US-12621392-B2 - Inspection apparatus, inspection method, and storage medium that provide position adjustment by at least one of linear transformation or non-linear transformation of inspection image

Abstract

The occurrence of an erroneous inspection is suppressed by preventing a failure of position adjustment by non-linear transformation. In position adjustment between an inspection image obtained by reading a printed material and a reference image, after performing position adjustment by linear transformation, only in a case where a certain condition is satisfied, position adjustment by non-linear transformation is further performed for the inspection image for which the position adjustment by linear transformation has been performed.

Inventors

• Riko MIURA

Assignees

• CANON KABUSHIKI KAISHA

Dates

Publication Date

20260505

Application Date

20230526

Priority Date

20220610

Claims (8)

1. 1 . An inspection apparatus for inspecting a printed material that is output from a printing apparatus, the inspection apparatus comprising: one or more memories storing instructions; and one or more processors executing the instructions to perform position adjustment, between an inspection image generated by reading an image printed on a sheet and a reference image that is used as a reference in the inspection, wherein in performing the position adjustment, the one or more processors: performs a linear transformation for the inspection image; determines whether a type of the reference image is a first type or a second type, wherein: the first type is where an image as the reference image is included in image data of a print job; and the second type is where an image as the reference image is obtained by reading a sheet having no print defect; and performs a linear transformation for the inspection image that has been performed with the linear transformation, in a state where the type of the reference image has been determined to be the first type.
2. 2 . The inspection apparatus according to claim 1 , wherein the one or more processors do not perform the non-linear transformation for the inspection image that has been performed with the linear transformation, in a state where the reference image has been determined to be the second type.
3. 3 . The inspection apparatus according to claim 1 , wherein the one or more processors further execute the instructions to: register information representing whether the type of the reference image to be applied in the inspection is the first type or the second type; and determine, based on the registered information, whether the type of the reference image is the first type or the second type.
4. 4 . The inspection apparatus according to claim 1 , wherein the one or more processors further execute the instructions to: register information representing whether or not a blank sheet was used to print the image; and determine, based on the registered information, whether the sheet used to print the image includes an object other than the image.
5. 5 . The inspection apparatus according to claim 1 , wherein the position adjustment by the linear transformation is position adjustment using affine transformation.
6. 6 . The inspection apparatus according to claim 1 , wherein the position adjustment by the non-linear transformation is position adjustment using Free-Form Deformations.
7. 7 . An inspection method of inspecting a printed material that is output from a printing apparatus, the inspection method comprising the step of: performing position adjustment, between an inspection image generated by reading an image printed on a sheet and a reference image that is used as a reference in the inspection, by: performing a linear transformation for the inspection image; determining whether a type of the reference image is a first type or a second type, wherein: the first type is where an image as the reference image is included in image data of a print job; and the second type is where an image as the reference image is obtained by reading a sheet having no print defect; and performing a non-linear transformation for the inspection image that has been performed with the linear transformation, in a state where the type of the reference image has been determined to be the first type.
8. 8 . A non-transitory computer readable storage medium storing a program executable by a computer to perform an inspection method of inspecting a printed material that is output from a printing apparatus, the inspection method comprising the step of: performing position adjustment, between an inspection image generated by reading an image printed on a sheet and a reference image that is used as a reference in the inspection, by: performing a linear transformation for the inspection image; determining whether a type of the reference image is a first type or a second type, wherein: the first type is where an image as the reference image is included in image data of a print job; and the second type is where an image as the reference image is obtained by reading a sheet having no print defect; and performing a non-linear transformation for the inspection image that has been performed with the linear transformation, in a state where the type of the reference image has been determined to be the first type.

Description

BACKGROUND Field The present disclosure relates to an inspection technique of a printed material. Description of the Related Art There is a case where soiling occurs in a printed material that is output from a printing apparatus, which is caused by a color material, such as ink and toner, sticking to an unintentional portion or the like. Alternatively, there is a case where a sufficient amount of color material does not stick to the portion at which an image is to be formed and color voids in which the color becomes paler than the original color occur. The so-called print defect, such as soiling and color voids, reduces the quality of a printed material. In order to secure the quality of a printed material, inspection of a print defect is performed. The visual inspection performed by an inspector visually inspecting the presence/absence of a print defect requires much time and cost, and therefore, an inspection system performing inspection automatically without relying on visual inspection has been proposed. For the inspection system, there is a method in which a scanned image (inspection image) obtained by reading an inspection-target printed material with a scanner and an image (reference image) registered in advance as an inspection reference are compared and the presence/absence of a print defect is inspected based on the difference between the two images. In a case of the inspection method such as this in which images are compared, the position adjustment between two images considerably affects the accuracy of the inspection, and therefore, it is important to perform position adjustment with a high accuracy. As the general position adjustment technique, position adjustment by linear transformation using affine transformation or the like is known. However, it is not possible for the position adjustment by linear transformation to deal with a local distortion (partial magnification variation) resulting from conveyance unevenness and stretch of paper, and therefore, there is such a problem that the position adjustment accuracy decreases. In this regard, as a technique to perform position adjustment between two images whose local distortions are different, for example, there is a position adjustment technique by non-linear transformation represented by FFD (Free-Form Deformations) In the FFD, a plurality of control points is arranged in an image, control points corresponding between a reference image and an inspection image are searched for, and the image is transformed so that the amount of shift between the corresponding control points becomes the minimum. Here, in a case where an object within the image is not the same between the inspection image and the reference image, for example, such as a case where the inspection image includes a character or graphics not existing in the reference image, it may happen that the corresponding control points are erroneously determined. In this case, the image is transformed so that the amount of shift between the control points becomes the minimum, which do not actually correspond to each other. As a result of that, the inspection is performed in the state where the position adjustment between both the images is not performed, and therefore, there is such a problem that an erroneous inspection is performed, in which a print defect is detected erroneously. SUMMARY The present disclosure has been made in view of the problem as above and an object thereof is to suppress the occurrence of an erroneous inspection by preventing a failure of position adjustment by non-linear transformation. The inspection apparatus according to the present disclosure is an inspection apparatus for inspecting a printed material that is output from a printing apparatus, the inspection apparatus including: one or more memories storing instructions; and one or more processors executing the instructions to: perform position adjustment between an inspection image generated by reading the printed material and a reference image that is used as a reference in the inspection, wherein in the position adjustment: position adjustment by linear transformation is performed for the inspection image; and in a case where a certain condition is satisfied, position adjustment by non-linear transformation is performed for the inspection image obtained by performing the position adjustment by linear transformation. Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a configuration of an inspection system; FIG. 2 is a function block diagram showing an internal configuration of an image processing unit 118; FIG. 3 is a diagram showing an example of a UI screen for registering sheet information; FIG. 4 is a schematic diagram explaining a process of printing processing in a case where a printed object exists on a sheet; FIG. 5 is a