外文翻译--CCD图像.doc

附录附录1翻译部分RawCCDimagesareexceptionalbutnotperfect.Duetothedigitalnatureofthedatamanyoftheimperfectionscanbecompensatedfororcalibratedoutofthefinalimagethroughdigitalimageprocessing.CompositionofaRawCCDImage.ArawCCDimageconsistsofthefollowingsignalcomponents:IMAGESIGNAL-Thesignalfromthesource.Electronsaregeneratedfromtheactualsourcephotons.BIASSIGNAL-InitialsignalalreadyontheCCDbeforetheexposureistaken.ThissignalisduetobiasingtheCCDoffsetslightlyabovezeroA/Dcounts(ADU).THERMALSIGNAL-Signal(DarkCurrentthermalelectrons)duetothethermalactivityofthesemiconductor.ThermalsignalisreducedbycoolingoftheCCDtolowtemperature.SourcesofNoiseCCDimagesaresusceptibletothefollowingsourcesofnoise:PHOTONNOISE-Randomfluctuationsinthephotonsignalofthesource.Therateatwhichphotonsarereceivedisnotconstant.THERMALNOISE-StatisticalfluctuationsinthegenerationofThermalsignal.Therateatwhichelectronsareproducedinthesemiconductorsubstrateduetothermaleffectsisnotconstant.READOUTNOISE-Errorsinreadingthesignal；generallydominatedbytheon-chipamplifier.QUANTIZATIONNOISE-ErrorsintroducedintheA/Dconversionprocess.SENSITIVITYVARIATION-SensitivityvariationsfromphotositetophotositeontheCCDdetectororacrossthedetector.ModernCCDsareuniformtobetterthan1%betweenneighboringphotositesanduniformtobetterthan10%acrosstheentiresurface.NoiseCorrectionsREDUCINGNOISE-ReadoutNoiseandQuantizationNoisearelimitedbytheconstructionoftheCCDcameraandcannotbeimproveduponbytheuser.ThermalNoise,however,canbereducedbycoolingoftheCCD(temperatureregulation).TheSensitivityVariationscanberemovedbyproperflatfielding.CORRECTINGFORTHEBIASANDTHERMALSIGNALS-TheBiasandThermalsignalscanbesubtractedoutfromtheRawImagebytakingwhatiscalledaDarkExposure.ThedarkexposureisameasureoftheBiasSignalandThermalSignalandmaysimplybesubtractedfromtheRawImage.FLATFIELDING-Arecordofthephotositetophotositesensitivityvariationscanbeobtainedbytakinganexposureofauniformlylitflatfield.ThesevariationscanthenbedividedoutoftheRawImagetoproduceanimageessentiallyfreefromthissourceoferror.Anylengthexposurewilldo,butideallyonewhichsaturatesthepixelstothe50%or75%levelisbest.TheFinalProcessedImageThefinalProcessedImagewhichremovesunwantedsignalsandreducesnoiseasbestwecaniscomputedasfollows:FinalProcessedImage=(Raw-Dark)/FlatAllofthedigitalimageprocessingfunctionsdescribedabovecanbeaccomplishedbyusingCCDOPSsoftwarefurnishedwitheachSBIGimagingcamera.ThestepstoaccomplishthemaredescribedintheOperatingManualfurnishedwitheachSBIGimagingcamera.AtSBIGweofferourtechnicalsupporttohelpyouwithquestionsonhowtoimproveyourimages.HOWTOSELECTTHECORRECTCCDIMAGINGCAMERAFORYOURTELESCOPEWhennewcustomerscontactSBIGwediscusstheirimagingcameraapplication.Wetrytogetanideaoftheirinterests.Wehavefoundthismethodisaneffectivewayofinsuringthatourcustomersgettherightimagingcamerafortheirpurposes.Someofthequestionsweaskareasfollows:Whattypeoftelescopedoyoupresentlyown?HavingthisinformationallowsustomatchtheCCDimagingCamerasparameters,pixelsizeandfieldofviewtoyourtelescope.WecanalsohelpyouinterfacetheCCDimagingcamerasautomaticguidingfunctionstoyourtelescope.AreyouaMACorPCuser?Sinceoursoftwaresupportsbothoftheseplatformswecaninsurethatyoureceivethecorrectsoftware.Wecanalsoanswerquestionsaboutanyuniquefunctionsinoneortheother.Wecansendyouademonstrationcopyoftheappropriatesoftwareforyourreview.Doyouhaveatelescopedrivebasewithanautoguiderport?Doyouwanttooperatefromaremotecomputer?CompanieslikeSoftwareBisquefullysupportourproductswithtelescopecontrolandimagingcamerasoftware.Doyouwanttotakephotographicqualityimagesofdeepspaceobjects,imageplanets,orperformwidefieldsearchesfornearearthasteroidsorsupernovas?InlearningaboutyourinterestswecanbetterguideyoutotheoptimumCCDpixelsizeandimagingareafortheapplication.Doyouwanttomakephotometricmeasurementsofvariablestarsordeterminepreciseasteroidpositions?FromthisinformationwecanrecommendaCCDimagingcameramodelandexplainhowtousethespecificanalysisfunctionstoperformthesetasks.Wecanhelpyoucharacterizeyourimagingcamerabyfurnishingadditionaltechnicaldata.Doyouwanttoautomaticallyguidelonguninterruptedastrophotographs?AsthecompanywiththemostexperienceinCCDautoguidingwecanhelpyouinstallandoperateaCCDautoguideronyourtelescope.TheModelSTVhasaworldwidereputationforaccurateguidingondimguidestars.Nomatterwhattypeoftelescopeyouownwecanhelpyoucorrectlyinterfaceitandgetitworkingproperly.SBIGCCDIMAGINGCAMERASTheSBIGproductlineconsistsofaseriesofthermoelectricallycooledCCDimagingcamerasdesignedforawiderangeofapplicationsrangingfromastronomy,tricolorimaging,colorphotometry,spectroscopy,medicalimaging,densitometry,tochemiluminescenceandepifluorescenceimaging,etc.Thiscatalogincludesinformationonastronomicalimagingcameras,scientificimagingcameras,autoguiding,andaccessories.Wehavetriedtoarrangethecatalogsothatitiseasytocompareproductsbyspecificationsandperformance.ThetablesintheproductsectioncomparesomeofthebasiccharacteristicsoneachCCDimagingcamerainourproductline.Youwillfindamoredetailedsetofspecificationswitheachindividualimagingcameradescription.HOWTOGETSTARTEDUSINGYOURCCDIMAGINGCAMERAItallstartswiththesoftware.IftheresanycompanywellknownforitsoutstandingimagingcamerasoftwareitsSBIG.OurCCDOPSOperatingSoftwareiswellknownforitsuserorientedcameracontrolfeaturesandstability.CCDOPSisavailableforfreedownloadfromourwebsitealongwithsampleimagesthatyoucandisplayandanalyzeusingtheimageprocessingandanalysisfunctionsoftheCCDOPSsoftware.Youcanbecomethoroughlyfamiliarwithhowourimagingcamerasworkandthecapabilitiesofthesoftwarebeforeyoupurchaseanimagingcamera.WealsoincludeCCDSoftV5andTheSkyfromSoftwareBisquewithmostofourcamerasatnoadditionalcharge.MacintoshusersreceiveafreecopyofEquinoXplanetariumandcameracontrolsoftwarefortheMacOS-Xoperatingsystem.NoothermanufactureroffersbettersoftwarethanyougetwithSBIGcameras.NewcustomersreceivingtheirCCDimagingcamerashouldfirstreadtheinstallationsectionintheirCCDOPSOperatingManual.OnceyouhavereadthatsectionyoushouldhavenodifficultyinstallingCCDOPSsoftwareonyourharddrive,connectingtheUSBcablefromtheimagingcameratoyourcomputer,initiatingtheimagingcameraandwithinminutesst