Inspection apparatus and inspection system

Abstract

To provide an inspection device and an inspection system for improving the accuracy of inspection in pre-print printing by correctly correcting a reflection influence when synthesizing a reference image.SOLUTION: In a printing system, an image acquiring unit of an inspection device that reads an image of a conveyed sheet and compares an inspection image with a reference image to determine whether a printed image is normal includes generating the reference image by performing additional image processing S1306 that is correction processing of adding noise components of light based on correction information corresponding to the noise components of light generated by a reading unit.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to an inspection device and an inspection system. [Background technology]

[0002] Printed materials output by a printing device may be contaminated by ink, toner, or other coloring materials adhering to unintended locations. Alternatively, insufficient coloring materials may be adhering to the areas where an image is to be formed, resulting in color loss, making the color appear lighter than it should. Such contaminants and color loss reduce the quality of printed materials. Therefore, it is necessary to inspect the quality of the images on printed materials and guarantee the quality of printed materials.

[0003] Visual inspection, in which an inspector visually checks the quality of printed matter, is time-consuming and costly, so in recent years, inspection systems have been proposed that perform inspections automatically without relying on visual inspection.

[0004] For example, there is a known inspection device that compares an image optically read from a printed material using a scanner (hereinafter referred to as the inspection image) with the image data actually used for printing (hereinafter referred to as the RIP image) as a reference image. Because the inspection image is read by a scanner, a phenomenon called glare can affect the inspection image. More details on glare will be provided later.

[0005] The effect of reflected light causes a difference between the reference image and the inspection image, resulting in a decrease in inspection performance. Therefore, Patent Document 1 proposes a method for correcting the effect of reflected light by comparing the reference image (RIP image) with the inspection image. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-8543 Summary of the Invention [Problem to be solved by the invention]

[0007] Consider the case of inspecting printed paper when a logo or similar has been printed on the paper used for printing (paper that has been printed on in advance in this way will be referred to as preprinted paper hereafter). The reference image that is compared with the inspection image obtained by scanning the printed material is generated by combining the image data obtained by scanning the preprinted paper (hereafter preprinted paper data) with the RIP image. Therefore, the reference image is a mixture of data that is affected by glare, with the preprinted paper data portion being affected by glare and the RIP image portion not being affected by glare.

[0008] Therefore, unless the effect of glare is properly corrected when synthesizing the reference image, there is a risk that the accuracy of the inspection will decrease. [Means for solving the problem]

[0009] The present invention is an inspection device that inspects image data obtained from an image formed on a printed matter based on a reference image, and is characterized in that it comprises a reading means that optically reads preprinted paper on which information is pre-printed and generates read image data, an image processing means that obtains reference data from the print data, and a generation means that combines the read image data with the reference data and generates composite image data, and the generation means generates the reference image by performing additional image processing, which is a correction process that adds light noise components generated by the reading means to at least an area of ​​the composite image data that corresponds to the reference data, using correction information that corresponds to the light noise components. [Effects of the Invention]

[0010] According to the present invention, it is possible to improve the accuracy of inspection in preprint printing. [Brief explanation of the drawings]

[0011] [Figure 1] Overall view of the printing system [Figure 2]Block diagram showing the system configuration of the printing system [Figure 3] Schematic cross-sectional view of the mechanism of an image forming device [Figure 4] Line sensor unit configuration diagram [Figure 5] Line sensor configuration diagram [Figure 6] Illustration of the reading position of the line sensor unit [Figure 7] Illustration of the optical path of reflected light from printed matter [Figure 8] An explanatory diagram of the optical path of reflected light from a printed material when a uniform black image with high image density is printed. [Figure 9] An example of a chart for measuring glare characteristics [Figure 10] Graph showing the distance characteristics of reflected light [Figure 11] Block diagram showing the functional configuration of the inspection device [Figure 12] Flowchart showing the procedure of inspection processing [Figure 13] Reference image generation process flowchart [Figure 14] An example of a weighting coefficient for reproducing glare [Figure 15] A diagram to explain glare removal and reproduction processing [Figure 16] Flowchart showing the procedure of detection processing [Figure 17] Example of enhancement filter shape [Figure 18] Example of the result display screen [Figure 19] An example of generating a reference image by combining preprinted paper data and RIP reference data [Figure 20] Flowchart of reference image generation processing according to Modification 1 [Figure 21] An example of the calibration recommendation screen for a new paper type [Figure 22] An example of the coefficient adjustment screen [Figure 23] A diagram to explain the effects of glare and glare reproduction processing [Figure 24]Reference image generation process flowchart [Figure 25] An example of the glare setting switching screen DETAILED DESCRIPTION OF THE INVENTION

[0012] Each embodiment 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 invention as claimed, and not all of the combinations of features described in each embodiment are necessarily essential to the solution of the present invention. In this embodiment, an image forming apparatus will be used as an example of an information processing apparatus, but the present invention is not limited to this.

[0013] Example 1 1 is an overall diagram of the hardware configuration of an image processing system according to this embodiment. The image processing system includes an image forming apparatus 101 and an external controller 102. The image forming apparatus 101 and the external controller 102 are communicatively connected via an internal LAN 105 and a video cable 106. Note that the video cable 106 may not have this configuration, and the internal LAN 105 may be configured to perform its function instead. The external controller 102 is communicatively connected to a client PC 103 via an external LAN 104, and a print instruction is sent from the PC 103 to the external controller 102.

[0014] A printer driver that has the function of converting print data into a print description language that can be processed by the external controller 102 is installed in the client PC 103. A user who wants to print can issue a print instruction from various applications via the printer driver. The printer driver sends print data to the external controller 102 based on the print instruction from the user. When the external controller 102 receives a print instruction from the PC 103, it performs data analysis and rasterization processing, and inputs the print data to the image forming apparatus 101 to issue a print instruction.

[0015] Next, a description will be given of the image forming apparatus 101. The image forming apparatus 101 is connected to a plurality of devices with different functions, and is configured to be capable of complex printing processes such as bookbinding.

[0016] The printing device 107 forms an image using toner on paper transported from a paper feed unit located below the printing device 107. The configuration and operating principle of this printing device 107 are as follows: The light beam device modulates light, such as a laser beam, according to image data and reflects it off a rotating polygon mirror or other such mirror to irradiate a photosensitive drum as scanning light. The electrostatic latent image formed on the photosensitive drum by the laser beam is developed with toner. The toner image is then transferred to paper attached to a transfer drum. This series of image formation processes is performed sequentially for yellow (Y), magenta (M), cyan (C), and black (K) toners, forming a full-color image on the paper. The paper on the transfer drum with the full-color image formed thereon is transported to a fuser. The fuser includes rollers, belts, etc., and incorporates a heat source, such as a halogen heater, within the rollers. The fuser fuses the toner on the paper with the transferred toner image by heat and pressure, fusing it to the paper.

[0017] The inserter 108 is a device for inserting an insert sheet. A sheet can be inserted from the inserter 108 at any position into a group of sheets printed by the printing device 107 and transported.

[0018] The inspection device 109 is a device for reading an image of the conveyed paper and comparing the inspection image with a reference image to determine whether the printed image is normal.

[0019] The large-capacity stocker 110 is a device capable of stacking a large amount of sheets. The finisher 111 is a device that performs finishing processes on the transported sheets. It is capable of performing finishing processes such as stapling, punching, and saddle stitching, and discharges the sheets to a paper discharge tray.

[0020] 1 is configured such that an external controller 102 is connected to the image forming apparatus 101, but the present invention is not limited to a configuration in which an external controller 102 is connected. That is, the printing system may be configured such that the image forming apparatus 101 is connected to an external LAN 104, and print data that can be processed by the image forming apparatus 101 is sent from a client PC 103. In this printing system, data analysis and rasterization processing are performed in the image forming apparatus 101, and printing processing is executed.

[0021] <System configuration diagram> FIG. 2 is a block diagram showing a system configuration of the image forming apparatus 101, the external controller 102, and the client PC 103. As shown in FIG.

[0022] First, the configuration of the printing device 107 of the image forming apparatus 101 will be described. The printing device 107 of the image forming apparatus 101 is composed of a communication I / F 217, a LAN I / F 218, a video I / F 220, a HDD 221, a CPU 222, a memory 223, an operation unit 224, and a display 225. The printing device 107 of the image forming apparatus 101 further includes a document exposure unit 226, a laser exposure unit 227, an image creation unit 228, a fixing unit 229, and a paper feed unit 230. Each of these components is connected via a system bus 231.

[0023] The communication I / F 217 is connected to the inserter 108, the inspection device 109, the large-capacity stacker 110, and the finisher 111 via a communication cable 254, and performs communication for controlling each device.

[0024] The LAN I / F 218 is connected to the external controller 102 via the internal LAN 105, and performs communication of print data, etc. The video I / F 220 is connected to the external controller 102 via the video cable 106, and performs communication of image data, etc.

[0025] The HDD 221 is a storage device that stores programs and data. The CPU 222 comprehensively controls image processing and printing based on the programs and other data stored on the HDD 221. The memory 223 stores programs and image data required for the CPU 222 to perform various processes and functions as a work area. The operation unit 224 accepts various settings and operation instructions from the user. The display 225 displays the image processing device's settings and the processing status of print jobs. The document exposure unit 226 reads documents when using the copy and scan functions. The document data is read by shining an exposure lamp on the paper placed by the user and capturing an image with a CMOS image sensor. The laser exposure unit 227 is a device that performs primary charging and laser exposure to irradiate the photosensitive drum with laser light to transfer a toner image. The laser exposure unit 227 first performs primary charging, charging the surface of the photosensitive drum to a uniform negative potential. Next, a laser driver irradiates the photosensitive drum with laser light, adjusting the reflection angle with a polygon mirror. This neutralizes the negative charge in the irradiated area, forming an electrostatic latent image. The image-forming unit 228 is a device for transferring toner to paper and is composed of a developing unit, a transfer unit, a toner supply unit, etc., and transfers the toner on the photosensitive drum to paper. In the developing unit, negatively charged toner from a developing cylinder adheres to the electrostatic latent image on the photosensitive drum surface, creating a visible image. The transfer unit applies a positive potential to the primary transfer roller to transfer the toner on the photosensitive drum surface to the transfer belt (primary transfer), and applies a positive potential to the secondary transfer outer roller to transfer the toner on the transfer belt to paper (secondary transfer). The fixing unit 229 is a device for melting and fixing the toner on the paper to the paper using heat and pressure, and is composed of a heater, a fixing belt, a pressure belt, etc. The paper feed and transport unit 230 is a device for feeding paper, and the paper feed and transport operations are controlled by rollers and various sensors.

[0026] Next, the configuration of the inserter 108 of the image forming apparatus 101 will be described. The inserter 108 of the image forming apparatus 101 is composed of a communication I / F 232, a CPU 233, a memory 234, and a paper feed control unit 235, and each of these components is connected via a system bus 236. The communication I / F 232 is connected to the printing device 107 via a communication cable 254, and communication required for control is performed. The CPU 233 performs various controls required for paper feeding in accordance with a control program stored in the memory 234. The memory 234 is a storage device in which the control program is saved. The paper feed control unit 235 controls the rollers and sensors based on instructions from the CPU 233, and controls the feeding and transport of paper sheets transported from the inserter's paper feed unit and the printing device 107.

[0027] Next, the configuration of the inspection device 109 of the image forming apparatus 101 will be described. The inspection device 109 of the image forming apparatus 101 is composed of a communication I / F 237, a CPU 238, a memory 239, a line sensor unit 240, a display unit 241, an operation unit 242, and an HDD 255, and each of these components is connected via a system bus 243. The communication I / F 238 is connected to the printing device 107 via a communication cable 254, and communication required for control is performed. The CPU 238 performs various controls required for inspection in accordance with a control program stored in the memory 239. The memory 239 is a storage device in which the control program is saved. The line sensor unit 240 takes an image of the conveyed paper based on instructions from the CPU 238. The CPU 238 saves the image taken by the line sensor unit 240 in the memory 239 as preprinted paper data or an inspection image. Furthermore, the CPU 238 compares the inspection image captured by the line sensor unit 240 with the reference image stored in the memory 239 to determine whether the printed image is normal. The method of acquiring the reference image will be described later. The display unit 241 displays the inspection results, setting screens, etc. The operation unit 242 is operated by the user and accepts instructions such as preprinted paper data and setting changes for the inspection device 109, and registration of reference images. The HDD 255 stores various setting information and images required for inspection. The stored setting information and images can be reused.

[0028] Next, the configuration of the large-capacity stacker 110 of the image forming apparatus 101 will be described. The large-capacity stacker 110 of the image forming apparatus 101 is composed of a communication I / F 244, a CPU 245, a memory 246, and a paper discharge control unit 247, and each of these components is connected via a system bus 248. The communication I / F 244 is connected to the printing device 107 via a communication cable 254, and communication required for control is performed. The CPU 245 performs various controls required for paper discharge in accordance with a control program stored in the memory 246. The memory 246 is a storage device in which the control program is saved. The paper discharge control unit 247 controls the transport of transported paper to a stack tray, an escape tray, or the subsequent finisher 111 based on instructions from the CPU 245.

[0029] Next, we will explain the configuration of the finisher 111 of the image forming apparatus 101. The finisher 111 of the image forming apparatus 101 is made up of a communication I / F 249, a CPU 250, a memory 251, a paper discharge control unit 252, and a finishing processing unit 253, and each of these components is connected via a system bus 256. The communication I / F 249 is connected to the printing device 107 via a communication cable 254, and communication required for control is carried out.

[0030] The CPU 250 performs various controls required for finishing and paper discharge in accordance with a control program stored in the memory 251. The memory 251 is a storage device in which the control program is saved. The paper discharge control unit 252 controls paper transport and paper discharge based on instructions from the CPU 250. The finishing processing unit 253 controls finishing processes such as stapling, punching, and saddle stitching based on instructions from the CPU 250.

[0031] Next, we will explain the configuration of the external controller 102. The external controller 102 is composed of a CPU 208, memory 209, HDD 210, keyboard 211, display 212, LAN I / F 213, LAN I / F 214, and video I / F 215, which are connected via a system bus 216.

[0032] The CPU 208 comprehensively executes processes such as receiving print data from the PC 103, Raster Image Processing (RIP), and transmitting print data to the image forming apparatus 101 based on programs and data stored in the HDD 210. It also performs RIP for reference images. Specifically, in the RIP for reference images, an image is generated by converting a resolution of, for example, 600 dpi to 300 dpi, while in the RIP for print data, an image is generated without reducing the resolution. The generated reference images (reference image data) are stored in memory 239 via the internal LAN 105 and communication cable 254.

[0033] The memory 209 stores programs and data required for the CPU 208 to perform various processes, and operates as a work area. The HDD 210 stores programs and data required for operations such as printing. The keyboard 211 is a device for inputting operation instructions to the external controller 102.

[0034] The display 212 displays information such as the application executed by the external controller 102 using video signals for still images and moving images. The LAN I / F 213 is connected to the client PC 103 via the external LAN 104, and performs communication such as printing instructions. The LAN I / F 214 is connected to the image forming apparatus 101 via the internal LAN 105, and performs communication such as printing instructions. The external controller 102 can exchange various types of data with the printing apparatus 107, inserter 108, inspection device 109, large-capacity stacker 110, and finisher 111 via the internal LAN 105 and a communication cable 254. The video I / F 215 is connected to the image forming apparatus 101 via a video cable 106, and performs communication such as printing data.

[0035] Next, the configuration of the client PC 103 will be described. The client PC 103 is composed of a CPU 201, memory 202, HDD 203, keyboard 204, display 205, and LAN I / F 206, which are connected via a system bus 207. The CPU 201 creates print data and executes print instructions based on a document processing program stored in the HDD 203. The CPU 201 also comprehensively controls each device connected to the system bus. The memory 202 stores programs and data required for the CPU 201 to perform various processes and functions as a work area. The HDD 203 stores programs and data required for operations such as printing. The keyboard 204 is a device for inputting operation instructions for the PC 103. The display 205 displays information such as applications executed by the client PC 103 using video signals for still images and moving images. The LAN I / F 206 is connected to the external LAN 104, and is used for communication such as print instructions.

[0036] In the above description, the external controller 102 and the image forming apparatus 101 are connected via the internal LAN 105 and the video cable 106. However, any other configuration is acceptable as long as the data necessary for printing can be transmitted and received; for example, a connection using only a video cable is also acceptable. Furthermore, the memory 202, the memory 209, the memory 223, the memory 234, the memory 239, the memory 246, and the memory 251 may each be a storage device for storing data and programs. For example, they may be replaced with volatile RAM, non-volatile ROM, an internal HDD, an external HDD, a USB memory, or the like.

[0037] <Image forming device> FIG. 3 is a cross-sectional view of the mechanism of the image forming apparatus 101. The printing device 107 forms an image to be printed on a sheet. Paper feed deck 301 and paper feed deck 302 can store various types of sheets, such as preprinted paper. Each paper feed deck can separate only the topmost sheet from the stored sheets and transport it to sheet transport path 303. Developing stations 304 to 307 form toner images using color toners of Y, M, C, and K, respectively, to form a color image. The toner images formed here are primarily transferred to intermediate transfer belt 308. Intermediate transfer belt 308 rotates clockwise in the figure and transfers the toner image to a sheet transported from sheet transport path 303 at secondary transfer position 309.

[0038] The display device 225 displays information for the printing status and settings of the image forming apparatus 101. The fixing unit 311 fixes the toner image to the sheet. The fixing unit 311 includes a pressure roller and a heating roller. As the sheet passes between these rollers, the toner is melted and pressed to fix the toner image to the sheet. After passing through the fixing unit 311, the sheet is transported to 315 via sheet transport path 312. If further melting and pressing is required for fixing depending on the type of sheet, the sheet passes through the fixing unit 311 and is then transported to the second fixing unit 313 via the upper sheet transport path. After the additional melting and pressing, the sheet is transported to 315 via sheet transport path 332. When the image formation mode is double-sided, the sheet is transported to the sheet inversion path 316, inverted at 316, and then transported to the double-sided transport path 317, where the image on the second side is transferred at the secondary transfer position 309.

[0039] The inserter 108 for inserting an insertion sheet includes an inserter tray 321, and merges a sheet fed via a sheet transport path 322 into the transport path. This makes it possible to insert a sheet at any position in a series of sheets transported from the printing device 107 and transport the sheet to a subsequent device.

[0040] The sheet that has passed through the inserter 108 is transported to the inspection device 109. Line sensor units 240a and 240b are arranged facing each other inside the inspection device 109. The line sensor unit 240a is a sensor for reading the upper surface of the sheet, and the line sensor unit 240b is a sensor for reading the lower surface of the sheet. A flow reading glass 332a is arranged between the line sensor unit 240a and the transport path 333. A flow reading glass 332b is arranged between the line sensor unit 240b and the transport path 333. When the sheet transported to the sheet transport path 333 reaches a predetermined position, the inspection device 109 reads the image of the sheet using the line sensor units 240a and 240b, and can determine whether the image of the device is normal. The inspection results performed by the inspection device 109 are displayed on the display device 241.

[0041] The large-capacity stacker 110 is capable of stacking a large number of sheets. The large-capacity stacker 110 has a stack tray 341 as a tray for stacking sheets. Sheets that have passed through the inspection device 109 are input into the large-capacity stacker 110 through a sheet transport path 344. The sheets are stacked on the stack tray 341 via a sheet transport path 345 from the sheet transport path 344. The stacker 340 also has an escape tray 346 as a paper output tray. The escape tray 346 is a paper output tray used to output sheets that have been determined to be defective by the inspection device 109. When outputting to the escape tray 346, the sheet is transported from the sheet transport path 344 to the escape tray 346 via a sheet transport path 347. When transporting the sheet to a post-processing device downstream of the large-capacity stacker 110, the sheet is transported via a sheet transport path 348. An inverting unit 349 inverts the sheet. This reversing unit 349 is used when stacking sheets on the stack tray 341. When stacking on the stack tray 341, the sheets are reversed once in the reversing unit 349 so that the orientation of the input sheets is the same as the orientation of the sheets at the time of output. When conveying to the escape tray 346 or a subsequent post-processing device, the sheets are discharged as is without being flipped when stacked, so the reversing operation in the reversing unit 349 is not performed.

[0042] The finisher 111 performs finishing processing on the conveyed sheets in accordance with a function specified by the user. Specifically, the finisher 111 has finishing functions such as stapling (one-point or two-point binding), punching (two-hole or three-hole), and saddle stitching. The finisher 111 has two paper output trays, paper output tray 351 and paper output tray 352, and outputs sheets to output tray 351 via sheet transport path 353. However, finishing processes such as stapling cannot be performed via sheet transport path 353. When finishing processes such as stapling are performed, the sheets are output to output tray 352 via sheet transport path 354, and the finishing function specified by the user is executed in processing section 355. The paper output tray 351 and paper output tray 352 can each be raised and lowered, and it is also possible to lower the paper output tray 351 and stack sheets that have been finished by processing section 355 on the paper output tray 351. When saddle stitching is specified, the saddle stitching processing unit 356 staples the sheet in the center, folds the sheet in half, and outputs it to a saddle stitching tray 358 via a sheet transport path 357. The saddle stitching tray 358 is configured as a belt conveyor, and the saddle stitched bundle loaded on the saddle stitching tray 358 is transported to the left side.

[0043] The inspection device 109 inspects the sent sheet image according to preset inspection items. The sheet image is inspected by comparing it with a preset reference image. Image comparison methods include comparing pixel values ​​for each image position, comparing object positions using edge detection, and extracting character data using OCR (Optical Character Recognition). Inspection items include misalignment of print position, color tone, density, streaks, faded print, and missing print.

[0044] <Line sensor unit 240> FIG. 4 is an explanatory diagram of the configuration of the line sensor unit 240. The line sensor units 240a and 240b include line sensors 401a and 401b, memories 400a and 400b, and A / D converters 402a and 402b. The line sensors 401a and 401b are, for example, contact image sensors (CISs). Note that the image sensors used for reading may be line scan cameras instead of CISs. The memories 400a and 400b store correction information such as light intensity variation adjustment values ​​for each pixel of the corresponding line sensors 401a and 401b. The A / D converters 402a and 402b acquire analog signals that are the results of reading by the line sensors 401a and 401b. The A / D converters 402a and 402b convert the acquired analog signals into digital signals and transmit them to the HDD 255. The digital signals are R (red), G (green), and B (blue) read data.

[0045] <Line sensor 401> 5 is an explanatory diagram of the configuration of line sensor 401a. Line sensor 401b has a similar configuration. Line sensor 401a is an optical sensor including light-emitting units 500a and 500b, light guides 502a and 502b, a lens array 503a, and a sensor chip group 501a. Line sensor 401a is a roughly rectangular parallelepiped and reads images with its longitudinal direction as the main scanning direction. Line sensors 401a and 401b are attached to inspection device 109 so that the main scanning direction is the same as the main scanning direction of printing device 107. Therefore, the transport direction of the paper to be read becomes the sub-scanning direction.

[0046] The light-emitting units 500a and 500b are light sources formed, for example, by LEDs (Light Emitting Diodes) that emit white light. The light-emitting unit 500a is disposed at an end of the light guide 502a, and the light emitted from the light-emitting unit 500a is directed toward the paper. The light-emitting unit 400b is disposed at an end of the light guide 502b, and the light emitted from the light-emitting unit 500b is directed toward the paper. The light guides 502a and 502b are formed linearly in the main scanning direction. Therefore, the line sensor 401 directs light in a straight line in the main scanning direction. The main scanning direction of the line sensor unit 240 and the main scanning direction of the printing device 107 are the same direction.

[0047] The lens array 503a is an optical system that guides light emitted from the light-emitting units 500a and 500b and reflected by the paper to the sensor chip group 501a. The sensor chip group 501a is a light-receiving unit configured with multiple photoelectric conversion elements (sensor chips) lined up in a straight line in the main scanning direction. One sensor chip reads the image of one pixel. In this embodiment, the multiple sensor chips are configured in three lines. One line is coated with an R (red) color filter, another line is coated with a G (green) color filter, and another line is coated with a B (blue) color filter. The light guided by the lens array 503a is imaged on the light-receiving surface of each sensor chip in the sensor chip group 501a.

[0048] Light emitted from light-emitting units 500a and 500b diffuses inside light guides 502a and 502b, and is emitted from the curved portions, illuminating the entire area of ​​the paper in the main scanning direction. Light guides 502a and 502b are arranged on either side of lens array 503a in the sub-scanning direction perpendicular to the main scanning direction. For this reason, line sensor 401a has a double-sided illumination configuration in which light is irradiated onto lens array 503a (image reading line) from two directions in the sub-scanning direction. The sub-scanning direction of line sensor unit 240a and the sub-scanning direction of printing device 107 are the same direction.

[0049] <The principle of reflection> Glare is a phenomenon in which the read luminance value changes due to the influence of reflected light from a main scanning position close to the target position. In other words, the luminance value of the target pixel will be different when the surrounding image is dark (there is little reflected light from the surrounding image) than when the surrounding image is bright (there is a lot of reflected light from the surrounding image). When the surrounding image is bright, there is a lot of reflected light from the surrounding image, so the read luminance value will be brighter than when it is dark.

[0050] <Explanation of the optical path of reflected light> The optical path of reflected light will be explained using Figures 6, 7, and 8. Figure 6 is a diagram for explaining the reading position of the line sensor unit. Figure 7 is an explanatory diagram of the optical path of reflected light from a printed material. Figure 8 is an explanatory diagram of the optical path of reflected light from a printed material when a uniform black image with high image density is printed. The reflected light shown in Figures 7 and 8 becomes an optical noise component.

[0051] First, the reading position of the line sensor unit will be described. Fig. 6 is an explanatory diagram of the reading position of line sensor unit 240a. In Fig. 6, the upper diagram shows printed matter 601 passing through reading position X of line sensor unit 240a as viewed from the conveyance path 333 side, and the lower diagram shows printed matter 601a as viewed from the downstream side to the upstream side in the conveyance direction of printed matter 601. Area A including a pixel of interest is provided. A peripheral area 605 including predetermined areas B and C is provided in the main scanning direction relative to the pixel of interest.

[0052] FIG. 7 is an explanatory diagram of the optical path of light reflected by the printed material 601 when the printed material 601 is read by the line sensor unit 240a. A″ is the light reflected from the pixel of interest (x, y). B′ and C′ are the light reflected from the specified areas B and C, respectively, that is reflected within the scanning glass 332a. The refraction condition of the scanning glass 332a is expressed by the following equation 1. N1*sinθ1=N2*sinθ2... Formula 1 N1: Refractive index of air N2: Refractive index of scanning glass 332a θ1: Incident angle from air to the scanning glass 332a θ2: Incident angle from the scanning glass 332a to the air

[0053] The larger the angle θ1, the larger the component that is totally reflected within the scanning glass 332a. Therefore, the larger the angle θ1, the stronger the reflected light from the specified areas B and C is, and the farther it can reach. When reflected light B' and C' reflects within the scanning glass 332a and illuminates the target pixel (x, y), reflected light B" and C" are reflected from the target pixel (x, y). Based on the distance to the target pixel (x, y), reflected light C' is reflected more times within the scanning glass 332a than reflected light B', and its light intensity is attenuated. Therefore, the intensity of the reflected light from the target pixel (x, y) has the relationship reflected light B" > reflected light C".

[0054] When the reflected light from the predetermined area C strikes the scanning glass 332a, part of it is reflected by the upper surface of the scanning glass 332a and becomes reflected light D' that returns to the printed material 601. However, the intensity of reflected light D' is significantly attenuated by reflection from the upper surface of the scanning glass 332a. As a result, the component of reflected light D' that is reflected again by the printed material 601 and strikes the scanning glass 332a again, and the component that reaches the pixel of interest (x, y) after repeatedly reflecting between the printed material 601 and the scanning glass 332a, become negligibly small.

[0055] Reflected light C' also generates reflected light D" that passes through the underside of the scanning glass 332a without being totally reflected. However, the line sensor unit 240a is designed so that the focus of the sensor chip group 501 is adjusted to the printed material 601 via the lens array 503. Therefore, reflected light D" is not focused on the line sensor 401a.

[0056] With the above configuration, reflected light, which is the sum of reflected light A", reflected light B", and reflected light C", is formed in the reading area 401aA of the line sensor 401a. The intensity of reflected light B" and C" changes depending on the brightness of the image in the peripheral area 605. For example, if no image is printed in the peripheral area 605 and it is just the background of the paper, which has the lowest image density, the intensity of reflected light B" and C" will be high.

[0057] FIG. 8 is an explanatory diagram of the optical path of light reflected by the printed material 601 when a uniform black image with high image density is printed in the peripheral area 605. A predetermined area S is provided in the area of ​​interest A. In the peripheral area 605, predetermined areas T and U are provided at different positions in the main scanning direction of the line sensor unit 240a. The predetermined area T is provided closer to the predetermined area S than the predetermined area U. The predetermined area S is white, and the predetermined areas T and U are black with uniform image density. For convenience, the predetermined areas S, T, and U are given different symbols than those in FIG. 7, but the areas shown are the same as the pixel of interest (x, y), B, and C.

[0058] T' and U' are the reflected lights reflected within the flow reading glass 332a out of the reflected lights from the specified areas T and U, respectively. S" is the reflected light from the specified area S. T" and U" indicate the reflected light resulting from the reflected lights T' and U' reflected within the flow reading glass 332a being irradiated onto the specified area S. In the reading area 401aS of the line sensor 401a where the reflected light from the specified area S is imaged, the reflected light that is the sum of the reflected light S", reflected light T", and reflected light U" is imaged.

[0059] The higher the image density of the image in the peripheral area 605, the lower the intensity of the reflected light. Therefore, there is a relationship of reflected light T"<reflected light B" and reflected light U"<reflected light C". When the image density becomes even higher and an image with the highest image density that the printing device 107 can print is printed in the peripheral area 605, there is a relationship of reflected light T"<<reflected light B" and reflected light U"<<reflected light C". In this case, almost only reflected light S" (=A") is imaged in the reading area 401aS of the line sensor 401a. This means that the reflected light imaged in the reading area 401aS of the line sensor 401 is not affected by glare from the peripheral area 605. As a result, the luminance value, which is the reading result of the specified area S, can be read accurately.

[0060] In Figure 8, the positions of reflected light T'', reflected light S'', and reflected light U'' have been shifted to improve visibility of the drawing, and in Figure 7, the positions of reflected light A'', reflected light B'', and reflected light C'' have been shifted to improve visibility of the drawing.

[0061] <Glare chart> Figure 9 shows an example of a chart used to acquire reflected light data. The dimensions shown in the figure are just an example of an A3 image. As shown in the figure, the reflected light data is a white triangular pattern that closes in the sub-scanning direction. The distance characteristics of the reflected light are calculated from the distance of the white area in the main scanning direction from evaluation area I.

[0062] <Distance characteristics of glare> 10 is a graph showing the distance characteristics of reflected glare. The horizontal axis represents the distance from the pixel of interest (x, y), and the vertical axis represents the amount of reflected glare. The solid line V represents the distance characteristics when the surrounding area 605 is the background (white) of the paper, the dashed-dotted line W represents the distance characteristics when the surrounding area 605 is halftone, and the dotted line Z represents the distance characteristics when the surrounding area 605 is black, which has the highest image density.

[0063] The closer the distance to the pixel of interest (x, y) or the lower the image density, the greater the amount of reflected glare. Conversely, the farther the distance to the pixel of interest (x, y) is, the smaller the amount of reflected glare, and when the distance reaches a predetermined distance Y, the amount of reflected glare becomes zero. In this embodiment, the image actually printed is composed of the colors cyan, magenta, yellow, and black. Since the diffusion characteristics when incident on each color are different, the distance characteristics of reflected glare differ for each color. Furthermore, the amount of reflected glare also differs depending on the paper on which the test image is printed.

[0064] <Inspection processing> Next, the processing procedure of the inspection process performed by the inspection device 109 according to this embodiment will be described with reference to Figs. 11 and 12. The processing described below is realized, for example, by the CPU 238 reading a program stored in the ROM in the memory 239 into the RAM in the memory 239 and executing it. In addition, the step number of each process is indicated by a number following S. Fig. 11 is a block diagram showing the functional configuration of the inspection device 109, which is executed by the CPU 238 as described above. Fig. 12 is a flowchart of the processing procedure of the inspection process.

[0065] In S1201, the image acquisition unit 1101 acquires a reference image from the RAM in the memory 239 or the HDD 255. However, it is assumed that the reference image data is data generated based on a user's input and is stored in advance in the RAM in the memory 239 or the HDD 255. The generation of the reference image will be described in detail later.

[0066] Next, in S1202, the inspection process selection unit 1102 and the parameter setting unit 1104 select multiple detection processes to be performed based on user input, and set parameters for each of the selected multiple detection processes. Of course, it is also possible to select only one detection process.

[0067] The inspection process selection unit 1102 accepts user selection of multiple detection processes via a selection screen (not shown) displayed on the display unit 241. For example, the selection screen allows the user to select the type of defect, and a detection process for detecting the selected defect is selected. The types of defects may include any type of defect, such as point-shaped defects and line-shaped (streak) defects described in this embodiment, as well as image unevenness and surface shape defects. If no user selection is made, a default detection process may be selected. The process parameter setting unit 1104 registers parameters for performing the defect detection selected by the inspection process selection unit 1102. The parameters include a filter according to the type of defect and a threshold for determining whether or not a defect is present. The threshold, among the parameters, is set based on a difference value sent from the inspection device 109. The parameter setting process will be described in detail later.

[0068] Furthermore, in S1203, the image acquisition unit 1101 acquires an image to be inspected by having the line sensors 204a and 204b read the printed material conveyed from the printing device 107. Note that the image to be inspected may be configured to be read in advance by the line sensors 204a and 204b and to acquire read data stored in the HDD 255.

[0069] Next, in S1204, the inspection process selection unit 1102 sets an initial value to a detection process to be executed from among a plurality of detection processes stored in the RAM in the memory 239. The initial value indicates the detection process to be executed first, and if there is no particular priority in the execution order of the detection processes, the initial value may be in any order, such as the order in which they were selected.

[0070] Next, in S1205, the registration processing unit 1103 and the image inspection unit 1105 align the inspection target image with the reference image and execute detection processing, details of which will be described later with reference to FIG.

[0071] Thereafter, in S1206, the image inspection unit 1105 determines whether all selected detection processes have been completed, and if all detection processes have been completed, proceeds to S1208, and if there are any detection processes that have not been completed, proceeds to S1207.

[0072] In S1207, the inspection process selection unit 1102 changes the inspection process type to an unprocessed one, and returns the process to S1205. Thereafter, the processes of S1205 to S1207 are repeated until all detection processes are completed. On the other hand, when all detection processes are completed, in S1208, the inspection result output unit 1106 generates inspection results and displays them on the display unit 241, and the process ends. Details of the display process will be described later.

[0073] <Reference image generation process> Next, the processing procedure of the reference image generation processing executed by the image acquisition unit 1101 according to this embodiment in S1201 will be described with reference to Fig. 13. The processing described below is realized, for example, by the CPU 238 reading a program stored in a ROM in the memory 239 into a RAM in the memory 239 and executing it. In addition, below, the step number of each processing is indicated by a number following S.

[0074] In S1301, the image acquisition unit 1101 acquires preprint sheet information. The image acquisition unit 1101 accepts information about preprint sheets stored in the paper feed decks 301 and 302 via a selection screen (not shown) displayed on the display unit 241. In this embodiment, the preprint sheet information includes the number of sheets in one preprint set, the paper type, paper size, paper basis weight, and the paper feed deck in which it is stored. The image acquisition unit 1101 saves the preprint sheet information in the memory 239.

[0075] Next, in S1302, the image acquisition unit 1101 acquires a scanned image of the preprinted paper. The image acquisition unit 1101 accepts the start of scanning the preprinted paper via a selection screen (not shown) displayed on the display unit 241. When the start of scanning is selected, the image acquisition unit 1101 creates RIP image data that matches the size of blank paper for one set of sheets, in accordance with the preprinted paper information stored in the memory 239. This RIP image data has signal values ​​of 0 for all of cyan, magenta, yellow, and black.

[0076] The image acquisition unit 1101 sends an instruction to print blank data on preprint paper to the printing device 107 via the communication I / F 238 in accordance with the preprint paper information. The image acquisition unit 1101 causes the licensers 204a and 204b to read the blank preprint paper that has been printed with blank data by the printing device 107 and transported thereto. In this way, the preprint paper data is acquired and stored in the memory 239. Note that blank preprint paper is paper on which printing processing based on the blank data has been executed and on which no color material has actually been transferred.

[0077] Next, in S1303, the image acquisition unit 1101 removes the effect of glare from the preprint paper data (read image data) stored in the memory 239. The removal of the effect of glare will be described in detail later.

[0078] Next, in S1304, the image acquisition unit 1101 acquires RIP reference data (reference data). Color conversion processing is performed using a color conversion table that has been generated in advance and stored in the memory 239. As an example, the RIP image is in CMYK color space with 8 bits per pixel and 600 dpi, and the scanned image is in RGB color space with 8 bits per pixel and 150 dpi. The image acquisition unit 1101 converts the resolution of the RIP image to 150 dpi, which is the same resolution as the scanned image, and converts the color space of the RIP image from the CMYK color space to the RGB color space using the color conversion table stored in the memory 239. The image acquisition unit 1101 saves the converted RIP image in the memory 239 as RIP reference data.

[0079] In S1304, the image acquisition unit 1101 generates composite image data by combining the preprint paper data and RIP reference data (reference data) stored in the memory 239. In this embodiment, the composite image data that has been corrected is called a reference image (standard image). The reference image is obtained by separating the RIP reference data into an overprinted portion and a background portion, and the overprinted portion is superimposed on the preprint paper. This case will be described with reference to FIG. 19.

[0080] FIG. 19 is a schematic diagram illustrating an example of the compositing process. The RIP reference data is separated into an overprint portion 1903, which is the image to be printed, and a background portion 1904. One separation method is, for example, a method using a histogram. Peaks in high-brightness areas are detected in the histogram to create a binarization threshold. Pixels with brightness lower than the threshold are determined to be overprinted portions, and pixels with brightness higher than the threshold are determined to be background portions, and flag data for each pixel is created. Specifically, flag data for each pixel is generated by setting pixels with brightness lower than the threshold to 1 and pixels with brightness higher than the threshold to 0. The setting of flag data for each pixel is not limited to the above; pixels with brightness lower than the threshold may be set to 0 and pixels with brightness higher than the threshold to 1. The image acquisition unit 1101 generates a composite image 1905 by superimposing the separated overprint portion 1903 on the preprint paper data 1901.

[0081] Next, in step S1306, the image acquisition unit 1101 performs a glare reproduction process on the synthesized image. The details of reproducing the effects of glare will be described later.

[0082] Furthermore, in S1307, the image acquisition unit 1101 stores the image reproduced by the reflection on the composite image in the memory 239 as a reference image, and ends the reference image generation process in S1201.

[0083] <Removing the effects of glare> This section describes the correction process performed by the image acquisition unit 1101 in S1303 to remove the effects of glare from the preprinted paper data. Removing the effects of glare here means performing a correction process (attenuation image processing) that attenuates the noise components of light. The preprinted paper data saved in the memory 239 in S1302 is scan data without any overprinted portions. In other words, since the data includes the effects of glare without any overprinted portions, it is necessary to remove the effects of glare before combining it with the RIP reference data (S1305). The image acquisition unit 1101 reads weighting coefficients (correction coefficients) stored in the HDD 255 for pixel values ​​of the surrounding image excluding the target area, performs weighting processing based on the weighting coefficients, estimates the amount of glare, and subtracts the estimated amount of glare from the target pixel.

[0084] The calculation is carried out using the following formula.

[0085]

number

[0086] Next, the reflectance of the pixel of interest is calculated using the following formula.

[0087]

number

[0088] In Equation 3, a and b are predetermined values ​​and can be experimentally determined.

[0089] Next, the following relational expression holds for the pixel of interest p(x, y):

[0090]

number

[0091] Next, by transforming Equation 4, the following equation is obtained.

[0092]

number

[0093] Next, by substituting Equation 5 into Equation 2, the following equation is obtained, which makes it possible to reproduce the glare on the pixel of interest from the pixel values ​​of the surrounding pixels and the weighting coefficient Fk.

[0094]

number

[0095] An example of the weighting coefficient Fk is shown in Fig. 14. The weighting coefficient for reproducing the glare is calculated by back-calculating from the distance characteristics shown in Fig. 10. While Fig. 10 shows only the distance characteristics on one side of the target position, Fig. 14 shows weighting coefficients that take into account the surrounding pixels on the left and right by expanding the characteristics in Fig. 10 to the left and right.

[0096] <Reproduce glare> Here, the correction process in S1306 in which the image acquisition unit 1101 reproduces glare in the composite image synthesized in S1305 will be described. Here, glare reproduction means performing correction processing (additional image processing) such as adding optical noise components. Because the composite image synthesized in S1305 is free from the effects of glare, glare reproduction processing must be performed to bring it closer to the image to be inspected. The glare reproduction processing performs correction that is the opposite of the glare removal processing in S1303. Weighting processing is performed based on the weighting coefficients acquired in S1303, excluding the region of interest, to estimate the amount of glare, and the estimated amount of glare is added to the pixel of interest.

[0097] The calculation is carried out using the following formula.

[0098]

number

[0099] Next, the reflectance of the pixel of interest is calculated using the following formula.

[0100]

number

[0101] In Equation 8, a and b are predetermined values ​​and can be experimentally determined.

[0102] Next, the following relational expression holds for the pixel of interest p(x, y):

[0103]

number

[0104] Next, by transforming Equation 9, the following equation is obtained.

[0105]

number

[0106] Next, by substituting Equation 10 into Equation 7, the following equation is obtained, which makes it possible to reproduce the glare on the pixel of interest from the pixel values ​​of the surrounding pixels and the weighting coefficient Fk.

[0107]

number

[0108] <Effects of removing glare and recreating glare> 15 is a diagram for explaining the processing. Object 1501 is part of the preprint paper data and is an object that has already been printed on preprint paper and read by scanning. Object 1502 is an overprinted portion of the RIP reference data and is an object before it is reproduced by reflection.

[0109] FIG. 15(a) shows the read signal value of the portion indicated by the dotted line in an object 1501 of preprint paper data that has not been overprinted, and is a read signal value that includes the effect of glare when reading the preprint paper.

[0110] FIG. 15(b) shows the signal values ​​of the print data at the location indicated by the dotted line in object 1502 of the RIP reference data, which are signal values ​​before the reflection is reproduced. FIG. 15(c) shows the read signal values ​​at the same position in the inspection image as in FIGS. 15(a) and (b). The read signal value near the edge 1503 of object 1501 in FIG. 15(c) is affected by the reflection of object 1502 after overprinting. Therefore, a difference occurs between the read signal value 1503 near the edge of object 1501 and the read signal value 1505 near the edge in FIG. 15(a).

[0111] Furthermore, due to the effects of reflected light, there is a difference between the read signal value 1504 near the edge of the object 1502 in Figure 15(c) and the signal value 1506 near the edge in Figure 15(b). The inspection device calculates the difference between the reference image and the inspection image and detects any areas with a difference as defects. Therefore, if a difference occurs due to the effects of reflected light, it may be determined that there is a defect even when there is no defect, and the inspection cannot be performed correctly.

[0112] Therefore, in this embodiment, the effect of glare from the preprinted paper data is removed, and the effect of glare is reproduced in the combined image (both the area corresponding to the scanned image data and the area corresponding to the RIP reference data) after combination. This makes the reference image closer to the inspection image, and improves the inspection accuracy of the inspection device.

[0113] The solid line in Fig. 15(d) is the signal value when combined without glare correction. That is, it is the signal value obtained by combining the read signal value of object 1501 in Fig. 15(a) and the signal value of object 1502 in Fig. 15(b). The dotted line in Fig. 15(d) is the signal value after glare correction according to this embodiment has been performed. That is, it is the signal value obtained by combining the signal value obtained by performing glare removal on the read signal value of object 1501 in Fig. 15(a) with the signal value of object 1502 in Fig. 15(b), and then applying glare reproduction processing.

[0114] Comparing Figures 15(c) and 15(d), it can be seen that the dotted line in Figure 15(d) after glare correction is closer to the image in Figure 15(c) than the original dotted line in Figure 15(d), and the difference is smaller.

[0115] As explained above, by removing the effects of glare from the preprinted paper data before synthesizing it, and then reproducing the glare in the synthesized image (synthetic image data) to bring the reference image closer to the test image, it is possible to improve the test accuracy.

[0116] The methods for removing and reproducing glare are not limited to those described above. For example, methods that change the resolution or weighting coefficients are also possible. To speed up processing, the resolution may be reduced to two levels, 1 / 4 and 1 / 16, and the weighting coefficients may be divided into three levels. Furthermore, the distance characteristics in FIG. 10 vary depending on the paper because the reflectance changes when the paper background changes. Therefore, the weighting coefficient Fk can be stored in advance in the HDD 255 for each paper type and switched according to the settings of the selected paper. The weighting coefficient Fk may be any coefficient that estimates the amount of glare, and a method of calculating the weighting coefficient Fk by saving the distance characteristics in the HDD 255 may also be used.

[0117] <Detection process> Next, the processing procedure of the detection processing executed in S1205 by the alignment processing unit 1103 and the image inspection unit 1105 according to this embodiment will be described with reference to Fig. 16. The processing described below is realized, for example, by the CPU 238 reading a program stored in the ROM in the memory 239 into the RAM in the memory 239 and executing it. In addition, below, the step number of each processing is indicated by a number following S.

[0118] First, in S1601, the alignment processing unit 1103 aligns the reference image and the image to be inspected. Next, in S1602, the image inspection unit 1105 acquires a difference image between the reference image and the image to be inspected, and the process proceeds to S1603. 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 brightness value for each RGB) for each pixel.

[0119] In S1603, the image inspection unit 1105 performs filter processing on the difference image acquired in S1602 to emphasize a specific shape. As an example, (a) in Fig. 17 shows a filter for emphasizing point-like defects, and (b) in Fig. 17 shows a filter for emphasizing line-like defects. These filters are changed depending on the type of detection processing selected in S1204.

[0120] For example, when detection of a point defect is selected as the detection process, the process is performed using the filter shown in Fig. 17(a). When detection of a line defect is selected as the detection process, the process is performed using the filter shown in Fig. 17(b).

[0121] Next, in S1604, the image inspection unit 1105 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".

[0122] Next, in S1605, the image inspection unit 1105 determines whether or not there are any pixels in the image that has been binarized that exceed the threshold value and become "1." If there are any, the process proceeds to S1606; if there are no such pixels, the process ends, assuming that there are no defects.

[0123] In S1606, the image inspection unit 1105 determines that a defective portion is present, associates the type of detection process that detected the defective portion with the coordinates of the defective portion, and stores the association, and then ends the process. The process described above using the flowchart in Figure 16 is a subroutine of S1205 and shows the flow of one detection process. Therefore, each time the subroutine of S1205 is called, the selected type of detection process is executed, and the filter process (S1603) corresponding to the selected type is executed.

[0124] In this embodiment, the detection process has been described using examples of a process for detecting point-like defects and a process for detecting linear defects, but the present invention is not limited to these. In other words, the present configuration is applicable to any process that can detect a defect desired by the user, and does not limit the type of defect.

[0125] <Processing parameters> Here, the processing parameters (detection parameters) set by the processing parameter setting unit 1104 in S1202 will be described. As described above, in this embodiment, filter processing (S1603) and binarization processing (S1604) are performed on the acquired difference image. In this case, if the shape of the filter shown in FIG. 17(a) is made smaller, smaller point defects are emphasized and become easier to detect. Furthermore, if the threshold value for the binarization processing is made smaller, smaller differences will exceed the threshold value in the binarization processing, become "1", and be detected as defects. In other words, even defects with smaller contrast can be detected. In this way, parameters related to the filter size and the threshold value for detection are set as processing parameters in S1202.

[0126] <How to display detection results> Here, the detection results displayed by the inspection result output unit 1106 in step S1208 will be described in detail. FIG. 18 shows an example of a result display screen in this embodiment. An entire image 1802 of the inspection-related image is displayed on a UI screen 1801. Here, for example, a defect 1803 detected using the filter of FIG. 17(a) is determined to be a point defect, and the words "point defect" are also displayed near the defect 1803. Furthermore, a defect 1804 detected using the filter of FIG. 17(b) is determined to be a line defect, and the words "line defect" are also displayed near the defect 1804. Furthermore, as shown in 1805 and 1806, the coordinates of each defect may also be displayed.

[0127] However, the method of displaying the inspection results is not limited to the above method, and is not limited to the method described above, as long as it is clear which of multiple detection processes detected the detected defect, for example, by displaying each type of detection process in a different color.

[0128] <Effects of this image processing> According to this embodiment, the influence of glare from the preprinted paper data is removed before it is combined with the RIP reference data, and the influence of glare is reproduced in the combined image. As a result, the difference between the inspection image affected by glare and the reference image is reduced, making it possible to prevent a decrease in defect detection accuracy.

[0129] In this embodiment, the reference image is made closer to the test image by performing a glare reproduction process on the composite image. Conversely, it goes without saying that the test image can be made closer to the reference image by performing a glare correction process on the test image. Specifically, the test image is subjected to image processing to attenuate glare, and the scanned image data is also subjected to image processing to attenuate glare, and then the resulting composite image is combined with the RIP reference data and used as the reference image.

[0130] (Variation 1) In the first embodiment, the removal of the effects of glare and the reproduction of glare were described using a weighting factor Fk stored in advance in the HDD 255. The distance characteristics in Figure 10 vary depending on the paper because the reflectance changes when the paper's background changes. When a weighting factor Fk is stored in advance in the HDD 255 for each paper, if an inspection is performed on a paper type that has not been stored, a new weighting factor Fk can be obtained to perform the inspection with higher accuracy. Therefore, in the first modification, a weighting factor Fk is obtained for a new paper type to remove glare and reproduce glare.

[0131] Only the differences from the first embodiment will be described in detail below.

[0132] 20, the processing procedure for the reference image generation processing executed in S1201 by the image acquisition unit 1101 according to this embodiment will be described. In S2001, the image acquisition unit 1101 determines whether or not a paper type for the weighting coefficient Fk stored in the HDD 255 exists (whether or not it is a new paper type) for the paper type acquired in S1301. If it is a new paper type (Yes in S2001), the processing proceeds to S2002. If it is a saved paper type (No in S2001), the processing proceeds to S2005.

[0133] Next, in S2002, the image acquisition unit 1101 recommends calibration to obtain the weighting coefficient Fk in the case of a new paper type. Figure 21 is an example of a display screen that notifies the user that calibration is recommended. A UI screen 2101 displays a message that the paper type is new and that calibration is recommended. Calibration involves printing the reflection chart used to obtain the reflection data in Figure 9 onto paper, and then reading the printed reflection chart to obtain the weighting coefficient Fk. For this reason, calibration requires a blank sheet of paper of the same paper type as the preprinted paper. If such blank paper is available, it is recommended that the user perform calibration.

[0134] Next, the image acquisition unit 1101 determines whether calibration is to be performed in S2003. If the calibration start button 2102 is pressed (Yes in S2003), the process proceeds to S2004. If the calibration not performed button 2103 or the screen close button 2104 is pressed (No in S2003), for example, when blank paper of the same paper type as the preprinted paper is not available, the process proceeds to S2005.

[0135] Next, in S2004, the image acquisition unit 1101 performs calibration and acquires the weighting coefficient Fk. Specifically, the image acquisition unit 1101 sends an instruction to the printing device 107 to print the glare chart of FIG. 9. The image acquisition unit 1101 reads the printout printed by the printing device 107 with the line sensor unit 210 and acquires glare data. The image acquisition unit 1101 then acquires the distance characteristics of the paper type from the glare data and performs reverse calculation to acquire the weighting coefficient Fk. The image acquisition unit 1101 associates the acquired weighting coefficient Fk with the recording paper type and saves it in the HDD 255.

[0136] Next, the image acquisition unit 1101 determines the glare coefficient in S2005. For the type of preprint paper acquired in S1301, the weighting coefficient Fk for the corresponding paper type stored in the HDD 255 is used as the glare coefficient and read from the HDD 255. If there is no corresponding paper type (as in the case of No in S2003, when there is no blank paper of the same paper type as the preprint paper and calibration cannot be performed), for example, a default weighting coefficient Fk is used and read from the HDD 255. Alternatively, a paper type with a similar surface property may be selected via a selection screen (not shown) displayed on the display unit 241, or may be selected automatically. Furthermore, a method in which the user adjusts the coefficient displayed on the display unit 241 may also be used. FIG. 22 shows an example of the display of an adjustment screen for adjusting the weighting coefficient. The weighting strength 2202 of the distance characteristic 2201 displayed on the display unit 241 and the distance 2203 from the pixel of interest can be adjusted according to the surface property of the paper. The weighting coefficient Fk is calculated according to the adjusted distance characteristic and used as the glare coefficient.

[0137] In the first modification, even in the case of a new paper type, the glare coefficient can be determined in accordance with the surface properties of the paper, so that glare can be corrected more accurately, improving detection accuracy.

[0138] Example 2 In the first embodiment, the process of removing the glare effect of preprinted paper data, synthesizing a reference image, and reproducing the glare in the reference image (hereinafter referred to as detailed correction) was described. In this embodiment, the process of reproducing the glare in RIP reference data while leaving the glare effect of preprinted paper data intact, and synthesizing a reference image (hereinafter referred to as simple correction) will be described.

[0139] Fig. 23 is a diagram for explaining the glare processing in this embodiment. Consider the case where the influence of glare on an object 2301 of preprint paper data and an object 2302 of overprint data in Fig. 23 is small.

[0140] FIG. 23(a) shows the read signal value of the portion indicated by the dotted line in the object 2301 of the preprint paper data before overprinting, and is the read signal value including the effect of glare when reading the preprint paper.

[0141] Figure 23(b) shows the signal values ​​at the dotted line in object 2302 of the RIP reference data. These signal values ​​are the signal values ​​before the reflection is reproduced. Figure 23(c) shows the read signal values ​​at the same position in the inspection image as Figures 23(a) and (b).

[0142] When the distance 2303 between the objects 2301 and 2302 is sufficiently large, the effect of glare on each other is small. Therefore, there is almost no difference between the read signal values ​​of the object 2301 originally on the preprinted paper, the read signal value 2304 in FIG. 23(a) before overprinting and the read signal value 2305 in FIG. 23(c) after overprinting. In contrast, for the object 2302, which is the overprinted portion, there is a difference between the signal value 2306 near the edge in FIG. 23(b), which is the RIP reference signal value, and the read signal value 2307 near the edge in FIG. 23(c), which is affected by glare during reading. In other words, it can be seen that there is a difference only in the signal value of the RIP reference data (FIG. 23(b)). Therefore, when the effect of glare on each other between the preprinted paper data is small (when the distance 2303 is sufficiently large), it is sufficient to reproduce glare only in the overprinted portion of the RIP reference. As a result, it is possible to reproduce glare at high speed without removing the effects of glare.

[0143] Only the differences from the first embodiment will be described in detail below.

[0144] The processing procedure of the reference image generation processing executed by the image acquisition unit 1101 according to this embodiment in S1201 will be described with reference to Fig. 24. The processing described below is realized, for example, by the CPU 238 reading a program stored in a ROM in the memory 239 into a RAM in the memory 239 and executing the program. In addition, the step number of each processing step will be indicated by a number following S.

[0145] The image acquisition unit 1101 acquires preprint paper information in S1301. Fig. 25 is an example of a setting screen on which detailed correction and simple correction for glare reproduction processing can be set. A case will be described in which detailed correction and simple correction settings for glare reproduction processing are selected via a selection screen (Fig. 25) displayed on the display unit 241 together with preprint paper information. Simple correction is set when the user determines that the preprint paper data and the overprinted portion of the RIP reference data are sufficiently far apart.

[0146] That is, in the case of FIG. 23, simple correction is set when the user determines that the object distance 2303 is sufficiently far. Also, simple correction may be selected when there is no blank preprinted paper for a new paper type and the effect of glare from the preprinted paper is to be used as is. When the simple correction button 2503 is pressed, the image acquisition unit 1101 sets the simple correction flag to 1 and the detailed correction flag to 0, and saves the results in the memory 239. Also, the user can set detailed correction when the preprinted paper data and the overprinted portion of the RIP reference data are close to each other. When the detailed correction 2502 is pressed, the image acquisition unit 1101 sets the detailed correction flag to 1 and the simple correction flag to 0, and saves the results in the memory 239.

[0147] Next, the image acquisition unit 1101 acquires a scanned image of the preprinted paper in step S1302.

[0148] Next, in S2401, the image acquisition unit 1101 determines whether the glare reproduction setting is detailed correction. If the detailed correction flag for the glare reproduction setting saved in the memory 239 is 1 (Yes in S2401), the process proceeds to S1303. If the detailed correction flag for the glare reproduction setting saved in the memory 239 is 0 (No in S2401), the process proceeds to S1304. Next, if the glare reproduction processing is detailed correction, the image acquisition unit 1101 executes glare removal processing for the preprinted paper data in S1303.

[0149] Next, the image acquisition unit 1101 acquires RIP reference data in S1304. Next, the image acquisition unit 1101 determines in S2402 whether the glare reproduction setting is simple correction. If the simple correction flag for the glare reproduction setting saved in the memory 239 is 1 (Yes in S2402), the process proceeds to S2403. If the simple correction flag for the glare reproduction setting saved in the memory 239 is 0 (No in S2402), the process proceeds to S1305.

[0150] Next, if the glare reproduction processing is detailed correction, the image acquisition unit 1101 performs glare reproduction on the entire RIP reference data in S2403. The glare reproduction processing is performed according to the preprint paper information stored in the memory 239 in S1301. Furthermore, the image acquisition unit 1101 stores the RIP reference data after glare reproduction in the memory 239.

[0151] Next, in step S1305, the image acquisition unit 1101 combines the preprinted paper data, which includes the effect of glare when the preprinted paper is read, with the additionally printed portion of the RIP reference data.

[0152] Next, in S2404, the image acquisition unit 1101 determines whether the glare reproduction setting is detailed correction. If the detailed correction flag for the glare reproduction setting saved in memory 239 is 1 (Yes in S2404), the process proceeds to S1306. If the detailed correction flag for the glare reproduction setting saved in memory 239 is 0 (No in S2404), the process proceeds to S1307, where the composite image is saved in memory 239 as a reference image.

[0153] It is sufficient if the glare reproduction setting can be set to either detailed correction or simple correction. For example, a configuration is possible in which detailed correction is set as the default and simple correction can be set to on or off. Also, instead of relying on user selection, an automatic setting method is also possible in which the distance between each object (distance 2303 in FIG. 23) is obtained after the preprint paper data and RIP reference data are obtained, and simple correction is set if the distance is greater than a threshold.

[0154] <Effects of this image processing> According to this embodiment, by compositing a reference image while leaving the influence of the glare of the preprinted paper data intact, it is possible to speed up the reproduction of the glare. Also, by reproducing and compositing the glare of the RIP reference data, it is possible to prevent a decrease in the accuracy of defect detection.

[0155] <Other Examples> The present disclosure can also be realized by providing a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0156] <Effects> As described above in each embodiment, even if the printed matter is printed on preprinted paper, by appropriately correcting the effects of glare, it is possible to inspect the printed matter without reducing the accuracy of defect detection.

[0157] (Other Examples) While various examples and embodiments of the present invention have been shown and described, the spirit and scope of the present invention should not be limited to the specific descriptions herein.

[0158] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0159] 109 Inspection equipment 238 CPU 239 memory 240 Line Sensor Unit 241 Display section 242 Operation section

Claims

1. An inspection device that inspects image data acquired from an image formed on a printed matter based on a reference image, a reading means for optically reading preprinted paper on which information is preprinted and generating read image data; image processing means for acquiring reference data from print data; a generating means for generating composite image data by combining the read image data and the reference data; The generating means An inspection device characterized in that the reference image is generated by performing additional image processing, which is a correction process that adds light noise components generated by the reading means to at least an area of ​​the composite image data that corresponds to the reference data, using correction information corresponding to the light noise components.

2. 2. The inspection device according to claim 1, wherein the reference data is data obtained by performing RIP processing on the print data.

3. The generating means The inspection device described in claim 1, characterized in that after performing attenuation image processing on the read image data, which is a correction process that attenuates the light noise components of the read image data using correction information corresponding to the light noise components of the read image data, the composite image data is generated, and the reference image is generated by performing the additional image processing on both the area of ​​the composite image data corresponding to the read image data and the area corresponding to the reference data.

4. a storage means for storing a correction coefficient corresponding to the noise component of light generated by the reading means; 4. The inspection device according to claim 3, wherein the correction information used in the attenuation image processing and the correction information used in the additional image processing are information calculated based on the correction coefficients.

5. the storage means stores a correction coefficient for each paper type; 5. The inspection device according to claim 4, wherein the correction information used in the attenuation image processing and the correction information used in the additional image processing are information calculated based on a correction coefficient according to the paper type.

6. a determining means for determining whether the preprinted paper is a new paper type for which a correction coefficient is not stored in the storing means before the reading means reads the preprinted paper; 6. The inspection device according to claim 5, further comprising a notification unit that prompts the user to perform calibration when the determination unit determines that the paper type is a new paper type.

7. 7. The inspection device according to claim 6, wherein the calibration is performed using a blank sheet of the same paper type as the preprinted sheet, rather than the preprinted sheet.

8. 6. The inspection apparatus according to claim 5, further comprising a display means for displaying an adjustment screen for adjusting the correction coefficients held by said holding means.

9. The inspection device according to claim 1, characterized in that the generation means has a setting means for setting whether or not to perform processing including the additional image processing on at least the area of ​​the composite image data corresponding to the reference data when generating the reference image.

10. The inspection device described in claim 3, characterized in that when the generation means generates the reference image, it has a setting means that can set whether or not to perform the additional image processing on both the area corresponding to the read image data on which the attenuation image processing was performed and the area corresponding to the reference data after performing attenuation image processing to attenuate the light noise components of the area corresponding to the read image data in the composite image data using correction information corresponding to the light noise components of the area corresponding to the read image data on which the attenuation image processing was performed.

11. An inspection system having a printing means for generating a printed matter based on print data, and an inspection means for inspecting image data acquired from an image formed on the printed matter based on a reference image, a reading means for optically reading preprinted paper on which information is preprinted and generating read image data; image processing means for acquiring reference data from the print data; a generating means for generating composite image data by combining the read image data and the reference data; The generating means An inspection system characterized in that the reference image is generated by performing additional image processing, which is a correction process that adds light noise components generated by the reading means to at least an area of ​​the composite image data that corresponds to the reference data, using correction information corresponding to the light noise components.

12. 12. The inspection system according to claim 11, wherein the reference data is data obtained by performing RIP processing on the print data.

13. The generating means The inspection system described in claim 11, characterized in that after performing attenuation image processing on the read image data, which is a correction process that attenuates the light noise components of the read image data using correction information corresponding to the light noise components of the read image data, the synthetic image data is generated, and the reference image is generated by performing the additional image processing on both the area of ​​the synthetic image data corresponding to the read image data and the area corresponding to the reference data.

14. a storage means for storing a correction coefficient corresponding to the noise component of light generated by the reading means; 14. The inspection system according to claim 13, wherein the correction information used in the attenuation image processing and the correction information used in the additional image processing are information calculated based on the correction coefficients.

15. the storage means stores a correction coefficient for each paper type; The inspection system according to claim 14 , wherein the correction information used in the attenuation image processing and the correction information used in the additional image processing are information calculated based on a correction coefficient according to the paper type.

16. a determining means for determining whether the preprinted paper is a new paper type for which a correction coefficient is not stored in the storing means before the reading means reads the preprinted paper; 16. The inspection system according to claim 15, further comprising: a notification unit that prompts the user to perform calibration when the determination unit determines that the paper type is a new paper type.

17. 17. The inspection system according to claim 16, wherein the calibration is performed using a blank sheet of the same paper type as the preprinted sheet, rather than the preprinted sheet.

18. 16. The inspection system according to claim 15, further comprising a display means for displaying an adjustment screen for adjusting the correction coefficients held by the holding means.

19. The inspection system according to claim 11, characterized in that the generation means has a setting means capable of setting whether or not to perform processing including the additional image processing on at least an area of ​​the composite image data corresponding to the reference data when generating the reference image.

20. The inspection system described in claim 14, characterized in that when the generating means generates the reference image, it has a setting means that can set whether or not to perform the additional image processing on both the area corresponding to the read image data on which the attenuation image processing has been performed and the area corresponding to the reference data.

Images