3D display systems. The improved diffraction structure includes an intermediate layer that resides between a waveguide substrate and a top grating surface. The top grating surface comprises a first material that corresponds to a first refractive index value, the underlayer comprises a second material that corresponds to a second refractive index value, and the substrate comprises a third material that corresponds to a third refractive index value.
1. An augmented reality (AR) display system for delivering augmented reality content to a user, comprising:
an image-generating source to provide one or more frames of image data;
a light modulator to transmit light associated with the one or more frames of image data;
a diffractive optical element (DOE) to receive the light associated with the one or more frames of image data and direct the light to the user's eyes, the DOE comprising a diffraction structure having a waveguide substrate, a surface grating, and an underlayer disposed between the waveguide substrate and the surface grating; and
wherein the surface grating has a surface grating refractive index, the underlayer has an underlayer refractive index, and the surface grating refractive index is greater than the underlayer refractive index.
2. The system of claim 1 , wherein the underlayer refractive index is approximately 1.79 or 1.84.
3. The system of claim 1 , wherein the waveguide substrate has a waveguide substrate refractive index, and the waveguide substrate refractive index is approximately 1.5, 1.7, or 1.8.
4. The system of claim 1 , wherein all of the waveguide substrate, the underlayer, and the surface grating correspond to different refractive index values.
5. The system of claim 1 , wherein the underlayer refractive index is higher value compared to a waveguide refractive index.
6. The system of claim 1 , wherein the waveguide substrate, the underlayer, and the surface grating correspond to different materials.
7. The system of claim 1 , wherein at least two of the waveguide substrate, the underlayer, and the surface grating correspond to a common refractive index value.
8. The system of claim 7 , wherein the at least two of the waveguide substrate, the underlayer, and the surface grating correspond to the same material.
9. The system of claim 1 , wherein the underlayer comprises a non-uniform thickness.
10. The system of claim 9 , wherein the non-uniform thickness of the underlayer changes from a relatively thin to a relatively thick as distance is increased from a light injection location.
11. The system of claim 1 , wherein the underlayer comprises a non-uniform underlayer refractive index.
12. The system of claim 11 , wherein the non-uniform underlayer refractive index of the underlayer changes from being relatively similar to the waveguide refractive index to being increasing different from the waveguide refractive index as distance is increased from a light injection location.
13. The system of claim 1 , wherein the underlayer comprises both a non-uniform thickness and a non-uniform underlayer refractive index.
14. The system of claim 1 , wherein the system comprises a stacked waveguide assembly having a plurality of the diffraction structure that are stacked together.
15. The system of claim 14 , wherein a plurality of the image-generating source injects the image data into each of the diffraction structure within the stacked waveguide assembly.
16. The system of claim 1 , wherein the waveguide substrate, the underlayer, and the surface grating correspond to at least one of polymer material, sapphire, or glass.
17. The system of claim 1 , wherein the DOE is switchable between an ON state and an OFF state.
18. The system of claim 1 , embodied as a head-mountable wearable system.
19. The system of claim 1 , where the diffraction structure further comprises a top surface layer over the surface grating.
20. The system of claim 1 , wherein the top surface layer forms an interstitial layer for stacking of the diffraction structure.