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EP-4737958-A1 - LIGHT GUIDE DEVICE, OPTICAL MODULE, AND HEAD-MOUNTED DISPLAY DEVICE

EP4737958A1EP 4737958 A1EP4737958 A1EP 4737958A1EP-4737958-A1

Abstract

Embodiments of the present application provide a light-guiding device, an optical module, and a head-mounted display device; wherein, the light-guiding device includes a light-guiding substrate and an in-coupling area and an out-coupling area provided on the light-guiding substrate; the out-coupling area is configured to perform pupil expansion on light from the in-coupling area and couple it out; the out-coupling area includes at least one first strip grating with grooves, and there are provided at least two grooves which are disposed on opposite sides of the first strip grating, the grooves being capable of being used to induce additional diffraction orders from the first strip grating and form a target diffraction efficiency corresponding to the diffraction orders, so that light propagating to the position of the first strip grating can be changed from originally diffracting on a single side of the first strip grating to having additional diffraction orders induced on the other side of the first strip grating. The solution provided by the embodiments of the present application can enable reasonable distribution of light energy in the out-coupling area, and can improve optical efficiency and imaging quality.

Inventors

  • CHENG, XIN

Assignees

  • Goertek Optical Technology (Shanghai) Co., Ltd.

Dates

Publication Date
20260506
Application Date
20231030

Claims (10)

  1. A light-guiding device, characterized by comprising a light-guiding substrate (1) and an in-coupling area (2) and an out-coupling area (3) provided on the light-guiding substrate (1); the out-coupling area (3) is configured to perform pupil expansion on light from the in-coupling area (2) and couple it out; and the out-coupling area (3) comprises at least one first strip grating (31) with grooves (4), and at least two grooves (4) are provided on opposite sides of the first strip grating (31), the grooves (4) being capable of being used to induce additional diffraction orders from the first strip grating (31) and form a target diffraction efficiency corresponding to the additional diffraction orders, so that light propagating to the position of the first strip grating (31) can be changed from originally diffracting on a single side of the first strip grating (31) to having additional diffraction orders induced on the other side of the first strip grating (31).
  2. The light-guiding device according to claim 1, characterized in that the out-coupling area (3) comprises a plurality of mutually independent sub-out-coupling areas; and the first strip grating (31) is provided in plurality, and is located in at least one of the sub-out-coupling areas to form a transition grating area (303) between a two-dimensional grating area and a one-dimensional grating area.
  3. The light-guiding device according to claim 2, characterized in that , in one sub-out-coupling area, the first strip grating (31) is provided in plurality; wherein, the plurality of first strip gratings (31) are adjacent and spaced apart from each other, to form a partitioned arrangement within the sub-out-coupling area; or, the plurality of first strip gratings (31) are adjacent and sequentially connected to each other, to form an integral whole within the sub-out-coupling area.
  4. The light-guiding device according to any one of claims 1 to 3, characterized in that a width of the first strip grating (31) is L, and a groove depth of the groove (4) is ≤ L; when the groove depth of the groove (4) is L, the groove (4) extends through the first strip grating (31) in a width direction of the first strip grating (31), causing a diffraction efficiency of the additional diffraction orders induced on the other side of the first strip grating (31) to be maximized.
  5. The light-guiding device according to any one of claims 1 to 3, characterized in that the groove (4) comprises a groove bottom (41) and a groove wall extending from the groove bottom (41); the groove wall comprises an opposing first surface (42) and second surface (43), the first surface (42) and the groove bottom (41) form a first included angle A1, the second surface (43) and the groove bottom (41) form a second included angle A2, the first included angle A1 and the second included angle A2 are from 0° to 180°; an included angle between the groove bottom (41) and a side edge (311) along a length direction of the first strip grating (31) is from 0° to 89°; dimensions of the first surface (42) and the second surface (43) along the width direction of the first strip grating (31) are from 0 to 1000 nm.
  6. The light-guiding device according to claim 2, characterized in that the plurality of sub-out-coupling areas comprise a two-dimensional grating area (301) and one-dimensional grating areas (302); wherein, the two-dimensional grating area (301) is located in a middle portion of the out-coupling area (3); there are provided at least two one-dimensional grating areas (302) which are disposed on opposite sides of the two-dimensional grating area (301); the transition grating area (303) is located between the two-dimensional grating area (301) and the respective one-dimensional grating areas (302).
  7. The light-guiding device according to claim 6, characterized in that the two-dimensional grating area (301) comprises a plurality of parallelogram gratings, and the plurality of parallelogram gratings are arranged to form a first target shape; the one-dimensional grating area (302) comprises a plurality of second strip gratings, and the second strip gratings are not provided with the groove (4), and the plurality of second strip gratings are arranged to form a second target shape.
  8. The light-guiding device according to claim 1, characterized in that the out-coupling area (3) is provided on one surface of the light-guiding substrate (1); within the out-coupling area (3): the opposite sides of a grating structure each form an included angle with the surface of the light-guiding substrate (1), and the included angle is 20° to 160°; or, the grating structure is a stepped grating.
  9. An optical module, characterized by comprising: the light-guiding device according to any one of claims 1 to 8; and a light engine, the light engine being configured to project light or an image into the light-guiding device.
  10. A head-mounted display device, characterized by comprising: a housing; and the optical module according to claim 9.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to a Chinese patent application No. 202310790430.7 filed with the China National Intellectual Property Administration on June 29, 2023 and entitled "LIGHT-GUIDING DEVICE, OPTICAL MODULE, AND HEAD-MOUNTED DISPLAY DEVICE", which is incorporated herein by reference in its entirety. TECHNICAL FIELD Embodiments of the present application relate to the technical field of optical imaging, and more particularly, to a light-guiding device, an optical module, and a head-mounted display device. BACKGROUND In existing diffractive optical waveguide solutions, an in-coupling region and an out-coupling region are respectively provided on the waveguide substrate. Currently, the structures of all gratings within the out-coupling region are identical; therefore, the diffraction efficiency for coupling out light is uniform across different positions within the out-coupling region. However, since the total energy of the light is constant, the light energy at the edge and trailing end portions of the out-coupling region progressively decreases during light transmission, causing the coupled-out light energy to diminish accordingly. This results in non-uniform image intensity and low overall optical efficiency. SUMMARY An objective of the present application is to provide a new technical solution for a light-guiding device, an optical module, and a head-mounted display device, thereby achieving different diffraction efficiencies in different areas within the out-coupling area. In a first aspect, the present application provides a light-guiding device. The light-guiding device includes a light-guiding substrate and an in-coupling area and an out-coupling area provided on the light-guiding substrate; the out-coupling area is configured to perform pupil expansion on light from the in-coupling area and couple it out; andthe out-coupling area includes at least one first strip grating with grooves, and at least two grooves are provided on opposite sides of the first strip grating, the grooves being capable of being used to induce additional diffraction orders from the first strip grating and form a target diffraction efficiency corresponding to the additional diffraction orders, so that light propagating to the position of the first strip grating can be changed from originally diffracting on a single side of the first strip grating to having additional diffraction orders induced on the other side of the first strip grating. Optionally, the out-coupling area includes a plurality of mutually independent sub-out-coupling areas; and the first strip grating is provided in plurality, and is located in at least one of the sub-out-coupling areas to form a transition grating area between a two-dimensional grating area and a one-dimensional grating area. Optionally, in one sub-out-coupling area, the first strip grating is provided in plurality; wherein, the plurality of first strip gratings are adjacent and spaced apart from each other, to form a partitioned arrangement within the sub-out-coupling area; or,the plurality of first strip gratings are adjacent and sequentially connected to each other, to form an integral whole within the sub-out-coupling area. Optionally, a width of the first strip grating is L, and a groove depth of the groove is ≤ L; when the groove depth of the groove is L, the groove extends through the first strip grating in a width direction of the first strip grating, causing a diffraction efficiency of the additional diffraction orders induced on the other side of the first strip grating to be maximized. Optionally, the groove includes a groove bottom and a groove wall extending from the groove bottom; the groove wall includes an opposing first surface and second surface, the first surface and the groove bottom form a first included angle A1, the second surface and the groove bottom form a second included angle A2, the first included angle A1 and the second included angle A2 are from 0° to 180°;an included angle between the groove bottom and a side edge along a length direction of the first strip grating is from 0° to 89°;dimensions of the first surface and the second surface along the width direction of the first strip grating are from 0 to 1000 nm. Optionally, the plurality of sub-out-coupling areas include a two-dimensional grating area and one-dimensional grating areas; wherein, the two-dimensional grating area is located in a middle portion of the out-coupling area;at least two one-dimensional grating areas are disposed on opposite sides of the two-dimensional grating area;the transition grating area is located between the two-dimensional grating area and the respective one-dimensional grating areas. Optionally, the two-dimensional grating area includes a plurality of parallelogram gratings, and the plurality of parallelogram gratings are arranged to form a first target shape; the one-dimensional grating area includes a plurality of second s