Abstract:
The invention provides an object recognition apparatus that removes virtual images without detecting a roadside object. When a predetermined vehicle is currently running on a lane, a detection area, outside of the currently running lane, is designated to include a first area and an assumed ghost area therein. The first area is enclosed by a boundary of the detection area, a boundary of the assumed ghost area adjacent thereto, and a boundary on the currently running lane whose distance is traveled by the vehicle during one control cycle. The invention detects an object for the first time in the assumed ghost area, not in the first area. When the object travels with a distance and a speed of a target vehicle, it is determined to be a ghost to be deleted.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to an object recognition apparatus and method thereof and a radar apparatus and method thereof that recognize an object in front of a predetermined vehicle, and more particularly to an object recognition apparatus and method thereof and a radar apparatus and method thereof, which prevent misrecognition of virtual images produced by reflection of roadside objects.  
           [0003]    2. Description of the Related Art  
           [0004]    [0004]FIG. 1 is a diagram for illustrating how a ghost is detected by a radar apparatus in the prior art. In the past, a radar apparatus is known that transmits radar waves to an object ahead and, using waves reflected by the object, measures a distance and a relative velocity to the object. The radar apparatus on a predetermined vehicle  100 , as shown in FIG. 1, is able to make a correct recognition of a distance and a relative velocity of a target vehicle  200  when it directly receives waves reflected by the target vehicle  200  ahead (a route {circle over ( 1 )} shown in FIG. 1). However, when there exists a roadside object  300  such as a guard rail, tunnel wall, or windbreak wall, and the waves from the target vehicle  200  are reflected by the roadside object  300  (a route from {circle over ( 2 )} to {circle over ( 3 )} shown in FIG. 1), the radar apparatus makes an erroneous recognition as if the waves were reflected outside of the roadside object  300  (a route from {circle over ( 2 )}′ to {circle over ( 3 )} shown in FIG. 1), and detects a virtual image of a vehicle that is not really existent, that is, a ghost  210 . This gives rise to a problem.  
           [0005]    As one technique to overcome the problem, there is Japanese Patent Application Laid-open No. 2001-116839. The Japanese Application discloses an invention by which a line having a width of three lanes around a lane on which a vehicle is currently running is designated as a basic line. When three of a series of stationary objects, for example, projectors (reflectors) continuously put on guardrails, are detected inside of the basic line, a new line consisting of a series of projectors is produced as a new basic line. When there exists an object outside of the basic line, the object is decided to be a ghost, which is to be deleted.  
           [0006]    The radar apparatus in the prior art may sometimes fail to recognize the roadside object  300 . A frequency modulated continuous wave (FMCW) radar apparatus, for example, receives reflected waves, but cannot know from where in the roadside object  300  the received waves are reflected when the roadside object  300  does not have a series of projectors. As a result, a combination of FFT power spectral peaks cannot be determined, which fails to recognize the roadside object  300 .  
           [0007]    In the technique disclosed in Japanese Patent Application Laid-open No. 2001-116839, when the roadside object  300  is not recognized, the ghost  210  may sometimes be erroneously detected. For example, when a vehicle is running on a lane having the roadside object  300  and two or more of a series of projectors cannot be detected, a line having a width of three lanes is designated as a basic line. Since the ghost  210  produced outside of the roadside object  300  are present inside of the basic line, it is recognized erroneously as a correct target, which is a problem.  
           [0008]    As mentioned above, since the radar apparatus in the prior art gives rise to the problems, there is a need to resolve the problem.  
         SUMMARY OF THE INVENTION  
         [0009]    The invention is directed to an apparatus and method that satisfy the need. The invention provides an object recognition apparatus and method thereof and a radar apparatus and method thereof that can recognize a virtual image without detecting a roadside object. The radar apparatus uses radar waves for detection of an object, while the object recognition apparatus and method thereof are related to lasers and infrareds for detection of an object.  
           [0010]    One aspect of the invention involves an object recognition apparatus. The apparatus comprises a judgment unit for judging whether an object is detected on a lane other than a lane on which a predetermined vehicle is currently running, an adjacent lane judgment unit for judging whether an adjacent lane exists adjacent to the currently running lane, and a recognition unit for recognizing that the object is a virtual image when the judgment unit has judged that the object is detected and the adjacent lane judgment unit has judged that the adjacent lane does not exist.  
           [0011]    According to the invention, although the adjacent lane does not exist, when the object like a vehicle on a lane other than the currently running lane, for example, a lane adjacent to the currently running lane is detected, it is judged that the object is a virtual image.  
           [0012]    Though there is no adjacent lane adjacent to the currently running lane, when the object like a vehicle is detected adjacent to the currently running lane, the invention judges that the object is a virtual image  
           [0013]    Advantageously, the adjacent lane judgment unit designates a first area where a vehicle running on the adjacent lane at a predetermined relative speed with respect to the predetermined vehicle is detected at least once, and a second area that is outside of the currently running lane and does not overlap the first area, and when the object is detected for the first time in the second area, not in the first area, judges that the adjacent lane is not existent.  
           [0014]    Since the first area is designated as an area where a vehicle running on the adjacent lane at a predetermined relative speed with respect to the predetermined vehicle is detected at least once, when there is an adjacent lane, the object is usually detected in the first area. Accordingly, when the object is detected for the first time in the second area, not in the first area, it is judged that the adjacent lane is not existent, and that the object is a virtual image.  
           [0015]    When a vehicle on the adjacent lane is running at a speed more than a predetermined relative speed, since the vehicle can be detected for the first time in the second area, not in the first area, the vehicle is erroneously judged to be a virtual image.  
           [0016]    Advantageously, when a first object has been detected in the second area for the first time, not detected in the first area, but a second object having the same distance and relative speed as the first object has not been detected on the currently running lane, the recognition unit does not recognize the first object as a virtual image. The recognition can be done because when a virtual image is produced, there always exists on the currently running lane an object that has the same distance and relative speed as a virtual image. The recognition leads to more precise judgment as to whether or not the object is the virtual image.  
           [0017]    Advantageously, the apparatus further comprises a stationary object line judgment unit for judging whether a stationary object line is detected having a plurality of stationary objects, wherein when the stationary object line judgment unit has judged that the stationary object line is detected, the recognition unit recognizes as a virtual image an object detected outside of the stationary object line. As a result, a erroneous recognition of virtual images can be prevented.  
           [0018]    Advantageously, when a virtual image is detected outside of the stationary object line, but a vehicle ahead is not detected that runs on the currently running lane at the same distance and relative speed as the virtual image, the recognition unit estimates a distance and a relative velocity of the vehicle ahead based on the virtual image.  
           [0019]    Advantageously, the recognition unit estimates a distance and a relative velocity of the virtual image as the distance and the relative velocity of the vehicle ahead.  
           [0020]    Advantageously, the recognition unit designates an area, based on the distance and the relative velocity of the virtual image, where the vehicle ahead is estimated to exits in the past, and, when the vehicle ahead is detected in the designated area, estimates a distance and a relative velocity of the vehicle ahead during a present control cycle, based on the distance and the relative velocity of the vehicle ahead detected in the past.  
           [0021]    As mentioned above, a virtual image is recognized outside of the stationary object line, it is presumed that there is a vehicle ahead on the currently running lane that runs at the same distance and relative velocity as those of the virtual image. However, thought a virtual image is recognized outside of the stationary object line, when a vehicle ahead, which produces, is not detected on the currently running lane, it is considered that the vehicle ahead on the currently running lane is lost. Accordingly, based on the virtual image recognized outside of the stationary object line, the lost vehicle ahead is extrapolated, which enables the object on the currently running lane to be precisely recognized without being lost.  
           [0022]    One aspect of the invention involves a radar apparatus for use on a vehicle. The apparatus comprises a transmitter for transmitting waves to an object ahead, a receiver for receiving the waves reflected by the object, a judgment unit, based on a signal from the receiver, for judging whether the object is detected on a lane other than a lane on which the vehicle is currently running, an adjacent lane judgment unit for judging whether an adjacent lane exists adjacent to the currently running lane, and a recognition unit for recognizing that the object is a virtual image when the judgment unit has judged that the object is detected and the adjacent lane judgment unit has judged that an adjacent lane does not exist. The radar apparatus has the same advantages as the object recognition apparatus does.  
           [0023]    One aspect of the invention involves a method of recognizing an object. The method comprises judging whether an object is detected on a lane other than a lane on which a vehicle is currently running judging whether an adjacent lane exists adjacent to the currently running lane, and recognizing that the object is a virtual image when the object is detected and the adjacent lane does not exist.  
           [0024]    One aspect of the invention involves a method of recognizing an object by the use of a radar apparatus on a vehicle. The method comprises transmitting waves to an object ahead, receiving the waves reflected by the object, based on a signal from the receiver, judging whether the object is detected on a lane other than a lane on which the vehicle is currently running, judging whether an adjacent lane exists adjacent to the currently running lane, and recognizing that the object is a virtual image when the judgment unit has judged that the object is detected and the adjacent lane judgment unit has judged that an adjacent lane does not exist.  
           [0025]    One aspect of the invention involves a method of recognizing an object by the use of a radar apparatus on a vehicle that can detect a range of velocities and have a detection period. The method comprises establishing a detection area in a traveling direction of the vehicle that is currently running on a lane, for detecting an object by radar waves of the radar apparatus, establishing a first area within the detection area on an adjacent lane adjacent to the currently running lane, the first area designated by a distance decided by a maximum velocity of the detection range and the detection period, establishing a second area within the detection area, not overlapping the first area, and detecting the object for the first time in the second area, not in the first area, whereby the object is judged to be a ghost.  
           [0026]    Advantageously, the distance is decided by multiplying the maximum velocity of the detection range by the detection period.  
           [0027]    One aspect of the invention involves a method of recognizing an object by the use of a radar apparatus on a vehicle that can detect a range of velocities and have a detection period. The method comprises establishing a detection area in a traveling direction of the vehicle that is currently running on a lane, for detecting an object by radar waves of the radar apparatus, establishing a first area within the detection area on an adjacent lane adjacent to the currently running lane, the first area designated by a distance decided by a maximum velocity of the detection range and the detection period, establishing a second area within the detection area, not overlapping the first area, detecting the object for the first time in the second area, not in the first area, and detecting a target vehicle that runs at the same distance and relative velocity of those of the object, whereby the object is judged to be a ghost.  
           [0028]    Advantageously, the distance is decided by multiplying the maximum velocity of the detection range by the detection period. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    These and other features of the invention will now be described with reference to the drawings summarized below. These drawings and the associated description are provided to illustrate preferred embodiments of the invention, and not to limit the scope of the invention.  
         [0030]    [0030]FIG. 1 is a diagram for illustrating how a ghost is detected by a radar apparatus in the prior art.  
         [0031]    [0031]FIG. 2 is a block diagram for illustrating an entire structure of a FMCW apparatus in accordance with one embodiment of the invention.  
         [0032]    [0032]FIG. 3 is a diagram for illustrating how an assumed ghost area is designated in accordance with one embodiment of the invention.  
         [0033]    [0033]FIG. 4 is a flowchart of entire process in accordance with the embodiment of the invention.  
         [0034]    [0034]FIG. 5 is a flowchart of ghost judgment process when a roadside object is recognized.  
         [0035]    [0035]FIG. 6 is a flowchart of ghost judgment process when a roadside object is not recognized.  
         [0036]    [0036]FIG. 7 is a flowchart of extrapolation process when a target vehicle is lost.  
         [0037]    [0037]FIG. 8 is a diagram for illustrating how a ghost area is designated.  
         [0038]    [0038]FIG. 9 is a diagram for illustrating how a real target area is designated when a target vehicle is lost.  
         [0039]    [0039]FIG. 10 is a diagram for illustrating how an assumed ghost area is designated.  
         [0040]    [0040]FIG. 11 is a diagram for illustrating how another assumed ghost area is designated.  
         [0041]    [0041]FIG. 12 is a diagram for illustrating how still another assumed ghost area is designated. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]    [0042]FIG. 2 is a block diagram for illustrating an entire structure of a FMCW (frequency modulated continuous wave) apparatus  1  in accordance with one embodiment of the invention. The FMCW apparatus  1  includes a transmitting and receiving unit  10  for transmitting and receiving radar waves, and a signal process unit  20  connected to the transmitting and receiving unit  10  for executing process of detecting an object. The signal process unit  20  provides a modulating signal Sm to and receives a beat signal B 1  from the transmitting and receiving unit  10 . The unit  10  includes a transmitter  12  for transmitting to an object (not shown) radar waves modulated at a predetermined frequency according to the modulating signal Sm, and a receiver  14  for receiving the radar waves reflected by the object.  
         [0043]    The transmitter  12  includes a modulator  12   a  connected to the signal process unit  20  for converting the modulating signal Sm to a predetermined level, a VCO (voltage controlled oscillator)  12   b  connected to the modulator  12   a  for generating high frequency signals of a millimeter wave band, a coupler  12   d  connected to the VCO  12   b  for distributing a transmission signal from the VCO  12   b  and generating a local signal, and a transmission antenna  12   e  connected to the coupler  12   d  for radiating radar waves according to the transmission signal. The transmission antenna  12   e  is mechanically scanned to a car width to designate a direction of an object ahead.  
         [0044]    The receiver  14  includes a receiving antenna  14   a  for receiving the radar waves radiated by the transmission antenna  12   e  and reflected back by the object, a mixer  14   b  connected to the receiving antenna  14   a  and the coupler  12   d  for mixing a reception signal from the receiving antenna  14   a  with the local signal from the coupler  12   d,  a pre-amplifier  14   c  connected to the mixer  14   b  for amplifying an output signal from the mixer  14   b,  a low pass filter (LPF)  14   d  connected to the pre-amplifier  14   c  for eliminating unnecessary higher frequency components of an output of the pre-amplifier  14   c  and deriving a beat signal that is a frequency difference between the transmission signal and reception signal, and a post-amplifier  14   e  connected to the LPF  14   d  for amplifying the beat signal to a predetermined signal level.  
         [0045]    The signal process unit  20  has a microcomputer  26 , a triangular wave generator  22  connected to the microcomputer  26  for generating the modulating signal Sm of triangular wave in response to a control signal C 1 , an analog to digital converter (A/D converter)  24   a  connected to the microcomputer  26  for converting the beat signal B 1  from the receiver  14  to digital data D 1  in response to a control signal C 2 , and an operational process unit  28  connected to the microcomputer  26  for executing operation of the Fast Fourier Transform (FFT) under the instructions from the microcomputer  26 . The microcomputer  26  includes a CPU (central processing unit)  26   a,  a ROM (read only memory)  26   b,  and a RAM (random access memory), sends out the control signals C 1  and C 2  to activate the triangular wave generator  22  and the A/D converter  24   a,  respectively, and calculates a distance and a relative speed of an object based on the digital data D 1  obtained from the A/D converter  24   a.  The CPU  26   a  functions as an object recognition apparatus in the invention.  
         [0046]    The embodiment is explained with respect to a system for mechanically scanning radar waves. However, a system for electronically scanning radar waves such as a digital bean forming system (DBF) can also be used.  
         [0047]    In a case where a roadside object  300  (corresponding to a stationary object line in the invention) is not recognized, an explanation will be given for a method of judging whether or not a ghost  210  exists. According to one embodiment of the invention, in a detection area, a first area and a second area (called “assumed ghost area” hereinbelow) are designated. The first area is an area where a vehicle running on an adjacent lane at a relative speed with respect to a predetermined vehicle can at least once be detected. The assumed ghost area is defined to be an area that is different from the first area in the detection area. An object not detected in the first area and detected in the assumed ghost area for the first time is judged to be a ghost.  
         [0048]    [0048]FIG. 3 is a diagram for illustrating how an assumed ghost area is designated in accordance with one embodiment of the invention. A predetermined vehicle  100  having a radar apparatus (not shown) is currently running on a lane  500 . There are two adjacent lanes  700  adjacent to the currently running lane  500 . The radar apparatus has a detection area  120  where an object can be detected. The detection area  130  has a side boundary  110  and a front boundary  130 .  
         [0049]    Assuming that the range of speeds detected by the radar apparatus on the predetermined vehicle  100  is given as Vmin to Vmax, and that a period of a detection cycle (control cycle) for detecting an object by the radar apparatus is designated as ΔT, the distance D the predetermined vehicle  100  runs during one period is calculated by D=Vmax×ΔT.  
         [0050]    The detection area  130  includes a first area  400  and an assumed ghost area  40 . The first area  400  is defined to be an area enclosed by the side boundary  110  of the detection area  120 , the distance D on a boundary between the currently running lane  500  and the adjacent lane  700 , a middle boundary  600  parallel to the side boundary  110  by the distance D apart in a traveling direction of the predetermined vehicle  100 , and the front boundary  130 . The assumed ghost area  40  is an area other than the first area  400  and the currently running lane  500  in the detection area  120 .  
         [0051]    Maximum relative speeds, usually set with respect to the predetermined vehicle  100 , are an ordinal value that vehicles can take. For example, a maximum relative speed can be a difference between a legal maximum speed and a legal minimum speed, and another speed derived by adding to the difference a predetermined speed such as a speed for passing another vehicle. When a navigation system is available that can distinguish roads from freeways, a value to be set can be variable on a road or a freeway.  
         [0052]    The first area  400  mentioned above is set to judge whether or not adjacent lanes  700  are existent. That is, when an adjacent lane  700  is existent, an object detected on the adjacent lane  700  is usually detected once in the first area  400 . This is because the first area  400  is designated as an area where a vehicle running at a maximum relative speed with respect to the predetermined vehicle can be detected once during one detection cycle. Therefore, when an object is detected in the assumed ghost area  40  for the first time, not detected in the first area  400 , it is judged that adjacent lanes  700  are not existent. In spite of the fact that adjacent lanes  700  are not existent, when an object like a vehicle is detected in the assumed ghost area  40 , the object is decided to be a ghost.  
         [0053]    To improve an accuracy of ghost judgment, not deciding that all the object detected for the first time in the assumed ghost area  40  are a ghost, only when a target vehicle  200  is present that runs at the same distance and relative speed as the object, the object may be judged as a ghost  210 .  
         [0054]    FIGS.  4 - 7  are flowcharts of the process for judging a ghost mentioned above in accordance with the embodiment of the invention. The flowcharts are executed at a control cycle of 100 msec by the CPU  26   a  of the microcomputer  26 .  
         [0055]    [0055]FIG. 4 is a flowchart of the entire process in accordance with the embodiment of the invention. Referring to FIG. 4, process of recognizing an object and transmitting data of a distance and a relative speed to a car space electronic control unit (ECU) (not shown) will be explained. At step  100 , data is received from the ECU. The data includes vehicle speed data used for judging whether an object is moving or stationary, and steering angle data used for calculating estimation R.  
         [0056]    Step  200 , applying the control signal C 1  to the triangle wave generator  22  generate a modulating signal Sm, which enables frequency modulated radar waves to be transmitted via the transmission antenna  12   e  in the transmitter  12 .  
         [0057]    At step  300 , the receiver  14  receives reflected waves from the object ahead to produce the beat signal B 1 , which is converted to digital data by the A/D converter  24   a  to be written into the RAM  26   c.    
         [0058]    At step  400 , applying the control signal C 1  to the triangle wave generator  22  is stopped, which stops sending frequency modulated radar waves.  
         [0059]    In step  500 , the beat signal B 1  is applied to the operation process unit  28  where frequency analysis is executed. As a result of the execution, at each of the rising and falling portions of the frequency modulated radar waves, a complex vector is obtained for each frequency.  
         [0060]    At step  600 , based on the absolute values of the complex vectors, that is, the amplitudes of the frequency components of the complex vector, all of the frequency components are detected that show a peak on frequency spectra. The frequency is designated as a peak frequency.  
         [0061]    At step  700 , a peak frequency regarded as reflected waves from the same object is designated among the peak frequencies of the rising and falling portions obtained at step  600 . Since making pairs is the same as before, no particular explanation of it is given.  
         [0062]    At step  800 , based on peak frequencies of the rising and falling portions designated at step  700 , a distance, a relative frequency and a position of the object are calculated to recognize the object.  
         [0063]    At step  900 , with regard to the object designated, ghost determination process is executed (a particular explanation will be made hereinbelow).  
         [0064]    At step  1000 , an object is selected for car space control (space means room between cars). As a method of selection, estimate R is calculated from steering angle data to obtain probabilities of the currently running lane. The object having a higher probability should be selected.  
         [0065]    At step  1100 , the distance, the data of the relative frequency and the position of the object selected are transmitted to the ECU.  
         [0066]    FIGS.  5 - 7  will be used to explain a subroutine for ghost judgment process of step  900 . At step  910 , it is judged whether or not the roadside object  300  is recognized. When three or more of a series of projections positioned on a guardrail are detected, it is judged that the roadside object  300  is recognized. When it is judged that the roadside object  300  is not recognized, the process goes to {circle over ( 1 )}.  
         [0067]    [0067]FIG. 5 is a flowchart of the ghost judgment process when the roadside object  300  is recognized. The process of {circle over ( 1 )} shows whether or not an object is the ghost  210  when the roadside object  300  is not recognized. At step  912 , it is judged whether or not an object is detected in the assumed ghost area  40  designated beforehand. When it is judged that the object is detected, the procedure goes to step  914 .  
         [0068]    At step  914 , it is judged whether or not the object detected in the assumed ghost area  40  is a newly appeared object. That is, when the object is detected for the first time in the assumed ghost area  40  without being detected in the first area  400 , it is judged that a new object has appeared, which is followed by step  916 .  
         [0069]    At step  916 , it is judged whether or not a distance and a relative velocity of the new object are identical to those of the target vehicle  200 , which is defined to be a vehicle to be controlled as a subject of car space control where the space means room between cars. The judgment is performed because when a new object is the ghost  210 , it always runs at the same distance and relative velocity of the target vehicle  200 . When it is judged that the distance and the relative velocity of the new object are identical to those of the target vehicle  200 , the procedure goes to {circle over ( 3 )}, where at step  960  the new object is judged to be the ghost  210 . Then the procedure goes to step  970  where the ghost  210  is deleted.  
         [0070]    When any one of steps  912 - 916  is judged to be negative, the procedure goes to {circle over ( 5 )} to end the subroutine.  
         [0071]    At step  910 , when it is judged that the roadside object is detected, the procedure proceeds to step  930 , where it is judged whether or not the target vehicle  200  is detected on the currently running lane  500 . When it is judged that the target vehicle  200  is detected on the currently running lane  500 , the procedure proceeds to step  932 .  
         [0072]    [0072]FIG. 8 is a diagram for illustrating how a ghost area  220  is designated. At step  932 , the ghost area  220  is designated as shown in FIG. 8. The ghost area  220  is defined as an area larger than one vehicle by a predetermined amount positioned at a position symmetrical to the target vehicle  200  around the roadside object  300 .  
         [0073]    At step  934 , it is judged whether or not an object is found in the ghost area  220 . At step  936 , it is judged whether or not the object has newly appeared in the ghost area  220 . At step  938 , it is judged whether or not the distance and the relative velocity of the object are identical to those of the target vehicle  200 . When all of steps  934 - 938  are judged to be affirmative, at step  960  it is determined that the object is the ghost  210 , followed by step  970  where the ghost  210  is deleted. On the other hand, any one of steps  934 - 938  is judged to negative, the subroutine ends.  
         [0074]    At step  930 , when it is judged that the target vehicle  200  is not existent on the currently running lane  500 , the procedure goes to {circle over ( 2 )}.  
         [0075]    [0075]FIG. 7 is a flowchart of extrapolation process when the target vehicle  200  is not detected although the ghost  210  is detected. The procedure at {circle over ( 2 )} starts the extrapolation process. The extrapolation process is necessary because since reflection intensity from the roadside object  300  is larger than that from the target vehicle  200 , peaks of the FFT power spectra of the waves reflected from the target vehicle  200  are buried in the FFT power spectra of the waves reflected from the roadside object  300 . Accordingly, the extrapolation process should be executed as explained below.  
         [0076]    At step  948 , it is judged whether or not an object is detected outside of the roadside object  300 . When it is judged that an object is not detected outside of the roadside object  300 , the procedure proceeds to {circle over ( 4 )}, where the subroutine ends. When, on the contrary, it is judged that an object is detected outside of the roadside object  300 , the procedure proceeds to  950 .  
         [0077]    At step  950 , it is determined that the object detected outside of the roadside object  300  is an assumed ghost. Here the object is determined to be an assumed ghost, not a ghost, because since the target vehicle  200  does not exist that runs with the object detected outside of the roadside object  300 , it can not be distinguished whether the object is the ghost  210  or a noise.  
         [0078]    [0078]FIG. 9 is a diagram for illustrating how a real target area  230  is designated when the target vehicle  200  is lost. At step  952 , the real target area  230  is designated based on an assumed ghost  211  as shown in FIG. 9. At step  954 , an area of the real target area  230  in a previous control cycle is calculated.  
         [0079]    At step  956 , it is judged whether or not the target vehicle  200  is detected in the predicted real target area  230  during the previous control cycle. That is, when position data, etc. of the target vehicle  200  recognized during the previous control cycle are stored in the RAM  26   c , it is judged whether or not the target vehicle  200  is recognized in the predicted real target area  230 . When it is judged that the target vehicle  200  is recognized in the predicted real target area  230 , the extrapolation process should be executed since the target vehicle  200  is lost.  
         [0080]    At step  958 , a distance and a relative velocity of the target vehicle  200  during a present control cycle are estimated based on the distance and the relative velocity of the target vehicle  200  during the present control cycle. The target vehicle  200  having the estimated distance and relative velocity is established in the real target area  230  (extrapolation process), followed by step  960 . Moreover, the relative speed for the extrapolation process, when an acceleration of the target vehicle  200  during the previous control cycle is known, is estimated based on the acceleration. In addition, the distance and the relative velocity during the previous control cycle may be estimated for extrapolation as the distance and the relative velocity of the lost the target vehicle  200 . The distance and the relative velocity of the assumed ghost  211  may also be estimated for extrapolation as the distance and the relative velocity of the lost the target vehicle  200 .  
         [0081]    At step  960 , the object judged as the assumed ghost  211  is determined as a real ghost  210 , followed by step  970  where the ghost  210  is deleted.  
         [0082]    At step  956 , on the contrary, when it is judged that the target vehicle  200  is not recognized in the real target area  230  during the previous control cycle, the procedure goes to step  959  where the assumed ghost  211  is deleted as a noise, not the ghost  210 . The procedure goes to {circle over ( 5 )} to end the subroutine.  
         [0083]    According to the embodiments of the invention, an object, which is detected for the first time in the assumed ghost area  40 , not in the first detection area  400  established beforehand, may be deleted as a ghost  210 , if the object runs at the same distance and relative speed as those of the target vehicle  200 . As a result, a false detection of a ghost  210  can be prevented, without recognizing a roadside object  300 .  
         [0084]    In a case where it is judged that a roadside object  300  is detected, a ghost area  220  is established outside of (adjacent to a currently running lane) a roadside object  300 . When an object is newly detected in the ghost area  220  and runs at the same distance and relative speed as those of a target vehicle  200 , the object is judged as a ghost  210  to be deleted. As a result, a false detection of a ghost  210  can be prevented.  
         [0085]    Even if only a ghost  210  is detected, when a target vehicle  200  is recognized in a predicted real target area  230  during a previous control cycle, extrapolation process should be executed. Accordingly, the target vehicle  200  can be detected without fail.  
         [0086]    A first area  400  as mentioned before is shown in FIG. 3. However, the shape of the first area  400  is not limited to the one in FIG. 3. That is, the shape of the first area  400  can be any shape, as long as the first area can be established which is outside of a currently running lane  500  and in which a vehicle running at a maximum relative velocity with respect to a predetermined vehicle  100  can be detected during one control cycle.  
         [0087]    [0087]FIG. 10 shows a second example of the shape of a first area. There are provided a side boundary  110  of a detection area  120 , and a middle boundary  610  that make a predetermined angle  130  with the side boundary  110 . A first area  410  is an area enclosed by the side boundary  110 , the middle boundary  610 , and an edge portion of the detection area  120 . The middle boundary  610  is defined to pass a point away from a center  111  of an adjacent lane (the center  111  is a position away from a center of a predetermined vehicle  100  by a lane width) by the distance D to a traveling direction of the predetermined vehicle  100 . An assumed ghost area is shown by reference numeral  40 .  
         [0088]    [0088]FIG. 11 shows a third example of the shape of a first area. A center point  111  is in an adjacent lane on a side boundary  110  of a detection area  120 . A middle boundary  620  is drawn vertically to a currently running lane  500  through a position away from the center point  111  by the distance D. A first area  420  is defined to be an area enclosed by the side boundary  110 , the middle boundary  620 , and the currently running lane  500 . An assumed ghost area is shown by reference numeral  40 .  
         [0089]    [0089]FIG. 12 shows a fourth example of the shape of a first area. In FIGS. 3, 10 and  11  when a vehicle running on the adjacent lane  700  outside of the detection area  120  comes into the detection area  120 , a vehicle is detected for the first time in the assumed ghost area  40 . Therefore, a vehicle that is really existent tends to be judged a ghost. Accordingly, as shown in FIG. 12, a first area  430  can be established in a front portion of the detection area  120 . The first area  430 , for example, is set as an area enclosed by a front boundary  112  of the detection area  120 , a parallel boundary  605  shifted in parallel to the front boundary  112  by the distance D, a middle boundary  600 , and a currently running lane  500 .  
         [0090]    A first area and an assumed ghost area may be established on one side of a currently running lane. For example, as for roads in Japan, since ghosts tend to appear on a left side of the currently running lane, an assumed ghost area may be set only on the left side of a currently running lane. As for roads in the United States, on the contrary, an assumed ghost area may be set only on the right side of a currently running lane. In addition, a first area and an assumed ghost area may be established only in a region on an adjacent lane adjacent to a currently running lane.  
         [0091]    When only a ghost  210  is detected and a target vehicle  200  is not detected, there is another extrapolation process other than the flowchart shown in FIG. 7, by which, during a previous control cycle, a predicted position from the target vehicle  200  in recognition to the target vehicle  200  to a present control cycle is calculated beforehand, and the extrapolation process may be executed if the predicted position is in a real target area  230 . The method brings about the same advantages as those of the embodiments described above.  
         [0092]    According to the flowchart shown in FIG. 5, in order to judge with certainty whether or not an object is a ghost  210 , when an object newly discovered in a ghost area  220  runs at the same distance and relative speed as those of a target vehicle  200 , the object is judged as a ghost  210  that is to be deleted. However, when an object is found outside of a roadside object  300 , the object may be deleted without other judgment. This is because the probability is high that an object found outside of the roadside object  300  is a ghost  210  or noise.  
         [0093]    The embodiments of the invention are related to a FMCW apparatus to which an object recognition apparatus is applied. The embodiments can be applied to a car space warning apparatus that notifies a driver of the existence of a vehicle that approaches the driver and shortens the car space, and a collision alleviation apparatus that varies the operation of an air bag in accordance with a vehicle ahead.  
         [0094]    Although described above in connection with the particular embodiments of the invention, it should be understood that the descriptions of the embodiments are illustrative of the invention and are not intended to be limiting. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claims.