视场光阑与孔径光阑doc.docx

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视场光阑与孔径光阑doc

视场光阑与孔径光阑[doc]

ChapterVFieldstopandaperturestop

视场光阑与孔径光阑

5.1Fieldstopandaperturestop视场光阑与孔径光阑

5.2Filedofview视场

5.3Vignettingandfieldlens渐晕与场镜5.4Telecentricsystem远心系统5.5Depthoffocusanddepthoffield焦深与景深

5.6Straylightinlenses透镜中的杂散光

5.1Fieldstopandaperturestop

一、Fieldstopandaperturestop

Aperturestop:

Thestopclosetolenslimitsthesizeofthebundlesofraysofaxispoint.Itdeterminestheamountoflightreachinganygivenpointintheimage,thereforecontrolsthebrightnessofimage（imageplane）.

Fieldstop:

Justfrontofthefocalplanelimitstheangleatwhichtheincidentbundlescangetthroughtothisplane（imageplane）.Itdeterminestheextentoftheobjectorthefield.（Fieldstopisusuallymadetocoincidewithimage.）

二、Entrancepupilandexitpupil

EP:

Theimageofaperturestopformedbyprecedingit.

':

Theimageofaperturestopformedbyfollowingit.EP

PLTheimageofthisstop,asformedbythelensisfoundtolieattheposition.

''*Sinceisinsidethefocalplane,itsimageliesintheobjectspaceandisvirtualanderect,PLPL

PLcalledentrancepupil.

''*liesintheimagespace,calledexitpupil.PL

'''`*,,arepairsofconjugatedpoints.AnyrayintheobjectspacedirectedthroughoneofPPLLEE

thesepointswillafterrefractionpassthroughitsconjugatepointintheimagespace.

三、Chiefray

Anyrayintheobjectspacethatpassesthroughthecenterofentrancepupiliscalledchiefray.After

refractingalsopassthroughthecenteroftheexitpupil.*Chiefrayisacentralrayofobliquerays.

preliminarydesignofanopticalinstrument,mustdeterminewhichoneactuallydoesthelimiting?

ln

Theentrancepupilofthecentricsystemistheimageoftheaperturestopformedbyalllensespreceding

it.

Theexitpupilistheimageformedbyalllensesfollowingit.

四、Stopbetweentwolenses

Chiefraypassthroughtheentrancepupil,thestopandtheexitpupil.

Howtodetermineaperturestop?

五、Twolenseswithnostop

Theperipheryofanylensinsystemisapotentialstop.

Objectatinfinity,:

entrancepupil.MN11

''ObjectatA,:

entrancepupilPL22

Determinationoftheaperturestop

Thesystemconsistsoftowlensesandastop.'isthevirtualimageofthefirst（）andastopformedby（）lens1lens2LLP1212

':

VirtualimageofthestopPformedby.lens2P0

:

Virtualimageofthestopformedby.lens1P0

:

Virtualimageofthesecondlensformedby.lens1P21

ForallaxialobjectpointslyingtotheleftofX,limitstheentrancebundleofraystothesmallestP0angle.

constitutestheentrancepupil.P0

'constitutestheexitpupil.P0

'ForallaxialobjectpointlyingtotherightofZ,istheentrancepupilandistheexitpupil.PP212

Nominalaperturestop:

Theaperturestopofanysystemmaychangewithachangeintheobjectposition.

Generalrule:

theaperturestopofthesystemisdeterminedbythatstoporimageofstopwhichsubtendsthesmallestangleasseenfromtheobjectpoint.

Telescopeandmicroscope（lowpower）:

usuallyaperturestopisselectedatthelarge-sizedobjectivelens.

5.2Fieldofview

一、Fieldofview

2W:

objectfieldandimagefield

Lookoutatlandscapethroughawindow.

Fig1:

Thefieldofviewislimitedbythesizeofwindowandbythepositionoftheeye.Windowisfieldstop.

Generalspeaking,fieldstopisatimageplane.（suchastelescope,microscope）Themarginofreticleorfilmisfieldstoporframe.

二、Fieldofaplanemirror

Thefieldofviewofferedbyaplanemirrorisverysimilartothatofasimplewindow.

'':

observer’seye,whichconstitutestheexitpupil.MN

:

Theentrancepupil,virtualimageoftheeyepupilformedbymirror.MN

Chiefraysdefinethefieldofview.

TheobjectBandentrancepupilMNareintheobjectspace.

三、Howcanyoudefinethefieldofviewofaconvexmirror?

四、Fieldofapositivelens

Thepupilofeyeisanexitpupilandaperturestop.

:

theimageofeyeisanentrancepupil.MN

Thefieldstopinthiscaseisthelensitself.

ABFPEObjectisinapositioninsidetheprimaryfocalpoint.Througheachofthreepoints、、

'L,raysaredrawnfromBtolens.

'''LRefractedraysaredirectedthroughP、E、,virtualimageislocatedatB.

*Whenconverginglensisusedasamagnifier,theeyeshouldbeplacedclosetothelens,sincethis

widenstheimage-fieldangle.

Forvisualvisionalopticalinstruments,theeyeshouldbeplacedtheexitpupilofopticalsystem,suchas

telescopesandmicroscopes.

五、Entrancewindowandexitwindow

Entrancewindowistheimageoffieldstoopformedbyalllensesprecedingit.

Exitwindowistheimageoffieldstoopformedbyalllensesfollowingit.

Bothentranceandexitwindowareatinfinity.六、ApertureangleandfieldangleApertureangle

:

Apertureangleintheobjectspace.On-axispointsubtendtothemarginofentrancepupil.u

':

Apertureangleintheimagespace.On-axisimagepointsubtendtothemarginofexitpupil.u

Fieldangle

:

Thecenterofentrancepupilsubtendedtothemarginofentrancewindow.w

':

Thecenterofexitpupilsubtendedtothemarginofexitwindow.w

5.3VignettingandFieldlens一、Vignetting

Atsmallfiledofview,thehighestandlowestrayspassingthroughthelens,strikethetopandbottom

'EPof,,.EPAS

Atgreaterfieldofview,entranceupperandlowerraysareoftenlimitedbythefrontandrearlensopenings.Thefailureofanobliquebeamisknownasvignetting.

Thebrightnessofanimagewillbegraduallydecreaseddarken,whenthefieldofviewincreased.

DwCoefficientofvignettingk,

D

Chiefray（principalray）:

passesthroughthemiddleofaperturestopfromoff-axisobjectpointortheraythatentersthelensmidwaybetweenthehighestandlowestraysofobliquebeam.

二、Fieldlens

（1）Inordertoreducethesizeoffollowingopticalsystem,fieldlensisusuallyattheimageplane.

'（SeechapterI）ll,,,,01,

FreefromSSSCCIIIIIIIII

Thereareonlyfieldcurvatureanddistortioncausedby.SSSIVVIV

（2）Fieldlenscanbeusedtochangethepositionofexitpupiltosatisfypupilconnection.

Exitpupilofprecedingsystemshouldbecoincidewithentrancepupiloffollowingsystem.

IGalileantelescope

Aperturestop:

rimofobjectivesoisentrancepupilFieldstop:

eyepiecesoisexitwindow

IIKeplertelescope

reticleisfieldstop.

Entrancewindowandexitwindowareatinfinity.Fieldangle:

D,1tgw,',2f,1,D'2,tgw,',2f2,

'Exitpupiliscloseto.F2

ifeyeirisislessthanexitpupil,irisisaperturestop.IIIMicroscopewithlowmagnification

Aperturestopistherimofobjectivesoisentrancepupil.Fieldstopistherimofreticle.

Entrancewindowcoincideswithobjectplane.Exitwindowcoincidewithimageplane（infinity）.

5.4TelecentricsystemIobjectspacetelecentricsystemIIimagespacetelecentricsystemIIIdoubletelecentricsystem

*Inmostcases,theaperturestopislocatedsomewhereinsidethelens,suchasphotographiccameras.

*eyepiecescondenserareexceptions.一、Telecentricsystem1）Telecentricsystemintheobjectspace:

'Theaperturestopisattherearfocalplane.F

Theenteringprincipalrayisparalleltoaxis.

2）Telecentricsystemintheimagespace:

FTheaperturestopisatthefrontfocus.Theenteringbeamcomefrominfinity,andexitingprincipalrayisparalleltoaxis.

3）Telecentricsystematthebothends:

''Theaperturestopisat.andarecoincided.FFFF2112

Thesystemusuallyusedasinvertingsystemandrelaylens.

二、Contourprojector

Contourorprofileprojectorisainstrumentforprojectingamagnifiedimageofasmallmechanicalpartstocheckitsdimensions.

，，，，1020505

Theopticalsystemisinvariabletelecentric,thevirtualofatelecentricsystemisthatthesizeoftheprojectedimagedoesnotalter,iftheimageisslightlyoutoffocus.

Thediameterofthelensaperturemustbegreaterthanthediameteroftheobject.

Condenserlensnearthelamp,providingcollimatedlight,mustalsobelargerthanthelargestobjecttobeprojected.

Finalimageisgenerallyprojectedonagroundglassscreen,sometimesequippedwithFresnellenstobrightenuptheouterpartsofscreen.

5.5Depthoffocusanddepthoffield

一、concept

Assumingthelensisfreefromallaberrations.

1）Therewillbeaceitainplaneintheobjectspacethatispreciselyconjugatetothefilmplaneinthe

imagespace.Thisisknownasthefocusedplaneintheobject.

2）Theobserver’seyeshavealimitedacuity.

Therewillbeasmallamountoftolerableblurinaphotographthatobserverwillbeunabletodistinguishitfromsharpimage.

apointobjectmaybeimagedasasmallcircleofconfusiononthefilm.,

Thedepthoffocusoflensisthedistancealongtheofsharpdefinitiontotheplanewheretheimageofapointsourcejustreachesthiscircleofconfusion.

Thedepthoffieldoflensisthecorrespondingdistanceofanobjectpointfromthefocusedplaneinobjectspacetotheplanewhereitsimagereachesthepermissiblecircleofconfusioninthefilmplane.

二、calculation

'1.DepthoffocusisobviouslyequaltotheproductofthediameterofthepermissiblecircleofC

confusiononthefilmandtheF-NumberFofthelens.

'f'''CNC,,*,*D

Thedistanceisthesamewhethertheimageisjustwithinorjustbeyondthe

filmplane.

'howlarge?

C,?

Whenapictureisviewedbyanobserver,mostpeopleareincapableofdistinguishingbetweenaperfectpointandasmallcircleofconfusionthatsubtendsabout2arc-min.

2.Thedepthoffield

Thediagramisbasedonthefactthateverythinglyinginthefocusedplanewillbeimagedsharplyonthe

fi