CN102253001A - Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic measurement device and method for measuring magnetostriction coefficient - Google Patents

Abstract

The invention relates to a Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic measurement device for measuring magnetostriction coefficient and a method thereof. The invention is brought forward to solve the problems of poor quality of acquired laser different frequency signals and slow operation speed of signal processing in present laser heterodyne measurement technologies for measuring the magnetostriction coefficient. The Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic measurement method for measuring the magnetostriction coefficient comprises the following steps of: demagnetizing a sample to be measured, arranging the positions of a planar mirror and a thin sheet of glass, turning on an H0 solid state laser, continuously acquiring measured second harmonic signals and processing electrical signals sent from a photodetector by a signal processing system to obtain the variable quantity of the distance between the planar mirror and the thickness-ignoring thin glass plate and obtain the magnetostriction coefficient of the sample to be measured. The measurement method provided by the invention has advantages of high quality of the acquired laser different frequency signals and high operation speed of signal processing, and can be widely applied in ultra-precision measurements, detection, processing equipment and laser radar systems.

Description

Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic is measured the device and method of magnetostriction coefficient

Technical field

The present invention relates to a kind of Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic and measure the device and method of magnetostriction coefficient, belong to micrometric displacement detection technique field.

Background technology

Can align under the magnetic domain outside magnetic field effect of ferromagnetics, thereby cause the change of spacing of lattice in the medium, cause the phenomenon of the variation of ferromagnet generation length to be called as magnetostrictive effect.Because this phenomenon is at first found in 1842 by joule, thereby is also referred to as Joule effect.Magnetostriction not only has significant effects to the magnetic of material, particularly to initial permeability, coercive force etc., and described magnetostrictive effect application in practice itself is also very extensive, can be used for mechanical vibration and ultrasonic transducer as magnetostrictive technology, important use be arranged at aspects such as laser radars.

Utilize the variation of material length under action of alternating magnetic field, can be made into ultrasonic generator and receiver:, can make sensors such as power, speed, acceleration and lag line, wave filter etc. by some special conversion equipments.Under the condition of identical external magnetic field, the magnetostrictive length variations of different magnetisable materials is different, uses magnetostriction coefficient α (α=Δ l/l) to characterize the size of its deformation usually.Therefore, the magnetostriction coefficient α that accurately measures material is very important.Because it is very small that the length of material that magnetostrictive effect causes changes relatively, the magnetostriction coefficient of general ferromagnetic material has only 10 ^-5～10 ^-6Therefore the order of magnitude needs to adopt some high-precision methods to be measured.

The mensuration of magnetostriction coefficient is summed up as the measurement that little length (displacement) changes.The method of measuring magnetostriction coefficient at present mainly contains the nonequilibrium bridge mensuration, survey method, optical lever, straingauge mensuration and optical interference method etc. are held in differential power transformation.But all there is shortcoming separately in these methods, so measuring accuracy can't improve.

And in optical measuring method, advantages such as the laser heterodyne measurement technology has that high room and time resolution, measuring speed are fast, precision is high, the linearity good, antijamming capability is strong, dynamic response is fast, good reproducibility and measurement range are big and enjoy Chinese scholars to pay close attention to, the laser heterodyne measurement technology has been inherited the plurality of advantages of heterodyne technology and Doppler technology, is one of present superhigh precision measuring method.This method has become one of significant technology of modern ultraprecise detection and surveying instrument, is widely used in ultra precise measurement, detection, process equipment, laser radar system etc.

But existing laser heterodyne measurement technology is lower in the collection laser difference frequency signal quality of measuring the magnetostriction coefficient existence, the problem that the arithmetic speed of signal Processing is slow.

Summary of the invention

The present invention is lower in the collection laser difference frequency signal quality of measuring the magnetostriction coefficient existence in order to solve existing laser heterodyne measurement technology, the problem that the arithmetic speed of signal Processing is slow, and the Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic that proposes is measured the device and method of magnetostriction coefficient.

A kind of Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic is measured the device of magnetostriction coefficient, this device by first hold-down bars, second hold-down bars, drive coil, iron-nickel alloy sample to be measured, D.C. regulated power supply, plane mirror, disregard thin thickness glass plate, polarizing beam splitter mirror PBS, H ₀Solid state laser, quarter-wave plate, galvanometer, convergent lens, photodetector and signal processing system are formed,

D.C. regulated power supply is used for providing working power to drive coil, iron-nickel alloy sample to be measured is placed in the drive coil between two parties, one end of fixedly connected first hold-down bars of one end of iron-nickel alloy sample to be measured, the other end of this first hold-down bars fixedly installs, one end of fixedly connected second hold-down bars of the other end of iron-nickel alloy sample to be measured, the non-reflecting surface of the bonding plane mirror of the other end of this second hold-down bars, the axis normal of the reflecting surface of plane mirror and iron-nickel alloy sample to be measured; First hold-down bars is identical with the second hold-down bars size, and two hold-down barss, iron-nickel alloy sample to be measured and the coaxial settings of drive coil; At the reflecting surface one lateral extent d place of plane mirror, be arranged with in parallel with this plane mirror and disregard the thin thickness glass plate;

H ₀The linearly polarized light that solid state laser sends is incident to quarter-wave plate after polarizing beam splitter mirror PBS reflection, light beam after this quarter-wave plate transmission is incident to the light receiving surface of galvanometer, light beam through this vibration mirror reflected is sent to polarizing beam splitter mirror PBS once more after the quarter-wave plate transmission, light beam after this polarizing beam splitter mirror PBS transmission is incident to disregards the thin thickness glass plate, light beam after this disregards the transmission of thin thickness glass plate is incident to the reflecting surface of plane mirror, light beam after this plane reflection mirror reflection obtains transmitted light through disregarding the transmission of thin thickness glass plate once more, light beam after this transmitted light and the light entrance face reflection through disregarding the thin thickness glass plate all converges to by convergent lens on the photosurface of photodetector, and described photodetector output electric signal is given signal processing system.

The device that adopts above-mentioned Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic to measure magnetostriction coefficient is realized the method for Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic measurement magnetostriction coefficient, and the process of this method is:

At first, the iron-nickel alloy sample is carried out AC demagnetization, utilize two-dimentional adjustment rack to regulate plane mirror and the position of disregarding the thin thickness glass plate, make plane mirror and disregard the thin thickness glass plate be parallel to each other, contour, and to make between the reflecting surface of disregarding thin thickness glass plate and plane mirror be 20mm apart from d;

Then, adjust D.C. regulated power supply, make its output current minimum, and the driving power of opening galvanometer makes galvanometer begin to do simple harmonic oscillation; Simultaneously, open H ₀Solid state laser,

At last, adjust the output current of D.C. regulated power supply, make the dull rising of its output current I, in this process, the electric signal of signal processing system continuous acquisition photodetector output, and the signal that collects handled, obtain plane mirror and disregard variable in distance amount between the thin thickness glass plate, obtain the magnetostriction coefficient of iron-nickel alloy sample to be measured according to this variable in distance amount:

α＝Δl/l，

In the formula, Δ l/ is the length variations amount of iron-nickel alloy sample to be measured in magnetic field, is plane mirror and disregards variable in distance amount between the thin thickness glass plate, and l is the original length of iron-nickel alloy sample to be measured.

Advantages such as the device and method that Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic of the present invention is measured magnetostriction coefficient not only has the laser heterodyne measurement technology and has that high room and time resolution, measuring speed are fast, precision is high, the linearity good, antijamming capability is strong, dynamic response is fast, good reproducibility and measurement range are big, also possesses the laser of collection difference frequency signal quality height, the outstanding advantage of the fast operation of signal Processing.It can be widely used in ultra precise measurement, detection, process equipment, laser radar system etc.

In order to collect laser difference frequency signal and the arithmetic speed that improves signal Processing preferably, this paper is based on the heterodyne technology, propose a kind of high precision precision multi-beam laser heterodyne second harmonic and measured the method for magnetostriction coefficient, promptly utilize the Doppler effect of galvanometer 10 that difference incident light is constantly carried out Sine Modulated, parameter information to be measured is modulated in the second harmonic of heterodyne signal, can accurately obtains parameter information to be measured by demodulation to heterodyne signal second harmonic.

The present invention is by introducing galvanometer 10 in light path, make the light signal of different incidents constantly add an optical frequency, satisfying under the condition of interfering through the light of disregarding more than 5 reflection of the reflected light of thin thickness glass plate 6 and plane mirror like this, produce multiple beam difference interference signal, thereby will treat that measurement information successfully is modulated in the difference on the frequency of intermediate frequency heterodyne second harmonic signal.In measuring samples magnetostriction coefficient process, the method has obtained comprising the frequency values of the information of metal length variable quantity at frequency domain, obtain the length variations amount after the signal demodulation, can obtain the variable quantity of accurate sample length with electric current by repeatedly measuring weighted mean.With the iron-nickel alloy is that example experimentizes, and the relative error that magnetostriction coefficient is measured has significantly improved measuring accuracy less than 0.8%.

Description of drawings

Fig. 1 is the structural representation of the device of Doppler's galvanometer Sine Modulated multi-beam laser heterodyne measurement magnetostriction coefficient of the present invention;

Fig. 2 is the multi-beam laser principle of interference figure between plane mirror and the thin glass plate;

Fig. 3 is the Fourier transform spectrogram of multi-beam laser heterodyne second harmonic signal.

Embodiment

Embodiment one: present embodiment is described below in conjunction with Fig. 1, the described Doppler's galvanometer of present embodiment Sine Modulated multi-beam laser heterodyne second harmonic is measured the device of magnetostriction coefficient, this device is by the first hold-down bars 1-1, the second hold-down bars 1-2, drive coil 2, iron-nickel alloy sample 3 to be measured, D.C. regulated power supply 4, plane mirror 5, disregard thin thickness glass plate 6, polarizing beam splitter mirror PBS7, H0 solid state laser 8, quarter-wave plate 9, galvanometer 10, convergent lens 11, photodetector 12 and signal processing system 13 are formed

D.C. regulated power supply 4 is used for providing working power to drive coil 2, iron-nickel alloy sample 3 to be measured is placed in the drive coil 2 between two parties, the end of the fixedly connected first hold-down bars 1-1 of one end of iron-nickel alloy sample 3 to be measured, the other end of this first hold-down bars 1-1 fixedly installs, the end of the fixedly connected second hold-down bars 1-2 of the other end of iron-nickel alloy sample 3 to be measured, the non-reflecting surface of the bonding plane mirror 5 of the other end of this second hold-down bars 1-2, the axis normal of the reflecting surface of plane mirror 5 and iron-nickel alloy sample 3 to be measured; The first hold-down bars 1-1 is identical with the second hold-down bars 1-2 size, and two hold-down barss, iron-nickel alloy sample 3 to be measured and drive coil 2 coaxial settings; At the reflecting surface one lateral extent d place of plane mirror 5, be arranged with in parallel with this plane mirror 5 and disregard thin thickness glass plate 6;

The linearly polarized light that H0 solid state laser 8 sends is incident to quarter-wave plate 9 after polarizing beam splitter mirror PBS7 reflection, light beam after these quarter-wave plate 9 transmissions is incident to the light receiving surface of galvanometer 10, after quarter-wave plate 9 transmissions, be sent to polarizing beam splitter mirror PBS7 once more through these galvanometer 10 beam reflected, light beam after this polarizing beam splitter mirror PBS7 transmission is incident to disregards thin thickness glass plate 6, light beam after this disregards 6 transmissions of thin thickness glass plate is incident to the reflecting surface of plane mirror 5, light beam after these plane mirror 5 reflections obtains transmitted light through disregarding 6 transmissions of thin thickness glass plate once more, light beam after this transmitted light and the light entrance face reflection through disregarding thin thickness glass plate 6 all converges on the photosurface of photodetector 12 by convergent lens 11, and described photodetector 12 output electric signal are given signal processing system 13.

Iron-nickel alloy sample 3 to be measured produces axial deformation in the present embodiment under the action of a magnetic field of drive coil 2.

Galvanometer 10 in the present embodiment is done simple harmonic oscillation under the effect of driving power, adopt galvanometer 10 to carry out Sine Modulated to the laser frequency that difference incides galvanometer 10 surfaces constantly.

The end of the second hold-down bars 1-2 and the non-reflecting surface of plane mirror 5 are bonding, can guarantee moving freely of the second hold-down bars 1-2, plane mirror 5 and disregard thin thickness glass plate 6 and can adopt two-dimentional adjustment rack to carry out position adjustments.

Can be provided with arbitrarily according to actual needs in the present embodiment apart from d.

Embodiment two: present embodiment is for to the further specifying of embodiment one, and described is 20mm apart from d.

Embodiment three: present embodiment is for to the further specifying of embodiment one or two, and two equal cementations of end face of the described first hold-down bars 1-1 and the second hold-down bars 1-2 have nonmagnetic substance.

Embodiment four: present embodiment is for to the further specifying of embodiment one, two or three, and the other end of the described first hold-down bars 1-1 fixedly installs and is fixed on the worktable or on the fixture for: the other end of the first hold-down bars 1-1.

Embodiment five: present embodiment is for to the further specifying of embodiment one to four, and described galvanometer 10 is Doppler's galvanometer, and its simple harmonic oscillation equation and rate equation are respectively x (t)=x ₀Cos (ω _cT) and v (t)=-ω _cx ₀Sin (ω _cT), x in the formula ₀Be the amplitude of Doppler's galvanometer vibration, ω _cBe the angular frequency of Doppler's galvanometer, c is the light velocity, and t is the time.

Embodiment six: present embodiment is described below in conjunction with Fig. 1, present embodiment is further specifying embodiment one to five, described signal processing system 13 is made up of bandpass filter 13-1, prime amplifier 13-2, modulus converter A/D 13-3 and digital signal processor DSP 13-4

The electric signal that described bandpass filter 13-1 exports the photodetector 12 that receives carries out sending to prime amplifier 13-2 after the filtering, signal after prime amplifier 13-2 amplifies is exported to modulus converter A/D 13-3, and the signal after described modulus converter A/D 13-3 will change sends to digital signal processor DSP 13-4.

Embodiment seven: in conjunction with Fig. 1 and Fig. 2 present embodiment is described, the described Doppler's galvanometer of present embodiment Sine Modulated multi-beam laser heterodyne second harmonic is measured the method for magnetostriction coefficient, and the process of described method is:

At first, the iron-nickel alloy sample is carried out AC demagnetization, utilize two-dimentional adjustment rack to regulate plane mirror 5 and the position of disregarding thin thickness glass plate 6, make plane mirror 5 and disregard thin thickness glass plate 6 be parallel to each other, contour, and to make between the reflecting surface of disregarding thin thickness glass plate 6 and plane mirror 5 be 20mm apart from d;

Then, adjust D.C. regulated power supply 4, make its output current minimum, and the driving power of opening galvanometer 10 makes galvanometer 10 begin to do simple harmonic oscillation; Simultaneously, open H0 solid state laser 8,

At last, adjust the output current of D.C. regulated power supply 4, make the dull rising of its output current I, in this process, the electric signal of signal processing system 13 continuous acquisition photodetectors 12 outputs, and the signal that collects handled, obtain plane mirror 5 and disregard variable in distance amount between the thin thickness glass plate 6, obtain the magnetostriction coefficient of iron-nickel alloy sample 3 to be measured according to this variable in distance amount:

α＝Δl/l，

In the formula, Δ l/ is the length variations amount of iron-nickel alloy sample 3 to be measured in magnetic field, is plane mirror 5 and disregards variable in distance amount between the thin thickness glass plate 6, and l is the original length of iron-nickel alloy sample 3 to be measured.

Embodiment eight: present embodiment is described in conjunction with Fig. 2 and Fig. 3, present embodiment and embodiment seven differences are the electric signal to 12 outputs of described signal processing system 13 continuous acquisition photodetectors, and the signal that collects handled, the process that obtains plane mirror 5 and disregard the variable in distance amount between the thin thickness glass plate 6 is:

Linearly polarized light is successively through shining on galvanometer 10 front surfaces behind polarizing beam splitter mirror PBS7 and the quarter-wave plate 9, the different reflected light of being modulated by galvanometer 10 constantly see through oblique being mapped to of polarizing beam splitter mirror PBS7 through quarter-wave plate 9 backs again and disregard on the thin thickness glass plate 6, light through disregarding 6 transmissions of thin thickness glass plate is converged on photodetector 12 photosurfaces by convergent lens 11 with passing through the light of disregarding 6 front surface reflections of thin thickness glass plate after being reflected by plane mirror 5, after the electric signal process prime amplifier 13-2 after photodetector 12 opto-electronic conversion, obtain different parameter informations constantly to be measured behind modulus converter A/D 13-3 and the digital signal processor DSP 13-4; As shown in Figure 2, because light beam is being disregarded reflection and transmission constantly between thin thickness glass plate 6 and the plane mirror 5, and this reflection and refraction for reflected light and transmitted light at infinity or the interference on the lens focal plane contribution is all arranged, so when interference is discussed, must consider repeatedly reflection and transmission effect, multi-beam laser promptly should be discussed interfere.

Because laser transmits the optical mixing of disregarding thin thickness glass plate 6 front surfaces after the reflected light of disregarding thin thickness glass plate 6 front surfaces and plane mirror 5 reflections k time are with k+1 time, produce the difference frequency signal that two amplitudes differ 2～3 orders of magnitude, through after the Fourier transform, in order to collect laser difference frequency signal and the arithmetic speed that improves signal Processing preferably, the humorous frequency difference of secondary in the described processing procedure of the application is by the E that is detected _kE behind light and the plane mirror 5k+2 secondary reflection _K+2What optical mixing produced;

When laser with incident angle θ ₀Incident field when thin thickness glass plate 6 front surfaces are disregarded in oblique incidence is E (t)=E _lExp (i ω ₀T), the simple harmonic oscillation equation of galvanometer 10 and rate equation are respectively x (t)=x ₀Cos (ω _cT) and v (t)=-ω _cx ₀Sin (ω _cT); Because the motion of galvanometer 10, catoptrical frequency becomes ω=ω ₀(1-2 ω _cx ₀Sin (ω _cT)/c), parameter ω in the formula ₀Be laser angular frequency, parameter x ₀Be the amplitude of galvanometer 10 vibrations, parameter ω _cBe the angular frequency of galvanometer 10, c is the light velocity; Then t-L/c arrives the reflection light field of plane mirror 5 front surfaces constantly and is:

E ₀(t)＝α ₀E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-L/c))/c)

Formula 1

(t-L/c)+ω ₀x ₀cos(ω _c(t-L/c))/c]}

In the formula, parameter alpha ₀=r, r are the reflection coefficient of thin glass plate (6); L is that galvanometer 10 is to the light path of disregarding thin thickness glass plate 6 front surfaces; E _lBe the amplitude constant;

Light through disregarding 6 transmissions of thin thickness glass plate is constantly repeatedly reflected by plane mirror 5 rear surfaces and repeatedly transmits the front surface of disregarding thin thickness glass plate 6 in difference, and the expression formula of its transmitted light is write as following form respectively:

E ₁(t)＝α ₁E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+2nd?cosθ)/c))/c)

(t-(L+2ndcosθ)/c)+ω ₀x ₀cos(ω _c(t-(L+2ndcosθ)/c))/c]}

E ₂(t)＝α ₂E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+4ndcosθ)/c))/c)

(t-(L+4ndcosθ)/c)+ω ₀x ₀cos(ω _c(t-(L+4ndcosθ)/c))/c]}

E ₃(t)＝α ₃E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+6ndcosθ)/c))/c)

(t-(L+6ndcos θ)/c)+ω ₀x ₀Cos (ω _c(t-(L+6ndcos θ)/c))/c] } formula

.

.

.

E _m(t)＝α _mE _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+2mndcosθ)/c))/c)

(t-(L+2mndcosθ)/c)+ω ₀x ₀cos(ω _c(t-(L+2mndcosθ)/c))/c]}

2

Wherein, the subscript m value is 0,1,2 ..., n is a refractive index of disregarding medium between thin thickness glass plate 6 and the plane mirror 5, α ₁=β ²R ' ..., α _m=β ²R ' ^mr ^M-1, β is a transmission coefficient of disregarding thin thickness glass plate 6, and r ' is the reflection coefficient of plane mirror 5, and parameter d is to disregard thin thickness glass plate 6 distance to plane mirror 5, and θ is that incident light sees through the refraction angle of disregarding behind the thin thickness glass plate,

Total light field that photodetector 12 receives is expressed as:

E (t)=E ₀(t)+E ₁(t)+... + E _m(t) formula 3

Then the photocurrent of photodetector 12 outputs is expressed as:

$I=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{1}{Z}\underset{S}{\&Integral;\&Integral;}\frac{1}{2}[E_0\left(t\right)+E_1\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;+E_m\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;]{[E_0\left(t\right)+E_1\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;+E_m\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;]}^{*}\mathrm{<figure-callout\; id="4"\; label="ds\; Formula"\; filenames="HDA0000065396530000011.png"\; state="\{\{state\}\}">ds</figure-callout>}$ Formula 4

Wherein, parameter e is an electron charge, and parameter Z is the intrinsic impedance of photodetector 12 surface dielectrics, and parameter η is a quantum efficiency, and parameter S is the area of photodetector 12 photosurfaces, and parameter h is a Planck's constant, and parameter v is a laser frequency, * number expression complex conjugate;

Owing to only consider E _kAnd E _K+2The difference frequency second harmonic signal that optical mixing produced, DC terms be through can filtering behind the bandpass filter 13-1, therefore, only considers here to exchange, and this exchanges item and is called electric current of intermediate frequency, and the electric current of intermediate frequency that arrangement obtains second harmonic signal is:

$I_{\mathrm{if}}=\frac{\mathrm{\&eta;e}}{2\mathrm{hv}}\frac{1}{Z}\underset{s}{\&Integral;\&Integral;}\underset{p=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{j=p+2}{\overset{\&infin;}{\mathrm{\&Sigma;}}}(E_p\left(t\right){E_j}^{*}\left(t\right)+{E_p}^{*}\left(t\right)E_j\left(t\right))\mathrm{ds}$ Formula 5

With (1) formula and (2) formula substitution (5) formula, net result is:

$\begin{array}{c}{I}_{\mathrm{IF}}=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{\mathrm{\&pi;}}{Z}{E}_0^2\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{m-p}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{j+p}{\mathrm{\&alpha;}}_j\cos [\frac{8\mathrm{nd}\cos {\mathrm{\&theta;\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0}{c^2}t+\frac{2{\mathrm{\&omega;}}_0{x}_0}{c}-\frac{4\mathrm{nd}{\mathrm{\&omega;}}_0\cos \mathrm{\&theta;}}{c}\\ -\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0(l+2\mathrm{pnd}\cos \mathrm{\&theta;})}{c^3}]\end{array}$ Formula 6

Ignore 1/c again ³Event after be reduced to:

$I_{\mathrm{IF}}=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{\mathrm{\&pi;}}{Z}{E}_0^2\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{m-p}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{j+p}{\mathrm{\&alpha;}}_j\cos (\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0}{c^2}t+\frac{2{\mathrm{\&omega;}}_0{x}_0-4\mathrm{nd}{\mathrm{\&omega;}}_0\cos \mathrm{\&theta;}}{c})$ Formula 7

Wherein parameter p and j are nonnegative integer;

According to formula 7, the frequency of second harmonic signal is designated as:

$f=8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left({2\mathrm{\&pi;c}}^2\right)=4\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left({\mathrm{\&pi;c}}^2\right)=\mathrm{<figure-callout\; id="8"\; label="Kd\; Formula"\; filenames="HDA0000065396530000011.png"\; state="\{\{state\}\}">Kd</figure-callout>}$ Formula 8

Learn according to formula 8, the frequency of second harmonic signal with disregard being directly proportional between thin thickness glass plate 6 and the plane mirror 5 apart from d, scale-up factor is:

$K=4n\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left({\mathrm{\&pi;c}}^2\right)$ Formula 9

By measuring the frequency of second harmonic signal, promptly measure disregard between thin thickness glass plate 6 and the plane mirror 5 apart from d, when d changes, measure the variation delta d of corresponding d according to formula 7, by repeatedly measuring Δ d and to the measured value weighted mean, just can improve the measuring accuracy of Δ d after handling, calculate the magnetostriction coefficient of iron-nickel alloy sample 3 to be measured according to formula α=Δ l/l after learning Δ d.

Emulation experiment:

Utilize the MATLAB software simulation to measure the magnetostriction coefficient of the iron-nickel alloy sample 3 to be measured of long 200mm, and the feasibility of checking multi-beam laser heterodyne second harmonic measuring method.Employed H _o Solid state laser 8 wavelength X=2050nm, this laser is to eye-safe; Drive coil 2 is 200 circles/cm; Generally plane mirror 5 and the refractive index of disregarding medium between the thin thickness glass plate 6 are got n=1; The photosurface aperture of photodetector 12 is R=1mm.The sensitivity of photodetector 12 is 1A/W.Get galvanometer 10 amplitude x ₀=0.0001m.In the emulation experiment process, magnetic saturation can not take place in the electric current that requires to be added in drive coil 2.

The Fourier transform frequency spectrum of the multi-beam laser heterodyne second harmonic signal that obtains through signal Processing as shown in Figure 3, wherein solid line is under the laser oblique incidence situation, the Fourier transform frequency spectrum of corresponding multi-beam laser heterodyne second harmonic signal when measuring iron-nickel alloy sample 3 length variations amount Δ l to be measured; Dotted line is under the laser normal incidence situation, the Fourier transform frequency spectrum of corresponding multi-beam laser heterodyne second harmonic signal when measuring iron-nickel alloy sample 3 length variations amount Δ l to be measured.

As can see from Figure 3, provided the theoretical curve under the situation of normal incidence in the experiment, purpose is: in multi-beam laser heterodyne second harmonic signal spectrogram, the numerical value of the centre frequency of theoretical curve when the centre frequency of multi-beam laser heterodyne second harmonic signal frequency spectrum and normal incidence in the time of can obtaining oblique incidence simultaneously, like this, be easy to the ratio of two centre frequencies obtaining:

ζ=cos θ formula 10

Obtaining can calculating the size of laser refraction angle θ after disregarding thin thickness glass plate 6 by formula 10 under the situation of centre frequency, owing to ignored the thickness of disregarding thin thickness glass plate 6, so the size that incident angle θ 0 is approximately equal to refraction angle θ is:

${\mathrm{\&theta;}}_0\stackrel{\&CenterDot;}{=}\mathrm{\&theta;}=\arccos \mathrm{\&zeta;}$ Formula 11

Try to achieve the numerical value of K at last by formula 9, the final value that obtains to disregard variable in distance amount Δ d between thin thickness glass plate 6 and the plane mirror 5, because Δ d=Δ l, thereby can calculate the magnetostriction coefficient of iron-nickel alloy sample 3 to be measured under any incident angle situation according to formula α=Δ l/l.

In theoretical derivation, ignored the thickness of disregarding thin thickness glass plate 6 and promptly do not considered of the influence of the reflected light of device rear surface the heterodyne second harmonic signal, but in fact the thickness of thin glass plate is the 1mm that is generally less than that exists, for overcoming this influence, according to formula 7 as can be seen, the frequency distribution of the multiple beam heterodyne second harmonic signal that the reflected light of thin glass plate rear surface produces has added the interference that wave filter just can filtering low frequency heterodyne second harmonic signal in the experiment light path near the zero-frequency of frequency spectrum.Utilize above-mentioned multi-beam laser heterodyne second harmonic mensuration, continuous analog eight groups of data, obtained the simulation result of iron-nickel alloy sample 3 magnetostriction coefficients to be measured under the different current conditions, as shown in table 1.

Under the different current conditions of table 1, the actual value α of magnetostriction coefficient and analogue value α _i

Need to prove: the emulation experiment data of utilizing table 1, can calculate the simulation value of magnetostriction coefficient under the different current conditions according to formula α=Δ l/l, finally obtaining the simulation result maximum relative error is 0.8%, like this we as can be seen the precision of this method be very high.Simultaneously, the analysis data it can also be seen that, under the situation of current stabilization, systematic error that environment brings and reading error are negligible in emulation, and the error in the emulation experiment mainly comes from trueness error after the Fast Fourier Transform (FFT) (FFT) and the round-off error in the computation process.

Above content be in conjunction with concrete preferred implementation to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For this person of an ordinary skill in the technical field, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to the definite scope of patent protection of claims that the present invention submits to.

Claims (8)

1. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic is measured the device of magnetostriction coefficient, it is characterized in that: this device by first hold-down bars (1-1), second hold-down bars (1-2), drive coil (2), iron-nickel alloy sample to be measured (3), D.C. regulated power supply (4), plane mirror (5), disregard thin thickness glass plate (6), polarizing beam splitter mirror PBS (7), H ₀Solid state laser (8), quarter-wave plate (9), galvanometer (10), convergent lens (11), photodetector (12) and signal processing system (13) are formed,

D.C. regulated power supply (4) is used for providing working power to drive coil (2), iron-nickel alloy sample to be measured (3) is placed in the drive coil (2) between two parties, one end of fixedly connected first hold-down bars of one end of iron-nickel alloy sample to be measured (3) (1-1), the other end of this first hold-down bars (1-1) fixedly installs, one end of fixedly connected second hold-down bars of the other end of iron-nickel alloy sample to be measured (3) (1-2), the non-reflecting surface of the bonding plane mirror of the other end (5) of this second hold-down bars (1-2), the axis normal of the reflecting surface of plane mirror (5) and iron-nickel alloy sample to be measured (3); First hold-down bars (1-1) is identical with second hold-down bars (1-2) size, and two hold-down barss, iron-nickel alloy sample to be measured (3) and the coaxial settings of drive coil (2); At the reflecting surface one lateral extent d place of plane mirror (5), be arranged with in parallel with this plane mirror (5) and disregard thin thickness glass plate (6);

H ₀The linearly polarized light that solid state laser (8) sends is incident to quarter-wave plate (9) after polarizing beam splitter mirror PBS (7) reflection, light beam after this quarter-wave plate (9) transmission is incident to the light receiving surface of galvanometer (10), after quarter-wave plate (9) transmission, be sent to polarizing beam splitter mirror PBS (7) once more through this galvanometer (10) beam reflected, light beam after this polarizing beam splitter mirror PBS (7) transmission is incident to disregards thin thickness glass plate (6), light beam after this disregards thin thickness glass plate (6) transmission is incident to the reflecting surface of plane mirror (5), light beam after this plane mirror (5) reflection obtains transmitted light through disregarding thin thickness glass plate (6) transmission once more, light beam after this transmitted light and the light entrance face reflection through disregarding thin thickness glass plate (6) all converges on the photosurface of photodetector (12) by convergent lens (11), and described photodetector (12) output electric signal is given signal processing system (13).

2. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic according to claim 1 is measured the device of magnetostriction coefficient, and it is characterized in that: described is 20mm apart from d.

3. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic according to claim 1 and 2 is measured the device of magnetostriction coefficient, and it is characterized in that: two equal cementations of end face of described first hold-down bars (1-1) and second hold-down bars (1-2) have nonmagnetic substance.

4. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic according to claim 1 and 2 is measured the device of magnetostriction coefficient, it is characterized in that: the other end of described first hold-down bars (1-1) fixedly installs and is fixed on the worktable or on the fixture for: the other end of first hold-down bars (1-1).

5. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic according to claim 1 and 2 is measured the device of magnetostriction coefficient, it is characterized in that: described galvanometer (10) is Doppler's galvanometer, and its simple harmonic oscillation equation and rate equation are respectively x (t)=x ₀Cos (ω _cT) and v (t)=-ω _cx ₀Sin (ω _cT), x in the formula ₀Be the amplitude of Doppler's galvanometer vibration, ω _cBe the angular frequency of Doppler's galvanometer, c is the light velocity, and t is the time.

6. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic according to claim 1 and 2 is measured the device of magnetostriction coefficient, it is characterized in that: described signal processing system (13) is made up of bandpass filter (13-1), prime amplifier (13-2), modulus converter A/D (13-3) and digital signal processor DSP (13-4)

The electric signal that described bandpass filter (13-1) is exported the photodetector (12) that receives carries out sending to prime amplifier (13-2) after the filtering, signal after prime amplifier (13-2) amplifies is exported to modulus converter A/D (13-3), and the signal after described modulus converter A/D (13-3) will be changed sends to digital signal processor DSP (13-4).

7. the device that adopts the described Doppler's galvanometer of claim 1 Sine Modulated multi-beam laser heterodyne second harmonic to measure magnetostriction coefficient is realized the method for Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic measurement magnetostriction coefficient, it is characterized in that the process of this method is:

At first, the iron-nickel alloy sample is carried out AC demagnetization, utilize two-dimentional adjustment rack to regulate plane mirror (5) and disregard the position of thin thickness glass plate (6), make plane mirror (5) and disregard thin thickness glass plate (6) be parallel to each other, contour, and to make between the reflecting surface of disregarding thin thickness glass plate (6) and plane mirror (5) be 20mm apart from d;

Then, adjust D.C. regulated power supply (4), make its output current minimum, and the driving power of opening galvanometer (10) makes galvanometer (10) begin to do simple harmonic oscillation; Simultaneously, open H ₀Solid state laser (8),

At last, adjust the output current of D.C. regulated power supply (4), make the dull rising of its output current I, in this process, the electric signal of signal processing system (13) continuous acquisition photodetector (12) output, and the signal that collects handled, obtain plane mirror (5) and disregard variable in distance amount between the thin thickness glass plate (6), obtain the magnetostriction coefficient of iron-nickel alloy sample to be measured (3) according to this variable in distance amount:

α＝Δl/l，

In the formula, Δ l/ is the length variations amount of iron-nickel alloy sample to be measured (3) in magnetic field, is plane mirror (5) and disregards variable in distance amount between the thin thickness glass plate (6), and l is the original length of iron-nickel alloy sample to be measured (3).

8. Doppler's galvanometer Sine Modulated multi-beam laser heterodyne second harmonic according to claim 7 is measured the method for magnetostriction coefficient, it is characterized in that: to the electric signal of described signal processing system (13) continuous acquisition photodetector (12) output, and the signal that collects handled, the process that obtains plane mirror (5) and disregard the variable in distance amount between the thin thickness glass plate (6) is:

Linearly polarized light shines on galvanometer (10) front surface after passing through polarizing beam splitter mirror PBS (7) and quarter-wave plate (9) successively, the different reflected light of being modulated by galvanometer (10) constantly pass through quarter-wave plate (9) back again and disregard on the thin thickness glass plate (6) through oblique being mapped to of polarizing beam splitter mirror PBS (7), after being reflected by plane mirror (5), light through disregarding thin thickness glass plate (6) transmission converged on photodetector (12) photosurface by convergent lens (11), after the electric signal process prime amplifier (13-2) after photodetector (12) opto-electronic conversion with passing through the light of disregarding thin thickness glass plate (6) front surface reflection, obtain different parameter informations constantly to be measured behind modulus converter A/D (13-3) and the digital signal processor DSP (13-4); Because laser transmits the optical mixing of disregarding thin thickness glass plate (6) front surface after the reflected light of disregarding thin thickness glass plate (6) front surface and plane mirror (5) reflection k time is with k+1 time, produce the difference frequency signal that two amplitudes differ 2～3 orders of magnitude, the humorous frequency difference of the secondary in the described processing procedure is by the E that is detected _kE behind light and plane mirror (5) the k+2 secondary reflection _K+2What optical mixing produced;

When laser with incident angle θ ₀Incident field when thin thickness glass plate (6) front surface is disregarded in oblique incidence is E (t)=E _lExp (i ω ₀T), the simple harmonic oscillation equation of galvanometer (10) and rate equation are respectively x (t)=x ₀Cos (ω _cT) and v (t)=-ω _cx ₀Sin (ω _cT); Because the motion of galvanometer (10), catoptrical frequency becomes ω=ω ₀(1-2 ω _cx ₀Sin (ω _cT)/c), parameter ω in the formula ₀Be laser angular frequency, parameter x ₀Be the amplitude of galvanometer (10) vibration, parameter ω _cBe the angular frequency of galvanometer (10), c is the light velocity; Then t-L/c arrives the reflection light field of plane mirror (5) front surface constantly and is:

E ₀(t)＝α ₀E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-L/c))/c)

Formula 1

(t-L/c)+ω ₀x ₀cos(ω _c(t-L/c))/c]}

In the formula, parameter alpha ₀=r, r are the reflection coefficient of thin glass plate (6); L is that galvanometer (10) is to the light path of disregarding thin thickness glass plate (6) front surface; E _lBe the amplitude constant;

Light through disregarding thin thickness glass plate (6) transmission is constantly repeatedly reflected by plane mirror (5) rear surface and repeatedly transmits the front surface of disregarding thin thickness glass plate (6) in difference, and the expression formula of its transmitted light is write as following form respectively:

E ₁(t)＝α ₁E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+2ndcosθ)/c))/c)

(t-(L+2ndcosθ)/c)+ω ₀x ₀cos(ω _c(t-(L+2ndcosθ)/c))/c]}

E ₂(t)＝α ₂Elexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+4ndcosθ)/c))/c)

(t-(L+4ndcosθ)/c)+ω ₀x ₀cos(ω _c(t-(L+4ndcosθ)/c))/c]}

E ₃(t)＝α ₃E _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+6ndcosθ)/c))/c)

(t-(L+6ndcos θ)/c)+ω ₀x ₀Cos (ω _c(t-(L+6ndcos θ)/c))/c] } formula 2

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E _m(t)＝α _mE _lexp{i[ω ₀(1-2ω _cx ₀sin(ω _c(t-(L+2mndcosθ)/c))/c)

(t-(L+2mndcosθ)/c)+ω ₀x ₀cos(ω _c(t-(L+2mndcosθ)/c))/c]}

Wherein, the subscript m value is 0,1,2 ..., n is for disregarding the refractive index of medium between thin thickness glass plate (6) and the plane mirror (5), α ₁=β ²R ' ..., α _m=β ²R ' ^mr ^M-1, β is the transmission coefficient of thin glass plate (6), and r ' is the reflection coefficient of plane mirror (5), and parameter d is for disregarding thin thickness glass plate (6) to the distance of plane mirror (5), and θ is that incident light sees through the refraction angle of disregarding behind the thin thickness glass plate,

Total light field that photodetector (12) receives is expressed as:

E (t)=E ₀(t)+E ₁(t)+... + E _m(t) formula 3

Then the photocurrent of photodetector (12) output is expressed as:

$I=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{1}{Z}\underset{S}{\&Integral;\&Integral;}\frac{1}{2}[E_0\left(t\right)+E_1\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;+E_m\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;]{[E_0\left(t\right)+E_1\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;+E_m\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;]}^{*}\mathrm{ds}$ Formula 4

Wherein, parameter e is an electron charge, and parameter Z is the intrinsic impedance of photodetector (12) surface dielectric, parameter η is a quantum efficiency, and parameter S is the area of photodetector (12) photosurface, and parameter h is a Planck's constant, parameter v is a laser frequency, * number expression complex conjugate;

The electric current of intermediate frequency that arrangement obtains the heterodyne signal second harmonic is:

$I_{\mathrm{if}}=\frac{\mathrm{\&eta;e}}{2\mathrm{hv}}\frac{1}{Z}\underset{s}{\&Integral;\&Integral;}\underset{p=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{j=p+2}{\overset{\&infin;}{\mathrm{\&Sigma;}}}(E_p\left(t\right){E_j}^{*}\left(t\right)+{E_p}^{*}\left(t\right)E_j\left(t\right))\mathrm{ds}$ Formula 5

With (1) formula and (2) formula substitution (5) formula, net result is:

$\begin{array}{c}{I}_{\mathrm{IF}}=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{\mathrm{\&pi;}}{Z}{E}_0^2\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{m-p}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{j+p}{\mathrm{\&alpha;}}_j\cos [\frac{8\mathrm{nd}\cos {\mathrm{\&theta;\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0}{c^2}t+\frac{2{\mathrm{\&omega;}}_0{x}_0}{c}-\frac{4\mathrm{nd}{\mathrm{\&omega;}}_0\cos \mathrm{\&theta;}}{c}\\ -\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0(l+2\mathrm{pnd}\cos \mathrm{\&theta;})}{c^3}]\end{array}$ Formula 6

Ignore 1/c again ³Event after be reduced to:

$I_{\mathrm{IF}}=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{\mathrm{\&pi;}}{Z}{E}_0^2\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{m-p}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{j+p}{\mathrm{\&alpha;}}_j\cos (\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0}{c^2}t+\frac{2{\mathrm{\&omega;}}_0{x}_0-4\mathrm{nd}{\mathrm{\&omega;}}_0\cos \mathrm{\&theta;}}{c})$ Formula 7

Wherein parameter p and j are nonnegative integer;

According to formula 7, the frequency of second harmonic signal is designated as:

$f=8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left({2\mathrm{\&pi;c}}^2\right)=4\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left({\mathrm{\&pi;c}}^2\right)=\mathrm{Kd}$ Formula 8

Learn that according to formula 8 frequency of second harmonic signal is with plane mirror (5) and disregard being directly proportional apart from d between the thin thickness glass plate (6), scale-up factor is:

$K=4n\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left({\mathrm{\&pi;c}}^2\right)$ Formula 9

By measuring second harmonic frequency, promptly measure disregard between thin thickness glass plate (6) and the plane mirror (5) apart from d, when d changes, measure the variation delta d of corresponding d according to formula 7, learn the magnetostriction coefficient that calculates iron-nickel alloy sample to be measured (3) behind the Δ d according to formula α=Δ l/l.

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