JP4529454B2 - Image forming apparatus, image inspection apparatus, and image inspection method - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printing machine, and more particularly to inspection of a formed image.

  An image forming apparatus that forms an image on a sheet based on image information is known. In this type of image forming apparatus, there is a demand for confirming or inspecting whether a formed image is formed according to the original image information. As a technique that satisfies such a requirement, for example, in Patent Document 1 below, image information that is the basis of printing is used as reference image information, and this is collated with read image information obtained by reading a formed image. A method is disclosed in which an inspection is performed by looking at a match between image information. In the case of this inspection method, based on the degree of coincidence between the reference image information and the read image information, a threshold value is provided that distinguishes between the case of normal printing and the case of occurrence of an abnormality, The judgment is normal or abnormal.

  By the way, in the case of the invention described in Patent Document 1 below, for example, even when an image is normally printed on paper, when the orientation of the paper is tilted when the formed image is read, the reference image information And the read image information do not match, there is a risk of erroneous determination that there is an abnormality. On the other hand, even if the image is not printed normally on the paper due to the inclination of the paper during image formation, it is determined as normal if the reference image information matches the read image information.

  As means for solving such problems, for example, there is an invention described in Patent Document 2 below. Japanese Patent Application Laid-Open No. 2004-228561 has means for detecting the inclination of the sheet based on the read image information, correcting the read image information based on the inclination, and then comparing the reference image information with the read image information. It is disclosed. According to such means, the posture (skew angle and vertex position) of the paper (paper sheets) can be accurately estimated based on the read image information, so that appropriate determination can be performed.

  The following patent documents 3 to 5 exist as documents disclosing this type of technology.

Japanese Patent No. 2866339 JP 05-258146 A Japanese Patent Laid-Open No. 06-226957 JP 07-125186 A Japanese Patent Application Laid-Open No. 08-212417

  However, since the above-described inspection method performs correction based only on the obtained image information, there is a problem that it takes a very long time for the processing. This is because the posture (skew angle and vertex position) of the sheet is extracted from only the captured image information, and image processing is performed to perform correction.

  In particular, in recent image forming apparatuses such as copying machines and printing machines, it is desired to increase the printing speed. In the above-described inspection method in which correction processing is performed based only on image information, the printing speed is increased. It is difficult to inspect the corresponding image.

  The present invention relates to an image forming apparatus, an image inspection apparatus, and an image inspection method capable of determining normality / abnormality of an image formed on a sheet even when the sheet is conveyed at high speed. is there.

An image forming apparatus according to the present invention includes an image forming unit that forms an image on a conveyed sheet based on reference image information serving as a reference, and read image information by reading the image formed on the sheet. An image reading means for acquiring the image, and an image inspection means for checking whether the difference between the reference image information and the read image information is within a predetermined range. A first paper attitude detecting means installed in the vicinity of the forming means for detecting the paper transport attitude; and a second paper attitude installed in the vicinity of the image reading means for detecting the paper transport attitude. comprising a detection unit, and based on the skew amount of each of the sheets of the image formation at the time of image reading obtained by said first and second sheet orientation detection unit, the reference image information or the read image Correcting at least one of the distribution is characterized by performing the verification after this correction.

  By detecting the paper transport posture both at the time of image formation and at the time of image reading, there is an advantage in that the inspection accuracy is improved and the inspection time is shortened.

  Further, in the image forming apparatus according to the present invention, the first and second paper attitude detection means are installed apart in a direction intersecting with the conveyance direction on the conveyance path of the paper, and the edge of the paper passing therethrough It is possible to include at least two edge detection sensors for detecting the paper skew, and a means for calculating the skew amount of the paper based on the paper edge information detected by the sensor.

  The paper edge detection sensor is preferably installed immediately before the image forming unit and the image reading unit to be installed. By shortening the distance between the image forming unit and the image reading unit and the sensor, the posture of the paper when the image is actually read can be detected, so that the detection accuracy of the paper posture is improved.

  Further, in the image forming apparatus according to the present invention, the image inspecting means is based on skew amounts of the respective sheets at the time of image formation and image reading acquired by the first and second paper attitude detecting means. It is possible to correct at least one of the reference image information or the read image information and perform the collation after the correction.

  Therefore, according to the present invention, even when the sheet is inclined on the conveyance path between image formation and image reading and the skew amount of the sheet changes, the skew amount can be corrected appropriately. The reference image information and the read image information can be collated. In addition, by acquiring the skew amount of each sheet at the time of image formation and image reading and performing image matching, processing time such as correction and determination can be shortened compared to the conventional technology. Excellent in inspection when paper is transported at high speed.

  Furthermore, in the image forming apparatus according to the present invention, the image reading unit can acquire the skew amount of the sheet by detecting the edge image of the sheet, and the image inspection unit includes the first and second image inspection units. Based on all the skew amounts of the paper skew amount based on the paper posture detecting means and the paper skew amount based on the edge image detected by the image reading means, at least the reference image information or the read image information One of them can be corrected, and the verification can be performed after this correction.

  By taking into account not only the amount of paper skew by the sensor but also the amount of paper skew based on the edge image detected by the image reading means, it is possible to perform determination processing with high inspection accuracy and high inspection speed.

  Furthermore, in the image forming apparatus according to the present invention, the second sheet orientation detecting unit is installed upstream of the image reading unit, and a third sheet detecting unit detects a sheet conveying posture downstream of the image reading unit. It is possible to further include a paper posture detecting means.

  By providing a paper posture detection means for detecting the paper transport posture upstream and downstream of the image reading means, it is possible to grasp the change in the posture of the paper passing through the image reading means, thereby improving the inspection accuracy. This is an advantage.

An image inspection apparatus according to the present invention is an apparatus connected to an image forming machine that forms an image on a sheet based on reference image information serving as a reference, and reads the reference image information and the formed image. Inspection is performed by collating the obtained read image information. The image inspection apparatus includes a first sheet attitude detection unit that acquires a skew amount of a sheet when an image is formed on the sheet by the image forming machine, and acquires read image information by reading the formed image. Second sheet posture detecting means for acquiring the skew amount of the sheet when the image is read, and the skew amount of each sheet at the time of image formation and image reading acquired by the first and second sheet posture detecting means. Based on the above, at least one of the reference image information or the read image information is corrected, and the collation is performed after the correction .

  Also, in the image inspection apparatus according to the present invention, the first and second paper attitude detection means are installed apart from each other in a direction intersecting with a conveyance direction on the conveyance path of the paper, and an edge of the paper passing therethrough It is possible to include at least two edge detection sensors for detecting the paper skew, and a means for calculating the skew amount of the paper based on the paper edge information detected by the sensor.

  Furthermore, in the image inspection apparatus according to the present invention, the reference image information or the reading is performed based on the skew amount of each sheet at the time of image formation and image reading acquired by the first and second sheet attitude detection units. It is possible to correct at least one of the image information and perform the collation after the correction.

  Still further, in the image inspection apparatus according to the present invention, the skew amount of the paper can be obtained by detecting the edge image of the paper based on the read image information, and the first and second paper attitude detections can be obtained. At least one of the reference image information or the read image information is corrected based on all the skew amounts of the paper skew amount based on the means and the paper skew amount based on the edge image of the paper, and after this correction The collation can be performed.

  Furthermore, in the image inspection apparatus according to the present invention, the second paper posture detection means can be provided both upstream and downstream of the image inspection apparatus.

  The image inspection method according to the present invention is a method used when an image inspection apparatus connected to an image forming machine that forms an image on a sheet is operated using a computer based on reference image information serving as a reference. Yes, an inspection process is executed by comparing the reference image information with the read image information obtained by reading the formed image. In the image inspection method, a first skew amount acquisition step of acquiring a skew amount of a sheet when an image is formed on the sheet by the image forming machine, and a read image by reading the formed image. A second skew amount acquisition step of acquiring a skew amount of the paper when acquiring information; an image reading step of acquiring read image information by reading an image formed on the paper; and the first and first steps The reference image information or the read image information is obtained based on the skew amounts of the respective sheets at the time of image formation and image reading acquired by the skew amount acquisition step 2 and the read image information acquired in the image reading step. A correction step for performing at least one correction, and the reference image information and the read image information after execution of the correction step. By matching bets, the difference therebetween is equal to or to execute the processing including an image checking step for checking whether within a predetermined range.

  In the image inspection method according to the present invention, a third skew amount acquisition step of acquiring a paper skew amount by detecting an edge image of the paper based on the read image information acquired in the image reading step. And the correction step can be executed based on the information acquired by the first to third skew amount acquisition steps.

  Furthermore, in the image inspection method according to the present invention, the second skew amount acquisition step may include a process of acquiring the skew amount of the paper both upstream and downstream of the image inspection apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 10 according to the present embodiment. The image forming apparatus 10 forms an image on the paper 16 conveyed by the image forming unit 14 based on the reference image information 12. Further, in this apparatus 10, the image formed on the paper 16 is read by the image reading means 18, and the read image (read image information) 20 and the original reference image information 12 are sent to the image inspection means 22. To determine whether image formation has been performed according to the reference image.

  The “paper” used in this specification is a concept including paper, film, OHP sheet, cardboard, postcard, and the like, and indicates all sheet-like recording media to be printed.

  The image forming unit 14 forms a toner image based on the reference image information 12. The image forming unit 14 includes a transfer unit 24 and a fixing unit 26, and the formed toner image is transferred by the transfer unit 24 onto the paper 16 sent from the paper feed tray. The paper 16 to which the toner image has been transferred is sent to the fixing unit 26 along the conveyance path, where the toner is fused and the image is fixed on the paper 16. The image formed on the paper 16 is sent to the image reading means 18. The image reading unit 18 includes a line sensor 28 that reads an image formed on the paper 16, reads the image on the paper 16 that has been conveyed, and sends the read image information 20 to the image inspection unit 22.

  In addition, the image forming apparatus 10 according to the present embodiment includes paper posture detection units 30 and 32 for detecting the paper conveyance posture upstream of the image forming unit 14 and upstream of the image reading unit 18. The paper posture detection means 30 installed upstream of the image forming means 14 can detect the skew amount of the paper when the image forming means 14 forms an image on the paper. Therefore, according to the paper posture detection means 30, it is possible to know what posture the paper was in at the time of image formation.

  On the other hand, the paper posture detection means 32 installed upstream of the image reading means 18 can detect the skew amount of the paper when the image formed on the paper is read by the image reading means 18. Therefore, according to the paper posture detection means 32, it is possible to know what posture the paper was in when reading the image.

  A specific configuration of the sheet orientation detection means 30 and 32 will be described with reference to FIG. The sheet orientation detection means 30 and 32 include, for example, a sheet edge detection sensor 36 as shown in FIG. In the sensor 36 according to the present embodiment, at least two sensors 36 are disposed apart from each other in a direction intersecting with the conveyance direction (arrow A) on the conveyance path of the paper 16. By arranging the sensor 36 in such a manner, the skew amount of the paper 16 can be detected. That is, before the start of image capture, the two sensors 36 each detect the front edge of the paper 16 (see FIG. 2A). Each sensor 36 sends, for example, the detection time to the control unit 40 included in the image inspection unit 22 as the paper attitude data 34. The control unit 40 can calculate the skew amount of the paper 16 based on the paper attitude data 34 including the paper edge detection time and the like. As a specific calculation method, it is possible to obtain the skew amount from the detection time difference between the two sensors 36 and the sensor interval.

  As for the installation position of the sensor 36, it is preferable that the sensor 36 can be arranged in a direction orthogonal to the conveyance direction (arrow A) on the conveyance path. May be. In this case, the skew amount can be calculated by adding a correction value that takes this deviation amount into consideration.

  What is necessary is just to determine the distance between each sensor 36 with the size of the paper 16 conveyed. Therefore, in the case of the image forming apparatus 10 that has to transport a plurality of sizes of paper 16, it is possible to cope by installing three or more sensors 36.

  Further, as shown in FIG. 2B, each sensor 36 can also detect the rear edge of the paper 16. By calculating the skew amount at both edges of the paper 16, the posture of the paper 16 such as rotation during image reading can be grasped, so that the paper 16 skew amount with higher accuracy can be calculated.

  Further, as shown in FIG. 3, a sensor 37 for detecting the conveyance posture of the paper 16 can be further provided downstream of the image reading area 38. When the sensor 36 is arranged only upstream of the image reading area 38, edge detection ends before the paper 16 completely passes through the image reading area 38, so that the posture of the paper 16 can be completely grasped. There will be no. Therefore, by installing the sensor 37 on the downstream side of the image reading area 38, it is possible to grasp all the postures of the paper 16 when passing through the image reading area 38, so that the detection accuracy of the paper 16 skew amount can be further improved. It can be done.

  Correction can be performed by rotating at least one of the reference image information 12 or the read image information 20 based on the skew amount calculated as described above. Therefore, in the related art, when a change in the paper orientation occurs during both image formation and image reading, correct image inspection cannot be determined. By detecting the amount of skew of the sheet at the time of image reading, correction corresponding to the change in the sheet posture can be performed, so that correct image inspection can be determined.

  The upstream sensor 36 is preferably installed immediately before the image forming unit 14 and the image reading unit 18, and the downstream sensor 37 is installed immediately after the image reading unit 18. Is preferable. This is because more accurate paper posture information can be obtained by reducing the distance between the image forming unit 14 and the image reading unit 18 and the sensor 36 as much as possible.

  As the sensors 36 and 37, all kinds of sensors such as a transmission optical sensor can be adopted. However, when a reflection sensor is used, the type of paper to be inspected is limited to white paper or the like, which is problematic in terms of versatility. On the other hand, when the reflection sensor is used, it is possible to install the sensor immediately below the image reading means 18, and therefore there is an advantage that the time difference between image reading and edge detection can be eliminated.

  Based on the information obtained as described above, the image inspection means 22 inspects and determines the image formed on the paper 16. Here, the image inspection unit 22 compares the reference image information 12 and the read image information 20 to determine whether the image on the paper 16 is normally formed or abnormal. Prior to this determination, at least one of the reference image information 12 and the read image information 20 is corrected based on the skew amount of the paper 16.

  Specifically, referring to FIG. 1, the image inspection means 22 includes a control unit 40 and a collation determination unit 42. The control unit 40 can acquire the reference image information 12 and the read image information 20 and can acquire the sheet posture data 34 from the sheet posture detection means 30 and 32. Based on the sheet orientation data 34, the control unit 40 calculates the skew amount of the sheet 16 when passing through the image forming unit 14 and the image reading unit 18. The control unit 40 corrects at least one of the reference image information 12 or the read image information 20 based on the skew amount of each sheet 16 at the time of image formation and image reading.

  For example, the case where the read image information 20 is corrected will be described as an example. If the paper 16 is rotated during image reading, the control unit 40 reads the image in consideration of the skew amount in the image reading unit 18. The image information 20 is corrected. Thereafter, the control unit 40 sends the reference image information 12 and the corrected read image information 20 to the collation determination unit 42. The collation determination unit 42 performs inspection by collating the received reference image information 12 with the corrected read image information 20. This inspection is performed, for example, depending on whether or not the difference between the image information 12 and 20 is within a predetermined range.

  It should be noted that the correction by the control unit 40 is also preferably considered in view of the read image information 20 read by the image reading means 18. That is, since the edge image of the paper 16 is recorded in the read image information 20, the control unit 40 can calculate the skew amount of the paper 16 from the read image information 20. Therefore, the control unit 40 determines the skew amount of the paper 16 based on the paper posture data 34 from the paper posture detection means 30 and 32 and the paper 16 based on the edge image included in the read image information 20 detected by the image reading means 18. Based on the skew amount, at least one of the reference image information 12 and the read image information 20 can be corrected. Considering the skew amount of the paper 16 based on the read image information 20, it is possible to further improve the accuracy of the image inspection and the inspection speed.

  The technical scope of the present invention is not limited to the scope described in the above embodiment, and various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

1 is a schematic configuration diagram of an image forming apparatus according to an exemplary embodiment. It is a figure which illustrates the specific structure of the paper attitude | position detection means which concerns on this embodiment. It is a figure which illustrates the specific structure of another paper attitude | position detection means which concerns on this embodiment.

Explanation of symbols

  10 image forming apparatus, 12 reference image information, 14 image forming means, 16 sheets, 18 image reading means, 20 read image information, 22 image inspection means, 24 transfer section, 26 fixing section, 28 line sensor, 30, 32 sheet orientation Detection means, 34 sheet orientation data, 36, 37 sensor, 38 image reading area, 40 control unit, 42 collation determination unit, A sheet conveyance direction.

Claims (12)

An image forming unit that forms an image on a conveyed sheet based on reference image information serving as a reference;
Image reading means for acquiring read image information by reading an image formed on the paper;
An image inspection means for verifying whether the difference between the reference image information and the read image information is within a predetermined range;
In an image forming apparatus having
A first paper attitude detection means installed in the vicinity of the image forming means for detecting the conveyance attitude of the paper;
A second paper attitude detection means installed in the vicinity of the image reading means for detecting the conveyance attitude of the paper;
And correcting at least one of the reference image information and the read image information on the basis of the skew amounts of the respective papers at the time of image formation and image reading acquired by the first and second paper posture detection means. An image forming apparatus that performs the collation after the correction . The image forming apparatus according to claim 1.
The first and second paper attitude detection means are at least two edge detection sensors that are installed apart from each other in a direction intersecting with the conveyance direction on the conveyance path of the paper and detect an edge of the paper passing therethrough. And
An image forming apparatus comprising: means for calculating a paper skew amount based on paper edge information detected by the sensor. The image forming apparatus according to claim 2.
The image inspection means includes
At least one of the reference image information or the read image information is corrected based on the skew amount of the respective sheets at the time of image formation and image reading acquired by the first and second sheet attitude detection means, and this correction is performed. An image forming apparatus that performs the collation later. The image forming apparatus according to claim 3.
The image reading means can acquire the skew amount of the paper by detecting the edge image of the paper,
The image inspection means includes
A skew amount of the sheet based on the first and second sheet attitude detecting means;
A skew amount of the paper based on the edge image detected by the image reading unit;
An image forming apparatus that corrects at least one of the reference image information or the read image information based on all the skew amounts, and performs the collation after the correction. The image forming apparatus according to claim 1, wherein:
The second paper attitude detection means is installed upstream of the image reading means,
An image forming apparatus, further comprising a third paper posture detection unit for detecting a paper conveyance posture downstream of the image reading unit. An image inspection apparatus connected to an image forming machine that forms an image on a sheet based on reference image information serving as a reference, and the read image information obtained by reading the formed image and the reference image information An image inspection apparatus that performs inspection by collating
First paper attitude detection means for obtaining a skew amount of a paper when an image is formed on the paper by the image forming machine;
A second paper attitude detecting means for acquiring a skew amount of paper when reading the formed image and acquiring read image information;
And correcting at least one of the reference image information and the read image information on the basis of the skew amounts of the respective papers at the time of image formation and image reading acquired by the first and second paper posture detection means. An image inspection apparatus that performs the collation after the correction . The image inspection apparatus according to claim 6,
The first and second paper attitude detection means are at least two edge detection sensors that are installed apart from each other in a direction intersecting with the conveyance direction on the conveyance path of the paper and detect an edge of the paper passing therethrough. And
An image inspection apparatus comprising means for calculating a skew amount of a sheet based on sheet edge information detected by the sensor. The image inspection apparatus according to claim 6 ,
By detecting the edge image of the paper based on the read image information, the skew amount of the paper can be acquired,
A skew amount of the sheet based on the first and second sheet attitude detecting means;
A paper skew amount based on the edge image of the paper;
An image inspection apparatus that corrects at least one of the reference image information or the read image information based on all the skew amounts and performs the collation after the correction. In the image inspection apparatus according to any one of claims 6 to 8 ,
2. The image inspection apparatus according to claim 1, wherein the second sheet orientation detection means is provided both upstream and downstream of the image inspection apparatus. An image inspection method used when an image inspection apparatus connected to an image forming machine that forms an image on a sheet based on reference image information serving as a reference is operated using a computer. An image inspection method for executing an inspection process by collating with read image information obtained by reading the formed image,
On the computer,
A first skew amount acquisition step of acquiring a skew amount of the paper when an image is formed on the paper by the image forming machine;
A second skew amount acquisition step of acquiring a skew amount of a sheet when reading the formed image and acquiring read image information;
An image reading step of acquiring read image information by reading an image formed on the paper;
Based on the skew amounts of the respective sheets at the time of image formation and image reading acquired by the first and second skew amount acquisition steps, and the read image information acquired in the image reading step, the reference image information or A correction step for correcting at least one of the read image information;
An image inspection step for comparing the reference image information with the read image information after execution of the correction step and inspecting whether a difference between the two is within a predetermined range;
An image inspection method characterized by causing a process including: The image inspection method according to claim 10 ,
A third skew amount acquiring step of acquiring a skew amount of the paper by detecting an edge image of the paper based on the read image information acquired in the image reading step;
An image inspection method, wherein the correction step is executed based on the information acquired by the first to third skew amount acquisition steps. The image inspection method according to claim 10 or 11 ,
The second skew amount acquiring step includes a process of acquiring a skew amount of a sheet both upstream and downstream of the image inspection apparatus.

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