To suppress the wrong detection of the image pattern, an image forming apparatus includes a plurality of image forming units respectively configured to form images of different colors, an intermediate transfer member to which a pattern to detect an amount of color misregistration of an image formed by the plurality of image forming units is transferred, a sensor configured to assure reflected light from the pattern on the intermediate transfer member to output an output value in accordance with a measurement result, a comparator configured to compare the output value output from the sensor with a threshold, and a controller configured to control the plurality of image forming units to respectively form a plurality of patterns of different colors on the intermediate transfer member, to control the sensor to measure reflected light from the plurality of patterns.

An image forming apparatus includes a toner pattern bearer to bear a first toner pattern having a first image area rate and a second toner pattern having a second image area rate different from the first image area rate. A toner adhesion amount detector detects a toner adhesion amount of toner of each of the first toner pattern and the second toner pattern. A toner degradation rate calculator calculates a first deviation in the toner adhesion amount of the first toner pattern and a second deviation in the toner adhesion amount of the second toner pattern based on the toner adhesion amount detected by the toner adhesion amount detector. The toner degradation rate calculator compares the first deviation with the second deviation and calculates a toner degradation rate based on a comparison result.

A differential correction data generating unit measures two density characteristics at a reference linear velocity and another linear velocity from scanned images of two test charts printed at the reference linear velocity and the another linear velocity, and generates differential correction data as a difference between correction amounts for the measured two density characteristics. A correction amount adjusting unit measures a density characteristic at the reference linear velocity from an adjustment toner pattern formed on an intermediate transfer member, and thereby adjusts a correction amount for the density characteristic at the reference linear velocity. A density characteristic of a printing image is corrected, (a) for the reference linear velocity, on the basis of the correction amount at the reference linear velocity, and (b) for the another linear velocity, on the basis of the correction amount at the reference linear velocity and the differential correction data.

An image forming apparatus that forms an image on a printing medium by an electrophotographic system in accordance with input image data, the apparatus including: a plurality of image forming units configured to form images in colors different from one another; a first determination unit configured to determine whether or not toner amount adjustment is necessary based on a possibility of the occurrence of a ghost for image data that is used for image formation in a second image forming unit located on the upstream side of a first image forming unit that is located on the downstream side in a conveyance direction of the printing medium of the plurality of image forming units; and a toner amount adjustment unit configured to make toner amount adjustment for the image data that is used for image formation in the second image forming unit in accordance with the determination results by the first determination unit.

A curling detection device includes an endless belt entrained around at least two rollers, a conveyance unit that conveys the endless belt by driving the rollers, an image forming unit that forms an image by transferring a toner image to either a surface of the endless belt directly or a recording medium on the endless belt, a pattern image forming controller that instructs the image forming unit to form lines of a curling detection pattern at predetermined intervals in a conveying direction of the endless belt and a predetermined angle against the conveying direction of the endless belt at a predetermined timing, a curling scanning unit that scans the curling detection pattern, and a detecting unit that detects a curling of the endless belt based on the interval of the curling detection pattern scanned by the curling scanning unit.

An image forming apparatus includes an image bearer, an image forming device, a toner concentration detector, a toner supply device, an image density detector, and a controller including a memory device. At a predetermined timing before image formation is started, the controller adjusts a developing potential to adjust an image density of a detection toner image on the image bearer and drives the toner supply device or the developing device to adjust a toner concentration in the developing device. After the image formation is started, the controller drives the toner supply device to adjust the toner concentration, and, in a predetermined sheet interval, adjusts the target concentration based on the image density of the detection toner image formed in a non-image area of the image bearer. When the toner concentration is higher than the target concentration plus a threshold, the controller suspends image formation and readjusts the developing potential.

An image forming apparatus includes a second cleaning section, an image formation control section configured to control an image forming section to form a high-coverage patch on a transfer belt, and a cleaning control section configured to control the second cleaning section to perform cleaning of the patch on the transfer belt.

The image forming apparatus controls each laser scanner by setting the writing start timing in the sub-scanning direction to form the color registration correction image for correcting color registration at position according to the detection result of the image detection sensor. When forming the image on the sheet, the image forming apparatus sets the writing start timing in the sub-scanning direction according to the detection result of the image detection sensor and the amount of skew of the sheet to control each laser scanner. When forming the density detection toner image for correcting the density, the image forming apparatus sets the writing start timing in the sub-scanning direction to form the image at a position shifted by a pixel unit from the image forming position on the sheet.

An image forming apparatus includes a photosensitive member having first and second areas at different positions at an axial end of the photosensitive member, the first and second areas not overlapping an image area in an axial direction of the photosensitive member; a detecting unit that detects an image; and a forming unit that forms a transfer-object image in the image area, the transfer-object image being transferred to a transfer area of continuous-form paper, the forming unit further forming first and second images in the first and second areas of the photosensitive member, respectively, the first image not being transferred to the transfer area but being detected by the detecting unit for use in an operation of controlling conditions for image formation, the second image not being transferred to the transfer area and not being used in the operation of controlling the conditions for image formation.

An image forming apparatus includes a toner image forming portion, an information acquisition portion and a control portion. The control portion carries out processes (i) and (ii). In the process (i), the control portion causes the toner image forming portion to form, as a test image, at least either one of a toner image of single dot and a toner image of dot line consisting of single dots arranged in one or more rows in a predetermined direction, and then causes the information acquisition portion to acquire optical information on the formed test image. In the process (ii), the control portion corrects a condition for forming the toner image in the toner image forming portion, based on a state (size, concentration distribution, edge shape) of the test image obtained from the optical information acquired by the information acquisition portion.