C D E
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L M N
O P Q
R S T
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Lambertian source or surface.
A surface is called a Lambert radiator or reflector
the surface is a primary or a secondary source of light) if it is
LAN. Local Area Network.
A short distance data communications network (typically within
a building or campus) used to link
together computers and peripheral devices
(such as printers,
CD ROMs, file servers and modems)
under some form of standard control.
Laser. Light Amplification
by Stimulated Emission of Radiation. A laser produces a very
parallel and coherent light (all
wave fronts in phase) of a single frequency.
LED. Light Emitting
Diode. A semiconductor diode, that produces light when a certain
voltage, forward bias, is applied
to it. Like a normal diode it conducts only in one direction.
Lens. An optical device
for focussing a desired scene onto the imaging device in a CCTV
Level. When relating
to a video signal it refers to the video level in volts. In CCTV
refers to the auto iris level setting
of the electronics that processes the video
signal in order
to open or close the iris.
Line-locked. In CCTV,
this usually refers to multiple cameras being powered by a common
alternative current (AC) source
(either 24 V AC, 110 V AC or 240 V AC)
have field frequencies locked to
the same AC source frequency (50 Hz in
CCIR systems and
60 Hz in EIA systems).
LCD. Liquid Crystal
display. A screen for displaying text/graphics based on a
called liquid crystal, where minute
currents change the reflectiveness or transparency
by changing the polarization angle.
The advantages of LCD screens are very small power
consumption (can be easily battery
driven) and low price of mass-produced units.
disadvantages are narrow viewing
angle, slow response, invisibility in the dark unless the
back lighted, and difficulties
displaying true colors with colour LCD displays.
Lumen [lm]. A light
intensity produced by the luminosity of 1 candela in one radian of a
angle (steradian - sr).
to the video signal information about the scene brightness. The
measurable, luminous intensity
of a video signal. Differentiated from brightness in
that the latter is non-measurable
and sensory. The colour video picture information contains
two components, luminance- Y (brightness
and contrast) and chrominance - C (hue and
Look-up table. A cross-reference
table in the computer memory that will return an output
value for any given input value.
It can be a programmed algorithm or data entered in a table.
Lux [lx]. Light unit
for measuring illumination. It is defined as the illumination of
when luminous flux of 1 lumen falls
on an area of 1 m2. It is also
as lumens per
square metre. One lux is
equal to approximately 0.09290 foot candle.