Laser radar device

Abstract

A laser radar device (100) comprises: a polarization direction rotation unit (7) that rotates a polarization direction by a predetermined angle with respect to an input laser beam; a polarizing beamsplitter (8) that branches the laser beam, the polarization direction of which has been rotated by the polarization direction rotation unit (7), into a first direction and a second direction different from the first direction; a rotation control unit (15) that realizes circular scanning by the laser beam branched in the first direction and conical scanning by the laser beam branched in the second direction by rotating the polarization direction rotation unit (7) and the polarizing beamsplitter (8) at mutually different rotational angular velocities; and a signal processing unit (14) that calculates a wind velocity field using reflected light reflected by an object irradiated by the laser beams in each scanning.

Description

Technical Field

[0001] The present disclosure relates to a lidar device.

Background Art

[0002] Regarding the present disclosure, a technique for measuring wind (wind speed) using a lidar device is known. For example, a lidar device irradiates laser pulse light (hereinafter also simply referred to as "laser light") into the atmosphere, receives scattered light from aerosol, and by heterodyne detection of the scattered light and continuous light of a single frequency that is the local light of the irradiated laser light, obtains the Doppler shift caused by the movement of the aerosol, and measures the wind speed in the irradiation direction of the laser light. The Doppler shift is calculated from the spectrum obtained by Fourier-transforming the signal after heterodyne detection (for example, Non-Patent Document 1).

[0003] The wind speed measured by the above lidar device is the wind speed in the direction parallel to the irradiation direction of the laser light, and this wind speed is usually referred to as "line-of-sight wind speed". On the other hand, when obtaining a three-dimensional wind direction and wind speed (hereinafter, this wind direction and wind speed is also referred to as "wind speed field" or "wind speed vector"), by performing multiple line-of-sight observations or scanning observations, switching the irradiation direction of the laser light, and using a conventionally known calculation method such as vector calculation and processing based on the VAD (Velocity Azimuth Display) method, a three-dimensional wind speed field is calculated.

[0004] As a lidar device capable of calculating such a wind speed field, for example, a vertical lidar device that performs multiple line-of-sight observations by constructing a plurality of optical systems so that laser light is irradiated in different directions in the atmosphere, or a scanning lidar device that refracts laser light by scanning a plurality of movable mirrors and scans so that the laser light is irradiated in different directions in the atmosphere is known. In the following description, the laser light irradiated into the atmosphere may be referred to as transmitted light, laser pulse light, transmitted beam, transmitted laser beam, etc., but all are synonymous.

Prior Art Documents

Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventionally, a lidar device for wind measurement (hereinafter also referred to as "wind measurement lidar" or simply "lidar") is used in various fields such as airports, wind power generation, and meteorological observation applications. However, the lidar device according to the present disclosure is intended for application to an airborne platform including a flying car. For the utilization of the lidar device on an airborne platform, it is extremely important to grasp the wind speed field in the flight path of the airborne platform, and flight support such as gust alerts and optimal route proposals based on the grasped results is required. Therefore, the lidar device needs to measure the wind speed field in the ground hemisphere space, and real-time performance is required for the measurement.

[0007] For example, in a conventional vertical lidar that observes only the zenith direction, it is possible to measure the wind speed field in a short time. However, in that case, the measurement result is a measurement result that is distance-resolved only in the altitude direction, and only the information of the wind speed field at one point where the lidar is installed can be obtained. On the other hand, in a scanning lidar, it is possible to measure the wind speed field three-dimensionally by scanning the laser light in the azimuth direction (AZ) and the elevation direction (EL), and it is possible to measure the wind speed field in the entire hemisphere space at multiple points and multiple altitudes. However, this lidar takes time to scan all directions of the hemisphere space and lacks real-time performance.

[0008] For example, in a scanning lidar, there is a time shift in the observation time between the observation data in the north direction and the observation data in the south direction. That is, in a scanning lidar, the simultaneity of the wind speed field is not guaranteed among the observation data obtained by scanning all directions in the hemispherical space. On the other hand, it is difficult to perform this measurement in a short time.

[0009] Taking the wind measurement lidar as a premise, which is a pulse type, that is, a wind measurement lidar using a method of decomposing distance by Time of fight (TOF) as an example, the reason why the above measurement takes time will be explained. In the case of the pulse type, the laser light transmitted by the wind measurement lidar into the atmosphere becomes pulsed light with a predetermined repetition frequency, but integration is required to obtain a sufficient signal-to-noise ratio (SNR). When the repetition frequency is PRF and the number of integrations is N, the time required for the integration to complete is PRF × N. Therefore, during the time required for this integration, the wind measurement lidar needs to stop scanning in a predetermined direction or scan at a low speed to approximately point in the same direction. Therefore, it takes time for the wind measurement lidar to scan the entire ground hemispherical space. Thus, it is difficult for a conventional wind measurement lidar to measure the wind speed field of the ground hemispherical space in a short time, and there are problems in applying it to an airborne platform.

[0010] The present disclosure has been made to solve the above problems, and an object thereof is to obtain a lidar device capable of measuring the wind speed field of the ground hemispherical space in a shorter time than before.

Means for Solving the Problems

[0011] The lidar device according to the present disclosure includes a polarization direction rotation unit that rotates the polarization direction of the input laser light by a predetermined angle, a polarization beam splitter that branches the laser light whose polarization direction has been rotated by the polarization direction rotation unit into a first direction and a second direction different from the first direction, and a rotation control unit that rotates the polarization direction rotation unit and the polarization beam splitter at different rotational angular velocities to realize a circular scan by the laser light branched in the first direction and a conical scan by the laser light branched in the second direction, and a signal processing unit that calculates a wind speed field using the reflected light reflected by the irradiation target of the laser light in each scan.

Effects of the Invention

[0012] According to the present disclosure, it is possible to measure the wind speed field in the ground hemisphere space in a shorter time than before.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment 1.

[0015] FIG. 1 is a diagram showing a configuration example of a lidar device 100 according to Embodiment 1. As shown in FIG. 1, for example, the lidar device 100 includes a light source 1, a branching unit 2, a modulation unit 3, an amplification unit 4, a transmission-side optical system 5, a transmit-receive separation unit 6, a polarization direction rotation unit 7, a reception-side optical system 11, a reception-side polarization beam splitter 12, an optical IQ detector 13, a signal processing unit 14, a rotation control unit 15 (15a, 15b), and a scan unit 17 (polarization beam splitter 8, polarization Towards optical element 9, window 10, and window 16).

[0016] The light source 1 outputs laser light that is continuous light having a substantially single frequency. This laser light is, for example, laser light having a wavelength band in which an irradiation target such as aerosol in the atmosphere can be reflected and having linearly polarized light characteristics. The light source 1 is composed of, for example, a semiconductor laser and a solid-state laser, and is connected to the branching unit 2.

[0017] The branching unit 2 distributes the laser light input from the light source 1 into a transmission optical signal and a local emission signal, and outputs the transmission optical signal to the modulation unit 3 and the local emission signal to the optical IQ detector 13, respectively. The branching unit 2 is composed of, for example, a 1:2 optical coupler and a half mirror. Here, the branching unit 2 will be described as being of a fiber type, but the branching unit 2 is not limited thereto and may be of a spatial type. The output end of the transmission optical signal of the branching unit 2 is connected to the modulation unit 3, and the output end of the local emission signal is connected to the optical IQ detector 13.

[0018] The modulation unit 3 has a function of performing pulse modulation on the transmitted optical signal input from the branching unit 2 and giving a desired frequency shift to generate pulsed light. The modulation unit 3 is composed of, for example, an LN (LiNbO3) modulator, an AOM (Acousto - Optics modulator), and an SOA (semiconductor optical amplifier), and is connected to the amplification unit 4.

[0019] The amplification unit 4 has a function of amplifying the peak power of the pulsed light input from the modulation unit 3 to generate transmitted light. The amplification unit 4 is composed of, for example, an optical fiber amplifier, and is connected to the transmission - side optical system 5.

[0020] The transmission - side optical system 5 has a function of shaping the transmitted light input from the amplification unit 4 into a desired beam diameter and divergence angle. The transmission - side optical system 5 is composed of, for example, convex lenses, concave lenses, aspherical lenses, and combinations thereof. However, the transmission - side optical system 5 is not limited to these, and may be composed of, for example, mirrors.

[0021] The transmission - side optical system 5 is optically connected to the transmit - receive separation unit 6. Here, "optically connected" means that it is not an electrical or physical connection, but is connected as a path through which light propagates.

[0022] In addition, in Embodiment 1, an example in which the path from the light source 1 to the transmission - side optical system 5 is composed of an optical fiber will be described. Specifically, in Embodiment 1, from the time when the light source 1 outputs laser light until the transmitted light exits the transmission - side optical system 5, the polarization direction of the transmitted light is maintained in the polarization direction determined by the light source 1. Therefore, in Embodiment 1, the above - mentioned path is composed of polarization - maintaining optical fibers. However, the above - mentioned path does not necessarily have to be composed of optical fibers, and may be composed of, for example, a free - space optical system. In Embodiment 1, the polarization direction of the transmitted light at the position where it exits from the transmission - side optical system 5 is defined as the reference optical axis.

[0023] The transmit-receive separation unit 6 is optically connected to the transmission-side optical system 5, the polarization direction rotation unit 7, and the reception-side optical system 11. The transmit-receive separation unit 6 is composed of, for example, a polarization-independent beam splitter. The transmit-receive separation unit 6 has a function of outputting the transmitted light input in the forward direction from the transmission-side optical system 5 to the polarization direction rotation unit 7. At this time, the transmit-receive separation unit 6 does not output the transmitted light to the reception-side optical system 11. Further, the transmit-receive separation unit 6 has a function of outputting the received light input in the reverse direction from the polarization direction rotation unit 7 to the reception-side optical system 11. At this time, the transmit-receive separation unit 6 does not output the received light to the transmission-side optical system 5.

[0024] The polarization direction rotation unit 7 is optically connected to the transmit-receive separation unit 6 and the polarization beam splitter 8. The polarization direction rotation unit 7 performs a process of rotating the polarization direction of the transmitted light having a specific polarization direction input from the transmit-receive separation unit 6 by a predetermined angle, and has a function of outputting the rotated transmitted light to the polarization beam splitter 8. The polarization direction rotation unit 7 is composed of, for example, a λ / 2 wave plate. Further, the polarization direction rotation unit 7 is connected to the rotation control unit 15 and rotates under the control of the rotation control unit 15.

[0025] The polarization beam splitter 8 is polarized Towards optically connected to the optical element 9 and the window 16. The polarization beam splitter 8 has a function of guiding the S polarization component to the first direction side and the P polarization component to the second direction side according to the polarization direction of the rotated transmitted light input from the polarization direction rotation unit 7. Here, the first direction is, for example, the horizontal direction (scanning direction), and the second direction is the vertical direction.

[0026] In the following description, the case where the first direction is the horizontal direction (scanning direction) and the second direction is the vertical direction will be described. Further, in the following description, the horizontal direction (scanning direction) side is also simply referred to as the "scanning side", and the vertical direction side is also simply referred to as the "vertical side".

[0027] Polarized Towards The optical element 9 is optically connected to the polarization beam splitter 8 and the window 10. Polarized TowardsThe optical element 9 has a function of giving a deflection angle to the transmitted light (P polarization component) guided to the vertical side by a predetermined angle and outputting it to the window 10.

[0028] The window 10 is Towards optically connected to the optical element 9. The window 10 is Towards has a function of transmitting the transmitted light output from the optical element 9 and guiding (irradiating) it into the atmosphere.

[0029] The window 16 is optically connected to the polarization beam splitter 8. The window 16 has a function of transmitting the transmitted light (S polarization component) guided from the polarization beam splitter 8 to the scan side and guiding it into the atmosphere.

[0030] In the first embodiment, the scan unit 17 is constituted by the polarization beam splitter 8, Towards the optical element 9, the window 10, and the window 16. Further, the scan unit 17 is connected to the rotation control unit 15 and rotates under the control of the rotation control unit 15.

[0031] The receiving-side optical system 11 is optically connected to the transmit-receive separation unit 6. The receiving-side optical system 11 has a function of receiving, as received light, the reflected light scattered when the transmitted light irradiated on the vertical side and the scan side hits the irradiation target. The optical axis of the receiving-side optical system 11 is inclined by 45 degrees with respect to the optical axis of the transmitting-side optical system 5 so as to receive the P polarization component and the S polarization component of the received received light by distinguishing between the fast axis and the slow axis. Thereby, the receiving-side optical system 11 can always receive each polarization component on the same optical axis.

[0032] The receiving-side polarization beam splitter 12 is connected to the receiving-side optical system 11 and the optical IQ detector 13. The receiving-side polarization beam splitter 12 has a function of separating the P polarization component and the S polarization component of the received light received by the receiving-side optical system 11 and outputting each of the separated components to the optical IQ detector 13.

[0033] The optical IQ detector 13 is connected to the branching unit 2, the reception-side polarization beam splitter 12, and the signal processing unit 14. Since the functions of the optical IQ detector 13 are known as the prior art, detailed descriptions of its internal configuration and functions are omitted here, and only an overview will be described.

[0034] From the above-described configuration and functions, the P-polarization component and the S-polarization component of the transmitted light are assigned to the vertical side and the scan side, and the P-polarization component and the S-polarization component of the received light received from the atmosphere are fixedly assigned to the optical axes of the fast axis and the slow axis of the reception-side optical system 11. When the optical IQ detector 13 receives the local light emission signal output from the branching unit 2, the received signal is branched into two, and a phase shift of π / 2 is given to one of the signals. Then, each of the branched signals is multiplexed with the P-polarization component and the S-polarization component branched by the reception-side polarization beam splitter 12. The light obtained by this multiplexing is branched by, for example, a function equivalent to a 2:2 coupler and a half mirror, and the branched light (interference light) is input to a balanced receiver or a differential amplification detector, thereby generating a beat signal (P-side RF signal and S-side RF signal) determined by the frequency shift given by the modulation unit 3 from the P-polarization component and the S-polarization component of the received light. The optical IQ detector 13 outputs the generated beat signal to the signal processing unit 14. Note that the internal configuration of the optical IQ detector 13 may be constructed by a fiber system.

[0035] The signal processing unit 14 is connected to the optical IQ detector 13 and the rotation control unit 15. The signal processing unit 14 includes components necessary for signal processing conventionally known in a wind measurement lidar, such as an AD converter and a Fourier transformer, and performs a process of calculating the wind speed from the spectrum after Fourier transform. Further, the signal processing unit 14 controls the rotation control unit 15.

[0036] For example, the signal processing unit 14 AD-converts the two beat signals generated by the P-polarization component and the S-polarization component by an AD converter configured for each of the beat signals, performs a fast Fourier transform (FFT) on each of the digitized signals, and generates a frequency spectrum. Then, based on the generated frequency spectrum, the signal processing unit 14 calculates the wind speed field for each distance in the vertical direction and the scan direction. Note that the signal processing unit 14 is configured by, for example, an FPGA (Field-Programmable Gate Array) for the calculation process of the wind speed field after the fast Fourier transform.

[0037] The rotation control unit 15 is connected to the polarization direction rotation unit 7, the signal processing unit 14, and the scan unit 17, and rotates the polarization direction rotation unit 7 and the scan unit 17 independently under the control of the signal processing unit 14. Specifically, the rotation control unit 15 consists of rotation control units 15a and 15b. The rotation control unit 15a has a function of rotating the polarization direction rotation unit 7, and the rotation control unit 15b has a function of rotating the scan unit 17 at a predetermined rotational angular velocity.

[0038] By rotating the scan unit 17, the rotation control unit 15b changes the irradiation direction of the transmitted light guided from the polarization beam splitter 8 to the scan side within a range of 0 to 360 degrees with respect to the azimuth angle direction. Also, by rotating the scan unit 17, the rotation control unit 15b changes the irradiation direction of the transmitted light on the vertical side that is guided from the polarization beam splitter 8 to the vertical side and has a polarization angle added by the optical element 9. Towards By rotating the scan unit 17, the rotation control unit 15b changes the irradiation direction of the transmitted light on the vertical side that is guided from the polarization beam splitter 8 to the vertical side and has a polarization angle added by the optical element 9.

[0039] The rotation control unit 15a has a function of rotating the polarization direction rotation unit 7, and this function includes the following two functions. One is a function of giving an offset angle to the rotation angle of the polarization direction rotation unit 7 with respect to the optical axis of the polarization beam splitter 8, and the other is a function of rotating the polarization direction rotation unit 7 at a rotational angular velocity different from that of the scan unit 17.

[0040] As an example, when the offset angle given to the rotation angle of the polarization direction rotating unit 7 is α, the rotational angular velocity of the polarization direction rotating unit 7 is ω2, and the rotational angular velocity of the scanning unit 17 is ωs, the following relationship of Equation (1) holds for ω2 and ωs. ωs = 2 × ω2 (1)

[0041] Also, the rotation angle θ2(t) of the polarization direction rotating unit 7 at time t is given by the following Equation (2), and the rotation angle θ S (t) of the scanning unit 17 at time t is obtained by the following Equation (3). θ2(t) = (ωs / 2) × t + α (2) θ S (t) = ωs × t (3)

[0042] Note that giving the offset angle α to the rotation angle of the polarization direction rotating unit 7 with respect to the optical axis of the polarization beam splitter 8 is synonymous with, for example, a state where the vector corresponding to the optical axis of the λ / 2 wavelength plate (7) constituting the polarization direction rotating unit 7 and the vector obtained by projecting the normal vector of the reflection surface of the polarization beam splitter (8) onto the λ / 2 wavelength plate (7) are not parallel.

[0043] By having the above-described configuration and functions, in the lidar device 100 according to the first embodiment, the transmitted light output from the transmission-side optical system 5 is not only separated into two directions, the scanning side and the vertical side, but also the P-polarization component of the transmitted light is always guided to the vertical side, and the S-polarization component of the transmitted light is always guided to the scanning side. Further, in the lidar device 100, by having the above-described configuration and functions, a circular scan by the S-polarization component of the transmitted light guided to the scanning side and a conical scan by the P-polarization component of the transmitted light guided to the vertical side are realized.

[0044] In the lidar device 100, light scattered by an irradiation target (such as an aerosol) in the atmosphere located in each of the vertical direction and the scan direction, that is, reflected light, is incident again on the polarization beam splitter 8 as received light and passes through the polarization direction rotation unit 7. At this time, the polarization direction of the received light from each direction is at an angle different from the polarization direction of the transmitted light, but the polarization direction of the composite component of the received light is always fixed in the same direction.

[0045] Next, an operation example of the lidar device 100 according to Embodiment 1 will be described. In the following description, the case where the polarization direction rotation unit 7 is composed of a λ / 2 wavelength plate will be described as an example.

[0046] First, the light source 1 outputs laser light that is continuous light having a substantially single frequency. The branching unit 2 distributes the laser light input from the light source 1 into a transmission optical signal and a local oscillation optical signal, and outputs the transmission optical signal to the modulation unit 3 and the local oscillation optical signal to the optical IQ detector 13, respectively. The modulation unit 3 performs pulse modulation on the transmission optical signal input from the branching unit 2 and gives a desired frequency shift to generate pulsed light.

[0047] The amplification unit 4 amplifies the peak power of the pulsed light input from the modulation unit 3 to generate transmission light. The transmission-side optical system 5 shapes the transmission light input from the amplification unit 4 into a desired beam diameter and divergence angle. The transmission light emitted from the transmission-side optical system 5 is input to the transmit-receive separation unit 6, which is a polarization-independent beam splitter, and further input from the transmit-receive separation unit 6 to the λ / 2 wavelength plate that constitutes the polarization direction rotation unit 7.

[0048] The change in the polarization direction of the transmission light input to the λ / 2 wavelength plate will be described in detail with reference to FIG. 2. In FIG. 2, the change in the polarization direction at time t = 0 seconds is explained in the left figure, and the change in the polarization direction at time t = 1 second is explained in the right figure. Here, for the sake of concreteness of the explanation, the rotational angular velocity ωs of the scanning unit 17 is set to 90 degrees / second, and the offset angle α given to the rotation angle of the polarization direction rotation unit 7 is set to 22.5 degrees. Therefore, the rotational angular velocity ω2 of the λ / 2 wavelength plate, which is the polarization direction rotation unit 7, is 45 degrees / second.

[0049] Also, from the above formulas (2) and (3), at time t = 0, the rotation angle θ2(t) of the λ / 2 waveplate is 22.5 degrees, and the rotation angle θ S (t) of the scanning unit 17 is 0 degrees. Note that the rotation angle θ2(t) of the λ / 2 waveplate corresponds to the optical axis of the λ / 2 waveplate. Also, the rotation angle θ S (t) of the scanning unit 17 is defined as the direction of the S polarization component reflected by the polarization beam splitter 8. Also, the rotation angle θ S (t) of this scanning unit 17 coincides with the reference optical axis described above.

[0050] At time t = 0, since the rotation angle θ2(t) of the λ / 2 waveplate is 22.5 degrees, the transmission light that has passed through the λ / 2 waveplate has its polarization direction rotated by 45 degrees with respect to the reference optical axis. Note that the transmission light passing through the λ / 2 waveplate propagates in a direction perpendicular to the paper surface, that is, from the back side of the paper surface to the front side of the paper surface.

[0051] The transmission light whose polarization direction has been rotated by 45 degrees enters the polarization beam splitter 8 of the scanning unit 17 where θ S (t) coincides with the reference optical axis, is branched by the polarization beam splitter 8, and the S polarization component reflected by the polarization beam splitter 8 is extracted. The extracted S polarization component is bent in the X - Y plane shown in FIG. 2 and converted into transmission light propagating in a horizontal direction with respect to the paper surface. Therefore, for example, when the X - axis direction shown in FIG. 2 is defined as the north, the extracted S polarization component becomes transmission light scanning in the north direction. At this time, the scan Light direction of the S polarization component coincides with the rotation angle θ S (t) of the scanning unit 17, which is because an offset angle α is given to the λ / 2 waveplate.

[0052] On the other hand, the transmission light whose polarization direction has been rotated by 45 degrees has θ SBy entering the scan unit 17 where (t) matches into the polarization beam splitter 8, the P-polarization component that is branched by the polarization beam splitter 8 and transmitted through the polarization beam splitter 8 is extracted. The extracted P-polarization component is not bent within the X-Y plane shown in FIG. 2 and becomes transmitted light that propagates forward in the direction perpendicular to the paper surface. Therefore, for example, when the positive direction of the Z-axis direction shown in FIG. 2 is defined as the zenith direction, the extracted P-polarization component becomes transmitted light that propagates in the zenith direction (vertical side).

[0053] polar Towards The optical element 9 gives a deflection angle to the transmitted light that has propagated to the vertical side by a predetermined angle and outputs it to the window 10. The window 10 irradiates the deflected transmitted light on the vertical side into the atmosphere. Also, the window 16 irradiates the transmitted light that has propagated to the scan side into the atmosphere. Then, each transmitted light scattered by the irradiation target (aerosol, etc.) in the atmosphere becomes reflected light and reaches each of the windows 10 and 16 again. At this time, the polarization direction of each reflected light is maintained.

[0054] The reflected light on the vertical side that reaches the window 10 passes through the polar Towards optical element 9 again as received light. polar Towards The optical element 9 gives a deflection angle again to the received light on the vertical side so as to coincide with the optical axis of the transmitted light before applying the deflection angle during transmission. Then, the received light on the vertical side returns to the λ / 2 wavelength plate, which is the polarization direction rotation unit 7, again along the same path as during transmission. Similarly, the reflected light on the scan side that reaches the window 16 returns to the λ / 2 wavelength plate, which is the polarization direction rotation unit 7, again along the same path as during transmission as received light. By each received light that has returned to the λ / 2 wavelength plate passing through the λ / 2 wavelength plate again, a rotation of the polarization direction occurs for each received light with respect to the optical axis of the λ / 2 wavelength plate.

[0055] At this time, for example, the received light (S polarization component) on the scan side has its polarization direction rotated counterclockwise by 45 degrees in the X - Y plane with respect to the transmitted light (S polarization component) on the scan side. Also, the received light (P polarization component) on the vertical side has its polarization direction rotated clockwise by 135 degrees in the X - Y plane with respect to the transmitted light (P polarization component) on the vertical side (see Fig. 2). Note that the combined wave component of the received light (S polarization component) on the scan side and the received light (P polarization component) on the vertical side coincides with the polarization direction of the transmitted light at the time when it exits the transmission - side optical system 5 during transmission.

[0056] Next, the state at t = 1 will be described. From the above equations (2) and (3), at time t = 1, the rotation angle θ2(t) of the λ / 2 waveplate is 67.5 degrees, and the rotation angle θ S (t) of the scan unit 17 is 90 degrees.

[0057] At time t = 1, since the rotation angle θ2(t) of the λ / 2 waveplate is 67.5 degrees, the polarization direction of the transmitted light passing through the λ / 2 waveplate rotates by 135 degrees with respect to the reference optical axis. The transmitted light whose polarization direction has rotated by 135 degrees enters the polarization beam splitter 8 of the scan unit 17 where θ S (t) has rotated by 90 degrees. Then, it is branched by the polarization beam splitter 8, and the S polarization component reflected by the polarization beam splitter 8 is extracted. The extracted S polarization component is bent in the X - Y plane shown in Fig. 2 and is converted into transmitted light propagating in the horizontal direction with respect to the paper surface.

[0058] Therefore, in the case of t = 1, the extracted S Light polarization component becomes transmitted light scanning in the west direction, for example, when the X - axis direction is defined as north. Also, this means that the scan direction of the S Light polarization component coincides with the rotation angle θ S (t) of the scan unit 17. This is because, as described above, the offset angle α is given to the λ / 2 waveplate so that the above - mentioned two coincide.

[0059] Also, similar to the case of t = 0, the P polarization that has passed through the polarization beam splitter 8 LightThe component is not bent within the X-Y plane and becomes transmitted light that propagates forward in the direction perpendicular to the plane of the paper. Therefore, for example, when the positive direction of the Z-axis is defined as the zenith direction, the P-polarized component becomes transmitted light that propagates in the zenith direction (vertical side).

[0060] Hereinafter, similar to the case when t = 0, the polarization Towards The optical element 9 gives a deflection angle to the transmitted light that has propagated to the vertical side by a predetermined angle and outputs it to the window 10. The window 10 irradiates the deflected transmitted light on the vertical side into the atmosphere. Also, the window 16 irradiates the transmitted light that has propagated to the scan side into the atmosphere. Thereafter, each transmitted light scattered by the irradiation target (aerosol, etc.) in the atmosphere becomes reflected light and reaches each of the windows 10 and 16 again. At this time, the polarization direction of each reflected light is maintained.

[0061] The reflected light on the vertical side that reaches the window 10 becomes received light and is polarized again Towards and passes through the optical element 9. The polarization Towards The optical element 9 applies a deflection angle again to the received light on the vertical side so as to coincide with the optical axis of the transmitted light before applying the deflection angle during transmission. Thereafter, the received light on the vertical side returns to the λ / 2 wavelength plate, which is the polarization direction rotation unit 7, again along the same path as during transmission. Similarly, the reflected light on the scan side that reaches the window 16 returns to the λ / 2 wavelength plate, which is the polarization direction rotation unit 7, again along the same path as during transmission as received light. By each received light that has returned to the λ / 2 wavelength plate passing through the λ / 2 wavelength plate again, a rotation of the polarization direction occurs for each received light with respect to the optical axis of the λ / 2 wavelength plate.

[0062] At this time, for example, the received light (S polarization component) on the scan side has a polarization direction that is rotated 45 degrees clockwise in the X-Y plane with respect to the transmitted light (S polarization component) on the scan side. Also, the received light (P polarization component) on the vertical side has a polarization direction that is rotated 225 degrees clockwise in the X-Y plane with respect to the transmitted light (P polarization component) on the vertical side (see Fig. 2). Note that the combined wave component of the received light (S polarization component) on the scan side and the received light (P polarization component) on the vertical side coincides with the polarization direction of the transmitted light at the time of exiting the transmission-side optical system 5 during transmission. Also, at t = 0 and t = 1, the polarization directions of the received light (S polarization component) on the scan side and the received light (P polarization component) on the vertical side after passing through the λ / 2 waveplate coincide.

[0063] In the above description, the cases of t = 0 and t = 1 were used as examples for explanation, but the above content holds at any time. That is, the polarization directions of the received light (P polarization component) on the vertical side and the received light (S polarization component) on the scan side after passing through the λ / 2 waveplate are always inclined at +45 degrees from the reference optical axis for the former and -45 degrees for the latter, and are fixed.

[0064] That is, in Embodiment 1, by adding an offset angle α to the rotation angle of the λ / 2 waveplate and rotationally controlling the rotation angular velocity of the λ / 2 waveplate to be 1 / 2 of the rotation angular velocity of the polarization beam splitter 8, it becomes possible to always keep the polarization directions of the received light (P polarization component) on the vertical side and the received light (S polarization component) on the scan side fixed with respect to the reference optical axis.

[0065] Therefore, in Embodiment 1, by tilting (rotating) the optical axis (fast axis and slow axis) of the reception-side optical system 11 by 45 degrees with respect to the reference optical axis so as to coincide with the polarization direction (+45 degrees from the reference optical axis) of the received light (P polarization component) on the vertical side and the polarization direction (-45 degrees from the reference optical axis) of the received light (S polarization component) on the scan side and fixing it, the fast axis of the reception-side optical system 11 has a P polarization Light component, and the slow axis has an S polarization LightThe components can always be combined. Therefore, in Embodiment 1, the received light always received from the vertical side is propagated along the fast axis of the receiving optical system 11, and the received light always received from the scanning side is propagated along the slow axis of the receiving optical system 11, so that the optical axis of the receiving optical system 11 can be fixed.

[0066] Hereinafter, the receiving-side polarization beam splitter 12 separates the P-polarization component and the S-polarization component of the received light received by the receiving optical system 11, and outputs each of the separated components to the optical IQ detector 13.

[0067] The optical IQ detector 13 performs the above-described multiplexing on the P-polarization component and the S-polarization component branched by the receiving-side polarization beam splitter 12 by using the local light emission signal received from the branch unit 2, and generates the above-described beat signal (P-side RF signal and S-side RF signal). The optical IQ detector 13 outputs the generated beat signal to the signal processing unit 14. The signal processing unit 14 calculates the wind speed field for each distance in the vertical direction and the scanning direction by performing the above-described processing using the two beat signals.

[0068] Next, with reference to FIG. 3, the state in which the propagation direction of the transmitted light in the atmosphere changes due to the scanning of the transmitted light on the vertical side and the scanning side irradiated from the laser radar device 100 will be described with reference to the above-described operation example.

[0069] <Vertical side> On the vertical side, as described above, the polarization Towards Since the optical element 9 causes a predetermined polarization angle in the transmitted light, scanning with an inclination by the polarization angle from the zenith direction, that is, conical scanning is performed. On the vertical side, when the scanning unit 17 rotates once from 0 degrees to 360 degrees, the wind speed field in a predetermined circular region is calculated. Therefore, on the vertical side, for example, between the transmitted lights polarized in opposite directions such as the south direction and the north direction, or the west direction and the east direction, the angle difference in the irradiation direction of the transmitted light becomes the maximum.

[0070] In this way, in the lidar device 100, from the data indicating the wind speed value (the absolute value of the wind speed field) in the line-of-sight direction for one scan scanned on the vertical side (hereinafter, also simply referred to as "wind speed value data"), the three-dimensional wind speed field in the area shaded with diagonal lines in FIG. 3 can be calculated. Note that this calculation process is performed using an existing method. For example, vector calculation and the VAD (Velocity Azimuth Display) method can be used.

[0071] Note that in FIG. 3, only one altitude is taken as an example, and the three-dimensional wind speed field obtained by calculation is shown by diagonal lines. However, the wind speed field can be acquired for each altitude. For example, in Embodiment 1, since the transmitted light is pulsed, it is a TOF method and it is possible to resolve in the distance direction. On the other hand, even if the transmitted light is continuous light (CW light), it is possible to perform distance resolution. In this case, by changing the beam divergence angle formed by the transmission-side optical system 5 and scanning the condensing position, wind measurement at the condensing position is performed. In this case, in the lidar device 100, pulsing in the modulation unit 3 is unnecessary, and it is only necessary to make the condensing position variable.

[0072] <Scan side> On the scan side, the transmitted light is bent in a direction perpendicular to the zenith (vertical) direction, so that it is irradiated in a horizontal direction with respect to the ground surface. The scan on the scan side makes one full circle when the scan unit 17 rotates once from 0 degrees to 360 degrees. That is, it becomes a PPI (Plan-position indicator) scan.

[0073] On the scan side, wind measurement at an altitude of approximately 0 m is performed. However, it is possible to perform measurements at a plurality of locations with different horizontal distances from the lidar device 100, and it is possible to obtain the wind speed fields at a plurality of points even at one altitude. For example, as shown in FIG. 4, from the wind speed value data in the line-of-sight direction from 0 degrees to 360 degrees calculated by PPI scan, by using the wind speed values in different line-of-sight directions, the wind speed field in a certain area is obtained by calculation. This method may use an existing method. For example, vector calculation and the VAD method etc. can be used.

[0074] Next, with reference to FIG. 5, the states of the wind speed fields on the vertical side and the scan side, which are calculated by vector operations and the VAD method, will be described.

[0075] In FIG. 5, the wind speed fields are indicated by thick arrows. Also, in FIG. 5, for the vertical side, the state where the wind speed fields at a plurality of altitudes at one point and for the scan side, the wind speed fields at a plurality of points at one altitude are obtained is shown.

[0076] Here, these wind speed fields are defined as variables. For example, the horizontal wind speed field obtained on the vertical side is defined as U V (U VX , U VY ; x = 0, y = 0, z i ). Here, z i represents altitude, and the altitude is distinguished using the subscript i. Also, U V is the horizontal wind speed vector, and its x - direction component and y - direction component are defined as U VX , U VY , respectively.

[0077] On the vertical side, when the position where the lidar device 100 is installed is defined as x = 0 and y = 0, there is no data indicating the wind speed field (hereinafter, also simply referred to as "wind speed field data") at other x and y positions, but there is wind speed field data at a plurality of altitudes in the altitude direction. Therefore, the wind speed field data in the altitude direction at x = 0 and y = 0 on the vertical side is a function of z i .

[0078] On the other hand, the horizontal wind speed field obtained on the scan side is defined as U S (U SX , U SY ; x, y, z0). On the scan side, when the altitude of the location where the lidar device 100 is installed is defined as z0, there is no wind speed field data at other altitudes, but there is wind speed field data at a plurality of points at altitude z0. Therefore, the wind speed field data at a plurality of points at altitude z0 on the scan side is a function of x and y.

[0079] Next, the signal processing unit 14 of the lidar device 100 uses the above wind speed fields U V and U S to approximately obtain a wind speed field at multiple points and multiple altitudes by calculation. An example will be described below. For simplicity of explanation, hereinafter, the above wind speed field U V is also referred to as a "wind speed field at one point and multiple altitudes", and the above wind speed field U S is also referred to as a "wind speed field at multiple points and one altitude".

[0080] The signal processing unit 14 calculates a wind speed field at multiple points and multiple altitudes from the wind speed field at one point and multiple altitudes obtained on the vertical side and the wind speed field data at multiple points and one altitude obtained on the scan side, for example, according to the following procedures (1) to (3).

[0081] (1) The signal processing unit 14 virtually generates data at altitude z0 that is not included in the vertical-side wind speed field data. For example, the signal processing unit 14 defines a circle with a radius R centered at x = 0 and y = 0 from the wind speed field data obtained on the scan side, and averages the wind speed field data within this range. Then, the signal processing unit 14 uses the averaged data as the wind speed field data at altitude z0 that is not included in the vertical-side wind speed field data. The above processing is represented, for example, by the following formula (4). TIFF0007693140000001.tif14166

[0082] (2) Next, the signal processing unit 14 obtains the ratio R i of the wind speed field based on the wind speed field data at altitude z0 from the vertical-side wind speed field data. The above processing is represented, for example, by the following formula (5). TIFF0007693140000002.tif13166

[0083] (3) Next, the signal processing unit 14 uses the ratio R i of the wind speed field to calculate the wind speed field U C at multiple altitudes and multiple points according to the following formula (6). TIFF0007693140000003.tif11166

[0084] In the above calculation, the signal processing unit 14 calculates the ratio R of the wind speed field data at each altitude with respect to the change in the wind speed field in the altitude direction at a single point where x = 0 and y = 0, based on the wind speed field data at altitude z0. i obtains this ratio R i and, based on the assumption that this ratio R i is maintained even at different points (arbitrary x, y), multiplies this ratio R i by the wind speed field data at each altitude, thereby performing a calculation to extend this ratio R C to multiple altitudes. The state of the thus calculated wind speed field U

[0085] Note that in the above example, the signal processing unit 14 can perform calculations on the absolute value of the wind speed field, that is, the wind speed value, but can also perform calculations in the same way for the wind direction. That is, the signal processing unit 14 obtains the change angle with respect to the change in the wind direction in the altitude direction at a single point where x = 0 and y = 0, based on the wind direction at altitude z0. And when calculating the wind speed field at altitude i, the wind speed field U S (U SX , U SY (U; x, y, z0) may be rotated.

[0086] Therefore, the signal processing unit 14 obtains the change in the altitude direction with respect to the value at altitude z0 at a single point where x = 0 and y = 0 for each of the wind speed value and the wind direction, and assumes that this tendency of change also holds outside x = 0 and y = 0. And the signal processing unit 14, based on this assumption, although it only has data at altitude z0, applies the above tendency of change to the scan-side data having data outside x = 0 and y = 0, thereby obtaining the wind speed values and wind directions at multiple altitudes and multiple points. Here, the "tendency of change" refers to the ratio or the change angle, and "applying" refers to multiplying or adding.

[0087] Next, the effects of the lidar device 100 according to Embodiment 1 will be described. By having the configuration as described above, the lidar device 100 according to Embodiment 1 can calculate the wind speed field of the ground hemispherical space in the time required to make one full scan of the transmitted light in both the vertical direction and the scan direction. This is equivalent to measuring the wind speed field of the ground hemispherical space in a shorter time than before. And thereby, the real-time performance in the calculation of the wind speed field of the ground hemispherical space is also improved. Further, the lidar device 100 according to Embodiment 1 can obtain the above effects as a single device, rather than using a plurality of lidar devices.

[0088] Also, the lidar device 100 according to Embodiment 1 can be changed to the function of only the vertical lidar or the function of only the scanning lidar by appropriately adjusting the offset angle α applied to the λ / 2 waveplate constituting, for example, the polarization direction rotating unit 7.

[0089] For example, in the above example, an example of setting the offset angle α applied to the λ / 2 waveplate to 22.5 degrees was described. This was intended to equally distribute the transmitted light (transmission power) to both the vertical side and the scan side. That is, in the lidar device 100 according to Embodiment 1, by appropriately adjusting the value of the offset angle α, it is also possible to always guide the transmitted light (transmission power) only to the vertical side, and it is also possible to always guide the transmitted light (transmission power) only to the scan side.

[0090] Therefore, according to the differences in the users and operation methods of the lidar device 100, by appropriately adjusting the offset angle α, it is possible to select the mode of measuring the wind speed field of the entire ground hemispherical space targeted in the present disclosure, and it is also possible to select the mode of observing only the vertical direction or the mode of observing only the scan direction. Further, for example, when the mode of observing only the vertical direction is selected, since all of the transmitted light (transmission power) is guided to the vertical side, the SNR increases and the observable distance extends, and it is possible to maintain the performance of the conventional vertical lidar.

[0091] That is, the lidar device 100 according to the first embodiment can exhibit the performance obtained by a conventional vertical lidar as a single lidar device, can also exhibit the performance obtained by a scanning lidar, and can measure the wind speed field of the entire ground hemisphere space, which is the object of the present disclosure, in a shorter time than before.

[0092] As another effect of the lidar device 100 according to the first embodiment, by improving the real-time performance in the calculation of the wind speed field of the ground hemisphere space, for example, the functions of the lidar device 100 can be utilized for navigation support and optimal route setting for airborne mobile platforms such as aircraft and drones.

[0093] For example, when setting an optimal route for an airborne mobile platform, there may be a case where multiple routes are candidates as the route from the starting point to the ending point. At this time, by considering the wind speed field obtained by the lidar device 100 and extracting the route that minimizes the required power and time, it is possible to extract and present the optimal route, and thus it is possible to effectively support route selection. Also, at this time, real-time performance is required for route selection support, but this problem is also solved by the lidar device 100 according to the first embodiment.

[0094] As described above, according to the first embodiment, the lidar device 100 includes a polarization direction rotation unit 7 that rotates the polarization direction of the input laser light by a predetermined angle, a polarization beam splitter 8 that branches the laser light whose polarization direction has been rotated by the polarization direction rotation unit 7 into a first direction and a second direction different from the first direction, and the polarization direction rotation unit 7 and the polarization beam splitter 8 are rotated at different rotational angular velocities from each other, so as to realize a circular scan by the laser light branched in the first direction and a conical scan by the laser light branched in the second direction. The lidar device 100 also includes a signal processing unit 14 that calculates the wind speed field using the reflected light reflected by the irradiation target of the laser light in each scan. Thereby, the lidar device 100 according to the first embodiment can measure the wind speed field of the ground hemisphere space in a shorter time than before.

[0095] Also, the first direction is the horizontal direction, and the second direction is the vertical direction. Thereby, the lidar device 100 according to the first embodiment can measure the wind speed field of the ground hemisphere space in a shorter time than before.

[0096] Also, a polarization optical element 9 is provided at the subsequent stage of the polarization beam splitter 8 in the vertical direction. Towards For the laser light branched in the vertical direction by the polarization beam splitter 8, Towards a conical scan by the laser light branched in the vertical direction is realized by giving a deflection angle by the polarization optical element 9 by a predetermined angle. Thereby, the lidar device 100 according to the first embodiment can realize a conical scan by the laser light branched in the vertical direction.

[0097] Further, the polarization direction rotation unit 7 is composed of a λ / 2 wave plate, and the rotation control unit 15 rotates the λ / 2 wave plate and the polarization beam splitter 8 at different rotational angular velocities while maintaining a state where the vector corresponding to the optical axis of the λ / 2 wave plate and the vector obtained by projecting the normal vector of the reflection surface of the polarization beam splitter 8 onto the λ / 2 wave plate are not parallel. Thereby, the lidar device 100 according to the first embodiment can make the first direction coincide with the rotation angle θ S (t) of the scanning unit including the polarization beam splitter 8.

[0098] Further, the polarization direction rotation unit 7 is composed of a λ / 2 wave plate, and the rotation control unit 15 rotates the λ / 2 wave plate and the polarization beam splitter 8 at different rotational angular velocities with an offset angle with respect to the optical axis of the polarization beam splitter (8) given to the rotation angle of the λ / 2 wave plate. Thereby, the lidar device 100 according to the first embodiment can make the first direction coincide with the rotation angle θ S (t) of the scanning unit including the polarization beam splitter 8.

[0099] Further, the magnitude of the offset angle can be arbitrarily set. Thereby, the lidar device 100 according to the first embodiment can also guide the transmitted light only to the first direction side at all times, and can also guide the transmitted light only to the second direction side at all times.

[0100] Further, the lidar device 100 includes a light source 1 that outputs laser light having a wavelength band in which the irradiation target of the laser light is reflectable and having linear polarization characteristics, a branching unit 2 that branches the laser light output from the light source 1, a modulation unit 3 that pulse-modulates one of the laser lights branched by the branching unit 2, an amplification unit 4 that amplifies the power of the laser light pulse-modulated by the modulation unit 3, a transmission-side optical system 5 that shapes the laser light amplified by the amplification unit 4, a transmission-reception separation unit 6 that separates the laser light shaped by the transmission-side optical system 5 and the reflected light from the irradiation target of the laser light, a reception-side optical system 11 that receives the reflected light separated by the transmission-reception separation unit 6, and a detector 13 that obtains a predetermined interference signal by combining the reflected light received by the reception-side optical system 11 and the other of the laser lights branched by the branching unit 2. The polarization direction rotation unit 7 rotates the polarization direction of the laser light separated by the transmission-reception separation unit 6 by a predetermined angle, and the signal processing unit 14 calculates the wind speed field based on the interference signal obtained by the detector 13. Thereby, the lidar device 100 according to Embodiment 1 can measure the wind speed field of the ground hemisphere space in a shorter time than before.

[0101] Further, the optical axis of the reception-side optical system 11 is arranged at an angle of 45 degrees with respect to the optical axis of the transmission-side optical system 5. Thereby, in the lidar device 100 according to Embodiment 1, the received light always received from the second direction (vertical direction) side is on the fast axis of the reception-side optical system 11, and the received light always received from the first direction (horizontal direction) side is on the slow axis of the reception-side optical system 11. It becomes possible to fix the optical axis of the reception-side optical system 11 so that they propagate respectively.

[0102] Further, the first direction is the horizontal direction, the second direction is the vertical direction, and the signal processing unit 14 is based on the data indicating the wind speed fields at a plurality of points at one altitude obtained by calculating the wind speed field in the horizontal direction and the data indicating the wind speed fields at one point at a plurality of altitudes obtained by calculating the wind speed field in the vertical direction. Generate data indicating the wind speed field at a plurality of altitudes and a plurality of points, and calculate the wind speed field at a plurality of altitudes and a plurality of points from the generated data. Thereby, the lidar device 100 according to Embodiment 1 can measure the wind speed field of the ground hemisphere space in a shorter time than before.

[0103] Further, the signal processing unit 14 virtually generates data indicating the wind speed field at a point with an altitude of 0 in the vertical direction, calculates the ratio of data indicating the wind speed fields at a plurality of altitude 1 points based on the generated data, and multiplies the calculated ratio by the data indicating the wind speed fields at a plurality of points at one altitude obtained by calculating the wind speed field in the horizontal direction, thereby generating data indicating the wind speed fields at a plurality of altitudes and a plurality of points. As a result, the lidar device 100 according to the first embodiment can measure the wind speed field in the ground hemisphere space in a shorter time than before.

[0104] Embodiment 2. In Embodiment 1, the lidar device 100 capable of measuring the wind speed field in the ground hemisphere space in a shorter time than before has been described. In Embodiment 2, a lidar device 100b will be described, which has fewer components than Embodiment 1 and can vary the elevation angle (EL) when scanning the transmission light on the scanning side.

[0105] FIG. 7 is a diagram showing a configuration example of the scanning unit 17b in the lidar device 100b according to the second embodiment. The lidar device 100b according to the second embodiment is different from the lidar device 100 according to the first embodiment shown in FIG. 1 in that the scanning unit 17 is changed to the scanning unit 17b. Since the other configurations of the lidar device 100b according to the second embodiment are the same as those of the lidar device 100 according to the first embodiment shown in FIG. 1, the same reference numerals are given and the description thereof is omitted.

[0106] The scanning unit 17b is composed of a deflection output polarization beam splitter rotation unit 18, a deflection output polarization beam splitter 19, a window 10, and a window 16. That is, in the scanning unit 17b, the polarization beam splitter 8 that constituted the scanning unit 17 in the first embodiment is replaced by a deflection output polarization beam splitter 19. Also, thereby, in the scanning unit 17b, the polarization TowardsThe optical element 9 becomes unnecessary. Note that the scanning unit 17b is rotated by the rotation control unit 15b in the same manner as the scanning unit 17 in the first embodiment.

[0107] The deflection output polarizing beam splitter 19 is optically connected to the polarization direction rotation unit 7, the windows 10 and 16. The deflection output polarizing beam splitter 19 is provided with an inclination on the P polarization component, that is, the surface on the transmitted light side guided to the vertical side. For example, a cube-shaped polarizing beam splitter has a cube shape and the opposing surfaces are horizontal, whereas the deflection output polarizing beam splitter 19 is configured such that one of the opposing surfaces is an inclined surface having a predetermined angle instead of being horizontal, taking into account the incident surface of the transmitted light from the polarization direction rotation unit 7.

[0108] By configuring in this way, according to the refractive index of the deflection output polarizing beam splitter 19, a deflection angle occurs in the light emitted from the deflection output polarizing beam splitter 19, that is, the transmitted light guided to the vertical side. As a result, in the scanning unit 17b, the polarization used in the first embodiment Towards The optical element 9 becomes unnecessary.

[0109] Note that the deflection output polarizing beam splitter 19 is not provided with an inclination on the S polarization component, that is, the surface on the transmitted light side guided to the scanning side. Therefore, the transmitted light guided to the scanning side is irradiated in the same manner as in the first embodiment.

[0110] The deflection output polarizing beam splitter rotation unit 18 is constituted by, for example, a rotation stage. The deflection output polarizing beam splitter rotation unit 18 rotates and fixes the deflection output polarizing beam splitter 19. The deflection output polarizing beam splitter rotation unit 18 is electrically connected to the signal processing unit 14 and rotates under the control of the signal processing unit 14.

[0111] Next, a description will be given of an operation example and effects of the laser radar device 100b according to embodiment 2. Note that the operation example of the laser radar device 100b according to embodiment 2 differs from the operation example of the laser radar device 100 according to embodiment 1 only in the operation example of the scanning unit 17b, and therefore, the operation example of the scanning unit 17b will be described here.

[0112] For example, in the first embodiment, the P-polarized component, i.e., the transmitted light guided to the vertical side by the polarized beam splitter 8 constituting the scan unit 17, has a traveling direction that differs by approximately 90 degrees from the scanning side. Therefore, for example, if the transmitted light output from the polarization direction rotation unit 7 is in the zenith direction (a direction at 90 degrees to the ground), the transmitted light on the scanning side is irradiated in a direction horizontal to the ground, and the transmitted light on the vertical side is irradiated in the zenith direction. Also, in the first embodiment, on the vertical side, the polarized component is guided to the rear of the polarized beam splitter 8. Towards By providing the optical element 9, the transmitted light on the vertical side becomes transmitted light tilted from the zenith direction. In the first embodiment, scanning this transmitted light results in a conical scan, and as described above, a wind field can be obtained by, for example, VAD processing.

[0113] On the other hand, in the second embodiment, as described above, a slope is provided on the surface of the P-polarized component, that is, the transmitted light side guided to the vertical side. れ (untranslatable without context) In the second embodiment, a polarized output polarized beam splitter 19 is provided in place of the polarized beam splitter 8. As a result, in the second embodiment, as in the first embodiment, a deflection angle can be imparted to the light emitted from the polarized output polarized beam splitter 19, i.e., the transmitted light guided to the vertical side. Towards The optical element 9 is no longer necessary, and the number of parts is reduced compared to the first embodiment.

[0114] Furthermore, in the second embodiment, for example, by controlling the polarized output polarized beam splitter rotation unit 18 via the signal processing unit 14 in response to instructions from a user, the polarized output polarized beam splitter 19 is rotated and fixed in a predetermined position, whereby the elevation angle of the transmitted light on the scan side can be changed to a predetermined elevation angle.

[0115] For example, in Embodiment 1, as described above, since the transmission light on the scan side is horizontal with respect to the ground, a PPI scan with an elevation angle of 0 degrees is performed on the scan side. However, for example, when it is desired to perform scanning while avoiding obstacles such as structures, it may be better to change the elevation angle. In this regard, in Embodiment 2, as described above, by rotating the deflection output polarization beam splitter 19 by the deflection output polarization beam splitter rotation unit 18, the elevation angle of the transmission light on the scan side can be changed to a predetermined elevation angle. This function is convenient when it is desired to perform scanning while avoiding obstacles such as the above-mentioned structures on the scan side.

[0116] As described above, according to Embodiment 2, the lidar device 100b branches the laser beam whose polarization direction is rotated by the polarization direction rotation unit 7 into a first direction and a second direction instead of the polarization beam splitter 8, and can give a deflection angle by a predetermined angle to the laser beam branched in the second direction. The lidar device 100b includes a deflection output polarization beam splitter 19, and the rotation control unit 15 rotates the polarization direction rotation unit 7 and the deflection output polarization beam splitter 19 at different rotational angular velocities. Thereby, in addition to the effects of Embodiment 1, the lidar device 100b according to Embodiment 2 reduces the number of components compared to Embodiment 1.

[0117] Further, the first direction is the horizontal direction, the second direction is the vertical direction, and the lidar device 100b according to Embodiment 2 includes a rotation unit 18 that rotatably fixes the deflection output polarization beam splitter 19 so that the elevation angle when performing scanning in the horizontal direction can be changed. Thereby, the lidar device 100b according to Embodiment 2 can change the elevation angle of the transmission light on the horizontal direction side to a predetermined elevation angle.

[0118] Note that in the present disclosure, free combinations of each embodiment, modifications of any components of the embodiment, or omissions of any components in the embodiment are possible.

Industrial Applicability

[0119] The present disclosure enables measurement of the wind speed field in the upper hemisphere space in a shorter time than before and is suitable for use in a lidar device.

Explanation of Signs

[0120] 1 Light source, 2 Branching section, 3 Modulation section, 4 Amplification section, 5 Transmission-side optical system, 6 Transmission-reception separation section, 7 Polarization direction rotation section, 8 Polarizing beam splitter, 9 Polar Towards Optical element, 10 Window, 11 Reception-side optical system, 12 Reception-side polarizing beam splitter, 13 Optical IQ detector (detector), 14 Signal processing section, 15 Rotation control section, 15a Rotation control section, 15b Rotation control section, 16 Window, 17 Scanning section, 17b Scanning section, 18 Deflection output polarizing beam splitter rotation section (rotation section), 19 Deflection output polarizing beam splitter, 100 Lidar device, 100b Lidar device, U C Wind speed field, U S Wind speed field, U V Wind speed field, rotation angle of θ2λ / 2 wavelength plate, θ S Rotation angle of the scanning section.

Claims

1. A polarization direction rotation unit that rotates the polarization direction of the input laser light by a predetermined angle, A polarization beam splitter that branches the laser light whose polarization direction has been rotated by the polarization direction rotation unit into a first direction and a second direction different from the first direction, A rotation control unit that rotates the polarization direction rotation unit and the polarization beam splitter at different rotational angular velocities to realize a circular scan by the laser light branched in the first direction and a conical scan by the laser light branched in the second direction, A signal processing unit that calculates a wind speed field using the reflected light reflected by the irradiation target of the laser light in each of the scans, comprising, The first direction is a horizontal direction, The second direction is a vertical direction, The polarization direction rotation unit is composed of a λ / 2 wavelength plate, The rotation control unit rotates the polarization beam splitter and the λ / 2 wavelength plate such that the rotational angular velocity of the polarization beam splitter is twice the rotational angular velocity of the λ / 2 wavelength plate in a state where an offset angle with respect to the optical axis of the polarization beam splitter is given with respect to the rotation angle of the λ / 2 wavelength plate. A lidar device characterized by the above.

2. A deflection optical element is provided at the subsequent stage of the polarization beam splitter in the vertical direction, By giving a deflection angle of a predetermined angle to the laser light branched in the vertical direction by the polarization beam splitter by the deflection optical element, a conical scan by the laser light branched in the vertical direction is realized. The lidar device according to claim 1, characterized by the above.

3. The rotation control unit, While maintaining a state where the vector corresponding to the optical axis of the λ / 2 wavelength plate and the vector obtained by projecting the normal vector of the reflection surface of the polarization beam splitter onto the λ / 2 wavelength plate are not parallel, rotate the λ / 2 wavelength plate and the polarization beam splitter The lidar device according to any one of claims 1 or 2, characterized in that.

4. The lidar device according to any one of claims 1 or 2, characterized in that the magnitude of the offset angle can be arbitrarily set.

5. A light source that outputs laser light having a wavelength band capable of reflecting the irradiation target of the laser light and having linear polarization characteristics, A branching unit that branches the laser light output from the light source, A modulation unit that pulse-modulates one of the laser lights branched by the branching unit, An amplification unit that amplifies the power of the laser light pulse-modulated by the modulation unit, A transmission-side optical system that shapes the laser light amplified by the amplification unit, A transmission / reception separation unit that separates the laser light shaped by the transmission-side optical system and the reflected light of the laser light by the irradiation target, A reception-side optical system that receives the reflected light separated by the transmission / reception separation unit, A detector that obtains a predetermined interference signal by combining the reflected light received by the reception-side optical system and the other of the laser lights branched by the branching unit, Comprising, The polarization direction rotation unit rotates the polarization direction of the laser light separated by the transmission / reception separation unit by a predetermined angle, The signal processing unit calculates the wind speed field based on the interference signal obtained by the detector The lidar device according to claim 1, characterized in that.

6. The lidar device according to claim 5, characterized in that the optical axis of the reception-side optical system is arranged at an angle of 45 degrees with respect to the optical axis of the transmission-side optical system.

7. The signal processing unit generates data indicating the wind speed fields at a plurality of points at a plurality of altitudes based on data indicating the wind speed fields at a plurality of points at one altitude obtained by calculating the wind speed field in the horizontal direction and data indicating the wind speed fields at one point at a plurality of altitudes obtained by calculating the wind speed field in the vertical direction, and calculates the wind speed fields at a plurality of points at a plurality of altitudes from the generated data. The lidar device according to claim 1, characterized in that.

8. The signal processing unit virtually generates data indicating the wind speed field at the point of altitude 0 in the vertical direction, calculates the ratio of the data indicating the wind speed fields at one point at a plurality of altitudes based on the generated data, and multiplies the calculated ratio by the data indicating the wind speed fields at a plurality of points at one altitude obtained by calculating the wind speed field in the horizontal direction, thereby generating data indicating the wind speed fields at a plurality of points at a plurality of altitudes. The lidar device according to claim 7, characterized in that.

9. A polarization direction rotation unit that rotates the polarization direction of the input laser light by a predetermined angle, a deflection output polarization beam splitter that branches the laser light whose polarization direction has been rotated by the polarization direction rotation unit into a first direction and a second direction different from the first direction, and can give a predetermined angle of deflection to the laser light branched into the second direction, a rotation control unit that rotates the polarization direction rotation unit and the deflection output polarization beam splitter at different rotational angular velocities to realize a circular scan by the laser light branched into the first direction and a conical scan by the laser light branched into the second direction, a signal processing unit that calculates the wind speed field using the reflected light reflected by the irradiation target of the laser light in each scan, comprising the first direction is the horizontal direction, the second direction is the vertical direction, the polarization direction rotation unit is composed of a λ / 2 wavelength plate, The rotation control unit rotates the deflection output polarization beam splitter and the λ / 2 wavelength plate such that, with respect to the rotation angle of the λ / 2 wavelength plate, the rotation angular velocity of the deflection output polarization beam splitter is twice that of the λ / 2 wavelength plate in a state where an offset angle with respect to the optical axis of the deflection output polarization beam splitter is applied. A lidar device characterized by the above.

10. A rotation unit that rotatably fixes the deflection output polarization beam splitter so that the elevation angle when performing scanning with respect to the horizontal direction can be changed. The lidar device according to claim 9, characterized by the above.

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