Light guide device and head-mounted display device

Abstract

A light guide device and a head-mounted display device. The light guide device comprises a substrate, wherein the substrate comprises a geometric coupling-in structure and a geometric coupling-out structure. The light guide device further comprises a micro-mirror array, wherein the micro-mirror array is embedded in the substrate and is opposite to the geometric coupling-out structure. The micro-mirror array comprises n micro-mirrors arranged in sequence, polarization reflection elements arranged on respective first surfaces of the n micro-mirrors, and phase retarders arranged on respective any surfaces of the first micro-mirror to the (n-1)-th micro-mirror; and the surface of each micro-mirror close to the geometric coupling-in structure is a first surface of the micro-mirror. The light guide device can satisfy the design requirement of mass production of geometric optical waveguide elements.

Description

Light guide device and head-mounted display device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 13, 2023, with application number 202311184051.X and invention name “A light guide device and a head-mounted display device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of augmented reality optical reality technology. More specifically, the embodiments of the present application relate to a light guide device and a head-mounted display device. Background Art

[0003] Geometric waveguides are based on traditional geometric optics principles and optical processing techniques. The image color and contrast they create far exceed the theoretical limits of diffraction waveguide components. However, in the production and processing of traditional geometric waveguide components, multiple lenses are stacked after coating and then cut at specific angles. This poses major manufacturing challenges, such as differentiated coating of the lens array, stringent requirements for lens parallelism, and cutting angles.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a new technical solution for a light-guiding device and a head-mounted display device.

[0006] In a first aspect, the present application provides a light guide device. The light guide device includes:

[0007] a substrate comprising a geometric coupling-in structure and a geometric coupling-out structure;

[0008] a micromirror array, wherein the micromirror array is embedded in the substrate and opposite to the geometric outcoupling structure;

[0009] The micromirror array includes n micromirrors arranged in sequence, a polarization reflection element arranged on the first surface of each of the n micromirrors, and a phase retarder arranged on any surface of each of the first micromirror to the (n-1)th micromirror; wherein the surface of each micromirror close to the geometric coupling structure is the first surface of each micromirror.

[0010] Optionally, the micromirror array further includes a first polarizer, and the first polarizer is arranged on any surface of the nth micromirror.

[0011] Optionally, the micromirror array is an n-stage micromirror array, wherein an angle θ1 formed by a slow axis of the phase retarder provided on the m-1th micromirror and a transmission axis of the polarization reflection element satisfies:

[0012] Wherein, a% is the film absorption loss of the phase retarder and polarization reflective element provided on the m-1th micromirror after the light is transmitted from the m-1th micromirror to the m-th micromirror; b% is the substrate absorption loss when the light is transmitted from the m-1th micromirror to the m-th micromirror.

[0013] Optionally, the micromirror array is an n-stage micromirror array, wherein an angle θ2 formed by a slow axis of the phase retarder provided on the m-1th micromirror and a transmission axis of the polarization reflection element satisfies:

[0014] θ2=arctan{(nm)*[Φ+n(a+b)] / Φ}, 1 <m≤n;

[0015] The absorption loss of the phase retarder and polarization reflective element provided on each micromirror is the same and is a. The absorption loss of the substrate when light is transmitted from the m-1th micromirror to the mth micromirror is the same and is b. Φ is the incident light flux in the eye box.

[0016] Optionally, a quarter-wave plate is provided on any surface of each of the first micromirror to the (n-2)th micromirror, and a half-wave plate is provided on any surface of the (n-1)th micromirror.

[0017] Optionally, a half-wave plate is provided on any surface of each of the first micromirror to the (n-1)th micromirror, and a quarter-wave plate is stacked on the polarization reflection element of each of the first micromirror to the (n-1)th micromirror.

[0018] Optionally, a light absorbing layer is provided on the side wall of the substrate close to the nth micromirror.

[0019] Optionally, the phase retarder and the polarization reflection element are stacked on the first surface of each of the first micromirror to the (n-1)th micromirror, the phase retarder is located between the polarization reflection element and the first surface, and a second polarizer is arranged between the phase retarder and the polarization reflection element.

[0020] Optionally, the light projected onto the micromirror array is elliptically polarized light.

[0021] Optionally, a compensation plate is provided on the light incident side of the geometric coupling structure for compensating for the polarization degree of the light projected onto the light guide device.

[0022] Optionally, the compensation plate is a phase delay plate, and the phase delay plate is configured to be rotatable relative to the geometric coupling structure.

[0023] Optionally, when the light incident on the geometric coupling structure is natural light, a second polarizer is provided on the light incident side of the geometric coupling structure for converting the natural light into linearly polarized light;

[0024] When the light incident on the geometric coupling structure is circularly polarized light, a third phase retarder is provided on the light incident side of the geometric coupling structure for converting the circularly polarized light into linearly polarized light;

[0025] When the light incident on the geometric coupling structure is linearly polarized light, a phase retarder is provided on the light incident side of the geometric coupling structure for modulating the polarization state of the linearly polarized light.

[0026] Optionally, the polarized reflective element is capable of reflecting a first linearly polarized light and transmitting a second linearly polarized light, wherein a phase difference between the first linearly polarized light and the second linearly polarized light is π / 2.

[0027] Optionally, the geometric coupling-in structure is arranged on a side wall of the substrate and forms a coupling-in slope; and the geometric coupling-out structure is arranged on a surface of the substrate.

[0028] In a second aspect, the present application provides a head-mounted display device. The head-mounted display device includes:

[0029] The light guiding device as described in the first aspect.

[0030] The beneficial effects of this application are:

[0031] According to the light-guiding device of the embodiment of the present application, a geometric light waveguide optical architecture based on polarization reflection is provided. By embedding a micromirror array including polarization reflection elements and phase delay devices in a substrate, the processing difficulty and production cost of the light-guiding device can be reduced, and the light transmitted through the light-guiding device has good brightness uniformity in the eye box.

[0032] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0034] FIG1 is one of the structural schematic diagrams of the light guide device provided in an embodiment of the present application.

[0035] FIG2 is a second schematic diagram of the structure of the light guide device provided in an embodiment of the present application.

[0036] Description of reference numerals:

[0037] 01. Human eye;

[0038] 1. Substrate; 11. Geometric coupling-in structure; 12. Geometric coupling-out structure; 2. Polarization reflection element; 3. Micromirror; 31. First surface; 32. Second surface; 4. Phase retarder; 5. First polarizer; 6. Light-absorbing layer. DETAILED DESCRIPTION

[0039] 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.

[0040] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0041] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0042] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0043] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0044] The optical module and head-mounted display device provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0045] According to one aspect of an embodiment of the present application, a light guide device is provided. The light guide device can be used in an augmented reality display device, such as an AR head-mounted display device. The AR head-mounted display device may be in the form of, for example, AR smart glasses or an AR smart helmet. The embodiments of the present application do not limit the specific form of the head-mounted display device.

[0046] The light guide device proposed in the embodiments of the present application, as shown in Figures 1 and 2, includes a substrate 1, which includes a geometric coupling-in structure 11 and a geometric coupling-out structure 12. The geometric coupling-in structure 11 is used to couple light into the substrate 1 in a geometric coupling manner. The geometric coupling-out structure 12 is used to couple light out of the substrate 1.

[0047] 1 and 2 , the light guide device further includes a micromirror array embedded within the substrate 1 and opposite the geometric outcoupling structure 12. The micromirror array comprises n sequentially arranged micromirrors 3, polarizing reflective elements 2 disposed on the first surfaces 31 of each of the n micromirrors 3, and phase retarders 4 disposed on any surface of each of the first to n-1 micromirrors 3. The surface of each micromirror 3 closest to the geometric incoupling structure 11 serves as its first surface 31.

[0048] The light-guiding device provided in the above-mentioned embodiments of the present application is, for example, a geometric light waveguide device.

[0049] According to the light guide device provided in the above embodiment, the micromirror array embedded in the substrate 1 may include two or more micromirrors 3 , that is, n≥2.

[0050] It should be noted that the number of micromirrors 3 in the micromirror array can be flexibly designed according to specific circumstances. This application does not impose any specific restrictions on the number of micromirrors 3. This application aims to protect this geometric light waveguide optical architecture based on polarization reflection.

[0051] According to the light-guiding device provided in the above-mentioned embodiment, a coupling-in portion and a coupling-out portion are provided on the substrate 1, wherein the coupling-in portion is a geometric coupling-in structure 11, and the coupling-out portion is a geometric coupling-out structure 12. The geometric coupling-in structure 11 may include but is not limited to a prism or a coupling-in bevel. The geometric coupling-out structure 12 may include but is not limited to a prism or a total reflection film. In other words, the light-guiding device provided in the embodiment of the present application does not use a diffraction grating as a coupling-in portion and / or a coupling-out portion, which can reduce the production cost and process difficulty of the light-guiding device, and can also avoid the disadvantages of low efficiency, large chromatic aberration and other optical performance issues caused by diffraction optical imaging.

[0052] According to the light guide device provided by the above embodiment, the substrate 1 is, for example, a high-refractive glass substrate.

[0053] According to the light guide device provided by the above embodiment, each micromirror 3 in the micromirror array is provided with a polarizing reflective element 2. The polarizing reflective element 2 is, for example, a polarizing reflective film.

[0054] For example, the polarized reflective element 2 can be disposed on one surface of the micromirror 3 by mounting or plating.

[0055] Specifically, the polarized reflective element 2 can be selectively disposed on the first surface 31 of the micromirror 3, as shown in Figures 1 and 2. The micromirror 3 includes two optical surfaces, namely the first surface 31 and the second surface 32, wherein the first surface 31 is closer to the geometric coupling structure 11 on the substrate 1 than the second surface 31.

[0056] In the technical solution provided in the embodiment of the present application, the polarized reflective element 2 is arranged on the first surface 31 of each micromirror 3, which has the advantage of reducing stray light and improving imaging quality.

[0057] If the polarized reflective element 2 is disposed on the second surface 32 of the micromirror 3, the projected light will pass through the first surface 31 and then the second surface 32. Stray light will be generated on the first surface 31 and enter the human eye 01, which will affect the optical performance of the entire light guide device.

[0058] According to the light guide device provided in the above embodiment, a phase retarder 4 is further introduced into the micromirror array. For example, the phase retarder 4 can be arranged between the polarization reflective element 2 and the micromirror 3, as shown in Figure 1. Of course, the phase retarder 4 can also be on the second surface 32 of the micromirror 3.

[0059] The phase retarder 4 is disposed between the polarizing reflective element 2 and the micromirror 3, that is, the polarizing reflective element 2 and the phase retarder 4 can be stacked on the first surface 31 of the micromirror 3. In this design, the polarizing reflective element 2 and the phase retarder 4 can form a laminated sheet, which helps reduce the number of film lamination process steps. Two film materials can be placed simultaneously in one assembly, thereby improving mass production yield.

[0060] The polarized reflective element 2 can reflect linearly polarized light in a fixed direction, and can transmit linearly polarized light with a phase difference of, for example, π / 2.

[0061] The phase retarder 4 can convert linearly polarized light into circularly polarized light, or convert circularly polarized light into linearly polarized light. The phase retarder 4 is, for example, a quarter-wave plate or other optical element that can achieve this function.

[0062] According to the light guide device provided by the above embodiment of the present application, in the micromirror array, the n micromirrors 3 arranged sequentially are all tilted. The tilt here refers to a target tilt angle relative to the surface of the substrate 1.

[0063] According to the light-guiding device of the embodiment of the present application, a geometric light waveguide optical architecture based on polarized reflection is provided. By embedding a micromirror array including a polarized reflection element 2 and a phase delay device 4 in the substrate 1, the processing difficulty and production cost of the light-guiding device can be reduced, and the light transmitted through the light-guiding device has good brightness uniformity in the eye box.

[0064] It should be noted that traditional geometric waveguide devices are usually formed by stacking multiple pre-coated lenses and then cutting them. The lenses need to be coated with many films, and the types of coatings on different lenses are also different. The process is complex and cannot meet the design requirements of mass production of geometric waveguides.

[0065] The technical solution provided in the embodiments of the present application provides a new polarization reflection geometric optical waveguide architecture, which at least solves the problem of mass production of differentiated multi-layer film coatings.

[0066] In some examples of the present application, referring to FIG. 1 , the micromirror array further includes a first polarizer 5 , which is disposed on any surface of the n-th micromirror 3 .

[0067] According to the above example, the first polarizer 5 is, for example, a linear polarizer.

[0068] According to the light-guiding device provided in an embodiment of the present application, an n-stage micromirror array is embedded in the substrate 1, which includes n micromirrors 3 arranged in sequence, wherein a polarization reflection element 2 and a phase retarder 4 are provided on the surface of the first n-1 micromirrors 3, and the first polarizer 5 and the polarization reflection element 2 mentioned in the above example can be provided on the last micromirror 3, that is, the nth micromirror 3. Providing the first polarizer 5 on the last micromirror 3 can prevent stray light from being emitted.

[0069] Among them, on the last micromirror 3 (i.e., the nth micromirror 3) in the micromirror array, the first polarizer 5 can be located between the polarization reflection element 2 and the micromirror 3, and of course can also be arranged on the second surface 32 of the micromirror 3.

[0070] The present invention proposes a geometric light waveguide optical architecture based on polarized reflection, in which pupil expansion and eyebox light homogenization are achieved through phase modulation. Referring to Figures 1 and 2, on one side of the geometric outcoupling structure 12, the outcoupling light is evenly distributed.

[0071] Specifically, in the light-guiding device provided in the embodiment of the present application, each micromirror 3 in the substrate 1 can reflect S light and transmit P light based on its own provided film layer.

[0072] The actual calculation of the phase modulation design may refer to different calculation rules according to different calculation methods of the absorption loss.

[0073] In some examples of the present application, the micromirror array is an n-stage micromirror array, wherein the angle θ1 formed by the slow axis of the phase retarder provided on the m-1th micromirror 3 and the transmission axis of the polarization reflection element 2 satisfies:

[0074] Wherein, a% is the film absorption loss of the phase retarder 4 and the polarization reflection element 2 provided on the m-1th micromirror 3 after the light is transmitted from the m-1th micromirror 3 to the m-th micromirror 3; b% is the substrate absorption loss when the light is transmitted from the m-1th micromirror 3 to the m-th micromirror 3.

[0075] According to the above example, the micromirror array includes n sequentially arranged micromirrors 3. The light flux entering the eye box is Φ. Light incident on the micromirror array passes through n micromirrors 3 in sequence. Based on the film layer on each micromirror 3, the light flux passing through each micromirror 3 is, for example, Φ / n.

[0076] The average absorption loss of light transmitted from the m-1th micromirror 3 (in this case, m<n) to the m-th micromirror 3 is the absorption loss of the film layer formed by the phase retarder 4 and the polarization reflective element 2 provided on the m-1th micromirror 3, for example, a%. Light also experiences a certain amount of substrate absorption loss when transmitted from the m-1th micromirror 3 to the m-th micromirror 3, for example, b%.

[0077] That is to say, in the above-mentioned n-level micromirror array, the film absorption loss on each micromirror 3 is different, and the substrate absorption loss of the substrate for each level of light is also different. In this case, the ratio of the luminous flux of each level in the n-level micromirror array can be seen in Table 1.

[0078] Table 1

[0079] Based on the intensity ratio and direction of the polarized reflected light and the polarized transmitted light at each level, the polarization state required by the transmitted light of the previous level can be obtained, thereby determining the axial angle between the phase retarder 4 and the polarized reflective element 2 set on the same micromirror 3.

[0080] Specifically, the angle θ1 formed by the slow axis of the phase retarder 4 provided on the m-1th micromirror 3 and the transmission axis of the polarization reflection element 2 satisfies:

[0081] Wherein, a% is the film absorption loss of the phase retarder 4 and the polarization reflection element 2 provided on the m_1-th micromirror 3 after the light is transmitted from the m-1-th micromirror 3 to the m-th micromirror 3; b% is the substrate absorption loss when the light is transmitted from the m-1-th micromirror 3 to the m-th micromirror 3.

[0082] That is to say, in the entire n-level micromirror array, there are n levels of transmission and emission for the projected light. When the film absorption loss and substrate absorption loss of each level are proportional to the incident light, the phase modulation is only related to the light transmission loss and is related to the absorption coefficient of the film and substrate materials.

[0083] In addition, since the phase modulation effect of the phase retarder is affected by the incident angle of the light, the FOV variable can be introduced in the actual design; the phase modulation effect will also be slightly affected by different wavelengths, so the spectrum variable can be introduced to further improve the calculation method.

[0084] In one example, the micromirror array includes five micromirrors 3 arranged in sequence, the eye brightness is controlled to be at least 1000 nits, the eye box size is 10 mm*10 mm, the field of view angle θ is 50°, and the corresponding solid angle Ω=∫dΩ=∫sinθdθdφ=2π(1-cosθ)=2.25sr. Then, the eye light flux φ is 1.2 lm, and the eye light flux of each level is 0.24 lm. The phase retarder 4 in the first three levels uses a quarter wave plate, and the phase retarder 4 in the fourth level uses a half wave plate. The film absorption loss and substrate absorption loss of each level are assumed to be proportional values, the film absorption loss is 0.5%, and the substrate absorption loss is 0.1%. Then, the incident and transmitted light fluxes of each level, and the angle between the slow axis of the phase retarder 4 at each level and the transmission axis of the polarization reflection element 2 are shown in Table 2.

[0085] Table 2

[0086] The optical path design of the geometric waveguide can be completed by matching the corresponding optical film material and the micromirror array based on the angle between the slow axis of the phase retarder 4 on each micromirror 3 in the micromirror array and the transmission axis of the polarization reflective element 2.

[0087] In some examples of the present application, the micromirror array is an n-stage micromirror array, wherein the angle θ2 formed by the slow axis of the phase retarder provided on the m-1th micromirror 3 and the transmission axis of the polarization reflection element 2 satisfies:

[0088] θ2=arctan{(nm)*[Φ+n(a+b)] / Φ}, 1 <m≤n;

[0089] The phase retarder 4 and polarization reflective element 2 provided on each micromirror 3 have the same absorption loss, which is a. The substrate absorption loss of light transmitted from the m-1th micromirror 3 to the mth micromirror 3 is the same, which is b. Φ is the incident light flux into the eye box.

[0090] According to the above example, the micromirror array includes n sequentially arranged micromirrors 3. The light flux entering the eye box is Φ. Light incident on the micromirror array passes through n micromirrors 3 in sequence. Based on the film layer on each micromirror 3, the light flux passing through each micromirror 3 is, for example, Φ / n.

[0091] Among them, the average absorption loss of the light transmitted from the (m - 1)-th (at this time, m < n) micromirror 3 to the m-th micromirror 3 is set as a, that is, the film absorption loss formed by the phase retarder 4 and the polarization reflection element 2 provided on each micromirror 3 is a fixed value a. The substrate absorption loss of the light transmitted from the (m - 1)-th micromirror 3 to the m-th micromirror 3 is a fixed value b.

[0092] That is to say, in the micromirror array, the film absorption losses on each micromirror 3 are the same, and the substrate absorption losses of the substrate for each level of light are also the same. In this case, the light flux ratios of each level in the micromirror array can be seen in Table 3.

[0093] Table 3

[0094] According to the light intensity ratios and directions of the polarization reflected light and polarization transmitted light at each level, the polarization state required for the light transmitted from the previous level can be obtained, and thus the axial angle between the phase retarder 4 and the polarization reflection element 2 provided on the same micromirror 3 can be determined.

[0095] Specifically: The included angle θ2 formed by the slow axis of the phase retarder provided on the (m - 1)-th micromirror 3 and the transmission axis of the polarization reflection element 2 satisfies θ2 = arctan{(n - m)*[Φ + n(a + b)] / Φ}, 1 < m ≤ n. Among them, the film absorption losses on each micromirror 3 are the same and all are a, the substrate absorption losses of the light transmitted from the (m - 1)-th micromirror 3 to the m-th micromirror 3 are the same and all are b, and Φ is the incident light flux in the eye box.

[0096] In an example, the micromirror array includes five micromirrors 3 arranged in sequence, the incident eye brightness is at least 1000 nits, the eye box size is 10 mm * 10 mm, the viewing angle θ is 50°, and the corresponding solid angle Ω = ∫dΩ = ∫sinθdθdφ = 2π(1 - cosθ) = 2.25 sr. Then the incident light flux is 1.2 lm, the incident light flux of each level is 0.24 lm, the phase retarders 4 of the first three levels use quarter-wave plates, the phase retarder 4 of the fourth level is a half-wave plate, and it is assumed that both the film absorption loss and the substrate absorption loss are fixed values. The film absorption loss is 1 * 10 -3 and the substrate absorption loss is 5 * 10 -4 Then, the incident and transmitted light fluxes of each level and the included angles between the slow axes of the phase retarders 4 of each level and the transmission axes of the polarization reflection elements 2 can be seen in Table 4.

[0097] Table 4

[0098] According to the included angles between the slow axes of the phase retarders 4 and the transmission axes of the polarization reflection elements 2 on each micromirror 3 in the micromirror array, and by matching with the corresponding optical film materials and the micromirror array, the optical path design of the geometric optical waveguide can be completed.

[0099] According to the optical architecture of the light guide device provided in the embodiments of the present application, the ratio of the luminous flux of the transmitted and reflected light at each level is calculated based on the eyebox brightness. This allows the corresponding phase delay ratio to be calculated, thereby determining the polarization state of each level of light (e.g., elliptically polarized light). This is achieved by combining a polarizing reflective element 2 with a phase retarder 4. Specifically, the transmission direction of the polarizing reflective element 2 remains unchanged at each level, while the phase delay angle is gradually varied to maintain the luminous flux in the outgoing direction within a stable range.

[0100] It's important to note that optical design calculations must account for the absorption losses of the substrate 1 material and the film during light transmission. The cutting angle of the micromirror array depends on optomechanical factors such as the incident angle of light projected onto the light guide and the field of view (FOV).

[0101] In mass production, since the polarization reflective element 2 and the phase retarder 4 are not ideal polarization elements, and there may be errors in the overlapping angle of the two, there may be a situation where the output luminous flux of each level of the eye box is not equal to the designed luminous flux. However, the human eye is not sensitive to brightness changes within 5% of the terminal. Therefore, the problem of non-ideal polarization state caused by film material problems can be quickly converged to the optimal solution through theoretical calculation and practical verification, thereby reducing the problem of uneven output light.

[0102] In the embodiments of the present application, the design methods vary according to different design methods of film layer absorption loss and substrate absorption loss. The calculation method that uses the film layer absorption loss and substrate absorption loss as the ratio of incident light is more in line with the initial design of different design schemes, and the calculation method that uses the film layer absorption loss and substrate absorption loss as fixed values ​​is conducive to design iteration based on the measured data of the existing design.

[0103] In some examples of the present application, a quarter-wave plate is disposed on any surface of each of the first micromirror 3 to the (n-2)th micromirror 3 , and a half-wave plate is disposed on any surface of the (n-1)th micromirror 3 .

[0104] According to the above example, in an n-stage micromirror array consisting of n micromirrors, the phase retarder 4 on the penultimate micromirror 3 can be set to a half-wave plate. At this time, the slow axis of the half-wave plate forms a 45° angle with the transmission axis direction of the polarization reflection element 2 of this stage, and the incident light of the last stage can be converted into linearly polarized light in the reflection direction of the polarization reflection element 2, thereby maximizing the utilization rate of light energy.

[0105] In some examples of the present application, a half-wave plate is provided on any surface of each of the first micromirror 3 to the (n-1)th micromirror 3 , and a quarter-wave plate is stacked on the polarization reflection element 2 of each of the first micromirror 3 to the (n-1)th micromirror 3 .

[0106] The above example creates a light guide device with higher optical efficiency. Specifically, a half-wave plate positioned on micromirror 3 converts light transmitted through substrate 1 from P-light to S-light. A quarter-wave plate is then positioned before each stage of polarized reflective element 2 to maintain circularly polarized light at each incident light stage. Because S-light has a higher reflection efficiency than P-light in the light guide device, the device achieves higher optical efficiency.

[0107] In some examples of the present application, a light absorbing layer 6 is provided on the side wall of the substrate 1 close to the n-th micromirror 3 .

[0108] The end of the substrate 1 near the last micromirror 3 can be defined as the light transmission end of the light guide device. A light absorbing layer 6 formed of a light absorbing material is coated, attached or evaporated on the light transmission end of the light guide device to reduce stray light reflection.

[0109] The function of the light absorbing layer 6 can be realized by various methods such as blackening with ink, sticking with black tape, and coating with an anti-reflection film.

[0110] In some examples of the present application, the phase retarder and the polarization reflection element 2 are stacked on the first surface 31 of each of the first micromirror 3 to the n-1th micromirror 3, the phase retarder is located between the polarization reflection element 2 and the first surface 31, and a second polarizer is arranged between the phase retarder and the polarization reflection element 2.

[0111] According to the above example, by adding a linear polarizer between the polarization reflection element 2 and the phase retarder 4 at each level, the polarization state of each level of output light can be accurately controlled, so that the polarization state deviation of each level of output light of the eye box will not accumulate and affect all subsequent levels, and the brightness uniformity can be compensated.

[0112] In some examples of the present application, the light projected onto the micromirror array is elliptically polarized light.

[0113] In order to make the brightness of the eye box uniform, the light entering the micromirror array is preferably elliptically polarized light.

[0114] The transmission axis direction of the polarizing reflective element 2 needs to form a certain angle with the slow axis direction of the phase retarder 4. By adjusting the angle between the transmission axis of the polarizing reflective element 2 and the slow axis direction of the phase retarder 4, the light flux reflected at each level of the micromirror array can be controlled to be the same.

[0115] The light guide device provided in the embodiment of the present application is designed so that S light is reflected at each micromirror 3, while P light can continue to propagate. When the light projected onto the micromirror array is elliptically polarized light, its P light and S light components are different. It should be noted that if the P light and S light components are the same (circularly polarized light), the first stage will emit the most light, and the last stage will emit the least light.

[0116] In order to ensure uniform brightness inside the eyebox, the solution of this application is designed to use elliptically polarized light, which can make the S light component in the first order less than the P light component, allowing more light energy to be transmitted backward.

[0117] In some examples of the present application, a compensation plate is provided on the light incident side of the geometric coupling-in structure 11 to compensate for the polarization degree of the light projected onto the light guide device.

[0118] The compensation plate is, for example, a phase delay plate, and the phase delay plate is configured to be rotatable relative to the geometric coupling structure 11 .

[0119] By using a phase delay plate to modulate the polarization degree of the incident light at the entrance pupil position of the light guide device, the light can be transmitted with higher efficiency in the light guide device.

[0120] The compensating plate can be stacked on the geometric coupling structure 11. Of course, the compensating plate can also be supported on the light incident side of the geometric coupling structure 11 by a flat support member.

[0121] In some examples of the present application, when the light incident on the geometric coupling structure 11 is natural light, a second polarizer is provided on the light-entry side of the geometric coupling structure 11 to convert the natural light into linearly polarized light. When the light incident on the geometric coupling structure 11 is circularly polarized light, a third phase retarder is provided on the light-entry side of the geometric coupling structure 11 to convert the circularly polarized light into linearly polarized light. When the light incident on the geometric coupling structure 11 is linearly polarized light, a phase retarder is provided on the light-entry side of the geometric coupling structure 11 to modulate the polarization state of the linearly polarized light.

[0122] The light projected onto the geometric coupling structure 11 of the light-guiding device can be emitted by a light projector or a display. The emitted light can be any one of natural light, circularly polarized light and linearly polarized light. By arranging different optical elements on the geometric coupling structure 11 on the substrate 1, the light can be converted into linearly polarized light.

[0123] In some examples of the present application, the polarized reflective element 2 is capable of reflecting a first linearly polarized light and transmitting a second linearly polarized light, wherein a phase difference between the first linearly polarized light and the second linearly polarized light is π / 2.

[0124] In some examples of the present application, the geometric coupling-in structure 11 is disposed on a sidewall of the substrate 1 and forms a coupling-in slope; and the geometric coupling-out structure 12 is disposed on a surface of the substrate 1 .

[0125] According to another embodiment of the present application, a head-mounted display device is provided, wherein the head-mounted display device includes the light guide device described above.

[0126] The head-mounted display device includes AR smart glasses or AR smart helmets, etc., which is not limited in the embodiments of the present application.

[0127] The specific implementation of the head-mounted display device in the embodiment of the present application can refer to the above-mentioned embodiments of the light guide device, so it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0128] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0129] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above examples may 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 guide device, characterized in that: include: A substrate (1), wherein the substrate (1) comprises a geometric coupling-in structure (11) and a geometric coupling-out structure (12); A micromirror array, the micromirror array being embedded in the substrate (1) and facing the geometric outcoupling structure (12); The micromirror array comprises n micromirrors (3) arranged in sequence, a polarized reflection element (2) arranged on a first surface (31) of each of the n micromirrors (3), and a phase retarder (4) arranged on any surface of each of the first micromirror (3) to the n-1th micromirror (3); wherein the surface of each micromirror (3) close to the geometric coupling structure (11) is the first surface (31) of each micromirror (3).

2. The light guide device according to claim 1, characterized in that: The micromirror array further comprises a first polarizing plate (5), wherein the first polarizing plate (5) is arranged on any surface of the nth micromirror (3).

3. The light guide device according to claim 1, characterized in that: The micromirror array is an n-stage micromirror array, wherein an angle θ1 formed by a slow axis of the phase retarder arranged on the m-1th micromirror (3) and a transmission axis of the polarized reflection element (2) satisfies: Wherein, a% is the film absorption loss of the phase retarder (4) and the polarization reflection element (2) arranged on the m-1th micromirror (3) after the light is transmitted from the m-1th micromirror (3) to the m-th micromirror (3); and b% is the substrate absorption loss when the light is transmitted from the m-1th micromirror (3) to the m-th micromirror (3).

4. The light guide device according to claim 1, characterized in that: The micromirror array is an n-stage micromirror array, wherein the angle θ2 formed by the slow axis of the phase retarder arranged on the m-1th micromirror (3) and the transmission axis of the polarization reflection element (2) satisfies: θ2=arctan{(nm)*[Φ+n(a+b)] / Φ}, 1 <m≤n; The phase retarder (4) and the polarized reflective element (2) arranged on each micromirror (3) have the same absorption loss and are both a, the substrate absorption loss of light transmitted from the m-1th micromirror (3) to the mth micromirror (3) is the same and is both b, and Φ is the light flux entering the eye box.

5. The light guide device according to any one of claims 1 to 4, characterized in that: A quarter wave plate is arranged on any surface of each of the first micromirror (3) to the n-2nd micromirror (3), and a half wave plate is arranged on any surface of the n-1th micromirror (3).

6. The light guide device according to any one of claims 1 to 4, characterized in that: A half-wave plate is arranged on any surface of each of the first micromirror (3) to the n-1th micromirror (3), and a quarter-wave plate is stacked on the polarized reflection element (2) of each of the first micromirror (3) to the n-1th micromirror (3).

7. The light guide device according to claim 1, characterized in that: A light absorbing layer (6) is provided on the side wall of the substrate (1) close to the nth micromirror (3).

8. The light guide device according to claim 1, characterized in that: The phase retarder and the polarization reflection element (2) are stacked on the first surface (31) of each of the first micromirror (3) to the n-1th micromirror (3); the phase retarder is located between the polarization reflection element (2) and the first surface (31); and a second polarizer is arranged between the phase retarder and the polarization reflection element (2).

9. The light guide device according to claim 1, characterized in that: The light projected onto the micromirror array is elliptically polarized light.

10. The light guide device according to claim 1, characterized in that: A compensation sheet is provided on the light incident side of the geometric coupling structure (11) for compensating the polarization degree of the light projected onto the light guide device.

11. The light guide device according to claim 10, characterized in that: The compensation plate is a phase delay plate, and the phase delay plate is configured to be rotatable relative to the geometric coupling structure (11).

12. The light guide device according to claim 1, characterized in that: When the light incident on the geometric coupling structure (11) is natural light, a second polarizer is provided on the light incident side of the geometric coupling structure (11) for converting the natural light into linearly polarized light; When the light incident on the geometric coupling structure (11) is circularly polarized light, a third phase retarder is provided on the light incident side of the geometric coupling structure (11) for converting the circularly polarized light into linearly polarized light; When the light incident on the geometric coupling structure (11) is linearly polarized light, a phase delay plate is arranged on the light incident side of the geometric coupling structure (11) for modulating the polarization state of the linearly polarized light.

13. The light guide device according to claim 1, characterized in that: The polarized reflection element (2) is capable of reflecting a first linearly polarized light and transmitting a second linearly polarized light, wherein a phase difference between the first linearly polarized light and the second linearly polarized light is π / 2.

14. The light guide device according to claim 1, characterized in that: The geometric coupling structure (11) is arranged on the side wall of the substrate (1) and forms a coupling slope; The geometric outcoupling structure (12) is arranged on the surface of the substrate (1).

15. A head mounted display device, characterized in that: include: A light guiding device as claimed in any one of claims 1 to 14.

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