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2.5
scanning system
The product warranty does not cover the damages
to the scanning system caused by improper use of the
scanning system or by incorrect programming. Therefore
it is essential to understand how the scanning works and
where are the limits of it. In this manual we will explain
only the basics of it but it is the responsibility of every user
to educate themselves so they can avoid damage being
caused to the scanning system and costly repairs.
A laser beam comes from a laser module and hits the two
moving mirrors of the scanning system. These mirrors are
mounted on the scanner shafts and are moved by the
scanner rotors, one on X and one on Y axis.
An effect such as tunnel (circle) is displayed by a repetitive
mechanical movement of the scanners. For each
scanning system and effect, there’s a maximal scan-rate
that is defined by mechanical load, scanner mirror size
and weight, complexity of displayed picture and size
of the projection (an angle under the laser beam is being
projected). A different scanning systems have different
scan-rate limits. It is essential to operate the scanning
system at scan-rates within its maximal limit at all times
to prevent it from overload damage.
How to establish correct Scan-rate and maximal
number of points in an effect
Each effect (picture) contains a different number of graphical
points which defines the actual shape of the effect. The
more points an effect contains, the lower the maximum
scan rate will be in relation to the scanning angle.
As an example we’ll work with the star effect shown below
and with the parameters of quality scanning system:
Let’s say the star effect is made of 300 graphical points
(including non-visible blanking points) and we know that
the maximal scan-rate of our scanning system is “35K”.
(The term “35K” refers to a metric that is achieved when
the original ILDA test pattern is projected at 8 degrees,
and all of its visual qualities are maintained. Note that all
other patterns may be scanned much wider, and in some
cases even faster, but the term “35K” only refers to a single
test pattern, and single test condition). We also know that
we display the star 35 times per second which is a default
frame rate of the control software we are using.
So we need to display 300 points 35 times per second =
10.500 pps. This means that we could display 3 of these
stars beside each other within one single laser effect and
that it would be quite close to the scanner limit (3 × 10.500
= 31.500pps). Given that the scanners noted above are
“35K” scanners, this seems easily achievable. However,
the projection of 3 separate stars necessitates a wider
scan angle, and – in general, the scan speed must
be reduced as the projection angle is increased. Thus,
it may be necessary to either lower the number of points
within the effect or drop down the scan-rate in the control
software (FPS) to a safe level – which may result in flicker.
