JP2017116378A - Corrugation molding inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrugation molding inspection method capable of easily inspecting whether a middle core is formed into a proper waveform with respect to a corrugation ball sheet during the running of a production line.SOLUTION: A corrugation molding inspection method is constituted such that a corrugation ball sheet 10 during running of a production line after a middle core 11 is molded in a wave form is projected with light from a light source located in a direction inclined to the perpendicular line of a sheet surface, a striped pattern image 30 is acquired in which a dark part 31 which is an image of a portion turned into a shadow with light interrupted by a crest part in the waveform by photographing the corrugation ball sheet by a camera at an angle different from the light source 21 alternates with a bright part 32 which is the image of the portion irradiated with the light, and determination is performed on whether or not the middle core is properly molded on the basis of image processing of the striped pattern image.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a corrugated forming inspection method for inspecting whether or not a core is formed into an appropriate waveform in a corrugated cardboard production line.

  In the manufacture of corrugated cardboard sheets, the corrugated crests are crushed and lowered in the process from when the core base paper is formed into a corrugated shape and bonded to the liner, and the core is partially removed from the liner. Defects such as “steps” that protrude and become higher due to peeling or the like may occur. In the past, the present applicant has proposed a method and an apparatus for detecting such a step-forming defect in a corrugated cardboard sheet that is traveling on a production line (see Patent Documents 1 and 2).

  The basic principle of the techniques of Patent Documents 1 and 2 is that light that is inclined with respect to the corrugated core is projected onto a corrugated cardboard sheet that is traveling on a production line, and is reflected at the peak portion of the corrugated waveform. Of the received light, the light projection condition or the light receiving condition is adjusted so that only the light reflected from the mountain whose height is within the allowable range is received by the light receiver. Light reflected by a high mountain outside the tolerance or a low mountain outside the tolerance does not enter the receiver. Therefore, it is possible to easily detect a step forming defect depending on whether the light receiver has detected light, in other words, “presence / absence of light”.

  As with the above-described technique, the present applicant can easily check whether or not the core is formed into an appropriate corrugated sheet for a corrugated cardboard sheet traveling on the production line. Has continued to consider. The present invention has been made in the study.

Japanese Patent No. 2571520 Japanese Patent No. 4857382

  As described above, the present invention provides a corrugated forming inspection method that can easily inspect whether or not the core is formed into an appropriate corrugated corrugated cardboard sheet that is traveling on the production line. Is an issue.

In order to solve the above problems, the step forming inspection method according to the present invention is:
“On the corrugated cardboard sheet that is running on the production line after the core is formed into a corrugated shape,
Project light from a light source in a direction inclined to the normal of the sheet surface,
By photographing the cardboard sheet with a camera at an angle different from the light source,
A dark pattern that is an image of a portion that is shaded by light being blocked by a mountain portion in the waveform and a bright pattern that is an image of a portion that is irradiated with light are obtained, and a striped pattern image is obtained.
Based on the image processing of the striped pattern image, it is determined whether or not the core is properly formed. "

  When light is projected onto a corrugated cardboard sheet with a corrugated core from a direction inclined with respect to the normal of the sheet surface, and taken from a direction different from the light source, the light is blocked by the peaks in the waveform and becomes a shadow. A striped pattern image is obtained in which a dark portion that is an image of a dark portion and a bright portion that is an image of a portion that is exposed to light are alternated. When the central core is formed in an appropriate waveform, the height of the peak portion is equal, and therefore the dark portion and the bright portion are each band-shaped with a constant width. However, if there are some peaks that are lower than the normal peaks due to crushing, etc., light will hit the shadowed areas, so the bright areas will appear partially in the dark bands. . Conversely, if there is a peak that is higher than the normal peak due to peeling of the core, etc., the part that should be exposed to light will be shadowed. The dark part appears partially.

  Therefore, the image processing of the striped pattern image is performed in parallel with the production of the corrugated cardboard sheet in the production line, and the time-series fluctuation of the striped pattern image is detected, or the acquired striped pattern image has a proper waveform at the center. It is possible to easily inspect whether or not the core is formed into an appropriate waveform by analysis such as comparison with a striped pattern image in the case where the core is formed.

  Note that image processing and determination based on the image processing can be performed while shifting the inspection area in units of the inspection area set in the striped pattern image.

The step forming inspection method according to the present invention has the above-described configuration.
“The decision is
This is performed based on the areas of the dark part and the bright part in the striped pattern image ”.

  The widths of the dark part and the bright part in the striped pattern image depend on the angle of the projected light and the angle of photographing, but are constant if the inspection is performed with the position of the light source and the position of the camera fixed. Therefore, for example, if an inspection area is set in a striped pattern image and the area ratio of the dark part and the bright part in the inspection area, the area ratio of the dark part in the inspection area, or the area ratio of the bright part in the inspection area is detected, If the measured value is constant, it can be determined that the core of the traveling corrugated cardboard sheet is formed into an appropriate waveform. On the other hand, when the detected value fluctuates as described above, it can be determined that a defect having a low peak or a high defect in the peak has occurred in the core waveform.

The step forming inspection method according to the present invention has the above-described configuration.
“The decision is
Of the rows of pixels arranged in the width direction of the cardboard sheet in the striped pattern image, the number of columns in which only the dark pixels are continuous, or the number of columns in which only the bright pixels are continuous Based on ".

  When the core is formed into an appropriate waveform, the widths of the dark part and the bright part in the running direction of the cardboard sheet are constant in the striped pattern image. Therefore, when focusing on the pixel rows arranged in the width direction in the striped pattern image, when the center is formed into an appropriate waveform, only the dark pixels are continuous or only the bright portions are continuous. There are only columns of pixels that are present. However, if there are some peaks that are lower than the normal peaks, the bright areas appear partially in the dark bands as described above, so that the pixel rows in which only the dark areas are aligned are discontinuous. Become. Similarly, if there is a part of the peak that is higher than the normal peak, a dark part partially appears in the band of the bright part, so that the pixel rows in which only the bright part is arranged are discontinuous. Therefore, it is possible to determine whether or not the core is formed into an appropriate waveform based on the number of columns in which dark pixels are continuous or the number of columns in which bright pixels are continuous. it can.

The step forming inspection method according to the present invention has the above-described configuration.
“The determination is performed based on the linearity of the pixels at the boundary by detecting pixels at the boundary between the dark portion and the bright portion in the striped pattern image”.

  In the striped pattern image, when attention is paid to the row of pixels lined up in the running direction of the cardboard sheet, it is possible to detect a boundary pixel that changes from a dark part to a bright part or a boundary pixel that changes from a bright part to a dark part. When the core is formed into an appropriate waveform, the pixels at these boundaries are arranged on a straight line parallel to the width direction of the cardboard sheet. On the other hand, when some of the peaks that are lower than the normal peaks and some bright parts appear in the dark band, the border pixels line up along the contour of the bright parts, The boundary pixels are not arranged on a straight line. Similarly, when some of the peaks that are higher than the normal peaks and some dark areas appear in the bright bands, the border pixels line up along the contours in the dark areas. The boundary pixels are not arranged on a straight line. Therefore, it can be determined whether or not the core is shaped into an appropriate waveform depending on whether or not the boundary pixel is on a straight line.

  As described above, as an effect of the present invention, a corrugated sheet forming inspection method that can easily inspect whether or not the core is formed into an appropriate corrugated sheet corrugated cardboard sheet traveling on the production line. Can be provided.

It is a figure which shows arrangement | positioning of the light source and camera in the step molding inspection method which is one Embodiment of this invention. It is a figure which shows typically the striped pattern image in case the center core is shape | molded by the appropriate waveform. It is a figure which shows typically a striped pattern image about the case where (a) a part of peak part is low, and (b) the part of peak part is high. (A), (b) It is a figure which illustrates the inspection area | region in a striped pattern image. (A), (b) It is explanatory drawing of the determination process of 2nd embodiment. (A), (b) It is explanatory drawing of the determination process of 3rd embodiment. It is a block diagram of the step forming inspection apparatus used for the step forming inspection method which is one Embodiment of this invention.

  Hereinafter, a step forming inspection method that is a specific embodiment of the present invention and an inspection apparatus 1 used for the step forming inspection method will be described with reference to FIGS. 1 to 7.

  First, the configuration of the step forming inspection apparatus 1 will be described. The corrugated molding inspection apparatus 1 includes a light source 21 that projects light onto a corrugated cardboard sheet 10 that is traveling along a production line, a camera 22 that photographs the corrugated cardboard sheet 10 onto which light is projected, and an image photographed by the camera 22. And a computer 50 that performs a process of determining whether or not the core 11 is formed into an appropriate waveform.

  As shown in FIG. 1, the light source 21 projects light from a direction inclined with respect to the perpendicular Z of the sheet surface of the cardboard sheet 10. Here, a case is shown in which light is projected obliquely from the rear during traveling of the single-sided cardboard sheet (corrugated cardboard sheet 10) after the back liner 12 is bonded to the molded core 11. Further, FIG. 1 illustrates a case where an inspection is performed in a part where a single-sided cardboard sheet is wound around a roll 20 in a production line, and the perpendicular Z on the sheet surface is a normal line of the roll 20. is there.

  The camera 22 is a line sensor camera 22 that acquires a one-dimensional image in a direction orthogonal to the traveling direction of the cardboard sheet 10 (Y direction in FIG. 2), that is, the width direction of the cardboard sheet 10 (X direction in FIG. 2). Then, a one-dimensional image continuously photographed as the cardboard sheet 10 travels is transmitted to the computer 50. Further, in the line sensor camera 22, even if the width is changed by changing the type of the cardboard sheet 10, the light receiving elements are arranged with a length sufficient to capture a one-dimensional image over the entire width of the cardboard sheet 10. Has been.

  Furthermore, an encoder 25 is attached to a portion synchronized with the drive unit in the mechanical configuration of the production line, for example, a rotation mechanism unit of the roll 20. An electrical signal from the encoder 25 is sent to the computer 50.

  The computer 50 includes a main storage device as a hardware configuration, a central processing unit (CPU) that performs processing according to a program stored in the main storage device, and an auxiliary storage device 53 such as a hard disk.

  Here, an image processing program for causing the computer 50 to function as the image processing means 51 is stored in the main storage device. A process based on this image processing program forms a two-dimensional image from the one-dimensional image transmitted from the camera 22. Then, the coordinates of the pixel in the two-dimensional image and the actual position on the corrugated cardboard sheet 10 are associated with each other by the electrical signal sent from the encoder 25 and the positional relationship between the photographing location by the camera 22 and the encoder 25. The main storage device also stores a determination program that causes the computer 50 to function as determination means 52 that performs a determination process as to whether or not the core 11 is formed into an appropriate waveform based on the two-dimensional image. Yes.

  The auxiliary storage device 53 stores one-dimensional image data transmitted from the camera 22, two-dimensional image data after image processing, cardboard information such as the type and pitch of the cardboard sheet 10 necessary for image processing, Reference values in image processing and determination processing, determination results as to whether or not the core 11 is formed into an appropriate waveform, and the like can be stored.

  The corrugated molding inspection apparatus 1 also includes a keyboard and a pointing device for inputting the corrugated cardboard information and reference values to the computer 50, and a monitor for displaying the process and results of processing by the computer 50. And an output device 62 such as a printer, and an alarm device 65 for notifying by an alarm light or an alarm sound when it is determined that the core 11 is not formed into an appropriate waveform as a result of processing by the computer 50. .

  Further, the computer 50 is connected to the office computer 67 of the manufacturer of the corrugated cardboard sheet 10 and the production management device 68 of the production line so as to be capable of wired communication or wireless communication. The cardboard information and the reference value can be input from the office computer 67 to the computer 50, and the process and results of the processing by the computer 50 can be transmitted from the computer 50 to the office computer 67. Alternatively, the cardboard information and the reference value may be transmitted from the office computer 67 to the production management device 68, stored in the production management device 68, and transmitted from the production management device 68 to the computer 50.

  Next, a step forming inspection method performed using the step forming inspection apparatus 1 having the above-described configuration will be described. In the step forming inspection method of the present embodiment, the light source 21 is in a direction inclined with respect to the perpendicular Z of the sheet surface to the corrugated cardboard sheet 10 that is running on the production line after the core 11 is formed into a corrugated shape. By projecting light from the light source and photographing the corrugated cardboard sheet 10 with a camera 22 at an angle different from that of the light source 21, a dark part 31 which is an image of a shadowed part by a light peak blocked by a mountain part in the waveform, A striped pattern image 30 in which bright portions 32 that are images of the hitting portions are alternately obtained is acquired, and whether or not the core 11 is appropriately formed based on the image processing of the striped pattern image 30 Is to do.

In addition, here, the reference numerals “F _N ” and “F” respectively denote a normal height peak portion in which the waveform is properly formed, a peak portion lower than the proper case, and a peak portion higher than the proper case. _L ", and it is using the" _{F H} ".

When light is projected onto the corrugated cardboard sheet 10 in which the core 11 is formed in a waveform from a direction inclined with respect to the normal Z of the sheet surface and taken from a direction different from the light source 21, the light is blocked by the peaks in the waveform. Thus, a striped pattern image 30 is obtained in which a dark portion 31 that is an image of a shadowed portion and a bright portion 32 that is an image of a portion that is exposed to light are alternated. Corrugated medium 11 is formed in the proper waveform, if the crests F _N of normal height is continuous, as shown in FIG. 2, dark portions 31 and light portion 32 each have a constant width It is strip-shaped. The width of each of the dark part 31 and the bright part 32 depends on the angle at which light is projected and the angle at which the image is taken. However, if the positions of the light source 21 and the camera 22 are fixed, these widths are constant.

However, the stage crushing or the like, to be in part ridges F _L which is lower than the normal height, since the originally light hits the portion to be a shadow, as shown in FIG. 3 (a), a dark portion 31 The bright part 32 partially appears in the band. On the other hand, if there is a peak portion F _H that is higher than the normal height due to the core 11 being peeled off from the back liner 12, the portion that is supposed to be exposed to light becomes a shadow. As shown in FIG. 3B, the dark part 31 partially appears in the band of the bright part 32.

  Therefore, by analyzing the dark part 31 and the bright part 32 in the striped pattern image 30, it can be determined whether or not the waveform is properly shaped.

  In order to clarify the dark part 31 and the bright part 32 in the striped pattern image 30, a two-dimensional image formed based on the one-dimensional image by the licensor camera 22 may be binarized with a predetermined threshold value. Good.

  In the present embodiment, in the striped pattern image 30, an inspection area 40 that is a unit of determination processing is set. When the determination process is completed for one inspection region 40, the determination process is performed by shifting the inspection region 40, and the determination process is performed for the entire range of the striped pattern image 30 by repeating this.

  The dimension of the inspection area 40 is preferably an integral multiple of the corrugated pitch (distance between vertices of adjacent peaks) in the running direction (Y direction) of the cardboard sheet 10. FIG. 2 illustrates the case where the length in the Y direction of the inspection region 40 is one pitch. For example, if a one-dimensional image is acquired for each travel distance of 0.1 mm based on the pulse signal of the encoder 25 and one pitch of the waveform is 6 mm, the inspection region 40 in FIG. There are 60 of them. The length in the Y direction of the two-dimensional image (stripe pattern image 30) formed by the line sensor camera 22 continuously taking one-dimensional images as the cardboard sheet 10 travels is the Y direction of the inspection region 40. The image processing and determination processing by the computer 50 is started when the length becomes equal to the length of the image. Then, while acquiring the next two-dimensional image, the inspection area 40 is shifted in the width direction (X direction) of the cardboard sheet 10 to perform image processing and determination processing.

  Therefore, the size of the inspection area 40 is determined by shifting the inspection area 40 in the X direction by the time required to acquire a two-dimensional image having a certain length in the Y direction. In consideration of the balance with the time required for performing image processing and determination processing over a period of time. For example, as shown in FIGS. 4A and 4B, when an inspection is performed on a corrugated cardboard sheet 10 having a short corrugated pitch, the inspection region 40 set in the striped pattern images 30b and 30c in the Y direction. If the length is a plurality of times the pitch of the waveform and the multiple is set to be larger as the pitch is shorter, the above time balance can be easily achieved.

Next, the determination process in the inspection area 40 will be described. The determination process of the first embodiment is performed based on the areas of the dark part 31 and the bright part 32 in the striped pattern image 30. 2 exemplifies a case where the area ratio of the dark part 31 and the bright part 32 in the inspection region 40 is 50:50. However, the area ratio of the dark part 31 and the bright part 32 depends on the projection angle of the light and the camera 22. It varies depending on the shooting angle. However, if the position of the light source 21 and the camera 22 is fixed, if the central core 11 is formed to the proper waveform, i.e., when the normal height ridges F _N are continuous, dark portions 31 and The area ratio of the bright part 32 is constant.

  Therefore, by detecting the area ratio between the dark part 31 and the bright part 32 in the inspection area 40, the area ratio of the dark part 31 in the inspection area 40, or the area ratio of the bright part 32 in the inspection area 40, and comparing this with the threshold value. It can be determined whether or not the core 11 is formed in an appropriate waveform. The threshold value can be set for the upper limit value and the lower limit value of the allowable range.

  If the computer 50 determines that the core 11 is not formed in an appropriate waveform, a failure detection signal is sent from the computer 50 to the alarm device 65, and a notification is given by the alarm device 65. At the same time, information regarding the occurrence position of the defect in the cardboard sheet 10 is output to the output device 62.

  Here, the threshold value may be a fixed value that is determined in advance and stored in the auxiliary storage device 53, or a fixed value that is input as needed by the operator via the input device 61.

  Alternatively, the computer 50 can be configured to change the threshold value as the determination process proceeds. For example, the moving average value of detection values used for determination, such as the area ratio of the dark portion 31 and the bright portion 32 in the inspection region 40, the area ratio of the dark portion 31 in the inspection region 40, or the area ratio of the bright portion 32 in the inspection region 40 Based on (the average value of the past N inspection areas 40) and the moving median value (the median value of the past N inspection areas 40), a threshold value can be set such as a plus or minus percentage. In this way, by changing the threshold value based on the actually detected value, even when the type of the cardboard sheet 10 traveling on the production line is changed, a new threshold value is input from the outside. Thus, the threshold value can be promptly corrected to an appropriate value without the need for setting.

  In the determination process of the second embodiment, the number of columns in which only the pixels of the dark portion 31 are continuous among the columns of pixels arranged in the width direction (X direction) of the cardboard sheet 10 in the striped pattern image 30 or This is based on the number of columns in which only the pixels of the section 32 are continuous.

  When the core 11 is formed into an appropriate waveform, in the striped pattern image 30, the widths of the dark part 31 and the bright part 32 in the running direction (Y direction) of the cardboard sheet 10 are constant. Therefore, when attention is paid to the column of pixels arranged in the width direction (X direction) in the inspection region 40, as shown in FIG. 5A, the column L1 in which only the pixels of the bright portion 32 are continuous in the inspection region 40. , L2 and only the columns L3 and L4 in which only the pixels of the dark part 31 are continuous exist. Actually, there are a large number of columns of pixels arranged in the X direction in one inspection region 40, but only a small number of columns are shown in FIG. 5 for the sake of clarity.

On the other hand, when the ridges F _L which is lower than the normal crest F _N is in part, as shown in FIG. 5 (b), since the bright part 32 appears partially in the band of the dark part 31 Originally, the columns L3 and L4 where only the pixels of the dark part 31 should have been continuous are discontinuous. May crests F _H which is higher than the normal crest F _N is in part, similarly, since the dark area 31 appears partially in the band light portion 32, the original pixels of the bright portion 32 Only the rows that should have been continuous become discontinuous. Therefore, by comparing the number of columns in which only the pixels of the dark portion 31 are continuous or the number of columns in which only the pixels of the bright portion 32 are continuous with the threshold value as described above, the core 11 is appropriate. It can be determined whether or not it is shaped into a simple waveform.

  The determination processing according to the third embodiment is performed based on the linearity of the alignment of the boundary pixels B by detecting the boundary pixels B between the dark portion 31 and the bright portion 32 in the striped pattern image 30. In the inspection area 40, focusing on the pixel rows in the running direction (Y direction) of the cardboard sheet 10, the boundary pixel B that changes from the bright part 32 to the dark part 31 can be detected. At this time, the boundary pixel B can be detected as the pixel of the bright part 32 immediately before the change to the dark part 31 or the pixel of the dark part 31 immediately after the change to the dark part 31. Similarly, when attention is paid to the column of pixels in the Y direction in the inspection region 40, the boundary pixel B that changes from the dark portion 31 to the bright portion 32 can be detected. At this time, the boundary pixel B can be detected as a pixel of the dark part 31 immediately before the change to the bright part 32 or a pixel of the bright part 32 immediately after the change to the bright part 32.

When the core 11 is formed into an appropriate waveform, the width of each of the dark part 31 and the bright part 32 in the Y direction is constant in the striped pattern image 30. Accordingly, the pixels B at the boundary in the inspection region 40 are arranged on a straight line parallel to the X direction, as shown in FIG. On the other hand, there crests F _L which is lower than the normal crest F _N is a part if the bright portion 32 in the belt of the dark part 31 partially appears, as shown in FIG. 6 (b), the boundary The pixels B are arranged along the outline at the bright portion 32, and therefore the pixels B at the boundary do not line up on a straight line parallel to the X direction. Similarly, case, the pixel B is part of the dark area 31 boundaries dark portion 31 partially appears in a normal crests F _N higher than going on ridges F _H is in some band of light portion 32 Therefore, the pixels B at the boundary do not line up on a straight line parallel to the X direction. Therefore, whether or not the core 11 is shaped into an appropriate waveform can be determined based on whether or not the boundary pixel B is on a straight line.

  Whether or not the boundary pixel B is on a straight line can be determined, for example, by comparing the difference between the X coordinates of the adjacent boundary pixels B with a threshold value.

  As described above, according to the corrugated molding inspection method of the present embodiment, light is projected from the inclined direction onto the corrugated cardboard sheet 10 in the course of traveling on the production line, and this is photographed by the camera 22 and dark portions 31 and bright portions. It is possible to determine whether or not the core 11 is formed into an appropriate waveform by acquiring a striped pattern image 30 that repeats alternately with 32 and analyzing this.

  The analysis of the striped pattern image 30 is performed by analyzing the area ratio or area ratio of the dark portion 31 and the bright portion 32 in the inspection region 40, the number of columns of pixels in which only the bright portion 32 or the dark portion 31 is continuous, or the dark portion 31 and This can be easily performed depending on whether or not the pixels B at the boundary with the bright part 32 are arranged on a straight line.

  In addition, in this embodiment, the line sensor camera 22 that can capture a one-dimensional image over the entire width of the cardboard sheet 10 is used as the camera 22, and the inspection area 40 is shifted in the width direction of the cardboard sheet 10. It is possible to inspect whether or not the core 11 is formed into an appropriate waveform over the entire area of the corrugated cardboard sheet 10 traveling on the production line.

  The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above-described embodiments, and various improvements can be made without departing from the scope of the present invention as described below. And design changes are possible.

  For example, when the inspection area 40 is shifted in the X direction or the Y direction, the inspection area 40 may be shifted so that the peripheral edge of the inspection area 40 slightly overlaps. Thereby, it can test | inspect whether the core 11 is shape | molded more appropriately by the corrugated board sheet 10 over the whole area.

  Further, a sensor that detects an end portion of the cardboard sheet 10 in the width direction may be used. Thereby, even if the size in the width direction of the corrugated cardboard sheet 10 to be inspected is changed, the range in the width direction in which the image is taken by the line sensor camera 22 can be a range that is not excessive or insufficient.

DESCRIPTION OF SYMBOLS 10 Cardboard sheet 11 Core 21 Light source 22 Camera 30 Striped pattern image 31 Dark part 32 Bright part B Boundary pixel Z Vertical X Cardboard sheet width direction L1-L4 Row of pixels lined up in the cardboard sheet width direction

Claims (4)

On the corrugated cardboard sheet running on the production line after the core is formed into a corrugated shape,
Project light from a light source in a direction inclined to the normal of the sheet surface,
By photographing the cardboard sheet with a camera at an angle different from the light source,
A dark pattern that is an image of a portion that is shaded by light being blocked by a mountain portion in the waveform and a bright pattern that is an image of a portion that is irradiated with light are obtained, and a striped pattern image is obtained.
A step forming inspection method, comprising: determining whether or not the core is appropriately formed based on image processing of the striped pattern image. Said determination is
The step forming inspection method according to claim 1, wherein the step forming inspection method is performed based on areas of the dark part and the bright part in the striped pattern image. Said determination is
Of the rows of pixels arranged in the width direction of the cardboard sheet in the striped pattern image, the number of columns in which only the dark pixels are continuous, or the number of columns in which only the bright pixels are continuous The step forming inspection method according to claim 1, wherein 2. The step forming inspection method according to claim 1, wherein the determination is performed by detecting a pixel at a boundary between the dark portion and the bright portion in the striped pattern image and based on linearity of the pixel at the boundary.

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