is the condition that prevails when the numerical aperture
or the beam diameter
of an optical
source, such as a laser
, light-emitting diode
, or optical fiber
, exceeds that of the driven element, e.g. an optical fiber core
. In optical communications
testing, overfill in both numerical aperture and mean diameter (core diameter or spot size) is usually required.
In polygonal mirror scanners, an overfilled type is one which uses each mirror facet at least in one dimension completely.