Browse Prior Art Database

Scan Correction for High-Speed Laser Printers

IP.com Disclosure Number: IPCOM000099659D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Gibson, BD: AUTHOR

Abstract

A method of determining and correcting for errors due to laser scanning in a high-speed laser printhead is described.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

Scan Correction for High-Speed Laser Printers

       A method of determining and correcting for errors due to
laser scanning in a high-speed laser printhead is described.

      The circuit presented can correct for facet-to-facet scanning
errors as well as motor speed variations of the scanner.  The design
uses a clock running at the pel clock rate and some relatively low
speed hardware in a simple configuration to achieve very accurate
scan frequency correction.  The figure shows a block diagram of the
system. The pel clock is a voltage controlled retriggerable gated
clock which is synchronized by the start-of-scan (SOS) pulse.  A
counter is initiated at the SOS time and counts to a predetermined
number.  This is the desired number of pel clock cycles that should
occur from the start to end of scan.  The end-of-scan signal latches
a speed error register to determine whether or not the desired count
was achieved during that interval. The output of the latch indicates
to a particular facet register if at the next revolution of the
polygon the clock frequency should be increased or decreased.  The
correct pel frequency is stored in the facet register and then used
to set the output of the digital-to-analog converter (DAC) when the
corresponding facet is used to scan the laser.

      Two integrators are also used in this design.  The average duty
cycle of the speed error registers' output indicates both the
polarity and rate of spindle speed changes.  Th...