Image formation system and method for processing image

Abstract

To reduce erroneous detection of defect parts due to characteristics of a sheet on image inspection.SOLUTION: An image formation system 100 includes a controller 30 that performs image processing to a printing image to be printed on a sheet and controls an image formation part to form a post-image processed printing image when it is determined that an inspection level capable of executing image inspection may fall below a set inspection level on the basis of characteristic information of a sheet on which an image is formed on the basis of a printing image and setting information of an inspection level indicating inspection accuracy required for image inspection of a printed matter on which an image is formed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming system and an image processing method. [Background technology]

[0002] Conventionally, image inspection devices may perform image inspection for the purpose of inspecting the image quality of printed matter, such as the presence or absence of streaks, checking the presence or absence of dirt such as dust, etc. Image inspection is performed by comparing image data obtained by reading an image on a printed matter with print image data that is the source of the image formed on the printed matter, and determining the presence or absence of defects in the image on the printed matter.

[0003] However, paper contains defects caused by the material constituting the paper, such as minor stains and foreign matter that do not affect the images and characters printed on the paper surface. For this reason, if the detection accuracy of the image inspection unit is high, even minor defects that do not affect the images and characters printed on the paper will be detected as defective paper.

[0004] Patent document 1 discloses an image forming system that includes an image inspection unit that acquires information about the surface of the paper before image formation and information about the surface of the paper after image formation, and a discrimination unit that excludes the information about the surface of the paper before image formation from the information about the surface of the paper after image formation to discriminate image formation defects during image formation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-037232 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to the technology described in Patent Document 1, non-conforming areas such as stains and foreign matter on paper before image formation are removed before they are judged to be defective. However, depending on the characteristics of the paper material, background color, pattern, etc., areas that are not stained or have foreign matter attached thereto may be detected as defective. In other words, the quality of the inspection will decrease. Patent Document 1 does not disclose any measures to prevent the deterioration of the quality of the inspection.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a decrease in the quality of inspection in image inspection. [Means for solving the problem]

[0008] In order to solve the above problem, an image forming system reflecting one aspect of the present invention includes a control unit that performs image processing on the print image printed on the paper and causes an image forming unit to form the print image after image processing when it is determined that the inspection level at which the image inspection can be performed may be lower than the set inspection level based on information about the characteristics of the paper on which an image based on the print image is formed and inspection level setting information indicating the inspection accuracy required for image inspection of the printed matter on which the image is formed. Effect of the Invention

[0009] According to the present invention, it is possible to prevent a decrease in the quality of inspection in image inspection. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing an overall configuration of an image forming system according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram showing an example of the configuration of a control system of a paper property detection device, an image forming device, and an image inspection device according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram showing an overview of image processing according to Example 1-1 of the present invention. [Figure 4]1 is a flowchart showing an example of a procedure of an image processing method according to Example 1-1 of the present invention. [Diagram 5] FIG. 1 is a diagram showing an overview of image processing according to Example 1-2 of the present invention. [Figure 6] FIG. 1 is a diagram showing an overview of image processing according to Example 1-2 of the present invention. [Figure 7] 11 is a flowchart showing an example of a procedure of an image processing method according to Example 1-2 of the present invention. [Figure 8] FIG. 11 is a diagram illustrating an overview of image processing according to a second embodiment of the present invention. [Figure 9] 10 is a flowchart showing an example of a procedure of an image processing method according to a second embodiment of the present invention. [Figure 10] FIG. 11 is a diagram showing an example of an area where wear is likely to occur in a sheet according to a third embodiment of the present invention. [Figure 11] 11A and 11B are diagrams illustrating an example of a configuration of a print image formed on the paper illustrated in FIG. 10 according to a third embodiment of the present invention. [Figure 12] FIG. 11 is a diagram showing an example of a wear warning area on a sheet according to a third embodiment of the present invention. [Figure 13] 12 is a diagram showing an example of the configuration of a print image formed on the paper shown in FIG. 11 according to the third embodiment of the present invention. FIG. [Figure 14] 13 is a flowchart showing an example of a procedure for image processing according to a third embodiment of the present invention. [Figure 15] FIG. 13 is a diagram showing an example of a wear warning area on a sheet according to a fourth embodiment of the present invention. [Figure 16] FIG. 16 is a diagram showing an example of inspection levels that can be performed in each area shown in FIG. 15 according to the fourth embodiment of the present invention. [Figure 17] FIG. 13 is a diagram showing an example of a wear warning area on a sheet according to a fifth embodiment of the present invention. [Figure 18] 18 is a diagram showing an example of a print image formed on the paper shown in FIG. 17 according to the fifth embodiment of the present invention. FIG. [Figure 19] FIG. 19 is a diagram showing an example of inspection levels that can be performed in each area shown in FIG. 18 according to the fifth embodiment of the present invention. [Figure 20]FIG. 20 is a diagram showing an example of a print image P11h obtained by rotating the print image shown in FIG. 18 by 180 degrees according to the fifth embodiment of the present invention. [Figure 21] FIG. 21 is a diagram showing an example of an inspection level that can be implemented for the print image shown in FIG. 20 according to the fifth embodiment of the present invention. [Figure 22] 13 is a flowchart showing an example of a procedure for image processing according to a fifth embodiment of the present invention. [Diagram 23] FIG. 13 is a diagram showing an example of a wear warning area on a sheet according to a sixth embodiment of the present invention. [Figure 24] 24A and 24B are diagrams showing examples of a print image formed on the front side sheet and a print image formed on the back side sheet shown in FIG. 23 according to the sixth embodiment of the present invention. [Diagram 25] FIG. 25 is a diagram showing an example of inspection levels that can be performed in each area shown in FIG. 23 and FIG. 24 according to Example 6 of the present invention. [Figure 26] FIG. 25 is a diagram showing an example in which the print image for the front side and the print image for the back side shown in FIG. 24 are interchanged according to the sixth embodiment of the present invention. [Figure 27] FIG. 27 is a diagram showing an example of an inspection level that can be implemented for the print image for the front side and the print image for the back side shown in FIG. 26 according to the sixth embodiment of the present invention. [Figure 28] 13 is a flowchart showing an example of a procedure for image processing according to a sixth embodiment of the present invention. [Figure 29] FIG. 13 is a diagram showing an example of a wear warning area on a sheet according to a seventh embodiment of the present invention. [Diagram 30] 30A and 30B are diagrams showing examples of print images formed on the respective sheets shown in FIG. 29 according to the seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment 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 denoted by the same reference numerals, and duplicated descriptions of the components will be omitted.

[0012] <Image forming system configuration> First, the overall configuration of an image forming system according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the overall configuration of an image forming system 100. Note that Fig. 1 shows elements necessary for explaining the present invention or related elements, and the image forming system of the present invention is not limited to the example shown in Fig. 1.

[0013] As shown in FIG. 1, an image forming system 100 includes a paper feeder 1, a paper characteristic detection device 2, an image forming device 3, an image inspection device 4, a relay unit 5, and a paper discharge unit 6.

[0014] [Paper Feeder] The paper feed device 1 includes paper feed trays 11 to 13, and paper Sh (an example of a recording material) of various paper types and sizes is stored in the paper feed trays 11 to 13. The paper feed device 1 feeds paper Sh from the paper feed trays 11 to 13 based on a print job transmitted from a terminal device (not shown) and conveys the paper Sh to the paper characteristic detection device 2. Note that while FIG. 1 shows an example in which the paper feed device 1 includes three paper feed trays, the present invention is not limited to this. The number of paper feed trays may be two or less, or may be four or more.

[0015] [Paper characteristic detection device] The paper characteristic detection device 2 is a device that detects the characteristics of the paper Sh, and includes media sensors such as a paper thickness sensor 21, a basis weight sensor 22, a surface property sensor 23, and a density sensor 24.

[0016] The paper thickness sensor 21 detects the thickness of the paper Sh (paper thickness) based on the distance between two members of a paper thickness detection unit (not shown) when the paper is sandwiched between the two members.

[0017] The basis weight sensor 22 is configured, for example, by a transmissive optical sensor (not shown) equipped with a light emitting section and a light receiving section, and detects the basis weight of the sheet Sh based on the attenuation rate (transmittance) of light transmitted through the sheet Sh.

[0018] The surface property sensor 23 includes a surface property sensor 23f for the front surface of the paper Sh, and a surface property sensor 23b for the back surface of the paper Sh. The surface property sensor 23 includes, for example, a housing, a light emitting unit, a collimating lens, and multiple light receiving units (all not shown). The surface property sensor 23 detects the surface properties, such as the smoothness, glossiness, and unevenness, of the paper surface based on the specular reflected light and diffuse reflected light from the paper surface received by the multiple light receiving units.

[0019] The density sensor 24 includes a density sensor 24f for the front side of the paper Sh, and a density sensor 24b for the back side of the paper Sh. The density sensor 24 has a light source (not shown) such as a tungsten halogen lamp, measures the intensity of light reflected from the paper Sh when the light is illuminated by the light source, and calculates the absolute reflection density based on the intensity of the reflected light. Note that, in this embodiment, an example is given in which the density sensor 24 calculates the absolute reflection density as the density (density) of the image, but the present invention is not limited to this. For example, the density sensor 24 may detect the amount of ink adhering to the paper Sh as the image density.

[0020] The detection results by the media sensors of the paper characteristic detection device 2 are transmitted to the subsequent image forming device 3. Then, the control unit 30 (see FIG. 2) of the image forming device 3 controls the paper feeding operation in the paper feeding device 1, the image forming operation in the image forming device 3, etc., based on the various detection results transmitted from the paper characteristic detection device 2.

[0021] The media sensor included in the paper characteristic detection device 2 and the types of paper characteristics detected by the media sensor are not limited to the example shown in FIG.

[0022] [Configuration of image forming device] The image forming device 3 is an image forming device that forms an image on paper Sh using an inkjet method, and forms (prints) an image on the front side (first side) or back side (second side) of the paper Sh based on a print job input from a terminal device or the like not shown.

[0023] As shown in FIG. 1, the image forming apparatus 3 includes a paper feed tray 31, a transport path 32, an image forming section 33, a fixing section , a paper reversing section 35, and an operation display section .

[0024] The paper feed tray 31 is a tray that accommodates paper Sh on which an image is formed by the image forming unit 33 . The conveying path 32 is a path for conveying the paper Sh fed from the paper feed device 1 or the paper feed tray 31 to the paper discharge tray 61a or the purge tray 61b of the paper discharge unit 6 via the paper characteristic detection device 2, the image forming device 3, the image inspection device 4, and the relay unit 5. The conveying path 32 is provided with a plurality of conveying rollers for conveying the paper Sh.

[0025] The image forming section 33 includes a head unit 331. The head unit 331 includes a head unit 331W, a head unit 331Y, a head unit 331M, a head unit 331C, and a head unit 331K. The head unit 331W is a unit that ejects white (W) ink, and the head unit 331Y is a unit that ejects yellow (Y) ink. The head unit 331M is a unit that ejects magenta (M) ink. The head unit 331C is a unit that ejects cyan (C) ink, and the head unit 331K is a unit that ejects black (K) ink.

[0026] Each of the head units 331W, 331Y, 331M, 331C, and 331K includes a recording head (not shown) having a plurality of nozzles. An image is formed on the paper Sh by ejecting ink droplets from the plurality of nozzles.

[0027] In this embodiment, the head units 331 are arranged in the order of W, Y, M, C, and K from the upstream side in the transport direction of the paper Sh, but the present invention is not limited to this. The arrangement order of the inks other than white (W) may be other than the arrangement order shown in FIG.

[0028] 1, the image forming unit 33 is an inkjet type, but the present invention is not limited to this. The image forming apparatus of the present invention can also be applied to image forming apparatuses using other image forming methods, such as an electrophotographic type.

[0029] The fixing unit 34 is disposed downstream of the head unit 331K in the transport direction of the paper Sh. The fixing unit 34 irradiates ultraviolet light onto the paper Sh on which ink has been applied by the head unit 331K, and cures the ink adhering to the paper Sh, thereby fixing the image onto the paper Sh.

[0030] The paper inverting section 35 inverts the paper Sh conveyed on the conveying path 32 , and conveys the inverted paper Sh to the image forming section 33 again.

[0031] The operation display unit 36 ​​(an example of an output unit) is composed of a display unit such as an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescence) display, and an operation input unit including keys, buttons, etc. The display unit and the operation input unit may be integrally formed as a touch panel.

[0032] [Image inspection device configuration] The image inspection device 4 includes a first reading unit 411 and a second reading unit 412. The first reading unit 411 and the second reading unit 412 are configured with a scanner that reads an image formed on a sheet of paper Sh. The first reading unit 411 is disposed above the transport path 32 in FIG. 1 (on the side of the first surface of the sheet of paper Sh transported on the transport path 32) and reads the first surface of the sheet of paper Sh transported from the image forming device 3. The second reading unit 412 is disposed below the transport path 32 in FIG. 1 (on the side of the second surface of the sheet of paper Sh transported on the transport path 32) and reads the second surface of the sheet of paper Sh transported from the image forming device 3.

[0033] Then, the image inspection device 4 performs image inspection on the read image read by the first reading unit 411 (hereinafter also referred to as the "first read image") or the read image read by the second reading unit 412 (hereinafter also referred to as the "second read image"). In this embodiment, the image inspection device 4 performs image inspection according to an inspection level set via the operation display unit 36 ​​of the image forming device 3, etc.

[0034] The relay unit 5 is a unit installed between the image inspection device 4 and the paper discharge unit 6, and transports the paper fed from the image inspection device 4 to the paper discharge unit 6. The relay unit 5 reverses the paper fed from the image inspection device 4 using a switching gate as necessary, and transports it to the paper discharge unit 6. In addition, when the height of the paper discharge section (not shown) of the image inspection device 4 differs from the height of the paper feed section (not shown) of the paper discharge unit 6, the relay unit 5 acts as a bridge between the two devices.

[0035] The paper discharge unit 6 includes a paper discharge tray 61a and a purge tray 61b. The paper discharge tray 61a is a tray onto which paper sheets Sh for which no abnormality has been detected by the image inspection device 4, i.e., which have been determined to be non-defective, are discharged. The purge tray 61b is a tray onto which paper sheets Sh for which an abnormality has been detected by the image inspection device 4, i.e., which have been determined to be defective, are discharged.

[0036] <Configuration of the control system of the paper characteristic detection device, image forming device, and image inspection device> Next, the configuration of a control system of the paper characteristic detection device 2, the image forming device 3, and the image inspection device 4 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing an example of the configuration of the control system of the paper characteristic detection device 2, the image forming device 3, and the image inspection device 4.

[0037] [Control system configuration of paper characteristic detection device] As shown in FIG. 2, the paper characteristic detection device 2 includes a control unit 20, a memory unit 204, a paper thickness sensor 21, a basis weight sensor 22, a surface property sensor 23, a shade sensor 24, and a communication unit 25.

[0038] The control unit 20 includes a CPU (Central Processing Unit) 201, a RAM (Random Access Memory) 202 used as a working area for the CPU 201, and a ROM (Read Only Memory) 203 for storing programs executed by the CPU 201, etc.

[0039] The CPU 201 of the control unit 20 reads out various control programs and setting data stored in the ROM 203 and loads them in the RAM 202 to execute the programs. The CPU 201 is also connected to each unit constituting the paper characteristic detection device 2 via a system bus B1, and controls the operation of each unit. For example, the CPU 201 controls the operation of each media sensor of the paper characteristic detection device 2, and also controls the transmission of the detection results of each media sensor to the image forming device 3 via the communication unit 25.

[0040] The RAM 202 provides a working memory space for the CPU 201 and stores temporary data. The ROM 203 stores various control programs and setting data executed by the CPU 201. The programs are stored in the form of computer-readable program codes in the ROM 203. Note that a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used instead of the ROM 203.

[0041] The storage unit 204 is configured, for example, with a hard disk drive (HDD) or a solid state drive (SSD). The programs stored in the ROM 203 may be stored in the storage unit 204. That is, the ROM 203 or the storage unit 204 is used as an example of a computer-readable non-transitory recording medium that stores a program executed by a computer.

[0042] The paper thickness sensor 21, the basis weight sensor 22, the surface property sensor 23 and the density sensor 24 have already been described with reference to FIG. 1, and therefore a description thereof will be omitted.

[0043] The communication unit 25 controls the transmission and reception of various signals, image data, and the like between the image forming apparatus 3 connected via a communication cable (not shown) or the like.

[0044] [Configuration of the control system of the image forming device] The image forming apparatus 3 includes a control unit 30 , a storage unit 304 , a transport control unit 321 , a halftone processing unit 330 , an image forming unit 33 , a fixing unit 34 , an operation display unit 36 ​​, and a communication unit 37 .

[0045] The control unit 30 includes a CPU 301, a RAM 302 used as a working area for the CPU 301, and a ROM 303 for storing programs executed by the CPU 301, etc.

[0046] A CPU 301 of the control unit 30 executes various control programs and setting data stored in a ROM 303 by loading the programs and setting data into a RAM 302. The CPU 301 is also connected to each unit constituting the image forming apparatus 3 via a system bus B2, and controls the operation of each unit.

[0047] For example, the CPU 301 performs control to form an image on a sheet Sh fed from the sheet feeder 1 or the sheet feed tray 31 (see FIG. 1) based on a print job input from a terminal device (not shown). The CPU 301 also performs image processing on a print image that is the source of an image to be formed on the sheet Sh based on information on characteristics such as the type of the sheet and information on a set inspection level.

[0048] The RAM 302 provides a working memory space for the CPU 301 and stores temporary data. The ROM 303 stores various control programs and setting data executed by the CPU 301. The programs are stored in the form of computer-readable program codes in the ROM 303. Note that a rewritable non-volatile memory such as an EEPROM or a flash memory may be used instead of the ROM 303.

[0049] The storage unit 304 is a large-capacity storage device including an HDD, an SSD, etc. The storage unit 304 stores an original image, data on the amount of ink droplets ejected from a group of multiple nozzles (not shown) of the head unit 171 (ink ejection amount data), and the like.

[0050] The transport control unit 321 controls the transport operation of the paper sheet Sh in the transport path 32 (see FIG. 1). The halftone processing unit 330 performs color conversion processing on the original image (image data) and also performs halftone processing such as dithering and error diffusion processing to reduce the number of gradations of each pixel of the image data to the number of gradations that can be represented by the image forming unit 33.

[0051] The image forming section 33 includes a head unit 331 and a head control section 332. The head unit 331 has already been described with reference to Fig. 1, and therefore its description will be omitted here. The head control section 332 controls the ink ejection operation by the head unit 331.

[0052] The fixing unit 34 and the operation display unit 36 ​​have already been described with reference to FIG. 1, and therefore will not be described here. The communication unit 37 transmits and receives various control signals and data between the paper characteristic detection device 2 and the image inspection device 4 .

[0053] [Configuration of the control system of the image inspection device] The image inspection device 4 includes a control unit 40 , a storage unit 404 , an image reading unit 41 , an image inspection unit 42 , and a communication unit 43 .

[0054] The control unit 40 includes a CPU 401, a RAM 402 used as a working area for the CPU 401, and a ROM 403 for storing programs executed by the CPU 401, etc.

[0055] The CPU 401 of the control unit 40 executes the programs by reading out various control programs and setting data stored in the ROM 403 and expanding the programs and setting data in the RAM 402. The CPU 401 is also connected to each unit constituting the image inspection device 4 via a system bus B3, and controls the operation of each unit.

[0056] For example, the CPU 401 controls the first reading section 411 or the second reading section 412 of the image reading unit 41 to read a printed material, and controls the image inspection unit 42 to inspect the first read image or the second read image obtained as a result of the reading.

[0057] The RAM 402 provides a working memory space for the CPU 401 and stores temporary data. The ROM 403 stores various control programs and setting data executed by the CPU 401. The programs are stored in the form of computer-readable program codes in the ROM 403. Note that a rewritable non-volatile memory such as an EEPROM or a flash memory may be used instead of the ROM 303. The storage unit 404 is a large-capacity storage device such as an HDD or SSD.

[0058] The image reading unit 41 includes a first reading unit 411 that reads a first side of the paper Sh to generate a first read image, and a second reading unit 412 that reads a second side of the paper Sh to generate a second read image.

[0059] The image inspection unit 42 performs an image inspection to detect the presence or absence of defects in the printed matter by comparing the first read image or the second read image with a printed image that is the source of the image formed on the paper. The image inspection unit 42 performs the image inspection based on a preset inspection level or an inspection level changed by the control unit 30 of the image forming device 3.

[0060] The inspection level is a standard indicating the inspection accuracy required for the image inspection by the image inspection unit 42, and the inspection levels include, for example, "high," "medium," and "low." The higher the inspection level set, the higher the accuracy (inspection quality) of the image inspection by the image inspection unit 42. In other words, even more minute defects are detected without omission.

[0061] The inspection level is set according to the importance of image inspection for objects to be discriminated, such as graphics, characters, images, etc., and is set, for example, through a user's operation on the operation display unit 36 ​​or a terminal device (not shown). For example, when characters, photographs, and graphics are mixed in printing based on a print job, the user can set the inspection level to "high" for parts that should not have defects, such as photo image parts, graphic image parts, and character image parts such as titles and large characters.

[0062] The communication unit 43 is connected to the image forming apparatus 3, and receives print jobs, various control signals, various data, and the like transmitted from the communication unit 37 of the image forming apparatus 3. In addition, the communication unit 43 transmits the results of the image inspection performed by the image inspection unit 42 to the image forming apparatus 3.

[0063] <Example 1> Next, an image processing method according to Example 1 of this embodiment will be described. [Example 1-1] In Example 1-1, the control unit 30 (see FIG. 2) of the image forming apparatus 3 acquires information on the type of paper Sh (one example of paper characteristics) based on the detection result by the paper characteristic detection device 2 or information input via operation on the operation display unit 36 ​​of the image forming apparatus 3. Then, the control unit 30 judges whether the detected type of paper Sh is likely to become worn (falsely detected as defective). Examples of paper Sh that is likely to become worn include embossed paper that has a textured surface and thus has a difference in color between light and dark, thin paper with a low basis weight, Japanese paper, recycled paper, wrapping paper, etc.

[0064] For example, when the paper Sh is embossed paper or the like as described above and is the subject of image inspection, and the inspection level is set to "high," the image inspection unit 42 may erroneously detect light and dark portions of the paper Sh as defective. One method for preventing the occurrence of such a situation is to perform image inspection after lowering the inspection level. However, in this embodiment, the control to lower the inspection level is not performed, and the control unit 30 of the image forming device 3 causes the image forming unit 33 to paint the entire surface of the paper Sh solidly with white ink and form a normal image on the white ink base.

[0065] Fig. 3 is a diagram showing an overview of image processing according to Example 1-1. By performing the above-mentioned image formation by the image forming unit 33, the printed matter according to Example 1-1 is formed by laminating a white ink image Pw and a print image P in this order on a sheet Sh, as shown in Fig. 3.

[0066] FIG. 4 is a flowchart showing an example of a procedure of an image processing method according to the embodiment 1-1. First, the control unit 30 (see FIG. 2) of the image forming apparatus 3 acquires information on the type of paper Sh based on the detection result by the paper characteristic detection device 2 or an operation on the operation display unit 36 ​​of the image forming apparatus 3 (step S1). Next, the control unit 30 determines whether or not the paper Sh is a paper that is likely to cause waste (a false detection of a defect) based on the type information acquired in step S1 (step S2).

[0067] If it is determined in step S2 that there is not a high possibility of wear (if step S2 is judged as NO), the control unit 30 (see FIG. 2) causes the image forming unit 33 to perform normal printing based on the print job (step S3). On the other hand, if it is determined in step S2 that there is a high possibility of wear on the paper (if step S2 is judged as YES), the control unit 30 determines whether or not there is a possibility that the possible inspection level is lower than the set inspection level (step S4).

[0068] For example, if the type of paper Sh is embossed paper and the set inspection level is "high," a highly accurate image inspection may result in the shading of the embossed paper being erroneously detected as defective. In such a case, step S4 will result in a YES determination. In other words, in step S4, the control unit 30 determines whether or not there is a possibility that the inspection level will be lower than the set level based on the information on the type of paper Sh acquired in step S1 and the information on the set inspection level.

[0069] If it is determined in step S4 that the inspection level is not below the set level (if step S4 is a NO judgment), the process of step S3 is performed. That is, normal printing is performed. On the other hand, if it is determined in step S4 that the inspection level may be below the set level (if step S4 is a YES judgment), the control unit 30 causes the image forming unit 33 to perform printing with white (W) ink as a base (step S5). As a result, the image forming unit 33 generates a printed matter in which a white ink print image P1 (an example of an image in a specific color) and a print image P2 are layered in this order on the paper Sh, as shown in FIG. 3. After the process of step S3 or step S5, the image processing according to the embodiment 1-1 is terminated.

[0070] According to Example 1-1, when the type of paper Sh on which an image is to be formed is embossed paper or the like that may be erroneously detected as defective in image inspection, printing is performed using white ink as a base. This smooths out the shading in the uneven parts of the paper Sh, thereby preventing the shading parts from being erroneously detected as defective. Therefore, according to this embodiment, the image inspection device 4 can accurately detect defects that should have been detected without performing control that lowers the inspection level.

[0071] In this embodiment, an example is given in which W ink is provided in addition to the Y, M, C, and K inks, but the present invention is not limited to this. White color may be generated by combining each of the Y, M, C, and K inks with a special color. Also, a color other than white may be used as the background color (specific color) as long as it is a color that can make the unevenness of the shading in the background color of the paper uniform.

[0072] [Example 1-2] In Example 1-2, when the paper Sh is thin paper with a low basis weight and double-sided printing is performed, the control unit 30 of the image forming device 3 prevents a decrease in the quality of the inspection in the image inspection by printing with white ink as a base only on the image forming area, rather than on the entire surface of the paper Sh.

[0073] 5 and 6 are diagrams showing an overview of image processing according to Example 1-2. In the example shown in Fig. 5, white inks Pw1 and Pw2 are printed as a base at the formation positions of the print image P1 of "A" and the print image P2 of "B". Note that if the density of the print image is low and therefore there is a low possibility of the print image showing through, printing with white ink as a base may not be performed.

[0074] 6 shows an example in which the print image P1 of "A" has a low density and the print image P2 of "B" has a high density. In this case, the control unit 30 of the image forming device 3 prints white ink as a base only in the formation position of the print image P2 of "B."

[0075] FIG. 7 is a flowchart showing an example of a procedure of an image processing method according to Example 1-2. First, the control unit 30 of the image forming apparatus 3 acquires information on the basis weight of the paper Sh (step S11). The control unit 30 can acquire information on the basis weight of the paper Sh based on the detection result by the paper characteristic detection device 2 or the basis weight of the paper Sh set in the print job.

[0076] Next, the control unit 30 determines whether the basis weight of the sheet Sh is less than a predetermined threshold, i.e., whether the sheet Sh is thin paper (step S12). If the basis weight of the sheet Sh is determined to be equal to or greater than the predetermined threshold in step S12 (if step S12 returns NO), the control unit 30 causes the image forming unit 33 to perform normal printing based on the print job (step S13).

[0077] On the other hand, if it is determined in step S12 that the basis weight of the sheet Sh is less than the predetermined threshold value (if step S12 is judged as YES), the control unit 30 determines whether or not double-sided printing is to be performed (step S14). If it is determined in step S14 that double-sided printing is not to be performed (if step S14 is judged as NO), the process of step S13 is performed. That is, normal printing is performed.

[0078] On the other hand, if it is determined in step S14 that double-sided printing is to be performed (if step S14 is a YES judgment), the control unit 30 determines whether the density of the print image is equal to or greater than a predetermined threshold (step S15). If it is determined in step S15 that the density of the print image is less than the predetermined threshold (if step S15 is a NO judgment), the process of step S13 is performed. That is, normal printing is performed.

[0079] On the other hand, if it is determined in step S15 that the density of the printed image is equal to or greater than the predetermined threshold (YES in step S15), the control unit 30 causes the image forming unit 33 to perform printing using white ink as a base (step S16). After the processing in step S13 or step S16, the image processing according to the embodiment 1-2 ends.

[0080] According to the embodiment 1-2, for example, during image inspection of the front side of the paper Sh, it is possible to prevent the image printed on the rear side of the thin paper from showing through and erroneously detecting that part as defective. Also, according to the embodiment 1-2, white ink is printed as a base only on the part where the printed image that may show through is formed, so that the consumption of white ink can be reduced. Note that the control unit 30 of the image forming device 3 may perform control to change the density of the white ink based on information on the basis weight of the paper Sh and the density of the printed image.

[0081] <Example 2> Next, an image processing method according to Example 2 of this embodiment will be described. In the second embodiment, the control unit 30 of the image forming device 3 determines whether the paper Sh on which the image is to be formed is paper such as colored paper that is highly likely to become worn (falsely detected as defective) and is likely to fall below the inspection level set in the image inspection by the image inspection device 4. If both determination results are YES, the control unit 30 causes the image forming unit 33 to perform image processing targeting the areas expected to fall below the inspection level, i.e., to print with white ink as a base.

[0082] Fig. 8 is a diagram showing an overview of image processing according to the second embodiment. The upper diagram in Fig. 8 shows that the upper left area of ​​the paper Sh is a photographic image area Arp where a photographic image is printed. The photographic image area Arp is shown as an example of an area where the detection level is set to "high". The lower diagram in Fig. 8 shows a state where a white ink image Pw is printed as a base on the photographic image area Arp, and a photographic image Pp is printed on top of that.

[0083] FIG. 9 is a flowchart illustrating an example of a procedure of an image processing method according to the second embodiment. The processes in steps S21 to S24 in FIG. 9 are the same as the processes in steps S1 to S4 in FIG. 4, and therefore will not be described.

[0084] If it is determined in step S24 that the inspection level may be lower than the set level (if step S24 is determined as YES), the control unit 30 causes a white ink image to be printed on the background of the area where it is determined that the inspection level may be lower than the set level (step S26). After the process of step S23 or step S26, the image processing according to the second embodiment is terminated.

[0085] According to the second embodiment, white ink underprinting is performed on an area where high-precision image inspection is required, that is, an area where the inspection level is set to "high", such as the photographic image area Arp. Therefore, according to the second embodiment, the influence of the paper Sh, such as colored paper, is suppressed in the photographic image area Arp by underprinting with white ink, so that the image inspection device 4 can detect defective parts with high precision without lowering the inspection level.

[0086] In addition, the control unit 30 of the image forming device 3 may adjust the density of the white ink printed on the base based on the minimum density of the image formed in an area where the inspection level is set to “high”, such as the photographic image area Arp, and information on the maximum density of the paper Sh.

[0087] Furthermore, in the second embodiment, the control unit 30 can perform, for example, the following controls (1) to (3) (adjustment of the density of the white ink in the background) and the like. (1) If the set inspection level is "high," the paper Sh is a light-colored paper, and the minimum density of the photographic image is higher than the threshold value set for the density of the paper Sh, it is determined that image inspection is possible at the set level, and white ink is not printed on the base. (2) If the minimum density of the photographic image is at the “medium” level, it is determined that image inspection at the set level is possible, and printing is performed with the white ink as the base, with the white ink density set to approximately half the maximum density. (3) When the minimum density of a photographic image is at the “small” level, in order to enable image inspection at the set level, the density of the white ink printed on the base is set to the maximum density, and printing is performed using the white ink as the base.

[0088] The threshold value set for the paper Sh is set in advance based on the verification results of whether or not the image inspection can be performed when the density of the paper Sh and the density of the photographic image are changed.

[0089] By performing such control, when a photographic image that requires high inspection accuracy is printed on paper Sh such as colored paper, the background is printed with the minimum amount of white ink necessary to maintain the inspection level. Therefore, according to the modified example of the second embodiment, it is possible to prevent a decrease in the inspection level in the image inspection while reducing the consumption of white ink.

[0090] <Example 3> Next, an image processing method according to a third embodiment of the present invention will be described. In the third embodiment, the control unit 30 of the image forming device 3 causes the image reading unit 41 (see FIG. 2) of the image inspection device 4 to read the paper Sh before image formation, and detects a portion of the paper Sh where wear is likely to occur. Then, when the control unit 30 predicts that the detected portion will fall below the set inspection level, it performs image processing, such as printing white ink on the background, on the print image formed in the corresponding portion.

[0091] Fig. 10 is a diagram showing an example of an area where wear is likely to occur in paper (hereinafter also referred to as a "wear warning area"). Fig. 10 shows an example where an upper left area of ​​paper Sh is detected as an area Ar1 where wear is likely to occur. Area Ar1 corresponds to an area that is likely to be erroneously detected as defective, such as an area with a higher density than the surrounding areas, or an area with a pattern or watermark.

[0092] For example, the control unit 30 measures and records the maximum density, minimum density, and average density of each area obtained by dividing the paper Sh before image formation into blocks. Then, based on the information obtained by the measurements, the control unit 30 determines whether or not the area is an area where waste is likely to occur.

[0093] Fig. 11 is a diagram showing an example of the configuration of a print image formed on the paper Sh shown in Fig. 10. Fig. 11 shows an example in which the upper left part of the paper Sh is the photographic image area Arp. In other words, the wear warning area Ar1 is included in the photographic image area Arp.

[0094] The control unit 30 of the image forming device 3 determines the inspection level of the image inspection that can be performed by the image inspection device 4, based on information about the difference between the maximum density of the paper Sh and the minimum density of the printed image. Since the density of the photographic image printed in the photographic image area Arp is often high, as shown in Fig. 11, when the wear warning area Ar1 is included in the photographic image area Arp, the possibility that the wear warning area Ar1 will be erroneously detected as defective is low.

[0095] Therefore, when the difference between the maximum density of the paper Sh and the minimum density of the printed image is equal to or greater than the threshold value, the control unit 30 determines that image inspection at the "high" inspection level is possible.

[0096] Fig. 12 is a diagram showing an example of a wear warning area on a sheet of paper. Fig. 12 shows an example in which a lower right area on a sheet of paper Sh is detected as a wear warning area Ar2.

[0097] Fig. 13 is a diagram showing an example of the configuration of a print image formed on the paper Sh shown in Fig. 11. Fig. 13 shows an example in which the upper left part of the paper Sh is a photographic image area Arp, and the other area is a character image area Arc. In other words, the wear warning area Ar2 is included in the character image area Arc. In the figure, the photographic image area Arp is shown by a bold solid line, and the character image area Arc is shown by a bold two-dot chain line. In this case as well, the control unit 30 judges the inspection level of the image inspection that can be performed by the image inspection device 4 based on information on the difference between the maximum density of the paper Sh and the minimum density of the printed image.

[0098] A character image is printed in the character image area Arc, and a character image often has many areas with low density compared to a photographic image. Therefore, as shown in Fig. 12, when the waste warning area Ar1 is included in the character image area Arc, the waste warning area Ar1 is likely to be erroneously detected as a defect.

[0099] Therefore, when the difference between the maximum density of the paper Sh and the minimum density of the printed image is less than the threshold value, the control unit 30 determines that image inspection is possible at the inspection level "low." Furthermore, when the maximum density of the paper is greater than the minimum density of the printed image, the control unit 30 determines that the inspection level is "undetectable" (hereinafter also referred to as "exclude detection").

[0100] If the set inspection level is "high" and the inspection level determined to be executable is "low" or "exclude detection," the control unit 30 performs image processing such as printing white ink on the background of the corresponding location. In other words, the control unit 30 performs control so that the inspection level in the image inspection to be performed approaches the set inspection level as closely as possible.

[0101] FIG. 14 is a flowchart illustrating an example of a procedure of image processing according to the third embodiment. First, the control unit 30 of the image forming apparatus 3 measures the maximum density, minimum density, and average density in each area obtained by dividing the paper Sh before image formation into blocks, and stores the measured values ​​in the memory unit 304 (see FIG. 2) or the like (step S31).

[0102] Next, the control unit 30 determines the inspection level that can be implemented based on the information on the difference between the density information of the paper Sh calculated in step S31 and the minimum density of the printed image (step S32). Next, the control unit 30 determines whether the inspection level set for that area is "high" (step S33). If it is determined in step S33 that the inspection level is "high" (if the determination in step S33 is YES), the control unit 30 causes the image forming unit 33 to perform normal printing (step S34).

[0103] On the other hand, if the inspection level is determined not to be "high" in step S33 (if step S33 returns NO), that is, if the inspection level is determined to be "low" or "detection excluded", the control unit 30 causes the image forming unit 33 to perform image processing such as printing white ink on the background of the print image (step S35). After the processing of step S34 or step S35, the image processing according to the third embodiment ends.

[0104] In the third embodiment, when it is expected that the inspection level to be performed in an area where the set inspection level is "high" will be "low" or lower, the control unit 30 performs image processing on the print image in the area. This makes it possible to bring the inspection level in the image inspection to be performed closer to the set inspection level.

[0105] In the third embodiment, an example was given in which image processing is performed to increase the inspection level only when the set inspection level is "high", but the present invention is not limited to this. Even if the set inspection level is "low", image processing may be performed on the print image of the corresponding area when the inspection level to be performed is the lower "detection exclusion". In addition, in the third embodiment, an example was given in which the inspection level to be determined is one of three levels, "high", "low", and "detection exclusion", but the present invention is not limited to this. Other levels, such as "medium", may be added.

[0106] In the third embodiment, if it is expected that the inspection level to be performed will be lower than the set inspection level and the difference falls below a preset threshold, the control unit 30 may notify the user of a warning, for example, by displaying a message on the screen of the operation display unit 36 ​​(see FIG. 2). By performing such control, the user can determine whether or not to continue the process, and therefore it becomes possible to execute the process according to the user's wishes. The warning to the user may be notified by voice via a speaker (one example of an output unit) not shown.

[0107] <Example 4> Next, an image processing method according to Example 4 of this embodiment will be described. In the fourth embodiment, the control unit 30 of the image forming device 3 causes the image reading unit 41 (see FIG. 2) of the image inspection device 4 to read the sheet Sh before image formation, and detects areas on the sheet Sh where wear is likely to occur. Then, the control unit 30 determines the inspection level that can be implemented based on information on the detected areas where wear is likely to occur and information on the inspection level set for those areas. Then, for areas where the inspection level that can be implemented is "medium" or lower, the control unit 30 performs image processing, such as printing with white ink as a base, to bring the inspection level that can be implemented closer to the set inspection level.

[0108] FIG. 15 is a diagram showing an example of a wear warning area on a sheet Sh. FIG. 15 shows an example in which seven areas, Ar11 to Ar17, where wear is likely to occur, are detected. In FIG. 15, the parts shown in ovals indicate the places where wear is likely to occur, and the size of the ovals indicates the extent of the influence that the corresponding areas have on the image inspection. For example, if the size of a pattern or watermark included in an area is large or the density is high, it cannot be completely corrected even if image processing such as printing with white ink as a base is performed. In other words, it is not possible to eliminate the possibility that the area will be erroneously detected as defective. Such areas are areas that have a large influence on the image inspection (hereinafter also referred to as "high wear warning areas"), and are shown in FIG. 15 as large ovals.

[0109] In addition, in FIG. 15, areas that have a medium effect on the image test (hereinafter also referred to as "medium fatigue warning areas") are shown with medium-sized ovals, and areas that have a small effect on the image test (hereinafter also referred to as "low fatigue warning areas") are shown with small-sized ovals.

[0110] In the example shown in FIG. 15, the low fatigue warning areas are areas Ar11, Ar14, Ar16, and Ar17, the medium fatigue warning areas are areas Ar13 and Ar15, and the high fatigue warning area is area Ar12.

[0111] Fig. 16 is a diagram showing an example of inspection levels that can be implemented in each area shown in Fig. 15. Fig. 16 shows an example of inspection levels that can be implemented when the set inspection level is "high".

[0112] As shown in Fig. 16, the inspection level that can be implemented in the area Ar12, which is a high wear warning area, is determined to be "exclude detection" (indicated as "EX" in the figure). Also, the inspection level that can be implemented in the area Ar11, which is a low wear warning area, is determined to be "medium" (indicated as "M" in the figure). Furthermore, the inspection level that can be implemented in the areas Ar13 to Ar17, which are medium wear warning areas, is determined to be "low" (indicated as "L" in the figure).

[0113] That is, in the areas Ar11 to Ar17, it is assumed that the inspection level at which the inspection can be performed falls below the set inspection level ("high"). In the fourth embodiment, the control unit 30 performs image processing such as printing with white ink as a base on these areas, thereby making it possible to bring the inspection level at which the inspection can be performed closer to the set inspection level.

[0114] <Example 5> Next, an image processing method according to Example 5 of this embodiment will be described. In the fifth embodiment, the control unit 30 of the image forming device 3 causes the image reading unit 41 (see FIG. 2) of the image inspection device 4 to read the sheet Sh before image formation, and detects locations on the sheet Sh where wear is likely to occur. If the detected location is expected to fall below the set inspection level and the control unit 30 determines that the possible inspection level can be improved by inverting (rotating 180°) the print image upside down, the control unit 30 rotates the print image 180° and then prints.

[0115] Fig. 17 is a diagram showing an example of a wear warning area on a sheet of paper Sh. Fig. 17 shows an example in which a wear warning area Ar21 is detected on the lower right side of the sheet of paper Sh.

[0116] Fig. 18 is a diagram showing an example of a print image P11 formed on the paper Sh shown in Fig. 17. In Fig. 18, an example is shown in which the upper left region is a photographic image region Arp, and the other region is a text image region Arc. The waste warning region Ar21 shown in Fig. 17 is included in the text image region Arc.

[0117] Fig. 19 is a diagram showing an example of inspection levels that can be implemented in each area shown in Fig. 18. Fig. 19 shows inspection levels that can be implemented when the set inspection level is "high." As shown in FIG. 19, the inspection level that can be implemented in the area Ar21, which is a high wear caution area, is determined to be "low" (denoted as "L" in the figure).

[0118] Fig. 20 is a diagram showing an example of a printed image P11h obtained by rotating the printed image P11 shown in Fig. 18 by 180°. In the printed image P11h, the position of the photographic image area Arp moves downward and to the right. Therefore, the waste warning area Ar21 shown in Fig. 17 is included in the photographic image area Arp.

[0119] Fig. 21 is a diagram showing an example of an inspection level that can be implemented for the printed image P11h shown in Fig. 20. As described above, in the printed image P11h, the wear warning area Ar21 is located within the photographic image area Arp. As a result, the density of the portion in the wear warning area Ar21 where wear is likely to occur and the photographic image printed in the photographic image area Arp is reduced, so the inspection level that can be implemented calculated by the control unit 30 is "high" (denoted as "H" in the figure).

[0120] FIG. 22 is a flowchart illustrating an example of a procedure of image processing according to the fifth embodiment. Steps S41 and S42 in FIG. 22 are the same as steps S21 and S22 in FIG. 14, and therefore a description thereof will be omitted.

[0121] After the process of step S42, the control unit 30 judges whether or not there is an area where the inspection level that can be performed is lower than the set level (step S43). If it is judged in step S43 that there is no area where the inspection level is lower than the set level (if the judgment in step S43 is NO), the image processing according to the fifth embodiment is terminated.

[0122] On the other hand, if it is determined in step S43 that there is an area below the set level (if step S43 is judged YES), it is determined whether the possible inspection level will be improved by rotating the print image 180 degrees (step S44). If it is determined in step S44 that the inspection level will be improved (if step S44 is judged YES), the control unit 30 rotates the print image 180 degrees and causes the image forming unit 33 to execute printing (step S45).

[0123] On the other hand, if it is determined in step S44 that the inspection level will not be improved (if step S44 is determined as NO), the control unit 30 causes the image forming unit 33 to perform image processing such as printing with white ink as a base and then printing (step S46). After step S45 or step S46 is executed, the image processing according to the fifth embodiment is terminated.

[0124] According to the fifth embodiment, the control unit 30 rotates the print image by 180 degrees, thereby making it possible to prevent a portion where wear is likely to occur from being erroneously detected as defective.

[0125] <Example 6> Next, an image processing method according to Example 6 of this embodiment will be described. In the sixth embodiment, the control unit 30 of the image forming device 3 causes the image reading unit 41 (see FIG. 2) of the image inspection device 4 to read the paper Sh before image formation, and detects locations on the paper Sh where wear is likely to occur. Then, if the detected location is expected to fall below the set inspection level and the control unit 30 determines that the possible inspection level can be improved by reversing the front and back of the printed image, the control unit 30 reverses the front and back of the printed image before printing. Reversing the front and back of the printed image means swapping the printed image for the front side and the printed image for the back side.

[0126] Fig. 23 is a diagram showing an example of a wear warning area in a sheet of paper Sh. The left side of Fig. 23 shows a front side of a sheet of paper Shf, and the right side shows a back side of a sheet of paper Shb. In the front side of a sheet of paper Shf, the lower areas Ar31 to Ar33 are detected as a wear warning area. Meanwhile, in the back side of a sheet of paper Shb, the upper areas Ar34 to Ar36 are detected as a wear warning area.

[0127] In the front side sheet Shf, an area Ar31 is a medium wear warning area, and areas Ar32 and Ar33 are low wear warning areas. In the back side sheet Shb, an area Ar34 is a low wear warning area, an area Ar35 is a high wear warning area, and an area Ar36 is a medium wear warning area.

[0128] Fig. 24 is a diagram showing an example of a print image P21f formed on the front side sheet Shf and a print image P21b formed on the back side sheet Shb shown in Fig. 23. The left side of Fig. 24 shows a print image P21f formed on the front side sheet Shf, and the right side shows a print image P21b formed on the back side sheet Shb.

[0129] In the front print image P21f shown on the left side of Fig. 24, the upper region is the photographic image region Arp, and the lower region is the text image region Arc. And the lower regions of the wear warning regions Ar31-Ar33 shown in Fig. 23 are included in the text image region Arc. Meanwhile, in the back print image P21b shown on the right side, the upper region is the text image region Arc, and the lower region is the photographic image region Arp. And the upper regions of the wear warning regions Ar34-Ar36 are included in the text image region Arc.

[0130] Fig. 25 is a diagram showing an example of inspection levels that can be implemented in each area shown in Fig. 23 and Fig. 24. Fig. 25 shows inspection levels that can be implemented when the set inspection level is "high."

[0131] As shown on the right side of Fig. 25, the inspection level that can be implemented in the area Ar35, which is a high wear warning area, is determined to be "exclude detection (EX)". The inspection level that can be implemented in the area Ar34, which is a medium wear warning area, is determined to be "low (L)". Furthermore, the inspection level that can be implemented in the areas Ar31 to Ar33 shown on the left side of Fig. 25 and the area Ar36 shown on the right side, which are low wear warning areas, is determined to be "medium (M)".

[0132] Fig. 26 is a diagram in which the print image P21f for the front side and the print image P21b for the back side shown in Fig. 24 are interchanged. That is, Fig. 26 shows a state in which the print image for the front side paper Shf is the print image P21b for the back side, and the print image for the back side paper Shb is the print image P21f for the front side.

[0133] In this way, by inverting the print image, the upper region of the print image P21b formed on the front sheet Shf shown on the left side of Fig. 26 becomes the character image region Arc and the lower region becomes the photographic image region Arp. And, the waste warning regions Ar31 to Ar33 are arranged within the lower photographic image region Arp.

[0134] 26, in the print image P21f formed on the back side paper Shb, the upper region is the photographic image region Arp and the lower region is the character image region Arc. The waste warning regions Ar34 to Ar36 are arranged within the upper photographic image region Arp.

[0135] Fig. 27 is a diagram showing an example of inspection levels that can be implemented for the print image P21f and print image P21b shown in Fig. 26. As described above, in the print image P21b formed on the front sheet Shf shown on the left side of Fig. 26, the areas Ar31-Ar33 where wear is likely to occur are located within the photographic image area Arp. As a result, the inspection level that can be implemented calculated by the control unit 30 is "high (H)".

[0136] Also, in the print image P21f formed on the back side paper Shb shown on the right side of Fig. 26, the areas Ar34 to Ar36 where wear is likely to occur are located within the photographic image area Arp. As a result, the inspection level that can be implemented is "high (H)".

[0137] FIG. 28 is a flowchart illustrating an example of a procedure of image processing according to the sixth embodiment. Steps S51 and S52 in FIG. 28 are the same as steps S21 and S22 in FIG. 14, and therefore a description thereof will be omitted.

[0138] After the process of step S52, the control unit 30 judges whether or not there is an area where the inspection level that can be performed is lower than the set level (step S53). If it is judged in step S53 that there is no area where the inspection level is lower than the set level (if the judgment in step S53 is NO), the image processing according to the sixth embodiment is terminated.

[0139] On the other hand, if it is determined in step S53 that there is an area below the set level (if step S53 is judged YES), it is determined whether or not the possible inspection level will be improved by flipping the print image over (step S54). If it is determined in step S54 that the inspection level will be improved (if step S54 is judged YES), the control unit 30 flips the print image over and causes the image forming unit 33 to execute printing (step S55).

[0140] On the other hand, if it is determined in step S54 that the inspection level will not be improved (if step S54 is determined as NO), the control unit 30 causes the image forming unit 33 to perform image processing such as printing with white ink as a base and then printing (step S56). After step S55 or step S56 is executed, the image processing according to the sixth embodiment is terminated.

[0141] According to the sixth embodiment, the control unit 30 inverts the print image, thereby making it possible to prevent a portion where wear is likely to occur from being erroneously detected as defective.

[0142] <Example 7> In the seventh embodiment, when the control unit 30 of the image forming device 3 detects an area where a decrease in the feasible inspection level is expected, it adjusts the density of the white ink printed as a base depending on the type of paper Sh, the density of the printed image, the size or density of the waste warning area, etc.

[0143] Fig. 29 is a diagram showing an example of a wear warning area on a sheet of paper Sh. Three different sheets of paper Sh31 to Sh33 are shown in Fig. 29. The left side of Fig. 29 shows sheet Sh31, the center shows sheet Sh32, and the right side shows sheet Sh33.

[0144] 29, wear warning areas Ar41 to Ar44 are detected in the lower half of the sheet Sh31 shown on the left side of Fig. 29. Area Ar41 is a high wear warning area, area Ar42 is a medium wear warning area, and areas Ar43 and Ar44 are low wear warning areas.

[0145] 29, wear warning areas Ar51 to Ar53 are detected in the upper half of the paper Sh32 shown in the center of Fig. 29. Area Ar52 is a high wear warning area, area Ar53 is a medium wear warning area, and area Ar51 is a low wear warning area.

[0146] 29, wear warning areas Ar61 to Ar67 are detected over the entire sheet Sh33. Area Ar62 is a high wear warning area, areas Ar63 and Ar65 are medium wear warning areas, and areas Ar61, Ar64, Ar66, and Ar67 are low wear warning areas.

[0147] Fig. 30 is a diagram showing examples of print images (print image P31 to print image P33) formed on each sheet of paper (sheet of paper Sh31 to sheet of paper Sh33) shown in Fig. 29. The left side of Fig. 30 shows print image P31 formed on sheet of paper Sh31, the center shows print image P32 formed on sheet of paper Sh32, and the right side shows print image P33 formed on sheet of paper Sh33.

[0148] In the print image P31 shown on the left side of Fig. 30, the upper region is a photographic image region Arp, and the lower region is a text image region Arc. The lower regions of the waste warning regions Ar41 to Ar44 shown in Fig. 29 are included in the text image region Arc.

[0149] In the print image P32 shown in the center of Fig. 30, the upper region is the photographic image region Arp and the lower region is the character image region Arc. And, in the regions Ar51 to Ar53 shown in Fig. 29 where waste is likely to occur, the lower regions are included in the character image region Arc.

[0150] In print image P33 shown on the right side of Fig. 30, the upper region is the photographic image region Arp and the lower region is the character image region Arc. And, in the regions Ar61-Ar64 shown in Fig. 29 where wear is likely to occur, the upper regions are included in the photographic image region Arp, and in the regions Ar65-Ar67, the lower regions are included in the character image region Arc.

[0151] [Processing when the waste warning area is included in the text image area] In the seventh embodiment, when the wear warning region is included in the character image region Arc, and when it is determined that white ink can be used for the base based on the paper detection results such as the paper quality and color of the paper Sh31, the control unit 30 prints white toner on the base of the wear warning region. Specifically, when the density of the warning regions Ar43 and Ar44, which are low wear warning regions, is low, the control unit 30 causes the image forming unit 33 to print white ink on the base with a "small" amount of ink adhesion. As a result, it is assumed that the feasible inspection level will be "high," so the control unit 30 causes the image inspection device 4 to perform image inspection at the "high" level as set.

[0152] In the wear warning area Ar42, which is a medium wear warning area, the control unit 30 causes the image forming unit 33 to print white ink on the base by setting the ink density to the highest density (maximum) that can be applied to the base. As a result, it is expected that the feasible inspection level will be "high," so the control unit 30 causes the image inspection device 4 to perform image inspection at the "high" level that is set.

[0153] Even in the attention area Ar41, which is a high-waste-warning area, the control unit 30 causes the image forming unit 33 to print white ink on the background with the ink density set to "maximum". However, in the high-waste-warning area, even if such processing is performed, the relevant area may be erroneously detected as a defective area. Therefore, the control unit causes the image inspection device 4 to perform image inspection at a "medium" level. This reduces the possibility that areas such as patterns and watermarks will be erroneously detected as defective areas, thereby improving the accuracy of the image inspection. Therefore, it is possible to bring the inspection level in the image inspection to be performed closer to the "high" level that is preset for the relevant area.

[0154] [Processing when the waste warning area is included in the photographic image area] In addition, in the seventh embodiment, when a wear warning area is included in the photographic image area Arp, and the minimum density of the photograph printed in the photographic image area Arp is sufficiently higher than the density in the wear warning area, and it is determined that image inspection at the inspection level "high" is possible, the control unit 30 causes the image forming unit 33 to perform normal printing without using white toner.

[0155] Furthermore, if the difference between the average density in the wear warning area and the minimum density of the photographic image printed in the photographic image area Arp is small, the control unit 30 also applies white toner to the background of the entire photographic area with an ink density that matches the area that has the highest impact on image processing (requires a high level of image processing) among the wear warning areas. As a result, it is expected that the inspection level that can be implemented in the corresponding wear warning area will be "high," so the control unit 30 causes the image inspection device 4 to perform image inspection at the "high" level that is set.

[0156] In addition, when the difference between the density in the high waste warning area (area Ar52) and the minimum density of the photographic image printed in the photographic image area Arp is small, and the density near the high waste warning area is low (below a predetermined threshold), the control unit 30 also prints white ink on the base for both the high waste warning area and the corresponding surrounding areas.

[0157] In addition, the control unit 30 may determine whether to use a method of changing the density of white ink for each area or a method of adjusting the density to the maximum density of the waste warning area, based on the following information. Number of areas printed with white ink as the base Information on whether the ratio of the area to the photographic image area Arp is equal to or less than a predetermined threshold -Information on the size of the area with concentration below the threshold, etc.

[0158] The size of the area with a density below the threshold can be calculated based on, for example, the minimum density, average density, maximum density, etc. in the waste caution area or the area with a density below the threshold.

[0159] In addition, the control unit 30 may perform two or all of the following processes in parallel: rotating the printed image upside down, swapping the printed image for the front side with the printed image for the back side, and printing white ink on the base of the waste warning area.

[0160] Furthermore, the present invention is not limited to the above-described embodiment, and various other applications and modifications are possible without departing from the gist of the present invention as set forth in the claims. For example, the above-mentioned embodiment describes the system configuration in detail and specifically in order to explain the present invention in an easily understandable manner, and is not necessarily limited to a system having all of the described configurations. In addition, it is also possible to add, delete, or replace part of the configuration of the present embodiment with other configurations. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0161] 2...paper characteristic detection device, 3...image forming device, 4...image inspection device, 30...control unit, 33...image forming unit, 41...image reading unit, 42...image inspection unit, 100...image forming system

Claims

1. a control unit that performs image processing on the print image printed on the recording material and causes an image forming unit to form the print image after the image processing when it is determined that the inspection level at which the image inspection can be performed is likely to be lower than the set inspection level based on information on characteristics of the recording material on which an image based on a print image is formed and setting information on an inspection level indicating an inspection accuracy required for an image inspection of a printed matter on which the image is formed on the recording material. Image forming system.

2. When the recording material includes an area that may be erroneously detected as defective in the image inspection and the set inspection level is high, the control unit determines that the executable inspection level may be lower than the set inspection level. The image forming system according to claim 1 .

3. The control unit determines whether or not there is a possibility that the executable inspection level is lower than the set inspection level, based on information on an area that may be erroneously detected as defective in the image inspection, information on the density of a print image formed in the area, and information on the set inspection level. The image forming system according to claim 2 .

4. The control unit determines whether or not there is a possibility that the executable inspection level will be lower than the set inspection level for each area obtained by dividing the recording material into blocks. The image forming system according to claim 3 .

5. The control unit performs a process of adding an image in a specific color to a background of the print image as the image processing. The image forming system according to any one of claims 1 to 4.

6. The control unit determines whether or not there is a possibility that the executable inspection level is lower than the set inspection level based on a difference between the density of the printed image and the density of the recording material. The image forming system according to claim 5 .

7. The control unit adjusts the density of the image in the specific color according to a magnitude of a difference between the density of the print image and the density of the recording material. The image forming system according to claim 5 .

8. When the control unit determines that there is a possibility that the inspection level at which the image inspection can be performed is lower than the set inspection level, and when the control unit determines that the inspection level at which the image inspection can be performed can be brought closer to the set inspection level by the image processing, the control unit performs a process of rotating the top and bottom of a print image as the image processing. The image forming system according to any one of claims 1 to 4.

9. when the control unit determines that there is a possibility that the inspection level at which the image inspection can be performed is lower than the set inspection level, and when the control unit determines that the inspection level at which the image inspection can be performed can be brought closer to the set inspection level by the image processing, the control unit performs a process of switching the print image for the front side and the print image for the back side of the recording material as the image processing. The image forming system according to any one of claims 1 to 4.

10. The control unit performs control to notify a warning via an output unit when there is a possibility that an inspection level at which the image inspection can be performed falls below the set inspection level and the difference between the levels exceeds a predetermined threshold. The image forming system according to any one of claims 1 to 4.

11. a step of performing image processing on the print image printed on the recording material and forming the print image after image processing in an image forming unit when it is determined that the inspection level at which the image inspection can be performed is likely to be lower than the set inspection level based on information on the characteristics of the recording material on which an image based on the print image is formed and on setting information on an inspection level indicating the inspection accuracy required for the image inspection of the printed matter on which the image is formed. Image processing methods.

Images