JPH01197633A - Liquid refractometer and liquid concentration meter using same - Google Patents

Abstract

PURPOSE:To measure the refractive index of liquid on an on-line basis at all times by connecting a probe, a light source, and a processing part by light guides or image guides consisting of optical fibers. CONSTITUTION:The probe 4 is dipped in the liquid to be measured and measurement light PA is guided 6 in the probe 4. Then the measurement light PA is entered into a prism 8 through an optical transmission part 9 and converted on its one surface (a). Measurement light PC below the critical angle as to the incident measurement light PA becomes refracted light and is projected toward the liquid 3 to be measured. Measurement light PB above the critical angle is reflected totally, projected from one surface C of the prism 8, and incident on the photodetection part 10. The measurement light PB is photodetected on the photodetection surface (f) of a start end part B through an objective 13. Consequently, a light-shade border image based upon the critical angle as a border is formed on the photodetection surface (f). The border image is transmitted 7 to the processing part 5. Then, the light-shade border position is detected based upon the border image and processed 5 according to optical logic to measure the refractive index from the obtained critical angle.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a fluid refractometer for liquids, gases, etc., and a fluid density meter using the same, and the present invention relates to a fluid refractometer for measuring liquids, gases, etc., and a fluid density meter using the same. This allows the refractive index and density of the measurement fluid to be measured online at all times.

[Prior Art and Its Problems J Conventionally, as a device for measuring the refractive index of a fluid such as a liquid, in addition to the Atsube method, which measures the angle of refraction of light by a prism, and the minimum deviation angle method, there are also methods that depend on the refractive index of the liquid to be measured. Liquid refractometers based on the law of refraction of light, such as the Duc de Charne method, which measures the focal length that changes due to the change in the focal length, are widely known. Further, since a certain relational expression holds between the refractive index and the density of the liquid to be measured as described later, a liquid density meter using the above-mentioned liquid refractometer is also known. However, in both the liquid refractometer and the liquid density meter using the liquid refractometer, the probe that detects the refractive index and density of the liquid to be measured is directly connected to other components such as a light source and a processing section, so that only the probe can be used. Difficult to separate. Therefore, it is necessary to sample the liquid to be measured each time the measurement is made, so it has been impossible to constantly measure the refractive index and density of the liquid to be measured online.

This invention was made to solve the above problems, and by connecting the probe, a light source, and a processing section with a light guide or an image guide made of optical fiber, only the probe can be directly immersed in the measurement fluid. The object of the present invention is to provide a fluid refractometer that can measure the refractive index and density of a fluid online at all times, and a fluid density meter using the fluid refractometer.

[Means for Solving the Problems] In the present invention, a light transmitting section that guides measurement light to the prism is included in a probe equipped with a prism whose one surface is in contact with the measurement fluid; An image in which a light guide that houses a light receiving section that receives measurement light from the prism and guides the measurement light to the light transmission section is connected to the light source and the light transmission section, and guides the measurement light from the light reception section. By connecting the guide to the light receiving section and the processing section, and determining the refractive index of the measuring fluid in the processing section based on the light receiving position information detected by the light receiving section, it is also possible to connect one surface to the measuring fluid. A light transmitting section that guides measurement light to the prism and a light receiving section that receives the measurement light from the prism are housed in a probe equipped with a prism that is brought into contact with the prism, and the measurement light is guided to the light transmitting section. A light guide is connected to the light source and the light transmitting section, an image guide for guiding the measurement light from the light receiving section is connected to the light receiving section and the processing section, and the light receiving position detected by the light receiving section is connected to the processing section. The above problem is solved by determining the density of the measured fluid based on the information.

[Function] In the fluid refractometer of the present invention and the fluid density meter using the same, the probe and each part are connected by a light guide or an image guide made of an optical fiber, so that only the probe can be immersed in the measurement fluid. can do.

Moreover, only the probe can be installed at a remote location.

Therefore, the refractive index and density of the fluid can be measured online at all times without sampling the fluid to be measured during measurement.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show an embodiment in which the present invention is used to measure the refractive index of a liquid. In FIG. 1, reference numeral 1 indicates a liquid refractometer. This liquid refractometer 1 includes a light source 2 that emits measurement light PA for refractive index measurement, and a measurement light PA that is immersed in a measurement liquid 3 at a contact surface with the measurement liquid 3.
It is roughly composed of a probe 4 that detects the critical angle of , and a processing section 5 that calculates the refractive index from the critical angle.
The probe 4 and the light source 2 are connected by a light guide 6, and the probe 4 and the processing section 5 are connected by an image guide 7, respectively. The light source 2 is composed of a lamp and an appropriate monochromatic interference filter. For example, a combination of a sodium lamp and an interference filter that selectively transmits only sodium D rays can be used. Suitable lamps and filters can be selected depending on the measurement wavelength range. Further, as shown in FIG. 2, the probe 4 includes a prism 8, a light transmitting section 9 that makes the measuring light PA enter the prism 8, and a light receiving section 10 that receives the measuring light PB emitted from the prism 8. It consists of The prism 8 has three optical planes a and b.
A triangular prism-shaped transparent body (e.g., quartz glass) made of S c is used, its − surface a is brought into contact with the measuring liquid 3, and −
The measuring light PA is made incident on the facing surface, and the measuring light P is totally reflected from the contact interface 7 with the measuring liquid from the C.
[3 is set to be ejected. In addition, the light transmitting section 9
is condenser lens 11 and mirror! It is composed of two optical members. A terminal end A of the light guide 6 is attached to the object space side of the condenser lens 11, and the condenser lens If is connected to the measurement light PA incident on the condenser lens 11.
For example, it is arranged so as to condense the light at the contact interface between the measuring liquid 3 and one surface C of the prism 8. The mirror I2 is provided between the condenser lens 11 and the prism 8, and its mounting position is adjusted so that the measurement light PA is incident on the prism 8 at a predetermined angle. Further, the starting end of the light guide 6 is attached to the light source 2. Here, as the light guide 6, a fiber bundle formed by bundling a plurality of fibers is used. Further, the light receiving section 0 is constituted by an optical system consisting of an objective lens I3, and this objective lens 13 is disposed on the optical path of the measurement light PB totally reflected by the prism 8 and emitted.

The starting end B of the image guide 7 is attached to the light receiving section IO so that the light receiving surface f of the image guide 7 overlaps the image forming surface of the objective lens I3.

On the other hand, the terminal end of the image guide 7 is attached to the processing section 5. Here, as the image guide 7, an image fiber capable of faithfully transmitting two-dimensional images is used.

The processing unit 5 is configured to obtain the refractive index based on the critical angle information of the measurement light FB transmitted by the image guide 7, for example, by performing program calculation processing or by measuring with a scale. . In the liquid refractometer 1 of this example, the probe 4 is provided with a protective container 14 that is liquid-tight to prevent the measuring liquid 3 from flowing in.
It is stored in. Suitable materials for use in the protective container 14 include those that do not dissolve into the liquid to be measured 3, such as metal materials such as stainless steel, inorganic materials such as glass, and hard plastic materials. moreover,
The parts of the light guide 6 and the image guide 7 that are immersed in the measurement liquid 3 are also covered with a flexible protective tube I5.

To measure the refractive index of the liquid to be measured 3 using the liquid refractometer 1 having the above configuration, first, as shown in FIG. is brought into contact with the measuring liquid 3. Next, the measurement light PA of a predetermined wavelength is
is guided to the probe 4 by the light guide 6. The measurement light PA guided in this way is made into a convergent light by the light transmitting section 9, and is made incident on the prism 8, where it is condensed. In this way, the measurement light PA enters the surface λ of the prism 8 from a wide angle, and the measurement light PC that is less than the critical angle becomes refracted light, and the measurement light PA enters the surface λ of the prism 8 at a wide angle.
is ejected towards. On the other hand, the measurement light PB above the critical angle
is totally reflected, exits from one surface C of the prism 8, and enters the received light *io. Measuring light FB incident on the light receiving section 10
is received by the objective lens 13 on the light receiving surface f of the starting end B of the image guide 7 attached to the light receiving section IO.

Therefore, as shown in FIG. 3, on this light-receiving surface f,
A bright and dark boundary image is formed around the critical angle. The above-mentioned critical angle varies depending on the refractive index n+qnt of the measuring liquid 3, and a boundary image is formed in which a bright and dark boundary line appears at a position corresponding to the critical angle, and this bright and dark boundary image is transmitted to the processing unit 5 by the image guide 7. be done. The processing unit 5 detects the boundary position between bright and dark based on the transmitted boundary image, and performs program calculation processing based on optical theory. In the program calculation process, for example, a critical angle is determined from a boundary position, and a refractive index is determined from the obtained critical angle.

This determines the refractive index of the measurement liquid 3 at the measurement wavelength. Alternatively, as another calculation method, the correlation between the boundary position and the refractive index may be determined in advance using a liquid with a known refractive index, and the refractive index may be calculated from this.

Next, an example in which the present invention is used to measure the density of a liquid will be described. The liquid density meter in this example has the same configuration as the liquid refractometer shown in Figures 1 and 2, except for the different processing section, so it has the same boundary line as shown in Figure 3. The process is similar to the liquid refractometer in the above example until the position information is guided from the image guide to the processing section. In this example, the processing section first calculates the refractive index of the liquid to be measured using an algorithm using the Lorentz-Lorentz equation shown below, and then uses the calculated refractive index to easily calculate its density. being done.

ρ = (n''-1)/r (n'+2) (where ρ represents the density of the liquid to be measured, n represents the refractive index of the liquid to be measured, and r represents the specific refraction of the liquid to be measured.) According to the liquid refractometer 1 and the liquid density meter using the same, the probe 4 can be separated from the light source 2 and the processing section 5 and only the probe 4 can be immersed in the measurement liquid 3. Therefore, the measurement The refractive index and density of a separated liquid can be measured online at all times without sampling the liquid 3 to be measured.

In particular, it is suitable for measuring the refractive index and density of cryogenic liquids such as liquefied gases, which cannot normally be sampled, and flowing liquids.

Further, by detecting the temporal position change (ΔX) of the boundary line, it is also possible to know the temporal change in the refractive index and density. Furthermore, by moving the probe within the liquid to be measured, the refractive index distribution and density distribution within the liquid to be measured can be determined.

This is useful for manufacturing and quality control of liquids (such as liquefied natural gas) stored in huge tanks.

In the above example, an image fiber is used as the image guide 7, but the present invention is not limited to this, and a fiber array capable of transmitting a -dimensional image may be used. In this case, a boundary point is transmitted instead of a boundary line by the probe light PB.

Furthermore, a CCD line sensor may be arranged on the light receiving surface f. In this case, an electric cable will be used instead of the image fiber.

Furthermore, as another configuration example, a diffusion plate may be provided within the light transmitting section 9 between the terminal end A of the light guide 6 and the condenser lens 11. In this way, the measurement light PA can be focused from a wider angle on one surface a of the prism, and a clearer boundary image can be obtained.

Furthermore, the processing unit 5 may detect the boundary image on a monitor television or the like. In this case, it is desirable to sharpen the boundary image by averaging or differentiating the image.

In addition to the above example, the boundary image may be a differential image obtained by differentiating the light sectional intensity in the direction perpendicular to the boundary line, as shown in FIG. 4. In this case, the change in the refractive index can be known from the amount of movement ΔX of the peak position of the differential image.

In addition, in the above-mentioned example of the liquid density meter of the present invention,
First, a case has been described in which the refractive index of the liquid to be measured is determined and the density is easily determined from the determined refractive index, but the configuration may be such that the density is directly determined from the positional information of the boundary line.

In the above embodiments, an example of measuring the refractive index and density of a liquid has been described, but the same method can be used when measuring the refractive index and density of a gas.

[Effects of the Invention] As explained above, the fluid refractometer of the present invention and the fluid density meter using the same connect a light source and a probe with a light guide made of an optical fiber, and connect the probe and a processing section. Since the probe is connected by an image guide made of optical fiber, only the probe can be immersed in the measurement fluid. Moreover, only the probe can be installed at a remote location. Therefore, the refractive index and density of the fluid can be measured online at all times without sampling the fluid to be measured during measurement.

In particular, it is suitable for measuring the refractive index and density of cryogenic liquids such as liquefied gases, which cannot normally be sampled, and flowing liquids.

Furthermore, since the refractive index distribution and density distribution in a liquid stored in a huge tank can be easily measured, it is useful, for example, in the production and quality control of liquefied natural gas and the like.

[Brief explanation of the drawing]

1 and 2 show an embodiment of a liquid refractometer according to the present invention. FIG. 1 is a schematic configuration diagram showing the overall configuration, and FIG. 2 is a main part of the detection section of this liquid refractometer. 3 and 4 are enlarged views of main parts showing the configuration, and are explanatory diagrams showing patterns in which the boundary positions of boundary images differ depending on the difference in the refractive index of the liquid to be measured. 1... Liquid refractometer 2... Light source 3... Measuring liquid 4... Probe 5... Processing section 6... - Light guide 7... Image guide 8... Prism PA, PB... Measuring light 9... Light transmitting section 10... Light receiving section.

Claims (2)

[Claims] (1) A light transmitting section that guides measurement light to the prism and a light receiving section that receives the measurement light from the prism are housed in a probe equipped with a prism whose one surface is in contact with the measurement fluid, A light guide that guides measurement light to the light transmitting section is connected to the light source and the light transmitting section, an image guide that guides the measurement light from the light receiving section is connected to the light receiving section and the processing section, and the above processing 1. A fluid refractometer, characterized in that the refractive index of the fluid to be measured is determined based on the light receiving position information detected by the light receiving section in the section. (2) A light transmitting section that guides measurement light to the prism and a light receiving section that receives the measurement light from the prism are housed in a probe equipped with a prism whose one surface is in contact with the measurement fluid, A light guide that guides measurement light to the light transmitting section is connected to the light source and the light transmitting section, an image guide that guides the measurement light from the light receiving section is connected to the light receiving section and the processing section, and the above processing A fluid density meter characterized in that the density of the fluid to be measured is determined based on the light receiving position information detected by the light receiving part in the part.