JP2016063368A - Image inspection device, image inspection system, and image inspection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine whether a color conversion table used to generate a master image needs to be updated by an image inspection device which determines a defect of a printed matter by comparing a read image with the master image.SOLUTION: An image inspection is characterized in: acquiring a read image generated by reading an image which is formed and output; converting density of the image as the object of image formation and output using conversion information representing a value for conversion of the density of the image as the object of image formation and output according to density of the read image; generating an inspection image for inspection on the read image by converting the density of the image as the object of image formation and output; determining a defect of the read image on the basis of a difference image showing differences between the read image and the generated inspection image; and updating the conversion information on the basis of the state of a defective region determined to be a defect in a flat region as a region to be compared with a region where variance in density of pixels included in the inspection image is within a predetermined range in a region included in the read image.SELECTED DRAWING: Figure 16

Description

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

  Conventionally, inspection of printed matter has been performed manually, but in recent years, an apparatus for performing inspection has been used as post-processing of offset printing. Such an inspection apparatus first generates a master image serving as a reference by manually selecting and reading a non-defective product from among the printed images. Then, the inspection apparatus compares the generated master image with the corresponding portion of the scanned image of the printed material to be inspected, and determines the defect of the printed material based on the degree of these differences.

  However, plateless printing devices such as electrophotography, which have become popular in recent years, are good at printing a small number of parts, and there are many cases where the content of printing on each page differs, such as variable printing, and a master image is generated from printed matter like an offset printer. In comparison, it is inefficient. In order to cope with this problem, it is conceivable to generate a master image from print data. Thereby, it is possible to efficiently cope with variable printing.

  In the process of generating the master image from the print data in this way, first, an image in the CMYK (Cyan, Magenta, Yellow, blackK) format in which the resolution is converted in accordance with the resolution of the read image is generated from the print data. The resolution-converted CMYK format image is converted to an RGB (Red, Green, Blue) format image, and a master image that matches the color tone of the read image is generated. A color conversion table is used for conversion from such a CMYK format image to an RGB format image.

  Due to repeated use of the printer and reader and changes over time according to the surrounding environment such as temperature, the color tone of the printed matter output by the printer and the color tone of the read image generated by reading the printed matter by the reader vary. May occur. When the color tone of the read image varies, the color tone of the master image generated using the color conversion table does not match the color tone of the read image, so that the accuracy of defect determination may deteriorate. For this reason, it is necessary to update the color conversion table in accordance with the change in color tone of the read image due to the influence of changes in the state of the printer and the reading device over time.

  For the purpose of such adjustment of the color conversion table, a uniform color area is extracted from the original image data, and in the extracted area, an image of the printed matter formed on the paper based on the original image data and the original image data is extracted. It has been proposed to correct the color variation when the color variation value with respect to the read image exceeds a specified value (see, for example, Patent Document 1).

  Since the technique disclosed in Patent Document 1 only determines the color fluctuation value between the original image data and the read image, not only the influence of the change in the state of the printer and the read image with time but also the dirt and streaks of the printed matter. The color conversion table is also updated due to the influence of defects such as the above. As described above, in the technique disclosed in Patent Document 1, whether or not the color conversion table needs to be updated is not accurately determined.

  The present invention has been made to solve such problems, and a color conversion table used for generating a master image in an image inspection apparatus that compares a master image with a read image to determine defects in a printed matter. The purpose is to more accurately determine whether or not the update is necessary.

  In order to solve the above problems, an aspect of the present invention is an image inspection apparatus that inspects a read image obtained by reading an image formed and output on a recording medium, and the image formed and output is read. The read image acquisition unit that acquires the read image generated in the above, and the image formation output target using conversion information indicating a value for converting the density of the image formation output target image according to the density of the read image A density conversion unit that converts the density of the image, an inspection image generation unit that generates an inspection image for inspecting the read image by converting the density of the image to be imaged and output, and acquisition A defect determination unit that determines a defect of the read image based on a difference image indicating a difference between the read image thus generated and the generated inspection image, and the inspection image among the regions included in the read image In A conversion information update unit that updates the conversion information based on the state of the defect area determined to be a defect in a flat area that is an area that is compared with an area in which the density variation of pixels included is within a predetermined range; It is characterized by including.

  According to the present invention, in an image inspection apparatus that compares a master image and a read image to determine a defect of a printed matter, it is possible to more accurately determine whether or not it is necessary to update a color conversion table used for generating a master image. it can.

It is a figure which illustrates the composition of the image inspection system containing the inspection device concerning the embodiment of the present invention. It is a block diagram which illustrates the hardware constitutions of the inspection apparatus which concerns on embodiment of this invention. It is a block diagram which illustrates functional composition of DFE, an engine controller, a print engine, and an inspection device concerning an embodiment of the present invention. It is a figure which illustrates the aspect of the comparison test | inspection which concerns on embodiment of this invention. 1 is a diagram illustrating a configuration of a print engine, an inspection apparatus, and a stacker according to an embodiment of the invention. It is a block diagram which illustrates the functional composition of the master image processing part concerning the embodiment of the present invention. It is a figure which illustrates the color conversion table which concerns on embodiment of this invention. It is a figure which illustrates the color profile which concerns on embodiment of this invention. It is a figure which illustrates the function structure of the test | inspection control part which concerns on embodiment of this invention. It is a flowchart which illustrates the test | inspection operation | movement which concerns on embodiment of this invention. It is a figure which illustrates the defect information which concerns on embodiment of this invention. It is a figure which illustrates the common information which concerns on embodiment of this invention. It is a figure which illustrates the master image, edge image, and flat area image which concern on embodiment of this invention. It is a figure which illustrates the aspect of the color fluctuation of the read image which concerns on embodiment of this invention. It is a flowchart which illustrates the process by the color conversion table update part which concerns on embodiment of this invention. It is a flowchart which illustrates the color variation determination process which concerns on embodiment of this invention. It is a figure which illustrates the defect range contained in the flat area | region of the read image which concerns on embodiment of this invention. It is a figure which illustrates the color conversion table which concerns on embodiment of this invention. It is a figure which illustrates the master image and read image containing the gradation area | region which concern on embodiment of this invention. It is a flowchart which illustrates the line-shaped color variation determination process which concerns on embodiment of this invention. It is a figure which illustrates the aspect in which another flat area exists on extension of the line in the flat area of the read image which concerns on embodiment of this invention. It is a figure which illustrates the aspect in which another flat area exists on extension of the line in the flat area of the read image which concerns on embodiment of this invention. It is a flowchart which illustrates another aspect of the line-shaped color variation determination process which concerns on embodiment of this invention. It is a figure which illustrates the aspect in case the same color fluctuation has generate | occur | produced in the other flat area | region of the read image which concerns on embodiment of this invention. It is a figure which illustrates the aspect when the same color fluctuation | variation has not generate | occur | produced in the other flat area | region of the read image which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, in an image inspection system including an inspection apparatus that inspects an output result by comparing a read image obtained by reading an output result of image formation output with a master image, a color used when generating a master image A function for accurately adjusting the conversion table will be described. FIG. 1 is a diagram illustrating the overall configuration of an image inspection system according to this embodiment.

  As shown in FIG. 1, the image inspection system according to the present embodiment includes a DFE (Digital Front End) 1, an engine controller 2, a print engine 3, an inspection device 4, and an interface terminal 5. The DFE 1 is an image processing apparatus that generates image data to be printed based on a received print job, that is, bitmap data that is an output target image, and outputs the generated bitmap data to the engine controller 2.

  The engine controller 2 controls the print engine 3 based on the bitmap data received from the DFE 1 to execute image formation output. Further, the engine controller 2 uses the bitmap data received from the DFE 1 as information serving as a basis of an inspection image to be referred to when the inspection device 4 inspects the result of image formation output by the print engine 3. Send to.

  The print engine 3 is an image forming apparatus that executes image formation output on a sheet as a recording medium based on bitmap data in accordance with control of the engine controller 2. As the recording medium, in addition to the above-described paper, a sheet-like material such as a film or plastic can be used as long as it is an object for image formation output.

  The inspection device 4 generates a master image based on the bitmap data input from the engine controller 2. The inspection device 4 is an image inspection device that inspects an output result by comparing a read image generated by reading a sheet output from the print engine 3 with a reading device with the generated master image.

  When the inspection device 4 determines that the output result is defective, the inspection device 4 notifies the engine controller 2 of information indicating the page determined as defective. Thereby, reprint control of the defective page is executed by the engine controller 2.

  The interface terminal 5 is an information processing terminal for displaying a GUI (Graphical User Interface) for confirming a defect determination result by the inspection apparatus 4 and a GUI for setting parameters in the inspection, and is a PC (Personal Computer). This is realized by a general information processing terminal such as.

  Here, hardware constituting the DFE 1, the engine controller 2, the print engine 3, the inspection apparatus 4, and the interface terminal 5 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a hardware configuration of the inspection apparatus 4 according to the present embodiment. In FIG. 2, the hardware configuration of the inspection apparatus 4 is shown, but the same applies to other apparatuses.

  As shown in FIG. 2, the inspection apparatus 4 according to the present embodiment has the same configuration as an information processing apparatus such as a general PC (Personal Computer) or a server. That is, the inspection apparatus 4 according to the present embodiment includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 20, a ROM (Read Only Memory) 30, an HDD (Hard Disk Drive) 40, and an I / F 50. Connected through. Further, an LCD (Liquid Crystal Display) 60, an operation unit 70, and a dedicated device 80 are connected to the I / F 50.

  The CPU 10 is a calculation means and controls the operation of the entire inspection apparatus 4. The RAM 20 is a volatile storage medium capable of reading and writing information at high speed, and is used as a work area when the CPU 10 processes information. The ROM 30 is a read-only nonvolatile storage medium and stores a program such as firmware. The HDD 40 is a non-volatile storage medium that can read and write information, and stores an OS (Operating System), various control programs, application programs, and the like.

  The I / F 50 connects and controls the bus 90 and various hardware and networks. The LCD 60 is a visual user interface for the user to check the state of the inspection apparatus 4. The operation unit 70 is a user interface such as a keyboard and a mouse for the user to input information to the inspection apparatus 4.

  The dedicated device 80 is hardware for realizing a dedicated function in the engine controller 2, the print engine 3, and the inspection apparatus 4. In the case of the print engine 3, A plotter device that executes image formation output on a paper surface. Further, the engine controller 2 and the inspection device 4 are dedicated arithmetic devices for performing image processing at high speed. Such an arithmetic unit is configured as an ASIC (Application Specific Integrated Circuit), for example. A reading device that reads an image output on a paper surface is also realized by the dedicated device 80.

  In such a hardware configuration, the software control unit is configured by the CPU 10 performing calculations in accordance with a program stored in the ROM 30 or a program read to the RAM 20 from a recording medium such as the HDD 40 or an optical disk (not shown). The A functional block that realizes the functions of the DFE 1, the engine controller 2, the print engine 3, the inspection apparatus 4, and the interface terminal 5 according to the present embodiment is configured by a combination of the software control unit configured as described above and hardware. Is done.

  FIG. 3 is a block diagram illustrating functional configurations of the DFE 1, the engine controller 2, the print engine 3, and the inspection device 4 according to the present embodiment. In FIG. 3, data transmission / reception is indicated by a solid line, and the flow of paper is indicated by a broken line. As illustrated in FIG. 3, the DFE 1 according to the present embodiment includes a job information processing unit 101 and a RIP processing unit 102. The engine controller 2 includes a data acquisition unit 201, an engine control unit 202, and a bitmap transmission unit 203. The print engine 3 includes a print processing unit 301. The inspection device 4 includes a reading device 400, a read image acquisition unit 401, a master image processing unit 402, an inspection control unit 403, and a comparative inspection unit 404.

  The job information processing unit 101 executes image formation output based on a print job input from outside the DFE 1 via a network or a print job generated based on image data stored in the DFE 1 by an operator's operation. Control. When executing the image formation output, the job information processing unit 101 causes the RIP processing unit 102 to generate bitmap data based on the image data included in the print job.

  The RIP processing unit 102 generates bitmap data for the print engine 3 to execute image formation output based on the image data included in the print job, under the control of the job information processing unit 101. Bitmap data is information of each pixel constituting an image to be imaged and output.

  The print engine 3 according to the present embodiment executes image formation output based on binary images of CMYK (Cyan, Magenta, Yellow, blackK). On the other hand, generally, image data included in a print job is a multi-valued image in which one pixel is expressed by multi-gradation such as 256 gradations. Therefore, the RIP processing unit 102 converts the image data included in the print job from a multi-valued image to a small-valued image, generates CMYK binary data for each color, and transmits it to the engine controller 2.

  The data acquisition unit 201 acquires bitmap data input from the DFE 1 and operates the engine control unit 202 and the bitmap transmission unit 203, respectively. The engine control unit 202 causes the print engine 3 to execute image formation output based on the bitmap data transferred from the data acquisition unit 201. The bitmap transmission unit 203 transmits the bitmap data acquired by the data acquisition unit 201 to the inspection apparatus 4 for generating a master image.

  The print processing unit 301 is an image forming unit that acquires bitmap data input from the engine controller 2, executes image formation output on printing paper, and outputs printed paper. The print processing unit 301 according to the present embodiment is realized by a general electrophotographic image forming mechanism, but other image forming mechanisms such as an ink jet method can also be used.

  The reading device 400 is an image reading unit that reads an image formed on a sheet of printing paper output by printing performed by the print processing unit 301 and outputs a read image. The reading device 400 is, for example, a line scanner installed in a conveyance path inside the inspection device 4 for printing paper output by the print processing unit 301. The scanning device 400 scans the paper surface of the printing paper to be conveyed on the paper surface. Read the formed image.

  The read image generated by the reading device 400 is an inspection target by the inspection device 4. Since the read image is an image generated by reading the paper surface of the paper output by the image forming output, the read image is an image indicating the output result. The read image acquisition unit 401 acquires information of a read image generated by reading the paper surface of the printing paper by the reading device 400. The information of the read image acquired by the read image acquisition unit 401 is input to the comparison inspection unit 404 for comparison inspection. Note that the input of the read image to the comparison inspection unit 404 is executed under the control of the inspection control unit 403. At that time, the inspection control unit 403 obtains the read image and inputs it to the comparison inspection unit 404.

  The master image processing unit 402 acquires the bitmap data input from the engine controller 2 as described above, and generates a master image that is an inspection image for comparison with the inspection target image. That is, the master image processing unit 402 functions as an inspection image generation unit that generates a master image, which is an inspection image for performing an inspection of a read image, based on an image that is an image formation output target. The master image generation processing by the master image processing unit 402 will be described in detail later.

  The inspection control unit 403 is a control unit that controls the operation of the entire inspection apparatus 4, and each component included in the inspection apparatus 4 operates according to the control of the inspection control unit 403. The comparison inspection unit 404 compares the read image input from the read image acquisition unit 401 with the master image generated by the master image processing unit 402, and determines whether or not the intended image formation output is being executed. . The comparison inspection unit 404 is configured by the ASIC described above in order to quickly process a huge amount of calculation. In the present embodiment, the inspection control unit 403 functions as an image inspection unit by controlling the comparative inspection unit 404 and also functions as an inspection result acquisition unit that acquires an inspection result by the comparative inspection unit 404.

  In the comparison inspection unit 404, as described above, the 200 dpi read image and the master image expressed in 8 bits for each RGB color are compared for each corresponding pixel, and the difference value between the 8 bit pixel values for each RGB color described above for each pixel. Is calculated. Based on the magnitude relationship between the absolute value of the difference value thus calculated (hereinafter simply referred to as “difference value”) and the threshold value, the inspection control unit 403 determines the presence or absence of a defect in the read image. That is, the inspection control unit 403 functions as an image inspection unit by controlling each unit included in the inspection apparatus 4.

  When comparing the read image and the master image, the comparison inspection unit 404 superimposes the master image divided for each predetermined range on the read image corresponding to the divided range, as shown in FIG. The pixel value of the pixel, that is, the density difference is calculated. Such processing is realized by the inspection control unit 403 acquiring images in the overlapping range from the master image and the read image and inputting them to the comparison inspection unit 404.

  Further, the inspection control unit 403 shifts the position where the divided range is superimposed on the read image vertically, that is, while shifting the range of the image acquired from the read image vertically and horizontally, the total difference value calculated is calculated. The smallest position is determined as an accurate overlay position, and the difference value of each pixel calculated at that time is adopted as a comparison result. Therefore, the comparison inspection unit 404 can output the vertical and horizontal shift amounts when determined as the overlay position together with the difference value of each pixel.

  As shown in FIG. 4, each square divided on the grid is a predetermined range in which the difference values of the pixels described above are summed. In addition, the size of each division range illustrated in FIG. 4 is determined based on a range in which the comparison / inspection unit 404 configured by the ASIC can compare pixel values at a time as described above, for example.

  By such processing, the difference value is calculated after the read image and the master image are aligned. By comparing the difference value calculated in this way with a predetermined threshold value, a defect in the image is determined. Further, for example, even if there is a difference in scale between the entire read image and the entire master image, the influence of the scale is reduced by dividing and positioning for each range as shown in FIG. Is possible.

  Further, in each of the divided ranges as shown in FIG. 4, it is predicted that the amount of positional deviation between adjacent ranges is relatively close. Therefore, when performing the comparison inspection for each divided range, the calculation is performed while shifting the image in the vertical and horizontal directions by performing the above-described calculation while shifting the image in the vertical and horizontal directions with the positional deviation amount determined by the comparative inspection of the adjacent region as the center. Even if the number of times of performing is reduced, there is a high possibility that the calculation based on the accurate overlay position is executed, and the calculation amount as a whole can be reduced.

  Next, the mechanical configuration of the print engine 3, the inspection device 4, and the stacker 6 and the sheet conveyance path will be described with reference to FIG. As shown in FIG. 5, the print processing unit 301 included in the print engine 3 according to the present embodiment includes photosensitive drums 12 </ b> Y, 12 </ b> M, 12 </ b> C, and 12 </ b> K (hereinafter referred to as “photosensitive drums”) along the conveyance belt 11 that is an endless moving unit. In general, the photosensitive drum 12 is arranged in a row, and is called a so-called tandem type. That is, along the conveyance belt 11 that is an intermediate transfer belt on which an intermediate transfer image to be transferred to a sheet (an example of a recording medium) fed from the sheet feed tray 13 is formed, Photosensitive drums 12Y, 12M, 12C, and 12K are arranged in order from the upstream side.

  Each color image developed with toner on the surface of the photosensitive drum 12 for each color is superimposed on the conveyor belt 11 and transferred to form a full color image. The full-color image formed on the transport belt 11 in this way has a sheet surface of the paper transported on the path by the function of the transfer roller 14 at a position closest to the paper transport path indicated by a broken line in the drawing. Transcribed above.

  The paper on which the image is formed on the paper surface is further conveyed, the image is fixed by the fixing roller 15, and then conveyed to the inspection device 4. In the case of double-sided printing, the sheet on which an image is formed and fixed on one side is conveyed to the reversing path 16 and is reversed and conveyed to the transfer position of the transfer roller 14 again.

  The reading device 400 is configured by an information processing device inside the inspection device 4 by reading each surface of the paper conveyed from the print processing unit 301 in the paper conveyance path inside the inspection device 4 and generating a read image. The image is output to the read image acquisition unit 401. Further, the sheet whose paper surface has been read by the reading device 400 is further conveyed inside the inspection device 4, conveyed to the stacker 6, and discharged to the paper discharge tray 601. 5 shows an example in which the reading device 400 is provided only on one side of the paper in the paper transport path in the inspection device 4, but in order to enable inspection of both sides of the paper, The reading device 400 may be arranged on each of both sides.

  Next, a functional configuration of the master image processing unit 402 according to the present embodiment will be described. FIG. 6 is a block diagram illustrating an internal configuration of the master image processing unit 402. As illustrated in FIG. 6, the master image processing unit 402 includes a small-value / multi-value conversion processing unit 421, a resolution conversion processing unit 422, a color conversion processing unit 423, an image output processing unit 424, and a color profile storage unit 425. Note that the master image processing unit 402 according to the present embodiment is realized by operating the dedicated device 80 described in FIG. 2, that is, hardware configured as an ASIC, according to software control.

  The low-value / multi-value conversion processing unit 421 generates a multi-value image by performing low-value / multi-value conversion processing on a binary image expressed in colored / colorless. The bitmap data according to the present embodiment is information to be input to the print engine 3, and the print engine executes image formation output based on CMYK (Cyan, Magenta, Yellow, blackK) color binary images. On the other hand, the read image, which is the image to be inspected, is a multi-valued image of RGB (Red, Green, Blue), which is the basic three primary colors, and is a multi-valued image. The image is converted into a multi-valued image. As the multivalued image, for example, an image expressed by 8 bits for each of CMYK can be used.

  The small value / multivalue conversion processing unit 421 performs an 8-bit extension process and a smoothing process as the small value / multivalue conversion process. The 8-bit extension process is a process of converting 0/1 data, which is 1 bit, into 8 bits, converting “0” to “0” and converting “1” to “255”. The smoothing process is a process of smoothing an image by applying a smoothing filter to 8-bit data.

  In this embodiment, the print engine 3 executes image formation output based on CMYK binary images, and the master image processing unit 402 includes a low-value multi-value conversion processing unit 421. Is an example. That is, when the print engine 3 executes image formation output based on a multi-value image, the low-value multi-value conversion processing unit 421 can be omitted.

  In addition, the print engine 3 may have a function of performing image formation output based on a low-value image such as 2 bits instead of 1 bit. In this case, it can be dealt with by changing the function of the 8-bit extension processing. That is, in the case of 2 bits, the gradation value is four values of 0, 1, 2, and 3. Therefore, in the case of 8-bit expansion, “0” is converted to “0”, “1” is converted to “85”, “2” is converted to “170”, and “3” is converted to “255”.

  The resolution conversion processing unit 422 performs resolution conversion so that the resolution of the multi-value image generated by the small-value multi-value conversion processing unit 421 matches the resolution of the read image that is the image to be inspected. In the present embodiment, since the reading device 400 generates a 200 dpi read image, the resolution conversion processing unit 422 converts the resolution of the multi-valued image generated by the small-value multi-value conversion processing unit 421 to 200 dpi. In addition, the resolution conversion processing unit 422 according to the present embodiment determines the size of the image after resolution conversion based on a predetermined magnification in consideration of the shrinkage of the paper output by the print processing unit 301 during resolution conversion. adjust.

  The color conversion processing unit 423 acquires the image whose resolution is converted by the resolution conversion processing unit 422 and performs conversion of the color expression format (hereinafter referred to as “color conversion”). The color conversion process is a process of converting a CMYK format image into an RGB format image. As described above, since the read image according to this embodiment is an RGB format image, the color conversion processing unit 423 converts the CMYK format image whose resolution has been converted to an RGB format.

  In the color conversion process, a CMYK format image is converted into an RGB format image and a gradation conversion process is performed. The tone conversion processing is color tone conversion processing for matching the color tone of the master image with the color tone of the image formed on the paper surface by the print processing unit 301 and the color tone of the image read and generated by the reading device 400. .

  The color conversion process and the gradation conversion process are performed using, for example, a color conversion table corresponding to the type (copy paper, coated paper, etc.) and size of paper on which image formation is output. FIG. 7 is a diagram illustrating a color conversion table. As illustrated in FIG. 7, the color conversion table is conversion information in which a CMYK format value that is an input value before conversion is associated with an RGM format value that is an output value after conversion.

  The input value before conversion is a pixel value (CMYK format) of each color patch in the original image for forming color patches of various gradation colors. The output value after conversion is the pixel value of each color patch (RGB format) in the read image generated by reading the paper after an image including each color patch of the input value is formed on the paper surface by the print processing unit 301. It is. Based on such a color conversion table, the CMYK format image output from the resolution conversion processing unit 422 is converted into an RGB format image, and the color tone (density) of the CMYK format image is an RGB format image. It is converted according to the color tone (density). That is, the color conversion processing unit 423 converts the density of the image forming output target image using the conversion information indicating the value for converting the density of the image forming output target image according to the density of the read image. It functions as a part.

  The color conversion table is included in the color profile stored in advance in the color profile storage unit 425 that is a storage medium. FIG. 8 is a diagram illustrating a color profile stored in the color profile storage unit 425. As shown in FIG. 8, the color profile is information in which the profile ID for identifying the profile, the paper type (copy paper, coated paper, etc.) to which the color conversion table is applied, the paper size, and the color conversion table described above are associated. .

  Through such processing, a 200 dpi multi-valued image expressed by 8 bits (24 bits in total) of each RGB color is generated for each pixel.

  The image output processing unit 424 outputs the master image generated by the processing up to the color conversion processing unit 423 and the image whose resolution is converted by the resolution conversion processing unit 422 (hereinafter referred to as “resolution conversion image”). Thereby, the inspection control unit 403 acquires the master image and the resolution conversion image from the master image processing unit 402.

  The state of the print engine 3 and the reading device 400 of the inspection device 4 in such an image inspection system changes over time according to the surrounding environment such as repeated use and temperature. Due to the influence of such a change over time, there are cases where the color tone of the printed matter output from the print engine 3 and the color tone of the read image generated by reading the printed matter by the reading device 400 may vary. The gist of the present embodiment is to determine a change in the color tone of the read image (hereinafter referred to as “color change”) due to the influence of the change over time of the print engine 3 or the reading device 400 based on the inspection result of the read image. Thus, it is necessary to accurately determine whether or not the color conversion table needs to be updated.

  Next, a functional configuration of the inspection control unit 403 according to the present embodiment will be described. FIG. 9 is a block diagram illustrating a functional configuration related to determination of color variation and update of the color conversion table in the functional configuration of the inspection control unit 403 according to the present embodiment. FIG. 10 is a flowchart showing an image inspection operation performed by the inspection control unit 403 according to this embodiment.

  As shown in FIG. 9, the inspection control unit 403 according to this embodiment includes an information input unit 431, a defect determination unit 432, an inspection information storage processing unit 433, an inspection information storage unit 434, a controller communication unit 435, and a display information generation unit. 436 and a color conversion table update unit 437. Hereinafter, first, an image inspection operation performed by the inspection control unit 403 according to the present embodiment will be described with reference to FIG.

  In the inspection control unit 403 according to the present embodiment, as illustrated in FIG. 10, first, the information input unit 431 acquires a master image from the master image processing unit 402 (S1001), and acquires a read image from the read image acquisition unit 401. Obtain (S1002). Note that the processing in S1001 and the processing in S1002 are not limited in context, and may be executed in the reverse order or may be executed in parallel. Further, the information input unit 431 acquires a resolution converted image from the master image processing unit 402. The acquired resolution conversion image is used in processing by the color conversion table update unit 437 described later.

  As described with reference to FIG. 4, the information input unit 431 that has acquired the master image and the read image extracts a predetermined range of images from the master image and the read image and inputs the images to the comparison inspection unit 404, thereby comparing the inspection unit. In step S <b> 1003, the image is subjected to a comparison inspection 404.

  By the processing in S1003, a difference image indicating a difference value between each pixel constituting the read image and each pixel constituting the master image is generated. The defect determination unit 432 acquires the generated difference image, and performs defect determination based on the acquired difference image (S1004). Specifically, in the process of S1004, the defect determination unit 432 has a total value (or average value) of pixel values of each pixel of the acquired difference image (hereinafter referred to as “difference total value”) equal to or greater than a threshold value. In this case, it is determined that the read image in the range input to the comparison inspection unit 404 is defective.

  When the defect determination process in S1004 is completed, the inspection information storage processing unit 433 stores the inspection information in the inspection information storage unit 434 (S1005). The inspection information is a determination result (hereinafter referred to as “defect information”) determined to be defective and common information (hereinafter referred to as “common information”) used for inspection of the read image (defect determination processing). is there. Details of the common information and the defect information will be described later.

  The controller communication unit 435 executes engine control such as a reprint request based on the determination result by the defect determination unit 432 (S1006). The display information generation unit 436 generates display information for displaying the defect information stored in the inspection information storage unit 434 on the display unit of the interface terminal 5, and outputs the display information to the interface terminal 5 to control the display of the determination result. (S1007).

  The interface terminal 5 displays a screen showing information on the defect based on the display information input from the display information generation unit 436. Such processing in the inspection control unit 403 is repeated until output of all pages is completed for one print job. When output and inspection of all pages is completed, the processing ends.

  Next, details of defect information and common information will be described. FIG. 11 is a diagram illustrating defect information stored in the inspection information storage unit 434. FIG. 12 is a diagram illustrating common information stored in the inspection information storage unit 434. As shown in FIG. 11, the defect information includes, for example, a job ID, a page ID, a defect ID, a defect range, and a difference total value.

  The job ID is information for identifying a job for printing a printed material to be inspected, and the page ID is information for identifying one of the print pages included in the job identified by the job ID. The defect ID is identification information for identifying one piece of defect information determined to have a defect in the read image of one page identified by the page ID.

  The defect range indicates a region (hereinafter referred to as “defect region”) in the read image of the defect indicated by the defect information identified by the defect ID. The defect range is, for example, a predetermined size of m × n pixels of several pixels to several tens of pixels, and the position in the read image is determined by the upper left coordinates and the lower right coordinates of the region. The difference total value is a total pixel value of each pixel of the difference image in the defect range.

  As shown in FIG. 12, the common information includes, for example, a job ID, a page ID, a resolution conversion image, a master image, a read image, a difference image, an edge image, and a flat area image. The job ID and page ID correspond to the job ID and page ID shown in FIG. That is, the defect information that is the same ID as the job ID and page ID of the common information is information related to the defect included in the read image for one page identified by the job ID and page ID of the common information.

  The resolution-converted image, master image, and read image are images for one page identified by the page ID, and are input from the information input unit 431. The difference image is an image for one page identified by the page ID, and is input from the defect determination unit 432.

  13A is a diagram illustrating a master image, and FIG. 13B is a diagram illustrating an edge image extracted from the master image illustrated in FIG. 13A, and FIG. FIG. 14 is a diagram illustrating a flat region image extracted from the master image shown in FIG.

  The edge image is an image representing an edge portion extracted from the master image for one page identified by the page ID. For example, the defect determination unit 432 extracts an edge portion by performing Laplacian filter processing or the like on the master image. For example, the edge image shown in FIG. 13B is extracted from the master image shown in FIG.

  The flat region image is an image that is extracted from a master image for one page identified by the page ID, and that represents a flat portion of the density undulation with variation in pixel density within a predetermined range. For example, the defect determination unit 432 extracts a flat portion by calculating a flatness that is a standard deviation or a variance of pixel values in a predetermined range, for example. For example, the flat area image shown in FIG. 13C is extracted from the master image shown in FIG. If no edge image or flat area image is extracted, the common information does not include the edge image or flat area image.

  In the present embodiment, the case has been described as an example where the difference information includes the difference information illustrated in FIG. However, the difference total value is not necessarily included in the defect information, and may be calculated based on the difference image included in the common information shown in FIG. 12 as necessary.

  Next, processing of the color conversion table update unit 437 illustrated in FIG. 9 will be described. Prior to the description of the processing of the color conversion table update unit 437, first, the color variation of the read image due to the influence of changes over time of the print engine 3 and the reading device 400 will be described. FIG. 14 is a diagram illustrating an example of the color variation of the read image. Due to changes with time of the print engine 3 and the reading device 400, for example, the color tone of the read image becomes darker in the order of FIGS. 14 (a), 14 (b), and 14 (c). That is, color variation of the read image occurs due to a change in state in the process of generating the read image.

  For example, when the color conversion table is generated so as to match the color tone of the read image shown in FIG. 14A, the master image generated using the color conversion table and the read image shown in FIG. May not match the color tone, and the accuracy of defect determination may deteriorate.

  Therefore, the color conversion table update unit 437 determines such color variation of the read image based on the inspection result of the read image, and updates the color conversion table to match the color tone of the read image. That is, the color conversion table update unit 437 functions as a conversion information update unit that updates a color conversion table that is conversion information based on the inspection result of the read image. Hereinafter, specific processing of the color conversion table updating unit 437 will be described.

  FIG. 15 is a flowchart illustrating the process performed by the color conversion table update unit 437. As illustrated in FIG. 15, the color conversion table update unit 437 acquires inspection information for one page in one print job from the inspection information storage unit 434 (S1501). The color conversion table update unit 437 that has acquired the inspection information determines whether or not a flat region image is included in the common information of the acquired inspection information (S1502). That is, the color conversion table update unit 437 determines whether or not there is a flat region in the master image for one page used for the inspection.

  When there is a flat area in the master image (S1502 / YES), the color conversion table update unit 437 is an area in the read image that is compared with the flat area included in the master image (any one flat area if there are multiple areas). The color variation determination process is executed (S1503). Hereinafter, the area in the read image that is compared with the flat area included in the master image is also referred to as “the flat area of the read image”.

  FIG. 16 is a flowchart illustrating the color variation determination process. As illustrated in FIG. 16, the color conversion table update unit 437 acquires defect information of defects determined in the determination target flat region from the inspection information storage unit 434 (S1601). Specifically, the color conversion table update unit 437 acquires defect information in which the coordinates of the center of the defect range included in the defect information illustrated in FIG.

  The color conversion table updating unit 437 that has acquired the defect information determines whether or not the number of acquired defect information is equal to or greater than a predetermined threshold (hereinafter referred to as “defect number threshold”) (S1602). FIG. 17 is a diagram illustrating a defect range included in a flat area of a read image. As shown in FIG. 17, for example, a plurality of defect ranges surrounded by a solid square are present in a star-shaped flat region of a read image. Further, for example, a range surrounded by a dotted rectangle is a region other than the defective region, that is, a region that has not been determined to be a defect (hereinafter referred to as “non-defect region”).

  The number of acquired defect information indicates, for example, the number of defects in the flat region shown in FIG. That is, in the process of S1602, the color conversion table update unit 437 determines whether or not the number of defects existing in the flat area is equal to or greater than the defect number threshold. Note that the number of defects means the number of defect areas having a predetermined size, which can be translated into the size of the defect area included in the flat area.

  When the number of defects is less than the defect number threshold (S1602 / NO), the color conversion table update unit 437 determines that the defect existing in the flat region is a defect other than the color variation of the read image (S1610). The process ends.

  When the number of defects in the flat area is small, the defects in the flat area are not caused by color fluctuations occurring over a wide area in the flat area, but are considered to be sudden defects such as small dirt and short streaks. is there. On the other hand, if the number of defects is equal to or greater than the defect number threshold (S1602 / YES), the defect in the flat region may be determined by color variation, and therefore the color conversion table update unit 437 continues the determination process. .

  The color conversion table update unit 437 has a maximum pixel value and a minimum pixel value of each pixel value (hereinafter referred to as “difference pixel value”) of the difference image in any one defect area (defect range) included in the flat area. Is acquired (S1603). The difference pixel value in the defect area is obtained, for example, by acquiring an image of the defect range included in the defect information illustrated in FIG. 11 from the difference image included in the common information illustrated in FIG.

  In the color conversion table update unit 437 that has acquired the maximum pixel value and the minimum pixel value, the difference between the acquired maximum pixel value and the minimum pixel value is equal to or less than a predetermined threshold (hereinafter referred to as “difference pixel threshold”). It is determined whether or not (S1604). When the difference is larger than the difference pixel threshold (S1604 / NO), the color conversion table update unit 437 determines that the defect is other than the color variation of the read image (S1610), and ends the process.

  If the difference is larger than the difference pixel threshold, the defect in the flat region is not caused by a small color variation in which each difference pixel value difference is small, but is considered to be a defect such as a large amount of dirt, a large area of dirt, or a long streak. Because. On the other hand, when the difference is equal to or smaller than the difference pixel threshold value (S1604 / YES), the defect in the flat region may be determined by the color variation, and therefore the color conversion table update unit 437 continues the determination process.

  The color conversion table update unit 437 acquires the pixel value of the non-defective area in the flat area from the master image and the read image (S1605). Specifically, for example, the color conversion table update unit 437 first determines a non-defective region having a predetermined size other than the defect range included in the defect information (for example, in FIG. 17) from the flat region image included in the common information. In the star-shaped flat region shown, a region surrounded by a dotted square is extracted. The color conversion table update unit 437 acquires an average value of each pixel in the extracted non-defective region (hereinafter referred to as “non-defective master pixel value”).

  Then, the color conversion table update unit 437 calculates an average value (hereinafter referred to as “non-defective read pixel value”) of each pixel value in the same area as the area from which the non-defective master pixel value is acquired from the read image included in the common information. ) To get. Note that the reason why the average value of the pixel values in the non-defective area is used is to consider color unevenness of the master image and the read image.

  The color conversion table update unit 437 that has acquired the non-defective master pixel value and the non-defective read pixel value obtains the absolute value of the difference value between the acquired non-defective master pixel value and the non-defective read pixel value (hereinafter referred to as “non-defective region difference”). Value ”) is acquired (S1606). In addition, the color conversion table update unit 437 acquires the absolute value of the average value of the difference pixel values in any one defective area in the flat area (hereinafter referred to as “defective area difference value”) (S1607). Note that the processing in S1605 and S1606 and the processing in S1607 are not limited in context, and may be executed in reverse order or in parallel.

  The color conversion table update unit 437 that has acquired the non-defective area difference value and the defective area difference value has the absolute value of the difference between the acquired non-defective area difference value and the defective area difference value as a predetermined threshold (hereinafter referred to as “area difference”). It is determined whether it is equal to or less than (threshold value) (S1608). When the absolute value of the difference is larger than the region difference threshold (S1608 / NO), the color conversion table update unit 437 determines that the defect is other than the color variation of the read image (S1610), and ends the process.

  When the absolute value of the difference is larger than the area difference threshold, the defect in the flat area is not due to color variation in which there is almost no difference in the difference value of each pixel of the master image and the read image in the entire flat area. This is because it is considered to be a defect due to in-plane density fluctuation in a somewhat large area such as banding. On the other hand, if the absolute value of the difference is equal to or smaller than the region difference threshold (S1608 / YES), the color conversion table update unit 437 determines that color variation has occurred in the flat region (S1609), and ends the process. .

  Returning to FIG. 15, when the color conversion table update unit 437 that has executed the color variation determination process determines that color variation has occurred in the flat area (S1504 / YES), for example, a color whose initial value is 0. The fluctuation determination number is increased by 1 (S1505). Then, the color conversion table update unit 437 updates the color conversion table when the color variation determination number is equal to or greater than a predetermined threshold (hereinafter referred to as “determination number threshold”) (S1506 / YES) (S1507). . Details of the color conversion table update processing will be described later.

  On the other hand, when it is determined that a defect other than color variation has occurred in the flat region (S1504 / NO) or when the color variation determination number is smaller than the determination number threshold (S1506 / NO), the color conversion table update unit 437. Determines whether there is another flat region in the read image (S1508). When there is another flat area (S1508 / YES), the color conversion table update unit 437 executes a color variation determination process in the other flat area (S1503), and repeats the subsequent processes.

  On the other hand, when there is no flat area in the read image (S1502 / NO) or when there is no other flat area (S1508 / NO), the color conversion table update unit 437 displays the page on which the color variation determination process has been executed. It is determined whether there is a next page (S1509). When there is a next page (S1509 / YES), the color conversion table update unit 437 acquires inspection information for the next page from the inspection information storage unit 434 (S1501), and repeats the subsequent processing. On the other hand, when there is no next page (S1509 / NO), the color conversion table update unit 437 ends the process without updating the color conversion table.

  Next, a specific example of the color conversion table update processing by the color conversion table update unit 437 will be described. For example, the color conversion table update unit 437 uses the pixel value (CMYK format) of each color patch in the resolution conversion image included in the common information as an input value, and the pixel value of each color patch in the read image included in the common information. The color conversion table is updated to (RGB format). Then, the color conversion table update unit 437 stores the updated color conversion table in the color profile storage unit 425, and updates the color profile including the color conversion table before update.

  Since the read image included in the common information is an image generated by reading the paper printed on the paper most recently, it can be updated to a color conversion table in accordance with the current state of the print engine 3. FIG. 18 is a diagram illustrating an updated color conversion table. As shown in FIG. 18, the updated output value of the color conversion table is updated from the color conversion table shown in FIG.

  By such processing, in the image inspection apparatus that compares the master image and the read image to determine the defect of the printed matter, it is possible to more accurately determine whether or not it is necessary to update the color conversion table used for generating the master image. It becomes possible. In addition, the color conversion table update unit 437 according to the present embodiment determines whether or not the color conversion table is updated based on the defect determination result of the printed matter, and thus separately generates information for determining whether or not the color conversion table is updated. The processing load and storage area usage can be reduced.

  In the above embodiment, when it is determined that there is a defect in the gradation region with a small density change extracted as a flat region, it is further determined whether or not the determination result is due to color variation of the read image. May be. Hereinafter, such a determination process will be described. FIG. 19 is a diagram illustrating a master image (FIG. 19A) and a read image (FIG. 19B) including a gradation region with a light density change.

  As shown in FIG. 19A, the star-shaped area extracted as a flat area is a gradation area with a light density change. For example, as shown in FIG. 19B, when color variation occurs in the star-shaped area of the read image, the density change in the gradation area becomes larger than that in the master image, and the central line portion of the star-shaped area (FIG. 19 ( In the case shown in b), it may be determined that there is a defect in a range surrounded by a rectangle).

  When defects are concentrated in the central line portion of the gradation area as shown in FIG. 19B, this defect is due to the color variation described above, or banding that occurs on the entire sheet in the same line as the central line portion. It is necessary to distinguish whether it is due to. In the present embodiment, a configuration for determining whether or not such a line-shaped defect determination result is due to color variation (hereinafter referred to as “line-shaped color variation determination processing”) will be described.

  FIG. 20 is a flowchart illustrating the line-shaped color variation determination process described above. As shown in FIG. 20, for example, after the processing of S1604 shown in FIG. 16, the color conversion table update unit 437 determines whether or not the defective area in the flat area is a line (S2001). Specifically, for example, the color conversion table update unit 437 determines from the coordinate information indicating each defect area whether each defect area exists at a position where a line is formed. When the defective area in the flat area is not in a line shape (S2001 / NO), the color conversion table update unit 437 performs the processing from S1605 onward without determining whether the defect is due to banding.

  On the other hand, when the defective area in the flat area is a line (S2001 / YES), the color conversion table update unit 437 determines whether another flat area exists on the extension of the line (S2002). 21 and 22 are diagrams illustrating an example in which another flat region exists on the extension of the line. As shown in FIGS. 21 and 22, a triangular flat region exists on the extension of the line-shaped defect included in the star-shaped region.

  When there is no other flat region on the extension of the line (S2002 / NO), the color conversion table update unit 437 performs the processing from S1605 onward without determining whether the defect is due to banding. On the other hand, when another flat region exists on the extension of the line (S2002 / YES), the color conversion table update unit 437 determines whether or not the other flat region also has a line-shaped defect region (S2003). ).

  For example, in the case shown in FIG. 21, in the triangular area, there is a line-shaped defect area on the line extension of the defect area in the star-shaped area. On the other hand, for example, as shown in FIG. 22, there is no line-shaped defect region in the triangular region. When there is a line-like defect area in another flat area (S2003 / YES), the color conversion table update unit 437 is caused by banding that occurs in the entire sheet in the same line, and is a defect other than color variation. It is determined that there is (S1610).

  On the other hand, when there is no line-like defect area in the other flat area (S2003 / NO), the color conversion table update unit 437 acquires a non-defective area difference value from other than the line-like area in the flat area ( S2004). Further, the color conversion table update unit 437 acquires a defect area difference value from other than the line-shaped area in the flat area (S2005), and performs the processing from S1608 onward. Note that the process of S2004 and the process of S2005 are not limited in context, and may be executed in the reverse order or may be executed in parallel.

  Next, another aspect of the above-described line color variation determination process will be described. FIG. 23 is a diagram illustrating another aspect of the line-shaped color variation determination process. As shown in FIG. 23, for example, after the process of S1604 shown in FIG. 16, the color conversion table update unit 437 determines whether or not the defect area in the flat area is a line, as in the process of S2001. Determination is made (S2301). When the defective area in the flat area is not in a line shape (S2001 / NO), the color conversion table update unit 437 performs the processing from S1605 onward without determining whether the defect is due to banding.

  On the other hand, when the defective area in the flat area is line-shaped (S2301 / YES), the color conversion table update unit 437 acquires color information of the master image in the line-shaped defective area (S2302). Specifically, the color conversion table update unit 437 acquires color information indicated by the pixel value of the master image at the position of the defective area. The color conversion table update unit 437 that has acquired the color information has another flat region that includes color information that is equivalent to the acquired color information (the difference from the pixel value indicated by the acquired color information is within a predetermined value). Is determined (S2303).

  When there is no other flat region including equivalent color information (S2303 / NO), the color conversion table update unit 437 performs the processing from S1605 onward without determining whether the defect is due to banding. On the other hand, when there is another flat area including equivalent color information (S2303 / YES), the color conversion table update unit 437 causes the same color variation in the other flat area as in the flat area having the line-shaped defect area. It is determined whether or not it has occurred (S2304).

  FIG. 24 is a diagram exemplifying a mode in which similar color variations occur in other flat regions, and FIG. 25 illustrates a mode in which similar color variations do not occur in other flat regions. It is a figure illustrated. FIGS. 24A and 25A are diagrams illustrating the master image, and FIGS. 24B and 25B are diagrams illustrating the read image.

  The central part of the star area and the heart-shaped area of the master image shown in FIG. 24A contain equivalent color information, and these areas of the read image shown in FIG. Color variation occurs. On the other hand, in the read image shown in FIG. 25B, color variation occurs only in the central portion of the star-shaped region, and no color variation occurs in the heart-shaped region.

  If the same color variation has occurred in other flat regions (S2304 / YES), the color conversion table update unit 437 has the same tendency in other regions, so the defect determination result is color. It is determined that there is a high possibility that it is due to fluctuation. Therefore, the color conversion table update unit 437 performs the same processing as S2004 and S2005 (S2305, S2306), and performs the processing after S1608.

  Note that the processing in S2305 and the processing in S2306 are not limited in context, and may be executed in the reverse order or may be executed in parallel. On the other hand, when the same color variation does not occur in other flat regions (S2304 / NO), the color conversion table update unit 437 determines that the defect is other than the color variation (S1610).

  When the area determined to be defective in the flat area is a line shape by the processing shown in FIG. 20 or FIG. 23, it is determined whether or not the defect determination result is due to color variation, so that the printer or the reading apparatus Therefore, it is possible to more accurately discriminate the variation in the color tone of the read image due to the influence of the change over time. In the present embodiment, the case where a vertical line-shaped defect region as shown in FIG. 19B is formed is described as an example. In addition, this embodiment can be similarly applied even when a horizontal line-shaped defect region is formed.

  Further, the processes shown in FIGS. 20 and 23 may be combined. That is, the color conversion table update unit 437 performs the line color variation determination shown in FIG. 23 when it is impossible to determine whether the defect is due to banding in the line color variation determination illustrated in FIG. It may be executed or may be executed in the reverse order.

  In the above embodiment, the case where the defect number threshold is a predetermined value has been described as an example. However, the defect number threshold may be set so as to increase as the area of the flat region increases. Even if the number of defect areas is equal to or larger than the defect number threshold, the defect area is sparse in a flat area having a relatively larger area than other flat areas, regardless of the size of the flat area. This is because there is a low possibility that the defect determination result is due to color variation. The flat area area is calculated from, for example, a flat area image included in the common information shown in FIG. With such a configuration, it is possible to execute color variation determination with higher accuracy.

  In the above embodiment, the case where the determination number threshold is a predetermined value has been described as an example. However, the determination number threshold may be changed according to the tendency of the color variation determination. Specifically, for example, the color conversion table update unit 437 first stores the color information of the master image in the defect area determined to be color variation in the process of S1503 in a storage medium.

  When the color information of the master image stored in the storage medium is the same over a plurality of flat regions and a plurality of continuous pages (within a predetermined pixel value range), For example, the determination number threshold is changed from a predetermined 8 times to 3 times. This is because if the same color information continues in the defect area determined to have color variation, the defect determination result is likely to be due to color variation. As described above, the configuration in which the color conversion table updating unit 437 sets the determination number threshold according to the occurrence state of the color variation for each color makes it possible to execute the color variation determination with higher accuracy.

  In addition, when the color conversion table update unit 437 determines that there is a color variation over a plurality of flat regions or a plurality of continuous pages even when the color information in the defect region is different, for example, a threshold value for determination number Is changed from the predetermined 8 times to 5 times. In this case, the changed determination number threshold value is larger than the changed determination number threshold value when the color variation determination of the equivalent color information continues.

  In the above-described embodiment, the color conversion table update unit 437 has been described by taking as an example the case where the color variation determination number is incremented by 1 when it is determined that there is a color variation in the processing of S1503. In addition, the color conversion table updating unit 437 may increase the number of color fluctuation determinations by 1 according to the comparison result of the non-defective area difference values in the flat area including the equivalent color information in the color fluctuation determination.

  Specifically, for example, the color conversion table update unit 437 first stores the color information of the master image and the non-defective area difference value in the flat area determined to be color variation in the processing of S1503 in the storage medium. Hold it. Then, the color conversion table update unit 437 is equivalent to the color information in which the color information of the master image in the flat area determined to be the next color variation is held, and is held as a non-defective area difference value. When the absolute value of the difference from the non-defective area difference value is less than a predetermined value, the number of color fluctuation determinations is increased by one.

  If the absolute value of the difference between the non-defective area difference value and the held non-defective area difference value is greater than or equal to a predetermined value, one of the defects is due to a sudden event and is due to color variation. This is because the possibility is low. With such a configuration, it is possible to execute color variation determination with higher accuracy.

  In addition, if the color conversion table update unit 437 determines that there is color variation and then does not determine that there is color variation in a flat region including equivalent color information more than a predetermined number of times, color variation determination The number may be reset (set to 0). The color conversion table update unit 437 also determines the color variation even if the color conversion table update unit 437 determines that the color variation is not detected in the flat region more than a predetermined number of times regardless of the color information. The determination number may be reset (set to 0).

  It should be noted that the predetermined number of times for resetting regardless of the color information may be set to be larger than the predetermined number of times for resetting with the equivalent color information. With such a configuration, it is possible to execute color variation determination with higher accuracy.

  Moreover, in the said embodiment, the color conversion table update part 437 demonstrated as an example the case where it was determined whether it was a color fluctuation based on the difference of a non-defective area | region difference value and a defective area difference value. In addition, the color conversion table update unit 437 may determine that the color variation is present when the non-defective region is not included in the flat region. In this case, it is determined that the entire flat region is defective, and it is highly possible that the defect determination result is due to color variation.

  Further, in the above-described embodiment, an example in which color variation determination is similarly performed when there is another flat region regardless of the result of color variation determination in a certain flat region in the read image for one page. As explained. In addition, when it is determined that a color variation has occurred in a certain flat area in the read image for one page, even if there is another flat region, the next color variation determination is not performed. Color variation determination may be performed on the page.

  In the above-described embodiment, the color conversion table update unit 437 has been described as an example in which the color conversion table is updated when the color variation determination number is equal to or greater than the determination number threshold. However, counting the number of color variation determinations is not an essential configuration, and the color conversion table may be updated when there is even one flat region where color variation has occurred.

  In the above embodiment, the color conversion table update unit 437 updates the color conversion table using the resolution conversion image and the read image included in the common information when it is determined to update the color conversion table. As explained. In addition, when it is determined that the color conversion table is to be updated, the color conversion table update unit 437 may request the display information generation unit 436 to notify that the color conversion table needs to be updated. Accordingly, the interface terminal 5 displays a screen for notifying that the color conversion table needs to be updated based on the display information input from the display information generation unit 436.

  An administrator of the image inspection system who confirms the screen displayed on the interface terminal 5 executes a print job for updating the color conversion table. The color conversion table update unit 437 updates the color conversion table using the resolution conversion image and the read image generated in the inspection apparatus 4 by executing the print job for updating the color update table. In addition, the administrator of the image inspection system that has confirmed the screen displayed on the interface terminal 5 may directly set the value of the color conversion table via the interface terminal 5 or the like.

  In the above embodiment, the case where the threshold value used for the defect determination in S1004 is the same value regardless of the image components has been described as an example. In addition, when an edge component is included in the image in the inspection target range, the threshold value used for defect determination in the range may be larger (for example, twice) than the threshold value in the other range. Since the edge portion has a rapid change in density, even if there is no defect, the difference value from the master image may be larger than the portion other than the edge portion.

  Therefore, it is possible to perform the defect determination of the edge portion with higher accuracy by setting the threshold value for the defect determination of the image including the edge portion larger than the threshold value for the defect determination of the other images. In this case, when an edge extraction process such as a Laplacian filter process is performed on the image for each inspection target range and an edge is extracted, the threshold used for defect determination of the image in this range is larger than the other thresholds. It is set to become.

1 DFE
2 Engine Controller 3 Print Engine 4 Inspection Device 5 Interface Terminal 6 Stacker 10 CPU
20 RAM
30 ROM
40 HDD
50 I / F
60 LCD
70 Operation Unit 80 Dedicated Device 90 Bus 11 Conveyor Belt 12, 12Y, 10M, 12C, 12K Photosensitive Drum 13 Paper Tray 14 Transfer Roller 15 Fixing Roller 16 Reverse Pass 101 Job Information Processing Unit 102 RIP Processing Unit 201 Data Acquisition Unit 202 Engine control unit 203 Bitmap transmission unit 301 Print processing unit 400 Reading device 401 Read image acquisition unit 402 Master image processing unit 403 Inspection control unit 404 Comparison inspection unit 410 Paper discharge tray 421 Low-value multi-value conversion processing unit 422 Resolution conversion processing unit 423 Color conversion processing unit 424 Image output processing unit 425 Color profile storage unit 431 Information input unit 432 Defect determination unit 433 Inspection information storage processing unit 434 Inspection information storage unit 435 Controller communication unit 436 Display information generation unit 437 Color conversion unit Bull updating section 601 paper output tray

JP 2006-211079 A

Claims (10)

An image inspection apparatus for inspecting a read image obtained by reading an image formed and output on a recording medium,
A read image acquisition unit that acquires the read image generated by reading an image that has been formed and output;
A density conversion unit that converts the density of the image forming output target image using conversion information indicating a value for converting the density of the image forming output target image according to the density of the read image;
An inspection image generation unit that generates an inspection image for inspecting the read image by converting the density of the image to be imaged and output; and
A defect determination unit that determines a defect of the read image based on a difference image indicating a difference between the acquired read image and the generated inspection image;
Of the areas included in the read image, the defect area is determined to be defective in a flat area that is compared with an area in which the variation in density of pixels included in the inspection image is within a predetermined range. And a conversion information update unit that updates the conversion information. The conversion information update unit updates the conversion information when a variation in color tone of the read image occurs due to a state change in the generation process of the read image in the defect area. apparatus. The conversion information update unit determines whether or not a change in the color tone has occurred based on the difference image in the flat region when the size of the defective region is equal to or larger than a predetermined size. The image inspection apparatus according to claim 2, wherein the conversion information is updated when the color tone variation occurs. The conversion information update unit, when the difference between the maximum pixel value and the minimum pixel value of the difference image in the defect area is equal to or less than a predetermined value, the difference image in the defect area and the flat area Based on the difference image in the non-defective area that is an area other than the defective area, it is determined whether or not the color tone variation has occurred, and the conversion information is updated when the color tone variation has occurred. The image inspection apparatus according to claim 3. When the difference between each pixel value of the difference image in the defective area and each pixel value of the difference image in the non-defective area is equal to or less than a predetermined value, the conversion information update unit changes the color tone. The image inspection apparatus according to claim 4, wherein the conversion information is updated when it is determined that the color tone has changed and the color tone has changed. The conversion information update unit, when a color variation determination number, which is the number of the flat regions including the defective region determined that the color tone variation has occurred, is equal to or greater than a predetermined determination number threshold, The image inspection apparatus according to claim 2, wherein the conversion information is updated. The image inspection apparatus according to claim 3, wherein the conversion information update unit increases the predetermined size as the area of the flat region increases. The image inspection apparatus according to claim 6, wherein the conversion information update unit sets the determination number threshold according to a generation state of the color variation for each color. An image inspection system for inspecting a read image obtained by reading an image formed and output on a recording medium,
An image forming unit that performs image forming output on the recording medium;
An image reading unit that reads the image formed on the recording medium and generates the read image;
A read image acquisition unit for acquiring the generated read image;
A density conversion unit that converts the density of the image forming output target image using conversion information indicating a value for converting the density of the image forming output target image according to the density of the read image;
An inspection image generation unit that generates an inspection image for inspecting the read image by converting the density of the image to be imaged and output; and
A defect determination unit that determines a defect of the read image based on a difference image indicating a difference between the acquired read image and the generated inspection image;
Of the areas included in the read image, the defect area is determined to be defective in a flat area that is compared with an area in which the variation in density of pixels included in the inspection image is within a predetermined range. And a conversion information updating unit that updates the conversion information based on the image inspection system. An image inspection program for inspecting a read image obtained by reading an image formed and output on a recording medium,
Obtaining the read image generated by reading the image formed and output; and
Converting the density of the image forming output target image using conversion information indicating a value for converting the density of the image forming output target image according to the density of the read image;
Generating an inspection image for inspecting the read image by converting the density of the image to be imaged and output; and
Determining a defect of the read image based on a difference image indicating a difference between the acquired read image and the generated inspection image;
Of the areas included in the read image, the defect area is determined to be defective in a flat area that is compared with an area in which the variation in density of pixels included in the inspection image is within a predetermined range. And an image processing program for causing an information processing device to execute the step of updating the conversion information.