Fourier transform method for self-mixing interference signal analysis

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1、Optics&LaserTechnology33(2001)409–416www.elsevier.com/locate/optlastecFouriertransformmethodforself-mixinginterferencesignalanalysisMingWanga;b;∗aDepartmentofPhysics,NanjingNormalUniversity,Nanjing210097,People’sRepublicofChinabDepartmentofPhysics,NanchangUniversity,Nanchang3

2、30029,People’sRepublicofChinaReceived15February2001;receivedinrevisedform29May2001;accepted15June2001AbstractSelf-mixinginterferometry(SMI)hasbeenusedtomeasurethedistanceanddisplacement.Althoughtheprincipleofself-mixinginterferenceisdi2erentconventionalinterference,weconclude

3、dthatFFTanalysistechniquecouldalsobeusedtodetectthesignalphaseandincreasethemeasurementprecisionofself-mixinginterferometry.FirsttheSMIsignalisobtainedbyfeedingthelightfromthetargettocavityoflaserdiode,thenitispre-processedbyananalogsubtractioncircuittoremovetheoverlappedoutp

4、utintensityduetotheinjectioncurrentmodulation.Finally,SMIsignalisanalyzedbyFFTphasedetectionmethod.Theoreticalanalysisandsimulationcalculationsarepresented.Experimentally,displacementofaPZT-driventargetwasmeasuredwithaprecisionof=50.c2001ElsevierScienceLtd.Allrightsreserved

5、.Keywords:Fouriertransform;Self-mixinginterference;Displacementmeasurementmethodswasalsoproposedtoincreasetheaccuracybeyond1.Introduction=2forself-mixinginterferometry.TheoutputintensityofSMIsignalchangeswiththevariationofopticalpathlengthSelf-mixinginterferencesystemissimpl

6、erthanthecon-andopticalfrequency.Somesignaldemodulationmethodsventionalinterferometers,becausemanyopticalelementshavebeenreported.Ovrynetal.usedtheelectro-opticallikethebeamsplitter,referencemirror,andexternalphoto-modulationmethodandthephase-shiftingtechniquetoana-detectorar

7、enotrequired.Basedontheself-mixinginter-lyzetheSMIsignal.Theyobtainedthehighersignal-to-noiseference,manysmartandsimplesensingsystemshavebeenratiosandthenanometerprecisionmeasurement[6].Sincedeveloped.Theprincipleofself-mixinginterferometryaphase-shiftingtechniquerequiresseve

8、raldiscretesteps(SMI)isexplainedasanexternalopticalfeedbacke2ecttoch