CN202614366U - Novel high-precision heterodyne laser vibration meter - Google Patents

Novel high-precision heterodyne laser vibration meter Download PDF

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CN202614366U
CN202614366U CN 201220124814 CN201220124814U CN202614366U CN 202614366 U CN202614366 U CN 202614366U CN 201220124814 CN201220124814 CN 201220124814 CN 201220124814 U CN201220124814 U CN 201220124814U CN 202614366 U CN202614366 U CN 202614366U
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frequency
signal
digital
light
heterodyne laser
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刘爱东
于梅
杨丽峰
左爱斌
马明德
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National Institute of Metrology
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Abstract

The utility model discloses a novel high-precision heterodyne laser vibration meter. The novel high-precision heterodyne laser vibration meter includes an optical component that is suitable for producing interference light by utilizing laser, wherein the interference light has a frequency component related with a first frequency shift caused by Doppler effect and a second frequency value of the frequency shift of reference light; a photoelectric converter configured to converting the interference light to electric measurement signals; a mixer configured to mixing the electric measurement signals with external vibration signals having third frequency, thereby obtaining mixed signals; a digital converter configured to convert the mixed signals into digital signals; a digital calculation unit configured to perform digital operation of the digital signals, thereby obtaining vibration information of a to-be-detected object; and a frequency discriminator coupled with the digital converter, thereby discriminating the first frequency shift from the digital signals. And the external vibration signals are generated based on the first frequency shift discriminated by the frequency discriminator.

Description

A kind of novel high-precision heterodyne laser vialog
Technical field
The utility model relates to the laser interferometry field, relates in particular to utilize Doppler's principle to measure the heterodyne laser vialog of the movable information of measurand.
Background technology
At present, the heterodyne laser vialog is widely used in the measurement to moving object, especially is applied in the vibration survey field.Heterodyne laser vialog general using Doppler's principle is measured.Fig. 1 shows the synoptic diagram according to the heterodyne laser vialog 100 of prior art.As shown in Figure 1, heterodyne laser vialog 100 can be divided into two parts on the whole, i.e. optics part 110 and signal processing 120.Generally speaking; Optics part 110 comprises measures required optics to testee 130; And output measures the electric signal cause signal processing 120 obtained and carries out signal Processing, to obtain various movable informations, the especially vibration information of relevant testee 130.
Particularly, in optics part 110, the light of lasing light emitter 1110 emissions is divided into reference light and measuring light by polarization spectroscope 1120.Measuring light focuses on the testee 130 through focus lens group 1130, when testee 130 motions, can produce a frequency displacement Δ f.In order to confirm the direction of vibration of testee 130, in the light path of reference light, use the frequency that generates by crystal oscillator unit 1140 to be f dThe crystal oscillator signal drive acousto-optic modulator 1150 (for example for bragg cell) and come reference light is carried out shift frequency.The measuring light of returning from testee 130 polarization spectroscope 1160 with have frequency offset f dReference light interfere, therefore interference light carries out opto-electronic conversion by photelectric receiver 1170, and comprises frequency component (f to signal processing 120 outputs d+ Δ f) modulation signal U 1, promptly
Figure 412945DEST_PATH_IMAGE001
In signal processing 120,, need carry out the frequency reducing demodulation to the electric signal that is received for the ease of data acquisition.For this reason, at first in frequency mixer 1210, with this electric signal U 1And have certain frequency f lOutside oscillator signal
Figure 540474DEST_PATH_IMAGE002
Carry out mixing.In low-pass filter 1220, carry out LPF subsequently and remove HFS; Thereby obtain signal and be modulated at the carrier signal on the low frequency signal, be i.e.
Figure 257894DEST_PATH_IMAGE003
.Carrier signal U on low frequency signal converts digital signal into via A/D data acquisition unit 1230 subsequently; And then in digital operation unit 1240, carry out digital operation and handle; Thereby obtain the speed of the vibration of relevant testee 130, physical parameters such as acceleration, displacement.The digital operation of carrying out in the relevant digital operation unit 1240 is handled, can be referring to the particular content of international standard ISO16063-II part, and this content is all incorporated at this by reference, is not giving unnecessary details.
Should be noted in the discussion above that in the heterodyne laser vialog 100 of prior art, have two reference frequencies, the modulating frequency f of a crystal oscillator signal when being used for that in optics part 110 reference light carried out frequency displacement d, another is the outside oscillator signal U that electric signal will carry out mixing with it in signal processing 120 2Frequency f lThese two signals are driven by two crystal oscillators respectively, and crystal oscillator can receive the influence in environmental factor such as temperature, magnetic field etc., so in fact the oscillation frequency of these two signals exists variation, promptly is respectively f d+
Figure 89321DEST_PATH_IMAGE004
With, f l+ Therefore the electric signal by photelectric receiver 1170 outputs is
Figure 975424DEST_PATH_IMAGE006
, and outside oscillator signal is
Figure 367091DEST_PATH_IMAGE007
.Low frequency carrier signal letter signal then and become and be
Figure 690625DEST_PATH_IMAGE008
.Therefrom can find out; These two variations and
Figure 477501DEST_PATH_IMAGE005
bring error can for measurement result Δ f; Δ f is along with speed reduces and can reduce; When Δ f and ( ) near the time; It is big that this error effect factor becomes, thereby make existing heterodyne laser vialog measuring error become big.
In addition because Δ f is the amount that changes with speed, but its but carrier wave at a fixed-bandwidth frequency (f l-f d) signal on, that is to say that for the AD data acquisition of same SF, no matter how Δ f changes, resolution is fixed.Therefore, when cause Δ f hour owing to speed is lower, can there be the not high problem of measuring accuracy in existing heterodyne laser vialog.
Therefore, be desirable to provide and a kind ofly can further improve the measuring accuracy of heterodyne laser vialog, and make the heterodyne laser vialog can be applied to the new heterodyne laser vialog in fields such as low-frequency vibration object measurement well.
The utility model content
For this reason, the utility model provides a kind of new heterodyne laser vialog that can solve or alleviate at least a portion of the problems referred to above.
An aspect according to the utility model; A kind of heterodyne laser vialog is provided; Comprise optics, be suitable for utilizing laser to generate interference light, wherein this interference light have with first frequency displacement that causes owing to Doppler effect and reference light by the relevant frequency component of the second frequency value of frequency displacement; Photoelectric commutator is configured to convert interference light into electric measurement signal; Frequency mixer is configured to electric measurement signal and the outside oscillator signal with the 3rd frequency are carried out mixing to obtain mixed frequency signal; Digital quantizer is configured to convert said mixed frequency signal into digital signal; Digital operation unit is configured to said digital signal is carried out digital operation to obtain the vibration information of relevant measurand.
Heterodyne laser vialog according to the utility model also comprises frequency discriminator, and it is couple to digital quantizer, thereby from digital signal, identifies first frequency displacement, and outside oscillator signal is based on first frequency displacement that frequency discriminator identified and generate.
Because the frequency of the outside oscillator signal that adopts during the frequency mixer mixing is relevant with first frequency displacement; Therefore, the low frequency part after the mixing no longer is a fixed-bandwidth frequency, but changes along with the variation of first frequency displacement; Like this; Just can lowly cause first frequency displacement hour crossing, still higher sampling resolution can be provided, thereby improve measuring accuracy owing to measurand speed.
Alternatively; Heterodyne laser vialog according to the utility model also comprises the local oscillation signal generator; Be configured to receive the outside oscillator signal that first frequency displacement that frequency discriminator identifies and the crystal oscillator signal with second frequency generate the 3rd frequency; Wherein the value of the 3rd frequency is set to the product and the second frequency sum of first frequency displacement and pre-determined factor, and pre-determined factor is the preset value greater than 1.
Alternatively, in the heterodyne laser vibration measurer, optics comprises first spectroscope, is configured to the laser beam that lasing light emitter generates is divided into reference light and measuring light; Object lens are configured to measuring light projected and have on the measurand and receive from the measuring light of measurand reflection; Acousto-optic modulator is driven by the crystal oscillator signal with second frequency said reference light is carried out frequency displacement; And second spectroscope, be configured to interfere to generate interference light to the reflection measurement light that receives by object lens with by the reference light after the acousto-optic modulator frequency displacement.
Alternatively, also comprise the crystal oscillator source according to the heterodyne laser vialog of the utility model, be used to provide the signal of the crystal oscillator with second frequency, wherein this crystal oscillator signal with second frequency is offered optics and local oscillation signal generator simultaneously.
Owing in optics, reference light is carried out the crystal oscillator signal of frequency displacement and crystal oscillator signal that the local oscillation signal generator is adopted from same crystal oscillator source; In the low frequency component of the mixed frequency signal that produces by the frequency mixer mixing; To reference light carry out frequency displacement and the foreign frequency introduced is disturbed and outside oscillator signal in frequency interferences can cancel out each other, thereby further improved the measuring accuracy of heterodyne laser vialog.
Description of drawings
Through reading the hereinafter detailed description of the preferred embodiment, various other advantage and benefits will become cheer and bright for those of ordinary skills.Accompanying drawing only is used to illustrate the purpose of preferred implementation, and does not think the restriction to the utility model.And in whole accompanying drawing, represent identical parts with identical reference symbol.Wherein in the accompanying drawings, the alphabetic flag after the reference number is indicated a plurality of identical parts, when these parts of general reference, with omitting its last alphabetic flag.In the accompanying drawings:
Fig. 1 schematically shows the synoptic diagram of heterodyne laser vialog 100 of the prior art; And
Fig. 2 schematically shows the synoptic diagram according to the heterodyne laser vialog 200 of the utility model embodiment.
Embodiment
Below in conjunction with accompanying drawing and concrete embodiment the utility model is done further to describe.
Fig. 2 schematically shows the synoptic diagram according to the heterodyne laser vialog 200 of an embodiment of the utility model.In Fig. 2, illustrate with identical or similar mode with the identical or similar parts of parts of heterodyne laser vialog 100 of the prior art shown in Figure 1, and no longer be explained in further detail.
As shown in Figure 2, be similar to existing heterodyne laser vialog shown in Figure 1, heterodyne laser vialog 200 can be divided into optics part 210 and signal processing 220 on the whole.The laser beam that optics part 210 comprises the lasing light emitter 2110 that is used to generate laser beam, utilize lasing light emitter 2110 to generate comes measurand 230 is carried out the optical module 2120 of difference interference measuring and the interference light that optical module generated is carried out optical transition to obtain the photoelectric commutator 2130 of electric signal.
Optical module 2120 have with Fig. 1 in the similar parts of respective optical parts put down in writing.As heterodyne laser interference measure desired; Optical module can be divided into reference light and measuring light with the laser beam that is generated; With measuring light project on the measurand 230 and receive from the measurand reflection, have the measuring light of frequency displacement Δ f, with frequency f of reference light frequency displacement d, to interfere to generate interference light to the measuring light that reflected with through the reference light of frequency displacement then, this interference light has frequency component (f aspect frequency d+ Δ f).Alternatively, frequency f dBe set to the 40M hertz.
Should be noted in the discussion above that the utility model is not limited to the specific optical components in the particular optical assembly 2120, any optics that is suitable in the heterodyne laser interferometry, adopting is all within the protection domain of the utility model.
According to an embodiment of the utility model, in optical module 2120, first spectroscope 2140 can be divided into reference light and measuring light with the laser beam that lasing light emitter 2110 generates.Objective lens 2150 projects measuring light on the measurand 230 and receives from the measuring light of measurand 230 reflections through for example optical processing such as polarization, focusing.Objective lens 2150 can adopt this area optical texture commonly used, and alternatively, objective lens 2150 can comprise spectroscope 2152 and lens 2154.Because Doppler effect, the measuring light that is reflected has frequency displacement Δ f.And in reference path, acousto-optic modulator 2160 utilizes the crystal oscillator signal with frequency f d to come reference light is carried out frequency displacement.Like this, when the measuring light that reflects from measurand 230 and through the reference light of frequency displacement when second spectroscope 2170 is interfered, the interference light that is generated has frequency component (f aspect frequency d+ Δ f).
Photoelectric commutator 2130 receives this interference light, and converts this light to electric signal
Figure 93476DEST_PATH_IMAGE001
.By signal processing 220 this electric signal is further handled to obtain the detailed movement information of measurand subsequently.
Signal processing 220 comprises frequency mixer 2210, and it can utilize has frequency f lOutside oscillator signal U 2(
Figure 554544DEST_PATH_IMAGE010
) and electric signal U 1Carry out mixing to obtain mixed frequency signal.Because mixed frequency signal can have frequency f l, f dWith the various array modes of Δ f, and for subsequent treatment, the low frequency component f in the mixed frequency signal l-f d-Δ f is just enough.Therefore; Alternatively; Signal processing 220 also comprises the low-pass filter 2220 that is couple to frequency mixer 2210; Come mixed frequency signal is carried out LPF to remove the HFS of mixed frequency signal; To obtain the low frequency component
Figure 171339DEST_PATH_IMAGE003
in the aliasing signal, subsequently low frequency signal U is sent to digital quantizer 2230 and convert mixed frequency signal into digital signal.Digital quantizer 2230 can be that any being suitable for analog signal conversion is the analog to digital converter of digital signal.2240 pairs of these digital signals of digital operation unit are carried out digital operation to obtain the movable information of relevant measurand.The digital operation of carrying out in the relevant digital operation unit 2240 is handled, can be referring to the particular content of international standard ISO16063-II part, and this content is all incorporated at this by reference, is not giving unnecessary details.
Signal processing 220 also comprises the frequency discriminator 2250 that is couple to digital quantizer 2230, from digital signal, to identify frequency displacement Δ f.Have multiple mode and from digital signal, identify CF.For example, just provide the correspondent frequency measurement function can be used for differentiating frequency from digital signal in the Labview kit, this frequency discrimination function can adopt in the frequency discriminator 2250 of the utility model.The frequency displacement Δ f that frequency discriminator 2250 is identified can be used for being created on the outside oscillator signal U2 that frequency mixer 2210 adopts, the therefore frequency f of outside oscillator signal U lInclude fixed frequency part f D1With with the relevant part of frequency displacement Δ f.Like this, lowly cause frequency displacement Δ f hour when crossing, f owing to measurand speed l-f d-Δ f is also corresponding less, thereby still higher sampling resolution can be provided, thereby has improved measuring accuracy.
Alternatively, signal processing 220 also comprises and is used for local oscillation signal generator 2260, is couple to frequency discriminator 2250 and receives frequency displacement Δ f, and receive simultaneously and have fixed frequency f D1Crystal oscillator signal f D1, carry out mixing to generate outside oscillator signal U and to send to frequency mixer 2210.The frequency f of the oscillator signal U that local oscillation signal generator 2260 is generated lWith fixed frequency f D1And has following relation, f between the frequency displacement Δ f l=f D1+ a 0* Δ f.Pre-determined factor a 0Be preset fixed value, it is set to greater than 1.In practice, can be with a 0Be set to 2 or 1.5.Like this, the digital signal that digital quantizer provided has (f D1-f d)+(a 0-1) low frequency component of * Δ f.If f D1And f dFully approaching, the digital signal that then offers digital operation unit has the frequency component relevant with Δ f, and it changes along with the variation of measurand speed, thereby higher resolution can be provided.
Can find out from above, for higher measuring accuracy, f are provided D1And f dShould be fully approaching.According to an embodiment of the utility model, can be with f D1And f dBe set to identical value.For example can be with f D1And f dAll be set to 40MHz.Yet as the utility model background technology part is introduced, if offering the crystal oscillator signal of local oscillation signal generator 2260 is provided by different crystal oscillator sources with the crystal oscillator signal that offers acousto-optic modulator 2160, even with f D1And f dValue is set to identical, also can cause f owing to there is different skews in each crystal oscillator source oscillation frequency that causes affected by environment D1And f dThere is actual difference.
Therefore, alternatively, in order to make f D1And f dFully approaching, according to an embodiment of the utility model, the heterodyne laser vialog also comprises single crystal oscillator source 240, is used for providing simultaneously having frequency f dThe crystal oscillator signal give acousto-optic modulator 2160 and local oscillation signal generator 2260.Like this, can further improve measuring accuracy.
Heterodyne laser vialog according to the utility model utilizes single crystal oscillator source to provide the crystal oscillator signal to optical module and local oscillation signal generator; Base when thereby the common use of the external reference signal that makes laser vibration measurer adopt is same, this reduces the disturbance that environmental factor causes.On the other hand, become one to the local oscillation signal that is used for frequency reducing according to the design through frequency discriminator and frequency mixer etc. of the heterodyne laser vialog of the utility model and follow one that frequency displacement changes and follow signal, this has further improved Measurement Resolution.
It should be noted that the foregoing description describes the utility model rather than the utility model is limited, and those skilled in the art can design alternative embodiment under the situation of the scope that does not break away from accompanying claims.In claim, should any reference symbol between bracket be configured to the restriction to claim.Word " comprises " not to be got rid of existence and is not listed in element or step in the claim.Being positioned at word " " or " " before the element does not get rid of and has a plurality of such elements.The utility model can be realized by means of the hardware that includes some different elements and by means of the computing machine of suitably programming.In having enumerated the unit claim of some devices, several in these devices can be to come imbody through same hardware branch.Any order is not represented in the use of word first, second and C grade.Can be title with these word explanations.

Claims (7)

1. heterodyne laser vialog is characterized in that comprising:
Lasing light emitter is configured to generate laser beam;
Optical module; Be configured to the laser beam that is generated is divided into reference light and measuring light; With measuring light project on the measurand and receive from the measurand reflection, have a measuring light of first frequency displacement; The reference light frequency displacement is reached the second frequency value, subsequently to from the measuring light of measurand reflection with frequency displacement reference light interfere with the generation interference light;
Photoelectric commutator is configured to convert said interference light into electric measurement signal;
Frequency mixer is couple to said photoelectric commutator and is configured to said electric measurement signal and the outside oscillator signal with the 3rd frequency are carried out mixing to obtain mixed frequency signal;
Digital quantizer is couple to said frequency mixer and is configured to and converts said mixed frequency signal into digital signal; And
Digital operation unit is couple to said digital quantizer and is configured to said digital signal is carried out digital operation obtaining the vibration information of relevant measurand, and
Frequency discriminator is couple to said digital quantizer, and from said digital signal, to identify said first frequency displacement, wherein said outside oscillator signal generates based on first frequency displacement that is identified.
2. heterodyne laser vialog as claimed in claim 1; It is characterized in that also comprising the local oscillation signal generator; Be couple to said frequency discriminator and be configured to receive the outside oscillator signal that first frequency displacement that said frequency discriminator identifies generates said the 3rd frequency; The value of wherein said the 3rd frequency is set to the product and the second frequency sum of first frequency displacement and pre-determined factor, and said pre-determined factor is the preset value greater than 1.
3. heterodyne laser vialog as claimed in claim 2; It is characterized in that also comprising the crystal oscillator source; Be used to provide said crystal oscillator signal with second frequency, the crystal oscillator signal of wherein said second frequency is offered said optical module and said local oscillation signal generator simultaneously.
4. like claim 2 or 3 described heterodyne laser vialogs, it is characterized in that said pre-determined factor is 2.
5. like claim 2 or 3 described heterodyne laser vialogs, it is characterized in that said second frequency is 40MHz.
6. like claim 2 or 3 described heterodyne laser vialogs; It is characterized in that also comprising low-pass filter; Be couple to said frequency mixer; So that said mixed frequency signal is carried out LPF removing the HFS of said mixed frequency signal, and the mixed frequency signal that will pass through filtering sends to said digital quantizer.
7. like claim 2 or 3 described heterodyne laser vialogs, it is characterized in that said optics comprises:
First spectroscope is configured to the laser beam that is generated is divided into reference light and measuring light;
Object lens are configured to measuring light projected and have on the measurand and receive from the measuring light of measurand reflection;
Acousto-optic modulator is driven by said crystal oscillator signal with second frequency said reference light is carried out frequency displacement; And
Second spectroscope is configured to interfering to generate interference light by the reflection measurement light of object lens reception with by the reference light after the acousto-optic modulator frequency displacement.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102620811A (en) * 2012-03-29 2012-08-01 中国计量科学研究院 Novel high-precision heterodyne laser vibration measuring instrument
CN103308149A (en) * 2013-06-24 2013-09-18 中国航空工业集团公司北京长城计量测试技术研究所 Machine vision synchronous focusing scanning type laser vibration measuring device
CN103884418A (en) * 2014-04-17 2014-06-25 山西大学 Tuning fork type quartz crystal oscillator resonant frequency measurement method based on sound excitation and device
CN104406626A (en) * 2014-11-05 2015-03-11 中国矿业大学 Laser vibration measurement-based impact ground pressure danger zone evaluation method
US20220390756A1 (en) * 2021-05-28 2022-12-08 Seiko Epson Corporation Laser interferometer and method for controlling laser interferometer

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102620811A (en) * 2012-03-29 2012-08-01 中国计量科学研究院 Novel high-precision heterodyne laser vibration measuring instrument
CN102620811B (en) * 2012-03-29 2014-04-16 中国计量科学研究院 Novel high-precision heterodyne laser vibration measuring instrument
CN103308149A (en) * 2013-06-24 2013-09-18 中国航空工业集团公司北京长城计量测试技术研究所 Machine vision synchronous focusing scanning type laser vibration measuring device
CN103884418A (en) * 2014-04-17 2014-06-25 山西大学 Tuning fork type quartz crystal oscillator resonant frequency measurement method based on sound excitation and device
CN103884418B (en) * 2014-04-17 2015-12-09 山西大学 Based on measuring method and the device of the tuning-fork type quartz crystal oscillator resonance frequency of acoustically-driven
CN104406626A (en) * 2014-11-05 2015-03-11 中国矿业大学 Laser vibration measurement-based impact ground pressure danger zone evaluation method
CN104406626B (en) * 2014-11-05 2017-04-19 中国矿业大学 Laser vibration measurement-based impact ground pressure danger zone early warning method
US20220390756A1 (en) * 2021-05-28 2022-12-08 Seiko Epson Corporation Laser interferometer and method for controlling laser interferometer

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