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Technical Library |
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Motion Detection |
Motion detection is the action of sensing physical movement in a given area. Motion
can be detected by measuring change in speed or vector of an object or objects in the field
of view. This can be achieved either by mechanical devices that physically interact with the
field or by electronic devices that quantifies and measures changes in the given environment.
The principal methods by which motion can be electronically identified are optical detection
and acoustical detection. Infrared light or laser technology may be used for optical detection.
Motion detection devices, such as motion detectors, have sensors that detect movement and send
a signals to a sound device that produces an alarm or switch on an image recording device.
There are motion detectors which employ cameras connected to a computer which stores and
manages captured images to be viewed later or viewed over a computer network.
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More complex algorithms are necessary to detect motion when the camera itself is moving,
or when the motion of a specific object must be detected in a field containing other movement
which can be ignored. An example might be a painting surrounded by visitors in an art gallery.
A simple algorithm for motion detection by a fixed camera compares the current image with
a reference image and simply counts the number of different pixels. Since images will naturally
differ due to factors such as varying lighting, camera flicker, and CCD dark currents,
pre-processing is useful to reduce the number of false positive alarms.
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The chief applications for such detection are (a) detection of unauthorized entry, (b)
detection of cessation of occupancy of an area to extinguish lighting and (c) detection
of a moving object which triggers a camera to record subsequent events. The motion detector
is thus a linchpin of electronic security systems, but is also a valuable tool in preventing
the illumination of unoccupied spaces.
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Motion Detection Information Links
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Motion Detection Manufacturer Links
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