An image forming system cyclically conveys an Nth sheet with an image formed on a first side to an image forming unit as a sheet subject to image formation after image formation on a subsequent (N+i)th sheet, and form an image on a second side of the Nth sheet. The system includes an obtaining unit that, during image forming processes, obtains respective updated adjustment values for the first and second sides, and a control unit that performs control to simultaneously store the updated adjustment value for the first side and an unupdated adjustment value for the second side in a part of a period of the processes, form an image on the first side of the (N+i)th sheet using the updated one for the first side, and form the image on the second side of the Nth sheet using the unupdated one for the second side.

An image forming apparatus includes a temperature sensor, a memory, a fixing device, and a controller. The temperature sensor is configured to detect a temperature of an inside of the image forming apparatus. The memory is configured to store temperature history information regarding a history of the temperature of the inside of the image forming apparatus detected by the temperature sensor. The fixing device is configured to fix a toner image onto the paper sheet by heating the paper sheet to a fixing temperature. The toner image is transferred to the paper sheet using a toner stored in a toner cartridge of the image forming apparatus. The controller is configured to control a fixing temperature at the fixing device based on the temperature history information stored in the memory.

In an example, a method includes printing a set of images by transferring print agent between a roller of a print agent source and an electrophotographic surface in a plurality of transfer operations, wherein the roller is controlled to have a first voltage profile during each of the transfer operations. A variation in optical density which is consistent across the set of printed images may be detected, and a second voltage profile correction may be determined based on the variation in optical density. The method may further comprise printing a subsequent image by transferring print agent between the print agent source roller and the electrophotographic surface in a subsequent transfer operation, wherein the roller is controlled to have the second voltage profile during the subsequent transfer operation.

An image forming apparatus includes an image forming unit (LBP) to form an image on a sheet, a conveyance unit configured to convey the sheet, a sensor, which is configured to move in a direction perpendicular to a conveying direction in which the conveyance unit conveys the sheet, and to read the image on the sheet, and a controller. The image forming unit forms a first trigger image and a first pattern image on the sheet, and the image forming unit forms a second trigger image and a second pattern image at a position on the sheet different from a position of both the first trigger image and the first pattern image in the conveying direction. A formation area of the first trigger image in the direction perpendicular to the conveying direction overlaps with a formation area of the second pattern image.

A processor generates an extraction image by extracting, from a test image, a target specific part that is a horizontal stripe extending in a horizontal direction or a noise point. The processor derives a vertical data sequence from a target area in the extraction image and converts the vertical data sequence to primary conversion data of a frequency domain. The processor converts, to secondary conversion data of a space domain, correction data that is obtained by removing, from the primary conversion data, data of frequency bands other than a particular frequency band corresponding to a target specific part that was determined as having periodicities. The processor classifies the target specific parts into periodic specific part and non-periodic specific part by comparing positions of the target specific parts with a peak position in a waveform represented by the secondary conversion data.

An image forming apparatus that includes an image bearing member which can bear a toner image, a transfer member used to transfer a toner image onto a recording material from the image bearing member, and a reading device which reads density information of images on recording material disposed on the platen. The image forming apparatus forms a first chart on a first recording material and a second chart on a second recording material by sequentially transferring a plurality of test images while applying a plurality of test voltages to the transfer member. The two charts are read by the reading device and the transfer voltage is adjusted based on the reading result.

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 reading apparatus includes a conveyance roller to convey a sheet, a light source to illuminate an image on the sheet while being moved in a predetermined direction above the conveyed sheet, a reading sensor to read the image on the sheet while being moved in the predetermined direction above the conveyed sheet, and a controller. The controller controls the reading sensor to read a first image for generating a color profile on a first sheet after the light source emits light for a duration of a first time. The controller controls the reading sensor to read a second image for detecting density unevenness in a main scanning direction of the image forming apparatus on a second sheet after the light source emits light for a duration of a second time shorter than the first time.

In an image forming apparatus, a calibration controller controls an exposure device to form a toner patch image for calibration in a non-printable area outside a printable area in a main scanning direction, and executes at least one of density adjustment and gradation adjustment based on a density measurement value of the toner patch image. A toner refresh controller controls the exposure device to form a toner band for toner refresh in accordance with a coverage rate. Further, when the length of the toner band to be formed in the non-printable area exceeds a predetermined threshold value, the toner refresh controller forms at least a part of the toner band to be formed in the non-printable area in parallel with a subsequent page image.

An image forming apparatus includes a developing roller, a photoconductor drum, a density detector, a current detector, and a controller. The developing roller carries a toner. The photoconductor drum carries a toner patch. The density detector detects toner density of the toner patch. The current detector detects developing current flowing to the toner patch. The controller calculates an inclination of an approximate straight line approximating a relation between the toner density and the developing current. The developing roller develops three or more toner patches, different in toner density and different in developing current from one another, on the photoconductor drum. The controller calculates the inclination, using different mathematical expressions depending on whether three toner patches or four toner patches are provided.