C-mount lensTelecentricityEdmund Lensnon-telecentricTelecentric lens designF opticsTelecentric illuminatorTelecentric illuminationTelecentric Lenses Tutorial - Thorlabs, Inc.
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Telecentric lenses are designed to have a constant magnification regardless of the object's distance or location in the field of view. ProductsHome / TechnicalResources / CameraandCameraLensTechnicalPublications / TelecentricLensesTutorial TelecentricLensesTutorial PleaseWaitTelecentricTutorial Feedback BrowseOurSelectionofTelecentricLenses TelecentricLenses Telecentriclensesaredesignedtohaveaconstantmagnificationregardlessoftheobject'sdistanceorlocationinthefieldofview.Thisattributeisidealformanymachinevisionmeasurementapplications,asmeasurementsofanobject'sdimensionwillbeindependentofwhereitislocated. TypesofTelecentricLensesInordertoachieveatelecentriclensdesign,allofthechiefrays(raysfromanoff-axispointthatpassthroughthecenteroftheaperturestop)havetobeparalleltotheopticalaxisineitherimagespaceorobjectspace,orboth.Foranobjectspacetelecentriclens,thechiefrayswillbeparalleltotheopticaxisontheobject'ssideofthelens(objectspace).Thisisaccomplishedbysettingtheaperturestopatthefrontfocalplaneofthelens,whichresultsinanentrancepupilatinfinity.Sincechiefraysaredirectedtowardsthecenteroftheentrancepupil,thechiefraysontheobjectsideofthelenswillbeparalleltotheopticalaxis.AnexampleofanobjectspacetelecentriclensisshowninFigure1. Figure1:Araytracethroughanidealizedobjectspacetelecentriclenssystem.Notethatthechiefrays(thecenterrayofeachcolor) areparalleltotheopticalaxisinobjectspace,butinimagespace,thechiefraysformananglewiththeopticalaxis. Foranimagespacetelecentriclens,thechiefrayswillbeparalleltotheopticalaxisontheimage'ssideofthelens(imagespace).Thisisaccomplishedbysettingtheaperturestopatthebackfocalplaneofthelens,whichresultsinanexitpupilatinfinity.Sincethechiefraysmustpassthroughthecenteroftheexitpupil,thechiefraysontheimagesideofthelensmustbeparalleltotheopticalaxis.Foradoubletelecentric,orbi-telecentric,lens,thefrontandbackfocalplanesaremadetooverlapsothattheaperturestopislocatedwhereboththeentranceandexitpupilsareatinfinity.Inabi-telecentriclens,neithertheimagenorobjectlocationwillaffectthemagnification.Thorlabs'telecentriclensesareallbi-telecentricdesigns.Figure2showsanexampleraytracethroughabi-telecentriclensandillustrateshowthechiefrayspassthroughthesystem. Figure2:Araytracethroughanidealizedbi-telecentriclenssystem.Notethatthechiefrays(thecenterrayofeachcolor)areparalleltotheopticalaxisinbothimageandobjectspace,whichmeansthatthemagnificationwillremainconstantregardlessofobjectdistance. ConventionalLensesInconventionallenses,theentranceandexitpupilsarenotlocatedatinfinity,sothechiefrayswillnotbeparalleltotheopticalaxis.Inthiscase,themagnificationoftheobjectdependsonitsdistancefromthelensanditspositioninthefieldofview.Figure3showsanexampleraytracethroughaconventionalcameralens;noticehowthechiefraysareangledwithrespecttotheopticalaxisinbothimageandobjectspace.NotethatbothFigures2and3featurethesamelensdesign;onlytheaperturestoplocationwasvariedtoshiftthetelecentricsystemtoanon-telecentricone. Figure3:Araytracethroughanidealizedconventionalcameralenssystem.Notethatthechiefrays(thecenterrayofeachcolor) arenotparalleltotheopticaxisinbothimageandobjectspace,whichmeansthatthemagnificationwillvarywithobjectdistance. ExampleImagesFigures4and5showphotographstakenwithatelecentriclensandastandardcameralens,respectively.Withthetelecentricimagingsystem(Fig.4),theheightofthetwoscrewsappearstobethesame,eventhoughtheobjectplanesareseparatedbyapproximately45mmalongtheopticalaxis.Withtheconventionalimagingsystem(Fig.5),thetwoscrewsappeartobedifferentheights,andthereforeamachinevisionsystembasedonthislenswillleadtoincorrectdimensionalmeasurements. ClicktoEnlargeFigure4:Animageoftwoidentical8-32capscrewsimagedwithourpreviousgeneration MVTC230130.128XTelecentricLens.Althoughthescrewsappeartobethesamesizeandinthesameobjectplane,theyareactuallyseparatedbyadistanceofapproximately45mmalongtheopticalaxis. ClicktoEnlargeFigure5:ThesametwoscrewsphotographedwithourMVL7000 conventionalzoomlens.Inthisimage,theperspectiveerrorduetotheseparationofthescrewswouldleadtoincorrectheightmeasurements.PleaseGiveUsYourFeedback1.FirstName 2.LastName SubmitAnonymously:3.Email ContactMe:4.FeedbackOn ALLPRODUCTSPresentationFeedbackPrefertoRequestaQuote?RequestQuote5.EnterCommentsBelow:Charactersremaining 8000 6.SubmitFeedback:CharactersareCase-SensitiveClickforanewcode.PostedComments:mojtabaseydi  (posted2019-06-0311:58:19.72)Hello.Thereisatypointhe"ConventionalLenses"part,whenyouwanttoreferfigure3."figure2iswrong"YLohia  (posted2019-06-0311:36:26.0)Hello,thankyouforbringingthistypotoourattention!We'reworkingtogetthiscorrected.×SubscribetobeNotifiedAboutUpcomingWebinars!*FirstNameRequired*LastNameRequired*EmailRequiredCompany/InstitutionJobTitleCharactersareCase-SensitiveClickforanewcode.AdditionalCameraandCameraLensTechnicalPublicationsScientificCameraBasicsCameraNoiseandSensorTemperatureCameraLensesTelecentricLenses
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