A device and a method for automatically adapting a light sensor to the light transmission properties of a windshield include determining the light transmission properties of the windshield for light having at least two different wavelengths. Light intensities of each of at least two different wavelengths of a light beam transmitted by a transmitter along a path through the windshield are measured by a light receiver. The measured light intensities are compared with reference light intensity values associated with clear glass. Transmission properties of the windshield are then calculated based on the comparison between the measured light intensities and the reference light intensity values. The light sensor is then adapted as a function of the calculated transmission properties of the windshield.