JPH0742575B2 - Liquid level monitor for molten material and liquid level controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for monitoring the liquid level of molten material and a device for controlling the liquid level.

2. Description of the Related Art For example, in order to form a thin film on a long film and produce a functional film, which is a material for capacitors, magnetic tapes, etc., by vacuum vapor deposition, a large amount of vapor is kept constant over a long period of time. It must be generated at the evaporation rate. For that purpose, it is necessary to monitor the amount of the vapor deposition material melted in the container and keep the amount constant. An apparatus for monitoring the amount of vapor deposition material is disclosed in, for example, Japanese Patent Laid-Open No. 63-312968. In this conventional example, the main container and the auxiliary container are connected by a communication pipe, and the amount of the evaporation material in the main container is indirectly monitored by monitoring the liquid level of the evaporation material in the auxiliary container. .

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, in addition to the main container, the auxiliary container, the communication pipe, and the heater for keeping the material in the communication pipe in a molten state are required, and the structure becomes very complicated. There was a problem.

In particular, in order to apply it to a high melting point material, it is necessary to make the above-mentioned structure from ceramics having heat resistance, but it was very difficult because of the complicated structure. Even if it could be manufactured, it had a short structure because its structure was complicated and cracks were likely to occur during heating or cooling. Further, in order to keep the material in the communicating tube in a molten state at a high temperature, the load on the heater is so large that the life of the heater is short and it is practically difficult to apply it to a high melting point material.

Therefore, the present invention provides a liquid level monitoring device and a liquid level control device capable of directly and optically monitoring the liquid level of a melted material with high accuracy and having a long life and excellent practicality. The purpose is.

Means for Solving the Problems The invention of the present invention, a molten material liquid level monitoring device, captures an image of this liquid surface from obliquely above the material liquid surface melted in a container, and outputs a signal corresponding to the position of the image. An optical system for forming an image of the liquid surface on an image pickup device for outputting, and an end shape between the optical system and the liquid surface and substantially parallel to a boundary portion between the liquid surface and the inner surface of the container. A shielding member, which shields a part of the liquid surface with respect to the optical system and exposes at least the liquid surface between the boundary portion and the end of the shielding member to the optical system, and the boundary. And a signal processing means for obtaining the length of the liquid surface image between the edge portion and the end of the shielding member from the signal from the image sensor, and the length of the liquid surface image between the boundary portion and the end of the shielding member. It is characterized in that the liquid level height change is detected from the change.

The molten material liquid level control device of the present invention captures an image of the liquid surface obliquely above the material liquid surface melted in the container, and outputs the signal corresponding to the position of the image to the image sensor of the liquid surface. An optical system for forming an image, and a shielding member having an end shape between the optical system and the liquid surface and substantially parallel to a boundary portion between the liquid surface and the inner surface of the container, Between the boundary portion and the end of the shielding member, and a shielding member that shields a part of the optical system from the optical system and exposes at least the liquid surface between the boundary portion and the end of the shielding member to the optical system. Signal processing means for obtaining the length of the liquid surface image from the signal from the image sensor,
Replenishing means for replenishing the material into the container, and control means for controlling the replenishing means so that the length of the liquid surface image reaches a target value based on the length signal of the liquid surface image from the signal processing means. It is characterized by having.

Effect of the Invention The invention of the present invention, the molten material liquid level monitoring device, by the above configuration, to detect the height change of the liquid level from the change in the length of the liquid surface image between the boundary portion and the end of the shielding member. You can
Therefore, the height of the liquid surface of the melted material can be directly optically monitored with high accuracy. Moreover, since the structure of the conventional example is complicated, cracks are likely to occur, and the load of the heater used therefor becomes large, resulting in a short heater life. Despite its drawbacks, it has a long life and is excellent in practicality.

The molten material liquid level control device of the present invention has the above configuration,
The height of the liquid surface of the melted material is directly and optically highly accurate,
Moreover, since the liquid level can be monitored with a long life, the liquid level can be controlled to a target height with high precision.

Examples Hereinafter, examples in which the present invention is applied to melting a vacuum deposition material, monitoring its liquid level height, and controlling its liquid level height will be described with reference to the accompanying drawings. To do.

1 to 3 are views showing a molten material liquid level monitoring device in a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a vapor deposition material housed in a container 2 such as a crucible, which is heated and melted by, for example, a known electron beam heating means (not shown). 3 is a transparent glass window,
It is provided at a position facing the liquid surface 5 of the melted vapor deposition material 1 on the wall surface 4 of the vacuum chamber obliquely from above.

A shielding member 6 is a liquid level monitoring camera (hereinafter abbreviated as camera).
7 and the container 2, the liquid level 5 and the container 2
Has an end portion 10 substantially parallel to a boundary portion 9 with an inner surface 8 of
A part of the liquid surface 5 is shielded from the camera 7, and the liquid surface between the boundary 9 and the end 10 is exposed to the camera 7.

The camera 7 is mainly composed of an image pickup device 11 and a lens 12 for forming an image of the liquid surface 5 on the image pickup device 11. Note that a known automatic diaphragm for keeping the amount of incident light constant, a known finder for confirming whether an image is accurately formed on the image pickup element 11, that is, whether the image is in focus, or an automatic focusing function is omitted.

The image pickup device 11 of the camera 7 is composed of, for example, a known photodiode linear array in which photodiodes P _{1 to} P ₅₁₂ , which are a plurality of (512 as an example) photoelectric conversion elements, are linearly arranged. There is. The photoelectric conversion element generates an output signal according to the amount of light incident on the element. Reference numeral 13 denotes a signal processing circuit, which is configured to obtain the length S of the formed image from the output signal 17 from the image pickup device 11. A method for obtaining the image formation length S is shown in FIGS.
It will be described with reference to the drawings. In FIG. 3, the focal length F of the lens 12 is shown to be long in order to make the drawing easy to see.

An image 14 of the liquid surface 5 is formed on the image pickup element 11, and an image 15 of the inner surface 8 of the container 2, the liquid surface 5 and the boundary portion 9 is also formed on the photodiode P ₃₀₀ of the image pickup element 11. It is assumed that an image of the end 10 of the shielding member 6, that is, an image 16 of the boundary of the liquid surface 5 shielded by the end 10 is formed on the diode P ₁₀₀ . Of course, the diaphragm is set to the depth of focus where both the boundary portion 9 and the end portion 10 are in focus.

The distance from the lens 12 to the boundary portion 9 is L _K , the distance to the end portion 10 is L _S, and the inclinations of the optical axis with respect to the liquid surface 5 are θ ₁ and θ ₂ , respectively. Let E be the actual length of the portion of the liquid surface 5 that is in the field of view of the camera 7, D be the projected length of the liquid surface 5 onto the inner surface 8 of the container 2, and S be the imaged length on the image pickup element 11. Here, in order to simplify the calculation, L = L _K = L _S ,
Let θ = θ ₁ = θ ₂ .

From the above, S = (D · F / L) cos θ (1) D = E · tan θ (2) Further, assuming that the variation of the height x of the liquid surface 5 is the variation of y on the image sensor 11, y = ( x · F / L) cos θ (3)

Here, as an example, the photodiode pitch is 0.03 mm,
When θ = 20 °, L = 1000mm, F = 100mm, the length of x corresponding to the photodiode pitch of 0.03mm is x = (y / cosθ) L / F = 0.32mm from equation (3), and the resolution is sufficient. Is.

Next, the output signal from the photodiode and its processing will be described.

As described above, the photodiode P ₃₀₀ of the image pickup device 11
Is an image of a boundary portion 9 between the inner surface 8 of the container 2 and the liquid surface 5.
15. Similarly, an image of the end 10 of the shielding member 6, that is, an image 16 of the boundary of the liquid surface 5 shielded by the end 10 is formed on the photodiode P ₁₀₀ .

Since the liquid surface 5 has a higher temperature than the inner surface 8 of the container 2 and the end portion 10 of the shield member 6, the liquid surface 5 has high brightness. Therefore, bright light is incident between the photodiodes P ₁₀₀ to P ₃₀₀ . Container 2
When the or shielding member 6 is cooled, the contrast of the light can be increased. Therefore, the output signal 17 from the image pickup device 11 is at a high level in the photodiode between P ₁₀₀ and P ₃₀₀ as shown in FIG. The signal processing circuit 13 receives the output signal 17 and, with a threshold value set to an intermediate level between the high level and the low level, as shown in FIG. 2B, a binarized signal 18 of the Hi level and the Lo level. Convert to. Assuming that the photodiodes that are in the Hi level after binarization are P ₁₀₀ to P ₃₀₀ , the signal processing circuit 13 determines the image forming length S from the photodiodes P ₁₀₀ to P ₃₀₀ to 0.03 mm × (300-100). ＝ 6mm, then calculate D = (6mm / cos20 °) 1000mm / 100mm = 63.85mm from equation (1). The detection of the imaging length S and the calculation of the projection length D are performed at required time intervals.

Therefore, by monitoring the change in the projection length D, the change in the height x of the liquid surface 5 can be monitored at the resolution of 0.32 mm as described above.

With the above configuration, even if the position of the camera 7 slightly moves during the measurement, the measurement of the image formation length S is hardly affected. Therefore, the change in the height x of the liquid surface 5 can be detected with high reliability. You can

Although the liquid surface 5 is shielded by the end portion 10 of the shielding member 6 in the above-described embodiment, the lens 12 of the container 2 may be used as long as the dimensional relationship of each component is appropriate as shown in FIG. The edge 19 on the side close to may be used as an alternative to the end 10.

Further, when using a container in which the boundary portion 9 has an arc shape, the shape of the end portion 10 may be set so as to be substantially parallel to the boundary portion as viewed from the camera 7.

The degree of parallelism may be set according to the required monitoring accuracy.

If the distance from the container 2 to the window 3 is not sufficient, the vapor from the vapor deposition material 1 may adhere to the window 3 and significantly block the light incident on the camera 7. In such a case, a rotary shutter plate or a swing type shutter plate having a known slit is provided on the container 2 side of the window 3, and the window 3 is alternately shielded and opened with respect to the container 2 at a required time ratio. The image of the liquid surface 5 may be captured by the camera 7. At this time, if necessary, the image may be captured in synchronization with the opening / closing timing of the shutter.

Further, the image pickup device is not limited to one in which a plurality of photoelectric conversion devices are linearly arranged as in the above example, and may be one arranged in a plane. By doing so, changes in the liquid surface can be monitored at a plurality of positions instead of at one place, or in a wide range, so that the reliability can be further improved.

Further, as shown in FIG. 5, a deposit 20 of vapor from the vapor deposition material 1 is formed on the end portion 10 of the shielding member 6, and the change e on the image pickup device 11 due to the change of the position of the end portion 10 is neglected. If this is not possible, for example, the amount by which the position changes with time may be measured in advance, and the data may be input to the signal processing circuit 13 to compensate for the change e.

Next, a molten material liquid level control device according to a second embodiment of the present invention will be described with reference to FIG. The first
The same components as those in the embodiment of FIG.

In the figure, 30 is a replenishment material rod of the vapor deposition material 1, which is sent toward the vapor deposition material 1 by a motor 33 which is sandwiched between a drive roller 31 and a guide roller 32 and drives the drive roller 31, and the liquid surface 5
The material is replenished by melting it in contact with. A control circuit 34 calculates a deviation between a value D from the signal processing circuit 13 and a target value D ₀ of this value D, and if D <D ₀ , drives a motor 33 to drive a motor 33 to replenish materials. Control. The shape of the replenishment material is not limited to the rod shape, but may be a wire shape, a plate shape, a granular shape, or any other shape.

According to the above configuration, when the vapor deposition material 1 decreases due to evaporation, the decrease is detected, and the vapor deposition material 1 is replenished so as to compensate for the decrease, so that the height of the liquid surface 5 is always kept constant. Therefore, it becomes possible to deposit at a constant evaporation rate for a long time. Although the case where the target value D ₀ is constant has been described, the present invention is not limited to this. For example, when it is desired to use up the vapor deposition material 1 in the container 2, the target value
It suffices to perform control so that D ₀ becomes smaller with the passage of time. Needless to say, at this time, it is necessary to keep the evaporation rate constant by decreasing the power for heating the vapor deposition material 1 as the vapor deposition material 1 decreases.

The present invention can be constructed in various modes in addition to the above-mentioned embodiments. For example, in the above embodiment, the monitoring of the liquid level of the vapor deposition material and its control have been described, but the present invention is not limited to the vapor deposition material, and the above monitoring and control at the time of melting the material in the process such as melting processing of metal etc. It can be applied wherever you need it.

EFFECTS OF THE INVENTION The molten material liquid level height monitoring device of the present invention has the above-described configuration.
The change in the height of the liquid surface can be detected from the change in the length of the liquid surface image between the boundary portion and the end portion of the shielding member. Therefore, the height of the liquid surface of the melted material can be directly optically monitored with high accuracy, and the liquid surface monitoring with a long life and excellent in practicality can be realized.

The molten material liquid level control device of the present invention has the above configuration,
The height of the liquid surface of the melted material is directly and optically highly accurate,
Moreover, since it can be monitored for a long time and with a long service life, highly accurate liquid level control can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a molten material liquid level height monitoring device according to a first embodiment of the present invention, and FIG. 2 is an enlarged view of an essential part of the device and a diagram for explaining signals, and FIG. Is an explanatory view of the principle of the present embodiment, FIGS. 4 and 5 are schematic views showing a modified example of the apparatus, and FIG. 6 is an outline of a molten material liquid level control apparatus in the second embodiment of the present invention. It is a block diagram. 1 ... Evaporation material, 2 ... Container, 3 ... Glass window, 5 ...
Liquid level, 6 ... Shielding member, 7 ... Liquid level monitoring camera, 9 ...
Boundary part, 10 ... Edge part, 11 ... Image sensor, 12 ... Lens,
13 ... Signal processing circuit, 30 ... Replenishing material rod, 31 ... Drive roller, 32 ... Guide roller, 33 ... Motor, 34 ... Control circuit, 35 ... Motor drive circuit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hidenobu Shintaku 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kayoko Kodama, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 56) References JP 58-31080 (JP, A)

Claims (5)

[Claims] 1. An optical system for taking an image of a liquid surface of a material melted in a container from obliquely above and forming an image of the liquid surface on an image pickup device which outputs a signal corresponding to the position of the image. When,
A shielding member having an end shape that is substantially parallel to the boundary between the liquid surface and the inner surface of the container between the optical system and the liquid surface, and a part of the liquid surface with respect to the optical system. A shielding member for shielding at least the liquid surface between the boundary and the end of the shielding member to the optical system, and a length of the liquid surface image between the boundary and the end of the shielding member. A molten material liquid level monitoring device comprising: a signal processing unit which is obtained from a signal from an image pickup device, and is configured to detect a liquid level change based on a change in the length of the liquid surface image. 2. The molten material liquid level monitoring device according to claim 1, wherein the end of the shielding member is an edge of the container opening near the optical system. 3. An optical system is configured to capture an image of a liquid surface through a shutter provided between a transparent window and a container and alternately performing blocking and opening of the transparent window with respect to the container at a required time ratio. 2. The molten material liquid level height monitoring device according to claim 1. 4. The signal processing means comprises means for compensating a liquid level length detection error due to a vaporized material adhering to the end of the shielding member and changing the position of the end according to a predetermined procedure. The molten material liquid level height monitoring device according to claim 1, characterized in that it has. 5. An optical system which captures an image of the liquid surface obliquely above the liquid surface of the material melted in a container and forms the image of the liquid surface on an image pickup device which outputs a signal corresponding to the position of the image. A shielding member having an end shape between the optical system and the liquid surface and being substantially parallel to a boundary portion between the liquid surface and the inner surface of the container, wherein a part of the liquid surface is provided to the optical system. The length of the liquid surface image between the boundary portion and the end of the shielding member, and the shielding member that shields the liquid surface between the boundary portion and the end of the shielding member toward the optical system. A signal processing means obtained from a signal from the image pickup device, a replenishing means for replenishing the material into the container, and a liquid surface image length based on a length signal of the liquid surface image from the signal processing means. Control means for controlling the replenishing means so that Apparatus.