COLOR SEPARATION IN WAVEGUIDES USING DICHROIC FILTERS

• US 20180180817A1
• Filed: 12/20/2017
• Published: 06/28/2018
• Est. Priority Date: 12/22/2016
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: YEOH, Ivan Li Chuen, EDWIN, Lionel Ernest, CHENG, Hui-Chuan
• Granted Patent: US 10,371,896 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/4205 having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
• CPC Class Codes: G02B 27/4277 being separated by an air space
• CPC Class Codes: G02B 27/44 Grating systems; Zone plate systems G02B27/46 takes precedence
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters

Abstract

An eyepiece for projecting an image to an eye of a viewer includes a first planar waveguide positioned in a first lateral plane, a second planar waveguide positioned in a second lateral plane adjacent the first lateral plane, and a third planar waveguide positioned in a third lateral plane adjacent the second lateral plane. The first waveguide includes a first diffractive optical element (DOE) coupled thereto and disposed at a lateral position. The second waveguide includes a second DOE coupled thereto and disposed at the lateral position. The third waveguide includes a third DOE coupled thereto and disposed at the lateral position. The eyepiece further includes a first optical filter disposed between the first waveguide and the second waveguide at the lateral position, and a second optical filter positioned between the second waveguide and the third waveguide at the lateral position.

Claims

1. An eyepiece for projecting an image to an eye of a viewer, the eyepiece comprising:

a first planar waveguide positioned in a first lateral plane, wherein the first waveguide comprises a first diffractive optical element (DOE) coupled thereto and disposed at a lateral position, the first DOE configured to diffract image light in a first wavelength range centered at a first wavelength;

a second planar waveguide positioned in a second lateral plane adjacent the first lateral plane, wherein the second waveguide comprises a second DOE coupled thereto and disposed at the lateral position, the second DOE configured to diffract image light in a second wavelength range centered at a second wavelength longer than the first wavelength;

a third planar waveguide positioned in a third lateral plane adjacent the second lateral plane, wherein the third waveguide comprises a third DOE coupled thereto and disposed at the lateral position, the third DOE configured to diffract image light in a third wavelength range centered at a third wavelength longer than the second wavelength;

a first optical filter disposed between the first waveguide and the second waveguide at the lateral position, wherein the first optical filter is configured to have;

a first transmittance value at the first wavelength range;

a second transmittance value at the second wavelength range and the third wavelength range that is greater than the first transmittance value; and

a first reflectance value at the first wavelength range that is greater than about 90%; and

a second optical filter positioned between the second waveguide and the third waveguide at the lateral position, wherein the second optical filter is configured to have;

a third transmittance value at the first wavelength range and the second wavelength range;

a fourth transmittance value at the third wavelength range that is greater than the third transmittance value; and

a second reflectance value at the second wavelength range that is greater than about 90%.

2. The eyepiece of claim 1 wherein each of the first DOE, the second DOE, and the third DOE comprises an incoupling grating.

3. The eyepiece of claim 1 wherein each of the first transmittance value and the third transmittance value is less than about 10%, and each of the second transmittance value and the fourth transmittance value is greater than about 90%.

4. The eyepiece of claim 3 wherein the first optical filter is configured to have the first transmittance value and the second transmittance value for angles of incidence ranging from about zero degree to about 45 degrees, and the second optical filter is configured to have the third transmittance value and the fourth transmittance value for angles of incidence ranging from about zero degree to about 45 degrees.

5. The eyepiece of claim 1 wherein the first wavelength range is centered substantially at 462 nm, the second wavelength range is centered substantially at 528 nm, and the third wavelength range is centered substantially at 635 nm.

6. The eyepiece of claim 1 further comprising an optical reflector positioned in a sixth lateral plane adjacent the fifth lateral plane at the lateral position and configured to reflect image light transmitted through the third waveguide.

7. The eyepiece of claim 1 further comprising:

a first short-pass filter optically coupled to the second lateral region of the first waveguide and configured to absorb image light in the second wavelength range; and

a second short-pass filter optically coupled to the second lateral region of the second waveguide and configured to absorb image light in the third wavelength range.

8. The eyepiece of claim 7 wherein the first short-pass filter is disposed inside the second lateral region of the first waveguide, and the second short-pass filter is disposed inside the second lateral region of the second waveguide.

9. The eyepiece of claim 7 wherein the first short-pass filter is disposed in a cavity inside the second lateral region of the first waveguide, and the second short-pass filter is disposed in a cavity inside the second lateral region of the second waveguide.

10. The eyepiece of claim 7 wherein the first short-pass filter is disposed on the first lateral surface of the second lateral region of the first waveguide, and the second short-pass filter is disposed on the first lateral surface of the second lateral region of the second waveguide.

11. An eyepiece for projecting image light to an eye of a viewer, the image light including image light in a first wavelength range centered at a first wavelength and image light in a second wavelength range centered at a second wavelength different from the first wavelength, the eyepiece comprising:

a first planar waveguide including a first diffractive optical element (DOE) optically coupled thereto, wherein the first DOE is positioned along an optical path of the image light and configured to couple a portion of the image light in the first wavelength range into the first planar waveguide to be propagated in the first planar waveguide;

a first optical filter positioned along the optical path downstream from the first DOE, wherein the first optical filter is configured to attenuate the image light in the first wavelength range incident thereon;

a second planar waveguide including a second DOE optically coupled thereto, wherein the second DOE is positioned along the optical path downstream from the first optical filter and configured to couple a portion of the image light in the second wavelength range transmitted through the first optical filter into the second planar waveguide to be propagated in the second planar waveguide; and

a second optical filter coupled to the first planar waveguide, wherein the second optical filter is configured to absorb image light in the second wavelength range propagating in the first planar waveguide.

12. The eyepiece of claim 11 wherein the second wavelength is longer than the first wavelength, and the first optical filter comprises a long-pass filter configured to have a first transmittance value for the first wavelength range that is less than about 10% and a second transmittance value for the second wavelength range that is greater than about 90%.

13. The eyepiece of claim 12 wherein the second optical filter comprises a short-pass filter configured to have a first transmittance value for the second wavelength range that is less than about 10%, and a second transmittance value for the first wavelength range that is greater than about 90%.

14. The eyepiece of claim 11 wherein the second wavelength is shorter than the first wavelength, and the first optical filter comprises a short-pass filter configured to have a first transmittance value for the first wavelength range that is less than about 10% and a second transmittance value for the second wavelength range that is greater than about 90%.

15. The eyepiece of claim 14 wherein the second optical filter comprises a long-pass filter configured to have a first transmittance value for the second wavelength range that is less than about 10%, and a second transmittance value for the first wavelength range that is greater than about 90%.

16. An eyepiece for projecting an image to an eye of a viewer, the eyepiece comprising:

a first planar waveguide positioned in a first lateral plane, wherein the first waveguide comprises a first incoupling element optically coupled thereto, and wherein the first incoupling element is configured to diffract image light in a first wavelength range centered at a first wavelength;

a second planar waveguide positioned in a second lateral plane adjacent the first lateral plane, wherein the second waveguide comprises a second incoupling element optically coupled thereto, and wherein the second incoupling element is configured to diffract image light in a second wavelength range centered at a second wavelength different from the first wavelength; and

a first optical element positioned between the first waveguide and the second waveguide in lateral alignment with the first incoupling element, wherein the first optical element is configured to reflect image light in the first wavelength range.

17. The eyepiece of claim 16 wherein the first waveguide comprises a first surface and a second surface opposite to the first surface, the second waveguide comprises a first surface and a second surface opposite to the first surface, and wherein the first surface of the second waveguide faces the second surface of the first waveguide.

18. The eyepiece of claim 17 wherein the first incoupling element is disposed on the second surface of the first waveguide adjacent the first surface of the second waveguide.

19. The eyepiece of claim 17 further comprising:

a second optical element positioned adjacent the second surface of the second waveguide in lateral alignment with the second incoupling element, wherein the second optical element is configured to reflect image light in the second wavelength range.

20. The eyepiece of claim 19 wherein the second incoupling element is positioned laterally offset from the first incoupling element.

21. The eyepiece of claim 20 wherein the first optical element is further configured to reflect image light in the second wavelength range.

22. The eyepiece of claim 19 further comprising:

a third planar waveguide positioned in a third lateral plane adjacent the second lateral plane, wherein the third waveguide comprises a third incoupling element coupled thereto, and wherein the third incoupling element is configured to diffract image light in a third wavelength range centered at a third wavelength different from the first wavelength and the second wavelength.

23. The eyepiece of claim 22 wherein the second incoupling element is positioned in lateral alignment with the third incoupling element.

24. The eyepiece of claim 22 wherein the second optical element is configured to have a reflectance value at the second wavelength range that is greater than about 90%.

25. The eyepiece of claim 24 wherein the second optical element is further configured to have a transmittance value at the third wavelength range that is greater than about 90%.

26. The eyepiece of claim 24 further comprising:

a third optical element positioned in lateral alignment with the third incoupling element, wherein the third optical element is configured to reflect image light in the third wavelength range.

27. The eyepiece of claim 26 wherein the third optical element is further configured to reflect image light in the second wavelength range.