Optical waveguide and head-mounted display device

Abstract

The invention discloses an optical waveguide and a head-mounted display device, and relates to the technical field of optical waveguides, and the optical waveguide comprises a waveguide substrate which is provided with a coupling-in grating and a coupling-out grating; the at least one polarization film layer is arranged in the waveguide substrate, and the polarization film layer is located on the side, away from the coupling-in grating, of the coupling-out grating; incident light enters the waveguide substrate and sequentially passes through the coupling-in grating and the coupling-out grating, and then energy of the light pre-entering the side wall of the waveguide substrate is dissipated through the polarization film layer so as to restrain stray light. According to the invention, the edge stray light of the optical waveguide can be effectively suppressed, so that the visual experience of a user is improved.

Description

Technical Field

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

[0002] With the rapid development of optical display devices for virtual reality (VR) and augmented reality (AR), optical waveguides have become a core component in this field due to their ability to create a larger eyebox area through pupil expansion technology. However, to ensure uniform pupil expansion, some light energy is transmitted to the edge of the waveguide, thus causing stray light problems.

[0003] Currently, the common method to absorb stray light is to blacken the edges. However, due to the limited refractive index of the inks available and the thinness of the coating layer, the absorption length of the light is limited, so this method is not very effective in suppressing stray light. Summary of the Invention

[0004] The main objective of this application is to provide an optical waveguide and a head-mounted display device that effectively suppresses stray light at the edges of the optical waveguide to improve the user's visual experience.

[0005] To achieve the above objectives, this application proposes an optical waveguide, comprising: A waveguide substrate, wherein the waveguide substrate is provided with an input grating and an output grating; At least one polarizing film layer is disposed within the waveguide substrate, and the polarizing film layer is located on the side of the output grating away from the input grating; The incident light enters the waveguide substrate and passes through the coupling grating and the coupling grating in sequence. Then, the energy of the light that is about to enter the sidewall of the waveguide substrate is dissipated by the polarization film layer to suppress stray light.

[0006] In one embodiment, the optical waveguide includes two polarization film layers, which are spaced apart and whose azimuth angles are perpendicular to each other.

[0007] In one embodiment, the spacing between the two polarization film layers is set according to the length of the coupling grating and / or the thickness of the waveguide substrate.

[0008] In one embodiment, the spacing between the two polarization film layers is greater than or equal to the product of the length of the coupling grating and a first preset scaling factor, and / or greater than or equal to the product of the thickness of the waveguide substrate and a second preset scaling factor.

[0009] In one embodiment, the area where the polarizing film layer is disposed completely covers the propagation range of the light rays that are to enter the sidewall of the waveguide substrate.

[0010] In one embodiment, the side of the polarizing film layer facing away from the coupling grating is an anti-reflection microstructure.

[0011] In one embodiment, a heat dissipation layer is provided on the side of the polarizing film layer facing away from the coupling grating.

[0012] In one embodiment, the waveguide substrate is further provided with a bend grating: The incident light enters the waveguide substrate and passes through the coupling grating, the turning grating and the coupling grating in sequence. Then, the energy of the light that is about to enter the sidewall of the waveguide substrate is dissipated by the polarization film layer to suppress stray light.

[0013] In one embodiment, the optical waveguide further includes: An absorption layer is disposed on the sidewall of the waveguide substrate near the polarizing film layer, and the absorption layer is used to absorb light transmitted from the polarizing film layer.

[0014] In addition, to achieve the above objectives, this application also proposes a head-mounted display device, which includes a device body and an optical waveguide as described above, wherein the optical waveguide is disposed on the device body.

[0015] This application provides an optical waveguide, comprising: a waveguide substrate having an input grating and an output grating; and at least one polarizing film layer disposed within the waveguide substrate, with the polarizing film layer located on the side of the output grating away from the input grating; wherein, incident light enters the waveguide substrate and passes through the input grating and the output grating in sequence, and then the polarizing film layer dissipates the energy of the light that is about to enter the sidewall of the waveguide substrate, thereby suppressing stray light.

[0016] Therefore, the technical solution provided in this application, by setting a polarizing film layer in the waveguide substrate and placing it on the side of the output grating away from the input grating, ensures that the light rays coupled out by the output grating, before entering the sidewall of the waveguide substrate, will experience energy loss due to the polarization effect of the polarizing film layer. This effectively suppresses stray light at the edge of the optical waveguide, thereby improving the user's visual experience. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 A diagram illustrating the diffraction principle of light when the edge of the optical waveguide provided in this embodiment is rough; Figure 2 A diagram illustrating the diffraction principle of light rays when the edge of the optical waveguide provided in this embodiment is smooth; Figure 3 This is a schematic diagram of the planar structure of the optical waveguide provided in the first embodiment of this application; Figure 4 A three-dimensional structural schematic diagram of the optical waveguide provided in the first embodiment of this application; Figure 5 This is a schematic diagram of the optical waveguide provided in the third embodiment of this application.

[0019] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0020] Explanation of icon numbers: 10. Waveguide substrate; 20. Polarizing film layer; 11. Coupled-in grating; 12. Coupled-out grating; 13. Turning grating. Detailed Implementation

[0021] 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 a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0023] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0024] With the rapid development of virtual reality and augmented reality technologies, the performance requirements for optical display devices (such as smart head-mounted displays) are also increasing. As a key component of these optical display devices, the design of optical waveguides has a crucial impact on the user's visual experience. For optical waveguide devices, the exit pupil is often expanded in one or two directions, a process known as pupil expansion. This allows a smaller entrance pupil to create a larger effective eyebox at the eye's end.

[0025] However, in practical applications, to ensure uniform pupil dilation, a significant amount of light energy is typically transmitted to the tail end and further propagated until it reaches the edge of the optical waveguide. This phenomenon causes several problems, one of the more significant being stray light at the edge of the optical waveguide. For example... Figure 1 As shown, when the edge is relatively rough, the light energy reaching the edge will return in the form of diffuse reflection. Many of these rays can satisfy the total internal reflection conditions of the upper and lower boundaries of the optical waveguide, thus successfully returning to the coupling region and forming a diffuse stray light noise floor. The other part of the rays, because they do not satisfy the total internal reflection conditions of the upper and lower boundaries, will quickly leak out after several reflections.

[0026] It should be noted that since optical waveguides are usually made of materials with high refractive index, the higher the refractive index, the smaller the critical angle of total internal reflection, and the more stray light can be successfully returned. Even if some special designs use optical waveguide substrates with low refractive index (such as resin substrates with a refractive index of about 1.6), a considerable amount of reflected light can still be successfully returned, which is usually higher than 40% according to calculations. Therefore, it also has a significant impact on imaging quality.

[0027] Currently, the common method to absorb stray light is to blacken the edges. However, due to the limited refractive index of the inks available and the thinness of the coating layer, the absorption length of the light is limited, so this method is not very effective in suppressing stray light.

[0028] It is worth noting that when the edges of the optical waveguide are relatively smooth, specular reflection occurs, which allows more stray light to return smoothly. For example... Figure 2 As shown, once the edge approaches specular reflection, according to simple geometric relationships, the returned light will 100% meet the total internal reflection condition, forming strong stray light. More seriously, if the tail light energy brought by the pupil expansion design is relatively strong, then the returned stray light will have an uncontrollable and significant impact on the display's color, field uniformity, and other performance characteristics, thus causing the product to fail.

[0029] Based on this, the first embodiment of this application proposes an optical waveguide, please refer to... Figure 3 and Figure 4 Optical waveguides may include: Waveguide substrate 10, waveguide substrate 10 is provided with coupling in grating 11 and coupling out grating 12; At least one polarizing film layer 20 is disposed within the waveguide substrate 10, and the polarizing film layer 20 is located on the side of the output grating 12 away from the input grating 11. In this process, the incident light enters the waveguide substrate 10 and passes through the coupling grating 11 and the coupling grating 12 in sequence. Then, the energy of the light that is about to enter the sidewall of the waveguide substrate 10 is dissipated by the polarization film layer 20 to suppress stray light.

[0030] It should be noted that the waveguide substrate 10 is a transparent dielectric layer that constrains and guides light propagation through the principle of total internal reflection. The coupling grating 11 is responsible for efficiently coupling the incident light into the waveguide interior, ensuring that the light satisfies the condition of total internal reflection propagation within the waveguide. The coupling grating 12 is responsible for efficiently coupling the light that has already propagated within the waveguide in the form of total internal reflection out of the waveguide, directing it towards the human eye. A portion of the grating region of the coupling grating 11 can be disposed on the upper or lower surface of the waveguide substrate 10, and at least a portion of the grating region of the coupling grating 11 is disposed within the waveguide substrate 10; this embodiment does not specifically limit this. Similarly, a portion of the grating region of the coupling grating 12 can be disposed on the upper or lower surface of the waveguide substrate 10, and at least a portion of the grating region of the coupling grating 12 is disposed within the waveguide substrate 10; this embodiment does not specifically limit this.

[0031] If a portion of the grating regions of the input grating 11 and the output grating 12 are located on the upper surface of the waveguide substrate 10, both operate in transmission mode, primarily guiding the direction of light by manipulating the transmission diffraction order (e.g., m=+1 order). If a portion of the grating regions of the input grating 11 and the output grating 12 are located on the lower surface of the waveguide substrate 10, both operate in reflection mode, primarily guiding the direction of light by manipulating the reflection diffraction order (e.g., m=-1 order).

[0032] Additionally, it should be noted that the polarizing film layer 20 is an optical thin film that allows light with only a specific vibration direction (i.e., polarization direction) to pass through, while absorbing or blocking light with other vibration directions. It can be composed of a polymer film with dichroic molecules attached, or formed by etching a metal wire grid structure; this embodiment does not specifically limit this. The dichroic molecules are typically iodine-based compounds or organic dyes, which exhibit selective absorption characteristics for light with different polarization directions; the metal wire grid structure is typically made of metals such as aluminum, silver, or gold, with linewidth and spacing on a subwavelength scale, and can achieve polarization selection through surface plasmon resonance.

[0033] Understandably, due to the complex polarization states of light within an optical waveguide, it's rare for a large number of rays to share a uniform polarization state. Since the polarization layer 20 only allows light with a specific vibration direction (i.e., polarization direction) to pass through, most of the light rays pre-entering the sidewall of the waveguide substrate 10 will be blocked by the polarization layer 20 after passing through it. Consequently, the light energy of this portion of the light will be converted into heat energy by the polarization layer 20, causing its energy to dissipate. Therefore, these rays with dissipated energy cannot return to form stray light.

[0034] In one feasible implementation, to ensure that all light rays coupled from the coupling grating 12 that are about to enter the sidewall of the waveguide substrate 10 can enter the polarization film layer 20, the polarization film layer 20 can be configured to partially or completely cover the propagation range of the light rays that are about to enter the sidewall of the waveguide substrate 10. In practical use, the polarization film layer 20 can be designed as a rectangle, trapezoid, or other geometry that matches the projected shape of the coupling grating 12; this embodiment does not impose any specific limitations on this.

[0035] In one feasible implementation, the side of the polarizing film layer 20 facing away from the coupling grating 12 can be an anti-reflection microstructure.

[0036] Anti-reflective microstructures refer to periodic structures (i.e., smaller than the wavelength of light) fabricated on optical surfaces. These structures can be moth-eye structures or other periodic nanogratings, etc., and this embodiment does not specifically limit them. Among them, the moth-eye structure is usually a conical or pyramidal nanoarray with a height of 100 nanometers to 300 nanometers and a period of 200 nanometers to 500 nanometers. It can effectively reduce surface reflection through the gradient refractive index effect.

[0037] It is understandable that, considering the light entering the sidewall of the waveguide substrate 10, after passing through the polarization film layer 20, a small portion of the light may undergo specular reflection on the smooth surface of the polarization film layer 20, thus forming stray light. To address this, this embodiment, in order to more effectively suppress stray light at the edge of the optical waveguide, sets an anti-reflection microstructure on the side of the polarization film layer 20 facing away from the coupling grating 12. Thus, this small portion of light is transmitted through the anti-reflection microstructure and is essentially not reflected back into the waveguide along its original path, thereby achieving secondary suppression of stray light.

[0038] In one feasible implementation, a heat dissipation layer may be provided on the side of the polarization film layer 20 facing away from the coupling grating 12.

[0039] It should be noted that the heat dissipation layer can be a graphene layer, metal foil, or other highly thermally conductive materials, and this embodiment does not specifically limit it.

[0040] In this embodiment, by providing a heat dissipation layer on the side of the polarization film layer 20 that is away from the coupling grating 12, thermal deformation or thermal stress caused by local heating of the optical waveguide can be effectively prevented, thereby ensuring the stability of the optical waveguide imaging quality and its service life.

[0041] In one feasible implementation, the sidewalls of the waveguide substrate 10 can be roughened. As a result, the light transmitted from the polarization film layer 20 undergoes a slight polarization state change after passing through the sidewalls of the waveguide substrate 10 due to the roughness of the sidewalls. Consequently, the light passes through the polarization film layer 20 again on its return journey, further reducing light energy loss. This more effectively suppresses stray light at the edge of the optical waveguide, thereby further enhancing the user's visual experience.

[0042] Based on the above, this embodiment provides an optical waveguide, including: a waveguide substrate 10, the waveguide substrate 10 having an input grating 11 and an output grating 12; at least one polarizing film layer 20, the polarizing film layer 20 being disposed within the waveguide substrate 10, and the polarizing film layer 20 being located on the side of the output grating 12 away from the input grating 11; wherein, incident light enters the waveguide substrate 10, and after passing through the input grating 11 and the output grating 12 in sequence, the energy of the light about to enter the sidewall of the waveguide substrate 10 is dissipated by the polarizing film layer 20, so as to suppress stray light.

[0043] Therefore, the technical solution provided in this embodiment provides a polarizing film layer 20 in the waveguide substrate 10, and positions it on the side of the coupling grating 12 away from the coupling grating 11. As a result, the light rays coupled out of the coupling grating 12 that are about to enter the sidewall of the waveguide substrate 10 will be polarized by the polarizing film layer 20, resulting in energy loss. This effectively suppresses stray light at the edge of the optical waveguide, thereby improving the user's visual experience.

[0044] Based on the first embodiment described above, a second embodiment of the optical waveguide of this application is proposed. In the second embodiment, to ensure that all light rays coupled out from the coupling grating 12 that are about to enter the sidewall of the waveguide substrate 10 can enter the polarization film layer 20, the polarization film layer 20 can be configured to completely cover the propagation range of the light rays that are about to enter the sidewall of the waveguide substrate 10. This design ensures that backlight rays emitted from any position of the coupling grating 12 will be intercepted by the polarization film layer 20, thereby achieving omnidirectional stray light absorption and interception.

[0045] When the polarizing film layer 20 is set to completely cover the propagation range of the light that is to enter the sidewall of the waveguide substrate 10, in one feasible embodiment, the orthogonal projection area of ​​the polarizing film layer 20 in the first direction can be set to be greater than or equal to the orthogonal projection area of ​​the coupling grating 12 in the first direction. The first direction can be a direction that is consistent with or approximately similar to the direction of the light rays that are about to enter the sidewall of the waveguide substrate 10, or it can be a direction that is consistent with or approximately similar to the normal direction of the sidewall of the waveguide substrate 10 (specifically, the sidewall of the waveguide substrate 10 into which stray light is about to enter).

[0046] It should be noted that the direction approximating the direction of the light ray entering the sidewall of the waveguide substrate 10 refers to a direction whose angle with the direction of the light ray entering the sidewall of the waveguide substrate 10 is within a certain angular range (e.g., within ±5 degrees). Similarly, the direction approximating the normal direction of the sidewall of the waveguide substrate 10 refers to a direction whose angle with the normal direction of the sidewall of the waveguide substrate 10 is within a certain angular range (e.g., within ±5 degrees).

[0047] The polarizing film layer 20 can be placed upright or obliquely within the waveguide substrate 10; this embodiment does not impose a specific limitation on this. Specifically, when the polarizing film layer 20 is placed upright within the waveguide substrate 10, the polarizing film layer 20 is perpendicular to the first direction, and the projected area of ​​the polarizing film layer 20 in the first direction is equal to the actual area of ​​the polarizing film layer 20. When the polarizing film layer 20 is placed obliquely within the waveguide substrate 10, the polarizing film layer is not perpendicular to the first direction, and the projected area of ​​the polarizing film layer 20 in the first direction is smaller than the actual area of ​​the polarizing film layer 20.

[0048] This embodiment establishes a clear and reliable geometric design criterion by setting the orthographic projection area of ​​the polarizing film layer 20 in the first direction to be greater than or equal to the orthographic projection area of ​​the coupling grating 12 in the same direction. This geometric design criterion ensures that all light rays emitted backward from the entire region of the coupling grating 12 are spatially intercepted by the polarizing film layer 20 without any omissions on their path toward the waveguide sidewall.

[0049] In another feasible implementation, the placement azimuth angle of the polarization film layer 20 on the waveguide substrate 10 can be set to be less than 90 degrees and greater than 0 degrees, and the placement azimuth angle is the angle between the polarization film layer 20 and the target axis direction. The target axis direction refers to the direction that is parallel to the base plane of the waveguide substrate 10 and perpendicular to the line connecting the center of the coupling grating 11 to the center of the coupling grating 12.

[0050] It is understandable that the target axis direction, i.e., the direction parallel to the base plane of the waveguide substrate 10 and perpendicular to the line connecting the center of the coupling grating 11 to the center of the coupling grating 12, is often the main direction for one-dimensional pupil expansion in practical applications. If the edge line of the polarizing film layer 20 is completely parallel to this direction (i.e., the placement azimuth angle approaches 0 degrees), its structure may not be able to adapt well to the optical path distribution extending along this direction, resulting in a decrease in the interception efficiency of stray light far from the central region. Conversely, if it is completely perpendicular (i.e., the placement azimuth angle approaches 90 degrees), a similar mismatch problem may also occur. To address this, this embodiment sets the placement azimuth angle of the polarizing film layer 20 on the waveguide substrate 10 to a range of less than 90 degrees and greater than 0 degrees. This ensures that the polarizing film layer 20 can provide consistent and effective interception regardless of whether the stray light is located at the center or edge of the optical field after pupil expansion, thereby eliminating the performance inhomogeneity or interception blind zone that may occur in the pupil expansion direction due to improper azimuth setting.

[0051] The above are only two implementation methods provided in this embodiment for setting the polarization film layer 20 to completely cover the propagation range of light that is about to enter the sidewall of the waveguide substrate 10. This embodiment does not specifically limit its specific implementation method.

[0052] Based on the first and / or second embodiments described above, a third embodiment of the optical waveguide of this application is proposed. In the third embodiment, please refer to... Figure 5 The optical waveguide may include two polarization film layers 20, which are spaced apart and whose azimuth angles are perpendicular to each other.

[0053] In one feasible implementation, to ensure that all light rays pre-entering the sidewall of the waveguide substrate 10 coupled out by the coupling grating 12 can be effectively absorbed by the polarization film layers 20 at different positions, the spacing between the two polarization film layers 20 can be set according to the length of the coupling grating 12 and / or the thickness of the waveguide substrate 10.

[0054] The spacing between the two polarization film layers 20 can be greater than or equal to the product of the length of the coupling grating 12 and the first preset scaling factor, and / or greater than or equal to the product of the thickness of the waveguide substrate 10 and the second preset scaling factor.

[0055] The first preset ratio coefficient can be a default value, such as 0.5, or it can be flexibly set by the user according to the actual situation. This embodiment does not impose a specific limitation on this. The second preset ratio coefficient can be a default value, such as 0.1, or it can be flexibly set by the user according to the actual situation. This embodiment does not impose a specific limitation on this.

[0056] It is understandable that by setting the interval between the two polarization film layers 20 to be greater than or equal to the product of the length of the coupling grating 12 and the first preset proportional coefficient, it can be ensured that stray light with a large lateral offset emitted from the far end of the coupling grating 12 can also be successfully intercepted by the second polarization film layer 20 in its propagation path, so as to achieve full coverage of the stray light source area.

[0057] By setting the spacing between the two polarization film layers 20 to be greater than or equal to the product of the thickness of the waveguide substrate 10 and the second preset scaling factor, the maximum divergence angle that light may generate in the optical waveguide due to thickness limitation is fully considered. This ensures that even stray light propagating at the extreme angle can fall into the absorption range of the second polarization film layer 20 after missing the first polarization film layer 20 due to its lateral displacement in the waveguide plane.

[0058] As can be seen from the above, this embodiment sets the optical waveguide to include two polarization film layers 20 with mutually perpendicular azimuth angles and spaced apart, in order to construct a stray light absorption mechanism that is complementary in both spatial and polarization states. This allows stray light propagating at different angles, regardless of its polarization direction, to be blocked by these two polarization film layers 20, thereby more effectively suppressing stray light at the edge of the optical waveguide and further improving the user's visual experience.

[0059] Based on the first, second, and / or third embodiments described above, a fourth embodiment of the optical waveguide of this application is proposed. In this fourth embodiment, please refer to... Figure 4 The waveguide substrate 10 may also be provided with a bend grating 13: The incident light enters the waveguide substrate 10 and passes through the coupling grating 11, the turning grating 13 and the coupling grating 12 in sequence. Then, the energy of the light that is about to enter the sidewall of the waveguide substrate 10 is dissipated by the polarization film layer 20 to suppress stray light.

[0060] It should be noted that the deflection grating 13 is typically positioned between the input grating 11 and the output grating 12. Its main function is to deflect the light path within the waveguide plane, achieving two-dimensional pupil expansion. The period and orientation of the deflection grating 13 are specially designed to control the direction of light propagation. In practical applications, the deflection grating 13 can be fabricated using the same process as the input grating 11 / output grating 12, but its diffraction efficiency distribution needs to be optimized separately to ensure uniform light energy distribution.

[0061] Understandably, when the waveguide substrate 10 is also equipped with a transition grating 13, the incident light enters the waveguide substrate 10 and passes sequentially through the coupling grating 11, the transition grating 13, and the coupling grating 12. The light rays that were about to enter the sidewall of the waveguide substrate 10 and are coupled out from the coupling grating 12 will also experience energy loss due to the polarization effect of the polarization film layer 20. Therefore, stray light at the edge of the optical waveguide can be effectively suppressed, thus improving the user's visual experience.

[0062] Based on the first, second, third, and / or fourth embodiments described above, a fifth embodiment of the optical waveguide of this application is proposed. In the fifth embodiment, the optical waveguide may further include: An absorption layer is disposed on the sidewall of the waveguide substrate 10 near the polarization film layer 20. The absorption layer is used to absorb light transmitted from the polarization film layer 20.

[0063] It should be noted that the absorption layer can be a light-absorbing ink coating layer, a metal thin film absorption layer, etc., and this embodiment does not specifically limit it. The light-absorbing ink coating layer is typically formed by dispersing carbon black particles in an organic solvent, and the coating thickness can range from 10 micrometers to 100 micrometers. The metal thin film absorption layer can be prepared by sputtering light-absorbing metals such as nickel and chromium, and the thickness can range from 0.1 micrometers to 1 micrometer. In practical applications, the absorbance of the absorption layer should be greater than 95% to ensure sufficient absorption effect.

[0064] In this embodiment, an absorption layer is provided on the sidewall of the waveguide substrate 10 near the polarization film layer 20 to absorb the light transmitted from the polarization film layer 20. This effectively prevents the residual light that is not absorbed by the polarization film layer 20 from continuing to propagate in the optical waveguide, thereby more effectively suppressing stray light at the edge of the optical waveguide and further improving the user's visual experience.

[0065] Based on the first, second, third, fourth, and / or fifth embodiments described above, a sixth embodiment of the optical waveguide of this application is proposed. In the sixth embodiment, the edge of the polarization film layer 20 can be designed with a slope or chamfer. This edge transition structure can effectively reduce the sudden refractive index change at the interface between the polarization film layer 20 and the waveguide substrate 10, thereby suppressing interface reflection and diffraction effects.

[0066] The slope angle can be between 30° and 60°, and the slope structure can be prepared by laser cutting followed by polishing or molding. The slope length can be set according to the thickness of the polarizing film layer 20, which is usually 1 to 3 times the thickness of the polarizing film layer 20.

[0067] In practical applications, the edge shape of the polarization film layer 20 has a significant impact on stray light suppression. Vertical edges are prone to edge diffraction, forming new stray light sources. A sloped design, on the other hand, allows for a smooth transition of light, reducing unnecessary scattering. Preferably, the slope angle is 45°, at which point the reflectivity is lowest.

[0068] This embodiment uses a sloped or chamfered design at the edge of the polarization film layer 20 to more effectively suppress stray light at the edge of the optical waveguide, thereby further enhancing the user's visual experience.

[0069] Based on the first, second, third, fourth, fifth and / or sixth embodiments described above, a seventh embodiment of the optical waveguide of this application is proposed. In the seventh embodiment, the surface of the polarizing film layer 20 may be provided with a hydrophobic and oleophobic coating, and the contact angle is greater than a preset angle threshold.

[0070] It should be noted that the hydrophobic and oleophobic coating can be composed of fluorosilane compounds or perfluoropolyether materials, and its thickness can range from 10 nanometers to 100 nanometers. The hydrophobic and oleophobic coating can be prepared by vapor deposition or spin coating processes to form a low surface energy protective layer. The preset angle threshold can be a default value, such as 110°, or it can be flexibly set by the user according to actual conditions; this embodiment does not impose specific limitations on this.

[0071] Understandably, during the use of augmented reality optical display devices, waveguide elements are susceptible to contamination from fingerprints, sweat, and dust. These contaminants scatter light, creating new stray light. To address this, this embodiment significantly improves the anti-contamination capability of the polarization film layer 20 by providing a hydrophobic and oleophobic coating on its surface, thereby reducing stray light caused by surface contamination. Furthermore, this hydrophobic and oleophobic coating facilitates cleaning and maintenance, extending the lifespan of the optical waveguide.

[0072] Based on the first, second, third, fourth, fifth, sixth, and / or seventh embodiments described above, an eighth embodiment of the optical waveguide of this application is proposed. The polarization film layer 20 can be patterned, and its absorption rate exhibits a spatial gradient distribution. Specifically, the absorption rate is lower (e.g., 70% to 80%) near the coupling grating 12 region and higher (e.g., up to 95%) further away from the coupling grating 12 region. This gradient distribution can be achieved by controlling the concentration of the dichroic dye or the density of the metal wire grid.

[0073] Understandably, the patterned design takes into account the intensity distribution characteristics of stray light in the waveguide. The region near the coupling grating 12 has higher stray light intensity, requiring some light transmission to balance thermal management; while the region far from the coupling grating 12 has lower stray light intensity, allowing for the use of high absorption to ensure sufficient suppression. Therefore, this embodiment, by employing a patterned design for the polarization film layer 20, can reduce heat accumulation while ensuring stray light suppression, thereby improving the thermal stability of the optical waveguide and ultimately enhancing its reliability.

[0074] Based on the first, second, third, fourth, fifth, sixth, seventh and / or eighth embodiments described above, a ninth embodiment of the optical waveguide of this application is proposed. In the ninth embodiment, the polarization film layer 20 can adopt a magnetic fixing structure, thereby allowing precise control of the position of the polarization film layer 20 through the action of a magnetic field.

[0075] It should be noted that the magnetic fixing structure may include a magnetic material layer disposed at the edge of the polarization film layer 20 and a corresponding magnetic conductive element disposed on the waveguide substrate 10. The thickness of the magnetic material layer may be 10 micrometers to 50 micrometers, and it may be made of neodymium iron boron or samarium cobalt permanent magnet material.

[0076] In one feasible implementation, micro-magnetic sheets can be embedded at the four corners of the polarization film layer 20, and nickel-iron alloy magnetic sheets can be disposed on the corresponding waveguide substrate 10. This allows the polarization film layer 20 to be precisely positioned without the use of adhesives, and facilitates subsequent maintenance and replacement.

[0077] As can be seen from the above, this embodiment can use a magnetic fixing structure to set the polarizing film layer 20, so that the polarizing film layer 20 can be accurately positioned without the use of adhesive. This not only improves the assembly accuracy and maintainability of the polarizing film layer 20, but also avoids stress deformation and aging problems that may be introduced by adhesive.

[0078] Based on the first, second, third, fourth, fifth, sixth, seventh, eighth and / or ninth embodiments described above, a tenth embodiment of the optical waveguide of this application is proposed. In the tenth embodiment, a refractive index matching layer may be provided between the polarization film layer 20 and the waveguide substrate 10.

[0079] It should be noted that the refractive index of the refractive index matching layer can be between the refractive index of the waveguide substrate 10 and the refractive index of the polarizing film layer 20, typically ranging from 1.50 to 1.65. The material of the refractive index matching layer can be a UV-curable optical adhesive or a thermoplastic polymer, and its thickness can be 0.1 to 1 μm. The refractive index matching layer is used to reduce Fresnel reflection at the interface between the waveguide substrate 10 and the polarizing film layer 20, thereby improving optical transmission efficiency. Simultaneously, the refractive index matching layer can also enhance the bonding strength between the polarizing film layer 20 and the waveguide substrate 10, thereby improving the mechanical reliability of the optical waveguide.

[0080] In actual preparation, the refractive index matching layer can be applied by spin coating or slot coating process, and then cured by ultraviolet light or heat.

[0081] In this embodiment, a refractive index matching layer is provided between the polarization film layer 20 and the waveguide substrate 10. This not only reduces Fresnel reflection at the interface between the waveguide substrate 10 and the polarization film layer 20 to improve optical transmission efficiency, but also enhances the bonding strength between the polarization film layer 20 and the waveguide substrate 10 to improve the mechanical reliability of the optical waveguide.

[0082] Based on the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth and / or tenth embodiments described above, an eleventh embodiment of the optical waveguide of this application is proposed. In the eleventh embodiment, the polarization film layer 20 can be made of an environmentally responsive material, and its optical properties can be automatically adjusted according to environmental conditions.

[0083] It should be noted that when the polarization film layer 20 uses environmentally responsive materials, the core material it uses can be a composite material of thermosensitive hydrogel and dichroic dye. The thermosensitive hydrogel can provide responsive characteristics, and the dichroic dye can provide polarization function.

[0084] It is understandable that when the polarizing film 20 uses an environmentally responsive material, its environmental response mechanism can be manifested as follows: when the ambient temperature changes, the hydrogel undergoes a volume phase transition, altering its microstructure and thus affecting the arrangement and polarization characteristics of the dichroic dyes. For example, within the operating temperature range of 20℃ to 35℃, the extinction ratio of the polarizing film 20 can be automatically adjusted; as the temperature increases, the extinction ratio increases accordingly to compensate for the stray light problem exacerbated by the increased temperature.

[0085] In this embodiment, the polarization film layer 20 can be made of an environmentally responsive material, allowing its extinction ratio to adaptively adjust with ambient temperature. Specifically, when the temperature rises, the polarization film layer 20 will automatically increase its extinction ratio to enhance stray light suppression; when the temperature decreases, the polarization film layer 20 will automatically decrease its extinction ratio to maintain high transmittance. This design can more effectively suppress stray light at the edges of the optical waveguide, further enhancing the user's visual experience.

[0086] In addition, this application embodiment also provides a head-mounted display device, which may include a device body and an optical waveguide as described in the above embodiment, the optical waveguide being disposed on the device body.

[0087] It should be noted that head-mounted display devices may include, but are not limited to, head-mounted display devices such as Mixed Reality (MR) devices (e.g., MR glasses or MR helmets), Augmented Reality (AR) devices (e.g., AR glasses or AR helmets), Virtual Reality (VR) devices (e.g., VR glasses or VR helmets), Extended Reality (XR) devices, or some combination thereof.

[0088] It is understood that since the above-mentioned optical waveguide is used in the head-mounted display device, the embodiments of the head-mounted display device include all the technical solutions of all the above-mentioned optical waveguide embodiments, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0089] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the content of this application's specification and drawings under the concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. An optical waveguide, characterized by, The light waveguide comprises: a waveguide substrate provided with an in-coupling grating and an out-coupling grating; at least one polarized film layer arranged in the waveguide substrate, and the polarized film layer is located on a side of the out-coupling grating away from the in-coupling grating; wherein the incident light rays enter the waveguide substrate, pass through the in-coupling grating and the out-coupling grating in sequence, and then the energy of the light rays that are about to enter the sidewall of the waveguide substrate is dissipated by the polarized film layer to suppress stray light.

2. The optical waveguide of claim 1, wherein, The light waveguide comprises two polarized film layers, and the two polarized film layers are arranged at an azimuth angle perpendicular to each other.

3. The optical waveguide of claim 2, wherein, The distance between the two polarized film layers is determined according to the length of the out-coupling grating and / or the thickness of the waveguide substrate.

4. The optical waveguide of claim 3, wherein, The distance between the two polarized film layers is greater than or equal to the product of the length of the out-coupling grating and a first preset proportionality coefficient, and / or greater than or equal to the product of the thickness of the waveguide substrate and a second preset proportionality coefficient.

5. The optical waveguide of claim 1, wherein, The arrangement area of the polarized film layer completely covers the propagation range of the light rays that are about to enter the sidewall of the waveguide substrate.

6. The optical waveguide of claim 1, wherein, The side of the polarized film layer away from the out-coupling grating is provided with an anti-reflection microstructure.

7. The optical waveguide of claim 1, wherein, The side of the polarized film layer away from the out-coupling grating is provided with a heat dissipation layer.

8. The optical waveguide of any one of claims 1 to 7, wherein, The waveguide substrate is further provided with a turning grating: The incident light rays enter the waveguide substrate, pass through the in-coupling grating, the turning grating and the out-coupling grating in sequence, and then the energy of the light rays that are about to enter the sidewall of the waveguide substrate is dissipated by the polarized film layer to suppress stray light.

9. The optical waveguide of any one of claims 1 to 7, wherein, The light waveguide further comprises: an absorbing layer arranged on the sidewall of the waveguide substrate close to the polarized film layer, and the absorbing layer is used to absorb the light rays transmitted from the polarized film layer.

10. A head-mounted display device, comprising: The head-mounted display device comprises a device body and the light waveguide according to any one of claims 1 to 9, and the light waveguide is arranged in the device body.

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