Grating, optical waveguide and near-eye display module

Abstract

This application discloses a grating, an optical waveguide, and a near-eye display module. The grating is disposed in the coupling region, coupling region, and / or relay region of the optical waveguide. The grating adopts a metasurface structure, and the metasurface structure is configured such that RGB light rays in a specific wavelength range have the same gradient change on the metasurface structure, and the phase changes generated under the same gradient change are quantitatively related to each other.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to a grating, 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 important technological directions for the development of consumer-grade AR glasses.

[0003] As a crucial optical component used in AR glasses, waveguides (often used as lenses in AR glasses) can be monolithically designed, which is advantageous for reducing size and weight while enhancing optical properties. However, when the incident light contains multiple wavelengths, monolithic waveguides may cause issues with brightness and color uniformity. Summary of the Invention

[0004] Based on the above, this application provides a grating, an optical waveguide, and a near-eye display module to solve the problems of brightness and color uniformity in monolithic optical waveguides as much as possible.

[0005] Based on one aspect of this application, an embodiment of this application provides a grating disposed in the coupling region, coupling region and / or relay region of an optical waveguide. The grating adopts a metasurface structure, and the metasurface structure is configured such that RGB light rays in a specific wavelength range have the same gradient change on the metasurface structure, and the phase changes generated under the same gradient change are quantitatively related to each other.

[0006] Optionally, the RGB light within the specific wavelength range includes:

[0007] Blue light with a wavelength range of 440nm to 460nm, green light with a wavelength range of 510nm to 530nm, and red light with a wavelength range of 628nm to 648nm.

[0008] Optionally, the phase response of the metasurface structure to the blue light is: The phase response for the green light is

[0009] Where k is the phase coefficient of the metasurface structure.

[0010] Optionally, the phase response of the metasurface structure to the red light wavelength range is:

[0011] Based on one aspect of this application, embodiments of this application further provide a grating disposed in the coupling region, coupling region and / or relay region of an optical waveguide. The grating adopts a metasurface structure, and the metasurface structure is configured such that RGB light rays in a specific wavelength range have different gradient changes on the metasurface structure, and the phase changes generated under the different gradient changes are quantitatively related to each other.

[0012] Optionally, the RGB light within the specific wavelength range includes:

[0013] Blue light with a wavelength range of 440nm to 460nm, green light with a wavelength range of 510nm to 530nm, and red light with a wavelength range of 628nm to 648nm.

[0014] Optionally, the phase response of the metasurface structure to the blue light is: The phase response for the green light is

[0015] Where k is the phase coefficient of the metasurface structure;

[0016] m B m G Each satisfies a phase change The number of metasurface units.

[0017] Optionally, the phase response of the metasurface structure to the red light is:

[0018] m R To satisfy phase change The number of metasurface units.

[0019] Based on one aspect of this application, an embodiment of this application provides an optical waveguide, including a waveguide substrate, on which at least an insertion region and an exit region are provided, wherein the aforementioned grating is provided in the insertion region and / or the exit region.

[0020] 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;

[0021] 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.

[0022] 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

[0023] 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:

[0024] Figure 1a This is a schematic diagram of the structure of an optical waveguide 10 provided in an embodiment of this application;

[0025] Figure 1b This is a schematic diagram of the structure of an optical waveguide 10' provided in an embodiment of this application;

[0026] Figure 2a This is a schematic diagram of the image ray 2 coupled into the optical waveguide 10 according to an embodiment of this application;

[0027] Figure 2b This is a schematic diagram of the propagation of the image ray 2 in the optical waveguide 10 provided in an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of the incident light entering the optical waveguide 30 according to an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the phase response of blue, green, and red light provided in the embodiments of this application;

[0030] Figure 5 This is a simplified model diagram of the metasurface grating provided in the embodiments of this application. Detailed Implementation

[0031] 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.

[0032] 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, which can be abbreviated as R, G and B in this application), and is transmitted to the user's eyes via total internal reflection (TIR) ​​in the optical waveguide, so that the user can view the corresponding AR image.

[0033] It should be noted that in the embodiments of this application, the descriptions of "incident light" and "incident ray" have the same meaning; similarly, the descriptions of "RGB ray" and "RGB light" have the same meaning; the descriptions of "R light," "red light," "red light," and "R ray" have the same meaning, and will not be enumerated here. It should be understood that the difference between the two descriptions of "light" and "ray" should not be construed as a limitation of this application.

[0034] refer to Figure 1a This application provides an exemplary optical waveguide 10, which is a monolithic structure comprising a waveguide substrate 100, an insertion region 101, and an exit region 103. The insertion region 101 and the exit region 103 are both located on the same side of the waveguide substrate 100 (when used as lenses for AR glasses, this side typically faces the user's eyes after wearing the glasses). Corresponding grating structures are configured within the insertion region 101 and the exit region 103.

[0035] Figure 1b Another exemplary optical waveguide 10' is shown, which is also a monolithic structure. The optical waveguide 10' includes: a waveguide substrate 100', a coupling region 101', a coupling out region 103', and a relay region 102'. Corresponding grating structures are also configured in the coupling region 101', the coupling out region 103', and the relay region 102' of the optical waveguide 10'.

[0036] It should be understood that Figure 1a and 1b The outlines, dimensions, and relative positions of the coupling-in region, relay region, and coupling-out region shown are exemplary and not limited to specific regions. Figure 1a and 1b As shown. For example, in practical applications, the contour shape of coupling region 101 or coupling region 101' may not be... Figure 1a and Figure 1b The circular outline shown can be rectangular, trapezoidal, or elliptical, etc.; the outline of relay region 102' can also be trapezoidal or rounded rectangle; for example, Figure 1b In this context, the relative positions of the three regions may be arranged obliquely; for example, the coupling region 101 may also be located on other surfaces of the waveguide substrate 100, rather than on the same side as the coupling region 103.

[0037] In the embodiments of this application, the grating structure set in the coupling region can be called a coupling grating, and the specific grating type is a one-dimensional grating or a two-dimensional grating; the grating structure set in the relay region can be called a relay grating, and the specific grating type is a one-dimensional grating; the grating structure set in the coupling out region can be called a coupling out grating, and the specific grating type is a one-dimensional grating or a two-dimensional grating.

[0038] exist Figure 1a and 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, vertical direction, or longitudinal direction; the direction parallel to the x-axis may also be referred to in this application as the second direction, horizontal direction, or 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 this embodiment, the direction perpendicular to the xy-plane can be considered as the z-axis direction. Figure 2a The diagram illustrates an xyz coordinate system. The direction parallel to the z-axis may 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-2a The coordinate system shown, and the descriptions of the corresponding direction names, are also applicable throughout the document.

[0039] In practical applications, light typically enters the optical waveguide from the coupling region. Taking the aforementioned optical waveguide 10 as an example, refer to... Figure 2a The diagram shows the incident light entering the optical waveguide 10. Specifically, the incident light 2 is coupled into the optical waveguide 10 from the coupling region 101 at a set angle, and the incident light 2 propagates within the waveguide substrate 100 via the coupling region 101.

[0040] Further reference Figure 2b The diagram illustrates the propagation of incident light ray 2 within optical waveguide 10. Incident light ray 2 contains RGB rays; different colors of light have different wavelengths. According to the propagation principle of gratings, when light of different wavelengths propagates in the same incident and exit media, the diffraction propagation angle after passing through a periodic grating is related to the grating period and wavelength. Therefore, the RGB rays entering the optical waveguide 10 after passing through the coupling grating 101 have different total internal reflection angles. (Continue to refer to...) Figure 2b In the optical waveguide 10, the B ray is represented by a solid line, and its corresponding total internal reflection angle is denoted as α; the G ray is represented by a dashed line, and its corresponding total internal reflection angle is denoted as β; the R ray is represented by a double-dotted dashed line, and its corresponding total internal reflection angle is denoted as γ. It can be seen that, due to the different total internal reflection angles of the three rays, the exit pupils after coupling out from the coupling grating 102 are often inconsistent, and each wavelength of light has different diffraction efficiencies when passing through the same grating, thus significantly affecting the uniformity of brightness and color in the display.

[0041] Therefore, this application provides a grating for use in optical waveguides to minimize the impact of light propagation of different wavelengths on brightness uniformity and color uniformity in monolithic optical waveguides.

[0042] refer to Figure 3A metasurface grating 3011 is disposed on the coupling region of the optical waveguide 30 as a coupling grating. The metasurface grating 3011 is a subwavelength structure, similar to a diffraction grating. The metasurface grating 3011 can form refracted light at a specific angle by changing the continuity of the outgoing phase. Figure 3 In the middle, Δ x The gradient change of the metasurface grating 3011 in the x direction results in the following effect: after the incident light 33a enters the waveguide substrate 300 of the waveguide 30, the refracted light 34a is normally refracted, while the refracted light 34b corresponding to the incident light 33b is abnormally refracted. The refracted light rays 34a and 34b converge at the same position C in the waveguide substrate 300.

[0043] In this process, the anomalous refraction produced by the metasurface grating 3011 can be expressed as:

[0044]

[0045] Where n1 is the refractive index of the incident medium, n2 is the refractive index of the waveguide substrate 300 of the optical waveguide 30, θ1 is the incident angle of the incident ray 33a, and θ2 is the refraction angle of the refracted ray 34a generated after the incident ray 33a passes through the metasurface grating 3011. Δ x To determine the gradient variation in the x-direction of the coupled grating 3011 metasurface structure, For light rays changing in gradient Δ x The phase change produced below.

[0046] When the incident medium is air, the above expression can be simplified to:

[0047]

[0048] For the three different wavelengths of light (RGB), equation (2) can be further expressed as:

[0049]

[0050] in, λ is the angle of refraction of blue light after it passes through the metasurface grating 3011 and enters the waveguide substrate 300. B The wavelength of blue light; The gradient variation Δ of the metasurface grating 3011 for blue light x The resulting phase change The meaning of this representation is the same as that described later. Mutual reference;

[0051] λ is the angle of refraction of green light after it passes through the metasurface grating 3011 and enters the waveguide substrate 300. G The wavelength of green light; This represents the phase change of the metasurface grating 3011 in response to the gradient change of green light. Similarly, the meaning of this representation is the same as that described later. Mutual reference;

[0052] λ is the angle of refraction of red light after it passes through the metasurface grating 3011 and enters the waveguide substrate 300. R The wavelength of red light; This represents the phase change of the metasurface grating 3011 in response to the gradient change of red light. The meaning of this representation is the same as that described later. Mutual reference.

[0053] In some embodiments of this application, the metasurface grating 3011 is configured such that, for RGB light, the refraction angles corresponding to the refraction after passing through the metasurface grating 3011 are the same. In these embodiments, combined with the above equation (3), the following relationship exists:

[0054]

[0055] Clearly, based on relation (4), the following relation can be further determined, namely:

[0056]

[0057] In practical applications, the metasurface grating 3011 can be further configured so that the gradient changes for different wavelengths of light are identical in pairs, or so that the gradient changes for different wavelengths of light are all different. These two cases will be analyzed in detail.

[0058] The gradient changes are all the same

[0059] In this embodiment, if the total internal reflection angles α, β, and γ of RGB light within the waveguide are essentially the same (generally, an angle difference of less than 2° can be considered essentially the same), for metasurface structures with the same gradient change, it is only necessary to ensure that the phase changes of their wavelengths under this gradient change are in a certain quantitative relationship. Specifically:

[0060] The metasurface grating 3011 is configured to have the same or substantially the same gradient changes for blue, green, and red light, i.e. Therefore, the relationship between blue light, green light, and red light in the above equation (5) can be expressed as:

[0061]

[0062] In some embodiments of this application, a specific range of variation for RGB wavelength values ​​is configured; that is, if the total internal reflection angle α = β = γ, the phase response at the blue light wavelength (440nm ~ 460nm) is... Where k is the phase coefficient of the metasurface, the phase response at the green light wavelength (510 nm~530 nm) is: The phase response at this time, under the red light wavelength (628nm~648nm), is

[0063] Taking incident light containing wavelengths of 450nm, 520nm, and 638nm as an example, the phase response of the metasurface grating 3011 for blue light with a wavelength of 450nm is: At this time, the phase response of the metasurface grating 3011 to green light with a wavelength of 520 nm is: The phase response of the metasurface grating 3011 for red light with a wavelength of 638 nm is:

[0064] Based on this configuration, the phase response of the metasurface grating 3011 for blue, green, and red light is as follows: Figure 4 As shown, in Figure 4 As can be seen from the diagram, with the gradient change Δ x As the concentration of light increases, the phase response difference among blue, green, and red light gradually increases. In practical applications, this phase response difference is beneficial for metasurface design. Figure 4 The phase response relationship shown makes it easier to obtain the phase response differences of blue, green, and red light.

[0065] The gradient changes are all different

[0066] In this embodiment, the structure of the metasurface grating 3011 can be represented using a simplified model, such as... Figure 5 As shown. In Figure 5 In the metasurface grating 3011, the metasurface structure comprises multiple periodic metasurface unit structures P, each of which is composed of three structures or materials. Each structure or material plays a dominant phase modulation role for only one wavelength, with minimal phase modulation changes for other wavelengths. Figure 5 As can be seen, the gradient change of the metasurface grating 3011 with respect to RGB light is... They are not the same; that is, the number of metasurface unit structures P required for RGB light is inconsistent.

[0067] If the RGB rays are reflected at approximately the same angles α, β, and γ within the waveguide after passing through the metasurface grating 3011, then, based on equation (4), the following relationship can be further determined:

[0068]

[0069] Where, m B m G m REach satisfies a phase change The number of metasurface units.

[0070] Relation (9) can be further transformed into:

[0071]

[0072] For the same gradient-changing metasurface, it is only necessary to ensure that the phase change of the wavelength under this gradient change is in a certain quantitative relationship.

[0073] In some embodiments of this application, the configuration is tailored to the range of RGB wavelength values; that is, the phase response at the blue light wavelength (440nm~460nm) is... Then the phase response at the green light wavelength (510nm~530nm) is: The phase response at this time, under the red light wavelength (628nm~648nm), is

[0074] Taking incident light containing wavelengths of 450nm, 520nm, and 638nm as an example, the phase response of the metasurface grating 3011 for blue light with a wavelength of 450nm is: At this time, the phase response of the metasurface grating 3011 to green light with a wavelength of 520 nm is: The phase response of the metasurface grating 3011 for red light with a wavelength of 638 nm is:

[0075] Based on the above quantitative relationships, the structure of the metasurface grating 3011 can be adopted in different ways according to the polarization state of the incident light:

[0076] In some embodiments, when the incident light is linearly polarized, the structure of the metasurface grating 3011 can achieve redirection of the incident light by varying the refractive index in the longitudinal direction or by combining multiple structures in the transverse direction.

[0077] In some embodiments, when the incident light is circularly polarized, the metasurface grating 3011 rotates around its own center by a certain angle to change the outgoing phase of the incident light.

[0078] Considering that metasurface structures can generally be composed of a single medium or a composite medium, and have a certain height, the top view shape of the structure can be a regular shape such as a rectangle, square, circle, or ellipse, or it can be an irregular shape. In some embodiments, the internal patterns of the metasurface grating 3011 can be arranged in a certain pattern, such as the center of each pattern being located on the same gradient direction.

[0079] In some embodiments, the internal pattern of the metasurface grating 3011 may also vary in a certain pattern, such as the pattern center being on concentric arcs of the same radius, or the pattern center rotating at different angles.

[0080] In this application, a metasurface grating is used. On the one hand, the metasurface grating exhibits low sensitivity to the incident angle of the incident light, thus meeting the requirement of uniform field of view under multiple fields of view in AR systems under small incident light angles within a certain range. On the other hand, the metasurface structure in the metasurface grating can change the propagation angle of RGB wavelength light in the optical waveguide, improving the brightness uniformity and color uniformity of the exit pupil of the AR system, and further enhancing the effect of full-color display of a single optical waveguide.

[0081] This application provides an optical waveguide, which is a monolithic structure comprising a waveguide substrate. At least an insertion region and an exit region are provided on the waveguide substrate. In some embodiments, a relay region is also provided on the waveguide substrate. A metasurface grating as described above is provided in the insertion region, exit region, and / or relay region.

[0082] Based on the optical waveguide described above, this application embodiment also provides a near-eye display module, which can be applied to AR glasses. The near-eye display module includes: an optical engine and the aforementioned optical waveguide. The optical engine is used to generate image light rays and project them onto the corresponding coupling area on the optical waveguide. The image light rays can be transmitted in the optical waveguide and coupled out through the coupling area to achieve display.

[0083] 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.

[0084] 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. A grating disposed in a coupling-in region, a coupling-out region, and / or a relay region of an optical waveguide, characterized in that, The grating employs a metasurface structure, which is configured such that RGB light rays within a specific wavelength range have the same gradient change on the metasurface structure, and the phase changes generated under the same gradient change are quantitatively related to each other.

2. The grating of claim 1, wherein, The specific wavelength range of RGB light includes: Blue light with a wavelength range of 440nm to 460nm, green light with a wavelength range of 510nm to 530nm, and red light with a wavelength range of 628nm to 648nm.

3. The grating as described in claim 2, characterized in that, The phase response of the metasurface structure to the blue light is: The phase response for the green light is Where k is the phase coefficient of the metasurface structure.

4. The grating as described in claim 3, characterized in that, The phase response of the metasurface structure to the red light wavelength range is:

5. A grating disposed in the coupling region, coupling region, and / or relay region of an optical waveguide, characterized in that, The grating employs a metasurface structure, which is configured such that RGB light rays within a specific wavelength range exhibit distinct gradient changes on the metasurface structure, and the phase changes generated under these distinct gradient changes are quantitatively related to each other.

6. The grating as described in claim 5, characterized in that, The specific wavelength range of RGB light includes: Blue light with a wavelength range of 440nm to 460nm, green light with a wavelength range of 510nm to 530nm, and red light with a wavelength range of 628nm to 648nm.

7. The grating as described in claim 6, characterized in that, The phase response of the metasurface structure to the blue light is: The phase response for the green light is Where k is the phase coefficient of the metasurface structure; m B m G They satisfy phase change The number of metasurface units.

8. The grating as described in claim 6, characterized in that, The phase response of the metasurface structure to the red light is: m R To satisfy phase change The number of metasurface units.

9. An optical waveguide, characterized in that, It includes a waveguide substrate, on which at least an insertion region and an exit region are provided, wherein a grating as described in any one of claims 1 to 8 is provided in the insertion region and / or the exit region.

10. A near-eye display module, characterized in that, Includes an image source and an optical waveguide as described in claim 9; 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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