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6Laser Terminology & FAQs
Apparent Power/Brightness:
The intensity of light as it appears to the human eye. The eye is most sensitive to wavelengths (colors) in the center of the visible spectrum. Hence, green light will appear brighter than any other color of light of the same power or magnitude.
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.
Beam Divergence
Angle of beam spread measured in radians or meliorations. 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. The longer the distance a laser beam travels, the more it spreads, or diverges.
Coherence
A term describing light as waves which are in phase in both time and space. Monochrome and low divergence are two properties of coherent light.
Constant Wave (CW)
The output of a laser that is operated in a continuous (pulse duration >0.25s) rather than a pulsed mode.
Diode
A device through which current can pass freely only in one direction. The diode is arguably one of the most important components in a laser. Oftentimes the lifetime of a laser is based on the quality of the diode.
