JP2012083311A - Polarimeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturizable high accuracy polarimeter by constituting the polarimeter without using a Faraday cell.SOLUTION: A polarimeter generates linearly polarized light by a polarizer 14, branches the linearly polarized light, which has passed through a sample in a sample cell 16, by a beam splitter 17, makes each branched linearly polarized light pass through analyzers 21 and 31 of which directions of transmission axes are mutually different, and thereafter detects the branched linearly polarized light by detectors 23 and 33. The polarimeter rotates the polarization plane of the linearly polarized light by rotating the polarizer 14 generating the linearly polarized light by a hollow motor 15, adjusts the rotation angle so that detection amounts of the light in the analyzers 21 and 31 become to be the same, and obtains the optical rotation of the sample from the rotation angle. It is possible to highly accurately measure the optical rotation of the sample without requiring a Faraday cell, so that the polarimeter can be miniaturizable.

Description

  The present invention relates to a polarimeter that measures the optical rotation of a substance.

  Optical rotation is a property of a substance that rotates the polarization plane of incident linearly polarized light, and the angle at which the polarization plane rotates when linearly polarized light is incident on a material having optical rotation is called optical rotation. The optical rotation per unit substance amount is a value specific to the substance. For example, the concentration of a substance in the solution can be measured by measuring the optical rotation of the solution. The method of measuring the concentration of a solution using the optical rotation is superior to the method of using light absorption in that the concentration of a substance that does not absorb light can be measured.

  A polarimeter that measures the optical rotation of a substance uses a polarizer to convert the light from the light source into linearly polarized light, enters the linearly polarized light into the sample, and enters the linearly polarized light that has passed through the sample into the analyzer. The amount of light that has passed through is detected. By rotating the analyzer while detecting the amount of light that has passed through the analyzer and obtaining the rotation angle of the analyzer at which the amount of light that passes through the analyzer becomes zero, the angle at which the sample has rotated the plane of polarization of the linearly polarized light, i.e. The optical rotation of the sample can be obtained. Conventionally, a polarimeter employing a Faraday cell has been used to measure the optical rotation with high accuracy.

  The Faraday cell has a configuration in which a Faraday glass is incorporated in a Faraday coil, and is arranged at a position where linearly polarized light passes through the inside of the polarimeter. The Faraday cell is supplied with a current to generate a magnetic field therein, and rotates the polarization plane of linearly polarized light passing through the magnetic field by the Faraday effect. The Faraday cell supplied with alternating current generates an oscillating magnetic field inside, and the polarization plane of the linearly polarized light passing through the Faraday cell changes in rotation angle and direction according to the oscillating magnetic field, and according to the alternating current. Oscillates with amplitude and frequency. In a state where the polarization plane is oscillating and oscillating, the magnitude of the linearly polarized light component parallel to the transmission axis of the analyzer varies, so that the detection signal for detecting the light transmitted through the analyzer is an AC signal. Specifically, as the angle at which the polarization plane of linearly polarized light intersects the transmission axis of the analyzer is closer to a right angle, the linearly polarized light component transmitted through the analyzer becomes smaller and the detection signal becomes smaller. Conversely, the detection signal increases as the angle increases from a right angle. When the transmission axis of the rotated analyzer and the vibration center of the polarization plane are orthogonal, the range of the angle at which the polarization plane that oscillates and the transmission axis intersects each other at a right angle so that the detection signal is minimized. . Therefore, the optical rotation of the sample can be measured by determining the rotation angle of the analyzer so that the detection signal is minimized. A polarimeter that employs a Faraday cell is disclosed, for example, in Patent Document 1.

JP-A-9-138231

  In a polarimeter that employs a Faraday cell, it is difficult to reduce the size because the size of the Faraday cell is large. Moreover, although the measurement accuracy of the optical rotation is improved as the vibration angle of the polarization plane of linearly polarized light is closer to 90 °, the actual vibration angle is a small angle of about 5 ° due to power consumption limitation. For this reason, the conventional polarimeter has a problem that there is a limit to improvement in measurement accuracy.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a highly accurate polarimeter capable of being downsized by configuring a polarimeter without using a Faraday cell. It is to provide.

  The polarimeter according to the present invention includes a polarizer that generates linearly polarized light, and the generated linearly polarized light is incident on the sample, and the optical rotation of the sample corresponding to the angle at which the polarization plane of the linearly polarized light passing through the sample rotates is measured. An optical component that branches the linearly polarized light after passing through the sample, a first analyzer that receives one of the branched linearly polarized light and that passes the linearly polarized light component parallel to a specific transmission axis, A first detector that detects light that has passed through the first analyzer; a second analyzer that has a transmission axis direction different from that of the first analyzer and into which the other branched linearly polarized light is incident; A second detector for detecting light that has passed through the two analyzers, a rotating means for rotating the polarization plane of linearly polarized light before entering the sample by rotating the polarizer, and the first detection The ratio of the amount of light detected by the detector and the second detector is a predetermined ratio. The adjusting means for adjusting the rotation angle for rotating the polarization plane by the rotating means, and the means for determining the optical rotation of the sample based on the rotation angle adjusted by the adjusting means. It is characterized by that.

  In the present invention, the polarimeter branches the linearly polarized light after passing through the sample, and detects each of the branched linearly polarized light after passing through analyzers having different transmission axis directions. Further, the polarimeter rotates the polarizer that generates linearly polarized light, thereby rotating the polarization plane of linearly polarized light, adjusting the rotation angle so that the detected amount of linearly polarized light becomes a predetermined ratio, and rotating the polarimeter. The optical rotation of the sample is obtained from the moving angle. This makes it possible to measure the optical rotation without a Faraday cell.

  The polarimeter according to the present invention is configured such that the adjusting means adjusts the rotation angle so that the detected amounts of light at the first detector and the second detector are the same. It is characterized by.

  In the present invention, the polarimeter is a sample by adjusting the rotation angle of the polarizer so that the ratio of the detected amounts of the two linearly polarized lights is 1: 1, that is, the detected amounts of the two linearly polarized lights are the same. Measure the optical rotation.

  In the polarimeter according to the present invention, the first detector and the second detector are configured to output a signal corresponding to a detected amount of light, and the adjusting means includes the first detector and the second detector. Means for generating a first frequency signal that vibrates at the first frequency by alternately taking in a signal output from the second detector at a first frequency, and generating the first frequency signal from the generated first frequency signal; Means for extracting a second frequency signal that vibrates at a second frequency that is ½ of one frequency, and means for adjusting the rotation angle so that the magnitude of the extracted second frequency signal is minimized. It is characterized by that.

  In the present invention, the polarimeter vibrates at a second frequency that is ½ of the first frequency from the first frequency signal obtained by alternately capturing the two linearly polarized detection signals that have passed through the analyzer at the first frequency. The second frequency signal is extracted, and the rotation angle of the polarizer is adjusted so that the intensity of the second frequency signal is minimized. The intensity of the second frequency signal indicates the difference between the detected amounts of the two linearly polarized lights. When the intensity of the second frequency signal is minimized, the detected amounts of the two linearly polarized lights are the same.

  The polarimeter according to the present invention is characterized in that directions of transmission axes of the first analyzer and the second analyzer are different from each other by 90 °.

  In the present invention, by changing the directions of the transmission axes of the two analyzers by 90 ° from each other, the change in the detected amount of the linearly polarized light with respect to the rotation of the polarization plane of the linearly polarized light is maximized, and the optical rotation is measured with high accuracy. It becomes possible to do.

  In the present invention, the polarimeter can improve the measurement accuracy of the optical rotation as compared with a conventional polarimeter using a Faraday cell whose vibration angle cannot be increased. In the present invention, since the optical rotation can be measured with high accuracy without using a Faraday cell, the polarimeter can be miniaturized. Furthermore, since the AC current supplied to the Faraday cell is unnecessary, the present invention has an excellent effect such that the power consumption of the polarimeter can be reduced.

FIG. 3 is a configuration diagram showing an internal configuration of the polarimeter according to the first embodiment. FIG. 3 is a schematic diagram showing a relationship between linearly polarized light incident on an analyzer and a transmission axis of the analyzer in the first embodiment. 3 is a flowchart illustrating a procedure of processing executed by a signal processing unit according to Embodiment 1. In Embodiment 1, it is a schematic diagram which shows the relationship between the polarization plane of the linearly polarized light produced | generated by the polarizer in an initial position, and the transmission axis of an analyzer. In Embodiment 1, it is a schematic diagram which shows the relationship between the polarization plane of the linearly polarized light after rotating with the liquid sample, and the transmission axis of an analyzer. It is a schematic diagram which shows the relationship between the polarization plane of the linearly polarized light produced | generated by the polarizer rotated to the position where the intensity | strength of a 1st detection signal and a 2nd detection signal becomes the same, and the transmission axis of an analyzer. It is a flowchart which shows the procedure of the process which the signal processing part of the form which receives a 1st detection signal and a 2nd detection signal continuously. FIG. 5 is a configuration diagram showing an internal configuration of a polarimeter according to a second embodiment. It is a schematic diagram which shows the example of a lighting current. In Embodiment 2, it is a schematic diagram which shows the relationship between the linearly polarized light which injects into an analyzer, and the transmission axis of an analyzer. 10 is a flowchart illustrating a procedure of processing executed by a signal processing unit according to Embodiment 2. FIG. 9 is a schematic characteristic diagram illustrating an example of a detection signal in the second embodiment. In Embodiment 2, it is a schematic diagram which shows the relationship between the linearly polarized light which injects into an analyzer, and the transmission axis of the analyzer in an initial position. In Embodiment 2, it is a schematic diagram which shows the relationship between the polarization plane of the linearly polarized light after rotating with the liquid sample, and the transmission axis of an analyzer. In Embodiment 2, it is a schematic diagram which shows the relationship between the polarization plane of two linearly polarized light, and the transmission axis of the analyzer rotated to the position where the amplitude of a detection signal becomes the minimum. FIG. 6 is a configuration diagram showing an internal configuration of a polarimeter according to a third embodiment. FIG. 6 is a configuration diagram showing an internal configuration of a polarimeter according to a fourth embodiment. FIG. 10 is a schematic characteristic diagram showing an example of a detection signal in the fourth embodiment.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
(Embodiment 1)
FIG. 1 is a configuration diagram showing an internal configuration of the polarimeter according to the first embodiment. An arrow in the figure is an optical path, and the polarimeter includes a light source 11, an interference filter 12, a lens 13, a polarizer 14, a hollow motor 15, a sample cell 16, and a beam splitter 17 arranged along the optical path. The optical path in the polarimeter is branched by a beam splitter 17. Further, the polarimeter has an analyzer (first analyzer) 21, a lens 22, and a detector (first detector) 23 arranged along one branched optical path, and an analyzer (second detector) along the other optical path. A photon 31, a lens 32, and a detector (second detector) 33 are arranged side by side. The light source 11 is an LED that emits monochromatic light, and emits light when supplied with lighting power from a lighting circuit (not shown). The light source 11 may be a light source other than an LED, such as a sodium lamp or a halogen lamp. The interference filter 12 is a band-pass optical filter that allows light having a wavelength used for measurement of optical rotation to pass and blocks light having other wavelengths.

  The polarizer 14 is a polarizing plate that transmits only a linearly polarized light component parallel to a single transmission axis, and converts light incident from the light source 11 through the interference filter 12 and the lens 13 into linearly polarized light. To do. Thereby, linearly polarized light is generated. The hollow motor 15 is an electric motor formed in a hollow cylindrical shape, and is disposed at a position where the optical path passes through the hollow portion. The polarizer 14 is fixed to the rotor of the hollow motor 15 at a position where the opening of the hollow motor 15 is closed. The hollow motor 15 is connected to the motor driver 42 and is configured to rotate the rotor by being supplied with a drive current from the motor driver 42. As the rotor of the hollow motor 15 rotates, the polarizer 14 fixed to the rotor rotates. As the polarizer 14 rotates, the transmission axis inherent to the polarizer 14 rotates, and the plane of polarization of the linearly polarized light generated rotates. The hollow motor 15 and the motor driver 42 correspond to the rotating means in the present invention.

  The sample cell 16 is a transparent cell into which a liquid sample is injected, and is arranged at a position where an optical path passes through the liquid sample. Linearly polarized light generated by passing light from the light source 11 through the polarizer 14 passes through the hollow portion of the hollow motor 15 and enters the sample cell 16. The beam splitter 17 is an optical component that branches the linearly polarized light that has passed through the sample cell 16. The beam splitter 17 is preferably configured to branch linearly polarized light so that the direction of the polarization plane of the linearly polarized light does not change. The beam splitter 17 is preferably configured so that the intensity of two branched linearly polarized lights becomes equal.

  The analyzers 21 and 31 are polarizing plates having a single transmission axis. One linearly polarized light branched by the beam splitter 17 is incident on the analyzer 21, and the other linearly polarized light is incident on the analyzer 31. Of the linearly polarized light incident on the analyzer 21 or 31, only the linearly polarized light component parallel to the transmission axis passes through the analyzer 21 or 31. The analyzers 21 and 31 are fixed in the polarimeter so that the directions of the transmission axes are different from each other. Specifically, the directions of the transmission axes of the analyzers 21 and 31 with respect to a plane including two optical axes, that is, an optical axis passing through the analyzer 21 and an optical axis passing through the analyzer 31 are different from each other. In the present embodiment, the direction of the transmission axis of the analyzer 21 with respect to the plane is different from the direction of the transmission axis of the analyzer 31 with respect to the plane by 90 °.

  The linearly polarized light that has passed through the analyzer 21 enters the detector 23 through the lens 22. The linearly polarized light that has passed through the analyzer 31 enters the detector 33 through the lens 32. The detectors 23 and 33 are configured using a light receiving element such as a photodiode, and when detecting light, output a detection signal indicating the detected amount of light in voltage. The detector 23 outputs a first detection signal, and the detector 33 outputs a second detection signal. Since the analyzers 21 and 31 have different transmission axis directions, the linearly polarized light components passing through the analyzers 21 and 31 are generally different, and the detection amounts at the detectors 23 and 33 are different from each other. Therefore, in general, the first detection signal and the second detection signal have different intensities.

  FIG. 2 is a schematic diagram showing the relationship between the linearly polarized light incident on the analyzers 21 and 31 and the transmission axes of the analyzers 21 and 31 in the first embodiment. The direction of the X axis in the figure indicates a direction parallel to the transmission axis of the analyzer 21, and the direction of the Y axis indicates a direction parallel to the transmission axis of the analyzer 31. The direction of the arrow in the figure indicates the direction parallel to the plane of polarization of linearly polarized light, and the length of the arrow indicates the intensity of linearly polarized light. In FIG. 2, the intensity of the first detection signal corresponds to the value of x obtained by projecting the intensity of linearly polarized light onto the X axis, and the intensity of the second detection signal is represented by y obtained by projecting the intensity of linearly polarized light onto the Y axis. Corresponds to the value. When the polarizer 14 is rotated by the hollow motor 15, the direction parallel to the polarization plane of linearly polarized light changes. That is, the directions of the arrows shown in FIG. 2 change, and the strengths of the first detection signal and the second detection signal change. When the direction parallel to the linearly polarized light is directed to an intermediate position that equally divides the angle formed by the X axis and the Y axis, the first detection signal and the second detection signal have the same intensity.

  The polarimeter further includes a signal processing unit 41 that performs signal processing for controlling the operation of the polarimeter based on the detection signals output from the detectors 23 and 33. Detectors 23 and 33 are connected to the signal processing unit 41 via an amplifier (not shown). The first detection signal and the second detection signal output from the detectors 23 and 33 are appropriately amplified by an amplifier (not shown) and then input to the signal processing unit 41. A motor driver 42 is connected to the signal processing unit 41. The signal processing unit 41 outputs a control signal for operating the motor driver 42. The signal processing unit 41 is an input / output interface for inputting / outputting various signals, an arithmetic unit such as a microprocessor or an integrated circuit for executing various arithmetic processes, and a memory for storing processing programs and data necessary for signal processing It is comprised including. The signal processing unit 41 is connected to an output unit 43 such as a display or a printer for outputting information such as the optical rotation measurement result.

  The signal processing unit 41 corresponds to the adjusting means in the present invention, and performs signal processing for adjusting the rotation angle at which the polarizer 14 is rotated by the hollow motor 15. FIG. 3 is a flowchart illustrating a procedure of processing executed by the signal processing unit 41 according to the first embodiment. The signal processing unit 41 generates a first frequency signal that vibrates at the first frequency by alternately taking in the first detection signal and the second detection signal at a predetermined first frequency (S11). In general, since the first detection signal and the second detection signal have different intensities, the envelope of the first frequency signal is not constant, and vibrates at a second frequency that is half the first frequency. Next, the signal processing unit 41 performs a filter process of passing the first frequency signal through a cut filter that cuts a frequency component equal to or higher than the first frequency, thereby oscillating at a second frequency that is 1/2 of the first frequency. A two-frequency signal is generated (S12). For example, if the first frequency is 2 hHz, the second frequency is hHz. The second frequency signal corresponds to the envelope of the first frequency signal. The intensity of the second frequency signal corresponds to the absolute value of the intensity difference between the first detection signal and the second detection signal. When the first detection signal and the second detection signal have the same intensity, the intensity of the second frequency signal is minimized.

  Next, the signal processing unit 41 measures the intensity of the second frequency signal, and determines whether or not the intensity of the second frequency signal is equal to or less than a predetermined allowable value stored in advance (S13). The signal processing unit 41 stores in advance the intensity of the second frequency signal obtained when the intensity of the first detection signal and the intensity of the second detection signal are substantially the same as an allowable value. When the intensity of the second frequency signal exceeds the allowable value (S13: NO), the signal processing unit 41 determines whether or not the intensity of the first detection signal is greater than the intensity of the second detection signal ( S14). When the intensity of the first detection signal is greater than the intensity of the second detection signal (S14: YES), the signal processing unit 41 performs a process of rotating the polarizer 14 in a direction in which the intensity of the first detection signal decreases. Perform (S15).

  In step S15, the signal processing unit 41 outputs to the motor driver 42 a control signal for causing the motor driver 42 to rotate the rotor of the hollow motor 15 by a predetermined angle in a direction in which the intensity of the first detection signal is reduced. . The motor driver 42 supplies a drive current corresponding to the control signal to the hollow motor 15, and the hollow motor 15 rotates the rotor by an angle corresponding to the drive current in a direction corresponding to the drive current. As the rotor of the hollow motor 15 rotates, the polarizer 14 rotates, and the polarization plane of linearly polarized light rotates about the optical axis. The direction in which the intensity of the first detection signal decreases is the direction in which the arrow rotates around the origin in FIG. 2 and moves away from the X axis, and the polarization plane of linearly polarized light rotates around the optical axis. Is a direction away from a direction parallel to the transmission axis of the analyzer 21. The signal processing unit 41 stores in advance the rotation direction of the rotor of the hollow motor 15 so that the intensity of the first detection signal is small, and a control signal for rotating the polarizer 14 in this rotation direction. Is output.

  When the intensity of the first detection signal is smaller than the intensity of the second detection signal in step S14 (S14: NO), the signal processing unit 41 rotates the polarizer 14 in a direction in which the intensity of the second detection signal is decreased. (S16). In step S <b> 16, the signal processing unit 41 outputs, to the motor driver 42, a control signal for causing the motor driver 42 to rotate the rotor of the hollow motor 15 by a predetermined angle in a direction in which the intensity of the second detection signal decreases. . Similar to step S15, the polarization plane of linearly polarized light rotates around the optical axis. The direction in which the intensity of the second detection signal decreases is the direction in which the arrow rotates about the origin and moves away from the Y axis in FIG. 2, and the polarization plane of linearly polarized light rotates about the optical axis and is polarized. Is a direction away from a direction parallel to the transmission axis of the analyzer 31. The signal processing unit 41 stores in advance the rotation direction of the rotor of the hollow motor 15 so that the intensity of the second detection signal is small, and a control signal for rotating the polarizer 14 in this rotation direction. Is output. That is, the polarizer 14 rotates in the direction opposite to that in step S15.

  After step S15 or S16 ends, the signal processing unit 41 returns the process to step S11. The signal processing unit 41 repeats the processes of steps S11 to S16 until the intensity of the second frequency signal becomes equal to or less than the allowable value. When the intensity of the second frequency signal is equal to or smaller than the allowable value in step S13 (S13: YES), the signal processing unit 41 ends the process of rotating the polarizer 14. When the intensity of the second frequency signal is equal to or lower than the allowable value, the intensity of the second frequency signal is the minimum, and the first detection signal and the second detection signal have the same intensity, that is, light from the detectors 23 and 33. This is a state in which the detected amount is the same. At the end of the processing, the rotation of the polarizer 14 is stopped, and the polarization plane of the linearly polarized light generated by the polarizer 14 is fixed. The signal processing unit 41 does not rotate the polarizer 14 by the same angle in the processing of step S15 or S16, but only an angle that becomes smaller as the intensity difference between the first detection signal and the second detection signal is smaller. A process of rotating the polarizer 14 may be performed. Further, the signal processing unit 41 may perform processing of repeating steps S11 to S16 until the strength of the second frequency signal becomes the minimum value in step S13.

  The signal processing unit 41 determines the initial position of the polarizer 14 rotated by the hollow motor 15 by executing the processes of steps S11 to S16 before the liquid sample is injected into the sample cell 16. I do. FIG. 4 is a schematic diagram showing the relationship between the polarization plane of linearly polarized light generated by the polarizer 14 in the initial position and the transmission axes of the analyzers 21 and 31 in the first embodiment. The direction of the arrow indicating the direction parallel to the polarization plane of the linearly polarized light faces the intermediate position that equally divides the angle formed by the X axis and the Y axis. At this time, the value of x is the same as the value of y. That is, the first detection signal and the second detection signal have the same intensity. The signal processing unit 41 may store the initial position of the polarizer 14 in advance and perform a process of rotating the polarizer 14 to the initial position.

  When a liquid sample having optical rotation is injected into the sample cell 16, the plane of polarization rotates when linearly polarized light passes through the liquid sample in the sample cell 16, and the detection amount of light detected by the detectors 23 and 33 is reduced. Change. FIG. 5 is a schematic diagram showing the relationship between the polarization plane of linearly polarized light after being rotated by the liquid sample and the transmission axes of the analyzers 21 and 31 in the first embodiment. In FIG. 5, the intermediate position is indicated by a broken line arrow. As shown in FIG. 5, the liquid sample in the sample cell 16 rotates the polarization plane of linearly polarized light by an angle α from the intermediate position. The angle α at which the polarization plane of linearly polarized light is rotated is the optical rotation α of the liquid sample.

  The signal processing unit 41 performs a process of steps S11 to S16 in a state where a liquid sample is injected into the sample cell 16, thereby performing a hollow motor to a position where the first detection signal and the second detection signal have the same intensity. 15 is used to rotate the polarizer 14. FIG. 6 shows the relationship between the polarization plane of linearly polarized light generated by the polarizer 14 rotated to a position where the intensities of the first detection signal and the second detection signal become the same, and the transmission axes of the analyzers 21 and 31. It is a schematic diagram. In FIG. 6, the polarization plane of linearly polarized light before rotating the polarizer 14 is indicated by a broken line arrow. The polarizer 14 is rotated by an angle −α from the initial position by rotating to a position where the first detection signal and the second detection signal have the same intensity. The signal processing unit 41 measures the angle −α at which the polarizer 14 is rotated from the initial position by integrating the angles at which the polarizer 14 is rotated in the processes of steps S11 to S16. The signal processing unit 41 performs a process of calculating the optical rotation α of the liquid sample by multiplying the measured angle −α by −1 and causing the output unit 43 to output the measurement result of the optical rotation α. With the above processing, the polarimeter measures the optical rotation of the liquid sample. The signal processing unit 41 further performs a process of calculating and outputting the specific rotation of the solute of the liquid sample from the optical rotation α, or a process of calculating and outputting the concentration of the solute of the liquid sample from the specific rotation. May be.

  As described above in detail, the polarimeter according to the present embodiment branches the linearly polarized light after passing through the liquid sample, and passes each of the branched linearly polarized light through analyzers having different transmission axis directions. Detect later. Furthermore, the polarimeter rotates the polarizer 14 that generates linearly polarized light with the hollow motor 15, thereby rotating the polarization plane of the linearly polarized light and adjusting the rotation angle so that the detected amount of linearly polarized light is the same. Then, the optical rotation of the liquid sample is obtained from the rotation angle. Since the directions of the transmission axes of the analyzer 21 and the analyzer 31 can be different from each other by 90 °, the change in the detection amount by the detectors 23 and 33 with respect to the rotation of the polarization plane of the linearly polarized light is maximized. At this time, the intensity change of the first detection signal and the second detection signal with respect to the rotation of the polarization plane of the linearly polarized light becomes the maximum, and the change in the direction of the polarization plane of the linearly polarized light can be detected with high accuracy. For this reason, in this invention, an optical rotation can be measured with the same precision as the case where the vibration angle of the polarization plane of a linearly polarized light is set to 90 degrees using a Faraday cell. Therefore, in comparison with the conventional polarimeter using a Faraday cell whose vibration angle can only be about 5 °, the polarimeter according to the present embodiment can improve the measurement accuracy of the optical rotation.

  The polarimeter according to the present embodiment can measure the optical rotation with high accuracy without using a Faraday cell. Since the space necessary for the components necessary for branching and detecting the linearly polarized light such as the beam splitter 17 is smaller than the space required for the Faraday cell, the polarimeter can be miniaturized. In addition, since no AC current is supplied to the Faraday cell, the power consumption of the polarimeter can be reduced.

  In the above embodiment, the signal processing unit 41 has shown a mode in which the first detection signal and the second detection signal are alternately captured at the first frequency. However, the present invention is not limited to this. The processing unit 41 may continuously receive the first detection signal and the second detection signal. FIG. 7 is a flowchart illustrating a procedure of processing executed by the signal processing unit 41 configured to continuously receive the first detection signal and the second detection signal. The signal processing unit 41 receives the first detection signal and the second detection signal from the detectors 23 and 33, and calculates the intensity difference between the first detection signal and the second detection signal (S21). Next, the signal processing unit 41 determines whether or not the calculated absolute value of the intensity difference is equal to or less than a predetermined allowable value stored in advance (S22). When the absolute value of the intensity difference exceeds the allowable value (S22: NO), the signal processing unit 41 determines whether or not the intensity of the first detection signal is greater than the intensity of the second detection signal (S23). ). When the intensity of the first detection signal is greater than the intensity of the second detection signal (S23: YES), the signal processing unit 41 performs a process of rotating the polarizer 14 in a direction in which the intensity of the first detection signal decreases. Perform (S24). When the intensity of the first detection signal is smaller than the intensity of the second detection signal (S23: NO), the signal processing unit 41 performs a process of rotating the polarizer 14 in a direction in which the intensity of the second detection signal decreases. Perform (S25). After step S24 or S25 ends, the signal processing unit 41 returns the process to step S21. When the absolute value of the intensity difference is equal to or smaller than the allowable value in step S22 (S22: YES), the signal processing unit 41 ends the process of rotating the polarizer 14. Note that the signal processing unit 41 may perform processing of repeating steps S21 to S25 until the absolute value of the intensity difference becomes the minimum value in step S22. Even in the form in which the signal processing unit 14 performs the above processing, the optical rotation of the liquid sample can be measured with high accuracy.

  In the present embodiment, the analyzer 21 and the analyzer 31 have different transmission axis directions by 90 °. However, the polarimeter is configured so that the analyzer 21 and the analyzer 31 have transmission axis directions. May be different, and the difference in the direction of the transmission axis may be an angle other than 90 °. In the present embodiment, the optical rotation is measured by rotating the polarizer 14 so that the detection amounts of linearly polarized light at the detectors 23 and 33 are the same. The polarizer 14 may be rotated so that the ratio of the detection amounts becomes a predetermined ratio. For example, the optical rotation meter rotates the polarizer 14 so that the ratio between the intensity of the first detection signal and the intensity of the second detection signal is a predetermined ratio other than 1: 1 such as 1: 2. The form which measures a degree may be sufficient. Also in this form, the polarimeter can measure the optical rotation of the liquid sample with high accuracy. Moreover, in this Embodiment, although the form which rotates the polarizer 14 with the hollow motor 15 was shown, a polarimeter is a form which rotates the polarizer 14 by means other than the hollow motors 15, such as a gearwheel. Also good. In addition, the polarimeter is not limited to a liquid sample, and may have a form in which the optical rotation can be measured for a sample in a state other than liquid such as an individual.

(Embodiment 2)
FIG. 8 is a configuration diagram showing an internal configuration of the polarimeter according to the second embodiment. The arrow in the figure is the optical path, and the polarimeter has a half mirror 55, a lens 56, an interference filter 57, a sample cell 58, an analyzer 59, a hollow motor 60, a lens 61, and a detector 62 arranged side by side along the optical path. Has been. The half mirror 55 is an optical component that joins two incident optical paths. In the polarimeter, the optical path is configured so that the two optical paths are joined by the half mirror 55. The polarimeter further includes a light source 51 and a polarizer 53 arranged along one optical path joined by a half mirror 55, and a light source 52 and a polarizer 54 arranged along the other optical path. The light sources 51 and 52 are LEDs that emit monochromatic light.

  The polarizers 53 and 54 are polarizing plates that transmit only a linearly polarized light component parallel to a single transmission axis. The polarizers 53 and 54 are arranged such that the directions of the transmission axes of the polarizers 53 and 54 are different from each other with respect to a plane including two optical axes, that is, an optical axis passing through the polarizer 53 and an optical axis passing through the polarizer 54. It is fixed in the polarimeter. The directions of the transmission axes of the polarizers 53 and 54 differ, for example, by about 0.5 ° to 20 °. Linearly polarized light generated when light from the light source 51 passes through the polarizer 53 and linearly polarized light generated when light from the light source 52 passes through the polarizer 54 have different polarization plane directions. . The optical paths of two linearly polarized light having different polarization plane directions are joined by the half mirror 55. The brightness of the light sources 51 and 52, the transmittance of the polarizers 53 and 54, and the transmittance and reflectance of the half mirror 55 are adjusted by the half mirror 55 so that the brightness of the two linearly polarized lights that join the optical path is the same. Has been. The linearly polarized light that has passed through the half mirror 55 passes through the lens 56 and the interference filter 57 and enters the sample cell 58. The linearly polarized light that has passed through the sample cell 58 is incident on the analyzer 59.

  The analyzer 59 is a polarizing plate having a single transmission axis. Of the linearly polarized light incident on the analyzer 59, only the linearly polarized light component parallel to the transmission axis passes through the analyzer 59. An analyzer 59 is fixed to the rotor of the hollow motor 60 at a position where the opening of the hollow motor 60 is closed. The hollow motor 60 is connected to a motor driver 72. As the rotor of the hollow motor 60 rotates, the analyzer 59 fixed to the rotor rotates. As the analyzer 59 rotates, the angle at which the plane of polarization of linearly polarized light incident on the analyzer 59 intersects the transmission axis of the analyzer 59 changes, and the linearly polarized light component that can pass through the analyzer 59 changes. Therefore, the amount of linearly polarized light passing through the analyzer 59 changes as the analyzer 59 rotates. The linearly polarized light that has passed through the analyzer 59 passes through the hollow portion of the hollow motor 60, passes through the lens 61, and is incident on the detector 62. When detecting the light, the detector 62 outputs a detection signal indicating the detected amount of light in voltage.

  The polarimeter further includes a signal processing unit 71 that performs signal processing for controlling the operation of the polarimeter. A detector 62 is connected to the signal processing unit 71 via an amplifier (not shown). The detection signal output from the detector 62 is appropriately amplified by an amplifier (not shown) and then input to the signal processing unit 71. A motor driver 72 and an output unit 73 are connected to the signal processing unit 71.

  Further, a lighting circuit 74 that lights the light sources 51 and 52 is connected to the signal processing unit 71. The lighting circuit 74 supplies a lighting current for lighting the light source 51 to the light source 51 at a predetermined frequency. The lighting circuit 74 supplies a lighting current having the same frequency as that of the light source 51 and having a reverse phase to the light source 52. FIG. 9 is a schematic diagram illustrating an example of a lighting current. The lighting current is an alternating current in which an on state and an off state are alternately repeated at a predetermined frequency. The lighting current supplied to the light source 51 and the lighting current supplied to the light source 52 have the same frequency and have opposite phases. The light sources 51 and 52 are alternately lit at the same frequency as the lighting current when supplied with the lighting current from the lighting circuit 74. Although FIG. 9 shows a rectangular wave current as an example of the lighting current, the lighting current supplied from the lighting circuit 74 to the light sources 51 and 52 may be a sine wave or a triangular wave current.

  The detector 62 detects the linearly polarized light generated by the light source 51 and the polarizer 53 and the linearly polarized light generated by the light source 52 and the polarizer 54. Since the polarization planes of the two linearly polarized lights are different, generally, the magnitudes of the components passing through the analyzer 59 are different from each other, and the detection amounts of the two linearly polarized lights detected by the detector 62 are different from each other. Since the light sources 51 and 52 are alternately lit at the frequency of the lighting current, the amount detected by the detector 62 varies at the same frequency as the lighting current, and the detection signal output by the detector 62 has the same frequency as the lighting current. It becomes a fluctuating AC signal. When the analyzer 59 is rotated by the hollow motor 60, the amount of linearly polarized light passing through the analyzer 59 changes, so that the amplitude of the detection signal changes.

  FIG. 10 is a schematic diagram showing the relationship between the linearly polarized light incident on the analyzer 59 and the transmission axis of the analyzer 59 in the second embodiment. The direction of the arrow U in the figure indicates the direction parallel to the polarization plane of the linearly polarized light generated by the light source 51 and the polarizer 53, and the length of the arrow U indicates the intensity of the linearly polarized light. Moreover, the direction of the arrow V in the figure indicates the direction parallel to the polarization plane of the linearly polarized light generated by the light source 52 and the polarizer 54, and the length of the arrow V indicates the intensity of the linearly polarized light. Further, the direction of the arrow Z in the figure indicates a direction parallel to the transmission axis of the analyzer 59. The intensity of the detection signal when the linearly polarized light generated by the light source 51 and the polarizer 53 passes through the analyzer 59 and is detected by the detector 62 corresponds to the value of u obtained by projecting the arrow U onto the arrow Z. . The intensity of the detection signal when the linearly polarized light generated by the light source 52 and the polarizer 54 passes through the analyzer 59 and is detected by the detector 62 corresponds to the value of v obtained by projecting the arrow V onto the arrow Z. . The amplitude of the detection signal corresponds to the absolute value of the difference between the u value and the v value. As the analyzer 59 is rotated by the hollow motor 60, the direction of the arrow Z changes. When the direction of the arrow Z is directed to an intermediate position where the angle between the arrow U and the arrow V is equally divided, the value of u is the same as the value of v, and the amplitude of the detection signal is a minimum value of almost zero. .

  The signal processing unit 71 performs signal processing for adjusting the rotation angle at which the analyzer 59 is rotated by the hollow motor 60. FIG. 11 is a flowchart illustrating a procedure of processes executed by the signal processing unit 71 according to the second embodiment. The signal processing unit 71 causes the lighting circuit 74 to alternately turn on the light sources 51 and 52 at a predetermined frequency, and acquires a detection signal from the detector 62 (S31). Next, the signal processing unit 71 measures the amplitude of the detection signal, and determines whether or not the amplitude of the detection signal is equal to or less than a predetermined allowable value stored in advance (S32). The signal processing unit 71 stores in advance a value that can be considered that the amplitude of the detection signal has become zero as an allowable value.

  FIG. 12 is a schematic characteristic diagram illustrating an example of a detection signal in the second embodiment. The horizontal axis in FIG. 12 is time, and the vertical axis is the signal strength of the detection signal. FIG. 12A shows the linearly polarized light generated by the light source 51 and the polarizer 53 in a direction parallel to the transmission axis of the analyzer 59 rather than the direction parallel to the polarization plane of the linearly polarized light generated by the light source 52 and the polarizer 54. The case where it is close to the direction parallel to the plane of polarization is shown. In this case, the component in which the linearly polarized light generated by the light source 51 and the polarizer 53 passes through the analyzer 59 has a higher intensity than the linearly polarized light generated by the light source 52 and the polarizer 54. Therefore, the detection signal is a signal having the same phase as the lighting current supplied from the lighting circuit 74 to the light source 51 as shown in FIG.

  FIG. 12B shows the linearly polarized light generated by the light source 52 and the polarizer 54 in a direction parallel to the transmission axis of the analyzer 59 rather than the direction parallel to the polarization plane of the linearly polarized light generated by the light source 51 and the polarizer 53. The case where it is close to the direction parallel to the plane of polarization is shown. In this case, the component in which the linearly polarized light generated by the light source 52 and the polarizer 54 passes through the analyzer 59 has a higher intensity than the linearly polarized light generated by the light source 51 and the polarizer 53. Therefore, the detection signal is a signal having a phase opposite to that of the lighting current supplied from the lighting circuit 74 to the light source 51. FIG. 12C shows a case where the direction parallel to the transmission axis of the analyzer 59 is at an intermediate position between the directions parallel to the polarization planes of the two linearly polarized light. Since the intensity of the components of the two linearly polarized light passing through the analyzer 59 is the same, the intensity of the detection signal corresponding to each linearly polarized light is the same, and the amplitude of the detection signal is zero.

  If the amplitude of the detection signal exceeds the allowable value in step S32 (S32: NO), the signal processing unit 71 determines whether the detection signal and the lighting current supplied from the lighting circuit 74 to the light source 51 are in phase. It is determined whether or not (S33). When the detection signal and the lighting current supplied from the lighting circuit 74 to the light source 51 have the same phase (S33: YES), the signal processing unit 71 detects the analyzer 59 in the same phase as the lighting current to the light source 51. A process of rotating in a direction in which the signal intensity decreases is performed (S34).

  In step S34, the signal processing unit 71 causes the motor driver 72 to rotate the rotor of the hollow motor 60 by a predetermined angle in a direction in which the intensity of the detection signal having the same phase as the lighting current to the light source 51 is reduced. A signal is output to the motor driver 72. The motor driver 72 supplies a drive current corresponding to the control signal to the hollow motor 60, and the hollow motor 60 rotates the rotor by an angle corresponding to the drive current in a direction corresponding to the drive current. The analyzer 59 is rotated by the rotation of the rotor of the hollow motor 60. The direction in which the intensity of the detection signal having the same phase as the lighting current to the light source 51 decreases is the direction in which the arrow Z rotates about the origin and moves away from the arrow U in FIG. Further, this direction is a direction in which the direction parallel to the transmission axis of the analyzer 59 moves away from the direction parallel to the polarization plane of the linearly polarized light generated by the light source 51 and the polarizer 53. The signal processing unit 71 stores in advance the rotation direction of the rotor of the hollow motor 60 so that the intensity of the detection signal having the same phase as the lighting current to the light source 51 is small. A control signal for rotating is output.

  When the detection signal and the lighting current supplied from the lighting circuit 74 to the light source 51 are in opposite phases in step S33 (S33: NO), the signal processing unit 71 reverses the analyzer 59 to the lighting current to the light source 51. A process of rotating in the direction in which the intensity of the phase detection signal is reduced is performed (S35). In step S35, the signal processing unit 71 causes the motor driver 72 to rotate the rotor of the hollow motor 60 by a predetermined angle in a direction in which the intensity of the detection signal having the opposite phase to the lighting current to the light source 51 is reduced. A signal is output to the motor driver 72. As in step S34, the analyzer 59 rotates. The direction in which the intensity of the detection signal having the opposite phase to the lighting current to the light source 51 decreases is the direction in which the arrow Z rotates about the origin and moves away from the arrow V in FIG. Further, this direction is a direction in which the direction parallel to the transmission axis of the analyzer 59 is away from the direction parallel to the polarization plane of the linearly polarized light generated by the light source 52 and the polarizer 54. The signal processing unit 71 stores in advance the rotational direction of the rotor of the hollow motor 60 so that the intensity of the detection signal having the opposite phase to the lighting current to the light source 51 is reduced. A control signal for rotating is output. That is, the analyzer 59 rotates in the direction opposite to that in step S34.

  After step S34 or S35 is completed, the signal processing unit 71 returns the process to step S31. The signal processing unit 71 repeats the processes of steps S31 to S35 until the amplitude of the detection signal becomes equal to or less than the allowable value. If the amplitude of the detection signal is equal to or smaller than the allowable value in step S32 (S32: YES), the signal processing unit 71 ends the process of rotating the analyzer 59. The state in which the amplitude of the detection signal is equal to or less than the allowable value is a state in which the amplitude of the detection signal has reached a minimum value of almost zero. By the end of the processing, the rotation of the analyzer 59 is stopped, and the transmission axis of the analyzer 59 is fixed. Note that the signal processing unit 71 does not rotate the analyzer 59 by the same angle in the processing of step S34 or S35, but rotates the analyzer 59 by an angle that decreases as the amplitude of the detection signal decreases. You may go. Further, the signal processing unit 71 may perform processing of repeating steps S31 to S35 until the amplitude of the detection signal becomes the minimum value in step S32.

  The signal processing unit 71 determines the initial position of the analyzer 59 rotated by the hollow motor 60 by performing the processes of steps S31 to S35 before the liquid sample is injected into the sample cell 58. I do. FIG. 13 is a schematic diagram showing the relationship between the linearly polarized light incident on the analyzer 59 and the transmission axis of the analyzer 59 at the initial position in the second embodiment. The direction of the arrow Z indicating the direction parallel to the transmission axis of the analyzer 59 faces the intermediate position where the angle between the arrow U and the arrow V is equally divided. The signal processing unit 71 may store the initial position of the analyzer 59 in advance and perform a process of rotating the analyzer 59 to the initial position.

  When a liquid sample having optical rotation is injected into the sample cell 58, the plane of polarization rotates when the linearly polarized light passes through the liquid sample in the sample cell 58, and the amount of linearly polarized light passing through the analyzer 59 changes. The detection amount of light detected by the detector 62 changes. FIG. 14 is a schematic diagram showing the relationship between the polarization plane of linearly polarized light after being rotated by the liquid sample and the transmission axis of the analyzer 59 in the second embodiment. In FIG. 14, the direction parallel to the polarization plane before the rotation of the linearly polarized light is indicated by a broken line arrow. As shown by the rotation of the arrows U and V in FIG. 14, the planes of polarization of the two linearly polarized light incident on the analyzer 59 are rotated by an angle α by the liquid sample in the sample cell 58. The angle α at which the polarization plane of linearly polarized light is rotated is the optical rotation α of the liquid sample.

  The signal processing unit 71 performs the processing of steps S31 to S35 in a state where the liquid sample is injected into the sample cell 58, thereby rotating the analyzer 59 by the hollow motor 60 to a position where the amplitude of the detection signal is minimized. Process to move. FIG. 15 is a schematic diagram showing the relationship between the polarization planes of two linearly polarized light and the transmission axis of the analyzer 59 rotated to a position where the amplitude of the detection signal is minimized in the second embodiment. In FIG. 15, the direction parallel to the transmission axis of the analyzer 59 at the initial position is indicated by a broken line arrow. The analyzer 59 rotates by an angle α from the initial position by rotating to a position where the amplitude of the detection signal is minimized. The signal processing unit 41 integrates the angles of the rotation of the analyzer 59 in the processes of steps S31 to S35, thereby measuring the angle α of the rotation of the analyzer 59 from the initial position, that is, the optical rotation α of the liquid sample. To do. The signal processing unit 71 performs processing for causing the output unit 73 to output the measurement result of the optical rotation α. With the above processing, the polarimeter measures the optical rotation of the liquid sample.

  As described in detail above, the polarimeter according to the present embodiment generates two linearly polarized lights having different directions of polarization planes, and alternately detects the two linearly polarized lights that have passed through the liquid sample and the analyzer 59. Further, the polarimeter rotates the analyzer 59 with the hollow motor 60, adjusts the rotation angle so that the detected amounts of two linearly polarized light alternately changing are the same, and rotates the liquid sample from the rotation angle. Find the degree. Also in this embodiment, the polarimeter can measure the optical rotation with high accuracy without using a Faraday cell. Since the space required for the components necessary for generating two linearly polarized light such as the half mirror 55 is smaller than the space required for the Faraday cell, the polarimeter can be miniaturized. In addition, since no AC current is supplied to the Faraday cell, the power consumption of the polarimeter can be reduced.

(Embodiment 3)
FIG. 16 is a configuration diagram showing an internal configuration of the polarimeter according to the third embodiment. The polarimeter includes light sources 51 and 52 arranged in a direction intersecting the optical axis, interference filter 57, lens 56, polarizers 53 and 54 arranged in a direction intersecting the optical axis, sample cell 58, analyzer 59, and hollow motor. 60, a lens 63 and a detector 62 are arranged side by side along the optical axis. An arrow in FIG. 16 indicates an optical path. The polarizer 53 is disposed at a position where light from the light source 51 passes, and the polarizer 54 is disposed at a position where light from the light source 52 passes. Further, the polarizers 53 and 54 are configured such that the directions of the transmission axes of the polarizers 53 and 54 are different from each other with respect to a plane including two optical axes, an optical axis passing through the polarizer 53 and an optical axis passing through the polarizer 54. Fixed in the polarimeter.

  The light from the light source 51 passes through the interference filter 57 and the lens 56 and passes through the polarizer 53, thereby becoming linearly polarized light. Further, the light from the light source 52 passes through the interference filter 57 and the lens 56 and passes through the polarizer 54 to become linearly polarized light. The two linearly polarized lights generated have different directions of polarization planes. The two linearly polarized lights are incident on the sample cell 58, and the linearly polarized light that has passed through the sample cell 58 is incident on the analyzer 59. The optical paths of the two linearly polarized light are parallel including the optical path from the light source to the polarizer.

  Similar to the second embodiment, the analyzer 59 is fixed to the rotor of the hollow motor 60 and is rotated by the hollow motor 60. The hollow motor 60 is connected to a motor driver 72. As the analyzer 59 rotates, the amount of linearly polarized light passing through the analyzer 59 changes. The two linearly polarized light beams that have passed through the analyzer 59 pass through the hollow portion of the hollow motor 60, are collected by the lens 63, and enter the detector 62 together. When detecting the light, the detector 62 outputs a detection signal indicating the detected amount of light in voltage.

  The polarimeter includes a signal processing unit 71, and a detector 62 is connected to the signal processing unit 71 via an amplifier (not shown). A motor driver 72 and an output unit 73 are connected to the signal processing unit 71. Further, a lighting circuit 74 that lights the light sources 51 and 52 is connected to the signal processing unit 71.

  The polarimeter according to the present embodiment measures the optical rotation of the liquid sample by executing the same processing as the polarimeter according to the second embodiment. Therefore, also in this embodiment, the polarimeter can measure the optical rotation with high accuracy without using a Faraday cell.

(Embodiment 4)
FIG. 17 is a configuration diagram showing an internal configuration of the polarimeter according to the fourth embodiment. The polarimeter includes a light source 64, an interference filter 57, a light shielding plate 65, a lens 56, polarizers 53 and 54 arranged in a direction crossing the optical axis, a sample cell 58, an analyzer 59, a hollow motor 60, a lens 63, and a detector. 62 are arranged along the optical axis. An arrow in FIG. 17 indicates an optical path.

  The light shielding plate 65 is configured to pass a part of the light beam emitted from the light source 64 and shield the other part. The shape of the light shielding plate 65 is such that the portion of the light flux that passes through the light shielding plate 65 is continuous, the shape of the portion that passes through the light shielding plate 65 is asymmetric with respect to the optical axis, and passes through the light shielding plate 65. It is formed so that the proportion of the portion is less than half. The light shielding plate 65 is configured to rotate around the optical axis by a motor directly connected to the rotation shaft. The light shielding plate 65 is connected to the light shielding plate driver 75 and is rotated by a driving current supplied from the light shielding plate driver 75. As the light shielding plate 65 rotates, the position of the portion of the light beam emitted from the light source 64 that passes through the light shielding plate 65 moves around the optical axis. In FIG. 17, the light path shielded by the light shielding plate 65 is indicated by a broken line arrow.

  The polarizers 53 and 54 are disposed at positions where light that has passed through the light shielding plate 65 and the lens 56 enters. Further, the polarizers 53 and 54 are configured such that the directions of the transmission axes of the polarizers 53 and 54 are different from each other with respect to a plane including two optical axes, an optical axis passing through the polarizer 53 and an optical axis passing through the polarizer 54. Fixed in the polarimeter. For this reason, when light passes through the polarizers 53 and 54, two linearly polarized lights having different directions of polarization planes are generated. As the light shielding plate 65 rotates, the position of the portion of the luminous flux that passes through the light shielding plate 65 moves around the optical axis, so that the amount of light incident on each of the polarizers 53 and 54 changes. Therefore, the ratio of the light amounts of the two linearly polarized light changes according to the rotation of the light shielding plate 65.

  Similar to the third embodiment, the analyzer 59 is fixed to the rotor of the hollow motor 60 and is rotated by the hollow motor 60. The hollow motor 60 is connected to a motor driver 72. As the analyzer 59 rotates, the amount of linearly polarized light passing through the analyzer 59 changes. The two linearly polarized light beams that have passed through the analyzer 59 pass through the hollow portion of the hollow motor 60, are collected by the lens 63, and enter the detector 62 together. When detecting the light, the detector 62 outputs a detection signal indicating the detected amount of light in voltage.

  The polarimeter includes a signal processing unit 71, and a detector 62 is connected to the signal processing unit 71 via an amplifier (not shown). The signal processing unit 71 is connected to a light shielding plate driver 75, a motor driver 72, and an output unit 73. Further, a lighting circuit 74 that turns on the light source 64 is connected to the signal processing unit 71.

  The lighting circuit 74 performs a process of continuously lighting the light source 64 by supplying a lighting current to the light source 64 continuously. The light shielding plate driver 75 rotates the light shielding plate 65 at a predetermined frequency. As a result, the ratio of the light amounts of the two linearly polarized lights generated by the polarizers 53 and 54 varies with the rotation frequency of the light shielding plate 65, and the light amount of the linearly polarized light passing through the analyzer 59 varies with the same frequency.

  FIG. 18 is a schematic characteristic diagram showing an example of a detection signal in the fourth embodiment. The horizontal axis in FIG. 18 is time, and the vertical axis is the signal intensity of the detection signal. FIG. 18A shows that the direction parallel to the transmission axis of the analyzer 59 is more parallel to the plane of polarization of the linearly polarized light generated by the polarizer 53 than the direction parallel to the plane of polarization of the linearly polarized light generated by the polarizer 54. The case close to the direction is shown. In this case, the component that the linearly polarized light generated by the polarizer 53 passes through the analyzer 59 has a higher intensity than the linearly polarized light generated by the polarizer 54. For this reason, the intensity of the detection signal increases when the amount of light passing through the light shielding plate 65 and passing through the polarizer 53 is larger than the amount of light passing through the polarizer 54, and the polarizer 54 exceeds the amount of light passing through the polarizer 53. When the amount of light passing through is larger, the intensity of the detection signal becomes smaller. Therefore, the detection signal is an AC signal that vibrates at the same frequency as the rotation of the light shielding plate 65.

  FIG. 18B shows that the direction parallel to the transmission axis of the analyzer 59 is more parallel to the plane of polarization of the linearly polarized light generated by the polarizer 54 than the direction parallel to the plane of polarization of the linearly polarized light generated by the polarizer 53. The case close to the direction is shown. In this case, the component of the linearly polarized light generated by the polarizer 54 that passes through the analyzer 59 has a higher intensity than the linearly polarized light generated by the polarizer 53. For this reason, when the amount of light passing through the polarizer 53 is larger than the amount of light passing through the polarizer 54, the intensity of the detection signal becomes small, and the amount of light passing through the polarizer 54 is more than the amount of light passing through the polarizer 53. When it is large, the intensity of the detection signal increases. Therefore, the detection signal vibrates at the same frequency as the rotation of the light shielding plate 65, and becomes an AC signal having a phase opposite to that shown in FIG. 18A.

  FIG. 18C shows a case where the direction parallel to the transmission axis of the analyzer 59 is at an intermediate position between the directions parallel to the polarization planes of the two linearly polarized light. Since the intensity of the component of the two linearly polarized light passing through the analyzer 59 is the same, even if the ratio of the light amount of the two linearly polarized light varies due to the rotation of the light shielding plate 65, the total amount of light passing through the analyzer 59 is Are the same. Therefore, the intensity of the detection signal is constant and the amplitude of the detection signal is zero.

  As in the second embodiment, the polarimeter according to the present embodiment determines the initial position of the analyzer 59 before the liquid sample is injected into the sample cell 58, and the liquid sample is injected into the sample cell 58. In this state, the signal processing unit 71 executes the processing of steps S31 to S35, thereby measuring the optical rotation of the liquid sample. In the present embodiment, in step S33, the signal processing unit 71 compares a predetermined reference signal that vibrates at the same frequency as the rotation of the light shielding plate 65 with the detection signal, and the detection signal and the reference signal have the same phase. The process which determines whether it is is is performed.

  As described above, the polarimeter according to the present embodiment measures the optical rotation of the liquid sample by executing the same process as the polarimeter according to the second embodiment. Therefore, also in this embodiment, the polarimeter can measure the optical rotation with high accuracy without using a Faraday cell.

  In the second to fourth embodiments, the analyzer 59 is rotated by the hollow motor 60. However, the polarimeter rotates the polarizer 14 by means other than the hollow motor 60 such as a gear. It may be a form to be made. In addition, the polarimeters according to Embodiments 2 to 4 are not limited to liquid samples, and may have a form in which the optical rotation can be measured for samples in a state other than a liquid such as a solid.

11, 51, 52, 64 Light source 14, 53, 54 Polarizer 15, 60 Hollow motor 16, 58 Sample cell 17 Beam splitter 21 Analyzer (first analyzer)
23 Detector (first detector)
31 Analyzer (second analyzer)
33 Detector (second detector)
41, 71 Signal processor (adjustment means)
55 Half mirror 59 Analyzer 62 Detector 65 Shading plate 74 Lighting circuit

Claims (4)

In a polarimeter that includes a polarizer that generates linearly polarized light, enters the generated linearly polarized light into the sample, and measures the optical rotation of the sample corresponding to the angle of rotation of the polarization plane of the linearly polarized light that passes through the sample.
Optical components that split linearly polarized light after passing through the sample;
A first analyzer that receives one of the branched linearly polarized light and passes a linearly polarized light component parallel to a specific transmission axis;
A first detector for detecting light that has passed through the first analyzer;
A second analyzer in which the direction of the transmission axis is different from that of the first analyzer and the other branched linearly polarized light is incident;
A second detector for detecting light that has passed through the second analyzer;
Rotating means for rotating the polarization plane of linearly polarized light before entering the sample by rotating the polarizer,
Adjusting means for adjusting a turning angle for turning the polarization plane by the turning means, so that a ratio of light detection amounts at the first detector and the second detector becomes a predetermined ratio;
And a means for determining the optical rotation of the sample based on the rotation angle adjusted by the adjusting means. The adjusting means is configured to adjust the rotation angle so that the detected amounts of light at the first detector and the second detector are the same. The polarimeter described. The first detector and the second detector are configured to output a signal corresponding to a detected amount of light,
The adjusting means includes
Means for alternately generating signals output from the first detector and the second detector at a first frequency to generate a first frequency signal that vibrates at the first frequency;
Means for extracting from the generated first frequency signal a second frequency signal that vibrates at a second frequency that is ½ of the first frequency;
The polarimeter according to claim 2, further comprising means for adjusting the rotation angle so that the magnitude of the extracted second frequency signal is minimized. The polarimeter according to any one of claims 1 to 3, wherein directions of transmission axes of the first analyzer and the second analyzer are different from each other by 90 °.

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