Image inspection apparatus, printing apparatus, and image inspection method

Abstract

To accurately inspect images recorded on both sides of a printing medium by two optical inspection means while suppressing an increase in footprint of a device.SOLUTION: In the image inspection apparatus and the printing apparatus according to the invention, the printing medium is transported by being wound around the first to fourth transport rollers, and the first inspection unit and the second inspection unit optically inspect the first region wound around the first transport roller and the second region wound around the second transport roller, respectively, on one main surface of the printing medium. In addition, in the other main surface of the printing medium, the third region wound around the third transport roller is optically inspected by the third inspection unit, and the fourth region wound around the fourth transport roller is optically inspected by the fourth inspection unit. The print medium conveyed between the first conveyance roller and the second conveyance roller, and the print medium conveyed between the third conveyance roller and the fourth conveyance roller, at least partially overlap in plan view.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image inspection device that inspects images recorded on both sides of a print medium, and a printing device equipped with the same. [Background technology]

[0002] In devices that form images on print media using various printing technologies, such as inkjet printing, the recorded images are optically detected and inspected to maintain good image quality. For example, Patent Document 1 discloses a technique for optically inspecting images recorded on a long web of print media that is stretched over and transported by multiple rollers. In this technique, the image is inspected using two types of optical detection means.

[0003] Specifically, an imaging unit having an imaging element such as a line scanner and a colorimeter that detects the color of the surface of the print medium are arranged opposite each of two rollers around which the print medium is wound and which transport the print medium horizontally. The imaging unit images the surface of the print medium, and the colorimeter detects the color of the print medium surface in order to evaluate the imaging results using a highly accurate color standard, and the imaging results are calibrated based on the results.

[0004] The printing device described in Patent Document 1 above is a device that records an image on one side (one main surface) of a print medium. Therefore, the image inspection is also performed only on that recorded side. On the other hand, Patent Documents 2 and 3 describe techniques for individually inspecting the images recorded on each side of a printing device that records images on both sides of a print medium.

[0005] Specifically, in Patent Document 2, after images have been recorded on both sides, a colorimeter for inspecting the front side and a colorimeter for inspecting the back side are arranged so as to sandwich the print medium, which is transported horizontally, from above and below. Also, in Patent Document 3, an inspection unit for the front side and an inspection unit for the back side are arranged so as to sandwich the recording medium, which is transported roughly in a vertical direction, from the sides. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-149111 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-200922 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-206454 Summary of the Invention [Problem to be solved by the invention]

[0007] When applying the technology described in Patent Document 1, which is for a single-sided printing device, to a double-sided printing device, it is possible to apply the technologies described in Patent Documents 2 and 3 to image inspection. However, the technology described in Patent Document 2 inspects print media that is not backed up by rollers or the like, which can lead to measurement errors due to fluctuations in the distance between each colorimeter and the transported print media, resulting in a decrease in inspection accuracy. Furthermore, because the colorimeters are positioned on either side of the print media, there is a concern that they may interfere with each other; specifically, the measurement illumination light emitted from one detector may enter the detector of the other detector, causing errors.

[0008] The technology described in Patent Document 3 is configured to irradiate illumination light onto a print medium wound around a roller and detect reflected light, which is thought to avoid the problem of distance fluctuations described above. However, because a pair of inspection units is arranged to sandwich the print medium from both sides, the footprint of the device inevitably becomes large. Furthermore, Patent Documents 2 and 3 do not mention image inspection using two optical detection means like Patent Document 1.

[0009] As such, in the technology of recording images on both sides of a printing medium and inspecting the images on both sides, it cannot be said that an equipment layout that enables accurate inspection using two optical means and also suppresses an increase in footprint has been established at present.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology that can accurately inspect images recorded on both sides of a printing medium using two optical inspection means, while minimizing an increase in the footprint of the device. [Means for solving the problem]

[0011] The present invention relates to an image inspection device that inspects images recorded on a first recording surface of a print medium and a second recording surface opposite to the first recording surface. This image inspection device includes a first transport roller and a second transport roller arranged at different positions in the horizontal direction, each of which wraps the printing medium around itself so that it abuts against the second recording surface and transports the printing medium in a first transport direction having a horizontal component; a third transport roller and a fourth transport roller arranged at different positions in the horizontal direction, each of which wraps the printing medium around itself so that it abuts against the first recording surface and transports the printing medium in a second transport direction having a horizontal component; a first inspection unit that optically inspects a first region of the first recording surface that is wrapped around the first transport roller; a second inspection unit that optically inspects a second region of the first recording surface that is wrapped around the second transport roller; a third inspection unit that optically inspects a third region of the second recording surface that is wrapped around the third transport roller; and a fourth inspection unit that optically inspects a fourth region of the second recording surface that is wrapped around the fourth transport roller.

[0012] In the first aspect of the present invention, the printing medium transported between the first transport roller and the second transport roller and the printing medium transported between the third transport roller and the fourth transport roller overlap at least partially in a planar view.

[0013] In addition, in a second aspect of the present invention, the pair of the first transport roller and the second transport roller is positioned above or below the pair of the third transport roller and the fourth transport roller, and the direction of the horizontal component is opposite between the first transport direction and the second transport direction.

[0014] In the image inspection device configured as described above, the image printed on the first recording side of the print medium is inspected by the first inspection unit and the second inspection unit, while the image printed on the second recording side opposite the first recording side is inspected by the third inspection unit and the fourth inspection unit. This allows both sides of the print medium to be inspected separately, each by two inspection units. These inspections are performed optically, but because the areas of the print medium backed up by the first through fourth transport rollers are inspected, the distance between each inspection unit and the transported print medium is maintained constant. This makes it possible to suppress degradation of inspection accuracy due to fluctuations in these distances.

[0015] This makes it possible to perform image inspection with high accuracy by using two types of optical inspection means in combination, as described in Patent Document 1. Such an effect can be obtained for images printed on both sides of the print medium.

[0016] Furthermore, this invention makes it possible to reduce the footprint of the printing medium device. The reason for this is as follows: In the first aspect of the invention, the printing medium transported between the first transport roller and the second transport roller and the printing medium transported between the third transport roller and the fourth transport roller at least partially overlap in a plan view. In this way, by having transport paths with horizontal movement components overlap in the vertical direction, it is possible to suppress an increase in the horizontal footprint.

[0017] In a second aspect of the present invention, the pair of first and second transport rollers is positioned above or below the pair of third and fourth transport rollers, and the horizontal components of the first and second transport directions are opposite. This allows the transport path for the print medium between the first and second transport rollers and the transport path for the print medium between the third and fourth transport rollers to be positioned without being separated horizontally. This also makes it possible to prevent an increase in the horizontal footprint.

[0018] Another aspect of the present invention is a printing device comprising: a transport unit that transports a printing medium; a printing unit that records an image on each of a first recording surface and a second recording surface opposite the first recording surface of the transported printing medium; and an image inspection unit that has the same configuration as any of the image inspection devices described above and inspects the image recorded on the printing medium by the printing unit.

[0019] In the invention configured in this manner, it is possible to inspect images recorded on both sides of a printing medium with high accuracy in the manner described above, and it is also possible to suppress the resulting increase in footprint.

[0020] Another aspect of the present invention is an image inspection method for inspecting an image recorded on a first recording surface of a print medium and a second recording surface opposite the first recording surface, the method comprising: transporting the print medium in a first transport direction having a horizontal component by a first transport roller and a second transport roller arranged at different positions in the horizontal direction and around which the print medium is wound so as to abut against the second recording surface; transporting the print medium in a second transport direction having a horizontal component opposite the first transport direction by a third transport roller and a fourth transport roller arranged at different positions in the horizontal direction and around which the print medium is wound so as to abut against the first recording surface; A first region of the recording surface that is wrapped around the first transport roller is optically inspected by a first inspection unit, a second region of the first recording surface that is wrapped around the second transport roller is optically inspected by a second inspection unit, a third region of the second recording surface that is wrapped around the third transport roller is optically inspected by a third inspection unit, and a fourth region of the second recording surface that is wrapped around the fourth transport roller is optically inspected by a fourth inspection unit, and the transport path of the printing medium between the first transport roller and the second transport roller and the transport path of the printing medium between the third transport roller and the fourth transport roller are at least partially overlapped in a planar view.

[0021] In the invention configured in this manner, similar to the above invention, the images recorded on both sides of the printing medium are inspected using two optical inspection means on each side, thereby enabling image inspection to be performed with excellent accuracy, and by stacking the transport path of the printing medium in the vertical direction, an increase in footprint can be suppressed. [Effects of the Invention]

[0022] As described above, according to the present invention, two inspection units are used for each side of the print medium, allowing for optically inspecting images on both sides of the print medium with high accuracy. Furthermore, the horizontal expansion of the print medium transport path can be suppressed, thereby reducing the footprint of the device. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a printing apparatus according to the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating the internal structure of a first printing mechanism. [Figure 3] FIG. 2 is a block diagram illustrating a hardware configuration of the print control device. [Figure 4] FIG. 2 is a diagram showing the configuration of an inspection unit. [Figure 5] 3A and 3B are diagrams illustrating the configuration and operation of an imaging unit. [Figure 6] FIG. 2 is a diagram illustrating a configuration of a color measurement unit. [Figure 7] FIG. 4 is a diagram showing a transport path in the inspection unit. [Figure 8] 10A and 10B are diagrams showing modified examples of the transport path of the print paper in the inspection unit; [Figure 9] FIG. 10 is a diagram showing a modified example of the second printing mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0024] Figure 1 is a schematic diagram showing one configuration example of a printing device according to the present invention. This printing device 10 comprises a printing press main body 200 and a print control device 100 that serves as its controller. The printing press main body 200 comprises a paper feed section 21 that supplies printing paper (here, roll paper) P, a first printing mechanism 20a that records an image by printing on the front side of the printing paper P, a reversing unit 27 that reverses the front and back sides of the printing paper P output from the first printing mechanism 20a, a second printing mechanism 20b that records an image by printing on the back side of the printing paper P, an inspection unit 28 that inspects the image printed on the printing paper P, and a paper winding section 29 that winds up the printing paper P after printing.

[0025] If the printing paper P after double-sided printing is to be subsequently sent to a subsequent process, a processing device for executing the subsequent process can be appropriately arranged in place of the paper winding section 29. In this case, the printing paper P after printing is delivered to the subsequent process as is without being wound up.

[0026] To clearly show the directional relationships in the following figures, an XYZ Cartesian coordinate system is introduced as shown in Figure 1. Here, the XY plane is the horizontal plane, and the Z direction represents the vertical upward direction. As shown in Figure 1, in this printing device 10, a paper feed section 21, a first printing mechanism 20a, a reversing unit 27, a second printing mechanism 20b, an inspection unit 28, and a paper winding section 29 are arranged in this order along the (+X) direction.

[0027] The first printing mechanism 20a prints an image on one main surface (hereinafter referred to as "front surface Pa") of the printing paper P. Meanwhile, the second printing mechanism 20b prints an image on the other of the two main surfaces of the printing paper P, the main surface opposite the front surface Pa (hereinafter referred to as "back surface Pb"). Note that the distinction between the front surface and back surface here is for the sake of convenience of explanation, and in this embodiment, there is no essential difference between the front surface Pa and back surface Pb of the printing paper P. However, printing media that have a distinction between the front surface and back surface, such as whether or not they are coated, may also be used.

[0028] 2 is a diagram showing a schematic diagram of the internal structure of the first printing mechanism. The first printing mechanism 20a is equipped with a first drive roller 22a for transporting the printing paper P inside, a plurality of support rollers 23a for transporting the printing paper P inside the first printing mechanism 20a, a printing unit 24a that ejects ink onto the printing paper P to perform printing, a drying unit 25a that dries the printing paper P after printing, and a second drive roller 26a for outputting the printing paper P from inside the first printing mechanism 20a.

[0029] In the following description, the components provided in the first printing mechanism 20a and involved in transporting the print paper P, i.e., the first drive roller 22a, the second drive roller 26a, the support roller 23a, etc., may be collectively referred to as the "transport section." In addition to the above, the transport section may also be provided with various other members, such as auxiliary rollers for defining the transport path of the print paper P.

[0030] The printing unit 24a is composed of, for example, rows of inkjet heads of C (cyan), M (magenta), Y (yellow), and K (black) colors arranged in the transport direction of the printing paper P. Each inkjet head row is composed of multiple inkjet heads (print heads) arranged in a staggered pattern. Each inkjet head includes a number of nozzles that eject ink.

[0031] The configuration of the second printing mechanism 20b is similar to that of the first printing mechanism 20a, and therefore a description thereof will be omitted. Note that in this specification, the components of the first printing mechanism 20a are designated by reference numerals ending in "a." In the following description, however, when referring to the components of the second printing mechanism 20b, the corresponding components in the first printing mechanism 20a are designated by reference numerals ending in "b" instead of "a."

[0032] The print control device 100 controls the operation of the printing press main body 200 configured as described above. When a print output instruction command is given to the print control device 100, the print control device 100 controls the operation of the printing press main body 200 so that the printing paper P is transported from the paper delivery section 21 to the inside. As a result, the printing paper P is delivered from the paper delivery section 21 with its front surface Pa facing upward, and is carried into the first printing mechanism 20a.

[0033] The first printing mechanism 20a executes printing processing in response to instructions commands from the print control device 100. That is, with the front surface Pa facing upward, printing is first performed by the printing unit 24a on the upper surface (front surface Pa) of the print paper P which is transported in a substantially horizontal direction, specifically in the (+X) direction, by the first drive roller 22a and the second drive roller 26a, and then the print paper P is dried by the drying unit 25a. In this way, an image is formed and fixed on the front surface Pa of the print paper P.

[0034] The print paper P discharged from the first printing mechanism 20a is reversed by the reversing unit 27. That is, the reversing unit 27 reverses the print paper P that is fed in with its front side Pa facing up, and discharges it with its back side Pb facing up. A known configuration can be applied as this reversing unit 27, so a description thereof will be omitted here.

[0035] The inverted print paper P is carried into the second printing mechanism 20b, which executes printing processing in response to instructions and commands from the print control device 100. That is, with the back side Pb facing up, the print paper P is transported in the (+X) direction by the first drive roller 22b and the second drive roller 26b. First, printing is performed on the upper surface (back side Pb) of the print paper P by the printing unit 24b, and then the print paper P is dried by the drying unit 25b. In this way, an image is formed and fixed on the back side Pb of the print paper P. The print paper P is discharged from the second printing mechanism 20b with images printed on both sides (front side Pa and back side Pb).

[0036] The printing paper P with images printed on both sides in this way is carried into the inspection unit 28. As will be described in detail later, the inspection unit 28 optically reads each of the images printed on both sides of the printing paper P and sends the results to the print control device 100. Based on the information sent from the inspection unit 28, the print control device 100 determines whether the images have been printed with the expected quality. In this way, the image inspection is performed. After inspection, the printing paper P is discharged from the inspection unit 28 and wound into a roll by the paper winding section 29.

[0037] While the configuration of an inkjet printer that performs color printing has been exemplified here, the present invention can also be applied when an inkjet printer that performs monochrome printing is used. Furthermore, while the configuration of an inkjet printer that uses aqueous ink has been exemplified here, the present invention can also be applied when a printing device that uses UV ink (ultraviolet-curable ink), such as an inkjet printer for label printing, is used. Furthermore, the printing device may be configured so that the printed printing paper is sent directly to a post-processing machine. The present invention can also be applied when a printing device other than an inkjet printer (for example, a laser printer) is used. As described above, there are no particular limitations on the type of printing device.

[0038] FIG. 3 is a block diagram showing the hardware configuration of a print control device. As shown in FIG. 3, the print control device 100 includes a CPU (Central Processing Unit) 11, memory 12, storage (auxiliary storage device) 13, and an interface (IF) unit 14. The CPU 11 performs various processes according to pre-prepared control programs. The memory 12 temporarily stores data generated during the processes. The storage 13 stores the processing result data and the control programs on a long-term basis. The IF unit 14 also handles communication between the print control device 100 and users or external devices. For this purpose, the IF unit 14 includes an input unit 141 having input devices such as a keyboard and a mouse, a display unit 142 consisting of, for example, a display device, and a network IF 143 for connecting to an external communication network such as a LAN (Local Area Network) or the Internet.

[0039] The storage 13 stores a print control program 131 and an inspection control program 132. The print control program 131 is a control program for controlling the execution of print processing by the printing press main body 200. The inspection control program 132 is a control program for controlling the execution of image inspection processing by the inspection unit 28.

[0040] The memory 12 includes a RAM and a ROM. The memory 12 functions as a work area when the CPU 11 executes the print control program 131 and the inspection control program 132 stored in the storage 13. The print control program 131 and the inspection control program 132 are stored in a computer-readable recording medium (non-transitory recording medium) or provided via an external communication network.

[0041] The CPU 11 reads out the print control program 131 and the inspection control program 132 stored in the storage 13 into the memory 12 and executes them to realize various functions of the print control device 100. For example, functional blocks such as an image processing unit 111, a print execution control unit 112, and an imaging and colorimetry control unit 113 are realized in software. The image processing unit 111 performs various processes on image data that indicates the content of the image to be printed on the printing paper P. The print execution control unit 112 controls the operation of the first printing mechanism 20a, the second printing mechanism 20b, and the transport units such as the drive rollers 22a and 22b. The imaging and colorimetry control unit 113 controls the operation of the inspection unit 28, which will be described in detail below.

[0042] 4 is a diagram showing the configuration of the inspection unit. Inspection unit 28 has an inspection transport section 280 including a plurality of transport rollers 281 to 289, and printing paper P is transported by being stretched across these transport rollers 281 to 289. All of the transport rollers 281 to 289 are driven rollers. In other words, these transport rollers 281 to 289 have the function of defining the transport path within inspection unit 28 of printing paper P that is sent out by drive roller 26a of second printing mechanism 20b and taken up by paper take-up section 29.

[0043] Each of the transport rollers 281-289 has a cylindrical or columnar shape with the Y direction as its longitudinal direction, and both ends of the central axis in the Y direction are rotatably supported by a pair of support frames (not shown) arranged on the front and back sides of the paper surface of Figure 4 so as to sandwich each roller in the Y direction. This allows each of the transport rollers 281-289 to rotate freely around a rotation axis with the Y direction as its axial direction.

[0044] The printing paper P is transported from the second printing mechanism 20b with the back surface Pb facing upward. Therefore, in the inspection transport section 280, the transport rollers 282 to 286 contact the front surface Pa of the printing paper P, while the transport rollers 281, 287 to 289 contact the back surface Pb of the printing paper P.

[0045] 4, solid arrows shown at various positions near the print paper P indicate the transport direction of the print paper P at that position. The transport direction of the print paper P carried in the (+X) direction from the second printing mechanism 20b is changed to upward, i.e., (+Z), by transport roller 281. The transport direction of the print paper P is then sequentially changed to approximately the (+X) direction by transport rollers 283-285, approximately the (-Z) direction by transport rollers 285, 286, approximately the (-X) direction by transport rollers 286-288, and approximately the (-Z) direction by transport rollers 288, 289, and finally the print paper P is discharged in the (+X) direction by transport roller 289.

[0046] When determining the positions of the transport rollers 281, 289, if the height (position in the Z direction) of the incoming print paper P and the Z direction position of the outgoing print paper P are made substantially the same, it is possible to eliminate changes in the transport path in the second print mechanism 20b and the paper take-up unit 29 that would occur if the inspection unit 28 were inserted between the second print mechanism 20b and the paper take-up unit 29. In other words, the inspection unit 28 has a configuration that is suitable as an inspection device that can be retrofitted to an existing print device that does not have such an inspection device.

[0047] In the transport path from transport roller 283 to transport roller 285, the print paper P is transported with its back surface Pb facing upward. On the other hand, in the transport path from transport roller 286 to transport roller 288, the print paper P is transported with its front surface Pa facing upward.

[0048] An imaging unit 31 is provided above one of the transport rollers 284. The imaging unit 31 captures an image of the back side Pb of the printing paper P that is wound around the transport roller 284 and transported. Another imaging unit 33 is provided above the other transport roller 287. The imaging unit 33 captures an image of the front side Pa of the printing paper P that is wound around the transport roller 287 and transported. It is preferable that these two imaging units 31, 33 have the same structure.

[0049] In addition, a colorimetric unit 32 is disposed above the transport roller 285. The colorimetric unit 32 performs color detection on a partial area of ​​the back surface Pb of the printing paper P that is wound around the transport roller 285 and transported. Another colorimetric unit 34 is disposed above the other transport roller 288. The colorimetric unit 34 performs color detection on a partial area of ​​the front surface Pa of the printing paper P that is wound around the transport roller 288 and transported. It is preferable that these two colorimetric units 32, 34 have the same structure.

[0050] A light shielding plate 35 is disposed between the imaging unit 31 and the colorimetric unit 32. As will be described later, the light shielding plate 35 has a function of blocking the illumination light emitted from the imaging unit 31 from traveling toward the colorimetric unit 32. Specifically, the light shielding plate 35 prevents the illumination light from entering the colorimetric unit 32 directly or after being reflected by surrounding components. Similarly, a light shielding plate 36 is disposed between the imaging unit 33 and the colorimetric unit 34. The light shielding plate 36 blocks the light that is emitted from the imaging unit 33 and traveling toward the colorimetric unit 34 directly or after being reflected by surrounding components.

[0051] FIG. 5 is a diagram illustrating the configuration and operation of the imaging unit. Here, one imaging unit 31 will be described as an example, but in this embodiment, the other imaging unit 33 has the same structure. As shown in FIG. 5(a), the imaging unit 31 has illumination light sources 311 and 312 that illuminate the back surface Pb of the printing paper P wound around the transport roller 284, and a line sensor 314 in which an imaging element 313 is disposed adjacent to and facing the back surface Pb. The imaging element 313 receives reflected light L3 of illumination light L1 and L2 incident from the illumination light sources 311 and 312, respectively, and captures an image of the back surface Pb of the printing paper P. Note that, although two illumination light sources 311 and 312 are provided here to illuminate the back surface Pb of the printing paper P from two directions, the number and arrangement of the illumination light sources are not limited to this.

[0052] As shown in FIG. 5(b), a large number of imaging elements 313 are arranged along the Y direction on the underside of the housing of line sensor 314, which is formed in a rod shape extending in the Y direction. The multiple imaging elements 313 are positioned at different positions in the Y direction, that is, the width direction of printing paper P wound around transport roller 284, and are arranged facing downward so as to cover the entire printing paper P from one end to the other. In other words, line sensor 314 is a one-dimensional image sensor whose longitudinal direction is the Y direction and whose imaging width Ws is larger than the width Wp of printing paper P. Note that if there are invalid areas where no image is printed at both ends of printing paper P in the width direction, it is sufficient for line sensor 314 to cover the effective area where the image is actually printed. In this case, imaging width Ws only needs to be larger than the width We of the effective area, and does not necessarily have to be larger than the width Wp of printing paper P.

[0053] As shown in Figure 5(c), the line sensor 314 is disposed opposite the back surface Pb of the printing paper P being transported while wrapped around the transport roller 284, and receives and captures light from a strip-shaped area (imaging area Rs) of the back surface Pb that is narrow in the X direction and long in the Y direction. This makes it possible to obtain an image of the imaging area Rs, i.e., a one-dimensional image of the back surface Pb. Then, by periodically capturing images as the transported printing paper P moves, it is possible to receive light from multiple imaging areas Rs at different positions and obtain a two-dimensional image of the back surface Pb from the light reception results.

[0054] The other imaging unit 33 also has illumination light sources 311, 312, a line sensor 314, etc. The imaging unit 33 captures an imaging area Rs that is part of the area of ​​the front surface Pa of the printing paper P that is wound around the transport roller 287 and that is a strip-shaped area that extends in the Y direction. In other words, the imaging area Rs captured by the imaging unit 31 is defined on the back surface Pb of the printing paper P, while the imaging area Rs captured by the imaging unit 33 is defined on the front surface Pa of the printing paper P.

[0055] The image data acquired by imaging is sent to the print control device 100, more specifically, to the imaging and colorimetry control unit 113. The imaging and colorimetry control unit 113 receives and analyzes the image data to determine whether the image printed on the printing paper P maintains the expected quality. If the imaging and colorimetry control unit 113 detects a deterioration in print quality, it appropriately modifies at least one of the image data processing in the image processing unit 111 and the operating parameters of each unit of the printing device main body 100 set by the print execution control unit 112. This maintains print quality. For this purpose, the imaging and colorimetry control unit 113 executes image inspection processing based on the imaging results obtained by the imaging units 31 and 33.

[0056] Imaging is performed on the back side Pb (front side Pa) of the printing paper P backed up by the transport rollers 384 (387). If the distance between the imaging area Rs on the printing paper P and the line sensor 314 (more specifically, the imaging element 313) fluctuates, the line sensor 314 will not be able to correctly capture the image on the printing paper P, which will reduce the accuracy of the image inspection process. By capturing an image of the printing paper P backed up by a member such as a roller, such problems can be avoided.

[0057] If there are wrinkles in the printing paper P wound around the transport rollers 384 (387), the printing paper P will be partially lifted from the transport rollers 384 (387). This causes the distance between the imaging area Rs and the line sensor 314 to vary depending on the position. When printing paper P is transported by multiple transport rollers, meandering and skewing of the printing paper P will inevitably occur, which can cause the printing paper P to wrinkle on the transport rollers. According to the knowledge of the inventors of this application, the likelihood of wrinkles occurring varies depending on the wrapping angle of the printing paper P with respect to the transport rollers (the angle indicated by the symbol θ in Figure 5(a)).

[0058] In other words, the larger the wrap angle θ, the more likely wrinkles due to meandering or the like will occur. On the other hand, if the wrap angle θ is too small, the backup function of the transport roller 384 (387) will be weakened. According to experiments conducted by the inventors of the present application, the preferable range of the wrap angle θ to prevent the occurrence of wrinkles in the printing paper P that would affect imaging is 2.5 degrees or more and 45 degrees or less. The wrap angle θ is the area of ​​the entire circumference of the transport roller 284, etc. that is in contact with the printing paper P, expressed in terms of the central angle of the roller. This concept of "wrap angle" is the same as the concept known as "wrap angle" in the technical field of film transport.

[0059] The imaging results from the imaging units 31 and 33 are affected by variations in the characteristics of the imaging units, drift due to ambient temperature, and other factors. To prevent this from reducing inspection accuracy, the imaging results are corrected using color detection results from a colorimeter. More specifically, the imaging results of the back surface Pb from the imaging unit 31 are corrected using the color detection results from the colorimeter 32 for the same back surface Pb. Similarly, the imaging results of the front surface Pa from the imaging unit 33 are corrected using the color detection results from the colorimeter 34 for the same front surface Pa. Patent Document 1 describes in detail a technology for incorporating a colorimeter and a line sensor into a printing device and combining their detection results to achieve high-precision image inspection. Since the same principle can be used in this embodiment, a detailed description will be omitted here. However, the inspection principle in this embodiment is not limited to this, and alternative inspection techniques may also be applied.

[0060] FIG. 6 is a diagram showing the configuration of the colorimetric unit. Here, one colorimetric unit 32 will be described as an example with reference to FIGS. 4 and 6, but the other colorimetric unit 34 has the same structure. As shown in FIGS. 4 and 6(a), the colorimetric unit 32 has a colorimeter 37 and a support mechanism 320 that supports it. The support mechanism 320 has a flat base member 321 that is disposed diagonally above the transport roller 285. Both ends of the base member 321 in the Y direction are fixed to a support frame (not shown) that pivotally supports the transport roller 285. In addition, the top surface of the flat base member 321 is inclined in the (+X) direction from the horizontal, and a pair of guide rails 322 is provided on the top surface extending in the Y direction.

[0061] 4, sliders 323 are engaged with each of the guide rails 322 so as to be movable in the Y direction, and plate members 324 are connected to the sliders 323. Support members 325 are attached to the plate members 324, extending in a direction perpendicular to the Y direction, which is the extension direction of the guide rails 322. Colorimeter 37 and an advancing / retracting mechanism 326 that moves colorimeter 33 back and forth along the longitudinal direction of support member 325 are attached to support member 325.

[0062] Therefore, in the colorimeter unit 32, the support member 325 is movable in the Y direction along the guide rails 322 relative to the base member 321, and the colorimeter 33 is movable back and forth relative to the support member 325 in a direction perpendicular to this. Therefore, the colorimeter 37 is movable in the Y direction and in a direction perpendicular to this, and can perform color detection at any position on the printing paper P. The support member 325 is inclined relative to the horizontal direction so that the (+X) side is lower, and the direction of forward and backward movement of the colorimeter 37 has an X direction component and a Z direction component.

[0063] When the colorimeter 37 is positioned at the position where it protrudes most in the (+X) direction, its bottom surface faces the back surface Pb of the printing paper P wound around the transport roller 285. As shown schematically in FIG. 6(b), the colorimeter 37 has an illumination light source 371 and a light receiver 372. These are provided on the bottom surface of the colorimeter 37, and the illumination light source 371 emits illumination light L5 toward the back surface Pb of the printing paper P that it faces. The light receiver 372 receives reflected light L6 from a color detection area Rc, which is a portion of the back surface Pb illuminated by the illumination light. The color detection area Rc is a very small area on the printing paper P, with the aim of accurately detecting the color at each point on the printing paper P.

[0064] The reflected light L6 received by the light receiver 372 is transmitted to the spectroscopic unit 374 via an optical fiber 373. The spectroscopic unit 374 separates the incident light into multiple wavelength components and outputs them. The spectroscopic unit 374 may be, for example, one that uses a grating or one that has multiple band-pass filters with different passing wavelengths. Each of the light components separated into wavelength components is incident on a photodetector 375 that has multiple light-receiving elements, and the photodetector 375 outputs the amount of light received for each wavelength as a detection result. This achieves color detection in the color detection region Rc.

[0065] The detection results are sent to the imaging and colorimetry control unit 113 of the print control device 100 and are used to correct the imaging results obtained by the imaging unit 31. That is, the imaging results obtained by the imaging unit 31 are corrected based on the color detection results obtained by the colorimetry unit 32, and the image printed on the back surface Pb of the printing paper P is inspected using the correction results.

[0066] The colorimetric unit 34 has the same configuration and functions as the colorimetric unit 32. That is, the colorimetric unit 34 has a colorimeter 37 having the same structure as that provided in the colorimetric unit 32, and a support mechanism 340. The support mechanism 340 has a base member 341, guide rails 342, a slider 343, a plate member 344, and a support member 345. The imaging result by the imaging unit 33 is corrected based on the color detection result by the colorimetric unit 34, and the image printed on the surface Pa of the printing paper P is inspected using the correction result.

[0067] As described above, in this embodiment, in the printing device 10 that prints images on both main surfaces (front surface Pa and back surface Pb) of the printing paper P, the inspection unit 28 is provided on the path of the printing paper P after printing on both sides has been completed. The inspection unit 28 inspects the image printed on the front surface Pa and the image printed on the back surface Pb of the printing paper P separately.

[0068] By inspecting both sides after printing on both sides, rather than inspecting the image each time printing on one side is completed, it is possible to inspect the image in a state close to the final output, which makes it possible to maintain the desired print quality at the final output unit.

[0069] Imaging by the imaging units 31, 33 and color detection by the colorimetry units 32, 34 are performed on the printing paper P backed up by the transport roller 284 etc. Therefore, fluctuations in the distance between the imaging units 31, 33 and the colorimetry units 32, 34 and the printing paper P are suppressed, making it possible to perform imaging and detection with high accuracy.

[0070] Furthermore, the imaging units 31 and 33 and the colorimetric units 32 and 34 are each installed with their light receiving parts facing downwards. Paper dust is scattered around the transport path of the printing paper P, and if this dust adheres to the light receiving parts, it increases detection errors. By placing the light receiving parts facing downwards, it is possible to prevent such problems from occurring.

[0071] Furthermore, in order to accurately correct the imaging results based on the color detection results using the color detection results, it is desirable that imaging by the imaging unit 31 and color detection by the colorimetric unit 32 be performed at the same position on the back surface Pb of the printing paper P. Similarly, it is desirable that imaging by the imaging unit 33 and color detection by the colorimetric unit 34 be performed at the same position on the printing paper P for the front surface Pa.

[0072] In this embodiment, the imaging unit 31 and the colorimetric unit 32 are provided facing the adjacent transport rollers 284, 285, respectively, and no components that come into contact with the print paper P exist between the transport rollers 284, 285. This minimizes the effects of the print paper P's meandering, skewing, and bending that inevitably occur during transport, making it easy to maintain the positional relationship between the image capture area Rs captured by the imaging unit 31 and the color detection area Rc captured by the colorimetric unit 32 on the back surface Pb of the print paper P. This makes it possible to perform accurate inspections using the results detected at corresponding positions. In particular, the absence of any components that come into contact with the image on the print paper P between the transport rollers 284, 285 is advantageous in that the image to be inspected is not altered during transport.

[0073] In this sense, it is preferable to reduce the distance between adjacent transport rollers 284, 285. Furthermore, it is also possible to perform both imaging and color detection on a single transport roller. In these cases, it is necessary to consider the possibility of optical interference between the imaging unit 31 and the colorimetric unit 32. That is, detection errors may occur if the illumination light emitted from the imaging unit 31 is received by the colorimetric unit 32 as stray light, or if the illumination light emitted from the colorimetric unit 32 is received by the light-receiving unit 31. In particular, the influence of stray light from the imaging unit 31 on the colorimetric unit 32 is significant. This is because the color detection results by the colorimetric unit 32 are used to correct the imaging results by the imaging unit 31, so higher accuracy is required. Also, the imaging unit 31 illuminates a wide imaging region Rs, so the illumination light amount is significantly greater than that of the colorimetric unit 32.

[0074] In this embodiment, this problem is solved by arranging the imaging unit 31 and the colorimetric unit 32 opposite transport rollers 284, 285, which are separate but adjacent to each other on the transport path, and by arranging a light shielding plate 35 between the imaging unit 31 and the colorimetric unit 32. Of the stray light components, the light that is directly incident on the colorimetric unit 32 from the imaging unit 31 has the largest amount of light, but primary reflected light from the surface Pa of the printing paper P can also have a relatively large amount of light. It is desirable that the light shielding plate 35 be arranged so as to block the optical path of such primary reflected light as well.

[0075] Furthermore, in the color measurement unit 32 of this embodiment, a support mechanism 320 that supports the colorimeter 37 is disposed between the transport rollers 284, 285, and of these, a base member 321 is a flat plate-like member that extends in the width direction of the printing paper P and also has the function of blocking stray light. Similarly, in the color measurement unit 34, a base member 341 is a flat plate-like member that extends in the width direction of the printing paper P and also has the function of blocking stray light. By arranging the lower ends of the base members 321, 341 as close as possible to the printing paper P, it is possible to further enhance the light blocking function, particularly for light reflected by the printing paper P.

[0076] Here, we have explained the various effects achieved by the imaging unit 31 and colorimetric unit 32, but these also apply to the combination of the imaging unit 33 and colorimetric unit 34. As mentioned above, there is essentially no difference between the front surface Pa and the back surface Pb of the printing paper P, so it is desirable to perform inspection of the front surface Pa and the back surface Pb under the same conditions. Measures for achieving this will be explained next.

[0077] In this embodiment, the imaging units 31 and 33 have the same configuration, and the colorimetric units 32 and 34 have the same configuration. For example, line sensors with the same specifications and consistent characteristics are used between the imaging units 31 and 33. Regarding the illumination light source, the direction of incidence of illumination light with respect to the imaging region Rs and the amount of light are the same between the imaging units 31 and 33. Similarly, colorimetric units 32 and 34 use colorimeters 37 with consistent characteristics. This can reduce differences in inspection conditions caused by variations in the characteristics of these components.

[0078] Furthermore, the positional relationship between the transport roller 284 and the imaging unit 31 is the same as the positional relationship between the transport roller 287 and the imaging unit 33. That is, the imaging unit 31 is disposed directly above the rotation axis of the transport roller 284 facing downward, while the imaging unit 33 is disposed directly above the rotation axis of the transport roller 287 facing downward. The distance between the imaging unit 31 and the transport roller 284 is equal to the distance between the imaging unit 33 and the transport roller 287. By aligning the positional relationships in this way, the imaging conditions can be made the same between the imaging unit 31 and the imaging unit 33.

[0079] The same is true between the colorimetry units 32 and 34. That is, the position of the colorimetry unit 32 as seen from the printing paper P being rewound on the transport roller 285 is the same as the position of the colorimetry unit 34 as seen from the printing paper P being rewound on the transport roller 288, and the distance between the transport roller 285 and the colorimetry unit 32 is equal to the distance between the transport roller 288 and the colorimetry unit 32.

[0080] Note that because the colorimetry units 32 and 34 are arranged symmetrically with respect to the Z axis due to the difference in the conveyance direction, the orientations of the colorimetry units 32 and 34 are also inverted. Therefore, strictly speaking, the absolute positional relationships cannot be said to be equal, but it can be said that at least the relative positional relationship between the conveyance roller 285 and the colorimetry unit 32 and the relative positional relationship between the conveyance roller 288 and the colorimetry unit 34 are equal. Furthermore, the colorimetry units 37 used are of the same specifications, and the magnitude of their inclination with respect to the horizontal plane during detection is also the same.

[0081] The inspection transport section 280 also employs a configuration for standardizing the inspection conditions. That is, the transport rollers 284 and 287 have the same diameter. The wrapping angle θ (FIG. 5(a)) of the printing paper P is also set to the same value. This results in the same curvature of the wrapped printing paper P, and the state of the printing paper P as viewed from the imaging sections 31 and 33 can be made the same.

[0082] Similarly, the transport rollers 285, 288 have the same diameter. Ideally, the wrap angles of the printing paper P around these rollers should also be the same, but when the printing paper P is wrapped deeply around the transport rollers 285, 288 (for example, at a wrap angle of 45 degrees or more), as in this embodiment, the curvature of the printing paper P is determined almost entirely by the curvature of the circumferential surface of the transport rollers, so if the two transport rollers have the same diameter, it is not necessarily necessary for the wrap angles between them to be the same.

[0083] Furthermore, the distance between transport roller 284 and transport roller 285 is equal to the distance between transport roller 287 and transport roller 288. In other words, the length of the transport path between transport roller 284 and transport roller 285 is equal to the length of the transport path between transport roller 287 and transport roller 288. Therefore, the relative positional relationship between imaging area Rs and color detection area Rc is the same on both the front surface Pa and back surface Pb of printing paper P.

[0084] To satisfy these conditions, in the inspection transport unit 280, the relative positional relationship between the transport rollers 283, 284, and 285 is the same as the relative positional relationship between the transport rollers 286, 287, and 288. In other words, when the transport rollers 286, 287, and 288 are inverted around the Z axis and translated in the X direction while maintaining the relative positions between them, they will closely overlap with the transport rollers 283, 284, and 285, respectively. More preferably, when the transport rollers 286, 287, and 288, the imaging unit 33, and the colorimetry unit 34 are inverted and translated while maintaining their relative positions, they will overlap with the transport rollers 283, 284, and 285, the imaging unit 31, and the colorimetry unit 32, respectively.

[0085] These various measures make it possible to sufficiently reduce the difference in inspection conditions between the front side Pa and the back side Pb of the printing paper P. Inspecting both sides at the same time after printing on both sides also contributes to reducing the difference in inspection conditions.

[0086] This embodiment also takes measures to prevent an increase in the footprint of the entire printing apparatus 10. First, as described above, double-sided image inspection is performed by a single inspection unit 28, which reduces the footprint compared to the case where two sets of inspection devices are provided to inspect the front surface Pa and the back surface Pb separately. Furthermore, as will be explained next, the transport path for the printing paper P is folded back and overlapped vertically, thereby preventing the transport path from expanding horizontally.

[0087] 7 is a diagram showing the transport paths in the inspection unit. As described above, in the inspection unit 28, the print paper P is wound around a plurality of transport rollers 281 to 289 and transported. Of these, the transport path between transport roller 284, which is opposed to the imaging unit 31, and transport roller 285, which is opposed to the colorimeter 37 of the colorimetric unit 32, will be referred to as the "first transport path." Furthermore, the transport path between transport roller 287, which is opposed to the imaging unit 33, and transport roller 288, which is opposed to the colorimeter 37 of the colorimetric unit 34, will be referred to as the "second transport path."

[0088] On the first transport path, the transport direction of the print paper P indicated by arrow D1 has a horizontal component in the (+X) direction, and at this time the print paper P is transported with its back surface Pb facing upward. On the other hand, on the second transport path, the transport direction of the print paper P indicated by arrow D2 has a horizontal component in the (-X) direction, and at this time the print paper P is transported with its front surface Pa facing upward. In this way, the transport direction and posture of the print paper P are opposite between the first and second transport paths.

[0089] 7, transport roller 284, which defines the (-X) end of the first transport path, is located closer to the (-X) side than transport roller 287, which defines the (+X) end of the second transport path. Therefore, the first transport path and the second transport path partially overlap each other in a plan view in the Z direction. This allows the footprint of the device to be smaller than if the transport paths were laid out horizontally.

[0090] Furthermore, by turning the transport path in this way, the print paper P can be transported with the back surface Pb facing upward on the first transport path whose transport direction has a horizontal component in the (+X) direction, and with the front surface Pa facing upward on the second transport path whose transport direction has a horizontal component in the (-X) direction. This makes it easy to arrange the imaging unit and the colorimetric unit with the light receiving unit facing downward for each of the front surface Pa and the back surface Pb.

[0091] 8 is a diagram showing a modified example of the transport path of the print paper in the inspection unit. In transport section 380 formed by transport rollers 381 to 389 shown in this figure, the first transport path between transport rollers 384 and 385 and the second transport path between transport rollers 387 and 388 do not overlap in a plan view. Even with a transport path configured in this way, the pair of transport rollers 384 and 385 and the pair of transport rollers 387 and 388 are arranged at different positions in the vertical direction, and the transport path is turned back, that is, the transport direction is reversed. This makes it possible to arrange imaging units 31 and 33 and colorimeters 37 in colorimetric units 32 and 34 above the transport rollers with their light receiving parts facing downward.

[0092] As a comparative example, if the transport path is not folded back in this way, and the first transport path and the second transport path are arranged horizontally, and the imaging units 31, 33 and the colorimeter 37 are arranged above the transport rollers, it would be necessary to provide a mechanism for turning over the print paper P between the first transport path and the second transport path, which would inevitably result in a significant increase in the footprint.However, by folding back the transport path as shown in Figure 8 so that the transport path having a horizontal component in the (+X) direction and the transport path having a horizontal component in the (-X) direction overlap in a plan view, it is possible to avoid this increase in the footprint.

[0093] In the above embodiment, an independent inspection unit 28 is disposed on the (+X side) of the second printing mechanism 20b that prints on the back side Pb of the printing paper P, that is, downstream in the transport direction of the printing paper P. This is because the first printing mechanism 20a and the second printing mechanism 20b can be configured identically. On the other hand, from the perspective of reducing the footprint of the entire printing device 10, it is also possible to provide an inspection unit inside the second printing mechanism, for example, as shown below.

[0094] FIG. 9 illustrates a modified second printing mechanism. In this modified second printing mechanism 20c, the same components as those in the second printing mechanism 20b of the above embodiment are denoted by the same reference numerals and will not be described again. In this modified second printing mechanism 20c, an inspection unit 28 is interposed on the transport path between the drying unit 25b and the second drive roller 26b. Since the transport rollers in the inspection unit 28 are all driven rollers and do not have the driving force to move the print paper P, locating the inspection unit 28 upstream of the drive roller 26b makes it possible to transport the print paper P using the driving force of the drive roller 26b. This also makes it possible to locate a processing unit that performs any post-process downstream of the second printing mechanism 20c. In addition, if a mechanism for driving the print paper P is provided in a post-process, such as the paper winding unit 29 of this embodiment, the inspection unit 28 may be located downstream of the drive roller 26b.

[0095] In this way, by incorporating the inspection unit into the printing mechanism, it is possible to further reduce the footprint compared to when the inspection unit is an independent device. Furthermore, if the transport rollers required for printing also function as transport rollers for the inspection transport section, the number of rollers used can be reduced, the transport path can be shortened, and the footprint can be further reduced.

[0096] As described above, in this embodiment, the printing device 10 and its inspection unit 28 function as the "printing device" and "image inspection device" of the present invention, respectively. The inspection unit 28 also functions as the "image inspection section" of the present invention. The printing paper P corresponds to the "printing medium" of the present invention, and the back surface Pb and front surface Pa of the printing paper P correspond to the "first recording surface" and "second recording surface" of the present invention, respectively.

[0097] Furthermore, transport rollers 284, 285, 287, and 288 function as the "first transport roller," "second transport roller," "third transport roller," and "fourth transport roller" of the present invention, respectively. Furthermore, imaging unit 31, colorimetric unit 32, imaging unit 33, and colorimetric unit 34 function as the "first inspection unit," "second inspection unit," "third inspection unit," and "fourth inspection unit," respectively. Furthermore, line sensor 314 corresponds to the "one-dimensional image sensor" of the present invention, and imaging element 313 corresponds to the "imaging element" of the present invention. Furthermore, light shielding plate 35 and base member 321 function as the "first light shielding unit" of the present invention, while light shielding plate 36 and base member 341 function as the "second light shielding unit" of the present invention.

[0098] Furthermore, for the back surface Pb of the printing paper P, the imaging area Rs and color detection area Rc correspond to the "first area" and "second area" of the present invention, respectively. For the front surface Pa of the printing paper P, the imaging area Rs and color detection area Rc correspond to the "third area" and "fourth area" of the present invention, respectively. Arrows D1 and D2 in Fig. 7 represent the "first transport direction" and the "second transport direction" of the present invention, respectively.

[0099] In the printing device 100 of this embodiment, the components that form the transport path for the print paper P within the first printing mechanism 20a and the second printing mechanism 20b, such as the drive roller 22a and the transport roller 23a, and the inspection transport unit 280, together form the "transport unit" of the present invention. In addition, the printing units 24a and 24b function as the "printing unit" of the present invention.

[0100] The present invention is not limited to the above-described embodiment, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, in the inspection unit 28 of the above-described embodiment, the imaging unit and the colorimetric unit are arranged in this order along the transport direction of the print paper P. However, this order is not limited to this, and for example, the colorimetric unit may be arranged upstream of the imaging unit. Furthermore, the two inspection units that inspect one side of the print medium are not limited to the combination of the imaging unit and the colorimetric unit described above.

[0101] Also, for example, in this embodiment, a reversing unit 27 that reverses the print paper P is disposed between the first print mechanism 20a that prints an image on the front surface Pa of the print paper P and the second print mechanism 20b that prints an image on the back surface Pb. However, the present invention is also applicable to printing devices that do not have a mechanism for reversing the print medium, such as a print mechanism in which a printing unit is disposed on each side of the print medium.

[0102] For example, although the printing device 10 of the above embodiment prints on printing paper P, which is continuous paper in the form of a long web, the present invention can also be applied to a device that prints on sheet-fed printing paper, for example.

[0103] Furthermore, although the inspection unit 28 in the above embodiment is configured as one component of the printing device 10, it is also possible to configure the inspection unit 28 independently as an image inspection device that performs image inspection by placing it on the conveying path of an existing printing device.

[0104] As described above with reference to specific embodiments, in the image inspection device according to the present invention, for example, the direction of the horizontal component may be opposite between the first transport direction and the second transport direction. With this configuration, reversing the transport direction makes it possible to stack the transport paths of the print medium one above the other, thereby further enhancing the effect of reducing the footprint.

[0105] Alternatively, for example, the first inspection unit may be disposed above the first transport roller, the second inspection unit above the second transport roller, the third inspection unit above the third transport roller, and the fourth inspection unit above the fourth transport roller. That is, each inspection unit may be disposed above its corresponding transport roller. With this configuration, each inspection unit inspects the print medium from top to bottom. Foreign matter such as paper dust is inevitably generated along the transport path of the print medium. If such foreign matter adheres to each inspection unit, it may interfere with optical inspection. By arranging the first through fourth inspection units facing downward, it is possible to reduce the adhesion of such foreign matter.

[0106] Furthermore, for example, the first inspection unit may be configured to direct illumination light to the first region and capture an image of the first region using an imaging element disposed opposite the first region, the second inspection unit may be configured to direct illumination light to the second region and receive the reflected light to perform color detection of the second region, the third inspection unit may be configured to direct illumination light to the third region and capture an image of the third region using an imaging element disposed opposite the third region, and the fourth inspection unit may be configured to direct illumination light to the fourth region and receive the reflected light to perform color detection of the fourth region. With this configuration, even if variations in characteristics or fluctuations over time occur in the first inspection unit or the third inspection unit, correction or calibration can be performed using the color detection results of the second inspection unit and the fourth inspection unit, respectively, making it possible to perform image inspection accurately and stably.

[0107] In this case, it is preferable that the wrap angle of the print medium around the first transport roller and the wrap angle of the print medium around the third transport roller be between 2.5 degrees and 45 degrees. If the print medium wrapped around the first transport roller and the third transport roller develops wrinkles or other imperfections and floats away from these rollers, the imaging results obtained by the imaging element will be adversely affected. The inventors of this application have determined this range of wrap angles through experiments as a condition that reduces the risk of wrinkles occurring in the print medium that could affect the imaging results.

[0108] For example, the imaging element of the first inspection unit may be a one-dimensional image sensor whose longitudinal direction is the axial direction of the first transport roller, and the first region may be a band-shaped region whose longitudinal direction is the axial direction of the first transport roller. Furthermore, the imaging element of the third inspection unit may be a one-dimensional image sensor whose longitudinal direction is the axial direction of the third transport roller, and the third region may be a band-shaped region whose longitudinal direction is the axial direction of the third transport roller. With this configuration, a two-dimensional image of the print medium can be acquired by periodically capturing images of the print medium being transported. Therefore, the entire image on the print medium can be inspected.

[0109] It is desirable to inspect images printed on both sides of a print medium under the same conditions. To this end, for example, the first inspection unit and the third inspection unit may be configured identically, and the relative positional relationship between the first inspection unit and the first transport roller may be made equal to the relative positional relationship between the third inspection unit and the third transport roller. Alternatively, for example, the second transport roller and the fourth transport roller may be configured to have the same roller diameter. Alternatively, for example, the distance between the first and second regions along the first recording surface may be configured to be equal to the distance between the third and fourth regions along the second recording surface. All of these contribute to uniform inspection conditions between the first and second recording surfaces.

[0110] For example, the first transport roller and the second transport roller may be arranged adjacent to each other with no components in contact with the print medium between them, and the third transport roller and the fourth transport roller may be arranged adjacent to each other with no components in contact with the print medium between them.

[0111] Correction of the imaging results is preferably performed using color detection results for the same area as the imaged area. However, meandering and flapping of the print medium during transport can cause the positional relationship between the imaged area and the color-detected area to fluctuate. Reducing the distance between the first and second transport rollers and the distance between the third and fourth transport rollers is effective in maintaining a stable positional relationship between these areas. Furthermore, the absence of any components that come into contact with the print medium between the rollers not only maintains the positional relationship described above, but also has the effect of preventing image deterioration during transport of the print medium.

[0112] In this manner, when the distances between the first and second transport rollers and between the third and fourth transport rollers are small, a first light-shielding unit that blocks illumination light emitted by the first inspection unit and directed toward the second inspection unit may be provided between the first and second inspection units, and a second light-shielding unit that blocks illumination light emitted by the third inspection unit and directed toward the fourth inspection unit may be provided between the third and fourth inspection units. This configuration makes it possible to prevent optical interference between the first and second inspection units, and between the third and fourth inspection units, which perform inspections optically, and to maintain good inspection accuracy.

[0113] Furthermore, the transport unit of the printing device according to the present invention may be configured to transport the print medium by suspending the print medium across multiple transport rollers, including, for example, a first transport roller, a second transport roller, a third transport roller, and a fourth transport roller. In other words, the first through fourth transport rollers, which are components of the image inspection device according to the present invention, may be incorporated as part of the transport unit that transports the print medium in the printing device. For example, if a transport roller provided for the purpose of printing can be used as any of the first through fourth transport rollers of the present invention, it is possible to further reduce the footprint of the entire printing device. [Industrial Applicability]

[0114] This invention can be applied to printing devices in general that print images on both sides of a printing medium, and is particularly suitable for printing devices that inspect images printed on both main sides of a printing medium using two inspection units each. [Explanation of symbols]

[0115] 10 Printing device 22a, 22b, 26a, 26b Drive rollers (transport section) 23a, 23b Support rollers (transport section) 24a,24b Printing Department 28 Inspection unit (image inspection device, image inspection section) 31 Imaging unit (first inspection unit) 32 Colorimetric unit (second inspection unit) 33 Imaging unit (third inspection unit) 34 Colorimetric Unit (4th Inspection Unit) 35 Light shielding plate (first light shielding part) 36 Light shielding plate (second light shielding part) 280 Inspection transport unit (transport unit) 284 Transport roller (first transport roller) 285 Transport roller (second transport roller) 287 Transport roller (third transport roller) 288 Conveyor roller (fourth conveyor roller) 313 Image sensor 314 Line sensor (one-dimensional image sensor) 321 base member (first light-shielding part) 341 Base member (second light-shielding part) P Printing paper (printing media) Pa (printing paper) surface (second recording surface) Pb (back side of printing paper) (first recording surface) Rs Imaging area (1st area, 3rd area) Rc Color detection area (2nd area, 4th area) D1 First conveying direction D2 Second conveying direction

Claims

1. An image inspection device that inspects an image recorded on a first recording surface of a print medium and a second recording surface opposite to the first recording surface, a first transport roller and a second transport roller arranged at different positions in the horizontal direction, each of which wraps the print medium around itself so as to contact the second recording surface, and which transport the print medium in a first transport direction having a horizontal component; a third transport roller and a fourth transport roller arranged at different positions in the horizontal direction, each of which wraps the print medium around itself so as to contact the first recording surface, and which transport the print medium in a second transport direction having a horizontal component; a first inspection unit that optically inspects a first region of the first recording surface that is wound around the first transport roller; a second inspection unit that optically inspects a second region of the first recording surface that is wound around the second transport roller; a third inspection unit that optically inspects a third region of the second recording surface that is wound around the third transport roller; a fourth inspection unit that optically inspects a fourth region of the second recording surface that is wound around the fourth transport roller; Equipped with An image inspection device in which the printing medium transported between the first transport roller and the second transport roller and the printing medium transported between the third transport roller and the fourth transport roller at least partially overlap in a planar view.

2. The image inspection device according to claim 1 , wherein the first conveying direction and the second conveying direction have opposite horizontal component directions.

3. An image inspection device that inspects an image recorded on a first recording surface of a print medium and a second recording surface opposite to the first recording surface, a first transport roller and a second transport roller arranged at different positions in the horizontal direction, each of which wraps the print medium around itself so as to contact the second recording surface, and which transport the print medium in a first transport direction having a horizontal component; a third transport roller and a fourth transport roller arranged at different positions in the horizontal direction, each of which wraps the print medium around itself so as to contact the first recording surface, and which transport the print medium in a second transport direction having a horizontal component; a first inspection unit that optically inspects a first region of the first recording surface that is wound around the first transport roller; a second inspection unit that optically inspects a second region of the first recording surface that is wound around the second transport roller; a third inspection unit that optically inspects a third region of the second recording surface that is wound around the third transport roller; a fourth inspection unit that optically inspects a fourth region of the second recording surface that is wound around the fourth transport roller; Equipped with an image inspection device in which the pair of the first transport roller and the second transport roller is arranged above or below the pair of the third transport roller and the fourth transport roller, and the direction of the horizontal component is opposite between the first transport direction and the second transport direction.

4. the first inspection unit is disposed above the first transport roller, the second inspection unit is disposed above the second transport roller, the third inspection unit is disposed above the third transport roller, The image inspection device according to claim 1 , wherein the fourth inspection unit is disposed above the fourth transport roller.

5. the first inspection unit causes illumination light to be incident on the first region and captures an image of the first region using an image sensor disposed opposite the first region; the second inspection unit detects the color of the second area by illuminating the second area and receiving the reflected light from the second area; the third inspection unit causes illumination light to be incident on the third region and captures an image of the third region using an image sensor disposed opposite the third region; 4. The image inspection device according to claim 1, wherein the fourth inspection unit detects the color of the fourth area by illuminating the fourth area with illumination light and receiving light reflected from the fourth area.

6. The image inspection device according to claim 5 , wherein a wrap angle of the print medium with respect to the first transport roller and a wrap angle of the print medium with respect to the third transport roller are equal to or greater than 2.5 degrees and equal to or less than 45 degrees.

7. the imaging element of the first inspection unit is a one-dimensional image sensor whose longitudinal direction is the axial direction of the first transport roller, and the first region is a band-shaped region whose longitudinal direction is the axial direction of the first transport roller, 6. The image inspection device of claim 5, wherein the imaging element of the third inspection unit is a one-dimensional image sensor whose longitudinal direction is the axial direction of the third transport roller, and the third region is a strip-shaped region whose longitudinal direction is the axial direction of the third transport roller.

8. 6. The image inspection device of claim 5, wherein the first inspection unit and the third inspection unit have the same configuration, and the relative positional relationship between the first inspection unit and the first transport roller is the same as the relative positional relationship between the third inspection unit and the third transport roller.

9. The image inspection device according to claim 5 , wherein the second transport roller and the fourth transport roller have the same roller diameter.

10. 6. The image inspection device according to claim 5, wherein a distance along the first recording surface between the first area and the second area is equal to a distance along the second recording surface between the third area and the fourth area.

11. the first transport roller and the second transport roller are disposed adjacent to each other with no member in contact with the print medium therebetween; The image inspection device according to claim 5 , wherein the third transport roller and the fourth transport roller are disposed adjacent to each other with no member in contact with the print medium therebetween.

12. a first light-shielding unit that blocks the illumination light emitted from the first inspection unit and directed toward the second inspection unit is provided between the first inspection unit and the second inspection unit; The image inspection device according to claim 11, wherein a second light-shielding section is provided between the third inspection section and the fourth inspection section to block the illumination light emitted by the third inspection section and directed toward the fourth inspection section.

13. a conveying unit that conveys the print medium; a printing unit that records an image on each of a first recording surface and a second recording surface opposite to the first recording surface of the print medium being conveyed; an image inspection unit having the same configuration as the image inspection device according to any one of claims 1 to 3, and inspecting the image recorded on the print medium by the printing unit; A printing device comprising:

14. The printing device according to claim 13 , wherein the transport unit transports the print medium by placing the print medium over a plurality of transport rollers including the first transport roller, the second transport roller, the third transport roller, and the fourth transport roller.

15. 1. An image inspection method for inspecting an image recorded on a first recording surface and a second recording surface opposite to the first recording surface of a print medium, comprising: The print medium is transported in a first transport direction having a horizontal component by a first transport roller and a second transport roller that are arranged at different positions in the horizontal direction and around which the print medium is wound so as to contact the second recording surface, and a third transport roller and a fourth transport roller, which are arranged at different positions in the horizontal direction and around which the print medium is wound so as to contact the first recording surface, transport the print medium in a second transport direction having a horizontal component opposite to the first transport direction; a first inspection unit optically inspecting a first region of the first recording surface that is wound around the first transport roller; a second inspection unit optically inspecting a second region of the first recording surface that is wound around the second transport roller; a third inspection unit optically inspecting a third region of the second recording surface that is wound around the third transport roller; a fourth region of the second recording surface wound around the fourth transport roller is optically inspected by a fourth inspection unit; and An image inspection method, in which a transport path of the printing medium between the first transport roller and the second transport roller and a transport path of the printing medium between the third transport roller and the fourth transport roller are at least partially overlapped in a planar view.

Images