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US-12625370-B2 - Holographic VR display

US12625370B2US 12625370 B2US12625370 B2US 12625370B2US-12625370-B2

Abstract

A holographic display includes an illuminator, a spatial light modulator (SLM) coupled to the illuminator, and an ocular lens coupled to the SLM. The illuminator provides a wide-area illuminating light beam to illuminate the SLM with a spatially homogeneous beam of light. The illuminator may include a slab waveguide with an evanescent out-coupler, or a beam expander based on a diffraction grating with an oblique angle of incidence and a near-normal angle of diffraction of the illuminating light. A low-pass spatial filter may be provided to filter out higher diffraction orders of the illuminating light diffracted on the SLM.

Inventors

  • Changwon JANG
  • Afsoon Jamali
  • Zhimin Shi

Assignees

  • META PLATFORMS TECHNOLOGIES, LLC

Dates

Publication Date
20260512
Application Date
20230202

Claims (19)

  1. 1 . A holographic display comprising: an illuminator comprising a substrate, a slab core layer on the substrate for guiding a light beam therein, a cladding layer on the slab core layer, and a light extractor on the cladding layer, the light extractor having a refractive index higher than an effective refractive index of a mode of propagation of light in the slab core layer, for evanescent out-coupling of the light beam from the slab core layer into the light extractor, thereby forming an illuminating light beam, wherein the light extractor further comprises a prism having first and second faces at an acute angle to one another, wherein: the first face is coupled to the cladding layer, and the second face includes a reflector with a curved outer surface defined by a radius of curvature having an optical power for at least one of focusing or defocusing; and a spatial light modulator (SLM) operably coupled to the illuminator for receiving and spatially modulating the illuminating light beam in amplitude and phase to provide an image light beam.
  2. 2 . The holographic display of claim 1 , wherein a thickness of the cladding layer decreases in a direction of propagation of the light beam to improve a spatial uniformity of light extraction by the light extractor.
  3. 3 . The holographic display of claim 1 , wherein the cladding layer and the slab core layer are configured for singlemode propagation of the light beam in the slab core layer.
  4. 4 . The holographic display of claim 1 , further comprising an ocular lens operably coupled to the SLM for receiving the image light beam and forming an image at an eyebox of the holographic display for observation by a user's eye.
  5. 5 . The holographic display of claim 4 , further comprising a beam redirector in an optical path of the image light between the SLM and the ocular lens, for controllably redirecting the image light beam.
  6. 6 . The holographic display of claim 5 , wherein the beam redirector comprises a tunable liquid crystal redirector of the image light beam.
  7. 7 . The holographic display of claim 5 , wherein the beam redirector comprises a stack of active Pancharatnam-Berry phase (PBP) layers configured for switching a direction of propagation of the image light beam.
  8. 8 . The holographic display of claim 5 , further comprising: an eye tracking system for determining a position of a pupil of the user's eye in the eyebox; and a controller operably coupled to the eye tracking system and the beam redirector for causing the beam redirector to controllably redirect the image light beam towards the eye pupil position determined by the eye tracking system.
  9. 9 . A holographic display comprising: a beam expander comprising a diffractive layer for diffracting a collimated light beam at an angle of incidence exceeding an angle of diffraction, whereby a lateral size of the collimated light beam increases upon diffraction on the diffractive layer; a spatial light modulator (SLM) operably coupled to the beam expander for receiving the light beam diffracted by the diffractive layer and spatially modulating the light beam in amplitude and phase to provide an image light beam, wherein in operation, the image light beam propagates through the diffractive layer; and a light extractor including a prism having first and second faces at an acute angle to one another, wherein the first face is coupled to a cladding layer, and the second face includes a reflector with a curved outer surface defined by a radius of curvature with an optical power for at least one of focusing or defocusing.
  10. 10 . The holographic display of claim 9 , wherein the angle of incidence is at least 75 degrees, and the angle of diffraction is no greater than 15 degrees.
  11. 11 . The holographic display of claim 9 , the diffractive layer comprises a polarization volume hologram.
  12. 12 . The holographic display of claim 9 , wherein the diffractive layer comprises a volume Bragg grating.
  13. 13 . The holographic display of claim 9 , wherein the beam expander further comprises first and second prismatic elements each comprising a diagonal face, the first prismatic element further comprising a side face joining the diagonal face of the first prismatic element; and wherein the diffractive layer is sandwiched between the diagonal faces of the first and second prismatic elements, and wherein in operation, the collimated light beam is received at the side face of the first prismatic element.
  14. 14 . The holographic display of claim 9 , further comprises an ocular lens operably coupled to the SLM for receiving the image light beam and forming an image at an eyebox of the holographic display for observation by a user's eye.
  15. 15 . The holographic display of claim 14 , further comprising a beam redirector in an optical path of the image light between the SLM and the ocular lens, for controllably redirecting the image light beam.
  16. 16 . The holographic display of claim 15 , wherein the beam redirector comprises a tunable liquid crystal beam redirector.
  17. 17 . The holographic display of claim 15 , wherein the beam redirector comprises a stack of active Pancharatnam-Berry phase (PBP) layers configured for switching a direction of propagation of the image light beam.
  18. 18 . The holographic display of claim 15 , further comprising: an eye tracking system for determining a position of a pupil of the user's eye in the eyebox; and a controller operably coupled to the eye tracking system and the beam redirector for causing the beam redirector to controllably redirect the image light beam towards the eye pupil position determined by the eye tracking system.
  19. 19 . A holographic display comprising: a frontlight illuminator for providing an illuminating light beam; a spatial light modulator (SLM) operably coupled to the frontlight illuminator for receiving and spatially modulating the illuminating light beam in amplitude and phase to provide an image light beam propagating through the frontlight illuminator; a light extractor including a prism having first and second faces at an acute angle to one another, wherein the first face is coupled to a cladding layer, and the second face includes a reflector with a curved outer surface defined by a radius of curvature with an optical power for at least one of focusing or defocusing; an ocular lens operably coupled to the SLM for receiving the image light beam and forming an image at an eyebox of the holographic display for observation by a user's eye; and a low-pass spatial filter in an optical path of the image light beam between the SLM and the ocular lens, for blocking higher orders of diffraction of the illuminating light beam on the SLM while propagating a zeroth order of diffraction of the illuminating light beam.

Description

REFERENCE TO RELATED APPLICATION This application claims priority from U.S. Provisional Patent Application No. 63/426,338 entitled “HOLOGRAPHIC VR DISPLAY”, filed on Nov. 17, 2022 and incorporated herein by reference in their entirety. TECHNICAL FIELD The present disclosure relates to optical devices, and in particular to holographic display systems and modules. BACKGROUND Head mounted displays (HMD), helmet mounted displays, near-eye displays (NED), and the like are being used for displaying virtual reality (VR) content, augmented reality (AR) content, mixed reality (MR) content, etc. Such displays are finding applications in diverse fields including entertainment, education, training and science, to name just a few examples. The displayed VR/AR/MR content can be three-dimensional (3D) to enhance the experience and to match virtual objects to real objects observed by the user. To provide better optical performance, display systems and modules may include various components such as lenses, waveguides, display panels, gratings, etc. Because a display of an HMD or NED is usually worn on the head of a user, a large, bulky, unbalanced, and/or heavy display device would be cumbersome and may be uncomfortable for the user to wear. Compact, lightweight, and energy-efficient head-mounted display devices and modules are desirable. BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments will now be described in conjunction with the drawings, in which: FIG. 1 is a schematic view of a replicating lightguide based holographic display of this disclosure; FIG. 2 is a cross-sectional exploded view of a display embodiment using an illumination replication lightguide; FIG. 3 is a cross-sectional exploded view of a full-aperture lightguide illuminator display of this disclosure; FIG. 4 is a cross-sectional exploded view of a display of this disclosure based on a full-aperture light steering stack; FIG. 5A includes plan and side cross-sectional views of a multi-beam expander for a holographic display of this disclosure, the multi-beam expander including an array of partial mirrors; FIG. 5B includes plan and side cross-sectional views of a multi-beam expander for a holographic display of this disclosure, the multi-beam expander including a surface-relief grating (SRG); FIG. 5C includes plan and side cross-sectional views of a multi-beam expander for a holographic display of this disclosure, the multi-beam expander including a volume Bragg grating (VBG); FIG. 6 is a schematic view of a holographic display with a single-beam expander; FIG. 7 is a side cross-sectional view of a singlemode slab waveguide embodiment of the single-beam expander of FIG. 6; FIG. 8A is a schematic view of a single-beam expander comprising a diffractive layer; FIG. 8B is a side cross-sectional view of an embodiment of the single-beam expander of FIG. 8A used to illuminate a reflective spatial light modulator (SLM); FIG. 9 is a side cross-sectional view of a compound SLM of this disclosure; FIG. 10 is a side cross-sectional view of a compound amplitude/phase SLM of FIG. 9 including serially coupled reflective microelectromechanical system (MEMS) and liquid crystal (LC) SLM panels; FIG. 11A is a side cross-sectional view of a compound amplitude/phase SLM of FIG. 9 including serially coupled in-plane switching (IPS) LC panels; FIG. 11B is a plan magnified of the view of four pixels of the compound amplitude/phase SLM of FIG. 11A; FIG. 12 is a flow chart of a method for displaying content to a user using a pair of SLM panels; FIG. 13 is a side cross-sectional view of an LC beam steering device for use in a holographic display of this disclosure; FIG. 14A is a side cross-sectional view of a Pancharatnam-Berry phase (PBP) beam deflector in a deflecting state, for use in a holographic display of this disclosure; FIG. 14B is a side cross-sectional view of the PBP beam deflector of FIG. 14A in a non-deflecting state; FIG. 15A is a side schematic view of an ocular lens for a holographic display of this disclosure; FIG. 15B is a polarization diagram of the ocular lens of FIG. 15A; FIG. 16A is a side view of an SLM showing multiple orders of diffraction; FIG. 16B is a side view of a low-pass spatial filter for blocking the higher orders of diffraction; FIG. 17 is a schematic view of a holographic display with multiple exit pupils generated in a time-sequential manner; FIGS. 18A and 18B are schematic views of the multiple exit pupils generated by the holographic display of FIG. 17; FIG. 19 is a flow chart of a method for displaying an image with multiple exit pupils generation; FIG. 20 is a view of an augmented reality (AR) display of this disclosure having a form factor of a pair of eyeglasses; and FIG. 21 is an isometric view of a head-mounted virtual reality (VR) display of this disclosure. DETAILED DESCRIPTION While the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to