WO2011153989A2 - Stereo camera system - Google Patents

Abstract

The invention relates to a stereo camera system (10) designed for use in motor vehicles behind an inclined windscreen (5; 12), wherein at least one of the at least two camera modules (14, 16) of the system has an additional, partially arranged optical element (8; 26) supplied at times or acting as a beam splitter and can thereby be used as an at least bifocal optical camera module having at least two different depth of field ranges on an image sensor (4), and the image sensor thereby comprises at least two partial regions having different optical object distances, wherein one optical object distance is provided for detecting an object in the near range which serves for aligning the stereo camera arrangement.

Description

 STEREO CAMERA SYSTEM

The invention relates to a stereo camera system according to claim 1.

To determine the distance of a vehicle to an object, a so-called stereo camera can be used. A stereo camera is understood here to mean an arrangement of two cameras, which are mounted at a predetermined distance from each other, in particular on the windshield of the vehicle. For determining the distance of objects, the images captured by the two cameras, in particular digital cameras, are compared and pixel differences between identical object edges are evaluated in order to determine the corresponding object distance therefrom. Irrespective of an object plane on which the cameras are focused, there is a depth of field range that extends in current, for object distance detection lenses used in cameras, for example, from about 2 m to infinity. This allows object distance detection approximately from the vehicle leading edge.

For an accurate object distance detection, it is necessary that the two cameras are aligned as accurately as possible to each other with a tolerance range to be defined, ie the predetermined position of the optical axes of the cameras is maintained as closely as possible to each other. For an adjustment of the cameras, for example, an image arranged in front of the vehicle with the stereo camera with defined objects can be used. Such an image is used for example when mounting the stereo camera in the vehicle. However, problems with the object distance detection occur, in particular, when the position of the optical axes of the cameras change, for example during operation with one another. As a result, in the object distance detection more or less large inaccuracies occur because then the determined with the stereo camera Distance to an object usually no longer matches the real distance.

The error due to a deviation depends on the distance of the object from the vehicle. Above all, three-dimensional deviations of the optical axes of the cameras are often due to the thermal-mechanical properties of the curved ones

Attributed to windshields of vehicles. In order to be able to compensate for the resulting errors in the distance determination, a deviation or positional difference of the optical axis of a camera from or to the predetermined position must be detected. Compensation can be done algorithmically, for example, by suitable software or mechanically by changing the position of the cameras. If the two cameras have been independently fixed to the windshield and adjusted in the assembly process, a positional difference of the optical axes during operation of the stereo camera can only be detected by defined objects in the street scene. Finding such defined objects worldwide and always is a great, if not impossible, challenge. A possible object for detecting a position difference could also be an edge on the own vehicle, which is always visible to the stereo camera, for example the front edge of the vehicle. However, this object depends on the vehicle manufacturer and type. Object of the present invention is therefore to provide a stereo camera system for vehicle applications, which is in principle suitable for detecting a deviation or positional difference of the optical axes of the cameras of the system from or to a predetermined position. This object is achieved by a stereo camera system for vehicle applications with the features of claim 1. Further embodiments of the invention will become apparent from the dependent claims. A stereo camera system is understood here to mean a stereo camera and corresponding software for controlling the stereo camera and image evaluation. The software is typically stored in a non-volatile memory of electronics of the stereo camera system and is executed by a processor of the electronics, which is configured by the software, especially for camera control and image analysis. An essential idea of the invention is to design at least one camera module of a stereo camera system in such a way that it can be used as an at least bifocal optical camera module with at least two different depths of field on an image sensor, wherein a depth of field range covers the vicinity of the stereo camera system, in particular the area of the windscreen , As a result, the system can sharply image at least a portion of the windshield and detect objects in this subarea which are located on the windshield with a focus that is suitable for further evaluation, in particular for automatic alignment of the system. For example, special, intended for alignment pattern (target pattern) can be displayed on the windshield. The system can evaluate the target patterns detected with sufficient sharpness, in particular by comparison with stored reference patterns, to detect a deviation or positional difference of the optical axes of the cameras of the system from or to a predetermined position. Depending on a detected deviation or positional difference, an automatic alignment of the camera modules can be carried out in embodiments of the invention.

An embodiment of the invention now relates to a stereo camera system adapted for use in motor vehicles behind a sloped windshield, wherein

at least one of the at least two camera modules of the system has an additional partially arranged, temporarily supplied or acting as a beam splitter optical element and thereby as at least bifocal optical camera module with at least two different ones

Depth of field can be used on an image sensor and the image sensor thereby includes at least two partial areas with different optical object widths, wherein an optical object distance for detecting an object in the vicinity, which is used to align the

Stereocamera arrangement serves, is provided.

The at least two image sensor subregions may have additional

Have filter elements to further detect different intensity distributions of the wavelength spectrum.

Components acting as filter elements can be integrated before, in or after the additional optical element and / or in optical

Be integrated into areas that belong to the optical field of view, the sectional area of the additional optical element does not or only partially cuts.

The additional optical element may be formed in at least one of the optical components of the at least one camera module as a partial partial lens in front of a lens of the camera module, as a partial optical element in particular as a plane-parallel plate behind the lens or as an optical beam splitter or mirror element and thus a bifocal image on at least allow two sections of the image sensor. The stereo camera system according to the invention can also be designed to achieve the at least two different focal depth regions simultaneously or separately by feeding the additional optical element, wherein the feeding of the additional optical element into the entire field of view of the at least two camera modules via a chopper wheel with lenses of one or more Refractive power and thickness in front of the lens, one or more plane-parallel elements that differ by their thickness or their refractive index behind the lens of a camera module or by filling a non-fixed, the desired wavelength range well-transmitting and differs in the refractive index of air medium behind the lens of a camera module takes place. The at least two depth-of-field regions of the individual camera modules of the stereo camera system according to the invention can be identical or differ in their depth-of-sharpness limits due to the at least one partially arranged additional optical element. The at least two different depth-of-field regions of the individual camera modules of the stereo camera system according to the invention can have one subarea of the image sensor for close-range focusing with a rear depth of field of about 1 meter and the other subarea of the image sensor for long-range focusing with a front

Use depth of field greater than approx. 1 meter.

Furthermore, the stereo camera system according to the invention can be formed, the at least two individual camera modules simultaneously or separately in time on the portion of the image sensor whose depth of field limits Nahbereichsfokussierung correspond to the detection of fog on the disk inside, rain, dirt or other the view

obstructing events to be used, wherein the depth of field is selected by targeted design of the additional optical components so that object edges of an edge detection, different objects by defined classifiers or deviations caused in the

Frequency spectrum can be detected by a relatively fast FFT (Fast Fourier Transformation) in a subsequent image processing stage by the system. The stereo camera system according to the invention can also be designed to target the at least two individual camera modules simultaneously or separately in time on the subregion of the image sensor whose depth of field boundaries correspond to near field focusing arranged target marks on the disk inside, within the

Windscreen or on a special support element in front of the

Disk inside, the system being further formed from detected deviations of the target mark shape, target mark size,

Picture sharpness and especially the picture position on one

 Shift the individual camera modules of the stereo camera assembly in all directions with respect to the target to close, with the aid of a stored in a non-volatile memory of the camera electronics sample pattern (master) deviations are detected.

The stereo camera system according to the invention can be further developed, a deviation of the target mark positions and a thus occurred

Changing the viewing directions or the distance of the at least two camera modules from each other as a compensation parameter for a

executed software of the various camera functions and / or for a compensation to be made by actuators mechanically on the stereo camera assembly.

The stereo camera system according to the invention can also be characterized in that a combined detection of objects on the

 Windshield as explained above and of targets for detecting deviations in the viewing direction is performed as explained above.

The stereo camera system according to the invention can also be designed to detect recognized objects in their type and their quantitative extent in a designated windshield field of view and issue depending on targeted messages to other control devices in motor vehicles whose content is activation of the windscreen wiper and or windscreen cleaning system or activation Ventilation and or

Slices heating causes.

In the stereo camera system according to the invention, a targeted

Lighting and / or a partially arranged heat source for support the detection of objects on the windshield may be provided, wherein a heating source may be provided to effect in particular a localized evaporation of fog on the windshield inside or a thawing of ice on the windshield outer side. This local difference of these special cases can be the

Image processing as a recognition feature e.g. as an edge for one

Edge detection by edge filtering e.g. with a simple one

So serve beloperator. Especially streaks on the

Windscreen outer side can be determined by a higher number of edges in the vertical direction in comparison to the horizontal direction and serve to assess the cleaning performance of the windscreen wiper system and to initiate appropriate measures.

In the mounted state of the stereo camera system according to the invention, the individual camera modules can not be in direct contact with the windshield, but be positioned at least one vehicle point relatively loose and stress-free.

The different depth of field depths of the individual camera modules of the stereo camera system according to the invention can be used for supporting distance detection of objects in the camera field of view.

Determined parameters regarding visual disabilities and extreme

Viewing direction changes can be made by the invention

Stereo camera system to determine the limit of a possible

Function execution can be used.

At least one of the camera modules of the invention

Stereo camera systems may be directed to an inclined mirror or beam splitter, which is used as a field mirror for windshield imaging, which mirror in particular as

Ambient light sensor, target carrier and or as Symmetrieebene may be provided to distinguish between near and far objects.

The inclined mirror element can in the inventive

Stereo camera system, a part of a lighting element for the field of view within the depth of field of Nahbereichsfokussierung

represent.

In the stereo camera system according to the invention, an additional

Illumination with a spectral optimized to the optical structure

Property for at least the depth of field, which is limited by the Nahbereichsfokussierung be provided, wherein the

Lighting can be done either by reflection on the disk inside, by total reflection on the inner surface of the disk outside or by a fluoroscopy of the disc.

The stereo camera system according to the invention can also be designed to use at least two different optical components to enable a bifocal imaging in combination or in cyclic alternation.

The stereo camera system according to the invention can also be designed and in particular be able to do so by the bifocal property

to recognize passing windshield wipers and in a given

To check the loop for correct movement, and in particular other camera functions tell the event of the passing windshield wiper.

The stereo camera system according to the invention can also be designed to evaluate the near focus on the windshield also for reading in applied codes that contain certain parameters of the windshield in the windshield black pressure. In the stereo camera system according to the invention, a coupling element of the individual camera modules by the detection and compensation of the changes in terms of camera distance and line of sight from a very cheap material, even with a large

 Thermal expansion coefficients, e.g. many plastics in a low cost production process e.g. Plastic injection molding are produced. The stereo camera system according to the invention can also be designed to use a target mark recognition as a sensor for compensation measures, which may be necessary in the case of a thermal change in the distances and refractive power of the optical components. The image sensor portions used to sharply image the front depth of field can also be used for others

Camera functions of the stereo camera system according to the invention can be used. This can e.g. by the extended imaging of spots of light from the optical far-away area, as very distant spots of light (e.g., other vehicle's headlights) that would otherwise be resolved at only one pixel can now be more reliably detected by extending the pixel over several pixels.

Finally, in the stereo camera system according to the invention a

Farbfilterarray be provided in front of the sensitive semiconductor surface of the image sensor to the object detection in the vicinity, in particular the

Windshield, and to improve the object distinction.

A further embodiment of the invention relates to a windshield for a vehicle adapted for use with a stereo camera system according to the invention and as previously described, and

Having targets for determining the relative position and the viewing direction of the individual Kameramodu! E of the stereo camera system. The targets for determining the relative position and the viewing direction of the individual camera modules can be determined by in or on the

Windscreen integrated, non-transparent heating wires or

Antenna arrangements are formed, which are located in the camera field of view.

Further advantages and possible applications of the present invention will become apparent from the following description in conjunction with the / in the drawing (s) illustrated embodiment (s). In the description, in the claims, in the abstract and in the drawing (s), the terms and associated reference numerals used in the list of reference numerals recited below are used. The drawing (s) show / show in

Fig. 1 is a windshield mounted thereon

 Stereo camera system according to the invention in a view from behind the windshield;

Fig. 2 is a windshield adapted for use with the stereo camera system of the present invention;

Fig. 3 is an example of a typical target pattern on the

 Windshield;

 FIG. 4 shows the windshield shown in FIG. 1 with the stereo camera system mounted thereon in a view from in front of the windshield; FIG.

 Fig. 5 is a tilted stereo camera system and the effect of

 Tilting on the camera images; and

 Fig. 6 shows an embodiment of a camera module

 the stereo camera system according to the invention;

 Fig. 7 is a side view of another schematically illustrated

Embodiment of an arranged behind a windshield according to the invention stereo camera system and a lighting docking device for the stereo camera system for improving a rain sensor function of the system. In the following, identical and / or functionally identical elements can be provided with the same reference numerals. The absolute values and dimensions given below are only exemplary values and do not restrict the invention to such dimensions. The stereo camera system 10 according to the invention shown in FIG. 1 is intended for mounting on the windshield 12 of a vehicle and for use in a driver assistance system for traffic detection , The system is designed as a mechanically coupled unit of two camera modules 14 and 16. The coupling of the camera modules 14 and 16 can be done in many ways. In the embodiment shown in FIG. 1, the stereo camera system 10 is in the range of the rearview mirror on the

Windshield 12 attached.

A camera module 14 or 16 of the system 10 comprises an image sensor, for example a CMOS or CCD camera chip, and an optical system, in particular a lens. The system 10 also includes electronics having a memory with software for evaluating the

Image sensors of the camera modules 14 and 16 have generated digital image data and for controlling the system 10 and a processor for executing the software.

The thermal expansion coefficients of the materials used in the stereoscopic camera system 10 according to the invention no longer play a dominant role with respect to errors in the object distance detection, since the thermal expansion by a software included in particular by the mentioned and in the stereo camera system according to the invention

implemented measuring method for detecting a deviation or Position difference of the optical axes of the cameras 14 and 16 of the system 10 can be detected relatively reliably from or to a predetermined position.

The distance between the individual camera modules 14 and 16 to each other must be known in order to reliably determine distances to objects with the stereo camera system 10 according to the invention. This distance determination can be done with a measuring method. Also, the direction of view of the cameras 14 and 16 must not change much to the reliability of the

Systems 10 not to lose.

The coupled camera system 10 may be attached to a horizontally centered slice centered area, e.g. with a windshield adhesive. In Fig. 1, the stereo camera system 10 has central fastening means 18, with which by means of a

Windshield adhesive the system 10 can be mounted on the windshield 12. Also, attachment to a mechanically stable vehicle point above the windshield is possible, for example on the vehicle roof. The two camera lenses of the stereo cameras or camera modules 14 and 16 are by their main function of traffic detection on their

Hyperfocal distance, e.g. at about 4 meters, focused. As a result, the area max. Depth of field (about 2 meters to infinity) exploited. In order to be able to detect a deviation or positional difference of the optical axes of the cameras or camera modules of the system from or to a predefined position with the measuring method, the front depth of field boundary must extend to the windscreen.

In order to be able to solve the resulting depth of field target conflict, an additional optical component is provided in at least one of the cameras. This additional optical component extends only over a partial area in the camera field of view. This conflict of objectives with the range of usable depth of field has the following cause: Is caused by focus adjustment If the front depth of field boundary is brought further to the objective main plane, the rear depth of field boundary also moves in a direction that is disproportionate to the objective main plane. As a result, more distant objects are no longer sharply focused.

The optical component can be implemented, for example, by a partial optical element in the image width, a graduated optical element or even a partial lens in front of the objective. The following describes a multifocal optic with the partial lens. The same principle can also be made possible with a partial optical element. The partial lens alters the focusing of the camera system, depending on the lens shape and refractive index, either to a more distant object plane than the hyperfocal distance, e.g. with a concave lens shape (diverging lens), or even on a closer object plane, e.g. in a convex shape

(Condensing lens) of the partial lens. Fig. 6 shows the camera module 14 in one

Front view of the lens 24 of the module 14. In front of the lens 24, the partial lens 26 is mounted.

The optical component can either be connected to the cameras or to the windshield. To the shape (e.g., lens radius in a spherical lens) and refractive index (depending on the choice of material or surface coating) and the positioning of the lens, the requirement to satisfy the collimator condition exists

Windscreen virtually in the focused hyperfocal distance of the

Imagine lens.

This system allows a sharp image of the windshield on a portion of the image sensor, which is determined by the size of the partial lens area in the field of view of the camera. At the same time, a picture of the street scene with the usual is on the remaining area of the image sensor

Depth of field covered. As can be seen in FIG. 2, a suitable imprint, referred to below as the target pattern 20, is mounted on the windshield 10. The target pattern 20 is chosen so that the best possible position changes between the camera system and windshield can be detected. A

Possibility for a target pattern would e.g. a cross 12, as shown in Fig. 3, which is formed by a printed scale in the horizontal direction and a scale in the vertical direction. The resist for the target pattern should have a refractive index approximately equal to that of the disc material. Alternatively, a glued foil in

Viewing range of the partial lens conceivable containing the target pattern.

On the windshield 12 shown in Fig. 2, a print 22 can be seen, the recesses for the camera lenses of

Stereo camera system 10 has. In the recesses, a target pattern 20 in the form of a cross is provided in each case.

In Fig. 4, the windshield 2 is shown with mounted stereo camera system 10 in a front view, so a view from outside the

Vehicle on the disc 12. The lenses of the camera modules 14 and 16 are arranged behind the recesses. In this case, the camera modules are aligned such that the respective partial lens in front of the lens of the module images the area with the target pattern on the windshield sharply in the image plane of the image sensor. The two mechanically coupled cameras of the stereo camera system with an assumed distance of 20 cm to each other see in their field of vision in one area the traffic situation and in another clearly smaller area to be selected the target pattern through the partial lens. Both pictures are sharply focused. A tilt of the partial lens after the

Scheimpflug condition enables a sharp image of the inclined

Windscreen cutout on the image sensor. The thermal

Coefficient of expansion of a windshield is significantly lower than that of metals and far below that of plastics which are considered mechanical Coupling of the cameras come into question, ie the target pattern is relatively stable in its position or the extent of thermal expansion is approximately known from the data of the windshield. Now move the stereo cameras by thermal expansion, vibration, shock or Matertalermüdung plastic as coupling element from her

 Starting position, prominent points of the target pattern are mapped to other pixel positions. These distinctive points are on the one hand the cross center and the distance of the scale lines from each other. A curvature of the disc can be recognized by the fact that the cross changes in its actual form rather than just changing the position. From this change, the radius of curvature of the disc in

Camera field of view are calculated or the change of

Camera viewing direction in a three-dimensional change of

Camera mounting in relation to the disc and each one

Camera. This information is important in determining when the cameras are looking in different directions. On the one hand this is possible by the lens effect of the curved windshield, on the other hand by a change in the camera viewing direction through the

Mounting. This change can be caused by a known deviation from the setpoint in a software of the stereo camera system or by

mechanical change in position of the optical axis can be compensated. A simple mechanical compensation represents a bow as an additional coupling element, which defines the squinting camera defined at a suitable roll angle.

Fig. 5 shows the effects of a tilted stereo camera system 10 mounted on the windshield 12. Beneath the system 10 are shown the images produced by the forming sensors of the respective camera modules. It can be clearly seen that the portion of the image sensor assigned to the near zone is the one shown on the windshield 12

attached target pattern is tilted, ie, the target pattern is shown on other than the intended pixels in the image generated by the image sensor. Through a software-technical evaluation of the images of the two Due to the "distorted" representation of the target pattern in the images, the type of tilting can be determined by means of a camera software module, for example, a suitable software solution would be an adapted image equalization.

The disk deflection or a position determination of the cameras to each other can also be done with optical measurement methods. By

Projection of a light source, e.g. with IR LEDs or laser projected through a suitable lens e.g. a cylindrical lens, may e.g. a line at a defined angle (cylindrical lens rotation) are projected onto the windshield. The light source is firmly connected to the camera system and is located farther away from the center of the stereo camera system than the corresponding camera. The projection can be defined in

At times occur, depending on temperature changes or fixed intervals, e.g. Engine start can be selected. The projected line, which receives on the image sensor due to the curved disk deviates from the line shape, undergoes a significant change in her with an additional disc curvature

Original shape. This change is made by image processing of

Stereo camera system recorded.

A second projection system on the other side, ie closer from

Center of the stereo camera system attached as the associated

Camera, allows determination of the position change of the camera by moving the intersection of the 2 projected lines.

Another possibility is given by above written line projection, with the difference that the cylindrical lens is rotatably mounted. The projection of the light source on the windshield in this case takes place at certain times and certain Drehwinkefn the cylindrical lens.

Alternatively, a projection of a light spot would be conceivable, which always stands out from the ambient lighting and on by its sanctity the image sensor occupies a certain pixel area in its extent. A shift of the camera system would be recognizable by a wander of the illuminated pixel area, and an angle change by a distortion of the light spot on the image sensor. Also, this variant of the detection of adjustment deviations requires a multifocal optics such as is created by the above-described partial lens.

The stereo camera system according to the invention has the following advantages:

Lower tolerance requirements for the coupling of the camera modules whose price advantages are higher than the costs for a multifocal optics, regardless of the possible additional functions due to the multifocal optics such as

Windscreen type recognition, rain sensor or wiper quality recognition of the windscreen wiper system. The stereo camera system according to the invention allows additional functions, which are explained in the following overview.

Through the enabled Nahfokussierung can different

Windscreens are detected. For example, a

Identification number, affixed or printed, can be used for individual camera settings by appropriate image processing.

The Nahfokussierung also allows use as a dirt and rain sensor system also taking advantage of the target pattern for determining object size and possibly object type by a comparison method.

This object-recognizing type of rain and dirt detection enables in the future e.g. a recognition and distinction of drop size, snow and especially insects on the windshield, which could trigger a special wiping program by a targeted detection.

Furthermore, a test for the function of the wiper system is made possible by the stereo camera system according to the invention: water or Not; Judgment on the wipe result with respect to streaks, and

Residues of e.g. Insects, dust etc. after a windscreen cleaning.

Fig. 7 shows in side views schematically another embodiment of the stereo camera system according to the invention.

In Fig. 7 is a side view of an inventive top

Stereo camera system shown with an additional rain sensor function. In front of the sensitive surface 4 of the image sensor of

Camera module of the system is a partial optical element 8 arranged for bifocal imaging on the sensitive surface of the image sensor. Before the partial optical element 8 is the lens 1 of the camera module with the main plane 2. The image sensor is further provided with a cover glass 3. The sensitivity of the rain sensor function can be limited by interference from remote light sources. A modulated approximately monochromatic illumination and the color filters of the Bayer pattern can be used for signal filtering. For a better differentiation of object edges and interfering light influences, a mirror (element) S1 is proposed, which also has a

Can be combined lighting element, as shown below in Fig. 7. The mirror S1 has an opposite pitch angle to the camera field of view as the inclined windshield 5. The mirror edge is located in the middle of the near-field image and thus represents a plane of symmetry. Regentropes 6 on the

Windshield 5 are on the image sensor 4 at this

 Symmetry plane once normal and once mirrored shown.

Interference factors from the far-end range, on the other hand, are only displayed on one of the two levels. This entire arrangement is arranged behind the curved windshield 5. The ray path of the

Close-range imaging S2 via a mirror element S1, the beam path of the near-field imaging S3 without mirror element and the beam path long-range imaging S4 are also shown. Especially in combination with a lighting coupling element, the mirror element S1 is an interesting possibility for distinguishing between near and far range. The lighting coupling can be done via a light guide with an integrated concave mirror profile in a cylindrical design. The image analysis uses symmetry as a parameter for separating objects on the windshield and disturbing factors in the surroundings of a captured image. In Fig. 7, such an arrangement for coupling a lighting is shown schematically below. Behind the windshield a is a

arranged on both sides mirror element d (corresponding to S1), the light emitted by a light emitter with optics (cylindrical lens) c light reflected on a concave free-reflecting mirror b. From concave free-reflecting mirror b, in turn, the light of the light emitter b is coupled into the windshield a, from which it is guided in the direction of the stereo camera system, which is above the shown. Arrangement is arranged, as shown in Fig. 7 above.

reference numeral

1 lens

 2 main level lens

 3 cover glass image sensor

 4 image sensor (sensitive area)

 5 windshield

 6 object on the windshield (here raindrops)

7 Lens hood

 8 partial optical element for bifocal imaging a Windscreen

b concave mirror (cylindric)

c light emitter with optics (to cylindrical lens)

d two-sided mirror element

 S1 mirror element

 S2 beam path Close-up imaging via mirror element

S3 beam path Nahbereichsabbildung

 S4 beam path long range imaging

 10 stereo camera system

 12 windshield

 14, 16 camera module

 18 fasteners

 20 target

 22 windshield print

 24 camera lens

 26 partial lens

Claims

 claims A stereo camera system (10), which is designed for use in motor vehicles behind an inclined windshield (5; 12), wherein at least one of the at least two camera modules (14, 16) of the system has an additional partially arranged, temporarily supplied or acting as a beam splitter optical Element (8; 26) and thereby as at least bifocal optical camera module with at least two different depth of field on a Image sensor (4) can be used and the image sensor thereby at least two subregions with different optical  Object lengths includes, with an optical object distance to  Detection of an object in the vicinity (S2, S3), which is used to align the stereo camera arrangement, is provided. 2. Stereo camera system according to claim  characterized in that  the at least two image sensor subregions have additional filter elements to further different intensity distributions of the Capture wavelength spectrum. 3. Stereo camera system according to one of the preceding claims, characterized in that  the additional optical element in at least one of the optical Components of the at least one camera module as a partial partial lens (26) in front of a lens (24) of the camera module (14), as a partial optical element (8), in particular as a plane-parallel plate behind the lens (1) or as an optical beam splitter or Mirror element is formed and thus allows a bifocal image on at least two subregions of the image sensor. 4. Stereo camera system according to one of the preceding claims, characterized in that  it is formed, the at least two different ones  To achieve depth of field parallel or temporally separated by a supply of the additional optical element (8; 26), wherein the supply of the additional optical element in the entire field of view of the at least two camera modules (14, 16) via a chopper wheel with lenses of a different refractive power and Thickness in front of the lens, one or more plane-parallel elements, which differ by their thickness or refractive index behind the lens of a camera module or by filling a non-solid, the desired wavelength range well-transmitting and refractive index of air deviating medium behind the lens of a Camera module is done. 5. Stereo camera system according to one of the preceding claims, characterized in that  it is formed, the at least two individual camera modules (14, 16) simultaneously or separately in time on the portion of the  Image sensor (4) whose depth of field limits a  Nahbereichsfokussierung correspond to detect fog on the inside of the window, rain, dirt or other obstructive events to use the focus depths are selected by targeted design of the additional optical components so that object edges of an edge detection, different objects by defined classifiers or by caused deviations in the frequency spectrum by an FFT in a subsequent image processing stage can be detected by the system relatively safe. 6. Stereo camera system according to one of the preceding claims, characterized in that it is formed, the at least two individual camera modules (14, 16) simultaneously or temporally separated on the portion of the  Image sensor (4) whose depth of field limits a  Corresponding to close range focusing, to use for the detection of targeted targets on the disk inside, within the windshield or on a special carrier element in front of the disk inside, wherein the system is further formed from detected deviations of the target shape,  Target size, image sharpness and especially the  Picture position on a shift of the individual  Close camera modules of the stereo camera assembly in all directions based on the target, using a stored in a non-volatile memory of the camera electronics  Pattern image deviations are detected. 7. Stereo camera system according to claim 6,  characterized in that  it is formed, a deviation of the target mark positions and thus a change in the viewing directions or the distance of the at least two camera modules from each other as  Compensation parameters for running software of the various camera functions and / or provide for compensation, which is done by actuators mechanically to the stereo camera assembly. 8. Stereo camera system according to one of the preceding claims, characterized in that  it is trained, recognized objects in their nature and their quantitative extent in a designated  Determine windshields visual field and issue depending on targeted messages to other control devices in motor vehicles, the content of which activates the windscreen wiper and / or Windscreen cleaning system or activation of ventilation and or heated pane causes. 9. Stereo camera system according to claim 8,  characterized in that  a targeted lighting and / or a partially arranged  Heat source is provided to assist the detection of objects on the windshield, wherein the heating source is intended to effect in particular a localized evaporation of fog on the windshield inside or a thawing of ice on the windshield outer side. The stereo camera system according to one of the preceding claims, characterized in that  at least one of the camera modules is directed to an inclined mirror or beam splitter, which serves as a field mirror for  Windshield image is used, this mirror is particularly intended for use as an ambient light sensor, carrier element for the target and or as a plane of symmetry to distinguish between near and far objects. 11. Stereo camera system according to claim 10,  characterized in that  the inclined mirror element forms part of a lighting element for the field of view within the depth of field of the field of view  Represents near-field focusing. 12. Stereo camera system according to one of the preceding claims, characterized in that  an additional illumination with a spectral feature optimized for the optical structure for at least the Depth of field, which is limited by the Nahbereichsfokussierung, is provided, wherein the illumination either by reflection on the disk inside, by total reflection at the Inner surface of the disk outside or by a  Transillumination of the disc takes place. 13. Stereo camera system according to one of the preceding claims, characterized in that  it is designed to have at least two different optical  Components for facilitating bifocal imaging in  Combination or use in cyclic change. 14. Stereo camera system according to one of the preceding claims, characterized in that  it is further adapted to detect also passing windshield wipers and to check in a given control loop for a correct course of motion, and in particular others  Camera functions to communicate the event of the passing windshield wiper. 15. Stereo camera system according to one of the preceding claims, characterized in that  it is further adapted to focus the near focus on the  Windscreen for reading in applied codes containing certain parameters of the windscreen, in  Evaluate windshield black print. 16. Stereo camera system according to one of the preceding claims, characterized in that  a color filter array is provided in front of the sensitive semiconductor surface of the image sensor in order to improve the object recognition in the vicinity, in particular the windshield, and the object discrimination. A windshield (12) for a vehicle adapted for use with a stereo camera system (10) as claimed in any one of the preceding claims, and target markers (20) for determining the Relative position and the viewing direction of the individual camera modules (14, 16) of the stereo camera system has. 18. Windshield according to claim 17,  characterized in that  the target marks (20) for determining the relative position and the viewing direction of the individual camera modules are formed by non-transparent heating wires or antenna arrangements which are integrated in or on the windscreen and which are located in the camera field of view.