JPS5818126A - Reflecting sensor - Google Patents

Abstract

PURPOSE:To obtain a reflecting sensor which can easily detect the presence/ absence or a liquid and the liquid level and is easily fitted, by providing a prism at one tip of an optical fiber branched into two optical paths and providing a light emitting element and a photodetector at another end of the optical paths branched into two, respectively. CONSTITUTION:At one end of an optical fiber 6 branched into two optical paths, made of a glass fiber or a polymer fiber, a conical prism 7 is fitted. At the other end of a branched optical path 61, a light emitting diode 8 is fitted and a phototransistor photodetector 9 is fitted. In the light from the diode 8, many reflected lights exist when the prims 7 enters a liquid 5, a large reflected output current is caused in the photodetector, and when the surface of the prism 7 is at a gas phase, reflected light is remarkably decreased and the output power is greatly reduced. Thus, the absence/presence of an object to be detected and the detection of liquid level can easily be measured, and a measuring device can easily be fitted even at a narrow place, the sensitivity is high, and the system can safely be used for the liquid level detection of gasoline requiring water resistance oil resistance and explosionproofness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflective sensor that uses optical coupling, and includes a prism having a predetermined shape attached to one end of an optical fiber that is branched into two optical paths. It is an object of the present invention to provide a reflective sensor that can easily detect the presence or absence of liquid or the liquid level by attaching a light emitting element and a light receiving element to the other ends of each branched optical path.

Recently, optical coupling devices in which a light-emitting element and a light-receiving element are placed facing each other or side by side have come to be used in various fields for the purpose of detecting an object, detecting the direction of movement, etc. Detection of the presence or absence of liquid and the position of the liquid level is one example. Conventionally, for such detection, a light emitting element 1 and a light receiving element 2 are arranged facing each other as shown in FIG. was used to detect the liquid level. Such a detection method has a high S/
Disadvantages include difficulty in removing nitrogen, poor liquid level detection accuracy, problems with waterproofing, and restrictions on installation location.

The present invention eliminates the above-mentioned drawbacks and provides a reflective sensor that can easily detect the liquid level or the presence or absence of liquid.

Hereinafter, the configuration of the reflective sensor of the present invention will be explained with reference to the drawings. FIG. 2 shows a reflective sensor according to an embodiment of the present invention, and the reflective sensor of the present invention is composed of a glass fiber 6, a conical prism 7, a light emitting diode, and a phototransistor 9. According to the reflective sensor of the present invention, the liquid level 4 and the liquid 6 can be detected in the following manner. That is, the light emitted from the light emitting diode 8 is transmitted inside the fiber 6 and reaches the conical prism 7, but if the area around the prism is air, most of the light that reaches the prism passes through the prism.

Therefore, less light is transmitted through the other optical path of the optical fiber and incident on the phototransistor 9 due to reflection on the inner surface of the prism.

On the other hand, as shown in FIG. 2, when the area around the prism 70 is liquid, the reflection on the inner surface of the prism increases, so most of the light that reaches the prism 7 is transmitted through the other optical path of the optical fiber and enters the phototransistor 9. However, the amount of light incident on the phototransistor 9 increases. In this way, the light reflection on the inner surface of the prism differs greatly depending on whether the area around the conical prism 70 attached to the tip of the optical fiber is air or liquid, causing a difference in the reflected output current flowing to the phototransistor 9, which is the light receiving element. , the presence or absence of liquid and the position of the liquid surface around the prism can be easily detected.

FIG. 3 is an enlarged view of the vicinity of the conical prism of an example of the reflective sensor of the present invention, and the optical fiber 6 has a first optical path 61 for transmitting the emitted light A from the light emitting element and a reflected light B to the light receiving element.
It consists of a second optical path 62 that transmits. A conical prism 7 is attached to the tip of this optical fiber. Note that the angle θ between the slope of the conical prism 7 and the above-mentioned optical path is
When the angle is set to 46°, the S/
I was able to get the largest N.

The reflective sensor according to the present invention has a completely sealed configuration↓
It can also be applied to systems that detect the level of liquids such as kerosene, gasoline, etc. For example, when the liquid level rises to the prism 7 attached to the tip of the reflection sensor, the amount of reflected light to the light receiving element increases, and the current flowing therein increases.

The inflow amount of liquid can be controlled to a set value by amplifying this amount of change to generate a control signal and turning off a motor etc. that feeds the liquid. The reflection sensor of the present invention uses optical fibers as described above, so that
It has the characteristic that it is not dangerous even when used for detecting the level of liquids such as kerosene and gasoline, which require violence resistance. In addition, since a prism is attached to the tip of the optical fiber, the S/N ratio for detecting the presence of liquid or liquid level is high.
It has excellent oil resistance and water resistance. Furthermore, since optical fibers are used, there are no restrictions on where the reflection sensor can be installed, and it is easy to install it in very narrow spaces.

Although the above explanation is an example in which a glass fiber is used as the optical fiber, substantially the same effect can be obtained by using a polyfiber. In addition, as the optical fiber 6, as shown in FIG.
It goes without saying that the same effect can be obtained by configuring randomly within the fiber and attaching conical prisms. Furthermore, the shape of the prism may be pyramidal.

As described above, the present invention greatly contributes to the realization of a reflective sensor that is easy to handle and has excellent performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the conventional detection method for detecting the presence or absence of liquid or the liquid level, and FIG. 3 is an enlarged view showing the vicinity of the prism of an example of the reflective sensor according to the present invention; FIG. 4 is a view showing another example of the configuration of the optical fiber according to the present invention; FIG. It is. 4...Liquid level, 5...Liquid, 6...
...Optical fiber, 61...First optical path, 62
...Second optical path, 611°°°°°°Emitting side fiber, 62°...Receiving side fiber, ku-17
... Prism, 8 ... Light emitting diode, 9 ... Phototransistor. Name of agent: Patent attorney Toshio Nakao and one other person II
1 Figure 2 Figure 35il Homare Figure 4 Exit G2 B ″″6

Claims (4)

[Claims] (1) In an optical fiber having a first optical path and a second optical path, a prism is attached to one end of the optical fiber that is the open end of the two optical paths, and a light emitting element is further attached to the other open end of the first optical path. . A reflective sensor characterized in that a light receiving element is attached to the other open end of the second optical path. (2) The reflective sensor according to claim 1, wherein the optical fiber is a glass fiber. (3) The reflective sensor according to claim 1, wherein the optical fiber is a polyfiber. (4) Attach the optical fiber prism to the first side open end. 2. The reflective sensor according to claim 1, wherein the optical path and the second optical path are divided into two. (Claim 1) characterized in that the angle between the inclined surface of the prism and the optical axis at the open ends of the first and second optical paths facing the prism is selected to be 46°. Reflection senna as described in.