Patent Publication Number: US-2011074956-A1

Title: Device, camera, and method for  generating images of the surrounding of a motor vehicle

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device, a camera, and a method for generating images of the surroundings of a motor vehicle. 
     2. Description of Related Art 
     A method for regulating the light range and light direction of headlights in a motor vehicle is known from published European patent application document EP 0 869 031 A2, in which a camera surveys the road space in front of the motor vehicle along with the roadway and records image data. The course of the road is ascertained on the basis of the recorded image data, and the headlight aiming is adjusted accordingly. Furthermore, published European patent application document EP 0 869 031 A2 discloses that oncoming motor vehicles are detected and the illumination is regulated such that the oncoming motor vehicle does not experience a glare. 
     SUMMARY OF THE INVENTION 
     In contrast, the device according to the present invention has the advantage of improving the detection of oncoming and preceding vehicles, as well as of other objects having active light sources. It is furthermore advantageous that measurement data may be ascertained from the generated images, which data are an index for the brightness of the surroundings. Because the images are generated in the dark phases of the headlight, the measurement of the brightness of the surroundings is not distorted by reflections of the host vehicle itself. The above may advantageously be used to detect an indirect illumination in towns, and thus to infer a traffic situation within a town and to switch off the high-beam headlights, since the use of high beams is prohibited by law within city limits. Thus, on the one hand, traffic safety is increased. On the other hand, this helps to ensure that legal requirements are met. 
     A synchronization connection between the camera and the headlight is advantageous, since this makes the synchronization particularly reliable and precise. 
     A camera is particularly advantageous that is designed such that the camera adjusts the recording times of the images as a function of the illumination of the surroundings of the motor vehicle by the headlights that is recorded in the images, such that the camera generates the images in the dark phases of the headlights. This eliminates the physical synchronization line. On the one hand, this helps reduce the cost of the device, and on the other hand, the cameras may be more simply combined with headlights since the camera itself performs the synchronization. 
     The dark phases are advantageously between one millisecond and five milliseconds, preferably four milliseconds, since a human being does not perceive dark phases selected in this manner. Instead, given suitably long bright phases, a human being perceives such light from the headlight as continual illumination. 
     The advantages mentioned for the device are correspondingly valid for the camera described below and the method according to the present invention. 
     Further advantages result from the subsequent description of exemplary embodiments with reference to the figures. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In the following, the present invention is elucidated in greater detail in light of the specific embodiment represented in the drawing. 
         FIG. 1  shows a motor vehicle. 
         FIG. 2  shows a block diagram of the first exemplary embodiment. 
         FIG. 3  shows a timing diagram of the first exemplary embodiment. 
         FIG. 4  shows a block diagram of the second exemplary embodiment. 
         FIG. 5  shows a block diagram of the third exemplary embodiment. 
         FIG. 6  shows a flow chart. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following describes a device for a motor vehicle or a device in a motor vehicle, the device including a headlight for illuminating surroundings of the motor vehicle using light pulses and a camera for generating images of the surroundings of the motor vehicle. The camera and the headlight are synchronized such that the camera generates the images in dark phases of the headlight. Furthermore, a camera and a method for generating images are provided. 
       FIG. 1  shows a motor vehicle  10  on a roadway  20  of the exemplary embodiments. Motor vehicle  10  includes a camera  12  and a headlight  14 . Both camera  12  and headlight  14  are connected to a control device  16 . Camera  12  is installed in the region of the windshield and directed such that camera  12  records the surroundings in front of motor vehicle  10  with image recording region  22 . In addition to a lens, camera  12  includes a CMOS image sensor or a CCD image sensor. A color camera is preferably used. Alternatively, a black-and-white camera is used. In the exemplary embodiments, a monoscopic camera, that is, an individual camera  12 , is used. Alternatively, one variant provides for the use of a stereo camera. A stereo camera is distinguished by the fact that it includes at least two cameras that essentially record the same scene. Camera  12  records light in the wavelength range between 400 nm and 750 nm at least, preferably up to 1000 nm. In the exemplary embodiments, control device  16  ascertains measurement data from oncoming or preceding objects, motor vehicles in particular, from the images generated by camera  12 . The images recorded by camera  12  in dark phases of headlights  14  are transmitted to control device  16  for this purpose. Control device  16  performs an image evaluation, in that the control device ascertains from the images active light sources in the surroundings. Preferably, control device  16  ascertains bright image regions and classifies these image regions as objects, in particular as headlights of oncoming motor vehicles and/or as tail lights of preceding motor vehicles and/or as light sources of cyclists and/or as traffic lights. Subsequently, control device  16  determines the position of the ascertained objects and transmits these measurement data to headlights  14 . In one variant, control device  16  ascertains from the recorded images measurement data that are an index for the brightness of the surroundings. To this end, control device  16  calculates the average brightness of a recorded image or of a predetermined partial region of a recorded image. Control device  16  determines the traffic situation as a function of the ascertained brightness of the surroundings. In particular, control device  16  determines whether motor vehicle  10  is located within city limits, in that control device  16  compares the measurement value for the brightness of the surroundings with a threshold value, and infers a location within city limits if the threshold value is exceeded. Subsequently, control device  16  transmits a value that indicates whether a location within city limits was detected and a value for the brightness of the surroundings to headlights  14 . As a function of the value that indicates a location within city limits, the high beam headlights of headlights  14  are deactivated if vehicle  10  is located within city limits. Headlights  14  are activated or deactivated as a function of the value for the brightness of the surroundings. To ensure the clarity of  FIG. 1 , only one single headlight  14  is drawn. Preferably, the exemplary embodiments use two headlights  14  that are disposed in the frontal region of motor vehicle  10  and illuminate the region in front of motor vehicle  10  with an illumination range  24 . Headlights  14  are distinguished by the fact that they output pulsed light and thus illuminate the surroundings in front of motor vehicle  10  in a pulsed manner, the pulse frequency being selected in such a way that the human eye perceives the light of headlights  14  as a continual illumination. The headlights in the exemplary embodiments are preferably LED headlights or, alternatively, laser headlights. In the exemplary embodiments, the LED headlights on the right and left sides of motor vehicle  10  are respectively made up of a low beam module and an additional high beam module. The low beam module uses a plurality of multi-chip LEDs that generate white light in that the originally generated blue light is transformed into white light by a converter material. The light distribution of the low beam module is generated by reflectors and projection lenses. Multichip LEDs are also correspondingly used in conjunction with reflectors in the high beam module. Headlights  14  are designed such that the light width and additionally or alternatively the longitudinal light range of headlights  14  may be adjusted. Thus, headlights  14  are designed such that they provide both the function of the low beam light and the function of the high beam light. Moreover, headlights  14  are designed such that headlights  14  selectively illuminate selectable regions of the low beam light region and/or the high beam light region on the basis of the measurement data transmitted by control device  14 , so that oncoming motor vehicles or preceding motor vehicles or cyclists are not blinded, but the region in front of motor vehicle  10  is nevertheless optimally illuminated. Furthermore, a display  18  is connected to control device  16 . Control device  16  transmits to display  18  measurement data regarding recorded traffic lights. Display  18  is preferably an optical display. Alternatively or additionally, an acoustic display and/or a haptic display are provided. Preferably, the signaling (red, green, yellow, red-yellow) of the recorded traffic lights is displayed on the display and thus informs or also warns the driver of motor vehicle  10 . 
       FIG. 2  shows a block diagram of the first exemplary embodiment, including one or a plurality of cameras  12  and one or a plurality of headlights  14 , in contrast to  FIG. 1 , only those elements being shown that are necessary to explain the synchronization of camera  12  and headlight  14 . As was already explained with regard to  FIG. 1 , headlight  14  illuminates surroundings  28  and camera  12  records at least one part of illuminated surroundings  28 . In  FIG. 2 , a bicycle  30 , a motorized road user  32 , such as a car or a truck or a motorcycle, and a traffic light  34  are drawn in surroundings  28 , by way of example. In the first exemplary embodiment, camera  12  and headlight  14  are synchronized via a synchronization connection  26  such that camera  12  generates the images in dark phases of headlight  14 . Preferably, synchronization connection  26  is implemented as a wire-bound line, the wire-bound line being implemented either as a bus, a CAN bus, for example, or as a permanently assigned and connected line. Alternatively or additionally, synchronization connection  26  is implemented as a radio communication. The temporal synchronization is explained below with the aid of  FIG. 3 . 
       FIG. 3  shows a time diagram of the first exemplary embodiment in a schematic illustration. Time t is plotted on the x axis of the time diagram. The upper partial diagram shows time characteristic  40  of the illumination of the headlights. The headlights emit in periodic succession pulsed light having bright phases  46  and dark phases  48 . In bright phases  46 , the headlights output light into the surroundings, while the headlights do not output any light in dark phases  48 . In bright phases  46 , the headlights are thus switched on and there are switch-on phases of the headlights, while in dark phases  48 , the headlights are switched off and there are thus switch-off phases of the headlights. In the first exemplary embodiment, but also in the additional exemplary embodiments, dark phase  48  is between 1 ms and 5 ms, preferably 4 ms. Preferably, dark phase  48  and bright phase  46  have a ratio of one to ten. Thus, bright phases  46  are ten times longer than dark phases  48 . In one variant of the exemplary embodiments, one to ten dark phases  48  are generated per second by the headlight, preferably ten dark phases  48 , having a duration between 1 ms and 5 ms, preferably 4 ms. Thus, dark phase  48  is selected such that a human being does not consciously perceive dark phases  48 . The switching times of the headlights, in particular of the LED and laser headlights, from a bright phase  46  to a dark phase  48  or the other way around, are less than 0.1 ms in the exemplary embodiments. The switching times are preferably in the nanosecond range. The middle partial diagram illustrates time characteristic  42  of the synchronization signal on the synchronization connection between camera and headlights. In dark phases  48  the headlight generates a short synchronization pulse  50  that is transmitted from the headlight to the camera. As illustrated in the lower partial diagram that illustrates time characteristic  44  of the image capturing of the camera, the camera, triggered by synchronization pulse  50 , performs an image capture  50  within dark phase  48  of the headlight illumination. In this variant of the first exemplary embodiment, the camera is thus designed such that the camera adjusts recording times of the images such that the camera generates the images in the dark phases  48  of the headlight. Thus, time characteristic  40  of the headlight illumination is predefined and time characteristic  44  of the image of the camera is variable and is synchronized with time characteristic  40  of the headlight illumination. Conversely, in one variant of the first exemplary embodiment, the headlight is triggered by a synchronization pulse  50  of the camera, in order to output a light pulse only if image capture  52  of the camera is complete. In this variant, synchronization pulse  50  is generated by the camera and the synchronization pulse is transmitted from the camera to the headlight. Thus, in this variant of the first exemplary embodiment, the headlight is designed such that the headlight adjusts the light pulses such that the camera generates images in the dark phases  48  of the headlight. Time characteristic  44  of the image capture of the camera is predefined and time characteristic  40  of the headlight illumination is variable and is synchronized with time characteristic  44  of the image capture. 
       FIG. 4  shows a block diagram of the second exemplary embodiment, including one or a plurality of cameras  12  and one or a plurality of headlights  14 , in contrast to  FIG. 1 , only those elements being shown that are necessary to explain the synchronization of camera  12  and headlights  14 . As already explained with regard to  FIG. 1 , headlight  14  illuminates surroundings  28  and camera  12  records at least one part of illuminated surroundings  28 . A bicycle  30 , a motorized road user  32 , such as a car or a truck or a motorcycle, and a traffic light  34  are drawn in surroundings  28  in  FIG. 4 , by way of example. In the second exemplary embodiment, camera  12  and headlight  14  are not synchronized via a synchronization connection. Rather, camera  12  is designed such that camera  12  adjusts the recording times of the images as a function of the illumination of the surroundings of the motor vehicle by headlights  14  that is recorded in the images such that camera  12  generates the images in the dark phases of headlight  14 . To this end, camera  12  captures a plurality of successive images, in that camera  12  records images of surroundings  28  of the motor vehicle. Depending on the offset between the time characteristic of the headlight illumination and the time characteristic of the image capturing, surroundings  28  are illuminated, intermittently illuminated, or not illuminated by headlights  14  during the capturing of an image. Subsequently, camera  12  determines for the individually recorded images whether headlight  14  was switched on, switched on for part of the time, or switched off during the image capturing. Camera  12  ascertains from this the time offset between the time characteristic of the headlight illumination and the time characteristic of the image capturing. On the basis of the time offset, camera  12  adjusts the recording times of the images such that camera  12  generates the images in the dark phases of headlight  14 . 
       FIG. 5  shows a block diagram of the third exemplary embodiment, including one or a plurality of cameras  12  and one or a plurality of headlights  14 , and at least one light sensor  36 , in contrast to  FIG. 1 , only those elements being shown that are necessary to explain the synchronization of camera  12  and headlights  14 . As was already explained with regard to  FIG. 1 , headlight  14  illuminates surroundings  28  and camera  12  records at least one part of illuminated surroundings  28 . In  FIG. 4 , a bicycle  30 , a motorized road user  32 , such as a car or a truck or a motorcycle, and a traffic light  34  are drawn in surroundings  28 , by way of example. In the third exemplary embodiment, camera  12  and headlight  14  are not synchronized via a synchronization connection. Instead, light sensor  36  detects the brightness in surroundings  28 , in particular the light pulses of headlights  14  in surroundings  28 . Light sensor  36  transmits the recorded brightness values to camera  12  via a line connection  38 . Camera  12  is designed such that camera  12  adjusts the recording times of the images as a function of the light pulses of headlight  14  recorded by light sensor  36  such that camera  12  generates the images in the dark phases of headlight  14 . To this end, camera  12  ascertains from the recorded brightness values of light sensor  36  the time characteristic of the headlight illumination. On this basis, camera  12  adjusts the recording times of the images such that camera  12  generates the images in the dark phases of headlight  14 . 
       FIG. 6  shows a flow chart of the method. On the headlight side, dark phases  48  and bright phases  46  alternate in a periodically repeating manner. Accordingly, image captures  52  and periods without image captures  54  alternate in a periodically repeating manner as well. The camera and the headlights are synchronized with each other by a synchronization  58  such that the camera generates image captures  52  in dark phases  48  of the headlight. The images recorded in dark phases  48  of the headlight are optionally supplied to an image evaluation  56 .