CN102353341B - Phase-modulating synchronous-integral phase-shifting interference-measuring method and device - Google Patents

Abstract

The invention belongs to an optical testing technology. In order to monitor and control a phase-modulating degree in real time and realize the high-precision dynamic measurement for the surface topography of an optical lens, the wave aberration of the optical lens, an optical transfer function and the like, the invention adopts a phase-modulating synchronous-integral phase-shifting interference-measuring method and device, and has the technical scheme that the phase-modulating synchronous-integral phase-shifting interference-measuring method comprises the following steps of: driving a laser device to generate laser by adopting a laser-device driver, enabling the laser to reach a measuring mirror after sequentially passing through a focusing lens, a semi-transmitting semi-reflecting mirror, a beam-expanding and collimating lens, a small semi-transmitting semi-reflecting mirror and a reference mirror, sending the reflected signal of the small semi-transmitting semi-reflecting mirror into a PD (Photoelectric Detector), and finally sending the reflected signal of the semi-transmitting semi-reflecting mirror to a computer for processing after entering a video camera; and carrying out the measurement and the stabilization of the phase-modulating degree and the synchronous control of phase differences theta according to a formula that phase information is only related to the phase differences theta among a CCD (Charge-Coupled Device)-camera measuring signal, the phase-modulating degree z, a CCD-camera exposure signal and a phase-modulating signal and phase-modulating coefficients m. The method and the device are mainly applied to optical testing.

Description

Phase-modulating synchronous-integral phase-shifting interference-measuring method and device

Technical field

The invention belongs to optical testing technology, relate to advanced optical instrument manufacture, specifically relate to phase-modulating synchronous-integral phase-shifting interference-measuring method and device.

Background technology

Optical interference detects and is divided into interference (as equal inclination interference and equal thickness interference) in general sense, difference interference and accurate difference interference.Generally interfere because precision is not high, poor stability, is difficult to optical surface and detects.Difference interference needs the light source that frequency difference degree of stability is high, and manipulate measurement data amount is very large, lacks measurement of full field ability, is used for high-precision dot information measurement.Accurate difference interference is called again phase shift interference, and it,, by stepping or phase shift continuously, has also reduced the requirement to light source when suppressing environmental interference, and along with the development of photoelectron technology and integrated circuit technique, the measurement of high precision whole audience phase shift interference is achieved.Phase shift mode comprises piezoelectric crystal method, photoelectric crystal method, polarization phase-shifting method, doppler shift method, magneto-optical method, liquid crystal Method and rotation optical flat method etc., but all has hysteresis, the shortcomings such as non-linear and mechanical vibration.Laser instrument internal modulation phase-shifting technique has overcome above-mentioned shortcoming, is used widely.It utilizes the characteristic of the output optical frequency variation of laser instrument to carry out respective phase adjusting, has method simple, insensitive to vibrating, and reduces the advantages such as environmental requirement, but also has frequency drift, the shortcomings such as output intensity variation.Phase-stepping is long-standing, solves phase method for position directly perceived by least square method, but responsive to phase displacement error, its measuring accuracy is mainly determined by phase-shifter.Continuous phase is adjusted to and overcomes spectrum leakage and light intensity variation, take sinusoidal phase modulation as main, also derives various algorithms simultaneously.

The people such as Osami Sasaki proposed sinusoidal phase modulation synchronous integration algorithm (integrating-bucket method) and were applied to interferometry [1] in 1986.By piezoelectric ceramic sinusoidal phase-modulation and CCD camera synchronization integration, control system parameter, obtains the PHASE DISTRIBUTION figure of body surface, and precision reaches 1.0-1.5nm.Arnaud Dubois proposes 4 step synchronous integration algorithms [2] in calendar year 2001, one-period is divided into four sections, in four sections, respectively light intensity is carried out to integration, analyzed the impact on measuring accuracy of shot noise and quantizing noise simultaneously, by optimizing, precision has reached 1nm.Takamasa Suzuki etc. are at the height [3] on use dual laser cooperation synchronous integration algorithm scaffold tower rank in 2002, and relative accuracy is better than 1.5%.Yu-Lung Lo etc. measured [4] to main shaft and phase delay by synchronous integration algorithm application in 2006 in whole audience heterodyne system polariscope system, it is sinusoidal wave as modulation signal that they adopt sawtooth wave to replace, 3 step synchronous integration algorithms have been proposed thus, only need integration can obtain the tangent value of phase place for three times, striped degree of stability and measuring accuracy all approach 4 step synchronous integration algorithms, have reduced calculated amount.Yuankai K.Tao etc. adopted N step synchronous integration algorithm [5] and in the limit of integration, have added the time delay of CCD camera in 2008.2010, Dongmei Guo, by synchronous integration algorithm application [6] in self-mixed interference instrument, was used 4 step synchronous integration algorithms, adds closed loop phase control, and precision has reached 0.15nm.

The above results shows the continuous phase-shift method strong anti-interference performance of sinusoidal phase modulation, can realize kinetic measurement, and precision reaches Subnano-class, but the measurement of phase-modulation degree and stable rare research, and this key of sinusoidal phase modulation just.

[1]Osami?Sasaki，Hirokazu?Okazaki，Makoto?Sakai，“Sinusoidal?phase?modulating?interferometer?using?the?integrating-bucket?method”，APPLIED?OPTIC，1987，Vol.26，No.6：1089-1093

[2]Arnaud?Dubois，“Phase-map?measurements?by?interferometry?with?sinusoidal?phase?modulation?and?four?integrating?buckets”，J.Opt.Soc..Am.A，2001，Vol.18，No.8：1972-1979.

[3]Takamasa?Suzuki，Takayuki?Yazawa，Osami?Sasaki，“Two-wavelength?laser?diode?interferometer?withtime-sharing?sinusoidal?phase?modulation”，APPLIED?OPTICS，2002，Vol.41，No.10：1972-1976.

[4]Yu-Lung?Lo，Hung-Wei?Chih，Cheng-Yen?Yeh，Tsung-Chih?Yu，“Full-field?heterodyne?polariscope?with?an?image?signal?processing?method?for?principal?axis?and?phase?retardation?measurements”，APPLIED?OPTICS，2006，Vol.45，No.31：8006-8012.

[5]Yuankai?K.Tao，Mingtao?Zhao，Joseph?A.Izatt.“High-speed?complex?conjugate?resolved?retinal?spectral?domain?optical?coherence?tomography?using?sinusoidal?phase?modulation”，OPTICS?LETTERS，2009，Vol.32，No.20：2918-2920.

[6]Dongmei?Guo，Ming?Wang，“Self-mixing?interferometry?based?on?sinusoidal?phase?modulation?and?integrating-bucket?method”，Optics?Communications，2010，283：2186-2192.

Summary of the invention

For overcoming the deficiencies in the prior art, on the basis of traditional phase shift interference technology, develop new phase shift interference measuring technique.Phase-modulation degree survey control technology is introduced in sinusoidal phase modulation synchronous integration phase shift interference measuring technique, Real-Time Monitoring and control phase degree of modulation, realization is with the sinusoidal phase modulation synchronous integration algorithm of degree of modulation feedback, realization is to optical lens surface topography, optical lens wave aberration, the Dynamic High-accuracy of optical transfer function etc. is measured.For reaching above-mentioned purpose, the technical scheme that the present invention takes is that phase-modulating synchronous-integral phase-shifting interference-measuring method, comprises the following steps:

Adopt laser driver drive laser to produce laser, through condenser lens, semi-transparent semi-reflecting lens, beam-expanding collimation lens, little semi-transparent semi-reflecting lens, reference mirror, arrive and measure mirror successively, little semi-transparent semi-reflecting specular signal is sent into photoelectric detector PD, and semi-transparent semi-reflecting specular signal finally send computing machine to process after entering video camera;

According to phase information just and CCD camera measuring-signal, phase-modulation degree z, differs θ, the following formula that power modulation factor m is relevant between CCD camera exposure signal and phase modulated signal:

α=arctg (M ∑ _s-N ∑ _c)/(P ∑ _c-Q ∑ _s), by above-mentioned formula, carry out the measurement of phase-modulation degree and stablize, differ the synchro control of θ;

Carry out measurement and stable being specially of phase-modulation degree: interference signal is as follows:

S(t)＝A+B?cos[z?cos(ωt+θ)+α]＝A+B?cos(α)[J ₀(z)-2J ₂(z)cos(2ωt+2θ)+...]

-B?sin(α)[2J ₁(z)cos(ωt+θ)-2J ₃(z)cos(3ωt+3θ)...]

After the bandpass filter that is ω by centre frequency by S (t), with amplitude be G ₁signal G ₁cos (ω t+ θ)) multiply each other, through low-pass filtering, obtain V ₁=-BG ₁sin (α) J ₁(z);

After S (t) is the bandpass filter of 2 ω by centre frequency, with amplitude be G ₂signal G ₂cos (2 ω t+2 θ) multiplies each other, and through low-pass filtering, obtains V ₂=-BG ₂cos (α) J ₂(z);

After S (t) is the bandpass filter of 3 ω by centre frequency, with amplitude be G ₃signal G ₃cos (3 ω t+3 θ) multiplies each other, and through low-pass filtering, obtains V ₃=BG ₃sin (α) J ₃(z);

Due to G ₁, G ₂, G ₃for constant, by V ₁, V ₂and V ₃?

And then iteration optimizing obtains phase-modulation degree z value, simultaneously by observing V ₂the monitoring of realization to semaphore size;

The synchro control that differs θ is specially: by CPU control module, produce control signal, control square wave and the sine wave of Direct Digital Frequency Synthesizers DDS output variable frequency, be respectively used to CCD camera exposure signal and phase modulated signal, make the two precise synchronization, by register, arrange simultaneously, control the phase differential between CCD camera exposure signal and phase modulated signal.

Carry out measurement and stable being specially of phase-modulation degree:

By pull-in frequency, be ω ₀and much smaller than the sinusoidal signal of ω together modulated laser, interference signal is:

S(t)＝A+B?cos[z?cos(ωt+θ)+α+h?cos(ω ₀t+θ)]

Due to α+h cos (ω in a short time ₀t+ θ) can regard stable direct current signal H as,

S(t)＝A+B?cos(H)[J ₀(z)-2J ₂(z)cos(2ωt+2θ)+...]

-B?sin(H)[2J ₁(z)cos(ωt+θ)-2J ₃(z)cos(3ωt+3θ)...]

After the bandpass filter that S (t) is ω by centre frequency, with amplitude be G ₁signal G ₁cos (ω t+ θ)) multiply each other, through low-pass filtering, obtain V ₁=-BG ₁sin (H) J ₁(z), after S (t) is the bandpass filter of 2 ω by centre frequency, with amplitude be G ₂signal G ₂cos (2 ω t+2 θ) multiplies each other, and through low-pass filtering, obtains V ₂=-BG ₂cos (H) J ₂(z), by V ₁, V ₂obtain:

${\left(\frac{V_1}{{\mathrm{BG}}_1{J}_1\left(z\right)}\right)}^2+{\left(\frac{V_2}{{\mathrm{BG}}_2{J}_2\left(z\right)}\right)}^2=1$

This formula is elliptic equation, by ellipse fitting, solves elliptic parameter, makes BG ₁j ₁(z)=a, BG ₂j ₂(z)=b,

$\frac{J_1\left(z\right)}{J_2\left(z\right)}=\frac{a{G}_2}{b{G}_1}$

And then phase-modulation degree z value is obtained in iteration optimizing.

Phase-modulating synchronous-integral phase-shifting interference measurement mechanism, structure is: laser driver drive laser produces laser, and line focus lens, semi-transparent semi-reflecting lens, beam-expanding collimation lens, little semi-transparent semi-reflecting lens, reference mirror arrive measurement mirror successively, little semi-transparent semi-reflecting specular signal is sent into photoelectric detector PD, and semi-transparent semi-reflecting specular signal finally send computing machine to process after entering video camera;

Photoelectric detector PD outputs to phase-stepping amount metering circuit;

Phase-stepping amount metering circuit comprises three passages, and three passages are: after the bandpass filter that connected centre frequency is ω successively, multiplier, low-pass filtering; Successively connected centre frequency be after the bandpass filter of 2 ω, multiplier, low-pass filtering; Successively connected centre frequency be after the bandpass filter of 3 ω, multiplier, low-pass filtering;

Also comprise:

CPU control module, for generation of control signal, controls square wave and the sine wave of Direct Digital Frequency Synthesizers DDS output variable frequency;

Direct Digital Frequency Synthesizers DDS, for exporting square wave and the sine wave of variable frequency, is respectively used to CCD camera exposure signal and phase modulated signal, makes the two precise synchronization;

Register, arranges by register, controls the phase differential between CCD camera exposure signal and phase modulated signal.

The present invention has following technique effect:

The invention provides sinusoidal phase modulation synchronous integration phase shift interference and measure new improving one's methods, the problem that can not accurately measure and control for phase-modulation degree in sinusoidal phase modulation integral algorithm and CCD collected by camera signal and phase modulated signal phase differential, introducing phase-modulation degree measures and control technology, realized the dynamic locking of phase-modulation degree, by CCD collected by camera signal and phase modulated signal phase differential synchronous control technique, stablize and differ, for realizing high-precision sinusoidal phase modulation algorithm, provide assurance.Because system adopts closed loop configuration, antijamming capability is strong, has avoided the shortcoming of common interferometer to environmental interference sensitivity, can be used for in-site measurement and correction.Simultaneity factor has kinetic measurement and monitoring capacity.Therefore native system can be realized optical lens surface topography, wave aberration, the dynamic high-accuracy measurement of optical transfer function etc.

Accompanying drawing explanation

Fig. 1 illustrates the phase shift interference measuring method method system chart based on exchanging little phase-modulation phase control of the present invention.

In Fig. 1: 1 is laser driver; 2 is laser instrument; 3 is condenser lens; 4 semi-transparent semi-reflecting lens; 5 is beam-expanding collimation lens; 6 is little semi-transparent semi-reflecting lens; 7 is reference mirror; 8 for measuring mirror; 9 is photodetector; 10 is phase-stepping amount metering circuit; 11 is phase-stepping amount stabilization control circuit; 12 is CCD camera; 13 is computer measurement software.

Measuring-signal when Fig. 2 is shown in phase-modulation degree and is 0.15rad.

Fig. 3 gathers the signal of four width images by CCD camera synchronization.

Embodiment

Adopt non-equilibrium interferometer structure, by laser instrument internal modulation, make laser output wavelength be sinusoidal variations, thereby realize sinusoidal phase modulation, utilize CCD camera at an inter-sync modulation period integration simultaneously, obtain multiple image.Theoretical analysis shows, when phase-modulation degree controls to certain definite value, can obtain quite high phase shift interference measuring accuracy.To phase-modulation degree, the phase differential between CCD camera exposure signal and phase modulated signal carries out accurately measuring and controlling, and by the method for CCD camera image signal direct solution optical element surface phase place, is the phase shift of sinusoidal phase modulation synchronous integration.

In synchronous integration algorithm, by quoted passage ^{[1] [2]}analyze, phase-modulation degree error, the error of CCD collected by camera signal and phase modulated signal phase differential is the major obstacle that measuring accuracy improves, when phase-modulation degree error and phase difference error are all less than 0.01rad, phase measurement accuracy surpasses λ/500.The present invention is directed to the feature of synchronous integration algorithm, phase-modulation degree feedback technique is introduced in sinusoidal phase modulating interferometer, by high-precise synchronization with differ control, realize the high-acruracy survey to phase place.

Below in conjunction with drawings and Examples, further describe the present invention.

Measuring principle is described:

As Fig. 1, adopt fizeau interferometer structure, the light of 7 and 8 reflections forms to interfere and is received respectively by CCD camera and PD, and the signal in PD is used for realizing real-time phase modulation measurement and control, and CCD camera measuring-signal is realized the measurement of optical element surface phase place by synchronous integration algorithm.

The interference signal of CCD collected by camera is:

S (t)=[1-m cos (ω t+ θ)] A+B cos[z cos (ω t+ θ)+α] } (formula 1)

M power modulation factor wherein, w modulates angular frequency, and CCD camera synchronization collection signal and modulating signal phase postpone for θ, and A and B are background light intensity coefficient and the contrast ratings of interferometer, and z is phase-modulation degree coefficient, α _dthe phase place variation that (x, y, t) causes for being tested surface,

α=4 π l/ λ+α _d(x, y, t) (formula 2)

Wherein l is the optical path difference of reference mirror and mirror to be measured, and λ is laser instrument output light wavelength, (x, y) coordinate figure for putting on being tested surface, and t is the time.

Being tested surface height change

D (x, y, t)=λ ₀α _d(x, y, t)/4 π (formula 3)

Order

(formula 4)

The signal that gathers four width images by CCD camera synchronization as Fig. 3 is:

$E_p={\∫}_{\frac{p-1}{4}T}^{\frac{p}{4}T}s\left(t\right)\mathrm{dt},$ P=1,2,3,4 (formulas 5)

Order:

(formula 6)

(formula 7)

Wherein, p=1,2,3,4.

Have:

$E_p=\frac{T}{4}[A+{\mathrm{BJ}}_0\left(z\right)\cos \mathrm{\α}]+\frac{T}{2\mathrm{\π}}m[A+{\mathrm{BJ}}_0\left(z\right)\cos \mathrm{\α}][\sin (\frac{\mathrm{p\π}}{2}+\mathrm{\θ})$

$+\cos (\frac{\mathrm{p\π}}{2}+\mathrm{\θ})]+B\cos \mathrm{\α}{U}_p-B\sin \mathrm{\α}{V}_P$

(formula 8)

Wherein, p=1,2,3,4.

Order:

N＝-U ₁+U ₂+U ₃-U ₄，M＝-U ₁+U ₂-U ₃+U ₄

P=V ₁-V ₂-V ₃+ V ₄, Q=V ₁-V ₂+ V ₃-V ₄(formula 9)

Have:

∑ _s=-E ₁+ E ₂+ E ₃-E ₄=NB cos α+PB sin α (formula 10)

∑ _c=-E ₁+ E ₂-E ₃+ E ₄=MB cos α+QB sin α (formula 11)

α=arctg (M ∑ _s-N ∑ _c)/(P ∑ _c-Q ∑ _s) (formula 12)

Thereby phase information just and CCD camera measuring-signal, phase-modulation degree z, differs θ between CCD camera exposure signal and phase modulated signal, and power modulation factor m is relevant.Therefore the measurement of phase-modulation degree and stable, the synchro control that differs θ between CCD camera exposure signal and phase modulated signal is the gordian technique of system.

Phase-modulation degree feedback control technology

Measuring method 1: when ignoring laser power variation, be ω by pull-in frequency ₀and much smaller than the sinusoidal signal of ω together modulated laser, interference signal is:

S (t)=A+B cos[z cos (ω t+ θ)+α+hcos (ω ₀t+ θ)] (formula 13)

Due to α+h cos (ω in a short time ₀t+ θ) can regard stable direct current signal H as,

S(t)＝A+B?cos(H)[J ₀(z)-2J ₂(z)cos(2ωt+2θ)+...]

-B?sin(H)[2J ₁(z)cos(ωt+θ)-2J ₃(z)cos(3ωt+3θ)...]

(formula 14)

After the bandpass filter that S (t) is ω by centre frequency, with amplitude be G ₁signal G ₁cos (ω t+ θ)) multiply each other, through low-pass filtering, obtain V ₁=-BG ₁sin (H) J ₁(z).

(formula 15)

After S (t) is the bandpass filter of 2 ω by centre frequency, with amplitude be G ₂signal G ₂cos (2 ω t+2 θ) multiplies each other, and through low-pass filtering, obtains V ₂=-BG ₂cos (H) J ₂(z).

(formula 16)

By formula 15 and formula 16, obtained:

${\left(\frac{V_1}{{\mathrm{BG}}_1{J}_1\left(z\right)}\right)}^2+{\left(\frac{V_2}{{\mathrm{BG}}_2{J}_2\left(z\right)}\right)}^2=1$ (formula 17)

This formula is elliptic equation, by ellipse fitting, solves elliptic parameter, makes BG ₁j ₁(z)=a, BG ₂j ₂(z)=b,

$\frac{J_1\left(z\right)}{J_2\left(z\right)}=\frac{a{G}_2}{b{G}_1}$ (formula 18)

And then phase-modulation degree z value is obtained in iteration optimizing.

Measuring method 2: when ignoring laser power and change, and while not introducing low frequency component:

S(t)＝A+B?cos[z?cos(ωt+θ)+α]＝A+B?cos(α)[J ₀(z)-2J ₂(z)cos(2ωt+2θ)+...]

-B?sin(α)[2J ₁(z)cos(ωt+θ)-2J ₃(z)cos(3ωt+3θ)...]

(formula 19)

J wherein ₀, J ₁... be Bezier expansion coefficient item, after the bandpass filter that S (t) is ω by centre frequency, with amplitude be G ₁signal G ₁cos (ω t+ θ)) multiply each other, through low-pass filtering, obtain V ₁=-BG ₁sin (α) J ₁(z).

(formula 20)

After S (t) is the bandpass filter of 2 ω by centre frequency, with amplitude be G ₂signal G ₂cos (2 ω t+2 θ) multiplies each other, and through low-pass filtering, obtains V ₂=-BG ₂cos (α) J ₂(z).(formula 21)

After S (t) is the bandpass filter of 3 ω by centre frequency, with amplitude be G ₃signal G ₃cos (3 ω t+3 θ) multiplies each other, and through low-pass filtering, obtains V ₃=BG ₃sin (α) J ₃(z).(formula 22)

Due to G ₁, G ₂, G ₃for constant, by formula 20 and formula 24, obtained (formula 23)

And then iteration optimizing obtains phase-modulation degree z value, simultaneously by observing V ₂the monitoring of realization to semaphore size.This measuring method can Real-time Feedback and measurement phase-modulation degree, simultaneously feedback stability phase-modulation degree.

By comparing and measuring method 1 and measuring method 2, method 1 method is directly perceived, need to introduce low frequency component, and method 2 can realize Real-Time Monitoring.Therefore when phase-modulation is spent, by method 1, be adjusted near optimum angle degree of modulation (as 2.45), by method 2, finely tune and realize the Real-time Feedback of phase-modulation degree.Due to l > > d (x, y, t), wherein d (x, y, t) optical element surface height change, z=4 π Δ λ _maxl/ λ ² ₀=4 π β Δ I _maxl/ λ ² ₀the wavelength-modulated coefficient that wherein β is laser instrument, Δ λ _max, I _maxbe respectively wavelength and electric current AC signal modulation amplitude.Thus can be by changing AC signal modulation amplitude, stable and control phase degree of modulation.As from the foregoing, can realize by photodetector (PD) measurement and the feedback of phase-modulation degree.CCD camera exposure signal is synchronizeed and phase differential control with phase modulated signal

Design hardware circuit, realizes CCD camera exposure signal and controls with phase differential with synchronizeing of phase modulated signal.As Fig. 2, by CPU control module (as FPGA, DSP etc.) produce control signal, control square wave and the sine wave of DDS (Direct Digital Frequency Synthesizers) output variable frequency, be respectively used to CCD camera exposure signal and phase modulated signal, make the two precise synchronization, by register, arrange simultaneously, control the phase differential between CCD camera exposure signal and phase modulated signal.

Claims (3)

1. a phase-modulating synchronous-integral phase-shifting interference-measuring method, is characterized in that, comprises the following steps:

Adopt non-equilibrium interferometer structure, by laser instrument internal modulation, make laser output wavelength be sinusoidal variations, thereby realize sinusoidal phase modulation, the light that laser instrument produces arrives and measures mirror through condenser lens, semi-transparent semi-reflecting lens, beam-expanding collimation lens, little semi-transparent semi-reflecting lens, reference mirror successively, little semi-transparent semi-reflecting specular signal is sent into photoelectric detector PD, and semi-transparent semi-reflecting specular signal finally send computing machine to process after entering CCD camera;

According to phase information just and CCD camera measuring-signal, phase-modulation degree z, differs θ, the following formula that power modulation factor m is relevant between CCD camera exposure signal and phase modulated signal:

α=arctg (M Σ _s-N Σ _c)/(P Σ _c-Q Σ _s), T=2 π/ω, by above-mentioned formula, carries out the measurement of phase-modulation degree and stablizes, differs the synchro control of θ;

Wherein, N=-U ₁+ U ₂+ U ₃-U ₄, M=-U ₁+ U ₂-U ₃+ U ₄

P=V ₁-V ₂-V ₃+ V ₄, Q=V ₁-V ₂+ V ₃-V ₄(formula 9)

Σ _s=NBcos α+PBsin α (formula 10)

Σ _c=MBcos α+QBsin α (formula 11)

α=arctg (M Σ _s-N Σ _c)/(P Σ _c-Q Σ _s) (formula 12)

(formula 6)

(formula 7)

P=1,2,3,4, a and B are background light intensity coefficient and the contrast ratings of interferometer;

Carry out measurement and stable being specially of phase-modulation degree: interference signal is as follows:

S(t)=A+Bcos[zcos(ωt+θ)+α]=A+Bcos(α)[J ₀(z)-2J ₂(z)cos(2ωt+2θ)+…]

-Bsin(α)[2J ₁(z)cos(ωt+θ)-2J ₃(z)cos(3ωt+3θ)...]

The bandpass filter that is ω by centre frequency by S (t), with amplitude be G ₁signal G ₁cos (ω t+ θ)) multiply each other, through low-pass filtering, obtain V ₁=-BG ₁sin (α) J ₁(z);

By S (t), by centre frequency, be the bandpass filter of 2 ω, with amplitude be G ₂signal G ₂cos (2 ω t+2 θ) multiplies each other, and through low-pass filtering, obtains V ₂=-BG ₂cos (α) J ₂(z);

By S (t), by centre frequency, be the bandpass filter of 3 ω, with amplitude be G ₃signal G ₃cos (3 ω t+3 θ) multiplies each other, and through low-pass filtering, obtains V ₃=BG ₃sin (α) J ₃(z);

Due to G ₁, G ₂, G ₃for constant, by V ₁, V ₂and V ₃?

And then iteration optimizing obtains phase-modulation degree z value, simultaneously by observing V ₂the monitoring of realization to semaphore size, wherein, J(z) is Bezier expansion coefficient item;

The synchro control that differs θ is specially: by CPU control module, produce control signal, control square wave and the sine wave of Direct Digital Frequency Synthesizers DDS output variable frequency, be respectively used to CCD camera exposure signal and phase modulated signal, make the two precise synchronization, by register, arrange simultaneously, control the phase differential θ between CCD camera exposure signal and phase modulated signal.

2. the method for claim 1, is characterized in that, described in carry out measurement and stable being specially of phase-modulation degree:

By pull-in frequency, be ω ₀and much smaller than the sinusoidal signal of ω together modulated laser, interference signal is:

S(t)=A+Bcos[zcos(ωt+θ)+α+hcos(ω ₀t+θ)]

Due to α+hcos (ω in a short time ₀t+ θ) can regard stable direct current signal H as,

S(t)=A+Bcos(H)[J ₀(z)-2J ₂(z)cos(2ωt+2θ)+…]

-Bsin(H)[2J ₁(z)cos(ωt+θ)-2J ₃(z)cos(3ωt+3θ)...]

The bandpass filter that S (t) is ω by centre frequency, with amplitude be G ₁signal G ₁cos (ω t+ θ)) multiply each other, through low-pass filtering, obtain V ₁=-BG ₁sin (H) J ₁(z), S (t) is the bandpass filter of 2 ω by centre frequency, with amplitude be G ₂signal G ₂cos (2 ω t+2 θ) multiplies each other, and through low-pass filtering, obtains V ₂=-BG ₂cos (H) J ₂(z), by V ₁, V ₂obtain:

${\left(\frac{V_1}{{\mathrm{BG}}_1{J}_1\left(z\right)}\right)}^2+{\left(\frac{V_2}{{\mathrm{BG}}_2{J}_2\left(z\right)}\right)}^2=1$

This formula is elliptic equation, by ellipse fitting, solves elliptic parameter, makes BG ₁j ₁(z)=a, BG ₂j ₂(z)=b,

$\frac{J_1\left(z\right)}{J_2\left(z\right)}=\frac{a{G}_2}{b{G}_1}$

And then phase-modulation degree z value is obtained in iteration optimizing.

3. a phase-modulating synchronous-integral phase-shifting interference measurement mechanism, it is characterized in that, structure is: laser driver drive laser produces laser, and line focus lens, semi-transparent semi-reflecting lens, beam-expanding collimation lens, little semi-transparent semi-reflecting lens, reference mirror arrive measurement mirror successively, little semi-transparent semi-reflecting specular signal is sent into photoelectric detector PD, and semi-transparent semi-reflecting specular signal finally send computing machine to process after entering CCD camera;

Photoelectric detector PD outputs to phase-stepping amount metering circuit;

Phase-stepping amount metering circuit comprises three passages, and three passages are: connected centre frequency is ω successively bandpass filter, multiplier, low-pass filtering; Connected centre frequency is bandpass filter, multiplier, the low-pass filtering of 2 ω successively; Connected centre frequency is bandpass filter, multiplier, the low-pass filtering of 3 ω successively;

Also comprise:

CPU control module, for generation of control signal, controls square wave and the sine wave of Direct Digital Frequency Synthesizers DDS output variable frequency;

Direct Digital Frequency Synthesizers DDS, for exporting square wave and the sine wave of variable frequency, is respectively used to CCD camera exposure signal and phase modulated signal, makes the two precise synchronization;

Register, arranges by register, controls the phase differential θ between CCD camera exposure signal and phase modulated signal.