System for determining the authenticity of an object

A system for identifying an object, comprising:

• an identification element comprising
• a reflective layer affixed to an object to be identified, said reflective layer having such a reflective directivity that when an incident light beam is impinged thereon the reflected light is directed at least in two directions which are 180 degrees apart around said incident light beam, and
• a polarization plane rotating layer placed on said reflective layer for rotating a polarization plane of light emitted from said reflective layer by 90 degrees relative to said incident light beam;
• light emitting means for producing said incident light beam as a linearly polarized light beam;
• light receiving means consisting of a plurality of pairs of light detecting segments arranged around said light emitting means, wherein each of said pairs of light detecting segments comprises a first segment and a second segment, said first segment and said second segment being positioned 180 degrees apart around said light emitting means;
• a first filter placed on said first segment of each of said pairs of light detecting segments, said first filter having the property of transmitting substantially only the light emitted from said identification element whose plane of polarization is rotated by said polarization plane rotating layer;
• a second filter placed on said second segment of each of said pairs of light detecting segments, said second filter having the property of transmitting substantially only the light emitted from said identification element whose plane of polarization is not rotated by said polarization plane rotating layer;
• and
• means for comparing intensities of light detected by said light detecting segments, and for determining the authenticity of said object according to a pattern of the intensities of light detected by said light detecting segments, wherein said means for comparing and for determining includes means for computing a ratio of the intensities of light received by said first segment and said second segment, respectively, in each of said pairs of light detecting segments, and for determining the authenticity of said object when said ratio is greater than a prescribed threshold level for a prescribed one of said pairs of light detecting segments.