Optical waveguide and near-to-eye display module

Abstract

The embodiment of the invention discloses an optical waveguide and a near-to-eye display module, and the optical waveguide comprises a waveguide substrate, the waveguide substrate is at least provided with a coupling-in region and a coupling-out region, and the substrate materials of the coupling-in region and the coupling-out region are made of a uniaxial crystal material; the optical axis of the crystal in the uniaxial crystal material is configured as follows: the angle of the optical axis of the uniaxial crystal material in the optical waveguide is related to the propagation angle and azimuth angle of each field of view light in different areas.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to an optical waveguide and a near-eye display module. Background Technology

[0002] Lightweight, compact, and energy-efficient consumer electronics products have a wide range of applications. As one type of consumer electronics product, consumer-grade augmented reality (AR) glasses are also developing towards thinner and more compact designs. Among these developments, manufacturing optical components with enhanced optical performance and reduced size and weight has become one of the key technological directions for the development of consumer-grade AR glasses.

[0003] As an important optical component used in AR glasses, optical waveguides (often used as lenses in AR glasses) can be fabricated using materials with high refractive index, which is advantageous for reducing size and weight as well as enhancing optical properties.

[0004] Some solutions use uniaxial crystal materials as the substrate material for optical waveguides. However, since the propagation direction of light entering the optical waveguide is not entirely along the optical axis of the uniaxial crystal, birefringence occurs. This phenomenon can easily lead to the generation of interference fringes, thus seriously affecting the display effect. Summary of the Invention

[0005] Based on the above, this application provides an optical waveguide and a near-eye display module to solve the display problem caused by the birefringence phenomenon generated in existing optical waveguides.

[0006] Based on one aspect of this application, an embodiment of this application provides an optical waveguide, comprising: a waveguide substrate, wherein at least a coupling-in region and a coupling-out region are provided on the waveguide substrate, and the substrate material of the coupling-in region and the coupling-out region is a uniaxial crystal material;

[0007] The optical axis of the crystal in the uniaxial crystal material is configured such that the optical axis angle of the uniaxial crystal material in the optical waveguide is related to the propagation angle and azimuth angle of the light rays in different regions of each field of view.

[0008] Optionally, a relay region is further provided on the waveguide substrate.

[0009] Optionally, the optical axis angle in the uniaxial crystal material of the optical waveguide is configured such that the optical path difference generated by birefringence of the light rays coupled into each field of view of the optical waveguide is greater than the coherence length.

[0010] Optionally, the angle between the optical axis and the direction perpendicular to the plane of the waveguide substrate is not less than 20°.

[0011] Optionally, the angle between the optical axis and the propagation axis of the extended beam and the propagating beam formed by the zero-degree field of view ray in the corresponding region is greater than the sum of 20° and the maximum angle difference of the incident field of view.

[0012] Optionally, the projection angle of the optical axis onto the waveguide substrate plane satisfies:

[0013] in, The azimuth angle of the extended ray formed by the zero-degree field-of-view ray in the relay region.

[0014] The azimuth angle of the propagating ray formed by the zero-degree field-of-view ray in the relay region;

[0015] The angle between the optical axis and the second direction on the plane of the waveguide substrate is given.

[0016] Based on one aspect of this application, an embodiment of this application provides a near-eye display module, including an image source and the aforementioned optical waveguide;

[0017] The image source is used to provide image light rays and output them to the optical waveguide, whereby the image light rays are used for imaging and display under the action of the optical waveguide.

[0018] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the technical solutions of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures and / or processes particularly pointed out in the description, claims and drawings. Attached Figure Description

[0019] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0020] Figure 1a This is a schematic diagram of the structure of an optical waveguide 1 provided in an embodiment of this application.

[0021] Figure 1b This is a schematic diagram of the structure of an optical waveguide 10 provided in an embodiment of this application;

[0022] Figure 1c This is a schematic diagram of the image ray 3 coupled into the optical waveguide 10 according to an embodiment of this application;

[0023] Figure 2a This is a schematic diagram of the image ray 3 coupled into the coupling region 101 according to an embodiment of this application;

[0024] Figure 2bThis is a schematic diagram of the propagation of image ray 3 in optical waveguide 10 provided in an embodiment of this application;

[0025] Figure 2c This is a schematic diagram of the optical path formed by light in the relay area according to an embodiment of this application;

[0026] Figure 3 This is a schematic diagram of the refractive index in a uniaxial crystal provided in an embodiment of this application;

[0027] Figure 4 This is a schematic diagram of the light propagation direction and the optical axis of a uniaxial crystal provided in an embodiment of this application;

[0028] Figure 5 This is a schematic diagram of the light propagation vector and the optical axis of a uniaxial crystal provided in an embodiment of this application;

[0029] Figure 6 This is a simulation diagram of the optical axis angle, total field-of-view optical path difference, and minimum interference optical path difference in the coupling region 101 provided in the embodiments of this application;

[0030] Figure 7a This is a simulation diagram of the optical axis angle and total field-of-view optical path difference in relay region 102 provided in the embodiments of this application;

[0031] Figure 7b This is a simulation diagram of the optical axis angle and minimum optical path difference in the relay region 102 provided in this application embodiment.

[0032] Figure 8 This is a schematic diagram of the optical axis angle that satisfies the minimum optical path difference in interference. Detailed Implementation

[0033] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0034] The aforementioned optical waveguide can be widely used in AR glasses. When used as an important optical device in AR glasses, the image light output from the image source can be coupled into the optical waveguide. The image light from the image source can include multiple colors (such as red, green and blue, i.e., RGB), and is transmitted to the user's eyes via total internal reflection (TIR) ​​in the optical waveguide, so that the user can see the corresponding AR image.

[0035] In this embodiment, the image source uses a broadband light source; some broadband laser sources are also applicable to the scheme of this application. In this embodiment, the image source may include a light source, a display element, or a combination thereof, such as: microLED display element, microOLED display element, LCOS display chip, MEMS galvanometer and laser source, fiber optic scanning device and laser source, etc.

[0036] The solution proposed in this application is applicable to optical waveguides with one-dimensional gratings, and is also applicable to optical waveguides with two-dimensional gratings.

[0037] refer to Figure 1a An exemplary optical waveguide 1 provided in this application embodiment includes: a waveguide substrate 100, on which a coupling-in region 101 and a coupling-out region 103 are disposed. Corresponding two-dimensional grating structures are formed in the coupling-in region 101 and the coupling-out region 103.

[0038] refer to Figure 1b Another exemplary optical waveguide 10 provided in this application embodiment includes: a waveguide substrate 100, a coupling region 101, a relay region 102, and a coupling out region 103. The coupling region 101, relay region 102, and coupling out region 103 are all disposed on the waveguide substrate 100. Corresponding grating structures (typically one-dimensional gratings) are formed in the coupling region 101, relay region 102, and coupling out region 103.

[0039] certainly, Figure 1a and Figure 1b The outlines, dimensions, and relative positions of the coupling region 101, relay region 102, and coupling region 103 shown are exemplary and not limited to specific regions. Figure 1a and Figure 1b As shown. For example, in practical applications, the contour shape of the coupling region 101 may not be... Figure 1a and Figure 1b The circular outline shown can be a rectangle, trapezoid, etc.; similarly, the outline of the relay region 102 can also be trapezoidal or rounded rectangle; for example, the relative positions of the three may be arranged obliquely; for example, in this embodiment, the coupling region 101, the relay region 102 and the coupling region 103 are disposed on the same side of the waveguide substrate 100, which faces the user's eyes when used as AR glasses, but in other embodiments, the coupling region 101 may also be located on other surfaces of the waveguide substrate 100 (related to the arrangement of the light source components), and not on the same side as the relay region 102 and the coupling region 103.

[0040] In this embodiment, the grating structure set in the coupling region 101 can be called a coupling grating, and the specific grating type can be a one-dimensional grating or a two-dimensional grating; the grating structure set in the relay region 102 can be called a relay grating, and the specific grating type can be a one-dimensional grating; the grating structure set in the coupling region 103 can be called a coupling grating, and the specific grating type can be a one-dimensional grating or a two-dimensional grating.

[0041] exist Figure 1a and Figure 1b The diagram illustrates an xy coordinate system: the direction parallel to the y-axis may also be referred to in this application as: the first direction, the vertical direction, or the longitudinal direction; the direction parallel to the x-axis may also be referred to in this application as: the second direction, the horizontal direction, or the transverse direction. The waveguide substrate 100 has a plane parallel to the xy-axis, which may be referred to as the waveguide substrate plane. Furthermore, in the embodiments of this application, the direction perpendicular to the xy-plane can be considered as the z-axis direction (in...). Figure 1c The diagram shows an xyz coordinate system, where the direction parallel to the z-axis can also be referred to as the "third direction" in this application. In subsequent embodiments, different perspectives will be used in some views; unless otherwise specified, all views will use the xyz coordinate system. Figures 1a-1c The coordinate system shown, and the descriptions of the corresponding direction names, are also applicable throughout the document.

[0042] refer to Figure 1c The image ray 3 enters the optical waveguide 1 or optical waveguide 10 at a set angle from the coupling region 101. The angle of the image ray entering the optical waveguide 1 or 10 can be described by the propagation angle and the azimuth angle. In some embodiments, the incident angle can be further decomposed into the propagation angle of the image ray 3 relative to the z-axis and the azimuth angle relative to the x-axis (in this embodiment, the propagation angle is denoted as θ and the azimuth angle is denoted as ψ). The image ray 3 propagates within the waveguide substrate 100 via the coupling region 101.

[0043] Typically, uniaxial crystal materials are used in the coupling region 101, relay region 102, and coupling region 103. In this embodiment, the uniaxial crystal material may include organic crystal materials and / or inorganic crystal materials. Since the propagation direction of image light is not entirely along the optical axis of the crystal, birefringence occurs, causing multiple propagation angles and azimuth angles to form in the same field of view, thus easily leading to interference. When the substrate in the coupling region 101, relay region 102, and coupling region 103 is thin, the optical path difference in some interference areas is less than 10 micrometers, making interference fringes easily generated even when using a broadband light source.

[0044] In the following content, the optical waveguide 10 will be used as an example for explanation. It should be understood that the principles, effects and other content of the one-dimensional grating in the optical waveguide 10 used as an example in the embodiments of this application are also applicable to the two-dimensional grating in the optical waveguide 1.

[0045] Specifically, refer to Figure 2a When image light 3 is coupled in Figure 2a After the coupling region 101, birefringence occurs due to the influence of the uniaxial crystal material, which produces image rays with different polarization states: rays with polarization state s and rays with polarization state p (where the propagation angles of rays with polarization state s and rays with polarization state p are different). After the two rays are coupled by the coupling grating 1011, they become rays with the same polarization state (both polarization state s or both polarization state p) and propagate in parallel. The propagation paths (i.e., optical paths) of the two parallel rays have an optical path difference, which will produce interference.

[0046] In this embodiment, the interference optical path difference generated in the coupling region 101 mainly depends on the angle difference between the image ray 3 and the optical axis in the uniaxial crystal material. Therefore, as an implementation of this application, since the coupling angle difference of the image ray 3 when entering the coupling region 101 is small, the optical axis angle can be configured so that the optical path difference difference generated by birefringence in each field of view only exists in the central zero order within the wavelength range.

[0047] As another embodiment of this application, the optical axis angle can be configured such that the optical path difference of the incident light is greater than the coherence length, thereby reducing the contrast of the interference fringes.

[0048] Furthermore, interference fringes are easily generated by birefringence when the azimuth angle of light changes. Even for broadband light sources with small coherence lengths, interference fringes will still be generated. The situations where the azimuth angle of light changes significantly mainly occur when image light rays are coupled into coupling region 101, when image light rays are deflected in relay region 102, and when image light rays are coupled out of coupling region 103.

[0049] refer to Figure 2b The diagram illustrates the propagation and azimuth angle changes of image ray 3 after it enters the waveguide substrate 100, passing through the coupling region 101, relay region 102, and coupling region 103 from the xy-plane perspective.

[0050] The image ray 3 has an azimuth angle of ψ relative to the grating vector (parallel to the x-axis) of the coupling grating 1011. After being deflected by the coupling grating 1011, the image ray 3 changes its azimuth angle to ψ1, forming a propagating ray 31. This propagating ray 31 propagates to the relay grating 1021. Under the action of the relay grating 1021, a portion of the propagating ray 31 continues to propagate while maintaining its azimuth angle ψ1, thus forming an extended ray. In this embodiment, this portion of the ray includes extended rays 311 and 312 formed in the relay grating 1021. A portion of the propagating ray 31 is deflected, and its azimuth angle further changes to ψ2. In this embodiment, this portion of the ray includes propagating rays 32 and 34 formed in the relay grating 1021.

[0051] The propagating rays 32 and 34 further propagate to the coupling grating 1031. Under the action of the coupling grating 1031, a portion of the rays in the propagating rays 32 and 34 continue to propagate while maintaining the azimuth angle ψ2. In this embodiment, this portion of the rays includes: the extended ray 321 formed by the propagating ray 32 in the coupling grating 1031, and the extended ray 341 formed by the propagating ray 34 in the coupling grating 1031.

[0052] Part of the propagating ray 32 is deflected, and its azimuth angle is further changed to ψ3, forming an outgoing ray. In this embodiment, this part of the ray includes outgoing rays 35 and 37. Similarly, part of the propagating ray 34 is also deflected, and its azimuth angle is also changed to ψ3, forming an outgoing ray. In this embodiment, this part of the ray includes outgoing rays 36 and 38.

[0053] It should be understood that the propagating ray and the detached ray described in the embodiments of this application are only for describing and distinguishing the propagation state of image rays during the propagation process, and they are essentially all image rays. Furthermore, the concepts of propagating ray and propagating beam, extended ray and extended beam, ray and image ray, etc., described in this application have the same meaning and should not be regarded as limitations on this application.

[0054] exist Figure 2b Further reference Figure 2c This illustrates the optical path formed by light propagating in relay region 102, where the polarization states of the light rays corresponding to optical paths 1, 2, 3, and 4 can be any polarization state, while the light ray corresponding to optical path 5 is in the same polarization state. Figure 2c The optical paths shown can be classified into the following categories based on their optical path difference:

[0055] The first category includes four polarization states of light corresponding to optical paths 1 to 4: ssss, spsp, psps, and pppp. In this category, there is no optical path difference and no interference fringes.

[0056] The second category includes four polarization states of light corresponding to optical paths 1 to 4: sssp, spss, pspp, and ppps.

[0057] The third category includes four polarization states of light corresponding to optical paths 1 to 4: ssps, sppp, ppsp, and psss.

[0058] The fourth category includes two polarization states of light corresponding to optical paths 1 to 4: sspp and ppss.

[0059] The fifth category includes two polarization states of light corresponding to optical paths 1 to 4: spps and pssp.

[0060] Interference fringes are produced in types two through five, and the optical path difference changes significantly with the optical axis.

[0061] Obviously, the optical path difference situation of interference generated in relay region 102 is more complex. It is difficult to configure the optical axis angle so that the differences of the above four types of optical path differences generated by light from different fields of view are all less than one wavelength. Therefore, in this embodiment, for relay region 102, the optical axis angle can be configured so that the optical path difference of the four types of interference is greater than the coherence length, thereby reducing the contrast of interference fringes.

[0062] To further determine the specific angle of the optical axis, the relationship between the optical axis and the direction of light propagation will be established. Specifically:

[0063] For a substrate without birefringence, the general expression for the ray deflection in coupling region 101 satisfies:

[0064]

[0065] Where n is the refractive index of the waveguide substrate;

[0066] θ1 is the propagation angle of the propagating ray 31;

[0067] λ is the wavelength of image ray 3;

[0068] d1 is the grating constant of the coupled grating 1011.

[0069] Similarly, the general expression for ray deflection in relay region 102 satisfies:

[0070]

[0071] Where A is the grating vector of relay grating 1021 (e.g. Figure 2b The blue straight line within the relay grating 1021 shown in the diagram) and the grating vector coupled to the grating 1011 (as shown in the diagram) Figure 2bThe angle between the black dashed lines shown in the diagram;

[0072] θ2 is the propagation angle of the propagating rays 32 and 34;

[0073] ψ2 is the azimuth angle of the propagating rays 32 and 34;

[0074] d2 is the grating constant of relay grating 1021.

[0075] Similarly, the general expression for ray deflection in coupling region 103 satisfies:

[0076]

[0077] Where A' is the grating vector of the coupled grating 1031 (e.g., Figure 2b The angle between the blue straight line within the coupling grating 1031 shown and the grating vector of the coupling grating 1011;

[0078] θ3 represents the propagation angles of the coupled rays at 35°, 36°, 37°, and 38°.

[0079] The azimuth angles of the coupled rays are 35, 36, 37, and 38.

[0080] d3 is the grating constant of the coupled grating 1031.

[0081] For a uniaxial crystal substrate with birefringence, the expressions (1a) and (1b) for the light bending in coupling region 101 can be transformed into:

[0082]

[0083] Where, n s,p is the refractive index of light rays in a uniaxial crystal material relative to polarization states s and p;

[0084] θ s,p Let be the propagation angle of light rays with polarization states s and p;

[0085] The azimuth angles are for rays with polarization states s and p.

[0086] For relay region 102, the expressions for light bending (2a) and (2b) can be transformed into:

[0087]

[0088] Where, θ s,p Let be the propagation angle of light rays with polarization states s and p;

[0089] The azimuth angles are for rays with polarization states s and p.

[0090] The expressions (3a) and (3b) for the light bending in the coupling region 103 can be transformed into:

[0091]

[0092] Where, θ s,p Let be the propagation angle of light rays with polarization states s and p;

[0093] The azimuth angles are for rays with polarization states s and p.

[0094] In this embodiment of the application, to ensure that (1a') to (3b') are true, it is only necessary to ensure that:

[0095]

[0096] Where, n s Let be the refractive index of the ray with polarization state s in the uniaxial crystal material;

[0097] n p Let p be the refractive index of the light ray in the uniaxial crystal material.

[0098] θ s ′ is the propagation angle of the ray with polarization state s in the relay region;

[0099] Let be the azimuth angle of the light ray with polarization state p in the relay region.

[0100] According to formulas (4) to (7), the azimuth angle of birefringent rays does not change. Therefore, formulas (4) to (7) can be simplified to:

[0101] n s sin(θ s ′)=n p sin(θ p ′) (8)

[0102] n s sin(θ s ) = n p sin(θ p (9)

[0103] refer to Figure 3 The diagram illustrates the refractive index in a birefringent crystal, where x1x2x3 represents the birefringent crystal coordinate system, and x'1x'2x'3 represents the polarization coordinate system along the propagation of light rays.

[0104] In the embodiments of this application, when light with polarization state s propagates in a birefringent crystal, it is ordinary light (which can be represented by o), and when light with polarization state p propagates in a birefringent crystal, it is extraordinary light (which can be represented by e). Figure 3 The refractive index satisfies:

[0105] n s =n o (10)

[0106]

[0107] Where, n o is the refractive index of the o-ray in a birefringent crystal;

[0108] n e Let be the refractive index of the e-ray in a birefringent crystal.

[0109] refer to Figure 4 This illustrates the relationship between the direction of light propagation and the optical axis of a birefringent crystal, based on... Figure 4 The unit vector of light propagation and the unit vector of the optical axis can be represented in xyz space as:

[0110]

[0111] Where, θ axis The angle of propagation of the optical axis;

[0112] The azimuth angle of the optical axis;

[0113] Let be the unit vector for the propagation of light.

[0114] is the unit vector of the optical axis.

[0115] The angle α between two vectors can be expressed as:

[0116]

[0117] Based on the above, the required angle for the optical axis can be calculated. First, the diffraction angle of the s-polarized ray (i.e., the o-ray) can be calculated, and then the corresponding diffraction angle of the p-ray can be calculated using the formula. In this embodiment, considering that for a uniaxial crystal, n... o and n e The differences Δn are all relatively small, approximately 5% of n. o Since the propagation angles of s-rays and p-rays are relatively similar, the propagation angle of s-rays can be conveniently approximated by using the propagation angle of s-rays to calculate the refractive index of p-rays. Finally, the diffraction angle of p-rays can be calculated by using the refractive index of p-rays.

[0118] Specifically, in this application embodiment, for the coupling region 101, it is matched with two implementation methods: in one implementation method, the optical axis angle can be configured such that when the optical axis angle θ axis When the angles are 0 degrees and 90 degrees, the difference in optical path difference caused by birefringence in each field of view is within the wavelength range; in another embodiment, the optical axis angle θ can be configured. axis An angle greater than a certain value will cause the optical path difference of the incident light to exceed the coherence length, thus reducing the contrast of the interference fringes.

[0119] For relay region 102, in some embodiments of this application, the propagating beam has a large birefringence effect. Calculations show that the angle between the optical axis and the propagation angle of the beam needs to be greater than 20 degrees. This can be achieved through differences in azimuth and propagation angle, and has a wide range.

[0120] In other embodiments of this application, the extended beam exhibits a significant birefringence effect; similarly, the angle between the optical axis and the propagation angle of the extended beam must be greater than 20 degrees. This can be achieved through differences in azimuth and propagation angles, and also has a wide range.

[0121] In other embodiments of this application, the birefringence effects of the extended beam and the propagating beam need to differ to a certain extent. This is evaluated here by the difference in the angles of the two types of beams with respect to the optical axis. Let the propagation direction of the extended beam in a certain field of view be [k]. x1 ,k y1 ,k z1 The propagation direction of the beam is [k]. x2 ,k y2 ,k z2 The optical axis direction is represented as The cosine of the angular difference between the two beams and the optical axis can be expressed as:

[0122]

[0123] As can be seen from the above formula, there are two situations that will cause Δ cosα Smaller:

[0124] Since it is not a single field of view, during propagation, a certain field of view may exist that satisfies k. z1 =k z2 Therefore, when θ axis When it is small, Δ cosα Will follow sinθ axis If it decreases, the condition for interference cancellation is not met. After calculation and analysis, θ... axis To ensure the temperature is above 20 degrees Celsius as much as possible.

[0125] When θ axis When the temperature is ≥20°, this also needs to be considered. The effect of this can be easily differentiated here:

[0126]

[0127] when When this happens, the following relationship can be derived:

[0128]

[0129] Its maximum point can be found, in order to obtain The range can be obtained through graphical methods, such as... Figure 5 As shown, the above equation can be viewed as the addition of two propagation vectors in the xy plane. From Figure 5 It is possible to obtain the maximum cosine value of the difference in angle between the two beams and the optical axis. In practical applications, since the azimuth angle of image rays in any field of view is within a certain range, the angle of the optical axis only needs to satisfy the following range:

[0130]

[0131] in, The azimuth angle of the extended ray formed by the zero-degree field-of-view ray in the relay region.

[0132] The azimuth angle of the propagating ray formed by the zero-degree field-of-view ray in the relay region;

[0133] The angle between the optical axis and the x-axis.

[0134] For the coupling region 103, the configuration of the optical axis angle of the uniaxial crystal material used therein can refer to the configuration conditions of the coupling region 101.

[0135] As a feasible implementation of this application, based on the configuration of the optical axis angles of the uniaxial crystal materials in the coupling region 101, relay region 102, and coupling out region 103, the configuration of the optical axis angles of the uniaxial crystal materials used in the optical waveguide 10 of this application can be determined. That is, the optical axis angles simultaneously satisfy the following three conditions:

[0136] 1. Optical axis angle θ axis ≥20°;

[0137] 2. The angle between the propagation axes of the extended beam and the propagating beam formed by the optical axis and the zero-degree field of view ray in the corresponding region is greater than 20° and the sum of the maximum angle difference of the incident field of view;

[0138] 3. The optical axis angle satisfies:

[0139] To further illustrate the effectiveness of this application's solution, simulation data examples are provided below:

[0140] The simulation data for the optical waveguide 10 of this application are shown in Table 1:

[0141]

[0142] Table 1

[0143] The interference phenomenon of the coupled grating 1011 was simulated based on the data shown in Table 1. Figure 6 These represent the relationships between the total field-of-view optical path difference difference in coupled region 101 and the minimum optical path difference in interference in coupled region 101, as well as the optical axis angle and azimuth angle. They respectively represent two cases for resolving interference fringes in coupled region 101.

[0144] According to the formula for calculating coherence length, the coherence length of this light source is 20 μm. Therefore, from... Figure 6 It can be seen that the conditions for interference cancellation are as follows:

[0145] θ axis =0° and θ axis =90° and θ axis ≥50°.

[0146] Similarly, based on the data shown in Table 1, the interference phenomenon of the relay grating 1021 is simulated. Figure 7 shows the relationship between the total field-of-view optical path difference difference and the optical axis angle and azimuth angle for the four possible combinations of relay region 102.

[0147] from Figure 7a As can be seen, it is difficult to satisfy the condition that the optical path difference across the entire field of view is less than the wavelength by rotating the optical axis, therefore, interference cancellation does not hold in this case.

[0148] Furthermore, the relationship between the minimum optical path difference in the relay region 102 interference and the optical axis angle and azimuth angle is simulated. (Reference) Figure 7b It can be seen that there are certain optical axis directions where the minimum optical path difference for the four types of interference is greater than 20 μm. These regions are as follows: Figure 8 As shown ( Figure 8 (The yellow part).

[0149] As can be seen from the above data examples, the configuration of the optical axis angle meets the aforementioned optical axis configuration conditions of this application.

[0150] Clearly, by optimizing the optical axis angle as proposed in this solution, the optical path difference of all interfering optical paths can be increased to be greater than the coherence length of the broadband light source. This solves the interference problem in optical waveguides using uniaxial crystal materials, further improving the display effect of the optical waveguide and enhancing the user's viewing experience.

[0151] The terms "first," "second," "first," or "second" as used in the various embodiments of this disclosure may modify various components regardless of their order and / or importance, but these terms do not limit the corresponding components. The above terms are configured only for the purpose of distinguishing one component from another.

[0152] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An optical waveguide, characterized in that, The optical waveguide includes: a waveguide substrate, wherein at least an insertion region and an exit region are provided on the waveguide substrate, and the substrate material of the insertion region and the exit region is a uniaxial crystal material. The optical axis of the crystal in the uniaxial crystal material is configured such that the optical axis angle of the uniaxial crystal material in the optical waveguide is related to the propagation angle and azimuth angle of the light rays in different regions of each field of view.

2. The optical waveguide as described in claim 1, characterized in that, A relay region is also provided on the waveguide substrate.

3. The optical waveguide as described in any one of claims 1 to 2, characterized in that, The optical axis angle in the uniaxial crystal material of the optical waveguide is configured such that the optical path difference generated by birefringence in each field of view coupled into the optical waveguide is greater than the coherence length.

4. The optical waveguide as described in any one of claims 1 to 2, characterized in that, The angle between the optical axis and the direction perpendicular to the plane of the waveguide substrate is not less than 20°.

5. The optical waveguide as described in claim 4, characterized in that, The angle between the propagation axes of the extended beam and the propagating beam formed by the optical axis and the zero-degree field of view ray in the corresponding region is greater than the sum of 20° and the maximum angle difference of the incident field of view.

6. The optical waveguide as described in claim 5, characterized in that, The projection angle of the optical axis onto the waveguide substrate plane satisfies: in, The azimuth angle of the extended ray formed by the zero-degree field-of-view ray in the relay region. The azimuth angle of the propagating ray formed by the zero-degree field-of-view ray in the relay region; The angle between the optical axis and the second direction on the plane of the waveguide substrate is given.

7. A near-eye display module, characterized in that, Includes an image source and an optical waveguide as described in any one of claims 1 to 6; The image source is used to provide image light rays and output them to the optical waveguide, whereby the image light rays are used for imaging and display under the action of the optical waveguide.

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