JP2020134685A - Image formation apparatus, and control method and program of the same - Google Patents

Abstract

To perform further delicate fixation temperature control by efficiently processing image data.SOLUTION: An image formation apparatus comprises: fixation means which fixes an image formed on a recording medium on the basis of image data; conversion means which converts the gradation of the image data into prescribed gradation; count means which generates a feature amount count value that is obtained by counting the feature amount of the image in the image data converted into the prescribed gradation by the conversion means for each prescribed region of the image data; correction means which corrects the feature amount count value for each prescribed region by using a prescribed correction value; and analysis means which generates information for adjusting the fixation temperature at the time of fixing the image on the recording medium by the fixation means by analyzing the feature amount count value for each prescribed region corrected by the correction means.SELECTED DRAWING: Figure 5

Description

The present invention relates to a technique for fixing an image on a recording medium by heat.

Image forming devices such as copiers and printers using the electrophotographic method have an image forming unit that forms an image (toner image) on printing paper (recording medium) and a fixing unit (fixing) that fixes an image formed on the printing paper. The device) and.

In such an image forming apparatus, it is required to reduce the power consumption while maintaining the fixing temperature at which the toner image is surely fixed on the recording medium. As a method for meeting this demand, a technique for finely controlling the fixing temperature for each predetermined region according to the amount of toner loaded on the printed image page and the content of the page is being studied.

Patent Document 1 discloses a technique for controlling a fixing temperature based on a density value or a size value of a drawing object in an image extracted from image data.

Japanese Unexamined Patent Publication No. 2015-118195

However, even if the amount of toner loaded per unit area is the same, the toner fixing temperature may differ depending on the arrangement of dots in the image. The arrangement of dots includes continuous arrangement, distributed arrangement, aggregated arrangement, and the like, and the fixing temperature of the toner differs depending on such an arrangement of dots. Therefore, the technique of Patent Document 1 cannot perform finer fixing temperature control. In addition, the feature amount of the image is derived by more detailed analysis processing of the page contents, but the image forming apparatus handles image data having various resolutions and gradation information, and the analysis processing uses the image data. It is performed according to each resolution and each gradation information. Therefore, the analysis process of the image data is complicated and the processing time is increased, and it may not be possible to perform more detailed fixing temperature control.

An object of the present invention is to efficiently process image data to perform finer fixing temperature control.

The image forming apparatus according to one aspect of the present invention is an image forming apparatus provided with fixing means for fixing an image formed on a recording medium based on the image data, and the gradation of the image data is set to a predetermined gradation. A conversion means for converting to, and a counting means for generating a feature amount count value obtained by counting the feature amount of the image in the image data converted to the predetermined gradation by the conversion means for each predetermined area of the image data. Then, the correction means for correcting the feature amount count value for each predetermined area by using the predetermined correction value and the feature amount count value for each predetermined area corrected by the correction means are analyzed. It is characterized by having an analysis means for generating information for adjusting a fixing temperature when an image is fixed on the recording medium by the fixing means.

According to the present invention, image data can be efficiently processed to perform more detailed fixing temperature control.

It is a figure which shows the system configuration example including the image forming apparatus. It is a figure which shows the structure of the image forming apparatus of an electrophotographic type. It is a block diagram of an image forming apparatus. It is a figure explaining the mesh. It is a block diagram which shows the functional structure example of the mesh data generation part. It is a flowchart which shows the example of the mesh data generation processing procedure. It is a figure explaining the storage state of the mesh data. It is a flowchart which shows the example of the notification processing procedure of the fixing temperature adjustment information. It is a flowchart which shows the example of the generation processing procedure of the fixing temperature adjustment information. It is a flowchart which shows the analysis processing procedure example of the required temperature for each mesh. It is a graph which shows the relationship between mesh data and fixing temperature. It is a figure explaining the relationship between the fixing temperature adjustment information and an image.

Prior to the description of the embodiment of the present invention, the fixing temperature control performed by the image forming apparatus will be described.

In the image forming apparatus, even if the amount of toner applied per unit area is the same, the toner fixability may differ depending on the feature amount of the image such as dots being continuous, dispersed, or aggregated in the image. .. Therefore, in addition to the amount of toner loaded on the printed image page, it is being studied to perform finer fixing temperature control according to the content of the page. That is, it is considered to derive a target value of the fixing temperature based on the analysis information of a plurality of printed images such as dot continuity information in addition to the toner loading amount information, and to control the fixing temperature so as to be the target value. ing.

If the printed image is analyzed by software, such as toner loading amount information and dot continuity information, more detailed fixing temperature control is possible based on the analysis result, but the printed image page content is analyzed in detail. It is necessary, and the processing load and processing time of the CPU increase. On the other hand, if detailed analysis of the printed image page contents is performed by hardware, the processing time can be shortened, but the circuit scale for executing the analysis processing becomes large. Further, once the circuit for executing the analysis process is mounted on the apparatus, the mounted circuit cannot be changed, so that it becomes difficult to change the analysis method according to the characteristics of the fixing portion.

Therefore, from the image data handled by the image forming apparatus, the analysis data necessary for software analysis for fixing temperature control is generated by hardware, and the generated analysis data is analyzed by the software according to the characteristics of the fixing part. Is being considered. The hardware counts the amount of toner and the discontinuity of dots for each predetermined area in which the image data on the bitmap is divided into small pieces, and generates the counted values as analysis data. The software analyzes the analysis data generated by the hardware according to the number and arrangement of heaters in the fixing unit and the temperature characteristics. The temperature of the fixing portion of the image forming apparatus is adjusted based on the analysis result.

Here, the image data that is the basis of the analysis data has various resolutions and gradation information. For example, the image data received by FAX is black and white with a resolution of 100 dpi × 100 dpi, but the image obtained by rasterizing the page description language (PDL) has a multi-value of 600 dpi × 600 dpi. Therefore, when the hardware counts each pixel of the image data, even if the toner image after image formation is the same, the analysis data is determined by the resolution and gradation of the image data. The values are different. As a result, the software often needs to be classified according to what kind of image data the analysis data is based on.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the components described in this embodiment are merely examples, and are not intended to limit the scope of the present invention to them. Further, not all of the combinations of components described in the embodiments are essential for the means for solving the problem, and various modifications and changes are possible.

[Embodiment]
<System configuration>
FIG. 1 is a diagram showing a configuration example of an image forming system including an image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming system 1 includes an image forming device 101, a print server 102, and a client PC 103. Also, they are communicably connected by the network 104.

The image forming apparatus 101 processes various input data, performs image forming (image formation), and outputs a printed matter. Specifically, the image forming apparatus 101 executes a printing process by using a copy function and a printing function of print data received from the print server 102 or the client PC 103. When executing the printing process, the image forming apparatus 101 controls the heaters 34 and 35 of the fixing apparatus 31 described later so as to have a fixing temperature suitable for the print data or printing conditions. The heaters 34 and 35 can independently control the temperature of each region divided into a predetermined size in the main scanning direction.

<Explanation of operation of image forming apparatus>
Next, the image forming operation in the electrophotographic image forming apparatus 101 will be described with reference to FIG. FIG. 2 is a diagram showing a configuration of a tandem color image forming apparatus using an intermediate transfer body, which is an example of an electrophotographic image forming apparatus.

The image forming apparatus shown in FIG. 2 includes four image forming portions for forming a toner image using each of the yellow (Y), magenta (M), cyan (C), and black (K) toners. .. Hereinafter, the image forming unit corresponding to each toner will be referred to as a first station, a second station, a third station, and a fourth station, respectively.

Each station is arranged in the order of the first to fourth stations along the peripheral surface of the intermediate transfer body from the upstream side to the downstream side with respect to the moving direction of the peripheral surface. The image forming operation is performed in the flow of charging, exposure, development, transfer and fixing. Each operation will be described below.

(Charged)
First, the photoconductor drums 22Y, 22M, 22C, 22K are charged by the injection chargers 23Y, 23M, 23C, 23K. Each injection charger is provided with sleeves 23YS, 23MS, 23CS, 23KS. Each photoconductor drum has a configuration in which the driving force of the drive motors 40Y, 40M, 40C, and 40K is transmitted and can rotate. The drive motor rotates each photoconductor drum in the counterclockwise direction according to the image forming operation. The injection chargers 23Y, 23M, 23C, 23K, sleeves 23YS, 23MS, 23CS, 23KS and the like constitute the charging means.

(exposure)
Next, the photoconductor drums 22Y, 22M, 22C, and 22K are irradiated with photosensitive light from the scanner units 24Y, 24M, 24C, and 24K, and the surface of each photoconductor drum is selectively exposed to electrostatic charge. Form a latent image. The scanner units 24Y, 24M, 24C, 24K and the like constitute the exposure means.

(developing)
Subsequently, the developing devices 26Y, 26M, 26C, and 26K visualize the electrostatic latent image, that is, form a monochromatic toner image on each photoconductor drum. Each developer is provided with sleeves 26YS, 26MS, 26CS, 26KS. Each developer can be attached and detached. Developers 26Y, 26M, 26C, 26K, sleeves 26YS, 26MS, 26CS, 26KS and the like constitute developing means.

(Transfer)
Then, the intermediate transfer body 28 is rotated in the clockwise direction, and the intermediate transfer body 28 is rotated by the rotation of the photoconductor drums 22Y, 22M, 22C, 22K and the primary transfer rollers 27Y, 27M, 27C, 27K located opposite to each other. Transfer the monochromatic toner image to. By applying an appropriate bias voltage to each primary transfer roller and making a difference between the rotation speed of each photoconductor drum and the rotation speed of the intermediate transfer body 28, a monochromatic toner image can be efficiently transferred onto the intermediate transfer body 28. Can be transferred to (primary transfer).

The yellow toner image formed on the photoconductor drum 22Y of the first station is transferred onto the intermediate transfer body 28 as the photoconductor drum 22Y rotates. The yellow toner image transferred to the intermediate transfer body 28 is conveyed as the peripheral surface of the intermediate transfer body 28 moves. Then, in synchronization with the movement of the yellow toner image on the intermediate transfer body 28, the magenta, cyan, and black toner images formed in the second to fourth stations are transferred from the photoconductor drums 22M, 22C, and 22K, respectively. Transferred overlaid on the yellow toner image. As a result, a multicolor toner image composed of four colors is formed on the surface of the intermediate transfer body 28. This multicolor toner image is conveyed to the secondary transfer roller 29 by the rotation of the intermediate transfer body 28. Then, the recording medium 11 is sandwiched and conveyed from the paper feed tray 21a or the paper feed tray 21b to the secondary transfer roller 29, and the multicolor toner image on the intermediate transfer body 28 is transferred to the recording medium 11. At this time, an appropriate bias voltage is applied to the secondary transfer roller 29, and the toner image is electrostatically transferred (secondary transfer). The secondary transfer roller 29 comes into contact with the recording medium 11 at the position of reference numeral 29a while transferring the multicolor toner image onto the recording medium 11, and is separated from the position of reference numeral 29b after processing. The photoconductor drum, the primary transfer roller, the intermediate transfer body 28, and the like constitute the transfer means.

(Fixed)
Then, the fixing device 31 melts and fixes the multicolor toner image transferred to the recording medium 11 on the recording medium 11. Therefore, the fixing device 31 includes a fixing roller 32 for heating the recording medium 11 and a pressure roller 33 for pressing the recording medium 11 against the fixing roller 32. The fixing roller 32 and the pressure roller 33 are formed in a hollow shape, and heaters 34 and 35 are built in, respectively. The fixing device 31 conveys the recording medium 11 holding the multicolor toner image by the fixing roller 32 and the pressure roller 33, and applies heat and pressure to fix the toner on the recording medium 11. The temperature control of the fixing roller 32 and the pressure roller 33 is performed as follows. The temperature on each roller is detected by a temperature sensor (not shown) attached to each roller, and the heater of the fixing device is controlled by the fixing temperature control unit described later based on the detected temperature and the fixing temperature adjustment information described later. The surface temperature of each roller is adjusted, and the fixing operation is performed in this state. The recording medium 11 after the toner is fixed is discharged to a paper ejection tray (not shown) by an ejection roller (not shown).

In this way, a series of image forming operations is completed.

After the image forming operation is completed, the toner remaining on the intermediate transfer body 28 is removed by the cleaning means 30. The waste toner remaining after transferring the multicolor toner image formed on the intermediate transfer body 28 to the recording medium 11 is stored in the cleaner container.

<Configuration of image forming apparatus>
Next, with reference to FIG. 3, a configuration related to fixing temperature control in the image forming apparatus 101 will be described. FIG. 3 is a block diagram showing a hardware configuration example of the image forming apparatus 101.

As shown in FIG. 3, the image forming apparatus 101 includes a system controller unit 300 and a print controller unit 320. Each controller unit has a CPU 301, a CPU 321 and a ROM 302, a ROM 322, a RAM 303, a RAM 323, a storage unit 304, and a storage unit 324, respectively. In addition, they are communicably connected by the corresponding buses 307 and 327. Each of the CPU 301 and CPU 321 reads the main program from the ROM 302 and ROM 322 according to the initial program in the corresponding ROM 302 and ROM 322, and stores the main program in the corresponding RAM 303 and RAM 323. The RAM 303 and RAM 323 are used as main memories for storing programs and for work.

The system controller unit 300 further includes a printer communication IF305, a network communication control unit 306, and an image processing unit 310. Also, they are communicably connected by bus 307. The system controller unit (system control unit) 300 controls the entire system.

The image processing unit 310 functions as an image processing means for copying, printing, and the like. The image processing unit 310 includes an image generation unit 311, a color conversion processing unit 312, a halftone processing unit 313, a mesh data generation unit 314, and a PWM processing unit 315. The image generation unit 311 has 256 gradations of RGB or CMYK color components or K single color components for each pixel based on print data (print information) received from a computer device such as a print server 102 or a client PC 103. Generate raster image data. Then, the image generation unit 311 outputs the generated raster image data for each pixel.

The image generation unit 311 may be configured to provide reading means in the image forming apparatus 101 itself and handle the image data read by the reading means instead of the image data received from the client PC 103 or the like. The reading means here includes at least a CCD (Charged Couple Device) or a CIS (Constance Image Sensor). Further, the read image data may be configured to be provided with a processing unit that performs predetermined image processing. Further, instead of providing the image forming apparatus 101 with a reading means, the image data may be received from an external reading means via an interface (not shown). Further, the image generation unit 311 may be configured to handle the image data received by receiving the fax.

As described above, as the resolution of various raster image data generated by the system controller unit 300, those having the following sizes can be used. For example, 600 dpi × 600 dpi, 1200 dpi × 1200 dpi, 300 dpi × 300 dpi, 100 dpi × 100 dpi, 200 dpi × 200 dpi, 400 dpi × 400 dpi, and the like can be used.

If the raster image data generated by the image generation unit 311 is additive mixed data such as RGB data, the color conversion processing unit 312 converts the raster image data into CMYK data or toner single color data according to the toner color and outputs the data. Specifically, the CMYK data converted by the color conversion processing unit 312 includes data for specifying the toner loading amount of each CMYK color, and the toner loading amount is represented by 8 bits of 0 to 255 in pixel units. When the toner loading amount of each color is 0, it indicates that the toner is not used, and the density increases as the toner loading amount of each color increases. Then, when the toner loading amount of each color reaches 255, the maximum density of each color is shown. The toner loading amount is 255, which indicates 100%, and the total value of the toner loading amounts of each color of CMYK represents the toner loading amount of the pixel. For example, when each of the two color toner loading amounts of CMYK indicates 255, the total value of these toner loading amounts is the toner loading amount of the pixel, and is indicated by a value of 200%. In this way, when the image forming apparatus 101 prints image data that makes maximum use of the CMYK four-color toner in the full-color printing mode, the amount of toner loaded increases, and when printing K single-color monochrome image data, the toner The amount of load is reduced.

The halftone processing unit 313 executes halftone processing for converting raster image data having multiple gradations such as 256 gradations per pixel into N values, and generates halftone image data. That is, the halftone processing unit 313 executes halftone processing on each color of the CMYK data output from the color conversion processing unit 312 or the color of the toner single color data to generate halftone image data. Specific configurations of the halftone processing unit 313 include, for example, screen processing and error diffusion processing. The screen process is a process of converting to N value using a plurality of predetermined dither matrices and input image data. Further, in the error diffusion processing, the attention pixel is converted to an N value by comparing the attention pixel of the input image data with a predetermined threshold value, and the difference between the attention pixel and the threshold value generated by the N value conversion processing is calculated. This is a process of diffusing the surrounding pixels to be N-valued thereafter.

The mesh data generation unit 314 has mesh data having image information for each small area (hereinafter, referred to as “mesh”) which is a predetermined rectangular area including a plurality of pixels from the halftone image data generated by the halftone processing unit 313. To generate. In the present embodiment, the halftone image data is raster image data having as few gradations as 2 to 16 gradations per pixel. Not only the image data after the halftone processing, but also the image data of two gradations per pixel received by the image generation unit 311 from the FAX reception or the external reading means is the halftone image data. The mesh data is data necessary for generating information for adjusting the fixing temperature (hereinafter, referred to as fixing temperature adjusting information) described later. The details of the mesh data generation process will be described later with reference to FIG.

The PWM processing unit 315 performs PWM conversion processing of the halftone image data generated by the halftone processing unit 313. The PWM processing unit 315 uses a table for PWM conversion of the image signal of the halftone image data, and information corresponding to ON or OFF of the laser for printing the image signal of the halftone image data by the image forming apparatus 101. Convert to. The PWM processing unit 315 may also be provided with a processing unit that converts the resolution when halftone image data having a resolution lower than the resolution to be printed by the image forming apparatus 101 is input.

The printer communication IF 305 and the controller communication IF 326 are IFs (interfaces) for communicating between the system controller unit 300 and the print controller unit 320. Communication is performed via the communication cable 308. The information communicated here includes, in addition to the image data to be printed, for example, a control signal from the system controller unit 300, a fixing temperature adjustment information derived by the CPU 301 based on the mesh data generated by the mesh data generation unit 314, and the like. is there. The details of the process of generating the fixing temperature adjustment information will be described later with reference to FIG.

The print controller unit 320 further includes a fixing temperature control unit 325. The fixing temperature control unit 325 uses the fixing temperature adjustment information transferred from the system controller unit 300 to the print controller unit 320 to set the heaters 34 and 35 of the fixing device 31 so that the fixing temperature becomes suitable for the print data or the printing conditions. To control.

The fixing device 31 performs an operation of fixing the toner image formed on the recording medium based on the print data to the recording medium at the fixing temperature controlled by the fixing temperature control unit 325.

<Mesh data generation process>
Next, the mesh data generation process by the mesh data generation unit 314 of the image forming apparatus 101 will be described with reference to FIGS. 4, 5, 6, and 7.

4 (a) to 4 (d) are diagrams showing examples of mesh data, respectively. FIG. 4A is a diagram showing a state in which the halftone image data 401 is divided into a plurality of meshes 410 in the main scanning direction and the sub-scanning direction. One mesh 410 is composed of a plurality of pixels in the main scanning direction and the sub scanning direction. In the present embodiment, the size of one mesh 410 is 1 mm × 1 mm in the main scanning direction and the sub-scanning direction. The size of one mesh 410 is not limited to this. In the mesh 410 at the most downstream position in the main scanning direction, the pixel 490 at the most downstream position in the main scanning direction and the sub-scanning direction is the end position of the mesh band.

4 (b) and 4 (d) are enlarged views of a certain mesh when the halftone image data 401 has a resolution of 600 dpi × 600 dpi, respectively. The pixel 411 located at the most downstream in the main scanning direction is the terminal position of the line for each mesh. The pixel 412 located at the uppermost stream in the main scanning direction is the head position of the line for each mesh. The pixel 413 located at the uppermost stream in the main scanning direction and the sub-scanning direction is the first position (starting position) for each mesh.

On the other hand, FIG. 4C is an enlarged view of a certain mesh when the halftone image data 401 has a resolution of 200 dpi × 100 dpi. The pixel 421 located at the most downstream in the main scanning direction is the terminal position of the line for each mesh. The pixel 422 located at the uppermost stream in the main scanning direction is the head position of the line for each mesh. The pixel 423 located at the uppermost stream in the main scanning direction and the sub-scanning direction is the first position (starting position) for each mesh.

The number of pixels processed per mesh, that is, the number of pixels constituting one mesh, differs depending on the resolution of the halftone image data processed by the mesh data generation unit 314. The mesh data generation unit 314 executes the mesh data generation process based on the mesh size (the number of pixels constituting one mesh) set by the instruction of the CPU 301.

FIG. 5 is a block diagram showing a detailed configuration of the mesh data generation unit 314. Further, the instruction from the CPU 301 to the mesh data generation unit 314 is executed by writing an appropriate value to the register unit (not shown) of the mesh data generation unit 314. Each block of the mesh data generation unit 314 will be described. The overall operation of the mesh data generation unit 314 will be described later with reference to FIGS. 6 and 7. A case where the feature amount of the image is a pixel value and an edge will be described.

The gradation conversion unit 501 executes the gradation conversion process based on the register setting every time one pixel of halftone image data is input. Then, the gradation conversion unit 501 outputs the data after the gradation conversion obtained by executing the gradation conversion process to the pixel value counting unit 510 and the edge counting unit 520, respectively. Table 1 is a gradation conversion table showing an example of gradation conversion processing executed by the gradation conversion unit 501. The Exp Mode indicates the register setting specified by the CPU 301. In this gradation conversion table, three examples of "1to4", "2to4", and "throw" are shown as Exp Modes. Input indicates the input halftone image data of a certain pixel, and Output indicates the halftone image data after the gradation conversion process. In "1to4", for example, when the halftone image data is 1 bpp (2 gradations of 0 to 1), the input halftone image data of one pixel is output at 4 bpp (16 gradations of 0 to 15). Indicates the mode to be used. "2to4" outputs, for example, when the halftone image data is 2 bpp (4 gradations of 0 to 3), the input halftone image data of one pixel is output at 4 bpp (16 gradations of 0 to 15). Indicates the mode to be used. "Through" indicates, for example, a mode in which when the halftone image data is 1 bpp (two gradations of 0 to 1), the input halftone image data of one pixel is output as it is. For example, when the input halftone image data is 1 bpp (2 gradations of 0 to 1), the gradation conversion unit 501 executes the gradation conversion process using "1to4" as the Exp Mode. For example, when the halftone image data of a certain pixel input to the gradation conversion unit 501 is 1'b0, the gradation conversion unit 501 outputs 4'b0000 for 1'b0.

The pixel value counting unit 510 counts the pixel values of the input data each time the data after gradation conversion output by the gradation conversion unit 501 is input. The pixel value counting unit 510 performs counting processing for each mesh. The pixel value counting unit 510 manages the pixel value count value obtained by the counting process for each mesh. The pixel value count value is one of the feature amount count values. The pixel value counting unit 510 is a pixel value count value for each mesh, specifically, a pixel value count value for one mesh band or a mesh band for a predetermined unit such as two mesh bands or three mesh bands. Has a count buffer that temporarily holds. As a result, the pixel value counting unit 510 can update the pixel value counting value for each mesh when the halftone image data after gradation conversion is input in order in one main scanning direction. For example, when the size of 210 mm in the main scanning direction is divided into meshes every 1 mm, the count buffer of the pixel value counting unit 510 is configured to have a capacity capable of holding the pixel value count values of 210 meshes. When the pixel value counting unit 510 determines that the pixel value count value for one mesh band or the mesh band of a predetermined unit is obtained, the pixel value count value is output to the pixel value count value correction unit 511. For example, the pixel value counting unit 510 is a process of adding 4'b1010 to 4'b0101 when 4'b1010 is input as data after gradation conversion following 4'b0101 which is data after gradation conversion. Is done. When this is expressed in a decimal number, the pixel value counting unit 510 adds 15 to 5 to derive 20.

The pixel value count value correction unit 511 executes a pixel value count value correction process for each mesh, including integer multiplication and shift operations, based on the register settings. The pixel value count value for each mesh before correction is Cpi, the pixel value count value for each mesh after correction is Cpo, the multiplication value set in the register is Pmul, and the shift amount is Pdiv. In the correction process by the pixel value count value correction unit 511, for example, the corrected pixel value count value is derived by using the calculation formula represented by the following formula (1).
Cpo = (Cpi × Pmul) >> Pdiv ・ ・ ・ Equation (1)

That is, after correction, the result obtained by multiplying the pixel value count value Cpi for each mesh before correction by the multiplication value Pmul is shifted to the right by the number of bits of the shift amount Pdiv (divided by 2 ^ Pdiv). The pixel value count value Cpo for each mesh is derived.

For example, it is assumed that the resolution (200, 100), 1 bpp, gradation conversion mode "1to4", Pmul is 18, and Pdiv is set to 0, which are shown in Table 3 described later. When Cpi is 100, Cpo is derived as follows.
Cpo = (100 × 18) ^ 2 0 = 1800

Further, for example, it is assumed that the resolution (200, 400), 1 bpp, the gradation conversion mode "1to4", Pmul is 9, and Pdiv is set to 1 as shown in Table 3 described later. When Cpi is 100, Cpo is derived as follows.
Cpo = (100 x 9) ^ 2 ¹ = 450

The edge counting unit 520 determines whether or not the difference between the pixel values of the pixel of interest and the pixels adjacent to it is equal to or greater than a predetermined value each time the data after gradation conversion output by the gradation conversion unit 501 is input. judge. When the edge counting unit 520 determines that the difference between the pixel values of the pixel of interest and the pixels adjacent to it is equal to or greater than a predetermined value, the edge is the edge, and the edge counting unit 520 executes a process of adding 1 to the edge counting value. The edge counting unit 520 performs counting processing for each mesh. The edge count unit 520 manages the edge count value obtained by the count process for each mesh. The edge count value is one of the feature amount count values. When the edge count unit 520 determines that the difference between the pixel values is not equal to or greater than a predetermined value, the edge count unit 520 executes a process of adding 0 to the edge count value because the portion is not an edge. The edge count unit 520 has a count buffer that temporarily holds an edge count value for each mesh, specifically, an edge count value for one mesh band or a mesh band of a predetermined unit. As a result, the edge count unit 520 can update the edge count value for each mesh when the halftone image data after gradation conversion is input in order in one main scanning direction. For example, when the size of 210 mm in the main scanning direction is divided into meshes every 1 mm, the count buffer of the edge counting unit 520 has a capacity capable of holding edge count values in the main scanning direction and the sub scanning direction for 210 meshes. Is configured. When the edge count unit 520 determines that the edge count value for one mesh band or the mesh band of a predetermined unit has been obtained, the edge count unit 520 outputs the edge count value to the edge count value correction unit 521. Further, in the present embodiment, the edge counting unit 520 individually counts the edge in the main scanning direction (hereinafter, also referred to as the main scanning edge) and the edge in the sub-scanning direction (hereinafter, also referred to as the sub-scanning edge). The scanning edge count value and the sub-scanning edge count value are output.

For example, as shown in Table 1, the pixel value of one adjacent pixel is 4'b0000 obtained by gradation conversion processing of 2'b00, and the pixel value of the other adjacent pixel is gradation conversion processing of 2'b10. The case of'b1010 will be described below.

The edge counting unit 520 determines that the edge is an edge when the difference between the pixel values is 15 or more in decimal. The pixel value of one adjacent pixel is 0 in decimal, the pixel value of the other adjacent pixel is 10 in decimal, and the difference between the pixel values is 10 in decimal. Therefore, the edge count unit 520 determines that the difference between the pixel values is not equal to or greater than a predetermined value, and executes a process of adding 0 to the edge count value.

The edge counting unit 520 determines that the difference between the pixel values is 10 or more in decimal and the edge is an edge. The pixel value of one adjacent pixel is 0 in decimal, the pixel value of the other adjacent pixel is 10 in decimal, and the difference between the pixel values is 10 in decimal. Therefore, the edge count unit 520 determines that the difference between the pixel values is equal to or greater than a predetermined value, and executes a process of adding 1 to the edge count value.

The edge count value correction unit 521 executes correction processing of the edge count value for each mesh, including multiplication and shift operations of integers based on the register settings. Let Cemi be the edge count value in the main scanning direction for each mesh before correction, and Cesi be the edge count value in the sub-scanning direction for each mesh before correction. Let Cemo be the edge count value in the main scanning direction for each corrected mesh, and Ceso be the edge count value in the sub-scanning direction for each corrected mesh. Let Emulm be the multiplication value for the edge count value in the main scanning direction set in the register, and Emuls be the multiplication value for the edge count value in the sub-scanning direction. Further, the shift amount with respect to the edge count value in the main scanning direction is set to Edivm, and the shift amount with respect to the edge count value in the sub scanning direction is set to Edivs. In the correction process by the edge count value correction unit 521, for example, the arithmetic expression represented by the following equation (2) is used for the main scanning direction, and the arithmetic expression expressed by the following equation (3) is used for the sub-scanning direction. Is used to derive the corrected edge count value.
Cemo = (Cemi x Emulm) >> Edivm ・ ・ ・ Equation (2)
Ceso = (Cesi x Emulus) >> Edivs ... Equation (3)

In the equation (2), with respect to the main scanning direction, the result obtained by multiplying the edge count value Cemi before correction by the multiplication value Emulm is shifted to the right by the number of bits of the shift amount Edivm (divide by 2 ^ Edivm). Then, the corrected edge count value Cemo is derived. In the equation (3), with respect to the sub-scanning direction, the result obtained by multiplying the edge count value Cesi before correction by the multiplication value Emuls is shifted to the right by the number of bits of the shift amount Edivs (divide by 2 ^ Edivs). Then, the corrected edge count value Ceso is derived.

For example, it is assumed that the resolution (100, 100), 1 bpp, the gradation conversion mode “1to4”, Emulm is 6, and Edivm is set to 0, which are shown in Table 3 described later. When Cemi is 100, Cemo is derived as follows.
Cemo = (100 × 6) ^ 2 0 = 600

Further, for example, it is assumed that the resolution (200, 400), 1 bpp, the gradation conversion mode "1to4", Emulus is set to 3, and Edivs is set to 1, as shown in Table 3 described later. When Cesi is 100, Ceso is derived as follows.
Ceso = (100 x 3) ^ 2 ¹ = 150

Here, in the correction process by the edge count value correction unit 521, the edge count values Cemo and Ceo in the main scanning direction and the sub-scanning direction for each corrected mesh are added to count the edges for each corrected mesh. The value Ceo is derived.
Ceo = Cemo + Ceo

For example, the resolution (200,400), 1bpp, gradation conversion mode "1to4", (Emuls, Emulm) are set to (3,3), and (Edivm, Edivs) are set to (0,1) shown in Table 3 below. Suppose it is set. When (Cemi, Cesi) is (100,100), Ceso is derived as follows.
Ceo = Cemo + Ceo = (100 × 3) ^ 2 ⁰ + (100 × 3) ^ 2 ¹ = 300 + 150 = 450

In the present embodiment, with respect to the edge count value, the correction process is executed by using different correction values for the values obtained by adding the number of edges in the main scanning direction and the number of edges in the sub-scanning direction. As shown in FIGS. 4 (b) and 4 (c), the number of pixels of one mesh is different, but even when a similar toner image is formed in 1 mm × 1 mm, different counting processes and different counting processes are performed. By executing the correction process, the same number of edges can be derived.

The mesh data output unit 530 shapes and outputs each count value corrected by the pixel value count value correction unit 511 and the edge count value correction unit 521 as mesh data. Here, the pixel value count value is derived by the following calculation. For example, the case where the halftone image data has a resolution of 600 dpi × 600 dpi and a mesh size of 24pixel × 24pixel, 4 bpp (16 gradations from 0 to 15) corresponding to 1 mm × 1 mm will be described. The maximum count value for each mesh is derived as follows. Note that "21C0" is a numerical value obtained by converting a decimal number 8640 into a hexadecimal number.
24 × 24 × 15 (4'b1111) = 8640 (16'h21C0)

The LUT processing is executed for each of the pixel value count value for each mesh and the edge count value for each mesh so that this value becomes a value normalized from 0 to 255. That is, 255 is set for the maximum count value which is the maximum value. 0 is set for the minimum count value, which is the minimum value. For the count value between the maximum count value and the minimum count value, a numerical value between 0 and 255 is set according to the magnitude of the count value based on the maximum count value and the minimum count value. By normalizing, it becomes easy to determine whether the density is high or low, or whether there are many or few edges, based on the value indicated by the count value after normalization. Further, by setting the amount of data per mesh to 1 byte unit or 2 byte unit, it becomes easy for the CPU 301 to read the mesh data of a desired area by designating the address of the RAM 303.

The operation of the mesh data generation unit 314 will be described with reference to FIG. FIG. 6 is a flowchart of the operation performed by the mesh data generation unit 314 when halftone image data is input in order from the most upstream stream in the main scanning direction to the downstream side in one mesh based on the instruction of the CPU 301. is there. When the processing of the halftone image data at the most downstream side in the main scanning direction is completed, the halftone image data is input in order from the most downstream side in the main scanning direction to the downstream side at a position adjacent to the downstream side in the sub-scanning direction. Will be done. In the following flow description, the symbol "S" represents a step.

The mesh data generation unit 314 starts the mesh data generation operation according to the instruction of the CPU 301. At this time, the CPU 301 tells the mesh data generation unit 314 the mesh size, the gradation conversion method (gradation conversion mode), the number of meshes, and the multiplication value used for the correction process, based on the gradation and resolution of the input image data. Indicate the shift amount. Table 2 is a table showing the 1 mm × 1 mm mesh size set by the CPU 301 based on the resolution of the halftone image data when the mesh data of the mesh of 1 mm × 1 mm is generated. Table 3 shows the gradation conversion mode (Exp Mode) and correction values (Pmul, Pdiv, Emul (Emul, Emulus), Ediv (Edivm, Edivs)) set by the CPU 301 based on the resolution and gradation of the halftone image data. It is a table showing. In Tables 2 and 3, "main" indicates the main scanning direction, and "sub" indicates the sub-scanning direction. In Table 3, "Exp Mode" is the same as in Table 1, and the description thereof will be omitted. "Pmul" and "Pdiv" are the same as those in the formula (1), and "Emul" and "Emuls" in "Emul" and "Edivm" and "Edivs" in "Ediv" are in formulas (2) and (3). ), And the description thereof will be omitted.

In S601, the initialization process is performed. In the initialization process, various variables such as a main scanning position of the pixel being processed, a position of the pixel in each mesh, and a counter or a pointer indicating the position of the mesh being counted are initialized. The mesh size, gradation conversion method, number of meshes, multiplication value and shift amount used for correction processing specified by CPU 301 are not initialized.

In S602, it is determined whether or not the pixel to be processed (the pixel of interest) is the pixel at the head position of the line for each mesh (for example, the pixel 412 in FIG. 4B and the pixel 422 in FIG. 4C). .. The pixel at the head position of the line for each mesh is a pixel located at the most upstream in the main scanning direction in each mesh. When it is determined that the pixel of interest is the pixel at the head position of the line for each mesh (YES in S602), the process shifts to S603. When it is determined that the pixel of interest is not the pixel at the head position of the line for each mesh (NO in S602), the process shifts to S604. The determination result of whether or not the pixel of interest is the pixel at the head position of the line for each mesh can be obtained by comparing the position of the pixel for each mesh with the mesh size specified by the CPU 301.

In S603, the pixel value counting unit 510 loads the pixel value count value for each mesh stored in the count buffer (not shown) from the count buffer. The edge count unit 520 loads the edge count value for each mesh stored in the count buffer (not shown) from the count buffer. As a result, in S607 described later, the pixel value counting unit 510 can count the pixel value count value for each mesh. The edge counting unit 520 can count the edge count value for each mesh.

In S604, it is determined whether or not the pixel of interest is the pixel at the first position for each mesh (for example, the pixel 413 in FIG. 4B and the pixel 423 in FIG. 4C). The pixel at the first position for each mesh is a pixel located at the most upstream in the main scanning direction and the sub-scanning direction in the mesh. When it is determined that the pixel of interest is the pixel at the first position of each mesh (YES in S604), the process shifts to S605. When it is determined that the pixel of interest is not the pixel at the first position of each mesh (NO in S604), the process shifts to S606. The determination result of whether or not the pixel of interest is the pixel at the first position of each mesh can be obtained by comparing the position of the pixel for each mesh with the mesh size specified by the CPU 301.

In S605, the pixel value counting unit 510 initializes the pixel value counting value. The edge count unit 520 initializes the edge count value.

In S606, the gradation conversion unit 501 receives one pixel of halftone image data, and executes gradation conversion processing on the received halftone image data of one pixel. Then, the gradation conversion unit 501 outputs the data after the gradation conversion processing to each of the pixel value counting unit 510 and the edge counting unit 520.

In S607, the pixel value counting unit 510 executes a process of counting the pixel values of the data after the gradation conversion process input from the gradation conversion unit 501. The edge counting unit 520 determines whether or not the difference between the data after the gradation conversion process input from the gradation conversion unit 501 and the pixel values of adjacent pixels is equal to or greater than a predetermined value. When the edge count unit 520 determines that the difference between the pixel values of the pixel of interest and the pixels adjacent thereto is equal to or greater than a predetermined value, the edge count unit 520 executes a process of adding 1 to the edge count value. If the edge count unit 520 determines that the difference between the pixel values is not equal to or greater than a predetermined value, the edge count unit 520 executes a process of adding 0 to the edge count value because it is not an edge. When the mesh is at the most upstream position in the main scanning direction and the pixel of interest is a pixel located at the most upstream in the main scanning direction, the edge counting unit 520 determines that it is an edge in the main scanning direction, and determines that the edge is the edge in the main scanning direction. Add 1 to the count value. When the mesh is at the most upstream position in the sub-scanning direction and the pixel of interest is a pixel located at the most upstream in the sub-scanning direction, the edge counting unit 520 determines that it is an edge in the sub-scanning direction, and determines that the edge is an edge in the sub-scanning direction. Add 1 to the count value.

In S608, the pixel value counting unit 510 and the edge counting unit 520 are pixels in which the pixel of interest is at the end position of the line for each mesh (for example, pixel 411 in FIG. 4B and pixel 421 in FIG. 4C). Determine if it exists. The pixel at the end position of the line for each mesh is a pixel located at the most downstream position in the main scanning direction in the line of each mesh. When it is determined that the pixel of interest is the pixel at the end position of the line for each mesh (YES in S608), the process shifts to S609. When it is determined that the pixel of interest is not the pixel at the end position of the line for each mesh (NO in S608), the process shifts to S610. The determination result of whether or not the pixel of interest is the pixel at the end position of the line for each mesh can be obtained by comparing the position of the pixel for each mesh with the mesh size specified by the CPU 301.

In S609, the pixel value counting unit 510 stores the pixel value count value in its own count buffer for each corresponding mesh. The edge count unit 520 stores the edge count value for each corresponding mesh in its own count buffer.

In S610, the pixel value counting unit 510 and the edge counting unit 520 each determine whether or not the pixel of interest is a pixel at the terminal position of the mesh band (for example, pixel 490 in FIG. 4A). The pixel at the terminal position of the mesh band is a pixel located at the most downstream in the main scanning direction and the sub-scanning direction in the mesh located at the most downstream in the main scanning direction. When it is determined that the pixel of interest is the pixel at the end position of the mesh band (YES in S610), the process shifts to S611. When it is determined that the pixel of interest is not the pixel at the end position of the mesh band (NO in S610), the process shifts to S614. The judgment result of whether or not the pixel of interest is the pixel at the end position of the mesh band is the position of the pixel for each mesh, the number of meshes processed in the main scanning direction, the mesh size specified by the CPU 301, and the number of meshes to be processed. Obtained by comparing with.

In S611, the pixel value counting unit 510 outputs the pixel value count value for one mesh band stored in its own count buffer to the pixel value count value correction unit 511 corresponding to the pixel value counting unit 510. The edge count unit 520 outputs the edge count value for one mesh band stored in its own count buffer to the edge count value correction unit 521 corresponding to the edge count unit 520.

In S612, the pixel value count value correction unit 511 executes the correction process for the pixel value count value for one mesh band input from the pixel value count unit 510. The pixel value count value correction unit 511 outputs the corrected pixel value count value for each mesh to the mesh data output unit 530. The edge count value correction unit 521 executes correction processing for the edge count value for one mesh band input from the edge count unit 520. The edge count value correction unit 521 outputs the corrected edge count value for each mesh to the mesh data output unit 530.

In S613, the mesh data output unit 530 of the corrected pixel value count value obtained by executing the shaping process on the corrected pixel value count value for each corrected mesh input from the pixel value count value correction unit 511. Output mesh data. The mesh data output unit 530 outputs the mesh data of the corrected edge count value obtained by executing the shaping process on the edge count value for each corrected mesh input from the edge count value correction unit 521. The mesh data of the corrected pixel value count value and the mesh data of the corrected edge count value output by the mesh data output unit 530 are stored in the RAM 303.

In S614, the mesh data generation unit 314 determines whether or not the generation of mesh data for one page is completed. When the mesh data generation unit 314 determines that the generation of the mesh data for one page is completed (YES in S614), the mesh data generation unit 314 ends this flow. When the mesh data generation unit 314 determines that the generation of mesh data for one page has not been completed (NO in S614), the process shifts to S615.

In S615, the mesh data generation unit 314 updates various variables such as the main scanning position of the pixel being processed, the position of the pixel in each mesh, and the counter and pointer indicating the position of the mesh being counted. That is, the mesh data generation unit 314 updates the pixel of interest to be processed to the next pixel in the mesh data for one page. For example, when there is a pixel at a position adjacent to the pixel of interest in the main scanning direction, the pixel of interest to be processed is updated to that pixel. If there is no pixel at a position adjacent to the pixel of interest in the main scanning direction but there is a pixel at a position adjacent in the sub-scanning direction, the pixel adjacent in the sub-scanning direction and at the most upstream position in the main scanning direction is processed. Update the attention pixel that becomes. After the various variables are updated, the process is returned to S602, and the processes of S602 to S615 are repeatedly executed until the generation of mesh data for one page is completed (YES in S614).

By executing the mesh data generation process described above, the mesh data generation unit 314 can generate mesh data that does not depend on the gradation and resolution of the halftone image data.

As the mesh data, the mesh data of the pixel value count value, the mesh data of the edge count value in the main scan direction, the mesh data of the edge count value in the sub scan direction, and the mesh data of the edge count values of the main scan and the sub scan. Can be mentioned. As an example, let P (b), P (c), and P (d) be the pixel value count values for the meshes shown in FIGS. 4 (b), 4 (c), and 4 (d), respectively. Let the edge count values for the meshes shown in FIGS. 4 (b), 4 (c), and 4 (d) be E (b), E (c), and E (d), respectively. It is possible to generate mesh data with the following results.
P (b) ≒ P (c) ≒ P (d)
E (b) ≒ E (c) <E (d)

That is, although the resolutions of FIGS. 4 (b), 4 (d) and 4 (c) are different, it is possible to generate mesh data having similar values as the pixel value count values.

Although the resolutions of FIGS. 4 (b) and 4 (c) are different, it is possible to generate mesh data having similar edge count values. Further, although the arrangement of dots such as continuous arrangement, distributed arrangement, and aggregated arrangement is different between FIGS. 4 (b), 4 (c), and 4 (d), the pixel value count values are the same. It is possible to generate mesh data.

FIG. 7 is a diagram showing a state in which the mesh data generated by the mesh data generation process executed in the flow shown in FIG. 6 and the halftone image data are stored in the RAM 303. In the A4 image, when the resolution is 600 dpi × 600 dpi, 4 bpp (16 gradations of 0 to 15), the halftone image data 701 is about 5000 pxel × 7000 pixel, and has a capacity of about 17 MB.

In the A4 image, when 1 mesh is 1 mm × 1 mm and 1 byte is used for each mesh, the mesh data 711 of the pixel value count value is the corrected data output by the mesh data output unit 530, which is about 64 KB. Will have capacity. Similarly, the mesh data 712 of the edge count value is also the corrected data output by the mesh data output unit 530, and has a capacity of about 64 KB.

Regarding the mesh data 712 of the edge count value, the mesh data of the edge count value in the main scanning direction, the mesh data of the edge count value in the sub scanning direction, and the mesh data of all these edge count values are individually stored in the RAM. Is possible.

<Notification processing of fixing temperature adjustment information>
8, 9, and 10 are explanatory views of notification processing of fixing temperature adjustment information in the image forming apparatus 101.

FIG. 8 is a flowchart showing an example of a notification processing procedure for fixing temperature adjustment information in the image forming apparatus 101. FIG. 9 is a flowchart showing details of S805 and an example of a procedure for generating fixing temperature adjustment information in the image forming apparatus 101. This flow is executed under the control of the CPU 301 included in the system controller unit 300. This control is executed based on the control program stored in the ROM 302.

In S801, the CPU 301 specifies various parameters to the mesh data generation unit 314 based on the image format such as the resolution / gradation of the halftone image data spooled in the RAM 303 and the image size. Examples of various parameters include a mesh size, a gradation conversion method (Exp Mode), the number of meshes, a multiplication value used for correction processing, and a shift amount.

In S802, the CPU 301 activates the mesh data generation unit 314. When the mesh data generation unit 314 is activated, the mesh data generation process is executed.

In S803, the CPU 301 transfers the halftone image data stored in the RAM 303 to the mesh data generation unit 314.

In S804, the CPU 301 waits until the mesh data generation process for one page by the mesh data generation unit 314 is completed. While the CPU 301 is on standby, the mesh data generation unit 314 executes the mesh data generation process described with reference to FIG. 6, and stores the generated mesh data for one page in the RAM 303.

In S805, the CPU 301 analyzes the mesh data for one page stored in the RAM 303 and generates the fixing temperature adjustment information for one page. The details of the process of generating the fixing temperature adjustment information will be described later with reference to FIGS. 9 and 10.

In S806, the CPU 301 notifies the fixing temperature control unit 325 of the print controller unit 320 via the printer communication IF305, the communication cable 308, and the controller communication IF326 of the fixing temperature adjustment information for one page generated in S805. The fixing temperature control unit 325 controls the heaters 34 and 35 of the fixing device 31 based on the notified fixing temperature adjustment information for one page and the temperature detected by the temperature sensor of the fixing device 31.

Next, the details of the example of the procedure for generating the fixing temperature adjustment information will be described with reference to FIG.

In S901, the CPU 301 first analyzes the required temperature for each mesh, that is, the temperature required for fixing the toner to the recording medium for each mesh with respect to the mesh data for one page. Then, as the analysis result, the CPU 301 derives the temperature required for fixing the toner on the recording medium for each mesh with respect to the mesh data for one page. Details of the analysis of the required temperature for each mesh will be described later with reference to FIG. In the present embodiment, with respect to the mesh data for one page, the temperature required for fixing the toner to the recording medium for each mesh is a graph showing an example of the relationship between the pixel value count value and the edge count value and the fixing temperature. Derived by FIG. In FIG. 11, the horizontal axis shows the pixel value count value, and the vertical axis shows the edge count value. The pixel value count value shows a larger value as it goes to the right, and the edge count value shows a larger value as it goes up. A large pixel value count value indicates that the amount of toner loaded on the mesh is large. The halftone image data in a mesh having a large edge count value includes, for example, a medium-density image that has been screen-processed, and a pattern image of very fine lines and grids. Basically, the larger the amount of toner loaded, that is, the larger the pixel value count value, the higher the temperature required for fixing the toner on the recording medium. On the other hand, even with the same toner loading amount, the halftone image data in an image having a large number of edges, that is, a mesh having a large edge count value is formed with the toner isolated, so that the force of bonding the toners to each other is weak. .. As a result, it is necessary to fix the toner on the recording medium with a larger amount of heat, so that the temperature required for fixing the toner on the recording medium becomes high.

<Required temperature analysis for each mesh>
FIG. 10 shows an example of the required temperature analysis processing procedure for each mesh, that is, the details of S901, and is the analysis processing of the temperature required for fixing the toner to the recording medium for each mesh with respect to the mesh data for one page. It is a flowchart which shows the procedure example. In this flow, either parallel processing or serial processing may be used for processing for each mesh.

In S1001, the CPU 301 determines whether or not the pixel value count value of the mesh to be processed (the mesh of interest) is equal to or greater than the threshold value Tv1. The pixel value count value is a corrected pixel value count value included in the mesh data output by the mesh data output unit 530 and corrected by the pixel value count value correction unit 511. When it is determined that the pixel value count value is equal to or higher than the threshold value Tv1 (YES in S1001), the process shifts to S1002. When it is determined that the pixel value count value is not equal to or higher than the threshold value Tv1 (NO in S1001), the process shifts to S1003.

In S1002, the CPU 301 determines and sets the fixing temperature required for fixing the toner on the recording medium to T1 with respect to the mesh of interest.

In S1003, the CPU 301 determines whether or not the pixel value count value for each mesh is equal to or greater than the threshold value Tv2, which is smaller than the threshold value Tv1. When it is determined that the pixel value count value is equal to or higher than the threshold value Tv2 (YES in S1003), the process shifts to S1004. When it is determined that the pixel value count value is not equal to or higher than the threshold value Tv2 (NO in S1003), the process shifts to S1007.

In S1004, the CPU 301 determines whether or not the edge count value is equal to or greater than the threshold value Te1. The edge count value is a corrected edge count value included in the mesh data output by the mesh data output unit 530 and corrected by the edge count value correction unit 521. When it is determined that the edge count value is equal to or higher than the threshold value Te1 (YES in S1004), the process shifts to S1005. When it is determined that the edge count value is not equal to or higher than the threshold value Te1 (NO in S1004), the process shifts to S1006.

In S1005, the CPU 301 determines and sets the fixing temperature required for fixing the toner on the recording medium to T3, which is a temperature lower than T2 described later, for the mesh of interest.

In S1006, the CPU 301 determines and sets the fixing temperature required for fixing the toner on the recording medium to T2, which is a temperature lower than T1, for the mesh of interest.

In S1007, the CPU 301 derives the edge count value threshold value Te2 based on the pixel value count value and the pixel value count value threshold value Tv2 of the mesh of interest and the edge count value threshold value Te1. This derives the edge count value threshold value Te2 because there may be cases where the toner image is isolated even when the pixel value count value is small and the number of edges is relatively small. In this embodiment, it is derived by linear interpolation as Te2 = Te1 × ((edge count value of attention mesh) ÷ Tv2).

Next, in S1008, the CPU 301 determines whether or not the edge count value of the mesh of interest is equal to or greater than the threshold value Te2 derived in S1007. When it is determined that the edge count value is equal to or higher than the threshold value Te2 (YES in S1008), the process shifts to S1009. When it is determined that the edge count value is not equal to or higher than the threshold value Te2 (NO in S1008), the process shifts to S1010.

In S1009, the CPU 301 determines and sets the fixing temperature required for fixing the toner on the recording medium to T4, which is a temperature lower than T3, with respect to the mesh of interest.

In S1010, the CPU 301 determines and sets the fixing temperature required for fixing the toner to the recording medium to T5, which is a temperature lower than T4, with respect to the mesh of interest.

When the fixing temperature required for fixing the toner to the recording medium is set for the mesh of interest in S1002, S1005, S1006, S1009, and S1010, this flow ends.

Returning to the explanation of the flow of FIG.

In S902, the CPU 301 derives the fixing temperature required for fixing the toner on the recording medium for each predetermined area on one page. For example, it is assumed that the heaters 34 and 35 included in the fixing device 31 are devices that can independently control the temperature for each region divided into five in the main scanning direction. When the fixing temperature control unit 325 of the print controller unit 320 can control the temperature independently, the fixing temperature required for fixing the toner to the recording medium is derived for each predetermined area corresponding to the independently controllable area. To do. The CPU 301 sets the highest temperature among the fixing temperatures required for fixing the toner on the recording medium derived in S901 in the plurality of meshes included in the predetermined areas to fix the toner on the recording medium in each area. Determined as the required fixing temperature. Then, the CPU 301 generates the fixing temperature required for fixing the toner on the recording medium in the determined plurality of regions as the fixing temperature adjustment information.

FIG. 12 is a diagram for explaining the fixing temperature adjustment information generated in the process flow for generating the fixing temperature adjustment information shown in FIG.

FIG. 12A is a diagram showing an example of halftone image data processed by the mesh data generation unit 314. Characters and photos are arranged on one page.

The halftone image data 1200 has a first lowercase area 1201, a bold uppercase area 1202, a second lowercase area 1203, a black object area 1204, a photographic area 1205, a third lowercase area 1206, and a fourth lowercase area 1207. ..

The first lowercase area 1201 is an area on which small characters are printed, is located in the center of the main scanning direction and upstream of the sub-scanning direction, and has a predetermined size in the main scanning direction and the sub-scanning direction. Is shown.

The bold uppercase area 1202 is an area in which large bold characters are printed, and is located near the center of the main scanning direction and downstream of the first lowercase area 1201 in the sub-scanning direction, and is located in the main scanning direction and the sub A predetermined size area is shown in the scanning direction.

The second lowercase area 1203 is an area on which small characters are printed, and is adjacent to the bold uppercase area 1202 on the downstream side in the sub-scanning direction near the center of the main scanning direction, and is adjacent to the main scanning direction and the sub-scanning direction. Indicates a region of a predetermined size.

The black object area 1204 is an area on which a black object (black image) is printed, and is adjacent to the bold uppercase area 1202 and the second lowercase area 1203 on the downstream side in the main scanning direction, and is adjacent to the main scanning direction and the secondary. A region of a predetermined size is shown in the scanning direction.

The photographic area 1205 is, for example, an area on which an image as a photograph is printed, which is adjacent to the second lower-case area 1203 on the upstream side of the center in the main scanning direction and adjacent to the second lower-sized area 1203 on the downstream side in the sub-scanning direction. A region of a predetermined size is shown in the direction and the sub-scanning direction.

The third lowercase area 1206 is an area on which small characters are printed, which is adjacent to the photographic area 1205 on the downstream side in the main scanning direction and has a predetermined size in the main scanning direction and the sub scanning direction. Is shown.

The fourth lowercase area 1207 is an area on which small characters are printed, which is adjacent to the photographic area 1205 and the third lowercase area 1206 on the downstream side in the sub-scanning direction at the center of the main scanning direction and in the main scanning direction. And a region of a predetermined size is shown in the sub-scanning direction.

FIG. 12B is a diagram showing an example of fixing temperature adjustment information generated by the CPU 301 of the system controller unit 300 based on the halftone image data shown in FIG. 12A. The fixing temperature required for fixing the toner to the recording medium is derived for each region in which one page is divided into a plurality of areas in the main scanning direction and the sub-scanning direction, and any one of T1 to T5 is set. In the fixing temperature adjustment information 1210 shown in FIG. 12B, each region divided in the main scanning direction and the sub-scanning direction corresponds to a region whose temperature can be controlled by the heaters 34 and 35 of the fixing device 31.

The highest fixing temperature of T1 to T5 is set as the fixing temperature required for fixing the toner to the recording medium in the area including the image having a large amount of toner, that is, the area corresponding to the black object area 1204. Will be done.

In the region where there are only small characters, that is, the regions corresponding to the first and fourth lowercase regions 1201 and 1207, the temperature of T1 to T5 is the highest as the fixing temperature required for fixing the toner to the recording medium. A low T5 is set.

In the region corresponding to the bold uppercase region 1202, T2, which is the second highest temperature after T1 among T1 to T5, is set as the fixing temperature required for fixing the toner on the recording medium. Further, in the region corresponding to the second lowercase region 1203, T2 is set as the fixing temperature required for fixing the toner to the recording medium, as in the region corresponding to the bold uppercase region 1202. This is because the region corresponding to the second lowercase region 1203 is included in the region where the temperatures of the heaters 34 and 35 can be controlled independently, which is the same as the region corresponding to the bold uppercase region 1202.

In the region corresponding to the photographic region 1205, T3, which is the second highest temperature after T2 among T1 to T5, is set as the fixing temperature required for fixing the toner on the recording medium. This is because the photographic area 1205 has a smaller toner loading amount than the area corresponding to the bold uppercase area 1202.

Among the regions corresponding to the third lowercase region 1206, in the region on the upstream side in the main scanning direction, T3 out of T1 to T5 is set as the fixing temperature required for fixing the toner to the recording medium. Of the regions corresponding to the third lowercase region 1206, in the region downstream of the main scanning direction, T5 out of T1 to T5 is set as the fixing temperature required for fixing the toner to the recording medium. This is a region in which the heaters 34 and 35 can be independently temperature controlled, in which the region on the upstream side in the main scanning direction of the region corresponding to the third lowercase region 1206 is the same as the region corresponding to the bold uppercase region 1202. This is because it is included in.

By executing the mesh data generation process described above, the mesh data generation unit 314 generates mesh data that does not depend on the gradation and resolution of the halftone image data. Further, the generated mesh data is sequentially stored in the RAM 303 to form one page of mesh data (mesh map data), and the mesh data is read out and analyzed by the CPU 301 to obtain the fixing temperature adjustment information. be able to. Further, in this way, the hardware is responsible for the analysis processing of the image data, while the software is responsible for the generation processing and the notification processing of the fixing temperature adjustment information. By sharing these processes between the hardware and the software, the analysis can be performed. It is possible to shorten the time required.

Further, at this time, the software can analyze the image without degrading the accuracy without classifying the cases according to the resolution and gradation of the image data to be printed. Therefore, it is possible to efficiently process the image data and perform more detailed fixing temperature control without depending on the resolution and gradation of the image data.

[Other Embodiments]
In the above-described embodiment, the image forming apparatus 101 provided with a developing station corresponding to four colors of CMYK has been described as an example. That is, an example of an image forming apparatus including four photoconductor drums and a scanner unit of each photoconductor drum has been described. However, it is not limited to this example. A development station other than four colors may be provided, or a single color development station may be provided.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

314 Mesh data generation unit 501 Gradation conversion unit 510 Pixel value count unit 511 Pixel value count value correction unit 520 Edge count value correction unit 521 Edge count value correction unit 530 Mesh data output unit

Claims (12)

An image forming apparatus provided with fixing means for fixing an image formed on a recording medium based on image data.
A conversion means for converting the gradation of the image data into a predetermined gradation, and
A counting means for generating a feature amount count value obtained by counting the feature amount of the image in the image data converted to the predetermined gradation by the conversion means for each predetermined area of the image data.
A correction means for correcting the feature amount count value for each predetermined region using a predetermined correction value, and
An analysis that analyzes the feature amount count value for each of the predetermined regions corrected by the correction means and generates information for adjusting the fixing temperature when the image is fixed on the recording medium by the fixing means. Means and
An image forming apparatus characterized by having. The image forming apparatus according to claim 1, wherein the conversion means converts the image data into the predetermined gradation according to the gradation of the image data. The image forming apparatus according to claim 1 or 2, wherein the counting means counts the feature amount of the image for each of the predetermined regions having a size corresponding to the resolution of the image data. The counting means
A first counting means for generating a pixel value count value by counting the pixel values of each pixel of the image data, and
A second counting means for generating an edge count value by counting the number of places where the difference between the pixel values of adjacent pixels of the image data is equal to or greater than a predetermined value.
The image forming apparatus according to claim 3, wherein the image forming apparatus has. The counting means is characterized in that the pixel value count value generated by the first counting means and the edge count value generated by the second counting means are counted as the feature amount count value. The image forming apparatus according to claim 4. The image forming apparatus according to claim 4, wherein the second counting means counts independently in the main scanning direction and the sub-scanning direction. The correction means
A first correction means for correcting the pixel value count value generated by the first counting means, and
The image forming apparatus according to any one of claims 4 to 6, further comprising a second correcting means for correcting the edge count value generated by the second counting means. The image forming apparatus according to claim 7, wherein the second correction means corrects the edge count value with correction values independent of the main scanning direction and the sub-scanning direction. The image forming according to claim 7 or 8, wherein the first correction means corrects the pixel value count value by using the predetermined correction value according to the gradation and resolution of the image data. apparatus. The image according to any one of claims 7 to 9, wherein the first correction means corrects the pixel value count value by using the predetermined correction value that performs an integer multiplication and shift operation. Forming device. It is a control method of an image forming apparatus provided with a fixing means for fixing an image formed on a recording medium based on image data.
A conversion step for converting the gradation of the image data into a predetermined gradation, and
A count step for generating a feature amount count value obtained by counting the feature amount of the image in the image data converted to the predetermined gradation in the conversion step for each predetermined area of the image data,
A correction step of correcting the feature amount count value for each predetermined region using a predetermined correction value, and
The feature amount count value for each of the predetermined regions corrected in the correction step is analyzed, and information for adjusting the fixing temperature when the image is fixed on the recording medium by the fixing means is generated. Analysis steps and
A method for controlling an image forming apparatus, which comprises. A program for causing a computer to function as each means of the image forming apparatus according to any one of claims 1 to 10.