Patent ID: 7902988

Claim:
An illuminance sensor for detecting brightness of outside a vehicle having a windshield comprising: a first light receiving element; a light emitting element arranged in the vehicle; and a second light receiving element, wherein the first light receiving element receives outside light of the vehicle through the windshield, the first light receiving element outputs a first output signal corresponding to the outside light, the light emitting element emits light to the windshield, the light emitted from the light emitting element is reflected at an outside surface of the windshield, which is opposite to inside of the vehicle, the second light receiving element receives the reflected light, the second light receiving element outputs a second output signal corresponding to the reflected light, the outside light passes through at least one of a first region of the windshield through which the light emitted from the light emitting element passes toward the outside surface of the windshield and a second region of the windshield through which the reflected light passes, at least one of the first region and the second region of the windshield overlaps with projections of both of the first and second light receiving elements on the windshield, and the first output signal is corrected based on the second output signal so that the brightness of outside the vehicle is detected from the corrected first output signal.