JPH1090197A - Flaw detector for filmy body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect flaw in a filmy body surely. SOLUTION: A film 1 is irradiated with a laser light 2 generated from a laser light generator 6. When a flaw 3 in the film 1 is irradiated with the laser light 2, a diffracted light 5 is generated and detected by a photodetector 7. The photodetector 7 may comprise a photoelectric conversion element for detecting the diffracted lights 5 from a predetermined range in the breadthwise direction of the film 1 individually. Alternatively, the photodetector 7 may comprise a linear image sensor or an area image sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting flaws on a film.

[0002]

2. Description of the Related Art In the process of producing a transparent film, the film is wound on a roller or fed out from the roller. At this time, the surface of the film may occasionally be scratched due to friction with a roller or contact with a foreign substance. In preparation for such a case, it may be required to industrially detect the presence or absence of a flaw on the surface of the film. In this case, conventionally, detection has been attempted by ordinary visual or optical detection means such as a visual or television camera.

[0003]

However, since the abrasion generated at this time is extremely fine and has low optical contrast, it is necessary to detect the abrasion stably by ordinary detection means such as the above-mentioned visual inspection or a television camera. There is a problem that can not be. In addition, in order to detect a flaw in a film running between rollers at high speed, there is a problem that there is a limit in terms of response speed in the above-described visual observation and a television camera.

[0004] Therefore, an object of the present invention is to solve such a problem and to surely detect a flaw on a film-like body.

[0005]

In order to achieve this object, the present invention provides a means for irradiating light to a film-like body, and a diffracted light generated when the light irradiates a scratch on the film-like body. Detecting means.

With such a configuration, if the film is not damaged, the light applied to the film is not affected at all. However, if there is a wound,
Since the diffracted light is generated based on the flaw, by detecting the generation of the diffracted light, the presence of the flaw in the film can be reliably detected. In this case, it is only necessary to detect the presence or absence of the diffracted light, so that the damage can be detected only by using a known appropriate light detecting means.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the film-like body flaw detector of the present invention will be described with reference to FIGS. Here, reference numeral 1 denotes a resin-made transparent film in a manufacturing plant, which has a constant width w and runs at a high speed along its length direction. It is assumed that the surface of the film 1 is irradiated with a plane parallel laser beam 2 which is linear on the surface. Reference numeral 3 denotes a scratch on the film 1, which is generated in the length direction of the film.

For convenience, as shown in the drawing, the running direction of the film 1, that is, the running direction of the flaw 3, is the X axis, the direction perpendicular to the surface of the film 1 is the Z axis, and the direction perpendicular to the plane formed by the X axis and the Z axis. That is, the width direction of the film 1 is defined as the Y axis. Then, it is assumed that the laser beam 2 is applied to the film in a direction from the front side to the back side of the paper surface in FIG. The laser light 2 is XZ when viewed in the Z-axis direction.
Has an angle of Ψ with respect to the plane, has an angle of Θ with respect to the XY plane when viewed in the direction of the X axis, and has an angle of Φ with respect to the YZ plane when viewed in the direction of the Y axis. It has an angle.

When the film 1 is set in this manner, the line 4 where the film 1 and the laser beam 2 intersect, that is, the film 1
The linearly irradiated portion of the laser beam 2 upward is a detection site of the flaw 3, but if the flaw 3 is located at the position of the line 4 as shown in the figure,
Diffracted light 5 is generated.

The diffracted light 5 has extremely high brightness, and its directivity is wide in a direction perpendicular to the flaw 3 and narrow in a direction parallel to the flaw 3 as shown in FIGS. . The main directions are as shown in FIG.
The angle formed with the YZ plane when passing through the intersection with the YZ plane and perpendicular to the XY plane and in the direction of the Y axis is the direction of the straight line of Φ.

When both な お and Θ are 90 degrees, the direction of the diffracted light 5 becomes the same as the plane of the laser light 2, and it becomes difficult to detect only the diffracted light 5. Therefore, at least one of Ψ or Θ must not be 90 degrees.

Further, scattered light is generated at a portion where the film 1 and the laser beam 2 intersect. The directivity of the scattered light is wide throughout, and the luminance is extremely lower than that of the diffracted light 5. Therefore, by detecting only this diffracted light 5,
The presence of the flaw 3 in the film 1 can be reliably detected.

Next, a specific configuration of the apparatus of the present invention will be described with reference to FIGS. Here, the way of obtaining the coordinates is the same as in the case of FIGS. 3 to 5, and the angles Ψ and Φ are both 90 degrees. Reference numeral 6 denotes a laser light generator which can irradiate the film 1 with the laser light 2. At this time, a lens 8 and a photodetector 7 are provided along the direction of the diffracted light 5 generated by the presence of the scratch 3 on the film 1. Here, it is assumed that an individual photoelectric conversion element such as a photoelectric tube, a photomultiplier tube, or a photodiode is used as the light detection element 7.

Now, assume that the focal length of the lens 8 is 10 mm, Z
Distance b from film 1 to lens 8 along the direction of the axis
Is 300 mm, and the size d of the detection site on the film 1 is 2
If it is 0 mm, the size a of the detected image on the light detecting element 7 is a
Is about 0.7 mm. Therefore, an element having a larger light receiving surface is required.

On the other hand, the laser light generator 6 generates a fan-shaped flat laser light 2 having a laser spread angle of Ω. The angle Θ between the center of the laser beam 2 and the XY plane is set to 4
5 degrees. In this case, the distance c from the laser light generator 6 to the film 1 along the direction of the Z axis is 200 mm,
Assuming that the spread angle Ω is about 5 degrees, the laser beam 2 can completely irradiate the detection site of the film 1 having the size d of 20 mm as described above.

According to this structure, the laser beam 2 transmitted through the film 1 travels in a direction different from the direction of the diffracted light 5 by going straight, and does not directly enter the lens 8. It will not be done. Also wound 3
As described above, the diffracted light 5 spreads greatly in the direction perpendicular to the flaw 3 as described above, so that it can be easily detected by the light detection element 7 by condensing it with the lens 8.

At this time, since the photodetecting element 7 utilizing the photoelectric tube or the like as described above can generally operate at high speed, the film 1 is moving at high speed as described above, and the scratch 3 is short. In such a case, the flaw 3 can be detected.

As described above, in addition to the diffracted light 5, scattered light is simultaneously generated on the surface of the film 1. However, since the luminance of the scattered light is lower than the luminance of the diffracted light 5, the scattered light is substantially reduced. Does not hinder. However, when the size d of the detection portion is increased, the sum of the energies also increases, and eventually the energy of the diffracted light 5 becomes larger than the energy of the diffracted light 5.
In some cases, it may be difficult to detect, so care must be taken not to detect a very large range.

In order to detect a large area, a plurality of laser light generators 6A to 6P are provided along the width direction of the film 1 as shown in FIG. Diffracted light 5 generated by laser light 2 from.
May be individually detected by a plurality of light detection elements 7A to 7P provided respectively corresponding to the laser light generators 6A to 6P.

However, in this case, the number of the laser light generators 6A to 6P and the number of the photodetectors 7A to 7P are increased, so that the laser light 2 which travels straight after passing through the film 1 is not related to the other. It may happen that the light enters the light detection element. Such a situation is caused by the photodetector 7
This cannot be solved by providing a lens hood of a certain length in A to 7P. For example, in the example of FIG. 6, the straight laser beam 2 from the laser beam generator 6N enters the photodetector 7A, and similarly, the straight laser beam 2 from the laser beam generators 6O and 6P respectively enters the photodetectors 7B and 7C. This is a problem because it is difficult to detect the original diffracted light 5.

Therefore, for example, the laser light generator 6A
6P and the corresponding laser light 2A-2P transmitted and received between the photodetectors 7A-7P can be modulated. This processing will be described with reference to FIG. In this FIG.
The laser light generator 6 is constituted by a laser diode, and the light detecting element 7 is constituted by a photodiode. The laser light generator 6 has a light modulation circuit
The synchronous detection circuit 12 is connected to the photodetector 7. Reference numeral 13 denotes a clock circuit, which controls each of the optical modulation circuits 11 of the laser light generators 6A to 6P shown in FIG. It is driven by a signal. That is, for example, the laser light generator 6A and the photodetector 7A are driven by clock signals of the same frequency. As a result, signals other than the same frequency can be sharply removed.

In the example shown in FIG. 6, laser light generators 6A to 6P and photodetectors 7A to 7P of 16 channels are provided. On the other hand, the clock circuit 13 of FIG.
Clock signals of different types can be generated. Therefore, in this case, the laser light generators 6A to 6A
P and the photodetectors 7A to 7P may be divided into two blocks each having eight channels, and eight types of frequencies may be assigned to each block. However, when both the straight laser beam 2 and the diffracted light 5 enter one photoelectric conversion element, it is necessary to assign frequencies so that the modulation frequencies of the straight laser beam 2 and the diffracted light 5 are always different. is there. In addition,
This allocation is performed by the laser light generator 6A of each channel.
-6P and the mounting pitch between the photodetectors 7A-7P,
It can be appropriately determined according to the distance from the surface of the film to the photodetectors 7A to 7P.

As the photodetector 7 in FIG. 1, a linear image sensor, an area image sensor, or the like can be used in place of the individual photoelectric conversion elements such as the above-described photoelectric tube, photomultiplier tube, and photodiode. That is, in FIGS. 1 and 2, the focal length of the lens 8 is set to 1
0 mm, and the distance b from the film 1 to the lens 8 is 3
000 m, and the size of the detection site d on the film 1 is 2
If it is 00 mm, the size a of the detection image on the photoelectric detection element 7 is about 7 mm.

The angle Θ between the laser beam 2 from the laser beam generator 6 and the XY plane is 45 degrees, the spread angle Ω is about 5 degrees, and the distance c from the laser beam generator 6 to the film 1 is If the thickness is 2000 mm, the laser beam 2 can completely irradiate a detection site on the film 1.

In this case, similarly, only the diffracted light 5 enters the light detecting element 7, and this light detecting element 7 is a linear image sensor whose pixel array direction is the Y-axis direction and the size of the detected image is large. Assuming that the number of effective pixels in the range a is 500, the size of an image on the film 1 per pixel is about 0.4 mm.

In the case of the individual photoelectric conversion elements described above, the size of the image on the film 1 detected by one element 7 was 20 mm. The size becomes 1/50.
When the size per pixel is small as described above, noise such as scattered light is less likely to enter, and the S / N ratio is improved, resulting in extremely high stability as compared with the case where individual photoelectric conversion elements are used. Detection in degrees is possible.

Since the spread of the diffracted light 5 on the XZ plane is small as described above, when a linear image sensor is used as the light detecting element 7, it is necessary to accurately position the light detecting element 7 in the X-axis direction. is there. On the other hand, if an area image sensor is used as the light detecting element 7, since there is an array of pixels also in the X-axis direction, it is not necessary to perform positioning with such high accuracy.

In the above description, as the film 1 to be measured, a transparent film made of resin running in a manufacturing plant is exemplified, but the present invention is not limited to this. For example, any material that does not generate large scattered light, such as glass or other thin film products, can be applied to the flaw detection. Further, as described above, although it is particularly advantageous for detecting the flaw 3 in the running direction of the film 1, a flaw in a different direction can be similarly detected.

[0029]

As described above, according to the present invention, a means for irradiating light to a film and a means for detecting diffracted light generated when the light irradiates a scratch on the film are provided. Therefore, if there is a flaw in the film, a diffracted light based on the flaw is generated, and by detecting the occurrence of the diffracted light, it is possible to reliably detect the presence of the flaw in the film. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a film-like body flaw detector according to the present invention.

FIG. 2 is a side view of the portion shown in FIG.

FIG. 3 is a principle view of a film-like flaw detector according to the present invention.

FIG. 4 is a side view of the portion shown in FIG. 3;

FIG. 5 is a plan view of a portion shown in FIG. 3;

FIG. 6 is a diagram showing an example of a specific configuration of a film-like body flaw detector according to the present invention.

FIG. 7 is a block diagram of an example of a drive circuit of the flaw detector of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film 2 Laser light 5 Diffracted light 6 Laser light generator 7 Photodetector

Claims (6)

[Claims] 1. A film-shaped object comprising: means for irradiating light to a film-shaped object; and means for detecting diffracted light generated when the light is applied to a scratch on the film-shaped object. Flaw detection equipment. 2. The film-like body travels in a length direction with a constant width, and the irradiation means can irradiate light in the width direction of the film-like body. The flaw detector for a film-like body according to claim 1. 3. An apparatus according to claim 1, wherein said irradiating means is capable of irradiating linear light on the surface of the film. 4. The diffractive light detecting means has a photoelectric conversion element for individually detecting diffracted light from a predetermined range in a width direction of the film-like body. A flaw detector for a film-like body according to the above. 5. The irradiating means has a plurality of light sources for irradiating the film with light for irradiating a predetermined range in a width direction of the film, and a plurality of photoelectric conversions corresponding to each light source. Means are provided, and for each set of each light source and the corresponding photoelectric conversion means, the light in the set is not so detected by the set of photoelectric conversion means so as to detect the light from the other set of light sources. 5. The flaw detection device for a film-like body according to claim 4, further comprising means for modulating with a signal different from a signal for a set of light. 6. An apparatus according to claim 1, wherein said diffracted light detecting means comprises a linear image sensor or an area image sensor.