Browse Prior Art Database

Improving Bar Code Modulation

IP.com Disclosure Number: IPCOM000114597D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Lee, HC: AUTHOR [+2]

Abstract

During impact printing, modulation is adversely affected by the black bars having relatively high reflectance values and by the white bars having relatively low reflectance values. The former is caused by voids, ink depletion, low print impact forces, etc. The latter is caused by ribbon smudge, paper background, etc.

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

Improving Bar Code Modulation

      During impact printing, modulation is adversely affected by the
black bars having relatively high reflectance values and by the white
bars having relatively low reflectance values.  The former is caused
by voids, ink depletion, low print impact forces, etc.  The latter is
caused by ribbon smudge, paper background, etc.

      In measuring reflectance by a scanning device or by a piece of
measurement equipment, the size of the aperture is finite and in fact
is a significant parameter.  The fact that the aperture size is
finite in size causes the ideal reflectance curve to become rounded.
Thus, it is possible that if the aperture is too wide or conversely
if the bar is too narrow a lower than ideal value of modulation will
be obtained.  If now we add to this the printer effects that
adversely effect reflectance, a reflectance curve shown in Fig. 1
will result.  In fact the curve depicted in Fig. 1 is typical of
reflectance curves obtained from impact printers.

      Today, an ANSI specification exists to measure the quality of
bar code.  One of the six or so key parameters used in this ANSI
specification is modulation.  The ANSI bar code grade for the 4234
line matrix printer, as in other printers of its like, is limited by
the resulting modulation quality.  In the 4234, the typical bar code
grade is between a C and a B, where modulation defects caused by
ribbon smudge is the key problem.  This typically is amplified in the
narrow white bars by the aperture effect mentioned above.  Efforts
made to improve this bar code grade via smudge removal have been
difficult to implement.  Even with heroic, non-practical solutions, a
resulting grade of a B is obtained.

      A simpler solution, one that can be implement via microcode is
now proposed.  In bar code, the typical w...