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CCD
Cameras or CMOS - the choice is yours...
It may surprise some of you to know that digital systems today still
utilize many analog components. This is particularly true for the
cameras that are selected. Most people claiming to be switching
to 'digital' don't necessarily mean that they will use digital cameras.
In fact, the vast majority of digital systems still use one of the
two most popular analog cameras. This article discusses the two
types of analog cameras used most frequently and the differences
between them.
In today's marketplace, the CCD or Charge-Coupled Device Cameras
predominate for both digital and non-digital systems. However, some
industry consultants and engineers predict that the Complementary
Metal Oxide Semiconductor, more commonly referred to as a CMOS Camera,
is about to give the CCD Cameras a run for the money.
So what is the difference between CMOS and CCD Cameras?
To begin with, CCD Cameras have one major flaw when used in a digital
system...the requirement for a digital signal processor to change
their signal from analog to digital. CMOS, on the other hand, always
transmits digital signals therefore no DSP is needed...
...the net result is a CMOS camera and chip the size of a half dollar...perfect
for limited short-range applications where aesthetics are a key
factor in camera selection.
Other factors affecting the choice between CCD Cameras and CMOS
include frame rate. The rate of capture for most CCD Cameras is
30 frames per second which translated means fluid motion. Standard
resolution for most monochrome CCD Cameras is 350-500 lines - the
highest available resolution for CCD Cameras being approximately
600 lines.
Resolution and color fidelity of CMOS are still regarded as weak
- if a picture needs to be enlarged it will become grainy. As image
quality greatly affects many security applications - these issues
will have to be resolved before the use of CMOS becomes more widespread.
On the flip side, advances have been made in CMOS with regard to
low-light indoor applications. The average CMOS camera requires
.5 or 1 foot candles. One major company now markets a CMOS camera
that requires just .0003 foot candles...meaning the camera can see
in almost total darkness.
(It should be noted that for most applications CCD Cameras still
operate better in low-light conditions than their CMOS counterparts.)
Another factor that makes CMOS less suitable is the set lens format.
In real terms this means the camera can only focus at one distance
or a limited range. "Crossover noise" is another area
in need of improvement. Additionally, CMOS is designed for mainly
indoor use further restricting the range of surveillance applications.
So who would choose CMOS over Charge Coupled Device Cameras?
What then would make anyone choose CMOS over CCD Cameras (Charge-Coupled
Device Cameras)...and why are experts predicting an increase in
usage of CMOS? The short answer is price...CMOS are much cheaper
to manufacture than are CCD Cameras.
The other deciding factor could well be the smaller size. CCD Cameras
are larger and therefore do not integrate as easily into the decor
of any given environment.
In conclusion, while CMOS is improving - CCD Cameras ( charged coupled
device cameras ) are still todays choice for both digital and non-digital
systems. Whether that will change remains to be seen...
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