AUGMENTED REALITY DISPLAY SYSTEM WITH VARIABLE FOCUS

• US 20170184848A1
• Filed: 12/29/2015
• Published: 06/29/2017
• Est. Priority Date: 12/29/2015
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Tuomas Vallius
• Inventors: VALLIUS, TUOMAS
• Granted Patent: US 9,927,614 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 2027/0127 comprising devices increasing the depth of field
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 2027/0185 Displaying image at variable distance
• 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 27/0955 Lenses lenses per se G02B3/00
• 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 27/4261 having a diffractive element with major polarization dependent properties
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 3/14 of variable focal length
• 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: G02F 1/29 for the control of the position or the direction of light beams, i.e. deflection
• CPC Class Codes: G02F 1/294 Variable focal length devices
• CPC Class Codes: G06T 11/00 2D [Two Dimensional] image generation

Abstract

A near-eye optical display system that may be utilized in augmented reality applications and devices includes a diffractive waveguide having diffractive optical elements (DOEs) configured for in-coupling, exit pupil expansion, and out-coupling. An electrically-modulated tunable liquid crystal (LC) lens is located between the diffractive grating and the eyes of the user. A polarizing filter is located on the other side of the diffractive grating so that light from the real world enters the system with a particular polarization state, for example, TM-polarized. The tunable LC lens is configured to impart variable focus on light that has an opposite polarization state, for example TE-polarized. The optical display system is arranged to be polarization-sensitive so that virtual images from an imager are out-coupled from the diffractive waveguide with TE-polarization. The tunable LC lens may thus impart variable focus to the virtual images due to the lens'"'"' sensitivity to TE-polarization.

Claims

1. An optical display system, comprising:

a polarizing filter configured to filter light from real-world objects into a first polarization state;

a tunable liquid crystal (LC) lens that is configured to impart variable focus on light that has a second polarization state, the second polarization state being orthogonal to the first polarization state; and

a waveguide including an out-coupling element for out-coupling light to the tunable LC lens

wherein the out-coupling element is configured for sensitivity to the second polarization state so that only light in the second polarization state is out-coupled to the tunable LC lens and subject to variable focus while light from real-world objects in the first polarization state is not subject to variable focus.

2. The optical display system of claim 1 in which the waveguide comprises

a first diffractive optical element (DOE) having an input surface and configured as an in-coupling grating to receive one or more optical beams from an imager having a second polarization state as an input,

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

a 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 out-couple, as an output to the tunable LC lens from the output surface, one or more optical beams with expanded pupil relative to the input.

3. The optical display system of claim 2 in which grating features in at least one of the DOEs are configured according to one or more of grating asymmetry, grating depth, or grating fill factor so as to impart polarization-sensitivity to the second polarization state.

4. The optical display system of claim 1 in which the waveguide is one of diffractive waveguide, refractive waveguide, reflective waveguide, holographic waveguide, prism waveguide, or combinations thereof, and the out-coupling element is one of diffractive optical element, dichroic mirror, polarization-selective coating, or prism, and further comprising an in-coupling element configured to in-couple light into the waveguide in which the in-coupling element is one of diffractive optical element, dichroic mirror, polarization-selective coating, or prism.

5. The optical display system of claim 1 in which the polarizing filter is disposed in a forward-facing portion of the optical display system upon which light from the real-world objects impinges and the tunable LC lens is disposed in a portion of the optical display system between the waveguide and eyes of a user.

6. An electronic device supporting an augmented reality experience including virtual images and real-world images, comprising:

a data processing unit;

an optical engine operatively connected to the data processing unit for receiving image data from the data processing unit and producing virtual images;

a polarizing filter configured to filter light from real-world images into a first polarization state;

an electrically-modulated tunable liquid crystal (LC) lens configured to impart variable focus to light having a second polarization state that is orthogonal to the first polarization state; and

an exit pupil expander, responsive to one or more input optical beams incorporating the virtual images, 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 out-coupled optical beams, using one or more of the DOEs, as a near-eye display with an expanded exit pupil, and

wherein at least one of the DOEs has a portion configured to be polarization-sensitive so the exit pupil expander outputs the virtual images having the second polarization state to the LC lens in the out-coupled optical beams.

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

8. The electronic device of claim 6 further including an imager operatively connected to the optical engine to form virtual images based on the image data and to generate one or more input optical beams incorporating the virtual images having the second polarization state.

9. The electronic device of claim 8 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 LC lens is configured to impart variable focus to one or more of virtual images or real-world images.

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 the LC lens comprises floating electrodes and concentric electrodes wherein the floating electrodes are configured to fill gaps between the concentric electrodes when the LC lens is electrically modulated to assume a particular wavefront shape to thereby impart variable focus to the virtual images.

13. The electronic device of claim 12 in which the LC lens includes a layer of LC material located between respective top and bottom substrates and further comprising a controller configured to electrically modulate the LC lens to assume the particular wavefront shape to thereby impart focus to the out-coupled optical beams, the controller being adapted to apply an electric profile to various portions of the LC material layer through electrical contacts to the concentric electrodes.

14. The electronic device of claim 6 in which the LC lens is further configured to be infinitely variable between a range of optical powers.

15. A method for providing variable focus to virtual images in an augmented reality display system that supports virtual images and real-world images, comprising:

utilizing a polarizing filter so that the real-world images have a first polarization state;

receiving, from an imager, light incorporating virtual images at an in-coupling diffractive optical element (DOE) disposed in an exit pupil expander;

expanding an exit pupil of the received virtual images 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;

outputting the virtual images to a tunable liquid crystal (LC) lens, the output virtual images having 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; and

electrically controlling the tunable LC lens to focus the virtual images on a virtual image plane of variable distance away from the system

wherein the LC lens is polarization-sensitive whereby the LC lens imparts focus to light in a second polarization state and does not impart focus to light in the first polarization state, and

wherein the out-coupling DOE is polarization-sensitive whereby the out-coupling DOE is configured to out-couple light in the second polarization state from the exit pupil expander to the LC lens and pass through light in the first polarization state without out-coupling.

16. The method of claim 15 in which the first and second polarization states include one of linearly-polarized or circularly-polarized.

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

18. The method of claim 15 in which the electric control comprises analog adjustability of LC material in the lens between various wavefront shapes by application of power to an arrangement of electrodes in the LC lens.

19. The method of claim 15 in which one or more of the in-coupling DOE, intermediate DOE, or out-coupling DOE include portions having grating features configured to perform a conversion on an input to the in-coupling DOE from the first polarization state to the second polarization state.

20. The method of claim 19 in which the polarization conversion is performed upstream from the outputting at the out-coupling DOE.