Liquid drop detection method and apparatus therefor

Abstract

In a method for detecting liquid drops adhering upon a front windshield with superior sensitivity but without obstructing drivers, a light beam emitted from a light emitting element 4 is guided into a light guiding body 7, and after undergoing total internal reflection within light guiding body 7, it is guided into a front windshield G. The light guided into the front windshield G is received by a light receiving element 5 after repeated total internal reflections within the front windshield G. In this instance, when raindrops adhere on the outside surface of the front windshield G and the adhering points are at the total internal reflection points of the light mentioned above, then the light beam guided into the front windshield G passes through and goes out from the windshield G without undergoing total internal reflection therein. As the result of this, the amount of the light beam received by the light receiving element decreases, thereby enabling detection of adhesion of raindrops based thereon, so as to output a signal for driving a wiper equipment or the like.

Dependencies are inferred from the claim text.