JP2009116061A - Image forming apparatus and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect various defects in image formation and to specify and deal with the cause of the defect. <P>SOLUTION: An image forming apparatus includes: an image forming part to form images; a reading part to read the image formed on a recording paper; a comparison part which compares reference image data by image data to be formed by the image forming part or image data read by the recording part when the normal image is formed, with the image data of the image read by the reading part and detects a difference between them; an internal pattern storage part to store image data of a prescribed internal pattern; and a control part to perform various controls. When the difference is detected by the comparison part in a normal image formation mode to form an image by normal image data other than the internal pattern, the image is formed and read based on the image data of the internal pattern, and also, the comparison with the internal pattern is performed by the comparison part, then, the cause of the difference is specified. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming system such as a copying machine and a printer, and more particularly to an image forming apparatus and an image forming system capable of coping with a defect in a formed image.

  When an image is formed in the image forming apparatus, the image on the recording paper is uneven due to a malfunction of each part in the image forming apparatus or adhesion of dirt. There are things to do.

For example, Patent Documents 1 to 2 listed below describe various methods for detecting or eliminating such image defects in the image forming apparatus.
JP-A-8-290553 (first page, FIG. 1) Japanese Unexamined Patent Publication No. 2006-162855 (first page, FIG. 1)

  In the above-described patent document 1, image data to be image-formed is used as a reference image, and read images obtained by reading an actually formed image are compared to detect a defective image formation. . In this case, there is an advantage that image defects can be detected in real time by performing comparison during image formation.

  However, depending on the type of image that is actually formed, there is a case where it is difficult to distinguish from a defect and the defect cannot be detected. For example, when an image in which a large number of horizontal stripes and horizontal lines appear is formed, it is difficult to detect an image defect in which horizontal stripes occur. Also, when forming a light image with many white backgrounds, it becomes difficult to detect uneven density due to lack of toner. In the cited document 1, a defect can be detected, but there is a problem that the cause cannot be specified from the detection result.

  Further, the one described in the cited document 2 describes a method of outputting a specific inspection pattern, detecting the occurrence of dirt, and continuously passing a blank sheet for cleaning. In this case, the cause is not specified, and the method is specialized for dirt. Further, since the content is specialized for the occurrence of dirt, the countermeasure is limited to the blank paper passing. For this reason, there is a problem that it is not possible to deal with any defect other than dirt with respect to discovery and resolution.

  The present invention has been made to solve the above-described problems, and is capable of finding various defects in image formation, and can identify and deal with the cause of the found defect and an image forming apparatus An object is to realize an image forming system.

That is, the present invention as a means for solving the problems is as described below.
(1) The invention according to claim 1 is an image forming unit that forms an image according to image data on a recording paper, a reading unit that reads an image formed on the recording paper by the image forming unit, and the image forming unit. A comparison unit that detects a difference by comparing the image data to be formed in the image data or the reference image data based on the image data read by the reading unit during normal image formation, and the image data of the image read by the reading unit; An internal pattern storage unit that stores image data of a predetermined internal pattern, and a control unit that performs various controls of image formation, and the control unit executes image formation using normal image data other than the internal pattern When a difference is detected in the comparison unit in the normal image formation mode, image formation and reading with the image data of the internal pattern are executed. Performing control to shift to cause specific image forming mode to identify the cause of the difference by performing a comparison of the internal pattern in serial comparison unit, it is an image forming apparatus according to claim.

  (2) In the invention according to claim 2, the control means has a function of performing control for eliminating the specified cause, and when the specified cause is eliminated, the normal image forming mode is changed from the cause specifying image forming mode. The image forming apparatus according to claim 1, wherein the normal image formation is executed by returning to the step.

  (3) In the invention according to claim 3, the control means performs control to shift from the normal image forming mode to the cause identifying image forming mode at a predetermined timing, except when the difference is detected. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

  (4) The invention according to claim 4 is an image forming unit for forming an image according to image data on a recording paper, image data to be formed by the image forming unit, or an image read by the reading unit during normal image formation. A comparison unit that detects a difference by comparing reference image data based on data and image data of an image read by the reading unit, an internal pattern storage unit that stores image data of a predetermined internal pattern, and various controls of image formation An image forming apparatus having a control unit that performs the image forming apparatus, and a reading device that reads an image formed on a recording sheet by the image forming apparatus. The control unit performs image formation using normal image data other than the internal pattern. When a difference is detected in the comparison unit in the normal image forming mode to be executed, image formation and reading with the image data of the internal pattern is performed. Performing control to shift to cause specific image forming mode to identify the cause of the difference by performing a comparison of the internal pattern by the comparison unit as well as the execution, an image forming system, characterized in that.

  (5) In the invention according to claim 5, the control means has a function of performing control for eliminating the specified cause, and when the specified cause is eliminated, the normal image forming mode is changed from the cause specifying image forming mode. 5. The image forming system according to claim 4, wherein the normal image formation is executed by returning to step S2.

  (6) In the invention according to claim 6, the control means performs control to shift from the normal image forming mode to the cause identifying image forming mode at a predetermined timing, except when the difference is detected. The image forming system according to claim 4, wherein the image forming system is an image forming system.

As described above, according to the present invention, the following effects can be obtained.
(1) In the invention of the image forming apparatus according to the first aspect, the control unit performs the reference image and the read image in the comparison unit during the execution of the normal image forming mode in which the image formation using the normal image data other than the internal pattern is executed. If a difference is detected between the two, the image formation and reading are performed using the image data of the internal pattern, and the comparison unit compares the internal pattern and shifts to a cause-specific image forming mode for specifying the cause of the difference. Take control.

  As a result, when any defect is detected during the execution of the normal image forming mode, the internal pattern is output and read as the cause specifying image forming mode to specify the cause, and the internal pattern and the reading result are obtained. Various causes of defects are identified by comparison. As a result, if any defect is found during normal image formation, it is possible to find and identify various defects in image formation by using the internal pattern by moving to the cause identification image formation mode. become.

  (2) In the invention of the image forming apparatus according to claim 2, the control means performs control to eliminate the specified cause, and when the specified cause is eliminated, the cause specifying image forming mode is changed to the normal image forming mode. By returning and executing normal image formation, normal image formation can be continued after dealing with various defects.

  (3) In the invention of the image forming apparatus according to claim 3, the control means changes from the normal image forming mode to the cause identifying image forming mode at a predetermined timing, except when a difference is detected in the normal image forming mode. By performing the shift control, it is possible to find and deal with defects that are difficult to find in normal image formation.

  (4) In the invention of the image forming system according to the fourth aspect, the control unit performs the reference image and the read image in the comparison unit during the execution of the normal image forming mode for executing the image formation using the normal image data other than the internal pattern. If a difference is detected between the two, the image formation and reading are performed using the image data of the internal pattern, and the comparison unit compares the internal pattern and shifts to a cause-specific image forming mode for specifying the cause of the difference. Take control.

  As a result, when any defect is detected during the execution of the normal image forming mode, the internal pattern is output and read as the cause specifying image forming mode to specify the cause, and the internal pattern and the reading result are obtained. Various causes of defects are identified by comparison. As a result, if any defect is found during normal image formation, it is possible to find and identify various defects in image formation by using the internal pattern by moving to the cause identification image formation mode. become.

  (5) In the invention of the image forming system according to claim 5, the control means performs control to eliminate the specified cause, and when the specified cause is eliminated, the cause specifying image forming mode is changed to the normal image forming mode. By returning and executing normal image formation, normal image formation can be continued after dealing with various defects.

  (6) In the invention of the image forming system according to claim 6, the control means changes from the normal image forming mode to the cause identifying image forming mode at a predetermined timing, except when a difference is detected in the normal image forming mode. By performing the shift control, it is possible to find and deal with defects that are difficult to find in normal image formation.

The best mode (embodiment) for carrying out the present invention will be described below in detail with reference to the drawings.
Hereinafter, the configuration of the first embodiment of the image forming apparatus 100 of the present embodiment will be described in detail with reference to FIG.

  In this embodiment, description will be made focusing on the configuration requirements regarding the characteristics of the image forming apparatus 100. Therefore, it is common for an image forming apparatus, and well-known constituent elements are omitted.

Embodiment
The control unit 110 is a control unit that performs various controls of image formation, and includes a print controller 111 and a defect controller 112.

  Here, the print controller 111 performs control related to execution of image formation. Note that the print controller 111 also executes control for performing normal image formation based on normal image data other than internal patterns described later and image formation using internal patterns described later.

  Further, when a difference is detected in the comparison unit in the normal image forming mode in which image formation using normal image data other than the internal pattern is executed, the print controller 111 executes image formation and reading using the image data of the internal pattern. At the same time, the comparison unit compares the internal patterns and controls to shift to the cause specifying image forming mode for specifying the cause of the difference.

  In addition, in the normal image forming mode, the failure controller 112 refers to the comparison result in the comparison unit and notifies the print controller 111 that there is no abnormality unless a difference is detected by the comparison, and the difference is detected by the comparison. If so, a notification output indicating abnormality is transmitted to the print controller 111. Further, the defect controller 112 has a function of identifying the cause of the difference in the comparison result in the cause identification image forming mode with reference to the comparison result in the comparison unit, and a function of performing control for eliminating the identified cause.

  The print controller 111 and the defective controller 112 in the control unit 110 may be realized by one CPU or processor, or may be realized by a plurality of CPUs or processors.

The internal pattern storage unit 120 stores various internal patterns for specifying various image defects in the cause specifying image forming mode.
The image forming unit 130 is a print engine such as an electrophotographic system that forms and outputs an image on a recording sheet.

The reference image storage unit 140 is a storage unit that stores image data output from the print controller 111 and image-formed by the image forming unit 130 as image data of a reference image.
The image reading unit 150 is a sensor that reads an image on recording paper that is formed and output by the image forming unit 130. The image reading unit 150 reads the recording paper discharged from the image forming unit 130 with a line sensor or the like, and obtains read image data.

The read image storage unit 160 is a storage unit that stores read image data obtained by being read by the image reading unit 150.
The comparison unit 170 compares the reference image data, the read image data, the internal pattern image data, and the like to detect a difference, and transmits the comparison result to the defect controller 112.

  Note that the image reading unit 150 may be disposed in the image forming apparatus 100 at a position where the recording paper image-formed by the image forming unit 130 is discharged, or a dedicated unit connected to the subsequent stage of the image forming apparatus 100. It may be an image reading device or an image reading unit built in a post-processing device connected to a subsequent stage of the image forming apparatus 100.

Hereinafter, the first operation (first embodiment) of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG.
Image data sent from an external computer (not shown) or a scanner (not shown) is developed for image formation by the print controller 111 (step S201 in FIG. 2).

  The image data for image formation developed by the print controller 111 is sent to the image forming unit 130 and also sent to the reference image storage unit 140 and stored as image data of the reference image (step S202 in FIG. 2).

  The image forming unit 130 receives the image data for image formation from the print controller 111, executes image formation, forms an image on the recording paper, and outputs it (step S203 in FIG. 2). Here, when the recording paper on which the image is formed is discharged, the image reading unit 150 reads the recording paper and generates read image data. The read image data is stored in the read image storage unit 160.

  Here, the reference image stored in the reference image storage unit 140 and the read image stored in the read image storage unit 160 are compared in the comparison unit 170 (step S204 in FIG. 2). If no difference, i.e., no defect is detected in this comparison (NO in step S <b> 205 in FIG. 2), the defect controller 112 that has received a notification of no difference from the comparison unit 170 notifies the print controller 111 of a notification of no abnormality. .

  Then, the print controller 111 that has received a notification of no abnormality from the defective controller 112 controls each unit to repeat the above image formation until a series of image formation is completed (NO in step S206 in FIG. 2, S201). The series of operations described above is the normal image forming mode.

  Here, if the reference image stored in the reference image storage unit 140 and the read image stored in the read image storage unit 160 are compared by the comparison unit 170 and any difference, that is, a defect is detected (in FIG. 2). In step S <b> 205, YES, the defective controller 112 that has received a notification of difference from the comparison unit 170 notifies the print controller 111 of a notification of abnormality.

  The print controller 111 that has received a notification of an abnormality from the defective controller 112 shifts from the normal image forming mode to the cause identifying image forming mode, temporarily stops normal image formation, and is read from the internal pattern storage unit 120. Each unit is controlled to execute image formation of the internal pattern (step S207 in FIG. 2).

  That is, the print controller 111 sends the image data of the internal pattern read from the internal pattern storage unit 120 to the image forming unit 130, and the image forming unit 130 forms an image of the internal pattern on a recording sheet and outputs it. This internal pattern includes various patterns such as vertical line patterns, horizontal line patterns, multiple charts with different colors or densities, and blank paper patterns (no full-surface image formation) so that the causes of various image formation defects can be easily identified. Prepare. In addition, as this internal pattern, it is preferable that the same pattern is formed on the entire surface of each recording sheet because it is easy to detect any position defect of the recording sheet.

  At this time, the internal pattern image data from the internal pattern storage unit 120 is sent to the image forming unit 130 and also directly to the comparison unit 170. Then, the internal pattern image (read internal pattern image) formed on the recording paper and read by the image reading unit 150 and the internal pattern image (raw internal pattern image) directly sent from the internal pattern storage unit 120 are compared with each other. The comparison is made at 170 (step S208 in FIG. 2).

  When a difference is detected in the comparison between the read internal pattern image and the raw internal pattern image (YES in step S209 in FIG. 2), the comparison unit 170 sends the content and state of the difference to the defective controller 112. The defect controller 112 refers to a predetermined correspondence table, table, or the like to determine the cause of the image defect, that is, which part of the image forming apparatus 100 is defective, from the content or state of the difference. Specify (step S211 in FIG. 2). In addition, the failure controller 112 similarly determines whether or not the specified failure can be repaired by referring to a correspondence table or a table (step S212 in FIG. 2).

  If it is determined that the defect cannot be repaired (NO in step S212 in FIG. 2), the defective controller 112 notifies the print controller 111 of the fact. The print controller 111 that has received this non-repairable notification stops the image forming operation of the image forming apparatus 100 (step S213 in FIG. 2). At this time, the print controller 111 performs a predetermined error display on a display unit (not shown) as necessary.

  Further, when it is identified that the defect can be repaired (YES in step S212 in FIG. 2), the defect controller 112 gives a repair instruction to the identified defect and its corresponding part.

  As this restoration, in addition to self-repairing instructing each unit from the defective controller 112 inside the image forming apparatus 100, a display is made on a display unit (not shown) to perform cleaning by the user. Also good.

  When the repair (step S214 in FIG. 2) is executed, the defective controller 112 notifies the print controller 111 to that effect. Then, the print controller 111 that has received this restoration execution notification executes image formation of the internal pattern read from the internal pattern storage unit 120 again (step S215 in FIG. 2). That is, the print controller 111 sends the image data of the internal pattern read from the internal pattern storage unit 120 to the image forming unit 130, and the image forming unit 130 forms an image of the internal pattern on a recording sheet and outputs it. In this case, image formation of an internal pattern that matches the specified defect is performed.

  At this time, the internal pattern image data from the internal pattern storage unit 120 is sent to the image forming unit 130 and also directly to the comparison unit 170. Then, the internal pattern image (read internal pattern image) formed on the recording paper and read by the image reading unit 150 and the internal pattern image (raw internal pattern image) directly sent from the internal pattern storage unit 120 are compared with each other. The comparison is made at 170 (step S216 in FIG. 2).

  If a difference is detected in the comparison between the read internal pattern image and the raw internal pattern image, the defect has not been eliminated by the above repair execution (step S214 in FIG. 2) (step in FIG. 2). In S217, NO), the defective controller 112 notifies the print controller 111 to that effect. The print controller 111 that has received the notification of defective continuation after repair stops the image forming operation of the image forming apparatus 100 (step S213 in FIG. 2). At this time, the print controller 111 performs a predetermined error display on a display unit (not shown) as necessary.

  On the other hand, if no difference is detected in the comparison between the read internal pattern image and the raw internal pattern image, the defect has been eliminated by the above repair execution (step S214 in FIG. 2) (YES in step S217 in FIG. 2). ), The defective controller 112 notifies the print controller 111 to that effect.

  The print controller 111 that has received the notification of defect elimination after the restoration returns the operation mode of the image forming apparatus 100 to the normal image formation mode, and resumes the interrupted image formation (step S201 in FIG. 2). Note that it is desirable to return to the image in which the occurrence of the defect is detected and resume.

  As a result, when any defect is detected during the execution of the normal image forming mode, the internal pattern is output and read as the cause specifying image forming mode to specify the cause, and the internal pattern and the reading result are obtained. Various causes of defects are identified by comparison. As a result, if any defect is found during normal image formation, it is possible to find and identify various defects in image formation by using the internal pattern by moving to the cause identification image formation mode. become. In addition, the normal image forming mode can be resumed by specifying and repairing.

  3A is a reference image based on image data output from the print controller 111 in the normal image formation mode, and FIG. 3B is a defect on the recording paper output from the image forming unit 130 in the normal image formation mode. An example of a state read image is shown.

  Here, as an example, a state in which horizontal streak stains are generated on an image-formed recording sheet is shown. The comparison unit 170 can detect the difference by comparing these images, but the cause cannot be identified from the difference. Therefore, as described above, the normal pattern forming mode is shifted to the cause identifying image forming mode to form an image of the internal pattern.

  FIG. 3C is a reference image based on an internal pattern based on a horizontal stripe pattern, and FIG. 3D is a read image obtained by forming an image of the internal pattern based on the horizontal stripe pattern on a recording sheet and reading it. In this case, the image defect and the internal pattern overlap, and the comparison unit 170 is in a state where it is difficult to detect the difference.

  FIG. 3E is a reference image based on an internal pattern based on a vertical stripe pattern, and FIG. 3F is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the vertical stripe pattern. In this case, the image defect and the internal pattern do not overlap, and the comparison unit 170 can easily detect the difference. From this difference, the failure controller 112 can identify the cause of the failure.

  FIG. 3G is a reference image with an internal pattern based on a color or density chart, and FIG. 3H is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the chart. In this case, the image defect and the internal pattern overlap, and the comparison unit 170 is in a state where it is difficult to detect the difference.

  FIG. 3 (i) is a reference image based on a blank paper internal pattern, and FIG. 3 (j) is a read image obtained by reading a recording paper having a blank paper internal pattern. In this case, an image is not formed due to a blank paper pattern, no defect is formed, and the comparison unit 170 cannot detect a difference.

  In the case of FIG. 3 described above, for example, since strip-like streaks in the feed direction have occurred, the defective controller 112 estimates possible causes such as contamination of the strip electrode, and displays it as necessary. Causes (not shown) and causes and countermeasures are displayed, and instructions for repair are sent to each unit.

  4A shows a reference image based on image data output from the print controller 111 in the normal image formation mode, and FIG. 4B shows a defect on the recording paper output from the image forming unit 130 in the normal image formation mode. An example of a state read image is shown.

  Here, as an example, a state where a color or density defect has occurred on the entire recording paper on which an image has been formed is shown. The comparison unit 170 can detect the difference by comparing these images, but the cause cannot be identified from the difference. Therefore, as described above, the normal pattern forming mode is shifted to the cause identifying image forming mode to form an image of the internal pattern.

  FIG. 4C is a reference image based on an internal pattern based on a horizontal stripe pattern, and FIG. 4D is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the horizontal stripe pattern. In this case, since the color or density defect is superimposed on the horizontal stripe pattern, it is difficult for the comparison unit 170 to detect the difference, or even if it can be detected, it is difficult to identify the cause.

  4E is a reference image based on an internal pattern based on a vertical stripe pattern, and FIG. 4F is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the vertical stripe pattern. In this case, since the color or density defect is superimposed on the vertical stripe pattern, it is difficult for the comparison unit 170 to detect the difference, or even if it can be detected, it is difficult to identify the cause. .

  FIG. 4G is a reference image based on an internal pattern based on a color or density chart, and FIG. 4H is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the chart.

  In this case, since the density or color of the internal pattern corresponding to the defect changes from the original state due to a defect in color or density, the comparison unit 170 can easily detect the difference. From this difference, the failure controller 112 can identify the cause of the failure.

  FIG. 4 (i) is a reference image based on a blank paper internal pattern, and FIG. 4 (j) is a read image obtained by reading a recording paper having a blank paper internal pattern. In this case, an image is not formed due to a blank paper pattern, no defect is formed, and the comparison unit 170 cannot detect a difference.

  In the case of FIG. 4 described above, for example, since a defect in color or density has occurred, the defect controller 112 can perform a deterioration of a specific color developer, a decrease in density, or a decrease in output of the secondary transfer unit. A possible cause is estimated, and if necessary, a cause and a countermeasure are displayed on a display unit (not shown), or a repair instruction is transmitted to each unit.

  FIG. 5A shows a reference image based on image data output from the print controller 111 in the normal image forming mode, and FIG. 5B shows a defect on the recording paper output from the image forming unit 130 in the normal image forming mode. An example of a state read image is shown. Here, a certain area of the recording paper on which the image is formed has a certain area. The comparison unit 170 can detect the difference by comparing these images, but the cause cannot be identified from the difference. Therefore, as described above, the normal pattern forming mode is shifted to the cause identifying image forming mode to form an image of the internal pattern.

  FIG. 5C is a reference image based on the internal pattern based on the horizontal stripe pattern, and FIG. 5D is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the horizontal stripe pattern. In this case, the image defect and the internal pattern do not overlap, and the comparison unit 170 can easily detect the difference.

  FIG. 5E is a reference image based on the internal pattern based on the vertical stripe pattern, and FIG. 5F is a read image obtained by forming an image on the recording paper and reading the internal pattern based on the vertical stripe pattern. In this case, the image defect and the internal pattern do not overlap, and the comparison unit 170 can easily detect the difference.

  FIG. 5G shows a reference image based on an internal pattern based on a color or density chart, and FIG. 5H shows a read image obtained by forming an image on the recording paper and reading the internal pattern based on the chart. In this case, since the density and color of the internal pattern change due to image defects, the comparison unit 170 can easily detect the difference.

  FIG. 5 (i) is a reference image based on a blank paper internal pattern, and FIG. 5 (j) is a read image obtained by reading a recording paper having a blank paper internal pattern. In this case, despite the blank paper pattern, a defect is formed and the comparison unit 170 can detect the difference. In this case, since a defect has occurred even on a blank sheet, the defect controller 112 can identify the cause of the defect if the contamination on the conveyance path is a defect that has adhered to the recording sheet.

  As described above, it is possible to identify the cause of failure (failure of the image forming apparatus) using various internal patterns and deal with the failure. It is also desirable to make a comprehensive judgment by repeatedly comparing each internal pattern until the cause of the defect becomes clear.

The internal pattern is not limited to the above specific example. It is also possible to use an internal pattern in which a plurality of different patterns are combined on one sheet of recording paper.
Further, in the above specific example, the image data from the print controller 111 is stored in the reference image storage unit 140. It can also be used as a reference image. Similarly, with respect to the internal pattern, it is also possible to use the normal read internal pattern image data obtained by reading the recording paper on which the internal pattern is normally formed as a reference internal pattern image for comparison.

  The image forming apparatus 100 or the image forming system described above can be applied not only to an electrophotographic image forming apparatus but also to various image forming system image forming apparatuses and image forming systems.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention. 6 is a flowchart illustrating an operation state of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation state of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation state of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation state of the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 110 Control part 111 Print controller 112 Defect controller 120 Internal pattern memory | storage part 130 Image forming part 140 Reference | standard image memory | storage part 150 Image reading part 160 Reading image memory | storage part 170 Comparison part

Claims (6)

An image forming unit that forms an image according to image data on a recording sheet;
A reading unit for reading an image formed on a recording paper by the image forming unit;
The image data to be formed by the image forming unit or the reference image data based on the image data read by the reading unit during normal image formation is compared with the image data of the image read by the reading unit to detect a difference. A comparison unit;
An internal pattern storage unit for storing image data of a predetermined internal pattern;
A control unit that performs various controls of image formation,
The control unit executes image formation and reading with the image data of the internal pattern when a difference is detected in the comparison unit in a normal image formation mode in which image formation with normal image data other than the internal pattern is executed. And a control to shift to a cause-specific image forming mode for identifying the cause of the difference by comparing the internal pattern in the comparison unit,
An image forming apparatus. The control means includes
It has a function to perform control to eliminate the specified cause,
When the identified cause is resolved, normal image formation is performed by returning from the cause identification image formation mode to the normal image formation mode.
The image forming apparatus according to claim 1. The control means includes
Except when the difference is detected, control is performed to shift from the normal image forming mode to the cause identifying image forming mode at a predetermined timing.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image forming unit that forms an image according to image data on a recording sheet, image data to be formed by the image forming unit, or reference image data based on image data read by the reading unit during normal image formation and reading by the reading unit An image forming apparatus having a comparison unit that compares image data of the obtained images and detects a difference, an internal pattern storage unit that stores image data of a predetermined internal pattern, and a control unit that performs various controls of image formation;
A reading device that reads an image formed on recording paper by the image forming apparatus,
The control unit executes image formation and reading with the image data of the internal pattern when a difference is detected in the comparison unit in a normal image formation mode in which image formation with normal image data other than the internal pattern is executed. And a control to shift to a cause-specific image forming mode for identifying the cause of the difference by comparing the internal pattern in the comparison unit,
An image forming system. The control means includes
It has a function to perform control to eliminate the specified cause,
When the identified cause is resolved, normal image formation is performed by returning from the cause identification image formation mode to the normal image formation mode.
The image forming system according to claim 4. The control means includes
Except when the difference is detected, control is performed to shift from the normal image forming mode to the cause identifying image forming mode at a predetermined timing.
The image forming system according to claim 4, wherein the image forming system is an image forming system.

Images