JPH0712935A - Range finder - Google Patents

Abstract

PURPOSE:To provide an inexpensive hiqh-performance range finder which can measure long distanbes by using a low-output optical pulse. CONSTITUTION:A range finder obtains the optimum time data fetching timing and calculates the distance to an object to be measured based on the time data obtained at the optimum timing by adding a preset key code to the pulsed light OPL1 emitted from a semiconductor laser 201 and scanning the presence/ absence of the key code in the reflected light of the pulsed light OPL1 by means of a clamp circuit 210 and key code discriminating section 216 by switching the outputting timing of a clamp pulse signal CLP and gate signal GT at every measurement based on a control signal CTL2 from a control section 212 at a clamp pulse delay switching section 214.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for emitting light to a target object and detecting the reflected light to measure the distance to the target object.

[0002]

2. Description of the Related Art Generally, a distance measuring device of this type emits pulsed light toward an object to be measured, such as an automobile, and the emitted laser light is reflected by the object to be measured 2. It is configured to detect light with a photodetector, measure a time Δt from emission of laser light to detection of reflected light, calculate a distance based on the following equation, and measure a distance to the object to be measured 2. . R = (C · Δt) / 2 (1) where C indicates the speed of light.

FIG. 3 is a block diagram showing a concrete example of the configuration of a conventional distance measuring device. In FIG. 3, 101 is a semiconductor laser as a pulsed light generating means, 102 is a half mirror, 103 and 106 lenses, 104 is a first photodetector, 105 and 108 are amplifiers, 107 is a second photodetector, and 109. Is a counter, 110 is an oscillator, 111 is a signal processing unit, and 112 is a control unit.

In such a structure, the semiconductor laser 101 oscillates at a predetermined wavelength in response to a control signal from the controller 112, and a pulsed laser beam OPL is emitted. The emitted light OPL of the semiconductor laser 101 is incident on the half mirror 102, part of which passes through the half mirror 102, and is emitted from the device toward the object 2 to be measured with a certain spread through the lens 103. The emitted light reaches an object to be measured (not shown) after a predetermined time (Δt / 2) and is reflected by, for example, a reflector attached thereto.

Further, a part of the emitted light of the semiconductor laser 101 is reflected by the half mirror 102 and is reflected by the first photodetector 10.
Light is received at 4. In the first photodetector 104, the received light is converted into an electric signal dt1 according to the light receiving level. This electric signal dt1 is input to the counter 109 after being subjected to a predetermined side effect by the amplifier 105. Counter 109
Then, the counting operation is started by the first input of an electric signal having a certain level or higher. That is, in the initial state, the semiconductor laser 101 emits the first pulsed laser light, and the count operation is started in the counter 109 in accordance with the input of the electric signal corresponding thereto.

The laser light reflected by the reflector attached to the object to be measured returns after a predetermined time (Δt / 2) from the reflection, is condensed by the lens 106, and is then collected by the second photodetector 107. Is received by. Second photodetector 10
7, the received light is an electric signal dt2 corresponding to the received light level.
Is converted to. This electric signal is input to the counter 109 after being subjected to a predetermined side effect by the amplifier 108. In the counter 109, the counting operation is stopped when the output signal of the amplifier 108 is input. As a result, the counter 109
Then, the time from the emission of laser light to the return of reflected light Δ
This means that t has been measured. The measurement value of the counter 109 is input to the signal processing unit 111.

The signal processing unit 111 calculates the distance to the object to be measured 2 based on the above equation (1) and outputs it as distance data.

[0008]

By the way, in the above-described distance measuring device, as shown in FIG. 4 (a), the light receiving level of the light reflected by the reflector is the second photodetector 107 or the amplifier 10.
Although it is possible to calculate the distance accurately when the noise generated by 8 is sufficiently high, but as shown in Fig. 4 (b), for example, when the reflected light level is not sufficiently high with respect to the noise, Noise may be erroneously detected as reflected light and detected, and accurate distance calculation cannot be performed. In order to obtain a reflected light level sufficiently higher than the noise level generated by the second photodetector 107 or the amplifier 108, the measurement distance is restricted, and in order to extend the measurement distance, pulsed light from a semiconductor laser or the like having a large output power is used. Since it is necessary to use a generating means, there is a problem that the cost becomes high.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an inexpensive and high-performance distance measuring device capable of extending the measuring distance with a low-power optical pulse. is there.

[0010]

In order to achieve the above object, in the present invention, pulsed light is emitted to a reflecting object,
A distance measuring device for measuring the distance to a reflecting object by detecting the reflected pulsed light, the pulsed light generating means for emitting pulsed light according to a preset key code, and the pulse of the pulsed light generating means. A time measuring means for measuring the time from the start of light emission, a light detecting means for detecting reflected pulsed light by a reflecting object among the pulsed light by the pulsed light generating means, and a clamp pulse signal for each pulsed light emission. Clamp pulse delay switching means for switching and outputting the output timing of the gate signal indicating the output period of the clamp pulse signal; clamp means for performing clamp processing on the detection signal by the photodetecting means based on the clamp pulse signal; The output signal of the clamp means is compared with the preset key code signal, and if both match, the key is When the key code signal identification means for outputting the code detection signal and the gate signal input period by the clamp pulse delay switching means have a key code detection signal input by the key code signal identification means, the time in the gate period And signal processing means for performing distance calculation processing based on time data of the measuring means.

[0011]

According to the present invention, the pulsed light generating means oscillates at a predetermined wavelength, and the pulsed light corresponding to the preset key code is emitted. The light emitted from the pulsed light generation means reaches, for example, after a predetermined time (Δt / 2), a reflector attached to the object to be measured, and is reflected here. Further, the time from the start of pulsed light emission of the pulsed light generation means is measured by the time measurement means. Further, at this time, the clamp pulse delay switching means outputs the clamp pulse signal to the clamp means after a predetermined time has elapsed from the emission of the pulsed light, and the gate signal identifies the key code signal only while the clamp pulse signal is being output. And the signal processing means.

The light reflected by the object to be measured reaches the light detecting means and is detected there. The light detection means generates a signal corresponding to the light reception level and outputs it to the clamp means. In the clamp means, the clamp pulse signal is clamped by the clamp pulse delay switching means, and the clamped signal is output to the key code signal identifying means. In the key code signal identification means, when the clamp signal is input by the clamp means during the gate signal input period by the clamp pulse delay switching means, the preset key code and the clamp signal are compared, and the two match. In this case, the key code detection signal is generated and output to the signal processing means. In the signal processing means, when the key code detection signal by the key code signal identifying means is input during the input period of the gate signal, the distance to the object to be measured based on the time data by the time measuring means during the gate period. Is calculated.

[0013]

1 is a block diagram showing an embodiment of a distance measuring device according to the present invention. In FIG. 1, 201 is a semiconductor laser as a pulsed light generating means, 202 is a half mirror, 203 and 207 are lenses, 204 is a first photodetector, 205 and 209 are amplifiers, 206 is a counter, 2
Reference numeral 08 is a second photodetector, 210 is a clamp circuit, 211
Is an oscillator, 212 is a controller, 213 is a drive signal generator,
Reference numeral 214 is a clamp pulse delay switching unit, 215 is a data storage unit, 216 is a key code signal identifying unit, and 217 is a signal processing unit.

The semiconductor laser 201 oscillates at a predetermined wavelength, and based on the drive signal DR from the drive signal generator 213, a predetermined key code, for example, digital "110".
The pulsed light OPL1 indicating The half mirror 202 receives the emitted light OPL1 of the semiconductor laser 201, transmits a part of the emitted light OPL1, and transmits the light to the lens 203.
To a light receiving portion of the first photodetector 204. The lens 203 is the half mirror 20.
The laser pulse light OPL1 that has passed through 2 is emitted toward the object to be measured (not shown) from the device with a predetermined spread.

The first photodetector 204 is a half mirror 2
Laser light O from the semiconductor laser 201 reflected by 02
PL1 is received, converted into an electric signal DT1 having a level corresponding to the amount of received light, and output to the amplifier 205. Amplifier 205
Outputs the output signal DT1 of the first photodetector 204 to the counter 206 after amplifying it with a predetermined gain. The counter 206 includes the first photodetector 204 via the amplifier 205.
Receiving the output signal DT1 of the pulse light OPL1, the time measurement from the start of the emission of the pulsed light OPL1 is started, the counter 211 counts up based on the reference signal CLK from the oscillator 211, and the count value indicating the measurement time is stored in the data storage unit 215.
Output to. The counter 206 is reset by the reset signal RST from the control unit 212.

The lens 207 collects the light, which is reflected by an object to be measured or an obstacle (not shown) and returned from the emitted light OPL1 of the semiconductor laser 201, and collects the second light detector 20.
The light is incident on the light receiving unit of No. The second photodetector 208 receives the light condensed by the lens 207, converts it into an electric signal DT2 of a level corresponding to the amount of received light, and outputs it to the amplifier 209. The amplifier 209 amplifies the output signal DT2 of the second photodetector 208 with a predetermined gain and clamps the clamp circuit 21.
Output to 0.

The clamp circuit 210 is composed of, for example, a capacitor C, a switching element SW and a constant voltage source VB, and when the clamp pulse signal CLP is input by the clamp pulse delay switching section 214, a second photodetector via an amplifier 209 is provided. The output signal DT2 of 208 is clamped and output as a clamp signal CL to the data storage section 215 and the key code signal identifying section 216.

The oscillator 211 uses a reference clock signal CLK having a predetermined frequency as a counter 206 and a drive signal generator 21.
3, data storage unit 215 and key code signal identification unit 2
Output to 16.

The control unit 212 outputs the signal CTL1 to the drive signal generation unit 213 to control the output of the drive signal DR and outputs the signal CTL2 to the clamp pulse delay switching unit 2 as well.
14 to give an output delay timing (for example, 100 ns) of the clamp pulse signal CLP, and also to output a reset signal RST to the counter 206 to perform counter reset control, and to output a start signal SRT to the signal processing unit 21.
7 to control the start of signal processing.

The drive signal generator 213 receives the control signal CTL1 from the controller 212 and outputs the drive signal DR to the semiconductor laser 20 so as to oscillate a pulse signal indicating "110".
In addition to the output to 1, the clamp pulse delay switching unit 214 is notified by the signal S213 that the drive signal DR has been output.

The clamp pulse delay switching section 214 delays the input of the signal S213 by the delay time indicated by the control signal CTL2, that is, the pulse signal OPL1.
From the output of the clamp pulse signal CLP consisting of three pulses after 100 ns to the clamp circuit 210, and the gate signal GT is output to the data storage unit 215 only during the period when the clamp pulse signal CLP is being output.
It is output to the key code signal identifying unit 216 and the signal processing unit 217.

When the clamp circuit 210 inputs the clamp signal CL during the input period of the gate signal GT by the clamp pulse delay switching unit 214, the data storage unit 215 captures and stores the count value of the counter 206, that is, the measurement time. .

When the clamp circuit 210 inputs the clamp signal CL during the input period of the gate signal GT by the clamp pulse delay switching unit 214, the key code signal identifying unit 216 sets a preset key signal "110".
And the clamp signal CL are compared, and when the input clamp signal digitally indicates “110”, the key code detection signal KD is output to the signal processing unit 217.

The signal processing unit 217 has a start signal SRT.
When the key code detection signal KD by the key code signal identifying unit 216 is input during the input period of the gate signal GT, the measurement time by the counter 206 stored in the data storage unit 215 during the gate period is started. The data Δt is read and the above-mentioned expression (1) {R = (C · Δ
The distance to the object to be measured is calculated based on t) / 2} and is output as distance data.

Next, the operation of the above configuration will be described with reference to FIG. According to the output drive signal DR of the drive signal generation unit 213 based on the control of the control unit 212, the semiconductor laser 20
1 oscillates at a predetermined wavelength, and a pulsed laser beam OPL1 corresponding to the key code "110" is emitted. The emitted light OPL1 from the semiconductor laser 201 is incident on the half mirror 202, part of which is transmitted through the half mirror 202, and is emitted from the present apparatus toward an object to be measured (not shown) through the lens 203 with a certain spread. Light O that was fired
PL1 reaches, for example, after a predetermined time (Δt / 2), a reflector attached to the object to be measured and is reflected here.

Further, the emitted light OPL of the semiconductor laser 201
Part of 1 is reflected by the half mirror 202 and received by the first photodetector 204. In the first photodetector 204,
The received light is converted into an electric signal DT1 according to the received light level. The electric signal DT1 is input to the counter 206 after being subjected to a predetermined side effect by the amplifier 205. In the counter 206, the counting operation is started by the first input of an electric signal having a certain level or higher. That is, in the initial state, the semiconductor laser 201 emits the first pulsed laser light, and with the input of an electric signal corresponding thereto,
The counter 206 starts counting operation, that is, measurement of time from the start of emission of the pulsed laser light OPL1.

At this time, the signal S213 is output from the drive signal generating section 213 to the clamp pulse delay switching section 214, and at the same time, the control section 212 delays a predetermined time (for example, 100 ns) from the emission of the pulsed light OPL1. A control signal CTL2 instructing to output the clamp pulse CLP is output to the clamp pulse delay switching unit 214.

In the clamp pulse delay switching unit 214, the signal S213 is inputted and then delayed by the delay time designated by the control signal CTL2, that is, the pulse signal OPL.
For example, 100 ns after the output of 1, the clamp pulse signal CL consisting of three pulses as shown in FIG.
The gate signal GT is output to the data storage unit 215 and the key code signal identifying unit 21 only while P is output to the clamp circuit 210 and the clamp pulse signal CLP is output.
6 and the signal processing unit 217.

The light reflected by the object to be measured reaches the lens 207 a predetermined time (Δt / 2) after being reflected, is condensed by the lens 207, and is received by the second photodetector 208. . The second photodetector 208 converts the received light into an electric signal DT2 according to the light receiving level. This electric signal is subjected to a predetermined increase side effect by the amplifier 209, and then, the clamp circuit 21 has a level as shown in (a) of FIG.
Input to 0.

In the clamp circuit 210, when the clamp pulse delay switching unit 214 inputs the clamp pulse signal CLP, the second photodetector 208 via the amplifier 209 is input.
Clamp processing is performed on the output signal DT2 of FIG.
The clamp signal CL as shown in (b) is output to the data storage unit 215 and the key code signal identification unit 216.

The data storage unit 215 stores the count value of the counter 206, that is, the measurement time, when the clamp signal 210 is input by the clamp circuit 210 during the input period of the gate signal GT by the clamp pulse delay switching unit 214. To be done.

Further, in the key code signal identifying section 216,
Gate signal GT by clamp pulse delay switching unit 214
Of the clamp signal C by the clamp circuit 210 during the input period of
When L is input, the preset key signal “110” is compared with the clamp signal CL, and when the input clamp signal digitally indicates “110”, the key code detection signal KD is generated. Signal processing unit 2
It is output to 17.

In the signal processing unit 217, the processing is started by the input of the start signal SRT from the control unit 212, and the key code signal identifying unit 21 is input during the input period of the gate signal GT.
When the key code detection signal KD by 6 is input, the measurement time data Δt by the counter 206 stored in the data storage unit 215 during the gate period is read,
The distance to the object to be measured is calculated based on the equation (1), and the distance data is output.

In the clamp pulse delay switching unit 214, the clamp pulse signal CLP and the gate signal GT are measured for each measurement based on the control signal CTL2 from the control unit 212.
Output timing is switched. As a result, the clamp circuit 210 and the key code signal identifying section 216 scan for the presence or absence of a key code in the reflected pulse light, and the distance is calculated.

As described above, according to this embodiment,
A preset key code is added to the pulsed light OPL1 emitted from the semiconductor laser 201, and the clamp pulse delay switching unit 214 controls the control signal CTL2 of the control unit 212.
Clamp pulse signal CLP for each measurement based on
The output timings of the gate signal GT and the gate signal GT are switched, and the clamp circuit 210 and the key code signal identifying unit 216 scan for the presence or absence of a key code in the reflected pulse light to obtain the optimum timing for capturing the time data. Since the distance is calculated based on the obtained time data, the second photodetector 20
8 and the amplifier 209 can prevent the influence of noise, and can extend the measurement distance with a low-output optical pulse, and realize an inexpensive and high-performance distance measuring device.

In the present embodiment, an example in which a semiconductor laser is used as the pulsed light generating means has been described, but the present invention is not limited to this, and for example, a light emitting diode or the like has a certain output power. If it is applicable, it is possible to obtain the same effect as described above. Further, in this embodiment, the key code is "110".
However, it is needless to say that various modes are possible.

[0037]

As described above, according to the present invention,
A low output optical pulse can be used to extend the measurement distance, and an inexpensive and high-performance distance measuring device can be realized.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining an operation according to the present invention.

FIG. 3 is a block configuration diagram of a conventional distance measuring device.

FIG. 4 is a diagram for explaining a problem of the conventional device.

[Explanation of symbols]

 201 ... Semiconductor laser 202 ... Half mirror 203,207 ... Lens 204 ... First photodetector 205,209 ... Amplifier 206 ... Counter 208 ... Second photodetector 210 ... Clamp circuit 211 ... Oscillator 212 ... Control section 213 ... Drive signal generation unit 214 ... Clamp pulse delay switching unit 215 ... Data storage unit 21 ... Key code signal identification unit 217 ... Signal processing unit

Claims (1)

[Claims] 1. A distance measuring device that emits pulsed light to a reflective object, detects the reflected pulsed light, and measures the distance to the reflective object, the pulsed light corresponding to a preset key code. Pulse light generating means for emitting the pulse light, time measuring means for measuring the time from the pulse light emitting start of the pulse light generating means, and light for detecting the pulse light reflected by the reflecting object in the pulse light by the pulse light generating means. Detection means, clamp pulse delay switching means for switching and outputting the output timing of the clamp pulse signal and the gate signal indicating the output period of the clamp pulse signal for each pulsed light emission, and based on the clamp pulse signal, Clamping means for performing clamp processing on the detection signal by the light detecting means, and the output signal of the above-mentioned clamping means are set in advance. And a key code signal identifying means for outputting a key code detection signal when both match, and the key code signal identifying means for inputting a gate signal by the clamp pulse delay switching means. A distance measuring device comprising: a signal processing means for calculating a distance based on time data of the time measuring means in the gate period when a key code detection signal is input.