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Widening :
Employment of LED lighter in artificial vision systems
Why spend hundred of Euro for a LED lighting system?
Is not sufficient one economic light bulb buyable in
whichever supermarket ?
Does it not carry out the same function ?
These are the questions that often place who for the first
time acquires a LED lighter for artificial vision systems.
Then carefully analyzing the LED lighter features we notice
that the obtainable performances with this type of luminous source are
difficulty reached from many other luminous sources. Moreover it is
always necessary to know that the lighting system performances, in an
artificial vision system, constitute a good 50% of the system global
performances and that the employment of expensive and sophisticated
cameras and frame grabber cannot replace that that a good lighter can
realize.
The main advantages offers from the LED lighters are :
- Possibility
to choose the wavelength .....
It's possible to choose between different wavelengths and therefore
between different colours of the emitted light (red, orange, amber,
yellow, green, blue, violet, white, infrared). All emitted light
colours, with the exception of white, are monochromatics.
- Long average life.
The average life of a LED source at semiconductor, correctly fed and
operating at temperature inside the admitted limit, exceed abundantly
the 100.000 hours.Moreover it maintains constant the own luminous
intensity for a period estimated of 50.000 hours of working. During the
remaining operating life, more than 50.000 hours, the LED undergoes a
light and graduates redction of the emitted luminous intensity. In the
greater part of the applications this light reduction of the emitted
luminous intensity doesn't provoke any variation of the system
behaviour.
- Good performances/cost ratio.
The LED lighter totally has a good performances/cost ratio
determined from its long average life of working and from the
stability of its luminous emission.
- Working at low tension.
With the exception of other luminous sources (for ex. fluorescent
sources) the LED lighter works with an operating tension of few volt.
This allow the installation of this type of lighter without particular
precautions or dangers for the user.
- Easiness of personalization.
The LED is constituted from one small junction of semiconductor
material realized on a substrate that is not larger than 1 mm².
This particularity renders the LED easily integrable in lighters with
the most varied shapes and dimensions, obtaining therefore personalized
lighting systems.
- Sturdness and resistant to the vibrations.
The LED lighters just because constituted from luminous sources at
semiconductor inserted in a seal container, are sturdy and adapted for
installations with vibrations and mechanical shocks.
- Possibility to realize directional light beams at high
intensity
Some LED lighter can be supplied in container with integrated lenses
and therefore with a determined output angle. Joining more LED sources
on an only support is possible to obtain light beams with output angles
very precise and therefore easily directionables on the object to
analyze. Is moreover possible to obtain light spot at high intensity by
converging more luminous sources in the same point.
- Modulation possibility and luminous intensity regulation
The LED lighters allow the emitted luminous intensity regulation.
Through special drivers is possible to vary the tension or the feeding
current of the LED matrix by consenting the emitted light quantity
variation from the lighter. If the tension or current variation is not
gradual but is instantaneously passes from 0% up to 100%, or vice
versa,is possible to obtain the controlled lighter turn on and turn off
. in this case is possible to turn on and turn off the lighter with an
external drive, by generating light flash of extremely short duration,
also in the order of 1 millionth of second (1 us). The limitation of
the emitted light, both reducing the emission level of the single LED,
and turning on the lighter only when necessary and turning off when the
vision system is not operating, allows further lighter average life
lengthening and a lowering of the medium temperature of working.
- Possibility to obtain brilliant light beams for short
periods.
It is possible to obtain through special drivers a luminous emission
also 5 times more intense than that nominal for short time periods
without compromise the lighter duration. This technique must be carried
out with special power supplies (driver) purposely realized for this
type of employment.
The main
disadvantages deriving from the LED lighter employment are:
- High working
temperature if they work in way "always ON".
If the lighter is employed in way "always ON" it can establish an high
working temperature that could accelerate the LED source decline
process and therefore a reduction of the light average life.
If there wasn't the possibility to employ the lighter in modular way,
we suggest the installation in places where there's an adapted produced
developed heat (through the equipment chassis or through external
wasters) or in presence of eventual cooling fans. We moreover suggest
that never set the lighter near heat sources or near warm elements.
- Homogeneity of
the emitted light not always comparable with other types of luminous
sources.
For the emission intrinsic feature of the LED (punctiform light source)
in some applications where is demanded a very high luminous emission
homogeneity, the light emitted from the LED lighters could be not
comparable with the homogeneity of some others types of lighters.
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