Image inspection device, image inspection method and image inspection program

Abstract

To more reliably detect a defect in a read image being the source of a reference image used in an image inspection, and facilitate identification of a cause of an abnormality and resolution.SOLUTION: An image formation apparatus 1 according to an aspect of the present invention includes: an image reading unit 26 which reads a printed matter to generate a read image; an image inspection unit 29 which compares a reference image previously generated on the basis of the read image of the printed matter with the read image of the printed matter based on a print job to perform an image inspection of the printed matter; and a control unit 40 which performs an image inspection on the read image being the source of the reference image by executing at least one of detection of a defect with higher detection accuracy than detection accuracy in the image inspection on the printed matter based on the print job and modification of the target range where the image inspection is performed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image inspection device, an image inspection method, and an image inspection program. [Background technology]

[0002] Image forming apparatuses are required to provide printed matter that is free of defects such as stains, and image inspection is performed to check for the presence or absence of defects in printed matter. Image inspection is performed by comparing a reference image with a scanned image of the printed matter, but if the reference image itself contains stains, image inspection cannot be performed appropriately.

[0003] Patent Document 1 discloses a technique for calculating the degree of difficulty in repairing anomalies based on anomalies detected from a candidate inspection reference image, setting an anomaly repair method based on the degree of difficulty in repairing anomalies, and repairing the anomalies in the candidate inspection reference image based on the anomaly repair method. According to the technique described in Patent Document 1, even if a scanned image of a raster image, which is a candidate for a reference image, contains an anomaly, the anomaly is repaired. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-215284 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the cause of the abnormality lies in the image formation process, the abnormality can be eliminated by automatic repair corresponding to the image formation process or regeneration of the inspection reference image, but if the cause of the abnormality is the contact of a mechanical part with the paper, the abnormality will be repeatedly detected even if regeneration is performed. In this case, it may take time to determine the cause of the abnormality, or printing to determine the cause may result in paper waste, which may consume materials (printing media, ink, etc.).

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to more reliably detect image defects in a read image that is the basis of a reference image used in image inspection, thereby making it easier to identify and resolve the causes of the above-mentioned abnormalities. [Means for solving the problem]

[0007] In order to solve the above problem, an image inspection device embodying one aspect of the present invention includes an image reading unit that reads a printed material on which an image is formed and generates a read image, an image inspection unit that performs image inspection to detect the presence or absence of defects in the printed material by comparing a reference image generated in advance based on the read image of the printed material with the read image of the printed material based on a print job, and a control unit that performs image inspection of the read image that is the basis of the reference image by performing at least one of the following: detection of defects with a detection accuracy higher than the detection accuracy in image inspection of printed material based on a print job, and changing the target range for image inspection. Effect of the Invention

[0008] According to the present invention, it is possible to more reliably detect image defects in a scanned image that is the basis of a reference image used in image inspection, and to easily identify and solve the cause of the abnormality. Problems, configurations, and effects other than those described above will become apparent from the description of the following embodiments. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic diagram showing a configuration of a head unit according to one embodiment of the present invention. [Diagram 3] 2 is a block diagram showing an example of the configuration of a control system of the image forming apparatus according to the embodiment of the present invention; [Figure 4] 1 is a diagram showing an overview of a defect detection accuracy improvement process when performing image inspection for generating a reference image according to an embodiment of the present invention; [Diagram 5] 11A and 11B are diagrams illustrating an example of a correspondence between the arrangement positions of the transport members in the paper width direction according to an embodiment of the present invention and the formation patterns of stains or scratches on the paper caused by these transport members. [Figure 6] 10 is a flowchart showing an example of a procedure of image inspection processing for a basic image by an image forming apparatus according to an embodiment of the present invention. [Figure 7] 10 is a flowchart showing an example of a procedure of image inspection processing for a basic image by an image forming apparatus according to a modified example of an embodiment of the present invention. [Figure 8] 5 is a flowchart illustrating an example of a procedure for printing and image inspection processing based on a print job according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, examples of embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions or configurations are given the same reference numerals, and duplicated descriptions of the components will be omitted. First, before describing configuration examples of various embodiments, the above-mentioned problems to be solved by the present invention will be described in more detail.

[0011] <General configuration of image forming device> First, the overall configuration of an image forming apparatus 1 according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing an example of the overall configuration of the image forming apparatus 1. The image forming apparatus 1 shown in Fig. 1 is an image forming apparatus that forms (records) an image on paper by an inkjet method, and includes a paper feed section 10, an image forming section 20, a paper discharge section 30, and a control section 40 (Fig. 3).

[0012] The image forming apparatus 1 (an example of an image inspection apparatus) transports paper Sh stored in the paper feed section 10 to the image forming section 20 under the control of the control section 40 shown in Fig. 3, forms an image on the paper Sh in the image forming section 20, and transports the paper Sh on which the image has been formed to the paper discharge section 30. Note that in this embodiment, an example is given in which the print medium on which the image forming apparatus 1 forms an image is paper such as plain paper or coated paper, but the present invention is not limited to this. The print medium on which the image forming apparatus 1 forms an image can be various print media such as fabric or sheet-like resin, on whose surface the ink that has landed can be fixed.

[0013] The paper feed unit 10 has a paper feed tray 11 that stores paper sheets Sh, and a medium supply unit 12 that transports and supplies paper sheets Sh from the paper feed tray 11 to the image forming unit 20. The medium supply unit 12 has a ring-shaped belt 123 supported on the inside by two rollers 121 and 122, and transports the paper sheets Sh from the paper feed tray 11 to the image forming unit 20 by rotating the rollers with the paper sheets Sh placed on the belt 123.

[0014] The image forming section 20 includes a conveying section 21, a delivery unit 22, a heating section 23, a head unit 24, a fixing section 25, an image reading section 26, a delivery section 27, and an inverting section 28.

[0015] The conveying section 21 holds the paper Sh placed on the conveying surface 211a of a cylindrical conveying drum 211, and performs a conveying operation by rotating and circularly moving the conveying drum 211 around a rotation axis (cylindrical axis) extending in the X direction, thereby conveying the conveying drum 211 and the paper Sh on the conveying drum 211 in the conveying direction (Y direction).

[0016] The transport drum 211 has claws and an air intake section (not shown) for holding the paper Sh on the transport surface 211a. The paper Sh is held on the transport surface 211a by having its edges pressed down by the claws and being drawn to the transport surface 211a by the air intake section. The transport section 21 is connected to a transport drum motor (not shown) for rotating the transport drum 211, and the transport drum 211 rotates by an angle proportional to the amount of rotation of the transport drum motor.

[0017] The delivery unit 22 is provided at a position between the medium supply unit 12 of the paper feed unit 10 and the transport unit 21. The delivery unit 22 has a swing arm unit 221 that holds one end of the paper Sh transported from the medium supply unit 12, and a delivery drum 222 that delivers the paper held by the swing arm unit 221 to the transport unit 21.

[0018] The heating section 23 is provided between the position where the delivery drum 222 is disposed and the position where the head unit 24 is disposed, and heats the paper Sh transported by the transport section 21 so that the temperature of the paper Sh falls within a predetermined temperature range. The heating section 23 has, for example, an infrared heater (not shown) and causes the infrared heater to generate heat by passing electricity therethrough based on a control signal supplied from the CPU 41 (FIG. 3).

[0019] The head unit 24 forms an image by ejecting ink onto the paper Sh from nozzle openings provided on an ink ejection surface facing the transport surface 211a of the transport drum 211 at appropriate timing according to the rotation of the transport drum 211 holding the paper Sh. The head unit 24 is disposed so that the ink ejection surface and the transport surface 211a are separated by a predetermined distance. In the image forming apparatus 1 of this embodiment, four head units 24 corresponding respectively to four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K), are arranged at predetermined intervals from the upstream side in the transport direction of the paper Sh in the order of Y, M, C, and K.

[0020] Here, the configuration of the head unit 24 will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the configuration of the head unit 24. Fig. 2 shows the surface of the head unit 24 that faces the transport surface 211a of the transport drum 211.

[0021] The head unit 24 includes four recording heads 242 attached to a mounting member 244. Each of the recording heads 242 includes a pressure chamber for storing ink, a piezoelectric element provided on the wall of the pressure chamber, and a plurality of recording elements (all not shown), each of which includes a nozzle 243. When a drive signal for deforming the piezoelectric element is input, the pressure chamber is deformed by the deformation of the piezoelectric element, the pressure in the pressure chamber changes, and ink is ejected from the nozzle communicating with the pressure chamber. The recording head 242 includes two nozzle rows formed of nozzles 243 arranged at equal intervals in a direction intersecting the transport direction of the paper Sh (in this embodiment, a direction perpendicular to the transport direction, i.e., the X direction). These two nozzle rows are arranged such that the arrangement positions of the nozzles 243 are shifted from each other in the X direction by half the arrangement interval of the nozzles 243 in each nozzle row.

[0022] The four recording heads 242 are arranged in a staggered pattern so that the arrangement range of the nozzle rows in the X direction is continuous without any breaks. The arrangement range of the nozzles 243 included in the head unit 24 in the X direction covers the width in the X direction of the area where an image is formed on the paper Sh transported by the transport unit 21, and the head unit 24 is used with its position fixed relative to the rotation axis of the transport drum 211 when forming an image. That is, the head unit 24 has a line head capable of ejecting ink over the image formable width in the X direction on the paper Sh, and the image forming apparatus 1 is a single-pass type image forming apparatus. The number of nozzle rows included in the recording head 242 may be one or three or more. The number of recording heads 242 included in the head unit 24 may be three or less or five or more.

[0023] The ink ejected from the nozzles of the recording element has a property of changing into a gel or sol state depending on the temperature and curing by irradiation with energy rays such as ultraviolet rays. In this embodiment, ink that is in a gel state at room temperature and becomes a sol state when heated is used. The head unit 24 has an ink heating section (not shown) that heats the ink stored in the head unit 24, and the ink heating section operates under the control of the CPU 41 to heat the ink to a temperature at which the ink becomes a sol. The recording head 242 ejects the ink that has been heated and turned into a sol state. When this sol-state ink is ejected onto the paper Sh, the ink droplets land on the paper Sh, and then the ink quickly turns into a gel state and solidifies on the paper Sh due to natural cooling.

[0024] 1, the explanation will be continued. The fixing unit 25 has a light-emitting unit (not shown) arranged across the width of the transport unit 21 in the X direction, and cures and fixes the ink ejected onto the paper Sh by irradiating the paper Sh placed on the transport unit 21 with energy rays such as ultraviolet rays from the light-emitting unit. The light-emitting unit of the fixing unit 25 is arranged to face the transport surface 211a between the position where the head unit 24 is arranged and the position where the delivery drum 271 of the delivery unit 27 is arranged in the transport direction.

[0025] The image reading unit 26 is disposed so as to be able to read the surface of the paper Sh on the transport surface 211a at a position in the transport direction between the position where the ink is fixed by the fixing unit 25 and the position where the delivery drum 271 is disposed. In this embodiment, the image reading unit 26 reads the surface of the paper Sh transported by the transport unit 21, and outputs the read image obtained by reading it to the control unit 40 (see FIG. 3).

[0026] When a normal print job is executed, the read image output to the control unit 40 is read by the image inspection unit 29 (see FIG. 3) and compared with a reference image stored in the storage unit 44 (see FIG. 3) to check for defects. The reference image is generated prior to the execution of a normal print job, and is composed of a read image read by the image reading unit 26 of a printout that is test printed by the image forming unit 20 based on the print job and does not contain image anomalies or defects. A printout that does not contain image anomalies or defects is, for example, a printout that has been visually proofread by a user and determined to be problem-free.

[0027] In this embodiment, in the image inspection for generating a reference image, the control unit 40 (see FIG. 3) performs processing to increase the accuracy of detecting defects in a specific area of ​​the sheet Sh so that scratches, stains, and the like that have adhered to the sheet Sh can be detected with high accuracy while the sheet Sh is being transported through the image forming apparatus 1. The processing by the control unit 40 when performing the image inspection for generating a reference image will be described later.

[0028] Furthermore, when a defect such as dirt or scratches is detected by the image inspection unit 29, the control unit 40 performs a defect response process. Specifically, as the defect response process, the control unit 40 performs control to identify the transport member that caused the defect based on information on the formation position of the defect on the paper Sh, and to execute cleaning of the transport member, etc. Alternatively, as the defect response process, the control unit 40 performs control to notify the user of information on the formation position of the defect on the paper Sh or information on the transport member that caused the defect through display on the screen of the display device of the operation display unit 52, etc.

[0029] By performing such defect handling processing by the control unit 40, stains or scratches caused by the transport member do not adhere to the paper Sh, so it becomes possible to generate a reference image that does not include defects such as stains or scratches. An example of the correspondence between defects such as stains or scratches and the transport member that caused the defect will be described in detail later with reference to FIG.

[0030] Furthermore, the control unit 40 also performs control to have the user make a final decision as to whether or not to register the read image as a reference image by showing the information of the read image after the defect response processing to the user via the screen of the operation display unit 52. By performing such control by the control unit 40, it becomes possible to further ensure the quality of the reference image.

[0031] The delivery section 27 has a belt loop 272 having a ring-shaped belt supported by two rollers on the inside, a cylindrical delivery drum 271 that delivers the paper Sh from the transport section 21 to the belt loop 272, and rollers 273 provided on the belt loop 272. The delivery section 27 transports the paper Sh delivered from the transport section 21 onto the belt loop 272 by the delivery drum 271, using the rollers 273 and the belt loop 272, and sends it to the paper discharge section 30. Note that in the process of transporting the paper Sh from the delivery drum 271 to the belt loop 272, a guide 274 is provided to prevent the paper Sh from deviating from the transport path.

[0032] The reversing unit 28 is a mechanism for reversing the front and back of the paper sheet Sh, and includes a first drum 281, a second drum 282, and a belt loop 283. The first drum 281 is disposed at a position where it contacts the transfer drum 271, and rotates in a counterclockwise direction following the rotation of the transfer drum 271. The second drum 282 is disposed at a position where it contacts the first drum 281, and rotates in a clockwise direction following the rotation of the first drum 281. The belt loop 283 is disposed at a position where it contacts the second drum 282, and rotates in a counterclockwise direction following the rotation of the second drum 282.

[0033] In the reversing section 28, the sheet Sh delivered from the delivery drum 271 is delivered and transported in the order of the first drum 281, the second drum 282, and the belt loop 283, thereby turning the sheet Sh upside down. Then, the sheet Sh, whose upside down has been turned upside down, is placed on the transport surface of the transport drum 211 on the upstream side of the delivery drum 222 in the transport direction. The configuration of the reversing unit 28 is not limited to the above, and any configuration is possible as long as it is possible to reverse the sheet Sh and deliver it to the transport drum 211.

[0034] <Configuration of the control system of the image forming apparatus> Next, the configuration of a control system of the image forming apparatus 1 according to one embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the configuration of the control system of the image forming apparatus 1.

[0035] 3, the image forming apparatus 1 includes a control unit 40, a transport drive unit 51, an operation display unit 52, an input / output interface 53, a heating unit 23, a head unit 24, a fixing unit 25, an image reading unit 26, an inverting unit 28, and an image inspection unit 29. These units constituting the image forming apparatus 1 are connected to each other via a bus 54 so as to be able to communicate with each other.

[0036] The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), and a storage unit 44.

[0037] The CPU 41 reads out various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various arithmetic processing. The CPU 41 also performs overall control over the overall operation of the image forming apparatus 1. The programs stored in the ROM 43 are stored in the form of computer-readable program codes, and the CPU 41 sequentially executes operations in accordance with the program codes.

[0038] The RAM 42 provides a working memory space for the CPU 41 and stores temporary data. The RAM 42 may include a non-volatile memory.

[0039] The ROM 43 stores various control programs and setting data executed by the CPU 41. Instead of the ROM 43, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

[0040] The storage unit 44 is configured with, for example, a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 44 stores a print job input from the external device 2 via the input / output interface 53, image data related to the print job, a reference image Ir referenced during image inspection by the image inspection unit 29, and the like. The program stored in the ROM 43 may be stored in the storage unit 44. In other words, the ROM 43 or the storage unit 44 is used as an example of a computer-readable non-transitory recording medium that stores a program executed by a computer.

[0041] The transport drive unit 51 supplies a drive signal to a transport drum motor of the transport drum 211 (see FIG. 1) based on a control signal supplied from the CPU 41, thereby rotating the transport drum 211 at a predetermined speed and timing. The transport drive unit 51 also supplies a drive signal to motors for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 27 based on a control signal supplied from the CPU 41, thereby supplying the paper Sh to the transport unit 21 and discharging it from the transport unit 21.

[0042] The operation display unit 52 includes a display device configured as a liquid crystal display or an organic EL display, etc., and an input device configured as operation keys or a touch sensor arranged over the screen of the display device, etc. The operation display unit 52 displays various information on the display device, and also converts the user's input operation on the input device into an operation signal and outputs it to the control unit 40.

[0043] The input / output interface 53 mediates transmission and reception of data between the external device 2 and the control unit 40. The input / output interface 53 is configured, for example, with any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0044] The external device 2 is configured by, for example, a personal computer, and supplies print jobs, image data, and the like to the control unit 40 via an input / output interface 53 .

[0045] The recording head drive section 241 of the head unit 24 supplies a drive signal to the recording element of the recording head 242 at an appropriate timing to cause the piezoelectric element to deform in accordance with image data, thereby causing the nozzle 243 of the recording head 242 to eject an amount of ink in accordance with the pixel value of the image data.

[0046] The heating section 23, the components other than the recording head drive section 241 in the head unit 24, the fixing section 25, the image reading section 26, the delivery section 27, the inversion section 28 and the image inspection section 29 have already been explained with reference to Figure 1, so their explanation will be omitted.

[0047] <Processing for improving defect detection accuracy when performing image inspection for generating reference images> Next, the defect detection accuracy improvement process performed by the control unit 40 (see FIG. 3) when performing image inspection for generating a reference image will be described with reference to Fig. 4. Fig. 4 is a diagram showing an overview of the defect detection accuracy improvement process performed when performing image inspection for generating a reference image.

[0048] 4 shows a sheet of paper (printed material) Sh on which an image I has been formed by the image forming unit 20 (see FIG. 1) of the image forming apparatus 1. The stain D1 on the right side of the image I in the figure, which has a shape like multiple ovals overlapping in the transport direction of the sheet of paper Sh, is a stain that is adhered by rollers (an example of a transport member) that press the sheet of paper Sh as it is transported. The stain D1 may be so faint that it is difficult to see, or the outline may be unclear, and therefore may not be detected in an image inspection performed with normal detection accuracy.

[0049] The stain D1 is the range where an image is formed, and may be within the print range Ar1 shown by the dashed line in the figure, but may also be outside the print range Ar1. Therefore, if the stain D1 is outside the print range Ar1, it may not be detected in a normal image inspection, because the normal image inspection targets the print range Ar1 shown by the dashed line in the figure.

[0050] The rod-shaped stain D2 on the lower left of the image I formed on the paper Sh is a scratch on the paper Sh caused by a guide plate (not shown, an example of a conveying member) provided on the conveying path of the paper Sh. If such a scratch is thin, it may not be detected in a normal image inspection.

[0051] Furthermore, stains on the paper Sh, which is a printed matter, include streaks D3 that are formed vertically across the image I. Such streaks D3 are formed when ink ejection from a specific nozzle 243 (see FIG. 2) of the recording head 242 of the head unit 24 is defective. Such streaks D3 can be detected, for example, by forming a test image outside the printing range Ar1, in an area Ar2 below the printing range Ar1 in the example shown in FIG. 4, and checking for the presence or absence of streaks in the test image. The test image can be formed, for example, by solid printing with an ink such as K (black). Then, the target range of the image inspection is changed to the area Ar2, which is different from the printing range Ar1 that is inspected in the normal image inspection, to enable detection of defects (the above-mentioned streaks D3) caused by defective ink ejection.

[0052] The control unit 40 (see FIG. 3) according to this embodiment performs control to improve the detection accuracy of the image reading unit 26 for defects that occur during the transport process of the paper Sh, such as stains D1 and scratches D2, when performing image inspection for generating a reference image. In the control to improve the defect detection accuracy, the control unit 40 first narrows down the target range of the image inspection (hereinafter also referred to as the "inspection area") to an area Ar3 where adhesion of the stains D1 and the like is expected due to contact of transport members such as transport rollers, rollers, and guides with the paper Sh. In other words, the target range of the image inspection is changed to an area Ar3 that is further limited than the print area Ar1 that is inspected in the normal image inspection.

[0053] Next, the control unit 40 increases the resolution of the image read by the image reading unit 26 (see FIG. 3) in the area Ar4 where scratches (such as the above-mentioned scratches D2) in the area Ar3 are expected to be attached to, to twice or four times, etc., compared to that during normal image inspection. For example, if the resolution of the image read during normal image inspection is 300 dpi, it is increased to 600 dpi or 1200 dpi, etc. The resolution of the image read can be improved by changing the resolution if the image reading unit 26 is capable of adjusting the resolution. In this way, when the image inspection is performed at a high resolution by narrowing the target range of the image inspection, it is possible to perform a high-precision image inspection while suppressing the load and processing time of the image inspection. Note that even if the image reading unit 26 does not allow adjustment of the resolution, it is possible to increase the resolution of the image read by lowering the conveying speed of the paper Sh.

[0054] It should be noted that although it is assumed that the area Ar4 is narrower than the area Ar3, the area Ar3 and the area Ar4 may be the same area. Also, the area Ar3 and / or the area Ar4 may be set by the user.

[0055] Furthermore, the detection accuracy of the stains D1 caused by rollers or the like can also be improved by performing detection using information on the periodic pattern of the outer diameter of the rollers of the rollers.

[0056] Furthermore, the accuracy of detecting defects such as stains D1 and scratches D2 that occur during the transport process of the paper Sh can also be improved by subjecting blank paper on which no image I is formed to image inspection. By subjecting blank paper to image inspection, stains and scratches that are difficult to recognize due to overlapping with the image I can be detected.

[0057] The setting of which of the above methods is to be used to improve the defect detection accuracy may be performed automatically or by the user depending on the type and printing purpose of the image forming apparatus 1. Furthermore, one of the above methods may be selected as the method to improve the defect detection accuracy, or two or more of the above methods may be selected.

[0058] The control unit 40 performs the above-mentioned control, which enables the image inspection unit 29 to detect defects caused by the conveying members that are difficult to detect with the detection accuracy during normal image inspection. This eliminates the need to print multiple times to detect defects in the read image that is the basis of the reference image, making it possible to prevent the generation of a large amount of waste paper and the occurrence of situations where the delivery deadline for printed matter cannot be met.

[0059] <Example of the location of the defect and the transport part that caused the defect> Next, an example of the correspondence between the location of a defect and the transport member that caused the defect will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of the correspondence between the arrangement positions of the transport members in the paper width direction and the formation patterns of stains or scratches on the paper Sh caused by these transport members.

[0060] The horizontal direction in Fig. 5 corresponds to the X direction, which indicates the width direction of the paper, and Fig. 5 (1) and (3) show the positions in the paper width direction of the rollers or guides that caused the stains or scratches. Fig. 5 (1) shows the position in the paper width direction of the rollers 273 in the transport path of the belt loop 272 (see Fig. 1) of the delivery unit 27. Fig. 5 (2) shows the formation pattern of stains that are expected to be caused by the rollers 273 and adhere to the paper Sh.

[0061] Also, Fig. 5 (3) shows the position in the paper width direction of the guide 274 in the process of transport from the delivery drum 271 (see Fig. 1) of the delivery section 27 to the belt loop 272. Fig. 5 (4) shows the formation pattern of scratches that are expected to be caused by the guide 274 and adhere to the paper Sh. The contact of the guide 274 with the surface of the paper Sh can occur, for example, due to a change in the state of the paper Sh.

[0062] In this way, since the transporting member of the paper Sh corresponds to the position of the stain or scratch formed on the paper Sh, the control unit 40 can identify the transporting member that is causing the stain or scratch by comparing the formation pattern of the stain or scratch formed on the paper Sh with each of the patterns (2) and (4) in Figure 5.

[0063] In addition, since the ink and the like used in image formation are likely to adhere to the transport members located downstream of the image forming unit 20, there is a high possibility that these transport members will cause stains on the paper Sh. Therefore, the control unit 40 may limit the target range of image inspection by the image inspection unit 29 to an area where stains or scratches are expected to occur due to the transport members coming into contact with the paper during the paper transport process after the image is formed. By performing such control by the control unit 40, defects caused by the transport members located downstream of the image forming unit 20 can be detected with high accuracy.

[0064] Furthermore, the positions of the conveying members in the paper width direction shown in Figures 5(1) and (3) and the patterns of stains or scratches shown in Figures 5(2) and (4) are merely examples, and the present invention is not limited to these examples.

[0065] <Image inspection processing> Next, the image inspection process for a basic image by the image forming apparatus 1 will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of the procedure of the image inspection process for a basic image by the image forming apparatus 1.

[0066] First, the control unit 40 (see FIG. 3) of the image forming apparatus 1 sets an inspection area to be subjected to image inspection based on the user's operation on the operation display unit 52, etc. (Step S1). The inspection area is an area where dirt or scratches are expected to adhere due to contact with a transport member, such as the area Ar3 in FIG. 4. The inspection area may be set in advance in the image forming apparatus 1. Furthermore, multiple inspection areas may be set depending on the number of transport members expected to cause dirt or scratches.

[0067] Next, the control unit 40 changes the mechanical state of the image forming apparatus 1 in preparation for increasing the reading resolution of the area Ar4 (see FIG. 4) in the area Ar3 (step S2). Next, the control unit 40 changes the reading resolution of the image reading unit 26 (see FIG. 3) to the reference image reading resolution (step S3). That is, the reading resolution is set to a higher resolution than the reading resolution during image inspection of printed matter based on a normal print job.

[0068] Next, the image forming unit 20 (see FIG. 1) of the image forming apparatus 1 prints a reference image on the paper Sh (step S4). The reference image formed on the paper Sh in step S4 may be, for example, a test image such as a chart. In this embodiment, the area in which the test image is formed on the paper Sh may be set to be smaller so that stains or scratches on the paper Sh caused by the transport member can be easily detected. In other words, the area may be adjusted so that there is more blank space. Next, the image reading unit 26 reads the printout (paper Sh) on which the reference image is printed in step S4 at the resolution set in step S3 (step S5).

[0069] Next, the image inspection unit 29 performs an image inspection of the reference image (step S6). In the image inspection of the reference image, the document image (raster image) of the reference image is compared with the read image read in step S5, similar to the image inspection for the actual printing.

[0070] Next, the image inspection unit 29 judges whether or not there is a defect in the read image of the reference image (step S7). If it is judged that there is a defect in step S7 (if the judgment in step S7 is YES), the control unit 40 performs a defect response process (step S8).

[0071] As a defect response process, the control unit 40 first identifies the transport member corresponding to the detected defect location. Then, the control unit 40 performs cleaning or the like on the identified transport member. Alternatively, the control unit 40 notifies the user of information on the location where the defect was detected and information on the transport member corresponding to the detected defect location via the screen of the operation display unit 52 or the like, thereby causing the user to perform cleaning or the like on the corresponding transport member. After the process of step S8, the control unit 40 stores the reference image in the storage unit 44 (see FIG. 3) (step S9). After the process of step S9, the image inspection process for the reference image by the image forming apparatus 1 ends.

[0072] After the defect response process in step S8 is performed, the process may be returned to step S4 again. By performing such control, even if the defect response process is insufficient, information on unprocessed defects can be detected and the defects can be dealt with, so that the quality of the reference image can be guaranteed more reliably.

[0073] When performing image inspection of the read image that is the basis of the reference image, the control unit 40 of the image forming apparatus 1 according to the embodiment described above performs control to perform at least one of detecting defects with higher detection accuracy than in the image inspection of the printed matter based on the print job and changing the target range for the image inspection. Therefore, according to this embodiment, it is possible to accurately detect image defects in the read image that is the basis of the reference image, and easily identify and solve the cause of the abnormality.

[0074] In addition to the image inspection process for the basic image by the image forming apparatus 1, a process for identifying stains or scratches (image inspection process) may be performed on blank paper on which no image is formed. In this case, the image inspection unit 29 detects the presence or absence of stains, scratches, etc. on the paper fed from the paper feed unit 10 and conveyed through the conveying unit 21. The execution or non-execution of the image inspection process on the blank paper is instructed, for example, by the user.

[0075] Fig. 7 is a flowchart showing an example of the procedure of image inspection processing for a basic image by the image forming apparatus 1 according to a modified example. In Fig. 7, the same processes as those shown in Fig. 6 are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0076] After the printout is read in step S5, the control unit 40 determines whether or not an instruction to perform blank printing has been given (step S11). Whether or not to perform blank printing is determined, for example, by a user's operation on the operation display unit 52. If it is determined in step S11 that an instruction to perform blank printing has been given (YES in step S11), the image forming unit 20 performs blank printing, that is, a process of transporting the paper Sh without forming an image (step S12). Note that an operation may be performed in which only blank printing in step S12 is performed without printing the reference image in step S4.

[0077] Next, the image reading unit 26 reads the blank printed matter (paper Sh) on which blank printing was performed in step S12 (step S13). After the process of step S13, the process of step S7 and the subsequent steps shown in Fig. 6 are performed. In this manner, by performing image inspection on blank paper, the image inspection unit 29 can detect stains or scratches that are difficult to distinguish on the surface of paper on which an image is printed.

[0078] <Printing and image inspection processing based on print jobs> Next, printing and image inspection processing based on a production print job that is performed after the above-mentioned defect handling processing will be described with reference to Fig. 8. Fig. 8 is a flowchart showing an example of the procedure of printing and image inspection processing based on a print job.

[0079] First, the control unit 40 (see FIG. 3) of the image forming device 1 changes the mechanical state of the image forming device 1 from the setting for printing a reference image to the setting for printing a production image (step S21) in preparation for executing production printing based on a normal print job. Next, the image forming unit 20 (see FIG. 1) executes printing based on the production job (step S22). Next, the image reading unit 26 reads the printed matter printed in step S22 (step S23).

[0080] Next, the image inspection unit 29 performs an image inspection to detect the presence or absence of defects in the printed matter by comparing the reference image stored in the storage unit 44 in step S12 of Fig. 6 with the read image read by the image reading unit 26 in step S23 (step S24). Next, the image inspection unit 29 judges whether or not there is a defect in the read image of the reference image (step S25). If it is judged that there is a defect in step S25 (if the judgment in step S25 is YES), the control unit 40 performs a defect response process (step S26).

[0081] The defects detected in step S25 are defects other than defects caused by the conveying member, that is, defects caused by the printing process such as nozzle discharge failure, misalignment of the image formation position, etc. Therefore, in step S26, the control unit 40 performs defect response processing according to these causes.

[0082] After the process of step S26, or if step S25 is judged as NO, the control unit 40 judges whether or not printing has finished (step S27). If it is judged as not finishing printing in step S27 (if step S27 is judged as NO), the control unit 40 returns to step S22 and continues the process. That is, the control unit 40 causes the image forming unit 20 to execute printing based on the print job. On the other hand, if it is judged as finishing printing in step S27 (if step S27 is judged as YES), the printing based on the print job and the image inspection process are terminated.

[0083] In the above embodiment, the image forming apparatus according to the present invention is applied to an image forming apparatus that forms images by an inkjet method, but the present invention is not limited to this. The image forming method of the image forming apparatus according to the present invention may be another method such as an electrophotographic method.

[0084] In addition, the above-mentioned embodiment describes the configuration of the device (image forming device) in detail and specifically in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to having all of the configurations described. Also, the control lines and information lines indicated by solid arrows in Figure 3 indicate those that are considered necessary for explanation, and do not necessarily indicate all of the control lines and information lines in the product. In reality, it can be considered that almost all of the configurations are connected to each other. [Explanation of symbols]

[0085] REFERENCE SIGNS LIST 1: image forming apparatus, 20: image forming section, 21: conveying section, 24: head unit, 26: image reading section, 29: image inspection section, 40: control section, 52: operation display section

Claims

1. an image reading unit that reads a printed matter, which is a print medium on which an image is formed, and generates a read image; an image inspection unit that performs an image inspection to detect the presence or absence of defects in the printed matter by comparing a reference image generated in advance based on the scanned image of the printed matter with a scanned image of the printed matter based on a print job; a control unit that performs image inspection of the read image that is the basis of the reference image by performing at least one of detecting the defect with a detection accuracy higher than the detection accuracy in an image inspection of the printed matter based on the print job and changing a target range for the image inspection. Image inspection equipment.

2. The reference image is an image generated based on a scanned image of a printed matter that has been image-formed prior to the print job.

2. The image inspection device according to claim 1.

3. The control unit limits a target range of the image inspection to an area where dirt or scratches are expected to adhere due to a conveying member contacting the printing medium during a conveying process of the printing medium on which the image is formed.

2. The image inspection device according to claim 1.

4. The change in the target of the image inspection includes a change from a print range, which is an area on the print medium where the image is printed, to an area other than the print range.

2. The image inspection device according to claim 1.

5. The control unit increases a resolution at which the image reading unit reads the read image, thereby improving the accuracy of detecting the defect.

5. The image inspection device according to claim 4.

6. The control unit controls the image inspection unit to perform an image inspection on the print medium on which an image is not formed, and to generate the reference image based on the image inspection.

6. An image inspection device according to claim 5.

7. The image forming unit further includes: The image inspection device according to any one of claims 2 to 5.

8. The control unit identifies the transport member that caused the defect based on information about the position of the defect detected on the print medium, and controls cleaning of the transport member.

8. An image inspection device according to claim 7.

9. The control unit controls to notify a user, via a screen of a display unit, of information on the position of the defect detected on the printing medium, or information on the conveying member that caused the defect, which is specified based on information on the position on the printing medium where the defect was detected.

8. An image inspection device according to claim 7.

10. The control unit identifies the transport member that caused the defect based on information about a period of stains or scratches that periodically adhere to the print medium in a transport direction of the print medium due to contact of the transport member with the print medium.

4. The image inspection device according to claim 3.

11. The control unit limits a target range of the image inspection to an area where dirt or scratches are expected to adhere due to a conveying member contacting the printing medium during a conveying process of the printing medium after the image is formed.

4. The image inspection device according to claim 3.

12. A step of performing an image inspection to detect the presence or absence of defects in a printed matter by comparing a reference image generated in advance based on a scanned image of the printed matter with a scanned image of the printed matter based on a print job; and performing an image inspection of the read image that is the basis of the reference image by performing at least one of detecting the defect with a detection accuracy higher than the detection accuracy in an image inspection of the printed matter based on the print job and changing a target range for the image inspection. Imaging methods.

13. An image inspection program that can be executed by a computer to perform an image inspection for detecting the presence or absence of defects in a printed matter by comparing a reference image that is generated in advance based on a scanned image of the printed matter with a scanned image of the printed matter based on a print job, the image inspection program comprising: The method includes a step of performing an image inspection of the read image that is the basis of the reference image by performing at least one of detecting the defect with a detection accuracy higher than the detection accuracy in an image inspection of the printed matter based on the print job and changing a target range for the image inspection. Image inspection program.

Images