The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 28, 1995
Filed:
Apr. 05, 1993
James S Bianco, Enfield, CT (US);
David J Horan, Westfield, MA (US);
Control Module Inc., Enfield, CT (US);
Abstract
In a preferred embodiment, a method of of of determining if a compound diffraction grating has been forged, the compound diffraction grating including a plurality of diffraction grating elements of different types, the compound diffraction grating being read by serially detecting light diffracted by the diffraction grating elements, including: determining the amplitude of diffracted light signals as the compound diffraction grating is being read; and determining that the compound diffraction grating is forged if the amplitude is below a selected threshold level. In another aspect of the invention, there is provided a method determining if such a diffraction grating has been forged, the method including: measuring the number of transitions between diffraction grating elements across the strip; and comparing the number with a pre-recorded number of the transitions and determining that the diffraction grating strip has been forged if the numbers are not the same. In a further aspect of the invention there is provided a method of determining if a compound diffraction grating has been forged, the method including: illuminating the compound diffraction grating with a beam of light substantially orthogonal to the compound diffraction grating; and determining that the compound diffraction grating has been forged when the beam of light is reflected substantially orthogonally from the compound grating.