Designation:E175−82(Reapproved2010)StandardTerminologyofMicroscopy1ThisstandardisissuedunderthefixeddesignationE175;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.Abbecondenser—seecondenser,Abbe.aberration—anyerrorthatresultsinimagedegradation.Sucherrorsmaybechromatic,spherical,astigmatic,comatic,distortion,orcurvatureoffield;andcanresultfromdesignorexecution,orboth.achromatic—literally,color-free.Alensorprismissaidtobeachromaticwhencorrectedfortwocolors.Theremainingcolorseeninanimageformedbysuchalensissaidtobesecondarychromaticaberration.achromaticobjective—anobjectivethatiscorrectedchro-maticallyfortwocolors,andsphericallyforone,usuallyintheyellow-greenpartofthespectrum.Airydisk—theimageofabrightpointobject,asfocusedbyalenssystem.Withmonochromaticlight,itconsistsofacentralpointofmaximumintensitysurroundedbyalternatecirclesoflightanddarknesscausedbythereinforcementandinterferenceofdiffractedrays.Thelightareasarecalledmaximaandthedarkareasminima.ThedistributionoflightfromthecentertotheouterareasofthefigurewasinvestigatedmathematicallybySirGeorgeAiry.Thediffrac-tiondiskformsabasisfordeterminingtheresolvingpowerofanideallenssystem.Thediameterofthediskdependslargelyontheapertureofthelens.ThediffractionoflightcausingtheAirydiskisafactorlimitingtheresolutionofawellcorrectedopticalsystem.analyzer—anopticaldevice,capableofproducingplanepolarizedlight,usedfordetectingthestateofpolarization.a˚ngströmunit—aunitoflinearmeasurenamedafterA.J.Ångström.Itis1×10−10metres;1µm=10,000Å.ItisgenerallyabbreviatedasA.intheUnitedStates;elsewhere,itisvariouslyabbreviatedÅ,A.,A.U.,Å.,orÅU.angularaperture—seeaperture,angular.aperture,angular—theanglebetweenthemostdivergentraysthatcanpassthroughal...
