JP6848286B2 - Inspection equipment, inspection methods and programs - Google Patents

Description

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

In printing that requires high quality such as production printing, quality inspection of printed matter is required. For example, on the printed matter, based on the difference between the reference image as an inspection standard generated by performing color conversion processing or the like on the original image from which the printed matter is generated and the scanned image generated by electrically reading the printed matter. There are known inspection devices that detect existing defects and inspect the quality of printed matter based on the detected defects.

Here, for example, Patent Document 1 discloses a technique for performing an inspection according to the type of region by using a tag bit indicating the type of region on the reference image for each pixel.

However, in the conventional technique as described above, when the original image is subjected to halftone processing using a plurality of types of halftones, the inspection accuracy cannot be improved.

In this case, the color conversion information used for the color conversion process applied to the original image to generate the reference image is generally generated from a predetermined halftone, and therefore is a half different from the halftone. The color reproducibility of the pixels on the reference image corresponding to the pixels on the original image that have been subjected to halftone processing with tones deteriorates.

Therefore, even if the inspection is performed according to the type of region as in the conventional technique as described above, if the printed matter is inspected without considering the deterioration of the color reproducibility due to the difference in the type of halftone, the printed matter is inspected. It causes a decrease in inspection accuracy.

The present invention has been made in view of the above circumstances, and even when the original image from which the printed matter is generated is subjected to halftone processing using a plurality of types of halftones, the inspection accuracy is improved. It is an object of the present invention to provide an inspection device, an inspection method and a program capable of performing.

In order to solve the above-mentioned problems and achieve the object, the inspection apparatus according to one aspect of the present invention acquires the original image of the generation source of the printed matter, which has been subjected to halftone processing using a plurality of types of halftones. The original image acquisition unit, the type image acquisition unit that acquires the type image indicating the type of the halftone used in the halftone processing for each pixel corresponding to the pixel constituting the original image, and the original image. On the other hand, a reference image generation unit that performs color conversion using color conversion information generated based on a predetermined type of halftone to generate a reference image as an inspection standard, and a scanned image obtained by reading the printed matter are displayed. The scanned image acquisition unit to be acquired, the difference image generation unit that generates a difference image showing the difference between the reference image and the scanned image, and the halftone of the predetermined type for each pixel constituting the difference image. The printed matter is compared with the inspection threshold based on the reference threshold determined from the reference threshold and the relaxation threshold for the reference threshold determined from the halftone of the type indicated by the pixel on the type image corresponding to the pixel, and the value of the pixel. The inspection unit includes an inspection unit for inspecting the image, and since the value of the pixel is larger than the inspection threshold value, the pixel on the difference image determined to be a defect candidate is a halftone of the predetermined type. When the pixel corresponds to the pixel on the original image that has been subjected to halftone processing using a halftone of a different type from the above, the pixel value and the reading of the pixel on the reference image corresponding to the pixel on the difference image. The difference value between the pixel value of the pixel on the image and the reference threshold value is calculated, and it is determined whether or not the tendency matches the plurality of threshold difference values calculated in the past, and the tendency is determined. If they match, the relaxation threshold of a halftone of a different type from the predetermined type of halftone is updated based on at least one of the calculated threshold difference value and the plurality of threshold difference values calculated in the past. you.

According to the present invention, even when the original image from which the printed matter is generated is subjected to halftone processing using a plurality of types of halftones, the inspection accuracy can be improved.

FIG. 1 is a schematic view showing an example of the printed matter inspection system of the present embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of the printing apparatus of the present embodiment. FIG. 3 is a block diagram showing an example of the hardware configuration of the printed matter inspection device of the present embodiment. FIG. 4 is a block diagram showing an example of the functional configuration of the printing device and the printed matter inspection device of the present embodiment. FIG. 5 is a flowchart showing an example of the flow of the procedure of the color conversion information generation process performed by the printed matter inspection apparatus of the present embodiment. FIG. 6 is a flowchart showing an example of the flow of the procedure of the quality inspection process of the printed matter performed by the printed matter inspection apparatus of the present embodiment. FIG. 7 is a flowchart showing an example of the flow of the procedure of the reference image generation process and the type image conversion process (process of step S207 shown in FIG. 6) performed by the reference image generation unit of the present embodiment. FIG. 8 is an explanatory diagram of an example of the resolution conversion method for the type image of the present embodiment. FIG. 9 is an explanatory diagram of an example of the resolution conversion method for the type image of the present embodiment. FIG. 10 is a flowchart showing an example of the flow of the procedure of the printed matter inspection process (process of step S211 shown in FIG. 6) performed by the inspection unit of the present embodiment. FIG. 11 is a flowchart showing an example of the flow of the procedure of the inspection threshold setting process (process of step S401 shown in FIG. 10) performed by the inspection unit of the present embodiment. FIG. 12 is a diagram showing an example of relaxation threshold information stored in the threshold information storage unit of the present embodiment. FIG. 13 is a flowchart showing an example of the flow of the procedure of the defect determination process (process of step S403 shown in FIG. 10) performed by the inspection unit of the present embodiment. FIG. 14 is a diagram showing an example of a list of threshold value difference values of the present embodiment. FIG. 15 is a flowchart showing an example of the flow of the procedure of the defect determination process (process of step S403 shown in FIG. 10) performed by the inspection unit of the modified example 1.

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

FIG. 1 is a schematic view showing an example of the printed matter inspection system 1 of the present embodiment. As shown in FIG. 1, the printed matter inspection system 1 includes a printing apparatus 100, 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, photoconductor drums 103Y, 103M, 103C, 103K, a transfer belt 105, a secondary transfer roller 107, a paper feed unit 109, a transfer roller pair 111, and a fixing roller 113. , Inverted path 115.

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

In each of the photoconductor drums 103Y, 103M, 103C, and 103K, a toner image is formed by performing an image forming process (charging step, exposure step, developing step, transfer step, and cleaning step), and the formed toner image is formed. Is transferred to the transfer belt 105. In the present embodiment, a yellow toner image is formed on the photoconductor drum 103Y, a magenta toner image is formed on the photoconductor drum 103M, a cyan toner image is formed on the photoconductor drum 103C, and the cyan toner image is formed on the photoconductor drum 103K. It is assumed that a black toner image is formed, but the present invention is not limited to this.

The transfer belt 105 conveys a toner image (full-color toner image) superimposed and transferred from the photoconductor drums 103Y, 103M, 103C, and 103K to the secondary transfer position of the secondary transfer roller 107. In the present embodiment, the yellow toner image is first transferred to the transfer belt 105, and then the magenta toner image, the cyan toner image, and the black toner image are sequentially superimposed and transferred, but the present invention is limited to this. It is not something that is done.

A plurality of recording media are superposed and accommodated in the paper feeding unit 109, and the recording media are fed. Examples of the recording medium include, but are not limited to, recording paper, and for example, a medium capable of recording an image such as coated paper, cardboard, OHP (Overhead Projector) sheet, plastic film, prepreg, and copper foil. Anything can be used as long as it is available.

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

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 transfer 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 pressurizing the recording medium on which the full-color toner image is transferred.

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

The inversion path 115 reverses the front and back surfaces of the recording medium by switching back the transmitted recording medium, and conveys the recording medium in the direction of arrow t. The recording medium conveyed by the inversion path 115 is retransmitted by the transfer roller pair 111, the full-color toner image is transferred to the surface opposite to the previous one by the secondary transfer roller 107, and fixed by the fixing roller 113 as printed matter. , The paper is discharged to the printed matter inspection device 200.

The printed matter inspection device 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 matter inspection device 200 and displays various screens. The operation panel 203 may be omitted. In this case, the operation panel 101 may also serve as the operation panel 203, or the externally connected PC (Personal Computer) may also serve as the operation panel 203.

The reading unit 201 electrically reads one side of the printed matter discharged from the printing device 100. The printed matter inspection device 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 matter may have the same configuration as the reading unit 201.

Then, the printed matter inspection device 200 discharges the read printed matter to the stacker 300.

The stacker 300 includes a tray 311. The stacker 300 stacks the printed matter discharged by the printed matter inspection device 200 on the tray 311.

FIG. 2 is a block diagram showing an example of the hardware configuration of the printing apparatus 100 of 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 overall control, drawing, communication, and input from the operation display unit 820 of the printing device 100. 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. In addition to the engine portion, the engine portion 860 also includes an image processing portion such as error diffusion and gamma conversion.

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 are provided, and the north bridge (NB) 813 and the ASIC 816 are connected by an AGP (Accelerated Graphics Port) bus 815. Further, the MEM-P812 further includes a ROM 812a and a RAM 812b.

The CPU 811 controls the entire printing apparatus 100, has a chipset including NB813, MEM-P812, and SB814, and is connected to other devices via this chipset.

The NB813 is a bridge for connecting the CPU 811 to the MEM-P812, SB814, and the AGP bus 815, and has a memory controller that controls reading and writing to the MEM-P812, a PCI master, and an AGP target.

The MEM-P812 is a system memory used as a memory for storing programs and data, a memory for expanding programs and data, a memory for drawing a printer, and the like, and includes a ROM 812a and a RAM 812b. The ROM 812a is a read-only memory used as a memory for storing programs and data, and the RAM 812b is a writeable and readable memory used as a memory for expanding programs and data, a memory for drawing a printer, and the like.

The SB814 is a bridge for connecting the NB813 to a PCI device and peripheral devices. The SB814 is connected to the NB813 via a PCI bus, and a network interface (I / F) unit or the like is 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 connecting the AGP bus 815, the PCI bus, the HDD 818, and the MEM-C817, respectively. 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-C817, and a plurality of DMACs (Direct Memory) that rotate image data by hardware logic or the like. It consists of an Access Controller) and a PCI unit that transfers data between the engine unit 860 via the PCI bus. A USB840 and an IEEE 1394 (the Institute of Electrical and Electronics Engineers 1394) interface (I / F) 850 are connected to the ASIC 816 via a PCI bus. The operation display unit 820 is directly connected to the ASIC 816.

The MEM-C817 is a local memory used as a copy image buffer and a code buffer, and the HDD 818 is a storage for accumulating image data, programs, font data, and forms.

The AGP bus 815 is a bus interface for graphics accelerator cards proposed to speed up graphics processing, and speeds up graphics accelerator cards by directly accessing MEM-P812 with high throughput. Is.

FIG. 3 is a block diagram showing an example of the hardware configuration of the printed matter inspection device 200 of the present embodiment. As shown in FIG. 3, the printed matter inspection device 200 has a configuration in which the controller 910 and the engine unit (Engine) 960 are connected by a PCI bus. The controller 910 is a controller that controls the entire control, drawing, communication, and input from the operation display unit 920 of the printed matter inspection device 200. The engine unit 960 is an engine that can be connected to the PCI bus, and is, for example, a scanner engine such as a scanner. In addition to the engine portion, the engine portion 960 also includes an image processing portion such as error diffusion and gamma conversion.

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 an AGP bus 915. Further, the MEM-P912 further includes a ROM 912a and a RAM 912b.

The CPU 911 controls the entire printed matter inspection device 200, has a chipset including NB 913, MEM-P912, and SB914, and is connected to other devices via this chipset.

The NB 913 is a bridge for connecting the CPU 911 to the MEM-P912, SB914, and the AGP bus 915, and has a memory controller that controls reading and writing to the MEM-P912, a PCI master, and an AGP target.

The MEM-P912 is a system memory used as a memory for storing programs and data, a memory for expanding programs and data, a memory for drawing a printer, 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 writeable and readable memory used as a memory for expanding programs and data, a memory for drawing a printer, and the like.

The SB914 is a bridge for connecting the NB913 to a PCI device and peripheral devices. The SB914 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 applications that has 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-C917, respectively. 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-C917, a plurality of DMACs that rotate image data by hardware logic, and an engine. It consists of a PCI unit that transfers data to and from the unit 960 via the PCI bus. A USB940 and an IEEE1394 interface (I / F) 950 are connected to the ASIC 916 via a PCI bus. The operation display unit 920 is directly connected to the ASIC 916.

The MEM-C917 is a local memory used as a copy image buffer and a code buffer, and the HDD 918 is a storage for accumulating image data, programs, font data, and forms.

The AGP bus 915 is a bus interface for graphics accelerator cards proposed to speed up graphics processing, and speeds up graphics accelerator cards by directly accessing MEM-P912 with high throughput. Is.

FIG. 4 is a block diagram showing an example of the configuration of the printing device 100 and the printed matter inspection device 200 of the present embodiment. As shown 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 device 200 includes a reading unit 251, a reading image acquisition unit 253, an original image acquisition unit 255, a color conversion information generation unit 257, a color conversion information storage unit 259, a type image acquisition unit 261 and a reference image. It includes a generation unit 263, a difference image generation unit 265, an inspection unit 267, and a threshold information storage unit 269.

In the present embodiment, the case where the printing device 100 includes the RIP section 121 will be described as an example, but the present invention is not limited to this, and a device different from the printing device 100 such as DFE (Digital Front End) uses the RIP section 121. You may be prepared.

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

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

The reading unit 251 is composed of a reading unit 201, and can be realized by, for example, an engine unit 960 or the like. The scanned image acquisition unit 253, the original image acquisition unit 255, the color conversion information generation unit 257, the type image acquisition unit 261 and the reference image generation unit 263 can be realized by, for example, a CPU 911 and a system memory 912. The color conversion information storage unit 259 and the threshold value information storage unit 269 can be realized by, for example, HDD 918. The difference image generation unit 265 and the inspection unit 267 may be realized by, for example, a CPU 911, a system memory 912, or the like, an ASIC 916, or the like, or may be realized by using these in combination.

Further, the operation panel 101 shown in FIG. 1 is realized by the operation display unit 820, and the operation panel 203 shown in FIG. 1 is realized by the operation display unit 920.

In the following, regarding the operations of the printing device 100 and the printed matter inspection device 200, first, the operation of generating color conversion information used in the color conversion process when generating a reference image from the original image of the printed matter will be described, and then the printed matter will be described. The inspection operation for inspecting the quality of the

First, the operation of generating color conversion information will be described.

When the RIP unit 121 receives a print instruction of the color chart from an external device such as a host device, the RIP unit 121 generates a RIP image as the original image of the color chart. In the present embodiment, the RIP image is assumed to be RIP image data of 600 dpi of each pixel of CMYK, but is not limited thereto. It is assumed that the color chart is a color chart for a predetermined type of halftone among a plurality of types of halftones that the RIP unit 121 uses properly according to the type of the area of the RIP image. Examples of the plurality of types of halftones include, but are not limited to, a halftone of 200 lpi (line per inch) halftone dots and a halftone of 150 lpi (line per inch) halftone dots.

The print control unit 123 transmits the original image of the color chart generated by the RIP unit 121 to the print unit 125. Further, the print control unit 123 transmits the original image of the color chart and the reference halftone ID for identifying which halftone the color chart is for to the printed matter inspection device 200.

The printing unit 125 executes a printing processing process such as an image forming process, prints a printed image based on the original image of the color chart on paper, and generates a printed matter of the color chart.

Hereinafter, the operation of generating the color conversion information on the printed matter inspection device 200 side will be described with reference to FIG. FIG. 5 is a flowchart showing an example of the flow of the procedure of the color conversion information generation process performed by the printed matter inspection device 200 of the present embodiment. However, the processing order is not limited to this, and for example, the processing of steps S101 to S103 and the processing of steps S105 to S109 may be interchanged or may be processed in parallel.

First, the reading unit 251 reads the printed matter of the color chart generated by the printing unit 125 to generate a scanned image of the color chart, and the scanned image acquisition unit 253 acquires the scanned image of the color chart (step S101). .. In the present embodiment, the scanned image of the color chart is assumed to be image data of 200 dpi for each pixel of RGB, but is not limited thereto.

Subsequently, the color conversion information generation unit 257 measures the color of the scanned image of the color chart acquired by the scanned image acquisition unit 253 (step S103).

Subsequently, the original image acquisition unit 255 acquires the original image of the color chart and the reference halftone ID from the printing apparatus 100 (step S105).

Subsequently, the color conversion information generation unit 257 converts the resolution of the original image of the color chart acquired by the original image acquisition unit 255 (step S107). In the present embodiment, the color conversion information generation unit 257 converts the resolution of the original image of the color chart from 600 dpi to 200 dpi.

Subsequently, the color conversion information generation unit 257 measures the color of the original image of the color chart whose resolution has been converted (step S109).

Subsequently, the color conversion information generation unit 257 associates the color measurement result of the original image of the color chart (CMYK color measurement result) with the color measurement result of the read image of the color chart (RGB color measurement result). Color conversion information is generated, and the generated color conversion information is associated with the reference halftone ID and stored (registered) in the color conversion information storage unit 259 (step S111). That is, the color conversion information is the color conversion information for performing the color space conversion from CMYK to RGB for the halftone indicated by the reference halftone ID.

In the present embodiment, as the color conversion information, the color conversion information for performing the color space conversion from CMYK to RGB will be described as an example, but the present invention is not limited to this, and the color space conversion from CMYK to Lab and RGB are described. It can also be applied to color conversion information for conversion to a different color space, such as color space conversion from to CMYK.

Next, an inspection operation for inspecting the quality of printed matter will be described.

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 as the original image of the printed matter. When generating the original image of the printed matter, the RIP unit 121 shall perform halftone processing using a plurality of types of halftones on the original image. Specifically, the RIP unit 121 shall perform halftone processing using halftones of the type corresponding to the type of the area for each area constituting the original image of the printed matter. Here, examples of the area constituting the original image include, but are not limited to, a character area, an edge area, a picture area, and a photographic area. In addition, the RIP unit 121 also generates a type image indicating the type of halftone used in the halftone processing applied to the pixels constituting the original image for each pixel corresponding to the pixels constituting the original image.

In the present embodiment, the print data includes job information described in a page description language (PDL) such as PostScript (registered trademark), image data in TIFF (Tagged Image File Format) format, and the like. However, it is not limited to this. Further, in the present embodiment, as described above, the RIP image is assumed to be RIP image data of 600 dpi of each pixel of CMYK, but the RIP image is not limited to this. Further, the type image is also assumed to be image data of 600 dpi for each pixel, but is not limited to this.

The print control unit 123 transmits the original image of the printed matter generated by the RIP unit 121 to the print unit 125. Further, the print control unit 123 transmits the original image and the type image of the printed matter generated by the RIP unit 121 to the printed matter inspection device 200.

Further, the print control unit 123 uses the inspection result transmitted (feedback) from the printed matter inspection device 200 to specify, for example, the output destination of the printed matter that has not passed the quality inspection for the stacker 300 and the quality inspection. Marking of printed matter that did not pass the above, or instructing the printing unit 125 to perform replacement printing.

The printing unit 125 executes a printing processing process such as an image forming process, prints a printed image based on the original image of the printed matter on paper, and generates a printed matter.

Hereinafter, the inspection operation for inspecting the quality of the printed matter on the printed matter inspection apparatus 200 side will be described with reference to FIG. FIG. 6 is a flowchart showing an example of the flow of the procedure of the quality inspection process of the printed matter performed by the printed matter inspection apparatus 200 of the present embodiment. However, the processing order is not limited to this.

First, the reading unit 251 reads the printed matter generated by the printing unit 125 to generate a scanned image of the printed matter, and the scanned image acquisition unit 253 acquires the scanned image of the printed matter (step S201). In the present embodiment, the scanned image of the printed matter is assumed to be image data of 200 dpi for each pixel of RGB, but is not limited thereto.

Subsequently, the original image acquisition unit 255 acquires the original image of the printed matter from the printing device 100 (step S203).

Subsequently, the type image acquisition unit 261 acquires the type image of the original image of the printed matter from the printing device 100 (step S205).

Subsequently, the reference image generation unit 263 generates a reference image as an inspection reference from the original image of the printed matter acquired by the original image acquisition unit 255 (step S207). Specifically, the reference image generation unit 263 stores the color conversion information (color conversion information storage unit 259) generated based on the resolution conversion and the halftone of a predetermined type with respect to the original image of the printed matter. A reference image is generated by performing color conversion or the like using the color conversion information).

At this time, the reference image generation unit 263 also performs resolution conversion on the type image acquired by the type image acquisition unit 261 in order to make the resolution correspond to the reference image. The details of the reference image generation process and the type image conversion process will be described later. In the present embodiment, the reference image is image data of 200 dpi for each pixel of RGB, but the reference image is not limited to this.

Subsequently, the difference image generation unit 265 generates a difference image showing the difference between the reference image generated by the reference image generation unit 263 and the scanned image of the printed matter acquired by the scanned image acquisition unit 253 (step S209). Specifically, the difference image generation unit 265 compares the reference image and the read image on a pixel-by-pixel basis, calculates the difference value of the pixel value of each RGB color for each pixel, and comprises the difference value of the pixel value for each pixel. Generate the difference image to be generated.

Subsequently, the inspection unit 267 inspects the printed matter based on the difference image generated by the difference image generation unit 265 (step S211). Specifically, the inspection unit 267 sets a reference threshold value determined from a predetermined type of halftone for each pixel constituting the difference image generated by the difference image generation unit 265, and a type image corresponding to the pixel. The printed matter is inspected by comparing the relaxation threshold value with respect to the reference threshold value determined from the halftone of the type indicated by the pixel, the inspection threshold value based on the halftone, and the value of the pixel.

For example, the inspection unit 267 determines the density defect of the printed matter generated by the printing device 100 based on the magnitude relationship between the difference value of each pixel constituting the difference image generated by the difference image generation unit 265 and the inspection threshold value. inspect. For example, a place where the difference value is large (pixel group) or a place where the area with the difference is wide (pixel group) becomes a density defect.

Then, the inspection unit 267 stores the inspection result such as the position and type of the density defect, the read image, and the reference image in association with each other in the HDD 918, or transmits (feedback) to the printing apparatus 100. The details of the inspection process by the inspection unit 267 will be described later.

FIG. 7 is a flowchart showing an example of the flow of the procedure of the reference image generation process and the type image conversion process (process of step S207 shown in FIG. 6) performed by the reference image generation unit 263 of the present embodiment.

First, the reference image generation unit 263 converts the resolution of the original image of the printed matter acquired by the original image acquisition unit 255 and the type image acquired by the type image acquisition unit 261 (step S301). In the present embodiment, the reference image generation unit 263 converts the resolution of the original image and the type image of the printed matter from 600 dpi to 200 dpi.

By the resolution conversion from 600 dpi to 200 dpi, 3 × 3 pixels are combined into one pixel, but for the type image, the pixel value is a value indicating the type of halftone used for the halftone processing. The reference image generation unit 263 is summarized as follows.

For example, as shown in FIG. 8, when all the values of the 3 × 3 pixels before the resolution conversion are common (0 in the example shown in FIG. 8), the reference image generation unit 263 is the one pixel after the resolution conversion. The values are grouped into the common value (0 in the example shown in FIG. 8). Further, for example, as shown in FIG. 9, when different values are included in the 3 × 3 pixels before the resolution conversion, the reference image generation unit 263 sets the value of one pixel after the resolution conversion as the mode (FIG. 9). In the example shown in (1), it may be summarized in 0), or it may be summarized in a value indicating that a plurality of types of halftones of different types are mixed.

Subsequently, the reference image generation unit 263 performs color conversion using the color conversion information stored in the color conversion information storage unit 259 on the original image of the printed matter whose resolution has been converted, and generates a reference image (step S303). ).

As described above, the color conversion information is the color conversion information for performing the color space conversion for the halftone indicated by the reference halftone ID associated with the color conversion information. Therefore, the color reproducibility of the region on the reference image corresponding to the region on the original image to which the halftone processing is performed with a halftone different from the halftone is slightly deteriorated.

Subsequently, the reference image generation unit 263 sets a reference point for the generated reference image (step S305). The reference point is a feature point that serves as a reference for alignment, and the difference image generation unit 265 described above aligns the reference image and the read image using this reference point to generate a difference image.

FIG. 10 is a flowchart showing an example of the flow of the procedure of the printed matter inspection process (process of step S211 shown in FIG. 6) performed by the inspection unit 267 of the present embodiment.

First, the inspection unit 267 performs an inspection threshold setting process for setting an inspection threshold for pixels on the difference image generated by the difference image generation unit 265 (step S401).

FIG. 11 is a flowchart showing an example of the flow of the procedure of the inspection threshold setting process (process of step S401 shown in FIG. 10) performed by the inspection unit 267 of the present embodiment.

Before explaining the processing of the flowchart shown in FIG. 11, the reference threshold value and the relaxation threshold value used for generating the inspection threshold value will be described. The reference threshold value and the relaxation threshold value are stored in the threshold value information storage unit 269.

The reference threshold value is a threshold value determined from the halftone used for generating the color conversion information, and is a threshold value assuming inspection in a region of the type in which the halftone processing is performed on the halftone. For example, when the halftone used for generating the color conversion information is the halftone used for the halftone processing in the character area, the reference threshold value is a threshold value assuming inspection in the character area on the difference image. ..

The relaxation threshold is a threshold prepared for each halftone that was not used for generating the color conversion information, and is a threshold for absorbing the difference from the halftone used for generating the color conversion information. As described above, when the halftone used for generating the color conversion information is the halftone used for the halftone processing in the character area, the original image in which the halftone processing is performed with the halftone for the picture area. The color reproducibility of the pattern area on the reference image corresponding to the upper pattern area is slightly lower than that of the character area on the reference image. For this reason, if the pattern area is inspected only with the reference threshold value assuming the inspection in the character area, the pixel value (difference value) due to the slightly reduced color reproducibility cannot be absorbed, and the inspection accuracy is lowered. Resulting in. That is, the relaxation threshold value is a threshold value for absorbing the pixel value (difference value) corresponding to the slight decrease in color reproducibility due to the difference in halftone.

Although details will be described later, in the present embodiment, the relaxation threshold value is set to a value that can absorb the pixel value (difference value) corresponding to the slight decrease in color reproducibility due to the difference in halftone from the beginning. This is not the case, and by updating the value of the relaxation threshold value while repeating the inspection, it is updated to such a value. This is to reduce the load on the initial setting of the relaxation threshold.

In the present embodiment, the inspection threshold value is generated by adding the relaxation threshold value to the reference threshold value, but the present invention is not limited to this.

FIG. 12 is a diagram showing an example of relaxation threshold information stored in the threshold information storage unit 269 of the present embodiment. In the example shown in FIG. 12, the relaxation threshold information is information in which the reference halftone ID, the halftone ID, the reference image pixel value, and the relaxation threshold are associated with each other. As described above, the reference halftone ID is an ID indicating the type of halftone used for generating the color conversion information. The halftone ID is an ID indicating the type of the corresponding halftone. The reference image pixel value indicates the pixel value of the pixel on the reference image corresponding to the pixel to be inspected. The relaxation threshold is prepared for each RGB.

In the example shown in FIG. 12, a relaxation threshold value is prepared for each set of pixel values of the reference image (set of RGB values) for the set of the reference halftone ID and the halftone ID. This is because the degree of color reproducibility may differ depending on the color. Further, in the example shown in FIG. 12, when the reference halftone ID and the halftone ID are the same, the relaxation threshold value is not set because the color reproducibility does not decrease in the corresponding pixel.

Further, since the type image after resolution conversion shows a value indicating that a plurality of types of halftones of different types are mixed, it is used when a plurality of types of halftones are mixed in the relaxation threshold information. The relaxation threshold of may be prepared. When the type image after resolution conversion shows a value indicating that a plurality of types of halftones of different types are mixed, the reference threshold value may be used as the inspection threshold value without using the relaxation threshold value.

The reference threshold is also stored in the threshold information storage unit 269 as information in which the reference halftone ID, the reference image pixel value, and the reference threshold are associated with each other in substantially the same format as the relaxation threshold information. ..

Returning to the description of FIG. 11, first, the inspection unit 267 acquires the halftone ID indicated by the pixel on the type image corresponding to the pixel for which the threshold value is set on the difference image (step S501).

Subsequently, the inspection unit 267 acquires the pixel value of the pixel on the reference image corresponding to the pixel for which the threshold value is set on the difference image (step S503).

Subsequently, the inspection unit 267 acquires the relaxation threshold value associated with the acquired halftone ID and the pixel value of the acquired reference image from the threshold information storage unit 269, acquires the reference threshold value, and acquires the relaxation threshold value. And the acquired reference threshold value are added together to generate an inspection threshold value, which is set to the threshold value for the pixel for which the threshold value is set (step S505).

Returning to FIG. 10, the inspection unit 267 performs a defect determination process for determining the presence or absence of a defect in the pixel using the inspection threshold set for the pixel to be inspected on the difference image (step S403).

The processing of steps S401 to S403 may be alternately performed for each pixel, or the processing of step S403 may be performed after the processing of step S401 for each pixel on the difference image. You may.

FIG. 13 is a flowchart showing an example of the flow of the procedure of the defect determination process (process of step S403 shown in FIG. 10) performed by the inspection unit 267 of the present embodiment.

First, the inspection unit 267 determines whether or not the pixel is a defect candidate based on the magnitude relationship between the difference value of the pixel to be inspected on the difference image and the inspection threshold value set for the pixel. Step S601).

When the difference value of the pixel to be inspected is larger than the inspection threshold value and the pixel to be inspected is a defect candidate (Yes in step S603), the relaxation threshold value is associated with the relaxation threshold value used to generate the inspection threshold value. If the values of the reference halftone ID and the halftone ID match (Yes in step S605), the inspection unit 267 determines that the pixel to be inspected is defective (step S619). This is because since the values of the reference halftone ID and the halftone ID match, the relaxation threshold value is not considered in the inspection threshold value, the error of the relaxation threshold value does not affect, and the determination result can be determined.

On the other hand, when the values of the reference halftone ID and the halftone ID do not match (No in step S605), the relaxation threshold is considered as the inspection threshold, and the defect determination result is regarded as a defect candidate due to the influence of the error of the relaxation threshold. Therefore, it is determined whether or not the pixel to be inspected can be determined to be defective by the following processing.

First, the inspection unit 267 determines the threshold difference value between the pixel value of the pixel on the reference image corresponding to the pixel to be inspected on the difference image and the pixel value of the pixel on the scanned image, and the reference threshold. Calculate (step S607).

Subsequently, the inspection unit 267 refers to the list of threshold value differences and determines whether or not the calculated tendency of the threshold difference values matches the tendency of the corresponding threshold difference values in the list (step S609).

FIG. 14 is a diagram showing an example of a list of threshold value difference values of the present embodiment. The list of threshold difference values is stored in the threshold information storage unit 269. In the example shown in FIG. 14, the list of threshold difference values is a list in which a reference halftone ID, a halftone ID, a reference image pixel value, and a pixel obtained by calculating the threshold difference value and the threshold difference value are associated with each other. It has become. The threshold difference value registered in the list of threshold difference values is the threshold difference value calculated in step S607 in the past. Registration of the threshold difference value in the list will be described later.

For example, in the inspection unit 267, in the list of threshold difference values, the reference halftone ID associated with the relaxation threshold used for generating the inspection threshold and the threshold difference value associated with the halftone ID are M (M is 2). If there are more than the above natural number) and the average value of the threshold difference values for the latest N (N ≧ M) cases is equal to or less than the latest threshold difference value calculated in step S607, the tendency of the calculated latest threshold difference value. Is determined to match the tendency of the corresponding threshold difference value in the list. The method for determining whether or not the tendencies match is not limited to this.

Then, when the calculated tendency of the threshold difference value does not match the tendency of the corresponding threshold difference value in the list (No in step S609), there is a high possibility that the pixel to be inspected is defective, so that the inspection unit 267 , The calculated threshold difference value and the pixel to be inspected (the pixel for which the threshold difference value was calculated) are the reference halftone ID and halftone associated with the relaxation threshold used for generating the inspection threshold in the threshold difference value list. It is registered in association with the ID (step S617), and it is determined that the pixel to be inspected is defective (step S619). This is because when the calculated tendency of the threshold difference value does not match the tendency of the corresponding threshold difference value in the list, it is unlikely that the defect determination result is a defect candidate due to the influence of the error of the relaxation threshold value.

On the other hand, when the tendency of the calculated threshold difference value matches the tendency of the corresponding threshold difference value in the list (Yes in step S609), the inspection unit 267 indicates the calculated threshold difference value and a plurality of thresholds calculated in the past. The relaxation threshold used to generate the test threshold is updated in the relaxation threshold information based on at least one of the difference values (step S611). For example, the inspection unit 267 adds at least one of the calculated latest threshold difference value and the average value, the median value, and the maximum value of the corresponding threshold value difference values in the list to the relaxation threshold value used for generating the inspection threshold value. At the same time, a predetermined margin α is added to update the relaxation threshold value. For example, if the relaxation threshold used for generating the inspection threshold is 20, the average value of the threshold difference values is 10, and the predetermined margin α is 5, the relaxation threshold after updating is 35. This is because when the tendency of the calculated threshold difference value matches the tendency of the corresponding threshold difference value in the list, the defect judgment result becomes a defect candidate due to the influence of the error of the relaxation threshold value, and it is necessary to update the relaxation threshold value. This is because it is done.

Subsequently, the inspection unit 267 describes the reference halftone ID associated with the relaxation threshold used for generating the inspection threshold and the past threshold difference value registered in association with the halftone ID in the threshold difference value list. For each pixel for which the above was calculated, the defect determination was canceled, that is, the non-defect was determined (step S613), and the past threshold difference value and the past threshold difference value were calculated from the list of threshold difference values. The pixels are erased (step S615).

In step S603, even when the difference value of the inspection target pixel is equal to or less than the inspection threshold value and the inspection target pixel is not a defect candidate (No in step S603), the inspection threshold value is generated in the threshold difference value list. The reference halftone ID associated with the relaxation threshold used, the past threshold difference value registered in association with the halftone ID, and the pixel from which the past threshold difference value is calculated are deleted (step S615). In this case, it can be determined that the defect of each pixel for which the past threshold difference value has been calculated is a defect that temporarily appears such as a spot.

As described above, according to the present embodiment, even when the original image is subjected to halftone processing using a plurality of types of halftones, the color reproducibility is slightly deteriorated due to the difference in halftones. Since the inspection is performed using the relaxation threshold for absorbing the pixel value (difference value) for the amount of the difference, the inspection can be performed in consideration of the decrease in color reproducibility due to the difference in the type of halftone, and the inspection accuracy can be improved. it can.

Further, according to the present embodiment, by updating the relaxation threshold value while repeating the inspection, the relaxation threshold value can absorb the pixel value (difference value) corresponding to the slight decrease in color reproducibility due to the difference in halftone. Update to a value like this. Therefore, according to the present embodiment, it is possible to reduce the load applied to the initial setting of the relaxation threshold value.

(Modification example 1)
In the method described in the above embodiment, when the value of the relaxation threshold value is larger than the pixel value (difference value) for which the color reproducibility is slightly reduced due to the difference in halftone, the relaxation threshold value cannot be updated. Therefore, this problem may be dealt with by preparing a list of threshold difference values even for pixels determined to be non-defects.

FIG. 15 is a flowchart showing an example of the flow of the procedure of the defect determination process (process of step S403 shown in FIG. 10) performed by the inspection unit 267 of the modified example 1. Here, the list of threshold difference values of the pixels determined to be defect candidates described with reference to FIG. 13 is referred to as a first difference list, and the list of threshold difference values of pixels determined to be non-defects is referred to as a second difference. Called a list.

First, the processes in steps S701 to S703 are the same as the processes in steps S601 to S603 of the flowchart shown in FIG.

When the difference value of the pixel to be inspected is larger than the inspection threshold value and the pixel to be inspected is a defect candidate (Yes in step S703), the inspection unit 267 used it to generate the inspection threshold value in the second difference list. The reference halftone ID associated with the relaxation threshold value, the past threshold value difference value registered in association with the halftone ID value, and the pixel from which the past threshold value difference value is calculated are deleted (step S705).

The subsequent processes in steps S707 to S721 are the same as the processes in steps S605 to S619 in the flowchart shown in FIG.

On the other hand, when the difference value of the pixel to be inspected is equal to or less than the inspection threshold value and the pixel to be inspected is not a defect candidate (No in step S703), it corresponds to the relaxation threshold value used for generating the inspection threshold value in the first difference list. The past threshold value difference value registered in association with the attached reference halftone ID and the halftone ID and the pixel from which the past threshold value difference value is calculated are deleted (step S723).

Subsequently, if the values of the reference halftone ID and the halftone ID associated with the relaxation threshold value used for generating the inspection threshold value do not match (No in step S725), the inspection unit 267 inspects the difference image. The threshold difference value of the difference value between the pixel value of the pixel on the reference image corresponding to the target pixel and the pixel value of the pixel on the scanned image and the reference threshold value is calculated (step S727). When the values of the reference halftone ID and the halftone ID associated with the relaxation threshold value used for generating the inspection threshold value match (Yes in step S725), the process ends.

Subsequently, the inspection unit 267 determines whether or not the calculated threshold difference value is equal to or greater than a predetermined value (step S729). When the calculated threshold difference value is less than a predetermined value (No in step S729), the inspection unit 267 slightly deteriorates the color reproducibility of the relaxation threshold value used for generating the inspection threshold due to the difference in halftone. It is determined that the value is smaller than the pixel value (difference value) of the minute (the value of the relaxation threshold value is not too large), and the reference halftone ID associated with the relaxation threshold value used for generating the inspection threshold value in the second difference list is used. The past threshold value difference value registered in association with the halftone ID and the pixel from which the past threshold value difference value is calculated are deleted (step S737).

On the other hand, when the calculated threshold difference value is equal to or greater than a predetermined value (Yes in step S729), the inspection unit 267 refers to the second difference list, and the tendency of the calculated threshold difference value is the corresponding threshold difference in the list. It is determined whether or not it matches the tendency of the value (step S731). As a method for determining whether or not the tendencies match, the same method as in the above embodiment may be adopted.

Then, when the calculated tendency of the threshold difference value matches the tendency of the corresponding threshold difference value in the second difference list (Yes in step S731), the inspection unit 267 calculated the calculated threshold difference value and the past. The relaxation threshold used for generating the test threshold is updated in the relaxation threshold information based on at least one of the plurality of threshold difference values (step S733). For example, the inspection unit 267 subtracts at least one of the calculated latest threshold difference value and the average value, the median value, and the maximum value of the corresponding threshold value difference values in the list from the relaxation threshold value used for generating the inspection threshold value. At the same time, a predetermined margin α is added to update the relaxation threshold value. For example, if the relaxation threshold used for generating the inspection threshold is 20, the average value of the threshold difference values is 10, and the predetermined margin α is 5, the relaxation threshold after updating is 15.

On the other hand, when the calculated tendency of the threshold difference value does not match the tendency of the corresponding threshold difference value in the second difference list (No in step S731), the inspection unit 267 requests the calculated threshold difference value and the pixel to be inspected. (The pixel on which the threshold difference value is calculated) is registered in the second difference list in association with the reference halftone ID and the halftone ID associated with the relaxation threshold used for generating the inspection threshold (step S735).

As described above, according to the modification 1, even when the relaxation threshold value is larger than the pixel value (difference value) for which the color reproducibility is slightly reduced due to the difference in halftone, the relaxation threshold value is set. It can be updated.

(Modification 2)
In the above embodiment and each modification, past inspection results are registered in a list of threshold difference values, and by observing the tendency, the influence of noise and defects can be excluded and the mitigation threshold can be updated. The larger the number of registered past inspection results (the larger the value of M or N), the larger the defect can be dealt with. However, if a global defect such as streaks, unevenness, or banding occurs, it will be dealt with. It is not desirable to increase the number of registrations to the extent that it can be covered, from the viewpoint of the amount of calculation and the storage area. Further, it is not a preferable printing result that the areas to be struck with the same color are different colors in the page.

Therefore, the inspection unit 267 may update the relaxation threshold value at the timing when the pages of the printed matter are switched. That is, the relaxation threshold value in the flowcharts shown in FIGS. 13 and 15 may be updated at the timing when the pages of the printed matter are switched (even if the relaxation threshold value is updated in the flowcharts shown in FIGS. 13 and 15). It may not be updated unless the printed page is switched). In this way, it is possible to perform processing that is not affected by defects that span a large area such as streaks.

Also, in this case, if a streak or the like occurs near the final line, it will be affected by it, so the counter is turned on the page and reset by switching the relaxation threshold value, and the relaxation threshold value with the largest number of counts is set. You may set it from the next page. That is, every time the inspection unit 267 updates the relaxation threshold value, the number of pixels inspected using the updated relaxation threshold value is counted, and when the printed matter page is switched, the count is updated to the relaxation threshold value having the largest count. It may be.

At that time, the inspection on the next page checks whether defects occur with the new mitigation threshold value, and if the defect judgment continues, returns to the original mitigation threshold value and sets the mitigation threshold value with the second highest count. You may. The inspection unit 267 may re-update the relaxation threshold value based on the inspection result using the relaxation threshold value updated at the timing when the pages of the printed matter are switched.

(Modification example 3)
In addition, the position of the defect candidate pixel registered in the threshold difference value list (first difference list) is simply monitored by the coordinates, and the registered points are dense, linear, strip-shaped, etc., which are unique to the defect. If there is a tendency, it may be regarded as a defect and not reflected in the mitigation threshold. That is, the inspection unit 267 may determine each pixel as a defect based on the position of each pixel on the difference image for which a plurality of threshold difference values have been calculated in the past.

(Modification example 4)
In the above embodiment and each modification, when the pixel to be inspected is not a defect, the inspection unit 267 deletes the list of threshold difference values (first difference list) (No in step S603 of FIG. 13, No. 15 in FIG. 15). In step S703, No), due to the influence of noise, it may be determined that the pixel to be inspected is not a defect even though the pixel to be inspected is a defect candidate. In order to exclude the influence of such noise, a counter is provided in the condition before erasing the threshold difference value list (first difference list), and the list is deleted when there is a transition to the difference list erasure a predetermined number of times. May be good.

That is, since the pixel value is equal to or less than the inspection threshold value, the inspection unit 267 may delete a plurality of threshold value difference values calculated in the past when the number of times of determination as non-defect reaches a predetermined number of times.

(Modification 5)
In the above embodiment and each modification, when generating a difference image, it is difficult to completely match the position of the edge portion of the image due to a slight deviation in printing or reading, and the difference tends to be large. Therefore, it is considered that the appearance tendency of the difference is different from the others in the vicinity of the edge. Therefore, the vicinity of the edge may be excluded from the monitoring target of the difference, and the relaxation threshold value may be acquired only in a region having a uniform density. Whether or not the region on the difference image is an edge can be specified from the type image because different halftones are used for each type of region in the present embodiment.

That is, when the pixel constituting the difference image is an edge region, the inspection unit 267 may inspect the printed matter by comparing the value of the pixel with the reference threshold value as the inspection threshold value.

(program)
The program executed by the inspection device of the above embodiment and each modification is a file in an installable format or an executable format, and is a CD-ROM, a CD-R, a memory card, a DVD (Digital Versatile Disk), or a flexible disk (a flexible disk). It is stored and provided on a computer-readable storage medium such as an FD).

Further, the program executed by the inspection device of the above embodiment and each modification may be provided by storing it on a computer connected to a network such as the Internet and downloading it via the network. Further, the program executed by the inspection device of the above embodiment and each modification may be provided or distributed via a network such as the Internet. Further, the program executed by the inspection device of the above-described embodiment and each modification may be provided by incorporating it in a ROM or the like in advance.

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

The above embodiments and modifications are presented as examples, and are not intended to limit the scope of the invention. The above-mentioned new embodiment can be implemented in various other forms, and various omissions, replacements, changes, and at least a part of cloud computing are performed without departing from the gist of the invention. be able to. These embodiments are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalent scope thereof.

1 Printed matter inspection system 100 Printing device 101 Operation panel 103Y, 103M, 103C, 103K Photoreceptor drum 105 Transfer belt 107 Secondary transfer roller 109 Feeding unit 111 Transfer roller pair 113 Fixing roller 115 Inversion path 121 RIP unit 123 Printing control unit 125 Printing unit 200 Printed matter inspection device 201, 251 Reading unit 203 Operation panel 253 Scanned image acquisition unit 255 Original image acquisition unit 257 Color conversion information generation unit 259 Color conversion information storage unit 261 Type image acquisition unit 263 Reference image generation unit 265 Difference image generation Department 267 Inspection Department 269 Threshold Information Storage Unit 300 Stacker 311 Tray

JP 2015-178971

Claims (12)

An original image acquisition unit that acquires the original image of the source of the printed matter, which has undergone halftone processing using multiple types of halftones.
A type image acquisition unit that acquires a type image indicating the type of halftone used in the halftone processing for each pixel corresponding to the pixels constituting the original image.
A reference image generation unit that performs color conversion using color conversion information generated based on a predetermined type of halftone on the original image to generate a reference image as an inspection standard, and a reference image generation unit.
A scanned image acquisition unit that acquires a scanned image obtained by scanning the printed matter, and
A difference image generation unit that generates a difference image showing the difference between the reference image and the read image,
For each pixel constituting the difference image, a reference threshold value determined from the predetermined type of halftone and a relaxation threshold value for the reference threshold value determined from the type of halftone indicated by the pixel on the type image corresponding to the pixel. The inspection unit that inspects the printed matter by comparing the inspection threshold value based on, and the value of the pixel.
Equipped with a,
Since the value of the pixel is larger than the inspection threshold value in the inspection unit, the pixel on the difference image determined as a defect candidate is a half using a halftone of a different type from the predetermined type of halftone. When the pixel corresponds to the pixel on the original image to which the tone processing has been performed, the difference between the pixel value of the pixel on the reference image corresponding to the pixel on the difference image and the pixel value of the pixel on the read image. The threshold difference value between the value and the reference threshold value is calculated, and it is determined whether or not the tendency matches the plurality of threshold value difference values calculated in the past. If the tendency matches, the calculated threshold value difference value and at least based on one of a plurality of threshold difference value calculated in the past, to update the relaxation threshold of the predefined type of halftone and different types of halftone test device. If multiple thresholds difference values and trends the threshold difference value the calculated is calculated on the past do not match, the inspection apparatus according to claim 1 for determining the pixel on the differential image determined as the defect candidate defect. When the calculated threshold difference value matches the tendency of the plurality of threshold difference values calculated in the past, the pixel on the difference image determined to be the defect candidate and the plurality of threshold difference values calculated in the past are said. The inspection device according to claim 1 or 2 , wherein each pixel on the difference image is determined to be non-defect. Since the value of the pixel is equal to or less than the inspection threshold value in the inspection unit, the pixel on the difference image determined to be non-defect is a half using a halftone of a different type from the predetermined type of halftone. When the pixel corresponds to the pixel on the original image to which the tone processing has been performed, the difference between the pixel value of the pixel on the reference image corresponding to the pixel on the difference image and the pixel value of the pixel on the read image. The threshold difference value of the value and the reference threshold value is calculated, and if the threshold difference value is equal to or more than a predetermined value, it is determined whether or not the tendency matches the plurality of threshold difference values calculated in the past, and the tendency is determined. If they match, the relaxation threshold of the halftone of a different type from the halftone of the predetermined type is set based on at least one of the calculated threshold difference value and the plurality of threshold difference values calculated in the past. The inspection device according to any one of claims 1 to 3 to be updated. The inspection device according to any one of claims 1 to 4 , wherein the inspection unit updates the relaxation threshold value at a timing when the pages of the printed matter are switched. Each time the inspection unit updates the relaxation threshold value, the inspection unit counts the number of pixels inspected using the relaxation threshold value after the update, and at the timing when the pages of the printed matter are switched, the claim is updated to the relaxation threshold value having the largest count. Item 5. The inspection device according to item 5. The inspection device according to claim 5 or 6 , wherein the inspection unit re-updates the relaxation threshold value based on an inspection result using the relaxation threshold value updated at the timing when the pages of the printed matter are switched. The inspection device according to claim 1 , wherein the inspection unit determines each pixel as a defect based on the position of each pixel on the difference image for which a plurality of threshold difference values have been calculated in the past. The inspection unit, the value of the pixel is below the test threshold, if the number of times of determining the non-defect has reached a predetermined number of times, according to claim 1 for erasing a plurality of threshold difference value calculated in the past Inspection equipment. The test unit, when pixels constituting the difference image is an edge region, the reference threshold value as the inspection threshold, compared to the value of the pixel, claim 1-9 for inspecting the printed matter The inspection device according to one. An original image acquisition step for acquiring the original image of the source of the printed matter, which has been subjected to halftone processing using multiple types of halftones,
A type image acquisition step of acquiring a type image indicating the type of halftone used in the halftone processing for each pixel corresponding to the pixels constituting the original image.
A reference image generation step of performing color conversion on the original image using color conversion information generated based on a predetermined type of halftone to generate a reference image as an inspection standard, and
A scanned image acquisition step of acquiring a scanned image obtained by scanning the printed matter, and
A difference image generation step of generating a difference image showing the difference between the reference image and the read image, and
For each pixel constituting the difference image, a reference threshold value determined from the predetermined type of halftone and a relaxation threshold value for the reference threshold value determined from the type of halftone indicated by the pixel on the type image corresponding to the pixel. An inspection step of inspecting the printed matter by comparing the inspection threshold value based on, and the value of the pixel.
Only including,
In the inspection step, since the value of the pixel is larger than the inspection threshold value, the pixel on the difference image determined as a defect candidate is a half using a halftone of a different type from the predetermined type of halftone. When the pixel corresponds to the pixel on the original image to which the tone processing has been performed, the difference between the pixel value of the pixel on the reference image corresponding to the pixel on the difference image and the pixel value of the pixel on the read image. The threshold difference value between the value and the reference threshold value is calculated, and it is determined whether or not the tendency matches the plurality of threshold value difference values calculated in the past. If the tendency matches, the calculated threshold value difference value and at least based on one of a plurality of threshold difference value calculated in the past, the inspection method to update the relaxation threshold of the predefined type of halftone and different types of halftone. An original image acquisition step for acquiring the original image of the source of the printed matter, which has been subjected to halftone processing using multiple types of halftones,
A type image acquisition step of acquiring a type image indicating the type of halftone used in the halftone processing for each pixel corresponding to the pixels constituting the original image.
A reference image generation step of performing color conversion on the original image using color conversion information generated based on a predetermined type of halftone to generate a reference image as an inspection standard, and
A scanned image acquisition step of acquiring a scanned image obtained by scanning the printed matter, and
A difference image generation step of generating a difference image showing the difference between the reference image and the read image, and
For each pixel constituting the difference image, a reference threshold value determined from the predetermined type of halftone and a relaxation threshold value for the reference threshold value determined from the type of halftone indicated by the pixel on the type image corresponding to the pixel. An inspection step of inspecting the printed matter by comparing the inspection threshold value based on, and the value of the pixel.
Including
In the inspection step, since the value of the pixel is larger than the inspection threshold, the pixel on the difference image determined as a defect candidate is a half using a halftone of a different type from the predetermined type of halftone. When the pixel corresponds to the pixel on the original image to which the tone processing has been performed, the difference between the pixel value of the pixel on the reference image corresponding to the pixel on the difference image and the pixel value of the pixel on the read image. The threshold difference value of the value and the reference threshold is calculated to determine whether or not the tendency matches the plurality of threshold difference values calculated in the past, and if the tendency matches, the calculated threshold difference value is obtained. And a program for causing a computer to update the relaxation threshold of a halftone of a type different from the halftone of the predetermined type based on at least one of a plurality of threshold difference values calculated in the past. ..

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