JP2024033823A - Printing system, print inspection device, and print inspection method - Google Patents

Abstract

The present invention provides a printing system that inspects prints printed by a printing device for show-through, which enables faster determination of an inspection threshold that does not determine show-through as a defect. [Solution] A printing system includes a read image acquisition unit that acquires a read image of a printed matter, a difference image generation unit that generates a difference image between a reference image and a read image, and a difference image based on the difference image and an inspection threshold. , an inspection section that inspects the printed matter for defects, and a determination section that determines an inspection threshold for not determining show-through on the printed matter as a defect, and the determination section includes a test chart including a gradation area and a test pattern. Double-sided printing is performed using a printing device, an initial value of the inspection threshold is set from the gradation area in the difference image of the test chart, and one or more candidates for the inspection threshold including the initial value of the inspection threshold are set. In the difference image of the test chart, an inspection threshold value is determined that does not determine show-through in the test pattern as a defect. [Selection diagram] Figure 3

Description

The present invention relates to a printing system, a print inspection device, and a print inspection method.

2. Description of the Related Art There is a print inspection device that inspects prints printed by a printing device for show-through. For example, the second side of a printed matter with an image printed on the first side is read, it is determined whether show-through has occurred, and the image of the first side and the second side of the printed matter where show-through has occurred is determined. A system is known that stores a density difference between the two as a density difference threshold (for example, see Patent Document 1).

In the technology disclosed in Patent Document 1, in order to determine the threshold for determining show-through, an image of the first side of a printed matter that has been determined to have show-through and an image of the second side of the printed matter are used. It is necessary to calculate the density difference between the image and the show-through image.

An embodiment of the present invention has been made in view of the above-mentioned problems, and includes an inspection threshold that does not determine show-through as a defect in a printing system that inspects show-through of printed matter printed by a printing device. Enable faster decision making.

In order to solve the above problems, a printing system according to an embodiment of the present invention includes a read image acquisition unit that acquires a read image obtained by reading a printed matter printed by a printing device based on print data, and a read image acquisition unit that compares the read image. a difference image generation unit that generates a difference image between a target reference image and the read image; an inspection unit that inspects the printed matter for defects based on the difference image and an inspection threshold; a determining unit that determines the inspection threshold for not determining show-through as the defect; the determining unit determines the gradation area in which the gradation value of a predetermined color changes stepwise; A test chart including a test pattern is printed on both sides by the printing device, an initial value of the inspection threshold is set from the gradation area in the difference image of the test chart, and an initial value of the inspection threshold is set. The inspection threshold that does not determine that show-through in the test pattern is determined to be the defect in the difference image of the test chart is determined from one or more candidates for the inspection threshold including the above.

According to an embodiment of the present invention, in a printing system that inspects prints printed by a printing apparatus for show-through, it becomes possible to more quickly determine an inspection threshold value that does not determine show-through as a defect.

FIG. 1 is a diagram illustrating an example of a system configuration of a printing system according to an embodiment. FIG. 1 is a diagram illustrating an example of a hardware configuration of a computer according to an embodiment. FIG. 1 is a diagram illustrating an example of a functional configuration of a printing system according to an embodiment. FIG. 3 is a diagram illustrating an example of job information according to an embodiment. 7 is a flowchart illustrating an example of inspection threshold determination processing according to the first embodiment. FIG. 3 is a diagram illustrating an example of an inspection level and a defect detection filter according to an embodiment. FIG. 3 is a diagram illustrating an example of a test chart according to an embodiment. FIG. 3 is a diagram for explaining an initial value of an inspection level according to an embodiment. FIG. 3 is a diagram showing an example of a read image of a test chart and a coordinate table according to an embodiment. FIG. 3 is a diagram illustrating an example of an inspection level setting screen according to an embodiment. 7 is a flowchart illustrating an example of inspection threshold determination processing according to the second embodiment.

Embodiments of the present invention will be described in detail below with reference to the drawings.

<System configuration>
FIG. 1 is a diagram illustrating an example of a system configuration of a printing system according to an embodiment. For example, as shown in FIG. 1, the printing system 1 includes a DFE (Digital Front End) 100, a printing device 110, a print inspection device 120, a stacker 130, and the like.

The DFE 100 performs RIP (Raster Image Processor) processing based on the received print job to generate print data to be printed, and transfers the generated print data and job information indicating the processing details of the print job to the printing device. This is an information processing device that outputs data to 110.

The printing device 110 is an image forming device that performs printing on paper, which is a recording medium, based on print data and job information received from the DFE 100. For example, the printing device 110 obtains paper from the paper feed unit 111 and transports the obtained paper along the transport path 112. Further, in the printing device 110, photoreceptor drums 113K, 113C, 113M, and 113Y of K (black), C (cyan), M (magenta), and Y (yellow) are arranged along the conveyor belt 114. . In the printing device 110, the photoreceptor drums 113K, 113C, 113M, and 113Y stack toner images of each color on the conveyor belt 114, the rollers 115 transfer the toner images onto the conveyed paper, and the rollers 117 transfer the toner images to the conveyor belt 114. Fix it on top.

In the case of single-sided printing, the printing device 110 discharges the paper as it is to the print inspection device 120, and in the case of double-sided printing, the printing device 110 reverses the paper in the reversing path 118 and conveys it again along the conveyance path 112. Thereby, the printing device 110 transfers and fixes the toner image on the back side of the paper in the same way as on the front side of the paper, and then discharges the paper to the print inspection device 120.

The print inspection device 120 is an inspection device that inspects printed matter printed by the printing device 110. For example, the print inspection device 120 uses the reading devices 121 and 122 to read both sides of a sheet on the transport path 123 to generate a read image. The print inspection device 120 discharges the read paper to the stacker 130.

The print inspection device 120 also generates a difference image between the read image and a reference image to be compared with the read image, and inspects the printed matter for defects based on the generated difference image and the inspection threshold. do.

The stacker 130 stacks the sheets discharged from the print inspection device 120 onto a tray 131.

In the example of FIG. 1, a printing device 110 has an operation panel 10. However, the system configuration of the printing system 1 shown in FIG. 1 is an example. For example, the print inspection device 120 may not include the operation panel 20, and the operation panel 10 of the printing device 110 may be used to perform settings for the print inspection device 120, display of inspection results, and the like. Further, the print inspection device 120 may be an information terminal such as a PC connected via a communication network, and may perform settings for the print inspection device 120, display inspection results, and the like.

<Hardware configuration>
The printing device 110 and the print inspection device 120 have, for example, the hardware configuration of a computer 200 including a dedicated device 209, as shown in FIG.

FIG. 2 is a diagram illustrating an example of the hardware configuration of the computer 200 according to one embodiment. The computer 200 includes, for example, a CPU (Central Processing Unit) 201, a RAM (Random Access Memory) 202, a ROM (Read Only Memory) 203, a storage device 204, a communication device 205, an I/F 206, etc. connected via a bus 210. has been done. Further, the I/F 206 is connected to, for example, an output device 207, an input device 208, a dedicated device 209, and the like.

The CPU 201 is a processor that controls the entire printing apparatus 110, print inspection apparatus 120, etc. by executing a predetermined program stored in a storage medium such as the storage device 204 or ROM 203, for example. The RAM 202 is, for example, a volatile memory used as a work area for the CPU 201. The ROM 203 is a nonvolatile memory that stores, for example, a program for starting the CPU 201 and the like. The storage device 204 is a large-capacity storage device that stores, for example, an OS (Operating System), applications, data, or information.

Communication device 205 includes a variety of wired or wireless communication interfaces for communicating with other computers 200. I/F 206 is an interface for connecting various hardware to bus 210. In the example of FIG. 2, an output device 207, an input device, a dedicated device, and the like are connected to the I/F 206.

The output device 207 includes various devices (for example, a display, a speaker, a light emitting element, etc.) that perform output to the outside. Input device 208 includes various devices (eg, touch panel, keyboard, pointing device, microphone, switch, button, etc.) that accept input from the outside. Note that the output device 207 and the input device 208 may be input/output devices such as a touch panel display, for example.

The dedicated device 209 is hardware for realizing dedicated functions in the printing apparatus 110 and print inspection apparatus 120. For example, the printing apparatus 110 is connected to a dedicated device 209 such as a printing device that prints on paper and a transport mechanism that transports the paper. Furthermore, a dedicated device 209 such as reading devices 121 and 122 for reading printed materials printed by the printing device 110 is connected to the print inspection device 120, for example. Furthermore, a dedicated device 209 such as an ASIC (Application Specific Integrated Circuit) or a GPU (Graphics Processing Unit) may be connected to the print inspection apparatus 120 to speed up image processing. Note that at least some of the dedicated devices 209 may be connected to the bus 210 without going through the I/F 206.

(Hardware configuration of DFE and stacker)
In this embodiment, it is assumed that existing devices are used as the DFE 100 and the stacker 130, and the hardware configuration thereof may be any configuration, so a description thereof will be omitted here.

<Functional configuration>
FIG. 3 is a diagram illustrating an example of a functional configuration of a printing system according to an embodiment.

(Functional configuration of printing device)
The printing device 110 includes, for example, a print control section 301, a printing section 302, a test chart generation section 303, a UI (User Interface) 304, a storage section 305, and the like.

The print control unit 301 is realized, for example, by a program executed by the CPU 201 of the printing apparatus 110. The print control unit 301 executes, for example, a first print control process that causes the print unit 302 to execute a print process based on the first print job (print data and job information) received from the DFE 100. Further, when the print control unit 301 according to the present embodiment receives a second print job for printing a test chart from the test chart generation unit 303, the print control unit 301 generates a test chart based on the second print job. The second print control process to be printed in step 302 is executed.

Further, the print control unit 301 transmits print data (RIP image) and job information to the print inspection device 120 when causing the printing unit 302 to execute print processing.

FIG. 4 is a diagram illustrating an example of job information according to an embodiment. As shown in FIG. 4, the job information 400 includes, for example, "job generation source", "generation time", "page ID", "print side", "paper ID", "copy ID", "job ID", It includes parameters such as "paper type", "paper size", "job type", and "defect detection".

“Job generation source” is information indicating the generation source of the print job. A DFE job indicates that the job is generated by the DFE 100, and an internal job indicates that the job is generated by the test chart generation unit 303 or the like. “Generation time” is information indicating the time when the job information 400 was generated by the generation source. "Page ID" is an identification number that identifies a print image, and is incremented by 1 every time one page is output from the time the power is turned on, for example. "Printing side information" is information that identifies whether the printed image is printed on one side, on the front side when printing on both sides (double-sided front), or on the back (double-sided back). be.

“Paper ID” is identification information that identifies the paper. For example, in the case of double-sided printing, two pages printed on the same paper are given the same paper ID. For example, 1 is added to the "paper ID" every time one sheet of paper is processed from when the power is turned on. The "copy ID" is identification information for each copy, and is incremented by 1 each time one copy is output from the time the power is turned on, for example. "Job ID" is identification information that identifies a print job, and is incremented by 1 each time one print job is output from the time the power is turned on, for example.

“Paper type” is information indicating the type of paper. “Paper size” is information indicating the size of paper. The "job type" is information indicating, for example, whether the print job is normal printing or test chart printing. “Defect detection” is information indicating, for example, whether the page is subject to defect detection, and whether or not to insert a slip sheet indicating that a defect has been detected on the page where the defect was detected.

Job information 400 is generated for each page of print data, for example, and is managed together with the print data. Furthermore, the printing device 110 prints each print data based on the job information 400.

Here, returning to FIG. 3, the description of the functional configuration of the printing apparatus 110 will be continued. The printing unit 302 is realized, for example, by a program executed by the CPU 201 of the printing apparatus 110 and a dedicated device 209 (printing device, transport mechanism, etc.) connected to the I/F 206 of the printing apparatus 110. The printing unit 302 executes printing processing to print printed matter based on instructions from the print control unit 301 and print data. Further, the printing unit 302 outputs a printed material, which is a printed sheet, to the print inspection device 120.

The test chart generation unit 303 is realized, for example, by a program executed by the CPU 201 of the printing device 110. For example, the test chart generation unit 303 generates a print job for printing a test chart including a test pattern for determining show-through in accordance with an instruction from the print inspection device 120, and sends the generated print job to the print control unit 301. Output. Note that the print data of the test chart is stored in advance in, for example, the storage unit 305 or the like.

The UI unit 304 is realized by, for example, a program executed by the CPU 201 of the printing apparatus 110, an output device 107 connected to the I/F 206 of the printing apparatus 110, an input device 108, and the like. The UI unit 304 displays, for example, an operation screen for operating the printing apparatus 110 or a setting screen for configuring the printing apparatus 110, and accepts input operations by the user.

The storage unit 305 is realized by, for example, a program executed by the CPU 201 of the printing apparatus 110, the storage device 204, the RAM 202, and the like. The storage unit 305 stores various print data, job information, setting information, etc., including, for example, the above-described print data for the test chart. Note that the storage unit 305 can be accessed from each functional configuration within the printing apparatus 110. Further, the storage unit 305 may be provided outside the printing device 110.

(Functional configuration of print inspection device)
The print inspection device 120 includes, for example, a read image acquisition section 321, a reference image generation section 322, a difference image generation section 323, a system control section 310, a UI section 324, a storage section 325, and the like.

The read image acquisition unit 321 is realized by, for example, a program executed by the CPU 201 of the print inspection device 120, the reading devices 121 and 122 connected to the I/F 206, an ASIC, and the like. The read image acquisition unit 321 executes read image acquisition processing to acquire a read image obtained by reading a printed matter printed by the printing device 110.

The reference image generation unit 322 is realized by, for example, a program executed by the CPU 201 of the print inspection apparatus 120, an ASIC connected to the I/F 206, and the like. The reference image generation unit 322 executes a reference image generation process to generate a reference image to be compared with the read image based on print data sent from the print control unit 301 of the printing device 110, job information 400, etc. do.

The difference image generation unit 323 is realized by, for example, a program executed by the CPU 201 of the print inspection apparatus 120, an ASIC connected to the I/F 206, and the like. The difference image generation unit 323 executes a difference image generation process to generate a difference image representing the difference between the reference image generated by the reference image generation unit 322 and the read image acquired by the read image acquisition unit 321.

The system control unit 310 is realized, for example, by a program executed by the CPU 201 of the print inspection device 120. The system control unit 310 includes, for example, a data management unit 311, an inspection unit 312, a slip sheet determination unit 313, a determination unit 314, and the like.

The data management unit 311 receives print data (RIP image) and job information from the printing device 110, and executes a data management process of storing and managing the received information in the storage unit 325. Further, the data management section 311 transfers necessary information to the read image acquisition section 321, reference image generation section 322, difference image generation section 323, inspection section 312, slip sheet determination section 313, stacker 130, and the like.

The inspection unit 312 executes inspection processing to inspect the printed matter for defects based on the difference image generated by the difference image generation unit 323 and the inspection threshold. Note that an example of the inspection process executed by the inspection unit 312 will be described later.

The interleaf sheet determination unit 313 determines whether or not an interleaf sheet can be inserted as a mark at the location where the defect is found, based on the inspection result by the inspection section 312. If it is determined that the interleaf sheet can be inserted, the interleaf sheet insertion information is transmitted to the printing device. 110 or a device for inserting interleaf sheets, such as the stacker 130.

The determining unit 314 executes a determination process to determine an inspection threshold value that does not determine that show-through on both sides is a defect. Note that an example of the determination process executed by the determination unit 314 will be described later.

The UI unit 324 is realized, for example, by a program executed by the CPU 201 of the print inspection device 120. The UI unit 324 displays, on the operation panel 20 or the like included in the print inspection apparatus 120, a setting screen for setting the inspection threshold value for show-through based on the inspection threshold value determined by the determination unit 314. Note that the UI unit 324 may display a setting screen for setting the show-through inspection threshold on the operation panel 10 or the like provided in the printing apparatus 110. Alternatively, the UI unit 324 may provide a web page that displays a setting screen for setting a show-through inspection threshold to an information terminal or the like that can communicate with the print inspection apparatus 120 via a communication network.

Preferably, the UI unit 324 displays the recommended value of the inspection threshold determined by the determination unit 314 on a setting screen for setting the inspection threshold for show-through.

The storage unit 325 is realized by, for example, a program executed by the CPU 201 of the print inspection apparatus 120, the storage device 204, the RAM 202, and the like. The storage unit 325 can be accessed from each functional configuration of the print inspection device 120, and stores, for example, print data and job information 400 received from the printing device 110, inspection level information to be described later, initial value setting information, and defect detection. Store filters, etc.

Note that the functional configuration of the printing system 1 shown in FIG. 3 is an example. For example, in FIG. 3, the test chart generation unit 303 included in the printing device 110 may be included in the print inspection device 120. In this case, the test chart generation unit 303 of the print inspection device 120 transmits the print job of the test chart to the print control unit 301 of the printing device 110 in the same manner as the DFE 100. Thereby, the printing system 1 according to the present embodiment may be realized using the existing printing device 110 that does not have the test chart generation unit 303.

<Processing flow>
Next, the flow of the inspection threshold determination process in the print inspection method according to the present embodiment will be described.

[First embodiment]
FIG. 5 is a flowchart illustrating an example of inspection threshold determination processing according to the first embodiment. This process is an example of a process in which the print inspection apparatus 120 having the functional configuration explained in FIG. It shows.

Note that the inspection level is an example of an inspection threshold. The print inspection apparatus 120 stores, for example, inspection level information 601 as shown in FIG. 6 in the storage unit 325 or the like. In the example of FIG. 6(A), inspection level information 601 includes inspection thresholds for point defects, linear defects (vertical), and linear defects (horizontal) corresponding to five inspection levels 1 to 5. It remembers the combination of Inspection levels 1 to 5 are examples of a plurality of inspection thresholds that the print inspection device 120 has. The number of inspection levels may be less than 5, or may be 6 or more. In the example of FIG. 6A, level 1 is the lowest (loose) inspection level, and level 5 is the highest (severe) inspection level.

In the inspection level information 601 shown in FIG. 6(A), inspection level 0 is a dummy inspection level and cannot be selected by the user. This inspection level 0 indicates the maximum value of the threshold value at which the inspection unit 312 does not detect any defects. In addition, the inspection level X is used to indicate that there is no recommended inspection level when show-through is determined to be a defect no matter which inspection level 1 to 5 is set.

Now, returning to FIG. 5, the flowchart will be explained. In step S501, the system control unit 310 of the print inspection apparatus 120 determines whether there is inspection threshold information. For example, the system control unit 310 stores inspection levels (inspection thresholds) in the storage unit 325 in association with paper (recording medium). Furthermore, if the inspection level corresponding to the set sheet is stored in the storage section 325, the system control section 310 determines that inspection threshold information is present.

If there is inspection threshold information, the system control unit 310 moves the process to step S502. On the other hand, if there is no inspection threshold information, the system control unit 310 moves the process to step S503.

When proceeding to step S502, the system control unit 310 determines whether to re-acquire inspection threshold information. As an example, the system control unit 310 may control the inspection threshold information when the hardware etc. constituting the printing system 1 is replaced or when a predetermined period of time has elapsed since the acquisition of the inspection threshold information. You may decide to reacquire it. Alternatively, the system control unit 310 may, for example, use the UI unit 324 to inquire of the user whether or not to re-acquire the test threshold information.

When reacquiring inspection threshold information, the system control unit 310 moves the process to step S503. On the other hand, if the test threshold information is not acquired again, the system control unit 310 ends the process of FIG. 5 . Note that when the inspection threshold information is not reacquired, the print inspection apparatus 120 inspects the printed matter for defects using the inspection level corresponding to the paper stored in the storage unit 325.

In step S503, the system control unit 310 acquires a difference image of the test chart.

For example, the determination unit 314 of the system control unit 310 instructs the test chart generation unit 303 of the printing device 110 to print a test chart (double-sided printing). Thereby, the test chart generation unit 303 outputs a test chart print job to the print control unit 301. The print control unit 301 of the printing device 110 uses the printing unit 302 to print the test chart on both sides based on the test chart print job received from the test chart generation unit 303.

The system control unit 310 uses the read image acquisition unit 321 to read the printout of the test chart printed on both sides by the printing device 110, and acquires a read image. The system control unit 310 also acquires a difference image generated by the difference image generation unit 323 that represents the difference between the reference image of the test chart and the read image. Note that the reference image of the test chart may be generated by the reference image generation unit 322, or a reference image of the test chart stored in advance in the storage unit 325 or the like may be used.

FIG. 7 is a diagram illustrating an example of a test chart according to an embodiment. As shown in FIG. 7, the front surface 710 of the test chart 700 includes a gradation area 711 in which the gradation value of a predetermined color changes stepwise, and a test pattern 712 for determining show-through. Further, the back side 720 of the test chart 700 includes a test pattern 721 for determining show-through. Note that the dashed-dotted line in FIG. 7 is for explaining the range of the gradation area 711 and the test patterns 712 and 721, and does not exist in the actual test chart 700.

In the example of FIG. 7, the gradation area 711 includes a gradation image 711C in which the gradation value of C (cyan) changes in steps, and a gradation image 811M in which the gradation value of M (magenta) changes in steps. It can be done. In addition, in the gradation area 711, Y (yellow)
A gradation image 711Y in which the gradation value of K (black) changes in steps, and a gradation image 811K in which the gradation value of K (black) changes in steps are included.

In step S504, the determination unit 314 of the system control unit 310 sets an initial value of the inspection level based on the obtained difference image. For example, the system control unit 310 stores initial value setting information 602 as shown in FIG. 6(B) in the storage unit 325 or the like. The initial value setting information 602 stores tone values of gradation areas for each color of C, M, Y, and K for each inspection level. Further, the determining unit 314 sets an initial value of the inspection level depending on in which region the difference image of the gradation region 711 is found.

FIG. 8 is a diagram for explaining the initial value of the inspection level according to one embodiment. For example, as shown in FIG. 8, assume that a difference indicating show-through is found at the gradation values of inspection levels 3, 4, and 5 in gradation images 711C, 711M, and 711K. Further, it is assumed that differences indicating show-through are found at the gradation values of inspection levels 2, 3, 4, and 5 in the gradation image 711Y. As an example, the determining unit 314 selects an inspection level 4 corresponding to a tone value 102, which is one level lower than the lowest tone value 153, where a difference indicating show-through was found among the respective colors. Set to initial value. In other words, the determining unit 314 sets, as the initial value of the inspection level, inspection level 4, which is one step higher in inspection level than inspection level 3, which is the highest inspection level in which a difference indicating show-through was found among each color.

In step S505, the inspection unit 312 of the system control unit 310 inspects the test chart for defects at the set inspection level. For example, in addition to the above-mentioned inspection level information 601, the system control unit 310 includes a point defect detection filter 603, a linear defect (vertical) detection filter 604, and The linear defect (horizontal) detection filter 605 is stored in the storage unit 325 or the like.

A point defect detection filter 603 shown in FIG. 6(C) is a defect detection filter used to detect point defects. The inspection unit 312 uses this point defect detection filter 603 to perform a convolution operation on each pixel of the difference image, and when the operation result exceeds the inspection threshold for a point defect, the inspection unit 312 converts the pixel into a point defect detection filter 603. Determined as defective.

Note that the values of the point defect detection filter 603 are adjusted so that the total value of positive values is 1 and the total value of negative values is -1. Thereby, the calculation result of the convolution calculation represents the difference between the pixel in question and the average value of eight adjacent pixels.

A linear defect (vertical) detection filter 604 shown in FIG. 6(D) is a defect detection filter used when detecting a linear defect (vertical). The inspection unit 312 uses the linear defect (vertical) detection filter 604 to perform a convolution operation on each pixel of the difference image, and if the operation result exceeds the inspection threshold for a point defect, the inspection unit 312 is determined to be a linear defect (vertical).

Note that the values of the linear defect (vertical) detection filter 604 are also adjusted so that the total value of positive values is 1 and the total value of negative values is -1. Thereby, the calculation result of the convolution calculation represents the difference between the average value of five pixels in the vertical direction centering on the pixel and the respective average values of the ten pixels adjacent to the left and right of the pixel.

A linear defect (horizontal) detection filter 605 shown in FIG. 6(E) is a defect detection filter used when detecting a linear defect (lateral). The inspection unit 312 uses the linear defect (horizontal) detection filter 605 to perform a convolution operation on each pixel of the difference image, and if the operation result exceeds the inspection threshold for a point defect, the pixel is is determined to be a linear defect (horizontal).

Note that the values of the linear defect (horizontal) detection filter 605 are also adjusted so that the total value of positive values is 1 and the total value of negative values is -1. Thereby, the calculation result of the convolution calculation represents the difference between the average value of each of the 5 horizontal pixels centering on the relevant pixel and the 10 pixels adjacent to the left and right of the pixel.

Now, returning to FIG. 5, the explanation of the flowchart will be continued. In step S506, the determination unit 314 of the system control unit 310 determines the show-through of the test chart based on the inspection result by the inspection unit 312, and stores the determination result in the storage unit 325 or the like. For example, the determining unit 314 stores a coordinate table 910 for horizontal reversal and a coordinate table 920 for vertical reversal, as shown in FIG. 9, in the storage unit 325 or the like.

Further, a read image (back side) 900 shown in FIG. 9 is an image of a read image obtained by reading the back side of a printed matter on which the test chart 700 is printed. The read image acquired by the read image acquisition unit 321 by printing the test chart 700 described in FIG. occurs. When show-through occurs, as shown in FIG. 9, the scanned image (back side) 900, the back side 720 of the test chart 700, and the front side 710 image become thinly superimposed. Note that depending on the direction of collation during double-sided printing, whether double-sided printing is performed by flipping left and right, or double-sided printing is performed by flipping vertically.

The coordinate table 910 during horizontal reversal shows coordinates (upper right coordinates and upper left coordinates) indicating the positions of objects 901, 902, 903, etc. for show-through determination when horizontally reversed and double-sided printing is performed. There is. In addition, the coordinate table 920 at the time of vertical reversal shows the coordinates (upper right coordinates and upper left coordinates) indicating the positions of objects 901, 902, 903, etc. for show-through determination when vertically reversed and double-sided printing is performed. It shows.

When the test chart 700 is horizontally flipped and printed on both sides, the determining unit 314 excludes the results detected by the inspection unit 312 from the show-through determination in the coordinate range that is not included in the coordinate table 910 at the time of horizontally flipping. , determine the presence or absence of show-through. For example, if at least one defect detected by the inspection unit 312 is included in each coordinate range stored in the coordinate table 910, the determination unit 314 determines that there is show-through.

Similarly, when the test chart 700 is upside down and printed on both sides, the determination unit 314 uses the results detected by the inspection unit 312 in the coordinate range that is not included in the coordinate table 920 at the time of upside down from the determination of show-through. The presence or absence of show-through is determined by excluding the image. For example, if at least one defect detected by the inspection unit 312 is included in each coordinate range stored in the coordinate table 920, the determination unit 314 determines that there is show-through.

Further, the determining unit 314 stores the determination result of show-through in the storage unit 325 or the like. For example, the determining unit 314 stores information on the coordinate area determined to have show-through and the inspection level in the storage unit 325 or the like.

In step S507, if the determination result is "no show-through", the determining unit 314 moves the process to step S508, and if the determination result is "show-through", the decision unit 314 moves the process to step S509.

In step S508, the determining unit 314 determines the current inspection level as the inspection threshold. Note that the inspection threshold determined here becomes a recommended value of the inspection level, which will be described later.

On the other hand, in step S509, the determining unit 314 determines whether show-through has been determined at all inspection levels lower than the initial value of the inspection level. If show-through is determined at all inspection levels lower than the initial value of the inspection level, the determining unit 314 moves the process to step S510. On the other hand, if show-through has not been determined for all inspection levels lower than the initial value of the inspection levels, the determining unit 314 moves the process to step S511.

In step S510, the determination unit 314 determines the inspection level X, which indicates that there is no inspection level at which show-through does not occur, as the inspection threshold value. In this case, there is no recommended inspection level value, which will be described later.

On the other hand, when proceeding to step S511, the determining unit 314 lowers the current inspection level by one level, and then returns the process to step S505.

In step S512, the determining unit 314 stores inspection threshold information in which the determined inspection level is associated with paper (recording medium) in the storage unit 325 or the like.

Through the process of FIG. 5, if the show-through in the test chart 700 is determined to be a defect at the initial value of the inspection level, the determining unit 314 determines that the show-through in the test pattern is a defect while lowering the inspection level step by step. Determine the inspection threshold that will not be used. As a result, in the printing system 1 that inspects prints printed by the printing device 110 for show-through, it is possible to more quickly determine an inspection threshold value that does not determine show-through as a defect.

In addition, since the print inspection device 120 stores the determined inspection threshold in the storage unit 325 in association with paper (recording medium) information, the next time when printing on the same paper, the storage unit 315 etc. The processing can be further sped up by using test thresholds stored in the .

(Inspection level setting screen)
The print inspection device 120 can display an inspection level setting screen as shown in FIG. 10, for example, based on the inspection threshold determined in the process of FIG.

FIG. 10 is a diagram illustrating an example of an inspection level setting screen according to an embodiment. This figure shows an example of an inspection level setting screen 1000 that the UI unit 324 of the print inspection apparatus 120 displays on the operation panel 10, 20, or an external information terminal. The UI unit 324 displays, on the inspection level setting screen 1000, a recommended inspection level 1001, inspection level change buttons 1002 and 1003, an "inspection level determination" button 1004, a "cancel" button 1005, and a defect detection result 1010. etc. will be displayed.

The recommended level 1001 is, for example, an inspection level corresponding to the inspection threshold determined in step S508 of FIG. 5. The user can change this inspection level using inspection level change buttons 1002 and 1003. Furthermore, the user can update the inspection level by selecting the "Determine inspection level" button 1004. Furthermore, if a defect other than show-through has occurred on the paper and the user wants to execute the process shown in FIG. 5 again, the user can cancel the determination of the inspection level by selecting the "Cancel" button 1005. be able to.

Note that in step S510 of FIG. 5, if inspection level It is desirable to display a message, etc. notifying that the

Preferably, the UI unit 324 includes, in the defect detection result 1010, a display element that shows the scanned image (back side) 900 and the coordinate range in which show-through is detected as a defect at the current inspection level, as described in FIG. 9, for example. 1011 is displayed. Thereby, the user can easily set the inspection level while checking the location where show-through is detected as a defect.

[Second embodiment]
By the inspection level setting process according to the first embodiment described with reference to FIG. 5, it is possible to more quickly determine an inspection threshold value that does not determine show-through as a defect. However, in this method, for example, when changing the inspection level on the inspection level setting screen 1000 as shown in FIG. 1011 may not be displayed. This is because in the inspection level setting process described with reference to FIG. 5, show-through on the test chart is determined using only the minimum inspection level.

In the second embodiment, a display element 1011 indicating the coordinate range in which show-through is detected as a defect can be displayed in the defect detection result 1010 at all inspection levels while suppressing an increase in processing time. An example of processing will be explained.

<Processing flow>
FIG. 11 is a flowchart illustrating an example of inspection threshold determination processing according to the second embodiment. Note that among the processes shown in FIG. 11, the processes in steps S501 to S503 are the same as the processes in the first embodiment described in FIG. 5, so they will be described here. Further, detailed explanation of similar processing contents of the first embodiment will be omitted here.

In step S1101, the determination unit 314 of the system control unit 310 sets an initial value of the inspection level based on the difference image acquired in step S503. In the second embodiment, the determining unit 314 sets, as the initial value of the inspection level, an inspection level that is one step lower than the lowest inspection level at which a difference indicating show-through was found among each color. do.

In step S1102, the inspection unit 312 of the system control unit 310 inspects the test chart for defects at the set inspection level in the same manner as in the first embodiment.

In step S1103, the determination unit 314 of the system control unit 310 determines the show-through of the test chart based on the inspection result by the inspection unit 312 in the same manner as in the first embodiment, and stores the determination result in the storage unit 325 or the like. Remember.

In step S1004, the system control unit 310 determines whether the current inspection level is the maximum. If the current inspection level is the maximum, the system control unit 310 moves the process to step S1106. On the other hand, if the current inspection level is not the maximum, the system control unit 310 moves the process to step S1105.

When proceeding to step S1105, the determining unit 314 of the system control unit 310 raises the inspection level by one level and returns the process to step S1102.

On the other hand, when proceeding to step S1106, the determining unit 314 determines whether there is an inspection level for which it has been determined that there is no show-through in the processing of steps S1102 to S1105. If there is an inspection level determined to be free of show-through, the determining unit 314 moves the process to step S1107. On the other hand, if there is no inspection level determined to be free of show-through, the determining unit 314 moves the process to step S1108.

In step S1107, the determining unit 314 determines the highest inspection level among the inspection levels determined to be free of show-through as the inspection threshold value. Note that the inspection threshold determined here becomes a recommended value of the inspection level.

On the other hand, in step S1108, the determination unit 314 determines the inspection level X, which indicates that there is no inspection level at which show-through does not occur, as the inspection threshold value. In this case, there is no recommended value for the inspection level, which will be described later.

In step S1109, the determining unit 314 stores inspection threshold information in which the determined inspection level is associated with paper (recording medium) in the storage unit 325 or the like.

Through the process shown in FIG. 5, the system control unit 310 can obtain the show-through determination results for all inspection levels higher than the initial value of the inspection level. Further, when the inspection level is lower than the initial value of the inspection level, it is determined that no show-through occurs, and the process for determining show-through is omitted, thereby speeding up the processing.

As described above, according to the second embodiment, when the inspection level is changed on the inspection level setting screen 1000, the display element 1011 indicating the coordinate range in which show-through is detected as a defect is displayed in the defect detection result 1010. will be able to be displayed.

As described above, according to each embodiment of the present invention, in the printing system 1 that inspects show-through of printed matter printed by the printing device 110, it becomes possible to more quickly determine an inspection threshold value that does not determine show-through as a defect. .

<Supplement>
Each function of each embodiment described above can be realized by one or more processing circuits. Here, the term "processing circuit" as used herein refers to a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, or a processor designed to execute each function explained above. This includes devices such as ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and conventional circuit modules.

<Additional notes>
This specification discloses a printing system, a print inspection device, and a print inspection method as described below.
(Section 1)
a read image acquisition unit that acquires a read image obtained by reading a printed matter printed by the printing device based on the print data;
a difference image generation unit that generates a difference image between a reference image to be compared with the read image and the read image;
an inspection unit that inspects the printed matter for defects based on the difference image and the inspection threshold;
a determining unit that determines the inspection threshold for not determining show-through of the printed matter as the defect;
has
The determining unit is
printing a test chart on both sides with the printing device, including a gradation area in which the gradation value of a predetermined color changes stepwise, and a test pattern for determining show-through;
setting an initial value of the inspection threshold from the gradation area in the difference image of the test chart;
From one or more candidates for the inspection threshold including the initial value of the inspection threshold, select the inspection threshold that does not determine the show-through in the test pattern as the defect in the difference image of the test chart. decide,
printing system.
(Section 2)
The determining unit stores the determined inspection threshold in a storage unit in association with information on a recording medium on which the test chart is printed on both sides,
The inspection unit inspects the printed matter for defects using the inspection threshold corresponding to the information of the recording medium stored in the storage unit when the printing device prints the printed matter on the recording medium.
The printing system according to paragraph 1.
(Section 3)
The determining unit is
If the inspection unit determines that the show-through in the test chart is a defect using the initial value of the inspection threshold,
determining the inspection threshold at which show-through in the test pattern is not determined to be a defect while changing the inspection threshold stepwise;
The printing system according to item 1 or 2.
(Section 4)
The printing system according to any one of items 1 to 3, wherein the test chart includes the gradation area corresponding to a plurality of colors.
(Section 5)
The determining unit determines an initial value of the inspection threshold for each of the plurality of colors, and sets the strictest threshold among the inspection thresholds determined for each of the plurality of colors as the inspection threshold. The printing system according to item 4, wherein the value is an initial value.
(Section 6)
It has a UI section that displays a setting screen for setting a show-through inspection threshold based on the inspection threshold determined by the determining section, and the inspection threshold can be changed on the setting screen. , the printing system according to any one of items 1 to 5.
(Section 7)
having a plurality of check-through thresholds,
The determination unit determines the show-through in the test pattern using all the test thresholds stricter than the initial value of the test threshold among the plurality of test thresholds for the show-through, and determines the show-through in the test pattern. Store the judgment result in the storage unit,
When the inspection level is changed on the setting screen, the UI unit determines that the show-through at the changed inspection threshold is a defect based on the show-through determination result stored in the storage unit. display the area that has been
The printing system according to paragraph 6.
(Section 8)
The test chart includes a front test chart and a back test chart,
a horizontally reversed coordinate set storing coordinates indicating a range of an image object on the test chart on the front surface when the test chart is horizontally reversed and stacked;
a vertically flipped coordinate set that stores coordinates indicating a range of an image object on the test chart on the front surface when the test chart is stacked vertically upside down;
has
The determining unit is
When the test chart is horizontally reversed and printed on both sides, a defect detected by the inspection unit in a coordinate range not included in the horizontally reversed coordinate set is excluded from the determination of show-through;
When the test chart is flipped upside down and printed on both sides, defects detected by the inspection unit in a coordinate range not included in the upside down coordinate set are excluded from the determination of show-through;
The printing system according to any one of items 1 to 7.
(Section 9)
a read image acquisition unit that acquires a read image obtained by reading a printed matter printed by the printing device based on the print data;
a difference image generation unit that generates a difference image between a reference image to be compared with the read image and the read image;
an inspection unit that inspects the printed matter for defects based on the difference image and the inspection threshold;
a determining unit that determines the inspection threshold for not determining show-through of the printed matter as the defect;
has
The determining unit is
printing a test chart on both sides with the printing device, including a gradation area in which the gradation value of a predetermined color changes stepwise, and a test pattern for determining show-through;
setting an initial value of the inspection threshold from the gradation area in the difference image of the test chart;
From one or more candidates for the inspection threshold including the initial value of the inspection threshold, select the inspection threshold that does not determine the show-through in the test pattern as the defect in the difference image of the test chart. decide,
Print inspection equipment.
(Section 10)
Print inspection system
an acquisition process of acquiring a scanned image of a printed matter printed by the printing device based on the print data;
a generation process that generates a difference image between a reference image to be compared with the read image and the read image;
a determination process that determines a defect in the printed matter based on the difference image and an inspection threshold;
a determination processing unit that determines the inspection threshold for not determining show-through of the printed matter as the defect;
Run
The determination process is
printing a test chart on both sides with the printing device, including a gradation area in which the gradation value of a predetermined color changes stepwise, and a test pattern for determining show-through;
setting an initial value of the inspection threshold from the gradation area in the difference image of the test chart;
From one or more candidates for the inspection threshold including the initial value of the inspection threshold, select the inspection threshold that does not determine the show-through in the test pattern as the defect in the difference image of the test chart. decide,
Print inspection method.

1 Printing system 110 Printing device 120 Print inspection device 306, 325 Storage unit 312 Inspection unit 314 Determination unit 321 Read image acquisition unit 322 Reference image generation unit 323 Difference image generation unit 324 UI unit 700 Test chart 711 Gradation area 712, 721 Test pattern 910 Coordinate table for horizontal reversal (horizontal reversal coordinate set)
920 Coordinate table when vertically flipped (vertically flipped coordinate set)
1000 Settings screen

Japanese Patent Application Publication No. 2015-178190

Claims (10)

a read image acquisition unit that acquires a read image obtained by reading a printed matter printed by the printing device based on the print data;
a difference image generation unit that generates a difference image between a reference image to be compared with the read image and the read image;
an inspection unit that inspects the printed matter for defects based on the difference image and the inspection threshold;
a determining unit that determines the inspection threshold for not determining show-through of the printed matter as the defect;
has
The determining unit is
printing a test chart on both sides with the printing device, including a gradation area in which the gradation value of a predetermined color changes stepwise, and a test pattern for determining show-through;
setting an initial value of the inspection threshold from the gradation area in the difference image of the test chart;
From one or more candidates for the inspection threshold including the initial value of the inspection threshold, select the inspection threshold that does not determine the show-through in the test pattern as the defect in the difference image of the test chart. decide,
printing system. The determining unit stores the determined inspection threshold in a storage unit in association with information on a recording medium on which the test chart is printed on both sides,
The inspection unit inspects the printed matter for defects using the inspection threshold corresponding to the information of the recording medium stored in the storage unit when the printing device prints the printed matter on the recording medium.
The printing system according to claim 1. The determining unit is
When the inspection unit determines that the show-through in the test chart is a defect using the initial value of the inspection threshold,
determining the inspection threshold at which show-through in the test pattern is not determined to be a defect while changing the inspection threshold stepwise;
The printing system according to claim 1. The printing system according to claim 1, wherein the test chart includes the gradation area corresponding to a plurality of colors. The determining unit determines an initial value of the inspection threshold for each of the plurality of colors, and selects the strictest inspection threshold among the inspection thresholds determined for each of the plurality of colors for the inspection. The printing system according to claim 4, wherein the threshold value is an initial value. It has a UI section that displays a setting screen for setting a show-through inspection threshold based on the inspection threshold determined by the determining section, and the inspection threshold can be changed on the setting screen. The printing system according to any one of claims 1 to 5. having a plurality of check-through thresholds,
The determination unit determines the show-through in the test pattern using all the test thresholds stricter than the initial value of the test threshold among the plurality of test thresholds for the show-through, and determines the show-through in the test pattern. Store the judgment result in the storage unit,
When the inspection threshold is changed on the setting screen, the UI unit determines that the show-through at the changed inspection threshold is a defect based on the determination result of the show-through stored in the storage unit. Displays locations where it has been determined that
The printing system according to claim 6. The test chart includes a front test chart and a back test chart,
a horizontally reversed coordinate set storing coordinates indicating a range of an image object on the test chart on the front surface when the test chart is horizontally reversed and stacked;
a vertically flipped coordinate set that stores coordinates indicating a range of an image object on the test chart on the front surface when the test chart is stacked vertically upside down;
has
The determining unit is
When the test chart is horizontally reversed and printed on both sides, a defect detected by the inspection unit in a coordinate range not included in the horizontally reversed coordinate set is excluded from the determination of show-through;
When the test chart is flipped upside down and printed on both sides, defects detected by the inspection unit in a coordinate range not included in the upside down coordinate set are excluded from the determination of show-through;
The printing system according to claim 1. a read image acquisition unit that acquires a read image obtained by reading a printed matter printed by the printing device based on the print data;
a difference image generation unit that generates a difference image between a reference image to be compared with the read image and the read image;
an inspection unit that inspects the printed matter for defects based on the difference image and the inspection threshold;
a determining unit that determines the inspection threshold for not determining show-through of the printed matter as the defect;
has
The determining unit is
printing a test chart on both sides with the printing device, including a gradation area in which the gradation value of a predetermined color changes stepwise, and a test pattern for determining show-through;
setting an initial value of the inspection threshold from the gradation area in the difference image of the test chart;
From one or more candidates for the inspection threshold including the initial value of the inspection threshold, select the inspection threshold that does not determine the show-through in the test pattern as the defect in the difference image of the test chart. decide,
Print inspection equipment. Print inspection system
an acquisition process of acquiring a scanned image of a printed matter printed by the printing device based on the print data;
a generation process that generates a difference image between a reference image to be compared with the read image and the read image;
a determination process that determines a defect in the printed matter based on the difference image and an inspection threshold;
a determination process for determining the inspection threshold for not determining show-through of the printed matter as the defect;
Run
The determination process is
printing a test chart on both sides with the printing device, including a gradation area in which the gradation value of a predetermined color changes stepwise, and a test pattern for determining show-through;
setting an initial value of the inspection threshold from the gradation area in the difference image of the test chart;
From one or more candidates for the inspection threshold including the initial value of the inspection threshold, select the inspection threshold that does not determine the show-through in the test pattern as the defect in the difference image of the test chart. decide,
Print inspection method.

Images