JPS62266447A - Method and apparatus for detecting foreign matter in liquid within container - Google Patents

Abstract

PURPOSE:To capture a foreign matter with a high accuracy, by receiving the scattered light of a laser beam from a foreign matter in a liquid with a photodetector provided below the liquid surface on the side not in the direction of irradiation to detect the foreign matter depending on changes in the quantity of light received. CONSTITUTION:A laser beam emitted from a laser beam source 2 is expanded in one way with a cylindrical lens 3 and made to scan vertically through a scanning means 4 as rotating polyhedron 4 to irradiate a fixed area of a transparent container 1 containing liquid. The laser beam which is incident into the container 1 and scattered from a foreign matter in the liquid is made incident into a light receiver 5 provided slantly below the liquid surface on the side not in the direction of irradiation through a condenser lens 8. Then, a signal corresponding to changes in the quantity of light received from the light receiver 5 is sent to a foreign matter detection circuit and then, applied to a circuit for selecting reject containers. Thus, a foreign matter floating in the liquid can be captured with a high accuracy.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention deals with foreign matter mixed in the liquid of a transparent or translucent container filled with liquid, and particularly foreign matter floating in the liquid at and near the liquid surface. The present invention relates to a method and apparatus for detecting foreign substances.

(Prior art) Conventionally, an ampoule is rotated at high speed and then suddenly stopped, a light beam is irradiated onto a foreign object that continues to float and rotate with the liquid inside, and a photodetector receives the light beam that has passed through the liquid or the light beam that has been reflected.
A method of determining whether a foreign object is present or not based on the degree of decrease in the amount of received light is known from Japanese Patent Application Laid-Open No. 55-119049. And the light uses a general light source.

(Problem to be Solved by the Invention) When attempting to inspect the entire container using the method described above, the light-receiving surface becomes large, and the amount of change from the large light-receiving surface cannot be detected by small fluctuations such as in the case of a small foreign object. Hateful.

Therefore, if the light-receiving surface is made smaller, in order to capture the entire area of the container, it is necessary to install many small light-receiving surfaces, or to allow the dust to move and cast a shadow on the light-receiving surface.In the former case, mechanical The latter has the drawback of poor detection efficiency.

In addition, with the conventional inspection method described above, heavy foreign objects such as glass pieces and solid foreign objects can be detected while they are floating before they sink to the bottom of the container after rotation has stopped, but extremely heavy foreign objects floating on the liquid surface can be detected. Light foreign objects, such as plastic pieces generated from synthetic resin packaging materials, often do not move into the liquid and float on the liquid surface.

However, in the conventional inspection method that uses transmitted light, the liquid surface area becomes dark because the amount of transmitted light is small, and in the method that measures reflected light, on the other hand, there is too much diffuse reflection, both of which are affected by the liquid level. Because it appears strongly, the liquid level must be excluded from the inspection target. Therefore, there was no method for automatically inspecting foreign objects floating on the liquid surface using a machine. Therefore, although checks are barely carried out by visual inspection by humans, the detection limit is subject to oversight due to foreign objects being overlooked and individual differences, resulting in extremely poor efficiency and accuracy.

(Means for solving the problem) Therefore, in order to improve the conventional drawbacks, a transparent or translucent container filled with liquid is scanned with a laser beam in at least one direction to irradiate a certain area. An attempt was made to detect foreign substances in liquid in a container by receiving scattered light from irradiation light and measuring changes in the amount of received light.The results showed that the sensitivity (S/N ratio) was good and the detection time was shortened. However, it was still not possible to detect foreign objects floating around the liquid surface or below the liquid surface.

Therefore, the technical problem of the present invention is to provide a detection method and device that can accurately detect foreign objects floating on the liquid surface and around the liquid surface, and the present invention solves this technical problem. The technical method is to irradiate the liquid surface of a transparent or translucent container filled with liquid with a laser beam from diagonally downward, and to detect the scattered light from foreign objects in the liquid and floating foreign objects on the liquid surface. It is characterized by detecting foreign matter in the liquid in the container by detecting the light by a light beam detector installed diagonally below the liquid level on the side different from the irradiation direction, and by detecting the change in the amount of the received light. Devices directly used to carry out the method include a laser beam irradiation device that can irradiate the liquid surface in a transparent or translucent container filled with liquid from obliquely downward; Scattered light from foreign objects and floating foreign objects on the liquid surface is received by a light receiving section.The foreign object is detected by a change in the amount of light received by a light receiving section provided diagonally below the liquid surface on a side different from the irradiation direction. This is a device for detecting foreign matter in a liquid in a container, which is composed of a photodetector that can detect foreign matter in a liquid inside a container. .

(Effect of the invention) This technical means provides the following effects.

In other words, the present invention uses a fingertip or condensing laser beam and receives the scattered light. By using this method, it is possible to strengthen the light reflection from foreign objects and capture them with extremely high sensitivity.

This is because when light is irradiated onto a foreign object and the scattered light (reflected light) is received, it is better to narrow down the irradiated light as much as possible and irradiate it with a small spot, because the ratio of the diameter of the foreign object to the spot diameter will be larger, and the scattered light from the foreign object will be reduced. This is because the detection sensitivity increases as the size increases.

(2) In the case of a method that uses laser light to detect changes in the amount of transmitted light, it is difficult to detect changes in the case of small foreign objects because it looks at the amount of reduction due to the projected image of dust compared to the light received as a whole. However, when receiving scattered light, there is no scattered light when there is no foreign object, and the scattered light enters the receiver only when there is a foreign object, so the sensitivity of the receiver can be increased even to small foreign objects. Detection sensitivity can be significantly increased compared to the transmission method.

(3) Laser light has high brightness and can be focused into a narrow beam, so it is less affected by the container when the light goes in and out of the container.

In the case of normal light, the light will be diminished by the influence of the bottle at the entrance and exit of the light.

(4) The laser beam can be scanned vertically and horizontally to irradiate a wide three-dimensional area, making it possible to detect even slow-moving foreign objects.This not only increases detection sensitivity but also improves inspection. Since the entire target area can be scanned with a narrow beam extremely quickly, inspection processing time can be shortened and efficiency can be improved.

(5) Therefore, in some cases, it is not necessarily necessary to rotate the container to collect the foreign matter at the center of the light-receiving surface as in the conventional case.

In addition to these advantages, in the present invention, the laser beam is irradiated from diagonally below the liquid surface, and the scattered light is then received from diagonally below the liquid surface, thereby eliminating the influence of the liquid surface and the container due to fluctuations in the liquid surface. It has the effect of being able to accurately detect foreign objects on and around the liquid surface without being affected by the liquid.

As described above, it is only by using a focused laser beam that it is possible to cause the light to enter and exit at obliquely downward angles of incidence and emission.

(Example) The embodiments shown in the drawings will be described below.

The one in Figure 1 is an example of an attempt to improve the conventional drawbacks, in which a transparent or translucent container filled with liquid is scanned with a laser beam in one direction to irradiate a fixed area. This is an example in which scattered light is received and changes in the amount of received light are measured.

In FIG. 1, (1) is a transparent or translucent container to be inspected containing a liquid, and a laser light source (2) oscillates a laser beam and irradiates the container (1).

The laser light emitted from the laser light source (2) is spread in one direction by a cylindrical lens (3), and then scanned in the vertical direction through scanning means of a rotating polyhedron (4) to irradiate a fixed area.

A receiver (
5) is provided on the side surface of the container in the direction perpendicular to the direction in which the laser beam is incident.

A condenser lens (8) is located between the light receiver (5) and the container (1).
will be provided.

A signal corresponding to a change in the amount of light received from the light receiver (5) is sent to a foreign object detection circuit (not shown), and the signal is applied to a circuit for selecting defective containers.

As described above, when the scattered light is received using a laser beam with a pointing or condensing property, even a small foreign object can be captured by a narrow and sharp laser beam, resulting in extremely high sensitivity.

In addition, since the method described above uses scattered light rather than transmitted light, even small foreign objects can be easily detected because the narrow laser beam is diffusely reflected and enters the receiver, increasing the sensitivity of the receiver. .

Furthermore, the laser beam is not affected by the container when it enters or exits the container, and by moving the beam vertically and horizontally, the entire area to be inspected on the container can be seen in a short time.

However, extremely light foreign objects, such as plastic pieces from synthetic resin packaging materials, often float on the liquid surface, but even with the above methods, they are susceptible to fluctuations in the liquid level and the influence of the container. Therefore, the above foreign matter could not be detected.

Therefore, in the present invention, a method and apparatus as shown below have been invented.

In other words, a laser beam is irradiated from diagonally below the liquid surface,
Then, by receiving the scattered light from diagonally below the liquid surface, foreign objects on the liquid surface and around the liquid surface can be detected with high accuracy without being affected by shadows from the liquid surface and the container due to fluctuations in the liquid surface. It has arrived.

In Fig. 2, (1) is a transparent or translucent container containing a liquid to be inspected, which is rotated in the same way as conventionally known containers during inspection, and then suddenly stopped to remove floating foreign matter. It is moved to the center of the container. (This may not be necessary in some cases.) Then, after the liquid level has settled down to a certain extent, the laser light source (2
) and irradiates the container (1) with laser light.

Laser light emitted from a laser light source (2) is fanned out to a constant width (a) in the vertical direction of the outer surface of the container (1) through a cylindrical lens (3).

The rotating glass column (4)
The laser beam is scanned to a certain width (b) in the horizontal direction orthogonal to the vertical direction by a scanning means such as the above, thereby expanding the area irradiated with the laser beam.

The light beam spread out and scanned in this way is diagonally downward with respect to the liquid level (x) of the container (1), that is, the incident angle <c> between the laser beam and the liquid surface (X) does not satisfy the condition for total reflection. It is incident within a range, specifically about 40 from Oo.
Irradiate so that it is incident within the range of

In the case of the example shown in Fig. 2, for a 500 m1 plastic container (1), 4 mW of He was applied to the laser light source (2).
- Using a Ne gas laser, a cylindrical lens (3
), the laser beam is expanded vertically to a constant width (a) of 2011, and then scanned to a constant width (b) of 16 mm by a rotating glass column (4) at an incident angle (C).
Irradiation was performed at 15°.

A light receiver (5) that receives the laser light incident in this way
is provided on the side surface of the container in a direction perpendicular to the direction in which the laser beam is incident, and is arranged at an oblique downward emission angle (d) with respect to the liquid level (x).

In the case of the embodiment shown in FIG. 2, the output angle (d) was selected to be 30°, widening the allowable range since the aperture of the light receiver is wide.

A lens (6), a field-limiting mask (7), and a condensing lens (8) are provided between the light receiver (5) and the container (1), and the lens (6) has a focal length of 50 mm. there was.

The field-of-view limiting mask (7) reduces the amount of scattered light generated on the outer wall of the container.
l) It functions to improve the S/N ratio by preventing noise, and in the example, the mask surface of the film surface of the camera was used.

Further, the image of the foreign matter restricted by the mask (7) is focused by a condensing lens (8) and guided to the light receiver through an interference filter (9) provided on the surface of the light receiver (5).

At this time, the laser beam can be received even in a somewhat dim room due to its monochromatic nature.

The photoreceiver (5) is, for example, a photomultiplier tube (16).
) etc. are used.

A signal corresponding to a change in the amount of light received from the light receiving section (5) is sent to a foreign object detection circuit (17), and the signal is applied to a circuit (18) for sorting out defective containers.

As described above, the incident angle (C) of the laser beam needs to be about 40° from Oo, which is a range that does not satisfy the conditions for total reflection.

This is because when irradiating from above the liquid surface, the scattered light is dispersed due to the refraction of the light by the liquid surface, and accurate measurements are impaired due to the influence of scattered light from water droplets adhering to the upper inner wall of the container. .

Therefore, an angle of incidence from diagonally downward, which is not subject to the above-mentioned negative factors, is used.

In addition, by spreading the laser beam in a fan shape using a cylindrical lens (3), etc., and then scanning from side to side, the detection probability can be improved by moving the light even when the detection probability decreases due to little movement of floating foreign objects. Moreover, the detection processing time can also be shortened.

The method of moving the light may be one of scanning first and then spreading it out in a fan shape using a cylindrical lens or the like, or scanning both horizontally and vertically (Lascous scanning).

As a means of scanning, as shown in Figure 3 (a) and (b), rotating mirror (10) or vibration S, Q (12) can be used.
This method uses a lens (11) to scan the laser beam and converts it into parallel light. Figure 3 (c) shows a method in which the parallel light is scanned using the refraction development of the glass of the rotating glass column (4). Therefore, when the scanning width is relatively small (for example, 1 to 3 cm), there is an advantage that a lens or the like is unnecessary and the number of parts can be reduced.

In order to further improve the detection sensitivity, instead of using the cylindrical lens (3) to spread it out in a fan shape, two scanning means (13) (13°) are used as shown in Figure 3 (d), and the laser beams are aligned with each other. Combine the lights so that they cross at right angles,
Scanning operations in the vertical and horizontal directions increase the sensitivity (S/N ratio) and enable the detection of small foreign objects.

As mentioned above, the direction of light reception is determined by the angle of emission from diagonally downward (
When light is received in d), it is not affected by both the scattered light from the container above the water surface and the scattered light from the container below the liquid surface, unlike when light is received from diagonally above.

To explain in more detail, as shown in Figure 4, when the refractive index of water is 1.33 (20°C), the total reflection angle is 41.4°.
Therefore, if the light is received at an angle above this, it will not be affected by the container above the liquid level.

However, since it is affected by light from the opposite direction to the light receiving direction, that is, from the direction of specular reflection on the liquid surface, it is necessary to block light on the back side of the container by using a different color light shielding method (14) or the like. From this point of view, it is desirable that the light receiving direction is a direction that intersects the irradiation direction, and the emission angle (d) may be any angle that falls within the range of total reflection.

As for the light receiving direction, in addition to the method shown in FIG. 2, in which the scattered light of the container is masked and removed at the time of incidence and exit, the light is focused, as well as the embodiment shown in FIG.

Figure 5 (a) shows the condenser lens (15) that collects all of the light above the container, including the light scattered by foreign objects and the light scattered by people coming into the container.
Figure 5 (b) shows the method of collecting and receiving light with a receiver (5).
) if the light-receiving area is large, use a direct field-of-view restriction mask (7)
Fig. 5(c) shows a method in which directly scattered light is received by an optical fiber bundle (19), and the lens (15) or optical fiber bundle is omitted.

According to the methods described above, it is possible to determine the characteristics of the laser beam's fingertip or paternal properties (the effect of emitting light into a thin, sharp beam over a long distance or concentrating it on a single point) and monochromatic light (a very narrow spectrum of light). In addition to being able to capture foreign matter floating in the liquid or on the liquid surface with high precision, it is possible to remove the influence of scattered light from the outer wall of the container by masking the light receiving system, and to use light shielding plates, etc. By removing noise components such as preventing reflections from behind the container, it is possible to use a highly sensitive device.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the method that is the premise of the method of the present invention, Figure 2 is an explanatory diagram of the method of the present invention, m3121 (a) (b) (c) (d) is an explanatory diagram showing the scanning means, FIG. 4 is an explanatory diagram when a different color light-shielding plate is used, and FIGS. 5(a), (b), and (c) are explanatory diagrams showing a light receiving method. (1)...Container (2)...Laser light source (3)...Cylindrical lens (4)...Rotating glass column (5)...Light receiving part (6)...・ ・ Lens (7) ・ ・ ・ ・ ・ ・ Visible restriction mask (8) ・ ・ ・ ・ ・ Lens lens (9) ・ ・ ・ Interference filter (10) ・ ・ ・ Rotus mirror (11) ・ ・ ・ Lens (lens (11) 12) ・ ・ ・ ・ ) Axial mirror (14) ... Unique color shielding plate

Claims (4)

[Claims] (1) A laser beam is irradiated from diagonally downward to the liquid surface in a transparent or translucent container filled with liquid, and the laser beam scatters light from foreign objects in the liquid and floating foreign objects on the liquid surface in a direction different from the irradiation direction. A method for detecting a foreign object in a liquid in a container, the method comprising detecting a foreign object in the liquid in the container by receiving light with a photodetector provided diagonally below the liquid level on the side and detecting the foreign object in the liquid in the container based on a change in the amount of received light. (2) When irradiating a laser beam, the beam of the laser light source is spread in either the horizontal or vertical direction, and then scanned in a direction that intersects that direction, so that the laser beam is applied to a certain area of the liquid including the liquid surface. Claim 1 characterized in that the beam is irradiated.
Method for detecting foreign matter in liquid in a container as described in Section 1. (3) Inside the container according to claim 1, wherein when irradiating the laser beam, the laser beam is irradiated onto a certain area of the liquid including the liquid surface by raster scanning the laser light source. A method for detecting foreign objects in liquid. (4) A laser beam irradiation device that can irradiate the liquid surface in a transparent or translucent container filled with liquid from diagonally downward, and foreign matter in the liquid and floating on the liquid surface that is irradiated with the laser beam of the device and a light detection device capable of detecting a foreign object by a change in the amount of light received by a light receiving section provided obliquely below the liquid level on a side different from the irradiation direction, the light receiving section receiving scattered light from the foreign object. A foreign object detection device in a liquid in a container, characterized in that: