Honeywell EQUIP HD4DIP, Справочное руководство, Страница: 77 / 82

Document 800-04191 Rev A 77
06/09
D
Glossary
AGC (Automatic Gain Control) Video Amplifier in a camera that boosts the amount of
video gain (including the noise) to maintain a 1V p-p (1-volt peak-to-peak) video signal
output. It becomes operational when the light level is low. The circuit is designed to
compensate for fluctuations in scene illumination which would cause the video output
level to be too low. If the video level is adequate, the circuit does not apply any gain to the
signal. As the video level (scene illumination) falls, more and more gain is applied by the
AGC circuit to the video signal.
ALC Setting in an Auto Iris lens to control the iris opening. Adjusts between peak and
average to respond to the bright part of the scene (peak setting) or the average value of
the video signal (average setting).
BLC (Backlight Compensation) Improves the image quality when you have a scene
where the brightest light in the scene comes from behind the subject of interest (for
example, a dark vehicle with the sun setting behind it or a person entering an office from
the brighter-lit outside). What happens is the camera’s exposure circuit sets itself to the
average light level in the scene and uses this to adjust the electronic iris. For example,
when someone opens the door, the exposure system reacts to the increased light level,
leaving a person entering the room in silhouette.
The backlight compensation feature uses a "window" — usually fixed to the central portion
of the scene —to set the exposure so that everything outside the window is ignored by
the exposure system. Some cameras allow you to select different windows, control the
size and position of the window, and select the amount of exposure compensation
applied to the selected areas.
DHCP (Dynamic Host Configuration Protocol) Allows a server to dynamically assign
IP addresses to nodes (workstations) automatically. Provides client information including
subnetwork mask, gateway address, and DNS (Domain Address Server) addresses.
Flickerless Eliminates the “flicker” that can appear in an image under certain lighting
conditions (for example, fluorescent lighting). This is usually caused by the interaction of
the shutter with the AC frequency of the lighting. The flickerless setting changes the
shutter speed of the camera to a value that will not cause flicker (1/100 sec, NTSC, 1/120
sec for PAL). The side effect is that the camera sensitivity is reduced because the
electronic iris feature has effectively been turned off and will no longer control the
optimum exposure setting for available light conditions.
FOV (Field of View) The part of the scene visible with a particular lens. The height
(horizontal) and width (vertical) picture size at a given distance that can be seen through
a lens. Generally, shorter focal length lenses have a wider field of view than those with
longer focal lengths.
Gain The amplification a system provides to a signal.
IP Address A unique, 32-bit identifier for a specific TCP/IP host computer on a network.