CN103322926B - Periodicity nonlinearity erron in signals transmission or interference inversion - Google Patents
Periodicity nonlinearity erron in signals transmission or interference inversion Download PDFInfo
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Abstract
Periodicity nonlinearity erron in signals transmission or interference inversion belong to field of signal transmissions, the method is in the signalling channel that there is periodically nonlinearity erron or interference component, reach out at least 3 road signals and make wherein respective periodicity nonlinearity erron or interference component at least 3 tunnels, phasing degree on the signal frequency composition that will be eliminated is within the scope of a corresponding angle of circumference or get rid of in a corresponding circle week angular region after integral multiple angle of circumference different, eliminated by follow-up electronics process again or suppress these periodically nonlinearity erron or interference components.The present invention can eliminate the particular harmonic composition of nonlinearity erron or interference, and its adjustment process is very easy to, and improves system performance, reduces cost.
Description
Technical field
The invention belongs to field of signal transmissions, be specifically related to the periodicity nonlinearity erron in a kind of signals transmission or interference inversion, laser heterodyne interference (HeterodyneInterferometry) fields of measurement in optical precision measurement technology can be applied to.
Background technology
For laser heterodyne interference measuring system, this system can be used for measuring the physical quantity such as displacement and length, is one of best nano measurement method.The method is in the frequency or phase place change tested displacement being converted to heterodyne signal, again by this measure of the change out, because the frequency of heterodyne signal is more much lower than optical frequency, photosignal easily processes, 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, this problem is present in the difference interference measuring of other kind fluctuation too, such as Ordinary Electromagnetic Wave, these factors can be the main source of error of displacement measurement, make its precision generally only have nanoscale to tens nanometer, its reason is that the light beam that frequency is different can not well be separated.These periodic nonlinearity erron problems are the obstacles of this art always.
Constantly invent some methods improved both at home and abroad for many years, but also there are some restriction or problems more, such as Badami and Pattersom uses ratemeter and frequency spectrograph directly measure nonlinearity erron composition in a mobile system and compensate; TaeBongEom and TaeYoungChoi etc. carry out compensating non-linear error to the method for carrying out ellipse fitting after phase signal integration.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 cycles and relative a large amount of computing, the real-time that impact is measured.Be disclose a kind of new method 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, also need point-device optics to regulate, this precise optical regulates usually more difficult.
Summary of the invention
In order to solve the system complex that existing signal transmission system (comprising laser heterodyne interference system) exists, operand is large, poor real, the coarse technical matters of result, the invention provides the periodicity nonlinearity erron in a kind of signals transmission or interference inversion, the particular harmonic composition of nonlinearity erron or interference can be eliminated, and the corresponding nonelectronic minute adjustment that can omit, the precision optics regulating device required for nonlinearity erron and minute adjustment process is eliminated as removed from laser heterodyne interference measurement, this adjustment is made to become very easy, and make adjustment automatically become possibility, significantly improve system performance simultaneously, reduce costs.
First for laser heterodyne interference system, this method is described.
The electric signal that the AC signal that the photodetector output terminal of laser heterodyne interference systematic survey light arm obtains is is frequency with alien frequencies optical frequency difference, its additional phase differential and measured position move into accurate proportionate relationship.But wherein contain so-called nonlinearity erron, be mainly 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 spectrum.Method of the present invention can eliminate the fundamental component of nonlinearity erron; In fact method of the present invention is all effective to arbitrary a certain frequency, and without the need to doing special minute adjustment to optical system.
Also exist in the signal light path of nonlinearity erron interference component in laser heterodyne interference system, obtain at least 3 road signals (passage), by by carry be detected signal light arm at least 3 interference light photodetecting part are set method obtain these signals, and to make wherein to have at least in 3 tunnels the phase angle of nonlinearity erron first harmonic (or other frequency content) contained separately different in a corresponding circumference, so just obtain sufficient information, the process such as weighted sum superposition in face after enable pass and fundamental frequency (or any one frequency) composition that eliminates in nonlinearity erron.The method different in a corresponding circumference of the phase angle realizing first harmonic (or other frequency content) 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, the amplitude and the starting phase angle that obtain first harmonic can be easy to.Generally, the phase angle of the several signals error of different light paths is usually unequal, if the situation having phase angle equal, can be known by the method measuring phase angle in prior art, and makes them unequal by adjustment light path.Furtherly, generally our optical system of setting up at random, do not have nonlinearity erron phasing degree in any 2 tunnels identical in a corresponding circumference, if but after completing the adjustment of optical system, the phase angle of 2 road nonlinearity erron first harmonics (or other frequency content that will be eliminated) is had at least to be more or less the same in 3 tunnels, the amplitude of the useful signal after may affecting weighted stacking, thus the signal to noise ratio (S/N ratio) of impact output signal, at this moment we roughly can adjust the difference of phase angle relative to (frequency content that will be eliminated of nonlinearity erron) signal phase angle corresponding in other passages of the frequency content that will be eliminated in 1-2 road wherein, it is made to increase to some extent fully till (namely enough).There are now a lot of detection nonlinearity erron first harmonic (or other frequency content that will be eliminated) phase places and the method for amplitude, 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., optoelectronic laser, 2005, etc.The method of adjustment phase angle can realize by regulating the optical path difference between two light participating in interference.Based on the periodicity of hamonic function, certainly as usually, several integral multiple angles of circumference comprised can be got rid of disregard (no longer doing similar prompting below) in above-mentioned phase differential.
Adopt and carry out subsequent treatment in the following method: first hypothesis only has the situation of 3 road signals, 3 road signals is carried out phase compare with reference signal respectively, until solve 3 displacements.The phase place of the nonlinearity erron at this moment in each passage is different.
Known by proof below, have non-vanishing weighting coefficient array can make superposition after 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 illustrates that content of the present invention also without loss of generality with first harmonic here; A is coefficient, and expressing nonlinearity erron amplitude, is generally an a small amount of, but does not make approximate processing in derivation afterwards.
be the initial phase angle of nonlinearity erron, λ is optical wavelength.Here the wave number in nonlinearity erron item
what represent is first harmonic composition, and by the situation of measuring prism individual reflection (measuring beam is turned back once).For the situation of second harmonic, this can become
By 3 result weighted stacking, be normalized into:
One group of new ki, just in order to neatly pro forma, can be regarded as 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:
k
1+k
2+k
3=b
Wherein, b ≠ 0
Can find out that the phase place of nonlinearity erron is in itself inessential with what physical quantity variation, importantly needs wherein have at least the phase angle of a certain characteristic frequency composition in the nonlinearity erron in 3 road signals different from above-mentioned system of equations.
The factor arrays of variable ki is 3 rank square formations of full rank, and the system of equations about ki has untrivialo solution.That is, can make
To sum up, demonstrated after such weighted stacking, the first harmonic composition of nonlinearity erron is eliminated.
If
in have any 2 difference 180 °, problem can be made to become simple and favourable, this situation generally needs accurate optics adjustment just can obtain, and the 2 road signals only needing non-linear component to differ 180 ° just enough eliminate the nonlinearity erron composition of characteristic frequency, than being illustrated in more detail in this that patent of invention mentioned in the introduction.
To this, we solve nonlinearity erron problem in 3 dimensional linear spaces of electronics, can find out, derivation above and the form of signal have nothing to do, and both can be the forms of light, also can be electricity or mechanical form etc.
For the situation with 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 signals and reservation, and changed into each 3 non-vanishing tunnels of phase angle difference in certain frequency of nonlinearity erron.So just dissolve the problem solved above becoming, i.e. the situation of 3 probe portions, and be proven.
Correct weighting coefficient array can be obtained by following method in practice and eliminate error percentage: (1) is by linear for 2 wherein superposition, because in 2 dimension spaces of this certain harmonic components nonlinear, one group of substrate of this two paths of signals Special composition, so any one vector can be generated by adjustment superposition coefficient, we allow the vector generated be just in time that direction is contrary with the 3rd signal (vector) on certain harmonic components nonlinear, then by the signal of generation and the 3rd signal (vector) linear superposition, adjustment weighting coefficient just can make certain harmonic components nonlinear be kept to zero completely mutually, and useful signal can still be retained.(2) electricity consumption tune method can repeat the weighting coefficient on alternate sweep at least 2 tunnel, measure nonlinearity erron value in the output after superposition simultaneously, make it constantly reduce, until be zero.(3) adopt the most basic method, after phase angle described in the every road of measurement and amplitude, directly calculated by analytic method, also can adopt the thinking in (1) here, but be 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 be applicable to can be selected according to the related content 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.
From the above, in laser heterodyne interferometry system, eliminate or reduce fundamental frequency (being also called first harmonic) or other frequency content of periodically nonlinearity erron, to improve the measuring accuracy of laser heterodyne interferometry, as long as adopt method proposed by the invention, namely in the signalling channel that there is nonlinearity erron interference component, reach out at least 3 road signals and periodicity nonlinearity erron interference component respective in making wherein at least 3 tunnels, phasing degree in the frequency content that will be eliminated is different within the scope of a corresponding angle of circumference (certainly can as usually, several integral multiple angles of circumference comprised in phase differential are got rid of and disregards).So just by electronics process such as follow-up weighting, superpositions, can eliminate or suppress these interference components.
The conveniently adjustment of wave paths (or light path), and effectively eliminate or suppress nonlinearity erron, and be conducive to retaining useful signal, select rational parameter.
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 that will be eliminated of 3 at least 3 road signals periodicity nonlinearity errons is made to be not less than 60 degree.This is because we always can, easily by regulating or arranging, make the declinate between any two-phase not too little in practice.Theoretical and experiment all illustrates, a rational numerical value using 60 ° of lower limits as this angle, this is beneficial to the signal to noise ratio (S/N ratio) after process, the amplitude of useful signal lower than single channel of output can not be made after weighted stacking, as long as attempt blindly fixingly affecting device in the light path of phase differential between 3 tunnels 3 to 5 times at random simultaneously, roughly just once chance meets this condition, thus " adjustment-free " that realize mechanically, and eliminate corresponding adjuster, make adjustment 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 mentioned, thus stop adjustment.Also can be eliminated by similar aforementioned reality method (1) (2) of error percentage, certain harmonic components nonlinear 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.
The method makes optic adjustment or the work that arranges become simple and easily, be a kind of method of exempting precision optical machinery and regulating or exempting from optics accurate adjustment, cost is significantly reduced, the accuracy requirement regulated optics 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.
Clearly, whether the ultimate principle of the method and the advantage itself existed and meaning, and adopt integrated optics mode, comprises optical fiber solutions, or bulk wave mode etc. is irrelevant.In the middle of the subsequent treatment of electric signal, also with which class means of employing, as simulation process, or digital processing etc. is irrelevant.Have nothing to do with the choosing method of required reference signal or reference signal, such as obtained by optical heterodyne or directly obtain its reference signal etc. by electric signal.
Mentioned above, just illustrate for the principle of work under any wave for light wave in our superincumbent explanation, in the process proved, we do not add condition specific to any optics self, so for the fluctuation of other form, as the electromagnetic wave and sound wave etc. of other wave band, principle proposed by the invention is all set up, and have identical correspondence, such as photodetector becomes ultraviolet, infrared eye, or being then Mike for sound wave, can be interdigital transducer etc. for surface acoustic wave.Existing photoelectric detector is all nonlinear element, output quantity is the amplitude of incident light, and in sound wave and electromagnetic wave etc. situation, Mike and antenna etc. directly can export the instantaneous amplitude of physical signalling linearly, but this does not affect the application of our other field outside optics, but also increases the dirigibility of application scheme.So the above-mentioned method that can realize in optical field, can realize too at other fluctuation detection or any form physical quantity transmission field.In laser heterodyne interference is measured, the first harmonic of nonlinearity erron is sixty-four dollar question, and in a more general case, we directly can discuss the optional frequency composition of periodic nonlinearity erron, and do not affect the conclusion drawn before us.
For measuring, this is transmitting procedure wherein, here transmission also can be not used in and draw measurement result, and be just transferred to next stage, the principle of this elimination or reduction nonlinear noise, can be applied in any type of signal communication process, when inevitably add external interference component in transmitting procedure time, such as can be applied in phase-modulation communication system.
To sum up, periodicity nonlinearity erron in signals transmission of the present invention or interference inversion, comprise: on the heterodyne interference signal path that there is nonlinearity erron interference component, obtain at least 3 road measuring-signals and 1 tunnel reference signal by Signal separator, and make the phasing degree of the respective periodicity nonlinearity erron of wherein at least 3 road measuring-signals in the frequency content that will be eliminated different within the scope of a corresponding angle of circumference; Calculate each road of above-mentioned at least 3 road measuring-signals and the phase differential of above-mentioned 1 tunnel reference signal respectively; Convert at least 3 road phase differential at least 3 displacement measurement, now contain nonlinearity erron in the displacement measurement of each road; Real number ranking operation and additive operation are carried out to above-mentioned at least three tunnel displacement measurement, can final measurement be obtained; Above-mentioned nonlinearity erron or interference inversion also comprise the first filtering.
The above-mentioned step calculating each road of above-mentioned at least 3 drive test amount analog electrical signals and the phase differential of above-mentioned 1 tunnel reference analog electrical signal respectively comprises: try to achieve phase differential by fft algorithm, or try to achieve phase differential by the digit phase method based on inner product of vectors method, or the time interval of the particular phases to be determined by timer try to achieve phase differential, or try to achieve phase differential by the time interval of charging capacitor determination particular phases.
The above-mentioned step calculating each road of above-mentioned at least 3 drive test amount analog electrical signals and the phase differential of above-mentioned 1 tunnel reference analog electrical signal respectively comprises: trigger by particular phases the square wave produced and try to achieve phase differential.
The step that square wave above by particular phases triggering generation tries to achieve phase differential comprises: the particular phases on each road of at least 3 drive test amount analog electrical signals triggers memory section, exports the first level; Memory section is triggered with reference to the particular phases of analog electrical signal in 1 tunnel, exports second electrical level; First level and second electrical level are not identical; Measure the dutycycle of the square wave of above-mentioned two level composition, be described phase differential.
Above-mentioned particular phases comprises: rise or declined zero angle time phase place.
The step of the above-mentioned duty cycle square wave of above-mentioned measurement comprises: first and second level equalization exported by described memory section, is transformed into stable output voltage by low-pass filtering by dutycycle, and above-mentioned voltage is the mean value of square wave, linear with duty cycle square wave.
Above-mentioned square wave is carried out can add in the low-pass filter of low-pass filtering and comprise and the trapper of reference signal with frequency and the trapper of several times frequency thereof.
Above-mentioned first filtering comprises employing single-stage or multistage resonant loop, or phase locked loop filter.
The phase differential of at least 3 periodicity nonlinearity errons in above-mentioned at least 3 road measuring-signals is not less than 60 °.
The step obtaining at least 3 road measuring-signals and 1 tunnel reference signal above by Signal separator comprises: the A road signal of output obtains A1, A2 respectively by least 4 signal separators successively ... An road signal, wherein n >=4; The B road signal with the A road signal exported with frequency difference obtains B1 road signal by Signal separator, obtains B2 successively after all the other signals of B road are reflected by reflection unit by Signal separator ... Bn road signal, wherein n >=4; A1 road signal and B1 road signal interference form reference signal, A2 ... An road signal and B2 ... the corresponding interference forms n-1 road measuring-signal to Bn road signal respectively.
In laser heterodyne interferometry system, also must obtain the measuring-signal on each road and the phase differential of reference signal.We are with duty cycle square wave qualitative modeling Lai Qiuge road measuring-signal below respectively and between reference signal, the phase differential in angle of circumference.By the particular phases on measuring-signal and a reference signal road (as reference signal) wherein (as risen, Angle Position during zero passage, transition edge can be generated according to this) output that triggers certain memory section (as trigger) is high level, the particular phases of the signal (as measuring-signal) on another road is then reverted to low level similarly, at this moment the phase differential between trigger output duty cycle and two signals is linear, measure its dutycycle and can obtain phase differential, method below can be adopted to measure dutycycle, the low and high level that described trigger exports is stablized, by low-pass filtering, dutycycle is transformed into stable output voltage, it is the mean value of square wave, linear with the dutycycle of described square wave, this simple circuit can obtain point-device result.When above-mentioned low level gets earth potential, the above-mentioned stable output voltage be transformed into by dutycycle is proportional to the phase differential between two signals, and when phase angle reaches maximal value, namely during 2 π radian, output voltage also reaches maximal value, i.e. high level voltage.The program can by very simple high speed circuit acquisition processing speed quickly and good precision.Corresponding circuit can be called the square wave average circuit of inspection phase angle difference.Whole system to this can without any numerical portion participate in signal transacting, more without the pressure of operand, and have stronger antijamming capability, such as anti-particle radiation ability.Enter numerical portion by analog to digital conversion after this to carry out displacement calculating, weighted sum superposition etc. and relatively simply process.
To sum up, the present invention adopts the phase differential obtained in the following method between each road measuring-signal and reference signal, the measuring-signal on Ji Youge road and the particular phases of reference signal trigger respectively and recover the output level state of certain memory section in each road, the low and high level that will export square wave (or the square wave after negate) is stablized, dutycycle to be transformed into stably by low-pass filter and phase differential has the output voltage of accurate linear relationship, then to carry out analog to digital conversion, displacement calculating, weighted sum overlap-add procedure etc.
This high level voltage can be follow-up part, such as analog to digital converter, provides witness mark (benchmark) voltage in order to improve measuring accuracy.
Above-mentioned square wave is carried out can add in the low-pass filter of filtering and comprise with reference signal with (frequency is f frequently
r) trapper and the trapper of front several integer multiple frequency (as 1 frequency multiplication and 2,3 frequencys multiplication, i.e. f
r, 2f
r, 3f
r, etc.), will to diminish the leeway that even output is certain to the design pressure of low-pass filter like this, the inversion frequency of low-pass filter can close to or exceed signal frequency, in order to faster processing time with improve precision.
Laser heterodyne interference signal is typical weak signal, in the exquisite system of this elimination nonlinearity erron, particularly more require that signal is pure, and the wave filter in analog electrical signal is a very important link in machine system.Consider that the useful signal of this system is single some composition frequently, and the wave filter that the inductance capacitance resonant tank of parallel connection in analog electronics or series connection is formed is operated in the natural frequency of single-point, just in time be mapped, the band that the narrow bandwidth of this wave filter be made up of resonant tank can make various noise, non-linear intermodulation and sampling thheorem require leads to outer spectrum component etc. and can be inhibited, and possesses noiseless, radioresistance, is easy to the feature that controls.Key property curve smoothing, analytic relationship are clear and definite, simple.So no matter whether there is the low-pass filter etc. in order to ensure set by sampling thheorem in system, in analog electrical signal passage, adding this resonant tank, to carry out filtering to signal be all useful.If but need very high precision, this resonant tank is just needed to have very high quality factor, and the quality factor of single this resonant tank are not unlimited, more important point is in addition, another consequence that quality factor are high is resonant tank also to be increased for response time of input signal phase place thereupon direct ratio, limited the movement velocity of object being measured.The method that this restriction can be used below is broken, be together in series by the above-mentioned resonant tank of more than 2 grades or 2 grades and (be a kind of wave filter of inductance capacitance resonant tank formation of two-stage series connection as shown in Figure 2, inter-stage have employed the weak coupling mode be made up of capacitor), to obtain new special-effect be thus overall is the multiplication relationship of single resonant tank to " passband " suppression outward, and corresponding time by contrast for input signal phase place is very low.These features can obviously promote complete machine index.So the wave filter that the inductance capacitance resonant tank of the parallel connection of two-stage or more level (namely more than two-stage) or series connection can be adopted in analog electrical signal passage to form carries out filtering to signal.
Resistance is added or equivalent resistance adjustment quality factor carry out filtering, to make quality factor adjustable and stable in resonant tank.Resistance is added (containing adjustable resistance in the filter circuits that the parallel connection of a relative high quality factor (Q value) or the inductance capacitance resonant tank of series connection are formed, potentiometer, or the method for equivalence), quality factor are mainly determined by lumped parameters such as resistors, instead of be distributed parameter decision, obtain desired, stable Q value.Q value has a lot of physical significances, as the here too high highest movement speed that also can affect under accuracy requirement of Q value.
For each basic resonant tank in the wave filter that the parallel connection of above-mentioned two-stage or more level or the inductance capacitance resonant tank of series connection are formed, and between the output terminal of its prime, and between the input end of rear class, adopt weak coupling method to ensure having certain quality factor and making it stablize of this resonant tank, the method of these weak couplings is at least realized by one of following method, 1) capacitive coupling, 2) inductive coupling, 3) resistively couple, 4) winding method is transformer coupled.
At the inductance capacitance resonant tank of the inner or series connection in parallel with each independently single-stage of the inductance capacitance resonant tank of the parallel connection of two-stage or more level or series connection for least unit, taken into apart two parts or more part and distribution diverse location in the channel.Such as independently insert gain section between single-stage resonant tank at two, form a kind of frequency-selecting amplifier, filtering, amplifier, interstage coupling etc. are combined.Also filtering part above can be used for prevent signal jam and intermodulation etc., below for filtering intermodulation and other interference components produced below.Filter circuit is distributed in the basic function that different positions can not affect wave filter self like this.
The key problem in technology of the practical machine system of the formation that the present invention provides is, by the resonant tanks of 2 or more to photosignal filtering, each road measuring-signal phase differential respectively and between reference signal is obtained by duty cycle square wave qualitative modeling, this combination has fabulous precision and high speed, lower cost and have good reliability and capability of resistance to radiation, under being suitable for the condition such as space and radiation pollution.
Three-channel different signal is weighted superposition by the adjustment of electronic manner by the present invention, the characteristic frequency composition of the interference that not only can receive in erasure signal, and also have longer channel part discrete to be separately convenient to detect these discrete channel parts.Such as the passage input short on three tunnels is inputted identical signal, both can compare and detect triple channel Output rusults and evaluation work state, this is conducive to detecting fast and remote control detection.
Another technical scheme of the present invention is: a kind of periodicity nonlinearity erron or interference blanking unit adopting above-mentioned periodicity nonlinearity erron or interference inversion, comprise: the first sub-signal tripping device, the signal beam splitting of A road is obtained A1, A2 ... An road signal, wherein n >=4; Second sub-signal tripping device, obtains B1 road signal and all the other signals by the B road signal beam splitting that the A road signal with output has frequency difference, and all the other signals described are obtained B2 by the beam splitting of secondary signal tripping device after reflection unit reflection ... Bn road signal, wherein n >=4; Interfere forming apparatus, make the reference signal that A1 road signal and B1 road signal interference are formed, A2 ... An road signal and B2 ... the corresponding interference forms n-1 road measuring-signal to Bn road signal respectively; Filtration module; Phase differential determination module, calculates each road of n-1 road measuring-signal and the phase differential of 1 tunnel reference signal; Displacement computing module, converts n-1 road phase differential to 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 explanation and the statement of some prior aries, row as omit the wiring board distribution filtering electric capacity of power-supply system, the details such as amplifier, sampling thheorem set by system-gain, the discussion of general foundation 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 process such as adjustment, signal transacting, weighted stacking of electronics respectively, with the length of electronics minute adjustment, light filling minute adjustment short, omitted complicated optics accurate adjustment or other non-electronic adjustment, the substitute is the adjustment and signal processing method elimination nonlinearity erron that adopt electronics, reduce the complexity of pH effect, reduce cost, improve efficiency.Meanwhile, effectively eliminate or reduce significantly the periodic interference components such as nonlinearity erron and then improve measuring accuracy or reduce interference.When being applied in laser heterodyne interference system, significantly can suppress primary components or the special component of nonlinearity erron, and the corresponding precision optics adjustment that omitted, be conducive to large-scale production, and reduce production cost.This method can also and other method, the patent comprising other uses simultaneously and can not affect respective effect, makes the periodic error of whole system obtain larger suppression.The specific implementation of the laser heterodyne interference system provided has structure simply, and precision is high, and speed is fast, reliably, and the features such as radioresistance.
Accompanying drawing explanation
Fig. 1 is the principle schematic of periodically nonlinearity erron removing method during the laser heterodyne interference in the present invention is measured.
Fig. 2 is the filter circuit schematic diagram that the two-stage parallel connection formula resonant tank in the present invention is formed.
Fig. 3 is the opticator principle schematic of periodicity nonlinearity erron in signals transmission of the present invention or interference inversion.
Fig. 4 is the principle schematic of periodicity nonlinearity erron in signals transmission of the present invention or interference inversion.
Embodiment
Below in conjunction with accompanying drawing, the present invention is described in further details.
Embodiment 1
The basic embodiment of nonlinearity erron removing method in the laser heterodyne interference measurement of corresponding precision optics adjustment can be removed from as shown in Figure 1.On the basis of an original laser heterodyne interference measuring instrument, invention increases the part in dotted line frame in figure, in order to complete structure of the present invention, principle and function with overall co-ordination.
First we set forth the principle of work of original heterodyne interferometry system, laser is sent by laser instrument 1, acousto-optical device 3 is incided through partially reflecting mirror 2, partially reflecting mirror 4 is shone after shift frequency, transmitted light is reflected by measuring prism 5, incide partially reflecting mirror 6, reflecting part and another Ray Of Light are interfered through polaroid 7.The light that reflected by partially reflecting mirror 2 (it provide reference ray for each road interference portion below) is through catoptron 8, again after partially reflecting mirror 9, partially reflecting mirror 22, partially reflecting mirror 16, catoptron 10, together incide polaroid 7 with the reflected light of partially reflecting mirror 6, the interference light of its outgoing converts the difference frequency part of two light to electric signal by photodetector 11.This electric signal, as measuring-signal, has wherein included the displacement information obtained above measuring prism 5, also containing nonlinearity erron composition.The signal exported by photodetector 11 and (electricity) reference signal carry out the cycle count of phase compare and phase differential at phase compare/result output 12, complete the displacement measurement of single channel.Also containing the nonlinearity erron destroying system accuracy in certain result.
(electricity) recited above reference signal obtains like this, the light that the light reflected by partially reflecting mirror 4 and partially reflecting mirror 9 reflect converges, incide polaroid 14, the interference light of its outgoing converts the difference frequency part of two light to electric signal by photodetector 15.This electric signal is exactly reference signal.
Laser instrument 1 recited above, partially reflecting mirror 2 and acousto-optical device 3 constitute the double-frequency laser generator that frequency has elementary errors, can be replaced by other scheme completely.
Invention increases the part in dotted line frame in Fig. 1, it mainly comprises two new measurement light arms (light path) and corresponding circuit part, together with original (being made up of the partially reflecting mirror 6 in figure, polaroid 7, photodetector 11 etc.) the 1st smooth arm, have 3 light arms, or be called 3 optical paths, also can comprise its circuit corresponding to 3 light paths here.
2nd measures in light arm, the transmitted light of partially reflecting mirror 6 is partly via the reflection of partially reflecting mirror 17, reflected light with partially reflecting mirror 16 together incides polaroid 18, two light phase dry doublings convert the difference frequency part of two light to ac signal by photodetector 19, to carry out the cycle count of phase compare and phase differential at phase compare/result output 20 with (electricity) reference signal, complete the displacement measurement on the 2nd tunnel.The same nonlinearity erron containing destroying system accuracy in certain result.
3rd structure measuring light arm and a upper light arm is duplicate with acting on substantially, the transmitted light of partially reflecting mirror 17 is through catoptron 23, reflected light with partially reflecting mirror 22 together incides polaroid 24, two light phase dry doublings convert the difference frequency part of two light to electric signal by photodetector 25, to carry out the cycle count of phase compare and phase differential at phase compare/result output 26 with (electricity) reference signal, complete the displacement measurement on the 3rd tunnel.The same nonlinearity erron containing destroying system accuracy in certain result.These 3 light paths (and respective corresponding circuit part), its structure and principle are identical completely.
The measurement result on 3 tunnels is sent into respectively respective ranking operation part 13, ranking operation part 21 and ranking operation part 27 and carry out real number ranking operation, then do additive operation in additive operation part 28 and just can draw last measurement result.The fundamental frequency of nonlinearity erron wherein can be eliminated or significantly suppress.
Embodiment 2
In the present embodiment, the wave filter be made up of two-stage or more level resonant tank to photosignal filtering, by the phase differential of duty cycle square wave qualitative modeling Qiu Ge road measuring-signal respectively and between reference signal.Whole laser heterodyne interference measuring system can be divided into opticator and electrical signal processing section afterwards.Wherein the principle of opticator as shown in Figure 3, and the present invention, on the basis of an original opticator, adds the part in dotted line frame in figure.
First the opticator principle of work of original heterodyne interferometry system is set forth: send laser by laser instrument 101, acousto-optical device 103 is incided through Part I catoptron 102, Part II catoptron 114 is shone after shift frequency, transmitted light is reflected by measuring prism 115, incide Part III catoptron 111, reflecting part and another Ray Of Light are interfered through the first polaroid 131.The light that reflected by Part I catoptron 102 (it provide reference ray for each road interference portion below) is through the first catoptron 125, again after Part IV catoptron 124, Part V catoptron 123, Part VI catoptron 122, second catoptron 121, together incide the first polaroid 131 with the reflected light of Part III catoptron 111, the interference light of its outgoing converts the difference frequency part of two light to electric signal by the first photodetector 141.This electric signal, as measuring-signal, has wherein included the displacement information obtained above measuring prism 115, also containing nonlinearity erron composition.
The light that the light reflected by Part II catoptron 114 and Part IV catoptron 124 reflect converges, incide the second polaroid 134, the interference light of its outgoing converts the difference frequency part of two light to electric signal by the second photodetector 144, and this electric signal is exactly reference signal.
Above-mentioned laser instrument 101, Part I catoptron 102 and acousto-optical device 103 constitute the double-frequency laser generator that frequency has elementary errors, also can be replaced by other scheme.
Opticator of the present invention adds the part in Fig. 3 in dotted line frame, and it mainly comprises two new measurement light arm/light paths and corresponding circuit part.Together with original the first smooth arm be made up of Part III catoptron 111, first polaroid 131, first photodetector 141 etc. in figure, have three light arms, or be called three optical paths, and obtain that measuring-signal exports 1 thus, measuring-signal export 2 and measuring-signal export 3, structurally smooth arm is identical to these two new measurement light arms with first.Add reference signal, four road signals export altogether, and this four roads signal just constitutes the output of opticator, is transferred to electrical signal processing section below, as described in Figure 4.
In electrical signal processing section, wave filter that its signal is formed respectively through the two-stage parallel connection formula inductance capacitance resonant tank shown in Fig. 2 (be respectively in Fig. 4 211,221,231,241 for first passage to the filtering part of four-way); Reduce the low-pass filter (to first to fourth passage difference correspondence 212,222,232,242 in the drawings) of high frequency interference composition; Through check phase differential square wave average circuit part (for the first to third channel be 213 in figure, 223,233) obtain phase differential; Three tunnel measurement data are sent to analog to digital conversion and displacement calculating section (for the first to third channel difference correspondence 214,224,234 in the drawings) respectively, complete corresponding analog to digital conversion, displacement calculating and cycle count, 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 stacking arithmetic section 301 respectively and is carried out real number ranking operation, and then do additive operation and just can draw last measurement result, the fundamental frequency of its nonlinearity erron has been eliminated or has significantly suppressed.
Claims (11)
1. the periodicity nonlinearity erron in signals transmission or interference inversion, is characterized in that: the method comprises:
On the heterodyne interference signal path that there is nonlinearity erron interference component, obtain at least 3 road measuring-signals and 1 tunnel reference signal by Signal separator, and make the phasing degree of the respective periodicity nonlinearity erron of wherein at least 3 road measuring-signals in the frequency content that will be eliminated different within the scope of a corresponding angle of circumference;
Calculate each road of above-mentioned at least 3 road measuring-signals and the phase differential of above-mentioned 1 tunnel reference signal respectively;
Convert at least 3 road phase differential at least 3 displacement measurement, now contain nonlinearity erron in the displacement measurement of each road;
Real number ranking operation and additive operation are carried out to above-mentioned at least three tunnel displacement measurement, can final measurement be obtained;
Above-mentioned nonlinearity erron or interference inversion also comprise the first filtering.
2. the periodicity nonlinearity erron in signals transmission as claimed in claim 1 or interference inversion, it is characterized in that: the described step calculating each road of above-mentioned at least 3 drive test amount analog electrical signals and the phase differential of above-mentioned 1 tunnel reference analog electrical signal respectively comprises: try to achieve phase differential by fft algorithm, or try to achieve phase differential by the digit phase method based on inner product of vectors method, or the time interval of the particular phases to be determined by timer try to achieve phase differential, or try to achieve phase differential by the time interval of charging capacitor determination particular phases.
3. the periodicity nonlinearity erron in signals transmission as claimed in claim 1 or interference inversion, is characterized in that: the described step calculating each road of above-mentioned at least 3 drive test amount analog electrical signals and the phase differential of above-mentioned 1 tunnel reference analog electrical signal respectively comprises: trigger by particular phases the square wave produced and try to achieve phase differential.
4. the periodicity nonlinearity erron in signals transmission as claimed in claim 3 or interference inversion, it is characterized in that: the step that the described square wave produced by particular phases triggering tries to achieve phase differential comprises: the particular phases on each road of at least 3 drive test amount analog electrical signals triggers memory section, exports the first level; Memory section is triggered with reference to the particular phases of analog electrical signal in 1 tunnel, exports second electrical level; First level and second electrical level are not identical; Measure the dutycycle of the square wave of above-mentioned two level composition, be described phase differential.
5. the periodicity nonlinearity erron in the signals transmission as described in claim 3 or 4 or interference inversion, is characterized in that: described particular phases comprises: rise or declined zero angle time phase place.
6. the periodicity nonlinearity erron in signals transmission as claimed in claim 4 or interference inversion, it is characterized in that: the step of the above-mentioned duty cycle square wave of described measurement comprises: first and second level equalization that described memory section is exported, by low-pass filtering, dutycycle is transformed into stable output voltage, above-mentioned voltage is the mean value of square wave, linear with duty cycle square wave.
7. the periodicity nonlinearity erron in signals transmission as claimed in claim 6 or interference inversion, is characterized in that: above-mentioned square wave is carried out can add in the low-pass filter of low-pass filtering comprise and reference signal with the trapper of trapper frequently and several times frequency thereof.
8. the periodicity nonlinearity erron in signals transmission as claimed in claim 1 or interference inversion, is characterized in that: described first filtering comprises employing single-stage or multistage resonant loop, or phase locked loop filter.
9. the periodicity nonlinearity erron in signals transmission as claimed in claim 1 or interference inversion, is characterized in that: the phase differential of at least 3 periodicity nonlinearity errons in described at least 3 road measuring-signals is not less than 60 °.
10. the periodicity nonlinearity erron in signals transmission as claimed in claim 1 or interference inversion, it is characterized in that: the step being obtained at least 3 road measuring-signals and 1 tunnel reference signal by Signal separator is comprised: the A road signal of output obtains A1, A2 respectively by least 4 signal separators successively ... An road signal, wherein n >=4; The B road signal with the A road signal exported with frequency difference obtains B1 road signal by Signal separator, obtains B2 successively after all the other signals of B road are reflected by reflection unit by Signal separator ... Bn road signal, wherein n >=4; A1 road signal and B1 road signal interference form reference signal, A2 ... An road signal and B2 ... the corresponding interference forms n-1 road measuring-signal to Bn road signal respectively.
11. 1 kinds of periodicity nonlinearity erron or interference blanking units adopting periodicity nonlinearity erron as described in any one of claim 1-10 or interference inversion, is characterized in that: comprising:
First sub-signal tripping device, obtains A1, A2 by the signal beam splitting of A road ... An road signal, wherein n >=4;
Second sub-signal tripping device, obtains B1 road signal and all the other signals by the B road signal beam splitting that the A road signal with output has frequency difference, and all the other signals described are obtained B2 by the beam splitting of secondary signal tripping device after reflection unit reflection ... Bn road signal, wherein n >=4;
Interfere forming apparatus, make the reference signal that A1 road signal and B1 road signal interference are formed, A2 ... An road signal and B2 ... the corresponding interference forms n-1 road measuring-signal to Bn road signal respectively;
Filtration module;
Phase differential determination module, calculates each road of n-1 road measuring-signal and the phase differential of 1 tunnel reference signal;
Displacement computing module, converts n-1 road phase differential to 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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