JP2023011238A - Image formation apparatus - Google Patents

Abstract

To provide an image formation apparatus which suppresses a variation in the hue of an image formed in the same job when executing the job in which the type of a recording medium and an instruction of a printing surface are mixed.SOLUTION: An image formation apparatus 101 comprises: a printer 107 which forms an image on a recording medium on the basis of an image formation condition; an image reading unit 241 which reads an image for adjustment of the image formation condition formed on the recording medium; and a CPU 222 which performs processing of determining a target value of the image formation condition on the basis of a result of reading of the image for adjustment by the image reading unit 241, adjusts the image formation condition on the basis of the target value and causes the printer 107 to form an image according to a job on the basis of the adjusted image formation condition. The CPU 222 determines the target value in correspondence with the combination of the type of the recording medium and an instruction of the printing surface for each page used in the job.SELECTED DRAWING: Figure 2

Description

The present invention relates to image forming apparatuses such as printers, copiers, facsimiles, and multi-function machines.

In recent years, the market for on-demand image forming apparatuses is expanding. For example, electrophotographic image forming apparatuses are becoming popular in the offset printing market. In addition, the market for on-demand image forming apparatuses of the ink-jet type image forming apparatus, which has been successfully developed in a wide range of markets due to its large format, low initial cost, ultra-high speed, etc., is expanding. However, expanding the market is not an easy task, and the image quality (hereinafter referred to as "image quality") of the preceding image forming apparatuses that have dominated the market must be maintained.

An electrophotographic image forming apparatus performs processing for improving the stability of image quality, for example, after warm-up at start-up. For example, an image forming apparatus forms an adjustment image for gradation correction on a recording medium such as paper and reads it with an image reading device such as a scanner. The image forming apparatus stabilizes the image quality by feeding back the reading result of the adjustment image to the image forming conditions such as the γ correction value. Gradation correction in an image forming apparatus is performed by correcting image forming conditions so that the gradation characteristics of the image forming apparatus match target gradation characteristics. In Japanese Patent Laid-Open No. 2002-100001, a belt-shaped pattern having a specific gradation and a predetermined length in the main scanning direction is formed on a recording medium, and feedback control is performed based on the results of reading the belt-shaped pattern at a plurality of positions. Disclosed is an image forming apparatus that suppresses the density unevenness of .

JP 2011-191414 A

The recording medium has different resistance values and surface properties depending on the type and brand (hereinafter simply referred to as "type"). Therefore, even if the amount of developer used for the image before being transferred to the recording medium is the same, a difference in image density occurs depending on the type of recording medium. Moreover, even if the recording media are of the same type, there may be a difference in the developed image density. For example, the number of times the recording medium passes through the fixing device differs between single-sided printing and double-sided printing. The fixing process by the fixing device affects the surface properties of the recording medium because it heats and presses the recording medium. For this reason, there may be a difference in the developed image density between single-sided printing and double-sided printing. Single-sided printing or double-sided printing is set according to the image forming mode. In order to cope with such changes in image density due to differences in recording medium characteristics, target gradation characteristics (target gradation) are set for each recording medium type and image forming mode.

For the target gradation, gradation characteristics acquired at the start of a job or at the time of switching between types of recording media and image forming modes are used. For this reason, when executing a job with mixed types of recording media or a job with mixed print side instructions such as single-sided printing and double-sided printing, even if it is a single job, the acquisition timing of the target gradation difference occurs. For example, in a job that prints on plain paper and thick paper, the target gradation for plain paper is set immediately before starting image formation on plain paper, and then the target gradation for thick paper is set when switching from plain paper to thick paper. is set.

In the image forming apparatus, there is a possibility that the internal state changes and the image density changes during the difference in acquisition timing of the target gradation. Changes in the internal state of the image forming apparatus include, for example, changes in development characteristics due to toner replenishment and changes in transfer characteristics due to changes in temperature and humidity. Due to changes in the internal state, the target gradation is not stable for each type of recording medium or for each image forming mode. This causes variations in color tone of images formed in the same job.

In view of the above problems, the present invention suppresses variations in the color tone of images formed within the same job even when executing a job that includes instructions on the type of recording medium and printing surface. An object of the present invention is to provide an image forming apparatus.

The image forming apparatus of the present invention comprises image forming means for forming an image on a recording medium based on image forming conditions, reading means for reading the image for adjusting the image forming conditions formed on the recording medium, and the reading means. determining a target value of an image forming condition based on the result of reading the adjustment image by the image forming means; adjusting the image forming condition based on the target value; and a control means for forming an image according to the job based on the target values, wherein the control means sets the target value in accordance with the combination of the instruction of the type of recording medium and the printing surface for each page used in the job. It is characterized by determining.

According to the present invention, it is possible to suppress variations in color tone of images formed in the same job even when executing a job in which instructions for the type of recording medium and print surface are mixed.

1 is a configuration diagram of an image processing system; FIG. FIG. 2 is a system configuration diagram for controlling the operation of the image processing system; 1 is a configuration diagram of an image forming apparatus; FIG. Explanatory drawing of CIS. FIG. 4 is an exemplary diagram of an adjustment chart; 4 is a 4th period chart for explaining how tones are reproduced. FIG. 10 is an exemplary diagram of analysis results of job data; Explanatory drawing of an operation pattern list. 4 is a flowchart representing image forming processing. 6 is a flowchart showing target tone acquisition processing; 4 is a flowchart showing target gradation update processing;

Hereinafter, embodiments will be described in detail with reference to the drawings.

(Image processing system)
FIG. 1 is a configuration diagram of an image processing system including an image forming apparatus of this embodiment. The image processing system includes an image forming apparatus 101 and an external controller 102 . The image forming apparatus 101 is, for example, a multi-function peripheral (MFP) or the like. The external controller 102 is, for example, an image processing controller, a digital front end (DFE), a print server, or the like.

The image forming apparatus 101 and the external controller 102 are communicably connected via an internal LAN (Local Area Network) 105 and a video cable 106 . The external controller 102 is connected to a client PC (Personal Computer) 103 via an external LAN 104 . The external controller 102 acquires a print instruction (print job) from the client PC 103 .

The client PC 103 is installed with a printer driver having a function of converting an image into a print description language that can be processed by the external controller 102 . A user can instruct printing via a printer driver using various applications. The printer driver transmits image data to the external controller 102 based on the job from the user. The external controller 102 receives a print job including image data from the client PC 103, performs data analysis and rasterization processing, and instructs the image forming apparatus 101 to perform printing (image formation) based on the image data.

The image forming apparatus 101 is configured by connecting a plurality of apparatuses having different functions, including a printing apparatus 107, and is capable of performing complicated print processing such as bookbinding. The image forming apparatus 101 of this embodiment includes a printing device 107 and a finisher 109 . The printing device 107 forms an image using a developer (for example, toner) on a recording medium fed from a paper feeding unit provided at the bottom of the main body. The printing device 107 forms yellow (Y), magenta (M), cyan (C), and black (K) images. A full-color image in which images of respective colors are superimposed is formed on the recording medium. A recording medium on which an image has been formed is conveyed from the printing apparatus 107 to the finisher 109 . The finisher 109 stacks recording media on which images are formed on the stack tray 332 .

This image processing system has a configuration in which an external controller 102 is connected to an image forming apparatus 101, but the external controller 102 is not necessarily required. For example, the image forming apparatus 101 may acquire a print job including image data directly from the client PC 103 via the external LAN 104 . In this case, the image forming apparatus 101 performs the data analysis and rasterization processing performed by the external controller 102 . That is, the image forming apparatus 101 and the external controller 102 may be integrated.

(System configuration)
FIG. 2 is a system configuration diagram for controlling the operation of the image processing system. Here, each system configuration of the image forming apparatus 101, the external controller 102, and the client PC 103 will be described.

-Printing Device The printing device 107 includes a communication interface (I/F) 217, a LAN I/F 218, and a video I/F 220 in order to communicate with other devices. The printing apparatus 107 includes a CPU (Central Processing Unit) 222 , a memory 223 , a storage 221 , an image reading section 241 and a job analysis section 226 in order to control the operation of the printing apparatus 107 . The printing device 107 includes an exposure unit 227, an image forming unit 228, a fixing unit 229, and a paper feeding unit 230 for forming an image. The printing device 107 includes an operation unit 224 and a display 225 as user interfaces. These components are communicatively connected to each other via a system bus 231 .

A communication I/F 217 is connected to the finisher 109 via a communication cable 279 and controls communication with the finisher 109 . When the printing apparatus 107 and the finisher 109 operate cooperatively, information and data are transmitted and received via the communication I/F 217 . LAN I/F 218 is connected to external controller 102 via internal LAN 105 and controls communication with external controller 102 . The printing device 107 receives job data such as print settings from the external controller 102 via the LAN I/F 218 . The print settings include instructions for the type of recording medium used for printing and instructions for single-sided/double-sided printing. Video I/F 220 is connected to external controller 102 via video cable 106 and controls communication with external controller 102 . The printing device 107 receives image data representing an image to be printed from the external controller 102 via the video I/F 220 .

The CPU 222 comprehensively controls image processing and printing by executing computer programs stored in the storage 221 . The memory 223 provides a work area when the CPU 222 executes various processes. When performing image forming processing (printing processing), the CPU 222 controls the exposure section 227 , the image forming section 228 , the fixing section 229 and the paper feeding section 230 .

The exposure section 227 includes a photoreceptor, charging wires that charge the photoreceptor, and a light source that exposes the photoreceptor to form an electrostatic latent image on the photoreceptor. The photosensitive member is, for example, a photosensitive belt having a photosensitive layer formed on the surface of a belt-like elastic member, or a photosensitive drum having a photosensitive layer formed on the surface of a cylinder. Also, a charging roller may be used instead of the charging wire. The exposure unit 227 charges the surface of the photoreceptor to a uniform negative potential with a charging wire. The exposure unit 227 outputs laser light from the light source based on image data. A laser beam scans the surface of a uniformly charged photoreceptor. As a result, the potential of the photoreceptor at the position irradiated with the laser light is changed, and an electrostatic latent image is formed on the surface of the photoreceptor. Four photoconductors are provided corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K). Electrostatic latent images corresponding to images of different colors are formed on the four photosensitive members.

The image forming unit 228 transfers the toner image formed on the photoreceptor onto a recording medium. The image forming section 228 includes a developing device, a transfer unit, and a toner supply section. The developing device deposits negatively charged toner from a developing cylinder onto an electrostatic latent image formed on the surface of the photoreceptor to form a toner image. Four developing devices are provided corresponding to the four colors of yellow (Y), magenta (M), cyan (C), and black (K). The developer visualizes the electrostatic latent image on the photoreceptor with toner of the corresponding color. When the amount of toner inside the developing device becomes insufficient due to the formation of the toner image, the toner is replenished by the toner replenishing unit.

The transfer unit has an intermediate transfer belt, and transfers toner images from each photoreceptor to the intermediate transfer belt. A primary transfer roller is provided at a position facing the photosensitive member with the intermediate transfer belt interposed therebetween. By applying a positive potential to the primary transfer roller, toner images are superimposed and transferred onto the intermediate transfer belt from each of the four photoreceptors. Thereby, a full-color toner image is formed on the intermediate transfer belt. A toner image formed on the intermediate transfer belt is transferred onto a recording medium by a secondary transfer roller, which will be described later. The secondary transfer roller transfers a full-color toner image from the intermediate transfer belt to the recording medium by being applied with a positive potential.

A fixing unit 229 fixes the transferred toner image on the recording medium. The fixing section 229 has a heater and a pair of rollers. The fixing unit 229 melts and fixes the toner image on the recording medium by heating and pressing the toner image on the recording medium with a heater and roller pair. An image is thereby formed on the recording medium. The paper feeding unit 230 includes a conveying roller and various sensors on a conveying path, and controls the feeding operation of the recording medium.

The image reading unit 241 reads an image formed on the conveyed recording medium based on an instruction from the CPU 222 . For example, when adjusting the image forming conditions, the CPU 222 uses the image reading unit 241 to read an image for adjusting the image forming conditions formed on the recording medium. A job analysis unit 226 analyzes setting information of the image forming apparatus 101 and print data and job data received from the external controller 102 . The operation unit 224 is an input device that receives various setting inputs and operation instructions from the user. The operation unit 224 is, for example, various input keys and a touch panel. A display 225 is an output device that displays setting information of the image forming apparatus 101 and the processing status (status information) of a print job.

Finisher The finisher 109 is, for example, a large-capacity stacker. The finisher 109 has a communication I/F 271 , a CPU 272 , a memory 273 , and a paper ejection control section 274 . These components are communicatively connected to each other via system bus 275 . A communication I/F 271 is connected to the printing device 107 via a communication cable 279 and controls communication with the printing device 107 . When the finisher 109 and the printing apparatus 107 operate cooperatively, information and data are transmitted and received via the communication I/F 271 . The CPU 272 executes a control program stored in the memory 273 and performs various controls necessary for paper ejection. The memory 273 stores control programs. Also, the memory 273 provides a work area when the CPU 272 executes various processes. The paper ejection control unit 274 ejects the transported recording medium to the stack tray 332 based on the instruction from the CPU 272 .

- External Controller The external controller 102 is provided with a LAN I/F 213, a LAN I/F 214, and a video I/F 215 in order to communicate with other devices. The external controller 102 comprises a CPU 208 , memory 209 and storage 210 to control the operation of the external controller 102 . The external controller 102 has a keyboard 211 and a display 212 as user interfaces. These components are communicatively connected to each other via system bus 216 .

A LAN I/F 213 is connected to the client PC 103 via the external LAN 104 and controls communication with the client PC 103 . The external controller 102 acquires a print job from the client PC 103 via the LAN I/F 213 . A LAN I/F 214 is connected to the printer 107 via the internal LAN 105 and controls communication with the printer 107 . The external controller 102 transmits job data and the like to the printing device 107 via the LAN I/F 214 . A video I/F 215 is connected to the printing device 107 via the video cable 106 and controls communication with the printing device 107 . The external controller 102 transmits image data to the printing device 107 via the video I/F 215 .

By executing a computer program stored in the storage 210 , the CPU 208 comprehensively performs processing such as reception of image data transmitted from the client PC 103 , RIP processing, and transmission of image data to the image forming apparatus 101 . A memory 209 provides a work area when the CPU 208 executes various processes. The keyboard 211 is an input device that receives input of various settings and operation instructions from the user. The display 212 is an output device that displays information on the application executed by the external controller 102 in the form of still images or moving images.

・Client PC
The client PC 103 has a CPU 201 , memory 202 , storage 203 , keyboard 204 , display 205 and LAN I/F 206 . These components are communicatively connected to each other via a system bus 207 .

The CPU 201 controls operations of the client PC 103 by executing computer programs stored in the storage 203 . In this embodiment, the CPU 201 performs image data creation and print job transmission processing. The memory 202 provides a work area when the CPU 201 executes various processes. Keyboard 204 and display 205 are user interfaces. The keyboard 204 is an input device that receives instructions from the user. A display 205 is an output device that displays information about an application executed by the client PC 103 in the form of still images or moving images. LAN I/F 206 is connected to external controller 102 via external LAN 104 and controls communication with external controller 102 . The client PC 103 transmits a print job to the external controller 102 via the LAN I/F 206 .

Note that the external controller 102 and the image forming apparatus 101 are connected by the internal LAN 105 and the video cable 106, but any configuration is sufficient as long as the data necessary for printing can be transmitted and received. may be The memory 202, the memory 209, the memory 223, and the memory 273 may be storage devices for holding data and programs, respectively. For these memories, for example, volatile RAM (Random Access Memory), non-volatile ROM (Read Only Memory), storage, USB (Universal Serial Bus) memory, etc. can be used.

(Configuration of image forming apparatus)
FIG. 3 is a configuration diagram of the image forming apparatus 101. As shown in FIG. A display 225 is provided on the top of the housing of the printing device 107 . A display 225 displays the printing status of the image forming apparatus 101 and information for setting. A recording medium on which an image has been formed by the printing device 107 is conveyed to a finisher 109 provided in the subsequent stage.

The printing apparatus 107 includes, as a paper feed unit 230, a plurality of paper feed decks 301 and 302, transport paths 303, 312, 314, 315, and 323, a reverse path 316, a double-sided transport path 317, a downstream transport path 325, an ejection path 326, and various rollers. Each paper feed deck 301, 302 can accommodate different types of recording media. The uppermost sheet of the recording media accommodated in each of the paper feed decks 301 and 302 is separated and fed to the transport path 303 . The printing apparatus 107 includes image forming units 304 , 305 , 306 , and 307 for forming images as an exposure unit 227 . The printing device 107 forms color images. Therefore, the image forming unit 304 forms a black (K) image (toner image). The image forming unit 305 forms a cyan (C) image (toner image). The image forming unit 306 forms a magenta (M) image (toner image). The image forming unit 307 forms a yellow (Y) image (toner image).

The printing apparatus 107 includes an intermediate transfer belt 308 and a secondary transfer roller 309 to which toner images are transferred from the image forming units 304 , 305 , 306 , and 307 as the image forming unit 228 . The intermediate transfer belt 308 rotates clockwise in FIG. Thereby, a full-color toner image is formed on the intermediate transfer belt 308 . The intermediate transfer belt 308 conveys the toner image to the secondary transfer roller 309 by rotating. The recording medium is conveyed to the conveying path 303 in synchronization with the timing at which the toner image is conveyed to the secondary transfer roller 309 . A secondary transfer roller 309 transfers the toner image on the intermediate transfer belt 308 onto the conveyed recording medium.

The printing apparatus 107 includes a first fixing device 311 and a second fixing device 313 as the fixing unit 229 . The first fixing device 311 and the second fixing device 313 have the same configuration, and fix the toner image on the recording medium. Therefore, the first fixing device 311 and the second fixing device 3 each have a pressure roller and a heating roller. A recording medium is nipped and conveyed by a pressure roller and a heating roller. At that time, the recording medium is heated and pressurized to melt and press the toner image. The recording medium that has passed through the second fixing device 313 is transported to a transport path 314 . The second fixing device 33 is arranged downstream of the first fixing device 311 in the conveying direction of the recording medium. used to ensure sexuality. Therefore, the second fixing device 313 may not be used depending on the type of recording medium and the content of the print job. A transport path 312 is provided to transport the recording medium fixed by the first fixing device 311 without passing through the second fixing device 313 .

After the transport path 314 and the transport path 312 merge, a transport path 315 and a reverse path 316 are provided. When double-sided printing is instructed, the recording medium is conveyed to the reverse path 316 . The recording medium conveyed to the reversing path 316 is reversed in the conveying direction by the reversing path 316 and conveyed to the double-sided conveying path 317 . The image-formed surface (first surface) of the recording medium is reversed by the reversing path 316 and the double-sided conveying path 317 . The recording medium is transported to the transport path 303 by the double-sided transport path 317 and passes through the secondary transfer roller 309 and the fixing unit 229 to form an image on the second surface.

When the face-up mode is instructed in single-sided printing, or when images are formed on both sides in double-sided printing, the recording medium is transported to transport path 315 . A transport path 323 is arranged downstream of the transport path 315 in the transport direction of the recording medium.
When the face-down mode is specified for single-sided printing, the print medium is conveyed to the reverse path 316 . The recording medium conveyed to the reversing path 316 is reversed in the conveying direction by the reversing path 316 and conveyed to the conveying path 323 . Once transported to the reversing path 316 , the recording medium is reversed with the image-formed side (first side) and transported to the transporting path 323 with the image-printed surface facing downward.

Contact Image Sensors (CIS) 321 and 322 as an image reading unit 241 are arranged on the transport path 323 so as to face each other with the transport path 323 interposed therebetween. FIG. 4 is an explanatory diagram of the CISs 321 and 322. As shown in FIG. The CIS 321 is an optical sensor that reads an image of the upper surface of the recording medium conveyed through the conveying path 323 . The CIS 322 is an optical sensor that reads an image of the bottom surface of the recording medium conveyed through the conveying path 323 .

The CIS 321 includes an LED (Light Emitting Diode) 350 as a light source and a reading sensor 351 as a light receiving portion. The LED 350 irradiates the upper surface of the recording medium with light at the timing when the recording medium conveyed on the conveying path 323 reaches the reading position. The reading sensor 351 includes a plurality of light receiving elements (photoelectric conversion elements) arranged in a direction perpendicular to the conveying direction of the recording medium. Therefore, the direction perpendicular to the conveying direction of the print medium is the main scanning direction of the CIS 321 . The reading sensor 351 receives reflected light from the recording medium with a light receiving element. A plurality of light receiving elements of the reading sensor 351 output an output value (electrical signal) based on the intensity of the received reflected light. Output values (electrical signals) output from the plurality of light receiving elements are transmitted to the CPU 222 . The image thus formed on the recording medium is read.

The CIS 322 has the same configuration as the CIS 321 and has an LED 353 and a reading sensor 354 . The CIS 322 operates in the same manner as the CIS 321 and reads an image formed on the bottom surface of the recording medium at the timing when the recording medium conveyed on the conveying path 323 reaches the reading position. In addition to the CISs 321 and 322, the image reading unit 241 can also be realized by a CCD or CMOS sensor.

The printing apparatus 107 of this embodiment can form adjustment images for adjusting image forming conditions on both sides of a recording medium. A recording medium on which an adjustment image is formed is called an adjustment chart. The printing device 107 prints the adjustment image on a recording medium to create an adjustment chart, and the CIS 321 and CIS 322 read the adjustment image. The results of reading the adjustment chart by the CIS 321 and CIS 322 are stored in the memory 223 . The CPU 222 refers to the memory 223, analyzes the results of reading by the CIS 321 and CIS 322, feeds them back to the image forming conditions, and adjusts the image forming conditions.

For example, when the temperature inside the printing apparatus 107 rises, the image density of the image formed on the recording medium fluctuates compared to when the temperature inside the printing apparatus 107 is low. The printing apparatus 107 creates an adjustment chart and detects the image density of the adjustment image based on the reading results of the CISs 321 and 322 . The CPU 222 acquires the variation amount of the detected image density with respect to the target image density, and adjusts the image forming conditions based on this variation amount. The CPU 222 converts the image data based on the image forming conditions. The printing apparatus 107 forms an image on a recording medium based on the image data converted by the CPU 222, thereby controlling the image density of the image formed on the recording medium. As a result, the printing apparatus 107 can suppress fluctuations in the image density of images caused by fluctuations in the internal temperature.

For example, the printing apparatus 107 adjusts the image density to the target image density by controlling the emission intensity of the light source of the exposure unit 227 based on the adjusted image forming conditions. Alternatively, the CPU 222 generates a one-dimensional gradation correction table for suppressing variations in image density based on the reading result of the CIS 321 (or CIS 322). The CPU 222 converts the image data based on the gradation correction table. The printing apparatus 107 forms an image on a recording medium based on the image data converted by the CPU 222, thereby adjusting the image density of the printing apparatus 107 to an ideal image density.

The adjustment image formed on the adjustment chart may be an image for detecting the geometric characteristics of the image or an image for detecting color misregistration, in addition to the image for detecting the image density. The geometric characteristics of the image are, for example, the perpendicularity, the print position of the image with respect to the recording medium, and the like. When the adjustment image for detecting the geometrical characteristics of the image is formed, the CPU 222 adjusts the image forming conditions to suppress variations in the geometrical characteristics based on the reading result of the CIS 321 (or CIS 322). The CPU 222 controls the light emission timing of the light source of the exposure unit 227 based on the image forming conditions, thereby adjusting the geometric characteristics of the image to ideal geometric characteristics.

Further, when an adjustment image for detecting color misregistration is formed, the CPU 222 detects color misregistration based on the reading result of the CIS 321 (or CIS 322). The CPU 222 adjusts the image forming conditions to suppress the color shift based on the detected color shift. The CPU 222 controls the position of the image formed on the photosensitive member by the exposure unit 227 based on the image forming conditions, thereby correcting the color misregistration.

The adjustment chart is excluded so as not to contaminate the printed matter corresponding to the print job. For this purpose, the printing apparatus 107 includes a flapper 324 , an ejection path 326 , a transport sensor 327 and an ejection tray 328 . The adjustment chart whose adjustment image has been read by the CISs 321 and 322 is conveyed to a discharge path 326 by a flapper 324 . The print medium conveyed to the ejection path 326 is ejected to an ejection tray 328 .

If the recording medium is not the adjustment chart, the recording medium is conveyed from the conveying path 323 to the downstream conveying path 325 by the flapper 324 . The print medium transported to the downstream transport path 325 is delivered to the finisher 109 . Note that when the printer 107 receives a notification of the occurrence of a transport jam from the finisher 109, the printer 107 switches the flapper 324 to the discharge path 326 side, regardless of whether the chart is for adjustment, and completes all the recordings in the machine. Eject the media (remaining paper) to the ejection tray 328 . By discharging the residual paper to the discharge tray 328, the user's load of jam processing is reduced.

A finisher 109 can stack recording media delivered from the printing apparatus 107 . The finisher 109 includes a transport path 331 and a stack tray 332 on which recording media are stacked. Transport sensors 333 , 334 , 335 , and 336 are provided on the transport path 331 . A recording medium transported from the printing apparatus 107 is stacked on a stack tray 332 via a transport path 331 . Conveyance sensors 333 , 334 , 335 , and 336 detect passage of the recording medium conveyed through the conveyance path 331 . The CPU 272 detects a transport jam ( transport error) has occurred. In this case, the CPU 272 notifies the printing apparatus 107 that a transport jam has occurred.

(Adjustment image)
FIG. 5 is an exemplary diagram of an adjustment chart. This adjustment chart 500 is conveyed in the longitudinal direction of the adjustment chart 500 . An adjustment image 501 for image density correction is formed for each color on one surface of the recording medium. The adjustment image 501 may be formed anywhere on the periphery of the recording medium. In this embodiment, the adjustment images 501 are formed at both ends of the print medium in a direction perpendicular to the transport direction of the print medium (short direction of the print medium). That is, the two-color adjustment image 501 is formed at one end of the print medium in the width direction, and the remaining two-color adjustment image 501 is formed at the other end in the width direction of the print medium. In this embodiment, cyan and magenta adjustment images 501C and 501M are formed at one end of the print medium in the width direction, and yellow and black adjustment images 501Y and 501K are formed at the other end in the width direction of the print medium. formed in As a result, the adjustment image 501 is not formed at the leading end of the recording medium in the conveying direction, and it is possible to more reliably suppress the occurrence of winding of the recording medium during the fixing process.

The adjustment image 501 is composed of a plurality of test images (11 gradations in FIG. 5) in which the gradation value of each color is changed stepwise. Each of the plurality of test images has, for example, a square shape with a side of approximately 8 [mm], and is arranged in a line in the transport direction. As for the test images of each color, test images for detecting the texture of the recording medium (that is, test images with a gradation value of 0) are arranged at both ends of a row of other test images. Nine test images with evenly assigned gradation values are arranged between test images with 0 gradation values. When the gradation values are represented by 0 to 255, the adjustment image 501 is made up of test images with gradation values of 0, 16, 32, 64, 86, 104, 128, 176, 224, 255, and 0. Configured. Note that the adjustment image 501 is not limited to yellow, magenta, cyan, and black, and may be composed of red, green, and blue, or process black. Also, the size and order of gradation are not limited.

(Image density correction)
FIG. 6 is a 4-limit chart for explaining how tones are reproduced. Quadrant I represents the relationship between the image density of the image to be printed (original image) and the input value (density signal) of the image data representing the image. Quadrant II represents a conversion condition (γLUT) for converting the density signal into a laser output signal representing the amount of laser light output from the exposure unit 227 . Quadrant III represents the gradation characteristics (printer characteristics) of the printing apparatus 107, which indicate the relationship between the laser output signal and the density of the image formed on the recording medium (image density). Quadrant IV shows the relationship between the image density of the original image and the image density of the image formed on the recording medium. That is, the 4-limit chart shows the total gradation reproduction characteristics of the printing apparatus 107 shown in FIG.

The printing apparatus 107 generates conversion conditions (γLUT) for the second quadrant so that the image density of the original image and the image density of the recording medium have an ideal relationship (linear relationship). Therefore, when the γLUT is generated based on the reading results of the reading sensors 351 and 353, the CPU 222 obtains the gradation characteristics from the reading results of the adjustment image 501, and adjusts the gradation characteristics so that the gradation characteristics become ideal gradation characteristics. to generate a γLUT. The image signal whose gradation characteristics have been converted by the γLUT is converted into a pulse signal corresponding to the dot width by a pulse width modulation (PWM) circuit of the laser driver and sent to the laser driver that drives and controls the exposure unit 227 . In this embodiment, a gradation reproduction method based on pulse width modulation is used for all colors of yellow, magenta, cyan, and black.

An electrostatic latent image having predetermined gradation characteristics is formed on the photosensitive drum by scanning the laser beam output from the exposure unit 227, the gradation being controlled by changing the dot area. This electrostatic latent image is developed into a toner image, which is transferred and fixed on a recording medium to reproduce a gradation image.

(Image density correction processing)
In this embodiment, the CPU 222 of the printing apparatus 107 creates an operation pattern list based on the analysis result of the job data received from the external controller 102 by the job analysis unit 226 . The job data is data including instructions for the type of recording medium and image forming mode for each page used in the print job. The image forming mode indicates the printing surface such as single-sided printing or double-sided printing. FIG. 7 is an exemplary diagram of analysis results of job data. FIG. 8 is an explanatory diagram of an operation pattern list.

The analysis result of the job data in FIG. 7 is a combination of the page ID, the type of recording medium, and the image forming mode (printing surface). The page ID is identification information of each page printed in one print job. The "first plain paper" and the "second plain paper" of the recording medium are plain paper of the same paper type, but different brands. The image forming mode "FU" indicates the face-up mode, and "FD" indicates the face-down mode.

The CPU 222 merges overlapping patterns into one with respect to such a combination of the type of recording medium and the instruction of the image forming mode (printing surface) for each page. The operation pattern list in FIG. 8 is a list of patterns of combinations of instructions for the type of recording medium and the image forming mode (printing surface). The operation pattern list has areas for storing corresponding page IDs and target gradations determined by target gradation determination processing described later. The target gradation is a target value for gradation correction.

The CPU 222 performs image density correction for all combinations (all patterns) of the operation pattern list before starting to print an image (hereinafter referred to as a “user image”) formed according to a job on a recording medium. , the target gradation (γLUT) is determined. Thereafter, the CPU 222 prints the user image on the recording medium while correcting the image density using the determined γLUT.

FIG. 9 is a flow chart showing the image forming process of this embodiment. The external controller 102 acquires the print job from the client PC 103, extracts the type of printing medium used in the print job and the instruction of the image forming mode for each page, and creates job data. The external controller 102 transmits the created job data to the printing device 107 .

The CPU 222 waits until job data is received from the external controller 102 (S901: N). When job data is received (S901: Y), the CPU 222 performs target tone acquisition processing, which will be described later. Thereby, the target gradation corresponding to each pattern in the operation pattern list is determined. After determining the target gradation, the CPU 222 sets a count value C for measuring the execution interval of the target gradation acquisition process to 0 (S903).

The CPU 222 refers to the operation pattern list and acquires the target gradation corresponding to the page ID (S904). For example, when using the operation pattern list of FIG. 8, the CPU 222 acquires the target gradation of the pattern with list number 1 when forming the image of the first page. If there is a change from the already acquired target gradation (S905: Y), the CPU 222 adjusts the image density according to the target gradation acquired in the process of S904, and performs the printing process of the user image (S906, S907). ). If there is no change from the already acquired target gradation (S905: N), the CPU 222 skips the processing of S906 and performs the printing processing of the user image (S907).

For example, when forming the image of the second page, in the example of FIG. 8, the target gradation is changed from the target gradation of the list number 1 pattern to the target gradation of the list number 2 pattern. In this case, the processing of S906 is performed. Further, for example, when forming the image of the third page, the target gradation remains the target gradation of the pattern with the list number of 2 in the example of FIG. In this case, the processing of S906 is skipped.

When the printing process ends, the CPU 222 adds 1 to the count value C (S908). The CPU 222 determines the end of the print job (S909). If the print job has not ended (S909: N), the CPU 222 determines whether or not the count value C has exceeded a predetermined value (S901). The predetermined value is assumed to be 1000 here. If the count value C is equal to or less than the predetermined value (1000 or less) (S910: N), the CPU 222 repeats the processing from S904 onwards.

When the count value C exceeds a predetermined value (exceeds 1000) (S910: Y), the CPU 222 performs target gradation update processing, which will be described later (S911). As a result, the target gradation of each pattern in the operation pattern list is updated. After updating the target gradation, the CPU 222 sets the count value C to 0 (S903), and repeats the processes after S904. In this manner, the target gradation is updated each time printing is performed on a predetermined number of recording media. Note that the predetermined value is not limited to 1000 and can be freely set by the user. Note that the update interval of the target gradation is not limited to the number of printed recording media, and may be set in terms of time. For example, the target gradation may be updated every time a predetermined time elapses after the target gradation is determined.

The CPU 222 repeats the above processing until it determines in the processing of S909 that the job has ended (S909: Y).

FIG. 10 is a flowchart showing the target gradation acquisition process of S902. The CPU 222 creates an operation pattern list and determines the target gradation of each pattern in the operation pattern list by the target gradation acquisition process.

The CPU 222 causes the job analysis unit 226 to analyze the job data received in the process of S901 (S1001). The CPU 222 creates an operation pattern list as illustrated in FIG. 8 based on the analysis result of the job data (S1002). The CPU 222 acquires the number of patterns (listMax) in the motion pattern list (S1003). In the example of FIG. 8, the number of patterns is five. The CPU 222 initializes the list number (listNo.) used for searching the operation pattern list to 1 (S1004). Based on the operation pattern list, the CPU 222 determines target gradations for all combinations of printing medium types and image forming mode instructions (S1005 to S1019). Here, the operation pattern list in FIG. 8 is used as an example to describe the process of determining the target gradation.

First, the CPU 222 determines whether or not the face-up mode (FU) is set as the image forming mode for the pattern with list number 1 (listNo.=1) (S1005). In the example of FIG. 8, the image forming mode of the pattern with list number 1 is FU (S1005: Y). Thick paper is registered as the recording medium of the pattern with list number 1 . Therefore, the CPU 222 conveys the thick paper in the face-up mode and prints the adjustment image 501 (S1006). The CPU 222 acquires the reading result of the adjustment image 501 from the image reading unit 241 (S1007). The CPU 222 determines the target gradation based on the reading result of the adjustment image 501 (S1008). This target gradation corresponds to a face-up mode (FU) pattern on thick paper. The CPU 222 stores the determined target gradation in the target gradation area of the face-up mode (FU) pattern on thick paper (S1017). As described above, the target gradation of the pattern with list number 1 (listNo.=1) is determined.

After saving the target gradation, the CPU 222 adds 1 to the list number (S1018). This brings the list number to 2. The CPU 222 determines whether or not the added list number is greater than the maximum list number of the operation pattern list (S1019). The maximum value of the list number is the number of patterns (listMax) acquired in the process of S1003. Here, since the list number is 2, it is smaller than the maximum list number (S1019: N). Therefore, the CPU 222 performs the processing of S1005.

The CPU 222 determines whether or not the face-up mode (FU) is set as the image forming mode for the pattern with list number 2 (listNo.=2) (S1005). In the example of FIG. 8, the image forming mode of the pattern with list number 2 is FU (S1005: Y). Also, the first plain paper is registered as the recording medium of the pattern with the list number of 2 . Therefore, the CPU 222 conveys the first plain paper in the face-up mode and prints the adjustment image 501 (S1006). The CPU 222 acquires the reading result of the adjustment image 501 from the image reading unit 241 (S1007). The CPU 222 determines the target gradation based on the reading result of the adjustment image 501 (S1008). This target gradation corresponds to the face-up mode (FU) pattern on the first plain paper. The CPU 222 stores the determined target gradation in the target gradation area of the face-up mode (FU) pattern on the first plain paper (S1017). As described above, the target gradation of the pattern with list number 2 (listNo.=2) is determined.

After saving the target gradation, the CPU 222 adds 1 to the list number (S1018). This brings the list number to 3. The CPU 222 determines whether or not the added list number is greater than the maximum list number of the operation pattern list (S1019). Here, since the list number is 3, it is smaller than the maximum list number (S1019: N). Therefore, the CPU 222 performs the processing of S1005.

In the example of FIG. 8, the image forming mode of the pattern with list number 3 (listNo.=3) is double-sided. In addition, the first plain paper is registered as the print medium of the pattern with the list number 3 . Therefore, the CPU 222 conveys the first plain paper in the double-sided mode and prints the adjustment image 501 (S1005: N, S1009: N, S1013: Y, S1014). The CPU 222 acquires the reading result of the adjustment image 501 from the image reading section 241 (S1015). The CPU 222 determines the target gradation based on the reading result of the adjustment image 501 (S1016). This target gradation corresponds to a double-sided mode pattern on the first plain paper. The CPU 222 stores the determined target gradation in the target gradation area of the pattern for the double-sided mode on the first plain paper (S1017). As described above, the target gradation of the pattern with list number 3 (listNo.=3) is determined.

After saving the target gradation, the CPU 222 adds 1 to the list number (S1018). This brings the list number to 4. The CPU 222 determines whether or not the added list number is greater than the maximum list number of the operation pattern list (S1019). Here, since the list number is 4, it is smaller than the maximum list number (S1019: N). Therefore, the CPU 222 performs the processing of S1005.

In the example of FIG. 8, the image forming mode of the pattern with list number 4 (listNo.=4) is the face-up mode (FU). Also, the second plain paper is registered as the recording medium of the pattern with the list number 4 . Therefore, the CPU 222 conveys the second plain paper in face-up mode (FU) and prints the adjustment image 501 (S1005: Y, S1006). The CPU 222 acquires the reading result of the adjustment image 501 from the image reading unit 241 (S1007). The CPU 222 determines the target gradation based on the reading result of the adjustment image 501 (S1008). This target gradation corresponds to the face-up mode (FU) pattern on the second plain paper. The CPU 222 stores the determined target gradation in the target gradation area of the face-up mode (FU) pattern on the second plain paper (S1017). As described above, the target gradation of the pattern with list number 4 (listNo.=4) is determined.

After saving the target gradation, the CPU 222 adds 1 to the list number (S1018). This brings the list number to 5. The CPU 222 determines whether or not the added list number is greater than the maximum list number of the operation pattern list (S1019). Here, since the list number is 5, it is equal to the maximum list number (S1019: N). Therefore, the CPU 222 performs the processing of S1005.

In the example of FIG. 8, the image forming mode of the pattern with list number 5 (listNo.=5) is the face-down mode (FD). Thick paper is registered as the recording medium of the pattern with list number 5 . Therefore, the CPU 222 conveys the thick paper in face-down mode (FD) and prints the adjustment image 501 (S1005: N, S1009: N, S1010). The CPU 222 acquires the reading result of the adjustment image 501 from the image reading section 241 (S1011). The CPU 222 determines the target gradation based on the reading result of the adjustment image 501 (S1012). This target gradation corresponds to a face-down mode (FD) pattern on thick paper. The CPU 222 stores the determined target gradation in the target gradation area of the face-down mode (FD) pattern on thick paper (S1017). As described above, the target gradation of the pattern with list number 5 (listNo.=5) is determined.

After saving the target gradation, the CPU 222 adds 1 to the list number (S1018). This brings the list number to 6. The CPU 222 determines whether or not the added list number is greater than the maximum list number of the operation pattern list (S1019). Here, since the list number is 6, it is larger than the maximum list number (S1019: Y). Therefore, the CPU 222 determines that acquisition of target gradations for all patterns in the operation pattern list has been completed, and terminates the target gradation acquisition process.

FIG. 11 is a flowchart showing target tone update processing in S911. In the target gradation update process, the CPU 222 resets the target gradation for the operation pattern list created in the process of S1002 of the target gradation acquisition process of S902. The processing contents of the target gradation update process are the same as those of S1004 to S1019 of the target gradation acquisition process, so the description is omitted (S1104 to S1119).

The image forming apparatus 101 of this embodiment as described above determines target gradations for all combinations of recording media and image forming modes used in a print job before starting printing of a user image. As a result, it is possible to minimize the deviation of the acquisition timing of the target gradation. Also, all target gradations are updated at predetermined intervals. Therefore, highly accurate image density correction is maintained.

By setting the target gradation in this way, even when executing a job that uses a mixture of types of recording media for printing, or a job that mixes single-sided printing and double-sided printing, the target gradation for each You can avoid out-of-tune. Therefore, it is possible to suppress variations in color within the same job.

Claims (7)

image forming means for forming an image on a recording medium based on image forming conditions;
reading means for reading the image for adjusting the image forming conditions formed on the recording medium;
performing a process of determining a target value of an image forming condition based on the result of reading the adjustment image by the reading means, adjusting the image forming condition based on the target value, and adjusting the image formed by the image forming means; a control means for forming an image according to a job based on forming conditions;
The control means determines the target value in accordance with the combination of the type of recording medium and the print surface instruction for each page used in the job,
Image forming device. The control means creates a pattern list in which patterns in which the combination of the type of the recording medium and the designation of the printing surface overlap are grouped into one and lists the target values corresponding to all combinations of the pattern list. characterized by determining
The image forming apparatus according to claim 1. The control means determines the target value before starting printing of the image corresponding to the job on the recording medium,
3. The image forming apparatus according to claim 1. The control means updates the target value each time image formation on a predetermined number of recording media is completed by the image forming means,
The image forming apparatus according to any one of claims 1 to 3. The control means updates the target value every time a predetermined time elapses after determining the target value,
The image forming apparatus according to any one of claims 1 to 3. The control means forms the adjustment image on the designated printing surface of the recording medium by the image forming means, and determines the type of the recording medium and the Determining the target value corresponding to the combination of instructions for the printing surface,
The image forming apparatus according to any one of claims 1 to 5. The control means forms the adjustment image for adjusting the gradation characteristics on the designated printing surface of the recording medium by the image forming means, and forms the image for adjustment on the designated printing surface of the recording medium based on the reading result of the adjustment image by the reading means. to determine the target gradation corresponding to the combination of the type of the recording medium and the instruction for the printing surface,
The image forming apparatus according to any one of claims 1 to 6.

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