Adhering substance detector and controller using the same

Abstract

An object sensor is provided, which has a high object detection rate with respect to an object such as a raindrop adhering to a detection surface, and which is capable of detecting the presence/absence of an object with a high sensitivity. A light source, a detection surface, a focusing lens, and a plurality of photodetecting elements of a photodetecting unitform a focusing system of equal magnification that is capable of catching an image in a size smaller than an object to be detected. Light emitted from the light sourceis incident on the detection surfacevia a prismat a predetermined incident angle. Without a raindrop, the total internal reflection condition is satisfied as shown by a pathof a beam, so that the beam is subjected to the total internal reflection. Then, the beam passes through a prism, and is focused on a photodetecting surface of the photodetecting unitby the focusing lens. On the other hand, with a raindrop, the total internal reflection condition is not satisfied as shown by a trailof a beam, so that the beam passes therethrough and is not focused on the photodetecting unit. A difference in signal level is determined on the photodetecting element basis, so that an object covering the detection surfaceis detected.