JPS639617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defect detection device that optically detects external defects in a sheet-like object.

As this type of defect detection device, a light projecting section capable of projecting light along the width direction perpendicular to the moving direction of the sheet-like object to be inspected is provided on one side of the sheet-like object, and of the projected light beam, the sheet-like object The light beam transmitted through the sheet-like object can be received on the other side of the sheet-like object, or the reflected light from a reflecting plate provided on the other side or the reflected light from the sheet-like object itself can be received on the same side. It is known to provide a light receiving section corresponding to the light projector 1 in which a large number of light receiving elements such as photoelectric switches or optical semiconductor elements are arranged in an array along the width direction of a sheet-like object. The electrical output of the light receiving section is amplified by an amplifier circuit consisting of an amplifier provided for each light receiving element, and then subjected to logical judgment processing by a discriminator circuit to determine the presence or absence of defects such as missing parts of the sheet-like object.

When using a light-receiving section in which a large number of light-receiving elements are arranged in an array like this, defects with a width dimension larger than the arrangement interval between individual light-receiving elements can be detected, but defects with a small width dimension, In particular, even if the length of the sheet in the direction of movement is sufficient, a defect with a small dimension in the width direction cannot be detected even if the defect is large in area. Therefore, in order to improve detection accuracy, it is necessary to arrange multiple sets of light-receiving element arrays that are slightly shifted from each other in the width direction of the sheet, or to use image sensors, etc., which is extremely complicated and expensive. It had become a thing.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an inexpensive defect detection device with a simple configuration that is not affected by the size, shape, orientation, etc. of defects in a sheet-like object.

According to the invention, this purpose is achieved by, as a light receiving section,
A light-receiving section is provided on both sides of an integrated optical semiconductor layer running in the width direction of a sheet-like object, each consisting of comb-shaped electrodes arranged so that the electrodes form a grid when viewed in the planar direction. It is achieved by doing so.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

1 and 2 show one embodiment of the present invention. In this device, a light projecting section 2 having a length approximately corresponding to the width dimension in the direction perpendicular to the moving direction P of the sheet-like object 1 is installed on one side of a sheet-like object 1 to be inspected, such as paper or a board. Further, a light receiving section 3 having approximately the same length as the light projecting section 2 is disposed on the other side so as to face the sheet-like object 1 between them. Light projecting section 2
Use a band-shaped light source such as a fluorescent light. For the light receiving section 3, a photovoltaic type or a photoconductive type can be used as appropriate.

The light receiving section 3 has an optical semiconductor layer 31 forming a photovoltaic element or a photoconductive element formed on an integrated insulating substrate 30, and further has comb-shaped electrodes 32 and 33 formed on both sides of the optical semiconductor layer 31, respectively. , both electrodes 32 and 33 are arranged in a lattice shape when viewed in a planar direction. Optical semiconductor layer 31 and electrode 3
2, 33 is a semiconductor film technology on an insulator substrate 30;
For example, it is integrally formed in the form of a film using thin film technology using vacuum evaporation or thick film technology using screen printing. The electrode portions of both electrodes 32 and 33 corresponding to individual comb teeth are arranged in substantially opposite directions with respect to the width direction of the sheet-like object 1 so as to form an angle of 90° with each other.
It extends at an angle of 45°.

In the defect detection device configured in this way,
What has the function of detecting defects is a relatively small-diameter circular region centered on the point where the upper and lower electrodes 32 and 33 intersect with each other with the layer 31 in between. Regardless of whether it is a photovoltaic type or a photoconductive type, it exhibits sensitivity only in a limited area due to the relatively large sheet resistance of the photosemiconductor layer. That is, point-like or small-diameter circular sensing regions are evenly distributed on the layer 31. Note that the width of the electrodes 32, 33 themselves and the spacing between the comb teeth are determined depending on the size of the defect to be detected.
It is possible to arbitrarily adjust the sensitivity depending on the sensitivity required. If a missing defect 11, 12, or 13 exists in the sheet-like object 1 to be inspected that is moving in the direction of the arrow P, a portion of the light beam Q from the light projecting section 2 passes through these defects and reaches the light receiving section 3 on the opposite side. The light reaches the optical semiconductor layer 31 and is converted into an electrical signal depending on the amount of light received. At this time, if the electrodes 32 and 33 exist within the light irradiation range (which exists in most cases), the electrical signal generated by the optical semiconductor layer 31 is transmitted to the terminals 34 and 33 via the electrodes 32 and 33.
5, and is further led to a discrimination circuit via an amplifier (not shown), where logical judgment is made and defects are detected. A feature of this device is that it not only detects the presence or absence of a defect, but also can estimate what kind of defect it is. In other words, for example, the point-like missing part shown by 11 is the first
If it passes as shown in the figure, the upper and lower electrodes 3
A pulse-like signal is generated every time the intersection point of 2 and 33 is passed. If the missing part 12 has passed, first,
1, then increases stepwise to 2, 3, and the missing part 12
After a period of time corresponding to the length of , the signal decreases from state 3 to 2, 1, and then 0. In the case of the missing portion 13, if the width in the traveling direction is narrow, that is, the missing portion is in the shape of a slit, a pulse-like signal, but larger than that at the point 11, is generated. Missing part 1 with a certain width as shown in the figure
3, an approximately trapezoidal output is produced.

In this way, it is possible to obtain an output according to the shape of the missing part, in other words, to estimate the shape of the missing part from the signal, the electrodes 32 and 33 are provided so as to cross each other with the semiconductor layer 31 in between, and the sheet resistance of the layer is This is because a large number of mutually separated sensing points are distributed and arranged using Moreover, this distribution is
It can be easily optimized according to individual targets.

In the conventional device, it was extremely difficult to detect small defects 11 and 12 that were narrower than the mounting interval of the light receiving elements, but according to the present invention, such defects can be detected easily. Of course, defects 13 that are narrow in the moving direction P of the sheet-like object and elongated in the width direction perpendicular thereto can also be detected. Electrode 32,3 by membrane technology
3 can be formed quite finely, so even fairly small defects can be detected accordingly.

In the embodiments described above, the sheet-like object 1
Although we have explained the transmissive type in which the light emitter 2 is placed on one side and the light receiver 3 is placed facing each other on the opposite side,
It is also possible to configure a reflective type in which the light projecting section 2 and the light receiving section 3 are arranged on the same side. In the case of a reflective type, the light beam from the light projector is directed onto a sheet-like object, and the reflected light from the sheet-like object is directly received (if the surface of the sheet-like object is configured as a light reflecting surface), or the sheet-like object is It may be configured to receive reflected light from a reflecting plate placed on the opposite side of the object (if the sheet-like object is light-transmissive). The method to be used may be selected depending on whether the object to be inspected is transparent or opaque, whether the defect to be detected is a defect or a stain, etc.

As described above, according to the present invention, comb-shaped electrodes are formed on both sides of an integrated optical semiconductor layer running in the width direction of a sheet-like object, so that the electrodes form a lattice shape when viewed in a planar direction. By arranging the light receiving section, almost any defect can be detected well regardless of size, shape, orientation, etc., and moreover, it can be detected with one sensor (light receiving section). Moreover, the light receiving section according to the present invention does not need to be arranged according to the shape of the defect to be detected or scanned vertically and horizontally, is easy to install, and is highly versatile.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the light receiving section in the defect detection device according to the present invention, and FIG. 2 is a cross-sectional view of the light receiving section of FIG. FIG. DESCRIPTION OF SYMBOLS 1... Sheet-shaped object, 2... Light projecting part, 3... Light receiving part, 30... Insulator substrate, 31... Optical semiconductor layer, 32, 33... Electrode.

Claims (1)

[Scope of Claims] 1. A light projecting section capable of projecting almost full light in the width direction perpendicular to the moving direction of a sheet-like object to be inspected moving in one direction; a light receiving section that receives light transmitted through or reflected from the object and outputs an electric signal according to the amount of the received light; and a discrimination circuit that digitally processes the output signal of the light receiving section to discriminate defects in the sheet-like object. In a sheet-like object defect detection device equipped with
The light-receiving section is formed by comb-shaped electrodes arranged on both sides of an integrated optical semiconductor layer running in the width direction of the sheet-like object so that the electrodes form a lattice shape when viewed in a planar direction. A defect detection device for a sheet-like object, characterized in that it is provided with a light receiving section. 2. A defect detection device for a sheet-like object according to claim 1, wherein the optical semiconductor layer and both electrodes are integrally formed in the form of a film on an insulating substrate. . 3. In the defect detection device according to claim 1 or 2, the electrode portions corresponding to the individual comb teeth of both the electrodes are aligned in the width direction of the sheet-like object such that they form an angle of approximately 90° to each other. A defect detection device for a sheet-like object, characterized in that the sheet-like object is tilted at an angle of approximately 45° in opposite directions to the sheet-like object.