Waveguide AR-HUD system and automobile

Abstract

The invention provides a waveguide AR-HUD system and an automobile, and relates to the technical field of head-up display, the waveguide AR-HUD system comprises a waveguide substrate, a coupling-out grating is arranged on the back of the waveguide substrate along a first direction, aberration correction elements are arranged on the opposite side of the coupling-out grating at intervals, a first air layer is formed between the aberration correction elements and the coupling-out grating, and a second air layer is formed between the first air layer and the coupling-out grating. The opposite side of the waveguide substrate away from the front face of the out-coupling grating is used for arranging the curved windshield glass and the eye box. Incident light enters the coupling-out grating from the front face of the waveguide substrate to generate coupling-out light transmitted towards the first air layer, the coupling-out light sequentially enters the first air layer and the aberration correction element after being refracted, is reversely transmitted to the first air layer, the coupling-out grating and the waveguide substrate after being diffracted by the aberration correction element, and then enters the curved windshield glass. And the light is reflected by the curved windshield glass to enter the eye box. The aberration correction element with the aberration correction function is adopted to reduce or eliminate aberration caused by the curved windshield glass, and driving safety and driving experience are improved.

Description

Technical Field

[0001] The present application relates to the field of head-up display technology, and in particular to a waveguide AR-HUD system and a car. Background Art

[0002] AR-HUD is the abbreviation of augmented reality head-up display technology, which is a development trend of automotive HUD technology. AR-HUD can display richer information content that is integrated with the environment in the distance in front of the driver's field of vision, such as navigation, vehicle speed, rotation speed, driving route, etc. Compared with the traditional HUD system, AR-HUD technology has added virtual reality technology, which can display route navigation integrated with the environment, and identify nearby buildings, cars, pedestrians, etc. in real time. That is, the driver sees not only pure digital information, but also information that can integrate the real world and the virtual world, which greatly improves the driver's driving experience and safety.

[0003] Among them, the optical waveguide AR-HUD is currently recognized by the industry as the next generation display technology. Compared with the AR-HUD based on the free-form reflector system, the optical waveguide AR-HUD has important advantages such as small size and large field of view. However, in the current optical waveguide display technology, the incident light and the outgoing light of the optical waveguide are both parallel light. When applied to the AR-HUD system with a windshield structure, the curved reflection of the windshield will cause aberration, and the existence of aberration will affect the display quality, and then affect the driver's driving experience. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a waveguide AR-HUD system and a car, which can reduce or eliminate the probability of aberration caused by the curved windshield of the car, thereby improving driving safety and driving experience.

[0005] In one aspect of an embodiment of the present application, a waveguide AR-HUD system is provided, including a waveguide substrate, wherein an outcoupling grating is disposed on the back side of the waveguide substrate in a first direction, an aberration correction element is disposed at intervals on the opposite side of the outcoupling grating, a first air layer is formed between the aberration correction element and the outcoupling grating, and a curved windshield and an eye box are disposed on the opposite side of the waveguide substrate away from the front side of the outcoupling grating;

[0006] The incident light is incident on the outcoupling grating from the front side of the waveguide substrate, generating outcoupling light transmitted toward the first air layer. The outcoupling light enters the first air layer and the aberration correction element in sequence after being refracted, and is diffracted by the aberration correction element and then transmitted back to the first air layer, the outcoupling grating, and the waveguide substrate, and then is incident on the curved windshield, and is reflected by the curved windshield and is incident on the eye box.

[0007] Optionally, the aberration correction element includes a quarter wave plate and a diffraction element 201 which are arranged in sequence, and the quarter wave plate is close to the outcoupling grating.

[0008] Optionally, the aberration correction element includes a quarter wave plate and a free-form surface reflector arranged in sequence, and the quarter wave plate is close to the outcoupling grating.

[0009] Optionally, a polarizer is also arranged at intervals on the front side of the waveguide substrate, and a second air layer is formed between the polarizer and the waveguide substrate, and the polarizer is used to block reflected image light of the outcoupled light reflected on the interface between the outcoupled grating and the first air layer.

[0010] Optionally, a mechanical structure is also included, which is connected to the aberration correction element to drive the aberration correction element to rotate around a central axis in a plane formed by the first direction and the second direction, the second direction is the width direction of the waveguide substrate, and the central axis is perpendicular to the plane formed by the first direction and the second direction and passes through the midpoint of the width of the outcoupling grating.

[0011] Optionally, the rotation angle α of the aberration correction element satisfies: L is the width of the waveguide substrate, w is the thickness of the first air layer along the first direction, and the position of the eye box is adjusted by controlling the rotation angle α.

[0012] Optionally, the diffractive element 201 includes three layers of full-color HOE, or a single layer of full-color HOE, or a double layer of HOE in which one layer corresponds to one color and the other layer corresponds to the other two colors.

[0013] Optionally, an optical machine is further included, wherein the optical machine is used to emit the incident light toward the front side of the waveguide substrate, and the image light emitted by the optical machine is polarized light, and the polarized light is orthogonal to the polarization state of the polarizer.

[0014] Another aspect of an embodiment of the present application provides a car, comprising: a waveguide AR-HUD system as described above.

[0015] The waveguide AR-HUD system and automobile provided in the embodiments of the present application are characterized in that a decoupling grating is arranged on the back side of the waveguide substrate along the first direction, an aberration correction element is arranged at intervals on the opposite side of the decoupling grating, a first air layer is formed between the aberration correction element and the decoupling grating, and a curved windshield and an eye box are arranged on the opposite side of the waveguide substrate away from the front side of the decoupling grating.

[0016] The incident light is incident on the out-coupling grating from the front of the waveguide substrate, generating out-coupling light that is transmitted toward the first air layer. The out-coupling light enters the first air layer and the aberration correction element in turn after refraction, and is diffracted by the aberration correction element and then transmitted back to the first air layer, the out-coupling grating, and the waveguide substrate, and then enters the curved windshield, and is reflected by the curved windshield into the eye box. The aberration correction element with aberration correction function is used to reduce or eliminate the aberration caused by the curved windshield, and the spatial position of the eye box is adjusted by mechanically rotating the aberration correction element to improve driving safety and driving experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is the optimized model diagram of the aberration-free waveguide AR-HUD;

[0019] Figure 2 This is one of the schematic diagrams of the waveguide AR-HUD system structure provided in this embodiment;

[0020] Figure 3 This is the second structural schematic diagram of the waveguide AR-HUD system provided in this embodiment;

[0021] Figure 4 This is the third structural schematic diagram of the waveguide AR-HUD system provided in this embodiment.

[0022] Icons: 101-decoupling area; 102-windshield; 201-diffraction element; 202-quarter wave plate; 203-first air layer; 204-decoupling grating; 205-waveguide substrate; 206-second air layer; 207-polarizer; 208-curved windshield; 209-eye box; 210-central axis; F1-first direction; F2-second direction. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0024] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0025] It should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0026] Waveguide displays always contain two indispensable elements: the coupling-in region and the coupling-out region, which respectively represent the regions where the image light is coupled in and coupled out on the waveguide, and whether the turning region is included is subject to the type of actual waveguide and is not limited. The coupling-in region can be a prism, a reflection surface, an SRG grating, or a volume holographic grating, and the coupling-out region can be an SRG grating, a volume holographic grating, or coupled out through the array reflection surface of the array waveguide. In this application, "the coupling-out region is a coupling-out grating" is used as an example to illustrate that the array waveguide is used for coupling out, a polarizer is used to eliminate the interface reflected light, and a quarter glass plate + HOE solution is used to correct the aberration, which is also applicable to the array waveguide and is within the scope of protection of this application.

[0027] Figure 1 This is an optimized model of an aberration-free waveguide AR-HUD, including an optical waveguide outcoupling region 101 and a windshield 102, wherein the light A from the optical waveguide outcoupling region, after being reflected by the windshield, deflects the direction of the reflected light A' due to the curved surface of the windshield, causing aberration. Schematically, Figure 1 The light in is a group of light rays emitted from the outcoupling region with a certain degree of randomness. Therefore, the key issue of this application is to optimize and correct the direction of the light rays from the outcoupling region of the optical waveguide so that they are parallel light rays after passing through the curved windshield.

[0028] Based on this, in order to reduce or eliminate the aberration caused by the curved windshield of the car, the embodiment of the present application provides a waveguide AR-HUD system, please refer to Figure 2As shown, it includes: a waveguide substrate 205, along the first direction F1, a coupling-out grating 204 is arranged on the back side of the waveguide substrate 205, an aberration correction element is arranged at intervals on the opposite side of the coupling-out grating 204, a first air layer 203 is formed between the aberration correction element and the coupling-out grating 204, and a curved windshield 208 and an eye box 209 are arranged on the opposite side of the waveguide substrate 205 away from the front side of the coupling-out grating 204.

[0029] The incident light is incident on the out-coupling grating 204 from the front side of the waveguide substrate 205, generating out-coupling light that is transmitted toward the first air layer 203. The out-coupling light is refracted and enters the first air layer 203 and the aberration correction element in sequence. After being diffracted by the aberration correction element, it is transmitted back to the first air layer 203, the out-coupling grating 204, and the waveguide substrate 205, and then enters the curved windshield 208. It is reflected by the curved windshield 208 and enters the eye box 209.

[0030] The waveguide substrate 205 and the outcoupling grating 204 together constitute an outcoupling region of the waveguide substrate 205 , and this application only focuses on the setting of the outcoupling region.

[0031] In some embodiments, the aberration correction element includes a quarter wave plate 202 and a diffraction element (HOE) 201 arranged in sequence, and the quarter wave plate 202 is close to the outcoupling grating 204; a polarizer 207 is also arranged at intervals on the front side of the waveguide substrate 205, and a second air layer 206 is formed between the polarizer 207 and the waveguide substrate 205.

[0032] Figure 2 In the figure, the incident light A is the image light transmitted by total reflection from the front end of the waveguide substrate 205, which is generally provided by an optical machine; when the incident light A is incident on the outcoupling grating 204 of the waveguide substrate 205, an outcoupling light transmitted downward is generated along the first direction F1, and the outcoupling light is refracted into the first air layer 203, and refracted into the quarter-wave plate 202 and the aberration correction element. The refraction of light between the interfaces can be calculated using the refraction theorem. For simplicity, Figure 2 The system is not expanded, and all are represented by refracted light B. The refracted light B is diffracted by the aberration correction element to form a reverse propagating light C, which passes through the quarter wave plate 202, the first air layer 203, the coupling grating 204, the waveguide substrate 205, the second air layer 206 and the polarizer 207 in sequence and then enters the curved windshield 208, and is reflected to form a light C' and enter the eye box 209, which is the area where the human eye can see the full image.

[0033] The waveguide AR-HUD system provided in the embodiment of the present application adopts an aberration correction element with an aberration correction function to reduce or eliminate the aberration caused by the curved windshield 208.

[0034] In other embodiments, the aberration correction element includes a quarter wave plate and a free-form surface reflector arranged in sequence, and the quarter wave plate is close to the outcoupling grating 204. The free-form surface reflector with a quarter wave plate attached thereto can also achieve the above-mentioned function of reducing or eliminating the aberration caused by the curved windshield 208, wherein the free-form surface reflector is a reflective optical element that optimizes the design of the entire system and can compensate for the aberration caused by the curved windshield 208, and can be designed and implemented using mature optical design software. The quarter glass plate attached thereto is used to change the polarization state so that it can be transmitted through the polarizer 207 on the other side of the waveguide.

[0035] The free-form surface reflector has high reflectivity and low energy loss, but the free-form surface reflector is a curved optical element and occupies a large volume. For waveguide AR-HUD, small volume is the biggest advantage, so it is more advantageous to use the diffraction element 201 to achieve a small volume setting.

[0036] The type of the waveguide substrate 205 of the present application is not limited, and may be an array waveguide, an SRG waveguide, or a volume holographic waveguide. The waveguide substrate 205 may be a one-dimensional pupil expansion waveguide or a two-dimensional pupil expansion waveguide.

[0037] Furthermore, no matter the waveguide substrate 205 is an array waveguide, an SRG waveguide or a volume holographic waveguide, there is a problem of reverse light leakage in its outcoupling region, that is, when viewing the image from the observer's perspective, a bright virtual image located in the distance can be seen, but when viewing from the back of the waveguide substrate 205, a virtual image located in the distance can still be seen with lower brightness. The phenomenon that the image can be seen from the back of the waveguide substrate 205 is the light leakage problem of the waveguide.

[0038] To eliminate the light leakage problem, polarization can be used to control the light to eliminate the interference of stray light caused by the light leakage. Specifically, the polarizer 207 is used to block the reflected image light reflected by the outcoupled light at the interface between the outcoupled grating 204 and the first air layer 203 .

[0039] Still refer to Figure 2 , the refracted light B enters the quarter wave plate 202 once, and then exits the quarter wave plate 202 once. Assuming that the incident image light is linearly polarized light, such as S light, after passing through the quarter wave plate 202 twice, the S light is converted into P light, and the polarizer 207 used allows P light to pass through and blocks S light from passing through. The reflected image light B' is the image light reflected by the outcoupled light on the interface between the outcoupled grating 204 and the first air layer 203, and its polarization state is S polarization. When it enters the polarizer 207, it is blocked by the polarizer 207 and cannot enter the subsequent system. In this system, polarization control is used to eliminate the stray light problem caused by light leakage.

[0040] The polarization state of the reflected image light reflected back from the interface between the out-coupling grating 204 and the first air layer 203 is not changed. After entering the quarter-wave plate and then the diffraction element 201, the reflected light passes through the quarter-wave plate twice, and the polarization state becomes an orthogonal polarization state, and can pass through the polarizer 207 on the other side of the waveguide.

[0041] As mentioned above, the incident light A is provided by an optical machine. The optical machine of the present application is a polarized light machine. The polarized light machine is used in conjunction with the waveguide AR-HUD system to eliminate stray light caused by light leakage. The image light emitted by the optical machine is polarized light, which is orthogonal to the polarization state of the polarizer 207 used on one side of the waveguide. The optical machine may include an LCoS optical machine, a DLP optical machine, etc.

[0042] It should be noted that the polarizer 207, quarter-wave plate 202 and diffraction element 201 in the present application are all thin film materials with very small thickness. Therefore, the thickness of the waveguide substrate 205 is negligible compared to the thickness of the waveguide substrate 205, and the increase in volume can be ignored, so it is convenient for the system to be applied in small-volume scenarios.

[0043] On the other hand, since different drivers have different heights, in order to simultaneously meet the needs of drivers of various heights to watch the AR-HUD, a very large eye box size is required, which greatly increases the size requirements of the waveguide substrate 205, and the difficulty of manufacturing a larger waveguide substrate 205 will increase dramatically.

[0044] Therefore, the present application satisfies the viewing needs of drivers of different heights by adjusting the position of the eye box 209. Specifically, Figure 3 , Figure 4 As shown, the quarter wave plate 202 and the aberration correction element can be regarded as a whole and connected by an external mechanical structure, so that the aberration correction element and the quarter wave plate 202 can rotate around the central axis 210 in the plane formed by the first direction F1 and the second direction F2, and the second direction F2 is the width direction of the waveguide substrate 205, and the central axis 210 is perpendicular to the plane formed by the first direction F1 and the second direction F2, and passes through the midpoint of the width of the outcoupling grating 204.

[0045] Among them, the rotation angle α satisfies: L is the width of the waveguide substrate 205 , w is the thickness of the first air layer 203 along the first direction F1 , and the position of the eye box 209 is adjusted by controlling the rotation angle α.

[0046] like Figure 4 As shown, when α=0, the eye box 209-1 is formed by the light C' after the light C is reflected. When the out-coupling grating 204 is incident on another point of the aberration correction element, the incident light A is offset by α relative to the normal direction of the aberration correction element. According to the grating equation, it can be calculated that the direction of the diffracted light is also deflected relative to the original angle. The specific angle of deflection can be calculated and confirmed by specific setting parameters and the grating equation. Figure 4 In the embodiment, the aberration-corrected light C1 is deflected, and is reflected from another position of the curved windshield 208 to form a light C1', and at the eye box distance, another longitudinally moving eye box 209-2 is formed, thereby realizing the position control of the eye box 209.

[0047] For the diffraction element 201, a volume holographic material with a high refractive index modulation, such as a photopolymer material with a refractive index modulation of 0.05, can support an angular bandwidth in the range of about 6°. For example, the adjustment range of the rotation angle α is [-3°, 3°], which can ensure high diffraction efficiency within the rotation angle range.

[0048] In addition, since the required rotation angle is very small, the thickness of the first air layer 203 is also small, so that the above system can still be kept compact.

[0049] The principle of achieving aberration elimination of the diffraction element 201 is that the diffraction element 201 is essentially the result of interference between the vertically incident image light and a free-form surface wavefront for aberration compensation, and can be optimized and designed according to the relative position and parameters of the curved windshield 208 and the outcoupling area. In addition, when the diffraction element 201 rotates and causes the emitted light C to be emitted to different reflection areas of the curved windshield 208, the optimization of the diffraction element 201 can also be taken into consideration and the design can be realized through optical design software; after the design is realized, the diffraction element 201 can be manufactured by reconstructing the required wavefront through a free-form surface lens and interfering with the vertically incident laser double beam.

[0050] For color display, the diffraction element 201 includes three layers of full-color HOE, or a single layer of full-color HOE, or a double layer of HOE with one layer corresponding to one color and the other layer corresponding to the other two colors. The diffraction element 201 matches the wavelength of the incident light to ensure maximum diffraction efficiency, thereby improving energy utilization.

[0051] Although part of the reverse-propagating corrected light will return to the waveguide substrate 205, due to the relatively low designed transmittance (when the optical waveguide is an array waveguide) or diffraction efficiency (when the optical waveguide is a diffraction waveguide), there is still enough light to pass through the waveguide substrate 205, be incident on the curved windshield 208, be reflected and enter the eye box 209.

[0052] For the array waveguide, the out-coupling light in the out-coupling area is the total reflected light and the partially reflected light coupled out from the waveguide substrate 205, rather than the light being incident on the out-coupling grating 204 plane and directly coupled out. Although the out-coupling method is different, there is reverse light leakage at the interface between the waveguide substrate 205 and the first air layer 203, which can be eliminated in the above system.

[0053] In summary, the waveguide AR-HUD system provided in the embodiment of the present application designs the outcoupling area of ​​the waveguide, introduces an aberration correction element, and can be used for aberration correction. The presence of two air layers separates the function of the waveguide from the aberration correction function, which is convenient for design, processing and manufacturing; and the aberration correction element is rotated in combination with the mechanical structure to adjust the position of the eye box 209. At the same time, polarization control means are used to eliminate the interference of stray light caused by reverse light leakage of the waveguide, so as to realize a waveguide AR-HUD system without stray light interference, with aberration correction capability and eye box 209 adjustment capability. The above-mentioned setting ensures a relatively compact volume of the system, which can be suitable for miniaturized applications.

[0054] On this basis, an embodiment of the present application also discloses a car, including a waveguide AR-HUD system as described above.

[0055] When the above-mentioned waveguide AR-HUD system is applied to a car, an on-board AR-HUD can be formed to solve the aberration problem caused by the existing curved windshield 208 and the position adjustment problem of the eye box 209 to accommodate drivers of different heights; in addition, polarization control is used to eliminate stray light interference caused by reverse light leakage, thereby improving driving safety and driving experience.

[0056] The car includes the same structure and beneficial effects as the waveguide AR-HUD system in the aforementioned embodiment. The structure and beneficial effects of the waveguide AR-HUD system have been described in detail in the aforementioned embodiment and will not be repeated here.

[0057] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A waveguide AR-HUD system, characterized in that: include: A waveguide substrate, wherein a coupling-out grating is arranged on the back side of the waveguide substrate along a first direction, an aberration correction element is arranged at intervals on the opposite side of the coupling-out grating, a first air layer is formed between the aberration correction element and the coupling-out grating, and a curved windshield and an eye box are arranged on the opposite side of the waveguide substrate away from the front side of the coupling-out grating; The incident light is incident on the outcoupling grating from the front side of the waveguide substrate, generating outcoupling light transmitted toward the first air layer. The outcoupling light enters the first air layer and the aberration correction element in sequence after being refracted, and is diffracted by the aberration correction element and then transmitted back to the first air layer, the outcoupling grating, and the waveguide substrate, and then is incident on the curved windshield, and is reflected by the curved windshield and is incident on the eye box.

2. The waveguide AR-HUD system according to claim 1, characterized in that: The aberration correction element comprises a quarter wave plate and a diffraction element which are arranged in sequence, and the quarter wave plate is close to the outcoupling grating.

3. The waveguide AR-HUD system according to claim 1, characterized in that: The aberration correction element comprises a quarter wave plate and a free-form surface reflector which are arranged in sequence, and the quarter wave plate is close to the outcoupling grating.

4. The waveguide AR-HUD system according to claim 2 or 3, characterized in that: A quarter wave plate is also arranged between the first air layer and the aberration correction element, and a polarizer is also arranged on the front side of the waveguide substrate to form a second air layer between the polarizer and the waveguide substrate. The polarizer is used to block the reflected image light of the outcoupled light reflected at the interface between the outcoupled grating and the first air layer.

5. The waveguide AR-HUD system according to any one of claims 1 to 3, characterized in that: It also includes a mechanical structure, which is connected to the aberration correction element to drive the aberration correction element to rotate around a central axis in a plane formed by the first direction and the second direction, wherein the second direction is the width direction of the waveguide substrate, and the central axis is perpendicular to the plane formed by the first direction and the second direction and passes through the midpoint of the width of the outcoupling grating.

6. The waveguide AR-HUD system according to claim 5, characterized in that: The rotation angle α of the aberration correction element satisfies: L is the width of the waveguide substrate, w is the thickness of the first air layer along the first direction, and the position of the eye box is adjusted by controlling the rotation angle α.

7. The waveguide AR-HUD system according to claim 2, characterized in that: The diffractive element includes a three-layer full-color HOE, or a single-layer full-color HOE, or a double-layer HOE in which one layer corresponds to one color and the other layer corresponds to the other two colors.

8. The waveguide AR-HUD system according to claim 4, characterized in that: It also includes an optical machine, which is used to emit the incident light toward the front side of the waveguide substrate, and the optical machine is used to emit image light as polarized light, and the polarized light is orthogonal to the polarization state of the polarizer.

9. A car, characterized in that: A waveguide AR-HUD system comprising the waveguide AR-HUD system as claimed in any one of claims 1 to 8.

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