JPH07301672A - Inter-vehicle distance radar device - Google Patents

Abstract

PURPOSE:To carry out high accuracy measurement of inter-vehicle distance and lengthen the service life of a laser diode by selectively using the laser diode(LD) and a light emission diode(LED) or using them jointly on the basis of the distance between a target and its own vehicle and the vehicle speed. CONSTITUTION:A CPU 1 computes inter-vehicle distance receiving data from a signal processing part 3, and controls a light transmitting-receiving element selective control circuit 9 receiving data from a vehicle speed sensor 7. The circuit 9 outputs a selection signal to a driving circuit 11 by the control signal of the CPU 1, and the circuit 11 drives a light transmitting part 13 with the specified pulse width and pulse spacing. The light transmitting part 13 is provided with an LED 15 wide in detection width but short in detection distance, and an LD 17 narrow in detection width but long in detection distance and short in the service life. The CPU 1 lights the LED 15 during the stop of a vehicle and lights the LD 17 at the time of being unable to detect inter-vehicle distance during travel. The CPU lights the LD 17 and LED 15 when the detected inter-vehicle distance is the specified value or more, and lights the LED 15 at the time of being the specified value or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-vehicle distance warning device for alerting a driver with an alarm sound or the like when the inter-vehicle distance from his vehicle to a target in front does not hold the inter-vehicle distance required for safe driving. The present invention relates to an inter-vehicle distance radar device used for such purposes.

[0002]

2. Description of the Related Art As a conventional inter-vehicle distance radar device, a device shown in FIG. 7 is known. This device measures the time from when a pulse signal such as a radio wave, radar, or light is transmitted in front of the host vehicle until the pulse signal reflected from the preceding vehicle (target in front) is received. The inter-vehicle distance is calculated based on the measurement result. The above device
Some use a laser diode (LD) and a light emitting diode (LED) as a light emitting source for transmitting light.

The pulse signal sending means 25 sends a pulse signal such as a radio wave or a radar toward the preceding vehicle ahead, and the reflected pulse signal receiving means 27 sends a radio wave, a laser or a light reflected from the preceding vehicle ahead. The pulse signal is received and converted into an electric signal. Further, the control means 29 controls the timing of sending the pulse signal, and the time measuring means 31 counts and measures the time from the pulse sending time to the reception of the reflected pulse signal based on the command of the control means 29.

FIG. 8 is a timing chart of various signals, and the trigger signal (1) is a signal repeatedly output every predetermined time Tr. The sending pulse signal (2) is a signal output from the pulse signal sending means 25 controlled by the control means 3, and is output in synchronization with the trigger signal (1). The reception pulse signal (3) is a signal received by the reflection pulse signal receiving means 27 by being reflected from an external obstacle, and when the amplitude of the reception pulse signal (3) exceeds a predetermined threshold value Vth, The detection signal is output by the reflected pulse signal receiving means 27. On the other hand, the clock pulse (4) is
It is a signal for counting the time from when the pulse signal (2) is sent out to when the detection signal is output by the time measuring means 31, and it is output at intervals Δt for a certain period of time. It was

[0005]

However, such a conventional inter-vehicle distance radar device has a laser diode (LD) and a light emitting diode (LED) as a light emitting source, and when the LD is used as a light emitting source, Although it is generally possible to detect a long distance, the detection width is narrow, and there are cases where it is inappropriate for long-time operation in an environment such as high temperature.
On the other hand, when an LED is used as the light emitting source, the detection width is generally widened but the detection distance is shortened.

As a countermeasure for the above, it is conceivable to use both an LD and an LED as a light emitting source at the same time, but in particular, since the signal strength is too strong when detecting a short distance,
There is a possibility that the value of the distance calculated by the inter-vehicle distance radar device may cause an error with respect to the actual distance. Further, from the viewpoint of the thermal durability characteristic of the LD having high emission intensity, there has been a conventional demand to shorten the total lighting time of the LD as much as possible.

The present invention has been made in view of such conventional problems, and an object thereof is to reduce an error between a measured distance and an actual distance within a distance measuring range of an inter-vehicle distance radar. An object of the present invention is to provide an inter-vehicle distance radar device which performs highly accurate distance measurement, shortens the lighting time of a laser diode as compared with the conventional one, prolongs the life of a light emitting element, and improves the reliability of a radar device.

[0008]

To achieve the above object, the first invention according to claim 1 uses the claim correspondence diagram of FIG. 1 to detect the vehicle speed of the host vehicle.
1 and a light sending means 107 for sending a predetermined number of times of light to a front target from a first light emitting element 103 and a second light emitting element 105 which send light to a front target. When,
The light sent from the light sending means 107 is reflected by a target in front, and an amplifying means 109 for amplifying a received light signal of the reflected light reflected by the target, and a received light signal amplified by the amplifying means 109 are sampled. Adding means 11 for adding
1, the distance calculation means 113 for calculating the distance between the target object in front and the own vehicle from the received light signals added by the addition means 111, the distance calculated by the distance calculation means 113 and the vehicle speed detection means 103. And a light emitting element selecting means 115 for selecting the first light emitting element 103 and the second light emitting element 105 of the light transmitting means 107 to emit light based on the detected vehicle speed of the own vehicle. To do.

According to a second aspect of the present invention, the light emitting element selecting means 115 is the first of the light transmitting means 107 when the own vehicle is stopped by the detection of the vehicle speed detecting means 101.
The gist is to select the light emitting element 103.

According to a third aspect of the present invention, the light emitting element selecting means 115 is configured such that the own vehicle is traveling by the vehicle speed detecting means 101 and the distance calculating means 113 is used.
Therefore, when the distance to the target in front is not detected, the second light emitting element of the light transmitting means 107 is selected.

According to a fourth aspect of the present invention, the light emitting element selecting means 115 is configured such that the vehicle speed detecting means 101 allows the vehicle to travel and the distance calculating means 113.
Therefore, the gist is to select the first light emitting element 103 and the second light emitting element 105 of the light transmitting means 107 when the distance to the target in front is a predetermined value or more.

According to a fifth aspect of the present invention, the light emitting element selecting means 115 is configured such that the own vehicle is traveling by the vehicle speed detecting means 101 and the distance calculating means 113 is used.
Therefore, when the distance to the target in front is less than the predetermined value, the first light emitting element 103 of the light transmitting means 107 is selected.

A sixth aspect of the present invention is to change the amplification factor for amplifying the light receiving signal of the amplifying means 109 in accordance with the added value of the light receiving signals added by the adding means 111. To do.

According to a seventh aspect of the present invention, when the peak value of the added value of the received light signals added by the adding means 111 is not less than a predetermined value, the amplification factor for amplifying the received light signal of the amplifying means 109 is set. The gist is to make it less than the specified value.

According to an eighth aspect of the present invention, when the peak value of the added value of the received light signals added by the adding means 111 is less than a predetermined value, the amplification factor for amplifying the received light signal of the amplifying means 109 is set. The gist is to make it a predetermined value or more.

An eighth aspect of the present invention is summarized in that a light emitting diode is used for the first light emitting element and a laser diode is used for the second light emitting element of the light transmitting means.

[0017]

With the above construction, the first aspect of the invention is as follows.
The vehicle speed of the host vehicle is detected by the vehicle speed detecting means 101. Further, the light sent from the first light emitting element and the second light emitting element of the light sending unit 107 is reflected by the target in front, and the amplifying unit 10 that amplifies the received light signal of the reflected light reflected by the target.
The light reception signal amplified by 9 is sampled and added by the adding means 111. After the addition, the distance calculation means 113 calculates the distance between the front target and the vehicle from the received light signals added. After the calculation, the light emitting element selecting unit 115 calculates the calculated distance and the vehicle speed detecting unit 1.
Since the first light emitting element 103 and the second light emitting element 105 of the light transmitting means 107 are selected based on the vehicle speed of the host vehicle detected by 03, the measurement is performed within the range of the inter-vehicle distance radar. The accuracy of distance measurement is reduced by reducing the error between the distance and the actual distance, and the lighting time of the laser diode is shortened compared with the conventional method to extend the life of the light emitting element and improve the reliability of the radar device. it can.

The second invention is the light emitting element selecting means 11
5 is the first light emitting element 10 of the light transmitting means 107 when the vehicle is stopped by the detection of the vehicle speed detecting means 101.
Since 3 is selected, the distance measurement can be performed with high accuracy as in the first aspect of the invention, and the lighting time of the laser diode can be shortened as compared with the conventional case, and the life of the light emitting element can be extended.

A third invention is the light emitting element selecting means 11
5 is a second light emitting element 105 of the light transmitting means 107 when the own vehicle is traveling by the vehicle speed detecting means 101 and when the distance calculating means 113 does not detect the distance to the target in front. Is selected, the distance measurement can be performed with high accuracy as in the first aspect of the invention, the lighting time of the laser diode can be shortened as compared with the conventional one, and the life of the light emitting element can be extended.

In a fourth aspect of the present invention, the light transmitting means is provided when the vehicle speed is detected by the vehicle speed detecting means 101 and when the distance calculation means 113 is more than a predetermined distance from the target ahead. 107 the first light emitting element 103 and the second
Since the light emitting element is selected, the distance measurement can be performed with high precision as in the first aspect of the invention, and the lighting time of the laser diode can be shortened as compared with the conventional case, and the life of the light emitting element can be extended.

A fifth aspect of the present invention is the light emitting element selecting means 11
5 is the first light emission of the light transmitting means 107 when the own vehicle is traveling by the vehicle speed detecting means 101 and when the distance calculating means 113 is less than a predetermined distance from the target in front. Since the element 103 is selected, the distance measurement can be performed with high accuracy as in the first aspect of the invention, and the lighting time of the laser diode can be shortened as compared with the related art, and the life of the light emitting element can be extended.

In a sixth aspect of the invention, the amplifying means 1 corresponds to the added value of the received light signals added by the adding means 111.
Since the amplification factor for amplifying the received light signal of 09 is changed,
As in the invention described above, the distance measurement can be performed with high accuracy, and the lighting time of the laser diode can be shortened as compared with the conventional case, so that the life of the light emitting element can be extended.

In a seventh aspect of the invention, when the peak value of the added value of the received light signals added by the adding means 111 is a predetermined value or more, the amplification factor for amplifying the received light signal of the amplifying means 109 is set to be less than a predetermined value. Therefore, the distance measurement can be performed with high accuracy as in the first aspect of the invention, and the lighting time of the laser diode can be shortened as compared with the conventional case, and the life of the light emitting element can be extended.

In the eighth aspect of the invention, when the peak value of the added value of the light receiving signals added by the adding means 111 is less than a predetermined value, the amplification factor for amplifying the light receiving signal of the amplifying means 109 is set to a predetermined value or more. Therefore, the distance measurement can be performed with high accuracy as in the first aspect of the invention, and the lighting time of the laser diode can be shortened as compared with the conventional case, and the life of the light emitting element can be extended.

A ninth aspect of the invention is the first aspect of the light transmitting means 107.
Since the light emitting diode is used as the light emitting element and the laser diode is used as the second light emitting element, the light emitting element can be selected according to the distance to the target in front.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment of the inter-vehicle distance radar device of the present invention. In addition, in this embodiment, the target is described as a preceding vehicle traveling in front of the host vehicle.

The inter-vehicle distance radar device includes a CPU 1, a signal processing unit 3, a distance sensor head 5 and a vehicle speed sensor 7. The CPU 1 controls the signal processing unit 3 and receives data from the signal processing unit 3 to calculate an inter-vehicle distance. In the present embodiment, the CPU 1 controls the transmission / reception element selection control circuit 9, which will be described later, as well as the calculation of the inter-vehicle distance, and also controls the amplification factor control circuit 23 as appropriate.
The signal processing unit 3 controls the drive circuit 11 by the control signal from the CPU 1 and outputs the data and the like from the signal amplification circuit 21. The vehicle speed sensor 7 detects the vehicle speed of the host vehicle.

The distance sensor head 5 includes a light transmitting / receiving element selection control circuit 9, a drive circuit 11, a light transmitting section 13, an LED 15,
The LD 17, the light receiving unit 19, the signal amplification circuit 21, and the amplification factor control circuit 23 are provided. Transmit / receive element selection control circuit 9
LED to the drive circuit 11 by the control signal from the CPU 1.
The selection signal of 15 and LD17 is output. Drive circuit 1
1 drives the light transmitting section 13 such as the LED 15 and the LD 17 with a predetermined pulse width and pulse interval. Further, the drive circuit 11 is controlled by the transmission / reception element selection control circuit 9
Is used as a light emitting source and is appropriately turned on or off.
The light transmitting unit 13 includes an LED 15 and an LD 17, and transmits light to a preceding vehicle or the like ahead. The LED 15 is a light emitting diode and has a wide detection width but a short detection distance. The LD 17 is composed of a laser diode and has a narrow detection width but a long detection distance. Although the LED 15 is used in this embodiment, a light emitting element having a function similar to that of the LED 15 may be used.
It is also possible to use L). The light receiving unit 19 is composed of a photodiode (PD) or the like and converts an optical signal into an electric signal. The converted electric signal is supplied to the signal amplification circuit 2
At 1, the signal is amplified to a predetermined level. The amplification factor of the signal amplification circuit 21 in this embodiment has a variable function that can be changed by an external control signal. The amplification factor control circuit 23 controls the signal amplification circuit 2 according to the strength of the received signal.
The signal amplification degree of 1 is changed, the amplification step number is set to a plurality of stages, and the amplification degree is changed according to the detection state (addition result) of the signal.

Next, the operation of this embodiment will be described with reference to the flow charts of FIGS.

First, the operations from signal transmission to reception, signal processing and distance calculation when the vehicle speed of the host vehicle is detected by the vehicle speed sensor 7 to be 0 Km / h will be described with reference to the flowchart of FIG. In the present embodiment, when the vehicle is stopped, it is not necessary to detect a long distance, so only the LED 15 is made to emit light.

First, the vehicle speed sensor 7 detects the vehicle speed Vf (S1), and if the vehicle speed Vf is 0 km / h, the process proceeds to step S3 by the determination in step S2. Here, since the vehicle speed is zero, the distance measurement is started without causing the LD 17 to emit light (S4). When the distance measurement is started, the drive circuit 13 responds to the control signal and directs the light from the LED 15 forward in a predetermined number of times within a predetermined time with a predetermined pulse width (for example, 130 nsec) and a pulse interval (for example, 6 μsec). (Eg 8
Light is transmitted 192 times) (S5), and reflected light from the target is received by a light receiving element such as a photodiode (PD) (S).
6).

The addition process is performed a number of times (for example, 8192 times) during one distance measurement from the reception of the reflected light from the target, and a plurality of temporally consecutive (for example, 81
(92 times) a predetermined number of bits of digital data b
The signal processing unit 3 performs a synchronous addition process on the third group (S7).

In the present embodiment, this addition processing is performed at 81
This is performed 92 times (S8), but this makes it possible to obtain the characteristic b4 of the added value level with respect to the distance (end of one distance measurement: S9). Here, the added value (Pk) at the portion showing the peak of the added value level is inspected (S10), and it is determined whether Pk is 7900 or more by the determination in step S11. When Pk is 7900 or more, it is in a state where the added value is saturated or is infinitely close to it, and the distance calculation method using the added values at the four sampling points cannot accurately calculate it. move on.

Here, FIG. 5 shows an example of the states of the amplification degrees set in a plurality of stages in the amplification factor control circuit 23. Switching to the amplification stages adjacent to each other according to the signal detection state. It is possible. When the process proceeds to step S12, the amplification degree in FIG. 5 is decreased by one step, and the process returns to step S4 to restart the distance measurement from the beginning.

On the other hand, when Pk is less than 7900,
In step S13, it is determined whether the Pk is less than 5000. Here, FIG. 6 shows the peak addition value (P
Although the relationship between k) and the distance calculation accuracy is illustrated,
For example, when the required distance calculation accuracy is ± 1 m or less, Pk needs to be 5000 or more. Pk is 5
If it is less than 000, the distance cannot be calculated accurately, so the amplification degree shown in FIG. 5 is increased by one step in step S14, and then the process returns to step S4 and the distance measurement is performed again.

On the other hand, when Pk is 5000 or more,
Since the addition result is sufficient for the distance calculation, the distance calculation is performed according to the following equation using the addition values at the four sampling points including the point that becomes the addition peak (S15).

D = (vlx2-v2xl-v3x4 + v4x3) / (v1-v2-v3 + V4) where D is a calculation distance and x1 to x4 are distances at sampling points (for example, 20, 30, 40, 50 m) , V1 to v4 are
It is the added value at the sampling points of x1 to x4. After completing the distance calculation, the process immediately returns to step S1.

Next, the operation when the host vehicle is traveling (S2) and there is no vehicle in front (S16) will be described. In this case, because it is necessary to immediately detect that the vehicle has entered the detection area of the radar,
The light transmitting unit 13 causes the LED 15 and the LD 17 to emit light at the same time and sets the amplification degree of the light receiving circuit to the maximum (FIG. 5).
Step 9: S17). When ranging starts (S18)
The light sending unit 13 sends the light forward by the LED 15 and the LD 17 at a predetermined pulse width (for example, 130 nsec) and a pulse interval (for example, 6 μsec) for a predetermined number of times within a predetermined time (S19), and the front ahead. Reflected light from the vehicle is received by a light receiving element such as a photodiode (PD) (S20). The flow from reception of reflected light to addition processing (S21, 22) is the same as the flow (S7-9) already described. While there is no vehicle ahead, no peak appears in the addition result, it is determined in step S24 that there is no detected vehicle, and the process immediately returns to step S1. Steps S1,2
When a vehicle or the like enters the detection area while repeating the operations from S16 to S23, the CPU 1 begins to show a peak in the addition result. Distance calculation is performed according to the following equation using the added values at the four sampling points including (S24).

D = (vlx2-v2xl-v3x4 + v4x3) / (v1-v2-v3 + V4) After the distance calculation is completed, the process immediately returns to step S1.
Regarding the operation after the preceding vehicle ahead is detected once,
The flow as described below is followed.

In the present embodiment, when the preceding vehicle is present in front, the light emission method is changed depending on whether or not the distance to the preceding vehicle is, for example, 15 m or less (S25). First, the case where the distance to the preceding vehicle ahead is 15 m or less will be described. When the distance is within 15 m, it is not necessary to detect the long distance, and therefore the LD 17 is not caused to emit light (S26). This makes the LD
The total light emission time of 17 can be shortened. When the distance measurement is started (S27), the LED 15 transmits light forward with a predetermined pulse width (for example, 130 nsec) and a pulse interval (for example, 6 μsec) a predetermined number of times within a predetermined time (S28). Reflected light from the preceding vehicle is received by a light receiving element such as a photodiode (PD) (S29).
The flow from the reception of the reflected light to the addition processing is (S30, 3
1) The same as the flow (S7 to 9) described above. The addition process ends (S32).

Here, the added value (Pk) at the portion showing the peak of the added value level is inspected (S33), and it is determined by the determination in step S34 whether PK is 7900 or more. When Pk is 7900 or more, it is in a state where the added value is saturated or is infinitely close to it, and the distance calculation method using the added value at the four sampling points cannot accurately calculate it. Then, the amplification degree is lowered by one step in FIG. Then, the process returns to step S27, and the distance measurement is performed again from the beginning. If Pk is less than 7900, the process proceeds to step S36, and it is determined whether the Pk is less than 5000. If Pk is less than 5000, it is not possible to calculate the distance accurately, so step S3
After the amplification degree is increased by one step in FIG. 5 at 7, the process returns to step S27 and the distance measurement is performed again. In the present embodiment, after the amplification level is raised to the ninth level (maximum amplification level), even if the added peak is less than 5000, no further improvement operation is performed. On the other hand, when Pk is 5000 or more, the addition result is sufficient for the distance calculation, so the distance calculation is performed according to the following equation using the addition values at the four sampling points including the point that becomes the addition peak (S38). ).

D = (vlx2-v2xl-v3x4 + v4x3) / (v1-v2-v3 + V4) After the distance calculation is completed, the process immediately returns to step S1.

Next, the operation when the distance to the vehicle in front exceeds 15 m in step S25 will be described. If the distance exceeds 15 m, it may not be possible to detect the vehicle ahead by the LED 15 alone.
The LD 17 is also caused to emit light along with 15 (S39). When the distance measurement is started (S40), the light transmitter 13 directs the light forward by the LED 15 and the LD 17 at a predetermined pulse width (for example, 130 nsec) and pulse interval (for example, 6 μse).
In c), light is transmitted a predetermined number of times within a predetermined time (S41), and the light receiving unit 19 receives the reflected light from the target by a light receiving element such as a photodiode (PD) (S42). The flow from the reception of the reflected light to the addition process (S43, 44) is the same as the flow (S7 to 9) already described, and the addition process ends (S45). Here, the added value (Pk) at the portion showing the peak of the added value level is inspected (S46), and it is determined in step 47 whether Pk is 7900 or more. When Pk is 7900 or more, it is in a state where the added value is saturated or is infinitely close to it, and the distance calculation method using the added value at the four sampling points cannot accurately calculate it. Then, the amplification degree is lowered by one step in FIG. Then, the process returns to step S40, and the distance measurement is restarted from the beginning. On the other hand, when Pk is less than 7900,
In step S49, it is determined whether the Pk is less than 5000. If Pk is less than 5000, the distance cannot be calculated accurately, so the amplification factor is increased by one step in FIG. 5 in step S50, and then the process returns to step S40 to perform distance measurement again. It should be noted that, similarly to the above, after the amplification degree is increased to the ninth stage (maximum amplification degree), even if the added peak is less than 5000, the operation for further improving is not performed. Pk is 5
If it is 000 or more, the addition result is sufficient for the distance calculation, so the distance calculation is performed according to the following equation using the addition values at the four sampling points including the point that becomes the addition peak (S51).

D = (vlx2-v2xl-v3x4 + v4x3) / (v1-v2-v3 + V4) After the distance calculation is completed, the process immediately returns to step S1.

As a result, the inter-vehicle distance between the host vehicle and the preceding vehicle can be measured with high accuracy at any point within the range of the inter-vehicle distance radar. Further, the lighting time of the LD 17 can be shortened as compared with the conventional case, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

[0047]

As described above, according to the first aspect of the invention, the light transmitted from the first light emitting element and the second light emitting element of the light transmitting means is the reflected light reflected by the target in front. The received signals are amplified and added. After the calculation, the light emitting element selection means, based on the calculated distance and the vehicle speed of the own vehicle,
Since the first light emitting element and the second light emitting element of the light transmitting means are selected, it is possible to reduce the error between the measured distance and the actual distance within the distance measurement range of the inter-vehicle distance radar, and to achieve a highly accurate distance. While performing the measurement, the lighting time of the laser diode can be shortened as compared with the conventional one, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

In a second invention, the light emitting element selecting means is
Since the first light emitting element of the light transmitting means is selected when the host vehicle is stopped by the detection of the vehicle speed detecting means, the distance measurement is performed with high accuracy as in the first aspect of the invention, and the laser diode is turned on. The time can be shortened as compared with the conventional one, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

In a third invention, the light emitting element selecting means is
Since the second light emitting element of the light transmitting means is selected when the own vehicle is traveling by the vehicle speed detecting means and when the distance to the target ahead is not detected by the distance calculating means, the first light emitting element is selected. As in the invention described above, the distance measurement can be performed with high accuracy, the lighting time of the laser diode can be shortened as compared with the prior art, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

In a fourth invention, the light emitting element selecting means is
The first light emitting element and the second light emission of the light transmitting means when the own vehicle is traveling by the vehicle speed detecting means and when the distance to the target in front by the distance calculating means is a predetermined value or more. Since the element is selected, the distance measurement can be performed with high accuracy as in the first aspect of the invention, the lighting time of the laser diode can be shortened as compared with the conventional one, and the life of the light emitting element can be extended to improve the reliability of the radar device. Improvement can be realized.

In a fifth aspect of the present invention, the light emitting element selecting means is
Since the first light emitting element of the light transmitting means is selected when the own vehicle is traveling by the vehicle speed detecting means and when the distance to the front target is less than the predetermined value by the distance calculating means, As in the first aspect, the distance measurement can be performed with high accuracy, the lighting time of the laser diode can be shortened as compared with the conventional one, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

According to the sixth aspect of the invention, the amplification factor amplified by the amplifying means is changed in accordance with the added value of the received light signals added by the adding means. In addition, the lighting time of the laser diode can be shortened as compared with the conventional case, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

In the seventh invention, when the peak value of the added value of the received light signals added by the adding means is equal to or more than a predetermined value, the amplification factor to be amplified by the amplification factor changing means is set to be less than the predetermined value. As in the first aspect of the invention, the distance measurement can be performed with high accuracy, the lighting time of the laser diode can be shortened as compared with the conventional case, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

In the eighth invention, when the peak value of the added value of the received light signals added by the adding means is less than a predetermined value, the amplification factor amplified by the amplifying means is set to a predetermined value or more. As in the invention, the distance measurement can be performed with high accuracy, the lighting time of the laser diode can be shortened as compared with the conventional case, the life of the light emitting element can be extended, and the reliability of the radar device can be improved.

In the ninth invention, since the light emitting diode is used as the first light emitting element and the laser diode is used as the second light emitting element of the light transmitting means, light is emitted in accordance with the distance to the target in front. Selection of elements can be realized.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing the present invention.

FIG. 2 is a block diagram showing the configuration of an embodiment of an inter-vehicle distance radar device of the present invention.

FIG. 3 is a flowchart showing the operation of the present invention.

FIG. 4 is a flowchart showing the operation of the present invention.

FIG. 5 is a diagram showing amplification level setting.

FIG. 6 is a diagram showing a relationship between a distance calculation accuracy and a peak addition value.

FIG. 7 is a block diagram showing a conventional configuration.

FIG. 8 is a time chart showing a conventional operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 3 Signal processing unit 7 Vehicle speed sensor 9 Transmitting / receiving element selection circuit 11 Driving circuit 15 LED 17 LD 23 Amplification factor control circuit 101 Vehicle speed detecting means 103 First light emitting element 105 Second light emitting element 107 Transmitting means 109 Amplifying means 111 Adding means 113 inter-vehicle distance calculating means 115 light emitting element selecting means

Claims (9)

[Claims] 1. A vehicle speed detecting means for detecting a vehicle speed of a host vehicle, and a first light emitting element and a second light emitting element for transmitting light to a target in front of the vehicle. Light transmitting means for transmitting light to the target in front, amplification means for amplifying the light reception signal of the reflected light reflected by the target in front of the light transmitted from the light transmitting means, and this amplifying means. Adding means for sampling and adding the received light signals amplified by the means, distance calculating means for calculating the distance between the front target and the vehicle from the received light signals added by the adding means, and the distance calculating means Light emitting element selecting means for selecting and emitting light from the first light emitting element and the second light emitting element of the light transmitting means based on the calculated distance and the vehicle speed of the vehicle detected by the vehicle speed detecting means, Inter-vehicle distance characterized by having Radar equipment. 2. The light emitting element selecting means selects the first light emitting element of the light transmitting means when the host vehicle is stopped by the detection of the vehicle speed detecting means.
The inter-vehicle distance radar device described. 3. The light emitting element selecting means of the light transmitting means when the own vehicle is traveling by the vehicle speed detecting means and when the distance calculating means does not detect the distance to the target in front. The inter-vehicle distance radar device according to claim 1, wherein the second light emitting element is selected. 4. The light emitting element selecting means transmits the light when the vehicle speed is detected by the vehicle speed detecting means and when the distance calculating means calculates a distance to a target ahead of the vehicle is a predetermined value or more. 2. The inter-vehicle distance radar device according to claim 1, wherein the first light emitting element and the second light emitting element of the means are selected. 5. The light emitting element selection means is configured to transmit the light when the vehicle speed is detected by the vehicle speed detection means and when the distance calculation means determines that the distance to the target ahead is less than a predetermined value. 2. The inter-vehicle distance radar device according to claim 1, wherein the first light emitting element of the means is selected. 6. The inter-vehicle distance according to claim 1, wherein the amplification factor for amplifying the light receiving signal of the amplifying means is changed according to the added value of the light receiving signals added by the adding means. Range radar device. 7. The amplification factor for amplifying the light receiving signal of the amplifying means is set to be less than a predetermined value when the peak value of the added value of the light receiving signals added by the adding means is equal to or more than a predetermined value. Item 6. The inter-vehicle distance radar device according to item 6. 8. The amplification factor for amplifying the light receiving signal of the amplifying means is set to a predetermined value or more when the peak value of the added value of the light receiving signals added by the adding means is less than a predetermined value. Item 6. The inter-vehicle distance radar device according to item 6. 9. The inter-vehicle distance radar device according to claim 1, wherein a light emitting diode is used for the first light emitting element and a laser diode is used for the second light emitting element of said light transmitting means.