简介:PuLsetransittime(FIT)isusedasanoninvasiveandcull-lessparametertoestimatebloodpressure.Inthispaper,wedevelopanalgorithmtoobtainFTTrapidly,whichisappropriateformicro-processorandcouldachievegoodaccuracyinPTT,eveninnoisymeasurements.Thealgorithmisbasedonfiniteimpulseresponse(FIR)filtertoreducethenoiseandanadaptivethresholdtodetectthesignificantpointsofECGandPPG.EvaluationofthismethodisbasedonthesignalsfromourPTr-basedbloodpressuredevices.ItisshownthatthemethodworkswellforPPTcalculation.
简介:ThisLetterproposesabrand-newfilamentdiametermeasurementmethodbasedonwhatiscalled'dualdiffraction,'inthatagratingisaddedbehindthefilamenttomakefulluseofitssubdivisionandamplificationcharacteristics.Highermeasurementaccuracyisachievedbythismethodcomparedwiththetraditionaldiffractionmethod.Toverifyitsaccuracy,threestandardfilamentswithnominalvaluesof100.2,120.1,and140.8μmaremeasuredbythedualdiffractionmethodandtraditionaldiffractionmethodunderthesameexperimentalconditions.Therelativemeasurementerrorsofthenewmethodarelessthan0.75%,anditsaveragerelativeerrorisreducedby56%comparedwiththetraditionaldiffractionmethod.
简介:Thenumericalmoirémethodwithsensitivityashighas0.03nmhasbeenpresented.Aquantitativedisplacementandstrainanalysisprogramhasbeenproposedbyusingthismethod.Itisappliedtoauedgedislocationandastackingfaultinaluminum.ThemeasuredstrainofedgedislocationiscomparedwiththeoreticalpredictiongivenbyPeierls-Nabarrodislocationmodel.Thedisplacementofstackingfaultisalsoobtained.
简介:Toconfirmtheexistenceandpropertiesofhumanmeridians,theopticaltransportpropertiesalongthepericardiummeridianandtissuesaroundthepericardiummeridianarestudiednoninvasivelyontwentyhealthyvolunteersinvivoandthencomparedwitheachother.Ourstudyshowsthatthelightpropagatingalongthemeridianandnon-meridiandirectionsbothconformtotheBeer’sexponentialattenuationlaw.However,statisticalanalysisoftheresultssuggeststhattheopticaltransportpropertiesofhumanmeridiandifferfromthoseofthesurroundingtissuesoveralowmodulatedfrequencyrange(P<0.01),andlightattenuationalongthepericardiummeridianissignificantlylessthanthatalongthenon-meridiandirection.Thesefindingsnotonlyindicatetheexistenceofacupuncturemeridianfromthepointofviewofbiomedicaloptics,butalsoshednewlightonanapproachtoinvestigationofhumanmeridians.更多还原
简介:ThespinHalleffectoflight(SHEL)canbeobservedbythedarkstripresultingfromweakmeasurement.WefindthattheSHELofapartiallycoherentbeam(PCB)hasasimilarphenomenonaswell.However,thedarkstripintheSHELofaPCBcannotbeexplainedbyconsideringthebeamasanassemblanceofcoherentspeckles.Also,thedarkstripinaPCBisnotpurelydark.Byanalyzingtheautocorrelation,weshowthattheSHELofaPCBistheresultofoverlappingcoherentspeckles'SHEL.Wefurtherproveourconclusionbyadjustingconvergenceandincidentangles.Finally,wedevelopaqualitativetheorytoclarifytheSHELofaPCB.
简介:Weproposeanovelphotonictechniqueformicrowavefrequencymeasurementbasedontransversalmicrowavefilterswithhighresolution.Twoparallelmicrowavefilterswithsineandcosinefrequencyresponsesareobtainedbycrossgainmodulationinasinglesemiconductoropticalamplifier,whichintroducestwodifferentfrequencyresponsestoachieveanamplitudecomparisonfunction.Wealsodemonstrateaproof-of-conceptexperiment.Themeasurementerrorislessthan±0.04GHzforthefirstbandrangeof0–3.45GHzandlessthan±0.03GHzforthesecondbandrangeof3.45–5.8GHz.Ourschemeisfoundtobecapableofbeingextendedforlargerfrequencyrangemeasurementsusingashorterfiberlength.
简介:Apavementreflectancemeasurementsystemisestablishedbasedonagonio-photometerexistingbychangingabrackettocarrytheroadsampleandluminancemeter,addingacollimatedlightsourcetoprovideincidentlight.Thisautomatedsystemcouldfinishthereflectionmeasurementofaroadsamplein4h.AnuncertaintybudgetofthismeasurementsystemismadeandthecombinedstandarduncertaintyofQ0is5.26%.
简介:Weproposeanovelsmall-anglemeasuringopticalmethodbasedontheastigmaticeffectoftwoorthogonallyplacedcylindricallenses.Accordingtotheone-to-onecorrespondencebetweenthelaserspotshapeandtheangle,theangleisdetermined.Wetheoreticallyanalyzethemeasuringrangeanddemonstratethatalongerdistancebetweentherotatingaxisandtheopticalaxisleadstoasmallermeasuringrange,butbettersensitivity.Also,anassociatedexperimentalsystemisestablishedandameasuringrangeof0.94mrad(cubicfitr=0.9993)aswellasagoodlinearrangeof0.37mrad(linearfitr=0.9994)witharesolutionof8μradisachieved.
简介:Targetdynamicsareassumedtobeknowninmeasuringdigitalspeckledisplacement.Useismadeofasimplemeasurementequation,wheremeasurementnoiserepresentstheeffectofdisturbancesintroducedinmeasurementprocess.Fromtheseassumptions,Kalmanfiltercanbedesignedtoreducevarianceofmeasurementnoise.Anopticalandanalysissystemwassetup,bywhichobjectmotionwithconstantdisplacementandconstantvelocityisexperimentedwithtoverifyvalidityofKalmanfilteringtechniquesforreductionofmeasurementnoisevariance.
简介:ThisLetterpresentsamethodofanopticalsensorformeasuringwavelengthshifts.Thesystemconsistsofadiffractiongratingandatotalinternalreflectionheterodyneinterferometer.Asaheterodynelightbeamstrikesagrating,thefirst-orderdiffractionbeamisgenerated.Thelightpenetratesintoatotalinternalreflectionprismatananglelargerthanthecriticalangle.Awavelengthvariationwillaffectthediffractiveangleofthefirst-orderbeam,thusinducingaphasedifferencevariationofthelightbeamemergingfromthetotalinternalreflectionsinsidethetrapezoidprism.Boththeexperimentalandtheoreticalresultsrevealthat,forthefirst-orderdiffractivebeam,thesensitivityandresolutionlevelsaresuperiorto5°/nmand0.006nm,respectively,intherangeofwavelengthfrom632to634nm,andaresuperiorto3.1°/nmand0.0095nmintherangefrom632to637nm.Forthetheoreticalsimulationofthefourth-orderdiffractivebeam,theyaresuperiorto6.4deg∕nmand0.0047nmintherangefrom632to637nm.
简介:AprototypeRamanlidarwasdesignedformonitoringtroposphericCO_2profileandotherscientificin-vestigations.ThethirdharmonicofNd:YAGlaser(354.7-nmwavelength)wasusedasstimulatedlightsourcetoprovidenighttimemeasurements.FilterwithhighrejectionratioperformancewasusedtoextractCO_2RamansignalsfromRayleigh-Miescatteringsignalseffectively.Toimprovetherealtimemonitoringfunction,atwo-channelsignalcollectionsystemwasdesignedtocollectCO_2andN_2Ramanscatteringsig-nalssimultaneously.TheN_2Ramanscatteringsignalswereusedtoretrieveaerosolextinctioncoefficient.TypicalfeaturesofCO_2concentrationprofileandaerosolextinctioncoefficientinHefeiwerepresented.ThemixingratioofatmosphericCO_2inHefeicanreachabout360-400ppmv.
简介:WeestablishasystemtomeasurethefunctionalabsorptioncrosssectionofphotosystemII(PSII)(σPSII)andmaximumquantumyieldofphotochemistryinPSII(Fv/Fm).Thesystemutilizesasequenceofhighfrequencyexcitationflashesatmicrosecondintervalstoinduceamicrosecond-levelfluorescenceyieldcurve.ParametersσPSIIandFv/Fmarecalculatedbyfittingthecurveusingnonlinearregression.Experimentalresultsshowthattherelativestandarddeviation(RSD)ofthesystemislessthan3%,andthecorrelationcoefficientofFv/Fmvaluesmeasuredbythissystemandthosemeasuredbypulseamplitudemodulationmethodis0.950.
简介:Wemeasurethehalf-wavevoltageofLiNbO3phasemodulatorsina26-GHzwidebandfrequencyrange,andthenanalyzeitbythephasemodulationphotonicpeakgainlinkedtotheinterferometricdemodulation.Theopticalinterferometerisconstructedwithtwo50:50couplersandtwofiberarmswitha1-mdifferenceinfiberlength.Thephotoniclinkgainpeaksarefrequencydependent,asindicatedbythedifferentialtimedelayintheinterferometer.Theproceduredescribedisanewandpracticalhalf-wavevoltagemeasurementmethodthatcanaccuratelypredictthenonlinearfrequencycharacteristicsofthephasemodulator.Moreover,themethodcanbeappliedtovarioustypesofLiNbO3phasemodulators.
简介:Wepresentamethodthataccuratelymeasureslargeopticalsurfacesbeforepolishingusingalasertracker.Usingthescanningmodeofthelasertrackerconsiderablyimprovesmeasurementefficiencyandminimizesthedominanterrorscausedbyenvironmentalchange.WeusethismethodtomeasureaΦ1.3-masphericmirrorandobtainameasurementuncertaintyof0.72μm(rootmeansquare,RMS).
简介:AnovelfiberBragggrating(FBG)withtwotransmissiondipsin1310-and1550-nmregionsisproposedandinscribedbyaninfraredfemtosecondlaser.Formedbymulti-photonionization,thistypeofgratingcanwithstandtemperatureashighas800℃whichmakesitsuitableforharshenvironmentsensing.Inaddition,thetemperatureandstrainaffectthesetwodipsindifferentways,whichenablessimultaneousstrainandtemperaturesensing.Thefabrication,spectrumcharacterization,andtemperatureperformanceofthisgratingareintroduced.
简介:Influenceoftemperatureonmeasurementofsurfaceplasmonresonance(SPR)sensorwasinvestigated.SampleswithvariousconcentrationsofNaClweretestedatdifferenttemperatures.Itwasshownthatiftheaffectionoftemperaturecouldbeneglected,measurementprecisionofsaltsolutionwas0.028wt.-%.Butmeasurementerrorofsalinityca,usedbytemperaturewas0.53wt.-%inaveragewhenthetemperaturedriftwas1℃.Toreducetheerror,adouble-cellSPRsensorwithsaltsolutionanddistilledwaterflowingrespectivelyandatthesametemperaturewasimplemented.更多还原
简介:Anewscreen-spotimagingmethodbasedonopticalmeasurementisproposed,whichisapplicabletotheclose-rangemeasurementofaircraft'sthree-dimensional(3D)attitudeparameters.Lasertrackerisusedtofinishtheglobalcalibrationsofthehigh-speedcamerasandthefixedscreensontestsite,aswellastoestablishmedia-coordinate-framesamongvariouscoordinatesystems.Thelasercooperationobjectmountedontheaircraftsurfaceprojectslaserbeamsonthescreensandthehigh-speedcamerassyn-chronouslyrecordthelight-spots'positionchangingwithaircraftattitude.Therecordedimagesequencesareusedtocomputetheaircraftattitudeparameters.Basedonthematrixanalysis,theerrorsourcesofthemeasurementaccuracyareanalyzed,andthemaximumrelativeerrorofthismathematicalmodelisestimated.Theexperimentalresultshowsthatthismethodeffectivelymakesthechangeofaircraftpositiondistinguishable,andtheerrorofthismethodisnomorethan3′whiletherotationanglesofthreeaxesarewithinacertainrange.
简介:Anovelno-guidelightpentype3D-coordinatemeasurementsystemwiththreesetsofpositionsensitivedevices(PSDs)torealizeintersectionconvergeinagingisintroduced.Itiscalledasthelightpentypemeasurementsystem,becausethemeasuringheadisshapedasapenwithseverallightsourcesonit.Thestructuredesign,measurementprincipleandexperimentalresultsarepresented.Thetheoreticalanalysisandexperimentalresultsprovethatthissystemhasadvancedfeaturesofsimplestructure,highautomation,andhighaccuracy,andcanbeusedinthemeasurementfieldsofmechanicalmanufacture,robot,auto,aviationandmedicineeffectively.
简介:Anovelmethodofmeasuringnon-uniformstrainalongafiberBragggrating(FBG)usingopticalfrequencydomainreflectometry(OFDR)isproposedandexperimentallydemonstrated.Thismethodcanovercometheproblemsoftraditionalnon-uniformstrainmeasurementmethodsforFBGs,i.e.,thelikelihoodofchirpingandmultiplepeakinginthespectrumwhenFBGissubjectedtoinhomogeneousstrainfields.WavelengthinterrogationisrealizedbyOFDRwithanarrow-line-widthtunablelaserastheopticalsource.Whennon-uniformstraindistributionsalongareasadjacenttostructuraldamagearemeasuredbythismethod,goodagreementisobtainedbetweenmeasurementsandtheoreticalsimulationresults.