Vehicle surroundings monitor with obstacle avoidance lighting

The vehicle surroundings monitor detects the sizes and positions of obstacles, ditches and humans as well as the depths of the ditches to provide the driver with sufficient information to secure safety during driving. The pattern light projector receives an incoming laser beam and projects a light spot matrix in the form of a regular grating onto the monitored area. The camera photographs the light spot pattern on the monitored area and sends image signals to the data processor which processes the image signals to detect the presence of any obstacle, ditch or human. Based on the steering angle detected by the steering angle sensor, the path the car will take is predicted and a possible contact or collision of the car with the obstacle is detected beforehand. The buzzer, voice synthesizer and display device are used to alert the driver and indicate the presence of the obstacles, the possible contact with them and the location where the possible contact will occur.

BACKGROUND OF THE INVENTION
 FIELD OF THE INVENTION
 This invention relates to a vehicle surroundings monitor and, more
 specifically, to a vehicle surroundings monitor which monitors the
 surroundings of a vehicle such as an automobile to support a driver in
 checking safety during vehicle driving.
 A vehicle surroundings monitor for automobiles has been available, in which
 the distance to an obstacle is detected by measuring the time it takes for
 an ultrasonic wave, which is emitted from an ultrasonic wave transmitter
 and reflected by the obstacle, to return to a wave receiver.
 There is also a method in which a television camera is mounted on the rear
 part of the roof of a vehicle so that the driver is given a rearward view
 on a TV monitor of an interested area when the vehicle is moving backward.
 Of the above-mentioned conventional apparatuses, the one which uses the
 ultrasonic wave transmitter and receiver cannot detect the positions and
 sizes of obstacles and ditches and the depths of the ditches. Hence, it
 cannot fully support the driver in confirming safety in the near
 surroundings of the vehicle during driving.
 In the method that uses a TV monitor, on the other hand, it may be
 difficult to distinguish the obstacles or ditches from the level ground
 depending on their shapes. Especially during nighttime, there may be cases
 where obstacles cannot be identified unless sufficiently illuminated.
 SUMMARY OF THE INVENTION
 This invention has been accomplished to overcome the above drawbacks and
 its object is to provide a vehicle surroundings monitor which can detect
 the sizes, positions and depths of obstacles, ditches or humans and
 thereby give adequate aid for the driver to confirm the safety in the near
 surroundings of the vehicle while driving.
 To solve the above problems, the vehicle surroundings monitor according to
 this invention comprises: a pattern light projector which receives a laser
 beam and projects a light spot pattern onto the monitored area; a camera
 for photographing the light spot pattern; and a data processor which
 processes images supplied from the camera to detect the presence of
 obstacles, grooves or humans.
 The data processor consists of: a reference data generating means which
 extracts a light spot pattern from pixel data, the pixel data being
 produced from the image signals supplied by the camera that photographed
 the light spot pattern thrown upon a flat road surface, and which
 generates reference data of the light spot pattern including the
 coordinates of each light spot; a detecting means which compares the light
 spots of the reference data with light spots which are extracted from
 pixel data, the pixel data being produced from the image signals supplied
 by the camera that photographed the light spot pattern thrown upon a road
 surface being examined, in order to detect the presence of obstacles,
 ditches or humans; a height correction means which corrects the reference
 data according to changes in the height of the pattern light projector and
 the camera from the road surface; and a brightness correction means which
 corrects the brightness of pixel data--which is produced from image
 signals supplied by the camera that photographed the light spot pattern
 thrown upon the road surface being examined--according to a difference
 between the brightness of a background other than the light spots and the
 background brightness of the reference data.
 The vehicle surroundings monitor also has a vehicle path prediction means
 to calculate the path the vehicle will take and thereby predict a possible
 contact or collision of the car with obstacles.
 The vehicle surroundings monitor also has at least one of a buzzer, voice
 synthesizer and display device to inform the driver of the presence of
 obstacles and the location where the automobile is predicted to contact
 the obstacles.
 In the above configuration, the pattern light projector receives an
 incoming laser beam and projects a light spot matrix in the form of a
 regular grating onto the monitored area (in the embodiment the monitored
 area is the ground surface being examined). When there is any obstacle,
 ditch or human within the monitored area, the three-dimensional positions
 of the light spots thrown onto these objects change resulting in local
 disturbances of the light spot projection image obtained from the camera.
 By processing the image disturbances it is possible to detect the sizes
 and positions of the obstacles.
 When the height of the pattern light projector and the camera from the road
 surface changes, the reference data is corrected accordingly. Therefore,
 when the car is weighed down by heavy goods or passengers, the vehicle
 surroundings monitor can detect obstacles, ditches or persons correctly.
 When the brightness of the background other than the light spots changes,
 the brightness of the pixel data on the monitored road surface can be
 corrected according to the amount of brightness change. This prevents
 erroneous detection of light spots, which would otherwise result from an
 increased brightness by brake lamp illumination. At the same time, the
 display device shows the size and position of the obstacle with or without
 an alarm buzzer sound. Further, the apparatus predicts the path the car
 will follow and shows on the display device the location where the car
 will contact or collide with the obstacle to alert the driver.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
 Now, embodiments of this invention will be described by referring to the
 attached drawings. FIG. 1 shows one embodiment configuration of the
 vehicle surroundings monitor according to this invention. In the figure,
 reference numeral 1 represents a laser beam source; 2 a laser beam source
 drive apparatus for driving the laser beam source 1; 3 a pattern light
 projection element which receives the laser beam 1a from the laser beam
 source 1 to project a light spot matrix onto the monitored area; 4 a CCD
 camera to photograph the light spot matrix; 5 a frame memory to
 temporarily store the video signal obtained from the CCD camera 4; 6 a
 data processor consisting of a computer that operates according to a
 predetermined program; 7 a reference data memory which stores beforehand
 the image data of a level ground without an obstacle as the reference
 data; 8 a steering angle detector that detects the steering angle of the
 steering wheel; 9 a buzzer for sounding an alarm; and 10 a display device.
 The pattern light projection element 3 may utilize a fiber grating 13 of
 FIG. 2a or a multi-beam projector 23 of FIG. 2b.
 The fiber grating 13 of FIG. 2a consists of two sheets, stacked together 90
 degrees out of phase, of about 100 optical fibers arranged side by side,
 each fiber measuring several tens of .mu.m in diameter and 10 mm in
 length. When the laser beam 1a generated by the laser beam source 1 is
 thrown upon the fiber grating 13, the laser beam is focused at focal
 points of individual fibers and thereafter expands as spherical wavefronts
 interfering with each other, with the result that the light spot matrix 14
 like a regular grating is projected onto the projection surface.
 The multi-beam projector 23 of FIG. 2b consists of a large number of
 microlenses integrated in a thin transparent plate. The laser beam 1a
 emitted from the laser beam source 1 is transformed into multiple beams by
 the multi-beam projector 23 so that the light spot matrix 14 of a regular
 grating is projected onto the projection surface.
 In the above configuration, the light spot matrix 14 projected by the
 pattern light projection element 3 (fiber grating 13 or multi-beam
 projector 23) onto the monitored area is photographed by the CCD camera 4.
 The video signal produced by the CCD camera 4 is temporarily stored in the
 frame memory 5 and then taken into the data processor 6. The data
 processor 6 compares the image data from the frame memory 5 with the
 reference data prestored in the reference data memory 7 to determine the
 distance of movement of the light spot on the image plane 4b of the CCD
 camera 4.
 FIG. 3 shows the optical arrangement of the embodiment of FIG. 1, in which
 the lens 4a of the CCD camera 4 is taken as an origin, the pattern light
 projection element 3 is located a distance d from the origin on the
 y-axis, and the image plane 4b is located a distance I from the origin on
 the Z-axis. In this optical arrangement, the light spot which is to be
 projected at point P.sub.n (X.sub.n, Y.sub.n, 0) when the monitored area
 4c (the field of view of the CCD camera) is a flat ground (flat road
 surface) without an obstacle is projected onto point P.sub.B (X.sub.B,
 Y.sub.B, Z.sub.B) on an object O because there is the object O in the
 monitored area 4c. On the image plane 4b of the CCD camera 4 that
 photographs the light spot, therefore, the point A (u, v) corresponding to
 the point P.sub.n (X.sub.n, Y.sub.n, 0) moves to the point B (u,
 v+.delta.) corresponding to the point P.sub.B (X.sub.B, Y.sub.B, Z.sub.B).
 In other words, the light spot moves in a certain direction.
 Hence, by determining the distance between the point A and the point B, the
 amount of movement .delta. can be detected. The data processor 6 performs
 processing on the distances d, I, the distance h from y-axis to the
 monitored area 4c, the angle .theta. formed by the CCD camera's light axis
 and the normal to the monitored area 4c, and the amount of displacement d
 in order to determine the three-dimensional position of the light spot (in
 FIG. 3 the point P.sub.B (X.sub.B, Y.sub.B, Z.sub.B)). In this way, the
 three-dimensional positions are determined for all light spots in the
 input image. The calculation is performed on the light spots whose
 three-dimensional positions have changed, thus determining the rough sizes
 and positions of obstacles, ditches or humans and showing them on the
 display apparatus 10.
 FIG. 4 shows one example arrangement where the sensor section S--made up of
 the pattern light projection element 3, the laser beam source 1 and the
 CCD camera 4--is fixed at the rear part of the vehicle at an angle .theta.
 with respect to the normal line to the ground.
 The processing performed by the data processor 6 consists largely of a
 reference picture data (reference data) generating processing and an
 obstacle detection processing shown in the flowcharts of FIGS. 5 and 6.
 In the reference data generating processing, as shown in the flowchart of
 FIG. 5, the image signal of the light spot matrix 14 photographed by the
 CCD camera 4 is taken in at step S1, transformed into pixel data of
 512.times.512 pixels with 0-255 gradations of shade and then temporarily
 stored in the frame memory 5. The pixel data temporarily stored in the
 frame memory 5 is processed by the data processor 6 to extract the light
 spots at step S2. Then step S3 determines the coordinates of the
 baricenter of the light spot. Step S4 determines the brightness of the
 light spot, i.e., the threshold value for extracting the light spot during
 inspection. The processing further moves to step S5 to read the background
 brightness data necessary for the correction of brightness.
 The light spot extraction processing of step S2 extracts light spots by
 comparing with the threshold value the brightness on each scanning line,
 as shown in FIG. 8, in the light spot projection image in the monitored
 area of FIG. 7. In this processing, if for each pixel data in the frame
 memory 5 the gradation value of the pixel is larger than the preset
 threshold value, the gradation value is left as is. If the gradation value
 is smaller than the threshold value, it is set to zero. This processing is
 carried out one pixel at a time for all pixels. As a result, clusters of
 pixels (light spots) as shown in FIG. 9 are extracted.
 Where there is a large difference in brightness between each light spot and
 thus the light spot cannot be extracted with a fixed threshold value, the
 following steps are taken. An average brightness is taken of a window of
 m.times.n pixels at the center of which is located the pixel being
 examined, as shown in FIG. 10, and the brightness of the pixel is compared
 with the average value to determine whether or not the pixel in question
 should be left as is. Similar processing is done for other pixels and the
 average threshold that varies from one pixel to another is used to extract
 the light spot.
 Next, we will explain about the processing of step S3, i.e., the processing
 for determining the coordinate position of the light spot baricenter. This
 processing determines the coordinate position of the light spot baricenter
 (U, V) by assigning the brightness weight to each pixel in the light spot.
 In the next step S4, which determines the brightness of the light spot
 (threshold value of the brightness), the minimum value of the pixels that
 form the light spot is taken to be the brightness of the light spot
 baricenter. As to the light spot shown in FIG. 11, I(min)=50 and therefore
 the brightness of the light spot baricenter is 50.
 With the above processing performed, it is possible to obtain for each
 light spot number the final reference light spot data (reference data)
 consisting of the light spot baricenter, its brightness and the background
 data (position and brightness) as shown in FIG. 12. The final reference
 light spot data is stored in the reference data storage section 7. By
 executing the flowchart of FIG. 5, the data processor 6 works as a
 reference data generating means to generate the reference data including
 the light spot coordinates, the threshold value of each light spot and the
 background data by using the pixel data transformed from the image signal
 from the camera that photographs the light spot pattern projected onto the
 flat road surface.
 The obstacle detection processing, as shown in the flowchart of FIG. 6,
 first takes in the reference data from the reference data storage section
 7 at step S11. At step S12, the sensor height changes are corrected. Then
 step S13 takes in a picture and step S14 detects changes in the brightness
 of the background of the picture taken in and also compensates for the
 brightness changes. The program then proceeds to step S15 which extracts a
 moved spot. This is followed by step S16 which calculates the
 three-dimensional coordinates of each spot. Step S17 performs the
 two-dimensional display of the monitored area. Step S18 takes in the
 steering angle value; step S19 predicts the path the vehicle will take;
 step S20 predicts collision with an obstacle; and step S21 displays the
 predictions before returning to step S13.
 The correction of the sensor height changes at step S12 is performed for
 the following reasons. To determine the three-dimensional position P.sub.B
 (X.sub.B, Y.sub.B, Z.sub.B), the distance h and the reference data
 including the three-dimensional coordinates on the image plane 4b are
 taken in. The reference data uses the coordinates when the vehicle is not
 loaded with heavy goods because the vehicle height h is the one measured
 when the car is not loaded. The reference data including the
 three-dimensional coordinates on the image plane 4b of each light spot
 that is on a flat road surface are stored in memory as reference values,
 which will be used for determining the actual positions of each light
 spot. When the vehicle is traveling on an uneven road surface, the actual
 three-dimensional coordinates of each light spot are determined based on
 the deviation of the light spot coordinates during the actual measurement
 from the reference values that were determined with no load carried.
 When the vehicle is used, it is loaded with passengers and goods, which
 might amount to several tens of kilograms to several hundred kilograms,
 weighing the vehicle down by several centimeters. The vehicle may not sink
 uniformly and may be inclined depending on the arrangement of the heavy
 goods.
 Since the vehicle surroundings monitor is fixed to the car body as shown in
 FIG. 4, the sinking of the vehicle makes the monitor come near the
 monitored area 4c of the road surface. In that case, when viewed from the
 vehicle surroundings monitor, the area 4c that was a distance h away from
 the CCD lens 4a rises upward by an amount equal to the vehicle sinking, so
 that the vehicle surroundings monitor decides that the road surface as a
 whole rises several centimeters. If the load carried is heavy, the amount
 of sinking is large causing the monitor to issue an erroneous alarm that
 there is a projecting object on the road which is high enough to be
 detrimental to normal running of the vehicle.
 To eliminate such inconveniences, it is necessary to measure the amount of
 road rising or the amount of vehicle sinking on an almost flat road
 surface with passengers and loads on board. For this purpose, as shown in
 FIG. 13, the amount of road rising for the monitored area is determined
 from the displacements of light spots 1, 2, 3, 4 at four corners of the
 monitored area. Based on the road rising value, it is possible to
 calculate the amount of rising of each light spot by linear approximation.
 The road surface rising thus detected occurred as a result of vehicle
 sinking and is used as a correction value in determining the
 three-dimensional coordinates of the actual uneven road surface.
 During the actual measurement, correction is made on the three-dimensional
 coordinates of the road surface determined from the light spots by using
 the correction value (by subtracting the correction value from the
 coordinates). Hence, accurate three-dimensional coordinates that are
 adjusted for the vehicle sinking can be obtained.
 In the above example, the correction values are calculated for the light
 spots 1-4 at four corners of the monitored area 4c. If the inclination of
 the vehicle is small when compared with the vehicle sinking, it is
 possible to determine the height of the road surface at only one point,
 for example, light spot 5 and use this height as the correction value for
 all light spots. In either case, the three-dimensional coordinates of
 light spots at several points on the flat road surface with passengers on
 board are used as vehicle sinking correction values during the actual
 measurement.
 The sensor height change correction processing at step S12 mentioned above
 is executed according to the flowchart of FIG. 14. In the flowchart of
 FIG. 14, when step S12a and S12b find that the door is closed and that the
 ignition switch is on, step S12c checks if the correction data retrieve
 switch is on. If the correction data retrieve switch is found not closed,
 the processing goes to step S12d which checks if the car speed is between
 5 km/h and 40 km/h.
 When the car is traveling at speed between 5 km/h and 40 km/h, step S12e
 calculates from the displacements of light spots at several points to see
 if the monitored area is flat. If the monitored area is found to be flat
 at step 12f, step S12g calculates the vehicle sinking correction data from
 the light spot displacements at several points. When the correction data
 retrieve switch is turned on and the decision of step S12c is "yes," the
 processing moves to step S12g to calculate the vehicle sinking correction
 data from the light spot displacements at several points. With the
 processing of the flowchart of FIG. 14 executed, the data processor 6
 works as a height correction means which corrects the reference data
 according to the changes in the camera height from the road surface.
 The correction values may be taken in by manual operation of switch after
 the driver has checked that the road is flat without an obstacle. The
 correction values may also be taken in automatically by the processor when
 the processor judges that the road surface detected by the monitor when
 the vehicle is traveling at such a low constant speed (5-40 km/h) that the
 air resistance does not affect the vehicle is almost flat. It is also
 possible to take in the correction values whenever the processor decides
 that the road surface is flat.
 The picture input processing at step S13 takes in the light spot projection
 image of the monitored area 4c as shown in FIG. 7. FIG. 8 shows the image
 signal output from the CCD camera 4 for one scanning line. Since the
 brightness of the light spots and the background are not uniform, the
 brightness threshold values for extracting the light spots are as
 indicated by the broken line (differing from one light spot to another).
 These threshold values are stored in memory as part of the reference data
 beforehand.
 The detection of changes in background brightness of the picture and the
 correction of the brightness threshold values, which are both performed at
 step S14, are carried out for the following reasons. When it is intended
 to check for any obstacles by taking the light spot projection image to
 determine the displacements of the light spots, it is first necessary to
 extract the light spots from the image taken in. At this time, if the
 monitored area 4c is illuminated by the brake lamp of the vehicle itself
 or headlights of other cars, the brightness distribution changes as shown
 in FIG. 15, making it impossible to extract the light spots with the
 preset brightness threshold values. This results in an inability to detect
 obstacles or large detection errors.
 To eliminate such troubles, when the light spot projection image is taken
 in to determine the displacements of the light spots, the brightness of
 the pixels prerecorded in the reference data that correspond to the
 background position are determined. Next, from the background brightness
 at several points thus determined, correction coefficients for the
 brightness threshold values are calculated. Based on these correction
 coefficients, the brightness threshold values in the reference data are
 corrected to extract the light spots.
 To describe in more detail by referring to FIG. 16, let us consider the
 upper left corner light spot and the lower right corner light spot in the
 monitored area 4c. On the basis of the brightness data of the pixels
 (marked x), which are considered the background of the two light spots,
 the correction coefficient A (brightness gradient in the direction of
 u-axis) is determined as indicated by equation (1). The brightness
 threshold values for individual light spots recorded in the reference data
 are corrected by equation (2).
 ##EQU1##
 Th'.sub.(i) =Th.sub.(i) +A.multidot.(u.sub.(i) -u.sub.LU)+(I.sub.LU
 -I.sub.BK) (2)
 where

A: correction coefficient;
 u.sub.LU : u coordinates of a specified pixel around
 the light spot at the upper left corner of
 the monitored area;
 I.sub.LU : brightness of a specified pixel around the
 light spot at the upper left corner of the
 monitored area;
 u.sub.RL : u coordinates of a specified pixel around
 the light spot at the lower right corner
 of the monitored area;
 I.sub.RL : brightness of a specified pixel around the
 light spot at the lower right corner of
 the monitored area;
 Th'.sub.(i) : brightness threshold value of an i-th
 light spot after being corrected;
 brightness threshold value of an i-th
 light spot before being corrected;
 Th.sub.(i) : brightness threshold value of an i-th
 light spot after being corrected;
 u.sub.(i) : u coordinates of an i-th light spot; and
 I.sub.BK : background brightness when the refer-
 ence data is retrieved.
 With the step S14 mentioned above executed, the data processor 6 determines
 the difference between the background brightness and the corresponding
 reference data on the basis of the pixel data, which was produced from the
 picture signal from the camera that photographed the light spot pattern
 projected onto the monitored road surface. Based on the background
 brightness difference thus obtained, the data processor 6 then corrects
 the brightness threshold values used for extracting the light spots.
 The extraction of the displaced spots performed at step S15 is carried out
 for each light spot by using the corrected brightness threshold values Th'
 that are determined for each light spot. Step S16 determines the
 displacement of each light spot by using the coordinates of the extracted
 light spots and the reference data of the light spot coordinates and
 calculates the three-dimensional positions of the obstacle. The
 calculation of the correction coefficient at step S14 may utilize the
 common interpolation. The correction may use the background brightness
 data of the points located around the light spots to increase the
 precision though it requires a longer processing time.
 The baricenter coordinates of the light spots thus extracted are determined
 from the pixels making up each of the light spots to determine the light
 spot coordinates on the image plane 4c. The calculation of the light spot
 coordinates can be applied both to determining the reference value of the
 flat road surface and to calculating the three-dimensional coordinates of
 the actual uneven road surface. The calculation of the light spot
 coordinates requires data of all pixels (for example 512.times.512 pixels)
 from the CCD camera. and therefore takes time. This means that while the
 light spot coordinates calculation does not pose any problem in
 determining the reference values for the flat road, it has the
 disadvantage of being slow in performing the actual monitoring.
 In the geometrical layout shown in FIGS. 3 and 4, the light spot
 coordinates B (u, v+.delta.) on the image plane 4b in the case of an
 uneven road move only in a certain direction with respect to a point A (u,
 v) for the flat road. As shown in the figure, the light spot moves only in
 the direction of v. When the road surface bulges, the light spot moves in
 the direction of positive v and, when it recesses, moves in the direction
 of negative v. By making use of this characteristic, it is possible to
 speed up the calculation of the three-dimensional coordinates as described
 below.
 In FIG. 18, A (u, v) represents a point on the image plane 4b that
 corresponds to a certain light spot on the flat road. The frame F
 indicates the area to be scanned during the three-dimensional coordinates
 measuring process. The sub-areas +S.sub.1, -S.sub.2 can be set arbitrarily
 according to the magnitude of the projections and depressions on the
 actual road. For example, in the case of passenger cars, the setting may
 be 1.5 m above the flat road surface and 0.5 m below the surface, and
 +S.sub.1 and -S.sub.2 can be set accordingly. It is noted that all the
 points shown in the figure represent the baricenter positions of the light
 spots. The distances in the direction of v between the adjacent light
 spots are so set that the light spots will not overlap each other when
 they move under the conditions mentioned above. They are arranged
 staggered in the direction of u for effective utilization of space.
 During the measuring process, it is necessary to determine the light spot
 coordinates only in the scan area mentioned above. The light spot
 coordinates can be obtained by assuming that the pixels with brightness
 higher than the specified threshold value make up the light spot and by
 calculating the baricenter or geometric center of the light spot.
 This is detailed in the following. As shown in FIG. 17, on the same line as
 the light spot baricenter of the reference data, V.sub.1 and V.sub.2 are
 detected. The light spot baricenter (V.sub.1 +V.sub.2)/2 is calculated to
 determine the amount of movement .DELTA.V, which is the distance between
 the two baricenters. If there is no light spot on the same line, the
 adjacent line, one level up or down, is scanned. V.sub.1 and V.sub.2 are
 detected by comparing the brightness of pixels with the brightness
 threshold value I. The scan region W may be one pixel line wide or
 multiple lines wide, for example, five pixel lines wide for better
 detection precision. While the above example uses a geometric center as
 the baricenter to increase the detection speed, it is however better to
 use the baricenter coordinates detection method, which was used in
 generating the reference data, to improve precision.
 As explained above, since the method of this invention requires calculation
 of the light spot coordinates only in the set scan region, the speed of
 the measuring process can be increased.
 FIG. 19 shows an example display on the display device 10 that shows the
 result of detecting the three-dimensional positions of light spots when
 there are a wall and a ditch in the monitored area 4c. In the figure,
 O.sub.1 is a wall and O.sub.2 a ditch.
 Next, we will describe the method of monitoring by using the steering angle
 sensor 8. In the embodiment, the path the automobile will take is
 predicted by using the steering angle detected by the steering angle
 sensor 8. The predicted path or route is superimposed on a two-dimensional
 map of the monitored area 4c showing obstacles to predict a possible
 contact or collision of the car body with obstacles. Upon detection of a
 possible contact or collision, an alarm is sounded from a buzzer or an
 alarm message which is generated by a voice synthesizing means in the data
 processor 6 is issued. The alarm may also be displayed on the display
 device 10 to alert the driver.
 FIG. 20 shows one example display on the display device 10 showing the
 point at which the edge of the car body Bo will come into contact with an
 obstacle like a wall O.sub.1 and the point at which the tire T falls into
 a ditch O.sub.2. While the car is moving back, the data processor 6
 processes the images supplied successively from the CCD camera 4 so that
 the obstacle O.sub.1 and the ditch O.sub.2 in the monitored area 4c are
 detected in real time, as shown in FIG. 20. Based on the predicted path
 the car will take, which is predicted from the steering angle from the
 steering angle detector 8, a possible contact with an obstacle is alerted
 to the driver beforehand, thus effectively helping the driver in assuring
 safety.
 While the above embodiment uses a steering angle detection signal supplied
 from the steering angle detector 8 in predicting the path of the car, it
 is possible to use a rotary angle speed sensor or a direction sensor
 consisting of a gyro and process signals from these sensors to predict the
 path the car will take.
 In the above embodiment we have described a case where the car driver is
 informed of the presence of obstacles or ditches in the monitored area.
 This invention, however, can also be applied to unmanned transport cars in
 factories and industrial robots in assembly lines.
 As mentioned in the foregoing, with this invention it is possible to
 quickly detect the presence of obstacles or ditches in the surrounding of
 the vehicle. Not only does the apparatus of this invention display the
 sizes and positions of the obstacles or ditches but it also predicts and
 indicates the location at which the car will contact or strike the
 obstacle or its tire will fall in the ditch. This provides the driver with
 sufficient information to ensure safety in driving. Particularly when
 there is not enough lighting on the monitored area during nighttime, this
 invention provides a better means for checking safety than a simple visual
 check.
 Another advantage of this invention is that even when the car is weighed
 down by passengers or heavy goods, the monitoring apparatus of the
 invention can precisely detect obstacles or ditches. Furthermore, when the
 monitored area is illuminated by brake lamps and its brightness increases,
 the apparatus has a means to prevent erroneous detection of light spots.
 A further advantage is that upon detection of an obstacle the size and
 position of the obstacle is shown on the display device with or without an
 alarm buzzer sound. At the same time, the apparatus predicts the path the
 car will take and shows on the display device the location where the car
 will contact or collide with the obstacle to alert the driver.