Patent ID: 9170541
Filing Date: 2015-10-27
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: an image forming unit configured to form an image on a conveyed recording medium; a density detecting unit configured to detect a density of the image formed on the recording medium by the image forming unit; a phase detecting unit configured to detect a phase of a predetermined periodic member which is a component part of the image forming unit and which is periodically actuated; a control unit configured to instruct the image forming unit to form a pattern for measuring a density unevenness in a conveying direction of the recording medium on the recording medium, and to prepare correction data for one period of the periodic member from density data obtained by detecting the density of the pattern with the density detecting unit, the correction data being used for correcting the density unevenness in the conveying direction, which is caused due to the periodic member; and a density unevenness correcting unit configured to correct image data to be supplied to the image forming unit by repeatedly applying the correction data for one period so as to match with the phase of the periodic member, which is detected by the phase detecting unit, and to correct the density unevenness in the conveying direction, which is caused due to the periodic member, wherein the control unit instructs the image forming unit to form a first reference mark and a second reference mark at an interval in the conveying direction and the pattern having a length corresponding to two or more periods of the periodic member between the first reference mark and the second reference mark in the conveying direction, on the recording medium, wherein the control unit obtains the phase of the periodic member at a first timing at which the first reference mark is formed on the recording medium or the phase of the periodic member at a second timing at which the second reference mark is formed on the recording medium, and number of the periods during which the periodic member is actuated between the first timing and the second timing in accordance with the phase detected by the phase detecting unit, wherein the control unit calculates a relation between each position in the density data and the phase of the periodic member in accordance with at least one of the phase of the periodic member at the first timing and the phase of the periodic member at the second timing, the number of the periods during which the periodic member is actuated between the first timing and the second timing, a position corresponding to the first reference mark in the density data and a position corresponding to the second reference mark in the density data, wherein the control unit obtains a portion corresponding to a plurality of periods from a predetermined phase of the periodic member in the density data in accordance with the relation, and calculates the density data for one period by summarizing the obtained portion, and wherein the control unit prepares the correction data for one period of the periodic member in accordance with the calculated density data for one period.