JP6409594B2 - Image forming apparatus, image adjusting method, and program - Google Patents

Description

  The present invention relates to an image forming apparatus, an image adjustment method, and a program.

  In image forming apparatuses such as copiers and printers, when forming an image on both sides of the paper, the position of the paper due to shrinkage of the paper due to fixing, or passing through a double-sided conveyance path for reversing the paper and supplying it to the image forming unit again Due to a shift or the like, the position and magnification of the image may be shifted between the front and back surfaces.

  In order to eliminate such an image shift between the front and back surfaces, “front and back adjustment” is performed. In “front and back adjustment”, an adjustment pattern is formed at a predetermined position on the front and back sides of the paper, and the amount of shift between the adjustment patterns formed on the front and back sides is detected, so that the front and back shifts are eliminated. Adjust the position and magnification. For detecting the deviation amount, a method of measuring with a ruler (manual) or a method of measuring with a scanner (automatic) is used.

  In addition, a technology has been developed in which when the adjustment pattern on the front side is read from the front side of the paper, the back side adjustment pattern on the back side is also read to adjust the front and back sides. In this case, since the adjustment patterns on both sides are read at the same time, the sheet only needs to pass once through the installation position of the image reading unit (sensor), and the front and back adjustment can be performed in a short time.

  As an image forming apparatus that performs front and back adjustment using show-through, for example, an apparatus that adjusts the amount of scan light to read a mark formed on the front and back of a recording sheet through one side is proposed (patent) Reference 1). Japanese Patent Laid-Open No. 2004-133620 further displays a message prompting to set another recording sheet when a mark on the back side cannot be detected, and selects a recording sheet having the smallest basis weight from a plurality of paper feed trays. It is also disclosed that paper is fed, and a display for prompting another recording sheet to be set when the basis weight of the recording sheet exceeds a predetermined value.

JP 2008-275991 A

  However, when adjusting the scanning light amount to enable show-through, a light amount adjusting means for changing the scanning light amount is necessary, which is costly and takes time to adjust the light amount. There are also papers such as thick paper that do not show through even if the amount of scanning light is increased.

  Also, since the image misalignment between the front and back sides changes depending on the paper, the front and back should be adjusted with the paper actually used.However, if you do not see through, the method of selecting another paper will change the front and back of the paper actually used. Image shift cannot be detected. In particular, in a PP (production print) machine, it is required to match the image positions of the front and back with high accuracy, and therefore it is necessary to adjust the front and back of each sheet.

  Further, in the method of changing the scanning light quantity and the paper when the show-through is not performed, the adjustment pattern is formed and read every time the condition is changed, so it takes time to adjust the front and back.

  Further, when the front / back adjustment cannot be performed with the already set paper, the user needs to replace the paper with a paper with a smaller basis weight, which is not convenient.

  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 shorten the adjustment time when adjusting front and back images using a sheet actually used.

  In order to solve the above problems, the invention described in claim 1 is an image forming apparatus that performs front and back adjustment for adjusting the position or magnification of an image formed on both sides of a sheet, the image forming an image on the sheet. Forming means, image reading means for reading an adjustment pattern formed on the paper, and causing the image forming means to form adjustment patterns on both sides of the paper, and the image reading means from the first surface side of the paper A first front / back adjustment means for performing the front / back adjustment based on read data obtained by simultaneously reading an adjustment pattern formed on one surface and an adjustment pattern formed on a second surface to show through; The image forming unit forms an adjustment pattern on the first side of at least the first sheet and the second side of the second sheet of the two sheets, and the image reading unit causes the first sheet to be adjusted. Read data obtained by reading an adjustment pattern formed on the first surface from the first surface side of the paper, and the second surface from the second surface side of the second sheet by the image reading means. Based on the read data obtained by reading the adjustment pattern formed on the second front and back adjustment means for performing the front and back adjustment, the type of the paper to be subjected to the front and back adjustment, or the image reading means Control means for switching between the first front / back adjustment means and the second front / back adjustment means according to the state when the paper is read.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the basis weight of the sheet to be subjected to the front / back adjustment is equal to or greater than a predetermined threshold, the control unit Switch to 2 front / back adjustment means.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, when the control target is a sheet designated in advance, the second adjustment target is the second Switch to front / back adjustment means.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit is an adjustment pattern formed on a second surface that shows through from the first surface side of the sheet by the image reading unit. Is switched to the second front / back adjusting means.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the second front / back adjusting unit includes a first sheet of the second sheet by the image forming unit. The formation of the adjustment pattern on the surface is omitted.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the second front / back adjusting unit is configured to perform the first sheet and the second sheet. The transport path is transported under the same conditions as the paper in the first front / back adjusting means.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, in the second front / back adjustment unit, the second sheet of the second sheet is scanned by the image reading unit. The orientation of the image in the paper conveyance direction when reading the adjustment pattern formed on the surface is the paper conveyance direction when the adjustment pattern formed on the first surface of the first sheet is read by the image reading unit. The second front / back adjustment means takes into account the orientation of the images on the first side of the first sheet and the second side of the second sheet. I do.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the second front / back adjustment unit is configured to supply a sheet to the image forming unit when performing the front / back adjustment. When forming an actual image, the order of the actual images formed on the first and second surfaces of the second sheet is changed.

  The invention according to claim 9 comprises image forming means for forming an image on a sheet and image reading means for reading an adjustment pattern formed on the sheet, and the position of the image formed on both sides of the sheet or An image adjustment method in an image forming apparatus that performs front / back adjustment for adjusting magnification, wherein the image is selected depending on a type of the paper to be subjected to the front / back adjustment or a state when the paper is read by the image reading unit. An adjustment pattern is formed on both sides of the paper by the forming unit, and the adjustment pattern formed on the first side of the paper from the first side of the paper by the image reading unit and the second side of the show-through are formed. Based on reading data obtained by simultaneously reading the adjustment pattern, the first front / back adjustment processing for performing the front / back adjustment, and at least one of the two sheets in the image forming unit An adjustment pattern is formed on the first side of the sheet and the second side of the second sheet, and the adjustment pattern formed on the first side from the first side of the first sheet by the image reading unit. Based on read data obtained by reading a pattern, and read data obtained by reading an adjustment pattern formed on the second surface from the second surface side of the second sheet by the image reading means. And a step of switching between the second front and back adjustment processing for performing the front and back adjustment.

  The invention according to claim 10 comprises image forming means for forming an image on a sheet and image reading means for reading an adjustment pattern formed on the sheet, and the position of the image formed on both sides of the sheet or The computer of the image forming apparatus that performs front / back adjustment for adjusting the magnification is formed on the first surface from the first surface side of the sheet by the image reading unit by causing the image forming unit to form adjustment patterns on both sides of the sheet. The first front / back adjustment means for performing the front / back adjustment based on the read data obtained by simultaneously reading the adjustment pattern and the adjustment pattern formed on the second surface to show through, and the image forming means Of the two sheets, an adjustment pattern is formed on the first surface of at least the first sheet and the second surface of the second sheet, and the image reading unit causes the first sheet of the first sheet to be adjusted. Read data obtained by reading the adjustment pattern formed on the first surface from the surface side, and formed on the second surface from the second surface side of the second sheet by the image reading means. Based on the read data obtained by reading the adjustment pattern, the second front / back adjustment means for performing the front / back adjustment, the type of the paper subject to the front / back adjustment, or when the paper is read by the image reading means This is a program for functioning as control means for switching between the first front / back adjustment means and the second front / back adjustment means in accordance with the state.

  According to the present invention, the adjustment time can be shortened when the front and back images are adjusted using the paper actually used.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. 2 is a block diagram illustrating a functional configuration of the image forming apparatus. FIG. (A) is an example of the surface adjustment pattern. (B) is an example of the back side adjustment pattern. It is an example of the surface adjustment pattern and the back surface adjustment pattern included in the read data read from the front surface side. It is a figure which shows the outline | summary of a 1st front / back adjustment process and a 2nd front / back adjustment process. It is a figure which shows the relationship of the direction of the image in a 1st front / back adjustment process and a 2nd front / back adjustment process. 4 is a flowchart illustrating front / back adjustment mode A processing executed in the image forming apparatus according to the first embodiment. It is a flowchart which shows a show-through front / back adjustment process. It is a flowchart which shows 2 sheets 1 set front and back adjustment processing. 10 is a flowchart illustrating front / back adjustment mode B processing executed in the image forming apparatus according to the second embodiment. 14 is a flowchart illustrating front / back adjustment mode selection processing executed in the image forming apparatus according to the third embodiment. 10 is a flowchart illustrating front / back adjustment processing based on a paper type executed in an image forming apparatus according to a fourth embodiment. (A) is an example of the surface adjustment pattern suitable for the first front and back adjustment processing. (B) is an example of the back side adjustment pattern suitable for the first front and back adjustment processing. (A) is another example of the surface adjustment pattern suitable for the first front / back adjustment processing. (B) is another example of the back side adjustment pattern suitable for the first front and back adjustment processing. (A) is another example of the surface adjustment pattern suitable for the first front / back adjustment processing. (B) is another example of the back side adjustment pattern suitable for the first front and back adjustment processing.

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

FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 according to the first embodiment.
The image forming apparatus 100 includes an operation unit 20, a display unit 30, an image forming unit 40, an image reading unit 50, a double-sided conveyance path 81, a paper reversing unit 82, a paper reversing unit 83, a paper feed tray T1, a paper discharge tray T2, and the like. Prepare.

  The operation unit 20 includes a touch panel formed so as to cover the display screen of the display unit 30 and various operation buttons such as numeric buttons and a start button, and controls operation signals based on user operations to the control unit 10 (see FIG. 2). ).

  The display unit 30 is configured by an LCD (Liquid Crystal Display), and displays various screens according to instructions of a display signal input from the control unit 10.

The image forming unit 40 forms an image on a sheet based on the image data.
The image forming unit 40 includes photosensitive drums 41Y, 41M, 41C, and 41K corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K), an intermediate transfer belt 42, and a secondary transfer roller. 43, a fixing unit 44, and the like.

After the photoreceptor drum 41Y is uniformly charged, it is 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 41Y, and development is performed.
Since the photosensitive drums 41M, 41C, and 41K are the same as the photosensitive drum 41Y except that the handled colors are different, the description thereof is omitted.

The toner images of the respective colors formed on the photosensitive drums 41Y, 41M, 41C, and 41K are sequentially transferred onto the rotating intermediate transfer belt 42 (primary transfer). That is, on the intermediate transfer belt 42, a color toner image is formed by superimposing four color toner images.
The color toner images on the intermediate transfer belt 42 are collectively transferred onto the paper by the secondary transfer roller 43 (secondary transfer).

  The fixing unit 44 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 image reading unit 50 includes a line sensor in which a plurality of light receiving elements are arranged at a predetermined interval in a direction orthogonal to the paper transport direction, reads an adjustment pattern formed on the paper, and reads read data (image data). Is output to the control unit 10. Each light receiving element outputs a signal corresponding to the intensity of light emitted from the light source and reflected from the surface of the paper. As the line sensor, for example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor is used.

  The double-sided conveyance path 81 is a conveyance path for reversing the front and back of the sheet and supplying the sheet to the image forming unit 40 again when forming images on both sides of the sheet.

  The paper reversing unit 82 can reverse the front and back of the paper while the paper is being conveyed from the image forming unit 40 to the image reading unit 50. When the double-sided image is formed, when the image reading unit 50 reads an image from the front side (the surface on which the image is formed first), the paper is reversed by the paper reversing unit 82 and conveyed. On the other hand, at the time of double-sided image formation, when the image reading unit 50 reads an image from the back side (the side on which the image is formed later), the paper is reversed by the paper reversing unit 82.

  The paper reversing unit 83 can reverse the front and back of the paper while the paper is being conveyed from the image reading unit 50 to the paper discharge tray T2.

The paper feed tray T1 stores paper of a predetermined paper type and size. The sheets stored in the sheet feed tray T1 are supplied to the image forming unit 40 one by one.
The paper after the image formation is discharged to the paper discharge tray T2.

FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 100.
As shown in FIG. 2, the image forming apparatus 100 includes a control unit 10, an operation unit 20, a display unit 30, an image forming unit 40, an image reading unit 50, a storage unit 60, a communication unit 70, a conveyance unit 80, and the like. Note that description of the functional units already described is omitted.

  The control unit 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads out various processing programs stored in the ROM in accordance with an operation signal input from the operation unit 20 or an instruction signal received by the communication unit 70, expands the program in the RAM, and displays an image according to the expanded program. The operation of each part of the forming apparatus 100 is centrally controlled.

  The storage unit 60 is configured by a hard disk, a flash memory, or the like, and stores various data. The storage unit 60 stores sheet information regarding sheets stored in the sheet feed tray T1. The paper information includes paper basis weight, paper type, and the like. When the image forming apparatus 100 includes a plurality of paper feed trays, paper information is stored for each paper feed tray.

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

  The transport unit 80 includes a transport roller for transporting the paper, and transports the paper in the image forming apparatus 100.

The control unit 10 controls the image forming unit 40 to form an adjustment pattern used for front / back adjustment on the sheet.
3A and 3B show examples of the front surface adjustment patterns P11 to P14 and the back surface adjustment patterns Q11 to Q14. As the adjustment patterns P11 to P14 and the adjustment patterns Q11 to Q14, register marks (crosses) are formed at the four corners of the sheet.

  The control unit 10 calculates a correction amount (adjustment value) such as an image position, an image density, and a color shift based on read data obtained by reading an adjustment image such as an adjustment pattern by the image reading unit 50. It feeds back to image formation on the subsequent paper.

  The control unit 10 performs front / back adjustment for adjusting the position or magnification of images formed on both sides of the sheet. Specifically, the control unit 10 sets the adjustment pattern P11 formed on the front surface of the paper and the adjustment pattern Q11 formed on the back surface of the paper shown in FIGS. 3A and 3B, and the front surface of the paper. A set of the adjustment pattern P12 formed on the back surface of the paper and the adjustment pattern Q12 formed on the back surface of the paper, a set of the adjustment pattern P13 formed on the front surface of the paper and the adjustment pattern Q13 formed on the back surface of the paper, the paper The shift with respect to the images formed on the front and back surfaces is based on the amount of deviation between the front and back adjustment patterns in each set of the adjustment pattern P14 formed on the front surface and the adjustment pattern Q14 formed on the back surface of the paper. The amount and magnification are calculated, and the position and magnification of the images formed on the front and back surfaces are adjusted.

  The control unit 10 causes the image forming unit 40 to form adjustment patterns on both sides of the sheet, and the adjustment pattern formed on the surface from the front side as the first side of the sheet by the image reading unit 50 and the show-through The front / back adjustment is performed based on the read data obtained by simultaneously reading the adjustment patterns formed on the back surface as the second surface (hereinafter referred to as “first front / back adjustment processing”). That is, the control unit 10 functions as a first front / back adjustment unit.

  FIG. 4 shows an example of the front surface adjustment pattern P11 and the back surface adjustment pattern Q11 included in the read data read from the front surface side. Since the adjustment pattern Q11 on the back surface is a show-through, the density is lower than that of the adjustment pattern P11 on the front surface. The controller 10 identifies both of them based on the density difference between the front surface adjustment pattern P11 and the back surface adjustment pattern Q11. The controller 10 is orthogonal to the amount of deviation ΔY in the paper conveyance direction between the front surface adjustment pattern P11 and the back surface adjustment pattern Q11, and the paper conveyance direction between the front surface adjustment pattern P11 and the back surface adjustment pattern Q11. Based on the shift amount ΔX in the direction, the position and magnification of the images formed on the front and back surfaces are adjusted.

  The control unit 10 causes the image forming unit 40 to form an adjustment pattern on the front surface as the first surface of at least the first sheet and the back surface as the second surface of the second sheet of the two sheets, Read data obtained by reading the adjustment pattern formed on the front surface of the first sheet by the image reading unit 50, and the back surface from the back side of the second sheet by the image reading unit 50 The front / back adjustment is performed based on the read data obtained by reading the adjustment pattern formed in the above (hereinafter referred to as “second front / back adjustment process”). That is, the control unit 10 functions as a second front / back adjustment unit.

  In the second front / back adjustment process, the control unit 10 detects the distance from the edge of the adjustment pattern in the read data of the front surface of the first sheet and the read data of the back surface of the second sheet, Find the difference between the front and back and adjust the front and back.

  FIG. 5 shows an outline of the first front / back adjustment processing and the second front / back adjustment processing. In the first front / back adjustment process, the adjustment pattern formed on the front surface of the first sheet and the adjustment pattern formed on the back surface of the first sheet are compared to perform front / back adjustment. In the second front / back adjustment process, the adjustment pattern formed on the front surface of the first sheet is compared with the adjustment pattern formed on the back surface of the second sheet, and the front / back adjustment is performed. Since the surface of the second sheet is not used for front / back adjustment, it is not necessary to form an adjustment pattern.

  The control unit 10 switches between the first front / back adjustment processing and the second front / back adjustment processing according to the state when the image reading unit 50 reads the paper.

  The control unit 10 switches to the second front / back adjustment process when the image reading unit 50 is unable to read the adjustment pattern formed on the back surface that shows through from the front side of the sheet.

  In the second front / back adjustment process, the controller 10 causes the image forming unit 40 to omit the formation of the adjustment pattern on the surface of the second sheet.

  In the second front / back adjustment process, the control unit 10 causes the first paper and the second paper to be transported on the transport path under the same conditions as the paper in the first front / back adjustment process. For example, the control unit 10 makes the conditions for the first sheet and the second sheet to pass through the fixing unit 44, the duplex conveyance path 81, and the like be the same as those during normal duplex image formation.

In the second front / back adjustment process, the image reading unit 50 uses the image reading unit 50 to read the adjustment pattern formed on the back side of the second sheet. This is opposite to the image orientation in the paper transport direction when reading the adjustment pattern formed on the surface of the paper.
In the second front / back adjustment process, the control unit 10 performs front / back adjustment in consideration of the orientations of the images on the front surface of the first sheet and the back surface of the second sheet.

FIG. 6 shows the relationship between the image orientations in the first front / back adjustment processing and the second front / back adjustment processing.
In the first front / back adjustment processing, after the adjustment pattern is formed on the back side of the paper by the image forming unit 40, the front side adjustment pattern and the back side adjustment pattern are read from the front side by the image reading unit 50. The paper is not reversed by the paper reversing unit 82. That is, the leading edge of the paper when the back surface is formed in the paper conveyance direction and the leading edge of the paper when the adjustment pattern is read coincide with each other. In order to match the positions of the front surface adjustment pattern and the back surface adjustment pattern in the sheet conveyance direction, the first sheet surface distance C1 and the first sheet back surface distance C2 and the first sheet surface distance D1 shown in FIG. And the image may be adjusted so that the distance D2 of the back surface of the first sheet matches.

  On the other hand, in the second front / back adjustment process, after the adjustment pattern is formed on the back side of the second sheet by the image forming unit 40, the back side adjustment pattern is read from the back side by the image reading unit 50. The second sheet is reversed by the sheet reversing unit 82 so that the back surface of the second sheet faces the image reading unit 50 side. That is, the leading edge of the sheet when the back surface is formed in the sheet conveying direction is opposite to the leading edge of the sheet when the adjustment pattern is read. In order to match the positions of the front surface adjustment pattern and the back surface adjustment pattern in the paper conveyance direction, the first sheet surface distance C1 and the second sheet back surface distance C3 and the first sheet surface distance D1 shown in FIG. And the image may be adjusted so that the distance D3 of the back surface of the second sheet matches.

  When the front and back adjustments are performed, the control unit 10 causes the image forming unit 40 to form an actual image on the sheet. In the second front and back adjustment process, the control unit 10 forms the actual images formed on the front and back surfaces of the second sheet. Change the order of the images. Unlike the adjustment pattern, the actual image is an image that is originally formed in the image forming apparatus 100.

Normally, face-down paper discharge is common, so the paper is discharged to the paper discharge tray T2 so that the surface of the paper faces the paper discharge tray T2.
Since the first sheet in the second front / back adjustment process does not need to be reversed in both the sheet reversing unit 82 and the sheet reversing unit 83, the actual image formation order may be the order in which it is desired to be output.
On the other hand, for the second sheet in the second front / back adjustment process, after the back side image is formed, the sheet reversing unit 82 reverses the sheet so that the image reading unit 50 reads the back side. In the paper reversing unit 83, it is necessary to reverse the second sheet so that the page order (page front and back) of the actual images is aligned.
Therefore, in this embodiment, the order of the actual images formed on the front and back surfaces of the second sheet is reversed in advance. For example, the control unit 10 forms the actual image of the first page on the front surface of the first sheet, forms the actual image of the second page on the back surface of the first sheet, and controls the surface of the second sheet. Then, the actual image of the fourth page is formed, and the actual image of the third page is formed on the back surface of the second sheet.

Next, the operation in the image forming apparatus 100 will be described.
FIG. 7 is a flowchart showing front / back adjustment mode A processing executed in the image forming apparatus 100. This process is realized by software processing in cooperation with the CPU of the control unit 10 and the program stored in the ROM.

  First, the control unit 10 controls the transport unit 80 to feed the first sheet among the sheets stored in the sheet feed tray T1 (step S1).

  Next, the control unit 10 controls the image forming unit 40 to form adjustment patterns on both sides of the first sheet (step S2). Specifically, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the surface of the first sheet supplied from the paper feed tray T1, and controls the transport unit 80 to perform the double-side transport path. The sheet is reversed by 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the back surface of the first sheet.

  Next, the control unit 10 tries to detect an adjustment pattern formed on the first sheet from the front side to the back side (step S3). Specifically, the control unit 10 uses the image reading unit 50 to read an image from the front side of the first sheet, and determines whether the back side adjustment pattern can be detected from the obtained read data. To do. For example, the control unit 10 extracts the adjustment pattern from the read data, and when the adjustment pattern having a lower density than the adjustment pattern considered to be the front adjustment pattern can be detected, the back surface adjustment is performed. It is determined that the pattern is for use.

  Here, when the show-through is performed (step S4; YES), that is, when the adjustment pattern on the back side can be detected from the front side of the first sheet, the control unit 10 performs the show-through front / back adjustment process. This is performed (step S5).

Here, the show-through front / back adjustment processing will be described with reference to FIG.
The control unit 10 simultaneously reads the adjustment pattern formed on the front surface side of the first sheet and the adjustment pattern formed on the back side of the show-through by the image reading unit 50, and obtained reading From the data, an adjustment pattern on the front surface and an adjustment pattern on the back surface of the first sheet are detected (steps S11 and S12).
Note that if the adjustment pattern for the front surface and the adjustment pattern for the back surface of the first sheet have already been detected in step S3, the processing in steps S11 and S12 is not necessary.

Next, the control unit 10 detects a front-back deviation based on the front surface adjustment pattern and the back surface adjustment pattern detected from the first sheet (step S13).
Next, the control unit 10 calculates a front / back adjustment value that eliminates the front / back deviation based on the detected front / back deviation (step S14). The front and back adjustment values include parameters for adjusting the positions and magnifications of the front and back images.
Next, the control unit 10 stores the calculated front / back adjustment value in the storage unit 60 and sets it as a value to be used in future double-sided image formation (step S15).
This is the end of the show-through front / back adjustment processing.

  In step S4, when the show-through is not performed (step S4; NO), that is, when the adjustment pattern on the back side cannot be detected from the front side of the first sheet, the control unit 10 controls the transport unit 80. Then, the second sheet is fed from the sheet feed tray T1 (step S6).

Next, the control unit 10 controls the image forming unit 40 to form an adjustment pattern on the back surface of the second sheet (step S7). Specifically, the control unit 10 controls the transport unit 80 without causing the image forming unit 40 to form an adjustment pattern on the surface of the second sheet supplied from the sheet feeding tray T1, and thereby controls the sheet. After passing through the fixing unit 44, the sheet is reversed by the double-sided conveyance path 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the back surface of the second sheet.
Next, the control unit 10 performs a two-sheet one-set front / back adjustment process (step S8).

Here, with reference to FIG. 9, a two-sheet one-set front / back adjustment process will be described.
The control unit 10 reads the adjustment pattern formed on the surface of the first sheet from the front side of the first sheet by the image reading unit 50 and detects the adjustment pattern on the surface of the first sheet from the obtained read data. (Step S21).
Note that if the adjustment pattern on the surface of the first sheet has already been detected in step S3, the process in step S21 is not necessary.

  Next, the control unit 10 reads the adjustment pattern formed on the back side of the second sheet from the back side of the second sheet by the image reading unit 50, and adjusts the back side of the second sheet from the obtained read data. A pattern is detected (step S22). For the second sheet, the sheet reversing unit 82 inverts the sheet so that the image reading unit 50 reads the adjustment pattern formed from the back side to the back side.

Next, the control unit 10 detects front-back deviation based on the front-side adjustment pattern detected from the first sheet and the back-side adjustment pattern detected from the second sheet (step S23). .
Next, the control unit 10 calculates a front / back adjustment value that eliminates the front / back deviation based on the detected front / back deviation (step S24). The front and back adjustment values include parameters for adjusting the positions and magnifications of the front and back images.
Next, the control unit 10 stores the calculated front / back adjustment value in the storage unit 60 and sets it as a value to be used in future double-sided image formation (step S25).
Thus, the two-sheet one-set front / back adjustment processing is completed.

After step S5 or step S8, the front / back adjustment mode A process ends.
In the front / back adjustment mode A process, step S1, step S2, and step S5 correspond to the first front / back adjustment process. The show-through front / back adjustment processing is processing after reading the adjustment pattern in the first front / back adjustment processing.
In the front / back adjustment mode A process, step S1, step S2, and step S6 to step S8 correspond to the second front / back adjustment process. The two-sheet one-set front / back adjustment processing is processing after reading the adjustment pattern in the second front / back adjustment processing.
In the front / back adjustment mode A process, step S1 and step S2 are common processes between the first front / back adjustment process and the second front / back adjustment process.

As described above, according to the first embodiment, when a paper subject to front / back adjustment is show-through, the adjustment pattern is not formed and read on the second sheet. Time can be shortened and waste paper is not generated. Accordingly, the adjustment time can be shortened when the front and back images are adjusted using the paper actually used.
On the other hand, if the paper subject to front / back adjustment does not show through, then the second sheet is fed to form an adjustment pattern, and a pair of front / back adjustment processing is performed. Only the adjustment pattern can be formed and read on the second sheet.

  In the second front / back adjustment process, the formation of the adjustment pattern on the surface of the second sheet is omitted, so unnecessary image formation can be avoided and toner can be saved.

  In the second front / back adjustment processing, the first paper and the second paper are transported along the transport path under the same conditions as the paper in the first front / back adjustment processing, so that the conditions for the paper are matched, Adjustment accuracy can be increased. Although the adjustment pattern does not have to be formed on the front surface of the second sheet, the sheet shrinkage rate is made the same by passing the sheet through the fixing unit 44 twice for the front surface and the back surface. Also, by passing the second sheet through the duplex conveyance path 81, the sheet conveyance deviation is made the same as when images are formed on both sides.

  In the second front / back adjustment processing, the second sheet can be reversed by the sheet reversing unit 83 by changing the order of the actual images formed on the front and back surfaces of the second sheet in advance. It becomes unnecessary.

[Second Embodiment]
Next, a second embodiment to which the present invention is applied will be described.
The image forming apparatus according to the second embodiment has the same configuration as that of the image forming apparatus 100 according to the first embodiment. Therefore, FIG. 1 and FIG. 2 are used, and the configuration is illustrated and described. Omitted. Hereinafter, a configuration and processing characteristic of the second embodiment will be described.

  The control unit 10 switches between the first front / back adjustment processing and the second front / back adjustment processing according to the state when the image reading unit 50 reads the paper.

  In the first embodiment, after confirming that the first sheet does not show through, the second sheet is fed, and the adjustment pattern is formed and read on the second sheet. As described above, in the second embodiment, the second sheet is fed in advance and an adjustment pattern is formed on the second sheet before determining whether to show through.

  FIG. 10 is a flowchart illustrating the front / back adjustment mode B process executed in the image forming apparatus according to the second embodiment. This process is realized by software processing in cooperation with the CPU of the control unit 10 and the program stored in the ROM.

First, the control unit 10 controls the transport unit 80 to feed the first sheet among the sheets stored in the sheet feed tray T1 (step S31).
Next, the control unit 10 controls the transport unit 80 to feed the second sheet from the sheet feed tray T1 (step S32).

  Next, the control unit 10 controls the image forming unit 40 to form adjustment patterns on both sides of the first sheet (step S33). Specifically, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the surface of the first sheet supplied from the paper feed tray T1, and controls the transport unit 80 to perform the double-side transport path. The sheet is reversed by 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the back surface of the first sheet.

  Next, the control unit 10 controls the image forming unit 40 to form an adjustment pattern on the back surface of the second sheet (step S34). Specifically, the control unit 10 controls the transport unit 80 without causing the image forming unit 40 to form an adjustment pattern on the surface of the second sheet supplied from the sheet feeding tray T1, and thereby controls the sheet. After passing through the fixing unit 44, the sheet is reversed by the double-sided conveyance path 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the back surface of the second sheet.

  Next, the control unit 10 tries to detect an adjustment pattern formed on the first sheet from the front side to the back side (step S35). Specifically, the control unit 10 uses the image reading unit 50 to read an image from the front side of the first sheet, and determines whether the back side adjustment pattern can be detected from the obtained read data. To do.

  Here, when the show-through is performed (step S36; YES), that is, when the adjustment pattern on the back side can be detected from the front side of the first sheet, the control unit 10 performs the show-through front / back adjustment process ( (See FIG. 8) (step S37). Since the show-through front / back adjustment processing has been described in the first embodiment, the description thereof is omitted.

  In step S36, when the show-through is not performed (step S36; NO), that is, when the adjustment pattern on the back side cannot be detected from the front side of the first sheet, the control unit 10 adjusts the front and back of the two sheets. Processing (see FIG. 9) is performed (step S38). Since the two-sheet one-set front / back adjustment processing has been described in the first embodiment, description thereof is omitted.

After step S37 or step S38, the front / back adjustment mode B processing ends.
In the front / back adjustment mode B process, step S31, step S33, and step S37 correspond to the first front / back adjustment process.
In the front / back adjustment mode B process, Steps S31 to S34 and Step S38 correspond to the second front / back adjustment process.
In the front / back adjustment mode B processing, Step S31 and Step S33 are common processing between the first front / back adjustment processing and the second front / back adjustment processing.

As described above, according to the second embodiment, since the adjustment pattern is formed by feeding two sheets in advance, when the sheet subject to front / back adjustment does not show through, The pair of front and back adjustment processing can be performed immediately. Accordingly, the adjustment time can be shortened when the front and back images are adjusted using the paper actually used.
On the other hand, if the paper subject to front / back adjustment is show-through, the second paper is not used and waste paper is generated, but the front and back sides of the same paper (first paper) are adjusted. Since the image pattern is read, the front and back images can be adjusted under conditions closer to the actual use state.

[Third Embodiment]
Next, a third embodiment to which the present invention is applied will be described.
Since the image forming apparatus in the third embodiment has the same configuration as the image forming apparatus 100 shown in the first embodiment, FIG. 1 and FIG. 2 are used, and the configuration is illustrated and described. Omitted. Hereinafter, a configuration and processing characteristic of the third embodiment will be described.

  The control unit 10 switches between the first front / back adjustment processing and the second front / back adjustment processing according to the type of the paper to be subjected to front / back adjustment and the state when the image is read by the image reading unit 50.

The control unit 10 selects the front / back adjustment mode B process (see FIG. 10) described in the second embodiment when the basis weight of the sheet to be subjected to front / back adjustment is equal to or greater than a predetermined threshold. Generally, the relationship between the paper type (here, thin paper / plain paper / thick paper) and basis weight is as follows: thin paper is about 60 g / m ² , plain paper is about 60 g / m ² to about 100 g / m ² , and thick paper is About 100 g / m ² to etc. are used. For example, 100 g / m ² is used as a basis weight threshold value for determining that no show-through occurs.

The control unit 10 performs the front / back adjustment mode B processing (FIG. 10) shown in the second embodiment when the paper to be subjected to front / back adjustment is a paper designated in advance (hereinafter referred to as “designated paper”). Select Browse.
Here, the designated paper is a paper that is considered not to show through, and examples thereof include coated paper, envelopes, and postcards.
The coated paper is a paper whose surface is coated with a paint. Examples of the coated paper include art paper, coated paper, embossed paper (embossed paper), and the like.

  FIG. 11 is a flowchart illustrating front / back adjustment mode selection processing executed in the image forming apparatus according to the third embodiment. This process is realized by software processing in cooperation with the CPU of the control unit 10 and the program stored in the ROM.

  First, the control unit 10 reads the basis weight of the paper corresponding to the paper feed tray T1 from the storage unit 60, and determines whether or not the basis weight of the paper to be subjected to front / back adjustment is equal to or greater than a predetermined threshold. (Step S41).

  When the basis weight of the paper to be subjected to front / back adjustment is less than the threshold (step S41; NO), the control unit 10 reads the paper type of the paper corresponding to the paper feed tray T1 from the storage unit 60, and performs front / back adjustment. It is determined whether or not the target paper is designated paper such as coated paper (step S42).

  When the paper to be subjected to front / back adjustment is not the designated paper (step S42; NO), the control unit 10 performs front / back adjustment mode A processing (see FIG. 7) (step S43). Since the front / back adjustment mode A processing has been described in the first embodiment, the description thereof is omitted.

  In step S41, when the basis weight of the paper to be subjected to front / back adjustment is equal to or greater than the threshold (step S41; YES), or in step S42, the paper to be subjected to front / back adjustment is the designated paper (step S42; YES), front / back adjustment mode B processing (see FIG. 10) is performed (step S44). Since the front / back adjustment mode B processing has been described in the second embodiment, the description thereof is omitted.

  After step S43 or step S44, the front / back adjustment mode selection processing ends.

As described above, according to the third embodiment, when it is predicted that no show-through will occur from the basis weight and the paper type, the front / back adjustment mode B process is performed assuming a pair of front / back adjustment process. Therefore, if a pair of front and back adjustment processing is performed as expected, the processing time is shortened compared to the front and back adjustment mode A processing.
On the other hand, when it is predicted that the show-through will occur from the basis weight and the paper type, the front-and-back adjustment mode A processing is performed assuming the show-through front / back adjustment processing. It is not necessary to form and read the adjustment pattern for the second sheet, the adjustment time can be shortened, and waste paper is not generated compared to the front / back adjustment mode B process.
Accordingly, the adjustment time can be shortened when the front and back images are adjusted using the paper actually used.

[Fourth Embodiment]
Next, a fourth embodiment to which the present invention is applied will be described.
The image forming apparatus according to the fourth embodiment has the same configuration as that of the image forming apparatus 100 according to the first embodiment. Therefore, FIG. 1 and FIG. 2 are used, and the configuration is illustrated and described. Omitted. Hereinafter, a configuration and processing characteristic of the fourth embodiment will be described.

  The control unit 10 switches between the first front / back adjustment process and the second front / back adjustment process according to the type of paper to be subjected to front / back adjustment.

The control unit 10 switches to the second front / back adjustment process when the basis weight of the paper to be subjected to front / back adjustment is equal to or greater than a predetermined threshold. For example, 100 g / m ² is used as the basis weight threshold. When the basis weight of the sheet is equal to or greater than the threshold value, the control unit 10 determines that the first front / back adjustment process cannot be performed without showing back and the second front / back adjustment process is performed.

  The control unit 10 switches to the second front / back adjustment process when the paper to be subjected to front / back adjustment is the designated paper. When the paper is a coated paper, envelope, postcard or the like, the control unit 10 determines that the first front / back adjustment processing cannot be performed without showing back, and performs the second front / back adjustment processing.

  FIG. 12 is a flowchart illustrating front / back adjustment processing based on the paper type executed in the image forming apparatus according to the fourth embodiment. This process is realized by software processing in cooperation with the CPU of the control unit 10 and the program stored in the ROM.

  First, the control unit 10 reads the basis weight of the paper corresponding to the paper feed tray T1 from the storage unit 60, and determines whether or not the basis weight of the paper to be subjected to front / back adjustment is equal to or greater than a predetermined threshold. (Step S51).

  When the basis weight of the paper to be subjected to front / back adjustment is less than the threshold (step S51; NO), the control unit 10 reads the paper type of the paper corresponding to the paper feed tray T1 from the storage unit 60, and performs front / back adjustment. It is determined whether or not the target paper is designated paper such as coated paper (step S52).

  If the sheet to be subjected to the front / back adjustment is not the designated sheet (step S52; NO), the control unit 10 controls the transport unit 80 to select the first sheet among the sheets stored in the sheet feed tray T1. A sheet is fed (step S53).

  Next, the control unit 10 controls the image forming unit 40 to form adjustment patterns on both sides of the first sheet (step S54). Specifically, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the surface of the first sheet supplied from the paper feed tray T1, and controls the transport unit 80 to perform the double-side transport path. The sheet is reversed by 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the back surface of the first sheet.

  Next, the control unit 10 performs a show-through front / back adjustment process (see FIG. 8) (step S55). Since the show-through front / back adjustment processing has been described in the first embodiment, the description thereof is omitted.

In step S51, when the basis weight of the paper to be subjected to front / back adjustment is equal to or greater than the threshold value (step S51; YES), or in step S52, the paper to be subjected to front / back adjustment is the designated paper (step (S52; YES), the control unit 10 controls the transport unit 80 to feed the first sheet among the sheets stored in the sheet feed tray T1 (step S56).
Next, the control unit 10 controls the transport unit 80 to feed the second sheet from the sheet feed tray T1 (step S57).

  Next, the control unit 10 controls the image forming unit 40 to form an adjustment pattern on the surface of the first sheet (step S58). Specifically, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the surface of the first sheet supplied from the paper feed tray T1, and controls the transport unit 80 to perform the double-side transport path. The sheet is reversed by 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 controls the transport unit 80 to transport the paper and pass the fixing unit 44 without causing the image forming unit 40 to form an adjustment pattern on the back surface of the first sheet.

  Next, the control unit 10 controls the image forming unit 40 to form an adjustment pattern on the back surface of the second sheet (step S59). Specifically, the control unit 10 controls the transport unit 80 without causing the image forming unit 40 to form an adjustment pattern on the surface of the second sheet supplied from the sheet feeding tray T1, and thereby controls the sheet. After passing through the fixing unit 44, the sheet is reversed by the double-sided conveyance path 81 and supplied to the image forming unit 40 again. Thereafter, the control unit 10 causes the image forming unit 40 to form an adjustment pattern on the back surface of the second sheet.

  Next, the control unit 10 performs a two-sheet one-set front / back adjustment process (see FIG. 9) (step S60). Since the two-sheet one-set front / back adjustment processing has been described in the first embodiment, description thereof is omitted.

After step S55 or step S60, the front / back adjustment processing based on the paper type ends.
In the front / back adjustment processing based on the paper type, steps S53 to S55 correspond to the first front / back adjustment processing.
Further, in the front / back adjustment processing based on the paper type, steps S56 to S60 correspond to the second front / back adjustment processing.

As described above, according to the fourth embodiment, when it is predicted that the show-through will not occur from the basis weight and the paper type, the second front / back adjustment process is performed, so it is determined that the show-through does not occur. The processing time is reduced as compared with the case where the adjustment pattern is formed and read from the second sheet to the second sheet.
On the other hand, if it is predicted that the show-through will occur from the basis weight and the paper type, the first front / back adjustment processing is performed, so it is not necessary to form and read the adjustment pattern for the second sheet, and the adjustment time is reduced. It can be shortened and waste paper is not generated compared to the second front / back adjustment process.
Accordingly, the adjustment time can be shortened when the front and back images are adjusted using the paper actually used.

  If it is determined in step S51 or step S52 that the second front / back adjustment process is to be performed, an adjustment pattern may be formed only on the first surface in step S58. It is not necessary to form an adjustment pattern on the back surface of the. In step S59, the adjustment pattern only needs to be formed on the back surface of the second sheet, and it is not necessary to form the adjustment pattern on the front surface of the second sheet. However, the conditions for the paper can be obtained by making the transport path of the first and second sheets in step S58 and step S59 the same as the transport path of the sheet in step S54 (conveyance path during normal double-sided image formation). To improve the accuracy of the front and back adjustment.

  The description in each of the above embodiments is an example of the image forming apparatus according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of each part constituting the apparatus can be changed as appropriate without departing from the spirit of the present invention. Moreover, it is good also as performing combining a characteristic process in each embodiment.

For example, the adjustment pattern used for the front and back adjustment is not limited to the example shown in FIGS.
FIGS. 13A and 13B show examples of the front surface adjustment patterns P21 to P24 and the back surface adjustment patterns Q21 to Q24 suitable for the first front / back surface adjustment processing. The back side adjustment patterns Q21 to Q24 are formed in a color (for example, red) different from the color (for example, black) of the front side adjustment patterns P21 to P24. Both can be identified by the difference in color between the adjustment patterns P21 to P24 on the front surface and the adjustment patterns Q21 to Q24 on the back surface included in the read data read from the front surface side.

  FIGS. 14A and 14B show other examples of the front surface adjustment patterns P31 to P34 and the back surface adjustment patterns Q31 to Q34 suitable for the first front / back surface adjustment processing. In addition to the adjustment patterns Q31 to Q34, an identification mark M1 indicating the back side is formed on the back side of the sheet. Based on the density of the identification mark M1 included in the read data read from the front side, the density of the back side adjustment patterns Q31 to Q34 is estimated, and the front side adjustment patterns P31 to P34 and the back side adjustment patterns Q31 to Q31 are estimated. Both can be identified by the difference in density between Q34 and Q34.

  15A and 15B show other examples of the front surface adjustment patterns P41 to P44 and the back surface adjustment patterns Q41 to Q44 suitable for the first front / back surface adjustment processing. In FIGS. 15A and 15B, the adjustment pattern (shown back) formed on the other surface viewed from one surface side of the front and back is shown in gray. The positions of the adjustment patterns Q41 to Q44 on the back surface are deviated from the positions of the adjustment patterns P41 to P44 on the front surface (adjustment pattern offset). By this difference in position, the front adjustment patterns P41 to P44 and the rear adjustment patterns Q41 to Q44 can be identified. When comparing the positions of the front and back adjustment patterns, the front and back adjustments are performed in consideration of the offset amount of the original front and back adjustment patterns.

  In each of the above embodiments, the front surface of the paper (the surface on which the image is formed first when the double-sided image is formed) is the first surface, and the back surface of the paper (the surface on which the image is formed later when the double-sided image is formed). Although described as the second surface, the back surface of the paper may be the first surface and the front surface of the paper may be the second surface. In this case, in the first front / back adjustment process, the paper reversing unit 82 inverts the paper when simultaneously reading the adjustment pattern formed on the back surface from the back surface and the adjustment pattern formed on the back surface. 1, the image reading unit 50 is installed on the opposite side of the position of the image reading unit 50 shown in FIG. 1 and the paper transport path so that the reading surface of the image reading unit 50 faces the back side of the paper. It is desirable.

  In the above description, an example in which a ROM is used as a computer-readable medium storing a program for executing each process is disclosed, but the present invention is not limited to this example. As other computer-readable media, a non-volatile memory such as a flash memory and a portable recording medium such as a CD-ROM can be applied. A carrier wave may be applied as a medium for providing program data via a communication line.

DESCRIPTION OF SYMBOLS 10 Control part 40 Image formation part 44 Fixing part 50 Image reading part 60 Memory | storage part 80 Conveyance part 81 Double-sided conveyance path 82 Paper reversing part 83 Paper reversing part 100 Image forming apparatus

Claims (10)

An image forming apparatus that performs front and back adjustment for adjusting the position or magnification of an image formed on both sides of a sheet,
Image forming means for forming an image on paper;
Image reading means for reading the adjustment pattern formed on the paper;
The image forming unit forms an adjustment pattern on both sides of the paper, and the image reading unit forms the adjustment pattern formed on the first surface from the first surface side of the paper and the show-through second surface. First adjustment means for adjusting the front and back based on the read data obtained by simultaneously reading the adjusted pattern,
The image forming unit forms an adjustment pattern on the first surface of at least the first sheet of the two sheets and the second surface of the second sheet of the two sheets, and the first sheet is formed by the image reading unit. Read data obtained by reading the adjustment pattern formed on the first surface from the first surface side, and the second surface side of the second sheet from the second surface side to the second surface by the image reading means. Based on read data obtained by reading the formed adjustment pattern, second front and back adjustment means for performing the front and back adjustment,
Control means for switching between the first front / back adjustment means and the second front / back adjustment means according to the type of paper to be subjected to the front / back adjustment or the state when the paper is read by the image reading means; ,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the control unit switches to the second front / back adjustment unit when a basis weight of the sheet to be subjected to front / back adjustment is equal to or greater than a predetermined threshold.   The image forming apparatus according to claim 1, wherein the control unit switches to the second front / back adjustment unit when the sheet to be subjected to front / back adjustment is a sheet designated in advance.   The control means switches to the second front / back adjustment means when the image reading means cannot read the adjustment pattern formed on the second surface show-through from the first surface side of the paper. Item 2. The image forming apparatus according to Item 1.   5. The image forming apparatus according to claim 1, wherein the second front / back adjusting unit omits the formation of the adjustment pattern on the first surface of the second sheet by the image forming unit. 6.   The said 2nd front and back adjustment means conveys a conveyance path | route on the same conditions as the paper in the said 1st front and back adjustment means about the said 1st sheet | seat and the said 2nd sheet | seat. The image forming apparatus according to one item. In the second front / back adjustment unit, the image reading unit reads the adjustment pattern formed on the second surface of the second sheet by the image reading unit. Opposite to the orientation of the image in the paper transport direction when reading the adjustment pattern formed on the first surface of the first paper,
The said 2nd front / back adjustment means performs the said front / back adjustment in consideration of the direction of the image of the 1st surface of the said 1st sheet | seat, and the 2nd surface of the said 2nd sheet | seat. The image forming apparatus according to claim 1.   The second front / back adjustment unit is formed on the first and second surfaces of the second sheet of paper when the image forming unit forms an actual image on the sheet when performing the front / back adjustment. The image forming apparatus according to claim 1, wherein the order of real images is changed. An image comprising image forming means for forming an image on a sheet and image reading means for reading an adjustment pattern formed on the sheet, and performing front and back adjustment for adjusting the position or magnification of the image formed on both sides of the sheet An image adjustment method in a forming apparatus,
According to the type of the paper subject to the front / back adjustment, or the state when the paper is read by the image reading means,
The image forming unit forms an adjustment pattern on both sides of the paper, and the image reading unit forms the adjustment pattern formed on the first surface from the first surface side of the paper and the show-through second surface. A first front / back adjustment process for performing the front / back adjustment based on the read data obtained by simultaneously reading the adjusted pattern,
The image forming unit forms an adjustment pattern on the first surface of at least the first sheet of the two sheets and the second surface of the second sheet of the two sheets, and the first sheet is formed by the image reading unit. Read data obtained by reading the adjustment pattern formed on the first surface from the first surface side, and the second surface side of the second sheet from the second surface side to the second surface by the image reading means. A second front / back adjustment process for performing the front / back adjustment based on the read data obtained by reading the formed adjustment pattern;
Image adjustment method including a step of switching. An image comprising image forming means for forming an image on a sheet and image reading means for reading an adjustment pattern formed on the sheet, and performing front and back adjustment for adjusting the position or magnification of the image formed on both sides of the sheet The forming machine computer,
The image forming unit forms an adjustment pattern on both sides of the paper, and the image reading unit forms the adjustment pattern formed on the first surface from the first surface side of the paper and the show-through second surface. A first front / back adjusting means for performing the front / back adjustment based on the read data obtained by simultaneously reading the adjusted pattern,
The image forming unit forms an adjustment pattern on the first surface of at least the first sheet of the two sheets and the second surface of the second sheet of the two sheets, and the first sheet is formed by the image reading unit. Read data obtained by reading the adjustment pattern formed on the first surface from the first surface side, and the second surface side of the second sheet from the second surface side to the second surface by the image reading means. A second front / back adjustment means for performing the front / back adjustment based on read data obtained by reading the formed adjustment pattern;
Control means for switching between the first front / back adjustment means and the second front / back adjustment means according to the type of the paper to be subjected to the front / back adjustment, or the state when the paper is read by the image reading means,
Program to function as.