Equipment: Luminaires - Road Lighting: Fundamentals, Technology and Application - page 153

Table 11.3 Maximum
lumens for BUG classes 0, 1
and 5 of the IES luminaire
classification system. (IES
2007 )

Solid angle area B0 B1 B5

BH 110 500 > 5000

BM 220 1000 > 8500

BL 110 500 > 5000

U0 U1 U5

UH 0 10 > 1000

UL 0 10 > 1000

FVH 10 75 -

BVH 10 75 -

G0 G1 G5

FVH 10 250 > 750

BVH 10 250 > 750

FH 660 1800 > 12000

BH 100 500 > 5000

11.2 Optical Characteristics

The desired light distribution of a luminaire is obtained through the application of one
or more of the physical phenomena: reflection, refraction, and diffuse transmission.
Many luminaires also make use of shielding in one form or another, principally to
obtain the required degree of glare control and to limit light pollution. The shielding
function may be performed by refractors, diffusers, mirror reflectors or, where very
stringent glare control is required, by black surfaces. The way in which these various
control techniques are employed in a given luminaire and the optical properties of
the materials used also determine the light output ratio of the luminaire.

11.2.1 Reflectors

Specular reflectors (also called high-gloss mirror reflectors) are often used when a
precise form of light distribution is required. The reflector creates multiple images of
the light source which, with a suitable reflector shape, overlap each other to form a
uniform luminance pattern on the area to be lighted. The most widely-used material
is sheet aluminium, which has the strength needed to produce a stable reflector. To
obtain a highly-specular finish, the aluminium is polished: mechanically, chemically,
electrolytically, or by a combination of these processes. Reflectance values are around
0.70. Alternatively, commercial-grade aluminium can be clad with a thin layer of
super-purity aluminium or silver. With aluminium, reflectance values of up to 0.80
can be obtained, while with silver a reflectance of more than 0.90 is possible. Finally,