An image forming apparatus includes: a developer carrier; a screw-shaped developer feeder that feeds developer to the developer carrier; an image carrier on which an image is imaged with toner of the developer; a developing current detector that detects developing current between the image carrier and the developer carrier during imaging; and a controller that detects image density failure that is periodic and oblique to a rotation direction of the image carrier. The controller causes a stripe image to be imaged on the image carrier and analyzes change of the developing current with time during imaging of the stripe image, thereby detecting the image density failure. The stripe image has a width in a length direction of the image carrier narrower than a period of a blade of the developer feeder and has a length in the rotation direction longer than a period of the image density failure.

An image forming system includes: a reading unit configured to read a test image, the test image having a determination image formed by overlapping a plurality of colors and a plurality of reference images formed with each of a plurality of reference colors; and a determination unit configured to determine a first color value of each of the plurality of reference colors based on a reading result of the reference images, determine a second color value of a plurality of pixels included in the determination image based on a reading result of the determination image, and determine whether an image defect has occurred based on an angle of a second vector corresponding to the second color value of the plurality of pixels with respect to a first vector corresponding to the first color value of each of the plurality of reference colors.

An image inspection apparatus includes the following. A reader reads a sheet in which an image is printed, reads the sheet together with a background, and obtains a read image. A background member is provided in a position which is to be a background of the sheet when the sheet is read by the reader. A hardware processor extracts sheet outline information of the sheet from the read image and measures a misalignment of a position of the image with relation to the sheet based on the extracted sheet outline information. The hardware processor performs control based on a measured result of the misalignment of the position of the image. The hardware processor adjusts a degree of control performed based on the measured result of the misalignment of the position of the image according to a density difference between the sheet and the background member.

An image forming apparatus forms a coverage rate adjustment patch having a coverage rate corresponding to a difference between a coverage rate measured by a coverage rate measurement unit and a coverage rate of an adjustment image pattern together with an adjustment image pattern by using the exposure device and the developing device in the calibration.

An image forming apparatus is configured to arrange a plurality of pages, including a first page and a second page adjacent to the first page, in print data, without providing a margin between adjacent pages in the plurality of pages. The image forming apparatus includes a changer configured to change at least one of a position or an angle of the second page, such that a color of a first edge portion region of the first page and a color of a second edge portion region, adjacent to the first edge portion region, of the second page, satisfy a predetermined condition.

A processor derives a plurality of unit density values which are each an average value of sensed densities for each of a plurality of unit areas sectioned for each unit length in a test toner image. The processor derives a weighted average of the plurality of unit density values to derive a test image density used for adjusting a control parameter in a printing portion. The unit length is a greatest common factor of two target lengths corresponding to perimeters of two types of target rotating members out of the plurality of rotating members. When a number of the plurality of unit areas is represented by n, n is a value obtained by subtracting 1 from an added value of a first constant and a second constant. The first constant and the second constant are values obtained by respectively dividing the two target lengths by the unit length.

An image forming apparatus including a plurality of sheet feeding cassettes includes a control unit. The control unit performs control. In a case where a predetermined condition is satisfied during execution of a print job to print image data, the control unit performs control to execute interruption processing of a correction job to print a correction patch. The control unit performs control to determine, from the plurality of sheet feeding cassettes, a sheet feeding cassette to be used for the correction job based on information on the sheet feeding cassette used for the print job.

An image forming apparatus includes an optical sensor configured to detect an image formed on an intermediate transfer belt. The optical sensor includes a first LED, a second LED, a first PD, and a second PD on a substrate. The first PD is arranged at a position at which specularly reflected light of light emitted from the first LED can be received, and scattered reflected light of light emitted from the second LED can be received. The second PD is arranged at a position at which scattered reflected light of light emitted from the second LED can be received. A light receiving surface of the first PD and a light receiving surface of the second PD are formed at different angles. The light receiving surface of the first PD has an area that is smaller than an area of the light receiving surface of the second PD.

An image forming apparatus includes: a developer carrier; a screw-shaped developer feeder that feeds developer to the developer carrier; an image carrier on which an image is imaged with toner of the developer; a developing current detector that detects developing current between the image carrier and the developer carrier during imaging; and a controller that detects image density failure that is periodic and oblique to a rotation direction of the image carrier. The controller causes a stripe image to be imaged on the image carrier and analyzes change of the developing current with time during imaging of the stripe image, thereby detecting the image density failure. The stripe image has a width in a length direction of the image carrier narrower than a period of a blade of the developer feeder and has a length in the rotation direction longer than a period of the image density failure.

An optical sensor includes a light source; and an optical detector detecting intensity of light that is reflected by a recording medium, the light from the light source and irradiated onto the recording medium. Further, when an incident angle of the light incident to the recording medium from the light source relative to a normal line of the recording medium is given as θ1, a formula 75°≤θ1≤85° is satisfied.