JPH0778473B2 - AGC device for transmitted scattered light of identification type defect detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a transparent plate material, such as a glass plate or a plastic plate, by scanning a light spot on a plate material (hereinafter referred to as a transparent plate material) that transmits at least light. It is a flying spot type defect detection device that detects the defects existing in, and particularly identifies the type, size, position, etc. of the detected defect. The present invention relates to an AGC device for transmitted scattered light of an identification type defect detection device that can detect.

[Conventional technology]

A defect detection device for detecting a defect existing in a transparent plate material, for example, in a transparent glass plate manufacturing line, detects a defect existing in a transparent glass plate to be manufactured, and feeds back the detection result to the transparent glass plate manufacturing process. Therefore, it is necessary to prevent the occurrence of defects at the locations where they occur and to improve the yield of products.

In a conventional transparent glass plate defect detection device, for example, as is known in Japanese Patent Laid-Open No. 51-29988, the presence of the glass plate by detecting only reflected light with respect to irradiation light by a light receiver. To know the disadvantages, or JP-A-51-1184
As known from Japanese Patent Laid-Open Publication No. JP-A-2003-242, there is one that detects a defect existing in a glass plate by detecting only transmitted light with respect to irradiation light with a light receiver.

The defect detection device disclosed in Japanese Patent Laid-Open No. 51-29988 described above can detect defects on the glass surface, but cannot detect defects inside the glass.

On the contrary, the defect detection device disclosed in Japanese Patent Laid-Open No. 51-1184 can detect defects inside the glass, but defects on the glass surface cannot be detected or are very difficult to detect. There is a problem.

Further, the defect detection device as described above cannot identify the type of defect (foreign matter, foam, stick, drip, etc.),
Further, since one light receiver detects bubbles and foreign matter at the same level, there is a defect that foreign matter is overlooked and bubbles and the like are overlooked.

As a defect detecting apparatus for improving such a defect, the present applicant has proposed an identification type defect detecting apparatus capable of identifying the type of defect. The outline of the already proposed discrimination type defect detection device will be described below.

For example, the disadvantages of existing glass plates include bubbles formed by bubbles remaining inside the glass plate, foreign substances formed when foreign substances remain inside the glass plate, and almost all melted foreign substances leaving a tail inside the glass plate. There are a brush formed by remaining in a pulled shape, a drip formed by the tin of the bath adhering to the surface of the glass plate, and the like.

When such a defect exists in the glass plate, when a light spot is projected on the defect, the states of transmission, transmission scattering, reflection, and reflection scattering differ depending on the type of the defect. As shown in FIG. 6, when the light beam 3 is projected onto the defect 2 existing on the transparent glass plate 1 at a constant incident angle α with respect to the normal line, fushi, foreign matter, and bubbles cause transmitted scattered light. In particular, in the case of a bush, the near paraxial transmitted scattered light 5 that is closest to the optical axis of the transmitted light 4 is generated, and in the case of a foreign substance, the paraxial transmitted scattered light 6 that is close to the optical axis of the transmitted light 4 is generated. In this case, the far-axis transmitted scattered light 7 that is far from the optical axis of the transmitted light 4 is generated. In addition, the amount of transmitted light 4 decreases for bubbles, foreign matters, bushes, and drip, and the amount of reflected light 8 increases for drip.

Therefore, a light receiver for individually detecting transmitted light, near-paraxial transmitted scattered light, paraxial transmitted scattered light, far-axis transmitted scattered light, and reflected light is provided to change the amount of transmitted light and reflected light and The types of defects can be identified by detecting the presence or absence of transmitted scattered light, paraxial transmitted scattered light, and far axis transmitted scattered light.

Table 1 shows a summary of the above relationships. The circles in the table indicate with which light the defect type can be identified.

Based on the above facts, the proposed identification type defect detection device
In the flying spot type defect detection device, a plurality of detecting at least two kinds of light among transmitted light, near paraxial transmitted scattered light, paraxial transmitted scattered light, far axial transmitted scattered light, reflected light, and reflected scattered light, respectively. Each light receiver is provided, the light from each light receiver is converted into an electric signal, and the obtained electric signal is processed to generate defect data including information indicating the type and size of the defect. Further processing is performed to create a defect pattern composed of a bit pattern corresponding to one defect of the glass plate, and the defect pattern thus obtained is collated with a defect identification pattern table prepared in advance to detect the defect. It is configured to determine the type, size, etc. of the.

FIG. 7 and FIG. 8 are a perspective view and a schematic side view of the scanner and the light receiver portion of the proposed defect detecting device, and the light receiver is exaggeratedly shown.

The scanner is centered on a laser light source 11 that emits laser light and an axis 13 parallel to the direction in which the laser light 12 from the laser light source 11 enters and the transparent glass plate 10 travels (hereinafter referred to as the Y-axis direction). The rotary polygon mirror 14 that rotates at a high speed and the axis 15 that is parallel to the Y-axis direction in which the transparent glass plate 10 travels, that is, the width direction of the glass plate (hereinafter referred to as the Y-axis direction) are rotated. Parallel mirror 16 for plate thickness correction that can change the angle
It has and. Although the position of the laser light source 11 shown in FIG. 8 is shown differently from the actual position,
This is to avoid obscuring the drawings. The scanner having the above structure is installed above the traveling transparent glass plate 10.

One photodetector D1 for detecting the transmitted light 17 is provided on the side opposite to the side where the scanner is provided, that is, below the transparent glass plate 10.
And two photodetectors D2 _A and D for detecting near paraxial transmitted scattered light
2 _B and two photodetectors D3 _A and D3 _B for detecting paraxial transmitted scattered light
And two photodetectors D4 _A and D4 _B for detecting far-axis transmitted scattered light. On the other hand, above the transparent glass plate 10, one light receiver D5 for detecting the reflected light 18 is arranged.

The plurality of light receivers basically have the same structure and have a linear light receiving surface elongated in the X-axis direction. The structure of the light receiver D1 will be described below as a representative.

FIG. 9 is a perspective view of the light receiver D1. This photodetector D1 is formed by arranging a large number of optical fibers 21, and one end of the optical fibers 21 is arranged in two rows as shown in the figure and fixed by being embedded in resin or the like, and the photodetector main body 22 Make up. The end faces 23 of 21 of a large number of arranged optical fibers are gathered to form an elongated linear light receiving face 24. The other ends of the optical fibers are bundled and connected to a photomultiplier tube described later.

When the photodetectors D1, D2 _A , D2 _B , D3 _A , D3 _B , D4 _A , and D4 _B for detecting transmitted light and transmitted scattered light having the above structure are arranged, the light of transmitted light 17 in FIG. The respective light receivers are arranged such that the light receiving surface is located within each effective light receiving angle with respect to the axis. Table 2 shows an example of the relationship between each light receiver and the effective light receiving angle.

The receivers D1, D2 _A , D2 _B , D3 _A , D3 _B , D4 _A , D4 _B arranged so that the light receiving surface is located within the effective light receiving angle as described above are
Fig. 10 shows the state viewed from the light-receiving surface side. The length direction of the light receiving surface of each light receiver is parallel to the X-axis direction. The use of two light receivers for detecting the near-paraxial transmitted scattered light, the paraxial transmitted scattered light, and the far-axis transmitted scattered light in this way is to prevent the generated transmitted scattered light from being overlooked.

7 and 8, the other end of the optical fiber of the photodetector D1 is connected to the photomultiplier tube PM1, and the other end of the optical fibers of the photodetectors D2 _A and D2 _B are bundled to form a photomultiplier tube PM2. , The other ends of the optical fibers of the photodetectors D3 _A and D3 _B are bundled and connected to the photomultiplier tube PM3, and the other ends of the optical fibers of the photodetectors D4 _A and D4 _B are bundled and the photoelectron amplifier tube is connected. Connected to PM4,
The other end of the light receiver D5 is connected to the photoelectron amplifier tube PM5.
In each photoelectron amplifier tube, the light received by each light receiver is converted into an electric signal.

Although not shown, a light receiver for forming a start pulse is provided between the rotary polygon mirror 14 and the parallel mirror 16 of the scanner, and the light transmitted by the optical fiber received by this light receiver is provided. Is provided with a photoelectric converter and a pulse shaper for converting the signal into an electric signal, and a start pulse ST indicating the start of scanning is formed.

Now, in the proposed identification type defect detection device including the scanner and the light receiver having the above-mentioned configuration, the laser light 12 emitted from the laser light source 11 is incident on the rotating polygon mirror 14 rotating at high speed, and the rotating polygon The laser beam 12 is shaken in the X-axis direction by the mirror 14, reflected by the parallel mirror 16, and then projected onto the traveling transparent glass plate 10 to scan the glass plate in the X-axis direction. The laser beam 12 repeatedly scans the transparent glass plate 10 every time the reflecting surface of the rotary polygon mirror 14 changes. Since the transparent glass plate 10 runs in the Y-axis direction, the entire surface of the glass plate is scanned by the laser light.

As shown in FIG. 8, the laser light 12 is projected onto the transparent glass plate 10 at an incident angle α in the Y-axis direction with respect to a normal line perpendicular to the glass plate surface. This is to prevent the light reflected on the back surface of the transparent glass plate 10 and subsequently reflected on the front surface from interfering with the transmitted light.

If there is a defect in the transparent glass plate, if the laser light hits this defect, the type of defect (foreign matter, bubble, stick, drip)
As a result, the amounts of transmitted light and reflected light are changed, and at the same time transmitted and scattered light is generated.

For example, when the type of defect is a bush, when the incident laser light hits the bush, the amount of transmitted light changes, and at the same time, near paraxial transmitted scattered light is generated. The change in the amount of transmitted light is
It is detected by the photodetector D1, sent to the photomultiplier tube PM1, and converted into an electric signal. On the other hand, the near paraxial transmitted scattered light is incident on the light receiving surfaces of the photo detectors D2 _A and D2 _B. The received near paraxial transmission scattered light is sent to the photomultiplier tube PM2 and converted into an electric signal.

Similarly, for example, when the type of defect is a foreign substance, when the incident laser beam hits the foreign substance, paraxial transmission scattered light is generated similarly as the amount of transmitted light changes. The transmitted and scattered light is received by the photo detectors D3 _A and D3 _B , and the received light is the photomultiplier tube.
It is sent to PM3 and converted into an electrical signal.

Similarly, for example, when the type of defect is bubbles, when the incident laser light hits the bubbles, the amount of transmitted light changes, and at the same time,
Far-axis transmitted scattered light is generated. This far-axis transmitted scattered light is received by the photodetectors D4 _A and D4 _B , and the received light is a photomultiplier tube.
It is sent to PM4 and converted into an electrical signal.

Similarly, for example, when the type of defect is a drip, when the incident laser beam hits the drip, the amount of transmitted light changes and the amount of reflected light changes at the same time. This change in reflected light is detected by the photodetector D5, sent to the photomultiplier tube PM5, and converted into an electric signal.

The electrical signal from the photomultiplier tube is sent to the processing unit, defect data including information indicating the type and size of the defect is generated, and these defect data are further processed to correspond to one defect of the glass plate. A defect pattern including a bit pattern is created, and the defect pattern thus obtained is collated with a defect identification pattern table created in advance to determine the type and size of the defect.

Since the configuration of the processing unit is not directly related to the present invention, the description is omitted.

[Problems to be solved by the invention]

In the proposed identification type defect detection device, the light transmittance changes, the laser output changes, or the sensitivity of the photomultiplier tube deteriorates based on the thickness and color of the glass plate that is the object to be inspected. In the case of occurrence of, it is necessary to keep the detection sensitivity constant in order to maintain the detection accuracy of the defect. For this purpose, the sensitivity of the photomultiplier tube, that is, the gain may be automatically controlled. In this case, the transmitted light and the reflected light are always incident on the photodetectors D1 and D5 during one scanning regardless of the defect of the glass plate, and the electric signals are always output from the photomultiplier tubes PM1 and PM5. Therefore, it is easy to detect the level of the electric signal portion that does not correspond to the defect and apply automatic gain control (AGC) to keep the level constant. However, the photodetectors D2 _A , D2 _B , which detect the near paraxial transmitted scattered light,
The photodetectors D3 _A and D3 _B for detecting paraxial transmitted scattered light and the photodetectors D4 _A and D4 _B for detecting far axial transmitted scattered light receive the transmitted scattered light only when the glass plate has a defect, Photomultiplier tube PM2,
Since PM3 and PM4 output electric signals only at that time,
There is a problem that the sensitivity of these photomultiplier tubes cannot be automatically controlled.

An object of the present invention is to provide an AGC device for transmitted and scattered light that solves the above problems.

[Structure of Invention]

The present invention scans a transparent plate material running in the length direction with a light spot in the width direction, receives at least transmitted light and transmitted scattered light with a plurality of light receivers, and converts the received light into an electric signal with a photoelectric converter. The converted AGC device for transmitted scattered light used in the identification type defect detection device for detecting defects existing in the transparent plate material, wherein the scanning light outside the effective scanning width transmitted through the transparent plate material is transmitted. A light diffusing plate that makes a light receiver for receiving scattered light enter as reference light, and a photoelectric converter connected to the light receiver for transmitted scattered light so that the level of the taken-in reference light is maintained at a predetermined value. And a control means for controlling the gain of.

Further, the present invention scans a transparent plate material running in the length direction with a light spot in the width direction, receives at least transmitted light and transmitted scattered light with a plurality of light receivers, and receives the received light with an electric signal by a photoelectric converter. And an AG for transmitted scattered light used in an identification type defect detection device for detecting defects existing in the transparent plate material
A device C, in which a light receiver for taking in reference light from scanning light outside the effective scanning width is connected to one end, and the other end is provided with a first optical fiber installed near one surface of the transparent plate material, and one end Is installed in the vicinity of the other surface of the translucent plate member so as to face the other end of the first optical fiber, and the other end electrically connects the light received by the light receiver for the transmitted scattered light. A second optical fiber connected to a photoelectric converter for converting into a signal, and a transmitted and scattered light so that the level of the reference light taken in via the first and second optical fibers is maintained at a predetermined value. Control means for controlling the gain of the photoelectric converter connected to the light receiver of.

Further, the present invention is an identification type defect detection device for detecting a defect existing in the light transmitting plate material by scanning the light transmitting plate material running in the length direction with a light spot in the width direction and converting it into an electric signal by a converter. An AGC device for transmitted and scattered light used for, which reflects the scanning light outside the effective scanning width, transmits the transparent plate material, and then makes it incident as a reference light on a light receiving device that receives the scattered light. A mirror and control means for controlling the gain of the photoelectric converter connected to the photodetector for the transmitted scattered light so that the level of the taken-in reference light is maintained at a predetermined value. .

〔Example〕

 Next, examples of the present invention will be described.

1 to 3 are diagrams showing a first embodiment of the present invention. FIG. 1 shows photodetectors D1, D2 _A , D2 _B , D3 _A , D3 _B , D for receiving transmitted light and transmitted scattered light of the identification type defect detection device.
4 shows a light receiver portion of _A, D4 _B, FIG. 1 (a) is a view of a light receiver portion from the Y-axis direction, FIG. 1 (b) is viewed from the light-receiving surface side of the light receiver section It is a figure. Incidentally, FIG. 1 (a)
In the figure, the light receiver is represented by a symbol D as a representative. In the figure, 14 denotes a rotating polygon mirror, 12 denotes a laser beam, 36 and 37 denote a photodetector and an optical fiber for the start pulse ST, respectively, and the laser light source and the parallel mirror are not shown.

As shown in FIG. 1, the AGC (automatic gain control) device according to the present embodiment is located above the end portion in the length direction of the photodetector D1 and below the glass plate 10 to be inspected, and polishes it outside the effective scanning width. A light diffusion plate 31 such as glass is provided.

Since the transmitted light always enters the light receiver D1 during one scan, when the transmitted light hits the light diffusion plate 31, the diffused light is received by the light receiver D1.
It is incident on 2 _A , D2 _B , D3 _A , D3 _B , D4 _A , and D4 _B. Hereinafter, the light thus taken in for AGC will be referred to as reference light.

FIG. 2 is a diagram showing an electric circuit portion of the AGC device of the present embodiment, typically a photoelectron multiplying device for converting the near paraxial transmission scattered light received by the photodetectors D2 _A and D2 _B into an electric signal. The electric circuit portion for the tube PM2 will be described. This electric circuit portion includes a sampling circuit 32 for sampling an electric signal corresponding to the reference light from the photomultiplier tube PM2, a hold circuit 33 for holding a sampled value, and a sampling value from the hold circuit. , Photomultiplier tube PM
2 and a control circuit 34 for controlling a high voltage generation circuit 35 that supplies a voltage applied to the circuit 2.

Next, the operation of this embodiment will be described with reference to the signal waveform diagram shown in FIG.

In FIG. 1A, the light spot is assumed to be scanned on the glass plate 10 in the X-axis direction from left to right. Light diffuser
When the light hits 31, the reference light is a near paraxial transmitted scattered light receiver.
It is incident on D2 _A and D2 _B. The reference light is sent to the photomultiplier tube PM2 and converted into a reference light signal RS. FIG. 3A shows the reference optical signal RS included in the output signal of the photomultiplier tube PM2. The level of the reference light signal RS depends on the light transmittance of the glass plate, the output change of the laser, and the sensitivity of the photomultiplier tube. The electric signal from the photomultiplier tube PM2 is sent to the processing section and at the same time, sent to the sampling circuit 32.

To the sampling circuit 32, the start pulse ST indicating the start of scanning and the clock CLK are input. The start pulse ST is shown in FIG. 3 (b), and the clock is shown in FIG. 3 (c).
Indicates CLK. The reference light signal RS is generated outside the effective scanning period starting from the generation time of the start pulse ST. The sampling circuit 32 counts clocks with the start pulse ST as a reference, samples the reference optical signal RS with a predetermined clock as a sampling pulse, and holds the sampling value in the hold circuit 33. The sampling value is input to the control circuit 34, and in the control circuit, the sampling value is compared with the reference level, and the photomultiplier tube generated by the high voltage generating circuit 35 is set so that the level of the reference light signal RS is always at a predetermined level. The sensitivity of the photomultiplier tube PM2 is adjusted by controlling the applied voltage applied to PM2.

As described above, according to the AGC device of the present embodiment, the light diffusing plate is provided on the end of the light receiver, and the reference light is made incident on the light receiver that receives the transmitted scattered light, and the level of this reference light is predetermined. By controlling the sensitivity of the photomultiplier tube so that the value is maintained, the detection sensitivity of the identification type defect detection device can be made constant.

In the above embodiments, the light diffusion plate is provided below the glass plate that is the object to be inspected, but it may be provided above the glass plate. Further, the light diffusion plate may be provided on the scanning start side of the light spot.

Next, a second embodiment of the present invention will be described. The second embodiment uses a light diffuser and an optical fiber, while the first embodiment uses a light diffuser plate to take in the reference light. FIG. 4 shows an example in which the reference light is taken into the photomultiplier tube PM2 as a representative. Note that FIG. 4 (a) is a diagram viewed from the Y-axis direction, and FIG. 4 (b) is a diagram viewed from the X-axis direction.

According to the present embodiment, the light receiver 40 is provided above the glass plate 10 and outside the effective scanning width of the scanning light, the optical fiber 41 is connected to this light receiver, and the other end of this optical fiber is connected to the glass plate. Install near the top of 10. Further, the optical fiber 42 is provided below the glass plate 10, and one end is near the lower surface of the glass plate 10,
It is installed so as to face the other end of the optical fiber 41. The other end of the optical fiber 42 is connected to the photomultiplier tube PM2 for the near paraxial transmission scattered light.

According to this embodiment, the reference light is taken into the photomultiplier tube PM2 from the scanning light via the fibers 41 and 42. The electric circuit for keeping the level of the reference light at a predetermined level is the same as that of the first embodiment, and the operation is also the same, so that the description will be omitted.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, as a means for taking in the reference light, a mirror 51 is installed on the glass plate 10 outside the effective scanning width of the scanning light. The scanning light reflected by the mirror 51 is incident on the light receiver for transmitted and scattered light as reference light, and based on this reference light, in the same manner as described in the first embodiment, the photomultiplier tube Automatic gain control is performed.

In each of the above embodiments, the photomultiplier tube is used as a means for converting the light from the light receiver into an electric signal, but in general, any photoelectric converter capable of automatic gain control may be used. Of course.

〔The invention's effect〕

As described above, according to the present invention, the reference light is made incident on the light receiver for the transmitted scattered light of the identification type defect detection device, and the sensitivity of the photoelectron converter is controlled so as to keep the level of the reference light at a predetermined level. By doing so, it becomes possible to make the detection sensitivity of the identification type defect detection device constant.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing an electric circuit portion of the first embodiment, and FIG. 3 is a diagram illustrating the operation of the first embodiment. FIG. 4 is a waveform diagram for this, FIG. 4 is a diagram showing a second embodiment of the present invention, FIG. 5 is a diagram showing a third embodiment of the present invention, and FIG. 6 is transmitted light and transmitted scattered light. FIG. 7 is a perspective view of an already proposed identification type defect detection device, FIG. 8 is a schematic side view of an already proposed identification type defect detection device, and FIG. 9 is a perspective view of a light receiver. FIG. 10 is a plan view of a light receiving surface of a plurality of light receivers for transmitted light and transmitted scattered light. D1 …… Receiver for transmitted light D2 _A , D2 _B …… Receiver for near-paraxial transmitted scattered light D3 _A ， D3 _B …… Receiver for paraxial transmitted scattered light D4 _A , D4 _B …… Far-axis transmitted scattering Optical receiver 31 …… Light diffusion plate 32 …… Sampling circuit 33 …… Hold circuit 34 …… Control circuit 35 …… High voltage generation circuit 36 …… Start pulse receiver 37 …… Start pulse optical fiber 40… … Receiver 41, 42 …… Optical fiber 51 …… Mirror

Claims (3)

[Claims] 1. A light-transmitting plate material running in the length direction is scanned with a light spot in the width direction, at least transmitted light and transmitted scattered light are received by a plurality of light receivers, and the received light is converted into an electric signal by a photoelectric converter. AGC for transmitted scattered light used in an identification type defect detection device that detects defects existing in the transparent plate material
In the device, a light diffusing plate that causes the scanning light outside the effective scanning width that has passed through the translucent plate material to enter into a light receiver that receives the transmitted scattered light as a reference light, and the level of the taken-in reference light is a predetermined value. And a control means for controlling the gain of a photoelectric converter connected to the photodetector for transmitted scattered light so that the AGC device for transmitted scattered light of an identification type defect detection device. 2. A translucent plate material running in the length direction is scanned with a light spot in the width direction, at least transmitted light and transmitted scattered light are received by a plurality of light receivers, and the received light is converted into an electric signal by a photoelectric converter. AGC for transmitted scattered light used in an identification type defect detection device that detects defects existing in the transparent plate material
In the device, a photodetector that takes in reference light from scanning light outside the effective scanning width is connected to one end, and the other end is a first optical fiber installed near one surface of the transparent plate material, and one end is , Installed near the other surface of the translucent plate material so as to oppose the other end of the first optical fiber, and the other end of the light received by the light receiver for transmitted scattered light is an electrical signal. A second optical fiber connected to a photoelectric converter for converting into a light source, and a light source for transmitting and scattering light so that the level of the reference light taken in through the first and second optical fibers is maintained at a predetermined value. An AGC device for transmitted and scattered light of an identification type defect detection device, comprising: a control unit for controlling a gain of the photoelectric converter connected to a light receiver. 3. A translucent plate material running in the length direction is scanned with a light spot in the width direction, at least transmitted light and transmitted scattered light are received by a plurality of light receivers, and the received light is converted into an electric signal by a photoelectric converter. AGC for transmitted scattered light used in an identification type defect detection device that detects defects existing in the transparent plate material
A device that reflects scanning light outside the effective scanning width, transmits it through the light-transmitting plate material, and then makes it incident as reference light on a receiver that receives transmitted scattered light, and the level of the reference light taken in. So as to be maintained at a predetermined value, the control means for controlling the gain of the photoelectric converter connected to the photodetector for the transmitted scattered light, for the transmitted scattered light of the identification type defect detection device, AGC device.