CN1019145B - Multi-way reused laser frequency modulation heterodyne interference optical fiber measuring instrument - Google Patents
Multi-way reused laser frequency modulation heterodyne interference optical fiber measuring instrument Download PDFInfo
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- CN1019145B CN1019145B CN 90110041 CN90110041A CN1019145B CN 1019145 B CN1019145 B CN 1019145B CN 90110041 CN90110041 CN 90110041 CN 90110041 A CN90110041 A CN 90110041A CN 1019145 B CN1019145 B CN 1019145B
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- optical fiber
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- gauge head
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Abstract
The present invention relates to a multiplex reused optical-fiber displacement measurer with laser frequency modulation and heterodyne interference, which belongs to precise measurement for displacement. The present invention leads light in the same light source to a fiber optic network loop to form a plurality of optical fiber interferometers which respectively and simultaneously meter all interference signals by frequency domain filters. The present invention is suitable for multipoint (multidimensional) long-distance simultaneous measurement. A range of measurement for each path is not less than 1mm, and the measuring accuracy is not lower than 0.05 micrometer. The present invention is also suitable for measuring objects with surface roughness of more than delta 3 smoothness. The present invention has the advantages of high sensitivity, electromagnetic interference resistance, noncontact type measurement, etc. A measuring head of the present invention has the advantages of small volume, compact structure and low cost, and has a wide application range.
Description
The invention belongs to the technical field of mechanical precision measurement, particularly belong to the precision measurement of displacement, and to other mechanical quantity that can be converted into displacement directly or indirectly and the measurement of physical quantity.
In the technical field of mechanical quantity precision measurement, utilize laser frequency-modulation, optical fiber sensing technology that displacement is carried out non-contact measurement and just beginning to enter practical application area at present.For example the applicant's application for a patent for invention " noncontact type displacement measurer for laser frequency-modulation optical fiber " (application number 88107425) of submitting to Patent Office on November 3rd, 88 is exactly the detector for displacement measuring of a kind of practicability wherein.This measuring instrument constitutes a kind of difference interference displacement surveying meter of optic fibre by semiconductor laser [1], laser frequency-modulation power supply [2], coupled lens [3], optical fiber [4], directional coupler [5], optical fiber gauge head [6], photoelectric detector parts such as [10], as shown in Figure 1.Its measuring principle is: make the laser of a branch of frequency modulation that semiconductor laser sends enter optical fiber [4] through coupled lens by the laser frequency-modulation power supply, be divided into by optical fiber directional coupler again and survey light [8] and demodulation reference light [9], respectively by two-way optical fiber [8], [9] conduction, surveying light penetrates from the optical fiber gauge head end face, emergent light is mapped on the measured object [7] and is reflected back toward gauge head, it and former detection light have a tested distance between the partial reflection light that the gauge head end face produces be the optical path difference of l (or have a relative time delay τ), this two bundles reflected light is interfered the formation beat signal mutually, the beat signal frequency spectrum is an each harmonic that is subjected to the δ sequence of function of Sinc FUNCTION MODULATION, the cycle of the δ sequence of function is former Laser Modulation frequencies omega s, and the position of beat frequency is positioned at the maximal value place of Sinc function.When carrying out displacement measurement, when optical path difference has subtle change amount △ τ, the beat frequency rate ω b that causes changes little, but at this moment the phase change of beat signal each harmonic is very big.This beat signal is received by photodetector, and the demodulation reference light receives the heterodyne frequency modulation of going to eliminate in the beat signal by another photodetector, utilizes the phase bit comparison to measure phase change then, thereby obtains displacement.
Adopt this laser fiber measuring technique to have advantages such as measuring accuracy height, range ability is big, interference resistance is strong.But this measuring instrument is only limited to spot measurement of measured object a part or monitoring, and in many fields such as industry, national defence, space flight, more and more needs and can measure simultaneously or certain part multiple spot is monitored simultaneously the measured object several sections.For satisfying the needs that multiple spot detects simultaneously, often need a plurality of identical measuring instruments, this can increase instrument cost, occupies than large space, but also can make troubles to use.
For overcoming the weak point of above-mentioned measuring instrument, the present invention proposes a kind of multiplex fibre optic detector for displacement measuring, can carry out displacement measurement simultaneously to the measured object multiple spot.
The present invention proposes the fine detector for displacement measuring of a kind of multi-way reused laser frequency modulation heterodyne interference optical, by semiconductor laser [1], laser frequency-modulation power supply [2], coupled lens [3], optical fiber [4] and optical fiber directional coupler [5], optical fiber gauge head [6], parts such as photoelectric detector [10] and signal detection system are formed, it is characterized in that by coupled lens, the fiber optic network loop that optical fiber and directional coupler constitute, form a plurality of common luminous source optical fiber heterodyne ineterferometers, promptly the modulated laser of frequency that is sent by semiconductor laser enters optical fiber through coupled lens, this optical fiber other end links to each other with a directed coupling mechanism, said laser beam is divided into multiple laser through directional coupler to be derived respectively by multi-channel optical fibre, every road fiber-optic output is equipped with gauge head, the part of this road light beam shines tested object point by gauge head, reflection is after gauge head enters optical fiber as surveying light, another part of this light beam directly reflects through the gauge head end face and returns optical fiber as reference light, said detection light and reference light are common light paths, they interfere the back to be received by photoelectric detector mutually, constitute an optical fiber heterodyne ineterferometer.Same each road optical fiber constitutes a plurality of optical fiber heterodyne ineterferometers, as shown in Figure 2.
The frequency modulation heterodyne principle of interference that is adopted by the present invention as can be known, the heterodyne beat signal frequency increases with delay time τ, be that single channel is measured in original technology, promptly have only one road signal to determine certain delay time τ, making this signal beat frequency rate ω b usually is first harmonic (ω b=ω s).And multiple signals are arranged in the multiplexed measurement of the present invention, such as two paths of signals, first via signal beat frequency rate ω b is set
1=ω s is provided with the delay time τ of the second road signal
2τ than first via signal
1Big some makes the difference △ ω b(△ ω b=ω b of beat frequency rate of two paths of signals
2-ω b
1) greater than ω s, (desirable ω b2=n ω s, n=1,2 ...), the beat frequency value difference of two paths of signals like this.The rest may be inferred, can have three the tunnel, the four tunnel ... the multiple signals that have nothing in common with each other Deng the beat frequency value.After these signals are received by same photodetector, more respectively by after the different bandpass filter of centre frequency, promptly exportable each drive test amount signal.
Above-mentioned fiber optic network loop can be combined by a plurality of 2 * 2 optical fiber directional couplers, also can be made up of the two-way output optical fibre coupling mechanism of multiterminal.The distance of the gauge head end face of a plurality of optical fiber heterodyne ineterferometers of forming of fiber optic network loop multi-channel optical fibre output terminal of being drawn and institute measuring point can be given the set a distance setting by different thus, partial reflection (transmission) surface perhaps is set in the middle of multi-channel optical fibre output terminal and optical fiber gauge head, make each road should the surface be different to give set a distance (at this moment with the distance of measured point, each road optical fiber gauge head is equated) with the distance of measured point, thereby make the beat signal of every drive test point different, these beat signals can be received by the photodetector in each road respectively, also can converge together and receive by same photodetector, take out each road signal by frequency domain filtering again and carry out the position and measure mutually, this is a kind of multiplexed scheme that adopts frequency division of the present invention.If be provided with between optical fiber gauge head end face and the institute measuring point in the such scheme to give set a distance identical, promptly the beat signal of Xing Chenging is identical, is received by the photodetector in each road respectively again, this is the another kind of multiplexed scheme that adopts framing of the present invention.The demodulation reference light that the present invention also can tell optical fiber directional coupler in the prior art omits.Save one road optical fiber and a photodetector, and restituted signal can be obtained by the Laser Modulation power supply.The present invention also can combine the multiplexed scheme that set of applications becomes framing to combine with frequency division with above-mentioned two kinds of schemes, the light input first order fiber optic network loop that is about to LASER Light Source is divided into the multichannel light beam, introduce the multi-channel optical fibre interferometer that fiber optic network loop, the second level forms the frequency domain frequency division more respectively, can avoid like this frequeney division multiple (FDM) multiplexing in, cross-talk effects between each time beat signal that frequency division causes too much, and the multiplexed middle too many shortcoming of photodetector of framing.
This detector for displacement measuring of the present invention is applicable to that multiple spot (dimension) detects at a distance simultaneously, the measurement characteristics on each road is identical, have highly sensitive, non-contact measurement, can be used for more coarse surperficial object detects, anti-electromagnetic interference (EMI), the gauge head volume is little, plurality of advantages such as whole surveying instrument compact conformation.This detector for displacement measuring of the present invention not only can be directly used in the Displacement Measurement amount, and can be used for measuring other mechanical quantity and the physical quantity that can directly or indirectly be converted into displacement, such as: because pressure causes the deformational displacement of film, thus can gaging pressure; Utilize the rising-heat contracting-cold effect of material, thereby can measure temperature; Utilize the magnetostrictive effect of some material, cause length of material to change, thereby can measure magnetic field; Utilize the piezoelectric effect of some crystal to cause the change in optical path length of crystal, thereby can measuring voltage or the like, promptly in above-mentioned various measurement applications as long as optical fiber gauge head of the present invention is linked to each other with parts with material to above-mentioned various mechanical quantity, physical quantity sensitivity again, can realize measurement to the difference amount.Therefore the present invention have, wide application.
Brief Description Of Drawings:
Fig. 1 is the displacement measurer for laser frequency-modulation optical fiber synoptic diagram of existing single channel gauge head
Fig. 2 is a multiplexed displacement measurer for laser frequency-modulation optical fiber synoptic diagram provided by the invention
Fig. 3 is an embodiment of the present invention general structure synoptic diagram
Wherein: [1] semiconductor laser [2] laser frequency-modulation power supply [3] coupled lens [4] optical fiber [5] optical fiber directional coupler [6] optical fiber gauge head [7] measured object [8] is surveyed light [9] demodulation reference light [10] photodetector [11] fiber optic network loop [12], [13] optical fiber directional coupler [14] temperature control system [15] divider [16] bandpass filter [17] phase detectors [18] numeration display
A kind of most preferred embodiment of the present invention is four road multiplexing fiber-optic detector for displacement measuring that frequency division combines with framing, general structure as shown in Figure 3, be described in detail as follows in conjunction with the accompanying drawings: this measuring instrument is by semiconductor laser [1], Laser Modulation power supply [2], coupled lens [3], optical fiber [4], optical fiber directional coupler [5,12,13], parts such as fibre-optical probe [6], photodetector [10] and detecting signal unit are formed.Laser Modulation power supply [2] provides semiconductor laser [1] bias current and makes this laser instrument send the laser beam that a branch of superposition has a sawtooth wave modulation signal.This light beam enters an optical fiber [4] through coupled lens [3], this optical fiber links to each other with first optical fiber directional coupler [5], derive by two road optical fiber respectively after making light beam be divided into two-beam, wherein first via optical fiber links to each other with second optical fiber directional coupler [12] again, make this road light beam be divided into first again, second bundle is surveyed light and is derived by two optical fiber that gauge head is housed respectively, and inject respectively on two tested object points [7], returning gauge head by the measured object point reflection again enters in the optical fiber, the reflected light of the tested object point of every bundle and the partial reflection light that produces from the gauge head end face have an optical path difference that equals tested distance 1 (or have a relative time delay τ), form and interfere, the two-way interference light is received by first photodetector [10] through second optical fiber directional coupler [12] again.Same the second road light beam of deriving by first optical fiber directional coupler, after entering the 3rd optical fiber directional coupler [13], optical fiber is divided into the 3rd, the 4th detecting light beam, equally, this third and fourth light beam forms interference by the light of measured object reflected back and the partial reflection light of the direct reflected back of this gauge head, and is together received by second photodetector [10 '] through the 3rd directional coupler [13].The detecting signal unit of this measuring instrument is by two groups of dividers [15] [15 '], four groups of bandpass filter [16a] [16b] [16 ' a] [16 ' b], phase rotation indicator [17a] [17b] [17 ' a] [17 ' b], numeration display [18a] [18b] [18 ' a] compositions such as [18 ' b].When using this instrument, at first first and second is surveyed the different distance of being arranged to of gauge head with the tested object point of light, different time delays is promptly arranged, make that first via beat frequency rate is ω s, the second the tunnel is 4 ω s, same the 3rd, the 4th detecting head gauge head and tested object point also are arranged to as above different distance, and first and second photodetector receives two bundles respectively and has different optical path difference (l like this
1, l
2) interference light, therefore produce the beat signal of different difference interferences, beat frequency signal can be eliminated former heterodyne modulation after the reference restituted signal of Laser Modulation power supply output is sent into the divider processing in addition, and obtaining beat frequency rate ω b again after bandpass filter is nw
(n=1,2 ... k), phase change is w
oThe beat signal ω of τ
oBe laser frequency, I(t)=A cos(nw
T+w
oτ).Utilize phase rotation indicator relatively to measure a phase w again
oThe variation of τ, thus record displacement.Can import the numeration display from the signal of phase rotation indicator output and demonstrate measurement result.This measuring instrument also can be input to by computer interface and carry out the data in real time processing in the computing machine.
Stable for the frequency of light wave that guarantees semiconductor laser, present embodiment also can adopt temperature control system [14].This temperature control system is made up of semiconductor cooler, thermal sensing element and temperature-adjusting circuit.Present embodiment Laser Modulation power supply adopts the sawtooth wave modulation, has advantages such as the system of separating method is easy, the modulation linearity scope is big, but also can adopt sine wave modulation.The position is detected mutually and can be adopted striped numeration or phase place comparative approach, and present embodiment adopts the phase bit comparison can improve measuring accuracy greatly.The optical fiber gauge head of present embodiment adopts GRIN Lens, and its parameter can be decided according to the characteristics of measured workpiece.The utility model semiconductor laser power is more than the 5mw.
The measurement range that light is surveyed on each road of present embodiment is all greater than 1mm, and measuring accuracy is better than 0.05 μ m, and can have surfaceness
The object of 3 above smooth finish carries out displacement measurement.
Claims (4)
1, the fine detector for displacement measuring of multi-way reused laser frequency modulation heterodyne interference optical, by semiconductor laser, the laser frequency-modulation power supply, coupled lens, optical fiber and optical fiber directional coupler, optical fiber gauge head, parts such as photoelectric detector and signal detection system are formed, it is characterized in that by said coupled lens, a plurality of common luminous source optical fiber heterodyne ineterferometers are formed in the fiber optic network loop that optical fiber and directional coupler constitute, promptly the modulated laser of frequency that is sent by said semiconductor laser enters optical fiber through said coupled lens, this optical fiber other end links to each other with said directional coupler, said laser beam is divided into multiple laser through this directional coupler, derive respectively by multi-channel optical fibre, every road fiber-optic output is equipped with said gauge head, this gauge head end face is a part reflecting face, the part of this road light beam shines tested object point by this gauge head, reflection is after this gauge head enters optical fiber as surveying light, another part of this light beam through the direct reflected back optical fiber of gauge head end face as reference light, said detection light and reference light be light path altogether, they interfere the back to be received by said photoelectric detector mutually, constitute an optical fiber heterodyne ineterferometer, same said each road light constitutes a plurality of optical fiber heterodyne ineterferometers, the gauge head end face of said multi-channel optical fibre output terminal is pressed different preset distance settings with the distance of institute's measuring point, thereby make the beat signal of every drive test point different, receive by same photoelectric detector, constitute the multiplexed of frequency division.
2, the fine detector for displacement measuring of multi-way reused laser frequency modulation heterodyne interference optical, by semiconductor laser, the laser frequency-modulation power supply, coupled lens, optical fiber and optical fiber directional coupler, optical fiber gauge head, parts such as photoelectric detector and signal detection system are formed, it is characterized in that by said coupled lens, a plurality of common luminous source optical fiber heterodyne ineterferometers are formed in the fiber optic network loop that optical fiber and directional coupler constitute, promptly the modulated laser of frequency that is sent by said semiconductor laser enters optical fiber through said coupled lens, this optical fiber other end links to each other with said directional coupler, said laser beam is divided into multiple laser through this directional coupler, derive respectively by multi-channel optical fibre, every road fiber-optic output is equipped with said gauge head, this gauge head end face is the total transmissivity face, the partial reflection surface is set in the middle of fiber-optic output and the gauge head, the part of this road light beam shines tested object point by this gauge head, reflection is after gauge head enters optical fiber as surveying light, another part of this light beam directly returns optical fiber as reference light through said partial reflection surface, said detection light and reference light be light path altogether, they interfere the back to be received by said photoelectric detector mutually, constitute an optical fiber heterodyne ineterferometer, partial reflection surface in said each road fiber-optic output is different preset distances with measured distance, thereby make the beat signal of every drive test point different, receive by same photodetector, constitute the multiplexed of frequency division.
3, instrument is surveyed in the fine displacement of multi-way reused laser frequency modulation heterodyne interference optical, by semiconductor laser, the laser frequency-modulation power supply, coupled lens, optical fiber and optical fiber directional coupler, optical fiber gauge head, parts such as photoelectric detector and signal detection system are formed, it is characterized in that by said coupled lens, optical fiber and directional coupler constitute first order fiberoptical networking loop, the light of said LASER Light Source is input to said first order fiberoptical networking loop, be divided into the multichannel light beam, each road light beam is input to by optical fiber, a plurality of framing frequency division combination multiplexing fiber-optic heterodyne ineterferometers are formed in the fiber optic network loop, the second level that directional coupler constitutes.
4, detector for displacement measuring as claimed in claim 3, it is characterized in that said Laser Modulation power supply provides the semiconductor laser bias current and makes this laser instrument send the laser beam that a branch of superposition has a sawtooth wave modulation signal, this light beam enters an optical fiber through coupled lens, this optical fiber links to each other with first optical fiber directional coupler, derive by two-way optical fiber respectively after making light beam be divided into two-beam, constitute said first order fiber optic network loop thus, wherein first via optical fiber links to each other with second optical fiber directional coupler again, make this road light beam be divided into first again, second bundle is surveyed light and is derived by two optical fiber that gauge head is housed respectively, same the second road light beam of deriving by first optical fiber directional coupler, after entering the 3rd optical fiber directional coupler, optical fiber is divided into the 3rd, the 4th detecting light beam, constitute fiber optic network loop, the said second level thus, said first, second bundle is surveyed light, inject respectively on two tested object points, returning gauge head by the measured object point reflection again enters in the optical fiber, the reflected light of the tested object point of every bundle has an optical path difference that equals tested apart from l with the partial reflection light that produces from the gauge head end face, form and interfere, the two-way interference light is received by first photodetector through second optical fiber directional coupler again, equally, this is the 3rd years old, four light beams form interference by the light of measured object reflected back and the partial reflection light of the direct reflected back of this gauge head, and are together received by second photodetector through the 3rd directional coupler.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 90110041 CN1019145B (en) | 1990-12-29 | 1990-12-29 | Multi-way reused laser frequency modulation heterodyne interference optical fiber measuring instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 90110041 CN1019145B (en) | 1990-12-29 | 1990-12-29 | Multi-way reused laser frequency modulation heterodyne interference optical fiber measuring instrument |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1052369A CN1052369A (en) | 1991-06-19 |
| CN1019145B true CN1019145B (en) | 1992-11-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 90110041 Expired CN1019145B (en) | 1990-12-29 | 1990-12-29 | Multi-way reused laser frequency modulation heterodyne interference optical fiber measuring instrument |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010045853A1 (en) * | 2008-10-21 | 2010-04-29 | 华为技术有限公司 | Method and device for monitoring submarine cable systems |
Families Citing this family (9)
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|---|---|---|---|---|
| DE502007001288D1 (en) * | 2007-01-02 | 2009-09-24 | Isis Sentronics Gmbh | Position detection system for contactless interferometric detection of the spatial position of a target object and thus equipped scanning system |
| CN101324445B (en) * | 2008-07-30 | 2010-06-02 | 哈尔滨工程大学 | Distributed optical fiber white light interference sensor array based on adjustable Fabry-Perot resonant cavity |
| CN102230826B (en) * | 2011-03-31 | 2012-08-22 | 上海理工大学 | Signal processing method for heterodyne interferometer |
| CN103854722A (en) * | 2012-12-06 | 2014-06-11 | 国家电网公司 | Mixed mode type temperature measurement communication phase conductor and temperature measurement communication system |
| CN106197289A (en) * | 2016-08-15 | 2016-12-07 | 桂林创研科技有限公司 | Optical fiber length measuring system |
| CN107917669B (en) * | 2017-11-15 | 2020-11-13 | 嘉兴鼎尚信息科技有限公司 | Demodulation method of optical fiber displacement sensor |
| 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 |
| CN110006349A (en) * | 2019-04-29 | 2019-07-12 | 西安交通大学 | A kind of high tolerance is total to optical path grating interferometer |
| CN110793445A (en) * | 2019-10-24 | 2020-02-14 | 中国工程物理研究院流体物理研究所 | Multi-channel synchronous absolute distance measuring method and device based on all-fiber frequency domain interference |
-
1990
- 1990-12-29 CN CN 90110041 patent/CN1019145B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010045853A1 (en) * | 2008-10-21 | 2010-04-29 | 华为技术有限公司 | Method and device for monitoring submarine cable systems |
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| CN1052369A (en) | 1991-06-19 |
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