CN111442716A - Interferometric measuring device and method for introducing reference light - Google Patents
Interferometric measuring device and method for introducing reference light Download PDFInfo
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Abstract
The invention discloses an interferometric measuring device and method for introducing reference light, which comprises a signal light DFB laser and a reference light DFB laser, wherein the two DFB lasers are respectively connected with a 2x2 optical fiber coupler, the 2x2 optical fiber coupler is respectively connected with a phase modulator and an optical fiber circulator, the phase modulator is also respectively connected with a D/A conversion circuit and a 3x3 optical fiber coupler, the optical fiber circulator is also respectively connected with an FP etalon and a 3x3 optical fiber coupler, the FP etalon is also connected with a detection reflector, the 3x3 optical fiber coupler is also correspondingly connected with two wavelength division multiplexers, one of the wavelength division multiplexers is connected with two photoelectric detectors, and the other wavelength division multiplexer is connected with one photoelectric detector; the three photoelectric detectors are connected with the microprocessor through the A/D conversion circuit, and the microprocessor is connected with the phase modulator through the D/A conversion circuit. The invention has the advantages that: the method and the device realize the suppression of environmental interference, ensure the accuracy of detection results, avoid the adoption of a high-voltage circuit and improve the working safety.
Description
Technical Field
The invention relates to the technical field of laser measurement, in particular to an interference measurement device and method for introducing reference light.
Background
Laser interferometry is a high-precision interferometry technique, and is widely applied to the fields of quality control, reverse engineering, medical diagnosis, aerospace and the like, and common interferometry structures include a michelson interferometer, a mach-zehnder interferometer, a sagnac interferometer and the like. Because the laser interferometry has the characteristics of high precision and high sensitivity, and is also easily influenced by various external factors, the influence on a spatial light path is relatively small, but for an optical fiber link, the influences of temperature, vibration and the like are coupled into an interference system through optical fibers.
In order to reduce the external influence and ensure the extraction of the detection signal, measures such as reducing the length of the optical fiber, adopting a non-sensitive optical fiber or reducing the environmental interference (such as a constant temperature vibration isolation experiment platform) and the like can be generally adopted. For an interference vibration measurement system, in the prior art, there is an optical fiber interference vibration measurement system based on phase compensation, which adopts a double DFB and a double fiber grating (FBG) to construct two approximately overlapped michelson interferometers, and adopts a piezoelectric ceramic optical fiber expander to compensate the phase to obtain a vibration signal. Although the scheme reduces the external influence to a certain extent, the influence from the fiber grating to the reflector section cannot be eliminated, and the piezoelectric ceramic is adopted to compensate the phase and needs the support of a high-voltage circuit.
Disclosure of Invention
Aiming at the problems in the background art, the invention aims to provide an interference measurement device and method for introducing reference light, which mainly compensate the disturbance of an optical fiber light path by introducing the reference light and inhibit the interference of the external environment; the unbalanced Mach-Zehnder interferometer is constructed to detect interference signals so as to obtain vibration (or displacement) information of a detection point, and the adoption of a high-voltage circuit is avoided.
In order to achieve the purpose, the invention adopts the technical scheme that:
an interferometric measuring device for introducing reference light comprises a DFB laser A, DFB, a 2x2 optical fiber coupler, a phase modulator, an optical fiber circulator, an FP etalon, a detection reflector, a 3x3 optical fiber coupler, a wavelength division multiplexer A, a wavelength division multiplexer B, a photoelectric detector A, a photoelectric detector B, a photoelectric detector C, A/D conversion circuit, a microprocessor and a D/A conversion circuit;
the DFB laser A and the DFB laser B are respectively connected with two input arms of a 2x2 optical fiber coupler; two output arms of the 2x2 optical fiber coupler are respectively connected with the input end of the phase modulator and the port A of the optical fiber circulator; the port B of the optical fiber circulator is connected with the input end of the FP etalon; the output end of the FP etalon is connected with the detection reflector; the port C of the optical fiber circulator and the output end of the phase modulator are respectively connected with two input arms in the 3x3 optical fiber coupler; two output arms in the 3x3 optical fiber coupler are respectively connected with an input arm of the wavelength division multiplexer A and an input arm of the wavelength division multiplexer B; a reference light output arm of the wavelength division multiplexer A is connected with the photoelectric detector A, and a signal light output arm is connected with the photoelectric detector B; a reference light output arm of the wavelength division multiplexer B is suspended, a signal light output arm is connected with a photoelectric detector C, the photoelectric detector A, the photoelectric detector B and the photoelectric detector C are all electrically connected with the A/D conversion circuit, the A/D conversion circuit is electrically connected with the microprocessor, and the microprocessor is electrically connected with the phase modulator through the D/A conversion circuit;
among them, the DFB laser a is used to output signal light, and the DFB laser B is used to output reference light.
Further, the wavelength of the signal light output by the DFB laser a and the wavelength of the reference light output by the DFB laser B are both matched with the applicable wavelengths of the wavelength division multiplexer a and the wavelength division multiplexer B.
Further, the transmission wavelength of the FP etalon is consistent with the wavelength of the signal light output by the DFB laser A,
further, the wavelength of the signal light output by the DFB laser a is 1550nm, and the wavelength of the reference light output by the DFB laser B is 1558 nm.
In the above measuring apparatus, the 3x3 optical fiber coupler includes three input arms and three output arms, one of the three input arms of the 3x3 optical fiber coupler is suspended, the other two input arms are respectively connected to the port C of the optical fiber circulator and the output end of the phase modulator, one of the three output arms of the 3x3 optical fiber coupler is suspended, and the other two output arms are respectively connected to the wavelength division multiplexer a and the wavelength division multiplexer B.
An interferometric method of introduced reference light is realized based on the interferometric device of introduced reference light, which comprises the following steps:
wherein: r1< R2, and R1 and R2 are both greater than 0 and less than 1.
In the above measurement method, in step 4, the normalized intensity I2 and the normalized intensity I3 obtained in step 3 are used to obtain the vibration or displacement information of the detection point, which specifically includes the following three cases:
when the normalized intensities I2 and I3 obtained in step 3 successively pass through thresholds R2 and R1 preset in a microprocessor, it is determined that the integer wavelength shift number N of the probe point is decreased by 1, i.e., N _ new ═ N-1, where N represents the integer wavelength shift number before the probe point is updated, i.e., the original integer wavelength shift number, and the initial value is 0; n _ new represents the integer wavelength shift number after the probe point is updated, i.e. the new integer wavelength shift number;
in this case, a phase threshold is introduced
The total displacement d L of the probe point can be obtained as shown in the following formula (1):
dL＝N_new*λ+dl； (1)
in formula (1), N _ new λ represents an integer wavelength shift portion, and dl represents a shift portion of less than 1 wavelength;
wherein the content of the first and second substances,
is the phase value corresponding to when I3 passes through R1 after I2;
the dl can be obtained by the reverse calculation of the light intensity expression of the interferometer, namely the light intensity change curve of the interference fringes caused by the vibration of the selected detection point can simultaneously meet the phase difference of I2 and I3
To obtain the result that,
the value range is [02 pi ]]；
When the phase difference is between
At the position of
And between 2 pi, then
When the phase difference is between
At 0 and
in between, then
(II) when the normalized intensities I3 and I2 obtained in the step 3 successively pass through thresholds R1 and R2 preset in a microprocessor, judging that the integer wavelength displacement number N of the detection point is increased by 1, namely N _ new is equal to N +1, wherein N represents the integer wavelength displacement number before the update of the detection point, namely the original integer wavelength displacement number, and the initial value is 0; n _ new represents the integer wavelength shift number after the probe point is updated, i.e. the new integer wavelength shift number;
in this case, a phase threshold is introduced
The total displacement d L of the probe point can be obtained as shown in the following formula (2):
dL＝N_new*λ-dl； (2)
in formula (2), N _ new λ represents an integer wavelength shift portion, and dl represents a shift portion of less than 1 wavelength;
wherein the content of the first and second substances,
is the corresponding phase value for I2 passing through R2 after I3;
for dl can be passedThe light intensity expression of the interferometer is obtained by reverse calculation, namely the light intensity change curve of the interference fringes caused by vibration of the selected detection point can simultaneously meet the phase difference of I2 and I3
To obtain the result that,
the value range is [02 pi ]]；
When the phase difference is between
At 0 and
in between, then
When the phase difference is between
At the position of
And between 2 pi, then
(III) for other situations not conforming to the first or second conditions, when N is not equal to 0, the total displacement d L of the detection point can be obtained by using the currently adopted calculation formula, namely the total displacement d L of the detection point is obtained by using the formula (1) or the formula (2), when N is 0, the total displacement d L of the detection point is less than 1 wavelength, at the moment, the total displacement d L of the detection point can be reversely calculated by using an interferometer light intensity expression, namely, the light intensity change curve of interference fringes caused by vibration of the detection point can be selected to simultaneously meet the phase difference of I2 and I3
To obtain that
The value range is [02 pi ]]。
In the measuring method, the value range of the threshold R1 is 0.2-0.4, and the value range of the threshold R2 is 0.6-0.8.
Compared with the prior art, the invention has the advantages that:
(1) the disturbance problem caused by external influence on the optical fiber light path is compensated by introducing the reference light, so that the suppression of the environmental interference in the interferometer is realized, and the detection accuracy of a vibration (or displacement) signal of a detection reflector (namely a detection point) is ensured;
(2) by constructing the unbalanced Mach-Zehnder interferometer, adopting methods such as fringe counting and reverse solving for displacement smaller than a single wavelength, the vibration (or displacement) information of the detection reflector (namely a detection point) can be obtained only by processing detection data, so that the adoption of a high-voltage circuit is effectively avoided, and the safety of test work is improved;
(3) the FP etalon is adopted to realize the separation of the signal light and the reference light, thereby improving the detection sensitivity; the optical path overlapping part of the signal light and the reference light is an optical fiber optical path, the signal light enters a space optical path after the signal light and the reference light are separated by the FP etalon and reaches a detection reflector (namely a detection point), and the signal light is only modulated by the detection point because the space optical path has little interference on the signal light, so the detection sensitivity is improved;
the innovation points of the invention are as follows: 1) the reference light is introduced to compensate the disturbance of the optical fiber optical path, so that the influence of environmental disturbance is effectively inhibited; 2) an unbalanced mach-zehnder interferometer is constructed, and vibration (or displacement) information of a detection reflector (namely a detection point) can be obtained by processing interference signals.
Drawings
FIG. 1 is a schematic diagram of the working principle of the interferometric measuring device of the present invention with reference light introduced;
FIG. 2 is a waveform diagram of vibration of a detection mirror;
FIG. 3 is a diagram illustrating the variation of the light intensity of interference fringes caused by the vibration of the detection mirror;
description of reference numerals: 1. DFB laser a; 2. a DFB laser B; 3. 2x2 fiber optic couplers; 4. a phase modulator; 5. a fiber optic circulator; 6. an FP etalon; 7. a detection mirror; 8. 3x3 fiber optic couplers; 9. a wavelength division multiplexer A; 10. a wavelength division multiplexer B; 11. a photodetector A; 12. a photodetector B; 13. a photodetector C; 14. an A/D conversion circuit; 15. a microprocessor; 16. a D/A conversion circuit.
Detailed Description
In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the following description further explains how the invention is implemented by combining the attached drawings and the detailed implementation modes.
Referring to fig. 1, the interferometric measuring device for introducing reference light provided by the present invention includes a DFB laser a1, a DFB laser B2, a 2x2 fiber coupler 3, a phase modulator 4, a fiber circulator 5, an FP etalon 6, a detection mirror 7, A3 x3 fiber coupler 8, a wavelength division multiplexer a9, a wavelength division multiplexer B10, a photodetector a11, a photodetector B12, a photodetector C13, an a/D conversion circuit 14, a microprocessor 15, and a D/a conversion circuit 16;
the DFB laser a1 and the DFB laser B2 are respectively connected to two input arms of the 2x2 fiber coupler 3; two output arms of the 2x2 optical fiber coupler 3 are respectively connected with the input end of the phase modulator 4 and the port A of the optical fiber circulator 5; the port B of the optical fiber circulator 5 is connected with the input end of the FP etalon 6; the output end of the FP etalon 6 is connected with the detection reflector 7; the port C of the optical fiber circulator 5 and the output end of the phase modulator 4 are respectively connected with two input arms in the 3 × 3 optical fiber coupler 8; two output arms in the 3x3 optical fiber coupler 8 are respectively connected with an input arm of the wavelength division multiplexer a9 and an input arm of the wavelength division multiplexer B10; a reference light output arm of the wavelength division multiplexer A9 is connected with the photoelectric detector A11, and a signal light output arm is connected with the photoelectric detector B12; a reference light output arm of the wavelength division multiplexer B10 is suspended, a signal light output arm is connected with a photoelectric detector C13, the photoelectric detector A11, the photoelectric detector B12 and the photoelectric detector C13 are all electrically connected with an A/D conversion circuit 14, the A/D conversion circuit 14 and a D/A conversion circuit 16 are all electrically connected with a microprocessor 15, and the microprocessor 15 realizes the control of the phase modulator 4 through the D/A conversion circuit 16;
among them, DFB laser a1 is used to output signal light, and DFB laser B2 is used to output reference light.
In the present invention, the FP etalon 6 functions as: the optical fiber is used for separating the signal light and the reference light, namely, the transmission of the signal light and the reflection of the reference light can be realized, one side of the optical fiber is connected to a port C of the optical fiber circulator 5 by adopting an optical fiber, and the other side of the optical fiber is of a spatial light path structure and is opposite to the detection reflector 7.
In the invention, the 3x3 optical fiber coupler 8 comprises three input arms and three output arms, one of the three input arms is suspended, the other two input arms are respectively connected with the port C of the optical fiber circulator 5 and the output end of the phase modulator 4, one of the three output arms is suspended, and the other two output arms are respectively connected with the wavelength division multiplexer A9 and the wavelength division multiplexer B10.
For the 3x3 fiber coupler 8, because there is a phase difference of 2 pi/3 between the output arms, the output light intensity of the three output ports is expressed as:
where n represents the different ports, m represents the interference fringe contrast,
representing the phase difference of the interference arms,
in the range of 0-2 pi.
In the present invention, the photodetector a11, the photodetector B12, and the photodetector C13 are used to convert the received optical signal into an electrical signal; the a/D conversion circuit 14 is used for converting the electrical signals of the photodetector a11, the photodetector B12 and the photodetector C13 into digital signals and transmitting the digital signals to the microprocessor 15; the D/a conversion circuit 16 is used for converting the digital signal output by the microprocessor 15 into an analog signal to the phase modulator 4, and controlling the phase modulator 4 to modulate.
As a first embodiment of the present invention: referring to fig. 1, the DFB laser a1 is used to output signal light, the DFB laser B2 is used to output reference light, and the wavelength of both the signal light output from the DFB laser a1 and the reference light output from the DFB laser B2 do not coincide.
Specifically, in this embodiment: the wavelength of the signal light output by the DFB laser A1 is 1550nm, and the wavelength of the reference light output by the DFB laser B2 is 1558 nm.
Since the FP etalon 6 in the present invention functions to separate the signal light from the reference light, that is, to transmit the signal light and reflect the reference light, in the embodiment of the present invention: the transmission wavelength of the FP etalon 6 coincides with the signal light wavelength output from the DFB laser a1, and is 1550 nm.
Specifically, in this embodiment: the wavelength of the signal light output by DFB laser a1 and the wavelength of the reference light output by DFB laser B2 also match the wavelengths available at wavelength division multiplexer a9 and wavelength division multiplexer B10.
The invention provides an interference measurement method of introduced reference light, which is realized based on the interference measurement device of introduced reference light, and specifically comprises the following steps:
wherein: r1< R2, and R1 and R2 are both greater than 0 and less than 1.
Specifically, in step 4 of the above-mentioned measurement method, the normalized intensity I2 and the normalized intensity I3 obtained in step 3 are used to obtain the vibration or displacement information of the detection point (i.e. the detection mirror 7), which specifically includes the following three cases:
when the normalized intensities I2 and I3 obtained in step 3 successively pass through thresholds R2 and R1 preset in a microprocessor, it is determined that the integer wavelength shift number N of the probe point is decreased by 1, i.e., N _ new ═ N-1, where N represents the integer wavelength shift number before the probe point is updated, i.e., the original integer wavelength shift number, and the initial value is 0; n _ new represents the integer wavelength shift number after the probe point is updated, i.e. the new integer wavelength shift number;
in this case, a phase threshold is introduced
The total displacement d L of the probe point can be obtained as shown in the following formula (1):
dL＝N_new*λ+dl； (1)
in formula (1), N _ new λ represents an integer wavelength shift portion, and dl represents a shift portion of less than 1 wavelength;
wherein the content of the first and second substances,
is the phase value corresponding to when I3 passes through R1 after I2;
the dl can be obtained by the reverse calculation of the light intensity expression of the interferometer, namely the light intensity change curve of the interference fringes caused by the vibration of the selected detection point can simultaneously meet the phase difference of I2 and I3
To obtain the result that,
the value range is [02 pi ]]；
When the phase difference is between
At the position of
And between 2 pi, then
When the phase difference is between
At 0 and
in between, then
(II) when the normalized intensities I3 and I2 obtained in the step 3 successively pass through thresholds R1 and R2 preset in a microprocessor, judging that the integer wavelength displacement number N of the detection point is increased by 1, namely N _ new is equal to N +1, wherein N represents the integer wavelength displacement number before the update of the detection point, namely the original integer wavelength displacement number, and the initial value is 0; n _ new represents the integer wavelength shift number after the probe point is updated, i.e. the new integer wavelength shift number;
in this case, a phase threshold is introduced
The total displacement d L of the probe point can be obtained as shown in the following formula (2):
dL＝N_new*λ-dl； (2)
in formula (2), N _ new λ represents an integer wavelength shift portion, and dl represents a shift portion of less than 1 wavelength;
wherein the content of the first and second substances,
is the corresponding phase value for I2 passing through R2 after I3;
the dl can be obtained by the reverse calculation of the light intensity expression of the interferometer, namely the light intensity change curve of the interference fringes caused by the vibration of the selected detection point can simultaneously meet the phase difference of I2 and I3
To obtain the result that,
the value range is [02 pi ]]；
When the phase difference is between
At 0 and
in between, then
When the phase difference is between
At the position of
And between 2 pi, then
(III) for non-compliance with (one) orIn other cases, when N ≠ 0, the total displacement d L of the probe point can be obtained by using the currently used calculation formula, that is, the total displacement d L of the probe point can be obtained by using the formula (1) or the formula (2), and when N ═ 0, the total displacement d L of the probe point is smaller than 1 wavelength, at this time, the total displacement d L of the probe point can be reversely calculated by using the light intensity expression of the interferometer, that is, the light intensity variation curve of the interference fringes caused by the vibration of the probe point can simultaneously satisfy the phase difference of I2 and I3
To obtain that
The value range is [02 pi ]]。
Specifically, in step 4 of the measurement method, the preferable range of the value of the threshold R1 is 0.2 to 0.4, and the preferable range of the value of the threshold R2 is 0.6 to 0.8.
FIG. 2 is a diagram showing a waveform of vibration of the detection mirror 7 in the interferometric measuring device using reference light according to the present invention, in which the abscissa represents time in the unit of S; the ordinate represents the displacement of the detection mirror 7 in m;
fig. 3 is a graph showing the change of the light intensity of the interference fringes caused by the vibration of the detection mirror 7 when the threshold R1 is 0.2 and the threshold R2 is 0.8 in step 4 of the interferometric method introduced into the reference light of the present invention, wherein the abscissa in the graph represents time and the unit is S; the ordinate represents the interference fringe contrast; the solid wavy line represents the wavy pattern of the normalized intensity I2, and the dashed wavy line represents the wavy pattern of the normalized intensity I3.
Finally, the above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures or equivalent processes performed by the present invention or directly or indirectly applied to other related technical fields using the contents of the present specification and the attached drawings are included in the scope of the present invention.
Claims (8)
1. An interferometric measuring device for introducing reference light, comprising: the optical fiber phase-change optical fiber laser comprises a DFB laser A (1), a DFB laser B (2), a 2x2 optical fiber coupler (3), a phase modulator (4), an optical fiber circulator (5), an FP etalon (6), a detection reflector (7), a 3x3 optical fiber coupler (8), a wavelength division multiplexer A (9), a wavelength division multiplexer B (10), a photoelectric detector A (11), a photoelectric detector B (12), a photoelectric detector C (13), an A/D conversion circuit (14), a microprocessor (15) and a D/A conversion circuit (16);
the DFB laser A (1) and the DFB laser B (2) are respectively connected with two input arms of a 2x2 optical fiber coupler (3); two output arms of the 2x2 optical fiber coupler (3) are respectively connected with the input end of the phase modulator (4) and the port A of the optical fiber circulator (5); the port B of the optical fiber circulator (5) is connected with the input end of the FP etalon (6); the output end of the FP etalon (6) is connected with the detection reflector (7); the port C of the optical fiber circulator (5) and the output end of the phase modulator (4) are respectively connected with two input arms in a 3x3 optical fiber coupler (8); two output arms in the 3x3 optical fiber coupler (8) are respectively connected with one input arm of the wavelength division multiplexer A (9) and one input arm of the wavelength division multiplexer B (10); a reference light output arm of the wavelength division multiplexer A (9) is connected with the photoelectric detector A (11), and a signal light output arm is connected with the photoelectric detector B (12); a reference light output arm of the wavelength division multiplexer B (10) is suspended, a signal light output arm is connected with a photoelectric detector C (13), the photoelectric detector A (11), the photoelectric detector B (12) and the photoelectric detector C (13) are all electrically connected with the A/D conversion circuit (14), the A/D conversion circuit (14) is electrically connected with the microprocessor (15), and the microprocessor (15) is electrically connected with the phase modulator (4) through a D/A conversion circuit (16);
among them, the DFB laser a (1) is used to output signal light, and the DFB laser B (2) is used to output reference light.
2. The interferometry device for introducing reference light according to claim 1, wherein: and the signal optical wavelength output by the DFB laser A (1) and the reference optical wavelength output by the DFB laser B (2) are matched with the applicable wavelengths of the wavelength division multiplexer A (9) and the wavelength division multiplexer B (10).
3. The interferometry device for introducing reference light according to claim 2, wherein: the transmission wavelength of the FP etalon (6) is consistent with the wavelength of the signal light output by the DFB laser A (1).
4. An interferometric measuring device introducing reference light according to claim 2 or 3, characterized in that: the wavelength of the signal light output by the DFB laser A (1) is 1550nm, and the wavelength of the reference light output by the DFB laser B (2) is 1558 nm.
5. The interferometry device for introducing reference light according to claim 1, wherein: the 3x3 optical fiber coupler (8) comprises three input arms and three output arms, one of the three input arms of the 3x3 optical fiber coupler (8) is suspended, the other two input arms are respectively connected with a port C of the optical fiber circulator (5) and an output end of the phase modulator (4), one of the three output arms of the 3x3 optical fiber coupler (8) is suspended, and the other two output arms are respectively connected with the wavelength division multiplexer A (9) and the wavelength division multiplexer B (10).
6. An interferometry method for introducing reference light, which is implemented based on the interferometry device for introducing reference light in claim 1, wherein: comprises the following steps:
step 1, simultaneously starting a DFB laser A (1) and a DFB laser B (2), scanning a phase modulator (4) for one circle to obtain a maximum detection value AD2_ max corresponding to a photoelectric detector B (12) and a maximum detection value AD3_ max corresponding to a photoelectric detector C (13);
step 2, adjusting a phase modulator (4) to ensure that a detection value AD1 of a photoelectric detector A (11) is continuously maximum, and locking the phase of a reference light path at the moment, namely effectively compensating the external influence on an optical fiber link of the unbalanced Mach-Zehnder interferometer constructed by a 2x2 optical fiber coupler (3), the phase modulator (4), an optical fiber circulator (5), an FP etalon (6), a detection reflector (7) and a 3x3 optical fiber coupler (8);
step 3, on the basis of the step 2, starting interferometric measurement of the detection point, reading a detection value AD2 corresponding to the photoelectric detector B (12) and a detection value AD3 corresponding to the photoelectric detector C (13) in real time in the measurement process, and respectively performing normalization processing on the read detection value AD2 of the photoelectric detector B (12) and the read detection value AD3 of the photoelectric detector C (13) to obtain corresponding normalized intensity I2 and normalized intensity I3; wherein: i2 ═ AD2/AD2_ max, I3 ═ AD3/AD3_ max;
step 4, presetting two different thresholds R1 and R2 in the microprocessor (15), and then acquiring the vibration or displacement information of the detection reflector (7) by using the normalized intensity I2 and the normalized intensity I3 obtained in the step 3, namely acquiring the vibration or displacement information of a detection point;
wherein: r1< R2, and R1 and R2 are both greater than 0 and less than 1.
7. The interferometry method according to claim 6, wherein said method comprises: in step 4, the normalized intensity I2 and the normalized intensity I3 obtained in step 3 are used to obtain the vibration or displacement information of the detection point, which specifically includes the following three situations:
when the normalized intensities I2 and I3 obtained in step 3 successively pass through thresholds R2 and R1 preset in a microprocessor, it is determined that the integer wavelength shift number N of the probe point is decreased by 1, i.e., N _ new ═ N-1, where N represents the integer wavelength shift number before the probe point is updated, i.e., the original integer wavelength shift number, and the initial value is 0; n _ new represents the integer wavelength shift number after the probe point is updated, i.e. the new integer wavelength shift number;
in this case, a phase threshold is introduced
The total displacement d L of the probe point can be obtained as shown in the following formula (1):
dL＝N_new*λ+dl； (1)
in formula (1), N _ new λ represents an integer wavelength shift portion, and dl represents a shift portion of less than 1 wavelength;
wherein the content of the first and second substances,
is the phase value corresponding to when I3 passes through R1 after I2;
the dl can be obtained by the reverse calculation of the light intensity expression of the interferometer, namely the light intensity change curve of the interference fringes caused by the vibration of the selected detection point can simultaneously meet the phase difference of I2 and I3
To obtain the result that,
the value range is [02 pi ]]；
When the phase difference is between
At the position of
And between 2 pi, then
When the phase difference is between
At 0 and
in between, then
(II) when the normalized intensities I3 and I2 obtained in the step 3 successively pass through thresholds R1 and R2 preset in a microprocessor, judging that the integer wavelength displacement number N of the detection point is increased by 1, namely N _ new is equal to N +1, wherein N represents the integer wavelength displacement number before the update of the detection point, namely the original integer wavelength displacement number, and the initial value is 0; n _ new represents the integer wavelength shift number after the probe point is updated, i.e. the new integer wavelength shift number;
in this case, a phase threshold is introduced
The total displacement d L of the probe point can be obtained as shown in the following formula (2):
dL＝N_new*λ-dl； (2)
in formula (2), N _ new λ represents an integer wavelength shift portion, and dl represents a shift portion of less than 1 wavelength;
wherein the content of the first and second substances,
is the corresponding phase value for I2 passing through R2 after I3;
the dl can be obtained by the reverse calculation of the light intensity expression of the interferometer, namely the light intensity change curve of the interference fringes caused by the vibration of the selected detection point can simultaneously meet the phase difference of I2 and I3
To obtain the result that,
the value range is [02 pi ]]；
When the phase difference is between
At 0 and
in between, then
When the phase difference is between
At the position of
And between 2 pi, then
(III) for other situations not conforming to the first or second conditions, when N is not equal to 0, the total displacement d L of the detection point can be obtained by using the currently adopted calculation formula, namely the total displacement d L of the detection point is obtained by using the formula (1) or the formula (2), when N is 0, the total displacement d L of the detection point is less than 1 wavelength, at the moment, the total displacement d L of the detection point can be reversely calculated by using an interferometer light intensity expression, namely, the light intensity change curve of interference fringes caused by vibration of the detection point can be selected to simultaneously meet the phase difference of I2 and I3
To obtain that
The value range is [02 pi ]]。
8. The interferometry method according to claim 7, wherein the interferometry method comprises: the value range of the threshold R1 is 0.2-0.4, and the value range of the threshold R2 is 0.6-0.8.
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Denomination of invention: An interference measuring device and method with reference light Effective date of registration: 20220310 Granted publication date: 20210416 Pledgee: Wuhan area branch of Hubei pilot free trade zone of Bank of China Ltd. Pledgor: Baoyu (Wuhan) laser technology Co.,Ltd. Registration number: Y2022420000056 |