JP3206256B2 - Objective distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object distance measuring apparatus which is capable of diagnosing abnormality each time a distance is measured by a diagnostic means provided in addition to the distance measuring means.

[0002]

2. Description of the Related Art An object distance measuring apparatus 1 shown in FIG. 1 is mounted on a vehicle for measuring an inter-vehicle distance, and forwards a distance measuring signal generated by a distance measuring signal generating circuit 2 via a transceiver 3. And receives a ranging signal reflected by an object 4 such as a vehicle ahead or a guardrail. During this time, the counter circuit 5
Starts the counting operation when the ranging signal is transmitted, and stops the counting operation when the ranging signal is received. The count value N of the counter circuit 5 is read by the CPU 6 and is subjected to a distance calculation by the CPU 6. That is, the CPU 6 obtains a transmission / reception time difference T (= Nτ) obtained by multiplying the count value N by the clock cycle τ of the counter circuit 5, and furthermore, １ ／ of the transmission / reception time difference T, the traveling speed v of the distance measurement signal. Multiplied by 4
Then, the distance Tv / 2 is calculated. Further, the CPU 6
The inter-vehicle distance data obtained by calculation is constantly monitored, and when a safe inter-vehicle distance cannot be maintained, warning of abnormal approach or automatic braking is performed to prevent collision.

[0003] As described above, the objective distance measuring apparatus 1 includes:
The distance to the obstacle 4 in front of the vehicle can be accurately measured using the ranging signal. However, when the transceiver 3 malfunctions, the abnormality is not noticed. If left unattended, the driver will be warned frequently as a dangerous inter-vehicle distance, or will be automatically braked when there is no need to do so, even if the vehicle is traveling with a safe inter-vehicle distance. In spite of the imminent approach to the vehicle, there is a problem in that, despite the danger of a rear-end collision, an alarm is not issued or automatic braking ends in a misfire.

In order to monitor such an operation failure of the objective distance measuring device 1, for example, Japanese Patent Laid-Open Publication No. 57-11627
No. 4 “Test device of laser distance measuring device” measures the distance to a target whose distance is known in advance so that it can diagnose whether the transceiver 3 of the objective distance measuring device 1 is operating correctly. Instead, the counting operation of the counter circuit 5 is stopped by a pseudo ranging signal generated when a certain time has elapsed since the counting of the counter circuit 5 was started,
A test device for testing the object distance measuring device 1 using a pseudo ranging signal is disclosed. FIG. 5 shows a test apparatus 1 of this type.
0 shows the schematic configuration of the objective distance measuring device 1
A ranging signal such as a laser beam emitted by the light-receiving element 11 is received by a light-receiving lens 11 and sent to a light-receiving element 13 via a filter 12. The light receiving output of the light receiving element 13 is amplified by the amplifier circuit 14 and then sent to the delay circuit 15. The delay circuit 14 delays the signal by a time Td set assuming a time required for the laser light to be reflected by the target object and returned, and outputs the delayed output to the light emitting element 17 via the amplifier circuit 16 as a pseudo ranging signal. Supplied. As a result, the light emitting element 17
The light is emitted when a time Td has elapsed from the light receiving time of the light receiving element 13, and the light emission output is returned to the objective distance measuring device 1 via the light emitting lens 18. At this time, the object distance measuring apparatus 1 measures the object distance based on the time difference between the transmission and reception of the distance measurement signal, and therefore calculates the round trip time T of the distance measurement signal back calculated from this object distance as the delay time Td in the delay circuit 15. The object distance measuring device 1 can be diagnosed based on the comparison and whether or not both coincide within a predetermined error range.

[0005]

The test apparatus 10 of the above-mentioned conventional object distance measuring apparatus 1 is a separate apparatus from the object distance measuring apparatus 1, and it goes without saying that the object distance measuring apparatus 1 is used for a test. Must be used facing
During the actual distance measurement period by the objective distance measurement device 1, it could not be used because it hindered the distance measurement. Further, it is usually used prior to the distance measurement by the objective distance measuring device 1. Therefore, in a device such as an inter-vehicle distance measuring device, which is mounted on a vehicle, a maintenance shop or the like is required at a regular inspection. It was limited to uses such as those used in The configuration of the test apparatus 10 is almost the same as the configuration of the objective distance measurement apparatus 1 except that the counter circuit 5 used for measuring the time difference T between transmission and reception is not included but a delay circuit 15 is included. In addition, there is a problem that the manufacturing cost is high due to the complicated structure.
Furthermore, since the delay time Td in the delay circuit 15 is fixed, the test is performed only in a case where a specific distance is measured, and various distances included in the measurement range of the objective distance measuring device 1 are measured. There was a problem that a comprehensive test could not be performed.

A device in which a diagnostic device is integrated with an objective distance measuring device is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 2-309282.
No. "Ranging device". This is a configuration in which an external light detection circuit detects that the light-emitting lens emits laser light, and operates a delay circuit based on the detection signal to generate a pseudo ranging signal. In some cases, laser light must always be emitted from the light-emitting lens to the outside, so that there is a problem that the direction of the light-emitting lens may adversely affect the human body. In addition, since the diagnostic mode and the measurement mode are strictly distinguished from each other, they are not suitable for use such as checking the reliability of the measurement distance before and after every measurement performed repeatedly at high speed. Although a plurality of switchings are also recommended for the delay time to be set, no specific method is disclosed at all, and it merely suggests a future technical problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and starts a timing operation at the same time as transmitting a ranging signal, and receives a ranging signal reflected by an object to be measured. At that time, a distance measuring means for measuring an object distance by multiplying 1/2 of the measured value by the traveling speed of the distance measuring signal;
A diagnostic signal separate from the distance measuring signal is supplied to the distance measuring means to start a timing operation, and a pseudo distance measuring signal generated by delaying the diagnostic signal for a predetermined time is received. Comparing the clock value at the time of reception with the delay time, and diagnosing means for diagnosing the distance measuring means from the degree of an error, the objective distance measuring device,
The means has completed the distance measurement once by the distance measuring means.
Later, a diagnostic signal is generated and the distance measuring means is timed.
A diagnostic signal generating circuit to be started;
Predetermined time shorter than the time margin before separation measurement starts
And provide it to the distance measurement means as a pseudo ranging signal.
And a delay circuit for supplying the same.

Also, the present invention provides a method for transmitting a ranging signal.
At the same time, start timing operation and
At the point when the projected ranging signal is received,
Rangefinder that measures the object distance by multiplying the travel speed of the ranging signal
Measuring means, and a separate diagnosis for the distance measuring means from the distance measuring signal.
A time-out operation is started by supplying a disconnection signal,
A pseudo ranging signal generated by delaying the
The measured value at the time of receiving the pseudo ranging signal and the delay.
Compared with the delay time, the distance measurement means from the degree of error
An objective distance measuring device comprising diagnostic means for diagnosing.
The diagnostic means may determine the delay time at a substantially constant cycle.
It is characterized in that switching is set stepwise .

Still further, the present invention provides the distance measuring device,
The stage emits laser light to the object whose distance is to be measured.
Optical element and laser reflected by the object whose distance is to be measured
A condenser lens for condensing light, and a condenser lens for condensing light.
Light-receiving element for receiving the laser light, and the output of the light-receiving element
An amplifier circuit for amplifying the light, and
Start counting and stop counting upon receiving the output of the amplifier circuit
Counter circuit, and の of the count value of the counter circuit.
To measure the object distance by multiplying the clock cycle by the speed of light
And a calculation circuit .

[0010]

[0011]

According to the present invention, the time measurement operation is started simultaneously with the transmission of the distance measurement signal, and when the distance measurement signal reflected by the object to be measured is received, the distance measurement signal is reduced to half of the time measurement value. While measuring the object distance by multiplying the traveling speed, a diagnostic signal separate from the ranging signal is supplied to start the timing operation, and further, the diagnostic signal is delayed for a predetermined time to receive a pseudo ranging signal generated. By comparing the measured time value at the time of receiving the pseudo ranging signal with the delay time, and diagnosing the distance measuring means from the degree of error, it is possible to always diagnose each distance measurement.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic block diagram showing an embodiment of an object distance measuring apparatus according to the present invention.
Is a signal waveform diagram of each part of the circuit shown in FIG. 1, and FIG.
6 is a flowchart for explaining a diagnostic operation by the CPU shown in FIG.

An object distance measuring device 21 shown in FIG. 1 is a counter circuit 2 commonly used for a distance measuring system, a diagnostic system, and both systems.
2 and a CPU 23 and the like. The distance measurement system includes a distance measurement signal generation circuit 24 that generates a distance measurement signal at a constant cycle;
A laser diode drive circuit 25 triggered by the distance measurement signal, a laser diode 26 driven by the laser diode drive circuit 25 to generate laser light, and a projection lens 27 for projecting the output of the laser diode 26 to the outside
A condenser lens 29 for condensing the laser light reflected by the object 28 to be measured, a photodiode 30 for receiving the laser light condensed by the condenser lens 29,
Amplifier circuit 31 for amplifying output of photodiode 30
And a photodiode 40 for receiving the output of the laser diode 26 in close proximity, a waveform shaping circuit 41 for shaping the waveform of the light receiving output of the photodiode 40 to be a distance measurement start signal, and the like. In this embodiment, the provision of the photodiode 40 and the waveform shaping circuit 41 does not cause the counter circuit 22 to start counting by the output of the ranging signal generating circuit 24, but synchronizes with the emission time of the laser diode 26. 22 can start counting.

The diagnostic system generates a diagnostic signal after the distance measurement system completes one distance measurement and causes the counter circuit 22 to start a counting operation. A delay circuit 33 that delays by a predetermined time Td, an LED drive circuit 34 triggered by a delay output of the delay circuit 33, and L that is driven by the LED drive circuit 34 and irradiates the focusing lens 29 with a pseudo ranging signal.
It has an ED 35 and an OR gate circuit 36 that allows the counter circuit 22 to pass both the distance measurement start signal and the diagnostic signal. The delay time Td set in the delay circuit 34
Is switched stepwise by the CPU 23 as described later, but the value obtained by adding the maximum measurement time by the distance measurement system to the delay time Td is considered so as to fall within the period of the distance measurement signal generated by the distance measurement signal generation circuit 24. Therefore, all the diagnostic operations can be performed by sewing between the distance measuring operations. In the case of this embodiment, the counter circuit 22 starts counting when the laser diode 26 or the laser diode 35 emits light or when a diagnostic signal is generated, and stops receiving the output of the amplifier circuit 31 when counting. Also, the CPU 23
Calculates the object distance by multiplying the count value of the counter circuit 22 by the clock cycle and the speed of light, and increases the delay time Td set in the delay circuit 33 by ΔT each time one distance measurement is completed. Work.

Incidentally, the diagnosis by the diagnosis system is performed once each time the distance is measured. That is, prior to the first measurement, the CPU 23 first sets the delay time Td (= To + k) set in the delay circuit 33 in step (101) of FIG.
ΔT) is reset, and the initial value To is selected by setting k = 0. Next, in step (102), the CPU 23 determines whether or not a time slightly exceeding a time corresponding to the maximum value of the measured object distance has elapsed. Judge that it is completed,
The measurement value of the counter circuit 22 is read and the object distance is calculated. When there is no obstacle, the reflected light does not return and the counter circuit 22 continues the counting operation up to the upper limit value. In this case, however, the measured value, that is, the upper limit value exceeds the maximum value. Judge. CPU23
In step (103), the delay circuit 33
After confirming that the delay time is Td, the diagnostic signal generation circuit 32 is triggered.

The diagnostic signal generated by the diagnostic signal generating circuit 32 is supplied to the counter circuit 22 via the OR gate circuit 36, and is also supplied to the delay circuit 33. As a result, the counter circuit 22 restarts the counting operation triggered by the diagnostic signal, and the delay circuit 33 delays the diagnostic pulse by the predetermined time Td (= To). However, since the counting by the counter circuit 22 is continuously performed even while the delay by the delay circuit 33 is being performed, if the counter circuit 22 is operating normally, the counter at the time when the delay by the delay circuit 33 is completed is completed. The count value of the circuit 22 is
3 corresponds to the delay time Td.

The diagnostic signal output from the delayed delay circuit 33 triggers the LED drive circuit 34 as a pseudo ranging signal. Therefore, the LED driving circuit 34
35 is driven, and the light emitted from the LED 35 is
9 and is received by the photodiode 30. The light receiving output of the photodiode 30 is amplified by the amplifier circuit 31 and then supplied to the counter circuit 22 as a count stop signal. For this reason, the counter circuit 22 stops counting when the delay time Td by the delay circuit 33 has elapsed from the time triggered by the diagnostic signal. Since the counter circuit 22 performs a counting operation in accordance with the reference clock having the period τ, if there is no abnormality in the distance measurement system from the condenser lens 29 to the counter circuit 22, the counting output N
Must be equal to the delay time Td of the delay circuit 33.

Then, the CPU 23 reversely calculates the pseudo round trip time T (= Nτ) from the distance measurement value based on the pseudo ranging signal,
In a step (105) following the step (104), the time T is compared with the delay time Td. As a result, T-
If the absolute value of Td is equal to or smaller than the allowable error ε, it is determined that there is no abnormality, and the process proceeds to step (106). Otherwise, an abnormality alarm is issued in step (107). The cause of the abnormality may be a surface contamination of the condenser lens 29, an abnormal light reception of the photodiode 30, an abnormal operation of the amplifier circuit 31, an abnormal count of the counter circuit 22, or the like. It is notified with an alarm that the operation has not been performed normally.

When the first diagnosis is completed and no abnormality is found, the value of k is increased by 1 in step (106), and then the value of k is increased by 1 in step (10).
After confirming in step 8) that the value of k has not reached the upper limit value of n + 1, the process returns to step (102) again to continue the diagnosis. Note that the delay time Td set in the delay circuit 33 after the second distance measurement is executed is the delay time Td shown in FIG.
As shown in (A) to (D), Td = To + ΔT, and the CPU 23 that has increased the delay time Td by ΔT
Diagnosis continues as before. Similarly, the delay time set in the delay circuit 33 every time the diagnosis is repeated is Td + kΔ
Rounded up gradually like T, and finally Td + n
After reaching ΔT, in step (109) following step (108), k = 0 is set, so that diagnosis is restarted from the delay time To.

As described above, the objective distance measuring device 21
The distance measurement system can be diagnosed at least once without any external irradiation of laser light before or after the distance measurement by the diagnosis system attached to the distance measurement system. Diagnosis is not performed only once at special occasions such as periodic inspections by the device, but is performed periodically by diagnostic means incorporated in the device. Therefore, the reliability of the distance measurement value can be constantly monitored. For this reason, for example, when applied to an automatic braking device or the like that automatically performs braking according to the following distance, the automatic braking is erroneously performed despite the sufficient following distance, or the following distance may cause a collision. The inconvenience that automatic braking does not occur despite the dangerous distance can be reliably eliminated.

Further, since the diagnostic system switches and sets the delay time Td step by step at a substantially constant cycle, a plurality of delay times Td are set within a given diagnostic period, and various measured values actually measured are set. By performing a diagnosis evenly under conditions close to the value, it is possible to eliminate omissions and errors in diagnosis as much as possible, compared to a method of diagnosing only with a fixed delay time, and to achieve a more reliable diagnosis. It is possible.

Further, even when the output level of the laser diode 26 is suppressed in consideration of the effect of the laser light on the human body, the laser light reflected by the distance measurement object is condensed by the condensing lens 29 and the photodiode The light receiving output of the photodiode 30 is further amplified by an amplifier circuit 31.
Therefore, even a weak laser beam can be accurately received. Also, every time a distance measurement is performed, the operation of the distance measurement system is checked for an abnormality. However, since the measurement period and the diagnosis period are shifted in time, a pseudo ranging signal used for diagnosis may be mistaken for a ranging signal. However, the distance to an object that does not actually exist is not measured.

In the above embodiment, the delay circuit 33
May be fixed to a fixed time,
In that case, the diagnostic signal generation circuit 32
It is preferable that the distance measurement signal generation circuit 24 itself triggers the diagnostic signal generation circuit 32 when the maximum time required for distance measurement elapses after generating the distance measurement signal. Further, the distance measurement signal is not limited to a laser beam, and may be, for example, an ultrasonic wave or an electromagnetic wave.

[0024]

As described above, according to the present invention, the time measurement operation is started at the same time as transmitting the distance measurement signal, and when the distance measurement signal reflected by the object to be measured is received,
Distance measuring means for measuring an object distance by multiplying 1/2 of the measured value by the traveling speed of the ranging signal, and receiving a pseudo ranging signal generated by delaying a diagnostic signal for a predetermined time, and receiving the pseudo ranging signal comparing the counting value and the delay time at the time, and a diagnostic means for diagnosing the distance measuring means from the degree of error, the diagnosis
The distance measuring means completes one distance measurement.
After that, a diagnostic signal is generated and the distance measuring means is timed.
A diagnostic signal generating circuit for starting the diagnostic signal;
At a predetermined time shorter than the time margin before the distance measurement starts
Delay to the distance measuring means as a pseudo ranging signal.
The diagnostic circuit provided with the distance measuring means can diagnose the distance measuring means at least once before or after distance measurement without externally transmitting a distance measuring signal. Therefore, like a conventional objective distance measuring device that diagnoses with a test device provided outside the device,
Rather than performing a single diagnosis prior to measurement at special occasions such as periodic inspections, the diagnosis can be performed periodically by the diagnostic means built into the device, and the reliability of the distance measurement value is constantly monitored. For example, when the present invention is applied to an automatic braking device or the like that automatically applies braking according to the following distance, the automatic braking is erroneously performed even though the following distance is sufficient, or the following distance is obtained. However, there is an excellent effect that an inconvenience that automatic braking does not occur despite the distance at which there is a danger of collision can be reliably eliminated. Also, every time distance measurement is performed,
It is possible to check for abnormal operation of the measuring
Since the measurement period and the diagnosis period are shifted in time,
The pseudo ranging signal used is mistaken for the ranging signal,
When measuring the distance to an object that does not exist
Effects, such as being able to reliably eliminate
I do.

Further, according to the present invention, when a ranging signal is transmitted,
At the same time, start timing operation and
At the point when the projected ranging signal is received,
Rangefinder that measures the object distance by multiplying the travel speed of the ranging signal
Measurement means and a pseudo signal generated by delaying the diagnostic signal by a certain time
Receiving the ranging signal and timing at the time of receiving the pseudo ranging signal
Compare the value with the delay time and determine the distance
Diagnostic means for diagnosing the condition, wherein the diagnostic means is substantially
A configuration in which the delay time is switched stepwise at a fixed cycle and
Multiple diagnostic times within a given diagnostic period.
In the condition close to various measured values actually measured
When the delay is fixed to a constant value by performing the diagnosis without
Omission of diagnosis or diagnosis error
As much as possible and a more reliable diagnosis
It has effects such as being possible.

[0026]

Further, according to the present invention, the distance measuring means includes a
A light emitting element that emits laser light to an object to be measured,
Focuses the laser beam reflected by the object whose distance is to be measured
Focusing lens and laser focused by the focusing lens
Light receiving element for receiving light and amplifying the output of the light receiving element
Start counting when the light emitting element emits light from the amplifier circuit
And a counter that stops counting upon receiving the output of the amplifier circuit.
Counter circuit and a half of the count value of the counter circuit.
An arithmetic circuit that measures the object distance by multiplying the light cycle and the light cycle
Laser light emitted from the light emitting element
Considering the effect on the human body, the output level of the light emitting element is suppressed.
The laser beam reflected by the distance measurement target
The light is condensed by the condenser lens and is received by the light receiving element.
By amplifying the light receiving output of the element with an amplifier circuit,
It can accurately receive even weak laser light.
It produces effects such as

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an embodiment of an object distance measuring apparatus according to the present invention.

FIG. 2 is a signal waveform diagram of each section of the circuit shown in FIG.

FIG. 3 is a flowchart for explaining the operation of the CPU shown in FIG. 1;

FIG. 4 is a schematic block diagram showing an example of a conventional objective distance measuring device.

FIG. 5 is a schematic block diagram showing an example of a conventional objective distance measuring device test apparatus.

[Explanation of symbols]

 Reference Signs List 21 Object distance measuring device 22 Counter circuit 23 Arithmetic circuit (CPU) 24 Distance measuring signal generating circuit 26 Light emitting element (laser diode) 28 Object 29 Condensing lens 30 Light receiving element (photodiode) 31 Amplifier circuit 32 Diagnostic signal generating circuit 33 Delay circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /48-7/51 G01S 17/00-17/95

Claims (3)

(57) [Claims] When a distance measurement signal is transmitted, a time measurement operation is started at the same time as the distance measurement signal is transmitted, and when a distance measurement signal reflected by an object to be measured is received, the speed of the distance measurement signal is reduced to half of the time measurement value. And a distance measuring means for measuring an object distance by multiplying the distance measuring signal by supplying a diagnostic signal separate from the distance measuring signal to start the timing operation and delaying the diagnostic signal by a predetermined time. An object distance measuring device comprising a pseudo ranging signal, a time value at the time of receiving the pseudo ranging signal, and the delay time, and a diagnostic means for diagnosing the distance measuring means from a degree of error. The diagnostic means may be configured such that the distance measuring means performs one distance measurement.
After completion, a diagnostic signal is generated and the distance measuring means is counted.
Diagnostic signal generating circuit for starting the operation when the diagnostic signal
Is less than the time margin before the next distance measurement starts
Delays by a predetermined time and measures the distance as a pseudo ranging signal
And a delay circuit for supplying to the means.
Distance measuring device . 2. A timing operation is performed simultaneously with transmitting a distance measurement signal.
The ranging signal that starts and is reflected by the object whose distance is to be measured
At the time of receiving, the traveling speed of the ranging signal is reduced to 1/2 of the measured value.
Distance measuring means for measuring an object distance by multiplying the degree, and the distance
Supply a diagnostic signal separate from the ranging signal to the measuring means
Start the timekeeping operation and output the diagnostic signal for a certain period of time.
The pseudo-ranging signal generated with the delay is received and the pseudo-ranging signal is received.
Compare the time value at the time of receiving the distance signal with the delay time
Diagnostic means for diagnosing the distance measuring means from the degree of error.
And an objective distance measuring device comprising: a stage, wherein the diagnostic means steps the delay time at a substantially constant cycle.
Objective distance measurement device characterized by switching
Place . 3. A distance measuring means comprising: a light emitting element for emitting laser light to an object to be measured; a condenser lens for collecting laser light reflected by the object to be measured; A light-receiving element that receives the laser light condensed by the optical lens, an amplifier circuit that amplifies the output of the light-receiving element, starts counting when the light-emitting element emits light, receives the output of the amplifier circuit, and starts counting. A counter circuit to stop,
The objective distance measuring device according to claim 1 or 2, further comprising: an arithmetic circuit that measures an objective distance by multiplying a half of a count value of the counter circuit by a clock cycle and a light speed.