CN102419441B - Four-channel detection technology based method for inter-satellite displacement measurement through weak-light phase lock and device for realizing same - Google Patents

Abstract

The invention relates to a four-channel detection technology based method for inter-satellite displacement measurement through weak-light phase locking and a device for realizing the same, belongs to the field of optics, and solves the problem that light beam energy can hardly meet the measurement requirement in the inter-satellite displacement measurement of ultralong distance. The method is used for measuring a displacement between two satellites, both of which are respectively called as a target end and a measurement end, and comprises the steps of: outputting a laser containing two longitudinal mode laser components with mutually vertical polarization states by using a double longitudinal mode laser module at the measurement end; regulating the laser and then transmitting the regulated laser to the target end as a measurement laser, and forming a reference signal Sref; after processing the measurement laser at the target end, combining the processed measurement laser with a laser transmitted by a laser module at the target end; returning a formed return laser to the measurement end; combining the return laser with the reference laser and performing frequency mixing to obtain ameasurement signal Smeas obtained through a heterodyne interferometry; and after respectively inputting the reference signal Sref and the measurement signal Smeas into a phase subdivision module, resolving the displacement of the target end relative to the measurement end according to an accumulated phase value by a displacement calculating module.

Description

Displacement measurement method and realize the device of this method between the phase-locked star of a kind of low light level based on the four-way Detection Techniques

Technical field

The present invention relates to displacement measurement method between the phase-locked star of a kind of low light level based on the four-way Detection Techniques and realize the device of this method, belong to optical field.

Background technology

To successfully moonfall, from exploring extraterrestrial life to carrying out the space gravitational wave detection, the exploration of human space-ward does not rest forever from the emission earth satellite.In this process, obtained great development for displacement measurement technology between the star of monitoring aircraft movements state.By adopting the laser heterodyne interference measuring method, under the prerequisite that guarantees micron even nano-precision, its detection range has expanded to millions of kilometers.Under detection range situation so far away, the method of tradition displacement and the passive reflection measurement laser of the employed destination end of range observation is no longer suitable, and measurement laser dispersing of light beam under the twice detection range will cause laser power to decay significantly and can't survey.

At this problem, the researchist has proposed in destination end the passback laser instrument to be set, and control passback laser carries out Frequency Phase Lock to incident laser to be realized the method that laser amplifies passback is measured in incident.2000 US National Aeronautics and Space Administration (NASA) jet power laboratory (Jet Propulsion Laboratory) Muthu Jeganathan and people such as Serge Dubovitsky utilize said method to carry out related experiment, it uses laser rrequency-offset-lock device (LOLA) to realize the frequency locking of destination end 1.319 mum wavelengths passback laser to transmitting terminal laser 50MHz.It has verified that by piezoelectric ceramics micro-displacement platform control reflector position is set in destination end the Measurement Resolution of measuring system reaches 2.6nm in the 350nm displacement range.Through experiment and analysis, the key that people such as Muthu Jeganathan propose to utilize this method to realize that distance displacement is measured is to guarantee that destination end returns laser is launched the laser frequency phase place to measuring junction accurate locking tracking.

Phase early 1990s, the optics phaselock technique develops moulding on the PHASE-LOCKED LOOP PLL TECHNIQUE basis of electricity field, owing to can realize the locking tracking to the laser frequency phase place, it is once the extensive concern that the researchist occurs just being subjected to.The optics phaselocked loop can be divided into homodyne formula optics phaselocked loop and heterodyne system optics phaselocked loop according to the difference that produces feedback control signal.Wherein, homodyne formula optics phaselocked loop directly extracts the phase difference value of passback laser and incident laser, and as feedback signal passback laser is controlled, the final passback laser phase locked track consistent with the incident laser frequency of realizing.Heterodyne system optics phaselocked loop then will return the frequency of laser and incident laser mixed frequency signal and the reference frequency of local oscillator compares, with the frequency departure signal feedback control passback laser that produces, final realization passback laser and incident laser frequency-splitting are constant to be the reference frequency of local oscillator.

At present, the optics phaselock technique has obtained application in this domestic and international hot research problem of space gravitational wave detection.The space gravitational wave detection need carry out real-time spacing and position measurement to the spacecraft of a plurality of overlength distances, certain tracks, and distance is generally millions of kilometers between spacecraft.Therefore phase-locked the becoming of the low light level of measuring laser guaranteed the gordian technique of carrying out the displacement precision measurement under detection range so far away.The plan of existing space gravitational wave detection have living space laser interference antenna plan (LISA) and laser astrodynamics space programme (ASTROD).Wherein, space laser interferes antenna plan (LISA) to be studied by American National space agency (NASA) and European Space Agency (ESA) cooperation, this project need be carried out precision measurement to the spacing that two distance reach 5,000,000 kilometers spacecrafts, and it chooses heterodyne system optics phase-locked loop to realize low light level passback.Nd:YAG laser instrument that two 1064nm are adopted in this plan is as light source, and it has been realized that reference frequency is that the adjustable heterodyne of 3～30MHz is phase-locked.When its light intensity differed maximum, the low light level was 2mW for the 320pW high light only.Spacecraft Doppler shift that relative motion is introduced can be eliminated to the phase-locked influence that causes in the selected heterodyne system low light level phase-locked loop of this project, but because it adopts local oscillator as phase-locked benchmark, the error that this oscillator brings can directly be introduced among the phase-locked result phase-locked precision is exerted an influence.In addition, the heterodyne phaselocked loop is because its selecting frequency difference as feedback signal, can't really realize returning the accurate locking of laser and incident laser phase differential.

Laser astrodynamics space programme (ASTROD) is carried out with European cooperation by China, for avoiding Doppler shift to the phase-locked influence that brings, this project still plans to use the phase-locked scheme of heterodyne that passback laser is controlled, but has carried out the phase-locked relevant exploration of homodyne in previous experiments.People such as the Ni Weidou of Taiwan Tsing-Hua University, Liao Anqi utilize two Nd:YAG laser instruments as light source, utilize the light obstructing instrument to control the output intensity of two-laser respectively to simulate the long-range incident low light level and local passback high light.Adopt balanced second order homodyne phase-locked loop, temperature by regulating local laser instrument and directly by two kinds of approach of piezoelectric ceramic actuator regulation and control resonant cavity length local laser optical signal phase is carried out FEEDBACK CONTROL, make the phase place of local passback laser be locked in long-range incident laser, form the light phase-locked loop.Experiment shows, this homodyne phaselocked loop has finally been realized phase-locked lastingly to the 2nW low light level and 2mW high light, realized the 200pW low light level and phase-locked more than the 200 μ W high light 2h.But it should be noted that two-laser is static relatively in this experiment, therefore do not test the doppler shift effect influence phase-locked to homodyne.Yet between the star of reality in the range finding process, the local Doppler shift that is caused by relative motion with the remote laser device is difficult to avoid, and is subject to the pullin banwidth that existing homodyne phaselocked loop has only tens kHz, and the phase locked track of the long-range incident low light level is difficult to realize.

In sum, the application in the displacement measurement between the overlength distance star compares to heterodyne system laser phaselocked loop and homodyne formula laser phaselocked loop: heterodyne system laser phaselocked loop has bigger acquisition bandwidth, and the two laser frequency differences that can effectively avoid Doppler shift to bring change phase-locked influence.But owing to have difference on the frequency between passback laser and the incident laser, it can not realize phase locked track truly.Owing to adopt local oscillator as phase-locked benchmark, its operating characteristic can produce a very large impact phase-locked precision simultaneously.Homodyne formula laser phaselocked loop can realize that the accurate frequency locking of two bundle laser is phase-locked, and it does not need local oscillator as phase-locked reference data simultaneously, but will be applied to the actual measurement environment, at first will solve Doppler shift to its phase-locked influence.

Summary of the invention

To the present invention seeks to that beam energy is difficult to satisfy the problem of measuring needs in the displacement measurement in order solving between the overlength distance star, displacement measurement method between the phase-locked star of a kind of low light level based on the four-way Detection Techniques to be provided and to have realized the device of this method.

Displacement measurement method between the phase-locked star of a kind of low light level based on the four-way Detection Techniques of the present invention,

This method may further comprise the steps:

Step 1, unlatching are in the laser module of destination end, enter steady-working state through this laser module behind the warm, utilize 1/2nd wave plates and polarization splitting prism that the linearly polarized laser of laser module output is divided into two parts, a part is designated as L as the passback laser of destination end with described passback laser _B, another part is used for the FEEDBACK CONTROL laser module as phase-locked laser, and described phase-locked laser is designated as L _L, phase-locked laser L _LBe the vertical curve polarization laser, passback laser L _BFrequency and phase-locked laser L _LFrequency identical, described passback laser frequency and phase-locked laser frequency are designated as v respectively _BAnd v _L

Step 2, unlatching are in the double longitudinal mode laser module of measuring junction, after preheating and frequency stabilization control procedure, double longitudinal mode laser module output laser comprises orthogonal two the longitudinal mode laser compositions of polarization state, and the polarization state of adjusting two longitudinal mode lasers makes described two longitudinal mode lasers become horizontal linear polarization laser L respectively _MWith vertical curve polarization laser L _R, the frequency of horizontal linear polarization laser is v _M, the frequency of vertical curve polarization laser is v _R, and v _MV _R

Step 3, utilize the depolarization Amici prism with described horizontal linear polarization laser L _MWith vertical curve polarization laser L _RBe divided into reflecting part and transmissive portion, the horizontal linear polarization laser L of reflecting part _MVertical curve polarization laser L with the reflecting part _RCarry out optical frequency mixing and obtain beat signal, by high-speed photodetector this beat signal is converted into electric signal, the reference signal of difference interference measuring is designated as S _Ref, the reference signal frequency of difference interference measuring is the difference on the frequency v of two longitudinal mode lasers _Ref=v _M-v _R

The vertical curve polarization laser L of transmissive portion _RPassback laser L as reference laser and destination end _BSwash combiner and optical frequency mixing, the horizontal linear polarization laser L of transmissive portion _MAfter being converted into circularly polarized light, penetrated to destination end by measuring junction as measuring laser;

Step 4, described measurement laser arrive after the destination end, earlier described measurement laser are converted to the linearly polarized light that the polarization direction is level by circularly polarized light, again with the phase-locked laser L of destination end _LSwash combiner formation and close the light light beam, utilize 1/2nd wave plates to adjust the described laser L in the light light beam that closes _MWith L _LThe polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles;

Step 5, utilize the depolarization Amici prism that the described light light beam that closes is divided into reflection and closes light light beam L _FClose light light beam L with transmission _T, wherein light light beam L is closed in reflection _FBeat frequency light signal through 180 ° of polarization splitting prism formation two-way phase phasic differences is converted to the beat frequency electric signal and is sent into the signal condition module by two high-speed photodetectors respectively, and light light beam L is closed in transmission _TAt first will close in the light light beam 90 ° of phase delays measuring laser through optical phase delay device, form the beat frequency light signal of 180 ° of two-way phase phasic differences then by polarization splitting prism, be converted to the beat frequency electric signal and send into the signal condition module by other two-way high-speed photodetector respectively;

Step 6, because destination end relative measurement end movement change to be introduced doppler shift effect, measure the frequency that laser arrives destination end and change, with described phase-locked laser L _LFrequency representation be v' _M, simultaneously reflection is closed light light beam L _FIn the measurement laser phase place that arrives photodetector be designated as

, light light beam L is closed in reflection _FIn phase-locked laser L _LThe phase place that arrives photodetector is designated as , the signal condition module is closed light light beam L with reflection _FCorresponding two-way beat frequency electric signal subtracts each other and obtains closing light reflection beat signal, will describedly close light and reflect beat signal and be designated as S _R,

Then work as v' _M=v _LThe time,

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

Step 7, signal condition module are closed transmission light light beam L simultaneously _TCorresponding two-way beat frequency electric signal subtracts each other and obtains closing light transmission beat signal, and the described light transmission beat signal that closes is designated as S _T, because the effect of optical phase delay device, light light beam L is closed in transmission _TIn the measurement laser phase place that arrives photodetector be designated as

, light light beam L is closed in transmission _TIn phase-locked laser L _LThe phase place that arrives photodetector is designated as

,

Then work as v' _M=v _LThe time,

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

The laser module of step 8, destination end enters the optical frequency locking control stage, at first gets and closes light reflection beat signal S _RWith close light transmission beat signal S _TCarry out frequency measurement, the frequency measurement result is designated as v _Meas,

v _meas=|v' _M-v _L|，

When closing light reflection beat signal S _RPhase place is closed light transmission beat signal S in advance _TIn the time of 90 °, show v' _MV _L, frequency measurement this moment result is

v _meas=v' _M-v _L，

Obtain measuring laser and phase-locked laser L _LThe frequency discrimination result be

△v _M-L=v' _M-v _L=v _meas，

When closing light reflection beat signal S _RPhase place lags behind and closes light transmission beat signal S _TIn the time of 90 °, show v' _M＜v _L, frequency measurement this moment result is

v _meas=v _L-v' _M，

Obtain measuring laser and phase-locked laser L _LThe frequency discrimination result be

△v _M-L=v' _M-v _L=-v _meas；

Step 9, with the frequency values △ ν that measures _M-LAs optical frequency locking signal input digit controller, according to the phase-locked laser L of laser module output _LThe phase-locked laser L of frequency and the output of described laser module _LThe corresponding relation of cavity length, adjust laser module resonator cavity temperature to realize the adjusting on a large scale to cavity length by temperature control modules, by the PZT drive control module cavity length is carried out directly regulating fast simultaneously, thus the phase-locked laser L of FEEDBACK CONTROL _LFrequency v _LMake △ ν _M-LBe tending towards 0, as △ ν _M-L=0 o'clock, the optical frequency locked stage of destination end laser module finished, and exports phase-locked laser L _LAnd passback laser L _BFrequency be locked as the frequency of the measurement laser of incident,

Be ν _B=ν _L=v' _M

The laser module of step 10, destination end enters the phase locked track control stage after the optical frequency locking control stage finishes, at first get and close light reflection beat signal S _RWith close light transmission beat signal S _TCarry out the arc tangent phase measurement, obtain measuring laser and phase-locked laser L _LIdentified result be

With the phase value that measures

As phase-locked closed-loop control signal input digit controller, by the PZT drive control module cavity length of laser module is carried out meticulous quick adjustment, the phase-locked laser L of FEEDBACK CONTROL _LPhase place

Make

Be tending towards 0, when

The time, the phase-locked control procedure of laser module is finished, and exports phase-locked laser L _LAnd passback laser L _BFrequency be locked as the phase place of the measurement laser of incident,

Namely

Step 11, when optics phase locked track system losing lock, repeating step nine and step 10, the phase-locked laser L of laser module _LAnd passback laser L _BCan be to measuring laser phase locked track again;

Step 12, utilize quarter-wave plate frequency and phase place all to be locked in the linear polarization passback laser L that measures laser _BBe converted into circularly polarized light, described circularly polarized light is back to behind the measuring junction by quarter-wave plate again circularly polarized light is converted into the linearly polarized light of polarization direction level, changed by destination end relative measurement end movement and causes the influence of doppler shift effect, passback laser L _BThe frequency that arrives measuring junction changes, and will return the laser measurement frequency representation is v' _B, then the approximate formula according to Doppler shift has

${v^{\′}}_B=v_M+\frac{2u}{\mathrm{\λ}};$

In the formula, u is the movement velocity of destination end relative measurement end, and λ is for measuring laser and passback laser L _BMean wavelength,

Step 13, will return laser L _BClose light and carry out the measuring-signal that mixing obtains difference interference measuring with reference laser, utilize high speed detector that this beat signal is converted into the beat frequency electric signal, the beat frequency electric signal is designated as S _Meas, beat signal frequency is reference laser L _R1With passback laser L _BDifference on the frequency

$v_{\mathrm{meas}}={v^{\′}}_B-v_R=v_M-v_R+\frac{2u}{\mathrm{\λ}};$

Step 14, with the reference signal S of difference interference measuring _RefWith measuring-signal S _MeasThe laggard line frequency of input phase segmentation module is subtracted each other respectively, the doppler shifted signal that obtains the destination end motion thus and produce, after described doppler shifted signal carried out phase subdivision and accumulation calculating, calculated the displacement of destination end relative measurement end according to the phase value of accumulative total by the displacement computing module.

Realize the device of displacement measurement method between the phase-locked star of above-mentioned a kind of low light level based on the four-way Detection Techniques, it comprises measuring junction and destination end,

Measuring junction comprises double longitudinal mode laser module, frequency stabilization control module, the 1/1st wave plate, the first depolarization Amici prism, first analyzer, first high-speed photodetector, first polarization splitting prism, first quarter-wave plate, the 4th quarter-wave plate, the 6th polarization splitting prism, second analyzer, the 6th high-speed photodetector, phase subdivision module and displacement computing module

Destination end comprises second quarter-wave plate, second polarization splitting prism, the 1/2nd wave plate, the second depolarization Amici prism, the 3rd polarization splitting prism, second high-speed photodetector, the 3rd high-speed photodetector, optical phase delay device, the 4th polarization splitting prism, the 4th high-speed photodetector, the 5th high-speed photodetector, the signal condition module, the frequency measurement module, quadrature phase demodulation module, digitial controller, temperature control modules, the PZT drive control module, laser module, the 1/3rd wave plate, the 5th polarization splitting prism, the 3rd quarter-wave plate

The output terminal of frequency stabilization control module links to each other with the input end of double longitudinal mode laser module, the 1/1st wave plate, the first depolarization Amici prism, first polarization splitting prism, first quarter-wave plate, second quarter-wave plate, second polarization splitting prism, the 1/2nd wave plate, the second depolarization Amici prism, optical phase delay device, the 4th polarization splitting prism and the 5th high-speed photodetector are placed on the emitting light path of double longitudinal mode laser module in turn

First analyzer and first high-speed photodetector are placed on after the reflection output face of the first depolarization Amici prism in turn,

The double longitudinal mode laser of double longitudinal mode laser module outgoing is transmitted through the first depolarization Amici prism through the 1/1st wave plate, the folded light beam of the first depolarization Amici prism is incident to first analyzer, light beam through the first analyzer transmission is incident to first high-speed photodetector, the electrical signal of first high-speed photodetector links to each other with the first input end of phase subdivision module

The transmitted light beam of the first depolarization Amici prism is incident to first polarization splitting prism, and the conduct after the first quarter-wave plate transmission of the transmitted light beam of first polarization splitting prism is measured Laser emission to destination end,

Second quarter-wave plate of destination end receives measures laser, and be transmitted through second polarization splitting prism, the linearly polarized laser that laser module sends is transmitted through the 5th polarization splitting prism through the 1/3rd wave plate, and the vertical curve polarization laser of the 5th polarization splitting prism reflection is as phase-locked laser L _LClose the light light beam with the transmitted light beam formation of second polarization splitting prism, the described light light beam that closes is transmitted through the second depolarization Amici prism through the 1/2nd wave plate,

The light folded light beam of closing through the reflection of the second depolarization Amici prism is incident to the 3rd polarization splitting prism, folded light beam through the reflection of the 3rd polarization splitting prism is incident to second high-speed photodetector, transmitted light beam through the 3rd polarization splitting prism transmission is incident to the 3rd high-speed photodetector

The light transmitted light beam that closes through the second depolarization Amici prism transmission is incident to optical phase delay device, the delay light beam of optical phase delay device output is incident to the 4th polarization splitting prism, folded light beam through the reflection of the 4th polarization splitting prism is incident to the 4th high-speed photodetector, transmitted light beam through the 4th polarization splitting prism transmission is incident to the 5th high-speed photodetector

Second high-speed photodetector, the 3rd high-speed photodetector, the signal of the 4th high-speed photodetector and the 5th high-speed photodetector collection is exported to the signal condition module respectively, the folded light beam difference signal output terminal of signal condition module links to each other with the input end of frequency measurement module and the input end of quadrature phase demodulation module simultaneously, the transmitted light beam difference signal output terminal of signal condition module links to each other with the input end of frequency measurement module and the input end of quadrature phase demodulation module simultaneously, the output terminal of frequency measurement module links to each other with the first input end of digitial controller, the output terminal of quadrature phase demodulation module links to each other with second input end of digitial controller, the control temperature signal output terminal of digitial controller links to each other with the input end of temperature control modules, the output terminal of temperature control modules links to each other with first control end of laser module, the PZT of digitial controller drives signal output part and links to each other with the input end of PZT drive control module, the output terminal of PZT drive control module drives the signal controlling end with the PZT of laser module and links to each other

The transmitted light beam of the 5th polarization splitting prism returns measuring junction as the passback Laser emission after the 3rd quarter-wave plate transmission, the 4th quarter-wave plate of measuring junction receives passback laser, and be transmitted through the 6th polarization splitting prism, be transmitted through the passback laser L of the 6th polarization splitting prism _BAfter closing light with the reference laser of first polarization splitting prism reflection, be transmitted through the 6th high-speed photodetector through second analyzer again, the electrical signal of the 6th high-speed photodetector links to each other with second input end of phase subdivision module, and the output terminal of phase subdivision module links to each other with the output terminal of displacement computing module.

Advantage of the present invention:

(1) with existing star between displacement measurement method compare, displacement measurement method will return laser and measure laser and increased optical frequency locking control procedure before phase-locked between the designed phase-locked star of the low light level of the present invention.Because the acquisition bandwidth of optical frequency locking is much larger than the acquisition bandwidth of phase locked track, when therefore the Doppler shift of real-time change is introduced in destination end and measuring junction relative motion, passback laser still can by first frequency locking more phase-locked process realize high precision phase locked track to measurement laser, significantly improve simultaneously the anti-interference of system, this is one of innovative point that is different from prior art.

(2) used high-precision integrated laser phase frequency detector in the displacement measuring device between the designed phase-locked star of the low light level of the present invention, laser frequency discrimination link wherein is when recording two bundle laser frequency difference absolute values, also according to two-way close photo-beat frequently the lead lag relationship of signal determined the frequency magnitude relationship of two bundle incident lasers really to have realized the accurate measurement to two bundle incident laser difference on the frequencies; Laser phase demodulation link then by arc tangent phase measurement and the signal sensing of two-way quadrature beat signal that four detection channels are generated, has realized high-precision phase measurement.The balance detection of its four passages makes laser power fluctuation obtain good restraining to the influence of measurement result, this be different from prior art innovative point two.

Description of drawings

Fig. 1 is the structural representation of apparatus of the present invention;

Fig. 2 is for arriving the measurement laser frequency v' of destination end _MGreater than phase-locked laser L _LFrequency v _LThe time, close light reflection beat signal S _RWith close light transmission beat signal S _TThe phase relation synoptic diagram;

Fig. 3 is for arriving the measurement laser frequency v' of destination end _MLess than phase-locked laser L _LFrequency v _LThe time, close light reflection beat signal S _RWith close light transmission beat signal S _TThe phase relation synoptic diagram.

Embodiment

Embodiment one: below in conjunction with Fig. 1 to Fig. 3 present embodiment is described, displacement measurement method between the phase-locked star of the described a kind of low light level based on the four-way Detection Techniques of present embodiment, this method may further comprise the steps:

Step 1, unlatching are in the laser module of destination end, enter steady-working state through this laser module behind the warm, utilize 1/2nd wave plates and polarization splitting prism that the linearly polarized laser of laser module output is divided into two parts, a part is designated as L as the passback laser of destination end with described passback laser _B, another part is used for the FEEDBACK CONTROL laser module as phase-locked laser, and described phase-locked laser is designated as L _L, phase-locked laser L _LBe the vertical curve polarization laser, passback laser L _BFrequency and phase-locked laser L _LFrequency identical, described passback laser frequency and phase-locked laser frequency are designated as v respectively _BAnd v _L

Step 2, unlatching are in the double longitudinal mode laser module of measuring junction, after preheating and frequency stabilization control procedure, double longitudinal mode laser module output laser comprises orthogonal two the longitudinal mode laser compositions of polarization state, and the polarization state of adjusting two longitudinal mode lasers makes it become horizontal linear polarization laser L respectively _MWith vertical curve polarization laser L _R, the frequency of horizontal linear polarization laser is v _M, the frequency of vertical curve polarization laser is v _R, and v _MV _R

Step 3, utilize the depolarization Amici prism with described horizontal linear polarization laser L _MWith vertical curve polarization laser L _RBe divided into reflecting part and transmissive portion, the horizontal linear polarization laser L of reflecting part _MVertical curve polarization laser L with the reflecting part _RCarry out optical frequency mixing and obtain beat signal, by high-speed photodetector this beat signal is converted into electric signal, the reference signal of difference interference measuring is designated as S _Ref, the reference signal frequency of difference interference measuring is the difference on the frequency v of two longitudinal mode lasers _Ref=v _M-v _R

The vertical curve polarization laser L of transmissive portion _RPassback laser L as reference laser and destination end _BSwash combiner and optical frequency mixing, the horizontal linear polarization laser L of transmissive portion _MAfter being converted into circularly polarized light, penetrated to destination end by measuring junction as measuring laser;

Step 4, described measurement laser arrive after the destination end, earlier described measurement laser are converted to the linearly polarized light that the polarization direction is level by circularly polarized light, again with the phase-locked laser L of destination end _LSwash combiner formation and close the light light beam, utilize 1/2nd wave plates to adjust the described laser L in the light light beam that closes _MWith L _LThe polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles;

Step 5, utilize the depolarization Amici prism that the described light light beam that closes is divided into reflection and closes light light beam L _FClose light light beam L with transmission _T, wherein light light beam L is closed in reflection _FBeat frequency light signal through 180 ° of polarization splitting prism formation two-way phase phasic differences is converted to the beat frequency electric signal and is sent into the signal condition module by two high-speed photodetectors respectively, and light light beam L is closed in transmission _TAt first will close in the light light beam 90 ° of phase delays measuring laser through optical phase delay device, form the beat frequency light signal of 180 ° of two-way phase phasic differences then by polarization splitting prism, be converted to the beat frequency electric signal and send into the signal condition module by other two-way high-speed photodetector respectively;

Step 6, because destination end relative measurement end movement change to be introduced doppler shift effect, measure the frequency that laser arrives destination end and change, with described phase-locked laser L _LFrequency representation be v' _M, simultaneously reflection is closed light light beam L _FIn the measurement laser phase place that arrives photodetector be designated as

, light light beam L is closed in reflection _FIn phase-locked laser L _LThe phase place that arrives photodetector is designated as , the signal condition module is closed light light beam L with reflection _FCorresponding two-way beat frequency electric signal subtracts each other and obtains closing light reflection beat signal, will describedly close light and reflect beat signal and be designated as S _R,

Then work as v' _M=v _LThe time,

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

Step 7, signal condition module are closed transmission light light beam L simultaneously _TCorresponding two-way beat frequency electric signal subtracts each other and obtains closing light transmission beat signal, and the described light transmission beat signal that closes is designated as S _T, because the effect of optical phase delay device, light light beam L is closed in transmission _TIn the measurement laser phase place that arrives photodetector be designated as

, light light beam L is closed in transmission _TIn phase-locked laser L _LThe phase place that arrives photodetector is designated as

,

Then work as v' _M=v _LThe time,

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

The laser module of step 8, destination end enters the optical frequency locking control stage, at first gets and closes light reflection beat signal S _RWith close light transmission beat signal S _TCarry out frequency measurement, the frequency measurement result is designated as v _Meas,

v _meas=|v' _M-v _L|，

When closing light reflection beat signal S _RPhase place is closed light transmission beat signal S in advance _TIn the time of 90 °, show v' _MV _L, frequency measurement this moment result is

v _meas=v' _M-v _L，

Obtain measuring laser and phase-locked laser L _LThe frequency discrimination result be

△v _M-L=v' _M-v _L=v _meas，

When closing light reflection beat signal S _RPhase place lags behind and closes light transmission beat signal S _TIn the time of 90 °, show v' _M＜v _L, frequency measurement this moment result is

v _meas=v _L-v' _M，

Obtain measuring laser and phase-locked laser L _LThe frequency discrimination result be

△v _M-L=v' _M-v _L=-v _meas；

Step 9, with the frequency values △ ν that measures _M-LAs optical frequency locking signal input digit controller, according to the phase-locked laser L of laser module output _LThe phase-locked laser L of frequency and the output of described laser module _LThe corresponding relation of cavity length, adjust laser module resonator cavity temperature to realize the adjusting on a large scale to cavity length by temperature control modules, by the PZT drive control module cavity length is carried out directly regulating fast simultaneously, thus the phase-locked laser L of FEEDBACK CONTROL _LFrequency v _LMake △ ν _M-LBe tending towards 0, as △ ν _M-L=0 o'clock, the optical frequency locked stage of destination end laser module finished, and exports phase-locked laser L _LAnd passback laser L _BFrequency be locked as the frequency of the measurement laser of incident,

Be ν _B=ν _L=v' _M

The laser module of step 10, destination end enters the phase locked track control stage after the optical frequency locking control stage finishes, at first get and close light reflection beat signal S _RWith close light transmission beat signal S _TCarry out the arc tangent phase measurement, obtain measuring laser and phase-locked laser L _LIdentified result be

With the phase value that measures

As phase-locked closed-loop control signal input digit controller, by the PZT drive control module cavity length of laser module is carried out meticulous quick adjustment, the phase-locked laser L of FEEDBACK CONTROL _LPhase place Make

Be tending towards 0, when

The time, the phase-locked control procedure of laser module is finished, and exports phase-locked laser L _LAnd passback laser L _BFrequency be locked as the phase place of the measurement laser of incident,

Namely

Step 11, when optics phase locked track system losing lock, repeating step nine and step 10, the phase-locked laser L of laser module _LAnd passback laser L _BCan be to measuring laser phase locked track again;

Step 12, utilize quarter-wave plate frequency and phase place all to be locked in the linear polarization passback laser L that measures laser _BBe converted into circularly polarized light, described circularly polarized light is back to behind the measuring junction by quarter-wave plate again circularly polarized light is converted into the linearly polarized light of polarization direction level, changed by destination end relative measurement end movement and causes the influence of doppler shift effect, passback laser L _BThe frequency that arrives measuring junction changes, and will return the laser measurement frequency representation is v' _B, then the approximate formula according to Doppler shift has

${v^{\′}}_B=v_M+\frac{2u}{\mathrm{\λ}};$

In the formula, u is the movement velocity of destination end relative measurement end, and λ is for measuring laser and passback laser L _BMean wavelength,

Step 13, will return laser L _BClose light and carry out the measuring-signal that mixing obtains difference interference measuring with reference laser, utilize high speed detector that this beat signal is converted into electric signal, beat signal is designated as S _Meas, beat signal frequency is reference laser L _R1With passback laser L _BDifference on the frequency

$v_{\mathrm{meas}}={v^{\′}}_B-v_R=v_M-v_R+\frac{2u}{\mathrm{\λ}};$

Step 14, with the reference signal S of difference interference measuring _RefWith measuring-signal S _MeasThe laggard line frequency of input phase segmentation module is subtracted each other respectively, the doppler shifted signal that obtains the destination end motion thus and produce, after described doppler shifted signal carried out phase subdivision and accumulation calculating, calculated the displacement of destination end relative measurement end according to the phase value of accumulative total by the displacement computing module.

When starting working, open the laser module 26 that is in destination end, it enters steady-working state through warm.Utilize the 1/3rd wave plate 27 and the 5th polarization splitting prism 28 linearly polarized lasers with its output to be divided into two parts, wherein see through the horizontal polarization component of polarization splitting prism as the passback laser of destination end, it is designated as L _B, as phase-locked laser, it is designated as L by the vertical polarized component of polarization splitting prism reflection _L, passback laser L _BWith phase-locked laser L _LFrequency identical, it is designated as v respectively _BAnd v _L

Unlatching is in the double longitudinal mode laser module 1 of measuring junction, and through it enters the frequency stabilization state by 2 controls of frequency stabilization control module behind the warm, its output laser comprises orthogonal two the linear polarization longitudinal mode compositions of polarization state.Utilize the 1/1st wave plate 3 that the polarization direction of two longitudinal mode lasers is adjusted into level and vertical direction respectively, level and vertical curve polarization longitudinal mode laser are designated as L respectively _MAnd L _R, its frequency is designated as v respectively _MAnd v _R, v wherein _MV _R

Use the first depolarization Amici prism 4 to extract the part of double longitudinal mode lasers, by first analyzer 5 two longitudinal mode lasers are converted into same polarization direction and carry out optical frequency mixing and obtain beat signal.By first high-speed photodetector 6 this beat signal is converted into electric signal, it is designated as S _Ref, its frequency is the difference on the frequency v of two longitudinal mode lasers _Ref=v _M-v _R

Two longitudinal mode components that utilize first polarization splitting prism 7 will remain in the double longitudinal mode laser separate.Horizontal polarization laser L wherein _MBe converted into circularly polarized light by first quarter-wave plate 8 after the transmission, launched by measuring junction as measuring laser then.Vertical polarization laser L _RInject the 6th polarization splitting prism 31 after directly being reflected, with it as reference laser L _R1Passback laser L with destination end _BCarry out optics and close bundle.

Measure laser and arrive after the destination end, by second quarter-wave plate 9 it is converted to the linearly polarized light that the polarization direction is level by circularly polarized light, the phase-locked laser L that utilizes second polarization splitting prism 10 that itself and the 5th polarization splitting prism 28 are reflected _LCarry out optics and close bundle.Introduce doppler shift effect because destination end relative measurement end movement changes, the frequency of measuring laser arrival destination end changes, and it is expressed as v' _MThis closes to comprise in the light measures laser and phase-locked laser L _LVibration equation when arriving high speed optoelectronic detection measuring device can be expressed as respectively:

Utilize the 1/2nd wave plate 11 to adjust and close measurement laser and phase-locked laser L in the light light beam _LThe polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles.Utilize the second depolarization Amici prism 12 will close the light light beam and be divided into reflection and transmission two parts, be expressed as L respectively _FAnd L _T, wherein light light beam L is closed in reflection _FBeat frequency light signal through 180 ° of the 3rd polarization splitting prism 13 formation two-way phase phasic differences is converted into the beat frequency electric signal by second high-speed photodetector 14 and the 3rd high-speed photodetector 15 respectively.

For eliminating the direct current biasing of introducing with laser power fluctuation in the beat signal, this two-way beat frequency electric signal is admitted to signal condition module 20 and subtracts each other the beat frequency AC signal S that obtains _R, its frequency magnitude relationship according to two incident lasers is expressed as follows:

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

Work as v' _M=v _LThe time,

Light light beam L is closed in transmission _TAt first will measure the laser component phase through optical phase delay device 16 and postpone 90 °, and close the vibration equation of measuring laser in the light this moment and become:

Light light beam L is closed in transmission _TEnter the beat frequency light signal that the 4th polarization splitting prism 17 forms 180 ° of two-way phase phasic differences, it is converted into the beat frequency electric signal through the 4th high-speed photodetector 18 and the 5th high-speed photodetector 19 respectively.Two-way beat frequency electric signal is transferred to signal condition module 16 equally and obtains the beat frequency AC signal, and this beat frequency AC signal is designated as S _T, its frequency magnitude relationship according to two incident lasers is expressed as follows:

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

Work as v' _M=v _LThe time,

After this enter phase-locked laser L _LTo measuring the optical frequency locking control stage of laser, close light reflection beat signal S _RWith close light transmission beat signal S _TBe transferred to frequency measurement module 21, the difference on the frequency that utilizes synchronous frequency measuring method of multicycle to measure two bundle laser is v _MeasWhat measure at this moment, just measures laser and phase-locked laser L _LThe absolute value of difference on the frequency can not determine that two restraint the frequency magnitude relationship of laser, i.e. v _Meas=| v' _M-v _L|.

By above-mentioned formula, corresponding laser and the phase-locked laser L of measuring _LThe different magnitude relationship of frequency are closed light reflection beat signal S _RWith close light transmission beat signal S _TPhase place lead-lag state also different thereupon.Therefore, utilize four segmentation sensing technology to judge and close light reflection beat signal S _RWith close light transmission beat signal S _TThe phase place lead lag relationship just can determine to measure laser and phase-locked laser L _LFrequency v' _MWith v _LMagnitude relationship.

As shown in Figure 2, if close light reflection beat signal S _RPhase place close light transmission beat signal S in advance _T90 °, according to S _RWith S _TExpression formula can judge v' _MV _L, this moment v _Meas=v' _M-v _L, then finally calculate and measure laser and phase-locked laser L _LAccurate difference on the frequency △ v _M-L=v' _M-v _L=v _MeasAs shown in Figure 3, if close light reflection beat signal S _RPhase lag transmission beat signal S _T90 °, according to S _RWith S _TExpression formula can judge v' _M＜v _L, this moment v _Meas=v _L-v' _M, then finally calculate and measure laser and phase-locked laser L _LAccurate difference on the frequency △ v _M-L=v _L-v' _M=-v _Meas

With incident and shoot laser frequency-splitting △ v _M-LInput digit controller 23, it is calculated controlled quentity controlled variable and is transferred to temperature control modules 24 and PZT drive control module 25 respectively by control algolithm.The both realizes passback laser L by the cavity length of adjusting laser module 26 _BWith phase-locked laser L _LThe control of frequency, but specific implementation difference.Temperature control modules 24 is according to the positive and negative of controlled quentity controlled variable and big or small laser module 26 is carried out in various degree heating or refrigeration, by changing its resonator cavity temperature cavity length is adjusted, though the slow range of adjustment of this mode response speed is big.25 of PZT drive control modules directly use piezoelectric ceramics (PZT) that the cavity length of laser module 26 is adjusted, this mode response speed fast and regulate meticulous, but adjustable extent is very little.By being used of temperature control modules 24 and PZT drive control module 25, realizing phase-locked laser L _LAfter the precise frequency locking of measuring laser, the optical frequency locking control stage finishes, at this moment v _B=v _L=v' _M

System enters phase-locked laser L immediately _LTo measuring the phase locked track control stage of laser, will close light reflection beat signal S _RWith close light transmission beat signal S _TBe transferred to quadrature phase demodulation module 22.By v' _M=v _LThe transmission beat frequency AC signal S of state _TDivided by reflection beat frequency AC signal S _R:

By following formula, right

Carry out arctangent cp cp operation and can record measurement laser and phase-locked laser L _LPhase difference value

With this phase difference value

Input digit controller 23, it is calculated controlled quentity controlled variable and is transferred to PZT drive control module 25 by control algolithm.Directly the cavity lengths of laser module 26 are carried out meticulously regulating fast by PZT drive control module 25, and with this to passback laser L _BWith phase-locked laser L _LPhase place accurately control, up to having realized phase-locked laser L _LTo measuring the phase place locking tracking of laser, phase place locking control procedure finishes, at this moment

When optics phase locked track system losing lock, repeat optical frequency locking control stage and phase locked track control stage, can realize the phase-locked laser L of destination end laser module 26 outputs _LAnd passback laser L _BTo measuring the phase locked track again of laser.

Frequency and phase place all are locked in the linear polarization passback laser L that measures laser _BAfter being converted into circularly polarized light by the 3rd quarter-wave plate 29, the passback emission from destination end to measuring junction.It is converted into horizontal linear polarization light by the 4th quarter-wave plate 30 after arriving measuring junction.Changed by destination end relative measurement end movement and cause the influence of doppler shift effect, passback laser L _BThe frequency that arrives measuring junction changes, and it is expressed as v' _BIf the destination end movement velocity is u, the laser mean wavelength is λ, and then the approximate formula according to Doppler shift has

To return laser L by the 6th polarization splitting prism 31 _BWith reference laser L _R1Close light, by second analyzer 32 two bundle laser mixing are obtained the difference interference measuring signal, utilize the 6th high-speed photodetector 33 that beat signal is converted to the beat frequency electric signal, it is designated as S _MeasIts frequency v _MeasBe passback laser L _BWith reference laser L _R1Difference on the frequency $v_{\mathrm{meas}}={v^{\′}}_B-v_R=v_M-v_R+\frac{2u}{\mathrm{\λ}}.$

Reference signal S with difference interference measuring _RefWith measuring-signal S _MeasInput phase segmentation module 34 is carried out frequency and is subtracted each other respectively, obtains the destination end motion thus and the doppler shifted signal that produces.After it is carried out phase subdivision and accumulation calculating, calculated the displacement of destination end relative measurement end according to the phase value of accumulative total by displacement computing module 35.

Embodiment two: below in conjunction with Fig. 1 present embodiment is described, realizes the device of displacement measurement method between the phase-locked star of the described a kind of low light level based on the four-way Detection Techniques of claim 1, it is characterized in that it comprises measuring junction and destination end,

Measuring junction comprises double longitudinal mode laser module 1, frequency stabilization control module 2, the 1/1st wave plate 3, the first depolarization Amici prism 4, first analyzer 5, first high-speed photodetector 6, first polarization splitting prism 7, first quarter-wave plate 8, the 4th quarter-wave plate 30, the 6th polarization splitting prism 31, second analyzer 32, the 6th high-speed photodetector 33, phase subdivision module 34 and displacement computing module 35

Destination end comprises second quarter-wave plate 9, second polarization splitting prism 10, the 1/2nd wave plate 11, the second depolarization Amici prism 12, the 3rd polarization splitting prism 13, second high-speed photodetector 14, the 3rd high-speed photodetector 15, optical phase delay device 16, the 4th polarization splitting prism 17, the 4th high-speed photodetector 18, the 5th high-speed photodetector 19, signal condition module 20, frequency measurement module 21, quadrature phase demodulation module 22, digitial controller 23, temperature control modules 24, PZT drive control module 25, laser module 26, the 1/3rd wave plate 27, the 5th polarization splitting prism 28, the 3rd quarter-wave plate 29

The output terminal of frequency stabilization control module 2 links to each other with the input end of double longitudinal mode laser module 1, the 1/1st wave plate 3, the first depolarization Amici prism 4, first polarization splitting prism 7, first quarter-wave plate 8, second quarter-wave plate 9, second polarization splitting prism 10, the 1/2nd wave plate 11, the second depolarization Amici prism 12, optical phase delay device 16, the 4th polarization splitting prism 17 and the 5th high-speed photodetector 19 are placed on the emitting light path of double longitudinal mode laser module 1 in turn

First analyzer 5 and first high-speed photodetector 6 are placed on the reflection output light path of the first depolarization Amici prism 4 in turn,

The double longitudinal mode laser of double longitudinal mode laser module 1 outgoing is transmitted through the first depolarization Amici prism 4 through the 1/1st wave plate 3, the folded light beam of the first depolarization Amici prism 4 is incident to first analyzer 5, light beam through 5 transmissions of first analyzer is incident to first high-speed photodetector 6, the electrical signal of first high-speed photodetector 6 links to each other with the first input end of phase subdivision module 34

The transmitted light beam of the first depolarization Amici prism 4 is incident to transmitted light beam conduct after 8 transmissions of first quarter-wave plate of first polarization splitting prism, 7, the first polarization splitting prisms 7 and measures Laser emission to destination end,

Second quarter-wave plate 9 of destination end receives measures laser, and be transmitted through second polarization splitting prism 10, the linearly polarized laser that laser module 26 sends is transmitted through the vertical curve polarization laser of the 5th polarization splitting prism 28, the five polarization splitting prisms 28 reflections as phase-locked laser L through the 1/3rd wave plate 27 _LClose the light light beam with the transmitted light beam formation of second polarization splitting prism 10, the described light light beam that closes is transmitted through the second depolarization Amici prism 12 through the 1/2nd wave plate 11,

The light folded light beam of closing through 12 reflections of the second depolarization Amici prism is incident to the 3rd polarization splitting prism 13, folded light beam through 13 reflections of the 3rd polarization splitting prism is incident to second high-speed photodetector 14, transmitted light beam through 13 transmissions of the 3rd polarization splitting prism is incident to the 3rd high-speed photodetector 15

The light transmitted light beam that closes through 12 transmissions of the second depolarization Amici prism is incident to optical phase delay device 16, the delay light beam of optical phase delay device 16 outputs is incident to the 4th polarization splitting prism 17, folded light beam through 17 reflections of the 4th polarization splitting prism is incident to the 4th high-speed photodetector 18, transmitted light beam through 17 transmissions of the 4th polarization splitting prism is incident to the 5th high-speed photodetector 19

Second high-speed photodetector 14, the 3rd high-speed photodetector 15, the signal that the 4th high-speed photodetector 18 and the 5th high-speed photodetector 19 are gathered is exported to four signal input parts of signal condition module 20 respectively, the folded light beam difference signal output terminal of signal condition module 20 links to each other with the input end of frequency measurement module 21 and the input end of quadrature phase demodulation module 22 simultaneously, the transmitted light beam difference signal output terminal of signal condition module 20 links to each other with the input end of frequency measurement module 21 and the input end of quadrature phase demodulation module 22 simultaneously, the output terminal of frequency measurement module 21 links to each other with the first input end of digitial controller 23, the output terminal of quadrature phase demodulation module 22 links to each other with second input end of digitial controller 23, the control temperature signal output terminal of digitial controller 23 links to each other with the input end of temperature control modules 24, the output terminal of temperature control modules 24 links to each other with first control end of laser module 26, the PZT of digitial controller 23 drives signal output part and links to each other with the input end of PZT drive control module 25, the output terminal of PZT drive control module 25 drives the signal controlling end with the PZT of laser module 26 and links to each other

The transmitted light beam of the 5th polarization splitting prism 28 returns measuring junction as the passback Laser emission after 29 transmissions of the 3rd quarter-wave plate, the 4th quarter-wave plate 30 of measuring junction receives passback laser, and be transmitted through the 6th polarization splitting prism 31, after the reference laser that is transmitted through the passback laser of the 6th polarization splitting prism 31 and the reflection of first polarization splitting prism 7 closes light, be transmitted through the 6th high-speed photodetector 33 through second analyzer 32 again, the electrical signal of the 6th high-speed photodetector 33 links to each other with second input end of phase subdivision module 34, and the output terminal of phase subdivision module 34 links to each other with the output terminal of displacement computing module 35.

Embodiment three: present embodiment is described further embodiment two, and optical phase delay device 16 is wave plate phase delay device, reflective phase delay mirror, liquid crystal phase delay device or electric light phase shifter.

Optical phase delay device 16 only carries out phase delay to measuring laser.

Below by reference to the accompanying drawings the specific embodiment of the present invention is illustrated; but according to law stipulates that these explanations can not limit the scope of the present invention; protection scope of the present invention is limited by the claims of enclosing, and the change that any that carry out on claim of the present invention basis, these those skilled in the art can make according to existing knowledge is all in protection scope of the present invention.

Claims (3)

1. displacement measurement method between the phase-locked star of the low light level based on the four-way Detection Techniques is measured carrying out relative displacement as two satellites of measuring junction and destination end respectively, it is characterized in that this method may further comprise the steps:

Step 1, unlatching are in the laser module of destination end, enter steady-working state through this laser module behind the warm, utilize 1/2nd wave plates and polarization splitting prism that the linearly polarized laser of laser module output is divided into two parts, a part is designated as L as the passback laser of destination end with described passback laser _B, another part is used for the FEEDBACK CONTROL laser module as phase-locked laser, and described phase-locked laser is designated as L _L, phase-locked laser L _LBe the vertical curve polarization laser, passback laser L _BFrequency and phase-locked laser L _LFrequency identical, described passback laser frequency and phase-locked laser frequency are designated as v respectively _BAnd v _L

Step 2, unlatching are in the double longitudinal mode laser module of measuring junction, after preheating and frequency stabilization control procedure, double longitudinal mode laser module output laser comprises orthogonal two the longitudinal mode laser compositions of polarization state, and the polarization state of adjusting two longitudinal mode lasers makes described two longitudinal mode lasers become horizontal linear polarization laser L respectively _MWith vertical curve polarization laser L _R, the frequency of horizontal linear polarization laser is v _M, the frequency of vertical curve polarization laser is v _R, and v _MV _R

Step 3, utilize the depolarization Amici prism with described horizontal linear polarization laser L _MWith vertical curve polarization laser L _RBe divided into reflecting part and transmissive portion, the horizontal linear polarization laser L of reflecting part _MVertical curve polarization laser L with the reflecting part _RCarry out optical frequency mixing and obtain beat signal, by high-speed photodetector this beat signal is converted into electric signal, the reference signal of difference interference measuring is designated as S _Ref, the reference signal frequency of difference interference measuring is the difference on the frequency v of two longitudinal mode lasers _Ref=v _M-v _R

The vertical curve polarization laser L of transmissive portion _RPassback laser L as reference laser and destination end _BSwash combiner and optical frequency mixing, the horizontal linear polarization laser L of transmissive portion _MAfter being converted into circularly polarized light, penetrated to destination end by measuring junction as measuring laser;

Step 4, described measurement laser arrive after the destination end, earlier described measurement laser are converted to the linearly polarized light that the polarization direction is level by circularly polarized light, again with the phase-locked laser L of destination end _LSwash combiner formation and close the light light beam, utilize 1/2nd wave plates to adjust the described laser L in the light light beam that closes _MWith L _LThe polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles;

Step 5, utilize the depolarization Amici prism that the described light light beam that closes is divided into reflection and closes light light beam L _FClose light light beam L with transmission _T, wherein light light beam L is closed in reflection _FBeat frequency light signal through 180 ° of polarization splitting prism formation two-way phase phasic differences is converted to the beat frequency electric signal and is sent into the signal condition module by two high-speed photodetectors respectively, and light light beam L is closed in transmission _TAt first will close in the light light beam 90 ° of phase delays measuring laser through optical phase delay device, form the beat frequency light signal of 180 ° of two-way phase phasic differences then by polarization splitting prism, be converted to the beat frequency electric signal and send into the signal condition module by other two-way high-speed photodetector respectively;

Step 6, because destination end relative measurement end movement change to be introduced doppler shift effect, measure the frequency that laser arrives destination end and change, with described phase-locked laser L _LFrequency representation be v' _M, simultaneously reflection is closed light light beam L _FIn the measurement laser phase place that arrives photodetector be designated as

, light light beam L is closed in reflection _FIn phase-locked laser L _LThe phase place that arrives photodetector is designated as

, the signal condition module is closed light light beam L with reflection _FCorresponding two-way beat frequency electric signal subtracts each other and obtains closing light reflection beat signal, will describedly close light and reflect beat signal and be designated as S _R,

Then work as v' _M=v _LThe time,

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

Step 7, signal condition module are closed transmission light light beam L simultaneously _TCorresponding two-way beat frequency electric signal subtracts each other and obtains closing light transmission beat signal, and the described light transmission beat signal that closes is designated as S _T, because the effect of optical phase delay device, light light beam L is closed in transmission _TIn the measurement laser phase place that arrives photodetector be designated as

Light light beam L is closed in transmission _TIn phase-locked laser L _LThe phase place that arrives photodetector is designated as

Then work as v' _M=v _LThe time,

Work as v' _MV _LThe time,

Work as v' _M＜v _LThe time,

The laser module of step 8, destination end enters the optical frequency locking control stage, at first gets and closes light reflection beat signal S _RWith close light transmission beat signal S _TCarry out frequency measurement, the frequency measurement result is designated as v _Meas,

v _meas=|v' _M-v _L|，

When closing light reflection beat signal S _RPhase place is closed light transmission beat signal S in advance _TIn the time of 90 °, show v' _MV _L, frequency measurement this moment result is

v _meas=v' _M-v _L，

Obtain measuring laser and phase-locked laser L _LThe frequency discrimination result be

△v _M-L=v' _M-v _L=v _meas，

When closing light reflection beat signal S _RPhase place lags behind and closes light transmission beat signal S _TIn the time of 90 °, show v' _M＜v _L, frequency measurement this moment result is

v _meas=v _L-v' _M，

Obtain measuring laser and phase-locked laser L _LThe frequency discrimination result be

△v _M-L=v' _M-v _L=-v _meas；

Step 9, with the frequency values △ ν that measures _M-LAs optical frequency locking signal input digit controller, according to the phase-locked laser L of laser module output _LThe phase-locked laser L of frequency and the output of described laser module _LThe corresponding relation of cavity length, adjust laser module resonator cavity temperature to realize the adjusting on a large scale to cavity length by temperature control modules, by the PZT drive control module cavity length is carried out directly regulating fast simultaneously, thus the phase-locked laser L of FEEDBACK CONTROL _LFrequency v _LMake △ ν _M-LBe tending towards 0, as △ ν _M-L=0 o'clock, the optical frequency locked stage of destination end laser module finished, and exports phase-locked laser L _LAnd passback laser L _BFrequency be locked as the frequency of the measurement laser of incident,

Be ν _B=ν _L=v' _M

The laser module of step 10, destination end enters the phase locked track control stage after the optical frequency locking control stage finishes, at first get and close light reflection beat signal S _RWith close light transmission beat signal S _TCarry out the arc tangent phase measurement, obtain measuring laser and phase-locked laser L _LIdentified result be

With the phase value that measures As phase-locked closed-loop control signal input digit controller, by the PZT drive control module cavity length of laser module is carried out meticulous quick adjustment, the phase-locked laser L of FEEDBACK CONTROL _LPhase place

Make Be tending towards 0, when

The time, the phase-locked control procedure of laser module is finished, and exports phase-locked laser L _LAnd passback laser L _BFrequency be locked as the phase place of the measurement laser of incident,

Namely

Step 11, when optics phase locked track system losing lock, repeating step nine and step 10, the phase-locked laser L of laser module _LAnd passback laser L _BCan be to measuring laser phase locked track again;

Step 12, utilize quarter-wave plate frequency and phase place all to be locked in the linear polarization passback laser L that measures laser _BBe converted into circularly polarized light, described circularly polarized light is back to behind the measuring junction by quarter-wave plate again circularly polarized light is converted into the linearly polarized light of polarization direction level, changed by destination end relative measurement end movement and causes the influence of doppler shift effect, passback laser L _BThe frequency that arrives measuring junction changes, and is v' with described passback laser measurement frequency representation _B, then the approximate formula according to Doppler shift has

${v^{\′}}_B=v_M+\frac{2u}{\mathrm{\λ}};$

In the formula, u is the movement velocity of destination end relative measurement end, and λ is for measuring laser and passback laser L _BMean wavelength,

Step 13, will return laser L _BClose light and carry out the measurement beat signal that mixing obtains difference interference measuring with reference laser, utilize high speed detector that this beat signal is converted into the beat frequency electric signal, the beat frequency electric signal is designated as S _Meas, beat frequency electric signal frequency is reference laser L _R1With passback laser L _BDifference on the frequency

$v_{\mathrm{meas}}={v^{\′}}_B-v_R=v_M-v_R+\frac{2u}{\mathrm{\λ}};$

Step 14, with the reference signal S of difference interference measuring _RefWith measuring-signal S _MeasThe laggard line frequency of input phase segmentation module is subtracted each other respectively, the doppler shifted signal that obtains the destination end motion thus and produce, after described doppler shifted signal carried out phase subdivision and accumulation calculating, calculated the displacement of destination end relative measurement end according to the phase value of accumulative total by the displacement computing module.

2. realize the device of displacement measurement method between the phase-locked star of the described a kind of low light level based on the four-way Detection Techniques of claim 1, it is characterized in that it comprises measuring junction and destination end,

Measuring junction comprises double longitudinal mode laser module (1), frequency stabilization control module (2), the 1/1st wave plate (3), the first depolarization Amici prism (4), first analyzer (5), first high-speed photodetector (6), first polarization splitting prism (7), first quarter-wave plate (8), the 4th quarter-wave plate (30), the 6th polarization splitting prism (31), second analyzer (32), the 6th high-speed photodetector (33), phase subdivision module (34) and displacement computing module (35)

Destination end comprises second quarter-wave plate (9), second polarization splitting prism (10), the 1/2nd wave plate (11), the second depolarization Amici prism (12), the 3rd polarization splitting prism (13), second high-speed photodetector (14), the 3rd high-speed photodetector (15), optical phase delay device (16), the 4th polarization splitting prism (17), the 4th high-speed photodetector (18), the 5th high-speed photodetector (19), signal condition module (20), frequency measurement module (21), quadrature phase demodulation module (22), digitial controller (23), temperature control modules (24), PZT drive control module (25), laser module (26), the 1/3rd wave plate (27), the 5th polarization splitting prism (28), the 3rd quarter-wave plate (29)

The output terminal of frequency stabilization control module (2) links to each other with the input end of double longitudinal mode laser module (1), the 1/1st wave plate (3), the first depolarization Amici prism (4), first polarization splitting prism (7), first quarter-wave plate (8), second quarter-wave plate (9), second polarization splitting prism (10), the 1/2nd wave plate (11), the second depolarization Amici prism (12), optical phase delay device (16), the 4th polarization splitting prism (17) and the 5th high-speed photodetector (19) are placed on the emitting light path of double longitudinal mode laser module (1) in turn

First analyzer (5) and first high-speed photodetector (6) are placed on the reflection output light path of the first depolarization Amici prism (4) in turn,

The double longitudinal mode laser of double longitudinal mode laser module (1) outgoing is transmitted through the first depolarization Amici prism (4) through the 1/1st wave plate (3), the folded light beam of the first depolarization Amici prism (4) is incident to first analyzer (5), light beam through first analyzer (5) transmission is incident to first high-speed photodetector (6), the electrical signal of first high-speed photodetector (6) links to each other with the first input end of phase subdivision module (34)

The transmitted light beam of the first depolarization Amici prism (4) is incident to first polarization splitting prism (7), and the conduct after first quarter-wave plate (8) transmission of the transmitted light beam of first polarization splitting prism (7) is measured Laser emission to destination end,

Second quarter-wave plate of destination end, (9) receive measurement laser, and be transmitted through second polarization splitting prism, (10), laser module, (26) linearly polarized laser that sends is through the 1/3rd wave plate, (27) be transmitted through the 5th polarization splitting prism, (28), the 5th polarization splitting prism, (28) Fan She vertical curve polarization laser is as phase-locked laser LL and second polarization splitting prism, (10) transmitted light beam forms and closes the light light beam, the described light light beam that closes is through the 1/2nd wave plate, (11) be transmitted through the second depolarization Amici prism, (12)

The light folded light beam of closing through the reflection of the second depolarization Amici prism (12) is incident to the 3rd polarization splitting prism (13), folded light beam through the 3rd polarization splitting prism (13) reflection is incident to second high-speed photodetector (14), transmitted light beam through the 3rd polarization splitting prism (13) transmission is incident to the 3rd high-speed photodetector (15)

The light transmitted light beam that closes through second depolarization Amici prism (12) transmission is incident to optical phase delay device (16), the delay light beam of optical phase delay device (16) output is incident to the 4th polarization splitting prism (17), folded light beam through the 4th polarization splitting prism (17) reflection is incident to the 4th high-speed photodetector (18), transmitted light beam through the 4th polarization splitting prism (17) transmission is incident to the 5th high-speed photodetector (19)

Second high-speed photodetector (14), the 3rd high-speed photodetector (15), the signal that the 4th high-speed photodetector (18) and the 5th high-speed photodetector (19) are gathered is exported to four signal input parts of signal condition module (20) respectively, the folded light beam difference signal output terminal of signal condition module (20) links to each other with the input end of frequency measurement module (21) and the input end of quadrature phase demodulation module (22) simultaneously, the transmitted light beam difference signal output terminal of signal condition module (20) links to each other with the input end of frequency measurement module (21) and the input end of quadrature phase demodulation module (22) simultaneously, the output terminal of frequency measurement module (21) links to each other with the first input end of digitial controller (23), the output terminal of quadrature phase demodulation module (22) links to each other with second input end of digitial controller (23), the control temperature signal output terminal of digitial controller (23) links to each other with the input end of temperature control modules (24), the output terminal of temperature control modules (24) links to each other with first control end of laser module (26), the PZT of digitial controller (23) drives signal output part and links to each other with the input end of PZT drive control module (25), the output terminal of PZT drive control module (25) drives the signal controlling end with the PZT of laser module (26) and links to each other

The transmitted light beam of the 5th polarization splitting prism (28) returns measuring junction as the passback Laser emission after the 3rd quarter-wave plate (29) transmission, the 4th quarter-wave plate (30) of measuring junction receives passback laser, and be transmitted through the 6th polarization splitting prism (31), after the reference laser that is transmitted through the reflection of the passback laser of the 6th polarization splitting prism (31) and first polarization splitting prism (7) closes light, be transmitted through the 6th high-speed photodetector (33) through second analyzer (32) again, the electrical signal of the 6th high-speed photodetector (33) links to each other with second input end of phase subdivision module (34), and the output terminal of phase subdivision module (34) links to each other with the output terminal of displacement computing module (35).

3. the implement device of displacement measurement method between the phase-locked star of a kind of low light level based on the four-way Detection Techniques according to claim 2, it is characterized in that optical phase delay device (16) is wave plate phase delay device, reflective phase delay mirror, liquid crystal phase delay device or electric light phase shifter.

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