Patent ID: 6404449
Filing Date: 2002-06-11
Classification: H04N

Abstract:
A color image forming apparatus, comprising:a photoreceptor; a plurality of exposure-scanning sections, each of which performs an exposure-scanning operation onto said photoreceptor by means of a laser beam deflected by a polygon mirror, the plurality of exposure-scanning sections including a horizontal-sync signal generator to generate a horizontal-sync. signal synchronized with a rotational period of said polygon mirror, wherein one of said plurality of exposure-scanning sections outputs a reference horizontal-sync. signal; a synchronizing section to synchronize said horizontal-sync. signal, output by said other exposure-scanning section, with said reference horizontal-type sync. signal, and to synchronize an image tip signal with said reference horizontal-sync. signal; an adjusting section to adjust a commencement of said exposure-scanning operation performed by each of said plurality of exposure-scanning sections, based on said reference horizontal-sync. signal output by one of said plurality of exposure-scanning sections; and a positional deviation detecting section to detect a positional deviation on the basis of a plurality of marks formed on said photoreceptor by said plurality of exposure-scanning sections, said positional deviation detecting section detecting said positional deviation in such a state that said horizontal-sync. signals are synchronized with each other and said image tip signal is synchronized with said reference horizontal-sync. signal; wherein said adjusting section adjusts said positional deviation in a unit of one scanning line by adjusting an interval between said horizontal-sync. signal and said image tip signal, and adjusts said positional deviation less than one scanning line by changing a phase of clock signals utilized for driving said polygon mirror, based on said positional deviation detected by said positional deviation detecting section; and wherein a unit adjustment for changing said phase of said clock signals, utilized for driving said polygon mirror, is greater than an amount of jitters generated by said polygon mirror.