CN103344175B - The optical heterodyne interference method of nonlinearity erron is eliminated based on phaselocked loop filtering and timer - Google Patents
The optical heterodyne interference method of nonlinearity erron is eliminated based on phaselocked loop filtering and timer Download PDFInfo
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Abstract
The optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer belongs to laser heterodyne interferometry field, the method is in the light path that there is nonlinearity erron interference component, reach out at least 3 road signals and make respective nonlinearity erron interference component at least a part of which 3 tunnel, phase angle on the signal frequency composition to be eliminated is different within the scope of a corresponding angle of circumference, and adopt phase locked loop filter that signal is filtered in analog electrical signal passage, timing counter is adopted to detect no less than the phase angle of 3 road signals respectively, record the time differed between every drive test amount signal and the particular phases of reference signal, it is then convert into phase contrast, carry out subsequent treatment again after being calculated displacement by displacement calculating section eliminate or suppress interference component.The present invention can eliminate the particular harmonic composition of nonlinearity erron or interference, and the process that adjusts is very easy to, and improves systematic function, reduces cost.
Description
Technical field
The invention belongs to laser heterodyne interferometry (HeterodyneInterferometry) fields of measurement, be specifically related to a kind of laser heterodyne interferometry measuring method eliminating nonlinearity erron fundamental frequency based on phaselocked loop filtering and timing counter algorithm exempting from accurate adjustment.
Background technology
Laser heterodyne interference system can be used to measure the physical quantity such as displacement, length, is one of best nano measurement method.This system is to be converted to by tested displacement in frequency or the phase place change of heterodyne signal, again by this measure of the change out, owing to the frequency ratio optical frequency of heterodyne signal is much lower, photosignal is easily processed, can through electronic fine-grained and reach higher Measurement Resolution, resolution can reach micromicron (pm) or better.
But ubiquity non-linear (nonlinearity) problem in optical heterodyne interference method, these factors can be the main source of error of displacement measurement, making its precision generally only have nanoscale to tens nanometers, its reason is that the light beam that frequency is different can not well separate.These periodic nonlinearity erron problems are always up the obstacle of this art.
The method constantly inventing some improvement both at home and abroad for many years, but also there are some restriction or problems more, for instance Badami and Pattersom uses speedometer and audiofrequency spectrometer directly measure nonlinearity erron composition in a mobile system and compensate；The method carrying out ellipse fitting after phase signal integration is carried out compensating non-linear error by TaeBongEom and TaeYoungChoi etc..These methods can when there is no other auxiliary interferometer compensating non-linear error, but system complex, and need substantial amounts of fluctuation signal cycle and relatively great amount of computing, the real-time that impact is measured.The Chinese invention patent that publication number is CN101660924 discloses a kind of new method, the method can efficiently solve this problem, but being it desired to obtain exactly accurate result, in addition it is also necessary to point-device optics regulates, this precise optical regulates generally relatively difficult.
Summary of the invention
In order to solve, system complex that existing laser heterodyne interference system exists, operand be big, the coarse technical problem of poor real, result, the present invention provides a kind of optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timing counter algorithm, the particular harmonic composition of nonlinearity erron or interference can be eliminated, and remove the precision optics eliminated required for nonlinearity erron from and regulate device and fine adjustment process, this adjustment is made to become very easy, systematic function is greatly improved simultaneously, reduces cost.
The signal of telecommunication that the AC signal that the photodetector outfan of laser heterodyne interference systematic survey light arm obtains is is frequency with alien frequencies light frequency difference, its additional phase contrast moves into accurate proportionate relationship with measured position.But wherein comprise so-called nonlinearity erron, be mainly distributed on the first harmonic (generally also can be called fundamental frequency according to Fourier space character, be a kind of spatial frequency) of Fourier spectrum.The method of the present invention can eliminate the fundamental component of nonlinearity erron；Actually arbitrary a certain frequency is all effective by the method for the present invention, and without optical system being done special fine adjustment.
Laser heterodyne interference system also exist in the signal light path of nonlinearity erron interference component, obtain at least 3 road signals (passage), by obtaining these signals by carry the method arranging at least 3 interference light photodetecting part on the light arm of detected signal, and make at least a part of which have the phase angle of respective contained nonlinearity erron first harmonic (or other frequency content) in 3 tunnels different in a corresponding circumference, thus obtain sufficient information, enable and processed by weighted sum superposition below etc. and eliminate fundamental frequency (or any one frequency) composition in nonlinearity erron.Method, it is possible to be readily available amplitude and the starting phase angle of first harmonic.Generally, the phase angle of the several signals error of different light paths is generally unequal, if there being the situation that phase angle is equal, it is possible to know by measuring the method for phase angle in prior art, and makes them unequal by adjusting light path.Furtherly, the optical system that generally we set up at random, do not have nonlinearity erron phase angle in any 2 tunnels identical in a corresponding circumference, if but after completing the adjustment of optical system, the phase angle having at least 2 road nonlinearity erron first harmonics (or other frequency content to be eliminated) in 3 tunnels is more or less the same, and may affect the amplitude of useful signal after weighted superposition, thus affecting the signal to noise ratio of output signal, at this moment we can substantially adjust the phase angle difference relative to (frequency content to be eliminated of nonlinearity erron) signal phase angle corresponding in other passages of the frequency content to be eliminated in 1-2 road therein, it is made to increase to some extent fully till (namely enough).Now with the method for a lot of detection nonlinearity erron first harmonic (or other frequency content to be eliminated) phase and amplitude, such as " measuring method of laser heterodyne interference nonlinearity erron " " Beijing University of Technology's journal " the 6th phase in 2010 of Chen Hongfang etc.；" a kind of laser heterodyne interference nonlinearity erron novelty measuring method " of Zhong Zhi etc., optoelectronic laser, 2005, etc..The method adjusting phase angle can be realized by the optical path difference that adjustment participates between two light interfered.
Periodicity based on hamonic function, it is of course possible to as generally, gets rid of several integral multiple angles of circumference comprised in above-mentioned phase contrast and disregards (no longer doing similar prompting below).
Method below is adopted to carry out subsequent treatment: to assume initially that the situation of only 3 road signals, with reference signal, 3 road signals being carried out phase bit comparison respectively, until solving 3 displacements.At this moment the phase place of the nonlinearity erron in each passage is different.
By following proof it can be seen that after having the weight coefficient array being not zero to enable to superposition the fundamental frequency of nonlinearity erron or the amplitude of other frequency contents be zero, and retain useful signal.
In above-mentioned 3 displacements solved, the displacement measurement on the i-th tunnel can be expressed as:
Wherein, equal sign right-hand member Section 1 χ is real physical displacement, and Section 2 is the primary components of nonlinearity erron, certainly with first harmonic, content of the present invention without loss of generality is described here；A is coefficient, expresses nonlinearity erron amplitude, is generally an a small amount of, but does not make approximate processing in derivation afterwards.Being the initial phase angle of nonlinearity erron, λ is optical wavelength.Here the wave number in nonlinearity erron itemWhat represent is first harmonic composition, and by the situation of measuring prism individual reflection.When second harmonic, this can become
By 3 result weighted superposition, it is normalized into:
One group of new ki be intended merely to pro forma neatly, it is possible to be regarded as new weight coefficient.Our purpose is to find one group of ki to make: X=x.
By above-mentioned condition, we can obtain following system of linear equations:
k1+k2+k3=b
Wherein, b ≠ 0
The factor arrays of variable ki is 3 rank square formations of full rank, and the equation group about ki has untrivialo solution.I.e., it is possible to make
To sum up, it has been demonstrated that after such weighted superposition, the first harmonic composition of nonlinearity erron is eliminated.
IfIn have any 2 differ 180 °, problem can be made to become simple and favourable, this situation is it is generally required to the optics of precision regulates and just can obtain, and the 2 road signals having only to non-linear component difference 180 ° are sufficient for eliminating the nonlinearity erron composition of characteristic frequency, in this that patent of invention stated in the background, ratio is illustrated in more detail.
To this, we have solved the nonlinearity erron problem in laser heterodyne interference in 3 dimensional linear spaces of electronics.
When having more than 3 road signals (passage), we at least can advance for the signal that 3 road phase angles are different, again by any one road Signal averaging in 3 tunnels of all the other several signals and reservation, and 3 tunnels that the phase angle difference being melted in certain frequency of nonlinearity erron is respectively not zero.Thus dissolve the problem solved above, the i.e. situation of 3 passages of becoming, and have been obtained for proving.Certainly also can not adopt the processing procedure being first simplified to 3 tunnels recited above, but together complete in weighted overlap-add procedure.
Correct weight coefficient array can be obtained by following method in practice and eliminate error percentage: (1) is by 2 linear superpositions therein, because in 2 dimension spaces of this certain harmonic components nonlinear, one group of substrate of two paths of signals Special composition, so any one vector can be generated by adjustment superposition coefficient, we allow the vector generated and the 3rd signal (vector) be exactly in opposite direction on certain harmonic components nonlinear, then by the signal generated and the 3rd signal (vector) linear superposition, adjusting weight coefficient just can make certain harmonic components nonlinear be kept to zero completely mutually, and useful signal can still be retained when.(2) electricity consumption method can being adjusted to repeat the weight coefficient on alternate sweep at least 2 tunnel, measuring nonlinearity erron value in the output after superposition so that it is constantly reduce, until being zero simultaneously.(3) adopt most basic method, measuring phase angle described in every road and after amplitude, directly calculate analytic method, also may be used herein the thinking in (1), but be not decompose to adjust, but decoupled method, no longer carefully solve here.That is, it is being found that first harmonic error can be weighted by superposition and cancel each other, thus after removing the above-mentioned principle of error percentage, the weighted superposition mode being suitable for can be selected according to the related content of present invention record, it becomes possible to realize the elimination of first harmonic error.The method of above-mentioned multiple acquisition weight coefficient is intended merely to facilitate enumerating of understanding, is not the restriction completely to technical scheme.
In order to remove corresponding optics accurate adjustment from, eliminate or suppress nonlinearity erron, and be conducive to retaining useful signal and selecting rational parameter, preferably, the difference between the phase angle on the signal frequency composition to be eliminated of 3 at least 3 road signals periodicity nonlinearity errons is made to be not less than 60 degree.This is because in practice we always can easily pass through adjustment or arrange, make arbitrarily biphase between declinate all less little.Theoretical and experiment all illustrates, it is a rational numerical value using 60 ° of lower limits as this angle, signal to noise ratio after processing is beneficial to by this, the useful signal amplitude lower than single channel of output will not be made after weighted superposition, as long as attempt the random fixing device that can affect between 3 tunnels in the light path of phase contrast blindly 3 to 5 times simultaneously, substantially once chance meets this condition, thus realizing " adjustment-free " mechanically, and eliminate corresponding adjuster so that regulate or arrange work and become simply and readily.Can judge whether to meet this condition according to the method for the starting phase angle measuring first harmonic error being previously mentioned, thus stopping adjusting.By the similar aforementioned actual method (1) (2) eliminating error percentage, certain harmonic components nonlinear can also be adjusted nothing, then reexamine the amplitude of useful signal, if too low, just illustrate do not have to meet " 60 degree of conditions " or similar standard.Checking whether to adjust complete, having eliminated error can judge by carrying out the methods such as results contrast for example with more accurate measurement instrument.
The method that the release precision optical machinery of this " fine adjustment " being replaced optics by " fine adjustment " of electronics regulates or exempts from optics accurate adjustment, makes cost be greatly reduced, and the required precision that optics is regulated can decline more than 2-3 the order of magnitude.And the precision that whole system shows on nonlinearity erron characteristic frequency is also significantly improved.
It is obvious that the ultimate principle of the method and the advantage itself existed and meaning, and whether adopting integrated optics mode, including optical fiber solutions, or bulk wave mode etc. is unrelated.The method is all effective for the periodic error in all of laser heterodyne interferometry system, as long as we can obtain the signal that its interference component phase place of at least 3 roads is different.
Laser heterodyne interference signal is typical weak signal, particularly more requires that signal is pure in the exquisite system of this elimination nonlinearity erron, and the wave filter in analog electrical signal is very important link in system.Consider that the useful signal of this system is single some frequency composition, when there is speed and acceleration when testee, will there is the rate of change of frequency displacement and frequency.The wave filter of simple inductance and capacitance type is longer for the response time inputting signal phase, limits the movement velocity of object being measured under the requirement of precision.Phase locked loop filter then can solve this problem preferably, it has very low phase noise and extraordinary transient phase error and static phase error index, the immediate movement of object in motion can be precisely measured out, the even immediate movement of object in acceleration, complete machine index can be promoted.The phase-detection between each road signal and reference signal can be carried out after phaselocked loop filtering.
Considering the symmetry requirement measuring signal at least 3 tunnels, the filtering part generally respectively measured in signalling channel should be identical.
Record, with timing counter, the time differed between the measurement signal on every road and reference signal particular phases (crossing zero angle position such as what rise) and be converted into phase contrast, method below can be adopted: record the time measuring signal or each complete cycle of reference signal on every road with timing counter, and by time (or phase contrast) divided by the whole cycle recorded simultaneously time differed between the particular phases (as rise or fall cross zero angle position) of the above-mentioned every drive test amount signal recorded and reference signal, in order to obtain " instantaneous " phase angle, effectively to suppress multiple drift, improve certainty of measurement.And in another case, owing to the cycle of reference signal is known, it is possible to directly try to achieve simply.
Timing counter is typically via the oscillator operation carried, and microwave counter works frequency is up to several 100GHz.For the laser difference frequency that difference frequency is MHz level, it is real that angle of circumference is subdivided into 1000 parts.The working method of this timing counter is real-time serial, working cycle completes within a difference frequency cycle, it seeks phase difference method than fast Fourier transform, even inner product asks the operand of phase difference method much smaller, hardly processor is required, it is just genuine process in real time, there is very high speed, when prime filtering is perfect, there is significantly high precision.So phaselocked loop filtering be a kind of succinct plus the above-mentioned timing counter phase place method of inspection and efficiently, accurately can measure the practical combination of high-speed moving object or even low cost.
After phase-detection and before being weighted superposition, each road information that we are obtained in that full amplitude, that obtain fully filtering, phase relation etc. including the phase relation between the signal of each road and interference component, this category information is useful in some cases, is such as conducive to determining weight coefficient array etc..
Based on foregoing, the present invention provides a kind of first harmonic that can eliminate or reduce periodically nonlinearity erron or other frequency content, improve certainty of measurement, the optical heterodyne interference method that the corresponding precision optics that omits adjusts, namely the optical heterodyne interference method of nonlinearity erron is eliminated based on phaselocked loop filtering and timing counter algorithm, the method is in the light path that there is nonlinearity erron interference component, at least 3 drive test amount signals and 1 tunnel reference signal is obtained by light splitting, and make each periodically nonlinearity erron phase angle in the frequency content to be eliminated of at least a part of which 3 drive test amount signal different within the scope of a corresponding angle of circumference；At least 3 drive test amount signals and 1 tunnel reference signal are separately converted to corresponding at least 3 drive test amount analog electrical signals and 1 LUSHEN examines analog electrical signal；Each road of described at least 3 drive test amount analog electrical signals is carried out the first filtering respectively, 1 LUSHEN is examined after analog electrical signal carries out the second filtering, input Timer module respectively, utilize timer to record each road of at least 3 drive test amount analog electrical signals and 1 LUSHEN examines the interval of particular phases between analog electrical signal, and be converted at least 3 road phase contrasts；At least 3 road phase contrasts are converted into corresponding displacement, obtain at least 3 tunnel displacement measurement, now containing nonlinearity erron in the displacement measurement of each road；At least 3 tunnel displacement measurement obtained are carried out real number ranking operation, then carries out additive operation and can obtain final measurement；Described first filtering includes adopting phaselocked loop ripple device.
The above-mentioned each road utilizing timer to record at least 3 drive test amount analog electrical signals and 1 LUSHEN examine the time difference of particular phases between analog electrical signal, and the step being converted to phase contrast includes: utilize timer to record each road of at least 3 drive test amount analog electrical signals and 1 LUSHEN examines the time differed between the particular phases of analog electrical signal, examine the cycle of analog electrical signal with this time each road divided by least 3 drive test amount analog electrical signals or 1 LUSHEN, obtain phase contrast；Described particular phases includes: rose or fell phase place during zero angle.
Above-mentioned first filtering adds low pass filter after being additionally included in described phase locked loop filter and is filtered.
The phase contrast of the periodically nonlinearity erron of at least 3 in above-mentioned at least 3 drive test amount signals is not less than 60 °.
The step obtaining at least 3 drive test amount signals and 1 tunnel reference signal above by light splitting includes: the A road optical signal of output passes sequentially through at least 4 light-dividing devices and respectively obtains A1, A2 ... An road optical signal, wherein n >=4；The B road optical signal with the A road optical signal of output with frequency difference obtains B1 road optical signal by light-dividing device, and all the other optical signals of B road are passed sequentially through light-dividing device after being reflected by reflection unit and obtain B2 ... Bn road optical signal, wherein n >=4；A1 road optical signal and B1 road optical signal interfere formation reference signal, A2 ... An road optical signal and B2 ... optical signal correspondence interference respectively in Bn road forms n-1 drive test amount signal.
Due to the operation principle of phase discriminator in phaselocked loop, it is possible to the interference of input signal noise and other frequency contents can be subject to, cause phase discriminator output noise.Therefore, adding the inductance by the serial or parallel connection of one or two or more multi-level before phase discriminator and narrow band filter that resonance circuit that electric capacity forms is constituted, it is useful that analogue signal is filtered.The effect of this wave filter is important, and any wave filter that it can not be phase locked after ring is made up.
Reference signal for simulation can adopt the wave filter that one or two or more multi-level inductance capacitance resonant tank in parallel or series is constituted to be filtered, the composition pure to obtain comparison.
Resonant tank adds resistance or equivalent resistance adjusts quality factor and is filtered, in order to make quality factor adjustable and stable.The filter circuits that the inductance capacitance resonant tank in parallel or series of a relatively high quality factor (Q-value) is constituted adds resistance (containing adjustable resistance, potentiometer, or the method for equivalence), quality factor are mainly determined by lumped parameters such as resistors, rather than determined by distributed constant, obtain desired, stable Q-value.Q-value has a lot of physical significances, such as the here too high highest movement speed that also can affect under required precision of Q-value.
For each basic resonant tank in the wave filter that the inductance capacitance resonant tank in parallel or series of above-mentioned single-stage, two-stage or more stages is constituted, and between the outfan of its prime, and between the input of rear class, adopt weak coupling method to ensure the stability of this resonant tank and sufficient quality factor, the method of these weak couplings realizes at least through one of following method, 1) Capacitance Coupled, 2) inductive, 3) resistance coupling, 4) winding method is transformer coupled.
The present invention another solution is that a kind of laser heterodyne interferometry device adopting above-mentioned optical heterodyne interference method, including: the first light-dividing device, the optical signal light splitting of A road is obtained A1, A2 ... An road optical signal, wherein n >=4；Second light-dividing device, obtains B1 road optical signal and remaining light signal thereof by the B road optical signal light splitting that the A road optical signal with output has frequency difference, and all the other optical signals described are obtained B2 by the second light-dividing device light splitting after being reflected device reflection ... Bn road optical signal, wherein n >=4；Interfere forming apparatus so that A1 road optical signal and B1 road optical signal interfere the reference signal formed, A2 ... An road optical signal and B2 ... Bn road optical signal corresponding interference the respectively forms n-1 drive test amount signal；Signal detecting device, is respectively converted into 1 road reference electrical signal, the n-1 drive test amount signal of telecommunication by above-mentioned 1 tunnel reference signal, n-1 drive test amount signal；First filtration module, carries out the first filtering respectively to n-1 drive test amount analog electrical signal；Second filtration module, examines analog electrical signal to 1 LUSHEN and carries out the second filtering；Timer module, each road of calculating n-1 drive test amount analog electrical signal after filtering and 1 LUSHEN examine the interval of analog electrical signal particular phases, and are converted to phase contrast；Displacement computing module, obtains n-1 road displacement measurement according to n-1 road phase difference calculating；Weighted superposition module, carries out real number ranking operation and additive operation by the n-1 road displacement measurement obtained.
Present invention omits the explanation of some prior aries and statement, row as omitted timing counter principle, adopt details, general base component discussion and the block diagrams etc. such as theorem, the wiring board distribution filtering electric capacity of power-supply system, amplifier set by system gain.
The invention has the beneficial effects as follows: the present invention is in common laser heterodyne interference system-based, creatively optical path is divided into multichannel, carry out the processes such as the adjustment of electronics, signal processing, weighted superposition respectively, length with electronics fine adjustment, light filling fine adjustment short, optics accurate adjustment or other non-electronic learning of the complexity that omitted adjust, the substitute is the adjustment adopting electronics and signal processing method eliminates nonlinearity erron, reduce the complexity of pH effect, reduce cost, improve efficiency.Simultaneously, effectively eliminate or be greatly reduced nonlinearity erron quasi-periodic interference component and then improve certainty of measurement or reduce interference, simultaneously the phase locked loop filter etc. of particular design makes the certainty of measurement of whole system improve, capacity of resisting disturbance is strong, stably, being conducive to large-scale production, production cost is low.
Accompanying drawing explanation
Fig. 1 is the opticator principle schematic that the present invention eliminates the optical heterodyne interference method of nonlinearity erron based on phaselocked loop filtering and timing counter algorithm.
Fig. 2 is the phase locked loop filter circuit diagram in the present invention.
Fig. 3 is the principle schematic that the present invention eliminates the optical heterodyne interference method of nonlinearity erron based on phaselocked loop filtering and timing counter algorithm.
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention is described in further details.
The system realizing the optical heterodyne interference method that the present invention eliminates nonlinearity erron based on phaselocked loop filtering and timing counter algorithm is segmented into opticator and electrical signal process part afterwards.Wherein the principle of opticator is as it is shown in figure 1, the present invention on the basis of an original opticator, adds the part in broken box in figure.
First, set forth the opticator operation principle of original heterodyne interferometry system: sent laser by laser instrument 101, acousto-optical device 103 is incided through Part I reflecting mirror 102, Part II reflecting mirror 114 is shone after shift frequency, transmission light is reflected by measuring prism 115, inciding Part III reflecting mirror 111, reflecting part and another Ray Of Light are interfered through the first polaroid 131.The light (it provides reference ray for each road interference portion below) reflected by Part I reflecting mirror 102 is through the first reflecting mirror 125, after Part IV reflecting mirror 124, Part V reflecting mirror 123, Part VI reflecting mirror the 122, second reflecting mirror 121, together inciding the first polaroid 131 with the reflection light of Part III reflecting mirror 111, the difference frequency fractional conversion of two light is become the signal of telecommunication by the first photodetector 141 by the interference light of its outgoing.This signal of telecommunication, as measuring signal, has wherein included from the previously obtained displacement information of measuring prism 115, has also contained nonlinearity erron composition.
The light that the light reflected by Part II reflecting mirror 114 and Part IV reflecting mirror 124 reflect converges, incide the second polaroid 134, the difference frequency fractional conversion of two light is become the signal of telecommunication by the second photodetector 144 by the interference light of its outgoing, and this signal of telecommunication is exactly reference signal.
Above-mentioned laser instrument 101, Part I reflecting mirror 102 and acousto-optical device 103 constitute frequency and have the double-frequency laser generator of elementary errors, it is also possible to replaced by other scheme.
Invention increases the part in broken box in Fig. 1, it mainly includes two new measurement light arm/light paths and corresponding circuit part.
Together with original the first smooth arm being made up of Part III reflecting mirror the 111, first polaroid the 131, first photodetector 141 etc. in figure, have three light arms, or it is called three optical paths, and thus obtain measuring signal output 1, measure signal output 2 and measure signal output 3, the new measurement light arm of the two is structurally identical with the first smooth arm.Plus reference signal, four road signal output altogether, this four roads signal just constitutes the output of opticator, is transferred to electrical signal process part below, as described in Figure 3.
Process in part at electrical signal, its signal respectively through shown in Fig. 2 phase locked loop filter (for the filtering part of first passage to fourth lane be respectively 211 in Fig. 3,221,231,241)；Low-pass filtering part (for first passage to fourth lane be respectively 212 in figure, 222,232,242)；Again by timing counter part (for the first to third channel be 213 in figure, 223,233) each road signal is obtained phase angle；Then three tunnel measurement data are converted into displacement at displacement calculating section (being 214,224,234 in figure respectively for the first to third channel) and carry out cycle count respectively, complete corresponding displacement measurement, obtain the measurement result on each road.The same nonlinearity erron containing respective destruction system accuracy in certain result.The measurement result on Zai Jiang tri-tunnel is delivered to weighted superposition arithmetic section 301 respectively and is carried out real number ranking operation, then does additive operation and just can draw last measurement result, and the fundamental frequency of its nonlinearity erron has been eliminated or has significantly suppressed.
Claims (10)
1. the optical heterodyne interference method of nonlinearity erron is eliminated based on phaselocked loop filtering and timer, it is characterised in that: the method includes:
In the light path that there is nonlinearity erron interference component, obtained at least 3 drive test amount signals and 1 tunnel reference signal by light splitting, and make at least a part of which 3 drive test amount signal each periodically nonlinearity erron phase angle in the frequency content to be eliminated is different within the scope of a corresponding angle of circumference；
At least 3 drive test amount signals and 1 tunnel reference signal are separately converted to corresponding at least 3 drive test amount analog electrical signals and 1 LUSHEN examines analog electrical signal；
Each road of described at least 3 drive test amount analog electrical signals is carried out the first filtering respectively, 1 LUSHEN is examined after analog electrical signal carries out the second filtering, input Timer module respectively, utilize timer to record each road of at least 3 drive test amount analog electrical signals and 1 LUSHEN examines the interval of particular phases between analog electrical signal, and be converted at least 3 road phase contrasts；
At least 3 road phase contrasts are converted into corresponding displacement, obtain at least 3 tunnel displacement measurement, now containing nonlinearity erron in the displacement measurement of each road；
At least 3 tunnel displacement measurement obtained are carried out real number ranking operation, then carries out additive operation and can obtain final measurement；
Described first filtering includes adopting phase locked loop filter.
2. the optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 1, it is characterized in that: the described each road utilizing timer to record at least 3 drive test amount analog electrical signals and 1 LUSHEN examine the time difference of particular phases between analog electrical signal, and the step being converted to phase contrast includes: utilize timer to record each road of at least 3 drive test amount analog electrical signals and 1 LUSHEN examines the time differed between the particular phases of analog electrical signal, the cycle of analog electrical signal is examined with this time each road divided by least 3 drive test amount analog electrical signals or 1 LUSHEN, obtain phase contrast；Described particular phases includes: rose or fell phase place during zero angle.
3. the as claimed in claim 1 optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer, it is characterised in that: described first filtering adds the narrow band filter that the resonant tank being made up of the inductance capacitance of one or more levels serial or parallel connection constitutes and is filtered before being additionally included in described phase locked loop filter.
4. the optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 1, it is characterised in that: described first filtering adds low pass filter after being additionally included in described phase locked loop filter and is filtered.
5. the optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 3, it is characterised in that: adopt weak coupling mode to couple between described resonant tank with its prime outfan and rear class input.
6. filter and the optical heterodyne interference method of timer elimination nonlinearity erron based on phaselocked loop as claimed in claim 3, it is characterised in that: described resonant tank adds resistance or equivalent resistance adjustment quality factor, so that quality factor are adjustable and stablize.
7. the as claimed in claim 5 optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer, it is characterised in that: described weak coupling mode is capacitive couplings or inductive method or resistance coupled method or the transformer coupled method of winding type.
8. the optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 1, it is characterised in that: the phase contrast of the periodically nonlinearity erron of at least 3 in described at least 3 drive test amount signals is not less than 60 °.
9. the optical heterodyne interference method eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 1, it is characterized in that: the step being obtained at least 3 drive test amount signals and 1 tunnel reference signal by light splitting is included: the A road optical signal of output passes sequentially through at least 4 light-dividing devices and respectively obtains A1, A2 ... An road optical signal, wherein n >=4；Having the B road optical signal of frequency difference with the A road optical signal of output and obtained B1 road optical signal and remaining light signal thereof by light-dividing device, all the other optical signals of B road are passed sequentially through light-dividing device after being reflected by reflection unit and obtain B2 ... Bn road optical signal, wherein n >=4；A1 road optical signal and B1 road optical signal interfere formation reference signal, A2 ... An road optical signal and B2 ... optical signal correspondence interference respectively in Bn road forms n-1 drive test amount signal.
10. the laser heterodyne interferometry device of the optical heterodyne interference method adopted as described in any one of claim 1-9, it is characterised in that: including:
First light-dividing device, obtains A1, A2 by the optical signal light splitting of A road ... An road optical signal, wherein n >=4；
Second light-dividing device, obtains B1 road optical signal and remaining light signal thereof by the B road optical signal light splitting that the A road optical signal with output has frequency difference, and all the other optical signals described are obtained B2 by the second light-dividing device light splitting after being reflected device reflection ... Bn road optical signal, wherein n >=4；
Interfere forming apparatus so that A1 road optical signal forms 1 tunnel reference signal, A2 ... An road optical signal and B2 with the corresponding interference respectively of B1 road optical signal ... optical signal correspondence respectively in Bn road interferes formation n-1 drive test amount signal；
Signal detecting device, is respectively converted into 1 LUSHEN examines analog electrical signal, n-1 drive test amount analog electrical signal by above-mentioned 1 tunnel reference signal, n-1 drive test amount signal；
First filtration module, carries out the first filtering respectively to n-1 drive test amount analog electrical signal；
Second filtration module, examines analog electrical signal to 1 LUSHEN and carries out the second filtering；
Timer module, each road of calculating n-1 drive test amount analog electrical signal after filtering and 1 LUSHEN examine the interval of analog electrical signal particular phases, and are converted to phase contrast；
Displacement computing module, obtains n-1 road displacement measurement according to n-1 road phase difference calculating；
Weighted superposition module, carries out real number ranking operation and additive operation by the n-1 road displacement measurement obtained.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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