DIFFRACTIVE OPTICAL ELEMENTS WITH ASYMMETRIC PROFILES

• US 20170003505A1
• Filed: 07/02/2015
• Published: 01/05/2017
• Est. Priority Date: 07/02/2015
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Lauri Sainiemi
• Inventors: Vallius, Tuomas, Sainiemi, Lauri
• Granted Patent: US 10,670,862 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/0172 characterised by optical 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 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1819 Plural gratings positioned on the same surface, e.g. array of gratings plural diffractive elements positioned sequentially along the optical path G02B27/4272
• CPC Class Codes: G02B 5/1852 using mechanical means, e.g. ruling with diamond tool, moulding

Abstract

In an optical display system that includes a waveguide with multiple diffractive optical elements (DOEs), gratings in one or more of the DOEs may have an asymmetric profile in which gratings may be slanted or blazed. Asymmetric gratings in a DOE can provide increased display uniformity in the optical display system by reducing the “banding” resulting from optical interference that is manifested as dark stripes in the display. Banding may be more pronounced when polymeric materials are used in volume production of the DOEs to minimize system weight, but which have less optimal optical properties compared with other materials such as glass. The asymmetric gratings can further enable the optical system to be more tolerant to variations—such as variations in thickness, surface roughness, and grating geometry—that may not be readily controlled during manufacturing particularly since such variations are in the submicron range.

Claims

1. An optical system, comprising:

a substrate of optical material;

a first diffractive optical element (DOE) disposed on the substrate, the first DOE having an input surface and configured as an in-coupling grating to receive one or more optical beams as an input; and

a second DOE disposed on the substrate and configured for pupil expansion of the one or more optical beams along a first direction,

wherein at least a portion of the second DOE includes gratings that are configured with a predetermined slant angle to a direction orthogonal to a plane of the substrate.

2. The optical system of claim 1 further including a third DOE disposed on the substrate, the third DOE having an output surface and configured for pupil expansion of the one or more optical beams along a second direction, and further configured as an out-coupling grating to couple, as an output from the output surface, one or more optical beams with expanded pupil relative to the input.

3. The optical system of claim 2 in which at least a portion of the third DOE includes gratings that are configured with a second predetermined slant angle to a direction orthogonal to a plane of the output surface.

4. The optical system of claim 3 in which at least a portion of the first DOE includes gratings that are configured with a third predetermined slant angle to a direction orthogonal to a plane of the input surface.

5. The optical system of claim 1 in which the one or more optical beams received at the first DOE emanate as a virtual image produced by a micro-display or imager.

6. 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 structure on which multiple diffractive optical elements (DOEs) are disposed,

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

wherein at least one of the DOEs is configured with gratings having an asymmetric profile.

7. The electronic device of claim 6 in which the asymmetric profile comprises one of gratings with slanted sidewalls or blazed gratings.

8. The electronic device of claim 6 in which the exit pupil expander provides pupil expansion in two directions.

9. The electronic device of claim 6 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 6 in which the imager comprises a micro-display operating in one of transmission, reflection, or emission.

11. The electronic device of claim 6 as implemented in a head mounted display device or portable electronic device.

12. The electronic device of claim 6 in which each of the one or more input optical beams is produced by a corresponding one or more sources.

13. The electronic device of claim 6 in which the structure is curved or partially spherical.

14. The electronic device of claim 6 in which two or more of the DOEs are non-co-planar.

15. A method, comprising:

receiving light at an in-coupling diffractive optical element (DOE) disposed in an exit pupil expander;

expanding an exit pupil of the received light along a first coordinate axis in an intermediate DOE disposed in the exit pupil expander;

expanding the exit pupil along a second coordinate axis in an out-coupling DOE disposed in the exit pupil expander; and

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

in which the intermediate DOE is configured with gratings that have non-orthogonal orientation relative to a plane of the exit pupil expander.

16. The method of claim 15 in which the non-orthogonal orientation comprises a slant angle of between 30 and 50 degrees from a normal to the plane.

17. The method of claim 15 in which the in-coupling DOE, the intermediate DOE, or the out-coupling DOE is formed with a polymer that is molded from a substrate that is etched using ion beam etching in which the substrate is rotatable relative to an ion beam source.

18. The method of claim 15 further in which at least a portion of the out-coupling DOE is an apodized diffraction grating having shallow grooves relative to the in-coupling DOE or the intermediate DOE.

19. The method of claim 15 as performed in a near eye display system.

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