CONTROL OF A DISPLAY OF AN AUGMENTED REALITY HEAD-UP DISPLAY DEVICE FOR A MEANS OF MOBILITY

Description

[0001] The present invention relates to a method, a computer program with instructions, and a device for controlling a display of an augmented reality head-up display for a means of transportation. The invention further relates to a means of transportation in which a method or device according to the invention is used.

[0002] With the continuous development of virtual and augmented reality technologies and applications, these are also finding their way into motor vehicles and other means of transportation. Augmented reality (AR) is the enhancement of the real world with virtual elements that are accurately registered in three-dimensional space and enable real-time interaction. Since the term "augmented reality" has prevailed over "extended reality" in the German-speaking world, the former will be used below. The term "mixed reality" is also used synonymously.

[0003] One possible technical implementation for enhancing the driver's workplace with perspective-correct, contact-analog virtual extensions is the head-up display (HUD). The light rays from a display installed in the dashboard are folded across several mirrors and lenses and reflected onto a projection surface into the driver's eye, allowing them to perceive a virtual image outside the vehicle. In the automotive sector, the windshield is often used as a projection surface, and its curved shape must be taken into account when displaying the image. Alternatively, an additional pane of glass or plastic is sometimes used, positioned on the dashboard between the driver and the windshield. The optical overlay of the display and the driving scene means fewer head and eye movements are required to read the information.In addition, the adaptation effort for the eyes is reduced, since, depending on the virtual distance of the display, less or no accommodation is required.

[0004] Augmented reality offers a wide range of application possibilities for supporting the driver through contact-analog marking of roadways and objects. Relatively obvious examples mostly relate to the field of navigation. While classic navigation displays in conventional head-up displays usually show schematic representations, e.g., a right-angled arrow indicating that a right turn should be made at the next opportunity, AR displays offer significantly more effective possibilities. Because the displays can be presented as "part of the environment," the driver can be very effectively presented with navigation instructions or hazard warnings directly at the real reference location.

[0005] The article by J.L. Gabbard et al., "Behind the Glass: Driver Challenges and Opportunities for AR Automotive Applications" [1], examines challenges in integrating augmented reality into automotive applications. Occlusion of driving-relevant information from the environment is one of the main disadvantages of contact-analog AR displays. Augmented reality head-up displays present information in the area immediately relevant to driving. Consequently, any information in the head-up display can obscure critical information, such as an obstacle in the roadway. This effect is amplified by increased clutter, the accumulation of elements in a small space.

[0006] In connection with the superimposed display of image information, DE 10 2012 020 568 A1 describes a method for operating a navigation system of a motor vehicle. In the method, an adaptation device of the navigation system receives a signal from at least one sensor relating to a physical or chemical property or a material quality of the surroundings of the motor vehicle that is visually perceptible to a driver of the motor vehicle. Depending on the signal, a true-to-life image of the surroundings is generated, which reproduces the property or quality of the surroundings identified by the signal. The true-to-life image of the surroundings is combined with a map of the surroundings, and a combined graphic generated thereby is transmitted to a display device.

[0007] DE 10 2017 220 268 A1 describes a method for detecting and visualizing system uncertainty when displaying augmented image content in head-up displays. The method involves adapting AR image content by changing the display format so that the existing display inaccuracies are not perceived as errors by the observer. For this purpose, a characteristic value is determined that quantifies the system uncertainty when displaying the AR image content. The display on the head-up display is adjusted based on this characteristic value.

[0008] DE 10 2012 210 145 A1 describes a method for assisting a driver in guiding a vehicle along a roadway. The method uses an image representing the vehicle's surroundings. Furthermore, an operating signal input by the driver is read in, based on which an object contained in the image is selected. A marker representing the object is then displayed on the display unit in an area. The object is then used to determine at least one longitudinal control parameter for a path to be traveled by the vehicle, in order to assist the driver in guiding the vehicle along the roadway.

[0009] US 2020 / 0005430 A1 describes a display device for a vehicle. The display device determines a display location and a movement direction of a virtual object to be displayed in a display area of ​​the display device to be superimposed on the real world, wherein the virtual object is to be moved relative to the movement of the mobile object. The display device also estimates a time required for the virtual object to move from the display location to an edge of the display area or a distance between the display location of the virtual object and the edge of the display area. Furthermore, the display device determines a display form of the virtual object based on the estimated time or the estimated distance and causes the virtual object to be displayed in the determined display form, such that the virtual object changes the display form as it moves within the display area.

[0010] DE 10 2019 202 113 A1 describes a near-vehicle system. The near-vehicle system uses sensors, a vehicle computing device, and a front display of a host vehicle to present near-vehicle graphical elements to a vehicle occupant, such as the driver of the host vehicle. The near-vehicle graphical elements are displayed using a front display and are projected onto a transparent surface of the host vehicle, such as the windows, windshield, a display screen, lenses, etc. The near-vehicle graphical elements indicate the presence of a vehicle near the host vehicle.

[0011] It is an object of the invention to provide solutions for controlling a display of an augmented reality head-up display for a means of transport, which enable a reduction of the disadvantages resulting from an overlap of driving-relevant information.

[0012] This object is achieved by a method having the features of claim 1, by a computer program with instructions according to claim 10, and by a device having the features of claim 11. Preferred embodiments of the invention are the subject of the dependent claims.

[0013] According to a first aspect of the invention, a method for controlling a display of an augmented reality head-up display for a means of transport comprises the steps: Determining at least one safety-relevant parameter, wherein the at least one safety-relevant parameter is a distance of the means of transport from a target element or a time until collision with the target element; and adjusting an intensity of a display element to be displayed by the augmented reality head-up display, which display element is positioned at the position of the target element perpendicular to the roadway, depending on the at least one safety-relevant parameter, wherein the intensity is reduced as the distance of the means of transport from the target element or as the time until collision with the target element decreases by adjusting an opacity of the display element and adjusting a portion of the display element area occupied by image elements, wherein the displayed display elements are reduced to contour lines.

[0014] According to a further aspect of the invention, a computer program contains instructions which, when executed by a computer, cause the computer to perform the following steps for controlling a display of an augmented reality head-up display for a means of transport: Determining at least one safety-relevant parameter, wherein the at least one safety-relevant parameter is a distance of the means of transport from a target element or a time until collision with the target element; and adjusting an intensity of a display element to be displayed by the augmented reality head-up display, which display element is positioned at the position of the target element perpendicular to the roadway, depending on the at least one safety-relevant parameter, wherein the intensity is reduced as the distance of the means of transport from the target element or as the time until collision with the target element decreases by adjusting an opacity of the display element and adjusting a portion of the display element area occupied by image elements, wherein the displayed display elements are reduced to contour lines.

[0015] The term "computer" should be understood broadly. In particular, it also includes control units, embedded systems, and other processor-based data processing devices.

[0016] The computer program may, for example, be made available for electronic retrieval or stored on a computer-readable storage medium.

[0017] According to a further aspect of the invention, a device for controlling a display of an augmented reality head-up display for a means of transport comprises: an analysis module for determining at least one safety-relevant parameter, wherein the at least one safety-relevant parameter is a distance of the means of transport from a target element or a time until collision with the target element; and a control module for adjusting an intensity of a display element to be displayed by the augmented reality head-up display, which display element is positioned at the position of the target element perpendicular to the roadway, depending on the at least one safety-relevant parameter, wherein the control module is configured to reduce the intensity as the distance of the means of transport from the target element or as the time until collision with the target element decreases by adjusting an opacity of the display element and adjusting a portion of the area of ​​the display element occupied by image elements, reducing the displayed display elements to contour lines.

[0018] The inventive solution dynamically reduces the occlusion or masking emanating from display elements. Depending on safety-critical parameters, the intensity of the display element is reduced. This can be achieved by adjusting the opacity of the display element or by adjusting the portion of the display element's surface occupied by image elements. Without this reduction in occlusion, for example, a turn arrow positioned in the distance with a constant high intensity would become increasingly larger as the object approaches due to the augmented reality display, thus leading to critical masking.

[0019] In order to avoid covering up driving-relevant information, the display elements shown are reduced to contour lines according to the invention.

[0020] According to one aspect of the invention, the contour lines of the display element remain unchanged. Since the contour lines of the display elements are too thin to obscure surrounding objects, they can easily remain constantly visible. This simultaneously ensures the consistent visibility and comprehensibility of the information conveyed by the display elements.

[0021] Furthermore, the size of the displayed display elements could be limited, so that a display element can only grow to a certain size. However, this would prevent the augmented reality effect. With the described solution, the increase in occlusion caused by the magnification is compensated by a reduction in intensity. The salience of display elements is thus only reduced when the occlusion is critical or problematic. Sufficient salience relative to the environment is required for the displays to be perceptible. This results in a compromise between perceptibility and occlusion reduction.

[0022] According to the invention, the at least one safety-relevant parameter is a distance of the means of transport to a target element or a time until collision with the target element. A small, immobile object that is obscured by the display element, e.g. a child, can be considered a particularly critical situation. Such a situation is most likely to occur in urban environments. The occlusion by the display element is most critical when it is at its greatest, i.e. when the distance between the virtual display element and the ego vehicle is small. In order to give a driver the opportunity to react to potentially obscured obstacles, the occlusion should be reduced below a critical distance. The critical distance depends on the speed of the ego vehicle, with the time until collision often being used as a safety indicator.For urban environments, values ​​of 1.5 s for the time to collision can be considered acceptable. However, in some situations, relying entirely on the time to collision is not sufficient. In situations with slow traffic, such as during rush hour, this could otherwise result in a very late reduction in occlusion. Therefore, it is useful if the intensity is also influenced by distance.

[0023] According to one aspect of the invention, the size of the display element is taken into account when adjusting the intensity. For example, an intensity adjustment can be limited to display elements that have a certain minimum size, e.g., in terms of height, width, or area. In this way, display elements that do not cause problematic occlusion are excluded. Furthermore, the size of the display element can be taken into account when determining the distance below which an intensity adjustment should occur.

[0024] According to one aspect of the invention, both the distance of the vehicle to the target element and the time until collision with the target element are determined, and the more critical parameter is selected for adjusting the intensity of the display element. The inclusion of the time parameter ensures speed-dependent occlusion reduction. This can guarantee that there is sufficient time for reaction and braking. For example, a relatively small display element at an ego speed of 150 km / h can obscure a distant obstacle due to the contact-analog representation, which means that a solution based solely on the distance or the size of the display element cannot guarantee sufficient time for reaction and braking. The time-dependent solution, on the other hand, ensures that obstacles are not obscured.

[0025] According to one aspect of the invention, the intensity can be adjusted between 100% and 0% of a nominal intensity depending on the at least one safety-relevant parameter. Depending on the design of the display elements, a display element can be composed of several parts with different nominal intensities. For example, a virtual signpost can consist of three directional arrows arranged side by side with intensities of 100%, 70%, and 50%. To simplify the adjustment of the intensity, it is therefore expedient to determine a percentage adjustment of the nominal intensity in each case.

[0026] According to one aspect of the invention, the intensity of the display element is only reduced but not increased again depending on the at least one safety-relevant parameter. In this way, fluctuations in the intensity are prevented, for example during heavy braking. If the intensity of the display element in a given situation were only influenced by the time until collision, this would lead to fluctuations in cases where a driver approaches an intersection quickly but then slows down, as the time until collision increases again. Therefore, the intensity is at least only influenced unidirectionally, i.e. only decreasingly, by the time until collision. If the time until collision increases again after a decrease, the intensity remains at the previous level and only decreases again when the time until collision falls below the previously lower value.

[0027] According to one aspect of the invention, functions for adjusting the intensity of the display element are adaptable depending on the at least one safety-relevant parameter. For example, the functions can be adapted based on the size of the display element, e.g., to specify the distance below which an adjustment of the intensity should take place. Likewise, the functions can be adaptable by a user of the means of transport, who can thus adapt the presentation of the display elements to their personal preferences. Furthermore, it is possible for the functions to be adaptable by the manufacturer of the means of transport or of the augmented reality head-up display. This allows them to react to changed regulations or the results of traffic research.

[0028] According to one aspect of the invention, the display element is a navigation instruction or a warning instruction. Since these types of display elements are particularly frequently used in contact-analog representations, the inventive solution is suitable for application to such display elements.

[0029] According to one aspect of the invention, the target element is an obstacle or an intersection. In the case of navigation instructions, the target element is usually an intersection where the navigation instruction is located. Warning instructions, on the other hand, are often used for obstacles, e.g., objects, other road users, or road damage.

[0030] A method or device according to the invention is particularly advantageously used in a (semi-)autonomous or manually controlled means of transport. The means of transport can be, in particular, a motor vehicle, but also a ship, an aircraft, e.g., a Volocopter, etc.

[0031] Further features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the figures. Fig. 1 schematically shows a method for controlling a display of an augmented reality head-up display for a means of transport; Fig. 2 shows a first embodiment of a device for controlling a display of an augmented reality head-up display for a means of transport; Fig. 3 shows a second embodiment of a device for controlling a display of an augmented reality head-up display for a means of transport; Fig. 4 schematically illustrates a means of transport in which a solution according to the invention is implemented; Fig. 5 schematically shows a general structure of an augmented reality head-up display for a means of transport; Fig. 6 schematically shows a first embodiment of a display element at a great distance from a means of transport; Fig. 7 schematically shows a first embodiment of a display element at a short distance from a means of transport; Fig.Fig. 8 schematically shows a second embodiment of a display element at a great distance from a means of transport; Fig. 9 schematically shows a second embodiment of a display element at a short distance from a means of transport; Fig. 10 schematically shows a function graph of the dependence of an intensity of a display element on a time until collision with a target element; and Fig. 11 schematically shows a function graph of the dependence of an intensity of a display element on a distance to a target element.

[0032] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. It is understood that the invention is not limited to these embodiments and that the described features may also be combined or modified without departing from the scope of the invention as defined in the appended claims.

[0033] Fig. 1shows a schematic representation of a method for controlling a display of an augmented reality head-up display for a means of transport. In a first step, at least one safety-relevant parameter is determined 10. The safety-relevant parameter is a distance of the means of transport to a target element or a time until collision with the target element. The target element can be, for example, an obstacle or an intersection. In the event that two or more safety-relevant parameters are determined 10, one of the determined parameters can optionally be selected as the more critical parameter 11. Subsequently, an intensity of a display element to be presented by the augmented reality head-up display at the position of the target element perpendicular to the roadway, e.g.a navigation instruction or a warning instruction, adapted 12 depending on at least one safety-relevant parameter, wherein a size of the display element can also be taken into account. The intensity is reduced as the distance of the means of transport from the target element or as the time until collision with the target element decreases. For this purpose, the opacity of the display element can be adjusted or a proportion of the area of ​​the display element occupied by image elements can be adjusted. The functions used for this purpose can be adjustable, e.g. by a user or by the manufacturer of the means of transport. Advantageously, the intensity is adjustable between 100% and 0% of a nominal intensity. Contour lines of the display element preferably remain visible unchanged. Advantageously, the intensity is only reduced but not increased again.Finally, the display element to be shown is output for display by the augmented reality head-up display 13.

[0034] Fig. 2shows a simplified schematic representation of a first embodiment of a device 20 for controlling a display of an augmented reality head-up display for a means of transport. The device 20 has an input 21, via which information is received, from which an analysis module 22 determines at least one safety-relevant parameter P. For example, the information is image data from a camera 43, data from a sensor system 44, or data from a navigation system 45. The sensor system 44 can, for example, have a laser scanner or a stereo camera for detecting objects in an environment of the means of transport. It is also possible for a safety-relevant parameter that was previously determined by an external component to be received directly via the input 21.The safety-relevant parameter P is a distance of the means of transport from a target element or a time until collision with the target element. The target element can be, for example, an obstacle or an intersection. In the event that two or more safety-relevant parameters are determined by the analysis module 22, one of the determined parameters can optionally be selected by the analysis module 22 as the more critical parameter. A control module 23 is configured to adapt an intensity of a display element, e.g. a navigation instruction or a warning instruction, to be presented by the augmented reality head-up display at the position of the target element perpendicular to the roadway, depending on the at least one safety-relevant parameter P, wherein a size of the display element can also be taken into account.The intensity is reduced as the distance between the means of transport and the target element decreases or as the time until collision with the target element decreases. For this purpose, the opacity of the display element can be adjusted or a proportion of the area of ​​the display element occupied by image elements can be adjusted. The functions used for this purpose can be adjustable, e.g., by a user or by the manufacturer of the means of transport. Advantageously, the intensity is adjustable between 100% and 0% of a nominal intensity. Contour lines of the display element preferably remain visible unchanged. Advantageously, the intensity is only reduced but not increased again. The display element to be shown can be output via an output 26 of the device 20 for display by the augmented reality head-up display, e.g., in the form of image data or in the form of control signals for a control unit 42 of the augmented reality head-up display.

[0035] The analysis module 22 and the control module 23 can be controlled by a control module 24. Settings of the analysis module 22, the control module 23, or the control module 24 can be changed via a user interface 27. The data generated in the device 20 can be stored in a memory 25 of the device 20 if necessary, for example, for later evaluation or for use by the components of the device 20. The analysis module 22, the control module 23, and the control module 24 can be implemented as dedicated hardware, for example, as integrated circuits. Of course, they can also be partially or completely combined or implemented as software running on a suitable processor, for example, a CPU or a GPU. The input 21 and the output 26 can be implemented as separate interfaces or as a combined bidirectional interface.In the example described, device 20 is a standalone component. However, it can also be integrated into the control unit 42 of the augmented reality head-up display device.

[0036] Fig. 3 shows a simplified schematic representation of a second embodiment of a device 30 for controlling a display of an augmented reality head-up display for a means of transportation. The device 30 has a processor 32 and a memory 31. For example, the device 30 is a computer or a control unit.

[0037] Instructions are stored in memory 31 which, when executed by processor 32, cause device 30 to perform the steps according to one of the described methods. The instructions stored in memory 31 thus embody a program executable by processor 32 which implements the method according to the invention. Device 30 has an input 33 for receiving information, for example, navigation data or data relating to the surroundings of the means of transport. Data generated by processor 32 are provided via an output 34. Furthermore, they can be stored in memory 31. Input 33 and output 34 can be combined to form a bidirectional interface.

[0038] The processor 32 may include one or more processor units, such as microprocessors, digital signal processors, or combinations thereof.

[0039] The memories 25, 31 of the described embodiments can have both volatile and non-volatile memory areas and can comprise a wide variety of storage devices and storage media, for example hard disks, optical storage media or semiconductor memories.

[0040] In the following, a preferred embodiment of the invention will be described with reference to Fig. 4 to Fig. 11 In this embodiment, the augmented reality head-up display is installed in a motor vehicle. Of course, the inventive solution is not limited to this application. The augmented reality head-up display can also be installed in other types of means of transportation.

[0041] Fig. 4schematically illustrates a means of transport 40 in which a solution according to the invention is implemented. In this example, the means of transport 40 is a motor vehicle. The motor vehicle has an augmented reality head-up display 41 with an associated control unit 42. Furthermore, the motor vehicle has a device 20 for controlling a display of the augmented reality head-up display 41. The device 20 can, of course, also be integrated into the augmented reality head-up display 41 or into the control unit 42 of the augmented reality head-up display 41. Further components of the motor vehicle are a camera 43 and a sensor system 44 for detecting objects, a navigation system 45, a data transmission unit 46, and a series of assistance systems 47, one of which is shown as an example. A connection to service providers can be established by means of the data transmission unit 46, for example, to retrieve map data.A memory 48 is provided for storing data. Data exchange between the various components of the motor vehicle takes place via a network 49.

[0042] Fig. 5schematically shows an augmented reality head-up display 41 for a means of transport 40, in this case a motor vehicle, with the aid of which content can be displayed on a projection surface 53 of the means of transport 40, for example on the windshield or on an additional pane made of glass or plastic, which is arranged between the driver and the windshield on the dashboard. The displayed content is generated by an imaging unit 50 and projected onto the projection surface 53 with the aid of an optical module 51. In a motor vehicle, the projection typically takes place in an area of ​​the windshield above the steering wheel. The position of an eyebox of the augmented reality head-up display 41 can be adjusted using an optical component 52 of the optical module 51. The imaging unit 50 can be an LCD-TFT display, for example.The augmented reality head-up display 41 is usually installed in a vehicle dashboard.

[0043] Fig. 6schematically shows a first embodiment of a display element 60 at a great distance from a means of transport. In this embodiment, the display element 60 is a signpost placed in the environment, which is displayed in a field of view 64 (FOV) of an augmented reality head-up display. This signpost is positioned at the position of the target element 61 perpendicular to the roadway and consists of three arrow elements positioned next to one another, which point in the direction of the maneuver. The target element 61 here is the intersection at which the maneuver is to take place. In the example shown, each arrow element in turn consists of individual image elements 63, here fully filled triangles. The triangles of the left arrow element, which is closest to the target road, have an intensity of 100%. The middle arrow element has an intensity of 70%, and the right arrow element has an intensity of 50%.The individual triangles are each bordered by a contour line 62. The different intensities of the filled triangles are indicated by the use of different hatching styles. In this embodiment, the intensities are determined by the opacity of the fill.

[0044] Fig. 7 shows schematically a first embodiment of a display element 60 at a short distance from a means of transport. The display element 60 is again the one already described in Fig. 6displayed signpost. Analogous to real objects, the signpost or the arrow elements enlarge as they approach, creating the desired impression of an object placed in the surroundings. This can lead to a significant obscuration of the driving scene, which can cause potentially dangerous situations, particularly for pedestrians. Furthermore, there is the possibility that the light intensity caused by the increasingly larger signpost at a certain point in time exceeds a threshold value defined as part of a functional safety assessment. This could lead to a complete deactivation of the augmented reality head-up display. Depending on safety-relevant parameters, the intensity of the filled triangles is therefore adjusted, i.e. the opacity is reduced, which in turn is indicated by the hatching.The contour lines 62 of the display element 60 remain constantly visible, as they are, on the one hand, too thin to obscure surrounding objects, and, on the other hand, ensure the consistent visibility and comprehensibility of the turn-by-turn information. To avoid undesirable side effects and improve the visibility and interpretability of the arrow elements, it may be advisable to choose a higher nominal intensity for the arrow elements and a more acute angle than is the case with previous applications using such signposts.

[0045] Fig. 8schematically shows a second embodiment of a display element 60 at a great distance from a means of transport. The display element 60 is again a signpost displayed in a field of view 64 of an augmented reality head-up display, which consists of three arrow elements positioned next to one another, which point in the direction of the maneuver. In the example shown, each arrow element in turn consists of individual image elements 63, here partially filled triangles. The triangles of the left arrow element, which is closest to the destination street, have an intensity of 100%. The middle arrow element has an intensity of 70% and the right arrow element has an intensity of 50%. The individual triangles are each delimited by a contour line 62. In this embodiment, the different intensities are determined by the area proportion of the display element 60 occupied by the image elements 63.

[0046] Fig. 9 shows schematically a second embodiment of a display element 60 at a short distance from a means of transport. The display element 60 is again the one already described in Fig. 8 To prevent dangerous situations that could result from the enlargement of the sign upon approach and the associated increasing occlusion, the intensity of the triangles is also adjusted in this embodiment depending on safety-relevant parameters. In this case, however, the area portion of the display element 60 occupied by the image elements 63 is reduced. The opacity of the filled portion of the individual triangles remains unchanged. Of course, it is also possible to combine both approaches, i.e., to also adjust the opacity.

[0047] The intensity of the individual triangles is preferably reduced as a function of both the distance between the ego vehicle and the target element, i.e., the position of the virtual signpost, and the time until collision with the virtual signpost. The intensity adjustment can, for example, be performed according to the following logic:

[0048] Here, f intensity (t) describes the intensity as a function of the time until collision with the target element, and f intensity (d) describes the intensity as a function of the distance between the ego vehicle and the target element. Current intensity is the intensity currently used to display the individual triangles.

[0049] Fig. 10shows a schematic diagram of the dependence of the intensity of the display element on the time t until collision with the target element. For urban environments, values ​​of 1.5 s for the time until collision can be considered acceptable. Accordingly, the intensity is gradually reduced from a maximum value f max to 0% between a first second value t 1 , e.g. t 1 = 3.83 s, and a second time value t 2 , e.g. t 2 = 1.50 s. In the event that the display element consists of several elements with different nominal intensities, such as the three arrows of the signpost described above, a different maximum value f max can be provided for each of the elements. Alternatively, a single maximum value f max can be used. This can then, for example, be multiplied for each of the elements by a correction factor corresponding to the nominal intensity.Preferably, the function graph is adaptable, particularly with respect to the times t 1 and t 2 . Furthermore, the course of the curve between the two points in time can also be adaptable.

[0050] Fig. 11shows a schematic of a function graph of the dependence of the intensity of a display element on a distance d to a target element. For example, the intensity can be reduced from a maximum value f max successively to 0% between a first distance d 1 , e.g. d 1 = 12.7 m, and a second distance d 2 , e.g. d 2 = 5 m. The variable d 2 can be defined as the distance at which the display element reaches a height that corresponds to 65% of the height of the field of view, i.e. at which the display element reaches a critical size with occlusion characteristics. The distance d 2 in this case depends on the specific design of the display element. The variable d1 can be defined as a function of d2, e.g. in the form d 1 = d 2 + 7.7 m. The function graph is preferably adaptable, in particular with regard to the distances d 1 and d 2 . In addition, the course of the curve between the two points in time can also be adaptable.

[0051] At slow speeds, it may happen that the time to collision is greater than t 1 , resulting in an intensity of f max , while the distance is already less than d 2 , resulting in an intensity of 0%. In such cases, the more critical parameter should always be chosen—in this case, distance. Consequently, the intensity is set to 0%.

[0052] The outlines or contour lines of the display element or the image elements that comprise the display element should preferably remain at 100% opacity until the entire display element is hidden. For example, the entire display element can be hidden with an animation duration of 500 ms once the display element has reached its maximum size. The height of the display element must not exceed the height of the field of view. Likewise, the bounding box around the individual elements of the display element, e.g., the three arrows of the signpost described above, must not exceed the width of the field of view. Both the distance at which the maximum size is reached and the duration of the animation should preferably be adjustable. References

[0053] [1] JL Gabbard et al.: "Behind the Glass: Driver Challenges and Opportunities for AR Automotive Applications", Proceedings of the IEEE, Vol. 102 (2014), pp. 124-136. List of reference symbols

[0054] 10Determining safety-relevant parameters 11Selecting a parameter 12Adjusting the intensity of a display element to be displayed 13Outputting the display element to be displayed 20Device 21Input 22Analysis module 23Control module 24Control module 25Memory 26Output 27User interface 30Device 31Memory 32Processor 33Input 34Output 40Means of transport 41Augmented reality head-up display 42Control unit of the augmented reality head-up display 43Camera 44Sensor system 45Navigation system 46Data transmission unit 47Assistance system 48Memory 49Network 50Imaging unit 51Optical module 52Optical component 53Projection surface 60Display element 61Target element 62Contour line 63Image element 64Field of view dDistance PParameter tTime

Claims

1. Method for controlling a display of an augmented-reality head-up display (41) for a means of transportation (40), comprising the steps of: - determining (10) at least one safety-relevant parameter (P), wherein the at least one safety-relevant parameter (P) is a distance (d) of the means of transportation (40) from a target element (61) or a time (t) until collision with the target element (61); and - adapting (12) an intensity of a display element (60), which is intended to be presented by the augmented-reality head-up display (41) and is positioned at the position of the target element (61) perpendicular to the road surface, in dependence on the at least one safety-relevant parameter (P), wherein the intensity is reduced as the distance (d) of the means of transportation (40) from the target element (61) decreases or the time (t) until collision with the target element (61) decreases, characterized in that an opacity of the display element (60) is set and a surface portion of the display element (60) occupied by image elements (63) is adapted, wherein the presented display elements are reduced to contour lines.

2. Method according to Claim 1, wherein a size of the display element (60) is taken into account when adapting (12) the intensity.

3. Method according to Claim 1 or 2, wherein both the distance (d) of the means of transportation (40) from the target element (61) and also the time (t) until collision with the target element (61) are determined and the more critical parameter (P) for the adaptation (12) of the intensity of the display element (60) is selected (11).

4. Method according to any of the preceding claims, wherein the intensity is adaptable between 100% and 0% of a nominal intensity in dependence on the at least one safety-relevant parameter (P).

5. Method according to any of the preceding claims, wherein the intensity of the display element (60) is only reduced in dependence on the at least one safety-relevant parameter (P), but not increased again.

6. Method according to any of the preceding claims, wherein contour lines (62) of the display element (60) remain unchangedly visible.

7. Method according to any of the preceding claims, wherein functions for the adaptation (12) of the intensity of the display element (60) are adaptable.

8. Method according to any of the preceding claims, wherein the display element (60) is a navigation message or a warning message.

9. Method according to any of the preceding claims, wherein the target element (61) is an obstacle or an intersection.

10. Computer program comprising instructions which, upon execution by a computer, cause the computer to perform the steps of a method according to any of Claims 1 to 9 for controlling a display of an augmented-reality head-up display (41) for a means of transportation (40).

11. Apparatus (20) for controlling a display of an augmented-reality head-up display (41) for a means of transportation (40), comprising: - an analysis module (22) for determining (10) at least one safety-relevant parameter (P), wherein the at least one safety-relevant parameter (P) is a distance (d) of the means of transportation (40) from a target element (61) or a time (t) until collision with the target element (61); and - a control module (23) for adapting (12) an intensity of a display element (60), which is intended to be presented by the augmented-reality head-up display (41) and is positioned at the position of the target element (61) perpendicular to the road surface, in dependence on the at least one safety-relevant parameter (P), wherein the control module (23) is configured to reduce the intensity as the distance (d) of the means of transportation (40) from the target element (61) decreases or the time (t) until collision with the target element (61) decreases, characterized in that it sets an opacity of the display element (60) and adapts a surface portion of the display element (60) occupied by image elements (63), wherein it reduces the presented display elements to contour lines.

12. Means of transportation (40) having an augmented-reality head-up display (41), characterized in that the means of transportation (40) has an apparatus (20) according to Claim 11 or is configured to carry out a method according to any of Claims 1 to 9 for controlling a display of the augmented-reality head-up display (41).