JP2005250327A - Image forming apparatus, printed result inspecting apparatus and printed result inspecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a more accurate inspection of printed results is possible. <P>SOLUTION: A printer 10 is provided with a printing part 12 printing an image to paper based on original image data and an inspecting means inspecting the printed result by a printing part 12. Furthermore, the inspecting part is provided with a before printing reading part 40 acquiring the image data before printing by reading paper surface of the paper before printing is carried out by the printing part 12 and an inspection image reading part 42 acquiring an inspection image data by reading the surface of the paper after printing is carried out by the printing part and an inspection control part. The inspection control part functions as a shape information acquiring means calculating the shape information of the paper based on the pre-printing image data and as a determination means to determine the printed results to be good or bad based on inspection image data and the shape information. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus including a printing result inspection unit by a printing unit, a printing result inspection apparatus for inspecting a printing result by the image forming apparatus, and a printing result inspection method.

  2. Description of the Related Art Conventionally, an image forming apparatus including an inspection unit that inspects a result of printing by a printing unit is known. In this method, an image printed on a sheet by a printing unit is read by a reading device, and a print result is inspected based on obtained inspection image data. According to this, it is possible to automatically determine whether the printing result is good or not, and in the case of printing failure, it is possible to take measures such as automatically performing a reprinting process. Therefore, more reliable image printing is possible.

  In recent years, various forms of paper are used for printing. For example, a specially shaped paper having punch holes or corners may be used. Use of such specially shaped paper is highly demanded according to the variety of printed materials. In view of this, a number of printing machines that use specially shaped paper have been proposed (for example, Patent Document 1).

Japanese Patent Laid-Open No. 7-177882

  However, when specially shaped paper is used, it is difficult to accurately inspect the printed result. That is, the inspection image data serving as a criterion for determining whether or not the printing result is good includes a part having a special shape, for example, an image caused by punch holes or corner missing. For this reason, an image caused by the punched holes or corner missing is also recognized as a part of the printing result, and even when the image is originally printed normally, it may be determined that the printing is defective.

  Accordingly, an object of the present invention is to provide an image forming apparatus, a print result inspection apparatus, and a print result inspection method capable of performing a more accurate print result inspection.

  An image forming apparatus of the present invention is an image forming apparatus that includes a printing unit that prints an image on a sheet based on document image data, and an inspection unit that inspects a printing result by the printing unit. A pre-printing reading unit that reads the paper surface of the paper before printing by the printing unit and acquires pre-printing image data; a shape information acquisition unit that calculates the shape information of the paper based on the pre-printing image data; An inspection image reading unit that reads the surface of the paper after printing by the printing unit and acquires inspection image data; a determination unit that determines whether the printing result is good or not based on the inspection image data and shape information; It is characterized by having.

  In a preferred embodiment, the shape information acquisition means calculates a special shape portion that is a portion different from a preliminarily stored reference paper shape, among the shapes of the paper, based on the pre-print image data. Preferably, the determination means has means for specifying a special shape image that is an image resulting from the special shape portion of the print image data based on the shape information, and the special shape image is excluded from the inspection image data. Then, the quality of the print result is judged.

  In another preferred aspect, the inspection unit includes an adjustment unit that adjusts a control parameter related to paper conveyance based on the shape information. In another preferred aspect, the apparatus includes defective sheet detection means for detecting a sheet having a defect in shape by comparing and collating shape information of a plurality of sheets conveyed continuously. In another preferred aspect, the determination unit determines whether the print result is good or not by comparing and comparing the document image data and the inspection image data.

  Another printing result inspection apparatus according to the present invention is a printing result inspection apparatus for inspecting a printing result by an image forming apparatus, and reads a paper surface of a sheet before printing is performed by the image forming apparatus and reads image data before printing. Pre-print reading means to be acquired, shape information acquisition means for calculating the shape information of the paper based on the pre-print image data, and the paper surface of the paper after being printed by the image forming apparatus, and inspection image data Inspecting image reading means for acquiring image data, and determining means for determining pass / fail of printing results based on inspection image data and shape information.

  Another printing result inspection method according to the present invention is a printing result inspection method for inspecting a printing result by an image forming apparatus, which reads a paper surface of a sheet before printing by the image forming apparatus, and reads image data before printing. A pre-print reading process to be acquired, a shape information acquisition process for calculating the shape information of the paper based on the pre-print image data, and a paper surface of the paper after being printed by the image forming apparatus, and inspection image data An inspection image reading step for acquiring the image, and a determination step for determining the quality of the print result based on the inspection image data and the shape information.

  Here, the paper refers to all sheet-like printing objects such as printing paper, cardboard, postcards, cloth, and OHP sheets. Examples of the image forming apparatus include a printer, a copier, a facsimile machine, and a digital multi-function machine that combines these functions, which generally form an image on paper. Further, the control parameters relating to paper conveyance refer to general control parameters of the image forming apparatus that should be adjusted during paper conveyance, such as parameters relating to a paper detector that detects the paper to be conveyed and pressing force of the conveyance roller.

  According to the present invention, since the quality of the print result is determined based on the shape of the paper and the inspection image data, it is possible to accurately determine the quality of the print result even if the image resulting from the paper shape is included in the inspection image. Therefore, it is possible to inspect the printing result more accurately.

  Hereinafter, a printer 10 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overall configuration diagram of the printer 10. In addition, FIG. 2 shows a schematic side view of the vicinity of the pre-printing reading unit 40 in the printer 10, and FIG. 3 shows a schematic top view thereof. The printer 10 described below is assumed to be a relatively large high-speed printer. However, it may be applied to other image forming apparatuses such as a copying machine and a small printer by appropriately changing a part of the configuration.

  The printer 10 is controlled by a printing control unit (not shown), and prints the same image as the original image stored in the printing control unit on paper. The paper stored in the storage unit 22 is appropriately fed to the main transport path 14. The fed paper is printed by the printing unit 12 after the pre-printing reading unit 40 reads the paper surface. The printed paper is conveyed to the inspection image reading unit 42 and the paper surface is read. The inspection control unit determines whether the printing result is acceptable based on the image data acquired by the two reading units 40. Then, according to the inspection result, the sheet is conveyed to the paper discharge unit 24 or the duplex conveyance path 18. Hereinafter, the printer 10 will be described in detail.

  The storage unit 22 includes two paper supply trays for storing paper. Each paper feed tray is connected to the main transport path 14 so that paper can be supplied as appropriate. Here, normally, the paper to be stored is a paper having a predetermined shape and a fixed shape, but in some cases, a special shape paper other than the fixed shape may be stored.

  The printing unit 12 is roughly divided into a transfer unit 26 that forms a toner image based on document image data and transfers the toner image onto a sheet, and a fixing unit 28 that fixes the toner transferred onto the sheet. The transfer unit 26 forms an electrostatic latent image on the photoconductor by a charging unit and an exposure unit (not shown), and attaches toner to the surface of the photoconductor by electrostatic force to form a toner image. The toner image formed here is formed based on the document image. The photoconductor or the transfer roller on which the toner image is transferred from the photoconductor is provided on the main conveyance path 14, and the toner is transferred onto the paper by conveying the paper here.

  The fixing unit 28 is provided on the main conveyance path 14 downstream from the transfer unit 26. This is a method in which the sheet to which the toner is attached is pressed against the fixing roller while heating, and the toner transferred onto the sheet is thereby fixed on the sheet.

  The pre-printing reading unit 40 is provided between the storage unit 22 and the printing unit 12 and reads the paper surface of the paper before printing (see FIGS. 2 and 3). This includes a reading device 50 for reading the paper surface of the paper transported along the main transport path 14. The reading device 50 includes a lamp 51, an imaging lens 52, a CCD sensor 54, and the like. The read image data is output to the inspection control unit as pre-print image data.

  The inspection image reading unit 42 is provided downstream of the printing unit 12 and reads the paper surface of the printed paper. This is provided with one reading device 50 so that the surface of the printed paper (printed surface) can be read out of the conveyed paper. Since the configuration of the reading device 50 is the same as that of the reading device 50 in the above-described pre-printing reading unit 40, description thereof is omitted here. The image data acquired by the inspection image reading unit 42 is output to the inspection control unit as inspection image data.

  The inspection control unit has functions corresponding to shape information acquisition means, determination means, adjustment means, and defective paper detection means. The inspection control unit includes a storage unit, and stores document image data, a reference shape that is a reference sheet shape, and the like in advance. Here, as the reference shape, for example, the shape of a standard paper sheet defined by JIS or the like can be used as the reference shape. In addition, image data read by the two reading units 40 and 42 is also stored and accumulated in the storage unit. Based on various image data stored in the storage unit, processing such as calculation of paper shape information, determination of pass / fail of printing results, adjustment of control parameters related to paper conveyance, and detection of defective paper are performed. . Then, the obtained print result inspection result, defective paper detection result, and the like are output to the print control unit.

  The paper discharge unit 24 includes a normal paper discharge tray 34 that normally discharges paper on which image formation has been completed, and an abnormal paper discharge that discharges paper that has been determined to have poor print results or paper that has a shape defect. And a paper tray 36.

  The main transport path 14 is a transport path for transporting paper in the forward direction from the storage unit 22 toward the paper discharge unit 24. Each part of the main transport path 14 is provided with a plurality of transport rollers 15, and the paper is transported by driving the transport rollers 15.

  The most downstream of the main conveyance path 14 is branched into a discharge conveyance path 20 and a double-side conveyance path 18. The paper discharge conveyance path 20 is connected to the paper discharge trays 34 and 36, and can guide the paper to the paper discharge trays 34 and 36. The double-sided conveyance path 18 turns the paper over and leads it to the main conveyance path 14, and is used for duplex printing.

  A switch provided at the branch point of each transport path determines whether the paper transported along the main transport path 14 is led to the normal paper discharge tray 34, the abnormal paper discharge tray 36, or the double-side transport path 18. (Not shown). This switch is controlled by the printing control unit.

  A paper detector 56 is provided in each part such as the conveyance path and the printing unit 12. This is for detecting the position, size, inclination, etc. of the conveyed paper. For example, an optical sensor comprising a projector and a light receiver can be used. When the optical sensor is used, the position, size, and inclination of the sheet are calculated from the timing at which the light from the projector is blocked by the conveyance of the sheet on the optical sensor (the timing at which the light cannot be detected by the light receiver). Then, according to the position, size, and inclination of the obtained paper, the control parameter of the transport roller, the print start timing, and the like are adjusted. For example, when the sheet being conveyed is tilted, it is possible to take measures such as changing the pressing force of the conveying roller to be asymmetric and correcting the tilt of the sheet.

  Next, the flow of image formation in the printer 10 will be described. In the following, a case where a specially shaped paper as shown in FIG. 4 is used will be described. That is, a sheet in which punch holes 62a are formed in a rectangular sheet 60 (see FIG. 4A)), a sheet in which corners 62b are formed in a rectangular sheet 60 (see FIG. 4B)), a rectangular sheet A case will be described in which a sheet (see FIG. 4C) on which a tongue portion 62c protruding to 60 is formed is used. Of course, a paper having a shape other than those described here may be used, or a rectangular (standard) paper having a normal shape may be used.

  When image formation is performed on paper, document image data that is an image to be printed is input to the printing control unit. The document image data is input, for example, by transmitting the document image data from another computer or the like to the printing control unit via the communication device. The input document image data is stored in the printing control unit and is output to the inspection control unit. The inspection control unit stores the document image data. Of course, the original image data may be acquired by reading a sheet on which a predetermined image is formed.

  The printing control unit develops the toner image on the photosensitive member by controlling the charging device, the exposure device, and the like based on the stored document image data. Further, the conveyance roller 15 is driven to feed the sheet from the storage unit 22 to the main conveyance path 14.

  The supplied paper is first read by the pre-printing reading unit 40 (see FIG. 2). The read image data is output to the inspection control unit as pre-print image data. The inspection control unit stores the pre-print image data in the storage unit. Here, based on the pre-print image data, the inspection control unit adjusts control parameters related to paper conveyance and detects paper with shape defects, which will be described later.

  The paper that has passed through the pre-printing reading unit 40 is further conveyed to the printing unit 12. In the printing unit 12, the toner image is transferred by the transfer unit 26 and the toner is fixed by the fixing unit 28. As a result, image printing based on the document image data is performed on the paper.

  The paper that has passed through the printing unit 12 is conveyed to the inspection image reading unit 42. Then, the printing surface is read by the reading device 50. The inspection image reading unit 42 outputs the acquired image data as post-print image data to the inspection control unit.

  The inspection control unit inspects the print result. That is, the document image data and the inspection image data are compared and collated, and the difference amount between the two image data is calculated. If the difference amount is smaller than the predetermined threshold value, it is determined that printing has been performed normally. If the difference amount is larger than the predetermined threshold value, it is determined that the printing result is defective. This inspection result is output to the printing control unit.

  When the printing is normally performed, the printing control unit conveys the paper to the normal paper discharge tray 34 or the duplex conveyance path 18. On the other hand, if it is determined that the printing result is defective, the paper is transported to the abnormal paper discharge tray 36, and a new paper is printed.

  Here, when the specially shaped paper as shown in FIG. 4 is used as the printing paper, the following problems occur when inspecting the printing result. The image data obtained by reading the specially shaped paper includes images resulting from specially shaped portions such as punch holes 62a, corner cuts 62b, and tongues 62c.

  Therefore, the inspection image data obtained by reading the paper surface of the special-shaped paper after printing includes an image (hereinafter referred to as “special-shaped image”) caused by the special-shaped portion in addition to the image printed by the printing unit 12. It will be. On the other hand, since the original image data is only an image to be printed by the printing unit 12, a special shape image is not included.

  When the inspection image data including such a special shape image and the original image data not including the special shape image are compared, the amount of difference increases, and even if the image was originally printed normally, There is a case where it is erroneously determined as a printing defect.

  Therefore, in the present embodiment, the following processing is performed before the comparison / collation between the inspection image data and the document image data. First, the shape of the paper is calculated from the pre-print image data obtained by reading the paper before printing. This is possible by detecting the paper boundary. Then, the obtained paper shape is compared with the reference shape stored in the storage unit, and a portion having two different shapes is extracted as a special shape portion. For example, when the paper 60 shown in FIG. 4A is an A4 paper, an A4 size rectangle is used as a reference shape, and the reference shape is compared with the paper 60 shown in FIG. In that case, since the punch hole 62a portion is a different portion, this portion is extracted as a special shape portion.

  Next, if the special shape portion can be calculated, an image (special shape image) resulting from the special shape portion is specified from the inspection image data and removed. As a result, only the image printed by the printing unit 12 remains in the inspection image data. Then, the quality of the print result is judged by comparing and comparing the inspection image data from which the special shape image is removed and the document image data. At this time, since the special shape image is not included in the inspection image data, it is possible to accurately determine whether the printing result is good or bad. That is, according to the present embodiment, it is possible to accurately inspect the printing result regardless of the shape of the paper.

  In the present embodiment, the special shape portion is obtained, but is not necessarily obtained. Only the paper shape information may be used. That is, the paper shape, in particular, paper boundary information is calculated from the pre-print image data, the image printed by the printing unit 12 is specified from the boundary information and the inspection image data, and the specified image and document image data are specified. May be compared. Further, not only the boundary information but also, for example, when using a paper having a convex portion (embossed paper), the print result may be inspected using the shape information about the convex portion.

In addition, when performing reverse side printing, image data before printing is not acquired again, but the image data before printing acquired at the time of front side printing is inverted and used. Of course, the pre-print image data may be acquired again at the time of backside printing.

  Next, a description will be given of a case in which parameters relating to paper conveyance are controlled based on paper shape information, particularly information on special shape portions. As described above, the paper is appropriately detected by the paper detector 56 in the conveyance process, and the position, size, and inclination of the paper are calculated. Then, control parameters relating to various types of conveyance are adjusted according to the position, size, and inclination.

  Here, as shown in FIG. 3, consider a case where a sheet 60 having punch holes 62a is being conveyed. An ON signal is output while the paper detector 56 provided on the main transport path 14 and the paper 60 are on it (while passing), and an OFF signal is output when there is no paper 60 above it. Therefore, for example, the size (length) of the paper can be calculated from the time during which the ON signal is output. Further, the inclination of the sheet can be known from the difference between the ON signal output start timings of the two sheet detectors 56 provided in the width direction of the conveyance path.

  However, when the paper 60 has a special shape such as a punch hole 62 a, an OFF signal is output when the punch hole 62 a reaches the paper detector 56. Therefore, in the example shown in FIG. 3, the ON signal is continuously output from the time when the front end portion (the right end portion in FIG. 3) of the paper 60 reaches the paper detector 56, and the punch hole portion 62 a is set to the paper detector. It will be a very short time until 56. Therefore, there is a possibility that the paper 60 is erroneously recognized as an extremely short paper. In this case, the printing control unit determines that the paper 60 is a non-printable paper and outputs an error. However, in reality, the paper 60 is a printable paper, although there are punch holes 62a partially. Therefore, it is not desirable that an error is output.

  Therefore, in the present embodiment, control parameters relating to paper conveyance are adjusted based on the paper shape information. That is, when the pre-print image data is input from the pre-print reading unit 40, the inspection control unit calculates paper shape information, particularly information related to the special shape portion. Then, the control parameters of the paper detector 56 are adjusted according to the paper shape, particularly the position and size of the special shape portion. That is, the signal for the portion corresponding to the special shape portion of the output signal of the paper detector 56 is invalidated, or the timing for detecting the paper is changed. The printing control unit adjusts various control parameters related to conveyance according to the output result from the paper detector 56 in which the control parameter is adjusted according to the shape of the paper.

  As described above, the paper shape information is calculated based on the pre-print image data, and the control parameters related to the paper detector are adjusted according to the shape information. It is possible to appropriately adjust various control parameters related to the detection of paper and, in turn, conveyance. In the above description, the control parameters related to the paper detector 56 are adjusted, but various control parameters related to other paper transport such as the pressing force of the transport roller may be directly adjusted. That is, the control parameters of the paper detector 56 may not be adjusted, and various control parameters may be adjusted according to the signal output from the paper detector 56 and the paper shape.

  Next, detection of a paper shape defect using the calculated paper shape information will be described. The flow of detection of a paper shape defect is as follows. First, pre-print image data is acquired by the pre-print reading unit 40. The inspection control unit calculates the shape information of the paper based on the print image data, and stores and accumulates the information in the storage unit. Then, the shape information of the sheet to be inspected is compared with the shape information of the sheet conveyed before and after the sheet.

  Usually, the shape of the continuously conveyed sheets is often the same, and among the continuously conveyed sheets, only a few intermediate sheets are unlikely to have different shapes. In such a case, it can be determined that there is a paper shape defect. Therefore, the inspection control unit compares the shape information of the paper to be inspected with the shape information of the paper conveyed before and after the paper. If the shape of the inspection target paper is different from the shape of the paper conveyed before and after the paper, it is determined that the inspection target paper has a shape defect. On the other hand, if all have the same shape, it is determined that the sheet to be inspected is a normal sheet having no shape defect.

  Then, the inspection control unit outputs the determination result to the printing control unit. When there is a shape defect, the printing control unit conveys the paper to the abnormal paper discharge tray 36. At that time, printing by the printing unit 12 and paper reading by the inspection image reading unit 42 are not performed. Then, the printing process on another sheet is started. If there is no shape defect, printing processing and printing result inspection are performed as usual.

  As described above, a sheet having a defect in shape can be detected by comparing and collating the shape information of a plurality of sheets conveyed continuously. Then, a sheet having a shape defect can be discharged as it is and printed on another sheet. Therefore, unnecessary printing processing can be prevented, and printing processing on another sheet can be automatically executed, so that more reliable image printing can be performed. In the above description, the comparison is made with the shape of the sheet conveyed before and after, but it may be compared with only the sheet conveyed last time or only with the sheet conveyed after that. Further, it may be compared not only with the previous time but also with a sheet conveyed a plurality of times before, such as two times before and three times before.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. FIG. 3 is a schematic side view of the periphery of a pre-printing reading unit of the printer. FIG. 3 is a schematic side view of the periphery of a pre-printing reading unit of the printer. It is a figure which shows an example of the paper of a special shape.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Printer, 12 Printing part, 14 Main conveyance path, 15 Conveyance roller, 18 Duplex conveyance path, 20 Discharge conveyance path, 22 Storage part, 24 Discharge part, 40 Pre-printing reading part, 42 Inspection image reading part , 50 reader, 56 paper detector, 60 paper.

Claims (8)

A printing unit that prints an image on paper based on the document image data;
Inspection means for inspecting the printing result by the printing section;
An image forming apparatus comprising:
Inspection means
A pre-printing reading unit that reads a paper surface of a sheet before printing by a printing unit and acquires pre-printing image data;
Shape information acquisition means for calculating the shape information of the paper based on the pre-print image data;
Inspection image reading means for reading the paper surface of the paper after printing by the printing unit and acquiring inspection image data;
A determination means for determining the quality of the print result based on the inspection image data and the shape information;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The shape information acquisition unit calculates a special shape portion that is a portion different from a preliminarily stored reference sheet shape, based on pre-print image data. The image forming apparatus according to claim 2,
The determination means has means for specifying a special shape image that is an image resulting from the special shape portion of the print image data based on the shape information,
An image forming apparatus characterized in that the quality of a print result is determined after removing a special shape image from inspection image data. The image forming apparatus according to claim 1, further comprising:
The image forming apparatus according to claim 1, wherein the inspection unit includes an adjustment unit that adjusts a control parameter related to paper conveyance based on the shape information. The image forming apparatus according to any one of claims 1 to 4,
An image forming apparatus comprising: a defective sheet detecting unit that detects a sheet having a defect in shape by comparing and collating shape information of a plurality of sheets conveyed continuously. The image forming apparatus according to any one of claims 1 to 5, wherein:
An image forming apparatus, wherein the determination unit determines whether the print result is good or not by comparing and comparing the document image data and the inspection image data. A printing result inspection apparatus for inspecting a printing result by an image forming apparatus,
A pre-printing reading unit that reads a paper surface of a sheet before being printed by the image forming apparatus and acquires pre-printing image data;
Shape information acquisition means for calculating the shape information of the paper based on the pre-print image data;
An inspection image reading means for reading the paper surface of the paper after printing by the image forming apparatus and acquiring inspection image data;
A determination means for determining the quality of the print result based on the inspection image data and the shape information;
A printing result inspection apparatus comprising: A printing result inspection method for inspecting a printing result by an image forming apparatus,
A pre-printing reading step of reading the paper surface of the paper before being printed by the image forming apparatus and acquiring pre-printing image data;
A shape information acquisition step of calculating the shape information of the paper based on the pre-print image data;
An inspection image reading step of reading the paper surface of the paper after being printed by the image forming apparatus and acquiring inspection image data;
A determination step for determining the quality of the print result based on the inspection image data and the shape information;
A printing result inspection method characterized by comprising:

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