CN102253002B - Method for measuring electrostriction coefficient of sinusoidal modulation multi-beam laser heterodyne second harmonic waves by utilizing Doppler vibration mirror - Google Patents

Abstract

The invention relates to a method for measuring the electrostriction coefficient of sinusoidal modulation multi-beam laser heterodyne second harmonic waves by utilizing a Doppler vibration mirror and particularly relates to a method for measuring electrostriction coefficient. The method is provided for solving the problems of low acquisition laser difference frequency signal quality and low signal processing computing speed of the existing laser heterodyne measuring technique in the measurement process of the electrostriction coefficient. In the method provided by the invention, the reflection surface of a second plane reflector is parallel to a thin glass plate; a vibration mirror starts simple harmonic vibration; an H0 solid laser is simultaneously turned on to adjust output voltage signals of a high-voltage power supply; simultaneously, a signal processing system continuously collects and processes electric signals which are output by a photoelectric detector to obtain the distance variable quantity between the second plane reflector and the rear surface of the thin glass plate, thereby obtaining the electrostriction coefficient of a piezoelectric ceramic pipe to be measured; and the method has the advantages that the quality of collected laser difference frequency signals is high and computation speed of signal processing computing is high. The method can be widely used in the fields of relative laser wind measuring radars and the like.

Description

Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic is measured the method for electrostriction coefficient

Technical field

The present invention relates to a kind of method of measuring electrostriction coefficient.

Background technology

All relate in the Mechatronic Systems and device of automatic control, driver often is considered to one of the most key factor that limits its performance and life-span, and in numerous type of drivers, the piezoelectric driver is fast because of its response, bearing capacity is high, energy consumption is low and price is low etc., and characteristics receive much concern.At present, the piezoelectric driver successfully is applied in numerous technical fields such as laser resonant cavity, precision positioning, Precision Machining, intelligence structure, bioengineering, Aero-Space, telecommunications, auto industry, joint of robot, medicine equipment, and is forming an industry that has a high potential.Therefore, the exploitation for piezoelectric new material, new technology and driver new technology has been subject to increasingly extensive attention with application.At occurring in nature, most of crystal all have piezoelectric effect, yet the piezoelectric effect of most of crystal is very faint, does not have practical value.Quartz is the good piezoelectric of crystal performance.Along with the development of science and technology, made piezoelectric ceramics is come out one after another such as polycrystalline piezoelectrics such as barium titanate, lead zirconate titanates (PZT), and uses more and more extensive.

The electrostriction coefficient of piezoelectric crystal has reflected the attribute of material itself, measures the electrostriction coefficient of material, and is not only significant to the development of new material, and is one of important indicator of the selection of material.At present, the method for mensuration electrostriction coefficient mainly contains laser interferance method, optical lever method, capacitance method, electric vortex method and Digital Speckle Correlation Method etc.But all there is the shortcoming of self in every kind of method, so precision can't improve again, can not satisfy the requirement of present high-acruracy survey.

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 large 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.The 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 electrostriction coefficient existence, the slow problem of arithmetic speed that signal is processed.

Summary of the invention

The present invention is lower in the collection laser difference frequency signal quality of measuring the electrostriction coefficient existence in order to solve the existing laser heterodyne measurement technology that adopts, the slow problem of arithmetic speed that signal is processed, and the Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic that proposes is measured the method for electrostriction coefficient.

Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic is measured the method for electrostriction coefficient, and it is based on Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic and measures the electrostriction coefficient realization, and described system is by H ₀Solid state laser, quarter-wave plate, galvanometer, the first plane mirror, polarizing beam splitter mirror PBS, convergent lens, thin glass plate, the second plane mirror, piezoelectric ceramic tube to be measured, two-dimentional adjustment rack, high-voltage power supply, photodetector and signal processing system form;

H ₀The linearly polarized light that solid state laser sends is incident to polarizing beam splitter mirror PBS after the reflection of the first plane mirror, light beam after this polarizing beam splitter mirror PBS reflection is incident to the light receiving surface of galvanometer after the quarter-wave plate transmission, light beam through this vibration mirror reflected is sent to polarizing beam splitter mirror PBS again after the quarter-wave plate transmission, light beam after this polarizing beam splitter mirror PBS transmission is incident to thin glass plate, light beam after this thin glass plate transmission is incident to the second plane mirror, this light beam interreflection and transmit thin glass plate repeatedly between the thin glass plate rear surface that is parallel to each other and the second plane mirror, obtain multi beam after the thin glass plate transmission light beam and the reflected light of thin glass plate front surface converge on the photosurface of photodetector by convergent lens together, described photodetector output electrical signals is to signal processing system; Distance between the reflecting surface of thin glass plate rear surface and the second plane mirror is d;

The center, the back side of described the second plane mirror is fixedly connected with an end of piezoelectric ceramic tube to be measured, the other end of this piezoelectric ceramic tube to be measured is fixed on the two-dimentional adjustment rack, and the reflecting surface of the central axis of described piezoelectric ceramic tube to be measured and described the second plane mirror is perpendicular; The inside surface of described piezoelectric ceramic tube to be measured is connected with outside surface by electrode and is connected with two voltage output ends of high-voltage power supply;

The method that described Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic is measured electrostriction coefficient is realized by following steps:

At first, by adjusting two-dimentional adjustment rack, reflecting surface and the thin glass plate of the second plane mirror that is fixedly connected with piezoelectric ceramic tube to be measured are parallel to each other, and to make between the reflecting surface of the second plane mirror and the thin glass plate be 4.25mm apart from d;

Then, adopt high-voltage power supply to provide driving voltage for piezoelectric ceramic tube to be measured, and the driving power of opening galvanometer make galvanometer begin vibration; Simultaneously, open H ₀Solid state laser;

At last, regulate the output voltage signal U of described high-voltage power supply, the electric signal of synchronous signal disposal system continuous acquisition photodetector output, and the signal that collects processed, and then obtain variable in distance amount between the second plane mirror and the thin glass plate rear surface, the electromagnetism that obtains piezoelectric ceramic tube to be measured according to the voltage signal of this variable in distance amount and high-voltage power supply output this moment causes coefficient of dilatation:

If after representing that with E piezoelectric ceramic tube surfaces externally and internally to be measured adds voltage, the electric field intensity of the radial electric field that between piezoelectric ceramic tube surfaces externally and internally to be measured, forms, represent the strain that piezoelectric ceramic tube to be measured is axial with ε, α represents the electrostriction coefficient of piezoelectric ceramic tube to be measured in the almostlinear zone, so obtain:

ε=α E formula 1

Have by following formula:

$\frac{\mathrm{\Δl}}{l}=\mathrm{\α}\frac{U}{d_0}$ Formula 2

Finally obtain:

$\mathrm{\α}=\frac{\mathrm{\Δ}{\mathrm{ld}}_0}{\mathrm{lU}}$ Formula 3

In the formula, Δ l is the length increment of piezoelectric ceramic tube to be measured before and after powering up, and namely equals the variable in distance amount between the second plane mirror and the thin glass plate, and l is the original length of the not powering state of piezoelectric ceramic tube to be measured; d ₀It is the wall thickness of piezoelectric ceramic tube to be measured;

Described signal processing system is according to the electric signal of continuous acquisition photodetector output, and the signal that collects is processed, and then the process that obtains the variable in distance amount Δ d between the second plane mirror and the thin glass plate is:

Because the optical mixing that transmit glass front of laser after the reflected light of thin glass plate front surface and the reflection of the second plane mirror plane of incidence k time are with k+1 time produces the difference frequency signal that two amplitudes differ 2～3 orders of magnitude,

The humorous frequency difference of the secondary of described method is the E that detects rear surface k secondary reflection _kWith the E behind the k+2 secondary reflection of rear surface _K+2Optical mixing produces;

Do not consider in the situation of thin glass plate self thickness, when laser with incidence angle θ ₀Incident field during oblique incidence thin glass plate front surface is E (t)=E _lExp (i ω ₀T),

The simple harmonic oscillation equation of galvanometer is x (t)=x ₀Cos (ω _cT);

The rate equation of galvanometer be v (t)=-ω _cx ₀Sin (ω _cT),

Catoptrical frequency becomes ω=ω ₀(1-2 ω _cx ₀Sin (ω _cT)/c), parameter ω in the following formula ₀Be laser angular frequency, parameter x ₀Be the amplitude of galvanometer vibration, parameter ω _cBe the angular frequency of galvanometer, c is the light velocity, and t is the time;

Then t-L/c constantly arrives the reflection light field of thin glass plate and is:

E ₀(t)=α ₀E _lExp{i[ω ₀(1-2 ω _cx ₀Sin (ω _c(t-L/c))/c) formula 4

(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; L is that galvanometer is to the distance of thin glass plate front surface; E _lBe the amplitude constant;

Constantly also repeatedly transmitted the front surface of thin glass plate by the second plane mirror rear surface Multi reflection in difference through the light of thin glass plate transmission, the expression formula of its transmitted light is write respectively as following form:

E _l(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 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 5

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 the refractive index of medium between thin glass plate and the second plane mirror, α ₁=β ²R ' ..., α _m=β ²R ' ^mr ^M-1, β is the transmission coefficient of thin glass plate, r ' is the reflection coefficient of the second plane mirror, parameter d be thin glass plate to the distance of the second plane mirror, θ is the refraction angle after incident light sees through thin glass plate,

Total light field that photodetector receives is expressed as:

E (t)=E ₀(t)+E ₁(t)+... + E _m(t) formula 6

Then the photocurrent of photodetector output is expressed as:

$I=\frac{\mathrm{\ηe}}{\mathrm{hv}}\frac{1}{Z}\∫\underset{S}{\∫}\frac{1}{2}[E_0\left(t\right)+E_1\left(t\right)+\·\·\·+E_m\left(t\right)+\·\·\·]{[E_0\left(t\right)+E_1\left(t\right)+\·\·\·+E_m\left(t\right)+\·\·\·]}^{*}\mathrm{ds}$ Formula 7

Wherein, parameter e is electron charge, and parameter Z is the intrinsic impedance of detector surface medium, and parameter η is quantum efficiency, and parameter S is the area of detector photosurface, and parameter h is Planck's constant, and parameter v is laser frequency, * number expression complex conjugate;

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

$I_{\mathrm{if}}=\frac{\mathrm{\&eta;e}}{2\mathrm{hv}}\frac{1}{Z}\&Integral;\underset{S}{\&Integral;}\underset{p=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{j=p+2}{\overset{\&infin;}{\mathrm{\&Sigma;}}}(E_p\left(t\right){E_j}^{*}\left(t\right)+{E_p}^{*}\left(t\right)E_j\left(t\right))\mathrm{<figure-callout\; id="8"\; label="ds\; Formula"\; filenames="HDA0000065401380000011.png"\; state="\{\{state\}\}">ds</figure-callout>}$ Formula 8

With formula 4 and formula 5 substitution formula 8, the result is:

$I_{\mathrm{IF}}=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{\mathrm{\&pi;}}{Z}{E}_0^2\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{m-p}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{j+p}{\mathrm{\&alpha;}}_j\cos [\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0}{c^2}t+\frac{2{\mathrm{\&omega;}}_0{x}_0}{c}-\frac{4\mathrm{nd}{\mathrm{\&omega;}}_0\cos \mathrm{\&theta;}}{c}$ Formula 9

$-\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0(L+2\mathrm{pnd}\cos \mathrm{\&theta;})}{c^3}]$

Ignore 1/c 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 10

Wherein, parameter p and j are nonnegative integer;

According to formula 10, the frequency of heterodyne 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 11

Draw according to formula 11, being directly proportional apart from d between the frequency of heterodyne second harmonic signal and thin glass plate and the second plane mirror, 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 12

By formula 11 measure between thin glass plate and the second plane mirror apart from d, when d changes, measure the variation delta d of corresponding d according to formula 11, obtain Δ d basis

Obtain piezoelectric ceramic tube electrostriction coefficient to be measured.

The described measurement mechanism of the application and method not only have the traditional optical angle measurement technique have untouchable, precision is high and advantages of simple structure and simple, also has the outstanding advantages of the fast operation of the high and signal processing of the laser difference frequency signal quality of collection.

This paper is by introducing galvanometer 13 in light path, make the light signal of different constantly incidents add an optical frequency, satisfying under the condition of interfering through the reflected light of thin glass plate 9 and the light of the second plane mirror 6 Multi reflections 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 the process of measuring piezoelectric ceramic tube 7 electrostriction coefficients to be measured, obtained simultaneously comprising the frequency values of the information of metal length variable quantity at frequency domain, obtain the length variations amount after the signal demodulation, by repeatedly measuring piezoelectric ceramic tube to be measured 7 length that accurately to obtain with the variable quantity of electric current.Test as an example of iron-nickel alloy example, the relative error that electrostriction coefficient is measured is 0.3% only, has significantly improved measuring accuracy.The advantages such as the described method of the application is compared with other measuring method, and the multi-beam laser heterodyne second harmonic method is surveyed electrostriction coefficient and had that high room and time resolution, measuring speed are fast, the linearity good, antijamming capability is strong, dynamic response is fast, good reproducibility and measurement range are large; Experimental provision is simple in structure, power consumption is little, easy to operate; The experimental result error is little, the high many-sided advantage of precision.Simultaneously, the method experimental phenomena is obvious, and experimental data is reliable, and has directly with the exploitation of new material and to contact, so have actual using value, can be widely used in the engineering design fields such as coherent laser windfinding radar.

Description of drawings

Fig. 1 is the structural representation that Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic is measured the electrostriction coefficient system; Fig. 2 is the cut-open view of piezoelectric ceramic tube 7 to be measured; Fig. 3 is the multi-beam laser principle of interference figure between thin glass plate and the second plane mirror; Fig. 4 is the Fourier transform spectrogram of multi-beam laser heterodyne second harmonic signal; Fig. 5 is spectrogram corresponding to PZT length variations measurement amount under the different voltage condition, among the figure, from left to right, every curve respectively high-voltage power supply output voltage is in the situation of 800V, 700V, 600V, 500V, 400V, 300V, 200V and 100V, the spectrum curve of acquisition.

Embodiment

Embodiment one: present embodiment is described in conjunction with Fig. 1 to Fig. 5, the described Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic of present embodiment is measured the method for electrostriction coefficient, it is based on Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic and measures the electrostriction coefficient realization, and described system is by H0 solid state laser 2, quarter-wave plate 12, galvanometer 13, the first plane mirror 3, polarizing beam splitter mirror PBS11, convergent lens 10, thin glass plate 9, the second plane mirror 6, piezoelectric ceramic tube 7 to be measured, two dimension adjustment rack 8, high-voltage power supply, photodetector 4 and signal processing system 5 form;

The linearly polarized light that H0 solid state laser 2 sends is incident to polarizing beam splitter mirror PBS11 after 3 reflections of the first plane mirror, light beam after this polarizing beam splitter mirror PBS11 reflection is incident to the light receiving surface of galvanometer 13 after quarter-wave plate 12 transmissions, light beam through these galvanometer 13 reflections is sent to polarizing beam splitter mirror PBS11 again after quarter-wave plate 12 transmissions, light beam after this polarizing beam splitter mirror PBS11 transmission is incident to thin glass plate 9, light beam after these thin glass plate 9 transmissions is incident to the second plane mirror 6, this light beam interreflection and transmit thin glass plate repeatedly between thin glass plate 9 rear surfaces that are parallel to each other and the second plane mirror 6, obtain multi beam after thin glass plate 9 transmissions light beam and the reflected light of thin glass plate front surface converge on the photosurface of photodetector 4 by convergent lens 10 together, described photodetector 4 output electrical signals are to signal processing system 5; Distance between the reflecting surface of thin glass plate 9 rear surfaces and the second plane mirror 6 is d;

The center, the back side of described the second plane mirror 6 is fixedly connected with an end of piezoelectric ceramic tube 7 to be measured, the other end of this piezoelectric ceramic tube 7 to be measured is fixed on the two-dimentional adjustment rack 8, and the reflecting surface of the central axis of described piezoelectric ceramic tube 7 to be measured and described the second plane mirror 6 is perpendicular; The inside surface 7-1 of described piezoelectric ceramic tube to be measured 7 and outside surface 7-2 are connected with two voltage output ends of high-voltage power supply by electrode 1 respectively;

The method that described Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic is measured electrostriction coefficient is realized by following steps:

At first, by adjusting two-dimentional adjustment rack 8, the reflecting surface of the second plane mirror 6 that is fixedly connected with piezoelectric ceramic tube 7 to be measured and thin glass plate 9 are parallel to each other, and to make between the reflecting surface of the second plane mirror 6 and the thin glass plate 9 be 4.25mm apart from d;

Then, adopt high-voltage power supply to provide driving voltage for piezoelectric ceramic tube 7 to be measured, and the driving power of opening galvanometer 13 make galvanometer 13 begin vibration; Simultaneously, open H0 solid state laser 2.

At last, regulate the output voltage signal U of described high-voltage power supply, the electric signal of synchronous signal disposal system 5 continuous acquisition photodetectors 4 outputs, and the signal that collects processed, and then obtain variable in distance amount between the second plane mirror 6 and thin glass plate 9 rear surfaces, the electromagnetism that obtains piezoelectric ceramic tube 7 to be measured according to the voltage signal of this variable in distance amount and high-voltage power supply output this moment causes coefficient of dilatation:

If after representing that with E piezoelectric ceramic tube 7 surfaces externally and internallies to be measured add voltage, the electric field intensity of the radial electric field that between piezoelectric ceramic tube 7 surfaces externally and internallies to be measured, forms, represent the strain that piezoelectric ceramic tube to be measured 7 is axial with ε, α represents the electrostriction coefficient of piezoelectric ceramic tube 7 to be measured in the almostlinear zone, so obtain:

ε=α E formula 1

Have by following formula:

$\frac{\mathrm{\&Delta;l}}{l}=\mathrm{\&alpha;}\frac{U}{d_0}$ Formula 2

Finally obtain:

$\mathrm{\&alpha;}=\frac{\mathrm{\&Delta;}{\mathrm{ld}}_0}{\mathrm{<figure-callout\; id="3"\; label="lU\; Formula"\; filenames="HDA0000065401380000011.png"\; state="\{\{state\}\}">lU</figure-callout>}}$ Formula 3

In the formula, Δ l is the length increment of piezoelectric ceramic tube 7 to be measured before and after powering up, and namely equals the variable in distance amount between the second plane mirror 6 and the thin glass plate 9, and l is the original length of the not powering state of piezoelectric ceramic tube 7 to be measured; d ₀It is the wall thickness of piezoelectric ceramic tube 7 to be measured;

Described signal processing system 5 is according to the electric signal of continuous acquisition photodetector 4 output, and the signal that collects is processed, and then the process that obtains the variable in distance amount Δ d between the second plane mirror 6 and the thin glass plate 9 is:

Because the optical mixing that transmit glass front of laser after the reflected light of thin glass plate 9 front surfaces and the reflection of the second plane mirror 6 planes of incidence k time are with k+1 time produces the difference frequency signal that two amplitudes differ 2～3 orders of magnitude,

The humorous frequency difference of the secondary of described method is the E that detects rear surface k secondary reflection _kWith the E behind the k+2 secondary reflection of rear surface _K+2Optical mixing produces;

Do not consider in the situation of thin glass plate 9 self thickness, when laser with incidence angle θ ₀During oblique incidence thin glass plate 9 front surface, establishing incident field is E (t)=E _lExp (i ω ₀T),

The simple harmonic oscillation equation of galvanometer 13 is x (t)=x ₀Cos (ω _cT);

The rate equation of galvanometer 13 be v (t)=-ω _cx ₀Sin (ω _cT),

Catoptrical frequency becomes ω=ω ₀(1-2 ω _cx ₀Sin (ω _cT)/c), parameter ω in the following formula ₀Be laser angular frequency, parameter x ₀Be the amplitude of galvanometer 13 vibrations, parameter ω _cBe the angular frequency of galvanometer 13, c is the light velocity, and t is the time;

Then t-L/c constantly arrives the reflection light field of thin glass plate 9 and is:

E ₀(t)=α ₀E _lExp{i[ω ₀(1-2 ω _cx ₀Sin (ω _c(t-L/c))/c) formula 4

(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 9; L is that galvanometer 13 is to the distance of disregarding thin thickness glass plate 9 front surfaces; E _lBe the amplitude constant;

Constantly also repeatedly transmitted the front surface of thin glass plate 9 by the second plane mirror 6 rear surface Multi reflections in difference through the light of thin glass plate 9 transmissions, the expression formula of its transmitted light is write respectively as following form:

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 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 5

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 the refractive index of medium between thin glass plate 9 and the second plane mirror 6, α ₁=β ²R ' ..., α _m=β ²R ' ^mr ^M-1, β is the transmission coefficient of thin glass plate 9, and r ' is the reflection coefficient of the second plane mirror 6, and parameter d is the distance of thin glass plate 9 to second plane mirrors 6, and θ is the refraction angle after incident light sees through thin glass plate 9,

Total light field that photodetector 4 receives is expressed as:

E (t)=E ₀(t)+E ₁(t)+... + E _m(t) formula 6

Then the photocurrent of photodetector 4 outputs is expressed as:

$I=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{1}{Z}\&Integral;\underset{S}{\&Integral;}\frac{1}{2}[E_0\left(t\right)+E_1\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;+E_m\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;]{[E_0\left(t\right)+E_1\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;+E_m\left(t\right)+\&CenterDot;\&CenterDot;\&CenterDot;]}^{*}\mathrm{<figure-callout\; id="7"\; label="ds\; Formula"\; filenames="HDA0000065401380000011.png"\; state="\{\{state\}\}">ds</figure-callout>}$ Formula 7

Wherein, parameter e is electron charge, and parameter Z is the intrinsic impedance of detector surface medium, and parameter η is quantum efficiency, and parameter S is the area of detector photosurface, and parameter h is Planck's constant, and parameter v is laser frequency, * number expression complex conjugate;

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

$I_{\mathrm{if}}=\frac{\mathrm{\&eta;e}}{2\mathrm{hv}}\frac{1}{Z}\&Integral;\underset{S}{\&Integral;}\underset{p=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{j=p+2}{\overset{\&infin;}{\mathrm{\&Sigma;}}}(E_p\left(t\right){E_j}^{*}\left(t\right)+{E_p}^{*}\left(t\right)E_j\left(t\right))\mathrm{<figure-callout\; id="8"\; label="ds\; Formula"\; filenames="HDA0000065401380000011.png"\; state="\{\{state\}\}">ds</figure-callout>}$ Formula 8

With formula 4 and formula 5 substitution formula 8, the result is:

$I_{\mathrm{IF}}=\frac{\mathrm{\&eta;e}}{\mathrm{hv}}\frac{\mathrm{\&pi;}}{Z}{E}_0^2\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{m-p}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_{j+p}{\mathrm{\&alpha;}}_j\cos [\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0}{c^2}t+\frac{2{\mathrm{\&omega;}}_0{x}_0}{c}-\frac{4\mathrm{nd}{\mathrm{\&omega;}}_0\cos \mathrm{\&theta;}}{c}$ Formula 9

$-\frac{8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0(L+2\mathrm{pnd}\cos \mathrm{\&theta;})}{c^3}]$

Ignore 1/c 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 10

Wherein, parameter p and j are nonnegative integer;

According to formula 10, the frequency of heterodyne second harmonic signal is designated as:

$f=8\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left(2\mathrm{\&pi;}{c}^2\right)=4\mathrm{nd}\cos \mathrm{\&theta;}{\mathrm{\&omega;}}_0{\mathrm{\&omega;}}_c^2{x}_0/\left(\mathrm{\&pi;}{c}^2\right)=\mathrm{<figure-callout\; id="11"\; label="Kd\; Formula"\; filenames="HDA0000065401380000011.png"\; state="\{\{state\}\}">Kd</figure-callout>}$ Formula 11

Draw according to formula 11, being directly proportional apart from d between the frequency of heterodyne second harmonic signal and thin glass plate 9 and the second plane mirror 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 12

By formula 11 measure between thin glass plate 9 and the second plane mirror 6 apart from d, when d changes, measure the variation delta d of corresponding d according to formula 11, obtain Δ d basis

Obtain piezoelectric ceramic tube 7 electrostriction coefficients to be measured.

Embodiment two: present embodiment and embodiment one difference are that piezoelectric ceramic tube 7 to be measured adopts the PZT piezoelectric ceramic body to make.Other composition is identical with embodiment one with connected mode.

Embodiment three: present embodiment and embodiment one difference are in the system of measuring electrostrictive coefficient by using multi-beam laser heterodyne quadratic harmonic method, signal processing system 5 is by filtering circuit 5-1, pre-amplification circuit 5-2, analog to digital conversion circuit A/D and digital signal processor DSP form, the electric signal that described filtering circuit 5-1 exports the photodetector 4 that receives carries out sending to pre-amplification circuit 5-2 after the filtering, signal after described pre-amplification circuit 5-2 amplifies is exported to analog to digital conversion circuit A/D, and the signal after analog-digital conversion circuit as described A/D will change sends to digital signal processor DSP.Other composition is identical with embodiment one with connected mode.

Based on multi-beam laser heterodyne second harmonic measuring system shown in Figure 1, utilize the MATLAB software simulation to measure long 15.00mm, thickness is the PZT material electrostriction coefficient of 1.50mm, and to get PZT material electrostriction coefficient theoretical value be 1.85 * 10 ^-9M/V, the feasibility of checking multi-beam laser heterodyne second harmonic measuring method.Employed H ₀Wavelength X=the 2050nm of solid state laser 2, this laser is to eye-safe; Generally the refractive index of medium is got n=1 between the second plane mirror 6 and the thin glass plate 9; The photosurface aperture of photodetector 4 is R=1mm, and the sensitivity of photodetector 4 is 1A/W.Get the amplitude x of galvanometer 13 ₀=0.0001m, vibration frequency is ω _c=10.365kHz.In the emulation experiment process, the voltage that requires to be added in piezoelectric ceramic tube 7 to be measured slowly is increased to approximately 800V according to certain step-length by 0V, records simultaneously piezoelectric ceramic tube 7 length variations numberical value of quantity Δ l to be measured.

Can obtain by emulation experiment, the Fourier transform frequency spectrum of processing the multi-beam laser heterodyne second harmonic signal obtain through signal as shown in Figure 4, solid line is in the laser oblique incidence situation among the figure, measures the Fourier transform frequency spectrum of piezoelectric ceramic tube 7 length variations amount Δ l to be measured and corresponding multi-beam laser heterodyne second harmonic signal; Dotted line is in the laser normal incidence situation among the figure, the Fourier transform frequency spectrum of corresponding multi-beam laser heterodyne second harmonic signal when measuring piezoelectric ceramic tube 7 length variations amount Δ l to be measured.

As shown in Figure 4, emulation experiment has provided the theoretical curve in the situation of normal incidence, purpose is: in multi-beam laser heterodyne second harmonic signal spectrum figure, the numerical value of the centre frequency of theoretical curve when the centre frequency of first main peak of multi-beam laser heterodyne second harmonic signal spectrum and normal incidence when obtaining oblique incidence simultaneously obtains the ratio of two centre frequencies with this:

ζ=cos θ formula 13

After obtaining centre frequency, calculate the size of laser refraction angle θ behind thin glass plate 9 by formula 13, and then obtain incidence angle θ according to refraction law ₀Size, try to achieve at last the numerical value of K by formula 12, the final value that obtains variable in distance amount Δ d between thin glass plate 9 and the second plane mirror 6 because Δ d=Δ l, thereby calculates the electrostriction coefficient of piezoelectric ceramic tube 7 to be measured in any incident angle situation according to formula 3.

Simultaneously, emulation experiment has obtained under the different voltage condition, multi-beam laser heterodyne second harmonic corresponding multi-beam laser heterodyne second harmonic signal Fourier transform frequency spectrum when measuring piezoelectric ceramic tube 7 length variations amount to be measured, as shown in Figure 5, as shown in Figure 5, along with the increase of voltage, the relative position of frequency spectrum moves namely along with the increase of voltage to the low frequency direction, and frequency reduces.Its reason is: in the situation that piezoelectric ceramic tube to be measured 7 electrostriction coefficients are constant, voltage and piezoelectric ceramic tube to be measured 7 length variations amounts are proportional, the distance that piezoelectric ceramic tube 7 length to be measured increase between thin glass plate 9 and the second plane mirror 6 thereupon when voltage increases reduces thereupon, because the pass apart from d between frequency f and the second plane mirror 6 and the convergent lens 10 is f=Kd, in the constant situation of K, frequency f and d are linear spectrum, therefore, frequency also reduces the increase along with voltage thereupon during reducing apart from d between plane mirror 6 and the convergent lens 10, the relative position of frequency spectrum moves to the low frequency direction, and Fig. 5 has verified the correctness of front theoretical analysis well.Need to prove, because heterodyne detection is a kind of detection mode of nearly diffraction limit, detection sensitivity is high, so the signal to noise ratio (S/N ratio) of the heterodyne second harmonic signal of Fig. 4 and Fig. 5 is very high.

In theoretical derivation, ignored the thickness of thin glass plate 9 and do not considered that namely the reflected light of its rear surface is on the impact of heterodyne second harmonic signal, but in fact the thickness of thin glass plate 9 is the 1mm that are generally less than that exist, for overcoming this impact, draw according to formula 12, the frequency distribution of the multiple beam heterodyne second harmonic signal that the reflected light of thin glass plate 9 rear surfaces produces has added the interference that wave filter just can filtering low frequency heterodyne second harmonic signal in the emulation 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 piezoelectric ceramic tube 7 length variations amounts to be measured under the different voltage condition, as shown in table 1.

Under the different voltage condition of table 1, the simulation result of piezoelectric ceramic tube 7 length variations amounts to be measured and corresponding electrostriction coefficient

Need to prove: utilize the emulation experiment data of table 1, the mean value that calculates the electrostriction coefficient of piezoelectric ceramic tube 7 to be measured according to formula 2 is 1.855143 * 10 ^-9M/V is 0.3% with regard to the relative error that obtains analog result like this, and the measuring accuracy that can find out the method is very high.Simultaneously, the analysis data it can also be seen that, slowly increasing in the alive situation, the 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 is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that implementation 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 (3)

1. Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic is measured the method for electrostriction coefficient, and it is based on Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic and measures the electrostriction coefficient realization, and described system is by H ₀Solid state laser (2), quarter-wave plate (12), galvanometer (13), the first plane mirror (3), polarizing beam splitter mirror PBS(11), convergent lens (10), thin glass plate (9), the second plane mirror (6), piezoelectric ceramic tube to be measured (7), two-dimentional adjustment rack (8), high-voltage power supply, photodetector (4) and signal processing system (5) form;

H ₀The linearly polarized light that solid state laser (2) sends is incident to polarizing beam splitter mirror PBS(11 after the first plane mirror (3) reflection), through this polarizing beam splitter mirror PBS(11) light beam after the reflection is incident to the light receiving surface of galvanometer (13) after quarter-wave plate (12) transmission, light beam through this galvanometer (13) reflection is sent to polarizing beam splitter mirror PBS(11 again after quarter-wave plate (12) transmission), through this polarizing beam splitter mirror PBS(11) light beam after the transmission is incident to thin glass plate (9), light beam after this thin glass plate (9) transmission is incident to the second plane mirror (6), this light beam interreflection and transmit thin glass plate repeatedly between the thin glass plate that is parallel to each other (9) rear surface and the second plane mirror (6), obtain multi beam after thin glass plate (9) transmission light beam and the reflected light of thin glass plate front surface converge on the photosurface of photodetector (4) by convergent lens (10) together, described photodetector (4) output electrical signals is to signal processing system (5); Distance between the reflecting surface of thin glass plate (9) rear surface and the second plane mirror (6) is d;

The center, the back side of described the second plane mirror (6) is fixedly connected with an end of piezoelectric ceramic tube to be measured (7), the other end of this piezoelectric ceramic tube to be measured (7) is fixed on the two-dimentional adjustment rack (8), and the reflecting surface of the central axis of described piezoelectric ceramic tube to be measured (7) and described the second plane mirror (6) is perpendicular; The inside surface (7-1) of described piezoelectric ceramic tube to be measured (7) is connected 7-2 with outside surface) be connected with two voltage output ends of high-voltage power supply by electrode (1) respectively;

The method that it is characterized in that described Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic measurement electrostriction coefficient is realized by following steps:

At first, by adjusting two-dimentional adjustment rack (8), reflecting surface and the thin glass plate (9) of the second plane mirror (6) that is fixedly connected with piezoelectric ceramic tube to be measured (7) are parallel to each other, and to make between the reflecting surface of the second plane mirror (6) and the thin glass plate (9) be 4.25mm apart from d;

Then, adopting high-voltage power supply is that piezoelectric ceramic tube to be measured (7) provides driving voltage, and the driving power of opening galvanometer (13) makes galvanometer (13) begin vibration; Simultaneously, open H ₀Solid state laser (2).

At last, regulate the output voltage signal U of described high-voltage power supply, the electric signal of synchronous signal disposal system (5) continuous acquisition photodetector (4) output, and the signal that collects processed, and then obtain variable in distance amount between the second plane mirror (6) and thin glass plate rear surface (9), obtain the electrostriction coefficient of piezoelectric ceramic tube to be measured (7) according to the voltage signal of this variable in distance amount and high-voltage power supply output this moment:

If after representing that with E piezoelectric ceramic tube to be measured (7) surfaces externally and internally adds voltage, the electric field intensity of the radial electric field that between piezoelectric ceramic tube to be measured (7) surfaces externally and internally, forms, represent the axial strain of piezoelectric ceramic tube to be measured (7) with ε, α represents the electrostriction coefficient of piezoelectric ceramic tube to be measured (7) in the almostlinear zone, so obtain:

ε=α E formula 1

Have by following formula:

Formula 2

Finally obtain:

Formula 3

In the formula, Δ l is the length increment of piezoelectric ceramic tube to be measured (7) before and after powering up, and namely equals the variable in distance amount between the second plane mirror (6) and the thin glass plate (9), and l is the original length of the not powering state of piezoelectric ceramic tube to be measured (7); d ₀It is the wall thickness of piezoelectric ceramic tube to be measured (7);

Described signal processing system (5) is according to the electric signal of continuous acquisition photodetector (4) output, and the signal that collects is processed, and then the process that obtains the variable in distance amount between the second plane mirror (6) and the thin glass plate (9) is:

Because the optical mixing that transmit glass front of laser after the reflected light of thin glass plate (9) front surface and the reflection of the second plane mirror (6) plane of incidence k time are with k+1 time produces the difference frequency signal that two amplitudes differ 2～3 orders of magnitude,

The humorous frequency difference of the secondary of described method is the E that detects rear surface k secondary reflection _kWith the E behind the k+2 secondary reflection of rear surface _K+2Optical mixing produces;

Do not consider in the situation of thin glass plate (9) self thickness, when laser with incidence angle θ ₀Incident field during oblique incidence thin glass plate (9) front surface is E (t)=E _lExp (i ω ₀T),

The simple harmonic oscillation equation of galvanometer (13) is x (t)=x ₀Cos (ω _cT);

The rate equation of galvanometer (13) be v (t)=-ω _cx ₀Sin (ω _cT),

Catoptrical frequency becomes ω=ω ₀(1-2 ω _cx ₀Sin (ω _cT)/c), parameter ω in the following formula ₀Be laser angular frequency, parameter x ₀Be the amplitude of galvanometer (13) vibration, parameter ω _cBe the angular frequency of galvanometer (13), c is the light velocity, and t is the time;

Then t-L/c constantly arrives the reflection light field of thin glass plate (9) and is:

E ₀(t)=α ₀E _lExp{i[ω ₀(1-2 ω _cx ₀Sin (ω _c(t-L/c))/c) formula 4

(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 (9); L is that galvanometer (13) is to the distance of disregarding thin thickness glass plate (9) front surface; E _lBe the amplitude constant;

Constantly also repeatedly transmitted the front surface of thin glass plate (9) by the second plane mirror (6) rear surface Multi reflection in difference through the light of thin glass plate (9) transmission, the expression formula of its transmitted light is write respectively as following form:

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

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

E ₂(t)=α ₂E _l?exp{i[ω ₀(1-2ω _cx ₀?sin(ω _c(t-(L+4nd?cosθ)/c))/c)

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

E ₃(t)=α ₃E _l?exp{i[ω ₀(1-2ω _cx ₀?sin(ω _c(t-(L+6nd?cosθ)/c))/c)

(t-(L+6nd cos θ)/c)+ω ₀x ₀Cos (ω _c(t-(L+6nd cos θ)/c))/c] } formula 5

.

.

.

E _m(t)=α _mE _l?exp{i[ω ₀(1-2ω _cx ₀?sin(ω _c(t-(L+2mnd?cosθ)/c))/c)

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

Wherein, the subscript m value is 0,1,2 ..., n is the refractive index of medium between thin glass plate (9) and the second plane mirror (6), α ₁=β ²R ' ..., α _m=β ²R ' ^mr ^M-1, β is the transmission coefficient of thin glass plate (9), r ' is the reflection coefficient of the second plane mirror (6), parameter d be thin glass plate (9) to the distance of the second plane mirror (6), θ is the refraction angle after incident light sees through thin glass plate (9),

Total light field that photodetector (4) receives is expressed as:

E (t)=E ₀(t)+E ₁(t)+... + E _m(t) formula 6

Then the photocurrent of photodetector (4) output is expressed as:

Formula 7

Wherein, parameter e is electron charge, and parameter Z is the intrinsic impedance of detector surface medium, and parameter η is quantum efficiency, and parameter S is the area of detector photosurface, and parameter h is Planck's constant, and parameter v is laser frequency, * number expression complex conjugate;

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

Formula 8

With formula 4 and formula 5 substitution formula 8, the result is:

Formula 9

Ignore 1/c ³Event after be reduced to:

Formula 10

Wherein, parameter p and j are nonnegative integer;

According to formula 10, the frequency of heterodyne second harmonic signal is designated as:

Formula 11

Draw according to formula 11, being directly proportional apart from d between the frequency of heterodyne second harmonic signal and thin glass plate (9) and the second plane mirror (6), scale-up factor is:

Formula 12

By formula 11 measure between thin glass plate (9) and the second plane mirror (6) apart from d, when d changes, measure the variation delta d of corresponding d according to formula 11, obtain Δ d basis

Obtain piezoelectric ceramic tube to be measured (7) electrostriction coefficient.

2. Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic according to claim 1 is measured the method for electrostriction coefficient, it is characterized in that piezoelectric ceramic tube to be measured (7) adopts the PZT piezoelectric ceramic body to make.

3. Doppler vibrating mirror sine modulation multi-beam laser heterodyne second harmonic according to claim 1 is measured the method for electrostriction coefficient, it is characterized in that in the system of measuring electrostrictive coefficient by using multi-beam laser heterodyne quadratic harmonic method, signal processing system (5) is by filtering circuit (5-1), pre-amplification circuit (5-2), analog to digital conversion circuit (A/D) and digital signal processor (DSP) form, the electric signal that described filtering circuit (5-1) is exported the photodetector (4) that receives carries out sending to pre-amplification circuit (5-2) after the filtering, signal after described pre-amplification circuit (5-2) amplifies is exported to analog to digital conversion circuit (A/D), and the signal after analog-digital conversion circuit as described (A/D) will be changed sends to digital signal processor (DSP).

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