Light guide device and head-mounted display equipment
By introducing energy recovery elements on each layer of the substrate of the double-layer optical waveguide device, the problem of light absorption waste caused by low grating diffraction efficiency in the prior art is solved, and the recycling and utilization of light energy and the improvement of optical efficiency are achieved.
Patent Information
- Application Number
- CN202311684811.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-08
- Publication Date
- 2025-06-10
AI Technical Summary
When the existing diffraction optical waveguide solution takes into account the uniformity of light transmission and the coupling area, the diffraction efficiency of the grating is designed with low design, resulting in most of the light being absorbed by the side wall of the waveguide and has low optical efficiency.
A two-layer optical waveguide device is designed to allow uncoupled light to be reused by the energy recovery element and recoupled through the optical output element of another layer of substrate by introducing an energy recovery element on each layer of substrate and positioning it in the optical path between the optical output element and the side wall of the substrate.
The recovery and utilization of light energy is realized, the optical efficiency of the light guide device is improved, the optical uniformity is improved, and the waste of light being absorbed by the side wall is reduced.
Smart Images
Figure CN120122335A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present application relate to the field of optical imaging technology, and more specifically, to a light guiding device and a head-mounted display device. Background Art
[0002] Augmented reality technology (AR) is a technology that combines virtual information with the real world and is gradually emerging in various industries. The diffractive waveguide solution is considered to be a better optical display solution in current augmented reality glasses. In the diffractive waveguide solution, in order to balance the uniformity of light transmission and meet a large coupling-out area, the diffraction efficiency of the grating is designed very low. Therefore, most of the light will be absorbed by the sidewalls of the waveguide, so that only a small part of the light can be coupled out and received by the user, which results in a low overall optical efficiency of the diffractive waveguide. Summary of the Invention
[0003] The purpose of the present application is to provide a new technical solution for a light guiding device and a head-mounted display device.
[0004] In a first aspect, the present application provides a light guiding device. The light guiding device includes a double-layer substrate, and an optical input element, an optical output element, and an energy recovery element provided on any one of the layers of the substrate;
[0005] On any one of the layers of the substrate, the energy recovery element is disposed in the optical path between one side of the optical output element and the edge of the substrate, and the energy recovery element is configured to couple the light that has passed through the optical output element but has not been coupled out into the other layer of the substrate and re-couple it out.
[0006] Optionally, the optical input element and the optical output element are diffractive gratings; the energy recovery element is a reflective element.
[0007] Optionally, the double-layer substrate includes a first substrate and a second substrate stacked up and down, and an air gap is provided between the first substrate and the second substrate.
[0008] Optionally, a first optical input element, a first optical output element, and a first energy recovery element are respectively provided on the first substrate, and a second optical input element, a second optical output element, and a second energy recovery element are respectively provided on the second substrate;
[0009] Wherein, the first energy recovery element and the second energy recovery element are reflective gratings, and the first energy recovery element and the second energy recovery element are respectively disposed on two surfaces of the first substrate and the second substrate facing away from each other.
[0010] Optionally, the grating vector of the first energy recovery element is the same as the grating vector of the first optical output element;
[0011] The grating vector of the second energy recovery element is the same as that of the second optical output element.
[0012] Optionally, the widths of the first energy recovery element and the second energy recovery element are both b, and b > 2d tanθ, where θ is the maximum total reflection angle and d is the thickness of any layer of the substrate.
[0013] Optionally, the lengths of the first energy recovery element and the second energy recovery element are both a1, the lengths of the first optical output element and the second optical output element are both a2, and a1 > a2.
[0014] Optionally, a first optical input element and a first optical output element are respectively disposed on the first substrate, and the first energy recovery element is embedded in the first substrate;
[0015] A second optical input element and a second optical output element are respectively disposed on the second substrate, and the second energy recovery element is embedded in the second substrate;
[0016] Wherein, the first energy recovery element and the second energy recovery element are inclined reflection films, and the first energy recovery element and the second energy recovery element are mirror-symmetrically arranged.
[0017] Optionally, a first optical input element and a first optical output element are respectively disposed on the first substrate, and a side wall of the first substrate close to the first optical output element is set as a first inclined surface, and the first energy recovery element is disposed on the first inclined surface;
[0018] A second optical input element and a second optical output element are respectively disposed on the second substrate, and a side wall of the second substrate close to the second optical output element is set as a second inclined surface, and the second energy recovery element is disposed on the second inclined surface;
[0019] Wherein, the first energy recovery element and the second energy recovery element are reflection films, and the first energy recovery element and the second energy recovery element are mirror-symmetrically arranged.
[0020] Optionally, the grating vector of the first optical output element is the same as that of the second optical output element.
[0021] Optionally, on any layer of the substrate, an expander grating is disposed on the optical path between the optical input element and the optical output element.
[0022] In a second aspect, the present application provides a head-mounted display device. The head-mounted display device includes:
[0023] A housing; and
[0024] A light guiding device as described in the first aspect.
[0025] One beneficial effect of the embodiments of the present application is that:
[0026] The light guiding device provided by the embodiments of the present application is a double-layer optical waveguide solution. By introducing energy recovery elements on each layer of the substrate and arranging the energy recovery elements in the optical path between the optical output element and the side wall of the substrate, when the light that has passed through the optical output element and has not been coupled out is about to propagate to the side wall of the substrate and be absorbed by the side wall, it will first be modulated by the added energy recovery elements. This enables some of the light that was originally absorbed by the side wall to be reused and can be re-coupled out through the optical output element of another layer of the substrate into the user's eyes, achieving the recycling of light energy and improving the optical efficiency of the light guiding device.
[0027] Other features and advantages of the present specification will become clear through the following detailed description of the exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present specification and, together with the description thereof, are used to explain the principles of the present specification.
[0029] Figure 1 A top view of the light guiding device provided by the embodiments of the present application;
[0030] Figure 2 One of the side cut-away optical path diagrams of the light guiding device provided by the embodiments of the present application;
[0031] Figure 3 Another side cut-away optical path diagram of the light guiding device provided by the embodiments of the present application;
[0032] Figure 4 A third side cut-away optical path diagram of the light guiding device provided by the embodiments of the present application.
[0033] Description of the reference numerals:
[0034] 100, optical input element; 200, optical output element; 300, energy recovery element; 400, pupil expansion grating; 500, substrate;
[0035] 1, first substrate; 11, first inclined surface; 2, second substrate; 21, second inclined surface; 3, first optical input element; 4, first optical output element; 5, first energy recovery element; 6, second optical input element; 7, second optical output element; 8, second energy recovery element; 9, ink glue; 01, incident light ray; 02, human eye; 03, optical engine. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0036] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application.
[0037] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application or its application or use.
[0038] Techniques and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques and devices should be regarded as part of the specification.
[0039] In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.
[0040] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, further discussion thereof is not required in subsequent drawings.
[0041] The light guiding device and the head-mounted display device provided by the embodiments of the present application will be described in detail below with reference to the accompanying drawings.
[0042] According to one aspect of the embodiments of the present application, a light guiding device is provided. The light guiding device is, for example, a diffractive optical waveguide element, which can be applied to an AR diffractive optical solution.
[0043] The light guiding device provided by the embodiments of the present application, see Figures 1 to 4 , the light guiding device includes a double-layer substrate 500, and an optical input element 100, an optical output element 200, and an energy recovery element 300 provided on any one layer of the substrate 500; on any one layer of the substrate 500, the energy recovery element 300 is disposed in the optical path between one side of the optical output element 200 and the edge of the substrate 500, and the energy recovery element 300 is configured to couple the light that has passed through the optical output element 200 but has not been coupled out into the other layer of the substrate 500 and re-couple it out.
[0044] According to the light guiding device provided by the above embodiments of the present application, see Figures 2 to 4 , the light guiding device is a double-layer optical waveguide solution. Please continue to see Figure 1 , on each layer of the substrate 500, at least an optical input element 100, an optical output element 200, and an energy recovery element 300 are provided.
[0045] It should be noted that the principle of the optical waveguide solution is as follows: Light rays are, for example, coupled into the substrate of the waveguide through a grating and then propagate by total internal reflection. After that, they are coupled out by the grating and received by the user's eyes, allowing the user to view the image. To ensure that the user can see the image within a certain eye movement range, the output grating needs to have the ability to expand the light beam, that is, utilize the multiple output effects of the output grating. To balance the optical energy output each time, the diffraction efficiency of the output grating is usually made very low, which results in most of the energy light rays ultimately reaching the sidewall of the optical waveguide and being absorbed by the ink glue attached to the sidewall, causing this part of the light rays to be wasted. In the optical waveguide, the function of the ink glue on the sidewall absorbing light is to avoid the influence of stray light on the output image from the sidewall.
[0046] The light guiding device provided by the embodiment of the present application is a double-layer optical waveguide solution. In the optical solution of the present application, referring to Figure 1 , an energy recovery element 300 is introduced on the substrate 500 of each layer of the waveguide, and the energy recovery element 300 is designed and arranged behind the optical output element 200 and on the propagation path of the uncoupled light rays. This layout enables the energy recovery element 300 to recover and utilize the light rays that have passed through the optical output element 200 but have not been coupled out. The principle of the energy recovery element 300 is as follows: Referring to Figure 3 , the energy recovery element 300 is located at the edge position of a layer of the substrate 500. When the light rays are about to propagate to the sidewall of the substrate 500 and be absorbed by the ink glue 9 ( Figure 2 and Figure 3 shown in), they will first encounter the energy recovery element 300 and can be modulated by this energy recovery element 300. The grating vector of the energy recovery element 300 can be designed to be exactly the same as the grating vector of the optical output element 200. Therefore, after being modulated by the energy recovery element 300, the light rays will be coupled out of this layer of the substrate 500 and enter another layer of the substrate 500 for propagation and be re-coupled out.
[0047] The light guiding device provided by the embodiment of the present application is a double-layer optical waveguide solution. By setting the energy recovery element 300 on the substrate 500 of each layer of the double-layer optical waveguide and arranging the energy recovery element 300 in the optical path between the optical output element 200 and the sidewall of the substrate 500, when the light rays that have passed through the optical output element 200 but have not been coupled out are about to propagate to the sidewall of the substrate 500 and be absorbed by the sidewall, they will first be modulated by the added energy recovery element 300. This enables some of the light rays that were originally absorbed by the sidewall to be reused and coupled out to the user's eyes, realizing the recycling and utilization of light energy and improving the optical efficiency of the overall light guiding device.
[0048] Moreover, the optical solution provided by the embodiments of the present application can also improve the optical uniformity of light guiding devices such as optical waveguides. The principle is that in the light coupled out by the optical output element 200, the coupling efficiency in the region close to the optical input element 100 (hereinafter referred to as proximal coupling) is stronger than that in the region far from the optical input element 100 (hereinafter referred to as distal coupling). In the optical solution of the present application, the introduction of the energy recovery element 300 can make up for some of the efficiency of distal coupling, thereby reducing the gap between proximal coupling and distal coupling and improving the optical uniformity of the optical waveguide.
[0049] In some examples of the present application, the optical input element 100 and the optical output element 200 are diffraction gratings. The energy recovery element 300 is a reflection element.
[0050] The light guiding device provided by the embodiments of the present application is, for example, a diffractive optical waveguide element.
[0051] Among them, the optical input element 100 is, for example, a coupling grating, and the optical output element 200 is, for example, a decoupling grating.
[0052] Optionally, the optical input element 100 and the optical output element 200 can be one-dimensional gratings or two-dimensional gratings.
[0053] Among them, the optical output element 200 can function as both pupil expansion and light coupling.
[0054] According to the above examples, the energy recovery element 300 is, for example, a reflection element, which can reflect the light that is not coupled out by the optical output element 200 on one layer of the substrate 500 to propagate in another layer of the substrate 500 with a very high reflectivity and be re-coupled out. That is to say, for the double-layer optical waveguide solution, the energy recovery element 300 on one layer of the substrate 500 will couple out the light that was originally absorbed by the side wall of this layer of the substrate 500 into another layer of the substrate 500 for utilization, which can improve the light efficiency and avoid waste of light energy.
[0055] In some examples of the present application, see Figures 2 to 4 The double-layer substrate 500 includes a first substrate 1 and a second substrate 2 that are stacked up and down, and an air gap is provided between the first substrate 1 and the second substrate 2.
[0056] It should be noted that there needs to be a certain spatial gap between the first substrate 1 and the second substrate 2, which can form a refractive index difference to ensure that the first substrate 1 and the second substrate 2 can meet the conditions for total internal reflection of light.
[0057] In addition, the size of this interval is not limited in this application and can be designed according to requirements such as the thickness dimension of the entire light guide device. For example, the interval can be designed to be very small.
[0058] In some examples of this application, referring to Figure 2 and Figure 3 , a first optical input element 3, a first optical output element 4, and a first energy recovery element 5 are respectively arranged on the first substrate 1, and a second optical input element 6, a second optical output element 7, and a second energy recovery element 8 are respectively arranged on the second substrate 2; wherein, the first energy recovery element 5 and the second energy recovery element 8 are reflective gratings, and the first energy recovery element 5 and the second energy recovery element 8 are respectively arranged on two surfaces of the first substrate 1 and the second substrate 2 facing away from each other.
[0059] According to the above example, the two energy recovery elements, that is, the first energy recovery element 5 and the second energy recovery element 8 above, can only be located outside the first substrate 1 and the second substrate 2.
[0060] Specifically, referring to Figure 2 and Figure 3 for the optical scheme shown, the first energy recovery element 5 and the second energy recovery element 8 can be reflective gratings, having a very high reflection diffraction efficiency. At the same time, because the energy recovery grating is located outside the double-layer substrate, the energy recovery element 300 of one layer of the substrate 500 will couple out the originally wasted light into the other layer of the substrate 500 and re-couple it out.
[0061] For example, referring to Figure 2 , the first energy recovery element 5 on the first substrate 1 couples out the light into the second substrate 2. Referring to Figure 3 , the second energy recovery element 8 on the second substrate 2 couples out the light into the first substrate 1.
[0062] Taking Figure 2 the optical path shown as an example, the optical engine 03 emits an incident light ray 01. The incident light ray 01 enters the first substrate 1 through the first optical input element 3 on the first substrate 1 and propagates by total internal reflection. After being coupled out by the first energy recovery element 5, it enters the second substrate 2, and then is modulated by the second energy recovery element 8 on the second substrate 2. Then the light ray propagates by total internal reflection in the second substrate 2 and is coupled out by the second optical output element 7 and enters the human eye 02. In this way, a part of the light ray originally absorbed by the ink glue 9 on the side wall of the first substrate 1 is re-coupled out by the second substrate 2, realizing the recycling of light energy and improving the optical efficiency of the light guide device.
[0063] Similarly, referring to Figure 3, part of the light originally absorbed by the ink glue 9 on the side wall of the second substrate 2 can also be re-coupled out by the first substrate 1. The principle is the same and will not be elaborated here.
[0064] In some examples of the present application, referring to Figure 2 , the grating vector of the first energy recovery element 5 is the same as the grating vector of the first optical output element 4. Referring to Figure 3 , the grating vector of the second energy recovery element 8 is the same as the grating vector of the second optical output element 7.
[0065] Referring to Figure 2 and Figure 3 The optical scheme shown. For each layer of substrate 500, the grating vector of the energy recovery element 300 thereon should be consistent with the grating vector of the optical output element 200, so that the light incident on another layer of substrate 500 after being modulated by the energy recovery element 300 can be re-coupled out.
[0066] In some examples of the present application, referring to Figure 1 , the widths of the first energy recovery element 5 and the second energy recovery element 8 are both b, and b > 2d tanθ, where θ is the maximum total reflection angle and d is the thickness of any layer of substrate 500.
[0067] Please continue to refer to Figure 1 , the lengths of the first energy recovery element 5 and the second energy recovery element 8 are both a1, the lengths of the first optical output element 4 and the second optical output element 7 are both a2, and a1 > a2.
[0068] Figure 1 For Figure 2 and Figure 3 is the top view of Figure 1 showing the structure of the substrate 500 located in the upper layer. It can be seen from Figure 1 that the width direction of the energy recovery element 300 is the transverse direction of the upper surface of the substrate 500, and the length direction of the energy recovery element 300 is the longitudinal direction of the upper surface of the substrate 500.
[0069] According to the constraints on the width and / or length of any layer of substrate 500 in the above examples, it can be ensured that the light that passes through the optical output element 200 and is not coupled out can be incident on the energy recovery element 300 on the same layer of substrate 500 as much as possible. That is, the energy recovery element 300 can recover and utilize as much light energy originally absorbed by the side wall of the substrate 500 as possible, maximizing the light efficiency.
[0070] In some examples of the present application, referring to Figure 4, a first optical input element 3 and a first optical output element 4 are respectively disposed on the first substrate 1, and a first energy recovery element 5 is embedded in the first substrate 1; a second optical input element 6 and a second optical output element 7 are respectively disposed on the second substrate 2, and a second energy recovery element 8 is embedded in the second substrate 2; wherein, the first energy recovery element 5 and the second energy recovery element 8 are inclined reflective films, and the first energy recovery element 5 and the second energy recovery element 8 are mirror-symmetrically arranged.
[0071] According to the above example, refer to Figure 4 , the reflective film embedded in any layer of the substrate 500 replaces the reflective grating, and the reflective films in the double-layer substrate 500 are mirror-symmetrically arranged. Its principle is similar to that of Figure 2 and Figure 3 The example shown is that the light wasted on the side wall (with ink glue on the side wall) of one layer of the substrate 500 will be reflected and coupled out by the reflective film, and then coupled into another layer of the substrate 500 and re-coupled out.
[0072] It should be noted that the grating vectors of the optical output elements 200 on the two layers of the substrate 500 must be the same, so as to ensure that the light entering another layer of the substrate 500 can be re-coupled out to the human eye 02.
[0073] Taking Figure 4 The optical path shown as an example, the optical engine 03 emits an incident light ray 01, the incident light ray 01 enters the first substrate 1 through the first optical input element 3 on the first substrate 1 and propagates by total reflection, is reflected and coupled out from the first energy recovery element 5, that is, the reflective film, and then enters the second substrate 2, and then is reflected and modulated by the second energy recovery element 8 and the reflective film on the second substrate 2, and then the light propagates by total internal reflection in the second substrate 2 to the second optical output element 7 and is coupled out into the human eye 02. In this way, part of the light originally absorbed by the ink glue 9 on the side wall of the first substrate 1 is re-coupled out by the second substrate 2, realizing the recycling of light energy and improving the optical efficiency of the light guiding device.
[0074] In some examples of the present application, refer to Figure 4, a first optical input element 3 and a first optical output element 4 are respectively disposed on the first substrate 1, and a side wall of the first substrate 1 close to the first optical output element 4 is provided as a first inclined surface 11, and a first energy recovery element 5 is disposed on the first inclined surface 11. A second optical input element 6 and a second optical output element 7 are respectively disposed on the second substrate 2, and a side wall of the second substrate 2 close to the second optical output element 7 is provided as a second inclined surface 21, and a second energy recovery element 8 is disposed on the second inclined surface 21; wherein, the first energy recovery element 5 and the second energy recovery element 8 are reflective films, and the first energy recovery element 5 and the second energy recovery element 8 are arranged in mirror symmetry.
[0075] According to the above two examples and referring to Figure 4 , the reflective film embedded in the substrate 500 can be disposed on the side wall of the substrate 500, and at this time, the side wall of the substrate 500 needs to form an inclined surface.
[0076] It should be noted that since the reflectivity of the reflective film can be close to 100%, the above two examples can have higher energy recovery efficiency, that is, the light guiding device has higher optical efficiency.
[0077] According to the above two examples, the grating vector of the first optical output element 4 is the same as the grating vector of the second optical output element 7. In this way, for the double-layer optical waveguide solution, the light rays coupled from one layer of the substrate 500 to the other layer of the substrate 500 can be smoothly recoupled from the optical output element 200 of the other substrate 500.
[0078] It should be noted that the optical solution provided by the embodiments of the present application can not only improve the optical efficiency of the light guiding device, but also improve the optical uniformity of the light guiding device. For the improvement of the optical uniformity, in the light rays coupled out by the optical output element 200, the coupling efficiency in the region close to the optical input element 100 (hereinafter referred to as proximal coupling) is stronger than that in the region far from the optical input element 100 (hereinafter referred to as distal coupling). In the optical solution of the present application, the introduction of the energy recovery element 300 can make up for some of the efficiency of the distal coupling, so as to reduce the gap between the proximal coupling and the distal coupling, thereby improving the optical uniformity of the optical waveguide.
[0079] In some examples of the present application, referring to Figure 1 , on any layer of the substrate 500, an expander grating 400 is disposed on the optical path between the optical input element 100 and the optical output element 200.
[0080] It should be noted that the expander grating 400 can be applied to Figure 2 and Figure 3 shown in the optical solution, and can also be applied in Figure 4In the optical scheme shown.
[0081] The pupil-expanding grating 400 is located on the path of light propagation from the optical input element 100 to the optical output element 200, and can expand the pupil of the light from the optical input element 100, increase the number of light rays, and then project them onto the optical output element 200.
[0082] In the light guide device provided in the embodiment of the present application, an optical input element 100, an optical output element 200, and an energy recovery element 300 are respectively arranged on the substrate 500 of any layer. It should be noted that the optical input element 100 and the optical output element 200 on the substrate 500 can be on the same surface of the substrate 500 or on different surfaces. In addition, the layouts of the optical input element 100 and the optical output element 200 on the two substrates 500 can be the same or different. That is to say, the layout positions of the optical input element 100 and the optical output element 200 can be not limited, which improves the design freedom of the double-layer optical waveguide scheme. However, the two energy recovery elements 300 can only be located outside the double-layer optical waveguide. Refer to Figures 2 to 4 , the first energy recovery element 5 is located on the surface of the first substrate 1 facing away from the second substrate 2, and the second energy recovery element 8 is located on the surface of the second substrate 2 facing away from the first substrate 1.
[0083] According to another aspect of the present application, the embodiment of the present application also provides a head-mounted display device. The head-mounted display device includes a housing and the light guide device as described above.
[0084] The light guide device is, for example, a diffractive optical waveguide element, which is arranged in the housing.
[0085] The head-mounted display device includes AR smart glasses or AR smart helmets, etc., and there is no limitation in the embodiment of the present application.
[0086] The specific implementation manners of the head-mounted display device in the embodiment of the present application can refer to the above-mentioned diffractive optical structures and each embodiment of the light guide device. Therefore, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated here one by one.
[0087] In the above embodiments, the differences between the embodiments are mainly described. As long as the different optimization features between the embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, it will not be elaborated here.
[0088] Although some specific embodiments of the present application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.
Claims
1. A light guiding device, characterized in that, it includes a double-layer substrate (500), and an optical input element (100), an optical output element (200) and an energy recovery element (300) provided on any one layer of the substrate (500); On any one layer of the substrate (500), the energy recovery element (300) is arranged in the optical path between one side of the optical output element (200) and the edge of the substrate (500), and the energy recovery element (300) is used to couple the light that has passed through the optical output element (200) but not coupled out into the other layer of the substrate (500) and recouple it out.
2. The light guiding device according to claim 1, characterized in that, the optical input element (100) and the optical output element (200) are diffraction gratings; the energy recovery element (300) is a reflection element.
3. The light guiding device according to claim 1 or 2, characterized in that, the double-layer substrate (500) includes a first substrate (1) and a second substrate (2) which are stacked up and down, and an air gap is provided between the first substrate (1) and the second substrate (2).
4. The light guiding device according to claim 3, characterized in that, a first optical input element (3), a first optical output element (4) and a first energy recovery element (5) are respectively provided on the first substrate (1), and a second optical input element (6), a second optical output element (7) and a second energy recovery element (8) are respectively provided on the second substrate (2); wherein, the first energy recovery element (5) and the second energy recovery element (8) are reflective gratings, and the first energy recovery element (5) and the second energy recovery element (8) are respectively arranged on two surfaces of the first substrate (1) and the second substrate (2) facing away from each other.
5. The light guiding device according to claim 4, characterized in that, the grating vector of the first energy recovery element (5) is the same as the grating vector of the first optical output element (4); the grating vector of the second energy recovery element (8) is the same as the grating vector of the second optical output element (7).
6. The light guiding device according to claim 5, characterized in that, the widths of the first energy recovery element (5) and the second energy recovery element (8) are both b, and b > 2d tanθ, where θ is the maximum total reflection angle and d is the thickness of any one layer of the substrate (500).
7. The light guiding device according to claim 6, characterized in that, the lengths of the first energy recovery element (5) and the second energy recovery element (8) are both a1, and the lengths of the first optical output element (4) and the second optical output element (7) are both a2, and a1 > a2.
8. The light guiding device according to claim 3, characterized in that, a first optical input element (3) and a first optical output element (4) are respectively provided on the first substrate (1), and the first energy recovery element (5) is embedded in the first substrate (1); A second optical input element (6) and a second optical output element (7) are respectively arranged on the second substrate (2), and a second energy recovery element (8) is embedded in the second substrate (2); Wherein, the first energy recovery element (5) and the second energy recovery element (8) are inclined reflection films, and the first energy recovery element (5) and the second energy recovery element (8) are arranged in mirror symmetry.
9. The light guiding device according to claim 3, Characterized in that, A first optical input element (3) and a first optical output element (4) are respectively arranged on the first substrate (1), and a side wall of the first substrate (1) close to the first optical output element (4) is set as a first inclined surface (11), and a first energy recovery element (5) is arranged on the first inclined surface (11); A second optical input element (6) and a second optical output element (7) are respectively arranged on the second substrate (2), and a side wall of the second substrate (2) close to the second optical output element (7) is set as a second inclined surface (12), and a second energy recovery element (8) is arranged on the second inclined surface (12); Wherein, the first energy recovery element (5) and the second energy recovery element (8) are reflection films, and the first energy recovery element (5) and the second energy recovery element (8) are arranged in mirror symmetry.
10. The light guiding device according to claim 8 or 9, Characterized in that, The grating vector of the first optical output element (4) is the same as the grating vector of the second optical output element (7).
11. The light guiding device according to claim 1, Characterized in that, On any layer of the substrate (500), a pupil expanding grating (400) is arranged on the optical path between the optical input element (100) and the optical output element (200).
12. A head-mounted display device, Characterized in that, Comprising: A housing; and, The light guiding device according to any one of claims 1-11.