Devices and methods for investigating the magnetic properties of objects

摘要

The invention relates to apparatuses and a corresponding method for examining magnetic properties of objects, in particular sheet material, such as bank notes (20). The apparatuses comprise a magneto-optic layer (10) whose optical properties are influenceable by the magnetic properties of the sheet material (20), a light source (11) for producing light that is coupled into the magneto-optic layer (10), and a detector (13) for detecting light that is transmitted and/or reflected by the magneto-optic layer (10). For reliable examination of the magnetic properties of sheet material it is provided that the direction of propagation of the coupled-in light extends parallel to a base surface (9) of the magneto-optic layer (10). The invention permits the magnetic properties in particular of sheet material with areas emitting very weak magnetic fields to be examined with very high sensitivity and reliability.