Optical waveguide and near-to-eye equipment

Abstract

The utility model discloses an optical waveguide and near-to-eye equipment, the optical waveguide comprises a waveguide body and a metasurface coupler, and the metasurface coupler is arranged on the waveguide body; the metasurface coupler is configured to enable light rays with different wavelengths and the same incident angle to be coupled into the waveguide body and propagate in a total reflection mode, and the light rays with different wavelengths coupled into the waveguide body have the same diffraction angle; and the metasurface coupler is configured to couple the light rays with different wavelengths coupled into the waveguide body out of the waveguide body at the same emergent angle, so that dispersion-free image transmission through a single optical waveguide can be realized, and the problem of dispersion of a diffraction optical waveguide in the prior art can be solved. Because the optical waveguide can transmit light with different wavelengths without dispersion, compared with a diffraction optical waveguide in the prior art, the monolithic optical waveguide provided by the utility model has the advantages of no dispersion, capability of realizing full-color display, relatively uniform color and relatively small size.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical systems, in particular to an optical waveguide and a near-eye device. BACKGROUND

[0002] Diffractive optical waveguide is a display technology for augmented reality (AR) devices, which transmits light to human eyes through diffraction and total internal reflection of light, to realize the fusion of virtual image and real environment. In the prior art, there are still a series of problems in the diffractive optical waveguide, such as chromatic dispersion, small field of view angle, poor color uniformity, etc. SUMMARY

[0003] In view of the above technical problems, the embodiments of the present application provide an optical waveguide, aiming to solve the problem of chromatic dispersion in the prior art diffractive optical waveguide.

[0004] According to an aspect of the embodiments of the present application, an optical waveguide is disclosed, comprising:

[0005] a waveguide body;

[0006] a metasurface coupler arranged in the waveguide body, the metasurface coupler being configured to couple light of different wavelengths and having the same incident angle into the waveguide body and propagate in a total reflection manner, and the light of different wavelengths coupled into the waveguide body has the same diffraction angle; and the metasurface coupler is configured to couple the light of different wavelengths coupled into the waveguide body out of the waveguide body at the same exit angle.

[0007] In some embodiments, the metasurface coupler has a preset grating constant and a preset phase gradient, so that the metasurface coupler is configured to couple light of different wavelengths and having the same incident angle into the waveguide body and propagate in a total reflection manner, and the light of different wavelengths coupled into the waveguide body has the same diffraction angle; and the metasurface coupler is configured to couple the light of different wavelengths coupled into the waveguide body out of the waveguide body at the same exit angle.

[0008] In some embodiments, the metasurface coupler comprises:

[0009] a coupling-in metasurface grating configured to couple light of different wavelengths and having the same incident angle into the waveguide body and propagate in a total reflection manner, and the light of different wavelengths coupled into the waveguide body has the same diffraction angle;

[0010] a coupling-out metasurface grating configured to couple the light of different wavelengths coupled into the waveguide body by the coupling-in metasurface grating out of the waveguide body at the same exit angle.

[0011] In some embodiments, the metasurface coupler satisfies:

[0012]

[0013] wherein, is the phase difference between any point on the in-coupling metasurface grating and the center of the in-coupling metasurface grating, x is the distance between any point on the in-coupling metasurface grating and the center of the in-coupling metasurface grating, n s is the refractive index of the in-coupling metasurface grating, θ m is the diffraction angle, n i is the refractive index of the out-coupling metasurface grating, θ i is the incident angle, m is the diffraction order, and λ is the wavelength of the light, and d is the grating constant of the in-coupling metasurface grating.

[0014] In some embodiments, the optical waveguide further comprises a filter, which is arranged in a stack with the out-coupling metasurface grating, or the filter is arranged on two sides of the waveguide body in the thickness direction, respectively.

[0015] In some embodiments, the in-coupling metasurface grating and the out-coupling metasurface grating are located on the same side of the waveguide body in the thickness direction.

[0016] Alternatively,

[0017] The in-coupling metasurface grating is located on one side of the waveguide body in the thickness direction, and the out-coupling metasurface grating is located on the other side of the waveguide body in the thickness direction.

[0018] In some embodiments, the in-coupling metasurface grating comprises at least two sub-in-coupling gratings, each of which has different characteristic parameters.

[0019] In some embodiments, the optical waveguide further comprises an anti-reflection film, which is arranged at the contact surface between the metasurface coupler and air and / or between the metasurface coupler and the waveguide body.

[0020] In some embodiments, the metasurface coupler comprises at least two sub-grating layers for coupling light into the waveguide body, each of which is arranged in a stack in the thickness direction of the waveguide body; and at least two sub-grating layers for coupling light out of the waveguide body, each of which is arranged in a stack in the thickness direction of the waveguide body.

[0021] A second aspect of the embodiments of the present application provides a near-eye device comprising the optical waveguide according to any one of the above.

[0022] The light waveguide provided in the present application can couple light rays with different wavelengths and the same incident angle into the waveguide body through the metasurface coupler for total reflection. The light rays with different wavelengths coupled into the waveguide body have the same diffraction angle, so that the transmission paths of the light rays with different wavelengths in the waveguide body are the same. In addition, the metasurface coupler can also couple the light rays with different wavelengths coupled into the waveguide body out of the waveguide body at the same exit angle, so that the single-piece light waveguide can realize non-dispersive transmission of images, and the problem of dispersion of the existing diffractive optical waveguide can be solved. Since the light waveguide can non-dispersively transmit light with different wavelengths, compared with the diffractive optical waveguide in the prior art, the single-piece light waveguide provided in the present application has the advantages of non-dispersion, full-color display, more uniform color, and smaller volume. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[0024] Figure 1 A structure schematic diagram of a diffractive optical waveguide in the prior art is shown.

[0025] Figure 2 A structure schematic diagram of a diffractive optical waveguide in the prior art is shown. Figure 1 A top view of the diffractive optical waveguide shown.

[0026] Figure 3 A structure schematic diagram of a diffractive optical waveguide in the prior art is shown. Figure 1 A K-space analysis diagram of the diffractive optical waveguide shown.

[0027] Figure 4 A structure schematic diagram of a light waveguide in an embodiment of the present application is shown.

[0028] Figure 5 A structure schematic diagram of a light waveguide in an embodiment of the present application is shown. Figure 4 A K-space analysis diagram of the diffractive optical waveguide shown.

[0029] Figure 6 A front view of a coupling-in metasurface grating in an embodiment of the present application is shown.

[0030] Figure 7 A front view of a coupling-in metasurface grating in an embodiment of the present application is shown. Figure 6 A top view of the coupling-in metasurface grating shown.

[0031] Figure 8 A structure schematic diagram of a light waveguide in an embodiment of the present application is shown.

[0032] Figure 9 A structure schematic diagram of a light waveguide in an embodiment of the present application is shown.

[0033] Figure 10 A structure schematic diagram of a light waveguide in an embodiment of the present application is shown.

[0034] Figure 11 A schematic diagram of the structure of an optical waveguide in an embodiment of the application is shown.

[0035] Figure 12 A schematic diagram of the structure of an optical waveguide in an embodiment of the application is shown.

[0036] Reference numerals

[0037] 100, optical waveguide;

[0038] 10, waveguide body;

[0039] 20, metasurface coupler; 210, in-coupling metasurface grating; 220, out-coupling metasurface grating;

[0040] 30, filter;

[0041] 200, diffractive optical waveguide;

[0042] 2100, waveguide;

[0043] 2200, in-coupling section;

[0044] 2300, out-coupling section. DETAILED DESCRIPTION

[0045] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example implementations to those skilled in the art. The accompanying drawings are included to provide a further understanding of example implementations and are incorporated in and constitute a part of this specification. The drawings are not intended to be restrictive in any way. Throughout the drawings, like references numerals denote like features, and thus, repeated description of these features will be omitted.

[0046] Furthermore, described features, structures, or characteristics can be combined in any suitable manner in one or more example implementations. In the following description, numerous specific details are provided to give a thorough understanding of example implementations. One skilled in relevant art will recognize, however, that the technology can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the technology.

[0047] In order to solve the dispersion problem, there are multi-piece optical waveguides and single-piece full-color optical waveguides in the prior art. Among them, in the multi-piece optical waveguide technical route, a plurality of waveguides are stacked, and each waveguide is provided with a grating, and each grating is used to couple light of a target wavelength into the corresponding waveguide to separate the color channels of the image and transmit them in different waveguides. Although this technical route can avoid the dispersion problem of the grating, it also has the problems of interlayer crosstalk, large volume and heavy weight.

[0048] There are two mainstream schemes in the single-piece full-color optical waveguide technical route. Specifically, one scheme uses a plurality of laterally distributed gratings to couple light of different wavelengths into the waveguide layer, but this scheme has high design difficulty, high production cost, and great challenges to the processing technology. The other scheme selects appropriate grating periods and diffraction orders to make the diffraction angles of light of different wavelengths in the diffraction optical waveguide close to each other to alleviate a series of problems caused by dispersion. However, in this scheme, the grating supporting multiple diffraction orders will also distribute part of the energy to other diffraction orders when working. The ghost image caused by multi-level diffraction will significantly reduce the projection imaging quality of the optical waveguide. Meanwhile, the similar diffraction angles only alleviate the dispersion problem, but do not completely solve it.

[0049] Please refer to Figure 1 and Figure 2 , wherein, Figure 1 is a structural schematic diagram of a diffraction optical waveguide 200 in the prior art, Figure 2 is a top view of Figure 1 . The diffraction optical waveguide 200 in the prior art usually includes a waveguide 2100, a coupling-in portion 2200, and a coupling-out portion 2300. The projected image is collimated to form R (Red), G (Green), and B (Blue) light rays as shown in Figure 1 . The RGB light rays irradiate to the coupling-in portion 2200, and the coupling-in structure couples and confines the light rays inside the waveguide 2100 and propagates them in the waveguide 2100 in a total reflection manner.

[0050] Figure 3 illustrates the K-space analysis diagram of the diffraction optical waveguide 200 shown in Figure 1 , wherein Figure 3 is the wave vector of red light, is the wave vector of green light, is the wave vector of blue light. As can be seen from , in order to satisfy that there is no chromatic aberration when the diffraction optical waveguide 200 outputs an image, the wave vectors provided by the coupling-in portion 2200 and the coupling-out portion 2300 for light of each wavelength need to satisfy formula (1): Figure 3

[0051] ​

[0052] wherein n is a wave vector of the in-coupling portion 2200, is a wave vector of the out-coupling portion 2300. The in-coupling portion 2200 and the out-coupling portion 2300 of the prior art diffractive optical waveguide 200 are usually grating couplers, which satisfy formula (2) for a conventional grating coupler:

[0053]

[0054] wherein n s1 is a refractive index of the in-coupling portion 2200, θ m1 is a diffraction angle, n i1 is a refractive index of the out-coupling portion 2300, θ i1 is an incident angle of the light, m1 is a diffraction order, λ1 is a wavelength of the light, and d1 is a grating constant of the in-coupling portion 2200. It can be found from formula (2) that, for the polychromatic light with the same incident angle, the diffraction angles of the lights with different wavelengths are different, although the in-coupling portion 2200 and the out-coupling portion 2300 provide a total wave vector of 0 for the incident light with different wavelengths, the transmission paths of the lights with different wavelengths in the waveguide 2100 are all different, which causes the prior art diffractive optical waveguide to have a chromatic dispersion problem as shown in formula (3): Figure 1 which affects the imaging quality and the theoretical performance parameters. In addition, the prior art diffractive optical waveguide also has problems such as a small field of view and poor color uniformity.

[0055] To overcome at least one of the above technical problems of the prior art diffractive optical waveguide, the present application provides an optical waveguide.

[0056] Please refer to Figure 4 , the optical waveguide 100 includes a waveguide body 10 and a metasurface coupler 20. The waveguide body 10 is in a sheet shape, and the waveguide body 10 is used to guide the light to propagate inside it.

[0057] The metasurface coupler 20 is arranged on the waveguide body 10, and the metasurface coupler 20 is configured to couple the light with different wavelengths and the same incident angle into the waveguide body 10 and propagate in a total reflection manner. The light with different wavelengths coupled into the waveguide body 10 has the same diffraction angle, so that the transmission paths of the light with different wavelengths in the waveguide body 10 are the same. In addition, the metasurface coupler 20 is configured to couple the light with different wavelengths coupled into the waveguide body 10 out of the waveguide body 10 at the same exit angle, thereby realizing the transmission of the image.

[0058] Figure 5 schematically shows a K-space analysis diagram of the optical waveguide 100 shown in Figure 4 , Figure 5 ​a wave vector of red light, a wave vector of green light, a wave vector of blue light. In combination Figure 4 and Figure 5 It can be known that the optical waveguide 100 provided by the present application can couple light rays of different wavelengths and having the same incident angle into the waveguide body 10 through the metasurface coupler 20 for total reflection, and the light rays of different wavelengths coupled into the waveguide body 10 have the same diffraction angle, so that the transmission paths of the light rays of different wavelengths in the waveguide body 10 are the same. In addition, the metasurface coupler 20 can also couple the light rays of different wavelengths coupled into the waveguide body 10 out of the waveguide body 10 at the same exit angle, so that the single-chip optical waveguide 100 can realize non-dispersive transmission of images, and the problem of dispersion of the existing diffractive optical waveguide 100 can be solved. Since the optical waveguide 100 can non-dispersively transmit light of different wavelengths, compared with the diffractive optical waveguide 100 in the prior art, the single-chip optical waveguide 100 provided by the present application has the advantages of non-dispersion, full-color display, more uniform color, and smaller volume.

[0059] For the waveguide body 10 described above, the material thereof can be an optically transparent material such as silicon nitride, silicon dioxide, titanium dioxide, silicon carbide, and polymer.

[0060] In some embodiments, the metasurface coupler 20 has a preset grating constant and a preset phase gradient, so that the metasurface coupler 20 can realize the following functions: (1) the light rays of different wavelengths and having the same incident angle can be coupled into the waveguide body 10 and propagate in a total reflection manner, and the light rays of different wavelengths coupled into the waveguide body 10 have the same diffraction angle; (2) the light rays of different wavelengths coupled into the waveguide body 10 can be coupled out of the waveguide body 10 at the same exit angle.

[0061] Please refer again to Figure 4 The metasurface coupler 20 includes a coupling-in metasurface grating 210 and a coupling-out metasurface grating 220, and the coupling-in metasurface grating 210 is arranged at intervals with the coupling-out metasurface grating 220.

[0062] The coupling-in metasurface grating 210 is arranged at the waveguide body 10, and by configuring the grating constant and the phase gradient of the coupling-in metasurface grating 210, the coupling-in metasurface grating 210 can be configured to couple the light rays of different wavelengths and having the same incident angle into the waveguide body 10 and propagate in a total reflection manner, and the light rays of different wavelengths coupled into the waveguide body 10 have the same diffraction angle.

[0063] The out-coupling metasurface grating 220 is arranged on the waveguide body 10. By configuring the grating constant and phase gradient of the out-coupling metasurface grating 220, the out-coupling metasurface grating 220 can be configured to couple out the light rays of different wavelengths coupled into the waveguide body 10 by the in-coupling metasurface grating 210 at the same exit angle. For example, the out-coupling metasurface grating 220 can couple out red light, green light and blue light at an exit angle of 0 degrees. The angle of light of different wavelengths coupled out of the waveguide body 10 is only used for illustration and should not be construed as a limitation on the angle of light coupled out of the waveguide body 10. In addition, the "incident angle" and "exit angle" in the present application are based on the normal.

[0064] For the in-coupling metasurface grating 210 described above, refer to Figure 6 and Figure 7 , Figure 6 is a front view of the in-coupling metasurface grating 210, Figure 7 is a top view of the in-coupling metasurface grating 210. The in-coupling metasurface grating 210 realizes the function of a traditional diffraction grating through a metasurface. The in-coupling metasurface grating 210 includes a plurality of arrayed micro-nano structures. The micro-nano structures form in-coupling grating units. The in-coupling grating units are the smallest repeating units of the metasurface coupler 20. The plurality of in-coupling grating units are periodically arranged along a preset direction to form the in-coupling metasurface grating 210.

[0065] In some embodiments, the in-coupling metasurface grating 210 includes at least two sub-in-coupling gratings (not shown in the figure). That is, the in-coupling metasurface grating 210 is partitioned to make each sub-in-coupling grating have different characteristic parameters. The characteristic parameters of the sub-in-coupling gratings include but are not limited to grating constant and phase gradient. Partitioning the in-coupling metasurface grating 210 can make the sub-in-coupling gratings have higher matching degree with incident light, thereby ensuring the uniformity of image brightness.

[0066] The in-coupling metasurface grating 210 can be composed of two materials with different refractive indices, and the refractive index difference between the two materials is greater than 0.5. The material with lower refractive index among the two materials can be selected from air, silicon dioxide, polymer, etc.

[0067] For the out-coupling metasurface grating 220 described above, the out-coupling metasurface grating 220 realizes the function of a traditional diffraction grating through a metasurface. The out-coupling metasurface grating 220 includes a plurality of arrayed micro-nano structures. The micro-nano structures form out-coupling grating units. The out-coupling grating units are the smallest repeating units of the metasurface coupler 20. The plurality of out-coupling grating units are periodically arranged along a preset direction to form the out-coupling metasurface grating 220.

[0068] The out-coupling metasurface grating 220 can be composed of two materials with different refractive indices, and the refractive index difference between the two materials is greater than 0.5. The material with lower refractive index among the two materials can be selected from air, silicon dioxide, polymer, etc.

[0069] In some embodiments, light rays of each wavelength are coupled out from a plurality of out-coupling points of the out-coupling metasurface grating 220, for each out-coupling point, a portion of the transmitted energy is coupled out, and another portion continues to transmit to the next out-coupling point, so as to achieve pupil expansion, thereby making the light waveguide 100 provided by the present application have a large eyebox size while being free of dispersion.

[0070] In some embodiments, the metasurface coupler 20 satisfies equation (3):

[0071]

[0072] wherein in equation (3), is the phase difference between any point on the metasurface coupler 20 and the center of the metasurface coupler 20, and x is the distance between any point on the metasurface coupler 20 and the center of the metasurface coupler 20. s is the refractive index of the in-coupling metasurface grating 210, m is the diffraction angle, n i is the refractive index of the out-coupling metasurface grating 220, i is the incident angle, m is the diffraction order, λ is the wavelength of the light, and d is the grating constant of the in-coupling metasurface grating 210.

[0073] Equation (3) is applicable to both the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220. Specifically, when equation (3) is for the in-coupling metasurface grating 210, is the phase difference between any point on the in-coupling metasurface grating 210 and the center of the in-coupling metasurface grating 210, and x is the distance between any point on the in-coupling metasurface grating 210 and the center of the in-coupling metasurface grating 210. When equation (3) is for the out-coupling metasurface grating 220, is the phase difference between any point on the out-coupling metasurface grating 220 and the center of the out-coupling metasurface grating 220, and x is the distance between any point on the out-coupling metasurface grating 220 and the center of the out-coupling metasurface grating 220.

[0074] According to equation (3), for the light waveguide 100 provided by the present application, when polychromatic light with the same incident angle is incident, the diffraction angles of light rays of different wavelengths are related to not only the grating constant d of the in-coupling metasurface grating 210, but also the phase gradient provided by the in-coupling metasurface grating 210 corresponding to the in-coupling metasurface grating 210 (i.e. ), and thus the grating constant d of the in-coupling metasurface grating 210, the phase difference between any point on the in-coupling metasurface grating 210 and the center of the in-coupling metasurface grating 210, The distance x between any point on the in-coupling metasurface grating 210 and the center of the in-coupling metasurface grating 210 can enable the light rays of different wavelengths and having the same incident angle to be coupled into the waveguide body 10 by the in-coupling metasurface grating 210 and propagate in the waveguide body 10 in a total reflection manner, and the light rays of different wavelengths coupled into the waveguide body 10 have the same diffraction angle.

[0075] In some embodiments, the optical waveguide 100 further comprises an antireflection film (not shown in the figure) disposed between the super surface coupler 20 and air and / or between the super surface coupler 20 and the waveguide body 10. Specifically, the antireflection film is disposed at any combination of the following positions:

[0076] (1) the contact surface between the in-coupling metasurface grating 210 and air;

[0077] (2) between the in-coupling metasurface grating 210 and the waveguide body 10;

[0078] (3) the contact surface between the out-coupling metasurface grating 220 and air;

[0079] (4) between the out-coupling metasurface grating 220 and the waveguide body 10.

[0080] The antireflection film can reduce the reflection of light at the interface between the super surface coupler 20 and air or the waveguide body 10, and can reduce the loss of energy. The specific forms of the antireflection film include but are not limited to an antireflection film formed by an optical coating layer, an antireflection film formed by a super surface.

[0081] Further, in some embodiments, the antireflection film is disposed at the contact surface between the in-coupling metasurface grating 210 and air, between the in-coupling metasurface grating 210 and the waveguide body 10, the contact surface between the out-coupling metasurface grating 220 and air, and between the out-coupling metasurface grating 220 and the waveguide body 10, which can enable the optical waveguide 100 to have a higher energy utilization rate.

[0082] In some embodiments, the super surface coupler 20 comprises at least two sub-grating layers (not shown in the figure), wherein at least one sub-grating layer is used for coupling light into the waveguide body 10, and at least one sub-grating layer is used for coupling light out of the waveguide body 10, and the sub-grating layers having the same function are stacked along the thickness direction of the waveguide body 10.

[0083] Specifically, the metasurface coupler 20 includes sub-grating layers for coupling light into the waveguide body 10 and sub-grating layers for coupling light out of the waveguide body 10. The sub-grating layers for coupling light into the waveguide body 10 are stacked along the thickness direction of the waveguide body 10 to form a coupling-in metasurface grating 210, and the formed coupling-in metasurface grating 210 has better coupling performance. The coupling-in metasurface grating 210 includes multiple layers of sub-coupling-in grating layers and can be implemented by multiple metasurface superpositions. The sub-grating layers for coupling light out of the waveguide body 10 are stacked along the thickness direction of the waveguide body 10 to form a coupling-out metasurface grating 220, and the formed coupling-out metasurface grating 220 has better coupling performance. The coupling-out metasurface grating 220 includes multiple layers of sub-coupling-out grating layers and can be implemented by multiple metasurface superpositions.

[0084] Further, in some embodiments, the coupling-in metasurface grating 210 and the coupling-out metasurface grating 220 each include at least one layer of sub-grating layers, so that the optical waveguide 100 can efficiently couple energy from the coupling-in metasurface grating 210 to the coupling-out metasurface grating 220 while avoiding unnecessary energy leakage.

[0085] Referring to Figures 8 to 12 In some embodiments, the coupling-in metasurface grating 210 is a transmissive or reflective grating.

[0086] It should be noted that when the coupling-in metasurface grating 210 is a reflective grating, the aforementioned anti-reflection film cannot be disposed between the coupling-in metasurface grating 210 and the waveguide body 10, but other film systems that improve coupling efficiency can be disposed, and the anti-reflection film can still be disposed at other positions.

[0087] Referring to Figures 8 to 12 In some embodiments, the coupling-out metasurface grating 220 is a transmissive or reflective grating.

[0088] It should be noted that when the coupling-out metasurface grating 220 is a reflective grating, the aforementioned anti-reflection film cannot be disposed between the coupling-out metasurface grating 220 and the waveguide body 10, but other film systems that improve coupling efficiency can be disposed, and the anti-reflection film can still be disposed at other positions.

[0089] Referring to Figures 8 to 12 In some embodiments, the coupling-in metasurface grating 210 and the coupling-out metasurface grating 220 are located on the same side of the waveguide body 10 along the thickness direction of the waveguide body 10.

[0090] Referring to Figures 8 to 12 In some embodiments, the coupling-in metasurface grating 210 is located on one side of the waveguide body 10 along the thickness direction of the waveguide body 10, and the coupling-out metasurface grating 220 is located on the other side of the waveguide body 10 along the thickness direction of the waveguide body 10.

[0091] The light waveguide 100 provided in the present application, since the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 can be located on the same side or opposite sides of the thickness direction of the waveguide body 10, so that the relative positions of the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 in the thickness direction of the waveguide body 10 are not limited, which can improve the design freedom of the light waveguide 100.

[0092] Please refer to Figure 9 and Figure 10 , by reasonably configuring the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220, the directions of the in-coupled light and the out-coupled light of the light waveguide 100 can be the same or opposite.

[0093] The working principle of the light waveguide 100 provided in the present application is roughly as follows: the projected image is collimated and then incident on the light waveguide 100, the incident light is irradiated on the in-coupling metasurface grating 210, the in-coupling metasurface grating 210 diffracts the incident light and provides a transverse wave vector to make the light be coupled into the waveguide body 10 and propagate in the form of total reflection, and the light of different wavelengths has the same diffraction angle. The light propagating in the form of total reflection propagates to the out-coupling metasurface grating 220 and obtains a wave vector with the same size and opposite direction to the wave vector provided by the in-coupling metasurface grating 210, so as to be coupled out into the air to realize image dispersionless transmission.

[0094] Please refer to Figure 11 and Figure 12 , in some embodiments, the light waveguide 100 further comprises a filter 30, the filter 30 is stacked with the out-coupling metasurface grating 220, that is, the filter 30 is arranged on the side of the out-coupling metasurface grating 220 away from the waveguide body 10. Alternatively, the filter 30 and the out-coupling metasurface grating 220 are arranged on the two sides of the waveguide body 10 in the thickness direction respectively. The filter 30 is used to pass the light with the same propagation direction as the light and prevent the light with different propagation directions.

[0095] Since there are many design parameters of the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220, if there is a large processing error, ghost image problem may be caused by stray light (the light shown by the dashed line in Figure 11 and Figure 12 ) generated in the in-coupling process, the filter 30 can pass the light with the same propagation direction as the incident light and prevent the crosstalk light from passing, so that the light in the field of view angle range can be coupled out.

[0096] When the filter 30 and the out-coupling metasurface grating 220 are located on the same side of the waveguide thickness direction, the performance of the filter 30 can be considered in the design of the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220. Considering the diffraction efficiency problem caused by the processing error, the stray light can be deflected out of the field of view angle range, and the ghost image problem can be further suppressed in combination with the filter 30. At the same time, the filter 30 can reduce the requirement for processing precision.

[0097] In an optional embodiment, the filter 30 is a band-pass filter 30, which can allow light of a target waveband to pass through while suppressing light of other wavebands.

[0098] Six embodiments are provided below to further illustrate the working principle of the optical waveguide 100 provided in the present application.

[0099] Embodiment 1

[0100] Please refer to Figure 4 The optical waveguide 100 includes a waveguide body 10, an in-coupling metasurface grating 210 and an out-coupling metasurface grating 220. The in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are both transmissive gratings, and the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are located on the same side of the waveguide body 10 thickness direction. The in-coupling light and the out-coupling light of the optical waveguide 100 are in opposite directions.

[0101] Embodiment 2

[0102] Please refer to Figure 8 The optical waveguide 100 includes a waveguide body 10, an in-coupling metasurface grating 210 and an out-coupling metasurface grating 220. The in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are both transmissive gratings, and the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are located on the same side of the waveguide body 10 thickness direction. The in-coupling light and the out-coupling light of the optical waveguide 100 are in opposite directions.

[0103] Embodiment 3

[0104] Please refer to Figure 9 The optical waveguide 100 includes a waveguide body 10, an in-coupling metasurface grating 210 and an out-coupling metasurface grating 220. The in-coupling metasurface grating 210 is a transmissive grating, and the out-coupling metasurface grating 220 is a reflective grating. The in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are located on opposite sides of the waveguide body 10 thickness direction. The in-coupling light and the out-coupling light of the optical waveguide 100 are in opposite directions.

[0105] Embodiment 4

[0106] Please refer to Figure 10, the optical waveguide 100 includes the waveguide body 10, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are both transmissive gratings, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are located on opposite sides of the thickness direction of the waveguide body 10, and the in-coupling light and the out-coupling light of the optical waveguide 100 are in the same direction.

[0107] Embodiment 5

[0108] See Figure 11 , the optical waveguide 100 includes the waveguide body 10, the in-coupling metasurface grating 210, the out-coupling metasurface grating 220 and the filter 30, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are both reflective gratings, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are located on the same side of the thickness direction of the waveguide body 10, and the filter 30 is arranged on the opposite side of the out-coupling metasurface grating 220 along the waveguide body 10, and the in-coupling light and the out-coupling light of the optical waveguide 100 are in opposite directions.

[0109] Embodiment 6

[0110] See Figure 12 , the optical waveguide 100 includes the waveguide body 10, the in-coupling metasurface grating 210, the out-coupling metasurface grating 220 and the filter 30, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are both reflective gratings, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 are located on the same side of the thickness direction of the waveguide body 10, the filter 30 is arranged on the same side of the out-coupling metasurface grating 220 along the waveguide body 10, and the filter 30 is located on the side of the out-coupling metasurface grating 220 away from the waveguide body 10, and the in-coupling light and the out-coupling light of the optical waveguide 100 are in opposite directions.

[0111] The application also provides a method for designing the above-mentioned optical waveguide 100, the design method comprising the following steps:

[0112] S10: determining the design requirements of the super surface coupler 20 based on the target performance indicators of the optical waveguide 100, wherein the super surface coupler 20 includes the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220.

[0113] The target performance indicators of the optical waveguide 100 include but are not limited to full-color non-dispersive transmission images. The specific design requirements of the super surface coupler 20 are determined according to the target performance indicators of the optical waveguide 100.

[0114] The design requirements of the coupler include but are not limited to non-dispersive diffraction efficiency of RGB light not less than a target value.

[0115] S20: obtaining the initial structure of the super surface coupler 20, and performing simulation based on the initial structure of the super surface coupler 20.

[0116] The source of the initial structure of the metasurface coupler 20 includes but is not limited to random generation, empirical setting, and algorithm-based design of the initial structure of the metasurface coupler 20. The algorithm for designing the initial structure of the metasurface coupler 20 includes but is not limited to a topology optimization algorithm based on a companion simulation.

[0117] According to the initial structure of the metasurface coupler 20, the grating constants and phase gradients of the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 can be determined. Simulation is performed based on the obtained initial structure of the metasurface coupler 20 to obtain the performance of the initial structure of the metasurface coupler 20.

[0118] S30: iteratively updating the metasurface coupler 20 based on the simulation result to update the initial structure of the metasurface coupler 20 until the updated metasurface coupler 20 meets the design requirements.

[0119] Based on the simulation result of step S20, the metasurface coupler 20 is iterated. If the simulation result of step S20 meets the design requirements, since the simulation result meets the design requirements, 0 iterations are performed to obtain the metasurface coupler 20 that meets the design requirements.

[0120] If the simulation result of step S20 does not meet the design requirements, the simulation result is iterated at least once to update the initial structure of the metasurface coupler 20, so that the grating constants and phase gradients of the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 can be changed, and the performance of the metasurface coupler 20 can be changed. The iteration of the initial structure of the metasurface coupler 20 can be realized by changing the parameters of the micro-nano structure, which includes but is not limited to the period, the shape of the micro-nano structure, the size of the micro-nano structure, the aspect ratio, etc.

[0121] The initial structure of the metasurface coupler 20 can be updated by an algorithm. The algorithm for updating the initial structure of the metasurface coupler 20 includes but is not limited to a gradient optimization algorithm.

[0122] S40: outputting the metasurface coupler 20 that meets the design requirements to obtain the optical waveguide 100.

[0123] After obtaining the metasurface coupler 20 that meets the design requirements, the in-coupling metasurface grating 210 and the out-coupling metasurface grating 220 of the metasurface coupler 20 can be determined, and thus the optical waveguide 100 can be obtained.

[0124] The application also provides a near-eye device, which includes the optical waveguide 100 described above. The near-eye device includes but is not limited to an augmented reality device.

[0125] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

Claims

1. An optical waveguide, characterized by, The light waveguide comprises: a waveguide body; a metasurface coupler arranged on the waveguide body, the metasurface coupler being configured to couple light rays of different wavelengths and having the same incident angle into the waveguide body and propagate in a total reflection manner, and the light rays of different wavelengths coupled into the waveguide body have the same diffraction angle; and the metasurface coupler being configured to couple the light rays of different wavelengths coupled into the waveguide body out of the waveguide body at the same exit angle.

2. The optical waveguide of claim 1, wherein, The metasurface coupler has a preset grating constant and a preset phase gradient, so that the metasurface coupler is configured to couple light rays of different wavelengths and having the same incident angle into the waveguide body and propagate in a total reflection manner, and the light rays of different wavelengths coupled into the waveguide body have the same diffraction angle; and the metasurface coupler is configured to couple the light rays of different wavelengths coupled into the waveguide body out of the waveguide body at the same exit angle.

3. The optical waveguide of claim 1, wherein, The metasurface coupler comprises: an in-coupling metasurface grating configured to couple light rays of different wavelengths and having the same incident angle into the waveguide body and propagate in a total reflection manner, and the light rays of different wavelengths coupled into the waveguide body have the same diffraction angle; an out-coupling metasurface grating configured to couple the light rays of different wavelengths coupled into the waveguide body by the in-coupling metasurface grating out of the waveguide body at the same exit angle.

4. The optical waveguide of claim 3, wherein, The metasurface coupler satisfies: wherein, is the phase difference between any point on the metasurface coupler and the center of the metasurface coupler, x is the distance between any point on the metasurface coupler and the center of the metasurface coupler, n s is the refractive index of the in-coupling metasurface grating, θ m is the diffraction angle, n i is the refractive index of the out-coupling metasurface grating, θ i is the incident angle, m is the diffraction order, λ is the wavelength of the light, d is the grating constant of the in-coupling metasurface grating.

5. The optical waveguide of claim 3, wherein, The light waveguide further comprises a filter, the filter is arranged in stack with the out-coupling metasurface grating, or the filter is arranged on two sides of the waveguide body in the thickness direction respectively with the out-coupling metasurface grating.

6. The optical waveguide of claim 3, wherein, The in-coupling metasurface grating and the out-coupling metasurface grating are located on the same side of the waveguide body in the thickness direction; or The in-coupling metasurface grating is located on one side of the waveguide body in the thickness direction, and the out-coupling metasurface grating is located on the other side of the waveguide body in the thickness direction. The in-coupling metasurface grating comprises at least two sub-in-coupling gratings, each of the sub-in-coupling gratings has different characteristic parameters.

7. The optical waveguide of claim 3, wherein, The light waveguide further comprises an anti-reflection film, the anti-reflection film is arranged on the contact surface between the metasurface coupler and air and / or between the metasurface coupler and the waveguide body.

8. The optical waveguide of claim 1, wherein, The metasurface coupler comprises at least two sub-grating layers, each of the sub-grating layers for coupling light rays into the waveguide body is arranged in stack along the thickness direction of the waveguide body; and each of the sub-grating layers for coupling light rays out of the waveguide body is arranged in stack along the thickness direction of the waveguide body.

9. The optical waveguide of claim 1, wherein, The light waveguide comprises any one of claims 1-9.

10. A near-eye device, comprising: ​

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