JPS61230005A - Method for inspecting joint of sheet-like material - Google Patents

Abstract

PURPOSE:To conduct a test at high accuracy by a simple device which makes its shift unnecessary by obtaining coordinates of at least one sheet end of an image picked up by lighting the joint of a sheet-like material at both sides of the joint. CONSTITUTION:The sheet 1 available from overlapping upper and lower sheets 1a and 1b is irradiated alternately by right and left light sources 3a and 3b of the joint. The image of the joint caused by the light source 3a is formed on a camera 2, stored in a frame memory 5a through a switch circuit SW4, and a window is set 6a. The luminous energy shading is corrected 7a and smoothed 8a, and a noise is removed to store the image in a frame memory 9a. Then after a picture signal is integrated 10a, coordinates of a density distribution in a direction intersecting orthogonally with the joint is detected 11a and inputted to a deciding circuit 12. The image caused by the light source 3b is processed in the same manner, and a smoothed 8b signal is subtracted 13 from the output of the frame memory 9a and then processed in the same way as the system of the light source 3a and inputted to the deciding circuit 12. Then the shift of the device can be unnecessary and the test can be conducted at high accuracy.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to sheet-like objects such as inner litchi, ply, tire molding members such as belts, resin film sheets,
This invention relates to a method for inspecting joints of thin metal sheets, conveyor belts, etc., especially joints formed by overlapping and joining.

(Prior Art) As a conventional method for inspecting seams of sheet-like objects, there is a method in which a roller is brought into contact with a sheet-like object to be inspected, and the displacement of the roller is detected using a potentiometer or a differential transformer to inspect the seams. A method of inspecting a seam by detecting the displacement of the surface of a sheet-like object using an optical microphone meter having a light source and a light receiving element. An image of a part of the seam is sent to a one-dimensional array sensor arranged in a direction perpendicular to the extending direction of the seam. A method for inspecting seams by forming an image on the seam and processing the image signal, which involves sequentially projecting slit light onto the seam in a direction perpendicular to the direction in which the seam extends. Scan the seam,
A method is known in which an image of the seam formed by projection of these slit lights is formed on a two-dimensional array sensor, and the seam is inspected based on the image signal.

(Problems to be Solved by the Invention) However, in the above method of bringing the roller into contact with the sheet-like object, there are problems in that the sheet-like object supports deformation, the resolution is low, and the accuracy is poor. The method using a meter requires a mechanism to relatively move the optical micrometer and the sheet-like object, and
Since spot photometry is used, there is a problem that erroneous measurements are likely to occur due to the influence of the color, gloss, and roughness of the surface of the sheet-like object. In addition, in the method using a -dimensional array sensor, since only one line of image signal is obtained, the influence of the color, gloss, and roughness of the surface of the sheet-like object is similar to the case of using the optical micrometer described above. In the method using a two-dimensional array sensor, slit light is projected sequentially, which causes the problem that the image signal processing logic becomes complicated and the processing time becomes long.

The purpose of the present invention is to solve the various problems mentioned above, and to provide a seam inspection method for sheet-like objects that can inspect seams quickly and with high accuracy without deforming the sheet-like object, and that can be easily carried out. That is.

(Means for Solving the Problems) The seam inspection method for a sheet-like object of the present invention involves illuminating and imaging the seam of a sheet-like object from one side and the other side with the seam direction as a boundary, Based on these image signals, the coordinates of both sheet ends at the joint are determined, at least the coordinates of one sheet end are determined based on the difference between the two image signals, and the joint is inspected based on the coordinates of both sheet ends. It is a “thing” that is characterized by

(Function) As shown in FIGS. 1A and B, the seam portion of the sheet-like objects 1 that are overlapped and joined is moved in the direction of the upper sheet la and the lower sheet lb with the extending direction, that is, the seam direction as the boundary.
When the images are illuminated from the respective directions and formed on the imaging device 2 having a two-dimensional array sensor, the images become as shown in FIGS. 2A and 2B, respectively. That is, when illuminating from the direction of the upper sheet 1a, as shown in FIG. is the darkest, and the others are intermediate densities. In addition, when the light is illuminated from the direction of the lower sheet 1b, as shown in FIG. Depending on the shape of the edge, it may be the brightest, or it may have an intermediate density like other parts. Therefore, if we take the difference between the image signals of the images shown in FIG. 2A and B, for example, the dark density will be in the area corresponding to the edge of the upper sheet 1a, and the bright density will be in the area corresponding to the edge of the lower sheet 1b. At the same time, variations in the intermediate density are canceled out and the contrast is increased, so the coordinates of the respective edges of the upper sheet 1a and the lower sheet 1b can be accurately determined from the density distribution. The quality of the seam can be determined by comparing the seam width obtained from the above with a reference value. Further, one image signal, for example, the dark density portion of the image signal when illuminated from the direction of the upper sheet la corresponds exactly to the edge of the upper sheet la. Therefore, the coordinates of the edge of the upper sheet 1a can be determined from the density distribution of the image signal when illuminated from the direction of the upper seam a, and the coordinates of the edge of the lower sheet 1b can also be determined from the density distribution of the difference between the two image signals. Conversely, the coordinates of the edge of the lower sheet 1b are determined from the density distribution of the image signal when illuminating from the direction of the lower sheet 1b, and the coordinates of the edge of the upper sheet 1a are determined from the density distribution of the difference between both image signals. You can also do that.

(Example) FIG. 3 is a configuration diagram of an example of a seam inspection apparatus that implements the method of the present invention. In this example, the joint portion of the sheet-like object 1 is positioned at an imaging position by an imaging device 2 having a two-dimensional array sensor and inspected. At the imaging position, light sources 3a and 3b are arranged on both sides of the sheet-like object 1 in the extending direction of the joint.

The light sources 3a and 3b are, for example, laser light sources that emit light with a wavelength of 830 nm, and by sequentially emitting these laser light sources, the light source 3a projects parallel light rays from the direction of the upper sheet 1a at an angle of 156 to 256 with respect to the sheet plane. The light source 3b projects parallel light rays from the direction of the lower sheet 1b at an angle of 15° to 20° with respect to the rate plane to illuminate the joint. The image of the seam illuminated by the light source 3a is formed on the imaging device 2, and the image signal is stored in the frame memory 5a via the switch circuit 4, and then the image signal in a predetermined range is extracted via the window setting circuit 6a. Then, the light amount unevenness correction circuit 7a corrects the light amount unevenness with respect to the extracted image signal.

In other words, when a flat surface is illuminated from an oblique direction by a light source, the illuminance distribution on the illuminated surface becomes larger the closer it is to the light source;
Furthermore, since the light emission density of the light source has a glass distribution in which the light density is high at the center, the illumination intensity at the center of the light beam is large. Therefore, due to these phenomena, the illuminance distribution in the projection direction of the illumination light on the irradiation surface and in the width direction perpendicular thereto is as follows:
This is shown by broken lines and solid lines in Figures A and B, respectively. Therefore, in this example, in the light amount unevenness correction circuit 7a,
The image signal is corrected so that the irradiation surface is illuminated with an equivalently uniform illuminance distribution by the light source 3a.

In FIG. 3, the image signal corrected for light intensity unevenness by the light intensity unevenness correction circuit 7a is supplied to a smoothing circuit 8a, where local integration processing is performed to determine variations in color, gloss, and roughness on the surface of the sheet-like object 1. After partial noise is removed, the data is stored in the frame memory 9a. The image signal stored in the frame memory 9a is supplied to an integrating circuit 10a, which integrates the image signal in the seam direction to obtain the density distribution in the length direction orthogonal to the seam direction, as shown in FIG. 5A. and supplies it to the coordinate detection circuit 11a. Coordinate detection circuit 11a
In FIG. 5A, the integral output from the integrating circuit 10a and
is compared with an appropriate darkness value indicated by a broken line to detect the coordinate x1 at which the integral output is below the threshold, that is, the coordinate of the edge of the upper i-sheet la, and supply this to the determination circuit 12.

On the other hand, the image signal of the joint obtained from the imaging device 2 by illumination by the light source 3b is stored in the frame memory 5b via the switch circuit 4, and is similarly processed in the window setting circuit 6b, the light intensity unevenness correction circuit 7b and the smoothing circuit 8b. After processing, the signal is supplied to one input terminal of the subtraction circuit 13, in this example, the inverting input terminal. An image signal generated by illumination from the light source 3a stored in the frame memory 9a is supplied to the non-inverting input terminal of the subtraction circuit 13, and the difference between the signals of corresponding pixels is sequentially determined and stored in the frame memory 9b. do. The difference signal stored in the frame memory 9b is supplied to the integrating circuit 10b, and the density distribution in the direction perpendicular to the extending direction of the similarly processed seam is determined. Here, integrating circuit 1
The density distribution found at 0b is stored in the frame memory 9
Since the signal stored in b is the image signal caused by the illumination from the light source 3a minus the image signal caused by the illumination from the light s3b, in the density distribution shown in FIG. 5A, rj
The contrast is high as shown in FIG. 5B, in which the A density and the dark density are each emphasized, and variations in the intermediate density are canceled out. The integrated output of the integrating circuit 10b is supplied to the coordinate detection circuit 11b, where it is compared with an appropriate darkness value shown by the broken line in FIG. The coordinates of the edge are detected and supplied to the determination circuit 12.

The determination circuit 12 detects the seam width, that is, the amount of overlap between the upper seam) 1a and the lower seam) 1b, based on the coordinate information (XLXh) from the coordinate detection circuits 11a and llb,
Compare this with an appropriate standard value to determine the quality of the seam,
The results are supplied to, for example, the display device 14 for display, or supplied to an alarm device to issue an alarm in the case of a defect.

According to this embodiment, the image signal due to the illumination from the light source 3a and the image signal due to the illumination from the light source 3b are subjected to light intensity unevenness correction processing and smoothing processing, respectively, and then the image signal due to the illumination from the light source 3a in the direction of the upper sheet 1a is processed. Based on the density distribution of
Since the coordinates of each edge are detected, both coordinates can always be detected with high precision and without contact without being affected by local noise, and therefore the seam can be accurately inspected.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified or modified in many ways. For example, the coordinates of the edges of the upper sheet 1a and the lower sheet 1b can be detected based on the density distribution of the difference between the two image signals, and the coordinates of the edges of the lower sheet 1b can be determined by the illumination from the light source 3b. The coordinates of the edge of the upper sheet la can also be detected from the density distribution of the difference between the two image signals. Also, a frame memory 5a.

5b, window setting circuits 6a, 6b, smoothing circuit 8
It is also possible to use one each of a and 8b for both image processing.

(Effects of the Invention) As described above, according to the present invention, since the inspection is performed without contact, there is no deformation of the sheet-like object, and at least the coordinates of one sheet edge are determined by the difference between the two image signals. Since the detection is based on a high contrast signal that cancels out variations in color, gloss, and roughness on the surface of a sheet-like object, seams can always be inspected with high precision.

In addition, since images are sequentially captured and processed by illumination from one side and the other side of the seam without relatively moving the illumination light source, imaging device, or sheet-like object, mechanical The configuration and the electrical configuration of the signal processing circuit are simple and therefore easy to implement.

[Brief explanation of the drawing]

FIGS. 1A and B and FIGS. 2A and B are diagrams for explaining the present invention in detail. FIG. 3 is a configuration diagram of an example of a seam inspection device that implements the method of the present invention. FIGS. 4A and B 5A and 5B are diagrams for explaining the operation. 1--sheet-like object 1a--upper sheet 1b
--Lower sheet 2-imaging devices 3a, 3b--
-Light source 4- Switch circuits 5a, 5b-.-
Frame memories 6a, 6b...Window setting circuits 7a, 7b...
- Light intensity unevenness correction circuits 8a, 8b --- Smoothing circuits 9a, 9b - Frame memories 10a, LOb - Integrating circuits 11a, 1
1b - Coordinate detection circuit 12 - - Judgment circuit
13--Subtraction circuit 14--Display device Fig. 4 A B Fig. 5 A B

Claims (1)

[Claims] 1. The joint of a sheet-like object is illuminated and imaged from one side and the other side with the seam direction as a boundary, and based on these image signals, the coordinates of both sheet edges at the joint are determined at least from one side. A seam inspection method for a sheet-like object, characterized in that the coordinates of the sheet edge are determined based on the difference between the two image signals, and the seam is inspected based on the coordinates of both sheet edges.