外文翻译CCD图像.docx

外文翻译CCD图像.docx

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外文翻译CCD图像

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RawCCDimagesareexceptionalbutnotperfect.Duetothedigitalnatureofthedatamanyoftheimperfectionscanbecompensatedfororcalibratedoutofthefinalimagethroughdigitalimageprocessing.

CompositionofaRawCCDImage.

ArawCCDimageconsistsofthefollowingsignalcomponents:

IMAGESIGNAL-Thesignalfromthesource.Electronsaregeneratedfromtheactualsourcephotons.

BIASSIGNAL-InitialsignalalreadyontheCCDbeforetheexposureistaken.ThissignalisduetobiasingtheCCDoffsetslightlyabovezeroA/Dcounts（ADU）.

THERMALSIGNAL-Signal（DarkCurrentthermalelectrons）duetothethermalactivityofthesemiconductor.ThermalsignalisreducedbycoolingoftheCCDtolowtemperature.

SourcesofNoise

CCDimagesaresusceptibletothefollowingsourcesofnoise:

PHOTONNOISE-Randomfluctuationsinthephotonsignalofthesource.Therateatwhichphotonsarereceivedisnotconstant.

THERMALNOISE-StatisticalfluctuationsinthegenerationofThermalsignal.Therateatwhichelectronsareproducedinthesemiconductorsubstrateduetothermaleffectsisnotconstant.

READOUTNOISE-Errorsinreadingthesignal;generallydominatedbytheon-chipamplifier.

QUANTIZATIONNOISE-ErrorsintroducedintheA/Dconversionprocess.

SENSITIVITYVARIATION-SensitivityvariationsfromphotositetophotositeontheCCDdetectororacrossthedetector.ModernCCD'sareuniformtobetterthan1%betweenneighboringphotositesanduniformtobetterthan10%acrosstheentiresurface.

NoiseCorrections

REDUCINGNOISE-ReadoutNoiseandQuantizationNoisearelimitedbytheconstructionoftheCCDcameraandcannotbeimproveduponbytheuser.ThermalNoise,however,canbereducedbycoolingoftheCCD（temperatureregulation）.TheSensitivityVariationscanberemovedbyproperflatfielding.

CORRECTINGFORTHEBIASANDTHERMALSIGNALS-TheBiasandThermalsignalscanbesubtractedoutfromtheRawImagebytakingwhatiscalledaDarkExposure.ThedarkexposureisameasureoftheBiasSignalandThermalSignalandmaysimplybesubtractedfromtheRawImage.

FLATFIELDING-Arecordofthephotositetophotositesensitivityvariationscanbeobtainedbytakinganexposureofauniformlylit'flatfield".ThesevariationscanthenbedividedoutoftheRawImagetoproduceanimageessentiallyfreefromthissourceoferror.Anylengthexposurewilldo,butideallyonewhichsaturatesthepixelstothe50%or75%levelisbest.

TheFinalProcessedImage

ThefinalProcessedImagewhichremovesunwantedsignalsandreducesnoiseasbestwecaniscomputedasfollows:

FinalProcessedImage=（Raw-Dark）/Flat

AllofthedigitalimageprocessingfunctionsdescribedabovecanbeaccomplishedbyusingCCDOPSsoftwarefurnishedwitheachSBIGimagingcamera.ThestepstoaccomplishthemaredescribedintheOperatingManualfurnishedwitheachSBIGimagingcamera.AtSBIGweofferourtechnicalsupporttohelpyouwithquestionsonhowtoimproveyourimages.

HOWTOSELECTTHECORRECTCCDIMAGINGCAMERAFORYOURTELESCOPE

WhennewcustomerscontactSBIGwediscusstheirimagingcameraapplication.Wetrytogetanideaoftheirinterests.Wehavefoundthismethodisaneffectivewayofinsuringthatourcustomersgettherightimagingcamerafortheirpurposes.Someofthequestionsweaskareasfollows:

Whattypeoftelescopedoyoupresentlyown?

HavingthisinformationallowsustomatchtheCCDimagingCamera'sparameters,pixelsizeandfieldofviewtoyourtelescope.WecanalsohelpyouinterfacetheCCDimagingcamera'sautomaticguidingfunctionstoyourtelescope.

AreyouaMACorPCuser?

Sinceoursoftwaresupportsbothoftheseplatformswecaninsurethatyoureceivethecorrectsoftware.Wecanalsoanswerquestionsaboutanyuniquefunctionsinoneortheother.Wecansendyouademonstrationcopyoftheappropriatesoftwareforyourreview.

Doyouhaveatelescopedrivebasewithanautoguiderport?

Doyouwanttooperatefromaremotecomputer?

CompanieslikeSoftwareBisquefullysupportourproductswithtelescopecontrolandimagingcamerasoftware.

Doyouwanttotakephotographicqualityimagesofdeepspaceobjects,imageplanets,orperformwidefieldsearchesfornearearthasteroidsorsupernovas?

InlearningaboutyourinterestswecanbetterguideyoutotheoptimumCCDpixelsizeandimagingareafortheapplication.

Doyouwanttomakephotometricmeasurementsofvariablestarsordeterminepreciseasteroidpositions?

FromthisinformationwecanrecommendaCCDimagingcameramodelandexplainhowtousethespecificanalysisfunctionstoperformthesetasks.Wecanhelpyoucharacterizeyourimagingcamerabyfurnishingadditionaltechnicaldata.

Doyouwanttoautomaticallyguidelonguninterruptedastrophotographs?

AsthecompanywiththemostexperienceinCCDautoguidingwecanhelpyouinstallandoperateaCCDautoguideronyourtelescope.TheModelSTVhasaworldwidereputationforaccurateguidingondimguidestars.Nomatterwhattypeoftelescopeyouownwecanhelpyoucorrectlyinterfaceitandgetitworkingproperly.

SBIGCCDIMAGINGCAMERAS

TheSBIGproductlineconsistsofaseriesofthermoelectricallycooledCCDimagingcamerasdesignedforawiderangeofapplicationsrangingfromastronomy,tricolorimaging,colorphotometry,spectroscopy,medicalimaging,densitometry,tochemiluminescenceandepifluorescenceimaging,etc.Thiscatalogincludesinformationonastronomicalimagingcameras,scientificimagingcameras,autoguiding,andaccessories.Wehavetriedtoarrangethecatalogsothatitiseasytocompareproductsbyspecificationsandperformance. ThetablesintheproductsectioncomparesomeofthebasiccharacteristicsoneachCCDimagingcamerainourproductline.Youwillfindamoredetailedsetofspecificationswitheachindividualimagingcameradescription.

HOWTOGETSTARTEDUSINGYOURCCDIMAGINGCAMERA

Itallstartswiththesoftware. Ifthere'sanycompanywellknownforitsoutstandingimagingcamerasoftwareit'sSBIG. OurCCDOPSOperatingSoftwareiswellknownforitsuserorientedcameracontrolfeaturesandstability. CCDOPSisavailableforfreedownloadfromourwebsitealongwithsampleimagesthatyoucandisplayandanalyzeusingtheimageprocessingandanalysisfunctionsoftheCCDOPSsoftware.Youcanbecomethoroughlyfamiliarwithhowourimagingcamerasworkandthecapabilitiesofthesoftwarebeforeyoupurchaseanimagingcamera. WealsoincludeCCDSoftV5andTheSkyfromSoftwareBisquewithmostofourcamerasatnoadditionalcharge. MacintoshusersreceiveafreecopyofEquinoXplanetariumandcameracontrolsoftwarefortheMacOS-Xoperatingsystem. NoothermanufactureroffersbettersoftwarethanyougetwithSBIGcameras. NewcustomersreceivingtheirCCDimagingcamerashouldfirstreadtheinstallationsectionintheirCCDOPSOperatingManual.OnceyouhavereadthatsectionyoushouldhavenodifficultyinstallingCCDOPSsoftwareonyourharddrive,connectingtheUSBcablefromtheimagingcameratoyourcomputer,initiatingtheimagingcameraandwithinminutesstarttakingyourfirstCCDimages. Manyofourcustomersareamazedathoweasyitistostarttakingimages. AdditionalinformationcanbefoundbyreadingtheimageprocessingsectionsoftheCCDOPSandCCDSoftV5Manuals.Thisinformationallowsyoutoprogresstomoreadvancedfeaturessuchasautomaticdarkframesubtractionofimages,focusingtheimagingcamera,viewing,analyzingandprocessingtheimagesonthemonitor,co-addingimages,takingautomaticsequencesofimages,photometricandastrometricmeasurements,etc.

APERSONALTOUCHFROMSBIG

AtSBIGwehavehadmuchsuccesswithaprograminwhichwecontinuallyreviewcustomer'simagessenttousondiskorviae-mail. Wecanoftendeterminethecauseofaproblemfromactualimagessentinbyauser.Wereviewtheimagesandcontacteachcustomerpersonally. Imagesdisplayingpoortelescopetracking,improperimagingcamerafocus,oversaturatedimages,etc.,aretypicalinitialproblems. Wewillhelpyouquicklylearnhowtoimproveyourimages. Youcanbeassuredofpersonaltechnicalsupportwhenyouneedit. ThecustomersupportprogramhasfurnishedSBIGwithalargecollectionofremarkableimages. ManycustomershavehadtheirimagespublishedinSBIGcatalogs,ads,andvariousastronomymagazines. Wewelcomethechancetoreviewyourimagesandhopeyouwilltakeadvantageofourtrainedstafftohelpyouimproveyourimages.

TRACKANDACCUMULATE （U.S.Patent#5,365,269）

UsinganinnovativeengineeringapproachSBIGdevelopedanimagingcamerafunctioncalledTrack&Accumulate（TRACCUM）inwhichmultipleimagesareautomaticallyregisteredtocreateasinglelongexposure. Sincethelongexposureconsistsofshortimagesthetotalcombinedexposuresignificantlyimprovesresolutionbyreducingthecumulativetelescopeperiodicerror. IntheTRACCUMmodeeachimageisshiftedtocorrectguidingerrorsandaddedtotheimagebuffer.Inthismodethetelescopedoesnotneedtobeadjusted. ThegreatsensitivityoftheCCDvirtuallyguaranteesthattherewillbeausableguidestarwithinthefieldofview.Thisfeatureprovidesdramaticimprovementinresolutionbyreducingtheeffectofperiodicerrorandallowingunattendedhourlongexposures. SBIGhasbeengrantedU.S.Patent#5,365,269forTrack&Accumulate.

DUALCCDSELF-GUIDING （U.S.Patent#5,525,793）

In1994withtheintroductionofModelsST-7andST-8CCDImagingCameraswhichincorporatetwoseparateCCDdetectors,SBIGwasabletoaccomplishthegoalofintroducingatrulyself-guidedCCDimagingcamera. TheabilitytoselectguidestarswithaseparateCCDthroughthefull