JPH0587767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polarizer that plane-polarizes light from the light source and an analyzer that faces the polarizer between a light source and a detector. One of the analyzers is configured to be rotatably driven via a worm and a worm wheel, and an alternating current is applied between the polarizer and the analyzer to vibrate plane polarized light from the polarizer, and a Faraday cell and a sample. and a control unit that controls the amount of rotational drive of the polarizer or analyzer based on the output signal from the detector, and a control unit that controls the amount of rotational drive of the polarizer or analyzer based on the amount of rotational drive controlled by the control unit. The present invention relates to a polarimeter comprising a computer that calculates and displays the angle of rotation of the light.

The above polarimeter is called a mechanical polarimeter using the optical zeroing method, and generally uses a worm and a worm wheel to mechanically rotate the analyzer. curves,
Eccentricity of the worm or worm wheel, etc.
Due to machining precision, etc., the rotation angle of the worm wheel is always constant for each rotation of the worm, but the rotation angle of the worm wheel during one rotation of the worm tends to change sequentially. , the correlation between the rotation angle of the worm and the worm wheel deviates from the theoretical straight line, and the error is about ±0.002°, which is considered to be the limit of measurement accuracy in conventional polarimeters of this type. There is.

The present invention has been made in view of the above circumstances, and its purpose is to achieve a very simple structure by effectively utilizing the Faraday cell and computer originally provided in this type of polarimeter. The objective is to achieve a dramatic improvement in the measurement accuracy of the angle of optical rotation, even though it is only an improvement.

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

Figure 1 is a schematic diagram showing the outline of the entire polarimeter, in which 1 is a light source such as a sodium lamp, 2 is a lens,
3 is a monochromatic filter that passes only light of a predetermined wavelength; 4
is a polarizer that plane-polarizes the light from the light source 1.
Reference numeral 5 denotes an analyzer, which is disposed opposite to the polarizer 4 and configured to be rotationally driven by a worm 7 and a worm wheel 8 that are interlocked with a stepping motor 6. A Faraday cell 9 and a sample cell 10 are located between the polarizer 4 and the analyzer 5, and behind the analyzer 5, a detector 11, such as a photomultiplier, is provided.

A is a control unit that rotates the analyzer 5 according to the optical rotation angle of the sample in the sample cell 10, and controls the coil 12 of the Faraday cell 9.
An oscillator 14 is connected via a power amplifier 13, the detector 11 is connected to a high voltage power source 15, the detector 11 is connected to a synchronous rectifier 17 via an amplifier 16, and the rectifier 17 has a connecting the oscillator 14 and the synchronous rectifier 17;
, V/F converter (or A/D converter)
(not shown), a motor controller 19 is connected via a counter 18 that counts the number of pulses from the motor controller 19, and this motor controller 19 is connected to the stepping motor 6. After the light from 1 passes through a lens 2 and a filter 3 and is plane-polarized by a polarizer 4, it reaches a Faraday cell 9, and a coil 12 of the Faraday cell 9 receives a modulated signal by an oscillator 14. Since an alternating current is flowing,
The plane of polarization is vibrated, the light passes through the sample in the sample cell 10 and the analyzer 5, and is received by the detector 11. Then, the output signal from the detector 11 is input to the synchronous rectifier 17, where it is rectified by the synchronous signal from the oscillator 14, and further,
The V/F converter (or A/D converter) outputs a pulse signal based on a voltage according to the optical rotation angle and optical rotation direction of the sample, and the pulse signal is counted by the counter 18, and the pulse signal is output according to the number of counts. A motor control 19 and a stepping motor 6 are used to drive the rotation.

20 is a computer that calculates and displays the optical rotation direction and optical rotation angle of the sample based on the amount of rotation control of the analyzer 5 by the control unit A, in other words, based on the count number of the pulse signal measured by the counter 18. .

Next, B is a DC current circuit from the computer 20, which is provided with an amplifier 21 and is connected between the power amplifier 13 and the oscillator 14.

When a direct current is passed through the coil 12 of the Faraday cell 9, the plane polarized light passing through the Faraday cell 9 rotates in one direction, and the correlation between the angle of optical rotation and the value of the current passed through the Faraday cell 9 is very excellent. Based on this, the mechanical error due to the worm 7 and the worm wheel 8 is measured, and the measurement error is calculated and stored in the computer 20, and then the actual sample is measured. When displaying the optical rotation angle, the calculated display value of the optical rotation angle is automatically corrected using the error as a correction coefficient.

To store the mechanical error in the computer 20, it is assumed that, for example, one rotation of the worm 7 causes the worm wheel 8 to rotate by 1 degree. In other words, one rotation of the worm 7 causes an optical rotation angle of 1 degree. is detected, and when a current of 1A is passed through the coil 12 of the Faraday cell 9, the plane polarized light is rotated by 1° in the Faraday cell 9, and the DC current is increased until the current value reaches 1A. is changed over time and sent to Faraday cell 9.

The current value at this time and the actually measured value of the rotation angle of the worm wheel 8 are plotted. Therefore, if the mechanical error were completely zero, a straight line indicated by a in Fig. 2 would be drawn, but this straight line a
is the same as the theoretical value, and in reality, it causes an error of about ±0.002 at most with respect to the theoretical straight line A. For example, the second
A curve close to a straight line as shown by b in the figure is drawn, and the difference between the measured value and the theoretical value is a mechanical error, and this error is calculated and stored in the computer 20.

When measuring the angle of optical rotation of the sample, an alternating current is applied to the Faraday cell 9 instead of a direct current, and the computer 20 calculates the actual measured value of the angle of optical rotation from the control unit A and the error to establish a linear relationship. The computer 20 displays the angle of optical rotation corrected so as to

The above correction is for each rotation of the worm 7, and the angle that can be rotated by direct current in the Faraday cell 9 is generally about 2 degrees, and the correction for each rotation of the worm 7 is considered to be the limit. However, for example, if the sample cell 10 has an optical rotation
By supplying samples of 1°, 2°, 3°, etc., it is possible to make corrections per several revolutions of the worm 7, and according to experiments, the mechanical correction for each revolution when the worm 7 is rotated multiple times is possible. The correlation of errors differs for each model, but is almost similar for the same model, and from this point of view, it can be said that just storing the error per revolution of the worm 7 is enough to perform the correction.

In addition, when measuring the optical rotation angle of the sample, an alternating current from the oscillator 14 and a correction direct current stored in the computer 20 are passed through the Faraday cell 9,
It is also possible to automatically correct the rotation of the motor 6 by controlling the DC current; in this case, the signal from the counter 18 itself has already been corrected, and the computer 20 will display the angle of optical rotation.

Furthermore, the mechanical error may be stored in the computer 20 prior to each measurement of the angle of rotation or for each engine, but it may be performed only once after assembly of the angle of rotation or after maintenance such as parts replacement. That alone is enough.

Furthermore, instead of passing direct current from the computer 20, direct current may be caused to flow to the Faraday cell 9 from another circuit.

Alternatively, the analyzer 5 may be fixed and the polarizer 4 may be rotated by the worm 7 and the worm wheel 8, and the sample cell 10 may be placed on the polarizer 4 side.

As is clear from the detailed description above, the polarimeter according to the present invention has the basic configuration as described at the beginning, and a direct current is applied to the Faraday cell in order to rotate the plane polarized light passing through the Faraday cell in one direction. A direct current circuit capable of applying a current is provided, and the applied direct current can be changed over time in order to cause optical rotation corresponding to at least one rotation of the worm in the Faraday cell, and the applied direct current By configuring the computer to calculate and store the difference between the actual measured value and the theoretical value of the rotation angle of the worm wheel with respect to the change in current over time, the difference between the stored actual measured value and the theoretical value can be calculated and stored. The present invention is characterized in that the computer is configured to automatically correct the calculated and displayed value of the optical rotation angle of the sample by the computer.

In other words, the Faraday cell focuses on the fact that by passing a direct current through it, plane-polarized light that passes through the Faraday cell rotates, and the correlation between the direct current and the angle of optical rotation exhibits excellent linearity. Then, by passing a direct current that is unnecessary for the optical rotation measurement of the sample itself into the Faraday cell, the mechanical error caused by the worm and worm wheel is detected, and the error is calculated and stored in the computer. By automatically correcting the displayed value of the sample's optical rotation angle by a computer using this mechanical error as a correction factor, it becomes possible to replace the measured value of the sample's optical rotation angle with a theoretical linear relationship. Although it is just an extremely simple structural improvement that makes effective use of the Faraday cell and computer that are originally included in the meter, ±
This greatly improved the error of about 0.002°, making it possible to measure the angle of rotation with high precision.

[Brief explanation of the drawing]

The drawings show an embodiment of the polarimeter according to the present invention, and FIG. 1 is a schematic diagram of the polarimeter, and FIG. 2 is a graph of error measurement. 1...Light source, 4...Polarizer, 5...Analyzer, 7
... Worm gear, 8 ... Worm wheel, 9
...Faraday cell, 10...Sample cell, 11...
...Detector, 20...Computer, A...Control unit, B...Direct current circuit.

Claims (1)

[Scope of Claims] 1. A polarizer that plane-polarizes the light from the light source and an analyzer facing the polarizer are provided between the light source and the detector, and A Faraday cell and a sample cell are provided, one of which is rotatably driven via a worm and a worm wheel, and an alternating current is applied between the polarizer and the analyzer to vibrate the plane polarized light from the polarizer. and a control section that controls the amount of rotational drive of the polarizer or analyzer based on the output signal from the detector, and an optical rotation angle of the sample based on the amount of rotational drive controlled by the control section. A polarimeter comprising: a computer for calculating and displaying the Faraday cell; and a DC current circuit capable of applying a direct current to the Faraday cell in order to optically rotate plane polarized light transmitted through the Faraday cell in one direction; at least one of the worms in
The worm wheel is configured to be able to change the applied DC current over time in order to perform optical rotation corresponding to rotation, and the difference between an actual value and a theoretical value of the rotation angle of the worm wheel with respect to the change over time of the applied DC current. By configuring the computer to calculate and store the angle of rotation of the sample, the calculated display value of the angle of rotation of the sample by the computer is automatically corrected based on the difference between the stored actual measured value and the theoretical value. A polarimeter characterized by comprising: