JP2000082143A - Surface defect inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to automatically detect even a defect of a minute and smooth undulation. SOLUTION: This inspection device is equipped with an illumination 4 for illuminating an inspected object 1 from almost just above with a light 3, an illumination 7 for unidirectionally illuminating the inspected object 1 with a light 6 almost right from a side, an image pickup device 9 for picking up a picture of the inspected object 1 illuminated with the light 3 and 6 from two kinds of illuminations 4 and 7, an image processor 11 for measuring an area value of a defective part from the image picked up by the image pickup device 9, and a normal/defective condition decision device 12 for performing normal/ defective condition decision by comparing the area value measured by the image processor 11 with a preset normal/defective condition reference value. Also, a line sensor camera, a photoelectric sensor, a camera controller, and a light source controller are provided and it is made possible to detect a defect while moving.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface defect inspection apparatus for detecting an appearance defect occurring on the surface of an object such as a roof tile.

[0002]

2. Description of the Related Art As means for irradiating light from right above and right beneath an inspection surface of an object to receive scattered light from a defect portion and to extract a feature amount of the defect, for example, Japanese Patent Laid-Open No. 1
Japanese Patent Application Laid-Open No. 90707 discloses an example.

The above-mentioned publication has a light emitting unit configured to obliquely surround a test surface of a subject, and irradiates the test surface uniformly with light from the periphery. It consists of an imaging device that receives the scattered light from the direction perpendicular to the inspection surface and captures an image of the inspection surface, and an image processing device that processes the image of the inspection surface. Even when a directional defect is detected, stable scattered light can be obtained.

[0004]

However, such conventional means have the following problems depending on the form of the defect.

That is, for example, when detecting minute and smooth undulating defects as indicated by reference numerals 14 and 15 in an object as indicated by reference numeral 1 in FIGS. If this is done, the scattered light will be extinguished, making it difficult to detect defects. The same result is obtained even when light irradiation is performed from above.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a surface defect inspection apparatus capable of automatically detecting even minute and smooth undulating defects.

[0007]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, there is provided an illumination for irradiating a subject with light from almost right above, and a method for irradiating the subject with a light from substantially right side in one direction. Illumination that irradiates light, an imaging device that captures an image of a subject irradiated with light from the above two types of light from almost directly above, and measures the area value of a defective portion from an image captured by the imaging device And a pass / fail determination device that determines pass / fail by comparing an area value measured by the image processing device with a preset pass / fail determination reference value.

According to the first aspect of the present invention, the subject is irradiated with light from almost right above using two kinds of illuminations, and the light is applied to the subject from one side to the other side. Irradiate.

Then, an image of the subject irradiated with light from almost right above and an image of the subject irradiated with light from almost right beside are respectively picked up by the imaging device from almost right above. Next, the image processing device measures the area value of the defective portion from each image captured by the imaging device. Lastly, the pass / fail judgment device compares the area value measured by the image processing apparatus with a preset pass / fail judgment reference value to make pass / fail judgment.

As described above, by irradiating light in one direction from almost right beside the subject, it becomes possible to automatically detect a smooth undulating defect. In addition, by irradiating light from almost directly with the same device, it is possible to automatically detect a defect without undulation. In addition, the number of imaging devices used can be reduced, and the cost of the device can be reduced.

According to a second aspect of the present invention, the image processing apparatus is characterized in that the image processing apparatus can perform an enhancement process on an image obtained when light is irradiated from one side to a side. I have.

According to the second aspect of the present invention, the image processing apparatus can correct the image obtained by irradiating light in one direction from right beside by the enhancement processing. .

According to the third aspect of the present invention, the image pickup apparatus has a plurality of image pickup devices arranged in a line in a direction substantially perpendicular to the moving direction of the subject, and can image the moving subject. It is a line sensor camera, and a photoelectric sensor for detecting that a subject has passed is provided on the input side of the imaging device, and further, an image input from the line sensor camera is built in for each line of the imaging device. It is characterized by comprising a camera controller for switching and inputting to a plurality of image memories, and a light source controller for switching between two types of illumination at high speed in conjunction with the camera controller.

According to the third aspect of the present invention, the photoelectric sensor disposed on the entrance side of the imaging device detects the passage of the subject, and moves the plurality of image sensors to the moving direction of the subject. A line sensor camera having a line in a substantially orthogonal direction captures an image of a moving subject, and a camera controller switches an image input from the line sensor camera to a plurality of built-in image memories for each image sensor line. type in,
In addition, the light source controller switches between the two types of illumination at high speed in conjunction with the camera controller.

By doing so, it is possible to detect a defect while the production line is moving without stopping the production line, so that there is no time loss and the production capacity can be further improved.

[0016]

First Embodiment A first embodiment of the present invention will be described below with reference to the drawings.

1 to 9 show a first embodiment of the present invention.

First, the structure will be described. In the first embodiment, as shown in FIG. 1, a transfer device 2 such as a conveyor for transferring a subject 1 such as a tile in a production line is provided at an intermediate position. To the subject 1 such as a roof tile
And a light source unit 5 for illuminating the subject 1 such as a roof tile, and a light source 7 for illuminating the subject 1 with light 6 in one direction from almost right beside. Provide.

At the irradiation position of the light 3 from the illumination 4 and the light 6 from the illumination 7 in the transport device 2, an image pickup device 9 such as a CCD camera for picking up an image of the subject 1 such as a tile from almost directly above. Provide.

Further, the output signal from the imaging device 9 is converted into an A / D signal.
An A / D converter 10 for conversion is provided. And the A /
The image processing signal A / D converted by the D conversion device 10 is subjected to a binarization process. In addition, an image obtained when the light 6 is irradiated from the lateral direction is subjected to a binarization process. And an image processing device 11 that performs differentiation processing (enhancement processing) and the like over the entire image and measures the area value and the like of the defective portion. Further, there is provided a pass / fail judging device 12 for judging pass / fail by comparing the area value measured by the image processing device 11 with a preset pass / fail judgment reference value.

2 and 3 show the shape of the object 1 such as a roof tile and the characteristics of the defect 13. The defect 13 includes, as shown in FIG. ,
There are foreign substances 15 of the same color as the surface of the subject 1 such as a roof tile.
Then, as shown in FIG. 3, the dewatering defect 14 having a change in brightness has no undulation, and the foreign matter 15 having no change in brightness is an undulated defect 13. In the defect inspection, it is desired that the method be able to detect both.

Next, the operation of the first embodiment will be described with reference to FIG.

When a subject 1 such as a tile flows to a specific position on a conveyor (transport device 2) in a production line,
Stop the conveyor (1). An unillustrated photoelectric sensor or the like is used for detecting the subject 1.

When the conveyor is stopped, first, a light 6 is irradiated from almost directly above the object 1 such as a tile by the illumination 4 (2), and a brightness such as the dehydration failure 14 shown in FIGS. A defect 13 having a change is detected. The defect 13 having only a change in brightness without undulation can clearly see the difference in brightness from the surroundings by illumination from directly above. Foreign matter 15 in FIGS. 2 and 3
The defect 13 having no change in brightness as described above is not detected by this illumination method. An image obtained by illumination from directly above is input to the A / D converter 10 (3).

Next, the illumination 7 irradiates light to the subject 1 such as a roof tile in almost one direction from right beside (4), and FIGS.
A defect 13 which has no difference in brightness like the foreign substance 15 but has undulations is detected. This undulation usually has a diameter of 10 to 30.
mm and a height of about 1 to 3 mm.
Since undulations occur smoothly as described above, it is easy to receive scattered light by irradiation at an angle of about 5 degrees from almost the side. An image obtained by illuminating light in one direction from the side is input to the A / D converter 10 (5). At this point, the conveyor (transfer device 2) is started, and the subject 1 such as the next tile is started.
Is transported (6).

Next, the A / D converter 10 performs A / D conversion of the input image (7). FIG. 5 shows the A / D converted image of (3). Since the light 3 is uniformly irradiated from above, the illumination is not uneven and an image of the defect 13 having a change in brightness can be obtained. FIG. 6 shows the brightness distribution between A and B.

Next, FIG. 7 shows the A / D converted image of (5). This is because the illumination in one direction from almost right besides causes a change in brightness on the left and right sides of the image. FIG. 8 shows the brightness distribution between A and B. Originally, A is the brighter side of A and B, but FIG. 8 shows light and dark in reverse. Here, the image processing device 11 performs a differentiation process in the x direction (irradiation direction) in order to perform correction to eliminate the inclination of the change in brightness (8). The equation of the differentiation process is as follows.

F (i, j) = | f (i + 1, j) -f
(I-1, j) | This differential processing has an effect of enhancing a portion where the brightness changes sharply from light to dark or from dark to light (ie,
Emphasis processing). FIG. 9 shows a brightness distribution obtained by performing a differentiation process on FIG.

The image processing device 11 performs a binarization process on the brightness distributions of FIGS. 6 and 9 with an appropriate threshold (9), and measures the area of the defective portion (10).

The area value serving as a criterion of pass / fail judgment (pass / fail judgment reference value) is previously registered in the pass / fail judgment device 12, and the pass / fail judgment device 12 compares the measured area value with the pass / fail judgment reference value. To determine the quality (11). FIG.
If there is a defect in any one of FIG.
2 is determined to be a defect 13. As a result of the pass / fail judgment, if the pass / fail is the defect 13, the pass / fail judgment device 12 outputs a defect signal (1).
2). All the detection results are stored in the pass / fail judgment device 12 (13). If a discharge device (not shown) is provided in the transport device 2, a defective signal can be received and a defective product can be automatically discharged.

As described above, according to the present embodiment, it is possible to automatically detect the smooth undulation defect 13 by irradiating the light 6 in one direction from almost right beside the subject 1 such as a roof tile. . In addition, by irradiating the light 3 from almost right above with the same device, it is possible to automatically detect the defect 13 having no undulation. In addition, the number of imaging devices 9 such as CCD cameras to be used can be reduced, and the cost of the devices can be reduced.

Further, the image processing device 11 can correct an image obtained by irradiating light in one direction from almost right beside by an enhancement process.

[0033]

Second Embodiment FIGS. 10 to 13 show a second embodiment of the present invention. Note that the same or equivalent parts as those in the first embodiment are described with the same reference numerals.

First, the structure will be described. In the second embodiment, a plurality of image pickup devices 20 (D1 to D1 in FIG. 11) are used.
D6) is the moving direction 21 of the transfer device 2
An imaging device 23 such as a line sensor camera which is arranged in a line in a direction substantially orthogonal to the direction (the width direction 22 of the subject 1) and which can image the moving subject 1 is provided.

Then, the imaging device 23 in the transport device 2
A photoelectric sensor 25 that generates a passage signal 24 indicating that the subject 1 such as a roof tile has passed is provided on the entry side of the sensor.

Further, a plurality of (two in FIG. 10) built-in image memories 26, each of which has an image input from an image pickup device 23 such as a line sensor camera, A camera controller 28 (alternately) for switching input to 27 is provided. Further, a light source controller 30 is provided which sends a switching signal 29 to each of the light source units 5 and 8 in conjunction with the camera controller 28 to switch between the two types of illuminations 4 and 6 at high speed.

Next, the operation of the second embodiment will be described.

When the moving subject 1 placed on the transfer device 2 in the operating production line passes through the photoelectric sensor 25, a passing signal 24 is generated from the photoelectric sensor 25, and the light source controller 30 is generated by the passing signal 24. Generates a start pulse signal as shown in FIG. 12, and the imaging by the imaging device 23 is started based on the start pulse signal.

At this time, in order to image the moving subject 1, the imaging device 23 is configured to input one line at a time in the width direction 22 of the subject 1.

First, as shown in FIG. 12, a clock signal K- based on a clock pulse driving the camera controller 28 and the like is obtained.
A pulse is created. The K-pulse is generated at time intervals corresponding to the reading speed of one line of the subject 1 by the imaging device 23.

First, when the start pulse signal is generated and the first K-pulse is generated, the illumination 4 is turned on,
The subject 1 is irradiated with the light 3 from above. At this time, lighting 6
Is off. At the same time, the imaging device 23 starts shooting with the illumination 4 from above.

Then, in the imaging device 23, the six imaging devices 20 (D
1 to D6) are sequentially turned on, and the image is
8 is entered. The camera controller 28 inputs image data to one image memory 26 provided therein.
When the input by the sixth image sensor D6 is completed, K-
A pulse is generated and the light 4 is turned off.

When the illumination 4 is turned off, the illumination 6 is turned on at the same time, and the subject 1 is irradiated with the light 7 from right beside.
The switching between the illuminations 4 and 6 is performed by the light source controller 30.
Here, the input for one line is performed in the same manner as when the light 3 is irradiated from above. The obtained image data for one line is input to the other image memory 27 built in the camera controller 28.

When the input of the sixth image sensor D6 is completed, a start pulse is generated, and the operation shifts to reading of the next line. At this time, the subject 1 has been moved to the next line position by the transport device 2.

The above processing is repeated over the entire length of the subject 1.

The above processing is performed at the speed of the production line,
The timing can be set according to the size of the subject 1.

During the above-mentioned imaging, the subject 1 is moved without being stopped by the transport device 2. For example, six imaging elements 20 are arranged for one line, and the clock pulse is 20 MHz. In this case, the reading speed (scan rate) of one line is 1 / (20 * 10 <6>) *
6 (sec), which is very slight, which is a practically acceptable level. This scan rate is 1
It changes depending on the number of imaging elements 20 arranged in the line.

Thereafter, as in the case of FIG. 4, the A / D conversion of the image data input to the image memories 26 and 27 is performed (7), and the image obtained by the light 7 from almost right beside is emphasized. Differentiation processing is performed (8), and then binarization processing is performed (9), and the area of the defective portion is measured (1).
0), pass / fail judgment is made (11), and if it is a defect, a defect signal is output (12) and data is saved (13).
It will be.

As described above, according to the second embodiment,
Since the defect 13 can be detected while the transfer device 2 is moving without stopping, the time loss is eliminated, and therefore, the production capacity can be improved as compared with the first embodiment.

Except for the above, it has the same configuration as that of the above embodiment, and can obtain the same operation and effect.

In the present embodiment, the emphasis processing by differentiation is performed. However, the emphasis processing is not limited to the differentiation processing, and may be a method that electrically amplifies the amount of change.

[0052]

As described above, according to the first aspect of the present invention, the subject is irradiated with light from almost right above using two kinds of illuminations, and the subject is irradiated in one direction from almost right beside. Irradiate light.

Then, an image of the subject irradiated with light from almost right above and an image of the subject irradiated with light from almost right beside are respectively picked up by the image pickup device from almost right above. Next, the image processing device measures the area value of the defective portion from each image captured by the imaging device. Lastly, the pass / fail judgment device compares the area value measured by the image processing apparatus with a preset pass / fail judgment reference value to make pass / fail judgment.

As described above, by irradiating light in one direction from almost right beside the subject, it is possible to automatically detect a smooth undulation defect. In addition, by irradiating light from almost directly with the same device, it is possible to automatically detect a defect without undulation. In addition, the number of imaging devices used can be reduced, and the cost of the device can be reduced.

According to the second aspect of the present invention, the image processing apparatus can perform correction by an enhancement process on an image obtained when light is irradiated in one direction from almost right beside. According to the present invention, a defect can be detected during the movement without stopping the production line, so that a practically useful effect of eliminating time loss and further improving the production capacity can be exhibited.

[Brief description of the drawings]

FIG. 1 is a device configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a shape of a subject such as a roof tile and features of defects.

FIG. 3 is a side view showing the shape of a subject such as a roof tile and features of defects.

FIG. 4 is a flowchart showing a flow of processing by the apparatus of FIG. 1;

FIG. 5 is an A / D converted image when a subject such as a roof tile is irradiated from almost right above.

FIG. 6 is a brightness distribution when a subject such as a roof tile is irradiated from almost right above.

FIG. 7 is an A / D converted image when a subject such as a roof tile is irradiated from almost the side.

FIG. 8 shows a brightness distribution when a subject such as a roof tile is irradiated substantially from the side, and a brightness distribution after further differentiation processing.

FIG. 9 is a brightness distribution after further differentiating FIG. 8;

FIG. 10 is an apparatus configuration diagram according to a second embodiment of the present invention.

FIG. 11 is a plan view showing an image sensor and a subject of the line sensor camera.

FIG. 12 is a time chart according to the second exemplary embodiment;

FIG. 13 is a flowchart showing a flow of processing by the apparatus of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Subject 3 Light from right above 4 Illumination 6 Light from right beside 7 Illumination 9 Imaging device 10 A / D conversion device 11 Image processing device 12 Pass / fail judgment device 13 Defect 14 Dehydration failure 15 Foreign material 20 Imaging device 21 Moving direction 22 Moving A direction substantially orthogonal to the direction 21 23 an imaging device 25 a photoelectric sensor 26, 27 an image memory 28 a camera controller 30 a light source controller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 21/88 G01N 21/88 Z

Claims (3)

[Claims] An illumination for irradiating the subject with light from almost right above; an illumination for irradiating the subject with light in one direction from almost right beside; and an illumination for irradiating the subject with light from the two types of illumination. An imaging device that captures an image from almost directly above, an image processing device that measures an area value of a defective portion from an image captured by the imaging device, and an area value measured by the image processing device and a predetermined pass / fail determination A surface defect inspection device, comprising: a quality judgment device that performs a quality judgment by comparing with a reference value. 2. The surface defect inspection apparatus according to claim 1, wherein the image processing apparatus is configured to perform an emphasis process on an image obtained when light is irradiated in one direction from almost right beside. . 3. A line sensor camera comprising a plurality of image sensors arranged in a line in a direction substantially perpendicular to a moving direction of a subject, and capable of capturing an image of the moving subject. A photoelectric sensor for detecting that a subject has passed is disposed on the input side, and an image input from a line sensor camera is switched and input to a plurality of built-in image memories for each line of the image sensor. 2. The camera according to claim 1, further comprising: a camera controller; and a light source controller that switches between two types of illumination at a high speed in conjunction with the camera controller.
Or the surface defect inspection device according to 2.