An image forming apparatus includes an image bearing member, a developing device, a toner content detecting portion, a toner supplying device, an image ratio calculating portion, a toner image density detecting portion, an adjusting portion, and a controller configured to control an execution frequency of the adjusting portion so that the adjusting portion is carried out after a number of times of image formation after occurrence of a larger change rate of the image ratio than a predetermined change rate reaches a first value, and the adjusting portion is carried out after the number of times of image formation after occurrence of a smaller change rate of the image ratio than the predetermined change rate reaches a second value larger than the first value.

A controller of an image forming apparatus calculates a density difference between a measurement result of a toner image having the highest density formed on a photosensitive drum, which is obtained by an image density sensor, and the highest density of a density target. When the density difference falls within a predetermined range, the controller generates a tone correction table based on a density value of a first toner image formed with a plurality of densities including the highest density, and sets, based on the density difference, an exposure amount of laser light to be applied to the photosensitive drum by an exposure device. When the density difference falls out of the predetermined range, the controller generates the tone correction table based on a density value of a second toner image having a larger number of tone levels than that of the first toner image.

A density correction unit (a1) obtains density measurement values of a surface in a measurement section of an image carrier at a first round, (a2) calculates as section background data at the first round respective differences between the density measurement values at the first round and an average value thereof, (a3) obtains density measurement values of a surface at least in the measurement section at a second round, (a4) calculates as section background data at the second round respective differences between the density measurement values at the second round and an average value thereof in a specific section with the same length as the measurement section, and (a5) determines the rotation period on the basis of a correlation between the section background data at the first round and at the second round. Here the measurement section is a part in a circulating direction of the image carrier.

An apparatus comprises a photosensitive member, an exposure light source including a plurality of light-emitting units that are arranged parallel to a rotation axis of the photosensitive member and that emit light that exposes the photosensitive member, and a controller configured to generate image data that is a group of bit data controlling lighting and extinguishing of the plurality of light-emitting units and that corresponds to an image, and to insert and/or remove the bit data in the image data. The image includes a test image for obtaining a shift amount in an image formation position relative to a reference position. The image data includes test image data corresponding to the test image. The controller does not insert and/or remove the bit data in a region of the image data that corresponds to the test image data.

The image forming apparatus includes an image carrier, a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning blade, and a controller. The controller detects printing-coverage rates on a basis of plural areas divided in the longitudinal direction of the image carrier. At a specified timing, the controller executes aging process in which the image carrier in a charged state is driven into rotation under light irradiation by the exposure unit. For the aging process, the controller sets a condition that a light quantity of the exposure unit for an area of larger coverage rate is larger than a light quantity of the exposure unit for an area of smaller coverage rate.

The image forming apparatus includes an image carrier, a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning blade, and a controller. The controller detects printing-coverage rates on a basis of plural areas divided in the longitudinal direction of the image carrier. Upon occurrence of a difference exceeding a specified threshold value among the coverage rates of the plural areas, the controller executes, for a duration of specified aging time, aging process in which the image carrier is driven into rotation in its charged state.

A control unit of an image forming apparatus can perform a density correction mode to correct toner density, based on detection results of toner density of a plurality of reference images formed with density gradations changed sequentially in a plurality of steps, detects presence or absence of a change in the voltage in each density gradation, based on the toner density detection value detected in the density correction mode, and if the density gradation has a specific density gradation in which a change in the voltage is detected, it corrects the toner density of the specific density gradation, using the detection values of density gradations before and after the specific density gradation.

An image forming apparatus that forms an image on a sheet based on an image forming mode, the image forming mode including a first image forming mode and a second image forming mode for forming an image which a maximum density different from a maximum density of an image in the first image forming mode, the image forming apparatus includes an image processor configured to convert an image signal based on a conversion condition, an image forming unit configured to form an image based on the image signal converted by the image processor, the image forming unit being controlled based on an image forming condition corresponding to the image forming mode, an image bearing member on which a pattern image is to be formed by the image forming unit, a sensor configured to detect the pattern image formed on the image bearing member.

An image forming apparatus includes a plurality of image forming units, an exposure device, and circuitry. Each image forming unit includes an image bearer, a charger, and a developer bearer. The circuitry acquires an image-density cycle fluctuation in a visible image for each image forming unit and performs image-density fluctuation-reduction control to cyclically change image forming conditions to reduce the image-density cycle fluctuation. The circuitry performs: first fluctuation-reduction control to correct a developing bias to cancel an image-density cycle fluctuation of a high-density image pattern; second fluctuation-reduction control to, after the first fluctuation-reduction control, correct a charging bias to cancel an image-density cycle fluctuation of a first low-density image pattern; and third fluctuation-reduction control to, after the first and second fluctuation-reduction controls, correct an exposure light amount to cancel an image-density cycle fluctuation of a second low-density image pattern.

In the image forming method, a halftone image is generated by performing halftone processing for an input image, a scanned image of a printed material on which on which the halftone image is printed is obtained, and a failure component of an image forming apparatus is identified based on a difference between the scanned image and the input image. In the generation, the halftone image is generated by representing a dot pattern of a halftone portion in a case where the input image is a test image for the failure diagnosis by a dot pattern whose frequency is relatively higher than that of a dot pattern that is applied to the halftone portion in a case where the input image is an image other than the test image.