Method for detecting liquid on a windowpane

A method for detecting liquid on a windowpane, in particular on a windowpane of a motor vehicle, wherein radiation is emitted by at least one radiation emitter, wherein the radiation is coupled into the windowpane via at least one optical element, and wherein after reflection in the windowpane the radiation is coupled out of the windowpane, and is directed via at least one optical element to a radiation receiver, and wherein at least one measuring section is formed for detecting the liquid on the windowpane by the reflections of the radiation in the windowpane,

• wherein
• the radiation coupled out of the windowpane and directed at the at least one radiation receiver is detected in single measurements,
• a measurement cycle is formed from a plurality of single measurements,
• an average value is formed from the measurement results of the single measurements of a measurement cycle,
• the average value of a measurement cycle is used as the reference value for the single measurements of the subsequent measurement cycle, currently in progress,
• the differences between the measured values of the single measurements of a measurement cycle currently in progress and the reference value are determined, and
• the differences between the measured values of the single measurements of the measurement cycle currently in progress and the reference value are evaluated statistically, and
• a conclusion is drawn regarding the condition of wetness with liquid on the measuring section on the windowpane from the statistical evaluation.