Method and apparatus for authenticating documents

• US 3,922,090 A
• Filed: 06/28/1974
• Issued: 11/25/1975
• Est. Priority Date: 06/28/1974
• Status: Expired due to Term

• Current Assignee: David L. Fain
• Original Assignee: David L. Fain
• Inventors: Fain, David L.
• Primary Examiner(s): McGraw, Vincent P.
• Assistant Examiner(s): Henry, Jon W.
• Application Number:
  US05/483,990
• Time in Patent Office: 515 Days
• Field of Search: 356/71,173,178,186,195 250/566
• US Class Current: 356/71
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation

Abstract

A document authentication apparatus for optically scanning document paper to verify the presence of colored fibers in the paper and for indicating the authenticity of the document if a predetermined number of fibers is present. The apparatus reflects white light off of the document and filters the white light into components of red and blue light. The red and blue light components are each incident on a photomultiplier tube that is connected to one channel of a signal processing circuit. The signal processing circuit produces two signals indicating the presence of the red and the blue fibers on the document and eliminates those signals representing the other colors on the document. The signal processing circuit includes a fiber width discriminator to eliminate signals not originating from fibers and an illumination level compensator for adjusting the circuit for variations in reflectivity of the documents. If a predetermined, minimum number of fibers of each color is counted on the document the apparatus indicates the document to be authentic.

Claims

1. Apparatus for authenticating documents by counting the number of fibers or lines or predetermined color and predetermined physical dimension on the document, comprising:

a light source producing illumination focusable on a document and reflectable thereoff;

means for moving the document with respect to the illumination focused thereon by the light source;

means for spectrally discriminating the illumination reflected from the document into signals representing the predetermined color;

means for measuring a physical dimension of the fibers or lines on the document from the signals representing the predetermined color; and

means responsive to the discriminating means and the measuring means for counting the number of fibers or lines having the predetermined color and predetermined physical dimension on the document.

2. Apparatus of claim 1 wherein the spectral discriminating means includes:

two optical filters each positioned to intersect the illumination reflected from the document;

two light sensitive detectors each responsive to the filtered illumination from one of the optical filters and each providing an output signal proportional to the intensity of the filtered illumination thereon;

automatic gain control means for normalizing the output signals from the two detectors for variations in reflectivity of the documents, said gain control means being responsive to the output signal from a detector;

means for generating a signal proportional to the difference between the two output signals from the light sensitive detectors, said optical filters being selected such that the two output signals from the detectors are substantially equal for all colors other than the predetermined color and substantially unequal for the predetermined color; and

logic means for determining whether said difference signal is within a predetermined tolerance and for providing a signal to the counting means indicating that the predetermined color is on the document when said tolerance is exceeded.

3. Apparatus of claim 1 wherein the spectral discriminating means includes:

two optical filters each positioned to intersect the illumination reflected from the document;

two light sensitive detectors each responsive to the filtered illumination from one of the optical filters and each providing an output signal proportional to the intensity of the filtered illumination thereon;

means for generating a signal proportional to the ratio of the two output signals from the light sensitive detectors, said optical filters being selected such that the two output signals from the detectors are substantially equal for all colors other than the predetermined color and substantially unequal fOr the predetermined color; and

logic means for determining whether said ratio signal from the signal generating means is within a predetermined tolerance and for providing a signal to the counting means indicating that the predetermined color is on the document when said tolerance is exceeded.

4. Apparatus for authenticating documents by counting the number of fibers or lines of predetermined color on the document, comprising:

a light source producing illumination focusable on the document and reflectable thereoff;

means for moving the document with respect to the illumination focused thereon by the light source;

a first light sensitive detector responsive to the reflected illumination from the document and indicating variations in the intensity of said illumination;

an optical filter positioned to intersect the reflected illumination from the document and to selectively pass only illumination having a predetermined wavelength;

a second light sensitive detector responsive to the illumination having the predetermined wavelength from the optical filter and indicating variations in the intensity of said illumination;

means responsive to the variations from the light sensitive detectors for counting the number of fibers having the predetermined color;

means for measuring a physical dimension of the fibers or lines on the document passing through the illumination and for preventing the counting means from counting fibers or lines having physical dimensions other than a predetermined value; and

logic means for authenticating those documents having a predetermined number of colored fibers or lines thereon.

5. Apparatus of claim 4 further including means connected to the light sensitive detectors for compensating the counting means for variations in reflectance of the documents.

6. Apparatus of claim 4 wherein the measuring means is responsive to the variations from the light sensitive detectors.

7. Apparatus for authenticating documents by counting the number of fibers or lines of two predetermined colors on the document, comprising:

a light source producing illumination focusable on the document and reflectable thereoff;

means for moving the document with respect to the illumination focused thereon by the light source;

a first optical filter positioned to intersect the reflected illumination from the document and to pass only illumination having substantially a first predetermined color;

a second optical filter positioned to intersect the reflected illumination from the document and to pass only illumination having a substantially second predetermined color;

a first light sensitive detector responsive to the illumination having the first predetermined color from the first optical filter and providing a first output signal proportional to the intensity of said illumination;

a second light sensitive detector responsive to the illumination having the second predetermined color from the second optical filter and providing a second output signal proportional to the intensity of said illumination;

automatic gain control means for normalizing the output signals from the first and second detectors for variations in reflectivity of the documents, said gain control means being responsive to the output signal from the second detector;

means for subtracting the second output signal from the first output signal and for generating a third output signal proportional to the difference therebetween;

means for subtracting the first output signal from the second output signal and for generating a fourth output signal proportional to the difference therebetween;

first logic means for determining whether said third output signal exceeds a predetermined value and for providing a fifth signal when said tolerance is exceeded;

second logic means for determining whether said fourth output signal exceeds a predetermined value and for providing a sixth signal when said tolerance is exceeded;

means for counting the occurrences of the fifth and sixth signals respectively and for providing an authenticatiNg signal when the numbers of the two occurrences exceed two predetermined minimum numbers.

8. Apparatus of claim 7 further including fiber width discriminator means responsive to said first and second output signals for measuring a physical dimension of the fibers or lines of said predetermined colors and for preventing said counting means from counting the fifth and sixth signals from those lines or fibers having dimensions exceeding a predetermined dimension.

9. Method for authenticating documents by computing the number of selected fibers or lines on each document, comprising the steps of:

reflecting illumination off of the document;

moving the document at a constant speed with respect to the illumination;

filtering the illumination into components, each having a predetermined wavelength, measuring the intensity of said components of predetermined wavelength; and

determining the number of fibers or lines of each wavelength on the document from the intensity measurements.

10. Method of claim 9 further including the steps of:

measuring a physical dimension of each fiber or line from the intensity measurements; and

preventing the fibers or lines not having a predetermined dimension from being computed.

11. Method for authenticating documents by computing the number of selected fibers or lines on each document, comprising the steps of:

reflecting illumination off of the document;

moving the document at a constant speed with respect to the illumination;

filtering the illumination into components, each having a predetermined wavelength;

measuring the intensity of each component of predetermined wavelength;

compensating the intensity measurements for variations in reflectivity of the documents;

subtracting the intensity measurements to obtain the differences therebetween;

determining the number of fibers or lines of each wavelength on the document from the differences; and

authenticating the document when the number of fibers and lines exceeds a predetermined number.