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The
Lighting Communications
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Incandescent and fluorescent lamps are currently prevailing as a
way of the lighting. However, white LED lighting has been widely
studied. As compared to the fluorescent lamps, etc, the white LED
lamp is characteristic of small in size, low power consumption (1/10
of the conventional), long life (maintenance free), high-speed response
and excellence in visibility. The efficiency of the electro-optic
conversion is reaching up to that of the fluorescent lamp. In the
very near future, the white LED lamps will replace the conventional
incandescent and fluorescent lamps due to their cleaner low power
energy, which is ecological to our daily life. It is, therefore,
considered as the lighting in the next generation.
Nakagawa Laboratory in Keio University, Japan, has been the world
first pioneer to study the LED light communication, which is electrically
controllable. The visible light communication has various advantages,
compared to the conventional communication.
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demo
-Stand lamptransmitter-
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Both the visible light and IR communications have the similar bandwidth
whose range is around a few 100 [THz]. The representative example
of IR is IrDA, which has been often utilized in notebook type computers,
etc. And, the cell phones are recently using the IrDA for their
data transmission. As described, IrDA has been widely utilized in
various devices. However, IrDA communication has an eye safety problem
in conjunction with the possible dangerous high energy density due
to its invisibility. Therefore, the higher data rate transmission
cannot be considered through IrDA communication. As compared to
IR communication, the visible light communication is suitable to
human eyes in terms of "Visibility". The system employs
LED, which can be transmitted by a few watt, a relatively high energy
for the use of lighting. This means that the visible light communication
is capable to transmit data by the higher data rate.
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The radio wave wireless communication has been employed everywhere
with cell phones and the wireless LAN, etc. However, it is noted that
it may provide the biological damages to humans by the electromagnetic
wave. And, the Radio Law does restrict the free usage of the radio
wave wireless communication. On the other hand, the visible light
communication does not require any license at present. Since no malfunction
such as aircraft equipment and medical instruments is anticipated,
it enables the visible light communication in airports and hospitals
where radio wave wireless communication cannot be used according to
electromagnetic wave interference. The visible light communication
is very suitable to the environment which requires human interface.
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