Cleaning device for a glass pane and method for cleaning a glass pane

The cleaning device has a sensor (14) which detects the degree of dirt on the glass (4), and a control unit (8) which in response produces the cleaning spray. The sensor is designed to detect visible or infra red light. Independent claim describes cleaning process where the cleaning spray is only triggered when there is a specific degree of dirt. A measuring program to detect the degree of dirt can be started up each time the headlight is switched on.