JP2592316Y2 - 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 a distance measuring device which emits light to a measuring object, receives reflected light from the measuring object, and measures a distance to the measuring object.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for mounting a distance measuring device on a moving body and using distance information for the purpose of improving safety, automation and labor saving. Specific representative examples include a sensor for preventing a collision of a robot, an automobile, a train, and the like, and a sensor used in a stop position control system in a transport vehicle on a factory line.

As an example of a distance sensor suitable for these applications, a range finder by measuring the round trip time of an optical pulse is used.
And a distance sensor by measuring the phase difference of the intensity-modulated light. The former emits a light pulse to the object to be measured,
The time required to receive the reflected light from the measurement target is measured, and the distance to the measurement target is determined from the speed of light. In the latter, the distance is obtained by emitting the intensity-modulated light to the measurement target and measuring the phase difference between the reflected light from the measurement target and the output light.

[0004] In recent years, in these distance sensors, higher accuracy and real-time performance of measured values have been further required.

[0005]

One of the major factors of the distance measurement error in the above-mentioned sensor is an error caused by a difference in received signal level. That is, even if the reflected light is from the same distance, if the signal level is different, the phase and slew rate of the signal change, resulting in a different measurement distance.

Conventionally, in order to suppress this kind of error, for example, Japanese Patent Publication No. Sho 51-8338 and Japanese Patent Publication No. Sho 51-833 are disclosed.
As described in Japanese Patent Publication No. 9 and Japanese Patent Publication No. 51-8340, there has been a method of providing a light amount adjuster in an optical path and controlling the magnitude of a received signal to a predetermined amount.

However, in this method, the time required for the distance measurement becomes longer depending on the response speed of the light amount adjuster. Further, in order to increase the accuracy of the measurement distance, more accurate light amount adjustment is required, so that the light amount adjustment time inevitably increases, and the entire apparatus becomes expensive. Further, in this method, since the signal level needs to be fielded back, the light quantity cannot be adjusted for the signal itself during distance measurement, and there is a problem that the measurement error becomes large when the light quantity itself fluctuates.

The present invention has been made to solve these conventional problems, and an object of the present invention is to provide a distance measuring device capable of performing distance measurement with high accuracy and high speed even when the signal level fluctuates. Aim.

[0009]

[Means for Solving the Problems]Distance measuring device of the present invention
Emits light to the object to be measured and
Distance to measure the distance to the measurement object after receiving the reflected light
A measuring device that generates a reception signal according to reflected light
Receiving signal generating means (for example, the light receiving element 3 of the embodiment of FIG. 3)
6 and an amplifier 37), and compares the received signal with a threshold value.
Generates a reception timing signal when the received signal matches the threshold.
The generated comparison means (for example, the comparator 38 in the embodiment of FIG. 3)
Receiving the reception timing signal from the comparing means,
Distance information output means for outputting distance information to a fixed object
(For example, the time measurement circuit 31 in the embodiment of FIG. 3) and the reception
Level detection means for detecting a signal level (for example, FIG. 3
Level detection circuit 40 and A / D converter
Barter 41) and the level detected by the level detecting means.
Depending on the levelReceived signal matches threshold value of comparison means
When it reaches the peak value and when it reaches the peak value
So that the time interval betweenComplement the threshold of the comparison means
Correction means (for example, the arithmetic and control unit of the embodiment of FIG. 3)
200).

[0010]

In the distance measuring apparatus according to the present invention , a received signal corresponding to the reflected light is generated, the level of the received signal is detected, and the threshold value of the comparing means is corrected according to the detected level. That is, the received signal is equal to the threshold value of the comparing means.
Timing when the value matches, and timing when the peak value
The threshold of the comparison means is set so that the time interval with the
Will be corrected. Therefore, it is possible to eliminate a measurement distance error caused by a signal level difference, so that distance measurement can be performed with high accuracy. Further, since it is not necessary to control the reception signal level to a predetermined amount as in the related art, distance measurement can be performed at high speed.

[0011]

FIG. 1 shows the configuration of an embodiment of the distance measuring device according to the present invention. When the pulse oscillator 1 receives the lighting permission signal 21 from the CPU 100, the pulse oscillator 1 outputs the lighting timing signal 22 to the laser driver 2 and outputs the clock signal 27
Is output to the counter 9.

The laser driver 2 supplies a short-duration lighting pulse 23 to the semiconductor laser 3 in synchronization with the rise of the lighting timing signal 22 to turn on the semiconductor laser 3. The light emitted from the semiconductor laser 3 passes through the light transmitting lens 4, is reflected by an object to be measured (not shown), and is condensed on the light receiving element 6 by the light receiving lens 5.

Thus, the light receiving element 6 outputs a received pulse signal which is an electric signal, and this signal is amplified by the amplifier 7. Received pulse signal 24 output from amplifier 7
Are supplied to a comparator 8 and a peak hold circuit 10. The comparator 8 converts the received pulse signal 24 into
Is converted into a light receiving timing signal 25 which is a digital signal,
Output to counter 9. The counter 9 uses the lighting timing signal 22 as a start signal,
Is used as a stop signal, the number of clock signals 27 from the pulse oscillator during that time is counted, and the obtained count value is supplied to the CPU 100 as distance data 28.

On the other hand, the peak hold circuit 10 holds the maximum value of the received pulse signal 24 input from the amplifier 7 and generates a DC voltage signal 26 corresponding to the level of the signal 24.
To the A / D converter 11. The A / D converter 11 converts the input DC voltage signal into a digital signal and converts it into a reception pulse level signal 29.
Supply 100. The CPU 100 corrects the distance data sent from the counter 9 according to the level indicated by the reception pulse level signal 29.

FIG. 2 is a flowchart showing the operation of the CPU 100 in the distance measuring state. Hereinafter, the operation of the embodiment of FIG. 1 will be described with reference to FIG. First, the distance measurement star
CPU 100 outputs a lighting permission signal 21 to the pulse oscillator 1 when the external command is input from the outside (step S).
1) Waiting for input of the light receiving timing signal 25 from the comparator 8. However, in order to cope with the case where the object to be measured does not exist, the elapsed time since the output of the lighting permission signal 21 is monitored, and the light receiving timing signal 25 is not input even if the set time is exceeded (step S3). N
O) determines that there is no received signal and ends the measurement.

Next, when the light receiving timing signal 25 is input (YES in step S2), the CPU 100 takes in the distance data 28 from the counter 9 (step S4).
At the same time, the reception pulse level signal 29 is fetched (step S5). Further, an error correction amount of the distance caused by the signal level difference is determined from the received reception pulse level signal 29 (step S6), and the error correction amount is added or subtracted from the captured distance data 28 (step S7). ),
The measured distance is obtained and output (step S8).

FIG. 3 shows another embodiment of the distance measuring device of the present invention. The feature of this embodiment resides in that the threshold level of the comparator for detecting the reception timing of the received signal is controlled according to the received light amount.

When the arithmetic and control unit 200 gives a distance measurement command to the time measurement circuit 31 via the data bus 30, the time measurement circuit 31 outputs a lighting timing signal to the laser drive circuit 32. Thereby, the laser drive circuit 32
A semiconductor laser 33 serving as a light source emits light, and the semiconductor laser 33 emits an optical pulse to an object to be measured (not shown) via a transmission optical system.

The light pulse reflected from the object to be measured is detected by a light receiving element 36 via a receiving optical system 35. The detected optical signal is photoelectrically converted by the light receiving element 36, amplified by the amplifier 37, and supplied as a received pulse signal to the comparator 38 and the peak level detection circuit 40. The comparator 38 detects the reception timing of the reflected light pulse from the measurement object. The time measuring circuit 31 measures the time from when the lighting timing signal is output to when the light receiving timing signal is received from the comparator 38, and outputs the measured time to the arithmetic and control unit 200 via the data bus 30.

The peak level detecting circuit 40 detects the peak level of the received pulse signal, and supplies a DC voltage signal corresponding to the received pulse signal level to the A / D converter 41. The A / D converter 41 converts the input DC voltage signal into a digital signal. This signal indicates the peak level of the received pulse signal.
Is supplied to the arithmetic and control unit 200 via the.

The arithmetic and control unit 200 sets the threshold value of the comparator 38 via the data bus 30 and the D / A converter 42 according to the level indicated by the digital signal thus input. The set value is a value by which the time from the threshold of the comparator 38 to the peak is made constant by the characteristic data stored in advance.

FIG. 4 shows a comparator 38 of the distance measuring device of FIG.
3 is a graph showing a relationship between a threshold value of the received signal and a generation time point of a reception timing signal. In FIG. 4, reference numeral 50 denotes a reception pulse signal waveform when the light amount is large, 51 denotes a reception pulse signal waveform when the light amount is small, 52 denotes a conventional fixed threshold level of the comparator 38, and 53 denotes a reception threshold level. Reference numeral 54 denotes a threshold level of the comparator 38 adapted to the large amount of light, and 54 denotes a threshold level of the comparator adapted to the small amount of received light.

In the case of the conventional configuration, the threshold value for detecting the reception timing in the comparator 38 is the fixed value Vth indicated by the reference numeral 52. Therefore, the reception pulse signal 50 when the amount of received light is large crosses the threshold value Vth. The time t (P1) from the point at which the received pulse signal 50 reaches the peak level point of the received pulse signal 50 and the received pulse signal 51 when the amount of received light is small.
From the point where the signal crosses the threshold Vth
Time t (P2) to peak level point of signal 51
Was different.

On the other hand, according to the embodiment of the present invention shown in FIG. 3, the threshold value for detecting the reception timing in the comparator 38 is variable. The threshold Vth1 indicated by reference numeral 53 is set (that is, the threshold is increased). When the received light amount is small, the threshold of the comparator 38 is set to the threshold Vth2 indicated by reference numeral 54 (that is, the threshold is reduced). Thus, the time t (COMP) from the point at which the received pulse signal 50 crosses the threshold value Vth1 when the received light amount is large to the peak level point of the received pulse signal 50, and the received pulse signal 51 when the received light amount is small. Is the same as the time t (COMP) from the point at which the signal crosses the threshold value Vth2 to the peak level point of the received pulse signal 51, which is caused by the difference in received light level. During measurement error or distance measurement error is to be eliminated.

[0025]

According to the distance measuring apparatus of the present invention , the threshold value of the comparator for detecting the reception timing of the reception signal is set to the value of the reception signal.
When the signal becomes a value that matches the threshold value of the comparison means
And the time interval between the peak value and
As described above, since it is changed in accordance with the received signal level, it is possible to correct the time measurement error due to the fluctuation of the received light amount, and therefore, it is possible to reduce the distance measurement error. There is an effect.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing an operation example of a CPU 100 of the distance measuring device of FIG .

FIG. 3 is a block diagram showing another embodiment of the distance measuring device of the present invention.

FIG. 4 is a graph showing a relationship between a threshold value of a comparator 38 of the distance measuring device of FIG. 3 and a generation time point of a reception timing signal.

[Explanation of symbols]

 Reference Signs List 1 pulse oscillator 2 laser driver 3 semiconductor laser 4 light transmitting lens 5 light receiving lens 6 light receiving element 7 amplifier 8 comparator 9 counter 10 peak hold circuit 11 A / D converter 30 data bus 31 clock measurement Circuit 32 Laser drive circuit 33 Semiconductor laser 34 Transmission optical system 35 Reception optical system 36 Light receiving element 37 Amplifier 38 Comparator 40 Peak level detection circuit 41 A / D converter 42 D / A converter 100 CPU 200 Operation control device

Continuation of the front page (56) References JP-A-2-49180 (JP, A) JP-A-63-81289 (JP, A) JP-A-56-39471 (JP, A) JP-A-4-339289 (JP, A) JP-A-5-100026 (JP, A) JP-A-5-34456 (JP, A) JP-A-5-297140 (JP, A) JP-A-5-223928 (JP, A) 3-73880 (JP, A) Japanese Utility Model Hei 5-4080 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01S 7/00-17/95

Claims (2)

(57) [Scope of request for utility model registration] 1. A distance measuring device that emits light to an object to be measured, receives reflected light from the object to be measured, and measures a distance to the object to be measured. Receiving signal generating means for generating, comparing the received signal with a threshold value, comparing means for generating a reception timing signal when the received signal matches the threshold value, receiving the reception timing signal from the comparing means, Distance information output means for outputting distance information to the object to be measured; level detection means for detecting the level of the received signal; and the received signal is compared with the level according to the level detected by the level detection means. A value that matches the means threshold
And the peak value
A distance measuring device comprising: a correcting unit that corrects a threshold value of the comparing unit so that an interval becomes constant . 2. The distance information output means measures the time from when light is emitted to the measurement target to when the reception timing signal is received, and outputs distance information to the measurement target. The distance measuring apparatus according to claim 1 , wherein the distance measurement is performed.