CN103592652A - Double-frequency Doppler laser radar detection system based on single solid body FP etalon four-edge technology - Google Patents

Abstract

The invention relates to a Doppler laser radar detection system, in particular to a double-frequency Doppler laser radar detection system based on the single solid body FP etalon four-edge technology. The double-frequency Doppler laser radar detection system based on the single solid body FP etalon four-edge technology is characterized in that atmosphere backward scattering signals are collected through a Cassegrain telescope, pass through a fourth convex lens and a spike filter, and enter one end of a 200-meter-long bare optical-fiber patch cord through coupling, and the other end of the 200-meter-long bare optical-fiber patch cord is connected with a branch end of a second 1*2 optical fiber coupler. The beam-combining end of the second 1*2 optical fiber coupler is connected with the end a of an optical loop device, the reflecting light beam of a beam-splitting mirror enters a branch end of a first 1*2 optical fiber coupler, and the beam-combining end of the first 1*2 optical fiber coupler and the other branch end of the first 1*2 optical fiber coupler are connected with a 100-meter-long bare optical fiber and the other branch end of the second 1*2 optical fiber coupler respectively. By means of the technical scheme, the double-frequency Doppler laser radar detection system based on the single solid body FP etalon four-edge technology has the advantages that the signal to noise ratio is improved, the frequency discrimination capability of the reflected signals is sufficiently used, frequency discrimination sensitivity is improved, and therefore the wind speed measuring accuracy of the system is improved.

Description

Bifrequency Doppler lidar measuring system based on single solid FP etalon four marginal technologys

Technical field

The present invention relates to a kind of Doppler lidar measuring system, particularly a kind of bifrequency Doppler lidar measuring system based on single solid FP etalon four marginal technologys.

Background technology

Since the eighties in last century, Direct-detection Doppler lidar technology has obtained swift and violent development, has successively occurred two kinds of Doppler frequency detection techniques: marginal technology and fringe technique.Marginal technology is based on FP interferometer single edges technology at first.1998, the people such as Korb were developed the dual edge technology based on FP interferometer.Except adopting FP interferometer as frequency discriminator, also developed afterwards and adopted iodine spectra to carry out the method for frequency discrimination.Calendar year 2001 Bruneau D has proposed to adopt Mach-Zehnder interferometer as the frequency discriminator of marginal technology.The FP interferometer that fringe technique adopts is at first as frequency discriminator.What produce due to FP interferometer is circular fringes, to direct-detection, makes troubles.2002, J A Mckay analyzed and has adopted Fizeau interferometer as the detection performance of frequency discriminator, and the same year, Bruneau D proposed to adopt Mach-Zehnder interferometer as the frequency discriminator of fringe technique.Comparatively speaking, the dual edge technology based on FP interferometer is the technology the most generally adopting at present.But by carefully analyzing discovery, this technology has only been utilized the discriminability of FP interferometer transmission signal, and does not utilize the discriminability of reflected signal.So no matter, from surveying signal to noise ratio (S/N ratio) angle, still from the sensitivity of system frequency discrimination, all may fully not excavate the spectral characteristic of FP interferometer.

Summary of the invention

Technical matters to be solved by this invention is: a kind of bifrequency Doppler lidar measuring system based on single solid FP etalon four marginal technologys is provided, can uses the bifrequency Doppler lidar measuring wind based on single FP etalon four marginal technologys.

The technical solution adopted for the present invention to solve the technical problems is: as shown in Figure 1, any one-level transmission spectrum of FP etalon and front and back two waists of reflectance spectrum intersect respectively measuring wind speed principle of the present invention, form four edges.For making full use of this four edges, Emission Lasers frequency v _0i(i=1,2) alternately change near two intersection points, thereby form " bifrequency four edges " Detection Techniques.Emission Lasers incides in atmosphere, runs into and has the particulate of macroscopic motion speed or atmospheric molecule (being wind speed), due to the Doppler effect of light, compares back scattering light frequency v with Emission Lasers _i(i=1,2) will exist and Laser emission direction wind speed component (radially wind speed) V _rcorresponding Doppler shift amount v _d=v _i-v _0i=2V _r/ λ, wherein λ is Emission Lasers wavelength.Like this, will there is respective change through transmitance and the reflectivity of FP etalon in back scattering light signal.According to the variable quantity of transmitance and reflectivity, according to prior known transmission spectrum and reflectance spectrum, can calculate to obtain Doppler shift amount, and then obtain the radially size and Orientation of wind speed.

Frequency is that transmitance and the reflectivity that the monochromatic collimated beam of v incides desirable Fabry-Perot etalon is respectively:

Wherein θ is incident angle; v _fSR=c/2nd is that etalon is freely composed spacing, and d is dull and stereotyped interval, and n is the refractive index between plate, and c is the light velocity in vacuum; Δ v _1/2for etalon bandwidth.

Yet the light signal of the actual FP of inciding etalon is by coupling fiber, and obtain after colimated light system, therefore be not strict directional light; Meanwhile, no matter be Emission Lasers, or backscatter signal light not strict monochromatic light.In addition there is the impacts such as absorption and scattering in actual FP etalon, on incident optical signal; Two planar surfaces of actual standard tool are strictly not smooth, have certain defect; Two flat boards also can not be accomplished strictly parallel, have certain nonparallelism.The full angle of divergence of light signal of supposing to incide actual FP etalon is 2 θ ₀, frequency spectrum is that Gaussian distribution (because being all approximately Gaussian distribution on Emission Lasers spectral line, rice back scattering spectrum and Rayleigh back scattering spectral theory) and light intensity are even, through deriving, transmitance and the reflectivity of this light signal after FP etalon is respectively

Wherein

$M\left(v\right)=1+2\underset{m=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{R}^m\cos \left[\frac{2\mathrm{\&pi;mv}}{v_{\mathrm{FSR}}}(1-\frac{{\mathrm{\&Omega;}}_{\mathrm{<figure-callout\; id="4"\; label="FP"\; filenames="HSA0000097229310000012.png"\; state="\{\{state\}\}">FP</figure-callout>}}}{4\mathrm{\&pi;}})\right]\exp \{-{\left[\frac{\mathrm{\&pi;m\&Delta;}{v}_e}{v_{\mathrm{FSR}}}(1-\frac{{\mathrm{\&Omega;}}_{\mathrm{<figure-callout\; id="4"\; label="FP"\; filenames="HSA0000097229310000012.png"\; state="\{\{state\}\}">FP</figure-callout>}}}{4\mathrm{\&pi;}})\right]}^2\}\sin c\left(\frac{2\mathrm{mv}}{v_{\mathrm{FSR}}}\frac{{\mathrm{\&Omega;}}_{\mathrm{<figure-callout\; id="4"\; label="FP"\; filenames="HSA0000097229310000012.png"\; state="\{\{state\}\}">FP</figure-callout>}}}{4\mathrm{\&pi;}}\right)$

In formula, A is the absorptivity of planar surface metal film; R is the reflectivity of corresponding wavelength etalon flat board; T _av=(1-R-A) ²/ (1-R ²) be the mean transmissivity of etalon; Ω _fP=2 π (1-cos θ ₀) be incident beam solid angle; V is incident light centre frequency; for equivalent incident laser 1/e height spectrum width, wherein Δ d _dfor the dull and stereotyped defective agent of etalon; α is the dull and stereotyped angles of two interference; ρ is the dull and stereotyped radius of circular aperture etalon; Δ v is the width of Gauss's incident light spectrum 1/e At The Height.For Emission Lasers itself or rice backscatter signal, Δ v=Δ v _l=δ v/ (4ln2) ^1/2, δ v is Laser emission spectrum width (FWHM); For Rayleigh backscatter signal, Δ v wherein _r=(8kT/M λ ²) ^1/2, T is atmospheric temperature; λ is optical maser wavelength; K is Boltzmann constant; M atmospheric molecule quality.

Definition Doppler frequency response function Q (v _d) be

$Q\left(v_d\right)=\frac{h(v_{10}+v_d)-h(v_{20}+v_d)}{h(v_{10}+v_d)+h(v_{20}+v_{\text{d}})}$

Wherein

radially wind speed is

$V_r=\frac{\mathrm{\&lambda;}}{2}{v}_d=\frac{\mathrm{\&lambda;}}{2}[Q\left(v_d\right)-Q\left(0\right)]{\left[\frac{\mathrm{dQ}\left(v_d\right)}{{\mathrm{dv}}_d}\right]}^{-1}{|}_{v_d=0}$

Utilize formula of error transmission to obtain radially measuring wind speed error to be:

${\mathrm{\&epsiv;}}_V=\frac{1}{\mathrm{SNR}\&CenterDot;{\mathrm{\&theta;}}_V}$

In formula: θ _vdoppler frequency response function velocity sensitivity; SNR is the total signal to noise ratio (S/N ratio) of system detectable signal.Suppose that reference signal is very strong, on the measurement of Emission Lasers frequency, can ignore the impact of noise, analyze and obtain θ _vcan be expressed as with SNR

$\mathrm{SNR}={[\frac{{\left({\mathrm{\&delta;I}}_{t1}\right)}^2}{I_{t1}^2}+\frac{{\left({\mathrm{\&delta;I}}_{r1}\right)}^2}{I_{r1}^2}+\frac{{\left({\mathrm{\&delta;I}}_{t2}\right)}^2}{I_{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HSA0000097229310000012.png"\; state="\{\{state\}\}">t</figure-callout>}2}^2}+\frac{{\left({\mathrm{\&delta;I}}_{r2}\right)}^2}{I_{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA0000097229310000012.png"\; state="\{\{state\}\}">r</figure-callout>}2}^2}]}^{-1/2}$

In formula: m _i=M (v _0i+ v _d); I _ti=I _t(v _0i+ v _d); I _ri=I _r(v _0i+ v _d), i=1,2.I _tiand I _ribeing respectively frequency is v _iback scattering light signal incide transmission signal and the reflected signal after etalon.

Structure of the present invention is comprised of four subsystems such as emission coefficient, receiving system, transmitting receiving optics and control system.Adopt the small-sized narrow line width regulatable semiconductor laser system of frequency stabilization of external cavity semiconductor laser and tubaeform diode amplifier composition MOPA structure as emissive source, the laser of transmitting 852nm high repetition frequency is surveyed for lower atmosphere layer wind field.Between seed light and amplifier, insert acousto-optic frequency shifter, after the certain umber of pulse of every accumulation, Laser emission program makes the pulse laser frequency of outgoing at v by controlling the driving of acousto-optic frequency shifter ₀₁, v ₀₂between alternately change.Emission Lasers, after through the second optoisolator, then is divided into two bundles by beam splitter.Occupy the reflected light of little energy as a Zhi Duan who enters the one 1 * 2 fiber coupler with reference to light, after one section of long bare fibre of about 100m, its rear orientation light is exported and is entered an input Zhi Duan of the 21 * 2 fiber coupler by another port of homonymy.Occupy the transmitted light of most energy after the beam expanding lens compression light beam angle of divergence, by two catoptrons of first, second, and third 45 degree catoptrons, two-dimensional scanner, finally with position angle the see through glass plate vertical with zenith angle of presetting, enter the tested region of atmosphere successively.Its atmospheric backscatter light is received by telescope, after the narrow band pass filter that is 852nm successively optical filtering and the time delay of one section of long bare fibre wire jumper of 200m, enters another input Zhi Duan of the 21 * 2 fiber coupler through centre wavelength.The light signal of exporting from the 21 * 2 fiber coupler is through a → b path of Optical circulator, and after being collimated by collimating mirror, normal incidence is to solid FP etalon.Its optical signal transmissive is received by the first avalanche photodide after utilizing the 5th convex lens to converge; And reflected light signal oppositely incides the b port of Optical circulator after collimating mirror is assembled, the b → c path through Optical circulator, is directly received by the second avalanche photodide.The output signal of two avalanche photodiode detectors is first gathered by double channels acquisition card, then carries out data processing, storage, wind speed inverting and result demonstration etc. by industrial computer.The laser instrument of whole system, acousto-optic frequency shifter, two-dimensional scanner, double channels acquisition card etc. all by RS232 interface by computer control.The present invention is by external cavity semiconductor laser, the first convex lens, acousto-optic frequency shifter, the first optoisolator, the second convex lens, the 3rd convex lens, tubaeform diode amplifier, the second optoisolator, beam splitter, beam expanding lens, the one 45 degree catoptron, the 2 45 degree catoptron, the 3 45 degree catoptron, two-dimensional scanner, glass plate, Cassegrain telescope, the 4th convex lens, narrow band pass filter, the one 1 * 2 fiber coupler, the long bare fibre of 100m, the long bare fibre wire jumper of 200m, the 21 * 2 fiber coupler, Optical circulator, collimating mirror, solid FP etalon, temperature controller, the 5th convex lens, optical patchcord, the first avalanche photodide, the second avalanche photodide, amplifier driving power, industrial computer, acousto-optic frequency shifter drives, trigger circuit, double channels acquisition card, Laser Driven power supply and two-dimensional scanner controller form, and it is characterized in that: external cavity semiconductor laser respectively and trigger circuit, Laser Driven power supply is connected, and the seed laser that external cavity semiconductor laser sends is first by the first convex lens, acousto-optic frequency shifter, the first optoisolator, the second convex lens, the 3rd convex lens, tubaeform diode amplifier, after the second optoisolator, by beam splitter, be divided into two bundles, after transmitted light beam expands by beam expanding lens, through the one 45 degree catoptron, after the 3 45 degree catoptron in the 2 45 degree catoptron and Cassegrain telescope, along in the optical axis direction directive two-dimensional scanner of Cassegrain telescope, after two-dimensional scanner leaded light, vertically see through glass plate and enter atmospheric exploration region, first catoptron of two-dimensional scanner and the optical axis of Cassegrain telescope are 45 degree angles, second catoptron of glass plate and two-dimensional scanner is 45 degree angles, two-dimensional scanner is connected with two-dimensional scanner controller by Data Control line, atmospheric backscatter signal is collected via Cassegrain telescope, through the 4th convex lens, after narrow band pass filter, be coupled into one end of the long bare fibre wire jumper of 200m, the other end of the long bare fibre wire jumper of 200m and a Zhi Luduan of the 21 * 2 fiber coupler are connected, the a end that closes Shu Duan and Optical circulator of the 21 * 2 fiber coupler is connected, the folded light beam of beam splitter is coupled into a Zhi Luduan of the one 1 * 2 fiber coupler, the one 1 * 2 fiber coupler close Shu Duan and another terminal respectively with the long bare fibre of 100m, the 21 * 2 another terminal of fiber coupler is connected, b end and the collimating mirror of Optical circulator, solid FP etalon, the 5th convex lens, one end of optical patchcord is light path and communicates, the other end of optical patchcord is connected with the first avalanche photodide, Optical circulator b brings out luminous point in the focus in object space of collimating mirror, the c end of Optical circulator is connected with the second avalanche photodide with optical fiber, temperature controller is connected with solid FP etalon, the first avalanche photodide, the second avalanche photodide is connected with double channels acquisition card respectively, double channels acquisition card is connected with trigger circuit, amplifier driving power, acousto-optic frequency shifter drives, trigger circuit, seed laser driving power, two-dimensional scanner controller is connected with industrial computer, by industrial computer is unified, control, amplifier driving power is connected with tubaeform diode amplifier, acousto-optic frequency shifter drives harmony optical frequency shift device to be connected.

Owing to adopting technique scheme, the advantage that the present invention has with good effect is: compare with the Doppler lidar system of the existing dual edge technology based on FP interferometer, both improved signal to noise ratio (S/N ratio), make full use of again the discriminability of reflected signal, improve frequency discrimination sensitivity, thereby improve the measuring wind speed precision of system.

Accompanying drawing explanation

Fig. 1 is measuring principle figure of the present invention.

Fig. 2 is structural drawing of the present invention.

1. external cavity semiconductor lasers in figure, 2. the first convex lens, 3. acousto-optic frequency shifter, 4, the first optoisolator, 5. the second convex lens, 6. the 3rd convex lens, 7. tubaeform diode amplifier, 8. the second optoisolator, 9. beam splitter, 10. beam expanding lens, 11. the 1 degree catoptrons, 12. the 2 45 degree catoptrons, 13. the 3 45 degree catoptrons, 14. two-dimensional scanners, 15. glass plates, 16. Cassegrain telescopes, 17. the 4th convex lens, 18. narrow band pass filters, 19. the one 1 * 2 fiber couplers, 20.100m long bare fibre, 21.200m long bare fibre wire jumper, 22. the 21 * 2 fiber couplers, 23. Optical circulators, 24. collimating mirrors, 25. solid FP etalon, 26. temperature controllers, 27. the 5th convex lens, 28. optical patchcords, 29. first avalanche photodides, 30. second avalanche photodides, 31. amplifier driving powers, 32. industrial computers, 33. acousto-optic frequency shifter drives, 34. trigger circuit, 35. double channels acquisition cards, 36. Laser Driven power supplys, 37. two-dimensional scanner controllers.

Embodiment

In Fig. 2, external cavity semiconductor laser (1) respectively and trigger circuit (34), Laser Driven power supply (36) is connected, the seed laser that external cavity semiconductor laser (1) sends is first by the first convex lens (2), acousto-optic frequency shifter (3), the first optoisolator (4), the second convex lens (5), the 3rd convex lens (6), tubaeform diode amplifier (7), after the second optoisolator (8), by beam splitter (9), be divided into two bundles, after transmitted light beam expands by beam expanding lens (10), through the one 45 degree catoptron (11), after the 3 45 degree catoptron (13) in the 2 45 degree catoptron (12) and Cassegrain telescope (16), along in the optical axis direction directive two-dimensional scanner (14) of Cassegrain telescope (16), after two-dimensional scanner (14) leaded light, the vertical glass plate (15) that sees through enters atmospheric exploration region, first catoptron of two-dimensional scanner (14) and the optical axis of Cassegrain telescope (16) are 45 degree angles, second catoptron of glass plate (15) and two-dimensional scanner (14) is 45 degree angles, two-dimensional scanner (14) is connected with two-dimensional scanner controller (37) by Data Control line, atmospheric backscatter signal is collected via Cassegrain telescope (16), through the 4th convex lens (17), after narrow band pass filter (18), be coupled into one end of the long bare fibre wire jumper of 200m (21), the other end of the long bare fibre wire jumper of 200m (21) is connected with a Zhi Luduan of the 21 * 2 fiber coupler (22), the a end that closes Shu Duan and Optical circulator (23) of the 21 * 2 fiber coupler (22) is connected, the folded light beam of beam splitter (9) is coupled into a Zhi Luduan of the one 1 * 2 fiber coupler (19), the one 1 * 2 fiber coupler (19) close Shu Duan and another terminal respectively with the long bare fibre of 100m (20), the 21 * 2 another terminal of fiber coupler (22) is connected, b end and the collimating mirror (24) of Optical circulator (23), solid FP etalon (25), the 5th convex lens (27), one end of optical patchcord (28) is light path and communicates, the other end of optical patchcord (28) is connected with the first avalanche photodide (29), Optical circulator (23) b brings out luminous point in the focus in object space of collimating mirror (24), the c end of Optical circulator (23) is connected with the second avalanche photodide (30) with optical fiber, temperature controller (26) is connected with solid FP etalon (25), the first avalanche photodide (29), the second avalanche photodide (30) is connected with double channels acquisition card (35) respectively, double channels acquisition card (35) is connected with trigger circuit (34), amplifier driving power (31), acousto-optic frequency shifter drives (33), trigger circuit (34), seed laser driving power (36), two-dimensional scanner controller (37) is connected with industrial computer (32), by industrial computer (32) is unified, control, amplifier driving power (31) is connected with tubaeform diode amplifier (7), acousto-optic frequency shifter drives (33) harmony optical frequency shift device (3) to be connected.

Claims (1)

1. the bifrequency Doppler lidar measuring system based on single solid FP etalon four marginal technologys, by external cavity semiconductor laser, the first convex lens, acousto-optic frequency shifter, the first optoisolator, the second convex lens, the 3rd convex lens, tubaeform diode amplifier, the second optoisolator, beam splitter, beam expanding lens, the one 45 degree catoptron, the 2 45 degree catoptron, the 3 45 degree catoptron, two-dimensional scanner, glass plate, Cassegrain telescope, the 4th convex lens, narrow band pass filter, the one 1 * 2 fiber coupler, the long bare fibre of 100m, the long bare fibre wire jumper of 200m, the 21 * 2 fiber coupler, Optical circulator, collimating mirror, solid FP etalon, temperature controller, the 5th convex lens, optical patchcord, the first avalanche photodide, the second avalanche photodide, amplifier driving power, industrial computer, acousto-optic frequency shifter drives, trigger circuit, double channels acquisition card, Laser Driven power supply and two-dimensional scanner controller form, and it is characterized in that: external cavity semiconductor laser (1) respectively and trigger circuit (34), Laser Driven power supply (36) is connected, and the seed laser that external cavity semiconductor laser (1) sends is first by the first convex lens (2), acousto-optic frequency shifter (3), the first optoisolator (4), the second convex lens (5), the 3rd convex lens (6), tubaeform diode amplifier (7), after the second optoisolator (8), by beam splitter (9), be divided into two bundles, after transmitted light beam expands by beam expanding lens (10), through the one 45 degree catoptron (11), after the 3 45 degree catoptron (13) in the 2 45 degree catoptron (12) and Cassegrain telescope (16), along in the optical axis direction directive two-dimensional scanner (14) of Cassegrain telescope (16), after two-dimensional scanner (14) leaded light, the vertical glass plate (15) that sees through enters atmospheric exploration region, first catoptron of two-dimensional scanner (14) and the optical axis of Cassegrain telescope (16) are 45 degree angles, second catoptron of glass plate (15) and two-dimensional scanner (14) is 45 degree angles, two-dimensional scanner (14) is connected with two-dimensional scanner controller (37) by Data Control line, atmospheric backscatter signal is collected via Cassegrain telescope (16), through the 4th convex lens (17), after narrow band pass filter (18), be coupled into one end of the long bare fibre wire jumper of 200m (21), the other end of the long bare fibre wire jumper of 200m (21) is connected with a Zhi Luduan of the 21 * 2 fiber coupler (22), the a end that closes Shu Duan and Optical circulator (23) of the 21 * 2 fiber coupler (22) is connected, the folded light beam of beam splitter (9) is coupled into a Zhi Luduan of the one 1 * 2 fiber coupler (19), the one 1 * 2 fiber coupler (19) close Shu Duan and another terminal respectively with the long bare fibre of 100m (20), the 21 * 2 another terminal of fiber coupler (22) is connected, b end and the collimating mirror (24) of Optical circulator (23), solid FP etalon (25), the 5th convex lens (27), one end of optical patchcord (28) is light path and communicates, the other end of optical patchcord (28) is connected with the first avalanche photodide (29), Optical circulator (23) b brings out luminous point in the focus in object space of collimating mirror (24), the c end of Optical circulator (23) is connected with the second avalanche photodide (30) with optical fiber, temperature controller (26) is connected with solid FP etalon (25), the first avalanche photodide (29), the second avalanche photodide (30) is connected with double channels acquisition card (35) respectively, and double channels acquisition card (35) is connected with trigger circuit (34), amplifier driving power (31), acousto-optic frequency shifter drives (33), trigger circuit (34), seed laser driving power (36), two-dimensional scanner controller (37) is connected with industrial computer (32), by industrial computer (32) is unified, control, amplifier driving power (31) is connected with tubaeform diode amplifier (7), and acousto-optic frequency shifter drives (33) harmony optical frequency shift device (3) to be connected.

Images