JP7602294B1 - Calibration sample holder and method for calibrating polarization measurement device using the same - Google Patents

Abstract

To provide a calibration sample holder that has excellent reproducibility of the installation angle on a V-shaped block and enables calibration using a calibration value assigned for each installation angle.
[Solution] A calibration sample holder 10 includes a cylindrical holder body 5 and a fixing means 8 for fixing a calibration sample 4 exhibiting optical anisotropy on the central axis inside the holder body 5, and at least a portion of the outer periphery of the holder body 5 has an outer diameter larger than other portions and has an axisymmetric regular polygonal cross section. A method for calibrating a polarization measurement device includes fixing the calibration sample 4 so that it is located on the central axis of the cylindrical holder body 5, providing a V-shaped block having the same opening angle as the angle formed by two sides of the axisymmetric regular polygon of the holder body 5 along the optical path of polarized light of the polarization measurement device, and installing the holder body 5 at a predetermined installation angle on the V-shaped block so that the center of the optical path of polarized light coincides with the central axis of the holder body 5, and measuring the polarization characteristic value of the calibration sample 4.
[Selected Figure] Figure 1

Description

The present invention relates to the calibration of a polarization measurement device.

There are various devices available for measuring the polarization properties of samples, but there is a need for a method to properly and easily calibrate such polarization measurement devices.

Patent Document 1 discloses a cylindrical liquid cell for use in a polarimeter, which is a type of polarization measurement device. Since such cylindrical cells are commonly used in polarimeters, when calibrating a polarimeter, a cylindrical holder for calibration can be placed in the sample chamber in the same way as a cylindrical cell by attaching a calibration sample (such as a quartz plate) to a cylindrical holder with the same external shape as the cylindrical cell.

Patent Document 2 also discloses a cylindrical holder that incorporates a quartz plate for calibration. The quartz plate inside the holder has its angle of rotation valued in advance by a high-precision polarimeter. When using such a cylindrical holder to calibrate the polarimeter, it is necessary to accurately reproduce the installation angle of the quartz plate at the time of valuation in order to avoid optical defects that the quartz plate has. In Patent Document 2, the shape of the cylindrical holder is utilized to enable the cylindrical holder to be installed in the polarimeter's sample chamber at various angles around its axis. Since the angle of rotation for each installation angle can be measured, the installation angle that is closest to the value is found from these, and calibration is performed at that installation angle.

JP 2007-33460 A International Publication No. 2017/108034

However, the calibration of the polarization measuring device is not performed only once, but is performed periodically or repeatedly as necessary. Therefore, when performing calibration by placing a cylindrical holder such as that obtained from Patent Document 1 in a V-shaped block of a sample chamber, the installation angle of the cylindrical holder with respect to the V-shaped block is not fixed and changes each time it is installed. In addition, although the calibration method shown in Patent Document 2 makes it easy to perform measurements at multiple installation angles by using the shape of the cylindrical holder, it is necessary to perform measurements at multiple installation angles each time calibration is performed to reproduce the installation angle of the quartz plate at the time of pricing, which is time-consuming. In other words, the contents shown in Patent Documents 1 and 2 left room for consideration regarding the reproducibility of the installation angle of the calibration sample (quartz plate) fixed to the cylindrical holder.

The object of the present invention is to provide a calibration sample holder with excellent reproducibility of the installation angle. It is also to provide a calibration sample holder that can be easily compared with the polarization characteristic values (also called calibration values here) that have been assigned in advance for each installation angle by changing the installation angle of the calibration sample holder in multiple ways and measuring the polarization characteristic values of the calibration sample at each installation angle. It is also to provide a method for calibrating a polarization measurement device using the same.

That is, the calibration sample holder according to the present invention is
A cylindrical holder body;
a fixing means for fixing a calibration sample exhibiting optical anisotropy on a central axis of the holder body inside the holder body;
The calibration sample;
A calibration sample holder for a polarimetry apparatus comprising :
At least a portion of the outer periphery of the holder body has an outer diameter larger than other portions and has an axisymmetric regular polygonal cross section,
the holder body is configured to be installable on a V-shaped block provided on the polarization measurement device such that the center of the polarized light path of the polarization measurement device and the central axis of the holder body coincide with each other, wherein the V-shaped block has an opening angle equal to an angle formed by two sides of the axisymmetric regular polygon, and the holder body is configured to be installable on the V-shaped block at a plurality of installation angles;
The calibration sample is characterized in that a calibration value is assigned to each of the installation angles of the holder body .

It is also preferable that the portion having the cross-sectional shape of the axisymmetric regular polygon is formed at two different locations along the central axis of the holder body.

Next, a method for calibrating a polarization measuring device according to the present invention includes the steps of:
Using a cylindrical holder body having an outer diameter larger than that of at least one portion of the outer periphery and having an axisymmetric regular polygonal cross-sectional shape in at least one portion of the outer periphery, and using a calibration sample exhibiting optical anisotropy fixed in the holder body so as to be positioned on the central axis of the holder body,
a V-shaped block having an opening angle equal to the angle formed by two sides of the axially symmetric regular polygon is provided along an optical path of the polarized light that is the measurement light of the polarization measurement device;
The holder body is installed on the V-shaped block at a predetermined installation angle so that the center of the optical path of the polarized light coincides with the central axis of the holder body;
measuring the polarization characteristic value of the calibration sample ;
The holder body is configured to be able to be installed on the V-block at a plurality of installation angles, the calibration sample is assigned a calibration value for each installation angle of the holder body, and the measured polarization characteristic value is compared with the calibration value corresponding to the specified installation angle .

Furthermore, it is preferable to measure the polarization characteristic values of the calibration sample at multiple installation angles by installing the holder body on the V-block at an installation angle different from the predetermined installation angle.

The above calibration sample holder configuration provides a calibration sample holder with excellent reproducibility of the installation angle on the V-block, improving the reliability of the analysis results of a polarimetry device calibrated using this holder. In addition, setting the same calibration sample at multiple installation angles with clear angles enables detailed calibration using the calibration values for each of the multiple installation angles, further improving the reliability of the analysis results of the polarimetry device.

Furthermore, according to the above calibration method, the installation angle of the calibration sample on the V-shaped block can be accurately reproduced, and by carrying out this calibration method, the reliability of the analysis results of the polarization measurement device is improved. In addition, detailed calibration is possible using the calibration values of the calibration sample at multiple installation angles with clear angles, making it possible to provide a polarization measurement device with excellent reliability of analysis results.

FIG. 2 is an exploded view of a calibration sample holder according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the calibration sample holder. 6A to 6F are six-sided views of the calibration sample holder. FIG. 2 is a perspective view showing an example of use of the calibration sample holder. FIG. 2 is a side view of the entrance side showing an example of use of the calibration sample holder. FIG. 2 is a diagram showing an apparatus configuration when calibrating a polarimeter using the calibration sample holder.

The following describes an embodiment of the calibration sample holder according to the present invention with reference to the drawings. As shown in the exploded view of FIG. 1, the calibration sample holder 10 has a spring holder 1, a coil spring 2, a spacer 3, a calibration sample 4, and a holder body 5. Here, the spring holder 1, the coil spring 2, and the spacer 3 constitute a fixing means 8 for fixing the calibration sample 4 to the holder body 5.

The calibration sample 4 is an anisotropic optical element, and a scale indicating the anisotropy is defined as a calibration value. For example, the calibration sample 4 for a polarimeter is given an optical rotation (α ^t _λ : λ indicates wavelength, t indicates temperature, and the unit is angle) that is traceable to an international standard as a calibration value. The shape of the calibration sample 4 is not limited, but is generally a disk, a square plate, or other regular polygonal plate.

In addition to the calibration sample 4 for optical rotation measurements, the calibration sample holder 10 can also be used for calibration samples in circular dichroism measurements, linear dichroism measurements, birefringence measurements, polarized transmission measurements, polarized reflection measurements, polarized Raman measurements (which refers to the measurement of the polarization direction dependence of Raman scattering intensity), and polarized light microscopy measurements.

Specific examples of the calibration sample 4 include standard specimens such as a polarizing plate and a wavelength phase plate. A linear polarizing plate, which is one type of polarizing plate, is an optical element in which the vibration direction of the linearly polarized light that passes through it is fixed. A quarter-wave plate, which is one type of wavelength phase plate, is an optical element that has orthogonal principal axes and generates a phase difference of a quarter wavelength in the polarized light components in the directions of the respective principal axes.

In addition, examples of polarization measurement devices to which the calibration sample holder 10 can be applied include circular dichroism spectrometers, linear dichroism spectrometers, birefringence measurement devices, infrared spectrophotometers, Raman spectrophotometers, and ultraviolet-visible-near-infrared spectrophotometers.

The holder body 5 is generally cylindrical and has a through hole 6 along its central axis. One of the through holes 6 is the incident side, and the other is the exit side. In detail, the shape along the central axis of the holder body 5 has a cylindrical portion at the end of the incident side, and a regular octagonal tube portion 5A with a larger outer diameter than the cylindrical portion on the exit side. A slightly longer cylindrical portion is located on the exit side of this regular octagonal tube portion 5A, and has the same outer diameter as the cylindrical portion on the incident side. On the exit side, there is again a regular octagonal tube portion 5B, which has the same outer diameter as the regular octagonal tube portion 5A on the incident side and forms the end of the exit side. In other words, at two locations along the central axis of the holder body 5, regular octagonal tube portions 5A and 5B with an outer shape in which eight planes are lined up along the outer periphery are provided, and both have a regular octagon of the same size in cross section perpendicular to the central axis. The cross-sectional shape is not limited to a regular octagon, but may be any regular polygon with an even number of sides of four or more, such as a square, regular hexagon, regular dodecagon, or regular hexagon.

The cylindrical part on the entrance side has markings at 45-degree intervals along the outer circumference. The numbers "-90", "0", and "90" degrees are marked next to the markings corresponding to each installation angle. Furthermore, eight thermometer sockets 7 are lined up along the outer circumference of the cylindrical part between the regular octagonal tube parts 5A and 5B. During calibration, a thermometer is inserted into one of the sockets 7 to measure the temperature inside the holder body 5. A socket 7 is formed for each installation angle so that measurements can be made approximately equally regardless of the installation angle of the holder body 5.

The state in which the calibration sample 4 is attached to the calibration sample holder 10 is shown in the cross-sectional view of FIG. 2. As shown in FIG. 2, the through-hole 6 of the holder body 5 has a different cross-sectional shape on the entrance side and the exit side. In the example of FIG. 2, the cross-sectional shape of the through-hole 6 is circular on both the entrance side and the exit side, but the inner diameter of the exit side is smaller than that of the entrance side. The disk-shaped calibration sample 4, the ring-shaped spacer 3, the coil spring 2, and the spring holder 1 all have an outer diameter that is approximately the same as the inner diameter of the through-hole 6 on the entrance side. These are inserted in order from the entrance side into the through-hole 6. The spring holder 1 is cylindrical and is screwed into the through-hole 6 on the entrance side. By screwing the spring holder 1, the coil spring 2 is compressed, and the biasing force of the coil spring 2 acts on the calibration sample 4 via the spacer 3, and the calibration sample 4 is fixed to the holder 5.

Here, the cross-sectional shape of the through hole 6 on the incident side may be determined according to the shape of the calibration sample 4. For example, if the external shape of the calibration sample 4 is not circular but rectangular, the cross-sectional shape of the through hole 6 on the incident side may also be formed to be rectangular.

The spring holder 1 is not limited to the screw-in type, but may be made of rubber. By fitting the rubber spring holder 1 into the through-hole 6 on the entrance side, the coil spring 2 is compressed, and the calibration sample 4 is fixed to the holder 5.

Figures 3(A) to (F) show six views (front view, plan view, bottom view, rear view, right side view, and left side view) of the calibration sample holder 10 of this embodiment. In addition, a calibration method using the calibration sample holder 10 will be explained using Figures 4 and 5.

(1) For example, the calibration sample holder 10 is placed in a V-shaped block 20 provided in the sample chamber of a polarimeter having the configuration shown in FIG. 6. In the case of regular octagonal cylinders 5A and 5B, the opening angle of the V-shaped block 20 is set to 90 degrees (see FIG. 5). In the case of a regular hexagonal cylinder, the opening angle is set to 60 degrees, and other V-shaped blocks 20 having opening angles according to the shape of an axisymmetric regular polygon are used. Therefore, regardless of the orientation in which the calibration sample holder 10 is placed, the two inclined surfaces of the V-shaped block 20 come into contact with the two outer faces (two faces intersecting at 90 degrees) of the regular octagonal cylinders 5A and 5B of the holder body 5, and the installation angle of the calibration sample 4 in the holder 10 is determined (see FIG. 5).

(2) After placing the calibration sample holder 10 on the V-shaped block 20, read the topmost scale from the scales on the entrance side cylindrical part of the holder body 5 and record it as necessary. In this way, the user can confirm the installation angle of the calibration sample 4 held in the calibration sample holder 10 based on the scale reading. In the case of Figure 4, the installation angle is 0 degrees. In addition to the method in which the user reads it himself, a mechanism may be provided in which the polarimeter automatically reads the scale of the calibration sample holder 10 placed in the sample chamber using a known method such as image recognition, and the read installation angle of the calibration sample 4 is recorded together with the measured value (angle of rotation).

(3) In order to avoid fluctuations in the angle of rotation due to the temperature of the calibration sample 4, a temperature control means (e.g., a temperature control device using a Peltier element) installed in the V-shaped block 20 is used to maintain the temperature of the calibration sample 4 in the calibration sample holder 10 at a predetermined temperature, and the polarimeter is operated to measure the angle of rotation of the calibration sample 4. The polarimeter is then calibrated by comparing the measured value of the angle of rotation with a calibration value (angle of rotation) previously assigned to the calibration sample 4. The measured temperature value of the calibration sample 4 may be recorded together with the above-mentioned installation angle and measured value (angle of rotation).
In the case of a polarimeter, for example, the emission line (D line) of a sodium lamp is used as the light source light, and the linearly polarized light extracted from this by a polarizer in front of the sample chamber is guided to the through hole on the entrance side of the calibration sample holder 10 installed in the sample chamber, thereby measuring the optical rotation of the calibration sample 4.

(4) The installation angle of the calibration sample holder 10 is changed and the angle of rotation of the calibration sample 4 is measured at multiple installation angles. Then, by comparing the measured angle of rotation at each installation angle with the calibration value (angle of rotation) for each installation angle assigned to the calibration sample 4, detailed calibration of the polarimeter can be performed. Note that the temperature measurement value, installation angle, and measurement value (angle of rotation) of the calibration sample 4 may also be recorded for each installation angle.

In the above calibration method, the calibration sample holder 10 is installed on the V-shaped block 20 in different orientations (eight installation angles from -180 degrees to +180 degrees) at 45-degree intervals around its central axis. This allows the user to easily reproduce the installation angle of the calibration sample 4 fixed to the holder 10. In other words, when previously calibrating using the same holder 10, the installation angle of the calibration sample 4 is read and recorded based on the scale (angle) on the holder body 5 (or is specified to be a constant angle), making it easy to install the calibration sample 4 at the same installation angle during the next calibration. Alternatively, instead of the same installation angle, it is also easy to select a desired orientation from different orientations at 45-degree intervals and install the calibration sample 4 at that installation angle.

In the conventional cylindrical holder, the installation angle of the calibration sample 4 at the time of calibration is often unknown. Without a clear direction of the calibration sample 4, the installation angle of the cylindrical holder is changed in multiple ways, and the average or median of the measured values measured at each installation angle is obtained. Alternatively, if the variation in the measured values at multiple installation angles is within a predetermined range, the representative value is obtained. The value obtained in this way is compared with the calibration value of the calibration sample 4, and the reproducibility of the installation angle of the calibration sample 4 at the next calibration is not obtained. In contrast, as described above, in the holder 10 of this embodiment, a predetermined installation angle is selected from multiple determined installation angles, and the optical rotation of the calibration sample 4 at a set angle that can be uniquely specified even after calibration can be measured, so that the installation angle of the calibration sample 4 can be accurately reproduced at the next calibration. Therefore, the polarimeter can be properly calibrated, and the reliability of the analysis results of the polarimeter is improved. In addition, by setting the same calibration sample 4 at multiple installation angles with clear angles, detailed calibration is possible using calibration values that are pre-assigned to each of the multiple installation angles, further improving the reliability of the analysis results of the polarization measurement device.

In particular, in optical rotation measurements, circular dichroism measurements, linear dichroism measurements, birefringence measurements, polarized transmission measurements, polarized reflection measurements, polarized Raman measurements, polarized microscopy measurements, and other measurements that measure the polarization state of a sample, the sample installation angle significantly affects the measurement results, so the reproducibility of the installation angle of the calibration sample 4 is extremely important, and by using the calibration sample holder 10 of this embodiment, the reliability of the analysis results of these polarization measurement devices is improved.

In addition, conventional cylindrical holders make line contact with the V-shaped block 20, resulting in a small contact area between the two. In contrast, the holder 10 of this embodiment makes surface contact with the V-shaped block 20, resulting in a larger contact area between the two. This has the advantage of improving the efficiency of heat transfer for temperature control and eliminating the effects of vibration, etc.

For example, if a Peltier element is installed in a V-shaped block 20 and the temperature of the calibration sample 4 in the calibration sample holder is controlled via the V-shaped block 20, surface contact makes it easier to adjust the temperature of the calibration sample holder.

In addition, even when the calibration sample 4 in the holder 10 is subjected to vibrations from outside the device (for example, vibrations caused by a person or object touching the device, or vibrations transmitted from nearby equipment such as a dehumidifier or circulating thermostatic bath), surface contact makes it less likely that vibrations will occur in the calibration sample holder 10, and the effect of suppressing the generation of vibrations is achieved.

In addition, the installation angle of the calibration sample 4 can now be easily changed, and the calibration process, which could only be carried out through complex operations with conventional cylindrical holders, can now be carried out with a simplified flow, making it possible to carry out more detailed calibration within a realistic work time.

The calibration sample holder 10 of this embodiment can also be used to measure the polarization of a sample by placing a sample, which is the object to be measured, instead of a calibration sample.

Finally, we will provide a concrete example showing how detailed calibration is possible by setting the calibration sample holder of this embodiment at multiple installation angles and calibrating the polarimeter at each installation angle.

First, the pass criterion is that the measured value of the optical rotation of the standard specimen, which is the calibration sample, falls within the following range.
Optical rotation of standard sample ± ([instrument accuracy] + [expanded uncertainty of standard sample])
Here, the instrument accuracy is a value that depends on the performance of the instrument, and is set, for example, to 0.2% of the optical rotation. If the optical rotation of the standard sample is 17.000°, the instrument accuracy is 17.000×0.2%＝0.034°.
The expanded uncertainty of the standard specimen represents the variation in the value of the optical rotation, and is the value stated in the calibration certificate of the standard specimen (optical rotation plate). For the sake of simplicity, the expanded uncertainty of the standard specimen is set to 0.

The four items used for the calibration are a polarimeter, a thermometer (for measuring the temperature of the standard sample), a valued standard sample, and the calibration sample holder of this embodiment.
The standard sample (optical rotatory plate) is always installed in the calibration sample holder and is never removed from the holder. Therefore, the relationship between the installation angle of the standard sample and the holder does not change, and the "installation angle of the holder = the angle of the standard sample". The optical rotation value at a wavelength of 589 nm and the pass criteria for each installation angle are, for example, as shown in the table below.

The calibration steps (1) to (5) are shown below.
(1) Set the calibration sample holder containing the standard sample on the polarimeter at an installation angle of 0°.
(2) Insert the thermometer into the thermometer socket.
(3) Check the temperature of the standard sample, and when it reaches 20±0.5°C, measure the optical rotation at a wavelength of 589 nm and record it along with the sample temperature at that time.
(4) Correct the measured value of the optical rotation to the optical rotation at a temperature of 20°C.
(5) If the corrected angle of rotation is within 17.000±0.034°, it is considered to pass.

When the above calibration procedure is performed using a conventional cylindrical holder, the installation angle of the standard sample (optical rotation plate) is not fixed, so the "angle of rotation of the standard sample" that is pre-specified among the above pass criteria has a certain range. As a result, even if the polarimeter's performance should have resulted in a pass, the calibration result may fail.
In contrast, if a calibration sample holder having an axisymmetric regular polygonal cross section as in this embodiment is used, the installation angle of the standard sample is determined, so that the performance of the polarimeter is correctly reflected in the calibration result. Furthermore, since it is not only accurate but also possible to value the standard sample at each angle, the amount of information available for calibration for one standard sample can be increased. For example, when the holder is a regular octagon, device calibration is possible at an installation angle of 0°, and similarly, device calibration can be performed in a total of eight ways at angles of 45° each, such as 45°, 90°, 135°, .... Although the calibration test is performed at only one installation angle, more reliable device calibration can be performed by performing measurements at other installation angles as reference data.

REFERENCE SIGNS LIST 1 Spring holder 2 Coil spring 3 Spacer 4 Calibration sample 5 Holder body 5A, 5B Regular octagonal cylinder 6 Through hole 7 Thermometer insertion port 8 Fixing means 10 Calibration sample holder 20 V-shaped block

Claims (4)

A cylindrical holder body;
a fixing means for fixing a calibration sample exhibiting optical anisotropy on a central axis of the holder body inside the holder body;
The calibration sample;
A calibration sample holder for a polarimetry apparatus comprising :
At least a portion of the outer periphery of the holder body has an outer diameter larger than other portions and has an axisymmetric regular polygonal cross section,
the holder body is configured to be installable on a V-shaped block provided on the polarization measurement device such that the center of the polarized light path of the polarization measurement device and the central axis of the holder body coincide with each other, wherein the V-shaped block has an opening angle equal to an angle formed by two sides of the axisymmetric regular polygon, and the holder body is configured to be installable on the V-shaped block at a plurality of installation angles;
A calibration sample holder, characterized in that the calibration sample is assigned a calibration value for each of the installation angles of the holder body . 2. The calibration sample holder of claim 1,
A calibration sample holder, characterized in that the portion having an axisymmetric regular polygonal cross-sectional shape is formed at two different locations along the central axis of the holder body. 1. A method for calibrating a polarimetry device, comprising:
Using a cylindrical holder body having an outer diameter larger than that of at least one portion of the outer periphery and having an axisymmetric regular polygonal cross-sectional shape in at least one portion of the outer periphery, and using a calibration sample exhibiting optical anisotropy fixed in the holder body so as to be positioned on the central axis of the holder body,
a V-shaped block having an opening angle equal to the angle formed by two sides of the axially symmetric regular polygon is provided along an optical path of the polarized light that is the measurement light of the polarization measurement device;
The holder body is installed on the V-shaped block at a predetermined installation angle so that the center of the optical path of the polarized light coincides with the central axis of the holder body;
measuring the polarization characteristic value of the calibration sample ;
The holder body is configured to be able to be installed on the V-block at a plurality of installation angles, the calibration sample is assigned a calibration value for each installation angle of the holder body, and the measured polarization characteristic value is compared with the calibration value corresponding to the specified installation angle . 4. The calibration method according to claim 3,
The calibration method further comprises measuring the polarization characteristic values of the calibration sample at a plurality of installation angles by installing the holder body on the V-block at an installation angle different from the specified installation angle.

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