Suppression of reflections on reflective display surfaces of mobile devices in a vehicle

Abstract

The invention relates to a method for suppressing reflections on display surfaces of mobile devices when capturing the display contents thereof in a vehicle, comprising the following steps: - capturing a display content of a mobile device by at least one interior camera of the vehicle using at least one predetermined polarisation filter; - analysing the captured display content for corresponding polarisation properties in the case of display light of this device on the one hand, and in the case of interfering light which is mixed with the display light via reflection on its display surface on the other hand; and - using polarisation properties of the display light and / or the interfering light extracted thereby for digital post-processing of said or subsequently captured display content, in which at least part of the interfering light is subtracted in individual image pixels in order to increase the proportion of display light therein and reduce, or almost completely remove, the proportion of interfering light.

Description

[0001] Description

[0002] Suppression of reflections on reflective display surfaces of mobile devices in a vehicle

[0003] The invention relates to a method for suppressing disruptive reflections on reflective display surfaces of mobile devices in a vehicle, in particular a motor vehicle. The invention also relates to a correspondingly configured control unit and a vehicle equipped therewith.

[0004] The interior of a motor vehicle is comparatively dark compared to external light sources such as the sun, streetlights, signal lights, or headlights. If light entering the vehicle from outside falls on the reflective display surface of a mobile device used in the vehicle, such as a smartphone, the reflection of this light from the display surface can cause glare, rendering the displayed content, such as text or images, invisible or unreadable.

[0005] In the prior art, it is known in various fields to use polarization filters, among other things to suppress disruptive light reflections. For example, polarization filters are used in photography, for example, to suppress sky reflections on a water surface. Recently, industrial cameras have also become available with multiple polarization filters directly on the sensor, arranged in a checkerboard pattern and thus capable of three different polarization angles and an unpolarized channel. The object of the present invention is to provide a concept for suppressing disruptive reflections on reflective display surfaces of mobile devices in a vehicle, in particular a motor vehicle.

[0006] This object is achieved by a method according to claim 1 for suppressing reflections on the display surfaces of mobile devices when capturing their display contents in a vehicle, as well as by a correspondingly configured control unit and a vehicle equipped therewith according to the independent claims. Further embodiments are specified in the dependent claims. All further features and effects mentioned in the claims and the following description for the method also apply to the control unit and the vehicle, and vice versa.

[0007] According to a first aspect, a method is provided for suppressing reflections on the display surfaces of mobile devices (such as smartphones, laptops, etc.) when capturing their display contents in a vehicle. The vehicle can be, in particular, a motor vehicle, but alternatively, any other land, air, or water vehicle.

[0008] In the method presented here, the vehicle is equipped with at least one interior camera designed and configured to optically capture display content from a mobile device used in the vehicle. Capturing and processing such display content can be useful for various applications in the vehicle that are not described in detail here.

[0009] The procedure includes the following steps:

[0010] The display content of a mobile device used in the vehicle is captured by at least one of these interior cameras using at least one predetermined polarization filter. Knowledge of the polarization properties of the respective filter is used to analyze the captured display content for the presence of corresponding polarization properties in the display light of this device, on the one hand, and in the presence of interfering light that is mixed with the display light via reflection from its display surface, on the other. The polarization properties of the display light and / or the interfering light obtained / extracted through this analysis are used for digital post-processing of this display content or subsequently captured display content.In this digital post-processing, at least a portion of the stray light in individual image pixels of the respective display content is subtracted in order to increase the proportion of display light therein and to reduce the proportion of stray light or, ideally, even to remove it completely.

[0011] One idea behind this method, or rather its working principle, is based on analyzing the different polarization properties of the interfering light, which can come, for example, from the sky or artificial light sources inside and outside the vehicle, and the display light that conveys the actual display content. The use of at least one polarization filter in the vehicle's interior camera(s) can help extract information about the various light sources within a captured image, which enables these light sources to be filtered during digital post-processing of the image. For example, during this post-processing of the captured display content, it is possible to filter out reflections coming from the sky and increase the proportion of display light generated by the mobile device itself. The display light can, but does not have to, be polarized in the present method.Nor is any connection between the vehicle and the mobile device required that could directly transmit any information about the polarization properties of its display light or about its display contents to the vehicle.

[0012] In this method, the stray light can originate from one or more light sources with different intensities and different polarization properties. Especially light sources outside the vehicle, such as the sun, headlights, or streetlights, can cause disturbing reflections on the display surface and even overshadow the display light due to their significantly higher light intensity compared to the display light.

[0013] The aforementioned analysis of the captured display content may, for example, include a pixel-by-pixel comparison. This comparison can be performed both within a single image capture and between multiple images captured with different polarization filters and otherwise under identical conditions.

[0014] For example, if the use of a predetermined linear polarizer in the indoor camera results in a uniformly illuminated display surface, while a crossed polarizer produces clear display content against a black background, then in this simple case, it can be concluded that the display light is linearly polarized (e.g., p-polarized), while a key interfering light source (e.g., atmospheric stray light) has a linear polarization perpendicular to this (e.g., s-polarized), so that this interfering light can be completely subtracted during digital post-processing of the image. In reality, the composition of light from different light sources is usually more complex and requires correspondingly more complex analysis steps.

[0015] The aforementioned post-processing of the display contents for their further processing or use in the vehicle can be implemented at least partially in the respective camera, but alternatively or additionally also in an outsourced control or processing unit that is connected to the camera wirelessly or wired.

[0016] According to one embodiment, at least one of the polarization filters mentioned is a static polarization filter designed to filter out (in the sense of transmitting or, conversely, blocking) light of a predetermined polarization typical of light coming from the sky. In this embodiment, the analysis checks the individual image pixels of the captured display content for the presence and proportion of light with this polarization, and from this, a proportion of this light to be subtracted (which can in particular, but not necessarily, be the same for all pixels) is determined. Thus, when using the method presented here with only one static polarization filter, reflections of light coming from the sky can be greatly reduced.

[0017] According to a further embodiment, the one or more interior cameras are configured for simultaneous image capture with and without a predetermined static polarization filter. In this embodiment, a display content of the mobile device is thus captured simultaneously with and without this polarization filter. The two images thus obtained are compared pixel by pixel to extract the polarization properties of the display light and the stray light.

[0018] For example, two cameras and a static filter can be used. This allows either two sensors (e.g., a CCD / CMOS chip), each with a separate optical system (e.g., a lens or lens combination), or a sensor with two lenses (focusing the same image on different parts of the sensor), with a fixed / static polarization filter added to only one of these optical systems. This makes it possible to assign the two simultaneously acquired images to each other pixel by pixel (and optionally also to calibrate any light intensity differences due to the other optical system), thus extracting information about a polarized noise or display light source.Similar to a movable filter with only two positions (on and off), this would allow some information about the stray light sources to be extracted for each pixel of the captured display content and thus subtracted / ignored. Unlike a movable polarizing filter, which allows the use of a single camera but requires both images to be captured consecutively, this embodiment captures both images simultaneously, which can significantly increase the precision of their comparative analysis.

[0019] According to a further embodiment, at least one of the interior cameras is designed to capture multiple images directly one after the other, each with a different predetermined polarization filter. This can be achieved in particular by a rotatable or rotating filter (for example, in the form of a disk) that positions a different polarization filter (for example, with a different polarization angle of a linear polarization) in front of the camera depending on its rotational position.

[0020] In this embodiment, a display content is captured multiple times in succession, each time using a different polarization filter. The resulting images are compared pixel by pixel to extract the polarization properties of the display light and the stray light. In this way, for example, the amounts of light coming from the sky, the display, and the environment can be separated: Ambient light is generally diffuse / non-polarized, whereas the display light and the atmospheric scattered light coming from the sky are polarized, most likely in different directions. Performing an analysis across multiple individual images with different polarization angles allows for a precise determination of the polarization angles of the light from different light sources.This can allow different light sources to be divided into individual / separate images so that any reflections on the screen (display), including diffusely scattered stray light, can be eliminated during subsequent post-processing of the display content.

[0021] As already mentioned, the display light can, in particular, have a predetermined polarization that differs from a typical polarization of the stray light coming from the sky. In this case, two or more different polarization filters can be used in the at least one interior camera, for example, which make it possible to separate the portion of the display light from the portion of the light coming from the sky and from the portion of the remaining, non-polarized ambient light in images of the display content captured simultaneously or directly one after the other using these different polarization filters.

[0022] As already mentioned, the respective display content of the mobile device can be passed on to a vehicle-mounted control unit after the aforementioned post-processing in order to be further used by it for specific applications in the vehicle.

[0023] According to a further aspect, a control unit is provided which is designed and configured for use (e.g., by installation or integration) in the above-mentioned vehicle or in the at least one interior camera and for automatically executing the above-mentioned method. For this purpose, a corresponding computer program (software) can be loaded into a processor of the control unit, for example, and run during operation of the vehicle or the camera.

[0024] According to a further aspect, the above vehicle is provided, which comprises at least the following: an interior for one or more vehicle occupants; at least one interior camera, which is designed and configured to capture display contents of a mobile device used in the vehicle and in this case comprises at least one predetermined polarization filter; and the above control unit.

[0025] The above aspects of the invention and their embodiments and specific configurations are explained in more detail below with reference to examples shown in the accompanying drawings. The drawings are to be understood as purely schematic illustrations of the basic functional principle and are not necessarily to scale. They show:

[0026] Figure 1 shows a schematic longitudinal section of a vehicle which is designed and equipped to carry out the method according to an embodiment of the invention; and

[0027] Figure 2 diagrams of a polarization angle-dependent light intensity of the total light emanating from a display surface in the vehicle of Fig. 1 as well as the components of the display light, the light originating from the sky and the remaining diffuse ambient light contained therein.

[0028] All of the various embodiments, alternatives, and specific design features of the method, the associated control unit, and the vehicle according to the above aspects of the invention mentioned above in the description and in the subsequent claims can be implemented in the examples shown in Figs. 1 and 2, in particular also alternatively or in addition to the features shown therein. Therefore, they will not all be repeated below. The same applies accordingly to the definitions and effects already given above with regard to individual features shown in Figs. 1-2.

[0029] Fig. 1 shows a highly simplified schematic longitudinal sectional view of a vehicle 1 according to an embodiment of the invention. In this example, the vehicle 1 is a motor vehicle, the individual components of which are only symbolically indicated in Fig. 1.

[0030] The vehicle 1 has an interior 2 for one or more vehicle occupants (not shown) and is equipped with at least one interior camera 3, which is designed and configured to optically capture display contents of a mobile device 4 used in the vehicle 1, for example a smartphone. The at least one interior camera 3 can comprise one or more individual cameras, which are not shown individually in Fig. 1 and can use one or more predetermined polarization filters 5 during their operation.

[0031] Furthermore, the vehicle 1 comprises a control unit 11, which is designed and configured for automated execution of a method according to an embodiment of the invention and for corresponding communication with the at least one interior camera 3. The method comprises the following steps:

[0032] A display content shown on a display surface 6 of the mobile device 4 is captured by the at least one interior camera 3 using the at least one polarization filter 5. The polarization properties of the respective filter used are known in advance and are used to analyze the captured display content for the presence of corresponding polarization properties in the display light and in the stray light reflected from the display surface 6. The polarization properties of the display light and / or the stray light thus extracted are used for digital post-processing of this display content or subsequently captured display content by subtracting at least a portion of the stray light in individual image pixels of the respective display content in order to increase the proportion of display light therein and reduce the proportion of stray light, and ideally, to remove it completely.

[0033] In one possible example, Fig. 2 shows individual diagrams of the polarization angle-dependent light intensity of the total light 10 emanating from the display surface 6 in the vehicle 1 of Fig. 1 and captured by at least one interior camera 3, as well as the individual components of the display light 7, the light 8 originating from the sky, and the remaining diffuse ambient light 9 contained therein. As can be seen from these diagrams, the display light 7 in this example has a polarization whose polarization angle dependence differs significantly from that of the sky light 8. The remaining ambient light 9 is not or diffusely polarized and therefore shows a constant intensity for each polarization angle. In this example, the above-mentioned stray light is therefore composed of the sky light 8 and the remaining ambient light 9.

[0034] Using the method described with reference to Fig. 1, in this example the amounts of light coming from the display, the sky and the rest of the environment can be separated from one another because these light sources have different polarization properties. Performing an analysis across multiple individual images with different polarization angles allows for precise determination of the respective polarization angles of the light 7, 8 and 9 from these different light sources. Through digital post-processing based on this, it is possible in this example to eliminate any reflections from the display surface 6 of the mobile device 4, including diffusely scattered light 9, in the display content of the mobile device 4 captured by the at least one interior camera 3.

[0035] List of reference symbols

[0036] vehicle

[0037] Interior at least one interior camera mobile device at least one polarization filter

[0038] Display area

[0039] Display light light coming from the sky remaining ambient light all the light that reaches the camera from the display surface control unit

Claims

Claims 1. A method for suppressing reflections on display surfaces (6) of mobile devices (4) when capturing their display contents in a vehicle (1), comprising the steps: Capturing a display content of a mobile device (4) used in the vehicle (1) by at least one interior camera (3) of the vehicle (1) using at least one predetermined polarization filter (5); Analyzing the captured display content for the presence of corresponding polarization properties in the display light (7) of this device (4), on the one hand, and in the case of stray light (8, 9) that is mixed with the display light (7) via reflection on its display surface (6), on the other hand; and using polarization properties of the display light (7) and / or the stray light (8, 9) extracted thereby for digital post-processing of this or subsequently captured display content, in which at least a portion of the stray light (8, 9) is subtracted in individual image pixels in order to increase the proportion of the display light (7) therein and to reduce or almost completely remove the proportion of the stray light (8, 9).

2. The method according to claim 1, wherein at least one of said polarization filters (5) is a static polarization filter designed to filter out the light of a predetermined polarization typical of the light (8) coming from the sky; During the analysis, the individual image pixels of the captured display content are checked for the presence and proportion of light (8) with this polarization and a proportion of this light (8) to be subtracted is determined therefrom.

3. The method according to claim 1 or 2, wherein the at least one interior camera (3) is configured for simultaneous image recording with and without a predetermined static polarization filter (5); a display content of the mobile device (4) is captured simultaneously with and without said polarization filter (5); and two images obtained thereby are compared pixel by pixel during said analysis of the polarization properties of the display light (7) and the stray light (8, 9).

4. Method according to one of the preceding claims, wherein at least one of the interior cameras (3) is designed to record a plurality of images directly one after the other, each with a different predetermined polarization filter; a display content of the mobile device (4) is captured directly one after the other with each of these polarization filters (5); and a plurality of images thus obtained are compared with one another pixel by pixel in the said analysis of the polarization properties of the display light (7) and the stray light (8, 9).

5. Method according to one of the preceding claims, wherein the display light (7) has a predetermined polarization which differs from a typical polarization of the light (8) coming from the sky; and in the at least one interior camera (3) two or more different polarization filters (5) are used, which make it possible to detect in images recorded simultaneously or directly one after the other with these different polarization filters (5) Images of the display content to separate the portion of the display light (7) from the portion of the light coming from the sky (8) and from the portion of the remaining, non-polarized ambient light (9).

6. Method according to one of the preceding claims, wherein the respective display content of the mobile device (4) is forwarded to a vehicle-mounted control unit for a predetermined further use after said digital post-processing.

7. Control unit (11) which is designed and configured to automatically execute the method according to one of the preceding claims.

8. A vehicle (1), in particular a motor vehicle, comprising: an interior (2) for one or more vehicle occupants; at least one interior camera (3) designed and configured to capture display contents of a mobile device (4) used in the vehicle (1) and comprising at least one predetermined polarization filter (5); and a control unit (11) according to claim 7.

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