JPH0534460A - Detecting device for target ahead - Google Patents

Abstract

PURPOSE:To ensure control without causing errors in detection even when a target ahead moves along a curve and being confused by disturbance caused by the head lamp of an oncoming car. CONSTITUTION:A detecting device for targets ahead is provided with a first detection means CL1 provided in a vehicle to detect the distance to a target moving ahead and a second detection means CL2 for detecting the moving state of the vehicle. The device is further provided with a means CL3 for computing the moving state of the vehicle relative to the target ahead according to the distance and the moving state, a means CL4 for emitting a signal when this relative movement satisfies a predetermined state, and a means CL5 for detecting the moving state of the target ahead illuminated by a laser radar by use of a light-receiving portion which detects only light of the same wavelength as the laser radar.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preceding target object detecting device which detects a vehicle or the like in front of a vehicle and enables safe traveling.

[0002]

2. Description of the Related Art As a conventional device of this type, for example,
There is one shown in FIG. 12 (see Japanese Utility Model Laid-Open No. 64-48687). That is, this device is used for the inter-vehicle distance measuring means 10
1 and the output signal of the vehicle speed detecting means 103
5 is input to the alarm device 107 from the arithmetic circuit 105.
It is designed to be output to. The inter-vehicle distance measuring means 101 uses ultrasonic waves or laser radar, and the vehicle speed detecting means 103 detects the vehicle speed of the own vehicle.
Then, the arithmetic circuit 105 calculates the safe inter-vehicle distance from the preceding vehicle from the relative speed with respect to the preceding vehicle or the vehicle speed of the own vehicle, and the actual inter-vehicle distance between the own vehicle and the preceding vehicle is calculated from the calculated safe inter-vehicle distance. When the distance is short, the alarm device 107 is activated to give a warning to the driver to keep an appropriate inter-vehicle distance to call attention.

[0003]

However, in the conventional device, as shown in FIG. 13, the own vehicle (vehicle to be controlled) OM.
_{Since 1} is configured to detect the preceding vehicle (vehicle traveling in front of the vehicle) OM ₂ in the lane in which ₁ is traveling,
In the case of multiple lanes, there is a risk that the preceding vehicle OM ₃ traveling in the adjacent lane, which does not need to be detected, may be erroneously detected. That is,
On a straight road, there is no problem for the own vehicle OM ₁ to detect the preceding vehicle OM ₂ traveling in the same traveling lane, but in a section where the road is curved, the preceding vehicle OM _{3 in the} adjacent lane is present. by but since that would be present on the extension of the travel lane of the vehicle OM _1, when the vehicle OM ₁ there is no preceding vehicle OM ₂ in front of the lane to travel, because thereby detecting the preceding vehicle OM ₃ is there.

Therefore, the preceding vehicle O traveling in the adjacent lane
Even when M ₃ is detected, when the inter-vehicle distance becomes shorter than the safe inter-vehicle distance, the calculation circuit 105 causes the alarm device 10 to operate.
A signal was output to 7 and an erroneous alarm was given, which might annoy the occupant.

As one of the methods for improving such a problem, a steering angle signal of the own vehicle OM ₁ is input, and the detection direction of the inter-vehicle distance measuring means 101 is changed according to the signal, so that it can be used even when traveling on a curve. A configuration in which the preceding vehicle OM _{2 in the} lane in which the own vehicle OM ₁ is traveling can be reliably detected is also conceivable. However, as is clear from FIG. 13, when the vehicle OM ₁ is traveling on a straight road, the preceding vehicle OM _{3 in the} adjacent lane is already traveling on a curve, so the steering angle signal of the vehicle OM ₁ is transmitted. It is difficult to completely prevent false alarms.

As another method, a configuration may be considered in which the front view of the own vehicle OM ₁ is input by a camera and the road shape and the preceding vehicle are detected from the image signal thereof. However,
It is costly to detect a preceding vehicle and the like by image processing with the current technology, and there is a possibility that a headlamp of an oncoming vehicle is erroneously detected as a preceding vehicle at night or the like.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a preceding target object detecting device capable of suppressing erroneous detection even when traveling on a curve or the like.

[0008]

First detecting means C provided on a vehicle for detecting a distance to a preceding target object moving forward.
L1, second detection means CL2 for detecting the moving state of the vehicle, and means CL3 for calculating the relative moving state of the vehicle with respect to the preceding target object from the distance and the moving state.
And a moving state of the preceding target irradiated to the laser radar using the means CL4 that emits a signal when the relative moving state is a predetermined state and the light receiving unit that detects only the light of the wavelength of the laser radar. And a means CL5 for doing so.

According to a second aspect of the present invention, in the preceding target detecting apparatus according to the first aspect, the moving state detecting means CL5 detects the lateral movement of the preceding target, and at the same time, the preceding target is detected. It is characterized in that the signal is canceled when the lateral movement exceeds a predetermined value.

Further, the invention of claim 3 is the preceding target object detecting device according to claim 1 or claim 2, further comprising a safety device CL6 provided in the vehicle and operated by the signal. .

[0011]

According to the moving state of the preceding target detected by the first detecting means CL1 and the moving state of the vehicle detected by the second detecting means CL2, the calculating means CL3 determines the relative movement of the vehicle with respect to the preceding target. Calculate the movement state. When the relative movement state is a predetermined state, a signal is output from the signal generating means CL4. Then, the moving state detecting means CL5 detects the moving state of the preceding target irradiated on the laser radar by detecting only the light of the wavelength of the laser radar. Therefore, the moving state of the preceding target is reliably detected without being confused by the headlights of the oncoming vehicle even at night.

According to the second aspect of the present invention, the moving state detecting means CL5 detects the lateral movement of the preceding target, and when the lateral movement of the preceding target exceeds a predetermined value, the signal of the signal generating means CL4 is canceled. .

Further, according to the invention of claim 3, the safety device can be operated.

[0014]

Embodiments of the present invention will be described below.

FIG. 2 is a block diagram of a vehicle safety running device according to an embodiment of the present invention. In FIG. 2, a laser radar transmitter / receiver 1 as the first detecting means CL1 and a vehicle speed sensor 2 as the second detecting means CL2 are provided and connected to the input port side of the arithmetic circuit 3. Further, the lateral movement detector 3 as the movement state detecting means CL5 is connected to the input port of the arithmetic circuit 4, and the alarm device 4 as the safety device CL6 is connected to the output port side of the arithmetic circuit 3.

The laser radar transmitter / receiver 1 is provided, for example, in the front part of the vehicle, and the vehicle (hereinafter referred to as the own vehicle OM ₁ ).
Prior target for moving forward the distance (hereinafter, the preceding vehicle OM ₂ referred) and detects the, for example, a preceding vehicle OM ₂
Is detected to detect the inter-vehicle distance from the own vehicle OM ₁ .

The vehicle speed sensor 2 detects the moving state of the own vehicle OM _1. For example, the vehicle speed of the own vehicle OM ₁ is detected by a signal from a speedometer.

The calculation circuit 3 constitutes a calculation means CL3 and a signal generation means CL4, calculates the relative movement state of the vehicle with respect to the preceding target object from the inter-vehicle distance and the vehicle speed, and this relative movement state. Emits a signal when is in a predetermined state. That is, the safe inter-vehicle distance is calculated based on the inter-vehicle distance between the preceding vehicle OM ₂ and the own vehicle OM ₁ and the vehicle speed of the own vehicle OM ₁ , and when the actual inter-vehicle distance falls below this safe inter-vehicle distance, the alarm device 5 is notified. It is designed to output an operation signal.

The lateral movement detector 3 detects the lateral movement of the preceding target from the moving state of the preceding target. For example, the lateral movement speed of the preceding vehicle OM ₂ irradiated by the laser radar is detected. It is like this. Then, the arithmetic circuit 3 cancels the operation signal to the safety device when the lateral movement of the preceding target exceeds a predetermined value. That is, the preceding vehicle O
When the lateral moving speed of M ₂ exceeds a predetermined value, it is determined that the preceding vehicle OM ₂ is traveling on a curve, and in such a case, the alarm device 5
To prevent the output to.

The specific structures of the laser radar transmitter / receiver 1 and the transverse detector 3 are as shown in FIG. 3, for example.

The laser radar transmitter / receiver 1 has a predetermined spread angle θ.
The laser radar is transmitted in front of the vehicle, the reflection signal of the preceding vehicle OM ₂ is received, and the distance is calculated based on the time difference.

The lateral movement detector 3 comprises a filter 6, a condenser lens 7 and a CCD element assembly 8.
The filter 6 is provided so that only the light of the wavelength of the laser radar is detected. As a configuration for detecting only the light of the wavelength of the laser radar, a shutter that controls so as to synchronize with the cycle of the laser radar is used in addition to the filter, or the signal after being received by the CCD element is processed. It is also possible to do by doing. The CCD element assembly 8 is one in which CCD elements are arranged in a line or a matrix.

Therefore, the laser radar transceiver 1 detects the inter-vehicle distance to the preceding vehicle OM _2, and the lateral movement detector 3 detects the irradiation of the preceding vehicle OM ₂ by the laser radar transceiver 1.
The reflected light from the reflector 9 is detected.

In this embodiment, the inter-vehicle distance is detected by the laser radar transmitter / receiver 1. However, by measuring the time until the CCD device assembly 8 detects the transmitted laser radar signal. It is also possible to adopt a configuration in which the distance is measured at the same time.

Then, the laser radar transceiver 1 transmits and receives to detect the preceding vehicle OM _{2 in the} lane in which the own vehicle OM ₁ is traveling as shown in FIG.
The inter-vehicle distance between M ₁ and OM ₂ can be calculated. Further, the vehicle speed V ₁ of the own vehicle OM1 is detected by the input from the vehicle speed sensor 2, and the safe inter-vehicle distance between the two vehicles OM ₁ and OM ₂ is calculated by the arithmetic circuit 4 from this vehicle speed V ₁ and the inter-vehicle distance, and If the vehicle-to-vehicle distance is less than the safe vehicle-to-vehicle distance, an operation signal is output to the alarm device 5, and an alarm prompts the driver to maintain the safe vehicle-to-vehicle distance.

Further, there is no preceding vehicle OM _{2 in the} lane in which the own vehicle OM ₁ is traveling, and there is a preceding vehicle OM _{3 in the} adjacent lane,
In addition, when the vehicle is traveling in a curve, the irradiation of the laser radar reflected by the reflector 9 is reflected by the CCD element assembly 8
And the reflector 9 of the preceding vehicle OM ₃ is detected from the image signal, and the lateral movement speed V _{h is} calculated by the arithmetic circuit 4.
Is calculated. When this _Vh is above a predetermined level, the preceding vehicle OM ₃
Therefore, even if the inter-vehicle distance between the own vehicle OM ₁ and the preceding vehicle OM ₃ becomes less than the safe inter-vehicle distance, no output is made to the alarm device 5, and the own vehicle OM ₁
There is no useless operation in which an alarm is issued even when there is no preceding vehicle ahead of the lane in which the vehicle is traveling, and there is no trouble caused by an erroneous alarm.

Further, since only the wavelength of the laser radar is input to the CCD element assembly 8 by the filter 6, it is not affected by the disturbance such as the headlamp of the oncoming vehicle at night. .

Next, the above operation will be further described with reference to the flow chart of FIG.

First, in step S ₁ , the CCD element assembly 8
The image signal is input, the reflector 9 of the preceding vehicle OM ₃ is detected from the image signal in step S ₂ , and the process proceeds to step S ₃ . This step S ₃ determines the whether there are vehicles in forward view, if the process proceeds to the preceding vehicle unless Step S ₄ have, as FLAG1 = 0, and repeats the steps S ₁ again.

[0030] If it is determined that there are preceding vehicle moves to step S ₅ in step S _3, the vehicle speed V ₁ of the vehicle OM ₁
Is input, and in step S ₆ , a laser radar signal is input. In step S ₇ , the distance between the preceding vehicle and the own vehicle is calculated from the laser radar signal. Then, in step S ₈ , FL
It is determined whether AG1 = 0 or not, and if FLAG1 = 0, the process proceeds to step S ₉ . In addition, FL in step S ₈
When AG1 = 0, the process proceeds to step S ₁₁ makes a determination from the position and distance of the reflector 9 to whether the vehicle has been detected last time. If the vehicle is different, the process proceeds to step S ₉ .
In step S _11, if the detected vehicle is determined to be the same as last time, the process proceeds to step S _12, to calculate the transverse movement velocity V _h, the routine proceeds to step S _13.

The signals of the vehicle which is currently input in the step S ₉ determines that a new one, preceding vehicle lateral velocity V _h
Is set to 0 km / h at present, and the process proceeds to step S ₁₀ .
Set FLAG1 = 1 and proceed to step S ₁₃ . Step S
_{In 13 the} traveling lane is calculated from the detected vehicle position, and in step S14 it is determined whether or not the vehicle is on the same lane as the own vehicle OM ₁ . When it is determined that the preceding vehicle is not traveling in the traveling lane of the own vehicle OM ₁ , the process directly returns to step S ₁ .

[0032] Also, when the preceding vehicle is determined to be traveling along the traveling lane of the vehicle in step S _14, the process proceeds to step S _15, the preceding vehicle lateral movement velocity V _h and the reference to the velocity V _B of When the comparison is made and it is determined that V _h is larger, it is determined that the preceding vehicle is currently traveling in the curve section, and the process directly returns to step S ₁ . This is in a relationship between the own vehicle OM ₁ and the preceding vehicle OM ₃ shown in FIG. 4, and when the preceding vehicle OM ₃ enters the curve section, the lateral speed V _h becomes equal to or higher than a predetermined value, and therefore this V False alarms can be prevented by detecting _h .

When it is determined in step S ₁₅ that the lateral movement speed V _h is lower than the reference speed V _B , the preceding vehicle O
It is determined that M ₂ is present, and the process proceeds to step S ₁₆ . Based on such a determination, it is possible to distinguish between a preceding vehicle that has entered the traveling lane of the own vehicle OM ₁ due to a lane change and a preceding vehicle other than the own lane that is traveling on a curve. In step S ₁₆ , the safe inter-vehicle distance L _s is calculated from the vehicle speed V _{1 of the} own vehicle, the relative vehicle speed with respect to the preceding vehicle OM ₂ or the inter-vehicle distance,
Performs a comparison between the step S ₁₇ in the detected inter-vehicle distance L, L is determined to be safe if exceeds the L _s, the flow returns to step S ₁ without warning. If the inter-vehicle distance L is less than the safe inter-vehicle distance L _s , the process proceeds to step S ₁₈ and the alarm device 5 gives an alarm.

Therefore, in this embodiment, the inter-vehicle distance between the own vehicle OM ₁ and the preceding vehicle OM ₂ is detected, and when the inter-vehicle distance is less than the safe inter-vehicle distance calculated based on the vehicle speed or the like, an alarm is given to the driver. It is possible to encourage the maintenance of a safe inter-vehicle distance. In addition, it is possible to prevent the useless operation of recognizing the curve traveling of the preceding vehicle by determining the lateral traveling speed of the preceding vehicle and issuing an alarm even when there is no preceding vehicle ahead of the lane in which the vehicle is traveling. You can

FIG. 6 is a step S of the flowchart of FIG.
_This is a subroutine for executing ₁₁ and determines whether or not the vehicle is the same as the previous vehicle.

That is, in step S ₁₁₁ , the distance l _OLD between the preceding vehicle OM _OLD and the own vehicle OM ₁ detected last time,
Distance l between the preceding vehicle OM _NEW and own vehicle OM ₁ detected this time
And the difference Δl (Δl = | l− _1OLD |) is calculated. Then it compares the △ l _B and △ l which is set in advance in step S _112, △ when l is greater than the △ l _B is the currently detected preceding vehicle and the previously detected preceding vehicle differs from the judge, the process proceeds to step S ₉ in FIG.

Here, Δl _B is the amount of change in distance from the preceding vehicle that may change for each sampling time, and for example, Δl _B = 1 / 2t ² (α _A -α _B ) + t × (V _A
-B _B) is calculated as (V _A, α _A: own vehicle speed and acceleration, V _B, α _B: preceding vehicle speed and acceleration). The △ when l is △ l smaller than _B, there is a possibility of the same vehicle as the previous, the process proceeds to step S _113.

The comparison of the steps in S _113, performs lateral movement amount △ theta calculation of the preceding vehicle, step S _114, an amount which can be moved in the same manner as △ theta and horizontal and when the distance △ theta _B If it is smaller than Δθ _B , it is judged as the same vehicle,
The process proceeds to step S ₁₂ in FIG.

If it is larger than Δθ _B , it is determined that they are not the same, and the process proceeds to step S ₉ in FIG. Where the distance is Δl
_B as well as △ theta _B is stored in advance as the lateral moveable amount, △ theta _B shall be changed by the distance l between the preceding vehicle. That is, when l ₁ <l ₂ , Δθ _B1 > Δ
It becomes θ _B2 .

Therefore, it is possible to determine whether the detected preceding vehicle is the same vehicle as the previous vehicle.

[0041] Next, in step S ₁₁₄ in FIG. 5, the detected preceding vehicle is per decision whether the traveling lane, FIG. 7,
This will be described with reference to FIG.

The own lane range is calculated from the width H (for example, about 3.5 m) of the traveling lane of the own vehicle stored in advance. Then, the own vehicle OM ₁ and the preceding vehicle OM ₂ detected in front of it
It is determined whether the position is within the lane or not based on the distance 1 and the angle θ.

[0043] In step S ₁₄₁ in FIG. 8, inputs the distance l ₁ and the angle theta of the preceding vehicle, setting criteria determined according to step S ₁₄₂ in the distance l angle theta _B (l) and the detected angle theta makes a comparison between, when θ is small, the step S ₁₅ of to Figure 5 determines that the traveling lane, and a large time returns to step S ₁ of FIG. 5 is not determined from the own vehicle lane.

Therefore, it is possible to judge whether the detected preceding vehicle is on the own lane.

FIG. 9 shows another embodiment of the present invention to which a brake signal detecting sensor 11 is further added. That is, in this embodiment, the signal from the brake signal detection sensor 11 is input, and when the inter-vehicle distance L is less than the safe inter-vehicle distance L _s , it is determined whether or not the brake is applied, and if the brake is not applied. The alarm device 5 gives an alarm.

The above operation will be further described with reference to the flow charts of FIGS.

[0047] First, in step S ₂₁ inputs the image signal of the CCD element 8 detects the preceding vehicle of the reflector 9 from the image signal in step S _22, the process proceeds to step S _23.
Step S vehicle forward view at ₂₃ it is determined whether there, when it is determined that the vehicle is not present the process proceeds to step S _24, the FLAG1 = 0, the process proceeds to step S _21. In step S _23, when it is determined that the vehicle is present, the process proceeds to step S ₂₅ by entering the vehicle speed V ₁ of the subject vehicle, inputting a laser radar signal in step S _26.
In step S ₂₇ calculates a distance L between the preceding vehicle and the subject vehicle.

In step S ₂₈ , the brake signal from the brake signal detection sensor 11 is input, and in step S ₂₉ F
Determine if LAG1 = 0 or, when the FLAG1 = 0 the process proceeds to step S _30. When FLAG1 = 0 in step S ₂₉ , the process proceeds to step S ₃₂ , and it is determined from the position and distance of the reflector 9 whether or not the vehicle is the previously detected vehicle. If it is determined that the vehicle is different, the process proceeds to step S ₃₀ . . Further, when it is determined that the same vehicle as the previous process proceeds to step S _33, to calculate the transverse movement velocity V _h of the preceding vehicle, the routine proceeds to step S _34. Step S ₃₀ the signal of the currently input vehicle is judged to new one, at the moment the lateral velocity V _h of the forward vehicle, the process proceeds to step S ₃₁ as 0 km / h, step a FLAG1 = 1 in step S _{31 Move} to S34. Performing a determination whether the vehicle and the same on the lane in step S ₃₅ to calculate the driving lane from the position of the step S ₃₄ in the detected vehicle. When a forward vehicle has been determined not to be traveling along the traveling lane of the host vehicle, the process returns to step S _21. Also performs comparison between lateral movement velocity V _h and the reference velocity V _B of the vehicle ahead, the process proceeds to step S ₃₆ when it is determined that traveling along the traveling lane of the vehicle, towards the V _h is Uwamaware field preceding vehicle is determined to be currently driving a curve section, it returns to step S _21. Therefore, false alarms can be prevented in the same manner as above.

If the lateral traveling speed V _h of the preceding vehicle exceeds the reference speed V _B , the process proceeds to step S ₃₇ , and the limit vehicle distance L _K is calculated from the vehicle speed V _{1 of the} own vehicle, the relative vehicle speed with respect to the preceding vehicle or the vehicle distance. It is calculated and the process proceeds to step S ₃₁ . The limit inter-vehicle distance L _K is a marginal distance at which the driver may collide unless the driver strongly presses the brake. Next, in step S ₃₈ , the calculated distance LK is compared with the actual inter-vehicle distance L. If the inter-vehicle distance L is less than the limit inter-vehicle distance L _K , the process proceeds to step S ₄₀ and the alarm device 5 outputs a secondary alarm. , Return to step S ₂₁ . In step S ₃₉ , the safe inter-vehicle distance L _S is calculated, and the process proceeds to step S ₄₁ . In step S ₄₁ , the actual inter-vehicle distance L and the safe inter-vehicle distance L _s are compared. When the actual inter-vehicle distance L is longer than the safe inter-vehicle distance L _s , it is determined that no alarm is necessary and the process returns to step S 21. When the actual inter-vehicle distance L is shorter than the safe inter-vehicle distance L _s , the process proceeds to step S ₄₂ .

In step S ₄₂ , the brake signal is judged,
When the brake signal is ON returns to step S _21, when the brake signal is OFF, the process proceeds to step S _43, FLAG2
To judge. When FLAG2 = 0, it is determined that not yet output an alarm, the routine proceeds to step S44 to output the warning by the warning device 5, the operation proceeds to Step S ₄₅ FLA
G2 = 1 and then returns to step S _21. It is determined that issued the alarm time in step S ₄₃ when the FLAG2 = 1 returns to step S _21.

Therefore, in addition to the same effects as the above embodiment, the following effects can be obtained. That is, if the brake is depressed, the driver is in the operation of maintaining the safe inter-vehicle distance between the own vehicle OM ₁ and the preceding vehicle OM ₂ , so there is no need to give a warning in such a case. By not performing it, there is no useless operation of the alarm device 5, and there is no trouble.

The present invention is not limited to the above embodiment. For example, an automatic brake or the like can be used as the safety device.

[0053]

As is apparent from the above, according to the configuration of the present invention, since the moving state detecting means detects only the light of the wavelength of the laser radar, it is confused by the disturbance such as the headlamp of the oncoming vehicle. It is possible to reliably detect the state. Further, when it is determined that the movement of the preceding target is more than the predetermined value, the signal is canceled, so that the malfunction can be prevented.

Further, by operating the safety device, the inter-vehicle distance can be maintained, and if the movement of the preceding target is equal to or more than the predetermined value, the safety device is not activated and erroneous operation can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a configuration diagram according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a laser radar transceiver and a lateral movement detector.

FIG. 4 is an operation explanatory view.

FIG. 5 is a flowchart according to one embodiment.

FIG. 6 is a flowchart for determining whether the vehicle is the same as the previous vehicle.

FIG. 7 is an explanatory diagram of whether or not a preceding vehicle is on the own lane.

FIG. 8 is a flowchart for determining whether or not a preceding vehicle is on the own lane.

FIG. 9 is a configuration diagram according to another embodiment.

FIG. 10 is a flowchart according to another embodiment.

FIG. 11 is a flowchart according to another embodiment.

FIG. 12 is a configuration diagram according to a conventional example.

FIG. 13 is an operation explanatory view.

[Explanation of symbols]

CL1 First detection means CL2 Second detection means CL3 calculation means CL4 signal generation means CL5 moving state detection means CL6 safety device

Claims (3)

[Claims] 1. A first detecting means for detecting a distance to a preceding target object which is provided on a vehicle and which moves forward, a second detecting means for detecting a moving state of the vehicle, and from the distance and the moving state. A means for calculating a relative movement state of the vehicle with respect to the preceding target object, a means for emitting a signal when the relative movement state is a predetermined state, and a light receiving section for detecting only light of the wavelength of the laser radar are used. And a means for detecting the moving state of the preceding target radiated to the laser radar. 2. The preceding target detecting apparatus according to claim 1, wherein the movement state detecting means detects a lateral movement of the preceding target, and when the lateral movement of the preceding target exceeds a predetermined value. A preceding target detection apparatus characterized by canceling a signal. 3. The preceding target object detecting apparatus according to claim 1 or 2, further comprising a safety device provided in the vehicle and operated by the signal.