JP2024017500A - Image forming device - Google Patents

Abstract

[Problem] To suppress deterioration in print image quality when performing calibration in parallel with printing. SOLUTION: An image processing unit 72 executes predetermined image processing by referring to characteristic data stored in a first storage area 81a in a memory 61c. The calibration processing unit 74 (a) sequentially derives specific data of a plurality of toner colors based on the detected density data, immediately stores the derived specific data in the second storage area 82a in the memory 61c, and (b) ) After all the specific data regarding the plurality of toner colors are stored in the second storage area 82a, during a period when the image processing unit 72 is not performing image processing on the image for printing, the plurality of specific data in the second storage area 82a are stored. The specific data for all of the plurality of toner colors in the first storage area 81a is updated at once with the specific data for all of the toner colors. [Selection diagram] Figure 3

Description

The present invention relates to an image forming apparatus.

Generally, an electrophotographic image forming apparatus executes calibration at a predetermined timing, and uses characteristic data such as gamma curves for tone adjustment so that the image density characteristics of the print match the target density characteristics. I'm making adjustments.

In calibration, a predetermined image pattern (a group of toner patch images) is formed on the intermediate transfer belt, the density of the image pattern is optically measured, and based on the measurement results, the above-mentioned density characteristics (multiple levels (key level distribution) is adjusted.

An image forming apparatus forms such a group of toner patch images in a non-printable area outside of a printable area where a print image can be formed in the main scanning direction (direction perpendicular to the conveying direction of the toner image). (For example, see Patent Document 1). Therefore, such an image forming apparatus can form a toner patch image group for calibration in a non-printable area while forming a toner image for printing in a printable area.

JP 2021-148927 Publication

However, in a color image forming apparatus, when performing calibration in parallel with printing (that is, when forming a group of toner patch images for calibration in parallel with the formation of toner images for printing), multiple toner colors are used. Since the density and gradation adjustments are performed individually for each of the toner colors, it is possible that the density and gradation adjustments are made for some toner colors and the density and gradation adjustments are not made for the remaining toner colors. Image processing (screen processing, etc.) of images for printing may be performed, resulting in a decrease in print quality. In particular, deterioration in image quality is likely to occur in areas of mixed colors such as composite black.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that suppresses deterioration in print image quality when performing calibration in parallel with printing.

An image forming apparatus according to the present invention includes a plurality of photoreceptor drums corresponding to a plurality of toner colors, an exposure device that irradiates the plurality of photoreceptor drums with light to form an electrostatic latent image, and a plurality of photoreceptor drums corresponding to the plurality of toner colors. A plurality of developing devices each attaching to the electrostatic latent images on the plurality of photoreceptor drums and developing them; an intermediate transfer belt to which the toner images on the plurality of photoreceptor drums are transferred; In the calibration, a toner patch image is formed for the plurality of toner colors using the photoreceptor drum, the exposure device, and the development device, and the toner patch image measured by the density sensor is Detected density data of a patch image is acquired, and at least one of density adjustment and gradation adjustment is performed individually for each of the plurality of toner colors based on the detected density data, and characteristic data for the plurality of toner colors are obtained. a calibration processing section that updates the image data, a storage device, and an image processing section that performs predetermined image processing by referring to the characteristic data stored in a first storage area of the storage device. The calibration processing unit (a) sequentially derives the specific data of the plurality of toner colors based on the detected density data, and stores the derived specific data in a second storage area in the storage device. (b) after all of the specific data regarding the plurality of toner colors are stored in the second storage area, during a period when the image processing for the image for printing is not performed by the image processing section; , the specific data for all of the plurality of toner colors in the first storage area is updated at once with the specific data for all of the plurality of toner colors in the second storage area.

According to the present invention, it is possible to obtain an image forming apparatus that suppresses deterioration in print image quality when performing calibration in parallel with printing.

These and other objects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a side view showing part of the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram showing a configuration example of the controller 61 in FIG. 2. As shown in FIG. FIG. 4 is a diagram illustrating an example of a toner patch image group formed during calibration. FIG. 5 is a flowchart illustrating the operation of the controller 61 during calibration in the image forming apparatus shown in FIGS. 1 to 4.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a side view showing part of the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is a device having an electrophotographic printing function, such as a printer, facsimile machine, copying machine, or multifunction device.

The image forming apparatus of this embodiment is a tandem type color image forming apparatus, and includes a plurality of photoreceptor drums 1a to 1d, exposure devices 2a to 2d, and a plurality of developing devices 3a to 3d. The photoreceptor drums 1a to 1d are photoreceptors of four colors: cyan, magenta, yellow, and black.

The exposure devices 2a to 2d are devices that scan and irradiate the photoreceptor drums 1a to 1d with laser light to form electrostatic latent images. The laser beam is scanned in a direction (main scanning direction) perpendicular to the rotation direction (sub scanning direction) of the photoreceptor drums 1a to 1d. The exposure devices 2a to 2d each have a laser scanning unit including a laser diode as a light source of laser light, and an optical element (lens, mirror, polygon mirror, etc.) that guides the laser light to the photoreceptor drums 1a to 1d.

Furthermore, a charger such as a scorotron, a cleaning device, a static eliminator, and the like are arranged around the photoreceptor drums 1a to 1d. The cleaning device removes residual toner on the photoreceptor drums 1a to 1d after the primary transfer, and the static eliminator removes static from the photoreceptor drums 1a to 1d after the primary transfer.

The developing devices 3a to 3d attach toner cartridges filled with toners of four colors, cyan, magenta, yellow, and black, respectively, and the toners conveyed from toner hoppers in the toner cartridges to the photoreceptor drums 1a to 1d. The toner is attached to the electrostatic latent images on the photoreceptor drums 1a to 1d to form toner images.

The photoreceptor drum 1a and the developing device 3a perform magenta development, the photoreceptor drum 1b and the developing device 3b perform cyan development, and the photoreceptor drum 1c and the developing device 3c perform yellow development. , the photosensitive drum 1d and the developing device 3d perform black development.

The intermediate transfer belt 4 is an annular image carrier (intermediate transfer member) that contacts the photoreceptor drums 1a to 1d and to which the toner images on the photoreceptor drums 1a to 1d are primarily transferred. The intermediate transfer belt 4 is stretched around a drive roller 5, and is rotated by a driving force from the drive roller 5 in a direction from a contact position with the photoreceptor drum 1d to a contact position with the photoreceptor drum 1a.

The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 onto the paper. Note that the paper onto which the toner image has been transferred is conveyed to the fixing device 9, and the toner image is fixed onto the paper.

The roller 7 has a cleaning brush, and brings the cleaning brush into contact with the intermediate transfer belt 4 to remove toner remaining on the intermediate transfer belt 4 after the toner image is transferred to the paper.

The density sensor 8 is an optical sensor that irradiates the intermediate transfer belt 4 with light and detects reflected light from the surface of the intermediate transfer belt 4 or the toner pattern on the surface. For example, when adjusting the toner density, the density sensor 8 irradiates a predetermined area of the intermediate transfer belt 4 with a light beam, detects the reflected light of the light beam, and outputs an electric signal corresponding to the amount of light.

FIG. 2 is a block diagram showing the electrical configuration of an image forming apparatus according to an embodiment of the present invention. For example, as shown in FIG. 2, the image forming apparatus according to the embodiment includes a print engine 10a and a sheet conveying section 10b as shown in FIG. 1, for example, as well as a controller 61 and an engine processor 62. The print engine 10a physically prints an image to be printed on a print sheet. The sheet conveyance unit 10b conveys print sheets from a paper feed cassette or the like to the print engine 10a, and also conveys the printed print sheets to a discharge tray or the like.

Here, the controller 61 and the engine processor 62 are implemented as a controller board and an engine board each equipped with an arithmetic processing unit, and operate independently of each other. The controller 61 generates image data of an image to be printed and transfers the image data to the engine processor 62. The engine processor 62 controls the print engine 10a to print an image to be printed.

The controller 61 includes an image generation section 71, an image processing section 72, an image output section 73, and a calibration processing section 74.

FIG. 3 is a block diagram showing a configuration example of the controller 61 in FIG. 2. As shown in FIG.

Specifically, as shown in FIG. 3, the controller 61 includes a processor 61a such as a CPU (Central Processing Unit) that executes a predetermined program, and an ASIC (Application Specific Integrated Circuit) 61b that executes specific data processing. The arithmetic processing section functions as an image generation section 71, an image processing section 72, an image output section 73, and a calibration processing section 74. Here, the ASIC functions as an image processing section 72, and the processor 61a functions as an image generation section 71, an image output section 73, and a calibration processing section 74. Further, the controller 61 includes a memory 61c (RAM here) as a storage device.

The image generation unit 71 generates raster image data of an image to be printed from print data written in a page description language.

The image processing unit 72 performs predetermined image processing on the image data. The image processing unit 72 executes predetermined image processing by referring to the characteristic data stored in the first storage area 81a in the memory 61c. Note that when the controller 61 is activated, the current characteristic data is stored in the first storage area 81a.

Here, the image processing includes screen processing (FM screen processing and/or AM screen processing), and the characteristic data is screen data or the like. The screen data indicates screens for each of a predetermined plurality (256 in this case) of gradation levels. Screen processing replaces each pixel in a page image with a screen pattern corresponding to its pixel value (gradation level).

The image output unit 73 transfers the generated image data to the subsequent engine processor 62. For example, the engine processor 62 transmits a synchronization signal to the controller 61 at a predetermined timing, and the controller 61 (image output unit 73) transfers image data according to the synchronization signal.

The engine processor 62 is equipped with an arithmetic processing unit such as a computer that executes a predetermined program, an ASIC that executes specific data processing, etc., and controls the print engine 10a according to the image data of the transferred page image to generate an image of the page image. The print engine 10a also controls the sheet transport section 10b to transport the print sheet on which the page image is to be printed.

The calibration processing unit 74 executes calibration in parallel with printing, and uses the print engine 10a (photoreceptor drums 1a to 1d, exposure devices 2a to 2d, and developing devices 3a to 3d) in the calibration. to form a toner patch image for a plurality of toner colors, obtain the detected density data of the toner patch image measured by the density sensor 8, and individually calculate the density based on the detected density data for each of the plurality of toner colors. Perform at least one of adjustment and gradation adjustment and update characteristic data regarding a plurality of toner colors.

FIG. 4 is a diagram illustrating an example of a toner patch image group formed during calibration. In the calibration, the controller 61 outputs a command to the engine processor 62, and for example, as shown in FIG. 4, the engine processor 62 causes the print engine 10a to form a toner patch image group 102 along with a page image 101. . As a result, on the intermediate transfer belt 4, a page image 101 is formed in a printable area, and a toner patch image group 102 is formed in a non-printable area outside the printable area.

Here, the toner patch image group 102 includes toner patch images of 8 gradation levels for AM screen (screen pattern toner images) and FM Contains a toner patch image (screen pattern toner image) with 8 gradation levels for the screen. Therefore, here, screen data of 256 gradation levels is derived from detected density data of 8 gradation levels. In other words, gradation adjustment (adjustment of the density of each gradation level) is performed so that the actual density of the 8 gradation levels becomes linear based on the detected density data, and the screen pattern corresponding to the density after gradation adjustment is A screen pattern of 256 gradation levels is selected by selecting and adding points by interpolation, etc., and thereby, screen data is derived.

Furthermore, the calibration processing unit 74 (a) sequentially derives the specific data (screen data, etc.) of the plurality of toner colors described above based on the detected density data, and stores the derived specific data in the second storage in the memory 61c. (b) After all the specific data regarding the plurality of toner colors are stored in the second storage area 82a, during a period when the image processing unit 72 is not performing image processing on the image for printing. , the specific data for all of the plurality of toner colors in the first storage area 81a are updated at once with the specific data for all of the plurality of toner colors in the second storage area 82a.

Here, the period is a period between image processing for two consecutive page images after the page image 101 in which toner patch images (toner patch image group 102) are formed in parallel. Note that the period may be a period between the print job of the print and the subsequent print job.

Further, the first storage area 81a described above is secured in the kernel space 81 of the operating system running on the processor 61a, and the second storage area 82a is secured in the user space.

Next, the operation of the image forming apparatus will be explained. FIG. 5 is a flowchart illustrating the operation of the controller 61 during calibration in the image forming apparatus shown in FIGS. 1 to 4.

The controller 61 performs predetermined image processing on the target image to be printed according to user operations, etc., and the engine processor 62 controls photosensitive drums 1a to 1d, exposure devices 2a to 2d, developing devices 3a to 3d, etc. Then, the target image after image processing is printed.

Then, when the calibration execution timing arrives, in the calibration, the calibration processing unit 74 first causes the engine processor 62 to form a toner patch image group 102 together with the page image 101 of the target image, and then creates a toner patch image group 102. The density of each toner patch image 102 is detected by the density sensor 8 (step S1), and the detected density data is obtained from the engine processor 62 (step S2).

Detected density data of a plurality of toner colors are sequentially acquired, and the calibration processing unit 74 starts generating characteristic data (screen data, etc.) in order from the toner color for which detected density data has been acquired (step S3).

Then, the calibration processing unit 74 stores the generated characteristic data (screen data, etc.) in the second storage area 82a (step S4). Note that, in parallel with the derivation of the characteristic data, the characteristic data in the first storage area 81a is read out for the subsequent page image, and image processing (screen processing, etc.) is performed using the characteristic data. .

Each time the generation of characteristic data for one toner color is completed, the calibration processing unit 74 determines whether generation of characteristic data for all toner colors is completed (step S5), and generates characteristic data for all toner colors. Characteristic data is generated and stored in the second storage area 82a until the generation of characteristic data is completed.

When the generation of characteristic data for all toner colors is completed, the calibration processing unit 74 determines whether image processing in the image processing unit 72 (image processing that refers to the characteristic data in the first storage area 81a) is being executed. If the image processing unit 72 is performing the image processing (step S6), it waits, and if the image processing unit 72 is not performing the image processing (for example, the image processing unit 72 processes the page image). After the image processing is completed, but before the image processing of the subsequent page image is started), the characteristic data in the second storage area 82a is transferred and the characteristic data in the first storage area 81a is overwritten. As a result, the characteristic data in the first storage area 81a is updated with the characteristic data in the second storage area 82a (step S7).

As described above, according to the embodiment described above, the image processing section 72 executes predetermined image processing by referring to the characteristic data stored in the first storage area 81a in the memory 61c. The calibration processing unit 74 (a) sequentially derives specific data of a plurality of toner colors based on the detected density data, immediately stores the derived specific data in the second storage area 82a in the memory 61c, and (b) ) After all the specific data regarding the plurality of toner colors are stored in the second storage area 82a, during the period when the image processing unit 72 is not performing image processing on the image for printing, the plurality of specific data in the second storage area 82a are stored. The specific data for all of the plurality of toner colors in the first storage area 81a is updated at once with the specific data for all of the toner colors.

This eliminates the need for printing with only some specific data of a plurality of toner colors updated, thereby suppressing deterioration in print image quality when performing calibration in parallel with printing.

Note that various changes and modifications to the embodiments described above will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. It is intended that such changes and modifications be included within the scope of the claims.

The present invention is applicable to, for example, an electrophotographic color image forming apparatus.

1a to 1d Photosensitive drum 2a to 2d Exposure device 3a to 3d Developing device 4 Intermediate transfer belt 5 Drive roller 6 Transfer roller 7 Roller 8 Density sensor 61 Controller 61a Processor 61b ASIC
61c Memory (an example of storage device)
72 Image processing section 74 Calibration processing section 81 Kernel space 81a First storage area 82 User space 82a Second storage area

Claims (4)

multiple photoreceptor drums that correspond to multiple toner colors;
an exposure device that irradiates the plurality of photoreceptor drums with light to form an electrostatic latent image;
a plurality of developing devices that perform development by respectively attaching the plurality of toner colors to the electrostatic latent images on the plurality of photoreceptor drums;
an intermediate transfer belt to which the toner images on the plurality of photoreceptor drums are transferred;
Calibration is performed in parallel with printing, and in the calibration, toner patch images are formed for the plurality of toner colors using the photoreceptor drum, the exposure device, and the development device, and the images are measured by a density sensor. the detected density data of the toner patch image that has been detected, and individually performs at least one of density adjustment and gradation adjustment based on the detected density data for each of the plurality of toner colors. a calibration processing unit that updates characteristic data about the
a storage device;
an image processing unit that performs predetermined image processing by referring to the characteristic data stored in a first storage area in the storage device;
The calibration processing unit (a) sequentially derives the specific data of the plurality of toner colors based on the detected density data, and immediately stores the derived specific data in a second storage area of the storage device. (b) After all of the specific data regarding the plurality of toner colors are stored in the second storage area, during a period when the image processing unit is not performing the image processing on the image for printing, the collectively updating the specific data for all of the plurality of toner colors in the first storage area with the specific data for all of the plurality of toner colors in a second storage area;
An image forming apparatus characterized by: 2. The image forming method according to claim 1, wherein the period is a period between the image processing for two consecutive page images subsequent to a page image in which the toner patch image is formed in parallel. Device. further comprising an ASIC that operates as the image processing section and a processor that operates as the calibration processing section,
The first storage area is secured in a kernel space of an operating system running on the processor,
the second storage area is secured in a user space;
The image forming apparatus according to claim 1, characterized in that: The image processing includes screen processing,
the characteristic data includes screen data including screen patterns for each of a plurality of predetermined gradation levels;
The image forming apparatus according to any one of claims 1 to 3, characterized in that:

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