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Energy
(Joules)
Energy
(Joules) = Output
Power (in Watts) x Time (in seconds)
Therefore
for a 100 milli-watt Laser, 1
Joule = 0.1 Watts x 10 Seconds
Energy
Density (Joules/cm2) Dosage
ED
(Joules/cm2) =
Output
Power (Watts) x Time (in seconds) / Area
of Beam (cm2)
Therefore
for a 100 milli-watt Laser with a beam area of 0.2cm2
0.1
Watts x 2 Seconds /
0.2cm2
Therefore
Energy Density = 1 Joule/cm2
Power
Density
Power
Density (Watts/cm2) =
Output
Power (in Watts) / Beam
Area (cm2)
Therefore
for a 100 milli-watt Laser with a Beam Area of 0.2 cm2
0.1
Watts / 0.2 (cm2
Power
Density = 0.5 Watts/cm2 Or
500 milli-watts/cm2
Thus
for Joules only Dosages, the operator only needs to know
the Output Power in Watts or milli-watts.
For
Joules/cm2 Dosages, the operator needs to know the
Output Power in Watts or milli-watts, plus the Beam
area.
Where
Lasers incorporate Frequency modulation, the operator
needs to know the "duty cycle" of the pulse in
order to calculate the "mean average" output
power.
The
"Peak" power cannot be used to calculate the
above parameters.
With
multiple Laser head units, where all emitters are Laser
diodes of the same output power, the additive total
output power eg 4 x 400 milli-watt Laser diodes = 1600
milli-watt plus the total treatment head area should be
considered for calculating Dosages.
Beam
area can be calculated using the following formula;
Circular
Beam: Beam Area (cm2) = Diameter (cm)2 x 0.7854
Elliptical
Beam Area (cm2) = Long Axis(cm) x Short Axis (cm) x
0.7854
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