JPH0328748A - Flaw detector - Google Patents

Abstract

PURPOSE:To detect even a flaw which causes neither transmitted light nor reflected light to shift in peak position by providing plural photosensors and detecting outputs of photosensors other than photosensors which detect the main light of the transmitted or reflected light. CONSTITUTION:A light receiving part S is arranged on the rear surface side of, for example, a sheet body 1 to be inspected and consists of the photosensors S1, S2 ... arrayed in matrix. One photosensor is almost as large as a circular light beam transmitted through the sheet body 1. When a light beam transmitted through a nondefective sheet body 1 reaches the sensor S5, the beam is received only by the sensor S5 and none of other sensors detects it. If the sheet body 1 has a flow an elliptic image is formed on the light receiving part S, so sensors other than the sensor S5 also detect the light even although the position of the main light is on the sensor S5. For the purpose, a detection part D removes the output of the sensor S5 and detects the outputs of the sensors at its periphery to detect the flaw.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention is applicable to surface defects (such as irregularities) of sheet-like materials such as resin films, etc., and internal defects (fish, etc.) caused by foreign matter taken in, etc. The present invention relates to a device for detecting eye (eye, etc.).

(Prior Art) Conventionally, a device for detecting surface defects and internal defects in a sheet-like object such as a traveling resin film has been designed to direct and scan a light beam onto the sheet-like object to be inspected. Among the light transmitted or reflected by a sheet-like object, there is one that receives light that is scattered or refracted by defects. In order to detect minute defects in a sheet to be inspected with such a device, it is of course necessary to detect very small changes in the amount of light caused by scattering or refraction caused by the defect. , for example, Special Public Interest Publication 57-
The device is devised as described in Publication No. 21047.

That is, in the conventional device described in Japanese Patent Publication No. 57-21047, when detecting a fisheye in a polyethylene film, the peak position of transmitted light received when a fisheye exists is determined by the presence of a fisheye. Noting that the peak position of the transmitted light that is received when no polyethylene film is present is shifted by a distance △ Either the light receiving section itself is shielded to a distance xc from the optical axis of the light beam when there is no polyethylene film. By placing them apart from each other, approximately half of the transmitted light cannot be received, and only the increase or decrease in the amount of light due to the fisheye can be received, making it easier to detect signal changes.

However, this conventional device is not effective at all for defects where the peak position of transmitted light cannot be shifted. Another problem is that when the sheet-like object to be inspected is regarded as an x, y plane, the detection sensitivity is different in the x-axis direction and the y-axis direction.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the above-mentioned problems of the conventional device, and to be able to detect even defects in which there is no deviation in the peak position of transmitted light. sheet-like material x
, y plane, it is possible to prevent the detection sensitivity from being different in the X-axis direction and the y-axis direction.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an apparatus for detecting defects in a running sheet-like object, which directs a light beam onto the sheet-like object to be inspected, and a light projecting section that scans; a light receiving section that includes a plurality of optical sensors arranged in a matrix that receives transmitted light or reflected light of the light beam from the sheet-like object to be inspected; A defect detection device is provided, comprising: a detection unit that determines the presence or absence of a defect based on the presence or absence of an output from an optical sensor other than the optical sensor receiving the principal light of the reflected light.

In this invention, the principal light of transmitted light or reflected light refers to circular transmitted light or It is reflected light.

A light projection unit that directs and scans a light beam onto a sheet-like object to be inspected is composed of a light source, a light beam scanner, a condenser lens combined therewith, and the like. As the light source, a laser light source is usually used. Further, as the light beam scanner, a well-known rotating polygon mirror is usually used.

The light receiving section includes a plurality of photodiodes, CCDs (C
It is made by arranging optical sensors such as harge coupled devices in an mXn matrix (m and n are integers). When it is desired to receive the light that has passed through the sheet-like object to be tested, the light-receiving section is placed on the back side of the sheet-like object to be tested, that is, on the opposite side of the installation side of the light-emitting section, and the reflected light is When you want to receive light, it is placed on the installation side of the light projector.

The detection unit determines whether or not there is a defect in the sheet-like object to be inspected based on the outputs of the plurality of optical sensors, and receives the main light of transmitted light or reflected light from the sheet-like object to be inspected. It consists of a circuit that adds the outputs of optical sensors other than the one that is used, a comparison circuit that determines whether the addition result is greater than zero, and so on.

By the way, defects detected by the apparatus of the present invention can be explained as shown in FIG. 3, assuming that the sheet-like object to be inspected is a light-transmitting film.

5 In FIG. 3, the sheet-like object 1 to be inspected is assumed to be an x- and y-plane, and the x-axis and y-axis are taken as shown in the figure, respectively. Further, assuming that the light receiving surface 8 is parallel to the sheet-like object 1 to be tested, the light receiving surface 8 is similarly regarded as the x, y plane, and the X' axis, y
′ axes are taken as shown. Here, the X axis and
' axis, y axis and y' axis are parallel to each other, and
Assume that the directions are the same. In addition, test sheet material 1
In the above, A is a part without defects, B is a part with a long defect in the y-axis direction, and C is a part with a long defect in the X-axis direction. FIG. 3 shows the images on the light receiving surface 8 when the light beam L is directed to the parts A, B, and C on the test sheet 1, respectively.
They are indicated by A-, B', and C-, respectively. Note that the light beam L has a circular cross section, and its diameter is smaller than the length of the defects in portions B and C.

Now, when the light beam L is directed to the defect-free portion A on the sheet-like object 1 to be inspected, the image on the light receiving surface 8 is the image of the light beam L.
6 (Projected image A-). On the other hand, defective parts B and C
When the light beam L is directed at a portion B, the image on the light receiving surface 8 becomes an ellipse (projected images B' and C''). The longitudinal direction of the image on the light-receiving surface 8 is the X'-axis direction.On the other hand, when the light beam L is directed at the portion C that has a long defect in the X-axis direction, the image on the light-receiving surface 8 is The elongated direction is the y-uniaxial direction.In other words, it can be seen that the elongated direction of the defect and the elongated direction of the oval image formed on the light-receiving surface are offset by 90 degrees.This phenomenon is explained as follows. It can be explained as follows.

That is, defects on the surface or inside the sheet-like object to be inspected include those that block, scatter, and refract light. Figure 3 shows the case where the defect is one that blocks light; when a light beam is directed at the light-blocking defect,
The well-known Fraunhofer 7
) occurs, producing a diffraction image in a direction rotated by 90° with respect to the longitudinal direction of the defect. If the defect is one that scatters light, the light is scattered at each point hit by the light beam;
This produces a scattered light image that is also rotated by 90 degrees. If the defect is in the shape of a concave groove that refracts light, for example, long in the y-axis direction, the defect will have a so-called concave lens effect in the Therefore, the light beam is spread in the X-axis direction and forms an image that is long in the X-axis direction.

In this way, when there is a defect in the sheet-like object to be inspected, when the light beam is directed at it, an oval image is created due to the defect, but as shown in Figure 3, Even if there is no defect, a circular image A' is formed, so it is necessary to remove it. Therefore, in this invention, the output of the optical sensor that receives the main light transmitted or reflected by the sheet-like object to be inspected is excluded from the observation target, and defects are detected based on the presence or absence of the output of the optical sensor other than the sensor. It determines the presence or absence of.

In the above, the case where the sheet-like object to be tested is one that transmits light has been described, but the same applies to the case that it is one that reflects light. That is, in the above, the diffraction image is the same as the light transmittance case, and the only difference in scattering is whether it is transmitted scattered light or reflected scattered light, and furthermore, the lens effect due to refraction is , can be treated as a mirror effect due to reflection.

(Function) The light beam directed and scanned onto the sheet-like object to be inspected by the light projector is transmitted through the sheet-like object to be inspected or reflected by the sheet-like object to be inspected, and the transmitted light or reflected light is is received by the light receiving section.

At this time, if there is no defect in the sheet-like object to be inspected, an output will appear only in the optical sensor receiving the main light of transmitted light or reflected light, and no output will appear in the other optical sensors. On the other hand, if there is a defect in the sheet-like object to be inspected and the light beam hits the defect, as shown in Figure 3,
The image formed by the transmitted light or reflected light becomes an ellipse, and outputs also appear on optical sensors other than the optical sensor receiving the main light of the transmitted light or reflected light.

Therefore, the detection unit calculates the sum P of the outputs of the optical sensors other than the optical sensor receiving the principal light 9 of transmitted light or reflected light.
Based on this, when the condition P>0 is satisfied, it is determined that there is a defect, and when the above condition is not satisfied, it is determined that there is no defect. At this time, the magnitude of the output of the optical sensor other than the optical sensor receiving the main light of transmitted light or reflected light corresponds to the size of the defect.

(Embodiment) FIG. 1 shows an apparatus for detecting defects in a light-transmissive sheet material.

In FIG. 1, the light projection unit P includes a laser light source 2, a reflecting mirror 3, a condensing lens 4, a reflecting mirror 5, and a rotating polygon mirror (
(polygon mirror) 6 and a condenser lens 7.

On the other hand, the light receiving section S is arranged on the back side of the sheet-like object 1- to be tested. Then, this light receiving section S includes a large number of optical sensors S1, S2, etc. arranged in a matrix.
・Equipped with Here, it is assumed that the size of one optical sensor 10 is approximately the same as the size of a circular light beam that reaches the optical sensor when there is no defect in the sheet-like object 1 to be inspected.

Further, the detection unit D includes optical sensors s1, s2,...
It is determined whether or not there is a defect in the sheet-like object to be inspected based on the output of the optical sensor other than the optical sensor that receives the main light transmitted or reflected by the sheet-like object to be inspected. It consists of a circuit that adds , a comparison circuit that determines whether the addition result is greater than zero, and the like.

To explain the operation of the above-mentioned device, a light beam emitted from a laser light source 2 passes through a reflecting mirror 3 and then enters a condensing lens 4.
After being made into an appropriate thickness, it passes through a reflecting mirror 5 to a rotating polygon mirror 6, and is directed and scanned onto the sheet-like object 1 to be inspected by the rotating polygon mirror 6. The light beam scanned by the rotating polygon mirror 6 is focused onto the sheet-like object 1 to be inspected by the condenser lens 7.

The light beam transmitted through the sheet-like object 1 to be inspected forms an image on the light receiving section S. Now, it is assumed that there is no defect in the object 1 to be inspected 1 and 11 and the light beam has reached the light receiving element S5 of the light receiving section S. Then, since there is no defect in the object to be inspected ↓, the light beam is directed to the optical sensor S.
The light is received only by the sensor 5 and not by the other photosensors. That is, the optical sensor S5 receives the main light.

On the other hand, if there is a defect in the sheet material to be inspected ↑, the third
As explained in the figure, since an oval image is formed on the light receiving part S, even if the principal light is on the same optical sensor S5 as when there is no defect in the sheet-like object 1 to be inspected, the optical sensor Light is also received by optical sensors other than S5. Therefore,
Defects can be detected by the detection unit D detecting the outputs of optical sensors located around the optical sensor S5, excluding the output of the optical sensor S5.

For example, if the defect in the inspected sheet 1/shaped object 1 is long in the y-axis direction shown in FIG. 3, the optical sensors S2 and 88 will have outputs in addition to the optical sensor S5. . Therefore, by detecting the outputs of the optical sensors S212 and S8, excluding the output of the optical sensor S5 to which the main light is incident, it can be determined that the defect is long in the y-axis direction. Furthermore, if the defect is long in the X-axis direction, the optical sensors S4 and 86 will have outputs in addition to the optical sensor S5.

Therefore, in this case, it can be determined that the defect is long in the X-axis direction by detecting the outputs of the optical sensors S4 and 86, excluding the output of the optical sensor S5 into which the main light is incident.

In the above, we have described the case where the main light of the light beam is correctly located on one optical sensor, but in reality, the main light may be located at the end of one optical sensor, or on an adjacent optical sensor. Sometimes it's in between. In this case, however, the same is true. For example, if the main light is at the end of the optical sensor S5 on the 88 side, the outputs of the optical sensors S5 and 88 may be excluded, and detection may be performed using the outputs of optical sensors located around them. Furthermore, even when the sensor is located exactly in the middle between the optical sensors S5 and 88, the outputs of the optical sensors S5 and S38 can be similarly excluded, and detection can be performed using the outputs of optical sensors located around them.

13 To generally explain the action of the detection part D, P (Sl),
P (82), . . . are respectively optical sensors S1,
S2, ......, and P (Sk) is the output of the optical sensor Sk that receives the main light, then p = p excluding the output P (Sk) of the optical sensor Sk. (Sl) + P (S2) +...
・10P (Sk-1)+ p (Sk+l)+...
From the output, if P>O, it is determined that there is a defect, and if this condition is not satisfied, it is determined that there is no defect.

In the above, the size of one optical sensor was set to be approximately the same as the size of the light beam that reaches the optical sensor when there is no defect in the sheet-like object to be inspected, but even if it is larger, it is still larger than that. It doesn't matter if it's small. However, to the same extent
If it is made larger than this, the number of optical sensors can be reduced.

The embodiment shown in FIG. 2 is configured as 1-4 so that defects can be detected when the sheet-like object 1 to be inspected reflects light. It is arranged on the surface side of the sheet-like object so that the reflected light of the light beam from the light projecting section P by the sheet-like object 1 to be inspected is guided to the light receiving section S. Note that in this figure, the detection section D shown in FIG. 1 above is not shown.

(Effects of the Invention) The present invention includes a light receiving unit including a plurality of optical sensors arranged in a matrix that receives transmitted light or reflected light of a light beam by a sheet-like object to be inspected; Since it is equipped with a detection section that determines the presence or absence of defects based on the presence or absence of output from optical sensors other than the optical sensor receiving the main light, there is no deviation in the peak position of the intensity of transmitted light or reflected light. Even such defects can be detected.

Moreover, since the light-receiving part is equipped with multiple optical sensors arranged in a matrix, when the sheet-like object to be inspected is regarded as an x, y plane, the detection sensitivity is different in the x-axis direction and the y-axis direction. can be prevented.

15

[Brief explanation of drawings]

1 and 2 are schematic perspective views showing defect detection devices according to different embodiments of the present invention, and FIG. 3 shows the direction of defects and the resulting image of a light-transmissive sheet-like object to be inspected. It is a figure explaining the relationship with a direction. A: Portion without defects Portion with defects long in the Bay axis direction C: Portion with defects long in the x-axis direction D: Detection section L: Light beam P: Light projecting section S: Light receiving sections S1, S2,... ...: Optical sensor 1: Test sheet 2: Laser light source 3: Reflection mirror 4: Condensing lens 5: Reflection mirror 6. Rotating polygon mirror (polygon mirror) 16 7・Condensing lens 8: Light receiving surface

Claims (1)

[Claims] A device for detecting defects in a moving sheet-like object, which includes: a light projector that directs and scans a light beam onto the sheet-like object to be inspected; and a light beam transmitted by the sheet-like object to be inspected from the light beam. Or, depending on the presence or absence of a light receiving section that receives reflected light and includes a plurality of optical sensors arranged in a matrix, and the output of an optical sensor other than the optical sensor that receives the main light of the transmitted light or reflected light. What is claimed is: 1. A defect detection device comprising: a detection unit that determines the presence or absence of a defect based on the detection unit.