| slovo | definícia |
aplanatic
(encz) | aplanatic,aplanatický adj: Zdeněk Brož |
Aplanatic
(gcide) | Aplanatic \Ap`la*nat"ic\, a. [Gr. 'a priv. + ? disposed to
wander, wandering, ? to wander.] (Opt.)
Having two or more parts of different curvatures, so combined
as to remove spherical aberration; -- said of a lens.
[1913 Webster]
Aplanatic focus of a lens (Opt.), the point or focus from
which rays diverging pass the lens without spherical
aberration. In certain forms of lenses there are two such
foci; and it is by taking advantage of this fact that the
best aplanatic object glasses of microscopes are
constructed.
[1913 Webster] |
aplanatic
(wn) | aplanatic
adj 1: free from or corrected for spherical aberration; "an
aplanatic mirror" |
| | podobné slovo | definícia |
aplanatic
(encz) | aplanatic,aplanatický adj: Zdeněk Brož |
aplanatický
(czen) | aplanatický,aplanaticadj: Zdeněk Brož |
Aplanatic focus
(gcide) | Focus \Fo"cus\ (f[=o]"k[u^]s), n.; pl. E. Focuses
(f[=o]"k[u^]s*[e^]z), L. Foci (f[=o]"s[imac]). [L. focus
hearth, fireplace; perh. akin to E. bake. Cf. Curfew,
Fuel, Fusil the firearm.]
1. (Opt.) A point in which the rays of light meet, after
being reflected or refracted, and at which the image is
formed; as, the focus of a lens or mirror.
[1913 Webster]
2. (Geom.) A point so related to a conic section and certain
straight line called the directrix that the ratio of the
distance between any point of the curve and the focus to
the distance of the same point from the directrix is
constant.
[1913 Webster]
Note: Thus, in the ellipse FGHKLM, A is the focus and CD the
directrix, when the ratios FA:FE, GA:GD, MA:MC, etc.,
are all equal. So in the hyperbola, A is the focus and
CD the directrix when the ratio HA:HK is constant for
all points of the curve; and in the parabola, A is the
focus and CD the directrix when the ratio BA:BC is
constant. In the ellipse this ratio is less than unity,
in the parabola equal to unity, and in the hyperbola
greater than unity. The ellipse and hyperbola have each
two foci, and two corresponding directrixes, and the
parabola has one focus and one directrix. In the
ellipse the sum of the two lines from any point of the
curve to the two foci is constant; that is: AG + GB =
AH + HB; and in the hyperbola the difference of the
corresponding lines is constant. The diameter which
passes through the foci of the ellipse is the major
axis. The diameter which being produced passes through
the foci of the hyperbola is the transverse axis. The
middle point of the major or the transverse axis is the
center of the curve. Certain other curves, as the
lemniscate and the Cartesian ovals, have points called
foci, possessing properties similar to those of the
foci of conic sections. In an ellipse, rays of light
coming from one focus, and reflected from the curve,
proceed in lines directed toward the other; in an
hyperbola, in lines directed from the other; in a
parabola, rays from the focus, after reflection at the
curve, proceed in lines parallel to the axis. Thus rays
from A in the ellipse are reflected to B; rays from A
in the hyperbola are reflected toward L and M away from
B.
[1913 Webster]
3. A central point; a point of concentration.
[1913 Webster]
Aplanatic focus. (Opt.) See under Aplanatic.
Conjugate focus (Opt.), the focus for rays which have a
sensible divergence, as from a near object; -- so called
because the positions of the object and its image are
interchangeable.
Focus tube (Phys.), a vacuum tube for R[oe]ntgen rays in
which the cathode rays are focused upon the anticathode,
for intensifying the effect.
Principal focus, or Solar focus (Opt.), the focus for
parallel rays.
[1913 Webster]Aplanatic \Ap`la*nat"ic\, a. [Gr. 'a priv. + ? disposed to
wander, wandering, ? to wander.] (Opt.)
Having two or more parts of different curvatures, so combined
as to remove spherical aberration; -- said of a lens.
[1913 Webster]
Aplanatic focus of a lens (Opt.), the point or focus from
which rays diverging pass the lens without spherical
aberration. In certain forms of lenses there are two such
foci; and it is by taking advantage of this fact that the
best aplanatic object glasses of microscopes are
constructed.
[1913 Webster] |
Aplanatic telescope
(gcide) | Telescope \Tel"e*scope\, n. [Gr. ? viewing afar, farseeing; ?
far, far off + ? a watcher, akin to ? to view: cf. F.
t['e]lescope. See Telegraph, and -scope.]
An optical instrument used in viewing distant objects, as the
heavenly bodies.
[1913 Webster]
Note: A telescope assists the eye chiefly in two ways; first,
by enlarging the visual angle under which a distant
object is seen, and thus magnifying that object; and,
secondly, by collecting, and conveying to the eye, a
larger beam of light than would enter the naked organ,
thus rendering objects distinct and visible which would
otherwise be indistinct and or invisible. Its essential
parts are the object glass, or concave mirror, which
collects the beam of light, and forms an image of the
object, and the eyeglass, which is a microscope, by
which the image is magnified.
[1913 Webster]
Achromatic telescope. See under Achromatic.
Aplanatic telescope, a telescope having an aplanatic
eyepiece.
Astronomical telescope, a telescope which has a simple
eyepiece so constructed or used as not to reverse the
image formed by the object glass, and consequently
exhibits objects inverted, which is not a hindrance in
astronomical observations.
Cassegrainian telescope, a reflecting telescope invented by
Cassegrain, which differs from the Gregorian only in
having the secondary speculum convex instead of concave,
and placed nearer the large speculum. The Cassegrainian
represents objects inverted; the Gregorian, in their
natural position. The Melbourne telescope (see Illust.
under Reflecting telescope, below) is a Cassegrainian
telescope.
Dialytic telescope. See under Dialytic.
Equatorial telescope. See the Note under Equatorial.
Galilean telescope, a refracting telescope in which the
eyeglass is a concave instead of a convex lens, as in the
common opera glass. This was the construction originally
adopted by Galileo, the inventor of the instrument. It
exhibits the objects erect, that is, in their natural
positions.
Gregorian telescope, a form of reflecting telescope. See
under Gregorian.
Herschelian telescope, a reflecting telescope of the form
invented by Sir William Herschel, in which only one
speculum is employed, by means of which an image of the
object is formed near one side of the open end of the
tube, and to this the eyeglass is applied directly.
Newtonian telescope, a form of reflecting telescope. See
under Newtonian.
Photographic telescope, a telescope specially constructed
to make photographs of the heavenly bodies.
Prism telescope. See Teinoscope.
Reflecting telescope, a telescope in which the image is
formed by a speculum or mirror (or usually by two
speculums, a large one at the lower end of the telescope,
and the smaller one near the open end) instead of an
object glass. See {Gregorian, Cassegrainian, Herschelian,
& Newtonian, telescopes}, above.
Refracting telescope, a telescope in which the image is
formed by refraction through an object glass.
Telescope carp (Zool.), the telescope fish.
Telescope fish (Zool.), a monstrous variety of the goldfish
having very protuberant eyes.
Telescope fly (Zool.), any two-winged fly of the genus
Diopsis, native of Africa and Asia. The telescope flies
are remarkable for having the eyes raised on very long
stalks.
Telescope shell (Zool.), an elongated gastropod ({Cerithium
telescopium}) having numerous flattened whorls.
Telescope sight (Firearms), a slender telescope attached to
the barrel, having cross wires in the eyepiece and used as
a sight.
Terrestrial telescope, a telescope whose eyepiece has one
or two lenses more than the astronomical, for the purpose
of inverting the image, and exhibiting objects erect.
[1913 Webster] |
aplanatic
(wn) | aplanatic
adj 1: free from or corrected for spherical aberration; "an
aplanatic mirror" |
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