WO2015087564A1 - レーザレーダ装置 - Google Patents
レーザレーダ装置 Download PDFInfo
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- WO2015087564A1 WO2015087564A1 PCT/JP2014/063724 JP2014063724W WO2015087564A1 WO 2015087564 A1 WO2015087564 A1 WO 2015087564A1 JP 2014063724 W JP2014063724 W JP 2014063724W WO 2015087564 A1 WO2015087564 A1 WO 2015087564A1
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- transmission
- laser radar
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
- G01S7/4815—Constructional features, e.g. arrangements of optical elements of transmitters alone using multiple transmitters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/95—Lidar systems specially adapted for specific applications for meteorological use
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
- H01S3/0085—Modulating the output, i.e. the laser beam is modulated outside the laser cavity
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
- H01S3/2383—Parallel arrangements
- H01S3/2391—Parallel arrangements emitting at different wavelengths
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
- H01S3/302—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects in an optical fibre
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0617—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium using memorised or pre-programmed laser characteristics
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Definitions
- the present invention relates to a laser radar device that emits laser light into the atmosphere, receives scattered light of the laser light from a target, and extracts information about the target from the scattered light.
- Non-Patent Document 1 As a conventional laser radar apparatus, there is a coherent laser radar apparatus in which transmission light is pulsed by using an acousto-optic (AO) element pulse-driven by an optical modulator (see, for example, Non-Patent Document 1).
- AO acousto-optic
- the peak power of the transmission light is limited by a nonlinear optical effect called stimulated Brillouin scattering that occurs in the optical fiber. Therefore, a method of measuring a high S / N ratio by increasing transmission power using a plurality of CW laser light sources having different frequencies has been invented (see, for example, Patent Document 1).
- Non-Patent Document 1 and Patent Document 1 only the line-of-sight direction of a transmission / reception optical system used for transmission / reception of laser light can be measured. For this reason, when measuring in different gaze directions, or when measuring a wider range and obtaining a distribution by calculation or the like, it is necessary to scan with laser light. For this reason, it may be used in combination with a scanner device using a reflection mirror, a rotating wedge plate, or the like capable of adjusting the angle. In addition, a plurality of laser radar devices may be arranged in order to simultaneously perform multi-gaze direction measurement.
- the method using the scanner device has a problem that the device becomes large and complicated. Further, the scanner device that mechanically drives the reflecting mirror and the wedge plate has a problem that the life and reliability of the device are lowered. In addition, in the method of scanning with laser light, the measurement time per line-of-sight direction is shortened, so that there is a problem that the received signal strength is reduced, and the measurable distance and accuracy are reduced.
- the present invention has been made to solve the above-described problems, and has a simple and inexpensive configuration and can simultaneously measure multi-gaze directions without using a mechanically driven scanner device.
- the object is to provide a radar device.
- a laser radar device includes a plurality of reference light sources that oscillate laser beams having different frequencies, and a plurality of lights that are provided corresponding to the reference light sources and branch the laser light oscillated by the corresponding reference light sources.
- a branching unit, a plurality of optical modulators that are provided corresponding to the optical branching units and modulate one of the laser beams branched by the corresponding optical branching unit, and laser beams modulated by the respective optical modulators are mixed.
- a transmission / reception optical system that emits the first mixed light output by the first optical multiplexer and receives the scattered light of the first mixed light by the target, and the scattered light received by the transmission / reception optical system and the second And the second mixed light output by the optical multiplexer of
- a third optical multiplexer that outputs a third mixed light, a photodetector that detects a beat signal from the third mixed light output by the third optical multiplexer, and a detector that detects the beat signal;
- An information extractor that extracts information about the target from the beat signal and a dispersive element that is arranged in front of or behind the transmission / reception optical system and emits the incident light in a specific direction according to the angle and frequency of the incident light. It is a thing.
- a laser radar device includes a reference light source that oscillates laser light of a specific frequency, the frequency of which is variable, an optical splitter that branches the laser light oscillated by the reference light source, and an optical splitter.
- An optical modulator that modulates one of the laser beams branched by the laser, a transmission / reception optical system that emits the laser light modulated by the optical modulator and receives the scattered light of the laser light by the target, and is received by the transmission / reception optical system
- a fourth optical multiplexer that outputs the fourth mixed light by mixing the scattered light and the other laser beam branched by the optical splitter, and the fourth optical multiplexer output by the fourth optical multiplexer
- a photodetector that detects a beat signal from the mixed light, an information extractor that extracts information about the target from the beat signal detected by the photodetector, and a front or rear of the transmission / reception optical system. frequency It is obtained by a dispersion element for emitting the incident light in a specific direction according to.
- FIG. 1 is a diagram showing a configuration of a laser radar apparatus according to Embodiment 1 of the present invention.
- the laser radar device receives the scattered light from the aerosol (particles such as dust floating in the atmosphere) by irradiating the laser light into the atmosphere, and measures the wind speed by detecting the Doppler shift of the scattered light.
- Coherent Doppler lidar device As shown in FIG.
- the laser radar apparatus includes a plurality of CW laser light sources (reference light sources) 1, a plurality of optical branching couplers 2, a plurality of optical modulators 3, and an optical multiplexing coupler (first multiplexer) 4.
- Optical multiplexer coupler (second multiplexer) 5 optical fiber amplifier 6, optical circulator 7, transmission / reception optical system 8, diffraction grating (dispersing element) 9, optical multiplexer coupler (third multiplexer) 10, light It comprises a detector 11 and a signal processing device (information extractor) 12.
- the propagation optical path of the laser beam in the apparatus is constituted by an optical fiber.
- FIG. 1 shows a case where two CW laser light sources 1a and 1b, two optical branching couplers 2a and 2b, and two optical modulators 3a and 3b are provided.
- the CW laser light source 1a oscillates a CW (Continuous Wave) laser beam having a specific frequency.
- the CW laser light oscillated by the CW laser light source 1a is coupled to the optical fiber and output to the optical branching coupler 2a.
- the CW laser light source 1b oscillates CW laser light having a specific frequency.
- the CW laser light oscillated by the CW laser light source 1b is coupled to the optical fiber and output to the optical branching coupler 2b.
- the frequencies of the CW laser beams oscillated by the CW laser light sources 1 a and 1 b are different from each other and are within the gain band of the optical fiber amplifier 6.
- the frequency difference is set to be larger than the gain bandwidth of stimulated Brillouin scattering generated in the optical fiber.
- each CW laser beam is preferably as narrow as possible to increase the accuracy of coherent detection, and for example, it is preferable to use one having a frequency of 100 kHz or less.
- CW laser light sources 1a and 1b for example, a DFB (Distributed Feed-Back) fiber laser, a DFB-LD (Laser Diode), or the like can be used.
- the optical branching coupler 2a is provided corresponding to the CW laser light source 1a, and branches the CW laser light from the CW laser light source 1a into two.
- One CW laser beam bifurcated by the optical branching coupler 2a is output to the optical modulator 3a as transmission seed light, and the other CW laser beam is output to the optical multiplexing coupler 5 as local oscillation light for coherent detection.
- the optical branching coupler 2b is provided corresponding to the CW laser light source 1b, and branches the CW laser light from the CW laser light source 1b into two.
- One CW laser beam branched into two by this optical branching coupler 2b is output to the optical modulator 3b as transmission seed light, and the other CW laser beam is output to the optical multiplexing coupler 5 as local oscillation light for coherent detection.
- the optical power branching ratio in the optical branching couplers 2a and 2b has a small dependence on the frequency of the CW laser light.
- the optical modulator 3a is provided corresponding to the optical branching coupler 2a, and pulsates the transmission seed light from the optical branching coupler 2a to add frequency modulation (add an intermediate frequency when performing coherent detection). It is.
- the transmission seed light modulated by the optical modulator 3 a is output to the optical multiplexing coupler 4.
- the optical modulator 3b is provided corresponding to the optical branching coupler 2b, and pulsates the transmission seed light from the optical branching coupler 2b to add frequency modulation (add an intermediate frequency when performing coherent detection). It is.
- the transmission seed light modulated by the optical modulator 3 b is output to the optical multiplexing coupler 4.
- the intermediate frequencies by the optical modulators 3a and 3b are set to different values, and the frequencies after the modulation by the optical modulators 3a and 3b are set to different values.
- an acousto-optic modulator (AOM) as the optical modulators 3a and 3b, pulsing by cutting out the CW laser light with a time gate and addition of a frequency shift are simultaneously performed.
- AOM acousto-optic modulator
- the intermediate frequency is usually a frequency of about several tens to several hundreds of MHz, and a value suitable for the system is selected.
- the optical multiplexing coupler 4 mixes the transmission seed light modulated by the optical modulator 3a and the transmission seed light modulated by the optical modulator 3b.
- the transmission seed light (first mixed light) mixed by the optical multiplexing coupler 4 is output to the optical fiber amplifier 6.
- the optical multiplexing coupler 5 mixes the local oscillation light from the optical branching coupler 2a and the local oscillation light from the optical branching coupler 2b.
- the local oscillation light (second mixed light) mixed by the optical multiplexing coupler 5 is output to the optical multiplexing coupler 10.
- At least one optical fiber amplifier 6 is provided on the transmission-side propagation optical path, and amplifies the optical power of the first mixed light from the optical multiplexing coupler 4.
- the first mixed light whose optical power is amplified by the optical fiber amplifier 6 is output to the optical circulator 7.
- the optical fiber amplifier 6 an amplifier suitable for the wavelength band of the laser light to be used is used.
- an optical fiber amplifier using an Nd (Neodymium) -doped fiber or a Yb (Yterbium) -doped fiber can be used.
- an optical fiber amplifier using an Er (Erbium) doped fiber can be used.
- These optical fiber amplifiers have a gain bandwidth of about several nanometers to several tens of nanometers, and can amplify laser beams of a plurality of wavelengths at the same time as long as they are within the gain band.
- the optical circulator 7 selects an output destination according to input light.
- the optical circulator 7 outputs the transmission seed light to the transmission / reception optical system 8.
- the scattered light is input from the transmission / reception optical system 8
- the scattered light is output to the optical multiplexing coupler 10.
- the transmission / reception optical system 8 emits the first mixed light that has passed through the optical circulator 7 as transmission light toward the target (aerosol) through the diffraction grating 9, and scatters the transmission light of the transmission light by the target through the diffraction grating 9. Is received via The scattered light received by the transmission / reception optical system 8 is coupled to the optical fiber and output to the optical circulator 7.
- a telescope or the like capable of making the emitted laser light substantially parallel and adjusting the focal length can be used.
- a fiber collimator or the like may be used as the transmission / reception optical system 8, but an optical system with a large aperture is suitable for reducing the divergence angle of the emitted laser light and further increasing the reception efficiency.
- the diffraction grating 9 is an optical element that diffracts the laser light so as to be emitted in a specific direction according to the angle and frequency of the incident laser light.
- the transmission light from the transmission / reception optical system 8 is a mixture of transmission seed lights having different frequencies, and the diffracted light by the diffraction grating 9 is emitted at different angles (directions of the transmission lights 101a and 101b).
- the aerosol moves according to the atmospheric flow (wind), the scattered light undergoes a Doppler shift.
- the optical multiplexing coupler 10 mixes the scattered light from the optical circulator 7 and the second mixed light from the optical multiplexing coupler 5.
- the mixed light (third mixed light) mixed by the optical multiplexing coupler 10 is output to the photodetector 11.
- the photodetector 11 receives the third mixed light from the optical multiplexing coupler 10 and detects a beat signal between the scattered light and the local oscillation light.
- the beat signal detected by the photodetector 11 is output to the signal processing device 12.
- the signal processing device 12 processes the beat signal from the photodetector 11, extracts information related to the target (for example, information such as received signal intensity of scattered light, round trip time, and Doppler frequency) and relates to the extracted target.
- the target motion specifications for example, distance to the target, velocity distribution
- the CW laser light source 1a oscillates CW laser light having a specific frequency f1 and outputs it to the optical branching coupler 2a.
- the CW laser light source 1b oscillates CW laser light having a specific frequency f2 and outputs it to the optical branching coupler 2b.
- the frequencies f1 and f2 of the CW laser light oscillated by the CW laser light sources 1a and 1b are different from each other, are within the gain band of the optical fiber amplifier 6, and the difference between the frequency f1 and the frequency f2 Let it be greater than the gain bandwidth of stimulated Brillouin scattering that occurs in the fiber.
- the optical branching coupler 2a bifurcates the CW laser light having the frequency f1 from the CW laser light source 1a, outputs one as a transmission seed light to the optical modulator 3a, and outputs the other as a local oscillation light for coherent detection. Output to the wave coupler 5. Further, the optical branching coupler 2b splits the CW laser light having the frequency f2 from the CW laser light source 1b into two, outputs one to the optical modulator 3b as transmission seed light, and the other as the local oscillation light for coherent detection. Output to the wave coupler 5.
- the optical modulator 3a pulses the transmission seed light having the frequency f1 from the optical branching coupler 2a, and adds frequency modulation (adds an intermediate frequency fM1 when performing coherent detection).
- the transmission seed light having the frequency f1 + fM1 modulated by the optical modulator 3a is output to the optical multiplexing coupler 4.
- the optical modulator 3b pulses the transmission seed light having the frequency f2 from the optical branching coupler 2b, and adds frequency modulation (adds an intermediate frequency fM2 when performing coherent detection).
- the transmission seed light having the frequency f2 + fM2 modulated by the optical modulator 3b is output to the optical multiplexing coupler 4.
- the intermediate frequencies fM1 and fM2 are set to different values, and are set so that the condition of (fM1 + fd1) ⁇ (fM2 + fd2) or (fM1 + fd1)> (fM2 + fd2) is satisfied.
- the signal processing device 12 at the subsequent stage can identify two frequency components (fM1 + fd1, fM2 + fd2) of the beat signal detected by the photodetector 11, and individually measure the signal intensity of each frequency component. Is possible.
- the Doppler shift amounts fd1 and fd2 corresponding to the frequency of the transmission light can be measured, respectively, the wind speed distribution in the line-of-sight direction corresponding to the frequency of the transmission light can be measured.
- the optical multiplexing coupler 4 mixes the transmission seed light having the frequency f1 + fM1 modulated by the optical modulator 3a and the transmission seed light having the frequency f2 + fM2 modulated by the optical modulator 3b.
- the transmission seed light (first mixed light having the frequencies f1 + fM1 and f2 + fM2) mixed by the optical multiplexing coupler 4 is output to the optical fiber amplifier 6.
- the optical multiplexing coupler 5 mixes the local oscillation light having the frequency f1 from the optical branching coupler 2a and the local oscillation light having the frequency f2 from the optical branching coupler 2b.
- the locally oscillated light (second mixed light having frequencies f1 and f2) mixed by the optical multiplexing coupler 5 is output to the optical multiplexing coupler 10.
- the optical fiber amplifier 6 amplifies the optical power of the first mixed light from the optical multiplexing coupler 4.
- the first mixed light whose optical power is amplified by the optical fiber amplifier 6 is output to the optical circulator 7.
- the optical power of the laser beam to be transmitted can be increased, the intensity of the received light can be increased, and the measurement accuracy and the measurable distance can be increased.
- the gain bandwidth of stimulated Brillouin scattering is about several tens to 100 MHz. Therefore, for example, when two laser beams having a frequency difference larger than 100 MHz (for example, if the wavelength of the laser beam is 1550 nm corresponds to a wavelength difference of about 0.8 pm) are incident on the optical fiber, the two The gain of stimulated Brillouin scattering with respect to the laser light can be made different.
- the two laser beams can input optical power up to the incident power that becomes the threshold for occurrence of stimulated Brillouin scattering.
- the power of the laser beam that can be incident on the optical fiber is increased. Is possible.
- the threshold of stimulated Brillouin scattering may be exceeded in the process of increasing the optical power of the laser light, and the peak output tends to increase particularly when the pulsed light is amplified. Stimulated Brillouin scattering is likely to occur. For this reason, normally, the output optical power is adjusted and used, for example, by limiting the pumping power supplied to the optical fiber amplifier 6 so that stimulated Brillouin scattering does not occur.
- the difference between the frequencies f1 and f2 of the CW laser light oscillated by the CW laser light sources 1a and 1b is larger than the gain bandwidth of the stimulated Brillouin scattering generated in the optical fiber. Therefore, these laser lights can increase the peak power of the output pulse light up to the respective stimulated Brillouin scattering thresholds PSBS1 and PSBS2.
- the average output power of each laser beam (the average output power is expressed by the product of the peak power of the pulsed light, the pulse width, and the pulse repetition frequency) is PS1 and PS2, the output light of the optical fiber amplifier 6
- the average power can be PS1 + PS2, and the optical power of the transmitted light can be made larger than when a single light source (for example, only one of the CW laser light source 1a and the CW laser light source 1b) is used.
- PS1 PS2
- the optical power of the transmission light can be doubled by using the two CW laser light sources 1a and 1b.
- the input power increases in the optical fiber amplifier 6 by using the plurality of CW laser light sources 1a and 1b.
- the energy extraction efficiency can be improved, and the generation of ASE (Amplified Spontaneous Emission) components during amplification of the laser beam can be reduced. Therefore, there are an efficiency improvement effect of the optical fiber amplifier 6 and a noise component reduction effect in the photodetector 11.
- the optical circulator 7 outputs the transmission seed light from the optical fiber amplifier 6 to the transmission / reception optical system 8.
- the transmission / reception optical system 8 emits the transmission seed light that has passed through the optical circulator 7 toward the target via the diffraction grating 9 as transmission light.
- the transmission light emitted from the transmission / reception optical system 8 is a mixture of laser light of frequency f1 + fM1 and frequency f2 + fM2, and these laser lights have different frequencies. Therefore, the diffracted light by the diffraction grating 9 is transmitted at different angles (here, the laser light having the frequency f1 + fM1 incident on the diffraction grating 9 propagates in the direction of the transmission light 101a, and the laser light having the frequency f2 + fM2 is in the direction of the transmission light 101b.
- a laser beam can be irradiated to two different gaze directions toward the atmosphere. Further, since the diffraction angle of the laser light by the diffraction grating 9 is determined by the structural parameter of the diffraction grating 9, the wavelength (frequency) of the laser light, and the incident angle, if these values are grasped, the outgoing light 101a and 101b are emitted. Each direction can be determined.
- the transmission lights 101a and 101b emitted from the transmission / reception optical system 8 through the diffraction grating 9 are scattered by the aerosol present in the atmosphere. Then, when the scattered light from the aerosol enters the diffraction grating 9, it reversibly returns to the transmission / reception optical system 8, and the transmission / reception optical system 8 receives this scattered light and outputs it to the optical circulator 7.
- the propagation angle of the laser beam can be changed according to the frequency, and the laser beam can be transmitted and received in two different viewing directions.
- the scattered light undergoes a Doppler shift.
- the Doppler shifts received by the laser beams having the frequencies f1 + fM1 and f2 + fM2 that are transmitted light are fd1 and fd2, respectively, the frequencies of the scattered light are f1 + fM1 + fd1, f2 + fM2 + fd2.
- the optical circulator 7 outputs the scattered light from the transmission / reception optical system 8 to the optical multiplexing coupler 10.
- the optical multiplexing coupler 10 mixes the scattered light from the optical circulator 7 and the second mixed light having the frequencies f1 and f2 from the optical multiplexing coupler 5.
- the mixed light (third mixed light) mixed by the optical multiplexing coupler 10 is output to the photodetector 11.
- the photodetector 11 receives the third mixed light from the optical multiplexing coupler 10 and detects a beat signal of the scattered light and the local oscillation light.
- the scattered light contained in the third mixed light received by the photodetector 11 is subjected to a frequency shift by the optical modulators 3a and 3b and a Doppler shift accompanying the movement of the aerosol. Therefore, the frequency of the beat signal detected by the photodetector 11 is fM1 + fd1, fM2 + fd2.
- the beat signal detected by the photodetector 11 is output to the signal processing device 12.
- the signal processing device 12 processes the beat signal from the photodetector 11, extracts information related to the target (for example, information such as received signal intensity of scattered light, round trip time, and Doppler frequency) and relates to the extracted target. From the information, the motion specifications of the target (for example, the distance to the target, velocity distribution) are calculated. In addition, since the process which calculates the motion specification of a target from the information regarding a target is a well-known technique, detailed description is abbreviate
- the intermediate frequencies fM1 and fM2 are set to different values, and are set so that the condition of (fM1 + fd1) ⁇ (fM2 + fd2) or (fM1 + fd1)> (fM2 + fd2) is satisfied.
- the signal processing device 12 can identify two frequency components (fM1 + fd1, fM2 + fd2) of the beat signal detected by the photodetector 11, and can individually measure the signal of each frequency component. Since the intermediate frequencies fM1 and fM2 are known values given by the optical modulators 3a and 3b, fd1 and fd2 can be obtained by calculation, respectively.
- fd1 is a Doppler shift received by the transmission light of frequency f1 + fM
- fd2 is a Doppler shift received by the transmission light of frequency f2 + fM2. Since the two transmission lights are emitted in different directions by the diffraction grating 9, Doppler shifts in two different line-of-sight directions can be measured simultaneously.
- laser light is transmitted and received based on the two CW laser light sources 1a and 1b by one transmission / reception optical system 8, and two different gaze directions are observed by the diffraction grating 9.
- the apparatus configuration can be simplified, and the apparatus can be reduced in size and price.
- the device configuration can be simplified, and the size and cost of the device can be reduced.
- a mechanical drive system is not required, the life of the apparatus can be extended and the reliability can be improved.
- the laser radar apparatus of FIG. 1 can be used for measuring the two-dimensional distribution of the wind direction and the wind speed and measuring the change in the instantaneous wind direction and the wind speed distribution.
- the polarization planes of the local oscillation light and the scattered light that is the received light coincide with each other in the photodetector 11, efficient coherent detection can be performed.
- the polarization planes of the local oscillation light and the scattered light can be matched using a polarization plane controller (not shown).
- a polarization-maintaining optical fiber is used as an optical fiber for coupling optical elements and a polarization-maintaining optical fiber component is used for each optical element, a polarization controller or the like is not required.
- the polarization planes of the local oscillation light and the scattered light can be matched. Thereby, the apparatus configuration can be simplified. As shown in FIG.
- the optical path of the laser light can be easily routed and the apparatus can be downsized.
- the device can be easily configured by connection.
- the alignment of the optical axis is unnecessary, the stability of the apparatus is increased, and a highly reliable apparatus configuration is possible.
- the polarization plane adjustment is not required, so that the device configuration can be simplified, and a compact and highly reliable device can be constructed. Is possible.
- the pulse timing of the laser beam may be synchronized using a signal generator (not shown).
- a signal generator not shown.
- the rise times of the pulse laser beams mixed by the optical multiplexing coupler 4 can be matched, and the transmission light emission timings of the respective frequencies can be matched. Processing such as measurement can be simplified.
- CW laser light sources 1a and 1b are used, but a larger number of CW laser light sources 1 may be used.
- the optical branching coupler 2 and the optical modulator 3 are added by the number of the CW laser light sources 1, all the transmission seed lights are mixed by the optical multiplexing coupler 4, and all the transmission seed lights are mixed by the optical multiplexing coupler 5.
- the frequencies of the CW laser light source 1 are different from each other, are within the gain band of the optical fiber amplifier 6, and the difference between the frequencies is larger than the gain bandwidth (approximately 100 MHz) of stimulated Brillouin scattering that occurs in the optical fiber.
- the intermediate frequency given by the optical modulator 3 is set to a magnitude that allows the received signal to be individually identified by the signal processing device 12.
- the diffraction grating 9 diffraction occurs according to the frequency of the laser light, and the laser light can be emitted in the direction corresponding to the quantity of the CW laser light source 1. Can be measured simultaneously. Thereby, the two-dimensional distribution of the wind direction and the wind speed can be obtained more accurately.
- the diffraction grating 9 shown in FIG. 1 has a configuration of a reflection type diffraction grating that reflects diffracted light
- a transmission type diffraction grating that transmits laser light and generates diffraction may be used.
- the diffraction grating 9 is designed so that the diffraction efficiency is high with respect to the wavelength band of the laser beam, the loss of the laser beam for transmission and reception can be reduced, and the efficiency of the apparatus can be increased. it can.
- high-order diffracted light generated by the diffraction grating 9 may be blocked using an opening (not shown).
- the diffraction grating 9 may be a dispersive element capable of changing the propagation angle according to the wavelength of the laser light, and a prism may be used instead of the diffraction grating.
- FIG. FIG. 2 is a diagram showing a configuration of a laser radar apparatus according to Embodiment 2 of the present invention.
- the laser radar device according to the second embodiment shown in FIG. 2 is obtained by changing the CW laser light sources 1a and 1b of the laser radar device according to the first embodiment shown in FIG. 1 to CW laser light sources 13a and 13b.
- Other configurations are the same, and only the different parts are described with the same reference numerals.
- the CW laser light source 13a can change the oscillation frequency in the range of f1 to f1 ′, and oscillates a CW laser beam having a set specific frequency.
- the CW laser light oscillated by the CW laser light source 13a is coupled to the optical fiber and output to the optical branching coupler 2a.
- the CW laser light source 13b can change the oscillation frequency in the range of f2 to f2 ′, and oscillates a CW laser beam having a set specific frequency.
- the CW laser light oscillated by the CW laser light source 13b is coupled to the optical fiber and output to the optical branching coupler 2b.
- the frequencies f1 to f1 ′ and f2 to f2 ′ of the CW laser beams oscillated by the CW laser light sources 13a and 13b are different from each other and are within the gain band of the optical fiber amplifier 6.
- the frequency difference is set to be larger than the gain bandwidth of stimulated Brillouin scattering generated in the optical fiber.
- each CW laser beam is preferably as narrow as possible to increase the accuracy of coherent detection, and for example, it is preferable to use one having a frequency of 100 kHz or less.
- CW laser light sources 13a and 13b for example, a DFB fiber laser, DFB-LD, or the like can be used.
- the oscillation frequency can be changed by temperature modulation of these laser light sources.
- the frequency of the transmission laser light based on the CW laser light source 13b is f2 ′ + fM2, which is a frequency different from f2 + fM2 in the configuration of FIG. become. Therefore, the diffraction angles by the diffraction grating 9 are different, and the light is emitted in the direction of the transmission light 102b. Thereby, it is possible to measure the wind speed distribution in the line-of-sight direction in a direction different from the case where the frequency of the CW laser light source 13b is f2 (the direction in which the transmission light 102b is emitted).
- the diffraction angle by the diffraction grating 9 is changed. It is possible to change the viewing direction of the measurement by changing the emitting direction of the laser beam. Further, since the diffraction angle of the diffraction grating 9 depends on the frequency of the incident laser beam, the laser beam can be transmitted in a desired direction by appropriately setting the oscillation frequency of the CW laser light sources 13a and 13b. it can. In this way, in the configuration of FIG. 2, it is possible to change the line-of-sight direction while simultaneously measuring two different line-of-sight directions.
- the laser beam emission direction can be changed continuously or stepwise, and the line-of-sight direction for measurement is changed continuously or stepwise. Can be changed. Thereby, a laser beam can be scanned. With this configuration, the laser beam can be scanned with a simple configuration, and the size and cost of the apparatus can be reduced. Furthermore, since a mechanical drive system is not required, the life of the apparatus can be extended and the reliability can be improved.
- the CW laser light sources 13a and 13b respectively oscillate CW laser light, two different sight line directions can be measured simultaneously, and the same effect as in the first embodiment can be obtained.
- two CW laser light sources 13a and 13b are used, but a larger number of CW laser light sources 13 may be used. In this case, the laser beam can be scanned in a wider range according to the number of CW laser light sources 13.
- FIG. 3 is a diagram showing the configuration of the laser radar apparatus according to Embodiment 3 of the present invention.
- the laser radar apparatus according to the third embodiment shown in FIG. 3 is driven by removing the optical branching coupler 2b, the optical modulator 3b, and the optical multiplexing couplers 4 and 5 from the laser radar apparatus according to the first embodiment shown in FIG. Circuits 14a and 14b, a controller 15 and an optical multiplexing coupler 16 are added.
- Other configurations are the same, and only the different parts are described with the same reference numerals.
- the drive circuit 14a is provided corresponding to the CW laser light source 1a and operates the CW laser light source 1a.
- the drive circuit 14b is provided corresponding to the CW laser light source 1b and operates the CW laser light source 1b.
- the controller 15 operates one of the drive circuits 14a and 14b on the basis of the processing result of the signal processing device 12 (the operating state of the CW laser light sources 1a and 1b), thereby alternately operating the CW laser light sources 1a and 1b. Is switched to.
- the optical multiplexing coupler 16 joins the path through which the CW laser light from the CW laser light source 1a passes and the path through which the CW laser light from the CW laser light source 1b passes.
- the optical branching coupler 2a bifurcates the CW laser light from the optical multiplexing coupler 16, outputs one CW laser light to the optical modulator 3a as transmission seed light, and uses the other CW laser light for coherent detection.
- the light is output to the optical multiplexing coupler 10 as local oscillation light.
- the laser light output from the CW laser light source 1a passes through the optical multiplexing coupler 16. Then, after passing through the optical multiplexing coupler 16, it is emitted in the direction of the transmission light 101a by the same process as in the first embodiment. At this time, the received light corresponds to the line-of-sight direction of the transmission light 101a, and the signal processing device 12 can obtain the wind speed in the line-of-sight direction of the transmission light 101a.
- the laser light output from the CW laser light source 1b passes through the optical multiplexing coupler 16. Then, after passing through the optical multiplexing coupler 16, the same process as the laser light from the CW laser light source 1a is performed. Is emitted. At this time, the received light corresponds to the line-of-sight direction of the transmission light 103b, and the signal processing device 12 can obtain the wind speed in the line-of-sight direction of the transmission light 103b.
- the CW laser light source 1a and the CW laser light source 1b are configured to be switched and operated, measurement can be performed by switching the line-of-sight direction to two directions. .
- the Doppler shift for two different gaze directions cannot be measured completely simultaneously.
- the time difference can be reduced and the two line-of-sight directions can be measured. And a two-dimensional distribution of wind speeds.
- the locally transmitted light input to the photodetector 11 is only a component based on the CW laser light sources 1a and 1b that generate the transmitted light. Therefore, the noise component in the photodetector 11 is reduced, and highly sensitive and highly accurate detection can be performed. Further, since only the reception signals corresponding to the CW laser light sources 1a and 1b being operated are detected, only one optical modulator 3a is required, and the apparatus can be simplified. Further, in the case of FIG. 1, since there is no restriction on the intermediate frequency in the optical modulator 3a for distinguishing the necessary received signals, it is easy to select components.
- FIG. 4 is a diagram showing a configuration of a laser radar apparatus according to Embodiment 4 of the present invention.
- the laser radar device according to the fourth embodiment shown in FIG. 4 is different from the laser radar device according to the second embodiment shown in FIG. 2 in the CW laser light source 13b, the optical branching coupler 2b, the optical modulator 3b, and the optical multiplexing couplers 4 and 5. Is deleted, and a drive circuit 14a and a controller 17 are added. Other configurations are the same, and only the different parts are described with the same reference numerals.
- the drive circuit 14a is provided corresponding to the CW laser light source 13a and operates the CW laser light source 13a.
- the controller 17 changes the oscillation frequency of the operating CW laser light source 13a by operating the drive circuit 14a based on the processing result of the signal processing device 12 (the operating state of the CW laser light source 13a).
- the optical branching coupler 2a bifurcates the CW laser light from the CW laser light source 13a, outputs one CW laser light to the optical modulator 3a as transmission seed light, and uses the other CW laser light for coherent detection.
- the light is output to the optical multiplexing coupler 10 as local oscillation light.
- the optical multiplexing coupler 10 according to the fourth embodiment is a fourth mixed light obtained by mixing the scattered light received by the transmission / reception optical system and the other laser beam branched by the optical splitter. Corresponds to a “fourth optical multiplexer”.
- the line-of-sight direction that can be measured instantaneously is only one direction, but by changing the oscillation frequency of the CW laser light source 13a, the emission direction of the laser light is changed in the range from the transmission light 101a to the transmission light 102a.
- the laser beam can be scanned.
- the two-dimensional distribution of the wind direction and the wind speed can also be obtained by processing such as calculation.
- the locally transmitted light input to the photodetector 11 is only a component based on the CW laser light source 13a that generates the transmission light. Therefore, the noise component in the photodetector 11 is reduced, and highly sensitive and highly accurate detection can be performed. Further, since only the reception signal corresponding to the CW laser light source 13a being operated is detected, only one optical modulator 3a is required, and the apparatus can be simplified. Furthermore, since there is no restriction on the intermediate frequency in the optical modulator 3a for distinguishing the received signal required in the case of FIG. 1, the selection of the components is facilitated.
- the operation of the plurality of CW laser light sources 1a and 1b is switched, and in the fourth embodiment, the frequency control of the single CW laser light source 13a is shown.
- a plurality of CW laser light sources 13a and 13b may be provided to perform operation switching and frequency control of the plurality of CW laser light sources 13a and 13b.
- FIG. FIG. 5 is a diagram showing the configuration of a laser radar apparatus according to Embodiment 5 of the present invention.
- Other configurations are the same, and only the different parts are described with the same reference numerals.
- the collimator 18 converts the transmitted light that has passed through the optical circulator 7 into substantially parallel light.
- the transmission light converted into substantially parallel light by the collimator 18 is incident on the diffraction grating 9. Thereafter, the diffracted light generated by the diffraction grating 9 is separated by the frequency of the transmitted light, propagates in the direction of the transmitted light 101a and 101b, and enters the transmission / reception optical system 8. Then, after passing through the transmission / reception optical system 8, the light is emitted in the directions of the transmission lights 104a and 104b, respectively.
- the outgoing directions of the transmission lights 104a and 104b after passing through the transmission / reception optical system 8 are determined by the magnification of the transmission / reception optical system 8 and the incident angle of the laser light. Therefore, if these values are known, the transmitted light 104a.
- the emission direction of 104b can be known. Thereby, like the case of Embodiment 1, two different gaze directions can be measured simultaneously.
- the diffraction grating 9 can be reduced in size, making the diffraction grating 9 easy to manufacture and selecting parts easily.
- the cost of the apparatus can be reduced.
- the apparatus can be reduced in size.
- the transmission / reception optical system 8 allows the transmission lights 101a and 101b to enter the incident aperture.
- the diffraction angle of the diffraction grating 9 is designed to a suitable value in consideration of the magnification of the transmission / reception optical system 8.
- the configuration in which the diffracted light by the diffraction grating 9 is allowed to pass through the transmission / reception optical system 8 can be applied to all the above embodiments.
- FIG. 6 is a diagram showing the configuration of a laser radar apparatus according to Embodiment 6 of the present invention.
- the laser radar device according to the sixth embodiment shown in FIG. 6 is obtained by adding a drive device 19 to the laser radar device according to the fifth embodiment shown in FIG.
- Other configurations are the same, and only the different parts are described with the same reference numerals.
- the driving device 19 is provided in the diffraction grating 9.
- the transmission lights 104a and 104b are emitted in the xy plane using the coordinate system written in the drawing.
- the drive device 19 is a device that changes the installation angle of the diffraction grating 9, and can change the installation angle of the diffraction grating 9 so that the incident surface of the diffraction grating 9 has an inclination with respect to the z-axis.
- the transmitted lights 104a and 104b are emitted with an inclination with respect to the xy plane.
- the driving device 19 can be a movable stage using a motor, a piezo element, or the like.
- the driving device 19 may rotate the diffraction grating 9 about the z axis.
- the incident angle of the laser beam with respect to the diffraction grating 9 can be changed, and the transmitted light can be scanned in the xy plane, and the measurable line-of-sight direction can be measured.
- the range can be expanded.
- the structure which provides the drive device 19 in the diffraction grating 9 is applicable to all the said embodiment.
- the optical fiber amplifier 6 is used. However, the optical power of the transmission light necessary for the desired device performance can be obtained only from the outputs of the CW laser light sources 1 and 13. If possible, the optical fiber amplifier 6 is not necessary.
- the optical fiber amplifier 6 When the optical fiber amplifier 6 is used, the optical power of the laser beam to be transmitted can be further increased, the intensity of the received light can be increased, and the measurement accuracy and the measurable distance can be increased.
- a spatial laser light amplifier may be used. Since the spatial laser light amplifier is less likely to cause a nonlinear phenomenon, the peak power of the output light can be made larger than that of the optical fiber amplifier 6.
- a spatial transmission / reception optical separator is required. As described above, by increasing the optical power of the laser light transmitted using the amplifier, the intensity of the received light can be increased, and the measurement accuracy and the measurable distance can be increased.
- Embodiment 7 FIG.
- the propagation path of the laser beam in the apparatus is configured using the optical fiber component.
- the spatial propagation of the laser beam is performed using the spatial optical component.
- the structure to be made may be sufficient.
- the optical couplers can be replaced by an optical element such as a mirror that reflects the laser light.
- an optical element such as a mirror that reflects the laser light.
- FIG. 1 when the configuration shown in FIG. 1 is a spatial propagation type configuration, as shown in FIG. 7, partial reflection mirrors, beam splitters, etc. (mirrors 20a to 20d in FIG. 7) can be used as the optical branching couplers 2a and 2b.
- the optical multiplexing couplers 4 5, and 10, partial reflection mirrors, beam splitters, band pass or band reflection mirrors, etc. (mirrors 20e to 20i in FIG. 7) can be used.
- These optical elements are used by appropriately selecting the wavelength band to be reflected and the reflectance in accordance with the branching ratio and wavelength of the laser light.
- optical modulators 3a and 3b, the optical fiber amplifier 6, and the optical circulator 7 are replaced with spatial elements (optical modulators 21a and 21b, laser amplifier 22, and optical circulator 23), respectively.
- the optical path of the laser light can be changed as appropriate by using a reflection mirror or the like.
- the polarization may be controlled using a wave plate.
- the use of a spatial optical element enables the components to be small and mounted with high density.
- the apparatus can be miniaturized.
- the spatial propagation type configuration can suppress the occurrence of nonlinear effects such as the above-described stimulated Brillouin scattering, and the peak power of the transmitted light can be increased without being limited by the nonlinear effects in the laser amplifier 22.
- an optical fiber component may be used as a part of the apparatus.
- an optical fiber coupler is used for a mirror for branching or multiplexing laser light, alignment adjustment is not necessary, and the apparatus can be configured easily.
- the peak power of the transmission light can be increased and the optical power of the transmission light can be increased without being limited by the nonlinear effect.
- the configuration using the spatial optical element can be applied to the configuration in which the driving device 19 is provided in the diffraction grating 9 shown in the sixth embodiment.
- the present invention is not limited to this.
- the atmosphere, a flying object, a building, or the like is detected as a target.
- the present invention can be similarly applied to cases.
- FIG. FIG. 10 is a diagram showing the configuration of a laser radar apparatus according to Embodiment 8 of the present invention.
- the laser radar device according to the eighth embodiment shown in FIG. 10 is obtained by changing the diffraction grating 9 of the laser radar device according to the first embodiment shown in FIG.
- Other configurations are the same, and only the different parts are described with the same reference numerals.
- the diffraction grating 26 is a transmission type diffraction grating using a birefringent material.
- the diffraction grating 26 has an optical axis arranged in a predetermined direction so that birefringence is generated with respect to incident transmission light.
- birefringent materials biaxial crystals such as KYW, LBO, and KTP, as well as uniaxial birefringent crystals such as quartz (SiO2), sapphire (Al2O3), and calcite (CaCO3) should be used. Can do. Also, in a birefringent crystal, if the crystal optical axis is perpendicular to the axis of the incident light of the laser light, the difference in refractive index between normal light and extraordinary light can be maximized.
- the laser light incident on the birefringent material is divided into a normal ray and an extraordinary ray depending on the polarization state and propagates.
- the refractive index for ordinary light and the refractive index for extraordinary light have different values. For this reason, the transmission light based on the CW laser light source 1a incident on the diffraction grating 26 and the transmission light based on the CW laser light source 1b propagate in a normal ray and an extraordinary ray, respectively.
- the transmitted light propagated through the diffraction grating 26 is refracted at the interface between the diffraction grating 26 and the air and is emitted into the air.
- the refractive indexes of the ordinary ray and the extraordinary ray are different, the ordinary ray and the extraordinary ray are emitted at different refraction angles.
- the transmission light based on the CW laser light source 1a and the transmission light based on the CW laser light source 1b have different frequencies, they are emitted at different diffraction angles.
- transmission light 105a indicates transmission light corresponding to a normal ray among transmission light based on the CW laser light source 1a.
- the transmission light 106a has shown the transmission light corresponding to an extraordinary ray among the transmission lights based on the CW laser light source 1a.
- the transmission light 105b has shown the transmission light corresponding to a normal ray among the transmission lights based on the CW laser light source 1b.
- the transmission light 106b has shown the transmission light corresponding to an extraordinary ray among the transmission lights based on the CW laser light source 1b.
- the normal ray and the extraordinary ray are emitted in a plane parallel to the paper surface.
- the normal ray and the extraordinary ray may have an angle in a plane perpendicular to the paper surface.
- the laser beam emission direction can be expanded in a two-dimensional direction, and a three-dimensional wind direction and wind speed distribution can be measured.
- one or both of the polarization direction of the transmission light based on the CW laser light source 1a and the polarization direction of the transmission light based on the CW laser light source 1b are made of birefringent material.
- the polarization direction of the transmission light may be switched and changed so as to be parallel or perpendicular to the plane formed by the optical axis and the incident optical axis of the transmission light.
- normal light and extraordinary light generated in the birefringent material can be selected, and the outgoing angle of the transmitted light can be selected, so that the transmitted light can be emitted only in a desired direction and observation can be performed.
- the polarization direction of the transmitted light by the polarization control means is controlled by directly controlling the output polarization state of the CW laser light source 1a and the CW laser light source 1b, or by using a polarizing element such as a wavelength plate or a polarization controller. It can be performed.
- the polarization direction of the received light and the locally transmitted light may be matched by using a polarization control means (not shown).
- a polarization control means not shown.
- the received light is separated for each polarization direction by a polarization separation element (polarization separation means) 27, and the local transmission light is switched for each polarization direction by a polarization switch (switching means) 28 and output.
- optical heterodyne detection may be performed by combining the received light and the locally transmitted light so that the polarization directions thereof coincide with each other. In this way, by switching the path according to the polarization direction of the locally transmitted light, the optical power required for the locally transmitted light can be reduced, and the optical heterodyne detection can be performed among the received light. It is only for one polarization direction. Therefore, observation in a desired direction can be performed with only one photodetector 11.
- the configuration using the transmission type diffraction grating 26 using a birefringent material can be applied to all of the second to seventh embodiments.
- the invention of the present application can be freely combined with each embodiment, modified with any component in each embodiment, or omitted with any component in each embodiment. .
- the laser radar device has a simple and inexpensive configuration and can simultaneously measure multi-gaze directions without using a mechanically driven scanner device. It is suitable for use in a laser radar device or the like that receives the scattered light of the laser beam and extracts information about the target from the scattered light.
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Abstract
Description
また、送信光(レーザ光)の伝送路に光ファイバを用いたコヒーレントレーザレーダ装置では、光ファイバで生じる誘導ブリルアン散乱と呼ばれる非線形光学効果によって、送信光のピークパワーが制限される。そこで、互いに周波数の異なる複数のCWレーザ光源を用いて送信パワーを増すことにより、高SN比の計測を行うという方式が発明されている(例えば特許文献1参照)。
このため、異なる視線方向の測定を行う場合や、より広い範囲を測定し演算等により分布を求める場合には、レーザ光を走査する必要がある。そのため、角度調整が可能な反射ミラー、回転ウェッジ板等を用いたスキャナー装置と組み合わせて用いることがある。また、多視線方向の測定を同時に行うために、複数台のレーザレーダ装置を配置する場合がある。
また、レーザ光を走査する方式では、1視線方向当たりの測定時間が短くなるため、受信信号強度が低下し、測定可能な距離や精度が低下するという課題があった。
実施の形態1.
図1はこの発明の実施の形態1に係るレーザレーダ装置の構成を示す図である。
レーザレーダ装置は、レーザ光を大気中に照射してエアロゾル(大気中を浮遊する塵等の粒子)からの散乱光を受信し、この散乱光のドップラーシフトを検出することによって風速の計測を行うコヒーレントドップラーライダ装置である。このレーザレーダ装置は、図1に示すように、複数のCWレーザ光源(基準光源)1、複数の光分岐カプラ2、複数の光変調器3、光合波カプラ(第1の合波器)4、光合波カプラ(第2の合波器)5、光ファイバ増幅器6、光サーキュレータ7、送受信光学系8、回折格子(分散素子)9、光合波カプラ(第3の合波器)10、光検出器11および信号処理装置(情報抽出器)12から構成されている。なお、装置内のレーザ光の伝搬光路は光ファイバにより構成されている。また図1では、2つのCWレーザ光源1a,1b、2つの光分岐カプラ2a,2b、2つ光変調器3a,3bを備えた場合を示している。
CWレーザ光源1bは、特定周波数のCWレーザ光を発振するものである。このCWレーザ光源1bにより発振されたCWレーザ光は光ファイバに結合されて光分岐カプラ2bに出力される。
光分岐カプラ2bは、CWレーザ光源1bに対応して設けられ、CWレーザ光源1bからのCWレーザ光を2分岐するものである。この光分岐カプラ2bにより2分岐された一方のCWレーザ光は送信種光として光変調器3bに出力され、他方のCWレーザ光はコヒーレント検出用の局部発振光として光合波カプラ5に出力される。
なお、光分岐カプラ2a,2bにおける光パワーの分岐比は、CWレーザ光の周波数に対する依存性が小さいものが好適である。
光変調器3bは、光分岐カプラ2bに対応して設けられ、光分岐カプラ2bからの送信種光をパルス化して、周波数の変調を付加(コヒーレント検出を行う際の中間周波数を付加)するものである。この光変調器3bにより変調された送信種光は光合波カプラ4に出力される。
なお、光変調器3a,3bによる中間周波数は互いに異なる値に設定され、光変調器3a,3bによる変調後の周波数が互いに異なる値となるように設定されている。
また、中間周波数は、通常、数10~数100MHz程度の周波数であり、システムに好適な値が選定される。
なお、光ファイバ増幅器6として、使用するレーザ光の波長帯に見合う増幅器を使用する。例えばレーザ光の波長が1μm帯であれば、Nd(Neodymium)添加ファイバ、Yb(Ytterbium)添加ファイバを用いている光ファイバ増幅器を使用することができる。また、レーザ光の波長が1.55μm帯であれば、Er(Erbium)添加ファイバを用いている光ファイバ増幅器を使用することができる。これらの光ファイバ増幅器では、数nm~数10nm程度の利得帯域幅を有し、利得帯域内であれば、複数の波長のレーザ光を同時に増幅させることが可能である。
なお、送受信光学系8としては、出射するレーザ光を略平行光化することができ、また、焦点距離の調整が可能な望遠鏡等を用いることができる。また、送受信光学系8としては、ファイバコリメータ等を用いてもよいが、出射するレーザ光の発散角を小さくし、さらに受信効率を上げるには開口が大きいものが好適である。
レーザレーダ装置の動作では、まず、CWレーザ光源1aは、特定周波数f1のCWレーザ光を発振し、光分岐カプラ2aに出力する。また、CWレーザ光源1bは、特定周波数f2のCWレーザ光を発振し、光分岐カプラ2bに出力する。
ここで、CWレーザ光源1a,1bにより発振されるCWレーザ光の周波数f1,f2は、互いに異なり、光ファイバ増幅器6の利得帯域内にあり、かつ、周波数f1と周波数f2との差が、光ファイバで生じる誘導ブリルアン散乱の利得帯域幅より大きいものとする。
この光変調器3aにより変調された周波数f1+fM1の送信種光は光合波カプラ4に出力される。また、光変調器3bは、光分岐カプラ2bからの周波数f2の送信種光をパルス化して、周波数の変調を付加(コヒーレント検出を行う際の中間周波数fM2を付加)する。この光変調器3bにより変調された周波数f2+fM2の送信種光は光合波カプラ4に出力される。
このため、例えば周波数差が100MHz(例えば、レーザ光の波長が1550nmであれば、約0.8pmの波長差に相当する)よりも大きい2つのレーザ光を光ファイバに入射させると、当該2つのレーザ光に対する誘導ブリルアン散乱の利得を異なるものとすることができる。そのため、当該2つのレーザ光は、それぞれが誘導ブリルアン散乱の発生しきい値となる入射パワーまで光パワーを入力することができる。
また、複数のレーザ光を入力する場合も同様であり、誘導ブリルアン散乱の利得帯域幅よりも大きい周波数差を有する複数のレーザ光を用いることにより、光ファイバに入射可能なレーザ光のパワーを大きくすることが可能である。
これにより、各レーザ光の平均出力パワー(平均出力パワーは、パルス光のピークパワーとパルス幅とパルス繰り返し周波数の積で表される)をPS1,PS2とすると、光ファイバ増幅器6の出力光の平均パワーをPS1+PS2とすることができ、送信光の光パワーを単一の光源(例えば、CWレーザ光源1aまたはCWレーザ光源1bのどちらか一方のみ)を用いる場合よりも、大きくすることができる。これにより、PS1=PS2となる場合には、2つのCWレーザ光源1a,1bを用いることで、送信光の光パワーを2倍にすることができる。
また、複数のCWレーザ光源1a,1bを用いることにより、光ファイバ増幅器6では、入力パワーが増加する。そのため、エネルギーの抜き出し効率を向上させることができ、レーザ光の増幅時のASE(Amplified Spontaneous Emission:自然放出光増幅)成分の発生を減少させることができる。よって、光ファイバ増幅器6の効率改善効果と、光検出器11での雑音成分の低減効果がある。
また、回折格子9によるレーザ光の回折角度は、回折格子9の構造パラメータとレーザ光の波長(周波数)および入射角によって決まるため、これらの値を把握しておけば送信光101a,101bの出射方向をそれぞれ求めることができる。
上記のように、回折格子9を用いることにより、周波数に応じてレーザ光の伝搬角度を変えることができ、異なる2つの視線方向へとレーザ光の送受信を行うことができる。
このため、送信光である周波数f1+fM1,f2+fM2のレーザ光が受けるドップラーシフトがそれぞれfd1,fd2であるとすると、散乱光の周波数はそれぞれf1+fM1+fd1,f2+fM2+fd2になる。
ここで、fd1は周波数f1+fM1の送信光が受けたドップラーシフトであり、fd2は周波数f2+fM2の送信光が受けたドップラーシフトである。そして、当該2つの送信光は回折格子9により異なる方向へと出射されているため、異なる2つの視線方向についてのドップラーシフトを同時に測定することができる。
また、スキャナー装置を用いることなく2つの視線方向の測定を行うことができるため、装置構成を単純化することができ、装置の小型化や低価格化を図ることができる。さらに、機械駆動系が必要ないため、装置の長寿命化することができ、信頼性を高めることができる。
さらには、各光学素子間を結合する光ファイバに偏波面保存型の光ファイバを用い、かつ、各光学素子に偏波面保存型の光ファイバ部品を用いると、偏波面コントローラ等を使用しなくとも、局部発振光と散乱光の偏波面を一致させることができる。これにより、装置構成を簡単化することができる。
なお図1の構成のように、光ファイバ部品を用い、レーザ光の伝搬光路に光ファイバを用いることにより、レーザ光の光路の取り回しが容易になり装置を小型化することができ、光ファイバの接続により装置を簡単に構成することができる。また、光軸のアライメントが不要なため装置の安定性が増し、信頼性の高い装置構成が可能となる。さらには、上述のように偏波面保存型の光ファイバおよび光学素子光ファイバ部品を用いることにより、偏波面の調整が不要なため、装置構成を簡単化でき、小型で信頼性の高い装置を構成が可能となる。
これにより、回折格子9では、レーザ光の周波数に応じて回折が生じ、CWレーザ光源1の数量分の方向へとレーザ光の出射させることができるため、レーザ光源の数量分の視線方向の風速を同時に測定することができる。これにより、風向および風速の2次元分布をより精度よく求めることができる。
図2はこの発明の実施の形態2に係るレーザレーダ装置の構成を示す図である。図2に示す実施の形態2に係るレーザレーダ装置は、図1に示す実施の形態1に係るレーザレーダ装置のCWレーザ光源1a,1bをCWレーザ光源13a,13bに変更したものである。その他の構成は同様であり、同一の符号を付して異なる部分についてのみ説明を行う。
CWレーザ光源13bは、発振周波数をf2~f2´の範囲で変化させることが可能であり、設定した特定周波数のCWレーザ光を発振するものである。このCWレーザ光源13bにより発振されたCWレーザ光は光ファイバに結合されて光分岐カプラ2bに出力される。
また、回折格子9の回折角は、入射するレーザ光の周波数に依存するため、CWレーザ光源13a,13bの発振周波数を適切に設定することにより、所望の方向へとレーザ光を送信することができる。このようにして、図2の構成では、2つの異なる視線方向を同時に測定しつつ、視線方向を変化させることができる。
この構成では、簡単な構成でレーザ光を走査することができ、装置の小型化や低価格化を図ることができる。さらに、機械駆動系が必要ないため、装置の長寿命化することができ、信頼性を高めることができる。
図3はこの発明の実施の形態3に係るレーザレーダ装置の構成を示す図である。図3に示す実施の形態3に係るレーザレーダ装置は、図1に示す実施の形態1に係るレーザレーダ装置から光分岐カプラ2b、光変調器3bおよび光合波カプラ4,5を削除し、駆動回路14a,14b、制御器15および光合波カプラ16を追加したものである。その他の構成は同様であり、同一の符号を付して異なる部分についてのみ説明を行う。
駆動回路14bは、CWレーザ光源1bに対応して設けられ、CWレーザ光源1bを動作させるものである。
なお、光分岐カプラ2aは、光合波カプラ16からのCWレーザ光を2分岐し、一方のCWレーザ光を送信種光として光変調器3aに出力し、他方のCWレーザ光をコヒーレント検出用の局部発振光として光合波カプラ10に出力する。
なおこの構成では、異なる2つの視線方向についてのドップラーシフトを完全に同時に測定することはできない。しかしながら、動作させるCWレーザ光源1a,1bの切替え間隔を短くすることにより、時間差を少なくして2つの視線方向の測定を行うことができ、演算等の処理により、より実時間の状況に近い風向および風速の2次元分布を求めることもできる。
また、動作させているCWレーザ光源1a,1bに対応する受信信号のみが検出されるため、光変調器3aは1個のみでよく、装置を簡単化することができる。さらに、図1の場合、必要となる受信信号を区別するための光変調器3aでの中間周波数の制限が無くなるため、部品の選定が容易になる。
図4はこの発明の実施の形態4に係るレーザレーダ装置の構成を示す図である。図4に示す実施の形態4に係るレーザレーダ装置は、図2に示す実施の形態2に係るレーザレーダ装置からCWレーザ光源13b、光分岐カプラ2b、光変調器3bおよび光合波カプラ4,5を削除し、駆動回路14aおよび制御器17を追加したものである。その他の構成は同様であり、同一の符号を付して異なる部分についてのみ説明を行う。
制御器17は、信号処理装置12による処理結果(CWレーザ光源13aの動作状態)に基づいて、駆動回路14aを動作させることで、動作するCWレーザ光源13aの発振周波数を変化させるものである。
また、実施の形態4における光合波カプラ10は、本発明の「前記送受信光学系により受信された散乱光と前記光分岐器により分岐された他方のレーザ光とを混合して第4の混合光を出力する第4の光合波器」に相当する。
また、動作させているCWレーザ光源13aに対応する受信信号のみが検出されるため、光変調器3aは1個のみでよく、装置を簡単化することができる。さらに、図1の場合に必要となる受信信号を区別するための光変調器3aでの中間周波数の制限が無くなるため、部品の選定が容易になる。
図5はこの発明の実施の形態5に係るレーザレーダ装置の構成を示す図である。図5に示す実施の形態5に係るレーザレーダ装置は、図1に示す実施の形態1に係るレーザレーダ装置の送受信光学系8の位置を回折格子9の後段に変更し、コリメータ18を追加したものである。その他の構成は同様であり、同一の符号を付して異なる部分についてのみ説明を行う。
このコリメータ18により略平行光化された送信光は回折格子9に入射される。その後、回折格子9により生じる回折光は、送信光の周波数によって分離され、送信光101a、101bの方向へと伝搬して送受信光学系8へと入射される。そして、送受信光学系8を通過後は、それぞれ送信光104a,104bの方向へと出射される。
なお、送受信光学系8は、送信光101a,101bが入射開口に入射できるようにする。また、所望の視線方向の測定を行うために、送受信光学系8の倍率を考慮して、回折格子9の回折角は好適な値に設計させる。
図6はこの発明の実施の形態6に係るレーザレーダ装置の構成を示す図である。図6に示す実施の形態6に係るレーザレーダ装置は、図5に示す実施の形態5に係るレーザレーダ装置に駆動装置19と追加したものである。その他の構成は同様であり、同一の符号を付して異なる部分についてのみ説明を行う。
駆動装置19は、回折格子9の設置角度を変化させる装置であり、回折格子9の入射面がz軸に対して傾きを持つように、回折格子9の設置角度を変化させることができる。これにより、送信光104a,104bはx-y平面に対して傾きを持って放射されようになる。このようにして、回折格子9の入射面のz軸に対する傾きを変化させることにより、送信光をz軸方向に走査することができる。よって、レーザ光の出射方向を2次元の方向に拡張でき、3次元の風向および風速分布を測定することができる。なお、駆動装置19には、モーターやピエゾ素子等を用いた可動ステージ等が利用できる。
光ファイバ増幅器6を用いた場合には、送信するレーザ光の光パワーをより増加させることができ、受信光の強度を高め、測定の精度や測定可能な距離を高めることができる。
また、光ファイバ増幅器6により増幅されたレーザ光をさらに増幅する場合には、空間型のレーザ光増幅器を用いてもよい。空間型のレーザ光増幅器では、非線形現象が発生しにくいため、光ファイバ増幅器6よりも出力光のピークパワーを大きくすることができる。
ただし、空間型のレーザ光増幅器を用いる場合には、空間型の送受信光分離器が必要となる。このように、増幅器を用いて送信するレーザ光の光パワーを大きくすることにより、受信光の強度を高め、測定の精度や測定可能な距離を高めることができる。
実施の形態1~6では、光ファイバ部品を用いて装置内のレーザ光の伝搬光路を構成しているが、図7~9に示すように、空間型の光部品を用いレーザ光を空間伝搬させる構成であってもよい。
図10はこの発明の実施の形態8に係るレーザレーダ装置の構成を示す図である。図10に示す実施の形態8に係るレーザレーダ装置は、図1に示す実施の形態1に係るレーザレーダ装置の回折格子9を回折格子(分散素子)26に変更したものである。その他の構成は同様であり、同一の符号を付して異なる部分についてのみ説明を行う。
このため、回折格子26に入射したCWレーザ光源1aに基づく送信光と、CWレーザ光源1bに基づく送信光は、それぞれ通常光線と異常光線に分かれて伝搬する。
また、CWレーザ光源1aに基づく送信光とCWレーザ光源1bに基づく送信光は、周波数が異なるため、それぞれ異なる回折角で出射される。
なお、図10において、送信光105aは、CWレーザ光源1aに基づく送信光のうち通常光線に対応する送信光を示している。また、送信光106aは、CWレーザ光源1aに基づく送信光のうち異常光線に対応する送信光を示している。また、送信光105bは、CWレーザ光源1bに基づく送信光のうち通常光線に対応する送信光を示している。また、送信光106bは、CWレーザ光源1bに基づく送信光のうち異常光線に対応する送信光を示している。
なお、偏光制御手段による送信光の偏光方向の切替えについては、CWレーザ光源1aおよびCWレーザ光源1bの出力偏光状態を直接制御するか、波長板や偏光コントローラなどの偏光素子を用いることにより、制御を行うことができる。
このように、局部発信光の偏光方向に応じて経路を切替えることにより、局部発信光に必要となる光パワーを少なくすることができ、さらに光ヘテロダイン検出を行うことができるのは受信光のうち一方の偏光方向性分のみである。そのため、1つの光検出器11のみで所望の方向の観測を行うことができるようになる。
Claims (27)
- 互いに異なる周波数のレーザ光を発振する複数の基準光源と、
前記基準光源に対応して設けられ、当該対応する基準光源により発振されたレーザ光を分岐する複数の光分岐器と、
前記光分岐器に対応して設けられ、当該対応する光分岐器により分岐された一方のレーザ光を変調する複数の光変調器と、
前記各光変調器により変調されたレーザ光を混合して第1の混合光を出力する第1の光合波器と、
前記各光分岐器により分岐された他方のレーザ光を混合して第2の混合光を出力する第2の光合波器と、
前記第1の光合波器により出力された第1の混合光を出射し、目標による当該第1の混合光の散乱光を受信する送受信光学系と、
前記送受信光学系により受信された散乱光と前記第2の光合波器により出力された第2の混合光とを混合して第3の混合光を出力する第3の光合波器と、
前記第3の光合波器により出力された第3の混合光からビート信号を検出する光検出器と、
前記光検出器により検出されたビート信号から前記目標に関する情報を抽出する情報抽出器と、
前記送受信光学系の前方または後方に配置され、入射光の角度および周波数に応じて当該入射光を特定方向に出射する分散素子とを備えた
ことを特徴とするレーザレーダ装置。 - 前記基準光源は、発振するレーザ光の周波数が可変である
ことを特徴とする請求項1記載のレーザレーダ装置。 - 前記基準光源の動作切替えを行う制御器を備えた
ことを特徴とする請求項1記載のレーザレーダ装置。 - 前記基準光源の動作切替えおよび周波数制御を行う制御器を備えた
ことを特徴とする請求項2記載のレーザレーダ装置。 - 装置内の光の伝搬光路は光ファイバにより構成された
ことを特徴とする請求項1記載のレーザレーダ装置。 - 装置内の送信側の伝搬光路上に少なくとも1つ以上設けられ、入力光の光パワーを増幅する光ファイバ増幅器を備えた
ことを特徴とする請求項5記載のレーザレーダ装置。 - 装置内の送信側の伝搬光路上に少なくとも1つ以上設けられ、入力光の光パワーを増幅する空間型のレーザ増幅器を備えた
ことを特徴とする請求項6記載のレーザレーダ装置。 - 前記各基準光源により発振されたレーザ光の周波数差は、前記光ファイバで生じる誘導ブリルアン散乱の利得帯域幅よりも大きい
ことを特徴とする請求項6記載のレーザレーダ装置。 - 特定の周波数のレーザ光を発振する、当該周波数が可変である基準光源と、
前記基準光源により発振されたレーザ光を分岐する光分岐器と、
前記光分岐器により分岐された一方のレーザ光を変調する光変調器と、
前記光変調器により変調されたレーザ光を出射し、目標による当該レーザ光の散乱光を受信する送受信光学系と、
前記送受信光学系により受信された散乱光と前記光分岐器により分岐された他方のレーザ光とを混合して第4の混合光を出力する第4の光合波器と、
前記第4の光合波器により出力された第4の混合光からビート信号を検出する光検出器と、
前記光検出器により検出されたビート信号から前記目標に関する情報を抽出する情報抽出器と、
前記送受信光学系の前方または後方に配置され、入射光の角度および周波数に応じて当該入射光を特定方向に出射する分散素子とを備えた
ことを特徴とするレーザレーダ装置。 - 前記基準光源の周波数制御を行う制御器を備えた
ことを特徴とする請求項9記載のレーザレーダ装置。 - 装置内の光の伝搬光路は光ファイバにより構成された
ことを特徴とする請求項9記載のレーザレーダ装置。 - 装置内の送信側の伝搬光路上に少なくとも1つ以上設けられ、入力光の光パワーを増幅する光ファイバ増幅器を備えた
ことを特徴とする請求項11記載のレーザレーダ装置。 - 装置内の送信側の伝搬光路上に少なくとも1つ以上設けられ、入力光の光パワーを増幅する空間型のレーザ増幅器を備えた
ことを特徴とする請求項12記載のレーザレーダ装置。 - 前記分散素子は、反射型または透過型の回折格子である
ことを特徴とする請求項1記載のレーザレーダ装置。 - 前記分散素子は、反射型または透過型の回折格子である
ことを特徴とする請求項9記載のレーザレーダ装置。 - 前記分散素子の設置角度を変化させる駆動機構を備えた
ことを特徴とする請求項1記載のレーザレーダ装置。 - 前記分散素子の設置角度を変化させる駆動機構を備えた
ことを特徴とする請求項9記載のレーザレーダ装置。 - 前記分散素子は、1軸性または2軸性の複屈折材料を用いた透過型の回折格子である
ことを特徴とする請求項1記載のレーザレーダ装置。 - 前記分散素子は、1軸性または2軸性の複屈折材料を用いた透過型の回折格子である
ことを特徴とする請求項9記載のレーザレーダ装置。 - 前記回折格子に対する入射光の軸と結晶の光学軸との角度が垂直である
ことを特徴とする請求項18記載のレーザレーダ装置。 - 前記回折格子に対する入射光の軸と結晶の光学軸との角度が垂直である
ことを特徴とする請求項19記載のレーザレーダ装置。 - 前記基準光源により発振されたレーザ光の偏光方向を制御する偏光制御手段を備えた
ことを特徴とする請求項18記載のレーザレーダ装置。 - 前記基準光源により発振されたレーザ光の偏光方向を制御する偏光制御手段を設けた
ことを特徴とする請求項19記載のレーザレーダ装置。 - 前記送受信光学系により受信された散乱光と前記第2の光合波器により出力された第2の混合光との偏光方向を一致させる偏光制御手段を備えた
ことを特徴とする請求項18記載のレーザレーダ装置。 - 前記送受信光学系により受信された散乱光と前記光分岐器により分岐された他方のレーザ光との偏光方向を一致させる偏光制御手段を備えた
ことを特徴とする請求項19記載のレーザレーダ装置。 - 前記送受信光学系により受信された散乱光を偏光方向ごとに分離する偏光分離手段と、
前記偏光分離手段により分離された散乱光に対し、前記第2の光合波器により出力された第2の混合光のうち、偏光方向が一致するものを切替えて出力する切替え手段とを備え、
前記第3の光合波器は、前記偏光分離手段により分離された散乱光と、前記切替え手段により切替えて出力された第2の混合光とを混合する
ことを特徴とする請求項18記載のレーザレーダ装置。 - 前記送受信光学系により受信された散乱光を偏光方向ごとに分離する偏光分離手段と、
前記偏光分離手段により分離された散乱光に対し、前記光分岐器により分岐された他方のレーザ光のうち、偏光方向が一致するものを切替えて出力する切替え手段とを備え、
前記第4の光合波器は、前記偏光分離手段により分離された散乱光と、前記切替え手段により切替えて出力されたレーザ光とを混合する
ことを特徴とする請求項19記載のレーザレーダ装置。
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US20160291137A1 (en) | 2016-10-06 |
JPWO2015087564A1 (ja) | 2017-03-16 |
JP6072301B2 (ja) | 2017-02-01 |
EP3081956A4 (en) | 2017-08-09 |
CN105814451A (zh) | 2016-07-27 |
EP3081956A1 (en) | 2016-10-19 |
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