JP4403810B2 - Printing inspection apparatus and printing system - Google Patents

Description

  The present invention relates to a print inspection apparatus that inspects the print quality of printed paper printed by a printing apparatus.

  In general, as a technique for quality inspection of a printed matter printed by a printing apparatus, a technique of reading an image of a printed matter and comparing the read image with a document image is often used as disclosed in Patent Document 1. Patent Document 1 receives and stores print data to be printed from a computer or the like, and reads the print result as image data for each print page in a computer printer that prints the print data on a predetermined sheet. A method is shown in which image data of only a specified area is cut out from image data, the cut-out image data is recognized as a character, and the result is checked with corresponding print data to determine pass / fail. This is for checking whether important portions on the printed matter, such as the amount of billing and the destination, are printed correctly.

  Further, as an apparatus for inspecting a printing result on a sheet, a device disclosed in Patent Document 2 is known. Compared to roll paper, with sheet paper, the inclination and misalignment of individual sheets at the reading position are irregular, but this conventional technique corrects the effect of such inclination and misalignment on the scanned image. Is disclosed.

  By the way, a sensor such as a CCD for optically reading a printed matter and a member such as a lamp for illuminating the printed matter for reading have individual differences in characteristics, and the characteristics change with time. Also in the print inspection apparatus, since the printed matter printed by the printing apparatus is read and inspected, it is necessary to compensate for the characteristics of the reading apparatus and its change with time.

  A conventional scanner device used for optical reading of a paper document generally performs a correction process called shading correction in order to compensate for such individual differences and changes with time. In general, in shading correction, correction data is obtained from the read data when the reflected light from the white reference member provided at the edge of the document table is read by the sensor and stored, and the reflected light from the document is read by the sensor. Is corrected using the correction data.

  Conventional scanner apparatuses having such a shading correction function include those shown in Patent Document 3 and Patent Document 4.

  The apparatus of Patent Document 3 is provided with a paper-like white reference member that can be rolled up instead of arranging the white reference member at the end of the document table.

  In Patent Document 4, in a compact facsimile machine in which a white reference member cannot be arranged, a pre-scan (pre-read) is executed before reading a document for transmission, and shading correction is performed from read data at the time of pre-scan. A configuration for obtaining data is shown. Further, Patent Document 4 discloses an apparatus including a correction data registration step of obtaining shading correction data by reading a white paper as a reference.

Japanese Patent Laid-Open No. 7-81191 JP 2002-63566 A JP 2002-209068 A JP 2002-252761 A

  Now, when creating a printed material with mixed pages of different paper types, printing devices that use roll paper as the paper need to print each type of roll paper individually and then cut them before collating There is. On the other hand, a printing apparatus using sheet paper includes a plurality of paper feed trays, and by dynamically selecting and printing a plurality of types of paper stored in the trays, such a printed matter can be obtained. There is an advantage that it can be created automatically.

  When trying to develop a print inspection device that inspects the printing results of such a sheet-based printing device, the paper quality, surface coat type, paper color, etc. will differ if the paper type is different. The light reflection characteristics are also different. For this reason, the appropriate shading correction data also differs for each paper type, so the print inspection apparatus needs to consider such a situation.

  On the other hand, in the conventional general shading correction of a scanner, only correction data is obtained based on the measurement result of a single white reference member. Therefore, a read image of a sheet whose light reflection characteristics are similar to that of the white reference member. However, there is a problem that it is difficult to ensure sufficient gradation when correcting a read image on a sheet that is not so. The apparatus of Patent Document 3 has the same problem as the white reference member only in a different form from a general one.

  The method of Patent Document 4 is a method for obtaining shading correction data by pre-scanning a document or white paper, and is suitable for applications such as a facsimile that reads a relatively small number of documents using the same type of paper. It may be. However, if this is applied as it is to a print inspection device connected to a sheet-fed printing device, each time it is necessary to read the print result of a different type of paper, it is corrected by pre-scanning the print result or paper. There is a problem that a process for obtaining data is required, and a series of processes of printing and inspection is hindered.

  The present invention solves at least one of the above-described problems of the prior art, and provides a technique for shading correction suitable for a print inspection apparatus.

The print inspection apparatus of the reference example is a print inspection apparatus that inspects the print quality of the printed paper based on the image data of the read result obtained by reading the printed paper on which the image is printed by the printing apparatus. For each of a plurality of paper feed trays provided in the printer, there are shown correction data storage means for storing shading correction data corresponding to the paper stored in the tray, and a paper feed tray as a paper feed source of printed paper to be inspected. Correction data reading means for acquiring shading correction data corresponding to the paper feed tray indicated by the information from the correction data storage means, and shading read by the correction data reading means for the image data of the read result Shading correction means for performing a shading correction calculation using the correction data. Inspecting the printing quality by using the image data of the reading results corrected by.

A printing system according to the present invention includes a plurality of paper feeding trays, a printing unit that prints an image on paper fed from the paper feeding trays, and the paper feeding tray, the printing unit, and the paper discharging unit. A sheet conveying unit that conveys the sheet; a reading unit that is provided in a subsequent stage of the printing unit in the sheet conveying unit and optically reads the printed sheet conveyed through the conveying unit; and a reading result by the reading unit A shading correction unit that performs a shading correction and includes, for each of the plurality of paper feed trays, a correction data storage unit that stores shading correction data corresponding to the paper stored in the tray, and the shading correction An inspection unit for inspecting the print quality of the printed paper based on the reading result subjected to shading correction by the unit, and the paper feed tray for each of the paper feed trays. Paper is fed from the printing unit to the reading unit without printing by the printing unit, shading correction data is obtained based on the reading result of the paper by the reading unit, and the obtained shading correction data is used as the paper. and a registration control unit that registers the correction data storage unit in association with the paper feed source of the sheet supply tray, the shading correction unit, the paper feed source of the sheet feeding trays of the printing paper sheets to be inspection A correction data reading unit that reads corresponding shading correction data from the correction data storage unit, and performs shading correction using the shading correction data read by the correction data reading unit.

  In another preferred aspect, the printing system further includes re-conveying means for returning the sheet read by the reading unit to the printing unit.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  First, an example of a schematic configuration of a printing system to which a mechanism according to the present invention is applied will be described with reference to FIG.

  This printing system generally includes a host computer 10, a printer controller 20, a printing device 100, and a print inspection device 200.

  The host computer 10 is a device that creates print data to be printed. The data to be printed may be, for example, data in which an image to be printed is described in a page description language, or may be raster image data indicating an image to be printed. In the case of fixed form printing such as form printing, values to be printed in each column of the fixed form (form) are set in accordance with a predetermined form such as CSV (Comma Separated Value) or LCDS (Line Conditioned Data Stream). Arranged data and the like are created as print data. The print data created by the host computer 10 is input to the printer controller 20 via a data communication network such as a LAN (Local Area Network) or a portable storage medium such as a CD-R / RW.

  The printer controller 20 acquires print data created by the host computer 10, generates image data (for example, raster image data) that can be handled by the printing apparatus 100 from this data, and supplies this to the printing apparatus 100. If the print data is page description language data, the printer controller 20 interprets it and creates image data for each page. In the case of standard printing, the printer controller 20 has data in a standard format (this data is registered in advance by the system operator), and each data value in the print data input from the host computer 10 is stored. Creates and outputs image data that fits the standard format. Image data supplied from the printer controller 20 to the printing apparatus 100 is referred to as “original image data”. Further, the printer controller 20 obtains print processing attributes such as information indicating the paper size or the paper feed tray to be used or single-sided / double-sided printing from the print data, and supplies control data indicating the print processing attributes to the printing apparatus 100. . The printer controller 20 supplies the original image data of each page created from the print data and the corresponding control data to the printing apparatus 100 in the order in which the printing apparatus 100 prints on the paper.

  The printing apparatus 100 receives document image data and control data from the printer controller 20, and prints document image data on a sheet in accordance with a print processing attribute indicated by the control data.

  The print inspection apparatus 200 is an apparatus that inspects the quality of print results on paper. Here, as an example, the optical reading result (hereinafter referred to as inspection image data) of the printing surface of the printed paper 150 printed by the printing apparatus 100 and the original image data (from the printer controller 20) This is an example of a print inspection apparatus 200 of a type that performs a print quality inspection by collating with a document image for the same page as the inspection image data.

  The outline of the printing system has been described above. Next, details of the printing apparatus 100 and the print inspection apparatus 200 will be described.

  The printing apparatus 100 includes an IF (interface) circuit 102, a control unit 105, a print engine 110, a paper transport system 112, a paper discharge destination switching gate 114, a plurality of paper feed trays 116, a normal paper discharge tray 120, and an abnormal paper discharge tray 125. including.

  The IF circuit 102 is an interface circuit for receiving document image data and control data from the printer controller 20. The received document image data is supplied to the print engine 110 via the control unit 105. The received control data is supplied to the control unit 105. In accordance with the control data, the control unit 105 executes various controls such as selecting a paper supply source from among a plurality of paper feed trays 116 and switching the paper conveyance path in duplex / single-sided printing. When the control data from the printer controller 20 includes information indicating the paper feed tray, the paper feed tray is selected. If the control data includes information indicating the paper size rather than directly indicating the paper feed tray, the paper feed tray 116 on which the paper of that paper size is set is selected. The control unit 105 can individually select a paper feed tray 106 as a paper feed source for each page in one print job.

  Each paper feed tray 116 may be a physically single tray or a logical tray in which a plurality of physical trays containing the same type of paper are logically handled as one tray. .

  Further, the IF circuit 102 supplies at least document image data among the data supplied from the printer controller 20 to the document image processing unit 210 of the print inspection apparatus 200.

  The print engine 110 is a device for printing a document image on a sheet 150 based on document image data input via the control unit 105. The present invention does not matter the format of the print engine 110. Various types such as an electrophotographic system and an inkjet system can be used. The electrophotographic print engine 110 includes a photoconductor, an exposure device, a developing device, a transfer mechanism, a fixing mechanism, and a cleaner mechanism.

  The paper transport system 112 is a mechanism for transporting paper within the printing apparatus 100 for printing. The paper transport system 112 transports the paper taken out from the paper feed tray 116 selected by the control unit 105 to the print engine 110, and the paper on which the image is printed by the print engine 110 is discharged from the normal paper discharge tray 120 to the abnormal discharge tray. Transport to the paper tray 125. In the case of double-sided printing, the paper on which the front surface has been printed is turned over and conveyed to the print engine 110 again. The paper transport system 112 is configured by a roller or a belt that is rotationally driven by a drive motor (not shown). FIG. 1 is a functional block diagram schematically illustrating the shape of the paper transport system 112 and the positional relationship between the paper transport system 112 and the print engine 110, the paper feed tray 116, the normal paper discharge tray 120, and the abnormal paper discharge tray 125. It is only an example.

  The normal paper discharge tray 120 is a tray in which printed sheets determined as non-defective products by the inspection of printed sheets by the print inspection apparatus 200 are accumulated. On the other hand, the abnormal paper discharge tray 125 is a tray in which printed sheets determined to be defective by the inspection are accumulated.

  The paper discharge destination switching gate 114 is a switching mechanism for switching the paper discharge destination of the printed paper between the normal paper discharge tray 120 or the abnormal paper discharge tray 125. The discharge destination switching gate 114 is controlled by the control unit of the printing apparatus 100 based on the inspection result signal supplied from the print inspection apparatus 200.

  Next, the print inspection apparatus 200 will be described. The print inspection apparatus 200 includes a reading device 205, an original image processing unit 210, an original image buffer 215, an inspection image processing unit 220, an inspection image buffer 225, a collation unit 230, and a display unit 230. Hereinafter, each of these elements will be described in order.

  The reading device 205 is provided at a position downstream of the print engine 110 and upstream of the paper discharge destination switching gate 114 in the paper transport system 112 of the printing apparatus 100. The reading device 205 includes a lamp for illuminating the printing surface of the printed paper 150, an imaging device, and an imaging optical system for imaging reflected light from the printing surface for the illumination on the imaging surface of the imaging device. Prepare. In a preferred example, a rod-shaped lamp can be used as the lamp, and a CCD (Charge Coupled Device) line sensor can be used as the imaging device. In this case, the line sensor and the imaging optical system are arranged so that lines in a direction perpendicular to the paper conveyance direction (referred to as a main scanning direction) at the position of the reading device 205 can be read at once by the line sensor. Then, one line of inspection image data is created by reading the lines in the main scanning direction line by line with the line sensor in synchronization with the conveyed paper passing through the reading position.

  The document image processing unit 210 is a functional module that receives document image data branched by the IF circuit 102 and performs image processing necessary for collation with inspection image data on the document image data. A representative example of image processing necessary for collation is resolution conversion. Of course, this is merely an example, and other image processing may be performed. In addition, a plurality of image processing may be performed on the document image data. These various image processing functions can be configured as a hardware circuit. Of course, a plurality of image processing functions can be incorporated into one hardware circuit.

  The document image buffer 215 is a buffer memory that temporarily stores document image data processed by the document image processing unit 210.

  The inspection image processing unit 220 is a functional module that performs image processing necessary for collation with the document image on the inspection image data generated by the reading device 205. Image processing executed by the inspection image processing unit 220 includes shading correction, exposure correction, positional deviation correction, magnification correction, binarization, and the like.

  Further, the inspection image processing unit 220 has a function of controlling an image reading operation by the reading device 205. In other words, the inspection image processing unit 220 instructs the reading device 205 to read each time the printed paper 150 reaches a predetermined reading position in synchronization with the paper conveyance of the printing device 100. In response to this instruction, the reading device 205 performs illumination with a lamp and reading of an image with an imaging device.

  Such an image processing function and control function executed by the inspection image processing unit 220 can be configured as a hardware circuit as in the case of the document image processing unit 210. The inspection image processing unit 220 can be configured as an aggregate of these hardware circuits.

  The inspection image buffer 225 is a buffer memory that temporarily stores inspection image data processed by the inspection image processing unit 220.

  The collation unit 230 reads out the original image data in the original image buffer 215 and the inspection image data in the inspection image buffer 225 and collates them, so that the print quality of the printed paper corresponding to the inspection image data is good or bad. Determine. At the time of this collation, the original image data and the inspection image data are compared. Since the process of the collation part 230 may be the same as that of the past, description is abbreviate | omitted. Although there is a difference between the timing at which the print inspection apparatus 200 acquires document image data and the timing at which inspection image data corresponding to the document image data is acquired, the document image buffer 215 provided in the print inspection apparatus 200. The buffer function such as the inspection image buffer 225 can absorb the difference until the collation by the collation unit 230.

  The collation unit 230 supplies a signal indicating the result of the quality determination to the printing apparatus 100. The control unit of the printing apparatus 100 switches and controls the discharge destination switching gate 114 according to this signal, so that the printed paper determined to be non-defective is transferred to the normal discharge tray 120, and the printed paper determined to be defective is The paper is discharged to the abnormal paper discharge tray 125.

  The processing result of the collation unit 230 can also be displayed on the display unit 240.

  The overview of the printing system according to the present embodiment has been described above. Next, details of the inspection image processing unit 220 will be described with reference to FIG.

  As shown in FIG. 2, the inspection image processing unit 220 includes a signal processing circuit 2202, an A / D conversion circuit 2204, a shading correction circuit 2206, an image processing system 2208, a shading correction data storage unit 2210, a shading correction control unit 2214, and A correction data registration control unit 2216 is provided.

  A signal processing circuit 2202 performs signal processing such as automatic gain control and offset control on an analog image signal output from the imaging device of the reading device 205. The A / D conversion circuit 2204 converts the signal signal subjected to signal processing into digital data. Conventional signal processing circuits 2202 and A / D conversion circuits 2204 can be used.

  The shading correction circuit 2206 is a circuit that performs a predetermined correction operation using the shading correction data as a parameter on the image data value digitized by the A / D conversion circuit 2204. In this example, as the shading correction calculation, the correction value is calculated by multiplying the image data value by the shading correction coefficient. The shading correction coefficient is, for example, a maximum luminance value, a value of an image signal (referred to as a white reference value) when a white reference member (a dedicated white reference plate or plain paper) is read with an imaging device under lamp irradiation. It is the value divided. In this case, the shading correction coefficient is shading correction data. The shading correction data is obtained individually for each light receiving pixel of the imaging device, and at the time of correction, the image data value of a certain light receiving pixel is corrected using the shading correction data corresponding to that pixel. Such correction compensates for the influence of pixel-to-pixel variation and lamp deterioration over time on the image data value of each light-receiving pixel.

  Note that the correction calculations described above are merely examples, and various other known shading correction calculations are known. For example, image data values obtained when the white reference member is read by the imaging device when the lamp is not illuminated are further used as black reference values, and correction calculation using a set of white reference values and black reference values as parameters is one of them. is there.

  The above is a general description of the shading correction calculation. In the present embodiment, when such correction calculation is performed, shading correction data corresponding to the paper feed tray 116 of the paper feed source is used.

  For this reason, in this embodiment, the LUT (look-up table) 2212-1 to 2212-that stores the shading correction data for the paper stored in the tray 116 for each paper feed tray 116 in the shading correction data storage unit 2210. N is stored. In each of the LUTs 2212-1 to 2212 -N, shading correction data for each light receiving pixel of the imaging device is registered. The LUT 2212 corresponding to each paper feed tray 116 can be obtained by using the paper fed from that paper feed tray as the white reference member.

  The shading correction control unit 2214 receives tray information indicating the paper feed tray from which the printed paper is fed from the control unit 105 of the printing apparatus 100, selects the LUT 2212 corresponding to the tray information, and sends it to the shading correction circuit 2206. Supply. Accordingly, the shading correction circuit 2206 can perform correction calculation using the LUT 2212 of the shading correction data suitable for the inspection image data to be corrected.

  The inspection image data subjected to the shading correction in this manner is subjected to further image processing necessary for the inspection in the image processing system 2208, and is then placed in the inspection image buffer 225 for verification by the verification unit 230. Provided. Note that image processing performed by the image processing system 2208 includes, for example, exposure correction, positional deviation correction, magnification correction, and binarization.

  The correction data registration control unit 2216 is a control unit that controls the correction data registration process of each LUT 2212 in the shading correction data storage unit 2210. This data registration process is executed at a registration timing determined based on a predetermined condition, for example, at the start of a print job.

  Next, the flow of execution of a print job in the system of this embodiment will be described with reference to FIG.

  When receiving a print job start instruction from the print controller 20, the control unit 105 of the printing apparatus 100 first cooperates with the correction data registration control unit 2216 of the inspection image processing unit 220 to the shading correction data storage unit 2210. The correction data registration process is executed (S100). In this registration process, first, the value n of the control counter is initialized to 1 (S102), and the steps S104 to S114 are repeated until n reaches the total number N of the paper feed trays 116. In step S <b> 104, the control unit 105 feeds paper from the n-th paper feed tray 116, and transports the paper to the reading position of the reading device 106 without printing on the print engine 110. The control unit 105 instructs the correction data registration control unit 2216 of the inspection image processing unit 220 to execute correction data registration processing, and each time the paper reaches the reading position, the paper source of the paper is supplied. Tray information indicating the paper feed tray is transmitted. When the reading device 205 detects that the paper has reached the reading position, the reading device 205 turns on the lamp and reads the paper (S106). The light reception signal of each light reception pixel obtained by this reading is processed by the signal processing circuit 2202, converted to a digital value by the A / D conversion circuit 2204, and input to the correction data registration control unit 2216. This value is a white reference value corresponding to the light receiving pixel. When the black reference value is also used, the period during which the paper passes the reading position of the reading device 205 is divided into a lamp irradiation period and a non-irradiation period, and the light reception signal value in the former is the white reference value and the light reception in the latter. The signal value is input to the correction data registration control unit 2216 as a black reference value. The correction data registration control unit 2216 obtains shading correction data by a known method based on the input value (S108), and the LUT 2212- corresponding to the nth paper feed tray 116 notified from the control unit 105. n is registered as shading correction data of the corresponding light receiving pixel (S110). Thereafter, the control unit 105 determines whether the counter value n has reached the total number N of trays (S112). If not, the control unit 105 increments the counter value n by 1 (S114), and repeats the processing from S104 onward. When the counter value n reaches the total number N of trays, the shading correction data corresponding to the paper in each paper feed tray 116 has been registered, so the printing process and the inspection for the printing result are executed (S200). ).

  Note that each sheet used for the correction data registration in S100 may be discharged to the abnormal sheet discharge tray 125. Alternatively, the paper used for the correction data registration can be returned to the printing position of the print engine 110 via the paper transport path for double-sided printing and used for printing. In this case, the reading position of the reading device 205 needs to be set before the entrance of the paper conveyance path for double-sided printing (that is, on the print engine 110 side). Further, instead of using the paper conveyance path for duplex printing, a paper conveyance path for returning the paper read by the reading device 205 to the print engine 110 may be provided.

  In addition, when a sheet on which a fixed form is printed in advance, such as an invoice sheet, is set in the sheet feeding tray, the shading correction data may be obtained from the reading result of the upper and lower margins (margins) of the sheet. Also. If the standard form is not printed on the back side of the paper, the paper fed from the paper feed tray 116 is reversed on the front and back sides of the paper transport path for double-sided printing, and shading correction data is obtained from the back side reading result.

  In the above example, the shading correction data is obtained and registered for all the sheets in the paper feed tray 116 provided in the printing apparatus 100. For example, when the job starts, the printer controller 20 sends a print job to the printing apparatus 100. When the paper or paper feed tray to be used is notified, the correction data can be obtained only for the paper in the paper feed tray corresponding thereto.

  Now, the flow of the printing and inspection process in S200 is as follows. That is, the print controller 20 supplies document image data of the page and control data of the page to the printing apparatus 100 for each page. The control unit 105 of the printing apparatus 100 selects the paper feed tray 116 according to the paper size or tray selection information included in the control data from the printer controller 20, and feeds paper from the tray 116 to the paper transport system 112. . Note that when the page is the back side of the sheet, the sheet is not fed from the sheet feeding tray. Then, when the fed paper reaches the printing position by the print engine 110, the control unit 105 supplies the original image data of the page corresponding to the paper to the print engine 110, and prints on the paper.

  The control unit 105 manages tray information indicating the paper feed tray that is the paper feed source for each fed paper, and manages the position of the paper transport system 112 where the paper is. When the control unit 105 detects that it is time to reach the reading position of the reading device 205 after printing a certain sheet based on the management information, the control unit 105 controls the shading correction control unit 2214 of the inspection image processing unit 220. Then, tray information indicating the paper feed tray of the paper feed source is supplied. The shading correction control unit 2214 selects the LUT 2212 corresponding to the paper feed tray indicated by the tray information from the shading correction data storage unit 2210 and supplies it to the shading correction circuit 2206. In parallel with this flow, the inspection image processing unit 220 causes the reading device 205 to read the printed paper that has reached the reading position at that time. The shading correction circuit 2206 performs a correction operation on the image data value of each light receiving pixel of the reading device obtained by the reading using the shading correction data of the pixel of the selected LUT 2212. The shading-corrected image data value is further processed by the image processing system 2208 and then verified by the matching unit 230 with the corresponding document image data.

  In the above description, the control unit 105 of the printing apparatus 100 absorbs the difference between the paper feeding timing and the timing at which the printing result of the fed paper is read. This is the shading correction control unit 2214. May be absorbed.

  The print job processing procedure in the system of this embodiment has been described above. In this process, since the LUT of shading correction data corresponding to the paper in each paper feed tray is created at the start of the job, it is possible to perform shading correction appropriate for each paper used in the job. In the case of a commercial printing system, a special type of paper (for example, paper on which a fixed form is printed) is often used for each print job, and various types of paper used for a job are set in the paper feed tray 116, respectively. After that, printing is often started. For this reason, it is appropriate to obtain shading correction data for various paper sheets set in the paper feed tray 116 group at the start of the print job. Note that in the case of a print job with a large number of printed sheets, the light amount of the lamp of the reading device 205 may change during the job. In order to cope with such a case, even during a print job, the shading correction data for the paper in each paper feed tray is obtained periodically or when a change in the light quantity is detected by monitoring the light quantity of the lamp. It is also preferable to perform registration update.

  Also, instead of calculating shading correction data for each paper feed tray at the start of the job, it monitors the attachment and detachment of the paper feed tray, and when it detects that the paper feed tray has been removed and reattached, It may be determined that the type of paper in the tray has been changed, and shading correction data may be calculated and registered for the paper in the tray.

  As described above, according to the present embodiment, in the print quality inspection in a job for creating a printed material using a plurality of types of paper set in a plurality of paper feed trays, the shading of the read result of the printed paper is performed. The correction can be executed using shading correction data corresponding to the paper. By performing appropriate shading correction in this way, it is possible to appropriately perform image processing on the correction result, such as binarization of inspection image data. In this embodiment, the shading correction data is acquired and registered for each paper feed tray at a predetermined timing such as when a job is started. Since the method of reading and using the correction data corresponding to the tray is adopted, the complexity of the processing as in the apparatus of Patent Document 4 is eliminated, and the influence on productivity can be reduced.

  In the above example, the print inspection apparatus 200 evaluates the print quality by comparing the inspection image data obtained by reading the printed paper with the document image data, but this is only an example. In addition to this, only inspection image data can be used, and print quality can be evaluated based on image characteristics (for example, edge strength) of the inspection image data. In such a case, the shading correction method of the present invention can be used. it can.

1 is a block diagram illustrating a schematic configuration of a printing system according to an embodiment. It is a block diagram which shows the structure for a shading correction | amendment. It is a flowchart which shows the procedure of the process of printing and an inspection.

Explanation of symbols

  10 host computer, 20 printer controller, 100 printing device, 102 IF circuit, 105 control unit, 110 print engine, 112 paper transport system, 114 paper output destination switching gate, 116 paper supply tray, 120 normal paper output tray, 125 abnormal discharge Paper tray, 200 print inspection device, 205 reading device, 210 original image processing unit, 215 original image buffer, 220 inspection image processing unit, 225 inspection image buffer, 230 collation unit, 240 display unit, 2202 signal processing circuit, 2204 A / D conversion circuit, 2206 shading correction circuit, 2208 image processing system, 2210 shading correction data storage unit, 222-1 to 2212-N LUT (look up table), 2214 shading correction data storage unit, 221 6 Correction data registration control unit.

Claims (2)

Multiple paper trays,
A printing unit that prints an image on paper fed from these paper feed trays;
A paper transport unit that transports paper between the paper feed tray, the printing unit, and the paper discharge unit;
A reading unit that is provided at a subsequent stage of the printing unit in the paper conveyance unit and optically reads a printed sheet conveyed through the conveyance unit;
A shading correction unit that performs shading correction on a reading result by the reading unit , and for each of the plurality of paper feed trays, a correction data storage unit that stores shading correction data corresponding to a sheet stored in the tray; A shading correction unit comprising:
An inspection unit that inspects the print quality of the printed paper based on the reading result subjected to the shading correction by the shading correction unit;
For each of the paper feed trays, paper is fed from the paper feed tray and transported to the reading unit without printing by the printing unit, and shading correction data based on the reading result of the paper by the reading unit. Registration control means for registering the obtained shading correction data in the correction data storage unit in association with the paper feed tray of the paper supply source;
With
The shading correction unit,
A correction data reading unit that reads out the shading correction data corresponding to the paper feed tray that is the paper source of the printed paper to be inspected from the correction data storage unit;
And performing shading correction using the shading correction data read by the correction data reading unit,
A printing system characterized by that. Multiple paper trays,
A printing unit that prints an image on paper fed from these paper feed trays;
A paper transport unit that transports paper between the paper feed tray, the printing unit, and the paper discharge unit;
A print inspection apparatus for inspecting the print quality of printed paper printed by a printing apparatus comprising:
A reading unit that is provided at a subsequent stage of the printing unit in the paper conveyance unit and optically reads a printed sheet conveyed through the conveyance unit;
A shading correction unit that performs shading correction on a reading result by the reading unit , and for each of the plurality of paper feed trays, a correction data storage unit that stores shading correction data corresponding to a sheet stored in the tray; A shading correction unit comprising:
An inspection unit that inspects the print quality of the printed paper based on the reading result subjected to the shading correction by the shading correction unit;
For each of the paper feed trays, paper is fed from the paper feed tray and transported to the reading unit without printing by the printing unit, and shading correction data based on the reading result of the paper by the reading unit. Registration control means for registering the obtained shading correction data in the correction data storage unit in association with the paper feed tray of the paper supply source;
With
The shading correction unit,
A correction data reading unit that reads out the shading correction data corresponding to the paper feed tray that is the paper source of the printed paper to be inspected from the correction data storage unit;
And performing shading correction using the shading correction data read by the correction data reading unit,
A printing inspection apparatus characterized by that.

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