Image forming device

Abstract

To provide an image forming device that can appropriately read out an adjustment pattern, without depending on reading resolution of a reading part.SOLUTION: An image forming device comprises: a conveying part that conveys a medium in a conveying direction; an image forming part that forms adjustment patterns (X1, Y1 and Z1) on a first surface of the medium conveyed by the conveying part; and a reading part arranged on a downstream side in the conveying direction from the image forming part, reading out the adjustment patterns (X1, Y1 and Z1) formed on the first surface of the medium conveyed by the conveying part to generate reading data. The adjustment patterns (X1, Y1 and Z1) include a first line segment (L1) and a second line segment (L2) extending in directions different from each other, where the first line segment (L1) and the second line segment (L2) respectively incline with respect to the conveying direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, image forming devices have been known that form images on both the front and back sides of sheet-like media. In such image forming devices, the media deforms as the image formed on the front side dries. When an image is then formed on the back side of the deformed media, there is a problem in that the position and size of the image differ between the front and back sides.

[0003] Therefore, some image forming devices with the above configuration have a function of having a reading unit read the adjustment pattern formed on the front side of the medium, and correcting the image formed on the back side of the medium based on the difference between the ideal position and the actual position of the adjustment pattern. Also, the adjustment pattern is often composed of a first line segment extending in the medium transport direction and a second line segment perpendicular to the transport direction, such as a cross, L-shape, or T-shape (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the reading unit reads the adjustment pattern while the medium is being transported. That is, to read the first line segment extending in the transport direction, the reading unit must continuously read in a direction perpendicular to the transport direction while the medium is being transported. Also, to read the second line segment perpendicular to the transport direction, the reading unit must continuously read the adjustment pattern while the medium is being transported. As a result, the reading accuracy of the adjustment pattern depends on the reading resolution (reading cycle) of the reading unit. Furthermore, the faster the medium transport speed, the more difficult it is to properly read the adjustment pattern unless a reading element with a higher reading resolution is installed.

[0005] The present invention has been made to solve such problems, and has an object to provide an image forming apparatus that can properly read an adjustment pattern without depending on the reading resolution of the reading unit. [Means for solving the problem]

[0006] In order to solve the above problem, one aspect of the present invention is a printing apparatus including: a conveying unit that conveys a medium in a conveying direction; an image forming unit that forms an adjustment pattern on a first surface of the medium conveyed by the conveying unit; and a reading unit that is disposed downstream of the image forming unit in the conveying direction and that reads the adjustment pattern formed on the first surface of the medium being conveyed by the conveying unit to generate read data. a control unit that analyzes the read data generated by the reading unit and calculates a correction value for correcting a second-side image to be formed on a second side of the medium opposite to the first side; the adjustment pattern includes a first line segment and a second line segment extending in different directions from each other, and the first line segment and the second line segment are each inclined with respect to the transport direction. The control unit identifies an intersection between the first line segment and the second line segment based on values ​​obtained by reading the first line segment and the second line segment at a first position and a second position on the medium spaced apart in the transport direction, and calculates the correction values ​​in the transport direction and a main scanning direction perpendicular to the transport direction using the positions of the intersections between the first line segment and the second line segment. It is characterized by: [Effects of the Invention]

[0007] According to the present invention, it is possible to obtain an image forming apparatus that can appropriately read an adjustment pattern without depending on the reading resolution of the reading unit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an image forming apparatus. [Figure 2] FIG. 1 is a block diagram showing a configuration of an image forming apparatus. [Figure 3] FIG. [Figure 4] 10 is a flowchart of an image forming process. [Figure 5] 5A and 5B are diagrams showing a surface image and an adjustment pattern formed on the surface of a medium. [Figure 6] 5A to 5C are diagrams illustrating a procedure for identifying intersections of adjustment patterns. [Figure 7] FIG. 10 is a diagram showing a back side image formed on the back side of the medium. DETAILED DESCRIPTION OF THE INVENTION

[0009] An image forming apparatus 1 according to the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing the overall configuration of the image forming apparatus 1. The image forming apparatus 1 has the function of forming an image on each of the front (first side) and back (second side) of a medium M. The medium M may be in the form of a sheet on which an image can be formed on both the front and back sides, and may be made of a material (e.g., paper, cloth, etc.) that expands and contracts as the substance (e.g., ink, toner, etc.) that makes up the image dries.

[0010] 1, the image forming apparatus 1 mainly includes a paper feed tray 10, a conveying section 20, a pre-coating section 30, an image forming section 40, a drying section 50, a reading section 60, and a paper discharge tray 70. Inside the image forming apparatus 1, a main conveying path R1 and a reverse conveying path R2 (hereinafter, these may be collectively referred to as "conveying paths R1, R2") are formed.

[0011] The main transport path R1 and the reverse transport path R2 are spaces within the image forming apparatus 1 through which the medium M can pass. The main transport path R1 is a path that runs from the paper feed tray 10 to the paper output tray 70 via the pre-coating unit 30, the image forming unit 40, and the drying unit 50. The reverse transport path R2 is a path that branches off from the main transport path R1 at a branch point B between the drying unit 50 and the paper output tray 70, and merges with the main transport path R1 at a junction point C between the pre-coating unit 30 and the image forming unit 40.

[0012] The transport unit 20 transports the medium M along the transport paths R1 and R2. More specifically, the transport unit 20 transports the medium M along the main transport path R1 in a direction (transport direction) from the paper feed tray 10 toward the paper output tray 70. The transport unit 20 also transports the medium M along the reverse transport path R2 in a direction (transport direction) from the branch point B toward the junction point C. The transport unit 20 has, for example, multiple transport roller pairs 21, a drum-type transport unit 22, and a transport belt 23.

[0013] Multiple conveying roller pairs 21 are arranged on conveying paths R1, R2 at a predetermined interval in the conveying direction. Each conveying roller pair 21 mainly comprises a drive roller and a driven roller arranged opposite each other with the conveying paths R1, R2 in between. The drive roller rotates when the driving force of a motor is transmitted to the drive roller. The driven roller abuts against the drive roller and rotates as the drive roller rotates. The drive roller and driven roller rotate while sandwiching the medium M, thereby conveying the medium M in the conveying direction.

[0014] Drum-type transport unit 22 is disposed facing image forming unit 40. Drum-type transport unit 22 mainly includes a drum 24, an entrance rotator 25, and an exit rotator 26. Entrance rotator 25 delivers medium M transported from the upstream side in the transport direction to drum 24. Drum 24 transports medium M by rotating with medium M adsorbed to its circumferential surface. Exit rotator 26 delivers medium M received from drum 24 to transport belt 23 downstream in the transport direction.

[0015] The conveyor belt 23 is disposed along the main conveying path R1, downstream in the conveying direction from the drum-type conveying unit 22 and upstream in the conveying direction from the branching point B. The conveyor belt 23 rotates while supporting the medium M on its upper surface, thereby conveying the medium M in the conveying direction along the main conveying path R1. The upper surface of the conveyor belt 23 contacts one of both surfaces of the medium M, the surface opposite to the surface on which an image was most recently formed by the image forming unit 40.

[0016] The pre-coating unit 30 is disposed downstream in the transport direction from the paper feed tray 10 and upstream in the transport direction from the image forming unit 40. The pre-coating unit 30 applies a pre-coating liquid to the medium M on which ink is difficult to fix, in order to fix the ink.

[0017] The image forming unit 40 is disposed downstream in the transport direction from the confluence C and upstream in the transport direction from the drying unit 50. The image forming unit 40 is disposed facing the main transport path R1 at the position of the drum 31. The image forming unit 40 forms an image on the medium M by ejecting ink toward the medium M being adsorbed to the drum 31 and transported.

[0018] The image forming unit 40 has ejection heads 40C, 40M, 40Y, 40B, 40LC, and 40LM that eject ink of each color (e.g., cyan, magenta, yellow, black, light cyan, and light magenta). The ejection heads 40C, 40M, 40Y, 40B, 40LC, and 40LM eject ink at predetermined timing to form an image on the medium M adsorbed to the drum 24. Note that the color combination of ink ejected by the image forming unit 40 is not limited to the example described above. Furthermore, although an example of an inkjet-type image forming unit 40 is described in this embodiment, the image forming unit 40 may also form images using an electrophotographic method.

[0019] The drying unit 50 is disposed downstream of the image forming unit 40 in the transport direction and upstream of the branch point B in the transport direction. The drying unit 50 is disposed facing the upper surface of the transport belt 23. The drying unit 50 dries ink adhering to the medium M transported by the transport belt 23. The drying unit 50 is, for example, a heater that heats the medium M on the transport belt 23, or a blower that blows warm air toward the medium M on the transport belt 23.

[0020] The reading unit 60 is disposed downstream of the drying unit 50 in the conveying direction. The reading unit 60 is also disposed facing the reverse conveying path R2. The reading unit 60 reads an image formed on the surface of the medium M on the reverse conveying path R2 and generates read data. The read data is image data that indicates the image read by the reading unit 60. The reading unit 60 is a line sensor in which multiple reading elements are arranged in a main scanning direction perpendicular to the conveying direction. For example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) can be used as the reading element.

[0021] The transport unit 20 transports the medium M stored in the paper feed tray 10 in the transport direction along the main transport path R1. The pre-coating unit 30 applies a pre-coating liquid to the surface of the medium M transported along the main transport path R1, the image forming unit 40 forms an image, and the drying unit 50 dries the ink.

[0022] Next, the conveying unit 20 guides the medium M with the image formed on its front side from the main conveying path R1 to the reverse conveying path R2 at the branching point B, conveys it in the conveying direction along the reverse conveying path R2, and guides it from the reverse conveying path R2 to the main conveying path R1 at the merging point C. As a result, the medium M with its front and back sides turned over is supplied again to the main conveying path R1.

[0023] Next, the transport unit 20 transports the inverted medium M in the transport direction along the main transport path R1. The image forming unit 40 forms an image on the back side of the medium M transported along the main transport path R1, and the drying unit 50 dries the ink. The transport unit 20 then ejects the medium M, with the images formed on both the front and back sides, onto the paper output tray 70.

[0024] 2 is a block diagram showing the configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 110. The control unit 110 controls the overall operation of the image forming apparatus 1.

[0025] 2, the control unit 110 includes a CPU 121, a ROM 122, a RAM 123, an external memory I / F (interface) 124, a communication I / F 125, an internal bus I / F 126, a PCIe I / F 127, an image output DMAC (Direct Memory Access Controller) 128, an image processing unit 129, and a compressor / decompressor 130. An internal bus 120 connects these units together.

[0026] The internal bus 120 further connects each unit to a PCIe bus 134 via an internal bus I / F 126 and a PCIe I / F 127 .

[0027] The CPU 121 performs various calculation processes to set up all system settings and activates the image output DMAC 128, image processing unit 129, and compressor / expander 130. The ROM 122 mainly stores operation control programs for the CPU 121. The RAM 123 is used as a temporary storage location for the calculation results of the CPU 121 and various data, and also functions as a memory for saving images. The ROM 122, RAM 123, etc. are collectively referred to as internal memory unless a distinction is required.

[0028] An image memory 133 is also used as a memory for storing images. The image memory 133 is connected to the CPU 121 via the external memory I / F 124. When the CPU 121 receives image data from the print server 210, it performs drawing in the image memory 133 via the external memory I / F 124 based on the printer language.

[0029] The communication I / F 125 is an I / F between the print server 210 and the CPU 121, and between the operation panel 131 and the CPU 121.

[0030] The internal bus I / F 126 is an I / F between the PCIe I / F 127 and the internal bus 120. This internal bus I / F 126 inputs and outputs image data between an address designated by the PCIe bus master and the image memory 133 (via the external memory I / F 124).

[0031] The PCIe I / F 127 exchanges data with the PCIe bus master in accordance with the protocol of the PCIe bus 134 .

[0032] The image output DMAC 128 and the image processing unit 129 are connected to the CPU 121, the external memory I / F 124, etc. via the internal bus 120. The image output DMAC 128 is also connected to the PCIe I / F 127.

[0033] The image output DMAC 128 functions as a DMA controller during printing. That is, when the image output DMAC 128 is started by the CPU 121, it reads image data from a pre-specified area of ​​external memory and outputs the image data to the PCIe I / F 127. This output is performed by exchanging handshakes as needed.

[0034] The image processing unit 129 corrects distortion of the read image.

[0035] The compressor / decompressor 130 is used to save memory, and is activated by the CPU 121 to compress or decompress various data.

[0036] Fig. 3 is a functional block diagram of the control unit 110. As shown in Fig. 3, the control unit 110 includes an image processing controller 111, a reading control unit 112, a correction value calculation unit 113, and an image correction unit 114. Each of these functions is realized by the CPU 121 loading a program stored in the ROM 122 into the RAM 123 and executing the program.

[0037] The image processing controller 111 converts the image data into a format that can be used by the writing unit 101 to form an image. The reading control unit 112 causes the reading unit 60 to read the image formed on the medium M at a predetermined timing, and transmits the read data generated by the reading unit 60 to the correction value calculation unit 113. The correction value calculation unit 113 analyzes the read data sent from the reading control unit 112 to calculate a correction value, and transmits the calculated correction value to the image correction unit 114. The image correction unit 114 corrects the image data using the correction value sent from the correction value calculation unit 113, and transmits the corrected image data to the image processing controller 111.

[0038] FIG. 4 is a flowchart of the image forming process. FIG. 5 is a diagram showing a front image and adjustment pattern formed on the front surface of the medium M. FIG. 6 is a diagram explaining the procedure for identifying intersections of the adjustment pattern. FIG. 7 is a diagram showing a back image formed on the back surface of the medium M. The control unit 110 executes the image forming process shown in FIG. 4 in response to, for example, acquiring an image formation instruction from the print server 210. The image formation instruction includes front image data indicating the front image (first surface image) and back image data indicating the back surface image (second surface image). However, the source of the image formation instruction is not limited to the print server 210.

[0039] First, the image processing controller 111 converts the surface image indicated by the surface image data acquired from the print server 210 and a predetermined adjustment pattern into a format that can be used by the writing unit 101 to form an image, and causes the writing unit 101 to form the image on the surface of the medium M (S41). That is, the writing unit 101 causes the ejection heads 40C, 40M, 40Y, 40B, 40LC, and 40LM to eject ink at predetermined timing onto the surface of the medium M that has been transported by the transport unit 20 to a position facing the image forming unit 40.

[0040] FIG. 5(A) shows the ideal positions of the front image "A" and adjustment patterns X1 to X4 formed on the surface of the medium M. The front image "A" is formed on the surface of the medium M at a position instructed by the print server 210. The adjustment patterns X1 to X4 are formed at predetermined positions on the outer edge of the surface of the medium M. Furthermore, the adjustment patterns X1 to X4 are formed outside the area on the surface of the medium M where the front image "A" can be formed (i.e., in the margins). The adjustment patterns X1 to X4 according to this embodiment are formed at each of the four corners of the surface of the medium M.

[0041] Next, the transport unit 20 transports the medium M, which has the front image "A" and the adjustment patterns X1 to X4 formed on its surface, in the main scanning direction along the main transport path R1, enters the reverse transport path R2 at branch point B, and transports the medium M in the main scanning direction along the reverse transport path R2. In addition, the drying unit 50 dries ink adhering to the medium M being transported on the main transport path R1 by the transport unit 20.

[0042] 5(B) shows the medium M after it has been dried in the drying unit 50. As shown in FIG. 5(B), the medium M after drying (solid line) has shrunk and become smaller in size than the medium M before drying (dashed line). As a result, the surface image "A" and adjustment patterns X1 to X4 on the medium M after drying are shifted in position on the medium M and change in size (shrinkage) compared to the ideal positions shown in FIG. 5(A).

[0043] Next, the reading control unit 112 causes the reading unit 60 to read the adjustment patterns X1 to X4 formed on the surface of the dried medium M (S42). As shown in FIG. 5(B), the extension length in the main scanning direction of the reading unit 60, which is a line sensor, is set to be longer than the maximum length in the main scanning direction of the medium M. Therefore, the reading unit 60 reads the adjustment patterns X1 to X4 from the medium M while it is being transported by the transport unit 20 (i.e., not stopped).

[0044] As shown in FIG. 6A, the adjustment pattern X1 according to this embodiment is composed of a first line segment L1 and a second line segment L2. The first line segment L1 and the second line segment L2 are inclined with respect to the transport direction. The first line segment L1 and the second line segment L2 extend linearly in different directions. More specifically, the first line segment L1 and the second line segment L2 are inclined in opposite directions with respect to the transport direction. The downstream ends of the first line segment L1 and the second line segment L2 intersect with each other in the transport direction. That is, the intersection point P1 of the adjustment pattern X1 formed in the front left corner of the medium M faces outside the medium M.

[0045] The adjustment patterns X2 to X4 have the same shape as the adjustment pattern X1. Furthermore, the adjustment patterns X1 and X2 are arranged at positions spaced apart in the main scanning direction on the medium M, at the same position in the transport direction and facing the same direction. On the other hand, the adjustment patterns X3 and X4 formed at the rear left corner and rear right corner of the medium M have a shape that is the inverse of the adjustment patterns X1 and X2 in the transport direction. Furthermore, the adjustment patterns X3 and X4 are arranged upstream of the adjustment patterns X1 and X2 in the transport direction. Furthermore, the adjustment patterns X3 and X4 are arranged at positions spaced apart in the main scanning direction on the medium M, at the same position in the transport direction and facing the same direction.

[0046] The reading control unit 112 causes the reading unit 60 to read the surface of the medium M at a first position (MSCAN1) and a second position (MSCAN2) on the medium M. This generates two pieces of read data representing an image of one line extending in the main scanning direction. The first and second positions are both positions where the adjustment patterns X1 and X2 are formed. The first and second positions are also positions spaced apart in the transport direction. That is, the image represented by the read data includes different locations of the first line segment L1 and the second line segment L2 of each of the adjustment patterns X1 and X2. The reading control unit 112 then transmits the two pieces of read data generated by the reading unit 60 to the correction value calculation unit 113. Similarly, the reading control unit 112 causes the reading unit 60 to read the surface of the medium M at two locations where the adjustment patterns X3 and X4 are formed.

[0047] A medium detection sensor may be provided on the reverse conveying path R2. The medium detection sensor detects that the medium M has passed a predetermined position upstream of the reading unit 60 in the conveying direction. The reading control unit 112 determines that a first position of the medium M faces the reading unit 60 when a predetermined time has elapsed since the medium detection sensor detected the leading edge of the medium M, and causes the reading unit 60 to execute reading. The reading control unit 112 also determines that a second position of the medium M faces the reading unit 60 when a predetermined time has elapsed since the reading unit 60 faced the first position, and causes the reading unit 60 to execute reading. As another example, the reading unit 60 may control the reading timing based on a pulse signal output from a rotary encoder of a motor that drives the conveying roller pair 21, instead of the elapsed time.

[0048] Next, the correction value calculation unit 113 calculates a correction value based on the read data acquired in step S42 (S43). First, the correction value calculation unit 113 identifies the positions of the first line segment L1 and the second line segment L2 on the medium M based on the read data acquired at the first position and the second position, respectively. The correction value calculation unit 113 also identifies the slope of the first line segment L1 and the second line segment L2 connecting the two identified positions. Furthermore, the correction value calculation unit 113 identifies the actual position of the intersection P1 of the first line segment L1 and the second line segment L2 on the medium M based on the identified positions and slope of the first line segment L1 and the second line segment L2. Similarly, the correction value calculation unit 113 identifies the actual positions of the intersections P2 to P4 of the adjustment patterns X2 to X4, respectively, on the medium M. These processes are already well known, so detailed explanations will be omitted.

[0049] Next, the correction value calculation unit 113 calculates correction values ​​for correcting the back-side image based on the ideal positions of the intersection points P1 to P4 of the adjustment patterns X1 to X4 shown in Fig. 5(A) and the actual positions of the intersection points P1 to P4 of the adjustment patterns X1 to X4 shown in Fig. 5(B). Specific examples of the correction values ​​are not particularly limited, but the following correction values ​​M1 and M2 are possible, for example.

[0050] The correction value calculation unit 113 calculates a correction value M1 (%) in the conveying direction, which is the ratio of the actual distance between the intersection points P1 and P3 shown in Figure 5(B) to the ideal distance H1 between the intersection points P1 and P3 shown in Figure 5(A).The correction value calculation unit 113 also calculates a correction value M2 (%) in the main scanning direction, which is the ratio of the actual distance between the intersection points P1 and P2 shown in Figure 5(B) to the ideal distance W1 between the intersection points P1 and P2 shown in Figure 5(A).The correction value calculation unit 113 then transmits the calculated correction values ​​M1 and M2 to the image correction unit 114.

[0051] Next, the image correcting unit 114 corrects the back side image indicated by the back side image data acquired from the print server 210 based on the correction values ​​M1 and M2 calculated in step S43 (S44). The image correcting unit 114 reduces the size H2 and W2 of the back side image before correction shown in FIG. 7A by the correction value M1 (%) in the transport direction and by the correction value M2 (%) in the main scanning direction. The image correcting unit 114 also moves the position of the back side image before correction on the medium M downstream in the transport direction by the correction value M1 (%) and toward the adjustment patterns X1 and X3 in the main scanning direction (to the left in the example of FIG. 7A) by the correction value M2 (%). Then, the image correcting unit 114 transmits back side image data indicating the corrected back side image to the image processing controller 111.

[0052] Next, the image processing controller 111 converts the back surface image corrected in step S44 into a format that can be used by the writing unit 101 to form an image, and causes the writing unit 101 to form the image on the back surface of the medium M (S45). That is, the writing unit 101 causes the ejection heads 40C, 40M, 40Y, 40B, 40LC, and 40LM to eject ink at a predetermined timing onto the back surface of the medium M that has been transported by the transport unit 20 to a position facing the image forming unit 40.

[0053] According to the above embodiment, for example, the following advantageous effects are achieved.

[0054] According to the above embodiment, by configuring the adjustment patterns X1 to X4 with the first line segment L1 and the second line segment L2 inclined with respect to the conveyance direction, the adjustment patterns X1 to X4 can be properly read even while the medium M is being conveyed, without relying on the reading resolution of the reading unit 60. This allows the misalignment between the front and back images to be properly corrected even if the conveyance speed of the medium M is increased. As a result, it is possible to achieve both high throughput and high image formation quality for the image forming apparatus 1. Furthermore, since there is no need to install a reading unit 60 with high reading resolution, this also contributes to reducing the cost of the image forming apparatus 1.

[0055] The specific shape of the adjustment pattern is not limited to the example shown in FIG. 6A. As an example, the adjustment pattern Y1 shown in FIG. 6B may have a triangular shape with the space between the first line segment L1 and the second line segment L2 filled in. As another example, the first line segment L1 and the second line segment L2 may be inclined in opposite directions relative to the main scanning direction, as shown in adjustment pattern Z1 shown in FIG. 6C. For adjustment pattern Z1 in FIG. 6C, the reading control unit 112 may read the first line segment L1 at a first position (MSCAN1) and a second position (MSCAN2) spaced apart in the conveying direction, and read the second line segment L2 at a third position (MSCAN3) and a fourth position (MSCAN4) spaced apart in the conveying direction. As another example, the first line segment L1 and the second line segment L2 may not intersect. In this case, the correction value calculation unit 113 may simply identify the intersection of the extensions of the first line segment L1 and the second line segment L2.

[0056] The control method described above may be realized, for example, by a program. That is, the control method is a method executed by a computer by causing an arithmetic unit, a storage unit, an input unit, an output unit, and a control unit to cooperate with each other based on the program. The program may be written to a storage unit or a storage medium and distributed, or distributed via a telecommunications line, etc.

[0057] The present invention is not limited to the above-described exemplary embodiments, and various modifications are possible without departing from the technical gist thereof. The present invention covers all technical matters included in the technical concept described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims. [Explanation of symbols]

[0058] 1: Image forming device 10: Paper feed tray 20: Transport unit 21: Pair of conveying rollers 22: Drum type conveying unit 23: Conveyor belt 24: Drums 25: Inlet rotor 26: Exit rotor 30: First coating section 31: Drums 40: Image forming unit 40B, 40C, 40LC, 40LM, 40M, 40Y: Discharge head 50:Drying section 60: Reading unit 70: Paper output tray 101: Write unit 110: Control unit 111: Image processing controller 112: Reading control unit 113: Correction value calculation unit 114: Image correction unit 120: Internal bus 121:CPU 122:ROM 123:RAM 124: External memory I / F 125: Communication I / F 126: Internal bus I / F 128: DMAC for image output 129: Image processing unit 130:Extender 131: Operation panel 133: Image memory 134: PCIe bus 210: Print Server [Prior art documents] [Patent documents]

[0059] [Patent Document 1] Patent Publication No. 2021-149094

Claims

1. a transport unit that transports the medium in a transport direction; an image forming unit that forms an adjustment pattern on a first surface of the medium transported by the transport unit; a reading unit that is disposed downstream of the image forming unit in the transport direction and that reads the adjustment pattern formed on the first surface of the medium being transported by the transport unit and generates read data; a control unit that analyzes the read data generated by the reading unit and calculates a correction value for correcting a second-side image to be formed on a second side of the medium opposite to the first side, the adjustment pattern includes a first line segment and a second line segment extending in different directions from each other, the first line segment and the second line segment are each inclined with respect to the transport direction, The control unit identifying an intersection between the first line segment and the second line segment based on values ​​obtained by reading the first line segment and the second line segment at a first position and a second position of the medium spaced apart in the transport direction, an image forming apparatus that calculates the correction values ​​in the transport direction and in a main scanning direction perpendicular to the transport direction using a position of an intersection of the first line segment and the second line segment;

2. 2. The image forming apparatus according to claim 1, wherein the first line segment and the second line segment are inclined in opposite directions with respect to the conveying direction.

3. 2. The image forming apparatus according to claim 1, wherein the first line segment and the second line segment are inclined in opposite directions with respect to a main scanning direction perpendicular to the transport direction.

4. 4. The image forming apparatus according to claim 1, wherein the adjustment pattern has a region between the first line segment and the second line segment filled in.

5. the reading unit is a line sensor in which a plurality of reading elements are arranged in a main scanning direction perpendicular to the transport direction, The control unit causing the reading unit to read the adjustment pattern at a plurality of positions spaced apart in the transport direction on the medium; 5. The image forming apparatus according to claim 1, wherein the actual position of the intersection of the first line segment and the second line segment is identified based on the plurality of pieces of read data generated by the reading unit.

6. the control unit corrects the second plane image based on an ideal position and the actual position of an intersection of the first line segment and the second line segment; The image forming unit includes: forming a first-surface image and the adjustment pattern on the first surface of the medium; The image forming apparatus according to claim 5 , wherein the second-side image corrected by the control unit is formed on the second side of the medium.

Images