DEVICE AND METHOD FOR PROJECTING IMAGE DATA ONTO A PROJECTION SURFACE OF A VEHICLE WINDOW

Description

[0001] The invention relates to a device for projecting image data onto a projection surface of a vehicle windshield. The invention further relates to a method for operating such a device and a vehicle having such a device.

[0002] Devices for projecting image data onto a projection surface of a vehicle windshield are known in the art as "head-up displays (HUDs). Such devices are typically used to project navigation data, vehicle operating data, and multimedia data that control multimedia applications in a vehicle. Typically, the projected image data is visible only to the driver.

[0003] In state-of-the-art projection systems (HUDs), image data is projected onto a projection surface of a vehicle windshield. The windshield can be any vehicle window, such as a windshield, a side window, etc. The respective vehicle window and the projection surface of the vehicle windshield are transparent. When projecting the image data, a projector projects image content onto the projection surface using light beams. The light beams are reflected by the projection surface toward the viewer, making the image content visible to the viewer.

[0004] Furthermore, projection systems are known that project different image data onto two different projection surfaces of a vehicle window.

[0005] For example, DE 10 2006 050 016 A1 discloses a display device in a vehicle, wherein the vehicle has a sensor arrangement for determining the viewing direction of a driver of the vehicle, and the display device has two separate projection surfaces on the vehicle windshield. The display device is controlled by a display controller such that, depending on the driver's viewing direction, information relating to the vehicle is displayed either on the first projection surface or the second projection surface.

[0006] The display of moving images, such as videos, in the driver's field of vision is not permitted by law because it could distract the driver.

[0007] Also known in the state of the art are so-called "multimedia HUDs," which allow the driver and passenger to display personalized media content without the other driver seeing it. These systems are currently particularly interesting for the passenger, as they don't distract or disturb the driver with image content visible only to the passenger.

[0008] In future autonomous vehicles, such projection systems will most likely also be used to project moving image content to the driver, provided the vehicle is moving autonomously. By projecting individualized image content, such a multimedia HUD enables the individual consumption of image data and image data streams in vehicles, buses, taxis, or other means of public transport.

[0009] DE 10 2016 223908 A1 discloses a method for adjusting the brightness of a virtual display image of a head-up display. According to the method, a brightness profile of an occlusion image is detected, and the brightness of at least one image area of ​​the projection image is adjusted depending on the brightness profile of the occlusion image.

[0010] The object of the present invention is to provide an improved device for projecting image data onto a projection surface of a vehicle window, which in particular enables trouble-free and non-tiring enjoyment of the projected image data.

[0011] The invention is based on the following finding of the inventors.

[0012] When image data is projected onto a vehicle windshield using a projection system known in the prior art, the image contrast is created by the brightness difference between the light and dark pixel contents. The darkest image content in this case is "pure black." Therefore, when the "pure black" image content is projected onto an image pixel on the projection surface, no light beam is emitted by the projector, and consequently, no light beam emanating from the projection system is reflected toward the viewer at this pixel. This pixel on the projection surface therefore essentially has the brightness, color, or tonal values ​​of the projection surface.

[0013] The result is that, because the projection surface is transparent, the viewer perceives the surroundings of the vehicle behind the pixel in the viewer's line of sight. Instead of appearing "purely black," this pixel takes on the brightness, color, or tone of the corresponding surroundings. Furthermore, since the vehicle is typically moving, the corresponding surroundings are constantly changing, which a viewer of the image data finds distracting.

[0014] Fatigue-free viewing of the image data projected onto the projection surface also requires that the viewer's eyes are kept as focused as possible on the projection surface. If image data with a large proportion of dark image content is projected onto the projection surface, a correspondingly large transparent area is created on the projection surface, through which the viewer perceives the environment behind the projection surface. In this case, the viewer's eyes alternately focus on the projection surface (in the case of bright image content) and the environment behind the projection surface (in the case of dark image content). This change in focus is disturbing and tiring for the viewer. This effect is more pronounced in bright vehicle environments, while it is reduced in dark vehicle environments.

[0015] A first aspect of the invention relates to a device for projecting image data onto a projection surface of a vehicle window, comprising: an interface for providing the image data BD1(t), an image data processing unit connected to the interface for generating image data BD2(t) from the image data BD1(t), a brightness sensor connected to the image data processing unit for detecting an ambient brightness H(t), and a projection unit connected to the image processing unit for projecting the image data BD2(t) onto the projection surface of the vehicle window, wherein the image data processing unit is designed and configured such that, depending on the detected ambient brightness H(t), a gradation curve GK(H(t)) is specified for generating the image data BD2(t) from the image data BD1(t) in such a way thatsuch that dark image areas below a predetermined color brightness threshold are brightened in comparison to image areas above the color brightness threshold in the image data BD2(t) with respect to their color or grayscale spectra, wherein a degree of brightening of the dark image areas in the image data BD2(t) increases with increasing ambient brightness H(t).

[0016] The gradation curve GK(H(t)) defines a unique mapping f of brightness values ​​in [%] of a range SPEC := [0% ... 100%] representing a color or grayscale spectrum to the same range SPEC: f : SPEC → SPEC %IN → %OUT with: %IN:Input brightness values ​​of the provided image data BD1(t) %OUTBrightness values ​​of the image data BD2(t) 0%minimum brightness = 0 = "pure black" 100%:maximum brightness.

[0017] This means that the definition domain SPEC of the function f is identical to the target domain SPEC of the function f. The domain SPEC represents brightness values ​​or color values ​​or tone values ​​of image pixels of the respective image data BD1(t) and BD2(t).

[0018] The gradation curve GK(H(t)) is changed in this case depending on the determined ambient brightness H(t).

[0019] Furthermore, in the present case, the term "dark image areas" advantageously refers to those image areas of the image data BD1 whose image pixels have brightness values ​​in [%] in the range between 0% and 50%, in particular between 0% and 40% or between 0% and 30% or between 0% and 20% or between 0% and 15%.

[0020] In other words, the dark image areas lie below a predefined threshold value for the brightness of their color or grayscale spectra, such as 50%, 40%, 30%, 20%, or 15%. The brightness values ​​of the gray and color values ​​that are complementary to the specified brightness values, i.e., those that lie above the predefined threshold value, are thus referred to as "bright image areas" of the image data BD1(t) and are output in the image data BD2(t) without brightening or at least with a lower brightening relative to the dark image areas. In addition to brightening the gray and color values, the light intensity can also be adjusted depending on the ambient brightness. For example, in dark environments such as driving through a tunnel, the intensity is reduced and in bright environments it is increased for better visibility on the projection surface.The light intensity is changed by changing the brightness, measured in lumens, of the color or grayscale spectra emitted by the light source of the projection unit.

[0021] The gradation curve GK(H(t)) is advantageously modified depending on the determined ambient brightness H(t) such that the input brightness value %IN = 0 := "pure black" of the provided image data BD1(t) is mapped to a brightness (target) value %OUT(%IN=0) > 0 of the image data BD2(t). The absolute value |%OUT(%IN=0)| of the brightness (target) value increases with increasing ambient brightness H(t) and decreases with decreasing ambient brightness H(t).

[0022] If the ambient brightness (e.g., during night) is very low (a corresponding brightness threshold GW can be specified), then the input brightness value %IN = 0 (= "pure black") of the provided image data BD1(t) is advantageously mapped to a brightness (target) value %OUT(%IN=0) = 0 := "pure black" of the image data BD2(t). In this case, the gradation curve GK(H(t)) advantageously corresponds to the diagonal between the points: (%IN=0, %OUT=0) and (%IN=100, %OUT=100) when entered into a linear rectangular coordinate system.

[0023] For ambient brightness H(t) > 0 or H(t) > GW, the gradation curve GK(H(t)) then runs continuously from a single point (%IN=0, %OUT > 0) towards its end point (%IN = 100, %OUT = 100). If the gradation curve GK is plotted in a linear, rectangular coordinate system, the gradation curve GK(H(t)) advantageously lies above a diagonal connecting the points (%IN=0, %OUT = 0) and (%IN=100, %OUT = 100) for the input brightness value range %IN B1 from [0% to 50%], and is advantageously identical to the diagonal connecting the points (%IN=50, %OUT = 50) and (%IN=100, %OUT = 100) for the input brightness value range %IN B2 from [50% to 100%].

[0024] According to the invention, the "brightening" or "degree of brightening" of the dark image areas in the image data BD2(t) depends on the determined ambient brightness H(t). The degree of brightening of the dark image areas increases with increasing ambient brightness H(t) and decreases with decreasing ambient brightness H(t). The degree of brightening of dark image areas is therefore adjusted in both directions depending on the determined ambient brightness H(t). This means, in particular, that the gradation curve GK(H(t)) is adjusted accordingly depending on the determined ambient brightness H(t).

[0025] An advantageous development of the proposed device is characterized in that a system connected to the image data processing unit is also provided for detecting a current viewing angle range BWB(t) of at least one occupant of the vehicle. The image data processing unit is designed and configured such that only those dark image areas in the image data BD2(t) are brightened which, when projected onto the projection surface of the vehicle window, lie within the viewing angle range BWB(t). A vehicle occupant can be, in particular, the driver or the front passenger. The vehicle window is advantageously a windshield or a side window of the vehicle.

[0026] The brightness sensor is advantageously a camera sensor. The brightness sensor advantageously has a detection range that essentially detects a brightness H(t) of the vehicle's surroundings that is perceptible to an occupant through the projection surface. This measures, in particular, the brightness H(t) of the surrounding area that is decisive for the aforementioned defocusing effect experienced by a viewer.

[0027] An advantageous development of the proposed device is characterized in that the image data processing unit is designed and configured in such a way that, in the event of a change ΔH(t) in the determined ambient brightness H(t), the dark image areas in the image data BD2(t) are brightened with a predetermined time delay Δt(ΔH(t)) dependent on ΔH(t). In particular, in the event of a change ΔH(t) in the determined ambient brightness H(t), the gradation curve GK(H(t)) is changed with a predetermined time delay Δt(ΔH(t)) dependent on ΔH(t). Due to the time delay Δt(ΔH(t)), a change in the degree of brightening generally only occurs with a delay.

[0028] If, for example, at a time t 0 the ambient brightness H(t 0 ) increases by 1000 lux and the corresponding time delay is Δt(ΔH(t)) = 2 sec, a change in the degree of brightening or a change in the gradation curve ΔGK(H(t)) would only begin or take effect after 2 seconds. If the ambient brightness H(t) changes by -1000 lux within the 2 seconds, i.e. back to the initial value, then advantageously there is no change in the degree of brightening or in the gradation curve GK(H(t 0 ) underlying the time t 0 . The time delay Δt(ΔH(t)) is advantageously shorter for large changes ΔH(t) in the ambient brightness H(t) than for small changes ΔH(t) in the ambient brightness H(t).

[0029] An advantageous development of the proposed device is characterized in that the image data processing unit is designed and configured such that, upon a change ΔH(t) in the determined ambient brightness H(t), a change in the brightening of the dark image areas in the image data BD2(t) or a change in the gradation curve GK(H(t)) occurs according to a predetermined continuous function HYS(t). This avoids any sudden changes in the projection of the image data BD2(t).

[0030] Advantageously, the continuous function HYS(t) depends on the sign of the change ΔH(t) in brightness H(t), whereby with a positive ΔH(t), the brightening of the dark image areas changes according to a predefined function HYS1(t), and with a negative ΔH(t), the brightening of the dark image areas changes according to a predefined function HYS2(t). This allows the specification of one function for an increase in the determined ambient brightness H(t) and another function for a decrease in the determined ambient brightness H(t).

[0031] The function HYS(t) is particularly advantageously represented as a hysteresis behavior, in particular a time-delayed hysteresis behavior when changing the brightening of dark image areas in the image data BD2(t).

[0032] A further aspect of the present invention relates to a vehicle, in particular a road vehicle, a rail vehicle, a watercraft or an aircraft, with a device as described above.

[0033] A final aspect of the present invention relates to a method for operating a device for projecting image data onto a projection surface of a vehicle window of a vehicle, comprising the following steps: Providing image data BD1(t) at an interface, detecting an ambient brightness H(t) with a brightness sensor, generating image data BD2(t) from the image data BD1(t) by means of an image data processing unit connected to the interface, and projecting the image data BD2(t) onto the projection surface of the vehicle window by means of a projection unit connected to the image processing unit, wherein the image data processing unit prescribes a gradation curve GK for generating the image data BD2(t) from the image data BD1(t) as a function of the detected ambient brightness H(t) in such a way that dark image areas below a predetermined color brightness limit value in comparison to image areas above the color brightness limit value in the image data BD2(t) are brightened with regard to their color or grayscale spectra compared to the image data BD1(t), wherein a degree of brightening of the dark image areas in the image data BD2(t) increases with increasing ambient brightness H(t).

[0034] Advantageously, the proposed method comprises the step of determining a current viewing angle range BWB(t) of at least one occupant of the vehicle by means of a system connected to the image data processing unit, wherein the image data processing unit brightens only those dark image areas in the image data BD2(t) which, when projected onto the projection surface of the vehicle window, lie in the viewing angle range BWB(t).

[0035] An advantageous development of the proposed method is characterized in that the brightness sensor has a detection range, and the detection range detects a brightness H(t) essentially of an environment of the vehicle that is perceptible to an occupant through the projection surface.

[0036] Advantageously, in the event of a change ΔH(t) in the determined ambient brightness H(t), the image data processing unit brightens the dark image areas in the image data BD2(t) with a predetermined time delay Δt(ΔH(t)) dependent on ΔH(t).

[0037] Advantageously, in the event of a change ΔH(t) in the determined ambient brightness H(t), the image data processing unit changes the degree of brightening of the dark image areas in the image data BD2(t) according to a predefined continuous function HYS(t). Advantageously, the continuous function HYS(t) depends on the sign of the change ΔH(t) in the ambient brightness H(t), whereby with a positive ΔH(t), the brightening of the dark image areas changes according to a predefined function HYS1(t), and with a negative ΔH(t), the brightening of the dark image areas changes according to a predefined function HYS2(t).

[0038] The function HYS(t) particularly advantageously represents a hysteresis behavior, in particular a time-delayed hysteresis behavior when changing the brightening of dark image areas in the image data BD2(t).

[0039] Further advantages, features, and details will become apparent from the following description, in which at least one embodiment is described in detail—possibly with reference to the drawings. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.

[0040] They show: Fig. 1 shows a highly schematic structure of a proposed device, Fig. 2 shows an example of a proposed gradation curve, and Fig. 3 shows a highly schematic flow chart of a proposed method.

[0041] Fig. 1 shows a highly schematic structure of a proposed device for projecting image data onto a projection surface of a vehicle windscreen, comprising: an interface 101 for providing the image data BD1(t), an image data processing unit 102 connected to the interface 101 for generating image data BD2(t) from the image data BD1(t), a brightness sensor 103 connected to the image data processing unit 102 for detecting an ambient brightness H(t), and a projection unit 104 connected to the image processing unit 102 for projecting the image data BD2(t) onto the projection surface of the vehicle windscreen.

[0042] The image data processing unit 102 is here designed and configured such that, depending on the detected ambient brightness H(t), a gradation curve GK(H(t)) is specified for generating the image data BD2(t) from the image data BD1(t) such that dark image regions below a predetermined color brightness threshold in the image data BD2(t) are brightened compared to image data BD1(t) above the color brightness threshold, wherein a degree of brightening of the dark image regions in the image data BD2(t) increases with increasing ambient brightness H(t). This means, in particular, that dark image regions in the image data BD2(t) are displayed with greater brightness as the ambient brightness H(t) increases and with less brightness as the ambient brightness H(t) decreases.

[0043] The device further comprises a system 105 connected to the image processing unit for determining a current viewing angle range BWB(t) of at least one occupant of the vehicle (driver and / or front passenger), wherein the image data processing unit brightens only those dark image areas in the image data BD2(t) which, when projected onto the projection surface of the vehicle window, lie in the viewing angle range BWB(t).

[0044] The brightness sensor preferably has a detection area that detects a brightness H(t) essentially of an environment of the vehicle that is perceptible to an occupant through the projection surface.

[0045] The image data processing unit is further designed and configured such that, upon a change ΔH(t) in the determined ambient brightness H(t), a brightening of the dark image areas in the image data BD2(t) is carried out with a predetermined time delay Δt(ΔH(t)) dependent on ΔH(t).

[0046] Fig. 2 shows an example of a suggested gradation curve GK(H(t)). The basis for this example is that a brightness sensor on the vehicle determines the ambient brightness H(t) between 1 and 100,000 lm / m². The gradation curve GK(H(t)) is determined depending on the ambient brightness H(t). This example is based on an algorithm that determines two points P1 and P2 of a gradation curve GK(H(t)). In the diagram shown, point P1 determines an assignment of %IN = 0 → %OUT(%IN=0) that is dependent on the ambient brightness H(t), where: %OUT(%IN=0) ≥ 0, and thus defines an increase (brightening) of the image data for the input value %IN=0. The assignment: %IN = 0 → %OUT(%IN=0) = 0 applies in this case only exceptionally in the case that the determined ambient brightness H(t) is lower than a limit value GW of an ambient brightness given for a dark night.

[0047] The point P2 determines an assignment depending on the ambient brightness H(t) of: % IN = 25 → % OUT % IN = 25 = % OUT % IN = 0 + % OUT % IN = 0 / 2 and thus defines an increase (brightening) of the image data for the input value %IN = 25, dependent on the ambient brightness H(t). Point P2 serves to determine the further course of the gradation curve GK(H(t)). The displayed gradation curve GK(H(t)) hugs the dashed diagonal from the point (%IN=50, %OUT=50) and continues towards the end point of the gradation curve (%IN=100, %OUT=100).

[0048] If the measured ambient brightness H(t) changes, a correspondingly modified gradation curve GK(H(t)) is determined. If the measured ambient brightness H(t) decreases, in this example, the value %OUT(%IN=0) of point P1 and the value %OUT(%IN=25) are reduced accordingly. If the measured ambient brightness H(t) decreases below the specified limit value GW, the gradation curve GK(H(t)) corresponds to the curve shown in the diagram as a dot-dashed diagonal.

[0049] Fig. 3shows a highly schematic flow chart of a proposed method for operating a device for projecting image data onto a projection surface of a vehicle window, comprising the following steps: providing 201 image data BD1(t) at an interface 101, detecting 202 an ambient brightness H(t) with a brightness sensor 103, generating 203 image data BD2(t) from the image data BD1(t) by means of an image data processing unit 102 connected to the interface 101, and projecting 204 the image data BD2(t) onto the projection surface of the vehicle window by means of a projection unit 104 connected to the image processing unit 102, wherein the image data processing unit 102, depending on the detected ambient brightness H(t), prescribes a gradation curve GK for generating the image data BD2(t) from the image data BD1(t), such that dark image areas in the image data BD2(t) are brightened compared to the image data BD1(t),where a measure of the brightening of the dark image areas in the image data BD2(t) increases with increasing ambient brightness H(t).

Claims

1. Device for projecting image data onto a projection surface of a vehicle window of a vehicle, the device comprising: - an interface (101) for providing the image data BD1(t), - an image data processing unit (102), connected to the interface (101), for generating image data BD2(t) from the image data BD1(t), - a brightness sensor (103), connected to the image data processing unit (102), for detecting an ambient brightness H(t), and - a projection unit (104), connected to the image data processing unit (102), for projecting the image data BD2(t) onto the projection surface of the vehicle window, characterized in that the image data processing unit (102) is designed and configured such that, depending on the detected ambient brightness H(t), for generating the image data BD2(t) from the image data BD1(t), a gradation curve GK(H(t)) is specified in such a way that dark image regions in the image data BD2(t), which regions are below a specified color brightness limit value compared to image regions above the color brightness limit value, are brightened with respect to their color spectra or grayscale spectra compared to image data BD1(t), a degree of brightening of the dark image regions in the image data BD2(t) increasing with increasing ambient brightness H(t).

2. Device according to claim 1, further comprising a system (105), connected to the image data processing unit (102), for detecting a current viewing angle range BWB(t) of at least one occupant of the vehicle, wherein the image data processing unit (102) is designed and configured such that only those dark image regions in the image data BD2(t) are brightened which are within the viewing angle range BWB(t) when projected onto the projection surface of the vehicle window.

3. Device according to either claim 1 or claim 2, in which the brightness sensor (103) has a detection range which detects a brightness H(t) substantially of an environment of the vehicle which can be perceived by an occupant through the projection surface.

4. Device according to any of claims 1 to 3, in which the image data processing unit (102) is designed and configured such that, in the event of a change ΔH(t) in the determined ambient brightness H(t), the dark image regions in the image data BD2(t) are brightened with a specified time delay Δt(ΔH(t)) dependent on ΔH(t).

5. Device according to any of claims 1 to 4, in which the image data processing unit (102) is designed and configured such that a change ΔH(t) in the determined ambient brightness H(t) results in a change in the brightening of the dark image regions in the image data BD2(t) according to a specified continuous function HYS(t).

6. Device according to claim 5, in which the continuous function HYS(t) is dependent on the sign of the change ΔH(t) in the brightness H(t), wherein in the case of a positive ΔH(t) the brightening of the dark image regions changes according to a specified function HYS1(t) and in the case of a negative ΔH(t) the brightening of the dark image regions changes according to a specified function HYS2(t).

7. Device according to either claim 5 or claim 6, in which the function HYS(t) represents a hysteresis behavior.

8. Vehicle, in particular road vehicle, rail vehicle, watercraft, aircraft, comprising a device according to any of claims 1 to 4.

9. Method for operating a device for projecting image data onto a projection surface of a vehicle window of a vehicle, the method comprising the following steps: - providing (201) image data BD1(t) at an interface (101), - detecting (202) an ambient brightness H(t) by means of a brightness sensor (103), - generating (203) image data BD2(t) from the image data BD1(t) by means of an image data processing unit (102) connected to the interface (101) and, - projecting (204) the image data BD2(t) onto the projection surface of the vehicle window by means of a projection unit (104) connected to the image processing unit (102), characterized in that the image data processing unit (102) specifies, depending on the detected ambient brightness H(t), for generating the image data BD2(t) from the image data BD1(t), a gradation curve GK(H(t)) in such a way that dark image regions in the image data BD2(t), which regions are below a specified color brightness limit value compared to image regions above the color brightness limit value, are brightened with respect to their color spectra or grayscale spectra compared to image data BD1(t), a degree of brightening of the dark image regions in the image data BD2(t) increasing with increasing ambient brightness H(t).

10. Method according to claim 9, comprising the step of: determining a current viewing angle range BWB(t) of at least one occupant of the vehicle by means of a system (105) connected to the image data processing unit (102), wherein the image data processing unit (102) only brightens those dark image regions in the image data BD2(t) which are within the viewing angle range BWB(t) when projected onto the projection surface of the vehicle window.