ASTM E175-82(2005)e1
(Terminology)Standard Terminology of Microscopy
Standard Terminology of Microscopy
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Designation:E175–82 (Reapproved 2005)
Standard Terminology of
Microscopy
This standard is issued under the fixed designation E175; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Terms were added editorially in July 2005.
Abbe condenser—see condenser, Abbe. aperture, effective—the diameter of the entrance pupil; it is
aberration—any error that results in image degradation. Such theapparentdiameterofthelimitingaperturemeasuredfrom
errors may be chromatic, spherical, astigmatic, comatic, the front.
distortion,orcurvatureoffield;andcanresultfromdesignor aplanatic—corrected for spherical aberration and coma.
execution, or both. apochromatic objective—a lens system whose secondary
achromatic—literally, color-free.Alens or prism is said to be chromatic aberrations have been substantially reduced. (See
achromatic when corrected for two colors. The remaining achromatic).
color seen in an image formed by such a lens is said to be axis, optical—thelineformedbythecoincidingprincipalaxes
secondary chromatic aberration. of a series of optical elements comprising an optical system.
achromatic objective—an objective that is corrected chro- It is the line passing through the centers of curvature of the
matically for two colors, and spherically for one, usually in optical surfaces.
the yellow-green part of the spectrum. axis, optic—the direction, or directions in an anisotropic
Airy disk—the image of a bright point object, as focused by a crystal along which light is not doubly refracted.
lens system. With monochromatic light, it consists of a balsam, Canada—aresinfromthebalsamfir Abies balsamea.
central point of maximum intensity surrounded by alternate Dissolved in xylene, toluene, or benzene it is used as a
circlesoflightanddarknesscausedbythereinforcementand mountant for permanent microscopical preparations. Its
interference of diffracted rays. The light areas are called refractive index may vary from 1.530 to 1.545 and its
maxima and the dark areas minima.The distribution of light softening point from room temperature to 100°C, these
from the center to the outer areas of the figure was properties varying with age and solvent content. If impure it
investigatedmathematicallybySirGeorgeAiry.Thediffrac- discolors with age.
tion disk forms a basis for determining the resolving power Bertrand lens—see lens, Bertrand.
of an ideal lens system. The diameter of the disk depends bisectrix, acute—in biaxial crystals, that principal axis of the
largely on the aperture of the lens. The diffraction of light ellipsoid of indexes which bisects the smaller angle between
causing theAiry disk is a factor limiting the resolution of a the optic axes.
well corrected optical system. bisectrix, obtuse—inbiaxialcrystals,thatprincipalaxisofthe
analyzer—an optical device, capable of producing plane ellipsoid of indexes which bisects the larger angle between
polarized light, used for detecting the state of polarization. the optic axes.
a˚ngström unit—a unit of linear measure named after A. J. calcite—a doubly refracting mineral used in the manufacture
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Ångström. It is 1 310 metres; 1 µm=10,000 Å. It is of polarizing prisms. It is uniaxial negative and in the
generally abbreviated asA. in the United States; elsewhere, trigonal diversion of the hexagonal system of crystals. Its
it is variously abbreviatedÅ , A., A.U., Å., or ÅU. indexes are ´=1.486, v =1.658; its hardness is 3 on the
angular aperture—see aperture, angular. Mohr scale and specific gravity 2.711.
aperture, angular—theanglebetweenthemostdivergentrays Canada balsam—see balsam, Canada.
that can pass through a lens to form the image of an object. chromatic aberration—a defect in a lens or lens system as a
result of which the lens possesses different focal lengths for
radiation of different wavelengths.
This terminology is under the jurisdiction of ASTM Committee E41on
collimation—the operation of controlling a beam of radiation
Laboratory Apparatus and is the direct responsibility of Subcommittee E41.01 on
so that if the light source were a point, the light rays would
Apparatus.
CurrenteditionapprovedMay1,2005PublishedJuly2005.Originallyapproved
become parallel. The total bundle of rays diverge as the
in 1961. Last previous edition approved in 1995 as E175–82(1995). DOI: 10.1520/
source size increases.
E0175-82R05E01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E175–82 (2005)
coma—a lens aberration occurring in that part of the image diaphragm—a fixed or adjustable aperture in an optical
field that is some distance from the principal axis of the system. Diaphragms are used to intercept scattered light, to
system. It results from different magnification in the various limit field angles, or to limit image-forming bundles or rays.
lens zones. Extra-axial object points appear as short comet- disk, Airy—see Airy disk.
likeimageswiththebrightersmallheadtowardthecenterof distance, interpupillary—see interpupillary distance.
the field (positive coma) or away from the center (negative dry objective—any microscope objective designed for use
coma). without immersion liquids.
compensating eyepieces—those designed for use with objec- electromagnetic lens—an electromagnet designed to produce
tives such as apochromats in order to correct chromatic a suitably shaped magnetic field for the focusing and
aberration. deflection of electrons or other charged particles in electron-
condenser or condenser lens—a term applied to lenses or optical instrumentation.
mirrors designed to collect, control, and concentrate radia- electron microscope—see microscope, electron.
tion in an illumination system. electron optics—the science that deals with propagation of
condenser, Abbe—originally a two-lens substage condenser electrons, as light optics deals with that of light and its
combination designed by Ernst Abbe. It lacks chromatic phenomena.
correction though designed for a minimum of spherical eye lens—see lens, eye.
aberration and has only a very low-angle aplanatic cone. It eyepiece—the lens system used in an optical for magnification
may be rated with a numerical aperture as high as 1.3. of the image formed by the objective.
condenser, darkfield—a condenser forming a hollow cone of eyepiece, parfocal—eyepieces with common focal planes so
light with its apex (or focal point) in the plane of the that they are interchangeable without refocusing.
specimen. When used with an objective having a numerical eyepiece, positive—aneyepieceinwhichtherealimageofthe
aperture lower than the minimum numerical aperture of the object is formed below the lower lens elements of the
hollow cone, only light deviated by the specimen enters the eyepiece.
objective. Objects are seen as bright images against a dark filar micrometer or filar eyepiece—an eyepiece equipped
background. with a fiducial line in its focal plane, that is movable by
condenser, darkfield, bispheric—a darkfield condenser con- means of a calibrated micrometer screw, in order to make
sisting of a convex spherical reflector mounted concentric accurate measurements of length.
with a larger concave reflector. The rays are formed into a focus, principal—the point at which a lens focuses an axial
diverging cone by the convex reflector.The annular concave object pint. Synonymous with focal point.
reflector then forms a hollow converging cone which is illumination, critical—the formation of an image of the light
focused on the subject. See condenser, darkfield. source in the object field. (Also known as Nelson illumina-
condenser, darkfield, paraboloid—a darkfield condenser tion)
consisting of a reflecting surface in the form of a segment of illumination, Köhler—a method of microscopical illumina-
a paraboloid of revolution. Parallel rays entering the con- tion, first described by A. Köhler, in which an image of the
denser around the periphery of the central stop are reflected source is focused in the lower focal plane of the condenser,
from the curved surfaces and converge at the focus of the and the field diaphragm is focused in the specimen plane.
paraboloid. See condenser, darkfield. illumination, oblique—illumination from light inclined at an
condenser, variable-focus—essentially anAbbe condenser in oblique angle to the optical axis.
whichtheupperlenselementisfixedandthelowermovable. image—a representation of an object produced by means of
The lower lens may be used to focus the illumination radiation usually with a lens or mirror system.
between the elements so that it emerges from the stationary immersion objective—an objective in which a medium of
lens as a large diameter parallel bundle. The field of high refractive index is used in the object space to increase
low-power objectives may thus be filled without removing the numerical aperture and hence the resolving power of the
thetopelement.Attheoppositeextremeitcanbeadjustedto lens.
have a numerical aperture as high as 1.3. interpupillary distance—the distance between the centers of
critical illumination—see illumination, critical. the pupils of the eye. The binocular microscope tubes must
crystal, birefringent—apertainingtotheuseofamicro
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