Optical waveguide device and display apparatus

Abstract

The invention discloses an optical waveguide device and display equipment comprising the same. The optical waveguide device includes: a waveguide substrate provided with a diffraction grating; and the cover plate is arranged opposite to the waveguide substrate, and a small-period grating is arranged on the cover plate corresponding to the diffraction grating. The grating period of the small-period grating is smaller than that of the diffraction grating, and the grating vector of the small-period grating is larger than that of the diffraction grating. The small-period grating is used for weakening or preventing light of a red light wave band and / or a green light wave band and / or a blue light wave band in large-angle incident external environment light from being transmitted to a user view range located on the side, opposite to the cover plate, of the waveguide substrate. Therefore, rainbow-like abnormal light spots in the superimposed image of the virtual image and the real image caused by the external ambient light can be avoided, and the display quality is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical display, and in particular relates to an optical waveguide device and a display apparatus. Background Art

[0002] In the field of augmented reality (AR) and mixed reality (MR), compared with Bird Bath (BB, semi-reflective and semi-transmissive), worm eye (off-axis reflective), free-form prism and other display solutions, the optical waveguide solution is thinner and lighter, and has a larger eye box, so it has broader application prospects.

[0003] In the diffraction optical waveguide solution, the free-space light beam (virtual image) projected by the light engine onto the optical waveguide is converted by the coupling-in area into a light beam transmitted in the optical waveguide substrate in the form of total reflection. The coupling-out area performs the reverse process, converting the light beam part transmitted in the form of total reflection into a free-space light beam to be received by the human eye. On the other hand, after the ambient light (real image) from the real world is incident on the optical waveguide, it is transmitted through the structureless area or transmitted through the zero-order transmission of the coupling-out area to be received by the human eye, so that the virtual image and the real image are superimposed on each other and reach the human eye. In addition to the coupling-in area and the coupling-out area, there may also be one or more intermediate turning areas, which are used to change the transmission direction of the light beam part transmitted in the form of total reflection, and continue the transmission in the form of total reflection in the new direction.

[0004] In existing diffraction waveguide solutions, diffraction gratings are usually used to expand pupils, such as one-dimensional gratings or two-dimensional gratings set in the outcoupling zone and the turning zone. The parameter design of these diffraction gratings needs to meet the RGB three-color transmission in the light engine projection beam, so the grating vector of the diffraction grating cannot be too long, that is, the grating period cannot be too small. However, when such parameter design of the diffraction grating in the optical waveguide meets the conditions of RGB three-color transmission in the light engine projection beam, it will cause the ambient light in the real world to diffract to the human eye and produce rainbow-like abnormal light spots. Figure 1 Shown, Figure 1 -(a) represents a virtual image, Figure 1 -(b) represents the real image, Figure 1 -(c) represents the desired superimposed image, Figure 1 -(d) represents the actual superimposed image. Figure 1 -(d), there is a rainbow-like abnormal light spot A in the actual superimposed image, which affects the display effect. Summary of the invention

[0005] In view of the above problems, the present invention provides an optical waveguide device and a display apparatus capable of avoiding the existence of rainbow-like abnormal light spots in superimposed images.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] An optical waveguide device, comprising:

[0008] A waveguide substrate, wherein a diffraction grating is arranged on the waveguide substrate;

[0009] A cover plate, arranged opposite to the waveguide substrate, wherein a small-period grating is arranged on the cover plate corresponding to the position of the diffraction grating;

[0010] Among them, the grating period of the small-period grating is smaller than the grating period of the diffraction grating, the grating vector of the small-period grating is larger than the grating vector of the diffraction grating, and the small-period grating is used to weaken or prevent the propagation of red light band and / or green light band and / or blue light band in the external ambient light incident at a large angle from reaching the user's field of view located on the side of the waveguide substrate facing away from the cover plate.

[0011] In a preferred solution, the grating period of the small-period grating is 100nm-400nm, and the duty cycle is 0.05-0.95.

[0012] In a preferred embodiment, the small-period grating includes a plurality of sub-divisions having different grating period sizes and / or grating period directions and / or microstructure unit morphologies and / or groove depths and / or refractive indices and / or absorptions.

[0013] In a preferred solution, the external ambient light incident at a large angle is external ambient light with an incident angle of more than 50°.

[0014] In a preferred solution, there is an air gap between the waveguide substrate and the cover plate, or the waveguide substrate and the cover plate are connected to each other via an optical adhesive having a refractive index less than 1.6.

[0015] In a preferred solution, the small-period grating is a one-dimensional grating or a two-dimensional grating.

[0016] In a preferred embodiment, the small-period grating is a surface relief grating or a volume holographic grating.

[0017] In a preferred embodiment, the small-period grating is a two-dimensional grating, and in the two-dimensional direction of the periodic arrangement of the microstructure units, in a parallelogram composed of two sets of opposite sides with two arrangement periods, the relatively small internal angle is 20° to 90°.

[0018] In a preferred solution, the diffraction grating is an outcoupling grating arranged in an outcoupling region of the waveguide substrate and / or a turning grating arranged in a turning region of the waveguide substrate.

[0019] In a preferred solution, the small-period grating is arranged on the surface of the cover plate facing the waveguide substrate and / or on the surface of the cover plate facing away from the waveguide substrate and / or inside the cover plate.

[0020] In a preferred embodiment, the projection of the small-period grating on the waveguide substrate completely covers the diffraction grating.

[0021] In a preferred solution, the small-period grating is provided with one or more layers of coating on a side away from the cover plate or close to the cover plate.

[0022] The present invention also provides a display device, which includes the optical waveguide device as described above.

[0023] The optical waveguide device and the display device provided by the embodiments of the present invention can weaken or prevent the propagation of light in the red light band and / or the green light band and / or the blue light band in the external ambient light incident at a large angle from the cover plate from reaching the user's field of view located on the side of the waveguide substrate facing away from the cover plate, thereby avoiding the presence of rainbow-like abnormal light spots in the superimposed image of the virtual image and the real image caused by the external ambient light, thereby improving the display quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an exemplary illustration of the existence of rainbow-like abnormal light spots in the display effect of the existing optical waveguide device;

[0025] Figure 2 is a schematic diagram of the relative position of the optical waveguide device in an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the principle of the optical waveguide device of the present invention;

[0027] Figure 4a to Figure 4b It is the zero-order transmittance distribution diagram of the small-period grating at different angles and wavelengths in the present invention;

[0028] Figure 5 is a schematic diagram of a dot matrix of a two-dimensional grating embodiment in a small-period grating in an embodiment of the present invention;

[0029] Figures 6a to 6f is a cross-sectional structural diagram of a small-period grating in some optional solutions of the present invention;

[0030] Figures 7a to 7e It is a diagrammatic representation of the position of the small-period grating on the cover plate in some optional solutions of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present invention clearer, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in the accompanying drawings and described according to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] It should be noted that when a component is referred to as being “disposed on” another component, it can be directly on the other component or indirectly on the other component.

[0034] It should also be noted that the same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0035] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0036] As mentioned above, the parameter design of the diffraction grating in the existing optical waveguide, when meeting the conditions for the transmission of the RGB three colors in the light engine projection beam, will cause the ambient light from the real world to diffract to the human eye and produce rainbow-like abnormal light spots. How to eliminate these rainbow-like abnormal light spots is a problem that needs to be solved. After exploration, the inventors of the present invention found that these rainbow-like abnormal light spots are mainly caused by the external ambient light incident at a large angle entering the waveguide substrate and being diffracted by the diffraction grating into the user's field of view. White light can be divided into red light band (R), green light band (G) and blue light band (B). For white light sources with the same incident angle, the diffraction angles of the red light band (R), green light band (G) and blue light band (B) are different, so they are separated into rainbow-like abnormal light spots. Figure 1 -As shown in the dotted circle A in (d). It should be understood that Figure 1-The long strip of abnormal light in (d) is not a gray spot, but a rainbow with color distribution.

[0037] Therefore, in order to solve the above technical problems, the embodiment of the present invention first provides an optical waveguide device, such as Figure 2 As shown, the optical waveguide device 100 comprises a waveguide substrate 10 and a cover plate 20 which are arranged opposite to each other, the waveguide substrate 10 is provided with a diffraction grating 30, and the cover plate 20 is provided with a small period grating 40 at a position corresponding to the diffraction grating 30. It should be noted that, Figure 2 There is no cover plate 20 or waveguide substrate 10 between the small-period grating 40 and the diffraction grating 30 . In other embodiments, there may be a cover plate 20 and / or a waveguide substrate 10 between the small-period grating 40 and the diffraction grating 30 .

[0038] Among them, the grating period of the small-period grating 40 is smaller than the grating period of the diffraction grating 30, and the grating vector of the small-period grating 40 is larger than the grating vector of the diffraction grating 30. The small-period grating 40 can weaken or prevent the propagation of light in the red light band and / or the green light band and / or the blue light band in the external ambient light incident at a large angle from the cover plate 20 from reaching the diffraction grating 30 located on the waveguide substrate 10, so that this part of the light cannot be diffracted by the diffraction grating 30 into the user's field of view located on the side of the waveguide substrate 10 facing away from the cover plate 20, thereby weakening or avoiding the rainbow-like abnormal light spots appearing in the user's field of view.

[0039] In the technical solution provided by the present invention, in the incident direction of the external ambient light, a small-period grating 40 is arranged in front of the diffraction grating 30 located on the waveguide substrate 10, and the small-period grating 40 has a grating period smaller than the diffraction grating 30 and a grating vector larger than the diffraction grating 30, and the external ambient light with different incident angles is selected by adjusting the grating vector on the optical path, so that the small-period grating 40 can weaken or prevent the red light band and / or green light in the external ambient light incident at a large angle from one side of the cover plate 20 The light of the wavelength band and / or blue light band propagates to the diffraction grating 30 located on the waveguide substrate 10, so that this part of the light cannot be diffracted by the diffraction grating 30 and enter the user's field of view located on the side of the waveguide substrate 10 facing away from the cover plate 20, thereby weakening or avoiding the rainbow-like abnormal light spots in the user's field of view; while the external ambient light with a smaller incident angle can pass through the small-period grating 40 and the waveguide substrate 10 in turn, and then enter the user's field of view after being diffracted by the diffraction grating 30 to realize the propagation of the real image. Therefore, the solution of the present invention can avoid the existence of rainbow-like abnormal light spots in the superimposed image of the virtual image and the real image caused by the external ambient light, thereby improving the display quality.

[0040] Figure 3It is a schematic diagram of the principle of the small-period grating of the present invention, showing the normalized projection relationship of the three-dimensional space vector of light in the xy plane. Figure 3 In the figure, the range within the dotted circle is the visible range of the human eye, the inner solid circle corresponds to the air refractive index of 1, the outer solid circle corresponds to the substrate refractive index of n1, and the gray annular area between the two solid circles represents the total reflection area. The light source is projected at the black dot position, and the small period grating 40 has a grating vector of k1, which is normalized according to the peak wavelengths k0B, k0G, and k0R of blue (B), green (G), and red (R), respectively, and can be represented as blue (B), green (G), and red (R) arrows with increasing lengths. For external ambient light incident at a large angle, since k1 is large, the ends of the blue, green, and red arrows have all exceeded the dotted circle, i.e., the visible range of the human eye, and fall into the gray annular area, indicating that the 1st-order transmitted light has entered the cover layer for total reflection propagation, so the 0th-order transmittance of the white light (RGB) at this angle can be greatly reduced, so that the white light at this angle can be weakened or prevented from generating rainbow-like abnormal diffraction spots when passing through the diffraction grating 30 of the waveguide substrate. Corresponding to different requirements, that is, different diffraction gratings 30, the length and orientation of k1 can be adjusted to make the 0th order transmittance the lowest in the target band, for example, only considering blue light, only considering green light, or only considering blue light and green light.

[0041] In a specific solution, the ambient light incident at a large angle is ambient light with an incident angle of more than 50°, that is, the grating parameters of the small-period grating 40 are designed as follows: most of the light in the red light band and / or green light band and / or blue light band in the ambient light with an incident angle of more than 50° is blocked by the small-period grating 40 and cannot propagate to the diffraction grating 30 located on the waveguide substrate 10, so that the 1st-order diffraction light of the diffraction grating 30 cannot enter the user's field of view on the side facing away from the cover plate 20 to become a rainbow-like abnormal light spot, and the ambient light with an incident angle less than 50° can pass through the small-period grating 40 and the diffraction grating 30 on the waveguide substrate 10 in sequence, and then enter the user's field of view through the 0th-order transmission of the diffraction grating 30 to realize the propagation of the real image. When the ambient light with an incident angle less than 50° is severely weakened, the human eye will feel that the field of view is blocked, so it is necessary to ensure a high 0th-order transmittance in the present invention.

[0042] like Figure 4a The figure shows the 0-order transmittance distribution diagram of different elevation angles and different wavelengths realized by a small-period grating embodiment of the present invention. Specifically, the grating period of the small-period grating is 268nm, the duty cycle is 0.59, and the small-period grating is mainly used to weaken blue light and green light incident at large angles. Figure 4aIn the 0th order transmittance of blue light and green light with an incident angle of more than 50° is less than 30%, and most of them are less than 20% or even less than 10%, achieving the expected effect. Red light and green light with an incident angle of less than 50°, and blue light with an incident angle of less than 20° have a 0th order transmittance greater than 85%, so they have good transmittance in a small angle range. The 0th order transmittance of blue light with an incident angle range of 20° to 50° fluctuates, but it is acceptable on the premise of achieving the above effects.

[0043] like Figure 4b The figure shows the 0-order transmittance distribution diagram of different elevation angles and different wavelengths realized by another small-period grating embodiment of the present invention. Specifically, the grating period of the small-period grating is 301nm, the duty cycle is 0.51, and the small-period grating is mainly used to weaken blue light, green light and red light incident at large angles. Figure 4b The 0-level transmittance of blue light, green light and red light with an incident angle of more than 50° is below 15%, and most of them are below 10%, achieving the expected effect. Red light and green light with an incident angle of less than 50°, and blue light with an incident angle of less than 20° all have a 0-level transmittance greater than 85%, so they have good transmittance in a small angle range. The 0-level transmittance of blue light with an incident angle range of 20° to 50° fluctuates, but it is acceptable on the premise of achieving the above effects.

[0044] In a specific solution, the diffraction grating 30 is an out-coupling grating arranged in the out-coupling region of the waveguide substrate 10, and the small-period grating 40 is arranged at a position corresponding to the out-coupling grating on the cover plate 20. In some technical solutions, the diffraction grating 30 also includes a turning grating arranged in the turning region of the waveguide substrate 10, and the small-period grating 40 may be not arranged or arranged at a position corresponding to the turning grating on the cover plate 20. As a preferred solution, in an embodiment of the present invention, the projection of the small-period grating 40 on the waveguide substrate 10 completely covers the diffraction grating 30. In other solutions, the projection of the small-period grating 40 on the waveguide substrate 10 may also expand outward by 0 to 3 mm (excluding 0) or shrink inward by 0 to 3 mm (excluding 0) relative to each side of the diffraction grating 30. In these cases, the cross-sectional view of the waveguide substrate 10 and / or the cover plate 20 may be a flat plate or have a curved surface.

[0045] Wherein, the small-period grating 40 can be a one-dimensional grating or a two-dimensional grating. When the small-period grating 40 is a two-dimensional grating, its grating period in the first dimension and the second dimension is smaller than the period of the diffraction grating 30. As a preferred solution, when the small-period grating 40 is a one-dimensional grating, the grating period of the small-period grating 40 is 50nm to 250nm smaller than the grating period of the diffraction grating 30. When the small-period grating 40 is a two-dimensional grating, the grating period of the small-period grating 40 is 0nm to 250nm smaller than the grating period of the diffraction grating 30; when the small-period grating 40 is an orthogonal two-dimensional grating, the grating period of the small-period grating 40 is 50nm to 250nm smaller than the grating period of the diffraction grating 30. The conversion of the grating period and grating vector of the non-orthogonal two-dimensional grating needs to be multiplied by the angle-related coefficient, so the period is larger. In a further preferred solution, the grating period of the small-period grating 40 may be 100 nm to 400 nm, and the duty cycle may be 0.05 to 0.95.

[0046] As a preferred solution, in the embodiment of the present invention, the small period grating 40 is a two-dimensional grating. Figure 5 The small-period grating 40 includes a substrate 41 and a plurality of microstructure units 42 formed on the substrate 41 and arranged periodically along the first dimension p1 and the second dimension p2. The period of the arrangement of the microstructure units 42 in the first dimension p1 is |p1|, and the period of the arrangement of the microstructure units 42 in the second dimension p2 is |p2|. It should be noted that Figure 5 The microstructure units 42 are shown as dots only to illustrate the array arrangement structure of the microstructure units 42 on the substrate 41, and do not mean that the microstructure units 42 are circular. The shape of the microstructure units 42 can be regular patterns such as circles, ellipses or squares, or other irregular patterns.

[0047] As a preferred solution, in the embodiment of the present invention, refer to Figure 5 In the first dimension direction p1 and the second dimension direction p2 where the microstructure units 42 are periodically arranged, in the parallelogram 43 formed by two sets of opposite sides with two arrangement periods, the angle of the relatively small internal angle α is 20° to 90°. The parallelogram 43 is the repeating unit with the smallest area and the smallest side length, so it is defined as a grating unit. The angle of the relatively small internal angle in the repeated grating unit is 20° to 90°.

[0048] In a specific solution, the small-period grating 40 can be implemented in the form of a surface relief grating or a volume holographic grating. Figures 6a to 6f 1 shows a cross-sectional view of a diffraction grating in some specific embodiments of the present invention. Figure 6aThis is a diagram of the structure of a relief grating surrounded by straight grooves. Figure 6b This is a diagram of the structure of the relief grating with helical teeth. Figure 6c This is a diagram of the structure of the embossed grating with a blazed envelope. Figure 6d This is a diagram of the structure of the relief grating with step envelope. Figure 6e This is a diagram of the structure of the relief grating surrounded by the curved surface. Figure 6f Schematic diagram of the structure of volume holographic grating.

[0049] In the embodiment of the present invention, the small-period grating 40 is composed of at least two optical materials with different optical properties, and the optical properties include refractive index, and / or absorption properties, and / or birefringence properties. Therefore, if the grating is in the air, the air is also considered as an optical material. For materials without birefringence, the optical properties of the material can be comprehensively described by the refractive index and absorption properties. When the two optical materials mainly differ in refractive index, the grating can be divided into a high refractive index part and a low refractive index part.

[0050] For the surface relief grating, the groove depth of the small-period grating 40 can be set in the range of 10nm to 2μm; for the volume holographic grating, the thickness of the small-period grating 40 can be set in the range of 50nm to 100μm. In some specific schemes, the microstructure unit 42 area in the small-period grating 40 is set as the high refractive index part, and the other areas surrounding the microstructure unit 42 area are set as the low refractive index part, the refractive index of the high refractive index part is between 1.5 and 3.0, and the refractive index of the low refractive index part is between 1.0 and 1.5. In other specific schemes, the microstructure unit 42 area in the small-period grating 40 is set as the low refractive index part, and the other areas surrounding the microstructure unit 42 area are set as the high refractive index part.

[0051] For a volume holographic grating with a gradient refractive index, the area of ​​the microstructure unit 42 is determined in this way: taking half of the grating thickness, with the contour line corresponding to the mean refractive index of the optical material as the boundary, the part with a refractive index greater than the mean refractive index is defined as a high refractive index part, and the part with a refractive index less than the mean refractive index is defined as a low refractive index part; the area of ​​the microstructure unit 42 is the part surrounded by the contour line corresponding to the mean refractive index of the optical material, which can be set as a high refractive index part or a low refractive index part.

[0052] In some specific schemes, the small-period grating 40 includes a plurality of sub-divisions with different grating period sizes and / or different grating period directions and / or different morphologies and / or groove depths and / or refractive indices and / or absorptions of microstructure units. Specifically, after the grating parameters of the diffraction grating 30 are set, the specific sites or regions where rainbow-like abnormal light spots exist in the user's field of view can be determined by optical simulation and / or testing, and the specific light band (red light band and / or green light band and / or blue light band) by which the rainbow-like abnormal light spots of each specific site or region are mainly caused is analyzed. According to the analysis results, when setting the grating parameters of the small-period grating 40, corresponding to each specific site or region where rainbow-like abnormal light spots exist, multiple sub-divisions are formed by adjusting the grating period sizes and / or grating period directions of the small-period grating 40 and / or the morphologies and / or groove depths and / or refractive indices and / or absorptions of microstructure units, so as to eliminate the rainbow-like abnormal light spots of each specific site or region in a targeted manner. By setting the small-period grating 40 to include different sub-divisions with different optical characteristics, the rainbow-like abnormal light spots at each specific location or region can be eliminated in a targeted manner, and the following effects can be achieved: (1) At locations where there were no rainbow-like abnormal light spots, the external ambient light incident at a large angle can still be transmitted normally and reach the user's field of view to participate in the display of the real image; (2) At locations or regions where there were rainbow-like abnormal light spots, for the external ambient light incident at a large angle, except for the specific light band that causes the rainbow-like abnormal light spots, the remaining light bands can still be transmitted to the user's field of view to participate in the display of the real image. Therefore, while the generation of rainbow-like abnormal light spots can be weakened or avoided, more external ambient light can be transmitted to the user's field of view to participate in the display of the real image, which can increase the brightness and field of view of the image and improve the display quality.

[0053] In the embodiment of the present invention, the waveguide substrate 10 and / or the cover plate 20 may be made of glass, resin, plastic, transparent ceramic, etc., or a combination of several thereof.

[0054] As a preferred solution, in the embodiment of the present invention, refer to Figure 2, there is an air gap between the waveguide substrate 10 and the cover plate 20. Specifically, the waveguide substrate 10 and the cover plate 20 can be connected to each other through other structural parts (not shown in the figure) or small-area optical glue with a refractive index less than 1.6 so that a certain distance is maintained between the two to form an air gap. In some other embodiments, the waveguide substrate 10 and the cover plate 20 can also be connected to each other through optical glue with a refractive index less than 1.6, that is, the air gap between the two is filled with optical glue with a refractive index less than 1.6 and adhered to each other. Preferably, the refractive index of the optical glue is below 1.2, at this time, the virtual image projected by the optical machine will not pass through the optical glue from the waveguide substrate 10 into the cover plate 20. Therefore, the small-period grating 40 is arranged on the cover plate 20 and is not in direct contact with the waveguide substrate 10, and has no effect on the light propagation of the waveguide substrate 10, thereby avoiding leakage of virtual image information.

[0055] As a preferred solution, in the embodiment of the present invention, refer to Figure 2 , the small-period grating 40 is disposed on the surface of the cover plate 20 facing the waveguide substrate 10. In other specific embodiments: Figure 7a As shown, the small-period grating 40 may also be disposed on the surface of the cover plate 20 facing away from the waveguide substrate 10; Figure 7b As shown, the small-period grating 40 may also be disposed inside the cover plate 20; or, as shown Figure 7c As shown, the small-period grating 40 is respectively arranged on the surface of the cover plate 20 facing the waveguide substrate 10 and the surface facing away from the waveguide substrate 10; or, as shown in Figure 7d As shown, the small-period grating 40 is disposed on the surface of the cover plate 20 facing away from the waveguide substrate 10 and inside the cover plate 20; or, as shown Figure 7e As shown, the small-period grating 40 is respectively disposed on the surface of the cover plate 20 facing the waveguide substrate 10 and the surface facing away from the waveguide substrate 10 as well as inside the cover plate 20 .

[0056] In some embodiments, in order to reduce the rainbow-like abnormal light spots generated by the large-angle external ambient light on the human eye side, a small-period grating located on the inner cover plate is also provided on the waveguide substrate 10 close to the human eye side.

[0057] In an optional solution, in the optical waveguide device 100 , the small-period grating 40 is provided with one or more layers of coating on a side away from the cover plate 20 or on a side close to the cover plate 20 .

[0058] Furthermore, the present invention also provides a display device, which is, for example, an augmented reality (AR) display device or an extended reality (XR) display device or a head-up display device (HUD). The display device includes an imaging device and an optical waveguide device 100 provided in the above embodiment of the present invention, wherein the imaging device is used to generate image light (light carrying virtual image information), the image light is coupled into the waveguide substrate by the coupling-in grating, transmitted to the coupling-out grating via the waveguide substrate, and then coupled out of the waveguide substrate by the coupling-out grating, and transmitted to the user's field of view, so that the human eye can observe the corresponding image information.

[0059] In summary, the optical waveguide device and the display device provided by the above embodiments of the present invention, in the incident direction of external ambient light, by arranging a small-period grating in front of the diffraction grating located on the waveguide substrate, the grating period of the small-period grating is smaller than the grating period of the diffraction grating and the grating vector is larger than the grating vector of the diffraction grating, can weaken or prevent the propagation of light in the red light band and / or the green light band and / or the blue light band in the external ambient light incident at a large angle from the cover plate from reaching the user's field of view located on the side of the waveguide substrate facing away from the cover plate, thereby avoiding the presence of rainbow-like abnormal light spots in the superimposed image of the virtual image and the real image caused by the external ambient light, thereby improving the display quality.

[0060] While the invention has been shown and described with reference to the particular embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims and their equivalents.

Claims

1. An optical waveguide device, characterized in that: include: A waveguide substrate, wherein a diffraction grating is arranged on the waveguide substrate; A cover plate, arranged opposite to the waveguide substrate, wherein a small-period grating is arranged on the cover plate corresponding to the position of the diffraction grating; Among them, the grating period of the small-period grating is smaller than the grating period of the diffraction grating, the grating vector of the small-period grating is larger than the grating vector of the diffraction grating, and the small-period grating is used to weaken or prevent the propagation of red light band and / or green light band and / or blue light band in the external ambient light incident at a large angle from reaching the user's field of view located on the side of the waveguide facing away from the cover plate.

2. The optical waveguide device according to claim 1, characterized in that The grating period of the small-period grating is 100nm-400nm, and the duty cycle is 0.05-0.

95.

3. The optical waveguide device according to claim 1, characterized in that The small-period grating includes a plurality of sub-regions with different grating period sizes and / or grating period directions and / or microstructure unit morphologies and / or groove depths and / or refractive indices and / or absorption.

4. The optical waveguide device according to claim 1, wherein: The external ambient light incident at a large angle is the external ambient light with an incident angle of more than 50°.

5. The optical waveguide device according to claim 1, wherein: There is an air gap between the waveguide substrate and the cover plate, or the waveguide substrate and the cover plate are connected to each other via an optical adhesive with a refractive index less than 1.

6.

6. The optical waveguide device according to any one of claims 1 to 5, characterized in that: The small-period grating is a one-dimensional grating or a two-dimensional grating.

7. The optical waveguide device according to claim 6, characterized in that The small-period grating is a surface relief grating or a volume holographic grating.

8. The optical waveguide device according to claim 6, characterized in that The small-period grating is a two-dimensional grating. In the two-dimensional direction of the periodic arrangement of the microstructure units, in a parallelogram formed by two groups of opposite sides with two arrangement periods, the angle of the relatively small internal angle is 20° to 90°.

9. The optical waveguide device according to claim 1, characterized in that The diffraction grating is an outcoupling grating arranged in an outcoupling region of the waveguide substrate and / or a turning grating arranged in a turning region of the waveguide substrate.

10. The optical waveguide device according to claim 1, wherein: The small-period grating is arranged on the surface of the cover plate facing the waveguide substrate and / or on the surface of the cover plate facing away from the waveguide substrate and / or inside the cover plate.

11. The optical waveguide device according to claim 10, characterized in that The projection of the small-period grating on the waveguide substrate completely covers the diffraction grating.

12. The optical waveguide device according to claim 10, characterized in that The small-period grating is provided with one or more layers of coating away from the cover plate side or close to the cover plate side.

13. A display device, characterized in that: The optical waveguide device comprises the optical waveguide device as claimed in any one of claims 1 to 12.

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