JPS6137569B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides, between a light source and a detector, a polarizer that linearly polarizes the light from the light source, and an analyzer whose polarization plane differs by 90 degrees from the polarizer. The present invention also relates to a polarimeter in which a Faraday cell and a sample cell are provided between the polarizer and the analyzer, and the light transmitted through the analyzer is received by a detector to measure the optical rotation of the sample.

By the way, this type of polarimeter includes a mechanical type based on the optical zeroing method and a type based on a purely electrical method.

In the former method, the analyzer is rotatably provided, and the analyzer is rotated so that the detector output is minimized when the light from the light source enters the detector after passing through the sample in the sample cell and the analyzer. The optical rotation angle of the sample is measured from the rotation angle, but this polarimeter involves mechanical rotation of the analyzer, resulting in poor response and, in addition, the mechanism is complex and expensive. In addition, the measurement accuracy depends on the mechanical accuracy of the detector rotation mechanism, and highly accurate measurement results cannot be expected.

In the latter case, an analyzer is fixedly installed, and the light transmitted through the polarizer is rotated by the sample in the sample cell.
The component of light shifted by the optical rotation passes through the analyzer and is received by the detector, and the resulting detector output (an electrical signal corresponding to the amount of light transmitted through the analyzer) becomes minimum (zero in the fundamental wave component). In this method, a current is passed through the Faraday cell, and the angle of rotation of the sample is measured from the value of the current passed through the Faraday cell, taking advantage of the fact that the amount of current is proportional to the angle of rotation of the plane of polarization by the Faraday cell.

This polarimeter uses a purely electrical measurement method that directly processes the detector output without rotating the analyzer, so it has good responsiveness and does not require a complicated rotation mechanism. Although it has advantages, it has the disadvantage that the angle of optical rotation that can be measured is narrow.
This is because the heavy flint glass (FD-6) used as Faraday glass has a small Weerde constant, and considering the size of the Faraday coil on the device and the effect of heat generation due to current, the measurement angle is 0 to ±3°. This is because the limit is the limit. Recently, a Faraday glass (trade name FR-5) with a Weerde constant 3 to 4 times larger than conventional glass has been commercially available, but it has poor temperature stability and optical rotation is based on a purely electrical method that allows measurement of high angles of rotation. The meter has not been put into practical use.

The present invention relates to the improvement of a polarimeter using the latter purely electrical method, although it employs a purely electrical method that has the advantages of good responsiveness and does not require a complicated rotation mechanism. Eliminate the conventional drawbacks,
The purpose of the present invention is to provide a polarimeter capable of high angle measurement.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention. In the figure, 1 is a light source, 2 is a lens, 3 is a monochromating filter that passes only light of a predetermined wavelength, and 4 is a light source 1. A polarizer that linearly polarizes the light of
5 is a Faraday cell equipped with a Faraday glass 5 ₁ and a Faraday coil 5 ₂ . 6 is a sample cell, and 7 is an analyzer. The polarizer 4 and the analyzer 7 are installed so that their planes of polarization are orthogonal to each other. 8 is a detector (e.g. photomal);
9 is a high voltage power supply, 10 is a counter, 11 is a power amplifier, 12 is a current detector, and 13 and 14 are amplifiers. In this embodiment, reflecting mirrors 1 are provided on both sides of the Faraday cell 5 (Faraday glass 5 ₁ ).
The light projected from the light source 1 and passed through the Faraday glass ₅₁ first passes through the reflecting mirror 15.
The light is reflected by the mirror 16, passes through the Faraday glass ₅₁ again, is reflected by the reflecting mirror 16, passes through the Faraday glass ₅₁ again, and is then sent to the sample cell 6 and analyzer 7. It's summery. As mentioned above, the polarizer 4 and analyzer 7 are arranged so that their polarization planes are perpendicular to each other, and when there is no sample in the sample cell 6, the angle of optical rotation is 0°, which is detected by the current detector. The current value of the Faraday cell 5 becomes 0, and the measured angle of optical rotation becomes 0°. When a sample with an optical rotation angle α° enters the sample cell 6, the polarization plane of the light on the analyzer 7 deviates from being orthogonal to the polarization plane of the analyzer 7 by α°, and the detector 8 detects this deviation. Then, a current automatically flows to the Faraday coil ₅₂ via the counter 10 and the power amplifier 11 so that the output of the detector 8 becomes 0, rotates the polarization plane of the light by -α°, and the analyzer 7 The polarization plane of the light becomes perpendicular to the polarizer 4 again. Incidentally, since the value of the current flowing through the Faraday coil ₅₂ and the rotation angle of the polarization plane of light are in a proportional relationship, the larger the angle of optical rotation of the sample is, the larger the value of the current flowing through the Faraday coil ₅₂ needs to be. However, as the current value increases, heat generation increases, so there is naturally a limit to the current value that can be passed. Furthermore, if the number of turns of the Faraday coil is increased or the length of the Faraday glass is increased, the angle that can be measured can be increased proportionally, but the size of the device is also naturally limited. However, in the above-mentioned embodiment, the measurement light passes through the same Faraday glass ₅₁ multiple times, so the current value is correspondingly smaller to measure the same angle of optical rotation as the conventional one using a Faraday cell of the same size as the conventional one. (In the case of Fig. 1, 1/3 of the conventional current value is sufficient.) Also, if a Faraday cell of the same size as the conventional one is used and the current value is the same as the conventional one, the optical rotation angle will be higher (3 in the case of Fig. 1).
This means that it is possible to perform measurements of
In the embodiment described above, the reflectors 15 and 16 were installed on both sides of the Faraday cell 5 so that the light passed through the same Faraday glass ₅₁ three times in total.
As shown in FIG. 2, a reflecting mirror 15 is provided only on one side of the Faraday cell 5 (the side opposite to the light source 1),
The light may pass through the same Faraday glass ₅₁ twice. (In this case, the sample cell 6, analyzer 7, etc. are placed on the light source side.)Although not shown, by appropriately selecting the size and angle of the reflecting surface of the reflecting mirror, the number of reflecting mirrors, etc. The number of times that light passes through the same Faraday glass can be varied.

Since the present invention has the above-mentioned configuration, it has good responsiveness, does not require a complicated rotating mechanism, and the measurement accuracy does not depend on the mechanical accuracy of the rotating mechanism, making it possible to perform high-precision measurements. Not only does it have the advantages of a conventional method, but it also greatly expands the measurement angle limit, which has traditionally been the biggest problem with this type of method, and has a simple structure that enables high-angle measurements without increasing the size of the device. This has been made possible and the practical effects are truly great.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing the main parts of another embodiment of the present invention. 1... Light source, 4... Polarizer, 5... Faraday cell, 5 ₁ ... Faraday glass, 6... Sample cell, 7... Analyzer, 8... Detector, 15, 16...
…Reflector.

Claims (1)

[Claims] 1. A polarizer that linearly polarizes the light from the light source, an analyzer fixedly provided between the light source and the detector so that the plane of polarization differs by 90 degrees from the polarizer, and these polarizers. , comprising a Faraday cell and a sample cell located between the analyzers, the light transmitted through the polarizer is optically rotated by the sample in the sample cell, and the component of light that is deviated by the optical rotation is transmitted through the analyzer and detected. A current is passed through the Faraday cell so that the light is received by the Faraday cell, and the resulting detector output is minimized.Using the fact that the amount of current is proportional to the angle of rotation of the plane of polarization by the Faraday cell, the value of the current flowing through the Faraday cell is calculated. A polarimeter configured to measure the angle of optical rotation of a sample from the angle of rotation of the sample, wherein a reflecting mirror is provided on at least one side of the Faraday cell opposite to the light source, and the light is reflected by the reflecting mirror,
A polarimeter characterized in that light is configured to pass through the same Faraday glass in a Faraday cell multiple times.