Pressure-type optical fiber is slightly variable sensorTechnical field
It is big in particular for high-precision the present invention relates to the optical fibre displacement sensor that a kind of measurement is greater than 100mm micro-displacementThe optical fibre displacement sensor of range measurement micro-displacement.
Background technique
Optical fiber sensing technology is using light wave as carrier, and optical fiber is medium, perceives and transmit the novel of extraneous measured signalSensing technology.Main problem of the fibre optical sensor for actual measurement is prolonged drift effect.The drift of fibre optical sensorDecaying of the effect from optical fiber transmission line, coupler and beam splitter characteristic is not perfect, light source output is unstable and the shadow of detectorRing etc..The research of single optical fiber sensor has entered practical stage, but it can not be suitable for the survey of multi-parameter, multivariableAmount, and actual measurand often needs to measure several different parameters, such as the running state monitoring of aircraft engine, just needsThe various physical parameters such as its temperature, strain, pressure are monitored simultaneously, it, can if measured using isolated sensorThe complexity and monitoring cost of raising system, can also reduce the reliability of system.
With the rapid development of optic fibre manufacturing technology and the further investigation of fiber optic materials, optical fiber sensing technology has also been obtained fastlySpeed development.Fibre optical sensor compared with traditional various kinds of sensors, have high sensitivity, anti-electromagnetic interference capability it is strong, it is corrosion-resistant,It is explosion-proof, structure is simple, small in size, a series of advantage of uniquenesses such as light-weight.Therefore it has in the fields such as miniature instrument and deviceFabulous application prospect.Present fibre optical sensor there has been new intension, i.e. circular waveguide is not used only in transducing part, also availableA variety of different optical waveguides and optical fiber together as one are formed so-called optical waveguide sensing by optical waveguide technique, integrated electronic technologyDevice.Sharpest edges using light as sensing and conductive medium are that transmission capacity is big, electromagnetism interference, and as light carrierChemical inertness and flexibility possessed by optical fiber (optical waveguide).In intellectual material and intelligence structure and large scale structure monitoring, high electricityPressure, high-intensity magnetic field, nuclear radiation and biomedicine etc., fibre optical sensor are competitive measurement means.By theseThe development in year, fibre optical sensor have occupied important one seat in scientific research and industrial application, have been mainly due toFundamental difference between optical fiber and plain conductor.This difference is that have the advantages that following some uniquenesses due to fibre optical sensor:(1) anti-electromagnetic interference capability is strong, is electrically insulated, corrosion-resistant, essential safety.Since fibre optical sensor is to utilize light wave transmissions information,Optical fiber is electrical isolation, corrosion resistant transmission medium again, and safe and reliable, this can be convenient it to be effectively used for various large sizesThe strong electromagnetics such as electromechanics, petrochemical industry, mine and the adverse circumstances such as inflammable, explosive.(2) high sensitivity.Fibre optical sensorSensitivity is better than general sensor, wherein some is via theoretical proof, some experiments verify that, such as measure the underwater sound plusThe fibre optical sensor of the physical quantitys such as speed, radiation, magnetic field measures the fibre optic chemical sensor of various gas concentrations and measures variousThe optical fiber biosensor etc. of biomass.(3) light-weight, small in size, deflection.Optical fiber is in addition to light-weight, small in sizeThe advantages of there are also deflections outside feature, therefore can use optical fiber is made different shapes, various sizes of various sensors.ThisBe conducive to aerospace and the application in narrow space.4 measurement objects are extensive.The different measurement of existing performance at present is variousPhysical quantity, chemical quantity fibre optical sensor use at the scene.5 is small on measured medium influence, is conducive to have in medicine, health etc.It is applied in the field of complex environment.6, convenient for multiplexing, are convenient for networking.Be conducive to form telemtry net with existing optical communication techniqueAnd optical fiber sensing network.7 is at low cost.There are many costs of the fibre optical sensor of type will be significantly lower than existing same type of sensor.More much higher than traditional sensors times of the sensitivity of fibre optical sensor, and it can be in high voltage, big noise, high temperature, strong corruptionWork normally, can also cooperate under many particular surroundings such as corrosion with optical fiber remote sensing, telemetry, formed optical fiber remote sensing system andOgticai Fiber Based Telemetering System.Main problem of the fibre optical sensor for actual measurement is prolonged drift effect, fibre optical sensorDecaying of the drift effect from optical fiber transmission line, coupler and beam splitter characteristic is not perfect, light source output is unstable and detectorInfluence etc..There is power deviation if there is length travel, lateral displacement or two fiber axis in two fiber end faces, can all make couplingClose efficiency decline.Optical fiber can generate the coupling of Mode Coupling, especially guided mode and radiation mode under micro-bend state, to make optical fiberTransmission loss increases.General optical fibre displacement sensor is the displacement that object is monitored using the Doppler effect of light, object pairIt has to put down in the reflecting surface of light, the reflection efficiency of light can be increased, while needing the direction of the movement of object relatively simple, noIt swings.
Fibre optical sensor it is many kinds of, application range is extremely extensive, thus the type of required optical fiber be not it is single,But there are a variety of different characteristics, such as the optical fiber (optically-active fine) of low-birefringence, high birefringence optical fiber, circular birefringent fiber, ellipseCircular birefringent fiber, special doped fiber, special new construction optical fiber, infrared optical fiber, plastic optical fiber, passes picture at special coating optic fibreBeam, photonic crystal fiber etc..Due in the positioning system of nano-micro level, it is desirable that sensor can detect small power and displacementInformation.Principle currently used for micro-displacement detection is more, such as optical profile type, optical displacement sensor, inductance type force-displacement sensingMultiple types such as device, capacitive displacement transducer, condenser type and piezoelectric type and ultrasonic type displacement sensor etc., but theseIt is mostly inconvenient to be used for acquisition of the robot to small multi-dimensional force and displacement information.Displacement sensor is also known as linear transducer,It is with one of widest sensor.Existing high accuracy displacement sensor measuring range is narrow, the problems such as vulnerable to electromagnetic interference.Wherein, the general range of capacitive displacement transducer all very littles are less than 1mm, and precision is especially high, is generally used for thickness measure.ButIt is to need in advance to demarcate the electric conductivity of measured body to measure again, several kilo hertzs to tens kilo hertzs of response frequency are differed, amountJourney is usually mm grades, and precision is usually μm grade.Ultrasonic sensor belongs to non-contact measurement sensor, and precision is high.ByThere are certain intervals between sound wave pulse, therefore, it can only realize displacement detecting quasi real time, and can not achieve real-time displacementMeasurement.Inductive displacement transducer is typically all to be made of fixed coil and movable core by its structure and principle, when iron core existsWhen in coil axially movable, detection displacement is achieved the purpose that by the variation of coil inductance.But this kind of sensor is for big positionIt is narrow in the prevalence of measurement range for shift measurement, the problems such as structure is more complex, and application is limited.
Fibre optical sensor according to modulation system of the measurand to light can be divided into intensity modulated formula, phase-modulation formula,The multiple types such as wavelength modulation system and Polarization Modulation formula；In addition it can which fibre optical sensor is divided into temperature according to measurandThe multiple sensors type such as degree, pressure, flow, displacement, speed and voltage, electric current, magnetic field.Fibre optical sensor presses functional form and biographyDefeated type is divided into reflective optical fiber displacement sensor and microbend sensor two major classes.
Reflective optical fiber displacement sensor is a kind of mode transmission fibre optical sensor.Its principle is closed using two-beam fibre one endAnd fibre-optical probe is formed together, the other end is divided into two respectively as luminous source optical fiber and reception optical fiber.Light from light source couples toLuminous source optical fiber transmits directive reflector plate by optical fiber, then is reflected to reception optical fiber, is finally received and is converted by photoelectric converterDevice, the light source received and reflector surface property, reflector to fibre-optical probe distance dependent.After reflecting surface position determinesThe reflected light light intensity received changes with fibre-optical probe to the variation of the distance of reflector.Obviously, when fibre-optical probe is close to insteadWhen penetrating piece, the light intensity that receiver receives is zero.With increase of the fibre-optical probe with a distance from reflecting surface, the light intensity received is graduallyIncrease and increases again with the distance of the two and reduce after reaching maximum of points.Reflective optical fiber displacement sensor is a kind of contactlessMeasurement has many advantages, such as that probe small fast response time measurement linearizes (within the scope of thin tail sheep), can within the scope of thin tail sheep intoThe detection of row high-speed displacement.
Micro-bend modulation type is the most common one kind of internal modulation type optical fibre displacement sensor.Optical fiber can generate under micro-bend stateThe coupling of Mode Coupling, especially guided mode and radiation mode, so that fiber transmission attenuation be made to increase.Most microbend sensor is allThe variation of external field is converted into the variation of the born pressure of optical fiber, they are also called pressure-type and is slightly variable sensor.Optical fiber is micro-Bend sensor is caused made of this principle for the light wave Strength Changes transmitted in fibre core or covering using fibre-optical bending deformationFull fiber type sensor.Since the output intensity of optical fiber is very sensitive to the variation of bending degree, micro-bend type fiber optics displacementThe measurement sensitivity of sensor is relatively high, and optical path is fully sealed, and is not easily affected by environmental factors, but it to transmitting strain it is micro-Bending apparatus requires very high.Optical fiber micro-bending sensor is a kind of intensity modulation optical fiber sensor, and sensor mechanism is to pass through measurementThe variation of transmission light intensity, to be measured to obtain displacement, pressure, temperature, acceleration, strain, flow, speed etc. caused by fiber optic microbendEnvironment parameter, have many advantages, such as it is of simple structure and low cost, be easily installed.Its main foundation microbend fibre cycle and optical-fiber deformation declineSubtract coefficient and carry out microbend fibre cycle, by the selection of the micro-bend number of teeth and micro-bend tooth pitch, completes differential optical fiber micro-bending, and use photoelectricity twoPole pipe across resistance amplification and two-stage amplifier photodetection circuit, complete the establishment of upper computer software.Highly sensitive and high-precisionIn the sensing system of degree, sensor received non electrical quantity measured signal be often it is very faint, typically contain noise, becauseThis, the amplifying circuit being connected with these sensors does not require nothing more than high-gain, and it is so more important that be must have low noise performance, alsoShould have low output impedance, Larger Dynamic range, good linear character additionally wants careful shielding, to eliminate interference letterNumber.Most microbend sensor is all the variation for the variation of external field being converted into the born pressure of optical fiber, and also they are calledPressure-type is slightly variable sensor.Since the output intensity of optical fiber is very sensitive to the variation of bending degree, micro-bend type optical fiber positionThe measurement sensitivity of displacement sensor is relatively high, and optical path is fully sealed, and is not easily affected by environmental factors, but what it strained transmittingMicro-bend device requires very high.Because the optical signal of optical fiber connector output is usually faint and there is the signal being centainly distorted, becauseThis photodetector must satisfy very high characteristic requirements.Due to the sensitivity characteristic of optical fiber itself, so that fibre optical sensor is externalOperating environment requirements it is more harsh, make slow progress always in practical problem, remain in laboratory stage mostly.LightWhen fibre is in bending state, originally except some light radiation to optical fiber that can be propagated inside straight optical fiber, optical power damage is generatedConsumption.Bending loss of optical fiber problem is a complicated theoretical question.Research work to bending loss of optical fiber, mainly passes through lightLineation opinion and pattern theory two approach are analyzed.Most documents be slave pattern point of theory to fibre loss intoRow analysis.Traditional optical fiber micro-bending sensor generally can only measuring force, displacement, stress, strain etc. size, can not know theseThe direction of parameter.For this purpose, the prior art devises a kind of differential optical fiber micro bend sensor, specific structure is in two skeletonsUpper that two deformation teeth are fixedly mounted respectively, two deformation teeth composition staggered relatively on different skeletons deforms tooth pair, forms twoFibre strain device.Two optical fiber are respectively placed in the backlash of two pairs of bent forming teeth pair.By increasing elastic device, deformationTooth limit and fiber orientation slot improve the performance of differential optical fiber micro bend sensor, and the shift position limit of design variations toothPosition prevents optical fiber by pinch off, and shortcoming is that measurement displacement range is smaller, and measurement accuracy is not high.
Summary of the invention
The technical problem to be solved by the present invention is to place, provides a kind of range more in view of the shortcomings of the prior artGreatly, measurement accuracy is higher, electromagnetism interference, and optical fiber type micro-displacement sensor resistant to high temperature is existed with solving current displacement sensorThe problems such as measuring inaccuracy under hot environment, being easy failure.
Above-mentioned purpose of the invention can be reached by the following measures, and a kind of pressure-type optical fiber is slightly variable sensor, comprising:Signal modulation part, displacement measurement part and signal demodulation part, it is characterised in that: in the upper surface of the rectangle frame of measurement part plateOn set collimation lens there are two symmetrical centre, the upper fixed tooth plate reflection as displacement measurement element is fixedly connected on the downside of top panelMirror 2, it is anti-in the lower moving tooth plate that the lower section of upper fixed tooth plate reflecting mirror 2 is equipped with tooth socket on the corresponding upper tooth plate angle of reflection of angle of reflection tooth topMirror 3 is penetrated, and their sawtooth is symmetrical in opposite directions, in hanging dislocation rake tooth coupling distribution；It is fixedly connected with below lower moving tooth plate reflecting mirror 3Spring 4 is fixed below the spring base and rectangle frame between plate by drive rod 6, drive rod 6 by spring base；Signal modulationThe optical signal that part is modulated is divided into two beams by fiber coupling, and a branch of optical signal is directly reached by fiber optic loop displacement sensorReference path of the pd1 photodetector 12 as optic fibre light path, and another beam optical signal is incident on down by the first collimation lens 1The lower tooth socket angle of reflection of moving tooth plate reflecting mirror 3 is reflected by the upper tooth socket that total reflection mirror tooth reflexes to upper fixed tooth plate reflecting mirror 2Angle, after incident light is by the multiple tooth angle multiple reflections between upper fixed tooth plate reflecting mirror 2 and lower 3 plate of moving tooth plate reflecting mirror, from secondCollimation lens 7 is incident on the pd2 electric explorer 13 connected by optical fiber；Displacement measurement part according to lower moving tooth plate reflecting mirror 3 withAfter measurement object movement between upper fixed tooth plate reflecting mirror 2, by the light beam distance of 6 pickup arm change in displacement of drive rod generationThe beam phase of generation changes, the signal phase difference of more above-mentioned two photodetector, demodulates change in displacement, calculates two teethThe phase changing capacity of moving distance or detection that plate reflecting mirror occurs, the micro-displacement amount of measurement object is detected by phase.
The present invention has the advantages that compared with the prior art.
Range is bigger.One group of parallel tooth plate is reflected microscope group by the present invention, is separately mounted in sensing cavity, is passed through transmissionThe displacement of bar makes two parallel tooth plate reflecting mirror distances change, and optical signal light velocity V reaches the time change of photodetectorΔ t passes through the optical path length amount of the changing Δ L between tooth plate, Δ L=V Δ t, so that optical path phase difference becomesChangeDisplacement parameter can be obtained by measurement lens distance variation.Due to comparator detection frequency 100M~Between 2.7G and 120 ° of π/3 of linear work interval width or so, modulated optical signal is less than by optical path phase changing capacity2 π f Δ L/V < 1, the range of displacement measurement of sensor meet displacement variableChange light source 9 by driving signal 8 to adjustFrequency processed is able to achieve the displacement measurement of wider range, so maximum detection range Z < (1/3) * 3*108/(2*4*100*106), about125mm or so.In linear work area, phase comparator precision is higher than 0.05%, it is possible to obtain higher displacement measurement essenceDegree.The result shows that: the measurement range of displacement increases with the number of teeth and is declined, increases with the period of light modulating signal and increase, setThe sensor measurement range of meter is up to 0~125mm relative measurement error less than 0.05%.Detection resolution can reach mute micron orderLevel of displacement.
Electromagnetism interference.The present invention sets that there are two the collimation of symmetrical centre is saturating on the upper surface of the rectangle frame plate of measurement partMirror, top panel downside is fixedly connected with the upper fixed tooth plate reflecting mirror 2 as displacement measurement element, in upper fixed tooth plate reflecting mirror 2Lower section is equipped with the lower moving tooth plate reflecting mirror 3 of tooth socket on the corresponding upper tooth plate angle of reflection of angle of reflection tooth top, and their sawtooth is right in opposite directionsClaim, in hanging dislocation rake tooth coupling distribution, displacement, pressure minor change can be measured, optical power is maintained into optical fiberInside, optical signal substantially electromagnetism interference, electromagnetic environment without influence, can all exempt the phase of optical signal, the parameters such as amplitudeThe interference of ambient enviroment, and sensitivity is very high, anti-electromagnetic interference capability with higher.
Measurement accuracy is higher.The optical signal that signal modulation part of the present invention is modulated is divided into two beams by fiber coupling, and oneBeam optical signal directly reaches reference path of the pd1 photodetector 12 as optic fibre light path by fiber optic loop displacement sensor, andAnother beam optical signal is incident on the lower tooth socket angle of reflection of lower moving tooth plate reflecting mirror 3 by the first collimation lens 1, is reflected by straight lineThe upper tooth socket angle of reflection of the supreme fixed tooth plate reflecting mirror 2 of back reflection, incident light pass through upper fixed tooth plate reflecting mirror 2 and lower moving tooth plateAfter multiple tooth angle multiple reflections between 3 plate of reflecting mirror, the periodically continued refraction of generation is bent by the triangle tooth socket of two pressure platesReflected light is incident on the light pd2 electric explorer 13 connected by optical fiber from the second collimation lens 7.When upper lower tooth plate is by the external worldWhen pressure or change in displacement, the distance between two plates can generate variation, then will lead to optical fiber and generate the continuous bend that the period is people, lightThe mode amplitude of fine bending part is changed, to be modulated to luminous intensity therein.When shift length is kept constant, twoThe distance that Shu Guang passes through is steady state value, therefore the optical signal phase difference for reaching photodetector is kept constant；When measurement objectIt after moving, changes by the light beam distance of drive rod sensor, therefore reaches the signal phase also phase of photodetectionIt should change, the moving distance of reflecting mirror generation can be calculated by comparing the signal phase difference variation of two photodetectors,Several physical quantitys can be measured simultaneously, substantially reduce the complexity and cost of system.Current displacement sensor is solved in high temperatureThe problems such as measuring inaccuracy under environment, being easy failure.On Newton's ring, multimode fibre receives upper two lens reflecting of lower tooth plate reflecting mirrorThe interference fringe that light is formed, so that it is determined that the distance that eyeglass is mobile, its precision can reach 10~-7m.Sensitivity is single biographyTwice of sensor sensitivity, and the size and Orientation of pressure, stress, strain, displacement, acceleration can be measured, or sentenceDisconnected temperature increaseds or decreases.
High temperature resistant.The present invention is using the optical element of low thermal coefficient of expansion as displacement measurement element quartz glass thermal deformation559 degree of temperature, as higher performance preferred embodiment, sapphire main component AL can be used2O3, operating temperature can be to 1300 degree of worksFor optical element, using the optical signal of modulation, by fiber coupling, it is divided into two beams, a branch of directly to reach photoelectricity by fiber optic loopDetector, and in addition a branch of optical signals fiber optic collimator mirror passes through two groups of reflecting mirrors of inside cavity, then reaches other one againA photodetector, realization " biography " is combined into one with " sense ", and small in size, anti-electromagnetic capability is strong, chemical stability is good, resistance to heightIntensity, that is, amplitude, phase, frequency, polarization and the wave of temperature, the refractive index of adjustable parameter many cases such as optical fiber, propagation constant, light waveIt is long etc., it may be achieved the measurement etc. to small physics variable quantity.Inductance and capacitive displacement sensor are solved due to its ownRealization principle be easy to occur failing and measuring in temperature and electromagnetic interference inaccurate phenomenon.Sensor section is without electronicsTemperature drift is not present in component, the problems such as failure under high temperature.
The present invention has that electromagnetism interference, high temperature resistant, high sensitivity, range are big, are easily installed and can monitor in real timeAdvantage can be used for the measurement such as displacement, power and acceleration.
Detailed description of the invention
Fig. 1 is that pressure-type optical fiber of the present invention is slightly variable sensor measurement schematic diagram
Fig. 2 is the overall system structure figure that pressure-type optical fiber of the present invention is slightly variable sensor.
In figure: 1 collimation lens, 2 reflecting mirrors, 3 reflecting mirrors, 4 springs, 5 cavitys, 6 drive rods, 7 collimation lenses, 8 driving lettersNumber source, 9 light sources, 10 couplers, 11 fiber optic loop displacement sensors, 12 photodetectors, 13 photodetectors, 14 phase bit comparisonsDevice, 15 voltage signal collectors, 16 processors,
Specific embodiment
Refering to fig. 1, Fig. 2.In the embodiment described below, a kind of pressure-type optical fiber is slightly variable sensor, comprising: signal tuneSystem part, displacement measurement part and signal demodulation part, wherein measurement portion point includes the cavity 5 surrounded by rectangle frame, from rectangleThe drive rod 6 of frame bottom insertion cavity 5, the one group of parallel lower moving tooth plate reflecting mirror 3 connected firmly by the suit drive rod 6 of spring 4,As the upper fixed tooth plate reflecting mirror 2 of displacement measurement element and setting above lower 3 backside of moving tooth plate reflecting mirror on, symmetricallyThe first collimation lens 1 and the second collimation lens 7 in upper 2 both sides of fixed tooth plate reflecting mirror, lower moving tooth plate reflecting mirror 3 and upper fixation2 sawtooth of tooth plate reflecting mirror is symmetrically uniformly distributed in hanging dislocation rake tooth coupling in opposite directions；By signal modulation part to luminous intensity thereinAfter being modulated, the optical signal modulated is divided into two beams by fiber coupling, passes wherein a branch of optical signal is displaced by fiber optic loopSensor generates periodic continuous bend optical signal, and fiber optic loop 11 generates certain optical path, directly arrival pd1 photodetectionAll the way reference path of the device 12 as signal demodulation part.And displacement is passed through by another beam optical signal of signal modulation partial modulationIt measures the first collimation lens 1 in part and enters tooth plate reflection microscope group, pass through the second collimation lens 7 and reach another pd2 electrical resistivity surveySurvey device 13.
After measurement object moves, changes by the light beam distance of drive rod sensor, reach photodetectionSignal phase also accordingly change, by phase comparator 14 compare two photodetectors signal phase difference change, resolveThe moving distance that tooth plate reflecting mirror occurs out is detected by phase and obtains micro-displacement amount.
Instantly when moving tooth plate reflecting mirror 3 and upper fixed tooth plate reflecting mirror 2 are by ambient pressure or change in displacement, drive rod 6Displacement produce the reflecting mirror sawtooth distance between two parallel 2 liang of plates of lower moving tooth plate reflecting mirror 3 and upper fixed tooth plate reflecting mirror canChanging obtains be connected coupler 10 and the corresponding phase change of 13 optical signal of pd2 photodetector generation.
Measurement portion point includes: the collimation lens set on the upper surface of rectangle frame plate there are two symmetrical centre, and top panel downside is solidIt is associated with the upper fixed tooth plate reflecting mirror 2 as displacement measurement element, is equipped with angle of reflection tooth in the lower section of upper fixed tooth plate reflecting mirror 2The lower moving tooth plate reflecting mirror 3 of tooth socket on the corresponding upper tooth plate angle of reflection in top, and their sawtooth is symmetrical in opposite directions, in hanging dislocation triangleTooth coupling distribution；Drive rod 6 is fixedly connected with below lower moving tooth plate reflecting mirror 3, spring 4 is fixed on institute by spring base by drive rod 6It states below spring base and rectangle frame between plate；The optical signal that signal modulation part is modulated is divided into two beams by fiber coupling,A branch of optical signal directly reaches reference path of the pd1 photodetector 12 as optic fibre light path by fiber optic loop displacement sensor,And another beam optical signal is incident on the lower tooth socket angle of reflection of lower moving tooth plate reflecting mirror 3 by the first collimation lens 1, is rolled over by straight lineThe upper tooth socket angle of reflection of the supreme fixed tooth plate reflecting mirror 2 of back reflection is penetrated, incident light passes through upper fixed tooth plate reflecting mirror 2 and lower movable toothAfter multiple tooth angle multiple reflections between 3 plate of plate reflecting mirror, the light pd2 electrical resistivity survey connected by optical fiber is incident on from the second collimation lens 7Survey device 13；Displacement measurement part is according between lower moving tooth plate reflecting mirror 3 and upper fixed tooth plate reflecting mirror 2, by ambient pressure or surveyAfter measuring object movement, change by the beam phase that the light beam distance that 6 pickup arm change in displacement of drive rod generates occurs, in comparisonState the signal phase difference of two photodetectors, demodulate change in displacement, calculate the generation of two tooth plate reflecting mirrors moving distance orThe phase changing capacity of detection detects the micro-displacement amount of measurement object by phase.
Refering to Fig. 2.Since the phase of optical signal has the phase that periodically will lead to variation when change in displacement is excessive superA cycle is crossed, so that the displacement of corresponding 2 π phase changes, therefore, the displacement model measured as needed occur in displacement detecting dataSize is enclosed, driving signal 8 increases modulation of source frequency cycle, reduces modulation of source signal frequency f, so that measurement portion is divided into displacement and passesThe phase change of optical path is less than 2 π in the maximum measurement range of sensor displacement.Similarly, small range of in detection sensorThe frequency modulating signal f of light source can be increased when displacement, realize phase large change within the scope of sensor thin tail sheep.
Signal solution tune part includes source driving signal 8 in sequential series, light source 9 and coupler 10, and driving signal 8 generatesModulated signal light source 9 is driven, adjust driving current defeated people's light intensity light source 9 be adjusted and issue central wavelengthLight is transmitted by large core fiber, and by being modulated when fiber optic loop displacement sensor, output intensity is with fiber optic loop displacement sensorChange in displacement and change, light intensity is converted into voltage signal, to increase modulation of source frequency cycle, increases the modulated signal of light sourceThere is the displacement of corresponding 2 π phase changes in the displacement detecting data that measurement portion is divided into displacement sensor in frequency f, generate oneSin (the 2 π ft) modulated optical signal of t moment to 9 modulated optical signal frequency f of light source.Modulated optical signal is divided into after coupler 10Two beams, a branch of to enter pd1 photodetector 12 by fiber optic loop displacement sensor 11, modulated optical signal reaches pd1 photodetectionThe distance of device 12 be it is constant, the modulated optical signal frequency f that photodetector 12 receives is constant, 9 phase of facing light sourcesIt producesLife one is expressed as constantPhase difference, this beam optic fibre light path is known as reference path；In addition a branch of by surveyingAmount part is that the optical path of displacement sensor reaches pd2 photodetector 13, and displacement sensor changes in 16 position of drive rodWhen will lead to measurement optical fiber light path change, so as to cause phaseIt changes, pd2 photodetector 13 connects at this timeThe signal received can be expressed asThis beam optic fibre light path is known as optical path.
10 1 road optical fiber of coupler passes through the series connection pd1 photodetector 12 of fiber optic loop displacement sensor 11, another way optical fiberGo deep into the first collimation lens 1, the second collimation lens 7 passes through outlet optical fiber series connection pd2 photodetector 13, pd1 photodetector12 and pd2 photodetector 13 is connected the positive input and reverse input end of demodulation part phase comparator 14 respectively.PhaseComparator 14 realized by common phase comparable chip, is inputted as 2 modulated signals, is exported as voltage value, voltage swing and phasePotential difference is at corresponding relationship.The phase difference of optical path and two optical signals of reference path is transformed into voltage letter by phase comparator 14Number, in the linear operating region of phase comparator, voltage is directly proportional to phase difference.
Demodulation part includes: 14 output end of phase comparator voltage signal collector 15 in sequential series and processor 16, phaseThe phase in two-way modulated signal is compared in the two-way modulated signal that bit comparator 14 acquires reference path and optical path obtains, detectionPositionPhaseThe analog-digital converter AD acquisition being connected by phase comparator 14 and its arm processor realize phase signalCalculation process, by phase signal be converted into displacement signal output.Phase in two-way modulated signalPhaseOptical path phasePotential differenceArm processor can export the displacement Z of detection range according to this relational expression, whereinF is frequency modulating signal, and Δ L indicates that optical path length variable quantity, V are light speed in air, and n is the lower tooth plate number of teeth.
It is movable plate that two pieces of parallel tooth plate reflecting mirrors being mounted in sensing cavity, which constitute one of, and another piece is solidThe triangle tooth socket pressing plate anamorphoser of fixed board passes through the displacement of drive rod 6 respectively, makes two parallel distances in tooth plate reflection microscope groupIt changes, displacement parameter can be obtained by measurement lens distance variation.When upper lower tooth plate reflecting mirror by ambient pressure orWhen change in displacement, the changing of distance of reflecting mirror between two plates, the time variation amount that optical signal reaches photodetector is Δ t, is madeThe displacement variable Δ L=V Δ t Δ L that optical path length between tooth plate occurs, optical path phase differenceThe variation of generationAmount isThen there is the relationship of phase changing capacity and displacement are as follows:Wherein, V is the light velocity, and f is to adjustSignal frequency processed.When displacement is excessive, f Δ L/V > 1, since frequency modulating signal f keeps constant constant, so optical pathOptical signal phase variation can be more than 2 π, phase comparator can only detect the phase within the scope of 2 π, and actually measured phase isTo generating loss of data, range of displacement measurement is excessive to lead to phase hit in order to eliminate, and can increase optical signalPeriod, i.e., when reduction modulating frequency f makes it meet maximum displacement, modulated optical signal is less than by optical path phase changing capacity2 π f Δ L/V < 1, so changing the displacement measurement that 9 modulating frequency of light source is able to achieve wider range by driving signal 8.It considersPhase comparator detects frequency between 100M~2.7G and 120 ° of π/3 of linear work interval width or so, with lower tooth plateThe number of teeth is n, and displacement variable Z, there are relationships: Δ L=by the optical path length variation delta L of two pieces of parallel tooth plate reflecting mirrors2nZ, when the range of displacement measurement of sensor meetsIf tooth plate number of teeth n=4, the change in displacement of maximum detection rangeMeasure Z < (1/3) * 3*108/(2*4*100*106)。
Whole system realizes the detection of displacement using phase-detection method, and the specific working principle is as follows: the light warp that light source 9 issuesOvercoupling device is divided into two beams, a branch of directly directly to reach photodetector 12 by fiber optic loop displacement sensor 11, in addition a branch ofLight, in the 3 direct multiple reflections of rake tooth of upper fixed tooth plate reflecting mirror 2 and lower moving tooth plate reflecting mirror, then is passed through by the first collimation lens 1It crosses the second collimation lens 7 and enters photodetector 13, by the optical signal phase for measuring photodetector 12 and photodetector 13Position variation can obtain the variation of the distance between fixed tooth plate reflecting mirror 2 and lower moving tooth plate reflecting mirror 3, pass through phase and positionShifting relationship is to realize displacement measurement.
The embodiment of the present invention has been described in detail above, and specific embodiment used herein carries out the present inventionIt illustrates, method of the invention that the above embodiments are only used to help understand；Meanwhile for the general technology of this fieldPersonnel, according to the thought of the present invention, there will be changes in the specific implementation manner and application range, in conclusion this theoryBright book content should not be construed as limiting the invention.