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CMOS
vs CCD - Haven't seen the light? Let's try...
CCD Sensors have been around for 25 years or so,
and in the World TECHampionships of imaging
technology, it is the depending champion
(See World
TECHampionships of Flash Memory Card). A
chip designed for imaging with a track record of
quality as proven by every major digital camera
manufacturer. The Challenger - a lower costing
chip, with on-chip processing capability and a
host of new imaging applications, the CMOS
sensor.
CMOS - Complementary Metal Oxide Semiconductor
CCD - Charge-Coupled Device
Both CMOS and CCD bring strengths and weaknesses
into the fray. Regardless of whether any
consumer will ever ask a sales clerk, or me for
that matter, if that cool-looking digital camera
is CMOS or CCD, understanding how these two
technologies compare with each other is
important to anyone who intends to buy Digital
Camera or everyone who has one.
Both CMOS and CCD imagers are manufactured in a
silicon foundry and the equipment used is
similar. It is in the alternative manufacturing
processes and device architectures that make
these sensors a bit different in both capability
and performance. CCD's birth began in the 1970s
and 1980s, specifically for imaging
applications, where the end result was to have
the best possible image quality. The technology
continues to improve and is still the choice of
manufacturers in applications where image
quality is the primary requirement.
A
CMOS chip too is made with standard silicon
processes but in high-volume foundries.
Peripheral electronics, such as digital logic,
clock drivers, or analog-to-digital converters,
can be readily integrated with the same
fabrication process. It is worth mentioning
that, CMOS imagers can also benefit from process
and material improvements made in mainstream
semiconductor technology. Therefore we can say,
the best is yet to come for CMOS technology.
Further discussing the inner sanctum of CMOS
and CCD tech would require me to discuss terms such
as memory cell, photosites, multiplexing, X-Y
matrix, photodiode, but me, not feeling so "googly"
now, we will just leave it at that.
Most PC camera manufacturers in China and Taiwan
have been concentrating on CMOS models because
they are cheaper and easier to make. An
advantage to using CMOS sensors is their
system-on-chip (SoC) layout, which uses less
space, therefore a more
compact digital camera. By using CMOS,
makers are able to produce more compact
architecture and versatile designs for PC
cameras-all at lower costs. In addition, CMOS
sensors are already digital video-compatible,
unlike CCD sensors that require separate signal
processing chips or dedicated digitizing boards
for the same effect. But CCD is still ruling the
higher end. In addition, the power consumption
of CMOS sensors is only a tenth that of CCD
sensors.
The biggest opportunities for CMOS sensors lie
in new product categories for which they are
uniquely suited. Applications where a need for
lower power usage or integration of additional
circuitry on-chip or low system cost are
required. These features make CMOS sensors ideal
for mobile apps like those camera phones here,
there and everywhere.
But the CMOS sensor have not completely
dislodged the CCD as sensor king for a number
reasons, primarily it performance related. Also,
it is related with the simple fact the CCDs have
been mass-produced for over 25 years, more R&D,
through a lot of refinements and has developed
over the years whereas CMOS technology has only
just begun.
But make no mistake about it, CMOS imaging
technology, as it is, could deliver quality
images and its weaknesses are slowly
disappearing. The fact that popular digital
camera brands are using CMOS on their line shows
the maturity of it. The CMOS technology industry
is only in the early stages of optimization for
digital imaging. Maybe, given developmental
years, and not even 25 years, an imminent blow
to the champion is in the digital horizon.
Source: ecBuyph.com Tech Support - July 2004 |
