An image forming apparatus includes an image forming device forming an image, a transfer belt having an image bearing surface on which the image moves to first and second regions, a sensor installed at an installation angle to the image bearing surface and including a light emitting element emitting light, a first and second light receiving elements receiving light reflected from the first and second regions, respectively, circuitry to generate first and second information according to light entered the first and second light receiving elements, respectively, generate, when the image moves, time information according to a difference between first and second times at each of which the first and second information, respectively, reach a threshold, obtain a tilt table based on the time difference information, and determine, by the tilt table, tilt information corresponding to the time information and indicating a difference between the installation angle and a reference angle.

An image forming apparatus includes a first plurality of image forming sections that form a first toner image for adjustment and transfer the first toner image for adjustment to a medium; a second plurality of image forming sections that form a second toner image for adjustment and transfer the second toner image for adjustment to the medium; and a detection device configured to detect a misregistration between the first toner image for adjustment transferred to the medium and the second toner image for adjustment transferred to the medium.

An image forming apparatus includes an image forming device forming an image, a transfer belt having an image bearing surface on which the image moves to first and second regions, a sensor installed at an installation angle to the image bearing surface and including a light emitting element emitting light, a first and second light receiving elements receiving light reflected from the first and second regions, respectively, circuitry to generate first and second information according to light entered the first and second light receiving elements, respectively, generate, when the image moves, time information according to a difference between first and second times at each of which the first and second information, respectively, reach a threshold, obtain a tilt table based on the time difference information, and determine, by the tilt table, tilt information corresponding to the time information and indicating a difference between the installation angle and a reference angle.

An image forming apparatus includes image forming units, secondary transfer units, and first and second detection devices. Each image forming unit includes image forming devices, and a primary intermediate transfer body. Toner images formed by the image forming devices are primarily transferred to the primary intermediate transfer body. The secondary transfer units are provided for the image forming units, respectively. Each secondary transfer unit is configured to secondarily transfer the toner images on a corresponding one of the primary intermediate transfer bodies to a transfer body. The first detection device is configured to detect the toner images downstream of the most downstream secondary transfer position. The second detection device is provided in at least one of the image forming units. The second detection device is configured to detect the toner images between the most downstream primary transfer position in the primary intermediate transfer body and a secondary transfer position.

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, which is configured to execute calibration for controlling an image forming condition, the image forming apparatus including: a first detection unit configured to detect an environmental state in which the image forming apparatus is installed; a prediction unit configured to predict, based on a plurality of detection results detected by the first detection unit in a first period, a change in the environmental state in a second period after the first period; and a setting unit configured to set a timing of executing the calibration in the second period based on the change in the environmental state predicted by the prediction unit.

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.

An image forming apparatus includes a photosensitive drum, a developing device, a transfer unit, an image sensor configured to detect a toner image on the transfer unit, and a processor. The processor is configured to determine whether the remaining amount of toner in a toner cartridge has decreased to a predetermined level or below. The processor is configured to carry out an image quality stabilization process when the remaining amount of toner is above the predetermined level. The image quality stabilization process being based on a detection result from the image sensor detecting a test pattern formed on the transfer unit. The processor is further configured to perform print process without performing an image stabilization process, without carrying out the image quality stabilization process.

An image forming apparatus includes a first plurality of image forming sections that form a first toner image for adjustment and transfer the first toner image for adjustment to a medium; a second plurality of image forming sections that form a second toner image for adjustment and transfer the second toner image for adjustment to the medium; and a detection device configured to detect a misregistration between the first toner image for adjustment transferred to the medium and the second toner image for adjustment transferred to the medium.