JP2017003490A - Laser radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the user to be informed of the occurrence of any system trouble without requiring mounting of a photodetector or the like.SOLUTION: A laser radar device is equipped with an SNR calculating unit 16 that calculates the SNR of the reception signal of diffuse light every time diffuse light is received by a laser beam transceiver unit 10; and a switchover determining unit 19 that determines whether or not the telescope has been correctly switched over by a telescope unit 3 by comparing SNRs, out of SNRs calculated by the SNR calculating unit 16, before and after the telescope switchover by the telescope unit 3. If an alarm presenting unit 20 presents a determination that the switchover determining unit 19 has not correctly switched over the telescope to be used, an alarm notifying the occurrence of a system trouble is presented.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser radar device that measures a wind speed from a Doppler shift amount of scattered light accompanying the movement of an aerosol.

The laser radar device disclosed in the following Patent Document 1 includes a plurality of laser openings that output laser light in different directivity directions, and a laser for any one of the plurality of laser openings. And an optical switch that outputs laser light oscillated by an oscillator.
Patent Document 2 below discloses a laser radar device that measures the wind speed from the Doppler shift amount of scattered light accompanying the movement of the aerosol. A plurality of laser radar devices disclosed in Patent Document 1 are disclosed for this laser radar device. If the laser aperture and the optical switch are applied, it is possible to obtain a vertical profile of the wind speed and to measure a wide range of wind speeds by measuring the wind speed while switching the line-of-sight direction of the laser light.

Japanese Patent Laying-Open No. 2005-9956 (FIG. 3) Japanese Patent Laying-Open No. 2003-307567 (FIG. 1)

Since the conventional laser radar apparatus is configured as described above, it can switch the line-of-sight direction of the laser light, but does not have means for confirming whether the line-of-sight direction of the laser light is actually switched. . For this reason, there has been a problem that even if a situation occurs in which the line-of-sight direction of the laser light is not switched due to the system abnormality of the laser radar apparatus, the user cannot be notified of the occurrence of the system abnormality.
In addition, if a photo detector that detects the line-of-sight direction of the laser light is mounted in the laser radar device, it can be confirmed whether the line-of-sight direction of the laser light is switched, but the amount of mounting the photo detector, etc. As the device size and weight increase, there arises a problem that the wiring for the photodetector and the like becomes complicated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser radar device that can notify a user of the occurrence of a system abnormality without mounting a photodetector or the like.

  A laser radar device according to the present invention includes a plurality of telescopes having different aperture diameters, a telescope switching unit that switches a telescope to be used for transmission / reception of laser light among the plurality of telescopes, and a laser beam that oscillates laser light. Using the telescope to be used switched by the oscillating unit and the telescope switching unit, the laser light oscillated by the laser light oscillating unit is radiated into the atmosphere, and then scattered by the aerosol and returned to the scattered light. A laser light transmission / reception unit that receives the signal, a signal-to-noise ratio calculation unit that calculates a signal-to-noise ratio of the received signal of the scattered light every time the scattered light is received by the laser light transmission / reception unit, and a signal-to-noise ratio calculation unit By comparing the signal-to-noise ratio before and after the target telescope is switched by the telescope switching unit in the signal-to-noise ratio calculated by A switching determination unit that determines whether or not the telescope has been switched normally, and if the alarm presenting unit determines that the telescope to be used has not been switched normally by the switching determination unit, an abnormality is detected. An alarm to the effect that it has occurred is presented.

  According to the present invention, every time scattered light is received by the laser light transmitting / receiving unit, the signal-to-noise ratio calculating unit that calculates the signal-to-noise ratio of the received signal of the scattered light is calculated by the signal-to-noise ratio calculating unit. Whether the telescope switching unit has switched the target telescope normally by comparing the signal-to-noise ratio before and after the target telescope is switched by the telescope switching unit. And a warning presenting unit presents a warning that an abnormality has occurred when the switching judging unit determines that the target telescope has not been switched normally. Since it comprised so, there exists an effect which can notify a user of generation | occurrence | production of abnormality, without mounting a photo detector etc.

It is a block diagram which shows the laser radar apparatus by Embodiment 1 of this invention. It is a hardware block diagram of the part which performs the digital signal processing in the signal processing part. It is a hardware block diagram in case the part which performs the digital signal processing in the signal processing part 14 is comprised with a computer. It is a flowchart which shows the processing content of the part which implements digital signal processing. It is explanatory drawing which shows the distance dependence of SNR in the case of using the large aperture telescope 1 and the small aperture telescope 2. It is explanatory drawing which shows the SNR characteristic in the shortest distance area | region in the large aperture telescope 1 and the small aperture telescope 2. FIG. It is explanatory drawing which shows the change of SNR when the telescope to be used is switched from the small-aperture telescope 2 to the large-aperture telescope 1. It is explanatory drawing which shows the change of SNR when the telescope to be used is switched from the large aperture telescope 1 to the small aperture telescope 2. It is a block diagram which shows the laser radar apparatus by Embodiment 2 of this invention. It is a flowchart which shows the processing content of the part which implements digital signal processing. It is explanatory drawing which shows the distance dependence of SNR in the case of using the large aperture telescope 1 and the small aperture telescope 2. It is explanatory drawing which shows the parameter which can be used as a determination parameter | index of switching of a telescope. It is explanatory drawing which shows the change of SNR when the telescope to be used is switched from the small-aperture telescope 2 to the large-aperture telescope 1. It is a block diagram which shows the laser radar apparatus by Embodiment 3 of this invention. It is a flowchart which shows the processing content of the part which implements digital signal processing. It is explanatory drawing which shows the change of SNR when the focal distance of the telescope after switching is shorter than the focal distance of the telescope before switching.

  Hereinafter, in order to describe the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
1 is a block diagram showing a laser radar apparatus according to Embodiment 1 of the present invention. The laser radar apparatus of FIG. 1 is a so-called coherent Doppler lidar apparatus.
In FIG. 1, a large aperture telescope 1 is a telescope having an aperture diameter larger than the aperture diameter of a small aperture telescope 2.
The small-aperture telescope 2 is a telescope whose aperture diameter is smaller than that of the large-aperture telescope 1.

The telescope switching unit 3 includes a telescope switching controller 4 and a telescope switching device 5.
The telescope switching controller 4 outputs a trigger signal to the telescope switching device 5 and the signal processing unit 14 when switching the telescope to be used for transmission / reception of laser light.
When receiving a trigger signal from the telescope switching controller 4, the telescope switching device 5 is a device for switching the telescope to be used.
That is, when the telescope to be used is the large-aperture telescope 1 when the telescope switching device 5 receives the trigger signal from the telescope switching controller 4, the telescope switching device 5 switches the telescope to be used to the small-aperture telescope 2, The pulse transmission light output from 11 is output to the small-aperture telescope 2, while the scattered light received by the small-aperture telescope 2 (scattered light of the pulse transmission light returned after being scattered by the aerosol) is sent to the transmission / reception separating unit 11. Output.
When the telescope switching device 5 receives the trigger signal from the telescope switching controller 4 when the current telescope to be used is the small-aperture telescope 2, the telescope switching device 5 switches the telescope to be used to the large-aperture telescope 1 and transmits / receives separation. The pulse transmission light output from 11 is output to the large-aperture telescope 1, while the scattered light received by the large-aperture telescope 1 is output to the transmission / reception separating unit 11.

The laser light oscillation unit 6 includes a light source 7, an optical distributor 8, and an optical modulator 9.
The light source 7 oscillates laser light that is continuous wave light having a single wavelength.
The optical distributor 8 divides the laser light oscillated by the light source 7 into two, outputs one laser light to the optical modulator 9, and outputs the other laser light to the optical mixer 12 as local light.
The optical modulator 9 shifts the frequency of the laser light output from the optical distributor 8, and pulse-modulates the laser light after the frequency shift, and transmits the pulse transmission light, which is the laser light after the pulse modulation, to the transmission / reception separator 11. Output.

The laser beam transmission / reception unit 10 includes a transmission / reception separation unit 11, an optical mixer 12, and an optical heterodyne receiver 13.
The transmission / reception separating unit 11 outputs the pulse transmission light output from the optical modulator 9 to the telescope switch 5, and outputs the scattered light output from the telescope switch 5 to the optical mixer 12.
The optical mixer 12 combines the local light output from the optical distributor 8 and the scattered light output from the transmission / reception separator 11 and outputs the combined light of the local light and the scattered light to the optical heterodyne receiver 13. .
The optical heterodyne receiver 13 performs heterodyne detection on the combined light output from the optical mixer 12, and outputs an analog electrical signal as a result of the heterodyne detection to the signal processing unit 14 as a reception signal.

The signal processing unit 14 includes an A / D converter 15, an SNR calculation unit 16, a wind speed calculation unit 17, an SNR acquisition unit 18, and a switching determination unit 19.
FIG. 2 is a hardware configuration diagram of a part (a part excluding the A / D converter 15) that performs digital signal processing in the signal processing unit 14.
The A / D converter 15 converts the analog reception signal output from the optical heterodyne receiver 13 into a digital signal (hereinafter referred to as “digital reception data”), and outputs the digital reception data to the SNR calculation unit 16. .

The SNR calculation unit 16 that is a signal-to-noise ratio calculation unit includes, for example, a semiconductor integrated circuit on which a CPU (Central Processing Unit) is mounted, or an SNR calculation processing circuit 31 including a one-chip microcomputer. By performing frequency analysis on the digital reception data output from the D converter 15 for each fixed distance gate set in advance, processing for calculating frequency spectra in a plurality of distance regions is performed.
In addition, the SNR calculation unit 16 does not change the SNR in the large-aperture telescope 1 and the small-aperture telescope 2 even if the focusing distances of the large-aperture telescope 1 and the small-aperture telescope 2 change in the frequency spectrum in a plurality of distance regions. A process of calculating the SNR of the frequency spectrum in the distance region where the relationship of the signal-to-noise ratio) does not change is performed.
That is, the SNR calculation unit 16 performs a process of calculating the SNR of the frequency spectrum in the shortest distance region among the frequency spectra in a plurality of distance regions.

The wind speed calculation unit 17 includes a semiconductor integrated circuit on which a CPU is mounted, or a wind speed calculation processing circuit 32 made up of a one-chip microcomputer or the like. The Doppler shift due to aerosol is performed from the frequency spectrum calculated by the SNR calculation unit 16. The amount is calculated, and the Doppler shift amount is converted into the wind speed (aerosol moving speed).
The SNR acquisition unit 18 is composed of, for example, a semiconductor integrated circuit on which a CPU and a memory are mounted, or an SNR acquisition processing circuit 33 including a one-chip microcomputer, and the SNR acquisition unit 18 is the closest range calculated by the SNR calculation unit 16. Among the SNRs of the frequency spectrum, the SNR calculated immediately before the trigger signal is output from the telescope switching controller 4 and the SNR calculated immediately after the trigger signal is output from the telescope switching controller 4 are acquired. Perform the process.

The switching determination unit 19 is configured by a switching determination processing circuit 34 including, for example, a semiconductor integrated circuit mounted with a CPU or a one-chip microcomputer, and immediately before the trigger signal acquired by the SNR acquisition unit 18 is output. Is compared with the SNR immediately after the trigger signal is output, to determine whether or not the telescope to be used has been normally switched by the telescope switch 5.
The alarm presenting unit 20 is composed of, for example, a liquid crystal display or a speaker. When the switching determining unit 19 determines that the target telescope is not normally switched, a system abnormality of the laser radar device occurs. Present an alert to the effect.

In FIG. 1, it is assumed that the digital signal processing part (the part excluding the A / D converter 15) in the signal processing unit 14 is configured by dedicated hardware, but the digital signal processing is performed. The portion to be configured may be a computer.
FIG. 3 is a hardware configuration diagram in the case where the part that performs the digital signal processing in the signal processing unit 14 is configured by a computer.
When the digital signal processing part is configured by a computer, a program describing the processing contents of the SNR calculation unit 16, the wind speed calculation unit 17, the SNR acquisition unit 18, and the switching determination unit 19 is stored in the memory 41 of the computer. Then, the computer processor 42 may execute the program stored in the memory 41.
FIG. 4 is a flowchart showing the processing contents of the portion that performs digital signal processing.

Next, the operation will be described.
The large-aperture telescope 1 and the small-aperture telescope 2 have a function of receiving the scattered light of the pulse transmission light that has been scattered by the aerosol and then returned to the atmosphere after emitting the pulse transmission light output from the telescope switch 5 to the atmosphere. However, the SNR in the large-aperture telescope 1 and the small-aperture telescope 2 has distance dependency.
FIG. 5 is an explanatory diagram showing the distance dependency of the SNR when the large-aperture telescope 1 and the small-aperture telescope 2 are used.

式（１）において、Ｌは計測距離［ｍ］、ｈはプランク定数［Ｊｓ］、Ｅはパルス送信光のエネルギー［Ｊ］、Ｂは受信帯域幅［Ｈｚ］、βはエアロゾル後方散乱定数［ｍ^−１ｓｒ^−１］、Ｋは大気透過率［km^−１］、Ｄは送信ビーム径（１／ｅ^２径）［ｍ］、λは波長である。
また、η_Ｄ（Ｌ）はシステム効率であり、下記の式（２）で表される。

式（２）において、Ｆは集光距離、η_ＦはＦａｒ Ｆｉｅｌｄ結合効率、Ａ_Ｃはビームのけられの影響を示す定数、Ｓ_０は横コヒーレント長さである。 The distance dependency of the SNR and the aperture diameter dependency of the reception optical system obtained by the coherent laser radar device as shown in FIG. 1 are expressed by the lidar equation of the following equation (1).

In equation (1), L is the measurement distance [m], h is the Planck constant [Js], E is the energy of the pulse transmission light [J], B is the reception bandwidth [Hz], and β is the aerosol backscattering constant [m. ⁻¹ sr ⁻¹ ], K is the atmospheric transmittance [km ⁻¹ ], D is the transmission beam diameter (1 / e ² diameter) [m], and λ is the wavelength.
Moreover, η _D (L) is system efficiency and is represented by the following formula (2).

In the formula (2), F is the condensing distance, eta _F is Far Field coupling efficiency, _{A C} is a constant that indicates the influence of the vignetting of the beam, _{S 0} is the lateral coherence length.

Therefore, when the small-aperture telescope 2 having a small aperture diameter corresponding to the transmission beam diameter D is used, a relatively high SNR is always obtained in the short-distance region regardless of the focusing distance F.
On the other hand, when the large-aperture telescope 1 having a large aperture diameter is used, when the condensing distance F changes, the obtained SNR changes greatly.
However, when the large-aperture telescope 1 is used, the amount of received light increases as the aperture diameter increases, so that it is possible to measure wind farther than when the small-aperture telescope 2 is used.
Therefore, by providing a plurality of telescopes having different aperture diameters and appropriately switching the telescope to be used, a plurality of operation methods are possible in the laser radar apparatus. Specifically, the following operation methods and the like are possible.
(1) Use the small-aperture telescope 2 when you want to stably measure the wind in the short-distance region, and use the large-aperture telescope 1 when you want to measure the wind speed at a longer distance. (2) By setting the large-aperture telescope 1 and the small-aperture telescope 2 in different vertical orientations and performing measurements while continuously switching the telescope that irradiates pulse transmission light, Operation method to obtain vertical profile of wind speed

The light source 7 of the laser light oscillator 6 oscillates laser light that is single-wave continuous wave light.
When the light source 7 oscillates the laser light, the light distributor 8 splits the laser light into two, outputs one laser light to the optical modulator 9, and uses the other laser light as local light to the optical mixer 12. Output.
When the light modulator 9 receives the laser light from the light distributor 8, the light modulator 9 shifts the frequency of the laser light, and pulse-modulates the laser light after the frequency shift. The data is output to the transmission / reception separating unit 11.

When receiving the pulse transmission light from the optical modulator 9, the transmission / reception separating unit 11 outputs the pulse transmission light to the telescope switch 5.
The telescope switching controller 4 of the telescope switching unit 3 outputs a trigger signal to the telescope switching unit 5 and the signal processing unit 14 when switching the telescope to be used.
As the trigger signal, a signal whose signal level is switched at High / Low, a signal whose signal output is switched at On / Off, or the like can be used.

When receiving the trigger signal from the telescope switching controller 4, the telescope switching device 5 switches the target telescope.
In other words, when the telescope to be used is the large-aperture telescope 1 when the telescope switch 5 receives the trigger signal from the telescope switching controller 4, the telescope switch 5 switches the target telescope to the small-aperture telescope 2 and performs transmission / reception separation. The pulse transmission light output from the unit 11 is output to the small aperture telescope 2.
In addition, when the telescope to be used is the small-aperture telescope 2 when the telescope switching device 5 receives the trigger signal from the telescope switching controller 4, the telescope switching device 5 switches the telescope to be used to the large-aperture telescope 1 and separates transmission and reception. The pulse transmission light output from the unit 11 is output to the large-aperture telescope 1.

When the large-aperture telescope 1 and the small-aperture telescope 2 receive the pulse transmission light from the telescope switch 5, the pulse transmission light is emitted into the atmosphere.
Further, the large-aperture telescope 1 and the small-aperture telescope 2 receive the scattered light of the pulse transmission light that has been scattered back by the aerosol and output the scattered light to the transmission / reception separating unit 11.

When the telescope to be used is the large-aperture telescope 1, the telescope switch 5 outputs the scattered light to the transmission / reception separating unit 11 when receiving the scattered light of the pulse transmission light from the large-aperture telescope 1.
In addition, when the telescope to be used is the small-aperture telescope 2, the telescope switch 5 outputs the scattered light to the transmission / reception separating unit 11 when receiving the scattered light of the pulse transmission light from the small-aperture telescope 2.

When receiving the scattered light from the telescope switch 5, the transmission / reception separating unit 11 outputs the scattered light to the optical mixer 12.
The optical mixer 12 combines the local light output from the optical distributor 8 and the scattered light output from the transmission / reception separator 11, and outputs the combined light of the local light and the scattered light to the optical heterodyne receiver 13. To do.
When receiving the combined light from the optical mixer 12, the optical heterodyne receiver 13 performs heterodyne detection on the combined light and outputs an analog electric signal as a result of the heterodyne detection to the signal processing unit 14 as a reception signal.

When the A / D converter 15 of the signal processing unit 14 receives an analog reception signal from the optical heterodyne receiver 13, the A / D converter 15 performs A / D conversion on the reception signal, and calculates SNR of the digital reception data which is a digital reception signal. To the unit 16.
When receiving the digital reception data from the A / D converter 15, the SNR calculation unit 16 performs a Fourier transform on the digital reception data.
That is, the SNR calculation unit 16 calculates the frequency spectrum in a plurality of distance regions by analyzing the frequency of the digital reception data for each fixed distance gate set in advance, and the frequency spectrum in the plurality of distance regions. Among them, the SNR of the frequency spectrum in the shortest range is calculated (step ST1 in FIG. 4).

Here, FIG. 6 is an explanatory diagram showing SNR characteristics in the shortest distance region in the large-aperture telescope 1 and the small-aperture telescope 2.
In particular, FIG. 6A shows the SNR characteristic in the shortest distance region when the condensing distance F of the large-aperture telescope 1 and the small-aperture telescope 2 is a long distance, and FIG. The SNR characteristic in the shortest distance region in the case of a short distance is shown.
As is clear from FIG. 6, the SNR in the shortest distance region is always small-aperture telescope 2> large-aperture telescope 1 regardless of whether the condensing distance F is long or short.
Therefore, for example, even in an operation in which wind measurement is performed by setting the condensing distance F of the large-aperture telescope 1 and the small-aperture telescope 2 to different distances, the SNR of the frequency spectrum in the shortest range is the switching of the telescope. It can be used as a determination index.
For this reason, in the first embodiment, the SNR of the frequency spectrum in the shortest range is calculated.

In the first embodiment, an example is shown in which the SNR of the frequency spectrum in the shortest distance region is calculated in order to determine the switching of the telescope. In FIG. 6, in the region where the distance is shorter than the distance L ₁ in FIG. Even if the condensing distance F of the large-aperture telescope 1 and the small-aperture telescope 2 changes, the SNR is always small-aperture telescope 2> the large-aperture telescope 1, and thus the SNR of the frequency spectrum in the shortest distance region is calculated. Alternatively, the distance from the distance L ₁ may calculate the SNR of the frequency spectrum in the region close.
Similarly, in the distance L ₂ from the long distance region, even after changing the condensing distance F of the large-diameter telescopes 1 and the small-diameter telescopes 2, SNR is always small diameter telescopes 2 <large aperture telescope 1, most instead of calculating the SNR of the frequency spectrum in the near zone, the distance from the distance L ₂ may calculate the SNR of the frequency spectrum in the region longer. However, the distance L ₃ from the distance is long area, for SNR in the small-diameter telescopes 2 becomes substantially zero, the distance from the distance L ₃ is required to calculate the SNR of the frequency spectrum in the region close.

When the SNR calculator 16 calculates the frequency spectrum, the wind speed calculator 17 calculates a Doppler shift amount due to the aerosol from the frequency spectrum, and converts the Doppler shift amount into a wind speed (aerosol moving speed). Since the process for calculating the Doppler shift amount from the frequency spectrum and the process for converting the Doppler shift amount into the wind speed are known techniques, detailed description thereof is omitted.
The alarm presenting unit 20 displays the wind speed converted by the wind speed calculating unit 17.

The SNR acquisition unit 18 calculates the SNR calculated immediately before the trigger signal is output from the telescope switching controller 4 among the SNRs of the frequency spectrum in the shortest range calculated by the SNR calculation unit 16 and the telescope switching control. The SNR calculated immediately after the trigger signal is output from the device 4 is acquired.
That is, every time the SNR calculation unit 16 calculates the SNR of the frequency spectrum in the shortest range, the SNR acquisition unit 18 acquires the SNR (step ST2), and still triggers from the telescope switching controller 4 at this time. If no signal is output (step ST3: NO), the SNR is overwritten and saved in the internal memory (step ST4).
When the trigger signal has already been output from the telescope switching controller 4 at the time when the SNR calculated by the SNR calculation unit 16 is acquired (step ST3: YES), the SNR acquisition unit 18 uses the acquired SNR. Then, it is output to the switching determination unit 19 as determination index information a _after indicating the SNR calculated immediately after the trigger signal is output. Further, the SNR stored in the internal memory is output to the switching determination unit 19 as determination index information a _before indicating the SNR calculated immediately before the trigger signal is output (step ST5).

When the switching determination unit 19 receives determination index information a _before indicating the SNR immediately before the trigger signal is output from the SNR acquisition unit 18 and determination index information a _after indicating the SNR immediately after the trigger signal is output, By comparing the determination index information a _before and the determination index information a _after , it is determined whether or not the telescope to be used has been normally switched by the telescope switch 5.
FIG. 7 is an explanatory diagram showing changes in SNR when the target telescope is switched from the small-aperture telescope 2 to the large-aperture telescope 1.
FIG. 8 is an explanatory diagram showing changes in SNR when the target telescope is switched from the large-aperture telescope 1 to the small-aperture telescope 2.
Hereinafter, the determination process by the switching determination unit 19 will be specifically described with reference to FIGS. 7 and 8.

When the telescope to be used is switched from the small-aperture telescope 2 to the large-aperture telescope 1, as shown in FIG. The SNR of the frequency spectrum at decreases.
a _after <a _before
On the other hand, when the telescope to be used is switched from the large-aperture telescope 1 to the small-aperture telescope 2, as shown in FIG. The SNR of the frequency spectrum in the distance domain increases.
a _after > a _before

When the switching determination unit 19 receives the determination index information a _before and a _after from the SNR acquisition unit 18, the switching target unit 19 changes the telescope to be used from the small-aperture telescope 2 to the large-aperture telescope 1 according to the trigger signal output from the telescope switching controller 4. (Step ST6: YES), as shown in the following equation (3), the switching determination threshold Th ₁ is used by using the switching determination change amount ΔA that is a constant set in advance. Is calculated (step ST7).
Th ₁ = a _before −ΔA (3)
The switching determination unit 19 counts the number of trigger signals output from the telescope switching controller 4 and confirms what number the trigger signal output this time is, so that It can be determined whether the telescope has been switched from the small aperture telescope 2 to the large aperture telescope 1 or from the large aperture telescope 1 to the small aperture telescope 2.

Further, the switching determination unit 19 uses the trigger signal output from the telescope switching controller 4 when the target telescope is switched from the large-aperture telescope 1 to the small-aperture telescope 2 (step ST6: NO). as shown in equation (4) below, using the switching determination change amount ΔA is a constant set in advance, it calculates the switching determination threshold Th ₂ (step ST8).
Th ₂ = a _before + ΔA (4)

When the switching determination unit 19 calculates the switching determination threshold Th ₁ , the switching determination unit 19 compares the determination index information a _after and the switching determination threshold Th ₁ , and the determination index information a _after is converted into the switching determination threshold Th as shown in FIG. If it is smaller than ₁ (in the case of YES at step ST9), it is determined that switching from the small-aperture telescope 2 to the large-aperture telescope 1 has been normally performed (step ST11).
On the other hand, if the determination index information a _after is greater than or equal to the switching determination threshold Th ₁ (step ST9: NO), it is determined that switching from the small-aperture telescope 2 to the large-aperture telescope 1 has not been performed normally. (Step ST12). That is, it is determined that the switching is abnormal.

When the switching determination unit 19 calculates the switching determination threshold Th ₂ , the switching determination unit 19 compares the determination index information a _after with the switching determination threshold Th ₂ , and the determination index information a _after is converted into the switching determination threshold Th as shown in FIG. If larger than ₂ (step ST10: YES), it is determined that switching from the large aperture telescope 1 to the small aperture telescope 2 has been performed normally (step ST11).
On the other hand, if the determination index information a _after is less than or equal to the threshold value for switching determination Th ₂ (step ST10: NO), it is determined that switching from the large aperture telescope 1 to the small aperture telescope 2 is not normally performed. (Step ST12). That is, it is determined that the switching is abnormal.

The alarm presenting unit 20 displays that the system is normal when the switching determining unit 19 determines that the target telescope has been switched normally (step ST13).
In addition, when the switching determination unit 19 determines that the target telescope is not normally switched, the alarm presenting unit 20 displays an alarm indicating that a system abnormality has occurred (step ST14).

  As is apparent from the above, according to the first embodiment, the SNR calculation unit 16 that calculates the SNR of the received signal of the scattered light every time the scattered light is received by the laser light transmitting / receiving unit 10, and the SNR calculation unit Whether or not the telescope to be used is normally switched by the telescope switching unit 3 by comparing the SNRs before and after the telescope to be used is switched by the telescope switching unit 3 among the SNRs calculated by 16. And a switch determining unit 19 for determining whether the telescope to be used has not been switched normally by the switch determining unit 19, indicating that a system abnormality has occurred. Since it is configured to present an alarm, it is possible to notify the user of the occurrence of a system abnormality without mounting a photodetector or the like.

Embodiment 2. FIG.
In the first embodiment, the SNR of the frequency spectrum in the shortest distance region among the frequency spectra in a plurality of distance regions is calculated, and the SNR before and after the trigger signal is output from the telescope switching controller 4 is compared. Thus, an example is shown in which the telescope switching unit 3 determines whether or not the telescope to be used has been switched normally.
In this case, it is possible to easily determine whether or not the switching has been performed normally. However, even in the large-aperture telescope 1, when the measurement is performed under a condition in which the SNR in the short-range region is large, before and after the switching of the telescope. Since the SNR does not change greatly, there is a possibility that the determination accuracy is lowered.
In the second embodiment, a laser radar device capable of performing accurate determination even when measurement is performed under such conditions will be described.

FIG. 9 is a block diagram showing a laser radar apparatus according to Embodiment 2 of the present invention. In FIG. 9, the same reference numerals as those in FIG.
Similar to the SNR calculation unit 16 in FIG. 1, the SNR calculation unit 21 includes a SNR calculation processing circuit 31 including, for example, a semiconductor integrated circuit mounted with a CPU or a one-chip microcomputer. The digital reception data output from the device 15 is subjected to frequency analysis for each fixed distance gate set in advance, thereby executing a process of calculating frequency spectra in a plurality of distance regions.
Further, the SNR calculation unit 21 calculates the SNR of the frequency spectrum in the shortest distance region among the frequency spectra in the plurality of distance regions.
Furthermore, the SNR calculation unit 21 calculates the SNR of the frequency spectrum in a plurality of distance regions, and sets the maximum measurable distance of the aerosol as the distance at which the aerosol can be measured from the SNR of the frequency spectrum in the plurality of distance regions. A process of specifying the SNR peak position, which is the distance region where the SNR peaks, is performed.

Similar to the SNR acquisition unit 18 in FIG. 1, the SNR acquisition unit 22 includes a SNR acquisition processing circuit 33 including, for example, a semiconductor integrated circuit in which a CPU and a memory are mounted, or a one-chip microcomputer. Among the SNRs of the frequency spectrum in the shortest range calculated by the unit 21, the SNR calculated immediately before the trigger signal is output from the telescope switching controller 4 and the trigger signal is output from the telescope switching controller 4. Immediately after that, a process of acquiring the calculated SNR is performed.
The SNR acquisition unit 22 also identifies the maximum measurable distance and SNR peak identified immediately before the trigger signal is output from the telescope switching controller 4 among the maximum measurable distance and SNR peak position identified by the SNR calculator 21. Processing for acquiring the position and the maximum measurable distance and SNR peak position specified immediately after the trigger signal is output from the telescope switching controller 4 is performed.

Similar to the switching determination unit 19 shown in FIG. 1, the switching determination unit 23 includes a semiconductor integrated circuit on which a CPU is mounted, or a switching determination processing circuit 34 including a one-chip microcomputer, for example, and the SNR acquisition unit 22. SNR comparison processing before and after trigger signal output acquired by SNR, comparison processing of maximum measurable distance before and after trigger signal output specified by SNR acquisition unit 22, SNR peak before and after trigger signal output acquired by SNR acquisition unit 22 A position comparison process is performed.
Moreover, the switching determination part 23 implements the process which determines whether the telescope to be used was switched normally by the telescope switch 5 from the result of those comparison processes.

In FIG. 9, it is assumed that the digital signal processing part (the part excluding the A / D converter 15) in the signal processing unit 14 is configured by dedicated hardware, but the digital signal processing is performed. The portion to be configured may be a computer.
When the digital signal processing is implemented by a computer, a program describing the processing contents of the SNR calculation unit 21, the wind speed calculation unit 17, the SNR acquisition unit 22, and the switching determination unit 23 is shown in FIG. The program stored in the memory 41 may be executed by the processor 42 of the computer.
FIG. 10 is a flowchart showing the processing contents of the part that performs digital signal processing.

Next, the operation will be described.
Except for the SNR calculation unit 21, the SNR acquisition unit 22, and the switching determination unit 23, the processing is the same as that of the first embodiment. Therefore, here, the processing contents of the SNR calculation unit 21, the SNR acquisition unit 22, and the switching determination unit 23 are mainly described. Will be explained.
FIG. 11 is an explanatory diagram showing the distance dependency of the SNR when the large-aperture telescope 1 and the small-aperture telescope 2 are used.
When the SNR obtained when using the large aperture telescope 1 and the SNR obtained when using the small aperture telescope 2 are compared, as shown in FIG. 11, the SNR of the frequency spectrum in the shortest range is different. In addition, the maximum measurable distance, which is the distance at which aerosol can be measured, and the SNR peak position, which is the distance region where the SNR peaks, are different.
Therefore, in the second embodiment, in addition to the SNR of the frequency spectrum in the shortest distance region, the maximum measurable distance and the SNR peak position are used as a determination index for switching the telescope.
Here, FIG. 12 is an explanatory diagram showing parameters that can be used as a determination index for switching the telescope.
In the example of FIG. 12, in addition to the SNR, the maximum measurable distance, and the SNR peak position of the frequency spectrum in the shortest distance region, the spectrum integration area and the SNR slope are listed as parameters that can be used as determination indices. doing.

When receiving an analog reception signal from the optical heterodyne receiver 13, the A / D converter 15 of the signal processing unit 14 performs A / D conversion on the reception signal in the same manner as in the first embodiment, and performs digital reception. Digital received data that is a signal is output to the SNR calculator 21.
When the digital reception data is received from the A / D converter 15, the SNR calculation unit 21 performs frequency analysis on the digital reception data for each fixed distance gate set in advance, like the SNR calculation unit 16 of FIG. 1. Thus, the frequency spectrum in a plurality of distance regions is calculated, and the SNR of the frequency spectrum in the shortest distance region among the frequency spectra in the plurality of distance regions is calculated (step ST21 in FIG. 10).

The SNR calculation unit 21 calculates SNRs of frequency spectra in a plurality of distance regions, and among these SNRs, a minimum SNR (for example, wind speed calculation) determined in advance according to the specifications of the laser radar device. The SNR smaller than the minimum SNR capable of calculating the wind speed in the unit 17 is excluded.
Then, the SNR in the farthest distance area among the remaining SNRs is specified, and the farthest distance area is set as the maximum measurable distance (step ST21).
Furthermore, the SNR calculation unit 21 identifies the SNR peak position, which is the distance region where the SNR peaks, by comparing the SNRs of the frequency spectra in a plurality of distance regions (step ST21).

The SNR acquisition unit 22 receives the SNR calculated immediately before the trigger signal is output from the telescope switching controller 4 out of the SNR of the frequency spectrum calculated by the SNR calculation unit 21 and the trigger signal from the telescope switching controller 4. The SNR calculated immediately after the output is obtained.
The SNR acquisition unit 22 also identifies the maximum measurable distance and SNR identified immediately before the trigger signal is output from the telescope switching controller 4 among the maximum measurable distance and SNR peak position identified by the SNR calculator 21. The peak position and the maximum measurable distance and SNR peak position specified immediately after the trigger signal is output from the telescope switching controller 4 are acquired.

That is, the SNR acquisition unit 22 calculates the SNR, the maximum measurable distance, and the SNR peak position each time the SNR calculation unit 21 calculates the SNR, the maximum measurable distance, and the SNR peak position of the frequency spectrum in the shortest range. If the trigger signal is not yet output from the telescope switching controller 4 at this time (step ST23: NO), the SNR, the maximum measurable distance, and the SNR peak position are stored in the internal memory. Overwrite and store (step ST24).
When the SNR acquisition unit 22 acquires the SNR, the maximum measurable distance, and the SNR peak position calculated by the SNR calculation unit 21, the trigger signal has already been output from the telescope switching controller 4 (step ST23: YES). In this case, the obtained SNR, the maximum measurable distance, and the SNR peak position are determined based on the determination index information a _after and b _after indicating the SNR, the maximum measurable distance, and the SNR peak position calculated immediately after the trigger signal is output. , C _after and output to the switching determination unit 23. Further, the SNR, maximum measurable distance, and SNR peak position stored in the internal memory are determined as index information a _before indicating the SNR, maximum measurable distance, and SNR peak position calculated immediately before the trigger signal is output. , B _before , c _before are output to the switching determination unit 23 (step ST25).

The switching determination unit 23 is used by the telescope switching unit 5 by performing comparison processing of SNR before and after the trigger signal output acquired by the SNR acquisition unit 22, comparison processing of the maximum measurable distance, and comparison processing of the SNR peak position. It is determined whether the target telescope has been switched normally.
FIG. 13 is an explanatory diagram showing changes in SNR when the target telescope is switched from the small-aperture telescope 2 to the large-aperture telescope 1.
Hereinafter, the determination process by the switching determination unit 23 will be described in detail with reference to FIG.

When the target telescope is switched from the small-aperture telescope 2 to the large-aperture telescope 1, as shown in FIG. 13A, the SNR of the frequency spectrum in the shortest range decreases.
a _after <a _before
Further, as shown in FIG. 13B, the maximum measurable distance increases.
b _after > b _before
Furthermore, as shown in FIG. 13C, the SNR peak position increases.
c _after > c _before

On the other hand, when the target telescope is switched from the large-aperture telescope 1 to the small-aperture telescope 2, the SNR of the frequency spectrum in the shortest range increases, the maximum measurable distance decreases, and the SNR peak position decreases. .
a _after > a _before
b _after <b _before
c _after <c _before

When the switching determination unit 23 receives the determination index information a _before , a _after , b _before , b _after , c _before , c _after from the SNR acquisition unit 22, the switching determination unit 23 uses the trigger signal output from the telescope switching controller 4. Is switched from the small-aperture telescope 2 to the large-aperture telescope 1 (in the case of YES at step ST26), as shown in the following formulas (5) to (7), the constant is set in advance. By using a certain switching determination change amount ΔA, ΔB, ΔC, switching determination threshold values Th ₁ , Th ₃ , Th ₅ are calculated (step ST 27).
Th ₁ = a _before −ΔA (5)
Th ₃ = b _before + ΔB (6)
Th ₅ = c _before + ΔC (7)
The switching determination unit 23 counts the number of trigger signals output from the telescope switching controller 4 and confirms what number of trigger signals the currently output trigger signal is, so It can be determined whether the telescope has been switched from the small aperture telescope 2 to the large aperture telescope 1 or from the large aperture telescope 1 to the small aperture telescope 2.

In addition, the switching determination unit 23, when the target telescope is switched from the large-aperture telescope 1 to the small-aperture telescope 2 by the trigger signal output from the telescope switching controller 4 (step ST26: NO), As shown in the following equations (8) to (10), the switching determination threshold values Th ₂ , Th ₄ , Th ₆ are set using the switching determination change amounts ΔA, ΔB, ΔC, which are constants set in advance. Calculate (step ST28).
Th ₂ = a _before + ΔA (8)
Th ₄ = b _before −ΔB (9)
Th ₆ = c _before −ΔC (10)

After calculating the switching determination threshold values Th ₁ , Th ₃ , Th ₅ , the switching determination unit 23 compares the determination index information a _after with the switching determination threshold value Th ₁ , and the determination index information a _after is determined as the switching determination threshold value Th _1. If it is above (step ST29: NO), it is determined that switching from the small-aperture telescope 2 to the large-aperture telescope 1 is not normally performed (step ST36). That is, it is determined that the switching is abnormal.
If the determination index information a _after is smaller than the switching determination threshold Th ₁ (in the case of YES at Step ST29), the switching determination unit 23 compares the determination index information b _after with the switching determination threshold Th ₃ , and determines the determination index information b. _{If after} is equal to or less than the switching determination threshold Th ₃ (step ST30: NO), it is determined that switching from the small-aperture telescope 2 to the large-aperture telescope 1 is not normally performed (step ST36).
If the determination index information b _after is greater than the switching determination threshold Th ₃ (in the case of YES at step ST30), the switching determination unit 23 compares the determination index information c _after with the switching determination threshold Th ₅ and determines the determination index information c. _{If after} is equal to or less than the switching determination threshold Th ₅ (step ST31: NO), it is determined that switching from the small-aperture telescope 2 to the large-aperture telescope 1 is not normally performed (step ST36).
If the determination index information c _after is greater than the switching determination threshold Th ₅ (in the case of YES at step ST31), the switching determination unit 23 _assumes that switching from the small-aperture telescope 2 to the large-aperture telescope 1 has been performed normally. Determination is made (step ST35).

When the switching determination unit 23 calculates the switching determination threshold values Th ₂ , Th ₄ , and Th ₆ , the determination index information a _after is compared with the switching determination threshold value Th ₂ , and the determination index information a _after is determined as the switching determination threshold value Th _2. If it is below (step ST32: NO), it is determined that the switching from the large aperture telescope 1 to the small aperture telescope 2 is not normally performed (step ST36). That is, it is determined that the switching is abnormal.
If the determination index information a _after is greater than the switching determination threshold Th ₂ (in the case of YES at step ST32), the switching determination unit 23 compares the determination index information b _after and the switching determination threshold Th ₄ to determine the determination index information b. _{If after} is greater than or equal to the switching determination threshold Th ₄ (in the case of step ST33: NO), it is determined that switching from the large aperture telescope 1 to the small aperture telescope 2 has not been performed normally (step ST36).
If the determination index information b _after is smaller than the switching determination threshold Th ₄ (in the case of YES at step ST33), the switching determination unit 23 compares the determination index information c _after with the switching determination threshold Th ₆ and determines the determination index information c. _{If after} is greater than or equal to the switching determination threshold Th ₆ (step ST34: NO), it is determined that switching from the large aperture telescope 1 to the small aperture telescope 2 has not been performed normally (step ST36).
If the determination index information c _after is smaller than the switching determination threshold Th ₆ (in the case of YES at step ST34), the switching determination unit 23 _assumes that switching from the large-aperture telescope 1 to the small-aperture telescope 2 has been normally performed. Determination is made (step ST35).

The alarm presenting unit 20 displays that the system is normal when the switching determining unit 23 determines that the target telescope has been switched normally (step ST37).
Further, when the switching determination unit 23 determines that the target telescope is not normally switched, the alarm presenting unit 20 displays an alarm indicating that a system abnormality has occurred (step ST38).

  As is apparent from the above, according to the second embodiment, not only the SNR comparison processing in the shortest range before and after the trigger signal is output, but also the comparison processing of the maximum measurable distance, the SNR peak position By performing the comparison process, it is configured to determine whether or not the telescope to be used has been normally switched by the telescope switching unit 5, so that a switching determination result with higher accuracy than the first embodiment can be obtained. There is an effect that can.

Embodiment 3 FIG.
In the first and second embodiments, the switching determination of the large-aperture telescope 1 and the small-aperture telescope 2 having different aperture diameters is performed. However, the switching determination of a plurality of telescopes having the same aperture diameter is performed. May be.

14 is a block diagram showing a laser radar apparatus according to Embodiment 3 of the present invention. In FIG. 14, the same reference numerals as those in FIG.
The telescopes 51 and 52 are telescopes having the same or similar aperture diameter, and after the pulse transmission light output from the telescope switch 5 is emitted into the atmosphere, the scattered light of the pulse transmission light returned after being scattered by the aerosol Has a function of receiving light.
When a trigger signal is output from the telescope switching controller 4, the focal length setting unit 53 sets different focal lengths for the telescopes 51 and 52, and after setting the focal length, the trigger signal is sent to the telescope switching device 5 and the signal processing. To the unit 14.

In the third embodiment, the provision of the two telescopes 51 and 52 enables the wind speed measurement in the two line-of-sight directions as in the first and second embodiments. In addition, by providing the focal length setting unit 53, it is possible to measure in a wide range from a short distance to a long distance.
However, when the aperture diameters of the two telescopes 51 and 52 are the same, the SNR distance dependence of the spectrum of the received signal obtained by wind measurement is the same under the condition that the focal lengths of the telescopes 51 and 52 are the same. Therefore, even if the change in SNR distance dependency is observed as it is, it is not possible to carry out the telescope switching determination.
Therefore, in the third embodiment, different focal lengths are set for the telescopes 51 and 52.

Similar to the SNR calculation unit 16 in FIG. 1, the SNR calculation unit 61 includes an SNR calculation processing circuit 31 including, for example, a semiconductor integrated circuit on which a CPU is mounted or a one-chip microcomputer. The digital reception data output from the device 15 is subjected to frequency analysis for each fixed distance gate set in advance, thereby executing a process of calculating frequency spectra in a plurality of distance regions.
In addition, the SNR calculation unit 61 calculates the SNR of the frequency spectrum in a plurality of distance regions, and specifies the maximum measurable distance that is the distance at which aerosol can be measured from the SNR of the frequency spectrum in the plurality of distance regions. Then, a process of specifying the SNR peak height, which is a value at which the SNR reaches a peak, is performed.

  Similar to the SNR acquisition unit 18 shown in FIG. 1, the SNR acquisition unit 62 includes a semiconductor integrated circuit on which a CPU and a memory are mounted, or an SNR acquisition processing circuit 33 including a one-chip microcomputer, for example. Among the maximum measurable distance and SNR peak height specified by the unit 61, the maximum measurable distance and SNR peak height specified immediately before the trigger signal is output from the focal length setting unit 53, and the focal length setting unit 53 The processing for obtaining the maximum measurable distance and the SNR peak height specified immediately after the trigger signal is output from is performed.

Similar to the switching determination unit 19 in FIG. 1, the switching determination unit 63 includes a switching determination processing circuit 34 including, for example, a semiconductor integrated circuit on which a CPU is mounted or a one-chip microcomputer, and the SNR acquisition unit 62. The comparison processing of the maximum measurable distance before and after the trigger signal output specified by the above and the comparison processing of the SNR peak height before and after the trigger signal output acquired by the SNR acquisition unit 22 are performed.
Further, the switching determination unit 63 performs a process of determining whether or not the telescope to be used has been normally switched by the telescope switching unit 5 from the result of the comparison processing.

In FIG. 14, it is assumed that the digital signal processing part (the part excluding the A / D converter 15) in the signal processing unit 14 is configured by dedicated hardware, but the digital signal processing is performed. The portion to be configured may be a computer.
When the digital signal processing is implemented by a computer, a program describing the processing contents of the SNR calculation unit 61, the wind speed calculation unit 17, the SNR acquisition unit 62, and the switching determination unit 63 is shown in FIG. The program stored in the memory 41 may be executed by the processor 42 of the computer.
FIG. 15 is a flowchart showing the processing contents of a portion that performs digital signal processing.

Next, the operation will be described.
The light source 7 of the laser light oscillator 6 oscillates laser light that is single-wave continuous wave light.
When the light source 7 oscillates the laser light, the light distributor 8 splits the laser light into two, outputs one laser light to the optical modulator 9, and uses the other laser light as local light to the optical mixer 12. Output.
When the light modulator 9 receives the laser light from the light distributor 8, the light modulator 9 shifts the frequency of the laser light, and pulse-modulates the laser light after the frequency shift, and applies the pulse transmission light that is the laser light after the pulse modulation. The data is output to the transmission / reception separating unit 11.

When receiving the pulse transmission light from the optical modulator 9, the transmission / reception separating unit 11 outputs the pulse transmission light to the telescope switch 5.
The telescope switching controller 4 of the telescope switching unit 3 outputs a trigger signal to the focal length setting unit 53 when switching the telescope to be used.
As the trigger signal, a signal whose signal level is switched at High / Low, a signal whose signal output is switched at On / Off, or the like can be used.

When the focal length setting unit 53 receives the trigger signal from the telescope switching controller 4, the focal length setting unit 53 outputs a focal length control signal instructing the setting of the focal length to the telescopes 51 and 52, thereby being different from each other with respect to the telescopes 51 and 52. Set the focal length.
When the focal length setting unit 53 sets the focal lengths of the telescopes 51 and 52, the focal length setting unit 53 outputs a trigger signal to the telescope switching unit 5 and the signal processing unit 14.
Here, the focal lengths set for the telescopes 51 and 52 are not particularly limited as long as they can distinguish the SNR distance dependence of the reception signals of the two telescopes 51 and 52. For example, (1) short distance and long distance, (2 The user can arbitrarily set a short distance and a medium distance, and (3) a medium distance and a long distance.
In addition, the measurement is performed with the focal lengths of the telescopes 51 and 52 set to different focal lengths in advance so that the SNR distance dependence of the received signals can be distinguished for the two telescopes 51 and 52. May be.
In this case, the focal length setting unit 53 does not need to set the focal length for the telescopes 51 and 52 every time a trigger signal is received from the telescope switching controller 4. Therefore, the trigger signal output from the telescope switching controller 4 is directly output to the telescope switching device 5 and the signal processing unit 14 as in the first and second embodiments.

When receiving the trigger signal from the focal length setting unit 53, the telescope switching unit 5 switches the telescope to be used.
That is, when the telescope 51 currently used is the telescope 51 and receives a trigger signal from the focal length setting unit 53, the telescope switching unit 5 switches the telescope to be used to the telescope 52 and outputs it from the transmission / reception separating unit 11. The transmitted pulse transmission light is output to the telescope 52.
When the telescope switch 5 currently receives the trigger signal from the focal length setting unit 53 when the current telescope to be used is the telescope 52, the telescope switch 5 switches the telescope to be used to the telescope 51 and outputs it from the transmission / reception separation unit 11. The transmitted pulse transmission light is output to the telescope 51.

When receiving the pulse transmission light from the telescope switch 5, the telescopes 51 and 52 emit the pulse transmission light into the atmosphere.
In addition, the telescopes 51 and 52 receive the scattered light of the pulse transmission light that has been scattered back by the aerosol and output the scattered light to the transmission / reception separating unit 11.

When the telescope switch 5 receives the scattered light of the pulse transmission light from the telescope 51 when the currently used telescope is the telescope 51, the telescope switch 5 outputs the scattered light to the transmission / reception separation unit 11.
When the telescope switch 5 currently receives the scattered light of the pulse transmission light from the telescope 52 when the currently used telescope is the telescope 52, the telescope switch 5 outputs the scattered light to the transmission / reception separation unit 11.

When receiving the scattered light from the telescope switch 5, the transmission / reception separating unit 11 outputs the scattered light to the optical mixer 12.
The optical mixer 12 combines the local light output from the optical distributor 8 and the scattered light output from the transmission / reception separator 11, and outputs the combined light of the local light and the scattered light to the optical heterodyne receiver 13. To do.
When receiving the combined light from the optical mixer 12, the optical heterodyne receiver 13 performs heterodyne detection on the combined light and outputs an analog electric signal as a result of the heterodyne detection to the signal processing unit 14 as a reception signal.

When receiving an analog reception signal from the optical heterodyne receiver 13, the A / D converter 15 of the signal processing unit 14 performs A / D conversion on the reception signal in the same manner as in the first embodiment, and performs digital reception. Digital received data that is a signal is output to the SNR calculator 61.
When the digital reception data is received from the A / D converter 15, the SNR calculation unit 61 performs frequency analysis on the digital reception data for each fixed distance gate set in advance, like the SNR calculation unit 21 of FIG. 9. Thus, frequency spectra in a plurality of distance regions are calculated.
When the frequency spectrum in a plurality of distance regions is calculated, the SNR calculation unit 61 can measure the aerosol by calculating the SNR of the frequency spectrum in the plurality of distance regions in the same manner as the SNR calculation unit 21 in FIG. A maximum measurable distance that is a short distance is specified (step ST41 in FIG. 15).

Moreover, the SNR calculation part 61 specifies SNR peak height which is a value by which SNR becomes a peak by comparing SNR of the frequency spectrum in a several distance area | region (step ST41).
In the third embodiment, the maximum measurable distance and the SNR peak height are specified as parameters that can be used as a determination index for switching the telescope. However, the present invention is not limited to this. For example, measurement is possible. The range and SNR peak position may be specified.

When the SNR calculation unit 61 calculates a frequency spectrum, the wind speed calculation unit 17 calculates a Doppler shift amount due to aerosol from the frequency spectrum, and converts the Doppler shift amount into a wind speed (aerosol moving speed).
The alarm presenting unit 20 displays the wind speed converted by the wind speed calculating unit 17.

  Of the maximum measurable distance and SNR peak height identified by the SNR calculator 61, the SNR acquisition unit 62 identifies the maximum measurable distance and SNR peak identified immediately before the trigger signal is output from the focal length setting unit 53. The height and the maximum measurable distance and SNR peak height specified immediately after the trigger signal is output from the focal length setting unit 53 are acquired.

That is, every time the SNR calculation unit 61 specifies the maximum measurable distance and the SNR peak height, the SNR acquisition unit 62 acquires the maximum measurable distance and the SNR peak height (step ST42), and is still at this time. If the trigger signal is not output from the focal length setting unit 53 (step ST43: NO), the maximum measurable distance and SNR peak height are overwritten and stored in the internal memory (step ST44).
When the SNR acquisition unit 62 has already obtained the trigger signal from the focal length setting unit 53 at the time of acquiring the maximum measurable distance and the SNR peak height specified by the SNR calculation unit 61 (step ST43: YES) And the obtained maximum measurable distance and SNR peak height are switched and determined as determination index information b _after and d _after indicating the maximum measurable distance and SNR peak height specified immediately after the trigger signal is output. To the unit 63. In addition, the maximum measurable distance and SNR peak height stored in the internal memory are determined by the determination index information b _before , d indicating the maximum measurable distance and SNR peak height specified immediately before the trigger signal is output. _It is output to the switching determination unit 63 as _before (step ST45).

The switching determination unit 63 performs the comparison process of the maximum measurable distance before and after the trigger signal output acquired by the SNR acquisition unit 62 and the comparison process of the SNR peak height before and after the trigger signal output, so that the telescope switch 5 It is determined whether the target telescope has been switched normally.
FIG. 16 is an explanatory diagram showing changes in SNR when the focal length of the telescope after switching is shorter than the focal length of the telescope before switching.
Hereinafter, the determination process by the switching determination unit 63 will be specifically described with reference to FIG.

When the focal length of the telescope after switching is shorter than the focal length of the telescope before switching, the maximum measurable distance decreases as shown in FIG.
b _after <b _before
Further, as shown in FIG. 16A, the SNR peak height increases.
d _after > d _before
On the other hand, when the focal length of the telescope after switching is longer than the focal length of the telescope before switching, the maximum measurable distance increases and the SNR peak height decreases.
b _after > b _before
d _after <d _before

When the switching determination unit 63 receives the determination index information b _before , b _after , d _before , d _after from the SNR acquisition unit 62, the focal length setting unit 53 causes the focal length of the telescope after switching to be the focal point of the telescope _before switching. When set shorter than the distance (step ST46: YES), as shown in the following formulas (11) and (12), the switching determination change amounts ΔB and ΔD which are constants set in advance are used. Then, threshold values Th ₄ and Th ₇ for switching determination are calculated (step ST47).
Th ₄ = b _before −ΔB (11)
Th ₇ = d _before + ΔD (12)

Further, when the focal length setting unit 53 sets the focal length of the telescope after switching to be longer than the focal length of the telescope before switching (step ST46: NO), the switching determination unit 63 determines the following formula ( 13) As shown in (14), threshold values Th ₃ and Th ₈ for switching determination are calculated using switching determination change amounts ΔB and ΔD which are constants set in advance (step ST48).
Th ₃ = b _before + ΔB (13)
Th ₈ = c _before −ΔD (14)

When the switching determination unit 63 calculates the switching determination thresholds Th ₄ and Th ₇ , the switching determination unit 63 compares the determination index information d _after and the switching determination threshold Th ₇ , and if the determination index information d _after is equal to or less than the switching determination threshold Th _7. If (step ST49: NO), it is determined that the telescope is not switched normally (step ST54). That is, it is determined that the switching is abnormal.
If the determination index information d _after is greater than the switching determination threshold Th ₇ (in the case of YES at step ST49), the switching determination unit 63 compares the determination index information b _after and the switching determination threshold Th ₄ and determines the determination index information b. _{If after} is greater than or equal to switching determination threshold Th ₄ (step ST50: NO), it is determined that the telescope has not been switched normally (step ST54).
If the determination index information b _after is smaller than the switching determination threshold Th ₄ (in the case of YES at step ST50), the switching determination unit 63 determines that the telescope has been switched normally (step ST53).

When the switching determination unit 63 calculates the switching determination thresholds Th ₃ and Th ₈ , the switching determination unit 63 compares the determination index information d _after and the switching determination threshold Th ₈ , and if the determination index information d _after is greater than or equal to the switching determination threshold Th _8. If (step ST51: NO), it is determined that the telescope is not switched normally (step ST54).
If the determination index information d _after is smaller than the switching determination threshold Th ₈ (step ST51: YES), the switching determination unit 63 compares the determination index information b _after with the switching determination threshold Th ₃ , and determines the determination index information b. _{If after} is equal to or less than the switching determination threshold Th ₃ (step ST52: NO), it is determined that the telescope has not been switched normally (step ST54).
If the determination index information b _after is greater than the switching determination threshold Th ₃ (in the case of YES at step ST52), the switching determination unit 63 determines that the switching of the telescope is normally performed (step ST53).

The alarm presenting unit 20 displays that the system is normal when the switching determining unit 63 determines that the telescope to be used is normally switched (step ST55).
Further, when the switching determination unit 63 determines that the target telescope is not normally switched, the alarm presenting unit 20 displays an alarm indicating that a system abnormality has occurred (step ST56).

  As is apparent from the above, according to the third embodiment, the focal length setting unit 53 that sets different focal lengths for the telescopes 51 and 52 is provided, and the maximum measurable distance before and after the trigger signal is output. And the SNR peak height comparison process are performed so as to determine whether or not the telescope to be used has been normally switched by the telescope switcher 5, and thus the telescope 51 having the same aperture diameter. , 52 can be used to notify the user of the occurrence of a system abnormality without mounting a photodetector or the like.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 large-aperture telescope (telescope) 2 small-aperture telescope (telescope) 3 telescope switching unit 4 telescope switching controller 5 telescope switching unit 6 laser light oscillation unit 7 light source 8 light distributor 9 light modulator DESCRIPTION OF SYMBOLS 10 Laser beam transmission / reception part, 11 Transmission / reception separation part, 12 Optical mixer, 13 Optical heterodyne receiver, 14 Signal processing part, 15 A / D converter, 16 SNR calculation part (signal-to-noise ratio calculation part), 17 Wind speed Calculation unit, 18 SNR acquisition unit, 19 switching determination unit, 20 alarm presentation unit, 21 SNR calculation unit (signal-to-noise ratio calculation unit), 22 SNR acquisition unit, 23 switching determination unit, 31 SNR calculation processing circuit, 32 wind speed calculation Processing circuit, 33 SNR acquisition processing circuit, 34 switching determination processing circuit, 41 memory, 42 processor, 51, 52 telescope, 53 focal length setting unit, 61 SNR calculation unit ( Signal-to-noise ratio calculation unit), 62 SNR acquisition unit, 63 switching determination unit.

Claims (7)

Multiple telescopes with different aperture diameters;
Among the plurality of telescopes, a telescope switching unit that switches a target telescope used for transmitting and receiving laser light; and
A laser beam oscillation unit for oscillating a laser beam;
Using the target telescope switched by the telescope switching unit, the laser beam oscillated by the laser beam oscillation unit is radiated into the atmosphere, and then the scattered light of the laser beam returned by the aerosol is returned. A laser beam transmitter / receiver for receiving;
A signal-to-noise ratio calculation unit that calculates a signal-to-noise ratio of a received signal of the scattered light every time scattered light is received by the laser light transmitting and receiving unit;
Among the signal-to-noise ratios calculated by the signal-to-noise ratio calculation unit, by comparing the signal-to-noise ratio before and after the telescope to be used is switched by the telescope switching unit, the telescope switching unit A switching determination unit that determines whether or not the target telescope has been switched normally;
A laser radar apparatus comprising: an alarm presenting unit that presents an alarm indicating that an abnormality has occurred when the switching determination unit determines that the target telescope has not been switched normally. The signal-to-noise ratio calculator is
The frequency spectrum in a plurality of distance regions in the received signal of the scattered light received by the laser beam transmitting / receiving unit is calculated, and the focusing distance of the plurality of telescopes changes in the frequency spectrum in the plurality of distance regions. 2. The laser radar device according to claim 1, wherein a signal-to-noise ratio of a frequency spectrum in a distance region in which a signal-to-noise ratio of the plurality of telescopes does not change is calculated. Multiple telescopes,
A focal length setting unit for setting different focal lengths for the plurality of telescopes;
Among the plurality of telescopes, a telescope switching unit that switches a target telescope used for transmitting and receiving laser light; and
A laser beam oscillation unit for oscillating a laser beam;
Using the target telescope switched by the telescope switching unit, the laser beam oscillated by the laser beam oscillation unit is radiated into the atmosphere, and then the scattered light of the laser beam returned by the aerosol is returned. A laser beam transmitter / receiver for receiving;
A signal-to-noise ratio calculation unit that calculates a signal-to-noise ratio of a received signal of the scattered light every time scattered light is received by the laser light transmitting and receiving unit;
Among the signal-to-noise ratios calculated by the signal-to-noise ratio calculation unit, by comparing the signal-to-noise ratio before and after the telescope to be used is switched by the telescope switching unit, the telescope switching unit A switching determination unit that determines whether or not the target telescope has been switched normally;
A laser radar apparatus comprising: an alarm presenting unit that presents an alarm indicating that an abnormality has occurred when the switching determination unit determines that the target telescope has not been switched normally. The signal-to-noise ratio calculation unit calculates a frequency spectrum in a plurality of distance regions in the received signal of the scattered light every time the scattered light is received by the laser light transmission / reception unit. The signal-to-noise ratio of the frequency spectrum is calculated, and the aerosol-measurable distance is identified from the signal-to-noise ratio of the frequency spectrum in the plurality of distance regions,
The switching determination unit compares the distances that can be measured before and after the target telescope is switched by the telescope switching unit among the distances that can be measured by the signal-to-noise ratio calculation unit. 4. The laser radar device according to claim 1, wherein the telescope switching unit determines whether or not the telescope to be used has been switched normally. 5. The signal-to-noise ratio calculation unit calculates a frequency spectrum in a plurality of distance regions in the received signal of the scattered light every time the scattered light is received by the laser light transmission / reception unit. Calculate the signal-to-noise ratio of the frequency spectrum and identify the distance region where the signal-to-noise ratio peaks,
The switching determination unit compares the peak distance range before and after the target telescope is switched by the telescope switching unit in the peak distance region specified by the signal-to-noise ratio calculation unit. 4. The laser radar device according to claim 1, wherein the telescope switching unit determines whether or not the telescope to be used has been switched normally. 5. The signal-to-noise ratio calculation unit calculates a frequency spectrum in a plurality of distance regions in the received signal of the scattered light every time the scattered light is received by the laser light transmission / reception unit. Calculate the signal-to-noise ratio of the frequency spectrum and identify the value at which the signal-to-noise ratio peaks,
The switching determination unit compares the peak values before and after the target telescope is switched by the telescope switching unit among the peak values specified by the signal-to-noise ratio calculation unit. 4. The laser radar device according to claim 1, wherein the telescope switching unit determines whether or not the telescope to be used has been switched normally. 5.   2. The apparatus according to claim 1, further comprising: a wind speed calculation unit that calculates a Doppler shift amount due to the aerosol from a received signal of scattered light received by the laser beam transmitting / receiving unit and converts the Doppler shift amount into a wind speed. The laser radar device according to claim 6.

Images