A transmission detector for a window body, in particular the windshield of a motor vehicle, has an optical sensor device which includes an imaging system and a position-sensitive optical detector. In addition, the transmission detector has an analyzing system for the image data recorded by the optical detector. The imaging system is arranged such that sections of a surface of the window body whose distance to one another is comparable to the size of the free aperture of the window body are projected on the optical detector. This allows for a precise allocation of the variables affecting the transmission of the window body. A cleaning system for a viewing area of a window body being equipped with this transmission detector also has a cleaning device which is controlled by the analyzing system. Such a cleaning system may be triggered as needed.