ELETTROLASER MS 3.5, End-User And Maintenance Manual

Page: 15 / 108

code: UMS012 review: 0.2 date: 20/04/2022
Laser Welding machine - MS 3.5
user and maintenance manual page 15 of 102
In general, in the case of exposures exceeding the threshold, the predominant mechanism mainly depends on the duration of the
exposure pulse.
Thus, following an ascending order of duration of the pulse,
the predominant effects in the following time intervals are:
•
For exposures lasting nanoseconds and lower than one nanosecond , micro-cavitation, transitory acoustic events and non-linear
effects;
•
Between 100 μs and a few seconds , thermal effects;
•
Above approximately 10 seconds , photochemical effects.
Laser radiation differs from all other known types of radiation due to its high radiance and collimation of the beam.
This fact, together with the high initial energy content, results in the transmission of noteworthy quantities of energy towards
biological tissues.
The main event in any type of damage caused by laser radiation to a biological system is the absorption of optical radiation by the
system in question . This absorption occurs on the atomic or molecular level and represents a specific process of the wavelength.
Thus, the wavelength determines which tissue may be damaged by a specific laser beam.
Fig. 4-1 – Examples of absorption of laser radiation based on time of exposure and dimensions of the beam
Key:
a)
Laser energy absorbed by the system.
b)
The absorbed energy generates heat which is
transmitted to surrounding tissues.
c)
In the case of long pulsed or continuous wave
lasers, the persistence of the thermal front
causes a progressive widening of the lesion.
d)
In the case of short pulsed lasers, the
noteworthy power density causes an
explosive rupture of the cells and movement-
induced injury.