JP5627176B2 - Lightwave radar device - Google Patents

Description

  The present invention relates to a light wave radar device that emits laser light into a space and measures the wind speed based on the Doppler shift of scattered light accompanying the movement of a hard target or an aerosol (fine dust floating in the atmosphere) in the space.

  Coherent Doppler lidar (CDL) technology for remotely observing the spatial distribution of wind speed is needed from various application viewpoints such as meteorological observation, weather prediction, turbulence detection for air and traffic safety, and survey of suitable locations for wind power use. There is. In a compact CDL device that requires portability over the maximum measurement distance, the all-optical fiber CDL technology, in which the optical transceiver is composed of an optical fiber and an optical fiber component, is downsized and highly reliable. (See, for example, Patent Documents 1 to 3).

JP 2003-307567 A International Publication No. 2004/106971 Pamphlet JP 2003-240853 A

  Here, FIG. 14 is a block diagram showing a conventional light wave radar apparatus as shown in Patent Document 1. In FIG. In FIG. 14, a series of optical paths of a conventional light wave radar apparatus is formed by an optical fiber (thick solid line in the figure). In addition, a conventional optical wave radar apparatus includes a reference light source 1001, an optical coupler 1002, a frequency intensity modulator 1003, an optical fiber amplifier 1004, an optical circulator 1005, a large aperture telescope (transmission / reception optical system) 1006, and a small aperture telescope (transmission / reception optical system). 1007, an optical heterodyne receiver 1008, and signal processing means 1009.

  The reference light source 1001 oscillates reference light that is laser light having a single wavelength. The optical path of the reference light from the reference light source 1001 is branched into two optical paths by the optical coupler 1002. One of the two optical paths from the optical coupler 1002 is connected to the frequency intensity modulator 1003. The other of the two optical paths from the optical coupler 1002 is connected to the optical heterodyne receiver 1008. The reference light of the optical coupler 1002 is sent to the optical heterodyne receiver 1008 as local oscillation light.

  The frequency intensity modulator 1003 modulates the light intensity and frequency of the reference light, and sends the modulated reference light to the optical fiber amplifier 1004. The optical fiber amplifier 1004 amplifies the reference light received from the frequency intensity modulator 1003, uses the amplified reference light as transmission light, and transmits the large diameter telescope 1006 or the small diameter through the optical circulator 1005 and the optical fiber terminal unit 1000a. Send to telescope 1007.

  The large-aperture telescope 1006 and the small-aperture telescope 1007 are alternatively connected to the optical fiber terminal portion 1000a. The large-aperture telescope 1006 and the small-aperture telescope 1007 emit the transmission light from the optical fiber terminal portion 1000a toward a desired target in the air. In addition, the large-aperture telescope 1006 and the small-aperture telescope 1007 collect backscattered light in which transmission light emitted into the air hits aerosol or the like, and receives the backscattered light as received light.

  The backscattered light collected by the large-aperture telescope 1006 is transmitted from the optical fiber terminal unit 1000a to the optical heterodyne receiver 1008 via the optical circulator 1005. The optical heterodyne receiver 1008 optically combines the local oscillation light from the optical coupler 1002 and the reception light from the large-aperture telescope 1006 or the small-aperture telescope 1007 and performs photoelectric conversion. Then, the optical heterodyne receiver 1008 generates an electric signal corresponding to the light intensity of the difference frequency component between the backscattered light and the local oscillation light as a beat signal.

  The signal processing means 1009 receives the beat signal from the optical heterodyne receiver 1008, and based on the Doppler frequency shift and the pulse arrival time difference based on the beat signal, the target information (distance to target, wind speed, wind direction, etc.) To extract.

  According to the conventional optical wave radar apparatus as shown in FIG. 14, the large-aperture telescope 1006 and the small-aperture telescope 1007 have a principle that the emission point of transmission light and the condensing point of reception light are physically coincident. Therefore, it is unnecessary to adjust the optical axes of the transmission light and the reception light, and it is extremely effective for reducing the coupling loss of the reception light. However, in the transmission / reception coaxial large-diameter telescope 1006 and small-diameter telescope 1007, since the transmission aperture and the reception aperture are common, in principle, the transmission aperture and the reception aperture are set to different aperture diameters. It is not possible. Problems caused by this will be described below.

但し、各パラメータは、λ：送信光波長、Ｅ：送信光１パルスあたりのエネルギー、Ｄｅ：送信ビーム径（１／ｅ^２径）、Ｌ：計測距離、β：エアロゾルの後方散乱係数、Ｋ: 大気透過係数、ｈ：Ｐｌａｎｋ定数、Ｂ_Ａ：受信帯域幅、η’：システム効率（光学系の損失、光電変換での量子効率等により決定）、η_Ｆ：Ｆａｒ Ｆｉｅｌｄ（集光距離）における送受信光学系の結合効率である。 The signal-to-noise ratio SNR obtained by the conventional optical wave radar apparatus when using a transmission / reception coaxial telescope such as the large-aperture telescope 1006 and the small-aperture telescope 1007 as described above is expressed by the lidar equation shown in the following equation (1). Can be represented.

However, each parameter is as follows: λ: transmission light wavelength, E: energy per one pulse of transmission light, De: transmission beam diameter (1 / e ² diameter), L: measurement distance, β: aerosol backscattering coefficient, K: Atmospheric transmission coefficient, h: Plank constant, B _A : reception bandwidth, η ′: system efficiency (determined by optical system loss, quantum efficiency in photoelectric conversion, etc.), η _F : transmission / reception at Far Field (condensing distance) This is the coupling efficiency of the optical system.

但し、Ａは、ビームのけられの影響を示す定数（０．７５以下の値）、Ｈは、定数（＝２．９１４３８３）、Ｃ_ｎ ^２は大気構造定数である。この大気構造定数は、地表付近で１×１０^−１４〜３×１０^−１３[ｍ^−２／３]程度の値をとることが知られている。 The SRF in the equation (1) is a constant depending on the defocus and coherent length of the receiving optical system, and the condensing distance F of the receiving optical system and the coherent length S _o at the aperture surface of the receiving optical system are used. And expressed by the following equations (2) and (3).

However, A is a constant (value of 0.75 or less) indicating the influence of beam displacement, H is a constant (= 2.9143383), and C _n ² is an atmospheric structure constant. It is known that this atmospheric structure constant takes a value of about 1 × 10 ^{−14 to} 3 × 10 ⁻¹³ [m ^−2/3 ] near the ground surface.

  Therefore, according to the equation (1), it is understood that the signal-to-noise ratio SNR can be increased by increasing the beam diameter De (matching the reception aperture diameter) of the transmission light. However, the sensitivity of the SRF in the expression (2) with respect to the focusing distance F increases as the beam diameter De of the transmission light increases. The influence of the difference in sensitivity with respect to the condensing distance F appears as shown in FIG.

  FIG. 15 is a graph showing measurement characteristics when the large-aperture telescope is used and when the small-aperture telescope is used by the conventional optical wave radar apparatus of FIG. 15A shows the signal-to-noise ratio characteristics when the large-aperture telescope (De = 200 mm) 1006 is used, and FIG. 15B shows the signal-to-noise ratio when the small-aperture telescope (De = 50 mm) 1007 is used. The signal-to-noise ratio characteristics will be described.

  Here, parameters other than the aperture diameter are all common, and the condensing distance F is 3 patterns (F = 0.5 km, 1 km, 2 km). In addition, broken lines V1 and W1 in FIGS. 15A and 15B are measurement characteristics when the condensing distance F is 0.5 km. Furthermore, alternate long and short dash lines V2 and W2 in FIGS. 15A and 15B are measurement characteristics when the condensing distance F is 1 km. In addition, two-dot chain lines V3 and W3 in FIGS. 15A and 15B are measurement characteristics when the condensing distance F is 2 km.

  First, in the case of the large-aperture telescope 1006, as shown by a two-dot broken line V3 in FIG. 15A, a relatively high signal can be obtained even at a long distance by setting the condensing distance F to a long distance (F = 2 km). The noise-to-noise ratio SNR can be ensured. For example, if the limit value (threshold value) of the signal-to-noise ratio SNR capable of detecting the wind speed is set to the limit value signal-to-noise ratio SNRth = 4.5 dB, the measurable range (maximum on the objective side of the telescope) can be measured. Measurement distance range) is about 1.83 km.

  On the other hand, in the case of the small-aperture telescope 1007, as shown by the two-dot broken line W3 in FIG. 15B, the measurable range is even when the condensing distance F is set to a long distance (F = 2 km). 1.38 km, which is smaller than 1.83 km, which is the measurable range of the large-aperture telescope 1006.

  Further, when the condensing distance F of the small-aperture telescope 1007 is changed from 1 km to 2 km, the profile with respect to the distance of the signal-to-noise ratio SNR as shown by the one-dot chain line W2 and the two-dot broken line W3 in FIG. It becomes clear that the effect of increasing the maximum measurement distance does not appear. Therefore, it is understood that the large-aperture telescope 1006 is effective when it is desired to increase the maximum measurement distance with the same transmission light energy.

  Here, when the large-aperture telescope 1006 is used, the signal-to-noise ratio SNR on the relatively short distance side is limited by the condensing effect of the transmission light. That is, with respect to the condensing distance F = 0.5 km, 1 km, and 2 km, the minimum measurement distance of the signal-to-noise ratio SNR limit value signal-to-noise ratio SNRth = 4.5 dB or more that can detect the wind speed is 0.17 km, respectively. , 0.34 km, and 0.69 km. Further, at F = 2 km at which the longest measurement distance can be obtained, the minimum measurement distance is limited to 0.69 km or more.

  On the other hand, when the small-aperture telescope 1007 is used, the influence of the condensing function of the transmitted light is small, and the signal-to-noise ratio SNR on the short distance side is reduced even when the condensing distance F = 0.5 km to 2 km. It can be maintained at a value higher than the limit value signal-to-noise ratio SNRth. Therefore, it can be understood that the small-aperture telescope 1007 is suitable for stably measuring the wind speed in the vicinity of a short distance to a medium distance (1 km or less).

  Due to the above characteristics, in the conventional lightwave radar device, as shown in FIG. 14, it is necessary to replace the large-aperture telescope 1006 and the small-aperture telescope 1007 according to the measurement conditions. In addition to this, when replacing the telescope, it is necessary to change the aperture diameter De and the focusing distance F so that the signal-to-noise ratio SNR in the measurable range is maximized. Due to these factors, there is a problem that the measurement work becomes complicated.

  Here, if a light wave radar device can be obtained at a low price in the future, a system configuration that measures the wind speed of the wind in the same space by combining a plurality of light wave radar devices with different aperture diameters of the telescope is assumed. Is done. In this case, it is necessary to match the observation fields of the plurality of optical antennas on the order of μrad, which not only increases the difficulty of adjusting the optical axis, but also affects the change in the surrounding environment (vibration, temperature) of the telescope. Appears, the advantage of the transmission / reception coaxial telescope is lost.

  The present invention has been made to solve the above-described problems, and allows a relatively wide measurable range in the line-of-sight direction without replacement of the telescope, and facilitates measurement work. An object of the present invention is to obtain a light wave radar device capable of achieving the above.

  An optical wave radar apparatus according to the present invention has a reference light source unit that oscillates a linearly polarized reference light having a single frequency, and generates a plurality of transmission lights and a plurality of local oscillation lights from the reference light And a plurality of collimator optical systems capable of adjusting the respective beam diameters and light collection distances of the plurality of transmission lights, and a plurality of collimator optical systems. A light-synthesizing unit that synthesizes a plurality of transmission lights, and a transmission / reception coaxial transmission / reception optical device that irradiates a plurality of transmission lights received from the light synthesis unit toward a desired target and receives a plurality of scattered lights from the target as a plurality of reception lights. System, a plurality of received light from the transmission / reception optical system, and a plurality of local oscillation light from the signal generation unit, and by heterodyne detection, for each of the plurality of reception light, the difference frequency component of the local oscillation light An optical heterodyne receiver to generate an electrical signal corresponding to the intensity, based on the electrical signal received from the optical heterodyne receiver, in which a signal processing means for extracting target information.

  According to the lightwave radar device of the present invention, the beam diameter and the focusing distance of each of the plurality of transmission lights can be adjusted by the plurality of collimator optical systems, and the plurality of transmission lights from the plurality of collimator optical systems are combined. Since it is synthesized by means and irradiated toward the target from the transmission / reception optical system, a plurality of transmission lights having different beam diameters and collection distances are combined and irradiated from the transmission / reception optical system toward the target, Without changing the telescope, the measurable range in the line-of-sight direction can be made relatively wide, and the measurement work can be facilitated.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing an optical wave radar apparatus according to Embodiment 1 of the present invention. In FIG. 1, among the connection lines of each block, a thick solid line indicates an optical path by an optical fiber, a thin solid line indicates an electric signal transmission path, and a broken line indicates a spatial propagation path of transmission light and reception light.
In FIG. 1, in the light wave radar device of the first embodiment, a series of optical paths is formed by a polarization-maintaining single mode optical fiber. This optical fiber has first and second optical fiber terminal portions 100a and 100b. The numerical apertures (NA) of the first and second optical fiber terminal portions 100a and 100b are designed (set) in advance to be 0.1.

  The lightwave radar apparatus of the first embodiment includes a reference light source (reference light source unit) 101, optical fiber type first and second optical couplers (optical path branching means) 102A and 102B, a frequency intensity modulator (frequency intensity modulating means). ) 103, optical fiber amplifier (optical fiber amplification means) 104, first and second optical circulators 105A and 105B, first and second collimator optical systems 106A and 106B, first and second polarization 90-degree rotation means 107A and 107B , Polarization combining / separating means (light combining means) 108, transmission / reception coaxial telescope (transmission / reception optical system) 109, first and second optical heterodyne receivers (optical heterodyne reception units) 110 A and 110 B, and signal processing means 111. Yes.

  Here, the reference light source 101, the optical fiber type first and second optical couplers 102A and 102B, the frequency intensity modulator 103, the optical fiber amplifier 104, the first and second optical circulators 105A and 105B, the first and second collimators. The optical systems 106A and 106B and the first and second polarization 90-degree rotation means 107A and 107B constitute an optical signal generation unit that generates a plurality of transmission lights and a plurality of local oscillation lights. The first and second optical couplers 102A and 102B and the first and second optical circulators 105A and 105B use polarization maintaining elements.

  The reference light source 101 oscillates a laser beam having a single wavelength and linearly polarized light (a polarization state parallel to the paper surface of FIG. 1) as the reference light A1. The optical path from the reference light source 101 is branched into three optical paths by the first optical coupler 102A. The reference light A1 from the reference light source 101 passes through the first optical coupler 102A, and is divided into seed light A1, a first local oscillation light A2, and a second local oscillation light A3.

  The seed light A1 from the first optical coupler 102A is sent to the frequency intensity modulator 103. The frequency intensity modulator 103 gives an offset frequency to the optical frequency of the seed light A1 while keeping the polarization state of the seed light A1, and cuts out the pulsed light. That is, the frequency intensity modulator 103 modulates the frequency and light intensity of the seed light A1. Here, an example of a typical frequency intensity modulator 103 is an acousto-optic modulator (AOM).

  The seed light A1 modulated by the frequency intensity modulator 103 is sent to the optical fiber amplifier 104. Then, the seed light A1 is amplified by the optical fiber amplifier 104. The optical path from the optical fiber amplifier 104 is branched into two optical paths by the second optical coupler 102B. By passing through the second optical coupler 102B, the seed light A1 from the optical fiber amplifier 104 is divided into the first transmission light A4 and the second transmission light A5 while maintaining the polarization state.

  The first transmission light A4 is transmitted to the first collimator optical system 106A via the first optical circulator 105A and the first optical fiber terminal portion 100a. In contrast, the second transmission light A5 from the second optical coupler 102B is transmitted to the first polarization 90-degree rotation means 107A. The polarization plane of the second transmission light A5 is rotated by 90 degrees by the first polarization 90-degree rotation means 107A. Then, the second transmission light A5 from the first polarization 90-degree rotation means 107A is transmitted to the second collimator optical system 106B via the second optical circulator 105B and the second optical fiber terminal portion 100b.

  The first and second collimator optical systems 106A and 106B substantially parallelize the first and second transmission lights A4 and A5, respectively. The first and second collimator optical systems 106A and 106B can adjust the respective beam diameters and condensing distances of the first and second transmission lights A4 and A5.

  The first collimator optical system 106A is set in advance so that the condensing distance of the first transmission light A4 is afocal (infinite) and the beam diameter of the first transmission light A4 is relatively large. In contrast, the second collimator optical system 106B is set in advance so that the condensing distance of the second transmission light A5 is relatively short and the beam diameter of the second transmission light A5 is relatively small. Yes. That is, the first transmission light A4 is used as transmission light for long-distance measurement, and the second transmission light A5 is used as transmission light for short-distance measurement.

Next, the structure relevant to the transmission path | route of 1st transmission light A4 of the light wave radar apparatus of Embodiment 1 is demonstrated. The numerical aperture (NA) of the polarization-maintaining single mode fiber of the first optical fiber terminal portion 100a is set to 0.1. Therefore, by setting the focal length f _col of the first collimator optical system 106A, the beam diameter d _col of the first transmission light A4 that is substantially collimated can be determined as in the following equation (4).

  The first transmission light A4 substantially collimated by the first collimator optical system 106A is spatially transmitted (coupled) to the telescope 109 via the polarization combining / separating means 108. Here, the polarization combining / separating means 108 is optically adjusted in advance so that a polarized light component parallel to the paper surface is transmitted and a polarized light component perpendicular to the paper surface is reflected. Accordingly, the first transmission light A4 emitted from the first collimator optical system 106A is transmitted (completely transmitted) through the polarization combining / separating means 108 and propagates in space to the telescope 109.

In the telescope 109, the first transmission light A4 (incident collimated beam) is converted into collimated light whose beam diameter is enlarged by an angular magnification M times. Note that when the effective aperture diameter on the objective side of the telescope 109 is D _tele , the condition under which collimated light is not destroyed by the telescope 109 is d _col ≦ D _tele / M.

なお、実施の形態１では、実効的な第１送信光Ａ４のビーム径ｄ_ｃｏｌは、例えば、２００ｍｍである。 Further, the beam diameter d _col of the first transmission light A4 has a relationship expressed by the following equation (5) in order to secure the maximum effective aperture diameter as the transmission light for long-distance measurement.

In the first embodiment, the effective beam diameter d _col of the first transmission light A4 is, for example, 200 mm.

  Furthermore, the transmission / reception condensing distance F of the first transmission light A4 is set by adjusting the distance between the first optical fiber terminal portion 100a and the first collimator optical system 106A. In the first embodiment, the transmission / reception condensing distance F of the first transmission light A4 is set far (for example, 2 km).

  Next, a configuration related to the transmission path of the second transmission light A5 of the light wave radar apparatus of the first embodiment will be described. The second transmission light A5 is transmitted to the second collimator optical system 106B via the second optical circulator 105B after the polarization state to be transmitted is rotated in the direction perpendicular to the paper surface by the first polarization 90-degree rotation means 107A. Is done.

The numerical aperture (NA) of the second optical fiber end portion 100b is set (designed) to 0.1. Therefore, by setting the second focal length f ₂ of the second collimator optical system 106B, the beam diameter d _col 2 of the second transmission light A5 that is substantially collimated is determined as in the following equation (6). Can do.

  The second transmission light A5 substantially collimated by the second collimator optical system 106B is spatially coupled to the telescope 109 via the polarization combining / separating means 108. Here, the polarization combining / separating means 108 is optically adjusted in advance so that the polarized light parallel to the paper surface is transmitted and the polarization state perpendicular to the paper surface is reflected, and the second light passing through the second collimator optical system 106B. The transmission light A5 is in a polarization state perpendicular to the paper surface. Therefore, the second transmission light A5 is reflected by the polarization combining / separating means 108 and is spatially propagated to the telescope 109.

In the telescope 109, the second transmission light A5 (incident collimated beam) is converted into collimated light whose beam diameter is enlarged by an angular magnification M times. When the effective aperture diameter on the objective side of the telescope 109 is D _tele , the condition under which the second transmission light A5 is not displaced by the telescope 109 is d _col 2 ≦ D _tele / M.

なお、実施の形態１における第２送信光Ａ５の実効的なビーム径は、例えば、対物側のビーム径Ｍ×ｄ_ｃｏｌ２換算で５０ｍｍとなる。 Further, the beam diameter d _col 2 of the second transmission light A5 is expressed by the following equation (7) in order to ensure the signal-to-noise ratio SNR at a short distance.

Note that the effective beam diameter of the second transmission light A5 in Embodiment 1 is, for example, 50 mm in terms of the beam diameter M × d _col 2 on the objective side.

  Furthermore, the condensing distance of the second transmission light A5 is set by adjusting the distance between the second optical fiber terminal portion 100b and the second collimator optical system 106B. In the first embodiment, the transmission / reception condensing distance F of the second transmission light A5 is set to 1 km.

  Accordingly, the respective condensing distances and beams of the first transmission light A4 and the second transmission light A5 are adjusted by the first collimator optical system 106A and the second collimator optical system 106B.

  Next, a configuration related to signal transmission / reception of the telescope 109 of the light wave radar apparatus according to the first embodiment will be described. The first transmission light A4 and the second transmission light A5 that have passed through the first collimator optical system 106A and the second collimator optical system 106B are combined with each other by the polarization combining / separating means 108. As a result, the first transmission light A4 and the second transmission light A5 are transmitted to the eyepiece side of the telescope 109 as orthogonally polarized transmission light. Then, the orthogonally two-polarized transmission light is irradiated by the telescope 109 toward a desired target in the atmosphere.

  The irradiated first and second transmission lights A4 and A5 are backscattered by a scattering target (for example, aerosol moving at the same speed as the wind speed) in the observation space, and undergo a Doppler frequency shift according to the moving speed of the scattering target. The back-scattered light of the first transmission light A4 and the back-scattered light of the second transmission light A5 are sent to the eyepiece side by the telescope 109, respectively, the first reception light (far-distance reception light) A6 and the second reception light (near-range). Distance received light) is collected as A7. The first and second received lights A6 and A7 collected on the eyepiece side of the telescope 109 are separated from each other by passing through the polarization combining / separating means 108 and transmitted (coupled) to different optical paths.

  Here, the backscattering by the aerosol to be scattered occurs isotropically, and the polarization rotation with respect to the backscattered light can be ignored. Therefore, the polarization state of the first transmission light A4 transmitted through the polarization combining / separating means 108 is the same as the polarization state of the first reception light A6 (backscattered light by aerosol). For this reason, the first received light A6 also passes through the polarization combining / separating means 108, is again condensed through the first collimator optical system 106A, and is transmitted to the first optical fiber terminal section 100a.

  Then, the first received light A6 transmitted from the first optical fiber termination unit 100a into the optical fiber is transmitted to the first optical heterodyne receiver 110A via the first optical fiber circulator 105A. The first local oscillation light A2 from the first optical coupler 102A is transmitted to the first optical heterodyne receiver 110A. The first optical heterodyne receiver 110A optically combines the first received light A6 and the first local oscillation light A2. Then, the first optical heterodyne receiver 110A photoelectrically converts the combined first received light A6 and the first local oscillation light A2, and combines the combined first received light A6 and the first local oscillation light A2 with the difference frequency component light. A beat signal corresponding to the intensity is generated.

  Similarly to the first transmission light A4 and the first reception light A6, the second transmission light A5 and the second reception light A7 also have the polarization state of the second transmission light A5 transmitted through the polarization combining / separating means 108, and The polarization state of the two received light A7 (backscattered light by aerosol) is the same as each other. For this reason, the second received light A7 is also reflected by the polarization combining / separating means 108, is again condensed through the second collimator optical system 106B, and is condensed at the second optical fiber terminal portion 100b and transmitted into the optical fiber. .

  Then, the second received light A7 transmitted into the optical fiber from the second optical fiber termination unit 100b is transmitted to the second optical heterodyne receiver 110B via the second optical fiber circulator 5B. The second local oscillation light A3 from the first optical coupler 102A is transmitted to the second optical heterodyne receiver 110B. The second optical heterodyne receiver 110B optically combines the second received light A7 and the second local oscillation light A3. Then, the second optical heterodyne receiver 110B photoelectrically converts the combined second received light A7 and second local oscillation light A3, and combines the difference frequency component light of the second received light A7 and second local oscillation light A3. A beat signal corresponding to the intensity is generated.

  The signal processing means 111 receives the beat signal generated by the first optical heterodyne receiver 110A and the beat signal generated by the second optical heterodyne receiver 110B. The signal processing unit 111 performs AD conversion on each beat signal to obtain a time series signal. Further, the signal processing unit 111 calculates a power spectrum by performing Fourier transform on the acquired time series signal for each time gate.

  Further, the signal processing unit 111 calculates the wind speed for each distance from the calculated peak value of each power spectrum. That is, the signal processing unit 111 extracts target information based on the beat signal from the first optical heterodyne receiver 110A and the beat signal from the second optical heterodyne receiver 110B. The signal processing unit 111 is, for example, a microcomputer or a computer.

  Next, measurement characteristics of the light wave radar device according to the first embodiment will be described. FIG. 2 is a graph showing measurement characteristics of the light wave radar apparatus of FIG. In FIG. 2, SNR = 4.5 dB is shown as the limit value signal-to-noise ratio SNRth (the same applies to the graphs in FIG. 5 and subsequent figures). In FIG. 2, the relationship between the measurement distance of the first transmission light A4 for long-distance measurement and the signal-to-noise ratio SNR is as indicated by the alternate long and short dash line X1 and the solid line X2.

  According to the one-dot chain line X1 and the solid line X2 in FIG. 2, the measurable range in which the signal-to-noise ratio SNR of the limit value signal-to-noise ratio SNRth = 4.5 dB or more for the first transmission light A4 is 0.69 km to 1. It will be up to 83km. Therefore, the measurable range on the long-distance side of the first embodiment is the same as the state (FIG. 15 (a)) in which light is collected over a long distance by the large-aperture telescope 1006 of the conventional optical wave radar device shown in FIG.

  In FIG. 2, the relationship between the measurement distance for the second transmission light A5 for short distance measurement and the signal-to-noise ratio SNR is as indicated by a broken line Y1 and a solid line Y2. According to the broken line Y1 and the solid line Y2 in FIG. 2, the measurable range in which the signal-to-noise ratio SNR is greater than or equal to the limit value signal-to-noise ratio SNRth = 4.5 dB for the second transmission light A5 is from 0 km to 1.38 km. It becomes. Therefore, the measurable range on the short-distance side of the first embodiment is the same as the state where the short-diameter telescope 1007 of the conventional optical wave radar apparatus shown in FIG.

  Therefore, the signal processing unit 111 combines the measurement result obtained by the first optical heterodyne receiver 110A and the measurement result obtained by the second optical heterodyne receiver 110B, thereby obtaining the solid line X2 and the solid line in FIG. A measurement distance-signal-to-noise ratio characteristic as indicated by Y2 is obtained. That is, the measurable range of the light wave radar device of the first embodiment is from 0 km to 1.83 km.

  Here, in the method of using both the replacement of the telescopes 1006 and 1007 and the adjustment of the focusing distance as in the conventional optical wave radar apparatus as shown in FIG. 14, a relatively wide measurable range can be set by a single measurement. It was difficult to obtain at the same time. Further, for example, even when a device capable of setting the focusing distance of the telescope at high speed within the measurement update time is added to the conventional optical wave radar device as shown in FIG. 14, it is necessary to replace the telescopes 1006 and 1007. .

  On the other hand, in the light wave radar device of the first embodiment, the first and second collimator optical systems 106A and 106B adjust the beam diameters and the focusing distances of the first transmission light A4 and the second transmission light A5. It is possible. Also, the first and second transmission lights A4 and A5 from the first and second collimator optical systems 106A and 106B are combined with each other by the polarization combining / separating means 108 and irradiated from the telescope 109 toward the target. With this configuration, the first and second transmission lights A4 and A5 having different beam diameters and condensing distances are combined and irradiated from the telescope 109 toward the target, so that the line-of-sight direction can be obtained without exchanging the telescope. The measurable range can be made relatively wide, and the measurement work can be facilitated.

  Here, a light wave radar apparatus using a 50:50 optical branching coupler instead of the polarization combining / separating means 108 in FIG. 1 will be briefly described. In an optical wave radar device using a 50:50 optical branching coupler, when two orthogonally polarized light beams (P-polarized light and S-polarized light) are input, both the P-polarized component and the S-polarized component are connected to the transmission port of the optical branching coupler. Branches to the reflection port at a ratio of 50:50. Therefore, when the P-polarized component is output from the first optical fiber terminal unit 100a and the S-polarized component is output from the second optical fiber terminal unit 100b, the transmission / reception telescope 109 receives two orthogonally polarized light beams that are orthogonal to each other. Only 50% of the input power can be transmitted. This phenomenon corresponds to a branch loss of 3 dB.

  On the other hand, in the light wave radar apparatus of the first embodiment, when the ideal polarization combining / separating unit 108 is used, the polarization combining / separating unit converts the P-polarized light out of the two orthogonally polarized light beams (P-polarized light and S-polarized light). When it is input in accordance with the polarization main axis 108, the P-polarized component is output to the transmission port of the polarization combining / separating means 108 and the S-polarized component is output to the reflection port of the polarization combining / separating means 108 without any loss. As a result, it becomes possible to output the P-polarized component from the first optical fiber termination unit 100a and to output the S-polarized component from the second optical fiber termination unit 100b. As a result, two orthogonally polarized light beams can be transmitted to the transmission / reception telescope 109 without loss.

  Therefore, in the light wave radar apparatus of the first embodiment, linearly polarized components having an orthogonal relationship are used for the first and second transmission lights A4 and A5, and the first and second transmission lights A4 and A5 are The light is synthesized / separated by the polarization synthesis / separation means 108. With this configuration, the loss of optical path branching at the time of transmission / reception on the eyepiece side of the transmission / reception coaxial telescope 109 can be improved by 3 dB compared to the case of using a 50:50 optical coupler (for each of transmission light and reception light). 3 dB improvement). Therefore, it is possible to receive backscattered light with relatively high sensitivity.

  In the first embodiment, an acousto-optic modulator is shown as an example of the frequency intensity modulator 103. However, the frequency intensity modulator 103 is not limited to the acousto-optic modulator, and any frequency intensity modulator that can realize optical frequency shift and light intensity modulation may be used.

Embodiment 2. FIG.
In the first embodiment, the first and second optical heterodyne receivers 110A and 110B that are independent of each other are used to detect the first received light A6 for long-distance measurement and the second received light A7 for short-range measurement. Using. On the other hand, in the second embodiment, the first reception light A6 and the second reception light A7 are used for the first reception by the single optical heterodyne receiver 210 by utilizing the feature that the polarization states of the first reception light A6 and the second reception light A7 are orthogonal to each other. The light A6 and the second received light A7 are detected.

  FIG. 3 is a block diagram showing an optical wave radar apparatus according to Embodiment 2 of the present invention. In FIG. 3, as in FIG. 1, the connection line of each block indicates a polarization-maintaining optical fiber, the thin solid line indicates an electrical signal, and the broken line indicates space propagation light. Also, the polarization state of the light transmitted into the polarization maintaining optical fiber is indicated by the direction of the arrow in the balloon of FIG. Specifically, the up and down arrows in FIG. 3 indicate the polarization state parallel to the paper surface, and the left and right arrows in FIG. 3 indicate the polarization state perpendicular to the paper surface (the same applies to FIG. 4 and subsequent figures). Furthermore, in the drawings after the second embodiment, the same reference numerals as those in the previous embodiment indicate the same configurations as those in the previous embodiment.

  In FIG. 3, the light wave radar apparatus of the second embodiment further includes first polarization combining means 208A and first polarization combining means 208A. The first polarization combining unit 208A receives the first local oscillation light A2 from the first optical coupler 102A and the second local oscillation light A3 from the first polarization 90-degree rotation unit 107B. The first polarized light combining means 208A combines the linearly polarized components of the received first local oscillated light A2 and second local oscillated light A3 (optically combined by reflection / transmission) to combine orthogonal two polarized lights. It is assumed that the local oscillation light A21.

  The second polarization synthesizer 208B receives the first received light A6 from the first optical circulator 105A and the second received light A7 from the second optical circulator 105B. The second polarization combining unit 208B combines the linearly polarized light components of the first received light A6 and the second received light A7 (optically combined by reflection / transmission), and the combined received light A22 having two orthogonal polarizations. To do.

  The lightwave radar apparatus of the second embodiment has one optical heterodyne receiver 210 instead of the first optical heterodyne receiver 110A and the second optical heterodyne receiver 110B in the first embodiment. The optical heterodyne receiver 210 receives the combined local oscillation light A21 from the first polarization combining unit 208A. In addition, the optical heterodyne receiver 210 receives the combined received light A22 from the second polarization combining unit 208B.

  Here, the optical path between the optical heterodyne receiver 210 and the first polarization combining unit 208A and the optical path between the optical heterodyne receiver 210 and the second polarization combining unit 208B are formed by polarization maintaining optical fibers, respectively. Yes. By this polarization maintaining optical fiber, the combined local oscillation light A21 and the combined received light A22 are transmitted to the optical heterodyne receiver 210 in a state where the respective polarization states are maintained.

  The optical heterodyne receiver 210 includes first and second local oscillation lights A2 and A3 included in the combined local oscillation light A21, and first and second reception lights A6 and A6 included in the combined reception light A22. Each of A7 is photoelectrically converted into incoherent (non-interference). Further, the optical heterodyne receiver 210 calculates the difference frequency component of each of the first and second received lights A6 and A7 from the first and second local oscillation lights A2 and A3 by heterodyne detection.

  Then, the optical heterodyne receiver 210 generates a beat signal for each of the first and second received lights A6 and A7 based on the calculated difference frequency component, and sends the beat signal to the signal processing unit 111. As in the case of the first embodiment, the signal processing unit 111 performs AD conversion, Fourier transform for each time series, and spectral peak detection on the beat signal from the optical heterodyne receiver 210, and wind speed for each distance. Is calculated. Other configurations are the same as those in the first embodiment.

  As a result, even the light wave radar apparatus of the second embodiment can obtain the measurement characteristics as shown in FIG. 2, and the threshold value signal-to-noise ratio SNRth is higher than a short range from a short distance to a long distance. Wind speed measurement can be realized.

  According to the light wave radar apparatus as described above, wind speed detection can be realized by a single optical heterodyne receiver 210 over a relatively wide range, as in the first embodiment. For this reason, the second optical heterodyne receiver 110B is omitted, although it is necessary to add the first and second polarization combining means 208A and 208B as compared with the first embodiment. Here, the first and second polarization combining units 208A and 208B do not require power supply. Therefore, in the lightwave radar apparatus of the second embodiment, the second optical heterodyne receiver 110B that requires power supply is omitted, and thus the power supply path and the electric signal transmission path are simplified as compared with the first embodiment. Is done. As a result, in the light wave radar device according to the second embodiment, the manufacturing cost can be reduced as compared with the first embodiment.

  In addition, since the single optical heterodyne receiver 210 is used for detection of the first and second received lights A6 and A7, the sensitivity between the first and second optical heterodyne receivers 110A and 110B in the first embodiment. There is no need to calibrate for variations, differences in bandwidth, differences in noise characteristics, and the like. For this reason, calibration work and adjustment work at the time of manufacture and operation can be reduced, and this also makes it possible to achieve high reliability.

Embodiment 3 FIG.
In the first and second embodiments, the seed light A1 is amplified by the optical fiber amplifier 104 to obtain the first and second transmission lights A4 and A5. That is, the amplification factors of the first and second transmission lights A4 and A5 are the same. In contrast, in the third embodiment, the amplification factors of the first and second transmission lights A4 and A5 are different from each other.

  4 is a block diagram showing an optical radar device according to Embodiment 3 of the present invention. In FIG. 4, the light wave radar apparatus of the third embodiment has first and second optical fiber amplifiers (optical fiber amplification means) 304 </ b> A and 304 </ b> B instead of the previous optical fiber amplifier 104. The first and second optical fiber amplifiers 304A and 304B are connected to each other in series. Here, the second optical coupler 102B of the third embodiment is interposed between the first optical fiber amplifier 304A and the second optical fiber amplifier 304B.

  The first optical fiber amplifier 304A receives the seed light A1 from the first optical coupler 102A. The first optical fiber amplifier 304A amplifies the seed light A1 and sends it to the second optical coupler 102B. The optical path of the seed light A1 after amplification is branched into two optical paths by the second optical coupler 102B. The seed light A1 divided into two by the second optical coupler 102B is sent to the second optical fiber amplifier 304B and the first polarization 90-degree rotation means 107A through different optical paths.

  The second optical fiber amplifier 304B further amplifies the seed light A1 amplified by the first optical fiber amplifier 304A to obtain the first transmission light A4. That is, the first transmission light A4 is amplified in two stages by the first and second optical fiber amplifiers 304A and 304B. The first transmission light A4 from the second optical fiber amplifier 304A is sent to the first collimator optical system 106A via the first optical circulator 105A and handled in the same manner as in the first and second embodiments.

  Further, the first polarization 90-degree rotation means 107A rotates the polarization plane of the seed light A1 from the second optical coupler 102B by 90 degrees to obtain the second transmission light A5. That is, the second transmission light A5 is amplified only by the first optical fiber amplifier 304A. The second transmission light A5 from the first polarization 90-degree rotation means 107A is sent to the second collimator optical system 106B via the second optical circulator 105B, and is handled in the same manner as in the first and second embodiments.

  Accordingly, the amplification factors of the first and second transmission lights A4 and A5 are different from each other, and an output power difference is set between the first and second transmission lights A4 and A5. As an example of the output power of each of the first and second transmission lights A4 and A5, the peak power of the first transmission light A4 for long-distance measurement is 10 W, and the second transmission light A5 for short-distance measurement The peak power is 2W. Other configurations are the same as those in the second embodiment.

  Next, measurement characteristics of the light wave radar device according to the third embodiment will be described. FIG. 5 is a graph showing measurement characteristics of the light wave radar apparatus of FIG. In FIG. 5, the relationship between the measurement distance and the signal-to-noise ratio SNR for the first transmission light A4 for long-distance measurement is as indicated by the alternate long and short dash line X3 and the solid line X4. According to the one-dot chain line X3 and the solid line X4 in FIG. 5, the measurement distance dependence characteristic of the signal-to-noise ratio SNR of the first transmission light A4 is the measurement distance of the signal-to-noise ratio SNR of the first transmission light A4 in the first embodiment. It becomes the same as the dependency characteristic.

  On the other hand, the relationship between the measurement distance and the signal-to-noise ratio SNR for the second transmission light A5 for short distance measurement is as shown by the solid line Y3 and the broken line Y4. According to the solid line Y3 and the broken line Y4 in FIG. 5, the measurement distance dependence characteristic of the signal-to-noise ratio SNR of the second transmission light A5 is dependent on the measurement distance of the signal-to-noise ratio SNR of the second transmission light A5 of the first embodiment. Compared to the characteristics, the overall reduction is 7 dB.

  Therefore, the measurement distance-signal-to-noise ratio characteristic of the light wave radar apparatus of the third embodiment is a characteristic obtained by synthesizing the solid line Y3 and the solid line X4 in FIG. Thereby, in the lightwave radar apparatus of the third embodiment, the signal-to-noise ratio SNR margin on the short distance side is reduced, but a measurement range equivalent to the measurement distance range obtained in the first and second embodiments can be obtained. I understand.

  In the optical wave radar apparatus as described above, the first and second optical fiber amplifiers 304A and 304B are connected in series, and the second optical coupler 102B is disposed between the first and second optical fiber amplifiers 304A and 304B. ing. With this configuration, the power of the second transmission light A5 for performing the short distance measurement can be reduced, and the power of the first transmission light A4 for performing the long distance measurement can be set large. Further, the SNR margin can be made flat over the entire measurable range, and the substantial transmission power and power consumption can be reduced.

  Further, the second optical coupler 102B is disposed in front of the second optical fiber amplifier 304B. With this configuration, the optical power input to the second optical coupler 102B is reduced. As a result, damage due to heat generation of the second optical coupler 102B and damage to the optical coating film of the second optical coupler 102B due to high peak power light input can be avoided. Since the damage of the second optical coupler 102B can be avoided, the failure rate of the light wave radar apparatus can be relatively reduced, and the reliability can be relatively improved.

  In the third embodiment, similarly to the second embodiment, the first and second received lights A6 and A7 are detected using a single optical heterodyne receiver 210. However, as in the first embodiment, the first and second received lights A6 and A7 may be detected independently of each other using the first and second optical heterodyne receivers 110A and 110B.

  In the third embodiment, each of the first and second optical fiber amplifiers 304A and 304B has a single-stage amplifier configuration. However, each of the first and second optical fiber amplifiers 304A and 304B has a multi-stage amplifier configuration. It may be. That is, the seed light A1 may be amplified by three or more stages to be the first transmission light A4, or the seed light A1 may be amplified by two or more stages to be the second transmission light A5.

Embodiment 4 FIG.
In the first to third embodiments, two types of beams of the first and second transmission lights A4 and A5 are used for wind speed measurement. On the other hand, in the fourth embodiment, three types of beams of the first transmission light A4, the second transmission light A41, and the third transmission light A43 are used for wind speed measurement.

  FIG. 6 is a block diagram showing an optical radar device according to Embodiment 4 of the present invention. 6, in addition to the first and second optical couplers 102A and 102B of the first to third embodiments, the light wave radar apparatus of the fourth embodiment includes a third optical coupler (optical path) as a middle-to-near combining / separating optical coupler. A branching / combining coupler) 402C. The third optical coupler 402C branches and combines the optical path between the polarization combining / separating means 108 and the second optical circulator 105B into two optical paths.

  In addition to the first and second optical fiber terminal portions 100a and 100b of the first to third embodiments, the optical fiber of the lightwave radar device of the fourth embodiment further includes a third optical fiber terminal portion 100c. Yes. The second and third optical fiber terminators 100b and 100c constitute an optical path terminator branched into two by the third optical coupler 402C.

  Further, in the light wave radar apparatus of the fourth embodiment, a second collimator optical system 406B is used instead of the second collimator optical system 106B of the first to third embodiments. The light wave radar apparatus further includes a third collimator optical system 406C in addition to the first and second collimator optical systems 106A and 406B of the first to third embodiments. The second collimator optical system 406B is disposed between the second optical fiber terminal portion 100b and the polarization combining / separating means 108. The third collimator optical system 406C is disposed between the third optical fiber terminal portion 100c and the polarization combining / separating means 108.

  Here, an optical signal (second transmission light A5 in the first to third embodiments) that has passed through the first polarization 90-degree rotation unit 107A and the second optical circulator 105B in the fourth embodiment is transmitted by the third optical coupler 402C. The transmission light is divided into two transmission lights of two transmission light A41 and third transmission light A42.

  The second transmission light A41 is transmission light for medium distance measurement. Further, the second transmission light A41 is sent from the third optical coupler 402C to the polarization beam combining / separating means 108 via the second optical fiber terminal portion 100b and the second collimator optical system 406B. The third transmission light A42 is transmission light for short distance measurement. The third transmission light A42 is sent from the third optical coupler 402C to the polarization beam combining / separating means 108 via the third optical fiber terminal portion 100c and the third collimator optical system 406C.

  Here, the optical axis of the first transmission light A4 in the telescope 109 is the same as the optical axis of the first transmission light A4 in the first to third embodiments. On the other hand, the optical axes of the second and third transmission lights A41 and A42 are arranged so as to be parallel to each other and not overlap each other on the objective surface of the telescope 109. That is, the second and third optical fiber terminal portions 100b and 100c and the second optical fiber terminal portions 100b and 100c and the second optical fiber end portions 100b and 100c are arranged so that the optical axes of the second and third transmission lights A41 and A42 are parallel to each other and do not overlap each other on the objective surface of the telescope 109. The orientations of the third collimator optical systems 406B and 406C are adjusted in advance.

  Next, the configuration related to the transmission paths of the second and third transmission lights A41 and A42 of the light wave radar apparatus of FIG. 6 will be described. The second collimator optical system 406B makes the second transmission light A41 substantially parallel and sets the beam diameter and the focusing distance of the second transmission light A41. Specifically, the condensing distance of the second transmission light A41 for intermediate distance measurement is set by adjusting the distance between the second optical fiber terminal portion 100b and the second collimator optical system 406B. An example of the condensing distance of the second transmission light A41 is 0.8 km.

但し、Ｄ_ｔｅｌｅは、望遠鏡１０９の対物側における有効開口径を示し、Ｍは、望遠鏡１０９の角度倍率を示す。 Further, the beam diameter d _col 3 of the second transmission light A41 is set as represented by the following equation (8). An example of the beam diameter d _col 3 of the third transmission light A42 is 100 mm.

Here, D _tele indicates the effective aperture diameter on the objective side of the telescope 109, and M indicates the angular magnification of the telescope 109.

  The third collimator optical system 406C makes the third transmission light A42 substantially parallel and adjusts the beam diameter and the focusing distance of the third transmission light A42. Specifically, the condensing distance of the third transmission light A42 for short-distance measurement is set by adjusting the distance between the third optical fiber terminal portion 100c and the third collimator optical system 406C. An example of the condensing distance of the third transmission light A42 is 0.5 km.

Further, the beam diameter d _col 4 of the third transmission light A42 for short distance measurement is set as represented by the following equation (9). An example of the beam diameter d _col 4 of the third transmission light A42 is 50 mm as in the first embodiment.

  Here, by setting the branching ratio (distribution ratio) between the second optical coupler 102B and the third optical coupler 402C, the first transmission light A4 for long distance measurement, the second transmission light A41 for medium distance measurement, And each power of the 3rd transmission light A42 for near field measurement can be adjusted. For example, in Embodiment 4, the peak power of the first transmission light A4 is 10 W, and the peak powers of the second and third transmission lights A41 and A42 are 2 W each. These powers can be appropriately changed according to the installation environment, product specifications, and the like. Other configurations are the same as those in the first and second embodiments.

  Next, measurement characteristics of the light wave radar apparatus of FIG. 6 will be described. FIG. 7 is a graph showing measurement characteristics of the light wave radar device of FIG. In FIG. 7, the relationship between the measurement distance and the signal-to-noise ratio SNR for the first transmission light A4 for long-distance measurement is as indicated by the alternate long and short dash line X5 and the solid line X6. According to the one-dot chain line X5 and the solid line X6 in FIG. 7, the measurement distance dependence characteristic of the signal-to-noise ratio SNR of the first transmission light A4 is the signal-to-noise ratio SNR of the first transmission light A4 in the first and third embodiments. It becomes the same as the measurement distance dependency characteristic.

  Further, the relationship between the measurement distance and the signal-to-noise ratio SNR for the second transmission light A41 for medium distance measurement is as shown by the two-dot broken line Y5, the solid line Y6, and the two-dot broken line Y7 in FIG. According to the two-dot broken line Y5, the solid line Y6, and the two-dot broken line Y7 in FIG. 7, the measurement distance dependency characteristic of the signal-to-noise ratio SNR of the second transmission light A41 is the signal-to-noise ratio SNR around the measurement distance of 0.7 km. It can be seen that a peak occurs.

  Furthermore, the relationship between the measurement distance and the signal-to-noise ratio SNR for the third transmission light A42 for short distance measurement is as shown by the solid line Z1 and the broken line Z2 in FIG. According to the solid line Z1 and broken line Z2 in FIG. 7, the measurement distance dependence characteristic of the signal-to-noise ratio SNR of the third transmission light A42 is the signal-to-noise ratio SNR of the second transmission light A5 in the third embodiment shown in FIG. This is the same as the measurement distance dependency characteristic.

  Therefore, the measurement distance-signal-to-noise ratio characteristic of the light wave radar apparatus according to the fourth embodiment is a characteristic obtained by combining the solid line Z1, the solid line Y6, and the solid line X6 in FIG. As a result, in the light wave radar apparatus of the fourth embodiment, the signal-to-noise ratio SNR is reduced near the measurement distance of 0.7 km compared to the measurement distance-signal-to-noise ratio characteristics of the light wave radar apparatus of the third embodiment. Has been. As a result, in the light wave radar apparatus of the fourth embodiment, a measurement range equivalent to that of the light wave radar apparatus of the first to third embodiments can be obtained, and a flatter distance signal-to-noise ratio SNR characteristic can be realized as a whole. I understand that.

  In the optical wave radar apparatus as described above, the second transmission light A41 for medium distance measurement is used in addition to the first transmission light A4 for long distance measurement and the third transmission light A42 for short distance measurement. . With this configuration, it is possible to realize wind speed measurement with a flat signal-to-noise ratio SNR margin from a short distance to a long distance. For this reason, the excessive signal-to-noise ratio SNR margin (FIG. 15B) that existed when the small-aperture telescope 1007 of the conventional optical wave radar apparatus as shown in FIG. The shortage of the signal-to-noise ratio SNR margin on the short distance side during distance focusing (FIG. 15A) can be improved. As a result, at the same transmission power, the measurable range can be expanded and the power consumption can be reduced as compared with the conventional optical radar device as shown in FIG.

  Here, in the polarization combining by the polarization combining / separating means 108, it is possible to combine only up to two beams having different apertures. For this reason, in order to irradiate space with the same telescope 109 by combining three or more types of beam diameters, the third optical coupler 402C (optical path branching / combining coupler) is used for synthesis. (For example, when using a 50:50 coupler, 3 dB with a single path). Thereby, in the light wave radar apparatus of the fourth embodiment, from the viewpoint of securing the SNR, the optical path branching and combining is performed using the polarization combining / separating unit 108 that does not generate surplus loss due to the light wave combining for long-distance measurement that requires a larger output power. In the middle distance measurement and the short distance measurement that can secure the SNR with relatively low power, the optical path branching / combining is performed using the third optical path branching / combining coupler 402C.

  Therefore, in the light wave radar apparatus of the fourth embodiment, the SNR margin is larger in the branching of the transmission light for the middle distance measurement and the short distance measurement, which requires a smaller transmission power than the long distance measurement, compared to the long distance measurement. Therefore, the third optical coupler 402C (normal optical branching coupler) is used. In addition, polarization combining / separating means 108 is used for branching with transmission light for long-distance measurement that requires a large required transmission power compared to medium-distance measurement and short-distance measurement. This makes it possible to reduce the substantial transmission power relatively, contributing to lower power consumption.

  In the fourth embodiment, the seed light A1 is amplified by the one-stage configuration of the optical fiber amplifier 104. However, the present invention is not limited to this example, and the seed light may be amplified in multiple stages using a plurality of optical fiber amplifiers as in the third embodiment.

  When a plurality of optical fiber amplifiers are used, the second optical coupler 102B may be provided between the optical fiber amplifiers connected in series (relay portion). That is, the seed light amplified by the first-stage optical fiber amplifier is converted by the second optical coupler 102B into the first transmission light A4 for long-distance measurement and the second and third transmission lights A41 for medium-distance / short-distance measurement. It may be divided into A42. In this case, the difference between the transmission power for long-distance measurement and the transmission power for medium-range / short-distance measurement can be set large. As a result, the measurable range can be made wider.

Embodiment 5 FIG.
In the fourth embodiment, three types of first to third transmission lights A4, A41, and A42 are generated from the reference light A1 oscillated at a single wavelength. On the other hand, in the fifth embodiment, first to third transmission lights A56, A57, A58 are generated from the first to third reference lights A51, A52, A53 having different wavelengths, respectively.

  FIG. 8 is a block diagram showing an optical radar device according to Embodiment 5 of the present invention. In FIG. 8, the light wave radar device of the fifth embodiment has first to third reference light sources (a plurality of reference light source units) 501A to 501C instead of the reference light source 101 of the first to fourth embodiments. . The first to third reference light sources 501A to 501C generate reference lights A51 to A53 having different wavelengths, respectively. The wavelengths of the first to third reference lights A51 to A53 are λ1 to λ3, respectively.

  The lightwave radar apparatus of the fifth embodiment further includes first wavelength combining means (reference light combining means) 512A and second wavelength combining means (received light combining means) 512B. The first and second wavelength combining units 512A and 512B combine a plurality of optical signals having different wavelengths into one optical signal. Furthermore, the light wave radar apparatus of the fifth embodiment has an optical coupler (optical path branching means) 502 instead of the first optical coupler 102A of the first to fourth embodiments. The optical coupler 502 branches one optical path into a plurality of optical paths, similarly to the first optical coupler 102A of the first to fourth embodiments.

  Furthermore, the light wave radar apparatus of the fifth embodiment has a wavelength synthesis / separation means (light synthesis means) 508 instead of the polarization synthesis / separation means 108 of the first to fourth embodiments. For the wavelength combining / separating means 508, a wavelength filter whose optical axis is adjusted in advance so that only the optical signal having the wavelength λ1 is transmitted and the optical signals having the wavelengths λ2 and λ3 are reflected is used.

  Further, the light wave radar apparatus of the fifth embodiment has a wavelength separation means 513 instead of the second optical coupler 102B of the first to fourth embodiments. The wavelength separation unit 513 separates the input optical signal for each wavelength included in the optical signal.

  Furthermore, the light wave radar apparatus of the fifth embodiment includes a third optical circulator 505C in addition to the first and second optical circulators 105A and 105B of the first to fourth embodiments. The function of the third optical circulator 505C is the same as the functions of the first and second optical circulators 105A and 105B in the first to fourth embodiments. Note that the frequency intensity modulator 103 and the optical fiber amplifier 104 of the light wave radar apparatus of the fifth embodiment constitute a modulation amplification means. Other configurations are the same as those of the first, second, and fourth embodiments.

  Here, the wavelengths λ1 to λ3 of the reference lights A51 to A53 are set within the amplification wavelength band of the optical fiber amplifier 104. As the optical fiber amplifier 104, for example, an Erbium-doped optical fiber amplifier is used. The amplification band of this Erbium-doped optical fiber amplifier is a 1.53 μm to 1.56 μm band (standard wavelength 1.55 μm band). Accordingly, by setting the wavelengths λ1 to λ3 to different values within this amplification band, optical signals of all wavelengths are amplified simultaneously.

  Next, transmission / reception of each optical signal of the light wave radar apparatus of FIG. 8 will be described. The reference lights A51 to A53 are combined by the first wavelength combining unit 512A. The combined reference lights A51 to A53 are divided by the optical coupler 502 into a combined seed light A54 and a combined local oscillation light A55.

  The combined seed light A 54 from the optical coupler 102 A is subjected to frequency and light intensity modulation by the frequency intensity modulator 103, amplified by the optical fiber amplifier 104, and sent to the wavelength separation means 513. Then, the synthesized seed light A54 is wavelength-separated by the wavelength separation means 513, the first transmission light A56 for long distance measurement, the second transmission light A57 for medium distance measurement, and the third transmission lights A56 to A58 for short distance measurement. And divided.

  The first transmission light A56 is transmitted to the first collimator optical system 106A via the first optical circulator 105A and the first optical fiber terminal portion 100a. The first transmission light A56 is substantially collimated by the first collimator optical system 106A. At the same time, the beam diameter and the focusing distance of the first transmission light A56 are adjusted by the first collimator optical system 106A as in the first and second embodiments. An example of the beam diameter of the adjusted first transmission light A56 is 200 mm, and an example of the focusing distance of the adjusted first transmission light A56 is 2 km. Then, the first transmission light A56 that has passed through the first collimator optical system 106A is incident on the wavelength combining / separating means 508.

  On the other hand, the second transmission light A57 is transmitted to the second collimator optical system 406B via the second optical circulator 105B and the second optical fiber terminal portion 100b. The second transmission light A57 is substantially collimated by the second collimator optical system 406B. At the same time, the beam diameter and the focusing distance of the second transmission light A57 are adjusted by the second collimator optical system 406B as in the first and second embodiments. An example of the beam diameter of the second transmission light A57 after adjustment is 100 mm, and an example of the condensing distance of the second transmission light A57 after adjustment is 0.8 km. Then, the second transmission light A57 that has passed through the second collimator optical system 406B is incident on the wavelength combining / separating means 508.

  On the other hand, the third transmission light A58 is transmitted to the third collimator optical system 406C via the third optical circulator 505C and the third optical fiber terminal portion 100c. The third transmission light A58 is substantially collimated by the third collimator optical system 406C. At the same time, the beam diameter and the focusing distance of the third transmission light A58 are adjusted by the third collimator optical system 406C as in the fourth embodiment. An example of the beam diameter of the adjusted third transmission light A58 is 50 mm, and an example of the focusing distance of the adjusted third transmission light A58 is 0.5 km. Then, the third transmission light A58 that has passed through the third collimator optical system 406C is incident on the wavelength combining / separating means 508.

  The first to third transmission lights A56 to A58 incident on the wavelength combining / separating means 508 are combined into one transmission light by the wavelength combining / separating means 508 and sent to the eyepiece side of the telescope 109. Then, the combined transmission lights A56 to A58 are irradiated from the telescope 109 toward a desired target in the atmosphere.

  As in the first, second, and fourth embodiments, the first to third transmission lights A56 to A58 irradiated into the atmosphere from the telescope 109 are scattered by an object to be scattered in the observation space (for example, aerosol that moves at the same speed as the wind speed). Backscattered and subjected to Doppler frequency shift according to the moving speed of the scattering object. Then, the backscattered light from the scattering target in the atmosphere is collected by the telescope 109 and guided to the wavelength combining / separating means 508. The backscattered light wave guided to the wavelength synthesizing / separating means 508 is separated into wavelength components by the wavelength synthesizing / separating means 508 to obtain first to third received lights A59 to A61.

  Here, backscattering by aerosol occurs isotropically. Moreover, the Doppler shift accompanying the movement of the aerosol in the backscattered light is so small as to be negligible when converted into a wavelength change. For example, when the Doppler shift is observed using a wavelength of 1.55 μm, the Doppler shift for a moving speed of 10 m / s is about 13 MHz. When this value is converted into the length of wavelength change, it is about 0.1 pm. On the other hand, the wavelength intervals of λ1, λ2, and λ3 are set to be sufficiently larger than the length of the wavelength change due to the Doppler shift. An example of the wavelength interval of λ1, λ2, and λ3 is 10 nm.

  Therefore, since the Doppler shift accompanying the movement of the aerosol in the backscattered light is negligibly small when converted into the wavelength change, the wavelengths of the first to third received lights A59 to A61 due to the backscattered light and the first to third transmissions. The wavelengths of the lights A56 to A58 are almost the same. As a result, the first to third received lights A59 to A61 pass through the same optical paths as the first to third transmitted lights A56 to A58, respectively.

  The first to third received lights A59 to A61 are guided to the second wavelength combining unit 512B by the first to third optical circulators 105A, 105B, and 505C, respectively. The first to third received lights A59 to A61 guided to the second wavelength combining means 512B are combined by the second wavelength combining means 512B to be combined received light A62 and sent to the optical heterodyne receiver 210.

  The optical heterodyne receiver 210 receives the combined local oscillation light A55 from the optical coupler 502, mixes the combined reception light A62 and the combined local oscillation light A55, and performs photoelectric conversion. Further, the optical heterodyne receiver 210 calculates a difference frequency component for each of the wavelengths λ1, λ2, and λ3 of the combined received light A62. Then, the optical heterodyne receiver 210 generates a beat signal for each of the wavelengths λ1, λ2, and λ3 of the combined received light A62 based on the calculated difference frequency component, and sends the beat signal to the signal processing unit 111. Signal processing by the signal processing unit 111 is the same as that in the fourth embodiment. As described above, in the light wave radar apparatus of the fifth embodiment, the measurement characteristics as shown in FIG. 7 are obtained in the same manner as the light wave radar apparatus of the fourth embodiment.

  Here, in the light wave radar apparatus of the fourth embodiment, since the third optical coupler 402C is used for the optical path branching between the middle distance and the short distance, for example, the 50:50 polarization maintaining branch is provided in the third optical coupler 402C. In the case of using a coupler, the power of the seed light A1 that has passed through the first polarization 90-degree rotation means 107A is distributed by ½ each. On the other hand, the received lights from the second and third collimator optical systems 406B and 406C are attenuated to ½ by the third optical coupler 402C. On the other hand, in the fifth embodiment, the first to third transmission lights A56 to A58 are combined and the first to third reception lights A59 to A59 are combined by transmission or reflection with respect to each wavelength of the wavelength combining / separating means 508. A61 is separated. Therefore, ideally, the optical path loss can be ignored. Therefore, optical path loss can be reduced, and high sensitivity and low power consumption can be achieved.

  Further, in the light wave radar apparatus of the fourth embodiment, the first to third transmission lights A56 to A58 are synthesized and irradiated from the telescope 109 to a desired target. Therefore, as with the light wave radar apparatus of the first embodiment, Without changing the telescope, the measurable range in the line-of-sight direction can be made relatively wide, and the measurement work can be facilitated.

  In the fifth embodiment, the reference light has three wavelengths λ1 to λ3. However, the reference light has four or more wavelengths as long as it is within the gain band of the optical fiber amplifier. Also good. In this case, it is possible to realize a flatter distance signal-to-noise ratio SNR characteristic by setting the beam diameter and focal length stepwise for each wavelength. As a result, a wider range of measurable distance can be measured with flat measurement characteristics.

  In the fifth embodiment, a wavelength filter whose optical axis is adjusted in advance so that only the wavelength λ1 is transmitted and the wavelengths λ2 and λ3 are reflected is used for the wavelength combining / separating means 508. However, as the wavelength combining / separating means 508, a wavelength filter that reflects only the wavelength λ1 and transmits the wavelengths λ2 and λ3 may be used.

Embodiment 6 FIG.
In the third embodiment, the second optical coupler 102B is interposed between the first and second optical fiber amplifiers 304A and 304B connected in series, and the transmission power for short distance measurement and the transmission power for long distance measurement are obtained. Output difference was set between. On the other hand, in the sixth embodiment, the second frequency intensity modulator 603B is interposed between the first and second optical fiber amplifiers 304A and 304B, and the second frequency intensity modulator 603B receives the input trigger. In response to the signal, the output destination of the seed light A1 is switched to one of the first and second optical signals A4 and A5.

  FIG. 9 is a block diagram showing an optical radar device according to Embodiment 6 of the present invention. In FIG. 9, the light wave radar apparatus of the sixth embodiment has first and second frequency intensity modulators 603A and 603B in place of the frequency intensity modulator 103 and the second optical coupler 102B of the first to fourth embodiments. doing. The lightwave radar apparatus according to the sixth embodiment further includes a trigger signal generator (drive signal generation means) 614 that generates (generates) a trigger signal as a drive signal.

  The first frequency intensity modulator 603A modulates the input seed light in response to the input of the trigger signal pulse wave from the trigger signal generator 614, and sends the modulated seed light to the first optical fiber amplifier 304A. The second frequency intensity modulator 603B is interposed between the first and second optical fiber amplifiers 304A and 304B.

  The second frequency intensity modulator 603B is, for example, an acousto-optic element (AOM). Further, the second frequency intensity modulator 603B has a 0th-order output port and a 1st-order output port (first-order diffraction port). The 0th-order output port of the second frequency intensity modulator 603B is connected to the optical path to the first polarization 90-degree rotation means 107A. The primary output port of the second frequency intensity modulator 603B is connected to the optical path to the second optical fiber amplifier 304B.

  In response to the input of the trigger signal pulse wave from the trigger signal generator 614, the second frequency intensity modulator 603B modulates the input seed light and sends it to the second optical fiber amplifier 304B (1). The modulated seed light is output from the next output port). On the other hand, when the pulse wave of the trigger signal from the trigger signal generator 614 is not input, the second frequency intensity modulator 603B does not modulate the input seed light and sends it to the first polarization 90-degree rotation unit 107A. Send (output seed light from the 0th-order output port).

  Here, the pulse wave of the trigger signal for the first frequency intensity modulator 603A and the pulse wave of the trigger signal for the second frequency intensity modulator 603B are synchronized with each other and have different periods. When the first frequency intensity modulator 603A is driven by a pulse wave having a repetition frequency F, the second frequency intensity modulator 603B is driven by a pulse wave having a repetition frequency F / 2. Other configurations are the same as those in the first to third embodiments.

  FIG. 10 is a waveform diagram showing signal output timing of each device in FIG. FIG. 10A shows the time change of the output power of the first optical fiber amplifier 304A. FIG. 10B shows the time change of the 0th-order light output of the second frequency intensity modulator 603B. FIG. 10C shows a temporal change in the primary light output of the second frequency intensity modulator 603B. FIG. 10 (d) shows the time change of the output power of the second optical fiber amplifier 304B. FIG. 10E shows a time change of the output signal of the second optical heterodyne receiver 110B. FIG. 10F shows a time change of the output signal of the first optical heterodyne receiver 110A.

  In FIG. 10, the second optical fiber amplifier 304B amplifies the input light corresponding to the pulse ON time shown in FIG. 10C, and becomes the output signal shown in FIG. The output signal of the second optical fiber amplifier 304B becomes the first transmission light for long-distance measurement.

  On the other hand, the first-order light and the zero-order light of the second frequency intensity modulator 603B are complementary outputs, so that the pulse-off period of the primary light output is as shown in FIGS. 10 (b) and 10 (c). This is the ON period of the 0th-order light output. Accordingly, the pulse output is shifted by a half cycle at the same cycle as the primary light output as shown in FIG. The 0th-order light output of the second frequency intensity modulator 603B becomes the second transmission light for short distance measurement.

  In the first optical heterodyne receiver 110A, as shown in FIG. 10 (f), at the same time as the generation of the pulse wave of the transmission light in FIG. 10 (d), the internal reflection light component of the telescope 109 and the local oscillation light The beat signal is output at a relatively large level. Subsequently, in the first optical heterodyne receiver 110A, a beat signal of an echo (that is, received light) of a backscattered light component from the atmosphere and local oscillation light is output.

  The air speed is detected by the signal processing unit 111 analyzing the frequency of the atmospheric echo signal. Further, the longer the delay time from the generation of the pulse wave of the transmission light to the atmospheric echo component, which is a desired target, means a signal from farther away. In other words, the longer the repetition period of the pulse wave, the larger the range of wind speed measurement distance that can be signal processed. Therefore, in the sixth embodiment, the first optical heterodyne receiver 110A observes at a period twice the repetition period of the output light from the first optical fiber amplifier 304A. The range can be expanded twice as compared with the light wave radar apparatus of the third embodiment.

  In the second optical heterodyne receiver 110B, as shown in FIG. 10 (e), at the same time as the generation of the pulse wave of the transmission light in FIG. 10 (b), the internal reflected light component of the telescope 109 and the local oscillation light The beat signal is output at a relatively large level. Subsequently, the second optical heterodyne receiver 110B outputs a beat signal of an echo (that is, received light) of the backscattered light component from the atmosphere and the local oscillation light. Accordingly, the range of the wind speed measurement distance that can be processed by the second optical heterodyne receiver 110B is equivalent to that of the first optical heterodyne receiver 110A.

  In the optical wave radar apparatus as described above, the spontaneous emission light component generated during the pulse OFF period of the first optical fiber amplifier 304A can be suppressed by the second frequency intensity modulator 603B. As a result, the spontaneous emission light component of the first optical fiber amplifier 304A is blocked before being input to the second optical fiber amplifier 304B. For this reason, the pumping energy of the second optical fiber amplifier 304B is not taken away for amplification of the spontaneous emission light of the first optical fiber amplifier 304A, and a decrease in amplification efficiency due to the spontaneous emission light can be suppressed. Therefore, it is possible to suppress noise components due to spontaneously emitted light.

  In the sixth embodiment, similarly to the first embodiment, detection is performed using the first and second optical heterodyne receivers 110A and 110B. However, as in the second embodiment, a single optical heterodyne reception is performed. Detection may be performed using the machine 210.

Embodiment 7 FIG.
The lightwave radar apparatus according to the first to sixth embodiments expands the measurable range as compared with the conventional lightwave radar apparatus as shown in FIG. On the other hand, the light wave radar device of the seventh embodiment changes the measurable range to a desired range.

  FIG. 11 is a block diagram showing an optical radar device according to Embodiment 7 of the present invention. In FIG. 11, a series of optical paths of the light wave radar device of the seventh embodiment is formed by an optical fiber (thick solid line in the figure). This optical fiber has an optical fiber termination 700a. The lightwave radar apparatus according to the seventh embodiment includes a reference light source (reference light source unit) 701, an optical coupler (optical path branching means) 702, a frequency intensity modulator (amplification modulation means) 703, and an optical fiber amplifier (optical fiber amplification means). 704, an optical circulator 705, a telescope (transmission / reception optical system) 706, an optical heterodyne receiver (optical heterodyne reception unit) 707, and a signal processing means 708.

  The reference light source 701 oscillates reference light that is laser light having a single wavelength. The optical path of the reference light from the reference light source 701 is branched into two optical paths by the optical coupler 702. One of the two optical paths from the optical coupler 702 is connected to the frequency intensity modulator 703. The other of the two optical paths from the optical coupler 702 is connected to the optical heterodyne receiver 707. The reference light from the optical coupler 702 is sent to the optical heterodyne receiver 707 as local oscillation light.

  The reference light from the optical coupler 702 is sent to the frequency intensity modulator 703 as seed light. The frequency intensity modulator 703 modulates the light intensity and frequency of the seed light, and sends the modulated seed light to the optical fiber amplifier 704. The optical fiber amplifier 704 optically amplifies the seed light received from the frequency intensity modulator 703 to a predetermined peak power. Then, the optical fiber amplifier 704 sends the amplified seed light as transmission light to the telescope 706 via the optical circulator 705 and the optical fiber terminal unit 700a.

  Here, when a polarization-maintaining single mode fiber is used as the optical fiber and a high peak output of the transmitted light is caused, backscattering by stimulated Brillouin scattering (hereinafter, SBS) is induced in the fiber. For this reason, the output peak power by the optical fiber amplifier 704 is set to be equal to or lower than the threshold value at which SBS occurs. Generally, the threshold value at which SBS is generated for a pulse width of 0.1 to 1 μsec used in a wind measurement lightwave radar apparatus is about 10 to 20 W.

  The telescope 706 is connected to the optical fiber terminal unit 700a. Further, the telescope 706 can independently adjust the condensing distance of the transmission light and the outgoing beam aperture, and is coaxial with transmission and reception. Further, the telescope 706 irradiates the transmission light from the optical fiber terminal unit 700a toward a desired target in the air. In addition, the telescope 706 collects backscattered light in which transmission light irradiated into the air hits aerosol or the like, and receives the backscattered light as received light.

  The backscattered light collected by the telescope 706 is transmitted from the optical fiber terminal unit 700 a to the optical heterodyne receiver 707 via the optical circulator 705. The optical heterodyne receiver 707 optically combines the local oscillation light from the optical coupler 702 and the reception light from the telescope 706 and performs photoelectric conversion. Then, the optical heterodyne receiver 707 generates an electrical signal corresponding to the light intensity of the difference frequency component between the backscattered light and the local oscillation light as a beat signal.

  The signal processing means 708 receives a beat signal having a differential frequency from the optical heterodyne receiver 707, and AD-converts the beat signal to obtain a time series signal. Then, the signal processing means 708 performs Fourier transform on the time series signal for each time gate, calculates a power spectrum, and measures a desired target wind speed and the like based on the power spectrum.

  Here, the telescope 706 has a condensing distance driving mechanism 710 for adjusting the condensing distance of the transmission light and a beam diameter adjusting mechanism 711 for adjusting the outgoing beam aperture of the transmission light. The condensing distance drive mechanism 710 and the beam diameter adjustment mechanism 711 each include a drive unit (for example, an actuator such as a motor or an electromagnet). The driving unit of the condensing distance driving mechanism 710 adjusts the condensing distance of the transmission light according to the control command value of the control signal from the signal processing unit 708. The driving units of the condensing distance driving mechanism 710 and the beam diameter adjusting mechanism 711 adjust the outgoing beam aperture of the transmission light in accordance with the control command value of the control signal from the signal processing unit 708.

  Next, the telescope 706 of the seventh embodiment will be specifically described. FIG. 12 is a block diagram specifically showing the telescope 706 of FIG. FIG. 12A shows the telescope 706 in a small aperture / afocal state. FIG. 12B shows the telescope 706 in a large aperture / afocal state. FIG. 12C shows the telescope 706 having a large aperture and a focused state.

  In FIG. 12, the telescope 706 includes a collimator optical system 720, a first concave lens 721, a first convex lens 722, a second concave lens 723, and a second convex lens 724. The collimator optical system 720 is connected to the optical fiber terminal portion 700a. The first concave lens 721, the first convex lens 722, the second concave lens 723, and the second convex lens 724 constitute an afocal optical system. Note that reference numeral 725 in FIG. 12 indicates a condensing point when parallel light is incident from the objective side of the telescope 706, that is, the objective side of the second convex lens 724.

  The transmission light output from the optical fiber terminal unit 700a can be handled as a point reference light source, and the collimator optical system 720 and the first concave lens 721 so that the point reference light source and the condensing point 725 are in an imaging relationship. And the optical arrangement of the first convex lens 722 are adjusted.

Now, when the focal length of the first convex lens 722 is F ′ and the distance from the optical fiber terminal portion 700a to the condensing point 725 is L ₀ , the distance from the condensing point 725 of the first convex lens 722 is (10). The imaging relationship is satisfied when the values of L _far and L _near shown in the equations (11) and (11) are set.

The imaging magnification M _far corresponding to the above equation (10) is given by the following equation (12) by geometric optics.

Further, the imaging magnification M _near corresponding to the above equation (11) is given by the following equation (13) by geometric optics.

Here, for example, when an image forming distance of L ₀ = 100 mm is realized by the first convex lens 722 having a focal length F ′ = 22.2 mm, the distance from the condensing point 725 of the first convex lens 722 is expressed by Equation (10). When adjustment is made to L _far = 66.67 mm, the imaging magnification is M _far = 2 from equation (12).

Further, when the imaging distance of L ₀ = 100 mm is realized by the first convex lens 722 having the same focal length F ′ = 22.2 mm, the distance from the condensing point 725 of the first convex lens 722 is expressed by Expression (11). When the lens is adjusted to a position of L _near = 33.33 mm, the imaging magnification is M _near = 0.5 according to the equation (13).

Now, when the imaging magnification determined by the second concave lens 723 and the second convex lens 724 is designed to be M ₀ = 10, the combined magnification of the afocal optical system is from the condensing point 725 of the first convex lens 722. When the distance is adjusted to L _far = 66.67 mm, M ₀ × M _far = 10 × 2 = 20. On the other hand, the composite magnification of the afocal optical system when the distance from the condensing point 725 of the first convex lens 722 is adjusted to L _near = 33.33 mm is M ₀ × M _near = 10 × 0.5 = 5.

  Therefore, by selecting the focal length of the collimator optical system 720 and adjusting the position of the first convex lens 722 at the exit aperture of the collimator optical system 720, for example, when the beam diameter is approximately parallel to 10 mm, The beam diameter of the transmission light at the exit aperture of the telescope 706 can be changed.

Specifically, as shown in FIG. 12B, when the distance from the condensing point 725 of the first convex lens 722 is adjusted to L _far = 66.67 mm, the beam diameter can be set to 200 mm, and the long distance It can be used as a beam diameter for measurement.

On the other hand, as shown in FIG. 12A, when the distance from the condensing point 725 of the first convex lens 722 is adjusted to L _near = 33.33 mm, the beam diameter can be set to 50 mm. It can be used as a beam diameter for distance measurement.

  Further, as shown in FIG. 12 (c), the transmission light is increased by increasing the distance between the optical fiber terminal portion 700a and the collimator optical system 720 from the distance in the complete collimated state (the light collection distance is infinite). Can be shifted to the vicinity (telescope 706 side).

  Therefore, in the light wave radar apparatus of the seventh embodiment, by using the internal structure of the telescope 706 shown in FIG. The beam diameter and the focusing distance of the transmission light can be changed according to a desired distance range (distance range to be measured) without exchanging the transmission / reception optical system.

  Next, the contour map registered in advance in the signal processing means 708 will be described. FIG. 13 is an explanatory diagram showing an example of a contour map registered in the signal processing means 708 of FIG. The contour map in FIG. 13 is obtained by calculating the measurement distance and effective aperture diameter dependence of the signal-to-noise ratio SNR in wind speed measurement based on the above equation (1). Further, the contour map of FIG. 13 shows that the measurable range is wider as the measurement distance that takes the signal-to-noise ratio SNR threshold or more is wider.

  FIG. 13A shows a contour map when the light collection distance is 0.5 km, and FIG. 13B shows a contour map when the light collection distance is 1 km. For example, when a measurement distance from 0 km to 1 km is set as a measurable range and it is desired to measure with a relatively high signal-to-noise ratio SNR margin, as shown in FIG. It can be seen that the combination with an aperture diameter (beam diameter) of 60 mm is optimal. On the other hand, when the measurement distance from 0 km to 1.4 km is set as a measurable range and it is desired to measure over a relatively wide range, as shown in FIG. It can be seen that the combination of (beam diameter) 100 mm is optimal.

  Accordingly, a contour map as shown in FIG. 13 is calculated in advance for a plurality of condensing distances and registered in advance in the signal processing means 708 as reference data, so that the condensing distance and effective aperture diameter (beam diameter) are obtained. Is output to the driving unit of the converging distance driving mechanism 710 and the beam diameter adjusting mechanism 711 at high speed (immediately) to adjust the condensing distance and effective aperture diameter (beam diameter) of the transmission light. Can do.

  By outputting and controlling the optimum values of the condensing distance and effective aperture diameter (beam diameter) obtained by the above method from the signal processing means 708 to the condensing distance driving mechanism 710 and the beam diameter adjusting mechanism 711. The measurable range can be maximized according to the maximum measurement distance of the wind speed to be measured, and measurement can be performed with the optimal setting of the telescope 706.

  In the light wave radar apparatus as described above, measurement can be performed with the optimum setting of the telescope 706 without replacing the telescopes 1006 and 1007 as in the conventional light wave radar apparatus as shown in FIG. For this reason, not only the trouble of exchanging the telescopes 1006 and 1007 is eliminated, but there is no need to prepare the telescopes 1006 and 1007 for replacement, and the entire system can be reduced in price and weight.

  Furthermore, the time for readjustment of the directivity to the observation space associated with the replacement of the telescopes 1006 and 1007 such as the conventional light wave radar apparatus as shown in FIG. Therefore, by adjusting the condensing distance and effective aperture diameter (beam diameter) of the transmitted light, the measurable range in the line-of-sight direction can be made relatively wide without replacing the telescope, and the measurement work Can be facilitated.

  Although the seventh embodiment has been described on the assumption that adjustment of the transmission / reception optical system is electrically controlled by the converging distance driving mechanism 710 and the beam diameter adjusting mechanism 711, the setting change is not required to be performed at high speed. Alternatively, the above two types of adjustment points may be manually adjusted with reference to the contour map calculated in FIG. In this case, the condensing distance driving mechanism 710 and the beam diameter adjusting mechanism 711 are not necessary, and it is possible to reduce the cost and weight by simplifying the device configuration.

  In the seventh embodiment, since only the position of the first convex lens 722 is set as an adjustment point of the optical system for adjusting the beam diameter, two types of beam diameters are set. However, by simultaneously adjusting the position of the first concave lens 721 in addition to the position of the first convex lens 722, the beam diameter of the transmitted light can be set to three or more types of beam diameters.

It is a block diagram which shows the light wave radar apparatus by Embodiment 1 of this invention. It is a graph which shows the measurement characteristic of the light wave radar apparatus of FIG. It is a block diagram which shows the light wave radar apparatus by Embodiment 2 of this invention. It is a block diagram which shows the light wave radar apparatus by Embodiment 3 of this invention. It is a graph which shows the measurement characteristic of the light wave radar apparatus of FIG. It is a block diagram which shows the light wave radar apparatus by Embodiment 4 of this invention. It is a graph which shows the measurement characteristic of the light wave radar apparatus of FIG. It is a block diagram which shows the light wave radar apparatus by Embodiment 5 of this invention. It is a block diagram which shows the light wave radar apparatus by Embodiment 6 of this invention. FIG. 10 is a waveform diagram showing signal output timing of each device of FIG. It is a block diagram which shows the light wave radar apparatus by Embodiment 7 of this invention. It is a block diagram which shows specifically the telescope of FIG. It is explanatory drawing which shows an example of the contour map registered into the signal processing means of FIG. 1 is a configuration diagram illustrating a conventional light wave radar device as disclosed in Patent Document 1. FIG. It is a graph which shows the measurement characteristic at the time of the large-diameter telescope use by the conventional optical wave radar apparatus of FIG. 14 and a small-diameter telescope use.

Explanation of symbols

  101 Reference light source (reference light source unit), 102A First optical coupler (optical path branching means), 102B Second optical coupler (optical path branching means), 103 Frequency intensity modulator (frequency intensity modulating means), 104 Optical fiber amplifier (optical fiber) Amplifying means), 105A first optical circulator, 105B second optical circulator, 106A first collimator optical system, 106B second collimator optical system, 107A first polarization 90 degree rotation means, 107B second polarization 90 degree rotation means, 108 polarization Combining / separating means (light combining means), 109 telescope (transmitting / receiving optical system), 110A first optical heterodyne receiver (optical heterodyne receiving section), 110B second optical heterodyne receiver (optical heterodyne receiving section), 111 signal processing means, 208A First polarization combining means, 208B Second polarization combining means, 21 Optical heterodyne receiver (optical heterodyne receiver), 304A first optical fiber amplifier (first optical fiber amplifying means), 304B second optical fiber amplifier (second optical fiber amplifying means), 402C third optical coupler (medium / close combination) Optical coupler for separation), 406B second collimator optical system, 406C third collimator optical system, 501A first reference light source (reference light source unit), 501B second reference light source (reference light source unit), 501C third reference light source (reference light source) Part), 502 optical coupler (optical path branching means), 505C third optical circulator, 508 wavelength combining / separating means, 512A first wavelength combining means (reference light combining means), 512B second wavelength combining means (received light combining means), 513 wavelengths Separation means, 603A first frequency intensity modulator (first frequency intensity modulation means), 603B second frequency Degree modulator (second frequency intensity modulating means), 614 trigger signal generator (driving signal generating means), 701 reference light source, 702 optical coupler (optical path branching means), 703 frequency intensity modulator (frequency intensity modulating means), 704 Optical fiber amplifier (optical fiber amplification means), 705 optical circulator, 706 telescope (transmission / reception optical system), 707 optical heterodyne receiver (optical heterodyne reception section), 708 processing means, 710 focusing distance drive mechanism, 711 beam diameter adjustment Mechanism, 720 collimator optical system, 721 first concave lens, 722 first convex lens, 723 second concave lens, 724 second concave lens.

Claims (11)

An optical signal generator having a reference light source unit that oscillates a linearly polarized reference light having a single frequency, and that generates a plurality of transmission lights and a plurality of local oscillation lights from the reference light;
A plurality of collimator optical systems capable of adjusting the respective beam diameters and collection distances of the plurality of transmission lights, while substantially paralleling the optical axes of the plurality of transmission lights;
Light combining means for combining the plurality of transmission lights from the plurality of collimator optical systems;
A transmission / reception coaxial transmission / reception optical system for irradiating a plurality of transmission lights received from the light combining means toward a desired target, and receiving a plurality of scattered lights from the target as a plurality of reception lights;
The difference between the plurality of received light from the transmission / reception optical system and the plurality of local oscillation light from the signal generation unit, and the difference between the plurality of reception light and each of the plurality of reception light by heterodyne detection An optical heterodyne receiver that generates an electrical signal according to the light intensity of the frequency component;
A light wave radar apparatus comprising: signal processing means for extracting the target information based on an electrical signal received from the optical heterodyne receiver. An optical path between the optical signal generation unit and the plurality of collimator optical systems, an optical path between the plurality of collimator optical systems and the transmission / reception optical system, an optical path between the transmission / reception optical system and the optical heterodyne reception unit And a polarization-maintaining optical fiber that forms optical paths between the optical signal generator and the optical heterodyne receiver, respectively.
The optical signal generation unit generates each polarization state of the plurality of transmission lights as linearly polarized light having an orthogonal relationship, and generates each polarization state of the plurality of local oscillation lights as linearly polarized light having an orthogonal relationship. The light wave radar apparatus according to claim 1. First polarization combining means for combining the linearly polarized light components of the plurality of received lights;
A second polarization combining unit for combining the linearly polarized light components of the plurality of local oscillation lights.
The optical heterodyne receiver generates an electrical signal corresponding to the intensity of a differential frequency component of the linearly polarized components of the plurality of received lights that have undergone polarization combining with the linearly polarized components of the plurality of local oscillation lights that have undergone polarization combining. The light wave radar device according to claim 2. The optical signal generator is
Frequency intensity modulation means for modulating the frequency and light intensity of the reference light;
A first optical fiber amplifying means for amplifying the reference light modulated by the frequency intensity modulating means to be the transmission light;
A second optical fiber amplifying means connected in series to the first optical fiber amplifying means and further amplifying the transmitted light;
An optical path branching unit interposed between the first and second optical fiber amplifying units and branching the optical path of the transmission light from the first optical fiber amplifying unit into the plurality of transmission lights. The light wave radar device according to any one of claims 1 to 3, wherein The plurality of collimator optical systems are a first collimator optical system, a second collimator optical system, and a third collimator optical system,
The first collimator optical system adjusts a beam diameter of a part of the plurality of transmission lights so as to coincide with an effective aperture diameter on the object side of the transmission / reception optical system, and the adjusted transmission light is a long distance Send to the transmission / reception optical system as transmission light for measurement,
The second collimator optical system adjusts the beam diameter of a part of the plurality of transmission lights so as to be smaller than the effective aperture diameter on the object side of the transmission / reception optical system. Send to the transmission / reception optical system as transmission light for distance measurement,
The third collimator optical system adjusts the beam diameter of a part of the plurality of transmission lights so as to be smaller than the effective aperture diameter on the object side of the transmission / reception optical system. Send to the transmission / reception optical system as transmission light for distance measurement,
In the second and third collimator optical systems, the optical axis of the short-distance measurement transmission light and the optical axis of the medium-distance measurement transmission light are parallel to each other and do not overlap with the objective surface of the transmission / reception optical system. The light wave radar device according to claim 1, wherein the light wave radar device is shifted as follows. An optical path between the optical signal generation unit and the plurality of collimator optical systems, an optical path between the plurality of collimator optical systems and the transmission / reception optical system, an optical path between the transmission / reception optical system and the optical heterodyne reception unit And a polarization-maintaining optical fiber that forms optical paths between the optical signal generator and the optical heterodyne receiver, respectively.
The optical signal generator is
Generating each polarization state of the plurality of transmission lights as linearly polarized light having an orthogonal relationship, and generating each polarization state of the plurality of local oscillation lights as linearly polarized light having an orthogonal relationship,
The plurality of transmission lights are branched and sent to the second collimator optical system and the third collimator optical system, and a plurality of reception lights from the second collimator optical system and the third collimator optical system are combined. It has an optical coupler for synthesis and separation,
The light combining unit is a deflection combining unit that combines and separates linearly polarized light components of the plurality of transmission lights input from the first collimator optical system and the second and third collimator optical systems, respectively. The light wave radar apparatus according to claim 5. A plurality of reference light source units that oscillate linearly polarized reference light at different wavelengths, a reference light combining unit that combines the plurality of reference lights from the plurality of reference light source units, and a reference light combining unit. Optical path branching means for dividing the combined reference light into combined seed light and combined local oscillation light, modulation amplification means for intensity-modulating and amplifying the combined seed light that has passed through the optical path branching means, and the modulation amplification means An optical signal generation unit having wavelength separation means for separating the combined seed light that has passed through each wavelength to generate a plurality of transmission lights;
A plurality of collimator optical systems capable of adjusting the respective beam diameters and collection distances of the plurality of transmission lights, while substantially paralleling the optical axes of the plurality of transmission lights;
Light combining means for combining the plurality of transmission lights from the plurality of collimator optical systems into a combined transmission light;
A transmission / reception coaxial transmission / reception optical system that irradiates the combined transmission light from the light combining means toward a desired target, and receives a plurality of scattered lights from the target as a plurality of reception lights;
Received light combining means for combining the plurality of received lights from the transmission / reception optical system;
Upon receiving the received light synthesized by the received light synthesizing means and the synthesized local oscillation light that has passed through the optical path branching means, the frequency difference between each of the plurality of received lights and the local oscillation light by heterodyne detection An optical heterodyne receiver that generates an electrical signal according to the intensity of the component;
A light wave radar apparatus comprising: signal processing means for extracting the target information based on an electrical signal received from the optical heterodyne receiver. The optical signal generator is
A first frequency intensity modulation which is provided before the first optical fiber amplifying means and modulates and transmits the frequency and intensity of the transmission light to the first optical fiber amplifying means when receiving a first drive signal from the outside. Means,
In place of the transmission light branching means, interposed between the first and second optical fiber amplifying means, having a zero-order output terminal and a primary output terminal, and receiving the second drive signal from the outside, When the transmission light from the first optical fiber amplifying means is sent to a part of a plurality of collimator optical systems from the 0th-order output end and the second drive signal is received from the outside, the plurality of collimator optics Second frequency intensity modulating means for modulating the frequency and intensity of the transmitted light from the first optical fiber amplifying means to be sent from the primary output terminal to the rest of the system;
The first drive signal to the first frequency intensity modulation means is generated in a predetermined cycle, and the second drive signal to the second frequency intensity modulation means is generated in the half of the predetermined period. Drive signal generating means for generating in synchronization with the signal ;
Laser Radar apparatus according to claim 4, characterized in that it has a.

A reference light source unit that oscillates a linearly polarized reference light having a single frequency, and an optical signal generation unit that generates transmission light and local oscillation light from the reference light;
A transmission / reception coaxial transmission / reception optical system that irradiates the transmission light received from the optical signal generation unit toward a desired target, and receives scattered light from the target as reception light;
The received light from the transmission / reception optical system and the locally oscillated light from the signal generating unit are subjected to heterodyne detection, and the electric power corresponding to the intensity of the difference frequency component of the received light from the locally oscillated light is detected. An optical heterodyne receiver for generating a signal;
Based on the electrical signal received from the optical heterodyne receiver, the signal processing means for extracting the target information, The transmission / reception optical system comprises:
A focusing distance adjusting mechanism for adjusting the focusing distance of the transmission light;
A light wave radar device comprising: a beam diameter adjusting mechanism for adjusting a beam diameter of the transmission light. The transmission / reception optical system includes:
A collimator optical system that substantially parallelizes the transmission light received from the optical signal generation unit;
An afocal optical system that includes first and second convex lenses and first and second concave lenses, and irradiates the transmission light received from the commerita optical system toward a desired target;
The condensing distance of the transmission light can be adjusted by adjusting the lens interval of the collimator optical system,
The light wave radar device according to claim 9, wherein a beam diameter of the transmission light can be adjusted by adjusting a position of the first convex lens of the afocal optical system. The signal processing means includes
Pre-stored a contour map calculated from the measurement distance of the signal-to-noise ratio of the Doppler spectrum and the effective aperture diameter of the transmission / reception optical system with respect to the focusing distance of the transmission / reception optical system,
Based on the contour map, a combination of parameters of an effective aperture diameter and a condensing distance of the transmission / reception optical system is calculated, and driving of the beam diameter adjusting mechanism and the condensing distance adjusting mechanism is controlled. The light wave radar device according to claim 9 or 10.

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