Page 313 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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296 Automobile mechanical and electrical systems

If the fi lament is positioned in front of the focal point, the refl ected beam will
converge towards the principal axis ( Fig. 3.84 ).
A common type of bulb arrangement is shown in Fig. 3.85 , where the dip fi lament
is shielded. This gives a nice sharp cut-off line when positioned in a refl ector like
that of Fig. 3.84 on dip beam (the other fi lament is at the focal point to give a
main beam).
A good headlight should have a powerful, far-reaching central beam, around
which the light is distributed both horizontally and vertically to illuminate as great
an area of the road surface as possible. The beam formation can be considerably
Key fact improved by passing the refl ected light rays through a transparent block of
lenses. It is the function of the lenses to partially redistribute the refl ected light
A headlight lens redistributes the
refl ected light beam. beam and any stray light rays. This gives better overall road illumination.
Many headlights are now made with clear lenses, such that all the redirection of
the light is achieved by the refl ector ( Fig. 3.86 ). A clear lens does not restrict

Bulb reflector

Figure 3.84 Light source in front of the
focal point Figure 3.85 Shielded dip fi lament (top) and main beam fi laments in a tungsten halogen bulb

Figure 3.86 Headlights with a clear lens and complex refl ector