22 August 2006
generally 20 m (65 ft.) or higher.
High-Pressure sodium (HPS) lamp a high intensity discharge (HID) lamp in which
light is produced by radiation from sodium vapor.
Illuminance the areal density
of the luminous flux incident
at a point
on a surface.
Illuminance (footcandle or lux) meter an instrument for measuring illuminance on a
plane. The instrument is comprised of some form of photodetector with or without a filter
driving a digital or analog readout through appropriate circuitry.
an alternative but deprecated term for illuminance.
Incandescent filament lamp a lamp in which light is produced by a filament heated
to incandescence by an electric current.
Indirect Component the portion
of the luminous flux from
a luminaire that arrives
the workplane after being reflected by room surfaces.
Indirect lighting lighting involving luminaires that distribute 90 to 100% of the emitted
Induction lighting lighting technology that uses electric current
electromagnetic field within the phosphor coated lamp. No filaments are used. Its
advantages include instant on/off operation, white light with good color rendering
characteristics, and a long lamp life of 100,000 hours.
Instant-start fluorescent lamp a fluorescent lamp designed for starting by a high
voltage without preheating of the electrodes.
Intensity (candlepower) distribution curve a curve, often polar, that represents the
variation of luminous intensity of a lamp or luminaire in the plane through the light
Isolux (Isofootcandle) line
a line plotted
on any appropriate set
show all the points on a surface where the illuminance is the same.
Kelvin the unit of temperature used to designate the color temperature of a light
a generic term for
a source created
to produce optical radiation.
Lamp Lumen Depreciation (LLD) Factor the fractional loss of lamp lumens at rated
operating conditions that progressively occurs during lamp operation.
Lens a glass or plastic element used in luminaires to change the direction and control
the distribution of light rays.
Light radiant energy that is capable of exciting the retina and producing a visual
Light-Emitting Diode (LED)
- a p-n junction solid state diode whose radiated output
a function of its physical construction, material used, and exciting current.
Light Loss Factor (LLF) formerly called maintenance factor. The ratio of illuminance
(or exitance or luminance) for a given area to the value that would occur if lamps