Abstract:
A system and method to support the driving of a motor vehicle comprising in particular a system capable of capturing images, wherein the system for capturing images comprises a stereoscopic image capturing system having at least a first camera and a second camera, with the first camera presenting a field of vision) greater than the field of vision of the second camera, and with the stereoscopic system thereby conferring a degree of multifunctionality to the device supporting the driving of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to French Application No. 0706533 filed Sep. 17, 2007, which application is incorporated herein by reference and made a part hereof. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Generally speaking, the sphere of application of the present invention is that of advanced driving support systems, and more particularly, of that of the detection and identification of obstacles, in particular other vehicles either crossing the vehicle&#39;s path or travelling in front of it. 
         [0004]    2. Description of the Related Art 
         [0005]    The detection and identification of obstacles is one of the most researched and key spheres in the field of research into advanced driving support systems introduced during the last fifteen years, in particular by manufacturers of motor vehicles and motor vehicle equipment. Numerous solutions have been envisaged and put into practice for the detection and identification of obstacles from within a motor vehicle, all of which are essentially based on radar, lidar and ultrasound technologies for close and low speed obstacles and also on processes involving the use of devices comprising cameras. 
         [0006]    Radar and lidar sensors are typically used for long distance detection such as the ACC system (Autonomous Cruise Control), which, for example, can directly provide information on the position and in some cases on the 3D speed of surrounding objects. This information allows the different objects to be assessed and to relate useful information to them such as their positions and even their speeds, together with their current coordinates in three dimensions, in relation to the vehicle fitted with the sensor device and also in relation to a fixed reference point if the position of the vehicle is properly established with regard to this reference point. 
         [0007]    But sensors of this type do not offer a wide range of vision and their angular positioning is never very precise. Moreover, they do not provide any information on the highway environment, such as the position of the vehicle within its traffic lane, the number of traffic lanes, the trajectory of the route, the classification of the obstacles, the possibility of recognizing infrastructural elements such as roadside panels, etc. Moreover, long range, narrow fields are unable to detect at a sufficiently early stage so-called &lt;&lt;cut-in &gt;&gt; scenarios, where a vehicle arriving from a different traffic lane to that of the vehicle fitted with the sensor threatens to &lt;&lt;cut in &gt;&gt; and the driver has to be responsible for controlling the situation. 
         [0008]    Methods for detecting obstacles by using on-board cameras can resolve such problems, which are otherwise beyond the capabilities of radar or lidar systems. The information provided by a camera comes in the form of a bi-dimensional image (2D), produced in general by the projection of a typical perspective of the real three-dimensional (3D) world onto the image plane. 
         [0009]    The methods that can be used for the detection of obstacles by the use of a camera can be divided into three main categories: the recognition of a two-dimensional shape, the recovery of three-dimensional information by interpreting the movement in monovision—in other words, from the movement captured by a single camera—and triangulation in stereovision. This last category is the most satisfactory in terms of the quality of the results obtained, as it provides relatively precise information on the distance from an obstacle. 
         [0010]    Furthermore, the different types of sensors in the form of cameras used up to now in motor vehicles to carry out driving support functions can be broken down into two main groups, both with advantages and disadvantages: 
         [0011]    grey levels cameras also known as black and white cameras; 
         [0012]    color cameras. 
         [0013]    A color camera, can, in particular, aid the identification and recognition of rear lights. In this way, the extent of the detection is increased as a result of the information provided in color. Conventionally, this type of camera is a grey levels camera, but a filter, known as a Bayer filter, is arranged in front of it, which enables the red, green and blue (RGB) components of each captured image to be calculated. However, these filters have the effect of reducing the spatial resolution of the sensor device used with the result that the calculation of the distance—often effected by measuring the distance between two projectors and a detected vehicle—obtained by the use of a single color sensor is less precise than a calculation carried out by a single grey levels sensor. In certain applications for driving support, in particular the BeamAtic™ function, this information is of crucial importance because the operation of switching the headlamp beam depends directly on the distance at which oncoming or followed vehicles are detected. However, above a certain distance, a grey levels sensor cannot enable the tail lamps of one vehicle to be distinguished from those of another and as it does not receive any color information it cannot enable tail lamps to be detected at all. For the grey levels sensors currently in use, this maximum distance is 450 meters. The choice between a color sensor and a grey level sensor is therefore a compromise between the scope of the detection and the accuracy of the assessment distance. 
         [0014]    The use of stereoscopic vision systems, regardless of whether the two cameras used are color cameras or grey levels cameras, enables the distance from detected objects to be accurately calculated so that the BeamAtic™ function is carried out in a satisfactory manner. Generally speaking, certain functions will require a higher level of resolution than others or alternatively a less wide field of vision. But the presence of two cameras for a dedicated function represents a major cost item, with the result that this solution is often prohibitive. 
         [0015]    There is, therefore, a need to provide a system and method that overcomes one or more problems of the past. 
       SUMMARY OF THE INVENTION 
       [0016]    The subject of the present invention proposes a solution to the problems raised above. The invention still proposes the use of a stereoscopic system for the capture of images contained within a device intended to support driving, but it proposes that the system be carried out in such a way that it offers and make possible a genuine multifunctionality in terms of driving support applications. The introduction of the aspect of multifunctionality is accompanied by a number of advantages, for example the integration of the different items of equipment required for the driving support systems is simplified, the amount of space required at a windscreen level is reduced and both the cost and the complexity of the linkages are reduced. To this end, the present invention proposes that the device intended to support driving a motor vehicle employs a stereoscopic system comprising two cameras having different fields of vision, thereby incorporating the advantages of both image capturing systems. Preferably, this would comprise both a grey levels camera and a color camera, thus allowing more functions to be employed. 
         [0017]    The object of the present invention is a device intended to support the driving of a motor vehicle comprising a system for the capture of images in the form of a stereoscopic system. The device supporting the driving, and more particularly, the stereoscopic image capturing system, is arranged inside a motor vehicle. The device according to the present invention is intended essentially to improve the supporting functions of driving developed within motor vehicles, while at the same time economically providing a number of these functions. By way of example, these functions can be said to include an automatic beam switching system, known as the BeamAtic™ function, which allows dipped headlamps to be switched to full beam headlamps and vice versa in accordance with prevailing traffic conditions. 
         [0018]    The present invention thus relates to a device intended to support driving a motor vehicle comprising in particular a system for capturing images and in which this system for capturing images is a stereoscopic system for capturing images having at least a first and a second camera, with the first camera having a greater field of vision than that of the second camera, so that the stereoscopic system confers a degree of multifunctionality on the device for driving support. 
         [0019]    In this way, the second camera is able to capture an image on a zone equivalent to a part of the image captured by the first camera, enabling a zoom effect to be created in the second image. 
         [0020]    In addition to the principal features mentioned in the previous paragraph, the device according to the present invention can also comprise one or more of the following additional features: 
         [0021]    the first camera and the second camera have an overlapping zone in their fields of vision, which is generally centered on the direction in which the vehicle is travelling; 
         [0022]    the first camera is of the grey levels camera type and the second camera is of the color camera type; in this way, the second camera supplies information on the colors of the objects that are detected; 
         [0023]    the field of vision of the first camera is between 30 and 50 degrees, in particular 40 degrees, while the field of vision of the second camera is between 15 and 25 degrees, in particular 20 degrees; 
         [0024]    the size of the field of vision of the first camera is a multiple of the size of the field of vision of the second camera; 
         [0025]    the field of vision of the first camera and the field of vision of the second camera are generally centered on the direction of travel the motor vehicle; 
         [0026]    the second camera is fitted with a sensor of the RGBi type or a sensor enabling an image to be captured in grey levels in association with the calculation of the red components of the captured image, such as a sensor of the type RedClear. 
         [0027]    In the same way as the RGB type sensors, sensors of the RGBi types and sensors of the RedClear type function by using a grey levels sensor in front of which is arranged a filter. In the case of the RGBi sensors, this filter enables the red, green, blue and infra-red components of the captured image to be calculated, while in the case of the RedClear sensor, the capture of the grey levels images is associated with the calculation of the red components of the captured image. The advantage of the RedClear sensors is that they provide important color information (e.g. red tail lights) and furthermore their resolution is better than that of an RGB or an RGBi sensor. 
         [0028]    Insofar as they are not mutually exclusive, the different additional features of the device according to the present invention can be combined on the basis of all possible permutations to achieve different embodiments of the invention. 
         [0029]    The present invention also relates to the process for capturing a stereoscopic image using a device according to the present invention, comprising the following steps: 
         [0030]    the capture of at least a first image using the first camera, 
         [0031]    the capture of a second image using the second camera, and 
         [0032]    the matching of the first image and the second image. 
         [0033]    Preferably during this last step, the matching of the first and the second image comprises the following sub-steps: 
         [0034]    the extraction of the portion from the first image that corresponds to the second image in its full resolution, and 
         [0035]    the extraction of a third image from the second image, with this third image corresponding to the undersampled second image in such a way that the third image and the portion of the first image present, in pixels, the same dimensions, with the pair of images obtained in this manner permitting the superimposition arrangement to be achieved. 
         [0036]    The present invention also relates to a motor vehicle fitted with a device to support driving according to the present invention, having the principle features and possibly one or more of the additional features indicated above. 
         [0037]    A better understanding of the present invention and its different applications will be obtained by studying the following description together with the accompanying figures. 
         [0038]    These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0039]    The figures are included as a guide only and are not intended to limit the scope of the invention. The figures show as follows: 
           [0040]      FIG. 1  is a schematic representation of a typical application of the device according to the present invention; and 
           [0041]      FIG. 2  is a schematic representation of an operating application based on the images captured by the device according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]      FIG. 1  shows a vehicle  100  fitted with a device according to the present invention. This latter comprises at least a first camera of the grey levels camera type, which does not therefore provide color information, and a second camera of the color camera type. In the example shown, the first camera has a first field of vision  101 , defined by a viewing angle centered on the direction of travel  106  of the vehicle  100 , the size of this angle being in the order of  40  degrees. The second camera has a second field of vision  102 , also centered on the direction of travel  106  of the vehicle  100 , with a lesser field of vision than the first camera, for example in the order of 20 degrees. Advantageously, the second field of vision  102  contains a complete glare zone  105 , representing a zone, in which any other vehicle  103  that is present risks being dazzled if the vehicle  100  uses its main beam headlamps. In this way, the two zones present an overlapping or covering zone  104 , for which the images can be acquired by the first and by the second camera, providing, in particular, stereoscopic vision within this zone. Any oncoming or followed vehicles located within one of these fields of vision will thus be detected and the detection information that is obtained can be subjected to at least one treatment stage that is specific to a driving support function. 
         [0043]    A device of this nature will enable in particular the following driving support functions to be carried out: 
         [0044]    mono camera functions such as LDWS, BeamAtic™, FPW etc., which require a sufficiently large viewing angle to cover three traffic lanes and capable of providing images on bends. Typically, the viewing angle used for these functions is 40 degrees. For such functions, the use of the grey levels camera is preferred. Wide angles, for example those of 40 degrees, but also others within the range of 30 and 50 degrees, are also used and enable the user to benefit from a wide field of vision providing information on both the traffic lane followed by the vehicle and also the two adjoining lanes. A field of 40 degrees is also necessary when overtaking, for entering bends and also for detecting streetlamps; 
         [0045]    mono camera functions, such as Night Vision or the detection of pedestrians, require a better level of resolution in respect of distant objects, which thus implies a narrower viewing angle—generally 20 degrees. For these functions, the use of the color image camera is preferred. Furthermore, using the color image camera improves the detection scale for tail lights; 
         [0046]    any function that requires a relatively precise estimation of detected objects; with its stereoscopic system, the device according to the invention enables these functions to be carried out. One such function, for example, is that of the progressive adjustment of the length of the typical coded headlamp beam in relation to the presence of other motor vehicles. 
         [0047]      FIG. 2  shows more particularly the use of the device according to the present invention to give a precise estimation of the distance from an obstacle. 
         [0048]    The grey levels camera enables any type of object to be detected within a range of distances from 0 meter to the maximum detection distance given for the camera, with a limit for the detection of tail lamps at long distances. At long distances, the main undipped beam of the headlamps of the vehicle  100  will only dazzle when the potential obstacle is approximately in line with the vehicle  100 . In this case, the obstacle appears in a first image  201  generated by the first camera and also in a second image  202  generated by the second camera because it is inevitably present in the covering zone  104 . 
         [0049]    In this way, the detection of an object, for example, the two headlamps  205  of a vehicle in the example shown, in the first image  201  is confirmed in the second image  202 , and benefits from a zoom effect in the second image  202 , in a zone equivalent to a portion  203  of the first image  201 , additionally providing information on the color of the objects detected. 
         [0050]    At these extended distances, the traditional means of estimating distances (vertical position, triangulation on the basis of the vehicle width etc.) provide results that are far from precise. In the device according to the invention, the principle of stereovision is used to estimate the distance from the obstacle. The principle of stereovision can be applied to any object detected within the covering zone  104 . Any object that is detected in this overlapping zone  104  is present on the first image  201  and also on the second image  202 , which are then matched. This matching effect is achieved according to the present invention by extracting the portion  203  from the first image  201 ; this portion  203  corresponds to the second image  202  in full resolution. To obtain equivalence, an image  204  is extracted from the second image  202  which corresponds to the undersampled second image  202 , in such a way that the image  204  and the portion  203  present, in the form of pixels, the same dimensions. The pair of images thus obtained enable the matching effect to be achieved. Although effected with two 400/200 cameras, the precision of the stereoscopic vision system of the device according to the present invention is the same as that achieved with a stereovision system employing two 400/400 cameras. 
         [0051]    A special zone, known as the proximity zone  107 , and visible in  FIG. 1 , is used to detect obstacles when overtaking or when encountering oncoming vehicles in a bend. At these short distances, the conventional principles of estimating distances by a mono camera can provide sufficient precision. 
         [0052]    Advantageously, in the present invention, the camera producing grey levels camera and the color camera use identical sensors, especially in terms of resolution. However, in certain embodiments, different types of sensors may be used. 
         [0053]    For certain embodiments of the device according to the present invention, the use of a color camera of the type RGBi is proposed, in which a large number of pixels in the sensor are sensitive to x-rays. Certain functions, in particular those connected with night vision are thus even more effective. 
         [0054]    The example described above is not intended to be limitative. For example, on the basis of the same principles, it would be possible to use two grey levels cameras with different fields of vision to carry out two different functions requiring different resolutions and fields of vision (in this case, evidently, the functions would not be based on color detection). 
         [0055]    While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.