| 摘要 |
PURPOSE:To enable the adequate raindrop response of a raindrop response apparatus such as a wiper, by providing a light emitting element and a light receiving element each having a predetermined incident angle to the back surface of a transparent plate to which raindrop is adhered on the front surface thereof to compare the obtained light receiving output with a freely settable reference value. CONSTITUTION:To the back surface 2b of a transparent plate 2 such as window glass in a wiper region, the attaching elements 3, 4 for a light emitting and a light receiving elements 1, 5 comprising the same material as the transparent plate 2 are secured by an adhesive having the same refractive index as the transparent plate 2. The incident angles theta of these elements 3, 4 satisfy the formula thetaa<theta<thetab (wherein thetaa and thetab respectively show critical angles of glass with air and water) and th incident light from the element 1 is subjected to total reflection two times on the surface 2a of the transparent plate 2 to be incident to the element 5. On the other hand, when raindrop 6 is present on the surface 2a, a part of incident light is permeated corresponding to a raindrop amount and the reflected amount from the surface 2a is changed. Therefore, when the output corresponding to the light receiving amount of the element 5 is compared with a set value changeable reference value to control a raindrop responsive apparatus, raindrop response such as a time to the first starting of wiping and a cycle after a second time is adequately performed. |
