Optical Testing Equipment Usage - Xerox 6100BD - Phaser Color Laser Printer Fundamentals

Optical testing equipment usage

Generic MICR Fundamentals Guide
• Character placement (0.125 inch/3.175 mm interval)
– MICR line registration is controlled by the right edge of a
single Transit character that is nominally 5.625 inches/
142.89 mm from the reference edge.
– Transport speed calibration accuracy, speed variations,
and document slippage over this distance contribute to
errors in MICR tester measurements of horizontal MICR
line placement.
– MICR testers can not measure vertical MICR line
placement.
NOTE: These errors and limitations never occur with a MICR
Position and Dimension Gauge.
The majority of automated optical MICR test equipment is aimed
at document design, for which stringent limitations on density
and contrast require sophisticated analysis. With different
analysis software, this optical test equipment can be used to
evaluate E13B font characters optically. However, there are
some issues to consider before accepting it as a replacement for
a MICR reticle on an eye loupe.
• The optical test equipment does registration, character
spacing, and character alignment well, because these
tolerances—0.0625 inch/1.588 mm, 0.010 inch/0.254 mm,
and 0.020 inch/0.508 mm respectively—are within the
resolution limits of all scanners. However, MICR dimensional
tolerances are ±0.0015, so the measuring device would
require twice this resolution to sense the tolerance. This
requires a 0.0008 inch/0.02 mm spot size and a 1200 dpi
sampling rate. It may be argued that the tolerance is 0.003
inch/0.076 mm—the sampling rate of a 300 dpi scanner; but
that is a cumulative tolerance for the two sides of a stroke. A
300 dpi scanner can evaluate only 0.0066 inch/0.168 mm
tolerances well.
• All dimensions are referenced to the "average edge," defined
as the line that bisects any edge noise so that half the black
area is on each side. The eye does this well, but automated
scanners do not have the processing advantages of an eye.
They need to resolve the edge noise due to the Yule-Neilsen
effect, which causes an unresolved object to appear darker
than the amount of ink coverage would predict.
Quality control
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