Advantage of the CMOS Sensor Latest image sensor ... · Advantage of the CMOS Sensor Latest image...
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pro.sony-asia.com/security Advantage of the CMOS Sensor Latest image sensor technology for HD security Contents 1. Introduction 2. Comparing CCD and CMOS 3. CMOS Sensor “Exmor” 4. New Wide-D Technology 5. Future Developments Introduction Since the replacement of imaging tube by solid image sensor in the early 80’s, 2 types of sensor, CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) have been used in the video equipments.The easier processing method and low manufacturing cost popularizes the CMOS image sensor in simple image capturing products like web cams and mobile phones, while the CCD technology remains dominant for professional and consumer video equipments. Security industry is one of the largest industry segments which adopted the CCD technology for CCTV camera products. CCD image sensors are used in the majority of analog cameras which are based on TV standard of NTSC or PAL.With the advancement of technology, we see a higher demand for digital security cameras which can transmit digital video signal over IP.The recent pursuit for higher resolution is also increasing the demand for the latest high definition (HD) video standard in the security industry.This rapid shift to HD based system is one of the main driver for the CMOS technology. Striving to merge the advantages of both the CCD and CMOS sensor, research and development are intensely focused on improving the CMOS sensor to become an imaging device which has an equivalent picture quality as the CCD image sensor. As a result, an improved CMOS sensor – “Exmor” CMOS sensor is developed.
Transcript of Advantage of the CMOS Sensor Latest image sensor ... · Advantage of the CMOS Sensor Latest image...
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Advantage of the CMOS SensorLatest image sensor technology for HD security
Contents1. Introduction2.ComparingCCDandCMOS3.CMOSSensor“Exmor”4.NewWide-DTechnology5.FutureDevelopments
IntroductionSince the replacement of imaging tube by solid image sensor intheearly80’s,2typesofsensor,CCD(ChargeCoupledDevice)andCMOS (Complementary Metal Oxide Semiconductor) have beenusedinthevideoequipments.Theeasierprocessingmethodandlowmanufacturing cost popularizes the CMOS image sensor in simpleimagecapturingproducts likewebcamsandmobilephones,whiletheCCDtechnologyremainsdominantforprofessionalandconsumervideoequipments.
SecurityindustryisoneofthelargestindustrysegmentswhichadoptedtheCCDtechnologyforCCTVcameraproducts.CCDimagesensorsareused in themajorityofanalogcameraswhicharebasedonTVstandard of NTSC or PAL. With the advancement of technology, weseeahigherdemandfordigitalsecuritycameraswhichcantransmitdigital video signal over IP.The recent pursuit for higher resolution isalso increasingthedemandfor the latesthighdefinition(HD)videostandardinthesecurityindustry.ThisrapidshifttoHDbasedsystemisoneofthemaindriverfortheCMOStechnology.
StrivingtomergetheadvantagesofboththeCCDandCMOSsensor,research and development are intensely focused on improving theCMOSsensortobecomeanimagingdevicewhichhasanequivalentpicture quality as the CCD image sensor. As a result, an improvedCMOSsensor–“Exmor”CMOSsensorisdeveloped.
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Comparing CCD and CMOSAlthoughbothsensorsareimagecapturingdevicesforacamera,thelatestCCDandCMOSsensorsareverydifferentinstructure.Figure1describesthesestructures.
Fig.1 Read out signals
The CCDs video applications requires all the vertical and horizontal shift registers to constantly relayreceivedimagedataaselectronicsignals.Asaresult,thereisalimitationtoachievehighresolutionandhighspeedsimultaneously.Powerconsumptionalsobecomescomparativelyhigh.Alternatively,theCMOSsensorsonlyneedtomoveonereadoutcolumnofcircuitry,sopowerconsumptionremainscomparativelylowevenwithincreasedprocessingspeed.
CMOS Sensor “Exmor”Inrecentyears,thegrowinginterestinsmallHighDefinitioncamcorderssparkedthesignificantdevelopmentofCMOSsensorswhicharelowpowerconsumptiondeviceswithhigh-speedimagereadoutcapabilities.Thehighdefinitiontrendisalsostartingtogrowinthevideosecurityindustry.CoupledwiththeprevalenceofIPnetworks,theIPvideocameranolongerdependsontheconventionalTVformat.Toaddressthedemandsofhigherresolutionfromthevideosecurity industry,SonystartedtheresearchanddevelopmentofanimprovedCMOSsensorusingitsimagequalityknowledgeaccumulatedinCCDs.TheresultisaCMOSsensorwithanentirelynewstructure,the“Exmor”CMOSsensor.BothCCDandCMOSsensorshavethesamecomponentthatconvertslightintoelectricity(akeyelementofimagequality).Withthe“Exmor”,however,SonyuseshighimagequalitypixeltechnologyaccumulatedinCCDdevelopmenttoenlargeasmuchaspossiblethelight-receivingsectionofthephotodiode.Tables1and2showspecificationsand ImageSensorCharacteristics for the“Exmor”CMOS,CMOSandCCDsensors.
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Anothermajorelementthataffects imagequality isnoisereduction. Inthe“Exmor”CMOSsensor,noiseontheanalogcircuit iseliminatedbythebuilt-inCorrelatedDoubleSampling(CDS)circuit.Othernewstructuralelementsincorporatedintothesensoralsodrasticallydecreasethenoise-contaminationlevel.Figure2andFigure3describethesestructures.
•TheA/Dconversionconventionallydonejustbeforesignalreadoutisnowperformedimmediatelyafterthelight-to-electricityconversionforeachcolumn.Thishelpstoreducenoisebecausetheanalogcircuitismadeshorter,andthefrequencylower.
•Noise-eliminationcircuits(CDScircuit)areequippedinthedigitaldomain.
Table1 Specifications
Table 2 Characteristics
Fig.2 Sensor structure
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Throughthesemethods,drasticimprovementshavebeenmadeinCMOSsensorimagequality,achievingthesameimagecaptureperformancelevelasCCDsensors.InthenewSonyIPvideosecuritycameras,theminimumobjectluminancespecificationsforcamerasequippedwitheitheraCCDoran“Exmor”CMOSsensorareasfollows:
SonyIPvideosecuritycamerawithCCD–SNC-CM120:1.3M,Minimumillumination:0.8lxSonyHDIPvideosecuritycamerawithCMOS–SNC-CH140:720PHD,Minimumillumination:0.2lx
Fig.3 Noise reduction
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View-DR : New Wide-D TechnologyVier-DRusestheHigh-speedReadoutoftheCMOSSensor.Whencomparingthenewlydeveloped“Exmor”CMOS sensor with the CCD sensor, not only has the sensitivity improved, but data (image) readout isdramaticallyfaster.Usingthesehigh-speedreadoutcapabilities,Sony’sHDIPcamerasnowcomeswithanewly-developedWide-Dtechnology,calledtheView-DRfunction.
WithaCCDsensor, theuser is restricted to takingsuccessive1/60-second imagesor two1/30-secondimagesandcombiningthem.InView-DR,theusercantakeone1/30-secondimageatlongexposure,andtakeotherimagesoverthesameperiodatshortexposure,andthenimageprocesstheminreal-timetoachieveanindustry-bestwidedynamicrange.
Figure4showsthestructureofthisindustry-bestWide-D(View-DRfunction)asusedbythe“Exmor”CMOSsensor:
Fig.4 View-DR structure
Future DevelopmentsThedemandforimagewithgreaterdetailsandlessnoisewillcontinuetogrow.Therequirementofhigherresolutioninvideosecurityapplicationswillcontinue,andthiswilldrivethedevelopmentofHDtechnologyinthevideosecuritymarket.Asaresult,CMOSsensors,whichhaveahigherspeedofreadoutdatathanCCDsensors,willbecomepredominantinthesecurityindustryandboththeprofessionalandconsumermarket.
Lookingintothefuture,SonyisresearchingonamoresensitiveCMOSsensorcalledthe“back-illuminatedhigh-sensitivityCMOSimagesensor”.ThisCMOSsensorisnowavailableinvideocamcordersanddigitalstillcameras.TheCMOSsensordeliversboth improvements insensitivityand reductionof imagenoise,bothcrucialinthecaptureofhighimagequality.
©2011 Sony Electronics Asia Pacific Pte. Ltd. All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Features and specifications are subject to change without notice. “Sony”, “make.believe”, “Exmor” and “View-DR” are trademarks of Sony Corporation.
