VS - Lighting Systems - Lighting - 998542

5. The lighting system: what is light?

5.3.3. The illuminance

E (lm/m 2 )

Illuminance levels on the road are specified according to automotive standards, they depend on the type of light source, such as incandescent (Halogen), gas discharge (Xenon) or LED (Light Emitting Diode) lamps. The diagram below is the illuminance projection of a headlamp equipped with a Xenon lamp. This curve is called an Isolux curve where lines indicate illuminance levels in steps. On this example, the illuminance reaches amaximum at 100 lux in the front of the car and minimum of 1 Lux on the outer line (1.0). The illumination level does not make allowance for the amount of light reflected off the surface. The reflected light is called the luminance; this depends on the nature of the surface, including its colour.

The luminous flux from a light source (lumens) falling on a unit of surface (m 2 ) is called illuminance.

l Symbol: E l Unit: Lumen/m 2 also called Lux

Roads and road markings are specified in standards that set minimum reflection levels.

m

0,1 lux

30

D2S

20

1.0

2.0

10

5.0

100 lux

0

100

2.0

1.0

-10

5.0

5.0

2.0

-20

1.0

1.0

m

-30

0

20

40

60

80

100

120

140

14