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Beam |
A
collection of rays that may be parallel, convergent, or divergent.
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Beam
Bender
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A
hardware assembly containing an optical device, such as a
mirror, capable of changing the direction of a laser beam;
used to repoint the beam, and in "folded," compact laser systems.
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Beam
Diameter |
The
distance between diametrically opposed points in the cross
section of a circular beam where the intensity is reduced
by a factor of 1/e (0.368) of the peak level (for safety standards).
The value is normally chosen at 1/e2 (0.135) of
the peak level for manufacturing specifications.
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Beam
Divergence
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Angle
of beam spread measured in radians or milliradians (1 milliradian
= 3.4 minutes-of-arc or approximately 1 mil). For small angles
where the cord is approximately equal to the arc, the beam
divergence can be closely approximated by the ratio of the
cord length (beam diameter) divided by the distance (range)
from the laser aperture.
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Beam
Expander |
An
optical device that increases beam diameter while decreasing
beam divergence (spread). In its simplest form consists of
two lenses, the first to diverge the beam and the second to
re-collimate it. Also called an upcollimator.
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Beam
Splitter |
An
optical device using controlled reflection to produce two
beams from a single incident beam.
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Brewster
Windows |
The
transmissive end (or both ends) of the laser tube, made of
transparent optical material and set at Brewster's angle in
gas lasers to achieve zero reflective loss for one axis of
plane polarized light. They are nonstandard on industrial
lasers, but some polarizing element must be used if a polarized
output is desired.
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Brightness |
The
visual sensation of the luminous intensity of a light source.
The brightness of a laser beam is most closely associated
with the radiometric concept of radiance.
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