An image forming apparatus includes a density-measuring unit that has a substantially circular measurement field and that measures a density of a to-be-measured image for density measurement, which is moving in a moving direction, and a density-control unit that controls a density of an image and includes a to-be-measured image forming unit that forms the to-be-measured image having a shape following an outline of a density-measurement area defined by a path of the measurement field during a measurement rather than a substantially rectangular shape extending in the moving direction and including a front end of the to-be-measured image in the moving direction, the shape being within the substantially rectangular shape, a density-measuring section that causes the density-measuring unit to measure a density of the to-be-measured image, and a gradation-correction unit that performs gradation correction on the image by using the density of the to-be-measured image measured by the density-measuring section.

An image forming apparatus includes a rotatable image bearer, a toner image forming device, an image reader, and a control unit. The toner image forming device forms a test toner image on the image bearer. The image reader reads the test toner image and a predetermined reference member. The control unit calculates an amount of toner contained in the test toner image based on image data from the test toner image. Based on image data from the reference member, the control unit selects a position of a pixel to be used for calculation of the amount of toner contained in the test toner image from pixels included in the image data from the reference member, to calculate the amount of toner contained in the test toner image from data of a pixel located at the position thus selected among pixels included in the image data from the test toner image.

An image forming apparatus forms a measurement image, controls a sensor to measure light reflected from a first area of an intermediate transfer member, controls the sensor to measure light reflected from a measurement image, and controls the sensor to measure light reflected from a second area of the intermediate transfer member. The apparatus determines first information relating to a tendency of the measurement results of the first area, determines second information relating to a tendency of the measurement results of the second area, and selects a computational equation for computing a correction value of a measurement result of the measurement image. The apparatus generates a correction value. The apparatus adjusts an image forming condition.

An image forming apparatus of the present invention acquires first correction characteristics representing an output density for an input gradation value at a reference position in a main scanning direction and second correction characteristics representing a relative relationship of an output density at a predetermined position in the main scanning direction with the output density at the reference position in the main scanning direction. Then, the image forming apparatus corrects image data corresponding to the predetermined position in the main scanning direction based on the first correction characteristics and the second correction characteristics.

The image forming apparatus includes an image processing section that converts image data into pixel data, an image forming section that forms a toner image based on the pixel data, and a fixing section that fixes the toner image to the recording material by heating the recording material with the toner image formed thereon while conveying the recording material through a nip portion, wherein the image processing section divides the pixel data corresponding to one recording material into a plurality of areas each formed of a predetermined number of pixels and acquires density information on some of the pixels within each of the areas as representative values, wherein the fixing section carries out a process of fixing the toner image for which the density information has been acquired, under a fixing condition according to a maximum value of the representative values.

An image forming apparatus includes an image forming section; a density detection section configured to detect the density of toner image formed on an image bearing member in a sub scanning direction; and a density-unevenness correction section configured to calculate a first correction amount based on the detection result of the density detection section and calculate a second correction amount different from the first correction amount in phase.

With reference to a correction value revision parameter table, a periodic non-uniformity correction value corresponding to changed rotational speed is obtained from the correction value revision parameter table, and set as a new periodic non-uniformity correction value corresponding to the rotational speed of a rotary component, and thereby a gradation which is an image formation parameter of image data is corrected.

An image forming apparatus includes an apparatus main body, a photoreceptor drum, a charging apparatus, a developing device, a transfer apparatus, a charging bias applying unit, a developing bias applying unit, a bias adjusting unit, and a print density measurement unit. The bias adjusting unit controls the charging bias applying unit to form a plurality of electric potential areas of electric potentials with different magnitudes. The bias adjusting unit applies a predetermined developing bias corresponding to a target electric potential to the developing roller, so as to form a plurality of toner images by electric potential differences between the developing bias and the plurality of electric potential areas. The bias adjusting unit decides a value of a charging bias corresponding to the target electric potential from measurement results of print densities of the plurality of toner images measured by the print density measurement unit.

An image forming apparatus includes an image bearing member; a toner image forming device; an image transferring device; a transfer bias applying device; an image fixing device; a sensor for detecting light reflected by the toner image fixed on the sheet; a controller for controlling a leading portion bias applied to the leading portion of the sheet with respect to a sheet feeding direction and a central portion bias applied to the central area of the sheet. The controller forms first and second test images on the leading and central portions, respectively, and sets conditions of the leading and central portion biases on the basis of an output of the sensor, in correlation with a kind of the sheet. A toner deposition amount per unit area of the first test image is smaller than that of the second test image.

An image forming apparatus includes a latent image bearer to rotate, an image forming unit including a charger and a developing device, a charge power supply to output a charging bias applied to a charger, a transfer device, a toner adhesion amount, and a controller. The controller causes the image forming unit to form a background fog pattern in a background area of the latent image bearer while changing a background potential, acquires toner adhesion amount values detected at different positions of the background fog pattern, having different potentials, sorts the toner adhesion amount values in an order of the background potential, determines a relation between the background potential and background fog amount based the toner adhesion amount values except any toner adhesion amount value out of monotonicity, and adjust the charging bias to an optimum value computed based on the determined relation.