Optical waveguide structure and head-up display device

Abstract

The invention relates to an optical waveguide structure and a head-up display device. The optical waveguide structure comprises a first optical waveguide and a second optical waveguide. The first optical waveguide comprises a plurality of sub-prisms; the plurality of sub-prisms comprise a plurality of first sub-prisms which are sequentially arranged along the first direction and a plurality of second sub-prisms which are sequentially arranged along the first direction; the plurality of second sub-prisms and the plurality of first sub-prisms are symmetrically arranged along the axis of the first coupling inlet of the first optical waveguide; a second coupling inlet of the second optical waveguide is coupled with a first coupling outlet of the first optical waveguide, and the second optical waveguide comprises a plurality of sub-prisms; the plurality of sub-prisms comprise a plurality of third sub-prisms which are sequentially arranged along the second direction and a plurality of fourth sub-prisms which are sequentially arranged along the second direction; the plurality of fourth sub-prisms and the plurality of third sub-prisms are symmetrically arranged along the axis of the second coupling inlet; the first direction is perpendicular to the second direction. The size of the head-up display device can be reduced.

Description

Technical Field

[0001] This application relates to the field of head-up display technology, and more specifically, to an optical waveguide structure and a head-up display device. Background Technology

[0002] Automotive HUDs (Head-Up Displays) project vehicle information onto the windshield, allowing drivers to access information without looking down. However, to meet the distance requirements between the eyepiece and the exit pupil, HUDs in related technologies require unidirectional pupil expansion to enlarge the original exit pupil of the image generation unit. The linear magnification characteristic of unidirectional pupil expansion necessitates an original exit pupil diameter of 15mm to 20mm. This requirement results in a relatively large HUD size, conflicting with the current trend towards miniaturization and integration in automobiles. Summary of the Invention

[0003] The technical problem to be solved by this application is to provide an optical waveguide structure and a head-up display device, which addresses the above-mentioned deficiencies of the prior art.

[0004] The technical solution adopted by this application to solve its technical problem is: constructing an optical waveguide structure, including: A first optical waveguide includes multiple sub-prisms; the multiple sub-prisms include: Multiple first sub-prisms, arranged sequentially along a first direction; and A plurality of second sub-prisms are arranged sequentially along the first direction; the plurality of second sub-prisms and the plurality of first sub-prisms are symmetrically arranged along the axis of the first coupling entrance of the first optical waveguide; and The second optical waveguide has a second coupling inlet coupled to the first coupling outlet of the first optical waveguide, and includes a plurality of sub-prisms; the plurality of sub-prisms include: Multiple third sub-prisms, arranged sequentially along the second direction; and Multiple fourth sub-prisms are arranged sequentially along the second direction; the multiple fourth sub-prisms and the multiple third sub-prisms are symmetrically arranged along the axis of the second coupling entrance; Wherein, the first direction is perpendicular to the second direction.

[0005] Furthermore, each of the multiple sub-prisms of the first optical waveguide and the multiple sub-prisms of the second optical waveguide includes a first side surface, a second side surface, an upper surface, and a lower surface; the first side surface is an inclined surface; The first side surfaces of the plurality of sub-prisms of the first optical waveguide are all located on the side of the sub-prism close to the first coupling entrance along the first direction; The first side of each of the plurality of sub-prisms of the second optical waveguide is located on the side of the sub-prism close to the second coupling entrance along the second direction.

[0006] Furthermore, the tangent of the angle between the first side surface and the lower surface of the sub-prism of the first optical waveguide is greater than or equal to the ratio of the thickness of the first optical waveguide to the length of the lower surface of the sub-prism along the first direction; and / or, The tangent of the angle between the first side surface and the lower surface of the sub-prism of the second optical waveguide is greater than or equal to the ratio of the thickness of the second optical waveguide to the length of the lower surface of the sub-prism along the second direction.

[0007] Furthermore, the length of the first coupling outlet in the second direction is obtained using Formula 1: ;Formula 1 in, The dimension of the first coupling outlet in the second direction; The thickness of the second optical waveguide; The angle between the first side surface and the lower surface of the sub-prism of the second optical waveguide The tangent value.

[0008] Furthermore, any two sub-prisms symmetrically arranged along the axis of the first coupling entrance of the first optical waveguide have equal reflectivity and equal transmittance on their first side surfaces; for any two sub-prisms of the first optical waveguide, the one with the smaller distance from the first coupling entrance along the first direction has a first side surface reflectivity less than or equal to the other one; and / or, Any two sub-prisms symmetrically arranged along the axis of the second coupling entrance of the second optical waveguide have equal reflectivity and transmittance on their first side surfaces; for any two sub-prisms of the second optical waveguide, the reflectivity of the first side surface of one of the two sub-prisms with the smaller distance from the second coupling entrance along the second direction is less than or equal to that of the other one.

[0009] Furthermore, the sum of the reflectivity and the transmittance is 1.

[0010] Furthermore, the length of the first optical waveguide in the first direction is greater than or equal to the product of the number of its plurality of sub-prisms and the length of the lower surface of the sub-prisms in the first direction; and / or, The length of the second optical waveguide in the second direction is greater than or equal to the product of the number of its plurality of sub-prisms and the length of the lower surface of the sub-prism in the first direction.

[0011] Furthermore, the number of the first sub-prisms is greater than or equal to 4 and less than or equal to 8; the number of the second sub-prisms is greater than or equal to 4 and less than or equal to 8; and / or, The number of the third sub-prism is greater than or equal to 4 and less than or equal to 8; the number of the fourth sub-prism is greater than or equal to 4 and less than or equal to 8.

[0012] Furthermore, the refractive index of the sub-prism of the first optical waveguide is greater than or equal to 1.5 and less than or equal to 2; and / or, The refractive index of the sub-prism of the second optical waveguide is greater than or equal to 1.5 and less than or equal to 2.

[0013] A head-up display device is constructed, comprising an image generation unit and an optical waveguide structure as described in any of the preceding claims; the output pupil of the image generation unit is coupled to the first coupling inlet.

[0014] Furthermore, the plurality of sub-prisms of the first optical waveguide and the plurality of sub-prisms of the second optical waveguide each include an inclined first side surface; the first side surface of the plurality of sub-prisms of the first optical waveguide is located on the side of the sub-prism closer to the first coupling entrance along the first direction; the first side surface of the plurality of sub-prisms of the second optical waveguide is located on the side of the sub-prism closer to the second coupling entrance along the second direction. The size of the output pupil in the first direction is obtained using Formula 2: ;Formula 2 in, The size of the output pupil in the first direction; The thickness of the first optical waveguide; The angle between the first side surface and the lower surface of the sub-prism of the first optical waveguide The tangent value; The dimension of the output pupil in the second direction is obtained using Formula 3: ;Formula 3 in, The size of the output pupil in the second direction; The thickness of the second optical waveguide; The angle between the first side surface and the lower surface of the sub-prism of the second optical waveguide The tangent value.

[0015] Implementing the technical solution constructed in this application has at least the following beneficial effects: This application achieves a two-dimensional array of optical waveguides by setting sub-prisms of the first optical waveguide extending along a first direction and sub-prisms of the second optical waveguide extending along a second direction, enabling hierarchical bidirectional pupil expansion along both directions. By symmetrically arranging multiple first and second sub-prisms along their first coupling entrances and multiple third and fourth sub-prisms along their second coupling entrances, the first coupling entrances are positioned approximately at the center of the optical waveguide structure. This structural arrangement allows the head-up display device to meet requirements while reducing its overall volume to less than 3L, resolving the conflict between the exit pupil diameter and overall volume, and facilitating the miniaturization and integration of vehicles. Attached Figure Description

[0016] The present application will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic diagram of the structure of a head-up display device according to an embodiment of this application; Figure 2 yes Figure 1 A schematic diagram of the head-up display device shown from another angle; Figure 3 yes Figure 1 A schematic diagram of the structure of the first optical waveguide in the diagram; Figure 4 yes Figure 3 The front view of the first optical waveguide shown; Figure 5 yes Figure 3 A schematic diagram of the structure of the first sub-prism in the middle; Figure 6 yes Figure 1 A schematic diagram of the structure of the second optical waveguide in the diagram; Figure 7 yes Figure 6 The front view of the second optical waveguide shown; Figure 8 yes Figure 1 The diagram shows the light transmission effect of the head-up display device during application. Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of this application, the specific embodiments of this application are now described in detail with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0018] In the description of this application, it should be understood that the terms "longitudinal", "lateral", "up", "down", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0020] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0022] like Figures 1 to 8 As shown, this application constructs an optical waveguide structure 20 and a head-up display device 1 incorporating the optical waveguide structure 20. The head-up display device 1 can be applied to devices such as vehicles, aircraft, and ships that require user head-up display. The head-up display device 1 also includes an image generation unit 10 (PGU), used to receive digital information from an in-vehicle system (e.g., navigation, speedometer), convert the digital information into an optical image that meets requirements for parameters such as FOV and brightness, and then output it. The optical waveguide structure 20 is used to expand the pupil of the optical image output by the image generation unit 10, so that the optical image reaching the eye box meets the requirements.

[0023] The image generation unit 10 may include an output pupil 101 that outputs an optical image, which may be coupled to the coupling inlet of the optical waveguide structure 20.

[0024] Specifically, such as Figure 1 and Figure 2 As shown, the output pupil 101 can be circular with a diameter of R.

[0025] In some other embodiments, the output pupil 101 may also be in other shapes such as ellipse, rectangle, polygon, etc.

[0026] It should be noted that the image generation unit 10 may specifically include a display chip, an imaging system, an electronic system, and an optical structure. The display chip may specifically be a self-emissive image source such as OLED or Micro LED. Of course, when the display chip is a transmissive or reflective image source such as TTF, Lcos, or DLP, in this embodiment, the image generation unit 10 will also include a light source and an illumination system. The image generation unit 10 can be implemented using existing technologies, so it will not be elaborated upon here.

[0027] like Figures 3 to 7 As shown, in some embodiments, the optical waveguide structure 20 may include a first optical waveguide 21 and a second optical waveguide 22. Along the transmission path of the optical image, the first optical waveguide 21 is disposed between the second optical waveguide 22 and the image generation unit 10. The first optical waveguide 21 may include a first coupling inlet 2101 and a first coupling outlet 2102, and the second optical waveguide 22 includes a second coupling inlet 2201 and a second coupling outlet 2202.

[0028] In this design, the output pupil 101 of the image generation unit 10 is coupled to the first coupling inlet 2101, and the first coupling outlet 2102 is coupled to the second coupling inlet 2201. Thus, the optical image output from the output pupil 101 of the image generation unit 10 can sequentially pass through the expansion pupils of the first optical waveguide 21 and the second optical waveguide 22, ensuring that the optical image meets the size requirements when it finally reaches the driver's eye box.

[0029] Specifically, such as Figure 3 and Figure 4 As shown, the first optical waveguide 21 may include a first portion 211 and a second portion 212 symmetrically arranged along a first direction X. Specifically, the first portion 211 and the second portion 212 may be symmetrically arranged along the first direction X with the axis L1 of the first coupling inlet 2101 as the axis of symmetry.

[0030] Both the first part 211 and the second part 212 include multiple sub-prisms arranged sequentially along the first direction X. The sub-prisms of the first part 211 are defined as first sub-prisms 2111, and the sub-prisms of the second part 212 are defined as second sub-prisms 2121. The number of first sub-prisms 2111 and second sub-prisms 2121 is the same, and each second sub-prism 2121 has a corresponding first sub-prism 2111. They are symmetrically arranged about the axis L1 of the first coupling entrance 2101. This allows the first optical waveguide 21 to expand its pupil in the first direction X.

[0031] like Figure 6 and Figure 7 As shown, the second optical waveguide 22 may include a third part 221 and a fourth part 222 symmetrically arranged along the second direction Y. Specifically, the third part 221 and the fourth part 222 may be symmetrically arranged along the second direction Y with the axis L2 of the second coupling inlet 2201 as the axis of symmetry.

[0032] Both the third part 221 and the fourth part 222 include multiple sub-prisms arranged sequentially along the second direction Y. The sub-prisms of the third part 221 are defined as third sub-prisms 2211, and the sub-prisms of the fourth part 222 are defined as fourth sub-prisms 2221. The number of third sub-prisms 2211 and fourth sub-prisms 2221 is the same, and each fourth sub-prism 2221 has a corresponding third sub-prism 2211. They are symmetrically arranged about the axis L2 of the second coupling entrance 2201. This allows the second optical waveguide 22 to expand its pupil in the second direction Y.

[0033] It should be noted that the extension direction of the axis L1 of the first coupling inlet 2101 roughly coincides with the extension direction of the axis L2 of the second coupling inlet 2201, and is parallel to the thickness direction of the first optical waveguide 21 and the thickness direction of the second optical waveguide 22. The first direction X is perpendicular to the second direction Y, and both the first direction X and the second direction Y are perpendicular to the extension directions of the axes L1 and L2.

[0034] It is important to understand that in practical applications, the pupil dilation effect of the optical waveguide needs to meet the requirement that the exit pupil distance reaches 800mm to 1200mm, and the size of the driver's eye box needs to meet the requirement. That's all. Meanwhile, from the demand side, current autonomous vehicles require head-up displays (HUDs) with lane-level navigation and obstacle warning functions, thus requiring a field of view of at least [insert value here]. .

[0035] Currently, optical waveguide structures can be divided into geometric waveguides and diffractive waveguides. The wavelength dependence of diffractive waveguides can cause red, blue, and green color dispersion, affecting display clarity. For geometric waveguides, unidirectional pupil-expanding waveguide structures are commonly used.

[0036] While unidirectional pupil-expanding waveguide structures can extend the field of view to meet requirements, their overall cost is high. Furthermore, sunlight reflected by the windshield can easily form focused spots within the waveguide, leading to problems such as overheating and brightness degradation in the image generation unit.

[0037] Meanwhile, to meet the aforementioned size requirements, head-up display devices with unidirectional pupil-expanding waveguide structures need an original exit pupil diameter of 15mm to 20mm for their image generation units. Such a large image generation unit not only accounts for over 40% of the total head-up display volume but also forces the waveguide to extend further along the pupil-expanding direction to accommodate the optical path, ultimately weakening the waveguide's core advantage of being thin and compact. Head-up displays constructed in this way generally have an overall volume greater than 5L, making them unsuitable for some vehicle models due to insufficient dashboard space.

[0038] This application effectively suppresses the dispersion phenomenon of traditional diffraction waveguides by setting up an optical waveguide structure 20 with two geometric optical waveguides.

[0039] This application enables the deployment of a two-dimensional array of optical waveguides by setting a sub-prism of the first optical waveguide 21 extending along a first direction and setting a sub-prism of the second optical waveguide 22 extending along a second direction, thereby achieving hierarchical bidirectional pupil expansion along the first and second directions.

[0040] This structural layout allows the head-up display device to achieve an exit pupil distance of 800mm to 1200mm and an eye box size of [missing information - likely related to eye box dimensions]. Above, field of view not less than This meets the requirements and also reduces the volume of the head-up display device to 1.5L to 3L, which is more than 40% smaller than the traditional solution.

[0041] Meanwhile, compared to one-dimensional arrayed waveguides with unidirectional pupil expansion, two-dimensional arrayed waveguide structures have lower production costs, and the hierarchical bidirectional pupil expansion structure can also optimize the propagation path of light and reduce the problem of overheating of the image generation unit caused by sunlight backflow.

[0042] Thus, the head-up display device 1 constructed in this application can meet the core requirements of current intelligent vehicles for head-up display devices, namely large field of view, small size, high performance, and low cost.

[0043] It's important to understand that for head-up display (HUD) devices with unidirectional pupil-expanding waveguide structures in related technologies, the image generation unit is typically located on one side of the waveguide structure. This can lead to optical path misalignment and installation interference issues. During vehicle assembly, the dashboard needs to have relatively large space to accommodate the irregular structure of the HUD. Furthermore, having the image generation unit on one side of the waveguide structure during application can cause unilateral edge brightness attenuation, negatively impacting the uniformity of brightness across the display.

[0044] This application arranges the first part 211 and the second part 212 symmetrically along the axis L1 of the first coupling entrance 2101, and the third part 221 and the fourth part 222 symmetrically along the axis L2 of the second coupling entrance 2201. The extension direction of the axis L1 of the first coupling entrance 2101 coincides with the extension direction of the axis L2 of the second coupling entrance 2201, thus positioning the first coupling entrance 2101 approximately at the center of the optical waveguide structure 20. This results in the optical waveguide structure 20 being approximately centrally symmetrical along its central axis, with the image generation unit 10 coupled to the first coupling entrance 2101 approximately positioned along the central axis of the optical waveguide structure 20, meaning the image generation unit 10 is centrally located.

[0045] During beam transmission, the first part 211 and the second part 212 can expand the beam output by the image generation unit 10 to the left and right along the opposite directions of the first direction X, respectively. The third part 221 and the fourth part 222 can expand the beam output by the first optical waveguide 21 to the front and back along the opposite directions of the second direction Y, respectively. The pupil expansion magnification of the first part 211 and the second part 212 can be controlled collaboratively, and the pupil expansion magnification of the third part 221 and the fourth part 222 can also be controlled collaboratively.

[0046] In this way, the original exit pupil size requirement of the image generation unit 10 can be fundamentally reduced. Compared with related technologies of unidirectional pupil expansion, the original exit pupil of the image generation unit 10 of this application does not need to reach 15mm to 20mm. After bidirectional pupil expansion by the optical waveguide structure 20, the exit pupil distance can reach 800mm to 1200mm and the eye box size can also be achieved. Above, field of view not less than Requirements.

[0047] Therefore, compared to the traditional unidirectional pupil expansion scheme, the bidirectional pupil expansion scheme constructed in this application can reduce the volume of the image generation unit 10 to 1 / 3 of its original size. Simultaneously, since the optical waveguide structure 20 can extend in two perpendicular directions without needing to extend excessively in only one direction, the overall length of the optical waveguide structure 20 can also be shortened by more than 30%. In summary, the volume of the head-up display device 1 can be controlled to within 3L.

[0048] Meanwhile, the centrally positioned image generation unit 10 also improves the uniformity of brightness within the eye box. Since the image generation unit 10 is approximately located at the axis of the two coupling entrances, the two parts of the two optical waveguides can simultaneously and symmetrically expand the pupils during application, forming a symmetrical optical path. This effectively reduces the edge brightness attenuation phenomenon that easily occurs with unilateral pupil expansion, increasing the uniformity of brightness within the eye box to over 90%.

[0049] Meanwhile, the centered arrangement of the image generation unit 10 can improve the regularity of the overall outer contour of the head-up display device 1, thereby optimizing the overall optical path and the vehicle dashboard, and better fitting the reserved space in the center of the dashboard to avoid installation interference problems.

[0050] Therefore, the head-up display device 1 constructed in this application adopts an architecture with the image generation unit 10 centrally arranged and the optical waveguide structure 20 hierarchically expanding the pupil. This not only achieves the advantages of a large field of view and a long virtual image distance, but also solves the contradiction between the exit pupil diameter and the overall volume through the collaborative design of the image generation unit 10 and the optical waveguide structure 20, which is especially suitable for the spatial layout requirements of the minimalist cockpit of the vehicle.

[0051] The following will provide a further explanation through a specific embodiment.

[0052] exist Figure 8 In the illustrated embodiment, the first optical waveguide 21 has a length of 340 mm in the first direction X, a length of 40 mm in the second direction Y, a thickness of 13 mm, and a volume of approximately 0.18 L. The first portion 211 and the second portion 212 of the first optical waveguide 21 each include 7 sub-prisms, meaning the first optical waveguide 21 includes a total of 14 sub-prisms. The second optical waveguide 22 has a length of 340 mm in the first direction X, a length of 210 mm in the second direction Y, a thickness of 7.5 mm, and a volume of approximately 0.53 L. The third portion 221 and the fourth portion 222 of the second optical waveguide 22 each include 6 sub-prisms, meaning the second optical waveguide 22 includes a total of 12 sub-prisms. The image generation unit 10 has a length of 110 mm, a width of 45 mm, a height of 45 mm, and a volume of approximately 0.22 L. The total volume of the three components is approximately 0.93 L, much less than 3 L. Based on this, by adding the volume of other components such as the outer casing, the overall volume of the head-up display device 1 can be controlled within 3L.

[0053] like Figures 3 to 7As shown, in some embodiments, the first sub-prism 2111, the second sub-prism 2121, the third sub-prism 2211, and the fourth sub-prism 2221 each include a first side surface, a second side surface, an upper surface, and a lower surface. The upper surface and the lower surface are parallel and spaced apart along the thickness direction of the first optical waveguide 21 (or the thickness direction of the second optical waveguide 22, or the extension direction of the axis L1 of the first coupling inlet 2101, or the extension direction of the axis L2 of the second coupling inlet 2201), and the first side surface and the second side surface are respectively connected between the upper surface and the lower surface.

[0054] The first side is located on the side of the sub-prism (first sub-prism 2111, or second sub-prism 2121, or third sub-prism 2211, or fourth sub-prism 2221) close to the coupling inlet (first coupling inlet 2101 or second coupling inlet 2201), and is an inclined surface.

[0055] Specifically, the end of the inclined first side that connects to the lower surface is positioned closer to the coupling inlet (first coupling inlet 2101 or second coupling inlet 2201) than the end of the first side that connects to the upper surface.

[0056] The first sub-prism 2111 and the second sub-prism 2121 are symmetrically arranged about the axis L1 of the first coupling inlet 2101, and their first side surfaces are also symmetrically inclined about the axis L1 of the first coupling inlet 2101. The third sub-prism 2211 and the fourth sub-prism 2221 are symmetrically arranged about the axis L2 of the second coupling inlet 2201, and their first side surfaces are also symmetrically inclined about the axis L2 of the second coupling inlet 2201.

[0057] Furthermore, in each part (part 211, part 212, part 221, and part 222), the first side surface of the sub-prisms that are far from the coupling entrance is provided with a total reflection film, while the first side surface of the other sub-prisms is provided with a semi-reflective and semi-transparent film.

[0058] like Figure 8 As shown, during beam transmission, the light carrying image information output by the image generation unit 10 enters the first optical waveguide 21 through the first coupling inlet 2101 and undergoes total internal reflection under the action of its upper and lower surfaces, propagating in a zigzag path along the first direction X to both sides. When it encounters the first side surface, part of the beam's energy is reflected and exits from the first coupling outlet 2102, while the remaining energy continues to propagate through the sub-prism. The beams that are sequentially transmitted to the first side surface of the sub-prism on the side away from the first coupling inlet 2101 are all reflected and output through the first coupling outlet 2102.

[0059] The light beam output from the first coupling outlet 2102 enters the second optical waveguide 22 through the second coupling inlet 2201 and undergoes total internal reflection under the action of its upper and lower surfaces, propagating in a zigzag path along the second direction Y to both sides. When it encounters the first side surface, part of the beam's energy is reflected and exits from the second coupling outlet 2202, while the remaining energy continues to propagate through the sub-prism. The beams that are sequentially transmitted to the first side surface of the sub-prism on the side away from the second coupling inlet 2201 are all reflected and output through the second coupling outlet 2202.

[0060] In this way, pupil dilation is achieved along the first direction X and the second direction Y.

[0061] It should be noted that the semi-reflective membrane can be implemented using existing technologies such as angle-selective reflective membranes, and no specific limitations are made here.

[0062] The following is based on Figure 5 Taking the first sub-prism 2111 as an example, we will further explain each sub-prism.

[0063] The first sub-prism 2111 is generally parallelogram-shaped, including a first side surface A, a second side surface B, an upper surface C, and a lower surface D. The upper surface C and lower surface D are parallel and spaced apart, with the distance between them equal to the thickness of the first optical waveguide 21. The second side surface B is parallel and spaced apart from the first side surface A along a first direction X. The first side surface A is located along the first direction X on the side of the first sub-prism 2111 closest to the first coupling inlet 2101, and both it and the second side surface B are inclined sides. The inclination angle of the first side surface A causes its end, which connects to the lower surface D, to be closer to the first coupling inlet 2101 than its end, which connects to the upper surface C.

[0064] Thus, during the sequential splicing of multiple first sub-prisms 2111, it can be ensured that the second side B of any two adjacent first sub-prisms 2111 with the same tilt angle can be fitted and connected with the first side A, thereby enabling multiple first sub-prisms 2111 to be sequentially connected and extended along the first direction X.

[0065] It should be noted that the second side surface B of the first sub-prism 2111, which is far from the first coupling inlet 2101 in the first part 211, may also have an angle with the first side surface A.

[0066] For example in Figure 3 and Figure 4In the illustrated embodiment, the second side of the first sub-prism 2111 in the first portion 211, which is away from the first coupling entrance 2101, is arranged perpendicular to the upper and lower surfaces, thus making the first optical waveguide 21 approximately rectangular. Of course, the first sub-prism 2111 in the first portion 211, which is away from the first coupling entrance 2101, can also be arranged parallel to the first side A, or neither parallel to the first side A nor perpendicular to the upper or lower surfaces. No specific limitation is made here.

[0067] The same applies to the second sub-prism 2121, the third sub-prism 2211, and the fourth sub-prism 2221, which will not be elaborated here.

[0068] In some embodiments, the tangent of the angle between the first side surface and the lower surface of each sub-prism is greater than or equal to the ratio of the thickness of the optical waveguide to which it belongs to the length of the lower surface of the sub-prism along the distance between its first side surface and the second side surface.

[0069] That is, such as Figures 3 to 5 As shown, the angle between the first side surface and the lower surface of the sub-prism (first sub-prism 2111, second sub-prism 2121) of the first optical waveguide 21 Thickness of the first optical waveguide 21 The length value of the lower surface of the sub-prism along the first direction X The relationship between these elements satisfies Formula 1.

[0070] Formula 1 like Figure 6 and Figure 7 As shown, the angle between the first side surface and the lower surface of the sub-prism (third sub-prism 2211, fourth sub-prism 2221) of the second optical waveguide 22 The thickness of the second optical waveguide 22 The length value of the lower surface of the sub-prism along the second direction Y. The relationship between these elements satisfies Formula 2.

[0071] Formula 2 It should be noted that both the first optical waveguide 21 and the second optical waveguide 22 are used to expand the output pupil 101 of the image generation unit 10.

[0072] Therefore, in some embodiments, the size of the output pupil 101 of the image generation unit 10 in the direction of the interval between the first and second sides of the subprism of the optical waveguide must be greater than or equal to the size of the two symmetrical inclined planes that are close to each other in the two parts of the optical waveguide in that direction.

[0073] That is, the dimensions R1 of the output pupil 101 in the first direction X, the dimensions of the projection of the first side of the first sub-prism 211 closest to the second part 212 on the first coupling entrance 2101 along the first direction X, and the dimensions of the projection of the first side of the second sub-prism 2121 closest to the first part 211 on the first coupling entrance 2101 along the first direction X, must satisfy Formula 3.

[0074] Formula 3 in, The output pupil 101 is the size in the first direction X; The thickness of the first optical waveguide 21; The angle between the first side surface and the lower surface of the sub-prism (first sub-prism 2111, second sub-prism 2121) of the first optical waveguide 21 The tangent value; The length of the lower surface of the sub-prism of the first optical waveguide 21 along the first direction X is given.

[0075] The dimensions R2 of the output pupil 101 in the second direction Y, the projection of the first side of the third sub-prism 2211 closest to the fourth part 222 onto the first coupling entrance 2101 along the second direction Y, and the projection of the first side of the fourth sub-prism 2221 closest to the third part 221 onto the first coupling entrance 2101 along the second direction Y, the relationship between these dimensions must satisfy Formula 4.

[0076] Formula 4 in, The output pupil 101 is the dimension in the second direction Y; The thickness of the second optical waveguide 22; The angle between the first side surface and the lower surface of the sub-prism (third sub-prism 2211, fourth sub-prism 2221) of the second optical waveguide 22. The tangent value; The length of the lower surface of the sub-prism of the second optical waveguide 22 along the second direction Y is given.

[0077] For example in Figure 2 In the embodiment shown, when the output pupil 101 is circular, its diameter W must be greater than or equal to... And must be greater than or equal to .

[0078] In this way, it can be ensured that the optical image output through the output pupil 101 is within the range covered by the two symmetrical inclined planes that are close to each other in the two parts of the two optical waveguides, so that it can be extended to both sides along the arrangement direction of the sub-prisms to achieve pupil expansion.

[0079] It should be understood that, since the output pupil 101 is coupled to the first coupling inlet 2101, the dimension R1 of the output pupil 101 in the first direction X satisfies Formula 3, and the dimension R2 in the second direction Y satisfies Formula 4. This can also be understood as the dimension of the first coupling inlet 2101 in the first direction X being greater than or equal to... The dimension in the second direction Y is greater than or equal to .

[0080] Furthermore, such as Figures 2 to 4 As shown, the dimension of the first coupling outlet 2102 along the second direction Y is approximately equal to the length of the first optical waveguide 21 in the second direction Y, and approximately equal to the dimension R2 of the output pupil 101 in the second direction Y.

[0081] The dimension of the first coupling outlet 2102 along the first direction X is approximately equal to the distance between the connection point of the first side surface of the first sub-prism 2111 away from the second part 212 and the upper surface, and the connection point of the first side surface of the second sub-prism 2121 away from the first part 211 and the upper surface, along the first direction. Simultaneously, the dimension of the first coupling outlet 2102 along the first direction X may also be equal to or slightly smaller than the dimension of the first optical waveguide 21 along the first direction X.

[0082] It should be understood that, since the first coupling outlet 2102 is coupled to the second coupling inlet 2201, the second optical waveguide 22 further expands the pupil based on the light output from the first optical waveguide 21.

[0083] Therefore, in some embodiments, the length of the first optical waveguide 21 in the second direction Y (the dimension of the first coupling outlet 2102 along the second direction Y) needs to be greater than or equal to the dimension of the two symmetrical inclined planes that are close to each other in the two parts of the second optical waveguide 22 in that direction.

[0084] That is, the length of the first optical waveguide 21 in the second direction Y (the dimension of the first coupling outlet 2102 along the second direction Y), the dimension of the projection of the first side of the third sub-prism 2211 closest to the fourth part 222 onto the first coupling inlet 2101 along the second direction Y, and the dimension of the projection of the first side of the fourth sub-prism 2221 closest to the third part 221 onto the first coupling inlet 2101 along the second direction Y, the relationship between these factors must satisfy Formula 5.

[0085] Formula 5 in, The length of the first optical waveguide 21 in the second direction Y (the dimension of the first coupling outlet 2102 along the second direction Y); The thickness of the second optical waveguide 22; The angle between the first side surface and the lower surface of the sub-prism (third sub-prism 2211, fourth sub-prism 2221) of the second optical waveguide 22. The tangent value; The length of the lower surface of the sub-prism of the second optical waveguide 22 along the second direction Y is given.

[0086] In this way, it can be ensured that the optical image output through the first coupling outlet 2102 is within the range covered by the two symmetrical inclined planes that are close to each other in the two parts of the second optical waveguide 22, so that the optical image after pupil expansion along the first direction X can continue to expand to both sides along the second direction Y, realizing graded bidirectional pupil expansion.

[0087] The first optical waveguide 21 is defined as having a dimension of A1 in the first direction X, a dimension of B1 in the second direction Y, and a dimension of h1 in the thickness direction. Furthermore, both the first part 211 and the second part 212 of the first optical waveguide 21 are defined to include n1 sub-prisms, resulting in a total of 2n1 symmetrical inclined surfaces.

[0088] The second optical waveguide 22 is defined with dimensions A1 in the first direction X, B2 in the second direction Y, and h2 in the thickness direction. The third part 221 and the fourth part 222 of the second optical waveguide 22 are each defined to include n2 sub-prisms, and have a total of 2n2 symmetrical inclined surfaces.

[0089] Therefore, in some embodiments, the dimension of each optical waveguide in its sub-prism along the spacing between its first and second sides is greater than or equal to the product of the number of its respective sub-prisms and the dimension of its sub-prism along the spacing between its first and second sides.

[0090] That is, such as Figure 3 and Figure 4 As shown, the dimensions A1 of the first optical waveguide 21 in the first direction X, the sum of the number of the first sub-prism 2111 and the second sub-prism 2121 2n1, and the length of the lower surface of the first sub-prism 2111 (second sub-prism 2121) in the first direction X are: The relationship between these elements satisfies Formula Six.

[0091] Formula Six like Figure 6 and Figure 7As shown, the dimensions B2 of the second optical waveguide 22 in the second direction Y, the sum of the numbers of the third sub-prism 2211 and the fourth sub-prism 2221 (2n2), and the length of the lower surface of the third sub-prism 2211 (fourth sub-prism 2221) in the second direction Y are... The relationship between these elements satisfies Formula Seven.

[0092] Formula 7 It should be noted that the aforementioned length values Length value All are based on sub-prisms with parallel and spaced-apart first and second sides. That is, this length value... Length value It can also be considered as the distance between the first and second sides of the sub-prism.

[0093] In some embodiments, the number of the first sub-prism 2111 and the second sub-prism 2121 are equal, and the number of both is greater than or equal to 4 and less than or equal to 8. The number of the third sub-prism 2211 and the fourth sub-prism 2221 are equal, and the number of both is greater than or equal to 4 and less than or equal to 8.

[0094] Specifically, the number of the first sub-prism 2111 and the second sub-prism 2121, and / or the number of the third sub-prism 2211 and the fourth sub-prism 2221 can be 4, 5, 6, 7, 8, etc.

[0095] It should be noted that the number of the first sub-prism 2111 and the second sub-prism 2121, and the number of the third sub-prism 2211 and the fourth sub-prism 2221 can be the same or different, and no specific limitation is made here.

[0096] In some embodiments, the refractive index of the sub-prism of the first optical waveguide 21 may be greater than or equal to 1.5 and less than or equal to 2.0. The refractive index of the sub-prism of the second optical waveguide 22 may be greater than or equal to 1.5 and less than or equal to 2.0.

[0097] Specifically, the substrate refractive index of the sub-prism of the first optical waveguide 21 and / or the substrate refractive index of the sub-prism of the second optical waveguide 22 may be 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, or any other value within that region.

[0098] It should be noted that the refractive index of the substrate of each sub-prism in the same optical waveguide must be the same. The refractive indices of the substrates of the first optical waveguide 21 and the second optical waveguide 22 may be the same or different, and no specific limitation is made here.

[0099] In some embodiments, any two first sub-prisms 2111 and 2121 symmetrically arranged about the axis L1 of the first coupling inlet 2101 have equal transmittance and equal reflectance on their first side surfaces. Similarly, any two third sub-prisms 2211 and 2221 symmetrically arranged about the axis L2 of the second coupling inlet 2201 have equal transmittance and equal reflectance on their first side surfaces.

[0100] Furthermore, for any two sub-prisms of the first optical waveguide 21, the reflectivity of the first side surface of one of the two sub-prisms with the smaller distance from the first coupling entrance 2101 along the first direction X is less than or equal to that of the other sub-prism. For any two sub-prisms of the second optical waveguide 21, the reflectivity of the first side surface of one of the two sub-prisms with the smaller distance from the second coupling entrance 2201 along the second direction Y is less than or equal to that of the other sub-prism.

[0101] Specifically, for any two adjacent first sub-prisms 2111, the reflectivity of the one closer to the first coupling inlet 2101 is less than or equal to the other. Similarly, for any two adjacent second sub-prisms 2121, the reflectivity of the one closer to the first coupling inlet 2101 is less than or equal to the other. For any two adjacent third sub-prisms 2211, the reflectivity of the one closer to the second coupling inlet 2201 is less than or equal to the other. And for any two adjacent fourth sub-prisms 2221, the reflectivity of the one closer to the second coupling inlet 2201 is less than or equal to the other.

[0102] It should be noted that the reflectivity changes of each first sub-prism 2111 and each second sub-prism 2121 are the same, as are the reflectivity changes of each third sub-prism 2211 and each fourth sub-prism 2221. However, the reflectivity changes of the first sub-prism 2111 and each second sub-prism 2121 may be the same as or different from the reflectivity changes of the third sub-prism 2211 and each fourth sub-prism 2221, and no specific limitation is made here.

[0103] In some embodiments, the relationship between the transmittance and reflectance of each sub-prism (first sub-prism 2111, second sub-prism 2121, third sub-prism 2211, and fourth sub-prism 2221) satisfies Formula 8.

[0104] Formula 8 Where T is the transmittance of the sub-prism; R is the reflectivity of the sub-prism.

[0105] It should be noted that the specific reflectivity and transmittance values ​​of each sub-prism need to be determined based on actual parameter requirements, so no specific limits are made here.

[0106] The optical waveguide structure 20 will be further described below through a specific embodiment.

[0107] In one embodiment, the optical waveguide structure 20 has six sub-prisms: the first sub-prism 2111, the second sub-prism 2121, the third sub-prism 2211, and the fourth sub-prism 2221.

[0108] Along the first direction X, from the side (inner side) of the axis L1 near the first coupling inlet 2101 to the side (outer side) away from the axis L1, the reflectivity R of the first sub-prism 2111 and the second sub-prism 2121 are 6%, 6%, 8%, 8%, 12%, 12%, respectively, and the transmittance T are 94%, 94%, 92%, 92%, 88%, 88%, respectively.

[0109] Along the second direction Y, from the side (inner side) of the axis L2 near the second coupling inlet 2201 to the side (outer side) away from the axis L2, the reflectivity R of the third sub-prism 2211 and the fourth sub-prism 2221 are 6%, 6%, 8%, 8%, 12%, 12%, respectively, and the transmittance T are 94%, 94%, 92%, 92%, 88%, 88%, respectively.

[0110] like Figure 3 and Figure 4 As shown, in some embodiments, the first optical waveguide 21 may further include a first connecting prism 213, which is disposed along the first direction X between the first portion 211 and the second portion 212, such that the three are connected to form a whole first optical waveguide 21. The first connecting prism 213 is connected along the first direction X to the first side surface of the first sub-prism 2111 near the end of the second portion 212 of the first portion 211 and the first side surface of the second sub-prism 2121 near the end of the first portion 211 of the second portion 212, respectively.

[0111] Thus, the upper surface of the first connecting prism 213, the upper surfaces of all the first sub-prisms 2111, and the upper surface of the second sub-prism 2121 are sequentially connected to form the upper surface of the first optical waveguide 21. The lower surface of the first connecting prism 213 (which may exist in some embodiments), the lower surfaces of all the first sub-prisms 2111, and the lower surface of the second sub-prism 2121 are sequentially connected to form the lower surface of the first optical waveguide 21. The first coupling inlet 2101 is located on the lower surface of the first optical waveguide 21, and the first coupling outlet 2102 is located on the upper surface of the first optical waveguide 21. The second optical waveguide 22 is coupled above the first optical waveguide 21.

[0112] See also Figure 6 and Figure 7The second optical waveguide 22 may further include a second connecting prism 223, which is disposed along the second direction Y between the third part 221 and the fourth part 222, so that the three parts are connected to form a whole second optical waveguide 22. The second connecting prism 223 is connected along the second direction Y to the first side of the third sub-prism 2211 near the end of the fourth part 222 of the third part 221 and the first side of the fourth sub-prism 2221 near the end of the third part 221 of the fourth part 222, respectively.

[0113] Thus, the upper surface of the second connecting prism 223, the upper surfaces of all the third sub-prisms 2211, and the upper surface of the fourth sub-prism 2221 are sequentially connected to form the upper surface of the second optical waveguide 22. The lower surface of the second connecting prism 223 (which may exist in some embodiments), the lower surfaces of all the third sub-prisms 2211, and the lower surface of the fourth sub-prism 2221 are sequentially connected to form the lower surface of the second optical waveguide 22. The second coupling inlet 2201 is located on the lower surface of the second optical waveguide 22, and the second coupling outlet 2202 is located on the upper surface of the second optical waveguide 22.

[0114] Specifically, the first connecting prism 213 is in the shape of an inverted triangular prism, with its two sides connected to the first part 211 and the second part 212 respectively, and the remaining side forming part of the upper surface of the first optical waveguide 21. The lower surface of the first sub-prism 2111 of the first part 211 is close to the lower surface of the second sub-prism 2121 of the second part 212, and the lower surface of the second sub-prism 2121 of the second part 212 is close to the lower surface of the first sub-prism 2121 of the first part 211.

[0115] The second connecting prism 223 is in the shape of an inverted triangular prism, with its two sides connected to the third part 221 and the fourth part 222, respectively. The remaining side forms part of the upper surface of the second optical waveguide 22. The lower surface of the third sub-prism 2211 of the third part 221 is close to that of the fourth part 222, and the lower surface of the fourth sub-prism 2221 of the fourth part 222 is close to that of the third part 221.

[0116] In some other embodiments, the first connecting prism 213 and the second connecting prism 223 may also be in other shapes such as isosceles trapezoids.

[0117] It should be noted that the shapes of the first connecting prism 213 and the second connecting prism 223 may be the same or different, and no specific limitation is made here.

[0118] Understandably, the above-mentioned technical features can be used in any combination without restriction.

[0119] The above embodiments merely illustrate specific implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application's patent. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of this application, and can also make several modifications and improvements, all of which fall within the protection scope of this application. Therefore, all equivalent transformations and modifications made within the scope of the claims of this application should fall within the coverage of the claims of this application.

Claims

1. An optical waveguide structure, characterized in that, include: The first optical waveguide (21) includes multiple sub-prisms; the multiple sub-prisms include: Multiple first sub-prisms (2111) are arranged sequentially along a first direction; and A plurality of second sub-prisms (2121) are arranged sequentially along the first direction; the plurality of second sub-prisms (2121) and the plurality of first sub-prisms (2111) are symmetrically arranged along the axis of the first coupling entrance (2101) of the first optical waveguide (21); and The second optical waveguide (22) has a second coupling entrance (2201) coupled to the first coupling exit (2102) of the first optical waveguide (21), and includes a plurality of sub-prisms; the plurality of sub-prisms include: Multiple third sub-prisms (2211) are arranged sequentially along the second direction; and Multiple fourth sub-prisms (2221) are arranged sequentially along the second direction; the multiple fourth sub-prisms (2221) and the multiple third sub-prisms (2211) are symmetrically arranged along the axis of the second coupling entrance (2201); Wherein, the first direction is perpendicular to the second direction.

2. The optical waveguide structure according to claim 1, characterized in that, Each of the multiple sub-prisms of the first optical waveguide (21) and the multiple sub-prisms of the second optical waveguide (22) includes a first side surface, a second side surface, an upper surface, and a lower surface; the first side surface is an inclined surface; The first side of each of the plurality of sub-prisms of the first optical waveguide (21) is located on the side of the sub-prism close to the first coupling entrance (2101) along the first direction; The first side of each of the plurality of sub-prisms of the second optical waveguide (22) is located on the side of the sub-prism close to the second coupling entrance (2201) along the second direction.

3. The optical waveguide structure according to claim 2, characterized in that, The tangent of the angle between the first side surface and the lower surface of the sub-prism of the first optical waveguide (21) is greater than or equal to the ratio of the thickness of the first optical waveguide (21) to the length of the lower surface of the sub-prism along the first direction; and / or, The tangent of the angle between the first side surface and the lower surface of the sub-prism of the second optical waveguide (22) is greater than or equal to the ratio of the thickness of the second optical waveguide (22) to the length of the lower surface of the sub-prism along the second direction.

4. The optical waveguide structure according to claim 2, characterized in that, The length of the first coupling outlet (2102) in the second direction is obtained by formula 1: Formula 1 in, The dimension of the first coupling outlet (2102) in the second direction; The thickness is the second optical waveguide (22); The angle between the first side surface and the lower surface of the sub-prism of the second optical waveguide (22) The tangent value.

5. The optical waveguide structure according to claim 2, characterized in that, Any two sub-prisms of the first optical waveguide (21) symmetrically arranged along the axis of the first coupling entrance (2101) have equal reflectivity and equal transmittance on their first side surfaces; for any two sub-prisms of the first optical waveguide (21), the reflectivity of the first side surface of one of the two sub-prisms with the smaller distance from the first coupling entrance (2101) along the first direction is less than or equal to that of the other one; and / or, The first side reflectance and transmittance of any two sub-prisms of the second optical waveguide (22) symmetrically arranged along the axis of the second coupling entrance (2201) are equal; the first side reflectance of any two sub-prisms of the second optical waveguide (22) that are smaller in distance from the second coupling entrance (2201) along the second direction is less than or equal to that of the other one.

6. The optical waveguide structure according to claim 5, characterized in that, The sum of the reflectivity and the transmittance is 1.

7. The optical waveguide structure according to any one of claims 1 to 6, characterized in that, The length of the first optical waveguide (21) in the first direction is greater than or equal to the product of the number of its plurality of sub-prisms and the length of the lower surface of the sub-prism in the first direction; and / or, The length of the second optical waveguide (22) in the second direction is greater than or equal to the product of the number of its plurality of sub-prisms and the length of the lower surface of the sub-prism in the first direction.

8. The optical waveguide structure according to any one of claims 1 to 6, characterized in that, The number of the first sub-prism (2111) is greater than or equal to 4 and less than or equal to 8; the number of the second sub-prism (2121) is greater than or equal to 4 and less than or equal to 8; and / or, The number of the third sub-prism (2211) is greater than or equal to 4 and less than or equal to 8; the number of the fourth sub-prism (2221) is greater than or equal to 4 and less than or equal to 8.

9. The optical waveguide structure according to any one of claims 1 to 6, characterized in that, The refractive index of the sub-prism of the first optical waveguide (21) is greater than or equal to 1.5 and less than or equal to 2; and / or, The refractive index of the sub-prism of the second optical waveguide (22) is greater than or equal to 1.5 and less than or equal to 2.

10. A head-up display device, characterized in that, It includes an image generation unit (10) and an optical waveguide structure as described in any one of claims 1 to 9; the output pupil (101) of the image generation unit (10) is coupled to the first coupling inlet (2101).

11. The head-up display device according to claim 10, characterized in that, The plurality of sub-prisms of the first optical waveguide (21) and the plurality of sub-prisms of the second optical waveguide (22) each include an inclined first side surface; the first side surface of the plurality of sub-prisms of the first optical waveguide (21) is located on the side of the sub-prism closer to the first coupling entrance (2101) along the first direction; the first side surface of the plurality of sub-prisms of the second optical waveguide (22) is located on the side of the sub-prism closer to the second coupling entrance (2201) along the second direction; The size of the output pupil (101) in the first direction is obtained by formula 2: Formula 2 in, The size of the output pupil (101) in the first direction; The thickness is the thickness of the first optical waveguide (21); The angle between the first side surface and the lower surface of the sub-prism of the first optical waveguide (21) The tangent value; The dimension of the output pupil in the second direction is obtained using Formula 3: Formula 3 in, The size of the output pupil (101) in the second direction; The thickness is the second optical waveguide (22); The angle between the first side surface and the lower surface of the sub-prism of the second optical waveguide (22) The tangent value.

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