Patent ID: 8299434

Claim:
A light detecting device to detect light traveling around a vehicle comprising: a case having an opening to be mounted to a windshield of the vehicle, a predetermined light passing through the windshield and the opening; a first light introducing member located adjacent to the opening, the first light introducing member having an inlet face into which the predetermined light is incident, and an outlet face to emit the light incident into the inlet face; and a first light receiving element arranged in the case so as to receive the light emitted from the outlet face, wherein the first light receiving element outputs a signal corresponding to an intensity of the light received by the first light receiving element, the outlet face has a convex lens shape so as to define a first distance between a top point of the outlet face and a focus of the first light introducing member, and a second distance between the top point of the outlet face and a light receiving face of the first light receiving element, and the first distance is smaller than the second distance.