The
CMOS image sensor has the last few
years evolved in
to a
competitor to the
Charged Coupled Device. There are
two
basic designs of CMOS sensors,
passive and
active array.
The
passive CMOS image sensor is basically just an
array
of
photodiodes with a
common amplifier for all diodes in a column.
But since the
photodiodes have a relatively low
sensitivity
to
light, this
system is
sensitive to
noise. This problem
rises the
further away the
diode is from the
amplifier.
In the
active sensor a
transistor is added to each diode,
thus the
signal is
stronger and
less susceptible to
noise.
But the
addition of a
transistor means that each
sensor
in the
array becoms bigger and this causes the
arrays resolution
to fall. The
CCD uses only one
component
and can be made with a
higher density. But one big
advantage
with the CMOS is that it uses
less power. This means a
lower
power drain on a portable device's
power source. The
technology to produce
CMOS sensors has also fallen in price
the last
years. This has made the
active CMOS image sensor
a
good choice in cheaper, low resolution,
digital cameras.
As the
technology behind
this type of
sensor advances,
it will probably have a
future in
mobile devices.