JP2018155736A - Inspection device, inspection system, method for inspection, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the accuracy of detection near an edge region under any printing circumstances.SOLUTION: The present invention includes: a reference image acquisition unit 255 for acquiring a reference image as the reference of inspection of a printed material; a reading image acquisition unit 253 for acquiring a reading image which read the printed material; a differential image generation unit 257 for generating a differential image showing the difference between the reference image and the reading image; an edge region extraction region 259 for extracting an edge region from the reference image; a near-by region detection unit 261 for detecting a near-by region near the edge region; a threshold value correction region 265 for correcting an inspection threshold value for each of the pixels forming the edge region or forming the near-by region on the basis of the concentration of the pixels, the concentration of one or more noted pixel of the pixels, and the distances between the pixels and each of the noted pixels; and an inspection unit 269 for inspecting the printed material on the basis of the differential image and the inspection threshold value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an inspection apparatus, an inspection system, an inspection method, and a program.

  In printing that requires high quality such as production printing, quality inspection for printed matter is required. For example, by detecting a difference between a reference image serving as an inspection reference for a printed matter and a read image generated by electrically reading the printed matter with an inspection threshold for defect inspection, a defect existing on the printed matter is detected, An inspection apparatus that inspects the quality of a printed material based on a detected defect is known.

  By the way, since the read image is generated by electrically reading the printed material, a fine deviation occurs for each read image due to the printing error when generating the printed material and the reading error when reading the printed material. End up. For this reason, even when a read image is generated from each of a plurality of printed materials on which the same content is printed, the pixels at the same position in the read image differ from one read image to another at the same position in the read image. The pixel value varies. In particular, in a portion where the density changes abruptly, such as an edge region, variation in pixel values becomes large.

  If such a situation is not taken into consideration and defect detection is performed by comparing the difference in the edge region between the reference image and the read image with the inspection threshold, there is a possibility that erroneous detection (overdetection) may be performed. . For this reason, in general, defect detection is often performed near the edge region by relaxing the inspection threshold. However, if the inspection threshold is relaxed without considering the state near the edge region, the inspection threshold is excessively relaxed. Thus, there is a possibility that a defect occurring near the edge region may be overlooked, or the inspection threshold value may not be relaxed, and a defect occurring near the edge region may be overdetected.

  Here, for example, in Patent Document 1, density fluctuations in the vicinity of an edge area are detected from a plurality of read images, and an inspection threshold is relaxed based on the detected density fluctuations, thereby matching the state near the edge area. A method has been proposed in which the inspection threshold is relaxed and the inspection accuracy near the edge region is improved.

  However, in the conventional technology as described above, a corresponding number of read images are required to detect density fluctuations in the vicinity of the edge region, and therefore it is necessary to prepare a corresponding number of printed materials on which the same contents are printed. is there. For this reason, it is not suitable for inspection in a printing environment in which only a small number of printed materials having the same content printed, such as variable printing, are produced.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an inspection apparatus, an inspection system, an inspection method, and a program capable of improving inspection accuracy in the vicinity of an edge region regardless of a printing environment. And

  In order to solve the above-described problems and achieve the object, an inspection apparatus according to an aspect of the present invention includes a reference image acquisition unit that acquires a reference image that is an inspection reference for a printed matter, and a read image obtained by reading the printed matter. A read image acquisition unit to acquire, a reference image acquired by the reference image acquisition unit, a difference image generation unit that generates a difference image indicating a difference between the read image acquired by the read image acquisition unit, and the reference An edge region extraction unit that extracts an edge region from the reference image acquired by the image acquisition unit, a neighborhood region detection unit that detects a neighborhood region located in the vicinity of the edge region extracted by the edge region extraction unit, and the edge For the pixels constituting either the edge region extracted by the region extracting unit or the neighboring region detected by the neighboring region detecting unit, the density of the pixel and the pixel For inspection based on the density of one or more pixels of interest that are the object of interest and located in either the edge region or the neighboring region, and the distance between the pixel and the one or more pixels of interest A threshold correction unit that corrects the inspection threshold, and an inspection unit that inspects the printed matter based on the difference image generated by the difference generation unit and the inspection threshold corrected by the threshold correction unit.

  According to the present invention, it is possible to improve the inspection accuracy in the vicinity of the edge region regardless of the printing environment.

FIG. 1 is a schematic diagram illustrating an example of a printed matter inspection system according to the present embodiment. FIG. 2 is a block diagram illustrating an example of a hardware configuration of the printing apparatus according to the present embodiment. FIG. 3 is a block diagram illustrating an example of a hardware configuration of the printed matter inspection apparatus according to the present embodiment. FIG. 4 is a block diagram illustrating an example of the configuration of the printing apparatus and the printed matter inspection apparatus according to the present embodiment. FIG. 5 is a diagram illustrating an example of an edge region and a neighboring region on the edge image according to the present embodiment. FIG. 6 is a diagram illustrating an example of an inspection threshold image according to the present embodiment. FIG. 7 is a flowchart illustrating an example of a procedure flow of processing performed by the printing apparatus according to the present embodiment. FIG. 8 is a flowchart illustrating an example of a flow of processing performed by the printed matter inspection apparatus according to the present embodiment.

  Hereinafter, embodiments of an inspection apparatus, an inspection system, an inspection method, and a program according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram illustrating an example of a printed matter inspection system 1 according to the present embodiment. As shown in FIG. 1, the printed matter inspection system 1 includes a printing apparatus 100 (an example of an image forming apparatus), a printed matter inspection apparatus 200 (an example of an inspection apparatus), and a stacker 300.

  The printing apparatus 100 includes an operation panel 101, photosensitive drums 103Y, 103M, 103C, and 103K, a transfer belt 105, a secondary transfer roller 107, a paper feeding unit 109, a conveyance roller pair 111, and a fixing roller 113. , And an inversion path 115.

  The operation panel 101 is an operation display unit that performs various operation inputs to the printing apparatus 100 and displays various screens.

  Each of the photosensitive drums 103Y, 103M, 103C, and 103K forms a toner image by performing an image forming process (charging process, exposure process, developing process, transfer process, and cleaning process), and the formed toner image. Is transferred to the transfer belt 105. In this embodiment, a yellow toner image is formed on the photoreceptor drum 103Y, a magenta toner image is formed on the photoreceptor drum 103M, a cyan toner image is formed on the photoreceptor drum 103C, and the photoreceptor drum 103K is formed. Although a black toner image is formed, the present invention is not limited to this.

  The transfer belt 105 conveys the toner image (full color toner image) transferred from the photosensitive drums 103Y, 103M, 103C, and 103K to the secondary transfer position of the secondary transfer roller 107. In this embodiment, a yellow toner image is first transferred to the transfer belt 105, and then a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred. Is not to be done.

  The paper feeding unit 109 accommodates a plurality of recording media in an overlapping manner, and feeds the recording media. Examples of the recording medium include, but are not limited to, recording paper. Examples of the recording medium include media capable of recording images, such as coated paper, cardboard, OHP (Overhead Projector) sheet, plastic film, prepreg, and copper foil. Anything is acceptable.

  The transport roller pair 111 transports the recording medium fed by the paper feed unit 109 in the direction of arrow s on the transport path a.

  The secondary transfer roller 107 collectively transfers the full-color toner image conveyed by the transfer belt 105 onto the recording medium conveyed by the conveyance roller pair 111 at the secondary transfer position.

  The fixing roller 113 fixes the full-color toner image on the recording medium by heating and pressing the recording medium on which the full-color toner image is transferred.

  In the case of single-sided printing, the printing apparatus 100 discharges a printed material, which is a recording medium on which a full-color toner image is fixed, to the printed material inspection apparatus 200. On the other hand, in the case of duplex printing, the printing apparatus 100 sends a recording medium on which a full-color toner image is fixed to the reverse path 115.

  The reverse path 115 reverses the front and back surfaces of the recording medium by switching back the sent recording medium and conveys it in the direction of the arrow t. The recording medium conveyed by the reversing path 115 is re-conveyed by the conveying roller pair 111, the full-color toner image is transferred to the surface opposite to the previous one by the secondary transfer roller 107, fixed by the fixing roller 113, and printed. The paper is discharged to the printed product inspection apparatus 200.

  The printed matter inspection apparatus 200 includes a reading unit 201 and an operation panel 203.

  The operation panel 203 is an operation display unit that inputs various operations to the printed material inspection apparatus 200 and displays various screens. Note that the operation panel 203 may be omitted. In this case, the operation panel 101 may also serve as the operation panel 203, or an externally connected PC (Personal Computer) may serve as the operation panel 203.

  The reading unit 201 electrically reads one surface of the printed matter discharged from the printing apparatus 100. The printed matter inspection apparatus 200 may further include a reading unit that optically reads the other surface of the printed matter. In this case, the reading unit that optically reads the other surface of the printed material may have the same configuration as the reading unit 201. The reading unit that optically reads the printed matter is realized by, for example, a configuration of a line sensor or a scanner with a built-in imaging device such as a CCD (Charged-coupled devices) or a CMOS (Complementary metal-oxide-semiconductor). The

  Then, the printed matter inspection apparatus 200 discharges the printed matter that has been read to the stacker 300.

  The stacker 300 includes a tray 311. The stacker 300 stacks the printed materials discharged by the printed material inspection apparatus 200 on the tray 311.

  FIG. 2 is a block diagram illustrating an example of a hardware configuration of the printing apparatus 100 according to the present embodiment. As shown in FIG. 2, the printing apparatus 100 has a configuration in which a controller 810 and an engine unit (Engine) 860 are connected by a PCI bus. The controller 810 is a controller that controls the entire control of the printing apparatus 100, drawing, communication, and input from the operation display unit 820. The engine unit 860 is an engine that can be connected to the PCI bus, and is, for example, a print engine such as a plotter. The engine unit 860 includes an image processing part such as error diffusion and gamma conversion in addition to the engine part.

  The controller 810 includes a CPU (Central Processing Unit) 811, a North Bridge (NB) 813, a system memory (MEM-P) 812, a South Bridge (SB) 814, a local memory (MEM-C) 817, and an ASIC. (Application Specific Integrated Circuit) 816 and a hard disk drive (HDD) 818, and the North Bridge (NB) 813 and the ASIC 816 are connected by an AGP (Accelerated Graphics Port) bus 815. The MEM-P 812 further includes a ROM 812a and a RAM 812b.

  The CPU 811 performs overall control of the printing apparatus 100, has a chip set including the NB 813, the MEM-P 812, and the SB 814, and is connected to other devices via this chip set.

  The NB 813 is a bridge for connecting the CPU 811 to the MEM-P 812, SB 814, and the AGP bus 815, and includes a memory controller that controls reading and writing of the MEM-P 812, a PCI master, and an AGP target.

  The MEM-P 812 is a system memory used as a memory for storing programs and data, a memory for developing programs and data, a memory for drawing printers, and the like, and includes a ROM 812a and a RAM 812b. The ROM 812a is a read-only memory used as a program / data storage memory, and the RAM 812b is a writable / readable memory used as a program / data development memory, a printer drawing memory, or the like.

  The SB 814 is a bridge for connecting the NB 813 to a PCI device and peripheral devices. The SB 814 is connected to the NB 813 via a PCI bus, and a network interface (I / F) unit and the like are also connected to the PCI bus.

  The ASIC 816 is an IC (Integrated Circuit) for image processing applications having hardware elements for image processing, and has a role of a bridge for connecting the AGP bus 815, the PCI bus, the HDD 818, and the MEM-C 817. The ASIC 816 includes a PCI target and an AGP master, an arbiter (ARB) that forms the core of the ASIC 816, a memory controller that controls the MEM-C 817, and a plurality of DMACs (Direct Memory) that rotate image data using hardware logic. Access Controller) and a PCI unit that performs data transfer between the engine unit 860 via the PCI bus. The ASIC 816 is connected to a USB 840 and an IEEE 1394 (the Institute of Electrical and Electronics Engineers 1394) interface (I / F) 850 via a PCI bus. The operation display unit 820 is directly connected to the ASIC 816.

  The MEM-C 817 is a local memory used as a copy image buffer and a code buffer, and the HDD 818 is a storage for storing image data, programs, font data, and forms.

  The AGP bus 815 is a bus interface for a graphics accelerator card proposed for speeding up graphics processing. The AGP bus 815 speeds up the graphics accelerator card by directly accessing the MEM-P812 with high throughput. It is.

  FIG. 3 is a block diagram illustrating an example of a hardware configuration of the printed matter inspection apparatus 200 according to the present embodiment. As shown in FIG. 3, the printed matter inspection apparatus 200 has a configuration in which a controller 910 and a CPU 961 of the reading unit 201 are connected by a PCI bus. The controller 910 is a controller that controls the overall control, drawing, communication, and input from the operation display unit 920 of the printed matter inspection apparatus 200. The reading unit 201 includes a CPU 961 and a memory (MEM-P) 962. The memory (MEM-P) 962 includes a ROM 962a and a RAM 962b. The CPU 961 reads the program and data stored in the ROM 962a and expands the program and data read to the RAM 962b. If the reading unit 201 does not have a CPU, ROM, or RAM, the CPU 911 may realize the function of the printed matter inspection apparatus 200.

  The controller 910 includes a CPU 911, a north bridge (NB) 913, a system memory (MEM-P) 912, a south bridge (SB) 914, a local memory (MEM-C) 917, an ASIC 916, and a hard disk drive (HDD). 918, and the north bridge (NB) 913 and the ASIC 916 are connected by the AGP bus 915. The MEM-P 912 further includes a ROM 912a and a RAM 912b.

  The CPU 911 performs overall control of the printed matter inspection apparatus 200, has a chip set including the NB 913, the MEM-P 912, and the SB 914, and is connected to other devices via the chip set.

  The NB 913 is a bridge for connecting the CPU 911 to the MEM-P 912, SB 914, and the AGP bus 915, and includes a memory controller that controls reading and writing to the MEM-P 912, a PCI master, and an AGP target.

  The MEM-P 912 is a system memory used as a memory for storing programs and data, a memory for developing programs and data, a memory for drawing printers, and the like, and includes a ROM 912a and a RAM 912b. The ROM 912a is a read-only memory used as a memory for storing programs and data, and the RAM 912b is a writable and readable memory used as a program / data development memory, a printer drawing memory, and the like.

  The SB 914 is a bridge for connecting the NB 913 to a PCI device and a peripheral device. The SB 914 is connected to the NB 913 via a PCI bus, and a network interface (I / F) unit and the like are also connected to the PCI bus.

  The ASIC 916 is an IC for image processing that includes hardware elements for image processing, and has a role of a bridge that connects the AGP bus 915, the PCI bus, the HDD 918, and the MEM-C 917. The ASIC 916 includes a PCI target and an AGP master, an arbiter (ARB) that forms the core of the ASIC 916, a memory controller that controls the MEM-C 917, a plurality of DMACs that rotate image data using hardware logic, and the like. And a PCI unit that performs data transfer via the PCI bus. The ASIC 916 is connected to a USB 940 and an IEEE 1394 interface (I / F) 950 via a PCI bus. The operation display unit 920 is directly connected to the ASIC 916.

  The MEM-C 917 is a local memory used as a copy image buffer and a code buffer, and the HDD 918 is a storage for storing image data, programs, font data, and forms.

  The AGP bus 915 is a bus interface for a graphics accelerator card proposed for speeding up graphics processing. The AGP bus 915 speeds up the graphics accelerator card by directly accessing the MEM-P 912 with high throughput. It is.

  In the present embodiment, the hardware configuration in the case where the printed matter inspection apparatus 200 is an apparatus dedicated to printed matter inspection has been described as an example, but the present invention is not limited to this. For example, when the printed matter inspection apparatus 200 is realized by a general-purpose computer such as a PC (Personal Computer), it can be realized by a hardware configuration using a general-purpose computer.

  FIG. 4 is a block diagram illustrating an example of the configuration of the printing apparatus 100 and the printed matter inspection apparatus 200 according to the present embodiment. As illustrated in FIG. 4, the printing apparatus 100 includes a RIP (Raster Image Processor) unit 121, a print control unit 123, and a printing unit 125. The printed matter inspection apparatus 200 includes a reading unit 251, a read image acquisition unit 253, a reference image acquisition unit 255, a difference image generation unit 257, an edge region extraction unit 259, a neighborhood region detection unit 261, and an inspection threshold storage unit. 263, a threshold correction unit 265, an inspection threshold image generation unit 267, and an inspection unit 269.

  In the present embodiment, the case where the printing apparatus 100 includes the RIP unit 121 will be described as an example. However, the present invention is not limited to this, and an apparatus different from the printing apparatus 100 such as DFE (Digital Front End) is used. You may make it provide.

  In this embodiment, it is assumed that the printing apparatus 100 and the printed matter inspection apparatus 200 are connected by a local interface such as USB (Universal Serial Bus) or PCIe (Peripheral Component Interconnect Express). The connection form between the apparatus 100 and the printed matter inspection apparatus 200 is not limited to this.

  The RIP unit 121 and the print control unit 123 can be realized by the CPU 811 and the system memory 812, for example. The printing unit 125 is realized by, for example, the photosensitive drums 103Y, 103M, 103C, and 103K, the transfer belt 105, the secondary transfer roller 107, and the fixing roller 113, but is not limited thereto. As described above, in this embodiment, an image is printed by an electrophotographic method, but the present invention is not limited to this, and an image may be printed by an inkjet method.

  The reading unit 251 includes the reading unit 201 and can be realized by, for example, the engine unit 960 that is realized by the CPU 961 or the CPU 911 executing a program stored in the ROM 962a. The read image acquisition unit 253, the reference image acquisition unit 255, the edge region extraction unit 259, the neighborhood region detection unit 261, the threshold correction unit 265, and the inspection threshold image generation unit 267 can be realized by the CPU 911 and the system memory 912, for example. The inspection threshold storage unit 263 can be realized by the HDD 918 or the like, for example. The difference image generation unit 257 and the inspection unit 269 may be realized by, for example, the CPU 911 and the system memory 912, may be realized by the ASIC 916, or the like, or may be realized by using these together.

  The RIP unit 121 receives print data from an external device such as a host device, performs RIP processing on the received print data, and generates a RIP image that is a drawing target image. In the present embodiment, the print data includes data described in a page description language (PDL) such as PostScript (registered trademark), image data in a TIFF (Tagged Image File Format) format, and the like. However, the present invention is not limited to this.

  In this embodiment, the RIP image is CMYK RIP image data, and the RIP image data of C (Cyan), M (Magenta), Y (Yellow), and K (Black) is 600 dpi. However, the present invention is not limited to this.

  The print control unit 123 transmits the RIP image generated by the RIP unit 121 to the printed matter inspection apparatus 200 and also to the printing unit 125. Further, the print control unit 123 uses the inspection result transmitted (feedback) from the printed material inspection apparatus 200 to specify, for example, the discharge destination of the printed material that has not passed the quality inspection for the stacker 300 or the quality inspection. The printed material that does not pass is marked, or the printing unit 125 is instructed to perform replacement printing.

  The printing unit 125 executes a printing process such as an image forming process, prints a RIP image on a recording medium, and generates a printed material that is a recording medium on which a drawing target image is drawn.

  The reading unit 251 reads the printed matter generated by the printing unit 125 and generates a read image. In the present embodiment, the read image is assumed to have 200 dpi of RGB image data, but is not limited to this.

  The read image acquisition unit 253 acquires the read image generated by the reading unit 251.

  The reference image acquisition unit 255 acquires a reference image (master image) that serves as an inspection reference for the printed matter generated by the printing apparatus 100. Specifically, the reference image acquisition unit 255 acquires a RIP image that is a drawing target image transmitted from the printing apparatus 100, and generates a reference image that serves as an inspection reference for a printed material based on the acquired RIP image. A reference image is acquired. Specifically, the reference image acquisition unit 255 performs resolution conversion processing, color conversion processing, and reference point setting processing on the acquired RIP image to generate a reference image.

  In the resolution conversion process, the reference image acquisition unit 255 converts the resolution of the RIP image from 600 dpi to 200 dpi. In the color conversion process, the reference image acquisition unit 255 performs color conversion of the RIP image on which the resolution conversion process has been performed from the CMYK color space to the RGB color space. Specifically, the reference image acquisition unit 255 supports colors expressed in the CMYK color space (combinations of values of CMYK color channels) and colors expressed in the RGB color space (combinations of values of RGB color channels). Using the LUT (Lookup Table) that is the attached color conversion information, the RIP image is color-converted from the CMYK color space to the RGB color space. Note that the color conversion information is stored in the HDD 918, for example.

  In the reference point setting process, the reference image acquisition unit 255 sets a reference point in the RIP image that has been subjected to the color conversion process. The reference point is a feature point that serves as a reference when positioning the reference image and the read image.

  Through the above processing, the reference image acquisition unit 255 generates a reference image of RGB 200 dpi from the RIP image of CMYK 600 dpi. However, the method of generating the reference image is not limited to the above method, and the processing to be used and the value to be converted may be appropriately modified according to the image format such as gradation, color space, and resolution.

  The difference image generation unit 257 generates a difference image indicating a difference between the read image acquired by the read image acquisition unit 253 and the reference image acquired by the reference image acquisition unit 255. Specifically, the difference image generation unit 257 obtains a positional deviation amount between the reference image and the read image by extracting a feature point from the reference image and specifying a point on the read image corresponding to the feature point. The reference image and the read image are aligned based on the positional deviation amount. Then, the difference image generation unit 257 compares the reference image after alignment and the read image in units of pixels, calculates the difference value of the pixel values of each RGB color for each pixel, and includes the difference value of the pixel value for each pixel. A difference image is generated.

  The edge region extraction unit 259 extracts an edge region from the reference image acquired by the reference image acquisition unit 255. Here, the edge region is a region formed by the edge portion extracted from the reference image. Specifically, the edge region extraction unit 259 generates an edge image obtained by extracting an edge region from the reference image by performing filtering processing such as a Laplacian filter on the reference image and performing edge determination based on a threshold value. The edge image is an image representing an edge region on the reference image.

  The neighborhood area detection unit 261 detects a neighborhood area located in the vicinity of the edge area extracted by the edge area extraction unit 259. Specifically, the neighborhood area detection unit 261 detects the neighborhood area based on the pixels constituting the edge area. For example, the neighborhood region detection unit 261 detects the neighborhood region by performing dilation processing or filter processing on the edge image generated by the edge region extraction unit 259. Thereby, the neighborhood area detection unit 261 detects, for example, an area composed of pixels located in a range of 2 pixels around the edge area as the neighborhood area.

  The inspection threshold storage unit 263 stores an inspection threshold for inspection for inspecting the printed matter generated by the printing apparatus 100.

  The threshold value correction unit 265 has, for the pixels constituting either the edge region or the neighboring region, the density of the pixel, and one or more located in either the edge region or the neighboring region as a target of interest for the pixel. The inspection threshold value for inspection stored in the inspection threshold storage unit 263 is corrected based on the density of the target pixel and the distance between the pixel and the one or more target pixels.

  Here, the pixel of interest for the pixels constituting the neighboring area is the opposite of the pixels constituting the neighboring area among the neighboring pixels neighboring the pixels constituting the edge area from which the pixels constituting the neighboring area are detected. This is an adjacent pixel located on the side. Further, the pixel of interest for the pixels constituting the edge region is an adjacent pixel having the largest density difference between the pixels constituting the edge region and the pixels constituting the edge region among the neighboring pixels adjacent to the edge region.

  Hereinafter, a method for correcting the inspection threshold for the pixels constituting either the edge region or the neighboring region will be described. Here, with reference to FIG. 5, a method for correcting the inspection threshold for the pixels constituting the neighborhood region will be described.

  FIG. 5 is a diagram illustrating an example of an edge region and a neighboring region on the edge image according to the present embodiment. In the example shown in FIG. 5, a region composed of pixels located in a range of two pixels around the edge region 401 on the edge image is the neighborhood region 402.

  Here, the inspection threshold value correction method for the pixels 411 constituting the neighboring region 402 will be described as an example.

  First, the threshold value correction unit 265 specifies the pixels 412 and 413 on the edge region 401 as the pixels constituting the edge region 401 that is the detection source of the pixels 411 constituting the neighboring region 402. In the example shown in FIG. 5, an area composed of pixels located in the range of two pixels around the edge area 401 is set as the neighboring area 402, and therefore the edge area 401 located within the range of two pixels around the pixel 411. This is because the pixels forming the edge region 401 become the pixels forming the edge region 401 from which the pixels 411 forming the neighboring region 402 are detected.

  Next, the threshold value correcting unit 265 is adjacent to the pixel 414 located on the opposite side of the pixel 411 and adjacent to the pixel 413 as adjacent pixels adjacent to the pixel 412 as the pixel of interest for the pixel 411 constituting the neighboring region 402. A pixel 415 located on the opposite side of the adjacent pixel 411 is specified.

  Next, the threshold correction unit 265 extracts the densities of the pixel 411, the pixel 414, and the pixel 415 on the reference image with reference to the reference image, and the distance between the pixel 411 and the pixel 414 on the reference image. , And the distance between the pixel 411 and the pixel 415 on the reference image.

  Next, the threshold correction unit 265 applies these values as parameters to the mathematical formula (1) to correct the inspection threshold for inspection, and the corrected inspection threshold applied to the pixel 411 on the difference image. Ask for.

  Here, Sc indicates the inspection threshold value after correction. So indicates an inspection threshold value before correction. N indicates the density of the pixel to which the corrected inspection threshold is applied (in the example illustrated in FIG. 5, the density of the pixel 411). Ei indicates the density of one or more pixels of interest (in the example illustrated in FIG. 5, the density of the pixels 414 and 415). Di represents the distance between the pixel to which the inspection threshold is applied and one or more target pixels (in the example illustrated in FIG. 5, the distance between the pixel 411 and the pixel 414, the distance between the pixel 411 and the pixel 415). A indicates a coefficient for the density difference. B represents a coefficient with respect to the distance. C represents a coefficient with respect to the number of pixels of interest (the number of pixels constituting the edge region that is the detection source of the pixels to which the inspection threshold is applied). In the present embodiment, it is assumed that the values of the coefficients A, B, and C are determined empirically. However, the method for determining the values of the coefficients A, B, and C is not limited to this.

  Then, the threshold correction unit 265 performs the above-described processing, taking the pixel 411 constituting the neighboring area 402 as an example, for each pixel constituting the neighboring area 402, so that each pixel constituting the neighboring area 402 is processed. The corrected inspection threshold value to be applied is obtained.

  Note that the inspection threshold value correction method for the pixels constituting the edge region 401 is such that the pixel of interest for the pixels constituting the edge region 401 is the edge region 401 of the neighboring pixels adjacent to the pixels constituting the edge region 401. The method is the same as that described above except that the adjacent pixel has the largest density difference from the pixels constituting the.

  Then, the threshold correction unit 265 performs this process on each pixel constituting the edge region 401, thereby obtaining a corrected inspection threshold applied to each pixel constituting the edge region 401.

  As described above, the corrected inspection threshold value is proportional to the density difference between the pixel constituting either the edge region or the neighboring region and one or more of the target pixels, and is either the edge region or the neighboring region. This value is inversely proportional to the distance between the pixels constituting the region and each of the one or more target pixels.

  The inspection threshold image generation unit 267 sets the inspection threshold stored in the inspection threshold storage unit 263 for the pixels constituting the region other than the edge region or the neighboring region, and selects either the edge region or the neighboring region. For the constituent pixels, an inspection threshold image in which the inspection threshold corrected by the threshold correction unit 265 is set is generated.

  FIG. 6 is a diagram illustrating an example of an inspection threshold image according to the present embodiment. In the inspection threshold image shown in FIG. 6, the inspection threshold value So before correction shown in Expression (1) is set for each pixel constituting the region other than the edge region 401 and the neighboring region 402 shown in FIG. For each pixel constituting either the edge region 401 or the neighboring region 402 shown, the corrected inspection threshold value Sc obtained by Equation (1) is set.

  The inspection unit 269 inspects the printed matter generated by the printing apparatus 100 based on the difference image generated by the difference image generation unit 257 and the inspection threshold value corrected by the threshold value correction unit 265. Specifically, the inspection unit 269 inspects the printed matter based on the difference image and the inspection threshold image generated by the inspection threshold image generation unit 267. Specifically, the inspection unit 269 inspects the density defect of the printed matter by comparing the difference image and the inspection threshold image for each pixel. For example, a density defect is caused at a location (pixel group) having a large difference value or a location (pixel group) having a large difference area.

  The inspection unit 269 associates the inspection result such as the position and type of the density defect, the read image, and the reference image with each other and saves them in the HDD 918 or transmits (feeds back) them to the printing apparatus 100.

  FIG. 7 is a flowchart illustrating an example of a procedure flow of processing performed by the printing apparatus 100 according to the present embodiment.

  First, the RIP unit 121 receives print data from an external device such as a host device, performs RIP processing on the received print data, and generates a RIP image that is a drawing target image (step S101).

  Subsequently, the print control unit 123 transmits the RIP image generated by the RIP unit 121 to the printed matter inspection apparatus 200 and also to the printing unit 125. The printing unit 125 performs a print processing process such as an image forming process. This is executed, the RIP image is printed on the recording medium, and a printed matter that is the recording medium on which the drawing target image is drawn is generated (step S103).

  FIG. 8 is a flowchart illustrating an example of a flow of processing performed in the printed matter inspection apparatus 200 according to the present embodiment.

  First, the read image acquisition unit 253 acquires the read image generated by the reading unit 251 (step S201).

  Subsequently, the reference image acquisition unit 255 acquires a reference image that serves as an inspection reference for the printed matter generated by the printing apparatus 100 (step S203).

  In addition, the process of step S201 and the process of step S203 may be performed in parallel regardless of the processing order.

  Subsequently, the difference image generation unit 257 performs position alignment between the reference image and the read image (Step S205), and generates a difference image that indicates the difference between the reference image after alignment and the read image in units of pixels (Step S205). S207).

  Subsequently, the edge region extraction unit 259 extracts an edge region from the reference image (step S209).

  Subsequently, the neighborhood area detection unit 261 detects a neighborhood area located in the vicinity of the edge area (step S211).

  Subsequently, the threshold value correction unit 265 determines, for the pixels constituting either the edge region or the neighboring region, the density of the pixel and the target of attention for the pixel, which is located in either the edge region or the neighboring region. The inspection threshold value for inspection stored in the inspection threshold value storage unit 263 is corrected based on the density of the one or more target pixel and the distance between the pixel and the one or more target pixel (step) S213).

  Subsequently, the inspection threshold image generation unit 267 sets the inspection threshold stored in the inspection threshold storage unit 263 for the pixels constituting the region other than the edge region or the neighboring region, and either the edge region or the neighboring region is set. For the pixels constituting the region, an inspection threshold image in which the inspection threshold corrected by the threshold correction unit 265 is set is generated (step S215).

  In addition, the process from step S205 to S207 and the process from step S209 to S215 may be executed in parallel regardless of the processing order.

  Subsequently, the inspection unit 269 compares the difference image and the inspection threshold image for each pixel, and inspects the printed matter (step S217).

  As described above, according to the present embodiment, by correcting the inspection threshold based on the density or distance of the edge region or the vicinity region, the inspection threshold is relaxed according to the state near the edge region, and the vicinity of the edge region Inspection accuracy can be improved.

  In particular, according to the present embodiment, since the inspection threshold value is corrected based on the density or distance of the edge region or the vicinity region, it is necessary to prepare a corresponding number of printed materials on which the same contents are printed as in the prior art. It is also suitable for inspection in a printing environment in which only a small number of printed materials having the same contents printed, such as variable printing, are produced.

  Therefore, according to the present embodiment, it is possible to improve the inspection accuracy near the edge region regardless of the printing environment.

(Modification)
The inspection threshold correction method described in the above embodiment may be substituted by a filter process for the reference image. In this case, the threshold value correction unit 265 uses, as a reference object, a pixel constituting either the edge region or the neighboring region, with the pixel constituting the edge region or the pixel constituting the neighboring region centered on the pixel. The inspection threshold value may be corrected based on the filter process.

  Note that the size of the filter used for the filtering process may be set according to the size of the neighboring region. For example, when the region in the range of 2 pixels around the edge region is set as the neighborhood region, the size of the filter can be 5 × 5 pixels. However, even if the pixel is included in the filter, the pixel applied to the filtering process is a pixel that constitutes either the edge region or the neighboring region, and does not constitute any region of the edge region or the neighboring region. Do not use about. This is because the inspection threshold value is to be corrected by the influence from the elements related to the edge, and the influence from the elements not related to the edge such as a picture that is not the edge is excluded. In the modification, it is assumed that the filter coefficient is determined empirically, but the method of determining the filter coefficient value is not limited to this.

(program)
The program executed by the inspection apparatus according to the embodiment and the modification is a file in an installable format or an executable format, and is a CD-ROM, CD-R, memory card, DVD (Digital Versatile Disk), flexible disk (FD). And the like stored in a computer-readable storage medium.

  In addition, the program executed by the inspection apparatus according to the embodiment and the modification may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. Further, the program executed by the inspection apparatus according to the embodiment and the modification may be provided or distributed via a network such as the Internet. In addition, a program executed by the inspection apparatus according to the embodiment and the modification may be provided by being incorporated in advance in a ROM or the like.

  The program executed by the inspection apparatus of the embodiment and the modification has a module configuration for realizing the above-described units on a computer. As actual hardware, for example, the CPU reads out a program from the ROM to the RAM and executes the program, so that each functional unit is realized on the computer.

  In addition, the said embodiment and modification are shown as an example and are not intending limiting the range of invention. The above-described novel embodiment can be implemented in various other forms, and various omissions, replacements, changes, and at least partial clouding are performed without departing from the spirit of the invention. be able to. These embodiments are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Printed product inspection system 100 Printing apparatus 101 Operation panel 103Y, 103M, 103C, 103K Photosensitive drum 105 Transfer belt 107 Secondary transfer roller 109 Paper feed part 111 Conveying roller pair 113 Fixing roller 115 Reverse path 121 RIP part 123 Print control part 125 Printing unit 200 Printed material inspection apparatus 201, 251 Reading unit 203 Operation panel 253 Read image acquisition unit 255 Reference image acquisition unit 257 Difference image generation unit 259 Edge region extraction unit 261 Neighborhood region detection unit 263 Inspection threshold storage unit 265 Threshold correction unit 267 Inspection Threshold image generation unit 269 inspection unit 300 stacker 311 tray

JP 2015-175706 A

Claims (9)

A reference image acquisition unit for acquiring a reference image serving as an inspection standard for printed matter;
A read image acquisition unit for acquiring a read image obtained by reading the printed matter;
A difference image generation unit that generates a difference image indicating a difference between the reference image acquired by the reference image acquisition unit and the read image acquired by the read image acquisition unit;
An edge region extraction unit that extracts an edge region from the reference image acquired by the reference image acquisition unit;
A neighborhood region detection unit for detecting a neighborhood region located in the vicinity of the edge region extracted by the edge region extraction unit;
For the pixels constituting either the edge region extracted by the edge region extraction unit or the neighborhood region detected by the neighborhood region detection unit, the density of the pixel and the target of interest for the pixel are A threshold value for correcting the inspection threshold value for inspection based on the density of one or more target pixels located in either the edge region or the neighboring region and the distance between the pixel and the one or more target pixels. A correction unit;
An inspection unit that inspects the printed matter based on the difference image generated by the difference image generation unit and the inspection threshold corrected by the threshold correction unit;
An inspection apparatus comprising: The neighborhood area detection unit detects the neighborhood area based on pixels constituting the edge area,
The pixel of interest for the pixels constituting the neighborhood area detected by the neighborhood area detection unit is the neighboring pixel adjacent to the pixels constituting the edge area that is the detection source of the pixels constituting the neighborhood area. The inspection device according to claim 1, wherein the inspection device is an adjacent pixel located on the opposite side of the pixels constituting the vicinity region.   The pixel of interest with respect to a pixel constituting the edge region is an adjacent pixel having a largest density difference from a pixel constituting the edge region among neighboring pixels adjacent to the pixel constituting the edge region. 2. The inspection apparatus according to 2.   The corrected inspection threshold is proportional to a density difference between a pixel constituting any one of the edge region and the neighboring region and the one or more target pixels, and the corrected inspection threshold value of the edge region or the neighboring region is The inspection apparatus according to claim 1, wherein the inspection apparatus has a value inversely proportional to a distance between a pixel constituting any region and the one or more target pixels. The inspection threshold value for the inspection is set for the pixels constituting the edge region or the region other than the neighborhood region, and the correction is performed for the pixels constituting either the edge region or the neighborhood region. An inspection threshold image generation unit that generates an inspection threshold image in which an inspection threshold is set;
The inspection apparatus according to claim 1, wherein the inspection unit inspects the printed matter based on the difference image and the inspection threshold image. A reference image acquisition unit for acquiring a reference image serving as an inspection standard for printed matter;
A read image acquisition unit for acquiring a read image obtained by reading the printed matter;
A difference image generation unit that generates a difference image indicating a difference between the reference image acquired by the reference image acquisition unit and the read image acquired by the read image acquisition unit;
An edge region extraction unit that extracts an edge region from the reference image acquired by the reference image acquisition unit;
A neighborhood region detection unit for detecting a neighborhood region located in the vicinity of the edge region extracted by the edge region extraction unit;
With respect to a pixel constituting either the edge region extracted by the edge region extraction unit or the neighborhood region detected by the neighborhood region detection unit, the pixel constituting the edge region around the pixel or the pixel A threshold value correcting unit that corrects an inspection threshold value for inspection based on a filtering process with reference to pixels constituting a neighboring region;
An inspection unit that inspects the printed matter based on the difference image generated by the difference image generation unit and the inspection threshold corrected by the threshold correction unit;
An inspection apparatus comprising: An inspection system comprising: an image forming apparatus that generates a printed material; and an inspection device that inspects the printed material,
The inspection device includes:
A reference image acquisition unit that acquires a reference image serving as an inspection reference for the printed matter from the image forming apparatus;
A read image acquisition unit for acquiring a read image obtained by reading the printed matter;
A difference image generation unit that generates a difference image indicating a difference between the reference image acquired by the reference image acquisition unit and the read image acquired by the read image acquisition unit;
An edge region extraction unit that extracts an edge region from the reference image acquired by the reference image acquisition unit;
A neighborhood region detection unit for detecting a neighborhood region located in the vicinity of the edge region extracted by the edge region extraction unit;
For pixels constituting either the edge region extracted by the edge region extraction unit or the neighborhood region detected by the neighborhood region detection unit, the density of the pixel and the target of interest for the pixel are: The inspection threshold for inspection is corrected based on the density of one or more target pixels located in either the edge region or the neighboring region and the distance between the pixel and the one or more target pixels. A threshold correction unit;
An inspection unit that inspects the printed matter based on the difference image generated by the difference image generation unit and the inspection threshold corrected by the threshold correction unit;
An inspection system comprising: A reference image acquisition step for acquiring a reference image as an inspection standard for printed matter;
A read image acquisition step of acquiring a read image obtained by reading the printed matter;
A difference image generation step for generating a difference image indicating a difference between the reference image acquired in the reference image acquisition step and the read image acquired in the read image acquisition step;
An edge region extraction step for extracting an edge region from the reference image before acquired in the reference image acquisition step;
A neighboring region detecting step for detecting a neighboring region located in the vicinity of the edge region extracted in the edge region extracting step;
For pixels constituting either the edge region extracted in the edge region extraction step or the neighborhood region detected in the neighborhood region detection step, the density of the pixel and the target of interest for the pixel are: The inspection threshold for inspection is corrected based on the density of one or more target pixels located in either the edge region or the neighboring region and the distance between the pixel and the one or more target pixels. A threshold correction step;
An inspection step of inspecting the printed matter based on the difference image generated in the difference image generation step and the inspection threshold corrected in the threshold correction step;
Including inspection methods. A reference image acquisition step for acquiring a reference image as an inspection standard for printed matter;
A read image acquisition step of acquiring a read image obtained by reading the printed matter;
A difference image generation step for generating a difference image indicating a difference between the reference image acquired in the reference image acquisition step and the read image acquired in the read image acquisition step;
An edge region extraction step of extracting an edge region from the reference image acquired in the reference image acquisition step;
A neighboring region detecting step for detecting a neighboring region located in the vicinity of the edge region extracted in the edge region extracting step;
For pixels constituting either the edge region extracted in the edge region extraction step or the neighborhood region detected in the neighborhood region detection step, the density of the pixel and the target of interest for the pixel are: The inspection threshold for inspection is corrected based on the density of one or more target pixels located in either the edge region or the neighboring region and the distance between the pixel and the one or more target pixels. A threshold correction step;
An inspection step of inspecting the printed matter based on the difference image generated in the difference image generation step and the inspection threshold corrected in the threshold correction step;
A program that causes a computer to execute.

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