JPH11352055A - Optical liquid refractive index measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized optical liquid refractive index measuring apparatus, high in resolving power and which is not affected by the fluctuations of a light source. SOLUTION: This optical liquid refractive index measuring apparatus uses a transparent crystal optical member 12. For example, the transparent crystal optical member 12 comprises a lithium niobate single crystal and has a bottom surface 12c coming into contact with the surface of a liquid 1 to be measured with a refractive index n1 , the incident surface 12a forming a predetermined angle with respect to the bottom surface 12c and the emitting surface 12b provided on a side opposed to the incident surface 12a, so as to form a predetermined angle with respect to the bottom surface 12c. Furthermore, the crystal optical member 12 has a double refractive index forming a discontinuous interface, with respect to the refractive index at the boundary surface of the bottom surface 12c and the liquid 1 to be measured. When light is made incident on the incident surface 12a of the transparent crystal optical member 12 from a light source 14, it passes through the transparent crystal optical member 12 to be reflected by the boundary surface of the bottom surface 12c and the liquid 1 to be measured to be separated into a vertical polarized component light 1s and a horizontal polarized component light 1p , and these lights are emitted from the emitting surface 12b. Light detection parts 22, 24 detect these polarized lights, and these signals are processed by a signal processor 26 to calculate the refractive index n1 of the liquid 1 to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical liquid refractive index measuring device for measuring the refractive index of a liquid. More specifically, the present invention relates to an optical liquid refractive index measuring device that can improve measurement sensitivity (accuracy) with a simple configuration when measuring the refractive index of a liquid to be measured using polarized light.

[0002]

2. Description of the Related Art Process management in a liquid manufacturing process,
BACKGROUND ART In the fields of fuel control in vehicles such as automobiles according to fuel components and quality control in a petroleum refining process, the refractive index of a liquid is often measured as one method of quality control of the liquid. In measuring the refractive index of such a liquid,
It is desirable that the measurement be performed continuously and automatically in real time, instantaneously or in a short time without sampling the liquid to be measured for the refractive index as a sample.

[0003] A method of measuring the refractive index of a liquid by observing the interface between the liquid and the solid with a microscope and obtaining the total reflection condition as in an Abbe refractometer has been known. However, the method of measuring the refractive index of a liquid using such a microscope is not a real-time measurement, not an instantaneous measurement,
It is not an automatic measurement. Therefore, such a measurement method using a microscope is not suitable for continuous measurement of the refractive index of a liquid in a process.

Therefore, various methods have been proposed for continuously and automatically measuring the refractive index of a liquid in real time, instantaneously or in a short time without sampling the liquid.

As one of such methods, a light guide (optical waveguide: optical fiber) made of an optical glass having a refractive index higher than that of a liquid whose refractive index is to be measured is immersed in the liquid.
A method of measuring the refractive index of a liquid using a method in which light from a semiconductor laser or a photodiode is introduced into a light guide and the intensity of guided light propagating in the light guide changes due to a refractive index difference between an optical guide and a liquid. Various proposals have been made.

However, few such methods have been put to practical use. The reasons can be considered variously as described below. The first reason is that it is difficult to measure the refractive index of a liquid that is stable over a long period of time because characteristics of optical elements such as a semiconductor laser and a photodiode are unstable during long-term operation. The second reason is that the characteristics of semiconductor elements such as semiconductor lasers and photodiodes greatly change due to temperature changes. Therefore, a desired measurement accuracy cannot be ensured in a required temperature range only by the guided light intensity. As a method of solving this problem, a method of measuring the temperature around the semiconductor laser and adjusting the output (gain) of the semiconductor laser due to the temperature change can be considered. The dimensions increase. Without temperature compensation, the ambient temperature conditions under which stable measurement can be performed are restricted.
It is not suitable for use in measuring the refractive index of a liquid at a plant site in the measurement of a manufacturing process. The third reason is that there is a problem that it is difficult to obtain a sufficient resolution in a required refractive index measurement range because the difference in refractive index between the light guide and the liquid whose refractive index is to be measured is small.

Techniques for measuring the index of refraction using polarized light with the aim of overcoming the above-mentioned problems, and in particular to be insensitive to changes in the intensity of the output of the light source, include, for example,
It is disclosed in Japanese Patent Application Laid-Open No. 1-250039. The technique will be described with reference to FIG. 1 of JP-A-1-250039. The bottom of the prism 3 is placed on the boundary surface of the liquid 4 whose refractive index is to be measured, and light is incident on the incident surface of the prism 3 from the light source 1, and the incident light is reflected on the boundary surface between the bottom surface of the prism 3 and the liquid 4. The light emitted from the exit surface of the prism 3 is received by the analyzer 6. The light from the analyzer 6 becomes the horizontal polarization component light 8 and the vertical polarization component light 9 and is incident on the photodetectors 10 and 11, respectively. 8 are detected separately and independently. The arithmetic circuit calculates the refractive index of the liquid from the ratio of the intensities of these two polarization components. As described above, according to the technique disclosed in Japanese Patent Application Laid-Open No. 1-250039, the reflected light from the boundary surface between the prism 3 and the liquid 4 is converted into the vertically polarized light component 9 and the horizontally polarized light component 8 by the analyzer 6. Since the liquids are separated and the refractive index of the liquid to be measured is obtained from their intensity ratio, stable refractive index measurement not affected by the fluctuation of the measurement light source 1 can be performed.

[0008]

However, the technique disclosed in Japanese Patent Application Laid-Open No. 1-250039 is based on the fact that the prism 4 and the analyzer 6 are used to form the bottom surface of the prism 3 and the liquid 4 using two optical elements. Since the incident light is reflected at the boundary surface of and the reflected light is separated into the vertically polarized light component 9 and the horizontally polarized light component 8 in the analyzer 6, the structure of the liquid refractive index measuring device becomes complicated, The assembly process is also complicated. The liquid refractive index measurement device disclosed in Japanese Patent Application Laid-Open No. 1-250039 is expensive, has a large scale,
There is a problem that applications are limited.

The technique disclosed in Japanese Patent Application Laid-Open No. 1-250039 is affected by the characteristics of the analyzer 6 and may cause a refractive index measurement error.

Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 1-250039, the vertical polarization component light and the horizontal polarization component light may not be sufficiently separated, and a sufficiently high resolution may not be obtained. Measurement accuracy of the refractive index cannot be increased.

It is an object of the present invention to provide a low-cost, non-scalable device configuration, no complicated assembly, no liquid sampling, real-time, instantaneous or short-time, continuous and An object of the present invention is to provide an optical liquid refractive index measuring device capable of automatically measuring the refractive index of a liquid. It is another object of the present invention to provide an optical liquid refractive index measuring device which can exhibit high resolution in a room temperature (or normal temperature) environment and can increase measurement accuracy. It is a further object of the present invention to provide an optical liquid refractive index measuring device which is not affected by fluctuations of the light source.

Another object of the present invention is to provide an optical liquid refractive index measuring device having a simple structure.

It is a further object of the present invention to provide an optical liquid refractive index measuring device capable of selecting a plurality of measuring ranges.

[0014]

According to a first aspect of the present invention, a bottom surface (12c) in contact with a surface of a liquid to be measured having a predetermined refractive index, and an incident surface forming a predetermined angle with the bottom surface. (12a), and an emission surface (12b) that forms a predetermined angle with the bottom surface and is provided on a side facing the incident surface,
A crystal optical member (12) having a birefringence that forms a discontinuous interface with respect to a refractive index at a boundary surface between the bottom surface (12c) and the liquid to be measured, and light at a predetermined angle on the incident surface of the crystal optical member. Incident light providing means (14, 1)
6) the incident light from the incident light providing means is incident on the incident surface (12a) of the crystal optical member, and the crystal optical member (12)
And reflected at the boundary surface between the bottom surface (12c) of the crystal optical member and the liquid to be measured, separated into a first polarization component and a second polarization component, and emitted from the crystal optical member. The first polarized light component emitted from the surface (12b) and the second polarized light component
First and second polarization component detection means (22, 24) for detecting the polarization component of the liquid, and the signals detected by the first and second polarization component detection means for calculating the refractive index of the liquid to be measured. And a refractive index calculating means (26) for calculating the refractive index of the liquid.

Preferably, the light from the incident light beam providing means is incident on the incident surface (12a) of the crystal optical member in an orthogonal state, and the light exit surface (12b) of the crystal optical member is incident on the liquid to be measured. At least one of the two reflected polarized light components reflected from the discontinuous interface on the bottom surface of the crystal optical member which is in contact with the surface and forms a discontinuous interface of the refractive index is orthogonal to the reflected polarized component light.

Preferably, the first polarized light component is a vertically polarized light component (l _s ), and the second polarized light component is a horizontal polarized light component (l _p) orthogonal to the first polarized light component. ).

Preferably, a plane including the incident light beam and the reflected polarized light beam is parallel to an optical axis of the crystal optical member.

Preferably, the crystal optical member having a birefringence is a uniaxial single crystal substrate. Preferably, the crystal optical member is a lithium niobate single crystal.

Preferably, the light emitted from the light source contains a total polarization component.

The incident light providing means (14, 16) includes a light source (14) for emitting light containing all polarized light components, and a light from the light source which is incident on the incident surface (12a) of the crystal optical member at a predetermined angle. And a waveguide circuit (16) for incidence.

The first polarized light component detecting means (18, 2)
2) a first waveguide circuit (1) for guiding a first reflected polarization component emitted from the emission surface (12b) of the crystal optical member;
8) and a first light receiving means (22) for receiving light from the first waveguide circuit and emitting an electric signal corresponding to the received light intensity.
And the second polarization component detecting means (20, 24).
A second waveguide circuit (20) for guiding a second reflected polarization component emitted from the emission surface (12b) of said crystal optical member.
And a second light receiving means (24) for receiving light from the second waveguide circuit and emitting an electric signal according to the received light intensity.

Preferably, the first waveguide has a multi-mode optical fiber, and the second waveguide has a multi-mode optical fiber.

[0023] The refractive index calculating means may include an intensity ratio between a detection signal of the first light receiving means and a detection signal of the second light receiving means, or an intensity of the whole detection signal and a detection of the first light receiving means. From the ratio of the intensity of the signal or the ratio of the intensity of the entire detection signal and the intensity of the detection signal of the second light receiving means,
The refractive index of the liquid to be measured is calculated.

[0024] The refractive index calculating means may calculate the intensity of the entire detection signal as the sum of the detection signal of the first light receiving means and the detection signal of the second light receiving means, and the detection signal of the first light receiving means. The refractive index of the liquid to be measured is calculated from the ratio of the intensity or the ratio of the intensity of the entire detection signal to the intensity of the detection signal of the second light receiving unit.

According to a second aspect of the present invention, the entrance surface (3
2a), a discontinuous refractive index interface (32c), a total reflection surface (32
b) wherein the discontinuous refractive index interface (32c) is in contact with the liquid to be measured (1) and forms a discontinuous interface of the refractive index at the contact interface of the liquid to be measured (1); A crystal optical member (32) having a birefringence index, wherein the total reflection surface (32c) is provided at an angle such that light reflected at the interface is reflected toward the incident surface (32a); Incident light providing means (3) for causing light to enter the incident surface at a predetermined angle.
4, 36), from the incident light providing means, is incident on the incident surface (32a) of the crystal optical member, passes through the inside of the crystal optical member (32), and has the discontinuous refractive index interface of the crystal optical member. The crystal is reflected at the boundary between the liquid crystal (32c) and the liquid to be measured (1), is separated into a first polarized light component and a second polarized light component, and is further reflected at the total reflection surface (32b). The incident surface (32a) of the optical member
First and second polarization component detecting means (38:44, detecting the first polarization component and the second polarization component emitted from the
40:42) and a refractive index calculating means (46) for calculating a refractive index of the liquid to be measured by calculating signals detected by the first and second polarized light component detecting means. A refractive index measurement device is provided.

Preferably, the transparent crystal optical member (32)
The refractive index discontinuous interface (32c) which is in contact with the liquid to be measured (1) to form a discontinuous refractive index interface; and two reflected lights from the discontinuous interface are totally reflected into the transparent crystal optical member. The angle formed with the total reflection surface (32b) is a right angle.

Preferably, the optical axis of the light beam from the light source (34) is parallel to the optical axis of the transparent crystal optical member (32).

The angle between the optical axis of the light beam from the light source (34) and the incident surface (32a) of the transparent crystal optical member (32) on which the light beam from the light source is incident is a right angle.

Preferably, the light from the light source (34) is incident on the transparent crystal optical member (32).
And 2a), said transparent crystal the two reflected light emitted from the optical member (32) (l _p, and the exit surface of the l _S) match,
And the optical axis of the incident light to the incident surface (32a) (l _i),
The optical axes of the two types of reflected light (l _p , l _s ) are substantially parallel.

The incident light providing means (34, 36) and the first and second polarization component detecting means (38:44,
40:42) have first to third optical fibers, and these optical fibers are directed to the incident surface (32a) of the crystal optical member (32).

According to a third aspect of the present invention, the plane of incidence (3
2a) an exit surface (52d) adjacent to the incident surface and forming a predetermined angle with the incident surface, and a first surface facing the incident surface and the output surface and forming a predetermined angle with the incident surface, respectively.
And a second discontinuous refractive index interface (52b, 52c), wherein the first and second discontinuous refractive index interfaces contact the liquid to be measured (1) and come into contact with the liquid to be measured (1). A crystal optical member (52) having a birefringence and forming a discontinuous interface with a refractive index at the interface and reflecting light reflected at the discontinuous interface toward the exit surface (52d); A first step of causing light to enter the first and second discontinuous refractive index interfaces of
And second incident light providing means (54:64, 55: 6
5) the incident light from the first and second incident light providing means is incident on the incident surface (52a) of the crystal optical member, and passes through the inside of the crystal optical member (52); The first and second discontinuous refractive index interfaces (52b, 52b)
c) is reflected at a boundary surface between the liquid to be measured (1) and separated into a first polarized light component and a second polarized light component, and the first polarized light component and the second polarized light component exiting from the exit surface (52d). First and second polarization component detection means (56:58, 57:59) for detecting the two polarization components, and the signals detected by the first and second polarization component detection means are calculated. A refractive index calculating means (60) for calculating a refractive index of the measurement liquid; and the first and second incident light providing means (54:64, 5).
5:65), and an optical liquid refractive index measuring device comprising a measuring system selecting means (62) for transmitting a result in the refractive index calculating means (60) based on the operation.

Preferably, the optical axis of said crystal optical member (52) and said first and second incident light providing means (54:
64, 55:65) are parallel to the optical axis of the light emitted from the light source.

Preferably, light of the light emitted from the incident surface (52a) of the crystal optical member (52) and the first and second incident light providing means (54:64, 55:65). The axis is orthogonal.

Preferably, the first and second incident light providing means (54:64, 55:65) emit light containing all polarization components.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical liquid refractive index measuring apparatus according to the present invention will be described with reference to the accompanying drawings.

[0036]First embodiment FIG. 1 shows an optical liquid refraction according to a first embodiment of the present invention.
It is a lineblock diagram of a rate measuring device. FIG. 2 shows the optics illustrated in FIG.
Of liquid crystal refractometers, focusing on transparent crystal members
FIG. Liquid to be measured illustrated in FIGS. 1 and 2
Optical liquid refractive index measuring device 10 for measuring the refractive index of 1
Is the crystal optical member 12, the light source 14, and the light from the light source 14.
(Incident ray l _i) On the incident surface 12a of the transparent crystal member 12.
It has an optical fiber 16 for incident light to be incident. Also optical
The liquid refractometer 10 comprises a liquid 1 to be measured and crystal optics.
The light is reflected at the interface with the member 12 and emitted from the crystal optical member 12.
Vertically polarized light component l emitted from the surface 12b_sA guide to guide
The optical fiber 18 for the vertical polarization component and the optical fiber 18 for the vertical polarization component
Vertical polarization component light detector 2 for detecting light from
2 Further, the optical liquid refractive index measuring device 10
Horizontally polarized light emitted from the emission surface 12b of the crystal optical member 12.
Component light l_pFiber 20 for horizontal polarization component for guiding
And the horizontal polarization component from the horizontal polarization component optical fiber 20
Light_pHas a horizontal polarization component light detection unit 24 for detecting
You. Further, the optical liquid refractive index measuring device 10 has a vertical polarization component.
For the divided light detection unit 22 and the horizontal polarization component light detection unit 24
Processing for inputting the detection signal in the refraction index calculation
Signal processing device 26 as a refractive index calculating means for performing
You.

The conditions for the crystal optical member 12 will be described. (1) The first condition of the crystal optical member 12 is that it has transparency with respect to the wavelength of the incident light beam l _i from the light source 14. Therefore, the crystal optical member 12 should be referred to as a transparent crystal optical member 12. Hereinafter, the transparent crystal optical member 1
Call it 2. (2) The second condition of the transparent crystal optical member 12 is to have birefringence characteristics. The birefringence refers to a phenomenon in which two refracted lights appear when light enters a medium having optical anisotropy. In the present embodiment, the transparent crystal optical member 1
2 the bottom and is emitted from the two exit surface 12b of the transparent crystal optical element 12 as refracted light of the vertically polarized component light l _s and horizontal polarization components l _p light reflected at the boundary surface between the liquid to be measured 1. (3) The third condition of the transparent crystal optical element 12, the refractive index n ₁ of the refractive index n ₀ is the measured liquid 1 of the transparent crystal optical element 12
It is higher. The greater the difference (n ₀ −n ₁ ) in the refractive index, the more accurately the refractive index n ₁ can be measured. The reason will become clear from the refractive index calculation formula described later.

Transparent crystal member 1 satisfying such conditions
As a second example, a lithium niobate single crystal is desirable.
The lithium niobate single crystal is a single crystal having optical anisotropy of a uniaxial crystal, and satisfies the above three conditions. The refractive index n ₀ of the substrate lithium niobate single crystal is 2.252 (when the wavelength of the used light is 85 nm). in this way,
By using a high refractive index material such as a single crystal of lithium niobate having a large difference from the refractive index n ₁ (about 1.3 to 1.5) of the liquid 1 to be measured, it is possible to expand the refractive index measurement range. .

The transparent crystal member 12 in the present embodiment is not limited to the lithium niobate single crystal, and other optical members satisfying the above conditions can be used. For example, such other optical members include uniaxial crystals belonging to tetragonal system, trigonal system, and hexagonal system, such as ammonium phosphate (ADP), potassium phosphate (KDP), lithium tantalate, and zinc oxide. , Quartz. However, in the following embodiment, the transparent crystal member 12
The case where a lithium niobate single crystal is used as a preferred example will be described.

Next, the shape of the transparent crystal optical member 12 will be described with reference to FIG. The transparent crystal optical member 12 using the lithium niobate single crystal is processed as follows. (A) The incident surface 12a of the transparent crystal optical member 12 is processed so that the light incident on the incident surface 12a of the transparent crystal optical member 12 is orthogonal to the incident surface 12a. In the present embodiment, the incident surface 1 of the transparent crystal optical member 12 emitted from the light source 14 via the incident light optical fiber 16 is applied to the bottom surface 12c of the transparent crystal optical member 12 that comes into contact with the liquid 1 to be measured.
The angle between the incident surface 12a and the bottom surface 12c of the transparent crystal optical member 12 is defined so that the light incident on the light incident surface 2a is orthogonal to the incident surface 12a. (B) The exit surface 12b of the transparent crystal optical member 12 is the light of the incident light beam l _i from the light source 14 reflected at the discontinuous refractive index portion at the boundary between the liquid 1 to be measured and the bottom surface 12c of the transparent crystal optical member 12. The angle between the bottom surface 12c and the emission surface 12b is defined so as to be orthogonal to the axis and the emission surface 12b. (C) In addition to the above, light l _i a transparent crystal and the plane containing the reflected ray emitted from the exit surface 12b of the optical member 12, single crystal of lithium niobate is used in the transparent crystal optical element 12 from the light source 14 The crystal direction of the transparent crystal optical member 12 (lithium niobate single crystal) and each surface 12a, 12b, 12c of the transparent crystal optical member 12 are set so that the optical axis of
Is defined. (D) Preferably, the optical axis of the transparent crystal optical member 12 (lithium niobate single crystal) and the incident light beam l _i from the light source 14
And the optical axis of.

As described above, the transparent crystal optical member (niobate)
When the lithium single crystal (12) is processed, a transparent crystal optical member
The light reflected from the output surface 12b of the light source 12 is emitted from the light source 14.
Incident light l_iAnd the transparent axis with the liquid 1 to be measured
Surface perpendicular to the boundary surface with the bottom surface 12c of the crystal optical member 12
Vertically polarized light component l having a vibration plane in a direction orthogonal to the direction _s
And the vibration direction in the direction parallel to the plane
Horizontal polarized component light l_pEasy and reliable separation
Wear. Vertically polarized light component l_sAnd the horizontal polarization component light l _pIs
Travels (propagates) via different optical paths.

(F) The incident angle φ ₀ of the light beam from the light source 14 to the incident surface 12 a of the transparent crystal optical member 12, that is, the incident surface 12 a of the transparent crystal optical member 12 and the light source 14
It is preferable that the angle formed by the light beam from the light source is not more than the critical angle and is close to the critical angle in order to maximize the measurement sensitivity to the refractive index n ₁ of the liquid 1 to be measured.

(G) Incident surface 12 of transparent crystal optical member 12
The a, so that the incident angle with respect to the boundary surface of the incident light l _i from the transparent crystal optical element 12 are in contact with the bottom surface 12c of the liquid to be measured 1 and the transparent crystal optical element 12 is less than the critical angle light source 14 is positioned and fixed. In this case, the light source 1
It is not necessary to fix the optical fiber 4 directly to the transparent crystal optical member 12. As shown in the figure, the incident light optical fiber 16 is interposed and fixed between the light source 14 and the incident surface 12 a of the transparent crystal optical member 12. 14 transparent crystal optical element of the incident light l _i of the incident light l _i of the entrance surface 12a of the transparent crystal optical element 12 from the light source 14 so as to satisfy the above conditions 1
It is sufficient to guide the light to the second incident surface 12a.

Birefringence such as lithium niobate single crystal
The incident light beam l
_iFrom the vertical polarization component light l_sAnd the vertically polarized component light
l_sHorizontal polarization component light l orthogonal to_pAnd separate
In order for the light rays from the light source 14 to be schematically illustrated in FIG.
As described above, the vertically polarized component light l_sAnd the horizontal polarization component light l _p
It must have a light component in all directions including
You. Of course, the normal light emission
A diode, a semiconductor laser, or the like can be used.

By adopting such a configuration and conditions,
The reflected light from the contact surface (boundary surface) between the liquid 1 to be measured and the bottom surface 12c of the transparent crystal optical member 12 is transmitted from the bottom surface 12c due to the birefringence of the transparent crystal optical member 12 made of lithium niobate single crystal. is separated into the vertically polarized component light l _s and horizontal polarization component light l _p, respectively from the emission surface 12b is emitted via different optical paths.

[0046] The exit surface 12b of the transparent crystal optical element 12 along the optical path of the horizontally polarized component light l _p of the vertical polarization component light l _s, respectively, for vertically polarized light component as a waveguide in the vertical polarization components An optical fiber 18 and a horizontal polarization component optical fiber 20 as a horizontal polarization component optical waveguide are provided, and a vertical polarization component light detection unit 22 and a horizontal polarization component light detection unit 2 are provided.
Lead to 4. As the light detection unit 22 for the vertical polarization component and the light detection unit 24 for the horizontal polarization component, a normal light receiving element, for example, a photodiode can be used.

The optical fiber 16 for incident light is used as a waveguide for guiding a light beam from the light source 14 to the incident surface 12a of the transparent crystal optical member 12, and the vertical polarization component light and the horizontal polarization component light from the output surface 12b of the transparent crystal member 12 are used. It is preferable to use the optical fiber 18 for vertical polarization component and the optical fiber 20 for horizontal polarization component as the waveguide from the viewpoint of converging light rays and eliminating external disturbance light. In addition, if the bendable optical fiber 16 for incident light is used, the condition for setting the position of the light source 14 and the position of the incident surface 12a of the transparent crystal member 12, which will be described later, is relaxed, and the light source 14 can be installed at an arbitrary position. It becomes possible. Similarly, when the vertical polarization component optical fiber 18 and the horizontal polarization component optical fiber 20 are used, the emission surface 12b of the transparent crystal member 12 and the vertical polarization component light detection unit 22 are used.
And the condition of the positional relationship with the horizontal polarization component light detection unit 24 is relaxed. The incident light optical fiber 16 guides the ordinary light from the light source 14 and is not particularly limited. However, the vertical polarization component optical fiber 18 and the horizontal polarization component optical fiber 2 are not specified.
Since 0 guides polarized light, a multimode optical fiber is preferable.

Hereinafter, the operation of the optical liquid refractive index measuring apparatus illustrated in FIG. 1 will be described. 1. The bottom surface 12c of the transparent crystal optical member 12 made of lithium niobate single crystal is brought into contact with the liquid 1 to be measured.

2. In this state, the light from the light source 14 is made incident on the incident surface 12a of the transparent crystal optical member 12 via the incident light optical fiber 16 in a state orthogonal to the incident surface 12a.
The transparent crystal optical member 12 ranging from the incident surface 12a of the transparent crystal optical member 12 to the boundary surface between the bottom surface 12c and the liquid 1 to be measured.
When the incident optical axis of the light beam from the light source 14 coincides with the optical axis of the transparent crystal optical member (lithium niobate single crystal) 12 which is a uniaxial crystal, the light propagates in the isotropic medium. The light ray incident on the incident surface 12a propagates (progresses) toward the boundary surface between the bottom surface 12c and the liquid 1 to be measured according to the same principle as described above.

3. Next, at the interface between the liquid 1 to be measured and the bottom surface 12c of the transparent crystal optical member 12, the refractive index n of the transparent crystal optical member (lithium niobate single crystal) 12
_0, the refractive index difference between the refractive index n ₁ of the liquid to be measured 1 (n ₀ -
In accordance with n ₁ ), a part of the incident light becomes reflected light and is reflected toward the emission surface 12 b of the transparent crystal optical member 12. Among the reflected light components, those which include the optical axis of the incident light beam and have a vibration direction orthogonal to a plane V orthogonal to the boundary surface between the liquid 1 to be measured and the bottom surface 12c of the transparent crystal optical member 12 are defined as vertical polarization component light l. is referred to as _s, those with a vibration direction parallel to the plane V is referred to as a horizontal polarization component light l _p. The vertical polarization component light l _s ordinary, in relationship to the plane V extending from the bottom surface 12c of the transparent crystal optical element 12 in the vertical direction, is reflected at an angle equal to the angle of incidence angles. Horizontally polarized component light l _p is the birefringence possessed by the lithium niobate single crystal 12, as the extraordinary light is reflected at a different angle than the vertical polarization component light l _s.

The transparent crystalline optical member reflected light using a lithium niobate single crystal of the horizontally polarized component light l _p of this time 12
Of the optical axis, i.e. the angle φ formed by the incident light l _i from the light source 14, the light of the reflected light lr _p and lithium niobate single crystal of the reflected light lr _s and horizontal polarization component light l _p of the vertical polarization component light l _s the angle between the axis theta, ordinary refractive index n _o, the extraordinary refractive index When n _e, for example, Sueda positive, "optoelectronics, Shokodo, 1988, as listed in the 140th page Is represented by the following equation.

[0052]

[Number 1] _{tanφ = (n o / n e} ) 2 tanθ ... (1)

[0053] As described above, the two reflected light polarization component (vertical polarization component light l _s and horizontal polarization components l _p) is via different optical paths from each other, transparent crystal optical element (lithium niobate single crystal) 12 emission of The light exits from the surface 12b.

[0054] vertical polarization component optical detection unit 22 receives the vertical polarization component light l _s incident via the vertical polarization component optical fiber 18. Horizontal polarization component optical detection unit 24 receives the horizontally polarized component light l _p incident via the horizontal polarization component optical fiber 20. Thus, the vertically polarized component light l _s
And the horizontal polarization component light lp are _converted to a vertical polarization component light detector 2
2 and the horizontal polarization component light detection unit 24 are separately and independently detected. The detection value of the vertical polarization component light detection unit 22 and the detection value of the horizontal polarization component light detection unit 24 are:
Signal processing device 2 as refractive index calculating means illustrated in FIG.
6 is input.

The signal processing device 26 performs the following calculation to calculate the refractive index n ₁ of the liquid 1 to be measured. Refractive index n ₁
There are several methods for calculating. The first calculation method is a method of calculating the ratio between the detection value of the vertical polarization component light detection unit 22 and the detection value of the horizontal polarization component light detection unit 24. The second calculation method is a method of calculating the ratio of the vertical polarization component light to the total reflection light amount or the ratio of the horizontal polarization component light to the total reflection light amount. The details are described below.

[0056] Each of the Fresnel reflection coefficient r _p of Fresnel reflection coefficients r _s and the horizontal polarization component of the vertical polarization component is represented by the following formula.

[0057]

(Equation 2)

Where n ₀ is the refractive index of the transparent crystal member 12, n ₁ is the refractive index of the liquid 1 to be measured, φ ₀ is the angle of incidence of light rays on the transparent crystal member 12, and φ ₁ is This is a transmitted light refraction angle in the transparent crystal member 12.

[0059]

(Equation 3)

In Expressions 2 and 3, the incident angle φ ₁ can be expressed by Snell's law shown in Expression 4 below.

[0061]

## EQU4 ## n ₀ sin φ ₀ = n ₁ sin φ ₁ (4)

The refractive index n ₀ of the transparent crystal optical member 12 using a lithium niobate single crystal is known and constant. At the time of actual measurement, the transparent crystal optical member 12
The incident angle of phi ₀ to which also constant. The incident angle phi ₁ can be measured.

Since the light intensity is proportional to the square of the electric field intensity,
Respectively energy reflectivity R _s of the vertical polarization component light l _s, is the energy reflectance R _p of horizontally polarized component light l _p, it can be expressed by the following equation.

[0064]

Equation 5] ^{_{R s = r s 2 ... (}} 5) R p = r p 2 ... (6) However, r _s is the Fresnel reflection coefficient of the vertically polarized component light l _s shown in Formula 2, r _p is a Fresnel reflection coefficient of the horizontally polarized component light l _p shown in formula 3.

The relationship shown in Equations 5 and 6 indicates that the measured liquid
Refractive index n of body 1₁Will be a value corresponding to. Therefore, transparent
At the boundary between the bottom surface 12c of the crystal member 12 and the liquid 1 to be measured.
With respect to the reflected light, the emission surface 12 of the transparent crystal member 12
Vertically polarized light component l emitted from b _sOr horizontal polarized light component l
_pIs measured, the refractive index n of the liquid 1 to be measured ₁
Can be requested. The signal processing device 26 is
Folding ratio n₁Perform the calculation for

[0066] Furthermore, the intensity ratio of the vertical polarization component light l _s and horizontal polarization component light l _p, or the total amount of reflected light (vertical polarized component light l _s + horizontally polarized component light l _p) vertical polarization component to the light l _s Ratio = l _s / (l _s + l _p ), in other words,
The ratio of the energy reflectance R _s of the vertical polarization component light l _s to the sum of the energy reflectance R _p of the energy reflectance R _s and horizontal polarization component light l _p of the vertical polarization component light _{l s = R s / (R} s
+ R _p ) and normalizing (normalizing) the detection signal in the vertical polarization component light detection unit 22, the influence of the fluctuation or change of the light of the light source 14 can be obtained without using the reference optical system. Can be offset.

[0067] Of course, the light intensity ratio of the vertical polarization component light l _s described _{above, l s / (l s +} l p), or,
Instead = R _s / energy ratio (R _s + R _p), the light intensity ratio of the horizontal polarization component light _{l p, l p / (l} s + l
_p ) or energy ratio = R _p / (R _s + R _p ).

[0068] For vertical polarization component light l _s, or in any case in the horizontal polarization component light l _p, as a signal processing unit 26, by using the means having an arithmetic processing function, such as a microcomputer, the ratio calculation and refractive The calculation of the rate n ₁ can be performed easily and with high accuracy.

As described above, the optical liquid refractive index measuring apparatus according to the embodiment of the present invention includes the transparent crystal optical member 12.
The bottom surface 12c of the liquid crystal may be kept in contact with the liquid 1 to be measured, so that measurement can be performed in real time without sampling the liquid. In addition, by using the signal processing device 26, the refractive index of the liquid can be measured continuously and automatically instantaneously or in a short time.

The optical liquid refractive index measuring apparatus according to the first embodiment of the present invention can exhibit high resolution and improve measurement accuracy in a room temperature (or normal temperature) environment.

First Example Hereinafter, an example based on the first embodiment of the optical liquid refractive index measuring device of the present invention will be described. As an example, as the liquid 1 to be measured, the refractive index n ₁ is 1.360 to 1.48.
When was varied in the range of 0, under the following conditions using an optical liquid refractive index measurement apparatus according to an embodiment of the present invention described above, it was measured refractive index n ₁ of the liquid to be measured 1 .

Measurement conditions a. As the light source 14, a light-emitting diode (LED) having a wavelength of 857 nm was used. b. The transparent crystal optical member 12 has a refractive index n ₀ = 2.25.
2 lithium niobate single crystal was used. c. The incident surface 12a and the exit surface 12b of the lithium niobate single crystal 12 are set such that the optical axis of the light beam incident on the incident surface 12a of the lithium niobate single crystal 12 from the light source 14 is the z-axis and the incident angle is 37.45 ° near the critical angle. The angle conditions of the bottom surface (contact surface with the liquid 1 to be measured) 12c and the crystal axis of the lithium niobate single crystal were determined. d. In order to guide a light beam to be incident on the incident surface 12a from the light source 14, an optical fiber 16 for an incident light was used as a waveguide to guide the light beam to the vicinity of the incident surface 12a of the transparent crystal member 12. A multi-mode optical fiber was used as the optical fiber 16 for incident light. e. Under this configuration and conditions, the transparent crystal optical member 1
The optical path length from the end face of the incident light optical fiber 16 of the second incident face 12a to the reflected light emitting face of the lithium niobate single crystal 12 was about 20 mm. f. Each of the optical path of the emission surface side vertical polarization component light l _s and the horizontal polarization component light l _p, respectively, the vertical polarization component optical fiber 18 and the horizontal polarization component optical fiber 20 is fixed in the multi-mode optical fiber The measurement light from the emission surface was guided to the vertical polarization component light detection unit 22 and the horizontal polarization component light detection unit 24, respectively.

[0073] Measurements on the basis of a measurement result above conditions, the vertical polarization component light l _s and horizontal of the reflected light from the wetted surface and the bottom surface 12c of the liquid to be measured 1 and the lithium niobate single crystal 12 exit surface 12 of the polarized component light l _p and the lithium niobate single crystal 12
It was confirmed that the light was emitted from different optical paths separated by a distance of about 0.7 mm in the horizontal distance at b. Thus, according to the present embodiment, when the lithium niobate single crystal 12 is used,
It was confirmed that the separation of the vertical polarization component light l _s and horizontal polarization components l _p is sufficiently performed. This means high resolution.

The results obtained by the signal processing device 26 are shown in FIGS.
This is illustrated in FIG. Figure 3 is a graph showing the relationship between the change of the refractive index n ₁ of the incident angle φ ₀ = 37.45 ° liquid to be measured 1 time of the energy reflectance R _s of the vertical polarization component light l _s. Figure 4 is a variation of the refractive index n ₁ of the liquid to be measured 1, the ratio of the energy reflectance R _p of the energy reflectance R _s and horizontal polarization component light l _p of the vertical polarization component light l _s: R _s / R _p 6 is a graph showing a relationship with the graph. FIG. 5 shows the refractive index n _{1 of the} liquid 1 to be measured.
And a change in a graph showing the relationship between the _{R s / (R s + R} p).

As is clear from these graphs, the liquid 1 to be measured is variously changed to obtain various refractive indices n ₁ (1.38).
~ 1.47), a good agreement with the theoretical values obtained from Equations 1 and 2 was obtained. As a result of the measurement, the deviation of the refractive index from the theoretical value was 0.005 or less, the accuracy was 0.4%, and the refractive index n ₁ of the liquid 1 to be measured (sample liquid) could be measured with good reproducibility.

Experiment of fluctuation of light ray Next, an experiment of fluctuation of the incident light l _i from the light source 14 was performed. FIG. 6 changes the voltage applied to the light source 14,
Alternatively, the light beam emitted from the light source 14 is attenuated, and the light beam l _i incident on the incident surface 12a of the lithium niobate single crystal 12 is obtained.
6 is a graph showing a change in R _s / (R _s + R _p ) with respect to various refractive indices n ₁ of various liquids to be measured when the intensity of the sample is changed. The embodiment illustrated in FIG. 6 reduces the light emitting diode (LED) output used for light source 14 from 100% to 20%.
It is an R _s / (R _s + R _p ) measurement result when changed (attenuated) up to. As apparent from the graph of FIG. 6, the output characteristics with respect to the refractive index n ₁ was confirmed that hardly receives the influence of light source intensity fluctuations.

FIG. 7 shows R _s / (R _s + R) when the intensity of the light beam from the light source 14 is changed as illustrated in FIG.
It is a graph which shows the change of _p ). However, the liquid to be measured 1
Is a result of measurement on the liquid to be measured ₁ having a refractive index n _{1 of} 1.466. The error is 0.47% in the case of a refractive index conversion (in the case of a refractive index of 1.466). Even if the intensity of the light source 14 fluctuates greatly to about 20%, the measurement accuracy at the output of 100% can be almost maintained. Was confirmed.

As described above, it has been proved that the optical liquid refractive index measuring device of the present invention can measure the refractive index stably without depending on the intensity fluctuation of the light source 14. Therefore, even if the optical liquid refractive index measuring apparatus of the present invention is installed in a severe measurement site such as a site of a manufacturing plant where the temperature greatly changes and the power supply to the light source 14 and the like fluctuates, the liquid to be measured 1 exactly the refractive index n ₁ of the can be used stably for a long time. Further, the optical liquid refractive index measuring device of the present invention does not require the analyzer 3 in addition to the prism 3, unlike the optical liquid refractive index measuring device exemplified in Japanese Patent Application Laid-Open No. 1-250039. Can be miniaturized and can be manufactured at a low price, which is advantageous when installed at a measurement site of a manufacturing plant.

Further, in the first embodiment of the present invention, light is guided using the optical fiber 16 for incident light, the optical fiber 18 for vertical polarization component, and the optical fiber 20 for horizontal polarization component. In addition to being hardly affected by disturbance light, the light source 14 and the incident surface 12a of the transparent crystal optical member 12
(Angle relationship), and the positional relationship between the outgoing surface 12b of the transparent crystal optical member 12, the vertical polarization component light detection unit 22, and the horizontal polarization component light detection unit 24 can be arbitrarily determined. This has the advantage that the dimensions of the device can be made smaller.

The case where a single crystal of lithium niobate is used as the transparent crystal optical member 12 and a light emitting diode is used as the light source 14 has been described above. It is not limited to the application of. For example, as the transparent crystal optical member 12, an optical element other than the lithium niobate single crystal satisfying the above conditions can be used. Further light source 1
As 4, a semiconductor laser can be used instead of a light emitting diode.

In the first embodiment described above, two polarized light components reflected from the discontinuous refractive index portion of the transparent crystal optical member 12 are divided into a vertical polarized light component l _p and a vertical polarized light component l.
it has dealt with the case where an orthogonal relationship between _p is the horizontal polarization component light l _s, without using the lithium niobate single crystal as the transparent crystal optical element 12, and in a state that fixes the above optical conditions, necessarily, 2 The two reflected polarization components need not be completely orthogonal. Of course, it is easy to their separation in the case of completely orthogonal to the two polarization components are as a vertical polarization component light l _p and the horizontal polarization component light l _s, detection of the two polarization components the spacing be separated sufficiently Becomes accurate, and the measurement accuracy of the refractive index n ₁ of the liquid 1 to be measured increases.

Second Embodiment An optical liquid refractive index measuring apparatus according to a second embodiment of the present invention will be described with reference to FIGS. Note that, with respect to matters other than the matters described below, the technology common to the first embodiment is the same as that of the above-described first embodiment.

The optical liquid refractive index measuring apparatus 10 according to the first embodiment described with reference to FIGS. 1 and 2 uses a birefringent transparent crystal optical member 12 as a light guide and uses the birefringence. Reflected light by the light guide (the transparent crystal optical member 1)
It utilizes the fact that 2) within which is separated into the vertical polarization component l _s and horizontal polarization component l _p emitted. In the second embodiment, the shape of the light guide is further improved to reduce the size and manufacture of the refractive index detector including the light guide.

The optical liquid refractive index measuring device 30 illustrated in FIG. 8 is in contact with the liquid to be measured 1 having a refractive index of n ₁ and forms a discontinuous refractive index interface with the liquid to be measured 1 at this interface. Crystal optical member having a refractive index of n ₀ (crystal optical member)
32, a light source 34, and an optical fiber for incident light (light source side fiber) for guiding the light from the light source 34 to the transparent crystal optical member 32
36, the vertical polarization component optical detection unit 42, the vertical polarization component (l _s) a light receiving fiber 40 for guiding the emitted from the transparent crystal optical element 32 vertical polarization component l _s vertically polarized component light detection unit 42, a horizontal polarization component optical detection unit 44, the horizontal polarization component (l _p) the light-receiving fiber 38 for guiding the horizontal polarization component l _p emitted from the transparent crystal optical member 32 in a horizontal polarization component optical detection unit 44, the vertical polarization component A signal processing device (refractive index calculating means) 46 for calculating the refractive index n ₁ of the liquid 1 to be measured based on the signals detected by the light detecting section for use 42 and the light detecting section for horizontal polarization component 44.

As compared with the first embodiment, the cross-sectional shape of the transparent crystal optical member 32 is different from that of the transparent crystal optical member 12. Light source 34 and light source 14 that emit all polarized light
For example, the incident light optical fiber 36 of the multi-mode optical fiber is the same as the incident light optical fiber 16, for example, the horizontal polarization component receiving fiber 38 of the multi-mode optical fiber is the same as the horizontal polarization component optical fiber 20. The vertical polarization component receiving fiber 40 may be the same as the vertical polarization component optical fiber 18.
However, based on the difference between the transparent crystal optical member 32 and the transparent crystal optical member 12, the angle of incidence of the measurement incident light beam l _{i on} the transparent crystal optical member 32 is different, and the vertical polarization component l _S from the transparent crystal optical member 32 is different. And the horizontal polarization component l _p
Are also different. These differences will be described later. For example, the vertical polarization component photodetector 42 using a photodiode can be the same as the vertical polarization component optical fiber 18, and the horizontal polarization component photodetector 44 can be the same as the horizontal polarization component photodetector 24. The same signal processing device 46 as the signal processing device 26 can be used.

The transparent crystal optical member 32 will be described. The transparent crystal optical member 32 is, like the transparent crystal optical member 12,
As in the first embodiment, a single crystal of lithium niobate was used as the transparent crystal member having birefringence and having a refractive index n ₀ higher than the refractive index n _{1 of the} liquid 1 to be measured. . That is, n ₁ <n ₀ .

As the transparent crystal optical member 32, it is desirable to use a single crystal substrate of a uniaxial crystal such as a lithium niobate single crystal.
The same effects as those of the present invention can be obtained by using any material other than the lithium niobate single crystal as long as it is a high refractive index material that is transparent to the wavelength _i and has birefringence. Such materials include tetragonal, trigonal,
A uniaxial crystal belonging to a hexagonal system, for example, ammonium phosphate (ADP), potassium phosphate (KDP), lithium tantalate, zinc oxide, and quartz.

The transparent crystal optical member 32 has an entrance surface (exit surface) 32a, a total reflection surface (total reflection mirror surface) 32b, and a liquid contact surface (refractive index discontinuous interface) 32c. To form the total reflection surface (total reflection mirror surface) 32b, a reflection film 33 is applied to the total reflection surface (total reflection mirror surface) 32b. As the reflection film 33, a metal film such as aluminum or a dielectric film is used. In addition, as the reflection film 33,
A total reflection mirror composed of an interface between air and the transparent crystal optical member 32 may be used without using a metal film such as aluminum or a dielectric film.

Transparent crystal optical part manufactured from the above-mentioned material
The material 32 is formed into a right-angled triangle whose cross section is shown in FIGS.
Process. Liquid contact surface (discontinuous refractive index interface) 32c and incident surface
(Outgoing surface) Angle φ with 32a _aTo the liquid contact surface 32c.
Incident angle φ_inEqual to, incident surface and transparent crystal optics
Processing so that the angle between the optical axis of the member 32 and the optical axis becomes a right angle
I do. The light emitted from the light source 34 toward the transparent crystal optical member 32
The emitted measuring light beam l_iIncident angle φ_inIs the liquid to be measured
To increase the measurement sensitivity for the refractive index of the body 1 as much as possible
For this reason, it is preferable that the angle be equal to or less than the critical angle,
Good.

The light from the light source 34 is incident on the incident surface 32a of the transparent crystal optical member 32 by the incident light optical fiber (light source side fiber) 36 as the measuring incident light beam l _i , and propagates through the transparent crystal optical member 32. The liquid-contacting surface (discontinuous refractive index interface) 32c is reached.
Reflected by At this time, due to the birefringence of the transparent crystal optical member 32, it is separated into a vertical polarization component l _S and a horizontal polarization component l _p . These vertical polarization component l _S and horizontal polarization component l
_p travels to the total reflection surface (total reflection mirror surface) 32b, is reflected by the total reflection surface (total reflection mirror surface) 32b, and exits from the incident surface (output surface) 32a.

The signal processing device (refractive index calculating means) 46
Similarly to the signal processing device (refractive index calculating unit) 26, the vertical polarization component light detection unit 42 and the horizontal polarization component light detection unit 44
Is calculated, and the refractive index n ₁ of the liquid 1 to be measured is calculated.

By processing the transparent crystal optical member 32 into the above-described shape, the vertical polarization component l _S and the vertical polarization component, which are light rays reflected from the liquid contact surface (discontinuous refractive index interface) 32 c of the transparent crystal optical member 32, are obtained. The incident surface (exit surface) 32 of the transparent crystal optical member 32 is set so that l _S is substantially parallel to the incident light beam l _i for measurement.
Emitted from a. As a result, the incident light optical fiber 36,
The horizontal polarization component receiving fiber 38 and the vertical polarization component receiving fiber 40 can be arranged in parallel at appropriate intervals, adjusted in optical axis, and then fixed. At this time, the optical axis of the measuring incident light l _i is perpendicular to the entrance surface (exit surface) 32a of the transparent crystal optical element 32, i.e. the transparent crystal is matched with the optical axis of the optical member 32, incident light l _i for further measurements
The incident surface (outgoing surface) 32a including the reflected light (horizontal polarized light component l _p and vertical polarized light component l _s ) is adjusted to be parallel to the optical axis.

As described above, the reflected light from the refractive index discontinuous interface 32c and the total reflection mirror surface 32b, that is, the vertical polarization component l _S and the horizontal polarization component l _p are converted to the incident surface 32a on which the measuring incident light beam l _i is incident. The light exits from the same plane perpendicular to the entrance plane (exit plane) 32a. Measurement incident light l _i
Is incident on the incident surface 32a at 90 degrees. Therefore, the incident light optical fiber 36 and the horizontally polarized light receiving fiber 3
8. The vertically polarized light receiving fiber 40 can be arranged perpendicular to the incident surface (emission surface) 32a. Optical fiber 36,
38 and 40 may be bundled and arranged at right angles to the entrance surface (exit surface) 32a. As a result, compared to the optical liquid refractive index measuring device of the first embodiment, the optical fibers 36, 3
8, 40 connection space can be reduced.

In particular, since the angle formed between the discontinuous refractive index interface 32c of the transparent crystal optical member 32 and the total reflection mirror surface 32b is a right angle, the ordinary light component of the reflected light from the discontinuous refractive index interface 32c, ie, , can be the emission optical axis of the vertical polarization component l _S parallel to the optical axis of the measuring incident light l _i, at the output side of the entrance surface (exit surface) 32a, the horizontal polarization component (l _p) the light-receiving fiber 38 and the vertical polarization component (l
_S ) Positioning of the light receiving fiber 40 is facilitated.

In the second embodiment, it is necessary to make the optical axis of the incident light beam for measurement l _i coincide with the optical axis of the transparent crystal optical member 32, but in the first embodiment, it is illustrated in FIGS. Since the cross-sectional shape of the transparent crystal optical member 12 is an isosceles triangle, when the transparent crystal optical member 12 is manufactured, the optical fiber 16 for the incident light, the optical fiber 18 for the vertical polarization component, and the optical fiber 20 for the horizontal polarization component In consideration of the above connection, a marking for specifying the incident surface 12a of the transparent crystal optical member 12 is required. On the other hand, in the second embodiment, the cross-sectional shape of the transparent crystal optical member 32 is asymmetric except that the incident angle of the incident light beam for measurement l _i with respect to the refractive index discontinuous interface 32c is 45 °. Therefore, the incident light optical fiber 36, the horizontally polarized light receiving fiber 38, and the vertically polarized light receiving fiber 4
0, the incident surface (outgoing surface) 32a, the liquid contact surface 32c, and the total reflection mirror surface 32 of the transparent crystal optical member 32
b can be determined from the cross-sectional shape of the transparent crystal optical member 32, and there is no need for marking as in the first embodiment. As a result, the manufacture of the optical liquid refractive index measuring device 30 is facilitated, the productivity is improved, and the optical liquid refractive index measuring device 30 can be manufactured at a lower price.

[0096] As described above, the second embodiment is compared with the first embodiment, the incident Hikari Mitsumochi fiber (light source side fiber) 36, the horizontal polarization component (l _p) the light-receiving fiber 38 and the vertical polarization component (L _s ) There are advantages such as a reduced connection space for the light receiving fiber 40, ease of alignment, and improvement in mass productivity.

The operation of the optical liquid refractive index measuring device 30 according to the second embodiment will be described. (1) A liquid contact surface (discontinuous refractive index interface) 32c of a transparent crystal optical member 32 having a refractive index n ₀ is brought into contact with the liquid 1 to be measured having a refractive index n ₁ , and a light beam is incident on the liquid contact surface 32c. . Since the incident optical axis coincides with the optical axis of the transparent crystal optical member 32, the incident light beam for measurement l _i propagates toward the liquid contact surface 32c in the same manner as it propagates in the isotropic medium. (2) On the liquid contact surface 32c of the transparent crystal optical member 32,
Some of measuring incident light l _i according to the refractive index difference between the transparent crystal optical element 32 having a refractive index n ₀ and the measured liquid 1 of refractive index n ₁ is reflected in the transparent crystal optical member 32. At this time, among the reflected light components, those having a vibration direction perpendicular to the plane perpendicular to the boundary surface, including the optical axis of the incident light beam for measurement l _i , are defined as a vertical polarization component l _s , a component of light having a parallel vibration direction. Is the horizontal polarization component l _p , the vertical polarization component l _S is reflected as ordinary light at an angle equal to the incident angle. In contrast, the birefringence horizontal polarization component l _p with transparent crystal optical element 32,
The extraordinary light is reflected at an angle different from the vertical polarization component l _S.

As described above, two reflected light polarization components, that is, a horizontal polarization component l _p and a vertical polarization component l _s ,
The light is reflected at different angles from the liquid contact surface 32c of the transparent crystal optical member 32, and is reflected toward the total reflection mirror surface 32b again into the transparent crystal optical member 32.
Since the entrance surface (exit surface) 32a is orthogonal to the total reflection mirror surface 32b, the horizontal polarization component I _p and the vertical polarization component l _S are reflected in a direction parallel to the optical axis. For this reason, the birefringence effect generated on the liquid contact surface 32c of the transparent crystal optical member 32 does not occur, and both polarized lights are incident light (emission surface) 3 as ordinary light.
The light exits from the incident surface (outgoing surface) 32a in a direction perpendicular to the incident surface (outgoing surface) 32a, that is, in parallel with the measuring incident light beam l _i . To be precise, it is the vertical polarization component l _S that is emitted in parallel with the incident light ray l _i for measurement. The horizontal polarized light component l _p is reflected at an angle slightly different from the vertical polarized light component l _s , so that when it exits from the entrance surface (exit surface) 32a, it is affected by the refractive index difference from the air layer, and _The light is refracted slightly to the _i side and emitted. However, the angle difference is as small as about 3 to 5 degrees, and can be almost neglected in consideration of the aperture of the multi-mode optical fiber used as the horizontal polarization component receiving fiber 38. The horizontal polarization component receiving fiber 38 and the vertical polarization component receiving fiber 40 can be arranged in parallel.

The method for calculating the refractive index n ₁ of the liquid 1 to be measured by using the signal processing device 46 from the results detected by the horizontal polarization component light detector 42 and the vertical polarization component light detector 44 is described in the first embodiment. This is the same as the processing in the signal processing device 26 in the embodiment. That is, the signal processing device 46 controls the intensity ratio between the detection signal of the horizontal polarization component light detection unit 42 and the detection signal of the vertical polarization component light detection unit 44, or
Preferably, the refractive index n ₁ of the liquid 1 to be measured is obtained from the ratio of the vertical polarization component l _{S to} the total amount of reflected light.

The second embodiment will be compared with the first embodiment illustrated in FIGS. Optical fiber for incident light 1
6: Optical fiber 36 for incident light, optical fiber 18 for vertical polarization component 18: Fiber 40 for receiving vertical polarization component, optical fiber 20 for horizontal polarization component: Fiber 38 for receiving horizontal polarization component
1 and FIG. 2, the different surfaces 12a, 1a of the isosceles triangle of the transparent crystal optical member 12 are shown.
While the optical axis of the connecting fiber must be adjusted for the light beam emitted from 2b, the transparent crystal optical member 32 in the second embodiment described with reference to FIGS.
Since the optical axis is adjusted with respect to the parallel light beam emitted from the same surface (incident surface (outgoing surface) 32a), the alignment is very easy.

Next, the fiber connection space will be considered. In the first embodiment, the angle between the optical axes of the incident light and the outgoing light is twice as large as the incident angle with respect to the liquid contact surface, and the optical fiber 16 for the incident light, the optical fiber 18 for the vertical polarization component, the horizontal polarization The component optical fiber 20 is also connected at a similar angle. Bundling these optical fibers is easier and more practical, but since the optical fibers cannot be bent with a very small curvature, these optical fibers are fixed in the directions illustrated in FIGS. In order to bundle the optical fibers in the state, the transparent crystal optical member 12 is required.
Requires a lot of space around it.

Furthermore, it is necessary to make the optical axis of the incident light beam for measurement l _i coincide with the optical axis of the transparent crystal optical members 12 and 32. Since the cross-sectional shape of the transparent crystal optical member 12 is an isosceles triangle, At this time, the incident surface (emission surface) 32a
Marking was required to identify this. On the other hand, in the second embodiment, as shown in FIG. 8, since the cross-sectional shape of the transparent crystal optical member 32 is an asymmetric right-angled triangle, when the optical fiber is connected, the incident surface (emission surface) 32a, The liquid contact surface 32c and the total reflection mirror surface 32b can be specified from the shape of the transparent crystal optical member 32, and the need for marking is eliminated. Here, when the incident angle of the incident light beam for measurement l _i is 45 degrees, the shape of the transparent crystal optical member 32 is a right-angled isosceles triangle. It is not necessary to mark any of the surfaces because any surface can be used as the liquid contact surface.

In addition, since the transparent crystal optical member 32 is a right triangle, it can be cut out from a rectangular substrate.
Processing is easy, and material cutting from the base material of the lithium niobate single crystal becomes efficient. As a result, the production of the transparent crystal optical member 32 is facilitated, productivity is improved, and mass production is possible.

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. The third embodiment is an invention in which the shape of a light guide (transparent crystal optical member) is improved to expand the refractive index measurement range. That is, in the third embodiment, the transparent crystal member is processed at the discontinuous refractive index interface of the transparent crystal member in contact with the measurement sample liquid so that the incident angles are different for the two light beams, and the refractive index of the liquid to be measured is changed. Dramatically expand the measurement range.

In the third embodiment described below, portions common to the first and second embodiments are as follows.
Since the description is omitted, it is assumed that it is the same as the first embodiment and the second embodiment.

The optical liquid refractive index measuring device 50 illustrated in FIG. 10 includes a transparent crystal member 52, first and second parallel light generating light sources 54 and 55 for emitting all polarized light, and a multimode optical fiber. Optical fibers 56, 57, and first and second photodetectors 58, 5 such as photodiodes.
9, a signal processing device (refractive index calculating means) 60, and a measurement system selecting device 62.

The transparent crystal member 52 is a crystal optical member having a birefringence with a refractive index n ₀ , and includes an incident surface 52a, first and second liquid contact surfaces (discontinuous refractive index interfaces) 52b, 52c.
And an emission surface 52d. The first and second liquid contact surfaces 52b and 52c come into contact with the liquid to be measured ₁ having the refractive index n ₁ , and the first and second liquid contact surfaces 52b and 52c form a discontinuity in the refractive index.

The transparent crystal member 52 has birefringence,
In addition, a lithium niobate single crystal was used as a material having a higher refractive index than the liquid 1 to be measured having a refractive index n ₁ . As the transparent crystal member 52, it is desirable to use a single-crystal substrate of a uniaxial crystal such as lithium niobate single crystal, but if it is a high refractive index material that is transparent to the wavelength of the measurement light source and has birefringence. However, the material is not limited to lithium niobate single crystal, and other materials can be used. Other materials include, for example, uniaxial crystals belonging to tetragonal, trigonal, and hexagonal systems, such as ammonium phosphate (ADP), potassium phosphate (KDP), lithium tantalate, zinc oxide, and quartz. I do.

As shown in FIG. 10, a lithium niobate single crystal or a transparent crystal member made of another material is formed into a shape having an entrance surface 52a, first and second liquid contact surfaces 52b and 52c, and an exit surface 52d. Process into In other words, the optical axis of the light beam emitted from the first and second parallel light source 54, 55 is orthogonal to the incident surface 52a of the transparent crystal member 52, and the optical axis of the crystal used for the transparent crystal member 52 and the first and second optical axes. The crystal is processed so that the incident light beams for measurement from the second parallel light source 54 and 55 are parallel.

FIG. 11 shows an intensity ratio Rs / (Rs) of two polarized lights.
+ Rp) is a graph showing the relationship between the sample refractive index. R_s
Is the vertical polarization component light l_sThe energy reflectivity of R_pIs
Horizontally polarized light component l _pShows the energy reflectivity of Accordingly
Rs / (Rs + Rp) is
The ratio of the vertically polarized component light is shown. Measured liquid contact surface normal
When the angle between the beam direction and the light incident direction changes, the sample refractive index
And the relationship between the polarization intensity ratio changes continuously. So two
Contact the liquid to be measured with the light beam and the crystal of the light beam
Angle φ with surface_1,φ_TwoSo that the transparent crystal member 5
The first and second liquid contact surfaces 52b and 52c are formed.
And the angle of the light beam incident on the surface in contact with the liquid 1 to be measured is
In contrast, it is necessary to expand the refractive index measurement range of the liquid 1 to be measured.
Can be.

The first and second liquid contact surfaces 52b and 52c form an obtuse angle, and the first and second liquid contact surfaces (discontinuous refractive index interfaces) 52b and 52c are both an incident surface 52a and an exit surface. It faces 52d. In addition, the first and second liquid contact surfaces (discontinuous interfaces of refractive index) 52b and 52c direct the measurement incident light beams l _i from the first and second parallel light source 54 and 55 toward the emission surface 52d. The reflected light (vertical polarized light component l _s , horizontal polarized light component l _p ) is set at an angle at which it can enter the optical fibers 56 and 57. Therefore, the first and second liquid contact surfaces (discontinuous interfaces of refractive index) 52b, 5b
The obtuse angle made by 2c is an obtuse angle close to 180 degrees. Incident surface 52a and first and second liquid contact surfaces (discontinuous refractive index interface)
As for the angle formed by 52b and 52c, an embodiment will be described later.

The first and second parallel light source 54,
Numerals 55 are arranged in parallel so that light beams are emitted toward the first and second liquid contact surfaces 52b and 52c through the incident surface 52a of the transparent crystal member 52, respectively. First
Both the light source 54 and the second parallel light source 54 and 55 emit all polarized light similarly to the light source 14 of the first embodiment or the light source 34 of the second embodiment.

The light from the first parallel ray generating light source 54
When the light enters the liquid contact surface 52b, it is reflected by the first liquid contact surface 52b, which is the interface with the liquid 1 to be measured, separated into two types of polarized light, and emitted from the light exit surface 52d. These two types of polarized light are a vertical polarized light component l _S and a horizontal polarized light component l _p , and are received by the first and second light detection units 58 and 59. Similarly,
The light from the second parallel ray generating light source 55 is applied to the second liquid contact surface 5.
2c, the second interface, which is the interface with the liquid 1 to be measured,
Is reflected on the liquid contact surface 52c of the light source and separated into two types of polarized light,
The light exits from the exit surface 52d. These two types of polarized light are a vertical polarized light component l _S and a horizontal polarized light component l _p , and are received by the first and second light detection units 58 and 59.

The two optical fibers 56 and 57 form four reflected lights (two systems of two kinds of reflected light) from two discontinuous interfaces 52b and 52c which travel in two due to the birefringence of the transparent crystal member 52. Light) intersect two points in the space.

The first and second light detectors 58 and 59 are:
The vertical polarization component light detection unit 22 and the horizontal polarization component light detection unit 24 in the first embodiment, or the vertical polarization component light detection unit 42 and the horizontal polarization component light detection unit 44 in the second embodiment. It is equivalent.

As described above, the optical liquid refractive index measuring device 10 illustrated in FIG. 10 includes (1) the first parallel ray generating light source 54, the first liquid contact surface 52b, and the emission surface 52 indicated by solid lines.
d, optical fibers 56 and 57, first and second light detecting units 58 and 59, and a first
And a second parallel light source 55, a second liquid contact surface 52c, an emission surface 52d, optical fibers 56 and 57, and first and second light detectors 58 indicated by broken lines (2). , 5
9, a second measurement system defined by the path of the signal processing device 60. However, the optical fibers 56 and 57, the first and second light detection units 58 and 59, and the signal processing device 60
Belongs to both measurement systems.

The signal processing device 60 is a device corresponding to the signal processing device 26 of the first embodiment or the signal processing device 46 of the second embodiment. The operation principle of the signal processing device 60 itself is the same as that of the signal processing device 26 of the first embodiment. However, the signal processing device 60 calculates the refractive index n ₁ of the liquid 1 to be measured in both the first measurement system and the second measurement system.

The measuring system selecting device 62 is a signal processing device 6
With reference to the result calculated at 0, one of the first and second measurement systems is selected as one of the measurement systems suitable for the refractive index measurement range of the liquid 1 to be measured.

The operation of the optical liquid refractive index measuring device 50 will be described. First, the measurement system selection device 62 operates the first measurement system. Specifically, the measurement system selection device 62 operates the first parallel light ray generation light source 54 and
That the first measurement system operates. The light emitted from the first light source 54 is transmitted to the transparent crystal member 52.
And propagates in the transparent crystal member 52. Since the optical axis of the incident light beam for measurement and the optical axis of the transparent crystal member 52 coincide with each other, the light beam incident on the inside of the transparent crystal member 52 is the same as the light beam propagating in the isotropic medium. To the liquid contact surface 52b. First liquid contact surface 5
In 2b, a part of the incident light is reflected by the first liquid contact surface 52b according to the refractive index difference between the transparent crystal member 52 having the refractive index n ₀ and the liquid 1 to be measured having the refractive index n ₁ . At this time, among the reflected light components, the vertically polarized light component is reflected as ordinary light at an angle equal to the incident angle, and the horizontal polarized light component is reflected at the transparent crystal member 52.
Due to the birefringence of, it is reflected as extraordinary light at an angle different from the vertical polarization component. The vertical polarization component l _S and the horizontal polarization component l _p exit from the exit surface 52d, enter the optical fibers 56 and 57, propagate through the optical fibers 56 and 57, and travel through the first and second light detection units 58. , 59 and is converted into an electric signal. The signal processing device 60 includes a first
Then, the refractive index of the liquid 1 to be measured is calculated from the polarization component intensity ratio detected by the second light detection units 58 and 59. Note that the method of calculating the refractive index n ₁ of the liquid 1 to be measured in the signal processing device 60 follows the calculation method of the signal processing device 26 of the first embodiment.

The measuring system selecting device 62 is a signal processing device 6
If the result calculated with 0 exceeds the set measurement range, the system switches to the second measurement system. Specifically, the measurement system selection device 62 operates the first parallel light source 54 and notifies the signal processing device 60 that the first measurement system is operating. The light emitted from the second light source 56 enters the incident surface 52 a of the transparent crystal member 52 and propagates through the transparent crystal member 52. The light ray incident on the inside of the transparent crystal member 52 propagates toward the second liquid contact surface 52c. At the second liquid contact surface 52c, a part of the incident light is changed to the first liquid contact surface 52b according to the refractive index difference between the transparent crystal member 52 having the refractive index n ₀ and the liquid 1 to be measured having the refractive index n _1. Reflected at. At this time, the reflected light component exits from the exit surface 52d as a vertical polarization component l _S and a horizontal polarization component I _p , enters the optical fibers 56 and 57, propagates through the optical fibers 56 and 57, and travels through the first and second components. Reach the light detection units 58 and 59 of
Converted to electrical signals. The signal processing device 60 calculates the refractive index n ₁ of the liquid 1 to be measured in the same manner as described above.

As described above, the optical liquid refractive index measuring device 5
According to 0, the refractive index n ₁ of the liquid ₁ to be measured can be measured in the optimum measurement range.

Note that, contrary to the above example, the second
When the accuracy is low as a result, the measurement system selection device 62 switches to the first measurement system and measures the refractive index n ₁ of the liquid 1 to be measured.

The measuring system selecting device 62 is unconditionally
Measurement by the first measurement system and measurement by the second measurement system are performed, and a highly accurate result can be output as a final result.

Embodiment 2 In the transparent crystal member 52, the angle between the liquid 1 to be measured and the first and second liquid contact surfaces 52b and 52c with the incident surface 52a is φ ₁ = 42. .5 ° and φ
_{When 2} = 35 °, the measurable refractive index range differs depending on each angle, so that the measurement range is expanded in a manner that complements each range.

Embodiment 3 In the transparent crystal member 52, the angle formed by the liquid 1 to be measured and the first and second liquid contact surfaces (discontinuity interfaces) 52b and 52c with the incident surface 52a is φ ₁ = 42. .5 ° and φ
₂ = 40 °, two angles φ ₁ and φ ₂ compared to the second embodiment.
When the difference is small, the range of change in the polarization intensity ratio with respect to the refractive index of the sample liquid 1 is large, that is, the range of high sensitivity can be increased.

As described above, the surface of the transparent crystal member 52 that comes into contact with the liquid 1 to be measured is changed to the first and second liquid contact surfaces 52b and 52b.
By providing two light sources 52c and the first and second parallel light sources 54 and 55 as in the case of 52c, measurement systems having different measurement ranges can be configured.

Further, the liquid contact surfaces 52b and 52c and the entrance surface 5
By appropriately setting the angle with 2a, the measurement range of the refractive index of the liquid 1 to be measured can be adjusted. As a result, one transparent crystal member 52 and the shared optical fiber 5
6, 57, the first and second light detectors 58, 59, and the signal processing device 60 enable two types of measurement according to the respective measurement ranges.

The implementation of the optical liquid refractive index measuring device of the present invention is not limited to the above-described exemplary embodiment, but can take various modifications.

[0129]

According to the first aspect of the present invention, it is inexpensive, does not require a large-scale device configuration, does not require complicated assembling, does not require sampling, etc., and is automatic and continuous. ,
An optical liquid refractive index measuring device capable of measuring the refractive index of the liquid to be measured in a short time was realized. Further, according to the first aspect of the present invention, it is possible to accurately measure the refractive index without using the reference light by normalizing the received vertical polarization component light and the horizontal polarization component light. became. This has led to an improvement in the measurement accuracy of the refractive index and a further miniaturization of the device configuration. Further, according to the first aspect of the present invention, in a room temperature (or room temperature) environment, high resolution is exhibited,
In addition, the measurement accuracy of the refractive index of the liquid to be measured could be improved. Further, according to the first aspect of the present invention, it is possible to provide an optical liquid refractive index measuring device which is not affected by the fluctuation of the light source. Further, according to the first aspect of the present invention, an optical liquid refractive index measuring device which is not affected by disturbance light or the like can be provided.

According to the second aspect of the present invention, since the transparent crystal member is provided with the reflection surface at an angle such that the light reflected at the discontinuous interface is totally reflected toward the light incident surface,
The light reflected from the discontinuous interface is emitted from the same surface as the light incident surface, so that the connection space of the optical fiber can be reduced. According to a second aspect of the present invention,
By making the angle between the discontinuous interface of the refractive index and the total reflection surface a right angle, it is possible to make the output optical axis of the ordinary light component, that is, the vertical polarization component, of the reflected light parallel to the optical axis of the incident light beam. Alignment of the output side fiber and the light receiving side fiber becomes easy. In the second aspect of the present invention, when the optical axis of an incident light beam is made coincident with the optical axis of a transparent crystal member, the shape of the transparent crystal member is asymmetric if the incident angle of the light beam with respect to the refractive index discontinuity interface is other than 45 degrees. Since the shape is used, the incident surface, the liquid contact surface, and the total reflection surface can be specified from the member shape when connecting the fiber, and there is no need for marking. Further, according to the second aspect of the present invention, the transparent crystal member can be formed into a right-angled triangular shape, so that it can be cut out from a rectangular substrate, so that it is easy to process and the material can be efficiently removed from the base material. Becomes As described above, according to the second embodiment of the present invention, the production of the transparent crystal member is facilitated, the productivity is improved, and the mass production is possible.

According to the third aspect of the present invention, the refractive index measurement range can be expanded by providing two discontinuous interfaces on the transparent crystal member and selecting an incident angle on the discontinuous interface by selecting an incident light source. . Further, according to the third aspect of the present invention, by providing two liquid contact surfaces to be measured on one transparent crystal member, it is possible to enlarge the refractive index measurement range by providing two transparent crystal members. Cost can be reduced. Further, according to the third aspect of the present invention, the number of parts can be reduced by arranging the light receiving section at the intersection of the reflected light axes of the two vertically polarized light components and two horizontally polarized light components emitted from the two light sources, respectively. Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical liquid refractive index measuring device as one embodiment of the present invention.

FIG. 2 is an enlarged view centering on a transparent crystal member in the optical liquid refractive index measuring device illustrated in FIG.

Figure 3 is a graph showing the relationship between the change of the refractive index n ₁ of the liquid to be measured when the incident angle φ ₀ = 37.45 °, the energy reflectance R _s of the vertical polarization component light l _s is there.

Figure 4 is a variation of the refractive index n ₁ of the liquid to be measured, the ratio of the energy reflectance R _p of the energy reflectance R _s and horizontal polarization component light l _p of the vertical polarization component light l _s: R _s 4 is a graph showing a relationship with / R _p .

FIG. 5 is a graph showing changes in the refractive index n ₁ of the liquid 1 to be measured and R
_s / is a graph showing the relationship between the (R _s + R _p).

FIG. 6 shows, as an embodiment of the present invention, changes in R _s / (R _s + R _p ) with respect to various refractive indexes n ₁ of various liquids to be measured when the light intensity of the light source is changed. It is a graph shown.

FIG. 7 shows, as an embodiment of the present invention, R _s / (R _s + R _p ) when the light intensity of the light source is changed when the refractive index n _{1 of the} liquid 1 to be measured is 1.466. FIG.

FIG. 8 is a configuration diagram of an optical liquid refractive index measuring device according to a second embodiment of the present invention.

FIG. 9 is an enlarged view centering on a transparent crystal member in the optical liquid refractive index measuring device illustrated in FIG. 8;

FIG. 10 is a configuration diagram of an optical liquid refractive index measuring device according to a third embodiment of the present invention.

FIG. 11 is a characteristic diagram according to the third embodiment of the present invention.

[Explanation of symbols]

1 ··· Liquid to be measured (refractive index n ₁ ) 10 ··· Optical liquid refractive index measuring device 12 ··· Transparent crystal optical member (crystal optical member) (refractive index n
₀ ) 14. Light source 16. Optical fiber for incident light 18. Optical fiber for vertical polarization component 20. Optical fiber for horizontal polarization component 22. Photodetector for vertical polarization component 24. Light for horizontal polarization component Detector 26 Signal processing device (refractive index calculation means) l _i ... Incident light φ ₀ .incident angle φ ₁ ... Transmitted light refraction angle l _s ... Vertical polarization component light l _p. r _s · · energy reflectance of the vertical polarized component light l _s of Fresnel reflection coefficient r _p · · Fresnel reflection coefficient of the horizontally polarized component light l _p R _s · · vertical polarization component light l _s R _p · · horizontally polarized component light l _p energy reflectance 30 ... optical liquid refractive index measuring apparatus 32 ... transparent crystal optical element (crystal optical member) (refractive index n
₀ ) 34 light source 36 optical fiber for incident light 38 optical fiber for vertical polarization component 40 optical fiber for horizontal polarization component 42 photodetector for vertical polarization component 44 light for horizontal polarization component Detecting unit 46: Signal processing device (refractive index calculating means) 50: Optical liquid refractive index measuring device 52: Transparent crystal optical member (crystal optical member) (refractive index n
₀ ) 54, 55 ··· parallel light source 56, 57 ··· optical fiber 58, 59 · · · photodetection unit 60 · · · signal processing device (refractive index calculating means) 62 · · · measurement system selection device

Claims (22)

[Claims] 1. A bottom surface (12c) contacting a surface of a liquid to be measured having a predetermined refractive index, an incident surface (12a) forming a predetermined angle with the bottom surface, and a predetermined angle with the bottom surface. A crystal optical member having an emission surface (12b) provided on a side facing the surface, and having a birefringence having a discontinuous interface with respect to a refractive index at a boundary surface between the bottom surface (12c) and the liquid to be measured. (12), incident light providing means (14, 16) for causing light to enter the incident surface of the crystal optical member at a predetermined angle, and an incident surface (1) of the crystal optical member from the incident light providing means.
2a), propagates inside the crystal optical member (12), is reflected at the boundary between the bottom surface (12c) of the crystal optical member and the liquid to be measured, and has a first polarization component and a second polarization component. First and second polarized light component detection means (2) for detecting a first polarized light component and a second polarized light component which are separated into polarized light components and exit from the exit surface (12b) of the crystal optical member.
2, 24) and a refractive index calculating means (26) for calculating a refractive index of the liquid to be measured by calculating a signal detected by the first and second polarized light component detecting means. Rate measuring device. 2. The light from the incident light beam providing means is incident on the incident surface (12a) of the crystal optical member in an orthogonal state, and the light exit surface (12b) of the crystal optical member is in contact with the surface of the liquid to be measured. 2. The optical liquid refraction according to claim 1, wherein at least one of the two reflected polarized light components reflected from the discontinuous interface on the bottom surface of the crystal optical member that is in contact with the discontinuous interface of the refractive index is orthogonal to the reflected polarized light. Rate measuring device. 3. The first polarized light component is a vertically polarized light component (l).
a _s), the second polarization component of the first polarization component light perpendicular to the horizontally polarized component light (l _p) an optical liquid refractive index measuring apparatus according to claim 1, wherein. 4. The optical liquid refractometer according to claim 3, wherein a plane including the incident light beam and the reflected polarized light beam is parallel to an optical axis of the crystal optical member. 5. An incident surface (32a), a refractive index discontinuous interface (3).
2c), having a total reflection surface (32b), the discontinuous refractive index interface (32c) being in contact with the liquid to be measured (1), and having a discontinuous refractive index at the contact interface of the liquid to be measured (1). Make an interface,
A crystal optical member (32) having a birefringent index, wherein the total reflection surface (32c) is provided at an angle such that light reflected at the discontinuous interface is reflected toward the incident surface (32a); Incident light providing means (34, 36) for causing light to enter the incident surface of the crystal optical member at a predetermined angle; and an incident surface (3) of the crystal optical member from the incident light providing means.
2a), is transmitted through the inside of the crystal optical member (32), and is provided at the discontinuous refractive index interface (3) of the crystal optical member.
The liquid crystal is reflected at the boundary between the liquid crystal 2c) and the liquid to be measured (1), is separated into a first polarized light component and a second polarized light component, and is further reflected at the total reflection surface (32b) to produce the crystal optics. The first light emitted from the incident surface (32a) of the member
First and second polarization component detection means (38:44, 40:42) for detecting the polarization component and the second polarization component, and a signal detected by the first and second polarization component detection means. An optical liquid refractive index measuring device, comprising: a refractive index calculating means (46) for calculating the refractive index of the liquid to be measured. 6. A discontinuous refractive index interface (32c) of the transparent crystal optical member (32), which is in contact with the liquid to be measured (1) and forms a discontinuous refractive index interface, and 2 6. The optical liquid refractive index measuring device according to claim 5, wherein an angle formed between the two reflected lights and the total reflection surface (32b) for totally reflecting the reflected light into the transparent crystal optical member is a right angle. 7. An optical liquid refractive index measuring apparatus according to claim 5, wherein an optical axis of a light beam from said light source is parallel to an optical axis of said transparent crystal optical member. 8. An optical axis of a light beam from said light source (34) and said transparent crystal optical member (3) on which a light beam from said light source is incident.
7. The optical liquid refractive index measuring device according to claim 5, wherein an angle between the incident surface and the incident surface is a right angle. 9. The light from said light source (34) is applied to said transparent crystal.
Said incident surface (32a) incident on the optical member (32);
The two types of light emitted from the transparent crystal optical member (32)
Reflected light (l_p, L_S) Coincides with the exit surface, and the incident light (l) on the entrance surface (32a)_i) Optical axis,
The two types of reflected light (l _p, L_S) Is almost parallel to the optical axis
9. The optical liquid refractive index measuring device according to claim 8, wherein: 10. The incident light providing means (34, 36) and the first and second polarization component detecting means (38: 4).
4,40: 42) has first to third optical fibers, and these optical fibers are directed to the incident surface (32a) of the crystal optical member (32). Liquid refractive index measuring device. 11. An entrance surface (52a), an exit surface (52d) adjacent to the entrance surface and forming a predetermined angle with the entrance surface, and a predetermined angle facing the entrance surface and the exit surface, respectively. The first and second discontinuous refractive index interfaces (52b, 52c) are adjacent to each other, and the first and second discontinuous refractive index interfaces come into contact with the liquid to be measured (1). Forming a discontinuous interface of the refractive index at the contact interface of the measurement liquid (1),
A crystal optical member (52) having a birefringent index for reflecting light reflected at the discontinuous interface toward the emission surface (52d);
First and second incident light providing means (54:64, 55:65) for making light incident on the first and second discontinuous refractive index interfaces of the crystal optical member; The incident light is provided to the incident surface (52a) of the crystal optical member, transmitted through the interior of the crystal optical member (52), and is transmitted through the first surface of the crystal optical member.
And at the boundary between the second discontinuous refractive index interface (52b, 52c) and the liquid to be measured (1), the light is separated into a first polarized light component and a second polarized light component, and the light exit surface ( 52d) first and second polarization component detection means (5) for detecting the first polarization component and the second polarization component emitted from
6:58, 57:59), a refractive index calculating means (60) for calculating a refractive index of the liquid to be measured by calculating signals detected by the first and second polarization component detecting means, First and second incident light providing means (54:64, 5
5:65), and a measuring system selecting means (62) for transmitting a result in the refractive index calculating means (60) based on the operated one. 12. An optical axis of said crystal optical member (52),
The first and second incident light providing means (54:64, 5
The optical liquid refractometer according to claim 11, wherein the optical axis of the light emitted from (5:65) is parallel to the optical axis. 13. The incident surface (52a) of the crystal optical member (52) and the optical axis of light emitted from the first and second incident light providing means (54:64, 55:65). The optical liquid refractive index measuring device according to claim 11, wherein? 14. An optical liquid refractive index measuring device according to claim 11, wherein said first and second incident light providing means (54:64, 55:65) emit light containing all polarization components. 15. The optical liquid refractive index measuring device according to claim 1, wherein the crystal optical member having a birefringence is a uniaxial single crystal substrate. 16. An optical liquid refractive index measuring apparatus according to claim 1, wherein said crystal optical member is a lithium niobate single crystal. 17. The optical liquid refractive index measuring device according to claim 1, wherein the light emitted from the light source includes a total polarization component. 18. The incident light providing means (14, 16) comprises:
The light source (14) that emits light including all polarization components, and a waveguide circuit (16) that causes light from the light source to enter the incident surface (12a) of the crystal optical member at a predetermined angle. 6. The optical liquid refractive index measuring device according to 1 or 5. 19. The first polarized light component detecting means (18, 2)
2) a first waveguide circuit (1) for guiding a first reflected polarization component emitted from the emission surface (12b) of the crystal optical member;
8) and a first light receiving means (22) for receiving light from the first waveguide circuit and emitting an electric signal corresponding to the received light intensity.
The second polarized light component detecting means (20, 24) includes a second waveguide circuit (20) for guiding a second reflected polarized light component emitted from the emission surface (12b) of the crystal optical member. ) And the second
12. The optical liquid refractive index measuring device according to claim 1, further comprising a second light receiving means (24) for receiving light from said waveguide circuit and emitting an electric signal according to said light receiving intensity. 20. The optical liquid refractive index measuring device according to claim 19, wherein said first waveguide circuit has a multi-mode optical fiber, and said second waveguide circuit has a multi-mode optical fiber. 21. An apparatus according to claim 21, wherein said refractive index calculating means comprises: an intensity ratio between a detection signal of said first light receiving means and a detection signal of said second light receiving means, or an intensity of an entire detection signal and said first light receiving means. The refractive index of the liquid to be measured is calculated from the ratio of the intensity of the detection signal or the ratio of the intensity of the entire detection signal to the intensity of the detection signal of the second light receiving means.
12. The optical liquid refractive index measuring device according to any one of 11). 22. An apparatus according to claim 19, wherein said refractive index calculating means detects an intensity of an entire detection signal as a sum of a detection signal of said first light receiving means and a detection signal of said second light receiving means, and detects said first light receiving means. The refractive index of the liquid to be measured is calculated from a ratio of a signal intensity or a ratio of an intensity of the entire detection signal to an intensity of a detection signal of the second light receiving unit. Optical liquid refractometer.