whats-CRA

SecurityB:HighlyConfidential1OmniVisionCRACorrectionMatchingSensorstoLensesforBetterImagingSystemsJune2009SecurityB:HighlyConfidential2AgendaWhatisCRA?HowCRAaffectslightcollectionefficiencyofthesensorHowtomakeyourselectionSummarySecurityB:HighlyConfidential3WhatisCRA?CRAisanacronymforChiefRayAngleTheangleoftheincidentrayspassingthroughthecenterofthelensaperture•MeasuredattheimagesensorCenterofthesensorCRA=0°CRAtypicallyincreasesforpixelsfurthestawayfromthecenterofthesensorLensImageSensorApertureChiefRay1ChiefRay2CRA1CRA2HalfFieldofViewOpticalaxisSecurityB:HighlyConfidential4LightcollectionefficiencyreductionOn-AxisPixelLightsensitiveregionCRA=0°MetalTracesLensletLightsensitiveregionCRA=25°RaysblockedOff-AxisPixelCommonCMOSpixelsbehavelike“photonbuckets”thatcollectlighttowardsthelight-sensitiveregionatthebottom•DoesnotapplytoOmniBSI™AstheCRAincreases,lightisblockedbymetaltraces,resultinginreducedlightcollectionefficiencySecurityB:HighlyConfidential5LargerpixelslesssusceptibletopixelefficiencyreductionathigherCRAsthansmallerpixelsSmallerpixelsmorelikelytogetblockedbeforereachingthelight-sensitiveregion•EspeciallywhenlightisincidentatanangleLightsensitiveregionCRA=25°RaysBlockedSmallerOff-AxisPixelLargerOff-AxisPixelLightsensitiveregionCRA=25°LessraysblockedwithwiderpixelsLargerpixelslesssensitivetoCRAvariationsSecurityB:HighlyConfidential6InOmniBSI™pixels,lightarrivesatthelight-sensitiveregionwithoutbeingblockedbymetaltracesOmniBSIpixelslesssusceptibletopixelefficiencyreductionathigherCRAsthanfront-sideillumination(FSI)pixelsOmniBSI™™pixelslesssusceptibletoCRAvariationsLightsensitiveregionCRA=25°RaysblockedFSIOff-AxisPixelBSIOff-AxisPixelLightsensitiveregionCRA=25°SecurityB:HighlyConfidential7LensletarraysshiftforCRAcorrectioninFSIFSIlensletarrayscommonlyshifttocollectmorelightintolight-sensitiveregionAmountofshiftproportionaltoCRALightsensitiveregionCRA=25°LightsensitiveregionCRA=13°LightsensitiveregionCRA=0°MetalTracesLensletOn-AxisPixelMid-FieldPixelCornerPixelFurtherLensletShiftLensletShiftSecurityB:HighlyConfidential8Quantumefficiency(QE)versusCRALargerpixelsorOmniBSI™pixelslesssusceptibletoQEreductionathigherCRAsForOVT(CRA=25°)FSIsensors,theon-axispixelsreachthepeakquantumefficiencyat0°CRACornerpixelsreachpeakquantumefficiencyat25°CRAmatchingthelensCRAof25°0102030-10ChiefRayAngle(deg)NormalizedQE10.5PixelEfficiencywithoutLensletShift(On-AxisPixels)0102030-10ChiefRayAngle(deg)NormalizedQE10.5CRACorrectedPixelEfficiency(CRA=25°CornerPixels)PeakQEatCRA=25°Largerpixels(orBSI)SmallerpixelsPeakQEatCRA=0°SecurityB:HighlyConfidential9MatchingLensandSensorCRAMatchingthemaximumCRAofthelenswiththemaximumCRAofthecorrectedsensorresultsinanimprovementofthelightcollectionefficiencyofthecornerpixelsLensletarrayshiftedforCRAmatchingImagingLensAperturePixelPixelPixelLensCRASecurityB:HighlyConfidential10WhatsensorstousewithwideangleLenses?RecommendusingOVTimagesensorswithCRA=25°orlargerorOmniBSI™withwideanglelenses(lenseswithlargefieldofviewandtypicallylargerCRA)ThiswillminimizepixelquantumefficiencyreductionatsensorcornersLensletarrayshiftedforCRAmatchingImagingLensAperturePixelPixelPixelLensCRASecurityB:HighlyConfidential11Whatsensorstousewithimage-spacetelecentriclenses?Image-spacetelecentriclenseshaveCRA=0°acrosstheentireimagesensorRecommendusingOVTsensorswithoutlensletarrayshiftImagingLensAperturePixelPixelPixelLensCRA=0°fNoLensletArrayShiftNeededSecurityB:HighlyConfidential12Telephotolensesusuallyhaveasmallfieldofview(lessthan10°)ThisresultsinsmallCRAsattheimagesensors(i.e.,5degreesorless)RecommendusingOVTsensorswithoutlensletarrayshiftWhatsensorstousewithtelephotolenses?TelephotoLensImageSensorApertureSmallLensCRASecurityB:HighlyConfidential13Whatsensorstousewithzoomlenses?ZoomlenseshavevariablefocallengthsanddifferentCRAswhenoperatingattelephotoorwideanglezoompositionsCRAatwide-anglezoompositionlargerthanCRAattelephotozoompositionNosingleimagesensorwillbeCRAmatchedatbothzoompositionsRecommendusinglargerpixelsorOmniBSI™™•OrmatchCRAtolensposition(wide-angleortelephoto)•OrmatchCRAtointermediateanglewithinthetotalrangeLens1VirtualImageofLens1Lens2Wide-anglezoompositionTelephotozoompositionLargerCRAatwide-anglezoompositionSmallerCRAattelephotozoompositionSecurityB:HighlyConfidential14SensorCRASelectionGuidelinesLensTypeCRAApplicationAreasOVTSensorsWideanglelensesLarge(25°)Mobilephones,Notebook/webcamsGames&ToysMedicalSecurityAutomotiveDSCLenslet-shiftedOVTsensors(e.g.CRA=25°orlarger)OrOmniBSI™sensorsTelephotoorImage-spacetelecentriclensesSmall(5°)DSCSecurityMachine-visionOVTsensorswithoutlensletshift(i.e.CRA=0°)ZoomlensesVariable(~1°-~30°)SecurityDSCApplication-dependent;LargepixelsensorsOrOmniBSI™sensorsSecurityB:HighlyConfidential15ConclusionsMatchingthelensCRAwiththerightOVTimagesensorsimproveslightcollectionefficiencyatcornersLargerpixelsorOmniBSI™pixelsarelesssensitivetoCRAvariationsthansmallerFSIpixelsManyOVTimagesensorsaredesignedtohavealensletarrayshifttomatchthelensCRA•Desig