CN104677295A - Laser interference nonlinear error self-compensation method and device - Google Patents
Laser interference nonlinear error self-compensation method and device Download PDFInfo
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- CN104677295A CN104677295A CN201510063857.2A CN201510063857A CN104677295A CN 104677295 A CN104677295 A CN 104677295A CN 201510063857 A CN201510063857 A CN 201510063857A CN 104677295 A CN104677295 A CN 104677295A
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Abstract
The invention relates to a laser interference nonlinear error self-compensation method and device, and belongs to the technical field of laser interference precision measurement. The device comprises an interference measuring module, an optical demodulation and modulation module, a frequency modulation control module, and a control and information output module. By adopting the laser interference nonlinear error self-compensation method and device, the problem of nonlinear error compensation in the conventional laser interference system is solved, and the problems of physical displacement adjustment and stepping fineness requirement in general laser interference nonlinear error compensation are solved. The device is relatively simple in structure, and has the characteristics of high adaptability and small synchronous measurement interference system errors. Interference phase nonlinear error automatic compensation at any point can be finished during measurement under the condition of no physical displacement, and the accuracy of an interference measuring system is increased.
Description
Technical field
The present invention relates to a kind of laser interference nonlinearity erron method of self compensation and device, belong to laser interference Technology of Precision Measurement field.
Background technology
Laser interferometry is widely used in Technology of Precision Measurement field, is the important means of current high-acruracy survey, is of great significance linear measure longimetry field tool.Laser interferometry can cause the nonlinearity erron of its measurement result due to the optical device of application and the combined influence of the factor such as electric device, this error has periodic feature, its cycle stops with the integral point initial sum of interference fringe, usually can reach varying degree that is several or tens nanometers.When the measurement that Length Quantity pin-point accuracy requires, when particularly measuring error requires to be less than 10nm, interferometry nonlinearity erron becomes the key factor affecting measurement result accuracy.The method of the nonlinearity erron correction of current application, utilize precision displacement table to produce displacement more, interferometer synchro measure obtains the redundant data of one group of interferometry phase place, optimum solution is obtained by method solution inconsistent equations such as least squares, complete nonlinearity erron correction, the method implements system complex, introduces displacement platform kinematic error in process, affect the precision of final non-liner revision, particularly particularly outstanding at nonlinearity erron large flex point place.Therefore the nonlinear error compensation problem how reducing interferometry principle is one of gordian technique promoting precision measurement level.
Summary of the invention
The nonlinearity erron that the object of the invention is to solve existing laser interference system adopts physical displacement modulation Problems existing, provides a kind of laser interference nonlinearity erron method of self compensation and device.This device has the characteristic compared with high-adaptability and synchro measure interference system error, without under the condition of physical displacement, the difference of interferometer measurement phase place and theoretical value can be determined by automatically regulating the frequency of laser instrument and then realizes the nonlinear error compensation of interference system.
The object of the invention is to be achieved through the following technical solutions.
A kind of laser interference nonlinearity erron self-compensating device, is characterized in that: it comprises: interferometry module (1), optical demodulation module (2), frequency modulation control module (3), control and message output module (4).
The effect of control and message output module (4) is: 1. produce optical frequency control signal, and be sent to frequency modulation control module (3).2. the interference signal that optical demodulation module (2) exports is processed, obtain the current location measured value of measurand.The integer level that described interference signal comprises interference signal is secondary secondary with decimal level.3. the secondary theoretical value of interference signal decimal level is calculated according to the current location measured value of measurand.4. the relation between the theoretical value that interference signal decimal level that is secondary according to the decimal level measuring the interference signal obtained and that calculate is secondary, compensates the nonlinearity erron of interferometry module (1).
The effect of frequency modulation control module (3) is: according to the optical frequency control signal controlled and message output module (4) sends, and exports the laser of optical frequency control signal assigned frequency, and is exported to interferometry module (1).
The effect of interferometry module (1) is: the change in displacement of laser to measurand of the assigned frequency utilizing frequency modulation control module (3) input to come in is measured, obtain the first mutually orthogonal sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module (2).
The effect of optical demodulation module (2) is: the first mutually orthogonal sinusoidal signal of send interferometry module (1) and the second sinusoidal signal process, obtain the interference signal of the current location of measurand, and send it to control and message output module (4).
The annexation of each module is:
The output terminal of control and message output module (4) is connected with the input end of frequency modulation control module (3); The output terminal of frequency modulation control module (3) is connected with the input end of interferometry module (1); The output terminal of interferometry module (1) is connected with the input end of optical demodulation module (2); The output terminal of optical demodulation module (2) is connected with the input end of control and message output module (4).
Use described laser interference nonlinearity erron self-compensating device to carry out the self-compensating method of laser interference nonlinearity erron, it is characterized in that: its concrete operation step is:
Step one, obtain the non-linear by mistake mapping table of laser interference.
Step 1.1: the relative position of fixing measurand and interferometry module (1).Frequency range [the F of optical frequency control signal is inputted externally to control and message output module (4)
1, F
2]; Setpoint frequency step-length, represents with symbol Δ f simultaneously.Described frequency range [F
1, F
2], be the frequency range needed for nonlinearity erron of an acquisition interference periods internal interference signal measurements, F
1∈ [0,4G], F
2∈ [0,4G].
Step 1.2: setting i is a variable, and to set its initial value be 0.
Step 1.3: control and message output module (4) generation i-th optical frequency control signal, its frequency symbol f specified
irepresent.If i=0, f
ifor [F
1, F
2] any frequency values in scope; Otherwise, f
i=f
i-1+ Δ f.
Step 1.4: control and message output module (4) judge f
i≤ F
2whether set up, if set up, then i-th optical frequency control signal is sent to frequency modulation control module (3); Otherwise, complete the manufacturing process of the non-linear mapping table by mistake of laser interference, perform the operation of step 2.
Step 1.5: frequency modulation control module (3) is according to i-th the optical frequency control signal controlled and message output module (4) sends, and output frequency is f
ilaser, and exported to interferometry module (1).
Step 1.6: the frequency that interferometry module (1) utilizes frequency modulation control module (3) input to come in is f
ithe change in displacement of laser to measurand measure, obtain i-th group of mutually orthogonal first sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module (2).
Step 1.7: the first sinusoidal signal that optical demodulation module (2) i-th group of sending interferometry module (1) is mutually orthogonal and the second sinusoidal signal process, obtain the interference signal of measurand, and send it to control and message output module (4).Use symbol N
irepresent the integer level time of the interference signal of measurand; Use symbol ε
irepresent the decimal level time of the interference signal of measurand.
Step 1.8: if i=0, then message output module (4) judges now ε
iwhether be 0; If ε
i=0, then perform the operation of step 1.9; If ε
i≠ 0, then by adjustment f
0value, make f
0value be closest to F
1, and the decimal level of the interference signal that optical demodulation module (2) is obtained time ε
ivalue be 0; Then the operation of step 1.9 is performed.If i ≠ 0, directly perform the operation of step 1.10.
Step 1.9: work as i=0, the integer level time N of the interference signal that message output module (4) utilizes optical demodulation module (2) to obtain
i, calculated the displacement variable (representing with symbol L) of measurand by formula (1), now, due to the decimal level time ε of the interference signal that optical demodulation module (2) obtains
ibeing 0, there is not error in the displacement variable L of the measurand therefore calculated.Then, make the value of i from increasing 1, the operation of repeated execution of steps 1.3 to step 1.12.
Wherein, λ
ifor working as pre-test optical maser wavelength, obtain by formula (2).
Wherein, c is the light velocity in vacuum.
Step 1.10: when i ≠ 0, message output module (4) calculates the theoretical value of the interference signal of measurand by formula (3), uses symbol M
irepresent; Then by M
iobtain the secondary theoretical value of the interference signal decimal level of measurand (with symbol ε '
irepresent), ε '
ibe M
ifraction part.
Step 1.11: message output module (4) calculates the nonlinearity erron of interference signal measured value by formula (4), with symbol Δ ε
irepresent.
Δε
i=ε′
i-ε
i(4)
Step 1.12: the decimal level time ε of the interference signal of the measurand that optical demodulation module (2) records by message output module (4)
iand the nonlinearity erron Δ ε of interference signal measured value
ibe saved in the non-linear mapping table by mistake of laser interference; Then make the value of i from increasing 1, the operation of repeated execution of steps 1.3 to step 1.12.
Through the operation of step one, obtained the decimal level time ε of the interference signal of measurand in an interference periods by the measuring method of laser frequency
iwith the nonlinearity erron Δ ε of interference signal measured value
icorresponding relation, and be stored in the non-linear by mistake mapping table of laser interference.
Step 2, to measuring phases produce laser interference nonlinearity erron carry out self compensation.
On the basis that step one operates, self compensation is carried out to the laser interference nonlinearity erron that measuring phases produces.Be specially:
Step 2.1: the position of retightening measurand; Input the frequency of optical frequency control signal externally to control and message output module (4), represent with symbol f.
Step 2.2: control and message output module (4) generation optical frequency control signal, its frequency of specifying is f; And send it to frequency modulation control module (3).
Step 2.3: frequency modulation control module (3) is according to the optical frequency control signal controlled and message output module (4) sends, and output frequency is the laser of f, and is exported to interferometry module (1).
Step 2.4: the frequency that interferometry module (1) utilizes frequency modulation control module (3) input to come in is that the change in displacement of laser to measurand of f is measured, obtain the first mutually orthogonal sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module (2).
Step 2.5: the first mutually orthogonal sinusoidal signal that optical demodulation module (2) is sent interferometry module (1) and the second sinusoidal signal process, obtain the interference signal of measurand, and send it to control and message output module (4).The integer level time of the interference signal of measuring phases measurand is represented with symbol N; The decimal level time of the interference signal of measuring phases measurand is represented with symbol ε.
Step 2.6: the decimal level time ε of the interference signal of the measurand that control and message output module (4) are preserved in the non-linear mapping table by mistake of laser interference
iin search ε, if find ε
p=ε, wherein ε
p∈ { ε
i, then by formula (5), ε is revised, obtain the modified value of ε, represent with symbol ε '.If do not found, then obtained the nonlinearity erron of the interference signal measured value corresponding with ε by method of interpolation, with symbol Δ ε '
prepresent, then obtained the modified value ε ' of ε by formula (6).
ε′=ε+Δε
p(5)
ε′=ε+Δε′
p(6)
Step 2.7: control and message output module (4) calculate the current displacement variable (representing with symbol L ') of measurand by formula (7), and export the current displacement variable L ' of measurand.
Wherein, λ, for working as pre-test optical maser wavelength, obtains by formula (8).
By the operation of above-mentioned steps, the laser interference nonlinearity erron completed measuring phases produces carries out self compensation, obtains the current displacement variable L ' of accurate measurand.
The self-compensating method of described laser interference nonlinearity erron, is characterized in that: by reducing the value of frequency step Δ f described in step one step 1.1, improve the self-compensating precision of laser interference nonlinearity erron.
Beneficial effect
The laser interference nonlinearity erron method of self compensation that the present invention proposes and device, compared with the prior art comparatively, have the following advantages: the method for the laser interference nonlinear error compensation of employing overcomes the problem that usual laser interference nonlinear error compensation needs the adjustment of physical displacement and the fineness of stepping to require, structure is relatively simple, and the compensation being easy to done with high accuracy interference nonlinear error realizes.Adopt frequency modulating method that nonlinearity erron in interference periods is traceable to optical wavelength exactly in enforcement, principle overcomes the problem that existing interference nonlinear error compensates matrix fitting calculating and the linear difference adopted, achieve the function of arbitrfary point phase measurement, effectively specific aim can measure a difficult problem for the accurate correction of nonlinearity erron local flex point, improve the compensation level of current interference nonlinear error comprehensively, and up time auto-compensation can be carried out during measuring, improve the accuracy of interferometer measuration system.
Accompanying drawing explanation
Fig. 1 is the structural representation of laser interference nonlinearity erron self-compensating device in the specific embodiment of the invention;
Wherein, 1-interferometry module, 2-optical frequency demodulation module, 3-frequency modulation control module, 4-control and message output module, 5-measurand.
Embodiment
Below in conjunction with drawings and Examples, the present invention will be further described.
Laser interference nonlinearity erron self-compensating device in the present embodiment, its structure as shown in Figure 1, comprising: interferometry module 1, optical demodulation module 2, frequency modulation control module 3, control and message output module 4.
The effect of control and message output module 4 is: 1. produce optical frequency control signal, and be sent to frequency modulation control module 3.2. the interference signal that optical demodulation module 2 exports is processed, obtain the current location measured value of measurand.The integer level that described interference signal comprises interference signal is secondary secondary with decimal level.3. the secondary theoretical value of interference signal decimal level is calculated according to the current location measured value of measurand.4. the relation between the theoretical value that interference signal decimal level that is secondary according to the decimal level measuring the interference signal obtained and that calculate is secondary, compensates the nonlinearity erron of interferometry module 1.
The effect of frequency modulation control module 3 is: according to the optical frequency control signal controlled and message output module 4 sends, and exports the laser of optical frequency control signal assigned frequency, and is exported to interferometry module 1.
The effect of interferometry module 1 is: the change in displacement of laser to measurand of the assigned frequency utilizing frequency modulation control module 3 input to come in is measured, obtain the first mutually orthogonal sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module 2.
The effect of optical demodulation module 2 is: the first mutually orthogonal sinusoidal signal of send interferometry module 1 and the second sinusoidal signal process, and obtain the interference signal of the current location of measurand, and sends it to control and message output module 4.
The annexation of each module is:
The output terminal of control and message output module 4 is connected with the input end of frequency modulation control module 3; The output terminal of frequency modulation control module 3 is connected with the input end of interferometry module 1; The output terminal of interferometry module 1 is connected with the input end of optical demodulation module 2; The output terminal of optical demodulation module 2 is connected with the input end of control and message output module 4.
Use described laser interference nonlinearity erron self-compensating device to carry out the self-compensating method of laser interference nonlinearity erron, its concrete operation step is:
Step one, obtain the non-linear by mistake mapping table of laser interference.
Step 1.1: the relative position of fixing measurand and interferometry module 1.Frequency range [the F of optical frequency control signal is inputted externally to control and message output module 4
1, F
2], F
1=0, F
2=1.2G; Setpoint frequency step delta f=100M simultaneously.Described frequency range [F
1, F
2], be the frequency range needed for nonlinearity erron of an acquisition interference periods internal interference signal measurements.
Step 1.2: setting i is a variable, and to set its initial value be 0.
Step 1.3: control and message output module 4 produce i-th optical frequency control signal, its frequency symbol f specified
irepresent.If i=0, f
ifor [F
1, F
2] any frequency values in scope; Otherwise, f
i=f
i-1+ Δ f.
Step 1.4: control and message output module 4 judge f
i≤ F
2whether set up, if set up, then i-th optical frequency control signal is sent to frequency modulation control module 3; Otherwise, complete the manufacturing process of the non-linear mapping table by mistake of laser interference, perform the operation of step 2.
Step 1.5: frequency modulation control module 3 is according to i-th the optical frequency control signal controlled and message output module 4 sends, and output frequency is f
ilaser, and exported to interferometry module 1.Laser is produced by 650nm Frequency Adjustable laser instrument, and optical maser wavelength is 632.89142nm.
Step 1.6: the frequency that interferometry module 1 utilizes frequency modulation control module 3 input to come in is f
ithe change in displacement of laser to measurand measure, obtain i-th group of mutually orthogonal first sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module 2.
Step 1.7: the first sinusoidal signal that optical demodulation module 2 pairs of interferometry modules 1 i-th group of sending is mutually orthogonal and the second sinusoidal signal process, and obtain the interference signal of measurand, and send it to control and message output module 4.Use symbol N
irepresent the integer level time of the interference signal of measurand; Use symbol ε
irepresent the decimal level time of the interference signal of measurand.
Step 1.8: if i=0, then message output module 4 judges now ε
iwhether be 0; If ε
i=0, then perform the operation of step 1.9; If ε
i≠ 0, then by adjustment f
0value, make f
0value be closest to F
1, and the decimal level of the interference signal that optical demodulation module 2 is obtained time ε
ivalue be 0; Then the operation of step 9 is performed.If i ≠ 0, directly perform the operation of step 1.10.
Step 1.9: work as i=0, the integer level time N of the interference signal that message output module 4 utilizes optical demodulation module 2 to obtain
i, calculated the displacement variable L of measurand by formula (1), now, due to the decimal level time ε of the interference signal that optical demodulation module 2 obtains
ibeing 0, there is not error in the displacement variable L of the measurand therefore calculated.Then, make the value of i from increasing 1, the operation of repeated execution of steps 1.3 to step 1.12.
Step 1.10: when i ≠ 0, message output module 4 calculates the theoretical value of the interference signal of measurand by formula (3), uses symbol M
irepresent; Then by M
iobtain the theoretical value ε ' that the interference signal decimal level of measurand is secondary
i, ε '
ibe M
ifraction part.
Step 1.11: message output module 4 calculates the nonlinearity erron Δ ε of interference signal measured value by formula (4)
i.
Step 1.12: the decimal level time ε of the interference signal of the measurand that optical demodulation module 2 records by message output module 4
iand the nonlinearity erron Δ ε of interference signal measured value
ibe saved in the non-linear mapping table by mistake of laser interference; Then make the value of i from increasing 1, the operation of repeated execution of steps 1.3 to step 1.12.
Through the operation of step one, obtained the corresponding relation of the nonlinearity erron of an interference periods inner modulation frequency and interference signal measured value by the measuring method of laser frequency, and be stored in the non-linear mapping table by mistake of laser interference, as shown in table 1.
The non-linear mapping table by mistake of table 1 laser interference
Sequence number | ε i | Δε i |
1 | 0.0100 | 0.0074 |
2 | 0.0200 | -0.0001 |
3 | 0.0300 | -0.0042 |
4 | 0.0400 | -0.0055 |
5 | 0.0500 | -0.0049 |
6 | 0.0600 | -0.0041 |
7 | 0.0700 | -0.0005 |
8 | 0.0800 | 0.0015 |
9 | 0.0900 | 0.0027 |
10 | 0.1000 | 0.0029 |
11 | 0.1100 | 0.0027 |
12 | 0.1200 | 0.0031 |
13 | 0.1300 | 0.0015 |
14 | 0.1400 | -0.0007 |
15 | 0.1500 | -0.0030 |
16 | 0.1600 | -0.0009 |
17 | 0.1700 | 0.0037 |
18 | 0.1800 | 0.0057 |
19 | 0.1900 | 0.0048 |
… | … | … |
91 | 0.9100 | -0.0007 |
92 | 0.9200 | 0.0045 |
93 | 0.9300 | 0.0019 |
94 | 0.9400 | -0.0025 |
95 | 0.9500 | 0.0042 |
96 | 0.9600 | 0.0009 |
97 | 0.9700 | -0.0009 |
98 | 0.9800 | 0.0006 |
99 | 0.9900 | 0.0013 |
Step 2, to measuring phases produce laser interference nonlinearity erron carry out self compensation.
On the basis that step one operates, self compensation is carried out to the laser interference nonlinearity erron that measuring phases produces.Be specially:
Step 2.1: the position of retightening measurand; The frequency f of optical frequency control signal is inputted externally to control and message output module 4.
Step 2.2: control and message output module 4 produce optical frequency control signal, and its frequency of specifying is f; And send it to frequency modulation control module 3.
Step 2.3: frequency modulation control module 3 is according to the optical frequency control signal controlled and message output module 4 sends, and output frequency is the laser of f, and is exported to interferometry module 1.
Step 2.4: the change in displacement of laser to measurand that the frequency that interferometry module 1 utilizes frequency modulation control module 3 input to come in is f is measured, obtain the first mutually orthogonal sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module 2.
Step 2.5: the first mutually orthogonal sinusoidal signal that optical demodulation module 2 pairs of interferometry modules 1 are sent and the second sinusoidal signal process, and obtain the interference signal of measurand, and send it to control and message output module 4.The integer level time of the interference signal of measuring phases measurand is represented with symbol N; The decimal level time of the interference signal of measuring phases measurand is represented with symbol ε.
Step 2.6: the decimal level time ε of the interference signal of the measurand that control and message output module 4 are preserved in the non-linear mapping table by mistake of laser interference
iin search ε, if find ε
p=ε, wherein ε
p∈ { ε
i, then by formula (5), ε is revised, obtain the modified value ε ' of ε.If do not found, then obtained the nonlinearity erron Δ ε ' of the interference signal measured value corresponding with ε by method of interpolation
p, the modified value ε ' of ε is then obtained by formula (6).
Step 2.7: control and message output module 4 calculate the current displacement variable L ' of measurand by formula (7), and export the current displacement variable L ' of measurand.
By the operation of above-mentioned steps, the laser interference nonlinearity erron completed measuring phases produces carries out self compensation, obtains the current displacement variable L ' of accurate measurand.
The above is preferred embodiment of the present invention, and the present invention should not be confined to the content disclosed in this embodiment and accompanying drawing.Every do not depart from spirit disclosed in this invention under the equivalence that completes or amendment, all fall into the scope of protection of the invention.
Claims (6)
1. a laser interference nonlinearity erron self-compensating device, is characterized in that: it comprises: interferometry module (1), optical demodulation module (2), frequency modulation control module (3), control and message output module (4);
The effect of control and message output module (4) is: 1. produce optical frequency control signal, and be sent to frequency modulation control module (3); 2. the interference signal that optical demodulation module (2) exports is processed, obtain the current location measured value of measurand; The integer level that described interference signal comprises interference signal is secondary secondary with decimal level; 3. the secondary theoretical value of interference signal decimal level is calculated according to the current location measured value of measurand; 4. the relation between the theoretical value that interference signal decimal level that is secondary according to the decimal level measuring the interference signal obtained and that calculate is secondary, compensates the nonlinearity erron of interferometry module (1);
The effect of frequency modulation control module (3) is: according to the optical frequency control signal controlled and message output module (4) sends, and exports the laser of optical frequency control signal assigned frequency, and is exported to interferometry module (1);
The effect of interferometry module (1) is: the change in displacement of laser to measurand of the assigned frequency utilizing frequency modulation control module (3) input to come in is measured, obtain the first mutually orthogonal sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module (2);
The effect of optical demodulation module (2) is: the first mutually orthogonal sinusoidal signal of send interferometry module (1) and the second sinusoidal signal process, obtain the interference signal of the current location of measurand, and send it to control and message output module (4);
The annexation of each module is:
The output terminal of control and message output module (4) is connected with the input end of frequency modulation control module (3); The output terminal of frequency modulation control module (3) is connected with the input end of interferometry module (1); The output terminal of interferometry module (1) is connected with the input end of optical demodulation module (2); The output terminal of optical demodulation module (2) is connected with the input end of control and message output module (4).
2. the self-compensating method of laser interference nonlinearity erron, is characterized in that: its concrete operation step is:
Step one, obtain the non-linear by mistake mapping table of laser interference;
The decimal level time ε of the interference signal of measurand in an interference periods is obtained by the measuring method of laser frequency
iwith the nonlinearity erron Δ ε of interference signal measured value
icorresponding relation, and be stored in the non-linear by mistake mapping table of laser interference;
Step 2, to measuring phases produce laser interference nonlinearity erron carry out self compensation;
On the basis that step one operates, self compensation is carried out to the laser interference nonlinearity erron that measuring phases produces.
3. the self-compensating method of a kind of laser interference nonlinearity erron as claimed in claim 2, is characterized in that: the concrete operation step obtaining the non-linear mapping table by mistake of laser interference described in step one is:
Step 1.1: the relative position of fixing measurand and interferometry module (1); Frequency range [the F of optical frequency control signal is inputted externally to control and message output module (4)
1, F
2]; Setpoint frequency step-length, represents with symbol Δ f simultaneously;
Step 1.2: setting i is a variable, and to set its initial value be 0;
Step 1.3: control and message output module (4) generation i-th optical frequency control signal, its frequency symbol f specified
irepresent; If i=0, f
ifor [F
1, F
2] any frequency values in scope; Otherwise, f
i=f
i-1+ Δ f;
Step 1.4: control and message output module (4) judge f
i≤ F
2whether set up, if set up, then i-th optical frequency control signal is sent to frequency modulation control module (3); Otherwise, complete the manufacturing process of the non-linear mapping table by mistake of laser interference, perform the operation of step 2;
Step 1.5: frequency modulation control module (3) is according to i-th the optical frequency control signal controlled and message output module (4) sends, and output frequency is f
ilaser, and exported to interferometry module (1);
Step 1.6: the frequency that interferometry module (1) utilizes frequency modulation control module (3) input to come in is f
ithe change in displacement of laser to measurand measure, obtain i-th group of mutually orthogonal first sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module (2);
Step 1.7: the first sinusoidal signal that optical demodulation module (2) i-th group of sending interferometry module (1) is mutually orthogonal and the second sinusoidal signal process, obtain the interference signal of measurand, and send it to control and message output module (4); Use symbol N
irepresent the integer level time of the interference signal of measurand; Use symbol ε
irepresent the decimal level time of the interference signal of measurand;
Step 1.8: if i=0, then message output module (4) judges now ε
iwhether be 0; If ε
i=0, then perform the operation of step 1.9; If ε
i≠ 0, then by adjustment f
0value, make f
0value be closest to F
1, and the decimal level of the interference signal that optical demodulation module (2) is obtained time ε
ivalue be 0; Then the operation of step 1.9 is performed; If i ≠ 0, directly perform the operation of step 1.10;
Step 1.9: work as i=0, the integer level time N of the interference signal that message output module (4) utilizes optical demodulation module (2) to obtain
i, calculated the displacement variable L of measurand by formula (1), now, due to the decimal level time ε of the interference signal that optical demodulation module (2) obtains
ibeing 0, there is not error in the displacement variable L of the measurand therefore calculated; Then, make the value of i from increasing 1, the operation of repeated execution of steps 1.3 to step 1.12;
Wherein, λ
ifor working as pre-test optical maser wavelength, obtain by formula (2);
Wherein, c is the light velocity in vacuum;
Step 1.10: when i ≠ 0, message output module (4) calculates the theoretical value of the interference signal of measurand by formula (3), uses symbol M
irepresent; Then by M
iobtain the theoretical value ε ' that the interference signal decimal level of measurand is secondary
i, ε '
ibe M
ifraction part;
Step 1.11: message output module (4) calculates the nonlinearity erron of interference signal measured value by formula (4), with symbol Δ ε
irepresent;
Δε
i=ε′
i-ε
i(4)
Step 1.12: the decimal level time ε of the interference signal of the measurand that optical demodulation module (2) records by message output module (4)
iand the nonlinearity erron Δ ε of interference signal measured value
ibe saved in the non-linear mapping table by mistake of laser interference; Then make the value of i from increasing 1, the operation of repeated execution of steps 1.3 to step 1.12.
4. the self-compensating method of a kind of laser interference nonlinearity erron as claimed in claim 2 or claim 3, is characterized in that: the laser interference nonlinearity erron produced measuring phases described in step 2 carries out self-compensating concrete operation step and is:
Step 2.1: the position of retightening measurand; Input the frequency of optical frequency control signal externally to control and message output module (4), represent with symbol f;
Step 2.2: control and message output module (4) generation optical frequency control signal, its frequency of specifying is f; And send it to frequency modulation control module (3);
Step 2.3: frequency modulation control module (3) is according to the optical frequency control signal controlled and message output module (4) sends, and output frequency is the laser of f, and is exported to interferometry module (1);
Step 2.4: the frequency that interferometry module (1) utilizes frequency modulation control module (3) input to come in is that the change in displacement of laser to measurand of f is measured, obtain the first mutually orthogonal sinusoidal signal and the second sinusoidal signal, and outputted to optical demodulation module (2);
Step 2.5: the first mutually orthogonal sinusoidal signal that optical demodulation module (2) is sent interferometry module (1) and the second sinusoidal signal process, obtain the interference signal of measurand, and send it to control and message output module (4); The integer level time of the interference signal of measuring phases measurand is represented with symbol N; The decimal level time of the interference signal of measuring phases measurand is represented with symbol ε;
Step 2.6: the decimal level time ε of the interference signal of the measurand that control and message output module (4) are preserved in the non-linear mapping table by mistake of laser interference
iin search ε, if find ε
p=ε, wherein ε
p∈ { ε
i, then by formula (5), ε is revised, obtain the modified value of ε, represent with symbol ε '; If do not found, then obtained the nonlinearity erron of the interference signal measured value corresponding with ε by method of interpolation, with symbol Δ ε '
prepresent, then obtained the modified value ε ' of ε by formula (6);
ε′=ε+Δε
p(5)
ε′=ε+Δε′
p(6)
Step 2.7: control and message output module (4) calculate the current displacement variable L ' of measurand by formula (7), and export the current displacement variable L ' of measurand;
Wherein, λ, for working as pre-test optical maser wavelength, obtains by formula (8);
By the operation of above-mentioned steps, the laser interference nonlinearity erron completed measuring phases produces carries out self compensation, obtains the current displacement variable L ' of accurate measurand.
5. the self-compensating method of a kind of laser interference nonlinearity erron as claimed in claim 3, is characterized in that: [the F of frequency range described in step one step 1.1
1, F
2], be the frequency range needed for nonlinearity erron of an acquisition interference periods internal interference signal measurements, F
1∈ [0,4G], F
2∈ [0,4G].
6. the self-compensating method of a kind of laser interference nonlinearity erron as claimed in claim 3, is characterized in that: by reducing the value of frequency step Δ f described in step one step 1.1, improve the self-compensating precision of laser interference nonlinearity erron.
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