JP2585947B2 - Refractive index measuring method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a refractive index.

[0002]

2. Description of the Related Art Conventionally, there is a total reflection method as a useful method for measuring the refractive index of a fluid. In this total reflection method, one surface of the prism is transmitted by illuminating one surface of the prism from a light source at a predetermined angle, and detecting the distribution of light reflected from the one surface of the prism. The critical angle at which reflection from the interface with the sample placed on the upper surface occurs is calculated, and the refractive index of the sample is calculated based on the critical angle.

Incidentally, since the refractive index generally varies according to the temperature of an object, it is necessary to adjust the temperature of the sample in order to ensure required measurement accuracy. FIG. 4 is a configuration diagram showing an example of a refractive index measuring device to which the above-mentioned total reflection method is applied.

A prism 101 is disposed with one surface 102 horizontal, and a heat exchange function is provided around the prism 101 by maintaining a measurement space 109 serving as a space for arranging a light source device and a photodetector (not shown). A provided water passage 111 is provided. Further, the water passage 111 and the measurement space 109 are surrounded by the closed case 103 except for the one surface 102 of the prism 101, that is, the sample placement portion.

[0005] The constant temperature water tank 104 is connected to the water passage 111.
The constant-temperature water supplied from the constant-temperature water is supplied from the prism 101.
The control circuit 107 controls the temperature adjusting means 107 based on the temperature sensor 106 embedded at a predetermined position and the temperature detected by the temperature sensor 106 so as to be maintained at a constant temperature.

In the above-mentioned apparatus, the upper space of the sample on one surface 102 is open. For example, as shown by a broken line in FIG. The sample channel 11 connected inside the partition 115
There is also an apparatus to which a configuration for supplying a sample through 6 is added.
As a result, a sample can be automatically supplied / discharged by a pump or the like via the sample flow path 116, so that measurement can be automated, and a change in the sample temperature with time can be reduced.

[0007]

However, according to the conventional configuration shown in FIG. 4, the measurement space 109 is provided between the constant temperature water in the water passage 111 and the sample on one surface 102.
And one surface 10 from where the prism 101 is interposed.
It takes a considerable time from the introduction of the sample onto the sample 2 until the sample can be stably measured at a predetermined temperature.

Moreover, the sample introduced onto the one surface 102 is easily affected by the external temperature, and even if the time from introduction to measurement is sufficiently taken into consideration, the sample temperature and the measurement conditions at the time of actual measurement are considered. There is a possibility that an error may occur between the sample temperature and the set sample temperature, so that a highly accurate temperature setting of ± 0.05 ° C. or less cannot be performed.

Further, according to the above configuration, the thermostatic water bath 10
4. Since a configuration such as a constant temperature water pipe and a pump 105 is required, there is a disadvantage that the apparatus becomes large. Therefore, prior to the present invention, in order to be able to adjust the sample to a predetermined temperature in a short time, to improve the control accuracy of the sample temperature, and to reduce the size, FIG. And a device for measuring the refractive index shown in FIG.

In the method and apparatus for measuring the refractive index according to the present invention shown in FIG. 5, a light beam is made incident on a prism 1 from a light source device 2 (only a light source is shown in FIG. 5) and reflected on one surface 3 of the prism 1. Is detected by the photodetector 4, the critical angle θ at which the total reflection occurs at the interface between the prism 1 and the liquid sample 5 placed on one surface 3 thereof.
And the refractive index of the sample 5 is determined from the critical angle θ by applying Snell's law. In order to control the temperature of the sample 5 to a certain temperature (for example, 30 ° C.), one surface 3 of the prism 1 is covered with a high thermal conductive block 6, and the sample 5 is placed in the high thermal conductive block 6. A sample chamber 70 for supplying a sample from the outside to the sample chamber 70, and the temperature of the sample 5 in the sample chamber 70 is increased by the high thermal conductive block 6. A temperature control element 8 (for example, a semiconductor element based on the Peltier effect) that is adjusted via the power supply is provided. The temperature control element 8 is provided with heat-dissipating and absorbing fins 11 to promote heat absorption and heat generation.

Further, according to the present invention, the high thermal conductive block 6 is provided.
A temperature sensor 12a is disposed in the inside, the temperature of the sample 5 is indirectly detected, and based on the temperature of the high thermal conductive block 6, the control circuit 13 controls the amount of heat absorption and heat generation of the temperature control element 8. .

Although FIG. 5 shows that a temperature sensor 12c is provided in the sample chamber 70, the temperature sensor 12c is provided for experimentally checking the temperature in the sample chamber 70 described later. It is difficult to maintain the airtightness of the sample chamber 70 and the sample flow path 7, and if the temperature sensor comes into contact with the interface between the prism 1 and the sample 5, the intensity of the reflected light by the light detection device 4 Since there is a problem that the distribution cannot be detected correctly, it is omitted in the actual measurement of the refractive index.

According to this method, the sample 5 having a high chemical activity and the temperature sensor 9 do not come into direct contact with each other. Also, there is no possibility that the sample 5 and the temperature sensor 9 react with each other, and therefore, it becomes possible to measure the refractive indices of all kinds of the samples 5 having different degrees of chemical activity.

The high thermal conductive block 6 is formed of a ceramic having excellent chemical resistance and high thermal conductivity, for example, silicon carbide. The temperature control element 8 is a semiconductor device in which a large number of Peltier elements, one of which generates heat when energized and the other absorbs heat, are arranged in a matrix, for example, in a matrix. It is possible to control the amount of absorbed and generated heat with high accuracy and high response.

The high thermal conductive block 6 is covered with a heat insulating material 9 in order to prevent a temperature change due to a change in the temperature of the surrounding atmosphere or a change in the flow state. The surface is covered with a sealed case 10 made of a heat insulating material in order to prevent a temperature change due to a change in the temperature of the surrounding atmosphere or a flow state.

According to the invention having the structure shown in FIG. 5, since the temperature sensors are not arranged in the sample chamber and the sample flow path, not only the sample 5 having poor chemical activity but also the sample 5 having high chemical activity are provided. However, there is no possibility that the sample 5 reacts with the temperature sensor, the processing of the high thermal conductive block 6 is easy, and the possibility that the temperature sensor contacts the boundary surface between the prism 1 and the sample 5 can be avoided. Measurement can be performed without any problem.

According to the present invention, since the heat exchange between the temperature control element 8 and the sample 5 is performed through the high thermal conductive block 6, the temperature of the sample 5 is higher than that of the conventional example shown in FIG. Can be stabilized at a predetermined temperature in a short time,
The time required for measuring the refractive index can be reduced.

Further, the temperature control element 8 which can control the amount of heat absorption and generation with high accuracy and high responsiveness has a high thermal conductivity block 6.
The temperature of the sample 5 is controlled directly through the interface, so that the accuracy of controlling the temperature of the sample 5 can be improved. In addition, since the periphery of the sample 5 is covered with the high thermal conductive block 6, the temperature of the sample 5 can Be less affected.

Further, the temperature control element 8 and the high thermal conductive block 6
Since the sample temperature is adjusted only by using the above, the refractive index measuring device can be made smaller than before. By the way, in measuring the refractive index, it is necessary to keep the sample temperature strictly constant. However, based on the configuration shown in FIG. 5, the temperature of the high thermal conductive block 6 and the temperature change of the sample chamber 70 with time are shown in a graph. As shown in FIG. 6, the temperature of the high thermal conductive block 6 is a predetermined value. Was reached, it was confirmed that the temperature of the sample chamber 70 continued to rise for a certain period of time even though the temperature of the high thermal conductive block 6 was kept constant. When strictness is not required for the measurement accuracy, this temperature fluctuation can be ignored, but it becomes a problem when high accuracy is required for the measurement.

The present invention has been completed based on the above findings, and provides a refractive index measuring method and apparatus capable of improving the control accuracy of the sample temperature and reducing the size. The purpose is to do.

[0021]

In order to achieve the above object, a method of measuring a refractive index according to the present invention is, for example, as shown in FIG. The sample 5 is connected to the temperature control element 8 via the high heat conductive block 6 covering at least one surface of the prism 1.
Is adjusted, and the temperature T of the high thermal conductive block 6 is adjusted.
b and the temperature T of the space facing the high thermal conductive block 6
Based on r, the output of the temperature control element S is controlled so that the sample temperature Ts becomes constant. More specifically, a high thermal conductive block 6 covering at least one surface of the prism 1, a temperature control element S for controlling the temperature of the high thermal conductive block 6 with the sample 5 placed on the upper surface of the prism 1, A first temperature sensor 12a for detecting a temperature Tb of the high thermal conductive block 6, a second temperature sensor 12b for detecting a temperature Tr of a space facing the high thermal conductive block 6, and the temperature sensors 12a and 12b. Based on the temperature Tb of the high thermal conductive block 6 detected in the above and the temperature Tr of the space facing the high thermal conductive block 6,
And a control circuit 13 for controlling the output of the temperature control element S so that the sample temperature Ts becomes constant.

When the high thermal conductive block 6 is arranged on the upper surface of the prism 1, a sample chamber 70 is provided on the interface between the high thermal conductive block 6 and the prism 1. When a closed case 10 is provided to cover the lower surface of the prism 1, the second temperature sensor 12b is disposed in the closed case 10.

[0023]

The heat (heat absorption, heating) from the temperature control element 8 changes the temperature of the sample 5 through the high thermal conductivity block 6 and is transmitted into the closed case 10 through the prism 1. Here, it is necessary to keep the sample temperature Ts constant,
If there is any law between the temperature Tb of the high thermal conductive block 6, the sample temperature Ts, and the temperature Tr in the closed case 10, the temperature Tb of the high thermal conductive block 6 and the temperature in the closed case 10 will be directly measured. It is possible to control the sample temperature Ts to be constant by the temperature Tr.

As the above-mentioned rule, the fact that Tb−Ts / Ts−Tr = constant holds, and the temperature Tb of the high thermal conductive block 6 is used.
Is controlled in inverse proportion to the temperature Tr in the closed case 10.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and an apparatus for measuring a refractive index according to an embodiment of the present invention will be described below in detail with reference to the drawings.

In the schematic diagram of FIG. 1 and the sectional view of FIG.
Configurations common to the invention described with reference to FIG. 5 will be omitted to avoid duplication. Although FIG. 1 shows that the temperature sensor 12c is provided in the sample chamber 70 similarly to FIG. 5, it is omitted in the embodiment shown in FIG. 2 for the same reason as described above.

As described with reference to FIG. 6, when the temperature of the sample in the sample chamber 70 is controlled so that the output of the temperature sensor 12a is constant, the temperature of the sample rises or falls over time, Conversely, the sample temperature may decrease. In any case, the cause is that the sealed case 1
This is because the temperature within 0 rises (falls) and the amount of heat dissipated from the prism 1 decreases (increases).

Therefore, as shown in FIGS. 1 and 2, in this method and apparatus, in addition to the structure shown in FIG. As shown in the characteristic diagram, both temperature sensors 12a, 12a
The sample temperature Ts in the sample chamber 70 is controlled based on the temperature Tb of the high thermal conductive block 6 detected by b and the temperature Tr in the closed case 10.

That is, assuming that the temperature of the high thermal conductivity block 6 is Tb, the temperature of the sample in the sample chamber 70 is Ts, and the temperature of the closed case is Tr, the principle is that (Tb−Ts) / (Ts−Tr) = constant. Assuming that this holds, the temperature Tb of the high thermal conductive block 6 can be controlled based on the temperature Tr in the closed case 10 so that the sample temperature Ts is constant.

In this embodiment, FIGS. 1 and 2
As shown in FIG. 2, a second temperature sensor 12b for detecting the temperature in the closed case 10 is disposed in a space below the prism 1. In the present invention, the temperature sensor 12b is connected to the prism 1 in the closed case 10. May be detected.

Table 1 below shows the temperature Tb of the high thermal conductivity block 6 detected by the first temperature sensor 12a, the temperature Tr in the closed case detected by the second temperature sensor 12b, and the sample in the above embodiment. The change with time of the sample temperature Ts detected by the temperature sensor 12c inserted into the chamber 70 (not provided for actual refractive index measurement) is described.
In this experiment, it is intended to adjust the sample temperature Ts to 30 ° C.

[0032]

[Table 1]

According to the above Table 1, the temperature Ts of the sample 5 rose from 15.03 ° C. to 29.99 ° C. in less than 9 minutes after the start of heating, and was thereafter kept almost exactly at 29.99 ° C. You can see that it is.

When the temperature Tb of the high thermal conductive block 6 reaches a predetermined temperature and the control of the amount of heat absorption / generation of the temperature control element 8 corresponding to the temperature Tr in the closed case 11 is started, and the sample temperature Ts is It is considered that the delay occurring between the time when the predetermined value is reached and the time when the heat transfer from the high thermal conductive block 6 to the sample 5 is mainly delayed.

Here, the following Table 2 shows a comparison between the case where the output control of the temperature control element 8 is performed by both the first and second temperature sensors 12a and 12b, as shown in FIG. When the output control of the temperature control element 8 is performed only by the temperature Tb of the high thermal conductive block 6 detected by the first temperature sensor 12a, the time elapse of the sample temperature Ts detected by the temperature sensor 12c inserted into the sample chamber 70. Changes are noted. Table 2 below shows the closed case 1 output from the second temperature sensor 12b.
The temperature Tr in 1 is also described.

[0036]

[Table 2]

According to the above Table 2, even if the temperature control element 8 is controlled so that only the temperature Tb of the high thermal conductive block 6 is kept constant, the sample temperature Ts in the sample chamber 70 is maintained.
Becomes about 30 ° C. after 12 minutes, but continues to rise thereafter after the temperature Tb of the high thermal conductive block 6 is constant.

In the above embodiment, the temperature control element 8 may be provided in any one of the lateral sides, the upper side and the lower side of each of the four sides of the high thermal conductive block 6, and the temperature controlling element 8 may be provided in any one of these directions. Although it may be provided in a plurality of directions, in this embodiment, the temperature control element 8 is provided only above the high thermal conductive block 6 in order to simplify the configuration and reduce the cost.

Further, the high heat conductive block 6 to which the heat generated by the temperature control element 8 is transmitted may be exposed to the atmosphere. However, as in the above embodiments, the surface of the high heat conductive block 6 is made of, for example, styrene foam. Covering with a heat insulating material 9 made of resin or the like prevents the temperature of the high thermal conductive block 6 from becoming unstable due to a change in the flow state of the atmosphere or a change in temperature, and thereby prevents the control accuracy of the sample temperature from being impaired. This is advantageous because

In the above description, the high heat conductive block 6
Is described as the upper surface of the prism 1 at the same position as the position of the sample 5 and the sample chamber 70 is provided at the boundary surface of the high thermal conductive block 6 with the prism 1. May of course be arranged on another surface of the prism 1, for example, on the side surface. Although only the case where the second temperature sensor 12b is disposed in the closed case 10 has been described, the second temperature sensor 12b is disposed in a position facing the high heat conductive block 6 without the closed case 10, that is, in an open space. It may be something. Further, in the above description, the sample flow path 7 is provided inside the high thermal conductivity block 6 and the sample is supplied to the sample chamber 70. However, the sample flow path 7 does not necessarily need to be provided in the high thermal conductivity block. .

[0041]

As described above, according to the present invention, the temperature of the high heat conductive block is corrected based on the temperature in the closed case, and the amount of heat absorption and heat generation of the temperature control element is controlled. Since the amount of heat supplied to the sample from the high thermal conductive block and the amount of heat released from the sample to the prism can be balanced in a short time, the temperature of the sample is fixed in a short time and the measurement time is reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a control method according to the present invention.

FIG. 2 is a sectional view of the device of the present invention.

FIG. 3 is a control characteristic diagram of a sample temperature control example of the present invention.

FIG. 4 is a configuration diagram of a conventional example.

FIG. 5 is a configuration diagram of an apparatus to which the present invention is applied.

6 is a control characteristic diagram of sample temperature control of the apparatus shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 prism 3 inclined surface 5 sample 6 high thermal conductive block 7 sample flow path 8 temperature control element 10 closed case 12 (12a, 12b) temperature sensor 13 control circuit 70 sample chamber Tb temperature of high thermal conductive block Ts sample temperature Tr closed case Temperature inside

Claims (4)

(57) [Claims] 1. A method for measuring a refractive index by a total reflection method using a prism (1), wherein a temperature control element (8) is provided through a high thermal conductive block (6) covering at least one surface of the prism (1). The above prism
The temperature of the sample (5) placed on the upper surface of (1) is adjusted, and the temperature (Tb) of the high thermal conductive block (6) and the temperature (Tr) of the space facing the high thermal conductive block (6) are adjusted. Based on the above, the output control of the temperature control element (8) is performed under the condition that (Tb−Ts) / (Ts−Tr) = constant so that the sample temperature (Ts) becomes constant. A method for measuring a refractive index, comprising: 2. A refraction index measuring apparatus by a total reflection method using a prism (1), wherein a high thermal conductive block (6) covering at least one surface of the prism (1) and a sample (5) are arranged on the prism (1). The temperature control element (8) for controlling the temperature of the high thermal conductive block (6) while being placed on the upper surface of the high thermal conductive block (6), and the temperature (T
b) a first temperature sensor (12a), a second temperature sensor (12b) for detecting a temperature (Tr) of a space opposed to the high thermal conductive block (6), and a temperature sensor (12a). ), (12b)
Based on the temperature (Tb) of the high thermal conductive block (6) detected in the above and the temperature (Tr) of the space facing the high thermal conductive block (6), the sample temperature (Ts) is made constant ( Tb-Ts) / (T
a refractive index measurement device comprising: a control circuit (13) for controlling the output of the temperature control element (8) under a condition of s-Tr) = constant. 3. The high thermal conductivity block (6) is a prism.
The refractive index measuring device according to claim 2, wherein the sample chamber (70) is disposed on the upper surface of (1), and a sample chamber (70) is provided at a boundary surface between the high thermal conductive block (6) and the prism (1). 4. The refractive index measuring device according to claim 2, wherein the space facing the high thermal conductive block (6) is a space in a closed case (10) covering a lower surface of the prism (1).