Abstract: In an early-middle stage of a photosensitive drum life cycle, an image forming apparatus uses only a second semiconductor laser having an oscillation wavelength 660 nm to perform writing of an electrostatic latent image on a photosensitive drum surface. In a middle-late stage of the photosensitive drum life cycle, the image forming apparatus starts using a first semiconductor laser having an oscillation wavelength of 440 nm in addition to the second semiconductor laser to perform writing of an electrostatic latent image on the photosensitive drum surface with a combined exposure spot formed at the same position. An exposure control unit gradually increases an output rate of the first semiconductor laser according to an increase in total output of the first and second semiconductor lasers.

Abstract: In an image forming apparatus, a separating unit separates each laser beam into a first laser beam used for measuring light intensity and a second laser beam used for scanning a photosensitive element, a photoelectric converting unit measures a light intensity of each of the first laser beams and outputs a voltage indicative of the light intensity. A control unit controls a light intensity of each of the laser beams based on a common drive current and a corresponding one of a current correction value, which is set by each of the laser beams to correct a light intensity of a corresponding one of the laser beams based on a corresponding one of the voltages output by the photoelectric converting unit.

Abstract: An image forming apparatus includes a photosensitive drum, a charging apparatus arranged to charge the photosensitive drum, and a developing apparatus arranged to supply toner to an electrostatic latent image in a development region, thereby developing the electrostatic latent image to a toner image. The image forming apparatus further includes a laser unit, an LED array unit which is located downstream of the laser unit in a moving direction of the photosensitive drum and is disposed inside the photosensitive drum to be able to perform exposure within the development region, and a control unit configured to control the laser unit and the LED array unit such that the LED array unit is able to expose the same area on the photosensitive drum which has been exposed by the laser unit.

Abstract: Image forming apparatus in which surface electric potentials of a plurality of surface areas are detected by charging a photoconductor with a different applied bias for each predetermined timing and exposing a plurality of surface areas of the photoconductor by scanning the photoconductor with an optical beam, while changing an exposure intensity of the optical beam for each of the surface areas of the photoconductor. Then, the applied bias necessary for obtaining a predetermined electric potential of a dark section and the exposure intensity of the optical beam necessary for obtaining a predetermined electric potential of a bright section are controlled, on the basis of the surface electric potentials that are detected respectively from the different applied biases and the different exposure intensities. Thereby, the adjustment time can be made shorter than the conventional case.

Abstract: An image forming apparatus includes a photoreceptor member; a LED head that includes a plurality of light emitting diodes arrayed in a line along a rotating axial direction of said photoreceptor member and that is modulated in response to image signals, so as to expose said photoreceptor member while said photoreceptor member is rotating; a deviation detecting sensor to detect deviations on a circumferential surface of said photoreceptor member; a filter to extract low frequency components including a rotational frequency component of said photoreceptor member from deviation signals detected by said deviation detecting sensor, so as to acquire deviation information with respect to said circumferential surface of said photoreceptor member; a driving section to move said LED head back and forth against said circumferential surface of said photoreceptor member; and a position controlling section to control said driving section, based on said deviation information acquired by said filter, so as to keep a distance

Abstract: An electrostatic latent image is formed by exposing the same exposure point on a photosensitive drum to a laser beam having an emission wavelength of 420 nm and a laser beam having an emission wavelength of 780 nm. The exposure is performed in a pulse-height modulation manner by changing a total output of these two laser beams to write the electrostatic latent image while changing an output ratio between the two laser beams depending on the total output.

Abstract: An image forming device and method in which, when double-sided printing is carried out, placing an image of a first side and an image of a second side at a position determined in accordance with the position of the image of the first side; if it is judged a predetermined interval or more is needed between the respective placed images and images which have already been placed and are adjacent to the placed images, and judged that the predetermined interval or more is not maintained between them, placing again the images of the first and second sides at positions where the predetermined interval is maintained, are performed, is provided.

Abstract: There is disclosed an image forming apparatus includes an image bearing member; a charging device to charge the image bearing member; an exposing device to form a latent image on the image bearing member; a developing device to form a toner image on the image bearing member; a transferring device to transfer the toner image onto an intermediate transfer member by applying a transfer bias voltage; an image stabilization controlling section for keeping a density of the toner image transferred onto the intermediate transfer member within a predetermined range; a transfer output controlling section for controlling a transfer output based on a density of a toner patch image; and an overall controlling section to control both the image stabilization controlling section and the transfer output controlling section, in such a manner that the image stabilization controlling operation is conducted preceding to the transfer output controlling operation.

Abstract: An image forming apparatus, incorporating a process cartridge, capable of determining optimum light exposure conditions suitable for both a charging potential and a film thickness of image bearing member, and performing the image formation even during the period from initiating to completing the setting of light exposure conditions. The image forming apparatus includes at least a charger unit, a light exposure unit, a developer unit, a detection unit, and a control unit. The detection unit is adapted to detect the total of rotation of the image bearing member. The control unit computes light exposure conditions to operate the light exposure unit based on an estimated thickness for a film of the image bearing member, which is calculated from the total of rotation obtained by the detection unit, and a first target uniform charging potential to control a uniform charging potential of the image bearing member, and to control the light exposure unit to be brought into the light exposure conditions.

Abstract: Provided is an exposure head controller that controls, via pulse width modulation control, the emission quantity of each light emitting element in an exposure head having a light emitting element array formed by arranging a plurality of light emitting elements in a main scanning direction and a sub scanning direction orthogonal thereto, comprising: a data retention unit that retains dot gathering control data showing whether to emit each light emitting element at the starting point side, terminal point side or in the middle of an emission period corresponding to a 1 pixel pitch in the sub scanning direction, or to divide and emit each light emitting element at the starting point side and terminal point side, emission time data showing the emission time of each light emitting element, and skew data showing the skew quantity of each light emitting element; a dot gathering operation circuit provided to each light emitting element and which operates the time in which the light emitting element is to be retained i

Abstract: A lithographic apparatus includes a shutter system constructed and arranged to mask out parts of a patterning device or a substrate from a beam of radiation. The shutter system includes at least one moveable shutter. The apparatus also includes a control unit arranged to receive information regarding the extent to which a patterned beam of radiation would extend across a periphery of the substrate when being projected onto the target region of the substrate. The control unit is configured to move the shutter by a predetermined amount to affect the parts of the patterning device or the substrate masked out from the beam of radiation if projecting the patterned beam of radiation onto the target portion would involve the patterned beam of radiation extending across the periphery of the substrate.

Abstract: In a disclosed image forming apparatus, a developing bias applied to a developer carrier or exposure energy with which an image carrier is exposed is adjusted such that an isolated one-dot image on the image carrier has a predetermined image density. When the image carrier is exposed to form dot images continuously arranged in a main scanning direction, the exposure time period for each dot image is shorter than that when the image carrier is exposed to form the isolated one-dot image.

Abstract: An image forming apparatus has a latent image writing device that writes an electrostatic latent image on an image bearing member, a developing device that develops a toner image based on the electrostatic latent image, a transferring device that transfers the toner image onto a recording material, a position correcting unit that corrects a position of the electrostatic latent image written by the latent image writing device, a recording material determining unit that determines whether or not the recording material has a long width, and a corrected amount changing unit that, when the recording material determining unit determines that the recording material has a long width, changes an amount of correcting the position of the electrostatic latent image to a value different from a set value for a recording material having a standard width.

Abstract: According to an aspect of the invention, an image forming apparatus having a plurality of processing velocities is characterized by a control for determining the image forming process conditions by redefining a first approximate expression for estimating the unexposed surface potential value Vo of a photoconductive drum as a continuous function of the charging potential Vd according to the change of the natural environmental temperature, the change of the surface temperature of the photoconductive drum, the change of the photoconductive drum due to fatigue, or the exposure value, and a second approximate expression for estimating the exposed surface potential value VL of the photoconductive drum as a continuous function of the charging potential Vd according to the change of the processing velocity, using the first approximate expression and the second approximate expression to determine the optimal values of the developing potential, the background potential, and the exposure value for the respective process

Abstract: Image forming apparatus in which surface electric potentials of a plurality of surface areas are detected by charging a photoconductor with a different applied bias for each predetermined timing and exposing a plurality of surface areas of the photoconductor by scanning the photoconductor with an optical beam, while changing an exposure intensity of the optical beam for each of the surface areas of the photoconductor. Then, the applied bias necessary for obtaining a predetermined electric potential of a dark section and the exposure intensity of the optical beam necessary for obtaining a predetermined electric potential of a bright section are controlled, on the basis of the surface electric potentials that are detected respectively from the different applied biases and the different exposure intensities. Thereby, the adjustment time can be made shorter than the conventional case.

Abstract: An image forming apparatus includes: a photoreceptor, a charging unit which charges the photoreceptor; an exposing unit which forms a latent image onto the photoreceptor; a developing unit which develops the latent image to a toner image; a sensor which detects a line width of a toner patch formed on the photoreceptor by the exposing unit and the developing unit; and a controller which changes a background voltage based on the line width detected by the sensor during an image forming operation so that the line width is secured within a predetermined line width. The controller returns the background voltage to value adjacent to an initial setting background voltage and changes the light amount of the exposing unit by a light amount corresponding to a returning amount of the background voltage.

Abstract: A drive device for outputting a drive signal for driving a plurality of light emitting elements time-divisionally, the drive device includes a plurality of input terminals receiving input of a drive control signal for the light emitting elements, and a plurality of output terminals connected to the light emitting elements, for outputting the drive signal based on the drive control signal input into the input terminals, in which the input terminals and the output terminals are arranged substantially in a line.

Abstract: Control circuitry associated with an electrophotographic imaging device is adapted to operate in conjunction with a sensor to adjust a difference in electrical bias between a photoconductive surface and an associated roller. The sensor detects a reflectance or luminosity of a developed image and the control circuitry uses this detected information and information related to reflectance or luminosity of the underlying surface and the developing toner to determine whether the developed image is produced as desired. The control circuitry adjusts the difference in electrical bias between the photoconductive surface and an associated roller in response to a comparison between the detected and desired images. In one embodiment, a predetermined test pattern is developed over a range of electrical bias differences and an optimum operating point is determined from the iterations.

Abstract: An optical scanning apparatus includes a laser diode, electro-optical crystal member, BD sensor, two light detection sensors and voltage control unit. The electro-optical crystal member is arranged in the optical path between the laser diode and a polygon mirror, and deflects the light beam in the sub-scanning direction by applied voltage. The BD sensor and two light detection sensors detect the light beam deflected in the sub-scanning direction. A scanning control unit controls, based on the detection results obtained by the BD sensor and two light detection sensors, the irradiation position of the light beam on a photosensitive drum. The BD sensor and two light detection sensors are arranged at positions distant in the sub-scanning direction from an optical path to the photosensitive drum and at the central portion and two end portions of an image forming region in the main scanning direction.

Abstract: An image forming apparatus includes devises for performing a detection method which detects an image characteristic of an image formed on an image bearing member; a first control method which controls a toner concentration in a developer, based on a detection result by the detection method, of an image characteristic of a first reference image for a first control for controlling the toner concentration; a second control method which controls an image parameter, different from the toner concentration, thereby controlling an image density, based on a detection result of an image characteristic of a second reference image for a second control, different from the first reference image; and a correction method which receives detection results of both image characteristics of the first and second reference images, and which, based on the detection result of the image characteristic of either of the reference images for the first and second controls, corrects the other control.

Abstract: Control circuitry associated with an electrophotographic imaging device is adapted to manage bias levels of components in an image forming unit. A photoconductive surface is charged to a first bias level, a developer member is charged to a second bias level, and an imaging unit selectively discharges image feature locations on the photoconductive surface to a third bias level. In certain regions having a predetermined image feature density, the imaging unit may discharge an area in the vicinity of the image features to a fourth bias level that is between the first and third bias levels. The amount by which the imaging unit discharges the area in the vicinity of the image features changes as image feature density changes and as the difference between the first and third bias levels change.

Abstract: An image forming apparatus, having a submodule that causes non-uniformity in density in a slow-scanning direction in accordance with rotation, includes a correction image forming unit that forms an image for density correction, in cooperation with the submodule, a density detector that detects a density of the image for density correction, a correction data generation unit that generates correction data to correct a density distribution based on a density distribution of the image for density correction in a slow-scanning direction detected by the density detector, a phase detector that detects a phase of the submodule, and a mark image forming unit that forms a mark image in synchronization with the phase of the submodule detected by the phase detector, in the image for density correction formed by the correction image forming unit.

Abstract: A developer cartridge, including: a container for containing developer; a shutter that is supported so that the shutter can linearly move relative to the container, and that opens and closes by moving linearly; a handle member that is supported so that the handle member can rotationally move relative to the container, and that includes a handle; and a conversion mechanism by which rotational-movement force that rotationally moves the handle member is converted into linear-movement force that linearly moves the shutter.

Abstract: Image forming apparatus in which surface electric potentials of a plurality of surface areas are detected by charging a photoconductor with a different applied bias for each predetermined timing and exposing a plurality of surface areas of the photoconductor by scanning the photoconductor with an optical beam, while changing an exposure intensity of the optical beam for each of the surface areas of the photoconductor. Then, the applied bias necessary for obtaining a predetermined electric potential of a dark section and the exposure intensity of the optical beam necessary for obtaining a predetermined electric potential of a bright section are controlled, on the basis of the surface electric potentials that are detected respectively from the different applied biases and the different exposure intensities. Thereby, the adjustment time can be made shorter than the conventional case.

Abstract: Control circuitry associated with an electrophotographic imaging device is adapted to operate in conjunction with a sensor to adjust operating parameters, including an imaging power. The sensor detects a reflectivity of a developed image and the control circuitry uses this detected information and information related to reflectivity of the underlying surface and the developing toner to determine whether the developed image is produced as desired. The control circuitry adjusts imaging power in response to a comparison between the detected reflectivity and a target reflectivity. In one embodiment, a predetermined halftone pattern is developed over a range of imaging powers and an optimum operating point is determined from the iterations. A predictive model may be generated based on many data points to select imaging power based on optimized surface potentials.

Abstract: An image forming apparatus includes: an image carrier; a fixing device disposed above the image carrier and fixing a transferred image on a recording medium to the recording medium, the transferred image being transferred from the image carrier; and a light blocking member disposed on the fixing device and blocking at least part of light reaching the image carrier.

Abstract: An image forming apparatus changes over an electric potential on an image bearing member in response to an attenuation region in which a remaining potential on a developing member is attenuating after a developing bias applied to the developing member has been turned off after completion of an image forming operations. Accordingly, it is possible to mitigate adherence of developer due to a large potential difference between the developing member and the image bearing member.

Abstract: Methods and devices for setting an operating point within an image forming device. The operating point for one or more image forming stations may be determined without performing a toner patch sensing procedure. The operating points are determined based on other information, such as the operating points of one or more other image forming stations, information about the device, and information about the image forming stations themselves. The different factors may be weighted to more accurately determine the operating parameter(s).

Abstract: An image forming apparatus includes: a photosensitive body; a print head for exposing the photosensitive body; a synchronous pattern detection unit which is disposed so as to be integrated into the print head, the synchronous pattern detection unit detecting a synchronous pattern which is previously formed on an unexposed part of the photosensitive body; a synchronous signal generation unit for generating a synchronous signal based on a detected signal from the synchronous pattern detection unit; and a control unit for controlling a drive of the print head based on the generated synchronous signal.

Abstract: A method of printing using an image-on-image device that includes a photoreceptor, including monochrome exposing the photoreceptor or monochrome charging the photoreceptor, wherein monochrome exposing the photoreceptor includes charging the photoreceptor, successively exposing the photoreceptor in a monochrome mode using a plurality of exposing devices during a single revolution of the photoreceptor relative to the exposing devices, and developing a monochrome image on the photoreceptor; and monochrome charging the photoreceptor includes successively charging the photoreceptor via a plurality of charging devices during a single revolution of the photoreceptor relative to the charging devices, exposing the photoreceptor using an exposing device, and developing an image on the photoreceptor. A marking device capable of implementing the method of printing.

Abstract: An image-forming apparatus comprises: an image carrier; a charging unit; a latent image forming unit; a developing unit that uses a toner maintaining a non-color-developing state when provided with coloring information through exposure to light; a coloring information providing unit that provides the toner image with coloring information by exposing the toner image to light having a predetermined wavelength determined depending on the color not to be developed based on color component information of image data; a transfer unit; a fixing unit; a color-developing unit that develops a color of the toner image provided with the coloring information; and a control unit that controls the coloring information providing unit to expose a background region on the image carrier to light having a predetermined wavelength for preventing color development of the toner.

Abstract: An image forming apparatus according to an aspect of this invention includes: a photoconductive unit; an exposure unit outputting a pulse-width-modulated light signal and exposing the photoconductive unit; a developing unit developing the photoconductive unit and forming a developed image on the photoconductive unit; a transfer unit transferring the developed image to a transfer target unit and forming a transferred image; an image patch generating unit generating an image patch formed by a predetermined pattern; a sensor unit detecting density information of the developed image of the image patch formed on the photoconductive unit or the transferred image of the image patch formed on the transfer target unit; and an image quality maintenance control unit deciding a proper quantity of exposure and a proper pulse width on the basis of the density information detected by the sensor unit and set the decided proper quantity of exposure and the proper pulse width in the exposure unit.

Abstract: In an electrophotographic image recording apparatus apparatus including a photoconductive image bearing member, a charging apparatus for uniformly charging the image bearing member, an exposure apparatus for effecting an imagewise exposure on a surface of the image bearing member after charging thereby forming an electrostatic latent image, a development apparatus for adhering a toner onto the electrostatic latent image thereby forming a toner image, and a transfer member for transferring the formed toner image onto a final support member such as plain paper, in case of forming an image with a hyperchromic toner and a hypochromic toner of a substantially same hue, image formation is executed with a writing resolution for the hypochromic toner larger than a writing resolution for the hyperchromic toner. Thus drawbacks of streak generation by a screen used for the hypochromic toner and a difficulty in obtaining a photographic texture can be resolved.

Abstract: The image forming apparatus for forming an image on a recording sheet based on an input image signal includes a halftone processor that applies a halftone process to an input image signal with a predetermined halftone processing period, and an add-on processor that attaches, to the image signal subjected to the halftone process, an add-on signal with an add-on period which is determined according to the halftone process period. The invention enables to suppress an image deterioration and to improve detection accuracy of the add-on signal.

Abstract: An optical scanning apparatus forms a latent image by scanning a laser beam emitted from a light source on an image bearing member. The apparatus includes first and second laser beam detectors for detecting the laser beam and a scanning-line slope detector for detecting a slope of a scanning line on the image bearing member on the basis of the result of detection obtained by the first and second laser beam detectors. The first laser beam detector detects the laser beam in a scanning area in front of an area in which the latent image is formed on the image bearing member and the second laser beam detector detects the laser beam in a scanning area behind the area in which the latent image is formed on the image bearing member.

Abstract: A driving apparatus of a multi-function machine includes a scanner unit scanning data recorded on a sheet of document and a document transport part to transport the sheet of document. A printer unit prints data on a sheet of paper for an output and includes a carrier including a print head with an ink jet nozzle mounted thereon to carry out the printing operation by moving the print head. The driving apparatus includes a driving motor, a scanner driving part driving the scanner unit, a printer driving part driving the printer unit, and a power switching part disposed with the driving motor, the scanner driving part, and the printer driving part. The power switching part selectively transmits a power of the driving motor to at least one of the scanner driving part and the printer driving part.

Abstract: In an image-forming apparatus having a photosensitive body and an intermediate transfer belt, the intermediate transfer belt is extendible/contractible in a longitudinal direction and a toner image formed on the photosensitive body transferred onto the intermediate transfer belt. The intermediate transfer belt has a mark formed from photo-reflective particles on one or both sides thereof, which mark has a different photo reflectivity to the intermediate transfer belt and is used for detecting a reference position of the intermediate transfer belt.

Abstract: An image forming apparatus is provided which can form an image without defective transfer even if a resistance value of a transfer device is so high that defective transfer tends to occur. Before starting operation of printing an image on a sheet, a transfer current is passed to a transfer roller so as to detect a voltage value V of a transfer voltage. When it is determined that the detected voltage value V does not exceed a reference voltage value Vr (resistance value of the transfer roller does not exceed a reference limiting value), an operation mode of the printing operation is set to a first printing mode. When it is determined that the detected voltage value V exceeds a reference voltage value Vr (resistance value of the transfer roller exceeds a reference limiting value), the operation mode of the printing operation is set to a second printing mode.

Abstract: An image formation apparatus includes an imaging light source, a photosensitive body and a correction light source. The imaging light source outputs light modulated in accordance with image data representing an image. An electrostatic latent image is formed at the photosensitive body by the light output from the imaging light source. The correction light source is provided separately from the imaging light source, and outputs light toward the photosensitive body for correcting one of variations in potential on the photosensitive body and irregularities in density distribution of an image, which image is to be formed in accordance with the electrostatic latent image that is formed on the photosensitive body by the imaging light source.

Abstract: An image forming method, includes a charging step of charging an image carrier; an image writing step of writing image data onto the image carrier; a developing step of developing a latent image area written by the image writing step on the image carrier; a transferring step of transferring a toner image developed by the developing step to a transferring member; an image writing position adjusting step of detecting a position of the image carrier where the image is written in a case where designated conditions are satisfied, and of adjusting an image writing position; and a voltage output control step of controlling voltages applied for charging, developing, and transferring in the charging step, the developing step, and the transferring step, respectively.

Abstract: A digital camera includes a CCD imager. When a display-use UYV signal is generated on the basis of an RGB signal of an object image photographed by the CCD imager, a CPU detects a color saturation degree of the RGB signal and reduces dynamic range of a U signal and a V signal on the basis of the detected color saturation degree. Thus, a color on the basis of the U signal and the V signal is aboundingly included within a color reproducing range of a monitor.

Abstract: An image forming apparatus is provided in which on-surface potential unevenness of an image carrier can be suppressed, and with which an output image having excellent on-surface uniformity of color or the like can be obtained. The image forming apparatus includes: a photoconductive image carrier; charger which charges the image carrier; image exposing unit which exposes an image on a surface of the image carrier after the charging to form a latent electrostatic image; developing unit which develops the latent electrostatic image by adhering toner to the latent electrostatic image to form a toner image; and transfer charger which transfers the obtained toner image to a final supporting member such as plain paper.

Abstract: An image formation apparatus is disclosed, wherein temperatures of two or more places on a transfer/conveyance belt are measured. Timing of writing to photo conductor drums based on pixel clock signals is controlled in reference to differences between the measured temperatures, while a printing medium is being conveyed.

Abstract: A method for calibrating a scanner that allows the scan to start quickly.

Abstract: An image forming apparatus which is capable of reducing a color misalignment in a color overlapping process, and a color misalignment due to variation of the circumferential length of an intermediate transfer member due to an environmental change over time during a successive copy operation. The image forming apparatus carries out image formation by primarily transferring an image electrophotographically formed on an image carrier onto the rotatably driven intermediate transfer member, and then secondarily transferring the images on the intermediate transfer member onto a recording medium. An image forming operation of primarily transferring the image onto the intermediate transfer member is controlled according to the length of the intermediate transfer member in a circumferentially moving direction thereof and a variation of a predetermined parameter relating to the intermediate transfer member.

Abstract: An image formation device changes the rotational rate of a polygon motor, i.e. the main-scanning rate, and selects one of pulse width conversion tables when an image formation is performed multiple times on a single sheet of transfer paper. The changing of the main-scanning rate is for preventing inconsistent sizes between a first recorded image and a second recorded image caused by shrinkage of transfer paper. The pulse width conversion tables allow the pulse widths to be modulated.

Abstract: An image formation apparatus includes a development unit using a developer support having a conductive surface layer, and a control unit for causing an idle operation of the developer support to be performed at a predetermined timing in a non-print state.

Abstract: An adjustment method for an image forming device, for adjusting image forming condition with respect to a sheet by using image forming means. The adjustment operation is performed in such a manner that: a first image, that is used for detecting scanning error of an image scanning device, is formed on an image carrying body and then transferred from the image carrying body to the sheet, the first image being formed over at least three corners of the sheet while extending outside the sheet. The sheet with the first image is scanned by the image scanning device to figure out a scanning error amount of the image scanning device, and a correction value of image forming condition of the image forming means is found in consideration of the scanning error amount. The image forming condition with respect to the sheet is modified based on the correction value.

Abstract: A high-precision image control method that can be conducted frequently without time or labor. When a sheet-passing operation starts, maximum exposure is performed at present settings in a predetermined non-image forming area and potential is detected by a potential sensor. Detected potential is compared with VH at a first control to judge whether a difference of 10 V or more exists. For a difference of 10 V or more, the signal is made responsive to laser output for achieving VH set at the first control. When the last image forming for that job is performed, potential returns to the potential set at the first control, and control ends. When the last image forming is completed in a consecutive job during short-term variability of VH, VH is restored to its original potential before the next job, whereby settings obtained with the first control are restored.

Abstract: A color image forming apparatus includes a developing unit to which a developing bias with an AC component superposed is applied, wherein the DC voltage of the developing bias is adjusted to set the detected density of a solid image at a specified value, the light amount of radiation for exposing an image area having a width of a few dots adjacent to the white paper is adjusted to set the detected density of an image developed under a peripheral electric field at a specified value, and the gradation density curve is regulated by alternately adjusting the DC voltage, the light amount of radiation for exposing the image area having a width of a few dots adjacent to the white paper, and the amplitude of the AC component until the detected density of a mesh point image having an area ratio from 60 to 80% falls within a specified range.