JP2014102442A - Image forming apparatus, image forming system, and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of improving stability of gradation of an image.SOLUTION: In the case where a difference between a potential of a developing electrode of a developing device and an exposure potential of a photoreceptor drum of an image forming apparatus is Vdeve, and a difference between a potential of the developing electrode of the developing device and a charge potential of the photoreceptor drum is Vcf, when the image forming apparatus forms images while controlling density of the images with Vdeve, the image forming apparatus determines whether or not a contrast ratio (Vdeve/Vcf) falls within a predetermined range; and when the contrast ratio falls out of the range, the image forming apparatus increases the number of patch patterns for gradation correction and reduces an interval to create the patch patterns for gradation correction compared to the case where the contrast ratio falls within the range, so as to enhance gradation control.

Description

  The present invention relates to an image forming apparatus, an image forming system, and an image processing program.

  2. Description of the Related Art In recent years, electrophotographic image forming apparatuses such as color printers and color copying machines have been demanded to improve the gradation and stability of image density, which greatly affects the image quality of output images.

  However, in the image forming apparatus, the density of the obtained image fluctuates due to a change in environment, a change with time of the apparatus, or a variation in characteristics of the apparatus itself. In particular, in an electrophotographic image forming apparatus, it is important to ensure the stability of the density characteristics because there is a risk that the color balance may be lost even by a slight change in density.

  Therefore, a patch pattern for gradation correction is formed on the intermediate transfer member and the photosensitive drum with toner of each color so that a stable gradation characteristic can be obtained even if fluctuation occurs in each part of the image forming apparatus. The patch pattern density due to unfixed toner is optically detected by an optical sensor, and the detection result is used to control the density of the output image by feeding back image forming conditions such as exposure amount and development bias. Yes.

  In some cases, the density of a patch pattern for gradation correction transferred and fixed on a recording medium such as paper is optically detected by an optical sensor, and the image forming conditions are controlled based on the detection result.

  Further, as a control method at the time of image formation, a gradation correction chart for gradation correction of image data is recorded in advance, and the gradation correction chart is selected in accordance with the saturation histogram of the image data. There is also a method for performing optimum gradation control (see, for example, Patent Document 1).

JP 2010-171591 A

  An object of this invention is to provide the technique which can improve the stability of the gradation of an image.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a photosensitive member, a charging device for charging the surface of the photosensitive member, and a surface of the photosensitive member charged by the charging device. An exposure apparatus for exposing, a developing apparatus for forming an image on the surface of the photoconductor exposed by the exposure apparatus, and a difference between a potential of the developing electrode of the developing apparatus and an exposure potential of the photoconductor is a first voltage. And a ratio expressed by dividing the first voltage by the second voltage when the difference between the potential of the developing electrode of the developing device and the charged potential of the photosensitive member is the second voltage. And a control device that performs control that enhances the gradation control more than the range within the range.

  According to a second aspect of the present invention, in the first aspect of the invention, the enhancement of the gradation control may increase the number of gradation correction images detected in the generation of gradation correction data, or It is characterized in that it is performed by increasing the number of times of gradation correction image creation per time, or by combining both.

  According to a third aspect of the present invention, in the image forming system of the present invention, the image forming apparatus according to the first or second aspect and an image data output device that outputs image data to the image forming apparatus are connected via a communication line. And the image forming apparatus performs an image forming process on the acquired image data.

  According to a fourth aspect of the present invention, there is provided an image processing program according to the present invention, comprising: a charging process for charging a surface of a photoconductor; an exposure process for exposing the surface of the photoconductor charged by the charging process; and the exposure process. A developing process for forming an image on the exposed surface of the photoconductor, and a difference between a developing electrode potential of a developing device that forms an image on the surface of the photoconductor in the developing process and an exposure potential of the photoconductor 1 and the difference between the potential of the developing electrode of the developing device and the charged potential of the photoconductor is the second voltage, the first voltage is divided by the second voltage. Whether the ratio is within a predetermined range, and if it is out of the range, causes the computer to execute a control process for performing control to enhance gradation control more than in the range It is characterized by that.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus of the present invention, a photoconductor, a charging device for charging the surface of the photoconductor, and an exposure device for exposing the surface of the photoconductor charged by the charging device. A developing device that forms an image on the surface of the photoconductor exposed by the exposure device, an image discriminating device that discriminates the type of image formed on the surface of the photoconductor, and the potential of the developing electrode of the developing device. When the difference between the exposure potential of the photosensitive member is the first voltage and the difference between the potential of the developing electrode of the developing device and the charging potential of the photosensitive member is the second voltage, the first voltage is It is determined whether the ratio represented by dividing by the second voltage is within a predetermined range. If the ratio is outside the range, the ratio is determined according to the type of image determined by the image determination device. And a control device that performs control for enhancing gradation control. And butterflies.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the enhancement of the gradation control may increase the number of gradation correction images detected in the generation of gradation correction data, or It is characterized in that it is performed by increasing the number of times of gradation correction image creation per hour, or by combining both.

  According to a seventh aspect of the present invention, in the image forming system of the present invention, the image forming apparatus according to the fifth or sixth aspect and an image data output apparatus that outputs image data to the image forming apparatus are connected via a communication line. And the image forming apparatus performs an image forming process on the acquired image data.

  According to an eighth aspect of the present invention, there is provided an image processing program comprising: a charging process for charging a surface of a photoconductor; an exposure process for exposing the surface of the photoconductor charged by the charging process; and the exposure process. A development process for forming an image on the exposed surface of the photoconductor, an image discrimination process for determining the type of image formed on the surface of the photoconductor, and a development for forming an image on the surface of the photoconductor in the development process When the difference between the developing electrode potential of the apparatus and the exposure potential of the photosensitive member is a first voltage, and the difference between the developing electrode potential of the developing device and the charging potential of the photosensitive member is a second voltage. Determining whether the ratio expressed by dividing the first voltage by the second voltage is within a predetermined range; otherwise, it is determined by the image determination process. Enhance tone control according to the type of image A control step for controlling, characterized by having a.

  The image forming apparatus of the present invention described in claim 9 is a photoconductor, a charging device for charging the surface of the photoconductor, and an exposure device for exposing the surface of the photoconductor charged by the charging device. A developing device that forms an image on the surface of the photoconductor exposed by the exposure device, an image discriminating device that discriminates the type of image formed on the surface of the photoconductor, and the potential of the developing electrode of the developing device. When the difference between the exposure potential of the photosensitive member is the first voltage and the difference between the potential of the developing electrode of the developing device and the charging potential of the photosensitive member is the second voltage, the first voltage is The toner density according to the type of image by the image discriminating device so that the correction by the first voltage can be performed under the condition that the ratio represented by dividing by the second voltage is within a predetermined range. And a control device that performs control to change It is characterized in.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the control device determines whether a ratio between the first voltage and the second voltage is within a predetermined range. If it is out of the range, control for enhancing the gradation control is performed according to the type of the image determined by the image determination device.

  In the image forming apparatus according to claim 9 or 10, the enhancement of gradation control increases the number of gradation correction images detected in the generation of gradation correction data. Or the number of gradation correction image creations per unit time is increased, or a combination of both is performed.

  According to a twelfth aspect of the present invention, in the image forming system of the present invention, the image forming apparatus according to the ninth, tenth, or eleventh aspect and an image data output apparatus that outputs image data to the image forming apparatus are connected via a communication line. And the image forming apparatus performs an image forming process on the acquired image data.

  According to a thirteenth aspect of the present invention, there is provided an image processing program according to the present invention, comprising: a charging process for charging a surface of a photoconductor; an exposure process for exposing the surface of the photoconductor charged by the charging process; and the exposure process. A developing process for forming an image on the exposed surface of the photoconductor, an image determining process for determining the type of image formed on the surface of the photoconductor, and an image on the surface of the photoconductor in the developing process When the difference between the potential of the developing electrode of the developing device and the exposure potential of the photosensitive member is the first voltage, and the difference between the potential of the developing electrode of the developing device and the charged potential of the photosensitive member is the second voltage In addition, the image discrimination process allows the correction by the first voltage to be performed under the condition that the ratio expressed by dividing the first voltage by the second voltage is within a predetermined range. Depending on the type of image identified Characterized in that it and a control step of performing control to change the toner density Te.

  According to the first aspect of the present invention, it is possible to improve the stability of the gradation of the image as compared with the case where the present invention is not applied.

  According to the second aspect of the present invention, it is possible to improve the stability of the gradation of the image as compared with the case where the present invention is not applied.

  According to the third aspect of the present invention, it is possible to provide an image forming system capable of improving the stability of gradation of an image.

  According to the fourth aspect of the present invention, it is possible to provide an image processing program capable of improving the stability of gradation of an image.

  According to the fifth aspect of the present invention, it is possible to enhance gradation control suitable for the type of image.

  According to the sixth aspect of the invention, it is possible to enhance gradation control suitable for the type of image.

  According to the seventh aspect of the present invention, it is possible to provide an image forming system capable of enhancing gradation control suitable for the type of image.

  According to the eighth aspect of the present invention, it is possible to provide an image processing program capable of enhancing gradation control suitable for the type of image.

  According to the ninth aspect of the present invention, the image forming apparatus can be controlled in advance so as not to be in a control state in which the gradation is unstable during image formation.

  According to the tenth aspect of the present invention, it is possible to control in advance so as not to be in a control state in which the gradation becomes unstable during image formation, and to enhance gradation control suitable for the type of image. Is possible.

  According to the eleventh aspect of the present invention, the image forming apparatus can be controlled in advance so as not to be in a control state in which the gradation is unstable during image formation.

  According to the twelfth aspect of the present invention, it is possible to provide an image forming system capable of controlling the image forming apparatus in advance so as not to be in a control state in which gradation is unstable during image formation. .

  According to the thirteenth aspect of the invention, it is possible to provide an image processing program capable of controlling the image forming apparatus in advance so as not to be in a control state in which gradation is unstable during image formation. .

1 is a schematic configuration diagram of an image forming system according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a function level of the image forming system in FIG. 1. FIG. 2 is a schematic configuration diagram of a mechanism system of an image forming unit in the image forming apparatus of the image forming system in FIG. 1. FIG. 2 is a schematic configuration diagram of a toner amount sensor when a regular reflection method is applied to an image forming unit in the image forming apparatus of the image forming system in FIG. 1. FIG. 2 is a schematic configuration diagram of a toner amount sensor when a diffuse reflection method is applied to an image forming unit in the image forming apparatus of the image forming system in FIG. 1. FIG. 2 is a schematic configuration diagram of an inline sensor of an image forming unit in the image forming apparatus of the image forming system of FIG. 1. It is the figure which showed the relationship of the electric potential of Vdev and Vcf which control the density of an image. FIG. 3 is a flowchart of image density control of the image forming apparatus according to the first embodiment. FIG. 6 is a plan view of an example of a patch pattern for gradation correction that serves as a reference in first gradation control. It is a top view of an example of the patch pattern for gradation correction used as the reference in the second gradation control. FIG. 10 is a flowchart of image density control of the image forming apparatus according to the second embodiment. FIG. 6 is a graph showing a relationship between toner density and Vdev. FIG. 10 is a flowchart of image density control of an image forming apparatus according to a third embodiment.

  Hereinafter, an embodiment as an example of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  (First embodiment)

  FIG. 1 is a schematic configuration diagram of an image forming system 1 according to a first embodiment of the present invention.

  The image forming system 1 includes an image forming apparatus 10 and a computer 20. The image forming apparatus 10 includes an image processing apparatus 100 and an image output apparatus 200. When print data is received from the computer 20, the image forming apparatus 10 performs image processing and image forming processing based on the print data.

  The image processing apparatus 100 includes a data receiving unit 110, storage units 120 and 150, a PDL (Page Description Language: hereinafter referred to as PDL) interpretation unit 130, a drawing unit 140, an image data analysis unit 160, and an image processing unit 170. Yes.

  The data receiving unit 110 stores print data received (acquired) from the computer 20 in the storage unit 120. This print data is described in, for example, a page description language (PDL).

  The print data from the computer 20 is, for example, image data expressed in any one of the RGB color space, L * a * b * color space, CMY color space, and CMYK color space.

  The RGB color space means a color space composed of red, green, and blue colors.

  The L * a * b * color space is a device-independent color space (uniform color space) such as an image output device, for example, a CIE (International Lighting Mark Commission) L * a * b * color space color space. Means.

  The CMY color space means a color space composed of cyan, magenta, and yellow colors.

  The CMYK color space means a color space composed of cyan, magenta, yellow, and black colors.

  The PDL interpretation unit 130 interprets the PDL data stored in the storage unit 120 and outputs the interpretation result to the drawing unit 140.

  The drawing unit 140 performs drawing processing for each processing unit (for example, page) related to drawing based on the interpretation result of the received PDL data, and stores the result of the drawing processing in the storage unit 150. In addition, the drawing unit 140 notifies the image data analysis unit 160 and the image processing unit 170 that the drawing processing for each processing unit has been completed. Note that the drawing data resulting from the drawing processing by the drawing unit 140 is bitmap format (raster format) image data.

  The image processing unit 170 of the image processing apparatus 100 includes a color conversion unit 171, a gradation correction unit 172, and a halftone dot generation unit 173, and performs color conversion processing and gradation correction processing on received image data (drawing data). And halftone dot generation processing.

  In addition, the image processing unit 170 outputs the image data that has been subjected to the image processing to the image output apparatus 200.

  The image output device 200 includes an image output device control unit (an example of a control device) 210 and an image forming unit 220.

  The image output device control unit 210 outputs the image data from the image processing unit 170 to the image forming unit 220 and outputs a command to start the image forming process (image forming process start command) to the image forming unit 220. To do.

  The image output device control unit 210 also includes information on at least the surrounding environment (defined as environment information) of the image forming unit 220 that functions as an image forming unit that performs image forming processing, and image forming processing performed by the image forming unit 220. Information on paper quality (an example of a recording medium) on which the result of printing is printed (defined as paper information) and information on time-dependent characteristics of the image output apparatus 200 (specifically, information on time-dependent characteristics of the image forming unit 220: time-dependent characteristics) At least one piece of information (defined as information) is output to the image data analysis unit 160 of the image processing apparatus 100.

  The image forming unit 220 has a function of an image forming unit, executes an image forming process based on the received image data in accordance with the image forming process start command, and a print output result as a result of the image forming process (Paper on which the image is printed) is output.

  Next, FIG. 2 shows a schematic configuration of functional levels of the image forming system 1 of FIG.

  The image forming system 1 is configured by connecting an image forming apparatus 10 and a computer (an example of an image data output apparatus) 20 via a communication line 30.

  The computer 20 functions as a processing device (client device), such as a CPU (Central Processing Unit) 20C, a storage device 20M1 such as a hard disk, and a RAM (Random Access Memory). A memory 20M2 and a communication interface (hereinafter referred to as communication I / F) 20IF are provided.

  The storage device 20M1 stores various types of data such as application software that issues document generation and print requests, a printer driver, and print data (PDL data).

  The memory 20M2 stores programs and data read from the storage device 20M1.

  The communication I / F 20 IF is an interface that transmits and receives data to and from the image forming apparatus 10 via the communication line 30.

  The CPU 20C controls the entire computer 20, and reads and executes a printer driver from the storage device 20M1 to the memory 20M2, for example. As a result, print data (PDL data) is transmitted to the image forming apparatus 10.

  On the other hand, the image processing apparatus 100 of the image forming apparatus 10 includes a CPU 100C, a storage device 100M1, such as a hard disk, a RAM 100M2, a ROM 100M3, and a communication I / F 100IF.

  The storage device 100M1 stores various programs and data necessary for performing print processing, such as an image processing program (an example of an image processing program) PD that is software.

  The image processing program PD is stored in each of the PDL interpretation unit 130, the drawing unit 140, the image data analysis unit 160, and the image processing unit 170 (the color conversion unit 171, the gradation correction unit 172, and the halftone generation unit 173) illustrated in FIG. The program (software) for realizing the function of is included.

  The ROM 100M3 stores data necessary for image processing, such as default values of color parameters, gradation parameters, and halftone dot parameters, and color range information.

  The RAM 100M2 stores the image processing program PD read from the storage device 100M1, print data received via the communication I / F 100IF, and the like.

  In addition, at least the following storage areas (a) to (d) are allocated to the RAM 100M2.

  (A) A storage area (area for storing print data) that functions as the storage unit 120 in FIG.

  (B) A storage area (area for storing drawing data) that functions as the storage unit 150 in FIG.

  (C) A storage area functioning as a color parameter storage unit of the color conversion unit 171 in FIG. 1, a gradation parameter storage unit of the gradation correction unit 172, and a halftone dot parameter storage unit of the halftone generation unit 173 (respectively as default values) Parameter storage area). That is, it is a storage area for storing parameters as default values read from the ROM 100M3.

  (D) Storage areas required when the image processing unit 170 in FIG. 1 performs image processing (such as storage areas for storing color conversion processing, tone correction processing, screen processing processes and processing results) It is.

  The CPU 100C controls the entire image forming apparatus 10. For example, the CPU 100C reads the image processing program PD from the storage device 100M1 into the RAM 100M2 and executes it to generate high-quality image data and send it to the image output device 200. Output toward.

  The communication I / F 100IF is an interface that transmits / receives data to / from the computer 20 via the communication line 30. For example, the communication I / F 100IF receives print data transmitted from the computer 20.

  The communication line 30 includes a local area network (hereinafter abbreviated as “LAN”), a wired communication line such as a telephone line, a wireless communication line such as a wireless LAN, and a combination of these communication lines. Is mentioned.

  Here, a case has been described in which each function of the image processing apparatus 100 is realized and an image processing program including a program indicating the processing procedure of the image processing is recorded in a storage device such as a hard disk as a recording medium. A processing program may be provided as follows.

  That is, the image processing program may be stored in the ROM, and the CPU may load the program from the ROM to the main storage device and execute it.

  The image processing program may be stored and distributed in a computer-readable recording medium such as a DVD-ROM, CD-ROM, MO (magneto-optical disk), or flexible disk. In this case, after the image processing apparatus 100 installs the program recorded on the recording medium, the CPU executes the program. As an installation destination of this program, there is a memory such as a RAM or a storage device such as a hard disk. Then, the image processing apparatus 100 loads the program stored in the storage device to the main storage device and executes it as necessary.

  Further, the image processing apparatus 100 is connected to a computer such as a server apparatus or a host computer via a communication line (for example, the Internet), and the image processing apparatus 100 downloads the image processing program from the server apparatus or the computer. Later, this program may be executed. In this case, the download destination of the program includes a memory such as a RAM and a storage device (recording medium) such as a hard disk. Then, the image processing apparatus 100 loads the program stored in the storage device into the main storage device and executes it as necessary.

  Next, FIG. 3 shows a schematic configuration mainly of a mechanical system of the image forming unit 220 of the image output apparatus 200.

  The image forming unit 220 forms an image by a tandem intermediate transfer method, and a plurality of image forming units 40Y, 40M, and 40C in which toner images of respective color components are formed by an electrophotographic method (electrophotographic process). , 40K, and the toner images of the respective color components formed by the image forming units 40Y, 40M, 40C, 40K are sequentially transferred (primary transfer) to the intermediate transfer belt 50 that is circulated and driven (rotated) in the direction of arrow B in the figure. Primary transfer portions 41Y, 41M, 41C, and 41K.

  In addition, the image forming unit 220 includes a secondary transfer unit 60 that collectively transfers (secondary transfer) the toner image (superimposed toner image) transferred onto the intermediate transfer belt 50 onto a sheet (an example of a recording medium) P; A fixing device 70 for fixing the next transferred image on the paper P, and a toner amount sensor (Auto Development capability) for optically detecting a plurality of unfixed patch patterns for gradation correction transferred onto the intermediate transfer belt 50 (Control: hereinafter abbreviated as ADC) 80, and an in-line sensor (In Line Sensor: hereinafter abbreviated as ILS) 90 for optically detecting the plurality of patch patterns for gradation correction fixed on the paper P. I have.

  The image forming unit 40Y includes a photosensitive drum (an example of a photosensitive member) 42Y that rotates in the direction of arrow A in the drawing. Around the photosensitive drum 42Y, a charging device 43Y for charging the photosensitive drum 42Y along the rotation direction, and a laser exposure device 44Y for writing an electrostatic latent image on the photosensitive drum 42Y (in the drawing, an exposure beam) And a color component formed on the photosensitive drum 42Y, and a developing device 45Y that accommodates the toner of the corresponding color component and visualizes the electrostatic latent image on the photosensitive drum 42Y with the toner. Electrophotographic devices such as a primary transfer roll 46Y that transfers the toner image to the intermediate transfer belt 50 and a drum cleaner 47Y that removes residual toner on the photoreceptor drum 42Y are sequentially disposed. The image forming unit 40Y includes a toner cartridge (not shown) for supplying a developer to the developing device 45Y.

  Each of the image forming units 40M, 40C, and 40K has photosensitive drums 42M, 42C, and 42K similar to the photosensitive drum 42Y, and the photosensitive drums 42M, 42C, and 42K are surrounded by the photosensitive drums 42M, 42C, and 42K. Electrophotographic devices similar to the electrophotographic devices (charging device, laser exposure device, developing device, primary transfer roll, drum cleaner) corresponding to the body drum 42Y are sequentially arranged. The image forming units 40M, 40C, and 40K are provided with toner cartridges (not shown) for supplying developer to the developing devices 45M, 45C, and 45K.

  Each of the image forming units 40Y, 40M, 40C, and 40K described above is provided with yellow (Y), magenta (M), cyan (C), and black from the upstream side in the rotation direction of the intermediate transfer belt 50 (the arrow B direction in the figure). They are arranged in the order of (K). Each of the photosensitive drums 42Y, 42M, 42C, and 42K is configured to be able to contact and separate from the intermediate transfer belt 50.

  The primary transfer roll 46Y is disposed at a position facing the photosensitive drum 42Y with the intermediate transfer belt 50 interposed therebetween. A primary transfer voltage source 48Y that applies a primary transfer voltage (primary transfer potential) is connected to the primary transfer roll 46Y. The primary transfer roll 46Y and the primary transfer voltage source 48Y are components constituting the primary transfer portion 41Y.

  Similarly to the above, the primary transfer rolls 46M, 46C, 46K corresponding to the photosensitive drums 42M, 42C, 42K are also arranged at positions facing the corresponding photosensitive drums 42M, 42C, 42K with the intermediate transfer belt 50 interposed therebetween. Has been. Primary transfer voltage sources 48M, 48C, and 48K that apply primary transfer voltages (primary transfer potentials) are connected to the primary transfer rolls 46M, 46C, and 46K, respectively. The primary transfer roll and the primary transfer voltage source corresponding to each of the photoconductive drums 42M, 42C, and 42K are components constituting the primary transfer units 41M, 41C, and 41K, respectively.

  Primary transfer voltages (primary transfer potentials) from primary transfer voltage sources 48Y, 48M, 48C, and 48K are applied to the primary transfer rolls 46Y, 46M, 46C, and 46K, and a primary transfer current is supplied. The primary transfer rolls 46Y, 46M, 46C, and 46K generate a primary transfer bias when a primary transfer current is supplied, and the photosensitive drums 42Y, 42M, 42C, and 42K of the photosensitive drums 42Y, 42M, 42K, and 42C. , 42K is transferred to the intermediate transfer belt 50.

  The intermediate transfer belt 50 described above is a member that sequentially transfers (primary transfer) and holds the toner images of the respective color components formed by the image forming units 40Y, 40M, 40C, and 40K. The intermediate transfer belt 50 is formed in an endless shape in a state of being stretched over a plurality of support rolls and a backup roll 60a, and is rotated in the counterclockwise direction (the direction indicated by the arrow B). The toner images of 40Y, 40M, 40C, and 40K are subjected to primary transfer.

  The secondary transfer unit 60 described above is a mechanism unit for forming a full-color image by batch transfer (secondary transfer) of the toner images transferred onto the intermediate transfer belt 50 onto the paper P or the like. A backup roll 60a and a secondary transfer roll 60b are provided so as to face each other with the belt 50 interposed therebetween. In batch transfer, a voltage having the same polarity as the charging polarity of the toner is applied to the backup roll 60a, or a voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roll 60b. As a result, a transfer electric field is formed between the backup roll 60a and the secondary transfer roll 60b, and an unfixed toner image held on the intermediate transfer belt 50 is transferred onto the paper P or the like.

  The fixing device 70 has a function of fixing the toner image to the paper P or the like by applying heat and pressure to the paper P or the like on which the toner image has been transferred. And a pressure roll 70b for pressing P.

  The charging process, the exposure process, and the development process of the electrophotographic process are realized by the image forming units 40Y, 40M, 40C, and 40K (actually, the charging process is performed by the charging devices 43Y, 43M, 43C, and 43K, and the exposure process is performed by the laser. With the exposure devices 44Y, 44M, 44C and 44K, the development process is realized with the development devices 45Y, 45M, 45C and 45K, respectively.) The transfer process is performed with the primary transfer portions 41Y, 41M, 41C and 41K and the secondary transfer portions. The fixing process is realized by the fixing device 70.

  The above-described ADC sensor 80 is a sensor that optically reads a plurality of patch patterns for gradation correction serving as a reference transferred to the intermediate transfer belt 50. A plurality of patch patterns for gradation correction, which are standards at this stage, are unfixed. The reference plurality of patch patterns for tone correction will be described later.

  The ADC sensor 80 performs intermediate transfer from the primary transfer position of the last stage (primary transfer roll 46K) to the secondary transfer position (secondary transfer roll 60b) along the rotational direction of the intermediate transfer belt 50. A plurality of reference tone correction patch patterns transferred to the belt 50 are arranged at positions where they can be read optically and stably.

  The optical signal detected by the ADC sensor 80 is converted into an electric signal, transmitted to the image processing unit 170 shown in FIG. 1, and used as data for gradation correction in the gradation correction unit 172. Yes.

  Here, FIG. 4 and FIG. 5 show a schematic configuration of an example of the ADC sensor 80 using both the regular reflection method (see FIG. 4) and the diffuse reflection method (see FIG. 5). The arrows in FIGS. 4 and 5 indicate the direction of light.

  The ADC sensor 80 includes a light emitting element 80LA for regular reflection, a light emitting element 80LB for diffuse reflection, a light receiving element 80LC for both regular reflection and diffuse reflection, a reflection reference plate 80RS, and a shutter 80S.

  The light emitting elements 80LA and LB are configured by, for example, a near infrared LED (Light Emitting Diode), and the light receiving element 80LC is configured by, for example, a photodiode.

  As shown in FIG. 4, the ADC sensor 80 uses a regular reflection method for black toner that hardly diffusely reflects, and as shown in FIG. 5, diffuse reflection that can be read up to a high density for color toner. The method is to be used.

  Here, a case has been described in which a plurality of reference tone correction patch patterns transferred onto the intermediate transfer belt 50 are detected by the ADC sensor 80. Instead, the photosensitive drums 42Y, 42M, The ADC sensor 80 may detect a plurality of patch patterns for gradation correction that are developed on the 42C and 42K and serve as the reference.

  On the other hand, the ILS 90 shown in FIG. 3 is a sensor that optically reads a plurality of patch patterns for gradation correction serving as the reference, which are transferred from the intermediate transfer belt 50 to the paper P or the like and fixed by the fixing device 70.

  The ILS 90 discharges the paper P so that the plurality of reference patch patterns for gradation correction fixed on the paper P can be optically and stably read in the subsequent stage of the fixing device 70 (downstream of the conveyance of the paper P). It is arranged near the part. In the vicinity of the discharge portion of the paper P, the curl of the paper P is removed and the posture of the paper P is stabilized, so that the density and position of the image fixed on the paper P can be read with high accuracy.

  The optical signal detected by the ILS 90 is converted into an electrical signal, transmitted to the image processing unit 170 shown in FIG. 1, and used as gradation correction data in the gradation correction unit 172.

  Here, FIG. 6 shows a schematic configuration of an example of the ILS 90. The ILS 90 is a sensor for reading an image fixed on the sheet P being conveyed and extracting the image information. The ILS 90 is an irradiation unit 90A, a CCD (Charge Coupled Device) sensor 90B, an image forming unit 90C, and a sensor. And a calibration unit 90D.

  The irradiation unit 90A is a unit that irradiates light toward the paper P on which an image is recorded, and includes a pair of lamps 90A1 and 90A2. The pair of lamps 90 </ b> A <b> 1 and 90 </ b> A <b> 2 are configured by, for example, linear xenon lamps, and are disposed at positions facing the image forming surface of the paper P. The pair of lamps 90A1 and 90A2 is set such that the length of the irradiation range is larger than the width of the largest sheet P to be conveyed, and provides stable reading accuracy when the sheet P is traveling. A sufficient illumination depth is secured to obtain.

  The CCD sensor 90B is means for receiving the light irradiated from the irradiation unit 90A and reflected by the paper P, and detecting the image or the paper P itself based on the intensity of the received light. The light focused on the CCD sensor 90B is converted into an electrical signal corresponding to the image density, transmitted to the image processing unit 170 shown in FIG. 1, and used as data for gradation correction in the gradation correction unit 172. Is done.

  The imaging unit 90C is a unit that images the light emitted from the irradiation unit 90A and reflected by the paper P onto the CCD sensor 90B. The imaging unit 90C is configured by, for example, a reduction projection optical system without mechanical operation, and includes a plurality of reflecting mirrors 90C1, 90C2, 90C3 and a lens 90C4.

  The sensor calibration unit 90D is a means for setting various standards and the like when using the ILS 90 and at the time of calibration. For example, the sensor calibration unit 90D includes a polygonal cylindrical reference roll 90D1 in which eight or more surfaces are formed in the circumferential direction. . As a result, various inspection targets are mounted at the image reading position, and automatic calibration of the reading accuracy of the ILS 90 is performed to ensure the performance as a measuring device.

  Next, image density control in the image forming apparatus 10 will be described.

  FIG. 7 shows the potential relationship between Vdev (an example of the first voltage) and Vcf (an example of the second voltage) that control the image density.

  VH is a surface potential of the photosensitive drums 42Y, 42M, 42C, and 42K charged by the charging devices 43Y, 43M, 43C, and 43K, and is called a dark potential or a charged potential.

  The VL irradiates the surface of the photosensitive drums 42Y, 42M, 42C, and 42K charged by the charging devices 43Y, 43M, 43C, and 43K with the exposure beam Bm by the laser exposure devices 44Y, 44M, 44C, and 44K, and electrostatic latent. The surface potential of the photosensitive drums 42Y, 42M, 42C, and 42K lowered by forming an image is called a bright potential or an exposure potential.

  Vb is called a developing bias, and is the potential of the developing electrode (mag roll) of the developing devices 45Y, 45M, 45C, and 45K (that is, the voltage applied between the photosensitive drums 42Y, 42M, 42C, and 42K and the developing electrode). The potential that determines

  Vdev is a voltage that determines the amount of toner supplied to the surfaces of the photoconductive drums 42Y, 42M, 42C, and 42K (that is, a voltage that determines the density of an image fixed on the recording medium), and is represented by Vb−VL. The

  Vcf is called a cleaning field voltage and is represented by VH−Vb.

  Here, in the image forming apparatus 10, when Vdev is controlled to control the image density, the Vdev is changed while keeping the Vdev / Vcf ratio called a contrast ratio stable in order to stabilize the gradation. At the same time, it is desirable to control Vcf as well.

  However, when the value of Vcf becomes smaller than a certain threshold value, toner is placed on a blank paper portion, so-called image defect called fogging occurs. On the other hand, when the value of Vcf becomes larger than the above threshold value, a carrier is placed on the blank paper portion. Since an image defect called ground (hereinafter referred to as BCO) occurs, Vcf needs to be controlled within a certain limit.

  Of course, when Vdev also increases, an image quality defect (BCO in the image) in which the carrier is placed on the image portion is generated. However, in the region of the generally used Vdev / Vcf ratio (for example, about 3.0 to 2.0), Vcf Since this causes image defects first, Vcf cannot be changed.

  Thus, in order to control the change in the density of the image, the Vcf is usually changed in accordance with the change of the Vdev so that the ratio to the Vcf is within a predetermined range, but the density of the image is stabilized. When the amount of Vdev for control increases, Vcf cannot be changed due to the limitation of the occurrence of image defects, and the ratio of Vdev / Vcf is destroyed by density control due to the change of Vdev. As a result, the gradation (especially the reproducibility in the highlight portion) changes greatly compared to the case where the control is performed with a stable ratio of Vdev / Vcf. Note that the highlight portion is a low-density region of the image and is a bright portion or a portion that appears white.

  Therefore, in the first embodiment, the following is performed.

  FIG. 8 is a flowchart of image density control of the image forming apparatus 10 according to the first embodiment. Here, job information (including image density information such as the type of image) for image formation from the computer 20 (server apparatus or the like) in FIG. 1 is provided to the image forming apparatus 10 before image formation. The case is not assumed.

  First, normally, the potential is controlled so that the Vdev / Vcf ratio is in a predetermined range. Therefore, in step 500 of FIG. 8, it is determined that the Vdev / Vcf ratio is within a predetermined range. In this case, gradation control is performed by the first gradation control (step 501).

  Here, FIG. 9 shows a plan view of an example of a patch pattern PP for gradation correction which is a reference in the first gradation control. In FIG. 9, for easy understanding, the area ratio (Coverage in: hereinafter referred to as Cin) of the image (halftone dot) is shown in percentage on the right side of each patch pattern PP. It is not transferred or fixed.

  Here, a case where four rectangular patch patterns PP25, PP50, PP75, and PP100 are arranged at predetermined intervals along one direction is illustrated as a reference patch pattern PP for gradation correction. Has been.

  The patch patterns PP25, PP50, PP75, and PP100 have different densities and are arranged so as to gradually become darker (or lighter) along one direction. Although not particularly limited, for example, patch patterns PP25, PP50, PP75, and PP100 with Cin of 25%, 50%, 75%, and 100% are shown.

  The reference patch pattern PP for gradation correction is developed on the photosensitive drums 42Y, 42M, 42C, and 42K for each of yellow, magenta, cyan, and black, and is transferred to the intermediate transfer belt 50. Further, it is fixed on the paper P or the like.

  Note that when the Vdev / Vcf ratio is within a predetermined range, gradation control is not performed (that is, the first gradation control is performed, for example, the patch pattern PP for gradation correction is not provided). Not)).

  Next, in the control of the image density, even when Vcf is limited, the Vdev / Vcf ratio is destroyed (that is, in a state where the Vdev / Vcf ratio is changed), and the Vdev is changed (controlled). In some cases, the density is corrected.

  For example, when the Vdev / Vcf ratio is changed by changing the Vdev (only the Vdev is changed due to the restriction of the Vcf) as described above, the Vdev / Vcf ratio is equal to or greater than a predetermined threshold value. (When the Vdev / Vcf ratio increases to a level at which a change in gradation can be visually judged, or when the Vdev / Vcf ratio changes due to the limitation of Vcf and the rate of change in Vdev increases compared to Vcf) May be included).

  In this case, in step 500 of FIG. 8, it is determined that the Vdev / Vcf ratio is outside the predetermined range, so that it is possible to suppress deterioration in gradation due to density correction due to change of Vdev or In order to prevent this, the gradation control is performed by the second gradation control that is strengthened over the first gradation control (step 502). Thereby, the gradation of the image is improved.

  As a determination criterion in step 500, for example, a threshold value of the Vdev / Vcf ratio and a threshold value of a change amount of Vdev with respect to Vcf are determined and stored in advance, and are determined by comparison with them.

  Further, as the enhancement of gradation control, for example, firstly, the number of reference patch patterns for gradation correction (particularly, a highlight portion having a low density) is set as compared with the case of the first gradation control. Secondly, the interval for creating the patch pattern for tone correction is shortened compared to the case of the first tone control (that is, the number of times the patch pattern for tone correction is created per unit time is increased). Third, by combining these first and second, the gradation control is strengthened as a result as compared with the first gradation control.

  Here, FIG. 10 shows a plan view of an example of a patch pattern PP for gradation correction which is a reference in the second gradation control. In FIG. 10, for easy understanding, Cin (%) is shown on the right side of each patch pattern PP, but this is not actually transferred or fixed.

  Here, an example is shown in which patch patterns PP5, PP10, PP20, PP25, PP30, PP50, PP75, and PP100 with Cin 5%, 10%, 20%, 25%, 30%, 50%, 75%, and 100% are created. Therefore, the number of tone correction patch patterns PP (particularly, highlight portions with low density) is increased as compared with the case of FIG.

  As described above, according to the first embodiment, even when the control state of the image forming apparatus 10 becomes an unstable control state for obtaining a good gradation property, a decrease in the gradation property is predicted. By switching to the control for enhancing the gradation control, the stability of the image density / gradation property (particularly the color tone of a highlight portion having a low density) is improved.

  (Second Embodiment)

  In the second embodiment, the image processing apparatus 100 of the image forming apparatus 10 shown in FIG. 1 will form an image in the future based on the image density information of the job information for image formation stocked on the computer 20 side. An image discriminating apparatus for discriminating the type of the image.

  In the image forming apparatus 10, when the image density is controlled by breaking the Vdev / Vcf ratio, tone control is strengthened according to information such as the type of image acquired from the image processing apparatus 100. .

  Here, a case has been described in which the image processing apparatus 100 includes an image determination apparatus that determines the type of image, but the present invention is not limited to this, and the computer 20 itself includes an image determination apparatus that determines the type of image. It is also good.

  FIG. 11 is a flowchart of image density control of the image forming apparatus 10 according to the second embodiment. Here, job information for image formation (including image density information such as the type of image) is provided from the computer 20 (server apparatus or the like) to the image forming apparatus 10 before image formation. .

  First, if it is determined in step 500 in FIG. 11 that the Vdev / Vcf ratio is out of the predetermined range, the image needs to have gradation stability based on information such as the type of image acquired from the image processing apparatus 100. A determination is made (step 600).

  As a result, when the image type is an image that does not require much gradation stability, such as characters and line drawings, a third gradation that is the same as or stronger than the first gradation control. The gradation control is performed by the control (step 601). As a result, excessive enhancement of gradation control is suppressed or prevented, so that creation of an extra patch pattern PP is suppressed or prevented. For this reason, toner consumption is suppressed. Further, a decrease in image formation productivity is suppressed.

  On the other hand, in step 600 of FIG. 11, when the image type is an image that requires gradation stability, such as a gradation image, a photographic image, or a highlight image, the first gradation control and A fourth gradation control that is stronger than the third gradation control is performed (step 602). This improves the stability of density / gradation of an image that requires gradation stability, such as a gradation image, a photographic image, or a highlight image.

  Note that the enhancement of gradation is the same as described above, and thus the description thereof is omitted (see the description using FIGS. 8, 9 and 10, etc.).

  As described above, according to the second embodiment, when it is predicted that the control state of the image forming apparatus 10 becomes an unstable control state for obtaining good gradation, the image processing apparatus 100 is used. By enhancing the gradation control according to the information such as the image type acquired from the above, it is possible to enhance the gradation control suitable for the image type.

  (Third embodiment)

  In the third embodiment, similar to the second embodiment, the image processing apparatus 100 of the image forming apparatus 10 shown in FIG. An image discrimination device for discriminating the type of image to be formed in the future based on the image density information.

  In the image forming apparatus 10, before forming an image that requires gradation stability, the image type is set so that the correction by Vdev can be performed under the condition that the Vdev / Vcf ratio is within a predetermined range. The toner density is changed accordingly.

  Here, the case where the image processing apparatus 100 includes an image determination apparatus that determines the type of an image has been described. However, the present invention is not limited to this, and the computer 20 itself includes an image determination apparatus that determines the type of image. It is also good.

  The above toner density is the toner density at the toner adhesion portion of the toner image formed on the surface of the photosensitive drum 42Y, 42M, 42C, 42K by the developing devices 45Y, 45M, 45C, 45K. This is the amount per unit area of toner adhering to the exposed portions of the drums 42Y, 42M, 42C, and 42K.

  Next, FIG. 12 is a graph showing the relationship between toner density and Vdev.

  As described above, in the control of the image density and Vdev, the BCO occurs when Vdev is a certain value VdH or more, and the fogging occurs when the Vdev is a certain value VdL or less. The BCO occurs when the toner density is a certain value TCL or less, and the fog occurs when the toner concentration is a certain value TCH or more. Therefore, the toner density, Vdev, and the characteristic line CL (CLH, CLM, CLL) are within the range of the latitude (latitude: exposure latitude, area surrounded by a broken line in FIG. 12) LR between the toner density and Vdev. Control.

  Here, in the case of normal image formation, the characteristic line CLM is located at the center of the latitude range. Vdm indicates an intermediate Vdev value between VdL and VdH.

  However, in the formation of a low density image, since the toner circulates in the developing devices 45Y, 45M, 45C, and 45K, the charge amount of the toner increases, and the charging potential of the developing electrodes of the developing devices 45Y, 45M, 45C, and 45K. And the toner becomes difficult to be supplied to the photosensitive drums 42Y, 42M, 42C, and 42K, so that the characteristic line CLL is higher than the center of the range of the latitude LR.

  In the formation of a high-density image, new toner is supplied into the developing devices 45Y, 45M, 45C, and 45K. Therefore, the charge amount of the toner decreases, and the developing electrodes of the developing devices 45Y, 45M, 45C, and 45K are charged. Since the potential decreases and the toner is easily supplied to the photosensitive drums 42Y, 42M, 42C, and 42K, the characteristic line CLH becomes lower than the center of the range of the latitude LR.

  In any case, if the toner density is lowered, Vdev can be raised, and if the toner density is raised, Vdev can be lowered. Therefore, by changing the toner density, Vdev is controlled to form an image that requires gradation stability. Is controlled so that the ratio Vdev / Vcf falls within a predetermined range.

  Next, FIG. 13 shows a flowchart of image density control of the image forming apparatus 10 of the third embodiment. Also in this case, job information for image formation (including image density information such as image type) is provided to the image forming apparatus 10 from the computer 20 (server apparatus or the like) before image formation.

  First, before starting the image formation, it is determined whether or not the image needs gradation stability based on the image type information acquired from the image processing apparatus 100 in step 700 of FIG.

  As a result, if the image type does not require much tone stability, such as characters and line drawings, the process proceeds to image formation without changing the toner density (step 701).

  On the other hand, in step 700 of FIG. 13, when the image type requires gradation stability such as a gradation image, a photographic image, or a highlight image, the Vdev / Vcf ratio is determined in advance. Change the toner density so that it is within the range. Thus, Vcf or Vdev is controlled to be in a predetermined target state (step 702). The process proceeds to image formation in such a controlled state.

  Here, a target example of the value of Vcf or Vdev will be described with reference to FIG.

  Target example 1 (normal image: characteristic line CLM)

  The approximate center value of the change limit width of Vcf or the Vdev value corresponding thereto is used. For example, if the change limit width of Vcf is in the range of 90V to 130V, the approximate center value of Vcf is around 110V. As a result, considering that the Vdev / Vcf ratio is within a predetermined range, for example, if Vdev / Vcf is 3.0, the center of Vcf is 110V, and the Vdev value is near 330V. That is, in FIG. 12, VdL = 270V, VdH = 390V, and Vdm = 330V.

  Target example 2 (in the case of an image having a higher or lower density than a normal image: characteristic lines CLH and CLL)

  In the case of forming a high-density image, the developability becomes high during the image formation as described above. Therefore, in order to stabilize the density, it is expected that the Vdev is controlled to decrease. For this reason, the target Vcf or Vdev is set to be larger than that in the target example 1 described above.

  Further, when a low-density image is formed, the developability is lowered during the image formation as described above. Therefore, in order to stabilize the density, it is expected that the Vdev is controlled to increase. For this reason, the target Vcf or Vdev is set to be smaller than that in the target example 1 described above.

  By changing the toner density in this way, the Vdev / Vcf ratio can be stabilized in accordance with changes in developability during image formation.

  Next, if the Vcf value is restricted even if the toner density is controlled before the start of image formation as described above, it may be combined with the second embodiment.

  That is, if it is determined that Vdev / Vcf is outside the predetermined range (step 500 in FIG. 13), whether or not the image requires gradation stability based on the image type information acquired from the image processing apparatus 100. Is determined (step 600).

  As a result, if the image type does not require much gradation stability, such as characters and line drawings, the third gradation control is the same as or stronger than the first gradation control. Gradation control is performed (step 601). This suppresses or prevents the creation of an extra patch pattern PP, thereby suppressing toner consumption and a decrease in image formation productivity.

  Further, in step 600 of FIG. 13, if the image type requires gradation stability such as a gradation image, a photographic image, or a highlight image, the first gradation control and the third gradation control are performed. Fourth gradation control that is reinforced more than gradation control is performed (step 602). This improves the stability of the density / gradation of an image that requires gradation stability.

  Note that the enhancement of gradation is the same as described above, and thus the description thereof is omitted (see the description using FIGS. 8, 9 and 10, etc.).

  As described above, according to the third embodiment, the state of the image forming apparatus (the gradation is not controlled by the control of Vcf or Vdev) before starting the image formation based on the information of the image to be formed in the future acquired from the computer 20. By improving the stable state), the image forming apparatus 10 is controlled in advance so as not to be in a control state in which the gradation becomes unstable during image formation.

  Although the invention made by the present inventor has been specifically described based on the embodiment, the embodiment disclosed in this specification is an example in all respects and is limited to the disclosed technology. Should not be considered. That is, the technical scope of the present invention should not be construed restrictively based on the description in the above-described embodiment, but should be construed according to the description of the scope of claims. All modifications are included without departing from the technical scope equivalent to the described technique and the gist of the claims.

  For example, in the above-described embodiment, the case where the toner image transferred to the intermediate transfer belt is applied to an intermediate transfer type image forming apparatus that transfers to a sheet is described. However, the present invention is not limited to this. The toner image may be applied to a direct transfer type image forming apparatus that directly transfers the toner image to a recording medium such as paper. In this case, as described above, a plurality of patch patterns for gradation correction are developed on the photosensitive drum, and the patch patterns are detected by the ADC sensor.

  In the above-described embodiment, the case where the recording medium is applied to paper has been described. However, the present invention is not limited to this. For example, the present invention is applied to various forms on which an image is formed, such as a film and a postcard. Also good.

  In the above description, the case where the present invention is applied to a printer has been described. However, the present invention may also be applied to other image forming apparatuses such as a copying machine, a facsimile, or an image forming apparatus having these functions.

DESCRIPTION OF SYMBOLS 1 Image forming system 10 Image forming apparatus 20 Computer 30 Communication line 42Y, 42M, 42C, 42K Photosensitive drum 43Y, 43M, 43C, 43K Charging device 44Y, 44M, 44C, 44K Laser exposure apparatus 45Y, 45M, 45C, 45K Development Device 50 Intermediate transfer belt 60 Secondary transfer unit 70 Fixing device 80 ADC sensor 90 ILS
100 Image processing apparatus 100C CPU
100M1 storage device 100M2 RAM
100M3 ROM
170 Image Processing Unit 172 Gradation Correction Unit 200 Image Output Device 220 Image Forming Unit P Paper PD Image Processing Program PP Patch Pattern

Claims (13)

A photoreceptor,
A charging device for charging the surface of the photoreceptor;
An exposure device that exposes the surface of the photoreceptor charged by the charging device;
A developing device for forming an image on the surface of the photoreceptor exposed by the exposure device;
The difference between the potential of the developing electrode of the developing device and the exposure potential of the photoconductor is a first voltage, and the difference between the potential of the developing electrode of the developing device and the charging potential of the photoconductor is a second voltage. In the case, it is determined whether the ratio represented by dividing the first voltage by the second voltage is within a predetermined range. If the ratio is outside the range, the ratio is within the range. A control device that performs control to enhance gradation control more than,
An image forming apparatus comprising:   The enhancement of the gradation control may increase the number of gradation correction images detected in the generation of gradation correction data, increase the number of times of gradation correction image creation per unit time, or The image forming apparatus according to claim 1, wherein both are performed in combination.   3. The image forming apparatus according to claim 1 and an image data output apparatus that outputs image data to the image forming apparatus are connected via a communication line, and the image forming apparatus forms an image on the acquired image data. An image forming system for performing processing. A charging process for charging the surface of the photoreceptor;
An exposure process for exposing the surface of the photoreceptor charged by the charging process;
A development process for forming an image on the surface of the photoreceptor exposed by the exposure process;
The difference between the potential of the developing electrode of the developing device that forms an image on the surface of the photoconductor in the developing process and the exposure potential of the photoconductor is a first voltage, and the potential of the developing electrode of the developing device and the photoconductor When the difference between the charging potential and the second voltage is the second voltage, it is determined whether the ratio expressed by dividing the first voltage by the second voltage is within a predetermined range; In the case of out of the range, a control process for performing control to enhance the gradation control than in the case of the range;
An image processing program for causing a computer to execute. A photoreceptor,
A charging device for charging the surface of the photoreceptor;
An exposure device that exposes the surface of the photoreceptor charged by the charging device;
A developing device for forming an image on the surface of the photoreceptor exposed by the exposure device;
An image discrimination device for discriminating the type of image formed on the surface of the photoreceptor;
The difference between the potential of the developing electrode of the developing device and the exposure potential of the photoconductor is a first voltage, and the difference between the potential of the developing electrode of the developing device and the charging potential of the photoconductor is a second voltage. In this case, it is determined whether or not the ratio represented by dividing the first voltage by the second voltage is within a predetermined range. A control device that performs control to enhance gradation control according to the type of image determined;
An image forming apparatus comprising:   The enhancement of the gradation control increases the number of gradation correction images detected in the generation of gradation correction data and / or increases the number of times of gradation correction image creation per unit time. 6. The image forming apparatus according to claim 5, wherein the image forming apparatus is combined.   The image forming apparatus according to claim 5 or 6 and an image data output apparatus that outputs image data to the image forming apparatus are connected via a communication line, and the image forming apparatus forms an image on the acquired image data. An image forming system for performing processing. A charging process for charging the surface of the photoreceptor;
An exposure process for exposing the surface of the photoreceptor charged by the charging process;
A development process for forming an image on the surface of the photoreceptor exposed by the exposure process;
An image discrimination process for discriminating the type of image formed on the surface of the photoreceptor;
The difference between the potential of the developing electrode of the developing device that forms an image on the surface of the photosensitive member and the exposure potential of the photosensitive member in the developing process is a first voltage, and the potential of the developing electrode of the developing device and the photosensitive member When the difference from the charging potential is the second voltage, it is determined whether the ratio expressed by dividing the first voltage by the second voltage is within a predetermined range; In the case of out of range, a control process for performing control to enhance gradation control according to the type of image determined by the image determination process;
An image processing program comprising: A photoreceptor,
A charging device for charging the surface of the photoreceptor;
An exposure device that exposes the surface of the photoreceptor charged by the charging device;
A developing device for forming an image on the surface of the photoreceptor exposed by the exposure device;
An image discrimination device for discriminating the type of image formed on the surface of the photoreceptor;
The difference between the potential of the developing electrode of the developing device and the exposure potential of the photoconductor is a first voltage, and the difference between the potential of the developing electrode of the developing device and the charging potential of the photoconductor is a second voltage. The image discriminating apparatus so that the correction by the first voltage can be performed under the condition that the ratio represented by dividing the first voltage by the second voltage is within a predetermined range. A control device that performs control to change the toner density according to the type of image by
An image forming apparatus comprising:   The control device determines whether or not a ratio between the first voltage and the second voltage is within a predetermined range. If the ratio is outside the range, the image determined by the image determination device is determined. The image forming apparatus according to claim 9, wherein control for enhancing gradation control is performed according to a type of the image forming apparatus.   The enhancement of the gradation control may increase the number of gradation correction images detected in the generation of gradation correction data, increase the number of times of gradation correction image creation per unit time, or The image forming apparatus according to claim 9, wherein both are performed in combination.   12. The image forming apparatus according to claim 9, 10 or 11 and an image data output apparatus for outputting image data to the image forming apparatus are connected via a communication line, and the image forming apparatus performs processing on the acquired image data. An image forming system for performing an image forming process. A charging process for charging the surface of the photoreceptor;
An exposure process for exposing the surface of the photoreceptor charged by the charging process;
A development process for forming an image on the surface of the photoreceptor exposed by the exposure process;
An image discrimination process for discriminating the type of image formed on the surface of the photoreceptor;
The difference between the potential of the developing electrode of the developing device that forms an image on the surface of the photoconductor in the developing process and the exposure potential of the photoconductor is a first voltage, and the potential of the developing electrode of the developing device and the photoconductor When the difference from the charging potential of the first voltage is the second voltage, the first voltage is calculated under the condition that the ratio expressed by dividing the first voltage by the second voltage is within a predetermined range. A control process for performing control to change the toner density in accordance with the type of the image determined by the image determination process so that correction by the voltage of
An image processing program comprising:

Images