Multi-layer diffractive eyepiece with wavelength-selective reflector

• US 10,725,223 B2
• Filed: 08/22/2017
• Issued: 07/28/2020
• Est. Priority Date: 08/22/2016
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Schowengerdt, Brian T., Lin, Dianmin, St. Hilaire, Pierre
• Primary Examiner(s): Dunning, Ryan S
• Application Number:
  US15/683,644
• Publication Number:
  US 20180052277A1
• Time in Patent Office: 1,071 Days
• Field of Search: 359558-576
• CPC Class Codes: G02B 2027/0114 comprising dichroic elements
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/012 comprising devices for attenuating parasitic image effects
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/0176 characterised by mechanical features
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 5/1823 in an overlapping or superposed manner
• CPC Class Codes: G02B 5/1857 using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 5/1871 Transmissive phase gratings
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence
• CPC Class Codes: G02B 6/0016 : Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0023 : provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0035 : provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0036 : 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0038 : Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/005 : provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0076 : Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/29325 : of the slab or planar or plate like form, i.e. confinement in a single transverse dimension only integrated circuit planar waveguide arrangements G02B6/12007; specially adapted for lighting G02B6/0011
• CPC Class Codes: G02B 6/34 : utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G02B 7/008 : with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: G02C 11/10 : Electronic devices other than hearing aids
• CPC Class Codes: G02C 5/16 : resilient or with resilient parts
• CPC Class Codes: G06F 1/163 : Wearable computers, e.g. on a belt
• CPC Class Codes: G06F 1/203 : for portable computers, e.g. for laptops
• CPC Class Codes: G06F 1/206 : comprising thermal management
• CPC Class Codes: G06F 3/011 : Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00
• CPC Class Codes: G06F 3/013 : Eye tracking input arrangements G06F3/015 takes precedence
• CPC Class Codes: G06F 3/147 : using display panels
• CPC Class Codes: G09G 2320/0233 : Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2330/045 : Protection against panel overheating
• CPC Class Codes: G09G 2340/0464 : Positioning
• CPC Class Codes: G09G 3/001 : using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/002 : to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT
• CPC Class Codes: G09G 3/2003 : Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2044 : using dithering
• CPC Class Codes: H04N 9/3102 : using two-dimensional electronic spatial light modulators micromechanical modulators as such G02B26/0833; liquid crystal modulators as such G02F1/13
• CPC Class Codes: H04N 9/3144 : Cooling systems cooling of liquid crystal cells in general G02F1/133382; cooling of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/16
• CPC Class Codes: H04N 9/3164 : using multiple light sources
• CPC Class Codes: H05K 7/20963 : Heat transfer by conduction from internal heat source to heat radiating structure H05K7/20972 takes precedence

Abstract

An eyepiece for projecting an image to an eye of a viewer includes a waveguide configured to propagate light in a first wavelength range, and a grating coupled to a back surface of the waveguide. The grating is configured to diffract a first portion of the light propagating in the waveguide out of a plane of the waveguide toward a first direction, and to diffract a second portion of the light propagating in the waveguide out of the plane of the waveguide toward a second direction opposite to the first direction. The eyepiece furthers include a wavelength-selective reflector coupled to a front surface of the waveguide. The wavelength selective reflector is configured to reflect light in the first wavelength range and transmit light outside the first wavelength range, such that the wavelength-selective reflector reflects at least part of the second portion of the light back toward the first direction.

Claims

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

a planar waveguide having a front surface and a back surface, the planar waveguide being configured to propagate light in a first wavelength range;

a grating coupled to the back surface of the planar waveguide and configured to diffract a first portion of the light propagating in the planar waveguide out of a plane of the planar waveguide toward a first direction and to diffract a second portion of the light propagating in the planar waveguide out of the plane of the planar waveguide toward a second direction opposite to the first direction; and

a wavelength-selective reflector coupled to the front surface of the planar waveguide and configured to reflect light in the first wavelength range and transmit light outside the first wavelength range, such that the wavelength-selective reflector reflects at least part of the second portion of the light back toward the first direction.

2. The eyepiece of claim 1 wherein the front surface of the planar waveguide faces away from the eye of the viewer, the back surface of the planar waveguide faces toward the eye of the viewer, the first direction is toward the eye of the viewer, and the second direction is away from the eye of the viewer.

3. The eyepiece of claim 1 wherein the wavelength-selective reflector is characterized by a reflectance spectrum having a reflectance peak in the first wavelength range.

4. The eyepiece of claim 3 wherein the first wavelength range corresponds to one of red light, green light, or blue light.

5. The eyepiece of claim 4 wherein the reflectance peak is characterized by a full-width-at-half-maximum that substantially matches a spectral band width of the light propagating in the planar waveguide.

6. The eyepiece of claim 4 wherein the reflectance peak is characterized by a full-width-at-half-maximum that is greater than a spectral band width of the light propagating in the planar waveguide.

7. The eyepiece of claim 1 wherein the wavelength-selective reflector comprises one of a multilayer thin film, a metasurface, or a volume phase hologram.

8. The eyepiece of claim 1 wherein the grating is optimized for diffracting light in a first polarization state toward the first direction and for diffracting light in a second polarization state orthogonal to the first polarization state toward the second direction, and the wavelength-selective reflector is optimized for reflecting light in the second polarization state.

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

a first planar waveguide having a first front surface and a first back surface, the first planar waveguide being configured to propagate first light in a first wavelength range;

a second planar waveguide disposed substantially parallel to and in front of the first planar waveguide, the second planar waveguide having a second front surface and a second back surface and being configured to propagate second light in a second wavelength range;

a third planar waveguide disposed substantially parallel to and in front of the second planar waveguide, the third planar waveguide having a third front surface and a third back surface and being configured to propagate third light in a third wavelength range;

a first grating coupled to the first back surface of the first planar waveguide and configured to diffract a first portion of the first light propagating in the first planar waveguide out of a plane of the first planar waveguide toward a first direction and to diffract a second portion of the first light out of the plane of the first planar waveguide toward a second direction opposite to the first direction;

a second grating coupled to the second back surface of the second planar waveguide and configured to diffract a first portion of the second light propagating in the second planar waveguide out of a plane of the second planar waveguide toward the first direction and to diffract a second portion of the second light out of the plane of the second planar waveguide toward the second direction;

a third grating coupled to the third back surface of the third planar waveguide and configured to diffract a first portion of the third light propagating in the third planar waveguide out of a plane of the third planar waveguide toward the first direction and to diffract a second portion of the third light out of the plane of the third planar waveguide toward the second direction;

a first wavelength-selective reflector coupled to the first front surface of the first planar waveguide and configured to reflect light in the first wavelength range and transmit light outside the first wavelength range, such that the first wavelength-selective reflector reflects at least part of the second portion of the first light back toward the first direction;

a second wavelength-selective reflector coupled to the second front surface of the second planar waveguide and configured to reflect light in the second wavelength range and transmit light outside the second wavelength range, such that the second wavelength-selective reflector reflects at least part of the second portion of the second light back toward the first direction; and

a third wavelength-selective reflector coupled to the third front surface of the third planar waveguide and configured to reflect light in the third wavelength range and transmit light outside the third wavelength range, such that the third wavelength-selective reflector reflects at least part of the second portion of the third light back toward the first direction.

10. The eyepiece of claim 9 wherein the first front surface of the first planar waveguide faces away from the eye of the viewer, the first back surface of the first planar waveguide faces toward the eye of the viewer, the second front surface of the second planar waveguide faces away from the eye of the viewer, the second back surface of the second planar waveguide faces toward the eye of the viewer, the third front surface of the third planar waveguide faces away from the eye of the viewer, the third back surface of the third planar waveguide faces toward the eye of the viewer, the first direction is toward the eye of the viewer, and the second direction is away from the eye of the viewer.

11. The eyepiece of claim 9 wherein each of the first wavelength-selective reflector, the second wavelength-selective reflector, and the third wavelength-selective reflector comprises one of a multilayer thin film, a metasurface, or a volume phase hologram.

12. The eyepiece of claim 9 wherein each of the first wavelength-selective reflector, the second wavelength-selective reflector, and the third wavelength-selective reflector comprises a metasurface or a volume hologram optimized for a predetermined range of angle of incidence.

13. The eyepiece of claim 9 wherein:

the first wavelength range corresponds to red light;

the second wavelength range corresponds to green light; and

the third wavelength range corresponds to blue light.

14. The eyepiece of claim 13 wherein the first wavelength-selective reflector is configured to transmit green light and blue light, and the second wavelength-selective reflector is configured to transmit blue light.

15. The eyepiece of claim 13 wherein each of the first wavelength-selective reflector, the second wavelength-selective reflector, and the third wavelength-selective reflector comprises a metasurface or a volume hologram, and includes a plurality of regions, each region optimized for a respective range of angle of incidence corresponding to light rays reaching the eye of the viewer.

16. The eyepiece of claim 15 wherein the plurality of regions partially overlap with each other.

17. The eyepiece of claim 9 wherein each of the first wavelength-selective reflector, the second wavelength-selective reflector, and the third wavelength-selective reflector comprises a metasurface including a plurality of interleaved regions, each region optimized for a respective range of angle of incidence.

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

a first planar waveguide having a first front surface and a first back surface and configured to propagate first light in a first wavelength range;

a second planar waveguide disposed substantially parallel to and in front of the first planar waveguide, the second planar waveguide having a second front surface and a second back surface and being configured to propagate second light in a second wavelength range;

a third planar waveguide disposed substantially parallel to and in front of the second planar waveguide, the third planar waveguide having a third front surface and a third back surface and being configured to propagate third light in a third wavelength range;

a first grating coupled to the first front surface of the first planar waveguide and configured to diffract a first portion of the first light propagating in the first planar waveguide out of a plane of the first planar waveguide toward a first direction and to diffract a second portion of the first light out of the plane of the first planar waveguide toward a second direction opposite to the first direction;

a second grating coupled to the second front surface of the second planar waveguide and configured to diffract a first portion of the second light propagating in the second planar waveguide out of a plane of the second planar waveguide toward the first direction and to diffract a second portion of the second light out of the plane of the second planar waveguide toward the second direction;

a third grating coupled to the third front surface of the third planar waveguide and configured to diffract a first portion of the third light propagating in the third planar waveguide out of a plane of the third planar waveguide toward the first direction and to diffract a second portion of the third light out of the plane of the third planar waveguide toward the second direction;

a first wavelength-selective reflector coupled to the second back surface of the second planar waveguide and configured to reflect light in the first wavelength range and transmit light outside the first wavelength range, such that the first wavelength-selective reflector reflects at least part of the second portion of the first light back toward the first direction;

a second wavelength-selective reflector coupled to the third back surface of the third planar waveguide and configured to reflect light in the second wavelength range and transmit light outside the second wavelength range, such that the second wavelength-selective reflector reflects at least part of the second portion of the second light back toward the first direction;

a front cover plate disposed substantially parallel to and in front of the third planar waveguide; and

a third wavelength-selective reflector coupled to a surface of the front cover plate, the third wavelength-selective reflector configured to reflect light in the third wavelength range and transmit light outside the third wavelength range, such that the third wavelength-selective reflector reflects at least part of the second portion of the third light back toward the first direction.

19. The eyepiece of claim 18 wherein each of the first wavelength-selective reflector, the second wavelength-selective reflector, and the third wavelength-selective reflector comprises a metasurface or a volume phase hologram, and includes a plurality of regions, each region optimized for a respective range of angle of incidence corresponding to light rays reaching the eye of the viewer.

20. The eyepiece of claim 18 wherein:

the first wavelength range corresponds to red light;

the second wavelength range corresponds to green light; and

the third wavelength range corresponds to blue light.