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Electronically Adjustable Alignment Scheme for LED Printer Head

IP.com Disclosure Number: IPCOM000101521D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Lean, EG: AUTHOR

Abstract

Misalignment of adjacent light-emitting diode (LED) bars in an LED printer head can be compensated by having extra "spare" LEDs at the ends of the bars. After running a print sample, if there is improper alignment of bars, some of these spares can be used to compensate for alignment errors.

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Electronically Adjustable Alignment Scheme for LED Printer Head

       Misalignment of adjacent light-emitting diode (LED) bars
in an LED printer head can be compensated by having extra "spare"
LEDs at the ends of the bars.  After running a print sample, if there
is improper alignment of bars, some of these spares can be used to
compensate for alignment errors.

      The figure illustrates an LED array comprising bars 1-M.  The
array may be used for printing on an adjacent light sensitive medium
which moves in the direction of the arrow with respect to the array.
Each bar carries n+2 LEDs spaced such that the region each covers of
the light sensitive medium slightly overlaps the region covered by
the preceding and following LEDs.  The first and last LEDs in each
bar are shaded to indicate that they are "spare" LEDs which are not
used if the bars are properly aligned with respect to each other.
When properly aligned, as shown, the last unshaded LED of one bar
(e.g., LED 1n) covers a field which slightly overlaps the first
unshaded LED of the next bar (e.g., LED 21), as suggested by the
dotted lines.

      Misalignment of bars will result in the last unshaded LED of
one bar either not overlapping the first unshaded LED of the next bar
at all or else in having an excessive overlap.  The spare LEDs may be
used to correct such misalignments.

      If there is no overlap, a spare LED next to one of the
nonoverlapping LEDs is electronically operated in time...