An image forming apparatus including a belt, a plurality of color information detectors, and a hardware processor. The belt is a belt on which images of a plurality of colors are formed to be laid on each other by a plurality of image formers that form the images of color components different from each other, the belt being colorless and transparent and having a transparency. The plurality of color information detectors are arranged on a front surface side and a back surface side of the belt, and detect, from the front and back surface sides, color information about a pattern image including two layers formed on the belt by two image formers among the plurality of image formers. The hardware processor calculates a color correction amount of an image formed by the two image formers based on detection results by the color information detectors.

An image forming apparatus includes an image bearer, an image forming section, an image density difference detector, and control circuitry. The image forming section is configured to form a gradation image pattern on a surface of the image bearer. The gradation image pattern includes gradation images having different image densities stepwise in a sub-scanning direction. The image density difference detector is configured to detect image density differences in a main scanning direction of the gradation images. The control circuitry is configured to execute an image density difference correction mode that corrects the image density differences in the main scanning direction based on detection results detected by the image density difference detector.

An image forming apparatus includes a detection unit that optically detects a density of a reference toner image for density measurement formed on an image carrier. Either a first detection method for detecting the density of the reference toner image by receiving specularly reflected light reflected by the image carrier and the reference toner image for density measurement formed on the image carrier or a second detection method for detecting the density of the reference toner image by receiving diffusely reflected light from the image carrier and the reference toner image, is selected in accordance with color information of a toner, the color information being stored beforehand in a storage unit, and the density of the reference toner image is optically detected.

An image forming apparatus includes an optical sensor for detecting an image formed on an intermediate transfer belt. The optical sensor includes first and second light emitting diodes (LEDs) and first and second photodiodes (PDs). The first and second LEDs irradiate an optical-axis center point of an intermediate transfer belt. The first PD is arranged at a position at which an optical axis of specularly reflected light of light emitted from the second LED and an optical axis along which specularly reflected light of light emitted from the first LED is received form a first angle. The second PD is arranged at a position at which the optical axis of the specularly reflected light of the light emitted from the second LED and an optical axis along which diffused reflected light of the light emitted from the second LED is received form a second angle different from the first angle.

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.

An image forming apparatus, configured to operate in first and second modes of which color gamut is different from each other, 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 the 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.

There is provided a method for controlling an electrophotographic apparatus including forming a first measurement image by performing first halftone processing on image data, forming a second measurement image by performing second halftone processing different from the first halftone processing on the image data, measuring densities of the first measurement image and the second measurement image, calculating a density difference between each of densities of the measurement images, determining whether the density difference satisfies a predetermined reference value, and applying a surface treatment on an electrophotographic photosensitive member if the density difference does not satisfy the reference value, during a non-image formation period.

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 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.

In accordance with an embodiment, a print head includes a first light emitting element line and a second light emitting element line. The first light emitting element line and the second light emitting element line each include a plurality of light emitting elements that emit light on the basis of image data. The plurality of light emitting elements of the second light emitting element line are arranged deviated from the plurality of light emitting elements of the first light emitting element line by a certain interval in a main scanning direction.