Image inspection apparatus and printing apparatus

Abstract

To prevent deterioration in measurement accuracy due to the influence of stray light in a technique for inspecting an image recorded on a print medium by using an imaging part and a colorimetric part.SOLUTION: In the image inspection apparatus and the printing apparatus according to the aspects of the invention, the printing medium is supported by being stretched between the first roller and the second roller. An imaging unit that images an imaging region by causing illumination light to be incident on a portion of the printing medium wound around the first roller and receiving reflected light from the imaging region on which the illumination light is incident, a colorimetry unit that performs color detection of a color detection region by causing the illumination light to be incident on a portion of the printing medium wound around the second roller and receiving light reflected from the color detection region on which the illumination light is incident and incident on a light receiver, and a light shielding unit that is disposed between the imaging unit and the light receiver on a first main surface side of the printing medium stretched between the first roller and the second roller and shields light from the imaging unit toward the light receiver.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image inspection device that inspects an image recorded on the surface of a printing 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 Documents 1 to 3 each disclose a technology for optically inspecting an image recorded on a long web of print media that is stretched over and transported by multiple rollers. In these technologies, the image is inspected using two types of optical detection means.

[0003] Specifically, the surface of the print medium is imaged by an imaging unit having an imaging element such as a line scanner. Then, in order to evaluate the imaged result using a more accurate color standard, a color measurement unit (colorimeter) detects the color of the print medium surface, and the imaged result is calibrated based on the result.

[0004] For example, in the technology described in Patent Document 1, an imaging unit and a colorimeter are respectively positioned to face two rollers that are arranged adjacent to each other and around which the print medium is wound. Also, in the technology described in Patent Document 2, both the imaging unit and the colorimeter are positioned to face a single roller around which the print medium is wound. Furthermore, in the technology described in Patent Document 3, a colorimeter is provided to face the roller around which the print medium is wound after being imaged by the imaging unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-149111 [Patent Document 2] Patent No. 3770328 [Patent Document 3] Patent No. 7367521 Summary of the Invention [Problem to be solved by the invention]

[0006] This type of inspection technology has the following problem that is not recognized in the above-mentioned conventional technology. The imaging unit and colorimetric unit each have a light source for illuminating the surface of the print medium, and stray light from these illumination lights can enter the print medium surface or the light-receiving element, resulting in measurement errors. In particular, in a colorimetric unit that operates under the assumption that the target object is illuminated with a specified amount of light, stray light from the imaging unit, which has a relatively large amount of illumination light, can reduce measurement accuracy.

[0007] Regarding this issue, the prior art described in Patent Documents 1 and 2 fails to consider the impact of stray light. In particular, in the technology described in Patent Document 2, imaging and colorimetry are performed on the same roller, making the impact of stray light particularly pronounced. Furthermore, in the prior art described in Patent Document 3, a roller disposed between the imaging unit and the colorimetry unit can be considered to have some effect in blocking stray light. However, because the roller contacts the surface of the print medium (image recording surface), changes in the image occur between the position facing the imaging unit and the position facing the colorimetry unit. Given the measurement principle of calibrating the imaging results of the imaging unit using the detection results of the colorimetry unit, this still results in a decrease in measurement accuracy. Furthermore, Patent Document 3 makes no mention of the impact of stray light on measurement accuracy.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to prevent a decrease in measurement accuracy due to the influence of stray light in a technology for inspecting images recorded on a printing medium using an imaging unit and a colorimetric unit. [Means for solving the problem]

[0009] One aspect of the present invention is an image inspection device for inspecting an image recorded on a first main surface of a print medium, the image inspection device having a first roller and a second roller that respectively contact a second main surface of the print medium opposite the first main surface, the print medium being wound between the first roller and the second roller, and a support unit that supports the print medium with no member in contact with the first main surface between the first roller and the second roller; and a light source disposed opposite the first roller that directs first illumination light onto the first main surface of the portion of the print medium wound around the first roller, and the first illumination light being incident on the first main surface of the portion of the print medium that is wound around the first roller. a colorimetric unit that is disposed opposite the second roller and that directs second illumination light onto the first main surface of the portion of the printing medium that is wound around the second roller, receives light that is reflected from a color detection region within the region onto which the second illumination light is incident and enters a light receiver, and performs color detection of the color detection region; and a light shielding unit that is disposed between the imaging unit and the light receiver on the first main surface side of the printing medium that is stretched between the first roller and the second roller and that shields light that travels from the imaging unit to the light receiver.

[0010] Another aspect of the present invention is an image inspection device for inspecting an image recorded on a first main surface of a print medium, the image inspection device being arranged to face the first main surface of a portion of the print medium wound around a first roller and a second roller, each of which is in contact with a second main surface of the print medium opposite the first main surface, with no member in contact with the first main surface between the first roller and the second roller, and illuminating first illumination light onto the first main surface and receiving reflected light from an imaging area within the area where the first illumination light is incident. The device is equipped with an imaging unit that images the imaging area, a colorimetric unit that is arranged opposite the first main surface of the portion of the printing medium that is wrapped around the second roller and that causes second illumination light to be incident on the first main surface, receives light that is reflected from a color detection area within the area where the second illumination light is incident and enters a photodetector, and performs color detection of the color detection area, and a light blocking unit that is arranged between the imaging unit and the photodetector on the first main surface side of the printing medium that is stretched between the first roller and the second roller and blocks light that travels from the imaging unit to the photodetector.

[0011] In the invention configured in this manner, an imaging unit and a colorimetric unit are provided facing the first roller and the second roller, respectively. Between the first roller and the second roller, there is no component that comes into contact with the first main surface (the surface on which the image is recorded) of the print medium. A light-shielding unit is disposed between the imaging unit and the light receiver of the colorimetric unit to block stray light.

[0012] More specifically, the light-shielding section is provided to prevent the first illumination light emitted from the imaging section from entering the light receiver of the colorimetry section. This prevents stray light resulting from the first illumination light from entering the light receiver and causing a decrease in measurement accuracy in the colorimetry section. By maintaining good measurement accuracy in the colorimetry section, excellent accuracy can also be ensured for the imaging results in the imaging section. Furthermore, because there is no component that comes into contact with the first main surface of the print medium between the first roller and the second roller, a decrease in measurement accuracy due to image deterioration caused by such contact can also be prevented.

[0013] Another aspect of the present invention is a printing device including a transport unit that transports a print medium, a printing unit that records an image on a first main surface of the transported print medium, and an image inspection unit that has the same configuration as the image inspection device described above and inspects the image recorded on the print medium by the printing unit. With this configuration, it is possible to accurately inspect the image recorded on the print medium while suppressing the effects of stray light as described above. [Effects of the Invention]

[0014] As described above, according to the present invention, the light-shielding section prevents stray light caused by the first illumination light emitted from the imaging section from entering the light receiver of the colorimetric section, and also prevents deterioration of the image due to contact of any member with the first main surface of the print medium. Therefore, it is possible to properly inspect the image recorded on the first main surface of the print medium while preventing a decrease in measurement accuracy due to the influence of stray light. [Brief explanation of the drawings]

[0015] [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] 2A and 2B 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] 1A and 1B are diagrams illustrating the optical path of stray light and the principle of blocking it. [Figure 8] 10A and 10B are diagrams showing modified examples of the configuration for blocking stray light. [Figure 9] FIG. 10 is a diagram showing a modified example of the second printing mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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.

[0017] If the printing paper P after double-sided printing is to be 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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."

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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)).

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Furthermore, in 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 along the width direction of the printing paper P, and this also has the function of blocking stray light. By positioning the bottom end of the base member 321 as close as possible to the printing paper P, it is possible to further improve the light blocking function, particularly for light reflected by the printing paper P.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] That is, as shown in FIG. 4, in the section of the transport path for print paper P formed by inspection transport section 280 from transport roller 283 to transport roller 285, the transport direction of print paper P has a horizontal component in the (+X) direction. In this section, print paper P is transported with its back surface Pb facing upward. On the other hand, the transport path is folded back by transport rollers 285 and 286, and in the section from transport roller 286 to transport roller 288, the transport direction of print paper P has a horizontal component in the (-X) direction. Print paper P is transported with its front surface Pa facing upward. With this configuration, it is possible to inspect both the images formed on the front surface Pa and back surface Pb of print paper P using the imaging section 31 and colorimeter 37, which are arranged above and facing downward of print paper P.

[0080] The set of transport rollers 286-288 is disposed below the set of transport rollers 283-285. Therefore, the transport path formed by transport rollers 283-285 and the transport path formed by transport rollers 286-288 are separated in the vertical direction and overlap each other in a plan view. Therefore, the area of ​​the footprint occupied by these two sections of the transport path is substantially the same as that of one section. In this way, the footprint is reduced.

[0081] Next, we will explain in more detail the problem of optical interference that may occur in this embodiment between the imaging unit 31 and the colorimetric unit 32, and between the imaging unit 33 and the colorimetric unit 34. As described above, in this embodiment, a light shielding plate 35 is disposed between the imaging unit 31 and the colorimetric unit 32, and a light shielding plate 36 is disposed between the imaging unit 33 and the colorimetric unit 34. These are provided for the purpose of preventing stray light of the illumination light emitted from the imaging units 31 and 33 from entering the colorimetric units 32 and 34.

[0082] 7 is a diagram illustrating the optical path of stray light and the principle of blocking it. Here, we consider a case where illumination light emitted from the image capture unit 31 enters the colorimetric unit 32 as stray light, but the same thing can happen between the image capture unit 33 and the colorimetric unit 34. For example, a white LED or lamp can be used as the illumination light source 311 of the image capture unit 31, but since it is intended simply for illumination, the light emitted from these light sources has a relatively wide spread.

[0083] As shown in FIG. 7(a), the light emitted from the illumination light source 311 and directed toward the light receiver 372 of the colorimeter 37 includes the following: (1) Light La going directly from the illumination light source 311 to the light receiver 372; (2) Light (primary reflected light) Lb that is specularly reflected by the upper surface (rear surface Pb) of the printing paper P and travels toward the light receiver 372; (3) Reflected light Lc from the casing and reinforcing metal fittings of the printer body 200, the conveying roller 285, and the reflective member 201 arranged near the colorimeter 37; (4) Light Ld that is incident from the illumination light source 311 onto the color detection area Rc on the printing paper P and is reflected from the color detection area Rc and incident on the light receiver 372; According to the knowledge of the inventors of the present application, the influence of these factors on the color detection results of the colorimeter 37 is generally greatest in the above order.

[0084] 7(b), in this embodiment, a light shielding plate 35 is disposed between the imaging unit 31 and the colorimeter 32, more specifically, between the colorimeter 37, and light emitted from the illumination light source 311 that could become stray light is blocked by the light shielding plate 35. The light shielding plate 35 is a plate-like member that extends in the Y direction, similar to the line sensor 314, and has a light-blocking effect over the entire width direction (Y direction) of the printing paper P. This prevents stray light emitted from the illumination light source 311 from heading toward the light receiver 372 of the colorimeter 37.

[0085] The light shielding plate 35 is provided in a position where it can block at least the light La that is directed directly from the illumination light source 311 toward the light receiver 372. More preferably, it is provided in a position where it can additionally block the light Lb that is primarily reflected by the printing paper P and directed toward the light receiver 372. Even more preferably, it is provided in a position where it can additionally block the light Lc that is directed from the illumination light source 311 toward the reflective member 201. If the light shielding plate 35 is provided in a position where it can block the light Lb that is primarily reflected by the printing paper P and directed toward the light receiver 372, it is thought that it will naturally be able to block the light Ld that is directed from the illumination light source 311 toward the color detection region Rc as well.

[0086] On the other hand, because there is a small gap between the light shielding plate 35 and the printing paper P, some light may pass through the gap, be reflected by the printing paper P, and travel toward the colorimeter 37. In this embodiment, the base member 321 of the support mechanism 320 (FIG. 6) that supports the colorimeter 37 has the function of blocking such light. That is, the support member 321 is a flat member that extends in the width direction (Y direction) of the printing paper P, and its upper surface is inclined from the horizontal toward the (+X) side. The lower end of the support member 321 is disposed close to the upper surface (back surface Pb) of the printing paper P. For example, the distance between the lower end of the base member 321 and the printing paper P can be made smaller than the distance between the lower end of the light shielding plate 35 and the printing paper P.

[0087] With this configuration, the base member 321 can block light that is incident on the printing paper P from below the light shielding plate 35 and reflected therefrom. This makes it possible to more effectively suppress the effects of stray light. In principle, the base member 321 can perform all of the functions of the light shielding plate 35. That is, if the shape and position of the base member 321 are configured to satisfy the above-mentioned conditions for installing the light shielding unit, the base member 321 will function as an alternative light shielding unit, making it possible to omit the light shielding plate 35. However, separating these functions allows for greater freedom in the shape and placement of each. Furthermore, by using both the light shielding plate 35 and the base member 321, which also functions as a light shielding member, to form a light shielding unit, the light shielding effect will be improved.

[0088] 7(a), with regard to the light reflected from the reflective member 201, the housing of the colorimeter 37 is tilted counterclockwise around the Y axis, so that the housing itself has the function of blocking light coming toward the light receiver 372 from the (+X) side of the colorimeter 37. This has a synergistic effect with the function of the light shielding plate 35 blocking the light going from the illumination light source 311 toward the reflective member 201, making it possible to effectively suppress the incidence of stray light through the reflective member 201 into the light receiver 372.

[0089] Figure 8 shows a modified example of the configuration for blocking stray light. In this modified example, a roller member 38 that contacts printing paper P from below is provided between transport rollers 284, 285. Roller member 38 is positioned so as to push printing paper P upward. More specifically, roller member 38 is positioned so that the upper end of roller member 38 protrudes above a plane that includes illumination light source 311 and light receiver 372, which is shown by a dashed line in Figure 8.

[0090] As a result, the printing paper P is supported in a convex shape in the section from the transport roller 284 to the transport roller 285. In other words, the top surface (back surface Pb) of the printing paper P has a positive curvature in this section. The roller member 38 and the printing paper P wrapped around it function to block light from the illumination light source 311 toward the light receiver 372. Stray light that enters the printing paper P is reflected in a direction away from the light receiver 372. In other words, in this modified example, the roller member 38 and the printing paper P wrapped around it function as a "light blocking section." Of course, even in this case, it is effective to also provide the light blocking plate 35. Furthermore, since the provision of the roller member 38 in the transport path changes the wrap angle of the printing paper P around the transport rollers 284 and 285, adjustments may be required regarding the arrangement of each roller.

[0091] If the sole purpose is to block light, it is also possible to provide a roller member that contacts the top surface (back surface Pb) of the printing paper P as the light-blocking section. This would eliminate the gap between the roller member and the printing paper P, thereby increasing the light-blocking effect. However, because the roller member comes into contact with the images to be inspected between the imaging unit 31 and the colorimetry unit 32, the consistency of the images could be lost, resulting in a decrease in inspection accuracy. It is desirable that there be no members that come into contact with the images between the imaging unit 31 and the colorimetry unit 32.

[0092] Although only the influence of the illumination light source 311 provided in the imaging unit 31 has been considered here, the influence from the other illumination light source 312 can also be addressed in a similar manner. That is, the shape and position of the light shielding plate 35 and the like can be determined appropriately depending on the number and arrangement of illumination light sources provided in the imaging unit 31, their light distribution characteristics, etc. The influence of stray light from the imaging unit 33 on the colorimetric unit 34 can also be considered in the same way as above.

[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.

[0097] Furthermore, of the inspection transport section 280, the pair of transport rollers 284, 285 and the pair of transport rollers 287, 288 each function as a "support section" of the present invention. In the pair of transport rollers 284, 285, the transport roller 284 corresponds to the "first roller" of the present invention, and the transport roller 285 corresponds to the "second roller" of the present invention. In this case, the back surface Pb of the printing paper P corresponds to the "first main surface" of the present invention, and the front surface Pa corresponds to the "second main surface". On the other hand, in the pair of transport rollers 287, 288, the transport roller 287 corresponds to the "first roller" of the present invention, and the transport roller 288 corresponds to the "second roller" of the present invention. In this case, conversely to the above, the front surface Pa of the printing paper P corresponds to the "first main surface" of the present invention, and the back surface Pb corresponds to the "second main surface".

[0098] Furthermore, the imaging units 31 and 33 each function as the "imaging unit" of the present invention, and the colorimetric units 32 and 34 each function as the "colorimetric unit" of the present invention. Furthermore, the line sensor 314 corresponds to the "one-dimensional image sensor" of the present invention, and the imaging element 313 corresponds to the "imaging element" of the present invention. Furthermore, the light shielding plates 35 and 36 function as the "light shielding unit" of the present invention. Furthermore, the roller member 38 in the modified example corresponds to the "third roller" and "light shielding unit" of the present invention.

[0099] Furthermore, the colorimeter 37 corresponds to the "colorimeter" of the present invention, and the support mechanism 320 that supports it corresponds to the "colorimeter support mechanism" of the present invention. The base member 321 of the support mechanism 320 functions as the "light-blocking member" of the "light-blocking section" of the present invention. Furthermore, the light receiver 372 of the colorimeter 37 corresponds to the "light receiver" of the present invention. Furthermore, the illumination light L1, L2 emitted by the imaging units 31, 33 corresponds to the "first illumination light" of the present invention, and the illumination light L5 emitted by the colorimeter units 32, 33 corresponds to the "second illumination light" of the present invention.

[0100] 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.

[0101] 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 embodiment, the imaging unit and colorimetric unit are arranged in this order along the transport direction of the printing paper P. However, this order is not limited, and for example, the colorimetric unit may be arranged upstream of the imaging unit.

[0102] Also, for example, in this embodiment, a reversing unit 27 that reverses the print paper P is disposed between the first printing mechanism 20a that prints an image on the front side Pa of the print paper P and the second printing mechanism 20b that prints an image on the back side 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 printing mechanism in which a printing unit is disposed on each side of the print medium. The present invention is also applicable to printing devices that record images on only one side of the print medium.

[0103] 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.

[0104] 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.

[0105] As described above with reference to specific embodiments, in the image inspection device according to the present invention, for example, the light-shielding unit is preferably positioned to block the optical path of the first illumination light that travels directly from the imaging unit to the light receiver. Furthermore, for example, the light-shielding unit is more preferably positioned to block the optical path of the primary reflected light of the first illumination light that is incident on the first main surface of the print medium between the first roller and the second roller and travels toward the colorimetric unit. Furthermore, the light-shielding unit is more preferably positioned to block the optical path of the reflected light of the first illumination light that is reflected by a member located on the opposite side of the colorimetric unit from the imaging unit and travels toward the light receiver. Furthermore, the light-shielding unit is more preferably positioned to block the optical path from the imaging unit to the color detection area. Any of these types of light can cause a decrease in color detection accuracy when they enter the light receiver. By blocking such light with the light-shielding unit, it is possible to effectively prevent a decrease in inspection accuracy.

[0106] For example, the imaging area may be a strip-shaped area extending longitudinally along the axial direction of the first roller, and the imaging unit may be a one-dimensional image sensor extending along the axial direction. 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.

[0107] In this case, it is preferable that the light-shielding unit has a plate-like member that extends from one end of the print medium to the other along the axial direction of the second roller. With this configuration, even if the area illuminated by the imaging unit spreads along the axial direction, the plate-like member can effectively block it.

[0108] Furthermore, for example, the colorimeter unit may include a colorimeter provided with a light receiver and performing color detection, and a colorimeter support mechanism that is positioned closer to the imaging unit than the colorimeter and supports the colorimeter while facing the print medium wound around the second roller, and a light-shielding member that functions as a light-shielding unit may be provided in the colorimeter support mechanism. With this configuration, stray light traveling from the imaging unit toward the light receiver of the colorimeter can be blocked by the light-shielding member provided in the colorimeter support mechanism.

[0109] For example, the imaging unit may be configured such that an imaging element that receives reflected light from the imaging area is positioned above the first roller and faces downward, while the colorimetric unit may be configured such that a light receiver is positioned above the second roller and faces downward. With this configuration, the imaging unit and colorimetric unit each inspect the print medium from top to bottom. Foreign matter such as paper dust inevitably occurs along the print medium transport path. If such foreign matter adheres to the imaging unit or colorimetric unit, it may interfere with optical inspection. By arranging these units facing downward, it is possible to reduce the adhesion of such foreign matter.

[0110] For example, a third roller may be provided between the first and second rollers to contact the second main surface of the print medium and impart a positive curvature to the first main surface, and at least one of the third roller and the print medium wrapped around it may form a light-blocking section. With this configuration, by providing the third roller so as to block the optical path of stray light traveling from the imaging section to the light receiver, it is possible to prevent such stray light from entering the light receiver.

[0111] Furthermore, the transport unit of the printing device according to the present invention may be configured to transport the print medium by placing the print medium across multiple transport rollers, including, for example, a first roller and a second roller. In other words, the first and second 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 at least one of the first and second rollers of the present invention, it would be possible to further reduce the footprint of the entire printing device. [Industrial Applicability]

[0112] This invention can be applied to printing devices in general that inspect images on the surface of a printing medium using an imaging unit and a colorimetric unit, and is particularly suitable for preventing interference caused by stray light that may occur between them. [Explanation of symbols]

[0113] 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) 31,33 Imaging unit 32,34 Color measurement section 35, 36 Light shielding plate (light shielding part) 37 Colorimeter 38 Roller member (third roller, light-shielding part) 284, 287 Conveyor roller (first roller, conveyor section) 285, 288 Transport roller (second roller, transport section) 313 Image sensor 314 Line sensor (one-dimensional image sensor) 320 Support mechanism (colorimeter support mechanism) 321 Base material (light-shielding part, light-shielding material) 372 Photoreceiver L1, L2 Illumination light (first illumination light) L5 Illumination light (second illumination light) P Printing paper (printing media)

Claims

1. An image inspection device that inspects an image recorded on a first main surface of a print medium, comprising: a support section having a first roller and a second roller that respectively contact a second main surface of the print medium opposite to the first main surface, the support section supporting the print medium with the print medium stretched between the first roller and the second roller and with no member in contact with the first main surface between the first roller and the second roller; an imaging unit disposed opposite the first roller, irradiating the first main surface of the portion of the print medium wound around the first roller with first illumination light, receiving reflected light from an imaging area within the area where the first illumination light is incident, and imaging the imaging area; a color measurement unit disposed opposite the second roller, which projects second illumination light onto the first main surface of the portion of the print medium that is wound around the second roller, receives light that is reflected from a color detection area within the area onto which the second illumination light is incident and enters a light receiver, and performs color detection of the color detection area; a light-shielding section that is disposed between the imaging section and the light receiver on the first main surface side of the print medium stretched between the first roller and the second roller, and that blocks light from the imaging section toward the light receiver; An image inspection device comprising:

2. An image inspection device that inspects an image recorded on a first main surface of a print medium, comprising: an imaging unit that is disposed opposite the first main surface of a portion of the printing medium that is wound around a first roller and a second roller that are in contact with a second main surface of the printing medium opposite the first main surface, with no member in contact with the first main surface between the first roller and the second roller, and that causes first illumination light to be incident on the first main surface and receives reflected light from an imaging area within the area where the first illumination light is incident, thereby imaging the imaging area; a colorimetric unit disposed opposite the first main surface of the portion of the print medium wound around the second roller, irradiating the first main surface with second illumination light, receiving light reflected from a color detection region within the region onto which the second illumination light is incident and incident on a light receiver, and detecting the color of the color detection region; a light-shielding section that is disposed between the imaging section and the light receiver on the first main surface side of the print medium stretched between the first roller and the second roller, and that blocks light from the imaging section toward the light receiver; An image inspection device comprising:

3. The image inspection device according to claim 1 or 2, wherein the light blocking section is disposed at a position where it blocks an optical path of the first illumination light that travels directly from the imaging section to the light receiver.

4. 3. The image inspection device according to claim 1, wherein the light-shielding portion is positioned at a position that blocks the optical path of the primary reflected light of the first illumination light that is incident on the first main surface of the printing medium between the first roller and the second roller, toward the optical receiver.

5. 3. The image inspection device according to claim 1, wherein the shading section is positioned at a position that blocks the optical path of the first illumination light reflected by a member provided on the opposite side of the colorimetric section from the imaging section toward the optical receiver.

6. The image inspection device according to claim 1 or 2, wherein the light blocking section is disposed at a position where it blocks a light path from the imaging section toward the color detection area.

7. 3. The image inspection device according to claim 1, wherein the imaging area is a strip-shaped area extending in the axial direction of the first roller, and the imaging unit is a one-dimensional image sensor extending along the axial direction.

8. The image inspection device according to claim 7 , wherein the light blocking portion has a plate-like member extending from one end to the other end of the print medium along the axial direction of the second roller.

9. The color measurement unit 3. The image inspection device according to claim 1, further comprising: a colorimeter that is provided with the light receiver and performs color detection; and a colorimeter support mechanism that is positioned closer to the imaging unit than the colorimeter and supports the colorimeter while facing the printing medium wound around the second roller, wherein a light-shielding member that serves as the light-shielding section is provided on the colorimeter support mechanism.

10. In the imaging unit, an imaging element that receives reflected light from the imaging area is disposed above the first roller and faces downward, The image inspection device according to claim 1 or 2, wherein in the color measurement unit, the light receiver is disposed above the second roller and facing downward.

11. 3. The image inspection device of claim 1, further comprising a third roller that contacts the second main surface of the printing medium between the first roller and the second roller to impart a positive curvature to the first main surface, and at least one of the third roller and the printing medium wrapped around it forms the light-shielding portion.

12. a conveying unit that conveys the print medium; a printing unit that records an image on a first main surface of the transported print medium; an image inspection unit having the same configuration as the image inspection device according to claim 1 or 2, and inspecting the image recorded on the print medium by the printing unit; A printing device comprising:

13. The printing device according to claim 12 , wherein the transport section transports the print medium by placing the print medium over a plurality of transport rollers including the first roller and the second roller.

Images