Cameras
Surveillance systems for the home use video cameras that convert the image
into a video composite or S-video signal for display on a video monitor. The
best type of camera for home systems uses charged coupled device (CCD)
technology. These cameras have high resolutions, low operating light, less
temperature dependence, and high reliability. A typical CCD camera used in
video surveillance systems is illustrated.
Camera Resolution and Sensitivity
The two important specifications for cameras are the light sensitivity rating
and the number of lines of resolution. The resolution of a camera is a measure-
ment of the horizontal lines it is capable of generating. Most standard TVs and
VCRs have a resolution of fewer than 300 lines, but video monitors can have
a resolution as high as 800 lines.
Surveillance cameras come in a range of costs
and are available with 300–500 lines of resolution. Higher resolutions make
distinguishing fine details and recognizing people at a distance easier.
The amount of light required to obtain a reasonable image is called the lux
rating. 1 lux is approximately the light from one candle measured from 1
meter. Typical camera ratings range between 0.5 and 1.0 lux.
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