Patent ID: 7019322

Claim:
An optical sensor for recording a wetting of a surface of a member, comprising: at least one transmitter; at least one receiver; at least one retroreflector for electromagnetic radiation; at least two sensing regions included on the surface and being exposable to an electromagnetic wave from the at least one transmitter; and a central region arranged in the member and into which are coupled the at least two sensing regions, wherein: a development of the wetting on the at least two sensing regions effects a change of a signal of the electromagnetic wave coupled out into the at least one receiver in the central region, the at least one retroreflector is developed and positioned in such a way that the at least one retroreflector feeds back the electromagnetic wave reflected by the surface of the member to the surface of the member, and from the surface of the member into the central region, and the at least two sensing regions are impinged upon by the electromagnetic wave via the central region.