激光测距 外文翻译.docx

激光测距 外文翻译.docx

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激光测距外文翻译

Laserrangefinder

Alongrangelaserrangefinderiscapableofmeasuringdistanceupto20km;mountedonatripodwithanangularmount.Theresultingsystemalsoprovidesazimuthandelevationmeasurements.

Alaserrangefinderisadevicewhichusesalaserbeamtodeterminethedistancetoanobject.Themostcommonformoflaserrangefinderoperatesonthetimeofflightprinciplebysendingalaserpulseinanarrowbeamtowardstheobjectandmeasuringthetimetakenbythepulsetobereflectedoffthetargetandreturnedtothesender.Duetothehighspeedoflight,thistechniqueisnotappropriateforhighprecisionsub-millimetermeasurements,wheretriangulationandothertechniquesareoftenused.

Pulse

Thepulsemaybecodedtoreducethechancethattherangefindercanbejammed.ItispossibletouseDopplereffecttechniquestojudgewhethertheobjectismovingtowardsorawayfromtherangefinder,andifsohowfast.

Precision

Theprecisionoftheinstrumentisdeterminedbytheriseorfalltimeofthelaserpulseandthespeedofthereceiver.Onethatusesverysharplaserpulsesandhasaveryfastdetectorcanrangeanobjecttowithinafewmillimeters.

Range

Despitethebeambeingnarrow,itwilleventuallyspreadoverlongdistancesduetothedivergenceofthelaserbeam,aswellasduetoscintillationandbeamwandereffects,causedbythepresenceofairbubblesintheairactingaslensesranginginsizefrommicroscopictoroughlyhalftheheightofthelaserbeam'spathabovetheearth.

Theseatmosphericdistortionscoupledwiththedivergenceofthelaseritselfandwithtransversewindsthatservetopushtheatmosphericheatbubbleslaterallymaycombinetomakeitdifficulttogetanaccuratereadingofthedistanceofanobject,say,beneathsometreesorbehindbushes,orevenoverlongdistancesofmorethan1kminopenandunobscureddesertterrain.

Someofthelaserlightmightreflectoffleavesorbrancheswhicharecloserthantheobject,givinganearlyreturnandareadingwhichistoolow.Alternatively,overdistanceslongerthan1200ft（365m）,thetarget,ifinproximitytotheearth,maysimplyvanishintoamirage,causedbytemperaturegradientsintheairinproximitytotheheatedsurfacebendingthelaserlight.Alltheseeffectshavetobetakenintoaccount.

Calculation

ThedistancebetweenpointAandBisgivenby

D=ct/2

wherecisthespeedoflightintheatmosphereandtistheamountoftimefortheround-tripbetweenAandB.

where

isthedelaywhichmadebythelighttravelingand

istheangularfrequencyofopticalmodulation.

ThensubstitutethevaluesintheequationD=ct/2,D=1/2ct=1/2c·φ/ω=c/（4πf）（Nπ+Δφ）=c/4f（N+ΔN）=U（N+）

inthisequation,Ustandsfortheunitlength.

Δφstandsforthedelaypartwhichdoesnotfulfillπ.

ΔNstandsthedecimalvalue.

Discrimination

Someinstrumentsareabletodeterminemultiplereturns,asabove.Theseinstrumentsusewaveform-resolvingdetectors,whichmeanstheydetecttheamountoflightreturnedoveracertaintime,usuallyveryshort.Thewaveformfromalaserpulsethathitsatreeandthenthegroundwouldhavetwopeaks.Thefirstpeakwouldbethedistancetothetree,andthesecondwouldbethedistancetotheground.

Usingwavefrontsensing,itispossibletodetermineboththeclosestandthefarthestobjectatagivenpoint.Thismakesitpossibleforaircraft-mountedinstrumentstosee"through"densecanopies[clarificationneededPleaseexplainhowlasersseethroughcanopies]andothersemi-reflectivesurfacesuchastheocean,leadingtomanyapplicationsforairborneinstrumentssuchas:

1.Creating"bareearth"topographicmaps-removingalltrees

2.Creatingvegetationthicknessmaps

3.Bathymetry（measuringtopographyundertheocean）

4.Forestfirehazard

Technologies

Timeofflight-thismeasuresthetimetakenforalightpulsetotraveltothetargetandback.Withthespeedoflightknown,andanaccuratemeasurementofthetimetaken,thedistancecanbecalculated.Manypulsesarefiredsequentiallyandtheaverageresponseismostcommonlyused.Thistechniquerequiresveryaccuratesub-nanosecondtimingcircuitry.

Multiplefrequencyphase-shift-thismeasuresthephaseshiftofmultiplefrequenciesonreflectionthensolvessomesimultaneousequationstogiveafinalmeasure.

Interferometry-themostaccurateandmostusefultechniqueformeasuringchangesindistanceratherthanabsolutedistances.

Applications

Military

AnAmericansoldierwithaGVS-5laserrangefinder.

ADutchISAFsniperteamdisplayingtheirAccuracyInternationalAWSM.338LapuaMagnumrifleandLeica/VectronixVECTORIVlaserrangefinderbinoculars.

Rangefindersprovideanexactdistancetotargetslocatedbeyondthedistanceofpoint-blankshootingtosnipersandartillery.Theycanalsobeusedformilitaryreconciliationandengineering.

Handheldmilitaryrangefindersoperateatrangesof2kmupto25kmandarecombinedwithbinocularsormonoculars.Whentherangefinderisequippedwithadigitalmagneticcompass（DMC）andinclinometeritiscapableofprovidingmagneticazimuth,inclination,andheight（length）oftargets.Somerangefinderscanalsomeasureatarget'sspeedinrelationtotheobserver.Somerangefindershavecableorwirelessinterfacestoenablethemtotransfertheirmeasurement（s）datatootherequipmentlikefirecontrolcomputers.Somemodelsalsoofferthepossibilitytouseadd-onnightvisionmodules.Mosthandheldrangefindersusestandardorrechargeablebatteries.

Themorepowerfulmodelsofrangefindersmeasuredistanceupto25kmandarenormallyinstalledeitheronatripodordirectlyonavehicleorgunplatform.Inthelattercasetherangefindermoduleisintegratedwithon-boardthermal,nightvisionanddaytimeobservationequipment.Themostadvancedmilitaryrangefinderscanbeintegratedwithcomputers.

Tomakelaserrangefindersandlaser-guidedweaponslessusefulagainstmilitarytargets,variousmilitaryarmsmayhavedevelopedlaser-absorbingpaintfortheirvehicles.Regardless,someobjectsdon'treflectlaserlightverywellandusingalaserrangefinderonthemisdifficult.

3-DModelling

ThisLIDARscannermaybeusedtoscanbuildings,rockformations,etc.,toproducea3Dmodel.TheLIDARcanaimitslaserbeaminawiderange:

itsheadrotateshorizontally,amirrorflipsvertically.Thelaserbeamisusedtomeasurethedistancetothefirstobjectonitspath.

Laserrangefindersareusedextensivelyin3-Dobjectrecognition,3-Dobjectmodelling,andawidevarietyofcomputervision-relatedfields.Thistechnologyconstitutestheheartoftheso-calledtime-of-flight3Dscanners.Incontrasttothemilitaryinstrumentsdescribedabove,laserrangefindersofferhigh-precisionscanningabilities,witheithersingle-faceor360-degreescanningmodes.

Anumberofalgorithmshavebeendevelopedtomergetherangedataretrievedfrommultipleanglesofasingleobjecttoproducecomplete3-Dmodelswithaslittleerroraspossible.Oneoftheadvantagesthatlaserrangefindersofferoverothermethodsofcomputervisionisthatthecomputerdoesnotneedtocorrelatefeaturesfromtwoimagestodeterminedepthinformationasinstereoscopicmethods.

Laserrangefindersusedincomputervisionapplicationsoftenhavedepthresolutionsoftenthsofmillimetersorless.ThiscanbeachievedbyusingtriangulationorrefractionmeasurementtechniquesasopposedtothetimeofflighttechniquesusedinLIDAR.

Forestry

LaserrangefinderTruPulseusedforforestinventories（incombinationwithField-Maptechnology）

Speciallaserrangefindersareusedinforestry.Thesedeviceshaveanti-leaffiltersandworkwithreflectors.Laserbeamreflectsonlyfromthisreflectorandsoexactdistancemeasurementisguaranteed.Laserrangefinderswithanti-leaffilterareusedforexampleforforestinventories.

Sports

Laserrangefindersmaybeeffectivelyusedinvarioussportsthatrequireprecisiondistancemeasurement,suchasgolf,hunting,andarchery.Someofthemorepopularmanufacturersare:

Opti-logicCorporation,Bushnell,LaserTechnology,Trimble,Leica,NewconOptik,Nikon,andSwarovskiOptik.

Industryproductionprocesses

AnimportantapplicationistheuseoflaserRangefindertechnologyduringtheautomationofstockmanagementsystemsandproductionprocessesinsteelindustry.

Safety

Laserrangefindersforconsumersarelaserclass1devicesandthereforeareconsideredeyesafe.Somelaserrangefindersformilitaryuseexceedthelaserclass1energylevels.

History

Developmentofthemethodsusedinmodernprintedcircuitboardsstartedearlyinthe20thcentury.In1903,aGermaninventor,AlbertHanson,describedflatfoilconductorslaminatedtoaninsulatingboard,inmultiplelayers.ThomasEdisonexperimentedwithchemicalmethodsofplatingconductorsontolinenpaperin1904.ArthurBerryin1913patentedaprint-and-etchmethodinBritain,andintheUnitedStatesMaxSchoopobtainedapatent[1]toflame-spraymetalontoaboardthroughapatternedmask.CharlesDurcasein1927patentedamethodofelectroplatingcircuitpatterns.

TheAustrianJewishengineerPaulEislerinventedtheprintedcircuitwhileworkinginEnglandaround1936aspartofaradioset.Around1943theUSAbegantousethetechnologyonalargescaletomakeproximityfusesforuseinWorldWarII.Afterthewar,in1948,theUSAreleasedtheinventionforcommercialuse.Printedcircuitsdidnotbecomecommonplaceinconsumerelectronicsuntilthemid-1950s,aftertheAuto-SemblyprocesswasdevelopedbytheUnitedStatesArmy.

Beforeprintedcircuits（andforawhileaftertheirinvention）,point-to-pointconstructionwasused.