Composition
Theaerialcameraismainlycomposedofmirrorbox,diaphragmandshutter,filmcassette,seatframe,powerandcontrolsystem,etc.Itisalsoequippedwithareceptacle,heightdifferenceAuxiliaryequipmentsuchasinstrument,colorfilter,etc.
Theaerialcameraiscomposedofamirrorboxbody,acameramountandapowerunit.
①Themirrorboxbody.Itisametalhardbox,theupperpartofwhichisconnectedtoacassetteforholdingphotographicfilm,andthelowerpartisfixedlyconnectedtoalenstubewithanobjectivelensandashutter.Mostofthelatestaerialcamerashaveasetofobjectivelensbarrelswithdifferentfocallengths,whichcanchangethephotographicscaleinawiderangetomeetdifferentworkneeds.
Aerialcameraisthemostcommonlyusedandmostimportantremotesensingsensorinaerialphotography.Itusesphotosensitivematerialstodirectlyrecordthereflectedspectrumenergyofgroundobjectsthroughanopticalsystem.Itsstructureissimilartoanordinarycamera,withlens,shutter,viewfinder,body,etc.Butaccordingtotherequirementsofaerialphotography,itslensqualityandstructurearemoresophisticatedandcomplex.Therearesingle-lenssingle-cameramodelswithsingle-bandphotography,single-cameramulti-lensmodelswithmulti-bandphotography,multi-cameramulti-lensmodels,beam-separationmodelswithsingle-camerasingle-lensmulti-spectralphotography,anddigitalcameras.Differenttypesofcamerasdeterminethegeometricaccuracyofremotesensingimagingandtheamountofinformationacquired.
②Cameramount.Itisusedtofixtheaerialcameraintheaircraftcabin.Itsstructurecanmaketheobjectiveopticalaxisoftheaerialcameraleadintotheverticaldirectionaccordingtothelevel,andmakethecamerarotatearoundtheverticalaxistomaketheimageframethenecessaryorientationtotheflightpath(theflightanglePlacement).Atthesametime,theseatframeisalsorequiredtopreventthevibrationoftheaerialcameracausedbytheoperationoftheaircraftengine.Therearemanytypesofmodernaerialcameramounts,mostofwhichhavespringorairshockabsorbers,automaticlevelingandflightdifferencecontroldevices.
③Powerplant.Mostofthepowerforthelatestaerialcamerascomesfromthegeneratorsintheaircraft,whichsupplythecamera'sautomaticleveling,autopilot(formeasuringandautomaticallycontrollingtheoverlapandflightdifferencecontrol),andtheautomaticexposurecontroldevice.
Features
Theaerialcamerahashighopticalgeometricaccuracy,themaindistanceisfixed,thereisaframemarkonthefocalplaneformeasurement,andcanautomaticallycontinueaccordingtothesettimeintervalFeaturessuchasphotography(openandcloseshutterandfilmroll).Modernhigh-precisionaerialcamerasarealsoequippedwithaforwardcompensationdevice,whichcanautomaticallycompensateforthedisplacementoftheimagepointcausedbytheforwardmovementoftheaircraft.Aerialcamerashavetwopurposes:singleaerialphotographsduringaerialreconnaissanceandmultipleaerialphotographywithfullcoverageoftopographicalphotogrammetry.
Classification
Accordingtodifferentfilmexposuremethods,aerialcamerasaredividedintoframetype,slottypeandpanoramictypeaerialcameras;accordingtodifferentlensanglesandfocallengths,theyaredividedintonarrowangle(long)Focallength),constantangle(normalfocallength),wideangle(shortfocallength)andextrawideangle(extrashortfocallength)aerialcameras;accordingtodifferentpurposes,theyaredividedintotopographicmappingandreconnaissanceaerialcameras.Thestructureoftheaerialcamerafortopographicmappingshouldkeeptheinternalazimuthelementsunchanged,andtheresultingaerialphotographsshouldbesuitableforhigh-precisionmeasurement;theaerialphotographstakenbythereconnaissanceaerialcameraaremainlyusedforinterpretationandrequirehighgroundresolution.However,therequirementfornon-distortionisnothigh,andprecisionmeasurementisgenerallynotcarriedout.
Technicalrequirements
Thetechnicalrequirementsofaerialcamerasare:①Theaerialcamerashouldbefullyautomatic,anditshouldalsohavethepossibilityofsemi-automaticorcompletelymanualphotography.②Theaerialcamerashouldbeequippedwithahigh-performanceandhigh-resolutionlensthatcancaptureblackandwhiteorcolorimagesinthevisibleandinfraredspectrum.Thedistortionofthelensshouldbeminimal,generallynomorethan10microns,andtheshuttershouldhavetheabilitytochangetheexposureSpeed,theminimumtimeintervalbetweentwoconsecutiveexposuresshouldbe5to90seconds.③Forthecamerausedforaerialphotogrammetry,atthemomentofexposure,theaerialfilmshouldbeveryflat,stableandtightlypressedagainstthecamera'spictureframe;thecenterofthefoursidesofthepictureframeshouldbemarkedwithaframemarkinordertodeterminetheimageTheprecisepositionofthemainpoint;thestructureofthecassetteandthefixedconnectionofthecassettetothelensboxbodyshouldensurethatthefocallengthoftheaerialcameraisfixed.④Theaerialcamerashallhavethefollowingdevices:eachphotographshallhavethecameranumber,thevalueofthefocallengthofthecamera,thesequencenumberofthefilm,theneedlepositionoftheshootingdateandtime,thedivisionoftheheightdifferencemeter,andtheimageofthelevelbubble.⑤Theaerialcamerashouldhaveareplacementcassette.Thecassetteshouldbeopaquewhenremovedfromthemirrorbox,anditshouldbeeasytoinstallandunload.Itcanbequicklyreplacedwithin1minuteduringflight.