Image forming system and image reading device

Abstract

It controls the orientation of the sheet as it is transported to the reading position. [Solution] The image forming system forms an image on a sheet using a print module 2000, a drying module 3000, a fixing module 4000, and a cooling module 5000. The image forming system includes a first inversion unit 4200 that inverts the front and back sides of the sheet in order to form an image on the back side of the surface on which the image has been formed, a double-sided transport path (3900) for transporting the sheet whose front and back sides have been inverted by the first inversion unit 4200 to the print module 2000, a second registration unit 3500 that corrects the orientation of the sheet transported in the double-sided transport path (3900), and a colorimetric unit 3600 that reads the image on the sheet whose orientation has been corrected by the second registration unit 3500 in the double-sided transport path (3900).

Description

Technical Field

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[0001] The present invention relates to an image reading device that reads an image formed on a sheet and an image forming system including such an image reading device.

Background Art

[0002] An image forming apparatus has a configuration for performing image adjustment (for example, density adjustment, color tone adjustment). Such an image forming apparatus incorporates, for example, an image reading sensor (for example, a color sensor) as an image reading device. The image forming apparatus reads an image for image adjustment (hereinafter referred to as "adjustment image") formed on a sheet by the image reading sensor and executes image adjustment based on the reading result (Patent Document 1).

[0003] Patent Document 2 discloses an image forming apparatus in which an image reading sensor is provided in a duplex conveyance unit. In this configuration, the posture of the sheet conveyed toward the transfer unit (secondary transfer unit) where the image is transferred onto the sheet is corrected, and the image is transferred to a predetermined position on the sheet. When image adjustment is executed, the posture of the sheet before the adjustment image is transferred is corrected so that the reading position of the image reading sensor passes through the adjustment image.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an adjustment image printed on a sheet is read by an image reading sensor, the adjustment image needs to be accurately transported to the reading position of the image reading sensor. In Patent Document 2, an adjustment image can be formed at a predetermined position on the sheet, but the orientation of the sheet may change between the transfer unit (secondary transfer unit) and the reading position of the image reading sensor. In this case, the adjustment image may not be accurately transported to the reading position of the image reading sensor, and the adjustment image on the sheet may not be read. In particular, the longer the distance the sheet travels as it is transported to the double-sided transport unit, the more the orientation of the sheet changes. Therefore, in the configuration described in Patent Document 2, the adjustment image may not be accurately transported to the reading position of the image reading sensor, and the adjustment image may not be read.

[0006] In view of the above-mentioned problems, the present invention primarily aims to control the orientation of a sheet being transported to a reading position. [Means for solving the problem]

[0007] The image forming system of the present invention is characterized by comprising: an image forming means for forming an image on a sheet; an inversion means for inverting the front and back sides of the sheet in order to form an image on the back surface of the sheet on which the image has been formed by the image forming means; a double-sided transport path for transporting the sheet, whose front and back sides have been inverted by the inversion means, to the image forming means; a registration means for correcting the orientation of the sheet transported in the double-sided transport path; and a reading means for reading the image on the sheet whose orientation has been corrected by the registration means in the double-sided transport path. The present invention relates to an image reading device provided in an image forming system capable of forming images on both sides of a sheet, the system comprising: an image forming means for forming an image on a sheet; an inversion means for inverting the front and back sides of the sheet in order to form an image on the back surface of the sheet on which the image has been formed by the image forming means; and a double-sided transport path for transporting the sheet, whose front and back sides have been inverted by the inversion means, to the image forming means, the image reading device further comprising: a registration means for correcting the orientation of the sheet transported in the double-sided transport path; and a reading means for reading the image on the sheet whose orientation has been corrected by the registration means in the double-sided transport path. [Effects of the Invention]

[0008] According to the present invention, accurate reading of the adjustment image becomes possible. [Brief explanation of the drawing]

[0009] [Figure 1] Configuration diagram of an inkjet recording device. [Figure 2] Configuration diagram of the fixing module and drying module. [Figure 3] Configuration diagram of the second registration unit. [Figure 4] Cross-sectional view of the colorimeter unit. [Figure 5] A view of the colorimeter unit from the sponge roller side. [Figure 6] An example diagram of a test chart. [Figure 7] A diagram illustrating the seating position. [Figure 8] Diagram explaining the reading position. [Figure 9] Diagram explaining the reading position. [Figure 10] Diagram explaining the reading position. [Figure 11] Configuration diagram of an inkjet recording device. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described below with reference to the attached drawings.

[0011] Figure 1 is a diagram of the configuration of an inkjet recording device, which is an image forming system according to this embodiment. The inkjet recording device 100 of this embodiment produces a finished product by forming an ink image on a sheet using two liquids, a reaction solution and ink. The inkjet recording device 100 includes a paper feeding module 1000, a print module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, an inversion module 6000, a paper discharge and stacking module 7000, and a control device 8000. Cut sheets on which images are printed are supplied from the paper feeding module 1000 and transported along a transport path, where predetermined processing related to image formation is performed in each module, and then discharged from the paper discharge and stacking module 7000.

[0012] The paper feed module 1000 is equipped with multiple (three in this embodiment) storage compartments 1100a to 1100c. Each storage compartment 1100a to 1100c is capable of storing a sheet. Each storage compartment 1100a to 1100c is designed to be pull out towards the front of the device, and a sheet is stored inside when it is pulled out towards the front of the device. The paper feed module 1000 feeds the sheets to the print module 2000 one by one. For this purpose, each storage compartment 1100a to 1100c is provided with a separation belt and a transport roller. The number of storage compartments 1100a to 1100c is just an example, and there may be one, two, or four or more levels.

[0013] The print module 2000 functions as an image forming apparatus that forms an image on a sheet fed from the paper feed module 1000. The print module 2000 comprises a first registration unit 2100, a print belt unit 2200, and a recording unit 2300. The first registration unit 2100 corrects the orientation of the sheet supplied from the paper feed module 1000, such as its tilt and position, and transports it to the print belt unit 2200.

[0014] The print belt unit 2200 and the recording unit 2300 are arranged to face each other across the sheet conveyance path on the downstream side of the first registration unit 2100 in the sheet conveyance direction. The print belt unit 2200 adsorbs and conveys the sheet conveyed from the first registration unit 2100. The recording unit 2300 is a sheet processing unit that forms an image by performing a recording process (printing) on the sheet conveyed by the print belt unit 2200 with a recording head from above. The recording head performs printing by discharging ink onto the sheet. The sheet is adsorbed and conveyed by the print belt unit 2200, so that the clearance with the recording head is kept constant.

[0015] A plurality of recording heads are arranged along the sheet conveyance direction. The recording heads of the present embodiment are five line-type recording heads corresponding to the reaction liquid in addition to the four colors of Y (yellow), M (magenta), C (cyan), and K (black). Note that the number of colors and the number of recording heads are not limited to five. For the inkjet method, a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS element, or the like can be adopted. The ink of each color is supplied from an ink tank (not shown) to the recording head through an ink tube.

[0016] The sheet printed by the recording unit 2300 is conveyed by the print belt unit 2200. An in-line scanner (not shown) is arranged on the downstream side in the sheet conveyance direction with respect to the recording unit 2300. The in-line scanner is used to detect the deviation and color density of the image formed on the sheet and correct the printed image.

[0017] The drying module 3000 dries the sheet on which the image is printed by the printing module 2000. The drying module 3000 reduces the liquid component contained in the ink by drying the sheet, and improves the fixing property between the sheet and the ink. The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, and a hot air blowing unit 3400.

[0018] The sheet printed in the recording unit 2300 of the print module 2000 is transported to the decoupling unit 3200 in the drying module 3000. The decoupling unit 3200 loosely holds and transports the sheet using air pressure from above and friction of the belt. This prevents the sheet from shifting while straddling the decoupling unit 3200 and the print belt unit 2200, with the portion remaining on the print belt unit 2200 being prevented from shifting.

[0019] The sheet conveyed from the decoupling unit 3200 is adsorbed and conveyed to the drying belt unit 3300, and at the same time, hot air is blown onto it from the hot air blowing unit 3400 located above the belt to dry the ink-applied surface (the printed surface of the image). In addition to the method of applying hot air, the drying method may also be configured by combining a method of irradiating the sheet surface with electromagnetic waves (such as ultraviolet or infrared rays) or a conductive heat transfer method by contact with a heating element.

[0020] The fixing module 4000 fixes the image to the sheet by heating the sheet dried by the drying module 3000 to dry the ink. The fixing module 4000 includes a fixing belt unit 4100 having an upper belt unit and a lower belt unit. The fixing module 4000 allows the ink solvent to sufficiently penetrate (fix) into the sheet by passing the sheet conveyed from the drying module 3000 between the heated upper belt unit and the lower belt unit.

[0021] The cooling module 5000 cools the sheet on which the image has been fixed by the fixing module 4000, thereby solidifying the ink that has softened due to heating and suppressing temperature changes of the sheet caused by downstream equipment. The cooling module 5000 is equipped with multiple cooling units 5001. The multiple cooling units 5001 cool the high-temperature sheet transported from the fixing module 4000. Each cooling unit 5001 is configured to increase the pressure inside the cooling box by drawing in outside air with a fan, and to cool the sheet by blowing air from nozzles formed in the transport guide onto the sheet. The multiple cooling units 5001 are arranged on both sides of the transport path, so that the sheet can be cooled from both sides.

[0022] A transport path switching unit is provided within the cooling module 5000. The transport path switching unit switches the transport path of the sheet depending on whether the sheet is being transported to the inversion module 6000 or to the double-sided transport path used during double-sided printing.

[0023] During double-sided printing, the sheet is transported to a transport path below the cooling module 5000 and then transported along the double-sided transport path of the fuser module 4000, drying module 3000, print module 2000, and paper feed module 1000. The double-sided transport section of the fuser module 4000 is provided with a first reversal section 4200 that reverses the printed side of the sheet. The sheet, on which images are formed on both sides, is first transported to the first reversal section 4200, then reversed and transported to the drying module 3000, thereby reversing the printed side of the image from the first side to the second side opposite the first side. By passing through the first reversal section 4200, the front and back sides of the sheet are reversed, making it possible to print on the back side of the sheet. After that, the sheet is transported again to the first registration unit 2100, print belt unit 2200, and recording unit 2300 of the print module 2000 for printing. Furthermore, a second registration unit is provided in the double-sided transport path of the drying module 3000 between the first reversal unit 4200 and the first registration unit 2100. Details of the second registration unit will be described later.

[0024] The reversing module 6000 includes a second reversing unit 6400. The reversing module 6000 can reverse the front and back sides of the conveyed sheets using the second reversing unit 6400. This allows the orientation of the front and back sides of the discharged sheets to be changed. The discharge and stacking module 7000 includes a top tray 7200 and a stacking unit 7500. The discharge and stacking module 7000 aligns and stacks the sheets conveyed from the reversing module 6000 onto the top tray 7200 or the stacking unit 7500.

[0025] The control device 8000 controls the operation of each module of the inkjet recording device 100. The control device 8000 is an information processing device that incorporates a CPU (Central Processing Unit), etc. The control device 8000 controls the operation of the inkjet recording device 100 and forms an image on the sheet in response to instructions obtained, for example, from an external device connected via a network (not shown) or from a user interface (not shown). The control device 8000 may be configured to directly control the operation of each module, or it may be configured to control the operation of each module by sending instructions to a controller (not shown) provided in each module.

[0026] (Double-sided transport route) Figure 2 is a configuration diagram of the fixing module 4000 and the drying module 3000. As described above, the fixing module 4000 has a first reversal unit 4200 in its double-sided transport path. The drying module 3000 has a second registration unit 3500 and a colorimetric unit 3600, which is an example of an image reading sensor, in its double-sided transport path 3900. The second registration unit 3500 is located downstream of the first reversal unit 4200 in the sheet transport direction and upstream of the colorimetric unit 3600.

[0027] The sheets transported to the second registration unit 3500 are printed on by the print module 2000 and then transported through the housings of multiple modules. Specifically, the sheets are transported through the drying module 3000, the fixing module 4000, and the cooling module 5000. In the case of double-sided printing, the sheets are further transported from the transport path below the cooling module 5000 to the double-sided transport paths 4300 and 3900 of the fixing module 4000 and the drying module 3000. In addition, the printing surface is reversed in the fixing module 4000 by passing through the first reversal unit 4200 located in the double-sided transport path 4300.

[0028] The sheets are transported by numerous transport rollers inside the housings of these multiple modules. Due to misalignment of the rotation axis of the numerous transport rollers, the orientation of the sheets relative to the transport direction of the sheets will be affected. This misalignment of the sheet orientation includes deviations in the angle of the sheet relative to the transport direction (skew) and deviations in the position of the sheet itself in a direction intersecting the transport direction (hereinafter referred to as the "width direction") (lateral registration deviation). The misalignment of the sheet orientation increases with the length of the path and the number of transport rollers until the sheet is transported to the colorimetric unit 3600. Therefore, it is necessary to correct for such misalignments of the sheet orientation relative to the transport direction before the sheet is read by the colorimetric unit 3600.

[0029] The second registration unit 3500 corrects the orientation of the sheet, such as skew or lateral registration misalignment, as it is transported from the fixing module 4000 along the double-sided transport path 3900. The colorimetric unit 3600 is an image reading device that reads the adjustment image formed on the sheet being transported along the double-sided transport path 3900. The reading result of the adjustment image is used for image adjustment. Here, image adjustment is, for example, a control that adjusts the color tone of the image to be formed on the sheet.

[0030] The colorimetric unit 3600 is installed adjacent to the second registration unit 3500 on the downstream side in the sheet transport direction. By installing the colorimetric unit 3600 immediately after the second registration unit 3500, the sheet enters the reading position of the colorimetric unit 3600 in a constant, stable posture after its posture has been corrected by the second registration unit 3500.

[0031] Figure 3 is a diagram of the configuration of the second registration unit 3500. Figure 3 illustrates the seat attitude correction operation performed by the second registration unit 3500.

[0032] The second registration unit 3500 has a skew correction unit 3510. The skew correction unit 3510 has a registration roller 3511, a registration roller 3512, a registration drive motor 3513, and a registration drive motor 3514. The registration roller 3511 is driven by the registration drive motor 3513. The registration roller 3512 is driven by the registration drive motor 3514. Since the registration rollers 3511 and 3512 are driven independently by different drive sources, their rotational speeds can be changed individually. By individually controlling the rotational speeds of the registration rollers 3511 and 3512, the skew of the sheet can be corrected. The skew correction unit 3510 adjusts the inclination of the sheet to an ideal angle. Here, the ideal angle is the angle at which the leading edge of the sheet is perpendicular to the conveying direction of the sheet.

[0033] The second registration unit 3500 has a lateral registration misalignment correction unit 3520 and a drive motor 3515 below the skew correction unit 3510. The lateral registration misalignment correction unit 3520 can move the entire second registration unit 3500 in the width direction by the driving force supplied by the drive motor 3515. By moving the entire second registration unit 3500 in the width direction, the lateral registration misalignment can be corrected. The lateral registration misalignment correction unit 3520 controls the position of the sheet in the width direction to the reference position.

[0034] The register roller 3511 forms a nip section with roller 3516, which is located opposite each other across the double-sided transport path 3900. The register roller 3512 forms a nip section with roller 3517, which is located opposite each other across the double-sided transport path 3900. Near these nip sections, upstream in the sheet transport direction, a plurality of register sensors 3518, as shown in Figure 2, are provided at the same position in the transport direction but at different positions in the width direction. The register sensors 3518 are sheet detection sensors that detect the sheet being transported. The control device 8000 calculates the current sheet skew (inclination of the leading edge of the sheet) based on the timing at which each of the plurality of register sensors 3518 detects the sheet and the sheet transport speed. Note that the sensor used to detect the sheet skew is not limited to a plurality of register sensors 3518; for example, a line sensor that reads the leading edge of the sheet may also be used.

[0035] An image sensor 3519, as shown in Figure 2, is provided near the register roller 3511 and register roller 3512. The image sensor 3519 is a sheet reading sensor that reads the sheet being transported to the nip section. The control device 8000 detects the edge position of the sheet in the width direction based on the sheet reading result from the image sensor 3519. Based on the detected edge position, the control device 8000 calculates the lateral register displacement of the sheet. The lateral register displacement is the amount of displacement of the sheet from the reference position in the direction intersecting the sheet transport.

[0036] The control device 8000 drives and controls the register drive motors 3513, 3514 and drive motor 3515 based on the amount of sheet skew and lateral register misalignment detected using the register sensor 3518 and the image sensor 3519. This corrects the sheet's skew and lateral register misalignment. When the tilt of the leading edge of the sheet is controlled to an ideal angle and the sheet's position in the width direction is controlled to a reference position, the adjustment image formed on the sheet after passing through the second registration unit 3500 can pass through the reading position of the color sensor 61.

[0037] In Figure 2, the image sensor 3519 is located upstream of the register sensor 3518 in the sheet transport direction. However, the image sensor 3519 may also be located downstream of the register sensor 3518 in the sheet transport direction. Furthermore, the amount of sheet skew can be detected by detecting the edge position of the leading edge of the sheet in the transport direction based on the sheet reading result from the image sensor 3519. For this reason, the amount of sheet skew and lateral register misalignment may be detected using only the image sensor 3519, without using the register sensor 3518.

[0038] (Colorimeter unit) Image adjustment (color adjustment) of an image performed using the colorimetric unit 3600 will be described. Figure 4 is a cross-sectional view of the colorimetric unit 3600. The double-sided transport path 3900 has two transport guides 53, and the sheet S is transported between the two transport guides 53. The colorimetric unit 3600 is equipped with a first transport roller pair 55, a color sensor 61, a sponge roller 62, and a second transport roller pair 56 along the transport guides 53. The first transport roller pair 55 is provided upstream of the second transport roller pair 56 in the transport direction of the sheet S. The color sensor 61 and the sponge roller 62 are positioned opposite each other with the transport guides 53 in between. The color sensor 61 and the sponge roller 62 are provided between the first transport roller pair 55 and the second transport roller pair 56.

[0039] The transport guide 53 is provided with a through-hole 54 as a detection window at the reading position of the color sensor 61. When the color sensor 61 reads the sheet S, the sheet S is held between both the first transport roller pair 55 and the second transport roller pair 56. By being held between the first transport roller pair 55 and the second transport roller pair 56, the sheet S is stretched to a predetermined tension and its posture is stabilized. The sponge roller 62 presses the sheet S toward the through-hole 54. The sponge roller 62 pressing the sheet S toward the through-hole 54 keeps the distance between the color sensor 61 and the sheet S constant. As a result, the color sensor 61 can read the image formed on the sheet S with high accuracy.

[0040] Figure 5 shows the colorimetric unit 3600 as viewed from the sponge roller 62 side. The color sensor 61 is configured with multiple detection units 65a, 65b, 65c, and 65d arranged linearly in the width direction intersecting the conveying direction of the sheet S. In this embodiment, there are four detection units.

[0041] Figure 6 is an example of a test chart with adjustment images printed on sheet S. The test chart T includes four rows of patch images 70a, 70b, 70c, and 70d as adjustment images. Each of the patch image rows 70a, 70b, 70c, and 70d consists of multiple patch images of different colors (19 colors in this embodiment) placed adjacent to each other.

[0042] Each of the patch image sequences 70a, 70b, 70c, and 70d corresponds to one detection unit. In the example in Figure 6, patch image sequence 70a corresponds to detection unit 65a. Patch image sequence 70b corresponds to detection unit 65b. Patch image sequence 70c corresponds to detection unit 65c. Patch image sequence 70d corresponds to detection unit 65d. Patch image sequences 70a, 70b, 70c, and 70d are read by their corresponding detection units 65a, 65b, 65c, and 65d. For this purpose, patch image sequences 70a, 70b, 70c, and 70d are printed on the test chart T so that they pass through the reading positions of their corresponding detection units 65a, 65b, 65c, and 65d.

[0043] In this embodiment, four rows of patch image sequences 70a, 70b, 70c, and 70d are printed for each of the four detection units 65a, 65b, 65c, and 65d. However, the number of patch image sequences is determined according to the number of detection units. In other words, as long as the number of detection units and patch image sequences are the same, the number of detection units and patch image sequences is not limited to four.

[0044] The control device 8000 pre-stores values ​​indicating the original color of each patch image sequence 70a, 70b, 70c, and 70d printed on the test chart T. The control device 8000 compares these pre-stored values ​​with the reading results of each patch image sequence 70a, 70b, 70c, and 70d by each detection unit 65a, 65b, 65c, and 65d, and obtains color correction values ​​based on the comparison results. The control device 8000 generates image formation conditions using the aforementioned correction values. By controlling the print module 2000 based on the aforementioned image formation conditions, the control device 8000 can control the color of the image to be formed after image adjustment to an ideal color. Note that image adjustment is not limited to color adjustment; it may also be a control that generates image formation conditions to adjust the density of the image to be formed.

[0045] When reading the adjustment image using the color sensor 61, the process is distinguished from the operation performed according to a normal print job, and for example, a patch image is printed on a predetermined size sheet S, such as A3. The number of patch images required is 1617 colors, in accordance with the Japan Color standards ("International standards for digital proofing: ISO 12647-7" and "ISO 12642-2 (1617 color chart)"). In this embodiment, since 4 rows x 19 colors of patch images are printed on one test chart T, 22 test charts T are required for color measurement.

[0046] The size of the sheet S used for the test chart T is preferably as large as possible. This is because a smaller size requires more test charts T, which reduces productivity. It is also preferable that each patch image row contains as many patch images as possible. The number of patch images in each patch image row is determined according to the reading speed of the color sensor 61 and the transport speed of the test chart T. In this embodiment, one row of patch images contains 19 colored patch images, but the number of patch images per row of patch images can be changed, for example, by changing the transport speed.

[0047] (Reading accuracy) This section explains the effect of the skew correction and lateral registration misalignment correction performed by the second registration unit 3500 on the reading accuracy of the colorimetric unit 3600. Figure 7 is an explanatory diagram of the orientation of the sheet S as it is transported to the second registration unit 3500 via the double-sided transport path 3900.

[0048] In Figure 7, sheet S is A3 size, used for test chart T, and is transported with its longitudinal direction as the transport direction 50. The sheet width 80 is 297 [mm]. In this case, the amount of skew 81 of sheet S is, for example, a maximum of about 21 [mm] with respect to the width direction intersecting the transport direction 50. Also, the amount of lateral registration deviation 82 is, for example, a maximum of ±17 [mm]. The skew and lateral registration deviation of sheet S occur because sheet S is affected during transport, such as being transferred between modules.

[0049] Figure 8 is an explanatory diagram of the reading position when the colorimetric unit 3600 reads the test chart T when no correction is performed by the second registration unit 3500. Figure 8 illustrates the case when the detection unit 65b of the color sensor 61 reads the patch image sequence 70b. The detection unit 65b reads the transported test chart T at the reading position 86. A lateral registration misalignment 87 occurs in the test chart T.

[0050] In this case, the test chart T being transported in the transport direction 50 has patch image sequences 70b in which some patch images are read by the detection unit 65b and others are not. Similarly, the other patch image sequences 70a, 70c, and 70d also have patch images that are read and others that are not. Because the lateral registration misalignment amount 87 is wider than the width of the patch image sequence 70b, the lateral registration misalignment occurs, resulting in reading errors over a wider area.

[0051] To read all patch images from a test chart T that is being transported with skew and lateral misalignment, the width of each patch image needs to be increased. Figure 9 is an explanatory diagram of the reading position when reading a test chart T with such patch images formed. The size of the test chart T and the lateral misalignment 87 are the same as in Figure 8.

[0052] The width 88 of the patch image 85 is determined based on the amount of skew and lateral registration deviation 8, and the reading range by the detection unit. For example, the width 88 of the patch image 85 needs to be at least 80 mm. Furthermore, when forming the patch image rows considering the positional deviation of the patch image formation and the installation position tolerance of the colorimetric unit 3600, a maximum of 3 rows of patch images can be formed on the test chart U.

[0053] If test chart U is transported without correction for skew and lateral registration misalignment, the number of patch images read by the colorimeter unit 3600 from one test chart U will be less than that from test chart T. As described above, reading 1617 color patch images requires approximately 29 test chart Us, resulting in reduced productivity.

[0054] For the reasons described above, in this embodiment, the second registration unit 3500 is positioned upstream of the colorimetric unit 3600 in the sheet transport direction to correct the skew and lateral registration misalignment of the test chart being transported to the colorimetric unit 3600. By correcting the skew and lateral registration misalignment, the test chart is transported to the reading position of the colorimetric unit 3600 in a stable position. Figure 10 is an explanatory diagram of the reading position when reading the test chart T after correcting the skew and lateral registration misalignment.

[0055] Each detection unit 65a, 65b, 65c, and 65d of the colorimetric unit 3600 (color sensor 61) reads each patch image sequence 70a, 70b, 70c, and 70d at reading positions 86a, 86b, 86c, and 86d. As the skew and lateral registration misalignment of the test chart T are corrected, each patch image contained in each patch image sequence 70a, 70b, 70c, and 70d is aligned linearly in the sheet transport direction 50. Therefore, each patch image contained in each patch image sequence 70a, 70b, 70c, and 70d passes through the reading positions 86a, 86b, 86c, and 86d of each detection unit 65a, 65b, 65c, and 65d. As a result, the colorimetric unit 3600 can ensure that all patch images (adjustment images) formed on the test chart T pass through their corresponding reading positions, enabling accurate reading of all patch images (adjustment images) formed on the test chart T.

[0056] The control device 8000 acquires the reading result of the adjustment image formed on the test chart T from the colorimeter unit 3600. Based on the acquired reading result of the adjustment image, the control device 8000 performs image adjustment and generates image formation conditions for the next image formation. In order to acquire accurate reading results of the adjustment image from the colorimeter unit 3600, the control device 8000 can adjust the image quality of the image formed by the image formation system with high precision.

[0057] Although the above explanation used an adjustment image for correcting color tones as an example, the adjustment image can be any image used for image adjustment. For example, the adjustment image may be an image used to correct gradation or image density. Furthermore, this embodiment is also effective for adjustment images used to correct geometric characteristics of an image, such as position or tilt.

[0058] Although the above describes a configuration in which the second registration unit 3500 and the colorimetric unit 3600 are provided in the double-sided transport path 3900, the arrangement of the second registration unit 3500 and the colorimetric unit 3600 is not limited to this. The second registration unit 3500 and the colorimetric unit 3600 may be provided after the image has been fixed to the sheet and before it is discharged or loaded from the paper discharge / loading module 7000.

[0059] For example, an image reading device having a second registration unit 3500 and a colorimetric unit 3600 may be provided between the cooling module 5000 and the inversion module 6000. Figure 11 is a diagram of the inkjet recording device 200 in this case. In this case, the test chart T is transported from the cooling module 5000 to the image reading device 9000. The image reading device 9000 stabilizes the orientation of the test chart T with the second registration unit 3500 and reads the adjustment image with the colorimetric unit 3600.

[0060] In this embodiment, an inkjet recording device 100 was described as the image forming system, but the image forming system may be configured to form images using other methods such as an electrophotographic method, not limited to the inkjet method. In any case, it is sufficient to have a registration unit that corrects the orientation of the sheet during transport, such as sheet skew and lateral registration misalignment, located upstream in the sheet transport direction from the image reading sensor that reads the adjustment image from the sheet on which the adjustment image has been formed.

Claims

1. Image forming means for forming an image on a sheet, In order to form an image on the back surface of the sheet on which the image has been formed by the image forming means, the inversion means is used to invert the front and back surfaces of the sheet, A double-sided transport path for transporting the sheet, whose front and back sides have been reversed by the reversing means, to the image forming means, A registration means for correcting the orientation of the sheet transported along the double-sided transport path, The system is characterized by comprising: a reading means for reading the image on the sheet whose orientation has been corrected by the registration means in the double-sided transport path; Image forming system.

2. A drying means for drying the sheet on which the image has been formed by the image forming means, A fixing means for fixing the image onto the sheet that has been dried by the drying means, The system includes a cooling means for cooling the sheet on which the image has been fixed by the fixing means, The cooling means transports the cooled sheet to the inversion means during double-sided printing. The fixing means includes the reversing means, The drying means is characterized by having the registration means and the reading means. The image forming system according to claim 1.

3. The reading means is characterized in that it is provided adjacent to the downstream side of the registration means in the conveying direction of the sheet. The image forming system according to claim 2.

4. The registration means is characterized in that it is provided downstream of the reversing means in the transport direction. The image forming system according to claim 3.

5. The image forming means forms an adjustment image on the sheet, The reading means is characterized by reading the adjustment image. The image forming system according to claim 1.

6. The reading means has a plurality of detection means arranged linearly in a direction intersecting the conveying direction of the sheet, The image forming means is characterized by forming the adjustment image at a position corresponding to the reading position of each of the plurality of detection means. The image forming system according to claim 5.

7. The invention is characterized by comprising a generation means for generating image formation conditions based on the reading result of the adjustment image by the reading means, The image forming system according to claim 5 or 6.

8. The registration means is characterized by comprising: a first correction means for correcting the skewness of the sheet; and a second correction means for correcting the positional displacement of the sheet in a direction intersecting the conveying direction of the sheet. The image forming system according to claim 1.

9. The registration means includes a plurality of sheet detection means arranged at different positions in a direction intersecting the sheet transport direction, The first correction means is characterized by correcting the skewness of the sheet based on the timing at which each of the plurality of sheet detection means detects the sheet and the amount of skewness of the sheet calculated from the conveying speed of the sheet. The image forming system according to claim 8.

10. The registration means includes a sheet reading means for reading the sheet, The second correction means is characterized by correcting the sheet's displacement based on the amount of displacement from a reference position of the edge position of the end of the sheet in a direction intersecting the transport direction, which is detected from the sheet reading result of the sheet reading means. The image forming system according to claim 8 or 9.

11. The registration means includes a sheet reading means for reading the sheet, The first correction means corrects the skew of the sheet based on the amount of skew of the sheet obtained from the edge position of the leading edge portion of the sheet in the transport direction, which is detected from the reading result of the sheet by the sheet reading means. The second correction means is characterized by correcting the sheet's displacement based on the amount of displacement from a reference position of the edge position of the end of the sheet in a direction intersecting the transport direction, which is detected from the sheet reading result of the sheet reading means. The image forming system according to claim 8.

12. An image reading device provided in an image forming system capable of forming images on both sides of a sheet, comprising: an image forming means for forming an image on a sheet; an inversion means for inverting the front and back sides of the sheet in order to form an image on the back side of the surface of the sheet on which the image has been formed by the image forming means; and a double-sided transport path for transporting the sheet, whose front and back sides have been inverted by the inversion means, to the image forming means, wherein an image reading device is provided in an image forming system capable of forming images on both sides of a sheet, A registration means for correcting the orientation of the sheet transported along the double-sided transport path, The double-sided transport path is characterized by comprising: a reading means for reading the image on the sheet whose orientation has been corrected by the registration means; Image reading device.

Images