Multilayer, cushioned liquid drop detector

Abstract

A liquid drop detector which may be fixed or attached by a simple operation, without machining, to a window glass, includes a light emitting element, a light receiving element and light guiding bodies wherein the light emitted by the light emitting element is introduced through a diffraction grating into a first light guiding body and after undergoing total internal reflection within the first light guiding body it is introduced through a silicon member, through an elongated light guiding body, through an additional silicon member, and into a windshield. After traveling within the windshield by total internal reflection, the light passes through a silicon member, reenters the elongated light guiding body, passes through another silicon member and enters a second light guiding body which guides it to a receiver. When rain drops adhere to the outside surface of the windshield at points corresponding to the total internal reflection points at the outer surface of the windshield, the light will leak out of the windshield. As a result of this, the amount of light received by the light receiving element is lessened, thereby providing for detection of the adhesion of rain drops based thereupon so as to output a signal for driving a device such as the windshield wiper.