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US-20260126653-A1 - LIGHT GUIDE DEVICE AND NEAR-EYE DISPLAY

US20260126653A1US 20260126653 A1US20260126653 A1US 20260126653A1US-20260126653-A1

Abstract

A light guide device including a light guide plate, a diffraction grating and a phase retardation element is provided. The diffraction grating is disposed on a first surface of the light guide plate. The diffraction grating is used to provide a plurality of diffraction beams, while a light beam is incident to the diffraction grating. The diffraction beams include a major diffraction beam, and the major diffraction beam propagates in the light guide plate. The phase retardation element is disposed on a transmission path of the major diffraction beam. The major diffraction beam has a first polarization state before being incident to the phase retardation element. The major diffraction beam has a second polarization state when leaving the phase retardation element. The first polarization state is different from the second polarization state. A near-eye display having an image light source and the light guide device is also provided.

Inventors

  • Yi-Chien Lo
  • Wen-Chun Wang

Assignees

  • CORETRONIC CORPORATION

Dates

Publication Date
20260507
Application Date
20251022
Priority Date
20241107

Claims (20)

  1. 1 . A light guide device, adapted to guide a light beam, comprising: a light guide plate; a diffraction grating, disposed on a first surface of the light guide plate, wherein when the light beam is incident on the diffraction grating, the diffraction grating is adapted to generate a plurality of diffraction beams, the plurality of diffraction beams comprise a major diffraction beam, and the major diffraction beam is transmitted in the light guide plate; and a phase retardation element, disposed on a transmission path of the major diffraction beam, wherein the major diffraction beam has a first polarization state before being incident on the phase retardation element, and the major diffraction beam has a second polarization state when leaving the phase retardation element, wherein the first polarization state is different from the second polarization state.
  2. 2 . The light guide device as claimed in claim 1 , wherein a part of the major diffraction beam passes through the phase retardation element once.
  3. 3 . The light guide device as claimed in claim 1 , wherein the first polarization state is perpendicular to the second polarization state.
  4. 4 . The light guide device as claimed in claim 1 , wherein the diffraction grating is a reflective diffraction grating.
  5. 5 . The light guide device as claimed in claim 4 , further comprising a first reflecting mirror disposed on the first surface of the light guide plate, wherein the diffraction grating is located between the first reflecting mirror and the light guide plate.
  6. 6 . The light guide device as claimed in claim 5 , further comprising a second reflecting mirror disposed on a second surface of the light guide plate, wherein the light guide plate is located between the first reflecting mirror and the second reflecting mirror.
  7. 7 . The light guide device as claimed in claim 4 , wherein the light beam penetrates through the phase retardation element before being incident on the diffraction grating.
  8. 8 . The light guide device as claimed in claim 7 , further comprising a first reflecting mirror disposed on the first surface of the light guide plate, wherein the diffraction grating is located between the first reflecting mirror and the light guide plate.
  9. 9 . The light guide device as claimed in claim 7 , wherein the light beam has a polarization state, and the phase retardation element is adapted to convert the polarization state into the first polarization state.
  10. 10 . The light guide device as claimed in claim 1 , wherein the diffraction grating is a transmissive diffraction grating.
  11. 11 . The light guide device as claimed in claim 10 , further comprising a first reflecting mirror disposed on a second surface of the light guide plate, wherein the first surface is opposite to the second surface.
  12. 12 . The light guide device as claimed in claim 11 , further comprising a second reflecting mirror disposed on the first surface of the light guide plate, wherein the diffraction grating is located between the second reflecting mirror and the light guide plate.
  13. 13 . The light guide device as claimed in claim 10 , wherein the plurality of diffraction beams further comprise a secondary diffraction beam, and the phase retardation element is disposed on a transmission path of the secondary diffraction beam.
  14. 14 . The light guide device as claimed in claim 13 , further comprising a first reflecting mirror, wherein the phase retardation element is located between the first reflecting mirror and the light guide plate.
  15. 15 . The light guide device as claimed in claim 10 , wherein the phase retardation element comprises a first phase retardation layer and a second phase retardation layer stacked to each other.
  16. 16 . The light guide device as claimed in claim 15 , further comprising a first reflecting mirror disposed on the first surface of the light guide plate, wherein the first phase retardation layer and the second phase retardation layer are located between the first surface of the light guide plate and the first reflecting mirror.
  17. 17 . The light guide device as claimed in claim 16 , wherein the first phase retardation layer is located between the first surface of the light guide plate and the second phase retardation layer.
  18. 18 . The light guide device as claimed in claim 17 , wherein the first phase retardation layer is disposed on the first surface of the light guide plate.
  19. 19 . The light guide device as claimed in claim 17 , wherein the second phase retardation layer is disposed on the first reflecting mirror.
  20. 20 . The light guide device as claimed in claim 1 , wherein the phase retardation element is parallel to the first surface of the light guide plate.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit of China application serial no. 202411578866.0 filed on Nov. 7, 2024. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. BACKGROUND Technical Field The invention relates to an optical device, and particularly relates to a light guide device and a near-eye display. Description of Related Art Diffractive waveguides may be thinner in thickness than geometric waveguides. Currently, diffractive waveguides include surface relief grating (SRG), volume holographic grating (VHG) and polarization volume grating (PVG). The surface relief grating (SRG) has advantages over other diffractive gratings in terms of efficiency and design freedom. In an ideal state, it is expected that a diffraction beam generated by a coupling-in grating may be completely transmitted to a waveguide outlet in a total reflection manner within the waveguide. However, the coupling-in grating usually has a certain area, so that the diffraction beam generated through the coupling-in grating re-enters the coupling-in grating after total reflection of the diffraction beam within the waveguide, resulting in further diffraction and undesired light leakage. The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art. SUMMARY The invention is directed to a light guide device with low energy consumption and good optical performance. Additional aspects and advantages of the present invention will be set forth in the description of the techniques disclosed in the present invention. In order to achieve one or a portion of or all of the objects or other objects, an embodiment of the invention provides a light guide device adapted to guide a light beam, and including a light guide plate, a diffraction grating and a phase retardation element. The diffraction grating is disposed on a first surface of the light guide plate, where when the light beam is incident on the diffraction grating, the diffraction grating is adapted to generate a plurality of diffraction beams, and the diffraction beams include a major diffraction beam, and the major diffraction beam is transmitted in the light guide plate. The phase retardation element is disposed on a transmission path of the major diffraction beam. The major diffraction beam has a first polarization state before being incident on the phase retardation element, and the major diffraction beam has a second polarization state when leaving the phase retardation element, where the first polarization state is different from the second polarization state. Another embodiment of the invention provides a near-eye display including an image light source and a light guide device. The image light source is adapted to emit a light beam. The light guide device is disposed on a transmission path of the light beam and is adapted to guide the light beam, and includes a light guide plate, a diffraction grating and a phase retardation element. The diffraction grating is disposed on a first surface of the light guide plate, where when the light beam is incident on the diffraction grating, the diffraction grating is adapted to generate a plurality of diffraction beams, and the diffraction beams include a major diffraction beam, and the major diffraction beam is transmitted in the light guide plate. The phase retardation element is disposed on a transmission path of the major diffraction beam. The major diffraction beam has a first polarization state before being incident on the phase retardation element, and the major diffraction beam has a second polarization state when leaving the phase retardation element, where the first polarization state is different from the second polarization state. Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. FIG. 1 to FIG. 8 are respectively schematic diagram of light guide devices according to a