Wind speed detection device, wind speed detection method, and flight vehicle control device

Abstract

To provide a wind speed detection device, a wind speed detection method, and a flight vehicle control device capable of sufficiently securing wind speed resolution and a CNR of signal light regardless of a level of linearity of frequency modulation.SOLUTION: The wind speed detection device 1 includes an output unit 2 that outputs laser light L whose frequency is linearly modulated with time, a splitting unit 3 that splits the laser light L into measurement light Lm and reference light Lr, a first amplification unit (conversion unit) 5 that converts the measurement light Lm into pulsed light, a measurement optical system 7 that outputs the measurement light Lm into the atmosphere M and receives scattered light Lf of the measurement light Lm in the atmosphere M as signal light Ls, and a detection unit 9 that outputs a detection signal D based on an interference result between the reference light Lr and the signal light Ls.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a wind speed detection device, a wind speed detection method, and an aircraft control device. [Background technology]

[0002] LIDAR (Light Detection and Ranging) is known as a sensing technology that uses light. LIDAR has recently been applied to autonomous driving, but it was originally widely used in fields such as meteorology. A well-known example of LIDAR used in the meteorological field is wind LIDAR, which detects wind speed. Wind LIDAR is used, for example, to survey wind conditions to select locations for wind turbines. In addition, it is expected to be applied in the safe operation management of unmanned aerial vehicles such as drones, and manned aerial vehicles such as advanced air mobility (AAM) and urban air mobility (UAM).

[0003] Coherent detection is used to detect wind speed in LIDAR. In this method, laser light output from a light source is split into measurement light and reference light, and the measurement light is modulated and amplified before being emitted into the atmosphere. The signal source in WindLIDAR is scattered light generated when the measurement light is scattered by countless aerosols in the atmosphere. When the wind blows, the aerosols move with the wind, causing a change in the frequency of the scattered light (Doppler shift). Therefore, the scattered light from the atmosphere is used as signal light to interfere with the reference light, and the amount of shift in the peak frequency in the beat spectrum of the interference light can be used to detect wind speed in the atmosphere (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0109218 [Non-patent literature]

[0005] [Non-Patent Document 1] Gerhard Peters, Piet Markmann, “Wind Ranger 100 / 200 FM-CW Doppler Wind Lidar for Wind Profiles for Low Range Wind Profiles” (METEK GmbH technical document) [Non-patent document 2] GerhardPeters, Piet Markmann, “Removal of range uncertainty of CW Wind Lidar by frequency modulation” (METEK GmbH technical document) Summary of the Invention [Problem to be solved by the invention]

[0006] One LIDAR method is the frequency-modulated continuous wave (FMCW) method, which uses frequency-modulated continuous wave (CW) light as the measurement light (see, for example, Non-Patent Documents 1 and 2). Non-Patent Documents 1 and 2 disclose that by using linearly frequency-modulated CW light as the measurement light, it is possible to distinguish between positive and negative Doppler shifts (tailwind and headwind). However, with the existing FMCW method, when the linearity of the frequency modulation is low, the spectral width of the beat spectrum of the interference light widens, resulting in a decrease in wind speed resolution and the carrier-to-noise ratio (CNR) of the signal light.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a wind speed detection device, a wind speed detection method, and an aircraft control device that can sufficiently ensure wind speed resolution and CNR of signal light regardless of the level of linearity of frequency modulation. [Means for solving the problem]

[0008] The gist of the present disclosure is as follows.

[0009] [1] A wind speed detection device comprising: an output unit that outputs laser light whose frequency is linearly modulated with time; a branching unit that branches the laser light into measurement light and reference light; a conversion unit that converts the measurement light into pulsed light; a measurement optical system that outputs the measurement light into the atmosphere and receives scattered light of the measurement light in the atmosphere as signal light; and a detection unit that outputs a detection signal based on the interference result between the reference light and the signal light.

[0010] In this wind speed detection device, laser light whose frequency is linearly modulated over time is converted into pulsed light and used as the measurement light. When coherent detection is performed using such measurement light, the pulsed light used as the measurement light contains only a portion of the frequency that is linearly modulated over time. This improves linearity within the time width of the pulsed light, even if the linearity of the frequency modulation is low, and suppresses the broadening of the spectral width of the beat spectrum of the interference light. Therefore, this wind speed detection device can ensure sufficient wind speed resolution and CNR of the signal light, regardless of the level of linearity of the frequency modulation.

[0011] [2] The wind speed detection device according to [1], wherein the output unit outputs light having an increasing region in which the frequency increases linearly with time and a decreasing region in which the frequency decreases linearly with time as the laser light, and the converter converts the measurement light into the pulsed light so as to generate at least one of a first pulsed light including only frequencies corresponding to the increasing region and a second pulsed light including only frequencies corresponding to the decreasing region. In this case, since the pulsed light does not include frequencies that straddle both the increasing region and the decreasing region, it is easy to associate changes in the beat spectrum of the interference light with the wind speed, and wind speed detection can be performed effectively.

[0012] [3] The wind speed detection device according to [2], wherein the converter converts the measurement light into the pulsed light so as to generate both the first pulsed light and the second pulsed light. In this case, it is possible to ensure sufficient accuracy in associating a change in the beat spectrum of the interference light with the wind speed, thereby improving the accuracy of wind speed detection.

[0013] [4] The wind speed detection device according to [3], wherein the converter converts the measurement light into the pulsed light so that the first pulsed light includes frequencies in the first half of the time axis in the increasing region, and the second pulsed light includes frequencies in the first half of the time axis in the decreasing region. The scattered light pulses tend to be shifted in a delayed direction. By including frequencies in the first half of the time axis in the signal light pulses, the time delay of the scattered light pulses can be sufficiently tolerated.

[0014] [5] The wind speed detection device according to any one of [1] to [4], wherein an optical path difference adjustment unit that adjusts the optical path difference between the reference light and the signal light is disposed in the optical path between the branching unit and the detection unit. By making the optical path length of the signal light longer than that of the reference light, it is possible to obtain a beat spectrum of the interference light with sufficient accuracy even when the detection distance is short. Furthermore, when the optical path length difference between the signal light Ls and the reference light Lr is reduced, PIIN (Phase Induced Intensity Noise) is reduced.

[0015] [6] The wind speed detection device according to any one of [1] to [5], wherein the measurement optical system has a light focusing adjustment unit that adjusts the focusing state of the measurement light output into the atmosphere. In this case, for example, by controlling the state of the measurement light based on the detection distance, optimal wind speed detection can be performed according to the detection distance.

[0016] [7] The wind speed detection device according to any one of [1] to [6], wherein the output unit outputs CW light as the laser light, and the detection unit outputs a detection signal based on the interference result between the reference light, which is CW light, and the signal light. By using CW light as the reference light, an interference signal between the signal light and the reference light can be obtained regardless of the setting of the detection distance, even if the signal light is pulsed light or a state in which multiple pulsed light beams are superimposed in time.

[0017] [8] The wind speed detection device according to any one of [1] to [7], wherein the measurement optical system has a deflector that deflects the output direction of the measurement light toward the atmosphere. In this case, the output direction of the measurement light is variable, making it possible to measure a three-dimensional wind speed vector including information on wind direction and wind speed.

[0018] [9] The wind speed detection device according to any one of [1] to [8], wherein at least the output section, the branching section, and the detection section are configured by optical integrated circuits. By configuring at least the output section, the branching section, and the detection section by optical integrated circuits, it is possible to achieve miniaturization of the device.

[0019]

[10] The wind speed detection device according to any one of [1] to [9], further comprising an analysis unit that analyzes the wind speed in the atmosphere based on the detection signal. In this case, a series of processes from outputting the laser light to analyzing the wind speed can be performed within a single device.

[0020]

[11] A wind speed detection method comprising: an output step of outputting laser light whose frequency is linearly modulated with time; a branching step of branching the laser light into measurement light and reference light; a conversion step of converting the measurement light into pulsed light; a measurement step of outputting the measurement light into the atmosphere and receiving scattered light of the measurement light in the atmosphere as signal light; and a detection step of outputting a detection signal based on the interference result between the reference light and the signal light.

[0021] In this wind speed detection method, laser light whose frequency is linearly modulated over time is converted into pulsed light and used as the measurement light. When coherent detection is performed using such measurement light, the pulsed light used as the measurement light contains only a portion of the frequency that is linearly modulated over time. This improves linearity within the time width of the pulsed light, even if the linearity of the frequency modulation is low, and suppresses the broadening of the spectrum width of the beat spectrum of the interference light. Therefore, this wind speed detection method can ensure sufficient wind speed resolution and CNR of the signal light, regardless of the level of linearity of the frequency modulation.

[0022]

[12] The wind speed detection method according to

[11] , wherein in the output step, light having an increasing region in which the frequency increases linearly with time and a decreasing region in which the frequency decreases linearly with time is output as the laser light, and in the conversion step, the measurement light is converted into the pulsed light so as to generate at least one of a first pulsed light including only frequencies corresponding to the increasing region and a second pulsed light including only frequencies corresponding to the decreasing region. In this case, since the pulsed light does not include frequencies that straddle both the increasing region and the decreasing region, it is easy to associate changes in the beat spectrum of the interference light with the wind speed, and wind speed detection can be performed effectively.

[0023]

[13] The wind speed detection method according to

[12] , wherein the converting step converts the measurement light into the pulsed light so as to generate both the first pulsed light and the second pulsed light. In this case, it is possible to ensure sufficient accuracy in associating the change in the beat spectrum of the interference light with the wind speed, thereby improving the accuracy of wind speed detection.

[0024]

[14] The wind speed detection method according to

[13] , wherein the conversion step converts the measurement light into pulsed light so that the first pulsed light includes frequencies in the first half of the time axis in the increasing region, and the second pulsed light includes frequencies in the first half of the time axis in the decreasing region. The scattered light pulses tend to be shifted in a delayed direction. By including frequencies in the first half of the time axis in the signal light pulses, the time delay of the scattered light pulses can be sufficiently tolerated.

[0025]

[15] The wind speed detection method according to any one of

[11] to

[14] , wherein the measurement step adjusts the optical path difference between the reference light and the signal light. By making the optical path length of the signal light longer than that of the reference light, it is possible to obtain a beat spectrum of the interference light with sufficient accuracy even when the detection distance is short. Furthermore, when the optical path length difference between the signal light Ls and the reference light Lr is reduced, PIIN (Phase Induced Intensity Noise) is reduced.

[0026]

[16] The wind speed detection method according to any one of

[11] to

[15] , wherein the measurement step adjusts the focusing state of the measurement light output into the atmosphere. In this case, for example, by controlling the state of the measurement light based on the detection distance, it is possible to perform optimal wind speed detection according to the detection distance.

[0027]

[17] The wind speed detection method according to any one of

[11] to

[16] , wherein the output step outputs CW light as the laser light, and the detection step outputs a detection signal based on the interference result between the reference light, which is CW light, and the signal light. By using CW light as the reference light, an interference signal between the signal light and the reference light can be obtained regardless of the setting of the detection distance, even if the signal light is pulsed light or a state in which multiple pulsed light beams are superimposed in time.

[0028]

[18] The wind speed detection method according to any one of

[11] to

[17] , wherein the measuring step includes a deflecting step of deflecting the output direction of the measurement light toward the atmosphere. In this case, the output direction of the measurement light is variable, and it is possible to measure a three-dimensional wind speed vector including information on wind direction and wind speed.

[0029]

[19] The wind speed detection method according to any one of

[11] to

[18] , further comprising an analysis step of analyzing the wind speed in the atmosphere based on the detection signal. In this case, a series of processes from outputting laser light to analyzing the wind speed can be performed within a single device.

[0030]

[20] An aircraft control device comprising: a wind speed detection device according to any one of [1] to

[10] ; and a control device that generates control signals related to takeoff and landing of the aircraft based on the detection signal output from the wind speed detection device.

[0031] This aircraft control device uses a wind speed detection device to detect complex turbulence with high distance resolution, enabling safe operation management of aircraft such as drones, AAMs, and UAMs. [Effects of the Invention]

[0032] According to the present disclosure, it is possible to ensure sufficient wind speed resolution and CNR of signal light regardless of the level of linearity of frequency modulation. [Brief explanation of the drawings]

[0033] [Figure 1] 1A and 1B are schematic diagrams of an aircraft control device according to an embodiment of the present disclosure. [Figure 2] 10 is a schematic diagram showing a beat spectrum of interference light when the linearity of the measurement light and the reference light is high in a conventional FMCW system. FIG. [Figure 3] 1 is a schematic diagram showing a beat spectrum of interference light when the linearity of measurement light and reference light is low in a conventional FMCW system. [Figure 4] 10 is a schematic diagram showing a beat spectrum of interference light when the linearity of the measurement light and the reference light is high in the FM pulse method of the present embodiment. FIG. [Figure 5] 10 is a schematic diagram showing a beat spectrum of interference light when the linearity of the measurement light and the reference light is low in the FM pulse method of the present embodiment. FIG. [Figure 6] 1 is a schematic diagram of a wind speed detection device according to an embodiment of the present disclosure. [Figure 7] 1A is a schematic diagram showing the time waveform of the intensity of the measurement light, and FIG. 1B is a schematic diagram showing the frequency modulation of the measurement light. [Figure 8] 1(a) and 1(b) are diagrams illustrating the principle of wind speed measurement in this embodiment. [Figure 9] 1(a) and 1(b) are diagrams illustrating the principle of wind speed measurement in this embodiment. [Figure 10] 1(a) and 1(b) are diagrams illustrating the principle of wind speed measurement in this embodiment. [Figure 11] 10A is a diagram showing the relationship between the detection distance and the CNR when the pulse width is 200 ns, and FIG. 10B is a diagram showing the relationship between the detection distance and the amount of frequency shift when the pulse width is 200 ns. [Figure 12]10A is a diagram showing the relationship between the detection distance and the CNR when the pulse width is 400 ns, and FIG. 10B is a diagram showing the relationship between the detection distance and the amount of frequency shift when the pulse width is 400 ns. [Figure 13] (a) shows the intensity spectrum when the pulse width Δt is 200 ns, the chirp rate γ is 10 THz / s, and the detection distance Z is 30 m, and (b) shows the intensity spectrum when the pulse width Δt is 400 ns, the chirp rate γ is 2.5 THz / s, and the detection distance Z is 60 m. [Figure 14] FIG. 1 is a diagram showing the relationship between chirp rate and CNR. [Figure 15] 1 is a flowchart illustrating an example of a wind speed detection method according to an embodiment of the present disclosure. [Figure 16] FIG. 10 is a schematic diagram of a wind speed detection device according to another embodiment of the present disclosure. [Figure 17] 10A and 10B are diagrams illustrating states of measurement light for each detection distance. [Figure 18] 10(a) and 10(b) are diagrams illustrating how wind speed is detected at detection distances of 60 m to 900 m in Example 1. FIG. [Figure 19] 10(a) and 10(b) are diagrams illustrating how wind speed is detected at detection distances of 60 m to 900 m in Example 1. FIG. [Figure 20] 10(a) to 10(c) are diagrams illustrating how wind speed is detected at a detection distance of 10 m in Example 2. [Figure 21] 10(a) to 10(c) are diagrams showing how wind speed is detected at a detection distance of 60 m in Example 2. [Figure 22] 10(a) and 10(b) are diagrams illustrating how wind speed is detected at detection distances of 90 m to 900 m in Example 2. FIG. [Figure 23] 10(a) and 10(b) are diagrams illustrating how wind speed is detected at detection distances of 90 m to 900 m in Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, preferred embodiments of a wind speed detection device, a wind speed detection method, and an aircraft control device according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0035] 1(a) and 1(b) are diagrams schematically illustrating an aircraft control device according to an embodiment of the present disclosure. As shown in Fig. 1(a) and 1(b), the aircraft control device 101 is configured to include a wind speed detection device 1 and a control device 102 that controls the operation of the aircraft H based on a detection signal D (see Fig. 6) output from the wind speed detection device 1. Examples of the aircraft H include unmanned aircraft such as drones, and manned aircraft such as AAM (Advanced Air Mobility) or UAM (Urban Air Mobility).

[0036] The aircraft control device 101 is installed, for example, near the ground surface. The installation height of the aircraft control device 101 is assumed to be, for example, a layer of the atmosphere called the ground layer. The ground layer refers to an atmospheric layer at a height of 100 m or less from the ground surface where the vertical gradient of wind speed and temperature is particularly large. The aircraft control device 101 may be installed on the ground surface, for example, as shown in FIG. 1(a). The aircraft control device 101 may be installed on the rooftop or roof of a building or other structure, as shown in FIG. 1(b). The aircraft control device 101 may be incorporated as a device in a control tower that operates the aircraft H.

[0037] The wind speed detection device 1 is a device that detects wind speed in the atmosphere. In the aircraft control device 101, the wind speed detection device 1 detects complex turbulence caused by many structures, particularly near the ground, and outputs a detection signal D to the control device 102. The control device 102 is a device that generates a control signal Q related to the takeoff and landing of the aircraft H. The control device 102 is physically a computer system equipped with memory such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, a storage unit such as a hard disk, and a display unit such as a display. Based on the detection signal D from the wind speed detection device 1, the control device 102 outputs a control signal Q to the aircraft H related to, for example, the speed, route, or permission / prohibition of takeoff and landing of the aircraft H during takeoff and landing.

[0038] The wind speed detection device 1 may transmit the detection signal D to a server owned by a weather information provider. In this case, for example, the weather information provider may make a weather forecast based on the detection signal D and weather data transmitted to the server, and transmit the generated weather forecast information from a terminal device or the like to an aircraft control device 101 in the control tower. The aircraft control device 101 in the control tower may generate a control signal Q based on the weather forecast information. The wind speed detection device 1 may transmit the detection signal D directly to the aircraft control device 101 in the control tower.

[0039] Next, we will explain the above-mentioned wind speed detection device 1. The wind speed detection device 1 is a device that uses LIDAR (Light Detection and Ranging) to detect wind speed in the atmosphere M. The wind speed detection device 1 detects wind speed in the atmosphere M by using measurement light Lm, which is a pulsed laser beam, and performing coherent detection using signal light Ls and reference light Lr.

[0040] Conventional LIDAR methods include the FMCW (Frequency-Modulated Continuous Wave) method, which uses frequency-modulated CW (Continuous Wave) light as the measurement light. The FMCW method uses linearly frequency-modulated CW light as the measurement light, making it possible to distinguish between positive and negative Doppler shifts (tailwinds and headwinds). However, the existing FMCW method has the problem that the wind speed resolution and the carrier-to-noise ratio (CNR) of the signal light depend on the linearity of the frequency modulation.

[0041] In the existing FMCW system, when the linearity of the frequency modulation of the measurement light and reference light is high, the linearity of the frequency modulation of the signal light from the atmosphere is also maintained, as shown in Figure 2. The frequency difference f between the signal light and the reference light at a wind speed of 0 m / s is SHIFT is determined by the chirp rate and the detection distance. Therefore, by Fourier transforming the interference signal between the signal light and the reference light, the frequency f SHIFT A beat spectrum of the interference light with a peak at

[0042] On the other hand, in the existing FMCW system, if the linearity of the frequency modulation of the measurement light and reference light is low, the linearity of the frequency modulation of the signal light from the atmosphere will also remain low, as shown in Figure 3. The frequency difference between the signal light and the reference light changes over time. Therefore, when the interference signal between the signal light and the reference light is Fourier transformed, the spectral width of the beat spectrum of the interference light will widen, which may result in a decrease in wind speed resolution and the CNR (Carrier to Noise Ratio) of the signal light.

[0043] As will be described later, the wind speed detection device 1 according to this embodiment employs a so-called FM pulse method, in which laser light whose frequency is linearly modulated over time is converted into pulsed light and used as the measurement light. In this method, as shown in Figures 4 and 5, the pulsed light serving as the measurement light contains only a portion of the frequency that is linearly modulated over time. When the frequency modulation of the measurement light and reference light is highly linear, as shown in Figure 4, wind speed resolution and signal light CNR (Carrier to Noise Ratio) similar to that of the existing FMCW method can be obtained.

[0044] Furthermore, with this method, even if the linearity of the frequency modulation of the measurement light and reference light is low, the linearity of the frequency modulation is improved within the time width of the pulsed light, as shown in Figure 5, and the broadening of the spectral width of the beat spectrum of the interference light can be suppressed. Therefore, the wind speed detection device 1 can ensure sufficient wind speed resolution and CNR of the signal light regardless of the level of linearity of the frequency modulation. Each component of the wind speed detection device 1 will be described below.

[0045] 6 is a schematic diagram of a wind speed detection device according to an embodiment of the present disclosure. The device includes an output unit 2, a branching unit 3, a first amplifier (converter) 5, a second amplifier 6, a measurement optical system 7, a multiplexing unit 8, a detector 9, a digitizer 10, and an analyzer 11. In this embodiment, the output unit 2 and the branching unit 3, the branching unit 3 and the first amplifier 5, the first amplifier 5 and the second amplifier 6, the second amplifier 6 and the measurement optical system 7, the measurement optical system 7 and the multiplexing unit 8, the branching unit 3 and the multiplexing unit 8, and the multiplexing unit 8 and the detector 9 are all optically connected by optical fibers F.

[0046] In the wind speed detection device 1, at least the output unit 2, branch unit 3, and detection unit 9 are configured by a photonic integrated circuit (PIC) 12. In this embodiment, the output unit 2, branch unit 3, first amplification unit 5, second amplification unit 6, multiplexing unit 8, detection unit 9, and the optical fiber F connecting these are configured by the photonic integrated circuit 12.

[0047] The output unit 2 is a part that outputs laser light L whose frequency is linearly modulated over time. Examples of laser devices that make up the output unit 2 include a distributed feedback (DFB) laser device, a distributed Bragg reflector (DBR) laser device, and an external cavity laser device. Here, the laser light L output from the output unit 2 is CW light. The laser light L is not light such as diffused light, but is beam-like light with a certain directivity.

[0048] A current control unit and a temperature control unit (not shown) are connected to the output unit 2. The current control unit is a controller that supplies a drive current to the laser device that constitutes the output unit 2. The current control unit modulates the drive current to modulate the frequency of the laser light L output from the output unit 2. The temperature control unit is a controller that maintains a constant temperature of the laser device that constitutes the output unit 2. The temperature control unit is configured to include, for example, a thermistor and a Peltier element, and drives the Peltier element to maintain a constant temperature of the laser device based on the temperature measurement value of the thermistor attached to the laser device.

[0049] A signal generating unit 13 is connected to the output unit 2. The signal generating unit 13 generates a modulation signal G for the laser light L. The signal generating unit 13 is composed of, for example, a waveform generator, a function generator, etc. The signal generating unit 13 generates a voltage signal for modulating the current waveform output from the current control unit connected to the output unit 2 into an arbitrary shape. The modulation signal G generated by the signal generating unit 13 is also output to the digitizer 10 in order to synchronize the operation of the output unit 2 with the operation of the analysis unit 11.

[0050] The branching unit 3 is a unit that branches the laser light L from the output unit 2 into measurement light Lm and reference light Lr. The branching unit 3 is configured, for example, by an optical fiber coupler. The measurement light Lm is output from one output port of the branching unit 3 to the first amplification unit 5, and the reference light Lr is output from another output port of the branching unit 3 to the multiplexing unit 8. The reference light Lr is input to the multiplexing unit 8 as CW light.

[0051] In this embodiment, a delay fiber (optical path difference adjusting unit) 16 is connected between the branching unit 3 and the first amplifying unit 5. The delay fiber 16 is configured, for example, by a polarization-maintaining fiber, a fiber coil, or the like. The delay fiber 16 can adjust the optical path length difference between the signal light Ls and the reference light Lr input to the multiplexing unit 8. By making the optical path length of the signal light Ls longer than the optical path length of the reference light Lr, it becomes possible to obtain the beat spectrum of the interference light Ld with sufficient accuracy even when the detection distance is short.

[0052] The first amplifier 5 converts the measurement light Lm from the branching unit 3 into pulsed light. The first amplifier 5 is composed of, for example, a semiconductor optical amplifier or an optical fiber amplifier. The first amplifier 5 converts the measurement light Lm, which is CW light, into pulsed light by amplifying a specific component of the measurement light Lm. A current control unit and a temperature control unit (not shown) are connected to the first amplifier 5. The current control unit is a controller that supplies a drive current to the amplifier device that constitutes the first amplifier 5. The current control unit controls the amplification factor of the measurement light Lm in the first amplifier 5 by modulating the drive current. The temperature control unit is a controller that maintains a constant temperature of the amplifier device that constitutes the first amplifier 5. The temperature control unit is composed of, for example, a thermistor and a Peltier element, and drives the Peltier element to maintain a constant temperature of the amplifier device based on the temperature measurement value of the thermistor attached to the amplifier device.

[0053] FIG. 7(a) is a schematic diagram showing the time waveform of the intensity of the measurement light Lm. As shown in FIG. 7(a), the measurement light Lm is generated by converting CW laser light L, whose frequency is linearly modulated over time, into pulsed light in the first amplifier 5. The measurement light Lm is light whose intensity increases intermittently on the time axis with a pulse width Δt. FIG. 7(b) is a schematic diagram showing the frequency modulation of the measurement light. In this embodiment, the output unit 2 outputs, as the laser light L, light having an increasing region in which the frequency increases linearly over time and a decreasing region in which the frequency decreases linearly over time. The laser light L having such frequency modulation is then converted into pulsed light in the first amplifier 5 to generate the measurement light Lm.

[0054] The measurement light Lm is frequency-modulated to have, for example, a ramp waveform. In the example of FIG. 7(b), the frequency is modulated to have an UP ramp (increasing region) L UP and a DOWN ramp (decreasing region) L where the frequency decreases linearly over time. DOWN The first amplifier 5 alternates between the UP lamp L UP The first pulsed light LpA contains only the frequency corresponding to the DOWN lamp L DOWNThe measurement light Lm is converted into pulsed light so as to generate at least one of the first pulsed light LpA and the second pulsed light LpB, which includes only the frequencies corresponding to the first and second pulsed light LpA and LpB. In this embodiment, the measurement light Lm is converted into pulsed light so as to generate both the first pulsed light LpA and the second pulsed light LpB.

[0055] The first amplifier 5 amplifies the first pulsed light LpA by the UP lamp L UP The second pulsed light LpB includes the frequency in the first half of the time axis, and the second pulsed light LpB is DOWN The measurement light Lm is converted into pulsed light so as to include the frequency in the first half of the time axis. UP The second pulsed light LpB is located before the midpoint of the period of the DOWN lamp L DOWN It is located before the midpoint of the period.

[0056] The second amplifier 6 amplifies the intensity of the measurement light Lm that has become pulsed light. The second amplifier 6 is composed of, for example, a semiconductor optical amplifier or an optical fiber amplifier. A current control unit and a temperature control unit (not shown) are connected to the second amplifier 6. The current control unit is a controller that supplies a drive current to the amplifier device that constitutes the second amplifier 6. The current control unit controls the amplification factor of the measurement light Lm in the second amplifier 6 by modulating the drive current. The temperature control unit is a controller that maintains a constant temperature of the amplifier device that constitutes the second amplifier 6. The temperature control unit is composed of, for example, a thermistor and a Peltier element, and drives the Peltier element to maintain a constant temperature of the amplifier device based on the temperature measurement value of the thermistor attached to the amplifier device.

[0057] The measurement optical system 7 outputs measurement light Lm into the atmosphere M and receives scattered light Lf of the measurement light Lm in the atmosphere M as signal light Ls. As shown in FIG. 6, the measurement optical system 7 includes a spatial optical system circulator 21, a movable stage (light focusing adjustment unit) 22, a lens 23, and a rotating stage (deflection unit) 25 on which a beam deflector 24 is mounted. The circulator 21 includes a polarizing beam splitter 26 and a λ / 4 wave plate 27. A lens 28 is disposed upstream of the polarizing beam splitter 26, and a lens 29 mounted on the movable stage 22 is disposed downstream of the λ / 4 wave plate 27. Furthermore, a lens 30 is disposed upstream of an optical fiber F connected to the detection unit 9, and is used to optically couple the signal light Ls to the optical fiber F.

[0058] To stabilize the performance of circulator 21, a temperature control unit (not shown) may be used to control the temperature of circulator 21 to be constant throughout the entirety. The temperature control unit includes, for example, a thermistor and a Peltier element, and drives the Peltier element based on the temperature measurement value of the thermistor attached to circulator 21 so that the temperature of the entirety of circulator 21 is maintained constant.

[0059] The movable stage 22 is a stage having a movable axis at least in the optical axis direction of the measurement light Lm. A driving element such as a stepping motor or a piezoelectric element is used to drive the movable stage 22. A stage controller (not shown) is connected to the movable stage 22. The stage controller outputs a control signal to the driving element to control the position of the movable stage 22.

[0060] The lens 23 is an optical element that collimates the measurement light Lm and outputs it into the atmosphere M. The lens 23 may be, for example, a convex lens, an achromatic lens, an aspherical lens, or a combination lens formed by combining multiple lenses. The lenses 23 and 29 form a pair of lenses that constitute a telescope. The distance between the lenses 23 and 29 is adjusted by displacing the movable stage 22 in the optical axis direction of the measurement light Lm. This allows the focal position of the measurement light Lm emitted into the atmosphere M via the lens 23 to be displaced in the optical axis direction of the measurement light Lm. In this embodiment, the distance between the lenses 23 and 29 is adjusted so that the measurement light Lm is output into the atmosphere M in a collimated state.

[0061] The beam deflector 24 is a component that deflects the output direction of the measurement light Lm toward the atmosphere M in any direction. For example, a wedge substrate can be used as the beam deflector 24. The rotation stage 25 is a stage that rotates the beam deflector 24 around the optical axis of the measurement light Lm. Driving elements such as a stepping motor and a piezoelectric element are used to drive the rotation stage 25. A stage controller (not shown) is connected to the movable stage 22. The stage controller outputs a control signal J to the driving element to control the position of the rotation stage. The control signal J is output to the signal generating unit 13 to synchronize the operations of the output unit 2 and the analyzing unit 11.

[0062] In the measurement optical system 7, the measurement light Lm emitted from the optical fiber F on the output side of the second amplifier unit 6 passes through a lens 23 and is emitted into the atmosphere M as a beam of light with a certain directivity. The output direction of the measurement light Lm changes based on the rotation angle of a beam deflector 24 caused by a rotation stage 25. The signal source in the wind speed detection device 1 is scattered light Lf generated when the measurement light Lm is scattered by countless aerosols P in the atmosphere M. A portion of the scattered light Lf returns to the measurement optical system 7 as signal light Ls via the lens 23. The signal light Ls is separated from the measurement light Lm by a circulator 21 and output to the multiplexer 8.

[0063] The multiplexing unit 8 multiplexes the reference light Lr from the branching unit 3 with the signal light Ls that has returned from the atmosphere M. The multiplexing unit 8 is configured, for example, by an optical fiber coupler. The multiplexing unit 8 generates interference light Ld between the reference light Lr and the signal light Ls. The interference light Ld is output from the output port of the multiplexing unit 8 to the detection unit 9.

[0064] The detection unit 9 is a part that outputs a detection signal D based on the interference result between the reference light Lr and the signal light Ls. In this embodiment, since the measurement light Lm is pulsed light, the scattered light Lf (signal light Ls) generated by scattering of the measurement light Lm at a specific distance is also pulsed light. On the other hand, the reference light Lr is a CW light that is obtained by branching a portion of the laser light L from the output unit 2 at the branch unit 3. Therefore, the detection unit 9 outputs a detection signal D based on the interference result between the reference light Lr, which is CW light, and the signal light Ls, which is a temporal superposition of multiple pulsed lights.

[0065] The detection unit 9 is composed of, for example, a photodetector, an avalanche photodiode, a balanced detector, etc. The detection unit 9 outputs an analog electrical signal based on the intensity of the interference light Ld input from the multiplexer 8 as a detection signal D to the digitizer 10. The digitizer 10 is a device that converts an analog electrical signal into a digital signal. The digitizer 10 is composed of, for example, an A / D converter, etc. The digitizer 10 converts the detection signal D, which is an analog electrical signal, into a digital signal and outputs the converted digital signal to the analysis unit 11.

[0066] The analysis unit 11 is a part that analyzes the wind speed in the atmosphere M based on the detection signal D. Physically, the analysis unit 11 is a computer system that includes memories such as RAM and ROM, processors such as CPU and GPU, a communication interface, and a storage unit such as a hard disk. Examples of such computer systems include personal computers, cloud servers, smart devices (smartphones, tablet terminals, etc.), microcomputers, and FPGAs (field-programmable gate arrays). The computer system functions as the analysis unit 11 by executing a program stored in the memory with the CPU or GPU.

[0067] As described above, the signal source in the wind speed detection device 1 is scattered light Lf generated when measurement light Lm is scattered by countless aerosols P in the atmosphere M. When wind blows in the atmosphere M, the aerosols P move with the wind, causing a change in frequency (Doppler shift) of the scattered light Lf. When the analysis unit 11 receives the detection signal D output from the digitizer 10, it refers to the peak frequency of the beat spectrum of the interference light Ld based on the detection signal D. The analysis unit 11 detects the wind speed in the atmosphere M by calculating the amount of shift in the peak frequency of the beat spectrum of the interference light Ld.

[0068] In the wind speed detection device 1, as shown in Figures 7(a) and 7(b), the laser light Lw whose frequency is linearly modulated with time is pulsed and used as the measurement light Lm. When there is no wind in the atmosphere M, as shown in Figure 8(a), the UP ramp L included in the first pulse LpA of the signal light Ls UP and the frequency difference between the reference light Lr and the DOWN ramp L included in the second pulse LpB of the signal light Ls. DOWN Therefore, as shown in FIG. 8(b), the frequency difference between the UP lamp L UP Intensity spectrum (average intensity spectrum) S UP The centroid frequency f UP and UP lamp L UP Intensity spectrum (average intensity spectrum) S DOWN The centroid frequency f DOWN is the reference frequency fSHIFT The match occurs at the reference frequency f SHIFT is expressed as follows: f where the chirp rate of the measurement light Lm is γ, the detection distance of the measurement light Lm is Z, and the speed of light is c. SHIFT =γ×((2×L) / 2).

[0069] When the wind in the atmosphere M is a tailwind blowing in the positive direction with respect to the optical axis of the measurement light Lm, as shown in FIG. 9(a), the UP ramp L included in the pulse of the signal light Ls UP The frequency of the DOWN ramp L included in the pulse of the signal light Ls DOWN The frequency of the UP ramp L UP Intensity spectrum (average intensity spectrum) S UP The centroid frequency f UP is the reference frequency f SHIFT The frequency shifts to the higher side than the DOWN ramp L DOWN Intensity spectrum (average intensity spectrum) S DOWN The centroid frequency f DOWN is the reference frequency f SHIFT The center of gravity frequency f UP and centroid frequency f DOWN The wind direction can be determined based on the direction of the shift of the reference frequency f SHIFT The centroid frequency f from UP and centroid frequency f DOWN Shift amount f dоpper The wind speed can be calculated based on the

[0070] When the wind in the atmosphere M is blowing in the negative direction (headwind) with respect to the optical axis of the measurement light Lm, as shown in FIG. 10(a), the DOWN ramp L included in the pulse of the signal light Ls DOWN The frequency of the UP ramp L included in the pulse of the signal light Ls UP The frequency of the UP ramp L increases due to the Doppler shift. UP Intensity spectrum (average intensity spectrum) S UP The centroid frequency f UP is the reference frequency f SHIFTThe frequency shifts to the lower side than the DOWN lamp L DOWN Intensity spectrum (average intensity spectrum) S DOWN The centroid frequency f DOWN is the reference frequency f SHIFT The center of gravity frequency f UP and centroid frequency f DOWN The wind direction can be determined based on the direction of the shift of the reference frequency f SHIFT The centroid frequency f from UP and centroid frequency f DOWN Shift amount f dоpper The wind speed can be calculated based on the

[0071] In this embodiment, the chirp rate γ of the frequency modulation of the laser light L is changed according to the pulse width Δt of the measurement light Lm. FIG. 11(a) shows the relationship between the detection distance Z and the CNR of the signal light Ls when a measurement light Lm with a pulse width Δt of 200 ns is used, and FIG. 11(b) shows the relationship between the detection distance and the amount of frequency shift when the pulse width is 200 ns. FIG. 12(a) shows the relationship between the detection distance Z and the CNR of the signal light Ls when a measurement light Lm with a pulse width Δt of 400 ns is used, and FIG. 12(b) shows the relationship between the detection distance and the amount of frequency shift when the pulse width is 400 ns. FIG. 13(a) shows the intensity spectrum when the pulse width Δt is 200 ns, the chirp rate γ is 10 THz / s, and the detection distance Z is 30 m, and FIG. 13(b) shows the intensity spectrum when the pulse width Δt is 400 ns, the chirp rate γ is 2.5 THz / s, and the detection distance Z is 60 m.

[0072] The results in Figures 11, 12, 13(a), and 13(b) show that as the chirp rate γ decreases, the signal component approaches DC as the detection distance Z decreases, making it difficult to detect the wind speed (difficult to detect the center of gravity frequency). Also, Figure 14 shows the relationship between the chirp rate γ and CNR when the pulse width Δt is 200 ns and 400 ns. As shown in Figure 14, in order to achieve a CNR similar to that achieved when a frequency shifter is used (approximately CNR 1.0), the chirp rate γ should be small.

[0073] From the results of Figure 14, when the pulse width Δt is 200 ns, it is preferable to set the chirp rate γ to approximately 10 THz / s or less. Furthermore, when the pulse width Δt is 400 ns, it is preferable to set the chirp rate γ to approximately 2.5 THz / s or less. Taking into account the results of Figures 11 to 13, it is preferable to select the chirp rate γ within a range that does not limit the detectable range as much as possible when the detection distance Z is short. As described above, by using the delay fiber (optical path difference adjustment unit) 16 between the branching unit 3 and the first amplification unit 5 to make the optical path length of the signal light Ls longer than the optical path length of the reference light Lr, it is possible to expand the detectable range when the detection distance is short.

[0074] Furthermore, as in another embodiment described later (see FIG. 16), when the detection distance Z is short, a method of focusing the measurement light Lm in the atmosphere M is adopted, and by setting the chirp rate γ and pulse width Δt appropriate for the focusing method, it is possible to expand the detectable range when the detection distance is short. Details of this embodiment will be described later.

[0075] 15 is a flowchart showing an example of a wind speed detection method according to an embodiment of the present disclosure. The wind speed detection method according to this embodiment is implemented using the above-described wind speed detection device 1. As shown in FIG. 15, this wind speed detection method includes a setting step S01, an output step S02, a branching step S03, a conversion step S04, a measurement step S05, a detection step S06, and an analysis step S07.

[0076] The setting step S01 is a step for setting various measurement conditions used for wind speed detection. In the setting step S01, first, parameters independent of the pulse width Δt are set. Examples of parameters independent of the pulse width Δt include the diameter of the lens 23, the pulse waveform of the measurement light Lm, and the pulse repetition frequency of the measurement light Lm. Next, in the setting step S01, the pulse width Δt is set, and the chirp rate γ of the laser light L is determined according to the set pulse width Δt. In addition, in the setting step S01, the intensity of the laser light L output from the output unit 2, the light amplification factors in the first amplifier unit 5 and the second amplifier unit, the output direction of the measurement light Lm by the beam deflector 24, etc. are set.

[0077] The output step S02 is a step of outputting laser light L whose frequency is modulated linearly and periodically. In the output step S02, the laser light L, which is a CW light, is output from the output unit 2. To modulate the frequency of the laser light L, a modulation signal G generated by the signal generating unit 13 is input to the output unit 2. This generates laser light L whose frequency is modulated linearly and periodically, and outputs it from the output unit 2. In this embodiment, the UP lamp L UP and DOWN lamp L DOWN The frequency of the laser light L is modulated so as to form a ramp waveform that alternately includes

[0078] The branching step S03 is a step of branching the laser light L into measurement light Lm and reference light Lr. In the branching step S03, the laser light L output from the output unit 2 is branched by the branching unit 3, one of which is the measurement light Lm and the other is the reference light Lr. The measurement light Lm is input to the first amplification unit 5 via the delay fiber 16, and the reference light Lr is input to the multiplexing unit 8.

[0079] The conversion step S04 is a step of converting the measurement light Lm into pulsed light. In the conversion step S04, the first amplifier 5 amplifies a specific component of the measurement light Lm, thereby converting the measurement light Lm, which is CW light, into pulsed light. In the conversion step S04, the UP lamp L UP The first pulsed light LpA contains the frequency in the first half of the time axis, and the DOWN lamp LDOWN The second amplifier 6 amplifies the intensity of the converted pulsed light Lm, and then the second amplifier 6 amplifies the intensity of the converted pulsed light Lm, which is then input to the measurement optical system 7.

[0080] The measurement step S05 is a step of outputting the measurement light Lm into the atmosphere M and receiving scattered light Lf of the measurement light Lm in the atmosphere M as signal light Ls. In the measurement step S05, the measurement light Lm is output into the atmosphere M in a collimated state via the measurement optical system 7. The measurement light Lm is scattered by countless aerosols P in the atmosphere M and becomes scattered light Lf. A portion of the scattered light Lf returns to the measurement optical system 7 and is input to the multiplexing unit 8 as signal light Ls. In the multiplexing unit 8, the reference light Lr and the signal light Ls, which are CW lights, are multiplexed to generate interference light Ld.

[0081] The detection step S06 is a step of outputting a detection signal based on the interference result between the reference light Lr and the signal light Ls. In the detection step S06, the interference light Ld generated in the multiplexing unit 8 is detected by the detection unit 9, and an analog electrical signal based on the interference light Ld is generated as the detection signal D. The generated detection signal D is analog-to-digital converted by the digitizer 10 and output to the analysis unit 11.

[0082] Analysis step S07 is a step of analyzing the wind speed in the atmosphere M based on the detection signal D. In analysis step S07, the peak frequency of the beat spectrum of the interference light Ld is referenced based on the detection signal D. Then, the wind speed in the atmosphere M is detected by determining the amount of shift in the peak frequency in the beat spectrum of the interference light Ld. If detection is to be performed at a different distance, the detection distance, etc. is reset in step S01, and steps S02 to S07 are executed again. After wind speed detection has been performed within the desired distance range, the process ends.

[0083] As described above, in the wind speed detection device 1, the laser light L, whose frequency is linearly modulated over time, is converted into pulsed light and used as the measurement light Lm. When coherent detection is performed using such measurement light Lm, the pulsed light that is the measurement light Lm contains only a portion of the frequencies that are linearly modulated over time. This improves the linearity within the time width of the pulsed light, even if the linearity of the frequency modulation is low, and suppresses the broadening of the spectral width of the beat spectrum of the interference light Ld. Therefore, in the wind speed detection device 1, sufficient wind speed resolution and CNR of the signal light can be ensured regardless of the level of linearity of the frequency modulation.

[0084] In this embodiment, the output unit 2 is an UP ramp L whose frequency increases linearly with time. UP (increase region) and a DOWN ramp L where the frequency decreases linearly over time. DOWN (reducing region) and outputs the light having the UP lamp L. UP The first pulsed light LpA contains only the frequency corresponding to the DOWN lamp L DOWN The measurement light Lm is converted into pulsed light so that at least one of the first pulsed light LpB and the second pulsed light LpB containing only the frequencies corresponding to the UP lamp L UP and DOWN lamp L DOWN By not including frequencies that straddle both the above ranges, it becomes easy to associate the change in the beat spectrum of the interference light Ld with the wind speed, and wind speed detection can be performed appropriately.

[0085] In this embodiment, the first amplifier 5 converts the measurement light Lm into pulsed light so as to generate both the first pulsed light LpA and the second pulsed light LpB. In this case, it is possible to ensure sufficient accuracy in associating the change in the beat spectrum of the interference light Ld with the wind speed, thereby improving the accuracy of wind speed detection.

[0086] In this embodiment, the first amplifier 5 amplifies the first pulsed light LpA by the UP lamp L UP The second pulsed light LpB includes the frequency in the first half of the time axis, and the second pulsed light LpB is DOWNThe measurement light Lm is converted into pulsed light so that it contains frequencies in the first half of the time axis. The pulses of the scattered light Lf tend to be shifted in the direction of delay in time. By including frequencies in the first half of the time axis in the pulses of the signal light Ls, the time delay of the pulses of the scattered light Lf can be sufficiently tolerated.

[0087] In this embodiment, a delay fiber (optical path difference adjuster) 16 that adjusts the optical path difference between the reference light Lr and the signal light Ls is disposed in the optical path between the branching unit 3 and the detection unit 9 (here, the optical path between the branching unit 3 and the first amplification unit 5). By making the optical path length of the signal light Ls longer than the optical path length of the reference light Lr, it becomes possible to obtain the beat spectrum of the interference light Ld with sufficient accuracy even when the detection distance is short.

[0088] In this embodiment, the measurement optical system 7 has a movable stage (light collection adjustment unit) 22 that adjusts the light collection state of the measurement light Lm output into the atmosphere M. In this case, by controlling the state of the measurement light Lm based on, for example, the detection distance, it is possible to perform optimal wind speed detection according to the detection distance.

[0089] In this embodiment, the output unit 2 outputs CW light as the laser light L, and the detection unit 9 outputs a detection signal D based on the interference result between the reference light Lr, which is CW light, and the signal light Ls. By using CW light as the reference light Lr, an interference signal between the signal light Ls and the reference light Lr can be obtained regardless of the setting of the detection distance, even if the signal light Ls is pulsed light or a state in which multiple pulsed light beams are superimposed in time.

[0090] In this embodiment, the measurement optical system 7 has a rotation stage 25 on which a beam deflector 24 is mounted as a deflection unit that deflects the output direction of the measurement light Lm toward the atmosphere M. By using such a deflection unit, the output direction of the measurement light Lm can be changed, making it possible to measure a three-dimensional wind speed vector including information on the wind direction and wind speed.

[0091] In this embodiment, of the components of the wind speed detection device 1, at least the output unit 2, branching unit 3, and detection unit 9 are configured using an optical integrated circuit 12. By configuring at least the output unit 2, branching unit 3, and detection unit 9 using an optical integrated circuit 12, it is possible to reduce the size of the device. Furthermore, in this embodiment, the device further includes an analysis unit 11 that analyzes the wind speed in the atmosphere M based on the detection signal D. This allows a series of processes from outputting the laser light L to analyzing the wind speed to be performed within a single device.

[0092] Fig. 16 is a schematic diagram of a wind speed detection device according to another embodiment of the present disclosure. As shown in Fig. 16, in the wind speed detection device 1A, a delay fiber 16 is disposed between the branching unit 3 and the multiplexing unit 8, and the optical path length of the signal light Ls is substantially equal to the optical path length of the reference light Lr. By reducing the optical path length difference between the signal light Ls and the reference light Lr, PIIN (Phase Induced Intensity Noise) is reduced. The wind speed detection device 1A also includes a control unit 15 that controls the state of the measurement light Lm output from the measurement optical system 7 based on the detection distance Z of the measurement light Lm.

[0093] Like the analysis unit 11, the control unit 15 is physically a computer system equipped with memories such as RAM and ROM, processors such as CPU and GPU, a communication interface, and a storage unit such as a hard disk. Examples of such computer systems include personal computers, cloud servers, smart devices (smartphones, tablet terminals, etc.), microcomputers, and FPGAs (field-programmable gate arrays). The computer system functions as the analysis unit 11 by executing a program stored in the memory with the CPU or GPU. The analysis unit 11 and the control unit 15 may be configured by the same computer system.

[0094] The control unit 15 receives an input of a setting for the detection distance Z of the measurement light Lm. As shown in FIG. 17 , the control unit 15 controls the state of the measurement light Lm output from the measurement optical system 7 based on the input setting for the detection distance Z. In this embodiment, a first threshold T1 is set for the detection distance Z. When the detection distance Z falls within a short distance range R1 that is equal to or less than the first threshold T1, the control unit 15 controls the measurement optical system 7 so that the measurement light Lm output into the atmosphere M is condensed. When the detection distance Z falls within a long distance range R2 that exceeds the first threshold T1, the control unit 15 controls the measurement optical system 7 so that the measurement light Lm output into the atmosphere M is collimated. In either distance range, pulsed light whose frequency changes linearly with time is used as the measurement light Lm.

[0095] In this embodiment, a second threshold T2 is set for the short distance range R1. When the detection distance Z falls within the ultra-short distance range R1a, where the detection distance Z is equal to or less than the second threshold T2, the control unit 15 controls the first amplifier 5 so that the pulse width Δt of the measurement light Lm is constant regardless of the detection distance Z. In the ultra-short distance range R1a, the distance resolution does not depend on the pulse width Δt. Generally, the larger the pulse width Δt of the measurement light Lm, the higher the CNR of the signal light Ls tends to be. Therefore, it is preferable to set the pulse width Δt of the measurement light Lm in the ultra-short distance range R1a larger than the pulse width Δt of the measurement light Lm in the medium-to-short distance range R1b and the long distance range R2.

[0096] Furthermore, when the detection distance Z falls within the ultra-short distance range R1a, the control unit 15 controls the output unit 2 so that the chirp rate γ of the measurement light Lm decreases linearly according to the detection distance Z. In the ultra-short distance range R1a, stray light components generated by the measurement optical system 7 and other components become larger than the signal component and overlap with each other in time, which may make it difficult to analyze the wind speed based on the interference results between the reference light Lr and the signal light Ls. In response to this, using frequency-modulated light as the laser light L makes it possible to separate the signal component and the stray light component on the frequency axis. Furthermore, reducing the chirp rate γ according to the detection distance Z also improves the CNR of the measurement light Lm (see FIG. 14, etc.).

[0097] When the detection distance Z falls within the intermediate-short distance range R1b, which exceeds the second threshold T2 set for the short distance range R1, the control unit 15 controls the first amplifier (converter) 5 so that the pulse width Δt of the measurement light Lm changes according to the detection distance. In the intermediate-short distance range R1b, the control unit 15 controls the first amplifier 5 so that the pulse width Δt of the measurement light Lm increases linearly in proportion to the detection distance. The pulse width Δt of the measurement light Lm is set within a range in which the distance corresponding to the pulse width Δt is shorter than the detection distance. This makes it possible to separate the stray light component and the signal component on the time axis.

[0098] When the detection distance Z falls within the medium-to-short distance range R1b, the control unit 15 controls the output unit 2 so that the chirp rate γ of the measurement light Lm decreases linearly according to the detection distance Z, as in the case of the very short distance range R1a. In the medium-to-short distance range R1b, by setting the pulse width Δt as described above, the stray light component and the signal component are separated on the time axis, while the chirp rate γ is reduced according to the detection distance Z, thereby improving the CNR of the measurement light Lm.

[0099] When the detection distance Z falls within the long distance range R2, the control unit 15 controls the first amplifier unit 5 so that the pulse width Δt of the measurement light Lm is constant regardless of the detection distance Z. The pulse width Δt in the long distance range R2 is set to a range that balances the CNR and distance resolution. As an example, the pulse width Δt in the long distance range R2 is set to a range smaller than the pulse width Δt in the very short distance range R1a. Furthermore, the pulse width Δt in the long distance range R2 is set to a range larger than the minimum pulse width Δt used in the medium to short distance range R1b and smaller than the maximum pulse width Δt. In the long distance range R2, the distance resolution is determined by the pulse width Δt of the measurement light Lm, and a constant distance resolution is maintained regardless of the detection distance Z.

[0100] Furthermore, when the detection distance Z falls within the long distance range R2, the control unit 15 controls the output unit 2 so that the chirp rate γ of the measurement light Lm is constant regardless of the detection distance Z. As an example, the chirp rate γ in the long distance range R2 is set to the same value as the minimum value of the chirp rate γ in the medium to short distance range R1b.

[0101] This wind speed detection device 1A also exhibits the same effects as the wind speed detection device 1. Even if the linearity of the frequency modulation is low, the linearity is improved within the time width of the pulsed light, and the broadening of the spectral width of the beat spectrum of the interference light can be suppressed. Therefore, regardless of the level of linearity of the frequency modulation, the wind speed resolution and CNR of the signal light Ls can be sufficiently ensured. Furthermore, the wind speed detection device 1A can perform optimal wind speed detection according to the detection distance Z by controlling the state of the measurement light Lm based on the detection distance Z.

[0102] Examples of the present disclosure will be described below. In this example, Example 1 introduces an example of wind speed analysis at a detection distance range of 30 m to 900 m using the wind speed detection device 1. Also, Example 2 introduces examples of wind speed analysis at a detection distance of 10 m (ultra-short distance range), 30 m (medium-short distance range), and 60 m to 900 m (long distance range) using the wind speed detection device 1A.

[0103] Example 1 In Example 1, in the wind speed detection device 1, the movable stage 22 was used to adjust the distance between the lens 23 and the lens 29 so that the measurement light Lm output into the atmosphere M was a parallel beam. Next, the diameter of the lens 23 was set to 50 mm as a parameter independent of the pulse width Δt. Furthermore, as shown in FIG. 18(a), the pulse waveform of the measurement light Lm was set to a rectangular shape, and the pulse repetition frequency of the measurement light Lm was set to 100 kHz (=pulse interval Δr=10 μs).

[0104] Here, the pulse width Δt was set to 200 ns. The frequency of the measurement light Lm was linearly and periodically modulated so that the UP ramp and DOWN ramp alternated for each pulse. The chirp rate γ was set to 10 THz / s according to the pulse width Δt. Under these conditions, the measurement light Lm was started to be output into the atmosphere M, and the signal light Ls from the atmosphere M was detected by coherent detection. As shown in Figure 18(b), the detection signal D output from the digitizer 10 is a continuous signal with a time interval corresponding to the pulse repetition frequency of the measurement light Lm. Each pulse component of this signal contains information on the peak frequency of the beat spectrum of the interference light Ld at multiple distances that are integer multiples of the detection distance of 30 m.

[0105] To analyze wind speed, the obtained detection signal D is first divided into time slots with a pulse interval (=10 μs). Each time slot is then divided into sub-slots #1 to #30 with a 200 ns interval. Each data point in sub-slots #1 to #30 is multiplied by a 200 ns window function based on the pulse width Δt, and then a Fourier transform is performed to calculate the intensity spectrum of each. For example, a Blackman function can be used as the window function.

[0106] For each calculated intensity spectrum, the intensity for 5000 time slots is averaged to obtain the average intensity spectrum S of the UP lamp for every 30 m of detection distance, as shown in Fig. 19(a). UP30 , S UP60 , …S UP900 and the average intensity spectrum S of the DOWN lamp at every 30 m of detection distance DOWN30 , S DOWN60 , …S DOWN900 Based on the obtained average intensity spectrum, the centroid frequency f UP30 , f UP60 , …f UP900 and the centroid frequency f DOWN30 , f DOWN60 , …f DOWN900 and get.

[0107] Line-of-sight wind speed V based on centroid frequency LOSThe calculation formulas for are as follows: (1) and (2). Using formulas (1) and (2), the radial wind speed can be detected at intervals of 30 m at distances of 30 m to 900 m, as shown in FIG. 19(b). In formula (1), λ is the wavelength of the measurement light Lm. Radial wind speed V LOS is the wind speed in the output direction of the measurement light Lm emitted into the atmosphere M. Note that the centroid frequency f UP ,f DOWN If only one of the above is available, f is calculated using the following formula (3) or (4). dоppler In the following equations (3) and (4), γ is the chirp rate, Z is the detection distance, c is the speed of light, and τ is the time difference between the signal light Ls and the reference light Lr at a detection distance of 0 m. V LOS =λ×(f dоppler / twenty one) f dоppler =(f UP -f DOWN ) / twenty two) f dоppler =γ×(((2×Z) / c)+τ)-f UP …(3) f dоppler =f DOWN -γ×(((2×Z) / c)+τ) …(4)

[0108] <Example 2> To analyze wind speed at a detection distance of 10 m, the focus position of the measurement light Lm in the wind speed detection device 1A was first adjusted to 10 m using the movable stage 22. Next, the diameter of the lens 23 was set to 50 mm, a parameter independent of the pulse width Δt. Furthermore, as shown in Fig. 20(a), the pulse waveform of the measurement light Lm was set to rectangular, and the pulse repetition frequency of the measurement light Lm was set to 100 kHz (= pulse interval Δr = 10 μs).

[0109] Here, the pulse width Δt was set to 800 ns. The frequency of the measurement light Lm was linearly and periodically modulated so that the UP ramp and DOWN ramp alternated for each pulse. The chirp rate γ was set to 94 THz / s according to the pulse width Δt. Under these conditions, the measurement light Lm was started to be output into the atmosphere M, and the signal light Ls from the atmosphere M was detected by coherent detection. As shown in Figure 20(b), the detection signal D output from the digitizer 10 is a pulse signal with a time interval corresponding to the pulse repetition frequency of the measurement light Lm. Each pulse component of this signal contains information about the peak frequency of the beat spectrum of the interference light Ld at a detection distance of 10 m.

[0110] In wind speed analysis, the obtained detection signal D is first divided into time slots with a pulse interval (=10 μs). Next, each time slot is multiplied by a window function in the range of 0 ns to 800 ns, and then a Fourier transform is performed to calculate each intensity spectrum. By averaging the intensity spectra for 500 time slots for each of the UP ramp and DOWN ramp, the average intensity spectrum S of the UP ramp at a detection distance of 10 m is obtained, as shown in Figure 20(c). UP and the average intensity spectrum of the DOWN lamp S DOWN is obtained separated from the stray light component on the frequency axis. The obtained average intensity spectrum of the UP lamp, S UP and the average intensity spectrum of the DOWN lamp S DOWN Based on the center of gravity frequency f UP and f DOWN Obtain the centroid frequency f UP and f DOWN The line-of-sight wind speed V based on LOS The above-mentioned formulas (1) and (2) can be used to calculate the centroid frequency f UP ,f DOWN If only one of the above is available, f dоppler may be calculated.

[0111] To analyze wind speed at a detection distance of 60 m, the focus position of the measurement light Lm in the wind speed detection device 1A was first adjusted to 60 m using the movable stage 22. Next, the diameter of the lens 23 was set to 50 mm, a parameter independent of the pulse width Δt. Furthermore, as shown in FIG. 21(a), the pulse waveform of the measurement light Lm was set to rectangular, and the pulse repetition frequency of the measurement light Lm was set to 100 kHz (= pulse interval Δr = 10 μs).

[0112] Here, the pulse width Δt was set to 400 ns. The frequency of the measurement light Lm was linearly and periodically modulated so that the UP ramp and DOWN ramp alternated for each pulse. The chirp rate γ was set to 20 THz / s according to the pulse width Δt. Under these conditions, the measurement light Lm was started to be output into the atmosphere M, and the signal light Ls from the atmosphere M was detected by coherent detection. The detection signal D output from the digitizer 10 is a pulse signal with a time interval according to the pulse repetition frequency of the measurement light Lm, as shown in Figure 21(b). Each pulse component of this signal contains information about the peak frequency of the beat spectrum of the interference light Ld at a detection distance of 60 m.

[0113] In analyzing wind speed, first, the obtained detection signal D is divided into time slots with a pulse interval (=10 μs). Next, each time slot is multiplied by a window function in the range of 400 ns to 800 ns, and then a Fourier transform is performed to calculate each intensity spectrum. By averaging the intensity spectra for 500 time slots for each of the UP ramp and the DOWN ramp, the average intensity spectrum S of the UP ramp at a detection distance of 60 m is obtained, as shown in Figure 21(c). UP and the average intensity spectrum of the DOWN lamp S DOWN The average intensity spectrum of the UP lamp obtained is S UP and the average intensity spectrum of the DOWN lamp S DOWN Based on the center of gravity frequency f UP and f DOWN Obtain the centroid frequency f UP and f DOWN The line-of-sight wind speed V based on LOSThe above-mentioned formulas (1) and (2) can be used to calculate the centroid frequency f UP ,f DOWN If only one of the above is available, f dоppler may be calculated.

[0114] For wind speed analysis at detection distances of 90 m to 900 m, the distance between the lens 23 and the lens 29 in the wind speed detection device 1A was adjusted using the movable stage 22 so that the measurement light Lm output into the atmosphere M would be a parallel beam. Next, the diameter of the lens 23 was set to 50 mm, which is a parameter independent of the pulse width Δt. Furthermore, as shown in FIG. 22(a), the pulse waveform of the measurement light Lm was set to rectangular, and the pulse repetition frequency of the measurement light Lm was set to 100 kHz (= pulse interval Δr = 10 μs).

[0115] Here, the pulse width Δt was set to 200 ns. The frequency of the measurement light Lm was linearly and periodically modulated so that the UP ramp and DOWN ramp alternated for each pulse. The chirp rate γ was set to 10 THz / s according to the pulse width Δt. Under these conditions, the measurement light Lm was started to be output into the atmosphere M, and the signal light Ls from the atmosphere M was detected by coherent detection. As shown in Figure 18(b), the detection signal D output from the digitizer 10 is a pulse signal with a time interval corresponding to the pulse repetition frequency of the measurement light Lm. Each pulse component of this signal contains information on the peak frequency of the beat spectrum of the interference light Ld at multiple distances that are integer multiples of the detection distance of 30 m.

[0116] To analyze wind speed, the obtained detection signal D is first divided into time slots with a pulse interval (=10 μs). Each time slot is then divided into sub-slots #1 to #30 with a 200 ns interval. Each data point in sub-slots #3 to #30 is multiplied by a 200 ns window function based on the pulse width Δt, and then a Fourier transform is performed to calculate the respective intensity spectra. For example, a Blackman function can be used as the window function.

[0117] For each calculated intensity spectrum, the intensities for 5000 time slots are averaged to obtain the average intensity spectrum S of the UP lamp every 30 m after the detection distance of 90 m, as shown in Fig. 23(a). UP90 , S UP120 , …S UP900 and the average intensity spectrum S of the DOWN lamp every 30 m after the detection distance of 90 m. DOWN90 , S DOWN120 , …S DOWN900 Based on the obtained average intensity spectrum, the centroid frequency f UP90 , f UP120 , …f UP900 and the centroid frequency f DOWN90 , f DOWN120 , …f DOWN900 and obtain the line-of-sight wind speed V based on the centroid frequency. LOS The above-mentioned formulas (1) and (2) can be used to calculate the line-of-sight wind speed f as shown in Fig. 23(b), which can be used to detect the line-of-sight wind speed at intervals of 30 m at a distance of 90 m to 900 m. Note that the centroid frequency f UP ,f DOWN If only one of the above is available, f dоppler may be calculated.

[0118] The present disclosure is not limited to the above-described embodiment. For example, in the above-described embodiment, a configuration in which the spatial optical system type circulator 21 is used in the measurement optical system 7 is exemplified, but an optical fiber device type circulator may also be used in the measurement optical system 7. For example, by mounting an end of an optical fiber connected to an output port of the optical fiber device type circulator on a movable stage and changing the distance from the end of the optical fiber to the lens 23 using the movable stage, the focal position of the measurement light Lm emitted into the atmosphere M via the lens 23 can be displaced in the optical axis direction of the measurement light Lm.

[0119] Furthermore, in the above embodiment, the beam deflector 24 is used to deflect the output direction of the measurement light Lm toward the atmosphere M in any direction, but deflection of the output direction of the measurement light Lm may be achieved using other configurations. For example, a mirror may be disposed outside the lens 23, and the output direction of the measurement light Lm toward the atmosphere M may be deflected in any direction by adjusting the angle of the mirror. In an example in which an optical fiber device-type circulator is used in the measurement optical system 7, the output direction of the measurement light Lm toward the atmosphere M may be deflected in any direction by moving the orientation of the end of the optical fiber up, down, left, or right. [Explanation of symbols]

[0120] 1...wind speed detection device, 2...output section, 3...branching section, 5...first amplification section (conversion section), 7...measurement optical system, 9...detection section, 11...analysis section, 12...optical integrated circuit, 15...control section, 16...delay fiber (optical path difference adjustment section), 22...movable stage (focus adjustment section), 24...beam deflection plate (deflection section), 25...rotation stage (deflection section), M...atmosphere, L...laser light, LpA...first pulse light, LpB...second pulse light, L UP …UP ramp (increasing area), L DOWN ...DOWN lamp (decreasing region), Lm... measurement light, Lf... scattered light, Ls... signal light, Lr... reference light, D... detection signal, 101... flying vehicle control device, 102... control device, H... flying vehicle, Q... control signal.

Claims

1. an output unit that outputs laser light whose frequency is linearly modulated with time; a branching unit that branches the laser light into a measurement light and a reference light; a converter for converting the measurement light into pulsed light; a measurement optical system that outputs the measurement light into the atmosphere and receives scattered light of the measurement light in the atmosphere as signal light; a detection unit that outputs a detection signal based on the result of interference between the reference light and the signal light.

2. the output unit outputs, as the laser light, light having an increasing region in which the frequency increases linearly with time and a decreasing region in which the frequency decreases linearly with time; 2. The wind speed detection device according to claim 1, wherein the conversion unit converts the measurement light into the pulsed light so as to generate at least one of a first pulsed light including only frequencies corresponding to the increasing region and a second pulsed light including only frequencies corresponding to the decreasing region.

3. The wind speed detection device according to claim 2 , wherein the conversion unit converts the measurement light into the pulsed light so that both the first pulsed light and the second pulsed light are generated.

4. 4. The wind speed detection device according to claim 3, wherein the conversion unit converts the measurement light into the pulsed light so that the first pulsed light includes a frequency in a first half of the time axis in the increasing region, and the second pulsed light includes a frequency in a first half of the time axis in the decreasing region.

5. 2. The wind speed detection device according to claim 1, wherein an optical path difference adjusting unit is disposed in the optical path between the branching unit and the detecting unit, for adjusting an optical path difference between the reference light and the signal light.

6. 2. The wind speed detection device according to claim 1, wherein the measurement optical system includes a light concentration adjustment unit that adjusts the concentration state of the measurement light output into the atmosphere.

7. the output unit outputs CW light as the laser light, 2. The wind speed detection device according to claim 1, wherein the detection unit outputs a detection signal based on the result of interference between the reference light, which is a CW light, and the signal light.

8. 2. The wind speed detection device according to claim 1, wherein the measurement optical system includes a deflector that deflects the output direction of the measurement light toward the atmosphere.

9. 2. The wind speed detection device according to claim 1, wherein at least the output section, the branching section, and the detection section are configured by an optical integrated circuit.

10. The wind speed detection device according to claim 1 , further comprising an analysis unit that analyzes the wind speed in the atmosphere based on the detection signal.

11. an output step of outputting laser light whose frequency is linearly modulated with time; a branching step of branching the laser beam into a measurement beam and a reference beam; a converting step of converting the measurement light into pulsed light; a measuring step of emitting the measurement light into the atmosphere and receiving scattered light of the measurement light in the atmosphere as signal light; a detection step of outputting a detection signal based on the interference result between the reference light and the signal light.

12. In the output step, light having an increasing region in which the frequency increases linearly with time and a decreasing region in which the frequency decreases linearly with time is output as the laser light; 12. The wind speed detection method according to claim 11, wherein the conversion step converts the measurement light into the pulsed light so as to generate at least one of a first pulsed light including only frequencies corresponding to the increasing region and a second pulsed light including only frequencies corresponding to the decreasing region.

13. The wind speed detection method according to claim 12 , wherein the converting step converts the measurement light into the pulsed light so that both the first pulsed light and the second pulsed light are generated.

14. 14. The wind speed detection method according to claim 13, wherein the conversion step converts the measurement light into the pulsed light such that the first pulsed light includes a frequency in a first half part of the time axis in the increasing region, and the second pulsed light includes a frequency in a first half part of the time axis in the decreasing region.

15. The wind speed detection method according to claim 11 , wherein the measuring step includes adjusting an optical path difference between the reference light and the signal light.

16. The wind speed detection method according to claim 11 , wherein the measuring step includes adjusting a focusing state of the measurement light output into the atmosphere.

17. In the output step, CW light is output as the laser light, 12. The wind velocity detection method according to claim 11, wherein the detecting step outputs a detection signal based on a result of interference between the reference light, which is a CW light, and the signal light.

18. The wind speed detection method according to claim 11 , wherein the measuring step includes a deflecting step of deflecting an output direction of the measurement light toward the atmosphere.

19. The wind speed detection method according to any one of claims 11 to 18, further comprising an analysis step of analyzing the wind speed in the atmosphere based on the detection signal.

20. The wind speed detection device according to any one of claims 1 to 10; An aircraft control device comprising: a control device that generates control signals related to takeoff and landing of the aircraft based on the detection signal output from the wind speed detection device.

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