Polarizer based detector
AssigneeMars, Incorporated
InventorsJeffrey T. Thawley, Edward M. Zoladz, Jr., Philippe S. Jard, David C. Deaville, Bernard Bouchet, Jerome Daout, Robert Clauser, Michael D. Nunn
Life of this patent
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Abstract
Apparatus and method for detecting strings attached to bills or other forms of payment in a currency validator. In one implementation a string fraud detector uses polarized light to detect a string. In another implementation, polarized light and light in a different range of wavelengths are used to detect a string.
Claims54
A string detector for a currency validator having a transport path comprising:
- string fraud detection means arranged along the transport path, wherein the string fraud detection means includes a light source, at least one polarizer active in a limited range of wavelengths, and a detector means to detect a string that causes rotation of the polarization of light passing through the string, wherein a signal in the detector means is indicative of the amount of light whose polarization has been rotated by the presence of the string.
A method of detecting a transparent string in a currency validator comprising:
- illuminating the string with polarized light, wherein the polarization of the light is rotated through the string;
- subsequently passing the light through a polarizer;
- and
- detecting light from the polarizer to provide a signal indicative of the amount of light whose polarization has been rotated by the presence of the string.
A method of making cross polarizers comprising:
- cutting a rectangular strip of polarizer material oriented at substantially 45° of the fast axis of the polarizer;
- and
- folding the extremities of the strip at a right angle to form two polarizers having their axis crossed at substantially 90°.
A currency validator comprising a currency transport path having at least one serpentine portion so that a taut string object will be positioned near a central region, sensor means, validation means, comparison means, memory means and fraud detection means, wherein the fraud detection means uses at least one light beam to detect a string in at least the serpentine portion, and wherein the light beam traverses a portion of the currency transport path a plurality of times.
A method for detecting a string in a currency validator comprising:
- illuminating the string with non-polarized light to obtain a first signal;
- illuminating the string with polarized light to obtain a second signal indicative of the amount of light whose polarization has been rotated by the presence of the string;
- and
- comparing the first and second signals to obtain information.
Dependencies are inferred from the claim text.