Browse Prior Art Database

Automated VOID Pantograph Detection

IP.com Disclosure Number: IPCOM000116256D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 107K

Publishing Venue

IBM

Related People

Rohrer, GD: AUTHOR [+2]

Abstract

A pantograph, as the term is used in this disclosure, is a pattern spread over the background of a check or other security document which contains a hidden pattern that becomes visible when copied by a xerographic or other nonlinear process. Typically the pattern which becomes apparent after copying consists of multiple instances of the word VOID. One technique for creating a pantograph is to use a mixture of large and small halftone screens in printing the background of the document.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Automated VOID Pantograph Detection

      A pantograph, as the term is used in this disclosure, is a
pattern spread over the background of a check or other security
document which contains a hidden pattern that becomes visible when
copied by a xerographic or other nonlinear process.  Typically the
pattern which becomes apparent after copying consists of multiple
instances of the word VOID.  One technique for creating a pantograph
is to use a mixture of large and small halftone screens in printing
the background of the document.

Typical VOID pantograph documents consist of a fine halftone screen
and a coarse halftone screen.  When copied using a common xerographic
copier, the dots in the fine halftone tend to disappear, whereas the
dots in the coarse halftone are reproduced.  The document is
patterned such that the areas occupied with the coarse halftone dots
form large block letters "VOID VOID VOID".  These words become quite
visible on a copied document.

It is possible to build a high-speed document processor scanner with
a feature which not only eliminates small spots (such as dirt
specks), but counts the number of eliminations.  Spots which are
eliminated are those black picture elements which are completely
enclosed by a 3 by 3 or 4 by 4 border of all white picture elements.
This eliminator or filter is called an isopel filter because isolated
picture elements activate the filter mechanism.  It is now disclosed
that this feature can be useful in fraud detection with the addition
of a means of reporting the count out of the scanner to a control
program within the scanner or to a host program which compares the
account number from the check codeline with a list to determine if
the count should be present, and what range the count should be in.
Any document not matching the criterion would be considered suspect.

The black/white images generated by the scanner would show the VOID
patterns created by the large dots, except for the isopel filter
which eliminates the coarse halftone dots from the scanner output.
(The fine halftone dots are eliminated because they are beyond the
resolution of the scanner.)  It is also possible to count white
isolated picture elements but it is not necessary to eliminate white
isopels in order to prevent the unwanted appearance of VOID patterns
since the VOID patterns consists of black dots, not white dots.
However, the white isopels may also be counted and/or removed if
special documents are designed with reverse printing.

There is a very inexpensive technique for verifying the presence of
VOID pantographs at a teller workstation.  This works best if the
document printer makes the ratio of the line spacing of the fine and
course halftone screens something other than a factor of two --
perhaps 2.3.  This would allow t...