Patent ID: 6160566
Filing Date: 2000-12-12
Classification: H04N

Abstract:
A registry adjusting device for use with a plurality of laser scanning units in a laser beam printer, said device comprising:(a) a reference clock generator;(b) phase-difference-measuring means for measuring a time-lag of a plurality of timing signals for recording an image in a main scanning direction by counting a reference clock supplied from said reference clock generator between said timing signals, and thereby said measuring means provides a plurality of count values, the plurality of timing signals produced by sensors, each of the sensors receiving a laser beam deflected by rotary polygons in said plurality of laser scanning units;(c) a plurality of registers storing said plurality of count values provided by said phase-difference measuring means;(d) frequency dividing means for dividing the reference clock by some value into a frequency divided signal, and outputting the frequency divided signal as a motor clock that drives the rotary polygons and(e) a pulse generator for generating a pulse to the frequency dividing means during a period equal to said count value of the reference clock so that operation of said frequency dividing means is halted during said period in order to adjust a rotation of rotary polygons.