JPS5912148B2 - Distance measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the distance to a target object from the phase difference of reflected and received waves from the target object using continuous waves.

- A distance measurement method using a general sidetone (SIDE Tl0NB) sequential transmission method will be explained.

This method calculates the distance to the target by measuring the phase difference between when the sidetone is transmitted and when it is received back from the target.

In order to improve the distance resolution, the frequency of the sidetone can be increased, but if the round trip distance to the target exceeds one period of the sidetone, the phase difference between the sidetone transmission and reception will increase in this sidetone l wave. It is not possible to determine how many cycles there are.

Therefore, in order to remove this ambiguity in the sidetone period, it is necessary to use sidetones with lower frequencies.

This sidetone is called ambiguity tone (AMBI).
GUTYTONB), and several types of eye visibility tones with normal frequency ratios are prepared.

On the other hand, the sidetone with the highest frequency is called a range tone.

A supplementary explanation of the above will be given with reference to FIG.

The phase difference between transmitting and receiving the range tone is d=(α+2πxn)
It is rad.

Here, the phase difference α rad (0≦α<2π) can be detected, but it is unclear which cycle n corresponds to.

In order to know this phase ambiguity n, for example, an ambiguity tone having a frequency f1 of 115 of the range tone frequency fO is transmitted.

In the case of the phase relationship of the transmitted and received waveforms shown in Figure 1, n is (3+5n
').

Furthermore, in order to know the above n', it is sufficient to repeat similar phase detection using an ambiguity tone of a lower frequency.

Note that there is no need to transmit the ambiguity tone except for the ambiguity of the n times period of the range tone.

An object of the present invention is to provide a distance measuring method and an apparatus therefor that can further reduce the distance measuring error rate in the distance measuring method described above.

That is, the present invention uses a range tone and an ambiguity tone, and shifts the transmitted wave of the ambiguity tone by the sum of the phase difference between transmitting and receiving the range tone and the phase difference determined by an integer indicating the ambiguity. In the method of finding an integer in the above shift amount such that the phase difference between the transmitted wave and the received wave reflected from the target object is O, and using the shift amount at this time to calculate the distance to the target object, the range tone is continuously set. while continuously detecting the phase difference between transmission and reception of the range tone, transmitting the continuous wave ambiguity tone in several parts, and detecting the shift amount of the ambiguity tone twice in a row. When the two positions are the same, the distance to the target is calculated using the amount of shift.

Embodiments of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 shows an example of the configuration of a phase verification circuit of a distance measuring device according to an embodiment of the present invention. In the figure, 1 is a phase detector (PSD), 2 and 8 are low-pass filters (LPF), and 3
．． Reference numeral 9 denotes an amplitude comparator, which has input/output characteristics shown in FIGS. 2 and 2C, respectively.

4 is a gate circuit that passes the clock, 5 is a reversible counter,
The count value n1(
nl is a positive integer).

6 is a phase thick, and continuous phase difference data of the range tone of the first frequency fO measured separately and a reversible counter 5
The amount of phase is controlled by the contents of .

7 is a reference oscillator that generates an ambiguity tone of a second frequency fl.

The ambiguity tones generated by the reference oscillator 7 are in exactly the same phase, and one is used for transmission, and the other is used as a reference ambiguity tone for phase detection of the received ambiguity tone.

The latter is determined by the phase shifter 6, which converts the phase difference α1 (0≦α1×2π) between the range tone transmission and reception waves into the ambiguity tone frequency fl, which is the phase amount ψ, that is, α1・f 1/
The phase difference between f O (α・115 rad in FIG. 1) and the phase difference 2π・nl−f1 according to the contents of the reversible counter 5
A phase shift equal to the sum of the phase amount /fO is given, and its output is used as the reference ambiguity tone of PSDI.

Frequency fO of range tone and ambiguity tone,
If the ratio of fl is 5:l, the phase difference between the received ambiguity tone and the reference ambiguity tone in PSDI is 0. ±2π15
．． There are five states of ±4π15 rad.

When this phase difference is 0 rad, the output of PSDI becomes O, so that the amplitude comparator 3 has no output and the amplitude ratio sensor 9 has an output.

The output of the amplitude comparator 9 at this time is called a capture completion signal,
This state is called capture completion.

In the case of the phase relationship of the ambiguity tone transmission and reception waveforms shown in FIG. 1, such a state can be realized by delaying the phase of the transmitted ambiguity tone by (α-2πX2) 15 rad.

That is, the phase amount of the phase shifter 6 at the time when the acquisition completion signal is received (α + 2π
±2) is the solution that eliminates the ambiguity of the phase difference of range tones.

Also, if the received ambiguity tone and the reference ambiguity tone are out of phase, the output of PSDl is 0.
Therefore, the amplitude comparator 9 does not receive a capture completion signal.

If the reference ambiguity tone lags behind the received ambiguity tone (2π15 or 4π/5 r
ad), there is an output on one side of the amplitude comparator 3, and a gate circuit 4 sends a countdown clock to a reversible counter 5.

When the reversible counter 5 counts up to the same number, the reversible counter 5 sends a signal to the phase shifter 6 to advance the reference ambiguity tone phase by 2π15 rad.

Next, if the reference ambiguity tone is in a leading phase with respect to the received ambiguity tone (2π15 or 4
π/5 rad), there is an output on the upper side of the amplitude comparator 3, and a gate circuit 4 sends a count up clock to a reversible counter 5.

When the reversible counter 5 reaches the number, the reversible counter 5
sends a signal delayed by 2π15 rad to the phase shifter 6.

In this way, when the phase difference between the received wave of the ambiguity tone and the reference wave becomes 0 rad, the output of PSDl becomes 0, so the amplitude comparator 3 has no output, and the reversible counter 5 receives the reference wave. A signal that shifts the phase of the ambiguity tone is not generated, and the phase difference between the received wave of the ambiguity tone and the reference wave is maintained at 0 rad.

During this time, the amplitude comparator 9 generates a capture completion signal, completing the capture of the ambiguity tone.

Furthermore, if it is necessary to remove ambiguity in the phase of the range tone, the tone is switched to an ambiguity tone with a lower frequency f2, and the same phase detection as above is performed.

A combination of a plurality of phase verification circuits 10 for one ambiguity tone shown in FIG. 2 will be described with reference to FIG. 3.

In FIG. 3, 10A to 1ON are the second and subsequent phase verification circuits, which are the reference oscillator 7, phase detector 1, low-pass filters 2, 8, amplitude comparators 3, 9, Each of them has the same components as the gate circuit 4 and the reversible counter 5.

Although not shown, a device similar to the reference oscillator 7 and phase detector 1, which output a continuous wave of frequency fO shown in FIG. 2, is used to output the phase signal El to the second phase verification circuit 10A. A first phase verification circuit is provided having a first phase verification circuit.

Here, if the frequency of the range tone is fO, the frequency f1 of the ambiguity tone of the phase verification circuit 10A is selected to be lower than the frequency fO of the range tone, and the frequency f2 of the ambiguity tone of the phase verification circuit 10B is selected for phase verification. Ambiguity tone frequency f of circuit 10A
Similarly, the frequency fN of the ambiguity tone of the phase verification circuit 1ON is selected to be the lowest value.

The transmitting ambiguity tones Al-AN having frequencies fl-fN are input to a selection circuit 12, where they are selected and transmitted by a selection signal from the control circuit 11.

The ambiguity tone reception signal reflected by the target object is input to the selection circuit 13, and similarly to the time of transmission, it is selected in accordance with the selection signal from the control circuit 11 and becomes the reception ambiguity tone B1-BN.

Phase shift signals C1-C of phase verification circuits 10A to 1ON
N and capture completion signals DI-DN are each sent to the control circuit 11.
is input.

The phase amount ψ1 of the phase signals E1 to BN. ψ2゜・・・・・・
, ψN corresponds to the input ψ to the phase shifter 6 shown in FIG. 2, ψ1 is the phase amount of the range tone phase difference converted to the ambiguity tone frequency fl,
N) is a phase amount obtained by converting the phase shift amount of the reference wave of the ambiguity tone frequency f(i-1) by the frequency fi of the ambiguity tone.

Suppose now that the frequency f(i-1) of the ambiguity tone has been captured.

The acquisition completion signal D(i-1) is sent to the acquisition sequence control circuit 1.
1, where it accepts the capture completion signal and at the same time issues a command to select the next ambiguity tone frequency fi.

This ambiguity tone selection signal sends out one wave of ambiguity tone frequency fi in the selection circuit 12,
The selection circuit 13 sends the received ambiguity tone frequency fi to the corresponding phase verification circuit 10i.

Then repeat this for each ambiguity tone,
If the acquisition completion signal DN of the lowest frequency ambiguity tone frequency fN is output, the ambiguity within the range of C/2fN (C is the speed of light) corresponding to one period of the frequency fN among the distance to the target object can be removed. It means that it has been lost.

Next, a phase difference error rate test will be explained.

Generally, an error in ambiguity tone capture (phase detection) in the sidetone sequential transmission method occurs when a capture completion signal occurs when the phase difference between the received ambiguity tone and the reference ambiguity tone is other than 0 rad. However, this is mainly due to causes such as thermal noise and phase jitter, and if an error occurs, the measurement distance error will be large.

In particular, the lower the frequency ambiguity tone, the larger the distance error area becomes.

Also, this method has the feature that after the acquisition of all ambiguity tone signals is completed, continuous distance measurement is possible by continuous phase measurement of only the range tone l wave, but if the acquisition is incorrect, continuous erroneous measurements will result. invite.

Another disadvantage of this method is that the measurement takes a long time because the distance is not known until the gold ambiguity tone is captured after the range tone phase measurement is completed.

Therefore, in order to shorten the time, (7') LPF
2. Fasten the time constant of 8, (a) lower the threshold level of amplitude comparator 3, (1) raise the threshold level of amplitude comparator 9, (fasten the count time of counter 5 using a high frequency clock) You can do something like this.

However, these methods only serve to worsen the acquisition error rate and are not fundamental solutions.

Therefore, if the target is moving, it is not possible to compare each data simply by measuring the distance multiple times because there is a time difference between the measurements. However, if a separate means is provided to continuously measure the phase of the range tone, The output of counter 5 in Figure 2 (
Multiple acquisition tests can be performed using a phase shift signal (referred to as a phase shift signal).

This measuring method will be explained using FIG.

First, after the acquisition of the first ambiguity tone is completed, the ambiguity tones are sequentially transmitted in the same way as the first time, while continuous phase measurement of the range tone is continued.

The second time, the phase amount of the phase shifter 6 in Fig. 2 is constantly updated using the continuous phase measurement data of the range tone.
Even if αrad in Figure 1 moves, the reference wave of the ambiguity tone is phase shifted by the phase shifter 6 in Figure 2 by the phase amount converted to the ambiguity tone frequency of the phase amount by which the range tone has moved Therefore, the received wave of the ambiguity tone and the reference wave should be in phase.

Therefore, the capture completion signal is output immediately.

However, if the phase relationship detected the first time (0 rad phase) and the phase relationship detected the second time are different (±2
π15. A phase shift signal of the reference ambiguity tone is output from the counter 5 in FIG. 2.

This phase shift signal indicates that the acquisition state of the ambiguity tone obtained in the first measurement must be corrected in the second measurement.
This means that there was a capture error in either or both of the first and second attempts.

Therefore, if there is a phase shift signal at the second time, this signal is used to immediately reacquire the ambiguity tone.

After all, during the n-th measurement, the n-1th measurement distance is determined to be correct only if no phase shift signal is output during the capture of each ambiguity tone and only a capture completion signal is output.

As described above, in the multiple acquisition test used in the embodiment of the present invention, all ambiguity tones are sequentially transmitted in the same way as the first time.

The measured distance is determined to be correct only when the phases of the ambiguity tones in the first and second measurements are all the same.

Therefore, in this device, the only case where the distance is incorrect is when the ambiguity is incorrect the first time and the phase difference (including whether positive or negative) is the same the second time.

In all other cases, it is confirmed that there is an error, and it is possible to redo the acquisition.

By the way, since the first and second times a given ambiguity tone is erroneous are completely independent events, it is not the case that a tone that is erroneous the first time is likely to be erroneous the second time.

Therefore, the probability that the same ambiguity tone will be wrong with this system is 1/square of the probability of the conventional system, but it is also possible to determine the phase difference between the tones.
The error rate of the system using multiple acquisition verification has the effect of being less than 1/2 of the square compared to conventional systems, and is almost zero, so the reliability of ranging data is dramatically improved compared to conventional systems. It turns out.

In addition, in this multiple acquisition test, by the time of the second sequence, the phase of the range tone has already been measured in the first sequence, and the phase synchronization of each ambiguity tone has been performed, so the time required for these phase synchronizations is be shortened.

Furthermore, in conventional systems, in order to confirm the authenticity of the data after the acquisition is completed, it is necessary to interrupt the acquisition and re-acquire the data.

In this case, if the target was moving, there was no way to verify the authenticity of the previous data.

However, the distance measuring device and its method according to the embodiments of the present invention have the great advantage of automatically verifying and correcting errors in acquisition results without interrupting acquisition during acquisition sequences that occur two or more times. .

This was not possible with conventional systems.

Here, in the above embodiment, the phase amount ψ of the phase signals E2 to EH
Although the explanation has been made assuming that 2~ψN is input from the output of the phase shifter of the previous phase verification circuit, the phase amount ψ2~2~ is input by each ambiguity tone as in the case where the phase amount ψl by the range tone is determined independently. It is clear that ψN can be found.

Further, it is preferable that the relationship between the frequency fl-fN of each ambiguity tone and the frequency fO of the range tone be selected to be an integer ratio.

Furthermore, when two ambiguity tone frequencies fl and f2 are used in this phase verification circuit, the relationship between the ambiguity tone frequencies f2 and fl and the ambiguity tone frequency fl and the range tone frequency f
By selecting the relationship with O to be a multiple of the same integer, the distance measuring device can be configured with an even simpler circuit.

Moreover, one or more ambiguity tones can be used depending on the measurement range.

Further, according to the apparatus of the above embodiment, since the control circuit is controlled by the acquisition completion signal from the reversible counter, multiple acquisition verification can be realized with a simple configuration.

As explained above, according to the distance measuring method and device of the present invention, a range tone and an ambiguity tone are used, and a transmission wave of the ambiguity tone is shifted by a predetermined amount and a target object for the transmission wave is used. In the method of finding an integer in the above shift amount such that the phase difference with the reflected received wave from the By calculating the distance to the target object using the shift amount when they are the same, it is possible to greatly reduce the error rate in measuring the distance to the target object.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram of a range tone and an ambiguity tone during transmission and reception, FIG. 2a is a block diagram showing a phase detection circuit of a distance measuring device according to an embodiment of the present invention, A characteristic diagram showing the characteristics of the amplitude comparators 3 and 9, FIG. 3 is a block diagram showing a distance measuring device according to an embodiment of the present invention, and FIG. 4 is a flowchart for explaining a distance measuring method according to an embodiment of the present invention. It is a diagram. In the figure, 1 is a phase detector, 2 and 8 are low-pass filters, 3 and 9 are amplitude comparators, 4 is a gate, 5 is a reversible counter, 6 is a phase shifter, and 7 is a reference for generating an ambiguity tone. A signal generator, 10 and 10A-1ON are phase verification circuits, 11 is a control circuit that performs acquisition sequence control,
12 and 13 are selection circuits. Note that the same reference numerals in the figures indicate the same or equivalent parts. =154-

Claims (1)

[Claims] 1. An oscillation output wave at a first frequency fO is continuously transmitted, and an oscillation output wave at a second frequency fl lower than the first frequency fO is transmitted in several parts. , the phase difference αl (0≦
α1 × 2π) is calculated, and the phase of the oscillation output wave of the second frequency f1 is calculated based on the phase difference α1 and 2π that are continuously input.
・The sum of nl (nl is an integer) and the 11th second frequency fO
, the phase difference (αl+2π・nl)・
The unambiguous first frequency f is shifted by f1/fO, and the phase of the shifted signal wave is equal to the phase of the reflected received wave of the second frequency f1.
The above-mentioned integer n1 for determining the value of the phase difference α1' between the oscillation output wave and the reflected received wave of O is determined, and if necessary, the same ambiguity detection method as above is applied to the third frequency f2. ..., the second to (i-1)th frequencies f without ambiguity using the i-th frequency f(i-1) for the (i-1)th frequency f(1-2).
Phase difference α between the oscillation output wave and the reflected reception wave of l=f(i-2)
Integer n2~n(i-
1) and repeating the above ambiguity detection method, the integer nl or n when the same value of the above integer 01 or nl or n(i-1) is obtained twice in a row.
A distance measuring method characterized by calculating the distance to a target using l to n(i-1). 2. A first oscillator that continuously generates an oscillation output wave at a first frequency fO, and a first reflection from a target object of the transmitted wave transmitted from the first oscillator at a first frequency fO. Phase difference α between the received wave and the output wave from the first oscillator
a first phase verification circuit including a first phase detector that continuously detects l (0≦αl<2π), and the first to i-1
The second ~! which is lower than the frequency fO~f(i-2) of ! The second to l generating oscillation output waves at frequencies f1 to f(i-1) of
oscillator, the count value n2~ which is added or subtracted according to the input signal
the second to l reversible counters that output n1;
The second to l frequencies f l=f (i
-1) is determined by the phase difference αl~α(i-1) (0≦α(i-1)<2) from the first to (i-1) phase detectors.
π) and the count value n2~ from the second to l reversible counters
n! The sum of the phase difference 2π·n2~ni according to The phase difference (α
1+2π・n2~ni)・fl−f(i −1)/
f 2nd to l phase shifters shifting by O to f(i-2), 2nd to i frequencies f from said 2nd to l oscillators;
2nd to i from the above target transmitted with l=f(i-1)
a second to i phase detector that detects a phase difference between the reflected received wave and the output wave from the second to i phase shifters; The count value n of the second to i reversible counters so that the output becomes zero
A 2nd to i phase testing circuit equipped with a 2nd to i comparison detector that adds or subtracts 2 to ni, and all 2nd to i phase detectors of the 2nd to i phase testing circuits. When the output phase difference of becomes zero twice in a row, the above count value n2~n
A distance measuring device comprising: a control circuit that calculates a distance to a target using i.