Abstract: A developing device includes a first developer transport path, called as first path hereinafter; a first transport screw that transports a developer in the first path; a first conveyance roller that is thicker than a shaft of the first transport screw, attracts by magnetic force the developer at a downstream end portion of a second developer transport path arranged next to the first path, and conveys the developer to an upper portion located upstream of the first path; a first scraping wall that scrapes and sends the attracted developer; and a first guide columnar body that is adjacent to the first conveyance roller, has a peripheral surface continuous to the first conveyance roller, receives, using the peripheral surface, and guides the sent developer to an upstream end portion of the first path, and has a length that the guided developer is not attracted by the magnetic force.

Abstract: An image forming apparatus includes an image bearing member, a developing device, a toner content detecting portion, a toner supplying device, an image ratio calculating portion, a toner image density detecting portion, an adjusting portion, and a controller. The controller is configured to control an execution frequency of the adjusting portion so that execution by the adjusting portion is carried out after a number of times of image formation after occurrence of a change rate of the image ratio that is greater than a predetermined change rate reaches a first value, and execution by the adjusting portion is carried out after the number of times of image formation after occurrence of a change rate of the image ratio that is less than the predetermined change rate reaches a second value greater than the first value.

Abstract: An image forming apparatus includes an image bearer, an image forming device to form a toner image on the image bearer, a transfer device to transfer the toner image to a recording medium, a line sensor as an image density sensor to detect image density of the toner image, and a controller operatively connected to the image density sensor. The image density sensor is disposed so as to be shorter in a rotational direction of the image bearer than in a width direction of the image bearer perpendicular to the rotational direction of the image bearer. The controller forms a shading pattern image including a plurality of patches on the image bearer, and detects image density of the plurality of patches, so as to control image density. The shading pattern image is shorter in the rotational direction of the image bearer than in the width direction of the image bearer.

Abstract: 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.

Abstract: An image forming apparatus includes an image bearer to bear a black toner pattern formed with a black toner image under an increased exposure amount and an increased developing bias. A first optical sensor detects an amount of reflection light reflected by the black toner pattern on the image bearer. The first optical sensor includes a light-emitting element to emit light toward the black toner pattern on the image bearer and a light-receiving element to receive the reflection light reflected by the black toner pattern on the image bearer. A toner adhesion amount converter converts the amount of the reflection light detected by the first optical sensor into a toner adhesion amount of toner adhered to the image bearer and adjusts an image density according to the toner adhesion amount.

Abstract: An image forming apparatus includes: an image carrier on which images formed by a plurality of image forming units are transferred; a sensor configured to irradiate the image carrier with light, and detect reflected light; a detection unit configured to detect, based on an output value of the sensor, a feature value of an edge of a patch image which has been formed by the image forming unit and transferred to the image carrier; a determination unit configured to determine a position of the patch image using the output value of the sensor corresponding to the patch image and the feature value of the edge; and a color registration control unit configured to perform color registration control based on the determined position of the patch image.

Abstract: An image forming apparatus includes a photosensitive member, a developing portion to develop an electrostatic image on the photosensitive member, and a sensor to detect a toner image formed by the developing portion to output density information depending on a toner amount per unit area. A controller controls a supply of developer on the basis of a detection result of a supply control toner image. The controller adjusts an exposure condition for forming the supply control toner image by the exposure portion after exchange of the photosensitive member on the basis of first information and second information. The first information is a detection result when a first control toner image, formed before an exchange of the photosensitive member, is detected by the sensor, and the second information is a detection result when a second control toner image, formed after the exchange of the photosensitive member, is detected by the sensor.

Abstract: An image forming apparatus includes a receiving unit configured to receive data via a network, a printing unit configured to print an image based on the data received from the receiving unit, and a control unit configured to control the receiving unit to refuse a data reception based on a simple mail transfer protocol (SMTP) when a toner remaining amount for the printing unit is less than a predetermined value, wherein the printing unit is configured to print, in the case that the receiving unit receives page description language (PDL) data, an image based on the received PDL data even if the toner remaining amount is less than the predetermined value.

Abstract: A controller controls a replenishing operation of the first replenishing device based on the first sensor, and controls a replenishing operation of the second replenishing device based on the second sensor. The controller prohibits the replenishing operation of the first replenishing device when the developer concentration in the first replenishing device reaches a first upper limit set to the first developing device, and the controller prohibits the replenishing operation of the second replenishing device when the developer concentration in the second replenishing device reaches a second upper limit set to the second developing device. The controller corrects the second upper limit based on the developer concentration in the second developing device when the developer concentration in the first developing device reaches the first upper limit.

Abstract: An image forming apparatus is provided. The image forming apparatus includes a developing unit which contains a mixture of toner and carrier, a toner sensor which is disposed in the developing unit, and a controller which determines a control voltage for the toner sensor using change information on a change in a quantity of electric charge which changes according to a time during which the image forming apparatus is used or paused, and drives the toner sensor using the determined control voltage and compensates for an output value of the toner sensor. Accordingly, toner can be prevented from being supplied excessively.

Abstract: A control apparatus includes the following elements. A toner density specifying unit specifies a toner density in a developer stored in a developing device. A toner density controller performs control such that the toner density approximates a predetermined toner density target value. A first calculator calculates a first value corresponding to an image density of an image to be output after a first timing. A correction amount specifying unit specifies a correction amount for the toner density target value at the first timing. When the condition that an absolute value of a difference between the first value and a second value is greater than a predetermined threshold is satisfied, the correction amount specifying unit specifies a smaller correction amount for the toner density target value, compared with when the condition is not satisfied. A correcting unit corrects the toner density target value on the basis of the correction amount.

Abstract: An image forming apparatus includes a developer containing part, a developer mixer, a mixer drive motor, a magnetic sleeve, a sleeve drive motor, a mixer rotation speed determination part and a motor drive controller. The developer containing part contains a two-component developer including a toner and a carrier. The developer mixer is provided in the developer containing part, agitates the two-component developer, and charges the toner and the carrier. The mixer rotation speed determination part determines the mixer rotation speed of the mixer drive motor according to a supply amount of the toner supplied to the developer containing part from a toner cartridge by driving of a toner supply motor. The motor drive controller independently performs rotation control of the sleeve drive motor and the mixer drive motor, and rotates and controls the mixer drive motor at the mixer rotation speed determined by the mixer rotation speed determination part.

Abstract: A method for monitoring development parameters of a liquid toner electrophotographic (LEP) printer, the method comprising defining an operational window for a current utilized by the printer and monitoring the current to determine a deviation of the current outside the operational window.

Abstract: An image forming apparatus includes an image forming unit configured to form an image under a control condition and including developing device; a toner cartridge configured to supply toner to the developing device; a measuring device configured to acquire measurement data; a first memory which is provided for the toner cartridge and includes a data reference destination for obtaining the control condition and a correction value of the control condition for standard data or a plurality of control data corresponding to the measurement data; a second memory configured to store the measurement data, the standard data, one of the correction value and the control data, and the obtained control condition; and a processing mechanism configured to read the standard data and the correction value, or the measurement data and the control data and to obtain the control condition.

Abstract: An image forming apparatus which forms an electrostatic latent image on a photosensitive drum, serving as an image carrier, develops the image using toners of a plurality of colors, and transfers a toner image onto a printing medium in accordance with an electrophotographic process. A toner consumption amount detection unit detects the toner consumption amount of each of the toners of the plurality of colors, a decision unit decides upon a color to form a patch, based on input image data and the detected toner consumption amount of each color, a patch sensor detects the density of a patch of the decided color by generating the patch at a predetermined position on the photosensitive drum serving as an image carrier outside an area to form a color image, and an adjustment unit adjusts the printing density based on the detected patch density.

Abstract: There is described an image forming apparatus, which makes it possible to prevent a final print product from getting its appearance worse due to such a drawback that a reference mark still remains on the final print product. The apparatus includes: a setting section to make the display section display a setting screen for inputting setting information therefrom, the setting information being in regard to a post-processing use page including a reference mark to be used for post processing; an image processing section to create image data representing a second image of the post-processing use page, based on the setting information inputted from the setting screen; and a print processing section to print the first images of the pages included in the document and the second image of the post-processing use page onto first paper sheets and a second paper sheet being separate from the first paper sheets, respectively.

Abstract: An image-forming apparatus includes: a forming unit that forms an image on an image holder that is a rotating body holding an image; a measuring unit that measures a rotation amount of the image holder with reference to a certain position on the image holder; a determining unit that: identifies a position on the image holder from which an image is to be formed by the forming unit, according to the rotation amount measured by the measuring unit; if, while a plurality of images are successively formed on the image holder, an image for density correction is to be formed, postpones forming of the image for density correction until a timing arrives at which one image of the plurality of images is to be formed from a predetermined position on the image holder, and when the timing arrives at which the one image of the plurality of images is to be formed from the predetermined position on the image holder, determines to start forming of the image for density correction from the predetermined position, instead of form

Abstract: In accordance with the invention, there is a method of forming a toner. The method can include blending two or more colorants to form a sample toner and forming a sample color specimen including a printed image comprising the sample toner. The method can further include comparing spectral distribution curves of the sample color specimen with that of a target color specimen including a target color and repeating the disclosed steps until acquiring a desired spectral match between the sample toner and the target color.

Abstract: A developing unit, which is incorporated in an image forming apparatus, includes a developer case to accommodate a two-component developer including toner and carrier, a developer bearing member bearing the two-component developer to supply the developer to an image, a developer supply path formed inside the developer case to supply the developer along the developer bearing member, an agitation and conveyance member disposed in the developer supply path, a toner collecting mechanism to collect toner after development, and a collected toner conveyance path formed inside the developer case and including a collected toner conveying member. The collected toner conveyance path and the developer supply path are arranged in communication with each other in the vicinity of one end portion of the collected toner conveyance path in a direction of conveyance of collected toner so as to circulate toner unused for development.

Abstract: Provided is a liquid developer concentration adjusting apparatus and a method so that the concentration can be adjusted easily and efficiently without using time and effort in liquid volume control. Further, the apparatus and method enable the concentration adjustment to be efficiently accomplished in a short period of time with reduced volume of required supply developer to be added for the adjustment independently of the initial concentration of the developer by concurrently measuring the concentration of developer, even if the concentration thereof is high. In the control of the concentration adjustment, the developer is allowed to overflow through an opening of the concentration adjusting container, and the concentration adjustment by using supply developer or the supply speed of the supply developer is started before the start of the overflow.

Abstract: An image forming apparatus which forms an electrostatic latent image on a photosensitive drum, serving as an image carrier, develops the image using toners of a plurality of colors, and transfers a toner image onto a printing medium in accordance with an electrophotographic process. A toner consumption amount detection unit detects the toner consumption amount of each of the toners of the plurality of colors, a decision unit decides a color to be calibrated, based on the detected toner consumption amount of each color, a patch sensor detects the density of a patch of the decided color by generating the patch at a predetermined position on the photosensitive drum serving as an image carrier, and an adjustment unit adjusts the printing density of the color decided by the decision unit, based on the detected patch density.

Abstract: A developing including a developer replenishing tank for replenishing a replenishment developer to a developer tank; a toner concentration detecting sensor; a discharging mechanism for discharging an excessive amount of the developer-tank-contained developer outside the developer tank when the amount of the developer-tank-contained developer inside the developer tank exceeds a predetermined amount; and control unit having a memory for storing the current toner concentration inside the developer tank, the reference toner concentration inside the developer tank, a corrected reference toner concentration calculated according to the formula of (the current toner concentration —a correction value), a predetermined replenishment amount to the developer tank and an allowable value for the current toner concentration with respect to the reference toner concentration, and a computer for calculating the corrected reference toner concentration and comparing the current toner concentration with the reference toner concen

Abstract: The color printing control device outputs color material reduction processed data generated by applying a color material reduction process to each pixel of bitmaps converted to color material colors to be used in printing, when it is judged that the color material reduction printing mode is specified. The color material reduction process includes chroma conversion that reduces chroma and under-color removal/black generation that replaces at least a portion of achromatic components generated by overlaying of a plurality of color materials.

Abstract: Toner images of reference patterns having different resolutions are formed on an image carrier, image densities of the toner images of reference patterns are detected by a density sensor, and an output of the density sensor, when the detected densities equate among the reference patterns having different resolutions formed with the same image forming condition, is memorized as a reference value for calibrating the output the density sensor.

Abstract: An image forming apparatus includes a developing container for containing a developer including toner and a carrier; a feeding member for feeding the developer contained in the developing container; a drive control portion, capable of selectively executing at least operations in a first mode in which the developer is fed at a first feeding speed by the feeding member to form an image and a second mode in which the developer is fed at a second feeding speed, different from the first feeding speed, by the feeding member to form an image, for controlling the feeding speed of the developer by the feeding member depending on the operation in the mode to be executed; a toner content detection sensor for detecting toner content by using magnetic permeability of the developer contained in the developing container; and a voltage control portion for controlling a control voltage to be inputted into the toner content detection sensor.

Abstract: An image forming apparatus and an image density control method for controlling image density in the image forming apparatus, involving adjusting a toner concentration control reference value in accordance with an amount of the toner replaced in a developing device so as to adjust the image density to maintain a consistent developability and changing image forming intervals in accordance with an amount of the toner replaced in the developing device during continuous printing operation.

Abstract: In an image forming apparatus and an image density control method that are capable of suppressing the amount of toner consumed for a purpose other than image formation and responding to variation in the development ability of a development device due to environmental variation and the like such that a constant image density is obtained, the image density is maintained at a substantially fixed level by first target output value correcting means in accordance with a toner replacement amount and without consuming toner, and adjustment of the image density accompanying variation in the development ability due to environmental variation and the like is dealt with by second target output value correcting means in accordance with a toner pattern detection result.

Abstract: An image forming apparatus includes a developing device, a replaceable developing material container that contains developing material, a coupling member that couples the developing device to the developing material container, and a controller. The controller calculates a value obtained by calculating replacement time of the developing material container, on a developing material amount obtained by subtracting a developing material amount filled in the coupling member from a developing material amount contained in the attached developing material container, when the developing material container is attached and an installation sequence to fill the coupling member with developing material is performed. The image forming apparatus further includes a display that displays information indicating the replacement time of the developing material container based on the value calculated by the controller.

Abstract: A pixel count section calculates a coverage rate corresponding to toner consumption. A control coefficient value setting section determines, based on the coverage rate, a stop threshold value representing reference concentration for toner replenishment and replenishment extension time. A magnetic permeability sensor measures permeability representing toner concentration in a housing portion. A toner concentration control section starts toner replenishment when an output value from the magnetic permeability sensor varies from a value less than a start threshold value to the start threshold value or above, and stops toner replenishment after lapse of replenishment extension time from the time at which an output value varied from a value greater than the stop threshold value to the stop threshold value.

Abstract: A reference developing image is formed on a photoreceptor drum under an image forming condition measured in advance, and the density of this reference developing image is detected. A development bias voltage is corrected based on the detection result, and when a correction value of the development bias voltage exceeds a predetermined range, a reference output voltage of an ATC sensor for detecting the density of toner in a developing device is corrected based on the detected value of humidity around the developing device, the frequency of use of the apparatus, and the agitation stress of developer.

Abstract: An image forming apparatus is provided with an image bearing member, a line test image forming section for forming a line test image made up of a plurality of line images arranged side by side on the image bearing member, an image density detecting section for detecting the density of the line test image formed on the image bearing member or the line test image transferred from the image bearing member to a transfer member, and a setting section for setting an image forming condition based on the density of the line test image.

Abstract: An system and related method for maintaining print quality based on development potential measurements that include comparing the current process measurements to a toner concentration related set-point; calculating a quality adjustment range based on current process measurements and the toner concentration related set-point, or a derivative thereof, indicative of print quality; and adjusting current process conditions related to the current process measurements to trend towards a new set point within the quality adjustment range so that a rate of change is proportional to the difference between the current process measurements and the set point.

Abstract: An image forming apparatus is configured that a developing unit develops a latent image with a toner, which is controlled by a toner-supply control unit based on a deference between a toner-density of the toner that is supplied to the developing unit and a reference-value. A reference-value determining unit determines the reference-value. A condition determining unit determines whether a predetermined condition is satisfied. The reference-value determining unit updates the reference-value with a different reference-value when the condition determining unit determines that the predetermined condition is satisfied.

Abstract: An image forming apparatus mounted with a toner cartridge having a memory unit includes a toner cartridge which stores a plurality of control data depending on toner in the memory unit, an acquisition unit which selects one of the plurality of control data in the memory unit and acquires image formation-related information and a setting unit which sets image formation parameters on the basis of the image formation-related information.

Abstract: An image density control method for an image forming apparatus in which, in order to keep the development capability constant over time, the toner density in the developer is manipulated to an appropriate range by changing the toner density control reference value in accordance with the toner replacement amount in a fixed time period by ascertaining changes in the image coverage of the output images, and by changing the image forming conditions at predetermined execution intervals.

Abstract: The image forming apparatus includes a developing device that holds a two-component developer to develop an image, a detecting unit that outputs a reference output value and a second output value when the two-component developer is stirred and carried at a stirring/carrying speed corresponding to a second image forming mode, a stirring/carrying member that stirs and carries the two-component developer, and a controlling unit that controls the toner concentration based on the reference output value when forming an image in a first image forming mode, and controls the toner concentration, when forming an image in the second image forming mode, a corrected output value obtained by correcting an output value in the second image forming mode with a difference value between the reference output value and the second output value.

Abstract: An amount of toner consumption accompanying development of an image corresponding to the image data is calculated based on image data, and a corrected consumption amount is calculated by multiplying the calculated amount of toner consumption by a predetermined correction ratio that is less than 1. Further, toner is supplied based on the calculated corrected consumption amount. As a result, it is possible to prevent excessive supply of toner, and to supply toner without time delay.

Abstract: In an image forming apparatus and an image density control method that are capable of suppressing the amount of toner consumed for a purpose other than image formation and responding to variation in the development ability of a development device due to environmental variation and the like such that a constant image density is obtained, the image density is maintained at a substantially fixed level by first target output value correcting means in accordance with a toner replacement amount and without consuming toner, and adjustment of the image density accompanying variation in the development ability due to environmental variation and the like is dealt with by second target output value correcting means in accordance with a toner pattern detection result.

Abstract: An image forming apparatus of the present invention includes an apparatus body. An image forming device included in the apparatus is at least partly implemented by a replaceable part. A counter counts prints output by the apparatus with the replaceable part. A memory and a first nonvolatile memory are built in the apparatus body. A second nonvolatile memory is built in the replaceable part. A controller writes a limit number of prints particular to the replaceable part in the first nonvolatile memory, stores, after image forming operation, a cumulative number of prints counted by the counter in the memory and second nonvolatile memory, and reports the time for replacing the replaceable part when the cumulative number stored in the memory exceeds the limit number of prints stored in the first nonvolatile memory.

Abstract: A method by which the target of a toner concentration (TC) sensor can be set up based on the equivalent developability concept without using an expensive patch generator. First, use a black toner area coverage (BTAC) sensor to measure the relative reflectance (RR) of a 100% area coverage developed patch (ROS generated) at a series of development levels (Vem or Vdev) to generate a pseudo development curve and estimate VdO in real-time (VdO is the Vdev level that starts to develop toner onto the photoreceptor belt.) Then, add a nominal delta Vdev to VdO to get the development level (Vdev) needed to generate 100% area coverage gray patch. Finally, using a BTAC sensor to measure the RR level of a 100% area coverage (AC) gray patch, move the target of the TC sensor, and converge the sensor's reading to the sensor's target continuously until the RR level of the gray patch hits the RR target (predefined) within the tolerance range. Thus, the target of the TC sensor is set for the xerographic system automatically.

Abstract: An image forming device includes: a toner image forming unit that forms a toner image onto a recording medium; a controlling unit that controls the toner image forming unit such that a test image is formed on the recording medium; a sheet transfer unit that transfers the recording medium having the toner image formed thereon by the toner image forming unit; a fixing unit that fixes the toner image formed by the toner image forming unit onto the recording medium; an image detecting unit, disposed downstream from the image fixing unit along the sheet transfer unit, that detects the test image formed on the recording medium; and a calibration unit that performs a color calibration process based upon the test image detected by the image detecting unit.

Abstract: An electrophotographic image-forming apparatus and method using a two-component developer comprises a charging roller for charging a surface of a photosensitive medium at a predetermined potential; a developing unit for developing an electrostatic latent image formed on the photosensitive medium; a control unit for determining a developing bias voltage to be applied to a developing roller in relation to a print density level selected by a predetermined selection unit out of a plurality of print density levels set in varying degrees, calculating a surface potential of the photosensitive medium charged by the charging roller, and controlling a charging voltage to be applied to the charging roller in order that an absolute value of a potential difference between the determined developing bias voltage and calculated surface potential becomes higher than a predetermined potential; and a charging voltage adjustment unit for variably adjusting the charging voltage to be applied to the charging roller.

Abstract: In order to prevent a toner residual amount from being erroneously judged as “toner present” after the toner residual amount has been judged to be insufficient, the toner residual amount detection apparatus of the present invention has a developing device for developing an electrostatic image formed on an image bearing member by a toner, the developing device being provided for movement relative to an apparatus main body, a sensor for outputting information corresponding to the toner residual amount in the developing device, a judging device for comparing the output of the sensor with a reference value to thereby judge the toner residual amount, wherein image forming is inhibited via a predetermined number of times of image forming after the toner residual amount is judged to be not sufficient, and a changing device for changing the reference value to a smaller value with the judgement that the toner residual amount is not sufficient.

Abstract: An embodiment of a digital recording apparatus real-time clock is disclosed. In particular, a real-time clock to mark when each recording is taken is described. The embodiment comprises a digital recording apparatus that contains a real-time clock powered by the main battery of the digital recording apparatus. The real-time clock resets when the digital recording apparatus's batteries are removed. When a recording is made, the digital recording apparatus marks the recording with the current value of the real-time clock, e.g., seconds since the batteries were changed. A computer then reads the media recorded by the digital recording apparatus and provides a date and time reference to which to relate the digital recording apparatus's real-time clock.

Abstract: An apparatus for controlling the supply of a developing agent, installed in a developer, is equipped with a developing-agent amount detector to detect an amount of the developing agent consumed by the developer; a driving-time detector to detect a driving time for actually shaking the developing agent provided in the developer; a developing-agent density calculator to calculate an actual density of the developing agent in the developer based on the consumed amount of the developing agent detected by the developing-agent amount detector and the actual driving time detected by the driving-time detector; a developing-agent amount controller to compare the actual density detected by the developing-agent density calculator and a reference developing-agent density to perform forcible supply of the developing agent when the actual density is lower than the reference density whereas forcible consumption of the developing agent when the actual density is equal to or higher than the reference density; and a consumed-am

Abstract: An image forming apparatus is able to maintain an image density at a constant level. The apparatus has a FC mode selecting key for allowing a user to selectively designate a low FC mode indicating that the apparatus is in a less-used state where the number of times of image formation is smaller than a predetermined value and a high FC mode indicating that the apparatus is in a highly-used state where the number of times of image formation is not smaller than the predetermined value, and a CPU for correctively setting a target value of toner density at a value higher than a target value of toner density at the low FC mode when the apparatus is in the high FC mode.

Abstract: A developer agitating system for agitating a developer includes a cartridge detachably mountable to a main body of an electrophotographic image forming apparatus and including a developing member for developing an electrostatic latent image formed on an electrophotographic photosensitive member, a developer container for containing the developer used for development of the electrostatic latent image by the developing member, an agitating member for agitating the developer contained in the developer container, and an informing member having information for indicating that the cartridge is a given cartridge, and a detector for detecting the information in the informing member when the cartridge is mounted to the main body of the electrophotographic image forming apparatus.

Abstract: A concentration controlling apparatus is provided for controlling the toner concentration of a developer contained in a developer unit. The developer contains a plurality of components including toner to be transferred to a photosensitive body for forming an electrostatic latent image. The concentration controlling apparatus includes a toner concentration detector for detecting the toner concentration of the developer, a supply determiner for determining a need for toner supply in response to detection output from the toner concentration detector, and a toner supplier for supplying a dose of the toner to the developer unit in accordance with the determination by the supply determiner. The supply determiner determines the need for toner supply at a higher toner concentration in a print-off state than in a print-on state.

Abstract: An image forming apparatus has a plurality of image forming devices for forming images in different colors. Each image forming device has an image bearing member, a charging device for charging the image bearing member, a developing device for developing an electrostatic latent image formed on the image bearing member by a developer containing toner and a carrier, and a detecting device for detecting information corresponding to the permeability of the developer in the developing device. The apparatus also has a control device for controlling the amount of the developer supplied to each developing device according to an output from the detecting device and a corresponding target value. Each charging device has magnetic particles which are brought into contact with the image bearing member. The permeability of the magnetic particles is different from the permeability of the carrier. The apparatus also has a correcting device for correcting each of the target values.

Abstract: The present invention relates to an image forming apparatus which has an image bearing member for bearing a latent image, charging device for charging the image bearing member by bringing ears of electrically conductive particles into contact with the image bearing member, developing device for visualizing the latent image formed on the image bearing member as a toner image by using a developer containing toner and carrier after the image bearing member has been charged by the charging device, a permeability of the carriers being different from a permeability of the electrically conductive particles, density control device for controlling density of the developer within the developing device, the density control device detecting a permeability of the developer, comparing a detected signal value based on the detected result with a reference value, and controlling the density of the developer on the basis of the comparison result, and reference value correcting device for correcting the reference value, the ref