CN102955043A - Laser self-mixing multi-dimensional measuring device and method based on triangular wave current modulation - Google Patents

Abstract

The invention provides a laser self-mixing multi-dimensional measuring device and method based on triangular wave current modulation. The laser self-mixing multi-dimensional measuring device comprises a laser device, optical fibers, an optical fiber beam splitter, an optical fiber focuser, a photoelectric detector and a signal processing circuit. A laser self-mixing sensing system comprises a plurality of paths of different optical path structures with the triangular wave current modulation, and a band-pass filtering signal processing circuit; and the multi-dimensional speed size and direction can be accurately measured on line by virtue of the single laser device and the single detector. The laser self-mixing multi-dimensional measuring device provided by the invention has the advantages of simple structure, easiness in adjustment, low cost and high space resolution, effectively expands a speed sensing method based on a laser self-mixing effect, and particularly provides a reliable solution scheme for non-contact online monitoring on the three-dimensional motion speed of a long-distance object.

Description

Laser based on the triangular current modulation mixes multidimensional velocity measuring device and method certainly

Technical field

The present invention relates to a kind of laser based on the triangular current modulation and certainly mix multidimensional velocity measuring device and method, be specially adapted to the quick non-cpntact measurement of water volume flow rate, solid particulate matter movement velocity.

Background technology

For the multi-dimensional movement velocity survey of complexity, be proved to be at present comparatively effectively laser Dppler veloicty measurement technology.That the laser Dppler veloicty measurement technology has is untouchable, the response fast, the spatial resolution advantages of higher, is widely used in the fluid-velocity survey, the particularly measurement of three-dimensional flow speed of the numerous areas such as fluid mechanics, chemical industry, water conservancy, biological medicine, environment.

In laser-Doppler multidimensional speed measurement techniques, mainly adopt the system architecture scheme of reference beam type.Coherence stack by incident laser and reference laser draws respectively the Doppler shift on the different directions, i.e. multidimensional speed component on the corresponding different directions.But owing to adopt a plurality of light-splitting devices and detector, and need optical path difference is remained within the laser coherence length, exist system complex, light path to be difficult to the problem such as adjustment and be difficult to be developed fully and use.Subsequently, progressively developed the schemes such as employing multiline laser and acousto-optic modulator, system architecture with all improve to some extent aspect signal separates, also produced new problem simultaneously: multiline laser is expensive, the life-span is short, is unfavorable for applying; The frequency displacement amplitude of acousto-optic frequency displacement device has certain limitation, and the light-splitting device of introducing has improved the complexity of system.

The laser that is developed by laser doppler technique (is that the emergent light of laser instrument is after exterior object scattering or reflection from hybrid technology, part light feeds back to laser cavity and forms new resonance, obtain the measuring technique of the information such as exterior object motion, pattern by the variation of measuring laser power, frequency), have system architecture simple, be easy to regulate and the advantage such as Stimulated Light device power swing impact not, can be widely used in the high-acruracy survey of the physical quantitys such as speed, displacement, distance.But aspect the multidimensional velocity survey, because the laser self-mixing measuring system generally all adopts built-in detector, the multidimensional speed component superposes mutually, has equally the problems such as the speed component signal can't extract, direction None-identified.

In theory, overlap laser more and carry out laser from mixing sensing in different directions or position simultaneously from commingled system, can realize multidimensional or multi-point sensing.1998, professor T.Bosch of France took the lead in adopting sweeping scheme to realize the Measurement accuracy of tri-dimensional facial type, adopted again subsequently two laser instruments to realize the solid surface two-dimension speed measurement of degree of precision.2008, the S.Ottonelli of Bari,Italy university etc. adopt three independently Distributed Feedback Laser as light source, successfully researched and developed can measure simultaneously three degree of freedom laser from mixing sensor-based system.2010, the Yah Leng Lim of Australia then adopted the vertical cavity surface emitting laser arrays of 1*12 to realize the real-time measurement of multiple spot flow velocity.But except the complicacy increase and cost rising of system, the subject matter that faces also is: 1. many cover single channel laser can't be consistent with the modulation of source characteristic from the signal drift of commingled system.The measurement of laser self-mixing effect all is based on the detection to the Laser output light intensity, and light intensity environment, pumping level are responsive to external world, different signal drifts is greatly affected the measurement result of many cover systems, and unavoidable measuring error will hinder real-time change process and the higher order dependencies of obtaining exactly multidimensional speed or multi-point displacement; Be difficult to realize the synchronous detection of signal when 2. multisystem is measured simultaneously, namely the Measurement accuracy of the physical quantity such as same point three-dimensional velocity is difficult to realize.

Summary of the invention

Technology of the present invention is dealt with problems: overcome the deficiencies in the prior art, provide the laser based on the triangular current modulation certainly to mix multidimensional velocity measuring device and method, kept laser from commingled system simple in structure, the advantage such as be easy to regulate in, by adopting triangular current modulation, the different light path structures of multichannel and bandpass filtered signal disposal route etc., use single laser instrument and detector, need not acousto-optic modulator, the noncontact high resolving power of realize target thing multi-dimensional movement speed is measured.

Technical solution of the present invention: the laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly, comprise photodetector 1, laser instrument 2, laser modulation module 3, the first optical fiber 4, fiber optic splitter 5, the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8, the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11, moving object 12 to be measured, differential amplifier circuit 13, triple channel bank of filters 14, triple channel counter group 15, computing machine 16,3 pairs of laser instruments of described laser modulation module 2 carry out the triangular current modulation, to realize the accurate differentiation of multidimensional velocity reversal, laser instrument 2 emitting lasers are coupled in the first optical fiber 4 and are transferred to fiber optic splitter 5, fiber optic splitter 5 is divided into three beams with laser, laser through the second optical fiber 6 and the first optical fiber focuser 9 incides in the moving object 12 to be measured at a certain angle from the first dimension, laser through the 3rd optical fiber 7 and the second optical fiber focuser 10 incides in the moving object 12 to be measured from the second dimension, laser through the 4th optical fiber 8 and the second optical fiber focuser 11 incides in the moving object 12 to be measured from third dimension degree, the second optical fiber 6 wherein, the different accurate differentiation that under the triangular current modulation, can realize the multidimensional rate signal of the length of the 3rd optical fiber 7 and the 4th optical fiber 8, the multichannel incident laser is after moving object 12 scatterings to be measured, part scattered light feeds back to laser instrument 2 by light path separately, produces the laser self-mixing effect.Laser behind the generation laser self-mixing effect is received by photodetector 1, and through differential amplifier circuit 13 amplifications, pass through subsequently triple channel bank of filters 14 and 15 filtering of triple channel counter group and counting, unit interval inside counting number is corresponding frequency values, respectively with the frequency ν of each channel signal rising edge and negative edge _Rise(ν is Greek alphabet, and the symbol of modern physics medium frequency is different with V.) and ν _DescendSend into and obtain each dimension velocity magnitude and direction after computing machine 16 is processed, the computing formula of speed V is:

V=| ν _Rise-ν _Descend| λ

Wherein, λ is laser instrument Output of laser wavelength, the light intensity change component rising edge frequency of each optical fiber focuser place light path during greater than the negative edge frequency movement velocity direction of moving object 12 to be measured identical with the laser emitting direction, movement velocity direction and the laser emitting opposite direction of the moving object 12 to be measured during less than the negative edge frequency of the light intensity change component rising edge frequency of each optical fiber focuser place light path.

Described photodetector 1 is the internal or external detector of laser instrument 2.Adopt built-in detector can simplify system and improve exploring laser light from the sensitivity of mixed signal.

Described laser instrument 2 is selected the high longitudinal mode semiconductor laser of the electric current wavelength index of modulation, the electric current wavelength index of modulation of semiconductor laser should surpass 0.1nm/mA, be easy to carry out the triangle wave circuit modulation, the discrete phenomenon of waveform that single longitudinal mode operation then can avoid the different mode stack to cause, thus the measuring precision improved.

Described laser modulation module 3 is with the work of triangular current modulation system, to realize the accurate differentiation of multidimensional velocity reversal.

Described fiber optic splitter 5 is selected the beam splitter with corresponding outgoing fiber count according to actual needs, then selects 1 * 3 single-mode fiber polarization-maintaining beam splitter for three-dimensional flow, and each is restrainted output intensity and can divide equally in proportion.

The length L of described the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8 ₂, L ₃, L ₄Different, concrete determine according to the velocity survey scope on the corresponding dimension separately.The first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber the focuser 11 separately corresponding maximal rate of measuring on the dimension are respectively V _2max, V _3max, V _4maxThe time,

Wherein, L ₂, L ₃, L ₄Be respectively the length of the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8, c, α, λ are respectively triangular wave frequency modulation (PFM) coefficient (unit is Hz/s), the optical maser wavelength of light velocity constant, laser instrument 2, V _2max, V _3max, V _4maxBe respectively the separately corresponding maximum speed value of measuring on the dimension of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11.

Described optical fiber focuser 9,10,11 insertion loss be general≤0.3dB, numerical aperture 〉=0.1, and to improve the coupling efficiency of scattered light.For the measurement of multidimensional plane speed, also can change the optical fiber focuser into optical fiber collimator.

Described triple channel bank of filters 14 is bandpass filter, the logical scope of its band respectively by the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 separately corresponding Doppler shift scope corresponding to velocity range of measuring on the dimension determine,

Wherein L and V _MaxBe respectively the separately corresponding corresponding fiber lengths of dimension and the maximum measured velocity value measured of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11.

Laser based on the triangular current modulation mixes the multidimensional speed measurement method certainly, may further comprise the steps:

The first step, 3 pairs of laser instruments of laser modulation module 2 are carried out the triangular current modulation, and the laser after the modulation is transferred to fiber optic splitter 5 through the first optical fiber 4;

Second step, fiber optic splitter 5 are divided into multi beam with laser, are transferred to corresponding the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 through the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8 respectively;

In the 3rd step, focus on the object under test 12 with different directions respectively through the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 emitting lasers;

In the 4th step, incide laser on the object under test 12 and turn back in the laser instrument 2 by former road through the light splitting of scattering rear portion and produce self-mixing effect;

In the 5th step, the light signal that photodetector 1 will produce self-mixing effect is converted into electric signal;

The 6th step, electric signal amplifies through differential amplifier circuit 13, send into subsequently and obtain different frequency values after triple channel bank of filters 14 and triple channel counter group 15 processed, wherein with the filter frequencies v of triple channel bank of filters 14 inner first, second, third passages ₂, v ₃, v ₄Scope be chosen to be respectively

$\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_3-\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{3\max }<{\mathrm{<figure-callout\; id="3"\; label="v"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">v</figure-callout>}}_3<\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">L</figure-callout>}}_3+\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{3\max },\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_4-\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{4\max }<{\mathrm{<figure-callout\; id="4"\; label="v"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">v</figure-callout>}}_4<\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4+\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{4\max },$ Wherein, L ₂, L ₃, L ₄Be respectively the length of the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8, c, α, λ are respectively triangular wave frequency modulation (PFM) coefficient (unit is Hz/s), the optical maser wavelength of light velocity constant, laser instrument 2, V _2max, V _3max, V _4maxBe respectively the separately corresponding maximum speed value of measuring on the dimension of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11;

The 7th step, each channel frequence v that triple channel counter group 15 is obtained ₂, v ₃, v ₄Rising edge and the frequency ν of negative edge _RiseAnd ν _DescendSend into and obtain separately corresponding velocity magnitude and the direction of measuring on the dimension of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 after computing machine 16 is processed, the computing formula of speed V is:

V=| ν _Rise-ν _Descend| λ

As the rising edge frequency ν of each dimension laser from mixed signal _RiseGreater than negative edge frequency ν _DescendThe time, the movement velocity direction determining is identical with the shoot laser direction of each dimension optical fiber focuser, as the rising edge frequency ν of each dimension laser from mixed signal _RiseLess than negative edge frequency ν _DescendThe time, the movement velocity direction determining is the shoot laser opposite direction with each dimension optical fiber focuser.

Measuring principle of the present invention is as follows:

At first certainly mix the three mirror cavity theory based on laser, the feedback face of extraneous moving object consists of laser external cavity and also forms new amplitude and phase condition.Exist the ambient light feedback lower, r ₁And r ₂Represent respectively laser instrument both ends of the surface M ₁And M ₂Amplitude reflectance, r ₃Represent the amplitude reflectance that exocoel namely feeds back body surface.

Suppose that initial light field is E ₀(t), light beam is divided into two bundles, and a branch of once round in the inner chamber experience, another bundle sees through M ₂Fed back to inner chamber by the external cavity surface scattering afterwards.At M ₁Light field after place's stack is:

$E\left(t\right)=r_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_2\exp \{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}\frac{\mathrm{nL}}{c}+(g-\mathrm{\&gamma;})L\}{E}_0\left(t\right)$

$+r_1(1-R_2){\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_3\exp \{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}\frac{\mathrm{nL}+L_3}{c}+(g-\mathrm{\&gamma;})L\}{E}_0\left(t\right)$

N is the complex index of refraction of laser medium in the formula, L and L ₃Represent respectively built in laser cavity and external cavity length, c is the light velocity in the vacuum, R ₂=| r ₂| ², g and γ represent respectively medium gain and light loss under the interior unit length of laser cavity.

Under multiple feedback, stack light field and M ₂Equivalent reflectivity also change thereupon, light field is expressed as:

$\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{E}_i\left(t\right)=r_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_2\exp \{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}\frac{\mathrm{nL}}{c}+(g-\mathrm{\&gamma;})L\}{E}_{i0}\left(t\right)$

$+r_1(1-R_2){\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_3\exp \{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}\frac{\mathrm{nL}+L_3}{c}+(g-\mathrm{\&gamma;})L\}{E}_{i0}\left(t\right)+...$

$+r_1(1-R_2)r_{i+2}\exp \{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}\frac{\mathrm{nL}+L_{i+2}}{c}+(g-\mathrm{\&gamma;})L\}{E}_{i0}\left(t\right)$

When system stability, the light field after the stack should be identical with initial light field.Simultaneously, light in the chamber, move one the week later phase differential be the integral multiple of 2 π.Can be drawn by Lang-Kobayashi rate equation and laser instrument steady state conditions the Changing Pattern of the laser power of the equivalent amplitude reflection coefficient of the right chamber of laser instrument face under the multiple feedback and laser self-mixing interference.

For three-dimensional flow, the luminous power behind the generation laser self-mixing effect can be expressed as:

$I\left(t\right)\&Proportional;a_x\cos \left[2\mathrm{\&pi;}(\&PlusMinus;\frac{{2L}_x\mathrm{\&alpha;}}{c}+{\mathrm{\&nu;}}_{\mathrm{Dx}})t\right]+a_y\cos \left[2\mathrm{\&pi;}(\&PlusMinus;\frac{{2L}_y\mathrm{\&alpha;}}{c}+{\mathrm{\&nu;}}_{\mathrm{Dy}})t\right]+a_z\cos \left[2\mathrm{\&pi;}(\&PlusMinus;\frac{{2L}_z\mathrm{\&alpha;}}{c}+{\mathrm{\&nu;}}_{\mathrm{Dz}})t\right]$ Wherein, a _x, a _y, a _zBe respectively on three directions from mixed signal amplitude, L _x, L _y, L _yBe respectively three light paths (different fiber length causes) on the direction, ν _Dx, ν _Dy, ν _DzBe respectively three Doppler shift amounts on the direction, α is triangular wave frequency modulation (PFM) coefficient (unit is Hz/s), and c is light velocity constant.

By signal is carried out Filtering Analysis, can obtain rising edge and negative edge frequency shift amount on the different directions, rising edge and negative edge frequency-splitting are 2 times of Doppler shift amount on the direction separately.Then by formula V=ν _Dλ/2 can draw the speed component on the different directions.

Meanwhile, each component rising edge frequency during greater than the negative edge frequency motion velocity reversal identical with the laser emitting direction, vice versa.

The present invention's advantage compared with prior art is:

(1) the present invention adopts single laser instrument and detector, utilizes the laser self-mixing effect, realizes simultaneously the accurate non-cpntact measurement of multi-dimensional movement speed, and simultaneity factor is simple in structure, compact, be easy to realize;

(2) the present invention adopts fiber optic splitter to carry out beam splitting, and the fiber lengths after the beam splitting is different, thereby realizes accurate differentiation and the velocity information extraction of multiple signals;

(3) the present invention adopts the triangular current modulation scheme, realizes the accurate differentiation of velocity reversal by the frequency difference of rising edge and negative edge;

(4) the present invention adopts longitudinal mode semiconductor laser and large-numerical aperture optical fiber focuser, thereby effectively reduces the video stretching phenomenon in the laser self-mixing effect, improves the measuring precision;

(5) the used Transmission Fibers length of the present invention can be much larger than laser coherence length, thereby realize the sensing of remote multidimensional speed, and avoid outside electromagnetic interference.

Description of drawings

Fig. 1 is that the laser based on the triangular current modulation mixes multidimensional velocity measuring device structural representation certainly among the present invention.

Embodiment

As shown in Figure 1, measurement mechanism of the present invention comprises: photodetector 1, laser instrument 2, laser modulation module 3, the first optical fiber 4, fiber optic splitter 5, the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8, the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11, moving object 12 to be measured, differential amplifier circuit 13, triple channel bank of filters 14, triple channel counter group 15, computing machine 16,3 pairs of laser instruments of described laser modulation module 2 carry out the triangular current modulation, light path is divided into three beams through fiber optic splitter and incides object under test 12 surfaces, each road part scattered light feeds back to laser instrument by former road and produces the laser self-mixing effect, photodetector 1 will be converted into electric signal from the mixed light signal, by differential amplifier circuit 13, obtain the Doppler frequency value of different dimensions after triple channel bank of filters 14 and triple channel counter group 15 are processed, and obtain multidimensional velocity magnitude and direction after machine 16 is processed as calculated.

Wherein, laser instrument 2 is selected the high longitudinal mode semiconductor laser of the electric current wavelength index of modulation, laser modulation module 3 is with the work of triangular current modulation system, and fiber optic splitter 5 is 1 * 3 single-mode fiber polarization-maintaining beam splitter, the length L of the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8 ₂, L ₃, L ₄Different, concrete determine according to the velocity survey scope on the corresponding dimension separately.Maximal rate on each dimension is respectively V _2max, V _3max, V _4maxThe time,

Wherein, L ₂, L ₃, L ₄Be respectively the length of the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8, c, α, λ are respectively triangular wave frequency modulation (PFM) coefficient (unit is Hz/s), the optical maser wavelength of light velocity constant, laser instrument 2, V _2max, V _3max, V _4maxBe respectively the separately corresponding maximum speed value of measuring on the dimension of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11.

Measuring method performing step of the present invention is as follows:

The first step, 3 pairs of laser instruments of laser modulation module 2 are carried out the triangular current modulation, and the laser after the modulation is transferred to fiber optic splitter 5 through the first optical fiber 4;

Second step, fiber optic splitter 5 are divided into multi beam with laser, are transferred to corresponding the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 through the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8 respectively;

In the 3rd step, focus on the object under test 12 with different directions respectively through the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 emitting lasers;

In the 4th step, incide laser on the object under test 12 and turn back in the laser instrument 2 by former road through the light splitting of scattering rear portion and produce self-mixing effect;

In the 5th step, the light signal that photodetector 1 will produce self-mixing effect is converted into electric signal;

The 6th step, electric signal amplifies through differential amplifier circuit 13, send into subsequently and obtain different frequency values after triple channel bank of filters 14 and triple channel counter group 15 processed, wherein with the filter frequencies v of triple channel bank of filters 14 inner first, second, third passages ₂, v ₃, v ₄Scope be chosen to be respectively

$\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_3-\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{3\max }<{\mathrm{<figure-callout\; id="3"\; label="v"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">v</figure-callout>}}_3<\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">L</figure-callout>}}_3+\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{3\max },\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_4-\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{4\max }<{\mathrm{<figure-callout\; id="4"\; label="v"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">v</figure-callout>}}_4<\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">L</figure-callout>}}_4+\frac{2}{\mathrm{\&lambda;}}\&CenterDot;{\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="HDA00002306732200011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{4\max },$ Wherein, L ₂, L ₃, L ₄Be respectively the length of the second optical fiber 6, the 3rd optical fiber 7, the 4th optical fiber 8, c, α, λ are respectively triangular wave frequency modulation (PFM) coefficient (unit is Hz/s), the optical maser wavelength of light velocity constant, laser instrument 2, V _2max, V _3max, V _4maxBe respectively the separately corresponding maximum speed value of measuring on the dimension of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11;

The 7th step, each channel frequence v that triple channel counter group 15 is obtained ₂, v ₃, v ₄Rising edge and the frequency ν of negative edge _RiseAnd ν _DescendSend into and obtain separately corresponding velocity magnitude and the direction of measuring on the dimension of the first optical fiber focuser 9, the second optical fiber focuser 10, the 3rd optical fiber focuser 11 after computing machine 16 is processed, the computing formula of speed V is:

V=| ν _Rise-ν _Descend| λ

As the rising edge frequency ν of each dimension laser from mixed signal _RiseGreater than negative edge frequency ν _DescendThe time, the movement velocity direction determining is identical with the shoot laser direction of each dimension optical fiber focuser, as the rising edge frequency ν of each dimension laser from mixed signal _RiseLess than negative edge frequency ν _DescendThe time, the movement velocity direction determining is the shoot laser opposite direction with each dimension optical fiber focuser.

In a word, adopt single laser instrument and detector, the different light path structures of multichannel, bandpass filtered signal treatment circuit, and carry out the accurate on-line measurement that triangular current modulates to realize multidimensional velocity magnitude and direction.The present invention is simple in structure, be easy to regulate, cost is low, spatial resolution is high, has effectively expanded the velocity pick-up method based on the laser self-mixing effect, provides reliable solution in particular for the noncontact on-line monitoring of remote object dimensional movement velocity.

The content that is not described in detail in the instructions of the present invention belongs to the known prior art of this area professional and technical personnel.

The above only is preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (8)

1. the laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly, it is characterized in that: comprise photodetector (1), laser instrument (2), laser modulation module (3), the first optical fiber (4), fiber optic splitter (5), the second optical fiber (6), the 3rd optical fiber (7), the 4th optical fiber (8), the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11), moving object to be measured (12), differential amplifier circuit (13), triple channel bank of filters (14), triple channel counter group (15), computing machine (16), described laser modulation module (3) is carried out the triangular current modulation to laser instrument (2), to realize the accurate differentiation of multidimensional velocity reversal, laser instrument (2) emitting laser is coupled to the first optical fiber (4) and is transferred to fiber optic splitter (5), fiber optic splitter (5) is divided into three beams with laser, laser through the second optical fiber (6) and the first optical fiber focuser (9) incides in the moving object to be measured (12) at a certain angle, laser through the 3rd optical fiber (7) and the second optical fiber focuser (10) incides in the moving object to be measured (12) from the second dimension, laser through the 4th optical fiber (8) and the second optical fiber focuser (11) incides in the moving object to be measured (12) from third dimension degree, the second optical fiber (6) wherein, the different accurate differentiation that under the triangular current modulation, namely realizes the multidimensional rate signal of the length of the 3rd optical fiber (7) and the 4th optical fiber (8), the multichannel incident laser is after moving object to be measured (12) scattering, part scattered light feeds back to laser instrument (2) by light path separately, produces the laser self-mixing effect; Laser behind the generation laser self-mixing effect is received by photodetector (1), and through differential amplifier circuit (13) amplification, pass through subsequently triple channel bank of filters (14) and (15) filtering of triple channel counter group and counting, unit interval inside counting number is corresponding frequency values, respectively with the frequency ν of each channel signal rising edge and negative edge _RiseAnd ν _DescendSend into and obtain each dimension velocity magnitude and direction after computing machine (16) is processed, the computing formula of speed V is:

V=| ν _Rise-ν _Descend| λ

Wherein, λ is laser instrument Output of laser wavelength, the movement velocity direction of the light intensity change component rising edge frequency of each optical fiber focuser place light path moving object to be measured (12) during greater than the negative edge frequency is identical with the laser emitting direction, movement velocity direction and the laser emitting opposite direction of the moving object to be measured (12) during less than the negative edge frequency of the light intensity change component rising edge frequency of each optical fiber focuser place light path.

2. 1 described laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly as requested, it is characterized in that: described photodetector (1) is the internal or external detector of laser instrument (2), adopts built-in detector can simplify system and improve exploring laser light from the sensitivity of mixed signal.

3. 1 described laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly as requested, it is characterized in that: described laser instrument (2) is selected longitudinal mode semiconductor laser, the electric current wavelength index of modulation of semiconductor laser surpasses 0.1nm/mA, be easy to carry out the triangle wave circuit modulation, the discrete phenomenon of waveform that single longitudinal mode operation can avoid the different mode stack to cause, thus the measuring precision improved.

4. 1 described laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly as requested, it is characterized in that: described fiber optic splitter (5) is selected the beam splitter with corresponding outgoing fiber count according to the needs of actual measurement, then select 1 * 3 single-mode fiber polarization-maintaining beam splitter for three-dimensional flow, each is restrainted output intensity and divides equally in proportion.

5. 1 described laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly as requested, it is characterized in that: the length L of described the second optical fiber (6), the 3rd optical fiber (7), the 4th optical fiber (8) ₂, L ₃, L ₄Different, concrete according to the corresponding velocity range of measuring on the dimension is definite separately, the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11) the separately corresponding maximal rate of measuring on the dimension are respectively V _2max, V _3max, V _4maxThe time,

Wherein, L ₂, L ₃, L ₄Be respectively the length of the second optical fiber (6), the 3rd optical fiber (7), the 4th optical fiber (8), c, α, λ are respectively light velocity constant, the triangular wave frequency modulation (PFM) coefficient of laser instrument (2), optical maser wavelength, V _2max, V _3max, V _4maxBe respectively the separately corresponding maximum speed value of measuring on the dimension of the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11).

6. 1 described laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly as requested, it is characterized in that: insertion loss≤0.3dB, numerical aperture 〉=0.1 of described the first optical fiber focuser (9), the second optical fiber focuser (10) and the 3rd optical fiber focuser (11), can improve the coupling efficiency of scattered light; For the measurement of multidimensional plane speed, also can change the optical fiber focuser into optical fiber collimator.

7. 1 described laser based on the triangular current modulation mixes the multidimensional velocity measuring device certainly as requested, it is characterized in that: described triple channel bank of filters (14) is bandpass filter, the logical scope of its band respectively by the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11) separately corresponding Doppler shift scope corresponding to velocity range of measuring on the dimension determine Wherein L and V _MaxBe respectively the separately corresponding corresponding fiber lengths of dimension and the maximum measured velocity value measured of the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11).

8. adopt the laser based on the triangular current modulation claimed in claim 1 certainly to mix the multidimensional speed measurement method, it is characterized in that may further comprise the steps:

The first step, laser modulation module (3) is carried out the triangular current modulation to laser instrument (2), and the laser after the modulation is transferred to fiber optic splitter (5) through the first optical fiber (4);

Second step, fiber optic splitter (5) is divided into multi beam with laser, be transferred to corresponding the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11) through the second optical fiber (6), the 3rd optical fiber (7), the 4th optical fiber (8) respectively, wherein with the length L of the second optical fiber (6), the 3rd optical fiber (7), the 4th optical fiber (8) ₂, L ₃, L ₄Be chosen to be

Wherein, L ₂, L ₃, L ₄Be respectively the length of the second optical fiber (6), the 3rd optical fiber (7), the 4th optical fiber (8), c, α, λ are respectively light velocity constant, the triangular wave frequency modulation (PFM) coefficient of laser instrument (2), optical maser wavelength, V _2max, V _3max, V _4maxBe respectively the separately corresponding maximum speed value of measuring on the dimension of the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11);

In the 3rd step, focus on respectively on the object under test (12) with different directions through the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11) emitting laser;

In the 4th step, the laser that incides on the object under test (12) turns back to generation laser self-mixing effect in the laser instrument (2) through the light splitting of scattering rear portion by former road;

In the 5th step, the light signal that photodetector (1) will produce self-mixing effect is converted into electric signal;

The 6th step, electric signal amplifies through differential amplifier circuit (13), send into subsequently and obtain different frequency values after triple channel bank of filters (14) and triple channel counter group (15) are processed, wherein with the filter frequencies v of inner first second, third passage of triple channel bank of filters (14) ₂, v ₃, v ₄Scope be chosen to be respectively

$\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_3-\frac{2}{\mathrm{\&lambda;}}\&CenterDot;V_{3\max }<v_3<\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_3+\frac{2}{\mathrm{\&lambda;}}\&CenterDot;V_{3\max },\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_4-\frac{2}{\mathrm{\&lambda;}}\&CenterDot;V_{4\max }<v_4<\frac{2\mathrm{\&alpha;}}{c}\&CenterDot;L_4+\frac{2}{\mathrm{\&lambda;}}\&CenterDot;V_{4\max };$

The 7th step, each channel frequence v that triple channel counter group (15) is obtained ₂, v ₃, v ₄Rising edge and the frequency ν of negative edge _RiseAnd ν _DescendSend into and obtain separately corresponding velocity magnitude and the direction of measuring on the dimension of the first optical fiber focuser (9), the second optical fiber focuser (10), the 3rd optical fiber focuser (11) after computing machine (16) is processed, the computing formula of speed V is:

V=| ν _Rise-ν _Descend| λ

As the rising edge frequency ν of each dimension laser from mixed signal _RiseGreater than negative edge frequency ν _DescendThe time, the movement velocity direction determining is identical with the shoot laser direction of each dimension optical fiber focuser, as the rising edge frequency ν of each dimension laser from mixed signal _RiseLess than negative edge frequency ν _DescendThe time, the movement velocity direction determining is the shoot laser opposite direction with each dimension optical fiber focuser.

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