First correction data for use in a first printing mode is generated by image density measurement in the first printing mode, and second correction data for use in a second printing mode, which is different from the first printing mode in peripheral speed ratio of a developing roller to a photosensitive drum, is generated by image density measurement in the second printing mode. First processing for generating first and second correction data for the first and second printing modes, respectively, by density measurement, or second processing for generating the first correction data by density measurement and generating the second correction data using the generated first correction data and a difference in image density between the first printing mode and the second printing mode is executed. The first processing is executed when a predetermined condition is satisfied.

A mode control section forms a plurality of reference toner images having different densities on a photosensitive drum, where the frequency of an alternating-current voltage of a development bias is varied with a potential difference between direct-current voltages of a development roller and the photosensitive drum maintained constant, generates a reference straight line indicating a relationship between a toner amount of each reference toner image obtained by converting the density of the measured reference toner image into weight, and a representative value of current values of a development current measured during formation of the reference toner image, and acquires the amount of electrostatic charge of toner using the reference straight line.

In one example of the disclosure, a set of scanned images is accessed. The scanned images are scans of distinct printouts of subject images produced utilizing a photo imaging plate. A set of defect maps is created by comparing the scanned images to reference data for the subject images. The set of defect maps are combined into an integrated defect map. A scratch defect on the PIP is identified utilizing the integrated defect map.

A mode control section forms a plurality of reference toner images having different densities on a photosensitive drum, where the frequency of an alternating-current voltage of a development bias is varied with a potential difference between direct-current voltages of a development roller and the photosensitive drum maintained constant, generates a reference straight line indicating a relationship between a toner amount of each reference toner image obtained by converting the density of the measured reference toner image into weight, and a representative value of current values of a development current measured during formation of the reference toner image, and acquires the amount of electrostatic charge of toner using the reference straight line.

A sensor unit detachably mounted in a main assembly of a image forming apparatus includes a sensor for detecting a detection object on a surface of a movable member, the sensor having a detecting surface positioned to the surface of the movable member at least when the sensor detects the detection object; a casing portion accommodating the sensor; an air feeding unit, provided in the casing portion, for to taking air in through an inlet portion formed by the casing; and a duct for feeding the air discharged from the air feeding unit, to between the detecting surface and the surface of the movable member.

A sensor unit includes a plurality of sensors configured to detect a toner image carried on an image bearing member; and a duct including a suction portion; a plurality of branch duct portions. The branch duct portions each includes a discharging portion having a discharge opening. At least one of the branch duct portions includes a first path for discharging the air in a direction, and a second path connected with the first path portion at a downstream position to discharge the air in the direction. The sensor unit further includes a guide portion provided in the second path and extended crossing with an extension of one of inner walls of the first path, the guide portion being capable of branching the air in the second path toward the discharge opening.

An image forming apparatus is provided. The image forming apparatus includes a sensor configured to sense a toner concentration, a processor configured to determine at least one of a coring level and a total area coverage (TAC) level according to the detected toner concentration, and an image former configured to print the rendered print data.

An example method of determining dot gain in a liquid electrophotographic printer is described. The method involves effecting a print operation based on a predetermined digital dot area and measuring an operating current of a binary ink development unit during the print operation. A dot gain between the digital dot area and a physical dot area of a developed image is determined based on a function of the measured operating current.

A density correction unit calculates a density change rate to a change in an exposure amount as a first density change rate based on a difference between a density of a part of reference patch images, in which a position in a main scanning direction is identical to a position of a first patch image. As for a second patch image, the density correction unit similarly calculates a second density change rate. A light amount when forming the first patch image is smaller than a reference light amount. A light amount when forming the second patch image is larger than the reference light amount. The density correction unit uses the first or the second density change rate based on whether a density of each position of the reference patch images in the main scanning direction higher or lower than a target density to correct the exposure amount.

An image forming apparatus including: a cyclone which centrifugally separates toner from air containing the toner scattered; a storage which stores the toner separated by the cyclone; a filtering portion which allows air to pass, the air being obtained after the toner is separated by the cyclone; a duct which guides the air that passes through the filtering portion; a fan which generates a flow of the air to discharge the air that passes through the filtering portion; and a hardware processor which measures a rotational speed of the fan, detects a full state in which the storage is filled with the toner based on change of the rotational speed of the fan, and issues a warning in a case in which a variation rate of rotational speeds of the fan measured a plurality of times is a predetermined value or more.