BMW M COUPE, Owner'S Manual

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Interior rearview mirror with automatic dimming feature
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 light sensor is mounted on the
front of the mirror housing. This sensor
is directed forward. It measures light
intensity in the area ahead of the
vehicle. A second light sensor is
located on the lower edge of the mirror.
The electronic control system
compares the light intensity from front
and rear. The difference provides the
basic parameter used to modulate an
electrical current and induce chemical
367de398
changes in a semisolid layer incorpo-
rated in the lens.
The semisolid reacts chemically to this
electrical current, thus providing infi-
nitely-variable dimming of the mirror
(electrochromic technology).
As a result, it is no longer necessary to
dim the inside rearview mirror manually,
and the driver can concentrate
completely on traffic conditions.