US 6,476,370 B1Granted

Method of controlling turn-on of light source and image forming apparatus

AssigneeFuji Xerox Co., Ltd.

InventorsTakayoshi Suzuki, Kohei Shioya

Life of this patent

Estimating the term…

Loading patent…

Abstract

An image forming apparatus and a method of controlling turn-on of light source used therefor are capable of conducting stable image forming operation and maintaining high effective scanning rate while switching the rotation control of the polygonal motor between the internal control by the internal encoder of the motor and the external control by the horizontal synchronous signal outside of the motor. With the apparatus and method, the period of detecting the timing of start of the fast scanning (referred to as SOS period) is T when the driving motor rotates at a predetermined number of revolutions. T becomes shorter by T2 due to the switching from the internal control to the external control. During the shift from the internal control to the external control, the light source is turned on so that the period T1 from turning-on the light source for detecting the SOS timing to the detection of the SOS signal becomes longer than T2. Thereby, turning-on of the light source is surely conducted earlier than the SOS signal detection timing when the rotational control is switched from the internal control to the external control.

Claims9

Dependent claims

A light source turn-on controlling method used for an image forming apparatus in which a laser beam output from a light source scans an image carrier by rotating a rotational polygonal mirror to form an image, the apparatus including a number-of-revolutions detecting unit that detects the number of revolutions of a driving motor which rotates the rotational polygonal mirror, an internal control unit that rotates the driving motor at a predetermined number of revolutions on the basis of the detection result of the number-of-revolutions detecting unit, a fast scanning timing detection unit which is provided out of an image forming area in the fast scanning direction of the laser beam and detects a fast scanning timing of the laser beam, an external control unit that rotates the driving motor at a predetermined number of revolutions on the basis of the detection result by the fast scanning timing detection unit, and a switching control unit that performs a switching operation between a rotational control based on the internal control unit and a rotational control based on the external control unit, the light source turn-on controlling method comprising the step of:

starting the turn-on of the light source to make the laser beam incident on the fast scanning timing detection unit to satisfy the relationship of T1>T2 during the shift period of the switching operation from the rotational control by the internal control unit to the rotational control by the external control unit, where T1 represents the period from a start time at which turn-on of the light source is started to make the laser beam incident on the fast scanning timing detection unit to a time at which the laser beam is incident on the fast scanning timing detection unit and the fast scanning timing is detected and T2 represents the time corresponding to a variation of one fast scan time due to a rotational variation of the driving motor which is caused by the switching operation from the rotational control by the internal control unit to the rotational control by the external control unit.

An image forming apparatus in which a laser beam output from a light source scans an image carrier by rotating a rotational polygonal mirror to form an image, comprising:

a number-of-revolutions detecting unit that detects the number of revolutions of a driving motor which rotates the rotational polygonal mirror;
an internal control unit that rotates the driving motor at a predetermined number of revolutions on the basis of the detection result of the number-of-revolutions detecting unit;
a fast scanning timing detection unit which is provided out of an image forming area in the fast scanning direction of the laser beam and detects a fast scanning timing of the laser beam;
an external control unit that rotates the driving motor at a predetermined number of revolutions on the basis of the detection result by the fast scanning timing detection unit;
a switching control unit that performs a switching operation between a rotational control by the internal control unit and a rotational control by the external control unit;
and
a turn-on control unit that turns on the light source earlier than a timing of incidence of the laser beam on the fast scanning timing detection unit by at least the time corresponding to a variation of one fast scanning time due to the rotational variation of the driving motor caused by the switching operation in a shift period during which the rotational control by the internal control unit is switched to the rotational control by the external control unit by the switching control unit.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/696,949Filed 27 Oct 2000
Priority: JP 11-35616215 Dec 1999
Granted: 5 Nov 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

G06K 15/1219
Involving the fast moving of an optical beam in the main scanning direction: detection, control or error compensation of scanning velocity or…
H04N 1/053
Detection, control or error compensation of scanning velocity or position: in main scanning direction, e.g. synchronisation of line start or…
H04N 1/1135
Using oscillating or rotating mirrors: for the main-scan only
H04N 2201/02439
Arrangements for positioning elements within a head: positioning method