| 摘要 |
Electro-optical apparatus for verifying the authenticity of security labels of the type having a series of lenticules of predetermined spatial frequency formed thereon. The apparatus is structured to accept and support a security label to be verified so that the lenticules thereof lie in a flat or nearly flat plane. A laser beam is directed at the flat plane at a predetermined angle of incidence so that the lenticules of the security label in the flat plane diffract the laser beam into a series of wavefronts which reinforce one another to form a diffraction pattern having principle maxima that are separated by equal or nearly equal angles. An optical system and associated electronic circuit operate to measure the angular separation between successive predetermined ones of the diffraction pattern principle maxima and determine the spatial frequency of the lenticules of the security label whereby the authenticity of the security label can be verified by comparing the spatial frequency of its lenticules with a predetermined standard spatial frequency. Methods inherent in the use of the apparatus are also included.
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