JPS6066137A - Liquid refractive index sensor head - Google Patents

Abstract

PURPOSE:To improve an explosion-proof property, and also to execute a remote sensing by detecting the output light of one optical waveguide which is varied in accordance with the difference of a liquid refractive index of the optical waveguide having a prescribed gap filled with the liquid to be measured. CONSTITUTION:A liquid refractive index sensor head 1 is provided with a main optical waveguide and a sub-optical waveguide 3 and 4, and 3 and having prescribed gaps 6, 7, respectively. When this head 1 is immersed into the liquid to be measured and the gaps 6, 7 are filled with the liquid, and also light is made incident on the waveguide 3 through an optical fiber 8, light which is varied in accordance with a refractive index of the liquid is emitted from the waveguide 3 because the degree of coupling of the waveguides 3 and 4, and 3 and 5 are different in accordance with the refractive index. Subsequently, the emitted light from the waveguide 3 is detected remotely through an optical fiber 9 and the refractive index is measured. In such a way, an explosion-proof property of the liquid refractive index sensor head is improved, and also a remote sensing of the refractive index is executed.

Description

Detailed Description of the Invention (a) Industrial Application Field This invention relates to a liquid refractive index sensor head for measuring the refractive index of a liquid to be measured, such as refined oil in an oil refining plant, etc. This invention relates to a refractive index sensor head.

(b) Conventional technology Conventionally, the method of measuring the refractive index of a liquid is

Monochromatic light enters the sample along the surface of the prism, and the resulting light beam corresponds to the refractive index of the fluid.

The light passes through a lens and a moving slit and is irradiated onto a photomultiplier tube.

The generated current rotates the balancing motor,
There is one in which the movement is transmitted to a slit in front of the photomultiplier tube, and the pointer is moved at the same time. However, since this method includes an electric circuit in the measurement system, there are problems with explosion protection and remote sensing.

In oil refinery plants, it is necessary to measure the refractive index of refined oil as one of the quality controls for refined oil.

Due to the characteristics of the product, special attention must be paid to explosion-proof properties during measurements, and remote sensing from the control room is also required.

(c) Purpose The purpose of this invention is to provide a device with excellent explosion-proof properties in view of the above.

It is an object of the present invention to provide a liquid refractive index sensor head capable of performing refractive index measurement capable of remote sensing.

B) Structure To achieve the above object, the present invention utilizes the principle that the coupling coefficient between two optical waveguides with a constant 9-interval depends on the refractive index between both waveguides. The liquid refractive index sensor head of the present invention includes a substrate, and a liquid refractive index sensor head formed on the substrate.
A first optical waveguide that receives input light of a predetermined amount of light, and a second optical waveguide arranged on the substrate with a predetermined gap from the first optical waveguide, and a second optical waveguide that is covered with the gap during measurement. A liquid to be measured is filled, and the refractive index of the liquid to be measured is detected by the light emitted from the first optical waveguide, which changes depending on the difference in the refractive index of the liquid to be measured.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a plan view of an optical waveguide-type liquid refractive index sensor head showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the liquid refractive index sensor head shown in FIG. 1 taken along line I-1. be.

In FIGS. 1 and 2, a liquid refractive index sensor head 1 has a main optical waveguide (first optical waveguide) 3 and sub optical waveguides (second optical waveguides) 4 and 5 formed on a substrate 2 made of glass, for example. It is composed of

The main optical waveguide 6 is composed of a straight portion 3a and an arcuate curved portion 3b. Furthermore, a circular sub-waveguide 4 is arranged inside the arc-shaped curved portion 3b of the main optical waveguide B at an interval 6 equidistant from one curved portion 3b, and further outside the curved portion 6b of the main optical waveguide B. 1 at an equidistant interval from the curved portion 6b.

A sub optical waveguide 5 having an arcuate end face is arranged.

An input optical fiber 8 and an output optical fiber 9 are coupled to the main optical waveguide 6, and an external light source is connected to the main optical waveguide 6.

A constant amount of input light is inputted into the main optical waveguide B via the input optical fiber 8, and output light from the main optical waveguide 6 is led out via the output optical fiber 9.

Note that the distance do between the gaps 6 and 7 is relatively small.

Wavelength of light source1. It is about 1 μn for a 571 m long one.

When measuring the refractive index of a liquid such as oil using the liquid refractive index sensor head 1 configured as shown in FIG. immersed in liquid. When immersed in the liquid to be measured, the gaps 6 and 7 will be filled with the liquid to be measured.

Generally, the degree of coupling between two optical waveguides depends on the refractive index of the interval, assuming that the interval between the nine optical waveguides is constant. That is, the higher the refractive index of the gap, the higher the degree of coupling. Therefore, in the examples above.

The refractive index n1 of the gaps 6 and 7 is such that ng
>ns) If the width is also very small, the degree of coupling between the main optical waveguide 5 and the sub optical waveguides 4 and 5 will also be small. Therefore, the light that enters from the input optical fiber 8 and provides the main optical waveguide 6 propagates as it is in the 1 main optical waveguide 6, separated by 1 interval.7.
does not propagate to the sub optical waveguide 4.5. That is, when the refractive index nl of the gaps 6 and 7 is small, as shown by the light intensity distribution a in the width direction of the optical waveguide in FIG. 6, the light intensity is distributed within the width d1 of the main optical waveguide 6, and 4, 5 width range d2. The light intensity of a3 is almost 0. Therefore, most of the light propagating within the main optical waveguide 6 is led out from the output optical fiber 9 as an output amount.

On the other hand, when one gap 6.7, that is, the refractive index nl of the illμ measurement liquid approaches the refractive index nf of each optical waveguide, the degree of coupling between the main optical waveguide 6 and the sub optical waveguides 4 and 5 also increases. Therefore, the light that is input from the input optical fiber 8 and propagates within the main optical waveguide 6 is only on the way.

It propagates into the sub optical waveguides 6 and 7 through the gap 6.7. In other words, as shown in the light intensity distribution in Fig. 6, the gap 6,
When the refractive indexes n and d of 7 are large, the light intensity is
Not only the width d1 of the waveguide 6 but also the width region d2 of the sub optical waveguides 4 and 5
．． It will also be distributed in d3. Therefore, the light propagating within the main optical waveguide 3 is.

It is attenuated and led out through the output optical fiber 9.

Since this degree of attenuation corresponds to the refractive index of the liJ]l sources 6 and 7, that is, the refractive index of the limb measurement liquid, the refractive index of the multiwave measurement liquid is detected based on the amount of output light derived from the output optical fiber 9. be able to.

Note that in the above example (in Example 5), the higher the mode of light propagating through the main optical waveguide, the greater the degree of coupling. The shape of the waveguide is circular.Therefore, the shape of the optical waveguide is not limited to this, and other shapes such as a zigzag shape may be used.

Further, in the above embodiment, the sub optical waveguides are provided on both sides of the main optical waveguide in the propagation direction, but they may be provided only on one side if the degree of coupling required for measurement can be obtained.

(f) Effect The refractive index sensor head of this invention is formed of an optical waveguide,
In addition, since input and output light can be input or led out using optical fibers, electrical circuits such as the signal processing section do not have to be placed in a remote location, and a highly explosion-proof device can be obtained. Also, by using it in conjunction with optical fiber, it becomes an ideal sensor for remote sensing. Also, since it handles optical signals, it has the advantage of not being affected by electromagnetic induction noise.

[Brief explanation of drawings]

FIG. 1 is a plan view of an optical waveguide type liquid refractive index sensor head showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the liquid refractive index sensor head shown in FIG. 1 taken along line I-I. , 5th
The figure shows the light intensity distribution in the width direction of each leading waveguide due to the difference in the refractive index of the limb measurement liquid when measuring using the same liquid refractive index sensor head. 1: Liquid refractive index sensor head, 2: Substrate. 6: Main optical waveguide, 4 and 5: Sub optical waveguide. 6/7: Gap. Patent applicant: Shimadzu Corporation

Claims (2)

[Claims] (1) A liquid refractive index sensor head that is immersed in a liquid to be measured and detects the refractive index of the liquid to be measured. a substrate, a first optical waveguide formed on the substrate and receiving a predetermined amount of input light, and a second optical waveguide disposed on the substrate with a predetermined gap from the first optical waveguide. At the time of measurement, the gap is filled with a liquid to be measured, and the refractive index of the liquid to be measured is determined by the output light from the first guide wavepath that changes depending on the difference in the refractive index of the liquid to be measured. Liquid refractive index sensor head to detect. (2) The first optical waveguide has a curved portion, and the second optical waveguide is also arranged with a predetermined gap from the curved portion of the first optical waveguide. 44S and 7L are also discharged to the liquid refractive index sensor described in item 1.