Head-up display (HUD) for vehicles

Abstract

A vehicle head-up display (HUD) for displaying an image to a user of a vehicle with a windshield (15) includes an image projector (14) that outputs a collimated image and an optical aperture expander. The optical aperture expander includes a light-guiding optical element (LOE) (10) having two main outer surfaces (30a, 30b). The image projector (14) injects the collimated image to propagate within the LOE via internal reflection at the main outer surfaces. The LOE also has a set of parallel partially reflective inner surfaces (12) that gradually couple the image illumination from the LOE. The optical aperture expander is deployed such that the image illumination coupled from the LOE (12) follows a light path including reflections from surfaces associated with the windshield (15) of the vehicle, making it visible to the user when observing a scene outside the windshield.

Description

[0001] Technical Field and Background Technology

[0002] This invention relates to displays, and more particularly to head-up displays for vehicles (e.g., automobiles).

[0003] There are numerous proposals and designs for mounting a HUD in front of a car driver to assist by providing a variety of visual functions, including but not limited to: driving navigation, obtaining dashboard information without taking one's gaze off the road, or projecting thermal images into the driver's eyes in low-visibility conditions.

[0004] Current solutions for projecting images onto the windshield have relatively limited eye motionboxes (EMBs) and fields of view (FOVs), or require relatively large projection optics to support wider EMBs and FOVs. Summary of the Invention

[0005] The present invention is a vehicle head-up display (HUD) for displaying images to vehicle users.

[0006] As introduced, a lightguide optical element (LOE) is a waveguide used for aperture expansion. The working principle of an LOE is presented in US Patent No. 6,829,095,B2, entitled "Substrate-guided optical beam expander." LOE-based HUDs allow for the realization of very compact, stand-alone HUDs that can be easily mounted in limited spaces. This HUD enables the use of very small collimating optics without compromising the field of view (FOV) or eye-motion box (EMB, which corresponds to the area where the image can be viewed). Therefore, LOE-based aperture expansion arrangements simplify the construction and fabrication of HUD-related optical systems and are thus suitable for compact, inexpensive consumer versions of HUDs for the automotive industry.

[0007] According to the teachings of embodiments of the present invention, a vehicle head-up display (HUD) is provided for displaying an image to a user of a vehicle with a windshield, the HUD comprising: (a) an image projector including an image generator and collimating optics, the image projector outputting an image illumination corresponding to a collimated image; and (b) an optical aperture expander including at least a first light-guide optical element (LOE) having a pair of mutually parallel main outer surfaces, the image projector being optically coupled to the optical aperture expander such that the image illumination propagates within the LOE via internal reflection at the main outer surfaces, the LOE further including at least a set of mutually parallel partially reflective surfaces within the LOE and inclined to the main outer surfaces, the set of partially reflective surfaces gradually coupling the image illumination out of the LOE, wherein the optical aperture expander is deployed such that the image illumination coupled out of the LOE follows a light path including reflections from surfaces associated with the windshield of the vehicle, so as to be visible to the user when the user observes a scene outside the windshield.

[0008] According to another feature of an embodiment of the invention, the optical aperture expander further includes a second set of mutually parallel partially reflective surfaces deployed non-parallel to the first set of partially reflective surfaces, the second set of partially reflective surfaces being deployed to gradually redirect image illumination from the image projector to the first set of partially reflective surfaces.

[0009] According to another feature of an embodiment of the invention, the second set of partially reflective surfaces is located within the LOE between a pair of main outer surfaces.

[0010] According to another feature of an embodiment of the invention, the second set of partially reflective surfaces is located within a second LOE defined by a second pair of primary outer surfaces.

[0011] According to another feature of an embodiment of the invention, the second LOE is deployed adjacent to the main outer surface of the first LOE that is farther from the windshield of the vehicle.

[0012] According to another feature of an embodiment of the invention, a group of partially reflective surfaces are deployed to couple image illumination from one of a pair of primary outer surfaces away from the windshield, and the HUD also includes reflective optical elements with optical power configured to at least partially compensate for optical aberrations introduced into the image by reflections from surfaces associated with the windshield.

[0013] According to another feature of an embodiment of the invention, the reflective optical element is also configured to limit the apparent distance of the image observed by the user after reflection from a surface associated with the windshield.

[0014] According to another feature of an embodiment of the invention, light reflected from the reflective optical element is transmitted through the LOE before being reflected from the surface associated with the windshield.

[0015] According to another feature of an embodiment of the invention, the image illumination coupled from the LOE follows a light path to be visible to the user when the user observes a scene outside the windshield, the light path including: a first reflection at a high angle of incidence from a surface associated with the windshield of the vehicle, an intermediate reflection from an additional reflective surface, and a second reflection from a surface associated with the windshield.

[0016] According to another feature of an embodiment of the invention, the surface associated with the windshield is an angle-selective reflector configured to have a first reflectivity for light incident normally onto the surface and a second reflectivity less than the first reflectivity for light incident at an angle greater than 45 degrees.

[0017] Another feature of an embodiment of the invention is that the additional reflective surface is a polarizing beam splitter, wherein a quarter-wave plate is inserted in the optical path between the surface associated with the windshield and the additional reflective surface.

[0018] Another feature of an embodiment of the invention is that both the surface associated with the windshield and the quarter-wave plate are integrated into the windshield.

[0019] Another feature of an embodiment of the invention is that a second quarter-wave plate is provided, which is integrated with the windshield and located on the surface at the distance from the user.

[0020] According to another feature of an embodiment of the invention, the polarization beam splitter is shaped to provide optical power to at least partially compensate for optical aberrations introduced into the image by reflections from surfaces associated with the windshield.

[0021] According to the teachings of embodiments of the present invention, a system including a first HUD and a second HUD is also provided, each of the first HUD and the second HUD being implemented as described above, wherein each of the first HUD and the second HUD provides different regions of the field of view visible to the user and / or makes the field of view visible from different regions of the eye-tracking box.

[0022] According to another feature of an embodiment of the invention, the first HUD and the second HUD are deployed side by side.

[0023] According to another feature of an embodiment of the invention, the first HUD and the second HUD are deployed in a relationship of at least partial overlap.

[0024] According to the teachings of embodiments of the present invention, a vehicle door having a display integrated with a window is also provided, the vehicle door comprising: (a) a door panel; (b) a window supported by the door panel, the window including a visible portion providing a view of a scene outside the window and a hidden portion extending into the interior of the door panel, the window including a light-guide optical element (LOE) having a pair of mutually parallel main outer surfaces and at least a first set of mutually parallel partial reflective surfaces within the LOE and inclined to the main outer surfaces; and (c) an image projector including an image generator and a collimating optics, the image projector being located within the door panel and optically coupled to a region of the LOE within the hidden portion of the window to introduce image illumination corresponding to a collimated image into the LOE, the image illumination propagating within the LOE via internal reflection at the main outer surfaces and gradually decoupled from the visible portion of the window by the set of partial reflective surfaces.

[0025] According to another feature of an embodiment of the invention, the image projector is optically coupled to the LOE via an air gap, and the door also includes a mechanism for lowering and raising the window. The image projector is deployed to be aligned so that when the window is in the raised position, it illuminates and couples an image into the LOE via the air gap.

[0026] According to another feature of an embodiment of the invention, the LOE is encapsulated within a window material, and at least the encapsulation layer adjacent to the LOE is formed of a material with a lower refractive index than the material of the LOE, in order to support internal reflection at the main outer surface of the LOE. Attached Figure Description

[0027] The invention is described herein by way of example only with reference to the accompanying drawings, in which:

[0028] Figure 1A This is a schematic side view of a vehicle head-up display (HUD) used to display images to users in the vehicle.

[0029] Figure 1B yes Figure 1A A schematic front view of the HUD;

[0030] Figure 2 yes Figure 1A A schematic side view of a variant implementation of a HUD;

[0031] Figure 3A yes Figure 1A A schematic side view of another variant implementation of the HUD;

[0032] Figure 3B yes Figure 3A A magnified view of the area marked III;

[0033] Figure 4 It is adopted according to Figure 1A A schematic front view of a system with multiple HUD units;

[0034] Figure 5A It adopts a stacked relationship with Figure 1A A schematic side view of a system with multiple similar HUD units to provide an extended field of view;

[0035] Figure 5B It adopts a stacked relationship with Figure 1A A schematic side view of a system with multiple similar HUD units to provide an extended eye-tracking box;

[0036] Figure 5C yes Figure 5A and Figure 5B A schematic front view of the system; and

[0037] Figure 6A and Figure 6B These are schematic side and front views, respectively, of a HUD suitable for implementation in a vertical window (particularly associated with a door panel) according to another aspect of the invention. Detailed Implementation

[0038] This invention is a vehicle head-up display (HUD) for displaying images to users in a vehicle.

[0039] The principle and operation of the head-up display according to the present invention can be better understood by referring to the accompanying drawings and description.

[0040] Now refer to the attached diagram, Figures 1A to 5C Various non-limiting embodiments of the first aspect of the invention are illustrated. This aspect of the invention provides a vehicle HUD for displaying images to a user of a vehicle (not fully shown) having a windshield 15. In the drawings, the user is represented by an image of the user's eyes 50, located in an area referred to as the "eye-motion box" (EMB), which corresponds to the range of the display's designed position. The "user" is typically the driver or operator of the vehicle, but in some cases, it can be a passenger in the vehicle other than the driver.

[0041] In summary, the HUD according to this aspect of the invention includes an image projector or "POD" 14, which includes an image generator and collimating optics to output image illumination corresponding to a collimated image. To facilitate the use of an image projector with a relatively small output optical aperture, the HUD also includes an optical aperture expander, which includes at least a first light-guide optical element (LOE) 10. The LOE 10 has a pair of mutually parallel primary outer surfaces 30a, 30b. The image projector 14 is optically coupled to the optical aperture expander such that image illumination propagates within the LOE 10 through internal reflections at the primary outer surfaces 30a, 30b. The LOE 10 also includes at least one set of mutually parallel partially reflective surfaces (or "facets") 12 located within the LOE and inclined to the primary outer surfaces 30a, 30b. This set of partially reflective surfaces 12 gradually couples the image illumination out of the LOE 10.

[0042] According to this aspect of the invention, the deployment of the optical aperture expander ensures that the image illumination coupled from the LOE follows a light path including reflections from a surface associated with the windshield 15 of the vehicle, so that it is visible to the user when the user 50 observes a scene outside the windshield.

[0043] What will be immediately apparent is that this invention provides a highly advantageous HUD construction. Specifically, using one or more LOEs to extend the optical aperture of the POD enables the use of a compact and lightweight POD, while the LOEs provide an extension of the required radial dimension of the optical aperture according to the desired field of view and EMB size. The LOE (not shown to scale) can be implemented as a thin flat panel with a small volume and weight. Using a windshield as a combiner ensures that the user's real-world view remains substantially uninterrupted.

[0044] In some embodiments, the optical aperture expander further includes a second set of mutually parallel partially reflective surfaces 22, which are deployed non-parallel to the first set of partially reflective surfaces 12 to progressively redirect image illumination from the image projector 14 to the first set of partially reflective surfaces 12. Thus, the partially reflective surfaces 22 achieve a first-dimensional optical aperture expansion, while the partially reflective surfaces 12 achieve a second-dimensional optical aperture expansion. Figure 1A and Figure 1BIn the example shown, the second set of partially reflective surfaces 22 is located within a second LOE 20 defined by a second pair of primary outer surfaces 32a, 32b. In the preferred but non-limiting implementation shown here, the second LOE 20 is deployed adjacent to the primary outer surface 30b of the first LOE 10 (i.e., on the side farther from the windshield 15 of the vehicle). In this way, the two LOEs are effectively stacked one on top of the other in a particularly compact configuration. Total internal reflection conditions within each LOE can be maintained by ensuring a small air gap between them, or more conveniently, by inserting an “isolation layer” of material having a relatively low refractive index than the material of the LOE itself. The material of the isolation layer can be a low-refractive-index optical adhesive, or any other transparent low-refractive-index material with suitable mechanical properties. (This is true in the various embodiments discussed below, where the two LOEs are shown as surfaces adjacent to each other.)

[0045] The POD used with the device of the present invention is preferably configured to generate collimated images (i.e., wherein the light for each image pixel is a collimated parallel beam having an angular direction corresponding to the pixel position up to infinity). Therefore, image illumination spans an angular range corresponding to a two-dimensional angular field of view.

[0046] Image projector 14 includes at least one light source, which is typically deployed to illuminate a spatial light modulator (e.g., an LCOS chip). The spatial light modulator modulates the intensity of the projection onto each pixel of the image, thereby generating the image. Alternatively, the image projector may include a scanning device typically implemented using a fast scanning mirror that scans the illumination from the laser light source across the image plane of the projector while synchronously changing the intensity of the beam on a pixel-by-pixel basis with motion, thereby projecting the desired intensity onto each pixel. In both cases, collimating optics are provided to generate an output projected image collimated up to infinity. Optionally, some or all of the above components may be arranged on the surface of one or more polarizing beam-splitter (PBS) cubes or other prism devices, as is known in the art.

[0047] The optical coupling from image projector 14 to the LOE (LOE 20 in this case) in the optical path can be achieved by any suitable optical coupling (e.g., via a coupling prism with an angled input surface, or via a reflective coupling device, via one of the side edges and / or the main outer surface of the LOE). Details of the coupling configuration are generally not critical to the invention and are chosen according to the preferred form factor of a particular implementation. In this exemplary embodiment, as... Figure 1BAs best seen, image illumination is coupled from image projector 14 to LOE 20 via internal reflector 23. Internal reflector 23 deflects the image illumination so that it propagates along LOE 20 via internal reflections from surfaces 32a and 32b until it reaches the partially reflective surface 22 that gradually couples the image illumination toward LOE 10. This achieves a first-dimensional aperture expansion relative to the optical aperture of the image projector. Then, as... Figure 1A As best seen here, the coupling of light from LOE20 to LOE10 is achieved via an internal reflector 13. The internal reflector 13 deflects the image illumination so that it propagates along LOE10 via internal reflections from surfaces 30a and 30b until it reaches a partially reflective surface 12, which gradually couples the image illumination toward the windshield 15 to reflect it toward the user's eye 50 located within the eye-tracking box. This coupling method facilitates the aforementioned compact stacked structure of the HUD. Other coupling options are also applicable, typically employing coupling prisms. Such options are discussed in detail in commonly assigned PCT patent application publication WO 2015 / 162611A1, but will not be elaborated upon here for the sake of brevity.

[0048] Several additional embodiments will be presented below to illustrate additional aspects of the invention. For simplicity, these embodiments will be described using a single LOE 10. However, it should be understood that each embodiment may also utilize [other embodiments]. Figure 1A and Figure 1B The arrangement is similar to a double LOE arrangement, as will be clear to those skilled in the art.

[0049] In some implementations, it is advantageous that the light reflected from the windshield is P-polarized (in the YZ plane), and the light guided within the LOE is generally advantageously S-polarized. To switch the polarization, an HWP (half-wave plate) 17 is advantageously introduced, as shown. Furthermore, in the case where two orthogonal LOEs are used for two orthogonal extensions of the optical aperture, as shown here, an HWP 27 is advantageously introduced between the LOEs to rotate the polarization and convert the S-polarization exiting LOE 20 to S-polarization according to the orientation of the surface of LOE 10.

[0050] Although partial reflective surfaces 12 and 22 are shown here in separate LOEs, an alternative implementation could be achieved using two non-parallel sets of partial reflective surfaces implemented within a single LOE (i.e., between the main outer surfaces 30a and 30b). In this case, one set of partial reflective surfaces 22 is deployed to progressively deflect image illumination within the LOE to propagate towards partial reflective surfaces 12 via internal reflection. Such LOE structures are discussed in detail in commonly assigned PCT patent application publication WO 2020 / 049542 A1.

[0051] In each example described herein, the internal reflection of the image propagating along the LOE can be, for example, total internal reflection (TIR) ​​or Fresnel reflection. Furthermore, unlike perspective near-eye displays, the optical aperture expander presented here does not require the use of a transparent LOE. Therefore, the rear (lower) surface (30b) of the waveguide can be opaque, allowing the use of a specular coating. This provides increased design flexibility for the HUD, as the specular-coated surface does not need to adhere to TIR conditions, enabling the waveguide to be mounted on or within a vehicle dashboard without an air barrier between the waveguide and the dashboard.

[0052] In some implementations, a relatively large distance between the observer's eye and the LOE will increase the observer's sensitivity to local non-uniformity of display brightness. In some cases, such an effect is mitigated by providing a partially reflective coating applied to the upper surface 30a of the LOE 10 and a specular coating applied to the lower surface 30b, the specular coating having the effect of causing mixing of different portions of the aperture and enhancing the uniformity of the output.

[0053] Now, in a special turn Figure 2 A key feature of the HUD of this invention is that the image illumination output from the projector 14 and propagated through the optical aperture expander is a collimated image. If the light is delivered to the user's eye optically unchanged, it provides the effect of an image at infinity. In some cases, it is desirable to introduce additional optical elements (or multiple optical elements), such as (refractive or diffractive) lenses, in the optical path between the waveguide and the windshield, which introduce additional optical power to provide one or more of the following functions:

[0054] 1. The focal plane observed by the occupants shifts from infinity to an intermediate focal plane. Therefore, it is possible to make some dashboard elements appear closer than others, or to place all elements at a preferred apparent distance.

[0055] 2. Compensate for astigmatism, defocus, barrel distortion, pincushion distortion, or any other image distortion caused by the windshield's non-planarity. (Some types of distortion can alternatively be corrected by synthetic adjustments to the digital image to compensate for image distortion caused by the windshield or other factors.)

[0056] 3. Lateral (X and / or Y) shift of the eyebox and / or field of view positioning. (Such a shift can also be achieved by means of mechanical movement and / or reorientation of the optical engine.)

[0057] exist Figure 2The diagram schematically illustrates one such implementation by introducing an optical element 199 (shown by dashed lines) between the LOE 10 and the windshield 15. However, adding such an element may affect the compactness of the implementation. Figure 2 An alternative implementation that may be particularly advantageous is shown (ignoring the dashed element 199), according to which light is coupled downwards from LOE 10 and then reflected upwards from reflective optics 19 toward the windshield. Optical element 19 provides functionality similar to that described above for element 199. In some cases, element 19 can be integrated with a polarization rotation element (particularly a quarter-wave plate (QWP) 18), and the coating providing the reflective properties of surface 12 can be implemented as a polarization-dependent coating. Thus, if S-polarization is coupled out by facet 12, the illumination is converted to P-polarization twice via QWP 18 before and after reflection at surface 19, and then the image illumination passes through facet 12 with minimal interference. Figure 2 As shown, the orientation of the facet 12 in LOE 10 is reversed such that the group of partially reflective surfaces 12 couples the image illumination from the main outer surface 30b (away from the windshield), wherein the image illumination is reflected from the reflective optics 19, which modifies the image illumination according to its optical power. Element 19 can at least partially compensate for optical aberrations in the image introduced by reflections from surfaces associated with the windshield. Additionally or alternatively, element 19 can be configured to limit the apparent distance of the image observed by the user after reflection from surfaces associated with the windshield.

[0058] In the preferred embodiment shown here, light reflected from the reflective optical element 19 is transmitted through the LOE before being reflected from the surface associated with the windshield. In an alternative implementation, by changing the orientation of the LOE and element 19, the return optical path from element 19 toward the windshield 15 can be made to bypass the LOE.

[0059] Turn now Figure 3A and Figure 3B In some implementations, employing a light path that includes two reflections from a surface associated with the windshield can be useful. In the example shown here, the image illumination coupled from LOE 10 follows a light path visible to the user's eye 50 when the user is observing a scene outside the windshield, including: a first reflection at a first angle of incidence from a reflector surface associated with the vehicle's windshield; an intermediate reflection from an additional reflective surface 18; and a second reflection from a surface associated with the windshield. This dual-reflection architecture is particularly advantageous for inconspicuous placement of the HUD system near the lower end of the windshield. Although a combination of these features is not shown, it is advantageous to combine this option with... Figure 1A and Figure 1BCombinations of two-dimensional optical aperture extensions, and / or with Figure 2 The use of reflective optical element 19 in combination.

[0060] This method can be enhanced by employing an angle-selective reflector surface 21 associated with the windshield, which has a first reflectivity for light normally incident on the surface and a second reflectivity less than the first reflectivity for light incident at an angle greater than 45 degrees. This ensures that the first reflection is a relatively high proportion of reflection, thereby making it easier to ensure that sufficient display intensity is retained after the second windshield reflection to provide an easily visible display. Such angle-selective reflective characteristics can be achieved using a multilayer dielectric coating, as is known in the art.

[0061] In some particularly optimized implementations of this method, various components are used to manage polarization and / or ensure sufficient image brightness. As a non-limiting specific example, the additional reflective surface 18 is advantageously implemented as a polarizing beam splitter, and a quarter-wave plate 17 is inserted in the optical path between the reflective surface associated with the windshield 15 and the additional reflective surface 18. Advantageously, a second quarter-wave plate 16 is included in the windshield, located on the far (outer) side of the surface from the user. Most preferably, the first QWP 16 and the second QWP 17, along with a portion of the reflector surface 21, are all integrated into the windshield 15, for example, as... Figure 3B The enlarged partial view is shown

[0062] Therefore, the operation of this configuration is as follows. Surface 18 preferably combines an HWP (half-wave plate) with a polarization beam splitter (polarization-dependent mirror) that reflects only S-polarized light. The HWP converts the S-polarization coupled from the LOE to P-polarization, and then the P-polarized light passes through reflector 18. Inside the windshield, light reflected from the partial reflective layer 21 passes twice through QWP 17 (which acts as a half-wave plate and converts the P-polarization back to S-polarization), and then the light is reflected by surface 18. The light reflected from surface 18, as S-polarized, is incident on the windshield at a larger angle of incidence (i.e., a shallower angle), and before being delivered to the observer's eye 50, before and after reflection at the partial reflector 21, is converted back to P-polarization by passing twice through QWP 17.

[0063] Furthermore, the presence of QWP 16 ensures that light passing through partial reflector 21 via the second reflection is also converted to P-polarization and incident on the outer surface of the windshield at an angle close to the Brewster angle. This light will not be significantly reflected, thus avoiding ghosting. For the high efficiency of this system, the reflectivity of surface 21 as a function of angle is significantly correlated, exhibiting high reflectivity for the first reflection at low angles of incidence (AOI) and low reflectivity for the second reflection at higher AOI.

[0064] Alternatively, the polarizing beam splitter of surface 18 may be shaped to provide optical power in a manner similar to element 19 described above to at least partially compensate for optical aberrations in the image introduced by reflections from surfaces associated with the windshield and / or to provide the desired display field of view.

[0065] Turn now Figure 4 as well as Figures 5A to 5C In some cases, it can be advantageous to combine two or more HUDs into a combined system, where each HUD provides a different area of ​​the field of view visible to the user and / or makes the field of view visible from different areas of the eye-tracking box. For example... Figure 4 As shown, these multiple HUDs can be deployed side-by-side, for example, arranged along the X direction. Alternatively, in some cases, multiple HUDs are deployed with at least partial overlap, as will be referred to Figures 5A to 5C As shown.

[0066] Therefore, in some cases, two or more optical engines, each including an LOE and a POD, are placed below the windshield of the car to reflect multiple images. Each optical engine has its own eye-tracking box and a field of view for the driver or passenger. The height, scale, and perceived focal plane of each of these images can be controlled independently, as will be described in detail below. Figure 4 This schematically illustrates multiple optical engines (OEs) projecting independent portions of an image without image stitching. "Image stitching" implies that two or more projected and / or coupled images contain partially overlapping image data.

[0067] In some implementations (also for a single HUD), the HUD system may include a controller configured to control one or more elements of the HUD. For example, the controller may be used to control the aforementioned additional optical elements, implemented as electro-optical elements, to achieve one of the aforementioned objectives. The controller may control the various HUD system elements independently of each other or in a coordinated and cooperative manner. For example, the controller may be used to adjust the depth of focus of the image individually and independently of each other. The controller preferably also includes all necessary electronic components (e.g., at least one processor or processing circuitry) to drive the image projector, all of which are known in the art.

[0068] According to another option, such adjustments / compensations can be performed independently on any of the three axes for each of the multiple optical engines. In the preferred implementation, such adjustments can be performed using electronically adjustable lenses, PZT actuators, or any other type of electrically variable optical element.

[0069] Certain preferred embodiments of the present invention may provide one or more of the following advantages:

[0070] 1. Expanded and adjustable eye-tracking box and field of view.

[0071] 2. The focal plane can be adjusted for static or dynamic different image elements.

[0072] 3. Compact shape factor for integration into vehicle dashboards.

[0073] 4. Compact optical components enable cost-effectiveness and high optical performance.

[0074] Figures 5A to 5C Another implementation is shown in which two optical aperture expanders are staggered in at least a partially overlapping relationship. The first HUD configuration includes: an image projector 14, and... Figure 1A and Figure 1B The corresponding elements of LOE20 and LOE10 are constructed in the same manner. A second HUD is constructed using similar components, labeled 14', 20', and 10', respectively. As shown, these elements can be neatly nested with suitable optical isolation layers between adjacent LOEs to maintain TIR conditions. Various polarization schemes can be used to minimize the interaction between the two HUDs in the overlapping regions. As a non-limiting example, LOE 10' can operate using a partially reflective surface implemented using a structural polarizer beamsplitter (e.g., a wire grid beamsplitter) that partially reflects P-polarization, which is then transmitted through the partially reflective surface of LOE 10. In all other respects, the structure and operation of LOE 10' will be understood by analogy with LOE 10.

[0075] Figure 5A This illustrates a scenario where different regions of the vertical field of view (FOV) are projected by two HUD subsystems. Depending on the image content, these images can be sub-regions of a continuous image, which are “stitched” together to provide a single, continuous, magnified field of view, larger than the field of view that would be provided by a single HUD system of a given size. Figure 5B Alternative applications are shown where the same FOV is provided by two systems, but they complement each other to cover a larger eye-tracking box area (by...). Figure 5B The vertical arrow in the EMB indicates that the required FOV is provided.

[0076] In the various embodiments disclosed herein, the desired parallelism of the optical surfaces and other optical properties of the HUD components can be affected by extreme temperature gradients. To avoid extreme temperature gradients, thermal control is preferably implemented for at least a portion of the HUD system in some cases. This can be achieved by mounting the various HUD components (PODs and / or LOEs) on a hot plate, which tends to maintain a uniform temperature across the components. Most preferably, thermoelectric temperature control components are associated with the hot plate to keep the optical components within a target temperature range.

[0077] In some embodiments, a UV blocking layer may preferably be provided integrated into the windshield 15 to protect the optical components of the HUD from UV degradation. Alternatively or additionally, the uppermost surface of the HUD optics (e.g., HWP 17, PBS 18, or upper LOE surface 30a) may be provided with a UV blocking layer.

[0078] In some cases, additional precautions may be necessary to prevent external radiation, especially direct sunlight, from reflecting off the surface of HUD optics (such as the LOE) at angles that could cause "ghosting" reflections that could reach the user's eyes. Such precautions could include using a polarizing strip across the lower edge of the windshield to allow only polarizations that will not reach the user's eyes (according to one of the polarization schemes described above). This can also be enhanced by providing an anti-reflective coating on any exposed surfaces of the LOE to minimize surface reflections of sunlight glare. Alternatively, in some cases, potential incident glare from certain directions can be blocked by carefully positioned mechanical baffles that shield the optics from incident solar glare at relevant angles that pose a risk of ghosting reflections.

[0079] In some implementations, the HUD system may include an eye-tracking sensor configured to detect the position of the driver's pupils. A controller coupled to the eye-tracking sensor may be used to control optics positioned between the waveguide and the windshield based on the position of the eyeball or the direction of observation. For example, if the driver is looking into the distance, the optics may be adjusted to increase the depth of focus of one or more images. Similarly, if the driver's eyes are focused on a relatively near point, the optics may be adjusted to decrease the depth of focus of one or more images. Likewise, the controller may adjust the lateral position of one or more images based on the driver's direction of observation detected by the eye-tracking sensor.

[0080] Another aspect of the present invention is Figure 6A and Figure 6BThe diagram is schematically illustrated. In this case, a waveguide (LOE) is introduced into or near the interior of a car side window, which is typically nearly vertically aligned. A preferred technique for this configuration is a composite LOE structure (e.g., described in "LOE with Two-Axis Internal Aperture Expansion"). Therefore, the image can be expanded both vertically and horizontally, providing a two-dimensional expansion of the image while also reducing the size and complexity of the imaging pod.

[0081] like Figure 6A As shown, the observer's eye 50, representing the EMB, is shown in front of window 15a, with LOE 10 adjacent to or integrated into window 15a. The LOE (“waveguide”) comprises: a set of mutually parallel partially reflective inner surfaces 12 that extend the optical aperture (“pupil”) in one dimension, in this case along the Y direction; and another set of mutually parallel partially reflective inner surfaces 11 that extend the optical aperture in an orthogonal direction, here along the Z direction. In the non-limiting example shown here, light is injected into the LOE from POD 14 via coupling prism 13. This structure can optionally be implemented within the side window 15 using different encapsulation methods, such as using an air gap, a low-refractive-index adhesive, or other low-refractive-index insulating layers that facilitate propagation via internal reflection. Therefore, the LOE is preferably encapsulated within the window material, wherein at least the encapsulation layer adjacent to the LOE is formed of a material with a lower refractive index than the LOE material to support internal reflection at the main outer surface of the LOE. Alternatively, an angle-selective reflective coating can be used to simulate TIR characteristics. Figure 6B In the image, the waveguide and POD are shown from another viewpoint, along the X direction.

[0082] According to one aspect of the invention, the HUD window structure is integrated into the window of a vehicle door 155. In this case, the system according to the teachings of the invention includes a door panel 155 and a window 15a supported by the door panel. The window 15a includes a visible portion 34a providing a view of the scene outside the window and a hidden portion 34b extending into the interior of the door panel 155. The LOE 10 integrated with the window 15a has a pair of mutually parallel main outer surfaces 30a, 30b and at least a first set of mutually parallel partial reflective surfaces 12 inside the LOE and inclined to the main outer surfaces. An image projector 14, including an image generator and collimating optics, is located within the door panel 155 and is optically coupled to a region of the LOE 10 within the hidden portion 34b of the window to introduce image illumination corresponding to a collimated image into the LOE. The image illumination propagates within the LOE through internal reflection at the main outer surfaces and is gradually coupled out of the LOE from the visible portion of the window through a set of partial reflective surfaces. In certain particularly preferred embodiments, similar to the configuration described in PCT patent application publication WO2020 / 049542A1, two-dimensional extension is achieved by incorporating an additional set of mutually parallel internal partial reflective surfaces 11. Particularly advantageously, the image projector 14 and the facet 11 (if present) are located within the door panel 155, thereby providing physical protection for the image projector and associated components, and preventing the facet 11 from generating problematic "ghosting" reflections of ambient light from the sky and other light sources or bright objects.

[0083] Vehicle doors and windows typically include mechanisms for lowering and raising the window relative to the door panel (in Figure 6A and Figure 6B (Indicated by arrow 40) This mechanism may increase the complexity of the HUD implementation. In some cases, it would be preferable that the image projector does not move with the window. In this case, optical coupling from the image projector 14 to the LOE 10 can be advantageously achieved via an air gap 36. The implementation shown here employs an air gap and a coupling prism 13 integrated with the LOE. The image projector 14 is then deployed to align with the window in the raised position to illuminate the image coupled into the LOE 100 via the air gap 36 and the prism 13, without hindering the lowering of the window.

[0084] It should be understood that the various HUDs of the present invention can be used to advantageously display a wide range of information related to vehicle operation. For example, in some particularly preferred implementations, the HUD system displays dashboard elements, including two or more selected from the group consisting of: speedometer, turn signals, fuel gauge, and thermometer. Additionally or alternatively, the system may include a controller configured to receive data from multiple sensors and generate multiple images corresponding to the data received from the multiple sensors for projection by the HUD for user viewing.

[0085] It should be understood that the above description is intended to be illustrative only, and many other embodiments are possible within the scope of the invention as defined by the appended claims.

Claims

1. A vehicle head-up display (HUD) for displaying an image to a user in a vehicle with a windshield, the HUD comprising: An image projector, comprising an image generator and a collimating optics, wherein the image projector outputs an image illumination corresponding to a collimated image; as well as An optical aperture expander includes at least a first optically opposed element (LOE) serving as a light-guiding optical element. The first LOE has a pair of mutually parallel primary outer surfaces. An image projector light is coupled to the optical aperture expander such that image illumination propagates within the first LOE via internal reflection at the primary outer surfaces. The first LOE also includes at least one set of mutually parallel partially reflective surfaces located within the first LOE and inclined to the primary outer surfaces. The set of partially reflective surfaces gradually couples out of the first LOE from the image illumination. The optical aperture expander is deployed such that image illumination coupled from the first LOE follows a light path including reflections from a surface associated with the vehicle's windshield, making it visible to the user when the user observes a scene outside the windshield. Image illumination coupled from the first LOE follows a light path to be visible to the user when the user observes a scene outside the windshield, the light path including: a first reflection at a high angle of incidence from a surface associated with the windshield of the vehicle, an intermediate reflection from an additional reflective surface, and a second reflection from the surface associated with the windshield.

2. The HUD according to claim 1, wherein, The optical aperture expander also includes a second set of partially reflective surfaces that are deployed parallel to each other and are not parallel to the first set of partially reflective surfaces. The second set of partially reflective surfaces is deployed to gradually redirect image illumination from the image projector to the first set of partially reflective surfaces.

3. The HUD according to claim 2, wherein, The second set of partially reflective surfaces is located within the first LOE between the pair of main outer surfaces.

4. The HUD according to claim 2, wherein, The second set of partially reflective surfaces is located within the second LOE defined by the second pair of main outer surfaces.

5. The HUD according to claim 4, wherein, The second LOE is deployed adjacent to the main outer surface of the first LOE that is farther from the windshield of the vehicle.

6. The HUD according to claim 1, wherein, The group of partially reflective surfaces is deployed to couple the image illumination from one of the pair of primary outer surfaces opposite to the windshield. The HUD also includes reflective optical elements with optical power, the reflective optical elements being configured to at least partially compensate for optical aberrations introduced into the image by reflections from surfaces associated with the windshield.

7. The HUD according to claim 6, wherein, The reflective optical element is also configured to limit the apparent distance of the image observed by the user after reflection from the surface associated with the windshield.

8. The HUD according to claim 6, wherein, Light reflected from the reflective optical element is transmitted through the first LOE before being reflected from the surface associated with the windshield.

9. The HUD according to claim 1, wherein, The surface associated with the windshield is an angle-selective reflector configured to have a first reflectivity for light incident normally onto the surface and a second reflectivity less than the first reflectivity for light incident at an angle greater than 45 degrees.

10. The HUD according to claim 1, wherein, The additional reflective surface is a polarizing beam splitter, and a quarter-wave plate is inserted in the optical path between the surface associated with the windshield and the additional reflective surface.

11. The HUD according to claim 10, wherein, The surface associated with the windshield and the quarter-wave plate are both integrated into the windshield.

12. The HUD of claim 11, further comprising a second quarter-wave plate integrated with the windshield and located on the surface at a distance from the user.

13. The HUD according to claim 10, wherein, The polarizing beam splitter is shaped to provide optical power to at least partially compensate for optical aberrations introduced into the image by reflections from the surface associated with the windshield.

14. A system comprising a first HUD and a second HUD, each of the first HUD and the second HUD being implemented according to claim 1, wherein, Each of the first HUD and the second HUD provides a different area of ​​the field of view visible to the user and / or makes the field of view visible from different areas of the eye-tracking box.

15. The system according to claim 14, wherein, The first HUD and the second HUD are deployed side by side.

16. The system according to claim 14, wherein, The first HUD and the second HUD are deployed in a relationship of at least partial overlap.

Images