Apparatus for testing colored securities

Details Apparatus for testing colored securities Apparatus for testing colored securities

1977-12-07

1980-05-27

McGraw, Vincent P.

Optics: measuring and testing

Document pattern analysis or verification

250556, G01K 908

Patent

active

042047650

ABSTRACT:
Apparatus for testing the authenticity of paper having colored areas thereon. A plurality of light emitting diodes, each emitting light of a different wavelength, are provided in juxtaposition to a paper having areas thereon which are reflective with respect to the light from the various diodes. A single photodetector is maintain closely adjacent the paper for receiving light reflected therefrom. A sequential timing circuit controls the illumination of the diodes such that the photodetector senses the light reflective characteristic of the paper with respect to each of the various wavelengths of light in a mutually exclusive manner. The outputs of the photodetector are passed to a sample and hold circuit which, at the end of a test cycle, maintains data relative to the light reflective characteristics of the paper for each of the various wavelengths of light. Comparator circuitry then tests the data and compares the reflectance values for each wavelength against the values for other wavelengths to determine the authenticity of the paper. The diodes may be selected to emit light in either the visible range or at either end of the light spectrum depending upon the nature of the paper to be tested.

REFERENCES:
patent: 3480785 (1969-11-01), Aufderheide
patent: 3910701 (1975-10-01), Henderson et al.

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