JPH05332811A - Liquid level measuring method and liquid level measuring device - Google Patents

Abstract

PURPOSE:To avoid the influence of print on a vessel and the like in optically measuring liquid level in a vessel having transparency. CONSTITUTION:To an edge part 3a running up along the vessel wall surface due to surface tension which is around the liquid level of the liquid in vessel 1, light is casted from an upward lighting a source 21 with a specific incident angle theta. An image sensor 22 is arranged in the position to receive the right reflection light reflected with the same angle as the incident light among the light reflected at the edge 3a of the liquid level and a very bright spot is produced by the right reflection light on the sensor surface 22a. This bright spot appears at the position corresponding to the liquid level. Even if a part of it disappears due to the influence of print on the vessel and the like, the liquid level can be exactly measured from other bright points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level measuring method and apparatus for optically measuring the height of the liquid level of a liquid having a light-transmitting property.

[0002]

2. Description of the Related Art For example, in a line for producing bottled beverages, the height of the liquid level is measured so that there is no excess or deficiency in the amount of the content infused into the container. It sorts out products and excess and deficiency products.

As a method for optically measuring the height of the liquid surface, as shown in FIG. 10 (a), illumination light parallel to the liquid surface 3 of the liquid 2 in the container 1 is supplied to one of the containers 1. Conventionally, a method of irradiating from the side surface side, transmitting through the container 1, and output from the other side surface side by the image sensor 10 has been taken.

In this method, of the illumination light incident on the inside of the container, only the illumination light incident on the outer edge portion 3a of the liquid surface raised along the inner wall surface 1a of the container 1 due to the surface tension is shown in FIG. As shown in FIG. 11B, the fact that the light is refracted or reflected by the outer edge portion 3a and does not reach the image sensor 10 is used, and the surface of the sensor 10a of the image sensor 10 is, as shown in FIG. A dark band 11 is formed at a position corresponding to the outer edge portion 3a.

Therefore, for example, the light reception signal of each pixel of the image sensor 10 is converted into binarized data corresponding to light and dark, and the y-coordinate of the barycentric position of the dark portion corresponding to the dark band 11 is within the allowable range. If it is determined whether or not it is possible to sort products according to the height of the liquid surface 3.

[0006]

However, as described above, in the method of measuring the height of the liquid surface by the illumination light parallel to the liquid surface, the liquid is printed on the outer surface of the container 1 or near the label. When there is a surface, there is a problem in that it is not possible to distinguish between a dark portion caused by the printing or the light shielding of the label and a dark band by the outer edge portion 3a of the liquid surface 3, and accurate level measurement cannot be performed.

It is an object of the present invention to provide a liquid level measuring method and apparatus for solving the above problem.

[0008]

In order to solve the above-mentioned problems, the liquid level measuring method of the present invention is to irradiate the liquid level portion of a liquid having a light-transmitting container with illumination light from outside the container. Then, in the liquid level measuring method of measuring the height of the liquid surface by imaging the light output from the inside of the container, the outer edge portion of the liquid surface raised along the inner wall surface of the container by the surface tension. The illumination light at a predetermined incident angle from a position higher than the outer edge portion, and based on the imaging position of specular reflection light reflected from the outer edge portion of the liquid surface at a reflection angle equal to the incident angle. Then, the height of the liquid surface is measured.

[0009]

As described above, according to the liquid level measuring method of the present invention, the bright portion is generated only at the image pickup position of the specular reflection light from the outer edge of the liquid surface, and even if the illumination light is changed by printing or a label. Even if a part is shielded from light, only a part of the bright part is missing, and the liquid level can be measured accurately.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a liquid level measuring device to which the liquid level measuring method of the present invention is applied.

In this liquid level measuring device, the outer edge 3a of the liquid surface raised from the illumination light source 21 arranged above one side surface of the container 1 along the inner wall surface 1a of the container 1 by surface tension. Illumination light is incident on a part of the outer peripheral portion 3a at a predetermined incident angle θ and at a reflection angle equal to the incident angle θ.
The specularly reflected light reflected from the image sensor 22 is received by the image sensor 22, and the sensor output of the image sensor 22 is processed by the processing device 23.

The illumination light from the illumination light source 21 has a width L according to the measurement range of the liquid level, and of this illumination light, the light incident on the outer edge 3a of the liquid surface is specularly reflected. Only light is strongly incident on the sensor surface 22a of the image sensor 22.

The sensor surface 22a of the image sensor 22 is formed by arranging a large number of pixels at a predetermined pitch, and the processing device 23 makes the light receiving level of each pixel bright and dark as shown in the flowchart of FIG. It is converted into corresponding binary data, the y-coordinate of the barycentric position of the bright portion on the sensor surface 22a is obtained from this binary data, and it is determined whether or not the y-coordinate is within a predetermined range. A selection signal corresponding to the determination result is output.

In the liquid level measuring device constructed as described above, for example, as shown in FIG. 3, when the liquid level 3 is at the height A and at the height B, the sensor for specular reflection light is used. Face 22
The image pickup position with respect to a differs by an amount proportional to the difference between A and B, and the barycentric coordinates of the bright portions Sa and Sb obtained from the binarized data also correspond to the height of the liquid surface, as shown in FIG. It appears in each position. In addition, if the range from Y ₁ to Y ₂ in FIG. 4 is set as an allowable range, it is determined that the product at the liquid level at A is a positive quantity product and the product at B height is an insufficient product. You can

In this measuring apparatus, the illumination light is emitted from above the liquid surface to be measured, and therefore
As described above, even when the non-translucent printing surface 5 is in the measurement range, it is possible to measure up to the liquid level which is considerably lower than the upper end 5a of the printing surface 5. Further, for example, as shown in FIG. 6, even if the non-translucent printed character is within the measurement range and a part of the illumination light to the outer edge of the liquid surface is blocked, the sensor of the image sensor 22 may be used. On the surface 22a, as shown in FIG. 7, bright portions S ₁ and S ₂ cut by printed characters appear. Since the y-coordinate of the center of gravity of these bright portions is equal to the y-coordinate of the bright portion when the printed characters are not shielded from light, the accurate height of the liquid surface can be detected from the center of gravity of the bright portions S ₁ and S _2. it can.

[0017]

Other Embodiments In the above embodiment, the case where the product to be measured does not move has been described, but as shown in FIG.
The present application can also be applied to an apparatus that measures the height of the liquid surface of the liquid while it is being conveyed on the conveyor 15. In this case, the passing timing of the product W is set to the projector 16 and the light receiver 1.
It is only necessary to start the measurement by the processing device 23 at the timing when it reaches the position between the illumination light source 21 and the image sensor 22 after the product has passed between the light emitting and receiving devices. Further, in the case of this embodiment, the illumination light source may be made to emit light only at the time of measurement.

Further, when the height of the liquid surface is measured while transporting the product as described above, it is possible that the image sensor 22 cannot receive the specularly reflected light from the outer edge of the liquid surface due to the shaking of the liquid surface. .. This phenomenon becomes more remarkable as the width of the illumination light is narrower than the width of the outer edge portion. In order to prevent this phenomenon, for example, as shown in FIG.
1 to the outer edge portion 3a of the liquid surface 3 with different incident angles θ
_The illumination light may be incident at ₁ and θ ₂ , respectively, and the image sensor 22 may be arranged at a position where each specularly reflected light can be imaged at substantially the same position.

Thus, if the reflection position has a width,
Even if the outer edge of the liquid surface is undulated, any specularly reflected light is incident on the image sensor 22, and the liquid surface level can be measured. The number of illumination light sources may be increased, and the light from the illumination light source is once reflected on a concave mirror or the like, and the reflected light is used as illumination light.
The light may be incident on the outer edge of the liquid surface at a number of different incident angles.

[0020]

As described above, the liquid level measuring method and apparatus according to the present invention can be applied to the outer edge of the liquid surface raised along the inner wall surface of the container by the surface tension from a position higher than the outer edge. Illumination light is incident at a predetermined incident angle,
Since the level of the liquid surface is detected based on the imaging position of specularly reflected light that is reflected at a reflection angle equal to this incident angle,
A bright portion occurs only at the imaging position of the specularly reflected light from the outer edge of the liquid surface, and even if a part of the illumination light is blocked by printing or a label, only a part of the bright portion is missing, The liquid level can be measured accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a main part of one embodiment.

FIG. 3 is a diagram showing a change in reflected light according to the height of a liquid surface in an example.

FIG. 4 is a diagram of a bright portion of a sensor surface of the image sensor according to the embodiment.

FIG. 5 is a diagram showing a measurement example in the case where a non-translucent printing surface is provided on the surface of the container.

FIG. 6 is a diagram showing a measurement example in which illumination light is blocked by non-translucent printed characters on the surface of a container.

7 is a diagram showing a bright portion at the time of measurement in FIG.

FIG. 8 is a diagram showing another embodiment of the present invention.

FIG. 9 is a diagram showing another embodiment of the present invention.

FIG. 10 is a diagram for explaining a conventional measuring method.

FIG. 11 is a diagram for explaining a conventional measuring method.

[Explanation of symbols]

 1 Container 2 Liquid 3 Liquid Level 3a Outer Edge 21 Illumination Light Source 22 Image Sensor 23 Processing Device

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 20, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 4]

[Figure 7]

[Figure 8]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 5]

[Figure 6]

[Figure 10]

[Figure 9]

FIG. 11

Claims (2)

[Claims] 1. The height of the liquid level is obtained by irradiating a liquid level portion of the liquid in the translucent container with illumination light from the outside of the container and imaging the light output from the inside of the container. In the liquid level measuring method for measuring, the illumination light is incident on a part of the outer edge of the liquid surface raised along the inner wall surface of the container due to surface tension from a position higher than the outer edge at a predetermined incident angle. The liquid level measuring method is characterized in that the height of the liquid level is measured based on the imaging position of specularly reflected light reflected from the outer edge of the liquid surface at a reflection angle equal to the incident angle. 2. A predetermined incidence from a position higher than the outer edge portion to a part of the outer edge portion of the liquid surface of the liquid container having a light-transmitting property, which is raised along the inner wall surface of the container due to surface tension. An illumination light source that makes illumination light incident at an angle, and an image sensor arranged at a position for receiving specular reflection light that is reflected at a reflection angle equal to the incident angle from the outer edge portion of the liquid surface on which the illumination light is made incident. A liquid level measuring device comprising: a height detecting unit that detects the height of the liquid level of the liquid in the container based on the imaging position of the specular reflection light imaged by the image sensor.