REFLECTIVE DISPLAY SYSTEM AND METHOD FOR OPERATING A REFLECTIVE DISPLAY SYSTEM WITH COVER DETECTION

Description

Technical area

[0001] The invention relates to windshield display systems, in particular reflective display systems, such as PHUD, for motor vehicles. In particular, the present invention relates to measures for detecting an object located in the optical beam path of the windshield display system. Technical background

[0002] Reflective display systems, such as PHUD, comprise a display unit mounted on top of the instrument panel. The display unit is reflected on the inside of the windshield, visible to a vehicle occupant. The display unit is positioned slightly recessed on top of the instrument panel, preventing direct view of the display surface and thus preventing glare from light directly hitting the user's eyes.

[0003] However, due to the placement of the display unit in such a recess on the top of the instrument panel, foreign objects resting on the display unit are not readily visible from the normal visual position of the vehicle occupants. However, these foreign objects lie in the optical path of the display image and can thus obscure parts of the display, so that legally relevant display symbols, such as the speedometer, chamber lights, remaining range, and the like, are not visible. The absence of these display symbols is also not noticeable, as they are not permanently displayed.

[0004] The use of a cover glass, such as that used in classic head-up displays, is disadvantageous for such reflective display devices, as it can result in new reflections of ambient light onto the windshield, which can significantly impair the perceptibility of the reflected image in high ambient brightness.

[0005] Previous approaches only provide for the detection of foreign objects resting on the display unit using additional devices, such as cameras or light barriers or the like.

[0006] Document WO2020 / 189646 A1 discloses a head-up display configured to display a predetermined image toward the vehicle's occupants. A housing has an upward opening and a transparent cover covering the opening of the housing. An image generation unit that emits light to generate the predetermined image is provided within the receiving portion formed by the transparent cover, and the light emitted by the image generation unit is irradiated onto the windshield. The head-up display includes a cleaner for cleaning the outer surface of the transparent cover.

[0007] US 2019 / 204592 A1 discloses a projection display device comprising a light modulation unit that spatially modulates the light emitted from a light source in accordance with input image data, a housing that houses the light modulation unit, a projection optical system that is housed in the housing and projects the spatially modulated light onto a projection surface of a vehicle through an opening portion of the housing, a cover that closes the opening portion, a movable protective member for protecting the cover, a drive unit that drives the protective member, and an object detection unit that detects an object approaching a front surface of the cover. The drive unit moves the protective member to a position above the cover and causes the protective member to cover the cover when the object detection unit detects an object.The drive unit retracts the protective element from the position above the cover, leaving the cover exposed when the object detection unit does not detect an object.

[0008] US2010 / 264835 A1 discloses a system comprising a plurality of light elements and a management system including a set of computing devices. The management system is configured to implement a method for managing the plurality of light elements, wherein at least one of the plurality of light elements is alternately operated as a light-emitting element and a light-sensing element, wherein the at least one of the plurality of light elements is operated as a light-sensing element while at least one other of the plurality of light elements is operated as a light-emitting element.

[0009] Document WO 2021 / 002055 A1 discloses a virtual image display device that projects a display light of an image toward a projection unit to visually display the image as a virtual image. A light-emitting display and a diffraction-reflecting element are provided that reflects the display light emitted by the display by diffraction, and that is formed in a plate shape in a posture along the horizontal plane of the vehicle. The device also includes a horizontally arranged diffraction-reflecting element that emits the incident display light toward the projection section arranged thereabove, and the angle of incidence of the displayed light on the horizontally arranged diffraction-reflecting element.

[0010] The document US 2013 / 221851 A1 discloses a method for light detection, wherein a light-emitting diode is reverse-biased and the photocurrent generated by the light-emitting diode in response to the ambient illumination is detected.

[0011] It is an object of the present invention to provide an improved method for detecting occlusions of a display image in a reflective display system. Disclosure of the invention

[0012] This object is achieved by a method for operating a reflection display system according to claim 1 and by a reflection display system according to the independent claims.

[0013] Further embodiments are specified in the dependent claims.

[0014] According to a first aspect, a method is provided for operating a reflective display system for displaying a display image for a vehicle occupant of a motor vehicle by reflecting the display image on a reflective surface, in particular on a windscreen, wherein a display unit is configured with a micro-LED display to output the display image via a display surface of the display unit, wherein the display unit is arranged on an upper side of an instrument panel such that a reflection of the display image via the windscreen is perceptible in an eye region of a vehicle occupant; comprising the following steps: Operating at least some of the LED diodes of the micro-LED display in a sensor-driven manner to detect a respective luminous intensity of incident ambient light; detecting the presence of a foreign object on the display surface depending on the measured luminous intensities in the sensor-driven LED diodes; and signaling a disruption of the display image upon detection of the foreign object on the display surface.

[0015] Foreign objects placed on the instrument panel can completely or partially obscure components used to display information on the windshield. However, if the reflective display system is used to display safety-relevant information, it is necessary to be able to distinguish between a non-display of information and a blockage of the information display caused by a foreign object.

[0016] Foreign objects within the meaning of this invention can be any objects that hinder the perception of a display image, such as items of clothing, papers and the like.

[0017] However, especially when the display unit is located in a recess on top of the instrument panel, foreign objects resting on the display unit are not readily visible from the normal visual position of the vehicle occupants. However, these foreign objects lie in the optical path of the display image and can thus obscure parts of the display, making safety-relevant and legally required display symbols, such as speedometer, chamber lights, remaining range, and the like, invisible. However, the absence of these display symbols may not be readily noticeable, as they are not permanently displayed.

[0018] Using the above-mentioned reflective display system, it is possible to determine whether the display surface of the display unit is free of any foreign objects resting on it. This makes it possible to detect whether the beam path of the reflective display system is disrupted by a foreign object on the display surface. Detecting such an interruption of the display of the reflective display system is essential for signaling a warning or other countermeasures. The above-mentioned reflective display system thus enables automated detection of a foreign object on the display surface of the display unit that is disrupting the display image.

[0019] Furthermore, the display unit can be arranged in the recess such that the display image shown on the display surface of the display unit is not directly visible in the eye area.

[0020] A micro-LED display features a matrix of LEDs configured as diodes. The LEDs can emit light when actively powered. The micro-LED matrix contains LEDs that emit light in different wavelength ranges. The LEDs in the matrix can be individually controlled to output corresponding images across the display area.

[0021] The design of the micro-LED display also allows the LEDs to be operated using sensors, so they function as photodiodes. These photodiodes are light-sensitive to the correspondingly designed wavelength and deliver a diode current as a brightness signal that depends on the intensity of the incident light. If a foreign object is placed on the display surface, it blocks the ambient light, allowing an area of ​​very low light intensity to be detected on the micro-LED display. This area of ​​very low light intensity can be interpreted as a foreign object lying on the display surface.

[0022] It can be provided that a light source is arranged in an area above the display unit, which makes it possible to increase the ambient light required for measuring the presence of a foreign object lying on it using the micro-LED display.

[0023] The detection of a foreign object can occur continuously. Since displaying an image and detecting a signal are not possible simultaneously, it is advantageous to read the light incidence on the LEDs periodically during a sufficiently short period, such as between 30 and 50 ms, so that this cannot be perceived as an interruption in the image displayed by the reflective display system.

[0024] In a further embodiment, some of the LEDs can be actively operated to emit light, while neighboring LEDs can be sensor-operated to detect incident light. The sensor-operated LEDs are arranged distributed over the display surface of the micro-LED displays between the actively operated LEDs. This makes it possible for the micro-LED matrix itself to provide light to detect the foreign object. In effect, the actively operated LEDs of the micro-LED matrix then emit light that is reflected by the foreign object, resulting in a characteristic pattern of reflected light that can be detected. For example, the actively operated LEDs and the sensor-operated LEDs as detectors can be arranged adjacent to one another in the matrix, in particular alternately adjacent to one another.If the active LEDs are now controlled with a pulse pattern, this pulsed light is reflected by any foreign object lying on them and bounced back to the sensor-driven LEDs below. These detect incoming light and recognize the presence of the foreign object based on the presence of light pulsed with the specific pulse pattern. LEDs that are not covered by a foreign object therefore do not detect the pulsed light of the active LEDs and can therefore determine that no foreign object is present on the display surface.

[0025] According to a further aspect, a reflection display system is provided for displaying a display image for a vehicle occupant of a motor vehicle by reflecting the display image on a reflection surface, in particular on a windscreen, comprising: a display unit which is designed with a micro-LED display in order to output the display image via a display surface of the display unit, wherein the display unit is arranged on an upper side of an instrument panel such that a reflection of the display image via the windshield is perceptible in an eye region of a vehicle occupant; a control unit which is designed ∘ to operate at least some of the LED diodes of the micro-LED display using sensors in order to detect a luminous intensity of incident ambient light; ∘ to detect the presence of a foreign object on the display surface depending on the measured luminous intensities in the sensor-operated LED diodes; and ∘ to signal a disruption of the display of the display image upon detection of the foreign object on the display surface.

[0026] According to a further aspect, a motor vehicle is provided, comprising: an instrument panel between a windshield of the motor vehicle and a steering column; the above reflective display system. Short description of the drawing

[0027] Embodiments are explained in more detail below with reference to the attached drawings. They show: Figure 1 shows a schematic cross-sectional view of a reflective display system in a motor vehicle; Figure 2 shows a plan view of an exemplary micro-LED display; and Figure 3 shows a flowchart illustrating a method for signaling the presence of a foreign object on the display surface of the display unit. Description of embodiments

[0028] Figure 1shows a schematic cross-sectional view of a motor vehicle with a reflective display system 1. The reflective display system is arranged on the upper side of an instrument panel 4 and has a display unit 2 comprising a display surface 3 for displaying a display image. The display unit 2 is arranged on the upper side of the instrument panel 4 below a windshield 5.

[0029] The display surface 3 is aligned with respect to the windscreen 5 such that a display image displayed on the display surface of the display unit 2 is reflected at a lower region of the inside of the windscreen 5 and can be perceived by a vehicle occupant in an eye area B. As a result, the alignment of the display unit 2 or its display surface can preferably be substantially parallel to the vehicle's longitudinal and transverse axes or deviate from them by an angle of no more than 0-20°.

[0030] The display unit 2 can be mounted in a recess 6 of the instrument panel so that the vehicle occupant cannot directly view the display surface 3 of the display unit 2 and the vehicle occupants are prevented from being dazzled by direct light from the display surface 3 into the eye area B. Furthermore, the display surface 3 of the display unit 2 is aligned such that a displayed image is reflected on the inside of the windscreen 5 and can be perceived by a vehicle occupant in an eye area B as a reflected image on the windscreen 5.

[0031] The display unit 2 is preferably designed as a micro-LED display unit in order to provide a bright display image so that the reflection generated can be perceived over the corresponding area of ​​the front screen 5 even in high ambient brightness.

[0032] Since the display unit 2 is arranged in the recess 6 on the upper side of the instrument panel 4, a foreign object 7 can also enter this recess 6 and thus come to rest on the display surface 3 of the display unit 2. A display image displayed on the display unit 2 may then not be perceived by a vehicle occupant, or may only be partially perceived as a reflected image.

[0033] The display unit 2 is designed as a micro-LED display unit in order to provide a bright display image so that the generated reflection can be perceived over the corresponding area of ​​the front screen 5 even in high ambient brightness. Figure 2 shows the structure of a micro-LED matrix, where groups of four pixels with different colors red R, green G, blue B are provided

[0034] To detect whether the foreign object 7 is resting on the display surface 3 or not, a control unit 10 can be designed to use the display unit 2, in addition to displaying the display image, also for sensory detection of the resting of a foreign object 7 on the display surface 3. For this purpose, the control unit 10 is designed to operate the LEDs of the micro-LED display or a portion of the LEDs of the micro-LED display as photodiodes at regular intervals for a short period of time. Due to the possibility of selectively controlling the micro-LED display during active operation, it is also possible to selectively operate the LEDs of the micro-LED display as photodiodes in sensory operation. The sensor-operated LEDs then deliver a brightness signal that indicates the brightness of the light received by them.

[0035] The short duration corresponds to a period of time for which the active display is interrupted, and in order for this period to be unnoticeable, it should be less than 50 ms.

[0036] During this short period of time, the presence of a foreign object 7 on the display surface 3 can be determined by evaluating an electrical quantity detected by the sensor-operated LEDs as a brightness signal. The electrical quantity represents the luminous intensity of the ambient light incident on the corresponding photodiode. The evaluation of whether a foreign object 7 is resting on the display surface 3 is preferably carried out by using all LEDs of the micro-LED display as photodiodes. Alternatively, only a portion of the LEDs, which in particular cover the entire display surface, can be used to detect a foreign object 7. The remaining LEDs can continue to be actively operated.

[0037] In particular, it can be detected whether there is an area on the display surface 3 where no light is incident. In particular, if additional sensor-operated LEDs simultaneously detect that the ambient brightness is sufficiently high to detect a corresponding light incidence on the relevant photodiodes, it can be concluded that a foreign object 7 is present. Thus, a foreign object 7 can be detected if the detected light intensities of, in particular, simultaneously sensor-operated LEDs differ by more than a predetermined difference.

[0038] Alternatively, an external light source 11 can be provided, which directs light onto the display surface 3 either permanently or only for the duration during which the LEDs or the corresponding portion of the LEDs are operated by sensors. In particular, it is advantageous to use the micro-LED display with LEDs with infrared light sensitivity for detecting a foreign object 7 lying on the display surface and to design the external light source 11 as an infrared light source. This avoids disturbances to the driver caused by the external light source 11 in the vehicle interior.

[0039] In an alternative embodiment, additional light can also be provided by the actively operated LEDs themselves. In particular, the LEDs can be arranged alternately during contact detection and can be actively and sensor-operated, so that an LED adjacent to a sensor-operated LED is actively operated. The light intensity detected by the sensor-operated LED can then vary depending on whether light from an adjacent active LED is reflected by a foreign object 7 resting directly on the display surface 3 or whether the emitted light leaves the area of ​​the micro-LED display unreflected.

[0040] In order to better distinguish foreign objects 7 from areas where no foreign object 7 is present, the light emitted by the actively operated LEDs can be pulsed, in particular with a specific pulse pattern that is detected by the other sensor-operated LEDs. If this pulse pattern is received by the sensor-operated micro-LEDs, the luminous intensity of the received brightness signal can be checked according to a threshold value comparison in order to filter out direct coupling of the emitted pulse pattern into the sensor-operated LEDs. If the luminous intensity of the pulse pattern received by the sensor-operated LEDs is above a predetermined threshold value, a foreign object can be detected. In this way, the reflective display system, and in particular the method for detecting a foreign object, can be designed to be immune to interference.

[0041] In further embodiments, obscuration of the display surface can be detected even without applying a pulse pattern by checking the sensor-detected light intensity (brightness signal) with a threshold comparison. The predetermined threshold can be dependent on the brightness of the ambient light. In the case of low ambient brightness, which leads to a brightness signal from the sensor-operated LEDs that is lower / weaker than the brightness signal from a foreign object 7 lying on the surface, an obscuration event can be detected if the light intensity is above a predetermined threshold. The predetermined threshold of the brightness signal is then set such that it represents a brightness signal that corresponds to a brightness signal such as that produced by a poorly or normally reflective foreign object 7 lying on the surface.

[0042] In high ambient brightness, which results in a brightness signal from the sensor-driven LEDs that is higher / stronger than the brightness signal from a foreign object 7 lying on the surface, an occlusion event can be detected if the light intensity or the detected brightness signal is below a predefined threshold. The predefined threshold of the brightness signal is then set such that it represents a brightness signal that corresponds to a brightness signal generated by a well- or normally reflective foreign object 7 lying on the surface. This results in two threshold values ​​that can be selected depending on the ambient brightness.

[0043] If the reflection display system 1 is implemented without an external light source, the evaluations can be combined over several consecutive detection cycles to mask out short-term shadows cast by houses, trees, and other building components during a journey. A foreign object can only be detected when several consecutive events are detected in which the detected light intensity is above a specified threshold.

[0044] Figure 3 shows a flowchart illustrating a method for detecting a foreign object 7, which can be carried out in the control unit 10.

[0045] In step S1, some of the LEDs of the display unit 2 are operated with a pulse pattern.

[0046] In step S2, some of the LEDs of the display unit 2 are sensor-operated.

[0047] In step S3, a check is made to determine whether any of the sensor-driven LEDs are receiving light or a brightness signal with the specified pulse pattern. If this is the case (alternative: yes), the method continues with step S4; otherwise (alternative: no), the method returns to step S1.

[0048] If it is detected in step S3 that a foreign object 7 is present on the display surface 3, the presence of a foreign object 7 on the display surface 3 is signaled in step S4. The signaling can be done by means of an optical or acoustic signal or in another way that alerts the vehicle occupants that the display is at least partially obscured. List of reference symbols

[0049] 1Reflection display system 2Display unit 3Display surface 4Instrument panel 5Windscreen 6Recess 7Foreign object 10Control unit 11External light source

Claims

1. Method for operating a reflection display system (1) for displaying a display image for a vehicle occupant of a motor vehicle by way of reflection of the display image at a reflection surface, in particular at a windshield (5), wherein a display unit (2) is configured with a micro-LED display in order to output the display image via a display surface (3) of the display unit (2), wherein the display unit (2) is arranged on an upper side of an instrument panel (4) such that a reflection of the display image is perceivable via the windshield (5) in an eye region (B) of a vehicle occupant, having the following steps: - operating (S1) at least one part of the LED diodes of the micro-LED display for sensing to detect a respective light intensity of incident light, in particular incident ambient light; - detecting (S2, S3) the presence of a foreign object (7) on the display surface (3) depending on the measured light intensities in the LED diodes which are operated for sensing; and - signalling (S4) a disruption of the display of the display image during the detection of the foreign object (7) on the display surface (3).

2. Method according to Claim 1, wherein the at least one part of the LED diodes of the micro-LED display is operated actively and for sensing in alternation, wherein in particular the at least one part of the LED diodes is operated for sensing for a time period which is not perceivable by a user.

3. Method according to Claim 1 or 2, wherein a part of the LEDs of the micro-LED display is at least temporarily operated actively to emit light and, at the same time, neighbouring LEDs are operated for sensing to detect the incidence of light, wherein the LEDs which are operated for sensing are distributed over the area of the display surface (3) of the micro-LED display between the actively operated LEDs, so that light that is provided by the actively operated LEDs of the micro-LED matrix is reflected at a foreign object (7) located on top and is detectable by the LEDs operated for sensing.

4. Method according to Claim 3, wherein the active LEDs are controlled in a pulsed manner with a specific pulse pattern, wherein light which is detected by the LEDs which are operated for sensing is evaluated by virtue of the fact that, when light that is pulsed with the specific pulse pattern is recognized, the presence of a foreign object (7) is detected.

5. Method according to Claim 3, wherein a foreign object (7) located on top is detected in dependence on a threshold value comparison, wherein a threshold value is determined depending on the ambient brightness.

6. Reflection display system (1) for displaying a display image for a vehicle occupant of a motor vehicle by way of reflection of the display image at a reflection surface, in particular at a windshield (5), comprising: - a display unit (2), which is configured with a micro-LED display in order to output the display image via a display surface (3) of the display unit (2), wherein the display unit (2) is arranged on an upper side of an instrument panel (4) such that a reflection of the display image is perceivable via the windshield (5) in an eye region (B) of a vehicle occupant, - a control unit (10), which is configured ∘ to operate at least one part of the LED diodes of the micro-LED display for sensing to detect a light intensity of incident light, in particular incident ambient light; ∘ to detect the presence of a foreign object (7) on the display surface (3) depending on the measured light intensities in the LED diodes which are operated for sensing; and ∘ to signal a disruption of the display of the display image during the detection of the foreign object (7) on the display surface (3).

7. Reflection display system (1) according to Claim 6, wherein the display unit (2) is arranged in the recess such that the display image which is represented on the display surface (3) of the display unit (2) is not directly perceivable in the eye region (B).

8. Reflection display system (1) according to Claim 6 or 7, wherein the micro-LED display has a matrix of LEDs.

9. Reflection display system (1) according to any of Claims 6 to 8, wherein an external light source (11) which increases the light intensity of the ambient light is provided.

10. Reflection display system (1) according to Claim 9, wherein the external light source (11) is configured for emitting infrared light, wherein at least the LEDs of the micro-LED display which are operated for sensing are configured to detect incident infrared light.

11. Motor vehicle comprising: - an instrument panel (4) between a windshield (5) of the motor vehicle and a steering column; - the reflection display system (1) according to any of Claims 6 to 10.