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41
EN
2.1
what is a laser and how does it work?
What is a LASER?
The laser is a device that creates continuous visible light energy waves (streams of photons that are referred to as “laser
radiation”) with the same amplitude and phase that are flowing in the same direction; meaning they are coherent – they
stick together and form a laser beam.
The width of a single wave is measured in nano-meters and defines the colour and visibility of the laser beam. The visible
spectrum of the human eye is roughly between 400nm and 700nm, going from violet to a dark red colour. A human eye
is most sensitive to a green light of around 555nm, meaning that a 1W of green laser will always appear more visible than
1W of any other colour laser. 1W of quality laser light is very powerful and although it doesn’t sound like much it can burn eye
retinas, skin and clothes or even start a fire!
Colours
Standard full colour analogue lasers use three primary
colours: Red, Green and Blue. By mixing those together
you can pretty much get any secondary colour:
Red
+
Blue
=
Magenta
Red
+
Green
= Yellow
Yellow
Green
+
Blue
=
Cyan
Red
+
Green
+
Blue
=
White
Of course the number and precision of the colours
is determined by the modulation, stability and linearity
of the system. If the system is not stable enough, it will
produce different colours every time it is used, making
it virtually impossible to match the colours of two systems
at any one time. This is very often the case with systems
from far east manufacturers and with re-branded lasers
that are being presented as European makes.
Scanning System
A scanning system is essentially two tiny mirrors, each
moving on X or Y axis. By working together they can “scan”
the laser beam over a wide angle in front of the projector.
The scanning system can not only direct the laser beam
to specific, static locations, but it can also create shapes
by rapidly moving the laser beam over a path. Once
a shape is scanned more than 20 times per second,
it appears static to the human eye. So any shape drawn
by a laser is actually produced by one single laser beam
being moved by these mirrors very quickly. Every scanning
system has a mechanical limit of how fast it can move its
mirrors and therefore how many points it can display at any
one second and that is usually represented in Points Per
Second at a certain scanning angle, i.e. 8 degrees.
How far does it travel?
Technically, the laser light will travel forever until it strikes
a surface and is absorbed. A better question is – how far will
the light travel and still be useful? Depending on the power
output of the system and weather conditions, the laser can
be visible for miles – that is why we need to be cautious
about aircrafts when performing outdoor shows. And if you
get a system that is powerful enough then yes, it can reach
the Moon.
What makes the laser visible in mid-air?
Mainly it is the particles of dust in the air that the laser beam
hits on its path, scattering the light. This dust or fog is called
a “scattering medium”. That’s why we “laserists” use haze
or smoke machines to make lasers more visible. Too much
of the haze or smoke will greatly attenuate the visibility,
but the right amount will make all the difference between
no show and a great show.
When outdoors, lasers mainly reflect off dust and mist in the
air but due to unpredictable wind conditions we can never
make sure the hazers or smoke machines will be effective
enough. And that’s why we use high power lasers for
outdoor shows – to substitute for the lack of dust, haze
and smoke.
