JPH11328409A - Device for inspecting sheet material defect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a defective part even at the time of the acceleration and deceleration of a carrying system by correcting the error of a defective part area extracted based on the resolution change of an image picked-up image corresponding to the carrying speed of the carrying system. SOLUTION: This device is provided with a resolution correction table for preliminarily calculating the rate of the acceleration and deceleration of a carrying system and the rate of the resolution of an image picked-up image, and an area correction calculating means 6 for error-correcting and calculating the area of an extracted area obtained by a labeling means based on the resolution correction table. Therefore, the error of a flattened image generated at the time of the acceleration and deceleration of the carrying system can be corrected, and the area can be calculated with the same resolution as that at a constant speed regardless of the acceleration and deceleration of the carrying system. Thus, a defective part 8 of a sheet member 9 can be exactly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet material defect inspection apparatus for detecting defects such as scratches and dents in a sheet material which is continuously conveyed. The present invention relates to a sheet material defect inspection apparatus for detecting a defect of a sheet material.

[0002]

2. Description of the Related Art In recent years, in various production facilities, a visual inspection apparatus for detecting a defect of an object from an image picked up by an image pickup device such as a line sensor camera has been widely used. A sheet material defect inspection device is used as a device for detecting defects such as scratches and dents in the sheet material from among the appearance inspection devices.

FIG. 5 is a block diagram showing a conventional sheet material defect inspection apparatus. As shown in FIG. 5, the sheet material defect inspection apparatus includes a line sensor camera 1 for imaging a sheet material 9 continuously conveyed by a conveyance system (not shown).
(Imaging means), and an electronic computer 2 for processing a grayscale image obtained by the line sensor camera 1. The line sensor camera 1 is disposed and fixed above the sheet material 9 and continuously captures an image of the surface state of the sheet material 9. Further, the computer 2 is a main memory 13 (gray-scale image storage means) for storing a gray-scale image among the images captured by the line sensor camera 1.
And a CPU 10 for detecting a defective portion 8 of the sheet material 9 based on the grayscale image.

The CPU 10 includes a binarizing unit 14, a labeling unit 15, an area calculating unit 16, and a defect detecting unit 17, and a series of processes in the CPU 10 can be performed by hardware or software. The binarizing means 14 reads out the grayscale image from the main memory 13 and stores the grayscale image in the background portion and the defective portion 8 of the sheet material 9.
And binarization. The above labeling means 15
Is to extract a black or white area indicating the area of the defective portion 8 binarized and divided by the binarization means 14. The area calculating means 16 calculates the area from the defective part area extracted by the labeling means 15. The defect detecting means 17 treats the calculated area calculated by the area calculating means 16 as a defective portion 8 of the sheet material 9 and detects the defect as a defect of the sheet material 9 if the calculated area is larger than a specified range. .

Next, the operation of the sheet material defect inspection apparatus will be described below. As shown in FIG. 5, the sheet material 9 moving in the direction of arrow E is imaged by the line sensor camera 1 to obtain an image. A grayscale image is obtained from the captured image, and the grayscale image is stored in the main memory 13 of the computer 2. Next, the grayscale image stored in the main memory 13 is read out, and the binarizing means 14 extracts the defective portion 8 from the background of the grayscale image.
The grayscale image is binarized into 0 and 1 by a threshold value for cutting out the region. Here, for example, when the area of the defective portion 8 is binarized as one white area, the white area is extracted by the labeling means 15 to extract the defective area. Then, the area occupied by the defective portion area is calculated by the area calculating means 16. The area calculation by the area calculation means 16 is performed by converting the defective partial area into coordinates as follows.

FIG. 6 schematically shows a defective portion area in the grayscale image binarized by the binarizing means 14. In FIG. 6, reference numeral 30 denotes a defective part area extracted by the labeling means 15, and reference numeral 31 denotes one line obtained by equally dividing the defective part area 30. Here, assuming that the y coordinate of the line 31 is Y, the y coordinates of the lines 311 and 312 before and after the line 31 are (Y−1),
(Y + 1). Reference numeral 32 denotes a starting point SX (Y) of the x coordinate of the line 31, and reference numeral 33 denotes an ending point EX (Y) of the x coordinate of the line 31. Then, the area of the line 31 can be represented by (EX (y) -SX (y)). The area of the other lines can be similarly obtained. That is,
The area occupied by the defective partial region 30 extracted by the labeling means 15 is represented by the following equation. Σ (EX (y) −SX (y)) (A) In this way, in the area calculating means 16, (A)
The area occupied by the defective portion region 30 is calculated by the equation. Next, if the calculated area calculated by the area calculating means 16 by the defect detecting means 17 is larger than the designated range, it is detected as a defect of the sheet material 9.

[0007]

However, in the above-described sheet material defect inspection apparatus, even at the same defect portion, at a constant speed of the transport system, the same defect portion is extracted by the labeling means 15 as shown in FIG. In the defective partial area 30, an equivalent image is obtained for each line, but when the transport system accelerates or decelerates, as shown in FIG.
An image in which 411, 412, and the like are extended is obtained.
The area calculating means 16 calculates the area of the extended image even when the transport system is accelerated or decelerated by the above equation (A). While a proportional calculated area is obtained, a calculated area larger than the actual defective portion 8 is obtained during acceleration / deceleration, and as a result, the defective portion 8 of the sheet material 9 is erroneously detected and determined. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In particular, the present invention focuses on a change in resolution of a captured image with respect to the transport speed of a transport system, and corrects an error in a defective partial area extracted based on the change in resolution. Accordingly, it is an object of the present invention to provide a sheet material defect inspection apparatus capable of accurately detecting a defective portion even during acceleration / deceleration of a transport system.

[0009]

A sheet material defect inspection apparatus according to the present invention is a sheet material defect inspection apparatus for detecting a defective portion from a grayscale image of a sheet material continuously conveyed by a conveyance system. An imaging unit that captures the sheet material that is continuously conveyed; a gray image storage unit that stores a gray image in a captured image captured by the imaging unit; and a gray image read from the gray image storage unit. A binarizing means for binarizing the grayscale image by a threshold value for dividing the sheet material into a background area and a defective area; and a defect area in the grayscale image binarized by the binarization means. A resolution correction table pre-calculating a resolution ratio representing a change in resolution of an image captured by the image capturing means with respect to the transport speed of the transport system, Area correction calculating means for calculating the area of the defective partial area extracted by the labeling means by performing error correction based on the resolution correction table; and if the calculated area calculated by the area correction calculating means is larger than a specified range. Defect detecting means for detecting a sheet material as a defect.

[0010] Further, the sheet material defect inspection apparatus of the present invention comprises:
In the above-described sheet material defect inspection apparatus, the resolution correction table is calculated based on a current transport speed of a transport system obtained by an external input unit.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sheet material defect inspection apparatus according to the present invention will be described below with reference to FIGS. Note that the sheet material defect inspection apparatus of the present invention includes an image pickup unit and an electronic computer as in the conventional apparatus shown in FIG. 5, but is one unit constituting the electronic computer.
The PU includes a resolution correction table and an area correction calculation unit that performs error processing based on the resolution correction table.

FIG. 1 is a block diagram showing a sheet material defect inspection apparatus according to an embodiment of the present invention. The sheet material defect inspection apparatus according to the present embodiment, as shown in FIG.
Line sensor camera 1 (imaging means) for imaging sheet material 9 continuously conveyed by a conveyance system (not shown)
And an electronic computer 2 for processing the grayscale image obtained by the line sensor camera 1. The line sensor camera 1 is disposed and fixed above the sheet material 9 and continuously captures an image of the surface state of the sheet material 9. In addition, the line sensor camera 1 starts or ends the imaging by an external signal. The above-mentioned computer 2
It comprises a main memory 3 (gray-scale image storage means) for storing a gray-scale image of images picked up by the line sensor camera 1 and a CPU 10 for detecting a defective portion 8 of the sheet material 9 based on the gray-scale image. . The main memory 3 is composed of a RAM capable of writing and reading a grayscale image.

The CPU 10 includes a binarizing means 4, a labeling means 5, a resolution correction table T, an area correction calculating means 6, and a defect detecting means 7. Note that this CP
The processing in U10 can be performed by hardware or software. The binarizing means 4 reads the grayscale image from the main memory 3 and binarizes the grayscale image by a threshold value for dividing the grayscale image into a background portion and a defective portion 8 of the sheet material 9. Are binarized such that 1 is a white region and the background portion is a black region of 0. The labeling means 5 is for extracting a defective part area of the defective part 8 divided by the binarizing means 4. The resolution correction table T is a table in which a resolution ratio indicating a relationship between a conveyance speed of the conveyance system of the sheet material 9 and a resolution change of a captured image obtained by the line sensor camera 1 is calculated in advance. The area correction calculation means 6 corrects the defective partial area extracted by the labeling means 5 based on the resolution correction table T and calculates the area occupied by the area. Note that the calculated area obtained by the area correction calculating means 6 is treated as the area of the defective portion 8 of the sheet material 9. The defect detecting means 7 detects the sheet material 9 as a defect if the calculated area calculated by the area calculating means 6 is larger than a specified range.

Next, the resolution correction table T will be described. FIG. 2 is a graph showing a resolution correction table T used by the area correction calculating means 6, in which the vertical axis indicates the capture line (Y) of the captured image in the feed direction, and the horizontal axis indicates the capture line (Y). ) Indicates the resolution ratio (f (Y)) of the captured image. Resolution correction table T
Represents a change in resolution of each line of the captured image, as shown in FIG. 2, and is defined as a resolution ratio (f (Y)) for each fetched line (Y).

Since the time from when the line sensor camera 1 starts taking the captured image to when the taking of the captured image is completed is a fixed time, the transport system is accelerated or decelerated in that unit time, so that the per unit area of the sheet material 9 is increased. The number of fetched lines changes, and the resolution of the captured image for each line at this time also changes.

FIG. 3 shows the relationship between the transport speed of the transport system and the resolution of the image captured by the line sensor camera 1. In FIG. 3, the vertical axis indicates the transport speed of the transport system, and the horizontal axis indicates the image captured by the line sensor camera 1. Indicates the resolution of the image. As shown in FIG. 3, when the transport speed of the transport system is 0, that is, when the transport system is stationary, the resolution of the captured image is highest, but as the transport speed increases, the wide range of the sheet material 9 at a time increases. Since the image is captured, the resolution of the captured image per unit area of the sheet material 9 is reduced. That is, the resolution has an inversely proportional relationship with the transport speed. Here, the transport speed S of the transport system at the y-th line of the captured image
If the resolution is set to 1 at the time, the change in resolution (f (y (S))) with respect to the change in transport speed can be expressed by the following equation. f (y (S)) = 1 / S (B) From the above equation (B), the resolution with respect to the speed of the transport system is expressed as the reciprocal of the speed component. If the transport speed of the transport system is set to a constant speed S, the transport system accelerates / decelerates (0 → S,
(S → 0), which is slower than the speed S, the resolution of the captured image at that time is higher than that at the constant speed S. Therefore, in order to set the resolution when the transport system is in acceleration or deceleration to the same condition as the resolution 1 when the transport system is at the constant speed S, it is sufficient to satisfy the relationship of the above equation (B).

When the ratio obtained by the above equation (B) is plotted for each captured image capturing line, a resolution correction table T shown in FIG. 2 is obtained. That is, as is apparent from FIG. 2, the resolution ratio (f (y)) of the resolution correction table T is constant when the transport system is at a constant speed (indicated by a range b in FIG. 2). When the transport system is accelerating (indicated by a range a in FIG. 2) or decelerating (indicated by a range c in FIG. 2), the lower the speed, the higher the resolution ratio (f (y)). Is obtained.

Next, the operation of the sheet material defect inspection apparatus according to the present embodiment will be described below. As shown in FIG. 1, a sheet material 9 moving in the direction of arrow E is picked up by a line sensor camera 1 arranged above to obtain a picked-up image. A grayscale image is obtained from the captured image, and the grayscale image is stored in the main memory 3 of the computer 2. Next, the grayscale image stored in the main memory 3 is read out, and the binary imager 4 binarizes the grayscale image into 0 and 1 by using a threshold for cutting out the area of the defective portion 8 from the background of the grayscale image. Here, for example, when the area of the defective portion 8 is binarized as one white area, the white area is extracted by the labeling means 5 to extract the defective area. Then, the area occupied by the defective portion area is calculated by the area calculating means 6. The area calculation by the area calculation means 6 is performed by converting the defective partial area into coordinates as follows.

FIG. 4 schematically shows a defective partial area whose error has been corrected by the area correction calculating means 6. In FIG.
Reference numeral 18 denotes an error-corrected defect partial area (calculated area), reference numeral 20 denotes a defect partial area extracted by the labeling unit 5, reference numeral 21 denotes an extraction area on the Y-th line of the y coordinate,
Reference numeral 22 denotes a starting point SX (Y) of the x coordinate of the line 21.
3 indicates an end point EX (Y) of the x coordinate of the line 21. Therefore, as in the conventional case, the area of the line 21 is (E
X (y) −SX (y)), the area of the defective partial region 20 extracted by the labeling unit 5 is represented by Σ (EX (y) −SX (y)).

Next, using the previously calculated resolution correction table T shown in FIG. 2 and taking into account the resolution ratio of each line having a different transport speed, the error of the defective partial area 20 extracted by the labeling means 5 was corrected. The area can be represented by the following equation. Σ (EX (y) −SX (y)) * f (y) (C) where f (y) is the resolution correction table T in FIG.
Is the resolution ratio for each line (y). The area calculated by the above equation (C) represents the area 18 whose error has been corrected by the resolution ratio of the captured image to the transport speed.

Thus, the area correction calculating means 6
Then, a calculated area 18 in which an error due to acceleration / deceleration of the transport system is corrected is obtained from the defective partial area 20 extracted from the labeling means 5 by the above equation (C) in consideration of the resolution correction table T. The calculated area 18 obtained here is treated as being equivalent to the area of the defective portion 8 of the sheet material 9. Next, if the calculated area 18 is larger than the specified range by the defect detecting means 7, it is detected as a defect of the sheet material 9.

As described above, according to the sheet material defect inspection apparatus according to the present embodiment, the ratio of the resolution of the captured image obtained by the line sensor camera 1 is calculated in advance according to the acceleration / deceleration of the conveyance system of the sheet material 9. Based on the resolution correction table T, the area 18 having the error corrected by the area correction calculating means 6 is calculated from the defective partial area 20 extracted by the labeling means 5, so that the same resolution as the constant speed regardless of the acceleration / deceleration of the transport system. The defect 8 of the sheet material 9 can be inspected by calculating the area of the defective portion 8 with the result, and as a result, the defect of the sheet material can be detected with high accuracy.

In the above-described embodiment, the resolution correction table T is obtained by calculating the resolution ratio f (y) in advance in accordance with the acceleration / deceleration of the transport system. Read sequentially from the external input device, create a resolution correction table according to the speed at that time,
This resolution correction table may be used.
Then, the area following the speed of the transport system can be calculated, and the defect of the sheet material can be detected with higher accuracy.

[0024]

According to the sheet material defect inspection apparatus of the present invention, there is provided a sheet material defect inspection apparatus for detecting a defective portion from a grayscale image of a sheet material continuously conveyed by a conveyance system. Imaging means for imaging the sheet material being conveyed, and a gray image storage means for storing a gray image in a captured image captured by the imaging means; and a gray image read from the gray image storage means.
A binarizing means for binarizing the grayscale image by a threshold value for dividing the sheet material into a background area and a defective area; and a defect area in the grayscale image binarized by the binarization means. A resolution correction table in which a resolution ratio representing a change in the resolution of the image captured by the imaging means with respect to the transport speed of the transport system is calculated in advance, and an area of the defective partial area extracted by the labeling means. An area correction calculation means for performing error correction based on the resolution correction table, and a defect detection means for detecting as a sheet material defect if the calculated area calculated by the area correction calculation means is larger than a specified range. Wherein the area correcting means extracts the defective portion area extracted by the labeling means, Since the area is calculated by performing an error correction based on the resolution correction table, an error due to the extension of an image generated when the transport system is accelerated / decelerated is removed from the calculated area, and therefore, regardless of the acceleration / deceleration of the transport system. The area can be calculated at the same resolution as the constant speed, and as a result, there is an effect that a defective portion of the sheet material can be accurately detected.

Further, according to the sheet material defect inspection apparatus of the present invention, the speed of the transport system is read by sequentially reading the speed of the transport system from an external input device such as an encoder and creating a resolution correction table according to the speed. This has the effect of calculating the area that follows, and more accurately detecting defects in the sheet material.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a sheet material defect inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing a resolution correction table.

FIG. 3 is a graph showing a relationship between a transport speed of a transport system and a resolution.

FIG. 4 is a schematic diagram showing a defect partial region (calculated area) whose resolution has been corrected.

FIG. 5 is a block diagram showing a configuration of a conventional sheet material defect inspection apparatus.

FIG. 6 is a schematic diagram showing a defective portion area detected by a conventional sheet material defect inspection apparatus when the conveyance system is at a constant speed.

FIG. 7 is a schematic diagram showing a defective portion area detected by a conventional sheet material defect inspection apparatus when the transport system is in acceleration or deceleration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Line sensor camera (imaging means) 2 Electronic computer 3 Main memory (shading image storage means) 4 Binarization means 5 Labeling means 6 Area correction calculation means 7 Defect detection means 8 Defective part 9 Sheet material 10 CPU 18 Calculation area 20 Labeling Defect part area 21 extracted by the means 21 1 line 22 Start point of x coordinate 23 End point of x coordinate 30 Defect part area extracted at the time of labeling means (at a constant speed) 31 1 line 32 Start point of x coordinate 33 End point of x coordinate 311 (Y-1) line 312 (y + 1) line a acceleration region b constant speed region c deceleration region T resolution correction table

Claims (2)

[Claims] 1. A sheet material defect inspection apparatus for detecting a defective portion from a grayscale image of a sheet material continuously conveyed by a conveyance system, wherein the imaging device picks up the continuously conveyed sheet material. Means, a gray-scale image storage means for storing a gray-scale image in the captured image captured by the image-capturing means, and a gray-scale image read from the gray-scale image storage means, divided into areas of a background portion and a defective portion of the sheet material. A binarizing unit for binarizing the grayscale image with a threshold value; a labeling unit for extracting a defective portion area in the grayscale image binarized by the binarizing unit; A resolution correction table in which a resolution ratio indicating a change in resolution of an image captured by the image capturing means is calculated in advance, and a defect portion extracted by the labeling means. Area correction calculating means for calculating the area of the area by performing error correction based on the resolution correction table; and defect detection for detecting as a sheet material defect if the calculated area calculated by the area correction calculating means is larger than a specified range. Means for inspecting sheet material defects. 2. The sheet material defect inspection apparatus according to claim 1, wherein the resolution correction table is calculated according to a current transport speed of a transport system obtained by an external input unit. Sheet material defect inspection equipment.