An image forming apparatus includes an intermediate transfer belt, a density sensor, a cleaning device and a density correction unit. The intermediate transfer belt carries a calibration toner image. The density sensor detects a density of the calibration toner image that passes at a predetermined position. The cleaning device contacts to a part of the intermediate transfer belt in a primary scanning direction, and removes from the intermediate transfer belt the calibration toner image that passed at the predetermined position. The density correction unit performs density correction of a printing toner image in the primary scanning direction. Further, the density correction unit changes a strength of the density correction for a contact range to which the cleaning device contacts on the intermediate transfer belt, the strength changed in accordance with the number of times of a calibration process.

An image forming apparatus includes image forming devices, image output devices, an endless conveyor, a transfer device, holders, a detector, and circuitry. The image forming devices include image bearers. The image output devices form latent images on the image bearers. The image forming devices form visible images from the latent images. The transfer device transfers the visible images onto the endless conveyor that conveys the visible images in an image conveyance direction. The holders hold the image forming devices interchangeable at holding positions aligned in the image conveyance direction. The detector detects the visible images. The circuitry compares a first visible image of the visible images formed at a specific holding position of the holding positions with a second visible image of the visible images formed at another holding position of the holding positions on the endless conveyor, to correct misalignment between the first and second visible images.

An image forming apparatus is configured to calculate an estimated value of a color misregistration amount based on a first estimation expression when a temperature of an exposure device is under a temperature increasing state. The image forming apparatus is configured to calculate the estimated value of the color misregistration amount based on the first estimation expression when the temperature of the exposure device is under the temperature decreasing state and the exposure device is not in a thermally-deformed state. The image forming apparatus is configured to calculate the estimated value of the color misregistration amount based on a second estimation expression when the temperature of the exposure device is in the temperature decreasing state and the exposure device is in the thermally-deformed state. The image forming apparatus is configured to correct color misregistration based on the calculated estimated value.

According to one embodiment, an image forming apparatus includes a plurality of process units, a transferring member, a sensor, and a processor. The plurality of process units include a photosensitive drum, an electric charger which charges the photosensitive drum, an exposing device which includes a plurality of light emitting element rows in a sub-scanning direction configured by the plurality of light emitting elements, and irradiates the photosensitive drum to form a latent image, and a developing device which attaches toner to the latent image to form a toner image. The transferring member receives the toner image from the photosensitive drum. The sensor detects the toner image transferred to the transferring member. The processor calculates a skew deviation amount based on the detection result of the sensor, and controls turning on and off the light emitting element based on a central tendency and the skew deviation amount.

An image forming apparatus configured to operate in first and second modes of which color gamut is different from each other, the image forming apparatus includes: an exposure unit configured to expose a photosensitive drum; a developing roller configured to form a toner image; a detection unit configured to detect density of the toner image transferred to an intermediate transfer member; and a controller configured to adjust the density based on a value of input image data. A dithering process for controller's controlling of the exposure unit is different depending on whether the operation is in the first mode or the second mode, and in at least a part of the input image data, the density of the toner image formed by the dithering process in the first mode is higher than the density of the toner image formed by the dithering process in the second mode.

An image forming apparatus includes an intermediate transfer body, a plurality of image formation units arranged in a direction along which the intermediate transfer body moves. The plurality of image formation units includes a first image formation unit and at least one second image formation unit disposed downstream of the first image formation unit.

An image forming apparatus includes a developing roller configured to develop an electrostatic latent image on a photosensitive drum to form a toner image; a belt onto which the toner image is transferred; a detection unit configured to detect a density of an image for detection formed on the belt; and a controller configured to perform hue adjustment based on a detection result of the detection unit. The image forming apparatus performs image formation in a second mode using a color gamut different from a color gamut in a first mode, and the controller obtains a lookup table, which indicates a correlation between image data to be used and input image data in the second mode, based on the detection result in the first mode and a correlation of density between the first mode and the second mode.

A color imaging device includes a plurality of developer rolls with a common operating point, such as a common operating voltage. To determine the operating point, an acceptable range of color density is determined for each toner, the range being lighter and darker than an optimum color density for that toner. A search range is devised such that values within the range are examined relative to deviations from the optimum color density per each toner. The common operating point is selected as that having the lowest deviation per all toners. Also, if the common operating point corresponds to a color density darker than the acceptable range of color density for any toner, additional halftoning occurs compared to traditional halftoning, such as for continuous tones or solids. In this way, four color developer rolls can be operated from a single power supply, yet still provide acceptable color images.

An image forming apparatus includes a developer information acquisition unit. The developer information acquisition unit performs a developer deterioration information acquisition operation. In the developer deterioration information acquisition operation, the developer information acquisition unit acquires a tilt of a measurement straight line representing the relationship between the change amount of the frequency in a first measurement toner image forming operation and the density change amount of the measurement toner image based on the change amount of the frequency in the first measurement toner image forming operation and a result of detecting density of the measurement toner image in a density detecting unit, and acquires a toner charging amount based on the acquired tilt of the measurement straight line and the reference information in the storage unit so as to acquire information relating to deterioration of developer based on the acquired toner charging amount.

An image forming apparatus includes an image bearer, a driver, an image forming device, a sensor, and circuitry. The driver drives and rotates the image bearer. The image forming device forms a toner image on the image bearer driven and rotated by the driver. The sensor emits light to the image bearer and receives reflected light. The circuitry controls the driver and the image forming device to form a first toner image with a first color and a second toner image with a second color different from the first color. The circuitry controls the sensor to detect specularly reflected light and diffusely reflected light from the first toner image and the second toner image. The circuitry calculates an amount of misalignment of the first toner image and the second toner image based on a value of the specularly reflected light and a value of the diffusely reflected light.