Light guide device and near-eye display

Abstract

A light guide device comprises a light guide plate, a diffraction grating and a phase delay element. The diffraction grating is arranged on the first surface of the light guide plate. When a light beam enters the diffraction grating, the diffraction grating is used for generating a plurality of diffracted light beams. The diffracted beams comprise main diffracted beams, and the main diffracted beams are transmitted in the light guide plate. The phase delay element is disposed on a transmission path of the main diffracted beam. The main diffracted beam has a first polarization state before entering the phase delay element and has a second polarization state when leaving the phase delay element, and the first polarization state is different from the second polarization state. A near-to-eye display is also provided. The light guide device and the near-eye display provided by the invention are low in energy loss and good in optical performance.

Description

Technical Field

[0001] This invention relates to an optical device, and more particularly to a light guide device and a near-eye display. Background Technology

[0002] Diffractive waveguides can be thinner and lighter than geometric waveguides. Currently, diffractive waveguides include surface relief gratings (SRGs), volume holographic gratings (VHGs), and polarization volume gratings (PVGs). Surface relief gratings (SRGs) offer advantages in efficiency and design freedom compared to other diffractive gratings.

[0003] Ideally, we expect the diffracted light generated by the coupling grating to be completely transmitted to the waveguide outlet via total internal reflection within the waveguide. However, coupling gratings typically have a certain area, causing the diffracted beam generated by the coupling grating to undergo total internal reflection within the waveguide and then re-enter the coupling grating, resulting in diffraction and undesirable light leakage.

[0004] The "Background Art" paragraph is only used to help understand the content of this invention. Therefore, the content disclosed in the "Background Art" paragraph may include some known technologies that are not known to those skilled in the art. The content disclosed in the "Background Art" paragraph does not mean that the content or the problems to be solved by one or more embodiments of this invention were known or understood by those skilled in the art prior to this application. Summary of the Invention

[0005] This invention provides a light guiding device with low energy consumption and good optical performance.

[0006] Other objects and advantages of the present invention can be further understood from the technical features disclosed herein.

[0007] To achieve one, some, or all of the above objectives, or other objectives, the light guiding device provided in this embodiment of the invention is used to guide a light beam, comprising a light guide plate, a diffraction grating, and a phase delay element. The diffraction grating is disposed on a first surface of the light guide plate, wherein when the light beam is incident on the diffraction grating, the diffraction grating generates a plurality of diffracted beams, including a main diffracted beam, which propagates within the light guide plate. The phase delay element is disposed on the propagation path of the main diffracted beam, which has a first polarization state before incident on the phase delay element and a second polarization state upon exiting the phase delay element, wherein the first polarization state is different from the second polarization state.

[0008] According to another embodiment of the present invention, a near-eye display is provided, including an image light source and a light guide device. The image light source is used to emit a light beam. The light guide device is disposed in the transmission path of the light beam 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, wherein when the light beam is incident on the diffraction grating, the diffraction grating generates a plurality of diffracted beams, including a main diffracted beam, which propagates within the light guide plate. The phase retardation element is disposed in the transmission path of the main diffracted beam, the main diffracted beam having a first polarization state before incident on the phase retardation element, and having a second polarization state when leaving the phase retardation element, wherein the first polarization state and the second polarization state are different.

[0009] Based on the above, the light guide device and near-eye display provided in the embodiments of the present invention have at least one of the following features and advantages: (1) By controlling the polarization state of the diffracted beam, the diffracted beam is prevented from diffracting again due to re-intrusion into the grating, resulting in energy loss; (2) The light emitted from the light guide plate is reflected back to the light guide plate by a reflector, thereby enhancing the intensity of the light transmitted in the light guide plate and reducing energy loss; (3) The 0th order diffracted beam is recovered, thereby enhancing the intensity of the light transmitted in the light guide plate.

[0010] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0011] Figures 1 to 8 Schematic diagrams of light guiding devices according to the first to eighth embodiments of the present invention are shown respectively.

[0012] Figure 9 A schematic diagram of a near-eye display according to the present invention is shown.

[0013] Explanation of reference numerals in the attached figures:

[0014] 1, 2, 3, 4, 5, 6, 7, 8, 9: Light guiding device

[0015] 10: Near-eye monitors

[0016] 100A, 100B: Diffraction gratings

[0017] 200: Light guide plate

[0018] 201, 202: Surface

[0019] 300A, 300B, 300B1, 300B2: Phase delay elements

[0020] 400, 500: Reflector

[0021] 600: Image source

[0022] L: Beam

[0023] L1: Principal diffraction beam

[0024] L0: Sub-diffracted beam. Detailed Implementation

[0025] The foregoing descriptions and other technical contents, features, and effects of this invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms used in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0026] Reference Figure 1 The diagram illustrates a light guiding device according to a first embodiment of the present invention. The light guiding device 1 includes a light guide plate 200, a diffraction grating 100A, and a phase delay element 300A. The light guide plate has two surfaces 201 and 202 disposed opposite to each other.

[0027] The diffraction grating 100A can be, for example, a surface relief grating (SRG), but is not limited thereto. The diffraction grating 100A, as a coupling grating, is disposed on the surface 202 of the light guide plate 200. In this embodiment, the diffraction grating 100A is formed by coating material onto the surface 202 of the light guide plate 200 and then imprinting it; however, it is not limited thereto. In other embodiments, the diffraction grating 100A can also be formed by directly etching the surface 202 of the light guide plate 200. In this embodiment, the diffraction grating 100A is, for example, a blazed grating, a binary grating, and a slanted grating, preferably a blazed grating. The light guiding device 1 is used to guide the light beam L. Specifically, the light beam L enters the light guide plate 200 along an incident direction (+Z direction) via the surface 201 of the light guide plate 200. A diffraction grating 100A is disposed on the propagation path of the beam L. When the beam L is incident on the diffraction grating 100A, multiple diffracted beams are generated, including 0th-order diffracted light, ±1st-order diffracted light, ±2nd-order diffracted light...±n-order diffracted light, ±(n+1)-order diffracted light, etc., where the 0th-order diffracted light is directly reflected along a direction parallel to the incident direction (-Z direction). In this embodiment, the main diffracted beam L1 propagated within the light guide plate 200 is a +1st-order diffracted light (or a -1st-order diffracted light) adjacent to the 0th-order diffracted light. When the diffraction efficiency is poor, the light intensity of the ±1st-order diffracted light will be slightly less than that of the 0th-order diffracted light; when the diffraction efficiency is good, the light intensity of the ±1st-order diffracted light can even be greater than that of the 0th-order diffracted light. The diffraction grating 100A can control the light output direction of the main diffracted beam L1 through its structural shape, such as... Figure 1 As shown, the diffraction grating 100A is a reflective diffraction grating. The main diffracted beam L1 will be emitted from the diffraction grating 100A at an angle relative to the incident direction, so it can be transmitted within the light guide plate 200.

[0028] It should be noted that, due to the directional structure of the diffraction grating 100A, polarization selectivity is easily generated, resulting in better diffraction efficiency for S-waves (or P-waves). Therefore, in this embodiment, the beam L incident on the light guide device 1 has a polarization state. The beam L can be either an S-wave or a P-wave depending on the design requirements, but it is not limited to this; the beam L can also be unpolarized light without a specific polarization state. Furthermore, the structure of the diffraction grating 100A is also repeatable. Therefore, when the area of ​​the diffraction grating 100A is much larger than the beam size of the main diffracted beam L1, the main diffracted beam L1 will... Figure 1 As shown, the light beam L1 is incident on the diffraction grating 100A through total internal reflection within the light guide plate 200. If the polarization state of the main diffracted beam L1 remains unchanged, diffraction will occur, resulting in energy loss.

[0029] To address the aforementioned energy loss problem, the light guiding device 1 provided in this embodiment utilizes a phase delay element 300A disposed on the transmission path of the main diffracted beam L1 before it enters the diffraction grating 100A to change the polarization state of the main diffracted beam L1. This results in the polarization state of the main diffracted beam L1 as it leaves the phase delay element 300A being different from its polarization state before entering the phase delay element 300A. Accordingly, even if the main diffracted beam L1 inevitably enters the diffraction grating 100A due to its large area, the degree of diffraction of the main diffracted beam L1 can be reduced, or diffraction of the main diffracted beam L1 can be avoided altogether.

[0030] In some embodiments provided by the present invention, such as Figure 1 As shown, the phase delay element 300A is located within the light guide plate 200 and is parallel to surfaces 201 and 202 of the light guide plate 200, but is not limited thereto. The main diffracted beam L1 passes through the phase delay element 300A only once before the incident diffraction grating 100A, and its polarization state is changed to reduce the degree of diffraction that occurs after the main diffracted beam L1 enters the diffraction grating 100A.

[0031] In some embodiments, the incident beam L of the diffraction grating 100A is an s-wave, therefore the main diffracted beam L1 generated by the beam L through the diffraction grating 100A is also an s-wave, and the phase delay element 300A is a half-wave plate. The phase delay element 300A is located within the light guide plate 200 and is parallel to surfaces 201 and 202 of the light guide plate 200. Since the main diffracted beam L1 exits the diffraction grating 100A at an angle relative to the incident direction, the main diffracted beam L1 is an inclined incident phase delay element 300A. Figure 1 As shown, by adjusting the position of the phase delay element 300A on the propagation path of the main diffracted beam L1, the main diffracted beam L1 passes through the phase delay element 300A only once. Accordingly, the main diffracted beam L1 is a p-wave when it leaves the phase delay element 300A, avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A. However, it should be understood that since the main diffracted beam L1 is not a collimated beam, the portion of the main diffracted beam L1 that passes through the phase delay element 300A again due to reflection and other factors is ignored here.

[0032] In other embodiments, the incident beam L of the diffraction grating 100A is a p-wave. Therefore, the main diffracted beam L1 generated by the beam L passing through the diffraction grating 100A is a p-wave. The phase delay element 300A is a half-wave plate, and the main diffracted beam L1 passes through the phase delay element 300A only once. Accordingly, the main diffracted beam L1 is an s-wave when it leaves the phase delay element 300A, thus avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A.

[0033] In other embodiments, the incident beam L of the diffraction grating 100A is unpolarized light. Therefore, the main diffracted beam L1 generated by the beam L after passing through the diffraction grating 100A is partly s-wave and partly p-wave. The phase delay element 300A is a half-wave plate, and the main diffracted beam L1 passes through the phase delay element 300A only once. Accordingly, when part of the main diffracted beam L1 is s-wave, the main diffracted beam L1 is p-wave when leaving the phase delay element 300A, thus avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A. When part of the main diffracted beam L1 is p-wave, the main diffracted beam L1 is s-wave when leaving the phase delay element 300A, thus avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A.

[0034] To fully illustrate the various embodiments of the present invention, other embodiments will be described below. It must be noted that the following embodiments use the same element reference numerals and some content as those in the foregoing embodiments, with the same reference numerals representing the same or similar elements, and descriptions of identical technical content omitted. For explanations of the omitted parts, please refer to the foregoing embodiments; these will not be repeated in the following embodiments.

[0035] Reference Figure 2 The diagram illustrates a light guide device according to a second embodiment of the present invention. The light guide device 2 includes a light guide plate 200, a diffraction grating 100A, and a phase delay element 300B.

[0036] The light beam L enters the light guide plate 200 along an incident direction (+Z direction) via the surface 201 of the light guide plate 200. A diffraction grating 100A, serving as a coupling grating, is disposed on the surface 202 of the light guide plate 200 and is a reflective diffraction grating. In this embodiment, the main diffracted beam L1 transmitted within the light guide plate 200 is a +1st order diffracted beam (or a -1st order diffracted beam) adjacent to the 0th order diffracted beam.

[0037] like Figure 2 As shown, the phase delay element 300B is located within the light guide plate 200 and parallel to surfaces 201 and 202 of the light guide plate 200, but is not limited thereto. In this embodiment, by adjusting the position of the phase delay element 300B on the propagation path of the main diffracted beam L1, the main diffracted beam L1 passes through the phase delay element 300B once before and once after total internal reflection at surface 201 of the light guide plate 200, so that the main diffracted beam L1 only passes through the phase delay element 300B twice, its polarization state is changed, and the degree of diffraction phenomenon after the main diffracted beam L1 enters the diffraction grating 100A is reduced.

[0038] In some embodiments, the incident beam L of the diffraction grating 100A is an s-wave. Therefore, the main diffracted beam L1 generated by the beam L through the diffraction grating 100A is an s-wave. The phase retardation element 300B is a quarter-wave plate. By adjusting the position of the phase retardation element 300A on the propagation path of the main diffracted beam L1, the main diffracted beam L1 passes through the phase retardation element 300B only twice. Accordingly, the main diffracted beam L1 is a p-wave when it leaves the phase retardation element 300B, avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A. However, it should be understood that since the main diffracted beam L1 is not a collimated beam, the portion of the main diffracted beam L1 that passes through the phase retardation element 300B again due to reflection and other factors is ignored here.

[0039] In other embodiments, the incident beam L of the diffraction grating 100A is a p-wave. Therefore, the main diffracted beam L1 generated by the beam L passing through the diffraction grating 100A is a p-wave. The phase delay element 300B is a quarter-wave plate, and the main diffracted beam L1 passes through the phase delay element 300B only twice. Accordingly, the main diffracted beam L1 is an s-wave when it leaves the phase delay element 300B, thus avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A.

[0040] In other embodiments, the incident beam L of the diffraction grating 100A is unpolarized light. Therefore, the main diffracted beam L1 generated by the beam L after passing through the diffraction grating 100A is partly s-wave and partly p-wave. The phase delay element 300B is a quarter-wave plate, and the main diffracted beam L1 passes through the phase delay element 300B only twice. Accordingly, when part of the main diffracted beam L1 is s-wave, the main diffracted beam L1 is p-wave when leaving the phase delay element 300B, thus avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A. When part of the main diffracted beam L1 is p-wave, the main diffracted beam L1 is s-wave when leaving the phase delay element 300B, thus avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A.

[0041] Reference Figure 3This diagram illustrates a light guide device according to a third embodiment of the present invention. The difference between the light guide device 3 and the light guide device 1 in this embodiment is that the light guide device 3 further includes a reflector 400 and a reflector 500. The reflector 400 is disposed on the surface 202 of the light guide plate 200, and the diffraction grating 100A is located between the reflector 400 and the light guide plate 200. The reflector 500 is disposed on the surface 201 of the light guide plate 200, and the light guide plate 200 is located between the reflector 400 and the reflector 500. In one embodiment, the orthographic projection area of ​​the diffraction grating 100A on the surface 202 of the light guide plate 200 is within the orthographic projection area of ​​the reflector 400 on the surface 202 of the light guide plate 200. This allows the reflector 400 to simultaneously cover both the area where the beam L is incident on the diffraction grating 100A and the area where the main diffracted beam L1 is incident on the diffraction grating 100A. However, this is not a limitation; in other embodiments, multiple reflectors can be arranged corresponding to the areas where the beam L is incident on the diffraction grating 100A and the area where the main diffracted beam L1 is incident on the diffraction grating 100A. In one embodiment, the reflector 500 is arranged corresponding to the area where the main diffracted beam L1 is incident on the diffraction grating 100A. Accordingly, the reflectors 400 and 500 can reflect the light passing through the diffraction grating 100A and exiting the light guide plate 200 back into the light guide plate 200, reducing energy loss.

[0042] Reference Figure 4 This diagram illustrates a light guide device according to a fourth embodiment of the present invention. The difference between the light guide device 4 and the light guide device 2 in this embodiment is that the light guide device 4 further includes a reflector 400 and a reflector 500, and a phase delay element 300B is attached to the surface 201. The arrangement and function of the reflectors 400 and 500 are the same as in the light guide device 3, and will not be described again here. In this embodiment, since the phase delay element 300B is located outside the light guide plate 200 and attached to the surface 201, the phase delay element 300B further includes a protective layer (not shown). This allows the main diffracted beam L1 to first pass through the surface 201 of the light guide plate 200 before entering and passing through the phase delay element 300B. After total internal reflection at the interface between the protective layer of the phase delay element 300B and the air, it passes through the phase delay element 300B again and enters the light guide plate 200 via the surface 201, then propagates towards the diffraction grating 100A. Thus, the main diffracted beam L1 passes through the phase delay element 300B only twice. The reflectors 400 and 500 reflect the light penetrating the diffraction grating 100A and exiting the light guide plate 200 back into the light guide plate 200, reducing energy loss.

[0043] Reference Figure 5The diagram illustrates a light guiding device according to a fifth embodiment of the present invention. The light guiding device 5 includes a light guide plate 200, a diffraction grating 100B, a phase delay element 300A, a reflector 400, and a reflector 500. The reflectors 400 and 500 reflect light passing through the diffraction grating 100B and exiting the light guide plate 200 back into the light guide plate 200, reducing energy loss.

[0044] Please refer to this at the same time. Figure 1 and Figure 3 For the parts of light guide device 5 that are the same as those of light guide devices 1 and 3, please refer to the foregoing description, which will not be repeated here. The difference between light guide device 5 and light guide device 3 is that the diffraction grating 100B, which serves as a coupling grating, is disposed on the surface 201 of the light guide plate 200, and is a through-type diffraction grating. In this embodiment, since the diffraction grating 100B is disposed on the surface 201 of the light guide plate 200, the reflector 400 is disposed on the surface 201 of the light guide plate 200, and the diffraction grating 100B is located between the reflector 400 and the light guide plate 200. The reflector 500 is disposed on the surface 202 of the light guide plate 200, and the light guide plate 200 is located between the reflector 400 and the reflector 500. Refer to Figure 6 This diagram illustrates a light guide device according to a sixth embodiment of the present invention. The difference between the light guide device 6 and the light guide device 5 in this embodiment is that the phase delay element 300A is not parallel to surfaces 201 and 202 of the light guide plate 200.

[0045] In this embodiment, as Figure 6 As shown, the main diffracted beam L1 passes through the phase delay element 300A only once, changing its polarization state and reducing the degree of diffraction after the main diffracted beam L1 enters the diffraction grating 100A. In some embodiments, the main diffracted beam L1 is an s-wave, the phase delay element 300A is a half-wave plate, and the main diffracted beam L1 passes through the phase delay element 300A only once. Accordingly, the main diffracted beam L1 is a p-wave when it leaves the phase delay element 300A, avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A. However, it is not limited to this; in some embodiments, the main diffracted beam L1 is a p-wave, also passing through the phase delay element 300A only once. Accordingly, the main diffracted beam L1 is an s-wave when it leaves the phase delay element 300A, avoiding diffraction after the main diffracted beam L1 enters the diffraction grating 100A.

[0046] Reference Figure 7This diagram illustrates a light guide device according to a seventh embodiment of the present invention. The difference between the light guide device 7 and the light guide device 4 in this embodiment is that the light guide device 7 does not have a reflector 500, and the phase delay element 300B extends not only along the transmission path of the main diffracted beam L1 before the diffraction grating 100A, but also along the transmission path of the beam L before the light guide plate 200. In this embodiment, the reflector 400 is disposed on the surface 202 of the light guide plate 200, and the diffraction grating 100A is located between the reflector 400 and the light guide plate 200.

[0047] A diffraction grating 100A, serving as a coupling grating, is disposed on the surface 202 of the light guide plate 200 and is a reflective diffraction grating. A light beam L enters the light guide plate 200 along an incident direction (+Z direction) via the surface 201 of the light guide plate 200, and passes through the phase retardation element 300B before incident on the diffraction grating 100A. In this embodiment, the light beam L has a polarization state before incident on the phase retardation element 300B and changes its polarization state after passing through the phase retardation element 300B. The primary diffracted beam L1 generated after the light beam L incident on the diffraction grating 100A is a +1st order diffracted beam (or a -1st order diffracted beam), and a secondary diffracted beam L0 is generated, wherein the secondary diffracted beam L0 is a 0th order diffracted beam (passing through the diffraction grating 100A). Figure 7 As shown, the primary diffracted beam L1 exits the diffraction grating 100A at an angle relative to the incident direction, thus enabling it to propagate within the light guide plate 200. Furthermore, the secondary diffracted beam L0 can be reflected back into the light guide plate 200 by the reflector 400, reducing energy loss.

[0048] In some embodiments, the phase retardation element 300B is a quarter-wave plate, and the light beam L is circularly polarized. After passing through the phase retardation element 300B, the light beam L transforms into an s-wave. Therefore, the main diffracted beam L1 generated after the light beam L enters the diffraction grating 100A is an s-wave. Since the phase retardation element 300B is disposed on the surface 201 of the light guide plate 200 and extends along the propagation path of the main diffracted beam L1 before entering the diffraction grating 100A, the main diffracted beam L1 becomes a p-wave after passing through the phase retardation element 300B twice. Therefore, the main diffracted beam L1 is a p-wave when leaving the phase retardation element 300B, avoiding diffraction caused by the main diffracted beam L1 entering the diffraction grating 100A. However, this is not the limitation; in some embodiments, the circularly polarized light beam L transforms into a p-wave after passing through the phase retardation element 300B. Accordingly, the main diffracted beam L1 is formed into an s-wave after passing through the phase delay element 300B twice, thus avoiding diffraction of the main diffracted beam L1 due to the incident diffraction grating 100A.

[0049] Reference Figure 8This diagram illustrates a light guiding device according to an eighth embodiment of the present invention. The light guiding device 8 includes a diffraction grating 100B, a light guide plate 200, a phase retardation element 300B1, a phase retardation element 300B2, and a reflector 400, stacked sequentially. Phase retardation elements 300B1 and 300B2 are located between the reflector 400 and the surface 202 of the light guide plate 200, and each includes a protective layer (not shown). In this embodiment, phase retardation element 300B1 is disposed on the surface 202 of the light guide plate 200, and is located between the surface 202 of the light guide plate 200 and phase retardation element 300B2. In some embodiments, phase retardation element 300B1 is attached to the surface 202 of the light guide plate 200, and phase retardation element 300B2 is attached to the reflector 400.

[0050] A diffraction grating 100B, serving as a coupling grating, is disposed on the surface 201 of the light guide plate 200, and is located outside the light guide plate 200. The diffraction grating 100B is a transmission diffraction grating. A light beam L passes through the diffraction grating 100B along an incident direction (+Z direction) and enters the light guide plate 200 via the surface 201. The primary diffracted beam L1 generated after the light beam L incident on the diffraction grating 100B is a +1st order diffracted beam (or a -1st order diffracted beam), and a secondary diffracted beam L0 is generated, where the secondary diffracted beam L0 is a 0th order diffracted beam. For example... Figure 8 As shown, the primary diffracted beam L1 exits the diffraction grating 100B at an angle relative to the incident direction, thus allowing it to propagate within the light guide plate 200. Furthermore, the secondary diffracted beam L0 can be reflected back into the light guide plate 200 by the mirror 400. Both phase delay elements 300B1 and 300B2 are quarter-wave plates.

[0051] In some embodiments, the beam L is an s-wave. The main diffracted beam L1 generated after the beam L incident on the diffraction grating 100B is an s-wave. The main diffracted beam L1 first passes through the light guide plate 200 and its surface 202, then incident on and passes through the phase retardation element 300B1. After total internal reflection at the interface between the protective layer of the phase retardation element 300B1 and air, it passes through the phase retardation element 300B1 again and enters the light guide plate 200 via its surface 202, propagating towards the diffraction grating 100A. This ensures that the main diffracted beam L1 only passes through the phase retardation element 300B twice. After passing through the phase retardation element 300B1 twice, the main diffracted beam L1 becomes a p-wave. Therefore, the main diffracted beam L1 is a p-wave when leaving the phase retardation element 300B1, avoiding diffraction caused by the main diffracted beam L1 incident on the diffraction grating 100B.

[0052] In addition, the light beam L is an s-wave, and the secondary diffracted beam L0 generated after the light beam L enters the diffraction grating 100B is also an s-wave. The secondary diffracted beam L0 from the diffraction grating 100B is converted into a p-wave after passing through phase delay elements 300B1 and 300B2. Then, reflected by the mirror 400 and propagating towards the light guide plate 200, the secondary diffracted beam L0 passes through phase delay elements 300B1 and 300B2 again, thus returning to the light guide plate 200 and being converted back into an s-wave. The secondary diffracted beam L0 enters the diffraction grating 100B and undergoes diffraction, generating diffracted light that can propagate within the light guide plate 200. Because the secondary diffracted beam L0 is an s-wave before entering the diffraction grating 100B, it possesses good diffraction efficiency. However, it is not limited to this. As described in the previous embodiments, the beam L can also be a p-wave or unpolarized light without polarization, which can also avoid the diffraction phenomenon of the main diffracted beam L1 due to the incident diffraction grating 100B. At the same time, the diffracted beam L0 can have good diffraction efficiency, which will not be elaborated here.

[0053] Reference Figure 9 The diagram illustrates a near-eye display 10 according to the present invention. The near-eye display 10 includes an image light source 600 and a light guide device 9. The image light source 600 emits a light beam L. The light guide device 9 is disposed in the transmission path of the light beam L and guides the light beam L. The light guide device 9 can be replaced with... Figures 1 to 8 Any one of the light guide devices 1 to 8 in the illustrated embodiment.

[0054] In summary, the light guiding device provided by the embodiments of the present invention has at least one of the following features and advantages: (1) by controlling the polarization state of the diffracted beam, the diffracted beam is prevented from diffracting again due to re-intrusion into the grating, thus avoiding energy loss; (2) by using a reflector to reflect the light emitted from the light guide plate back to the light guide plate, thereby enhancing the intensity of the light transmitted in the light guide plate and reducing energy loss; (3) by recovering the 0th order diffracted beam, thereby enhancing the intensity of the light transmitted in the light guide plate.

[0055] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the invention are still within the scope of this patent. Furthermore, no embodiment or claim of the present invention needs to achieve all the objectives, advantages, or features disclosed in the invention. In addition, the abstract and title (invention title) are only used to assist in patent document retrieval and are not intended to limit the scope of the invention. Furthermore, the terms "first," "second," etc., mentioned in this specification or claims are only used to name elements or distinguish different embodiments or scopes, and are not used to limit the upper or lower limit of the number of elements.

Claims

1. A light guiding device for guiding a light beam, characterized in that, The light guiding device includes a light guide plate, a diffraction grating, and a phase delay element, wherein: The diffraction grating is disposed on a first surface of the light guide plate, wherein when the light beam is incident on the diffraction grating, the diffraction grating generates a plurality of diffracted beams, the plurality of diffracted beams including a main diffracted beam, the main diffracted beam being transmitted within the light guide plate; and The phase delay element is disposed on the propagation path of the main diffracted beam. The main diffracted beam has a first polarization state before entering the phase delay element and a second polarization state when leaving the phase delay element. The first polarization state is different from the second polarization state.

2. The light guiding device according to claim 1, characterized in that, Part of the main diffracted beam passes through the phase delay element once.

3. The light guiding device according to claim 1, characterized in that, The first polarization state is perpendicular to the second polarization state.

4. The light guiding device according to claim 1, characterized in that, The diffraction grating is a reflective diffraction grating.

5. The light guiding device according to claim 4, characterized in that, The light guiding device further includes a first reflector disposed on the first surface of the light guiding plate, wherein the diffraction grating is located between the first reflector and the light guiding plate.

6. The light guiding device according to claim 5, characterized in that, The light guiding device further includes a second reflector disposed on the second surface of the light guiding plate, wherein the light guiding plate is located between the first reflector and the second reflector.

7. The light guiding device according to claim 4, characterized in that, The beam passes through the phase delay element before entering the diffraction grating.

8. The light guiding device according to claim 7, characterized in that, The light guiding device further includes a first reflector disposed on the first surface of the light guiding plate, wherein the diffraction grating is located between the first reflector and the light guiding plate.

9. The light guiding device according to claim 7, characterized in that, The beam has a polarization state, and the phase delay element is used to convert the polarization state into the first polarization state.

10. The light guiding device according to claim 1, characterized in that, The diffraction grating is a through-type grating.

11. The light guiding device according to claim 10, characterized in that, The light guiding device further includes a first reflector disposed on the second surface of the light guiding plate, the first surface being opposite to the second surface.

12. The light guiding device according to claim 11, characterized in that, The light guiding device further includes a second reflector disposed on the first surface of the light guiding plate, wherein the diffraction grating is located between the second reflector and the light guiding plate.

13. The light guiding device according to claim 10, characterized in that, The plurality of diffracted beams also include a secondary diffracted beam, and the phase delay element is disposed on the propagation path of the secondary diffracted beam.

14. The light guiding device according to claim 13, characterized in that, The light guiding device further includes a first reflector, wherein the phase delay element is located between the first reflector and the light guiding plate.

15. The light guiding device according to claim 10, characterized in that, The phase delay element includes a first phase delay layer and a second phase delay layer stacked together.

16. The light guiding device according to claim 15, characterized in that, The light guiding device further includes a first reflector disposed on the first surface of the light guiding plate, wherein the first phase delay layer and the second phase delay layer are located between the first surface of the light guiding plate and the first reflector.

17. The light guiding device according to claim 16, characterized in that, The first phase delay layer is located between the first surface of the light guide plate and the second phase delay layer.

18. The light guiding device according to claim 17, characterized in that, The first phase delay layer is disposed on the first surface of the light guide plate.

19. The light guiding device according to claim 17, characterized in that, The second phase delay layer is disposed on the first reflector.

20. The light guiding device according to claim 1, characterized in that, The phase delay element is parallel to the first surface of the light guide plate.

21. The light guiding device according to claim 1, characterized in that, The phase delay element is not parallel to the first surface of the light guide plate.

22. A near-eye display, characterized in that, The near-eye display includes an image light source and a light guide device, wherein: The image light source is used to emit a light beam; and The light guiding device is disposed in the transmission path of the light beam and is used to guide the light beam. The light guiding device includes a light guide plate, a diffraction grating, and a phase delay element, wherein: The diffraction grating is disposed on a first surface of the light guide plate, wherein when the light beam is incident on the diffraction grating, the diffraction grating generates a plurality of diffracted beams, the plurality of diffracted beams including a main diffracted beam, the main diffracted beam being transmitted within the light guide plate; and The phase delay element is disposed on the propagation path of the main diffracted beam. The main diffracted beam has a first polarization state before entering the phase delay element and a second polarization state when leaving the phase delay element. The first polarization state is different from the second polarization state.

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