JP2018082219A - Image reading device and image forming system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate a correct image position even when a reading position is shifted due to variations in conveyance speed of a sheet during image reading.SOLUTION: An image forming system comprises: a conveying part that conveys a sheet on which an image is formed; a scanner that reads an image formed on the sheet; and a storage part that stores a period of variations in conveyance speed of the sheet when the image is read by the scanner. The image forming system forms a plurality of register marks while shifting the positions by 1/2 of the speed variation period in a sheet conveyance direction (step S8), while conveying the sheet on which the plurality of register marks are formed (step S9), causes the scanner to read the plurality of register marks formed on the sheet (step S10), and calculates the positions at which the plurality of register marks are formed on the basis of the positions at which the plurality of register marks are read (step S11).SELECTED DRAWING: Figure 8

Description

  The present invention relates to an image reading apparatus and an image forming system.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, an image on a sheet after image formation is used to adjust the color, position, magnification, etc. of the image and to check whether the image is appropriate. An image reading apparatus for reading is used. The image reading apparatus is disposed downstream of the image forming apparatus main body, and a scanner that reads an image formed on one or both sides of a sheet is provided in the sheet conveyance path. Information read by the image reading apparatus is fed back to the image forming apparatus.
In addition, in order to correct the color information read by the scanner to correct color information, a colorimeter capable of measuring the color information with high accuracy is provided in the paper conveyance path.

In an image forming apparatus that forms images on both sides of a sheet, before outputting the image to be printed, the images on both sides of the sheet formed by the image forming apparatus body are read by a scanner, and the read image information is fed back to the image forming apparatus body. Then, align the front and back images.
The alignment of the front and back images is performed using the distance between the registration mark of the front and back images read by the scanner and the edge of the paper. Both sides of the paper are read by a scanner, the positions of the registration marks on the front and back sides are detected from the read images, and these positions are corrected so that they are set in advance from the edges of the paper, thereby matching the image positions.

  In addition, an image processing apparatus that forms a registration mark on the edge side of the sheet from the cutting position is used in order to prevent unnecessary lines from remaining on the sheet after the cutting process (see Patent Document 1).

JP 2012-019309 A

  However, when the paper is transported along the transport path, an impact is applied to the leading or trailing edge of the paper, and the transport roller and the paper that sandwich the paper vibrate, thereby causing a speed fluctuation in the paper transport. Due to fluctuations in the sheet conveyance speed during image reading, a reading position shift in the sheet conveyance direction occurs. If there is a discrepancy between the registration mark position actually formed on the paper and the registration mark position read by the scanner, accurate reading results cannot be obtained, and image alignment is performed correctly on the image forming device main unit. There was a problem that could not be done.

  The present invention has been made in view of the above-described problems in the prior art, and it is an object of the present invention to calculate a correct image position even if the reading position is misaligned due to a paper conveyance speed variation during image reading. .

  In order to solve the above-described problems, the invention described in claim 1 includes a conveying unit that conveys a sheet on which an image is formed by the image forming apparatus, an image reading unit that reads an image formed on the sheet, and the image reading unit. A storage unit that stores a speed variation period of the sheet conveyance by the conveyance unit when an image is read by the unit, and a speed variation in which a plurality of registration marks are stored in the storage unit in the sheet conveyance direction by the image forming apparatus. The image reading unit reads the registration marks formed on the one sheet while the sheet formed by shifting by half of the cycle is conveyed by the conveyance unit, and the image reading unit reads the image. An image reading apparatus comprising: a control unit that calculates formation positions of the plurality of registration mark marks based on reading positions of the plurality of registration mark marks obtained by the reading unit. That.

  According to a second aspect of the present invention, there is provided a conveying unit that conveys a sheet on which an image is formed by the image forming apparatus, an image reading unit that reads an image formed on the sheet, and an image read by the image reading unit. The storage means for storing the speed fluctuation cycle of the paper transport by the transport means, and the registration mark on each of a plurality of sheets by the image forming apparatus is one of the speed fluctuation cycles stored in the storage means in the paper transport direction. / Each registration mark formed on each sheet is read by the image reading unit while each sheet formed by being shifted by 2 is conveyed by the conveyance unit, and each registration mark obtained by the image reading unit is read. And a control unit that calculates the formation position of each registration mark based on the mark reading position.

  According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the storage unit stores the speed variation period for each combination of paper type and paper transport speed.

  According to a fourth aspect of the present invention, in the image reading apparatus according to the third aspect, the paper type is classified by basis weight, stiffness, thickness, size, or a combination thereof.

  According to a fifth aspect of the present invention, in the image reading apparatus according to any one of the first to fourth aspects, the control unit has a plurality of straight lines arranged at equal intervals in the paper conveyance direction by the image forming apparatus. Based on the reading results of a plurality of straight lines obtained by the image reading unit, the image reading unit reads the image formed on the paper while the sheet on which the formed image is formed is conveyed by the conveying unit. Then, the speed fluctuation period is calculated, and the calculated speed fluctuation period is stored in the storage means.

  The invention according to claim 6 is the image reading apparatus according to any one of claims 1 to 5, wherein the image reading apparatus is connected to another image reading apparatus of the same model as that of the own apparatus connected via a communication network. Communication means for transmitting and receiving data, and the control means shares the speed fluctuation period with the other image reading apparatus via the communication means.

  The invention described in claim 7 is an image forming system comprising the image reading apparatus according to any one of claims 1 to 6 and the image forming apparatus, wherein the image forming apparatus is configured to calculate the calculation. The image forming apparatus includes a correction unit that aligns the position of the image formed by the image forming apparatus based on the registration mark formation position.

  According to the present invention, a correct image position can be calculated even if the reading position is misaligned due to fluctuations in the sheet conveyance speed during image reading.

1 is a schematic configuration diagram of an image forming system according to a first embodiment of the present invention. 1 is a block diagram illustrating a functional configuration of an image forming system. It is a figure which shows the example of a speed fluctuation period table. FIG. 6 is a diagram illustrating a reading position shift amount corresponding to a distance in a sheet conveyance direction. This is an example in which a plurality of registration marks are formed on one sheet by shifting each half of the speed variation period in the sheet conveyance direction. It is an example of a chart image. (A) is a figure which shows the example in which the register mark was formed in the four corners of a paper. (B) is an enlarged view of a region where a register mark is formed. It is a flowchart which shows a 1st image position alignment process. In the second embodiment of the present invention, the registration mark is formed on each of a plurality of sheets with a shift of ½ of the speed variation period in the sheet conveyance direction. It is a flowchart which shows a 2nd image position alignment process. It is a block diagram of the information sharing system in the 3rd Embodiment of this invention.

[First Embodiment]
First, with reference to the drawings, a first embodiment of an image reading apparatus and an image forming system according to the present invention will be described. The present invention is not limited to the illustrated example.

FIG. 1 shows a schematic configuration of an image forming system 100 according to the first embodiment.
As shown in FIG. 1, the image forming system 100 includes an image forming apparatus main body 10, an image reading unit 20, a paper feed unit 30, and a paper discharge unit 40. The sheet on which the image is formed by the image forming apparatus main body 10 is carried into the image reading unit 20 as it is.

The image forming apparatus main body 10 includes an image forming unit 50.
The image forming unit 50 forms an image on a sheet based on the image data.
The image forming unit 50 includes photosensitive drums 51Y, 51M, 51C, 51K corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K), an intermediate transfer belt 52, a secondary transfer roller. 53, a fixing unit 54, a reversing mechanism 55, and the like.

The photosensitive drum 51Y is uniformly charged and then scanned and exposed with a laser beam based on yellow image data to form an electrostatic latent image. Then, yellow toner is attached to the electrostatic latent image on the photosensitive drum 51Y, and development is performed.
Since the photosensitive drums 51M, 51C, and 51K are the same as the photosensitive drum 51Y except that they handle different colors, the description thereof is omitted.

The toner images of the respective colors formed on the photosensitive drums 51Y, 51M, 51C, 51K are sequentially transferred onto the rotating intermediate transfer belt 52 (primary transfer). That is, on the intermediate transfer belt 52, a color toner image in which four color toner images are superimposed is formed.
The color toner images on the intermediate transfer belt 52 are collectively transferred onto the paper supplied from the paper supply unit 30 by the secondary transfer roller 53 (secondary transfer).

The fixing unit 54 includes a heating roller that heats the sheet on which the color toner image is transferred and a pressure roller that pressurizes the sheet, and fixes the color toner image on the sheet by heating and pressing.
The reversing mechanism 55 is a conveyance path for reversing the front and back of the paper and supplying the paper to the secondary transfer position again when images are formed on both sides of the paper.

  The image reading unit 20 includes a first scanner 21A, a second scanner 21B, a spectrocolorimeter 22, and the like. The first scanner 21A, the second scanner 21B, and the spectrocolorimeter 22 are provided on the downstream side of the image forming apparatus main body 10 in the paper conveyance path, and the image forming surface of the paper after image formation is disposed outside the paper. Can be read before being discharged.

The first scanner 21A and the second scanner 21B are configured by line sensors in which CCDs (Charge Coupled Devices) are arranged in a line in a direction (paper width direction) that is orthogonal to the paper transport direction and parallel to the paper surface. ing. The first scanner 21A and the second scanner 21B are image reading means for reading an image formed on the conveyed paper, and output the obtained image data to the control unit 11 (see FIG. 2).
Hereinafter, when the first scanner 21A and the second scanner 21B are not particularly distinguished, the first scanner 21A and the second scanner 21B are collectively referred to as the scanner 21.

  The spectrocolorimeter 22 detects the spectral reflectance for each wavelength of the image formed on the paper, and measures the color of the image. The spectrocolorimeter 22 recognizes color information with high accuracy and is used to correct color information read by the first scanner 21A and the second scanner 21B to correct color information.

The paper feed unit 30 includes a plurality of paper feed trays and supplies paper to the image forming unit 50. Each paper feed tray stores paper of a predetermined paper type for each paper feed tray.
The paper discharge unit 40 includes a paper discharge tray and discharges paper after image formation.

FIG. 2 is a block diagram illustrating a functional configuration of the image forming system 100.
As shown in FIG. 2, the image forming system 100 includes a control unit 11, an operation unit 12, a display unit 13, an image forming unit 50, a paper feeding unit 30, a paper discharging unit 40, an image reading unit 20, a transport unit 60, a communication. Unit 70, storage unit 80, and the like. Note that description of the functional units already described is omitted.

  The control unit 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads various processing programs stored in the ROM, expands them in the RAM, and centrally controls the operations of the respective units of the image forming system 100 according to the expanded programs.

  The operation unit 12 includes a touch panel formed to cover the display screen of the display unit 13 and various operation buttons such as numeric buttons and a start button, and outputs an operation signal based on a user operation to the control unit 11.

  The display unit 13 is configured by an LCD (Liquid Crystal Display), and displays various screens according to instructions of display signals input from the control unit 11.

  The transport unit 60 includes a transport roller for transporting the paper, and transports the paper in the image forming system 100. Specifically, the transport unit 60 transports the paper from the paper feeding unit 30 to the image forming apparatus main body 10, transports the paper on which the image is formed by the image forming apparatus main body 10, in the image reading unit 20, and reads the image. The paper is conveyed from the unit 20 to the paper discharge unit 40.

  The communication unit 70 transmits and receives data to and from an external device connected to a communication network such as a LAN (Local Area Network) or the Internet.

  The storage unit 80 is configured by a hard disk, a flash memory, or the like, and stores various data. The storage unit 80 stores, for each combination of the paper type and the paper conveyance speed, the speed fluctuation cycle of the paper conveyance by the conveyance unit 60 when the image is read by the scanner 21. Paper types are classified by basis weight, stiffness, thickness, size, or combinations thereof.

  FIG. 3 shows an example of the speed fluctuation period table 81 stored in the storage unit 80. The speed fluctuation period table 81 stores a speed fluctuation period for a combination of the paper type (rigidity and size) and the conveyance speed.

At the time of image reading, when the paper is transported, the impact applied to the leading edge or the trailing edge of the paper causes the transport roller (roller driving unit) that sandwiches the paper and the paper to vibrate in the same manner, thereby causing a speed fluctuation in the paper transport. Occur. This speed variation is highly reproducible, and if the paper type and transport speed of the transported paper are constant, the reading position shift in the paper transport direction occurs in the same manner every time.
The speed fluctuation at the time of image reading is periodic along the paper conveyance direction, and the length of one vibration in the paper conveyance direction is called a speed fluctuation period.

  FIG. 4 shows a reading position shift amount corresponding to a distance (each position on the paper) from the front end of the paper in the paper conveyance direction when a certain type of paper is conveyed at a certain conveyance speed. Here, the amount of misalignment of the reading position is expressed as a plus or minus value including the direction of misalignment (deviation toward the front end side of the paper or deviation toward the rear end side of the paper).

Since the speed fluctuation cycle varies depending on the distance from the front end of the paper in the paper transport direction, the speed fluctuation cycle around the area where the registration mark is formed is used. The storage unit 80 stores a speed fluctuation period around the area where the registration mark is formed.
The registration mark may be any mark used for image alignment, and its shape is not limited to a cross.

It is assumed that the speed fluctuation period stored in the storage unit 80 has reproducibility, and the fluctuation due to the use state and environment is not more than a predetermined amount.
This predetermined amount is determined by the accuracy required as the final image forming position. It is desirable that the reading position deviation amount is ½ or less of the positional deviation amount allowed with the accuracy required as the final image forming position.

  The control unit 11 reads the speed fluctuation cycle stored in the storage unit 80 and controls the image forming unit 50 to place a plurality of registration marks on a single sheet and ½ the speed fluctuation cycle in the paper transport direction. Shift them one by one.

  FIG. 5 shows an example in which the registration marks M1 to M6 are formed on the paper P1 while being shifted by ½ of the speed fluctuation period T in the paper transport direction.

The interval between the registration mark marks formed by the image forming apparatus main body 10 is ½ of the speed fluctuation period. However, the positional deviation in the distance between the two registration mark marks caused by the image forming apparatus main body 10 is It shall be below the fixed amount. Specifically, the distance from the end of the sheet to the first registration mark is allowed to have a positional shift caused by the image forming apparatus main body 10, but the positional shift between the registration mark marks is not allowed ( Must be less than a predetermined amount).
This predetermined amount is determined by the accuracy required as the final image forming position. It is only necessary that the corrected image forming position adjusted (aligned) based on the finally calculated corrected reading position can ensure the accuracy required as the image forming position of the image forming apparatus main body 10. .

  The control unit 11 conveys a sheet of paper formed by shifting a plurality of registration marks by half of the speed variation period stored in the storage unit 80 in the sheet conveyance direction by the image forming apparatus body 10. The plurality of registration mark marks formed on the one sheet of paper are read by the scanner 21 while being conveyed by the unit 60, and based on the reading positions of the plurality of registration mark marks obtained by the scanner 21, The formation position (read position after correction) is calculated.

  When the speed variation period is not stored in the storage unit 80 for the combination of the paper type and the conveyance speed that the user wants to use, the control unit 11 calculates the speed variation period for the corresponding paper type and the conveyance speed, It is added to the storage unit 80.

When acquiring a new speed fluctuation period, the control unit 11 controls the image forming unit 50 to form an image (chart image) in which a plurality of straight lines are arranged at equal intervals in the paper conveyance direction. Let FIG. 6 shows an example of the chart image. As the chart image, for example, an image having a straight line interval of 0.254 mm and a straight line thickness of 0.085 mm can be used, but the present invention is not limited to this. The chart image does not need to be formed on the entire surface of the paper, and may be formed at least in an area where the speed fluctuation period of the paper is desired.
The control unit 11 causes the image forming apparatus main body 10 to convey the image formed on the sheet while the conveyance unit 60 conveys the sheet on which an image having a plurality of straight lines arranged at equal intervals in the sheet conveyance direction. The scanner 21 reads it, calculates a speed fluctuation period based on the reading results of a plurality of straight lines obtained by the scanner 21, and stores the calculated speed fluctuation period in the storage unit 80.

It is assumed that the positional deviation caused by the image forming apparatus main body 10 when forming a chart image used for determining the speed fluctuation period is not more than a predetermined amount.
If the chart image formed by the image forming apparatus main body 10 originally has a positional deviation, an incorrect speed fluctuation cycle is calculated, but the adjustment is made based on the corrected reading position calculated in the wrong speed fluctuation period. It is only necessary that the corrected image forming position to be (positioned) can ensure the accuracy required as the image forming position of the image forming apparatus main body 10.

  The control unit 11 aligns the position of the image formed by the image forming apparatus main body 10 based on the calculated registration mark mark formation position. That is, the control unit 11 functions as a correction unit. The image registration using the registration mark may be performed every time image formation is performed in the image forming system 100 or may be performed at a predetermined number of image formation intervals.

  FIG. 7A shows an example in which register marks are formed at the four corners of the paper P. FIG. FIG. 7B is an enlarged view of the region Q shown in FIG. Based on the position of the register mark 91 formed on the surface of the paper P, the position of the register mark 91 is adjusted so that the distance of the register mark 91 from the end of the paper becomes predetermined setting values H1 and H2. adjust. The same applies to the register mark 92 formed on the back surface of the paper.

  The control unit 11, the scanner 21, the transport unit 60, and the storage unit 80 constitute an image reading apparatus according to the present invention.

Next, the operation in the image forming system 100 of the first embodiment will be described.
FIG. 8 is a flowchart showing a first image alignment process executed in the image forming system 100. This process is realized by software processing in cooperation with the CPU of the control unit 11 and the program stored in the ROM.

  First, when the user selects the paper type and the conveyance speed of the paper to be image-formed from the operation unit 12, the control unit 11 performs setting according to the selected paper type and the conveyance speed (step S1). When the paper transport speed is determined according to the selection of the paper type, it is not necessary to select the transport speed.

Next, the control unit 11 determines whether or not a speed variation period corresponding to the set paper type and transport speed is stored in the storage unit 80 (step S2).
When the speed variation period corresponding to the set paper type and transport speed is not stored in the storage unit 80 (step S2; NO), the control unit 11 controls the image forming unit 50 to set the speed change period. A chart image in which a plurality of straight lines are arranged at equal intervals in the paper conveyance direction is formed on the paper type paper (step S3).

  When the sheet on which the chart image is formed by the image forming unit 50 is carried into the image reading unit 20, the control unit 11 conveys the sheet on which the chart image is formed at the conveyance speed set by the conveyance unit 60. (Step S4), the chart image formed on the sheet is read by the scanner 21, and the result of reading the chart image from the scanner 21 (read image data) is acquired (Step S5).

  Next, the control unit 11 calculates a speed fluctuation period based on the reading results of a plurality of straight lines obtained by the scanner 21 (step S6). Specifically, the control unit 11 detects the positions of a plurality of straight lines from the read image data, and obtains a reading position deviation amount (see FIG. 4) or a speed variation with respect to the paper conveyance direction. Then, the control unit 11 calculates the length of one vibration in the paper transport direction as the speed fluctuation period for the reading position deviation amount or the speed fluctuation.

  Next, the control part 11 memorize | stores the calculated speed fluctuation period in the memory | storage part 80 (step S7). Specifically, the control unit 11 stores the calculated speed fluctuation period in the speed fluctuation period table 81 in association with the paper type and the conveyance speed.

  In step S2, if the speed variation period corresponding to the set paper type and transport speed is stored in the storage unit 80 (step S2; YES), or after step S7, the control unit 11 stores the storage unit 80. Read out the speed variation period corresponding to the set paper type and transport speed, and control the image forming unit 50 to transport a plurality of registration marks on one sheet (the set paper type paper). The direction is shifted by ½ of the speed fluctuation period in the direction (step S8).

  When a sheet on which a plurality of registration mark marks are formed by the image forming unit 50 is carried into the image reading unit 20, the control unit 11 determines that the plurality of registration mark marks are formed by shifting each half of the speed variation period. While conveying a sheet of paper at the conveyance speed set by the conveyance unit 60 (step S9), the scanner 21 reads a plurality of registration marks formed on the one sheet, and the scanner 21 reads a plurality of registration marks. Is obtained (read image data) (step S10).

  Next, the control unit 11 detects the reading positions of a plurality of registration marks from the read image data acquired by the scanner 21. The control unit 11 calculates the formation positions (corrected reading positions) of the plurality of registration marks based on the reading positions of the registration marks (step S11).

Next, the control unit 11 aligns the position of the image formed in the image forming apparatus main body 10 based on the calculated registration mark mark formation position (step S12). The result of the alignment is applied in subsequent image formation.
This completes the first image alignment process.

Here, a method for correcting the reading position obtained by the scanner 21 will be described.
A plurality of registration mark positions are formed on one sheet by shifting the position of the registration mark by 1/2 of the speed fluctuation period. The formation positions of the plurality of registration mark marks are x1, x2, x3,... From the side closer to the front end of the paper along the paper transport direction (see FIG. 5). If the speed fluctuation period is T,
x2 = x1 + T / 2 (1)
And so on.

The reading positions of a plurality of registration mark marks obtained by the scanner 21 are z1, z2, z3,.
It is assumed that reading position shift amounts of a plurality of registration mark marks read by the scanner 21 are y1, y2, y3,.

As shown in FIG. 4, since the reading position deviation amount with respect to each position in the paper conveyance direction has periodicity, the reading position deviation amount between two points shifted by ½ period in the paper conveyance direction is large. The direction is the same and the directions (plus and minus) are reversed.
y1 = −y2 (2)

It is assumed that the reading positions of the plurality of registration marks after correcting the reading position deviation amount are w1, w2, w3,.
w1 = z1-y1 (3)
w2 = z2-y2 (4)

The registration mark mark reading positions w 1, w 2, w 3,... Corrected for the reading position deviation amount are the same as the registration mark mark formation positions x 1, x 2, x 3,.
w1 = x1 (5)
w2 = x2 (6)

From equation (1),
x1 + x2 = x1 + (x1 + T / 2)
= 2 × x1 + T / 2 (7)

From equations (5), (6), (3), (4),
x1 + x2 = w1 + w2
= (Z1-y1) + (z2-y2) (8)

From equations (8) and (2),
x1 + x2 = z1 + z2 (9)

From equations (7) and (9),
x1 + x2 = 2 × x1 + T / 2 = z1 + z2
Therefore,
x1 = (z1 + z2-T / 2) / 2 (10)

Similarly, x2, x3,... Are also obtained.
Regardless of the reading position deviation amounts y1, y2, y3,..., The registration mark mark formation positions x1, x2, x3,. Can be calculated.

As described above, according to the first embodiment, since the interval between the register marks adjacent in the paper conveyance direction is ½ of the speed fluctuation period, the reading position shift directly from the register mark reading position. The formation position of the registration mark not including the amount can be calculated. Therefore, the correct image position can be calculated even if the reading position is misaligned due to fluctuations in the sheet conveyance speed during image reading.
In addition, the registration mark mark formation position is accurately calculated and fed back to the image forming operation in the image forming apparatus main body 10 so that the image position can be accurately adjusted.

In addition, since the speed fluctuation cycle differs for each paper type and paper transport speed, the registration position of the registration mark can be accurately calculated by storing the speed fluctuation period for each paper type and transport speed. .
Further, when using a speed variation period with respect to the paper type and transport speed that is not stored in the storage unit 80, the paper on which an image in which a plurality of straight lines are arranged at equal intervals in the paper transport direction is read, The speed fluctuation cycle can be calculated.

  In addition, since a plurality of registration marks are formed on one sheet, the correction time is short and the number of sheets is not increased. However, since the number of registration mark is large, the image area other than the registration mark becomes narrow.

[Second Embodiment]
Next, a second embodiment to which the present invention is applied will be described.
Since the image forming system in the second embodiment has the same configuration as that of the image forming system 100 shown in the first embodiment, FIG. 1 and FIG. Description to be omitted is omitted. Hereinafter, a configuration and processing characteristic of the second embodiment will be described.

  The control unit 11 reads the speed variation period stored in the storage unit 80 and controls the image forming unit 50 to place a register mark on each of a plurality of sheets, and ½ the speed variation period in the sheet conveyance direction. Shift them one by one.

  FIG. 9 shows an example in which the register marks M11, M12, and M13 are formed on the papers P11, P12, and P13 while being shifted by T / 2 in the paper transport direction.

  The control unit 11 uses the image forming apparatus main body 10 to form each sheet of paper on which a registration mark is shifted by a half of the speed variation period stored in the storage unit 80 in the paper transport direction. , The registration marks formed on the respective sheets are read by the scanner 21 while being conveyed by the conveyance unit 60, and the formation positions of the registration marks are determined based on the reading positions of the registration marks obtained by the scanner 21. Is calculated.

Next, an operation in the image forming system of the second embodiment will be described.
FIG. 10 is a flowchart illustrating a second image alignment process executed in the image forming system according to the second embodiment. This process is realized by software processing in cooperation with the CPU of the control unit 11 and the program stored in the ROM.

  Since the process of step S21-step S27 is the same as the process of step S1-step S7 of a 1st image position alignment process (refer FIG. 8), description is abbreviate | omitted.

  In step S22, when the speed variation period corresponding to the set paper type and transport speed is stored in the storage unit 80 (step S22; YES), or after step S27, the control unit 11 stores the storage unit 80. Is read out, and the image forming unit 50 is controlled to form one register mark on one sheet (the sheet of the set sheet type). (Step S28).

  When the sheet on which the registration mark is formed by the image forming unit 50 is carried into the image reading unit 20, the control unit 11 conveys the sheet on which the registration mark has been formed at the conveyance speed set by the conveyance unit 60. (Step S29) The registration mark formed on the paper is read by the scanner 21, and the result (read image data) obtained by reading the registration mark from the scanner 21 is acquired (Step S30).

Here, the control unit 11 determines whether or not a predetermined number of registration marks have been formed and read (step S31).
If the predetermined number of registration mark formation and reading has not been completed (step S31; NO), the control unit 11 sets the position of the registration mark to be formed next to 1/2 of the speed fluctuation period in the paper transport direction. Shift (step S32), return to step S28, and repeat the process.

  In step S31, when the registration mark formation and reading is completed for a predetermined number of sheets (step S31; YES), the control unit 11 reads the registration marks from the plurality of read image data acquired by the scanner 21. To get. Based on the reading position of each registration mark, the control unit 11 calculates the formation position (corrected reading position) of each registration mark (step S33).

Next, the control unit 11 aligns the position of the image formed in the image forming apparatus main body 10 based on the calculated registration mark mark formation position (step S34). The result of the alignment is applied in subsequent image formation.
Thus, the second image alignment process is completed.

The second embodiment is different from the first embodiment in that each registration mark is formed on a separate sheet, but the method for calculating the formation position from the reading position of each registration mark is the first. This is the same as the embodiment.
For example, as shown in FIG. 9, the registration marks M11, M12, and M13 are formed on the papers P11, P12, and P13 at positions x1, x2, and x3 from the side closer to the front of the paper along the paper transport direction. Assuming that the reading positions of M11, M12, and M13 are z1, z2, and z3 and the speed fluctuation period is T, as in the above equation (10),
x1 = (z1 + z2-T / 2) / 2
x2 = (z2 + z3-T / 2) / 2
Etc.

As described above, according to the second embodiment, the position of the registration mark formed on each of the plurality of sheets is shifted by ½ of the speed fluctuation period in the sheet conveyance direction. The registration mark formation position that does not include the reading position deviation amount can be calculated directly from the reading position. Therefore, the correct image position can be calculated even if the reading position is misaligned due to fluctuations in the sheet conveyance speed during image reading.
In addition, the registration mark mark formation position is accurately calculated and fed back to the image forming operation in the image forming apparatus main body 10 so that the image position can be accurately adjusted.

In addition, since the speed fluctuation cycle differs for each paper type and paper transport speed, the registration position of the registration mark can be accurately calculated by storing the speed fluctuation period for each paper type and transport speed. .
Further, when using a speed variation period with respect to the paper type and transport speed that is not stored in the storage unit 80, the paper on which an image in which a plurality of straight lines are arranged at equal intervals in the paper transport direction is read, The speed fluctuation cycle can be calculated.

  In addition, since one registration mark is formed on each of a plurality of sheets, an image area other than the registration mark is widened. However, since a large number of sheets are used, the correction time becomes long and a plurality of sheets are required.

[Third Embodiment]
Next, a third embodiment to which the present invention is applied will be described.
In the third embodiment, a case will be described in which image forming systems of the same model are connected via a communication network and share information.

  FIG. 11 shows the configuration of the information sharing system 200. The information sharing system 200 includes image forming systems 101 to 106. The image forming systems 101 to 106 are No. 1 to No. 6 of the same model having the same specifications.

The image forming systems 101 to 103 are installed at the base A and are connected to each other via a company network NA so that data communication is possible.
The image forming systems 104 to 106 are installed at the base B, and are connected to each other via a company network NB so that data communication is possible.
The base A and the base B are connected to each other via the Internet NC, and the image forming systems 101 to 106 can perform data communication with an image forming system installed at a base different from the own system. .

  Since the image forming systems 101 to 106 have the same configuration as the image forming system 100 shown in the first embodiment, the illustration and the description common to the image forming system 100 are omitted with reference to FIGS. To do.

  When the control unit 11 of the image forming system 101 uses the speed variation period corresponding to the paper type and the conveyance speed that are not stored in the storage unit 80, step S1 of the first image alignment process (see FIG. 8). Step S7 is performed, and the calculated speed fluctuation period is stored in the storage unit 80 in association with the paper type and the transport speed.

  The control unit 11 of the image forming system 101 uses the communication unit 70 to set the image forming system 102 in the base A connected via the in-house network NA to the newly acquired speed fluctuation period together with the paper type and transport speed conditions. , 103. The control unit 11 of the image forming systems 102 and 103 stores the speed variation period received from the image forming system 101 in the storage unit 80 in the own system in association with the paper type and the conveyance speed.

  Further, the control unit 11 of the image forming system 101 uses the communication unit 70 to set the image forming system in the base B connected via the Internet NC with the newly acquired speed fluctuation period together with the paper type and transport speed conditions. It transmits to 104-106. The control unit 11 of the image forming systems 104 to 106 stores the speed variation period received from the image forming system 101 in the storage unit 80 in the own system in association with the paper type and the conveyance speed.

  As described above, the speed fluctuation period acquired by the image forming system 101 can be shared with other image forming systems 102 to 106 of the same model, and the newly acquired speed fluctuation is also obtained in the image forming systems 102 to 106. The cycle becomes available.

  As described above, according to the third embodiment, the speed fluctuation period is set between other image forming systems of the same model as the own system, which are connected via the in-house networks NA, NB and the Internet NC. Since it is shared, the speed fluctuation period acquired in one image forming system is also used in other image forming systems, and the correct image position is calculated even if the reading position is misaligned due to paper feed speed fluctuation during image reading. can do.

  Note that the image forming systems 102 to 106 may receive the speed fluctuation period from the image forming system 101 in response to a user instruction from the image forming systems 102 to 106.

  Also in the third embodiment, as in the image forming system shown in the second embodiment, one registration mark is formed on each of a plurality of sheets, and the registration position of each registration mark is formed. May be calculated.

  Note that the descriptions in the above embodiments are examples of the image reading apparatus and the image forming system according to the present invention, and the present invention is not limited thereto. The detailed configuration and detailed operation of each part of the apparatus or system can be changed as appropriate without departing from the spirit of the present invention.

  In each of the above-described embodiments, the case where the control unit 11 of the image forming apparatus (the image forming apparatus main body 10 or the like) also serves as the control unit of the image reading apparatus (the scanner 21, the conveyance unit 60 or the like) has been described. And the image reading apparatus may have separate control means. In this case, the registration mark mark formation position (corrected reading position) may be calculated on the image reading apparatus side and transmitted to the image forming apparatus, or a correction value for image formation may be calculated on the image reading apparatus side. Then, it may be transmitted to the image forming apparatus.

  In addition, when the first scanner 21A and the second scanner 21B have different speed fluctuation cycles when reading an image, the speed fluctuation cycles are separately managed, and the first scanner 21A or the second scanner 21B that reads an image is supported. The speed fluctuation period to be used may be used.

In each of the above embodiments, the case where two scanners (the first scanner 21A and the second scanner 21B) for reading the front and back surfaces of the paper are provided in the image forming system has been described. It may be a reading device.
In addition, in an image reading apparatus having one scanner and a reversing mechanism, after reading one side of a sheet on which an image is formed, the reversing mechanism reverses the front and back of the sheet and reads the other side of the sheet. Also good.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus main body 11 Control part 21A 1st scanner 21B 2nd scanner 50 Image forming part 60 Conveying part 70 Communication part 80 Storage part 100 Image forming system 101-106 Image forming system 200 Information sharing system M1-M6 Registration mark M11- M13 Dragonfly mark NA Internal network NB Internal network NC Internet

Claims (7)

Conveying means for conveying the paper on which the image is formed by the image forming apparatus;
Image reading means for reading an image formed on a sheet;
Storage means for storing a speed fluctuation period of paper conveyance by the conveyance means when an image is read by the image reading means;
While the image forming apparatus transports a sheet of paper, in which a plurality of registration marks are shifted by half of the speed fluctuation period stored in the storage unit in the sheet transport direction, by the transport unit. The plurality of registration mark marks formed on the one sheet are read by the image reading unit, and the plurality of registration mark marks are formed based on the reading positions of the plurality of registration mark marks obtained by the image reading unit. Control means for calculating
An image reading apparatus comprising: Conveying means for conveying the paper on which the image is formed by the image forming apparatus;
Image reading means for reading an image formed on a sheet;
Storage means for storing a speed fluctuation period of paper conveyance by the conveyance means when an image is read by the image reading means;
Each of the plurality of sheets formed by the image forming apparatus with a registration mark shifted by a half of the speed variation period stored in the storage unit in the sheet conveying direction is transferred by the conveying unit. While conveying, each image mark mark formed on each sheet is read by the image reading means, and the formation position of each mark mark is calculated based on the reading position of each mark mark obtained by the image reading means. Control means to
An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein the speed change period is stored in the storage unit for each combination of a paper type and a paper transport speed.   The image reading apparatus according to claim 3, wherein the paper type is classified by basis weight, stiffness, thickness, size, or a combination thereof.   The control means causes the image forming apparatus to transfer the image formed on the paper while the paper on which the image in which a plurality of straight lines are arranged at equal intervals in the paper transport direction is transported by the transport means. 5. The image reading unit reads the calculated speed fluctuation period based on a plurality of straight line reading results obtained by the image reading unit, and stores the calculated speed fluctuation period in the storage unit. The image reading apparatus according to any one of the above. Comprising a communication means for transmitting and receiving data to and from another image reading apparatus of the same model as the own apparatus connected via a communication network;
The image reading apparatus according to claim 1, wherein the control unit shares the speed variation period with the other image reading apparatus via the communication unit. An image forming system comprising: the image reading device according to any one of claims 1 to 6; and the image forming device.
The image forming apparatus is an image forming system including a correcting unit that aligns the position of an image formed by the image forming apparatus based on the calculated registration mark mark forming position.

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