JPH06289127A - Distance measuring device - Google Patents

Abstract

PURPOSE:To provide a distance measuring device which is simple in circuit regulation and inexpensively manufactured. CONSTITUTION:A time width enlarging circuit 5 enlarges a pulse response time from the emission of an electromagnetic wave pulse to a target article till the detection of its reflecting pulse. An enlarged pulse response time is measured by a counter, and the measured enlarged pulse response time is converted into a distance to the target article through a distance computing circuit. In this case, a time width enlarging circuit 5 stores an electric charge at a fixed current value in a capacitor 20 through the constant current source 16 of a charging means for a pulse response time, and the constant current source 17 of a discharging means discharges the electric charge stored in the capacitor 20 at a fixed current value lower than a supplied current value at the same time as the detection of the reflecting pulse, and a discharging time is set up longer than the charging time of the capacitor for enlarging the pulse response time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring the distance to a target using electromagnetic waves such as laser light.

[0002]

2. Description of the Related Art Generally, a distance measuring device is a practically open type Sho 60-1.
As disclosed in Japanese Patent No. 93485, by emitting a laser pulse toward a target object and receiving the reflected pulse thereof, the time required from the laser pulse emission time to the light reception time is measured, It is designed to calculate the distance to the target.

The distance measuring device described above will be described with reference to a block diagram. As shown in FIG.
The laser light oscillated from is condensed by the transmission optical system 30 and is emitted to the target object, and the reflected light which reaches the target object and is reflected is condensed by the reception optical system 33. Then, the distance to the target object is calculated as follows.

The photodetector 32 detects the laser oscillation timing of the laser oscillator 31 and outputs this oscillation timing to the gate circuit 37 as a start pulse signal S22. Then, the photodetector 34 detects the reflected light condensed by the receiving optical system 33 and outputs the reflected light detection signal to the amplifier 35. The amplifier 35 outputs the stop pulse signal S21 to the gate circuit 37 as the reflected light reception timing. As shown in FIG. 5, the gate circuit 37 uses the time t from the input of the start pulse signal S22 to the input of the stop pulse signal S21 as the pulse response time during the pulse response time t from the clock oscillator 36. The input clock pulse signal is gated and the clock pulse signal is output to the counter 38. Then, the counter 38 measures the number of clock pulse signals input from the gate circuit 37, calculates the pulse response time from the measured number of clock pulses and the frequency of the clock oscillator, and outputs the calculated response time. The distance to the target is calculated from the spatial propagation velocity of the laser light and the like.

The calculated distance is displayed on the distance display 39.
Is output and displayed.

By the way, since an electromagnetic wave pulse such as a laser beam travels in space at the speed of light, the pulse response time t is extremely short. Therefore, as described above, in the distance measuring device that directly measures the pulse response time t of this extremely short time, extremely high time measurement accuracy is required.

For example, during the pulse signal interval between the start pulse signal S22 and the stop pulse signal S21, that is, during the pulse response time t, the gate circuit 28 must output the gate with high accuracy without timing deviation. Therefore, as shown in FIG. 6, the start pulse signal S2
2 and the stop pulse signal S21 has a threshold value T
High-precision adjustment of pulse characteristics such as A and amplitude is required.
Further, since the reflected light detection signal is a pulse signal accompanied by an abrupt change, the amplifier 26 which receives the reflected light detection signal and outputs the stop pulse signal S21 follows the abrupt change of the reflected light detection signal. Therefore, it is necessary to use a high-speed slew rate amplifier whose frequency characteristic and the like are adjusted with high accuracy.

As described above, this high-speed slew rate amplifier requires high-precision circuit adjustment such as frequency characteristics and is more expensive than a general-purpose amplifier, which causes the cost of the device to increase.

Further, in order to count the extremely short pulse response time, it is necessary to increase the clock frequency of the clock oscillator 27, which also causes a cost increase.

As described above, in the distance measuring apparatus for directly measuring the pulse response time of an extremely short time with high accuracy, there is a problem that various adjustments of each circuit with high accuracy are required and the cost becomes high. .

Therefore, a distance measuring device that expands the pulse response time by using an integrating circuit of an operational amplifier instead of directly measuring the pulse response time has been put into practical use. That is, the distance to the target is calculated by measuring the expanded pulse response time. This eliminates the need for highly accurate adjustment of the threshold values of the start pulse signal S22 and the stop pulse signal S21, pulse characteristics, and the like, as well as the distance measurement device that directly measures the pulse response time, and the clock frequency of the clock oscillator 27. The cost can be reduced because the cost can be reduced.

[0012]

However, when the integrating circuit of the operational amplifier is used to extend the pulse response time, the operational amplifier is required to follow a rapid input change of the pulse response time in a very short time. A fast slew rate amplifier must still be used to perform the integral operation. Therefore, not only the cost can not be sufficiently reduced, but also highly accurate circuit adjustment such as the frequency characteristic is required, and improvement in these points has been demanded.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a distance measuring device capable of reducing cost and simplifying circuit adjustment as much as possible.

[0014]

In order to achieve the above object, the present invention provides a pulse emitting means for emitting an electromagnetic wave pulse to a target object and a reflected pulse detecting means for detecting the electromagnetic wave pulse reflected by the target object. A response time expanding means for expanding the response time from the emission of the electromagnetic wave pulse by the pulse emitting means to the detection of the reflected pulse by the reflected pulse detecting means, and the time expanded by the response time expanding means. Distance measurement including expansion time measuring means for measuring, and distance calculation means for converting the expansion time measured by the expansion time measuring means into a distance from the pulse emitting means or the reflected pulse detecting means to the target object. In the device, the response time expanding means is configured to charge the capacitor with a constant current value at the same time when the electromagnetic wave pulse is emitted from the pulse emitting means. A storage means for starting the supply and stopping the supply of electric charges at the same time when the reflection pulse is detected by the reflection pulse detecting means, and a reflection pulse is detected by the reflection pulse detecting means, and a supply by the storage means at the same time. Discharge means for discharging the electric charge stored in the capacitor at a constant current value lower than the current value (claim 1).

Here, the expansion time measuring means includes a charge emission detecting means for detecting a discharge completion time of the electric charge by the discharging means, and a charge emission completion time of the charge discharging detection means from a charging start time of the capacitor. Until the detection, the end signal output means for outputting the end signal and the start for a little longer than the time corresponding to the maximum detection distance detectable by the reflected pulse detection means after the discharge of the electric charge by the discharge means is started. It is desirable to include a start signal output means for outputting a signal, and a time measuring means for measuring a time during which both the end signal output means and the start signal output means output a signal (claim 2).

[0016]

According to the present invention having the above construction, the pulse response time from the emission of the electromagnetic wave pulse to the target to the detection of the reflected pulse is expanded by the response time expanding means, and the expanded pulse response time is obtained. Is measured by the expansion time measuring means, and the distance calculating means converts the distance to the target object based on the measured expansion pulse response time. At this time, the response time expansion means expands the pulse response time as follows. That is, during the pulse response time,
The storage means supplies electric charge to the capacitor at a constant current value and stores it, and the electric charge stored in this capacitor is discharged at a constant current value lower than the current value supplied by the storage means at the same time as the detection of the reflection pulse, thereby storing the electric charge. The discharge time is made longer than the time to extend the pulse response time (claim 1).

Further, when the expansion time measuring means is composed of the charge emission detecting means, the end signal outputting means and the time measuring means, the end signal outputting means operates from the start of charging the capacitor to the end of discharging. While the end signal is output, the start signal output means outputs the start signal for a time slightly longer than the time corresponding to the maximum detection distance detectable by the reflection pulse detection means from the time when the discharge means starts discharging the charge, and the time measurement is performed. The means measures the time during which both the start signal and the end signal are output, that is, the discharge time. Here, the time for the capacitor to discharge is
The storage time, that is, the pulse response time is an extended time, and is not longer than the time corresponding to the maximum detection distance (claim 2).

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in the block diagram of FIG. 1, the distance measuring apparatus of this embodiment has a laser pulse emitting section 11 as a pulse emitting means for emitting an electromagnetic wave pulse to a target and an electromagnetic wave pulse reflected by the target. And a reflected pulse light receiving unit 12 as a reflected pulse detecting unit for detecting a pulse, and a response time expansion for extending a response time from the emission of the electromagnetic wave pulse by the pulse emitting unit to the detection of the reflected pulse by the reflected wave pulse detecting unit. Time width expansion circuit 5 as means
And a distance calculating unit 13 having a function as an expansion time measuring unit for measuring the time expanded by the response time expanding unit and a function as a distance calculating unit for converting the measured expansion time into a distance to the target object. And a distance display unit 10 that displays the calculated distance.

The laser pulse emitting section 11 is composed of a controller 4, a high voltage generating circuit 3, a driving circuit 2 and a laser diode 1, and the reflected pulse receiving section 12 is a photodiode 6, a light receiving amplifier 7, a light receiving level detecting circuit 8 and It is composed of a pulse generation circuit 9. Since the laser pulse emitting section 11, the reflected pulse receiving section 12 and the distance display section 10 are almost common to the above-mentioned conventional example shown in FIG. 7, detailed description thereof will be omitted.

The specific circuit configuration of the time width expanding circuit 5 and the operation thereof will be described in detail below with reference to FIGS. 1, 2 and 3. Here, FIG. 2 is a time width expansion circuit diagram showing a specific circuit configuration of the time width expansion circuit 5, and FIG.
3 is a time chart showing the operation timing of each circuit of the time width expanding circuit 5.

As shown in FIGS. 1 and 2, the time width enlarging circuit 5 has a flip-flop 14, which includes a laser pulse emission signal S1 and a reflection pulse from the controller 4 and the pulse generating circuit 9, respectively. The reception signal S2 is input. Then, as shown in FIG. 3, the set output S3 of the flip-flop 14 is set at the rising edge of the laser pulse emission signal S1 and reset at the rising edge of the reflected pulse reception signal S2. The set output S of this flip-flop 14
3 is an ON signal of the switch 18 of the storage means and an input signal of the monostable multivibrator 15. Switch 18
While the set output S3 is being input to the capacitor 20, that is, during the pulse response time, the constant current source 1 of the storage means is stored in the capacitor 20.
6, a constant current value I1 is supplied to store electric charges, and as shown in S6 of FIG.
C rises.

Further, the time width expanding circuit 5 has a flip-flop 24, and the set output of the flip-flop 24 is the reflected pulse reception signal S2 as shown at S9 in FIG.
Is set at the rising edge of, and is reset at the rising edge of the repetition period signal S5 described later. The output signal S9 of the flip-flop 24 turns on the switch 19.
Become a signal. When this output signal S9 is input to the switch 19, the constant current source 17 of the discharging means causes the capacitor 20 to
The electric charge stored in the capacitor 20 is discharged, and the voltage VC of the capacitor 20 drops as indicated by S6 in FIG.

Here, the constant current source 17 is the capacitor 2
The electric charge is discharged from the capacitor 20 at a constant current value I2 obtained by multiplying the supply current value I1 during storage by 1 / K so that the discharge time of 0 becomes longer than the storage time. Therefore,
As shown in the following equation, the discharge time T of the capacitor 20
2 becomes T1 * K which is K times the storage time T1. If the total amount of charge stored in the capacitor is Q, the storage time is T1, and the time when all the stored charge Q is discharged is T2, then Q = I1 * T1 Q = I2 * T2 = (I1 / K) * T2, and from the above two equations, T2 = T1 * K (K> 1).

Further, in this embodiment, as shown in FIG.
The monostable multivibrator 15 starts the output of the start signal S4 to the AND circuit 26 in synchronization with the falling edge of the operation signal S3 of the flip-flop 14, and the time corresponding to the maximum detectable distance of the light receiving level detection circuit 8. The output is stopped after a slightly longer time T3 has elapsed. As a result, when performing an AND operation in the AND circuit 25 described later, A
The ON signal from the ND circuit 25 should not be stopped during the discharge of the capacitor 20.

As shown in FIG. 3, the controller 4
Is the capacitor 20 from when the laser pulse emission signal S1 is input until after the start signal S4 is turned off.
The signal that enables the battery discharge is output as the repeated periodic signal S5. That is, while the repeating cycle signal S5 is being output to the switch 21, the switch 21 is in the OPEN state, so that the capacitor 20 is in the state capable of storing and discharging. Further, the repetition period signal S5 is started to be output by being triggered by the laser pulse emission signal S1.

The voltage VC of the capacitor 20 is input to the buffer amplifier 22 as an analog signal, and is binarized (converted into a digital signal) via the comparator 23. That is, as shown in S8 of FIG. 3, the capacitor voltage V
After being amplified by the buffer amplifier 22, C is converted into an ON signal or an OFF signal by the comparator 23 and digitally output.

Here, the buffer amplifier 22 is an interface between the capacitor 20 as an analog signal source and the comparator 23 which outputs a binary logic of the analog signal. The buffer amplifier 22 determines the input impedance of the comparator 23 to stabilize it, and It serves to amplify the power for driving 23.

Then, the AND circuit 26 is connected to the comparator 2
The AND operation of the end signal S7 from 3 and the start signal S4 is performed, and the ON signal S15 is output as shown in FIG. That is, while the capacitor 20 is discharging, the ON signal S8 is output from the AND circuit 26 to the distance calculator 13.

The distance calculation unit 13 including a clock oscillator and the like calculates a time signal S10 obtained by pulse counting the input ON signal S8 by the counter 27 based on the clock signal of the clock oscillator 29 and calculating the distance calculation circuit 28. Output to. The distance calculation circuit 28 receives the input time signal S10.
The distance signal S1 is calculated by calculating the distance to the target object based on
It is output to the display unit 10 as 1, and the display unit 10 displays the distance to the target object.

That is, the comparator 23 constitutes the charge emission detection means and the end signal output means, the monostable multivibrator 15 constitutes the start signal output means, and the counter 27 constitutes the time measuring means.

If the condenser 20 is of a variable capacity type and the value of the time expansion coefficient K can be changed automatically or manually, for example, the distance of the condenser 20 is short because the distance to the target is short in the previous distance measurement. When the discharge characteristics are so sharp that the buffer amplifier 22 and the comparator 23 cannot follow, the value of the expansion coefficient K is increased at the next distance measurement to make the discharge characteristics gentle.
Precise distance measurement is possible.

In the present embodiment described in detail above, since the interface between the capacitor 20 and the AND circuit 26 only requires the buffer amplifier 22 and the comparator 23 which are general-purpose operational amplifiers, the adjustment of parts and circuits can be simplified as much as possible. The cost can be reduced at the same time.

[0034]

As described above in detail in the embodiments,
According to the present invention, the pulse response time from the emission of the electromagnetic pulse to the target to the detection of the reflected pulse,
Since it is expanded by using the response time expanding means consisting of a storage means for supplying electric charge to the capacitor at a constant current value and a discharging means for discharging the electric charge stored in the capacitor at a constant current value lower than the supply current value at the time of storage, Compared with the case where the high-speed slew rate operational amplifier is used as the response time extending means, the cost can be reduced as much as possible and the circuit adjustment such as the frequency characteristic can be simplified as much as possible.

When the expansion time measuring means is composed of the charge emission detecting means, the end signal outputting means, the start signal outputting means and the time measuring means, the end signal outputting means is stored after the capacitor starts charging. While the end signal is output until all the charges are discharged, the start signal output means corresponds to the maximum detection distance that can be detected by the reflected pulse detection means after the discharge of the charges accumulated in the capacitor is started. The start signal is output for a little longer than the specified time, and the time measuring means measures the discharge time during which both the start signal and the end signal are output. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of a distance measuring device according to the present invention.

FIG. 2 is a time width expansion circuit diagram of an embodiment of a distance measuring device according to the present invention.

FIG. 3 is a time chart showing the operation timing of each circuit of the time width expanding circuit of one embodiment of the distance measuring device according to the present invention.

FIG. 4 is a block diagram of a conventional distance measuring device.

FIG. 5 is a diagram showing a change in gate opening / closing time due to a change in a start pulse and a stop pulse of a conventional distance measuring device.

FIG. 6 is a diagram showing a time relationship between waveforms of respective parts of a conventional distance measuring device.

[Explanation of symbols]

1 Laser Diode 4 Controller 5 Time Width Enlarging Circuit as Response Time Enlarging Unit 6 Photodiode 11 Laser Pulse Emitting Unit as Pulse Emitting Unit 12 Reflection Pulse Receiving Unit as Reflecting Pulse Detecting Unit 13 As Enlarging Time Measuring Unit and Distance Computing Unit Distance calculation unit 14 flip-flop 15 monostable multivibrator as start signal output means 16 constant current source for storage means 17 constant current source for discharge means 20 capacitor for storage means 22 buffer amplifier 23 charge emission detection means and end signal output means 24 flip-flops 26 AND circuits 27 counters as time measuring means

Claims (2)

[Claims] 1. A pulse emitting means for emitting an electromagnetic wave pulse to a target object, a reflected pulse detecting means for detecting the electromagnetic wave pulse reflected by the target object, and an electromagnetic wave pulse emitted by the pulse emitting means, Response time expansion means for expanding the response time until the reflection pulse is detected by the reflection pulse detection means, expansion time measurement means for measuring the time expanded by the response time expansion means, and measurement by the expansion time measurement means In the distance measuring device provided with the distance calculating means for converting the expanded time to the distance from the pulse emitting means or the reflected pulse detecting means to the target object, the response time expanding means is provided from the pulse emitting means. At the same time when the electromagnetic wave pulse is emitted, the electric charge is started to be supplied to the capacitor at a constant current value, A storage means for stopping the supply of electric charge at the same time when the reflection pulse is detected by the stage, and a capacitor having a constant current value lower than the current value supplied by the storage means at the same time when the reflection pulse is detected by the reflection pulse detection means. A distance measuring device comprising: a discharging unit that discharges the electric charge stored in the unit. 2. The extension time measuring means detects a charge emission detecting means for detecting a charge discharge completion time point by the discharging means, and a charge release completion time point detected by the charge discharge detecting means from a charge storage start time on the capacitor. Up to a time longer than the time corresponding to the maximum detection distance detectable by the reflected pulse detection means after the end signal output means for outputting an end signal and the discharge of the charge by the discharge means is started. 2. A start signal output means for outputting a signal, and a time measuring means for measuring a time during which both the end signal output means and the start signal output means output a signal. The described distance measuring device.