高速摄影.docx

高速摄影.docx

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高速摄影

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Highspeedphotography

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Sequenceofaracehorsegalloping.PhotostakenbyEadweardMuybridge,firstpublishedin1887.

Highspeedphotographyisthescienceoftakingpicturesofveryfastphenomena.In1948,theSocietyofMotionPictureandTelevisionEngineers（SMPTE）definedhigh-speedphotographyasanysetofphotographscapturedbyacameracapableof128framespersecondorgreater,andofatleastthreeconsecutiveframes.Highspeedphotographycanbeconsideredtobetheoppositeoftime-lapsephotography.

Incommonusage,highspeedphotographymayrefertoeitherorbothofthefollowingmeanings.Thefirstisthatthephotographitselfmaybetakeninawayastoappeartofreezethemotion,especiallytoreducemotionblur.Thesecondisthataseriesofphotographsmaybetakenatahighsamplingfrequencyorframerate.Thefirstrequiresasensorwithgoodsensitivityandeitheraverygoodshutteringsystemoraveryfaststrobelight.Thesecondrequiressomemeansofcapturingsuccessiveframes,eitherwithamechanicaldeviceorbymovingdataoffelectronicsensorsveryquickly.

Otherconsiderationsforhigh-speedphotographersarerecordlength,reciprocitybreakdown,andspatialresolution.

Contents

[hide]

∙1Earlyapplicationsanddevelopment

∙2Stroboscopyandlaserapplications

∙3Highspeedfilmcameras

o3.1Intermittentpinregister

o3.2Rotaryprism

o3.3Rotarymirror

o3.4StreakPhotography

∙4Video

o4.1CCD

o4.2IS-CCD

o4.3CMOS

o4.4Infrared

∙5Seealso

∙6References

o6.1Furtherreading

∙7Externallinks

[edit]Earlyapplicationsanddevelopment

Thissectiondoesnotciteanyreferencesorsources.

Pleasehelpimprovethisarticlebyaddingcitationstoreliablesources.Unsourcedmaterialmaybechallengedandremoved.（February2008）

NuclearexplosionphotographedbyRapatroniccameralessthan1millisecondafterdetonation.Thefireballisabout20metersindiameter.Thespikesatthebottomofthefireballareduetowhatisknownastheropetrickeffect.

Thefirstpracticalapplicationofhigh-speedphotographywasEadweardMuybridge's1878investigationintowhetherhorses'feetwereactuallyalloffthegroundatonceduringagallop.

BellTelephoneLaboratorieswasoneofthefirstcustomersforacameradevelopedbyEastmanKodakintheearly1930s[1].Bellusedthesystem,whichran16mmfilmat1000frame/sandhada100-foot（30m）loadcapacity,tostudyrelaybounce.WhenKodakdeclinedtodevelopahigher-speedversion,BellLabsdevelopeditthemselves,callingittheFastax.TheFastaxwascapableof5,000frame/s.BelleventuallysoldthecameradesigntoWesternElectric,whointurnsoldittotheWollensakOpticalCompany.Wollensakfurtherimprovedthedesigntoachieve10,000frame/s.RedlakeLaboratoriesintroducedanother16mmrotatingprismcamera,theHycam,intheearly1960s[2].Photo-Sonicsdevelopedseveralmodelsofrotatingprismcameracapableofrunning35mmand70mmfilminthe1960s.VisibleSolutionsintroducedthePhotecIV16mmcamerainthe1980s.

TheD.B.Millikencompanydevelopedanintermittent,pin-registered,16mmcameraforspeedsof400frame/sin1957[2].Mitchell,RedlakeLaboratories,andPhoto-Sonicseventuallyfollowedinthe1960swithavarietyof16,35,and70mmintermittentcameras.

[edit]Stroboscopyandlaserapplications

HaroldEdgertonisgenerallycreditedwithpioneeringtheuseofthestroboscopetofreezefastmotion[3][4].HeeventuallyhelpedfoundEG&G,whichusedsomeofEdgerton'smethodstocapturethephysicsofexplosionsrequiredtodetonatenuclearweapons.See,forexample,thephotographofanexplosionusingaRapatroniccamera.

Advancingtheideaofthestroboscope,researchersbeganusinglaserstostophighspeedmotion.RecentadvancesincludetheuseofHighHarmonicGenerationtocaptureimagesofmoleculardynamicsdowntothescaleoftheattosecond[5][6]

[edit]Highspeedfilmcameras

A5millisecondscaptureofcoffeeblownoutofastraw

Adropletiscaughtwithastrobeafterreboundingupward

Highspeedmotionpicturesstartedin1916byGermanweaponsscientists[7].

Methodsdevelopedusingstationarymediumwithframesinturnactivatedbyarotatingmirrortorotatingprismcamerasusingfastmovingfilm[8].

Asfilmandmechanicaltransportsimproved,thehigh-speedfilmcamerabecameavailableforscientificresearch.KodakeventuallyshifteditsfilmfromacetatebasetoEstar（Kodak'snameforaMylar-equivalentplastic）,whichenhancedthestrengthandallowedittobepulledfaster.TheEstarwasalsomorestablethanacetateallowingmoreaccuratemeasurement,anditwasnotaspronetofire.

Eachfilmtypeisavailableinmanyloadsizes.Thesemaybecutdownandplacedinmagazinesforeasierloading.A1,200-foot（370m）magazineistypicallythelongestavailableforthe35mmand70mmcameras.A400-foot（120m）magazineistypicalfor16mmcameras,though1,000-foot（300m）magazinesareavailable.Typicallyrotaryprismcamerasuse100ft（30m）filmloads.Theimageson35mmhigh-speedfilmaretypicallyrectangularwiththelongsidebetweenthesprocketholesinsteadofparalleltotheedgesasinstandardphotography.16mmand70mmimagesaretypicallysquareratherthanrectangular.AlistofANSIformatsandsizesisavailable[9][10].

Mostcamerasusepulsedtimingmarksalongtheedgeofthefilm（eitherinsideoroutsideofthefilmperforations）producedbysparksorlaterbyLEDs.Theseallowaccuratemeasurementofthefilmspeedandinthecaseofstreakorsmearimages,velocitymeasurementofthesubject.Thesepulsesareusuallycycledat10,100,1000Hzdependingonthespeedsettingofthecamera.

[edit]Intermittentpinregister

Theintermittentpinregistercameraactuallystopsthefilminthefilmgatewhilethephotographisbeingtaken.Inhigh-speedphotography,thisrequiresacomplexmechanismforkeepingthefilmmovingquicklythroughthecamerafromthesupplyreel,butthenstoppingitforimaging,andthenstartingitagaintomoveitontothetakeupreel.Inmanycases,aloopisformedbeforeandafterthegatetocreateandthentakeuptheslack.Pull-downclawsgrabthefilmandmoveitintoplaceandthenmoveitbackoutofthefilmgateaftertheexposure.Registerpinssecurethefilmwhileitisbeingexposed.Insomecases,vacuumsuctionisusedtokeepthefilm,especially35mmand70mmfilm,flatsothattheimagesareinfocusacrosstheentireframe.

∙16mmpinregister:

D.B.MillikenLocam,capableof500frame/s;thedesignwaseventuallysoldtoRedlake.Photo-Sonicsbuilta16mmpin-registeredcamerathatwascapableof1000frame/s,buttheyeventuallyremoveditfromthemarket.

∙35mmpinregister:

EarlycamerasincludedtheMitchell35mm.Photo-SonicswonanAcademyAwardforTechnicalAchievementforthe4ERin1988[11].The4Eiscapableof360frame/s.

∙70mmpinregister:

CamerasincludeamodelmadebyHulcher,andPhoto-Sonics10Aand10Rcameras,capableof125frame/s.

[edit]Rotaryprism

Therotaryprismcameraallowedhigherframerateswithoutplacingasmuchstressonthefilmortransportmechanism.Thefilmmovessmoothlypastarotatingprismwhichissynchronizedtothemainfilmsprocket.Eachrevolutionoftheprism"paints"thesamenumberofframesontothefilmastherearefacesontheprism.Ashutteralsoimprovestheresultsbyonlyopeningastheprismfacesarenearlyparallel,andthenclosingagain.

∙16mmrotaryprism-RedlakeHycamandFastaxcamerasarecapableof10,000frame/swithafullframeprism（4facets）,20,000frame/swithahalf-framekit,and40,000frame/swithaquarter-framekit.VisibleSolutionsalsomakesthePhotecIV.

∙35mmrotaryprism-Photo-Sonics4Ccamerasarecapableof2,500frame/swithafullframeprism（4facets）,4,000frame/swithahalf-framekit,and8,000frame/swithahalf-framekit.

∙70mmrotaryprism-Photo-Sonics10Bcamerasarecapableof360frame/swithafullframeprism（4facets）,and720frame/swithahalf-framekit.

[edit]Rotarymirror

TheCordinDynafaxheldastripoffilmstillwhileamirrorrotatedathighspeeds.Attheappropriatemoment,thecappingshutterwasopenedandthemirrorsteeredimagesontothefilm.Thistypeofsystemwascapableof1,000,000frame/sforafewhundredframes.Morerecentrotatingmirrorcamerashaveachievedspeedsinexcessof3,000,000frame/sandhavetakenadvantageofCCDs（seebelow）,providingtheenduserwithimmediateresultsfromtheirphotographedevents.

[edit]StreakPhotography

Forthedevelopmentofexplosivestheimageofalineofsamplewasprojectedontoanarcoffilmviaarotatingmirror.Theadvanceofflameappearedasanobliqueimageonthefilm,fromwhichthevelocityofdetonationwasmeasured[12].

Byremovingtheprismfromtherotaryprismcamerasandusingaverynarrowslitinplaceoftheshutter,itispossibletotakeimageswhoseexposureisproportionaltothefilmspeedacrosstheslit.Theimagethatresultshasseveralusefulproperties.Thefilmadvancedirectionisessentiallyameasureoftime.Ifthesubject'smotionisperpendiculartotheslit,itmayshowgrowthormotionperpendiculartotheslit.

Motioncompensationphotography（alsoknownasBallisticSyncroPhotographyorSmearPhotographywhenusedtoimagehighspeedprojectiles）isaformofstreakphotography.Whenthemotionoft