Optical waveguide, display device and vehicle

Abstract

The embodiment of the invention discloses an optical waveguide, a display device and a vehicle, relates to the field of optical structures, and solves the problem of low light utilization rate of a diffraction waveguide. According to the specific scheme, the optical waveguide comprises a transparent body, a first grating and a second grating. The first grating is arranged in the middle of the second grating. Therefore, light coupled into the transparent body by the first grating can be transmitted to the second grating when being transmitted in any direction parallel to the direction of the preset surface, and then is coupled out of the transparent body through the second grating to the viewing side. The light entering the first grating is fully utilized, and the structural compactness of the optical waveguide is improved while the loss is reduced. In addition, the light-in surface and the light-out surface of the optical waveguide face opposite directions, when the optical machine transmits light to the optical waveguide, the optical machine does not shield the light transmitted to the viewing side by the optical waveguide, and the utilization rate is improved. If the optical waveguide is integrated in AR-HUD or virtual image desktop display equipment and the like, the size of the equipment can be reduced. And the user experience is improved.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of optical structures, and in particular, to an optical waveguide, a display device, and a vehicle. Background Art

[0002] As consumers' requirements for display performance increase, various display technologies are seeking breakthroughs. Among them, diffraction waveguides are mainly used to couple the light beam emitted by the optical machine to the human eye. At present, most diffraction waveguides have the problem of low light utilization efficiency. Summary of the invention

[0003] Embodiments of the present application provide an optical waveguide, a display device, and a vehicle to improve the problem of low light utilization efficiency of a diffraction waveguide.

[0004] In order to achieve the above-mentioned purpose, this application adopts the following technical solution.

[0005] In a first aspect, an embodiment of the present application provides an optical waveguide, which includes a transparent body, a first grating, and a second grating. The transparent body has a first surface and a second surface opposite to each other; the first grating is arranged on the first surface; the projection of the first grating on the first surface is the first projection. The second grating is arranged on the first surface or the second surface; the second grating is a ring-shaped structure, and the projection of the second grating on the first surface is the second projection. The area enclosed by the inner contour of the second projection coincides with the first projection; the first grating is used to couple the incident light into the transparent body, and the transparent body is used to transmit the light from the first grating to the second grating. The second grating is used to couple the light from the transparent body out of the transparent body. Since the light coupled out by the second grating comes from the first grating, the area enclosed by the inner contour of the second projection coincides with the first projection, so the light emitted from the first grating in any direction parallel to the direction of the first surface can be propagated to the second grating, and then coupled out of the transparent body to the viewing side through the second grating. As a result, the loss of the light emitted through the first grating is small and the utilization rate is high. In addition, the first projection and the second projection are more compact, and the total area and volume occupied by the first grating and the second grating are smaller, thereby increasing the structural compactness of the optical waveguide.

[0006] In combination with the first aspect, in some achievable methods, the geometric center of the area enclosed by the inner contour of the second projection overlaps with the geometric center of the area enclosed by the outer contour of the second projection. In the process of the incident light being coupled into the transparent body by the first grating and then coupled out through the diffraction points of the second grating, the intensity of the light transmitted to the diffraction points of the second grating is negatively correlated with the distance from the diffraction points to the first grating. Because the geometric center of the area enclosed by the inner contour of the second projection overlaps with the geometric center of the area enclosed by the outer contour of the second projection, the distances from each point on the outer contour of the second grating to the first grating are nearly the same. Therefore, the light intensity of the light from the first grating transmitted to each diffraction point on the outer contour of the second grating is close, and the light intensity coupled out by each diffraction point on the outer contour of the second grating is also close. The light with the same intensity coupled out by the second grating is distributed in concentric circles, and the light intensity distribution of the picture received by the viewing side is more uniform. The better the viewing effect.

[0007] In combination with the first aspect, in some achievable methods, the light incident surface of the first grating and the light emitting surface of the second grating face oppositely. The light entering the viewer's eyes is coupled out from the light emitting surface of the second grating, and the light incident surface of the first grating does not block the light entering the viewer's eyes. The structure for emitting incident light (e.g., an optical machine) is located on the side of the optical waveguide facing the light incident surface of the first grating, and the structure does not block the light entering the viewer's eyes. In addition, after the incident light is diffracted by the first grating, part of the light will be emitted from the side of the first grating away from the light incident surface. The emission direction of this part of the light is parallel to the light coupled out by the second grating, and this part of the light can also enter the viewer's eyes. Part of the light that is not coupled into the transparent body by the first grating can be utilized, further increasing the utilization efficiency of the incident light entering the first grating.

[0008] In combination with the first aspect, in some achievable ways, the second grating includes a first diffraction segment and a second diffraction segment connected to each other, and the second diffraction segment and the first diffraction segment are distributed along the diffraction direction of the first grating. The diffraction efficiency of the second diffraction segment is greater than the diffraction efficiency of the first diffraction segment. Each time the light is diffracted by the diffraction point of the second grating, part of the light is coupled out to the viewing side, and the remaining light continues to propagate in the transparent body. In addition, the greater the diffraction efficiency, the greater the ratio of the intensity of the coupled light after diffraction to the intensity of the light before diffraction. Since the first diffraction segment and the second diffraction segment are distributed along the diffraction direction of the first grating, the light propagating in the diffraction direction must first be diffracted by the diffraction point in the first diffraction segment, and then propagate to the second diffraction segment and be diffracted by the diffraction point in the second diffraction segment. Obviously, the intensity of the light propagating to the diffraction point of the first diffraction segment is greater than the intensity of the light propagating to the diffraction point of the second diffraction segment. The diffraction efficiency of the second diffraction section is greater than that of the first diffraction section. The light propagating in the diffraction direction first couples out a weaker light intensity in the first diffraction section with a smaller diffraction efficiency, and the remaining stronger light continues to diffract in the second diffraction section with a larger diffraction efficiency. This makes the difference between the intensity of the coupled light from the second diffraction section and the intensity of the coupled light from the first diffraction section smaller. The brightness of the coupled light from the first diffraction section and the coupled light from the second diffraction section received by the viewer is closer, and the viewing experience is better.

[0009] In combination with the first aspect, in some feasible methods, the first diffraction section is a ring-shaped structure, and the second diffraction section is a ring-shaped structure. The light propagating in any direction away from the first grating will gradually weaken in intensity as the propagation distance increases. In the process of propagation in any of the aforementioned directions, the light will first be diffracted by the first diffraction section with lower diffraction efficiency. In this process, the intensity of the light propagating in the transparent body is high, and the intensity of the coupled-out light is low, and then it will be diffracted by the second diffraction section with higher diffraction efficiency. In this process, the intensity of the light propagating in the transparent body is low, and the intensity of the coupled-out light is high. The first diffraction section is a ring-shaped structure, and the second diffraction section is a ring-shaped structure. The light propagating in any direction away from the first grating will first be diffracted by the first diffraction section and then by the second diffraction section. Make the intensity of the coupled-out light of the first diffraction section and the coupled-out light of the second diffraction section in any of the aforementioned directions closer, and the brightness closer.

[0010] In combination with the first aspect, in some achievable ways, the size of the first diffraction section along the diffraction direction of the first grating is less than or equal to the size of the first diffraction section along a preset direction, and the preset direction is the radial direction of the first grating and is different from the diffraction direction of the first grating. The size of the second grating with lower diffraction efficiency in the diffraction direction is larger than the size of the second grating with lower diffraction efficiency in the preset direction. Thus, among the light rays coupled into the transparent body by the first grating, the light rays propagating along the diffraction direction of the first grating are diffracted less times in the first diffraction section before entering the second diffraction section. The light rays propagating along the preset direction are diffracted more times in the first diffraction section before entering the second diffraction section. In this way, the number of diffraction times of the light rays with low diffraction efficiency in the diffraction direction is reduced, and the number of diffraction times of the light rays with low diffraction efficiency in the preset direction is increased. The difference in the intensity of the light rays propagating to the second diffraction section along the preset direction and the diffraction direction is smaller, and the intensity of the coupled-out light is closer.

[0011] In combination with the first aspect, in some achievable ways, the projections of the first diffraction section and the second diffraction section on the first surface are rotationally symmetric or centrally symmetric about the geometric center of the first projection. As a result, the intensity of the light coupled out from each diffraction point in the first diffraction section is slightly different, and each diffraction point is distributed in a rotationally symmetric or centrally symmetric manner. The intensity of the light coupled out from each diffraction point in the second diffraction section is slightly different, and is also distributed in a rotationally symmetric or centrally symmetric manner. After the light coupled out from the second grating enters the viewer's eyes, the light with uniform brightness is rotationally symmetric or centrally symmetric, making the brightness of the entire image relatively uniform.

[0012] In combination with the first aspect, in some achievable ways, the projection of the first diffraction section on the first surface is in the shape of a circular ring, an elliptical ring, or a rectangular ring. Thus, diffraction points with the same diffraction efficiency are distributed in the aforementioned shape, and within the aforementioned shape, the intensity of the coupled-out light is relatively uniform. Moreover, the intensity of the light that continues to propagate in the transparent body after diffraction by the aforementioned diffraction points is close, and can continue to propagate in the second diffraction section. This makes the light coupled out of the entire second diffraction section relatively uniform.

[0013] In combination with the first aspect, in some achievable manners, the projection of the second diffraction segment on the first surface is in the shape of a circular ring, an elliptical ring, or a rectangular ring. Thus, diffraction points with the same diffraction efficiency are distributed in the aforementioned shape, and within the aforementioned shape, the intensity of the outcoupled light is relatively uniform.

[0014] In combination with the first aspect, in some achievable manners, the grating depth of the second diffraction section is greater than the grating depth of the first diffraction section. The deeper the grating depth, the greater the diffraction efficiency, and the diffraction efficiency of the second diffraction section is greater than the diffraction efficiency of the first diffraction section.

[0015] In combination with the first aspect, in some achievable ways, the second grating further includes a third diffraction section, the third diffraction section is connected to a side of the second diffraction section away from the first diffraction section, and the diffraction efficiency of the third diffraction section is greater than the diffraction efficiency of the second diffraction section. The light diffracted by the second diffraction section is reflected by the transparent body and coupled out by the third diffraction section, the intensity of the light entering the third diffraction section is less than the intensity of the light entering the second diffraction section, and the diffraction efficiency of the third diffraction section is greater than the diffraction efficiency of the second diffraction section, which can reduce the difference between the intensity of the light coupled out by the second diffraction section and the intensity of the light coupled out by the third diffraction section. Thereby, the intensity uniformity of the light coupled out by each diffraction point of the second grating is increased.

[0016] In combination with the first aspect, in some achievable methods, the optical waveguide further includes: an optical element, the optical element is connected to the side of the first grating away from the light incident surface, and the optical element includes an attenuator or a reflective film. After the incident light is diffracted by the first grating, part of the light will be emitted from the side of the first grating away from the light incident surface, and the intensity of this part of the light is relatively strong. The attenuator can attenuate the energy of the light and reduce the intensity of this part of the light. Similarly, the reflective film can reflect part of the light and reduce the intensity of this part of the light. In this way, the glare of light can be avoided by reducing the intensity of the light. In addition, in an embodiment where the optical element is a reflective film, the reflective film reflects part of the light to the transparent body and then is diffracted by the second grating, thereby avoiding the glare of light while further increasing the utilization rate of the incident light.

[0017] In conjunction with the first aspect, in some achievable manners, the first grating is a two-dimensional grating or a one-dimensional grating. Therefore, the solution provided in the embodiment of the present application can be applicable to a variety of gratings.

[0018] In a second aspect, an embodiment of the present application provides a display device. The display device includes: an optical machine and any one of the optical waveguides provided in the first aspect, the optical machine is used to generate the incident light and input the incident light into the first grating. Since the optical waveguide has a high light utilization rate, it is obvious that the entire display device has a high light utilization rate.

[0019] In a third aspect, an embodiment of the present application provides a vehicle, the vehicle comprising: a vehicle frame and any one of the display devices provided in the second aspect, the display device being connected to the vehicle frame. Thus, the display device has a high utilization rate of light, thereby improving the performance of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1a A schematic diagram of the structure of a vehicle.

[0021] Figure 1b Schematic diagram of the optical path structure of an AR-HUD.

[0022] Figure 2 A schematic diagram of the exploded structure of an optical waveguide provided in an embodiment of the present application.

[0023] Figure 3a A schematic diagram of the structure of a diffraction waveguide in related technology.

[0024] Figure 3b It is another structural schematic diagram of a diffraction waveguide in the related technology.

[0025] Figure 4a A schematic diagram of the structure of an optical waveguide provided in an embodiment of the present application.

[0026] Figure 4b A schematic diagram of the structure of another optical waveguide provided in an embodiment of the present application.

[0027] Figure 5a A schematic structural diagram of a second grating and a first grating provided in an embodiment of the present application.

[0028] Figure 5b A schematic structural diagram of yet another second grating and a first grating provided in an embodiment of the present application.

[0029] Figure 5c A schematic structural diagram of another second grating and a first grating provided in an embodiment of the present application.

[0030] Figure 5d A schematic structural diagram of another second grating and a first grating provided in an embodiment of the present application.

[0031] Figure 6a A schematic diagram of the structure of a second grating and another first grating provided in an embodiment of the present application.

[0032] Figure 6b A schematic structural diagram of another second grating and another first grating provided in an embodiment of the present application.

[0033] Figure 6c for Figure 6b The intensity distribution diagram of light coupled out by the second grating is shown.

[0034] Figure 7a for Figure 3a The intensity distribution of light coupled out of the outcoupling grating in the diffraction waveguide is shown.

[0035] Figure 7b for Figure 3b The intensity distribution of light coupled out of the outcoupling grating in the diffraction waveguide is shown.

[0036] In the figure: 01-diffraction wave; 02-waveguide body; 03-coupling grating; 04-coupling grating; 05-turning grating; 10-display device; 20-vehicle; 21-vehicle frame; 22-windshield; 11-optical machine; 100-optical waveguide; 110-first grating; 120-second grating; 102-second projection; 101-first projection; 121-first diffraction section; 122-second diffraction section; 123-third diffraction section; 130-transparent body; 131-first surface; 132-second surface; 140-optical element. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings.

[0038] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0039] In addition, in the present application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to the changes in the orientation of the components in the drawings.

[0040] Figure 1a FIG. 2 is a schematic diagram of the structure of a vehicle 20. Figure 1a As shown, the vehicle 20 includes a vehicle frame 21 and a display device 10 , and the display device 10 is connected to the vehicle frame 21 .

[0041] The embodiment of the present application does not limit the relative position of the frame 21 and the display device 10. In some embodiments, the display device 10 is integrated into a head up display (HUD), which can project navigation information, instrument information, etc. into the driver's front field of view to prevent the driver from looking down to view this information, thereby affecting driving safety. The image projected by the HUD is reflected by the windshield to form a virtual image outside the vehicle. Among them, the types of HUD include but are not limited to a combined head-up display system (combiner-HUD, C-HUD), a windshield head-up display (windshield-HUD, W-HUD) and an augmented reality head-up display system (augmented reality HUD, AR-HUD).

[0042] In other embodiments, the display device may also be integrated into a near eye display (NED) device. The NED device may be, for example, an augmented reality (AR) device or a virtual reality (VR) device. The AR device may include, but is not limited to, AR glasses or AR helmets, and the VR device may include, but is not limited to, VR glasses or VR helmets. Alternatively, the display device may also be integrated into a desktop display.

[0043] The embodiment of the present application is described by taking the display device 10 integrated into an AR-HUD as an example. Figure 1b This is a schematic diagram of the optical path structure of an AR-HUD. Figure 1b The display device 10 includes an optical engine 11 and an optical waveguide 100. The light emitted by the optical engine 11 enters the optical waveguide 100, and the light propagates in the optical waveguide 100 and then exits. The light emitted by the optical waveguide 100 is projected onto the inner surface of the windshield 22, and is reflected by the windshield 22 and enters the human eye, thereby realizing augmented reality display.

[0044] The embodiment of the present application does not limit the structure of the optical engine 11. Exemplarily, the optical engine 11 includes a picture generation unit (PGU).

[0045] Figure 2 This is a schematic diagram of the exploded structure of an optical waveguide 100 provided in an embodiment of the present application. Figure 2 The optical waveguide 100 includes a first grating 110, a second grating 120 and a transparent body 130. The first grating 110 and the second grating 120 are both disposed on the transparent body 130. The first grating 110 and the second grating 120 can be disposed on the same surface of the transparent body 130, or on different surfaces of the transparent body 130.

[0046] When in use, the optical machine 11 (such as Figure 1b As shown in FIG. 1 , the light carrying the image information is incident on the first grating 110, and the first grating 110 diffracts the incident light and couples it into the transparent body 130. The diffracted light of the first grating 110 is propagated after multiple reflections on the two surfaces of the transparent body 130. When the light propagates to the second grating 120, the intersection of the light and the second grating 120 is the diffraction point, and the light is coupled out of the transparent body 130 at the diffraction point of the second grating 120. Therefore, the second grating 120 has the effect of coupling out and expanding the pupil. The light coupled out of the transparent body 130 is projected onto the windshield 22 (as shown in FIG. 1 ). Figure 1b The light reflects off the inner surface of the lens and enters the viewer's eye after being reflected.

[0047] Figure 3a Schematic diagram of a diffraction waveguide 01 in the related art. Figure 3a , the diffraction waveguide 01 includes a waveguide body 02, an in-coupling grating 03 and an out-coupling grating 04. The in-coupling grating 03 and the out-coupling grating 04 are both arranged on the waveguide body 02, and the in-coupling grating 03 and the out-coupling grating 04 are arranged at intervals; the in-coupling grating 03 is located on one side of the out-coupling grating 04. When the diffraction waveguide 01 is working, light is coupled into the optical waveguide body 02 through the in-coupling grating 03, and the light is reflected multiple times in the optical waveguide body 02 and propagates forward, and the light is coupled out after propagating to the out-coupling grating 04.

[0048] Figure 3a The arrow in the middle indicates the direction of light propagation in the diffraction waveguide 01. Figure 3a It can be seen that only a part of the light emitted by the coupling grating 03 ( Figure 3a The solid arrow part) is coupled into the waveguide body 02, and the remaining part ( Figure 3a The portion indicated by the dotted arrow in the middle is not utilized, resulting in low light utilization efficiency of the diffraction waveguide 01.

[0049] Figure 3b FIG. 1 is another structural diagram of a diffraction waveguide 01 in the related art. Figure 3a and Figure 3b , Figure 3a and Figure 3b The difference is that Figure 3b The diffraction waveguide 01 further includes a turning grating 05, which is arranged on the waveguide body 02 and is located on one side of the coupling-in grating 03. When the diffraction waveguide 01 is working, light is coupled into the optical waveguide body 02 through the coupling-in grating 03, and the light enters the turning grating 05 after being reflected multiple times in the optical waveguide body 02 and propagating forward, and the turning grating 05 changes the transmission direction of the light and couples it into the optical waveguide body 02 again, and the optical waveguide body 02 transmits the light to the coupling-out grating 04 and then couples it out.

[0050] and Figure 3a The example shown is similar. Figure 3b Only a part of the light emitted from the coupling grating 03 is coupled into the optical waveguide body 02. The remaining part is not used, and part of the light emitted from the turning grating 05 is also not used. Figure 3b The dashed arrows in the middle represent unused light, and the light utilization efficiency of the diffraction waveguide 01 is low.

[0051] The embodiment of the present application provides an optical waveguide 100 , which has high efficiency in utilizing incident light.

[0052] like Figure 2As shown, the transparent body 130 includes a first surface 131 and a second surface 132, and the first surface 131 and the second surface 132 are arranged opposite to each other. The projection of the second grating 120 on the first surface 131 is surrounded by the projection of the first grating 110 on the first surface 131. For the convenience of description, the projection of the first grating 110 on the first surface 131 is named as the first projection 101, and the projection of the second grating 120 on the first surface 131 is named as the second projection 102. Figure 2 The areas enclosed by the dotted lines in the first surface 131 are respectively the first projection 101 and the second projection 102. In the embodiment of the present application, the projections are all positive projections. For example, the first projection 101 is the projection of the first grating 110 in the first surface 131 along a direction perpendicular to the first surface 131, and the second projection 102 is the same.

[0053] In the embodiment of the present application, the second grating 120 is an annular structure, and the second projection 102 is also annular. The area enclosed by the inner contours of the first projection 101 and the second projection 102 overlap. In the process of the transparent body 130 transmitting the light from the first grating 110 to the second grating 120, the light of each diffraction direction of the first grating 110 can be coupled out by the second grating 120 after passing through the transparent body 130. The light coupled into the transparent body 130 by the first grating 110 is coupled out to the viewing side by the second grating 120, and the light in the first grating 110 does not need to be turned through the turning grating before entering the second grating 120, thereby reducing the light efficiency loss caused by the turning of the light. The loss of the light emitted through the first grating 110 is small, which improves the utilization rate of the light coupled out by the first grating 110, thereby improving the utilization efficiency of the incident light by the optical waveguide 100.

[0054] In addition, the total area and volume occupied by the first grating 110 and the second grating 120 are smaller, which increases the compactness of the structure of the optical waveguide 100. Figure 3a and Figure 3b Compared to the diffractive waveguide 01 shown, Figure 2 The light emitting surface area of ​​the optical waveguide 100 is larger, the field of view (FOV) is larger, and the user experience is improved. In an embodiment where the optical waveguide 100 is integrated into a device such as an AR-HUD or a virtual desktop display, the volume of the AR-HUD or virtual desktop display can be reduced.

[0055] In the embodiment of the present application, since the first surface 131 and the second surface 132 are arranged relative to each other, the projection of the first grating 110 on the first surface 131 and the projection of the first grating 110 on the second surface 132 have the same shape. The projection of the second grating 120 on the first surface 131 and the projection of the second grating 120 on the second surface 132 have the same shape. The positional relationship of the projections of the first grating 110 and the second grating 120 on the first surface 131 is the same as the positional relationship of the projections of the first grating 110 and the second grating 120 on the second surface 132. The embodiment of the present application is described by taking the orthographic projection of the first grating 110 on the first surface 131 as an example, and the orthographic projection of the first grating 110 on the second surface 132 is the same, which will not be repeated here.

[0056] In the embodiment of the present application, the area enclosed by the inner contours of the first projection 101 and the second projection 102 overlaps, including: the inner contour of the second projection 102 overlaps with the outer contour of the first projection 101. Alternatively, part of the inner contour of the second projection 102 is located inside the outer contour of the first projection 101, and part of the inner contour of the second projection 102 overlaps with part of the outer contour of the first projection 101. Alternatively, the entire inner contour of the second projection 102 is located inside the outer contour of the first projection 101.

[0057] Since light can propagate in the transparent body 130, the embodiment of the present application does not limit the positional relationship between the light incident surface of the first grating 110 and the transparent body 130. For example, the light incident surface of the first grating 110 and the transparent body 130 are respectively located on two opposite sides of the first grating 110. Alternatively, the light incident surface of the first grating 110 and the transparent body 130 are located on the same side of the first grating 110. Similarly, the light incident surface of the second grating 120 and the transparent body 130 can be located on the same side of the second grating 120, or on two opposite sides of the second grating 120.

[0058] The embodiment of the present application does not limit the directions of the incident light and the outgoing light of the optical waveguide 100. For example, Figure 2 The arrow of the incident light represents the direction of the incident light, and the arrow of the outgoing light represents the direction of the outgoing light. Figure 2 As shown, the incident light and the outgoing light directions of the optical waveguide 100 are parallel. In other words, the incident light is input into the first grating 110 from one side of the optical waveguide 100, and is coupled out from the other side of the optical waveguide 100 by the second grating 120. The light incident surface of the first grating 110 is located in the direction of the first grating 110 facing the incident light, and the light exit surface of the second grating 120 is located in the direction of the second grating 120 away from the incident light. In other words, Figure 2 In the embodiment, the light incident surface of the first grating 110 and the light emitting surface of the second grating 120 are oriented in opposite directions, facing opposite sides of the transparent body 130 respectively.

[0059] The light incident surface of the first grating 110 and the light exit surface of the second grating 120 face in opposite directions. Therefore, the directions of incident light and exit light of the optical waveguide 100 are opposite. In this way, when a viewer watches the light exiting the optical waveguide 100 at the light exit side, the light incident surface of the first grating 110 will not block the light entering the viewer's eyes. Figure 1b As shown, the light input side and the light output side of the optical waveguide 100 are located on opposite sides of the optical waveguide 100. The light output side of the optical waveguide 100 is on the side away from the optical engine 11. The optical engine 11 will not block the light on the light output side of the optical waveguide 100. In addition, the overall structure is smaller, more compact, and has a high degree of aggregation.

[0060] Furthermore, in an embodiment where the optical waveguide 100 is integrated in an AR-HUD or a desktop display, since the viewer does not need to view the scenery on the light incident side of the optical waveguide 100 (such as an object or a road scene), the installation of the optical machine 11 on the light output side of the optical waveguide 100 will not affect the use of the AR-HUD or the desktop display, and can also increase the integration of the AR-HUD or the desktop display.

[0061] In addition, in the embodiment where the light incident surface of the first grating 110 and the light emitting surface of the second grating 120 are respectively facing opposite sides of the transparent body 130, the side of the first grating 110 away from the light incident surface and the light emitting surface of the second grating 120 are both facing the same side of the transparent body 130. After the incident light is diffracted by the first grating 110, part of the light will be emitted from the side of the first grating 110 away from the light incident surface, and the emission direction of this part of the light is parallel to the light coupled out of the second grating 120, and this part of the light can also enter the eyes of the viewer. Part of the light that is not coupled into the transparent body 130 by the first grating 110 can be utilized, further increasing the utilization efficiency of the incident light entering the first grating 110.

[0062] In addition, since the areas enclosed by the inner contours of the first projection 101 and the second projection 102 overlap, the projection of the side of the first grating 110 away from the light incident surface on the first surface 131 overlaps with the area enclosed by the inner contour of the second projection 102, and light is emitted from the entire area enclosed by the outer contour of the second projection 102, thereby avoiding the problem of no light being emitted from part of the display area (or a partial area being black).

[0063] In some embodiments of the present application, the optical waveguide 100 further includes an optical element 140, which is connected to the side of the first grating 110 away from the light incident surface, and the optical element 140 includes an attenuator or a reflective film. As mentioned above, after the incident light is diffracted by the first grating 110, part of the light will be emitted from the side of the first grating 110 away from the light incident surface, and the intensity of this part of the light is relatively strong. The attenuator can attenuate the energy of the light, reduce the intensity of this part of the light, and make the light emitted from the light-emitting side of the optical waveguide 100 more uniform. Similarly, the reflective film can reflect part of the light and reduce the intensity of this part of the light. In this way, the glare of the light can be avoided by reducing the intensity of the light. In addition, in the embodiment where the optical element 140 is a reflective film, the reflective film reflects part of the light to the transparent body 130 and then is diffracted by the second grating 120, thereby avoiding the glare of the light while further increasing the utilization rate of the incident light.

[0064] The embodiment of the present application does not limit the connection method between the optical element 140 and the side of the first grating 110 away from the light incident surface. For example, the optical element 140 and the surface of the first grating 110 away from the light incident surface are in contact and connected. Alternatively, the optical element 140 is connected to the surface of the first grating 110 away from the light incident surface through the transparent body 130.

[0065] It is understandable that, in some embodiments, the light incident surface of the first grating 110 and the light emitting surface of the second grating 120 are respectively oriented toward the same side of the transparent body 130. For example, in an embodiment where the area of ​​the first grating 110 is relatively small, although no light is transmitted to the viewer's eyes from the side of the first grating 110 away from the light incident surface, the impact on the picture is relatively small due to the small area. In other words, Figure 1b In the example, the optical engine 11 may be located at the light output side of the optical waveguide 100 .

[0066] The embodiment of the present application does not limit the relative positions of the first grating 110 and the second grating 120 on the transparent body 130. Figure 4a and Figure 4b This is explained as an example.

[0067] In some embodiments, the first grating 110 and the second grating 120 may be disposed on the same surface of the transparent body 130. The surface may face the light incident side of the optical waveguide 100, or may face the light exiting side of the optical waveguide 100. Figure 4a A schematic structural diagram of an optical waveguide 100 provided in an embodiment of the present application. Figure 4a In the embodiment, the first grating 110 and the second grating 120 are both disposed on the first surface 131. In other embodiments, the first grating 110 and the second grating 120 may both be disposed on the second surface 132.

[0068] exist Figure 4aIn the example, the first grating 110 and the second grating 120 are connected to each other. The inner edge of the second grating 120 is connected to the outer edge of the first grating 110. In this way, the light-emitting surface of the second grating 120 is arranged around the first grating 110, and the utilization rate of the light transmitted from the first grating 110 to the transparent body 130 is high. In the embodiment in which the light-incident surface of the first grating 110 and the light-emitting surface of the second grating 120 are respectively facing the opposite sides of the transparent body 130, the first grating 110 and the second grating 120 are connected to each other, so that the entire first grating 110 and the second grating 120 both emit light to the eyes of the viewer.

[0069] In some other embodiments, the first grating 110 and the second grating 120 are disposed on two opposite surfaces of the transparent body 130 . Figure 4b This is a schematic diagram of the structure of another optical waveguide 100 provided in an embodiment of the present application. Figure 4b , the first grating 110 is disposed on the first surface 131 , and the second grating 120 is disposed on the second surface 132 . Alternatively, in other embodiments, the first grating 110 is disposed on the second surface 132 , and the second grating 120 is disposed on the first surface 131 .

[0070] exist Figure 4b In the example, the projection of at least part of the outer contour of the first grating 110 on the first surface 131 is located within the area of ​​the second grating 120. In the embodiment where the light incident surface of the first grating 110 and the light exit surface of the second grating 120 are respectively facing opposite sides of the transparent body 130, the light emitted from the side of the first grating 110 away from its light incident surface and the light emitted from the exit surface of the second grating 120 can both be transmitted to the eyes of the viewer. The problem of no light exiting between the first grating 110 and the second grating 120 can be avoided.

[0071] The present embodiment does not limit the structures of the first grating 110 and the second grating 120. For example, the first grating 110 may be a rectangular grating, a blazed grating, or a tilted grating, etc. Similarly, the second grating 120 may be a rectangular grating, a blazed grating, or a tilted grating, etc.

[0072] The embodiment of the present application does not limit the angle of the diffracted light of the first grating 110. Exemplarily, the angle of the diffracted light of the first grating 110 satisfies the total reflection condition of the transparent body 130, so that the diffracted light of the first grating 110 continues to propagate after multiple reflections in the transparent body 130.

[0073] The embodiment of the present application does not limit the shapes of the inner and outer contours of the second grating 120. For example, the inner contour of the second grating 120 may be a circle, a quadrilateral, a pentagon, a triangle, an ellipse, or an irregular shape, etc. Similarly, the outer contour of the second grating 120 may be a circle, a quadrilateral, a pentagon, a triangle, an ellipse, or an irregular shape, etc.

[0074] The embodiment of the present application does not limit the shape of the first grating 110, and the shape of the first grating 110 can be set according to the shape of the inner contour of the second grating 120. In the embodiment where the first grating 110 and the second grating 120 are located on the same surface of the transparent body 130, the shape of the outer contour of the first grating 110 is the same as the shape of the inner contour of the second grating 120. In the embodiment where the first grating 110 and the second grating 120 are located on two opposite surfaces of the transparent body 130, the shape of the first grating 110 can be the same as the shape enclosed by the inner contour of the second grating 120, for example, it can be a circle, a quadrilateral, a pentagon, a triangle, an ellipse or an irregular shape. Alternatively, the first grating 110 can completely cover the shape enclosed by the inner contour of the entire second grating 120.

[0075] In some embodiments of the present application, the geometric center of the inner contour enclosed area of ​​the second projection 102 overlaps with the geometric center of the outer contour enclosed area of ​​the second projection 102. For example, the inner contour of the second projection 102 and the outer contour of the second projection 102 are concentric circles. In this way, the geometric center of the first projection 101 overlaps with the geometric center of the outer contour enclosed area of ​​the second projection 102. In the process of the incident light being coupled into the transparent body 130 by the first grating 110 and then coupled out through the diffraction point of the second grating 120, the intensity of the light transmitted to the diffraction point of the second grating 120 is negatively correlated with the distance from the diffraction point to the first grating 110. The more the geometric center of the area enclosed by the inner contour of the second projection overlaps with the geometric center of the area enclosed by the outer contour of the second projection, the smaller the deviation of the geometric center of the first projection 101 from the outer contour enclosed area of ​​the second projection 102. The closer the light intensity transmitted to each diffraction point on the contour of the second grating 120 is, the closer the light intensity coupled out of each diffraction point on the outer contour of the second grating 120 is, and the more uniform the light coupled out of the entire second grating 120 is, the better the viewing effect is.

[0076] The geometric center of the inner contour enclosed area of ​​the second projection 102 overlaps with the geometric center of the outer contour enclosed area of ​​the second projection 102. This includes: the distance between the geometric center of the inner contour enclosed area of ​​the second projection 102 and the geometric center of the outer contour enclosed area of ​​the second projection 102 is less than or equal to 4 mm, and illustratively, the distance between the geometric center of the inner contour enclosed area of ​​the second projection 102 and the geometric center of the outer contour enclosed area of ​​the second projection 102 is 0, 1 mm, 2 mm, 3 mm or 4 mm, etc.

[0077] The embodiment of the present application does not limit the type of the first grating 110. For example, the first grating 110 can be a one-dimensional grating or a two-dimensional grating. The optical waveguide 100 provided in the embodiment of the present application is applicable to various types of first gratings 110, which are not limited in the embodiment of the present application.

[0078] Figure 5a A schematic structural diagram of a second grating 120 and a first grating 110 provided in an embodiment of the present application. Figure 5a In the example of FIG. 1 , the first grating 110 is a one-dimensional grating, and the first grating 110 has two diffraction orders, each of which has a diffraction direction. For example, the direction of one diffraction order is the a1 direction, and the direction of the other diffraction order is the a2 direction. After the incident light enters the first grating 110, part of the light is coupled into the transparent body 130 along the a1 direction, and part of the light is coupled into the transparent body 130 along the a2 direction. Due to the second projection 102 (such as Figure 2 The area enclosed by the inner contour of the projection 100 (shown) coincides with the first projection 101. The light coupled into the transparent body 130 along the a1 direction and the light coupled into the transparent body 130 along the a2 direction can both be coupled out from the second grating 120, making full use of the light coupled out from the first grating 110. Generally, the light coupled into the transparent body 130 along the a1 direction and the light coupled into the transparent body 130 along the a2 direction from the first grating 110 have similar intensities.

[0079] As mentioned above, the light will be coupled out of the transparent body 130 and enter the eyes of the viewer at the diffraction point of the second grating 120. The light propagates in the process of being reflected by the transparent body 130 and diffracted by the second grating 120. Since the light from the first grating 110 is coupled into the transparent body 130 along the a1 direction and the a2 direction, part of the light is coupled out as the light propagates in the transparent body 130 and is split by the diffraction point of the second grating 120. As the number of times the light is coupled out by the diffraction point of the second grating 120 increases, the intensity of the light transmitted to each diffraction point of the second grating 120 gradually decreases, and the intensity of the light coupled out by the second grating 120 gradually decreases. After the light is diffracted by each diffraction point of the second grating 120 in the a2 direction or the a1 direction, it propagates to each diffraction point of the second grating 120 that is neither in the a2 direction nor in the a1 direction (for example, in the b direction). Obviously, when the diffraction order is the same, the intensity of the light propagating to each diffraction point of the second grating 120 in the a2 direction or the a1 direction is higher than the intensity of the light propagating to each diffraction point of the second grating 120 that is neither in the a2 direction nor in the a1 direction (for example, the b direction). The above-mentioned diffraction order is related to the distance from the diffraction point to the first grating 110, and is also related to the grid line density of the second grating 120. The embodiment of the present application does not limit the grid line density of the second grating 120, and it can be set according to requirements.

[0080] In order to reduce the difference in intensity of light emitted from different diffraction points of the second grating 120 and make the intensity of light coupled from different diffraction points to the viewer's eyes more uniform, in an embodiment of the present application, the diffraction efficiency of the second grating 120 is set.

[0081] Figure 5a In the embodiment, the second grating 120 includes a first diffraction section 121 and a second diffraction section 122, the first diffraction section 121 and the second diffraction section 122 are connected to each other, and the first diffraction section 121 and the second diffraction section 122 are distributed along the diffraction direction of the first grating 110. The diffraction efficiency of the second diffraction section 122 is greater than the diffraction efficiency of the first diffraction section 121. Figure 5a The dashed line is only used to illustrate the area where the first diffraction segment 121 and the second diffraction segment 122 are located.

[0082] Since the light is diffracted once by the diffraction point of the second grating 120, part of the light is coupled out to the viewing side, and the remaining light continues to propagate in the transparent body 130. Since the first diffraction section 121 and the second diffraction section 122 are distributed along the diffraction direction of the first grating 110, the light propagating in the diffraction direction must first be diffracted by the diffraction point in the first diffraction section 121, and then propagate to the second diffraction section 122 and be diffracted by the diffraction point in the second diffraction section 122. Obviously, the intensity of the light propagating to the first diffraction section 121 is greater than the intensity of the light propagating to the second diffraction section 122. In addition, the greater the diffraction efficiency, the greater the ratio of the intensity of the coupled light after diffraction to the intensity of the light before diffraction. If the diffraction efficiency of the second diffraction section 122 is the same as the diffraction efficiency of the first diffraction section 121, the intensity of the coupled light from the second diffraction section 122 is smaller than the intensity of the coupled light from the first diffraction section. The diffraction efficiency of the second diffraction section 122 is greater than that of the first diffraction section 121, and the difference between the intensity of the outcoupled light of the second diffraction section 122 and the intensity of the outcoupled light of the first diffraction section 121 is small. The brightness of the outcoupled light of the first diffraction section 121 and the outcoupled light of the second diffraction section 122 received by the viewer is closer, and the viewing experience is better.

[0083] Figure 5a In the embodiment, the second grating 120 includes two first diffraction segments 121 and two second diffraction segments 122. One first diffraction segment 121 and one second diffraction segment 122 are distributed along the a1 direction, and another first diffraction segment 121 and another second diffraction segment 122 are distributed along the a2 direction.

[0084] Figure 5b A schematic diagram of the structure of another second grating 120 and the first grating 110 provided in an embodiment of the present application. Figure 5b and Figure 5a The difference is that Figure 5b In the embodiment, the second grating 120 includes a first diffraction section 121 and a second diffraction section 122. The first diffraction section 121 is arranged around the first grating 110, and the second diffraction section 122 is arranged around the first diffraction section 121. The first diffraction section 121 and the second diffraction section 122 are distributed along the a1 direction and the a2 direction at the same time.

[0085] In other embodiments, the second grating 120 may include only one first diffraction section 121 and one second diffraction section 122, the first diffraction section 121 and the second diffraction section 122 are distributed along the a1 direction, and the first diffraction section 121 and the second diffraction section 122 are not distributed along the a2 direction. Alternatively, the first diffraction section 121 and the second diffraction section 122 are distributed along the a2 direction, but not along the a1 direction.

[0086] The embodiment of the present application does not limit the positional relationship between the first diffraction section 121 and the second grating 120. For example, the first diffraction section 121 covers at least part of the inner contour of the second grating 120. In other words, the first diffraction section 121 is located at the end of the inner ring of the second grating 120. Alternatively, the distance between the first diffraction section 121 and the inner contour of the second grating 120 is greater than 0.

[0087] Similarly, the embodiment of the present application does not limit the positional relationship between the second diffraction section 122 and the second grating 120. Along the diffraction direction of the first grating 110, the second diffraction section 122 and the first diffraction section 121 are adjacent and connected. For example, the second diffraction section 122 covers at least part of the outer contour of the second grating 120. Alternatively, the distance between the second diffraction section 122 and the outer contour of the second grating 120 is greater than 0.

[0088] like Figure 5b As shown, in the process of light propagating to the second grating 120, it is first diffracted by the diffraction points in the a2 direction or the a1 direction on the inner contour of the second grating 120, and the diffracted light is then propagated to the diffraction points on the inner contour of the second grating 120 that are neither in the a2 direction nor in the a1 direction (for example, in the b direction). Obviously, under the same diffraction order, the intensity of light propagating to the diffraction points in the a2 direction or the a1 direction of the second grating 120 is higher than the intensity of light propagating to the diffraction points in the a2 direction or the a1 direction of the second grating 120 that are neither in the a2 direction nor in the a1 direction (for example, in the b direction). The aforementioned diffraction order is proportional to the distance from the diffraction point to the first grating 110.

[0089] The embodiment of the present application does not limit the relationship between the first diffraction section 121 or the second diffraction section 122 and the first grating 110. For example, in some embodiments, the first diffraction section 121 is a ring structure, and the second diffraction section 122 is a ring structure. In this way, the projection of the first diffraction section 121 on the first surface 131 is arranged around the periphery of the first projection 101, and the second diffraction section 122 is arranged around the periphery of the first diffraction section 121. In other words, the shapes of the first diffraction section 121 and the second diffraction section 122 are both rings connected end to end.

[0090] The greater the distance between the diffraction point of the second grating 120 and the first grating 110, the more times the light needs to be diffracted to propagate to the diffraction point, and the lower the intensity of the light in the transparent body 130. The light propagating in any direction away from the first grating 110 (for example, direction a1, direction a2 or direction b) gradually weakens in intensity as the propagation distance increases. During the propagation process in any of the aforementioned directions, the light needs to be diffracted by the first diffraction section 121 with a lower diffraction efficiency first. During this process, the intensity of the light propagating in the transparent body 130 is higher, and the intensity of the coupled light is lower. Then, the light is diffracted by the second diffraction section 122 with a higher diffraction efficiency. During this process, the intensity of the light propagating in the transparent body 130 is lower, and the intensity of the coupled light is higher. In this way, the intensity of the light coupled out by the second diffraction section 122 in any of the aforementioned directions is more uniform.

[0091] In some embodiments, the sizes of the first diffraction section 121 in various radial directions of the first grating 110 are not completely the same. The radial direction of the first grating 110 is the direction from the center of the first grating 110 to any point of the outer contour of the first grating 110.

[0092] Exemplarily, the size of the first diffraction section 121 along the diffraction direction of the first grating 110 (for example, the a1 direction or the a2 direction) is less than or equal to the size of the first diffraction section 121 along a preset direction. The preset direction is the radial direction of the first grating 110, and the preset direction is different from the a1 direction and the a2 direction. In other words, among the many directions along the radial direction of the first grating 110, the first diffraction section 121 has the smallest size in the diffraction direction of the first grating 110. For example, the size of the first diffraction section 121 along the a1 direction is less than or equal to the size of the first diffraction section 121 along the b direction.

[0093] In this way, among the light rays coupled into the transparent body 230 by the first grating 110, the light rays propagating along the diffraction direction of the first grating 110 (for example, the a1 direction) are diffracted the least times in the first diffraction section 121, and then enter the second diffraction section 122. The light rays propagating along the preset direction (for example, the b direction) are diffracted more times in the first diffraction section 121, and then enter the second diffraction section 122. Therefore, the dimension of the second grating 120 with lower diffraction efficiency in the a2 direction is larger than the dimension of the second grating 120 with lower diffraction efficiency in the b direction. The number of diffraction of the light rays with low diffraction efficiency in the a2 direction is reduced, and the number of diffraction of the light rays with low diffraction efficiency in the b direction is increased. The difference in the intensity of the light rays propagating to the second diffraction section 122 along the a2 direction and the b direction is made smaller, and the intensity of the coupled-out light is closer. In addition, when the distance from the diffraction point along the a1 direction in the second diffraction segment 122 to the first grating 110 is the same as the distance from the diffraction point along the b direction in the second diffraction segment 122 to the first grating 110, the difference in the intensity of the light propagating to the aforementioned two diffraction points is small, the difference in the intensity of the coupled-out light is small, and the coupled-out light intensity is closer.

[0094] Similarly, during the light propagation process, the high-intensity light propagating along the a2 direction needs to pass through multiple low diffraction efficiencies before reaching the second diffraction section 122 with high diffraction efficiency. Correspondingly, the low-intensity light propagating along the b direction needs to pass through fewer low diffraction efficiencies before reaching the second diffraction section 122 with high diffraction efficiency. This makes the intensities of the light entering the second diffraction section 122 along the a2 direction and along the b direction close, and the intensity difference of the light propagating along the a2 direction and the light propagating along the b direction in the second diffraction section 122 being coupled out is small, making the intensity of the light coupled out of the second diffraction section 122 closer.

[0095] Figure 5c A schematic structural diagram of another second grating 120 and a first grating 110 provided in an embodiment of the present application. Figure 5c and Figure 5b The difference is that the shapes of the first diffraction section 121 and the second diffraction section 122 are different.

[0096] exist Figure 5c In the example, the first diffraction segment 121 and the second diffraction segment 122 are both quadrilateral ring structures. The diagonal length of the first diffraction segment 121 along the a1 direction is smaller than the diagonal length of the second diffraction segment 122 along the b direction. The diagonal length of the second diffraction segment 122 along the a1 direction is smaller than the diagonal length of the second diffraction segment 122 along the b direction. In other words, the size of the first diffraction segment 121 along the a1 direction is smaller than the size of the first diffraction segment along the b direction. Obviously, the light intensity of the light propagating along the b direction to each diffraction point in the second diffraction segment 122 is close to the light intensity of the light propagating along the a1 direction to each diffraction point in the second diffraction segment 122, and the coupled-out light intensity is also close.

[0097] Figure 5d A schematic structural diagram of another second grating 120 and a first grating 110 provided in an embodiment of the present application. Figure 5d and Figure 5c The difference is that the shapes of the first diffraction section 121 and the second diffraction section 122 are different. Figure 5d In the figure, the second diffraction segment 122 is an irregular shape connected end to end, and the size of the second diffraction segment 122 along the a1 direction is smaller than the size of the second diffraction segment 122 along the b direction.

[0098] Obviously, Figure 5d In the figure, the light intensity of the light propagating along the b direction to each diffraction point in the second diffraction section 122 is close to the light intensity of the light propagating along the a1 direction to each diffraction point in the second diffraction section 122, and the outcoupled light intensity is also close.

[0099] The embodiment of the present application does not limit the shape of the first diffraction segment 121 and the second diffraction segment 122. For example, the projections of the first diffraction segment 121 and the second diffraction segment 122 on the first surface 131 are rotationally symmetric or centrally symmetric about the geometric center of the first projection 101. With the geometric center of the first projection 101 as the center, the diffraction points with smaller diffraction efficiency are distributed in a rotationally symmetric or centrally symmetric manner, and the intensity of light coupled out of these diffraction points is uniform. The viewer can observe a pattern with consistent brightness that is rotationally symmetric or centrally symmetric. The diffraction points with larger diffraction efficiency are distributed in a rotationally symmetric or centrally symmetric manner. The intensity of light coupled out of these diffraction points is uniform. The viewer can observe a pattern with consistent brightness that is rotationally symmetric or centrally symmetric.

[0100] Exemplarily, the projection of the first diffraction section 121 on the first surface 131 is in the shape of a circular ring, an elliptical ring, or a rectangular ring. In this way, the diffraction points with the same diffraction efficiency are distributed in the aforementioned shape, and within the aforementioned shape, the intensity of the coupled light is relatively uniform. The light coupled out of the entire first diffraction section 121 is relatively uniform. And the intensity of the light that continues to propagate in the transparent body 130 after diffraction by the aforementioned diffraction points is close, and can continue to propagate in the second diffraction section 122. The light coupled out of the entire second diffraction section 122 is relatively uniform.

[0101] Exemplarily, the projection of the second diffraction section 122 on the first surface 131 is in the shape of a circular ring, an elliptical ring, or a rectangular ring. Similarly, during the propagation of light in the transparent body 130, the light coupled out of the entire first diffraction section 121 is relatively uniform. The light coupled out of the entire second diffraction section 122 is relatively uniform.

[0102] In the embodiment of the present application, the second grating 120 may be a one-dimensional grating or a two-dimensional grating. In the embodiment where the second grating 120 is a two-dimensional grating, a grid may be partially located in the first diffraction section 121 and partially located in the second diffraction section 122. In other words, a grid may have a high diffraction efficiency in part and a low diffraction efficiency in part.

[0103] The embodiment of the present application does not limit the parameters that determine the diffraction efficiency in the first diffraction section 121 and the second diffraction section 122. For example, the depth of the grating lines of the second diffraction section 122 is greater than the depth of the grating lines of the first diffraction section 121. The deeper the depth of the grating lines, the higher the diffraction efficiency. Alternatively, the duty cycle of the second diffraction section 122 is greater than the duty cycle of the first diffraction section 121.

[0104] In the embodiment of the present application, the second grating 120 may further include a third diffraction section 123, which is connected to the side of the second diffraction section 122 away from the first diffraction section 121, and the diffraction efficiency of the third diffraction section 123 is greater than the diffraction efficiency of the second diffraction section 122. In this way, the light diffracted by the second diffraction section 122 is reflected by the transparent body 130 and coupled out by the third diffraction section 123, the intensity of the light entering the third diffraction section 123 is less than the intensity of the light entering the second diffraction section 122, and the diffraction efficiency of the third diffraction section 123 is greater than the diffraction efficiency of the second diffraction section 122, which can reduce the difference between the intensity of the light coupled out of the second diffraction section 122 and the intensity of the light coupled out of the third diffraction section 123. Thereby, the intensity uniformity of the light coupled out of each diffraction point of the second grating 120 is increased.

[0105] The structure and shape of the third diffraction segment 123 can refer to the description of the second diffraction segment 122. The relative relationship between the third diffraction segment 123 and the second diffraction segment 122 can refer to the relative relationship between the first diffraction segment 121 and the second diffraction segment 122, which will not be repeated here.

[0106] The embodiment of the present application does not limit the relationship between the sizes of the first diffraction segment 121, the second diffraction segment 122, and the third diffraction segment 123 along the radial direction of the first grating 110. For example, the sizes of the first diffraction segment 121, the second diffraction segment 122, and the third diffraction segment 123 along the a1 direction are the same. Alternatively, the sizes of the first diffraction segment 121, the second diffraction segment 122, and the third diffraction segment 123 along the a1 direction gradually increase or decrease. Alternatively, along the a1 direction, the size of the second diffraction segment 122 is larger than the size of the first diffraction segment 121, and further larger than the size of the third diffraction segment 123.

[0107] Similarly, in some embodiments, the second grating 120 may further include a fourth diffraction segment, a fifth diffraction segment, and so on. The second diffraction segment, the third diffraction segment 123, the fourth diffraction segment, and the fifth diffraction segment are sequentially arranged along the diffraction direction of the first grating 110, and the diffraction efficiencies of the second diffraction segment, the third diffraction segment 123, the fourth diffraction segment, and the fifth diffraction segment increase one by one. For example, Figure 5c In the figure, there is a diffraction section between two adjacent dotted lines, and the diffraction efficiency of each diffraction section is equal.

[0108] Figure 5a , Figure 5b , Figure 5c as well as Figure 5d In the example of FIG. 1 , the first grating 110 is a one-dimensional grating. In some embodiments, the first grating 110 may be a two-dimensional grating. Figure 6a An exemplary introduction is made on the first grating 110 being a two-dimensional grating.

[0109] Figure 6aA schematic structural diagram of a second grating 120 and another first grating 110 provided in an embodiment of the present application. Figure 6a In the embodiment, the first grating 110 is a two-dimensional grating, and the first grating 110 has six diffraction directions, namely c1 direction, c2 direction, c3 direction, c4 direction, c5 direction and c6 direction. The c1 direction is opposite to the c4 direction, the c2 direction is opposite to the c5 direction, and the c3 direction is opposite to the c6 direction. In opposite directions, the intensity of the light coupled into the transparent body 130 by the first grating 110 is slightly different.

[0110] and Figure 5b Similarly, Figure 6a In the example, the second grating 120 includes a first diffraction segment 121 and a second diffraction segment 122 connected to each other, the second diffraction segment 122 and the first diffraction segment 121 are distributed along the diffraction direction of the first grating 110, and the diffraction efficiency of the second diffraction segment 122 is greater than the diffraction efficiency of the first diffraction segment 121.

[0111] Accordingly, in Figure 6a In the example of , the second grating 120 includes a second diffraction section 122 and a first diffraction section 121; the second diffraction section 122 is arranged at the periphery of the first diffraction section 121. The directions from the first diffraction section 121 to the second diffraction section 122 include c1 direction, c2 direction, c3 direction, c4 direction, c5 direction and c6 direction. In other words, Figure 6a In the process of light outputted by the first grating 110 propagating in any direction of c1, c2, c3, c4, c5 and c6, part of the light may be coupled out by the first diffraction section 121 with low diffraction efficiency first, and then part of the light may be coupled out by the second diffraction section 122 with high diffraction efficiency. This makes the brightness of the part of light coupled out by the first diffraction section 121 and the part of light coupled out by the second diffraction section 122 more uniform.

[0112] It can be understood that, in some embodiments, the second grating 120 may include a plurality of second diffraction segments 122 and a plurality of first diffraction segments 121, the plurality of second diffraction segments 122 are arranged at intervals, and the plurality of first diffraction segments 121 are arranged at intervals. One second diffraction segment 122 and one first diffraction segment 121 are distributed along the c1 direction, one second diffraction segment 122 and one first diffraction segment 121 are distributed along the c2 direction, and so on.

[0113] The shapes and positions of the diffraction segments in the second grating 120 are shown in FIG. Figure 5a The shapes and positional relationships of the diffraction segments in the second grating 120 in the illustrated example will not be described in detail herein.

[0114] In the embodiment where the first grating 110 is a two-dimensional grating, the size of the first diffraction section 121 in the diffraction direction of the first grating 110 (for example, any direction of the c1 direction, c2 direction, c3 direction, c4 direction, c5 direction, and c6 direction) is smaller than the size of the first diffraction section 121 in the diffraction direction other than the first grating 110 (for example, the d direction). In this way, since the intensity of the light propagating in the diffraction direction of the first grating 110 in the transparent body 130 is greater than the intensity of the light propagating in the d direction in the transparent body 130, the light is diffracted less times by the first diffraction section 121 in the diffraction direction of the first grating 110 and then propagates to the second diffraction section 122. The light is diffracted more times by the first diffraction section 121 in the d direction and then propagates to the second diffraction section 122. Therefore, when the light propagating along the diffraction direction of the first grating 110 (for example, any direction among the c1 direction, c2 direction, c3 direction, c4 direction, c5 direction and c6 direction) reaches the second diffraction section 122, the light intensity is close to the light intensity of the light propagating along the d direction when it reaches the second diffraction section 122. The light intensity coupled out of the diffraction points in the above two directions of the second diffraction section 122 is close.

[0115] For example, Figure 6b A schematic structural diagram of another second grating 120 and another first grating 110 provided in an embodiment of the present application. Figure 6b and Figure 5c The difference is that the first grating 110 is a two-dimensional grating.

[0116] Figure 6b In the embodiment, the first diffraction section 121 and the second diffraction section 122 are both quadrilateral ring structures. Figure 6b In the example, the size of the first diffraction segment 121 along the d direction is the largest, which is larger than the size of the first diffraction segment 121 along any of the c1 direction, c2 direction, c3 direction, c4 direction, c5 direction and c6 direction.

[0117] Obviously, compared with the partial light coupled out from the first grating 110 to the transparent body 130 propagating in the c1 direction, the partial light coupled out from the first grating 110 to the transparent body 130 propagating in the d direction is diffracted more times by the first diffraction section 121. In this way, the intensities of the partial light propagating in the d direction when it reaches the second diffraction section 122 and the partial light propagating in the c1 direction when it reaches the second diffraction section 122 are close. When the aforementioned two partial light rays continue to propagate in the second diffraction section 122, the intensities of the light coupled out from the second diffraction section 122 are close. The light intensity received by the viewer is closer. The same is true for the partial light coupled out from the first grating 110 to the transparent body 130 propagating in the c2 direction, the c3 direction, the c4 direction, the c5 direction or the c6 direction, which will not be repeated here.

[0118] Figure 6c for Figure 6b FIG. 1 is a diagram showing the intensity distribution of light coupled out of the second grating 120 . Figure 6c In the , the grayer the gray, the stronger the light intensity. Figure 6c It can be seen that the light intensity coupled out of each area of ​​the second grating 120 is relatively uniform. The light intensity coupled out of each diffraction point of the second grating 120 in the c1 direction and the c4 direction is relatively uniform. The light coupled out in the c2 direction, the c3 direction, the c5 direction or the c6 direction is relatively uniform. Figure 6c The efficiency of the optical waveguide of the second grating 120 and the first grating 110 is 1189.1 nit / lm (nits per lumen).

[0119] Figure 7a for Figure 3a The intensity distribution diagram of the light coupled out by the outcoupling grating 04 in the diffraction waveguide 01 is shown. Figure 7a In the figure, the grayer the grayscale, the weaker the light intensity. Figure 7a The light intensity distribution in the image is uneven. Figure 3a The efficiency of the diffraction waveguide 01 is 302.8 nit / lm.

[0120] Figure 7b for Figure 3b The intensity distribution diagram of the light coupled out by the outcoupling grating 04 in the diffraction waveguide 01 is shown. Figure 7b In the figure, the grayer the grayscale, the weaker the light intensity. Figure 7b The light intensity distribution in the Figure 3b The efficiency of the diffraction waveguide 01 is 173.0 nit / lm.

[0121] Description, including Figure 6b The light utilization rate of the light waveguides of the second grating 120 and the first grating 110 is high, and the intensity of the light coupled out of the second grating 120 is uniform, which can provide a better viewing experience for the viewer.

[0122] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An optical waveguide, characterized in that: The optical waveguide comprises: A transparent body; the transparent body has a first surface and a second surface opposite to each other; a first grating, wherein the first grating is disposed on the first surface; a projection of the first grating on the first surface is a first projection; and a second grating, wherein the second grating is arranged on the first surface or the second surface; the second grating is a ring-shaped structure, and the projection of the second grating on the first surface is a second projection; and the area enclosed by the inner contour of the second projection coincides with the first projection; The first grating is used to couple incident light into the transparent body; the transparent body is used to transmit light from the first grating to the second grating; and the second grating is used to couple light from the transparent body out of the transparent body.

2. The optical waveguide according to claim 1, characterized in that A geometric center of an area enclosed by an inner contour of the second projection overlaps with a geometric center of an area enclosed by an outer contour of the second projection.

3. The optical waveguide according to claim 1 or 2, characterized in that The light incident surface of the first grating and the light emitting surface of the second grating face in opposite directions.

4. The optical waveguide according to any one of claims 1 to 3, characterized in that: The second grating includes a first diffraction segment and a second diffraction segment connected to each other, the second diffraction segment and the first diffraction segment are distributed along the diffraction direction of the first grating; the diffraction efficiency of the second diffraction segment is greater than the diffraction efficiency of the first diffraction segment.

5. The optical waveguide according to claim 4, characterized in that The first diffraction section is a ring-shaped structure, and the second diffraction section is a ring-shaped structure.

6. The optical waveguide according to claim 4 or 5, characterized in that A size of the first diffraction section along a diffraction direction of the first grating is smaller than or equal to a size of the first diffraction section along a preset direction, where the preset direction is a radial direction of the first grating and is different from the diffraction direction of the first grating.

7. The optical waveguide according to any one of claims 4 to 6, characterized in that: The projections of the first diffraction segment and the second diffraction segment on the first surface are both rotationally symmetric or centrally symmetric about the geometric center of the first projection.

8. The optical waveguide according to claim 7, characterized in that The projection of the first diffraction segment on the first surface is in the shape of a circular ring, an elliptical ring, or a rectangular ring.

9. The optical waveguide according to claim 7 or 8, characterized in that The projection of the second diffraction segment on the first surface is in the shape of a circular ring, an elliptical ring, or a rectangular ring.

10. The optical waveguide according to any one of claims 4 to 9, characterized in that: The grating line depth of the second diffraction section is greater than the grating line depth of the first diffraction section.

11. The optical waveguide according to any one of claims 4 to 10, characterized in that: The second grating further includes a third diffraction segment, the third diffraction segment is connected to a side of the second diffraction segment away from the first diffraction segment, and the diffraction efficiency of the third diffraction segment is greater than the diffraction efficiency of the second diffraction segment.

12. The optical waveguide according to any one of claims 1 to 11, characterized in that: The optical waveguide further includes an optical element, which is connected to a side of the first grating away from the light incident surface, and includes an attenuator or a reflective film.

13. The optical waveguide according to any one of claims 1 to 12, characterized in that: The first grating is a two-dimensional grating or a one-dimensional grating.

14. A display device, characterized in that: The display device comprises: an optical machine and the optical waveguide according to any one of claims 1 to 13, wherein the optical machine is used to generate the incident light and input the incident light into the first grating.

15. A vehicle, characterized in that: The vehicle comprises: a vehicle frame and the display device according to claim 14, wherein the display device is connected to the vehicle frame.

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