Browse Prior Art Database

Scanning Laser Printhead Clock

IP.com Disclosure Number: IPCOM000101487D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Price, CW: AUTHOR

Abstract

Disclosed is a "pel-clock" which compensates for the non-constant beam scanning velocity of a known scanning laser printhead.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 86% of the total text.

Scanning Laser Printhead Clock

       Disclosed is a "pel-clock" which compensates for the
non-constant beam scanning velocity of a known scanning laser
printhead.

      The figure shows a schematic diagram for the present embodiment
in which the existing printhead end-of-scan signal (feos) is used as
the reference for a phase-locked loop frequency synthesizer which
generates pel-clock output (fpc).  Phase Detector 1 delivers a signal
(Ipd) at its output that is related to the phase (frequency) error
between the end-of-scan signal (feos) and the generated pel-clock
signal (fpc).  The (Ipd) signal is smoothed by Low-Pass Filter 2
controlling Oscillator 3 whose output frequency (fpc) is
proportionally related to this input. Counter 4 produces an output
signal (fpc)/N that is harmonically related to the pel-clock by a
programmable factor 1/N, where N is the number of addressable
locations along the photoreceptor surface for each scan line.

      Pel-clock compensation is achieved by a second input (Icomp) to
Low-Pass Filter 2 which is dynamically adjusted on a pel-by-pel basis
to achieve the desired correction.  A correction profile is stored in
Look-up Table 6 whose outputs control the magnitude and polarity of
the (Icomp) signal.  Look-up Table 6 is sequenced by Counter 5 which
is initialized by the (feos) signal and sequenced by the (fpc)
signal.

      Since the velocity profile is cyclic with each mirror facet,
the pel-clock is adjusted back to its...