JPH0443810Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Industrial application field) This invention relates to a liquid refractive index measuring device.

(Prior Art) Conventionally, devices for measuring the specific gravity, concentration, etc. of liquids have been used to measure liquids by transmitting light from a light source through a light transmitting body, as typified by the structure shown in Japanese Patent Publication No. 58-42419. There is a known device in which the light is irradiated at a constant angle of incidence onto the light incident interface in contact with the liquid, and the reflected light corresponding to the refractive index of the liquid is received by a light receiving element. Since the angle of incidence is fixed, there is a disadvantage that the measurement range is limited. In order to solve this problem, a measuring device with an arc-shaped light entrance interface has been proposed (Japanese Patent Application Laid-Open No. 1690509/1983).

(Problem that the invention aims to solve) In conventional devices that use prisms with arc-shaped light entrance interfaces, light is reflected on the interface according to the law of total internal reflection, so it can cope with changes in the refractive index of the liquid. However, this reflected light is subject to changes in characteristics due to changes in the light transmittance of the liquid, changes in the temperature of the prism, dirt on the interface, and changes in the temperature of the light source and receiver.
It is affected by various disturbance factors, and in order to measure the true refractive index, it is necessary to compensate for these disturbances with a complicated mechanism.

(Means for solving the problem) This idea was made as a result of intensive research into a device that can perform the above-mentioned compensation with a simple means. In a liquid refractive index measuring device provided with a prism, the prism 7 is a plate-shaped body, and the measurement light L- at the lower and upper measurement limits is placed on the arcuate light incident interface 9.
At points P-1 and P-2, where the incident angles β-1 and β-2 of 1 and L-2 are the critical angles of total reflection, respectively, and at the incident angle β-3, which is larger than the incident angle β-2, The light incident point P-3 of the incident control light L-3 is located,
Reflected light L-1', L-2' and L-1' to L at the points P-1, P-2 and the area between P-1 and P-2
This problem can be solved by independently providing the light receiving element 13 which receives the light L-2' and the light receiving element 14 which receives the reflected light L-3' from the point P-3.

(Function) Light 4 emitted from the light source section 1 is converted into parallel light 5 by the collimator 3 and enters the arc-shaped light incident interface 9 that is immersed in and in contact with the liquid 10. At this time, the measurement lights L-1 to L-2 that enter the area between points P-1 and P-2 on the interface 9 in accordance with the refractive index of the liquid 10 follow the total internal reflection law, and The reflected lights L-1' to L-2' are received by the light receiving element 13. On the other hand, a part of the parallel light 5 enters the point P-3 on the interface 9 as the control light L-3 in the same way as the measurement lights L-1 to L-2, and becomes the reflected light L-3'. The light is received by a light receiving element 14 provided independently of the light receiving element 13.

Reflected light L− received by the light receiving elements 13 and 14
1' to L-2' and L-3' are the physical conditions such as the optical transparency of the liquid 10, the shape of the prism 7, and the light source section from the light source 1 through the prism 7 to the light receiving elements 13 and 14. 1 and the light receiving sections 13 and 14 in exactly the same manner, the reflected light L-
The reflected light L-3' is reflected in the physical quantities measured by 1' to L-2'.
By relating the physical quantities measured by , it becomes possible to eliminate errors due to disturbance and determine the true refractive index.

(Example) This invention will be explained in detail with reference to an example shown in the drawings.

A light source 1 is a light emitting diode or a tungsten lamp, and is stably supported by a support 2. A collimator 3 converts the light beam 4 from the light source 1 into a parallel light beam 5. Reference numeral 6 denotes an optical fiber for a light source portion that guides the parallel light beam 5, and its upper end is in contact with the support 2 and its lower end is in contact with the prism 7. The prism 7 is a light transmitting body having an opposite surface 8 and a light entrance interface 9 directly related to measurement, and is a plate-shaped body with a rectangular cross section as shown in FIG. For the prism 7, a material with an appropriate refractive index is selected depending on the type of liquid 10 to be measured, the range of measurement, etc., but normally a material with a refractive index greater than the refractive index of the liquid 10 is selected. The opposite surface 8 of the prism 7 is for total reflection of the incident parallel light beam 5.
This structure is not particularly limited, but for example, it may be possible to glue a reflective mirror, apply reflective paint, or provide a vacuum or a thin layer filled with a gas that does not absorb light to achieve total reflection. This is a good structure. As explained in an enlarged view in FIG. 3, the light incident interface 9 of the prism 7 has the incident angles β-1, β- of the measurement beams L-1 and L-2 at the lower and upper limits of the measurement incident from the opposite surface 8. OP-1, OP-2 (OP-1 = OP-2) so that the plane connecting points P-1 and P-2, where 2 is the total reflection angle, forms an arc.
This arcuate surface extends below the point P-2 (in the drawing), and the incident point P- of the control light L-3, which is outside the above measurement limit, is formed.
3 is located. In this case, the angle of incidence β-1 and β
-2, β-1<β-2, and the point P-
3 is located below point P-2 (in the drawing), the incident angle β-3 has the relationship β-2<β-3, and the incident angles β-1, β-2, and β-3 All of them satisfy the total internal reflection law.

In order to provide the prism 7 with such a function, the light entrance interface 9 of the prism 7 requires at least an arcuate surface extending from the point P-1 to the point P-3 as the contact interface with the liquid 10. .

The reflected lights L-1' to L-2' and L-3' reflected at the region between points P-1 and P-2 on the light incident interface 9 and at the point P-3 are directed toward the upper surface of the prism 7, respectively. The light travels, is guided by optical fibers 11 and 12, which are arranged independently, and is received by light-receiving elements 13 and 14, which are also arranged independently. In this case, optical fibers 11 and 12 and light receiving elements 13 and 14 are arranged independently.
have the same characteristics as possible and are placed in the same environment.

This idea, as described above, differs from the conventional measuring device in which only one light-receiving element receives reflected light within the measurement limits. The main feature is that the light is irradiated onto the light input interface in parallel with the light within the measurement limit, and each reflected light is received by an independent light-receiving element placed in the same environment. The biggest difference from the conventional method (effect of the invention) When using the measuring device of this invention, physical conditions such as turbidity of the liquid and subtle temperature of the prism on the optical path, which have traditionally been considered important error factors, can be detected. This eliminates troublesome problems such as changes in the refractive index due to changes in the refractive index, or changes in characteristics due to temperature in the light source and light receiving sections, and always provides reproducible and highly accurate measurement results, and the device does not have a complex mechanism. Since it does not require a

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of this invention, FIG. 2 is a sectional view taken along the line A-A in FIG. . 1... Light source, 5... Parallel light beam, 7... Prism, 9... Light entrance interface, 10... Measurement liquid, 13,
14... Light receiving element, L-1, L-2... Measuring light,
L-3...Control light, β-1, β-2, β
-3...Incidence.

Claims (1)

[Scope of utility model registration request] In a refractive index measurement device for a liquid, in which a prism is provided as a light entrance interface in contact with the liquid on an optical path from a light source to a light receiver, the prism 7 is a plate-shaped body and is placed on an arcuate light entrance interface 9 for measurement at the lower and upper limits of measurement. Light L
Points P-1 and P-2 where the incident angles β-1 and β-2 of -1 and L-2 are critical angles for total reflection, respectively, and the incident angle β-3 which is larger than the incident angle β-2. The incident point P-3 of the control light L-3 is located at the points P-1, P-2, and P-1 to P-2.
Reflected light L-1', L-2' and L-1' in the area between
A liquid refractive index measuring device characterized by independently providing a light receiving element 13 for receiving light L-2' and a light receiving element 14 for receiving reflected light L-3' from point P-3.