JPH0448524Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a liquid refraction technique that calculates the refractive index of the liquid by using the relationship between the change in the incident angle and the critical angle at the contact boundary of a prism immersed in the liquid. This invention relates to a rate measuring device.

(Prior Art) Many devices have been known for optically measuring the refractive index of a liquid. For example, special public relations
In the device of Publication No. 40474, as shown in Fig. 6,
Using the laser beam 1 as a parallel beam, the incident angle θ of the laser beam 1 that enters one point O of the interface 2a where the prism 2 and the measurement material 3 contact is continuously changed, and from the interface 2a generated by this conversion, The reflected light 4 is detected by a light receiver 5, and the critical angle at the interface 2a is detected. In this case, as a device for changing the incident angle θ, an incident light projecting section 6 is disposed on the incident side of the prism 2, and a rotating prism 7 is installed in the incident light projecting section 6. The rotating prism 7 has a square cross section. It has a wedge shape and is built into the incident light projection unit so as to rotate around the same rotation axis as the optical axis of the incident light. Therefore, the light incident on this rotating prism 7 is
One point O of the laser beam is refracted and reaches point O, but is swung by the rotating prism 7 and irradiates one point O of the interface 2a.
The incident angle θ changes.

Furthermore, in the device disclosed in Japanese Patent Publication No. 56-21092, as shown in FIG. The light emitted from the light source is adjusted to diverge at an angle equal to the difference between the maximum and minimum total reflection angles θmax and θmin occurring at and the measurement surface 12 are oriented so that they form an angle equal to the total reflection angle θ _T at the average value of the liquid density, and the light beam 15 from the measurement surface 12 is directed entirely or partially to the reflection surface 13 depending on the density of the liquid. The light is reflected toward the light receiving section 18 and is integrated so as to be received by the light receiving section 18.

(Problem to be solved by the invention) In the above conventional technology, for example,
In the case of the device described in the publication, it is extremely difficult in practice to condense multiple single beams (laser beam 1) with different optical paths onto one point on the interface. In the case of the device described in the publication, there are variations in the light intensity distribution of the light source, and manufacturing precision and skill are required to form the measurement surface 12 and the reflection surface 13 at the free end of one transparent rod. Each of these had problems in that they were practically difficult to manufacture and use.

In view of the above-mentioned problems, the purpose of the present invention is to form the interface between the prism and the measurement liquid into an arc shape, and to provide a light beam moving device that moves the light beam incident on the prism in parallel, thereby facilitating manufacturing. Another object of the present invention is to provide a liquid refractive index measuring device that can easily measure the refractive index of a liquid and solves the above problems.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a light source using a prism having an arcuate contact interface with the liquid to be measured when configuring a liquid refractive index measuring device. and a light-receiving device, each facing the surface opposite to the contact interface, and
A light flux moving device is disposed between the light source and the prism, and includes a light flux regulating body that moves the light flux incident on the prism in parallel.

(Function) With the above configuration, the present invention can respond to changes in the angle of incidence when the light flux incident from the surface opposite to the contact interface of the prism is translated in parallel by the light flux shifting device and the angle of incidence on the interface is changed. It is now possible to detect the amount of reflected light that appears when the incident angle changes beyond the critical angle, and by detecting the incident position of the light beam at that time, it is easy to use the first-order relational expression from the incident position. The refractive index of a liquid can be calculated and determined, and a liquid refractive index measuring device with a simple structure and capable of measuring a wide range with high accuracy can be realized.

(Example) The following is an example of the present invention in Figures 1 to 5.
This will be explained based on the diagram.

A prism 22 made of a translucent material with a refractive index n ₂ is immersed in a measuring liquid 21 with a refractive index n ₁ . prism 2
The end surface of No. 2 on the side to be immersed in the measurement liquid 21 is formed into a semicircular shape with a radius R to serve as a contact interface 23. However, the contact interface 23 is not limited to a semicircle, but may be formed as a part of a circular arc. prism 22
An end surface 24 facing the contact interface 23 is formed into a planar shape, and both ends of the planar end surface 24 are used as an entrance surface 25 and an exit surface 26 of the light beam, respectively. prism 2
The thickness from the inlet surface 25 side to the outlet surface 26 side of No. 2 is formed to be constant. A fixture 27 that brings the planar end surfaces 24 into close contact and immerses the prism 22 in the measurement liquid 21
, holes 28 and 29 are bored at positions corresponding to the entrance surface 25 and exit surface 26 of the prism 22, respectively.

Above the entrance surface 25 of the prism 22 in the direction perpendicular to the entrance surface 25, there is a light flux regulating body 33 in which a light source section 32 is formed into a flat plate and includes a light source 30 and a collimator 31 that transforms the light beam emitted from the light source 30 into a homogeneous parallel light beam.
A narrow slit 34 long in the thickness direction of the prism 22 is bored in the center of the light flux regulating body 33 at the position where the collimator 31 is disposed, and the slit 34 is provided substantially parallel to the slit 34. The shaft 3 has a threaded member 35 protruding from an end located outside the prism 22, and a threaded portion 36a formed at the tip of the threaded member 35.
6 is screwed together, and a light flux moving device 38 is provided in which the end of the shaft 36 opposite to the threaded portion forming side is connected to a drive device 37 such as a motor. The light flux regulating body 33 and the driving device 37 are not limited to this. For example, as shown in FIG. A light flux moving device including a shaft 39 and a drive device 40 such as a motor for rotating the shaft 39 may be used. As described above, various types of devices may be considered as long as the light flux regulating body 33 and the light flux moving device 38 have the same function and are configured to move the light flux in parallel.

Above the exit surface 26 of the prism 22 in a direction perpendicular to the exit surface 26, a photoelectric conversion type light receiving device 41 using a photocell or the like as a light receiving surface is arranged with the light receiving surface facing the exit surface 26 side. By this light receiving device 41, the exit surface 26
From this, an electromotive force corresponding to the amount of light irradiated onto the light receiving surface can be obtained.

When this embodiment configured in this way is used, the parallel light beam from the collimator 31 is restricted by the light flux regulating body 33 into a light flux 45 of a predetermined size through the slit 34, and the light flux is parallelized from the right side to the left side in FIG. 1 or 5. When moving, the angle of incidence β at the contact interface 23 changes as β ₁ , β ₂ , β ₃ , . . . This angle of incidence β
Reflected luminous flux 46 reaching the light receiving device 41 as a result of changes in
The amount of light also changes. That is, the refractive index of the measurement liquid 21
Assuming that n ₁ and the refractive index n ₂ of the prism 22 are n ₁ < n ₂ , the critical angle α for total reflection at the contact interface 23 from both refractive indexes n ₁ and n ₂ is α=sin ^-1 n ₁ / n ₂ ...(1), and assuming that the incident angle β ₂ at point P is equal to the critical angle α, the light beam 45 enters the prism 22 and the irradiation position at the contact interface 23 reaches the point P. When the threshold is exceeded, the amount of reflected light beam 46 is rapidly attenuated. Therefore, the power photoelectrically converted by the light receiving device 41 rapidly decreases after reaching the position of the critical angle α.
The degree of change can be easily known by recording it on a chart or the like. Then, as shown in FIG. 5, the position of the slit 34 of the light flux regulating body 33 is translated by a distance l necessary for the light flux 45 to move from the starting point Q to the point P, so that the angle of incidence β ₂ becomes the critical angle α. Assuming that they are equal, sinβ ₂ = n ₁ /n ₂ ...(2) from the formula (1) for the critical angle of total reflection, and sinβ ₂ = R−l from the radius R of the prism 22 and the distance l. /R...(3) From the second and third equations, the refractive index n ₁ of the liquid to be measured 21
is n ₁ = n ₂ (R-l)/R...(4), where (R-l) is x and n ₂ /R is k, the fourth equation is n ₁ = k・x...(5) Thus, the refractive index n ₁ of the measurement liquid 21 has a linear relationship with respect to the moving distance l of the light beam 45. As a result, the moving distance l of the light beam 45 or x=(R-l)
By knowing, the refractive index n ₁ of the liquid to be measured 21 can be easily determined, and since the above relational expression (5) is a linear expression, measurement is possible. Therefore, by determining the relationship between the refractive index and concentration of the liquid to be measured in advance, the desired characteristic value can be easily determined.

In the above-mentioned embodiment, there is no limitation on the measurement range that occurs when using a prism having a horizontal plane as an interface, as typified by conventionally known devices, such as the device disclosed in Japanese Patent Publication No. 51-40474. In other words, in the case of a horizontal interface such as in a device, as is known from equation (1), the change in the refractive index n ₁ of the liquid to be measured with respect to the rate of change of the critical angle α that appears as the critical angle α gradually increases As the ratio decreases, the range of the incident angle β that can be used for measurement is naturally limited as the accuracy of the measured value decreases, but in the case of the above example, the prism interface is Since the moving distance l of the incident parallel light beam and the refractive index _n1 of the liquid to be measured l have a simple linear relationship, the measurement is not subject to the constraints of conventional devices,
It has the advantage of being able to measure refractive indices over a wide range (in practice, up to the refractive index of a prism) with high precision.

The above-mentioned embodiments have been specifically described for better understanding of the gist of the present invention, and do not control other aspects unless otherwise specified. For example, the light flux regulating pair 33 or the prism 38 formed on a flat plate may be operated by a drive device such as an electromechanical operation such as a motor, or may be purely mechanical or manual operation. The output side of the electromotive force or the like may be electrically coupled to the drive device, and the position of the light flux regulating body may be read when the output side suddenly changes. In addition, the luminous flux regulating body 3
3. Replace the slit 34 with a rectangle as shown in the figure,
A spiral shape may also be used, and in this case, the driving device may be a driving device that gives a swirl to the spiral slit.

(Effects of the invention) As described above, in the present invention, the light flux incident on the prism whose contact interface is formed in an arc shape can be moved in parallel by the light flux moving device, so that the incident light flux is moved. The incident angle at the contact interface can be changed by changing the reflection position at the arc-shaped contact interface, and the incident position of the parallel light can be detected from the sudden change in the reflected light at the critical angle point.
The refractive index of the liquid can be determined from that position. In addition, since the contact interface of the prism is formed in an arc shape, it is easy to manufacture the prism. Due to the linear relationship between the parallel movement distance of light and the refractive index of the liquid to be measured, the refractive index of the liquid can be easily determined over a wide range with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a liquid refractive index measuring device according to the present invention, FIG. 2 is a plan view showing a liquid refractive index measuring device according to the present invention, and FIG. 3 is taken along the - line in FIG. 4 is a perspective view showing another embodiment of the light flux moving device according to the present invention, FIG. 5 is an explanatory diagram of measurement in the device according to the present invention, and FIG. 6 is a side view showing a conventional liquid refractive index measuring device. Explanatory diagram,
FIG. 7 is an explanatory side view showing another embodiment of a conventional liquid refractive index measuring device. 21... Measuring liquid, 22... Prism, 23...
...Contact interface, 24... End surface, 25... Inlet surface, 2
6... Exit surface, 27... Fixture, 28, 29...
hole, 30... light source, 31... collimator, 32...
... light source section, 33 ... light flux regulating body, 34 ... slit, 37 ... drive device, 38 ... light flux moving device,
41... Light receiving device.

Claims (1)

[Scope of utility model registration request] A prism having an arc-shaped contact interface with respect to the liquid to be measured is disposed on each of the light source and the light receiving device, with the surface opposite to the contact interface facing, and between the light source and the prism, a light beam incident on the prism is arranged. 1. A refractive index measuring device for a liquid, characterized in that a light flux moving device is provided with a light flux regulating body that moves the light flux in parallel.