JP2010127839A - Laser radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser radar device capable of measuring a distance by transmitting and receiving a laser light signal whose intensity is modulated by a CW (Continuous Wave) modulation signal, and detecting an accurate distance by removing uncertainty in each period by utilizing foresight information. <P>SOLUTION: This device includes a GPS (Global Positioning System) 10, an INS (Inertial Navigation System), a map information holding part 12, a light source 1, a light intensity modulator 2 for performing intensity modulation by a CW modulation signal to a laser light signal from the light source 1, a transmission optical system 5 and a reception optical system 6 for transmitting a laser light signal 30a subjected to intensity modulation toward a target 30 and receiving a scattered light signal 30b from the target 30, a light receiver 7 for performing intensity detection of the scattered light signal 30b and converting it into an electric signal, a phase detector 8 for detecting a phase difference Δϕ between the CW modulation signal and a reception signal, and a distance detector 9 for detecting a distance L to the target 30 based on the phase difference Δϕ and the foresight information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention transmits and receives a CW laser light signal (hereinafter also simply referred to as “laser light signal”), which is intensity-modulated with a CW modulation signal composed of CW (Continuous Wave), to a target to receive light ( CW received signal) is intensity-detected, and the laser measures the distance from the device to the target (hereinafter referred to as “device-target”) based on the phase difference between the CW modulation signal and the received signal obtained by the detection. The present invention relates to a radar device.

  Conventionally, this type of laser radar device modulates the intensity of the laser light signal and transmits it to the space, receives the scattered light from the target, detects the intensity, and uses the phase difference of the modulation component between the transmission and reception. Thus, the distance between the device and the target is measured (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 9-15334

In the conventional laser radar apparatus, in the case of the technique described in Patent Document 1, since the same phase is generated for each distance between the apparatus and the target corresponding to one period of the modulation frequency, for example, when 1 MHz is used as the modulation frequency, The same phase occurs every time the distance between the device and the target changes by 150 m, and there is a problem that the distance cannot be uniquely determined from the phase of the received signal.
Further, the conventional laser radar device has a problem that there is no means for avoiding the uncertainty of the distance measurement value that occurs in principle.

  The present invention has been made in order to solve the above-described problems, and performs distance measurement by transmitting and receiving a laser light signal intensity-modulated with a CW modulation signal, as well as position information, posture information, map information, and the like. An object of the present invention is to obtain a laser radar device capable of detecting an accurate distance by removing uncertainty for each period using the foresight information.

  A laser radar device according to the present invention generates a position information on the earth, an INS that generates attitude information for inertial navigation, a map information storage unit that stores map information, and a laser light signal. An optical signal generating means for performing an intensity modulation on the laser light signal from the optical signal generating means with a CW modulation signal, and a laser light signal modulated by the light intensity modulating means directed toward the target. An optical system means for transmitting and receiving a scattered light signal from the target, an optical receiving means for detecting the intensity of the scattered light signal from the target and converting it into a received signal comprising an electric signal, a CW modulation signal and a received signal; Phase detection means for detecting the phase difference between the GPS, the INS and the position information and attitude information obtained from the GPS, INS and map information storage unit. And based on one or more look-ahead information in the map information, in which a distance detecting means for detecting a distance to the target.

  According to the present invention, a distance measurement is performed by transmitting and receiving a laser light signal intensity-modulated with a CW modulation signal, and an accurate distance is obtained by removing uncertainty for each period using foresight information. Can be detected.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIGS.
FIG. 1 is a block diagram schematically showing the configuration of a laser radar apparatus according to Embodiment 1 of the present invention, and shows an example of a laser radar apparatus 13 mounted on an aircraft 14.

  In FIG. 1, a laser radar apparatus 13 includes a light source 1, a light intensity modulator 2, an oscillator 3, a distributor 4, a transmission optical system 5, a reception optical system 6, an optical receiver 7, and a phase detection. A device 8, a distance detector 9, a GPS (Global Positioning System) 10, an INS (Internal Navigation System) 11, and a map information storage unit 12.

In FIG. 1, the entire system of the laser radar device 13 is mounted on the aircraft 14 as an example. However, for example, it may be mounted on a satellite or installed on the ground.
In FIG. 1, transmission means between the light source 1 and the light intensity modulator 2, transmission means between the light intensity modulator 2 and the transmission optical system 5, and between the reception optical system 6 and the optical receiver 7. Each transmission means is constituted by an optical circuit (for example, an optical fiber).

The distributor 4 has an input terminal connected to the oscillator 3 and an output terminal connected to the light intensity modulator 2 and the phase detector 8, and the CW modulation signal input from the oscillator 3 is converted into the light intensity modulator 2 and A distribution input is made to the phase detector 8.
The phase detector 8 has an input terminal connected to the optical receiver 7 and an output terminal connected to the distance detector 9. The distance detector 9 is connected to the GPS 10, the INS 11, and the map information storage unit 12. Connection means among the oscillator 3, the distributor 4, the phase detector 8 to the map information storage unit 12 are each constituted by an electric signal line.

The light source 1 has a function of generating and transmitting a laser light signal.
The light intensity modulator 2 has a function of performing CW intensity modulation on the laser light signal from the light source 1 based on the CW modulation signal from the oscillator 3 input via the distributor 4.
In FIG. 1, the laser light signal from the light source 1 is modulated by the light intensity modulator 2, but the light source 1 may be directly modulated without using the light intensity modulator 2.

The transmission optical system 5 shapes the laser light signal modulated by the light intensity modulator 2 into a predetermined beam size and beam shape, and directs the laser light signal toward a target 30 (for example, the ground) existing in the space. It has a function of emitting 30a.
On the other hand, the reception optical system 6 has a function of receiving the scattered light signal 30b from the target 30 and sending it to the optical receiver 7 as a CW reception signal (hereinafter also simply referred to as “reception signal”).

The optical receiver 7 has a function of detecting the intensity of the scattered light signal 30 b received from the target 30 via the receiving optical system 6, converting it into an electrical signal, and sending it to the phase detector 8.
The phase detector 8 performs phase detection between the received signal from the optical receiver 7 and the CW modulation signal from the oscillator 3 input via the distributor 4, and detects the phase difference Δφ between the two signals to detect the distance. It has a function to send to the detector 9.

The GPS 10, the INS 11, and the map information storage unit 12 each have a function of sending various information such as a flight position, a flight posture, and map information to the distance detector 9 as foresight information.
The distance detector 9 performs signal processing on the phase difference information from the phase detector 8 using any one or more of the foresight information obtained from the GPS 10, the INS 11, and the map information storage unit 12. , Has a function of obtaining the distance L between the device and the target.

Next, the operation of the laser radar apparatus according to Embodiment 1 of the present invention shown in FIG. 1 will be described.
First, the light source 1 transmits a CW laser light signal to the light intensity modulator 2.
In parallel with this, the oscillator 3 generates a CW modulation signal having a certain modulation frequency fm, the distributor 4 distributes the CW modulation signal into two, and the one CW modulation signal is distributed to the light intensity modulator 2. The other CW modulation signal is input to the phase detector 8.

  Thereby, the light intensity modulator 2 applies intensity modulation of the modulation frequency fm to the laser light signal from the light source 1 using the CW modulation signal, and inputs the intensity-modulated laser light signal to the transmission optical system 5. To do. Subsequently, the transmission optical system 5 shapes the laser light signal transmitted from the light intensity modulator 2 into a predetermined beam size and beam shape to form a laser light signal 30a for radiation, which is directed toward the target 30 in space. Radiate.

Next, the receiving optical system 6 receives the scattered light signal 30b from the target 30 and sends it to the optical receiver 7. The optical receiver 7 detects the intensity of the received signal, thereby converting the received signal into an electric signal. The signal is converted and input to the phase detector 8.
At this time, since the transmission optical system 5 and the reception optical system 6 transmit and receive the laser light signal 30a and the scattered light signal 30b that have been intensity-modulated with the CW modulation signal, the reception signal becomes a CW signal having the modulation frequency fm. .

FIG. 2 is an explanatory diagram schematically showing the relationship between the CW modulated signal and the received signal.
As can be seen from FIG. 2, the CW modulation signal and the reception signal are CW signals having the modulation frequency fm, but the reception signal has a delay time τ (including phase difference Δφ) with respect to the CW modulation signal.
At this time, the phase difference Δφ between the two signals corresponds to the distance L between the apparatus and the target, and is given by the following equation (1) using the light velocity c and the distance L.

  Δφ = 2π × (2L / c) × fm [rad] (1)

However, as apparent from the equation (1), the phase difference Δφ has uncertainty because the same phase difference is generated for each distance corresponding to one period of the modulation frequency fm of the CW modulation signal.
Subsequently, the phase detector 8 detects the phase difference Δφ between the received signal from the optical receiver 6 and the CW modulated signal, detects the phase difference Δφ between the CW modulated signal and the received signal, and converts the phase difference information into the distance detector. 9

On the other hand, the GPS 10 and the INS 11 measure the flight position and the flight attitude, and input to the distance detector 9 as foresight information together with the map information from the map information storage unit 12.
The distance detector 9 first predicts the approximate distance between the device and the target (the range in which the true value can be obtained) based on the foresight information, and then determines the true distance based on the phase difference information from the phase detector 8. The distance L is detected.

FIG. 3 is an explanatory diagram schematically showing the relationship between the distance L and the phase difference Δφ.
In FIG. 3, the phase difference Δφ periodically changes within the range “0 to 2π” for each distance L corresponding to one period Tm (= 1 / fm) of the CW modulation signal (modulation frequency fm).
Therefore, not only the true value (black square point) of the distance L with respect to the detection phase (see the broken line) but also a plurality of candidate points (black circle points) are generated due to the uncertainty for each period Tm.

As described above, when the distance L is simply determined from only the phase difference Δφ, uncertainty (black dot) occurs for each period Tm of the modulation frequency fm.
However, if the range of the approximate distance predicted by the distance detector 9 (the one-dot chain line in FIG. 3) is smaller than the period T, the correspondence between the phase difference Δφ and the distance L in the predicted range is “ It becomes possible to specify and measure the distance L of the true value (black square point) uniquely from the phase difference information.

  As described above, the laser radar device according to Embodiment 1 (FIGS. 1 to 3) of the present invention includes the GPS 10 that generates position information on the earth, the INS 11 that generates attitude information for inertial navigation, A map information storage unit 12 that stores map information, a light source (optical signal generating means) 1 that generates a laser light signal, and a light intensity that modulates the laser light signal from the light source 1 with a CW modulation signal. The transmitter 2 transmits the laser light signal 30a intensity-modulated by the light intensity modulator 2 to the target 30 and receives the scattered light signal 30b from the target 30 and the receiving optical system 6 ( Optical system means), an optical receiver 7 for detecting the intensity of the scattered light signal 30b from the target 30 and converting it into a received signal consisting of an electrical signal, and detecting the phase difference Δφ between the CW modulated signal and the received signal. The phase detector 8 to be output; the phase difference Δφ detected by the phase detector 8; and one or more foresights of position information, attitude information, and map information obtained from the GPS 10, the INS 11, and the map information storage unit 12 And a distance detector 9 for detecting a distance L to the target 30 based on the information.

The distance detector 9 performs rough prediction on the distance L between the device and the target based on any one or more of the foresight information from the GPS 10, the INS 11, and the map information storage unit 12, and the CW modulation signal The laser light signal 30a and the scattered light signal 30b that have been intensity-modulated in (1) and (2) are transmitted and received, and the distance L is measured using the phase difference Δφ between the CW modulated signal and the received signal.
Thus, by predicting the approximate distance using the foresight information from the GPS 10, the INS 11, and the map information storage unit 12, the CW modulation signal generated in principle at the time of distance measurement using the phase difference Δφ is obtained for each period. Uncertainty can be removed and a uniquely accurate distance L can be detected.

Further, a frequency setting means (not shown) related to the oscillator 1 is provided, and the modulation frequency fm of the CW modulation signal is variably set according to the accuracy of one or more pieces of foresight information among position information, posture information, and map information. You may comprise.
In this case, even when the information accuracy of the GPS 10, the INS 11, and the map information storage unit 12 changes depending on time and place, the accuracy of the foreseeing information is grasped, and one wavelength of the modulation frequency is equal to or higher than the prediction accuracy. By variably setting as described above, the prediction range (one-dot chain line in FIG. 3) becomes one period T or less, so that it is possible to reliably realize a highly accurate distance measuring function.

Embodiment 2. FIG.
In the first embodiment, the function of detecting the gas concentration in the space is not mentioned, but as shown in FIG. 4, two light sources 1a, 1b, two light intensity modulators 2a, 2b, and two While transmitting and receiving using the oscillators 3a and 3b, a light absorption amount detector 18 and a gas concentration detector 19 may be provided to measure the concentration of the measurement target gas between the apparatus and the target.

The second embodiment of the present invention will be described below with reference to FIG.
4 is a block diagram schematically showing the configuration of a laser radar apparatus according to Embodiment 2 of the present invention. The same components as those described above (see FIG. 1) are denoted by the same reference numerals as those described above and described in detail. Is omitted.

  In FIG. 4, the laser radar device 13A is based on the configuration of a known differential absorption lidar device (see, for example, Japanese Patent Application Laid-Open No. 2007-248126), and two laser light signals 30a and scattered light signals 30b having different wavelengths are obtained. Then, it is sent to and received from the target 30 (see FIG. 1), and the concentration of the measurement target gas existing between the apparatus and the target is measured.

In this case, the light source is composed of two light sources 1a and 1b, and each of the light sources 1a and 1b individually transmits CW laser light signals having different wavelengths λON and λOFF.
Similarly, the light intensity modulator includes two light intensity modulators 2a and 2b, and laser light signals from the light sources 1a and 1b are individually input to the light intensity modulators 2a and 2b.
The oscillator includes two oscillators 3a and 3b. The oscillators 3a and 3b individually input CW modulation signals having different modulation frequencies fm1 and fm2 to the light intensity modulators 2a and 2b.

Between the optical intensity modulators 2a and 2b and the transmission optical system 5, an optical multiplexer 15 for combining the laser optical signals from the optical intensity modulators 2a and 2b, and a laser optical signal from the optical multiplexer 15 are combined. An amplifying optical amplifier 16 is inserted in series.
A distributor 4a, a filter 17b, and a distributor 4b are inserted in series between the optical receiver 7 and the phase detector 8.

A light absorption amount detector 18 is connected to the other output terminal of the distributor 4a through a filter 17a. A light absorption amount detector 18 is connected to the other output terminal of the distributor 4b.
A gas concentration detector 19 is connected to the output terminal of the light absorption detector 18.
The apparatus-target distance L detected by the distance detector 9 is input to the gas concentration detector 19.

  In FIG. 4, the transmission means between the light source 1a and the light intensity modulator 2a, the transmission means between the light source 1b and the light intensity modulator 2b, the optical multiplexer 15, the light intensity modulators 2a and 2b, and the optical amplifier 16 The transmission means between the optical amplifier 16 and the transmission optical system 5, and the transmission means between the reception optical system 6 and the optical receiver 7 are all optical circuit lines (for example, optical fibers). ).

  On the other hand, transmission means between the oscillator 3a and the light intensity modulator 2a, transmission means between the oscillator 3b and the distributor 4, transmission means between the distributor 4, the light intensity modulator 2b and the phase detector 8 Transmission means between the optical receiver 7 and the distributor 4a, transmission means between the distributor 4a and the filters 17a and 17b, transmission means between the filter 17b and the distributor 4b, and the filter 17a and the light absorption amount Transmission means between the detector 18, transmission means between the distributor 4 b, the light absorption detector 18 and the phase detector 8, a concentration detector 19, a gas absorption detector 18, and a distance detector 9. The transmission means between the distance detector 9 and the phase detector 8, the GPS 10, the INS 11, and the map information storage unit 12 are all constituted by electric cables.

The light source 1a transmits a laser light signal having a wavelength λON, and the light source 1b transmits a laser light signal having a wavelength λOFF.
At this time, for the measurement target gas, the wavelength λON is set to a wavelength having a large absorption coefficient, and the wavelength λOFF is set to a wavelength having a small absorption coefficient.

The oscillator 3a outputs a CW modulation signal having a modulation frequency fm1 and transmits it to the light intensity modulator 2a. The oscillator 3b outputs a CW modulation signal having a modulation frequency fm2 and transmits it to the light intensity modulator 2b. Here, the modulation frequencies fm1 and fm2 are baseband frequencies, respectively.
The light intensity modulators 2a and 2b modulate the intensity of the laser light signals from the light sources 1a and 1b with the CW modulation signals from the oscillators 3a and 3b.

  The optical multiplexer 15 multiplexes the intensity-modulated laser light signals from the optical intensity modulators 2 a and 2 b and transmits them to the optical amplifier 16, and the optical amplifier 16 receives the multiplexed 2 from the optical multiplexer 15. After amplifying the laser light signal of the wavelength, it is transmitted to the transmission optical system 5.

The transmission optical system 5 shapes the amplified laser light signal from the optical amplifier 16 into a predetermined beam size and beam shape and radiates it into the space. The reception optical system 6 transmits the scattered light signal 3b from the target 30. Is coupled to an optical circuit line (optical fiber) and transmitted to the optical receiver 7.
The optical receiver 7 detects the intensity of the scattered light signal 30b received via the receiving optical system 9, converts it into an electrical signal, and transmits it to the distributor 4a. The distributor 4a distributes the electric signal from the optical receiver 7 in two, and transmits one to the filter 17a and the other to the filter 17b.

  The filters 17a and 17b filter the electrical signal (received signal) from the distributor 4a, and the output signal (fm1) of the filter 17a is directly input to the gas absorption amount detector 18, and the output signal (fm2) of the filter 17b. Is input to the gas absorption amount detector 18 via the distributor 4b.

  The filters 17a and 17b are band-pass filters that extract only predetermined frequency components. The frequency value extracted by the filter 17a is set to the modulation frequency fm1 of the CW modulation signal from the oscillator 3a, and the frequency extracted by the filter 17b. The value is set to the modulation frequency fm2 of the CW modulation signal from the oscillator 3b.

The distributor 4 taps a part of the CW modulation signal (fm2) from the oscillator 3b and transmits it to the phase detector 8, and the distributor 4b taps a part of the output signal (fm2) from the filter 17b. To the phase detector 8.
The phase detector 8 detects each signal from the distributors 4 and 4b, detects a phase difference Δφ between the two signals, and inputs the detected signal to the distance detector 9.

  Hereinafter, as described above, the distance detector 9 includes one or more of position information from the GPS 10, flight attitude information from the INS 11, and map information from the map information storage unit 12, and from the phase detector 8. The distance L between the apparatus and the target is measured using the information of the phase difference Δφ.

On the other hand, the light absorption amount detector 18 performs signal processing on the filtering output signals from the filters 17a and 17b, and obtains the light absorption amount by the measurement target gas existing in the atmosphere.
The concentration detector 19 calculates the concentration of the measurement target gas between the apparatus and the target from the light absorption amount by the measurement target gas obtained by the light absorption amount detector 18 and the distance L obtained by the distance detector 9.

Next, the operation of the laser radar apparatus according to Embodiment 2 of the present invention shown in FIG. 4 will be described.
First, CW laser light signals of two wavelengths are transmitted from the light sources 1a and 1b and input to the light intensity modulators 2a and 2b. Subsequently, CW modulation signals having two different modulation frequencies fm1 and fm2 are output from the oscillators 3a and 3b, and are transmitted to the light intensity modulators 2a and 2b, respectively.

At this time, a part of the CW modulation signal from the oscillator 3 b is tapped by the distributor 3 a and transmitted to the phase detector 8.
The light intensity modulators 2a and 2b modulate the intensity of the CW laser light signals from the light sources 1a and 1b based on the CW modulation signals from the oscillators 3a and 3b.
Thus, the intensity of the transmission laser light signal having the wavelength λON from the light source 1a is modulated at the modulation frequency fm1, and the intensity of the transmission laser light signal having the wavelength λOFF from the light source 1b is modulated at the modulation frequency fm2. Modulated.

Next, the optical multiplexer 15 combines the intensity-modulated laser light signals from the optical intensity modulators 2 a and 2 b and transmits them to the optical amplifier 16, and the optical amplifier 16 combines the optical signals from the optical multiplexer 15. The two-wavelength laser light signals thus amplified are amplified and transmitted to the transmission optical system 5.
The transmission optical system 5 shapes the laser light signal into a predetermined beam size and beam shape, and emits the laser light signal 30a into the space.

Between the two-wavelength signals of the laser light signal 30a radiated into the space, the absorption coefficient relating to the measurement target gas differs, so that a difference occurs in the amount of attenuation in the process of propagating in the space. Therefore, a difference in attenuation occurs between the two-wavelength laser light signals in the round-trip propagation process between the apparatus and the target.
That is, even if two-wavelength laser light signals are transmitted with the same transmission power, a difference in attenuation occurs between the two-wavelength signals in the received light quantity.

The receiving optical system 6 receives the scattered light signal 30 b from the target 30, couples it to the optical circuit line (optical fiber), and transmits it to the optical receiver 7.
Next, the optical receiver 7 detects the intensity of the received light received via the receiving optical system 6, converts it into an electric signal, and transmits it to the distributor 4a.

  At this time, when the laser light signal is emitted, the component of the wavelength λON is modulated with the modulation frequency fm1, and the component of the wavelength λOFF is modulated with the modulation frequency fm2, so even in the electric signal from the optical receiver 7, The component of wavelength λON has a modulation frequency fm1, and the component of wavelength λOFF has a modulation frequency fm2. As described above, the modulation frequencies fm1 and fm2 are baseband frequencies.

  It is known that the transimpedance gain of the optical receiver 7 can be set to a high gain value by lowering the reception frequency band. Therefore, by setting the modulation frequencies fm1 and fm2 to the baseband, it is possible to increase the transimpedance gain of the optical receiver 7, increase the optical reception sensitivity, and realize a high reception S / N ratio. It becomes.

Next, the distributor 4a distributes the electric signal from the optical receiver 7, transmits one to the filter 17a, and transmits the other to the filter 17b.
The filters 17 a and 17 b filter the electrical signal from the distributor 4 a and transmit it to the light absorption amount detector 18.

At this time, since the filter 17a extracts only the component of the modulation frequency fm1, and the filter 17b extracts only the component of the modulation frequency fm2, the filtering output signal (fm1) from the filter 17a becomes a component of the wavelength λON, and the filter 17b The filtered output signal (fm2) from is a component of wavelength λOFF.
The distributor 4b taps a part of the output signal from the filter 17b and transmits it to the phase detector 8.

The light absorption amount detector 18 uses the output signals from the two filters 17a and 17b to determine the light absorption amount by the measurement target gas between the apparatus and the target.
Specifically, first, the respective output signals from the two filters 17a and 17b are A / D converted, whereby the time waveforms of the two digital signals are converted into signals of the modulation frequencies fm1 and fm2.

Next, the amplitudes of the time waveforms of the two digital signals are compared.
At this time, when there is almost no measurement target gas in the space between the apparatus and the target, the effects of absorption of the two wavelengths in the propagation process in the space hardly occur, so the amplitudes of the two time waveforms are It will be almost the same.

On the other hand, when the measurement target gas is present in a large concentration in the space between the apparatus and the target, the influence of absorption of the two wavelengths in the propagation process in the space is large, and accordingly, the time waveforms of the two digital signals There is also a large difference in the amplitude of
Specifically, the amplitude of the time waveform of the component of the modulation frequency fm1 corresponding to the wavelength λON is significantly smaller than the amplitude of the time waveform of the component of the modulation frequency fm2 corresponding to the wavelength λOFF.

The difference between the amplitudes of the time waveforms of the two digital signals can be associated with the difference between the received light amounts of the two wavelengths λON and λOFF. Can be associated with differences.
That is, the difference in absorption amount corresponds to the number of molecules of the measurement target gas between the apparatus and the target, and the light absorption amount detector 18 inputs the number of molecules of the measurement target gas to the gas concentration detector 19 as light absorption amount information. To do.

The phase detector 8 obtains the phase difference Δφ between the CW modulated signal from the distributors 4 and 4b and the received signal. As described above, the phase difference Δφ corresponds to the distance L, but 1 of the modulation frequency fm2. Since the same phase appears for every distance corresponding to the period, it has uncertainty.
Therefore, similarly to the above, the uncertainty at the time of distance detection based on the phase difference Δφ is used as the prediction range (one-dot chain line in FIG. 3) based on the foresight information from the GPS 10, the INS 11, and the map information storage unit 12. To remove.

  Next, the concentration detector 19 uses the number of molecules of the gas to be measured between the device and the target obtained by the light absorption amount detector 18 and the distance L between the device and the target obtained by the distance detector 9 as a device. The concentration of the measurement target gas between the targets is calculated.

As described above, the laser radar device according to the second embodiment (FIG. 4) of the present invention is based on the distance L to the target 30 detected by the distance detector 9 and the measurement existing between the target 30 and the target 30. A gas concentration detector 19 for detecting the concentration of the target gas is provided.
In this case, the optical signal generating means includes a plurality of light sources 1a and 1b that generate a plurality of laser light signals having different wavelengths λON and λOFF.

Similarly, the light intensity modulation means includes a plurality of light intensity modulators 2a and 2b that modulate the intensity of each wavelength component of a plurality of laser light signals with CW modulation signals having different modulation frequencies fm1 and fm2.
The optical system means includes a transmission optical system 5 that multiplexes and transmits the laser light signals from the plurality of light intensity modulators 2 a and 2 b to the target 30, and a reception optical system 6 that receives the scattered light signal from the target 30. Including.

The optical receiving means extracts a plurality of frequency components used for intensity modulation from the received signal obtained from the receiving optical system 6, and a plurality of filters 17a and 17b and each frequency component extracted by the plurality of filters 17a and 17b. And a light absorption amount detector 18 for detecting the light absorption amount by the measurement target gas from the difference in amplitude or intensity.
The gas concentration detector 19 obtains the concentration of the measurement target gas based on the distance L to the target 30 and the light absorption amount detected by the light absorption amount detector 18.

Accordingly, it is possible to further realize a function of detecting the distance L between the apparatus and the target based on the configuration of a known differential absorption lidar apparatus.
Further, in the known differential absorption lidar apparatus, when obtaining the concentration of the measurement target gas between the apparatus and the target from the light absorption amount, another apparatus for knowing the distance L between the apparatus and the target is required. According to the second embodiment of the present invention, the distance detector 9 is added to eliminate the need for another device, and the distance L between the device and the target is detected by a single laser radar device, and the measurement target gas It becomes possible to obtain | require the density | concentration of.

Embodiment 3 FIG.
In the first and second embodiments (FIGS. 1 and 4), the CW modulation signal from the oscillators 3 and 3b is branched and introduced into the phase detector 8 by tapping using the distributor 4. As shown in FIG. 5, a part of the laser light signal actually transmitted and emitted may be tapped and introduced into the phase detector 8.

Hereinafter, a laser radar apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. Here, the case where it applies to the structure of above-mentioned Embodiment 2 (FIG. 4) is shown typically.
FIG. 5 is a block diagram showing a laser radar apparatus according to Embodiment 3 of the present invention. The same components as those described above (see FIG. 4) are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.

In FIG. 5, an optical distributor 20 is inserted on the output side of the optical amplifier 16, and a monitor light receiver 21 and a filter 17 c are inserted between the optical distributor 20 and the phase detector 8. Yes.
The optical distributor 20 taps a part of the laser light signal for transmission, and inputs the branched laser light signal to the monitor light receiver 21.

The monitor light receiver 21 converts the laser light signal tapped via the optical distributor 20 into an electric signal and inputs it to the filter 17c.
The filter 17c is composed of a bandpass filter whose pass frequency is set to the modulation frequency fm2, extracts a component of the modulation frequency fm2, and inputs it to the phase detector 8.
Thereby, the phase detector 8 can obtain the phase difference Δφ between the component of the modulation frequency fm2 at the time of transmission and the component of the modulation frequency fm2 in the received signal.

  As described above, according to the third embodiment of the present invention, the laser light signal (CW modulation signal) from the light intensity modulator 9 or a part of the laser light signal combined by the optical multiplexer 15 is monitored. The phase detector 8 includes a monitor optical receiver 21 that extracts as a signal, and the phase detector 8 has a component having the same modulation frequency as the monitor signal extracted from the monitor optical receiver 21 and the monitor signal extracted from the received signal. The phase difference Δφ is detected, and the same effects as described above can be obtained without using the distributor 4.

  Note that, as described in the above-described second embodiment, all processing after conversion to an electrical signal by the optical receiver 7 may be executed in the digital domain. That is, the same operation as in the second embodiment is performed by directly AD-converting the electrical signal from the optical receiver 7 and a part of the CW modulation signal input to the phase detector 8 that has been tapped. Can also be performed in the digital domain.

It is a block diagram which shows the laser radar apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the phase difference which arises between the CW modulation signal and received signal in Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the phase difference in Embodiment 1 of this invention, and the distance to a target. It is a block diagram which shows the laser radar apparatus which concerns on Embodiment 2 of this invention. It is a block diagram which shows the laser radar apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

  1, 1a, 1b light source, 2, 2a, 2b light intensity modulator, 3, 3a, 3b oscillator, 4, 4a, 4b distributor, 5 transmission optical system, 6 reception optical system, 7 optical receiver, 8 phase detection , 9 Distance detector, 10 GPS, 11 INS, 12 Map information storage unit, 13, 13A, 13B Laser radar device, 14 Aircraft, 15 Optical multiplexer, 16 Optical amplifier, 17a-17c filter, 18 Optical absorption detection , 19 concentration detector, 20 light distributor, 21 monitor light receiver, 30 target, 30a laser light signal, 30b scattered light signal, Δφ phase difference.

Claims (5)

GPS that generates location information on the earth,
INS for generating attitude information for inertial navigation;
A map information storage unit storing map information;
An optical signal generating means for generating a laser optical signal;
A light intensity modulating means for modulating the intensity of the laser light signal from the light signal generating means by a CW modulation signal;
An optical system means for transmitting a laser light signal intensity-modulated by the light intensity modulation means toward a target, and receiving a scattered light signal from the target;
Light receiving means for detecting the intensity of the scattered light signal from the target and converting it into a received signal comprising an electrical signal;
Phase detection means for detecting a phase difference between the CW modulation signal and the reception signal;
Based on the phase difference detected by the phase detection means and one or more foresight information of the position information, posture information, and map information obtained from the GPS, the INS, and the map information storage unit, A laser radar device comprising: distance detection means for detecting a distance to the target.   The distance detecting means transmits and receives a laser light signal intensity-modulated with the CW modulation signal, measures a distance to the target, and predicts an approximate distance using the look-ahead information, whereby the CW modulation is performed. The laser radar apparatus according to claim 1, wherein the distance is detected by removing uncertainty for each period of the signal. Frequency setting means for variably setting the modulation frequency of the CW modulation signal;
The frequency setting means variably sets the modulation frequency of the CW modulation signal so that one period of the CW modulation signal is equal to or greater than the predicted range of the approximate distance according to the accuracy of the look-ahead information. The laser radar device according to claim 2. Based on the distance to the target detected by the distance detection means, the gas concentration detection means for detecting the concentration of the measurement target gas existing between the target,
The optical signal generating means includes a plurality of optical signal generating means for generating a plurality of laser optical signals having different wavelengths,
The light intensity modulation means includes a plurality of light intensity modulation means for performing intensity modulation with CW modulation signals having different modulation frequencies for each wavelength component of the plurality of laser light signals,
The optical system means includes
A transmission optical system that multiplexes and transmits the laser light signals from the plurality of light intensity modulation means to the target;
Receiving optical system for receiving the scattered light signal from the target,
The optical receiving means includes
A plurality of filter means for extracting a plurality of frequency components used for the intensity modulation from a reception signal obtained from the reception optical system;
A light absorption amount detection means for detecting a light absorption amount by the measurement target gas from a difference in amplitude or intensity of each frequency component extracted by the plurality of filter means,
The said gas concentration detection means calculates | requires the density | concentration of the said measurement object gas based on the distance to the said target, and the light absorption amount detected by the said light absorption amount detection means. 4. The laser radar device according to any one of up to 3. A monitor light receiving means for extracting, as a monitor signal, a part of the laser light signal from the light intensity modulating means or the laser light signal combined by the transmission optical system;
The phase detection unit detects a phase difference between a monitor signal extracted by the monitor light receiving unit and a component having the same frequency as the monitor signal among components extracted from the reception signal. The laser radar device according to any one of claims 1 to 4.

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