Apparatus for detecting an object located ahead of a vehicle using plural cameras with different fields of view

What is claimed is:

1. An apparatus for detecting an object located ahead of a vehicle comprising:

a first camera means for taking a picture of a first scene of a wide view angle inclusive of a road surface located at a near distance forward of the vehicle;

a second camera means for taking a picture of a second scene of narrow view angle inclusive of a road surface located at a far distance forward of the vehicle;

means for detecting an object located forward of the vehicle on the road surface contained in at least one of the first and second scenes on the basis of image data which forms a picture screen of the first and second scene;

first camera direction control means for altering the direction of the first camera transverse to the fore-and-aft axis of the vehicle in a direction such that a substantially full profile of the object located forward of the vehicle and detected in the first scene is contained in the first scene; and

second camera direction control means for altering the direction of the second camera transverse to the fore-and-aft axis of the vehicle in a direction such that a substantially full profile of the object located forward of the vehicle and detected in the second scene is contained in the second scene.

2. An apparatus according to claim 1 in which the first camera direction control means alters the first angle in a direction to bring the substantial center of the object located forward of the vehicle and detected in the first scene to the center of the first scene, and the second camera direction control means alters the second angle in a direction to bring the substantial center of the object located forward of the vehicle and detected in the second scene to the center of the second scene.

3. An apparatus according to claim 2 in which the fis camera means and the second camera means take a picture of white lines located at the left and right end of a lane on which the vehicle is running, the first and the second camera direction control means altering the first and the second angle in a direction to bring a median point between white lines at the left and the right end in each of the first and second scene to the center of each scene.

4. An apparatus according to claim 2 in which the object located forward of the vehicle includes a vehicle running ahead of the first mentioned vehicle, the first and the second camera direction control means altering the first and the second angle in a direction to bring the center position of the vehicle located ahead in each of the first and second scene to the center of each scene.

5. An apparatus according to claim 2 in which said means for detecting an object also detects white lines located at the left and the right end of a lane on which the vehicle is running and detects the presence or absence of any vehicle located forward of the first mentioned vehicle intermediate the detected white lines, the first and the sec camera direction control means altering the first and the second angle in a direction to bring a median point between the detected white lines to the center of each scene whenever any vehicle running ahead is not detected in either the first or second scene, the first and the second camera direction control means being responsive to the detection of a vehicle running ahead by said means for detecting an object to alter the first angle in a direction to bring the detected vehicle to the center of the first scene when the detected vehicle is located in the first scene, the second camera direction control means being responsive to the detection of a vehicle running ahead by said means for detecting an object to alter the second angle in a direction to bring the detected vehicle to the center of the second scene when the detected vehicle is located in the second scene.

6. An apparatus according to claim 1 in which the first camera means includes a first television camera of wide view angle which takes a picture of a road surface located at a near distance forward of the vehicle an a first rotary drive unit for rotatively driving the camera in order to alter the direction of the first television camera transverse to the fore-and-aft axis of the vehicle, and the second camera means includes a second television camera of a narrow view angle which takes a picture of a road surface located at a far distance forward of the vehicle and a second rotary drive unit for rotatively driving the camera in order to alter the direction of the second television camera transverse to the fore-and-aft axis of the vehicle, said means for detecting an object being operable to detect an object located forward of the vehicle as the object appears on the road surface in a picture screen formed by the first and the second television camera, on the basis of image data which forms such picture screen.

7. An apparatus according to claim 6 in which the firs camera direction control means alters the direction of the first television camera through the first rotary drive unit in a direction to bring the substantial center of the object located forward of the vehicle and detected on the picture screen formed by the first television camera to the center of the screen, and the second camera direction control means alters the direction of the second television through the second rotary drive unit in a direction to bring the substantial center of the object located forward of the vehicle and detected on the picture screen formed by the second television camera to the center of the screen.

8. An apparatus according to claim 7 in which said means for detecting an object detects white lines located at the left and the right end of a lane on which the vehicle is running at it appears on the road surface in the screen, based on image data from the first and the second television camera which form a picture screen, and calculates a typical one left end line representative of both white lines at the left end of the picture screens produced by the first and the second television cameras and a typical one right end line representative of white lines at the right end in the picture screens produced by the first and the second television cameras, thus detecting the presence or absence of a vehicle running ahead in a region sandwiched between the left end and the right end line.

9. An apparatus according to claim 8 in which the first and the second camera direction control means alters the direction of the first and the second television camera through the first and second rotary drive unit respectively, respectively in a direction such that a median line between the left end and the right end line is brought to the center of the respective picture screens produced by the first and the second television cameras when said means for detecting an object does not detect a vehicle running ahead in a region sandwiched between the left end and the right end line, and is also responsive to the detection by said means for detecting an object of a vehicle running ahead to alter the direction of the first television camera through the first rotary drive unit in a direction to bring the vehicle running ahead which is detected to the center of the picture screen produced by the first television camera when the vehicle detected lies in a region of the picture screen produced by the first television camera which is sandwiched between the left end and the right end line, and to alter the direction of the second television camera through the second rotary drive unit in a direction to bring the vehicle running ahead which is detected to the center of the picture screen produced by the second television camera when the detected vehicle lies in a region of the picture screen produced by the second television camera which is sandwiched between the left end and the right end line.

10. An apparatus for detecting an object located ahead of a vehicle comprising:

a first television camera of wide view angle which takes a picture of a road surface located at a near distance forward of the vehicle;

a first rotary drive unit for rotatively driving the camera to alter the direction of the first television camera transverse to the fore-and-aft axis of the vehicle;

a second television camera of a medium view angle which takes a picture of a road surface located at a medium distance forward of the vehicle;

a second rotary drive unit for rotatively driving the camera to alter the direction of the second television camera transverse to the fore-and-aft axis of the vehicle;

a third television camera of a narrow view angle which takes a picture of a road surface located at a far distance forward of the vehicle;

a third rotary drive unit for rotatively driving the camera to alter the direction of the third television camera transverse to the fore-and-aft axis of the vehicle;

means for detecting an object located forward of the vehicle as it appears on a road surface in the picture screen of each camera, based on image data from the first, the second and the third television cameras, each of which produce a picture screen;

and camera direction control means for altering the direction of the first television camera, through the first rotary drive unit, in a direction to bring the object located forward of the vehicle and detected on the picture screen produced by the first television camera to the center of the picture screen, for altering the direction of the second television camera, through the second rotary drive unit, in a direction to bring the object located forward of the vehicle and detected on the picture screen produced by the second television camera to the center of the picture screen, and for altering the direction of the third television camera, through the third rotary drive unit, in a direction to bring the object located forward of the vehicle which is detected on the picture screen produced by the third television camera to the center of the picture screen.

11. An apparatus according to claim 10 in which the camera direction control means alters the direction of the first television camera, through the first rotary drive unit, in a direction to bring a substantial center of the object located forward of the vehicle and detected on the picture screen produced by the first television camera to the center of the picture screen, alters the direction of the second television camera, through the second rotary drive unit, in a direction to bring a substantial center of the object located forward of the vehicle which is detected on the picture screen produced by the second television camera to the center of the picture screen, and alters the direction of the third television camera, through the third rotary drive unit, in a direction to bring a substantial center of the object located forward of a vehicle which is detected on the picture screen produced by the third television camera to the center of the picture screen.

12. An apparatus according to claim 11 in which said means for detecting an object detects white lines located at the left and right ends of a lane on which the vehicle is running as the lines appear on the road surface in a picture screen, based on image data from the first, the second and the third television cameras, each of which produce a picture screen, and calculates one left end line which is representative of three white lines located at the left end of the lane on picture screens produced by the first, the second and third television cameras and one right end line which is representative of three white lines located at the right end, thereby detecting the presence or absence of a vehicle running ahead in a region which is sandwiched between the left end and the right end line.

13. An apparatus according to claim 12 in which the camera direction control means alters the direction of the first, the second and the third television cameras through the first, the second and the third rotary drive unit, respectively, in a direction to bring a median line between the left end and the right end line to the center of the picture screen produced by the first, the second and the third television cameras whenever said means for detecting an object does not detect a vehicle running ahead in a region sandwiched between the left end and the right end line, and also responsive to the detection by said means for detecting an object of the presence of a vehicle running ahead to alter the direction of the first television camera through the first rotary drive unit in a direction to bring the detected vehicle running ahead to the center of the picture screen produced by the first television camera when the detected vehicle lies in a region on the picture screen produced by the first television camera which is sandwiched between the left end and the right end line, to alter the direction of the second television camera through the second rotary drive unit in a direction to bring the detected vehicle running ahead to the center of the picture screen produced by the second television camera when the detected vehicle lies in a region on the picture screen produced by the second television camera which is sandwiched between the left end and the right end line, and to alter the direction of the third television camera through the third rotary drive unit a direction to bring the detected vehicle running ahead to the center of the picture screen produced by the third televison camera when the detected vehicle lies in a region on the picture screen produced by the third television camera which is sandwiched between the left end and the right end line.

Description Submit all comments and votes

FIELD OF THE INVENTION

The invention relates to the detection of an object located ahead of a vehicle, and while not intended to be limited thereto, in particular to an on-road object detecting apparatus in which a scene located ahead of a vehicle, including a road surface, is photographed on the vehicle and in which on a picture screen, white lines partitioning a lane or lanes on the road surface, any vehicle running ahead and any obstacle located ahead is detected and in which a distance from an own vehicle to the detected vehicle which runs ahead is calculated.

BACKGROUND OF THE INVENTION

An example of such detecting apparatus is disclosed in Japanese Laid-Open Patent Application No. 15,605/89 wherein a television camera onboard a vehicle takes a picture of a scene, including a road surface, located ahead of the vehicle, and image data from the camera is displayed on a picture screen defined in x-y orthogonal coordinate system. A derivative of the image data in a direction which forms an angle of 45.degree. with respect to the x-axis is calculated, and locations defined in terms of x- and y- orthogonal coordinates where the derivative exceeds a given value are selected as feature points. A succession of feature points are converted into a thin line, and a thin line or lines having a length which exceeds a given value are picked out. A thin line which satisfies a certain condition determined on the basis of features which are exhibited by a white line on the screen when it is photographed by a television camera onboard the vehicle is recognized as a white line on the road surface. In this manner, a pair of rectilinear lines which represents the white lines defining the left and the right end of a lane on which an own vehicle is running are obtained. A point of intersection between the pair of rectilinear lines is determined, and the presence or absence of an object in a triangular region defined by the pair of rectilinear lines extending between the point of intersection and the own vehicle is detected. When an object is detected, a distance from the own vehicle to such object or vehicle-to-vehicle distance if the object is a vehicle running ahead is calculated.

When the lane on which the own vehicle is running extends straightforward, any vehicle running ahead of the own vehicle on the lane exists in the triangular region. If a roof of such vehicle is displaced out of sight, the base of the vehicle lies within the region. It is to be noted that the pair of rectilinear lines which approximate the white lines on the left and the right end are determined on the basis of an image of these white lines at a location close to the camera. Accordingly, when the lane on which the own vehicle is running is curved near the own vehicle or at a point located forward of the own vehicle, the point of intersection between the pair of rectilinear lines, which can be viewed as a point of infinity for a straight lane, will be displaced to the left of a far point on this lane if the lane is curved to the right, or displaced to the right of the far point if the lane is curved to the left. Accordingly, where the road is curved, the probability that the detection of an object located ahead such as a vehicle running ahead or an obstacle located ahead, in particular, an object located far ahead fails will be high when relying upon only the search for any object in the triangular region.

Japanese Laid-Open Patent Application No. 276,214/89 proposes an automatic vehicle driving scheme in which a picture of an index along the roadside is taken by a camera onboard a vehicle to produce vehicle position information, which is compared against destination information to determine an optimum route, thus controlling a vehicle speed and a wheel steering in accordance with the route thus determined. It also proposes a two dimensional attitude changing mechanism for the camera for changing the direction, in which the camera takes a picture of the index along the roadside, in both horizontal and vertical directions. However, it will be noted that this proposal premises that the road actually exists in accordance with the optimum route determined and that there is no vehicle which is running ahead of the own vehicle on that road. In actuality, a recognition of the fact that such a road exists in fact and the reliable detection of the presence or absence of any vehicle running ahead as well as vehicle-to-vehicle distance therebetween are required.

Japanese Laid-Open Patent Application No. 124,345/94 proposes a tracking system which allows a camera to track a vehicle running ahead, by controlling the focal length and zooming so that an image of the vehicle running ahead occupies a substantially constant size on the screen, and by controlling the attitude of the camera in other horizontal and vertical directions such that the image of the vehicle running ahead is located substantially at the center of the screen. While such tracking control must premise a detection and/or identification of an initial vehicle which is running ahead, and also a search for a next succeeding vehicle when the initial vehicle running ahead which has been being tracked takes a different course and disappears from the sight forward of the own vehicle, but there is no corresponding teaching. In addition, there is no teaching about the method to deal with an erroneous tracking which may result when the vehicle being tracked takes a different course and deviates from the direction in which the own vehicle is traveling.

A pending U.S. patent application Ser. No. 08/183,369, filed by Jun SATO et al, entitled "METHOD OF DETECTING LINES APPROXIMATING AN IMAGE" corresponding to Japanese Laid-Open Patent Application No. 213,660/94 discloses an apparatus for detecting a vehicle located ahead of an own vehicle in which a camera onboard a vehicle derives an image of a road surface ahead of an own vehicle and displayed on a screen which is defined in x-y orthogonal coordinate system. A rectilinear line appearing on the screen is detected by Hough transformation, and on the basis of the line detected, a distribution on the screen of the lane on which an own vehicle is running is calculated. Subsequently, any vehicle running ahead or an obstacle located ahead on this lane is searched, and a distance to the vehicle which is found by such search is calculated.

The detection of a lane and a vehicle thereon which runs ahead of an own vehicle must cover a long distance for the search because the own vehicle is running. For example, an automatic vehicle-to-vehicle distance control may be conducted in which a vehicle running ahead is detected, a distance from the own vehicle to the detected vehicle is calculated, and a calculated distance is compared against a target distance which is established in accordance with a running speed of the own vehicle, and the own vehicle is decelerated if the detected distance is less than the target distance or the own vehicle is accelerated if the detected distance is greater than the target distance. In such instance, as a simplified example, when the own vehicle is running at a speed on the order of 40 km per hour, it may be tentatively assumed that the safety is assured if the search covers 30 m ahead. However, when the own vehicle is running at a speed on the order of 80 km, it may become necessary to detect any vehicle running ahead over a section of an increased length of 50 m or longer. In any event, because the vehicle runs at a speed over an extensive range, it is preferred that the automatic detection of any vehicle running ahead may cover a long section of 50 m or longer, assuming a high speed running.

However, it will be seen that at short distances, it is preferable to detect a vehicle with a wider angle in order to provide against lateral approach of a neighboring vehicle or to provide for a lane change, and thus it is preferred to use a camera having a wide view angle. However, this degrades the resolution for an object located at a far distance, and hence the accuracy of detection. When a narrow field of view or telescoping capability is chosen for detecting of an object located at a far distance, objects located at a near distance, in particular, a neighboring lane, will be left out, preventing a vehicle which is running on a neighboring lane from being detected. In addition, where the road is curved, a region located beyond the curvature will be removed from the screen, thus preventing a recognition of a vehicle there located.

Accordingly, while it is relatively simple to provide a tracking control of a target which is reliably identified as a vehicle running ahead on a lane on which an own vehicle is running, it is difficult to provide an extended coverage from an area located immediately in front of an own vehicle to a point far ahead which is prerequisite to such tracking control, namely, the detection of a road condition (whether it is curved or straightforward), the detection of the presence or absence of any vehicle running ahead or an obstacle located ahead, and a decision whether the detected vehicle or object is located on the lane on which the own vehicle is running. It is desirable to provide such a detection and decision technique with a high accuracy.

SUMMERY OF THE INVENTION

It is a first object of the invention to detect an object located ahead of a road, in particular, ahead of a curved road as early as possible, that is to say, while it is located at a far point, and it is a second object of the invention to improve the accuracy of such detection.

In accordance with the invention, camera means is employed for taking a picture of a first scene of wide view angle defined by a first angle A transverse to the fore-and-aft axis of the vehicle and located ahead of an own vehicle, inclusive a road surface at a near distance, and a second scene of narrow view angle defined by a second angle B transverse to the fore-and-aft axis of the vehicle and located ahead, including a road surface at a far distance. An image processor provides a picture screen of the first and second scene on the basis of image data, and detects an object on a road surface in either the first or the second scene such as white line, a vehicle running ahead or an obstacle located ahead. A camera direction controller alters the first angle A in a direction such that a substantially full profile of the object located on the first scene is contained in the first scene, and also alters the second angle B in a direction such that a substantially full profile of the object detected on the second scene is contained in the second scene.

The first scene covers an extensive area forward of the own vehicle and which extends laterally therefrom at a near distance. Accordingly, the first scene contains a portion of the lane on which the own vehicle runs and which is located at a near distance, for example, at a distance from 10 to 30 m, and any vehicle running ahead on that lane, and any other vehicle on adjacent lane or lanes which are located slightly forward of the own vehicle. The resolution of these objects on the screen displaying the first scene is high. Consequently, a lane on which an own vehicle runs, any vehicle running ahead and any lateral vehicle (running on an adjacent lane) can be reliably detected on the basis of image data representing the first scene.

On the other hand, the second scene covers a far distance, for example, from 30 to 60 m, ahead of the vehicle with a narrow view angle, and thus present a high resolution for the road surface and a vehicle located at a far distance on the screen of the second scene. Accordingly, a road surface and a vehicle located at a far distance can be detected with a high accuracy on the basis of image data which produce the second scene on the screen.

Because the camera means takes a picture of the first and the second scene, and the image processor detects an object or objects located on the road surface in the first and second scene on the basis of image data which produce the first and second scene, a lane on which an own vehicle runs, any vehicle running ahead and any lateral vehicle located at the near distance forward of the own vehicle can be reliably detected while a road surface and any vehicle located at a far distance forward of the own vehicle can be detected with high accuracy.

If the direction in which the camera means is directed relative to the fore-and-aft axis of the vehicle is fixed, there is a high likelihood that a road surface and any vehicle located at a far distance may go out of the first and second scene in the event the road is curved. However, the camera direction controller alters the first angle A in a direction such that a substantially full profile of any object detected on the first scene is contained in the first scene, and also alters the second angle B in a direction such that a substantially full profile of an object detected on the second scene is contained in the second scene. As a result, if the road is curved, the first and second scene are both capable of containing any on-road object, thus permitting the detection of a road surface and any vehicle which is located a relatively far distance and beyond the point of curvature and enhancing the reliability of detection of a road surface and any vehicle which is located at a near distance and/or far distance forwardly of the own vehicle, by the image processor.

In a preferred embodiment of the invention, the camera direction controller determines the first angle A such that the substantial center of an object detected on the first scene and located forward of the own vehicle defines the center of the first scene, and also determines the second angle B such that the substantial center of an object detected on the second scene and which is located forward of the own vehicle defines the center of the second scene. In this manner, any object detected and located ahead of the own vehicle is positioned at the center of the screen on which the first and the second scene are displayed, thus presenting a high accuracy in detecting any object.

In the preferred embodiment of the invention, the image processor applies Hough transformation to image data which creates the first and second scene on the screen to detect a white line which partitions a lane on which the own vehicle is running. On the basis of white lines detected, a vehicle search region is defined on the first and the second scene. Any vehicle which is located forward of the own vehicle and which is contained in these scenes are detected, and a distance or distances to these vehicles from the own vehicle are calculated. The camera direction controller determines the first angle A and the second angle B so that the centerline of the lane on which the own vehicle is running coincides with the centerline of the first and second scene. In this manner, the camera direction controller tracks the lane on which the own vehicle is running. This enhances the accuracy of detecting the lane on which the own vehicle is running, also improving the accuracy of the determining whether or not a vehicle detected forward of the own vehicle lies on the lane on which the own vehicle is running.

In the preferred embodiment of the invention, the camera means includes a first television camera of a wide view angle which takes a picture of a road surface located at a near distance from 10 to 30 m forward of an own vehicle, a first rotary drive unit for rotatively driving the camera in order to alter a camera direction A of the first television camera transverse to the fore-and-aft axis of the vehicle, a second television camera of medium view angle taking a picture of a road surface located at a medium distance from 30 to 60 m forward of the own vehicle, a second rotary drive unit for rotatively driving the second camera in order to alter the camera direction B of the second television camera transverse to the fore-and-aft axis of the vehicle, a third television camera of narrow view angle taking a picture of a road surface at a far distance from 60 to 90 m forward of the own vehicle, and a third rotary drive unit for rotatively driving the third camera in order to alter the camera direction of the third television camera transverse to the fore-and-aft axis of the vehicle. On the basis of image data from the respective television cameras which are used to create a first, a second and a third scene on a picture screen, the image processor detects an object located on the road surface of each scene such as a white line, a vehicle running ahead or an obstacle located ahead. The camera direction controller alters the first angle A in a direction such that a substantially full profile of an object detected on the first scene and which is located forward of the own vehicle is contained in the first scene, alters the second angle B in a direction such that a substantially full profile of an object detected on the second scene and which is located forward of the own vehicle is contained in the second scene, and also alters the third angle C in a direction such that a substantially full profile of an object detected on the third scene and which is located forward of the own vehicle is contained in the third scene. In this manner, a white line, any vehicle running ahead or any obstacle which is located on the road in the range from 10 to 90 m forward of the own vehicle can be detected with a high accuracy.

Other objects and features of the invention will become apparent from the following description of a preferred embodiment with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a block diagram illustrating a general arrangement of a preferred embodiment of the invention;

FIG. 1b is a side elevation of a driver's seat on a vehicle, also illustrating the disposition of television cameras 16b, 26b and 36b shown in FIG. 1a;

FIG. 2 is a plan view of a picture screen indicating a scene taken by the television camera 16b shown FIG. 1a;

FIG. 3 is a plan view illustrating coverages ARa, ARb and ARc of the television cameras 16b, 26b and 36b shown in FIG. 1a, in the direction forward of an own vehicle;

FIG. 4a graphically illustrates the lateral coverage or breadth of the television cameras 16b, 26b and 36b shown in FIG. 1a, as viewed forward from an own vehicle;

FIG. 4b graphically illustrates a resolution of the television cameras 16b, 26b and 36b shown in FIG. 1a, indicating the length of an object being taken per picture element of the photoelectric conversion unit, or resolution .sigma.;

FIG. 5 is a plan view indicating the coverages ARa, ARb and ARc of the television cameras 16b, 26b and 36b shown in FIG. 1a and their steering angles A, B and C;

FIG. 6 is a block diagram of a first image processor 100 shown in FIG. 1a;

FIG. 7 is a block diagram of a second image processor 200 shown in FIG. 1a;

FIG. 8 is a block diagram of a third image processor 300 shown in FIG. 1a;

FIG. 9 is a flow chart indicating part of the operation performed by CPU 11 shown in FIG. 6, including a processing of image data and the detection of any vehicle running ahead;

FIG. 10 is a flow chart continuing from the flow chart shown in FIG. 9 and illustrating another part of the operation performed by CPU 11;

FIG. 11 is a flow chart continuing from FIG. 10 and illustrating the remainder of the operation performed by CPU 11 shown in FIG. 6;

FIG. 12a is a flow chart illustrating the detail of "set-up of feature points detecting window 1" C1 shown in FIG. 9;

FIG. 12b is a plan view indicating a region on the picture screen produced by the television camera 16b shown in FIG. 1a which corresponds to the feature points detecting window 1;

FIG. 13a is a flow chart showing the detail of "bonnet detection" C3 shown in FIG. 9;

FIG. 13b is a plan view, showing the distribution of feature points on the picture screen produced by the television camera 16b shown in FIG. 1a and rectilinear lines which are detected by "line fitting" 13R shown in FIG. 13a;

FIG. 14 is a plan view indicating a roll angle and a pan travel on the picture screen produced by the television camera 16b shown in FIG. 1a;

FIG. 15 is a plan view showing the distribution of picture elements a to d which are referred to when calculating image data from a picture element of interest at "interpolation" C8 shown in FIG. 9;

FIG. 16 is a plan view indicating a lane detecting window on the picture screen produced by the television camera 16b, which is set up at "set-up of lane detecting window" A3 shown in FIG. 10;

FIG. 17 is a side elevation illustrating the general geometrical relationship between a lens and camera element within the television camera 16b shown in FIG. 1a and a vehicle running ahead of an own vehicle;

FIG. 18a is a side elevation indicating the general geometrical relationship between a lens and a camera element within the television camera 16b shown in FIG. 1a and a point P on the road surface located forward of an own vehicle; and

FIG. 18b is a plan view illustrating the general geometrical relationship between a lens and a camera element within the television camera 16b shown in FIG. 1a and a point P on the road surface located froward of an own vehicle.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1a which shows one embodiment of the invention, a first, a second and a third television camera 16b, 26b and 36b are supported by respective rotary mechanisms 16d, 26d and 36d, respectively, and are connected to a first, a second and a third image processor 100, 200 and 300, respectively. Each of the rotary mechanisms 16d, 26d and 36d internally houses an electrical motor for rotary drive and a reduction gearing having an output rotating shaft on which the camera 16b, 26b or 36b is fixedly mounted.

All of the first to the third rotary mechanisms 16d to 36d are supported by a single support frame, and are located adjacent to the top center of a front window within the compartment of a vehicle MCR, as shown in FIG. 1b. Each of the first to the third television camera 16b to 36b delivers a video signal or analog picture signal comprising 512.times.512 picture elements per frame by taking a picture of scene located forward of an own vehicle.

The first camera 16b is a wide view angle camera, and projects an area measuring about 24 m.times.24 m located up to 30 m forward of an own vehicle and extending in a direction perpendicular to the centerline of the field of view onto 512.times.512 picture elements disposed in an array along x and y coordinates. When the road is horizontal, the centerline of the field of view intersect with the road surface at a distance of about 15 m forward of the own vehicle. The first camera 16b is focused to this point of intersection. A picture screen produced by the first camera 16b is illustrated in FIG. 2. As an example, assuming that the road surface is horizontal, a road surface at located y=150 on the screen corresponds to a distance of 30 m forward of the own vehicle, and a road surface located at y=350 corresponds to a distance of 10 m forward of the own vehicle. The detection of a white line and vehicle, which will be described later, takes place in a range from y=150 to y=350 (which is feature points detecting window 2).

The second camera 26b represents a camera having a standard view angle, and projects an area measuring about 19 m.times.19 m, located up to 60 m forward of the own vehicle and extending in a direction orthogonal to the centerline of the field of view, onto 512.times.512 picture elements disposed in an array along x and y coordinates. The centerline of the field of view intersects with a road surface at about 45 m forward of the own vehicle when the road surface is horizontal. The second camera 26b is focused to this point of intersection. On the picture screen produced by the second camera 26b, a road surface located at y=150 is at a distance of 60 m forward of the own vehicle, and a road surface located at y=350 is at a distance of 30 m forward of the own vehicle. The detection of a white line and vehicle, which will be described later, takes place in a range from y=150 to y=350 (feature points detecting window 2).

The third camera 36b is a telescopic camera, and projects an area measuring about 13 m.times.13 m and located up to 90 m forward of the own vehicle and extending in a direction orthogonal to the centerline of the field of view onto 512.times.512 picture elements disposed in an array along the x and y coordinates. When the road surface is horizontal, the centerline of the field of view intersects with a road surface at about 75 m forward of the own vehicle. The third camera 36b is focused to this point of intersection. On the picture screen produced by the third camera 36b, a road surface located at y=150 is at a distance of 90 m forward of the own vehicle, and a road sur face located at y=350 is at a distance of 60 m forward of the own vehicle. The detection of a white line and a vehicle, which will be described later, takes place in a range from y=150 to y=350 (feature points detecting window 2).

FIG. 3 shows a coverage (the entire screen) of each of the cameras 16b, 26b and 36b in relation to the distance measured forward of the own vehicle, and a region where the detection of a white line and a vehicle takes place (corresponding to y=150 to y=350: the region corresponding to the feature points detecting window 2). FIG. 4a indicates the breadth or lateral coverage of the respective cameras in relation to the distance measured forward from the own vehicle, and FIG. 4b indicates the relationship between the resolution .sigma. and the distance measured forward from the own vehicle. The resolution .sigma. represents a minimum distance which can be determined at a particular distance forward of the own vehicle, and the accuracy in which the distance can be determined is improved as the field of view of the camera becomes narrower.

When the road is curved, if a camera having a narrow angle of view is used, the possibility that the camera may take a picture in a direction away from the road surface increases. Accordingly, in the present embodiment, the rotary mechanisms 16d, 26d and 36d are used to support the cameras 16b, 26b and 36b, respectively, and principally using CPU 11, to be described later, of the image processor 100, a lane and any vehicle running ahead which lie in a range of distance from 10 m to 90 m forward of the own vehicle is detected. When a vehicle running ahead is not detected, the cameras 16b, 26b and 36b are individually steered so that the center of the field of view of each of the cameras be brought into alignment with a center of the lane, as shown in FIG. 5. A camera which has detected the presence of a vehicle within the field of view (corresponding to a range from y=150 to y=350) is steered to place the detected vehicle at the center of the field of view. A square mark, a triangle mark and a circle mark within the coverages ARa, ARb and ARc of the cameras 16b, 26b and 36b, respectively, shown in FIG. 5, indicate the positions on the centerline of the field of view where an image having the greatest sharpness is obtained. Characters A, B and C represent steer angles of the cameras 16b, 26b and 36b, which represent in each instance an angle formed between the projection of the fore-and-aft axis Lmcr of the vehicle onto the horizontal plane and the projection of the centerline of the field of view of each camera onto the horizontal plane.

FIG. 6 shows the arrangement of the first image processor 100. The image processor 100 essentially comprises a microcomputer (here-after referred to as CPU 11) including buses, to which a read only memory (ROM) 12 having a control program stored therein, a read-write memory (RAM) 13 having parameters being processed stored therein, and input/output ports (I/O) 15, 16 are connected. Various components are additionally connected to these input/output ports. An analog picture signal delivered by the first camera 16b is applied to an A/D converter 16c. The converter 16c converts the analog picture signal from the first camera 16b into digital data or gradation data having a number of digits capable of representing 256 gradations (gradation 0 representing a black level and gradation 255 representing a white level) for each picture element, and feeds such data to an image memory 15a. It is to be noted that the image memory 15a includes a gradation data storage area for storing several pages and a binary data storage area capable of storing a bit information or binary data, representing whether a particular picture element represents a black or a white, where one page is defined as an area for storing gradation data or binary data for one screen (512.times.512 picture elements).

CPU 11 controls the diaphragm and the output level of the analog picture signal from the first camera 16b through a television camera controller 16a, and also synchronously controls the input/output to or from the A/D converter 16c and the write-in into the image memory 15a. The image memory 15a is connected to a DMA unit 14, into which image data delivered from the image processor 200 or 300 is written into at a memory area specified by CPU 11.

The rotary mechanism 16d includes an electrical motor, not shown, which is connected to a motor driver, not shown, contained in a steering controller 16e. CPU 11 delivers a target angle to the controller 16e, which drives the electric motor of the rotary mechanism 16d for rotation in either the forward (in the right-hand) direction or in