JP6827603B1 - Laser radar device - Google Patents

Abstract

The laser radar device (1) measures the HT (100) existing in the measurement target space and the ST (101) existing up to the HT (100) in the measurement target space, and measures the irradiation direction of the laser beam. Based on the data showing the correspondence between the distance and the SNR of the received signal of the laser light and the detection limit value of the SNR, the laser light reflected by the HT (100) is discriminated from the received laser light, and the discriminated laser is discriminated. Control so that the intensity of the received light signal is not saturated.

Description

The present invention relates to a laser radar device.

A laser radar device that measures wind speed using laser light irradiates the atmosphere with pulsed laser light and receives the scattered light of the laser light scattered in the aerosol existing in the atmosphere to move the aerosol. The Doppler shift of the scattered light is obtained, and the wind velocity in the laser irradiation direction is measured based on the Doppler shift of the scattered light.

Further, some laser radar devices measure a hard target (HT) in addition to a soft target (ST) such as an aerosol. HT is a target that is significantly larger, optically thicker, and has extremely low transmittance than aerosols. HTs include moving objects such as vehicles, aircraft or ships.

In a laser radar device that measures HT, when the intensity of the laser beam is increased with reference to the detection of the HT existing at a long distance, the intensity of the laser beam becomes excessive when detecting the HT existing at a short distance. When the laser radar device receives the reflected light of the laser light reflected by the HT existing at a short distance, the intensity of the received signal of the reflected light is saturated and an error occurs in the measured value.

For example, Patent Document 1 describes a laser radar device that increases the transmittance of a laser beam irradiating a long distance and lowers the transmittance of a laser beam irradiating a short distance. In the laser radar device, the object (HT) existing at a short distance is detected even when the intensity of the laser light is increased, based on the detection of the object (HT) existing at a long distance. The intensity of the laser beam is attenuated.

Japanese Unexamined Patent Publication No. 2013-19790

In a conventional laser radar device, the intensity of scattered light in the aerosol of laser light irradiated in the space up to HT is extremely small, and the intensity of the received signal of the scattered light is also extremely small. On the other hand, since the HT is an optically thick target with extremely low transmittance, the intensity of the scattered light in the HT is much higher than that in the aerosol even if the HT exists at a long distance.

In the laser radar device described in Patent Document 1, the transmittance of the laser light irradiated at a long distance is set high, and the transmittance of the laser light irradiated at a short distance is set low. Therefore, when both the HT measurement and the ST measurement are performed, there is a problem that the measurement accuracy of the HT is lowered due to the saturation of the intensity of the received signal of the scattered light in the HT existing in the distance.

The present invention solves the above problems, and an object of the present invention is to obtain a laser radar device capable of performing both HT measurement and ST measurement while suppressing a decrease in HT measurement accuracy.

The laser radar device according to the present invention includes an optical system unit that irradiates a frequency-shifted laser light to a measurement target space and receives the scattered or reflected laser light in the measurement target space, and a scattered or reflected laser light. , The signal that is combined with the local light that is not frequency-shifted and the optical signal that is combined by the combined part are input, and the input optical signal is used to generate the laser light received by the optical system. The signal processing unit includes a strength control unit that controls the strength of the received signal and a signal processing unit that measures the HT existing in the measurement target space and the ST existing between the HT in the measurement target space. In HT from the laser light received by the optical system unit based on the data showing the correspondence between the distance in the irradiation direction of the laser light and the signal-to-noise ratio (SNR) of the received signal of the laser light and the detection limit value of the SNR. By discriminating the reflected laser light and controlling the intensity control unit so that the intensity of the received signal of the laser light determined by the signal processing unit is not saturated , the signal processing unit can reach the HT in the measurement target space. The position of the ST existing between them is measured, the position of the HT is measured, the moving speed of the aerosol is measured, and the moving speed of the HT is measured .

According to the present invention, the measurement of the HT existing in the measurement target space and the measurement of the ST existing up to the HT in the measurement target space are performed. Based on the data showing the correspondence between the distance in the irradiation direction of the laser beam and the SNR of the received signal of the laser beam and the detection limit value of the SNR, the laser beam reflected in the HT is discriminated from the received laser beam. The intensity of the discriminated laser light received signal is controlled so as not to be saturated. As a result, the laser radar device according to the present invention can perform both HT measurement and ST measurement while suppressing a decrease in HT measurement accuracy.

It is explanatory drawing which shows the outline of the generation of the scattered light of the laser light irradiated from the laser radar apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the outline of the saturation of the intensity of the received signal of the reflected light in HT, and the measurement error of HT. It is explanatory drawing which shows the outline of the measurement of HT and the measurement of ST by the laser radar apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the A-scope of the received SNR in the laser radar apparatus which concerns on Embodiment 1. FIG. It is a block diagram which shows the structure of the laser radar apparatus which concerns on Embodiment 1. FIG. It is a block diagram which shows the structure of the distance characteristic calculation part of FIG. It is a waveform diagram which shows the waveform of the received signal in Embodiment 1. FIG. It is a flowchart which shows the operation of the laser radar apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the outline of the identification process of the HT position using the A-scope of the received SNR. FIG. 10A is a waveform diagram showing the waveform of the received signal amplified by the amplifier, FIG. 10B is a waveform diagram showing the waveform of the received signal not amplified by the amplifier, and FIG. 10C is a saturation suppression process. It is a waveform diagram which shows the waveform of the received signal. It is a block diagram which shows the structure of the laser radar apparatus which concerns on Embodiment 2.

Embodiment 1.
FIG. 1 is an explanatory diagram showing an outline of generation of scattered light of the laser beam A emitted from the laser radar device 1 according to the first embodiment. In the wind measurement by the laser radar device 1, the pulsed laser beam A is irradiated into the atmosphere, and the scattered light s1 in the aerosol is received. Heterodyne detection of single-frequency continuous light, which is the local light of laser light A, and scattered light s1, calculates the Doppler shift caused by the movement of the aerosol, and measures the wind speed along the irradiation direction (line-of-sight direction) of the laser light. Will be done.

The laser light A is frequency-modulated with respect to the local light. Therefore, the interference between the scattered light s1 and the local light in the heterodyne detection generates a signal having a beat frequency which is an intermediate frequency. The beat frequency signal is a beat signal. As the aerosol moves, a Doppler shift is added to this beat frequency. The Doppler shift is calculated from the spectrum obtained by Fourier transforming the heterodyne-detected signal. The direction in which the wind speed is measured is changed by switching the emission direction of the laser beam.

In wind measurement, the aerosol, which is a soft target (ST), is treated as a three-dimensional volume target, whereas in the measurement of the hard target (HT) 100, the HT 100 is treated as a two-dimensional target. The moving speed of the HT 100 is calculated based on the Doppler shift caused by the movement of the HT 100. The laser radar device 1 simultaneously performs wind measurement and measurement of the HT100 by detecting an aerosol that is ST existing between the laser radar device 1 and the HT100. The HT100 may be, for example, the surface of the sea.

The measurement of the HT100 means measuring the moving speed of the HT100 while measuring the distance from the laser radar device 1 to the HT100. Further, in the wind measurement by the coherent method, as shown in FIG. 1, the received signal of the scattered light s1 in which the laser beam A is scattered in the aerosol in the atmosphere is used for the measurement. The intensity of the scattered light s1 is generally extremely small, and the intensity of the received signal of the scattered light s1 is also extremely small. Further, the amplitude of the beat signal generated by interfering the scattered light s1 with the local light is also small.

The beat signal corresponding to the received signal of the scattered light s1 can improve the SNR by increasing the amplitude while suppressing noise before the AD conversion is performed. Since the HT 100 is a solid, liquid, or optically thick volume target having extremely low transmittance, the intensity of the reflected light s2 reflected by the laser beam A in the HT 100 is high, and the intensity of the received signal of the reflected light s2 is also very high. As a result, when the aerosol measurement and the HT100 measurement are performed at the same time, the received signal of the reflected light s2 is saturated.

FIG. 2 is a diagram showing an outline of saturation of the intensity of the received signal of reflected light in HT and measurement error of HT. The upper view of FIG. 2 shows the waveform of the received signal in which the laser light emitted from the laser radar device 1 is scattered in the aerosol which is ST and reflected in the HT, and the scattered light and the reflected light are received by the laser radar device 1. It is a waveform diagram which shows. In this waveform diagram, SV1 is the lower limit of the received signal voltage, and SV2 is the upper limit of the received signal voltage. That is, when the voltage of the received signal exceeds the upper limit value SV2, the strength of the received signal is saturated. The lower view of FIG. 2 is a waveform diagram showing an integrated spectrum Sa or Sb. The integrated spectrum is a combination of a plurality of spectra obtained by performing a fast Fourier transform (FFT) on a received signal (beat signal) for each range bin for a certain period of time.

When the voltage of the beat signal exceeds the upper limit value SV2 and the beat signal is saturated, a false signal is superimposed in the frequency band of the spectrum Sa in which the beat signal is FFTed. As shown in the lower diagram of FIG. 2, a frequency shift occurs between the spectrum Sb and the spectrum Sa in which the FFT is executed on the beat signal without saturation. The moving speed of the target is calculated based on the Doppler shift amount, and the Doppler shift amount is the shift of the peak frequency (center frequency) of the spectrum in which the FFT is executed on the beat signal. Therefore, when the strength of the received signal is saturated, an error occurs in the amount of Doppler shift, and an error also occurs in the moving speed of the target.

FIG. 3 is an explanatory diagram showing an outline of measurement of HT100 and measurement of ST101 by the laser radar device 1. The laser radar device 1 discriminates the laser light reflected by the HT 100 from the received laser light by detecting the decrease in coherency caused by the laser light reflected by the HT 100. Assuming that the HT100 is an ideal specular reflection surface, among the laser beams A emitted from the laser radar device 1, the laser light A1 that is specularly reflected by the HT100 propagates in the atmosphere and then the laser radar device. Received by 1.

As shown in FIG. 3, the laser light A2 that is specularly reflected by the HT 100 becomes scattered light Sc by being scattered in the aerosol that is ST101. The reflected light Sd, which is specularly reflected by the scattered light Sc in the HT100, propagates in the atmosphere and then is received by the laser radar device 1. However, the reflective surface of the HT100 is not an ideal specular reflective surface, and the unevenness of the reflective surface is often sufficiently large with respect to the wavelength of the laser beam A.

FIG. 4 is a diagram showing an A-scope of the received SNR in the laser radar device 1. In FIG. 4, the A-scope of the received SNR is data showing the correspondence relationship between the distance in the irradiation direction of the laser beam A from the laser radar device 1 and the SNR of the received signal of the laser beam A by the laser radar device 1. Further, the A-scope D1 is A-scope data relating to the HT located at a distance close to the laser radar device 1, and the A-scope D2 is A-scope data relating to the HT located at a distance far from the laser radar device 1.

When the unevenness of the reflecting surface of the HT 100 is sufficiently large with respect to the wavelength of the laser beam A, the laser beam A reflected on the reflecting surface of the HT 100 is disturbed on its wave surface and the coherency is lowered. When the coherency of the reflected light reflected on the reflecting surface of the HT 100 decreases, the coherency of the scattered light Sc scattered in ST101 also decreases. As shown in FIG. 3, the scattered light Sc is scattered light in ST101 existing at a distance farther from the laser radar device 1 than the HT100.

In the A-scope D1 and the A-scope D2, as indicated by the reference numeral E, the reception SNR of the scattered light Sc in the ST101 existing at a distance farther from the laser radar device 1 than the HT100 as the coherence of the scattered light Sc decreases. The signal-to-noise ratio) drops to the detection limit SNR1. The laser radar device 1 determines the laser light reflected by the HT 100 from the received laser light by utilizing the characteristic that the received SNR of the scattered light Sc is lowered to the detection limit value SNR1.

FIG. 5 is a block diagram showing the configuration of the laser radar device 1 according to the first embodiment. In FIG. 5, the laser radar device 1 includes a light source 2, an optical distributor 3, a pulse modulator 4, an optical system unit 5, a telescope 6, an optical coupler 7, a light receiving unit 8, an intensity control unit 10, and an AD conversion unit 11. It includes a signal processing unit 12 and a trigger generation circuit 13. The optical system unit 5 includes a transmission side optical system 5a, a transmission / reception separation unit 5b, and a reception side optical system 5c. The strength control unit 10 includes a switch unit 9a and an amplifier 9b. The signal processing unit 12 includes a distance characteristic calculation unit 12a, a signal processing switching unit 12b, a moving speed calculation unit 12c, an HT position specifying unit 12d, and a gate position setting unit 12e.

The light source 2 is a light source that outputs continuous light having a single frequency, and is connected to the light distributor 3. The light distributor 3 divides the light output from the light source 2 into two, outputs one of the divided lights to the pulse modulator 4, and outputs the other light to the optical coupler 7. For the optical distributor 3, for example, a 1: 2 fiber coupler is used. Further, some optical distributors 3 are configured by using a half mirror.

The pulse modulator 4 pulse-modulates the light input from the light source 2 via the optical distributor 3 and frequency-shifts the pulse-modulated optical signal to generate transmitted light. The transmitted light is a pulse-shaped laser light emitted from the laser radar device 1 to the measurement target space. The transmitted light is output to the optical system unit 5. As the pulse modulator 4, for example, an acousto-optic modulator (AOM) is used.

The transmitting side optical system 5a shapes the beam diameter and beam spreading angle of the transmitted light input from the pulse modulator 4, and outputs the transmitted light having the shaped beam diameter and beam spreading angle to the transmission / reception separation unit 5b. The transmitting side optical system 5a is configured by using, for example, a lens group including a concave lens and a convex lens. Further, the transmitting side optical system 5a may be a reflection type optical system using a mirror.

The transmission / reception separation unit 5b is provided between the transmission side optical system 5a and the telescope 6 and on the optical axis of the transmission light, outputs the transmission light to the telescope 6, and outputs the reception light from the telescope 6. Output to the receiving optical system 5c. A circulator or a polarizing beam splitter (PBS) can be used for the transmission / reception separation unit 5b.

The receiving side optical system 5c shapes the beam diameter and the beam spreading angle of the received light, and outputs the received light having the shaped beam diameter and the beam spreading angle to the optical coupler 7. The received light is scattered light or reflected light in which the transmitted light is scattered or reflected in the measurement target space. The receiving side optical system 5c is configured by using, for example, a lens group including a concave lens and a convex lens. Further, the receiving side optical system 5c may be a reflection type optical system using a mirror.

The telescope 6 irradiates the measurement target space with the transmitted light input from the transmission / reception separation unit 5b, and receives the received light from the measurement target space. The telescope 6 is configured by using, for example, a lens group including a concave lens and a convex lens. Further, the telescope 6 may be a reflection type optical system using a mirror.

The optical coupler 7 combines the light input from the optical distributor 3 and the received light input from the receiving side optical system 5c, and outputs the combined light to the light receiving unit 8. The optical signal combined by the optical coupler 7 is a beat signal. A fiber type combiner can be used for the optical coupler 7. The optical signal combined by the optical coupler 7 is a beat signal corresponding to the frequency shift _fIF (center frequency). In the received light, if the Doppler shift frequency corresponding to the movement of the wind speed and HT have occurred, the frequency of the beat signal has a value obtained by adding the Doppler shift frequency Δf to the center frequency f _IF.

The light receiving unit 8 is, for example, a balanced receiver, converts a beat signal input from the optical coupler 7 into an electric signal, and outputs the beat signal (received signal) of the electric signal to the switch unit 9a. The intensity control unit 10 controls the intensity of the received signal of the received light received by the optical system unit 5. The switch unit 9a switches between a path for outputting the received signal input from the light receiving unit 8 to the amplifier 9b and a path for outputting to the AD conversion unit 11 based on the gate position information set by the gate position setting unit 12e. .. The amplifier 9b is an amplification unit that amplifies the strength of the received signal input via the switch unit 9a. The received signal amplified by the amplifier 9b is output to the AD conversion unit 11.

The AD conversion unit 11 inputs a reception signal via the intensity control unit 10, and converts the input reception signal into a digital signal. The received signal AD-converted by the AD conversion unit 11 is output to the signal processing unit 12. The AD conversion unit 11 shown in FIG. 5 is a 2-channel AD converter that inputs a signal that has passed through the amplifier 9b and a signal that does not pass through the amplifier 9b. However, a one-channel AD converter can be used for the AD conversion unit 11 by bundling the signal that has passed through the amplifier 9b and the signal that has not passed through the amplifier 9b by an analog multiplexer.

The signal processing unit 12 is configured by using, for example, an FPGA (Field Programmable Gate Array). In the signal processing unit 12, the distance characteristic calculation unit 12a, the signal processing switching unit 12b, the movement speed calculation unit 12c, the HT position specifying unit 12d, and the gate position setting unit 12e transmit digital signals and TTL (Transistor-Transistor-Logic) signals. It is used to instruct or exchange data.

The distance characteristic calculation unit 12a calculates the spectrum data and the A-scope data of the received signal of the laser beam. For example, the distance characteristic calculation unit 12a divides the received signal AD-converted by the AD conversion unit 11 into each range bin corresponding to the pulse width of the transmitted light, and executes FFT processing on the signal of each range bin. , Generate spectral data for each range bin. The distance characteristic calculation unit 12a integrates the spectral data for each range bin in the spectral space and calculates the peak value from the spectral data of each range bin, so that the distance and peak along the irradiation direction of the transmitted light from the laser radar device 1 A-scope data showing the correspondence with the value is calculated. The distance characteristic calculation unit 12a outputs the spectrum data and the A-scope data of each range bin to the signal processing switching unit 12b.

The signal processing switching unit 12b outputs the integrated spectrum data and the A-scope data to either the movement speed calculation unit 12c or the HT position identification unit 12d, so that the movement speed calculation unit 12c calculates the movement speed. And the HT position specifying process by the HT position specifying unit 12d are switched.

The moving speed calculation unit 12c calculates the Doppler shift amount based on the peak frequency of the spectrum data of each range bin, and calculates the moving speed of the target for each range bin based on the Doppler shift amount. The HT position specifying unit 12d identifies the HT position based on the A-scope data, and based on the specified HT position, from the transmission light being transmitted from the telescope 6 to the reflection of the transmitted light in the HT. Calculate the time _THT . Gate position setting unit 12e, based on the time T _HT calculated by HT position specifying unit 12d, generates a gate indicating the time and to output the received signal to the time and the AD conversion unit 11 to output to the amplifier 9b, produces The gate is set in the switch unit 9a.

The trigger generation circuit 13 generates a trigger signal that pulses the light output from the optical distributor 3 to the pulse modulator 4, and sets the generated trigger signal in the gate position setting unit 12e to pulse the transmitted light. Control the time to change. The trigger generation circuit 13 generates a trigger signal based on a preset pulse width and pulse period. For the trigger generation circuit 13, for example, a pulse generator or a function generator is used. Further, the trigger generation circuit 13 is configured by using, for example, FPGA.

Further, the AD conversion of the received signal by the AD conversion unit 11 is performed using the trigger signal from the trigger generation circuit 13 as a start trigger. The start time of the AD conversion coincides with the timing at which the pulse of the transmitted light is transmitted, and the AD conversion is executed in a period corresponding to the pulse of the transmitted light and the interval between the pulses. The signal that has been AD-converted after the time Δt (= 2L / c) has elapsed since the AD conversion by the AD conversion unit 11 was started is a target (for example, ST101) that exists at a position separated by a distance L from the laser radar device 1. Alternatively, it is a received signal corresponding to the transmitted light scattered or reflected in HT100). c is the speed of light. The AD conversion unit 11 outputs a reception signal (digital signal) corresponding to the transmitted light for each pulse to the distance characteristic calculation unit 12a.

FIG. 6 is a block diagram showing the configuration of the distance characteristic calculation unit 12a. As shown in FIG. 6, the distance characteristic calculation unit 12a includes a range bin division processing unit 12a-1, an FFT processing unit 12a-2, an integration processing unit 12a-3, an SNR calculation unit 12a-4, and an A-scope calculation unit 12a. It has -5.

The range bin division processing unit 12a-1 divides the received signal corresponding to the transmitted light for each pulse input from the AD conversion unit 11 at regular time width intervals. Here, the division means that the received signal is associated with a section for each fixed time width. Further, in the process of dividing the received signal corresponding to one pulse of the transmitted light into fixed time widths, the transmitted light scattered or reflected by the targets existing at different distances (ranges) from the laser radar device 1 is used. Corresponds to the process of separation. The width of the range bin corresponds to the pulse width of the transmitted light, and the pulse width is a value preset in the laser radar device 1.

The FFT processing unit 12a-2 performs FFT processing on the received signal divided for each range bin by the range bin division processing unit 12a-1, and generates spectrum data for each range bin. The optical system unit 5 transmits the transmitted light a plurality of times for each pulse, and receives the received light corresponding to each of the plurality of pulses. The FFT processing unit 12a-2 performs FFT processing on the received signals corresponding to each of the plurality of received lights and divided for each range bin.

The integration processing unit 12a-3 integrates the spectrum data calculated for each range bin by the FFT processing unit 12a-2. The SNR calculation unit 12a-4 calculates the received SNR, which is the ratio of the received signal to the noise outside the used frequency band, using the peak intensity of the integrated spectrum of each range bin. The peak intensity is the spectral intensity corresponding to the position of the peak frequency in the spectrum. Further, the peak intensity may be the spectral intensity corresponding to the center of gravity frequency position obtained by performing the center of gravity calculation on the spectral data.

The SNR calculation unit 12a-4 transfers the range bin information including the value of the label that identifies each range bin, the spectrum data integrated by the integration processing unit 12a-3, and the received SNR to the A-scope calculation unit 12a-5. Output. The A-scope calculation unit 12a-5 calculates the A-scope data using the received SNR calculated by the SNR calculation unit 12a-4. The A-scope data is data showing the distance characteristic of the received SNR.

FIG. 7 is a waveform diagram showing the waveform of the received signal according to the first embodiment, and shows the time change of the received signal corresponding to the transmitted light for one pulse. n represents the label of the range bin in which the received signal is divided. The received signal having a small value of the label n corresponds to the light in which the transmitted light is scattered or reflected by the target existing in the vicinity of the laser radar device 1.

The received signal in the section (label n = 1 to 4) indicated by reference numeral B corresponds to the light in which the transmitted light is scattered in the aerosol existing between the laser radar device 1 and the HT. Further, the received signal in the section (label n = 5) indicated by the reference numeral C corresponds to the light reflected by the transmitted light in the HT. Although the HT exists at a position far from the laser radar device 1, the intensity of the received signal corresponding to the light reflected by the transmitted light in the HT is saturated beyond the upper limit value SV2 as shown in FIG. 7.

The A-scope calculation unit 12a-5 uses the range bin information (information including the label n), the range bin width Δt, and the light velocity c to determine the distance L (= c × Δt /) from the laser radar device 1 to the position where the target exists. 2) is calculated for each range bin, and A-scope data showing the correspondence between the calculated distance L and the received SNR is calculated. As a result, A-scope data as shown in FIG. 4 can be obtained.

FIG. 8 is a flowchart showing the operation of the laser radar device 1 according to the first embodiment. When the measurement of the target by the laser radar device 1 is started, the value 0 is set in the parameter i (step ST1). The pulse width is set for the trigger generation circuit 13 (step ST2). As a result, the processing up to the calculation of the A-scope data described above is executed. Next, the signal processing switching unit 12b confirms whether the value of the parameter i is 0 or 1 (step ST3).

When the value of the parameter i is 0 (step ST3; i = 0), it is a stage before the measurement of the target by the laser radar device 1 is started and the HT position is specified. The signal processing switching unit 12b outputs the A-scope data calculated by the distance characteristic calculation unit 12a to the HT position specifying unit 12d.

The HT position specifying unit 12d specifies the HT position based on the A-scope data and the detection limit value of the received SNR (step ST4). FIG. 9 is a diagram showing an outline of HT position identification processing using the A-scope of the received SNR. In FIG. 9, the A-scope D1 is A-scope data relating to the HT at a distance close to the laser radar device 1, and the A-scope D2 is the HT at a distance far from the laser radar device 1. A-scope data for.

Since the surface of the HT to be measured has undulations (unevenness) equal to or larger than the wavelength of the transmitted light, the reflected light is reflected in the HT, so that the coherency of the reflected light is reduced. Further, when the light reflected by the transmitted light in the HT is scattered in an aerosol existing at a distance farther from the laser radar device 1 than the HT, the received SNR of the scattered light is lowered to the detection limit value SNR1.

HT position specifying unit 12d, A- values of SNR in scope data, by up to monitor from the range _{R MAX} to become closer direction to the laser radar apparatus 1 of the measurement, the received SNR is greater than the detection limit SNR1 specifying the distance (range _{bins) L HT.} The _HT position is a position separated from the laser radar device 1 by a distance L _HT along the irradiation direction of the transmitted light. The HT position specifying unit 12d calculates the time T _HT (= 2 L _HT / c) at which the transmitted light is reflected in the HT using the distance L _HT and the speed of light c (step ST5).

For example, in the A-scope D1, the distance _LHT1 is specified and the time _THT1 (= 2L _HT1 / c) is calculated. In the A-scope D2, the distance _LHT2 is specified and the time _THT2 (= 2L _HT2 / c) is calculated. As a result, the laser light reflected by the HT is discriminated from the laser light received by the optical system unit 5. The distance L _HT and the time T _HT obtained by the HT position specifying unit 12d are output to the moving speed calculation unit 12c. The HT position specifying unit 12d sets the value 1 in the parameter i.

When the process of step ST5 is completed, the series of processes shown in FIG. 8 returns to the process of step ST3. Since the value of the parameter i is 1 (step ST3; i = 1), the signal processing switching unit 12b outputs the range bin information, the integrated spectrum data, and the A-scope data to the moving speed calculation unit 12c. The movement speed calculation unit 12c calculates the wind speed and the movement speed of the HT, which are the movement speeds of the aerosol, based on the information input from the signal processing switching unit 12b and the distance L _HT and the time T _HT input from the HT position specifying unit 12d. Calculate (step ST6).

The trigger generation circuit 13 sets the time T ₀ and the pulse width Δt for pulse the transmitted light in the gate position setting unit 12e as a trigger signal. The gate position setting unit 12e outputs the time T ₀ , the time _THT, and the pulse width Δt to the switch unit 9a. A gate having a time width corresponding to the pulse width Δt is set in the switch unit 9a. Switch unit 9a, and the received signal from time T ₀ to time T _{time HT} has elapsed, the reception signal after the time obtained by adding a pulse width Δt worth of time to the time T _HT, to the amplifier 9b for each pulse width Δt Output.

FIG. 10A is a waveform diagram showing the waveform of the received signal amplified by the amplifier 9b, and shows the waveform of the digital signal obtained by AD-converting the received signal amplified by the amplifier 9b. The strength of the received signal corresponding from the time T ₀ to the time when the time _THT has elapsed is amplified by the amplifier 9b. As a result, the intensity of the received signal (label n = 1 to 4) corresponding to the scattered light in the ST (aerosol) existing in the space from the laser radar device 1 to the HT is amplified without being saturated.

The reception signal is amplified without strength similarly saturation of the received signal after the time obtained by adding a pulse width Δt worth of time to the time T _HT, as indicated at C, which corresponds to the reflected light in the HT The intensity of (label n = 5) saturates. The reception signal after the time obtained by adding a pulse width Δt worth of time to the time T _HT, since not used in the wind measuring in space from the laser radar apparatus 1 to HT, may not be passed through the amplifier 9b.

The switch unit 9a outputs the received signal corresponding to the time T _HT until the time the pulse width Δt worth of time has elapsed, without passing through the amplifier 9b to the AD converter 11. FIG. 10B is a waveform diagram showing a waveform of a received signal that has not been amplified by the amplifier 9b. The received signal corresponding from the time when the time _THT has elapsed to the time after the time of the pulse width Δt has elapsed is AD-converted. As a result, as shown in FIG. 10B, the unsaturated received signal (label n = 5) corresponding to the reflected light in the HT is converted into a digital signal.

Moving speed computing unit 12c extracts the peak frequency f _m from the spectral data after integration of each range bin, based on the difference between the frequency f _IF of the extracted frequency f _m and the beat signal, the Doppler shift amount Δf for each range bin (N) is calculated. The moving speed calculation unit 12c calculates the moving speed v (n) (= λ × Δf (n) / 2) of the target for each range bin by using the wavelength λ of the transmitted light and the Doppler shift amount Δf (n). .. As a result, the moving speed (wind speed) of the aerosol existing in the space from the laser radar device 1 to the HT is calculated based on the received signal corresponding to the label n = 1 to 4, and the received signal corresponding to the label n = 5 is calculated. The moving speed of the HT is calculated based on.

The received signal converted into a digital signal by the AD conversion unit 11 includes a signal that has passed through the amplifier 9b and a signal that has not passed through the amplifier 9b. Therefore, the moving speed calculation unit 12c calculates the moving speed of ST based on the received signal that has passed through the amplifier 9b at the distance L corresponding to one range bin, and HT is based on the received signal that does not pass through the amplifier 9b. Calculate the moving speed of. That is, the moving speed corresponding to each of the two received signals is calculated.

In the calculation process of the moving speed (wind speed) of the aerosol existing in the space from the laser radar device 1 to the HT, the reception signal in the time domain that does not pass through the amplifier 9b is unnecessary, and in the calculation processing of the moving speed of the HT. The received signal in the time domain through which the amplifier 9b is passed is unnecessary. Therefore, the distance characteristic calculation unit 12a determines the moving speed of the target based on a single system of received signals generated by trimming and combining the signals in the time domain used for ST measurement and HT measurement from the received signals. It may be calculated.

FIG. 10C is a waveform diagram showing a waveform of a received signal that has been subjected to saturation suppression processing. The received signal shown in FIG. 10C is a signal (label n = 5) in the time domain indicated by reference numeral F in the received signal that has passed through the amplifier 9b, and is a signal in the same time domain in the received signal that has not passed through the amplifier 9b. It is a replacement. For example, the distance characteristic calculation unit 12a trims the signal in the time domain corresponding to the label n = 5 in the received signal that did not pass through the amplifier 9b, and the trimmed signal is used in the received signal that did not pass through the amplifier 9b. Combine for signals in the same time domain. As a result, the signal shown in FIG. 10C is generated.

The signal in the time domain corresponding to the label n = 5 is a signal corresponding to the reflected light from the HT, and the intensity is saturated when passing through the amplifier 9b. On the other hand, in the signal shown in FIG. 10C, the signal in the time domain corresponding to the label n = 5 is replaced with the signal in the same time domain that is not saturated in the received signal that did not pass through the amplifier 9b. There is. As a result, the saturation of the signal strength in each time domain is suppressed. The moving speed calculation unit 12c can measure ST and HT by using the signal shown in FIG. 10C.

As described above, in the laser radar device 1 according to the first embodiment, the measurement of the HT existing in the measurement target space and the measurement of the ST existing up to the HT in the measurement target space are performed. Based on the A-scope data and the detection limit value of the received SNR, the laser light reflected by the HT is discriminated from the received laser light, and the intensity of the received signal of the discriminated laser light is controlled so as not to be saturated. Laser. As a result, the laser radar device 1 can perform both HT measurement and ST measurement while suppressing a decrease in HT measurement accuracy.

In the laser radar device 1 according to the first embodiment, the intensity control unit 10 includes a switch unit 9a and an amplifier 9b. The switch unit 9a does not amplify the intensity of the received signal of the laser light reflected by the HT 100 by the amplifier 9b, but amplifies the intensity of the received signal of the laser light scattered in the ST 101 by the amplifier 9b. As a result, the intensity of the received signal of the laser beam reflected by the HT 100 is changed to an intensity that does not saturate.

Embodiment 2.
FIG. 11 is a block diagram showing a configuration of the laser radar device 1A according to the second embodiment. The laser radar device 1A includes a light source 2, an optical distributor 3, a pulse modulator 4, an optical system unit 5, a telescope 6, an optical coupler 7, a light receiving unit 8, an intensity control unit 10A, an AD conversion unit 11, and a signal processing unit 12. And a trigger generation circuit 13. The intensity control unit 10A includes an optical variable attenuator 14 and a gain setting unit 15. In FIG. 11, the same components as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

The intensity control unit 10A attenuates the intensity of the laser light reflected by the HT 100 so that the intensity of the received signal of the laser light is not saturated. The optical variable attenuator 14 is an attenuation unit that attenuates the intensity of the optical signal according to the gain (attenuation amount) set by the gain setting unit 15.

The optical variable attenuator 14 may be a fiber type or a spatial type. For example, the spatial variable optical attenuator 14 has filters having different optical densities (OD) arranged on the optical axis. Further, some optical variable attenuators 14 use a wedge prism to shift the optical axis position or the optical axis angle of the optical coupler 7 and the light receiving unit 8.

The gain setting unit 15 is a setting unit that sets the gain (attenuation amount) according to the gate position set by the gate position setting unit 12e to the optical variable attenuator 14. The gate position is information indicating the time for attenuating the intensity of the optical signal and the time width thereof.

The light receiving unit 8 converts the received light whose intensity has not been attenuated by the light variable attenuator 14 into an electric signal, and the amplifier 9b amplifies the intensity of the received signal converted into an electric signal by the light receiving unit 8. The AD conversion unit 11 converts the received signal amplified by the amplifier 9b into a digital signal. Of the received signals AD-converted by the AD conversion unit 11, the signal in the time domain corresponding to the laser light reflected by the HT is amplified and saturated by the amplifier 9b.

The distance characteristic calculation unit 12a divides the received signal AD-converted by the AD conversion unit 11 into each range bin corresponding to the pulse width of the transmitted light, and performs FFT processing on the signal of each range bin to perform FFT processing for each range bin. Generate spectral data for. Then, the distance characteristic calculation unit 12a integrates the spectral data for each range bin in the spectral space and calculates the peak value from the spectral data of each range bin, so that the distance along the irradiation direction of the transmitted light from the laser radar device 1A A-scope data showing the correspondence between the peak value and the peak value is calculated.

HT position specifying unit 12d is calculated by the distance characteristic calculating unit 12a A- values of SNR in scope data, by monitoring the maximum range _{R MAX} measuring the near becomes direction to the laser radar apparatus 1, the received SNR There identifies the distance _{L HT} larger than the detection limit value SNR1. The _HT position is a position separated from the laser radar device 1A by a distance L _HT along the irradiation direction of the transmitted light. The HT position specifying unit 12d calculates the time T _HT (= 2 L _HT / c) at which the transmitted light is reflected in the HT using the distance L _HT and the speed of light c.

The trigger generation circuit 13 sets the time T ₀ and the pulse width Δt for pulse the transmitted light in the gate position setting unit 12e as a trigger signal. The gate position setting unit 12e sets the time T ₀ , the time _THT, and the pulse width Δt in the gain setting unit 15.

Gain setting unit 15, an optical signal corresponding to the received signal after the time obtained by adding a pulse width Δt worth of time to the optical signal and time T _HT corresponding to the received signal from time T ₀ to time T _{time HT} has passed The gain at which the amount of attenuation becomes 0 is set in the optical variable attenuator 14 so that the attenuation is not attenuated. The gain setting unit 15, as an optical signal corresponding to the received signal corresponding to the time T _HT until the time the pulse width Δt worth of time has elapsed is attenuated, light a greater gain than attenuation 0 Set to the variable attenuator 14. As a result, a received signal having a waveform as shown in FIGS. 10A and 10B can be obtained.

Moving speed computing unit 12c, based on the received signal from time T ₀ to time T _{time HT} has elapsed, it calculates the moving velocity of the aerosol which is present in the space from the laser radar apparatus 1 to HT (wind speed), the time based on the received signal corresponding to the T _HT to time the pulse width Δt worth of time has elapsed, it calculates the moving speed of the HT.

As described above, in the laser radar device 1A according to the second embodiment, the intensity control unit 10A has an optical variable attenuator 14 that attenuates the intensity of the laser beam and a gain setting unit 15 that sets the attenuation amount in the optical variable attenuator 14. And. The light variable attenuator 14 does not attenuate the intensity of the laser beam scattered in the ST, but attenuates the intensity of the laser beam reflected in the HT. Since the intensity of the received signal of the laser light reflected by the HT 100 is controlled so as not to be saturated, the laser radar device 1A can perform both HT measurement and ST measurement while suppressing a decrease in HT measurement accuracy. It can be carried out. Further, since the intensity of the received light in the previous stage of being input to the light receiving unit 8 is controlled, the AD conversion unit 11 shown in FIG. 11 may have one input channel. Therefore, the configuration of the laser radar device 1A is simplified.

The present invention is not limited to the above-described embodiment, and within the scope of the present invention, any combination of the embodiments or any component of the embodiment may be modified or the embodiment. Any component can be omitted in each of the above.

The laser radar device according to the present invention can be used, for example, in a laser radar device that measures various targets.

1,1A laser radar device, 2 light source, 3 optical distributor, 4 pulse modulator, 5 optical system, 5a transmitter optical system, 5b signal-to-noise ratio, 5c receiver optical system, 6 telescope, 7 optical coupler, 8 Light receiving unit, 9a switch unit, 9b amplifier, 10,10A intensity control unit, 11 AD conversion unit, 12 signal processing unit, 12a distance characteristic calculation unit, 12a-1 range bin division processing unit, 12a-2 FFT processing unit, 12a -3 Integration processing unit, 12a-4 SNR calculation unit, 12a-5 A-scope calculation unit, 12b signal processing switching unit, 12c movement speed calculation unit, 12d HT position identification unit, 12e gate position setting unit, 13 trigger generation circuit , 14 Optical variable attenuator, 15 Gain setting section.

Claims (4)

An optical system unit that irradiates the measurement target space with a frequency-shifted laser beam and receives the scattered or reflected laser light in the measurement target space.
A combiner that combines the laser light received by the optical system unit with the local light that has not been frequency-shifted.
An intensity control unit that inputs an optical signal combined by the combiner and controls the intensity of the received signal of the laser light received by the optical system unit using the input optical signal .
And a signal processing unit for measuring the soft target present until the hard target at the measurement and the measurement target space of the hard target present in the measurement target space,
The signal processing unit uses the optical system unit based on data indicating the correspondence between the distance in the irradiation direction of the laser light and the signal-to-noise ratio of the received signal of the laser light and the detection limit value of the signal-to-noise ratio. From the received laser light, the laser light reflected by the hard target is discriminated.
By controlling the intensity control unit so that the intensity of the received signal of the laser beam determined by the signal processing unit is not saturated , the signal processing unit exists between the hard target in the measurement target space. A laser radar device for measuring the position of the soft target, measuring the position of the hard target, measuring the moving speed of the aerosol, and measuring the moving speed of the hard target . The signal processing unit sets the signal-to-noise ratio of the received signal of the laser beam to the signal-to-noise ratio of the received signal of the laser beam scattered by the aerosol located at a distance farther from the laser radar device than the hard target. By monitoring in the direction closer to the laser radar device from the detection limit value, the signal-to-noise ratio of the received signal of the laser light is separated from the laser radar device in the irradiation direction of the laser light by a distance larger than the detection limit value. To specify the position as the position of the hard target
The laser radar apparatus according to claim 1. The intensity control unit includes an amplification unit that amplifies the intensity of the laser light reception signal, and a switch unit that switches the laser light reception signal to a path that passes through the amplification unit or a path that does not pass through the amplification unit.
The switch unit does not amplify the intensity of the received signal of the laser light reflected by the hard target by the amplification unit, but amplifies the intensity of the received signal of the laser light scattered by the soft target by the amplification unit. The laser radar apparatus according to claim 1. The intensity control unit includes an attenuation unit that attenuates the intensity of laser light and a setting unit that sets an attenuation amount in the attenuation unit.
The attenuation unit does not attenuate the intensity of the laser light scattered by the soft target, but attenuates the intensity of the laser light reflected by the hard target by the amount of attenuation set by the setting unit. The laser radar apparatus according to claim 1.

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