US Patent 6853897 Windshield fog detector

The system of the present invention is configured to detect moisture on a surface and includes a sensor that may be divided into a plurality of subwindows. At least one of the subwindows has a sensitivity that is independently variable. The system may further include an optical system operative to direct light rays from at least a portion of the surface onto the sensor, and a processing system in communication with the sensor and operative to independently adjust the sensitivity of the at least one subwindow and to analyze data from the sensor to detect moisture. The processing system may control the windshield wipers based upon a number of subwindows in which moisture is detected.