JPH07134177A - Objective distance measuring device - Google Patents

Abstract

PURPOSE:To perform an abnormality diagnosis every distance measurement by comparing the count value at the point of time when a pseudo distance measurement signal in which diagnosis signal is delayed for a fixed time is received with the delay time. CONSTITUTION:Timer counting is started simultaneously with the transmission of a distance measurement signal 24, and at the point of time when the distance measurement signal reflected by an object 28 is received, 1/2 of the timer count value is multiplied by the advancing speed of the measurement signal to measure the objective distance. A counter circuit 22 restarts counting by a diagnosis signal 32 every completion of distance measurement, a delay circuit 33 delays a diagnosis pulse by a prescribed time Td. A LED driving circuit 34 inputs the diagnosis signal outputted after delay as a pseudo distance measurement signal to drive a LED 35. The circuit 22 inputs a counting stop signal which received 30 this emission, and stops the counting at the point of time when the time Td passes from the counting restart point. A CPU 23 inversely operates a pseudo reciprocating time T from the distance measurement value by the pseudo distance measurement signal, compares times T, Td to each other, judges no abnormality when T-T0 is less than an allowable error, and gives an abnormality alarm when it is the allowable error or more.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An objective distance measuring apparatus 1 shown in FIG. 4 is mounted on a vehicle for measuring an inter-vehicle distance, and a distance measuring signal generated by a distance measuring signal generating circuit 2 is transmitted to a front side via a transceiver 3. And receives the distance measurement signal reflected by the object 4 such as a vehicle ahead or a guardrail. During this time, the counter circuit 5
Starts the counting operation at the time of transmitting the distance measurement signal, and stops the counting operation at the time of receiving the distance measurement signal. The count value N of the counter circuit 5 is read by the CPU 6 and subjected to 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 further, to 1/2 of this transmission / reception time difference T, the traveling speed v of the distance measurement signal. Multiply by object 4
The distance Tv / 2 to is calculated. Furthermore, the CPU 6
The vehicle-to-vehicle distance data calculated is constantly monitored, and when a safe vehicle-to-vehicle distance cannot be maintained, an abnormal approach is warned or automatic braking is applied to prevent a collision.

As described above, the objective distance measuring device 1 is
The distance to the obstacle 4 in front of the vehicle can be accurately measured by using the distance measurement signal, but when the transceiver 3 malfunctions, this abnormality is not noticed. If left unattended, a dangerous inter-vehicle distance will be frequently alerted, even if the vehicle is traveling with a safe inter-vehicle distance, or automatic braking will be applied when it is not necessary, and vice versa. Although there was a danger of a rear-end collision due to abnormally approaching the car, there was a problem that an alarm was not issued or automatic braking ended unsuccessfully.

Therefore, in order to monitor the malfunction of the objective distance measuring device 1, for example, Japanese Patent Laid-Open No. 57-11627.
No. 4 "Testing device for laser distance measuring device" measures the distance to the target object whose distance is known in advance so that it can be diagnosed 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 the pseudo distance measurement signal generated when a certain time has elapsed after the counter circuit 5 started counting.
A test device for testing the objective distance measuring device 1 using a pseudo ranging signal is disclosed. FIG. 5 shows a test apparatus 1 of this type.
1 shows a schematic configuration of the objective distance measuring device 1
A distance measurement signal such as a laser beam emitted by is received by the light receiving lens 11 and sent to the light receiving element 13 via the 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 for a time Td set by assuming the time until the laser light is reflected by the target and returns, and the delayed output is transmitted 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 is
Light is emitted when the time Td elapses from the time when the light receiving element 13 receives light, and the light emission output is returned to the objective distance measuring device 1 via the light emitting lens 18. At this time, since the objective distance measuring device 1 measures the objective distance based on the time difference between the transmission and reception of the distance measuring signal, the round-trip time T of the distance measuring signal calculated back from the objective distance is used as the delay time Td in the delay circuit 15. The objective distance measuring device 1 can be diagnosed by comparing and determining whether the two match within a predetermined error range.

[0005]

The test apparatus 10 for the above-mentioned conventional objective distance measuring apparatus 1 is a separate apparatus from the objective distance measuring apparatus 1 and, as a matter of course, in the test, the objective distance measuring apparatus 1 is required. Must be used in direct contact with
During the actual distance measurement period by the objective distance measuring device 1, it cannot be used because it interferes with the distance measurement. In addition, it is usually used before the distance measurement by the object distance measuring device 1. Therefore, in the case of a device such as an inter-vehicle distance measuring device which is mounted on a vehicle, it may be used at a maintenance shop or the like at the time of periodic inspection. It was limited to such uses as. Further, the configuration of the test apparatus 10 is almost the configuration of the objective distance measuring apparatus 1 itself, except that the delay circuit 15 is included instead of the counter circuit 5 used for measuring the transmission / reception time difference T. However, 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 the 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 it was not possible to comprehensively test.

A device in which a diagnostic device is integrally attached to an object distance measuring device is disclosed in, for example, Japanese Patent Laid-Open No. 2-309282.
No. “Ranging device”. This is a configuration in which the light emitting lens emits a laser beam is detected by an external light detection circuit, and the delay circuit is activated by the detection signal to generate a pseudo ranging signal. However, there is a problem in that the laser beam must be emitted from the light emitting lens to the outside, and therefore the human body may be adversely affected depending on the direction of the light emitting lens. In addition, since the diagnostic mode and the measurement mode are strictly distinguished, they are not suitable for usage such as always checking the reliability of the measured distance before and after each high-speed repeated measurement. Although a plurality of switchings for the delay time to be set to are recommended, the specific method is not 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 problems, and at the same time as transmitting a distance measurement signal, a timekeeping operation is started and a distance measurement signal reflected by an object as a distance measurement target is received. Distance measuring means for measuring the object distance by multiplying 1/2 of the measured value by the traveling speed of the distance measurement signal at the time
A diagnostic signal separate from the distance measuring signal is supplied to the distance measuring means to start a time measuring operation, and a pseudo distance measuring signal generated by delaying the diagnostic signal for a predetermined time is received to generate the pseudo distance measuring signal. It is characterized by comprising a diagnostic means for comparing the timed value at the time of reception with the delay time and diagnosing the distance measuring means based on the degree of error.

Further, according to the present invention, the distance measuring means is
A light emitting element that emits a laser beam to an object that is a distance measurement target, a condenser lens that condenses the laser light reflected by the object that is a distance measurement target, and a laser beam that is condensed by the condenser lens A light receiving element, an amplifier circuit that amplifies the output of the light receiving element, a counter circuit that starts counting when the light emitting element emits light, and stops counting when receiving the output of the amplifier circuit, and a counter circuit An arithmetic circuit for measuring an object distance by multiplying a half of the numerical value by a clock period and a speed of light is provided.

Still further, according to the present invention, the diagnostic means generates a diagnostic signal after the distance measuring means completes one distance measurement, and causes the distance measuring means to start a timing operation. And a delay circuit for delaying the diagnostic signal by a predetermined time shorter than a time margin until the start of the next distance measurement and supplying it as the pseudo distance measuring signal to the distance measuring means. It is a thing.

Further, the present invention is characterized in that the diagnosis means sets the delay time in a stepwise manner at substantially constant intervals.

[0011]

According to the present invention, the time measuring operation is started at the same time as the distance measuring signal is transmitted, and when the distance measuring signal reflected by the object as the distance measuring object is received, the distance measuring signal is reduced to 1/2 of the time measuring value. While measuring the objective distance by multiplying the traveling speed, a diagnostic signal separate from the ranging signal is supplied to start the timekeeping operation, and the diagnostic signal is delayed for a certain period of time to generate a pseudo ranging signal. The time measuring value at the time of receiving the pseudo distance measuring signal is compared with the delay time, and the distance measuring means is diagnosed based on the degree of the error so that the diagnosis can be surely performed every time the distance is measured.

[0012]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic block configuration diagram showing an embodiment of an object distance measuring apparatus of the present invention, FIG.
Is a signal waveform diagram of each part of the circuit shown in FIG. 1, and FIG.
5 is a flowchart for explaining a diagnostic operation by the CPU shown in FIG.

The objective distance measuring device 21 shown in FIG. 1 is a counter circuit 2 which is shared by a distance measuring system, a diagnostic system and both systems.
2 and the 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 a 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 condensing lens 29 that condenses the laser light reflected by the object 28 that is the distance measurement target, and a photodiode 30 that receives the laser light condensed by the condensing lens 29.
Amplifier circuit 31 for amplifying the output of the photodiode 30
And a photodiode 40 which receives the output of the laser diode 26 up close and a waveform shaping circuit 41 which shapes the received light output of the photodiode 40 as a distance measurement start signal. In the embodiment, since the photodiode 40 and the waveform shaping circuit 41 are provided, the counter circuit 22 does not start counting by the output of the distance measurement signal generation circuit 24, but the counter circuit is synchronized with the light emission time of the laser diode 26. 22 can be started to count.

The diagnostic system generates a diagnostic signal after the distance measuring system completes one distance measurement and causes the counter circuit 22 to start the counting operation, and the diagnostic signal is switched in stages. A delay circuit 33 that delays by a predetermined time Td, an LED drive circuit 34 that is triggered by the delay output of the delay circuit 33, and an L drive circuit 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, an OR gate circuit 36 and the like which allows passage of both the distance measurement start signal and the diagnostic signal to the counter circuit 22. The delay time Td set in the delay circuit 34
Is gradually changed by the CPU 23 as will be described later, but the value obtained by adding the maximum measurement time by the distance measurement system to the delay time Td is considered to be 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 measurement operations of each time. In the case of the embodiment, the counter circuit 22 starts counting when the laser diode 26 or the laser diode 35 emits light or when the diagnostic signal is generated, and stops counting upon receiving the output of the amplifier circuit 31. In addition, the CPU 23
Measures the object distance by multiplying ½ of the count value of the counter circuit 22 by the clock period 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.

By the way, the diagnosis by the diagnosis system is performed once for each distance measurement. 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.
The initial value To is selected by resetting ΔT) and setting k = 0. Next, in step (102), the CPU 23 determines whether or not a time slightly longer than the time corresponding to the maximum value of the object distance measurement value has elapsed, and if this time has elapsed, one object distance measurement is performed. Judged that it was completed,
The measured value of the counter circuit 22 is read and the objective distance is calculated. If 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, since the measured value, that is, the upper limit value, exceeds the maximum value, there is no obstacle. To judge. CPU23
Further includes the delay circuit 33 in step (103).
After confirming that the delay time is Td, the diagnostic signal generating 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 also to the delay circuit 33. As a result, the counter circuit 22 is triggered by the diagnostic signal to restart the counting operation, and the delay circuit 33 delays the diagnostic pulse by a predetermined time Td (= To). However, since the counter circuit 22 continuously counts while the delay circuit 33 delays, if the counter circuit 22 is operating normally, the counter at the time when the delay circuit 33 completes the delay is counted. The count value of the circuit 22 is the delay circuit 3
3 corresponds to the delay time Td.

The diagnostic signal output from the delay circuit 33, which has finished the delay, triggers the LED drive circuit 34 as a pseudo ranging signal. Therefore, the LED drive circuit 34
35 is driven, and the light emitted by the LED 35 is condensed by the condenser lens 2
The light passes through 9 and is received by the photodiode 30. The received light output of the photodiode 30 is amplified by the amplifier circuit 31 and then supplied to the counter circuit 22 as a counting stop signal. Therefore, the counter circuit 22 stops counting when the delay time Td of the delay circuit 33 elapses from the time when it is triggered by the diagnostic signal. Since the counter circuit 22 performs the counting operation in accordance with the reference clock of the period τ, if the distance measuring system from the condenser lens 29 to the counter circuit 22 is normal, the count output N
The time Nτ obtained by multiplying by the period τ must match the delay time Td in the delay circuit 33.

Therefore, the CPU 23 back-calculates the pseudo round-trip time T (= Nτ) from the distance measurement value by the pseudo distance measurement signal,
In step (105) following 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 less than the allowable error ε, it is determined that there is no abnormality and the process proceeds to step (106) and subsequent steps. If not, an abnormality alarm is issued in step (107). The cause of the abnormality may be surface contamination of the condenser lens 29, abnormal light reception of the photodiode 30, abnormal operation of the amplifier circuit 31, abnormal counting of the counter circuit 22, or the like. An alarm informs that the operation is not normally performed.

In this way, when the first diagnosis is completed and it is found that there is no abnormality, the value of k is incremented by 1 in step (106), and then the subsequent step (10
In 8), after confirming that the value of k has not reached the upper limit value of n + 1, the process returns to step (102) and the diagnosis is continued. The delay time Td set in the delay circuit 33 after the second distance measurement is executed is as shown in FIG.
As shown in (A) to (D), Td = To + ΔT, and the CPU 23 which has increased the delay time Td by ΔT,
Continue the diagnosis as before. Similarly, the delay time set in the delay circuit 33 each time the diagnosis is repeated is Td + kΔ
Rounded up like T, and finally Td + n
After reaching ΔT, the diagnosis is restarted from the delay time To again by setting k = 0 in the step (109) following the step (108).

As described above, the above-mentioned objective distance measuring device 21
Is capable of diagnosing the distance measurement system once before and after the distance measurement by the diagnostic system attached to the distance measurement system without irradiating the laser beam to the outside. Since the device does not make a diagnosis only once at a special occasion such as a periodic inspection, but the diagnosis means built in the device makes a periodic diagnosis, so that the reliability of the distance measurement value can be constantly monitored. Therefore, for example, when applied to an automatic braking device or the like that automatically applies braking according to an inter-vehicle distance, the automatic braking may be accidentally applied even though the inter-vehicle distance is sufficient, or the inter-vehicle distance may cause a collision. It is possible to reliably eliminate the inconvenience that automatic braking does not occur despite a dangerous distance.

Further, since the diagnostic system sets the delay time Td in a stepwise manner with a substantially constant cycle, a plurality of delay times Td are set within a given diagnostic period, and various actually measured measurements are made. By performing diagnosis evenly under conditions close to the value, it is possible to eliminate missed diagnoses and mistakes as much as possible, compared to a method that diagnoses only with a fixed delay time, and a more reliable diagnosis can be made. It is possible.

Further, even when the output level of the laser diode 26 is suppressed in consideration of the influence of the laser light on the human body, the laser light reflected by the distance measuring object is condensed by the condenser lens 29 and the photodiode. 30 receives light, and further the received light output of the photodiode 30 is amplified by the amplifier circuit 31.
Since it is amplified by, it is possible to accurately receive even weak laser light. In addition, the operation abnormality of the distance measurement system is checked every time the distance measurement is performed, but since the measurement period and the diagnosis period are temporally shifted, the pseudo distance measurement signal used for diagnosis is mistaken for the distance measurement signal. , There is no need to measure the distance to an object that does not actually exist.

In the above embodiment, the delay circuit 33 is used.
The delay time Td set to may be fixed to a fixed time,
In that case, the diagnostic signal generating circuit 32 is the distance measuring signal generating circuit 24.
After generating the distance measurement signal, the distance measurement signal generation circuit 24 itself may trigger the diagnostic signal generation circuit 32 at the time when the maximum time required for distance measurement has elapsed. Furthermore, the distance measurement signal is not limited to laser light, and may be ultrasonic waves or electromagnetic waves, for example.

[0024]

As described above, according to the present invention, when the distance measurement signal is transmitted, the timekeeping operation is started at the same time, and the distance measurement signal reflected by the object as the distance measurement object is received,
Distance measuring means for measuring the object distance by multiplying 1/2 of the measured value by the traveling speed of the distance measuring signal, and a pseudo distance measuring signal generated by delaying the diagnostic signal for a predetermined time are received, and the pseudo distance measuring signal is received. Since the time measuring value at the time point and the delay time are compared, and the distance measuring means is diagnosed based on the degree of the error, the diagnostic means provided along with the distance measuring means can be used before or after the distance measurement. It is possible to diagnose the distance measuring means at least once without transmitting the distance measurement signal to the outside. Therefore, as in the conventional object distance measuring device that performs the diagnosis by the test device provided outside the device, special inspection such as periodic inspection is performed. Opportunity to make a diagnosis only once prior to measurement, it is possible to make a diagnosis periodically by the diagnosis means built into the device.
Moreover, since the reliability of the distance measurement value can be constantly monitored, when it is applied to, for example, an automatic braking device that automatically brakes according to the inter-vehicle distance, even if the inter-vehicle distance is sufficient, the It is possible to surely eliminate the inconvenience that the vehicle is braked or the automatic braking does not occur even though the inter-vehicle distance is a distance at which there is a risk of collision.

Further, according to the present invention, the distance measuring means includes a light emitting element for emitting a laser beam to an object as a distance measuring object,
A condenser lens that condenses laser light reflected by an object that is a distance measurement target, a light receiving element that receives the laser light that is condensed by the condensing lens, and an amplifier circuit that amplifies the output of the light receiving element. , A counter circuit that starts counting at the time when the light emitting element emits light and stops counting upon receiving the output of the amplifier circuit, and an object distance by multiplying ½ of the count value of the counter circuit by a clock period and the speed of light. Since it is configured with an arithmetic circuit for measuring, the laser light reflected by the distance measurement target is suppressed even when the output level of the light emitting element is suppressed in consideration of the influence of the laser light emitted by the light emitting element on the human body. Is collected by the condenser lens and received by the light receiving element, and the light receiving output of the light receiving element is amplified by the amplifier circuit,
There is an effect such that even a weak laser beam can be accurately received.

Further, according to the present invention, the diagnostic means is a diagnostic signal generation circuit for generating a diagnostic signal after the distance measuring means completes one distance measurement and causing the distance measuring means to start a time counting operation. , Delaying the diagnostic signal by a predetermined time shorter than the time margin until the next distance measurement is started,
Since the delay circuit for supplying the pseudo distance measuring signal to the distance measuring means is provided, it is possible to check the operation abnormality of the distance measuring means every time the distance measuring is performed once, and further, the measuring period and the diagnostic period are provided. Since the time shifts are erroneous, it is possible to reliably eliminate the inconvenience of mistaking the pseudo ranging signal used for diagnosis as the ranging signal and measuring the distance to an object that does not actually exist. Produce the effect of.

Further, according to the present invention, since the diagnosis means is configured to switch and set the delay time stepwise at a substantially constant cycle, a plurality of diagnosis times are set within a given diagnosis period and actually measured. By making a diagnosis evenly under conditions close to various measured values, it is possible to eliminate omissions and mistakes in diagnosis as much as possible, compared to the method of diagnosing only the delay time fixed to a fixed value, and more reliable. There is an effect such that highly accurate diagnosis is possible.

[Brief description of drawings]

FIG. 1 is a schematic block configuration diagram showing an embodiment of an objective distance measuring device of the present invention.

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

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

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

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

[Explanation of symbols]

 21 Objective Distance Measuring Device 22 Counter Circuit 23 Arithmetic Circuit (CPU) 24 Distance Measuring Signal Generation 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

Claims (4)

[Claims] 1. When the distance measuring signal is transmitted, the time measuring operation is started at the same time, and when the distance measuring signal reflected by an object as a distance measuring object is received, the traveling speed of the distance measuring signal is reduced to 1/2 of the time measuring value. Is generated by multiplying the distance measurement means by which the objective distance is measured, and a diagnostic signal separate from the distance measurement signal is supplied to the distance measurement means to start a time counting operation, and the diagnostic signal is generated by delaying for a certain time. A diagnostic means for receiving the pseudo distance measuring signal, comparing the time value at the time of receiving the pseudo distance measuring signal with the delay time, and diagnosing the distance measuring means based on the degree of error. Objective distance measuring device. 2. The distance measuring means includes a light emitting element that emits laser light to an object that is a distance measurement target, a condenser lens that collects laser light reflected by the object that is the distance measurement target, and the collection lens. A light-receiving element that receives the laser light focused by the optical lens, an amplifier circuit that amplifies the output of the light-receiving element, and counting is started when the light-emitting element emits light. A counter circuit to stop,
The objective distance measuring device according to claim 1, further comprising: an arithmetic circuit for measuring an object distance by multiplying a count value of the counter circuit by a clock period and a speed of light. 3. The distance measuring means is 1 in the diagnosing means.
A diagnostic signal generation circuit for generating a diagnostic signal after completing the distance measurement once to start the time measuring operation of the distance measuring means, and the diagnostic signal is shorter than the time margin until the next distance measurement is started. The objective distance measuring device according to claim 1, further comprising a delay circuit which delays the signal by a predetermined time and supplies it to the distance measuring means as a pseudo distance measuring signal. 4. The objective distance measuring device according to claim 1, wherein the diagnostic means switches and sets the delay time stepwise in a substantially constant cycle.