Inspection device, method for controlling inspection device, inspection system, and program

Abstract

To solve the problem in which: inspection of an image may be conducted by printing the image on a pre-printed sheet on which an image is printed in advance; however, since an inspection area is limited to a peripheral area of print data, inspection of the entire sheet cannot be conducted.SOLUTION: An inspection device reads an image printed on a pre-printed sheet on which information on a specific color is printed in advance, and the information, removes the specific color included in image data obtained through the reading, and inspects the image after the specific color is removed on the basis of a reference image. The inspection device can correctly perform inspection of the image printed on the pre-printed sheet on which the information on the specific color is printed in advance by removing the specific color included in the image data.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an inspection apparatus, a control method for an inspection apparatus, an inspection system, and a program. [Background technology]

[0002] In recent years, an inspection system has become known that allows an inspection device to inspect a sheet printed by a printing device (hereinafter referred to as a printed sheet) while it is being transported. In the inspection of the printed sheet, the inspection device reads an image of the transported printed sheet and judges whether the printing on the printed sheet is normal or not by image analysis of the read image. The inspection device is capable of detecting printing defects and color misalignment. In addition, an image may be printed on preprinted paper on which an image has been printed (hereinafter referred to as a preprinted image) and the image may be inspected. In Patent Document 1, when performing image inspection on the preprinted paper, mask data is generated based on the print data and the surrounding area of ​​the print data is set as an inspection area in order to check whether the print data has been printed reliably. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-310567 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the inspection area is limited to the peripheral area of ​​the print data, and therefore there is a problem in that the entire paper cannot be inspected. [Means for solving the problem]

[0005] The inspection device of the present invention is characterized by having an image printed on preprinted paper on which information of a specific color has been pre-printed, a reading means for reading the information, a processing means for removing the specific color contained in the image data read by the reading means, and an inspection means for inspecting the image after the specific color has been removed by the processing means based on a reference image. Effect of the Invention

[0006] According to the present invention, by removing the specific color contained in the image data, it is possible to correctly inspect an image printed on a preprinted sheet on which information of the specific color is printed in advance. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing the overall configuration of an inspection system including an image processing apparatus according to an embodiment. [Diagram 2] FIG. 1 is a block diagram showing a functional configuration of an image processing apparatus according to an embodiment. [Diagram 3] 5 is a flowchart showing the processing procedure of an inspection process performed by the image processing apparatus according to the embodiment. [Figure 4] 10 is a flowchart showing a processing procedure of an inspection setting process performed by the image processing apparatus according to the embodiment. [Diagram 5] 5 is a flowchart showing a processing procedure of an inspection execution process performed by the image processing apparatus according to the embodiment. [Figure 6] 13 is an example of a result display screen according to the embodiment. [Figure 7] 4 is an example of a display screen according to the embodiment. [Figure 8] 4 is an example of a display screen according to the embodiment. [Figure 9] 4 is an example of a display screen according to the embodiment. [Figure 10] FIG. 4 is a detailed flowchart of an LUT generation process according to the embodiment. [Figure 11] 5A to 5C are conceptual diagrams showing an example of three-dimensional LUT processing according to the embodiment. [Figure 12] FIG. 13 is a diagram showing an example of removing a specified color according to an embodiment; [Figure 13] 5A and 5B are diagrams showing examples of parameters used in designated color removal according to the embodiment. [Figure 14] 1A to 1C are views showing sample images before and after processing according to an embodiment. [Figure 15] 10 is a flowchart showing a processing procedure of an inspection setting process performed by the image processing apparatus according to the embodiment. [Figure 16] 4 is an example of a display screen according to the embodiment. [Figure 17] 10 is a flowchart showing a processing procedure of an inspection setting process performed by the image processing apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the present invention, and not all of the combinations of features described in the embodiments are essential to the solution of the present invention. Note that the same components are given the same reference numbers and descriptions are omitted. EXAMPLES

[0009] <Inspection system configuration> A first embodiment of the present invention will be described below. First, with reference to Fig. 1, an example of the overall configuration of an inspection system that outputs and inspects printed matter, including an image processing device (inspection device) 100 according to this embodiment, will be described.

[0010] The inspection system according to the present embodiment includes at least an image processing device 100 and a printing device 190. The printing server 180 may be included in the inspection system. The printing server 180 has a function of generating a print job of a document to be printed and inputting the print job to the printing device 190. The printing server 180 may be communicably connected to a plurality of external devices (not shown) via a network, and may receive requests to generate print jobs and print data from these external devices. The printing server 180 may also perform RIP processing for a reference image. Specifically, in the RIP processing for the reference image, for example, a resolution of 600 dpi is converted to 300 dpi to generate an image, and in the RIP processing for print data, an image is generated without reducing the resolution.

[0011] The printing device 190 has a function of forming an image on a recording medium (printing paper) based on a print job input from the printing server 180. The printing device 190 can be an offset printing device, an electrophotographic device, an inkjet device, or the like. In this embodiment, an electrophotographic printing device will be described, but this is not intended to limit the present invention. The printing device 190 has a paper feed unit 191, and the user sets printing paper in the paper feed unit 191 in advance. When a print job is input, the printing device 190 transports the printing paper set in the paper feed unit 191 along a transport path 192, forms an image on one or both sides of the paper, and transports it to the image processing device 100.

[0012] The image processing device 100 of this embodiment executes an inspection process for checking the presence or absence of image defects on a sheet (also called paper, recording medium, etc.) that is conveyed through a conveying path 192 on which an image is formed by a printing device 190, i.e., a printed matter. That is, the image processing device 100 functions as an inspection device. Note that, here, the overall process of inspecting the presence or absence of image defects is referred to as an inspection process, and the process of detecting each of a plurality of types of image defects included in the inspection process is referred to as a defect detection process (or simply a detection process). The image processing device 100 includes a CPU 101, a RAM 102, a ROM 103, a main storage device 104, and an image reading device 105. The image processing device 100 also includes an interface (I / F) 106 with the printing device, a general-purpose interface (I / F) 107, a user interface (UI) panel 108, and a main bus 109. Furthermore, the image processing device 100 includes a transport path 110 for printed materials connected to a transport path 192 of the printing device 190, an output tray 111 for printed products that have passed inspection, and an output tray 112 for printed products that have been found to have defects and failed inspection. Note that the classification of printed products is not limited to just two types, that is, pass and fail of image inspection, but may be more finely classified.

[0013] The CPU 101 is a processor that controls the entire image processing device 100. The RAM 102 functions as a main memory, a work area, etc. of the CPU 101. The ROM 103 stores a group of programs executed by the CPU 101. The main storage device 104 stores applications executed by the CPU 101, data used in image processing, etc. The image reading device (scanner) 105 can read one side or both sides of a printed material sent from the printing device 190 on the conveying path 110 and acquire the image data. Specifically, the image reading device 105 reads one side or both sides of the printed material being conveyed using one or more reading sensors provided near the conveying path 110. The reading sensors may be provided only on one side, or may be provided on both the front side and the back side of the printed material being conveyed in order to simultaneously read both sides. If it is provided on only one side, after one side is read, the printed material being transported on the transport path 110 using a double-sided transport path (not shown) may be inverted and the other side may be read by the reading sensor again.

[0014] The printing device I / F 106 is connected to the printing device 190, and can synchronize the timing of processing printed matter with the printing device 190 and can communicate each other's operating status. The general-purpose I / F 107 is a serial bus interface such as USB or IEEE1394, and allows the user to take out data such as logs and import some data into the image processing device 100. The UI panel 108 is, for example, a liquid crystal display (display unit), and functions as a user interface for the image processing device 100, displaying the current status and settings and conveying them to the user. It is also a touch panel liquid crystal display, and can accept instructions from the user by the user operating the displayed buttons.

[0015] A main bus 109 connects each unit of the image processing device 100. Each internal part of the image processing device 100 and the inspection system can be operated by instructions from the CPU 101 via the main bus 109. For example, it is possible to synchronously move the conveying path 110, and to switch whether the printed matter is sent to an output tray 111 for pass or an output tray 112 for fail depending on the inspection result. Also, a GPU may be provided in addition to the CPU.

[0016] The image processing device 100 according to this embodiment transports the printed matter transported from the printing device 190 along the transport path 110, while executing the inspection process described below based on the image data of the printed matter read by the image reading device 105. If the result of the inspection process shows that the printed matter passes the inspection, the printed matter is transported to the pass output tray 111, and if not, the printed matter is transported to the fail output tray 112. In this way, only the printed matter whose quality has been confirmed can be collected in the output tray 111 as deliverables for delivery.

[0017] <Overall inspection flow> Next, the overall flow from the registration work before the start of the inspection to the execution of the inspection will be described with reference to Figures 2 and 3. The processing described below is realized, for example, by CPU 101 reading a program stored in ROM 103 into RAM 102 and executing it. In addition, below, the step number of each process is indicated by a number following S. Figure 2 is a block diagram showing the functional configuration of image processing device 100. Figure 3 is a flowchart showing the processing procedure of the inspection process.

[0018] In step S301, the image acquisition unit 201 registers an image that is to be a reference image for the inspection. The image acquisition unit 201 acquires the reference image (reference image data) from the RAM 102 or the main storage device 104. However, it is assumed that the reference image data is stored in advance in the RAM 102 or the main storage device 104. Image data after RIP processing, which analyzes a print job and generates image data, is used as the reference image.

[0019] Next, in step S302, the inspection process selection unit 202 sets various inspection parameters such as the inspection level and whether or not the inspection is to be performed on preprinted paper, in accordance with the user's inspection settings. Details of step S302 in this embodiment will be described later.

[0020] Next, in step S303, the image acquiring unit 201 acquires an inspection target image by having the image reading device 105 read the printed matter conveyed from the printing device 190. Note that the inspection target image may be configured to be read in advance by the image reading device 105 and to acquire read data stored in the main storage device 104.

[0021] Furthermore, if inspection of preprinted paper is selected for the inspection target image in step S302, the color conversion unit 203 executes a color correction process, which will be described later.

[0022] Then, the registration processing unit 204 and the image inspection unit 205 perform registration between the inspection object image after the color correction processing and the reference image, and execute the defect detection processing. Details of step S303 in this embodiment will be described later.

[0023] In step S304, the inspection result output unit 206 generates the inspection result and displays it on the UI panel 108, and the process ends.

[0024] 6 shows an example of a result display screen in this embodiment. An overall image 1202 of the inspection corresponding image is displayed on a UI screen 1201. A defect 1203 is determined to be a point defect, and the words "point defect" are also displayed near the defect 1203. A defect 1204 is determined to be a line defect, and the words "line defect" are also displayed near the defect 1204. Furthermore, as shown in 1205 and 1206, the coordinates of each defect may also be displayed.

[0025] The above is a description of the overall flow from the registration work before the start of the examination to the execution of the examination in this embodiment.

[0026] <Test setting process> Next, the inspection setting process in S302 according to this embodiment will be described with reference to Fig. 4 and Fig. 7. Fig. 4 is a flowchart showing the inspection setting process. Fig. 7 is a diagram showing an example of a UI for setting the inspection settings.

[0027] In step S401, the inspection process selection unit 202 sets the detection items and their detection levels for detecting defects in the print image inspection of the UI 707. The detection items of the print image inspection are items related to the features of defects to be detected when inspecting a printed matter, such as point defects (dots) and linear defects (streaks). The detection level is a parameter set in stages for determining the size of each feature of a detected defect to be a defect. For example, there are five levels from level 1 to level 5, and level 5 can detect thinner and smaller defects than level 1. In addition, a level can be set for each inspection item, such as inspection level 5 for dots and inspection level 4 for streaks. The UI 707 shows that the user has selected level 4 for the inspection level setting for defects (dots) and level 4 for the inspection level setting for defects (streaks).

[0028] In step S402, the inspection process selection unit 202 sets the settings of the inspection paper. The inspection paper refers to whether the inspection paper is a preprinted paper on which an image is printed in advance. In this embodiment, a case will be described in which a specific color of a preprinted paper on which information of the specific color is printed in advance is specified as a specified color. Then, by removing the specified color from the preprinted image, inspection with the reference image is realized without obtaining information of the image printed on the preprinted paper.

[0029] A UI 709 is an example of a case where the test paper is a preprinted paper. By selecting a radio button 708, the user notifies the test process selection unit 202 that the test paper is a preprinted paper.

[0030] In step S403, the inspection process selection unit 202 determines whether or not an inspection is to be performed on a preprinted sheet, based on whether or not the radio button 708 of the UI 709 is selected. If it is determined that an inspection is to be performed on a preprinted sheet, the process proceeds to step S404. If it is determined that an inspection is not to be performed on a preprinted sheet, the process ends.

[0031] In step S404, the inspection process selection unit 202 accepts the color of the preprint image from the user. For example, the user can select the radio button 711 with red as the designated color, the radio button 712 with green as the designated color, and the radio button 713 with blue as the designated color. The types of colors that can be specified do not have to be the three colors of red, blue, and green, and may be other colors. When the inspection process selection unit 202 accepts the selection of the color from which the designated color has been removed from the user, the inspection process selection unit 202 accepts the pressing of any one of the radio buttons 711 with red as the designated color, 712 with green as the designated color, and 713 with blue as the designated color, and accepts the instruction of the color to be removed. In this embodiment, the description will be given assuming that the user has selected the radio button 711 with red as the designated color. It is also possible to select multiple colors.

[0032] In step S404, the inspection process selection unit 202 stores the removal color selected by the user as a setting value in the RAM 102. In addition, in step S404, more detailed setting tuning for specified color removal can be selected. For example, after deciding on a specified color, it is possible to expand the removal range of the specified color and perform settings that allow a wider range of colors to be removed. Details of more detailed setting tuning for specified color removal will be described later. This makes it easy to set colors that are difficult to specify or colors that change at the edge due to the effects of printing or reading.

[0033] In step S405, the inspection process selection unit 202 calculates a 3D LUT that can remove the received specified color component. Details will be described later.

[0034] The above is a description of the procedure for setting up an examination in this embodiment.

[0035] <Test execution process> Next, the procedure of the inspection execution process executed in step S303 by the color conversion unit 203, the alignment processing unit 204, and the image inspection unit 205 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the procedure of the inspection execution process in step S303.

[0036] First, in S501, the color conversion unit 203 determines whether or not an inspection is to be performed on preprinted paper. Whether or not an inspection is to be performed on preprinted paper is determined in step S402 based on whether or not the radio button 708 indicating an inspection on preprinted paper is pressed. If it is determined that this inspection is an inspection on preprinted paper, the process proceeds to step S502, where correction processing is performed on the preprinted paper. If it is determined that this inspection is not an inspection on preprinted paper, the color conversion unit 203 proceeds to step S503 without making any corrections to the inspection image.

[0037] In S502, the color conversion unit 203 performs a correction process on the inspection target image using the LUT generated in step S405. The details of the correction process will be described later.

[0038] In S503, the registration processing unit 204 performs registration between the reference image and the inspection target image. Here, the registration can be performed by a known method such as affine transformation.

[0039] In S504, the image inspection unit 205 acquires a difference image between the reference image and the image to be inspected, and proceeds to S505. Here, the difference image is generated by, for example, comparing the reference image and the image to be inspected pixel by pixel, and acquiring the difference value of the pixel value (for example, the density value for each RGB) for each pixel.

[0040] In S505, the image inspection unit 205 performs a filter process on the difference image acquired in S504 to emphasize a specific shape.

[0041] In S506, the image inspection unit 205 performs binarization processing on the difference image that has been subjected to the enhancement processing, so that if the difference value is equal to or greater than a threshold value, it becomes "1", and if it is equal to or less than the threshold value, it becomes "0".

[0042] In S507, the image inspection unit 205 judges whether or not there is a pixel in the image that has been subjected to the binarization process that exceeds the threshold value and becomes "1", and if there is, the process proceeds to S508, and if there is not, the process ends since it is determined that there is no defect. In S508, the image inspection unit 205 determines that there is a defect, stores the type of defect detection process that detected the defect and the coordinates of the defect in association with each other, and ends the process.

[0043] <3D LUT generation method for specified color removal> 10 shows a flow for calculating a 3D LUT capable of removing a specified color component received by the inspection processing selection unit 202. This flow is performed by the inspection processing selection unit 202, and is realized by the CPU 101 included in the image processing device 100 executing a control program.

[0044] The input data is R, G, and B on the output side of the 3D LUT, and signal values ​​for all tables (in this embodiment, the table is 16×16×16 increments of 15) are processed. In addition, the saturation width threshold, hue central angle, and hue width threshold for each specified color are input as processing parameters. The 3D LUT that performs the processing and the input parameters used for the processing are stored in the ROM 103. The input parameters will be described later.

[0045] In step 1001, if the specified color is red, green, or blue, the input Ri, Gi, and Bi are converted from the RGB color space to a luminance-chrominance color space (for example, the YUV color space). The conversion from RGB to YUV is based on the following formula:

[0046] Yi=0.299×Ri+0.587×Gi+0.114×Bi Ui=-0.169×Ri-0.331×Gi+0.50×Bi Vi=0.50×Ri-0.419×Gi-0.081×Bi Note that i indicates the LUT number currently being processed among all tables, and takes values ​​from 0 to 4095.

[0047] In step 1002, the distance from the origin (0,0) to the (Ui,Vi) value is calculated based on the converted color difference signals (Ui and Vi out of Yi, Ui, Vi). The calculation is performed, for example, using the following formula:

[0048] DISTi = sqrt((Ui × Ui) + (Vi × Vi)) Here, the calculated value is called a saturation value.

[0049] In step 1003, it is determined whether the calculated saturation value is higher or lower than a specific threshold (saturation threshold). The saturation threshold is stored as a parameter in the ROM 103 as a preset, and this value is used to make the determination. Note that the saturation threshold may be a different value for each specified color. If the calculated saturation value is higher than the saturation threshold (in the case of high saturation), the process proceeds to step 1004, and if the calculated saturation value is lower than the saturation threshold (in the case of low saturation), the process proceeds to step 1012.

[0050] At this point, if the saturation value of the input signal value is on the lower saturation side of the saturation threshold, it is determined that removal is not to be performed. On the other hand, if it is on the higher saturation side of the saturation threshold, it is determined that it is a candidate for removal. Here, by determining that low saturation colors are not to be removed, it is possible to prevent colors close to achromatic colors from being removed. The hatched patch area in FIG. 12(a) is a candidate for removal, and if the input LUT can be plotted at a point of LUTα, it is determined that it is a candidate for removal, and if it can be plotted at a point of LUTβ, it is determined not to be removed.

[0051] In step 1004, the process branches depending on whether the designated color accepted by the inspection process selection unit 202 is red, green, or blue. If the designated color accepted by the inspection process selection unit 202 is red, the process proceeds to 1005. If the designated color accepted by the inspection process selection unit 202 is green, the process proceeds to 1006. If the designated color accepted by the inspection process selection unit 202 is blue, the process proceeds to 1007.

[0052] In steps 1005, 1006, and 1007, the central angle of the hue on the reference UV plane of the designated color among R, G, and B is set. As shown in Fig. 12(b), the reference hue angle of each color is stored as a preset parameter within a range from the origin on the UV plane, the apex side being 0°, to 359° clockwise, and these values ​​are used. For example, values ​​such as 340° for the hue central angle of red, 200° for the hue central angle of green, and 100° for the hue central angle of blue are set as shown in Fig. 12(b).

[0053] In step 1008, an angle on the UV plane (U·V hue angle) is calculated based on the converted color difference signals (U and V out of Y, U, and V). Figure 12(b) shows an example in which an angle of 350° is calculated for both LUTα and LUTβ.

[0054] In step 1009, the angle difference (hue angle difference) between the reference hue angle set in step 1005, step 1006, and step 1007 and the U·V hue angle of each LUT calculated from the color difference signal converted in step 1008 is calculated using the following formula.

[0055] DIFF_DEG = |(U·V hue angle of each LUT)-(reference hue angle)| For example, when the designated color accepted by the inspection process selection unit 202 is red, the angle difference between the value set in step 1005 and the value calculated in step 1008 is calculated. When the designated color accepted by the inspection process selection unit 202 is red, the reference hue angle value set in step 1005 is 340°, and the U·V hue angles calculated in step 1008 are both 350° for LUTα and LUTβ. Therefore, the hue angle difference is 10° for both LUTα and LUTβ. In step 1010, it is determined whether the hue angle difference calculated in step 1009 exceeds the hue width threshold of each color. If the hue angle difference is equal to or less than the hue width threshold, the process proceeds to step 1011, and if the hue angle difference is greater than the hue width threshold, the process proceeds to step 1012. Explaining with reference to FIG. 12(c), it is determined whether the hue angle falls within the region of the hue width threshold in both directions around the hue central angle of red. For example, if the hue width threshold is set to 30 degrees, the removal range is the points within the red hue angle of 340°±30° of the hue width threshold. Therefore, the color gamut within the hue angle from 340°-30° (=310°) to 340°+30° (=370°(=10°)) is removed.

[0056] In step 1011, the RGB values ​​of the LUT determined to be removed in step 1010 are changed to signal values ​​that will not be printed. For example, in the case of luminance signal values, the values ​​are changed to (R, G, B)=(255, 255, 255), which indicates white.

[0057] In step 1012, the RGB values ​​of the LUT determined not to be removed in step 1010 are not changed and are left as they are in the input signal.

[0058] In step 1013, a branch is made as to whether or not all LUTs (in this embodiment, since the LUTs are in increments of 15, there are 16×16×16 tables) have been judged, and if judgment of all signals has not been completed, i is incremented in step 1014 to process the next LUT. Then, the processing from step 1001 is carried out. If judgment of all signals has been completed, the processing ends.

[0059] Through the above processing, it is possible to generate an LUT that can remove an input three-dimensional LUT according to the designated color component received by the inspection processing selection unit 202.

[0060] Furthermore, in this embodiment, a configuration has been described in which the setting values ​​are switched within a range of several stages in the UI, and preset parameter values ​​are used, but a configuration in which the parameter values ​​can be directly adjusted by providing a UI that allows the user to directly change the parameters may also be used.

[0061] <Adjustment of removal range> An example of parameters when "widen removal range" indicated by 714 is specified in step S403 is shown in the widen removal range mode in FIG. 13 (Table 1). A value that allows a wider range of removal is held compared to the standard. The saturation width threshold when red, green, and blue are specified is set to a value that is more achromatic than the default, thereby providing a coefficient that allows removal further to the achromatic side. In addition, the hue width threshold when red, green, and blue are specified is set to a wider hue than the default, thereby providing a coefficient that allows removal further to the different hue side. The hue central angle is not changed from the default.

[0062] The method of designation by the user can be set on the UI 800 in Fig. 8. For example, when button 801 is selected, a parameter with a narrower removal range than the standard can be selected. When button 803 is selected, a parameter with a wider removal range than the standard can be selected.

[0063] As for the parameters described here, the saturation width threshold is used in 1003, the hue central angle is used in 1005, 1006, and 1007, and the hue width threshold is used in 1010 for processing.

[0064] <Color Adjustment> FIG. 13 (Table 2) shows an example of parameters when "color tone adjustment" indicated by 715 is specified in step S403. The hue central angle is changed from the default. For example, when the specified color is red, the default hue central angle can be changed to a magenta- or yellow-oriented angle at several levels. The user can specify the hue central angle by setting it in the UI shown in FIG. 9. For example, when the radio button 711 is selected as the specified color and the color tone adjustment mode 715 is selected, the color tone adjustment setting UI 900 shown in FIG. 9 is displayed. Even if the color is red, the color tone of the color to be removed can be adjusted to a magenta- or yellow-oriented color. For example, if you want to remove red that is closer to magenta, press 902 to move it to the magenta side. Also, if you want to remove red that is closer to yellow, press 903 to move it to the yellow side. The adjusted setting is confirmed by the mark indicated by 901.

[0065] Regarding the parameters explained here, the hue central angle is used in 1005, 1006, and 1007 for processing.

[0066] In this embodiment, the case where red is designated has been described, but it is also possible to set blue or green, and adjustment can be made in the color direction that constitutes the designated color.

[0067] In addition, "widen removal range" indicated by 714 and "color adjustment" indicated by 715 can be adjusted independently, and it is possible to specify only one of them or to execute both at the same time.

[0068] In addition, a previously specified color can be stored and set. For example, radio button 717 can select the color specified in the previous inspection, the setting of the hue adjustment, and the setting of the removal range. Various settings of the removal color in the previous inspection are stored in the main memory device 104. Similarly, it goes without saying that radio button 718 may be setting information of the removal color specified and saved by the user.

[0069] Moreover, when a radio button 716 other than black is selected, all chromatic colors other than black are removed.

[0070] <Specified color removal processing> Next, the three-dimensional LUT processing performed in the color conversion unit 203 and the method of removing a designated color when a designated color is specified will be described.

[0071] When removing a specified color in the color conversion unit 203, an R, G, B image is generated by removing the preprinted image of the preprinted paper from the R, G, B image having device-dependent characteristics for the image acquired by the image acquisition unit 201.

[0072] There are various methods for conversion, but as an example, conversion processing using a 3D LUT is shown.

[0073] Figure 11(a) shows an example of a 4096 table where the values ​​are thinned out in increments of 15. The outputs R, G, and B that are output in response to input R, G, and B are determined as a table. For example, if the input is (0,0,15), the output is converted to (0,0,15). If the input is not a value in increments of 15, the output is found by interpolation from adjacent numbers.

[0074] When performing specified color removal, this can be realized by changing the 3D LUT used in the conversion process performed by the color conversion unit 203. For example, when the R, G, and B signals on the output side of the 3D LUT correspond to the specified color accepted by the inspection process selection unit 202, this can be realized by converting the contents of this 3D LUT. That is, the specified color can be removed by converting the RGB of the color into (output R, output G, output B) = (255, 255, 255) and making it a value that represents white in the luminance signal. The 3D LUT may be generated each time using the setting value of the removal color and removal area specified by the user, or a 3D LUT may be stored for each specified color.

[0075] For example, when blue (0, 0, 255) is specified, the output for an input of (0, 0, 255) at Index 15 is changed to (255, 255, 255), as shown in FIG. 11(b).

[0076] <Explanation of effect> Figure 14(a) shows an example of an inspection image obtained by reading a recording medium, in which print data has been printed on preprint paper (Figure 14(d)), using the image reading device 105. Reference numeral 1401 denotes a preprint image printed in red. Line 1402 is a black line defect caused during printing.

[0077] 14(b) shows an example of the inspection image after the specified color (red in this embodiment) has been removed by the color conversion unit 203. It can be seen that the preprint image 1401 has been removed, but the black streak 1402 remains as 1403.

[0078] An example of the reference image is shown in Fig. 14(c). By aligning and comparing the inspection image from which the specified color has been removed in Fig. 14(b) with the reference image in Fig. 14(c) and comparing them, it is possible to detect streaks 1403. According to this embodiment, the preprint image 1401 is removed and is no longer erroneously detected as a defect, making it possible to correctly inspect the entire sheet even when inspecting preprinted paper. Note that Fig. 14(d) is an example in which only the preprinted image is printed on preprinted paper.

[0079] <Effects of this embodiment> According to this embodiment, even when an image is printed on preprint paper on which a preprint image has already been printed and the image is inspected, the color of the preprint image can be specified and removed from the inspection image, making it possible to properly inspect the entire paper. EXAMPLES

[0080] In the first embodiment, a method in which the user specifies the color of the preprint image using a radio button on the UI is described. In the second embodiment, a method in which a preprint paper on which a preprint image is printed is read during inspection setting, and the user specifies the color of the preprint image is described. In this embodiment, by reading the preprint image in advance, it is possible to prevent the user from selecting a wrong color as the color of the preprint image.

[0081] Only the differences from the first embodiment will be described in detail below.

[0082] <Test setting process> The inspection setting process in S302 according to this embodiment will be described with reference to Fig. 15 and Fig. 16. Fig. 15 is a flowchart showing the inspection setting process. Fig. 16 is a diagram showing an example of a UI for setting the color of a preprint image.

[0083] In step S1501, the inspection process selection unit 202 sets the detection items and their detection levels for detecting defects in the print image inspection of the UI 707. In step S1502, the inspection process selection unit 202 sets the settings for the inspection paper. The inspection paper refers to whether or not the inspection paper is a preprinted paper on which an image has been printed in advance. In this embodiment, the preprinted image is removed to realize inspection with a reference image without obtaining information about the image printed on the preprinted paper. In the UI 709, the user indicates that a preprinted image is printed on the inspection paper by selecting radio button 708.

[0084] In step S1503, the inspection process selection unit 202 determines whether or not an inspection is to be performed on a preprinted sheet, based on whether or not the radio button 708 of the UI 709 is selected. If it is determined that an inspection is to be performed on a preprinted sheet, the process proceeds to step S1504. If it is determined that an inspection is not to be performed on a preprinted sheet, the process ends.

[0085] 16A to read the preprinted paper with the image reading device 105. Then, the preprinted paper set in the paper feed unit 191 is transported along the transport path 192 to the image processing device 100 without printing anything on it. The image reading device (scanner) 105 reads one or both sides of the printed matter sent from the printing device 190 on the transport path 110 and acquires it as a preprinted image.

[0086] In step S1505, the inspection process selection unit 202 accepts the color of the preprint image from the user. The inspection process selection unit 202 displays the image data read by the image reading device 105 on the UI 1600 in Fig. 16(b) (display control). Then, as shown in Fig. 16(c), the position selected by the user from the displayed image is displayed as a designated color, and is acquired as the designated color.

[0087] In step S1506, the inspection process selection unit 202 calculates a 3D LUT that can remove the received specified color component. This completes the description of the inspection setting process in this embodiment.

[0088] <Effects of this embodiment> According to this embodiment, by reading in advance a preprinted paper on which a preprinted image has already been printed and specifying the color of the preprinted image from the read image, it is possible to prevent the user from selecting the wrong color as the color of the preprinted image. EXAMPLES

[0089] In the second embodiment, a method is described in which a preprinted paper on which a preprinted image has already been printed is read in advance, and the color of the preprinted image is manually specified from the read image. In the third embodiment, a method is described in which the color of the preprinted image is automatically acquired.

[0090] In this embodiment, a preprinted paper on which a preprinted image has been printed is read in advance, and the color of the preprinted image is determined and specified from the read image, thereby improving user convenience. Only the differences from the first embodiment will be described in detail below.

[0091] <Test setting process> Next, the inspection setting process in S302 according to this embodiment will be described with reference to Fig. 17. Fig. 17 is a flowchart showing the inspection setting process.

[0092] In step S1701, the inspection process selection unit 202 sets the detection items and their detection levels for detecting defects in the print image inspection of the UI 707. In step S1702, the inspection process selection unit 202 sets the settings of the inspection paper.

[0093] In step S1703, the inspection process selection unit 202 determines whether or not an inspection is to be performed on a preprinted sheet based on whether or not the radio button 708 of the UI 709 is selected. If it is determined that an inspection is to be performed on a preprinted sheet, the process proceeds to step S1704. If it is determined that an inspection is not to be performed on a preprinted sheet, the process ends.

[0094] In step S1704, the printing device 190 conveys the preprinted paper set in the paper feed unit 191 along the conveying path 192 to the image processing device 100 without printing anything on it. The image reading device (scanner) 105 reads one side or both sides of the printed matter sent from the printing device 190 on the conveying path 110 and obtains it as a preprinted image.

[0095] In step S1705, the inspection process selection unit 202 determines the color of the preprint image. The acquired preprint image is subjected to binarization processing using a predetermined brightness as a threshold to generate a binary image. In the binarization processing, pixels with a brightness lower than the predetermined brightness are replaced with black pixels indicating foreground pixels, and pixels with a brightness equal to or higher than the predetermined brightness are replaced with white pixels indicating background pixels. Note that the method of binarization processing of the image may be any known technique as long as it is a method capable of converting into two gradations of black and white.

[0096] Then, the pixel values ​​of the pixels of the acquired preprint image corresponding to the pixel positions determined to be black pixels in the binarized image are registered as the designated colors of the preprint image.

[0097] In step S1706, the inspection process selection unit 202 calculates a 3D LUT that can remove the received specified color component.

[0098] The above is a description of the procedure for setting up an examination in this embodiment.

[0099] <Effects of this image processing> According to this embodiment, by reading in advance preprint paper on which a preprint image has already been printed and determining the color of the preprint image from the read image, it is possible to prevent the user from selecting the wrong color as the color of the preprint image.

[0100] (Other Examples) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

Claims

1. An image printed on a preprinted sheet on which information of a specific color is printed in advance, and a reading means for reading the information; a processing unit for removing the specific color included in the image data read by the reading unit; and an inspection means for inspecting the image after the specific color has been removed by the processing means, based on a reference image.

2. 2. The inspection apparatus according to claim 1, wherein the reference image corresponds to the image printed on the preprinted paper.

3. 2. The inspection apparatus according to claim 1, wherein the specific color is set via a user interface.

4. 2. The inspection apparatus according to claim 1, wherein a plurality of colors are set as the specific color via a user interface.

5. The image forming apparatus further includes a display control unit that reads the preprint paper using the reading unit and displays the image obtained by reading the preprint paper on a display unit, 2. The inspection apparatus according to claim 1, wherein the specific color is set from the image displayed on the display unit through a user interface.

6. The preprint paper is read by the reading means, and an acquisition means is provided for acquiring the color of the image obtained by the reading.

2. The inspection device according to claim 1, wherein the specific color is a color acquired by the acquisition means.

7. 2. The inspection apparatus according to claim 1, wherein the inspection means inspects the presence or absence of defects in the image after the specific color has been removed based on a result of comparing the reference image with the image after the specific color has been removed.

8. 2. The inspection apparatus according to claim 1, wherein the reference image is an image that does not include information about the specific color and corresponds to the image printed on the preprinted paper.

9. an image printed on a preprinted sheet on which information of a specific color is printed in advance, and a reading step of reading the information; a processing step of removing the specific color included in the image data obtained by the reading step; and an inspection step of inspecting the image after the specific color has been removed by the processing step, based on a reference image.

10. 10. The method of claim 9, wherein the reference image corresponds to the image printed on the preprinted paper.

11. 10. The method for controlling an inspection apparatus according to claim 9, wherein the specific color is set via a user interface.

12. 10. The method for controlling an inspection apparatus according to claim 9, wherein a plurality of colors are set as the specific color via a user interface.

13. The preprinted paper is read in the reading step, and the image obtained by the reading is displayed on a display unit.

10. The method for controlling an inspection apparatus according to claim 9, further comprising the step of setting the specific color from the image displayed on the display unit via a user interface.

14. The preprinted paper is read in the reading step, and a color of the image obtained by the reading step is acquired.

10. The method for controlling an inspection apparatus according to claim 9, wherein the specific color is a color acquired in the acquiring step.

15. 10. The control method for an inspection apparatus according to claim 9, wherein the inspection step inspects for the presence or absence of defects contained in the image after removal of the specific color based on a result of comparing the reference image with the image after removal of the specific color.

16. 10. The method of controlling an inspection apparatus according to claim 9, wherein the reference image is an image that does not include information about the specific color and corresponds to the image printed on the preprinted paper.

17. a printing means for printing an image on a preprinted sheet on which information of a specific color is printed in advance; a reading means for reading the image printed by the printing means and the information; a processing unit for removing the specific color included in the image data read by the reading unit; and an inspection means for inspecting the image after the specific color has been removed by the processing means, based on a reference image.

18. A program for causing a computer to function as each of the means of the inspection apparatus according to any one of claims 1 to 8.

Images