CN103344175A - Non-linear error removing optical heterodyne interferometry based on phase-locked loop filter and timer - Google Patents
Non-linear error removing optical heterodyne interferometry based on phase-locked loop filter and timer Download PDFInfo
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Abstract
The invention discloses a non-linear error removing optical heterodyne interferometry based on a phase-locked loop filter and a timer, and belongs to the field of optical heterodyne interference. The non-linear error removing optical heterodyne interferometry based on the phase-locked loop filter and the timer comprises the steps that at least three paths of signals are tried to be obtained, phase angles, on the signal frequency components to be removed, of own non-linear error interference elements of the at least three paths of the signals are made to be different to one another in a corresponding circumference angle range, the phase-locked loop filter is used for filtering the signals in an analog electrical signal channel, the timing counter is used for detecting the phase angles of the at least three paths of signals, the time difference between the specific phase of each path of measuring signal and the specific phase of each path of reference signal is measured, the time difference is converted into phase difference, follow-up processing is conducted after displacement is calculated through a displacement calculation portion, and interference components are removed or restrained. According to the non-linear error removing optical heterodyne interferometry based on the phase-locked loop filter and the timer, specific harmonic components of non-linear errors or interference can be removed, the adjustment process is simple, system performance is improved, and cost is reduced.
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 based on phaselocked loop filtering and timing counter algorithm elimination nonlinearity erron fundamental frequency of exempting from accurate adjustment.
Background technology
The laser heterodyne interference system can be used for measuring physical quantitys such as displacement, length, is one of best nano measurement method.This system is converted to tested displacement in the frequency or phase place variation of heterodyne signal, again this measure of the change is come out, because the frequency ratio optical frequency of heterodyne signal is much lower, photosignal is handled easily, can be through electronic fine-grained and reach higher Measurement Resolution, resolution can reach micromicron (pm) or better.
But ubiquity non-linear (nonlinearity) problem in the laser heterodyne interferometry method, these factors can be the main source of error of displacement measurement, make its precision generally have only nanoscale to tens nanometer, its reason is that the different light beam of frequency can not well separate.These periodic nonlinearity erron problems are the obstacles of this art development always.
Constantly invent the method for some improvement for many years both at home and abroad, but also have some restrictions or problems more, for example Badami and Pattersom use ratemeter and frequency spectrograph are directly measured the nonlinearity erron composition and are compensated in mobile system; TaeBong Eom and TaeYoungChoi etc. come the compensating non-linear error to the method for carrying out ellipse fitting behind the phase signal integration.These methods can be when the auxiliary interferometer that does not have other exists the compensating non-linear error, but system complex, and need a large amount of fluctuation signal cycle and relative a large amount of computing, the real-time of influence measurement.In being the Chinese invention patent of CN101660924, publication number announced a kind of new method, this method can address this problem effectively, if but wish to obtain very accurate result, also need point-device optics to regulate, this precise optical is regulated usually relatively difficulty.
Summary of the invention
In order to solve big, poor, the coarse technical matters of result of real-time of system complex, operand that existing laser heterodyne interference system exists, the invention provides a kind of laser heterodyne interferometry method based on phaselocked loop filtering and timing counter algorithm elimination nonlinearity erron, can eliminate the particular harmonic composition of nonlinearity erron or interference, and remove the needed precision optics regulating device of nonlinearity erron and the minute adjustment process eliminated from, make this adjustment become very easy, simultaneously significantly improve system performance, reduce cost.
The AC signal that the photodetector output terminal of laser heterodyne interference systematic survey light arm obtains is to be the electric signal of frequency with alien frequencies optical frequency difference, and its additional phase differential and measured position moves into accurate proportionate relationship.But wherein comprising so-called nonlinearity erron, mainly be distributed on the first harmonic (also can be called fundamental frequency according to Fourier series character generally speaking, be a kind of spatial frequency) of Fourier spectrum.Method of the present invention can be eliminated the fundamental component of nonlinearity erron; In fact method of the present invention all is effectively to a certain frequency arbitrarily, and need not optical system is done special minute adjustment.
In the laser heterodyne interference system, exist on the signal light path of nonlinearity erron interference component, obtain at least 3 road signals (passage), obtain these signals by carrying the method that at least 3 interference light photodetection parts are set on the light arm that is detected signal, and make have wherein in 3 the tunnel separately that the phase angle of contained nonlinearity erron first harmonic (or other frequency content) has nothing in common with each other at least in the circumference of a correspondence, so just obtained sufficient information, enable pass later face processing such as weighted sum stack and eliminate fundamental frequency (or any one frequency) composition in the nonlinearity erron.Method can be easy to obtain amplitude and the starting phase angle of first harmonic.Generally speaking, the phase angle of the several signals error of different light paths is unequal usually, if the situation that has phase angle to equate can be known by the method for measuring phase angle in the prior art, and make them unequal by the adjustment light path.Furtherly, our optical system of setting up at random generally speaking, it is identical in a corresponding circumference not have in any 2 the tunnel nonlinearity erron phasing degree, if but finish after the adjusting of optical system, has the phase angle of 2 road nonlinearity erron first harmonics (or other frequency content that will be eliminated) to be more or less the same then may to influence the amplitude of the useful signal after the weighted stacking in 3 the tunnel at least, thereby influence the signal to noise ratio (S/N ratio) of output signal, at this moment we can roughly adjust the phase angle of the frequency content that will be eliminated in wherein the 1-2 road with respect to the difference of (frequency content that will be eliminated of nonlinearity erron) signal phase angle corresponding in other passages, and it is increased to fully till (namely enough) to some extent.The method that a lot of detection nonlinearity erron first harmonics (or other frequency content that will be eliminated) phase place and amplitude are arranged now is as " measuring method of laser heterodyne interference nonlinearity erron " " Beijing University of Technology's journal " the 6th phase in 2010 of Chen Hongfang etc.; " the novel measuring method of a kind of laser heterodyne interference nonlinearity erron " of Zhong Zhi etc., photoelectron laser, 2005, etc.The method of adjusting phase angle can realize by the optical path difference of regulating between two light that participate in interfering.
Based on the periodicity of hamonic function, can several integral multiple angles of circumference eliminatings that comprise in the above-mentioned phase differential be disregarded as usually certainly (following no longer do similar prompting).
Adopt and carry out subsequent treatment in the following method: at first hypothesis has only the situation of 3 road signals, 3 road signals is carried out the phase bit comparison with reference signal respectively, until solving 3 displacements.At this moment the phase place of the nonlinearity erron in each passage is different.
By following proof as can be known, there is non-vanishing weighting coefficient array can make that the amplitude of the fundamental frequency of nonlinearity erron after the stack or other frequency contents is zero, and keeps useful signal.
In above-mentioned 3 displacements that solve, the displacement measurement on i road can be expressed as:
Wherein, first χ of equal sign right-hand member is real physical displacement, and second is the primary components of nonlinearity erron, with first harmonic content of the present invention is described here certainly and is without loss of generality; A is coefficient, expresses the nonlinearity erron amplitude, is an a small amount of generally speaking, but does not make approximate processing in the derivation afterwards.
Be the initial phase angle of nonlinearity erron, λ is optical wavelength.Here the wave number in the nonlinearity erron item
Expression be the first harmonic composition, and by the situation of measuring prism individual reflection.For the situation of second harmonic, this can become
With 3 weighted stacking as a result, be normalized into:
One group of new ki just for pro forma clean and tidy, can be regarded as new weighting coefficient.Our purpose is to find one group of ki to make: X=x.
We can obtain following system of linear equations by above-mentioned condition:
k
1+k
2+k
3=b
Wherein, b ≠ 0
The factor arrays of variable ki is 3 rank square formations of full rank, about the system of equations of ki untrivialo solution is arranged.That is, can make
To sum up, verified after such weighted stacking, the first harmonic composition of nonlinearity erron is eliminated.
If
In have any 2 to differ 180 °, can make problem become simple and favourable, this situation generally needs accurate optics adjusting just can obtain, and only need non-linear component to differ 180 ° the 2 road signals enough nonlinearity erron composition of elimination characteristic frequency just, in this that patent of invention of in background technology, having mentioned than being illustrated in more detail.
We have solved the nonlinearity erron problem in the laser heterodyne interference in 3 dimensional linear spaces of electronics to this.
For having the above situation of 3 road signals (passage), we can keep the signal that 3 road phase angles have nothing in common with each other at least in advance, again with all the other several signals and reservation 3 the tunnel in the stack of any one road signal, and with its change on certain frequency of nonlinearity erron phase angle difference each non-vanishing 3 the tunnel.So just dissolve the problem that has solved above becoming, i.e. the situation of 3 passages, and obtained proof.Certainly also can not adopt recited abovely at first to be simplified to 3 tunnel processing procedure, but in weighted overlap-add procedure, together finish.
Can obtain correct weighting coefficient array by following method in practice and eliminate error percentage: (1) incites somebody to action 2 route stacks wherein, because in 2 dimension spaces of this nonlinear certain harmonic components, two paths of signals has constituted one group of substrate in space, so can generate any one vector by adjusting the stack coefficient, we allow the vector that generates just in time be that direction is opposite with the 3rd signal (vector) on nonlinear certain harmonic components, then with the signal and the 3rd signal (vector) linear superposition that generate, adjust weighting coefficient and just can make nonlinear certain harmonic components be kept to zero fully mutually, and useful signal can still be retained.(2) weighting coefficient that can electricity consumption accent method repeats alternate sweep at least 2 tunnel is measured nonlinearity erron value in the output after the stack simultaneously, and it is constantly reduced, until being zero.(3) adopt fundamental method, after measuring phase angle described in every road and amplitude, directly calculated by analytic method, also can adopt the thinking in (1) here, but be not to decompose to adjust, but substep calculates, no longer carefully separate here.That is to say, can cancel each other by weighted stacking having found the first harmonic error, thereby remove after the above-mentioned principle of error percentage, the related content of record can be selected the weighted stacking mode that is fit to according to the present invention, just can realize the elimination of first harmonic error.The method of above-mentioned multiple acquisition weighting coefficient only is for the ease of enumerating of understanding, and is not the restriction fully to technical scheme.
In order to remove corresponding optics accurate adjustment from, eliminate or the inhibition nonlinearity erron, and be conducive to keep useful signal and select reasonable parameter, as preferred version, make the difference between the phase angle on the signal frequency composition that will be eliminated of 3 periodicity nonlinearity errons at least 3 road signals be not less than 60 degree.This is because we always can make the declinate between any two-phase not too little easily by regulating or arranging in practice.Theoretical and experiment all illustrates, are rational numerical with 60 ° of lower limits as this angle, this is beneficial to the signal to noise ratio (S/N ratio) after handling, can not make the useful signal of output be lower than the amplitude of single channel after the weighted stacking, simultaneously as long as attempt device 3 to 5 times on the fixing light path that can influence phase differential between 3 tunnel at random blindly, roughly just once chance meet this condition, thereby realize mechanically " exempting to adjust ", and saved corresponding adjuster, made adjusting or the work that arranges become simple and easy.Can judge whether to meet this condition according to the method for the starting phase angle of the aforementioned measurement first harmonic error of mentioning, thereby stop to adjust.Also can nonlinear certain harmonic components be transferred nothing, and then check the amplitude of useful signal by the similar aforementioned actual method (1) (2) of eliminating error percentage, if low excessively, just explanation dissatisfied " 60 degree condition " or similarly standard.Whether check is adjusted and is finished, and has eliminated error and can relatively wait method to judge by for example adopting more accurate surveying instrument to carry out the result.
This " minute adjustment " by electronics replaces the release precision optical machinery of " minute adjustment " of optics to regulate or exempts from the optics The method of fine adjustment, and cost is significantly reduced, and the accuracy requirement that optics is regulated can descend 2-3 more than the order of magnitude.And the precision that total system shows on the nonlinearity erron characteristic frequency also can be significantly improved.
Clearly, whether advantage and meaning that the ultimate principle of this method and itself exist and adopt the integrated optics mode, comprise the optical fiber mode, or bulk wave mode etc. is irrelevant.This method all is effectively for the periodic error in all laser heterodyne interferometry systems, as long as we can access the different signal of at least 3 road its interference component phase places.
The laser heterodyne interference signal is typical weak signal, particularly more requires signal pure in the exquisite system of this elimination nonlinearity erron, and the wave filter in the analog electrical signal is important link in the system.The useful signal of considering this system is single some frequency composition, when testee exists speed and acceleration, will have the rate of change of frequency displacement and frequency.The wave filter of simple inductance and capacitance type is longer for the response time of input signal phase place, has limited the movement velocity of object being measured under the requirement of precision.Phase locked loop filter then can address this problem preferably, it has very low phase noise and extraordinary transient state phase error and static phase error index, can accurately measure the immediate movement of object in the motion, even the immediate movement of object in the acceleration, the complete machine index can be promoted.Can carry out the phase-detection between each road signal and the reference signal after the phaselocked loop filtering.
Consider the symmetry requirement of at least 3 tunnel measuring-signal, the part of the filtering in each measuring-signal passage should be identical generally speaking.
Record the time that differs between the measuring-signal on every road and the reference signal particular phases (as the zero angle position of crossing that rises) and be converted into phase differential with timing counter, can adopt in the following method: the time that records measuring-signal or each complete cycle of reference signal on every road with timing counter, and the time that differs between the particular phases (as the zero angle position of crossing that rises or descend) by the above-mentioned every drive test amount signal that records and reference signal is divided by the time (or phase differential) in the whole cycle that records simultaneously, in order to obtain " instantaneous " phasing degree, in order to suppress multiple drift effectively, improve measuring accuracy.And in another case, because the cycle of reference signal is known, can directly try to achieve simply.
Timing counter is the oscillator work by carrying generally, and microwave counter works frequency can reach several 100GHz.Be the laser difference frequency of MHz level for difference frequency, it is real that angle of circumference is subdivided into 1000 parts.The working method of this timing counter is real-time serial, work period finishes in the cycle at a difference frequency, it asks the phase differential method than Fast Fourier Transform (FFT), even inner product asks the operand of phase differential method much smaller, hardly processor there is requirement, be just really to handle in real time, have very high speed, under the perfect situation of prime filtering, have very high precision.So it is a kind of succinctly and efficiently, accurately can measure high-speed moving object or even practical combination cheaply that phaselocked loop filtering adds the above-mentioned timing counter phase place method of inspection.
After phase-detection and be weighted before the stack, we can obtain each road information full amplitude, that obtain abundant filtering, comprise phase relation between each road signal and phase relation of interference component etc., this category information is useful in some cases, such as being conducive to determine weighting coefficient array etc.
Based on foregoing, the invention provides a kind of first harmonic or other frequency content that can eliminate or reduce the periodicity nonlinearity erron, improve measuring accuracy, the laser heterodyne interferometry method that the corresponding precision optics that omits is adjusted, namely eliminate the laser heterodyne interferometry method of nonlinearity erron based on phaselocked loop filtering and timing counter algorithm, this method is on the light path that exists the nonlinearity erron interference component, obtain at least 3 drive test amount signals and 1 tunnel reference signal by light splitting, and make at least 3 drive test amount signals wherein separately periodically nonlinearity erron in the angle of circumference scope of the phasing degree on the frequency content that will be eliminated a correspondence, have nothing in common with each other; 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 tunnel with reference to analog electrical signal; First filtering is carried out on each road of described at least 3 drive test amount analog electrical signals respectively, 1 the tunnel carry out second filtering with reference to analog electrical signal after, import the timer module respectively, utilize timer to record each road and 1 tunnel time interval with reference to particular phases between the analog electrical signal of at least 3 drive test amount analog electrical signals, and be converted at least 3 road phase differential; At least 3 road phase differential are converted into corresponding displacement, obtain at least 3 tunnel displacement measurement, contain nonlinearity erron in each road displacement measurement this moment; At least 3 tunnel displacement measurement that obtain are carried out the real number ranking operation, carry out additive operation again and can obtain final measurement; Described first filtering comprises employing phaselocked loop ripple device.
Above-mentioned each road and 1 tunnel mistiming with reference to particular phases between the analog electrical signal of utilizing timer to record at least 3 drive test amount analog electrical signals, and the step that is converted to phase differential comprises: utilize timer to record the time that differs between the particular phases of each road and 1 tunnel with reference to analog electrical signal of at least 3 drive test amount analog electrical signals, with each road or 1 tunnel the cycle with reference to analog electrical signal of this time divided by at least 3 drive test amount analog electrical signals, obtain phase differential; Described particular phases comprises: the phase place when rising or descending zero angle.
Above-mentioned first filtering also is included in and adds low-pass filter after the described phase locked loop filter and carry out filtering.
The phase differential of at least 3 periodicity nonlinearity errons in the above-mentioned at least 3 drive test amount signals is not less than 60 °.
Above-mentioned step by light splitting acquisition at least 3 drive test amount signals and 1 tunnel reference signal comprises: the A road light signal of output obtains A1, A2 respectively by at least 4 light-dividing devices successively ... An road light signal, wherein n 〉=4; The B road light signal that has frequency difference with the A road light signal of exporting obtains B1 road light signal by light-dividing device, and all the other light signals of B road obtain B2 by light-dividing device after reflecting by reflection unit successively ... Bn road light signal, wherein n 〉=4; A1 road light signal and B1 road light signal are interfered formation reference signal, A2 ... An road light signal and B2 ... the corresponding interference forms n-1 drive test amount signal to Bn road light signal respectively.
Because the principle of work of phase detector in the phaselocked loop may be subjected to the interference of input signal noise and other frequency contents, causes the phase detector output noise.Therefore, added the narrow band filter that is made of the inductance of one-level or two-stage or more multistage serial or parallel connection and resonant circuit that electric capacity is formed before phase detector, it is useful that simulating signal is carried out filtering.The effect of this wave filter is important, and it can not be remedied by any wave filter after the phaselocked loop.
The wave filter that can adopt the inductance capacitance resonant tank of one-level or two-stage or more plural parallel stage or series connection to constitute for the reference signal of simulation carries out filtering, to obtain purer composition.
Adding resistance or equivalent resistance adjustment quality factor are carried out filtering in resonant tank, in order to make quality factor adjustable and stable.In the wave filter loop that the inductance capacitance resonant tank of the in parallel of a relative high quality factor (Q value) or series connection constitutes, add resistance and (contain adjustable resistance, potentiometer, or method of equal value), make quality factor mainly be determined by lumped parameters such as resistors, rather than be distributed the parameter decision, obtain desirable, stable Q value.The Q value has a lot of physical significances, as the too high highest movement speed that also can influence under the accuracy requirement of Q value here.
Each basic resonant tank in the wave filter that constitutes for the inductance capacitance resonant tank of above-mentioned single-stage, two-stage or more multistage in parallel or series connection, and between the output terminal of its prime, and stability and the sufficient quality factor of employing weak coupling method to guarantee this resonant tank between the input end of back level, the method of these weak couplings realizes by one of following method at least, 1) capacitive coupling, 2) inductive coupling, 3) resistance coupling, 4) the winding mode is transformer coupled.
Another technical scheme of the present invention is: a kind of laser heterodyne interferometry device that adopts above-mentioned laser heterodyne interferometry method comprises: first light-dividing device obtains A1, A2 with the light signal light splitting of A road ... An road light signal, wherein n 〉=4; Second light-dividing device, the B road light signal light splitting that will have frequency difference with the A road light signal of output obtains B1 road light signal and all the other light signals, and described all the other light signals are obtained B2 by the second light-dividing device light splitting after the reflection unit reflection ... Bn road light signal, wherein n 〉=4; Interfere to form device, make A1 road light signal and B1 road light signal interfere the reference signal that forms, A2 ... An road light signal and B2 ... the corresponding interference forms n-1 drive test amount signal to Bn road light signal respectively; Signal detecting device is converted to 1 road reference electrical signal, n-1 drive test amount electric signal respectively with above-mentioned 1 tunnel reference signal, n-1 drive test amount signal; First filtration module carries out first filtering respectively to n-1 drive test amount analog electrical signal; Second filtration module carries out second filtering to 1 the tunnel with reference to analog electrical signal; The timer module is calculated each road and 1 tunnel time interval with reference to the analog electrical signal particular phases through the n-1 drive test amount analog electrical signal of filtering, and is converted to phase differential; The displacement computing module obtains n-1 road displacement measurement according to n-1 road phase difference calculating; The weighted stacking module is carried out real number ranking operation and additive operation with the n-1 road displacement measurement that obtains.
The present invention has omitted explanation and the statement of some prior aries, row as omitted the timing counter principle, adopt theorem, power-supply system wiring board distribution filtering electric capacity, be set discussion details such as amplifier, general foundation of system-gain and block diagram etc.
The invention has the beneficial effects as follows: the present invention is on common laser heterodyne interference system-based, creatively will measure the light path demultiplexing, carry out the process such as adjustment, signal processing, weighted stacking of electronics respectively, length with the electronics minute adjustment, light filling is learned the weak point of minute adjustment, the optics accurate adjustment that has omitted complicated or other non-electronics adjustment, the substitute is the adjustment and the signal processing method that adopt electronics and eliminate nonlinearity erron, reduced the complexity that optics is adjusted, reduce cost, improved efficient.Simultaneously, eliminate effectively or reduced periodicity interference component such as nonlinearity erron significantly and then improve measuring accuracy or reduce interference, the phase locked loop filter of while particular design etc. improves the measuring accuracy of total system, antijamming capability is strong, stable, be conducive to large-scale production, production cost is low.
Description of drawings
Fig. 1 is the opticator principle schematic that the present invention is based on the laser heterodyne interferometry method of phaselocked loop filtering and timing counter algorithm elimination nonlinearity erron.
Fig. 2 is the phase locked loop filter circuit diagram among the present invention.
Fig. 3 is the laser heterodyne interferometry ratio juris synoptic diagram that the present invention is based on phaselocked loop filtering and timing counter algorithm elimination nonlinearity erron.
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further details.
The system that realization the present invention is based on the laser heterodyne interferometry method of phaselocked loop filtering and timing counter algorithm elimination nonlinearity erron can be divided into opticator and electronics signal processing afterwards.Wherein the principle of opticator as shown in Figure 1, the present invention has increased the part in the frame of broken lines among the figure on the basis of an original opticator.
At first, set forth the opticator principle of work of original difference interference measuring system: send laser by laser instrument 101, incide acousto-optical device 103 through first's catoptron 102, shone second portion catoptron 114 behind the shift frequency, transmitted light is reflected by measuring prism 115, incide third part catoptron 111, reflecting part and another bundle light are interfered through first polaroid 131.The light (it provides reference ray for each road interference portion of back) that is reflected by first's catoptron 102 is through first catoptron 125, again through after the 4th partially reflecting mirror 124, the 5th partially reflecting mirror 123, the 6th partially reflecting mirror 122, second catoptron 121, together incide first polaroid 131 with the reflected light of third part catoptron 111, the interference light of its outgoing partly converts the difference frequency of two light to electric signal by first photodetector 141.This electric signal has wherein included the displacement information that obtains as measuring-signal above measuring prism 115, also contain the nonlinearity erron composition.
The light that the light that is reflected by second portion catoptron 114 and the 4th partially reflecting mirror 124 reflect converges, incide second polaroid 134, the interference light of its outgoing partly converts the difference frequency of two light to electric signal by second photodetector 144, and this electric signal is exactly reference signal.
Above-mentioned laser instrument 101, first's catoptron 102 and acousto-optical device 103 have constituted the double-frequency laser generator that frequency has elementary errors, also can be replaced by other scheme.
The present invention has increased the part in the frame of broken lines among Fig. 1, and it mainly comprises two new measuring light arm/light paths and corresponding circuit part.
With original first smooth arm that is constituted by the third part catoptron 111 among the figure, first polaroid 131, first photodetector 141 etc., have three light arms, or be called three and measure light paths, and obtaining measuring-signal output 1, measuring-signal output 2 and measuring-signal output 3 thus, these two new measuring light arms are identical with the first smooth arm structurally.Add reference signal, four road signals output altogether, this four road signal has just constituted the output of opticator, is transferred to the electronics signal processing of back, as described in Figure 3.
In the electronics signal processing, its signal passes through phase locked loop filter shown in Figure 2 (the filtering part for first passage to the four-way is respectively 211 among Fig. 3,221,231,241) respectively; Low-pass filtering part (respectively be in figure 212,222,232,242 for first passage to the four-way); Again by timing counter part (for first to third channel be 213 among the figure, 223,233) each road signal is obtained phase angle; Then three drive test amount data respectively the displacement calculating section (for first to third channel be respectively 214 among the figure, 224,234) be converted into displacement and carry out cycle count, finish corresponding displacement measurement, obtain the measurement result on each road.Certainly the nonlinearity erron that contains destruction system accuracy separately among the result equally.Again three tunnel measurement result is delivered to weighted stacking arithmetic section 301 respectively and carry out the real number ranking operation, do additive operation then and just can draw last measurement result, the fundamental frequency of its nonlinearity erron has been eliminated or has significantly suppressed.
Claims (10)
1. based on the laser heterodyne interferometry method of phaselocked loop filtering and timer elimination nonlinearity erron, it is characterized in that: this method comprises:
On the light path that exists the nonlinearity erron interference component, obtain at least 3 drive test amount signals and 1 tunnel reference signal by light splitting, and make at least 3 drive test amount signals wherein separately periodically nonlinearity erron in the angle of circumference scope of the phasing degree on the frequency content that will be eliminated a correspondence, have nothing in common with each other;
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 tunnel with reference to analog electrical signal.
First filtering is carried out on each road of described at least 3 drive test amount analog electrical signals respectively, 1 the tunnel carry out second filtering with reference to analog electrical signal after, import the timer module respectively, utilize timer to record each road and 1 tunnel time interval with reference to particular phases between the analog electrical signal of at least 3 drive test amount analog electrical signals, and be converted at least 3 road phase differential.
At least 3 road phase differential are converted into corresponding displacement, obtain at least 3 tunnel displacement measurement, contain nonlinearity erron in each road displacement measurement this moment;
At least 3 tunnel displacement measurement that obtain are carried out the real number ranking operation, carry out additive operation again and can obtain final measurement;
Described first filtering comprises employing phaselocked loop ripple device.
2. the laser heterodyne interferometry method of eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 1, it is characterized in that: described each road and 1 tunnel mistiming with reference to particular phases between the analog electrical signal of utilizing timer to record at least 3 drive test amount analog electrical signals, and the step that is converted to phase differential comprises: utilize timer to record the time that differs between the particular phases of each road and 1 tunnel with reference to analog electrical signal of at least 3 drive test amount analog electrical signals, with each road or 1 tunnel the cycle with reference to analog electrical signal of this time divided by at least 3 drive test amount analog electrical signals, obtain phase differential; Described particular phases comprises: the phase place when rising or descending zero angle.
3. as claimed in claim 1ly eliminate the laser heterodyne interferometry method of nonlinearity erron based on phaselocked loop filtering and timer, it is characterized in that: described first filtering also is included in and adds the narrow band filter that the resonant tank be made up of one or more levels the inductance capacitance of serial or parallel connection constitutes before the described phase locked loop filter and carry out filtering.
4. as claimed in claim 1ly eliminate the laser heterodyne interferometry method of nonlinearity erron based on phaselocked loop filtering and timer, it is characterized in that: described first filtering also is included in and adds low-pass filter after the described phase locked loop filter and carry out filtering.
5. the laser heterodyne interferometry method based on phaselocked loop filtering and timer elimination nonlinearity erron as claimed in claim 3 is characterized in that: adopt the weak coupling mode to be coupled between described resonant tank and its prime output terminal and the back level input end.
6. the laser heterodyne interferometry method based on phaselocked loop filtering and timer elimination nonlinearity erron as claimed in claim 3 is characterized in that: add resistance or equivalent resistance adjustment quality factor in the described resonant tank, so that quality factor are adjustable and stable.
7. as claimed in claim 5ly eliminate the laser heterodyne interferometry method of nonlinearity erron based on phaselocked loop filtering and timer, it is characterized in that: described weak coupling method is capacitive couplings or inductive coupling method or resistance coupled method or the transformer coupled method of winding type.
8. as claimed in claim 1ly eliminate the laser heterodyne interferometry method of nonlinearity erron based on phaselocked loop filtering and timer, it is characterized in that: in the described at least 3 drive test amount signals at least 3 periodically the phase differential of nonlinearity errons be not less than 60 °.
9. the laser heterodyne interferometry method of eliminating nonlinearity erron based on phaselocked loop filtering and timer as claimed in claim 1, it is characterized in that: the step that obtains at least 3 drive test amount signals and 1 tunnel reference signal by light splitting comprises: the A road light signal of output obtains A1, A2 respectively by at least 4 light-dividing devices successively ... An road light signal, wherein n 〉=4; The B road light signal that has frequency difference with the A road light signal of exporting obtains B1 road light signal by light-dividing device, and all the other light signals of B road obtain B2 by light-dividing device after reflecting by reflection unit successively ... Bn road light signal, wherein n 〉=4; A1 road light signal and B1 road light signal are interfered formation reference signal, A2 ... An road light signal and B2 ... the corresponding interference forms n-1 drive test amount signal to Bn road light signal respectively.
10. the laser heterodyne interferometry device of an employing such as the described laser heterodyne interferometry method of claim 1-9 is characterized in that: comprising:
First light-dividing device obtains A1, A2 with the light signal light splitting of A road ... An road light signal, wherein n 〉=4;
Second light-dividing device, the B road light signal light splitting that will have frequency difference with the A road light signal of output obtains B1 road light signal and all the other light signals, and described all the other light signals are obtained B2 by the second light-dividing device light splitting after the reflection unit reflection ... Bn road light signal, wherein n 〉=4;
Interfere to form device, make A1 road light signal and B1 road light signal interfere the reference signal that forms, A2 ... An road light signal and B2 ... the corresponding interference forms n-1 drive test amount signal to Bn road light signal respectively;
Signal detecting device is converted to 1 road reference electrical signal, n-1 drive test amount electric signal respectively with above-mentioned 1 tunnel reference signal, n-1 drive test amount signal;
First filtration module carries out first filtering respectively to n-1 drive test amount analog electrical signal;
Second filtration module carries out second filtering to 1 the tunnel with reference to analog electrical signal;
The timer module is calculated each road and 1 tunnel time interval with reference to the analog electrical signal particular phases through the n-1 drive test amount analog electrical signal of filtering, and is converted to phase differential;
The displacement computing module obtains n-1 road displacement measurement according to n-1 road phase difference calculating;
The weighted stacking module is carried out real number ranking operation and additive operation with the n-1 road displacement measurement that obtains.
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