System for determining the authenticity of an object

Details System for determining the authenticity of an object System for determining the authenticity of an object

1993-08-16

1996-03-05

Gonzalez, Frank

Optics: measuring and testing

Document pattern analysis or verification

359 2, 235457, 235487, G06K 974, G06K 710, G03H 100

Patent

active

054972272

ABSTRACT:
Provided is an identification system which is highly effective in identifying the authenticity of an object and extremely difficult to analyze for the purpose of forgery. The object to be identified is affixed with an identification element comprising a reflective layer including a hologram, a diffraction grating or the like, which directs incident light of a prescribed wave length into a plurality of point symmetric directions, and a polarization plane rotating layer which rotates the polarization plane of the light as it passes through the polarization rotating layer. A linearly polarized light is impinged upon the identification element, and is received by a multisegment photodiode arranged in an annular fashion. Those photodiode segments located on one side of a diametric line is covered by a first filter adapted to transmit substantially only the light emitted from the identification element whose plane of polarization is rotated by the polarization plane rotating layer while remaining segments are covered by a second filter adapted to transmit substantially only the light emitted from the identification element whose plane of polarization is not rotated by the polarization plane rotating layer. Thus, by detecting the ratios of the intensities of light received by each pair of diametrically opposing photodiode segments, the authenticity of the identification element or the authenticity of the object can be reliably detected.

REFERENCES:
patent: 4501439 (1985-02-01), Antes
patent: 4568141 (1986-02-01), Antes
patent: 5101184 (1992-03-01), Antes
patent: 5200794 (1993-04-01), Nishiguma et al.
patent: 5291006 (1994-03-01), Nishiguma et al.
patent: 5300764 (1994-04-01), Hoshino et al.
patent: 5347111 (1994-09-01), Hoshino

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