BMW 2001 325CI, Manual

Page: 191 / 215

191 n
Index
Data
Technology
Repairs
Car care
Controls
Overview
Interior rearview mirror with automatic dimming feature
*
Rain sensor
*
The interior rearview mirror with auto-
matic dimming feature reduces blinding
from following traffic by adapting the
intensity of the reflected images to
correspond to levels of light registered
by the unit's sensors. The mirror reverts
to its undimmed setting as soon as the
light source disappears. One lamp
sensor is mounted on the front of the
mirror housing. This sensor, which is
directed forward, measures light inten-
sity in the area ahead of the vehicle.
The second sensor is integrated within
the mirror's glass. The electronic
control system compares the light
intensity from front and rear. The differ-
ence provides the basic parameter
used to modulate an electrical current
and induce chemical changes in a
semisolid layer incorporated in the lens.
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The semisolid reacts chemically to this
electrical current, thus providing
dimming of the mirror through an infi-
nitely-variable range (electrochromic
technology).
As a result, it is no longer necessary to
dim the mirror manually, and the driver
can concentrate completely on traffic
conditions.
Depending on the degree of wetness on
the windshield, the rain sensor controls
the operation of the windshield wipers.
Infrared light is carried along the surface
of the windshield in an optical conductor
in such a manner that it is reflected
completely when the windshield is dry.
The quantity of reflected light is
measured. If there is moisture on the
glass, the amount of light reflected is
reduced since the infrared light at the
surface of the windshield can escape.
The quantity of reflected light is thus a
means of gauging the degree of wetness
on the windshield. When the system is
set to the "Intermittent" wiper speed, the
wipers react immediately – if water is
splashed onto the windshield by vehicles
traveling ahead of you, for example. As a
result, the rain sensor provides a contri-
bution to driving safety and comfort.
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