JP2024121964A - Image forming device, image reading device - Google Patents

Abstract

[Problem] To provide an image forming apparatus having an image reading device that performs shading correction at an appropriate timing. [Solution] The image forming apparatus includes an image forming section that prints an image on paper, and an image reading device 10 that reads the paper on which the image has been printed by the image forming section. The image reading device 10 includes a reading unit 101 that reads the paper, a shading reference plate 108 for performing shading correction by the reading unit 101, and a control unit 20 that determines whether or not shading correction is required based on the type of adjustment to be performed using the results of reading the paper by the reading unit 101. The control unit 20 causes the reading unit 101 to read the shading reference plate 108 when shading correction is to be performed, and does not cause the reading unit 101 to read the shading reference plate 108 when shading correction is not to be performed. [Selected Figure] Figure 1

Description

The present invention relates to an image forming apparatus that incorporates an image reading device that reads images printed on paper.

The printing press market is expanding in the commercial and industrial printing fields. Printing methods used by such presses include electrophotography, which is also expanding into the offset printing market, and inkjet methods, which have been successful in cultivating a wide range of markets thanks to their large format, low initial cost, and ultra-high speed.

Inkjet printers include, for example, line-head recording devices in which a recording head fixed to the main body ejects droplets in conjunction with the transported paper to print an image on the paper. When a line-head recording device is used in commercial or industrial printing fields where high image quality is required, an image reading device is provided downstream of the recording head in the paper transport direction. The image reading device reads the image printed on the paper. The results of reading by the image reading device are used to detect droplet ejection defects by the recording head, and to adjust color shifts, uneven image density, and the geometric characteristics of the image to be printed. Here, the geometric characteristics of the image include the shape of the image, the printing position, etc.

Image reading devices read paper by shining light onto the paper and receiving the reflected light. When reading the paper, the image reading device performs shading correction. Shading correction is performed to correct variations in the light intensity distribution of the light irradiated onto the paper and variations in the sensitivity of the light receiving elements that receive the reflected light. While shading correction is being performed, the image reading device is unable to read the paper. However, printing machines in the commercial and industrial printing fields are required to have a high operating rate. For this reason, it is preferable for the frequency with which shading correction is performed while the printing machine is printing to be as low as possible.

Patent document 1 discloses an image reading device that determines whether or not to perform shading correction again based on the time it takes to read an original document and the time elapsed since the end of the previous shading correction. Patent document 2 discloses an image forming device that reads an image and determines whether or not calibration is required depending on the type of adjustment to be performed, for calibration performed between sheets of paper during job execution.

JP 2002-305633 A JP 2017-19201 A

For adjustments that are made based on the shape of the paper or the position where the image is printed, such as adjusting the geometric characteristics of an image or color misalignment, shading correction before the adjustment is not necessary. In contrast, for adjustments that require an accurate reading of the color of the printed image, such as adjusting image density unevenness, shading correction must be performed before the adjustment. Image quality is maintained by performing shading correction before adjustments that require an accurate reading of the color of the printed image.

When determining whether or not to perform shading correction again based on time as in Japanese Patent Laid-Open No. 2009-133999, shading correction is performed periodically, and the type of adjustment to be performed is not taken into consideration. As a result, shading correction may be performed before an adjustment that does not require shading correction. This causes a decrease in the operating rate of the image forming apparatus due to unnecessary shading correction.
When performing shading correction between multiple sheets of paper that are printed in succession (between sheets of paper) as in Patent Document 2, it is necessary to widen the interval between sheets of paper depending on the time required for the shading correction, which causes a decrease in productivity of the image forming apparatus.

In view of the above problems, the main objective of the present invention is to provide an image forming apparatus having an image reading device that performs shading correction at appropriate timing.

The image forming apparatus of the present invention comprises an image forming means for printing an image on paper, and an image reading means for reading the paper on which the image has been printed by the image forming means, and the image reading means comprises a reading means for reading the paper, a reference member for performing shading correction by the reading means, and a control means for determining whether or not the shading correction is necessary based on the type of adjustment to be made using the results of reading the paper by the reading means, and for causing the reading means to read the reference member if the shading correction is to be performed, and for not causing the reading means to read the reference member if the shading correction is not to be performed.
The image reading device of the present invention is an image reading device that reads paper transported from an image forming device that prints an image on the paper, and is characterized in that it comprises a reading means for reading the paper, a reference member for performing shading correction of the reading means, and a control means for determining whether or not the shading correction is necessary based on the type of adjustment that the image forming device performs using the reading result of the paper by the reading means, and for causing the reading means to read the reference member if the shading correction is to be performed, and for not causing the reading means to read the reference member if the shading correction is not to be performed.

According to the present invention, by performing shading correction at the appropriate time, it is possible to suppress a decrease in productivity while maintaining image quality.

FIG. 1 is a diagram illustrating the configuration of an image reading device. FIG. 6 is an explanatory diagram of a shading correction process performed during execution of a print job. 6 is a flowchart showing a shading correction process performed during execution of a print job. 10 is another flowchart showing the shading correction process performed during execution of a print job.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings.

Figure 1 is a diagram showing the configuration of an image reading device. This image reading device 10 is provided inside an image forming device (not shown). The image reading device 10 reads paper S that is transported by a print belt 111 after an image has been printed by the image forming device. The results of reading by the image reading device 10 are fed back to the image forming device and are used for various adjustments such as color shifts, uneven image density, and adjustment of geometric characteristics of the image by the image forming device. For example, electrophotography or inkjet printing is used as a printing method for the image forming device. Note that when the image forming device is an inkjet type, the results of reading by the image reading device 10 are also used to detect defective droplet ejection by the recording head.

The image reading device 10 includes a box-shaped housing 100. The housing 100 incorporates a reading unit 101 that reads paper S, a reading glass 107, a shading reference plate 108, a motor 109, a photosensor 110, and a control unit 20. The reading unit 101 includes light sources 102a and 102b, reflecting mirrors 103a, 103b, 103c, 103d, and 103e, an imaging lens 104, a light receiving unit 105, and a sensor board 106.

The light sources 102a and 102b are light-emitting units that irradiate light onto the paper S. The light sources 102a and 102b each include a light-emitting element row that is configured by arranging a plurality of light-emitting elements, such as LEDs (Light Emitting Diodes), in a line. The light-receiving unit 105 receives the light that is irradiated from the light sources 102a and 102b and reflected by the paper S. The reflecting mirrors 103a to 103e are an optical system that guides the light reflected by the paper S to the imaging lens 104. The imaging lens 104 forms an image of the reflected light guided by the reflecting mirrors 103a to 103e on the light-receiving surface of the light-receiving unit 105.

The light receiving unit 105 outputs an analog electrical signal (hereinafter simply referred to as "analog signal") corresponding to the reflected light received on the light receiving surface. The analog signal represents the reading result of the paper S. The light receiving unit 105 has a light receiving element row in which a plurality of photoelectric conversion elements, such as CCD (Charge Coupled Device) sensors, are arranged in the same direction as the light emitting element row. The light receiving unit 105 is mounted on a sensor board 106. The sensor board 106 is connected to the control unit 20, and transmits the analog signal output from the light receiving unit 105 to the control unit 20. The configuration of the control unit 20 will be described later.

The reading unit 101 reads an image in the main scanning direction, which is the direction in which the rows of light-emitting elements of the light sources 102a and 102b and the row of light-receiving elements of the light-receiving unit 105 are aligned. The print belt 111 transports the paper S in a direction (transport direction SS) that intersects (here, perpendicular to) the main scanning direction. The transport direction SS is the sub-scanning direction. The reading unit 101 reads the image on the paper S transported in the transport direction SS, line by line, in the main scanning direction.

The reading glass 107 is a transparent member provided between the reading unit 101 and the print belt 111. The reading glass 107 prevents, for example, paper dust generated from the transported paper S from entering the inside of the reading unit 101 and affecting the reading result. Light output from the light sources 102a and 102b passes through the reading glass 107 and irradiates the paper S. The light reflected by the paper S passes through the reading glass 107 and is received by the light receiving unit 105. A shading reference plate 108 is provided on the reading glass 107 on the print belt 111 side. The shading reference plate 108 is a reference member for performing shading correction, and is, for example, a white member on the reading unit 101 side.

The shading reference plate 108 is read by the reading unit 101 during shading correction. The light receiving unit 105 has manufacturing variations for each photoelectric conversion element (each pixel). In addition, it is not easy to make the light emitted from the light sources 102a and 102b uniform in the main scanning direction. For this reason, even if an image is read from paper S on which an image of uniform image density is printed, the digital values of the image data, which are the reading results, will vary for each position in the main scanning direction. In order to suppress such variations, shading correction is performed.

Specifically, the reading glass 107 moves, and the shading reference plate 108 moves to the reading position (the position irradiated by the light sources 102a and 102b) by the reading unit 101. The reading unit 101 reads the shading reference plate 108 that has moved to the reading position. From the reading result of the shading reference plate 108, a correction value is calculated so that the reading result in the main scanning direction (e.g., luminance value) becomes uniform within a predetermined range. This correction value corrects the amount of irradiation by the light sources 102a and 102b, the sensitivity variation of the photoelectric conversion element of the light receiving unit 105, or the reading result of the image of the paper S, thereby correcting the manufacturing variation and the variation in the amount of light. The shading correction is performed in this manner. When the shading correction is completed, the reading glass 107 returns to the position shown in FIG. 1, and the shading reference plate 108 retreats from the reading position of the reading unit 101.

The movement of the reading glass 107 during shading correction is performed by the driving force output from the motor 109. In other words, the motor 109 serves as the driving source for moving the reading glass 107. The photosensor 110 detects whether the shading reference plate 108 is located at the reading position of the reading unit 101. For example, the photosensor 110 is turned on when the shading reference plate 108 is located at the reading position of the reading unit 101, and is turned off when the shading reference plate 108 is retracted from the reading position of the reading unit 101 to read the paper S.

A paper detection sensor 112 is provided upstream of the image reading device 10 in the transport direction SS to detect paper S being transported from the image forming device. The paper detection sensor 112 is used to determine the presence or absence of paper S being transported by the print belt 111. When the paper detection sensor 112 detects paper S, the control unit 20 starts reading the paper S with the reading unit 101 and turns on the light sources 102a and 102b.

Figure 2 is a configuration diagram of the control unit 20. The control unit 20 is electrically connected to the light sources 102a, 102b and the light receiving section 105 of the reading unit 101. The control unit 20 is further electrically connected to the motor 109, the photosensor 110, and the paper detection sensor 112. In Figure 2, the image reading device 10 is connected to an image forming device 30 such as a printer.

The control unit 20 is a computer system including a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, and a RAM (Random Access Memory) 203. The CPU 201 uses the RAM 203 as a working area to execute a computer program stored in the ROM 202, thereby controlling the operation of the image reading device 10. In addition, the control unit 20 includes an illumination control unit 204 for controlling the operation of the light sources 102a and 102b, and a drive control unit 205 for controlling the operation of the motor 109. The control unit 20 includes an A/D conversion unit 206 and an image processing unit 207 for performing predetermined image processing on the reading result (analog signal) obtained from the light receiving unit 105. Such a control unit 20 may be realized by a discrete product or a one-chip semiconductor product. The one-chip semiconductor product is, for example, a micro-processing unit (MPU), an application specific integrated circuit (ASIC), or a system-on-a-chip (SOC).

The lighting control unit 204 controls the on and off operation of the light sources 102a and 102b under the control of the CPU 201. When the paper S is detected by the paper detection sensor 112, the CPU 201 causes the lighting control unit 204 to turn on the light sources 102a and 102b. When the paper S is no longer detected by the paper detection sensor 112, the CPU 201 causes the lighting control unit 204 to turn off the light sources 102a and 102b.

Drive control unit 205, under the control of CPU 201, transmits a drive signal to motor 109 to move reading glass 107 on which shading reference plate 108 is provided. CPU 201 transmits a control signal to drive control unit 205 so that shading reference plate 108 moves to the reading position of reading unit 101 when shading correction starts. Based on this control signal, drive control unit 205 transmits a drive signal to motor 109 to move reading glass 107 from the position shown in FIG. 1. When shading correction ends, CPU 201 transmits a control signal to drive control unit 205 so that shading reference plate 108 moves away from the reading position of reading unit 101. Based on this control signal, drive control unit 205 transmits a drive signal to motor 109 to return reading glass 107 to the position shown in FIG. 1.

During shading correction, the CPU 201 controls the output of the drive control unit 205 based on the detection result of the photosensor 110. When starting shading correction, the CPU 201 stops the motor 109 through the drive control unit 205 when the photosensor 110 detects that the shading reference plate 108 has reached the reading position. When ending shading correction, the CPU 201 stops the motor 109 through the drive control unit 205 when the photosensor 110 detects that the shading reference plate 108 has retreated from the reading position.

Under the control of the CPU 201, the A/D conversion unit 206 receives an analog signal representing the result of reading the paper S from the light receiving unit 105, and converts the analog signal into a digital signal. The A/D conversion unit 206 transmits this digital signal to the image processing unit 207. Under the control of the CPU 201, the image processing unit 207 performs various image processing on the digital signal obtained from the A/D conversion unit 206, and generates image data representing the image read from the paper S. The image data is transmitted from the control unit 20 to the image forming device 30, a personal computer, etc.

The image forming device 30 includes an image analysis unit 301, a paper transport unit 302, and an image forming unit 303. The image analysis unit 301 analyzes image data acquired from the control unit 20 of the image reading device 10 and calculates various correction values. The correction values calculated by the image analysis unit 301 are fed back to the paper transport unit 302 and the image forming unit 303 and are used for various adjustments such as color shift, uneven image density, and geometric characteristics of the image. The paper transport unit 302 transports the paper S on which the image is printed. The image forming unit 303 prints an image on the paper S according to the print job. When printing the image, the image forming unit 303 adjusts color shift, uneven image density, and geometric characteristics of the image based on the correction values. The paper S on which the image is printed by the image forming device 30 is transported to the image reading device 10 and read by the reading unit 101. If the image forming device 30 is an inkjet type, the image analysis unit 301 analyzes the image data obtained from the control unit 20 to detect whether or not there is a problem with the ejection of droplets by the recording head.

(Shading correction processing)
3 is an explanatory diagram of shading correction processing performed during execution of a print job. Various adjustments performed by a printing machine (image forming device 30) in the commercial printing field or industrial printing field using the image reading device 10 differ in the frequency of image reading for adjustment and the necessity of re-shading before image reading. Here, as adjustments performed by the image forming device 30 using the image reading device 10, geometric adjustment for adjusting geometric characteristics, image density unevenness adjustment for adjusting image density unevenness of a printed image, and detection of droplet ejection defects when the image forming device 30 is an inkjet type will be described.

The geometric characteristics of the multiple sheets of paper S differ due to differences in cutting errors and shrinkage of the sheets S. The geometric adjustment is performed according to the geometric characteristics of each sheet S. For this reason, the geometric adjustment must be performed in real time. To perform the geometric adjustment in real time, the image reading device 10 basically needs to read all sheets S. However, the information required for the geometric adjustment is the shape of the sheet S, specifically the coordinates of the four corners of the sheet S, and the color of the image printed on the sheet S is not used for the geometric adjustment. For this reason, when performing the geometric adjustment, shading correction before image reading is not required. In FIG. 3, the sheet SC of "C" is used for the geometric adjustment. Only the image corresponding to the print job (hereinafter referred to as "user image") is printed on the sheet SC.

For example, when the image forming device 30 is an inkjet type, image density unevenness occurs due to reasons such as unevenness in the amount of droplets ejected from the ink head. Also, when the image forming device 30 is an electrophotographic type, image density unevenness occurs due to reasons such as poor charging of the photoconductor, poor exposure, and poor adhesion of the developer.

Image reading for image density unevenness adjustment only needs to be performed at a predetermined time interval or when a predetermined number of sheets have been passed, and does not need to be performed on all sheets S. When adjusting image density unevenness, an adjustment image for adjusting image density unevenness is printed on the sheet S. The image reading device 10 needs to read the sheet S so that the color of the adjustment image printed on the sheet S can be distinguished. For this reason, shading correction needs to be performed before reading the image for image density unevenness adjustment. This is because if shading correction is not performed before image reading, the adjustment image is read after a certain amount of time has passed since the previous shading correction, and the color of the read image changes due to changes over time in the light sources 102a and 102b. In FIG. 3, the sheet SA of "A" is used for image density unevenness adjustment, and an adjustment image is printed on it. The adjustment image printed on the sheet SA is printed, for example, on the entire sheet. For this reason, the sheet SA does not have a user image printed on it.

Reading of the detection image to detect discharge defects does not need to be performed on all sheets of paper S. Furthermore, detection of discharge defects is not performed based on the color of the detection image. Therefore, it is not necessary to perform shading correction before reading of the image to detect discharge defects. In FIG. 3, the paper SB labeled "B" is for discharge defects, and has a detection image printed on it. The detection image printed on paper SB is printed, for example, on the entire surface of the paper. Therefore, no user image is printed on paper SB.

Whether or not to perform shading correction in this way is determined by the types of adjustment processes performed by the image forming device 30. In the above example, shading correction is not required for geometric adjustment and detection of ejection defects, but is required for image density unevenness adjustment. The control unit 20, for example, obtains a notification from the image forming device 30 indicating which of the sheets SA, SB, and SC is being transported, and determines whether or not to perform shading correction based on this notification.

When a print job is started, multiple sheets of paper S are transported continuously along the transport direction SS. Most of the papers are papers SC for geometric adjustment. Since geometric adjustment only requires detecting the coordinates of the four corners of the paper, only the user's image is printed on the papers SC, and no dedicated images for geometric adjustment are printed. As described above, adjustment images and detection images are printed on papers SA and SB. Papers SA and SB are inserted between papers SC at a specified time interval or when a specified number of sheets have been passed through.

As described above, shading correction is required before adjusting image density unevenness. To achieve this, the control unit 20 performs shading correction the amount of time required for shading correction before the paper SA passes through the reading position of the reading unit 101 (the irradiation position of the light sources 102a and 102b). In other words, the control unit 20 determines whether or not shading correction is required the amount of time required for shading correction before the paper to be read for adjustment passes through the reading position of the reading unit 101.

When shading correction starts, the control unit 20 drives the motor 109 to move the reading glass 107 so that the shading reference plate 108 is positioned at the reading position of the reading unit 101. The control unit 20 reads the shading reference plate 108 with the reading unit 101, and performs shading correction based on the reading result of the shading reference plate 108. The control unit 20 then drives the motor 109 to move the reading glass 107 to its original position shown in FIG. 1. This moves the shading reference plate 108 away from the reading position of the reading unit 101, allowing the reading unit 101 to read the paper S.

In this embodiment, the spacing between multiple sheets of paper S that are continuously transported remains constant even while shading correction is being performed. This makes it possible to suppress a decrease in productivity even when shading correction is being performed.

However, reading of paper SC passing through the reading unit 101 while shading correction is being performed is skipped. Paper SC is for geometric adjustment. The reading process for geometric adjustment is preferably performed on all sheets of paper SC in order to correct the geometric characteristics of the image due to differences in cutting error and shrinkage amount of paper S. However, because cutting error and shrinkage amount change gradually, skipping the reading process of several sheets immediately before image reading for image density unevenness adjustment has little impact if geometric adjustment is performed using the correction value before the skip.

Geometric adjustment and detection of ejection defects do not require shading correction before image reading because the color of the read image is not used to generate correction values. Therefore, when papers SA and SB are transported, shading correction is not performed. By determining whether or not shading correction can be performed based on the type of adjustment made based on the results of reading paper S, the frequency with which shading correction is performed can be adjusted appropriately, and skipping of reading due to shading correction can be suppressed.

Figure 4 is a flowchart showing the shading correction process performed during execution of a print job. This process is performed by the image reading device 10 when the image forming device 30 prints a user image on paper S in accordance with the print job.

The control unit 20 waits until a print job is started (S401:N). The start of a print job is notified to the control unit 20 by, for example, a main control unit (not shown) that controls the operation of the image forming device 30. When the print job is started (S401:Y), the control unit 20 performs shading correction (S402). When the shading correction is completed, the control unit 20 reads the paper S on which a user image has been printed by the image forming device 30 in accordance with the print job (S403). The control unit 20 transmits the reading result of the paper S to the image forming device 30. The image forming device 30 generates correction values for various adjustments based on the reading result acquired from the control unit 20, and performs printing processing that reflects the correction values at the time of the next print.

The control unit 20, having read the paper S, judges whether or not there is a subsequent paper (S404). The presence or absence of a subsequent paper is judged, for example, by the main control unit of the image forming device 30 based on a print job and sending the judgment result to the control unit 20. If there is a subsequent paper (S404: Y), the control unit 20 judges whether or not re-shading correction is required for the paper S that will pass the reading position of the reading unit 101 after the time required for shading correction (S405). The control unit 20 judges whether or not re-shading correction is required depending on the type of adjustment to be made based on the reading result of the paper S. Also, in order to complete re-shading correction before starting to read a paper S that requires re-shading correction, the necessity of re-shading correction is judged at a point in time prior to the time required for shading correction.

If re-shading correction is required (S405: Y), the control unit 20 moves the reading glass 107 so that the shading reference plate 108 is positioned at the reading position of the reading unit 101 (S406). When the movement of the shading reference plate 108 is completed, the control unit 20 reads the shading reference plate 108 with the reading unit 101 (S407). The control unit 20 performs shading correction based on the reading result of the shading reference plate 108 (S408). The control unit 20 moves the reading glass 107 to retract the shading reference plate 108 from the reading position of the reading unit 101 so that the reading unit 101 can read the image of the paper S (S409). This completes the re-shading correction. When the re-shading correction is completed, the control unit 20 returns to the process of S403 and causes the reading unit 101 to read the image of the subsequent paper.

If re-shading correction is not required (S405: N), the control unit 20 returns to the process of S403 without performing re-shading correction, and causes the reading unit 101 to read the subsequent sheet. If there is no subsequent sheet after reading the image on the sheet S (S404: N), the control unit 20 receives a notification of the end of the print job from the main control unit of the image forming device 30 (S410), and ends the process.

The image reading device 10 described above determines whether or not shading correction needs to be performed based on the type of adjustment made based on the results of reading the paper S. The shading correction is performed without widening the paper spacing. For this reason, the shading correction is performed at an appropriate timing. The image forming device 30 can suppress a decrease in productivity while maintaining image quality.

Figure 5 is another flowchart showing the shading correction process performed while a print job is being executed. This process adds a process to the process of Figure 4 for checking the time elapsed since the previous shading correction or the number of sheets that have passed. As a result, if a predetermined time has elapsed since the previous shading correction or if a predetermined number of sheets have not passed, shading correction will not be performed again.

The process of S501 to S504 is the same as the process of S401 to S404 in FIG. 4, so the description will be omitted. If there is a subsequent sheet (S504: Y), the control unit 20 judges whether a predetermined time has passed since the previous shading correction (S505). If the predetermined time has not passed (S505: N), the control unit 20 returns to the process of S503 without performing shading again, and causes the reading unit 101 to read the subsequent sheet.

If the predetermined time has elapsed (S505: Y), the control unit 20 determines whether or not re-shading correction is required for the subsequent paper that passes the reading position after the time required for shading correction has elapsed (S506). When checking the number of sheets of paper that have passed, if the number of sheets of paper that have passed since the previous shading correction is equal to or greater than a predetermined number in the process of S505, the process of S506 is performed.

If re-shading correction is not required (S506: N), the control unit 20 returns to the process of S503 without performing re-shading correction, and causes the reading unit 101 to read the subsequent paper. If re-shading correction is required (S506: Y), the control unit 20 performs re-shading correction similarly to the processes of S406 to S409 in FIG. 4 (S507 to S510). If there is no subsequent paper (S504: N), the control unit 20 receives a notification of the end of the print job from the main control unit of the image forming device 30 (S511), and ends the process.

The image reading device 10 described above determines whether or not shading correction needs to be performed based on the time elapsed since the previous shading correction and the type of adjustment performed based on the results of reading the paper S. The shading correction is performed without widening the paper spacing. Therefore, the shading correction is performed at an appropriate timing. The image forming device 30 can suppress a decrease in productivity while maintaining image quality.

In the above description, an example has been described in which the reading glass 107 moves to position the shading reference plate 108 at the reading position of the reading unit 101 during shading correction. In this embodiment, the reading unit 101 may also be configured to move the shading reference plate 108 to a position where it can be read during shading correction. In this case, the positions of the reading glass 107 and the shading reference plate 108 are fixed. The motor 109 is a drive source that moves the reading unit 101. The photosensor 110 is a sensor that detects that the reading unit 101 has moved to a position where it can read the shading reference plate 108.

In addition, the image reading device 10 does not necessarily have to be built into the image forming device 30. The image reading device 10 may be an external device to the image forming device 30, as long as the image reading device 10 is configured to transport paper S on which an image is printed by the image forming device 30.

Claims (10)

an image forming means for printing an image on a sheet;
an image reading means for reading the paper on which an image is printed by the image forming means,
The image reading means includes:
A reading means for reading the paper;
a reference member for performing shading correction of the reading means;
and a control means for determining whether or not the shading correction is required based on a type of adjustment to be made using the result of reading the paper by the reading means, and for making the reading means read the reference member when the shading correction is to be performed, and for not making the reading means read the reference member when the shading correction is not to be performed.
Image forming device. the control means determines whether or not the shading correction is necessary at a time point a time required for the shading correction before the paper to be read for adjustment passes through a reading position of the reading means.
2. The image forming apparatus according to claim 1. The control means determines whether or not the shading correction is required when a predetermined time has elapsed since the previous shading correction.
2. The image forming apparatus according to claim 1. The control means determines whether or not the shading correction is required when the number of sheets passed since the previous shading correction is equal to or greater than a predetermined number.
2. The image forming apparatus according to claim 1. The control means determines to perform the shading correction when adjustment is performed using a color tone of the image printed on the paper based on the reading result by the reading means.
2. The image forming apparatus according to claim 1. The control means determines not to perform the shading correction when adjustment is performed without using a color tone of the image printed on the paper from the reading result by the reading means.
6. The image forming apparatus according to claim 1 or 5. The control means determines to perform the shading correction when adjusting image density unevenness.
2. The image forming apparatus according to claim 1. The control means determines not to perform the shading correction when performing geometric adjustment of an image.
2. The image forming apparatus according to claim 1. the image forming means has a recording head for printing an image on the paper by an inkjet method,
the control means determines not to perform the shading correction when detecting a droplet ejection defect of the recording head from the reading result by the reading means.
2. The image forming apparatus according to claim 1. 1. An image reading device that reads paper conveyed from an image forming device that prints an image on paper, comprising:
A reading means for reading the paper;
a reference member for performing shading correction of the reading means;
and a control means for determining whether or not the shading correction is required based on a type of adjustment performed by the image forming apparatus using the result of reading the paper by the reading means, and for making the reading means read the reference member when the shading correction is to be performed, and for not making the reading means read the reference member when the shading correction is not to be performed.
Image reading device.

Images