A DEVICE FOR DETECTING THE PRESENCE OF AT LEAST ONE HUMAN FINGER ON A SURFACE, AND A METHOD OF USING THE DEVICE IN THE USER INTERFACE OF A MACHINE, A DEVICE (IN PARTICULAR A PORTABLE DEVICE), OR A SYSTEM

摘要

A device (1) for detecting the presence of at least one human finger on a surface (10)comprises: -at least one element (22) having piezoelectric characteristics, located under a surface (10) that is visible, the element (22) arranged in the device (1) in such a manner that a force (F) when exerted on the surface (10),such as when the surface (10) is pressed by finger, is transferred to mechanical stress of the element (22), the element (22) then producing a voltage output (V) in response to the mechanical stress; -means (R2, R3, C3, IC1) for measuring the voltage output (V)in a predefined time period; and -means (IC1) for determining the degree of stability of the measured voltage output (V), configured to indicate that: i) if the degree of stability shows that the measured voltage output is highly stable, or at least sufficiently stable, a physical contact between a human finger and the surface (10) does not exist; and ii) if the degree of stability shows that the measured voltage output is not stable but contains vibrations characteristic to a human finger, a physical contact between a human finger and the surface (10) does exist. Application comprises also a method claim.