JP2005227452A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of correcting the nonuniformity of density of a printed image without attaching a special device such as a circuit for detecting the surface potential of an image carrier. <P>SOLUTION: When a peripheral position calculation part receives reference position information showing a reference position set on a peripheral surface of a photoreceptor drum (YES in step S1), on the basis of this reference position signal and a drive pulse output from a drum drive, the part calculates a position in the peripheral direction of the photoreceptor drum (step S2). A record data getting part gets the position in the peripheral direction of the photoreceptor drum calculated in the step S2, gets the surface potential of the photoreceptor drum corresponding to the position from a memory, and inputs the get surface potential into a control signal output part (step S3). The control signal output part reads a correction value of light exposure corresponding to the surface potential from a table, produces a control signal corresponding to the correction value (step S4), and transmits the control signal to a scanning unit (step S5). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine.

  In recent years, in an image forming apparatus using an electrophotographic method or an electrostatic recording method, a photosensitive drum (hereinafter, a-Si) formed using amorphous silicon (amorphous silicon) as a photosensitive drum as an image carrier. Drum) may be used. The a-Si drum has a feature of high durability and long life, and is mounted on a high-speed machine that forms an image at a relatively high speed.

  However, it is known that the a-Si drum often generates non-uniformity (so-called film thickness unevenness, composition unevenness) along the circumferential direction in the film thickness and composition in the manufacturing process. When these non-uniformities occur, non-uniform charging potentials occur in the circumferential direction even when uniform charging is performed with a constant applied voltage. That is, the a-Si drum has a defect that the charging characteristics are likely to be uneven along the circumferential direction. As a result, there is a problem that non-uniformity occurs in the density of the printed image.

In Patent Document 1, a surface potential meter for detecting the surface potential of the a-Si drum is provided, and when the image forming apparatus is started up, the surface potential of the a-Si drum is measured by the surface potential meter while performing uniform charging processing. When performing printing, the surface potential of the a-Si drum at the time of printing is made uniform by performing charging while applying a voltage having a phase opposite to that based on the detected surface potential. A technique intended for the above is disclosed.
JP 2002-207350 A

  However, in Patent Document 1, a circuit or the like for measuring the surface potential in the circumferential direction is required, and the provision of this circuit or the like increases the cost and measures the surface potential when the image forming apparatus is activated. Therefore, there is a problem that the time required for starting the image forming apparatus becomes long.

  The present invention has been made in view of the above circumstances, and it is possible to correct nonuniformity in the density of a printed image without separately providing a special device such as a circuit for detecting the surface potential of the image carrier. It is an object of the present invention to provide an image forming apparatus that can be used.

  According to a first aspect of the present invention, a cylindrical image carrier configured to be rotatable, a charging means for charging the surface of the image carrier, and the surface of the image carrier after charging are based on image data. An image forming apparatus comprising: an exposure unit that exposes the image; a developing unit that develops the electrostatic latent image formed on the surface of the image carrier after the exposure with toner; and a transfer unit that transfers the toner image onto a recording sheet. In the apparatus, storage means for storing characteristic information that is information corresponding to a pre-measured charge characteristic distribution in the image carrier, and based on the characteristic information, the non-uniformity in image density is suppressed. An image forming apparatus comprising: an exposure control unit that controls an exposure operation of the exposure unit.

  Here, the characteristic information may be information indicating the density distribution of the image when the exposure processing is performed under uniform conditions in the circumferential direction and the axial direction, for example, but is associated with the surface potential distribution. For example, it may be information indicating how the exposure unit should be corrected and controlled in order to suppress non-uniform image density due to non-uniform charging characteristics.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image carrier is formed including amorphous silicon.

  According to the first aspect of the present invention, the characteristic information corresponding to the distribution of the charging characteristic in the image carrier measured in advance is stored, and the non-uniformity of the image density is suppressed based on the characteristic information. Thus, since the exposure operation of the exposure means is controlled, non-uniformity in image density can be suppressed without providing a special device.

  According to the second aspect of the present invention, since the image carrier is formed including amorphous silicon, the image carrier is formed including amorphous silicon in which nonuniformity of the film thickness and composition is particularly problematic. When the image carrier thus used is used, it is possible to effectively suppress non-uniformity of the image density.

  FIG. 1 is a diagram showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 1 is positioned on the downstream side of the recording paper supply unit 2 positioned below, the image forming unit 3 positioned above the recording paper supply unit 2, and the image forming unit 3. And a fixing unit 4.

  The recording paper supply unit 2 includes a paper feeding cassette CST, and biases the recording paper P placed in a stacked state on the paper feeding cassette CST to the recording paper P side by an unillustrated biasing mechanism including a spring or the like. When the uppermost recording sheet P is fed to the image forming unit 3 one by one by a rotating operation of the unillustrated sheet feeding roller or the like and conveyed to a predetermined position of the image forming unit 3, a registration roller (not illustrated) Thus, the conveyance timing is set so that the toner image formed on the surface of the photosensitive drum (image carrier) 5 described later and the leading end position of the recording paper P are aligned, and then the photosensitive drum 5 and the transfer roller 9 are aligned. Carry between.

  The image forming unit 3 includes a photoconductor drum 5 having photoconductivity that is rotatably supported, a laser scanning unit 6, a charger 7, a developer around the photoconductor drum 5 along the rotation direction thereof. A unit 8 and a transfer roller 9 are provided, and a predetermined toner image is formed on the photosensitive drum 5 by an electrophotographic process, and the toner image is transferred to the recording paper P.

  The photosensitive drum 5 is formed of amorphous silicon as a material, and is a cylindrical member whose surface is coated with a photoconductive substance. The image forming apparatus 1 according to the present embodiment is characterized in that the density unevenness of an image caused by the film thickness unevenness or composition unevenness of the photosensitive drum 5 is corrected with a simple configuration. Yes.

  Although not shown in detail, the laser scanning unit 6 includes a unit including a laser emitter and a polygon mirror, and a reflecting mirror, and outputs laser light, which is strengthened according to the image data of the document, from the laser emitter. The exposure area of the positively charged photosensitive drum 5 is irradiated through a polygon mirror and a reflecting mirror to form image dots on the surface of the photosensitive drum 5. By this irradiated laser light, the surface potential of the photosensitive drum 5 is reduced according to the image, and an electrostatic latent image corresponding to the image data of the document is formed on the surface of the photosensitive drum 5. This light irradiation is repeatedly scanned in the width direction of the rotating photosensitive drum 5 (direction perpendicular to the paper surface in FIG. 1) to the exposure region between the charger 7 and the developing unit 8 by the rotation of the polygon mirror. The

  As described above, since the film thickness unevenness or the like occurs on the photosensitive drum 5, even if the entire surface of the photosensitive drum 5 is exposed with a constant exposure amount, the surface of the photosensitive drum 5 is not affected. Pixels formed in a uniform manner are not formed in a uniform size, and the image size varies in the circumferential direction. Accordingly, when the surface of the photoconductive drum 5 is exposed to light according to only the image data of the document as in the prior art and is visualized, the image obtained after the visualization corresponds to the image of the document. Don't be.

  Hereinafter, this phenomenon will be described. FIG. 2 is a diagram showing the relationship between the magnitude of the charged potential on the surface of the photosensitive drum 5 and the size of one pixel (dot) of the electrostatic latent image formed by the exposure process by the laser scanning unit 6. As shown in FIG. 2, the charging potential on the surface of the photosensitive drum 5 increases as it goes in the direction of the arrow, and the charging potential indicated by the dotted line A represents the charging potential of a portion having a normal film thickness or the like. .

  Now, only the film thickness unevenness is considered as a factor causing the image density unevenness. In this case, the film thickness corresponds to the charging potential, and the charging potential increases as the film thickness increases (the amount of positive charge existing on the surface of the photosensitive drum 5 increases). As described above, when the exposure operation is performed at a constant exposure amount on the portions having different charging potentials (film thicknesses), the positive charge corresponding to the exposure amount is removed from each portion.

  At that time, the smaller the film thickness, the smaller the amount of positive charges, so that not only the portion directly irradiated with light but also the surrounding positive charges are removed. The smaller the film thickness, the more positive charges are removed. The range becomes larger. That is, as shown in FIG. 2, assuming that the relationship of magnitude of the film thickness is D <C <A <B in the four portions A to D on the surface of the photosensitive drum 4, the film thickness is as follows. Since the amount of positive charge decreases as the value decreases, the magnitude relationship between the magnitudes of the charging potentials also satisfies D <C <A <B. In addition, since the range in which the positive charges are removed increases as the film thickness decreases, the size relationship of the range in which the positive charges are removed, as indicated by arrows A to D, is D> C> A>. B, and the lower the charging potential, the larger the size of one pixel of the electrostatic latent image.

  As a result of such a phenomenon, when the image is developed and visualized by the developing unit 8 which will be described later, the density unevenness of the image due to the difference in size of one pixel occurs. That is, the larger the film thickness, the lighter the image density.

  Therefore, in order to eliminate such a problem, the image forming apparatus 1 according to the present embodiment is positioned at a circumferential position (film thickness, etc.) so that the image after the visible image processing corresponds to the image of the document. In response to this, the exposure amount is changed by the laser emitter, that is, the exposure operation is performed while taking into account the variation in charging potential due to the variation in film thickness unevenness and the like. The density unevenness of the image is eliminated or suppressed.

  Returning to FIG. 1, although not shown in detail, the charger 7 is a corona including a shield, a discharge wire as a discharge member, and a grid electrode as a control electrode to which a predetermined voltage (for example, +850 V) is applied. A charger, which charges the surface of the photosensitive drum 5. The charger 7 applies a high voltage to the discharge wire by a high voltage unit (not shown), and controls the ion flow obtained by corona discharge to the shield by the grid electrode, thereby controlling the surface potential of the photosensitive drum 5 to a desired potential. To control.

  The developing unit 8 includes a developing roller 13 disposed opposite to the photosensitive drum 5 and a toner container 14 storing toner, and the positive charge on the photosensitive drum 5 is reduced (the potential is reduced) by the laser beam. The toner having the same polarity in the developing region, that is, positively charged toner is attached to the portion of the electrostatic latent image by using the developing roller 13. As a result, the electrostatic latent image formed on the photosensitive drum 5 is developed with toner, and a toner image is formed as a visible image on the surface of the photosensitive drum 5.

  The transfer roller 9 is disposed so as to face the photoconductive drum 5 in a non-contact state, and a negative voltage is applied from the back surface of the recording paper P in the transfer area of the photoconductive drum 5 so as to be placed on the photoconductive drum 5. The formed toner image is electrostatically transferred onto the recording paper P.

  Although not shown in FIG. 1, the image forming apparatus 1 includes a cleaning unit and a static eliminator around the photosensitive drum 5 in addition to the above-described devices. A cleaning blade having a length substantially the same as the dimension in the width direction is provided, and the front end of the cleaning blade is urged against the surface of the photosensitive drum 5 by the urging force of the urging means. The residual toner adhering to the surface of the photosensitive drum 5 is scraped off. The static eliminator has a plurality of LED lamps arranged in a single row or a plurality of rows in the entire width direction of the photosensitive drum 5, and the LED lamp light is applied to the surface of the photosensitive drum 5. Irradiation removes the residual charge on the photosensitive drum 5.

  The fixing unit 4 performs a fixing process for fixing the toner transferred onto the recording paper P by pressurizing and heating the recording paper P onto which the toner image has been transferred. A fixing roller 16 having a built-in heater and disposed in the upper part of the heat shielding box 15; and a pressure roller 17 disposed in pressure contact with the fixing roller 16 in the lower part of the heat shielding box 15.

  FIG. 3 is a block diagram showing a configuration of a portion related to the correction of the surface potential of the photosensitive drum 5. The memory 18 is unitized as a drum unit 30 together with the photosensitive drum 5. The drum unit 30 may include a charger 7 or a light emitting element 20 and a light receiving element 21 described later. The memory 18 stores information on the number of sheets of paper on which image formation has been performed using the photosensitive drum 5 in the drum unit 30, information on a serial number assigned to the image forming apparatus 1, and the like.

  As described above, the photosensitive drum 5 has non-uniform charging characteristics in the circumferential direction due to uneven film thickness and the like. For this reason, the memory 18 also stores characteristic information which is information corresponding to the distribution of the charging characteristics or the distribution. Here, as an example of the characteristic information, the memory 18 stores information indicating the distribution of charging characteristics, that is, the surface potential D along the circumferential direction when the charging process is performed under uniform conditions. Thus, by using the memory 18 that stores the number of sheets of paper as the one that stores the surface potential D, an increase in the number of parts can be suppressed. In addition, since the components including the memory 18 and the photosensitive drum 5 are mounted and exchanged in units of the drum unit 30, there is a correspondence relationship between the characteristic information of the different photosensitive drums 5 and the characteristic information stored in the memory 18. Guaranteed.

  In order to correct the density unevenness of the image due to the non-uniformity of the surface potential D in the circumferential direction of the photosensitive drum 5, the image processing apparatus 1 according to the present embodiment performs an exposure amount according to the circumferential position of the photosensitive drum 5. A correction value U is generated, and this correction value U is used as a control signal for the laser scanning unit 6 to correct the exposure amount on the photosensitive drum 5.

  By the way, in order to perform such control, it is necessary to specify the circumferential position on the surface of the photosensitive drum 5. For this purpose, a circumferential reference position is set on the photosensitive drum 5, and the image forming apparatus 1 includes a reference position detection sensor 19 that detects this reference position.

  The reference position detection sensor 19 includes, for example, a light emitting element 20 and a light receiving element 21 that are opposed to each other in the main body of the image forming apparatus 1, and a light shielding member 22 that is attached to the photosensitive drum 5. The light shielding member 22 is attached at a position corresponding to the reference position, and the light shielding member 22 shields light transmitted and received between the light emitting element 20 and the light receiving element 21 so that the reference position is detected. The reference position detection sensor 19 transmits reference position information Rs, which is a reference position detection signal, to the MPU 24.

  The drum drive unit 23 includes a motor such as a well-known brushless DC motor that rotationally drives the photosensitive drum 5 in the circumferential direction, and the MPU 24 uses a drive pulse Q applied to the brushless DC motor as a drive signal. Also type in.

  The MPU (micro processing unit) 24 generates a correction value U based on the surface potential D, the reference position information Rs, and the drive pulse Q. FIG. 4 is a block diagram showing functions of the MPU 24. As shown in FIG. As shown in FIG. 4, the MPU 24 includes a circumferential position calculation unit 25, a recording data acquisition unit 26, a table 27, and a control signal output unit 28. The MPU 24 implements the functions of the elements shown in FIG. 4 by operating according to a program stored in a built-in program memory (not shown). The table 27 is stored in a memory (not shown) built in the MPU 24. The program that defines the operation of the MPU 24 and the contents of the table 27 can be supplied through a recording medium such as a ROM or a CD-ROM, or can be supplied through a transmission medium such as a communication line.

  The circumferential position calculation unit 25 calculates a circumferential position L of the photosensitive drum 5. Specifically, the circumferential position calculation unit 25 performs an exposure operation by the laser scanning unit 6 based on the drive pulse Q output from the drum drive unit 23 and the reference position information Rs output from the reference position detection sensor 19. A circumferential position L of the photosensitive drum 5 to be performed is calculated. That is, the rotation angle of the photosensitive drum 5 and the diameter of the photosensitive drum 5 corresponding to one drive pulse Q are derived in advance, and the moving distance along the circumferential direction of the surface of the photosensitive drum 5 from these values. Since the reference position is detected and the movement distance from the reference position is obtained, the circumferential position L is derived.

  The recording data acquisition unit 26 acquires the surface potential D corresponding to the circumferential position L of the photosensitive drum 5 calculated by the circumferential position calculation unit 25 from the memory 18.

  The table 27 shows the surface potential D of the photosensitive drum 5 and the exposure amount set corresponding to the surface potential D so as to correct the image after the visible image processing so as to correspond to the original image. The correction value U is stored in a table format. In the present embodiment, as schematically shown in FIG. 5, the correction value U is set to be higher as the surface potential D is higher. In the example of FIG. 5, the correction value U is given so as to change stepwise for each section of the surface potential D from the relationship of storing data.

  Returning to FIG. 4, the control signal output unit 28 reads the correction value U corresponding to the surface potential D acquired from the recording data acquisition unit 26 from the table 27, and transmits this correction value U to the laser scanning unit 6 as a control signal. Is.

  In FIG. 6, the surface potential D of the photosensitive drum, the correction value U output from the control signal output unit 28, and the entire surface of the photosensitive drum 5 are exposed with the exposure amount based on the correction value U. 4 is a graph illustrating the relationship with the size E of pixels formed on the surface of the photosensitive drum 5 in this case.

  It is assumed that the relationship between the surface potential D of the photosensitive drum 5 and the circumferential position L is as shown by the curve in FIG. Assuming that the memory 18 stores the relationship between the correction value U and the surface potential D illustrated in FIG. 5, the correction value U changes, for example, in four steps within the range of the maximum value Dmax and the minimum value Dmin of the surface potential D. If so, the control signal (correction value) U output from the control signal output unit 28 is expressed as shown in FIG. According to FIG. 5, the correction value U is set to be higher as the surface potential D is higher (the exposure amount is increased as the film thickness is larger), so the control signal (correction value) U and the surface potential D are Will change in positive phase. When this control signal (correction value) U is input to the laser scanning unit 6, the laser scanning unit 6 performs an exposure operation on the photosensitive drum 5 with an exposure amount corresponding to the control signal (correction value) U. As a result, as shown in FIG. 6C, the size E of the pixels formed on the surface of the photoconductor drum 5 after correction becomes a substantially constant value over the entire circumference.

  FIG. 7 is a flowchart showing exposure correction processing by the MPU 24. As shown in FIG. 7, when the circumferential position calculation unit 25 receives the reference position information Rs indicating the reference position set on the circumferential surface of the photosensitive drum 5 (YES in step S1), the reference position signal and the drum drive are received. Based on the drive pulse Q output from the unit 23, the laser scanning unit 6 calculates the circumferential position L of the photosensitive drum 5 to be exposed (step S2).

  The recording data acquisition unit 26 acquires the circumferential position L of the photosensitive drum 5 calculated in step S2, acquires the surface potential D of the photosensitive drum 5 corresponding to the position L from the memory 18, and acquires it. The surface potential D is input to the control signal output unit 28 (step S3).

  The control signal output unit 28 reads the correction value U for the exposure amount corresponding to the surface potential D from the table 27, generates a control signal corresponding to the correction value U (step S4), and laser scans the control signal. The information is transmitted to the unit 6 (step S5).

  If the processes in steps S2 to S5 have not been completed for the entire circumference of the photosensitive drum 5 (NO in step S6), the processes in steps S2 to S5 are repeatedly executed, and the steps for the entire circumference of the photosensitive drum are performed. When the processes of S2 to S5 are finished (YES in step S6), the exposure correction process is finished.

  Thus, by storing the surface potential D of the photosensitive drum 5 in the memory 18, the exposure processing by the laser scanning unit 6 is corrected without measuring the surface potential D of the photosensitive drum 5 with a surface potential meter. In addition, the non-uniformity of the pixel size E after the exposure processing can be eliminated or suppressed. Accordingly, since a circuit for measuring the surface potential is not required, the pixel size E is set in the circumferential direction without causing problems such as an increase in cost and a long time required to start up the image forming apparatus 1. It can be flattened.

  Further, since the correction value U for the exposure amount corresponding to the surface potential D is generated by referring to the table 27 showing the relationship between the surface potential D and the correction value U, the calculation is performed quickly and the correction is performed. The configuration of the device for generating the value U can be simplified.

  The present invention is not limited to the above-described embodiment, and for example, the following modifications (1) to (6) may be employed.

  (1) In the above-described embodiment, the occurrence of image density unevenness due to non-uniformity (so-called film thickness unevenness, composition unevenness) along the circumferential direction of the film thickness or composition of the surface of the photosensitive drum 5 is prevented or suppressed. However, even when the film thickness and composition of the surface of the photosensitive drum 5 are non-uniform along the axial direction, the same treatment as described above causes the non-uniformity along the axial direction. It is possible to prevent or suppress the occurrence of density unevenness in the image.

  For example, assuming that the relationship between the surface potential D of the photosensitive drum 5 and the axial position L is as shown by the curve in FIG. 8A, the memory 18 uses the correction value U and the surface potential illustrated in FIG. Assuming that the relationship with D is stored, if the correction value changes in, for example, four stages within the range of the maximum value D′ max and the minimum value D′ min of the surface potential D, the control signal output unit 28 Outputs a control signal (correction value) U as shown in FIG. When this control signal (correction value) U is input to the laser scanning unit 6, the laser scanning unit 6 performs an exposure operation on the photosensitive drum 5 with an exposure amount corresponding to the control signal (correction value) U. As a result, as shown in FIG. 8C, the size E of the pixels formed on the surface of the photoconductor drum 5 after correction becomes a substantially constant value in the axial direction.

  By processing in this way, it is possible to prevent or suppress the occurrence of image density unevenness due to non-uniformity along the axial direction of the photosensitive drum 5. Further, by combining the exposure amount correction technique in the axial direction of the photosensitive drum 5 and the exposure amount correction technique in the circumferential direction of the photosensitive drum 5 according to the first embodiment, the surface of the photosensitive drum 5 is combined. It is possible to prevent or suppress the occurrence of density unevenness in the image in both the circumferential direction and the axial direction.

  (2) In the above embodiment, the memory 18 stores the circumferential distribution of the surface potential D as characteristic information, that is, the surface potential D with respect to the circumferential position L. However, the exposure amount correction for the circumferential position L is corrected as characteristic information. The value U may be stored. For example, the circumferential distribution of the correction value U shown in FIG. 6B may be stored in the memory 18. In this case, the table 27 is useless, and the control signal output unit 28 may output the correction value U acquired by the recording data acquisition unit 26 from the memory 18 as a control signal.

  (3) In the above embodiment, the correction value U corresponding to the surface potential D is generated by referring to the table 27 indicating the relationship between the surface potential D and the correction value U. However, the surface potential D and the correction value U are generated. Is stored in a memory (not shown) included in the MPU 24 or stored in a program memory as a part of the program, and the control signal output unit 28 is based on the relational expression. Thus, the correction value U may be derived from the surface potential D.

  (4) In the above embodiment, a memory for storing information on the number of sheets on which image formation has been performed using the photosensitive drum 5 in the drum unit 30, information on a serial number assigned to the image forming apparatus 1, and the like. 18 is also used as a memory for storing the surface potential D to suppress an increase in the number of parts. However, a memory is provided separately from the memory for storing the number of paper sheets, and the surface potential D is You may make it memorize | store in memory.

  (5) The structure for detecting the reference position is not limited to the above, and for example, the light emitting element 20 and the light receiving element 21 are disposed in the main body of the image forming apparatus 1 and the position corresponding to the reference position on the photosensitive drum 5. The reference position may be detected by attaching a reflecting mirror to the light receiving element 20 and reflecting the light output from the light emitting element 20 toward the light receiving element by the reflecting mirror.

  (6) Image forming apparatuses include all apparatuses that form images on paper, such as facsimiles, printers, copiers, etc., and the present invention is applicable to all of them.

1 is a diagram illustrating an internal configuration of an embodiment of an image forming apparatus according to the present invention. It is a figure which shows the relationship between the magnitude | size of the charging potential of the surface of a photoconductor drum, and the magnitude | size of 1 pixel of the electrostatic latent image formed by the exposure process by a laser scanning unit. FIG. 3 is a block diagram illustrating a configuration of a portion related to correction of a surface potential of a photosensitive drum. It is a block diagram which shows the function of MPU. It is a figure which shows the relationship between a surface potential and a correction value. It is a graph which illustrates the surface potential before correction, the correction value, and the surface potential after correction. It is a flowchart which shows the surface potential correction process by MPU. 6 is a graph illustrating a surface potential before correction, a correction value, and a surface potential after correction in another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image forming part 5 Photosensitive drum 7 Charger 8 Developing part 18 Memory 19 Reference position detection sensor 23 Drum drive part 24 MPU
25 circumference position calculation unit 26 record data acquisition unit 27 table 28 control signal output unit

Claims (2)

A cylindrical image carrier configured to be rotatable, a charging unit for charging the surface of the image carrier, an exposure unit for exposing the surface of the charged image carrier based on image data, and the exposure In an image forming apparatus comprising: a developing unit that develops an electrostatic latent image formed on the surface of a subsequent image carrier with toner; and a transfer unit that transfers the toner image onto a recording sheet.
Storage means for storing characteristic information which is information corresponding to the distribution of charging characteristics in the image carrier measured in advance;
An image forming apparatus comprising: an exposure control unit that controls an exposure operation of the exposure unit so as to suppress non-uniformity in image density based on the characteristic information.   The image forming apparatus according to claim 1, wherein the image carrier is formed including amorphous silicon.

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