Calibration sample holder, and method for calibrating polarization measuring device employing the same

Abstract

To provide a calibration sample holder that excels in reproducibility of installation angles onto a V-shaped block and enables calibration using a calibration value assigned to each installation angle.SOLUTION: A calibration sample holder 10 comprises a cylindrical holder body 5, and fixing means 8 for fixing a calibration sample 4 that exhibits optical anisotropy on a central axis inside the holder body 5. At least a portion of the outer periphery of the holder body 5 has an outer diameter larger than that of other portions and also has an axisymmetric regular polygonal cross-sectional shape. In addition, in a method for calibrating a polarization measuring device, the calibration sample 4 is fixed so as to be located on the central axis of the cylindrical holder body 5; 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 is disposed along an optical path of polarized light in the polarization measuring device; the holder body 5 is installed at a predetermined installation angle on the V-shaped block such that the center of the optical path of the polarized light coincides with the central axis of the holder body 5; and a polarization characteristic value of the calibration sample 4 is measured.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to calibration of a polarization measuring device.

Background Art

[0002] There are various devices for measuring the polarization characteristics of a sample, but a method that can properly and easily calibrate such a polarization measuring device is required.

[0003] Patent Document 1 discloses a cylindrical liquid cell for use in a polarimeter, which is one of the polarization measuring devices. Since such a cylindrical cell is generally used in a polarimeter, when calibrating the polarimeter, a calibration sample (such as a quartz plate) is attached to a cylindrical holder having the same outer shape as the cylindrical cell, so that the calibration cylindrical holder can be installed in the sample chamber in the same manner as the cylindrical cell.

[0004] Further, Patent Document 2 discloses a cylindrical holder incorporating a calibration quartz plate. The quartz plate in the holder has been previously assigned a value of its optical rotation angle by a high-precision polarimeter. When calibrating a polarimeter using such a cylindrical holder, it is necessary to correctly reproduce the installation angle of the quartz plate during value assignment in order to avoid optical defects of the quartz plate. In Patent Document 2, the shape of the cylindrical holder is utilized so that the cylindrical holder can be installed in the sample chamber of the polarimeter at various angles around its axis. Since the optical rotation angle for each installation angle can be measured, the installation angle closest to the value assignment is found from among them, and calibration is performed at that installation angle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the calibration of the polarization measuring device is not a one-time operation, but is repeatedly performed regularly or as needed. Therefore, when a cylindrical holder as obtained from Patent Document 1 is installed on the V-block in the sample chamber for calibration, the installation angle of the cylindrical holder with respect to the V-block is not determined and changes each time it is installed. Further, although the calibration method disclosed in Patent Document 2 enables measurement at a plurality of installation angles by utilizing the shape of the cylindrical holder, it is necessary to perform measurements at a plurality of installation angles each time calibration is performed and reproduce the installation angle of the quartz plate at the time of value assignment, which is time-consuming. That is, in the content disclosed in Patent Documents 1 and 2, there was room for examination regarding the reproducibility of the installation angle of the calibration sample (quartz plate) fixed to the cylindrical holder.

[0007] An object of the present invention is to provide a calibration sample holder having excellent reproducibility of the installation angle. Further, an object of the present invention is to provide a calibration sample holder in which the installation angle of the calibration sample holder is changed in a plurality of ways, the polarization characteristic values of the calibration sample are measured at each installation angle, and comparison with the polarization characteristic values (also referred to as calibration values herein) pre-assigned for each installation angle is easy. And, an object of the present invention is to provide a calibration method for a polarization measuring device using the same.

Means for Solving the Problems

[0008] That is, the calibration sample holder according to the present invention includes: a cylindrical holder body; fixing means for fixing a calibration sample showing optical anisotropy on the central axis of the holder body inside the holder body, characterized in that at least a part of the outer periphery of the holder body has an outer diameter larger than that of other parts and has a cross-sectional shape of an axisymmetric regular polygon.

[0009] Further, it is preferable that the portions having the cross-sectional shape of the axisymmetric regular polygon are formed at two different positions along the central axis of the holder body.

[0010] Next, the calibration method of the polarization measuring apparatus according to the present invention is as follows: Using a cylindrical holder body having an outer diameter larger than that of other parts at at least a part of the outer periphery and having a cross-sectional shape of an axisymmetric regular polygon at that part, a calibration sample showing optical anisotropy is fixed in the holder body so as to be located on the central axis of the holder body. A V-block having the same opening angle as the angle formed by two sides of the axisymmetric regular polygon is provided along the optical path of the polarized light which is the measurement light of the polarization measuring apparatus. The holder body is installed on the V-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, which is characterized in that.

[0011] Furthermore, by installing the holder body on the V-block at an installation angle different from the predetermined installation angle, it is preferable to measure the polarization characteristic values of the calibration sample at a plurality of installation angles.

Effect of the Invention

[0012] According to the configuration of the calibration sample holder described above, a calibration sample holder with excellent reproducibility of the installation angle on the V-block can be obtained, and the reliability of the analysis result of the polarization measuring apparatus calibrated using this holder is improved. In addition, by setting the same calibration sample at a plurality of installation angles with clear angles, detailed calibration using the calibration values at each of the plurality of installation angles becomes possible, and the reliability of the analysis result of the polarization measuring apparatus is further improved.

[0013] Also, according to the calibration method described above, the installation angle of the calibration sample on the V-block can be executed with good reproducibility. By executing this calibration method, the reliability of the analysis result of the polarization measuring apparatus is improved. In addition, detailed calibration using the calibration values of the calibration sample at a plurality of installation angles with clear angles becomes possible, and a polarization measuring apparatus with excellent reliability of the analysis result can be provided.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the calibration sample holder according to the present invention will be described with reference to the drawings. The calibration sample holder 10 has a spring retainer 1, a coil spring 2, a spacer 3, a calibration sample 4, and a holder body 5 as shown in the exploded view of FIG. 1. Here, the spring retainer 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.

[0016] The calibration sample 4 is an anisotropic optical element, and a scale indicating its anisotropy is defined as a calibration value. For example, the calibration sample 4 for a polarimeter has a specific rotation (α t λ : λ represents wavelength, t represents temperature, and the unit is degrees. ) that is traceable to international standards and is assigned as a calibration value. The shape of the calibration sample 4 is not limited, but generally, it is often disc-shaped, square plate-shaped, or other regular polygon plate-shaped.

[0017] In addition to the calibration sample 4 for measuring specific rotation, the calibration sample holder 10 can also be applied to calibration samples in circular dichroism measurement, linear dichroism measurement, birefringence measurement, polarized light transmission measurement, polarized light reflection measurement, polarized Raman measurement (this refers to the measurement of the polarization direction dependence of Raman scattering intensity), and polarized light microscopy.

[0018] Specific examples of the calibration sample 4 include standard samples such as a polarizing plate and a wavelength retardation plate. A linear polarizing plate, which is one type of polarizing plate, is an optical element in which the vibration direction of the transmitted linearly polarized light is defined. Also, a quarter-wave plate, which is one type of wavelength retardation plate, is an optical element that has two orthogonal principal axes and generates a phase difference of a quarter wavelength in the polarization components in the directions of the respective principal axes.

[0019] Examples of the polarization measuring device to which the calibration sample holder 10 can be applied include a circular dichroism spectrometer, a linear dichroism spectrometer, a birefringence measuring device, an infrared spectrophotometer, a Raman spectrophotometer, an ultraviolet-visible-near-infrared spectrophotometer, and the like.

[0020] The holder body 5 is generally cylindrical and has a through-hole 6 along its central axis. One side of the through-hole 6 is the incident side, and the other side is the exit side. More specifically, along the central axis of the holder body 5, there is a cylindrical portion at the incident-side end, and on the exit side from this, there is a regular octagonal cylindrical portion 5A with an outer diameter larger than that of the cylindrical portion. On the exit side from this regular octagonal cylindrical portion 5A, there is a slightly longer cylindrical portion with the same outer diameter as the cylindrical portion on the incident side. On its exit side, there is again a regular octagonal cylindrical portion 5B, which has the same outer diameter as the regular octagonal cylindrical portion 5A on the incident side and forms the exit-side end. That is, at two locations along the central axis of the holder body 5, regular octagonal cylindrical portions 5A and 5B with an outer shape in which eight planes are arranged along the outer periphery are provided, and both have a regular octagon with the same cross-sectional shape perpendicular to the central axis. Note that the cross-sectional shape is not limited to a regular octagon, and may be a regular polygon cross-sectional shape with an even number of sides of 4 or more, for example, an axisymmetric regular polygon such as a square, a regular hexagon, a regular dodecagon, or a regular hexadecagon.

[0021] Note that on the cylindrical part on the incident side, graduations are engraved at 45-degree intervals along the outer circumference. The numbers "-90", "0", and "90" are engraved beside the graduations corresponding to the respective installation angles. Also, on the cylindrical part between the regular octagonal cylindrical parts 5A and 5B, eight thermometer insertion ports 7 are arranged along the outer circumferential direction. During calibration, a thermometer is inserted into any one of the insertion ports 7 to measure the temperature inside the holder body 5. The insertion ports 7 are formed for each installation angle so that the temperature can be measured almost equivalently regardless of the installation angle of the holder body 5.

[0022] The state where 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 different cross-sectional shapes on the incident side and the exit side. In the example of FIG. 2, on both the incident side and the exit side, the cross-sectional shape of the through-hole 6 is circular, but the inner diameter on the exit side is smaller than that on the incident side. The disc-shaped calibration sample 4, the ring-shaped spacer 3, the coil spring 2, and the spring retainer 1 all have an outer diameter that is approximately the same as the inner diameter of the through-hole 6 on the incident side. These are inserted into the through-hole 6 in order from the incident side. The spring retainer 1 is cylindrical and is screw-in type with respect to the through-hole 6 on the incident side. By screwing in the spring retainer 1, the coil spring 2 is compressed, 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.

[0023] 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, when the outer shape of the calibration sample 4 is not circular but square, the cross-sectional shape of the through-hole 6 on the incident side may also be formed as square.

[0024] Note that the spring retainer 1 is not limited to the screw-in type and may be made of rubber. By fitting the rubber spring retainer 1 into the through-hole 6 on the incident side, the coil spring 2 is compressed and the calibration sample 4 is fixed to the holder 5.

[0025] 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 the present embodiment. Also, with reference to FIGS. 4 and 5, a calibration method using the calibration sample holder 10 will be described.

[0026] (1) For example, the calibration sample holder 10 is installed on the V-block 20 provided in the sample chamber of the polarimeter having the configuration shown in FIG. 6. When the regular octagonal cylindrical portions 5A and 5B are provided, the opening angle of the V-block 20 is set to 90 degrees (see FIG. 5). In addition, in the case of a regular hexagonal cylindrical portion, a V-block 20 having an opening angle corresponding to the shape of the axisymmetric regular polygon, such as setting the opening angle to 60 degrees, is used. Therefore, no matter in which posture the calibration sample holder 10 is installed, the two inclined surfaces of the V-block 20 and the two outer peripheral surfaces (two surfaces intersecting at 90 degrees) of the regular octagonal cylindrical portions 5A and 5B of the holder body 5 are in contact, and the installation angle of the calibration sample 4 in the holder 10 is determined (see FIG. 5).

[0027] (2) After the calibration sample holder 10 is installed on the V-block 20, the graduation at the top is read from the graduation of the incident side cylindrical portion of the holder body 5 and recorded as necessary. In this way, the user can confirm the installation angle of the calibration sample 4 held by the calibration sample holder 10 based on the read value of the graduation. The installation angle in the case of FIG. 4 is 0 degrees. In addition to the method of reading by the user himself / herself, a mechanism may be provided that automatically reads the graduation of the calibration sample holder 10 placed in the sample chamber of the polarimeter using a known method such as image recognition, and records the installation angle of the read calibration sample 4 together with the measured value (optical rotation).

[0028] (3) In order to avoid fluctuations in the optical rotation due to the temperature of the calibration sample 4, the temperature of the calibration sample 4 in the calibration sample holder 10 is maintained at a predetermined temperature using temperature control means (for example, a temperature control device using a Peltier element) installed in the V-shaped block 20, and the polarimeter is operated to measure the optical rotation of the calibration sample 4. Then, the polarimeter is calibrated by comparing the measured value of the optical rotation with the calibration value (optical rotation) previously assigned to the calibration sample 4. The measured temperature value of the calibration sample 4 may be recorded together with the above installation angle and the measured value (optical rotation). In the case of a polarimeter, for example, the spectral line (D line) of a sodium lamp is used as the light source light, and the linearly polarized light extracted from this by the polarizer in front of the sample chamber is guided to the through hole on the incident side of the calibration sample holder 10 installed in the sample chamber, and the optical rotation of the calibration sample 4 can be measured.

[0029] (4) The installation angle of the calibration sample holder 10 is changed, and the optical rotation of the calibration sample 4 at a plurality of installation angles is measured. Then, by comparing the measured value of the optical rotation at each installation angle with the calibration value (optical rotation) for each installation angle assigned to the calibration sample 4, the calibration of the polarimeter can be carried out in detail. For each installation angle, the measured temperature value of the calibration sample 4, the installation angle, and the measured value (optical rotation) may be recorded together.

[0030] In the above calibration method, the calibration sample holder 10 is installed in the V-shaped block 20 in different postures with a 45-degree pitch around its central axis (8 installation angles from -180 degrees to +180 degrees). Therefore, the user can easily reproduce the installation angle of the calibration sample 4 fixed to the holder 10. That is, previously, when calibrating using the same holder 10, the installation angle of the calibration sample 4 is read and recorded based on the scale (angle) of the holder body 5 (or it is stipulated to set it at a certain angle), so that it becomes easy to install the calibration sample 4 at the same installation angle during the next calibration. Alternatively, instead of the same installation angle, it also becomes easy to select a desired posture from different postures with a 45-degree pitch and install the calibration sample 4 at that installation angle.

[0031] In the case of a conventional cylindrical holder, the installation angle of the calibration sample 4 during calibration is often unknown. With the direction of the calibration sample 4 unclear, the installation angle of the cylindrical holder is changed in multiple ways, and the average value or median value of the measured values measured at each installation angle is obtained. Or, if the variation of 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 cannot be obtained during the next calibration. In contrast, as described above, in the holder 10 of the present embodiment, a predetermined installation angle is selected from a plurality of determined installation angles, and the optical rotation of the calibration sample 4 at a setting angle that can be uniquely specified even after calibration can be measured. Therefore, during the next calibration, the installation angle of the calibration sample 4 can be accurately reproduced. As a result, appropriate calibration can be performed on the polarimeter, and the reliability of the analysis results of the polarimeter is improved. In addition, by setting the same calibration sample 4 at a plurality of installation angles with clear angles, detailed calibration using the calibration values pre-assigned to each of the plurality of installation angles becomes possible, and the reliability of the analysis results of the polarization measuring device is further improved.

[0032] In particular, in optical rotation measurement, circular dichroism measurement, linear dichroism measurement, birefringence measurement, polarized light transmission measurement, polarized light reflection measurement, polarized light Raman measurement, polarized light microscopy measurement, etc. for measuring the polarization state of a sample, the installation angle of the sample greatly affects the measurement result. Therefore, the reproducibility of the installation angle of the calibration sample 4 is very important. By using the calibration sample holder 10 of the present embodiment, the reliability of the analysis results of these polarization measuring devices is improved.

[0033] Also, in the case of a conventional cylindrical holder, since it is in line contact with the V-shaped block 20, the contact area between the two is small. In contrast, the holder 10 of the present embodiment is in surface contact with the V-shaped block 20, so the contact area between the two becomes large. For this reason, there are advantages such as improvement of heat transfer efficiency such as temperature control and elimination of the influence of vibration and the like.

[0034] For example, assume a case where a Peltier element is installed in the 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. In this case, for surface contact, it is easier to adjust the temperature of the calibration sample holder.

[0035] Also, when vibrations from outside the apparatus (for example, vibrations generated when a person or an object contacts the apparatus, or vibrations propagated from equipment such as a dehumidifier or a circulating thermostat in the vicinity) are applied to the calibration sample 4 in the holder 10, for surface contact, it is less likely for vibrations to occur in the calibration sample holder 10, and an effect of suppressing vibration generation can be obtained.

[0036] Also, the installation angle of the calibration sample 4 can be easily changed, and in the case of a conventional cylindrical holder, a calibration process that could only be carried out by a complex operation can now be carried out in a simple flow, and more detailed calibration can be carried out within a realistic working time.

[0037] Also, the calibration sample holder 10 of the present embodiment can also be used for polarization measurement of a sample by installing the sample to be measured instead of the calibration sample.

[0038] Finally, a specific example is shown in which detailed calibration becomes possible by setting the calibration sample holder of the present embodiment at a plurality of installation angles and calibrating the polarimeter at each installation angle.

[0039] First, the acceptance criteria are that the measured value of the optical rotation of the standard sample, which is the calibration sample, falls within the following range. Optical rotation of the standard sample ± ([apparatus accuracy] + [expanded uncertainty of the standard sample]) Here, the apparatus accuracy is a value that depends on the performance of the apparatus and is set, for example, to 0.2% of the optical rotation. When the optical rotation of the standard sample is 17.000°, the apparatus accuracy is 17.000 × 0.2% = 0.034°. The expanded uncertainty of the standard sample represents the variation in the value of the specific rotation and is the value described in the calibration certificate of the standard sample (polarization plate). Here, for simplicity of explanation, the expanded uncertainty of the standard sample is set to 0.

[0040] What is used for calibration are a polarimeter, a thermometer (for measuring the temperature of the standard sample), a calibrated standard sample, and the calibration sample holder of this embodiment, a total of four items. The standard sample (polarization plate) is always installed in the calibration sample holder and is not removed from the holder. Therefore, the relationship between the standard sample and the installation angle of the holder is not changed, and "installation angle of the holder = angle of the standard sample". The specific rotation values assigned at a wavelength of 589 nm and the pass criteria at each installation angle are as shown in the following table, for example.

[0041]

Table 1

[0042] The calibration procedures (1) to (5) are shown. (1) Set the calibration sample holder with the built-in standard sample on the polarimeter at an installation angle of 0°. (2) Insert the thermometer into the thermometer insertion port. (3) Check the temperature of the standard sample. When it reaches 20 ± 0.5 °C, measure the specific rotation at a wavelength of 589 nm and record it together with the sample temperature at that time. (4) Correct the measured value of the specific rotation to the specific rotation at a temperature of 20 °C. (5) If the corrected specific rotation is within 17.000 ± 0.034 °, it is considered qualified.

[0043] When the above calibration procedure is performed using a conventional cylindrical holder, since the installation angle of the standard sample (polarization plate) is not determined, among the above pass criteria, the "specific rotation of the standard sample" assigned in advance will have a certain range. As a result, even though the polarimeter should originally pass in terms of performance, the calibration result may be unqualified. On the other hand, if a calibration sample holder having a cross-sectional shape of an axisymmetric regular polygon as in the present 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, not only is it accurate, but since the standard sample can be valued at each angle, the number of information that can be used for calibration for one standard sample can be increased. For example, when the holder is a regular octagon, the device can be calibrated at the installation angle of 0°, and similarly, a total of eight device calibrations can be performed at angles of 45°, 90°, 135°, … every 45°. Although the calibration test is performed at only one installation angle, a more reliable device calibration can be performed by measuring at other installation angles as reference data.

Explanation of Signs

[0044] 1 Spring retainer 2 Coil spring 3 Spacer 4 Calibration sample 5 Holder body 5A, 5B Regular octagonal cylinder part 6 Through hole 7 Thermometer insertion port 8 Fixing means 10 Calibration sample holder 20 V-block

Claims

1. A cylindrical holder body, and fixing means for fixing a calibration sample exhibiting optical anisotropy on the central axis of the holder body inside the holder body, and comprising: A calibration sample holder, characterized in that at least a part of the outer periphery of the holder body has an outer diameter larger than that of other parts and has a cross-sectional shape of an axisymmetric regular polygon.

2. The calibration sample holder according to Claim 1, wherein the part having the cross-sectional shape of the axisymmetric regular polygon is formed at two different positions along the central axis of the holder body, and is a calibration sample holder characterized by this.

3. A method for calibrating a polarization measuring device, comprising: using a cylindrical holder body having an outer diameter larger than that of other parts at least on a part of the outer periphery and having a cross-sectional shape of an axisymmetric regular polygon on this part, and fixing a calibration sample exhibiting optical anisotropy inside the holder body so as to be located on the central axis of the holder body; providing a V-block having an opening angle the same as the angle formed by two sides of the axisymmetric regular polygon along the optical path of the polarized light which is the measurement light of the polarization measuring device; installing the holder body at a predetermined installation angle on the V-block 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, and being a calibration method characterized by this.

4. The calibration method according to Claim 3, wherein further, by installing the holder body on the V-block at an installation angle different from the predetermined installation angle, the polarization characteristic values of the calibration sample at a plurality of installation angles are measured, and being a calibration method characterized by this.

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