Method and device for detecting the passage of objects

A method for detecting the passage of objects, wherein said method comprises the steps of:

• causing said objects to pass in front of a background whose brightness is distinctly different from that of the objects, aligning a collimator in a direction of observation such that the path of the objects intersects a line defining the direction of observation of the collimator, eliminating the light which comes from directions other than the direction of observation, detecting the variation of light intensity corresponding to the passage of the object by means of an electrical signal which is delivered by a photoreceiver and is a function of the luminous flux picked up by said photoreceiver, and differentiating said electrical signal with respect to time by means of an electronic differentiating circuit so that there is consequently obtained an output signal which is a function of the variations of said luminous flux on said photoreceiver.