Brightness adjustment of a head-up display depending on eye or head position

Abstract

The invention relates to a method for operating a field-of-view display device in a vehicle, comprising an image transmitter, a semi-transparent reflective disc arranged in the field of view of a user, and imaging and / or projection optics, such that the display content is presented to the user as a floating real or virtual image via reflection on the reflective disc.The method comprises changing the direction of beam propagation by adjusting the imaging and / or projection optics and / or the image sensor; determining a current image position from the user's perspective based on the aforementioned adjustment and / or on position data of the user, their eyes and / or their viewing direction; determining, based on vehicle design data, whether and which vehicle components and with what darkness values ​​have entered the image background for the determined image position; and adjusting the brightness of the displayed content accordingly to generate the real or virtual image with predetermined contrast properties.

Description

[0001] The invention relates to a method for operating a head-up display device in a motor vehicle or other land, air, or water vehicle, also known as a head-up display (HUD). Such devices are designed to generate a real or virtual image projected into the user's field of vision by reflection off an at least partially transparent reflective screen, such as the front or rear window of the vehicle, or off a specially provided combiner screen located in the user's field of vision. The invention also relates to a correspondingly configured control unit, a projection unit designed to emit a suitable beam of light, a head-up display device containing this unit, and a vehicle equipped therewith.

[0002] It is common practice, particularly in motor vehicles, to use a head-up display (HUD) to overlay information such as speed limits or other useful navigation and vehicle operating instructions onto a virtual image of the real-world surroundings in front of the vehicle, allowing the driver to keep their eyes on the road. A conventional HUD typically uses a projection unit located below the windshield, inside the instrument panel, to generate this information.This typically includes a display to generate a beam of light with the desired display content, as well as imaging and projection optics, usually with a concave mirror, to shape the beam of light and direct it onto the windshield so that it is reflected from there to the driver's eyes, allowing him to see the virtual image at a suitable size and distance beyond the windshield.

[0003] In addition to virtual image display, for example from CN 217821128 U the generation of a real image floating in the air for one or more viewers in a vehicle by means of an imaging concave mirror, wherein the beam path leads via reflection at the windshield to the eyeboxes of a driver and a passenger.

[0004] Furthermore, DE 10 2012 204 303 B4 discloses a method for controlling the brightness of the image emitted by an imaging device of a head-up display in a motor vehicle, which is reflected into the driver's field of vision so that the driver perceives a virtual image. For this purpose, a brightness profile for the background area behind the virtual image, as seen from the driver's perspective, is determined from a suitable camera image, and the brightness of the image emitted by the imaging device is controlled segment by segment for different image segments depending on the brightness profile. In this process, the brightness of displayed information in the image segment of a bright background area is increased, and the brightness of displayed information in the image segment of a dark background area is decreased.

[0005] To adjust the image and eyebox position for each driver, state-of-the-art systems typically use a suitable rotation of the concave mirror to move the image of a HUD system vertically. When the HUD image is intentionally superimposed on the real-world environment, it is assumed that the HUD image always has a correspondingly transparent background due to a semi-transparent reflective screen. However, in some vehicles, particularly for taller users, a transparent background may not be possible for certain user positions, and other vehicle components, such as windshield wipers, the hood, or the instrument panel, may appear in the background.

[0006] The object of the present invention is to provide an alternative and / or improved method for operating a field-of-view display device and a correspondingly designed projection unit and field-of-view display device for a vehicle, with regard to the display possibilities, image quality, robustness and / or other aspects.

[0007] This problem is solved by a method according to claim 1 for operating a field-of-view display device in a vehicle, and by a corresponding control unit, projection unit, a field-of-view display device containing these, and a vehicle equipped therewith according to the dependent claims. Further embodiments are specified in the dependent claims. All further features and effects mentioned in the claims and in the following description of the method also apply to the control unit, the projection unit, the field-of-view display device, and the vehicle, and vice versa.

[0008] According to a first aspect, a method for operating a field-of-view display device designed for use in a vehicle is provided. The field-of-view display device can, for example, be configured as a head-up display (HUD). The vehicle can be a motor vehicle, but also any other land, air, or water vehicle. Unless otherwise specified, the positional data and spatial orientation terms mentioned herein, such as "vertical," "horizontal," "in front of," "behind," "below," "above," etc., always refer to the standard vehicle-mounted Cartesian coordinate system with mutually perpendicular longitudinal, lateral, and vertical directions of the vehicle.

[0009] The field-of-view display device comprises an image generator for producing a beam of light with the desired display content, a semi-transparent reflective disc positioned within the user's field of vision, and imaging and / or projection optics designed to direct the beam of light onto the reflective disc, so that the display content is presented to the user as an image appearing to float in mid-air via reflection from the reflective disc. Depending on the application-specific design of the field-of-view display device, and in particular the imaging and / or projection optics, either a real image is generated that appears to float in the air between the user and the reflective disc, or a virtual image is generated that appears to float beyond the reflective disc. The user could be, for example, a driver, passenger, or another occupant of the vehicle.

[0010] The process includes the following steps: Depending on the user and / or the situation, the direction of propagation of the light beam is changed by adjusting the imaging and / or projection optics and / or the image transmitter, ensuring that the light beam always reaches the user's eyes. For example, the image and eyebox position can be adjusted to the individual user or tracked according to their head movements, in a manner known per se. Here, the eyebox is understood, as usual, to be a spatial area within the vehicle from which the image is visible in the intended display quality.

[0011] Subsequently, in real time or at a predetermined interval, a current image position relative to the vehicle is determined from the aforementioned adjustment (e.g., from the associated control and / or sensor data) and / or from position data of the user, their eyes, and / or their viewing direction. For example, the currently set eyebox position and propagation direction of the light beam, an image distance along this direction, and a current image size can be determined solely from control and adjustment data of the imaging and / or projection optics and the image sensor. If position data of the user, their eyes, or their viewing direction is used for adjustment, this data can also be used to determine the current image position from the user's perspective or added to the current adjustment data.For control purposes, it is also possible to additionally / redundantly determine the current image position from independent sensor or camera data.

[0012] The next step involves determining, based on vehicle design data, whether and which vehicle components, and with their associated darkness values, form a background for the determined image position. For example, black windshield wipers and a black or dark gray upper surface of the instrument panel have significantly higher darkness values ​​(or correspondingly lower brightness values) than a white-painted upper surface of the hood. Vehicle design data can be, for example, CAD (computer-aided design) data of the vehicle. Subsequently, the brightness of the display content generated by the image sensor is adjusted to the vehicle components currently identified in the image background and their darkness values ​​in order to produce the image with predetermined contrast properties.

[0013] One aspect of this method is to determine the precise position of the displayed real or virtual image in the vehicle by calculating or otherwise ascertaining the user's eye position and / or viewing direction using HUD settings, particularly from an adjustable mirror position in its projection and / or imaging optics. The corresponding viewing angle is then used to determine the background of the image, and vehicle design data is used to ascertain whether opaque vehicle components such as windshield wipers, the hood, or interior trim are visible in the background. If so, the brightness of the image as a whole, or locally (e.g., by locally dimming the light sources used in the image generator), is adjusted to match the corresponding darkness levels of these vehicle components.

[0014] According to one embodiment, both the detection of vehicle components with their associated darkness values ​​in the image background and the corresponding brightness adjustment of the displayed content are performed spatially (i.e., locally with a predetermined spatial resolution) within the image to be displayed. This enables flexible, area-by-area contrast adjustment in cases where one image area has a transparent background (i.e., when no vehicle components beyond the semi-transparent reflector enter the virtually continued beam path), while in another image area, opaque vehicle components have entered the image background.

[0015] According to one embodiment, the brightness of the displayed content generated by the image sensor is reduced more significantly the darker the detected vehicle components are in the image background. Depending on the detected image background and its darkness values, different brightness values ​​of the displayed image are required to achieve, for example, the same contrast. This allows the floating image to be generated with largely constant or homogeneous contrast properties over time and / or space. In other words, this makes it possible to achieve contrast compensation between a transparent background and a comparatively darker image background formed by vehicle components and their surfaces.

[0016] According to one embodiment, the brightness of the displayed content is adjusted via its grayscale values ​​and / or by controlling light sources used in the image sensor to match the required brightness. For example, in an image sensor in the form of a liquid crystal display or another transmissive display layer, the backlight can be selectively dimmed to reduce the image brightness globally or locally. If local variation of the light source brightness is not possible in an image sensor, location-dependent brightness control within the displayed image can also be achieved via its grayscale values. A combination of both methods is also possible.

[0017] In particular, when determining the darkness values ​​of vehicle components identified in the image background, in addition to the vehicle design data, sensor and environmental data available on board the vehicle can also be used. This can include, for example, sensor data measured or derived by vehicle sensors regarding the vehicle's location, the prevailing time of year and day, or the ambient brightness. Furthermore, it can include data received from the vehicle control unit about currently activated interior lighting or sunroof activation, etc., and / or environmental data from external data sources regarding weather, ambient brightness, and much more. Such data can be used as parameters or to correct the darkness values ​​of the relevant vehicle components contained in the vehicle design data.It is also possible for control purposes to independently / redundantly determine the aforementioned darkness values ​​from sensor or camera data from sensors or cameras that optically detect the relevant vehicle components, for example.

[0018] According to another aspect, a control unit is provided which is designed and configured to automatically execute the procedure presented herein. For this purpose, for example, a corresponding computer program (software) can be loaded into a processor of the control unit and run during operation of the field-of-view display device.

[0019] According to another aspect, a projection unit for a viewfinder display device is intended for use in a vehicle. The projection unit can, for example, be enclosed in a protective housing (with or without a transparent cover). It includes an image sensor designed to generate a beam of light with the desired display content. In principle, any image-generating technology suitable for use in a vehicle is suitable for the image sensor, such as a flat panel display or a waveguide display, but also a projector-based image sensor.Furthermore, the projection unit comprises an imaging and / or projection optic arranged and adjustable in the beam path of the light beam such that the light beam leaves the projection unit in a predetermined shape and direction, and is subsequently reflected by an at least partially transparent reflecting disc located in the user's field of vision to the user's eyes, thereby presenting the display content to the user as a floating real or virtual image. The projection unit also includes the control unit described above, which is designed to control the image generator and the adjustable imaging and / or projection optic in order to execute the method described herein.

[0020] According to one embodiment, the imaging and / or projection optics comprise at least one concave mirror whose angle of inclination relative to an optical axis of the projection unit is adjustable in order to change the direction of propagation of the light beam and thus the image and eyebox position to adapt to a user. The respective concave mirror can, for example, be designed for a deflecting, magnifying, imaging, collimating, and / or image-correcting optical function. Alternatively or additionally, the imaging and / or projection optics can also comprise other optical elements such as lenses, plane mirrors, etc., with this or other optical functionality.

[0021] According to another aspect, a field-of-view display device for a vehicle is provided, comprising the projection unit mentioned above and a reflective disc, at least partially transparent, arranged in the beam path of the emitted light beam. The reflective disc is positioned and designed within the user's field of vision in such a way that it reflects the light beam to a predetermined eyebox for the user, thereby displaying the content as a floating real or virtual image.

[0022] According to another aspect, the vehicle described above is designed. The vehicle comprises a passenger compartment and a vehicle window that at least partially delimits it, in particular a windshield. Furthermore, the vehicle includes the view indicator device described above, the projection unit of which is located in the passenger compartment, in particular inside an instrument panel arranged below the windshield, and the reflector of which is designed as a section of the vehicle window or as a combiner lens arranged in the passenger compartment.

[0023] The above aspects of the invention and its embodiments and specific configurations are explained in more detail below with reference to the examples shown in the accompanying drawings. The drawings are to be understood as schematic illustrations and not to scale. They show: Fig. 1 a longitudinal section view of a vehicle with a view display device according to an embodiment of the invention, which is designed for a virtual image display; Fig. 2 a longitudinal section view of a vehicle with a field-of-view display device according to a further embodiment of the invention, which is designed to generate a real image floating inside the vehicle; and Fig. 3 a schematic example of a vehicle from the perspective of the driver of the vehicle Fig. 1 or Fig. 2 image background determined by a method according to an embodiment of the invention, in which vehicle components of varying darkness are contained.

[0024] All the various embodiments, variants, and specific design features of the method, control unit, projection unit, field-of-view display device, and vehicle mentioned above in the description and in the subsequent claims, according to the aspects of the invention above, can be found in the Fig. Examples 1 to 3 shown, in particular also as alternatives or in addition to the features shown therein, may be implemented. Therefore, they are not all repeated below. The same applies accordingly to the definitions and effects of individual features already given above, which are described in Fig. 1-3 are shown.

[0025] Fig. Figure 1 shows, in a highly simplified schematic longitudinal section, an embodiment of a vehicle 1 with a field-of-view display device 2 presented herein, which is designed to generate a virtual image V in the user's field of vision in a purely exemplary, almost horizontal virtual image plane in front of the vehicle 1. In this example, the vehicle 1 is a motor vehicle that is in Fig. 1 is only indicated by its windscreen 3, which serves as a reflector for the field-of-view display device 2. Below this, in an instrument panel 4 (not shown in detail), a projection unit 5 of the field-of-view display device 2 is arranged. This is, again purely by way of example, a head-up display (HUD).

[0026] The projection unit 5 contains an image generator 6 designed to produce the desired display content, in this example an LCD (liquid crystal display). The light beam L emanating from its display surface, which transports the generated display content to an eyebox E of the user (for example, a driver or passenger, not shown separately) in the vehicle 1 and is also referred to here as "projection light", is simplified by its central beam, which leads approximately from the center of the display surface to the center of the eyebox E.

[0027] In the further path of the light beam L, the projection unit 5 comprises an imaging and / or projection optic, which includes a concave mirror 7 whose inclination to the optical axis or to the indicated central ray is adjustable. The image generator 6 and the concave mirror 7 are arranged and designed such that the light beam L leaves the projection unit 5 in a suitable shape and direction, in order to be reflected by the at least partially transparent reflective disk (here, the front disk 3) to the eyebox E, thereby displaying the content to the user as a virtual image V with the desired display properties. The image generator 6, in this example its image-generating display surface, is positioned at a suitable display tilt angle relative to the aforementioned central ray in order to achieve the desired tilt angle of the virtual image plane.As indicated by a double arrow, the display tilt angle can also be different than in . Fig. 1 may be chosen, for example to create a nearly vertically oriented virtual image V.

[0028] Furthermore, the projection unit comprises a control unit 8, which is configured to carry out a method according to an embodiment of the invention and is designed to control and, if necessary, also read out the image sensor 6 and the concave mirror 7. The method includes, among other things, the following steps: - Changing the direction of propagation of the light beam L by adjusting the tilt angle of the concave mirror 7 accordingly, so that the light beam L always reaches the user's eyes; - Determining the current image position from the user's perspective (see below). Fig. 3) based on the aforementioned adjustment and / or on position data of the user, their eyes and / or their direction of gaze used for this purpose; - a determination, based on vehicle design data, of whether and which vehicle components and with which associated darkness values ​​are in the image background 10 (see Fig. 3) have guessed the determined image position; and - Adjusting the brightness of the display content generated by the image generator 6 to the vehicle components currently determined in the image background 10 and their darkness values ​​in order to generate the virtual image V with predetermined contrast properties.

[0029] Fig. Figure 2 shows a longitudinal section view of a vehicle 1 with a field-of-view display device 2 according to a further embodiment of the invention, which, in contrast to Fig. 1. To generate a real image R floating inside the vehicle (instead of the virtual image V). Fig. 1) is trained. Furthermore, to avoid repetition, reference is made to the above description of the Fig. 1 referred to, which also applies here analogously.

[0030] Fig. Figure 3 shows a schematic example from the perspective of the driver of vehicle 1. Fig. 1 or Fig. 2. The background image 10, determined using the above method, contains vehicle components of varying darkness. Vehicle 1 is again distinguished here by its (in Fig. 3 (not shown in detail) windscreen 3 and additionally a steering wheel 9 indicated.

[0031] In this example, the background image 10, which the driver sees behind or within the displayed real or virtual image R / V (only symbolically indicated by the word "Hello"), contains, as a result of an adjustment of the concave mirror 7 for eyebox adaptation, not only a largely transparent background area 10a, which comprises only the windshield 3 and the surroundings visible from it in front of the vehicle 1. In the lower image area, from this driver's perspective, additional vehicle components such as a dark-colored hood and windshield wipers have entered the background image 10 and form correspondingly darker background areas 10b and 10c, whose position in the background image 10 and associated darkness values, indicated by hatching of varying intensity, were determined in this example using design data of the vehicle 1.Accordingly, in the darker background areas 10b and 10c, a slightly lower brightness of the projection light L is required than in the transparent background area 10a to achieve the same contrast across the entire image R / V. The image transmitter 6 is controlled accordingly by the control unit 8. The image brightness can be adjusted via the grayscale values ​​of the image R / V or by actively controlling the LCD backlight (for example, through so-called "local dimming"). Reference symbol list 1 vehicle 2. Viewing field indicator device 3 Windscreen 4 Instrument panel 5 projection units 6 image sensors 7 Concave mirrors 8 Control unit 9 Steering wheel 10 Image background 10a-10c differently light or dark background areas L Light beam bundle, also called projection light E Eyebox V virtual image R real image, floating QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 217821128 U

[0003] DE 10 2012 204 303 B4

[0004]

Claims

[1] Method for operating a field of view display device (2) in a vehicle (1), which comprises an image generator (6) for generating a light beam (L) with the desired display content, a partially transparent reflection disc arranged in the field of view of a user and an imaging and / or projection optics designed to direct the light beam (L) onto the reflection disc, so that the display content is presented to the user as a floating real or virtual image (R, V) via reflection on the reflection disc, comprising the steps: - Changing a propagation direction of the light beam (L) by adjusting the imaging and / or projection optics and / or the image generator accordingly; - Determining a current image position from the user's perspective based on this adjustment and / or on the position data of the user, his eyes and / or his direction of view used for this purpose; - determining, based on vehicle design data, whether and which vehicle components and with which associated darkness values ​​form an image background (10) for the determined image position; and - Adapting a brightness of the display content generated by the image generator (6) to the vehicle components currently determined in the image background (10) and their darkness values ​​in order to generate the real or virtual image (R, V) with predetermined contrast properties. [2] The method according to claim 1, wherein - both the determination of vehicle components with associated darkness values ​​in the image background (10) and the corresponding brightness adjustment of the display content generated by the image generator (6) are carried out location-dependently with respect to positions within the image (R, V) to be displayed. [3] Method according to claim 1 or 2, wherein - the brightness of the display content generated by the image generator (6) is reduced more the darker the determined vehicle components in the image background (10) are, in order to generate the image (V, R) with contrast properties that are essentially constant over time and / or space. [4] Method according to one of the preceding claims, wherein - the adjustment of the brightness of the display content generated by the image generator (6) is carried out via its grey values ​​and / or via a control of light sources used in the image generator (6) corresponding to the required brightness. [5] Method according to one of the preceding claims, wherein - when determining the darkness values ​​of the vehicle components identified in the image background (10), in addition to the vehicle design data, sensor and environmental data available on board the vehicle (1) are also used. [6] Control unit (8) which is designed and arranged to automatically carry out the method according to one of the preceding claims. [7] Projection unit (5) for a field of view display device (2) for use in a vehicle (1), comprising: - an image generator (6) designed to generate a light beam (L) with the desired display content; - an imaging and / or projection optics arranged in the beam path of the light beam (L) and adjustable in such a way that the light beam (L) leaves the projection unit (5) in a predetermined shape and direction, in order to be subsequently reflected by an at least partially transparent reflection disc arranged in the field of vision of a user to the user's eyes and thereby present the display content to the user as a floating real or virtual image (R, V); and - a control unit (8) according to claim 6, which is designed to control the image generator (6) and the adjustable imaging and / or projection optics in order to carry out the method according to one of claims 1 to 5. [8] Projection unit (5) according to claim 7, wherein - the imaging and / or projection optics comprise at least one concave mirror (7) whose angle of inclination is adjustable with respect to an optical axis of the projection unit (5) in order to change the propagation direction of the light beam (L). [9] A field of view display device (2) for a vehicle (1), comprising: - a projection unit (5) according to claim 7 or 8; and - an at least partially transparent reflection disc arranged in the beam path of the light beam (L) emitted by the projection unit (5), which is arranged and designed in the field of vision of a user in such a way that it reflects the light beam (L) to an eyebox (E) predetermined for his eyes, whereby the display content can be presented to him as a floating real or virtual image (R, V). [10] Vehicle (1), in particular a motor vehicle, with mutually perpendicular longitudinal, transverse and height directions of a vehicle-fixed Cartesian coordinate system, comprising: - a passenger compartment with a vehicle window which at least partially delimits the passenger compartment, in particular a windscreen (3); and - a field of view display device (2) according to claim 9, whose projection unit (5) is arranged in the passenger compartment, in particular in the interior of an instrument panel (4) arranged under the windscreen (3), and whose reflection disc is designed as a section of the vehicle windscreen or as a combiner disc arranged in the passenger compartment.

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