Multilayer dichroic phase matching for Fresnel optics
An optical structure includes a refractive material having a refractive index and a multilayer dichroic reflective coating. The multilayer dichroic reflective coating is disposed on the refractive material. The average refractive index of the multilayer dichroic reflective coating is substantially the same as the refractive index of the refractive material.
1. An optical structure comprising:
a refractive material having a refractive index; and
a multilayer dichroic reflective coating disposed on the refractive material, wherein an average refractive index of the multilayer dichroic reflective coating is substantially the same as the refractive index of the refractive material.
2. The optical structure of claim 1 , wherein a Fresnel surface is formed in the refractive material, and wherein the Fresnel surface includes active surfaces and draft surfaces, the multilayer dichroic reflective coating selectively disposed on the active surfaces.
3. The optical structure of claim 2 further comprising:
a transparent material having a same refractive index as the refractive material, wherein the multilayer dichroic reflective coating and the draft surfaces are immersed in the transparent material.
4. The optical structure of claim 3 , wherein a top of the transparent material is flat and in parallel with a flat bottom of the refractive material, the Fresnel surface disposed between the top of the transparent material and the flat bottom of the refractive material.
5. The optical structure of claim 4 , wherein the multilayer dichroic reflective coating is configured to pass visible light and reflect near-infrared light.
6. The optical structure of claim 3 , wherein the transparent material is bonded to the multilayer dichroic reflective coating and the draft surfaces with a bonding material.
7. The optical structure of claim 6 , wherein the bonding material is index-matched to the transparent material.
8. The optical structure of claim 3 , wherein the transparent material is cured and adhered to the multilayer dichroic reflective coating and the draft surfaces.
9. The optical structure of claim 1 , wherein the refractive material includes at least one of poly-methyl-methacrylate (PMMA), polycarbonate, cyclic-olefin polymer, styrene, or polyester.
10. A head mounted display (HMD) comprising:
a camera; and
an optical combiner configured to pass visible light to an eyebox area and configured to direct infrared light to the camera, wherein the infrared light is received from the eyebox area, the optical combiner including:
a refractive material having a refractive index; and
a multilayer dichroic reflective coating disposed on the refractive material, wherein an average refractive index of the multilayer dichroic reflective coating is substantially the same as the refractive index of the refractive material.
11. The HMD of claim 10 , wherein a Fresnel surface is formed in the refractive material, and wherein the Fresnel surface includes active surfaces and draft surfaces, the multilayer dichroic reflective coating selectively disposed on the active surfaces.
12. The HMD of claim 11 , wherein the optical combiner further comprises:
a transparent material having a same refractive index as the refractive material, wherein the multilayer dichroic reflective coating and the draft surfaces are immersed in the transparent material.
13. The HMD of claim 12 , wherein a top of the transparent material is flat and in parallel with a flat bottom of the refractive material, the Fresnel surface disposed between the top of the transparent material and the flat bottom of the refractive material.
14. The HMD of claim 12 , wherein the transparent material is bonded to the multilayer dichroic reflective coating and the draft surfaces with a bonding material.
15. The HMD of claim 14 , wherein the bonding material is index-matched to the transparent material.
16. The HMD of claim 12 , wherein the transparent material is cured and adhered to the multilayer dichroic reflective coating and the draft surfaces.
17. The HMD of claim 11 , wherein the Fresnel surface is configured as an off-axis reflector.
18. The HMD of claim 10 , wherein the multilayer dichroic reflective coating is configured to pass the visible light and reflect the infrared light.
19. The HMD of claim 10 further comprising:
at least one infrared source configured to emit the infrared light toward the eyebox area, wherein the camera includes a filter that is configured to pass the infrared light emitted by the at least one infrared source and reject other light.
20. The HMD of claim 10 , wherein the refractive material includes at least one of poly-methyl-methacrylate (PMMA), polycarbonate, cyclic-olefin polymer, styrene, or polyester.