CN109541621A - A kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system - Google Patents
A kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system Download PDFInfo
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- CN109541621A CN109541621A CN201811193617.4A CN201811193617A CN109541621A CN 109541621 A CN109541621 A CN 109541621A CN 201811193617 A CN201811193617 A CN 201811193617A CN 109541621 A CN109541621 A CN 109541621A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
Abstract
The invention discloses a kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system, the beat signal for having Doppler shift information is generated using single-frequency laser and two acousto-optic modulators, tunable laser can also generate the measurement beat signal containing doppler information by measurement optical interference circuit simultaneously, the two measurement beat signals are handled with the influence that can eliminate vibration to frequency scanning interference Models of Absolute Distance Measurement Based system.The invention is compared to double tunable laser measuring systems, reduce hardware cost and device complexity, single-frequency laser is compared to tunable laser volume simultaneously and quality is smaller, it is easier to integrated and uses at the scene, double tunable laser are also required for same frequency modulation(PFM) speed, this does not accomplish almost at present, because the phenomenon that tunable laser generally existing Nonlinear frequency modulation, and the present invention uses single-frequency laser, avoids this problem well.
Description
Technical field
The present invention relates to frequency scannings to interfere Models of Absolute Distance Measurement Based field, in particular to a kind of frequency scanning interferes Models of Absolute Distance Measurement Based system
The method for compensating vibration of system.
Background technique
Absolute distance measurement system can be used for range measurement and be up to tens meters, and relative uncertainty degree is less than 3ppm, this is being surveyed
Amount field is of great significance.Large-scale assembly parts can be improved in aircraft manufacturing in absolute distance measurement system, automobile engineering and existing
For the manufacture efficiency and precision in the fields such as air vane production.Current absolute distance measurement system be typically based on three kinds it is different
Optical means: time-of-flight method, composite wave regular way frequency scan interferometry.Frequency scanning interferes Models of Absolute Distance Measurement Based technology to be
One kind without target or mark point, can rapid survey diffuse reflector surface information and the very high distance measuring method of measurement accuracy,
Therefore the extensive concern of people has been obtained.
But in actual measurement, as the presence for vibrating caused Doppler effect, distance spectrum can broaden, this will lead to survey
1000 times bigger than the actual change of optical path difference of error of amount or more.In order to solve the influence of this vibration, Swinkels etc. uses one
The laser of a triangular wave frequency scanning resolves the distance value eliminating vibration and influencing by four continuous phase measurements；Jia etc.
Frequency scanning interference Models of Absolute Distance Measurement Based technology is combined with time-varying Kalman filter to track the transient motion of target, for fortune
The target that dynamic speed is 1mm/s, measurement standard difference is only 2.5 μm.
Summary of the invention
For existing object to be measured practical application, it is difficult to ensure that measurement in it is totally stationary under the conditions of, it is traditional
The very big situation of frequency scanning interference Models of Absolute Distance Measurement Based systematic measurement error, the present invention propose a kind of frequency scanning interference Models of Absolute Distance Measurement Based
The method for compensating vibration of system is generated respectively using single-frequency laser plus two acousto-optic modulators, tunable laser comprising vibration
It is absolute to frequency scanning interference to eliminate vibration by being handled the two beat signals for the measurement beat signal of dynamic information
The influence of range-measurement system, and assist beat signal to be used to eliminate tunable laser Nonlinear frequency modulation and measurement beat signal is generated
Influence.The present invention is not necessarily to two tunable laser, but by a tunable laser in double tunable laser systems
Device has changed single-frequency laser into, reduces hardware cost and device complexity, at the same do not use real-time measurement go out vibration displacement into
The mode of row compensation, but the distance value for offsetting vibration displacement is directly acquired by two synchronous measurement beat signals, simplify
Algorithm, so that frequency scanning interference Models of Absolute Distance Measurement Based systematic difference range is wider.
The technical scheme adopted by the invention is that: a kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system,
Utilize single-frequency laser, tunable laser, two acousto-optic modulators, several couplers, optical circulator, collimation lens, piezoelectricity
Displacement platform, target mirror, Coarse Wave Division Multiplexer obtain two measurement beat signals containing Doppler shift information, two surveys
Amount beat signal contains the vibration information of object to be measured mirror；Auxiliary beat frequency is obtained using tunable laser, time delay optical fiber to believe
Number；Eliminate what tunable laser Nonlinear frequency modulation generated two measurement beat signals using the auxiliary beat signal
After influence, two measurement beat signals are handled, eliminate vibration to the shadow of frequency scanning interference Models of Absolute Distance Measurement Based system
It rings, is calculated and eliminates the distance value that vibration influences.
Further, the present invention it is a kind of frequency scanning interference Models of Absolute Distance Measurement Based system method for compensating vibration, specifically include with
Lower step:
The generation of distance measuring signal:
1-1 step, single-frequency laser generate simple signal, and tunable laser generates frequency signal；The single-frequency
Signal is divided into the road A and the road B by the first beam splitter, and the frequency signal is divided into the road C and the road D, A by the second beam splitter
Road, the road B, the road C enter measurement interference system, and the road D enters auxiliary interference system；
In 1-2 step, measurement interference system: the road A signal reaches the first coupler, the road C letter by second sound-optic modulator
Number it is divided into the road E and the road F by third beam splitter, the road E signal couples in the first coupler with the road A signal and is sent into optical circulator；
The optical circulator, which uses, has the first, second, third port, for light is cyclically transferred to second end from first port
Mouthful, 3 ports light rings of third port, the first port of the optical circulator and first coupling are transferred to from second port
The output of clutch is connected, and second port is connected with collimation lens, and third port is connected to an input of third coupler
End；The road B signal reaches the second coupler by first sound-optic modulator, and the road F signal couples simultaneously with the road B signal in the second coupler
It is sent into another input terminal of third coupler；The road A and the road E laser are saturating by the first coupler, optical circulator, collimation
Mirror, after target mirror reflects, backtracking enters the optical circulator, enters back into an input terminal of the third coupler,
Wherein the road A laser converges and interferes in third coupler with the road B laser, and the road E laser and the road F laser converge in third coupler
Merging interferes, due to the road A laser, the road B laser and the road E laser, F from tunable laser from single-frequency laser
Road laser is the laser signal of two frequency bands, is separated the laser signal of two frequency bands using Coarse Wave Division Multiplexer, and the road A is swashed
Light and the road B laser form the first measurement beat signal on the first photodetector, and the road E laser and the road F laser are in the second photoelectricity
The second measurement beat signal is formed on detector；
In 1-3 step, auxiliary interference system: the road D signal is divided into the road G and the road H by the 4th beam splitter, and the road G laser passes through
Enter the 4th coupler after the time delay optical fiber of consistent length and known optical path difference, the road G laser and the road H laser converge in the 4th coupler
Merging interferes, and the output end of the 4th coupler is connected to third photodetector, and the road G laser and the road H laser are in third light
Auxiliary beat signal is formed on electric explorer；
Wherein, the road A and the road B form measurement optical interference circuit, the road E and the road F all the way and form another way measurement optical interference circuit,
The road G and the road H are formd with reference to optical interference circuit；
Synchronous data collection:
The the first measurement beat signal and the second measurement beat frequency letter that Channels Synchronous Data Acquisition System generates measurement interference system
Number and auxiliary interference system generate auxiliary beat signal synchronize sampling, steps are as follows:
Sampling time t is arranged in the initialization of 2-1, Channels Synchronous Data Acquisition Systems, sample frequency fs；
2-2, data acquire, and collect the first measurement beat signal, second to Channels Synchronous Data Acquisition System in collection process
It measures beat signal and auxiliary beat signal carries out error detection judgement, carry out next step if without mistake, otherwise weigh
It is new to execute 2-2 step；
Data processing:
The light frequency of tunable laser output used at present is not fairly linear modulation, when the light frequency of output is not
When fairly linear modulation, serious broadening phenomenon can occur for measurement beat signal, so as to cause great measurement error, therefore,
The influence of the Nonlinear frequency modulation of measurement interference system is eliminated using auxiliary interference system, specifically includes the following steps:
3-1 step, using the auxiliary beat signal Jing Guo Channels Synchronous Data Acquisition System as clock signal, the first measurement is clapped
Frequency signal and the second measurement beat signal carry out etc. optical frequencies resampling simultaneously；
3-2 step will generate interference for moving object, the road A laser and the road B laser, due to the first measurement beat signal
With the second measurement beat signal containing the motion information of object, thus by etc. the first measurement beat signal after optical frequencies resampling
It is multiplied to obtain new signal with the second measurement beat signal, how general it includes in one of frequency that new signal includes two cosine terms
The cosine term for strangling frequency displacement is distracter, and the cosine term that Doppler frequency shift is not included in another frequency is required item；Using quick
Fourier transformation or chirp-z transformation acquire the frequency of required item, acquire actual distance value to be measured according to the frequency of required item.
Wherein, 3-1 step specifically includes:
The first measurement beat signal indicates are as follows:
P1(t)=Acos { 2 π [(106-fd)t+fdτ+f0τ+80×106τ]} (1)
In formula (1), P1It (t) is the first measurement beat signal, A indicates the amplitude of the first measurement beat signal, fdIndicate due to
Object of which movement causes to measure the Doppler frequency shift introduced in beat signal, f0Indicate the frequency of single-frequency laser, τ indicates measured
From corresponding time delay, t indicates the time；
The second measurement beat signal indicates are as follows:
In formula (2), P2It (t) is the second measurement beat signal, B indicates the amplitude of the second measurement beat signal, α1Indicate adjustable
The modulating speed of humorous laser, f1Indicate the original frequency of tunable laser transmitting laser, ε1(t) it indicates to deviate ideal linearity
The frequency non-linear error of frequency sweep；
Assist the expression formula of beat signal are as follows:
In formula (3), P3It (t) is auxiliary beat signal, M indicates the amplitude of auxiliary beat signal, τrIt indicates to refer to optical interference circuit
The corresponding time delay of optical path difference.
The peak-to-valley value location point of auxiliary beat signal is taken to carry out the first measurement beat signal and the second measurement beat signal
Resampling, as a result:
In formula (4), P1It (k) is the first measurement beat signal after resampling；In formula (5), P2It (k) is the after resampling
Two measurement beat signals.
Wherein, 3-2 step specifically includes:
By etc. the first measurement beat signal after optical frequencies resampling and the second measurement beat signal be multiplied to obtain new signal:
In formula (6), P4(k) for etc. the first measurement beat signal and the second measurement beat signal phase after optical frequencies resampling
It is multiplied to arrive new signal；By formula (6) it is found that the frequency term of first cosine termIn contain it is how general
Strangle frequency displacement fd, it is distracter；The frequency term of second cosine termIn without Doppler frequency shift fd, for institute
Need item；
If the points of the first measurement beat signal and the second measurement beat signal after resampling are N, new signal is carried out
Chirp-z transformation acquires required item frequency, and the spectrum peak position of required item frequency is p, then peak value dot frequency fbeatIt calculates public
Formula are as follows:
By the frequency term of (6) second cosine terms of formulaIt obtains:
Convolution (7) and formula (8), can obtain:
The calculation formula of testing distance are as follows:
In formula (10), R is actual distance value to be measured, and c is the light velocity.
The beneficial effects of the present invention are:
A single-frequency laser and two acousto-optics are increased on the basis of original frequency scanning interferes Models of Absolute Distance Measurement Based system
Modulator, the purpose is to generate the beat signal for having target mirror vibration information, and the light that tunable laser issues is by surveying
The beat signal containing target mirror vibration information can be also generated after amount interference system, the two beat signals are handled, just
It can obtain and eliminate the distance value that vibration influences, the method reduces hardware cost for double tunable laser methods
With device complexity, and be not necessary to guaranty that the sweep velocity of two tunable laser it is consistent (often this requirement is extremely difficult to,
Because the light of tunable laser output at present on the market is not fairly linear modulation), at the same time, for actually answering
With environment, this system it is integrated also more convenient, often volume is larger for tunable laser, and single-frequency laser it is then small in size,
Light-weight, system availability designed by the present invention is stronger.
Detailed description of the invention
Fig. 1 is a kind of flow chart of the method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system of the present invention；
Fig. 2 is the structural schematic diagram of frequency scanning interference Models of Absolute Distance Measurement Based system and device used in the present invention.
Attached drawing mark: 1, single-frequency laser；2, the first beam splitter；3, second sound-optic modulator；4, third beam splitter；5,
One acousto-optic modulator；6, the first coupler；7, the second coupler；8, optical circulator；9, third coupler；10, collimation lens；
11, Coarse Wave Division Multiplexer；12, piezoelectric position moving stage and target mirror；13, the first photodetector；14, the second photodetector；15,
Measure interference system；16, interference system is assisted；17, third photodetector；18, the 4th coupler；19, time delay optical fiber；20,
4th beam splitter；21, the second beam splitter；22, tunable laser；23, Channels Synchronous Data Acquisition System；24, data processing system；
P1, the first measurement beat signal；P2, the second measurement beat signal；P3, auxiliary beat signal；After P4, resampling
First measurement beat signal and the second resulting new signal of measurement beat signal multiplication.
Specific embodiment
In order to further understand the content, features and effects of the present invention, the following examples are hereby given, and cooperate attached drawing
Detailed description are as follows:
Interfere absolute measuring plus original frequency scanning using single-frequency laser, acousto-optic modulator the invention proposes a kind of
Method for compensating vibration away from system, and its feasibility is demonstrated by theory deduction.
Frequency scanning used in the present invention interferes Models of Absolute Distance Measurement Based system and device as shown in Fig. 2, including 1 He of single-frequency laser
Tunable laser 22, the single-frequency laser 1 divide by the first beam splitter 2 for the road A and the road B, the tunable laser 22
Divide by the second beam splitter 21 for the road C and the road D, the road A, the road B, the road C enter measurement interference system 15, and the road D enters auxiliary interference system
System 16.
In the measurement interference system 15: the road A signal reaches the first coupler 6, the road C letter into second sound-optic modulator 3 is crossed
Number divide by third beam splitter 4 for the road E and the road F, the road E signal couples in the first coupler 6 with the road A signal and is sent into optical circulator
8；The optical circulator 8 is using the first, second, third port is had, for light is cyclically transferred to second from first port
Port, is transferred to 3 ports light rings of third port from second port, the first port of the optical circulator 8 and described the
The output of one coupler 6 is connected, and second port is connected with collimation lens 10, and third port is connected to third coupler 9
One input terminal；The road B signal reaches the second coupler 7 by first sound-optic modulator 5, and the road F signal and the road B signal are in the second coupling
Clutch 7 couples and is sent into another input terminal of third coupler 9；The road A and the road E laser pass through the first coupler 6, the ring of light
Shape device 8, collimation lens 10, after target mirror reflects, backtracking enters the optical circulator 8, enters back into the third coupling
One input terminal of device 9, wherein the road A laser converges and interferes in third coupler 9 with the road B laser, the road E laser and the road F
Laser converges and interferes in third coupler 9, due to from single-frequency laser 1 the road A laser, the road B laser with from can
The road the E laser of tuned laser 22, the laser signal that the road F laser is two frequency bands are (that is, the road A laser, the road B laser are in same
One frequency band, the road E laser, the road F laser are in the same frequency band, and the two frequency bands and non-intersecting), therefore by third coupling
Output one Coarse Wave Division Multiplexer 11 of termination of clutch 9, laser signal of the Coarse Wave Division Multiplexer 11 to separate two frequency bands,
The road A laser and the road B laser form the first measurement beat signal P1 on the first photodetector 13, and the road E laser and the road F laser exist
The second measurement beat signal P2 is formed on second photodetector 14.
In the auxiliary interference system 16: the road D signal divides by the 4th beam splitter 20 for the road G and the road H, the road G laser process
Enter the 4th coupler 18 after the time delay optical fiber 19 of consistent length and known optical path difference, the road G laser is coupled with the road H laser the 4th
Device 18 converges and interferes, and the output end of the 4th coupler 18 is connected to third photodetector 17, and the road G laser and the road H are swashed
Light forms auxiliary beat signal P3 on third photodetector 17.
The output of first photodetector 13, the second photodetector 14, third photodetector 17 is respectively connected to
Three channels of Channels Synchronous Data Acquisition System 23, the output of Channels Synchronous Data Acquisition System 23 are connected to data processing system 24.
A kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system of the present invention, utilizes single-frequency laser 1, adjustable
Humorous laser 22, first sound-optic modulator 5 and second sound-optic modulator 3, several couplers, optical circulator 8, collimation lens 10,
Piezoelectric position moving stage and target mirror 12, Coarse Wave Division Multiplexer 11 etc. obtain the first measurement beat signal containing Doppler shift information
The measurement of P1 and second beat signal P2, the first measurement beat signal P1 and the second measurement beat signal P2 contain mesh to be measured
The vibration information of index glass；Auxiliary beat signal P3 is obtained using tunable laser 22, time delay optical fiber 19 etc.；Using the auxiliary
Beat signal P3 eliminates 22 Nonlinear frequency modulation of tunable laser to the first measurement beat signal P1 and the second measurement beat frequency
After the influence that signal P2 is generated, the first measurement beat signal P1 and the second measurement beat signal P2 are handled, eliminated
The influence to frequency scanning interference Models of Absolute Distance Measurement Based system is vibrated, is calculated and eliminates the distance value that vibration influences.It is implemented
The step of it is as follows:
According to experimental provision is built shown in Fig. 2, then as shown in Figure 1, in frequency scanning interference Models of Absolute Distance Measurement Based system and device
Tunable laser 22 and single-frequency laser 1 are first opened, then parameter (sweep bandwidth and the scanning of tunable laser 22 are set
Speed), the parameter (vibration frequency and Oscillation Amplitude) of piezoelectric position moving stage, the parameter (sample frequency of Channels Synchronous Data Acquisition System 23
And the sampling time).
After equipment preheating and initialization, start to perform a scan interference Models of Absolute Distance Measurement Based, the specific steps are as follows:
The generation of distance measuring signal
1-1 step, single-frequency laser 1 generate the single simple signal of frequency, and tunable laser 22 generates frequency scanning
Signal；The simple signal divides by the first beam splitter 2 for the road A and the road B, and the frequency signal passes through the second beam splitter 21
It is divided into the road C and the road D, the road A, the road B, the road C enter measurement interference system 15, and the road D enters auxiliary interference system 16；
In 1-2 step, measurement interference system 15: the road A signal reaches the first coupler 6, C into second sound-optic modulator 3 is crossed
Road signal divides by third beam splitter 4 for the road E and the road F, and the road E signal couples in the first coupler 6 with the road A signal and is sent into the ring of light
Shape device 8；The optical circulator 8 is using the first, second, third port is had, for light to be cyclically transferred to from first port
Second port is transferred to 3 ports light rings of third port, the first port of the optical circulator 8 and institute from second port
The output for stating the first coupler 6 is connected, and second port is connected with collimation lens 10, and third port is connected to third coupler
9 input terminal；The road B signal reaches the second coupler 7 by first sound-optic modulator 5, and the road F signal and the road B signal are the
Two couplers 7 couple and are sent into another input terminal of third coupler 9；The road A and the road E laser by the first coupler 6,
Optical circulator 8, collimation lens 10, after the reflection of target mirror 12, backtracking enters the optical circulator 10, enters back into described the
One input terminal of three couplers 9, wherein the road A laser converges and interferes in third coupler 9 with the road B laser, the road E laser
Converge and interfere in third coupler 9 with the road F laser, due to from single-frequency laser 1 the road A laser, the road B laser and come
From the road the E laser of tunable laser 22, laser signal that the road F laser is two frequency bands (that is, at the road A laser, the road B laser
In the same frequency band, the road E laser, the road F laser are in the same frequency band, and the two frequency bands and non-intersecting), therefore by
The output of three couplers 9 terminates a Coarse Wave Division Multiplexer 11, laser of the Coarse Wave Division Multiplexer 11 to separate two frequency bands
Signal, the road A laser and the road B laser form the first measurement beat signal P1, the road E laser and the road F on the first photodetector 13
Laser forms the second measurement beat signal P2 on the second photodetector 14；
In 1-3 step, auxiliary interference system 16: the road D signal divides by the 4th beam splitter 20 for the road G and the road H, the road G laser
By entering the 4th coupler 18 after the time delay optical fiber 19 of consistent length and known optical path difference, the road G laser and the road H laser are the 4th
Coupler 18 converges and interferes, and the output end of the 4th coupler 18 is connected to third photodetector 17, the road G laser and H
Road laser forms auxiliary beat signal P3 on third photodetector 17；
Wherein, the road A and the road B form measurement optical interference circuit, the road E and the road F all the way and form another way measurement optical interference circuit,
The road G and the road H are formd with reference to optical interference circuit.
Synchronous data collection
The the first measurement beat signal P1 and the second measurement that 23 pairs of Channels Synchronous Data Acquisition System measurement interference systems 15 generate
The auxiliary beat signal P3 that beat signal P2 and auxiliary interference system 16 generate synchronizes sampling, and steps are as follows:
Sampling time t is arranged in the initialization of 2-1, Channels Synchronous Data Acquisition System 23s, sample frequency fs；
2-2, data acquisition, in collection process to Channels Synchronous Data Acquisition System 23 collect the first measurement beat signal P1,
Second measurement beat signal P2 and auxiliary beat signal P3 carry out error detection judgement, carry out if without mistake in next step
Suddenly, 2-2 step is otherwise re-executed.
Data processing
The light frequency that tunable laser 22 used at present exports fairly linear can not modulate, when the light frequency of output
Not when fairly linear modulation, measurement beat signal can occur serious broadening phenomenon so as to cause great measurement error and be
The influence of this Nonlinear frequency modulation for needing to assist interference system 16 to eliminate measurement interference system 15 herein, specifically includes following
Step:
3-1 step, using the auxiliary beat signal P3 Jing Guo Channels Synchronous Data Acquisition System 23 as clock signal, surveyed to first
The measurement of amount beat signal P1 and second beat signal P2 carries out etc. optical frequencies resampling simultaneously；
3-2 step will generate interference for moving object, the road A laser and the road B laser, due to the first measurement beat signal
Beat signal P2 is containing the motion information of object for the measurement of P1 and second, thus by etc. the first measurement beat frequency after optical frequencies resampling
The measurement of signal P1 and second beat signal P2 is multiplied to obtain new signal P4, and new signal P4 includes two cosine terms, one of packet
Cosine term containing Doppler frequency shift is distracter, another cosine term for not including Doppler frequency shift is required item；Using quick
Fourier transformation or chirp-z transformation accurately acquire the frequency of required item, acquire actual distance to be measured according to the frequency of required item
Value.
Method for compensating vibration below with reference to specific formula frequency scanning interference Models of Absolute Distance Measurement Based system a kind of to the present invention is made
It further illustrates:
Setting 5 frequency of first sound-optic modulator is 81MHz, and 3 frequency of second sound-optic modulator is 80MHz, then for movement
For target, the first measurement beat signal P1 that the first photodetector 13 detects can be indicated are as follows:
P1(t)=Acos { 2 π [(106-fd)t+fdτ+f0τ+80×106τ]} (1)
In formula (1), P1(t) amplitude of the first measurement beat signal P1, f are indicated for the first measurement beat signal P1, AdIt indicates
Since object of which movement causes to measure the Doppler frequency shift introduced in beat signal, f0Indicate the frequency of single-frequency laser 1, τ is indicated
The corresponding time delay of testing distance, t indicate the time.
The second measurement beat signal P2 that second photodetector 14 detects can be indicated are as follows:
In formula (2), P2(t) amplitude of the second measurement beat signal P2, α are indicated for the second measurement beat signal P2, B1It indicates
The modulating speed of tunable laser 22, f1Indicate that tunable laser 22 emits the original frequency of laser, ε1(t) it indicates to deviate
The frequency non-linear error of ideal linearity frequency sweep.
In order to eliminate the influence of Nonlinear frequency modulation, herein using the auxiliary beat signal P3 of auxiliary interference system 16 to first
It measures the measurement of beat signal P1 and second beat signal P2 and carries out resampling (although there is no non-thread by the first measurement beat signal P1
Property item, but in order to first measurement beat signal P1 and second measurement beat signal P2 synchronize processing, so herein
Also resampling is carried out to the first measurement beat signal P1), assist the expression formula of beat signal P3 are as follows:
In formula (3), P3(t) amplitude of auxiliary beat signal P3, τ are indicated for auxiliary beat signal P3, MrIt indicates with reference to interference
The corresponding time delay of the optical path difference of optical path.
Take the peak-to-valley value location point of auxiliary beat signal P3 to the first measurement beat signal P1 and the second measurement beat signal
P2 carries out resampling, as a result:
In formula (4), P1It (k) is the first measurement beat signal P1 after resampling, in formula (5), P2(k) for after resampling
Second measurement beat signal P2.By formula (4) it can be seen that the nonlinear terms in the first measurement beat signal P1 have been eliminated, will weigh
The first measurement beat signal P1 after sampling is multiplied and can obtain with the second measurement beat signal P2:
In formula (6), P4It (k) is new signal P4, by formula (6) it is found that the frequency term of first cosine termIn contain Doppler frequency shift fd, it is distracter；The frequency term of second cosine termIn without Doppler frequency shift fd, it is the single item of frequency, as required item, and relative to formula (2) second
A cosine term greatly reduces phase-modulation.The frequency phase-difference 2MHz or so of distracter and required item, therefore the two is distributed in frequency
(difference on the frequency determines the different zones in domain by the difference on the frequency of first sound-optic modulator 5 and second sound-optic modulator 3, can be according to reality
Need to select), therefore can easily distinguish required item.
If the points of the first measurement beat signal P1 and the second measurement beat signal P2 after resampling are N, to new signal
P4Carry out chirp-z (Fast Fourier Transform (FFT) or other can get precise frequencies algorithm) transformation acquire required item frequency,
The spectrum peak position of required item frequency is p, then peak value dot frequency fbeatCalculation formula are as follows:
By the frequency term of (6) second cosine terms of formulaIt obtains:
Convolution (7) and formula (8), can obtain:
The calculation formula of testing distance are as follows:
In formula (10), R is actual distance value to be measured, and c is the light velocity.By formula (10) it is found that by means of the present invention, vibrating
Influence to frequency scanning interference Models of Absolute Distance Measurement Based technology has been eliminated.
Although the preferred embodiment of the present invention is described above in conjunction with attached drawing, the invention is not limited to upper
The specific embodiment stated, the above mentioned embodiment is only schematical, be not it is restrictive, this field it is common
Technical staff under the inspiration of the present invention, without breaking away from the scope protected by the purposes and claims of the present invention, may be used also
By make it is many in the form of, within these are all belonged to the scope of protection of the present invention.
Claims (4)
1. it is a kind of frequency scanning interference Models of Absolute Distance Measurement Based system method for compensating vibration, which is characterized in that using single-frequency laser, can
Tuned laser, two acousto-optic modulators, several couplers, optical circulator, collimation lens, piezoelectric position moving stage, target mirror, thick wave
Division multiplexer obtains two measurement beat signals containing Doppler shift information, two measurement beat signals contain to
Survey the vibration information of target mirror；Auxiliary beat signal is obtained using tunable laser, time delay optical fiber；Using the auxiliary beat frequency
After signal eliminates the influence that tunable laser Nonlinear frequency modulation generates two measurement beat signals, to two surveys
Amount beat signal is handled, and eliminates influence of the vibration to frequency scanning interference Models of Absolute Distance Measurement Based system, elimination vibration is calculated
The distance value of influence.
2. a kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system according to claim 1, feature exist
In, specifically includes the following steps:
The generation of distance measuring signal:
1-1 step, single-frequency laser generate simple signal, and tunable laser generates frequency signal；The simple signal
It is divided into the road A and the road B by the first beam splitter, the frequency signal is divided into the road C and the road D, the road A, B by the second beam splitter
Road, the road C enter measurement interference system, and the road D enters auxiliary interference system；
In 1-2 step, measurement interference system: the road A signal reaches the first coupler, the road C signal warp by second sound-optic modulator
It crosses third beam splitter and is divided into the road E and the road F, the road E signal couples in the first coupler with the road A signal and is sent into optical circulator；It is described
Optical circulator, which uses, has the first, second, third port, for light is cyclically transferred to second port from first port, from
Second port is transferred to 3 ports light rings of third port, the first port of the optical circulator and first coupler
Output be connected, second port is connected with collimation lens, and third port is connected to an input terminal of third coupler；B
Road signal reaches the second coupler by first sound-optic modulator, and the road F signal is coupled and is sent into the second coupler with the road B signal
Another input terminal of third coupler；The road A and the road E laser pass through the first coupler, optical circulator, collimation lens, warp
After target mirror reflection, backtracking enters the optical circulator, enters back into an input terminal of the third coupler, wherein A
Road laser converges and interferes in third coupler with the road B laser, and the road E laser and the road F laser converge simultaneously in third coupler
It interferes, since the road A laser, the road B laser and the road the E laser from tunable laser from single-frequency laser, the road F are sharp
Light be two frequency bands laser signal, the laser signal of two frequency bands is separated using Coarse Wave Division Multiplexer, the road A laser with
The road B laser forms the first measurement beat signal on the first photodetector, and the road E laser and the road F laser are in the second photodetection
The second measurement beat signal is formed on device；
In 1-3 step, auxiliary interference system: the road D signal is divided into the road G and the road H by the 4th beam splitter, and the road G laser passes through length
Enter the 4th coupler after the time delay optical fiber of constant and known optical path difference, the road G laser and the road H laser converge simultaneously in the 4th coupler
It interferes, the output end of the 4th coupler is connected to third photodetector, the road G laser and the road H laser and visits in third photoelectricity
It surveys on device and forms auxiliary beat signal；
Wherein, the road A and the road B form measurement optical interference circuit, the road E and the road F all the way and form another way measurement optical interference circuit, the road G
It forms with the road H with reference to optical interference circuit；
Synchronous data collection:
Channels Synchronous Data Acquisition System to measurement interference system generate first measurement beat signal and second measurement beat signal with
And the auxiliary beat signal that auxiliary interference system generates synchronizes sampling, steps are as follows:
Sampling time t is arranged in the initialization of 2-1, Channels Synchronous Data Acquisition Systems, sample frequency fs；
2-2, data acquire, and collect the first measurement beat signal, the second measurement to Channels Synchronous Data Acquisition System in collection process
Beat signal and auxiliary beat signal carry out error detection judgement, carry out next step if without mistake, otherwise hold again
Row 2-2 step；
Data processing:
The light frequency of tunable laser used at present output is not fairly linear modulation, when the light frequency and non-fully of output
When linear modulation, serious broadening phenomenon can occur for measurement beat signal, so as to cause great measurement error, therefore, use
Interference system is assisted to eliminate the influence of the Nonlinear frequency modulation of measurement interference system, specifically includes the following steps:
3-1 step, using the auxiliary beat signal Jing Guo Channels Synchronous Data Acquisition System as clock signal, to the first measurement beat frequency letter
Number and the second measurement beat signal carry out etc. optical frequencies resampling simultaneously；
3-2 step will generate interference for moving object, the road A laser and the road B laser, due to the first measurement beat signal and the
Two measurement beat signals containing the motion information of object, therefore by etc. the first measurement beat signal after optical frequencies resampling and the
Two measurement beat signals are multiplied to obtain new signal, and new signal includes two cosine terms, include Doppler's frequency in one of frequency
The cosine term of shifting is distracter, and the cosine term that Doppler frequency shift is not included in another frequency is required item；Using in quick Fu
Leaf transformation or chirp-z transformation acquire the frequency of required item, acquire actual distance value to be measured according to the frequency of required item.
3. a kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system according to claim 2, feature exist
In 3-1 step specifically includes:
The first measurement beat signal indicates are as follows:
P1(t)=Acos { 2 π [(106-fd)t+fdτ+f0τ+80×106τ]} (1)
In formula (1), P1It (t) is the first measurement beat signal, A indicates the amplitude of the first measurement beat signal, fdIt indicates due to object
Movement causes to measure the Doppler frequency shift introduced in beat signal, f0Indicate the frequency of single-frequency laser, τ indicates testing distance pair
The time delay answered, t indicate the time；
The second measurement beat signal indicates are as follows:
In formula (2), P2It (t) is the second measurement beat signal, B indicates the amplitude of the second measurement beat signal, α1It indicates tunable to swash
The modulating speed of light device, f1Indicate the original frequency of tunable laser transmitting laser, ε1(t) it indicates to deviate ideal linearity frequency sweep
Frequency non-linear error；
Assist the expression formula of beat signal are as follows:
In formula (3), P3It (t) is auxiliary beat signal, M indicates the amplitude of auxiliary beat signal, τrIndicate the light with reference to optical interference circuit
The corresponding time delay of path difference；
The peak-to-valley value location point of auxiliary beat signal is taken to adopt the first measurement beat signal and the second measurement beat signal again
Sample, as a result:
In formula (4), P1It (k) is the first measurement beat signal after resampling；In formula (5), P2(k) it is surveyed for second after resampling
Measure beat signal.
4. a kind of method for compensating vibration of frequency scanning interference Models of Absolute Distance Measurement Based system according to claim 3, feature exist
In 3-2 step specifically includes:
By etc. the first measurement beat signal after optical frequencies resampling and the second measurement beat signal be multiplied to obtain new signal:
In formula (6), P4(k) for etc. the first measurement beat signal after optical frequencies resampling and the second measurement beat signal it is mutually multiplied
To new signal；By formula (6) it is found that the frequency term of first cosine termIn contain Doppler frequency
Move fd, it is distracter；The frequency term of second cosine termIn without Doppler frequency shift fd, it is required item；
If the points of the first measurement beat signal and the second measurement beat signal after resampling are N, new signal is carried out
Chirp-z transformation acquires required item frequency, and the spectrum peak position of required item frequency is p, then peak value dot frequency fbeatIt calculates public
Formula are as follows:
By the frequency term of (6) second cosine terms of formulaIt obtains:
Convolution (7) and formula (8), can obtain:
The calculation formula of testing distance are as follows:
In formula (10), R is actual distance value to be measured, and c is the light velocity.
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