CN100545633C - The method and apparatus of laser gas remote measurement - Google Patents

Abstract

The method of laser gas remote measurement, employing is to the direct Modulated Semiconductor Laser device of electric current that the injects measurement light source as emission, transmit and receive optical system and adopt the transmitting-receiving coaxial configuration, adopt logarithm second harmonic detection method that gas absorption signal is surveyed and handled; Measurement light source is promptly measured main laser (1) and is sent modulated continuous narrow-linewidth laser, through optical fiber wave multiplexer (3), from placing optical fiber collimator (4) outgoing of lens (5) axis part, emitting laser target (7) reflection that is reflected after by gas to be measured (6), reflected light converges at photodetector (8) through lens (5) and is converted to electric signal, through the amplification and the filtering of detecting module (9), obtain gas concentration to be measured by microprocessor control system (13) collection and after adopting logarithm second harmonic algorithm process.

Description

The method and apparatus of laser gas remote measurement

Technical field

The present invention relates to a kind of method and apparatus of gas detection, specially refer to the gas method of telemetering and device, be mainly used in the remote measurement of gaseous substance concentration based on laser spectrum tech.

Background technology

The detection of gas, the detection of especially flammable, explosive, toxic and harmful, most important to industrial and agricultural production, people's lives, scientific research and national security.

At present, the technology of monitoring gas has multiple scheme, as: optical profile type, catalytic combustion type, semiconductor-type, enzyme and biological formula, galvanochemistry direct oxidation formula etc.Optical sensor have an incomparable advantage of many other sensors, as highly sensitive, response speed is fast, dynamic range is big etc.The detection principle of optical sensor roughly has: (1) absorption spectroscopy, survey the characteristic absorpting spectruming line of tested gas.(2) index method is surveyed the variations in refractive index that tested gas causes.(3) Raman spectroscopy is surveyed the Raman spectrum of tested gas.(4) fluorescent spectrometry is surveyed the fluorescence spectrum that tested gas produces under optical excitation.By contrast, therefore advantage such as the absorption spectrum formula has selectivity height, reliability height, the life-span is long, cost is low is subjected to extensive attention.

The high monochromaticity that laser has, directivity and high strength make it become the ideal tools of detection of gas.One of prior art [Liu Wenqing etc., the concentration change of methane in the tunable diode laser absorption spectroscopy method monitoring of environmental air, Chinese laser, the 32nd volume, the 9th phase, in September, 2005] a kind of gas detection scheme based on tunable semiconductor laser absorption spectrum technology is proposed, by adopting multiple reflectance cell, obtained the accuracy of detection of higher methane gas.The opticator of its system mainly comprises near infrared semiconductor laser with tunable, the reference gas absorption cell as light source and repeatedly reflects gas absorption cell.But this scheme can only be used for the gas detection of single-point owing to adopt the gas absorption cell of enclosed construction, can not realize the remote measurement of gas.

Two [people such as Yin Wangbao of prior art, the research of single lasing light emitter harmonic wave remote sensing methane, Chinese laser, the 30th the volume, the 10th phase, in October, 2003] in the single extenal cavity tunable semiconductor laser light resource of a kind of use has been proposed, utilize the harmonic wave Detection Techniques to carry out the scheme of remote sensing methane, this scheme adopts begin to speak sample pool structure and light transmitting-receiving coaxial configuration, is detection signal with the reflectance spectrum of landform target, can realize the methane remote sensing monitoring in certain zone.But this scheme has used baroque external cavity semiconductor laser as light source, and volume is bigger, is not suitable for portable use.And adopted first harmonic and second harmonic ratioing technigue to carry out concentration and calculated, it is not high to measure the signal to noise ratio (S/N ratio) and the linearity.

Summary of the invention

The object of the invention is: overcome the deficiencies in the prior art, the method and apparatus that proposition utilizes laser that gas is taken remote measurement, especially propose the directly laser gas remote measurement method of the logarithm second harmonics technique of modulation of a kind of based semiconductor laser instrument injection current, and a kind of laser gas remote measurement device with high stability, highly sensitive suitable portable use is provided.

The method of laser gas remote measurement, employing is to the direct Modulated Semiconductor Laser device of electric current that the injects measurement light source as emission, transmit and receive optical system and adopt the transmitting-receiving coaxial configuration, adopt logarithm second harmonic detection method that gas absorption signal is surveyed and handled, for the gas telemetry provides new implementation method: concrete grammar is, measurement light source is promptly measured main laser 1 and is sent modulated continuous narrow-linewidth laser, through optical fiber wave multiplexer 3, from placing optical fiber collimator 4 outgoing of lens 5 axis parts, emitting laser target 7 reflections that are reflected after by gas 6 to be measured, reflected light converges at photodetector 8 through lens 5 and is converted to electric signal, amplification and filtering through detecting module 9, obtain gas concentration to be measured by embedded control system 13 collections and after adopting logarithm second harmonic algorithm process, show measurement results by display unit 14.

Inject (electric current) modulation waveform of Laser Measurement device: modulation constitutes to high frequency sine sweep ripple for low frequency triangular wave or sawtooth wave, and sine wave freuqency is generally greater than 1KHz, and especially 1KHz-1000KHz is typically 10-100KHz, and legend is 10kHz; The triangle wave frequency is generally less than 100Hz, 1-100Hz especially, and legend is 10Hz; Sine wave freuqency should be far longer than the triangle wave frequency, generally at least at two more than the order of magnitude.In a triangular wave or sawtooth period, the wavelength-modulated center overlaps once with the gas absorption peak.Obtain this amplitude of logarithm second harmonic constantly, calculate gas concentration.

The principle of work of laser gas remote measurement method of the present invention: the drive current of light source 1 is to be modulated by a sinusoidal waveform on a direct current biasing, superpose simultaneously a sawtooth wave or low frequency triangular wave, and laser instrument output intensity and operation wavelength are correspondingly modulated:

I＝I ₀[1+a ₁cos(ωt+φ ₁)+a ₂cos(2ωt+φ ₂)](1)

λ＝λ _L+Δλcosωt (2)

ω is the angular frequency of modulation in the formula, and Δ λ is the wavelength-modulated amplitude.

According to Bill-lambert's theorem, process space distribution length is that the light intensity behind the gas absorption of l and the target reflection that is reflected is I _Out=kIexp[-α (λ) cl], c is a gas concentration in the formula, and k is for receiving spectrum number (promptly not having under the tested gas situation power that receives of system and the ratio of emergent power), α (λ) is an absorption lines of gases, has Lorentzian lineshape: α=α at normal temperatures and pressures ₀/ [1+ (λ-λ _p) ²/ (δ λ) ²].Wherein δ λ is half high half-breadth.Output intensity can be written as:

$I_{\mathrm{out}}=k{I}_0(1+a_1\cos \mathrm{\&omega;t}+a_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t})\exp \frac{-{\mathrm{\&alpha;}}_0\mathrm{<figure-callout\; id="1"\; label="cl"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">cl</figure-callout>}}{1+{(\mathrm{\&mu;}+M\cos \mathrm{\&omega;t})}^2}---\left(3\right)$

μ in the formula=(λ _L-λ _p)/δ λ is the irrelevance of optical maser wavelength with respect to absorption peak; M=Δ λ/δ λ is the wavelength-modulated degree.

(3) fraction of exponential term can be made Fourier expansion in the formula, obtains:

$\frac{1}{1+{(\mathrm{\&mu;}+M\cos \mathrm{\&omega;t})}^2}=\underset{n=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{S}_n\cos \left(\mathrm{n\&omega;t}\right)---\left(4\right)$

$S_n=\{\frac{j^n{[(1+\mathrm{j\&mu;})-\sqrt{{(1+\mathrm{j\&mu;})}^2+M^2}]}^n}{M^n\sqrt{{(1+\mathrm{j\&mu;})}^2+{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">M</figure-callout>}}^2}}+c.c.\}(1-\frac{{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="C20071013394500102.png,C20071013394500103.png"\; state="\{\{state\}\}">n</figure-callout>}0}}{2})---\left(4a\right)$

LnI is taken the logarithm on formula (3) both sides _Out=lnkI-α cl.Wherein lnkI can expand into:

$\ln \mathrm{kI}=\ln k{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="C20071013394500102.png,C20071013394500103.png"\; state="\{\{state\}\}">I</figure-callout>}}_0+\ln (1+a_1\cos \mathrm{\&omega;t}+a_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t})$

$=\ln k{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="C20071013394500102.png,C20071013394500103.png"\; state="\{\{state\}\}">I</figure-callout>}}_0+a_0^{*}+a_1^{*}\cos \mathrm{\&omega;t}+a_2^{*}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t}+......---\left(5\right)$

A in the formula ₀ ^*, a ₁ ^*, a ₂ ^*Be laser modulation parameter a ₁, a ₂Function.Note $I_{\mathrm{out}}^{*}=\ln I_{\mathrm{out}},$ ${\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="C20071013394500102.png,C20071013394500103.png"\; state="\{\{state\}\}">I</figure-callout>}}_0^{*}=\mathrm{<figure-callout\; id="0"\; label="ln\; k\; I"\; filenames="C20071013394500102.png,C20071013394500103.png"\; state="\{\{state\}\}">ln</figure-callout>}k{I}_{}{}_0+a_0^{*},$ Can get the expression formula of light signal harmonic wave under the logarithmic coordinate:

$I_{\mathrm{out}}^{*}=I_0^{*}+a_1^{*}\cos \mathrm{\&omega;t}+a_2^{*}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t}-{\mathrm{\&alpha;}}_0\mathrm{cl}\underset{n=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{S}_n\cos \left(\mathrm{n\&omega;t}\right)---\left(6\right)$

The process of taking the logarithm as can be seen, is expressed as total light intensity the form of each harmonic amplitude linearity combination.The amplitude that obtains second harmonic from (6) formula is: ${\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">I</figure-callout>}}_2^{*}=a_2^{*}-{\mathrm{\&alpha;}}_0\mathrm{<figure-callout\; id="2"\; label="cl\; S"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">cl</figure-callout>}{S}_{}{}_2.$ The computing formula that can get the path integral concentration of gas thus is:

$\mathrm{cl}=\frac{a_2^{*}-{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="C20071013394500092.png"\; state="\{\{state\}\}">I</figure-callout>}}_2^{*}}{{\mathrm{\&alpha;}}_0{S}_2}---\left(7\right)$

(7) each amount and light source power I of formula ₀Count k with the receipts spectrum and have nothing to do, not only made things convenient for processing, but also weakened the error that factors such as light source intensity fluctuation, reflectance target reflection coefficient, the change of photodetection circuit gain coefficient are introduced greatly.Cl, S ₂α ₀Definition: cl is the path integral concentration of gas; S ₂Be the secondary Fourier coefficient, see formula (4) and (4a); α ₀Peak absorbance coefficient for gas.

The laser gas remote measurement device shown in Fig. 1 block diagram, comprises measurement light source 1, target indication light source 2, optical fiber wave multiplexer 3, optical fiber collimator 4, lens 5, gas 6 to be measured, reflectance target 7, photodetector 8, detecting module 9, laser instrument temperature control module 10, laser instrument direct drive module 11, laser instrument AC driving module 12, microprocessor control system 13, display unit 14 constitutes; The photodetector 8 that receives in the optical module is connected microprocessor control system 13 through amplifying with the detecting module 9 of filtering and through amplifier, microprocessor control system 13 comprises embedded Control and signal processing circuit, and output interface connects display circuit, communication interface circuit, keyboard, warning circuit; Its output terminal of the output of embedded control system connects laser control circuit; Laser control circuit comprises laser high frequency modulated circuit, laser temperature control circuit, laser low frequency sweep circuit, laser instrument dc drive circuit; The output of laser control circuit drives measures main laser.Microprocessor especially adopts embedded Control and signal processing circuit (as arm processor).

The groundwork process of laser gas remote measurement device of the present invention is as follows:

As shown in Figure 1, by laser instrument temperature control module 10, laser instrument direct drive module 11, laser instrument AC driving module 12 provides temperature control for measurement light source 1, direct current biasing and ac modulation, measurement light source 1 is sent modulated continuous narrow-linewidth laser, this narrow-linewidth laser and the indication laser process optical fiber wave multiplexer 3 that sends from target indication light source 2, from placing optical fiber collimator 4 outgoing of lens 5 axis parts, target 7 reflections that are reflected after by gas 6 to be measured of the narrow-linewidth laser of outgoing, reflected light converges at photodetector 8 through lens 5 and is converted to electric signal, amplification and filtering through detecting module 9, obtain gas concentration to be measured by embedded control system 13 collections and after adopting logarithm second harmonic algorithm process, show measurement results by display unit 14.

Above said measurement light source 1 be semiconductor laser, its live width should be far smaller than the absorption peak width of gas 6 to be measured, its wavelength scanning range should be greater than the absorption peak width of gas 6 to be measured.Generally can be distributed feed-back (DFB) semiconductor laser or distributed Blatt reflective (DBR) semiconductor laser of optical fiber coupling output.

Said target indication light source 2 is the semiconductor laser of visible light wave range, as red light semiconductor laser or blue-light semiconductor laser instrument.

Said optical fiber wave multiplexer 3 is to be used for realizing that measurement light source 1 and target indication light source 2 close the fiber optic component on road, can be fiber coupler or sonet multiplexer.

Said optical fiber collimator 4 be meant emergent light be directional light fiber optic component.

Said lens 5 are the plus lens that are used for collecting from the reflectance target laser light reflected, are weight reduction and volume, can be Fresnel lenses.

Said gas to be measured 6 is measuring objects of the present invention, and it can be to have any gaseous material that absorptiometry light source 1 sends the luminous energy characteristic, as methane, carbon dioxide, carbon monoxide etc.

Said reflectance target 7 can be the material that trees, ground, wall, pipeline etc. have certain reflection and scattering properties, and electricity can be the catoptron that specially is provided with.

The function of said photodetector 8 is that light signal is converted to electric signal, and the response wave length of photodetector should be at the wave band of the light signal of measurement light source 1 emission, and they can be photodiodes, or photoelectric cell etc.

The function of said detecting module 9 is that signal is amplified and filtering.

The function of said laser instrument temperature control module 10 is that measurement light source 1 is carried out temperature control, with the centre wavelength of stably measured light source.

The function of said laser instrument direct drive module 11 is direct current biasings that high stability is provided for measurement light source 1.

The function of said laser instrument AC driving module 12 is to provide high_frequency sine wave modulation and low frequency sawtooch sweep electric current for measurement light source 1.

Said embedded control system 13 is responsible for the parameter setting of control laser instrument temperature control module 10, laser instrument direct drive module 11, laser instrument AC driving module 12, signal from detecting module 9 is carried out A/D conversion and synchronous acquisition, and logarithm second harmonic method according to the present invention calculates the concentration information of gas to be measured.Generally can adopt the single-chip microcomputer of low-power consumption to realize, for example the ARM flush bonding processor.

The function of said display unit 14 is to show measurement result, is generally the LCD or light emitting diode (LED) display of low-power consumption.

From as can be known above-mentioned, the present invention has following characteristics and advantage:

1) the present invention adopts the direct Modulated Semiconductor Laser device of injection current as transmitting illuminant, transmits and receives optical system and adopts the transmitting-receiving coaxial configuration, compares with other first technology, have simple in structure, volume is small and exquisite, is convenient to portable use;

2) adopt logarithm second harmonic Detection Techniques that gas absorption signal is surveyed and handled, measure with light source power fluctuation and reflectance target characteristic unglazed, not only made things convenient for processing, also weakened the error that factors such as light source intensity fluctuation, reflectance target reflection coefficient, the change of photodetection circuit gain coefficient are introduced greatly, measured signal to noise ratio (S/N ratio) and measure stable high.

Description of drawings

The system architecture of Fig. 1 laser gas remote measurement device of the present invention.

Fig. 2 is an oscillogram of the present invention

Fig. 3 is apparatus of the present invention system construction drawings

Fig. 4 is the absorption spectra of methane gas at near-infrared band

Fig. 5 is the absorption spectra of acetylene gas at near-infrared band

Fig. 6 is the absorption spectra of ammonia gas at near-infrared band

Fig. 7 is the absorption spectra of CO gas at near-infrared band

Fig. 8 is the absorption spectra of hydrogen sulfide gas at near-infrared band

The optical maser wavelength of semiconductor laser is in near-infrared band among the figure, therefore as long as have the gas of absorption peak to measure with the technology of the present invention at near-infrared band.Horizontal ordinate is a wavelength among the figure, and unit micron, ordinate are absorption coefficient.

Embodiment

Structure as shown in Figure 1.Wherein, measurement light source 1 employing wavelength is 1.65 microns distributed feed-back (DFB) semiconductor laser, output power 5 milliwatts, the gas absorption peak of the corresponding methane of this wave band.Provide ac modulation by laser instrument AC driving module 12, modulation system is to adopt Sine Modulated to add the method for triangular modulation, and sine wave freuqency is 4kHz, and the triangle wave frequency is 3Hz.Laser instrument temperature control module 10 is controlled in laser instrument centre wavelength near the methane adsorption line, and accuracy of temperature control is about 0.1 degree Celsius.

Target indication light source 2 adopts the red-light source of 650 nanometers.Optical fiber wave multiplexer 3 adopts the fused biconical taper optical fibre wavelength division multiplexer.Optical fiber collimator 4 is a single mode fiber collimator.Lens 5 employing focal lengths are 5 centimetres Fresnel lens.Photodetector adopts the InGaAs photodetector.Display unit 14 is a LCDs.

Embedded control system 13 adopts arm processor.As the S3C44B0 embedded type CPU module of ARM7, comprise the dynamic read-write memory SDRAM0122 and the Serial E of setting up ²PROM, power supply, S3C44B0 embedded type CPU module connects the display screen chip and connects display again; Communication interface adopts RS-485 or RS-232 etc.

During measurement, embedded control system 13 systems at first will collect original signal and carry out Fast Fourier Transform (FFT), obtain second harmonic component, take the logarithm then.Triangular wave or sawtooth wave owing to superposeed on injection current, wavelength-modulated center move back and forth on every side at the gas absorption peak, and in the cycle, the wavelength-modulated center overlaps secondary with the gas absorption peak at a triangular wave.When both overlapped, the amplitude of second harmonic should have maximal value.Obtain the second harmonic amplitude in the maximal value of half triangular wave in the cycle, calculate the path integral concentration of gas according to formula (7).

Present embodiment is that example illustrates with the methane gas detection just, is not limited to methane and measures.The wavelength that only need change measurement light source 1 is aimed at the absorption peak of gas with various, just can measure corresponding gas.For example, the ethene absorption peak is 1532.8nm, and ammonia is 1544nm, and carbon monoxide is 1567nm, and carbon dioxide is 1572nm, etc.

In addition, be pointed out that the present invention just is not used for the measurement of pure gas, can also be used for the measurement of multiple composition gas.When measurement light source 1 is a tunable semiconductor laser, in its tuning range, exist the gas of absorption peak just can measure.

Claims (7)

1, the method for laser gas remote measurement, it is characterized in that adopting to the direct Modulated Semiconductor Laser device of electric current that injects measurement light source as emission, transmit and receive optical system and adopt the transmitting-receiving coaxial configuration, adopt logarithm second harmonic detection method that gas absorption signal is surveyed and handled; Semiconductor laser (1) sends modulated continuous narrow-linewidth laser, through optical fiber wave multiplexer (3), from placing optical fiber collimator (4) outgoing of lens (5) axis part, emitting laser target (7) reflection that is reflected after by gas to be measured (6), reflected light converges at photodetector (8) through lens (5) and is converted to electric signal, through the amplification and the filtering of detecting module (9), obtain gas concentration to be measured by microprocessor control system (13) collection and after adopting logarithm second harmonic algorithm process; The current-modulation waveform that injects semiconductor laser is: modulation constitutes to high frequency sine sweep ripple by low frequency triangular wave or sawtooth wave, sine wave freuqency 1KHz-1000KHz, triangular wave or sawtooth wave frequency are 1-100Hz, in a triangular wave or sawtooth period, the wavelength-modulated center overlaps once with the gas absorption peak, obtain this amplitude of logarithm second harmonic constantly, calculate gas concentration; The computing formula of the path integral concentration of gas is:

$\mathrm{cl}=\frac{a_2^{*}-I_2^{*}}{{\mathrm{\&alpha;}}_0{S}_2}$ Cl is the path integral concentration of gas, S ₂Be secondary Fourier coefficient, α ₀Peak absorbance coefficient for gas; a ₀ ^*, a ₁ ^*, a ₂ ^*Be laser modulation parameter a ₁, a ₂Function, I ₂ ^*It is the amplitude of second harmonic.

2, the method for laser gas remote measurement according to claim 1 is characterized in that being provided with in addition target indication light source (2), and described light source is the semiconductor laser of visible light wave range; Said optical fiber wave multiplexer (3) is to be used for realizing that semiconductor laser (1) and target indication light source (2) close the fiber optic component on road, and the optical fiber wave multiplexer is fiber coupler or sonet multiplexer.

3, the method for laser gas remote measurement according to claim 1, it is characterized in that described semiconductor laser (1) semiconductor laser, its live width is much smaller than the absorption peak width of gas to be measured (6), and its wavelength scanning range should be greater than the absorption peak width of gas to be measured (6); Described semiconductor laser is distributed feed-back (DFB) semiconductor laser or distributed Blatt reflective (DBR) semiconductor laser of optical fiber coupling output.

4, the method for laser gas remote measurement according to claim 1, it is characterized in that said optical fiber collimator (4) be meant emergent light be directional light fiber optic component.

5, the method for laser gas remote measurement according to claim 1 is characterized in that said lens (5) are the plus lens that is used for collecting from the reflectance target laser light reflected, and plus lens is a Fresnel lens.

6, the method for laser gas remote measurement according to claim 1, the function that it is characterized in that said photodetector (8) is that light signal is converted to electric signal, the response wave length of photodetector should be at the wave band of the light signal of measurement light source (1) emission, and they are photodiode or photoelectric cell.

7, the device of laser gas remote measurement is characterized in that comprising and measures semiconductor laser (1) that target is indicated light source (2), optical fiber wave multiplexer (3), optical fiber collimator (4), lens (5), gas to be measured (6), reflectance target (7), photodetector (8), detecting module (9), laser instrument temperature control module (10), laser instrument direct drive module (11), laser instrument AC driving module (12), microprocessor control system (13), display unit (14) constitutes; Semiconductor laser (1) sends modulated continuous narrow-linewidth laser, through optical fiber wave multiplexer (3), from placing optical fiber collimator (4) outgoing of lens (5) axis part, emitting laser target (7) reflection that is reflected after by gas to be measured (6), reflected light converges at photodetector (8) through lens (5) and is converted to electric signal, through the amplification and the filtering of detecting module (9), obtain gas concentration to be measured by microprocessor control system (13) collection and after adopting logarithm second harmonic algorithm process; Photodetector (8) connects to amplify and is connected microprocessor control system (13) with the detecting module (9) of filtering and through amplifier, microprocessor control system (13) comprises embedded Control and signal processing circuit, and output interface connects display circuit, communication interface circuit, keyboard, warning circuit; Its output terminal of the output of embedded control system connects laser control circuit; Laser control circuit comprises laser high frequency modulated circuit, laser temperature control circuit, laser low frequency sweep circuit, laser instrument dc drive circuit; The output of laser control circuit drives measures semiconductor laser; Lens (5) employing focal length is 5 centimetres a Fresnel lens, and photodetector adopts the InGaAs photodetector; Semiconductor laser (1) adopts distributed feed-back (DFB) semiconductor laser or distributed Blatt reflective (DBR) semiconductor laser of optical fiber coupling output, and target indication light source (2) adopts the red-light source of rice in 650; Optical fiber wave multiplexer (3) adopts the fused biconical taper optical fibre wavelength division multiplexer; Optical fiber collimator (4) is a single mode fiber collimator.

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