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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Aberration,_Optical
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1992-09-02
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755b
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20 lines
Any of a number of defects that impair the
image in an optical instrument. Aberration
occurs because of minute variations in lenses
and mirrors, and because different parts of
the light spectrum are reflected or refracted
by varying amounts. In chromatic aberration
the image is surrounded by coloured fringes,
because light of different colours is brought
to different focal points by a lens. In
spherical aberration the image is blurred
because different parts of a spherical lens
or mirror have different focal lengths. In
astigmatism the image appears elliptical or
cross-shaped because of an irregularity in
the curvature of the lens. In coma the images
appear progressively elongated towards the
edge of the field of view.
Subject by: Russell Webb