JPH11275361A - Image forming device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output an image of high quality by preventing unevenness in the density of the image. SOLUTION: A correcting circuit 50 corrects an input image signal and binarizes it. In accordance with it, a laser is driven to form an image. A correcting table to be used in the circuit 50 is prepared so as to temporarily output a prescribed test pattern so that the density in the main scanning direction becomes uniform, to read it by an image reading part, to pay attention to the prescribed line of the read image data and the uniform the density. Further, a video monitor is arranged in a paper feeding part or a paper discharge part etc., inside a printer and monitored from a host computer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer and an electrostatic recording apparatus, and more particularly to an image forming apparatus having a long life and high output.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus has been actively proposed as a digital data information transmission by a data communication network and a hardware output device of the information. FIGS. 21 and 22 show schematic configuration diagrams of such a conventional image forming apparatus, for example, a digital multifunction peripheral having the functions of an image scanner and a printer.

In FIG. 21, a photoconductor (photosensitive drum) 1
Is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a scoro-to-cone charger 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the direction of rotation, and the original is read, based on an image signal proportional to the density of the surface image. An exposure device that exposes the photosensitive drum 1 to form an electrostatic latent image; a developing device 7 that attaches toner to the electrostatic latent image to form a toner image; and transfers a toner image formed on the photosensitive drum 1 A corona transfer charger (transfer charger) 8 for transferring onto a transfer paper P which is a material, an electrostatic separation charger (separation charger) 9 for separating the transfer paper P on which the toner image has been transferred from the photosensitive drum 1, a toner Cleaning device 1 for removing residual toner on photosensitive drum 1 after transferring an image
3. Pre-exposure lamp 3 for removing residual charges on photosensitive drum 1
0 is arranged. The transfer paper P on which the toner image has been transferred is conveyed to the fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed. Is discharged to the outside.

The exposure apparatus scans the photosensitive drum with a laser beam in accordance with digital image data, and forms an electrostatic latent image on the photosensitive drum 1. In FIGS. 21 and 22, RG
When the digital image data of each B is input to the monochrome signal generation circuit 22, the G signal is selected as Bk (black) data, converted to a density signal by log conversion, and input to the binarization circuit 23. Is done. Therefore, a signal corresponding to the on-time and off-time of the laser is generated from the input density signal and input to the laser drive circuit 24.
The laser drive circuit 24 drives the semiconductor laser 20 according to an input signal. Thus, the emitted laser beam is turned on / off in accordance with the image signal. At this time, since the modulated laser beam is emitted in synchronization with the rotation of the polygon mirror 28, the photosensitive drum 1 is raster-scanned by the laser beam to form an electrostatic latent image.

In the image scanner section, a reader section 18 is provided.
Is converted into an electric signal corresponding to image information by irradiating an original 15 placed on an original glass table 14 with light by an illumination lamp 16 and forming an image of the reflected light on a one-line CCD 19 of a photoelectric conversion element. I do. Here lighting lamp 1
The reflected light from the document 15 illuminated by the light 6 is guided to mirrors 17a, 17b, and 17c and is imaged on the photoelectric conversion element 19 by the lens 17d. The electric signal output by the photoelectric conversion element 19 is subjected to A / D conversion by the A / D converter 21 to become digital image data of 8 bits for each of RGB.

When the digital multifunction peripheral is used as a copier, the digital image data is input to the monochromatic signal generation circuit 22 and converted into density information as described above, and is formed as a latent image on the photosensitive drum.

There are two known circuits for generating a signal corresponding to turning on / off a laser beam. Here, a pulse width modulation (PWM) circuit as the first circuit and a pseudo gradation circuit as the second circuit will be described.

FIG. 5 shows an example of a signal generated by the PWM circuit. The PWM circuit modulates the light emission time for turning on / off the semiconductor laser according to the magnitude of the input image density signal. For example, when the image data for each pixel is input in the laser scanning direction as shown in FIG. 5A, the drive signal for turning on / off the laser depends on the signal value as shown in FIG. 5B. It is modulated so that the duty ratio is adjusted. In the example of FIG. 5, the on-duty of the laser drive signal when the image data is 00 hex is 5% of one pixel scan time, and the on-duty of the laser drive signal when the image data is FF hex is 85% of one pixel scan time. Thus, shading is realized by expressing the gray scale by the area of one pixel.

FIG. 6 shows an example of a signal generated by the pseudo gradation circuit. Even when the laser driving in two values changes the image data as shown in FIG. 6A, the lighting time is constant as shown in FIG. 6B. As described above, when attention is paid to one pixel, it takes a binary state of whether or not it is recorded, but changes the ratio of the number of lit pixels to the total number of pixels in a wide area (00 hex / FF hex, 10 hex). /
FFhex, 20hex / FFhex, 30hex / F
(Fhex,..., FFhex / FFhex), the intensity of the integrated irradiation in a wide area is modulated by binarization to realize shading.

FIG. 7 shows general IL characteristics (driving current-light amount characteristics) of the laser.
The drive currents used at the time of off are Ion / Iof, respectively.
Because of f, the laser drive current for the image signal of FIG. 5A is as shown in FIG. 5C, which is the current for driving the laser by the PWM circuit.

Similarly, in the laser driving using the pseudo gradation circuit, the laser driving current for the image signal is as shown in FIG. 6B, and this is the current for driving the laser 20 by the laser driving circuit 24. At this time, Ioff is 0 mA
Not the minimum drive current value for emitting laser
It is known that the rise in the amount of light when the laser is turned on can be improved by setting it to be slightly smaller than the threshold. Note that a 680 nm visible light laser is used here.

As described above, the laser beam driven and emitted according to the image signal is raster-scanned and written on the photosensitive drum 1 via the polygon mirror scanner 28 and the mirror 17f rotating at high speed, and a digital electrostatic latent image is formed as image information. Form. Here, an amorphous silicon drum was used for the photosensitive drum 1. The amorphous silicon drum has characteristics such as high stability of characteristics, high durability and long life on the conductive substrate.

[0013]

However, in the above-mentioned prior art, when digital data information is transmitted by a data communication network and an image is formed as a hard output device of the information, a terminal processing unit (for example, a personal computer or the like is used). Expecting a desired print output image having the same impression as the image displayed on the display screen of (2), printout is performed, and it is only after looking at the printed document that the output image has a different impression from the desired image. Often. In such a case, it is necessary to return to the personal computer again and re-execute the image output command, and it is often necessary to perform inefficient and useless work.

[0014] In addition, as a result, paper resources are wastefully consumed. In particular, transfer paper forms a desired print image and is ejected to the outside of the image forming apparatus main body. Conventionally, however, the state of the apparatus after ejection, the state of output printing, the state of transfer paper before image formation, and the like of the image forming apparatus The terminal could not reliably grasp the job reception status and the like.

For example, the transfer paper may run short during printing, and the user may notice that the printing was interrupted without paper for the first time after the collection was completed at the scheduled printing end time, or the paper stopped similarly due to a paper jam. Things often happened. In addition, before the print command is issued, the reception status of the job of the image forming apparatus is not known, and the print command is issued during the execution of a long job, which may cause a long wait for the printout to be completed. Was.

In the conventional image formation, uniform image formation is obtained when there is no characteristic variation point (uneven point) in the photoreceptor or developing section, especially in the longitudinal direction (laser main scanning direction). In the case where there is a variation point in the charging characteristics of the photoreceptor (partial charging unevenness), when there is a variation point in the photosensitive characteristics (partial sensitivity unevenness), and when there is a variation point in the developing characteristics (partial At present, it is impossible to improve the density unevenness of the image (developing density unevenness).

The variation point of each characteristic may cause uneven density due to uneven electrostatic latent image potential on the photoreceptor, or uneven density due to a locally reduced developing efficiency due to a portion where development efficiency is reduced. Which is a major obstacle to image quality.

In particular, an amorphous silicon (a-Si) photoreceptor having a surface layer SiC hardening type and a high photosensitivity, which is a photoreceptor having a long service life and a high speed output, is manufactured by dipping in a solution such as an organic optical semiconductor photoreceptor OPC. Instead, it is conventionally manufactured by a manufacturing method based on a vapor deposition method. For this reason, it is difficult to control the film thickness in the film forming process, so that a uniform and uniform film is not formed, but a variation point is easily generated in charging characteristics and photosensitive characteristics, and unevenness in density is easily generated. For this reason, when the film thickness is controlled in the film forming process in order to ensure high quality image performance, the production yield of the photoreceptor is low, resulting in high cost.

The present invention has been made in view of the above-mentioned conventional example, and suppresses the occurrence of unevenness in a photosensitive member and a developing section during print recording, thereby preventing image density unevenness and outputting a high-quality image. Accordingly, it is an object of the present invention to provide an image forming apparatus and method which reduce the cost of a photoconductor and prevent an image different from a displayed image from being printed.

Further, an image forming apparatus which can be used without wasting time by monitoring the state of the image forming apparatus at the time of image formation regardless of the place where the image forming apparatus is arranged. The aim is to provide a method.

[0021]

To achieve the above object, an image forming apparatus according to the present invention has the following arrangement.
That is, the image forming apparatus is connected to a control device and forms an image on a transfer material. The image input unit inputs an image of a scene including the transfer material after image formation, and transmits the input image to the control device. And a transmitting unit that performs the processing.

Alternatively, an image forming section for correcting given image data under given correction conditions and then forming it on a print medium, a reading section for reading an image formed on the print medium, A predetermined test pattern image is formed by the section, the formed image is read by the reading section, and the correction conditions are set so that the density distribution of the read image matches the density distribution of the formed test pattern image. And setting means for setting.

Alternatively, the image forming method of the present invention has the following configuration.

A predetermined test pattern image is formed by the image forming unit, and the formed image is read by the reading unit. The density distribution of the read image matches the density distribution of the formed test pattern image. And a setting step of setting an image correction condition in the image forming unit.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. First Embodiment <Configuration of Image Forming Apparatus> FIGS. 1 and 2 are schematic structural views showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view showing a mechanism centering on the developing unit of FIG.

First, in FIG. 2, a photoconductor (photosensitive drum)
No. 1 is provided with a photoconductive layer on a cylindrical conductive substrate,
It is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a scoro-to-cone charger 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the direction of rotation, and the original is read, based on an image signal proportional to the density of the surface image. An exposure section for exposing the photosensitive drum 1 to form an electrostatic latent image; a developing section 4 for attaching toner to the electrostatic latent image to form a toner image; and transferring the toner image formed on the photosensitive drum 1 A corona transfer charger (transfer charger) 8 for transferring onto a transfer paper P which is a material, an electrostatic separation charger (separation charger) 9 for separating the transfer paper P on which the toner image has been transferred from the photosensitive drum 1, a toner A cleaning device 13 for removing residual toner on the photosensitive drum 1 after transferring the image,
Pre-exposure (lamp) 3 for removing residual charges on the photosensitive drum 1
0 and the like are arranged.

In the exposure unit, a single-color signal is generated by the single-color signal generation circuit 22 based on the image signal read from the reader unit 18 or the data sent from the personal computer 106, and once passed through the data storage unit 50. The laser light is converted into a binarized signal by the binarization circuit 23, and a signal for modulating the laser as described above is generated. The laser light modulated by the laser driver 24 and the semiconductor laser 20 in accordance with the image signal is generated. Be emitted.

FIGS. 3 (a) to 3 (c) show respective steps for explaining the image forming process of the present embodiment. In each figure, the relationship between the surface potential of the photosensitive member and the developing bias is schematically shown. ing.

In FIG. 3A, the photosensitive member is uniformly charged to +420 V by a corona charger.

In FIG. 3B, image information is exposed, and the surface potential of the image information exposed portion is attenuated to +50 V to form an electrostatic latent image. Since the image exposure is a pulse width modulated light amount as described above, the actual photosensitive drum potential after exposure is, in principle, only a laser-off portion potential and a laser-on portion potential. In a general non-contact surface voltmeter that measures the integrated potential in a sufficiently large area with respect to the diameter, it is apparently measured as a halftone potential. That is, in the non-image portion (image data 00hex) of the image region, the surface potential is attenuated to +400 V because the slight exposure is performed as described above, and the image portion of one image region (image data FFhe) is exposed.
In x), the surface potential attenuates to +50 V to form an electrostatic latent image.

Next, in FIG. 3C, a developing bias voltage (for example, AC to DC, DC to DC) is applied to the sleeve of the developing device.
Which are superimposed by + 300V. The direct-current DC component is indicated by a broken line) to reversely develop the exposed portion. Here, the developing unit uses a well-known one-component magnetic toner to perform development without contacting the photoconductor. Thus, an electrostatic latent image is formed from the image data.

The transfer paper P on which the toner image generated on the photosensitive drum is transferred is transported to the fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print is formed. An image is formed and is discharged outside the image forming apparatus main body.

FIG. 1 is a diagram showing a schematic configuration of the entire image forming apparatus and its system.

In the main body 101 of the image forming apparatus, image forming elements such as the reader unit 18 and the photosensitive drum 1 are housed.

The paper feeder 103 stores and supplies transfer paper. The device also serves as a device for carrying in double-sided or multiplex printing and for performing double-sided multiplex feeding.

The document feeder 102 has a function of sequentially feeding and collecting a plurality of documents and the like to the document 15 reading position on the reader unit 18. Also, the document feeder 1
Reference numeral 02 indicates that the original can be inverted and sent to the reader unit 18 so that a two-sided image can be read even for an original such as a two-sided original.

The transfer material finishing machine 104 sorts or staples the transfer material on which the fixing of the image by the fixing device 12 has been completed.

When the image forming apparatus 101 receives, from a personal computer 106 having a user interface, a print command obtained by converting image data or document data in accordance with a specified print setting rule via a communication cable network, the signal is stored in a data storage unit. The data is received and stored at 50, and a desired image is formed by performing spot writing according to the data. This image is transferred and fixed to the transfer paper P as described above, and the paper transport direction branching unit 107 determines the transport path according to the command transmitted together with the print command, and is transported. The transport direction includes a direction path P1 of the sheet feeding device 103 and a direction path P3 of the transfer material finishing machine 104.

Further, the operation image monitors (image input units) 109 and 11 which are the feature of the present invention are provided at portions where the transfer material on the paper transport paths P1 and P3 temporarily stops or reliably passes.
Set 0. The transfer material being conveyed or stopped by the image input units 109 and 110 is
A still image or a moving image (including a continuously sampled image of a still image at short intervals) in a state where it can be determined whether the image is in a normal state is input, and the image data is stored in the data storage unit 50 (not shown). Sent through the data transmission path. The data is stored as an image file and transmitted to the personal computer 106 via the communication cable network 1.
05.

In the personal computer 106, the transmitted image data file is opened by a browser program, which is an image display application, and restored and displayed as an image. By doing so, the state of the transfer material in the image forming apparatus can be displayed on a personal computer as a real scene,
It becomes possible to respond quickly to troubles.

Similarly, when the job receiving state and the job effective state of the printer main body displayed on the operation display section 111 of the printer are transmitted to the personal computer 106 as a real scene by the image input section 108, the print command is also transmitted. It is possible to select an optimal printer waiting for a job before issuing the job, thereby improving the time efficiency. It should be noted that data representing the job reception and job execution status of the printer can be transmitted to the personal computer 106 and visualized.

Here, the image input units 108 to 110 are capable of capturing an image of 350,000 to 800,000 pixels, capable of photoelectric conversion by combining a lens imaging system and a CCD device, and are various depending on the application used. An image file format that can support JPEG, for example, is effective.

The image input units 108 to 110 are constructed so as to be able to perform a zooming operation of a lens image forming system capable of changing an image input area, a swing operation in the vertical and horizontal directions, and the like. By issuing the operation command from the personal computer 106, a command signal is transmitted to an image input unit operation control circuit (not shown) in the data storage unit 50, and the image input setting of the image input unit can be freely changed. . This allows the personal computer 10
6, the operator can operate the image input units 108 to 110.
06, it is possible to grasp accurately and a reliable measure can be efficiently performed in terms of time.

The video signals from the image input units 108 to 110 can be directly transferred to a personal computer 10 via a demultiplexer or a booster cable or the like.
It is also effective to branch to 6 and directly display the video signal on a television or the like to display a continuous moving image.

<Operation in Motion View Mode>
Here, an operation flow in the motion view mode in which an image is formed while monitoring the operation of the printer by the image input units 108 to 110 will be described with reference to FIG. 1) The motion view mode is started by issuing a command from the terminal personal computer 106. 2) As the motion view mode, one of mode 1: before paper feeding, mode 2: after printout, mode 3: operation display section, and mode 4: all items are selected. 3) Start printout by the image forming apparatus. 4) The image forming apparatus main body starts a document image forming operation. 5) The image forming apparatus checks whether the print output operation has been started. When the operation signal and the start are confirmed, the process proceeds to step (6). If the operation cannot be confirmed, it is recognized that the image forming operation cannot be started due to some trouble (paper jam, etc.), and the display on the printer main body is displayed. A display indicating that a trouble has occurred is displayed, and a signal indicating that a trouble has occurred is similarly sent to the personal computer 106.
After the terminal operator has processed the troubled paper jam or the like, the terminal starts printout from step (3) again at the terminal. As a result, even if there is a trouble, trouble processing can be performed again in a short time. 6) When either the mode 1 (before paper feeding) or the mode 4 (all items) is selected at the stage when the printer operation starts, the image input unit 109 controls the paper transport path P1 near the paper feeding part. An image is taken. If the mode 2 (after printout) or the mode 4 (all items) is selected, the image input unit 1 performs photographing near the paper transport path P3.
10 sequentially. Further, if the mode 3 (operation display section) or the mode 4 (all items) is selected, the image on the operation display section 111 is also captured by the image input section 108 from the point where the image forming operation is started. Here, since the image input unit 110 is configured to be able to also input the image of the image forming surface formed on the discharged transfer material, the image itself can be viewed from the personal computer 106 as the image. 7) The read image is converted into a data file by the data storage unit 50. 8) The data file is transmitted to the personal computer 106 via the network 105. 9) Open the received data file on the display device of the personal computer 106 and display the captured image as it is. 10) The operator indicates to the personal computer 106 whether or not the displayed image is equivalent to the desired image forming operation or image by inputting YES / NO to the personal computer. YES
In the mode, the mode is ended, and in the case of NO, the print print setting or the change of the paper size and paper type of the printer main body to the paper feed guide setting of the special paper are performed. In this case, in order to temporarily set the image forming apparatus in the job reception stop state, a display indicating that the job reception is stopped is displayed on the printer main body display, and after the setting is changed, a printout instruction is received again.

When the printout image has some unevenness in the image density and the impression of the image is bad, not only the change of the print setting but also the entering of the improving image mode (described later) to calibrate the printer. You can also choose to perform an action. 11) If normal operation can be confirmed, return to the normal mode or proceed to the next printout operation in the motion view mode. 12) When printing a plurality of prints, a plurality of print commands are issued.

At the time of printing, the above procedure is executed, so that the operator can monitor the progress of image formation on the screen of the personal computer 106, and immediately stops the output if the printed matter is different from what is originally desired. To change the settings. In addition, it is possible to know from the personal computer that a problem such as running out of paper occurs in the image forming apparatus or that a large amount of printing is being performed, so that time wasted due to unnecessary waiting time during printing can be reduced. And efficient document creation activities.

As described above, since the image forming state can be confirmed as a sight image, the terminal device can check the device state after paper discharge, the output print state, the transfer paper state before image formation, and the job receiving state of the image forming apparatus. Because you can reliably grasp and check the actual scene, you can perform printout work with peace of mind, you can estimate the time schedule reliably, there is no mental load in print work, and work efficiency is enormous To improve. Note that the reader unit 18 in FIG. 2 has the same configuration as the reader unit 18 in FIG.

<Correction of Image Unevenness> Next, in the image forming apparatus having the configuration shown in FIGS. 1 and 2, even if the film pressure on the photoreceptor or the image developed by the developing unit is non-uniform, it is overcome. A technique for forming a high quality image will be described.

Hereinafter, a method of correcting unevenness in the main scanning direction of the photosensitive drum 1 will be described in detail.

FIG. 8 is a schematic diagram of the cause of the occurrence of density unevenness in the main scanning direction. The vertical axis indicates the surface potential on the photosensitive drum, and the horizontal axis indicates the position in the main scanning direction.

FIG. 8A shows an example of the potential distribution when there is a place where a target potential of 400 V is obtained and a place where only a potential lower than the target potential is obtained. Is shown. Such uneven distribution occurs because the surface potential of the photosensitive drum obtained by the current applied to the corona wire of the primary charger differs depending on the position of the drum, as shown by the three types of characteristic curves in FIG. This is because it has such a charging ability characteristic that it becomes Further, even if the charging ability characteristic of the photosensitive drum is uniform, if the charging ability of the primary charger is not uniform depending on the position in the main scanning direction, surface potential unevenness occurs.

FIG. 8B shows that the surface potential is formed uniformly by charging, but where the target potential of 50 V is normally obtained as the potential of the exposed portion, and higher than the target potential. An example of a potential distribution when there is a location of a potential is shown. This is the surface potential unevenness that occurs because the ability of the photosensitivity characteristics of the photosensitive drum differs depending on the region, as shown by the three types of characteristic curves in FIG. Even if the photosensitivity characteristics of the photosensitive drum are uniform, if the light irradiation amount is not uniform depending on the position in the main scanning direction, uneven surface potential occurs.

FIG. 8 (c) shows an exposed portion where development is normally performed, although the surface potential formation by charging and the surface potential formation by potential decay by exposure are uniform, and the toner amount is smaller than normal. 9 shows an example of the toner distribution when there are exposed portions having a small amount of toner. This occurs because, as shown by the three types of characteristic curves in FIG. 11, the developing capability for the developing contrast, which is the difference between the surface potential of the photosensitive drum and the DC voltage applied to the developing sleeve that carries and transports the developing toner, is different. The density is uneven. This uneven density occurs when the charging characteristics of the toner are not uniform in the main scanning direction, or when the gap between the drum and the developing sleeve is not uniform depending on the position in the main scanning direction.

Further, there is density unevenness due to non-uniformity in the main scanning direction of transfer efficiency at the time of transfer or separation (not shown).

In the image forming apparatus according to the present invention, all the causes of the unevenness are comprehensively detected and corrected from the output printout image.

FIG. 14 shows an outline of a flow of the unevenness correction operation in the improving image mode of the present invention. 1) The image forming apparatus of this embodiment has an "improving image mode" as an image unevenness improvement mode in the input interface, and starts the mode. 2) Next, the process stands by until the axial unevenness (unevenness in the main scanning direction) correction mode is selected. 3) When the key for starting the axial unevenness correction mode is pressed, the correction mode starts. 4) The image forming apparatus outputs a test image sample as shown in FIG. As an example, in order to form an image of solid black, halftone halftone, solid white, etc., an 8-bit signal is used to form F0, 80, 00hex in FIG.
Irradiates the photosensitive drum with a laser having a PWM level of, forms an electrostatic latent image, develops, transfers, fixes the sample, and outputs a sample. 5) The output sample is placed on the document table with the leading end in the sheet passing direction and the near side or the back side as a specific position, and it is determined whether or not the placement completion is detected by a document recognition unit (not shown).
Note that the document after printing is transferred to the paper transport direction branching device 10.
An automatic process may be used in which the document is conveyed to the document reading position of the reader unit 18 by the reader 7 and the normal installation is confirmed by a document detection device (not shown). 6) When the placement is determined to be completed, the original is read by the reader unit 18 as described above. This reader reads 4
It is desirable to read at a resolution of about 00 to 600 pi. 7) It is determined whether the read document is a test image sample based on whether or not the density gradation is the same pattern. 8) If it is determined that the sample is a test image sample, the density distribution in the axial direction (main scanning direction) is calculated as shown in FIG. When a test image sample is formed at the PWM level of F0, 80, and 00 hex, the read density distribution of the halftone portion of 80 hex where unevenness is most easily detected is calculated. Note that the density distribution may be calculated for each of F0, 80, and 00 hex. 9) When the target density is set to 0.5 in FIG. 15B, an increase / decrease from 0.5 in the read density distribution of the halftone portion is calculated so as to correspond to each pixel in the main scanning direction. If the minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density is as shown in FIG.
The required correction density is such that the polarity of (b) is inverted. 10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. For example, in FIG. 16, when the required correction density is +0.8, the surface potential is -200 V, and the drum surface light amount is +0.25.
μJ indicates that +80 hex correction is required for image data. In this manner, a correction amount level corresponding to each pixel in the main scanning direction is allocated so as to be corrected at the stage of multi-valued image data, and a correction table is created.

Thus, this mode is completed, and the operation panel as the input interface unit of the image forming apparatus returns to the normal copy or print mode.

Using the correction table described above, 8
Data correction such as image unevenness is performed at the bit multi-level signal stage. Therefore, uniform data is formed at the time of binarization, and density unevenness is completely corrected at the time of laser writing, and a high-quality image without density unevenness in the longitudinal direction (main scanning direction) is always provided. You can do it.

It is also possible to display the uneven distribution diagram and the correction table diagram described above on the display unit of the printer main body, and change the correction table according to the operator's preference. A manual setting may be made so that it can be performed.

The multi-valued image data before binarization, the multi-valued image data corrected by the correction table, and / or the density data obtained by converting the multi-valued image data into the density data are output to the image output unit. The command can also be sent to the host computer that generated the command. By doing so, the corrected image data can be obtained even in the host computer.

The image information input by the image input units 109 to 110 is stored in an Internet server as required, and the image information can be downloaded to a desired host computer via a data communication line or a network line. You can also. Second Embodiment A second embodiment according to the present invention will be described below with reference to the drawings.

FIG. 17 is a schematic configuration diagram showing an image forming apparatus according to the present invention. The photoconductor (photosensitive drum) 1 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a first scoro-to-cone charger 2 for uniformly charging the surface of the photosensitive drum 1 in order along the rotation direction, a document is read, and one of the color surfaces separated into two colors is read. A first exposure device that exposes the photosensitive drum 1 based on a first image signal proportional to the image density to form a first electrostatic latent image, and attaches toner to the first electrostatic latent image to form a first toner A first developing device 4 for forming an image, a second scorotron charger (hereinafter referred to as a recharger) 5 for charging the photosensitive drum 1 after carrying the first toner image, and a density of the other color image separated A second exposure device that forms a second electrostatic latent image by performing exposure of an amount obtained by adding a certain exposure amount to an exposure amount based on a second image signal proportional to the second image signal; Developing device 7 for forming a second toner image by adhering A corona transfer charger (transfer charger) 8 for transferring the color superimposed image formed thereon onto a transfer paper P as a transfer material, and an electrostatic device for separating the transfer paper P on which the color superimposed image is transferred from the photosensitive drum 1 A separation charger (separation charger) 9, a cleaning device 13 for removing the residual toner on the photosensitive drum 1 after transferring the color superposed image, a pre-exposure (lamp) 30 for removing the residual charge on the photosensitive drum 1, and the like are provided. Have been. The transfer paper P on which the color superimposed image has been transferred is separated from the photosensitive drum 1 and then conveyed to the fixing device 12, where the toner image on the surface is fixed, and a desired print image is formed. It is discharged outside the body.

The image scanner section 18 scans the original 15 placed on the original glass table 14 by scanning with an illumination lamp 16 and converts image information into an electric signal by a photoelectric conversion element 19. The reflected light from the original 15 scanned by the mirror 16 is reflected by mirrors 17a and 17a.
7b, 17c, led by lens 17d,
Photoelectric conversion element 1 with built-in green and blue filters
9 is formed. The electric signal from which the red, green, and blue components are output by the photoelectric conversion element 19 is digitized by the A / D converter 21,
The signal is sent to the signal processing unit 22 as a color separation unit, and is converted into an image signal proportional to the image density of each of the red and black components.

Here, the image data is corrected for each pixel by the axial direction (main scanning direction) unevenness correction circuit 50 of the present invention (see FIG. 19).

The red image signal (first image signal) and the black image signal (second image signal) are sent from the correction circuit 50 via the binarization circuit 23 to the laser drivers 24b and 24a as signal generators. To turn on / off the lasers 20b and 20a according to the red and black image signals.
f. The laser beam emitted according to the red signal writes a first electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirror 17e as first image information. The laser light emitted in an amount corresponding to the black signal writes a second electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirrors 17f and 17g as second image information.

In this embodiment, an amorphous silicon drum is used for the photosensitive drum 1. Amorphous silicon drums have features such as high durability and long life.

Further, similarly to the first embodiment, the image input devices 108 to 110 are installed at the same positions as those shown in FIG.

FIGS. 18A to 18F illustrate the image forming process in the two-color image forming mode of this embodiment. FIGS. 18A to 18F show the respective steps, and in each figure, the surface potential of the photosensitive member is schematically shown. Is shown in In (a), the photoconductor is charged to, for example, +400 V by a corona charger. In (b), the first exposure of the image information is performed, and the surface potential of the exposed portion is attenuated to, for example, +50 V to form a first electrostatic latent image.
In (c), a developing bias voltage (for example, +300 V: indicated by a broken line) is applied to the sleeve of the first developing device to reversely develop the exposed portion. In (d), recharging is performed after the first development.
A voltage of 600 V larger than 00 V is applied to control the non-image portion by the first development to be charged to, for example, 600 V.
At that time, the image area by the first development is charged to 500V.
This is because it is difficult for the developed image portion to pass the laser beam by the developer, and the value for decreasing the pressure during the formation of the electrostatic latent image in the subsequent configuration (e) is small. In (e), the second
When performing exposure in accordance with the image information, a larger exposure is performed over the entire surface by a fixed exposure amount (for example, by an exposure amount that attenuates the first developed non-image area by 200 V) as compared with the case of developing with a single color. . At this time, in the image area by the first development, the exposure at the constant exposure amount does not attenuate as much as the potential attenuation in the non-image area by the first development. For example, the light transmittance of the first developer is reduced by 50%.
As a percentage, only 100 V is attenuated. This is because in the image area formed by the first development, the adhered developer does not transmit light but scatters the light. The amount of exposure added in the second exposure is from 40 V recharged after the first development to 40
Exposure amount to attenuate 200V to return to 0V,
That is, it is understood from FIG. 16 that it is 0.25 μJ. Since the toner layer transmittance is 50%, the amount of light reaching the image area by the first development is 0.125 μJ, which is half of the added exposure amount of 0.25 μJ. For this reason, it can be seen that the attenuation is 100 V, and the potential after recharging of the image area by the first development in (d) must be 500 V.

In this embodiment, a semiconductor laser is used as the second exposure means. Since the amount of laser light is determined by the laser drive current, in the two-color mode in which two-color printing is performed using the two developing units, the second development single-color mode (the second A constant offset current is added to the drive current in the mode of forming a monochromatic black image using only the two developing units. This offset current is a value that can realize an additional exposure amount of 0125 μJ. As a result, a weak exposure is performed even in a portion where the second image signal is off, and an exposure is added to a portion where the second image signal is on by a substantially equivalent amount of exposure. For this reason, FIG.
As shown in (2), in the portion where the second image signal is off, the potential of the image portion by the first development is 400 V, and the potential of the non-image portion by the first development is also 400 V. Further, the laser is controlled so that the portion where the second image signal is on is charged to 50V. (F) Thereafter, 3 is applied to the second developing sleeve in the developing process.
The toner is developed by applying a bias of 00V. The non-image portion on the photosensitive drum in the second development is 400 V, which is higher in potential than the bias (300 V) of the developing sleeve.
Therefore, a sufficient second image density can be obtained without the second developer being mixed into the image area formed by the first development and the non-image area not being developed.

As described above, in order to switch between the second developing single-color mode (mode for forming a black monochromatic image using only the second developing unit) and the two-color mode using two developing units, In the color mode, it suffices to add an offset current to the second image signal, and does not require complicated processing.

A two-color image is formed by the above steps. In this image formation, as in the first embodiment, the unevenness of the image due to the non-uniform charging and the non-uniform thickness of the amorphous silicon film of the photosensitive drum is eliminated by the improving mode. The procedure for creating the correction table 50 used for the correction will be described with reference to the operation flow of FIG. 1) The image forming apparatus of this embodiment has an "improving image mode" as an image unevenness improvement mode in the input interface, and starts the mode. 2) Next, the process stands by until the axial unevenness (unevenness in the main scanning direction) correction mode is selected. 3) When the key for starting the axial unevenness correction mode is pressed, the correction mode starts. 4) The image forming apparatus outputs a test image sample as shown in FIG. As an example, in order to form an image of solid black, halftone halftone, solid white, etc., an 8-bit signal is used to form F0, 80, 00hex in FIG.
Irradiates the photosensitive drum with a laser having a PWM level of, forms an electrostatic latent image, develops, transfers, fixes the sample, and outputs a sample.

Here, as a feature of this embodiment, a test image sample is output for each of two colors (for example, red and black). After this, the following operations 5) to 10) are performed in color (red and black)
Perform for each color. 5) The output sample is placed on the document table with the leading end in the sheet passing direction and the near side or the back side as a specific position, and it is determined whether or not the placement completion is detected by a document recognition unit (not shown).
Note that the document after printing is transferred to the paper transport direction branching device 10.
An automatic process may be used in which the document is conveyed to the document reading position of the reader unit 18 by the reader 7 and the normal installation is confirmed by a document detection device (not shown). 6) When the placement is determined to be completed, the original is read by the reader unit 18 as described above. This reader reads 4
It is desirable to read at a resolution of about 00 to 600 pi. 7) It is determined whether the read document is a test image sample based on whether or not the density gradation is the same pattern. 8) If it is determined that the sample is a test image sample, the density distribution in the axial direction (main scanning direction) is calculated as shown in FIG. When a test image sample is formed at the PWM level of F0, 80, and 00 hex, the read density distribution of the halftone portion of 80 hex where unevenness is most easily detected is calculated. Note that the density distribution may be calculated for each of F0, 80, and 00 hex. 9) When the target density is set to 0.5 in FIG. 15B, an increase / decrease from 0.5 in the read density distribution of the halftone portion is calculated so as to correspond to each pixel in the main scanning direction. If the minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density is as shown in FIG.
The required correction density is such that the polarity of (b) is inverted. 10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. For example, in FIG. 16, when the required correction density is +0.8, the surface potential is -200 V, and the drum surface light amount is +0.25.
μJ indicates that +80 hex correction is required for image data. In this manner, a correction amount level corresponding to each pixel in the main scanning direction is allocated so as to be corrected at the stage of multi-valued image data, and a correction table is created.

Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

Using the correction table described above, 8
Since data correction such as image unevenness is performed at the bit multi-value signal stage, data without unevenness is formed at the time of binarization, and the uneven density is colored (red and black) at the time of laser writing.
By correcting each time, a high-quality two-color image without density unevenness in the longitudinal direction (main scanning direction) can always be provided.

Also, the motion view mode shown in FIG. 13 can be used in the present embodiment, and a two-color image can be confirmed on a personal computer display screen, and an efficient printout operation without errors can be performed. <Third Embodiment> FIG. 20 is a schematic structural view showing an image forming apparatus using LEDs according to a third embodiment of the present invention.

The photoreceptor (photosensitive drum) 1 has a photoconductive layer provided on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a scoro-to-cone charger 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the direction of rotation, and the original is read, based on an image signal proportional to the density of the surface image. An exposure device that exposes the photosensitive drum 1 to form an electrostatic latent image;
A developing device 4 for adhering toner to the electrostatic latent image to form a toner image; a corona transfer charger (transfer charging) for transferring the toner image formed on the photosensitive drum 1 onto transfer paper P as a transfer material Device) 8, an electrostatic separation charger (separation charger) for separating transfer paper P on which a toner image has been transferred from photosensitive drum 1
9, a cleaning device 13 for removing residual toner on the photosensitive drum 1 after transferring the toner image, a pre-exposure (lamp) 30 for removing residual charges on the photosensitive drum 1, and the like. The transfer paper P on which the toner image has been transferred is conveyed to the fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed. Is discharged to the outside.

The reader section 18 irradiates the original 15 placed on the original glass table 14 with light from the illumination lamp 16 and forms the reflected light on the one-line CCD 19 of the photoelectric conversion element to form image information. Convert to the corresponding electric signal. Here, the reflected light from the original 15 illuminated by the illumination lamp 16 is reflected by mirrors 17a, 17b, and 17c.
And an image is formed on the photoelectric conversion element 19 by the lens 17d. The electric signal output by the photoelectric conversion element 19 is A / D converted by the A / D converter 21 to become 8-bit digital image data. The image data is log-converted by the black signal generation circuit 22 to be converted from luminance information to density information to be image density data.

Here, as shown in FIG. 1 or FIG. 4, the image density data is corrected for each pixel in the main scanning direction by the main scanning unevenness correction circuit 50 according to the present invention. The correction method in the main scanning unevenness correction circuit will be described later in detail.

The 8-bit digital image data signal generated as described above is converted by the binarizing circuit 23 into two signals, an ON light emission signal and an OFF signal of a specific ON time according to the pixel size.
The signal is converted into a step signal and input to the LED drive circuit 24c, which is a feature of the present invention, to turn on / off the LED 20c.
The LED 20c is configured by arranging LEDs for one raster line in the axial direction of the drum.
The light is turned on / off in accordance with the image signal input from c, and the surface of the photosensitive drum is exposed.

Binarization from an 8-bit signal to a 1-bit signal is performed by changing the ratio of the number of black pixels to the number of pixels in a wide area (00 hex) by a dither method, an error diffusion method, or the like.
/ FFhex, 10hex / FFhex, 20hex /
FFhex, 30hex / FFhex, ..., FFhex
/ FFhex), thereby modulating the integrated irradiation light amount in a wide area, and performing the shading in a pseudo manner.

As described above, the photosensitive drum 1 is exposed with the LED light driven and emitted according to the image signal, and a digital electrostatic latent image is formed as image information.

In this embodiment, an amorphous silicon drum is used as the photosensitive drum 1. The amorphous silicon drum has characteristics such as high stability of characteristics, high durability and long life on the conductive substrate.

The steps for explaining the image forming process of this embodiment are the same as those of the first embodiment. Description will be made using the flow of the correction operation in FIG. 14 as in the first embodiment. 1) The image forming apparatus of this embodiment has an "improving image mode" as an image unevenness improvement mode in the input interface, and starts the mode. 2) Next, the process stands by until the axial unevenness (unevenness in the main scanning direction) correction mode is selected. 3) When the key for starting the axial unevenness correction mode is pressed, the correction mode starts. 4) The image forming apparatus outputs a test image sample as shown in FIG. As an example, in order to form an image of solid black, halftone halftone, solid white, etc., an 8-bit signal is used to form F0, 80, 00hex in FIG.
The electrostatic latent image is formed by irradiating the photosensitive drum with the amount of LED light corresponding to the above, developed, transferred, fixed and output as a sample. 5) The output sample is placed on the document table with the leading end in the sheet passing direction and the near side or the back side as a specific position, and it is determined whether or not the placement completion is detected by a document recognition unit (not shown).
Note that the document after printing is transferred to the paper transport direction branching device 10.
An automatic process may be used in which the document is conveyed to the document reading position of the reader unit 18 by the reader 7 and the normal installation is confirmed by a document detection device (not shown). 6) When the placement is determined to be completed, the original is read by the reader unit 18 as described above. This reader reads 4
It is desirable to read at a resolution of about 00 to 600 pi. 7) It is determined whether the read document is a test image sample based on whether or not the density gradation is the same pattern. 8) If it is determined that the sample is a test image sample, the density distribution in the axial direction (main scanning direction) is calculated as shown in FIG. When a test image sample is formed with an image signal of F0, 80, and 00 hex, a read density distribution of a halftone portion of 80 hex at which unevenness is most easily detected is calculated. Note that the density distribution may be calculated for each of F0, 80, and 00 hex. 9) When the target density is set to 0.5 in FIG. 15B, an increase / decrease from 0.5 in the read density distribution of the halftone portion is calculated so as to correspond to each pixel in the main scanning direction. If the minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density is as shown in FIG.
The required correction density is such that the polarity of (b) is inverted. 10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. For example, in FIG. 16, when the required correction density is +0.8, the surface potential is -200 V, and the drum surface light amount is +0.25.
μJ indicates that +80 hex correction is required for image data. In this manner, a correction amount level corresponding to each pixel in the main scanning direction is allocated so as to be corrected at the stage of multi-valued image data, and a correction table is created.

Thus, this mode ends, and the operation panel, which is the input interface of the image forming apparatus, returns to the normal copy or print mode.

Using the correction table described above, 8
Since data such as image unevenness is corrected at the bit multi-level signal stage, uniform data is formed at the time of binarization, and there is no write unevenness at the LED write level, and the longitudinal direction (main scanning direction) is always present. Therefore, it is possible to provide a high-quality image without density unevenness.

Also, as in the first embodiment, by mounting the image input unit on a portion corresponding to the image input units 109 to 110 in FIG. 1, the motion view mode shown in FIG. 13 can be executed. The image formed on the display screen of the personal computer, the state of the recording medium, and the like can be checked, and an efficient printout operation without errors can be performed.

[0088]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU) of the system or apparatus.
Or MPU) reads and executes the program code stored in the storage medium.

In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

Examples of the storage medium for supplying the program code include a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, and CD.
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) Performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, The case where the CPU of the function expansion board or the function expansion unit performs part or all of the actual processing, and the function of the above-described embodiment is realized by the processing.

[0094]

As described above, by suppressing the occurrence of unevenness in the photoreceptor and the developing section during print recording, unevenness in image density is prevented, and a high-quality image is output. It is possible to reduce the cost and prevent an image different from an image viewed in advance from being printed as a display image.

Further, since the user monitors the state of the image forming apparatus at the time of image formation irrespective of the place where the image forming apparatus is arranged, useless time can be prevented.

[0096]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus having an operation image monitor and performing density unevenness correction.

FIG. 2 is a schematic configuration diagram of an image forming unit of the image forming apparatus according to the first embodiment.

FIG. 3 is a diagram illustrating a potential for image formation.

FIG. 4 is a schematic configuration diagram of a correction circuit of the image forming apparatus that performs density unevenness correction according to the first embodiment.

FIG. 5 is an explanatory diagram of pulse width modulation.

FIG. 6 is an explanatory diagram of binarization capable of expressing a gradation in a pseudo manner.

FIG. 7 is a graph of current-light amount when the light source driving circuit is driven and when it is not driven.

FIG. 8 is an explanatory diagram of a cause of uneven density.

FIG. 9 is an explanatory diagram of a cause of uneven density.

FIG. 10 is an explanatory diagram of a cause of uneven density.

FIG. 11 is an explanatory diagram of a cause of uneven density.

FIG. 12 is a graph showing the relationship between the value of image data and the amount of exposure and pixel ratio in a wide area.

FIG. 13 is a flowchart of a motion view mode.

FIG. 14 is a flowchart of density unevenness correction according to the first embodiment.

FIG. 15 is an explanatory diagram of a density unevenness correction method.

FIG. 16 is an explanatory diagram of a density unevenness correction method.

FIG. 17 is a schematic configuration diagram of an image forming unit of the image forming apparatus according to the second embodiment.

FIG. 18 is a diagram illustrating an image forming procedure according to the second embodiment.

FIG. 19 is a schematic configuration diagram of a correction circuit of an image forming apparatus that performs density unevenness correction according to the second embodiment.

FIG. 20 is a schematic configuration diagram of an image forming unit of the image forming apparatus according to the third embodiment.

FIG. 21 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 22 is a drive circuit diagram of a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 primary charging device 3 image exposure 7 developing device 8 transfer charging device 12 fixing device 13 cleaner 30 pre-exposure device 20 image exposure light source 50 data storage device and image unevenness correction circuit device 108, 109, 110

Claims (14)

[Claims] 1. An image forming apparatus connected to a control device for forming an image on a transfer material, comprising: an image input unit for inputting an image of a scene including the transfer material after image formation; An image forming apparatus, comprising: a transmitting unit that transmits the image to the apparatus. 2. The image forming apparatus according to claim 1, further comprising a second image input unit for inputting an image of a scene including a transfer material before image formation. 3. The image forming apparatus according to claim 1, further comprising: an operation unit for inputting an operation by an operator; and a third image input unit for inputting an image of a scene including the operation unit. apparatus. 4. An image forming section for correcting given image data under given correction conditions and forming the image on a print medium, a reading section for reading an image formed on the print medium, A predetermined test pattern image is formed by the section, the formed image is read by the reading section, and the correction conditions are set so that the density distribution of the read image matches the density distribution of the formed test pattern image. An image forming apparatus comprising: 5. The image according to claim 4, wherein the image forming unit forms an image based on multi-valued image data, and the setting unit sets a correction condition for the multi-valued image data. Forming equipment. 6. The image forming unit forms an image by an electrophotographic method, and the setting unit determines a density distribution in a main scanning direction for a predetermined line in the read image.
5. The image forming apparatus according to claim 4, wherein a correction condition is set so as to match a density distribution that should have been generated as a test pattern image. 7. An image forming section, comprising: a photosensitive drum in which a photoconductor for forming an electrostatic latent image is formed in a thin layer on a cylindrical conductive substrate; and a minute point exposure according to image information to form an electrostatic latent image. The image forming apparatus according to claim 6, further comprising an exposure unit and a developing unit that visualizes the electrostatic latent image. 8. The image forming apparatus according to claim 7, wherein said photosensitive drum uses an amorphous silicon photosensitive member. 9. The image forming apparatus according to claim 7, wherein the exposure unit has an optical system that performs digital exposure for each pixel and scans a cylindrical surface of the photosensitive drum in a cylindrical axis direction. 10. The image forming apparatus according to claim 4, wherein said image forming apparatus forms a multi-color image. 11. The image forming apparatus according to claim 4, wherein the image forming apparatus includes an LED for exposing the photosensitive drum along the main scanning direction on the photosensitive drum. 12. The image processing apparatus further comprises means for storing input image information, and means for storing the stored image information in an Internet server as necessary and downloading the image information through a communication line. The image forming apparatus according to claim 1. 13. A predetermined test pattern image is formed by an image forming unit, and the formed image is read by a reading unit. The density distribution of the read image matches the density distribution of the formed test pattern image. A setting step of setting an image correction condition in the image forming unit. 14. The image forming method according to claim 13, wherein said setting step sets a correction condition for multi-valued image data.