Method and apparatus for determining the presence and/or absence and/or a characteristic of an object on a support

摘要

A method of determining the presence and/or absence and/or a characteristic of an object on a support (4). The method includes the steps of: a) acquiring a target signal indicative of vibration of the support at a first location; b) acquiring a reference signal, the reference signal being indicative of vibration of the support at a second location; c) calculating a ratio of the target signal and the reference signal; and d) determining the presence and/or absence and/or a characteristic of an object on the support in accordance with the ratio determined in step c).