JP2011164618A - Image forming apparatus, and control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of obtaining a stable print image, and to provide a control method for the image forming apparatus. <P>SOLUTION: The image forming apparatus includes an image forming means 2, an image reading means Si, an extraction means 51 and a control means 51. The image forming means 2 forms an image in accordance with a processing condition. The image reading means Si reads the image including a pixel being an isolated point, which is formed by the image forming means 2. The extraction means 51 extracts feature quantity from the pixel being the isolated point and pixels around it included in the image data read by the image reading means Si. The control means 51 corrects the processing condition applied to the image forming means 2 according to the feature quantity extracted by the extraction means 51. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present embodiment relates to an image forming apparatus for forming an image on an image forming medium and an image forming method applied to the image forming apparatus.

  In an image forming apparatus such as a digital multi-function peripheral, various parameters for printing an image can be corrected. For example, the image forming apparatus can correct parameters used for registration control, image quality maintenance control, transfer current control, and the like. By correcting the parameters, the image forming apparatus can correct the laser light output control by the laser optical component, the drive control of the driving component, the process condition, and the like. Further, in recent years, image data to be printed on an image forming medium may be corrected in order to adjust print image quality in the image forming apparatus.

JP-A-10-214336

  According to the present embodiment, an object is to provide an image forming apparatus capable of obtaining a stable print image and a method for controlling the image forming apparatus.

  According to the embodiment, the image forming apparatus includes an image forming unit, an image reading unit, an extracting unit, and a control unit. The image forming unit forms an image according to processing conditions. The image reading unit reads an image including pixels that are isolated points formed by the image forming unit. The extracting unit extracts a feature amount from isolated point pixels and surrounding pixels included in the image data read by the image reading unit. The control unit corrects a processing condition applied to the image forming unit according to the feature amount extracted by the extraction unit.

FIG. 1 is a perspective view illustrating an external configuration example of a digital multifunction peripheral. FIG. 2 is a cross-sectional view schematically showing an example of the internal configuration of the digital multifunction peripheral. FIG. 3 is a block diagram for explaining a configuration example of a control system in the digital multi-function peripheral. FIG. 4 is a block diagram illustrating a configuration example of the output image processing unit. FIG. 5 is a diagram illustrating a configuration of isolated points included in the adjustment pattern image. FIG. 6 is a flowchart for explaining the flow of image quality adjustment processing.

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

First, the configuration of a digital multifunction peripheral (MFP, Multi-Functional Peripheral) as an image forming apparatus will be described.
FIG. 1 is a perspective view illustrating an external configuration example of a digital multifunction peripheral. FIG. 2 is a cross-sectional view schematically showing an example of the internal configuration of the digital multifunction peripheral. As shown in FIG. 1, the digital multifunction peripheral includes a scanner 1, a printer 2, a finisher 3, a control panel 4, and a system control unit 5.

The scanner 1 is installed on the upper part of the main body of the digital multifunction peripheral. The scanner 1 is controlled by the system control unit 5. The scanner 1 is an apparatus that reads an image of a document and converts it into image data. The scanner 1 outputs image data of a document to the system control unit 5.
The scanner 1 includes an image reading unit 10 as a photoelectric conversion unit including a CCD line sensor that converts an image of one line in the main scanning direction of a document into image data. The image reading unit 10 reads an image of the entire original by scanning the original with a CCD line sensor in the sub-scanning direction of the original.

  The scanner 1 has a document table glass 11 and a document sensor 12. The document table glass 11 places a document to be scanned by the image reading unit 10. The image reading unit 10 scans a document on the platen glass 11 through the glass of the platen glass 11. The document sensor 12 detects a document on the platen glass 11. The document sensor 12 outputs a signal indicating the presence or absence of a document on the document table glass 11. The document sensor 12 detects the document size on the document table glass 11.

  The scanner 1 has an automatic document feeder (ADF) 13. The ADF 13 has a paper feed tray 14. The paper feed tray 14 holds a document to be read. The ADF 13 conveys originals held by the paper feed tray 14 one by one. The scanner 1 reads an image of a document conveyed by the ADF 13. In the scanner 1, the ADF 13 also functions as a cover for the document placed on the document table glass 11.

The printer 2 functions as an image forming unit. The printer 2 is controlled by the system control unit 5. The printer 2 prints the image data supplied from the system control unit 5 on a sheet as an image forming medium.
The printer 2 includes paper feed cassettes 21A, 21B, and 21C. These paper feed cassettes 21A, 21B, and 21C store sheets as image forming media on which images are printed. For example, each of the paper feed cassettes 21A, 21B, and 21C can be attached to and detached from the lower part of the digital multi-function peripheral body. Each of the paper feed cassettes 21A, 21B, and 21C has paper feed rollers 22A, 22B, and 22C, respectively. Each of the paper feed rollers 22A, 22B, and 22C takes out one sheet at a time from each of the paper feed cassettes 21A, 21B, and 21C.

  The transport unit 23 transports the paper within the printer 2. The conveyance unit 23 includes a plurality of conveyance rollers 23 a to 23 f and a registration roller 24. The transport unit 23 transports the paper taken out by the paper feed rollers 22 </ b> A, 22 </ b> B, and 22 </ b> C to the registration roller 24. The registration roller 24 conveys the paper to the transfer position at the timing of transferring the image.

  The plurality of image forming units 25 (25Y, 25M, 25C, 25K) each form an image of each color (yellow, magenta, cyan, black). The exposure unit 26 serves as an image to be developed in each color on a photosensitive drum D (Dy, Dm, Dc, Dk) as an image carrier in each image forming unit 25 (25Y, 25M, 25C, 25K) by laser light. An electrostatic latent image is formed. The exposure unit 26 irradiates the photosensitive drum D with a laser beam controlled according to the image data through an optical system such as a polygon mirror. An electrostatic latent image is formed on the surface of the photosensitive drum irradiated with the laser light. The exposure unit 26 controls the laser beam according to a control signal from the system control unit 5. For example, the exposure unit 26 controls the power of the laser light according to a control signal from the system control unit 5. Further, the exposure unit 26 also controls the modulation amount of the pulse width for controlling the emission of the laser light according to the control signal from the system control unit 5.

  Each image forming unit 25 (25Y, 25M, 25C, 25K) converts the electrostatic latent image formed on the photosensitive drum D (Dy, Dm, Dc, Dk) into each color (yellow, magenta, cyan, black). A toner image is formed by developing with this toner. The intermediate transfer belt 27 is an intermediate transfer member. Each image forming unit 25 (25Y, 25M, 25C, 25K) transfers the toner image of each color formed on the photosensitive drum D (Dy, Dm, Dc, Dk) onto the intermediate transfer belt 27 (primary transfer). To do.

  Each image forming unit 25 (25Y, 25M, 25C, 25K) includes sensors such as a potential sensor Sv and a density sensor Sd. The potential sensor Sv is a sensor that detects the surface potential of the photosensitive drum. In each image forming unit 25 (25Y, 25M, 25C, 25K), the surface of each photoconductive drum D is charged by the charging charger before being exposed by the exposure unit 26. The charging condition of the charging charger can be changed by a control signal from the system control unit 5. The potential sensor Sv detects the surface potential of the photosensitive drum after the surface is charged by the charging charger. The density sensor Sd detects the density of the toner image transferred onto the intermediate transfer belt 27. Further, the density sensor Sd may detect a toner image formed on the photosensitive drums Dy, Dm, Dc, and Dk.

  Each of the image forming units 25Y, 25M, 25C, and 25K superimposes and transfers (primarily transfers) a toner image developed with toner of each color (yellow, magenta, cyan, and black) onto the intermediate transfer belt 27. The intermediate transfer belt 27 holds a color image in which toner images of respective colors are overlapped. The transfer unit 28 transfers a color image of a plurality of color toners on the intermediate transfer belt 27 to a sheet at the secondary transfer position. The secondary transfer position is a position where the toner image on the intermediate transfer belt 27 is transferred to a sheet. The secondary transfer position is a position where the support roller 28a and the secondary transfer roller 28b face each other.

  An image sensor Si as an image reading unit is provided between the time when the surface of the transfer belt 27 passes through each image forming unit 25 and reaches the secondary transfer position. The image sensor Si reads a toner image formed on the transfer belt 27 by each image forming unit 25. The image sensor Si functions as a sensor that detects the density value of each pixel constituting the image formed on the transfer belt 27. That is, the image sensor Si reads an image on the transfer belt 27 as two-dimensional image data composed of predetermined pixel units. Image data acquired by the image sensor Si is output to the system control unit 5. The system control unit 5 detects the image quality of the image formed on the transfer belt 27 by analyzing the image data from the image sensor Si.

  The registration roller 24 conveys the sheet to the secondary transfer position in synchronization with the toner image on the intermediate transfer belt 27. The transfer unit 28 supplies the sheet on which the toner image is transferred at the secondary transfer position to the fixing unit 29. The fixing unit 29 fixes the toner image on the sheet. The fixing unit 29 heats the paper on which the transfer unit 28 has transferred the toner image in a pressurized state. The fixing unit 29 conveys (discharges) the fixed sheet to either the paper discharge unit 30 or the finisher 3. The transfer current used for the transfer process, the fixing temperature used for the fixing process, and the like can be controlled by the system control unit 5.

The finisher 3 includes a paper discharge mechanism 32 that processes the paper on which the printer 2 has formed an image and a paper discharge tray 33 that stacks the paper. The finisher 3 may have a function of stapling sheets stacked on the paper discharge tray 33 or a function of hole punching.
The control panel 4 is a user interface. For example, the user inputs information such as setting information on the control panel 4. The control panel 4 is controlled by the system control unit 5. The control panel 4 outputs information input by the user to the system control unit 5.
Note that the printer 2 shown in FIG. 2 is an electrophotographic printer. However, the printer of this embodiment is not limited to the electrophotographic system. This embodiment can also be applied to printers other than electrophotographic systems such as an ink jet system or a thermal transfer system.

Next, the configuration of the control system of the digital multi-function peripheral will be described.
FIG. 3 is a block diagram for explaining a configuration example of a control system in the digital multi-function peripheral.
The digital multi-function peripheral has a system control unit 5 that controls the entire apparatus. The system control unit 5 is connected to the scanner 1, printer 2, finisher 3, and control panel 4 via a system bus or the like.

  The system control unit 5 includes a CPU (processor) 51, a main memory 52, a ROM 53, a nonvolatile memory 54, an HDD 55, a page memory 56, a printer controller 57, a FAX controller 58, an electronic data creation unit 59, and an external interface (I / F). 57a, 58b, 59a and an image processing unit 60.

  The CPU 51 controls the entire digital multi-function peripheral. The CPU 51 is a processor that realizes processing by executing a program. The CPU 51 is connected to each unit in the apparatus via the system bus. The CPU 51 connects not only each unit in the system control unit 5 but also the scanner 1, the printer 2, the finisher 3, the control panel 4, and the like via the system bus. The CPU 51 outputs an operation instruction to each unit and acquires various information from each unit through bidirectional communication with the scanner 1, the printer 2, and the control panel 4. In addition, the CPU 51 inputs information indicating detection signals and operation states of various sensors installed in each unit in the apparatus.

  The main memory 52 is constituted by a RAM or the like. The main memory 52 functions as a working memory or a buffer memory. The ROM 53 is a non-rewritable nonvolatile memory that stores programs, control data, and the like. The CPU 51 implements various processes by executing programs stored in the ROM 53 (or the non-volatile memory 54 and the HDD 55) while using the main memory 52. For example, the CPU 51 functions as an extraction unit and a control unit by executing a program.

  The nonvolatile memory 54 is a rewritable nonvolatile memory. The nonvolatile memory 54 stores a control program executed by the CPU 51 and control data. The nonvolatile memory 54 stores setting information, processing conditions, and the like. The hard disk drive (HDD) 55 is a large-capacity storage device. The HDD 55 stores image data and various history information. The HDD 55 may store a control program and control data. The HDD 55 may store setting information and processing conditions.

  The page memory 56 is a memory for developing image data to be processed. For example, the image data read by the scanner 1 is stored in the page memory 56 after being subjected to image processing. The image data stored in the page memory 56 is subjected to image processing for printing and output to the printer 2, stored in the HDD 55, or transmitted to an external device via the external interface 57a.

  The printer controller 57 controls print processing in response to a print request from an external device. The printer controller 57 is connected to an external device via an external interface 57a. The printer controller 57 receives print data from an external device via the external interface 57a. The FAX controller 58 controls FAX communication (transmission / reception of facsimile data). The FAX controller is connected to a public line via a FAX interface 58a. The FAX controller 58 transmits and receives facsimile data via the FAX interface 58a and the public line. The electronic data creation unit 59 creates electronic data including image data read by the scanner 1. The external interface 59a is an interface for transmitting electronic data to an external device. For example, the external interfaces 57a and 59a may be network interfaces via a network.

The image processing unit 60 includes an input image processing unit 61, a compression unit 62, a decompression unit 63, and an output image processing unit 64.
The input image processing unit 61 functions as a scanner-type image processing unit that processes an image read by the scanner 1 as an input image. The input image processing unit 61 executes shading correction processing, gradation conversion processing, interline correction processing, and the like on the image data read by the scanner 1.

  The shading correction process is a process for correcting image data in accordance with the sensitivity variation of each photoelectric conversion element such as a CCD or the light distribution characteristic of a lamp for illuminating a document. The gradation conversion process is a process of converting the value of each pixel constituting the image data (for example, each signal value of R, G, and B) according to a lookup table. The inter-line correction process is a process for correcting a physical positional shift of each of the RGB sensors in the CCD line sensor of the scanner 1. The input image processing unit 61 may perform resolution conversion, brightness adjustment, contrast adjustment, saturation adjustment, sharpness adjustment, and the like on the image data acquired by the scanner 1.

  The compression unit 62 compresses the image data processed by the input image processing unit 61. The compression unit 62 stores the compressed image data in the page memory 56. Note that the compression unit 62 may output the compressed image data to the HDD 55 or the like.

  The decompression unit 63 decompresses the compressed image data. The decompressing unit 63 reads the compressed image data from the page memory 56 and decompresses the compressed image data. The decompression unit 63 outputs the decompressed image data to the output image processing unit 64. Note that the decompressing unit 63 may output the decompressed image data to the HDD 55 or the like.

  The output image processing unit 64 converts the image data into image data for printing. The output image processing unit 64 functions as a printer-type image processing unit that generates image data for printing as an output image. In the copy process, the output image processing unit 64 converts the image data read by the scanner 1 supplied through the input image processing unit 61, the page memory 56, and the like into image data for printing. In the printing process, the output image processing unit 64 converts the image data acquired by the printer controller 57 from the external device via the external interface 57a into image data for printing.

FIG. 4 is a block diagram illustrating a configuration example of the output image processing unit 64.
In the configuration example illustrated in FIG. 4, the output image processing unit 64 includes a color conversion unit 71, a sharpening unit 72, a gradation correction unit 73, a dither processing unit 74, and the like.
The color conversion unit 71 converts the color of the image data. For example, the color conversion unit 71 converts color image data composed of R (red), G (green), and B (blue) signals into C (cyan), M (magenta), Y (yellow), and K (black) signals. Convert to color image data consisting of For example, the scanner 1 reads a document image as color image data composed of R (red), G (green), and B (blue) signals, and the printer 2 reads C (cyan), M (magenta), and Y (yellow). , K (black) signal color image data is printed. In this case, in the copy process, the color conversion unit 71 prints image data composed of C, M, Y, and K signals that the printer 2 prints color image data composed of R, G, and B signals read by the scanner 1. Convert to data.

The sharpening unit 72 sharpens the image data according to the characteristics of the printer. For example, the sharpening unit 72 performs image data correction processing such as filter processing, inking processing, and gamma correction processing. The tone correction unit 73 corrects the tone in the sharpened image data. The gradation correction unit 73 converts the value of the image data in accordance with the gradation characteristics in the printer 2. The dither processing unit 74 performs dither processing on the tone-corrected image data. Parameters for each process such as the color conversion unit 71, the sharpening unit 72, the gradation correction unit 73, and the dither processing unit 74 are set by the CPU 51 of the system control unit 5. For example, the number of screen lines generated by the dither processing can be set by the CPU 51 of the system control unit 5.
According to the output image processing unit 64 as described above, the printer 2 is supplied with CMYK image data after various image processing and dither processing.

Next, image quality adjustment processing for the printer 2 will be described.
In the printer 2, the image sensor Si captures an image formed on the intermediate transfer belt 27 serving as an image carrier and acquires two-dimensional image data. The image sensor Si may read an image formed on each photosensitive drum D. The printer 2 according to the present embodiment forms an adjustment pattern image or image data including an adjustment pattern image on the intermediate transfer belt 27 for image quality adjustment processing, and is formed on the intermediate transfer belt 27. It is assumed that the image sensor Si reads the pattern image for adjustment.

  The adjustment pattern image is composed of a pattern that allows the image forming state in the printer 2 to be observed. It is assumed that the adjustment pattern image includes isolated points. FIG. 5 is a diagram illustrating a configuration of isolated points included in the adjustment pattern image. As shown in FIG. 5, the isolated points are formed by only the target pixel, and no pixels are formed in the surrounding eight pixels with respect to the target pixel. For example, the target pixel may have the maximum maximum density value, and the eight pixels around the target pixel may have the minimum density value. In the present embodiment, an image including a plurality (for example, N) of isolated points as shown in FIG. 5 is used as an adjustment pattern image. The pattern image for adjustment is formed on the intermediate transfer belt 27 and the photosensitive drum D as an image carrier.

  In the pattern image for adjustment, a plurality of isolated points are formed at least in the entire main scanning direction with respect to the image forming area on the transfer belt 27 and the photosensitive drum D. The pattern image for adjustment is formed on the transfer belt or the photosensitive drum in the image quality adjustment process. However, the adjustment pattern image may be formed outside a predetermined image forming area for the image forming medium in a normal print process.

FIG. 6 is a flowchart for explaining the flow of image quality adjustment processing.
First, the printer 2 forms an adjustment pattern image including N isolated points on a transfer belt 27 as an image carrier. The image sensor Si reads a pattern image formed on the transfer belt 27. Image data obtained by reading the adjustment pattern by the image sensor Si is supplied to the system control unit 5 and stored in the main memory 52, the HDD 55, or the page memory 56.

  In the system control unit 5, the CPU 51 performs image quality adjustment processing based on image data read by the image sensor Si by executing an image quality adjustment program. First, the CPU 51 calculates a feature amount for each isolated point in the image data of the pattern image acquired by the image sensor Si. That is, the CPU 51 initializes a variable n for counting the number of isolated points (ACT 13). The CPU 51 increments a variable n for specifying an isolated point to be processed (ACT 14). When n is incremented, the CPU 51 determines the nth isolated point as the pixel of interest (ACT 15).

  When the target pixel as an isolated point to be processed is determined, the CPU 51 determines the density value of the target pixel and each pixel around the target pixel (eight surrounding pixels) in the image data of the pattern image acquired by the image sensor Si. The density difference (feature value) from each density value is calculated (ACT 16). For example, in the example illustrated in FIG. 5, the CPU 51 uses | a22-a11 |, | a22-a12 |, | a22-a13 |, | a22-a21 |, | a22-a23 |, | a22-a31 |, | a22. Each absolute value of −a32 | and | a22−a33 | is calculated as eight density differences (feature values).

  When the density difference between the surrounding 8 pixels with respect to the target pixel is calculated, the CPU 51 determines whether or not all density differences (feature values) are equal to or greater than the first threshold (Th1) (ACT 17). When all the feature values are equal to or greater than the first threshold value (ACT17, YES), the CPU 51 determines that the isolated point as the target pixel is reproduced well. The CPU 51 determines that the isolated point is reproduced well when a predetermined number (for example, 7) or more of the eight feature amounts is equal to or more than the first threshold value. Also good. That is, the first threshold value is a reference value for determining whether or not the isolated point is reproduced well due to the density difference between the target pixel and the surrounding pixels, and may be set as appropriate.

  When it is determined that all the feature values are equal to or greater than the first threshold (ACT 17, YES), the CPU 51 determines that the isolated point as the target pixel is reproduced well, and the sum of the determination results (overall) The determination value is incremented by “+1” (ACT 18). When the overall determination value is “+1”, or when it is determined that all the feature values are not equal to or greater than the first threshold (ACT 17, NO), the CPU 51 determines whether the variable n is the total number N of isolated points in the pattern image. It is determined whether or not (ACT 19).

  When the variable n is not N (ACT19, NO), the CPU 51 returns to ACT14, increments the variable n, and repeatedly executes the processes from ACT15 to ACT19. When the variable n is N (ACT 19, YES), the CPU 51 determines whether or not the comprehensive determination value is equal to or greater than the second threshold (Th2) (ACT 20). If the overall determination value is equal to or greater than the second threshold (ACT 20, YES), the CPU 51 determines that isolated points are reproduced well in the entire pattern image and image formation (image point formation) is good. When the comprehensive determination value is equal to or greater than the second threshold value, that is, when it is determined that the image formation is good, the CPU 51 ends the process without performing the image quality adjustment process (correction of various parameters).

  The second threshold value is a reference value for determining the reproducibility of isolated points and the image forming state in the printer based on the reading results of a plurality of isolated points in the pattern image, and may be set as appropriate. . The overall determination value is not limited to the sum of the determination results for each isolated point, and may be an average value of the determination results for each isolated point, and indicates the frequency of isolated points with good reproducibility. It may be a value.

  When the comprehensive determination value is less than the second threshold value (ACT20, NO), the CPU 51 determines that image formation (image point formation) is poor because the reproducibility of isolated points is poor as a whole pattern image. . When the comprehensive determination value is less than the second threshold value, that is, when it is determined that the image formation is poor, the CPU 51 corrects the processing conditions in the printer (image quality adjustment) in order to improve the image quality. Processing is performed (ACT21).

  The image quality adjustment only needs to improve the reproducibility of isolated points. For example, as the image quality adjustment, the number of screen lines generated by the dither processing may be reduced in accordance with the total determination value (the total sum of the determination results or the average value of the determination results). In addition, the image quality adjustment may increase the power for the exposure unit 26 to emit laser light in accordance with the overall determination value. In addition, the image quality adjustment may correct the modulation amount of the pulse width by the exposure unit 26, the charging condition for the photosensitive drum D, or the latent image of the toner according to the total judgment value. The development conditions may be corrected, or the toner image transfer conditions may be corrected. Furthermore, the image quality adjustment may be performed by correcting the fixing conditions for the fixing unit 29 to fix the toner image on the paper according to the comprehensive determination value.

  As described above, the image forming apparatus includes a forming unit that forms a two-dimensional pattern image including an isolated point on an image carrier, a photographing unit that photographs a pattern image formed on the image carrier, and a photographing unit. Based on the image data of the photographed two-dimensional pattern image, a calculation unit that calculates the feature amount indicating the reproducibility of the isolated point, and according to the feature amount calculated by the calculation unit, the image processing condition, the image formation condition, etc. Adjusting means for adjusting.

  That is, the image forming apparatus forms a two-dimensional pattern image including an isolated point on the transfer belt, reads an image including the isolated point formed on the transfer belt with an image sensor, and reproduces the isolated point from the read image data. Corresponding feature amounts are extracted, and image processing conditions and image forming conditions are adjusted so as to improve the reproducibility of isolated points according to the extracted feature amounts. According to the image forming apparatus as described above, it is possible to control the reproducibility of isolated points, to obtain a highly reliable print quality, and to make a print image stably and highly reproducible.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Scanner, 2 ... Printer, 5 ... System control part, 24 ... Registration roller, 25 ... Image forming part, D ... Photosensitive drum, 26 ... Exposure part, 27 ... Intermediate transfer belt (transfer belt), Si ... Image sensor , 28 ... transfer section, 29 ... fixing section, 51 ... CPU, 60 ... image processing section, 71 ... color conversion section, 72 ... sharpening section, 73 ... gradation correction section, 74 ... dither processing section.

Claims (10)

An image forming apparatus,
Image forming means for forming an image according to processing conditions;
An image reading unit that reads an image including a pixel that is an isolated point formed by the image forming unit;
Extraction means for extracting feature values from pixels of isolated points and peripheral pixels of the isolated points included in the image data read by the image reading means;
Control means for correcting processing conditions applied to the image forming means according to the feature amount extracted by the extracting means;
An image forming apparatus comprising: The image forming unit forms an image to be transferred to an image forming medium on an image carrier,
The image reading means reads an image formed on the image carrier;
The image forming apparatus according to claim 1, wherein: The extraction means extracts a value indicating the reproducibility of a pixel as an isolated point as a feature amount.
The image forming apparatus according to claim 2, wherein: The extraction unit calculates a density difference between a pixel serving as an isolated point and a peripheral pixel of the isolated point as a feature amount,
The control unit corrects the processing condition applied to the image forming unit to a condition that enhances reproducibility of isolated points when the feature amount is smaller than a first threshold.
The image forming apparatus according to claim 3, wherein: The extraction means calculates a plurality of density differences between a pixel that is an isolated point and a plurality of pixels that surround the isolated point as a feature amount,
The control unit corrects the processing condition applied to the image forming unit to a condition that increases the reproducibility of isolated points when any of the plurality of density differences is smaller than a first threshold value.
The image forming apparatus according to claim 3, wherein: An image forming apparatus control method comprising:
Form an image that includes isolated pixels according to the processing conditions,
Read the image including the pixel that becomes the isolated point formed as image data,
A feature amount is calculated from pixels of isolated points in the read image data and surrounding pixels,
Correcting processing conditions used for image formation in accordance with the calculated feature amount;
A control method for an image forming apparatus, comprising: The image including the pixels to be isolated points is formed on an image carrier that holds an image to be transferred to an image forming medium,
The reading reads an image formed on the image carrier,
The method of controlling an image forming apparatus according to claim 6, wherein: The feature amount is calculated by calculating a value indicating reproducibility of a pixel that is an isolated point.
The method of controlling an image forming apparatus according to claim 7, wherein: The feature amount is calculated by calculating a density difference between a pixel that is an isolated point and a peripheral pixel of the isolated point,
In the correction of the condition, when the feature amount is smaller than a first threshold value, the processing condition used for the image forming process is corrected to a condition in which the reproducibility of isolated points is increased.
The method of controlling an image forming apparatus according to claim 8, wherein: The feature amount is calculated by calculating a plurality of density differences between a pixel that is an isolated point and a plurality of pixels that surround the isolated point,
In the correction of the condition, when any one of the plurality of density differences is smaller than the first threshold, the processing condition used for the image forming process is corrected to a condition for improving the reproducibility of the isolated point.
The method of controlling an image forming apparatus according to claim 8, wherein:

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