JP2013036815A - Inspection apparatus, inspection method, computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide image alignment means achieving both accuracy and excellent performance in a realtime inspection system for a printed matter in synchronization with printing.SOLUTION: An inspection system measures a skew angle through detecting a plurality of paper edges of a desired print document, extracts, for misalignment correction, feature points from print contents of print data and image data of the print data, and estimates a linear misalignment amount by fitting processing of respective feature points. At that time, the fitting processing can be accelerated by referencing the screw angle.

Description

  The present invention relates to an inspection apparatus, an inspection method, and a computer program.

  In commercial printing, conventionally, offset printing of a small quantity and mass printing has been performed using an offset plate-making printing machine. In recent years, on-demand printing (print-on-demand, POD) has attracted attention as digital printers such as electrophotographic and ink-jet image forming apparatuses become faster and have higher image quality. In offset printing and on-demand printing as described above, an inspection process for inspecting a printed matter for defects is automated.

  Conventionally, inspection processing has been performed by taking a printed material to be inspected from a sensor such as a camera or a line sensor into an image memory and comparing it with a reference image set in advance as a reference. In this inspection process, the target image captured from the sensor is distorted due to various misalignments such as skew during transport of the printed material to be inspected and the optical misalignment of the sensor. The inspection accuracy is low only by comparing with the image. Therefore, it is necessary to align both images.

  In Patent Document 1, the inclination of a printed material is measured, and alignment is performed by primary conversion using the measured inclination as a rotation parameter. Further, in Patent Document 2, the target image and the reference image are divided, pattern matching processing is performed between the divided reference images, and alignment is performed based on the result of the pattern matching processing.

JP-A-7-89063 JP2008-064486

  The skew shift and the optical shift include nonlinear components such as distortion, and the shift amount differs depending on the image area. Therefore, in the method described in Patent Document 1 in which the target image is uniformly converted and corrected from local image information uniformly, the accuracy of alignment is low. Further, what is corrected by the alignment method described in Patent Document 2 is a shift (parallel movement) shift amount, and the shift amount due to rotation or enlargement / reduction cannot be corrected. Low.

  An object of the present invention is to perform alignment between images in consideration of rotational misalignment.

  The inspection apparatus of the present invention acquires a reading unit that acquires a read image obtained by reading a printed material on which an original image is printed, a receiving unit that receives the original image, and acquires skew information indicating a skew direction of the printed material. Obtaining means, extracting means for extracting a patch image including an edge feature from the original image received by the receiving means, rotating the patch image extracted by the extracting means based on the skew information, the rotation The alignment unit that aligns the original image by searching for the portion of the read image corresponding to the patch image that has been aligned, and the original image that has been aligned by the alignment unit and the read image are compared. And determining means for determining the quality of the printed matter.

  In the inspection device for printed matter, it is possible to perform image alignment processing in consideration of rotational misalignment.

Block diagram showing the configuration of the inspection system Inspection system configuration diagram Paper detection sensor Line sensor Inspection control block diagram Illustration of each image data and patch Explanatory drawing of rotation amount estimation means Explanatory drawing of division of image data and shift amount of each divided block Image verification diagram of reference image data and scanned image data Flow chart of inspection system processing Flow chart of image alignment processing Flow chart for estimating the amount of rotation between patches

Example 1
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of an inspection system (in-line inspection system) synchronized with printing in this embodiment. The inspection system 1 includes a printing apparatus unit 10, a printed document reading unit 500, an inspection control unit 600, a printed document discharge unit 700, a finisher unit 800, and a discharge unit 1000, and is connected to a PC (not shown) via a network. ing. FIG. 10 is a processing flowchart in each processing unit in the inspection system 1. The inspection control unit 600 executes the processing flow shown in FIG.

  FIG. 2 is a hardware configuration diagram of the inspection system 1 according to the present embodiment. The printing apparatus unit 10 includes an image reading unit 100, a printing apparatus operation unit 200, a printer unit 300, and a printing apparatus control unit 400. The processing flow of FIG. 10 will be described with reference to FIG.

  The user sets a print job to be executed by the printing apparatus unit 10 using the printing apparatus operation unit 200 (UI) (S100). The print job includes discharge mode setting information (discharge setting value) in the print document control unit, which will be described later, and finishing process setting information (finishing setting value) in the finisher unit 800. At this time, the inspection control unit 600 also sets the inspection accuracy of the printed matter on the UI.

  Next, the printing apparatus control unit 400 performs execution control of the print job set in step S100, and transmits the set print job and inspection accuracy setting information (inspection setting value) to the inspection control unit 600 for printing. Each setting value of the job is transmitted to the finisher unit 800. (S101, S102). In the present embodiment, the inspection setting value is a threshold value for determining whether the inspection result is a non-defective product determination or a defective determination, and a setting value of each item set by the user. The threshold includes items such as density difference and defect image size. Items set by the user include selection of defects to be detected such as dirt, rubbing, and streaks, and setting of inspection levels such as resolution for inspection.

  The image reading unit 100 reads a document image conveyed by the document conveying device 110. The document conveying device 110 conveys the documents set on the document tray 111 one by one from the first page in order, and conveys them onto the document table glass 114 through a curved path. There are two methods for reading a single-sided original. The first method is a document fixed reading mode in which a document is read by transporting and stopping the trailing edge of the document to the reading position R1 on the platen glass 114 and moving the scanner unit 121 from left to right. There is. The second method includes a document transport reading mode in which the document is transported to the reading position R1 at a constant reading speed and the document is read while the scanner unit 121 is fixed at the reading position R1. In the above-described two methods for reading a single-sided original, the read original is discharged to the paper discharge tray 112. As a method of reading a double-sided document, there is a method of reading the front surface with the scanner unit 121 and reading the back surface using the optical unit 113 disposed in the document conveying device 110. In the optical unit 113, an image sensor and a light source (not shown) are arranged.

  An image of a document read by the image sensor 123 via the lens 122 is subjected to image processing, stored in the storage device 430, and transferred to the printing device control unit 400. The printing device controller unit 410 communicates with the printer control unit 301 that controls the printer unit 300 to print the image data stored in the storage device 430 on a sheet. When PDL data is input from the PC 2, the RIP unit performs RIP (Raster Image Processor) processing (S103).

  The RIP data is stored in the storage device 430, communicates with the printer control unit 301, and prints the image data on a sheet (S104). The printer control unit 301 outputs laser light corresponding to the image signal. When this laser light is irradiated onto the photosensitive drum 302, an electrostatic latent image is formed on the photosensitive drum 302. The electrostatic latent image on the photosensitive drum 302 is developed by the developing unit 303, and the developer on the photosensitive drum 302 is transferred by the transfer unit 306 to a sheet fed from one of the cassettes 311, 312 and the manual sheet feeding unit 313. Is done. When the sheet onto which the developer has been transferred is guided to the fixing unit 304, a fixing process for the developer is performed.

  The printed sheet is discharged from the printing apparatus unit 10 and conveyed to the print document reading unit 500. At this time, the printing apparatus controller unit 410 transmits digital data (for example, RIP data) that is the basis of the print image and job attribute information to the inspection control unit 600 (S105). The sheet that has passed through the fixing unit 304 is once guided from the path 307 to the path 310 by a flapper (not shown), and after the trailing edge of the sheet has passed through the path 307, the sheet is switched back and guided from the path 308 to the discharge roller 305. . As a result, the surface onto which the developer has been transferred can be turned downward (face down) and discharged from the printer unit 300 by the discharge roller 305. This is called reverse paper discharge. In this way, by discharging face down, image formation is performed in the correct page order from the first page, such as when printing an image obtained by reading a plurality of documents using the document conveying device (image reading unit) 100. Is possible. When an image is formed on the hard sheet such as an OHP sheet from the manual sheet feeding unit 313, the image is not guided to the pass 307, and the surface onto which the developer is transferred is left facing upward (face up) from the discharge roller 305. Discharge. In addition, when forming an image on both sides of a sheet, the sheet is guided from the fixing unit 304 to pass 307 and pass 310, and the sheet is switched back immediately after the rear end of the sheet passes through the path 307, and is conveyed on both sides by a flapper (not shown). Guide to path 309.

  The electrostatic latent image is transferred again to the sheet guided to the duplex conveyance path 309 by the transfer unit 306 and subjected to fixing processing by the fixing unit 304. In this way, it is possible to carry even a state where five half-size sheets such as A4, B5, etc. are contained in one pass that returns from the transfer unit 306 to the transfer unit 306 via the duplex conveyance path 309 again. The path length, roller arrangement, and drive system are divided. Note that the discharge page order by these processes is discharged so that odd-numbered pages face downward, so that the page order during duplex copying can be matched. The printed output (printed matter) 20 discharged from the discharge roller 305 is sent to the print original reading unit 500.

  The print document reading unit 500 includes a print document reading controller unit 510, a paper detection sensor 511, and a line sensor 512. First, the print output 20 fed by the paper detection sensor 511 is detected (S106). As shown in FIG. 3, the paper detection sensor 511 detects the presence or absence of the print output 20 at the edge of the paper end of the white print output 20 with respect to the black paper transport belt (transport means) 513. At this time, the presence / absence of the printed output 20 is detected, and at the same time, the passage times of the two corners of the leading paper edge of the printed output 20 are measured.

  The print original reading controller unit 510 calculates the skew angle Θ 514 of the printed output 20 shown in FIG. 3 from the passage time measured in step S106 and the conveyance speed of the paper conveyance belt 513. This skew angle Θ 514 is skew information, and indicates not only the skew angle of the printed output 20 but also the skew direction. At this time, the print document reading controller unit 510 transmits information on the skew angle Θ 514 to the inspection control unit 600 (S107).

  Next, the print original reading controller unit 510 controls the line sensor 512 using a signal that detects the presence or absence of paper as a trigger, and reads the image data of the printed output 20 as shown in FIG. 4 (S108). The print document reading controller unit 510 transmits the read image data to the inspection control unit 600. After reading the image data, the printed output 20 is conveyed to the print document discharge unit 700.

  As shown in FIG. 5, the inspection control unit 600 includes an inspection controller unit 610, an image processing unit 620, a feature point extraction unit 630, a storage device 640, an alignment processing unit (alignment unit) 650, a comparison determination unit (determination unit). 660. The inspection controller unit 610 includes an image processing unit 620, a feature point extraction unit 630, a storage device 640, an alignment processing unit 650, a comparison determination unit 660, a printing device controller unit 410, a print document reading controller unit 510, a print document discharge unit. Connect to the paper controller unit 710.

  The inspection controller unit 610 receives each setting value and inspection setting value of the print job set by the user in the printing apparatus operation unit 200 in step S101 and stores them in the storage device 640 (S109). Subsequently, the inspection controller unit 610 receives digital data (reference image data) such as RIP data that is the basis of the print image, and job attribute information from the printing device controller unit 410 and stores them in the storage device 640. (S110). Here, the inspection controller unit 610 functions as a receiving unit that receives an original image (reference image data). An example of the reference image data 900 is shown in FIG. As the reference image data, when the job performed by the printing apparatus unit 10 is a copy job, image data (bitmap data) of a document read by the image sensor 123 is used, and in the case of a PDL job, the PDL data is subjected to RIP processing. RIP data is used. Any image data is received by the inspection controller unit 610.

  Further, the inspection controller unit 610 receives information on the skew angle Θ 514 of the printed output 20 calculated in step S107 from the print document reading controller unit 510 and stores it in the storage device 640 (S111). Here, the inspection controller unit 610 functions as an acquisition unit that acquires skew information of the printed matter (printed output matter 20).

  Further, the inspection controller unit 610 receives the print original image data (scanned image data) read by the line sensor 512 in step S108 and stores it in the storage device 640 (S112). Here, the inspection controller unit 610 functions as a reading unit that acquires a read image (scanned image data) obtained by reading a printed matter. An example of the scanned image data 910 is shown in FIG.

  Further, the inspection controller unit 610 controls image inspection processing of processing S113 to S115 described later using the stored reference image data and scan image data, and transmits the result to the print document discharge controller unit 710 (S116). ). In step S116, the inspection controller unit 610 transmits each set value of the print job received in step S109 and stored in the storage device 640 to the print document discharge controller unit 710.

  The image processing unit 620 performs image processing as preprocessing for comparing and collating the scanned image data and the reference image data. Specifically, descreen processing, resolution conversion processing, and color space conversion processing are performed.

  The feature point extraction unit 630 extracts the feature point 901 of the image of the reference image data 900 image-processed by the image processing unit 620 (S113). The feature point 901 here means a corner edge point (corresponding to the corner of the print image “A” in FIG. 6C) of the image data as shown in FIG. Edge feature). A square patch image 902 having a plurality of pixels and a plurality of pixels including the edge feature is extracted from the reference image data 900. As an extraction method, for example, a general method such as a corner detection algorithm of Harris and Stephens can be used. However, the extraction method is not limited to this.

  FIG. 11 shows a processing flow of the alignment processing in S114 performed by the alignment processing unit 650.

  First, the alignment processing unit 650 searches for a corresponding patch image 912 (FIG. 6D) in the scan image data 910 using the patch image 902 including the feature point 901 in the extracted reference image data 900. Thus, the shift amount (parallel movement amount) between both patch images is calculated and obtained (S1141). The obtained shift amount is used when affine transformation parameters are calculated in S1142 described later. The shift amount is obtained by the following method. Note that the shift amount obtained in S1141 is not only one, but a plurality of shift amounts obtained for a plurality of patch images in the reference image data.

  First, the alignment processing unit 650 performs a rotation process of a predetermined angle (for example, 0.1 °) on the patch image 902 extracted by the feature point extraction unit 630. The alignment processing unit 650 performs alignment by obtaining a correlation between the image subjected to the rotation processing and the patch image in the scan image data 910 corresponding to the position of the patch image 902. As one of the methods for obtaining the correlation, for example, there is a method for obtaining the correlation between patch images using Fourier transform. Specifically, a Fourier transform is performed on both patch images to obtain a product, and an inverse Fourier transform is performed on the product to obtain a correlation between both patch images. The correlation obtained in this way is obtained as a correlation function between each shift amount between patch images and a correlation coefficient corresponding to the shift amount. In this correlation function, the correlation coefficient corresponding to the shift amount so that the patch images match each other has a high numerical value.

  Based on this correlation, the alignment processing unit 650 searches for a patch image (partial image in the scanned image data 910) 912 corresponding to the patch image 902, and determines the parallel movement amount of the center coordinates of the patch images 902 and 912. Obtained as a shift amount. As a result of such a search, the patch image 912 that has been found is a scanned image of the patch image 902 that has been displaced. In the following, the fact that the misaligned patch image 902 and the found patch image 912 substantially match is referred to as fitting. The shift amount is calculated for a patch image including a plurality of other feature points in the reference image data 900, and a shift amount between the plurality of patch images is obtained. The above is the method for obtaining the shift amount between patch images. In addition, in order to obtain a shift amount that matches between patch images, a correlation coefficient is obtained using Fourier transform, but this method is applicable to any method that obtains a shift amount that matches patch images. It does not have to be limited.

  When calculating the shift amount between the above patch images, the patch image 902 is rotated, which will be described in detail with reference to FIGS.

  A conventional rotation process is shown in FIG. Conventionally, the rotation process performed on the patch image 902 of the reference image data is to rotate the clock image alternately and counterclockwise. At this time, the rotation angle of the rotation process is increased by, for example, 0.1 °, and the fitting process is performed. The fitting process is a process for finding a patch image 902 and a patch image 912 to be fitted. In this fitting process, a correlation function between an image obtained by rotating the patch image 902 (original image after rotation) and the patch image in the scanned image data is obtained, and the correlation coefficient in this correlation function is equal to or greater than the correlation threshold. This is processing for searching for a patch image 912. The method for obtaining the correlation function in the present embodiment is as described above. When the correlation coefficient is equal to or greater than the correlation threshold, the fitting process (positioning process) is completed. When the correlation coefficient is less than the threshold, the patch image 902 is further rotated and the fitting process is continued. That the correlation coefficient is equal to or greater than the correlation threshold is also referred to as the correlation is equal to or greater than the correlation threshold, and that the correlation coefficient is less than the correlation threshold is also referred to as the correlation is less than the correlation threshold.

  In the example of FIG. 7A, the patch image 912 is obtained after performing rotation processing 914 to 917 four times. An arrow extending from the center of the patch image 912 in the scanned image data 910 corresponds to an edge vector corresponding to the feature point 901 of the patch image 902.

  On the other hand, the processing flow of FIG. 7B and FIG. 12 is the method of the present embodiment. First, the alignment processing unit 650 refers to the skew angle Θ 514 of the printed output 20 stored in the storage device 640. Then, the rotation direction for the fitting process is determined (S11411).

  In the present embodiment, the rotation direction in the fitting process is determined by the alignment processing unit 650 referring to the skew angle Θ 514 and determining whether the skew direction of the printed output 20 is the clockwise direction (S11413). . For example, when the print output 20 is skewed clockwise from the value of the skew angle Θ 514, the fitting process is performed by rotating the patch image 902 clockwise only by a predetermined angle (0.1 °). It performs (S11414, S11416). In the example of FIG. 7B, two rotation processes 918 to 919 are sufficient, and the processing time of the fitting process is reduced. When the printed output 20 is skewed counterclockwise, the patch image 902 is rotated only counterclockwise by 0.1 ° to perform the fitting process (S11415, S11416). That is, the patch image 902 is rotated in the skew direction indicated by the skew information.

  With the above process, the fitting process is completed at a higher speed than in the prior art.

  Next, the alignment processing unit 650 calculates affine transformation parameters for the entire image between the reference image data 900 and the scanned image data 910 based on the plurality of shift amounts obtained in S1141 (S1142). The affine transformation parameters are expressed by the image rotation amount, enlargement / reduction ratio, and shift amount. The affine transformation (two-dimensional affine transformation) is expressed by the following expression when the input image gi (x, y) is the output image go (X, Y). The affine transformation parameter is represented by Γ for the counterclockwise rotation amount, k for the enlargement / reduction ratio, and s and t for the shift amounts in the main scanning direction and the sub scanning direction.

  Next, the registration processing unit 650 divides the reference image data 900 and the scanned image data 910 into blocks (S1143). In the example shown in FIG. 8, the page image data is divided into 3 × 5 blocks. The alignment processing unit 650 performs affine transformation on the patch image of each block using the above-described affine transformation parameters of the entire image, and obtains a shift amount before and after the affine transformation for each patch image. Then, a difference (nonlinear distortion amount) between the shift amount and the shift amount obtained in S1141 is obtained for each patch image, and based on this, the nonlinear distortion amount of each block is obtained. For a block having no patch image, the nonlinear distortion amount of the block having the patch image is interpolated to obtain the nonlinear distortion amount of the block (S1144). FIG. 8B shows the nonlinear distortion amount of each block. Here, the amount of nonlinear distortion of each block is simply expressed as a vector. Based on the obtained non-linear distortion amount, the reference image data 900 is aligned with the scanned image data 910 for each block.

  The comparison determination unit 660 performs image collation between the reference image data 940 and the scan image data 910 that have been aligned in block units by the alignment processing unit 650 (S115).

  In the image collation, as shown in FIG. 9, one pixel of the scan image data 910 is set as a target pixel 920. Pixel comparison is performed between the target pixel 920 and each pixel (reference pixel 930) in a square area including the pixel on the reference image data 940 after the alignment processing of the same coordinates as the target pixel 920. If the difference data with a certain reference pixel 930 is less than a certain value, the target pixel 920 of the scanned image data 910 exists in the square area of the reference image data 940 after the alignment processing, and the target pixel is correct data. to decide. If the difference data from all the reference pixels 930 is equal to or greater than a certain value, the target pixel 920 of the scanned image data 910 does not exist in the square area of the reference image data 940 after the alignment process, and the target pixel is defective data. Judge that there is. Such image collation is performed for all the pixels of the scanned image data 910.

  Thereafter, if the number of defect data is less than the threshold set by the user using the printing apparatus operation unit 200, the scan image data 910 is determined to be good, and if it is equal to or greater than the threshold, the scan image data 910 is determined to be defective. That is, the comparison / determination unit 660 functions as a determination unit that determines the quality of the printed material that is the basis of the scanned image data. The comparison determination unit 660 transmits the inspection result to the print document discharge controller unit 710 (S116).

  In the print document discharge unit 700, the print document discharge controller unit 710 receives the scan image data inspection result and the discharge setting value from the inspection controller unit 610 (S117), and is sent to the print document discharge unit 700. Paper discharge control of the printed output 20 is performed.

  If the inspection result received in S117 is a non-defective product determination (S118), the print document discharge controller 710 discharges the printed output 20 to a non-defective product tray (OK tray) 701 (S119), and the inspection result is determined to be defective. If so (S118), discharge control is performed so that the printed output 20 is discharged to the defective tray (NG tray) 702 (S120).

  The print output 20 sent to the OK tray 701 is discharged after the completion of all jobs to the paper discharge unit 1000 according to the paper discharge setting value received in S117 (S121), or for each number of copies. The paper is discharged (S122). The print document discharge controller unit 710 conveys the discharged print output 20 to the finisher unit 800. The finisher unit 800 receives each setting value of the print job transmitted in S101 (S123), and based on each received setting value, the cutting process, the binding process, the punching process, and the folding process for the printed output 20 A finishing process such as the above is performed (S124). Then, the finisher unit 800 discharges the printed output 20 after the finishing process to the paper discharge unit 1000 (S125).

  The above is the description of this embodiment. According to the inspection apparatus of the present embodiment, since the rotation direction of the fitting process is uniquely determined based on the skew information of the printed matter, the alignment process can be speeded up.

  In this embodiment, the fitting process is performed regardless of the magnitude of the skew angle of the skew information. However, when the skew angle of the skew information exceeds a threshold value, the inspection processing unit performs the fitting process. The error processing may be performed without performing the above. The error processing here is processing for discharging the printed matter to the defective tray 702. In the error processing, the printing apparatus operation unit 200 may indicate that the error is due to skew of the printed matter, or the number of errors due to skew is counted. May be displayed on the printing apparatus operation unit 200.

(Example 2)
In the first embodiment, the direction of rotation is determined from the value of the skew angle Θ 514 in the fitting process of the edge vector in the patch including the feature point. In the second embodiment, the edge vector of the reference image data is first rotated by the value of the skew angle Θ514. Then, with the rotation position of the edge vector of the reference image data rotated in advance as a reference, the fitting process is alternately performed in the clockwise direction and the counterclockwise direction as in the conventional example. The rotation amount estimation processing flow in the present embodiment will be described with reference to FIG. Unless otherwise specified, the other configurations are the same as those in the first embodiment.

  The alignment processing unit 650 refers to the skew angle Θ 514 of the printed output 20 stored in the storage device 640 (S11421), and rotates the patch including the edge vector of the reference image data by the skew angle Θ 514 (S11422). ).

  Next, the alignment processing unit 650 determines whether or not the rotated edge vector matches the edge vector of the scanned image data (S11426). The coincidence between the edge vectors here is as described in the first embodiment. If it is determined that the edge vectors match, the alignment processing unit 650 ends the rotation amount estimation process. If it is determined that the edge vectors do not match, it is determined whether the rotation direction of the edge vector of the reference image data performed in the immediately preceding fitting process is counterclockwise (S11423).

  Next, in step S11423, when the alignment processing unit 650 determines that the rotation direction is counterclockwise, the alignment processing unit 650 performs a fitting process of rotating the edge vector of the reference image data by 0.1 ° clockwise. The process proceeds to S11426. If it is determined in S11423 that the rotation direction is clockwise, the alignment processing unit 650 performs a fitting process for rotating the edge vector of the reference image data by 0.1 ° in the counterclockwise direction. The process proceeds to S11426.

  The rotation amount of the edge vector of this embodiment is estimated by the above fitting process.

  According to the present embodiment, compared with the first embodiment, when the skew angle measurement accuracy is high and the amount of misalignment with respect to the paper during printing by the printing apparatus unit 10 is small, the alignment processing time is further shortened.

(Other examples)
Note that the object of the present invention can also be achieved by supplying a computer-readable storage medium storing a program code (computer program) of software that implements the functions of the above-described embodiments to a system or apparatus. It can also be achieved by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a nonvolatile memory card, a ROM, or the like can be used.

  Further, the functions of the above-described embodiments are realized by executing the program code read by the computer. In addition, an OS (operating system) running on a computer performs part or all of actual processing based on an instruction of a program code, and the above-described embodiment is realized by the processing.

Claims (8)

Reading means for acquiring a read image obtained by reading a printed matter on which an original image is printed;
Receiving means for receiving the original image;
Obtaining means for obtaining skew information indicating a skew direction of the printed matter;
Extracting means for extracting a patch image including edge features from the original image received by the receiving means;
Positioning means for aligning the original image by rotating the patch image extracted by the extracting means based on the skew information and searching for a portion of the read image corresponding to the rotated patch image When,
A determination unit that determines the quality of the printed matter by comparing the read image with the original image that has been aligned by the alignment unit;
An inspection apparatus comprising: Having a conveying means for conveying the printed matter;
The inspection apparatus according to claim 1, wherein the acquisition unit acquires the skew information obtained by detecting a passing time of an end of a printed material conveyed by the conveyance unit. The skew information is information indicating a skew direction and a skew angle of the printed matter,
3. The inspection apparatus according to claim 2, wherein when the skew angle indicated by the skew information exceeds a threshold value, the acquisition unit performs error processing without performing processing by the positioning unit. The alignment means includes
When the extracted patch image is rotated in the skew direction indicated by the skew information, the correlation between the rotated patch image and the partial image in the read image is obtained, and the correlation is equal to or greater than a correlation threshold When the alignment of the original image is completed and the correlation is less than the correlation threshold, the rotated patch image is further rotated in the skew direction indicated by the skew information to perform the alignment. The inspection apparatus according to any one of claims 1 to 3, wherein the inspection apparatus is characterized in that: The alignment means includes
The extracted patch image is rotated based on the skew direction and the skew angle indicated by the skew information, a correlation between the rotated patch image and the partial image in the read image is obtained, and the correlation is If the correlation image is equal to or greater than the correlation threshold, the alignment of the original image is completed. If the correlation is less than the correlation threshold, the rotated patch image is further rotated by a predetermined angle to perform alignment. The inspection apparatus according to any one of claims 1 to 3, wherein the inspection apparatus is characterized in that: Reading means for acquiring a read image obtained by reading a printed matter on which an original image is printed;
Receiving means for receiving the original image;
Obtaining means for obtaining skew information indicating a skew direction of the printed matter;
Alignment means for aligning the original image by rotating the original image received by the receiving means based on the skew information;
A determination unit that determines the quality of the printed matter by comparing the original image subjected to the alignment and the read image;
An inspection apparatus comprising: A reading step in which a reading unit acquires a read image obtained by reading a printed matter on which the original image is printed;
A receiving step for receiving the original image;
An acquiring step for acquiring skew information indicating a skew direction of the printed matter;
An alignment step of aligning the original image by rotating the original image received in the reception step based on the skew information;
A determination step of determining the quality of the printed matter by comparing the original image subjected to the alignment and the read image;
An inspection method comprising:   A computer program that causes a computer to function as each means according to claim 1.

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