Optical filters, optical waveguides and display devices

Abstract

This application provides a light filter, an optical waveguide, and a display device. The light filter includes at least one first thin film and at least one second thin film. The first thin film has isotropic optical properties, and the second thin film has anisotropic optical properties. The second thin film and the first thin film are stacked alternately in sequence. The second thin film is made of a target anisotropic material, and the optical axis tilt angle of the target anisotropic material is within a target tilt angle range, so that the transmittance of the light filter to incident light varies with the incident angle of the incident light. The optical axis tilt angle is the angle between the optical axis of the target anisotropic material and the surface of the thin film. The light filter provided by this application has low transmittance for light incident at large angles, making it difficult for light incident at large angles to pass through the light filter, thus making it difficult for light incident at large angles to form rainbow patterns.

Description

Technical Field

[0001] This application relates to the field of optical waveguide technology, and in particular to a filter film, an optical waveguide, and a display device. Background Technology

[0002] Most near-eye display devices utilize diffractive waveguides to achieve near-eye display. A grating on the diffractive waveguide expands the pupil to ensure the user can see all the light rays in the field of view for a complete image display. However, to ensure all light is transmitted, a large grating period is required. A large grating period causes rainbow patterns to appear on the waveguide when external light sources are incident on the grating, thus affecting the user's viewing experience. Related technologies have attempted to reduce rainbow patterns by using high-refractive-index substrates or stacked misaligned gratings. However, high-refractive-index substrate solutions have high manufacturing costs for diffractive waveguides, while stacked misaligned grating solutions suffer from low yield rates. Therefore, how to reduce rainbow patterns has become a pressing issue. Summary of the Invention

[0003] This application provides a filter film, an optical waveguide, and a display device, aiming to solve the problem that light rays incident at a large angle onto a diffractive optical waveguide are easily diffracted into rainbow patterns, and to reduce the fabrication cost of optical waveguides with reduced rainbow patterns while ensuring the optical performance of the optical waveguide.

[0004] In a first aspect, this application provides a filter film, the filter film comprising:

[0005] At least one first thin film, wherein the optical properties of the first thin film are isotropic;

[0006] At least one second thin film, the second thin film having anisotropic optical properties, and the second thin film and the first thin film being stacked alternately in sequence;

[0007] The second film is made of a target anisotropic material, and the optical axis tilt angle of the target anisotropic material is within the target tilt angle range so that the transmittance of the filter film to incident light changes with the incident angle of the incident light; the optical axis tilt angle is the angle between the optical axis of the target anisotropic material and the surface of the film.

[0008] In one embodiment, the target tilt angle range α satisfies the following relationship: 2°≤θ≤88°.

[0009] In one embodiment, the refractive index difference Δn of the target anisotropic material satisfies the following relationship: 0.001≤Δn≤0.6.

[0010] In one embodiment, the target anisotropic material includes rod-shaped liquid crystal and / or dish-shaped liquid crystal.

[0011] In one embodiment, the target anisotropic material is a uniaxial material and / or a biaxial material.

[0012] In one embodiment, the difference between the refractive index of the first film and the refractive index of the second film for ordinary light in the incident light is less than or equal to a preset refractive index difference.

[0013] In one embodiment, each of the first films has the same thickness, and / or each of the second films has the same thickness.

[0014] In one embodiment, the thickness of the first film is the same as the thickness of the second film.

[0015] In one embodiment, the thickness of the filter film is greater than or equal to 20 nanometers and less than 200 micrometers.

[0016] In one embodiment, the filter film is prepared by at least one of the processes of coating, spin coating, deposition, and electron beam evaporation.

[0017] Secondly, this application also provides an optical waveguide, which includes:

[0018] A waveguide layer comprising a waveguide substrate and a diffraction microstructure, the diffraction microstructure being used to couple incident light into the waveguide substrate and to couple light propagating in the waveguide substrate out.

[0019] A protective layer is provided to protect the diffraction microstructures on the waveguide layer.

[0020] A filter film, wherein the filter film is as provided in the first aspect, and the filter film is disposed in the waveguide layer or the protective layer.

[0021] Thirdly, this application also provides a display device, including: an optomechanism and an optical waveguide as provided in the second aspect.

[0022] This application provides a filter film, an optical waveguide, and a display device. The filter film includes at least one first thin film with isotropic optical properties and at least one second thin film with anisotropic optical properties. The optical axis tilt angle of the target anisotropic material used to prepare the second thin film is within the target tilt angle range, so that the transmittance of the filter film is negatively correlated with the incident angle of the incident light. This achieves the effect of high transmittance for light with small incident angles and low transmittance for light with large incident angles. When the filter film is placed on the optical waveguide, the low transmittance of the filter film for light incident at large angles makes it difficult for light incident at large angles to pass through the filter film, thus making it difficult for these lights to form rainbow patterns. This achieves the effect of reducing or eliminating rainbow patterns. Moreover, the filter film has low manufacturing cost and simple manufacturing process, thereby reducing the manufacturing complexity and cost of optical waveguides with rainbow pattern reduction effect, improving the yield of finished optical waveguides, and ensuring the optical performance of optical waveguides. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a filter film provided in one embodiment of this application;

[0025] Figure 2 A graph showing the relationship between the incident angle of incident light and the transmittance of the filter film in one embodiment of this application;

[0026] Figure 3 A graph showing the relationship between the wavelength of incident light and the transmittance of the filter film in one embodiment of this application;

[0027] Figure 4 This is a schematic diagram of a filter film provided in one embodiment of this application;

[0028] Figure 5a The transmittance spectrum of a filter film provided in an embodiment of this application;

[0029] Figure 5b for Figure 5a Another transmittance spectrum of the filter film provided in the embodiment;

[0030] Figure 6a A transmittance spectrum of a filter film provided in another embodiment of this application;

[0031] Figure 6b for Figure 6a Another transmittance spectrum of the filter film provided in the embodiment;

[0032] Figure 7 This is a schematic diagram of an optical waveguide provided in an embodiment of this application;

[0033] Figure 8a This is a schematic diagram of an optical waveguide provided in another embodiment of this application;

[0034] Figure 8b This is a schematic diagram of an optical waveguide provided in yet another embodiment of this application;

[0035] Figure 9 This is a schematic diagram of a display device provided in an embodiment of this application.

[0036] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0039] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0040] In existing technologies, near-eye displays are generally achieved on near-eye display devices through diffractive waveguides. In this scenario, the grating period of the grating in the diffractive waveguide is set to be relatively large to meet the needs of the field of view. However, a large grating period can easily cause ambient light to be diffracted at a large angle, forming rainbow patterns that enter the user's eyes, thus affecting the display quality of the near-eye display device.

[0041] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a filter film provided in an embodiment of this application. The filter film provided in this application has low transmittance for light incident at large angles. Therefore, when the filter film is placed in the optical waveguide, ambient light incident at large angles is difficult to pass through the filter film, making it difficult to form rainbow patterns on the user side, thereby achieving the effect of reducing or eliminating rainbow patterns.

[0042] like Figure 1 As shown, the filter film 10 includes at least one first thin film 11 with isotropic optical properties and at least one second thin film 12 with anisotropic optical properties. The first thin film 11 and the second thin film 12 are stacked alternately in sequence. Specifically, the first thin film 11 is made of a target isotropic material, and the second thin film 12 is made of a target anisotropic material. The optical axis tilt angle of the target anisotropic material is within the target tilt angle range, so that the transmittance of the filter film 10 to incident light changes with the incident angle of the incident light.

[0043] It should be noted that when incident light is incident on the target anisotropic material along a specific direction, birefringence does not occur; this specific direction is the direction of the optical axis. The optical axis tilt angle is the angle between the target anisotropic material and the surface of the prepared thin film (substrate surface). When the optical axis tilt angle of the target anisotropic material is any angle within the target tilt angle range, if the incident angle of the incident light is greater than or equal to a preset angle, the refractive index difference between the target polarization and the target wavelength light in the incident light is large in the first thin film 11 and the second thin film 12. Furthermore, under the influence of the physical thickness of the thin film, the target polarization light and the target wavelength light can achieve a similar effect of coherence and destructive force when penetrating the filter film, resulting in a low transmittance of the filter film 10 for incident light with an incident angle greater than or equal to the preset angle. When the incident angle of light is less than the preset angle, the difference in refractive index between the target polarized light and the light of the target wavelength band in the incident light is small in the first thin film 11 and the second thin film 12, making it difficult to achieve the effect of coherence and cancellation. As a result, the transmittance of the filter film 10 for incident light with an incident angle less than the preset angle is high, and the filter film 10 achieves the effect of different transmittance for light with different incident angles and different wavelength bands. Therefore, by setting the corresponding optical parameters of the filter film 10, such as refractive index, film thickness and the number of layers of the first thin film 11 and / or the second thin film 12, the filter film 10 can have a lower transmittance for the wavelength bands that are prone to rainbow patterns, thereby achieving the effect of reducing or eliminating rainbow patterns.

[0044] Please see Figure 2 and Figure 3 , Figure 2 This is a graph showing the relationship between the incident angle of incident light and the transmittance of the filter film 10 according to an embodiment of this application. Figure 3 This is a graph showing the relationship between the wavelength of incident light and the transmittance of the filter film 10 in one embodiment of this application.

[0045] In specific implementation, the filter film 10 is formed by alternating stacking of at least four layers of first thin film 11 and four layers of second thin film 12 to achieve wavelength-band and polarization-band filtering characteristics; the transmittance curve of the filter film 10 for light of specific polarization and specific wavelength band can be as follows: Figure 2As shown in curve a, the transmittance curve of the filter film 10 for other situations can be approximated as shown in curve a. Figure 2 As shown by curve b in the figure, other types of light include, but are not limited to, any light whose polarization does not belong to a specific polarization and / or whose wavelength is outside the specific wavelength band, and are not limited herein. Figure 2 It is known that the transmittance of light with a specific polarization and wavelength band is correlated with the incident angle. While the transmittance decreases as the incident angle increases linearly, the rate of change is not constant. The specific relationship can be adjusted by modifying the thickness, refractive index, and other optical parameters of the filter film 10 to control the transmittance of light with a specific polarization and wavelength band. No restrictions are imposed here. The transmittance curve of the filter film 10 for light with a specific polarization and a fixed incident angle is shown below. Figure 3 As shown by curve c in the figure, the light transmittance curves for other cases can be approximated as follows. Figure 3 As shown by curve d in the figure, it can be seen that the transmittance of the filter film 10 for the target wavelength band is low. By adjusting the optical parameters of the filter film 10, the size of the target wavelength band can be adjusted. Therefore, when the target wavelength band is set to a wavelength band that easily produces rainbow patterns, the filter film 10 can achieve a better effect of reducing or eliminating rainbow patterns. It should be understood that through the above settings, the filter film 10 can achieve transmittance variations based on polarization and wavelength band, thus reducing rainbow patterns and improving the applicability of the filter film 10.

[0046] In some embodiments, the target tilt angle range α satisfies the following relationship: 2°≤θ≤88°.

[0047] For example, the optical axis tilt angle corresponding to the target anisotropic material is between 2° and 88°, in order to achieve a filtering effect on the incident light in conjunction with the set film thickness. In specific implementation, the optical axis tilt angle corresponding to the target anisotropic material is set between 10° and 80°.

[0048] In some embodiments, the refractive index difference Δn of the target anisotropic material satisfies the following relationship: 0.001≤Δn≤0.6.

[0049] For example, since the target anisotropic material has different refractive indices for incident light incident at a specific angle and in a direction other than the optical axis, the incident light will undergo birefringence in the target anisotropic material under the action of different refractive indices. The difference between the different refractive indices of the target anisotropic material for incident light needs to be within the range of 0.001 to 0.6, so that the filter film 10 can achieve low transmittance for incident light with an incident angle greater than or equal to a preset angle, and high transmittance for incident light with an incident angle less than a preset angle, thereby achieving the effect of reducing or eliminating rainbow patterns.

[0050] In some embodiments, the target anisotropic material includes rod-shaped liquid crystal and / or dish-shaped liquid crystal.

[0051] For example, the second thin film 12 is prepared by rod-shaped liquid crystal and / or dish-shaped liquid crystal to make the optical properties of the second thin film 12 anisotropic, wherein the rod-shaped liquid crystal and / or dish-shaped liquid crystal are nematic or cholesteric phases.

[0052] In some embodiments, the target anisotropic material is a uniaxial material and / or a biaxial material.

[0053] For example, the target anisotropic material is a uniaxial material and / or a biaxial material. In specific implementations, the second film 12 can be configured in ways including but not limited to all second films 12 being made of uniaxial material; or all second films 12 being made of biaxial material; or at least one layer being made of uniaxial material and at least one layer being made of biaxial material; or at least one layer being made of a mixture of uniaxial and biaxial materials, to increase the design freedom of the filter film 10, thereby enabling the filter film 10 to achieve better filtering effects according to actual usage requirements.

[0054] In some embodiments, the difference between the refractive index of the first film 11 and the refractive index of the second film 12 for ordinary light in the incident light is less than or equal to a preset refractive index difference.

[0055] For example, the refractive index of the first thin film 11 is determined by the refractive index of the target isotropic material used to prepare the first thin film 11, and the target anisotropic material used to prepare the second thin film 12 has a refractive index distribution difference only for a specific polarization, while exhibiting isotropy for another polarization. Specifically, it exhibits a refractive index distribution difference for extraordinary light (e-ray), while exhibiting isotropy for ordinary light (o-ray). Therefore, by setting the difference between the refractive index of the target isotropic material and the refractive index of the target anisotropic material for ordinary light to be less than or equal to a preset refractive index difference, the ordinary light experiences a smaller refractive index difference in the first thin film 11 and the second thin film 12, making it less likely for coherent cancellation to occur, thus making it easier to pass through the filter film 10. This allows the filter film 10 to achieve different transmittances for different incident light, thereby achieving the desired filtering effect.

[0056] It should be noted that the preset refractive index difference can be set according to the filtering requirements, the number of layers of the first thin film 11 and / or the second thin film 12 in the filter film 10, the refractive index of the first thin film 11 and / or the second thin film 12, etc., and this application does not impose any restrictions.

[0057] In the specific implementation process, the target isotropic material for preparing the first thin film 11 includes organic and / or inorganic materials. The organic materials include, but are not limited to, polyethylene (PE), polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), polymethyl methacrylate (PMMA), and polystyrene (PS). The inorganic materials include, but are not limited to, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, hafnium oxide, niobium oxide, tantalum oxide, yttrium oxide, magnesium fluoride, and cryolite. It should be noted that the first thin film 11 can be prepared using one or more of the above materials, and the difference between the refractive index of the prepared first thin film 11 and the refractive index of the target anisotropic material for preparing the second thin film 12 for ordinary light is less than or equal to a preset refractive index difference. This allows the filter film 10 to achieve different transmittances for different incident lights, thereby reducing or eliminating rainbow patterns.

[0058] Please see Figure 4 , Figure 4 This is a schematic diagram of a filter film 10 provided in an embodiment of this application.

[0059] In some embodiments, each of the first films 11 has the same thickness, and / or each of the second films 12 has the same thickness.

[0060] For example, such as Figure 4 As shown, when the filter film 10 includes multiple layers of first film 11 and multiple layers of second film 12, the thickness of each first film 11 layer is the same, and the thickness of each second film 12 layer is the same. This simplifies the fabrication process of the filter film 10, thereby reducing the difficulty and cost of fabricating the filter film 10, while also reducing or eliminating rainbow patterns.

[0061] In another embodiment, the filter film 10 includes multiple layers of first film 11 and multiple layers of second film 12, and the thickness of at least one first film 11 is different from the thickness of the remaining at least one first film 11.

[0062] In another embodiment, the filter film 10 includes multiple layers of first film 11 and multiple layers of second film 12, wherein the thickness of at least one second film 12 is different from the thickness of the remaining at least one second film 12.

[0063] It should be noted that when the filter film 10 includes multiple layers of first film 11 and multiple layers of second film 12, the thickness of each first film 11 layer may be the same or different, and the thickness of each second film 12 layer may also be the same or different. As described in the above embodiments, this application does not limit whether the thickness of each first film 11 layer is the same or whether the thickness of each second film 12 layer is the same.

[0064] In some embodiments, the thickness of the first film 11 is the same as the thickness of the second film 12.

[0065] Please continue reading. Figure 4 , Figure 4 The illustration shows a case where the thickness of the first film 11 is the same as the thickness of the second film 12, and the thickness of each layer of the first film 11 is the same as the thickness of each layer of the second film 12, thereby ensuring that the thickness of each layer in the filter film 10 is the same. In another embodiment, the thickness of each layer of the first film 11 is the same, and the thickness of each layer of the second film 12 is the same, but the thickness of the first film 11 is not the same as the thickness of the second film 12; in yet another embodiment, at least one layer of the first film 11 has the same thickness as at least one layer of the second film 12. It should be noted that this application does not limit whether the thickness of the first film 11 is the same as the thickness of the second film 12, nor the number of first films 11 with the same thickness as the second film 12.

[0066] In some embodiments, the thickness of the filter film 10 is greater than or equal to 20 nanometers and less than 200 micrometers.

[0067] It should be noted that, in order to ensure the optical performance of the filter film 10, the total thickness of the filter film 10 is between 20 nanometers and 200 micrometers. This application does not limit the thickness of each first film 11, the thickness of each second film 12, the number of layers of the first film 11, and the number of layers of the second film 12. According to actual tests, the optical performance achieved when the total thickness of the filter film 10 is between 500 nanometers and 10 micrometers is better than that of the filter film 10 with a total thickness in other ranges.

[0068] Please see Figure 5a and Figure 5b , Figure 5a This is a transmittance spectrum of a filter film 10 provided in an embodiment of this application. Figure 5b for Figure 5a Another transmittance spectrum of the filter film 10 provided in the embodiment.

[0069] In the specific implementation process, the filter film 10 includes 7 first films 11 and 7 second films 12. The first films 11 are made of polyethylene terephthalate (PET) with a refractive index of 1.58. The second films 12 correspond to target anisotropic materials with refractive indices of 1.51 and 2.1, respectively. The optical axis tilt angle is set between 20° and 30°. The thickness of each first film 11 and each second film 12 is the same, with the thicknesses of the first films 11 and second films 12 ranging from 30 nm to 100 nm, so that the total thickness of the filter film 10 is between 0.5 μm and 0.7 μm. The transmittance spectrum of the filter film 10 prepared with the above parameters is shown below. Figure 5a And as shown in Figure b. Wherein, Figure 5a The transmittance spectra of s-polarized light at various incident angles are shown for filter film 10. Figure 5b The transmittance spectra of filter film 10 for p-polarized light incident at 70 degrees are shown below. Figure 5a It can be seen that the transmittance of the filter film 10 for all bands of s-polarized light is basically the same. As the incident angle increases, the transmittance of each band decreases rapidly. When incident at an angle less than 60 degrees, the visible light transmittance is greater than 70%, and when incident at 70 degrees, the visible light transmittance is greater than 60%. Figure 5b As can be seen, when the incident light is incident at 70 degrees, the transmittance of p-polarized light in the 400nm–470nm wavelength range drops below 50%, while the transmittance in the green and red wavelength ranges is above 85%. This demonstrates that the filter film 10 achieves angle selectivity for p-polarized light and maintains high transmittance for s-polarized light, meaning it filters at least p-polarized light. Furthermore, the transmittance of the filter film 10 is related to the incident angle and wavelength, thus enabling filtering of light at different incident angles and wavelengths, thereby reducing or eliminating rainbow patterns.

[0070] Please see Figure 6a and Figure 6b , Figure 6a This is a transmittance spectrum of a filter film 10 provided in another embodiment of this application. Figure 6b for Figure 6a Another transmittance spectrum of the filter film 10 provided in the embodiment.

[0071] In its specific implementation, the filter film 10 comprises seven first thin films 11 and seven second thin films 12. The first thin film 11 is made of polyethylene terephthalate (PET) with a refractive index of 1.58. The second thin films 12 correspond to target anisotropic materials with refractive indices of 1.51 and 1.71, respectively, and their optical axis tilt angles are set between 30° and 40°. The thickness of each film varies, but all fall within the range of 10 nm to 150 nm, resulting in a total thickness of the filter film 10 between 0.5 μm and 5 μm. Figure 6a The transmittance spectra of filter film 10 for p-polarized light at various incident angles are shown. Figure 6b The transmittance spectra of filter film 10 pairs of s-polarized light incident at 70 degrees are shown. Figure 6a It can be seen that when the incident light is incident at 70°, the transmittance of the filter film 10 for each p-polarized band of the incident light is still above 85%, and when the incident light is incident at 80°, the transmittance of the filter film 10 for each p-polarized band is still above 75%. Figure 6b It can be seen that when the incident light is incident at 70°, the transmittance of the filter film in the 400nm-450nm band of the 10 pairs of s-polarizations drops to 50% or more, while the transmittance of the green band is above 80% and the transmittance of the red band is above 70%.

[0072] As can be seen from the above, under different settings of the first thin film 11 and the second thin film 12 in the filter film 10, for example, by using different target anisotropic materials to prepare the second thin film 12, by setting the number and thickness of the first thin film 11 and the second thin film 12, the filter film 10 prepared can have different optical properties, so that the filter film 10 can be set according to actual needs, so that the filter film 10 prepared can achieve low transmittance for light with target polarization and target wavelength, thereby enabling the filter film 10 to reduce or eliminate rainbow patterns.

[0073] In some embodiments, the filter film 10 is prepared by at least one of the processes of coating, spin coating, deposition, and electron beam evaporation.

[0074] For example, the fabrication process of the filter film 10 includes one or more processes such as coating, spin coating, deposition, and electron beam evaporation. Specifically, the formation process of the second thin film 12 includes, but is not limited to, blowing air onto a heated liquid crystal film at a specific angle. During heating, the liquid crystal molecules exhibit disordered isotropic characteristics, and after cooling, they form anisotropic properties. A positioning material thin layer is set on the bottom of the film of the target anisotropic material, and then an anisotropic material film is coated. Different doses and / or different angles of exposure are applied to the liquid crystal layer using photosensitivity to complete the orientation of the liquid crystal layer. The liquid crystal layer is irradiated by friction or an ion beam to complete the orientation of the liquid crystal layer. It should be noted that the above-mentioned fabrication process is simpler than the fabrication process of the stacked misaligned grating, thus reducing the fabrication difficulty and cost of diffractive waveguides that can achieve the effect of reducing rainbow patterns, while improving the yield of the finished product.

[0075] Please see Figure 7 , Figure 7 This is a schematic diagram of an optical waveguide 100 provided in an embodiment of this application.

[0076] like Figure 7 As shown, the optical waveguide 100 includes a waveguide layer 20, a protective layer 30, and a filter film 10. The waveguide includes a waveguide substrate 21 and a diffraction microstructure 22 disposed on the surface of the waveguide substrate 21. The diffraction microstructure 22 couples incident light into the waveguide substrate 21 and couples out light propagating within the waveguide substrate 21, thereby achieving directional light transmission. The protective layer 30 protects the diffraction microstructure 22 on the waveguide layer 20. The filter film 10 is disposed on the surface of the waveguide layer 20 or the surface of the protective layer 30. It should be noted that the filter film 10 can be as described in any of the preceding embodiments, and the filter film 10 can achieve low transmittance for incident light entering from outside the optical waveguide 100 at an angle greater than or equal to a preset angle, thereby reducing or eliminating rainbow patterns on the optical waveguide 100.

[0077] Figure 7The filter film 10 is shown to be disposed on the side surface of the protective layer 30 away from the waveguide substrate 21. In specific implementation, the filter film 10 may be disposed on the side surface of the protective layer 30 close to the waveguide substrate 21, or disposed on the waveguide substrate 21. This application does not impose any restrictions.

[0078] See Figure 8a , Figure 8a This is a schematic diagram of an optical waveguide 100 provided in another embodiment of this application.

[0079] In some embodiments, the optical waveguide 100 includes two filter films 10, and the filter films 10 are disposed on the surface of the protective layer 30 near the waveguide substrate 21. The projection of the filter films 10 along the direction of the waveguide substrate 21 partially overlaps with the diffraction microstructure 22.

[0080] For example, by setting multiple filter films 10 on the optical waveguide 100, and making different filter films 10 have different transmittance for light with different wavelengths, polarization states and incident angles, it is possible to filter different light according to actual conditions to meet different usage requirements and improve the applicability of the optical waveguide 100. In specific implementation, the multiple filter films 10 included in the optical waveguide 100 can also be all set on the waveguide substrate 21, or at least one filter film 10 can be set on the protective layer 30 and at least one filter film 10 can be set on the waveguide substrate 21. This application does not limit the number of multiple filter films 10 or their specific placement.

[0081] Please see Figure 8b , Figure 8b This is a schematic diagram of an optical waveguide 100 provided in another embodiment of this application.

[0082] In this embodiment, the filter film 10 is disposed on one side of the waveguide substrate 21, and the diffraction microstructure 22 is disposed on the other side of the waveguide substrate 21. It should be noted that multiple filter films 10 may also be disposed on the waveguide substrate 21, and this application does not impose any limitation.

[0083] In the specific implementation process, the waveguide layer 20 includes one or more waveguide substrates 21, and each waveguide substrate 21 is made of one or more materials selected from glass, resin, plastic or ceramic. The waveguide substrate 21 is planar or curved to adapt to different application requirements.

[0084] Please see Figure 9 , Figure 9 This is a schematic diagram of a display device provided in an embodiment of this application.

[0085] like Figure 9As shown, the display device includes an optical engine and an optical waveguide as described in the previous embodiments. Specifically, the display device includes near-eye display devices implemented using optical waveguides, including but not limited to augmented reality (AR) display devices, extended reality (XR) display devices, head-up display (HUD) devices, etc. The optical waveguide can directionally transmit the signal light emitted from the optical engine to the human eye to realize the display of corresponding images or videos. Furthermore, by using the optical waveguide provided in this application, ambient light incident at a large angle can pass through the filter film, making it difficult to form rainbow patterns on the user side. This effectively reduces or eliminates rainbow patterns that may occur during the operation of the display device, thereby improving the user experience.

[0086] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0087] It should also be understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. It should be noted that, herein, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0088] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. The above descriptions are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A filter film, characterized in that, The filter film includes: At least one first thin film, wherein the optical properties of the first thin film are isotropic; At least one second thin film, the second thin film having anisotropic optical properties, and the second thin film and the first thin film being stacked alternately in sequence; The second film is made of a target anisotropic material, and the optical axis tilt angle of the target anisotropic material is within the target tilt angle range so that the transmittance of the filter film to incident light changes with the incident angle of the incident light; the optical axis tilt angle is the angle between the optical axis of the target anisotropic material and the surface of the film.

2. The filter film as described in claim 1, characterized in that, The target tilt angle range α satisfies the following relationship: 2°≤θ≤88°.

3. The filter film as described in claim 1, characterized in that, The refractive index difference of the target anisotropic material The following relationship must be satisfied: 0.001 ≤ ≤0.

6.

4. The filter film as described in claim 1, characterized in that, The target anisotropic material includes rod-shaped liquid crystal and / or dish-shaped liquid crystal.

5. The filter film as described in claim 1, characterized in that, The target anisotropic material is a uniaxial material and / or a biaxial material.

6. The filter film according to any one of claims 1-4, characterized in that, The difference between the refractive index of the first film and the refractive index of the second film for ordinary light in the incident light is less than or equal to a preset refractive index difference.

7. The filter film according to any one of claims 1-4, characterized in that, Each of the first films has the same thickness, and / or each of the second films has the same thickness.

8. The filter film as described in claim 7, characterized in that, The thickness of the first film is the same as the thickness of the second film.

9. The filter film as described in claim 7, characterized in that, The thickness of the filter film is greater than or equal to 20 nanometers and less than 200 micrometers.

10. The filter film according to any one of claims 1-4, characterized in that, The filter film is prepared by at least one of the following processes: coating, spin coating, deposition, and electron beam evaporation.

11. An optical waveguide, characterized in that, The optical waveguide includes: A waveguide layer comprising a waveguide substrate and a diffraction microstructure, the diffraction microstructure being used to couple incident light into the waveguide substrate and to couple light propagating in the waveguide substrate out. A protective layer is provided to protect the diffraction microstructures on the waveguide layer. A filter film, wherein the filter film is the filter film as described in any one of claims 1-10, and the filter film is disposed in the waveguide layer or the protective layer.

12. A display device, characterized in that, The display device includes an optomechanical system and an optical waveguide as described in claim 11.

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