Diffractive optical element with integrated in-coupling, exit pupil expansion, and out-coupling

• US 10,429,645 B2
• Filed: 10/07/2015
• Issued: 10/01/2019
• Est. Priority Date: 10/07/2015
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Vallius, Tuomas
• Primary Examiner(s): Chang, Audrey Y
• Application Number:
  US14/877,281
• Publication Number:
  US 20170102543A1
• Time in Patent Office: 1,455 Days
• Field of Search: 359 13, 359569, 359 34, 359571, 359572, 359630
• CPC Class Codes: G02B 2027/0134 of stereoscopic type
• CPC Class Codes: G02B 2027/015 involving arrangement aiming to get less bulky devices
• CPC Class Codes: G02B 2027/0152 involving arrangement aiming to get lighter or better balanced devices
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/0176 characterised by mechanical features
• CPC Class Codes: G02B 27/4205 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 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G06T 19/006 Mixed reality object pose determination, tracking or camera calibration for mixed reality G06T7/00

Abstract

In an optical near eye display system, a monolithic three-dimensional optical microstructure is formed by a waveguide substrate with at least one DOE having grating regions that integrate the functions of in-coupling of incident light into the waveguide, exit pupil expansion in one or two directions, and out-coupling of light from the waveguide within a single optical element. An in-coupling region of the DOE couples the incident light into the waveguide and to a beam steering and out-coupling region. The beam steering and out-coupling region provides exit pupil expansion and couples light out of the waveguide. The beam steering and out-coupling region of the DOE can be configured with a two-dimensional (2D) grating that is periodic in two directions.

Claims

1. An optical element, comprising:

a monolithic substrate of optical material forming a waveguide in which one or more optical beams are propagated;

an in-coupling region integrated into the monolithic substrate, the in-coupling region having an input surface and configured with a one dimensional (1D) grating that is periodic in one direction to couple one or more optical beams incident on the input surface into the waveguide; and

a beam steering and out-coupling region integrated into the monolithic substrate and configured for pupil expansion of the one or more optical beams along a first direction,

wherein the beam steering and out-coupling region is configured with a two-dimensional (2D) grating that is periodic in two directions,

wherein the 2D grating is configured to provide at least two diverse optical paths to each of any given point in the 2D grating for the propagating optical beams, wherein differences between lengths of the at least two diverse optical paths to each of any given point exceed a coherence length of the propagating optical beams in the beam steering and out-coupling region so as to increase uniformity of output optical beams and thereby reduce optical interference.

2. The optical element of claim 1 in which the 2D grating includes one of symmetric or asymmetric features.

3. The optical element of claim 2 in which the asymmetric features include one of slanted gratings or blazed gratings.

4. The optical element of claim 1 in which the beam steering and out-coupling region includes an output surface and is configured for pupil expansion of the one or more optical beams along a second direction, and further configured to couple, as an output from the output surface, the one or more optical beams with expanded pupil relative to the input.

5. An electronic device, comprising:

a data processing unit;

an optical engine operatively connected to the data processing unit for receiving image data from the data processing unit;

an imager operatively connected to the optical engine to form images based on the image data and to generate one or more input optical beams incorporating the images; and

an exit pupil expander, responsive to the one or more input optical beams, comprising a monolithic waveguide structure in which one or more optical beams are propagated and on which multiple diffractive optical elements (DOEs) are integrated,

in which the exit pupil expander is configured to provide one or more output optical beams, using one or more of the DOEs, as a near eye virtual display with an expanded exit pupil, and includes an in-coupling region having an input surface and configured with a one dimensional (1D) grating that is periodic in one direction to couple the one or more input optical beams incident on the input surface into the monolithic waveguide structure,

wherein at least one of the DOEs has a region configured to implement beam steering and out-coupling of the one or more output optical beams from the monolithic waveguide structure, and

wherein at least one of the DOEs includes a two-dimensional (2D) grating that is periodic in two directions and configured to provide at least two diverse optical paths to each of any given point in the 2D grating for the propagating one or more optical beams, wherein differences between lengths of the at least two diverse optical paths to each of any given point exceed a coherence length of the propagating one or more optical beams in the beam steering and out-coupling region so as to increase uniformity of the one or more output optical beams and thereby reduce optical interference.

6. The electronic device of claim 5 wherein at least one of the DOEs has a region configured to in-couple the one or more input optical beams into the monolithic waveguide structure.

7. The electronic device of claim 5 in which the one or more input optical beams received at the exit pupil expander emanate as a virtual image produced by a micro-display or imager.

8. The electronic device of claim 5 in which the exit pupil expander provides pupil expansion in two directions.

9. The electronic device of claim 5 in which the imager includes one of light emitting diode, liquid crystal on silicon device, organic light emitting diode array, or micro-electro mechanical system device.

10. The electronic device of claim 5 in which the imager comprises a micro-display operating in one of transmission, reflection, or emission.

11. The electronic device of claim 5 as implemented in a head mounted display device or portable electronic device.

12. The electronic device of claim 5 in which the monolithic waveguide structure is curved or partially spherical.

13. The electronic device of claim 5 in which two or more of the DOEs are non-co-planar.

14. A method, comprising:

receiving light at an in-coupling region of a diffractive optical element (DOE) disposed in an exit pupil expander formed of a unitary optical structure in which one or more optical beams are propagated, wherein the in-coupling region has an input surface and is configured with a one dimensional (1D) grating that is periodic in one direction to couple the received light incident on the input surface into the exit pupil expander;

expanding an exit pupil of the received light along a first coordinate axis in a beam steering and out-coupling region of the DOE;

expanding the exit pupil along a second coordinate axis in a beam steering and out-coupling region of the DOE; and

outputting light with an expanded exit pupil relative to the received light at the in-coupling region of the DOE along the first and second coordinate axes using the beam steering and out-coupling region,

in which the beam steering and out-coupling region includes gratings configured to provide a periodic contoured surface having a first periodicity along a first direction and a second periodicity along a second direction, and

wherein the gratings of the DOE are configured to provide at least two diverse optical paths to each of any given point in the gratings for the propagating one or more optical beams, wherein differences between lengths of the at least two diverse optical paths to each of any given point exceed a coherence length of the propagating one or more optical beams in the beam steering and out-coupling region so as to increase uniformity of output optical beams and thereby reduce optical interference.

15. The method of claim 14 in which the periodic contoured surface comprises one of quadrangular elements, cylindrical elements, polygonal elements, elliptical elements, pyramidal elements, curved elements, or combinations thereof.

16. The method of claim 14 in which the DOE is formed as the unitary optical structure using a polymer that is molded from a substrate that is etched using ion beam etching in which the substrate has changeable orientation relative to an ion beam source.

17. The method of claim 14 in which the in-coupling region includes gratings configured to provide a periodic contoured surface having a third periodicity along a third direction and a fourth periodicity along a fourth direction.

18. The method of claim 14 as performed in a near eye display system.

19. The method of claim 18 in which the output light provides a virtual display to a user of the near eye display system.