5-2 System Operation
Laser Tube Assembly
The laser tube assembly is a very sophisticated device. It is composed of a plasma tube filled
with a special mixture of CO2 and other gases, and RF (radio frequency) electronics. The
function of the entire assembly is to turn electrical energy into concentrated light energy. The
word LASER is an acronym for Light Amplified Stimulated Emission of Radiation.
The laser tube assembly It receives power from the 48VDC power supply and its “trigger signal”
from the motherboard. When the laser system is power on and the trigger signal comes from
the motherboard, the RF electronics produce a high frequency AC signal across the electrodes
located inside the plasma tube. This causes spontaneous photon emissions from the gas
mixture that produce an invisible, infrared light beam at a frequency of 10.6 microns.
The laser beam exits the laser tube through its output optics, bounces off the #1 mirror, passes
through the beam window, bounces off the #2 and #3 mirror, and finally passes through the
focus lens. The #2 and #3 mirror and the focusing lens are all mounted to the motion system.
The width of the laser beam as it exits the tube, called the “Beam Diameter”, is about 4 mm.
The focus lens focuses the beam into a very small spot whose “Spot Size” is dependent on the
“Focal Length” of the lens. The “Focal Length” is the distance from about the center of the lens
to the point where it converges the beam into the smallest spot possible. Using a standard 2
inch focal length lens, the spot size produced is approximately .005 inches.
The “Focal Range” of the lens, where the beam is considered to be “in focus”, is equivalent to
+/- 5% above and below the focus point. Shorter lenses produce a smaller spot size but also
have a very narrow focal range. This means that it would only be useful for engraving very flat
objects. The longer lenses have a much wider range of focus but also produce a larger spot
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