英文Design of operation parameters of a high speed.docx

英文Design of operation parameters of a high speed.docx

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英文Designofoperationparametersofahighspeed

Designofoperationparametersofahighspeed

CCDlinescancamera

CHENXiaoli'，FENGYong'，LIANGDaqiang2

（1.Dept.ofElectricalEnginrering,HarhinInstituteofTechnology,Harhin150001,China;

2.DepartmentofPhysics,DaqingCollege,Daqing163712,China）

Abstract:

Thispaperanalyzestheoperationparametersofthetimedelayandintegration（TDI）linescanCCDcamera,suchasresolution,Linerate,clackfrequency,etc.andtheirmathematicalrelationshipisdeduced.Byanalyzingandcalculatingtheseparameters,theworkingclocksoftheTDICCDlinescancameraarcdesigned,whichguaranteesthesynchronizationofthelinescanrateandthecameramovementspeed.TheIL-E2TDICCDofDALSACo.isusedasthesensorofthecamerainthepaper.TheworkingclockgeneratorusedfnrtheTDICCDsensorisrealizedbyusingtheprogrammablelogicdevice（PLD）.TheexperimentalresultsshowthattheworkingclockgeneratorcircuitsatisfiestherequirementofhighspeedTDICCDlinescancamera.

Keywords:

linescanCCD;timedelayandintegration（TDI）;programmablelogicdevice（PLD）

CLCnumber:

TN386.5Documentcode:

AArticleID:

1005-9113（2006）06-0683-05

HighspeedTDICCDlinescancamerahasbeenusedinsatellitecameras.Satellitecamerasareahightechnologyproductthatconsistsofmanycomponentsandconcernsmanydisciplines，suchasoptics，computertechnology，mechanics，electronics,controlengineering,flightdynamics,etc.Itisalsoasignofanationsspacetechnologylevel.

Satellitesflyinhighspaceandsenddynamicimagesofobjectstoearth.Themainapplicationconditionsarehighscanspeedandlowlightluminance.SoacommonCCDsensorcannotsatisfytheconditions.

ThispaperusesTDICCDsensorsasthecorede-viceofthecamera.TheTDI.CCDisideallysuitedforapplicationsrequiringhighspeedoperationunderlowlightlevelconditions.ThecharacteristicsofTDTCCDinclude;widespectrumresponse，highsensitivity,bigdynamicrange，highprecisiongeometricpositionofpixel,etc.

ForthespecialscanningmethodofTDICCDsensor,theTDICCDcamerarequiresaguaranteeofsynchronizationofthelinescanrateandthecameramovementspeed.Ifthelinescanrateandthecameramovementspeedcannotkeepsynchronization,thequalityofimagingwillhedegradedandtheimagingsystemcannotworknormally.

ThispaperanalysestheoperationparametersoftheTDIlinescanCCDcamera,suchasresolution，linerate，clockfrequency，etc.andtheirmathematicalrelationshipisdeduced.Byanalyzingandcalculatingtheseparameters，theworkingclocksoftheTDICCDlinescancameraaredesigned,whichguaranteesthesynchronizationofthelinescanrateandthecameramovementspeed.TheIL—E2TDICCDofDALSACo.isusedasthesensorofthecamerainthispaper.TheworkingclockgeneratorusedfortheTDICCDsensorisrealizedbyusingtheprogrammablelogicdevice（PLD）.

1ThePrincipleofTDICCD

TDTCCDisaspecialCCDsensor.TDIisamethodofscanningwhichprovidesgreatersensitivitythanothercommonlinearsensors.Byintegratingoverthe6，12,24，48，96lines,TDICCDincreasetheexposuretime.TheTDICCDoperationmaybevisualizedastakingmultipleexposuresofthesameobjectandaddsthem,andthenumberofelectronscreatedbyaCCDsensorincreaseslinearlywiththenumberofTDIstages.ThechargepacketcreatedbytheTDICCDarray（imagingdata）isthentransferredtothereadoutshiftregister.SoTDICCDhasgreatersensitivitythanothercommonlinearsensors，andhaveoftenbeenusedinlowlevellightconditionswhilemaintaininglinescandate.

TheinternalstructureofTDICCDisshownin

Fig.1.

CI1-4showninFig.IareimageregionclocksofaCCD.ThetransferofthechargepacketcreatedinaCCDsensorisachievedinthewellsbyclockingCIl-4.CSSxarethestageselectclocks.TheTDIstagecanbeselectedbyclockingCSSx.TCKisthetransferclock.WhenTCKishigh,thechargepacketcreatedintheTDICCDarrayistransferredtothereadoutshiftregisterofthesensor.CRlandCR2arereadoutclocksofthesensor.VSETisalowvoltage,anditsvalueisbetweenthehighandlowvaluesofCRl.VSETandCR1actasswitcheswhichcontrolthechargepacketinthereadoutshiftregistercanbetransferredtotheoutputstage.Attheoutputstage,VSET,theinputcontrolsignalofthesensor,drivesthechargeofeachindividualpixeltothesensecapacitor

.Thechargepacketwilldevelopavoltageacrosscapacitor

，representingthelightintensityfortheparticularpixel.TheswitchingonandoffoftheSWalternatelycausesadynamicprocessintheoutputstageinsideaCCDsensor.TheswitchSW

RST.ThefrequencyiscontrolledbytheresetsignalofRSTisthedatareadout

oftheCCDsensor.GenerallythereadoutrateisgivenbytheperformanceoftheCCDsensor.Maximumcharacteristics

2.TheAnalysisandCalculationoftheTDICCDTiming

ThecamerausestheIL-E2TDICCDsensor（manufacturedbyDalsaInc.）asthecoredevice.Itsmainperformancecharacteristicsaredescribedasfollows：

（1）2048pixelsperline;

（2）dynamicallyconfigurableas96，48，24，12or6stageTDI;

（3）13μm（H）x13μm（V）pixelsize;

（4）Verticallyandhorizontallysummedsignalsforhighsensitivity;

（5）Upto30MHzeffectivedatarate;

（6）Dynamicrange1600:

1

TheoveralltimingdiagramoftheTDICCDsensorisshowninFig.2.TheCCDclocksignalshaveastricttimingrelationship,theIL-E2timingparametersisillustratedinTab.1.

2.1TheAnalysisandCalculationofLineScanRateofIL-E2TDICCD

TheTDICCDcamerarequiresaguaranteeofthesynchronizationofthelinescanrateandthecameramovementspeed.Ifthelinescanrateandthecameramovementspeedcannotkeepsynchronization,thequalityofimagingwillbedegradedandtheimagingsystemcannotworknormally.

Therelationshipbetweenthelinescanrate

andcameramovementspeedv（km/s）andcameraresolutionp（m）oftheTDICCDsatellitecameraisgivenby

Therelationshipbetweenthelinescanrate

andtheintegrationtime

（asshowninFig.2.）oftheTDICCDsensorisgivenby:

Giventhecameraresolution,throughregulationoftheintegrationtime

，namelythelinescanrate

oftheTDICCDsensor,wecanguaranteethesynchronizationofthelinescanrateandthecameramovementspeed.

Intheimagingsystem，thelinescanrate

ofIL-E2TDICCD（accordingtoformula

（1））designas;

=4kHz.

2.2TheCalculationofClockFrequencyofIL-E2TDICCD

AccordingtothecorrelativeparametersoftheTDICCDsensor,wecandeducethecalculatingformulaoftheclockfrequency:

Where,

istheintegrationtime（asshowninFig.2）.Therelationshipbetweenthelinescanrate

andtheintegrationtime

isgivenbyformula

（2），whereTisthetimetransferringthechargepacketfromimageregiontothereadoutshiftregisteroftheIL-E2TDICCDsensor,anditisillustratedby:

Where,

istheMinimumCIHIGHduration，

3.0μs;

isthetimeofTCKrisingedgetoCI3fallingedge,

0ns;

isthetimeofTCKfallingedgetoCI4risingedge,

0ns（asshowninFig.2）.

AccordingtothecorrelativeparametersoftheTDICCDsensor,the

and

isdesignedas:

=5.0μs，

=100.0ns，

=100.0ns.Then,accordingtoformula（3），wecanobtaintheminimumvalueofclockfrequencyofIL-E2TDICCD.Inpractice，theclockfrequencyisrequiredasf

.Inthisimagingsystem,wechoosethefas:

f=10MHz.

3.DesignoftheWorkingClocksofIL-E2TDICCD

3.1DesignoftheWorkingClocks

Insection2，wegivetheanalysisandcalculationofthelinescanrateandclockfrequency.Now,wecandesigntheworkingclockgeneratorcircuitoftheTDICCDcamera.Inordertoenhanceintegration，reducepowerconsumption,reducesizeandweightofthecamera,thefieldprogrammablegainamplifier（FPGA）ortheprogrammablelogicdevice（PLD）hasbeenchosenasthehardwaredesignplatform.

TheresearchusesEPM7128SLC84-6（Max7000Sseries）manufacturedbyAitera,Inc.togeneratetheworkingclockofTDICCD.TheMax7000SseriesPLDintegrates600~10000gates,32~256macrocelland36~212I/Opins.EPM7128SLC84-6have5000gates，128macrocells,8logicarrayblocksand84pins.

DesignofPLDisrealizedbyusingMaxplusIIsoftware.Thewholedesigncanbedividedintotheseparts:

designofinput,designofcompile，layout,functionandtimingsimulation,deviceprogram，etc.

IL-E2timingdiagramgeneratedbyPLDisshowninFig.3.

3.2DesignofTDICCDStageSelectTiming

ThisimagingsystemchoosesTDICCDsensorasthecoredevice,thusthereisaproblemofhowtoselecttheTDICCDstage.Accordingtothelightintensityofthebackgroundandtherelativemovementspeedbetweenthesatelliteandthesceneryontheearth，settingtheTDICCDstagecorrectlyisveryimportant.

TherearetwobasicrequirementstoTDICCDstageselection;

（1）IL-E2TDICCDstagescanbesetarbitrarilyin96,48,24，12,6;

（2）IL-E2TDICCDstagescanbesetatanyTime

IL-E2TDICCDstageselectionneedspecialin-putclocks.TherelationshipofIL-E2TDICCDstageselectionisshowninTab.2.InTab.2CSSxarethestageselectinputclocks.BysettingtheCSSxto-7V,andremainingCSSxidenticallytoCI4，IL-E2TDICCDstagescanbesetarbitrarily.IL-E2TDICCDstageselecttimingdiagramisdepictedinFig.4.The

stageselectcircuitdiagramisgiveninFig.5.Theproblemneededresolvingistofindhowthesameinputnodecanbedrivenby+12Vpulseaswellas-7Vvoltage.

3.3TheAdjustmentofTDICCDLineScanFrequency

TDICCDisappliedtosatellitecamerasandneedtosolvetheproblemofadjustingthelinescanfrequency.TheTDICCDca