JPH01213592A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To improve the measuring accuracy of the title instrument and at the same time, to measure a long distance with the instrument by changing the modulating signal of a signal generating source to pulse train modulating signals and increasing the short-time energy density of radiated light. CONSTITUTION:A distance measuring instrument is provided with a light emission driving section 3 and the section 3 changes the modulating signal from a signal generator 2 to pulse signals so that the modulated light radiated from a light emitting element 4 can become pulse trains. When an analog switch 6 is opened and closed by using the received pulse train signals, the voltage of the magnitude indicated by the black circles of local oscillation signals shown in figure (C) charges a hold capacitor 7. Therefore, the stepped signals indicated by the solid line of the figure (D) are outputted from a sample-hole circuit 8. When the analog switch 6 is closed by means of the received pulse train signals shown in figure (B) which have a time lag of Ts/n+1 (where the Ts is period) against the signals of figure (A), the signals shown by the broken line of figure (D) are outputted from the circuit 8. The time lags among these signals are enlarged to (n) times as long as the time lag of the received pulse train signals.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a distance measuring device using light waves.

(Prior Art) As conventional n1 distance devices using light waves, a pulse transit time method and a phase comparison method are known.

The pulse transit time method is a method in which pulsed light is emitted toward a target, the time it takes to receive the reflected pulsed light after emission is measured, and the distance to the target is determined from the round trip time of this light. The comparison method is a method in which light whose brightness is modulated in a sinusoidal manner is emitted toward a target, the phase difference between the emitted light and the reflected light is measured, and the distance to the target is determined from this phase difference.

FIG. 4 shows an example of a phase comparison method.

In FIG. 4, a is a reference signal oscillator and b is a signal oscillator. The signal generator 1 generates a sine wave local oscillation signal SL1 having a predetermined frequency f with respect to the reference signal using a PLL circuit or a frequency dividing circuit based on the reference signal of the reference signal oscillator a. A sine wave modulation signal Ss having a different frequency fS and a rectangular wave reference signal SR having a frequency fR equal to IfL-fsl of the frequency of the local oscillation signal SL and the modulation signal s5 are output. The modulated signal S
s is added to the light-emitting element d via the light-emitting driver C, and the light-emitting element d emits modulated light toward the target.

Reference numeral e denotes a light receiving element that converts reflected modulated light from the target object into an electrical signal, and its output is input to the mixing section via an amplifier g.

This mixing section mixes the local oscillation signal SL and the output signal s's of the light receiving element e, and from the output, the frequency f+-l ft fs l=1/nfs-flI
A measurement signal s1 (where n is a time expansion ratio) is output, and this APJ constant signal 51 is input to a phase difference counter i. The phase difference counting section i calculates the phase delay of the measurement signal S1 from the reference signal SR and the output signal s'5 of the light receiving cable e when the light transmitting optical path system is switched to the fixed optical path system l inside the aPI device main body. Measure the phase delay from the reference signal SR. The microcomputer j determines the difference between the two phase delays and calculates the distance to the target. The calculated distance is displayed on the display.

The output signal s's of the light receiving element e has a phase delay (time delay) depending on the distance to the target, and all constant signals s's
1 receives the delayed phase angle of the output signal S's as it is, and the delay time is expanded by n times, so when the phases of the measurement signal S and the reference signal SR are compared,
The delayed phase of the 11'I11 constant signal, that is, the distance, can be accurately determined by Δ-1.

(Problems to be Solved by the Invention) In the conventional pulse transit time method, since the light to the target is pulsed light, it is possible to irradiate light with high energy density.
Measurement can be performed without installing a reflective optical member such as a reflective prism at the target point, and long-distance API determination is possible, but since the time from emitting light to receiving reflected light is very short,
It is difficult to insert interpolated pulses, and measurement accuracy inevitably deteriorates.

Since the phase comparison method can expand the time by changing the frequency of the received signal, it has excellent resolution and good J-determined accuracy, but there is a limit to the ability to emit synchrotron radiation with high energy density. It is difficult to perform long-distance measurements similar to the pulse transit time method. Furthermore, since the energy density of light is generally lower than that of the pulse transit time method, a reflecting prism is generally installed at the target point.

The object of the present invention is to eliminate the drawbacks of the above three conventional methods and to provide a distance measuring device that has high measurement accuracy and is capable of long-distance measurement.

(Means for Solving the Problems) In order to achieve the above object, the 11t11 distance device of the present invention includes a light emitting element, a modulation signal for emitting modulated light from the light emitting element, and a different modulation signal. a signal generation source that outputs a frequency local oscillation signal and a reference signal;
a light-receiving element that converts reflected modulated light from a target object into an electrical signal; a conversion means for obtaining a measurement signal having a frequency that is the difference between the frequencies of both signals from an output signal of the light-receiving element and the local oscillation signal; In a distance measuring device comprising a measuring means for measuring a time delay of a signal with respect to a reference signal, and determining a distance to a target from the time delay, emitted from the light emitting element by a modulated signal of the signal generation source is provided. The modulated light is an optical pulse train, and the converting means is a sample-holding means that samples and holds the local oscillation signal by an electric pulse train that is an output signal of the light receiving element, and the converting means includes: The sample-and-hold circuit may include a sample-and-hold circuit connected to the output circuit of the local oscillation signal, and the switch of the sample-and-hold circuit may be opened and closed by the electric pulse train that is the output signal of the light-receiving element. It may be constructed of a flip-flop to which the local oscillation signal and the electric pulse train, which is the output signal of the light-receiving element, are inputted as input signals and clock pulse signals, respectively.

(Function) Since the modulation signal of the signal generation source is a pulse train modulation signal,
Since the short-time energy density of the synchrotron radiation can be increased, long-distance measurements can be made in the same way as the conventional pulse transit time method, and short-distance measurements can be made without a reflecting prism.

In addition, since the local oscillation signal is sampled and held using an electric pulse train having a slightly different frequency than the local oscillation signal output from the light receiving element, it is converted into a signal equivalent to the n1 constant signal in the conventional phase comparison method, resulting in high measurement accuracy. is obtained.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the Apl distance device of the present invention.

In the figure, 1 is a reference oscillator, 2 is a signal generator, 3 is a light emitting driver, and 4 is a light emitting element. The light emitting driver 3 outputs a modulation signal and a pulse train signal from the signal generator 2. The modulated light emitted by the light-emitting cable 4 is made into a light pulse train.

The signal generator 2 outputs a sine wave local oscillation signal S with a frequency fL, a reference signal SR with a frequency fR, and the modulation signal 85 with a frequency f, as in the conventional phase comparison method. Between fLSfR and fs, fL-f5 (1±l/n), f R-1/n f
It has a relationship of s.

A sample-and-hold circuit 8 consisting of an analog switch 6 and a hold capacitor 7 and a low-pass filter 9 are connected to the output circuit 5 of the local oscillation signal SL, and the output side of the low-pass filter 9 and the output of the reference signal SR are connected. Each circuit IO is connected to a phase difference counting section 11.

The analog switch 6 is connected to a light receiving element 14 via a comparator 12 and a video amplifier 13, and is opened and closed by a light receiving pulse train signal output from the light receiving cable 14.

The comparator (2) is for cutting noise components, and the computer 15 and display 16 are the same as the conventional ones.

When the analog switch 6 is opened and closed using the received light pulse train signal shown in FIG. 2(A), the voltage of the magnitude shown by the black circle of the local oscillation r= (shown as a sawtooth wave for convenience) shown in FIG. 2(C) is held. Since the capacitor 7 is charged, the sample-and-hold circuit 8 outputs a step-like signal shown by the solid line in FIG. 2(0). From Figure 2 (A), Ts /nil (Ts
When the analog switch 6 is opened and closed using the received light pulse train signal shown in FIG.
Since the voltage of the local oscillation signal indicated by the white circle shown in FIG. 2(C) charges the hold capacitor 7, the sample-and-hold circuit 8 outputs a stepwise signal shown by the broken line in FIG. 2(0). The time difference between these two step signals is T L −
n/n+I T s, and the time difference Ts of the light-receiving pulse train signal is expanded to n times +l.

The sample and hold circuit 8 shown in the first diagram can be replaced with a D-type flip-flop 17 as shown in the third diagram. That is, a rectangular-wave local oscillation signal is input to the D input terminal of the D-type flip-flop 17, and a light-receiving pulse train signal is manually input from the light-receiving element 14 through the video amplifier 13 and comparator 12 to the clock terminal C of the flip-flop 17. When the local oscillation signal is sampled at the rising edge of the received light pulse train signal, when the received light pulse train signal with a time difference of Ts/ni1 from the reference is input to the clock terminal C, there is a time difference of n/nil Ts from the Q output terminal. Outputs a square wave signal.

(Effects of the Invention) Since the present invention is configured as described above, it has an effect that distance measurement accuracy is high and long-distance measurement is possible.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the circuit of the distance measuring device of the present invention, and Figure 2 (
A) to (D) are explanatory diagrams of the operation, FIG. 3 is a block diagram of the circuit on the other side of the distance measuring device of the present invention, and FIG. 4 is the conventional All
1 is a block diagram of the lid device path; FIG. 2...Signal generator 4...Light emitting element 8...Sample and hold circuit 11...Phase difference counting circuit 14...Light receiving element 15...Microcomputer 16...Outside the display 3 Figure 1 Figure 2 Figure 3 j k

Claims (1)

[Claims] 1. A light emitting element, a modulation signal for emitting modulated light from the light emitting element, a signal generation source that outputs a local oscillation signal and a reference signal of a frequency different from that of the modulation signal, and a target object. a light-receiving element that converts reflected modulated light from the light-receiving element into an electrical signal, a conversion means for obtaining a measurement signal having a frequency that is the difference between the frequencies of the two signals from the output signal of the light-receiving element and the local oscillation signal; In a distance measuring device comprising a measuring means for measuring a time delay with respect to a reference signal and measuring a distance to a target based on the time delay, modulated light emitted from the light emitting element by a modulated signal from the signal generation source. is an optical pulse train, and the converting means is a sample and hold means that samples and holds the local oscillation signal using an electric pulse train that is an output signal of the light receiving element. 2. The conversion means comprises a sample and hold circuit connected to the output circuit of the local oscillation signal, and the switch of the sample and hold circuit is opened and closed by the electric pulse train that is the output signal of the light receiving element. A distance measuring device according to claim 1. 3. The conversion means comprises a flip-flop to which the local oscillation signal of a rectangular wave and the electric pulse train which is the output signal of the light receiving element are respectively inputted as an input signal and a clock pulse signal. Distance measuring device described in section.