JP2001318059A - Defect inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device having high detection precision, capable of preventing the influence of a formation spot of a test body, and detecting a defect even if the defect having very little difference in reflectance between itself and the test body exists. SOLUTION: This inspection device has a reflector 1 installed close to the test object 2, an illumination device 3 for illuminating the test object 2 from the opposite direction to the reflector 1, a sensor 5 for receiving reflected light from the test object 2 illuminated from the illumination device 3, and having a filter 4 installed on the front and having a color having low transmissivity in a wavelength region other than a defect absorption wavelength, and an image processing device 6 for processing a detection signal of the sensor 5, and detecting the defect included in the test object 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object to be inspected having a non-uniform reflectance, such as a fibrous material such as a tow band or a nonwoven fabric, an object having a high light transmittance or having a through hole. The present invention relates to a defect inspection apparatus in which a body or a plurality of inspected objects are arranged with a gap therebetween, and inspects the plurality of inspected objects simultaneously.

[0002]

2. Description of the Related Art As a technique for detecting a defect of a non-woven fabric having a non-uniform formation density, for example, Japanese Patent Publication No. 5-40
There is a defect detection method described in US Pat. This is to dispose a reflector having substantially the same gray gradation as that of the nonwoven fabric below the nonwoven fabric, to prevent the influence of uneven formation of the nonwoven fabric, and to detect a defect with a low gray gradation.

[0003]

However, in such a defect detection method, although the influence of unevenness of formation of the nonwoven fabric can be prevented, light yellow defects such as oil stains adhering to the nonwoven fabric and the like can be eliminated from the surface of the white nonwoven fabric. There was almost no difference from the reflectance, and it was difficult to detect. In addition, in such a defect detection method, a reflector having substantially the same gray gradation as that of the nonwoven fabric is arranged, so that the nonwoven fabric and the reflector cannot be distinguished from each other. Or
There was a problem that it was not possible to follow the meandering of a sheet traveling at high speed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to prevent the influence of the formation irregularities of the object to be inspected without erroneously determining the dirt attached to the reflector as a defect. When there is a defect such as a pale yellow included in the object to be inspected that has little difference in reflectance when the object is white, such a defect can be detected and a defect inspection apparatus can be used. The purpose is to provide. Also,
It is an object of the present invention to provide a device for inspecting a defect of an object to be inspected without erroneously determining dirt attached to a reflector as a defect and improving defect detection accuracy.

[0005]

According to a first aspect of the present invention, there is provided a defect inspection apparatus, comprising: a reflector provided so as to be close to one surface of an object to be inspected; An illumination device that illuminates the body from a direction opposite to the reflector, receives reflected light from the inspection object illuminated from the illumination device, and has a transmittance in a wavelength region other than the absorption wavelength of the defect. It is characterized by including a sensor having a filter having a low color mounted on the front surface, and an image processing device that processes a detection signal of the sensor and detects a defect included in the inspection object.

In the sheet defect inspection apparatus according to the first aspect, a filter having a color having a low transmittance in a wavelength region other than the absorption wavelength of the defect is attached to the front surface of the sensor, so that the object to be inspected is white. In the case where there is a defect such as light yellow included in the test object that has almost no difference in reflectance from the test object, the defect can be apparently remarkable.

[0007] The invention described in claim 2 is the first invention.
The defect inspection apparatus described above further includes a second sensor to which no filter is attached. Since the defect inspection apparatus according to the second aspect further includes the second sensor to which no filter is attached, the edge coordinates of the inspection object can be detected, and the inspection area can be set based on the detected edge coordinates. In addition, it is possible to prevent dirt or the like adhering to the reflector from being detected as a defect of the inspection object.

[0008] The invention described in claim 3 is the first invention.
Or the defect inspection device according to 2, wherein the image processing device processes the detection signals of the two sensors, and
Detecting the edge coordinates of the inspection object based on the detection output of the sensor, and setting the inspection range of the inspection object based on the edge coordinates, and detecting the first sensor within the set inspection range. A defect included in the inspection object is detected based on a detection output. Claim 3
The defect inspection apparatus described in (1) can set an inspection area based on the detected edge coordinates by the image processing apparatus described above, thereby preventing detection of dirt or the like attached to the reflector as a defect of the inspection object. it can.

The invention described in claim 4 is the first invention.
3. The defect inspection apparatus according to any one of items 1 to 3, wherein the filter has a color that is complementary to the defect. In the defect inspection apparatus according to the fourth aspect, the filter attached to the front surface of the sensor has a color that is complementary to the defect, so that when the inspection object is white, the inspection object such as pale yellow included in the inspection object. Even in the case where there is a defect having almost no difference between the inspection object and the reflectance, the defect can be apparently remarkably remarkable and the defect can be detected.

[0010] The defect inspection apparatus according to claim 5 is
5. The sheet defect inspection apparatus according to claim 1, wherein the reflector has a low reflectance in a wavelength region other than an absorption wavelength region of a defect included in the inspection object. In the sheet defect inspection apparatus according to the fifth aspect, the reflectance of the reflector is reduced in a wavelength region other than the absorption wavelength region of the defect included in the inspection object, whereby the inspection is performed when the inspection object is white. Even when there is a defect such as light yellow contained in the body, which has almost no difference in reflectance from the inspected object, the defect can be apparently remarkably remarkable and the defect can be detected.

[0011] The invention according to claim 6 is the first invention.
The defect inspection apparatus according to any one of to 5, wherein the object to be inspected transmits a part of light illuminated from a lighting device,
The light reflected by the reflector is transmitted again. The defect inspection apparatus according to any one of claims 1 to 5, performs inspection of an object to be inspected such that a part of light illuminated from an illuminating device is transmitted and reflected light from the reflector is transmitted again. It is particularly suitable for the defect inspection apparatus according to the present invention.

The invention according to claim 7 is the first invention.
5. The defect inspection apparatus according to any one of 5), wherein a plurality of inspected objects are arranged with a gap, and the plurality of inspected objects are inspected simultaneously. The defect inspection apparatus according to any one of claims 1 to 5, wherein a plurality of inspection objects are arranged with a gap, and the plurality of inspection objects are inspected simultaneously. Particularly suitable.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration of a sheet defect inspection apparatus according to an embodiment of the present invention. In the figure, a sheet defect inspection apparatus according to an embodiment of the present invention includes a reflector 1 installed in contact with a traveling sheet 2 and a traveling sheet 2 in a direction opposite to the reflector 1. , An illumination device 3 for illuminating from a light source, a sensor 5 receiving a reflected light from the sheet 2 illuminated by the illumination device 3 and having a filter 4 having a color complementary to the defect and having a color complementary to the defect, and a sensor 5, The image processing device 6 processes the detection signal of the sheet 2 to detect a defect included in the sheet 2, a host computer 7, and a display 8.

Although the embodiment shown in FIG. 1 shows a case where the sheet 2 to be inspected travels between the reflector 1 and the illuminating device 3, in the present invention, the sheet 2 to be inspected is May be fixed and the illumination device 3 and the sensor 5 or the reflector 1 move on the inspection object. Examples of the inspection object inspected by the defect inspection apparatus of the present invention include an inspection object having non-uniform reflectance such as a fibrous material such as a tow band and a nonwoven fabric, an inspection object having high light transmittance, and an inspection object having a through hole. Particularly suitable for inspection objects. Alternatively, the defect inspection apparatus of the present invention is particularly suitable for a case where a plurality of inspected objects are arranged with a gap and the plurality of inspected objects are inspected simultaneously.

The reflector 1 preferably uses a color having a low reflectance of a color other than the absorption wavelength region of the defect 9 (FIG. 2). This is because by setting the reflectance of the reflector 1 in this way, a defect having a small difference in reflectance from the object to be inspected such as light yellow included in the object to be inspected when the object to be inspected 2 is white exists. In such a case, the sensor output difference between the defect 9 and the inspection object 2 is made larger than the sensor output difference between the inspection object 2 and the reflector 1 when passing through the filter attached to the sensor, and the defect is apparent. It is possible to detect even a defect having a small difference in reflectance with the object to be inspected. For example, when the white object 2 such as a nonwoven fabric has a light yellow defect 9 such as oil stain, the reflector 1 is preferably blue. Further, it is preferable to select an appropriate color for the reflector 1 according to the wavelength characteristics of the filter 4.

Here, the proper color is defined as the difference between the output value of the sensor 5 due to the reflected light from the reflector 1 and the output value of the sensor 5 due to the reflected light from the sheet 2 when the filter 4 is not used. Large, when the filter 4 is used, the reflector 1
A color in which the difference between the output value of the sensor 5 due to reflected light from the sensor 5 and the output value of the sensor 5 due to reflected light from the sheet 2 is small. The reflector 1 is installed so as to be in contact with the sheet 2 so that flutter of the sheet is reduced. Note that the positional relationship between the reflector 1 and the sheet 2 can be brought into contact as in this embodiment, but the reflector 1 and the sheet 2 may be provided with a gap of about several mm.

As the reflector 1, various shapes can be used according to the purpose, but a plate or a cylindrical shape is preferable. As the filter 4 attached to the front surface of the sensor 5, a filter having a color having a low transmittance in a wavelength region other than the absorption wavelength of the defect 9 is used. By using such a filter 4, when the test object is white, the difference in reflectance from the test object such as pale yellow included in the test object is small and it is difficult to detect with a normal sensor alone. However, by passing through the filter 4, the defect can be apparently remarkable and the sensor output can be increased. In particular, it is preferable to use the filter 4 of a color having a complementary color relationship with the defect because the sensor output can be maximized.

The detection output (hereinafter, referred to as sensor output) of the sensor 5 based on the reflected light from each of the reflector 1, the sheet 2, and the defect is represented by the illumination light from the illumination device 3, the filter 4, It changes according to the wavelength characteristic of the sensor 5. The sensor outputs of the following equations are the sum of the integrated values for each wavelength. Drk = Lk × Rk × Ck (1) Dfrk = Lk × Rk × Ck × Fk (2) Dsk = Lk × Sk × Ck (3) Dfsk = Lk × Sk × Ck × Fk (4) Ddk = Lk × Dk × Ck (5) Dfdk = Lk × Dk × Ck × Fk (6) where, Drk: sensor output of reflector (without filter) Dfrk: sensor output of reflector (with filter) Dsk: sensor output of sheet (without filter) Dfsk: Sheet sensor output (with filter) Ddk: Defect sensor output (without filter) Dfdk: Defect sensor output (with filter) Lk: Lighting wavelength characteristic (k: wavelength) Rk: Reflector wavelength characteristic ( k: wavelength) Sk: wavelength characteristic of sheet (k: wavelength) Dk: wavelength characteristic of defect (k: wavelength) Fk: wavelength characteristic of filter (k: wavelength) Ck: wavelength characteristic of sensor (k: wavelength) .

Reflector 1 and filter 5 used in the present invention
Is a range satisfying the following expression. Drk <Dsk (7) Dfrk ≒ Dfsk (8) Dfdk <Dfsk (9) As the sensor 5, a line CCD camera or the like can be used, and appropriate scanning is performed according to the resolution in the width direction and the resolution in the flow direction. Set the cycle.

The image processing device 6 processes the detection signal of the sensor 5 to detect a defect included in the sheet 2. The image processing device 6 performs A / D conversion, binarization, and run-length encoding on an analog video signal, which is a detection signal of the sensor 5, and then measures the size and position of a defect on the sheet 2. The measured value of the defect included in the sheet 2 transferred from the image processing device 6 is displayed on the display 8 using the host computer 7. The display 8 displays the position (width direction, flow direction) of each defect, the size of the defect (area,
(Width, length) etc. are displayed.

FIG. 2 shows the relationship between the sheet 2 and the inspection position. In the figure, three sheets (2-1, 2-
2, 2-3) It is running. 11 is a sensor reading position. The reflector 1 is installed below the sensor reading position 11 so as to contact these sheets 2. 9 is
This is a defect attached to the reflector 1 and is not a target to be detected but 10 is a defect existing on the sheet 2 to be detected. FIG. 3 shows the relationship between the sheet 2 and the inspection area. In the figure, the field of view of the sensor 5 is from the start point (S ₀ ) to the end point (E ₀ ).

In the above configuration, the sheet 2 and the reflector 1
Is illuminated by the illumination device 3, and the reflected light of the illumination light is received by the sensor 5. Since the sheet 2 and the reflector 1 are white and blue and have different color tones, when the filter 4 is not attached to the sensor 5, the detection output of the sensor 5 by the reflected light of the sheet 2 and the reflected light of the reflector 1 There is a sufficient output difference with the detection output of the sensor 5. For this reason,
In the image processing device 6, each sheet (2-1, 2-2, 2-
The edge coordinates (start point: S ₁ , S ₂ , S ₃ , end point: E ₁ , E ₂ , E ₃ ) indicating the boundary position with the reflector 1 in ₃ ) are detected, and the sensor 5 when the filter 4 is used. Set the inspection area on the side.

A designated threshold is set inside the inspection area, and a threshold value at which no defect is detected outside the inspection area, for example, 0 is set for a dark defect. By setting the inspection area outside by the specified number of elements from the edge coordinates, it is possible to detect a defect in the peripheral portion of the sheet 2. Thus, the filter 4 is connected to the sensor 5.
, 2-2, 2-2
By setting the inspection area for each sheet by detecting the edge coordinates of -3), the defect 9 attached to a position outside the sheet 2 is not detected, and the defect 10 attached to the sheet 2 is not detected. Only can be detected.

Next, another embodiment of the present invention will be described with reference to FIG. In this figure, the defect inspection apparatus includes a first sensor 5-1 to which a filter 4 is attached.
In addition to (corresponding to the sensor 5 in FIG. 1), the second embodiment differs from the defect inspection apparatus shown in FIG. 1 in that a second sensor 5-2 without the filter 4 is added. In FIG. 6, a defect inspection apparatus includes a reflector 1 installed so as to be in contact with a traveling sheet 2, an illumination device 3 for illuminating the traveling sheet 2 from a direction opposite to the reflector, and an illumination device. A filter 4 having a color complementary to the defect receiving the reflected light from the sheet 2 illuminated from 3
Sensor 5-1 and the sheet 2 illuminated from the illumination device 3
A second sensor 5-2 to which no filter for receiving the reflected light from the camera is attached, an image processing device 6, a host computer 7, and a display 8.

The second sensor 5-2 is connected to the first sensor 5-
1 is read, but the filter is not attached, so that the detection output of the sensor 5-2 by the reflected light from the sheet 2 and the detection output of the sensor 5-2 by the reflected light from the reflector 1 The sensor output difference from the detection output increases. Therefore, edge coordinates indicating the boundary position between the reflector 1 and the sheet 2 (start point: S ₁ , S ₂ , S ₃ , end point: E ₁ ,
E ₂ , E ₃ ). An inspection area by the first sensor 5-1 is set based on the edge coordinates detected by the second sensor 5-2.

By setting the inspection area to be set several pixels outside the detected edge coordinates, it is possible to stably detect a defect in the peripheral portion of the sheet 2. First
Sensor 5-1 and the second sensor 5-2 read reflected light from the same position, so that even if the sheet 2 has meandering, no deviation of the inspection area occurs. Further, even if foreign matter adheres to the reflection plate 1, it can be excluded from the inspection area. The detection signals of the second sensors 5-1 and 5-2 are processed by the image processing device 6, and the measured values of the defects contained in the sheet 2 transferred from the image processing device 6 are displayed on the display 8 using the host computer 7. To be displayed.

[0027]

Example 1 Using the inspection apparatus shown in FIG. 1, a defect inspection of a sheet-like tow 2 in which thousands to tens of thousands of continuous fibers were assembled was performed. The toe sheet 2 is white and has a width of about 50 mm. As shown in FIG. 2, three toe sheets (2-1, 2-2, 2-
3) is traveling in the sensor reading area 11 at a traveling speed of about 600 m / min. The illumination device 3 is a reflection illumination device (model name: manufactured by Kyoto Denki Co., Ltd.) using a twin type 32 W white fluorescent lamp that reduces the influence of shadows due to the unevenness of the toe sheet 2.
The distance between the lighting device 3 using FLT-32) and the sheet 2 was 50 mm.

As the sensor 5, a line CCD camera (model: SCD-2048B) manufactured by Mitsubishi Rayon Co., Ltd. was used. The number of elements of the sensor 5 was 2048, and the resolution in the element direction was 0.4 mm / element. The reading range of the sensor 5 is about 80
0 mm, and covers three ranges of the toe sheet 2. The lens of the sensor 5 used had a focal length of 50 mm manufactured by PENTAX. The distance between the sensor 5 and the toe sheet 2 is 1595 mm. The scanning cycle of the sensor 5 is 0.133 ms, and the traveling speed of the toe sheet 2 is 600 m.
Minute, the resolution in the running direction of the toe sheet 2 is 1.33.
mm / pixel.

On the surface of the sensor 5, a blue filter 4, which is a color complementary to the light yellow defect, was attached. Among the various blue filters 4, a Kenko Corporation blue filter (model name: B-44) in which the difference between the defect and the sensor 5 output of the sheet 2 is large.
0) was adopted. As the image processing device 6, a line image processing device (model name: LSC-300) manufactured by Mitsubishi Rayon Co., Ltd. was used. The host computer 7 is a PC-98 manufactured by NEC Corporation.
21, the position (width direction, flow direction) of each defect, the size (area, width, length) of each defect, etc. are displayed on the display 8.

The reflector 1 of blue (9B7.5 / 5.5) is installed below the sensor reading position 11 so as to contact the three toe sheets 2. Toe sheet 2
Is running at a high speed and meanders by several mm. Therefore, the sensor 5 detects the edges (starting points: S ₁ , S ₂ ,
S ₃ , the end point: E ₁ , E ₂ , E ₃ ) was detected and the inspection area was set. FIG. 4 shows an image captured by the sensor 5 when the filter 4 is used. In FIG.
2 is a waveform reading position, and 10 is a defect. Since the blue reflector 1 and the blue filter 4 are used, the difference in brightness between the area 14 of the toe sheet 2 and the area of the reflector 1 is small, and only the defect 10 is imaged with high contrast.

FIG. 5 shows an output waveform 15 of the sensor 5 at the waveform display position 12 in FIG. In the figure,
Reference numeral 14 denotes a range of the toe sheet 2, and reference numeral 13 denotes an output waveform of the defect 10. At the defective portion, the light reflected from the defect 10 is absorbed by the filter 4 of a color complementary to the pale yellow defect, which is an oil stain, so that the light receiving level of the input to the sensor 5 is reduced only at the defective portion. I have. Since the difference between the sensor output of the reflector 1 and the sensor output of the toe sheet 2 is small in the portion other than the defect, the defect could be detected without any problem even when the whole was set to the same threshold value.

Table 1 shows the configuration of the apparatus used.

[Table 1] The inspection was performed under the conditions shown in Table 2.

[Table 2]

Example 2 The same defect inspection of the toe sheet 2 as in Example 1 was performed using the defect inspection apparatus shown in FIG. This defect inspection device
First Sensor 5-1 Using Filter 4 of First Embodiment
In addition to (corresponding to the sensor 5 in FIG. 1), the configuration is the same except that a second sensor 5-2 that does not use the filter 4 is added. The inspection conditions were the same as in Example 1.

In this defect inspection apparatus, the edge coordinates (starting point: S ₁ , S ₂ , S ₃ , end point: E ₁₎ indicating the boundary position between the reflector 1 and the toe sheet 2 are detected by the second sensor 5-2.
E ₂ , E ₃ ), and obtains the first sensor 5-1 of the toe sheet 2.
While the inspection area is set, a defect included in the toe sheet 2 is detected based on the detection output of the first sensor 5-1 within the set inspection range. First sensor 5-
Since the first and second sensors 5-2 read the reflected light from the same position, no deviation of the inspection area occurred even if the toe sheet 2 meandered. By performing the inspection area setting in parallel with the defect detection in this manner, the inspection area can be set following the toe sheet 2. Could be detected.

Comparative Example A defect inspection of a sheet was performed by using a defect inspection apparatus similar to that shown in FIG. The difference from the first embodiment is that a defect inspection apparatus similar to the first embodiment is used except that the filter 4 is not attached to the sensor 5 and a white sheet having the same reflectance as the toe sheet 2 is used as the reflector 1. The same defect inspection of the tow sheet 2 was performed. Although dark yellow defects could be detected, light yellow defects could not be detected. Further, the defect 9 of the toe sheet 2 and the defect 10 outside the sheet could not be distinguished.

[0036]

According to the present invention, by attaching a filter having a color having a low transmittance in a wavelength region other than the absorption wavelength of a defect to the front surface of the sensor, it is possible to prevent the influence of the formation unevenness of the inspection object, Even when there is a defect such as light yellow contained in the object to be inspected that has little difference in reflectance with the object to be inspected when the object to be inspected is white, the detection accuracy of such a defect can be detected. A high defect inspection device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a configuration of a defect inspection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between a sheet and an inspection position.

FIG. 3 is an explanatory diagram showing a positional relationship between a sheet and an inspection area.

FIG. 4 is an explanatory diagram of an image showing a state in which a sheet has a defect.

FIG. 5 is a waveform chart showing an output waveform of a sensor at a defective portion in FIG. 4;

FIG. 6 is a block diagram showing another example of the configuration of the defect inspection device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflector 2 Sheet, toe sheet (inspection object) 3 Illumination device 4 Filter 5 Sensor 6 Image processing device 7 Host computer 8 Display 9 Defect (outside sheet) 10 Defect (in sheet) 11 Sensor reading position 12 Waveform display position 13 Defect Unit output 14 Toe sheet range 15 Sensor output waveform

Claims (7)

[Claims] 1. A reflector installed to be close to one surface of an object to be inspected, an illumination device for illuminating the object to be inspected from a direction opposite to the reflector, and A sensor in which a filter having a color having a low transmittance in a wavelength region other than the absorption wavelength of the defect is received on the illuminated reflected light from the inspection object, and a filter having a color attached to the front surface, and a detection signal of the sensor is processed. An image processing apparatus for detecting a defect included in the object to be inspected. 2. The defect inspection apparatus according to claim 1, further comprising a second sensor to which no filter is attached. 3. The image processing device processes detection signals of the two sensors, detects edge coordinates of the object to be inspected based on detection outputs of the second sensor, and performs processing based on the edge coordinates. In addition to setting the inspection range of the inspection object,
The defect inspection apparatus according to claim 1, wherein a defect included in the inspection object is detected based on a detection output of the first sensor within the set inspection range. 4. The defect inspection apparatus according to claim 1, wherein the filter has a color having a complementary color relationship with the defect. 5. The defect inspection apparatus according to claim 1, wherein the reflector has a low reflectance in a wavelength region other than an absorption wavelength region of a defect included in the inspection object. . 6. The inspection object according to claim 1, wherein the inspection object transmits a part of light illuminated from a lighting device, and transmits the reflected light reflected by the reflector again. The inspection device according to item 1. 7. The inspection apparatus according to claim 1, wherein a plurality of inspected objects are arranged with a gap, and the plurality of inspected objects are inspected simultaneously.