Xerox 6100BD - Phaser Color Laser Printer Fundamentals page 110

Quality control
6-24
– Waveforms measure only vertical stroke locations, while
optical standards apply also to horizontal strokes. Some
recognition technologies do not use waveforms, relying
on locations of both horizontal and vertical strokes in a
two-dimensional matrix.
– MICR test equipment precision is limited by digitizer
resolution. The minimum encoding interval limits the
precision of a single measurement. In Xerox's RDM MICR
Qualifier GTs, this interval is 0.00104 inch/0.026 mm—
one-third of the tolerance.
– Digital MICR font designs are optimized for recognition
performance in the full range of equipment used in check
processing. As a result, some characters—typically the 4
and the 6—are frequently flagged for character width.
Fonts could be changed to eliminate these flags, but bank
rejection rates would be higher if the font were optimized
to meet magnetic dimensional limits imposed by MICR
tester manufacturers.
NOTE: Excessive or persistent dimensional flags may
indicate a real problem, which must be verified by optical
inspection.
• Character-to-character spacing (±0.010 inch/0.254 mm
tolerance)
– Character spacing controlled by the font varies cyclically
by a small amount: ±0.00167 inch/0.042 mm (1/600)
every other character at 300 DPI.
– In LCDS data streams, a spacing algorithm is required to
prevent accumulation of errors.
– Any variation beyond this, or any adjacent characters
shifting in the same direction, indicate a problem.
The best way to check for character spacing issues is to
inspect the entire MICR line in the Position and Dimension
Gauge, to see if characters remain a consistent distance from
their cell boundaries. If one character is aligned to its cell
boundary, all characters should be very close to theirs. Any
cumulative change in character spacing that reaches the
±0.010 inch/0.124 mm tolerance level should be investigated
as a potential application or machine problem, even though it
is not an ANSI specification failure.
Using the MICR Position and Dimension Gauge to check
registration is a basic task that the operator performs at the
printer whenever checks are being printed.
Generic MICR Fundamentals Guide