Projector-based head-up display with high dynamic range for vehicle

Abstract

The invention relates to a projection unit for a field-of-view display device, which is designed to display a virtual image by reflection on a vehicle glass not only in the black printing region thereof but also in the transparent region thereof, comprising: a projector-based imager, the imager comprises a projector for generating a light beam with desired display content and a projection screen illuminated by the projector, the projector being configured to generate a real image on the projection screen and the projection screen being configured to project the light beam thus generated onto the vehicle glass; and an absorber or light distribution device which is arranged inside or outside the projector and is configured to enable the light beam to have a light intensity which varies along the cross section of the light beam, the brightness of the virtual image in the black printing area does not exceed a predetermined first brightness value and is not lower than a predetermined second brightness value in the transparent surface area of the virtual image, and the second brightness value is at least twice the first brightness value.

Description

Technical Field

[0001] The present invention relates to a projection unit for a field-of-view display device, also known as a heads-up display (HUD), which can be used in a motor vehicle or other type of land, air, or water vehicle. Such a device generates a virtual image that gradually appears in the field of view of a vehicle occupant by reflection off a reflective glass surface of the vehicle, such as the front windshield, rear windshield, or side windows. The present invention also relates to a field-of-view display device and a vehicle equipped with the same. Background Art

[0002] For example, in motor vehicles, a head-up display can be used to display speed information and other useful navigation, warning, and vehicle operation instructions, or entertainment content, in the form of virtual images for the driver and / or other passengers when they look out the windshield. For generating a panoramic virtual display, a simplified HUD design is known that includes an imager positioned in the glass bottom region of the windshield so that the real image generated by it is reflected directly onto the windshield without requiring additional imaging or deflection optics in between.

[0003] Until now, the technical implementation of such head-up displays has typically used liquid crystal screens (LCDs) with matrix backlighting. However, this technology faces limitations in terms of thermal management and power consumption if the virtual image is to be displayed in a transparent area of ​​the windshield (located above a lower black printed area of ​​the windshield that has been tinted or coated with a dark or black color). This results in a tenfold increase in the required image brightness compared to displaying the virtual image entirely within the black printed area of ​​the windshield to ensure the required visibility of the HUD image even in sunny conditions. To achieve such high image brightness, expensive micro-LED displays can be used, for example. A less expensive alternative is a projector-based imager, in which a projection screen (also called a screen or screen) is used instead of a luminous display surface, on which the real image is generated by the projector.

[0004] In the future, the display surface of such head-up displays (HUDs) must be able to cover not only the black printed area of ​​the windshield, but also the transparent area located above the black printed area. This requires a large variation in brightness across the image height: in the black printed area, the maximum brightness of the virtual image should not exceed 1000-3000 cd / m² to avoid the risk of glare for passengers. At the same time, in the transparent area, the brightness should reach above 10,000 cd / m².

[0005] LCD-based matrix-backlit imagers can easily accommodate these locally varying brightness requirements by dimming the corresponding LEDs via pulse-width modulation. This option is eliminated with projector-based imagers, as the image-generating surface within the projector is always uniformly illuminated in typical projector systems. The only current solution in these systems is to reduce local brightness by omitting the imager's brightest grayscale. However, this is suboptimal, as it reduces the available grayscale dynamic range in the "darker" image segments and thus results in a loss of image quality in these segments. For example, while 255 grayscale shades are available for each color in bright image segments, only 200 are available in darker image segments. Summary of the Invention

[0006] The present invention is based on the object of providing an alternative and / or improved projection unit for a field of view display device used in a vehicle, which projection unit is particularly suitable for displaying large-area and / or panoramic virtual images by reflection on the windshield. Compared to known devices, the projection unit and field of view display device can achieve improvements in energy efficiency, cost, image quality, visibility of virtual images, and / or other aspects.

[0007] This object is achieved by a projection unit according to claim 1 and by a field of view display device comprising the projection unit and a vehicle equipped with the field of view display device according to the coordinated claims. Further refinements are given in the dependent claims. All further features and effects mentioned in the claims and in the following description of the projection unit also apply to the field of view display device and the vehicle, and vice versa.

[0008] According to a first aspect, a projection unit for a field of view display device for use in a vehicle is provided. The vehicle may be a motor vehicle, but may also be any other land, air, or water vehicle. The field of view display device is configured to gradually display a virtual image by reflection on the vehicle window pane, not only in black or dark-printed or tinted black-printed areas thereof, but also in adjacent, substantially transparent surface areas thereof. The field of view display device may be configured, for example, as a heads-up display (HUD).

[0009] The projection unit is configured to output a suitable light beam during operation of the field-of-view display device and project it onto the vehicle window in such a manner that the light beam is reflected by the vehicle window into the eye or an eyebox designed therefor of at least one vehicle occupant, thereby displaying a virtual image thereto. The eyebox of the field-of-view display device is generally understood to be a spatial region from which a virtual image can be viewed without restriction.

[0010] To this end, the projection unit includes a projector-based imager comprising a projector for generating a light beam with the desired display content and a projection screen (also referred to as a screen or screen) illuminated by the projector. The projection screen can be illuminated by the projector in reflection or, in an alternative embodiment, in transmission. The projector is configured to generate a real image on the projection screen. The projection screen is configured to project the generated light beam in a predetermined shape and direction onto a reflective glass surface in order to produce a virtual image with the desired display characteristics for the respective passenger.

[0011] The projection unit also includes an absorber or light distribution device disposed internally or externally to the projector. The absorber or light distribution device is configured to impart a light beam with a varying intensity along its beam cross-section such that the brightness of the virtual image in the black printed area of ​​the vehicle window does not exceed a predetermined first brightness value and in the transparent surface area does not fall below a predetermined second brightness value, the second brightness value being at least twice the first brightness value. For example, but not by way of limitation, it can be assumed that the vehicle window has identical reflection properties for the light beam incident from the projection unit in its black printed area and its transparent surface area, and that the different brightness values ​​in the virtual image are therefore primarily caused by the absorber or light distribution device.

[0012] The concept of this projection unit is therefore to address the aforementioned problem of the significant difference in image brightness requirements between the black-printed and transparent areas of the windshield by adjusting the light distribution using absorbers or light distribution devices designed for this purpose in the illumination optics. This prevents the reduction in grayscale dynamic range in the black-printed areas of the windshield, which is unavoidable with conventional projector-based imagers, and thus enables high-quality virtual image display there as well.

[0013] In particular, the second brightness value may be approximately three to ten times the first brightness value. For example, the first brightness value may be approximately 1000 to 3000 cd / m 2 and the second luminance value may be at least about 10000 cd / m 2 .

[0014] According to one embodiment, the absorber or light distribution device is designed as a transparent plate with a transmission coefficient that varies along the beam cross section to achieve the above effect. In particular, the transparent plate can be designed with a corresponding absorption gradient for this purpose, so that this is a pure absorption device.

[0015] For example, a projector may include a light source and illumination optics for generating a uniform, collimated illumination beam, as well as an image generation surface (e.g., in the form of an LCOS (liquid crystal on silicon) or a DMD (digital micromirror device)) illuminated by this illumination beam, on which corresponding display content is generated. In the above-described embodiment, the transparent plate may, for example, be positioned within the projector in the beam path of the illumination beam, between the illumination optics and the image generation surface. For reasons of position and / or accuracy, it is ideally positioned directly on or upstream of the image generation surface. Alternatively, however, the transparent plate may be positioned at any other location within the projector, for example, between the image generation surface and a light exit opening in the projector housing, or, if necessary, integrated into a transparent projector cover that closes the light exit opening.

[0016] Alternatively, the transparent plate in the projection unit can also be arranged outside the projector, i.e., between the projector and the projection screen in the optical path of the light beam or behind the projection screen. In this case, a conventional projector can be used in particular. In a specific embodiment, in which the entire projection unit is at least partially surrounded by a protective housing having a light exit opening for the output light beam, the transparent plate can, for example, form a cover that mechanically closes this light exit opening or be integrated into this cover.

[0017] According to another embodiment, the absorber or light distribution device is designed as a light distribution device in which the light is not absorbed but only redistributed. In this case, the projector also includes a light source and illumination and imaging optics with one or more lenses to generate the light beam. The light distribution device is formed by at least one lens, such as a cylindrical lens, which is oriented obliquely to the beam propagation direction of the light beam or the illumination light beam, so that the resulting uneven light distribution (due to imaging errors known as coma) produces the aforementioned variations in light intensity in the light beam cross section.

[0018] According to another aspect, a field of view display device is provided, which is designed for use (i.e., installation) in a vehicle. In addition to the projection unit described herein, the field of view display device also includes a reflective glass in the form of a vehicle window, arranged in the beam path of a light beam output by the projection unit. The reflective glass has a black or darkly printed or tinted black printed area and a substantially transparent surface area adjacent to the black printed area. The reflective glass is positioned and configured in the field of view of at least one vehicle occupant so that it reflects the light beam into their eye box, thereby presenting the display content to them in the form of a virtual image and also displaying it during operation of the field of view display device.

[0019] According to one embodiment, the reflective glass is positioned directly opposite the projection screen, with the exception of any covering element of the projection unit (e.g., in the form of a cover plate that allows the light beam to pass through), which has no optical effect on the light beam, such as beam shaping, deflection, or imaging. In other words, in this particular embodiment, the field of view display device includes no additional optical elements, such as deflection mirrors, concave mirrors, or lenses, in the beam path between the projection screen and the reflective glass. However, optically functional coatings of the projection screen or reflective glass are still possible. This embodiment, in particular, allows for a vertically compact projection unit, making it particularly suitable for large-area and / or panoramic virtual displays.

[0020] According to another aspect, a vehicle as described above is provided. Spatial orientation terms such as "above it", "below it", "laterally", "horizontally", "vertical" and the like used herein generally relate to a conventional vehicle-fixed Cartesian coordinate system having mutually perpendicular longitudinal, transverse and vertical axes of the vehicle. The vehicle has at least one vehicle glass of the type described herein having a black or darkly printed or tinted black printed area extending along the bottom of its glass, such as a front windshield having an instrument panel extending below it. The vehicle is equipped with the above-described field of view display device, the projection unit of which can, for example, be mounted directly in the upper side of the instrument panel or below the upper side, so that a light beam is projected by the projection unit onto the front windshield, and the light beam is reflected by the front windshield into the eyes of the driver and / or at least one other passenger. However, the projection unit can also be integrated in any other suitable installation position in the vehicle, and other vehicle glass can also be used as reflective glass.

[0021] In particular, the front windshield can be used as a reflective glass for the field of view display device at least with its horizontally extended major part. Therefore, in particular, a panoramic virtual display can be realized for the driver and / or co-driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above aspects of the present invention and their implementation and specific design solutions are described in more detail below with reference to the examples shown in the accompanying drawings. The accompanying drawings should be understood as purely schematic illustrations of the basic optical structural principles, i.e., they are not drawn to scale. The accompanying drawings are as follows:

[0023] Figure 1 A portion of a vehicle having a field of view display device according to an exemplary embodiment of the present invention is shown in vertical longitudinal section, wherein the beam path of the projector light is schematically illustrated;

[0024] Figure 2 Show Figure 1 A schematic cross-sectional view of the optical structure of a projector of a field display device having an absorber or a light distribution device configured as a transparent plate with an absorption gradient; and

[0025] Figure 3 Show Figure 1 Schematic cross-sectional view of the optical structure of a projector of a field display device having an absorber or light distribution device formed by tilted cylindrical lenses of the illumination optical device. DETAILED DESCRIPTION

[0026] All the above-mentioned different embodiments, alternatives and specific design features of the projection unit, the field of view display device and the vehicle according to the above-mentioned aspects of the invention mentioned in the description and the following claims can be Figures 1 to 3 The examples shown are implemented, in particular, can also be implemented instead of or in addition to the features shown therein. Therefore, they will not be repeated in full below. This is for the above-mentioned Figures 1 to 3 The definitions of terms and effects related to the various features shown in also apply.

[0027] Figure 1 A highly simplified vertical longitudinal section shows a portion of a vehicle 1 having a field of view display device 2 according to an exemplary embodiment of the present invention. The spatial orientation terms used below, such as "horizontal", "vertical", "above", "below", "beneath", etc., relate to a conventional vehicle-fixed Cartesian coordinate system with mutually perpendicular longitudinal, transverse and vertical directions of the vehicle 1. The vehicle 1 is a motor vehicle in this example, which is Figure 1 In the figure, only the front windshield 3 is shown, which serves as the above-mentioned reflective glass of the field of view display device 2. Below the front windshield, the projection unit 5 of the field of view display device 2 is arranged in the instrument panel 4 not shown in detail.

[0028] The field of view display device 2 is designed to generate a virtual image in the image areas V1 and V2 in front of the windshield 3 in the field of view of at least one vehicle occupant who is in the Figure 1 , only the spatial area (eye box) E in vehicle 1 intended for the vehicle's eyes is represented. The vehicle occupants may be, for example, the driver and / or front passenger of vehicle 1 . The visual display device 2 may be designed, in particular, for a panoramic virtual display by using the windshield 3 with substantially its entire horizontal extent as a reflective pane for the visual display device 2 . This relates purely to a head-up display (HUD) by way of example.

[0029] The projection unit 5 includes a projector-based imager. This imager comprises a projector 6 for generating a light beam with the desired display content and a projection screen 7 (screen or screen) illuminated by the projector. In this example, the projector 6 is configured to generate a real image on the projection screen 7 in reflection, thereby illuminating it from obliquely above. The projection screen 7 is configured to project the generated and reflected light beam L onto the windshield 3 in a predetermined shape and direction, thereby displaying a virtual image with the desired display characteristics for the respective passenger outside the windshield 3.

[0030] The light beam L is represented by its edge rays, which define its beam cross section required for generating the virtual image. A portion of the light beam L is reflected by the windshield 3 in its black printed area, which extends along the lower edge of the windshield and has a black print 8 formed in or on the windshield 3 (at Figure 1 (shown only symbolically in the image). Alternatively, the windshield 3 can also be partially or completely darkened in this area through other means (such as tinting). The remaining portion of the light beam L is reflected by the substantially transparent surface area of ​​the windshield 3 located above the black print. This requires a large variation in brightness across the image height: in the black print area, the maximum brightness in the corresponding virtual image area V1 should not exceed 1000-3000 cd / m² to avoid the risk of dazzling passengers. At the same time, in the transparent area, the brightness in the corresponding virtual image area V2 should reach above 10,000 cd / m².

[0031] This is solved in the projection unit 5 proposed here by means of a controlled light distribution in the illumination optics, i.e. without reducing the overall available grayscale dynamic range of the imager in the image region V1 relative to the image region V2. Some examples of absorbers or light distribution devices suitable for this are explained below (only in the case of Figure 2 and 3 shown in ).

[0032] Figure 2 Shown in a highly simplified schematic cross-sectional view Figure 1 A first example of an optical structure of a projector 6 of a field of view display device 2 is shown. The projector 6 comprises a light source 11 (e.g. in the form of at least one LED) and a cylindrical converging lens 12 as an illumination optical device for generating a uniform, collimated illumination beam L0. Thus, an image generation surface 9, e.g. in the form of an LCOS or DMD chip, is illuminated in order to generate the corresponding display content. The generated light beam L (which is output by the projector 6) is Figure 2 In the figure, the continuation direction of the illumination beam L0 is shown only schematically. In practice, the beam L in this example does not leave the image generating surface 9 in transmission, but in reflection and is reflected by means of suitable imaging optics (which are in the Figure 2 (omitted for display reasons) to focus on Figure 1 On the projection screen 7.

[0033] In this example, an absorber or light distribution device in the form of a transparent plate 10 with a locally varying absorptivity is arranged directly upstream of the image generating surface 9 in the beam cross section of the uniform, collimated illumination beam L0. The absorption gradient of the transparent plate 10 extends only in one dimension: in the region of the transparent plate. Figure 2In the lower section 101 (which ultimately corresponds to the portion of the light beam L reflected on the transparent area of ​​the front windshield 3 (see Figure 1 ), the absorption rate is significantly lower than the absorption rate in the section 102 located above it (the section corresponds to the part of the light beam L reflected in the black printed area of ​​the front windshield 3). Figure 1 As shown, the maximum achievable image brightness in the black printed area is reduced to a maximum of 3000 cd / m² in this example. 2 The expected value is achieved without reducing the dynamic range of grayscale.

[0034] Figure 3 Again with something like Figure 2 A highly simplified schematic cross-sectional view shows Figure 1 Another example of the optical structure of the projector 6 of the field display device 2. In order to avoid repetition, only the optical structure of the projector 6 of the field display device 2 is described below. Figure 2 difference.

[0035] Instead of the transparent plate 10, a cylindrical lens 12 is also placed in the beam path of the illumination optics. However, the cylindrical lens is not positioned perpendicularly to the optical axis of the projector 6, but is tilted relative to its position and thus produces a coma effect in one dimension. This causes an uneven light distribution on the DLP / LCOS chip and thus in the virtual image. Figure 1 The brightness variation shown in FIG. Therefore, the tilted cylindrical lens 12 forms the absorber or light distribution device in this example. Figure 3 The implementation method and Figure 2 This has the advantage that the light is not absorbed by the absorber or light distribution device, but is only redistributed.

[0036] Reference Signs List

[0037] 1 vehicle

[0038] 2-field display device

[0039] 3Front windshield

[0040] 4Dashboard

[0041] 5 projection units

[0042] 6 Projector

[0043] 7 Projection Screen

[0044] 8 Black printing part

[0045] 9 Image generating surface inside the projector

[0046] 10 Transparent plates with absorption gradients

[0047] 101 The lower section of the transparent plate with low absorption rate

[0048] 102 upper section of the transparent plate with high absorption rate

[0049] 11 Light Source

[0050] 12 cylindrical converging lens, cylindrical lens

[0051] L A beam of light with displayed content, also known as a projector light

[0052] L0 is the illumination beam used to illuminate the image generating surface inside the projector

[0053] E eye box

[0054] V1 Virtual image area in the black printed area of ​​the front windshield

[0055] V2 Virtual image area in the transparent area of ​​the front windshield

Claims

1. A projection unit (5) for a visual display device (2), the visual display device being designed to gradually display a virtual image by reflection on a vehicle window both in its black or dark-printed or tinted black-printed areas and in its adjacent, essentially transparent surface areas, the projection unit comprising: - a projector-based imager comprising a projector (6) for generating a light beam (L) having a desired display content and a projection screen (7) illuminated by the projector, wherein the projector (6) is configured to generate a real image on the projection screen (7), and the projection screen (7) is configured to project the light beam (L) generated thereby onto a vehicle window in a predetermined shape and direction; and - an absorber or a light distribution device arranged inside or outside the projector (6), which is designed to give the light beam (L) a light intensity that varies along its beam cross section, so that the brightness of the virtual image in the black printed area of ​​the vehicle window does not exceed a predetermined first brightness value and does not fall below a predetermined second brightness value in the transparent surface area of ​​the vehicle window, the second brightness value being at least twice the first brightness value.

2. The projection unit (5) according to claim 1, wherein The second brightness value is about three to ten times the first brightness value; or the first brightness value is about 1000 to about 3000 cd / m 2 and the second luminance value is at least about 10000 cd / m 2 .

3. The projection unit (5) according to claim 1 or 2, wherein: The absorber or light distribution device is configured as a transparent plate (10) having a transmission coefficient that varies along a beam cross section of the light beam (L) or an illumination light beam (L0) for generating display content.

4. The projection unit (5) according to claim 3, wherein For this purpose, the transparent plate (10) is formed with a corresponding absorption gradient.

5. The projection unit (5) according to claim 3 or 4, wherein: The projector (6) comprises a light source (11) and illumination optics for generating an illumination beam (L0) and an image generating surface (9) illuminated thereby for generating display content; and The transparent plate (10) is arranged inside the projector (6) in the beam path of the illumination light beam (L0) between the illumination optics and the image generating surface (9), preferably directly on or upstream of the image generating surface (9).

6. The projection unit (5) according to claim 3 or 4, wherein: The transparent plate (10) is arranged outside the projector (6) in the light path of the light beam (L) between the projector (6) and the projection screen (7) or behind the projection screen (7); and Preferably, the projection unit (5) is at least partially surrounded by a protective housing having a light exit opening for the light beam (L) to be output, and the transparent plate (10) forms a cover that mechanically closes the light exit opening or is integrated into the cover.

7. The projection unit (5) according to claim 1 or 2, wherein: The projector (6) comprises a light source (11) and an illumination and imaging optical device having one or more lenses for generating a light beam (L); and The absorber or light distribution device is a light distribution device formed by at least one lens, which is oriented obliquely to the beam propagation direction of the light beam (L) or the illumination light beam (L0) for generating display content, so that the resulting uneven light distribution produces the above-mentioned change in light intensity in its beam cross section.

8. A field of view display device (2) for use in a vehicle (1), the field of view display device comprising: - a projection unit (5) according to any one of the preceding claims; and - a reflective glass in the form of a vehicle window, which is to be arranged in the beam path of the light beam (L) emitted by the projection unit (5), and which has a black or dark-printed or pigmented black printed area and a substantially transparent surface area adjoining the black printed area; - the reflective glass is arranged and configured in the field of view of at least one vehicle passenger so that it reflects the light beam (L) to an eye box (E) intended for the passenger's eyes, thereby being able to present the display content to the passenger in the form of a virtual image outside the reflective glass; and The reflective glass is preferably arranged directly opposite the projection screen (7), with the exception of any covering element of the projection unit (5), which has no optical effect on the light beam (L) in terms of beam shaping, deflection or imaging.

9. A vehicle (1), in particular a motor vehicle, having longitudinal, transverse and vertical directions perpendicular to each other fixed to a Cartesian coordinate system of the vehicle, said vehicle comprising: - vehicle glazing having a black or dark-printed or tinted black printed area extending along its lower edge and a substantially transparent surface area located above the black printed area; as well as - The field of view display device (2) according to claim 8, wherein the reflective glass is formed by the vehicle glass, in particular the front windshield (3); - At least a portion of the black printed area and of the transparent surface area located above the black printed area acts as a reflective glass.

10. The vehicle (1) according to claim 9, wherein The vehicle (1) has a dashboard (4) disposed below a front windshield (3); and The projection unit (5) of the field of view display device (2) and its projection screen (7) are arranged in the upper side of the instrument panel (4) or below the upper side, so that the front windshield (3) is used as a reflective glass for the field of view display device (2) at least with a large part of its horizontal extension.

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