A transparent substrate having a function of liquid detection

摘要

In a transparent substrate having a function of optically detecting liquid without using prisms, diffraction gratings (2 and 3) are formed on the surface of the glass (1) at an interior side thereof, and a light emitting element (4) and a light receiving element (5) are positioned in the vicinity of the diffraction gratings (2 and 3), respectively. When water is attached at a total reflection point on the surface of the glass (1), a light propagating to the diffraction gratings (3) is reduced, and if the water covers the total reflection point as a whole, it reduces down to one fiftieth (1/50). Namely, it can detect the existence of water on the glass surface with high sensitivity and reflect in the strength of the ejected light.