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Glossary - L

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Lambert: Lambert-ian source or surface. A surface is referred to as a "Lambert" radiator or reflector (depending if its a primary or secondary source of light) if it is a perfectly diffusing surface.
LASER: This is an abbreviation for Light Amplification by Stimulated Emission of Radiation. A laser produces a very strong and coherent light of a single frequency.
LED: Light Emitting Diode. A semiconductor that produces light when a certain low voltage is applied to it in one direction.
Lens: An optical device for focusing a desired scene onto the imaging device in a CCTV camera.
Level: When relating to a video signal it refers to the video level in Volts. In CCTV optics, it refers to the auto iris level of 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 a multiple of cameras being powered by a common alternative current(AC) source (either 24VAC or 240VAC) and consequently have field frequencies locked to the same AC source frequency (50Hz in CCIR systems and 60Hz in EIA systems).
Lumen: A light intensity produced by the luminosity of 1 candela in one radian of a solid angle.
Luminance: Means brightness, but in TV refers to the video signal information about the scene brightness
Lux: Light unit for measuring illumination. It is defined as the illumination of a surface when luminous flux of 1 lumen falls on an area of 1m�. It is also known as lumen per square metre, or, metre-candelas.

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Glossary - L