Glossary of Laser Terms

Glossary of Laser Terms

Beam   A collection of rays that may be parallel, convergent, or divergent.

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 e-1 (0.368) of the peak level (for safety standards).  The value is normally chosen at e-2 (0.135) of the peak level for manufacturing specifications.

Beam Divergence   Angle of beam spread measured in radians or milliradians (1 milliradian = 3.4 minutes of arc). 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.

Blink Reflex   See aversion response.

Brightness   The visual sensation of the luminous intensity of a light source. The brightness of a laser beam is most closely associated with the radio-metric concept of radiance.