CN111023982B - Contact laser interferometer displacement sensor and measurement method - Google Patents
Contact laser interferometer displacement sensor and measurement method Download PDFInfo
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- CN111023982B CN111023982B CN202010005142.2A CN202010005142A CN111023982B CN 111023982 B CN111023982 B CN 111023982B CN 202010005142 A CN202010005142 A CN 202010005142A CN 111023982 B CN111023982 B CN 111023982B
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- measuring rod
- collimator
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- optical fiber
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 29
- 238000000691 measurement method Methods 0.000 title claims description 3
- 238000005259 measurement Methods 0.000 claims abstract description 31
- 239000013307 optical fiber Substances 0.000 claims abstract description 16
- 238000005096 rolling process Methods 0.000 claims abstract description 6
- 230000003287 optical effect Effects 0.000 claims description 18
- 230000035559 beat frequency Effects 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 10
- 238000005516 engineering process Methods 0.000 description 9
- 239000000523 sample Substances 0.000 description 8
- 238000009434 installation Methods 0.000 description 2
- 238000005305 interferometry Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000002173 cutting fluid Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000004556 laser interferometry Methods 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
- G01B9/02002—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies
- G01B9/02003—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies using beat frequencies
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention relates to a contact type laser interference displacement sensor and a measuring method, which solve the problem that the measurement of large-size and high-precision parts cannot be directly realized in the prior art, and realize the precise measurement of the large-size and high-precision parts. The invention comprises a sensor shaft sleeve, a hollow measuring rod is arranged on the sensor shaft sleeve through a rolling pair fixed at the front end of the sensor shaft sleeve, a measuring rod and a reflecting mirror are sequentially arranged at the front end of the measuring rod, a collimator is arranged at the rear end of the sensor shaft sleeve, the collimator is connected with an optical fiber, and the optical fiber is connected with a frequency modulation continuous wave interference signal processor. The front end and the rear end of the measuring rod are respectively provided with a front limiting block and a rear limiting block, and the front limiting block and the rear limiting block are connected with the measuring rod through threads.
Description
Technical field:
The invention relates to a laser displacement sensor, in particular to a contact type laser interference displacement sensor and a measuring method.
The background technology is as follows:
In recent years, in the field of aerospace, automobile and ship manufacturing industry, the geometric measurement requirements of large-size and high-precision parts are higher and higher, and particularly, the requirements for real-time and large-scale production field measurement are more and more prominent, and as a displacement measurement medium, the development of a displacement sensor technology is also gradually changed. Currently, more displacement sensors are used in factories of factories, such as inductance sensors (LVDT), pneumatic sensors, grating displacement sensors, hall displacement sensors, laser triangulation displacement sensors and the like. In particular to an inductance displacement sensor, which is widely applied in the mechanical equipment industry due to the characteristics of contact type, anti-interference, corrosion resistance and the like. However, the inductance sensor has an inverse relation between the measurement range and the measurement precision due to the limitation of the measurement principle, and the measurement range of the inductance sensor meets the precision of 0.1 μm and only 2mm, and the measurement range of the inductance sensor meets the precision of 10mm and only 20 μm, so that the measurement of large-size and high-precision parts cannot be directly realized.
The laser calculates the displacement variation by adopting the laser wavelength by virtue of the characteristics of strong coherence, high resolution, good monochromaticity, strong interference resistance, frequency in the light wave frequency band and the like, has traceability of the length value, avoids errors caused by secondary or multiple value transmission substitution, and has very obvious advantages in precision measurement application, and the laser has the technologies of a pulse method, a phase method, a time flight method, an interferometry and the like at present. The frequency modulation continuous wave (Frequency Modulated Continuous Wave, FMCW) laser ranging system is an optical non-contact laser interferometry displacement measurement technique. Compared with other laser ranging methods, the interference signal obtained by the FMCW interferometry technology is a dynamic signal related to time, has stronger anti-interference capability, and has simpler distinguishing, whole period counting and phase subdivision of the phase shifting party of the interference signal. The FMCW interference adopts a DFB semiconductor laser with low cost and simpler structure, thereby having wide development prospect in large-size high-precision measurement.
The invention comprises the following steps:
The invention aims to provide a contact type laser interference displacement sensor and a measuring method, which solve the problem that the measurement of large-size and high-precision parts cannot be directly realized in the prior art, and realize the precise measurement of the large-size and high-precision parts.
In order to achieve the above purpose, the invention adopts the following technical scheme:
A contact type laser interference displacement sensor is characterized in that: the sensor comprises a sensor shaft sleeve, a hollow measuring rod is arranged on the sensor shaft sleeve through a rolling pair fixed at the front end of the sensor shaft sleeve, a measuring rod and a reflecting mirror are sequentially arranged at the front end of the measuring rod, a collimator is arranged at the rear end of the sensor shaft sleeve, the collimator is connected with an optical fiber, and the optical fiber is connected with a frequency modulation continuous wave interference signal processor.
The front end and the rear end of the measuring rod are respectively provided with a front limiting block and a rear limiting block, and the front limiting block and the rear limiting block are connected with the measuring rod through threads.
The cross sections of the measuring rod and the sensor shaft sleeve are round.
The reflector is connected with the measuring rod through threads or is adhered.
A measuring method of a contact type laser interference displacement sensor is characterized in that:
The linear frequency modulation continuous wave laser light wave enters a collimator through an optical fiber, a part of reflecting mirror in the collimator divides a light beam into two paths, one path returns to serve as a reference signal, the other path passes through the collimator and passes through a hollow measuring rod, and irradiates onto a total reflecting mirror arranged at the front end of the measuring rod, measurement light is reflected, in the optical fiber, the measurement light and the reference light meet and overlap to form an interference signal, a measuring probe contacts with the outline of a measured object during measurement and moves along with the change of the outline of the measured object, the measuring probe drives the reflecting mirror to move, so that the measuring optical path difference changes, a dynamic beat frequency interference signal with initial phase changing along with the linear change of the optical path difference is generated, the signal is demodulated by a frequency modulation continuous wave interference signal processor, and the change of displacement is calculated, wherein the calculation formula is as follows:
where OPD is the optical path difference, phi b0 is the primary phase of the interference beat signal, and lambda 0 is the center wavelength of the light wave.
Compared with the prior art, the invention has the following advantages and effects:
The laser has the characteristics of traceability, strong coherence, high resolution and the like, the frequency modulation continuous wave laser ranging is an optical non-contact laser interference displacement measurement technology, an interference signal is a dynamic signal related to time, the interference signal has stronger anti-interference capability, the interference signal phase shifting party is simpler to distinguish, count the whole period and subdivide the phase, and the displacement measurement with a large range (more than or equal to 1 m) and high precision (less than or equal to 0.01 mu m) can be realized.
The invention is based on FMCW laser continuous wave frequency modulation technology, fully utilizes the characteristics of small size, flexibility and easy installation of optical fiber sensing, innovatively combines the advantages of simple structure and convenient installation of a contact sensor to develop a wide-range and high-precision contact displacement sensor based on laser interference, not only effectively avoids the fatal influence of a workpiece on a production site caused by cutting fluid, lubricating fluid and the like on optical measurement, but also can adopt a cooperative target measurement technology to replace a non-cooperative target technology, reduce the difficulty and cost of an optical system, convert non-contact measurement into contact measurement, realize submicron-level precise detection of a part indication contour, expand the contradiction between the range and precision of a conventional inductance sensor and effectively solve the measurement problem of large size and high precision on an industrial site.
Description of the drawings:
Fig. 1 is a schematic structural view of the present invention.
In the figure, 1-measuring element, 2-reflecting mirror, 3-front limiting block, 4-measuring rod, 5-rolling pair, 6-rear limiting block, 7-laser beam, 8-sensor shaft sleeve, 9-collimator and 10-optical fiber.
The specific embodiment is as follows:
Referring to fig. 1, the invention relates to a contact type laser interference displacement sensor, which comprises a measuring probe 1, a reflecting mirror 2, a front limiting block 3, a measuring rod 4, a rolling pair 5, a rear limiting block 6, a laser beam 7, a sensor shaft sleeve 8, a collimator 9, an optical fiber 10 and a frequency modulation continuous wave interference signal processor. The front end of the measuring rod 4 is sequentially provided with a measuring probe 1 and a reflecting mirror 2, the measuring probe 1 and the measuring rod 4 are connected at the front end through threads, and the end part of the spherical measuring probe can be contacted with the outline of an object to be measured, so that the outline of the object is measured. The reflector 2 and the measuring rod 4 are connected or adhered through screw threads. The measuring rod 4 is arranged on the sensor shaft sleeve 8 through the rolling pair 5 fixed at the front end of the sensor shaft sleeve 8, the measuring rod 4 is of a hollow structure, the measuring rod 4 can move along the axial direction of the sensor shaft sleeve 8, and the sections of the measuring rod 4 and the sensor shaft sleeve 8 are circular. The front limiting block 5 and the rear limiting block 6 arranged at the front end and the rear end of the measuring rod are connected through threads, and the axial movement amount of the measuring rod 4, namely the measuring range of the sensor, can be adjusted by adjusting the feeding amount of the threads. The collimator 9 is arranged at the rear end of the sensor shaft sleeve 8, the laser beam 7 emitted by the collimator 9 irradiates onto the reflecting mirror 2 through the hollow measuring rod 4, the reflected beam returns to enter the collimator 9 in a primary path and forms an interference signal (or beat signal) with a reference beam of the collimator 9, the interference signal is sent into the frequency modulation continuous wave interference signal processor through the optical fiber 10, and the processor can calculate the optical path difference variable quantity through demodulation so as to realize displacement measurement.
The working principle of the invention is as follows: accurate measurement is realized by utilizing a laser interference technology, and the beat frequency signal light intensity is obtained under the assumption that the average light intensity of the reference light is I 1 and the average light intensity of the signal light is I 2
Wherein I 0＝I1+I2,vb is the frequency of the interferometric beat signal, Δv is the optical frequency modulation range, v m is the frequency of the modulated signal, c is the speed of light, phi b0 is the primary phase of the interferometric beat signal, and lambda 0 is the center wavelength of the optical wave.
It is obvious that the process is not limited to,
When in actual measurement, when a beam of linear frequency modulation continuous wave laser light waves enters the collimator 9 through the optical fiber 10, a part of reflecting mirrors in the collimator 9 divide the light beams into two paths, one path of the light beams returns to serve as reference signals, the other path of the light beams passes through the collimator and passes through the hollow measuring rod 4 to irradiate on a total reflecting mirror arranged at the front end of the measuring rod, and the reflected light beams are measuring light, and the two reflecting mirrors form the extrinsic Fabry-Perot cavity interferometer. Within the optical fiber 10, the measurement light and the reference light meet and overlap and form an interference signal. During measurement, the measuring probe 1 contacts with the outline of the measured object and moves along with the change of the outline of the measured object, the measuring probe 1 drives the reflecting mirror 2 to move, so that the measured optical path difference changes, a dynamic beat frequency interference signal with the initial phase changing linearly along with the optical path difference is generated, and the signal is received by the photoelectric detector and demodulated by the microprocessor, so that the change amount of displacement can be calculated. The calculation formula is shown as the following formula.
Where OPD is the optical path difference, phi b0 is the primary phase of the interference beat signal, and lambda 0 is the center wavelength of the light wave.
It can be seen that for each wavelength change in the optical path difference OPD, the cosine signal initial phase changes by 2pi and the beat signal moves by one period. Therefore, the optical path difference OPD can be calculated by measuring the amount of change (phase shift) of the primary phase of the beat signal.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and some practical embodiments, and variations and modifications may be made by those skilled in the art without departing from the inventive concept, which are all within the scope of the present invention.
Claims (3)
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| CN202010005142.2A CN111023982B (en) | 2020-01-03 | 2020-01-03 | Contact laser interferometer displacement sensor and measurement method |
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| CN111023982B true CN111023982B (en) | 2024-11-26 |
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| CN211121068U (en) * | 2020-01-03 | 2020-07-28 | 西安工业大学 | Contact displacement sensing device |
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| US7139446B2 (en) * | 2005-02-17 | 2006-11-21 | Metris Usa Inc. | Compact fiber optic geometry for a counter-chirp FMCW coherent laser radar |
| US9778022B1 (en) * | 2016-09-14 | 2017-10-03 | Asml Netherlands B.V. | Determining moving properties of a target in an extreme ultraviolet light source |
| CN108050941A (en) * | 2017-12-25 | 2018-05-18 | 西安工业大学 | A kind of CW with frequency modulation laser interference optical fiber displacement sensor and its displacement detecting method |
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