A surface sensor device (1) with an electromagnetic radiation emitter (3) and a radiation detector (2) disposed on opposite sides of an instrument outlet (6), which instrument outlet (6) is required to be placed in close proximity to a surface (30). The surface sensor (1) also having a member (8)...http://www.google.de/patents/US5731582?utm_source=gb-gplus-sharePatent US5731582 - Surface sensor device
