JP2017188713A - Image inspection device and image inspection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more accurately inspect an image on a read surface of a paper sheet to form images on double sides.SOLUTION: An image inspection device comprises: a patch image storage part for inspection for storing a patch image for read surface inspection obtained by reading a patch image formed on a surface of a paper sheet and a patch image for set-off inspection obtained by the patch image for inspection formed on the paper sheet from a side opposite to an image formation surface; a mirror image storage part for storing a mirror image that is a mirror image of an image formed on a surface opposite to the surface read by a first reading part; and an abnormal image discrimination part for collating a read image which is read by the first reading part, with a document image of the image formed on the read surface of the paper sheet, thereby discriminating the presence/absence of abnormality in the read image. In the case where there is abnormality in the read image, when a printing part of the mirror image is present at least at a position where the abnormality occurs, the abnormal image discrimination part collates the read image with the patch image for set-off inspection, thereby discriminating quality of the abnormality in the read image.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an image inspection apparatus and an image inspection program for inspecting an image on a reading surface of a sheet on which images are formed on both sides.

  In recent years, there has been a demand for imparting values to printed materials, and an increasing number of cases print on thin paper or colored paper. In addition, printing may be performed on both the front surface and the back surface.

  On the other hand, there is a technique for optimizing an output image by inspecting original image data based on read image data obtained by reading an image (output image) formed on a sheet and correcting the original image data. In this technique, there is a need to realize more accurate image correction by optimizing the read image data.

  As described above, images may be formed on both sides of a sheet. However, in the case of thin paper printing, a show-through in which an image on the back surface is transmitted to the front surface is likely to occur. When this show-through occurs, a show-through image that is not an abnormal image is erroneously detected as an abnormal image, and the original image data may not be correctly inspected.

  To solve such a problem, a technique described in Patent Document 1 is disclosed as a technique for realizing an appropriate inspection when images are formed on both sides of a recording medium. The technique described in Patent Literature 1 acquires information on an image formed on the inspection target surface of the recording medium and information on an image formed on the back surface of the inspection target, and forms an image formed on one surface of the recording medium. Obtains a transmittance indicating a ratio of the first to the other surface. The inspection image generated based on the image formed on the surface to be inspected is corrected by the correction value generated based on the information and transmittance of the image formed on the back surface. Thereafter, the read image is inspected based on the result of comparing the corrected inspection image and the read image.

  FIG. 1 is an explanatory diagram (1) of the prior art and shows an outline of an image inspection apparatus described in Patent Document 1. In the image inspection apparatus 100 of FIG. 1, the image forming unit 110 forms an image on a sheet that has been conveyed in the direction of the arrow along the conveyance path 120 and sends the image to the fixing unit 112. The sheet that has passed through the fixing unit 112 is discharged to the outside or joined to the conveyance path 120 on the upstream side of the secondary transfer unit 111 by the reverse conveyance path 121. A transmittance measuring unit 130 is provided on the upstream side of the secondary transfer unit 111. The transmittance of the sheet is measured using the transmittance measuring unit 130.

  Further, as a technique for realizing an appropriate inspection when images are formed on both sides of a recording medium, a technique described in Patent Document 2 is disclosed. The technique described in Patent Literature 2 reads an image formed on the front surface after printing on the front surface and before printing on the back surface to obtain surface inspection image data. Further, the light transmission amount of the paper is detected by a transmitted light sensor, the density of the surface inspection image is corrected based on the light transmission amount of the paper, and the show-through image is estimated by inverting the surface inspection image. After the back side printing, corrected back side inspection image data in which the show-through is eliminated is obtained by subtracting the previous show-through image data from the back side inspection image data obtained by reading the back side. The printed image is inspected by comparing this with the back side original image data.

  FIG. 2 is an explanatory diagram (2) of the prior art and shows an outline of the printing apparatus described in Patent Document 2. The basic configuration of the printing apparatus 100A in FIG. 2 is the same as the configuration in FIG. In FIG. 2, the reading unit 135 is provided on the downstream side of the fixing unit 112 in the sheet conveyance direction.

JP2015-178190A JP 2005-217932 A

However, in the technique described in Patent Document 1, the transmittance of the recording medium is calculated before image formation, and the show-through image data on the read image after image formation is estimated. Will come out.
Further, in the technique described in Patent Document 2, a show-through image on a read image is estimated from an image on the back surface, and an error occurs because the image after show-through is not read directly.

  The present invention has been made in consideration of the above-described situation, and an object thereof is to more accurately inspect an image on a reading surface of a sheet on which images are formed on both sides.

An image inspection apparatus according to an aspect of the present invention includes a sheet conveyance unit that conveys a sheet, and a first surface of the image provided on a downstream side in a sheet conveyance direction of an image forming unit that forms an image on the sheet. A first reading unit that reads and obtains a read image, a reading surface inspection patch image obtained by reading an inspection patch image formed on the surface of the paper, and the inspection patch image formed on the paper as an image forming surface An inspection patch image storage unit for storing a show-through inspection patch image obtained by reading from the opposite surface of the image, and a mirror image that is a mirror image of an image formed on the surface opposite to the reading surface by the first reading unit The mirror image storage unit for storing the image and the read image read by the first reading unit and the original image of the image formed on the reading surface of the paper are collated to determine whether the read image is abnormal. And an abnormal image determination unit.
Then, when there is an abnormality in the read image, the abnormal image determination unit obtains the read image and the show-through inspection patch image at least when the mirror image printing unit exists at the position where the abnormality has occurred. Collation is performed to determine whether the read image is abnormal.

According to one embodiment of the present invention, it is possible to inspect an image on a reading surface of a paper having images formed on both sides with higher accuracy.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is explanatory drawing (1) of a prior art. It is explanatory drawing (2) of a prior art. 1 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus to which an image inspection apparatus according to a first embodiment of the present invention is applied. 1 is a block diagram illustrating a hardware configuration example of an image forming apparatus according to a first embodiment of the present invention. FIG. 4 is a diagram illustrating an example of an inspection patch formed outside an image forming area of a sheet. FIG. 6 is a diagram illustrating an example in which an inspection patch formed outside an image forming area of a sheet is shown through. 5 FIG. 7A is a diagram illustrating an example of the inspection patch formed on the front surface of the paper, and FIG. 7B is a diagram illustrating an example of the inspection patch formed on the back surface of the paper. FIG. 8A is a read image obtained by reading the back surface of the paper in FIG. 7B by the first reading unit, and FIG. 8B is a read image obtained by reading the front surface of the paper in FIG. 7A by the second reading unit. It is a flowchart which shows the patch image reading process for an inspection. It is a flowchart which shows the abnormal image determination process which concerns on the 1st Embodiment of this invention. It is explanatory drawing of the abnormal image determination process which concerns on the 1st Embodiment of this invention. FIG. 4 is a schematic diagram illustrating a main part of an image forming apparatus according to a second embodiment of the present invention. It is a figure which shows the distribution arrangement | positioning of the patch for a test | inspection which concerns on the 3rd Embodiment of this invention. It is an example of the table which shows the correspondence of the kind of paper type and inspection patch which concerns on the 4th Embodiment of this invention. It is a figure which shows the example of the linear test | inspection patch which concerns on the 5th Embodiment of this invention.

  Hereinafter, an example of an embodiment for carrying out the present invention will be described with reference to the accompanying drawings. In addition, in each figure, about the component which has the substantially same function or structure, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

<1. First Embodiment>
[Configuration example of image forming apparatus]
FIG. 3 is a schematic diagram of an overall configuration example of an image forming apparatus to which the image inspection apparatus according to the first embodiment is applied.
The image forming apparatus 1 employs an electrophotographic system that forms an image using static electricity. For example, toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are used. Is a tandem type color image forming apparatus. The image forming apparatus 1 includes sheet feed trays 20A and 20B, an image forming unit 30, an image input unit 11 including an automatic document feeder (ADF) 12, and an operation display unit 13. In addition, the image forming apparatus 1 includes a conveyance path 21 that conveys the paper S fed from the paper feed trays 20A and 20B or the manual feed tray. The transport path 21 is provided with a plurality of rollers (transport rollers) for transporting the paper S.

  The image forming unit 30 includes four image forming units 31Y, 31M, 31C, and 31K in order to form toner images of colors of yellow, magenta, cyan, and black. The image forming units 31Y, 31M, 31C, and 31K may be collectively referred to as the image forming unit 31. Each image forming unit 31 includes a charging unit (not shown), an LED writing unit (laser light source), a developing unit, and a photosensitive drum. The image forming unit 30 also includes an intermediate transfer belt 34, a secondary transfer unit 35, and the like, on which images formed on the photosensitive drums 33Y, 33M, 33C, and 33K of the image forming units 31Y, 31M, 31C, and 31K are transferred. A fixing unit 36 is provided downstream of the secondary transfer unit 35 in the sheet conveyance direction. The photosensitive drums 33Y, 33M, 33C, and 33K may be collectively referred to as the photosensitive drum 33.

  On the downstream side of the fixing unit 36 in the paper conveyance direction, the conveyance path 21 extends and is connected to the paper discharge tray 16. Further, a reverse conveyance path 23 is connected to the conveyance path 21 so as to branch on the downstream side of the fixing unit 36 and join the conveyance path 21 on the upstream side of the secondary transfer unit 35. A reversing unit 22 for reversing the paper S is provided in the reversing conveyance path 23. The reversing unit 22 reverses the sheet S conveyed from the fixing unit 36 and conveys the sheet S to the conveying path 21 on the upstream side of the secondary transfer unit 35 through the reversing conveying path 23. Further, the reversing unit 22 can return the reversed paper S to the transport path 21 on the downstream side of the fixing unit 36 and discharge it as it is.

  An operation display unit 13 is installed on the upper portion of the image forming apparatus 1. The operation display unit 13 has a function as an operation unit that instructs the start of a job such as an image forming process. The operation display unit 13 is provided with a display unit 15 made of a liquid crystal panel or the like and an operation unit 14 made of a touch panel or the like. The display unit 15 can display details of operations performed by the user, setting information, and the like. The operation display unit 13 may be configured with a mouse, a tablet, or the like, and may be configured separately from the display unit 15.

  In the image forming mode, the image forming apparatus 1 charges the photosensitive drum 33 included in the image forming unit 31 of each color and exposes the surface of the photosensitive drum 33 in accordance with the document image. Form an image. Then, toner is attached to the electrostatic latent image on the photosensitive drum 33 corresponding to each of yellow, magenta, cyan, and black by using a developing unit, and a toner image of each color is formed. Next, the toner images formed on the yellow, magenta, cyan, and black photosensitive drums 33 are sequentially primary-transferred onto the surface of the intermediate transfer belt 34 that is rotationally driven.

  Next, each color toner image primarily transferred onto the intermediate transfer belt 34 is secondarily transferred onto the paper S supplied from the paper supply unit 20 by the secondary transfer unit 35 (secondary transfer roller). The toner images of the respective colors on the intermediate transfer belt 34 are secondarily transferred to the paper S, whereby a color image is formed. The image forming apparatus 1 discharges the sheet S on which the color toner image is formed to the fixing unit 36.

  The fixing unit 36 is a device that performs a fixing process on the sheet S on which a color toner image is formed, which is supplied from the image forming apparatus 1. The fixing unit 36 pressurizes and heats the conveyed paper S, and fixes the transferred toner image on the paper S. The fixing unit 36 includes, for example, an upper fixing roller and a lower fixing roller that are fixing members. The upper fixing roller and the lower fixing roller are arranged in pressure contact with each other, and a fixing nip portion is formed as a pressing portion between the upper fixing roller and the lower fixing roller.

  A heating unit is provided inside the fixing upper roller. The roller part at the outer peripheral part of the fixing upper roller is heated by the radiant heat from the heating part. The sheet S is transported to the fixing nip so that the surface (fixed target surface) onto which the toner image is transferred by the secondary transfer unit 35 faces the fixing upper roller. The sheet S passing through the fixing nip portion is pressed by the upper fixing roller and the lower fixing roller and heated by the heat of the roller portion of the upper fixing roller. The paper S on which the fixing process has been performed by the fixing unit 36 is discharged to the paper discharge tray 16.

  A first reading unit 37 and a second reading unit 38 are provided downstream of the fixing unit 36 in the sheet conveyance direction. The first reading unit 37 is provided above the conveyance path 21 and reads the upper surface of the sheet S being conveyed. The second reading unit 38 is provided below the conveyance path 21 and reads the lower surface of the sheet S being conveyed. For the first reading unit 37 and the second reading unit 38, for example, a line sensor in which a plurality of photoelectric conversion elements are arranged linearly along a direction (main scanning direction) perpendicular to the paper transport direction is used. As the line sensor, for example, a CCD type image sensor or a CMOS type (including MOS type) image sensor can be used.

  A paper type reading unit 24 using a photodetector is disposed in the vicinity of the paper feed unit of the paper feed trays 20A and 20B (on the downstream side in the paper transport direction). The paper type reading unit 24 outputs a detection signal corresponding to the presence / absence of the paper sent out from the paper feed trays 20A and 20B to the transport path 21 and the state of the paper. A reflective or transmissive optical sensor is used for the photodetector.

[Control system of image forming apparatus]
Next, a control system of the image forming apparatus 1 will be described.
FIG. 4 is a block diagram illustrating a hardware configuration example of the image forming apparatus 1.

  The image forming apparatus 1 includes a main CPU (Central Processing Unit) 40 that comprehensively controls the operation of the image forming apparatus 1. The main CPU 40 is an example of a control unit.

  The main CPU 40 can transmit / receive data or control signals to / from the system memory 41, the nonvolatile memory 42, the RTC 43, the mass storage device 44, the communication unit 45, the first reading unit 37, and the second reading unit 38. It is connected to the. Further, the main CPU 40 exchanges data or control signals with the operation unit 14, display unit 15, RIP processing unit 50, paper transport unit 51, image forming unit 30, abnormal image determination unit 52, and paper type reading unit 24. Etc. are connected so that they can be transmitted and received.

  The main CPU 40 is based on an OS (Operating System) program and executes programs such as middleware and application programs. The processing of each unit executed by the main CPU 40 will be described later. Various programs are stored in a ROM (not shown) or the mass storage device 44.

  Various programs are stored in a ROM (not shown), and each function of the image forming apparatus 1 is realized by the main CPU 40 executing processes according to these programs.

  The system memory 41 is used as a work memory that temporarily stores various data when the main CPU 40 executes a program. The system memory 41 temporarily stores a job acquired by the image forming apparatus 1. That is, the system memory 41 is a main memory and is configured by a RAM (Random Access Memory).

  As the nonvolatile memory 42, for example, a semiconductor memory is used, and various setting information and the like are stored. The non-volatile memory 42 stores various inspection patch images (FIGS. 5 to 8) and an inspection patch table (FIG. 15), which will be described later, as an example. Further, a document image and a read image may be stored. The nonvolatile memory 42 is an example of an inspection patch image storage unit and a mirror image image storage unit. In the following description, the inspection patch image may be referred to as “inspection patch”.

  An RTC (Real Time Clock) 43 is a chip dedicated to timekeeping that is mounted on the motherboard, and notifies the main CPU 40 of the current date and time.

  For example, a hard disk device is used as the large-capacity storage device 44, and job output settings, image data, and the like received by the communication unit 45 are stored.

  The communication unit 45 communicates with a network such as a LAN or the Internet under the control of the main CPU 40.

The operation unit 14 and the display unit 15 are components of the operation display unit 13.
The operation unit 14 includes various operation switches such as a start button and a touch panel provided on the display surface of the display unit 15. The user uses the operation unit 14 to give an instruction (print instruction or the like) to the image forming apparatus 1. The touch panel detects a coordinate position pressed with a touch pen or a finger. As the operation unit 14, an operation key may be used in addition to the touch panel.
The display unit 15 is composed of a liquid crystal display (LCD) or the like, and fulfills a function of displaying various operation screens, setting screens, and the like.

  The RIP processing unit 50 performs rasterization processing (RIP processing) on input data (an example of image data) extracted from a print job received via the communication unit 45, and performs tag bit plane, Y plane, M plane, and C plane. , K plane is generated. The RIP processed input data is temporarily stored in a buffer memory (not shown).

  The paper transport unit 51 outputs drive signals to the drive units of the transport path 21, the reversing unit 22, and the reverse transport path 23 in order to transport the paper S according to the control of the main CPU 40.

  The image forming unit 30 performs image forming processing for forming an image on a sheet based on a job received from the communication unit 45 or the operation unit 14 under the control of the main CPU 40.

  The abnormal image determination unit 52 collates the read image read by the first reading unit 37 or the second reading unit 38 with the original image of the image formed on the reading surface of the paper S, and determines whether there is an abnormality in the read image. judge. The determination result is output to the main CPU 40. The operation of the abnormal image determination unit 52 will be described in detail later. Examples of abnormalities in the read image include toner contamination, dust adhesion, and paper breakage.

  The paper type reading unit 24 outputs a detection signal corresponding to the presence / absence of the paper S sent from the paper supply trays 20A and 20B to the transport path 21 and the state of the paper. The main CPU 40 determines the type (paper type) of the paper S sent to the transport path 21 based on the detection signal input from the paper type reading unit 24.

[Example of patch image for inspection]
Next, an example of the inspection patch used in the present invention will be described.

(Example of forming an inspection patch screen on only one side of the paper)
FIG. 5 shows an example of the inspection patch formed outside the image forming area of the paper.
An inspection patch 63 is formed near the leading edge 61f of the front surface 61 (odd page, first surface) of the paper S and outside (above) the effective image forming area 62. The inspection patch 63 includes images of CMYK colors and RGB colors. The portions of the inspection patch 63 described as CMYK and RGB represent the color of the image. RGB represents R (red), G (green), and B (blue) of the RGB color model, respectively. An upward arrow in the figure represents the same paper feeding direction as in FIGS. 1 and 2.

FIG. 6 shows an example in which the inspection patch formed outside the image forming area of the paper is shown through. The example of FIG. 6 represents a state in which the paper S on which the inspection patch 63 of FIG. 5 is formed is turned over.
A show-through inspection patch 63r is formed near the leading edge 61f of the back surface 65 (even page, second surface) of the sheet S and above the effective image forming area 62. Since the show-through inspection patch 63r is a show-through of the inspection patch 63, it includes images of each color of CMYK and each color of RGB. In the show-through inspection patch 63r, the right and left of the printed content of the inspection patch 63 is determined.

(Example of forming inspection patch screens on both sides of the paper)
FIG. 7A is a diagram illustrating an example of the inspection patch formed on the front surface of the paper, and FIG. 7B is a diagram illustrating an example of the inspection patch formed on the back surface of the paper.
In FIG. 7A, an inspection patch 72 is formed near the front end 71f of the front surface 71 of the sheet S, and an inspection patch 73 is formed near the rear end. As an example of the inspection patch 72, Arabic numerals from 1 to 28 are printed. Further, as the inspection patch 72, uppercase alphabets A to N are printed.

  In FIG. 7B, an inspection patch 74 is formed near the rear end of the back surface 75 of the paper S. As an example of the inspection patch 74, Arabic numerals from 1 to 28 and alphabets from an uppercase letter O to a lowercase letter b are printed.

[Example of reading inspection patch]
FIG. 8A is a read image obtained by reading the back surface 75 of the paper S in FIG. 7B by the first reading unit 37.
As shown in FIG. 8A, after the image is formed on the back surface 75, the back surface 75 of the paper S becomes the upper side (upper surface), and the first reading unit 37 reads the back surface 75 and generates a read image 81. The read image 85 in FIG. 8A has a back inspection patch 72r of the inspection patch 72 in the upper stage and a reading surface inspection patch 84 having Arabic numerals 1 to 21 of the inspection patch 74 in the middle stage. In the lower part of the read image 85, an image composed of the alphabets O to b of the inspection patch 74 overlaps a back-up of the images of alphabets A to N of the inspection patch 73, and O 'to b'. The image is composed of A region where a part of the inspection patch 74 overlaps the show-through of the inspection patch 73 is used as an overlay inspection patch 84 ′ for inspection of the show-through.

FIG. 8B is a read image obtained by reading the front surface 71 of the paper S in FIG. 7A by the second reading unit 38.
As shown in FIG. 8B, after the image is formed on the back surface 75, the front surface 71 of the sheet S becomes the lower side (lower surface), and the second reading unit 38 reads the front surface 71 and generates a read image 85. The read image 85 of FIG. 8B has a reading surface inspection patch 82 composed of 1 to 28 Arabic numerals of the inspection patch 72 in the upper stage, and a back surface composed of Arabic numerals 1 to 28 of the inspection patch 74 in the middle stage. A copy inspection patch 74r is provided. The lower part of the read image 85 is composed of A ′ to N ′, where the image composed of the inspection patches 73 A to N overlaps the back-up of the alphabetical images O to b of the inspection patch 74. Image. The overlay inspection patch 83 ′, which is an area where the inspection patch 73 and a part of the inspection patch 74 overlap each other, is used for inspection of the show-through.

  In this way, inspection patches are formed at different positions on the front surface and the back surface of the paper S (when the print-through is performed), and the positions are adjusted. As a result, a “reading surface inspection patch” without a show-through, a “print-out inspection patch with only a show-through”, and an “overlay inspection patch” that is an overlapping region of two patches are generated.

  FIG. 9 is a flowchart showing the inspection patch image reading process. The main CPU 40 implements the process shown in FIG. 9 by executing a program recorded in a ROM (not shown).

  First, as preparation before inspecting an image formed on a sheet, the main CPU 40 controls the image forming unit 30 to form an inspection patch (for example, FIG. 7A) on the surface of the sheet (S1). The inspection patch is read from the surface opposite to the surface on which the patch is formed (S2). As the reading unit, the first reading unit 37 that reads the upper surface of the sheet from above or another reading unit dedicated to the inspection patch is used. In this way, the inspection patch is read from the surface opposite to the surface on which the inspection patch is formed, thereby showing a back-up image of the inspection patch reflecting the transmittance of the sheet (for example, FIGS. 6B, 8A, and 8B). Is obtained.

  Next, the main CPU 40 saves the read image, which is the reading result of the reading unit, in a storage unit, for example, the nonvolatile memory 42 or the mass storage device 44 (S3).

  When the inspection patch is formed on both sides and the double-sided back-out inspection image as shown in FIG. 8 is read, the main CPU 40 executes the processing of S1 to S3 for two cycles instead of one cycle. For example, in the second cycle, the processing in step S1 forms an inspection patch (for example, FIG. 7B) on the back side of the paper whose front and back sides are reversed by the reversing unit 22.

[Abnormal image determination processing]
Next, the abnormal image determination process according to the first embodiment will be described.
FIG. 10 is a flowchart showing an abnormal image determination process according to the first embodiment. FIG. 11 is an explanatory diagram of an abnormal image determination process according to the first embodiment. The main CPU 40 implements the processing shown in FIG. 10 by executing a program recorded in a ROM (not shown).

  In the present embodiment, it is assumed that a duplex print job is executed in the image forming apparatus 1 as a premise of the abnormal image determination process. First, the main CPU 40 feeds paper from the paper feed trays 20 </ b> A and 20 </ b> B and controls the paper transport unit 51 and the image forming unit 30 to form an image on the surface of the paper S. Next, the reverse side of the sheet S is reversed by the reversing unit 22, and the sheet S is transferred to the intermediate transfer belt 34 and the secondary transfer unit with the reverse side of the sheet S facing up via the reversing conveyance path 23 and the conveyance path 21. It conveys to the nip part of 35. The sheet S on which the image is formed on the back surface is conveyed directly below the first reading unit 37.

  Here, the first reading unit 37 reads the image (output image) formed on the upper surface (back surface) of the paper S (S11), and determines the abnormal image as the read image (for example, the read image 91 of the alphabet Y in FIG. 11). Send to section 52.

  Next, the abnormal image determination unit 52 collates the read image on the upper surface (back surface) with the original image of the image formed on the upper surface (back surface) of the paper S, and determines whether or not an abnormality has occurred in the read image. Is determined (S12). If there is no abnormality (No in S12), the process proceeds to step S26.

  If there is an abnormality in step S12 (Yes in S12), the abnormal image determination unit 52 reads the image data on the reading surface side (the document image on the back surface) and the mirror image data on the opposite surface side (the mirror image image of the document image on the front surface). Is read from the nonvolatile memory 42 (S13). For example, an abnormal portion 90 exists in the read image 91 on the back surface of FIG. When the original document image 92 on the front side is reversed left and right, a mirror image 92r is obtained.

  Here, when there is an abnormality in the read image on the upper surface (back surface), the abnormal image determination unit 52 determines an overlapping state between the read image and the mirror image on the opposite surface, and the reading surface is determined according to the determination result. It is determined whether to use an inspection patch, a show-through inspection patch, or an overlay inspection patch. Hereinafter, this determination process will be described.

  The abnormal image determination unit 52 determines whether or not there is print data, that is, an actually printed portion (print portion) at a position corresponding to the abnormal portion of the document image on the reading surface (back surface) side (S14).

  If there is print data in step S14 (Yes in S14), the abnormal image determination unit 52 determines whether there is print data in the corresponding portion of the mirror image on the opposite surface of the reading surface (S15).

  If there is print data in step S15 (Yes in S15), the abnormal image determination unit 52 determines that there is a region overlapping the document image on the reading surface side and the mirror image on the opposite surface. For example, in the superimposed image 93 of FIG. 11, the read image 91 and the mirror image 92 r do not overlap with respect to the position of the abnormal portion 90. The abnormal image determination unit 52 reads, from the nonvolatile memory 42, an overlay inspection patch (see FIGS. 8A and 8B) corresponding to the overlay region of the document image on the reading surface side and the mirror image on the opposite surface (S16). ).

  Next, the abnormal image determination unit 52 compares the read image on the upper surface (back surface) with the read overlay inspection patch (S17), and determines whether or not the abnormal portion matches the corresponding portion of the overlay inspection patch. Is determined (S23).

  If the abnormal part matches the corresponding part of the overlay inspection patch (Yes in S23), it is determined that the abnormal part is a normal image (S24). If they do not match (S23 No), it is determined that the abnormal part is an abnormal image (S25). And after the process of step S24 or S25 is complete | finished, it progresses to step S26.

  On the other hand, when there is no print data in step S15 (No in S15), the abnormal image determination unit 52 determines that there is no region overlapping the document image on the reading surface side and the mirror image on the opposite surface. The abnormal image determination unit 52 reads the reading surface side inspection patch (see FIGS. 8A and 8B) from the non-volatile memory 42 (S18).

  Next, the abnormal image determination unit 52 compares the read image on the upper surface (back surface) with the read reading surface inspection patch (S19), and determines whether the abnormal portion matches the corresponding portion of the reading surface inspection patch. (S23), and proceeds to the next step according to the determination result.

  Furthermore, when there is no print data at a position corresponding to the abnormal portion of the original image on the reading surface (back surface) side in step S14 (No in S14), the abnormal image determination unit 52 is a mirror image on the opposite surface of the reading surface. It is determined whether there is print data in the corresponding part of (S20).

  When there is print data in step S20 (Yes in S20), the abnormal image determination unit 52 determines that there is no area overlapping the original image on the reading surface side and the mirror image on the opposite surface, and there is only show-through. . For example, in the superimposed image 93 of FIG. 11, there is a print portion of the mirror image 92 r with respect to the position of the abnormal portion 90. The abnormal image determination unit 52 reads the original image on the reading surface side and the show-through inspection patch (see FIGS. 8A and 8B) on the opposite surface from the nonvolatile memory 42 (S21).

  Next, the abnormal image determination unit 52 compares the read image on the upper surface (back surface) with the read-through inspection patch (S22), and determines whether the abnormal portion matches the corresponding portion of the show-through inspection patch. (S23), and proceeds to the next step according to the determination result.

  After any one of steps S12, S24, and S25 is completed, the abnormal image determination unit 52 determines whether the inspection of both sides of the sheet S is completed (S26). If the double-sided inspection has not been completed (No in S26), the process returns to Step S11, and the image formed on the lower surface (front surface) of the paper S conveyed immediately above the second reading unit 38. Is read by the second reading unit 38. Then, the main CPU 40 executes the processes of subsequent steps S12 to S26 on the read image that has been read.

  If it is determined in step S26 that the double-sided inspection has been completed (Yes in S26), the abnormal image determination unit 52 ends the series of processes.

  According to the first embodiment described above, when there is an abnormality in the read image, the overlapping state between the read image and the mirror image on the opposite surface is determined, and the reading surface inspection patch, back surface is determined according to the determination result. It is determined whether to use a reflection inspection patch or an overlay inspection patch. Thereby, according to the overlapping state of the read image and the mirror image on the opposite side, that is, the show-through state, the inspection patch is selected and collated with the read image, so that the determination accuracy of the abnormal image is improved. Can do.

  Also, since the image when the inspection patch on the opposite side is actually show-through is used as the show-through inspection patch, the inspection patch reflects the state of the show-through and uses a read image that takes correction values into consideration. Thus, an image inspection can be performed. Therefore, the output image after image formation can be read accurately.

  For example, even when colored paper is used as the paper, it is possible to determine that the paper is colored paper by reading a specific color inspection patch, and high-precision correction can be performed. For example, in the example of FIG. 11, cyan, yellow, or a mixed color thereof can be selected for the inspection patch depending on the position of the abnormal portion 90.

  That is, the abnormal image determination unit 52 extracts a region having color information similar to the abnormal portion of the read image from the read image and the reading surface inspection patch, the show-through inspection patch, or the overlay inspection patch, and reads Used for matching with images. Note that not only color information but also gradation information may be used. Accordingly, it can be applied not only to color image inspection but also to monochrome image inspection.

<2. Second Embodiment>
In the second embodiment, one reading unit is deleted from the two reading units provided in the first embodiment.

FIG. 12 is a schematic diagram illustrating a main part of an image forming apparatus 1A according to the second embodiment.
Here, only the first reading unit 37 is disposed on the downstream side of the fixing unit 36. In this case, since double-sided inspection in one pass is impossible, after the upper surface (back surface) of the paper S is inspected, the front and back of the paper are reversed, the reverse conveying path 23 is conveyed, and the upper surface of the paper S is again formed. Conduct (surface) inspection.

  According to the second embodiment described above, only one reading unit is required, and the configuration of the image forming apparatus 1A can be simplified and the cost can be reduced.

<3. Third Embodiment>
The third embodiment is an example in which a plurality of areas for forming paper inspection patches are set in one page of paper, or an area for forming paper inspection patches is set over a plurality of pages. .

FIG. 13 is a diagram showing a distributed arrangement of inspection patches according to the third embodiment.
The left diagram in FIG. 13 is an example in which a sheet of paper 150 is divided into three regions D1 to D3 to form inspection patches. The left figure of FIG. 13 is an example in which inspection patches are formed in areas D1 to D3 at different positions on three pages of paper 151 to 153, respectively.

  According to the third embodiment described above, when a plurality of inspection patch formation areas are set in one sheet of paper, the show-through inspection patch can be acquired with a small number of sheets.

<4. Fourth Embodiment>
FIG. 14 is a diagram illustrating an example of a linear inspection patch according to the fourth embodiment.
For example, as shown in FIG. 14, a linear inspection patch 160 is formed along the main scanning direction of the paper (the vertical direction in the figure is the paper conveyance direction), and this is read by a reading unit and a register mechanism (not shown) To give feedback. Thereby, it is possible to detect the deviation of the paper with respect to the main scanning direction (or the paper conveyance direction).

<5. Fifth Embodiment>
FIG. 15 is an example of a table showing the correspondence between the paper type and the inspection patch type according to the fifth embodiment.

  In the fifth embodiment, an image is formed by an input unit that inputs the paper type of the paper on which an image is formed by the image forming unit 30, a paper type storage unit that stores the paper type of the paper input by the input unit, and the image formation. A table that holds the inspection patch image and the paper type in association with each other. For example, the operation display unit 13 can be used as the input unit, and the system memory 41 can be used as the paper type storage unit. Further, the table is stored in the nonvolatile memory 42 or the like. In such a configuration, the abnormal image determination unit 52 selects an inspection patch image according to the paper type of the paper transported to the image forming unit 30 by the paper transport unit 51. Note that the paper type reading unit 24 can also be used as the input unit.

  According to the fifth embodiment, even if the transmittance varies depending on the paper type, the inspection accuracy can be maintained at a certain level or more by selecting an appropriate inspection patch.

<6. Sixth Embodiment>
In the sixth embodiment, the abnormal image determination unit 52 or the main CPU 40 acquires information about a document image that is an image formed on the paper by the image forming unit 30, and the document image is based on the information about the document image. Is analyzed. Then, an inspection patch image to be formed on the sheet by the image forming unit 30 may be determined according to the analysis result.

  According to the sixth embodiment, an appropriate inspection patch is selected according to the print content of an image formed on a sheet, and the inspection accuracy is improved. For example, if an image has a lot of text, a character is selected as an inspection patch, and if there are a lot of photographs and graphical data, a colored inspection patch is printed.

<7. Seventh Embodiment>
In the seventh embodiment, the abnormal image determination unit 52 may extract a feature point from a histogram of pixel values of a read image, and form an inspection patch based on the feature point.

  According to the seventh embodiment, an appropriate inspection patch is selected according to the characteristics of the image formed on the paper, and the inspection accuracy is improved. For example, for an image with a lot of blue, an inspection patch having a color characteristic close to blue is created.

<8. Eighth Embodiment>
As an eighth embodiment, the inspection patch formed on the paper by the image forming unit 30 may be a gradation pattern of the same color having a predetermined gradation. The number of gradations may be 255 gradations or 32 gradations. This increases the number of inspection patches that can be used, and can flexibly handle various image inspections.

  Furthermore, the present invention is not limited to the above-described embodiments, and various other application examples and modifications can be taken without departing from the gist of the present invention described in the claims. is there.

  For example, the above-described exemplary embodiments are detailed and specific descriptions of the configuration of the apparatus and the system in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described above. . Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. In addition, the configuration of another embodiment can be added to the configuration of a certain embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each exemplary embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  Further, in this specification, the processing steps describing time-series processing are not limited to processing performed in time series according to the described order, but are not necessarily performed in time series, either in parallel or individually. The processing (for example, parallel processing or object processing) is also included.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 15 ... Operation part 24 ... Paper type reading part 30 ... Image forming part 37 ... 1st reading part 38 ... 2nd reading part 40 ... Main CPU, 51 ... Paper conveyance part, 52 ... abnormal image determination unit 61 ... front surface 62 ... effective image forming area 63 ... inspection patch 63r ... back-up inspection patch 65 ... back surface 71 ... front surface 72, 73, 74 ... inspection patch 72r 74r ... Back-up inspection patch, 75 ... Back surface, 81 ... Read image (back surface), 82 ... Reading surface inspection patch, 83 ', 84' ... Overlay inspection patch, 84 ... Reading surface inspection patch, 85 ... Reading image (front side) 91 ... Reading image 92 ... Back side image 92r ... Mirror image 93

Claims (15)

A paper transport unit for transporting paper,
A first reading unit provided on the downstream side in the paper conveyance direction of an image forming unit that forms an image on the paper to obtain a read image by reading a first surface of the image;
Reading surface inspection patch image obtained by reading the inspection patch image formed on the surface of the paper and show-through inspection obtained by reading the inspection patch image formed on the paper from the opposite surface of the image forming surface An inspection patch image storage unit for storing an image patch image;
A mirror image storage unit for storing a mirror image that is a mirror image of an image formed on a surface opposite to a reading surface by the first reading unit;
An abnormal image determination unit that compares the read image read by the first reading unit with a document image of an image formed on the reading surface of the paper and determines whether there is an abnormality in the read image;
The abnormal image determination unit compares the read image with the show-through inspection patch image when there is an abnormality in the read image and at least the mirror image printing unit exists at the position where the abnormality has occurred. An image inspection apparatus for determining whether or not the read image is abnormal. When there is an abnormality in the read image, the abnormal image determination unit determines an overlapping state of the read image and the mirror image, and according to the determination result, the read image and the reading surface inspection patch image The patch image for show-through inspection or the patch image for reading surface inspection and the overlay image for patch inspection which is an overlap region of the show-through inspection patch image are collated to determine whether the read image is abnormal. The image inspection apparatus according to claim 1. The abnormal image determination unit uses the overlay inspection patch image for the collation when the read image and the mirror image printing unit exist at the abnormality occurrence position, and sets the abnormality occurrence position at the abnormality occurrence position. When only the read image printing portion exists, the reading surface inspection patch image is used for the collation, and when only the mirror image print portion exists at the abnormality occurrence position, the back surface inspection patch image is used. The image inspection apparatus according to claim 2, wherein a reflection inspection patch image is used for the collation. The abnormal image determination unit has gradation information similar to an abnormal portion of the read image from the read image and the reading surface inspection patch image, the show-through inspection patch image, or the overlay inspection patch image. The image inspection apparatus according to claim 2, wherein a region is extracted and used for collation with the read image. The abnormal image determination unit has color information similar to an abnormal portion of the read image from the read image and the reading surface inspection patch image, the show-through inspection patch image, or the overlay inspection patch image. The image inspection apparatus according to claim 2, wherein an image is extracted and used for collation with the read image. The image inspection apparatus according to claim 2, wherein the image forming unit forms the reading surface inspection patch image and the show-through inspection patch image outside an effective image forming area. An image obtained by forming the inspection patch image on only one side of the sheet by the image forming unit and reading the inspection patch image from the surface opposite to the image forming surface is used as the show-through inspection patch image. The image inspection apparatus according to claim 2, wherein the image inspection apparatus is stored in a patch image storage unit. A first inspection patch image is formed on the front surface of the sheet by the image forming unit and a second inspection patch image is formed on the rear surface of the sheet, and the first inspection patch image and the second inspection patch image are formed. Images obtained by reading the patch images from the surface opposite to the image forming surface are stored in the inspection patch image storage unit as the first show-through inspection patch image and the second show-through inspection patch image. The image inspection apparatus according to claim 2. The second reading unit, which is provided on the downstream side of the image forming unit in the paper conveyance direction, further reads a surface opposite to the first surface of the image to obtain the read image. Image inspection device. The area for forming the inspection patch image on the sheet is set in a plurality of pages in one page, or the area for forming the inspection patch image on the sheet is set over a plurality of pages. The image inspection apparatus according to 1. An input unit for inputting a paper type of the paper on which an image is formed by the image forming unit;
A paper type storage unit for storing the paper type of the paper input by the input unit;
A table that holds the test patch image to be imaged and the paper type in association with each other;
The image inspection apparatus according to claim 2, wherein the inspection patch image is selected according to a paper type of the paper conveyed to the image forming unit by the paper conveyance unit. The image forming unit acquires information on the original image that is an image formed on the paper, analyzes the original image based on the information on the original image, and forms on the paper according to the analysis result The image inspection apparatus according to claim 2, wherein a patch image is determined. The image inspection apparatus according to claim 2, wherein the abnormal image determination unit extracts a feature point from a pixel value histogram of the read image, and forms the inspection patch based on the feature point. The image inspection apparatus according to claim 2, wherein the inspection patch image formed on the sheet by the image forming unit is a gradation pattern of the same color having a predetermined gradation. A sheet conveying unit that conveys the sheet, and a first reading unit that is provided on the downstream side in the sheet conveying direction of the image forming unit that forms an image on the sheet and reads a first surface of the image to obtain a read image; A reading surface inspection patch image obtained by reading an inspection patch image formed on the surface of the paper, and a show-through obtained by reading the inspection patch image formed on the paper from the surface opposite to the image forming surface An inspection patch image storage unit that stores an inspection patch image, a mirror image storage unit that stores a mirror image that is a mirror image of an image formed on a surface opposite to the reading surface of the first reading unit, and the reading An abnormal image determination unit for detecting an abnormal image, and a computer of an image inspection apparatus including
A procedure of collating the read image read by the first reading unit with a document image of an image formed on the reading surface of the paper, and determining whether there is an abnormality in the read image;
In the case where there is an abnormality in the read image, when there is a print portion of the mirror image at least at the position where the abnormality has occurred, the read image is compared with the show-through inspection patch image, An image inspection program for executing the procedure for determining pass / fail.

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