JPH0672807B2 - Optical rotation measuring device - Google Patents

Description

Detailed Description of the Invention a. TECHNICAL FIELD The present invention relates to an optical rotation measuring device suitable for continuously measuring optical rotation of a sample for a long period of time.

B. 2. Description of the Related Art A conventional optical rotation measuring device capable of continuously measuring optical rotation has a structure as shown in FIG. In FIG. 3, 1 is a light source, 2 is a polarizer, and 3 is a Faraday element, which modulates the polarization direction of the polarized light transmitted through the polarizer 2 by applying an AC voltage to positive or negative. Reference numeral 4 is a flow cell through which a sample whose optical rotation is to be measured is circulated. An analyzer 5 is rotatable about an optical axis and is driven by a servo motor 6. 7
Is a light receiving element, the output of which is input to the signal processing circuit 8. When the polarizers 2 and 5 are made orthogonal to each other and the flow cell is left empty, the light entering the light receiving element 7 is blocked when the voltage is not applied to the Faraday element 3, but an alternating voltage is applied to the Faraday element. Then, since the polarization directions swing positively and negatively, a polarized component that passes through the analyzer 5 is generated, and the output of the light receiving element 7 changes at a frequency twice the frequency of the alternating voltage applied to the Faraday element. When the polarization direction of the analyzer 5 is rotated from the direction orthogonal to the polarizer 2 by an angle larger than the amplitude of the deflection of the polarization plane by the Faraday element, the output of the light receiving element 7 fluctuates at the same cycle as the voltage applied to the Faraday element. To do. Therefore, if the signal processing circuit 8 is configured to control the servo motor 6 so that the AC component having the same frequency as the voltage applied to the Faraday element is minimized (the voltage applied to the Faraday element at this time is The doubled AC component becomes maximum.) The rotation angle of the analyzer 5, that is, the control amount by which the signal processing circuit 8 drives the servo motor 6 represents the optical rotation of the sample, and this is recorded in the recording device 9. .

C. Problems to be Solved by the Invention As described above, the conventional optical rotation measuring device has a configuration in which the analyzer 5 is driven by the servo mechanism to detect the position where the light passing through the analyzer 5 is minimized. Since it has a mechanical moving part, and the mechanical moving part always causes wear when it is operated, it is not suitable for long-term continuous use. On the other hand, for process control and quality control in the manufacturing process, it is necessary to constantly and continuously extract a sample from the process and continuously measure the optical rotation of the sample. When the above-mentioned conventional device is used in such a case, since it has a mechanical structure portion, it is very unsatisfactory in terms of durability and reliability.

The present invention solves the above-mentioned problems of the conventional device, and provides a polarimetric device for continuous measurement which does not include a movable part and thus has extremely excellent durability.

D. Means for Solving the Problem The present invention uses an analyzer such as a Wollaston prism or a position prism that separates linearly polarized light transmitted through a sample into two light beams whose polarization directions are orthogonal to each other. It is an optical rotation measuring device which is decomposed into two polarizations orthogonal to each other and the optical rotation of a sample is calculated from the relationship between the intensities of the two polarizations.

E. Action A polarizer arranged on the front surface of the sample (light incident side) is called a polarizer, and a polarizer arranged on the rear side of the sample (light emitting side) is called an analyzer. The present invention uses an analyzer that obtains a single linearly polarized light as the polarizer and an analyzer that obtains orthogonal two-polarized light as the analyzer. When the sample cell is an empty or non-optically rotating sample, the analyzer is arranged so as to separate the linearly polarized light transmitted through the polarizer into two polarized lights which are orthogonal to each other in the direction of ± 45 °. In this case, the two polarized lights separated by the analyzer have the same intensity. When the sample is optically active, the linearly polarized light transmitted through the sample cell is slightly rotated from the polarization direction of the polarizer. This rotation angle is α. As shown in FIG. 2, the amplitude of the linearly polarized light emitted from the polarizer is A ′, the amplitude of the linearly polarized light emitted from the sample is Ao, and the polarization components in the two orthogonal directions separated by the analyzer are A (+ α), A. If (-α), the light intensity is proportional to the square of the amplitude, so the intensity I of the polarization component is
(+ Α), I (-α) is Arranging the above two equations and calculating I (+ α) / I (-α) When α is calculated from the above equation, Therefore, the optical rotation angle α of the polarized light can be calculated from the intensity ratio I (+ α) / I (−α) of the polarization components.

Since the rotation angle α is relatively small here, sin ^{-1 in} the above equation
In addition, α is simply expressed by the ratio of the sum and difference of the intensities of the polarized components, the calculation contents are very simple, and the measurement result can be immediately obtained for the sample in circulation.

F. Embodiment FIG. 1 shows an embodiment of the present invention. Reference numeral 1 is a light source, 2 is a polarizer, 4 is a sample cell, and 5 is an analyzer for separating incident light into two orthogonal polarizations. In this example, a Wollaston prism is used. Reference numerals 71 and 72 denote light receiving elements that separately receive the two light beams separated by the Wollaston prism 5, and the respective outputs are input to the arithmetic unit 12 via the preamplifiers 10 and 11. Preamp 1
The outputs of 0 and 11 correspond to I (+ α) and I (-α) described in the previous section, and the arithmetic unit 12 performs the operation of the equation (1) to obtain the optical rotation angle α.
Is calculated and the calculation result is sent to the display device 13 for display. 14 is a monochromatic filter.

As described in the previous section, the analyzer 5 makes incident linearly polarized light, that is, transmitted light of the polarizer 2 equal and orthogonal to each other when the polarization direction of the light passing through the sample cell 4 is not rotated. It is arranged in the direction of decomposing into polarized light components. In this direction, the incident polarized light is decomposed into two components polarized in the direction ± 45 ° with respect to that direction.

G. Effect The present invention uses the analyzer that separates the transmitted light of the sample into two light beams whose polarization directions are orthogonal to each other as described above, and calculates the optical rotation angle of the polarized light by the sample from the intensity ratio of the two separated light beams. Since it does not include any moving parts, it can respond quickly to changes in the sample, there is no fear of mechanical failure, there is no wear of the mechanism, it is extremely durable, and the sample transmitted light with respect to the polarization direction of the incident polarization Since the measurement is performed by dividing it into two components in the direction of positive and negative 45 °, the calculation of the optical rotation is remarkably simple, and the measurement results can be obtained quickly, making it suitable for tracking the change over time of the flow sample and for a long period of time. A high degree of reliability is obtained for continuous use.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a polarization vector diagram for explaining calculation and derivation, and FIG. 3 is a block diagram of a conventional example. 1 ... Light source, 2 ... Polarizer, 4 ... Sample cell (flow cell), 5 ... Analyzer, 71, 72 ... Light receiving element, 12 ... Computing device.

Claims (1)

[Claims] 1. A sample cell in which a sample liquid is circulated, a means for injecting linearly polarized light into the sample cell, and an analyzer of a type for separating a sample transmitted light beam into two light beams whose polarization directions are orthogonal to each other.
It consists of a light receiving element that separately receives the two light beams separated by the analyzer, and an arithmetic unit that calculates the polarization rotation angle of the sample from the output of the light receiving element. The analyzer does not rotate the plane of polarization by the sample. In this case, the optical rotation measuring device is arranged so that the incident linearly polarized light in this case is decomposed into two polarization components which are equal to each other and whose polarization direction is ± 45 °.