Filter film, optical waveguide and display device

Abstract

The invention provides a filter film, an optical waveguide and a display device, the filter film comprises at least one layer of first film and at least one layer of second film, the optical property of the first film is isotropic, the optical property of the second film is anisotropic, and the second film and the first film are sequentially and alternately stacked; wherein the second thin film is prepared from a target anisotropic material, and the optical axis inclination angle of the target anisotropic material is within a target inclination angle range, so that the transmittance of the filter film to the incident light is changed along with the change of the incident angle of the incident light; the optical axis inclination angle is an included angle between the optical axis of the target anisotropic material and the film surface. The light filtering film provided by the invention has relatively low transmittance for light incident at a large angle, so that the light incident at the large angle is difficult to penetrate through the light filtering film, and the light incident to the light filtering film at the large angle is difficult to form rainbow lines.

Description

Technical Field

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

[0002] Most near-eye display devices use diffraction waveguides to achieve near-eye display. The grating on the diffraction waveguide is used to expand the pupil to ensure that the user can fully see all the field of view light to fully display the image. However, to ensure that all light is transmitted, a larger grating period needs to be set. The larger grating period causes rainbow lines to appear on the waveguide when the external light source is incident on the grating, thereby affecting the user's viewing experience. In related technologies, the purpose of reducing rainbow lines is achieved by using high-refractive-index substrates or stacked dislocated gratings. However, the high-refractive-index substrate solution has the problem of high preparation cost of diffraction waveguides, and the stacked dislocated grating solution has the problem of low finished product yield. Therefore, how to reduce rainbow lines has become an urgent problem to be solved. Summary of the invention

[0003] The present application provides a filter film, an optical waveguide and a display device, aiming to solve the problem in the related art that light is easily diffracted into rainbow patterns when incident on a diffraction optical waveguide at a large angle, and to reduce the preparation cost of an optical waveguide with a reduced rainbow pattern effect, thereby ensuring the optical performance of the optical waveguide.

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

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

[0006] at least one layer of a second film, the optical property of the second film is anisotropic, and the second film and the first film are alternately stacked in sequence;

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

[0008] In one embodiment, the target inclination angle range a 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-like liquid crystal and / or discotic liquid crystal.

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

[0012] In one embodiment, a difference between a refractive index of the first film and a 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, the thickness of each of the first films is the same, and / or the thickness of each of the second films is the same.

[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 process of coating, spin coating, deposition, and electron beam evaporation.

[0017] In a second aspect, the present application further provides an optical waveguide, the optical waveguide comprising:

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

[0019] A protective layer, the protective layer being used to protect the diffraction microstructure on the waveguide layer;

[0020] The optical filter film is the optical filter film provided in the first aspect, and the optical filter film is arranged on the waveguide layer or the protective layer.

[0021] In a third aspect, the present application further provides a display device, comprising: an optical machine and an optical waveguide as provided in the second aspect.

[0022] The present application provides a filter film, an optical waveguide and a display device. The filter film provided by the present application includes at least one first film with isotropic optical properties and at least one second film with anisotropic optical properties, and the size of the optical axis tilt angle of the target anisotropic material for preparing the second 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, thereby achieving the effect of high transmittance of light with a small incident angle and low transmittance with a large incident angle. Furthermore, when the filter film is arranged on the optical waveguide, since the filter film has a lower transmittance to light incident at a large angle, it is difficult for light incident at a large angle to pass through the filter film, so that it is difficult for such light to form rainbow patterns, thereby achieving the effect of reducing or eliminating the rainbow patterns. The filter film has a low preparation cost and a simple preparation process, so that the preparation complexity and preparation cost of the optical waveguide with the effect of reducing the rainbow patterns can be reduced, the finished product yield of the optical waveguide is improved, and the optical performance of the optical waveguide is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A schematic diagram of a filter film provided in one embodiment of the present application;

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

[0026] Figure 3 A graph showing the relationship between the wavelength of incident light and the transmittance of a filter film provided in an embodiment of the present application;

[0027] Figure 4 A schematic diagram of a filter film provided in one embodiment of the present application;

[0028] Figure 5a A transmittance spectrum of a filter film provided in one embodiment of the present 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 the present application;

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

[0032] Figure 7 A schematic diagram of an optical waveguide provided in an embodiment of the present application;

[0033] Figure 8a A schematic diagram of an optical waveguide provided in another embodiment of the present application;

[0034] Figure 8b A schematic diagram of an optical waveguide provided in yet another embodiment of the present application;

[0035] Fig. 9 A schematic diagram of a display device provided in one embodiment of the present application.

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

[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0039] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0040] In the prior art, near-eye display is generally achieved on a near-eye display device through a diffraction optical waveguide. In this scenario, the grating period of the grating in the diffraction optical waveguide is set to be larger to meet the needs of the field of view. However, the larger grating period can easily cause ambient light to be diffracted to form rainbow patterns and enter the user's eyes when it is incident at a larger angle, thereby affecting the display quality of the near-eye display device.

[0041] Please refer to Figure 1 , Figure 1 Schematic diagram of a filter film provided in one embodiment of the present application. The filter film provided in the present application has a low transmittance for light incident at a large angle, so that when the filter film is set in an optical waveguide, ambient light incident at a large angle 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 film 11 with isotropic optical properties and at least one second film 12 with anisotropic optical properties, and the first films 11 and the second films 12 are alternately stacked in sequence. Specifically, the first film 11 is made of a target isotropic material, and the second film 12 is made of a target anisotropic material, and the optical axis inclination angle of the target anisotropic material is within a target inclination angle range, so that the transmittance of the filter film 10 to the incident light changes with the incident angle of the incident light.

[0043] It should be noted that when the incident light is incident on the target anisotropic material along a specific direction, no birefringence occurs. The specific direction is the direction of the optical axis. The optical axis tilt angle is the angle between the target anisotropic material and the prepared film surface (substrate surface). When the magnitude of 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 the preset angle, the target polarization and the target wavelength light in the incident light have a large difference in refractive index in the first film 11 and the second film 12. Under the influence of the physical thickness of the film, the target polarization and the target wavelength light can achieve an effect similar to coherent destructive in the filter film 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. If the incident light is When the incident angle of light is less than the preset angle, the refractive index difference between the target polarized light and the light of the target wavelength band in the incident light in the first film 11 and the second film 12 is small, and it is difficult to achieve the effect of coherent destructive interaction, resulting in the filter film 10 having a higher transmittance for the incident light with an incident angle less than the preset angle, thereby achieving the effect that the filter film 10 has different transmittances for lights of different incident angles and different wavelength bands. Therefore, by setting the corresponding optical parameters of the filter film 10, such as the refractive index, film thickness, and the number of layers of the first film 11 and / or the second film 12, the filter film 10 can have a lower transmittance for the wavelength band that is prone to rainbow stripes, thereby achieving the effect of weakening or eliminating the rainbow stripes.

[0044] See also Figure 2 and Figure 3 , Figure 2 is a graph showing the relationship between the incident angle of the incident light and the transmittance of the filter film 10 provided in one embodiment of the present application. Figure 3 The graph is a relationship between the wavelength of incident light and the transmittance of the filter film 10 provided in one embodiment of the present application.

[0045] In a specific implementation process, the filter film 10 is formed by at least four layers of first films 11 and four layers of second films 12 alternately stacked to achieve band-by-band and polarization-by-polarization filtering characteristics; the transmittance curve of the filter film 10 for light of a specific polarization and a specific band can be as follows: Figure 2As shown by curve a in FIG. 1 , the transmittance curve of the filter film 10 for light in other situations can be approximated as follows: Figure 2 As shown by curve b in FIG. 1 , light in other situations includes but is not limited to any light whose polarization does not belong to a specific polarization and / or whose wavelength is outside a specific wavelength band, which is not limited here. Figure 2 It can be seen that the transmittance of light of a specific polarization and a specific wavelength band is correlated with the incident angle, and when the incident angle increases linearly, the transmittance decreases with the increase of the incident angle, but the rate of change is not constant. The specific change relationship can be adjusted according to actual needs by adjusting the thickness, refractive index and other optical parameters of the filter film 10 to adjust the transmittance of the filter film 10 for light of a specific polarization and a specific wavelength band, and is not limited here. The transmittance curve of the filter film 10 for light of a specific polarization and a fixed incident angle can be as follows: Figure 3 As shown by curve c in the figure, the light transmittance curves in other cases can be approximated as follows: Figure 3 As shown in the curve d in FIG. 1 , it can be seen that the transmittance of the filter film 10 for the light in 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. When the target wavelength band is set to the light in the wavelength band that easily generates rainbow stripes, the filter film 10 can achieve a good effect of reducing or eliminating rainbow stripes. It should be understood that through the above settings, the filter film 10 can achieve the change of transmittance in polarization and wavelength band, achieve the effect of reducing rainbow stripes, and improve the applicability of the filter film 10.

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

[0047] Exemplarily, the optical axis inclination range of the target anisotropic material is between 2° and 88°, so as to achieve a filtering effect on the incident light in accordance with the set film thickness. In a specific implementation process, the optical axis inclination range of 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] Exemplarily, 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, under the action of different refractive indices, the incident light will undergo birefringence in the target anisotropic material, wherein the difference between the different refractive indices reflected by the target anisotropic material for the incident light must be within a 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 achieve 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-like liquid crystals and / or discotic liquid crystals.

[0051] Exemplarily, the second film 12 is prepared by rod-like liquid crystal and / or disc-like liquid crystal, so that the optical properties of the second film 12 are anisotropic, wherein the rod-like liquid crystal and / or disc-like liquid crystal are in a nematic phase or a cholesteric phase.

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

[0053] Exemplarily, the target anisotropic material is a uniaxial material and / or a biaxial material. In a specific implementation, the configuration of the second film 12 includes but is not limited to that all second films 12 are made of uniaxial materials; or all second films 12 are made of biaxial materials; or at least one layer is made of uniaxial materials and at least one layer is made of biaxial materials; or at least one layer is made of a mixture of uniaxial materials and biaxial materials, so as to increase the degree of freedom in the design of the filter film 10, thereby enabling the filter film 10 to achieve a better filtering effect according to actual usage requirements.

[0054] In some embodiments, a difference between a refractive index of the first film 11 and a 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] Exemplarily, the refractive index of the first film 11 is determined by the refractive index of the target isotropic material for preparing the first film 11, and the target anisotropic material for preparing the second film 12 has a refractive index distribution difference only for a specific polarization, but is isotropic for another polarization. Specifically, there is a refractive index distribution difference for extraordinary light (e-light), but is isotropic for ordinary light (o-light); 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 refractive index difference felt by ordinary light in the first film 11 and the second film 12 is smaller, and it is less likely to cause coherence destructive phenomenon, so that ordinary light can easily pass through the filter film 10, and then the filter film 10 can achieve different transmittances for different lights in the 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 film 11 and / or the second film 12 in the filter film 10, the refractive index of the first film 11 and / or the second film 12, etc., and this application does not impose any restrictions.

[0057] In a specific implementation process, the target isotropic material for preparing the first film 11 includes organic materials and / or inorganic materials, wherein 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 film 11 can be prepared by one or more of the above materials, and the difference between the refractive index of the prepared first film 11 and the refractive index of the target anisotropic material for preparing the second film 12 for ordinary light is less than or equal to the preset refractive index difference, so that the filter film 10 can achieve different transmittances for different incident lights, thereby achieving the effect of reducing or eliminating rainbow stripes.

[0058] See also Figure 4 , Figure 4 A schematic diagram of a filter film 10 provided in accordance with an embodiment of the present application.

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

[0060] For example, Figure 4 As shown, when the filter film 10 includes multiple layers of first films 11 and multiple layers of second films 12, the thickness of each layer of the first films 11 is the same, and the thickness of each layer of the second films 12 is the same. When the filter film 10 can weaken or eliminate rainbow patterns, the preparation process of the filter film 10 is simplified to reduce the difficulty and cost of preparing the filter film 10.

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

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

[0063] It should be noted that, when the filter film 10 includes multiple layers of first films 11 and multiple layers of second films 12, the thickness of each layer of the first film 11 may be the same or different, and the thickness of each layer of the second film 12 may be the same or different, as described in the above embodiments. The present application does not limit whether the thickness of each layer of the first film 11 is the same or whether the thickness of each layer of the second film 12 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 case where the thickness of the first film 11 is the same as the thickness of the second film 12 is shown, 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, so 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 different from the thickness of the second film 12; in 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 the present application does not limit whether the thickness of the first film 11 is the same as the thickness of the second film 12, and the number of first films 11 having 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. The present 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 by the filter film 10 with a total thickness between 500 nanometers and 10 micrometers is better than the optical performance of the filter film 10 with a total thickness in other ranges.

[0068] See also Figure 5a and Figure 5b , Figure 5a This is a transmittance spectrum of the filter film 10 provided in one embodiment of the present application. Figure 5b for Figure 5a Another transmittance spectrum of the filter film 10 provided in the embodiment.

[0069] In a specific implementation process, the filter film 10 includes 7 layers of first films 11 and 7 layers of second films 12, wherein the preparation material of the first film 11 is polyethylene terephthalate (PET) with a refractive index of 1.58; the refractive indexes of the target anisotropic materials corresponding to the second films 12 are 1.51 and 2.1 respectively, the optical axis inclination angle is set between 20° and 30°, and the thickness of each first film 11 is the same, the thickness of each second film 12 is the same, and the thickness of the first film 11 and the second film 12 is between 30nm and 100nm, so that the total thickness of the filter film 10 is between 0.5um and 0.7um. The transmittance spectrum of the filter film 10 obtained with the above parameters can be shown as follows: Figure 5a As shown in Figure b. Among them, Figure 5a is the transmittance spectrum of the filter film 10 for s-polarized light at various incident angles, Figure 5b is the transmittance spectrum of the filter film 10 for p-polarized light incident at 70 degrees, Figure 5a It can be seen that the transmittance of the filter film 10 to each band of s-polarized light is basically the same. When the incident angle increases, the transmittance of each band decreases rapidly. When the incident angle is less than 60 degrees, the visible light transmittance is greater than 70%, and when the incident angle is 70 degrees, the visible light transmittance is greater than 60%. Figure 5b It can be seen that when the incident light is incident at 70 degrees, the transmittance of p-polarized light in the 400nm-470nm band drops below 50%, while the transmittance of the green light band and the red light band is above 85%. It can be seen that the filter film 10 achieves angle selection for p-polarization and maintains high transmittance for s-polarization, that is, at least p-polarized light is filtered. The transmittance of the filter film 10 is related to the incident angle and the band, so that light with different incident angles and different bands can be filtered, thereby achieving the effect of reducing or eliminating rainbow patterns.

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

[0071] In a specific implementation process, the filter film 10 includes 7 layers of first films 11 and 7 layers of second films 12, wherein the first film 11 is made of polyethylene terephthalate (PET) with a refractive index of 1.58; the refractive indexes of the target anisotropic materials corresponding to the second film 12 are 1.51 and 1.71 respectively, and the optical axis inclination angle is set between 30° and 40°; the thickness of each film is different, but is within the range of 10nm to 150nm, so that the total thickness of the filter film 10 is between 0.5um and 5um. Figure 6a is the transmittance spectrum of the filter film 10 for p-polarized light at various incident angles, Figure 6b is the transmittance spectrum of filter film 10 for s-polarized light incident at 70 degrees, Figure 6a It can be seen that when the incident light is incident at 70°, the transmittance of the filter film 10 to each p-polarized band in the incident light is still above 85%, and when the incident light is incident at 80°, the transmittance of the filter film 10 to 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 10 for the 400nm-450nm band in s-polarization drops to 50% or above, the transmittance of the green light band is above 80%, and the transmittance of the red light band is above 70%.

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

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

[0074] Exemplarily, the preparation process of the filter film 10 includes one or more processes of coating, spin coating, deposition, and electron beam evaporation. Specifically, the formation process of the second film 12 includes but is not limited to blowing air at a specific angle to the heated liquid crystal film, so that the liquid crystal molecules show disordered isotropic characteristics when heated and form anisotropy after cooling; a thin layer of positioning material is set at the bottom of the target anisotropic material film, and then the anisotropic material film is coated; the liquid crystal layer is exposed to different doses and / or different angles using light sensitivity to complete the orientation of the liquid crystal layer; the liquid crystal layer is irradiated by friction or ion beam to complete the orientation of the liquid crystal layer. It should be noted that the above-mentioned preparation process is simpler than the preparation process of the stacked dislocation grating, thereby reducing the difficulty and cost of preparing the diffraction optical waveguide that can achieve the effect of reducing the rainbow pattern, and at the same time improving the yield of the finished product.

[0075] See also Figure 7 , Figure 7 A schematic diagram of an optical waveguide 100 provided in an embodiment of the present 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 is used to couple incident light into the waveguide substrate 21 and to couple out light propagating in the waveguide substrate 21, thereby achieving directional transmission of light. The protective layer 30 is used to protect 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 the filter film 10 described in any of the above embodiments, and the filter film 10 can achieve low transmittance for incident light incident from the outside of the optical waveguide 100 at an angle greater than or equal to a preset angle, thereby reducing or eliminating the rainbow pattern on the optical waveguide 100.

[0077] Figure 7As shown, the filter film 10 is arranged on a side surface of the protective layer 30 away from the waveguide substrate 21. In a specific implementation process, the filter film 10 is arranged on a side surface of the protective layer 30 close to the waveguide substrate 21, or is arranged on the waveguide substrate 21, and this application does not limit this.

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

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

[0080] Exemplarily, by disposing a plurality of filter films 10 on the optical waveguide 100, and making different filter films 10 have different transmittances for light with different wavelengths, polarization states, and incident angles, it is possible to filter different lights according to actual conditions to meet different usage requirements and improve the applicability of the optical waveguide 100. In a specific implementation process, the plurality of filter films 10 included in the optical waveguide 100 can also be disposed on the waveguide substrate 21, or at least one filter film 10 is disposed on the protective layer 30, and at least one filter film 10 is disposed on the waveguide substrate 21. The present application does not limit the number of the plurality of filter films 10 and the specific arrangement positions.

[0081] See also Figure 8b , Figure 8b A schematic diagram of an optical waveguide 100 provided in yet another embodiment of the present 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 a plurality of filter films 10 may also be disposed on the waveguide substrate 21, and this application does not limit this.

[0083] In a specific implementation process, the waveguide layer 20 includes one or more layers of waveguide substrates 21, and each layer of the waveguide substrates 21 is made of one or more materials selected from glass, resin, plastic or ceramics. The shape of the waveguide substrates 21 is flat or curved to meet different usage requirements.

[0084] See also Fig. 9 , Fig. 9 A schematic diagram of a display device provided in one embodiment of the present application.

[0085] like Fig. 9As shown, the display device includes an optical machine and an optical waveguide as described in the previous embodiments. Specifically, the display device includes a near-eye display device implemented by using an optical waveguide, including but not limited to an augmented reality (AR) display device, an extended reality (XR) display device, a head-up display (HUD), etc. The optical waveguide can transmit the signal light emitted from the optical machine in a direction to the human eye to realize the display of the corresponding image or video, and the optical waveguide provided by the present application is used to pass through the filter film with ambient light incident at a large angle, so that it is difficult to form rainbow patterns on the user side, thereby achieving the effect of effectively reducing or eliminating the rainbow patterns that may appear during the operation of the display device, thereby improving the user experience.

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

[0087] It should also be understood that the term "and / or" used in the specification of this application and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations. It should be noted that, in this article, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "including a..." does not exclude the presence of other identical elements in the process, method, article or system including the element.

[0088] The serial numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments. The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A filter film, characterized in that: The filter film comprises: at least one first film, wherein the optical properties of the first film are isotropic; at least one layer of a second film, the optical property of the second film is anisotropic, and the second film and the first film are alternately stacked in sequence; Among them, the second film is made of a target anisotropic material, and the size of the optical axis inclination angle of the target anisotropic material is within the target inclination angle range, so that the transmittance of the filter film to the incident light changes with the incident angle of the incident light; the optical axis inclination angle is the angle between the optical axis of the target anisotropic material and the film surface.

2. The filter film according to claim 1, characterized in that: The target inclination angle range a satisfies the following relationship: 2°≤θ≤88°.

3. The filter film according to any one of claims 1 to 4, characterized in that: The refractive index difference Δn of the target anisotropic material satisfies the following relationship: 0.001≤Δn≤0.

6.

4. The filter film according to claim 1, characterized in that: The target anisotropic material includes rod-like liquid crystal and / or discotic liquid crystal.

5. The filter film according to 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 to 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 to 4, characterized in that: The thickness of each of the first films is the same, and / or the thickness of each of the second films is the same.

8. The filter film according to 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 according to 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 to 4, characterized in that: The filter film is prepared by at least one process of coating, spin coating, deposition, and electron beam evaporation.

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

12. A display device, characterized in that: The display device comprises an optical engine and the optical waveguide as claimed in claim 11.

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