Image forming apparatus, image forming system, and image density adjustment method

An image forming system comprising:

• an image forming apparatus including:
• an image forming section which forms a belt-shaped pattern on a sheet, the belt-shaped pattern having a prescribed length extending in a main-scanning direction;
• and
• a control section which performs control regarding image formation, and
• a color measurement device which receives the sheet on which the belt-shaped pattern is formed by the image forming section, measures a density of the belt-shaped pattern at prescribed measurement-distance intervals staring from a measurement starting position corresponding to a formation starting position of the belt-shaped pattern formed on the sheet, and outputs a result of the measurement, wherein
• the control section allows the image forming section to form the belt-shaped pattern on a plurality of sheets, and allows the image forming section to form the belt-shaped pattern on a plurality of sheets in such a way that the formation starting position of the belt-shaped pattern is shifted for a distance in the main-scanning direction sheet by sheet, the distance which is obtained by dividing the measurement-distance by a number of sheets on which the belt-shaped pattern is to be formed;
• collects a plurality of pieces of density information sheet by sheet, the pieces of density information each of which indicates the density of the belt-shaped pattern at a measurement position of a plurality of measurement positions;
• creates data in which the pieces of density information respectively correspond to the measurement positions arranged in the main-scanning direction on each of the sheets;
• and corrects density unevenness of image data in the main-scanning direction based on the created data, and
• the image forming section forms an image on a sheet based on the image data of which the density unevenness is corrected.

An image density adjustment method comprising:

• forming a belt-shaped pattern on a plurality of sheets, the belt-shaped pattern having a prescribed length extending in a main-scanning direction, in such a way that a formation starting position of the belt-shaped pattern is shifted for a prescribed distance in the main-scanning direction sheet by sheet;
• measuring a density of the belt-shaped pattern formed on each of the sheets at prescribed measurement-distance intervals starting from a measurement starting position of the belt-shaped pattern, the measurement starting position corresponding to the formation starting position;
• collecting a plurality of pieces of density information sheet by sheet, the pieces of density information each of which indicates the measured density of the belt-shaped pattern at a measurement position of a plurality of measurement positions;
• creating data in which the collected pieces of density information respectively correspond to the measurement positions arranged in the main-scanning direction on each of the sheets;
• and
• correcting density unevenness of image data in the main-scanning direction based on the created data, wherein
• in the forming, the belt-shaped pattern is formed on the sheets in such a way that the formation starting position of the belt-shaped pattern is shifted for the distance in the main-scanning direction sheet by sheet, the distance which is obtained by dividing the measurement-distance by a number of sheets on which the belt-shaped pattern is to be formed.