CN105092877B - Triangular wave phase-modulation semiconductor laser mixes tachymeter and its measurement method certainly - Google Patents
Triangular wave phase-modulation semiconductor laser mixes tachymeter and its measurement method certainly Download PDFInfo
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- CN105092877B CN105092877B CN201510258149.4A CN201510258149A CN105092877B CN 105092877 B CN105092877 B CN 105092877B CN 201510258149 A CN201510258149 A CN 201510258149A CN 105092877 B CN105092877 B CN 105092877B
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Abstract
A kind of triangular wave phase-modulation semiconductor laser of present invention offer mixes tachymeter and measurement method certainly.The structure of its tachymeter is：Driving circuit connects semiconductor laser diode, and aspherical offset lens, the polarizer, ray density filter, electrooptical crystal modulator and object to be measured are disposed on the forward direction transmission end axis of semiconductor laser diode；Laser diode is built-in with light sensitive diode, semiconductor laser and photodetector, and light sensitive diode is for detecting the light beam being reflected back in semiconductor laser resonator, and output is to operational amplifier after photodetector receives self-mixing interference；Signal generator exports triangular signal and trigger signal to electrooptical crystal modulator and operational amplifier respectively；Operational amplifier, data collecting card and computer are sequentially connected.The present invention detects micro/nano level vibration in a non-contact manner, can synchronize and obtain object under test speed and displacement, have the feature that high sensitive, nano-precision, noise are low, demodulation speed is fast.
Description
Technical field
Present invention relates particularly to a kind of triangular wave phase-modulation semiconductor lasers from mixing tachymeter and its measurement method, belongs to
In optical interferometry technical field.
Background technology
Speed be weigh microvibration, displacement, acceleration fundamental physical quantity；To the micro electronmechanical or sensor of vibration sensing
Etc. for advanced manufacturing industries, generally require speed instrument to take up space and want small, high sensitivity, testee such as cannot be contacted at the spies
Point.
Certain achievement is obtained using the interference-type tachymeter that various laser is light source, for example existing Michelson is done
Interferometer, fabry perot interferometer, homodyne or heterodyne ineterferometer, Doppler vibrometer, LIDAR speed guns etc..These are existing
Tachymeter needs to refer to signal and ancillary hardware, and reference mirror, beam splitter, polarization splitting prism, acousto-optic frequency modulation are commonly used in light path
Deng Data processing need to coordinate high-frequency count circuit, dsp system etc., make in the market that optical velocimeters structure is big, it is more empty to occupy
Between, of high cost, hardware is complicated, system is more fragile, there is an urgent need to improve for these disadvantages.
In laser self-mixing effect laser only influenced by feedback light, without auxiliary, have it is compact-sized, easily collimation etc. it is excellent
It puts and has attracted much attention, the hardware circuit of auxiliary is few, and demodulation error rate is low, but precision only has hundreds of nanometers, cannot still meet advanced
Manufacturing industry makes excessive demands precision.The typical precision methods that improve are to inject electricity to the self-mixed interference instrument based on semiconductor laser
Stream carrys out modulating light frequency, but electric current injection can also change output intensity simultaneously, introduce extra intensity noise, this is equally urgently solved
Certainly.
Existing sound ranging or piezoelectric type, current vortex, condenser type vibrating sensor are in measurement range, precision or mode
There are many limitations.For example sound wave is longer compared with the wavelength of light wave, precision is low, is lost in propagation process of sound wave greatly apart from short, signal matter
Amount is far below highly coherent laser beam signal, strongly limits range and the accuracy of measurement；Piezoelectric transducer need to be close to
Measured object surface is easily damaged micro mechanical system or sample；Current vortex or condenser type vibrating sensor are limited by electrical characteristic, quilt
The frequency and amplitude for surveying movement are restricted；Other mechanical velocity sensors are similarly difficult to reach the resolution of micron or more
Rate, with less the ability to micro/nano level vibration or displacement perception.
For existing precision optics speed-measuring structure, such as large-scale German PloyTec5000 types Doppler vibrometer, the instrument
Device includes Mach Zehnder interferometer, and laser sensing module, the hardware demodulation circuit and complex software of high integration, price is higher than 40
Ten thousand RMB, it is sufficiently expensive, and application conditions are harsh, it is cumbersome.
Invention content
For the above defect existing in the prior art, the purpose of the present invention is to provide a kind of triangular wave phase-modulations half
Conductor Laser from mixing tachymeter, the instrument be it is a kind of using Electro-optical Modulation effect and optical feedback effect generate from mixed signal
The fine measuring instrument of Real-time demodulation object vibration speed and displacement.Another object of the present invention be to provide using the tachymeter into
The method that row measures.
The technical solution adopted by the present invention to solve the technical problems is：
Triangular wave phase-modulation semiconductor laser mixes tachymeter, including driving circuit, semiconductor laser diode, system certainly
Cold, temperature controller, aspherical offset lens, the polarizer, ray density filter, electrooptical crystal modulator, signal occur
Device, operational amplifier, data collecting card and computer；Driving circuit connects semiconductor laser diode, two pole of semiconductor laser
It is disposed with aspherical offset lens, the polarizer, ray density filter, electro-optic crystal tune on the forward direction transmission end axis of pipe
Device processed and object to be measured；The semiconductor laser diode is built-in with light sensitive diode, semiconductor laser and photodetector,
The light sensitive diode is for detecting the light beam being reflected back in semiconductor laser resonator, and the photodetector is received from mixed
Output is to the operational amplifier after closing interference signal；The signal generator exports triangular signal and square wave triggering letter respectively
Number to electrooptical crystal modulator and operational amplifier；The operational amplifier, data collecting card and computer are sequentially connected；It is described
Computer is based on cross derivative demodulation techniques and obtains rate curve, from which further follows that displacement and the acceleration of object to be measured, and by
Display terminal exports.
The cooling piece is arranged in the bottom of semiconductor laser diode, and institute is controlled using pid algorithm by temperature controller
State the on off operating mode of cooling piece.
The object to be measured is fixed on the vertical surface of vibration source.
The polarizer is consistent with the polarization direction of electrooptical crystal modulator.
Further, the semiconductor laser uses operation wavelength for the laser of 635nm.
Further, the operational amplifier built-in current voltage conversion device.
The method that the present invention is measured using above-mentioned tachymeter, is as follows：
(1) driving circuit starts semiconductor laser diode to semiconductor laser diode Injection Current, rotates the polarizer
Keep the angle through Laser Beam Polarization state after aspherical offset lens and electrooptical crystal modulator polarization state minimum；It is close to rotate light
It spends FILTER TO CONTROL laser and is in weak feedback level from mixing, i.e., the interference fringe observed with external oscillograph does not tilt existing
As when, you can test；
(2) signal generator generates triangular signal driving electrooptical crystal modulator and carries out phase-modulation to light beam；It is in
The object to be measured of micro-vibration state will be reflected by modulated light beam into coupling in semiconductor laser diode resonant cavity, be occurred
Self-mixing interference effect, the light intensity of self-mixing interference are received by being encapsulated in photodetector in diode, receive from
It includes vibration information to mix light intensity signal；
(3) what photodetector exported completes analog-to-digital conversion after operational amplifier from mixed signal by data collecting card,
Signal of the data collecting card synchronous acquisition through the amplified light sensitive diode output of operational amplifier；
(4) object vibration changes over time as L (t), and the phase generated by self-mixing effect is expressed as
λ represents optical maser wavelength in formula, whenWhen known, vibration position is expressed asUnder weak feedback condition, after modulation
Laser be from mixed-phase mathematic(al) representationG (t) is the triangular signal introduced by modulation, it is clear that works as g
(t) be equal to-pi/2,0, pi/2 when, the phase bit position of corresponding interference signal is respectively
The discrete digital signal that data collecting card is converted to is extracted into this three roads signal respectively by three data buffers；Centre is all the way
Signal is as phaseCosine functionAnother two paths of signals is used as phase after subtracting each otherSIN functionBy just, cosine signal be divided by after do arctangent cp cp operation and obtainBy the correspondence between vibration and phase, solution
The oscillating curve of object to be measured can be found out after package；By just, cosine signal normalized make amplitude be equal to 1, then willWithIt is multiplied,WithIt is multiplied, two products, which are subtracted each other, immediately arrives at mesh to be measured
Target rate curve.
The invention has the advantages that：
(1) present invention detection micro/nano level vibration in a non-contact manner, can synchronize and obtain object under test speed and displacement, have
The feature that high sensitive, nano-precision, noise are low, demodulation speed is fast.
(2) measurement result is expressed as the variation of micro-displacement, speed, acceleration, more intuitively, reliably.
(3) compared with the optically measuring speeds structure of existing foreign countries, the light path of tachymeter of the present invention is simple, small, at low cost
In its 20%, and it is also low to the flatness requirement of tested surface, allow reflect target surface have roughness.
(4) light path of the device of the invention design is the linear structure of "-" type, is not necessarily to auxiliary optical component, and system is in light
The soft integration of electricity；And the linearity of the triangular modulation introduced is high, and modulating signal source fluctuation is small；Meanwhile the single mode of use half
Conductor laser is system source, at low cost, long working life, and working laser is in red color visible, is easily collimated.
(5) data processing of the invention is completed by computer, is easily programmed and is installed；The present invention is close with computer technology
In conjunction with can display real-time experiment curv.
(6) it when the vibration amplitude of object under test is less than 5um, measures displacement accuracy and is higher than 20nm, relative error is less than
0.2%, for velocity accuracy up to 10nm/s, the upper limit that tests the speed is 10mm/s.
(7) measurement object of the present invention is in extensive range, can be in industry or the daily material in vibrational state, such as
Naval vessels, automobile, aircraft etc. in the even movement of blocks of solid, instrument, mechanical device, bridge.Due to the high-resolution of the present invention
And anti-noise ability, it can be applied to sensor manufacturing industry, micro-nano mechanical processing, accurate national defence, medical information engineering, aerospace
Industry, or for needing the research and development of dynamic monitoring, experiment and metering class R＆D institution to use, be particularly suitable for vibration frequency in sound
Frequency range or within micro-displacement, speed, the measurement accuracy of acceleration require high place.
Description of the drawings
Schematic diagram of Fig. 1 triangular wave phase modulation-type semiconductor lasers of the present invention from mixing tachymeter device；
Fig. 2 present invention acquires the flow chart with demodulated signal.
Specific implementation mode
The following further describes the present invention with reference to the drawings.
Present invention mainly solves the technical issues of have：The problem of tachymeter light channel structure and auxiliary circuit complexity；Tradition swashs
The phase of light self-mixed interference is not easy extraction and resolution limitations in the half wavelength the problem of；He-Ne lasers volume is big and work
Make the problem that the service life do not grow.
In principle use triangular wave phase-modulation laser self-mixing interference signal, remove reference path in Amici prism,
The devices such as reference mirror, external PD, constitute the most simple light path of line-styled, and signal processing can be completed by common computer, also exempt from
Peripheral circuit is removed；The phase of modulated signal periodically-varied self-mixed interference, the phase signal in single modulation period are easy to
Extraction, resolution ratio significantly improve；Semiconductor laser diode is small compared to gas laser as measuring system light source, work
Make long lifespan, existing manufacturing process is highly developed.
It is consistent with crystalline material by polarizing film selection after the Gaussian beam focusing of realization method semiconductor-on-insulator laser tube output
Polarization state；Apply triangle wave voltage on electro-optic crystal, changes refractive index when light passes through crystalline material, and then change light
Journey does not change laser optical frequency during this, and without the fluctuation in light intensity, laser power depends on itself；Entire light path exists
Building or must be fixedly arranged at when installing in vibration isolation optical table or precise guide rail ensures to collimate.
One of programme element is to introduce triangular wave phase-modulation with electro-optic phase modulator, and modulating frequency, which must be far above, shakes
Dynamic frequency is usually above 100 times or more, and modulation, which is equivalent to, is finely divided interference signal；Secondly as modulating frequency it is known that
The sine and cosine phase in subdivided interval can be accurately extracted, the displacement of vibration is measured by arctangent cp cp operation reconciliation technique for packing, by
Cross derivative measures speed；Furthermore modulating frequency is higher, and the section quantity of subdivision can increase, and demodulation accuracy, which corresponds to, to be improved；Phase
Modulation-demodulation mode breaches half-wavelength limitation, and the variation of direction of vibration is provided automatically by phase, and precision is better than 1/20th
Wavelength；Finally in data demodulation, what it is due to delta modulation introducing is linear modulation, can overcome sampling error, effectively improve
The anti-interference ability of system.
The technology that the laser velocimeter of the present invention is related to mainly has following several：
(1) semiconductor laser light source and Refrigeration Technique：Band Quantum Well semiconductor laser diode is by current driven emissive wavelength
For the visible Gauss red beams of 635nm, system source is used as after being focused by offset lens.Light sensitive diode detection is anti-built in laser tube
It is emitted back towards the laser of intracavitary.Semiconductor chilling plate is based on Peltier effect, and hot-cast socket is fast, and space hold is small, is easy to by pid algorithm essence
Really control, is suitable as heat circulating system.
(2) triangular wave phase modulation technique：Has high efficiency, broadband does not introduce the characteristics of light intensity changes.Extra electric field
Electrooptic crystal material refractive index is linearly changed, it is round-trip to be changed correspondingly by the laser beam light path of modulator, it is equivalent to modulation phase
Position.It is needed unanimously with electro-optic crystal polarization direction when the polarizing film of laser polarization state being selected to place.Triangular wave is in cyclic-symmetry structure,
Linearly degree after phase modulation is high, and algorithm steps are few.Since modulating frequency is far above from mixing frequency signal, passed through from mixed signal
It is subdivided after phase-modulation to microsecond stage time interval.
(3) weak feedback laser self-mixing effect：According to laser self-mixed interference phase condition, when feedback level is 0.1
Hereinafter, the fraction of laser light of testee reflection is coupled into semiconductor laser again, laser output power and output frequency are modulated
Rate forms the interference signal of near sinusoidal.Shape of stripes and quantity and vibration existence anduniquess correspondence in signal, to mixing certainly
Signal, which carries out numerical analysis, can obtain real-time vibration.When laser is in appropriateness or higher level from mixed feedback, from mixing
The interference fringe of formation obviously has tilt phenomenon, is unfavorable for demodulating, and when measurement should avoid as possible.
As shown in Figure 1, the primary structure of the present embodiment triangular wave phase-modulation semiconductor laser from mixing tachymeter includes：
Driving circuit 1, semiconductor laser diode 2, semiconductor chilling plate 3, temperature controller 4, aspherical offset lens 5, the polarizer
(polarizing film) 6, ray density filter 7, electrooptical crystal modulator 8, object to be measured 9, signal generator 10, operational amplifier
11, data collecting card 12, computer unit 13；Wherein, aspherical offset lens 5, the polarizer (polarizing film) 6, ray density filter
Wave device 7, electrooptical crystal modulator 8, object to be measured 9 are placed sequentially on the forward direction transmission end axis of semiconductor laser diode 2；
Operational amplifier 11, data collecting card 12 and computer unit 13 are sequentially connected；10 exportable triangular signal of signal generator
It is respectively acting on electrooptical crystal modulator 8 and operational amplifier 11 with square wave trigger signal；The inside of semiconductor laser diode 2
It is provided with light sensitive diode and photodetector, light sensitive diode is for detecting the light beam being reflected back in resonant cavity, photodetection
What device received directly acts on operational amplifier 11 from mixed signal.
Wherein, driving circuit 1 provides stable electric current driving；
Semiconductor laser diode 2 encapsulates light sensitive diode as photodetector and single mode 635nm semiconductor lasers
Device, concrete model are the HL6312G type semiconductor lasers that Soret wins photoelectricity company；
Semiconductor chilling plate 3 is placed on the bottom of semiconductor laser diode 2, absorbs the waste heat that laser tube distributes；
Temperature controller 4 controls the break-make of semiconductor chilling plate 3, semiconductor laser temperature is maintained 25 DEG C；
Aspherical offset lens 5 does up focussing force to the gauss laser of diverging；
The polarizer (polarizing film) 6, polarization state that is coaxial with laser beam and selecting laser；
Ray density filter 7, using visual intensity filter；
Electrooptical crystal modulator 8 carries out round-trip laser beam using damp proof magnesia-lithium niobate as working media
Triangular wave phase-modulation；
Object to be measured 9 is fixed on accurate piezoelectric ceramics or the vertical surface of other vibration sources；
Signal generator 10 exports triangular wave and TTL trigger signals using Tektronix Oscilloscope；Triangular signal is sent out
Raw device, generation frequency are fmTriangular signal for driving electrooptical crystal modulator 7；
Operational amplifier 11, preposition current-to-voltage convertor part, exports amplified voltage signal；
Data collecting card 12, NI companies USB-6331 type data collecting cards, for synchronizing double channels acquisition from mixed signal
With trigger signal；
Computer unit 13 calculates collected digital signal, shows speed and displacement curve.
In order to realize that above-mentioned triangular wave phase modulation-type semiconductor laser chasing after the real-time of micro-vibration from mixing tachymeter
Track, measurement method mainly include the following steps that：The HL6312G semiconductor lasers injection of company is won from driving circuit 1 to Soret
Electric current, representative value 45mA, makes it be operated in threshold value；The rotation polarizer (polarizing film) 6 makes output polarization state and electro-optic crystal
Polarization state is consistent；Selection is controlled the attenuation degree of outgoing beam by gradual change neutrality ray density filter 7；Signal generator 10 produces
Raw triangular signal driving electro-optic crystal modulation light beam carries out phase-only modulation；It is reflected by measured target by modulated light beam
After be coupled into semiconductor laser resonator, self-mixing interference effect occurs, the light intensity of self-mixing interference is by built-in photoelectricity
Detector receives.
Photodetector output completes modulus turn after current-voltage is converted from mixed signal by data collecting card 12
It changes, data collecting card is set as triggering collection, i.e., starts to acquire in square wave trigger signal rising edge, corresponding modulated triangular wave
Phase is zero, and it is poor not introduce extra phase in this way.Object vibration changes over time as L (t), velocity variations V (t), the two presence
Integral relation, i.e. d L (t)/dt=V (t).The phase generated by self-mixing effect is expressed asλ is represented in formula
Optical maser wavelength, whenWhen known, vibration position is expressed asReal-time speed is expressed as
Under weak feedback condition, modulated laser is from mixed-phase mathematic(al) representationG (t) be by
The triangular signal introduced is modulated, round-trip laser beam is modulated twice, i.e. 2g (t).Obviously when 2g (t) be equal to-pi/2,0, pi/2
When, the phase value of corresponding interference signal is respectivelyBy data collecting card
The discrete digital signal being converted to extracts this three roads signal respectively by three data buffers；Intermediate signal all the way is as phaseCosine functionAnother two paths of signals is used as phase after subtracting each otherSIN functionIt will just, cosine letter
Arctangent cp cp operation is done after number being divided by obtainBy the correspondence between vibration and phase, mesh to be measured can be found out after unpacking
Target oscillating curve；By just, cosine signal normalized make amplitude be equal to 1, then willWithPhase
Multiply,WithIt is multiplied, two products subtract each other the rate curve for immediately arriving at object to be measured.
It is measuring principle of the triangular wave phase modulation-type semiconductor laser of the present invention from mixing tachymeter below：
Electric field E (t) of the single mode semiconductor laser output light after polarizing film 5 in polarization state be：
E (t)=E0exp[-i(ωt+φ0)] (1)
In formula, E0For the amplitude of light field, ω is laser angular frequency, φ0For the initial phase of optical output field.
In exocoel, shoot laser carries out phase-modulation by electrooptical crystal modulator 8, is modulated again in return course
Electric field E afterwards1(t) it is
E1(t)=E0exp[-i(ωt+φ0)]exp{-i[2g(t)]}exp(-iωτ) (2)
In formula, τ is time delay of the light beam in exocoel, and g (t) is triangular wave phase modulated signal, and expression formula is：
The undulate quantity of laser frequency is far smaller than laser own frequency under weak feedback condition, the output work of consideration laser
Rate Δ P (t)：
Δ P (t)=GE0cos[ωτ+2g(t)] (4)
In formula, G is gain term related with laser inherent parameters, and assumes initial phase φ0It is zero.
Δ P (t) extracts discrete series of the g (t) at 0 ,-π/4, π/4 with three groups of data buffers respectively：
ΔP(t)1=GE0cos(ωτ-π/2) (5)
ΔP(t)2=GE0cos(ωτ) (6)
ΔP(t)3=GE0cos(ωτ+π/2) (7)
(5) subtract each other and normalize with (7) formula, obtain：
SR=sin (ω τ) (8)
CR=cos (ω τ) (9)
The derivative of ω τ is found out by cross derivative, wherein including speed：
DSR/dt*cos (ω τ)-dCR/dt*sin (ω τ)=d (ω τ)/dt=4 π V (t)/λ (10)
By phase is unfolded after arctangent cp cp operation, wherein including displacement：
Arctangent (the SR/CR)=π L (t) of ω τ=4/λ (11)
The data buffer length used must ensure to be more than sampling number * fm/ sample rate, prevents data from overflowing.
Then, it is described in further details in conjunction with Fig. 1, specific measuring process is as follows：
(1) driving circuit 1 exports stabling current, and size is between the threshold value and maximum current of semiconductor laser diode 2；
Temperature control device 4, which controls cooling piece 3, makes laser tube temperature stablize at 25 ± 0.1 DEG C；Rotatory polarization piece 6 makes saturating through aspherical compensation
The Laser Beam Polarization state of mirror 5 is minimum with the angle of 8 polarization state of electrooptical crystal modulator；Ray density filter 7 is rotated, eliminates and swashs
For light from fringe inclination is mixed, it is in sinusoidal waveform to make waveform.
(2) start the servomechanism of piezoelectric ceramics, micro-vibration occurs for object to be measured 9, is tested target surface and is not necessarily to secondary optic；
Electrooptical crystal modulator 8 introduces the triangular wave phase-modulation that depth is π/4, and modulating frequency is up to 500KHz；Semiconductor laser
The signal of light sensitive diode built in device is after operational amplifier 11 amplifies 1000 times with the trigger signal of modulated signal by DAQ equipment
Synchronous acquisition.
It is illustrated in combination with fig. 2 signal flow：
1) under LabVIEW2014 versions environment, configuration data capture card 12 (NI USB-6331) collecting work mode is to connect
Continuous sampling, acquires, sampling time 0.2s, collected data are by conversion array by the upper edge of trigger signal；Sampling
The sample rate that point quantity is multiplied by capture card by the sampling time is calculated.
2) three groups of signals are extracted by data buffer, wherein signal is proportional to the cosine function of phase to be measured all the way, another two
The SIN function of phase to be measured is proportional to after the signal subtraction of road, normalized makes the amplitude of cosine and sine signal be equal to 1.
3) speed and displacement are found out by cross derivative and arc tangent, so moved in circles, and shown in real time on display terminal
Show the displacement of object to be measured.
The running software time is less than 100 milliseconds, and 1s continuously displays 3 times or more and reconstructs curve.Software support acquires signal
With the real-time display of demodulation result, historical data can be stored and called.Specific measurement parameter and range are as shown in table 1：
1 triangular wave phase modulation-type laser of table mixes tachymeter parameter certainly
Note:In measurement process, phase modulation depth remains π/4, and it is π/4 to show as the triangular signal amplitude introduced.
Compared with prior art, hardware filtering circuit, meter frequency or counting circuit, number are eliminated in relevant configuration of the invention
Logic circuit, LCD MODULE etc., measurement are directly completed by computer, and patterned labview softwares provide visual, intelligence
The demodulating process of change, built-in filtering, logical operation, caching function, oscillogram substitution hardware circuit and display device, greatly
Cost is saved, and is easy to modification and error correction.
Two physical quantitys of displacement and speed functionally are shown by two kinds of calculations to the cosine and sine signal of phase, more in detail
Carefully characterize the characteristic of tested vibration.Due to photoelectric crystal modulation bandwidth, the factors such as the capture card sample rate upper limit, system restriction is such as
Shown in table 1, the frequency range of vibration is measured within 5K, and amplitude is micro/nano level；Displacement does not answer superelevation when measuring displacement
10 millimeters, speed should be per second less than 10 millimeters.
The semiconductor laser that the present invention uses is easy to volume production, simple from mixed structure, and modulation technique is efficient and does not introduce
Light intensity, high resolution is interfered to be demodulated compared with phase carrier or frequency analysis in 1/20th wavelength, directly data cached mode
More succinct, the present invention can be widely applied in the real-time monitoring of contactless precision vibration or displacement.
Claims (7)
1. triangular wave phase-modulation semiconductor laser includes driving circuit, partly leads from the measurement method for mixing tachymeter, tachymeter
Volumetric laser diode, cooling piece, temperature controller, aspherical offset lens, the polarizer, ray density filter, electro-optic crystal
Modulator, signal generator, operational amplifier, data collecting card and computer；It is characterized in that, driving circuit connects semiconductor
Laser diode, be disposed on the forward direction transmission end axis of semiconductor laser diode aspherical offset lens, the polarizer,
Ray density filter, electrooptical crystal modulator and object to be measured；The semiconductor laser diode be built-in with light sensitive diode,
Semiconductor laser and photodetector, the light sensitive diode is for detecting the light being reflected back in semiconductor laser resonator
Beam, output is to the operational amplifier after the photodetector receives self-mixing interference；The signal generator difference
Triangular signal and square wave trigger signal are exported to electrooptical crystal modulator and operational amplifier；The operational amplifier, data
Capture card and computer are sequentially connected；The computer is based on cross derivative demodulation techniques and obtains rate curve, from which further follows that
The displacement of object to be measured and acceleration, and exported by display terminal；Measurement method is as follows：
(1) driving circuit starts semiconductor laser diode to semiconductor laser diode Injection Current, and the rotation polarizer makes
The angle of Laser Beam Polarization state and electrooptical crystal modulator polarization state is minimum after crossing aspherical offset lens；Rotate ray density filter
Wave device controls laser and is in weak feedback level from mixing, when the interference fringe observed with external oscillograph does not have tilt phenomenon,
It can test；
(2) signal generator generates triangular signal driving electrooptical crystal modulator and carries out phase-modulation to light beam；It shakes in micro-
The object to be measured of dynamic state will be reflected by modulated light beam into coupling in semiconductor laser diode resonant cavity, be occurred from mixed
Interference effect is closed, the light intensity of self-mixing interference is received by being encapsulated in photodetector in diode, and what is received mixes certainly
Light intensity signal includes vibration information；
(3) what photodetector exported completes analog-to-digital conversion, data after operational amplifier from mixed signal by data collecting card
Signal of the capture card synchronous acquisition through the amplified light sensitive diode output of operational amplifier；
(4) object vibration changes over time as L (t), and the phase generated by self-mixing effect is expressed asλ in formula
Optical maser wavelength is represented, whenWhen known, vibration position is expressed asUnder weak feedback condition, modulated laser
It is from mixed-phase mathematic(al) representationG (t) is the triangular signal introduced by modulation, it is clear that as g (t) etc.
When-pi/2,0, pi/2, the phase bit position of corresponding interference signal is respectively
The discrete digital signal that data collecting card is converted to is extracted into this three roads signal respectively by three data buffers；Centre is all the way
Signal is as phaseCosine functionAnother two paths of signals is used as phase after subtracting each otherSIN functionBy just, cosine signal be divided by after do arctangent cp cp operation and obtainBy the correspondence between vibration and phase, unpack
The oscillating curve of object to be measured can be found out after wrapping up in；By just, cosine signal normalized make amplitude be equal to 1, then willWithIt is multiplied,WithIt is multiplied, two products, which are subtracted each other, immediately arrives at object to be measured
Rate curve.
2. triangular wave phase-modulation semiconductor laser as described in claim 1 mixes the measurement method of tachymeter, feature certainly
It is, the cooling piece is arranged in the bottom of semiconductor laser diode, and the system is controlled using pid algorithm by temperature controller
Cold on off operating mode.
3. triangular wave phase-modulation semiconductor laser as described in claim 1 mixes the measurement method of tachymeter, feature certainly
It is, the object to be measured is fixed on the vertical surface of vibration source.
4. triangular wave phase-modulation semiconductor laser as described in claim 1 mixes the measurement method of tachymeter, feature certainly
It is, the polarizer is consistent with the polarization direction of electrooptical crystal modulator.
5. triangular wave phase-modulation semiconductor laser as described in Claims 1 to 4 is one of arbitrary is from the measurement for mixing tachymeter
Method, which is characterized in that the semiconductor laser uses operation wavelength for the laser of 635nm.
6. triangular wave phase-modulation semiconductor laser as described in Claims 1 to 4 is one of arbitrary is from the measurement for mixing tachymeter
Method, which is characterized in that the operational amplifier built-in current voltage conversion device.
7. triangular wave phase-modulation semiconductor laser as claimed in claim 6 mixes the measurement method of tachymeter, feature certainly
It is, current-to-voltage convertor part is equipped with before the operational amplifier is interior.
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