应用光学chapter3.ppt

1、Chapter3Instrumentsforhumaneyes,Visualopticalsystem:Theinstrumentsworkingwiththehumaneyes,Contents,ThecharacteristicsofthehumaneyesPrinciplesandstructuresofmicroscopesandtelescopesHowdoestheopticalinstrumentworkwiththehumaneyes?Defectsoftheeyesanddiopteraccommodationofopticalinstruments,3-1Character

2、isticsoftheeye,VisualopticalsystemisusedtoimproveourvisionabilityItworkswithhumaneyesHumaneyesactsasasub-opticalsystemofthewholesystem,F,Fo,Fe,Telescope+eyes,Structureoftheeye,LensFilmStop,Theeyecanbecalledasupercamera.Itcanautomaticallyzoomandfocus,itcanalsoadjusttheeneryenteringtheeyes.,Inopticalv

3、iewpoint,thehumaneyeshavethreeimportantpartscorrespondingtothefollowingcomponents：,Cornea:Transparentsphericalmembrane,theincidentrayspassthecorneafirstly.n=1.3771,Frontalchamber:Theroombehindthecornea,fullofclear,wateryfluid,n=1.3374,convergestheray.,Lens:Biconvexlens,themusclearoundthelenscontract

4、stomaketheradiusoftheformersurfaceofthelensdiminish,whichleadstotheshorteningoftheeyeseffectivefocallength.itisconsistedofseverallayswithdifferentindex.,Cornea,frontalchamberandlensactsasthepartofalensofacamera.,Retina:Opticnervecellandopticnervefiber,actsasasensitivefilm.,Yellowspot(macularfovea):T

5、hemostsensitiveareaonretina.,Retinaandyellowspotactasthephoto-sensitiveportionofacamera,Blindspot:Locatedwherethenervefibersleavetheeyeball,nosensitivecellonitandnovisioncanbeformed.,Testoftheblindspot,Itactsasanvariablestop(irisdiaphragm)ofacamera.,Iris:Themembranesuspendedbetweenthecorneaandlens.I

6、nthecenteroftheirisisthepupilwhichregulatestheamountoflightenteringtheeye,question：acameraformsaninvertedimageonthefilm,howabouthumaneyes?,Theoutsideraysenterhumaneye,formsanimageontheretina,andtheimpulsesignalsaregeneratedbyopticnervecells,thesignalstransmittobrainthroughtheopticalnerve.Thevisionfo

7、rmsafterprocessingbythenervecenter.,Theprocessofphysics,physiologyandpsychology.,Theformofvision,Opticalaxis:Thelinkofthemacularfoveaandtheimagenodalpointoftheeye.,Viewingfieldofhumaneye:Thefieldofvisionofaneyecanextendto150degree.Keepingourheadstill,wecanonlygetaclearimageof68aroundthecenterofoptic

8、alaxis.Inordertoseewidely,theeyeballcanrotateautomatically,andtheheadmovesaswell.,Termsdescribingtheopticalcharacteristicsofhumaneyes,Whenthepositionoftheobjectchanges,theeyewillautomaticallyadjustitsfocallengthtomaketheimagefallstillontheretina.Thisprocessiscalledthediopteraccommodation.,F2,Diopter

9、accommodationpupilaccommodation,Theaccommodationsoftheeye,Eye=asupercamera,1.Diopteraccommodation,F1,Forannormalrelaxedeye,theinfiniteobjectimagesontheretina;whenobservetheobjectnearby,thefocalpointoftheeyemoveforward.,Expressionoftheaccommodationdegree:Diopter,Thereciprocalofthedistance,whichisfrom

10、theobjectplane(conjugateofretina)totheeye,1,l,SD=,Theunitoflismeter,Example:whenobservingobjectwitha2mdistance,sinceThusthediopteroftheeyeis-0.5.,NormalReadingDistance,NearPointandFarPoint,Normalreadingdistance:250mminfrontoftheeye，SD=(1/(-0.25)=-4,Nearpoint:Theshortestdistancewhichtheeyecanseeclear

11、lybyaccommodation.,Farpoint:Thelongestdistancewhichtheeyecanseeclearly.,Maximumaccommodationrange=SDofnearpointSDoffarpoint,Differentaccommodationrangesofpeopleindifferentages,2.Pupilaccommodation,Theiriscanexpandorcontracttocontroltheamountoflightadmittedtotheeye.Underverybrightconditions,daytimeD=

12、2mm;Atnight,D=8mmWhenwedesignanopticalsystem,theexitpupiloftheopticalinstrumentmustmatchwiththepupilofthehumaneye.Whenitisusedonthedaytime,theexitpupilcanbesmaller;andwhenusedatnight,itmustbebigger.,Thebrightnessoftheoutsideobjectwillchangewithobjects,weatherandtimes.,VisualAcuityoftheEye,Supposetwo

13、pointobjectsimagedontheretina.Ifthedistancebetweenthetwoimagesislongenough,theycanberecognizedbynakedeye,howeverifthedistanceistooshort,theymaynotberecognizedbythehumaneye.,Visualacuity(VA)oftwopointobjects：definition:distancebetweentheimagesoftwopointsonretinawhichcanbejustrecognized.,TheStructureo

14、fretina,Retinaiscomposedoftheopticalnervecells,whichconsistofconecellsandrodcells,Conecells:Workunderverybrightconditions(photopicvision)Rodcells:Workinverydimlight(Scotopicvision),y,Ifthedistancebetweentwopointimagesarenolessthantwotimesthediameterofthenervecells,orifthetwopointimageslocateontwocel

15、lswhoarenotadjacenttoeachother,thetwopointimagescanberecognized.,Thediameterofanervecellisabout0.001-0.003mm,sowecantake0.006mmasthestandardoftheeye.,Usually,weusethecorrespondingangularintheobjectspacetoexpressvisualacuity,whichiscalledtheangularresolutionoftheeye.Itistheminimumanglesubtendedbytwoo

16、bjectswhichcanbejustrecognizedbytheeye,Whenymin=-0.006mm，f=-16.68mmWeget,Fromthefigure,wehave,Conclusion:fortwopoints,theangularresolutionis60”.,Inmanyactualopticalinstrumentssuchmodeofalignmentisalwaysadoptedtoimprovethemeasureprecision.,Thevisualacuityofthelineiscalledaimingprecision,asshowninther

17、ightpicture,itcanreach10”.,Thevisualacuityoftheline:Thevisualacuityoftheeyecanbeimprovedupto10”,Necessarycondition:,Sufficientcondition:,fortwopoints,fortwolines,Imagingonretina,Summary:,Conditionsforseeingclearly,3-2PrinciplesofMagnifierandMicroscope,Iftheanglesubtendedbytheobjecttotheeyecannotreac

18、htheeyesangularresolution,howcanwedoinordertodiscerntheobjects?,Question:,Visualopticalsystem,Whatsthecommonrequirementsforvisualopticalsystems,1,Whatstheprincipleofthemagnifier,2,Whatstheprincipleofthemicroscope,3,3.2PrinciplesofMagnifierandMicroscope,Enlargingtheviewingangle,Observingdirectly:,Obs

19、ervingthroughanopticalinstrument:,-ye=tge,-yi=tgi,1Commonrequirementsforvisualopticalsystems,Theratiooftheimageheightswhenobservingthroughopticalinstrumentandobservingdirectlybytheeyedenotesthemagnifyingpoweroftheinstrument,expressedwithasymbol.,yi,ye,tgi,tge,tgi,tge,Thebiggeris,thehigherthemagnifyi

20、ngpoweris.canbepositiveornegative.:positive,erectimage;:negative,invertedimage,yi,ye,tgi,tge,tgi,tge,isanimportantpropertyofvisualinstruments.,Imagingatinfinity,1Commonrequirementsforvisualopticalsystems(continue),F,Fo,Fe,Inordertoavoidtheeyesfatiguewhenobseringthroughtheinstrument,theeyeneedstobein

21、normal,relaxedsituation.Inthiscase,theinfiniteobjectwilljustimageontheretina.,Astheobjectofeyeisjusttheimageoftheopticalinstrument,theconditionaboverequiresthattheinstrumentmustformanimageatinfinity.,Commonrequirementsforvisualopticalsystem,Imagingatinfinity,Enlargingtheviewingangle,Whatsthecommonre

22、quirementsforvisualopticalsystems?,Commonrequirementsforvisualopticalsystems,1,Whatstheprincipleofthemagnifier,2,Principleofthemicroscope,3,3.2PrinciplesofMagnifierandMicroscope,y,-l,y,Anglewhenviewingdirectly,Thecommonrequirement,Discuss：Thefactorswhichinfluencetheviewingangle,Theminimumviewangle,I

23、nordertoenlargetheviewangle：,reducel？,Increasey？,Magnifieranopticalsystemwhichpresentstotheeyeanenlargedimageofnear,tinyobject,Principlesofmagnifier,F,-f=f,y,i,Thedesignfollowsthe2commonrequirementsforvisualopticalsystem,1Imagingatinfinity,F,-f=f,y,i,tgi,tge,=,250,f,tge,=,y,f,=,tgi,y,-l,=,y,250,2.en

24、largingviewangle?,y,Themagnifyingpowerofthemagnifier,Ifweexpect,therequirementisf0,thesignsofandaresame,formingerectimage0,thesignsofandarereversed,forminginvertedimage,Typesoftelescopes:,Kepleriantelescope:Bothobjectiveandeyepiecearepositivelenses.,0,formsanerectimage,itdoesnotneedtoaddanerectingle

25、ns.volumeissmaller.SincethereisnorealimageintheGalileantelescope,wecannotputareticuleinsidethesystem.Itcantbeusedforaimingandmeasuring.itsusuallyusedforwatching.,Question:,CantheobjectiveandeyepieceofaGalileantelescopechangewitheachother?,CantheobjectiveandeyepieceofaKepleriantelescopechangewitheach

26、other?,WhereisthereticuleofaKepleriantelescopelocatedin?,Canatelescopebemadeupbytheobjectiveandeyepiecebothwithnegativefocallengths?,characteristicofthemagnifyingpowerofatelescope,Theincidentrayareparallel,thefieldangleofeachrayandtheaxisarethesame.Theemergentraysaresimilar.,eachraycanberegardedasem

27、ittingfromdifferentpointonaxis,andtheirconjugatepointsaretheintersectionpointsoftheircorrespondingemergentraysandtheaxis.Thisequationmeansthattheangularmagnificationofatelescopeisindependentofthepositionsoftheconjugateplanes,numericallyequalstoitsmagnifyingpower.,Theincidentrayandtheemergentraysarep

28、arallel.,Themagnifyingpowerofatelescope,Thelateralmagnificationisindependentofthepositionsoftheconjugateplanes,numericallyequalstothereciprocalofitsmagnifyingpower.,Anotherformof,Methodofmeasuringthemagnifyingpower:Dynameter,Example:Themethodofalignmentofageodetictelescopeadoptstwostraitlines.Theaim

29、ingerrorislessthan2mmwhentheobjectdistanceis1km.Determinethemagnifyingpowerofthetelescope.,3-4DefectofEyesandDiopterAccommodationofOpticalInstruments,AFocalpointF,thenearpointandthefarpointofnormaleyes,1.DefectofEyes,Passingthrougharelaxednormaleye,theinfiniteobjectwillimageattheretina,viz.thefocalp

30、ointFfallsontheretina.,F,whenthenormaleyesobservecloserobject,Fcanbemovedforwardbydiopteraccommodation,thentheeyere-imageitagainontheretina.,Thelongestdistancetheeyecanseeclearlyiscalledthefarpointdistance.Whentheeyesarerelaxed,thefarpointcoincideswiththeconjugateobjectplaneoftheimageontheretina,The

31、nearestdistancetheeyecanseeclearlybyaccommodationiscalledthenearpointdistance.,F,B.Thecharacteristicofnearsightedness(myopia),Sincethesecondfocalpointofanearsightedeyefallsaheadoftheretina,theimageofaninfiniteobjectcannotbefocusedclearlyontheretina.,Thenearsightedeyecannotseetheinfiniteobjectclearly

32、,itcanonlyseeobjectswithincertaindistance(thefarpointdistance).Thefarpointiswheretheobjectconjugateplaneoftheretinaofanearsightedeyelocates.Itcanonlyseetheobjectswithinthefarpointdistancebyaccommodation.,Themyopicdegreeisoftenexpressedbythediopterofthefarpointdistanceofthenearsightedeye.,Forexample,

33、apersonwhosefarpointdistanceis0.5m,thecorrespondingdiopterofmyopiaisSD=1/(-0.5)=-2,iatricaldegreecorrespondstodiopter,quantitatively1diopter100Thus,themyopicdegreeofthepersonis200,Thenearestdistanceofmyopiceye,thenormalreadingdistance,C.Thecorrectionofthenearsightedeye,F,Farpoint,Negativelensisused,

34、thefocallengthofthenegativelens=thefarpointdistanceoftheeye,Problem:apersonwhosefarpointdistanceis200mm,howmuchisthedegreeoftheglassesheneeded?Andhowmuchistheeffectivefocallengthoftheglasses?,F,D.Thecharacteristicofthefarsightedeye(hyperopia),Thesecondfocalpointofthefarsightedeyefallsbehindtheretina

35、.Afarsightedpersoncanpossiblyseetheinfiniteobjectbyaccommodation.,F,F,retina,Thefarpointofthefarsightedeyelocatesbehindtheeye.Thenearpointdistancewillbeincreased.,A1,A2,A3,A4,E.Thecorrectionoffarsightedeye,F,Farpoint,Hyperopiacanbecorrectedbytheuseofapositivelens.thefocallengthofthepositivelens=thef

36、arpointdistanceoftheeye,Example:Apersoncannotseetheobjectclearlywhichisfartherthan1m,howmuchisthedegreeoftheglassesheneeded?Theotherpersoncannotseetheobjectclearlywhichisnearerthan1m,howmuchisthedegreeoftheglassesheneeded?,Thefirstperson,Thesecondperson:Thenearpointdistanceis1m,theobjectlocatedin250

37、mmneedstobeimagedatthedistanceof1m.,2.DiopterAccommodationofOpticalInstruments,objective,Normaleye,eyepiece,F,F,Myopia,Fo,Fe,Fe,F,hyperopia,Fe,farpoint,farpoint,CalculationofAccommodation,Accordingtoxx=ff,Notice：WhenSDis“”,xis“”,theeyepiecewillmovetowardstheobjective;WhenSDis“”,xis“”,theeyepiecewill

38、moveawayfromtheobjective.,F,Fe,Fe,CalculationofAccommodation,Inpracticalapplications,thegraduationofthediopterisengravedontheeyesightframe.Byturningtheeyepiecethedioptercanbeaccommodated.,Inpracticalopticalsystems,reticuleisontheimagefocalplane.Inordertoavoideyepieceandreticuletouchingmutuallywhiled

39、iopteraccommodating,thedistancebetweenthereticuleandthefirstsurfaceoftheeyepieceshouldbelongenough.,3-5SpatialDepthofFocusandStereoscopiceffect,1ThespatialdepthperceptionfeelingofasingleeyeTojudgedistancesbyasingleeye:Whentheheightoftheobjectisknown,thedistancecanbejudgedbycomparingitsviewingangle;b

40、yobservingtheirdefiladingrelationshipsandthesunsshade;bythedetailsandthetransparenceoftheair;Bytheaccommodationdegreeoftheeye.,B,2.ThespatialdepthperceptionfeelingoftwoeyesA.Thecontractivedegreeofthemusclesbyturningopticalaxiswhilefocusingontheobject.,Opticalaxis:Thelinkofthemacularfoveaandtheimagen

41、odalpointoftheeye,A,1,2,B.Stereoscopicvisionstereoscopiceffect,Stereoscopiceffect(parallaxangle),B,B,A,A,b1,b2,a2,a1,A,Bareatthesamedistancefromtheeyes,then:,A,B,b1、b2locateatthesamesidesofa1、a2；a1b1=a2b2,ThedistancesofAandBisnotequal,twosituations:,b1,b2locateatthedifferentsidesofa1,a2,b1,b2located

42、atthesamesidesofa1,a2a1b1a2b2,A,A,B,B,a1,b2,a2,b1,B,B,A,A,b1,b2,a2,a1,A,B,Stereoscopicacutance,Radiusofstereoscopicvision,Stereoscopicvisionerror,Thedifferenceofparallaxangleindicatesthelocationdifferenceofobjects,when10,theeyecannotdifferentiateAfromB,theminimumvalueofiscalledstereoscopicacutance.,

43、Themaximumdistancewhichtheeyecandifferentiateiscalledtheradiusofstereoscopicvision.,Withinthestereoscopicvisionrangethatthelocationdifferenceofobjectscanbedifferentiated,theerrorinjudgingwhetherthetwoobjectsareinthesamespatialdepthornotiscalledthestereoscopicvisionerror,Theformulaisreasonableonlywhen,stereoscopicvisionerror,l(m)510501005001