Head-up display having a pulse-width-modulated light-emitting diode of a backlighting device, and method for operating a head-up display

Abstract

The invention relates to a head-up display (2) for a vehicle (1), having an image-generating unit (2) and a backlighting device (4) for illuminating the background of the image (7) generated by the image-generating unit (3), wherein the backlighting device (4) has at least one light-emitting diode (4a), wherein the light-emitting diode (4a) can be operated as a light source in a light-emitting mode and can be operated as a light detector for detecting sunlight in a sunlight-detecting mode, and having a control unit (9) by means of which a pulse width of a control signal (S), with which it is possible to switch between the light-emitting mode and the sunlight-detecting mode, can be adjusted by pulse width modulation such that the duration (T1) of the light-emitting mode and / or the duration (T2) of the sunlight-detecting mode can be adjusted.

Description

[0001] Head-up display with pulse-width modulated light-emitting diode of a background lighting device, and method for operating a head-up display

[0002] One aspect of the invention relates to a head-up display for a vehicle. The head-up display comprises an image generation unit and a backlighting device for illuminating the background of the image generated by the image generation unit. The backlighting device comprises at least one light-emitting diode.

[0003] A reflective display system for a vehicle is known from WO 2023 / 025434 A1. The reflective display system is designed to detect a covered state of a light emission zone of this reflective display system. For this purpose, a light-emitting diode is operated both to emit light and as a photodiode. Depending on the light incidence during photodiode operation, it can be determined whether this area is covered.

[0004] In head-up displays that also feature such a backlighting device, image generation can be impaired by heating the head-up display. In particular, this can also lead to a so-called "bonanza effect." This means that the entire image generation device, or parts of it, goes black. As a result, the image content being displayed can no longer be recognized.

[0005] It is an object of the present invention to provide a head-up display, a vehicle and a method with which or in which an impairment of image generation due to heat influences is at least reduced.

[0006] This object is achieved by a method, a vehicle and a head-up display according to the independent claims.

[0007] One aspect of the invention relates to a head-up display for a vehicle. The head-up display has an image generation unit. Furthermore, the head-up display has a backlighting device. This is designed to illuminate the background of the image generated by the image generation unit. The backlighting device has at least one light-emitting diode. In the proposed head-up display, the light-emitting diode is designed to be operable as a light source in a light emission mode. Furthermore, it is operable as a light detector for detecting sunlight in a sunlight detection mode that is different from the light emission mode. Furthermore, the head-up display has a control unit with which a pulse width of a control signal generated by the control unit can be adjusted by pulse width modulation.The control signal can be used to switch between the light emission mode and the sunlight detection mode. This pulse-width modulated control signal allows the duration of the light emission mode and / or the sunlight detection mode to be adjusted depending on the situation, in particular depending on an influencing parameter. Such a head-up display therefore makes it particularly advantageous for the LED to function as a light source on the one hand and as a light detector on the other, depending on the needs and situation. By not specifying the time periods available for the light emission mode on the one hand and the sunlight detection mode on the other, but rather allowing these time periods to be dynamically changed through this pulse-width modulation of the control signal, the thermal management of the head-up display is also significantly improved.This allows the light emission mode to be changed depending on the incoming sunlight. This significantly reduces, and in particular prevents, overheating of the head-up display, especially the image generation unit. For example, if strong and / or prolonged sunlight hits the head-up display, especially the image generation unit, and this is detected, the duration of the light emission mode of the LED can be reduced. This reduces the heat emitted by the LED in light emission mode. The sum of the heat from the sunlight and the heat from the LED can therefore be reduced.

[0008] On the other hand, if there is no or only little sunlight, it is possible to extend the light emission mode in time.

[0009] In one embodiment, the sunlight detection mode is activated in a pulse pause of the control signal set by the pulse width modulation.

[0010] In one embodiment, the pulse width of the control signal can be varied depending on the brightness of the sunlight detected in the sunlight detection mode. In particular, the duration of the light emission mode is reduced depending on this if the brightness is increased and / or exceeds a threshold value. This can affect both the brightness value itself and the duration of sunlight incidence.

[0011] In one embodiment, the light-emitting diode is a white-light light-emitting diode. This means that it emits white light in light emission mode. Such a white-light light-emitting diode can also advantageously be used as a light detector. In this context, it is also possible for light in the visible spectral range and / or light in the IR (infrared) spectral range to be detected in sunlight detection mode or sunlight detection mode. In one embodiment, it is thus very advantageous to detect whether sunlight is incident, particularly in the area of ​​the image generation unit. Such a white-light light-emitting diode can then be used with a corresponding detection circuit, for example, when infrared radiation from sunlight is present and particularly strikes the image generation unit or impairs image generation in this regard.

[0012] Therefore, it is not only advantageous in this context to know, in terms of time and / or quantity, but especially generally, when sunlight hits the head-up display, in particular the image generation unit. This allows for appropriate responses to the aforementioned potential disadvantages that may arise, or for the occurrence of such a disadvantage to be prevented.

[0013] In one embodiment, the LED operates as a solar cell in sunlight detection mode. This allows for particularly advantageous detection of sunlight, especially specific spectral ranges. Last but not least, it also enables simple yet precise analysis of the incoming sunlight.

[0014] In particular, the open-circuit voltage of the LED can be evaluated for sunlight detection in sensor light detection mode. This electrical parameter is particularly advantageous when the LED operates as a solar cell in sunlight detection mode. This open-circuit voltage can then be determined using a simple voltmeter.

[0015] The open circuit voltage of solar modules is the highest voltage that can be measured when they are not connected to an electrical system. In one embodiment, the backlighting device has a plurality of light-emitting diodes, i.e. at least two light-emitting diodes. Both light-emitting diodes can be operated in a light emission mode as a light source and in a sunlight detection mode as a light detector for detecting sunlight. With such a configuration, it is possible to additionally determine the position of incoming sunlight depending on the positions of the light-emitting diodes. By localizing the incoming sunlight in this way, the advantages mentioned above can be further improved. In particular, it can be determined even more precisely whether and to what extent sunlight is incident on the head-up display, in particular on the image generation unit.This allows for even more needs-based adaptation of the head-up display's further operating mode, particularly the pulse-width modulated control of the durations of the light emission mode on the one hand and the sunlight detection mode on the other. This is particularly important with regard to preventing excessive heat buildup in the head-up display.

[0016] A further aspect of the invention relates to a vehicle with a head-up display according to the above-mentioned aspect or an advantageous embodiment thereof. The vehicle can be a passenger car or a truck. Other vehicle types or models can also be provided.

[0017] A further aspect of the invention relates to a method for operating a head-up display. The head-up display can be designed, in particular, according to the above-mentioned aspect or an advantageous exemplary embodiment. At least one light-emitting diode of a backlighting device of the head-up display illuminates a background of an image generated by an image generation unit of the head-up display. The light-emitting diode is operated as a light source in a light emission mode and as a light detector for detecting sunlight in a sunlight detection mode. In particular, a control unit of the head-up display adjusts a pulse width of the control signal used to switch between the light emission mode and the sunlight detection mode by pulse width modulation, so that the duration of the light emission mode and / or the duration of the sunlight detection mode is changed, in particular dynamically changed.In particular, this pulse width modulation is varied depending on the respective incident sunlight, particularly with a view to avoiding overheating of the head-up display, in particular of the image generation unit. In one exemplary embodiment, the durations of the aforementioned modes are adjusted depending on the brightness of the detected light. In particular, the durations of the sunlight incidence can also be adjusted. It can be provided that the brightness of the light emitted by the LED in the light emission mode is varied depending on the brightness of the detected sunlight. In particular, the brightness of the emitted light is reduced if too much sunlight is incident. This means that the brightness of the sunlight is, for example, greater than at least one threshold value.

[0018] In one embodiment, the light emission of the light-emitting diode is changed depending on a temperature of the image generation unit.

[0019] It is possible for the head-up display to have at least one temperature sensor. This is arranged and configured to detect the temperature of the head-up display, in particular of the image generation unit. In particular, the duration of the light emission mode of the LED is changed depending on the temperature of the image generation unit, which is generated at least by the incidence of sunlight, in particular IR radiation from sunlight.

[0020] Display panels are the common technology used in today's automotive HUD systems. They utilize a display transmission technology and LED backlighting that illuminates the entire image as soon as light is passed through them. The illuminated image is magnified, reflected by a folding mirror, and projected onto the windshield in the driver's field of vision.

[0021] Embodiments of the invention are explained in more detail below with reference to schematic drawings. They show:

[0022] Fig. 1 shows an embodiment of a vehicle according to the invention with an embodiment of a head-up display according to the invention; and

[0023] Fig. 2 is a diagram showing a pulse width modulated control signal.

[0024] In the figures, identical or functionally equivalent elements are provided with the same reference numerals. Fig. 1 shows a schematic representation of a vehicle 1. The vehicle 1 has a head-up display 2. The head-up display 2 has an image generation unit 3. This can be a TFT display or an LCD display, for example. The head-up display 2 also has a background lighting device 4. This is designed to illuminate the background of the image generated by the image generation unit 3. In the exemplary embodiment, the head-up display 2 has a first mirror 5. This can be a so-called folding mirror. The first mirror 5 deflects the image generated and emitted by the image generation unit 3 to a second mirror 6, which can be a magnifying mirror. The second mirror 6 projects the image 7 into a field of view 8.The field of vision 8 is in particular the field of vision of a vehicle occupant in the vehicle 1, in particular a vehicle occupant positioned on a driver's seat.

[0025] In one embodiment, the head-up display 2 has a control unit 9.

[0026] The backlight device 4 has at least one light-emitting diode 4a. In particular, a plurality of light-emitting diodes 4a are provided. The at least one light-emitting diode 4a can be operated in a light-emitting mode. In this case, the light-emitting diode 4a functions as a light source. In particular, the light-emitting diode 4a is a white-light light-emitting diode.

[0027] Furthermore, the at least one light-emitting diode 4a can be operated in a sunlight detection mode that differs from the light emission mode. The light-emitting diode 4a then serves as a light detector, in particular a photodiode or a solar cell, for detecting sunlight, in particular also IR radiation.

[0028] The control unit 9 is designed to generate a pulse-width modulated control signal. This means, in particular, that a control signal from the control unit 9 for controlling the light emission mode and the sunlight detection mode can be varied in pulse width depending on an influencing parameter, in particular incident sunlight and / or the position of the incidence of the sunlight on the head-up display 2 and / or a temperature of the image generation unit 3. By means of such a control signal, which can be varied by pulse width modulation, the duration of the light emission mode and / or the sunlight detection mode of the at least one light-emitting diode 4a can be individually adjusted. A simple diagram is shown in this context in Fig. 2. The time period t is plotted on the horizontal axis. An electrical voltage U in volts is plotted on the vertical axis. An exemplary control signal S is shown in Fig. 2.A pulse width extends over a time period T. A time period T1 characterizes the duration of a light emission mode. A time period T2 of this total time period T characterizes the duration of the sunlight detection mode. Thus, the sunlight detection mode is activated during a pulse pause of the control signal S, which is set by the pulse width modulation and is characterized by the time period T2. These time periods T1 and T2 are changed individually and dynamically by the pulse width modulation. This depends in particular on the detection of incident sunlight. Depending, for example, on the brightness and / or the duration and / or the location of the incidence of such sunlight, the time period T1 and / or the time period T2 can be adjusted by the pulse width modulation.

[0029] In particular, in the sunlight detection mode, light in the visible spectral range and light in the IR spectral range can be detected. The at least one light-emitting diode 4a operates in particular as a solar cell in this sunlight detection mode. Preferably, the open-circuit voltage of the light-emitting diode 4a is evaluated to detect sunlight in the sunlight detection mode. This is done in particular by means of the control unit 9.

Claims

Patent claims 1. A head-up display (2) for a vehicle (1), comprising an image generation unit (2) and a backlighting device (4) for illuminating the background of the image (7) generated by the image generation unit (3), wherein the backlighting device (4) comprises at least one light-emitting diode (4a), wherein the light-emitting diode (4a) is operable as a light source in a light emission mode and as a light detector for detecting sunlight in a sunlight detection mode, and comprising a control unit (9) with which a pulse width of a control signal (S), with which it is possible to switch between the light emission mode and the sunlight detection mode, can be adjusted by pulse width modulation, so that the time duration (T1) of the light emission mode and / or the time duration (T2) of the sunlight detection mode can be adjusted.

2. Head-up display (2) according to claim 1, wherein the sunlight detection mode is activated in a pulse pause of the control signal (S) set by the pulse width modulation.

3. Head-up display (2) according to claim 1 or 2, wherein depending on the brightness of the sunlight detected in the sunlight detection mode, the pulse width of the control signal (S) is variable, in particular the time duration (T1) of the light emission mode is reduced when the brightness is increased and / or exceeds a threshold value.

4. Head-up display (2) according to one of the preceding claims, wherein the light-emitting diode (4a) is a white light light-emitting diode.

5. Head-up display (2) according to one of the preceding claims, wherein in the sunlight detection mode light in the visible spectral range and light in the IR spectral range can be detected.

6. Head-up display (2) according to one of the preceding claims, wherein the light-emitting diode (4a) operates as a solar cell in sunlight detection mode.

7. Head-up display (2) according to one of the preceding claims, wherein the open circuit voltage of the light-emitting diode (4a) can be evaluated for detecting sunlight in the sunlight detection mode.

8. Head-up display (2) according to one of the preceding claims, wherein the backlight device (4) has a plurality of light-emitting diodes (4a) which can be operated as light sources in a light emission mode and as light detectors for detecting sunlight in a sunlight detection mode, wherein the position of an incident sunlight can be determined depending on the positions of the light-emitting diodes (4a).

9. Vehicle (1) with a head-up display (2) according to one of the preceding claims.

10. A method for operating a head-up display (2), in particular according to one of the preceding claims, wherein at least one light-emitting diode (4a) of a background lighting device (4) illuminates a background of an image (7) generated by an image generation unit (3) of the head-up display (2), wherein the light-emitting diode (4a) is operated as a light source in a light emission mode and as a light detector for detecting sunlight in a sunlight detection mode, wherein a control unit (9) of the head-up display (2) sets a pulse width of a control signal (S), which is used to switch between the light emission mode and the sunlight detection mode, by pulse width modulation, so that the time duration (T1, T2) of the light emission mode and / or the sunlight detection mode is changed.

11. Method according to claim 10, wherein the time periods (T 1 , T 2) are adjusted depending on the brightness of the detected sunlight.

12. The method according to claim 10 or 11, wherein the brightness of the light emitted by the light-emitting diode (4a) in the light emission mode is varied depending on the brightness of the detected sunlight.

13. The method according to one of the preceding claims 10 to 12, wherein the The time duration (T1) of the light emission mode of the light-emitting diode (4a) is changed depending on a temperature of the image generation unit (3) generated at least by the incidence of sunlight.

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