CN103322906B - The optical heterodyne interference method of non-linear error is eliminated based on capacitor charging chronometric method - Google Patents
The optical heterodyne interference method of non-linear error is eliminated based on capacitor charging chronometric method Download PDFInfo
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Abstract
The optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method belongs to laser heterodyne interferometry field, the method is in the light path that there is non-linear error interference composition, manage to obtain at least 3 road signals and the non-linear error interference composition of periodicity respective in making wherein at least 3 tunnels, phasing degree on the signal frequency composition to be eliminated is within the scope of a corresponding inscribed angle or gets rid of within the scope of a corresponding inscribed angle after integral multiple inscribed angle different, and adopt wave filter that signal is carried out filtering in analog electrical signalling channel, and adopt capacitor charging chronometric method to obtain the phase differential between each road measurement signal and reference signal, displacement calculating is carried out after this by analog to digital conversion, weighted sum superposition, to eliminate or to suppress these interference components. the present invention can eliminate the particular harmonic composition of non-linear error or interference, and its adjustment process is very easy to, it is to increase system performance, reduces cost.
Description
Technical field
The invention belongs to laser heterodyne interferometry (HeterodyneInterferometry) fields of measurement, it is specifically related to a kind of laser heterodyne interferometry measuring method eliminating non-linear error based on capacitor charging chronometric method exempting from accurate adjustment.
Background technology
Laser heterodyne interference system can be used for the physical quantity such as Displacement Measurement, length, is one of best nano measurement method. This system is in the frequency or phase change that tested displacement amount is converted to heterodyne signal, again by this kind of measure of the change out, owing to the frequency ratio optical frequency of heterodyne signal is much low, photoelectricity signal easily processes, can through electronic fine-grained and reach higher Measurement Resolution, resolving power can reach skin rice (pm) or better.
But in optical heterodyne interference method, generally there is non-linear (nonlinearity) problem, these factors can be the main source of error of displacement measurement, making its precision generally only have nano level to tens nanometer, its reason is that the light beam that frequency is different can not well be separated. These periodic non-linear error problems are the obstacles of this art development always.
Domestic and international methods constantly invented some and improve for many years, but also there are some restriction or problems more, such as Badami and Pattersom use speed indicator and spectrometer are directly measured non-linear error percentage in a mobile system and are compensated; The method carrying out ellipse fitting after phase place 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 a large amount of fluctuation signal periods and relative a large amount of computing, the real-time that impact is measured. It it is a kind of new method that discloses in the Chinese invention patent of CN101660924 at publication number, the method can address this problem effectively, if but wish to obtain very accurate result, in addition it is also necessary to point-device optical adjustment, this kind of precise optical regulates usually relatively difficult.
Summary of the invention
In order to solve, system complex that existing laser heterodyne interference system exists, computing amount are big, the coarse technical problem of poor real, result, the present invention provides a kind of optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method, the particular harmonic composition of non-linear error or interference can be eliminated, and remove the precision optics setting device required for the non-linear error of elimination and minute adjustment process from, this kind of adjustment is made to become very easy, significantly improve system performance simultaneously, reduce costs.
The exchange signal that the photodetector output terminal of laser heterodyne interference systematic survey light arm obtains is the electrical signal taking different frequency optical frequency difference as frequency, and its additional phase differential becomes accurate proportionlity with tested displacement. But wherein contain so-called non-linear error, mainly it is distributed on the first harmonic (generally also can be called fundamental frequency according to Fourier series character, be a kind of spatial frequency) of Fourier's frequency spectrum. The method of the present invention can eliminate the fundamental frequency composition of non-linear error; In fact arbitrary a certain frequency is all effective by the method for the present invention, and without the need to optical system being done special minute adjustment.
Laser heterodyne interference system also exist in the signal light path of non-linear error interference composition, obtain at least 3 road signals (passage), by obtaining these signals by carry the method arranging at least 3 interference light photodetection parts on the light arm being detected signal, and make wherein have at least the phase angle of non-linear error first harmonic (or other frequency composition) contained separately in 3 tunnels different in a corresponding circumference, so just obtain sufficient information, after enable pass, the weighted sum superposition in face etc. process and eliminate the fundamental frequency in non-linear error (or any one frequency) composition. the method realizing the phase angle of first harmonic (or other frequency composition) different in a corresponding circumference is a lot, the phase angle of corresponding first harmonic such as can be changed by adjustment light path, by the error measurement method of disclosed first harmonic in prior art, it is possible to be easy to obtain amplitude and the prima facies parallactic angle of first harmonic. generally, the phase angle of several roads signal error of different light paths is usually inequal, if the situation having phase angle equal, it is possible to would know by prior art is measured the method for phase angle, and make them inequal by adjustment light path. furtherly, the optical system that generally we set up at random, do not have non-linear error phase angle in any 2 tunnels completely identical in a corresponding circumference, if but after completing the adjustment of optical system, in 3 tunnels, the phase angle of non-linear error first harmonic (or other frequency composition to be eliminated) is more or less the same, the amplitude of the useful signal after may affecting weighted stacking, thus affect the signal to noise ratio of output signal, at this moment we can roughly adjust the difference of phase angle relative to (the frequency composition to be eliminated of non-linear error) signal phase angle corresponding in other passages of the frequency composition to be eliminated in 1-2 road wherein, it is made to increase to some extent fully till (namely enough). the method having now the non-linear error first harmonic of a lot of detections (or other frequency composition to be eliminated) phase place and amplitude, such as " measuring method of the non-linear error of laser heterodyne interference " " Beijing University of Technology's journal " the 6th phase in 2010 of Chen Hongfang etc., " a kind of novel measuring method of the non-linear error of laser heterodyne interference " of Zhong Zhi etc., photoelectron laser, 2005, etc. the method of adjustment phase angle can by regulating the path difference between two light participating in interference to realize.
Based on the periodicity of harmonic function, it is of course possible to as usually, some the integral multiple inscribed angle comprised are got rid of disregard (no longer doing similar prompting below) in above-mentioned phase differential.
Adopt and carry out subsequent disposal in the following method: 3 road signals are carried out phase compare with reference signal, until solving 3 displacement amounts by situation respectively that first assume only 3 road signals. At this moment the phase place of the non-linear error in each passage is different.
By proof below it will be seen that after having the weighting coefficient array being not zero can make superposition the fundamental frequency of non-linear error or the amplitude of other frequency compositions be zero, and retain useful signal.
In above-mentioned 3 the displacement amounts solved, the displacement measurement on the i-th tunnel can represent and is:
Wherein, equal sign right-hand member Section 1 �� is real physical displacement, and Section 2 is a composition of non-linear error, certainly illustrates that content of the present invention does not lose generality with first harmonic here; A is coefficient, expresses non-linear error amplitude, is generally an a small amount of, but does not make rough handling in derivation afterwards.Being the initial phase angle of non-linearity error, �� is optical wavelength. Here the wave number in non-linear error termWhat represent is first harmonic composition, and by measuring the situation of prism individual reflection measuring beam (turning back once). When second harmonic, this can become
By 3 result weighted stacking, it is normalized into:
One group of new ki is just in order to formal clean and tidy, it is possible to being seen as is new weighting coefficient. Our object finds one group of ki to make: X=x.
By above-mentioned condition, we can obtain system of linear equations below:
The factor arrays of variable ki is 3 rank square formations of full rank, and the system of equations about ki has untrivial solution. Namely, it is possible to make
To sum up, it has been demonstrated that after such weighted stacking, the first harmonic composition of non-linear error is eliminated.
IfIn have any 2 difference 180 ��, problem can be made to become simple and favourable, this kind of situation is it is generally required to the optical adjustment of precision just can obtain, and only need the non-linear error percentage of 2 road signals that non-linear component differs 180 �� just enough specific frequency of elimination, than being illustrated in more detail in this that patent of invention mentioned in the introduction.
To this, we solve the non-linear error problem in laser heterodyne interference in 3 dimensional linear spaces of electronics.
When having more than 3 road signals (passage), we at least can retain the different signal of 3 road phase angles in advance, again by any road Signal averaging in 3 tunnels of all the other several roads signals and reservation, and 3 tunnels that the phase angle difference being melted in certain frequency of non-linear error is respectively not zero. So just dissolve the problem solved above becoming, i.e. the situation of 3 passages, and it is proven. Certainly also can not adopt the treating processes being first simplified to 3 tunnels recited above, but together complete in weighted overlap-add procedure.
Obtain correct weighting coefficient array by following method in practice and eliminate error percentage: (1) is by 2 tunnel linear superposition wherein, because in 2 dimension spaces of this certain non-linear subharmonic composition, this two paths of signals has formed one group of substrate in space, so any one vector can be generated by adjustment superposition coefficient, we allow the vector generated be just that direction is contrary with the 3rd signal (vector) on certain non-linear subharmonic composition, then by signal and the 3rd signal (vector) linear superposition of generation, adjustment weighting coefficient just can make certain non-linear subharmonic composition be kept to zero completely mutually, and useful signal can still be retained. (2) electricity consumption tune method can repeating the weighting coefficient on alternate sweep at least 2 tunnel, measuring non-linear error magnitude in the output after superposition so that it is constantly reduce, until being zero simultaneously. (3) adopt the most basic method, measuring phase angle described in every road and after amplitude, directly calculate by analytic method, also can adopt the thinking in (1) here, but it is not decompose adjustment, but decoupled method, no longer carefully separate here. that is, finding that first harmonic error can be cancelled each other by weighted stacking, thus after removing the above-mentioned principle of error percentage, the weighted stacking mode being applicable to can be selected according to the associated viscera of the present invention's record, just can realize the elimination of first harmonic error. the method of above-mentioned multiple acquisition weighting coefficient is only used to be convenient to enumerating of understanding, is not the restriction completely to technical scheme.
In order to remove corresponding optics accurate adjustment from, eliminate or suppress non-linear error, 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 non-linear errors of periodicity at least 3 road signals is made to be not less than 60 degree. This is because we always easily by regulating or arrange, can make the poor angle between any two-phase not too little in practice. Theoretical and experiment all illustrates, it is a rational numerical value using 60 �� of lower limits as this angle, signal to noise ratio after process is beneficial to by this, the amplitude of useful signal lower than single channel of output can not be made after weighted stacking, as long as blindly attempt the random fixing device that can affect in the light path of phase differential between 3 tunnels 3 to 5 times simultaneously, roughly just once chance meets this condition, thus realize " adjustment-free " mechanically, and eliminate corresponding accurate adjustment device so that regulate or work is set and become simple and easily. Can judge whether to meet this condition according to the method for the prima facies parallactic angle of the aforementioned measurement first harmonic error mentioned, thus stop adjustment. Can also be eliminated by similar aforementioned reality method (1) (2) of error percentage, certain non-linear subharmonic composition be adjusted nothing, and then checks the amplitude of useful signal, if too low, just illustrate and do not have to meet " 60 degree of conditions " or similar standard. It is complete whether inspection adjusts, and having eliminated error can judge by such as adopting more accurate surveying instrument to carry out the methods such as results contrast.
This kind is replaced the release precision optical machinery of " minute adjustment " of optics regulate or exempt from the method for optics accurate adjustment by " minute adjustment " of electronics, makes cost much slower, more than 2-3 the order of magnitude that the accuracy requirement in optical adjustment can be declined. And the precision that whole system shows on the specific frequency of non-linear error is also significantly improved.
It is apparent that the ultimate principle of the method and the advantage itself existed and meaning, and whether adopt integrated optics mode, comprise optical fiber mode, or bulk wave mode etc. is unrelated. The method is all effective for the periodic error in all laser heterodyne interferometry systems, as long as we can obtain the different signal of its interference component phase place of at least 3 roads.
The method adopting the electrical condenser to known capacity to charge measures the phase differential between measurement signal and reference signal. By measurement signal and reference signal Zhong mono-tunnel (such as reference signal) particular phases (as rise zero passage time Angle Position), the moment of its correspondence was called for the first moment, it is possible to generate transition along triggering signal (first triggering signal) at this; The moment of the correspondence of the particular phases of another road (such as measurement signal) signal was called for the 2nd moment similarly, generate another transition along triggering signal (the 2nd triggering signal), then have corresponding to the first paragraph time between first triggering signal and two moment of the 2nd triggering signal. Being charged by the electrical condenser of known capacity by a current source (can be constant current source) within the first paragraph time, above-mentioned first triggering signal makes current source start electrical condenser charging, and above-mentioned 2nd triggering signal stops current source to the charging of electrical condenser. Determine the described first paragraph time by the magnitude of voltage at the end of charging, and determine described phase differential with this.
The first paragraph time is exactly the relative phase differences of two signals in inscribed angle compared with the signal period, obtains its radian numerical value, and the cycle of signal or frequency are known after being multiplied by 2 ��. Available same method or same circuit measuring go out the timed interval from the 2nd moment to the first moment (being called the 2nd period) and are added with the above-mentioned first paragraph time and obtain a complete signal period, it is possible to the complete cycle of same method or the whole signal of the direct one-shot measurement of same circuit. Namely the first paragraph time is obtained compared with the complete signal period phase differential (per-cent) of two signals in inscribed angle, major part drift equal error can be balanced out like this, it is to increase precision. After data output, the voltage on electrical condenser is reset and wait and measuring next time.
The rising of duration of charging and electric capacity both end voltage can be made proportional capacitor charging by constant current source, if but do not adopt point-device constant current source, tentatively it is called current source, then measuring result is corrected, point-device measuring result can be obtained equally, also can improve total cost performance. If above-mentioned two moment put upside down, or first paragraph time and the 2nd period put upside down, the essence of this measuring method can not be changed, same result can be obtained.
The feature of this capacitor charging chronometric method almost just obtains the accurate result corresponding to this cycle at the end of each signal period in real time by the method for simulation completely, there is no the problem of digital operation amount, circuit self very simple and reliable again, and have stronger immunity from interference, the such as ability of anti-bombardment interference. Another actual cause adopting this kind of processing mode is that various analog to digital converter obtains good long-run development up to now, and for applying analog to digital converter in systems in which, we can ignore considering of cost, reliability and performance aspect. It is divided into line position and moves calculating, weighted sum superposition etc. by entering digital section after analog to digital conversion and relatively simply process.
In a word, determine described (between every road measurement signal and reference signal) phase differential, as long as we are by the first paragraph time between the particular phases of reference signal and the particular phases of measurement signal, by a current source, the electrical condenser of a known capacity is charged, determine the described first paragraph time by voltage rise value, and determine described phase differential with this; Complete cycle or the complete cycle residue part except the above-mentioned first paragraph time is measured in available same method or same set of circuit timesharing; Namely the above-mentioned first paragraph time is obtained compared with the complete signal period phase differential (per-cent) of two signals in inscribed angle. It is divided into line position and moves calculating, weighted sum superposition etc. by entering digital section after analog to digital conversion and relatively simply process.
In fact laser heterodyne interference signal is typical weak signal, particularly eliminates at this kind in the exquisite system of non-linear error and more requires that signal is pure, and the wave filter in analog electrical signal is the extremely important link of in machine system. The useful signal considering this system is single some composition frequently, when there is speed and acceleration when testee, will there is the velocity of variation of frequency displacement and frequency. The wave filter of simple inductance and capacitance type is longer for the time of response of input signal phase place, limits 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 place noise and extraordinary transient phase error and static phase error index, be conducive to accurately measuring the instantaneous displacement of object in motion, the even instantaneous displacement of object in acceleration, can promote complete machine index. The phase-detection between each road signal and reference signal can be carried out after phase-locked filtering. Considering the symmetry requirement of the measurement signal at least 3 tunnels, generally the filtering part in each measurement signal passage should be completely identical.
After phaselocked loop filtering and phase measurement and before weighted stacking, sufficient each road information can be obtained, comprising the phase relationship etc. of the phase relationship between the signal of each road and interference component, this category information is useful in some cases, is such as conducive to determining weighting coefficient array etc.
Based on foregoing, the present invention provides a kind of first harmonic or other frequency composition that can eliminate or reduce periodically non-linear error, improve measuring accuracy, exempt from the optical heterodyne interference method of corresponding precision optics adjustment, namely the optical heterodyne interference method of non-linear error is eliminated based on capacitor charging chronometric method, the method is: in the light path that there is non-linear error interference composition, at least 3 road measurement signals and 1 tunnel reference signal is obtained by light splitting, and make the phasing degree of the non-linear error of respective periodicity of wherein at least 3 road measurement signals on the frequency composition to be eliminated different within the scope of a corresponding inscribed angle, at least 3 road measurement signals and 1 tunnel reference signal are separately converted to corresponding at least 3 tunnel measure analog electrical signal and 1 tunnel reference analog electrical signal, each road of described at least 3 tunnel measure analog electrical signal is carried out the first filtering process respectively, 1 tunnel is carried out the 2nd filtering process with reference to analog electrical signal, phase detecting module determines the very first time interval between the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and the particular phases of filtered 1 tunnel reference analog electrical signal based on capacitor charging method, and thus determines phase differential, phase differential is converted into displacement, obtains at least 3 tunnel displacement measurement, now containing non-linear error in the displacement measurement of each road, the at least 3 tunnel displacement measurement obtained are carried out real number ranking operation, then carries out additive operation and can obtain final measuring result, described first filtering process comprises employing phase locked loop filter.
Above-mentioned phase detecting module determines that the step in the timed interval between the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and the particular phases of 1 tunnel reference analog electrical signal comprises: record the first moment during each road arrival particular phases of filtered at least 3 tunnel measure analog electrical signal, correspondingly, the 2nd moment when filtered 1 tunnel arrives particular phases with reference to analog electrical signal is recorded; Or record the first moment when filtered 1 tunnel arrives particular phases with reference to analog electrical signal, correspondingly, record the 2nd moment during each road arrival particular phases of filtered at least 3 tunnel measure analog electrical signal, above-mentioned first moment is the described timed interval to the time difference in the 2nd moment, within the described timed interval, by a current source, the electrical condenser of a known capacity is charged, determine described very first time interval by voltage rise value.
Above-mentioned particular phases comprises the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and filtered 1 tunnel with reference to phase place during zero passage in analog electrical signal process of rising or falling.
Above-mentioned determine that the step of phase differential comprises: the described timed interval divided by each road of filtered at least 3 tunnel measure analog electrical signal or filtered 1 tunnel with reference to the analog electrical signal period.
The method of calculation in above-mentioned cycle comprise: record described 2nd moment, and the first moment again arrived, and the time difference in the 2nd moment to the first moment again arrived is described 2nd timed interval; Very first time interval and the 2nd timed interval and be the described cycle.
The phase differential of the non-linear error of at least 3 periodicity in above-mentioned at least 3 road measurement signals is not less than 60 ��.
The step obtaining at least 3 road measurement signals and 1 tunnel reference signal above by light splitting comprises: the A road optical signal of output obtains A1, A2 respectively by least 4 light-dividing devices successively ... An road optical signal, wherein n >=4; The B road optical signal with the A road optical signal exported with frequency difference obtains B1 road optical signal by light-dividing device, and all the other optical signals of B road obtain B2 by light-dividing device after being reflected by reflection unit successively ... 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 ... the corresponding interference forms n-1 road measurement signal to Bn road optical signal respectively.
Due to the principle of work of phase sensitive rectifier in phaselocked loop, it is possible to the interference of input signal noise and other frequency compositions can be subject to, phase sensitive rectifier is caused to export noise. Therefore, adding the narrow band filter that the tank circuit being made up of the inductance of the series connection of one or two or more multi-level or parallel connection and electric capacity is formed before phase sensitive rectifier, simulating signal is carried out filtering is useful. The effect of this wave filter is important, and it can not be made up by any wave filter after phaselocked loop.
Resonance loop adds resistance or equivalent resistance adjustment quality factor carry out filtering, to make quality factor adjustable and stable. The wave filter loop that the parallel connection of a relative high quality factor (Q value) or the inductance capacitance resonance loop of series connection are formed adds resistance (containing adjustable resistance, potentiometer, or the method for equivalence), quality factor are mainly determined by concentrated parameters such as resistors, instead of it is distributed parameter decision, obtain Q value desired, stable. Q value has a lot of physical significances, such as the too high highest movement speed that also can affect under accuracy requirement of Q value here.
For each the basic resonance loop in the wave filter that the parallel connection of above-mentioned single-stage, two-stage or more level or the inductance capacitance resonance loop of series connection are formed, and between the output terminal of its prime, and between the input terminus of rear class, adopt weak coupling method to ensure this resonance loop and have certain quality factor and to stabilize it, the method of these weak couplings is at least realized by one of following method, 1) condenser coupling, 2) jigger coupling, 3) resistively couple, 4) winding method is transformer coupled.
Another program of the present invention is: a kind of laser heterodyne interferometry device realizing above-mentioned optical heterodyne interference method comprises: the first light-dividing device, and the optical signal light splitting of A road is obtained A1, A2 ... An road optical signal, wherein n >=4; 2nd 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 2nd light-dividing device light splitting after reflection unit reflects ... 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 ... the corresponding interference forms n-1 road measurement signal to Bn road optical signal respectively; Signal detecting device, is converted to 1 tunnel with reference to analog electrical signal, n-1 road measure analog electrical signal respectively by above-mentioned 1 tunnel reference signal, n-1 road measurement signal; First filtering module, carries out the first filtering process respectively to n-1 road measure analog electrical signal; 2nd filtering module, carries out the 2nd filtering process to 1 tunnel with reference to analog electrical signal; Phase detecting module, it is determined that the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and 1 tunnel are with reference to the very first time interval between the particular phases of analog electrical signal, and thus determine phase differential; Analog to digital conversion module, changes into numerary signal by described phase differential; Displacement calculates module, has changed into the phase differential of numerary signal according to n-1 road, has calculated n-1 road displacement measurement; Weighted stacking 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 omit the details such as the flow process to weighting part, sampling theorem, the wiring board distribution filtering electric capacity of power-supply system, the amplifier set by system-gain, the discussion of general basic component and block diagram etc.
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 stacking respectively, with the length of electronics minute adjustment, mend the short of optical precision adjustment, complicated optics accurate adjustment or other non-electronic adjustment are exempted from, the substitute is and adopt the adjustment of electronics and signal processing method to eliminate non-linear error, reduce the complexity of pH effect, reduce cost, it is to increase efficiency. Simultaneously, effectively eliminate or reduce significantly non-linear error quasi-periodic interference component and then improve measuring accuracy or reduce interference, simultaneously the capacitor charging phase difference detection method of particular design and phase locked loop filter etc. make whole the measuring precision height, speed is fast, immunity from interference is strong, stablize, being conducive to 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 non-linear error based on capacitor charging chronometric method.
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 non-linear error based on capacitor charging chronometric method and phaselocked loop filtering.
Embodiment:
Below in conjunction with accompanying drawing, the present invention is described in further details.
Realize the present invention based on capacitor charging phase-detection, phaselocked loop filtering and in 3 dimensional linear spaces the system of optical heterodyne interference method eliminating non-linear error of weighted stacking can be divided into opticator and electronics signal processing. Wherein the principle of opticator is as shown in Figure 1, and the present invention, on the basis of an original opticator, adds the part in broken box in figure. First the opticator principle of work of original heterodyne interferometry system is set forth: send laser by laser apparatus 101, acousto-optical device 103 is incided through first part's speculum 102, moved after frequently and shone second section speculum 114, by measuring, prism 115 reflects transmitted light, inciding Part III speculum 111, reflecting part and another bundle light are interfered through the first polaroid 131. The light (it is for each road interference portion offer below is with reference to light) reflected by first part's speculum 102 is through the first speculum 125, again after Part IV speculum 124, Part V speculum 123, Part VI speculum 122, two-mirror 121, together inciding the first polaroid 131 with the reflected light of Part III speculum 111, the difference frequency fractional conversion of two light is become electrical signal by the first photodetector 141 by the interference light of its outgoing. This electrical signal, as measurement signal, has wherein included from measuring the displacement information obtained above prism 115, also containing non-linear error percentage.
The light that the light reflected by second section speculum 114 and Part IV speculum 124 reflect converges, incide the 2nd polaroid 134, the difference frequency fractional conversion of two light is become electrical signal by the 2nd photodetector 144 by the interference light of its outgoing, and this electrical signal is exactly reference signal.
Above-mentioned laser apparatus 101, first part's speculum 102 and acousto-optical device 103 constitute the double-frequency laser producer that frequency has elementary errors, it is also possible to replace by other scheme.
Invention increases the part in broken box in Fig. 1, it mainly comprises two new measurement light arm/light paths and corresponding circuit part. Together with original the first smooth arm being made up of Part III speculum 111, first polaroid 131, first photodetector 141 etc. in figure, have three light arms, or it is called three optical paths, and thus obtain measurement signal output 1, measurement signal output 2 and measurement signal and export 3, structurally smooth arm is completely identical to these two new measurement light arms with first. Adding reference signal, four road signals export altogether, and this four roads signal just constitutes the output of opticator, is transferred to electronics signal processing below, as described in Figure 3.
In electronics signal processing, its signal is respectively through the phase locked loop filter (be respectively in Fig. 3 211,221,231,241 for first channel to the filtering part of four-way) shown in Fig. 2; Phase-detection by foregoing capacitor charging chronometric method realize (for the 1st, 2,3 passages be respectively 212 in figure, 222,232), then by analog to digital conversion part (for the 1st, 2,3 passages be 213 in figure, 223,233) 3 road phase signals are quantized into numerary signal; Then three tunnel take off data respectively displacement calculating section (for the 1st, 2,3 passages be 214 in figure, 224,234 respectively) carry out the cycle counting of displacement calculating and phase differential, complete corresponding displacement measurement, obtain the measuring result on each road; The same non-linear error containing respective destruction system precision in certain result. The measuring result on Zai Jiang tri-tunnel is delivered to weighted stacking computing part 301 respectively and is carried out real number ranking operation, then does additive operation and just can draw last measuring result, and the fundamental frequency of its non-linear error has been eliminated or has significantly suppressed.
Claims (12)
1. the optical heterodyne interference method of non-linear error is eliminated based on capacitor charging chronometric method, it is characterised in that: the method comprises:
In the light path that there is non-linear error interference composition, obtained at least 3 road measurement signals and 1 tunnel reference signal by light splitting, and make the phasing degree of the non-linear error of respective periodicity of wherein at least 3 road measurement signals on the frequency composition to be eliminated different within the scope of a corresponding inscribed angle;
At least 3 road measurement signals and 1 tunnel reference signal are separately converted to corresponding at least 3 tunnel measure analog electrical signal and 1 tunnel reference analog electrical signal;
Each road of described at least 3 tunnel measure analog electrical signal is carried out the first filtering process respectively; 1 tunnel is carried out the 2nd filtering process with reference to analog electrical signal;
Phase detecting module determines the very first time interval between the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and the particular phases of filtered 1 tunnel reference analog electrical signal based on capacitor charging method, and thus determines phase differential;
Phase differential is converted into displacement, obtains at least 3 tunnel displacement measurement, now containing non-linear error 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 measuring result;
Described first filtering process comprises employing phase locked loop filter.
2. the optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method as claimed in claim 1, it is characterized in that: described phase detecting module determines that the step at the very first time interval between the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and the particular phases of 1 tunnel reference analog electrical signal comprises: record the first moment during each road arrival particular phases of filtered at least 3 tunnel measure analog electrical signal, correspondingly, the 2nd moment when filtered 1 tunnel arrives particular phases with reference to analog electrical signal is recorded; Or record the first moment when filtered 1 tunnel arrives particular phases with reference to analog electrical signal, correspondingly, record the 2nd moment during each road arrival particular phases of filtered at least 3 tunnel measure analog electrical signal, above-mentioned first moment is the described timed interval to the time difference in the 2nd moment, within the described timed interval, by a current source, the electrical condenser of a known capacity is charged, determine described very first time interval by voltage rise value.
3. the as claimed in claim 2 optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method, it is characterised in that: described particular phases comprises the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and phase place during zero passage in filtered 1 tunnel reference analog electrical signal process of rising or falling.
4. the as claimed in claim 2 optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method, it is characterised in that: described determine that the step of phase differential comprises: the described timed interval divided by each road of filtered at least 3 tunnel measure analog electrical signal or filtered 1 tunnel with reference to the analog electrical signal period.
5. the optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method as claimed in claim 4, it is characterized in that: the method for calculation in described cycle comprise: record described 2nd moment, and the first moment again arrived, the time difference in the 2nd moment to the first moment again arrived was for the 2nd timed interval; Very first time interval and the 2nd timed interval and be the described cycle.
6. the as claimed in claim 1 optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method, it is characterised in that: described first filtering process adds the narrow band filter that the resonance loop being made up of the inductance capacitance of one or more levels series connection or parallel connection forms and carries out filtering before being also included in described phase locked loop filter.
7. the optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method as claimed in claim 6, it is characterised in that: described resonance loop adds resistance or equivalent resistance adjustment quality factor, so that quality factor are adjustable and stable.
8. the optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method as claimed in claim 6, it is characterised in that: adopt weak coupling mode to be coupled between described resonance loop with its prime output terminal and rear class input terminus.
9. the as claimed in claim 8 optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method, it is characterised in that: described weak coupling mode is capacitive couplings or jigger coupling method or resistively couple method or the transformer coupled method of winding type.
10. the optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method as claimed in claim 1, it is characterised in that: the phase differential of the non-linear error of at least 3 periodicity in described at least 3 road measurement signals is not less than 60 ��.
11. optical heterodyne interference method eliminating non-linear error based on capacitor charging chronometric method as claimed in claim 1, it is characterized in that: the step being obtained at least 3 road measurement signals and 1 tunnel reference signal by light splitting is comprised: the A road optical signal of output obtains A1, A2 respectively by least 4 light-dividing devices successively ... An road optical signal, wherein n >=4; The B road optical signal with the A road optical signal exported with frequency difference obtains B1 road optical signal by light-dividing device, and all the other optical signals of B road obtain B2 by light-dividing device after being reflected by reflection unit successively ... 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 ... the corresponding interference forms n-1 road measurement signal to Bn road optical signal respectively.
12. 1 kinds adopt the laser heterodyne interferometry device of the optical heterodyne interference method described in claim 1-11, it is characterised in that: comprising:
First light-dividing device, obtains A1, A2 by the optical signal light splitting of A road ... An road optical signal, wherein n >=4;
2nd 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 2nd light-dividing device light splitting after reflection unit reflects ... 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 ... the corresponding interference forms n-1 road measurement signal to Bn road optical signal respectively;
Signal detecting device, is converted to 1 tunnel with reference to analog electrical signal, n-1 road measure analog electrical signal respectively by above-mentioned 1 tunnel reference signal, n-1 road measurement signal;
First filtering module, carries out the first filtering process respectively to n-1 road measure analog electrical signal;
2nd filtering module, carries out the 2nd filtering process to 1 tunnel with reference to analog electrical signal;
Phase detecting module, it is determined that the particular phases on each road of filtered at least 3 tunnel measure analog electrical signal and 1 tunnel are with reference to the very first time interval between the particular phases of analog electrical signal, and thus determine phase differential;
Analog to digital conversion module, changes into numerary signal by described phase differential;
Displacement calculates module, has changed into the phase differential of numerary signal according to n-1 road, has calculated n-1 road displacement measurement;
Weighted stacking module, carries out real number ranking operation and additive operation by the n-1 road displacement measurement obtained.
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