DEVICE TESTING AUTHENTICITY OF SECURITIES HAVING MAGNETIC IMPRINTS Russian patent published in 1997 - IPC

FIELD: test and flaw detection of materials having magnetic inclusions, test of authenticity of securities, specifically banknotes with magnetic protection against forgery as well as magnetic cards. SUBSTANCE: essence of invention lies in usage of magnetooptical crystals for visualization of magnetic imprints. Scattering fields of magnetic patterns create spatial magnetization of crystal in proportion to which turn of polarization plane of linearly polarized light passing through crystal takes place. Light from monochromatic source 1 passes through collimator 2, polarizer 3 and hits rectangular prism 4 on which reflecting (hypotenuses) face magnetooptical crystal 5 is fixed on optical contact. Tested object 6 is pressed against crystal 5. Light reflected from crystal 5 passes through analyzer 7 and forming objective 8 and is observed visually or by TV camera 9 and monitor 10. Tested object is maximally pressed against crystal 5 with the aid of pressing unit 11. Electromagnetic coil 12 creates magnetic field in region of crystal 5 by means of A.C. generator 13 connected to it. Transportation of tested object 6 is realized with the help of mechanical drive 14. Preliminary magnetization of tested object 6 can be carried out by source 15 of permanent magnetic field which can be manufactured in the form of electromagnet fed from D.C. source or in the form of permanent magnet. EFFECT: enhanced functional efficiency and reliability of device. 6 cl, 1 dwg