JPH08220233A - Light wave range finding device - Google Patents

Abstract

PURPOSE: To shorten measuring time by respectively mixing a pair of frequency signals received by a pair of mixers and a frequency signal lower by a constant frequency than the respective ones, extracting a component of the constant frequency from the respective ones by a pair of BPFs, and finding a distance from a phase difference between the mutual ones. CONSTITUTION: A phase synchronizing oscillator 1 respectively outputs a generated signal having frequencies (f1 and f2 ) to a wave multiplexer 2 and a signal having frequencies (f1 -f3 and f2 -f3 ) to mixers 6 and 7. A signal whose wave is mixed by the wave multiplexer 2 emits the multiple modulated light to a measured object 4 from a light transmitter 3. A light receivers 5 converts its reflected light into an electric signals, and outputs it to the mixers 6 and 7. The mixers 6 and 7 respectively mixes this signal and the frequencies (f1 -f3 and f2 -f3 ) respectively inputted from an oscillator, and outputs it to BPFs 8 and 9. The BPFs 8 and 9 extracts a component of the frequency (f3 ) among them, and a phase difference between its mutual ones is measured by a phase difference measuring unit 10, and a distance up to the object 4 is found on the basis of this. Therefore, even when the object 4 moves, continuous range finding becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical distance measuring device,
In particular, the present invention relates to an optical distance measuring device that measures a distance from a phase difference between a transmission signal and a reception signal.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional lightwave distance measuring apparatus.

Conventionally, in this type of optical distance measuring device,
As shown in FIG. 2, the switch 11 switches between the signal of frequency f _{1 and} the signal of frequency f ₂ generated in the phase-locked oscillator 1. The optical transmitter 3 outputs the light modulated by the signal switched by the switch 11 to the device under test 4.

The optical receiver 5 receives the light reflected by the object 4 to be measured, converts it into an electric signal, and outputs it to the mixer 7. In the mixer 6, the signal selected by the switch 11 and the switch 1
The signal selected in 2 is integrated and output to the bandpass filter 8. In the mixer 7, the signals of the frequencies f ₁ and f ₂ converted into electric signals by the optical receiver 5 and the switching device 12
The signal selected in (1) is mixed and output to the bandpass filter 9.

In the bandpass filter 8, the mixer 6
Frequency f of the signals output from₃Only the signal component of
And outputs it to the phase difference measuring device 10. Band pass fill
The frequency of the signal output from the mixer 7
f₃Only the component of is extracted and output to the phase difference measuring device 10.
In the phase difference measuring device 10, the band pass filter 8 and the band
The phase difference of the output signal of the pass filter 9 is measured. In addition,
The frequency f at the switch 11 ₁When the signal of is selected,
The frequency f in the converter 12₁-F₃However, the frequency f₂
When the signal of is selected, the frequency f₂−
f₃Signal is selected.

The phase difference measured by the phase difference measuring device 10 is φ ₁ when the signal of the frequency f ₁ is selected by the switcher 11, and the phase difference measuring device 10 is selected when the signal of the frequency f ₂ is selected. If the phase difference measured at is φ ₂ , then the measured object 4
The distance R to is calculated by the following equation.

R = C (φ ₁ −φ ₂ ) / 4π (f ₁ −f ₂ ) ... (1) However, in the equation (1), 0 <f ₁ −f ₂ <C / 2R, C is the speed of light.

[0008]

In such a conventional optical distance measuring apparatus, the signal of frequency f _{1 and} the signal of frequency f ₂ are switched by the switching device 12 and the phase difference between them is measured by the phase difference measuring device 10. Since it is necessary to measure and calculate the distance R from the phase difference to the measured object 4 based on the equation (1),
There is a problem that measurement takes time.

Further, if the measured object 4 moves between the measurement of the phase difference when the signal of the frequency f ₁ is selected and the measurement of the phase difference when the signal of the frequency f ₂ is selected, an error occurs in the measurement value. There is a problem that occurs.

The present invention has been made in order to eliminate the above-mentioned problems of the conventional one, and can shorten the measurement time, and can continuously perform measurement error even when the object to be measured is moving. An object of the present invention is to provide an optical wave distance measuring device that enables distance measurement.

[0011]

In order to achieve the above object, the optical distance measuring apparatus of the present invention has frequencies f ₁ , f ₂ , f _1-.
A phase-locked oscillator that generates signals f ₃ and f ₂ −f _3, a multiplexer that combines the signals f ₁ and f ₂ generated by the phase-locked oscillator, and a multiplexer that combines the signals. Frequency f
Optical transmitting means for outputting to the object to be measured the light multiplexed and modulated with the signals ₁ and f ₂ , and light receiving means for converting the light output from the optical transmitting means and reflected by the object to be measured into an electric signal. , The frequency f ₁ converted into an electric signal by the optical receiving means
And a first mixer for mixing an output signal of the frequency f ₁ -f ₃ signal f ₂ from the phase locked oscillator, frequency f ₁ is converted into an electrical signal by the optical receiver and f ₂
And the frequency f ₂ − output from the phase-locked oscillator.
a second mixer for mixing the signal of f _3, a first band-pass filter for extracting a signal of a frequency f ₃ from signals output from the first mixer is output from the second mixer a second band-pass filter for extracting a signal of a frequency f ₃ from signals, the signal of the first band-pass frequency f ₃ extracted by the filter and the second
And a phase difference measuring means for measuring the phase difference with the signal of the frequency f ₃ extracted by the band pass filter, and the distance to the object to be measured is obtained from the measurement result of the phase difference measuring means. It is characterized by

Further, the distance R to the object to be measured is expressed by the following equation R = C.Δφ / 4π (f ₁ -f) where Δφ is the phase difference measured by the phase difference measuring means and C is the light velocity. ₂ ) is required.

[0013]

In the present invention constructed as described above, the optical transmission means outputs the light multiplexed and modulated with the signals of the frequencies f ₁ and f ₂ generated by the phase locked oscillator to the object to be measured. The light receiving means converts the reflected light from the object to be measured into an electric signal and outputs the electric signal to the first mixer and the second mixer, respectively.

The first mixer mixes the signals of the frequencies f ₁ and f ₂ output from the optical receiving means and the signals of the frequencies f ₁ -f ₃ output from the phase locked oscillator, and outputs the first bandpass signal. Output to the filter. The second mixer mixes the signals of the frequencies f ₁ and f ₂ output from the optical receiver with the signals of the frequency f ₂ -f ₃ output from the phase-locked oscillator, and outputs them to the second bandpass filter. To do.

The first bandpass filter extracts the signal component of the frequency f ₃ from the signal output from the first mixer, and the second bandpass filter extracts the signal component of the frequency f ₃ from the signal output from the second mixer to obtain the phase difference. Output to measuring means.

The phase difference measuring means measures the phase difference Δφ between the signals of the frequency f ₃ extracted by the first bandpass filter and the second bandpass filter.

In the present configuration, the distance R to the object to be measured is given by the following equation R = C.Δφ / 4π (f ₁ -f) where Δφ is the phase difference measured by the phase difference measuring means and C is the light velocity. ₂ )

[0018]

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

FIG. 1 is a block diagram showing the construction of an embodiment of the lightwave distance measuring apparatus of the present invention. In this figure, the same components as those shown in FIG. 2 are designated by the same reference numerals.

As shown in FIG. 1, the light wave distance measuring apparatus according to the present embodiment has frequencies f ₁ , f ₂ , f ₁ -f ₃ , and f _2-.
a phase locked oscillator 1 for generating a signal f _3, the phase synchronous oscillator 1 multiplexer 2 for multiplexing signal of frequency f ₁ and f ₂ generated by, multiplexer 2 multiplexes frequency f ₁ And f ₂
An optical transmitter 3 that outputs the light multiplexed and modulated with the signal to the object to be measured 4, and an optical receiver 5 that converts the light output from the optical transmitter 3 and reflected by the object to be measured 4 into an electric signal. A first mixer 6 for mixing the signals of the frequencies f ₁ and f ₂ converted into electric signals by the optical receiver 5 and the signals of the frequencies f ₁ -f ₃ output from the phase locked oscillator 1; and an optical receiver From the first mixer 6 and the second mixer 7 that mixes the signals of the frequencies f ₁ and f ₂ converted into electric signals with the signal of the frequency f ₂ -f ₃ output from the phase-locked oscillator 1. a first band-pass filter 8 for extracting the signal of frequency f ₃ from the signal output, a second band-pass filter 9 which extracts a signal of a frequency f ₃ from the signal outputted from the second mixer 7, first bandpass frequency f ₃ which is extracted by a filter 8 Signal and the second band-pass filter 9
And a phase difference measuring device 10 for measuring the phase difference with the signal of the frequency f ₃ extracted in step 1.

Next, distance measurement by the above-mentioned apparatus will be described.

In FIG. 1, the phase locked oscillator 1 generates signals of frequencies f ₁ , f ₂ , f ₁ -f ₃ and f ₂ -f ₃ ,
Among them, the signals of frequencies f ₁ and f ₂ are fed to the multiplexer 2 and the frequency f
Outputs ₁ -f ₃ and f ₂ -f ₃ signals to the respective mixers 6 and 7. The optical transmitter 3 has a frequency f multiplexed by the multiplexer 2.
_The light multiplexed and modulated with the signals of ₂ and f ₃ is output to the measured object 4.

The optical receiver 5 is reflected by the object 4 to be measured.
After receiving light and converting it into an electrical signal, the electrical signal is mixed.
Output to sir 6 and 7. Mixer 6 from the optical receiver 5
Output frequency f₁And f₂Signal, and phase-locked oscillation
Frequency f output from the unit 1 ₁-F₃Mix the signals of
Output to the low pass filter 8. Meanwhile, with mixer 7
Is the frequency f output from the multiplexer 2.₁And f₂Signal of
And the frequency f output from the phase-locked oscillator 1.₂-F₃Belief
The signals are mixed and output to the bandpass filter 9.

The band pass filters 8 and 9 receive the signals output from the mixers 6 and 7, respectively, extract the signal component of the frequency f ₃ from the signals, and output the extracted signals to the phase difference measuring device 10. To do. The phase difference measuring device 10 measures the phase difference Δφ between the signals of the frequency f ₃ output from the bandpass filters 8 and 9.

In FIG. 1, the signal S ₁ output from the bandpass filter 8 is expressed by the following equation.

S ₁ = A ₁ · cos (2πf ₃ t−4πf ₁ R / C) (2) where A ₁ is the amplitude and C is the speed of light.

The signal S ₂ output from the bandpass filter 9 is expressed by the following equation.

S ₂ = A ₂ · cos (2πf ₃ t−4πf ₂ R / C) (3) Here, A ₂ is the amplitude.

Therefore, the phase difference Δφ between the signals S ₁ and S ₂ measured by the phase difference measuring device 10 is given by the following equation.

Δφ = 4πR / C (f ₁ −f ₂ ) ... (4) From the equation (4), the distance R to the object to be measured 4 is obtained by the following equation.

R = C · Δφ / 4π (f ₁ −f ₂ ) ... (5) In this case, the distance R to the object 4 to be measured is based on the phase difference Δφ measured by the phase difference measuring device 10. It is obtained according to the equation (5).

Therefore, the measurement time for obtaining the distance R to the object to be measured 4 can be shortened because it can be performed by one measurement, and even if the object to be measured 4 is moving, it can be continuously measured without error. Distance measurement is possible.

[0033]

As described above, according to the present invention, since the distance to the object to be measured can be measured without switching the frequency, the measuring time can be shortened,
Moreover, there is an effect that continuous distance measurement can be performed without a measurement error even when the object to be measured is moving.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of a conventional lightwave distance measuring device.

[Explanation of symbols]

 1 Phase-locked oscillator 2 Multiplexer 3 Optical transmitter 4 Object to be measured 5 Optical receiver 6 First mixer 7 Second mixer 8 First bandpass filter 9 Second bandpass filter 10 Phase difference measuring instrument

Claims (2)

[Claims] 1. Frequencies f ₁ , f ₂ , f ₁ -f ₃ , and f ₂
A phase-locked oscillator that generates a signal of -f _3, a multiplexer that combines the signals of f ₁ and f ₂ that are generated by the phase-locked oscillator, and a frequency f ₁ that is combined by the multiplexer. optical transmitting means for outputting to the object to be measured the light multiplexed and modulated with the signal of f ₂ , and light receiving means for converting the light output from the optical transmitting means and reflected by the object to be measured into an electric signal, A first mixer for mixing the signals of the frequencies f ₁ and f ₂ converted into electric signals by the optical receiving means and the signals of the frequencies f ₁ -f ₃ output from the phase-locked oscillator; A second mixer for mixing the signals of the frequencies f ₁ and f ₂ converted into a signal and the signal of the frequency f ₂ -f ₃ output by the phase-locked oscillator; and a signal output from the first mixer To frequency f ₃
And a frequency f ₃ from the signal output from the second mixer.
A second bandpass filter for extracting the signal of the frequency band, and a frequency f extracted by the first bandpass filter.
₃ signal and the phase difference measuring means for measuring the phase difference between the signal of the frequency f ₃ extracted by the second band pass filter, from the measurement result of the phase difference measuring means to the object to be measured. An optical wave distance measuring device, characterized in that the distance of is measured. 2. The distance R to the object to be measured, where Δφ is the phase difference measured by the phase difference measuring means and C is the speed of light, the following equation R = C · Δφ / 4π (f ₁ −f ₂ ) The optical distance measuring device according to claim 1, which is obtained by