CN113219545B - Double compensation method and device for vibration noise and wavefront distortion error of atomic interference gravimeter - Google Patents
Double compensation method and device for vibration noise and wavefront distortion error of atomic interference gravimeter Download PDFInfo
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Abstract
The invention discloses double compensation for vibration noise and wavefront distortion error of an atomic interference gravimeterThe method comprises the following steps: step S1: static laser wavefront distortion measurement: measuring wave front distortion distribution of a pair of Raman lights acting with atoms in static state for atom interference gravimeter system
Step S2: measuring dynamic vibration noise and laser wavefront distortion: measuring vibration signals S (x, y, z, t) of the Raman light reflector, filtering, and measuring wave front distortion of the dynamic Raman laser in real time
Step S3: real-time compensation of vibration noise and laser wavefront distortion: and driving the deformable mirror to deform by using a self-adaptive PID feedback control algorithm, and compensating vibration noise and laser wavefront distortion in real time. The device is used for implementing the method. The invention has the advantages of improving the measurement sensitivity, precision, stability, portability and the like.
Description
Technical Field
The invention mainly relates to the technical field of high-precision absolute gravity measurement, in particular to a method and a device for double compensation of vibration noise and wavefront distortion error of an atomic interference gravimeter.
Background
The high-precision absolute gravity information has wide application prospects in many fields such as basic scientific research, national defense construction, earth information monitoring, industrial application, resource exploitation, archaeology and the like. The cold atom interferometer is a new generation high-precision measuring instrument which takes atomic substance waves instead of light waves as a measuring medium, the measuring performance of the quantum absolute gravimeter taking cold atom interference as a core is superior to the most advanced FG5X type commercial laser interference absolute gravimeter, and the cold atom interferometer is the development direction of the next generation high-precision absolute gravimeter. In order to further improve performance indexes such as measurement sensitivity, accuracy and long-term stability of the atomic interference gravimeter, wavefront distortion compensation of Raman light and suppression of vibration noise of a reflector are two major problems which need to be solved.
For the suppression of vibration noise of the reflection mirror of the atomic interference gravimeter, there are three main methods at present, including: the influence degree of vibration noise on the atomic interference gravimeter is reduced by using a heavy passive vibration isolation platform (A.Peters, K.Y.Chung, S.Chu, Nature, 1999, 400 (6747): 849-; measuring vibration noise of a Raman light reflector by using an inertial instrument such as a seismometer or an accelerometer, feeding the vibration noise back to a voice coil motor, and modifying a passive vibration isolation platform by using the voice coil motor to form an active vibration isolation system (B.Tang, L.Zhou, Z.Xiong, J.Wang, M.Zhan, Rev.Sci.Instrum., 2014, 85 (9): 093109 and patent CN 106054615B); the vibration noise power spectral density of the raman mirror is measured by an inertial instrument such as a seismometer or an accelerometer, the phase shift caused by vibration is solved by a sensitivity function and an integration operation of an atomic interferometer, and data correction is performed in the total interference phase shift (s.merlet, j.le Gouet, q.bodart, a.clairon, a.landragin, f.p.dos santos, p.rouchon, Gravity, Geoid and Earth Observation, 2010, 135, 115, and patents CN110596785B, CN 109298457B). In the three methods, the first two methods need to additionally increase a passive vibration isolation platform, and the third method has limited compensation precision, so that the requirements of field, vehicle-mounted, ship-mounted and other small-sized, portable, high-dynamic and high-real-time scene measurement are difficult to meet.
For compensation of raman wavefront distortion, research groups have measured the effect of raman laser wavefront distortion on the measurement error of atomic interference gravimeters at different probe light diameters (v.schkolnik, b.leykauf,m.hauth, c.freier, a.peters, appl.phys.b, 2015, 120 (2): 311- > 316), and the effect of raman laser wavefront distortion on atomic interferometric gravimetry measurement error at different raman optical diameters (m. -k.zhou, q.luo, l. -1.Chen, x. -c.duan, z. -k.hu, phys.rev.a, 2016, 93 (4): 043610), it was found that the maximum distortion of the laser wavefront could produce 600nm/s2Gravity measurement error of (2). The research group also uses a deformable mirror to control the wave front of the Raman laser to prove that the maximum wave front distortion of the laser can generate 5 mu m/s2Gravity measurement error (A. Trimeche, M.Langlois, S.Merlet, F.Pereira Dos Santos, Phys.Rev.applied, 2017, 7 (3): 034016.).
According to investigation, no technology or method capable of effectively compensating for the distortion of the raman wavefront and the vibration noise of the mirror at the same time exists.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the technical problems in the prior art, the invention provides a double compensation method and device for vibration noise and wavefront distortion error of an atomic interference gravimeter, which can improve the measurement sensitivity, precision, stability and portability.
In order to solve the technical problems, the invention adopts the following technical scheme:
a vibration noise and wavefront distortion error double compensation method for an atomic interference gravimeter is characterized by comprising the following steps:
step S1: static laser wavefront distortion measurement: measuring wave front distortion distribution of a pair of Raman lights acting with atoms in static state for atom interference gravimeter system
Step S2: measuring dynamic vibration noise and laser wavefront distortion: measuring vibration signals S (x, y, z, t) of the Raman light reflector, filtering, and measuring wave front distortion of the dynamic Raman laser in real time
Step S3: real-time compensation of vibration noise and laser wavefront distortion: and driving the deformable mirror to deform by using a self-adaptive PID feedback control algorithm, and compensating vibration noise and laser wavefront distortion in real time.
As a further improvement of the process of the invention: the process of step S1 includes:
step S101: solving the wave front distortion distribution function of a pair of Raman lights which act with atoms in static state
Step S102: measuring the wave front distribution of the Raman laser which propagates downwards by taking the vertical upward propagation direction of the Raman light as the z direction
And upward propagating Raman laser wavefront distribution
Step S103: according to the wavefront superposition relation:
obtaining:
and
the above-mentioned
The distribution of the wave front of the Raman laser which only passes through the top glass window and the bottom glass window of the vacuum chamber and downwards propagates through the 1/4 wave plate; the above-mentioned
The Raman laser wave front distribution is transmitted upwards after passing through a Raman light reflector; the above-mentioned
The static laser wavefront distortion caused by the vacuum chamber top glass window, the vacuum chamber bottom glass window, the 1/4 wave plate and the Raman reflector are respectively.
As a further improvement of the process of the invention: the process of step S2 includes:
step S201: the vibration of the ground or carrier platform in 3 directions is measured.
Step S202: respectively carrying out high-frequency noise filtering and phase frequency and amplitude frequency distortion filtering processing caused by limited measurement bandwidth on the measured three-dimensional vibration signal;
step S203: acquiring the measured three-dimensional vibration signal in real time in a voltage simulating mode to obtain S (x, y, z, t) and outputting the S (x, y, z, t) to a microprocessor in real time;
step S204: real-time measurement of the distribution of the Raman laser wavefront propagating downwards only through the top and bottom glass windows of the vacuum chamber and the 1/4 wave plate
And Raman laser wavefront distribution propagating upward through Raman light reflector
And outputs the wavefront profile to the microprocessor in real time.
As a further improvement of the process of the invention: the process of step S3 includes:
step S301: determining a deformable mirror response matrix A;
step S302: calculation of drive voltage: calculating a driving voltage matrix K required for enabling the deformable mirror to deform so as to compensate the vibration of the reflector and the wave front distortion of the laser by using a self-adaptive PID (proportion integration differentiation) method according to the dynamic reflector vibration noise signal after filtering processing, the total real-time laser wave front distortion distribution and the response matrix A of the deformable mirror;
step S303: driving of the deformable mirror: and feeding back the calculated driving voltage matrix signal K to a high-voltage amplifier, and outputting a current signal of a corresponding channel by the high-voltage amplifier to drive the deformable mirror to deform so as to compensate the Raman light reflector vibration and Raman laser wavefront distortion caused by vibration noise in real time.
As a further improvement of the method of the present invention, the method further comprises step S4: and evaluating the vibration noise and laser wavefront distortion compensation effect, namely evaluating the vibration noise and laser wavefront distortion compensation effect by using the atomic interference signal and providing real-time correction for the driving voltage applied by the deformable mirror.
As a further improvement of the process of the invention: the process of step S4 includes:
step S401: preparing cold radicals;
step S402: realizing atomic interference;
step S403: atomic transition probability detection: normalization detection of transition probability of cold atomic group in atomic interferometer by detection light-return pump light-detection light and piezoelectric multiplier tube PMT
Step S404: and (3) evaluating the vibration noise compensation effect: by recording the Raman laser pulse phase over a long period of time
Probability of transition with cold atom
The corresponding relation between the atomic transition probability and the atomic transition probability becomes smaller under a specific Raman laser phase after the deformable mirror is used for compensating the vibration noise; evaluating deformable mirror by calculating Allan variance of atomic transition probability jitterPre-use and post-use vibration noise compensation effects;
step S405: and (3) real-time correction of the driving voltage of the deformable mirror:
as a further improvement of the process of the invention: in the step S401, the cold atom interference gravimeter is operated at the moment when t is 0, the ith M-Z type atom interference gravity measurement circulation is carried out, the magneto-optical trap is used for cooling and trapping atoms, the temperature of the atomic group is less than or equal to 10 mu k, the number of the atoms is more than or equal to 107A plurality of; selecting the atomic speed and the atomic state by utilizing microwave and Raman light to obtain a cold atomic group with the longitudinal temperature less than or equal to 400nk, and preparing the atomic group into a specific internal state.
As a further improvement of the process of the invention: in step S402, the atoms fall or are thrown upward into the vacuum interference chamber, where t is t1At the moment, three beams of Pi/2-Pi/2 Raman laser pulses with the interval time of T and the duration time of tau, 2 tau and tau are acted with atoms to make the radicals coherently split, reflect and combine to form an M-Z interferometer, wherein the phases phi of the first beam of Raman laser pulse and the second beam of Raman laser pulse1、φ2Set to 0, phase of the third Raman laser pulse
Set to a constant value.
As a further improvement of the process of the invention: in the step S405, the deformable mirror controller performs the wavefront mirror vibration and laser wavefront distortion compensation by iteration using an adaptive PID method, and performs atomic interference gravity measurement synchronously in the process, and evaluates the influence of the raman mirror vibration noise and dynamic wavefront distortion by the jitter degree of the atomic transition probability under a specific raman optical phase; if the Allan variance of the atomic transition probability jitter is converged and is less than a certain threshold value P, the microprocessor does not need to execute any operation after receiving the feedback signal; and if the Allan variance of atomic transition probability jitter is increasing or diverging, the microprocessor adjusts the parameters of the adaptive PID algorithm to obtain a new driving voltage matrix signal K' of the deformable mirror.
The present invention further provides an apparatus for carrying out the above method, comprising:
the vibration noise and laser wavefront distortion measuring unit comprises a vibration noise measuring module Z1-1 and a wavefront distortion measuring module Z1-2 which can be respectively realized by an inertia instrument which is stably placed on the ground or a carrier platform and is tightly fixed with a Raman light reflector and a laser wavefront detector which is arranged on the side surface of a gravity sensing head;
the vibration noise and laser wavefront distortion compensation unit comprises a deformable mirror with a known or measurable response matrix, a microprocessor capable of executing an adaptive PID algorithm, and a high-voltage amplifier for driving the deformable mirror to deform;
the unit for evaluating the vibration noise and laser wavefront distortion compensation effect comprises an atomic interference gravimeter and Raman laser phase-atomic transition probability jitter information obtained through measurement.
Compared with the prior art, the invention has the advantages that:
1. the double compensation method and the double compensation device for the vibration noise and the wavefront distortion error of the atomic interference gravimeter can realize the simultaneous double compensation of the vibration noise and the laser wavefront distortion. The invention can realize the simultaneous double compensation of Raman optical phase integral jitter caused by vibration noise and Raman laser wavefront distortion in an x-y plane caused by optical elements and atmospheric flow by using the multi-channel quick response deformable mirror, greatly improves the measurement sensitivity, precision, stability and portability of the atomic interference gravimeter, and enables the atomic interference gravimeter to be applied to dynamic scenes such as field, vehicle-mounted, ship-mounted and the like.
2. The double compensation method and the device for the vibration noise and the wavefront distortion error of the atomic interference gravimeter have the advantages of simple principle and low cost. The invention utilizes the deformable mirror to replace the traditional active vibration isolation system realized by modifying the passive vibration isolation platform based on the voice coil motor, can save the complex and heavy passive vibration isolation platform and the modification based on the passive vibration isolation platform, and has the advantages of miniaturization, low cost, high precision, real-time compensation and the like.
3. The double compensation method and the double compensation device for the vibration noise and the wavefront distortion error of the atomic interference gravimeter can fully utilize the original gravimeter system and information, and have high compensation precision. The invention evaluates the real-time compensation effect of the deformable mirror on vibration noise and wavefront distortion error by using the stability of the original Raman laser phase-atom transition probability signal of the M-Z type atomic interference gravimeter, provides a correction reference for the feedback voltage applied by each channel of the deformable mirror, and can more directly, efficiently and accurately obtain the influence of the vibration noise, so that the compensation precision of the vibration noise compensation loop is higher.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
Fig. 2 is a schematic structural diagram of the present invention in embodiment 1.
Fig. 3 is a schematic structural diagram of the present invention in embodiment 2.
Fig. 4 is a schematic diagram of a deformable mirror structure and a driver encoding sequence used in embodiment 1 of the present invention.
Detailed Description
The invention will be described in further detail below with reference to the drawings and specific examples.
As shown in fig. 1, fig. 2 and fig. 3, the method for compensating vibration noise and wavefront distortion error of an atomic interference gravimeter according to the present invention includes the steps of:
step S1: static laser wavefront distortion measurement: measuring laser wavefront distortion distribution in a static time raman optical path for a particular atomic interferometric gravimeter system
Step S2: measuring dynamic vibration noise and laser wavefront distortion: measuring vibration signals S (x, y, z, t) of the Raman light reflector by using an inertial instrument, filtering, and simultaneously measuring wave front distortion of the dynamic Raman laser in real time by using a wave front detector
Step S3: real-time compensation of vibration noise and laser wavefront distortion: and driving the deformable mirror to deform by using an optimized adaptive PID feedback control algorithm and a high-voltage amplifier, and compensating vibration noise and laser wavefront distortion in real time.
In a specific application example, the procedure of measuring the static laser wavefront distortion in step S1 includes:
step S101: solving the wave front distortion distribution function of a pair of Raman lights which act with atoms in static state
That is, on the premise of keeping the raman laser wavefront constant (e.g. keeping the raman laser optical path free from the external influences of atmospheric turbulence, wind current, water vapor, dust, etc.), the method of "raman optical diameter adjustment method", "probe optical diameter adjustment method", "inverse wave vector method", "quad configuration measurement", and "difference method" is used to measure the gravity measurement error (interference phase shift) caused by the laser wavefront distortion in the raman optical path, and then the wavefront distortion distribution function is used to measure the gravity measurement error (interference phase shift) generated by the laser wavefront distortion in the raman optical path
Fitting the integral of the atomic distribution function to the gravity measurement error to solve the wave-out Raman optical wave front distortion distribution function
These methods are well known to those skilled in the art and will not be described in detail herein.
Step S102: measuring the wave front distribution of the Raman laser which propagates downwards by taking the vertical upward propagation direction of the Raman light as the z direction
And upward propagating Raman laser wavefront distribution
That is, with the vertical upward propagation direction of Raman light as the z direction, the laser wavefront detectors 1 and 2 measure the Raman laser wavefront distribution propagating downward only through the top and bottom glass windows of the vacuum chamber and the 1/4 wave plate, respectively
And the Raman laser wavefront distribution propagating upward after passing through a Raman optical reflector (deformable mirror, or deformable lens plus plane mirror)
Step S103: according to the wavefront superposition relation:
analyze out
And
wherein
The static laser wavefront distortion caused by the vacuum chamber top glass window, the vacuum chamber bottom glass window, the 1/4 wave plate and the Raman reflector are respectively. The above static laser wavefront distortion is analyzed here to provide a reference for the later calculation of the effective dynamic laser wavefront distortion. Since the vacuum chamber bottom glass window and the 1/4 wave plate are always present at the same time, only the cumulative wavefront distortion distribution of the two needs to be known and does not need to be solved separately.
In a specific application example, the flow of measuring the dynamic vibration noise and the laser wavefront distortion in step S2 includes:
step S201: the vibrations in 3 directions of the ground or carrier platform are measured using a seismometer (or accelerometer).
Due to the periodic characteristic of the atomic interference gravimeter, the influence of vibration noise in the low-frequency range of 0-50 Hz on the atomic interference phase is large, so that the selected seismometer (such as Guralp 3ESPC) has high measurement precision (10 nm/s) in the measurement range of 120 s-50 Hz2/Hz1/2) And lower self-noise (e.g., self-noise of the Guralp 3ESPC seismograph in the range of 0.04Hz to 10Hz is lower than the global low background noise model NLNM);
step S202: utilizing two low-pass filters to respectively filter high-frequency noise and filter phase frequency and amplitude frequency distortion caused by limited measurement bandwidth of the measured three-dimensional vibration signal;
step S203: acquiring the measured three-dimensional vibration signal in real time in an analog voltage mode by using a self-made high-speed acquisition card (24 bits, the sampling rate is more than 10K) to obtain S (x, y, z, t), and outputting the S (x, y, z, t) to a microprocessor in real time;
step S204: real-time measurement of the distribution of the Raman laser wavefront propagating downward only through the top and bottom glass windows of the vacuum chamber, 1/4 wave plates, using laser wavefront detectors 1 and 2
And the Raman laser wavefront distribution propagating upward after passing through a Raman optical reflector (deformable mirror, or deformable lens plus plane mirror)
And outputting the wavefront distribution to a microprocessor in real time through a high-speed signal transmission cable.
In a specific application example, in step S3, the real-time compensation process of the vibration noise and the laser wavefront distortion includes:
step S301: determination of the deformable mirror response matrix:
the deformable mirror may be, but not limited to, one of a piezoelectric ceramic deformable mirror (PDM), a mechanical thin film deformable mirror (MMDM), a liquid deformable lens (LAL), and the like. For example, the current MEMS driver based on electromagnetic field driving can reach more than 1000 drivers, the stroke of a single driver reaches 100 μm, the surface roughness is less than 1nm, the surface quality RMS error is less than 7nm, the response time of a deformable mirror is less than 500 μ s, the bandwidth is more than 2kHz, the integral translation and the local deformation perpendicular to the direction of the reflecting mirror surface can be generated, and therefore, the real-time compensation can be completely realized for the dynamic vibration noise and the wave front distortion below 2 kHz.
Fig. 4 is a schematic diagram showing a structure of a piezoelectric deformable mirror of a 108-channel driver and a coding sequence of the driver, and this embodiment is described by taking the specific deformable mirror as an example. For the deformable mirror, the response matrix a is a 12 × 12 matrix, which is typically provided at the factory, if not automatically determined before use. Take the deformable mirror control software of the OKO company as an example, the software can also give Singular Value Decomposition (SVD) values U, S and V of a at the same time when automatically measuring the response matrix a, and the relationship a ═ USVTWhere the column elements of U constitute an orthogonal set of deformable mirror modes, the values of the diagonal matrix S represent the gains of these modes.
Step S302: calculation of drive voltage:
according to the dynamic reflector vibration noise signal S (x, y, z, t) after filtering processing and the total real-time laser wavefront distortion distribution
And a response matrix A of the deformable mirror, which is calculated by using an adaptive PID method to enable the deformable mirror to generate M12×12The driving voltage matrix K required by the deformation to compensate the vibration of the reflector and the wave front distortion of the laser meets the relation formula:
wherein
Dynamic laser wavefront distortion caused by the deformable mirror and the atmosphere respectively; total real time laser wavefront distortion
Dynamic laser wavefront distortion measured for wavefront sensor 1
Subtracting the static laser wavefront distortion generated by the glass window at the top of the vacuum cavity
And; k is a radical ofzuThe component along the z direction of a Raman laser wave propagating upwards after passing through a bottom reflector in a pair of Raman lights acted with atoms; the laser wavefront detector 2 measures the distribution of the raman laser wavefront propagating upward through a raman mirror (deformable mirror, or deformable lens plus plane mirror)
The method is used for monitoring the effect of the deformable mirror on real-time compensation of the Raman optical dynamic wavefront distortion.
Step S303: driving of the deformable mirror: and feeding back the calculated driving voltage matrix signal K or K' to a high-voltage amplifier, outputting a corresponding current signal by the high-voltage amplifier to drive a 108-channel deformable mirror to deform, and compensating the Raman light reflector vibration and Raman laser wavefront distortion caused by vibration noise in real time.
In a specific application example, the method further includes step S4: and evaluating the vibration noise and laser wavefront distortion compensation effect, namely evaluating the vibration noise and laser wavefront distortion compensation effect by using the atomic interference signal and providing real-time correction for the driving voltage applied by the deformable mirror.
The specific characteristics of the vibration noise and laser wavefront distortion compensation effect evaluation in the step S4 are as follows: firstly, an atomic interference gravimeter is started, the influence of vibration noise and laser wavefront distortion is evaluated according to the jitter of an atomic transition probability signal measured under a specific Raman optical phase, then a deformable mirror is started to compensate the vibration noise and laser wavefront distortion closed loop, then the change of atomic transition probability jitter is measured, the compensation effect is evaluated, and the deformable mirror driving voltage is corrected in real time.
As a preferred embodiment, the specific process of step S4 in this example includes:
step S401: preparing cold atomic groups: operating the cold atom interference gravimeter at the time when t is 0, carrying out interference gravity measurement circulation on the ith M-Z type atom, cooling and trapping atoms through a magneto-optical trap, so that the temperature of the atomic group is less than or equal to 10 mu k, and the number of the atoms is more than or equal to 107A plurality of; selecting atomic speed and atomic state by microwave and Raman light to obtain cold atomic group with longitudinal temperature less than or equal to 400nk, and preparing the atomic group into specific internal state, such as | g |>State;
step S402: realizing atomic interference: the atoms fall or are thrown upwards into a vacuum interference chamber, t being t1At the moment, three beams of Pi/2-Pi/2 Raman laser pulses with the interval time of T and the duration time of tau, 2 tau and tau are acted with atoms to make the radicals coherently split, reflect and combine to form an M-Z interferometer, wherein the phases phi of the first beam of Raman laser pulse and the second beam of Raman laser pulse1、φ2Set to 0, phase of the third Raman laser pulse
Set to a constant value, e.g., may be set to 0, ± pi/2, etc.;
step S403: probability of atomic transitionDetecting: normalization detection of transition probability of cold atomic group in atomic interferometer by detection light-return pump light-detection light and piezoelectric multiplier tube PMT
Step S404: and (3) evaluating the vibration noise compensation effect: by recording the Raman laser pulse phase over a long period of time
Probability of transition with cold atom
The corresponding relation between the atomic transition probability and the atomic transition probability becomes smaller under a specific Raman laser phase after the deformable mirror is used for compensating the vibration noise. And calculating the Allan variance of atomic transition probability jitter so as to evaluate the vibration noise compensation effect of the deformable mirror before and after use.
Step S405: and (3) real-time correction of the driving voltage of the deformable mirror: the deformable mirror controller executes wavefront reflector vibration and laser wavefront distortion compensation through a series of iterations by using a self-adaptive PID method, atomic interference gravity measurement can be synchronously implemented in the process, the influence of vibration noise and dynamic wavefront distortion of the Raman light reflector is evaluated according to the jitter degree of atomic transition probability under a specific Raman light phase, and if the Allan variance of atomic transition probability jitter is converged and is less than a certain threshold value P, the microprocessor does not need to execute any operation after receiving a feedback signal; if the Allan variance of the atomic transition probability jitter is increasing or diverging, the microprocessor needs to adjust the parameters of the adaptive PID algorithm to obtain a new driving voltage matrix signal K' of the deformable mirror and repeatedly perform step S303.
Referring to fig. 2 and 3, the present invention further provides an apparatus for implementing the compensation method, comprising:
z1. vibration noise and laser wavefront distortion measuring unit: the device mainly comprises a vibration noise measurement module Z1-1 and a wavefront distortion measurement module Z1-2 which can be respectively realized by an inertial instrument (comprising a seismograph, an accelerometer and the like) which is stably placed on the ground or a carrier platform and is tightly fixed with a Raman light reflector, and a laser wavefront detector (comprising a Shack-Hartmann wavefront detector, a curvature sensor, a Pyramid wavefront detector, a shearing interferometer wavefront detector, a phase acquisition wavefront detector and the like) which is arranged on the side surface of a gravity sensing head;
z2. vibration noise and laser wavefront distortion compensation unit: the device mainly comprises a deformable mirror (a deformable reflector or a deformable lens) with a known or measurable response matrix, a microprocessor capable of executing an adaptive PID algorithm, a high-voltage amplifier for driving the deformation of the deformable mirror, a signal transmission cable and the like;
z3. vibration noise and laser wavefront distortion compensation effect evaluation unit: the method mainly comprises the existing laser, vacuum, magnetic field, time sequence control and other modules of the atomic interference gravimeter, and information such as Raman laser phase-atomic transition probability jitter and the like obtained through measurement.
The difference between the two embodiments of fig. 2 and 3 is that the vibration noise and wavefront distortion compensation unit employs a deformable mirror in the former and a combination of a deformable lens and a plane mirror in the latter.
Therefore, the vibration noise and laser wavefront distortion compensation unit based on the deformable mirror has the characteristics of miniaturization, low cost, high precision, real-time compensation and the like, and the compensation effect evaluation module is a module for implementing the M-Z type atomic interferometer and does not need to additionally add components or generate signals.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (9)
1. A vibration noise and wavefront distortion error double compensation method for an atomic interference gravimeter is characterized by comprising the following steps:
step S1: static laser wavefront distortion measurement: to atomic stemGravimeter system for measuring laser wavefront distortion distribution function in static time-dependent Raman optical path
Step S2: measuring dynamic vibration noise and laser wavefront distortion: measuring vibration signals S (x, y, z, t) of the Raman light reflector, filtering, and measuring wave front distortion of the dynamic Raman laser in real time
Step S3: real-time compensation of vibration noise and laser wavefront distortion: driving the deformable mirror to deform by using a self-adaptive PID feedback control algorithm, and compensating vibration noise and laser wavefront distortion in real time;
the process of step S1 includes:
step S101: solving the laser wavefront distortion distribution function of a pair of Raman lights acting with atoms in static state
Step S102: measuring the wave front distribution of the Raman laser which propagates downwards by taking the vertical upward propagation direction of the Raman light as the z direction
And upward propagating Raman laser wavefront distribution
Step S103: according to the wavefront superposition relation:
obtaining:
and
the above-mentioned
The distribution of the wave front of the Raman laser which only passes through the top glass window and the bottom glass window of the vacuum chamber and downwards propagates through the 1/4 wave plate; the above-mentioned
The Raman laser wave front distribution is transmitted upwards after passing through a Raman light reflector; the above-mentioned
The static laser wavefront distortion caused by the vacuum chamber top glass window, the vacuum chamber bottom glass window, the 1/4 wave plate and the Raman reflector are respectively.
2. The method for double compensation of vibration noise and wavefront distortion error of atomic interferometer according to claim 1, wherein the process of step S2 includes:
step S201: measuring the vibration of the ground or the carrier platform in 3 directions;
step S202: respectively carrying out high-frequency noise filtering and phase frequency and amplitude frequency distortion filtering processing caused by limited measurement bandwidth on the measured three-dimensional vibration signal;
step S203: acquiring the measured three-dimensional vibration signal in real time in a voltage simulating mode to obtain S (x, y, z, t) and outputting the S (x, y, z, t) to a microprocessor in real time;
step S204: real-time measurement of the distribution of the Raman laser wavefront propagating downwards only through the top and bottom glass windows of the vacuum chamber and the 1/4 wave plate
And Raman laser wavefront distribution propagating upward through Raman light reflector
And outputs the wavefront profile to the microprocessor in real time.
3. The method for double compensation of vibration noise and wavefront distortion error of atomic interference gravimeter according to claim 1 or 2, wherein the process of step S3 includes:
step S301: determining a deformable mirror response matrix A;
step S302: calculation of drive voltage: calculating a driving voltage matrix K required for enabling the deformable mirror to deform so as to compensate the vibration of the reflector and the wave front distortion of the laser by using a self-adaptive PID (proportion integration differentiation) method according to the dynamic reflector vibration noise signal after filtering processing, the total real-time laser wave front distortion distribution and the response matrix A of the deformable mirror;
step S303: driving of the deformable mirror: and feeding back the calculated driving voltage matrix signal K to a high-voltage amplifier, and outputting a current signal of a corresponding channel by the high-voltage amplifier to drive the deformable mirror to deform so as to compensate the Raman light reflector vibration and Raman laser wavefront distortion caused by vibration noise in real time.
4. The method for double compensation of vibration noise and wavefront distortion error of atomic interference gravimeter according to claim 1 or 2, further comprising step S4: evaluating the compensation effect of vibration noise and laser wavefront distortion; namely, the atomic interference signal is utilized to evaluate the vibration noise and laser wavefront distortion compensation effect, and real-time correction is provided for the driving voltage applied by the deformable mirror.
5. The method for double compensation of vibration noise and wavefront distortion error of atomic interferometer according to claim 4, wherein the process of step S4 includes:
step S401: preparing cold radicals;
step S402: realizing atomic interference;
step S403: atomic transition probability detection: normalization detection of transition probability of cold atomic group in atomic interferometer by detection light-return pump light-detection light and piezoelectric multiplier tube PMT
Step S404: and (3) evaluating the vibration noise compensation effect: by recording the Raman laser pulse phase over a long period of time
Probability of transition with cold atom
The corresponding relation between the atomic transition probability and the atomic transition probability becomes smaller under a specific Raman laser phase after the deformable mirror is used for compensating the vibration noise; calculating an Allan variance of atomic transition probability jitter so as to evaluate the vibration noise compensation effect of the deformable mirror before and after use;
step S405: and real-time correction of the driving voltage of the deformable mirror.
6. The dual compensation method for vibration noise and wavefront distortion error of atomic interference gravimeter according to claim 5, wherein in step S401, the cold atomic interference gravimeter is operated at time t-0, the ith M-Z type atomic interference gravimeter cycle is measured, and atoms are cooled and trapped by the magneto-optical trap, so that the temperature of atomic groups is less than or equal to 10 μ k, and the number of atoms is greater than or equal to 107A plurality of; selecting the atomic speed and the atomic state by utilizing microwave and Raman light to obtain a cold atomic group with the longitudinal temperature less than or equal to 400nk, and preparing the atomic group into a specific internal state.
7. The method for dual compensation of vibration noise and wavefront distortion error of atomic interference gravimeter according to claim 5, wherein in step S402, the atom falls or is thrown upward into the vacuum interference chamber, and t is t1At the moment, three beams of Pi/2-Pi/2 Raman laser pulses with the interval time of T and the duration time of tau, 2 tau and tau are acted with atoms to make the radicals coherently split, reflect and combine to form an M-Z interferometer, wherein the phases phi of the first beam of Raman laser pulse and the second beam of Raman laser pulse1、φ2Set to 0, phase of the third Raman laser pulse
Set to a constant value.
8. The dual compensation method for vibration noise and wavefront distortion error of atomic interference gravimeter according to claim 5, wherein in step S405, the deformable mirror controller uses an adaptive PID method to iteratively perform wavefront mirror vibration and laser wavefront distortion compensation, during which atomic interference gravimetry is synchronously performed, and the influence of Raman mirror vibration noise and dynamic wavefront distortion is evaluated according to the jitter degree of atomic transition probability under a specific Raman optical phase; if the Allan variance of the atomic transition probability jitter is converged and is less than a certain threshold value P, the microprocessor does not need to execute any operation after receiving the feedback signal; and if the Allan variance of atomic transition probability jitter is increasing or diverging, the microprocessor adjusts the parameters of the adaptive PID algorithm to obtain a new driving voltage matrix signal K' of the deformable mirror.
9. An apparatus for carrying out the method of any one of claims 1 to 8, comprising:
the vibration noise and laser wavefront distortion measuring unit comprises a vibration noise measuring module Z1-1 and a wavefront distortion measuring module Z1-2 which can be respectively realized by an inertia instrument which is stably placed on the ground or a carrier platform and is tightly fixed with a Raman light reflector and a laser wavefront detector which is arranged on the side surface of a gravity sensing head;
the vibration noise and laser wavefront distortion compensation unit comprises a deformable mirror with a known or measurable response matrix, a microprocessor capable of executing an adaptive PID algorithm, and a high-voltage amplifier for driving the deformable mirror to deform;
the unit for evaluating the vibration noise and laser wavefront distortion compensation effect comprises an atomic interference gravimeter and Raman laser phase-atomic transition probability jitter information obtained through measurement.
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