CN1320812A - Phase difference measurer and heterodyne interference measuring system using it - Google Patents

Abstract

A phase-difference measurer and its heterodyne interference measuring system are disclosed. A differential amplifier is used to find out the difference value between two phase modulated measured signals with same amplitude and phase modulated reference signal or the light signal from heterodyne interferometer and then amplifying it in order to reduce background noise and convert the phase modulated signals to amplitude modulated signals. A amplitude demodulator is used to take instantaneous amplitude value which is used to determine the phase change and further the phase difference value. Its advantages are high speed and high sensitivity.

Description

Phase difference measuring apparatus and use the difference interference measuring system of this device

The present invention relates to a kind of phase demodulating device, a kind of phase difference measuring apparatus and use the difference interference measuring system of this phase difference measuring apparatus, particularly relate to and a kind ofly phase modulated signal can be demodulated into amplitude-modulated signal, can reach demodulating equipment, and the instant measuring system of contactless polarized light difference interference phase place of instant measurement effect.

Phase demodulating device (phase demodulator, PD) can be applicable to phase modulated signal (phasemodulation, PM) carry out phase demodulating in, also can be applicable to communication, the information transmission, in precision measurement and other association areas, and general phase demodulating device is to utilize phase detectors (phase meter), lock-in amplifier (lock in amplifier) and PLL (phase lock loop, method demodulation such as PLL), also can (frequency modulation, FM) signal be measured the frequency number f of test signal immediately by counter (counter) with the circuit of zero-crossing via frequency modulation (PFM) _s, and and reference signal in frequency number f that counter read _rSubtract each other, and obtain frequency-splitting Δ f=f _s-f _r, utilize integrating circuit to try to achieve the variation of phase place again.General phase demodulating device also can utilize phase comparator, with the method compare test signal of numerical digit and the phase differential of reference signal, and the phase place size conversion is become voltage signal output.These methods all are to utilize the mode of analogy or numerical digit to come the phase differential of compare test signal and reference signal with Measurement Phase.

On the other hand, how in the precision measurement field of meter level, how with the benchmark of the interference between light wavelength and light wave as comparison, with the change application of measured phase place (phase) in the measurement of displacement, angle, speed, length, vibration or other related physical quantities.Because the high coherence of laser (Laser) aspect the time and space is so be to be used as light source with laser in this class interferometer.The optical heterodyne interferometer is applied in the precision measurement of physical quantitys such as displacement, angle, speed, length, vibration with Measurement Phase quite ripe.But, all can cause the phase measurement accuracy of optical heterodyne interferometer to reduce such as the variation of environmental factors such as temperature.Therefore, the framework of optical heterodyne interferometer must satisfy optics co-route (optical common path configuration) makes environmental factor remain on equal state, just can make phase place avoid the interference of external environment.

Polarization optics co-route difference interference vibration gauge in the past, not only using the Mach-Zehnder interferometer aspect the configuration of optical path, and break through, the improvement conventional art, during but because of final sensing phase differential, be by phase-locked loop (phase lock loop), phase-detection instrument (phase sensitive detector) for example, lock-in amplifier methods such as (lock-in amplifier) is come the Measurement Phase size, cause the speed of Measurement Phase or Doppler frequency reaction slower, can't take into account simultaneously for desired high precision of phase measurement and rapid-action ability, so that seriously limit the function of this type of heterodyne ineterferometer.

The object of the present invention is to provide a kind of phase demodulating device, convert phase modulated signal to amplitude-modulated signal, and come Measurement Phase, with the instant Measurement Phase delicately that reaches with the amplitude size of amplitude-modulated signal.

Another object of the present invention is to provide a kind of phase differential instant measurement mechanism, will handle by differential amplifier and export from the optical signalling of laser heterodyne interference instrument, with rapid reaction in the Modulation and Amplitude Modulation mode.

A further object of the present invention is to provide the instant measuring system of contactless polarized light difference interference phase place of the instant measurement mechanism of a kind of application phase difference, reaches the instant measurement effect of high precision.

Another purpose of the present invention is to provide the instant measuring system of contactless polarized light difference interference phase place of the instant measurement mechanism of a kind of application phase difference, when making measured phase change amplitude very big, and can its variation of simple count mode quantitative measurment.

Of the present invention again again a purpose be to provide the instant measuring system of contactless polarized light difference interference phase place of the instant measurement mechanism of a kind of application phase difference, the variation that can clearly distinguish the tolerance phase place is towards increasing or reduce direction.

The invention is characterized in: utilize differential amplifier that the phase modulation (PM) test signal and the phase modulation (PM) reference signal of two same-amplitude are subtracted each other and amplified, or the optical signalling of self-heterodyne interferometer subtracts each other and amplifies with differential amplifier in the future, not only reduce ground unrest, more convert phase modulated signal to amplitude-modulated signal, and measure the amplitude size immediately with the amplitude demodulation device, can define phase change by its amplitude size of direct tolerance, with so try to achieve phase difference value, effectively improve the speed and the sensitivity of measuring.

Phase demodulating device of the present invention is in order to measure the phase modulation (PM) test signal I of a fixed carrier frequency _s(ω t)=2k ₁Cos (ω t+ φ _s) and the phase modulation (PM) reference signal I of a same carrier frequencies _r(ω t)=2k ₂Cos (ω t+ φ _r) between each other phase differential, wherein Δ φ=φ _s-φ _r, this two phase place modulation signal comprises carrier frequency and time product term respectively, and the function of phase term.This measurement mechanism comprises: two automatic gain control equipments, be used for adjusting the amplitude of this two phase modulation signal respectively, and make the amplitude equal and opposite in direction (k of this two phase modulation signal ₁=k ₂=k).One differential amplifier, two phase modulation signal from this two automatic gain control equipment is respectively subtracted each other and amplifies, to obtain an amplitude-modulated output signal, the amplitude of this output signal is proportional to the function that comprises frequency and time product, and the product of phase function.One signal processing apparatus comprises an amplitude demodulation device, in order to demodulation and measure amplitude size and/or its variable quantity of the Modulation and Amplitude Modulation output signal of this differential amplifier output.

Phase difference measuring apparatus of the present invention, in order to measure the electric signal of changing out respectively by the mutual perpendicular linear polarization optical signalling of two bundles of a polarization optics heterodyne ineterferometer, a branch of at least reflected light that exposes to a determinand gained that comprises in the two beam optics signals of this heterodyne ineterferometer, and the light intensity equal and opposite in direction of this optical signalling respectively, and comprise the function of difference on the frequency and time product term and phase differential item respectively.This measurement mechanism comprises: a differential amplifier, also subtract each other and amplify for two electric signal inputs, thus, acquisition comprise difference on the frequency and time product sine function, with and with the product of phase differential sine function.One signal processing apparatus is in order to amplitude and/or its variable quantity of tolerance phase function.

The present invention is described in detail below in conjunction with drawings and Examples, in the accompanying drawing:

Fig. 1 is the phase demodulating schematic representation of apparatus of the present invention's first preferred embodiment.

Fig. 2 is the synoptic diagram of the single-frequency Frequency Stabilized Lasers linearly polarized light co-route heterodyne ineterferometer of the present invention's second preferred embodiment.

Fig. 3 is the synoptic diagram of the mutual perpendicular linear polarization laser heterodyne interferometry of the double frequency instrument of the present invention's the 3rd preferred embodiment.

Fig. 4 is the synoptic diagram that the analysis of polarized light sheet of Fig. 3 causes P ripple and S wave interference.

Fig. 5 is the synoptic diagram of the single-frequency Frequency Stabilized Lasers polarized light co-route annular heterodyne ineterferometer of the present invention's the 4th preferred embodiment.

Fig. 6 is the synoptic diagram of the mutual perpendicular linear polarization ring of light of the double frequency shape heterodyne ineterferometer of the present invention's the 5th preferred embodiment.

Fig. 7 is the synoptic diagram of the single-frequency Frequency Stabilized Lasers linearly polarized light co-route optical fibre ring heterodyne ineterferometer of the present invention's the 6th preferred embodiment.

Fig. 8 is the synoptic diagram of the single-frequency Frequency Stabilized Lasers Michelson interferometer of the present invention's the 7th preferred embodiment.

Fig. 9 is the experimental result of the present invention's second preferred embodiment.

As shown in Figure 1, phase differential demodulating equipment of the present invention is with phase modulation (PM) test signal I _s(ω t)=2k ₁Cos (ω t+ φ _s) and phase modulation (PM) reference signal I _r(ω t)=2k ₂Cos (ω t+ φ _r) filter via the bandpass filter 10,11 that with the carrier frequency is centre frequency respectively after, separately the corresponding automatic gain controller of input (automatic gain control, AGC) in 12,13, (k ₁, k ₂) be respectively the amplitude size of phase modulation (PM) test signal and phase modulation (PM) reference signal, (φ _s, φ _r) be respectively the phase place of phase modulation (PM) test signal and phase modulation (PM) reference signal, and automatic gain controller is identical with general structure, thus no longer be described in detail at this, via automatic gain controller 12,13, make the amplitude equal and opposite in direction of two signals, just k ₁=k ₂=k.Then measured phase modulation (PM) test signal I _sWith phase modulation (PM) reference signal I _rCan be expressed as I respectively _s(ω t)=2k ₁Cos (ω t+ φ _s) and I _r(ω t)=2k ₂Cos (ω t+ φ _r).Again respectively with phase modulation (PM) test signal I _sWith phase modulation (PM) reference signal I _rIn phase deviation $\frac{1}{2}({\mathrm{\φ}}_s-{\mathrm{\φ}}_r),$ Then can be expressed as again respectively $I_s\left(\mathrm{\ωt}\right)=2k\cos [\mathrm{\ωt}+\frac{1}{2}({\mathrm{\φ}}_s-{\mathrm{\φ}}_r)]$ With $I_r\left(\mathrm{\ωt}\right)=2k\cos [\mathrm{\ωt}-\frac{1}{2}({\mathrm{\φ}}_s-{\mathrm{\φ}}_r)]$ 。This two signal is input to differential amplifier (differential amplifier) 14, and the identical and equal-sized phase modulated signal of amplitude subtracts each other and amplifies with two carrier frequencies, and then output signal can be write as $I_{\mathrm{out}}\left(\mathrm{\ωt}\right)=\left|4\mathrm{\γ}k\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|\sin \left(\mathrm{\ωt}\right),$ Δ φ=(φ _s-φ _r), γ is the gain (gain) of differential amplifier.At this time, phase change Δ φ can utilize the amplitude size through a signal processing apparatus 15 $\left|4\mathrm{\γ}k\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Relation calculate: as | Δ φ |＜10 °, then because sinx ≌ x, output signal can be write as I _Out(ω t)=| 4 γ k Δ φ | sin (ω t), because this amplitude size directly is proportional to Δ φ, therefore, can smoothly phase modulated signal be converted to amplitude-modulated signal (amplitudemodulation, AM), by the 150 instant Measurement Phase sizes of the amplitude demodulation device in this signal processing apparatus 15, not only increase substantially the reaction velocity of measurement, and because amplitude size and the phase signal that will measure $\left|\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Be directly proportional, and amplify 4 γ k doubly, make the sensitivity of phase measurement significantly improve synchronously.

Comprise a phase comparator 151 in this signal processing apparatus 15, the phase modulation (PM) test signal that automatic gain controller 12,13 can be exported and the phase place of phase modulation (PM) reference signal compare mutually, and distinguish the positive negative value of Δ φ immediately, and differentiate the change direction of Δ φ.Also can comprise an electronic counter 152 in this signal processing apparatus 15, when the phase differential of measuring can be expressed as Δ φ=2n π+δ, n is integer, during and 0＜δ＜π, then by n pulse signal of these electronic counter 152 records, cooperation amplitude size $\left|4\mathrm{\γ}k\sin \left(\frac{\mathrm{\δ}}{2}\right)\right|$ Direct measure phase difference δ is with the phase measurement scope can (n δ) and effectively extends by parameter.

In addition, because of I _OutThe amplitude size be | 2 γ k Δ φ |, the signal processing apparatus 15 of present embodiment also can provide a control signal (error signal), feedback at any time control makes phase place make zero (nulling) and reaches the purpose of control.For another with the amplitude of output signal size through the differentiating circuit 153 in the signal processing apparatus 15 with the amplitude size to time diffusion, then $\frac{d}{\mathrm{dt}}\left|2\mathrm{\γk\Δ\φ}\right|=2\mathrm{\γk}\frac{d\left(\mathrm{\Δ\φ}\right)}{\mathrm{dt}}=2\mathrm{\γk}{\mathrm{\ω}}_S,$ The present invention is the instantaneous frequency ω of measuring-signal immediately _sAnd having the function of frequency demodulation, it measures sensitivity can improve 2 γ k doubly, measures reaction and also significantly improves.If can preestablish phase deviation (bias) Δ φ on the other hand ₀, then output signal can be write as $I_{\mathrm{out}}\left(\mathrm{\ω}t\right)=|4\mathrm{\γ}k\sin \left(\frac{\mathrm{\Δ\φ}+\mathrm{\Δ}{\mathrm{\φ}}_0}{2}\right)\sin \left(\mathrm{\ωt}\right),$ So can be at 0＜Δ φ ₀Preestablish fixing phase difference value Δ φ between＜π ₀Measure phase signal Δ φ.Work as setting $\mathrm{\Δ}{\mathrm{\φ}}_0=\frac{\mathrm{\π}}{2},$ | I _Out| to Δ φ ₀Formation center symmetry, can be further by | I _Out| the amplitude size variation and determine the change direction of Δ φ.

When the signal source of handling be come by the optical heterodyne interferometer optical signalling the time, phase difference measuring apparatus of the present invention can cooperate described in the past polarization optics co-route heterodyne ineterferometer operate together, constitute second preferred embodiment of difference interference measuring of the present invention system, as shown in Figure 3, the polarized lights that penetrated by a light source (be in this example be example with a linearly polarized light single-frequency frequency stabilization He-Ne Lasers) 20 are through a polarization angle adjusting gear, adjust its polarization angle as the half-wave plate in the present embodiment (λ/2 wave plate) 21, laser is divided into the signal beams L that is incident to determinand 90 through light splitting piece 231 again ₁, and in order to the contrast reference beam L ₂

This signal beams L ₁And reference beam L ₂Respectively through a frequency adjusting device, be respectively in this example an acousto-optic modulator (acousto-optic modulator, AOM) 241,242, each acousto-optic modulator 241,242 is to be driven by it device 251,252 respectively to activate, and makes this signal beams L ₁Frequency change ω a little into through acousto-optic modulator 241 ₁, this signal beams L ₂Frequency change ω a little into through acousto-optic modulator 242 ₂, thus, the frequency of two light beams will produce the Δ of the difference on the frequency a little ω that can separate after the beam split.Certainly, as know this technology as can be known, frequency adjusting device herein, can electrooptical modulation or other any similar devices reach.

This signal beams L ₁Through a light splitting piece 232 and polarized light light splitting piece 261, electromagnetic field is shaken the orthogonal P of direction again ₁Ripple and S ₁Wavelength-division is opened, and wherein a branch of at least be (to be in the present embodiment with P by determinand 90 reflection ₁Expose to determinand 90 and get its reflected light, S ₁Then by plane mirror 272 reflections), after this polarization spectro sheet 261 and light splitting piece 232 reflect and turn to, overlap at light splitting piece 233 places again with the P2 ripple and the S2 ripple of the reference beam that is subjected to catoptron 271 reflections merely.

To polarized light light splitting piece 262 places, again will perpendicular each other difference interference P ripple (P ₁+ P ₂) signal and difference interference S ripple (S ₁+ S ₂) signal separates again, and with two photodetectors 281,282 detection line polarization difference interference P ripple (P respectively ₁+ P ₂) signal, and difference interference S ripple (S ₁+ S ₂) signal and be converted to electric signal output.This P involves S ripple electrical signal converted, and warp is with Δ ω=ω respectively ₁-ω ₂Bandpass filter 291,292 for centre frequency to leach the interference signal of fixed frequency, obtains following result: $I_{P1+P2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{P1}{I}_{P2}}\cos (\mathrm{\Δ\ωt}+\mathrm{\Δ}{\mathrm{\φ}}_P)\·\·\·\·\·\·\·\·\·\·\·\left(1\right)$ $I_{S1+S2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{S_1}{I}_{S_2}}\cos (\mathrm{\Δ\ωt}+\mathrm{\Δ}{\mathrm{\φ}}_S)\·\·\·\·\·\·\·\·\left(2\right)$ Be output as I after by differential amplifier (differential amplifier) 30 electric signal that is constituted being subtracted each other and amplifies _OutWherein:

I _out(Δωt)=γ[I _P1+P2(Δωt)+I _S1+S2(Δωt)………………………(3)

(I _P1, I _P2) be respectively P ₁Involve P ₂The intensity size of ripple.(I _S1, I _S2) be respectively S ₁Involve S ₂The intensity size of ripple.Δ φ _PBe P ₁Involve P ₂The phase differential of ripple, Δ φ _SBe S ₁Involve S ₂The phase differential of ripple.Δ ω is the difference frequency of difference interference.γ is moving Amplifier Gain.

Make as the position angle of adjusting this half-wave plate 21 repeatedly (azimuth angle) θ $\sqrt{I_{S_1}{I}_{S_2}}=\sqrt{I_{P_1}{I}_{P_2}}=K$ The time, the P ripple signal in above-mentioned two groups of orthogonal linear polarization difference interference signals will become:

I _P1+P2(Δωt)=2Kcos(Δωt+Δφ _P)…………………………………(4)

S ripple signal will become:

I _S1+S2(Δωt)=2Kcos(Δωt+Δφ _S)…………………………………(5)

By with the coordinate translation simultaneously of this two interference signal $\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_P-\mathrm{\Δ}{\mathrm{\φ}}_S),$ Then formula (1) becomes respectively with formula (2) $I_{P1+P2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{P_1}{I}_{P_2}}\cos (\mathrm{\Δ\ωt}+\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_P-\mathrm{\Δ}{\mathrm{\φ}}_S)$ With $I_{S1+S2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{S_1}{I}_{S_2}}\cos (\mathrm{\Δ\ωt}-\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_p-{\mathrm{\Δ\φ}}_s)$ 。At this moment, differential amplifier is with I _P1+P2(Δ ω t) and I _S1+S2The signal I that (Δ ω t) two difference interference signal subtractions and amplification are exported _OutCan be write as: $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\mathrm{\γ}[I_{P1+P2}\left(\mathrm{\Δ\ωt}\right)-I_{S1+S2}\left(\mathrm{\Δ\ωt}\right)]=\left|4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|\sin \left(\mathrm{\Δ\ωt}\right)\·\·\·\·\·\·\·\·\left(6\right)$

Δ φ=(Δ φ wherein _P-Δ φ _S) for difference interference P involves the phase differential of difference interference S ripple, $4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)$ Be the amplitude size.By (6) the formula signal I of differential amplifier 30 output as can be known _Out(Δ ω t) belongs to Modulation and Amplitude Modulation (AM) signal, and its carrier frequency is Δ ω=ω ₁-ω ₂(ω ₁, ω ₂) be respectively the driving frequency of two acousto-optic modulators 241,242 in the Mach-Zehnder heterodyne ineterferometer.

Be with amplitude demodulator (amplitude demodulator in the present embodiment; AD) the 310 phase delta phi signals that the institute desire is measured by signal processing apparatus 31 immediately by measure the big trumpet of amplitude $\left|4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Calculate.Thus, when the determinand position change, the P of reflection ₁One phase shift will appear in component, and this phase change is with in the amplitude size variation that just is presented on final output.

Certainly, can understand easily in this technician, as with P as ripe ₁With S ₁Intermodulation is with S ₁Be incident to determinand, P ₁Simple reflection also belongs to selectable enforcement aspect.Especially such as measuring relatively moving or vibrate between disk drive rotating disk diverse location, more can P ₁With S ₁Be incident to the different parts of determinand respectively and reach.And promptly the light source that provides of toilet is two vertical each other circular component, also can carry out similar measurement.

Though phase difference measuring apparatus of the present invention includes only a differential amplifier 30 and a signal processing apparatus 31, but in the difference interference measuring field, differential amplifier 30 generally only is used to reduce noise total between two signals, use in order to removing noise, disclose by the present invention, differential amplifier is used as a light-electric conversion processing unit, with (the Δ φ=Δ φ of the phase differential in (1) formula and (2) formula _P-Δ φ _S) directly the Modulation and Amplitude Modulation with electric signal present, and comprise an amplitude-modulated signal demodulating equipment 310 at least in this signal processing apparatus 31.Thus, not only convert the measurement amplitude-modulated signal to by general phase measurement method, the phase signal that makes desire measure directly is proportional to the amplitude size, significantly improve sensing speed, and when the variation of phase delta phi was very little, by the relation of sinx ≌ x, but the output electric signal abbreviation that then obtains was: $4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\≅2\mathrm{\γK\Δ\φ}\·\·\·\·\·\·\·\·\·\·\left(7\right)$

At this moment, the amplitude size that obtains of measuring is directly proportional with Δ φ, and more because the amplitude demodulation signal magnitude is 2 γ K Δ φ, therefore the sensitivity of tolerance will be 2 γ K times of phase difference φ, this measure utilizes method Measurement Phase Δ φ such as phase-locked loop than in the past, significantly improve in sensitivity.

In addition, after in conjunction with backfeed loop (feedback loop) 32, can utilize these catoptron 272 front and back positions shown in the regulation and control present embodiment, making phase change Δ φ maintain phase place makes zero and provides control signal (error signal) under the condition of (nulling), be used near the Δ φ ≌ 0, the amplitude signal size and the Δ φ of these differential amplifier 30 outputs are linear, and its slope is the characteristic of 2 γ K, enable the instant minimum phase changing capacity of measuring.Certainly, this control of making zero also can be implemented by other feasible alternative.

That is to say, because Δ φ is the phase differential that difference interference P involves the S ripple, involves the S wavelength-division as difference interference P and do not cause the physical quantity of phase change as institutes such as temperature, optical index, electromagnetic fields from the relative displacement of test point and reference point, relative angle or other.It can directly utilize simple, rapid and ripe amplitude demodulation technology, in the size of the utmost point instant acquisition phase delta phi in the short time, and obtains corresponding physical quantity respectively.Thus, the present invention can be applied in instant measurement such as displacement, angle, speed, length, vibration and other the relevant optical sensors (optical sensor) widely.

In addition, the present invention both can be applicable to the measurement of 2 relatively little displacements (small displacement), also can be applicable to the instant measurement and the control of relative low-angle (small angle) and other relevant little change such as physical quantity naturally.Especially can be by in this signal processing apparatus 31, adding a differentiator (figure does not show), differential amplitude demodulation signal $\frac{d{I}_{\mathrm{out}}}{\mathrm{dt}}=2\mathrm{\γK}\·\frac{d}{\mathrm{dt}}\left[\mathrm{\Δ\φ}\right],$ Obtain the time variation amount of measured phase place rapidly $\frac{d\left[\mathrm{\Δ\φ}\left(t\right)\right]}{\mathrm{dt}}$ By ${\mathrm{\ω}}_D=\frac{d\left[\mathrm{\Δ\φ}\left(t\right)\right]}{\mathrm{dt}}$ Relation, the present invention can cause Doppler frequency skew ω to the instantaneous variation of little phase place _D, measure Doppler frequency skew ω with the amplitude-modulated signal size _D, its sensitivity can improve 2 γ K doubly, the microvibration that can measure tested surface immediately.So the present invention not only can be applicable to the vibration and the instant measurement of displacement,, can be locked in the start-phase state of having set accurately and be applied in the relevant field particularly in conjunction with backfeed loop and utilize the susceptibility of phase change and produce control signal.

As mentioned above, be proportional to the sine function of phase differential because of the amplitude-modulated signal size $\left|\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|,$ When the phase change that determinand caused excessive, when making Δ φ can be expressed as 2 π n+ δ, also can in this signal processing apparatus 31, set up an electronic counter (up-and-down counter) 312, effectively n pulse signal be counted and the phase place δ that it is remaining utilizes the amplitude size $4\mathrm{\γ}K\sin \left(\frac{\mathrm{\δ}}{2}\right)$ Calculate, wherein n is an integer, 0＜δ＜π.Therefore, (n, δ), the present invention not only can effectively measure large-scale phase change, also can obtain phase variation rate simultaneously by differentiating circuit, is applied in physical quantitys such as speed, vibration by parameter.

Especially for for the purpose of the difference phase change direction, more can in this signal processing apparatus 31, set up a phase comparator (phase comparator) 311, the difference interference signal that this two photodetector 281,282 is exported through bandpass filter 291,292 is imported in this phase comparator 311 simultaneously, more can measure the positive and negative of Δ φ immediately, reach the effect of difference phase change direction.

On the other hand, consider to be adjusted by this backfeed loop 32 position of face mirror 272, change the light path of S1, the phase differential that also difference interference P can be involved the S ripple is set in advance in Δ φ (t=O)=△ φ ₀Condition under, then final output signal is $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\left|4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}+\mathrm{\Δ}{\mathrm{\φ}}_0}{2}\right)\right|\sin \left(\mathrm{\Δ\ωt}\right),$ So can be at O＜Δ φ ₀Preestablish fixing phase difference value Δ φ between A＜π ₀Measure phase signal Δ φ (t).

In addition, be the 3rd preferred embodiment of the present invention as shown in Figure 3, remove aforementioned with the single-frequency He-Ne Lasers as light source, and outside the optics framework of beam split, also can adopt the laser (as Zeeman laser) 40 of two mutually vertical (orthogonal) linear polarizations (P involves the S ripple) and different frequency to be light source, and laser beam is divided into reference beam (P through light splitting piece 431 ₂+ S ₂) and signal beams (P ₁+ S ₁), the P that vertically can't interfere each other originally in the reference beam ₂Component and S ₂Component is divided into orthogonal two components more one by one through analysis of polarized light sheet (analyzer) 422 respectively as shown in Figure 4, thus, and P ₂With S ₂Interfere mutually at analysis of polarized light sheet 422 polarization direction components, constitute the difference interference signal of reference light, be converted to electric signal through photodetector 482, and with △ ω=ω _P-ω _SIn input differential amplifier 50 after bandpass filter 492 filtering of centre frequency.Signal beams then passes through polarized light light splitting piece 461 with S ₁Ripple and P ₁Wavelength-division light is with P in the present embodiment ₁Be incident to determinand 91 and reflect S through determinand ₁Then by plane mirror 471 reflection, merge and after light splitting piece 432 turns to, again through analysis of polarized light sheet 421, equally with orthogonal P at polarized light light splitting piece 461 ₁Component and S ₁Component is divided into two vertical components separately, interferes mutually at these analysis of polarized light sheet 421 polarization direction components, constitutes the difference interference signal of flashlight, also sends in the differential amplifier 50 through photodetector 481 and bandpass filter 491.Wherein, the difference interference signal of flashlight as shown in the formula: $I_{\mathrm{sig}}\left(\mathrm{\Δ\ωt}\right)=I_{P1+S1}\left(\mathrm{\Δ\ωt}\right)=\sqrt{I_{P_1}{I}_{S_1}}\sin 2{\mathrm{\θ}}_S\cos (\mathrm{\Δ\ωt}+\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{sig}})\·\·\·\·\·\·\·\·\·\left(8\right)$

Wherein, θ _sPolarization angle for analysis of polarized light sheet 421 in the signal beams. ${\mathrm{\Δ\φ}}_{\mathrm{sig}}={\mathrm{\φ}}_{P_1}-{\mathrm{\φ}}_{S_1}$ Be S ₁With P ₁The phase differential of ripple.△ ω=ω _P-ω _SBe P wave frequency ω _PWith S wave frequency ω _SThe difference frequency that difference interference produced. With

Be respectively P ₁Ripple and S ₁The light intensity of ripple.

In like manner, the difference interference signal of reference light then is: $I_{\mathrm{ref}}\left(\mathrm{\Δ\ωt}\right)=I_{P2+S2}\left(\mathrm{\Δ\ωt}\right)=\sqrt{I_{P_2}{I}_{S_2}}\sin 2{\mathrm{\θ}}_r\cos (\mathrm{\Δ\ωt}+{\mathrm{\Δ\φ}}_{\mathrm{ref}})-----\left(9\right)$

θ _rBe the polarization angle of analysis of polarized light sheet 422 in the reference beam, ${\mathrm{\Δ\φ}}_{\mathrm{ref}}={\mathrm{\φ}}_{P_2}-{\mathrm{\φ}}_{S_2}$ Be P ₂With S ₂The phase differential of ripple.Adjust the polarization angle θ of the analysis of polarized light sheet 421,422 in flashlight and the reference light path _sAnd θ _r, above-mentioned difference interference signal amplitude size is satisfied $\sqrt{I_{P_1}{I}_{S_1}}\sin {2\mathrm{\θ}}_S=\sqrt{I_{P_2}{I}_{S_2}}\sin {2\mathrm{\θ}}_r=2\mathrm{\χ}$ Relation.Then above-mentioned I _Ref(Δ ω t) and I _Sig(Δ ω t) can be rewritten as respectively: I _Sig(Δ ω t)=I _P1+S1(Δ ω t)=2 χ cos (Δ ω t+ Δ φ _Sig) ... (10) I _Ref(Δ ω t)=I _P2+S2(Δ ω t)=2 χ cos (Δ ω t+ Δ φ _Ref) ... (11)

Process is with the coordinate translation simultaneously of this two interference signal $\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{sig}}+\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{ref}}),$ Then formula (10) becomes respectively with formula (11) $I_{\mathrm{si}g}\left(\mathrm{\Δ\ωt}\right)=2\mathrm{\χ}\cos (\mathrm{\Δ\ωt}+\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{sig}}-\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{ref}})$ With $I_{\mathrm{ref}}\left(\mathrm{\Δ\ωt}\right)=2\mathrm{\χ}\cos (\mathrm{\Δ\ωt}-\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{sig}}-\mathrm{\Δ}{\mathrm{\φ}}_{\mathrm{ref}})$ 。After input differential amplifier 50 subtracts each other and amplifies, can be write as $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\mathrm{\γ}[I_{\mathrm{ref}}\left(\mathrm{\Δ\ωt}\right)-I_{\mathrm{sig}}\left(\mathrm{\Λ\ωt}\right)]=\left|4\mathrm{\γ\χ}\sin (\frac{\mathrm{\Δ\φ}}{2}\right)|\sin \left(\mathrm{\Δ\ωt}\right)\·\·\·\·\·\left(12\right)$

Δ φ=Δ φ wherein _Ref-Δ φ _SigBe the phase differential of reference beam and signal beams, γ is the gain of differential amplifier 50.

Certainly, also adjust face mirror 471 positions, change S herein by a backfeed loop 52 ₁The light path of ripple is with difference interference signal wave (P ₁+ S ₁) and difference interference reference wave (P ₂+ S ₂) phase differential be set in Δ φ (t=0)=Δ φ ₀, make the differential amplifier output signal $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\left|4\mathrm{\γ\χ}\sin \left(\frac{\mathrm{\Δ\φ}+\mathrm{\Δ}{\mathrm{\φ}}_0}{2}\right)\right|\sin \left(\mathrm{\Δ\ωt}\right)$ Middle Δ φ ₀Can be set at 0＜Δ φ ₀In＜π the scope, and the variation of phase signal Δ φ (t) is with Δ φ ₀Be basic point (bias), thereby can distinguish the direction of phase change.In addition, as difference interference signal wave (P ₁+ S ₁) and difference interference reference wave (P ₂+ S ₂) phase differential satisfy $\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\≅\frac{\mathrm{\Δ\φ}}{2}$ The time, I then _Out(Δ ω t)=| 2 γ χ Δ φ | sin (Δ ω t).Amplitude-modulated signal I _OutThe amplitude size of (Δ ω t) be phase signal Δ φ 2 γ χ doubly, and be basic point with Δ φ=0.

Again, as difference interference signal wave (P ₁+ S ₁) and difference interference reference wave (P ₂+ S ₂) phase difference φ=2n π+δ, when n is integer and 0＜δ＜π, then can in signal processing apparatus, increase an electronic counter (figure does not show), note down n pulse signal, cooperation amplitude size $\left|4\mathrm{\γ\χ}\sin \left(\frac{\mathrm{\δ}}{2}\right)\right|,$ Direct measure phase difference δ is therefore by parameter (n, δ) scope of extensible phase measurement.After this, configuration as last embodiment, after this differential amplifier 50, place the signal processing apparatus 51 comprise an amplitude demodulation device 510, just the signal of the original phase difference amplitude with electric signal can be presented, effectively accelerate measuring rate and improve sensing sensitivity.

As shown in Figure 5, signal beams L in second preferred embodiment ₁After frequency modulating device 241 its frequencies of fine tune, polarization spectro sheet 263 is with the P of signal beams ₁Wave component and S ₁Wave component separates, enter an annular optical path component respectively in the opposite direction as determinand, in the present embodiment should the annular optical path component be with the reflection of three plate plane catoptrons, 273,274,275 right angles, a common annular light path of transmitting for signal beams, the P in the signal beams of forming of institute ₁Ripple and S ₁Wavelength-division Jing Guo this annular light path reverse direction propagate, overlap at polarization spectro sheet 263 places again, and by this light splitting piece 233 reference beam and signal beams overlapped again and interfere mutually.In case should the annular light path rotate, and cause P ₁Ripple and S ₁The light path of ripple changes and causes the phase change of measurement, constitutes thus altogether with path annular heterodyne ineterferometer (Ring Interferometer), rotates or changes with the environment that measures this ring interferometer place.With aforementioned principle, can be write as by the signal that differential amplifier is exported: $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\left|4\mathrm{\γ\Θ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|\sin \left(\mathrm{\Δ\ωt}\right)\·\·\·\·\·\·\·\left(13\right)$

Wherein, Θ is difference interference P ripple and difference interference S wave amplitude size, and Δ φ is P ₁Ripple and S ₁The phase change that ripple is produced in annular light path.When Δ φ ≈ 0, (13) formula can be expressed as

I _out(Δωt)=|2γΘΔφ|sin(Δωt)……(14)

Thus, the signal amplitude size of these differential amplifier 30 outputs and the phase differential of measuring are directly proportional, and can provide a control signal by a backfeed loop as previous embodiment, this phase change that makes zero at any time, and the ability that provides accurate control phase to change.Its detection sensitivity is more directly measured Δ φ and is strengthened 2 γ Θ doubly.

Again as shown in Figure 6, consideration will be as signal beams P in the 3rd preferred embodiment ₁+ S ₁Through the P of polarization spectro sheet 462 with signal beams ₁Wave component and S ₁Wave component separates, enter an annular optical path component respectively in the opposite direction as determinand, in the present embodiment should the annular optical path component be with the reflection of three plate plane catoptrons, 472,473,474 right angles, a common annular light path of transmitting for signal beams, the P in the signal beams of forming of institute ₁Ripple and S ₁Wavelength-division Jing Guo this annular light path reverse direction propagate, overlap at polarization spectro sheet 462 places again, and produce difference interferences through this analysis of polarized light sheet 421 again, in case annular light path produces rotation and causes P ₁Ripple and S ₁The light path of ripple changes and causes the phase change of measurement to constitute a pair of frequency deviation ring of light shape heterodyne ineterferometer that shakes thus.With aforementioned principle, the signal of being exported by differential amplifier 50: $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\left|4\mathrm{\γ\Γ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|\sin \left(\mathrm{\Δ\ωt}\right)\·\·\·\·\·\·\·\·\left(15\right)$

Wherein Γ is difference interference P ripple and difference interference S wave amplitude size, and Δ φ is P ₁Ripple and S ₁The phase change that ripple is produced in annular light path.When Δ φ ≈ 0, (15) formula can be expressed as

I _out(Δωt)=|2γГΔφ|sin(Δωt)……………(16)

Thus, the signal amplitude size and the Δ φ of these differential amplifier 50 outputs are directly proportional, an and exportable control signal, thus, as the direction that is used for aircraft is when stablizing, but this control signal of mat returns control at any time, make aircraft when the skew prearranged heading, be detected immediately, and recover prearranged heading, this phase change that makes zero, and the ability that provides accurate control phase to change.

As shown in Figure 7, when keeping single-mode fiber (polarization maintain single mode optical fiber) 60 with a polarized light state, the annular light path with Fig. 5 replaces, to constitute an optical fibre ring interferometer (fiber optical ring interferometer), thus, also can be applicable in the relevant optical sensor such as take measurement of an angle immediately rotation, electromagnetic intensity size and control etc.Certainly, the optical fiber that cited herein complex number plane catoptron, annular are laid all only uses for the annular light path of explanation, is not construed as limiting condition.

Certainly, phase difference measuring apparatus of the present invention also can cooperate as Michelson's interferometer use, as shown in Figure 8, the linearly polarized lights that penetrate when a light source (be in the present embodiment be example with a linearly polarized light single-frequency frequency stabilization He-Ne Lasers) 70 are through a polarization angle adjusting gear, adjust its polarization angle as the half-wave plate in the present embodiment (λ/2 wave plate) 71, laser is divided into the signal beams P that is incident to polarization spectro sheet 761 through light splitting piece 731 again ₁Ripple adds S ₁Involve reference beam P in order to contrast ₂Ripple adds S ₂Ripple.Signal beams P ₁Ripple and S ₁After this polarization spectro sheet 761 of ripple process separated, the polarized light state of passing through in the opposite direction respectively kept one of single-mode fiber 60 formations annular light path, overlaps in these polarization spectro sheet 761 places again, arrives light splitting piece 732, light beam P through catoptron 772 ₂Ripple and S ₂Then be incident to a catoptron 771 that moves in time, make the frequency of reference beam be subjected to this catoptron 771 to move generation and change a little, consider that the translational speed when this catoptron 771 is a fixed value v ₀, then the frequency of two light beams will produce the difference on the frequency slightly that can separate $\mathrm{\Δ\ω}=\frac{4\mathrm{\π}}{\mathrm{\λ}}{v}_0=2\frac{{\mathrm{\ω}}_0}{C}{v}_0,$ The Doppler frequency that the catoptron 771 of fixed speed displacement is just produced.Signal beams is the P with the reference beam that is subjected to catoptron 771 reflections merely in light splitting piece 732 places again ₂Ripple and S ₂Ripple overlaps and produces difference interference.

To polarized light light splitting piece 762 places, again will perpendicular each other difference interference P ripple (P ₁+ P ₂) signal and difference interference S ripple (S ₁+ S ₂) signal separates again, and with two photodetectors 781,782 detection line polarization difference interference P ripple (P respectively ₁+ P ₂) signal, and difference interference S ripple (S ₁+ S ₂) signal and be converted to electric signal output.This P involves S ripple electrical signal converted, and warp is with Δ ω=ω respectively ₁-ω ₂Bandpass filter 791,792 for centre frequency to leach the interference signal of fixed frequency, obtains following result: $I_{P1+P2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{P_1}{I}_{P_2}}\cos (2\mathrm{k\Δl}\left(t\right)+\mathrm{\Δ}{\mathrm{\φ}}_P)\·\·\·\·\·\·\·\·\·\left(17\right)$ $I_{S1+S2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{S_1}{I}_{S_2}}\cos (2\mathrm{k\Δl}\left(t\right)+\mathrm{\Δ}{\mathrm{\φ}}_S)\·\·\·\·\·\·\·\·\left(18\right)$

Wherein, $k=\frac{2\mathrm{\π}}{\mathrm{\λ}}$ Light path l for signal beams _sLight path l with reference beam _rOptical path difference.When adjusting these half-wave plate 71 polarization angles, make $\sqrt{I_{P_1}{I}_{P_2}}=\sqrt{I_{S_1}{I}_{S_2}}=\mathrm{\ρ}$ The time, the respectively just phase deviation in formula (17) and the formula (18) $\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_P-\mathrm{\Δ}{\mathrm{\φ}}_S),$ Then formula (17) becomes respectively with formula (18): $I_{P1+P2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{P_1}{I}_{P_2}}\cos (2\mathrm{k\Δl}\left(t\right)+\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_P-\mathrm{\Δ}{\mathrm{\φ}}_S))\·\·\·\·\·\·\·\·\left(19\right)$ With $I_{S1+S2}\left(\mathrm{\Δ\ωt}\right)=2\sqrt{I_{S_1}{I}_{S_2}}\cos \left(2\mathrm{k\Δl}(t\right)-\frac{1}{2}(\mathrm{\Δ}{\mathrm{\φ}}_P-\mathrm{\Δ}{\mathrm{\φ}}_S)\·\·\·\·\·\·\·\left(20\right)$

Be output as I after by differential amplifier 80 this binary signal being subtracted each other and amplifies _OutWherein: $I_{\mathrm{out}}\left(\mathrm{\Δ\ωt}\right)=\mathrm{\γ}|I_{P1+P2}\left(\mathrm{\Δ\ωt}\right)+I_{S1+S2}\left(\mathrm{\Δ\ωt}\right)|=\left|4\mathrm{\γ\ρ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|\sin \left(\mathrm{\Δ\ωt}\right)\·\·\·\·\·\·\·\left(21\right)$

Be respectively P ₁Involve P ₂The wave intensity size. Be respectively S ₁Involve S ₂The wave intensity size.△ φ _PBe P ₁Involve P ₂The phase differential of ripple, △ φ _SBe S ₁Involve S ₂The phase differential of ripple.△ ω is the difference frequency of difference interference.Y is the gain of differential amplifier.By formula (21) the signal I of this differential amplifier 80 outputs as can be known _Out(△ ω t) belongs to Modulation and Amplitude Modulation (AM) signal, and its carrier frequency is △ ω=ω ₁- ₂So: the phase place of with amplitude demodulator 81 the institute desire being measured in the present embodiment immediately by measure the big trumpet of amplitude $4\mathrm{\γ\ρ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)$ Calculate.Certainly, above-described various signal processing apparatus also can cooperate present embodiment to use and not hinder.

The chart of following one page is to finish the experimental result that instant Measurement Phase changes according to Fig. 3 optics framework.

Wherein determinand 90 is the plane mirror that promotes with piezoelectric crystal, P ₁Ripple and S ₁A catoptron 272 and determinand 90 and reflection are not incided in wavelength-division, by changing reflected P ₁The amplitude-modulated amplitude size of the instant measurement in the position of plane mirror, the measured experimental result and the theoretical prediction of (6) formula match, and are enough to illustrate the feasibility and the sensitivity of this phase measurement method.

Especially, the framework of above-mentioned all component arrangements is simple, reaction velocity is accelerated, than phase detection device sensitivity in the past.

In sum, this practicality invention provides a kind of phase difference measuring apparatus and uses the difference interference measuring system of this device, with said apparatus, really can be diverted to directly and handled only be used as the differential amplifier of filtering environmental noise and signal processing apparatus in the past as optical signalling, effectively phase modulated signal is converted to amplitude deep pool system signal and presents the effect that reach effective quickening phase measurement speed, improve measurement sensitivity, cost reduces.

Claims (24)

1. a phase demodulating device is characterized in that: in order to measure the phase modulation (PM) test signal I of a fixed carrier frequency _s(ω t)=2k ₁Cos (ω t+ φ _s) and the phase modulation (PM) reference signal I of a same carrier frequencies _r(ω t)=2k ₂Cos (ω t+ φ _r) between phase differential, and Δ φ=φ _s-φ _r, described two phase place modulation signal comprises the function of carrier frequency and time product term and phase term respectively, described measurement mechanism comprises:

Two automatic gain control equipments are used for adjusting the amplitude of two phase modulation signal respectively, make the amplitude equal and opposite in direction (k of two phase modulation signal ₁=k ₂=k);

One differential amplifier, two phase modulation signal from two automatic gain control equipments is respectively subtracted each other and amplifies, obtaining an amplitude-modulated output signal, the amplitude of described output signal is proportional to the function that comprises frequency and time product and the product of phase function;

One signal processing apparatus, comprise an amplitude demodulation device, measure described Modulation and Amplitude Modulation output amplitude size and/or its variable quantity of described differential amplifier output in order to demodulation, thus, the phase difference φ that is comprised in the described differential amplifier output signal and/or its variable quantity are by the amplitude size of amplitude demodulation device from described Modulation and Amplitude Modulation output signal $\left|4\mathrm{\γ}k\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Draw.

2. demodulating equipment as claimed in claim 1 is characterized in that:

Described signal processing apparatus also comprises a phase comparator, in order to the phase differential of two more above-mentioned phase modulated signals and confirm the positive negative value of Δ φ, to distinguish the positive and negative of described phase difference φ and to distinguish the change direction of Δ φ.

3. demodulating equipment as claimed in claim 2 is characterized in that:

Described signal processing apparatus also comprises a counter, and when described phase meter being shown as Δ φ=2n π+δ, n is an integer, and 0＜δ＜π, then described Modulation and Amplitude Modulation output amplitude size $|4$ $\mathrm{\γ}k\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)|$ Write as $\left|4\mathrm{\γ}k\sin \left(\frac{\mathrm{\δ}}{2}\right)\right|,$ Described counter is in order to n pulse signal of record, and with (n, the δ) variation of the described phase differential of expression, thus, extension phase change measurement range.

4. demodulating equipment as claimed in claim 3 is characterized in that:

Described signal processing apparatus also comprises a differentiating circuit, in order to described amplitude demodulation output signal to time diffusion, when the phase differential of measuring change 0＜| Δ φ | in the time of in＜10 ° the scope, by described differentiating circuit with the amplitude size of described Modulation and Amplitude Modulation output signal to time diffusion, promptly $\frac{d\left|I_{\mathrm{out}}\right|}{\mathrm{dt}}=2\mathrm{\γk}\frac{d\left|\mathrm{\Δ\φ}\right|}{\mathrm{dt}}=2\mathrm{\γk}{\mathrm{\ω}}_s,$ Wherein ${\mathrm{\ω}}_s=\frac{d\left|\mathrm{\Δ\φ}\right|}{\mathrm{dt}},$ With instant measurement instantaneous frequency.

5. demodulating equipment as claimed in claim 1 is characterized in that:

Described demodulating equipment also comprises a backfeed loop, in order to a control signal to be provided, makes phase delta phi make zero (nulling) at any time.When phase differential 0＜| Δ φ | in＜10 ° the scope, the amplitude-modulated signal size of output equals | 2 γ k Δ φ |, directly by amplitude size measure phase difference Δ φ, and amplify 2 γ k doubly,

6. phase difference measuring apparatus is characterized in that:

In order to measure two electric signal of changing out respectively by the mutual perpendicular linear polarization optical signalling of two bundles of a polarization optics heterodyne ineterferometer, a branch of at least in the described two beam optics signals of described heterodyne ineterferometer, comprise the reflected light that shines a determinand, and the light intensity equal and opposite in direction of each described optical signalling, and be respectively the function that comprises difference on the frequency and time product term and phase differential item, described measurement mechanism comprises:

One differential amplifier also subtracts each other amplification for the input of described two electric signal, and obtaining an amplitude-modulated output signal, the amplitude of described signal is proportional to the product of the function of the function that comprises frequency and time product and phase differential;

One signal processing apparatus comprises an amplitude demodulation device, measures described amplitude-modulated signal amplitude size and/or its variable quantity of described differential amplifier output in order to demodulation.

7. phase difference measuring apparatus as claimed in claim 6 is characterized in that:

Described signal processing apparatus also comprises a counter, when described phase differential changes when surpassing 2 π, reads the some integral multiples that comprise 2 π in the variation of described phase differential with described counter.

8. difference interference measuring system is characterized in that it comprises in order to measure a determinand:

One coherence light source;

One heterodyne ineterferometer, in order to will being a signal beams and a reference beam from the light beam beam split of described coherence light source, described two light beams comprise orthogonal two linear polarization (P involves the S ripple) component, has a difference on the frequency between each described light beam, and at least one in two components of described signal beams, be to comprise the optical signalling that is irradiated to above-mentioned determinand and gets, and interfere two groups of amplitude equal and opposite in directions of generation mutually, and comprise the difference interference signal of the function of described difference on the frequency and time product term and phase differential item respectively;

Two photodetectors are in order to be converted to described two interference signals respectively the output of one electric signal;

One differential amplifier also subtracts each other amplification for the input of described two electric signal, and obtaining an amplitude-modulated output signal, the amplitude of described signal is proportional to the product of the function of the function that comprises frequency and time product and phase differential;

One signal processing apparatus, described signal processing apparatus comprise an amplitude demodulation device, measure described amplitude-modulated signal amplitude size and/or its variable quantity of described differential amplifier output in order to demodulation.

9. difference interference measuring as claimed in claim 8 system is characterized in that:

Described light source is a single-frequency Frequency Stabilized Lasers; Described heterodyne ineterferometer comprises a polarization angle adjusting gear, a light-dividing device and two class frequency modulating devices; And described signal processing apparatus comprises an amplitude-modulated signal demodulating equipment;

Described polarization angle adjusting gear comprises 1/1st wave plate, in order to adjust the linearly polarized light beam polarization angle of described single-frequency Frequency Stabilized Lasers output; Described light beam is to be divided into above-mentioned reference beam and signal beams via described light-dividing device, and adjusts described 1/2nd wave plate polarization angles, and the light intensity of described two each described component of light beam is satisfied $\sqrt{I_{P1}{I}_{P2}}=\sqrt{I_{S1}{I}_{S2}}=K$ Requirement; The frequency of described two light beams is transferred to slightly variant each other respectively by described two frequency modulating devices, cause described each P phase of wave to be interfered mutually and produce a difference interference P ripple signal I _P1+P2(Δ ω t)=2Kcos (Δ ω t+ Δ φ _P), described each S ripple also interfere to produce a difference interference S ripple signal I mutually _S1+S2(Δ ω t)=2Kcos (Δ ω t+ Δ φ _S), and identical, the amplitude equal and opposite in direction of frequency of described difference interference P ripple signal and described difference interference S ripple signal, and be respectively the function that comprises described difference on the frequency and time product term and phase differential item; Thus, the phase difference φ item that is comprised in the described differential amplifier output signal is by the amplitude size of described amplitude demodulation device from described Modulation and Amplitude Modulation output signal $\left|4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Draw.

10. difference interference measuring as claimed in claim 9 system is characterized in that: comprise a backfeed loop, the light path in order to the component that changes described at least two light beams maintains Δ φ (t=0)=Δ φ with the phase difference φ that described difference interference P is involved the S ripple ₀Near scope one of the initial point.

11. difference interference measuring as claimed in claim 9 system, it is characterized in that: described signal processing apparatus also comprises the phase comparator in order to more described two photodetector output signals, to distinguish the positive and negative of described phase difference φ, distinguish the change direction of described determinand position.

12. difference interference measuring as claimed in claim 9 system, it is characterized in that: described signal processing apparatus also comprises a counter, changes Δ φ=2n π+δ, then described differential amplifier output amplitude size when defining described phase differential $\left|4\mathrm{\γ}K\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Write as $4\mathrm{\γ}K\sin \left(\frac{\mathrm{\δ}}{2}\right),$ 0＜δ＜π wherein, n is an integer, and with n pulse signal of described counter record, by (n δ) reads the variation of described phase differential, thus, and the measurement range of extension phase change.

13. difference interference measuring as claimed in claim 9 system is characterized in that: perpendicular each other P in the described signal beams ₁Ripple and S ₁Ripple is to separate by a light splitting device that is arranged in the described signal beams light path, and described determinand is an annular optical path component, and described light splitting device position causes P perpendicular each other in the described signal beams in described frequency modulating device downstream ₁Ripple and S ₁Ripple is separated by described light splitting device, and the annular light path that described annular optical path component constituted of oppositely passing through, overlap in described polarized light light-dividing device place again, when described annular optical path component environment of living in rotated, the phase difference φ of described differential amplifier output was by the amplitude size of described amplitude-modulated signal $\left|4\mathrm{\γ\Θ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Draw.

14. difference interference measuring as claimed in claim 13 system is characterized in that:

Described annular optical path component comprises the complex number plane catoptron.

15. difference interference measuring as claimed in claim 13 system is characterized in that: described annular optical path component comprises that a polarized light state keeps single-mode fiber.

16. a difference interference measuring system is characterized in that it being in order to measuring a determinand, comprising:

One coherence light source;

One heterodyne ineterferometer, in order to will being a signal beams and a reference beam from the light beam beam split of described coherence light source, described two light beams all comprise orthogonal two linear polarization (P involves the S ripple) component, has a difference on the frequency between each described polarization direction component, and at least one in two components of described signal beams, be to comprise the optical signalling that is irradiated to above-mentioned determinand and gets, and interfere two groups of amplitude equal and opposite in directions of generation mutually, and comprise the difference interference signal of the function of described difference on the frequency and time product term and phase differential item respectively;

Two photodetectors are converted to electric signal output respectively with described two interference signals;

One differential amplifier also subtracts each other amplification for the input of described two electric signal, and obtaining an amplitude-modulated output signal, the amplitude of described signal is proportional to the product of the function of the function that comprises frequency and time product and phase differential;

One signal processing apparatus comprises an amplitude demodulation device, and described amplitude-modulated signal amplitude size and/or its variable quantity of described differential amplifier output measured in demodulation.

17. difference interference measuring as claimed in claim 16 system is characterized in that:

Described light source is the laser of a bifrequency and mutual perpendicular linear polarization, to provide two bundle frequencies slightly variant linearly polarized laser bundle in orthogonal two directions respectively; Described heterodyne ineterferometer comprises a light-dividing device and two analysis of polarized light sheets; And described signal processing apparatus comprises an amplitude-modulated signal demodulating equipment;

Light beam from described light source is to be divided into reference beam and signal beams through described light-dividing device, makes described reference beam comprise mutually two slightly variant component P of frequency vertically and each other of linear polarization ₂And S ₂, described signal beams then comprise linear polarization mutually vertically, two slightly variant component P of frequency each other ₁And S ₁

The described two component P of described signal beams ₁, S ₁In at least one is to be irradiated to described determinand, and described reference beam and described signal beams are respectively through each described corresponding analysis of polarized light sheet, make each other and interfere mutually along each described component of analysis of polarized light sheet polarization direction, the position angle of each described analysis of polarized light sheet is adjusted, and the light intensity of each described component is satisfied $\sqrt{I_{P1}{I}_{S1}}\sin 2{\mathrm{\θ}}_S=\sqrt{I_{P2}{I}_{S2}}\sin {\mathrm{\θ}}_r=2\mathrm{\χ}$ Relation, thus, described signal beams produces a difference interference signal wave I _Sig(Δ ω t)=2 _{χ cos}(Δ ω t+ Δ φ _Sig), described reference beam also produces a difference interference reference wave I _Ref(Δ ω t)=2 _{χ cos}(Δ ω t+ Δ φ _Ref), and described difference interference signal wave is identical with reference to wave frequency with described difference interference, the amplitude equal and opposite in direction, and be respectively the function that comprises described difference on the frequency and time product term and phase differential item; Thus, the phase difference φ item that is comprised in the described differential amplifier output signal is by the amplitude size of described amplitude demodulation device from described Modulation and Amplitude Modulation output signal $\left|4\mathrm{\γ\χ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Draw.

18. difference interference measuring as claimed in claim 17 system is characterized in that:

Comprise a backfeed loop, change the light path of a component of described at least two light beams, the phase difference φ that described difference interference P is involved the S ripple maintains initial point Δ φ (t=0)=Δ φ ₀Near one of scope.

19. difference interference measuring as claimed in claim 17 system is characterized in that:

Described signal processing apparatus also comprises the phase comparator in order to more described two photodetector output signals, distinguishes the positive and negative of described phase difference φ thus, distinguishes the change direction of described determinand position.

20. difference interference measuring as claimed in claim 17 system is characterized in that:

Described signal processing apparatus also comprises a counter, changes Δ φ=n π+δ, then described differential amplifier output amplitude modulation signal amplitude size when defining described phase differential $\left|4\mathrm{\γ\χ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)\right|$ Write as $4\mathrm{\γ\χ}\sin \left(\frac{\mathrm{\δ}}{2}\right),$ 0＜δ＜π wherein, and with n pulse signal of described counter record is by (n δ) reads the variation of described phase differential, extends the phase change measurement range thus.

21. difference interference measuring as claimed in claim 17 system is characterized in that:

Perpendicular each other P in the described signal beams ₁Ripple and S ₁Ripple is to separate by a light splitting device that is arranged in the described signal beams light path, and described determinand is an annular optical path component, makes P perpendicular each other in the described signal beams ₁Ripple and S ₁Ripple is separated by described light splitting device, and the annular light path that described annular optical path component constituted of oppositely passing through each other, overlap in described polarized light light-dividing device place again, when described annular optical path component environment of living in rotated, the phase difference φ of described differential amplifier output was by the amplitude size of described amplitude-modulated signal $|4$ $\mathrm{\γ\Γ}\sin \left(\frac{\mathrm{\Δ\φ}}{2}\right)|$ Draw.

22. difference interference measuring as claimed in claim 21 system, it is characterized in that: described annular optical path component comprises the complex number plane catoptron.

23. difference interference measuring as claimed in claim 21 system is characterized in that: described annular optical path component comprises that a polarized light state keeps single-mode fiber.

24. a difference interference measuring system is characterized in that it being in order to measure a determinand, to comprise: a coherence light source;

One heterodyne ineterferometer, in order to will being a signal beams and a reference beam from the light beam beam split of described coherence light source, described two light beams all comprise orthogonal two linear polarization (P involves the S ripple) component, in two components of described signal beams at least one, be to comprise the optical signalling that is irradiated to above-mentioned determinand and gets, described reference beam then is irradiated to a mobile mirror, making described reference beam produce a Doppler frequency changes, and described two light beams are interfered mutually produce two groups of amplitude equal and opposite in directions, and comprise described difference on the frequency and time product term respectively, and the difference interference signal of the function of phase differential item;

Two photodetectors are converted to electric signal output respectively with described two interference signals;

One differential amplifier also subtracts each other amplification for the input of described two electric signal, and obtaining an amplitude-modulated output signal, the amplitude of described signal is proportional to the product of the function of the function that comprises frequency and time product and phase differential;

One signal processing apparatus comprises an amplitude demodulation device, and described amplitude-modulated signal amplitude size and/or its variable quantity of described differential amplifier output measured in demodulation.

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