A
control system for automatically detecting
moisture on the
windshield of a vehicle. The automatic
moisture detecting
system includes an optical
system for imaging a portion of the
windshield on to an image array sensor, such as a
CMOS active pixel sensor. The voltages of each of the pixels which represents the illumination level is converted to a corresponding gray scale value by an analog
digital converter. The gray scale values corresponding to the image are stored in memory. The
spatial frequency composition of the gray scale values are analyzed to determine the amount of rain present. In order to provide a
control signal to control the operation of the
windshield wipers of the vehicle as a function of the amount of
moisture present. The
system is also adapted to detect the level of
fog both on the interior of the windshield as well as the exterior of the windshield. By providing a system for automatically detecting the presence of
fog on the interior and exterior of the windshield, serious performance limitations of known automatic rain sensors are eliminated.