JPH04118579A - Distance measuring device - Google Patents

Abstract

PURPOSE:To shorten the measuring time without decreasing the measurement accuracy by allowing a signal generating means to generate moduration signals and a light emitting means to emit modulation light based on the signals. CONSTITUTION:A driving means 3 drives a light emitting means 4 based on input signals (wave 3) to generate modulation light. The light emitted from the light emitting means 4 is reflected by a reflection mirror arranged at a measuring point and received by a light receiving means 5. The light receiving means 5 carries out photo-electric conversion to form reflection modulation signals. The signals are amplified by a first amplifier 51, and thereafter sent out to a phase difference detection means 6. The reflection modulation signal amplified by the first amplifier 51 is further amplified by a second amplifier 52 and supplied to a delay time measuring means 7. Then, the phase difference comparison between the frequence f3 being the output signal of a wave conversion circuit 63 and the frequency f3' being the output signal of a second divider 92 is carried out by a phase comparison circuit 64. By using the phase difference, a microcomputer 8 can compute the distance between the optical wave distance meter and the reflector.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a distance measuring device using a modulation frequency of 2Ii, and in particular detects a phase difference between a modulation signal emitted by a light emitting means and a reflected modulation signal. A precise VMill determination is performed by this, and a rough measurement is performed by measuring the delay time between the modulation signal and the reflected modulation signal, and by combining the precise measurement result and the coarse measurement result, the VMill is placed at the measurement point. This invention relates to a light wave distance meter that measures the distance to a reflective mirror.

"Conventional technology" A conventional light wave distance meter consists of a light wave range meter body and a reflector, and the modulated wave emitted from the light wave range meter body is reflected by the reflector, and the reflected modulated wave is returned to the light wave range meter. The phase difference between the modulated wave emitted from the 9-lightwave rangefinder body and the reflected modulated wave, which was configured to receive light on the main body, corresponds to the distance between the lightwave rangefinder and the reflector, so this phase difference can be calculated by By detecting it, the distance between the light wave distance meter and the reflector was calculated.

In addition, for short-distance measurements, no reflecting mirror is provided.
In some cases, the object to be measured is used as a reflecting part, and the reflection from the object is used.

By the way, a light wave distance meter requires highly accurate measurement, so it is necessary to measure using a modulated wave with a relatively short wavelength.For example, in order to obtain a measurement accuracy of about ±5, A first wavelength λ1=20m should be used. However, the relationship between measurement distance and phase is that every time the measurement distance changes by 10m (optical path length 20m), the phase changes from 0 to
It varies within a range of 2π. Therefore, it is only possible to perform measurements at 10 mt. (Measurement period" Om).

Therefore, λ2, which is a wavelength with a longer measurement period than the above-mentioned precise measurement,
It was necessary to perform rough measurements using the .

Furthermore, in order to enable long-distance measurements, the system was configured to perform large-abbreviation measurements using wavelength λ3, which has a longer measurement cycle than coarse measurements.

Then, these precise measurements, flfl measurements (rough measurements),
The final measurement results were obtained by combining the results of multiple measurements. That is, a light wave distance meter that performs measurement using modulated waves of three types of frequencies, λ1, λ2, and λ3, has been known.

"Problems to be Solved by the Invention" However, the above-mentioned conventional optical distance meter uses a measurement frequency of 3N class or higher, so it is necessary to switch each measurement wavelength every time and take a measurement, which takes a long time. There was a problem with that. In order to shorten the measurement time, it is necessary to shorten the measurement time at each measurement frequency, which poses the problem of lowering accuracy.

Therefore, there has been a strong desire for a light wave distance meter that can shorten the closing time during measurement without reducing measurement accuracy.

"Means for Solving the Problems" The present invention was devised in view of the above problems, and is used in a distance measuring device that measures distance by detecting reflected light from a reflecting section placed at a measurement point. a signal generating means for generating a signal, a light emitting means for generating modulated light based on the signal from the signal generating means, and a modulated light emitted from the light emitting means and reflected by the reflecting section disposed at the measurement point. a light receiving means for receiving light and forming a reflected modulation signal; and a phase difference for performing precise measurement by detecting a phase difference between a modulation signal emitted by the light emitting means and a reflected modulation signal from the light receiving means. It is comprised of a detection means, and a delay time measuring means for performing a rough measurement by measuring the delay time between the modulation signal emitted by the light emitting means and the modulation signal reflected from the light receiving means.

"Operation" In the present invention configured as described above, the signal generating means generates a modulated signal, and the light emitting means emits modulated light based on the signal of the signal generating means. The light receiving means receives the modulated light emitted from the light emitting means and reflected by the reflecting section disposed at the measurement point to form a reflected modulation signal. Furthermore, the phase difference detection means performs precise measurement by detecting the phase difference between the modulation signal emitted by the light emitting means and the reflected modulation signal formed by the light receiving means. The delay time measuring means performs rough measurement by measuring the delay time between the modulation signal emitted by the light emitting means and the modulation signal reflected from the light receiving means. By combining the M fine measurement and the coarse measurement, it is possible to measure the distance to the reflecting section placed at the measurement point.

"Example" An example of the present invention will be described based on the drawings. FIG. 1 shows the configuration of this embodiment, and the optical distance meter includes a reference signal oscillator 1, a synchronization circuit 2, a drive circuit 3, a light emitting means 4, a light receiving means 5, and a phase difference detecting means 6. , a delay time measuring means 7, and a microcomputer 8.

The reference signal oscillator-1 corresponds to a signal generation means,
It generates a modulated signal. The reference signal oscillator 1 can oscillate a signal with a frequency f1, and can also supply a signal with a frequency f2 via the first frequency divider 11. The synchronous circuit 2 receives the frequency f1 from the reference signal oscillator 1 or the frequency f2 from the first frequency divider 11.
This is to form a signal synchronized with the

The drive circuit 3 is for driving the light emitting means 4, and can drive the light emitting means 4 based on the signal synchronized by the synchronization circuit 2. The light emitting means 4 is capable of driving the light emitting means 4 based on the input drive signal. It is used to generate light,
The light receiving means 5, which is a laser diode in this embodiment, is a photoelectric conversion element for receiving modulated light reflected by a reflecting mirror placed at a measurement point. The reflected modulation signal obtained by the light receiving means 5 is amplified by an amplifier 51 and then supplied to a phase difference detecting means 6 and a delay time measuring means 7. Note that the reflecting mirror corresponds to a reflecting section.

The phase difference detection means 6 is for performing precise measurement by detecting the phase difference between the modulated signal emitted by the light emitting means 4 and the reflected modulated signal from the light receiving means 5, and includes a mixer 61,
A low-pass filter 62, a waveform conversion circuit 63, a phase comparison circuit 64, a switch 65, and a first frequency generator 66
and a second frequency generator 67.

The delay time measuring means 7 is for performing rough measurement by measuring the delay time between the modulation signal emitted by the light emitting means 4 and the reflected modulation signal from the light receiving means 5.
1, a counter 72, and a reference voltage generator 73.

The microcomputer 8 controls the operation of each circuit, calculates distances, and the like.

The operation of the present invention configured as described above will be described with reference to FIGS. 1 and 2.9 First, the microcomputer 8 selects which of the frequencies f1 and f2 to perform measurement.

First, a case will be explained in which operation is performed at frequency f.

A frequency f1 (waveform 1) is supplied to the synchronization circuit 2 from the reference signal generator l. When the measurement start signal (waveform 2) is output from the microcomputer 8, a signal (waveform 3) synchronized with the frequency f1 supplied from the reference signal generator 1
is sent to the driving means 3, and at the same time, a start signal (waveform 4) is sent to the counter 72 of the delay time measuring means 7.

The driving means 3 drives the light emitting means 4 based on the input signal (waveform 3) to generate modulated light.

The light emitted from the light emitting means 4 is reflected by a reflecting mirror placed at the measurement point, and is received by the light receiving means 5.

Photoelectric conversion is performed in the light receiving means 5, and a reflected modulation signal is formed. This reflected modulation signal is amplified by the first amplifier 51 and then sent to the phase difference detection means 6. The reflected modulation signal amplified by the first amplifier 51 is further transmitted to the second amplifier 5.
2 and supplied to the delay time measuring means 7.

First, the operation of the delay time measuring means 7 will be explained.

Reflection modulation signal amplified by second amplifier 52 (waveform 5)
is input to the comparator 71. The comparator 71 compares the reference voltage from the reference voltage generation circuit 73 with the input reflected modulation signal, and outputs a stop signal (waveform 6) when the reflected modulation signal exceeds the reference voltage. . The stop signal (waveform 6) and the start signal (waveform 4) are configured to be input to a counter 72, and the counter 72 is a reference signal oscillator l input between the start signal and the stop signal. The clock is counted (waveform 7). Based on the counted clock number and the frequency of the reference signal oscillator l, the microcomputer 8 can calculate the distance between the reflector and the optical distance meter.

For example, the time difference between the start signal and stop signal is 25
μS, and when the oscillation frequency of the reference signal oscillator l is 15 MHz, the counter 72 counts "375". Since one power unit of the reference signal oscillator 1 corresponds to 20 m, the round trip distance between the light wave range meter and the reflector is 375 x 20 m = 7500 m, and the distance between the light wave range meter and the reflector is 3750 m.

Similar results can also be obtained when frequency f2 is used.

Next, the operation of the phase difference detection means 6 will be explained.

The reflected modulation signal amplified by the first amplifier 51 is input to a mixer 61 and subjected to frequency conversion. At this time, the frequency f! A signal from the first frequency generator 66 corresponding to the signal is supplied to the mixer 61.

Note that when measurement is performed at frequency f2, the switch 65 is switched so that the signal from the second frequency generator 67 is transmitted to the mixer 6.
It is configured to be supplied with 1.

The reflected modulation signal subjected to frequency conversion by the mixer 61 passes only a predetermined frequency f3 by the low-pass filter 62, and is subjected to waveform shaping by the waveform conversion circuit 63. Then, the signal generated by the reference signal oscillator 1 is frequency-divided by the second frequency divider 92 to generate a signal of f3' (same frequency as f3).

Then, the phase comparison diagram 164 compares the phase difference between the frequency f3, which is the output signal of the waveform conversion circuit 63, and the frequency f3', which is the output signal of the second frequency divider 92. Using this phase difference, the microcomputer 8 can calculate the distance between the optical distance meter and the reflector.

Note that in the actual M example above, the case where measurement is performed at the frequency f was explained, but the output signal of the reference signal oscillator 1 is transmitted to the first frequency divider 9.
Divide the frequency by 1 to generate frequency f2, and send this signal to the synchronization gate N.
2, and by switching the switch 65 of the phase difference detection means 6 and connecting it to the second frequency generator 67, it is possible to measure at the frequency f2.

For example, frequency f1 is 15MHz, frequency f2 is 1
In the case of 50 kHz, if the phase difference measured at frequency f1 is 90 degrees and the phase difference measured at frequency f2 is 271 degrees, frequency f1 corresponds to a distance of 10 m when the phase difference is 360 degrees, and frequency f2 corresponds to a distance of 10 m. 1000rn when phase difference is 360 degrees
Therefore, when measured at frequency f1, the converted distance is 2°5 m, and when measured at frequency f2, the converted distance is 753 m.

As a result, the microcomputer 8 detects the phase difference detecting means 6.
and the three types of distances obtained from the delay time measuring means 7 are combined to calculate the measured distance. That is, distances of 10 m or less are determined from phase difference measurements obtained at frequency f1, distances of 10 m or more and 1,000 m and zero grooves are determined from phase difference measurements obtained at frequency f2, and distances of 1,000 m or more are determined from delay time measurements. Using this distance, we find 3752.5 m.

In this 81st example configured as above, the phase difference detection means 6 performs precise measurement using the frequency f1 and the frequency f2, and the delay time measurement means 7 performs rough measurement.
This has the advantage of being able to perform highly accurate measurements at two frequencies. Therefore, it has the outstanding effect of being able to shorten the measurement time compared to a light wave distance meter that uses three frequencies.

Note that the frequency f1, the frequency f2, the oscillation frequency of the reference signal oscillator 1, etc. are not limited to those in the above embodiment.
Needless to say, it is selected as appropriate.

"Effects" The present invention configured as described above includes a signal generating means for generating a modulated signal, a light emitting means for generating modulated light based on a signal from the signal generating means, and a light emitting means for generating modulated light based on the signal from the signal generating means. a light receiving means for receiving modulated light emitted and reflected by the reflecting section disposed at a measurement point to form a reflected modulated signal; a modulated signal emitted by the light emitting means; and a reflected modulated signal from the light receiving means. phase difference detection means for performing precise measurements by detecting the phase difference between the light emitting means and the light receiving means; and rough measurement by measuring the delay time between the modulation signal emitted by the light emitting means and the reflected modulation signal from the light receiving means Since the phase difference detection means can perform precise measurements, the delay time measurement means can perform rough measurements using the signal used by the phase difference detection means. This has the advantage that it is not necessary to use signals of separate frequencies for rough measurements.

Therefore, even if the modulation wavelength is used in a time-division manner, the number of types of modulation frequencies is reduced, which has the outstanding effect of shortening the measurement time.

Furthermore, since the rough measurement uses the delay time, there is an effect that there is no limit to the measurement distance as long as the light emitted from the light emitting means is reflected.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a diagram for explaining the configuration of this embodiment, and FIG. 2 is a diagram showing waveforms for explaining the operation of this embodiment. 1... Reference signal oscillator 2... Synchronous circuit 3 ・ ・ 4 ・ ・ 5 ・ ・ 6 ・ ・ 61 ・ 62 ・ 63 ・ 64 ・ 65 ・ 66 ・ 67 ・ 7 ・ ・ 7I ・ 72 ・ 73 ・ 8 ・・ 91 ・ 92・Delay time measuring means ・Comparator ・Counter ・Reference voltage generation circuit ・Microcomputer ・First frequency divider ・Second frequency divider

Claims (1)

[Claims] (1) In a distance measuring device that measures distance by detecting reflected light from a reflecting part placed at a measurement point, there is provided a signal generating means for generating a modulated signal, and a modulated light based on the signal from the signal generating means. a light-receiving means for receiving modulated light emitted from the light-emitting means and reflected by the reflecting section disposed at a measurement point to form a reflected modulation signal; a phase difference detection means for performing precise measurement by detecting a phase difference between the emitted modulation signal and the reflected modulation signal from the light receiving means;
A distance measuring device comprising delay time measuring means for performing rough measurement by measuring a delay time between a modulated signal emitted by the light emitting means and a reflected modulated signal from the light receiving means.