An AR display element and AR device based on metasurface
By introducing reflective metasurface lenses and narrowband bandstop metasurface filters into AR devices, the problem of stray light in AR devices is solved, and the coupled waveguide system is simplified and the display effect is improved.
Patent Information
- Application Number
- CN202521547403.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2026-05-26
- Estimated Expiration
- 2035-07-23
Smart Images
Figure CN224287254U_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of optical components, and specifically relates to an AR display element and AR device based on metasurface. Background Technology
[0002] With the introduction of the concept of "metaverse", AR technology has developed rapidly.
[0003] Typically, AR research involves coupling the light projected from the display screen into an optical waveguide via a coupling lens group, and then finally coupling it out from the other end.
[0004] In this coupling method, strong stray light is generated due to the multiple reflections and transmissions of light in the waveguide, which affects the customer's use. Utility Model Content
[0005] This application provides an AR display element and AR device based on metasurfaces to at least solve the above-mentioned technical problems existing in the prior art.
[0006] One embodiment of this application provides an AR display element based on metasurfaces, including a reflective metasurface lens and a narrowband bandstop metasurface filter stacked together, with a spacer layer between the reflective metasurface lens and the narrowband bandstop metasurface filter; the reflective metasurface lens includes a transparent substrate and a first microstructure array disposed on the transparent substrate; the spacer layer is the transparent substrate and / or an air layer of the reflective metasurface lens, and the thickness of the spacer layer is 100 nm to 1 mm; the reflective metasurface lens is used to reflect and focus a projection beam with a specific polarization, and the narrowband bandstop metasurface filter is used to reflect a projection beam with a specific polarization and wavelength and transmit external light.
[0007] In one possible implementation, the first microstructure array and / or the second microstructure array are arranged in a periodic structure or a quasicrystalline arrangement.
[0008] In one embodiment, the first microstructure array is composed of periodically arranged nanopillars or nanopores.
[0009] In one embodiment, the second microstructure array is composed of multiple microstructures coupled together or symmetry-broken structures.
[0010] In one embodiment, the unit structure of the first microstructure array and / or the second microstructure array is a nanocylinder, a nanocross column, a nanocircular hole, or a nanocross hole.
[0011] In one embodiment, the transparent substrate is a sapphire substrate or a silicon oxide substrate, with a visible light transmittance greater than 90%.
[0012] In one embodiment, the unit structure size of the first microstructure array varies radially to achieve beam focusing.
[0013] In one embodiment, in the second microstructure array: the height of a single pillar is 200-400nm, the length is 180-250nm, and the width is 50-100nm; the spacing between adjacent double pillars is 50-100nm, and the arrangement period is 200-400nm.
[0014] In one embodiment, in the first microstructure array: the height of the nanopillars is 500-700nm, the width is 70-300nm, the length is 150-500nm, and the arrangement period is 300-450nm.
[0015] Another embodiment of this application provides an AR device, including any of the above-mentioned AR display elements, wherein the AR display elements are integrated in the optical path of the AR device, the narrow-band bandstop metasurface filter is located on the human eye side, and the reflective metasurface lens is located on the projection light source side.
[0016] Compared with the prior art, this application has the following advantages:
[0017] The AR element of this application uses a polarization-dependent reflective superlens in conjunction with a narrowband bandstop metasurface filter to simplify the coupled waveguide system while improving the stray light problem, thus realizing an AR projection scheme. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the structure of the AR display element in the embodiments of this application;
[0019] Figure 2 This is a top view schematic diagram of the reflective metasurface lens in the embodiments of this application;
[0020] Figure 3 This is a schematic diagram of the unit structure of the reflective metasurface lens in the embodiments of this application;
[0021] Figure 4 This is a schematic diagram showing the relationship between the phase and transmittance of the reflective metasurface lens under y-polarization and the length of the microstructure in an embodiment of this application.
[0022] Figure 5 This is a top view schematic diagram of the narrowband bandstop metasurface filter in the embodiments of this application;
[0023] Figure 6 This is a schematic diagram of the unit structure of the narrowband bandstop metasurface filter in the embodiments of this application;
[0024] Figure 7 This is a schematic diagram of the reflectance curve of the narrowband bandstop metasurface filter under y-direction polarization in the embodiments of this application. Detailed Implementation
[0025] The present application will now be described in further detail with reference to the accompanying drawings.
[0026] In the description of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.
[0027] This application discloses an AR element based on metasurfaces, which includes a reflective metasurface lens 1 and a narrowband bandstop metasurface filter 2 stacked together. The light beam emitted by the projection light source is reflected and focused by the reflective metasurface lens 1, and then reflected by the narrowband bandstop metasurface filter 2 to the human eye for imaging; at the same time, ambient natural light directly passes through the narrowband bandstop metasurface filter 2 and enters the human eye, realizing the AR display effect.
[0028] The reflective metasurface lens 1 includes a transparent substrate and a first microstructure array disposed on the transparent substrate. The narrowband bandstop metasurface filter 2 includes a transparent substrate and a second microstructure array disposed on the surface of the transparent substrate. The reflective metasurface lens 1 is used to reflect and focus a projection beam with a specific polarization, and the narrowband bandstop metasurface filter 2 is used to reflect a projection beam with a specific polarization and wavelength and transmit external light.
[0029] A spacer layer exists between the reflective metasurface lens 1 and the narrow-band bandstop metasurface filter 2. The spacer layer is a transparent substrate and / or air layer of the reflective metasurface lens 1, and the thickness of the spacer layer is 100 nm to 1 mm.
[0030] Understandably, the spacing layer can be set according to specific design requirements. Its purpose is to ensure that light with the same polarization as the projected light can be narrow-band band-stop filtered, that is, the light incident from the projection lens will be reflected to the human eye, while orthogonal polarization is not controlled, that is, external light will directly enter the human eye.
[0031] In some embodiments, the spacer layer is simply an air layer. For example, the thickness of the air layer is 500 μm.
[0032] In some embodiments, the spacer layer is composed solely of the transparent substrate of the reflective metasurface lens 1. For example, the thickness of the transparent substrate is 500 μm.
[0033] In some embodiments, the spacer layer is composed of a transparent substrate of the reflective metasurface lens 1 and an air layer. For example, the thickness of the air layer is 300 μm, and the thickness of the transparent substrate is 300 μm.
[0034] In this embodiment, the first microstructure array and / or the second microstructure array are arranged in a periodic structure or a quasi-crystalline arrangement. The periodic structure arrangement includes, but is not limited to, a tetragonal arrangement and a hexagonal arrangement.
[0035] Furthermore, the first microstructure array and / or the second microstructure array may be composed of periodically arranged nanopillars or nanopores.
[0036] Furthermore, the unit structure of the first microstructure array and / or the second microstructure array is one or more of nanocylinders, nanocross pillars, nanopores, or nanocross pores.
[0037] Furthermore, the second microstructure array is composed of multiple microstructures coupled together or symmetry-broken structures.
[0038] In this embodiment, the transparent substrate may be, but is not limited to, a sapphire substrate or a silicon oxide substrate, with a visible light transmittance greater than 90%.
[0039] Understandably, the high transparency and specific refractive index (e.g., sapphire n = 1.76 @ 550 nm) of sapphire / silicon oxide substrates are necessary structural conditions for achieving visible light transmission and microstructure phase modulation.
[0040] In this embodiment, the microstructure materials of the first microstructure array and / or the second microstructure array are materials with high refractive index for the visible light band, such as titanium oxide, gallium nitride, silicon carbide, gallium phosphide, etc.
[0041] In some embodiments, in the first microstructure array: the height of the nanopillars is 500-700nm, the width is 70-300nm, the length is 150-500nm, and the arrangement period is 300-450nm.
[0042] In the second microstructure array: the height of a single pillar is 200-400nm, the length is 180-250nm, and the width is 50-100nm; the spacing between adjacent double pillars is 50-100nm, and the arrangement period is 200-400nm.
[0043] Taking a wavelength of 532nm as an example, this paper explains the working principle of an AR display element by substituting specific parameters.
[0044] Figure 1A schematic diagram of an AR display element based on a polarization-controlled metasurface is provided. A reflective metasurface lens 1 and a narrow-band bandstop metasurface filter 2 are stacked sequentially from the projection light source side to the human eye side of the AR display element. The reflective metasurface lens 1 uses a sapphire substrate with a diameter of 20 mm and a thickness of 10 μm (average visible light transmittance > 92%). This substrate can be used as a spacer layer between the metasurface lens and the bandstop filter; that is, in this embodiment, the spacer layer is only composed of the transparent substrate of the reflective metasurface lens 1, and its surface is provided with a rectangular nanopillar array (…). Figures 2-3 The array is arranged in a square pattern with a period of 400 nm; the height of each nanopillar is fixed at 600 nm, the width is fixed at 80 nm, and the length varies radially (range 200-500 nm), achieving beam focusing through the length gradient. The narrow-band bandstop metasurface filter 2 uses a 20 mm diameter silicon oxide substrate (average visible light transmittance > 95%), and its surface is covered with a paired array of rectangular nanopillars. Figures 5-6 The array is arranged in a square pattern with a period of 350nm; each column is 350nm high, 200nm long, and 60nm wide, and the spacing between adjacent columns is fixed at 55nm. The 532nm narrowband reflection function is achieved through the double-column coupling structure.
[0045] Specifically, such as Figure 1 As shown, the light projected by the AR optical engine module after passing through the light source is obliquely incident on the reflective metasurface lens 1 after being polarized. The wavelength of the emitted light is 532nm. It is reflected and converged into the human eye to form a projected pattern. The reflection effect is achieved by the narrow-band bandstop metasurface filter 2. The effect of the narrow-band bandstop metasurface filter 2 is to reflect narrow-band incident light with a specific angle and polarization, while its orthogonally polarized light will pass through directly. Thus, external light can pass directly through the metasurface, ultimately achieving the AR display effect. The reflective metasurface lens 1 and the narrow-band bandstop metasurface filter 2 are described below:
[0046] The top view of the reflective metasurface lens 1 is shown below. Figure 2 As shown, it consists of a series of rectangular microstructures of different lengths.
[0047] Single microstructures such as Figure 3 As shown, for this 532nm wavelength design, the period p1 is chosen to be 400nm, the microstructure height h1 is 600nm, and the width w1 is fixed at 80nm. The phase delay is adjusted by changing l1. The results of l1, phase delay, and transmittance are as follows. Figure 4 As shown. When y-polarized light is incident on the reflective metasurface lens 1, the propagation direction of the beam changes, while when x-polarized light is incident, the propagation direction does not change. For this design, the phase delay of the reflective metasurface lens 1 must satisfy the following formula:
[0048]
[0049] The total phase is divided into two parts: the grating phase φgrating and the focusing phase φfocusing. These two phases are represented by the following formulas:
[0050]
[0051] Where λ is the incident light wavelength, θ is the incident angle, and the purpose of this phase delay is to uniformly deflect the incident light rays; αi is the polynomial coefficient of the focusing phase, and x and y are the coordinate positions on the metasurface, respectively. The purpose of this phase delay is to converge the light rays. After the y-direction polarized light passes through the reflective metasurface lens 1, it is reflected and converged into the human eye due to the effect of the narrow-band bandstop metasurface filter 2. The goal of the narrow-band bandstop metasurface filter 2 is to achieve narrow-band reflection of y-polarized light, but to allow complete transmission of x-direction polarized light. Figure 5 A bandstop filter structure based on a metasurface is demonstrated, which generates a corresponding narrowband reflection peak due to the coupling of the two microstructures.
[0052] Figure 6 This is a schematic diagram of a two-unit structure of a narrowband bandstop metasurface filter. In this design, the period p2 is set to 350 nm, the microstructure length l2 is 200 nm, the width w2 is 60 nm, the microstructure height is fixed at 350 nm, and the spacing g between the two microstructures is 55 nm.
[0053] Figure 7 The corresponding transmittance curves are shown, revealing that the narrow-band bandstop metasurface filter 2 exhibits high reflectivity near 532nm under y-polarized incident light, while its reflectivity is lower in other wavelength bands, with a reflectivity of >95% for 532nm beams. The narrow-band bandstop metasurface filter 2 can achieve the function of selecting the transmission mode based on polarization and wavelength. Combined with the reflective metasurface lens 1, it can realize the function of AR display.
[0054] This application also discloses an AR device, including any of the aforementioned AR elements. The AR display element is integrated into the optical path of the AR device, a narrow-band stop metasurface filter is located on the human eye side, and a reflective metasurface lens is located on the projection light source side.
[0055] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.
Claims
1. A metasurface-based AR display element, characterized by: It includes a reflective metasurface lens and a narrowband bandstop metasurface filter stacked together, with a spacer layer between the reflective metasurface lens and the narrowband bandstop metasurface filter; The reflective metasurface lens includes a transparent substrate and a first microstructure array disposed on the transparent substrate; The narrowband bandstop metasurface filter includes a transparent substrate and a second microstructure array disposed on the surface of the transparent substrate; The spacer layer is a transparent substrate and / or air layer of the reflective metasurface lens, and the thickness of the spacer layer is 100 nm to 1 mm; The reflective metasurface lens is used to reflect and focus a projection beam with a specific polarization, and the narrowband bandstop metasurface filter is used to reflect a projection beam with a specific polarization and wavelength and transmit external light.
2. The AR display element according to claim 1, characterized in that: The first microstructure array and / or the second microstructure array are arranged in a periodic structure or a quasicrystalline arrangement.
3. The AR display element according to claim 2, characterized in that: The first microstructure array is composed of periodically arranged nanopillars or nanopores.
4. The AR display element according to claim 2, characterized in that: The second microstructure array is composed of multiple microstructures coupled together or symmetry-broken structures.
5. The AR display element according to claim 2, characterized in that: The unit structure of the first microstructure array and / or the second microstructure array is a nanocylinder, a nanocross column, a nanocircular hole, or a nanocross hole.
6. The AR display element according to claim 1, characterized in that: The transparent substrate is a sapphire substrate or a silicon oxide substrate, with a visible light transmittance greater than 90%.
7. The AR display element according to claim 1, characterized in that: The unit structure size of the first microstructure array varies radially to achieve beam focusing.
8. The AR display element according to claim 5, characterized in that: In the second microstructure array: the height of a single pillar is 200-400nm, the length is 180-250nm, and the width is 50-100nm; the spacing between adjacent double pillars is 50-100nm, and the arrangement period is 200-400nm.
9. The AR display element according to claim 5, characterized in that, In the first microstructure array: the height of the nanopillars is 500-700nm, the width is 70-300nm, and the length is 150-500nm; the arrangement period is 300-450nm.
10. An AR device, characterized in that: The device includes any one of the AR display elements of claims 1-9, wherein the AR display element is integrated in the optical path of the AR device, the narrow-band bandstop metasurface filter is located on the human eye side, and the reflective metasurface lens is located on the projection light source side.