JP4977671B2 - Polarization modulator and measuring device - Google Patents

Description

  The present invention relates to a polarization modulator used in a measurement device that measures the optical rotation of a measurement target, and a measurement device that measures the optical rotation of a measurement target.

2. Description of the Related Art Conventionally, an optical rotation measuring device for measuring the optical rotation and concentration of a substance having optical activity such as sugars and amino acids is known. As a typical optical rotation measuring device, devices using a rotating polarizer method or a Faraday modulation method are known. However, these methods have a problem that the apparatus becomes large due to the need for mechanical drive, and a problem that a high voltage is required. As an optical rotation measuring apparatus for solving these problems, there is an apparatus using a polarization modulator that modulates linearly polarized light incident on a sample using two liquid crystal elements whose principal axis directions are shifted. As such a technique, for example, there is a conventional technique disclosed in Japanese Patent Application Laid-Open No. 2007-93289.
JP 2007-93289 A

  However, in the conventional optical rotation measuring device, depending on the wavelength of light incident on the sample, in order to obtain a predetermined birefringence phase difference, it is necessary to use a liquid crystal element with a slow response speed and a large cell gap, and the measurement time is long. There was a problem of becoming.

  The present invention has been made in view of the problems as described above, and an object of the present invention is to be used in a measuring device and a measuring device capable of measuring the optical rotation of a measurement target in a short measurement time. It is to provide a polarization modulator.

(1) The present invention provides a first polarizer that transmits a predetermined polarization component of light including a predetermined band component, and a polarization modulator that modulates light transmitted through the first polarizer into arbitrary polarization. A second polarizer that transmits a predetermined polarization component of the light that has passed through the measurement object via the polarization modulator, and a detector that detects the light transmitted through the second polarizer and converts it into an electrical signal The polarization modulator used in a measuring device for measuring the optical rotation of the measurement object,
A first liquid crystal element and a second liquid crystal element having different principal axis directions;
A voltage control unit for controlling a voltage applied to the first liquid crystal element and the second liquid crystal element,
Each of the first liquid crystal element and the second liquid crystal element includes a plurality of liquid crystal cells.

  According to the present invention, each of the first liquid crystal element and the second liquid crystal element is composed of a plurality of liquid crystal cells, so that the first and second liquid crystals can be formed using a liquid crystal cell having a fast response speed and a small cell gap. An element can be comprised and the optical rotation of a measuring object can be measured in a short measurement time.

(2) In the polarization modulator according to the present invention,
The first liquid crystal element and the second liquid crystal element have different principal axis directions due to different rubbing directions.

  In the present invention, the rubbing direction refers to the rubbing treatment direction (orientation direction) for aligning the liquid crystal, and the rubbing treatment may be a treatment of rubbing the alignment film with a rubbing cloth, or irradiating the alignment film with high energy light. It may be a process to do.

  According to the present invention, the operation of adjusting the main axis direction in which one of the first and second liquid crystal elements is inclined at a predetermined angle by making the rubbing directions of the first and second liquid crystal elements different from each other. Since it becomes unnecessary, the first and second liquid crystal elements can be integrated by being overlapped in parallel. The apparatus can be reduced in size by integrating the first and second liquid crystal elements to form a polarization modulator.

(3) In the polarization modulator according to the present invention,
The liquid crystal cell is a parallel alignment liquid crystal cell.

(4) In the polarization modulator according to the present invention,
The liquid crystal cell is a twist alignment liquid crystal cell.

  According to the present invention, by using the twist alignment liquid crystal cell, the optical rotation of the measurement object can be accurately measured even when there is an error in the principal axis orientation when the first and second liquid crystal elements are installed. Can do.

(5) In the polarization modulator according to the present invention,
The first liquid crystal element has a main axis direction inclined by an odd multiple of 45 ° with respect to the main axis direction of the first polarizer,
The second liquid crystal element has a main axis direction inclined at an even multiple of 45 ° with respect to the main axis direction of the first polarizer.

(6) Moreover, this invention is a measuring device which measures the optical rotation of a measuring object,
A first polarizer that transmits a predetermined polarization component of light including a predetermined band component;
A polarization modulation unit that modulates light transmitted through the first polarizer into arbitrary polarization;
A second polarizer that transmits a predetermined polarization component of the light transmitted through the measurement object via the polarization modulator;
A detector that detects the light transmitted through the second polarizer and converts it into an electrical signal;
The polarization modulator is
A first liquid crystal element and a second liquid crystal element having different principal axis directions;
A voltage control unit for controlling a voltage applied to the first liquid crystal element and the second liquid crystal element,
Each of the first liquid crystal element and the second liquid crystal element includes a plurality of liquid crystal cells.

  According to the present invention, each of the first liquid crystal element and the second liquid crystal element is composed of a plurality of liquid crystal cells, so that the first and second liquid crystals can be formed using a liquid crystal cell having a fast response speed and a small cell gap. An element can be comprised and the optical rotation of a measuring object can be measured in a short measurement time.

(7) In the measuring device according to the present invention,
It further includes an arithmetic processing unit that performs arithmetic processing for calculating the optical rotation of the measurement object based on the light intensity detected by the detection unit.

  Hereinafter, this embodiment will be described. In addition, this embodiment demonstrated below does not unduly limit the content of this invention described in the claim. In addition, all the configurations described in the present embodiment are not necessarily essential configuration requirements of the present invention.

1. Configuration of Measuring Device FIG. 1 is a block diagram for explaining the configuration of the measuring device of the present embodiment. The measuring device 1 is a device that measures the optical rotation of a sample 30 that is a measurement target. The measuring device 1 includes an optical system 10 and a control device 40. The control device 40 includes an arithmetic processing unit 50, which performs arithmetic processing for calculating the optical rotation of the sample 30 based on the optical elements included in the optical system 10 and the light intensity transmitted through the sample 30. Hereinafter, the device configuration of the measuring device 1 will be described.

1-1. Optical system 10
The optical system 10 includes a light source 12 and a detection unit 34. The optical system 10 includes a collimator lens 13, an interference filter 16, an analyzer 18 (first polarizer), first and second liquid crystal elements provided on an optical path L connecting the light source 12 and the detection unit 34. And a polarization modulator 20 (polarization modulator) including 22 and 24, and an analyzer 32 (second polarizer). These optical elements transmit light emitted from the light source 12 through the collimating lens 13, the interference filter 16, the analyzer 18 (first polarizer), the first liquid crystal element 22, and the second liquid crystal element 24. Light that is incident on the sample 30 and transmitted through the sample 30 is arranged so as to be incident on the detection unit 34 via the analyzer 32. Each will be described below.

  The light source 12 is a white light source such as a tungsten halogen lamp, and emits white light including a wide range of wavelength components.

  The collimating lens 13 converts the white light from the light source 12 guided by the optical fiber into parallel light, and causes the parallel light to enter the interference filter 16.

  The interference filter 16 transmits a predetermined wavelength component of parallel light. The interference filter 16 of the present embodiment transmits light having a center wavelength of 880 nm.

  The polarizer 18 is an incident-side polarizer that makes light transmitted through the interference filter 16 linearly polarized light. That is, the polarizer 18 transmits linearly polarized light having a polarization plane in the direction of the transmission axis (main axis direction). The polarizer 18 of this embodiment is installed so that the principal axis direction is 0 ° in the horizontal direction.

The polarization modulator 20 modulates the linearly polarized light transmitted through the polarizer 18 into arbitrary polarized light. The polarization modulation unit 20 controls the voltage applied to the liquid crystal element 21 including the first liquid crystal element 22 and the second liquid crystal element 24, and the first and second liquid crystal elements 22 and 24, respectively. And first and second voltage control units 23 and 25 that change the birefringence phase differences δ ₁ and δ ₂ of the second liquid crystal elements 22 and 24, and a temperature control unit 26 that controls the temperature of the liquid crystal element 21. Including.

The first liquid crystal element 22 installed in front of the light advance direction has a main axis in a direction rotated 45 ° counterclockwise toward the light advance direction with respect to the main axis direction (horizontal 0 °) of the polarizer 18. Further, the second liquid crystal element 24 installed on the back side in the light traveling direction has a main axis parallel to the main axis direction (horizontal 0 °) of the polarizer 18. Accordingly, the principal axis directions of the first and second liquid crystal elements 22 and 24 are deviated from each other by 45 °. Each of the first and second liquid crystal elements 22 and 24 includes a plurality of liquid crystal cells. Thus the birefringence phase difference of the first liquid crystal element 22 and [delta] _1, n pieces crystal cell of the respective birefringent phase difference constituting the first liquid crystal element 22 [delta] _{1 /} n, and the second liquid crystal element When the birefringence phase difference of 24 and [delta] _2, n pieces of liquid crystal cells each birefringent phase difference constituting the second liquid crystal element 24 becomes [delta] _{2 /} n. A nematic liquid crystal may be used as the liquid crystal of each liquid crystal cell, or a cholesteric liquid crystal or a ferroelectric liquid crystal may be used.

In this manner, the phase modulation is performed using the two liquid crystal elements 22 and 24 whose principal axis directions are 45 ° and 0 °, respectively, and the birefringence phase differences δ ₁ and δ ₂ are variable. The transmitted predetermined linearly polarized light can be changed to arbitrary linearly polarized light, elliptically polarized light or circularly polarized light.

  2A and 2B are diagrams schematically showing the liquid crystal element 21 including the first and second liquid crystal elements 22 and 24 of the present embodiment. FIG. 2A is a top view of the liquid crystal element 21.

  As shown in FIG. 2A, the liquid crystal element 21 includes a first liquid crystal element 22 and a second liquid crystal element. The first liquid crystal element 22 is composed of two liquid crystal cells 27, and the second liquid crystal element 24 is composed of two liquid crystal cells 28.

  Each of the liquid crystal cells 27 and 28 includes two transparent substrates TS, a transparent electrode EL provided on the inner surface of the transparent substrate TS, and a nematic liquid crystal LC sealed between the two transparent substrates TS. An alignment film AL1 is provided at the interface between the transparent substrate TS of the liquid crystal cell 27 and the nematic liquid crystal LC, and an alignment film AL2 is provided at the interface between the transparent substrate TS of the liquid crystal cell 28 and the nematic liquid crystal LC. The two liquid crystal cells 27 are overlapped on the transparent substrate TS to constitute the first liquid crystal element 22, and the two liquid crystal cells 28 are overlapped on the transparent substrate TS to constitute the second liquid crystal element 24. The first and second liquid crystal elements 22 and 24 are superimposed on the transparent substrate TS to form the liquid crystal element 21. Here, a configuration is adopted in which the number of transparent substrates TS where the liquid crystal cells 27 and 28 are overlapped is one, and the number of transparent substrates TS included in the liquid crystal element 21 is five as shown in FIG. Also good. At this time, a transparent electrode EL and an alignment film AL are provided on both surfaces of the transparent substrate TS excluding the transparent substrates TS at both ends.

  FIG. 3 is a diagram showing the relationship between applied voltage and response time for two liquid crystal cells having different cell gaps. In FIG. 3, the black dots indicate the response time for each applied voltage for a liquid crystal cell A having a small cell gap (5 μm) manufactured so that the birefringence phase difference is 360 ° or more with light having a wavelength of 589.3 nm. The white dots are for the liquid crystal cell B having a large cell gap (7 μm) manufactured so that the birefringence phase difference is 360 ° or more with light having a wavelength of 880.0 nm (light incident on the sample in this embodiment). The response time for each applied voltage is shown.

  As shown in FIG. 3, at any applied voltage, the liquid crystal cell B having a larger cell gap has a longer response time (lower response speed) than the liquid crystal cell A having a smaller cell gap. That is, when the birefringence phase difference is changed by 360 ° or more with light having a wavelength of 880.0 nm, the first and second liquid crystal elements 22 and 24 are measured using liquid crystal cells B each having a large cell gap. The time will be longer.

  Therefore, in the present embodiment, as shown in FIGS. 2A and 2B, the first and second liquid crystal elements 22 and 24 are each composed of a liquid crystal cell A (liquid crystal cell) having a small cell gap and a fast response speed. 27, 28) are configured using a plurality (two). Thus, the cell gap of each of the first and second liquid crystal elements 22 and 24 can be increased (5 × 2 = 10 μm), and the response speed of the first and second liquid crystal elements 22 and 24 can be increased. Can be fast. That is, a polarization modulation unit that can change the birefringence phase difference of the first and second liquid crystal elements 22 and 24 by 360 ° or more with light having a wavelength of 880.0 nm and can shorten the measurement time is configured. be able to.

  4A is a front view of the liquid crystal cell 27 that constitutes the first liquid crystal element 22, and FIG. 4B is a front view of the liquid crystal cell 28 that constitutes the second liquid crystal element 24.

  As shown in FIG. 4A, in the liquid crystal cell 27, the rubbing direction RD (alignment direction) is 45 ° with respect to the reference direction HD, and thus the main axis direction of birefringence is also 45 °. . As shown in FIG. 4B, in the liquid crystal cell 28, the rubbing direction RD (alignment direction) is 0 ° with respect to the reference direction HD, thereby the main axis direction of birefringence is also 0 °. Yes. That is, the direction of rubbing treatment applied to the two alignment films AL1 (see FIG. 2A) of the liquid crystal cell 27 is 45 ° with respect to the reference direction HD, and the two alignment films AL2 ( The direction of the rubbing process performed in FIG. 2 (A) is 0 ° with respect to the reference direction HD. The liquid crystal cell 28 may be configured such that the rubbing direction RD is 90 ° with respect to the reference direction HD. The reference direction HD is the same direction as the main axis direction (horizontal 0 °) of the polarizer 18.

  Thus, the rubbing directions of the liquid crystal cells 27 and 28 constituting the first and second liquid crystal elements 22 and 24 are set to 45 ° and 0 ° (or 90 °), respectively, so that the first and second liquid crystal elements are formed. The main axis directions of the first and second liquid crystal elements 22 and 24 can be shifted from each other by 45 ° without installing any one of 22 and 24 at 45 ° with respect to the other. Therefore, the first and second liquid crystal elements 22 and 24 can be integrated by being overlapped in parallel. And the apparatus can be reduced in size by comprising the polarization modulation part 20 with the liquid crystal element 21 which comprised the 1st and 2nd liquid crystal elements 22 and 24 integrally.

  FIG. 5 is a diagram schematically showing the polarization modulator 20 (polarization modulator) of the present embodiment.

  The polarization modulation unit 20 includes a temperature control unit 26 that controls the temperature of the liquid crystal element 21. The temperature control unit 26 includes a copper case CC, a temperature sensor TS, a Peltier element PD, a heat sink HS, and a cooling fan CF, and the temperature of the liquid crystal element 21 configured by integrating the first and second liquid crystal elements 22 and 24. Is controlled to be constant. The liquid crystal element 21 is housed in a copper case CC using copper having excellent heat conduction. Further, a temperature sensor TS such as a thermistor for detecting the temperature of the copper case CC and a Peltier element PD (thermoelectric element) for cooling (heat absorption) or heating the copper case CC are provided at a position in contact with the copper case CC. A heat sink HS (heat radiating plate) for dissipating the heat of the Peltier element PD is provided at a position in contact with the Peltier element PD, and a cooling fan CF is attached below the heat sink HS to supplement the heat diffusion capability of the heat sink HS. It has been. The copper case CC is provided with an opening OM through which incident light to the liquid crystal element 21 passes and an opening OM (not shown) through which light emitted from the liquid crystal element 21 passes, and the Peltier element PD and the heat sink HS are provided with , Each has an opening OM through which incident light to the liquid crystal element 21 passes.

  As shown in FIG. 5, by controlling the temperature of the liquid crystal element 21 to be constant by using the temperature control unit 26 including the copper case CC, the temperature sensor TS, the Peltier element PD, the heat sink HS, and the cooling fan CF, It is possible to prevent an error (fluctuation) from occurring in the birefringence phase difference of the first and second liquid crystal elements 22 and 24 with respect to the same applied voltage due to a change in environmental temperature. Further, by using the temperature control unit 26 to control the temperature of the liquid crystal element 21 formed by integrating the first and second liquid crystal elements 22 and 24, the liquid crystal element 21 and the temperature control unit 26 can be controlled. The apparatus can be configured in an integrated manner, and the apparatus can be reduced in size as compared with the case where a temperature control unit is provided for each of the two liquid crystal elements that are not integrated (the temperature of each liquid crystal element is individually controlled). . Note that the temperature of the liquid crystal element 21 is preferably controlled to be constant at a temperature higher than the environmental temperature in order to prevent condensation.

  Referring again to FIG. 1, the analyzer 32 is an output-side polarizer that uses light that has passed through the sample 30 as linearly polarized light. That is, the analyzer 32 transmits linearly polarized light having a polarization plane in the direction of the transmission axis (main axis direction). The polarizer 32 of this embodiment is installed so that the principal axis direction is horizontal 45 °.

  The detection unit 34 includes, for example, a photoelectric sensor (photodetector), detects the light intensity of light emitted from the analyzer 32, converts the light intensity into a voltage, and outputs the light intensity information.

1-2. Control device 40
The control device 40 includes an arithmetic treatment unit 50, a control signal generation unit 60, and a storage unit 70.

  The arithmetic processing unit 50 performs arithmetic processing for calculating the optical rotation of the sample 30 based on the light intensity information output from the detection unit 34.

The control signal generation unit 60 generates a control signal, and the first voltage control unit 23 (the liquid crystal driver of each liquid crystal cell 27 constituting the first liquid crystal element 22) and the second voltage control unit 25 (the second voltage control unit 25). The liquid crystal driver of each liquid crystal cell 28 constituting the liquid crystal element 24 is controlled to change the birefringence phase differences δ ₁ and δ ₂ of the first and second liquid crystal elements 22 and 24.

  Further, the control signal generation unit 60 controls the operation of the temperature control unit 26. For example, a control signal is generated based on the output from the temperature sensor TS shown in FIG. 5, and the operations of the Peltier element PD and the cooling fan CF shown in FIG. 5 are controlled.

The storage unit 50 has a function of temporarily storing various data. For example, the light intensity information output from the detection unit 34 is used as the birefringence phase differences δ ₁ , δ of the first and second liquid crystal elements 22, 24. ₂ and stored in association with each other.

2. Optical rotation measurement principle Next, the optical rotation measurement principle employed by the measurement apparatus of the present embodiment will be described.

2-1. Theoretical expression of the light intensity of the light detected by the detection unit 34 When the Stokes parameter of the monochromatic light incident on the polarizer 18 is S _in and the Stokes parameter of the light transmitted through the sample 30 and emitted from the analyzer 32 is S ′. , S ′ can be expressed by the following equation.

Note that I ₀ is the light intensity of monochromatic light incident on the polarizer 18. P _{0 °} is a Mueller matrix of the polarizer 18 whose principal axis direction is 0 °. The _R δ1,45 _° is the Mueller matrix of the first liquid crystal element 22 birefringence phase difference is the principal axis direction is 45 ° is [delta] _1. The _R δ2,0 _° is the Mueller matrix of the second liquid crystal element 24 the principal axis direction is ₂ birefringent phase difference δ is 0 °. _Tφ is the Mueller matrix of the sample 30 whose optical rotation is φ. A _{45 °} is a Mueller matrix of the analyzer 32 whose principal axis orientation is 45 °.

Here, assuming that the light intensity of the light detected by the detection unit 34 is I (δ ₁ , δ ₂ , φ), the I (δ ₁ , δ ₂ , φ) is a Stokes parameter of the light emitted from the analyzer 32. Since S ₀ ′, from equation (1),

It becomes.

2-2. Calculation principle of the optical rotation of the sample 30 The optical rotation of the sample 30 is obtained as follows by measuring the light intensity of the light passing through the sample 30 and the analyzer 32 while changing the polarization state of the light incident on the sample 30. .

For example, the birefringence phase differences δ ₁ and δ ₂ of the first and second liquid crystal elements 22 and 24 are set as δ ₁ = δ and δ ₂ = δ + π / 2, and δ is continuously from 0 ° to 360 °. Change. At this time, assuming that the light intensity detected by the detection unit 34 is I (δ, δ + π / 2, φ), the I (δ, δ + π / 2, φ) is obtained from the equation (2):

It becomes. Where _a (= I 0 / _4sin2φ) and _b (= I 0 / _8cos2φ) indicate respectively the coefficients of the Fourier function cosδ and Sin2deruta. From equation (3), it can be seen that when δ is continuously modulated in the range of 0 ° to 360 °, the light intensity I (δ, δ + π / 2, φ) changes periodically. Therefore, the optical rotation φ of the sample 30 is obtained by performing Fourier analysis on the periodic change of the light intensity I (δ, δ + π / 2, φ) detected by the detector 34 and obtaining the coefficients a and b.

Can be calculated.

Further, the birefringence phase differences δ ₁ and δ ₂ of the first and second liquid crystal elements 22 and 24 are modulated four times, 0, π / 2, π, and 3π / 2, respectively, and the detection unit 34 detects at this time. From the four light intensity values, the optical rotation φ of the sample 30 is

Can be calculated. Here, I ₁ is the light intensity detected by the detection unit 34 when the birefringence phase differences δ ₁ and δ ₂ of the first and second liquid crystal elements 22 and 24 are set to 0. I ₂ is the light intensity detected by the detector 34 when the birefringence phase differences δ ₁ and δ ₂ are set to π / 2. I ₃ is the light intensity detected by the detector 34 when the birefringence phase differences δ ₁ and δ ₂ are set to π. I ₄ is the light intensity detected by the detector 34 when the birefringence phase differences δ ₁ and δ ₂ are set to 3π / 2. According to this method (phase modulation method), since the birefringence phase differences δ ₁ and δ ₂ of the first and second liquid crystal elements 22 and 24 need only be modulated four times, the optical rotation φ is calculated at high speed. It becomes possible.

3. Modifications The present invention is not limited to the above-described embodiment, and various modifications can be made. The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  For example, in the present embodiment, the case where parallel alignment liquid crystal cells having parallel alignment directions are used as the plurality of liquid crystal cells constituting the first and second liquid crystal elements 22 and 24 has been described. As the plurality of liquid crystal cells constituting the liquid crystal elements 22 and 24, twist alignment liquid crystal cells having twisted alignment directions may be used.

  An arbitrary polarization state can be obtained by changing the birefringence phase difference of the first and second liquid crystal elements 22 and 24 by setting the principal axis directions of the first and second liquid crystal elements 22 and 24 to 45 ° and 0 °, respectively. However, if the first and second liquid crystal elements 22 and 24 are constituted by parallel alignment liquid crystal cells, the angle (main axis direction) at the time of installation of the first and second liquid crystal elements 22 and 24 is shifted. In this case, the polarization state necessary for measuring the optical rotation may not be produced.

  FIG. 6 is a Poincare sphere showing the polarization state of the light emitted from the second liquid crystal element 24. The polarization state of the emitted light when the birefringence phase difference of the first and second liquid crystal elements 22 and 24 is changed from 0 ° to 720 ° is indicated by the trajectory D on the Poincare sphere shown in FIG.

  Here, if the principal axis orientations (45 °, 0 °) of the first and second liquid crystal elements 22 and 24 are shifted by −5 ° and + 5 °, respectively, the first and second liquid crystal elements 22 and 24 are respectively connected to the plurality of first and second liquid crystal elements 22 and 24. When the liquid crystal cell is composed of parallel alignment liquid crystal cells (when the twist angles of the first and second liquid crystal elements 22 and 24 are each 0 °), the polarization state of the region A on the Poincare sphere shown in FIG. 6 cannot be created.

  Therefore, when the first and second liquid crystal elements 22 and 24 are respectively composed of twist-aligned liquid crystal cells, and the twist angles of the first and second liquid crystal elements 22 and 24 are 10 °, respectively, as shown in FIG. The region A becomes smaller, and when the twist angles of the first and second liquid crystal elements 22 and 24 are each 20 °, the region A disappears. That is, the region A can be reduced as the twist angle of the first and second liquid crystal elements 22 and 24 is increased.

  As described above, when the first and second liquid crystal elements 22 and 24 are respectively constituted by twist alignment liquid crystal cells, there is an error in the principal axis directions of the first and second liquid crystal elements 22 and 24. It is also possible to create a polarization state necessary for measuring the optical rotation.

  FIG. 8 is a diagram (top view) schematically showing the first and second liquid crystal elements 22 and 24 configured using twist alignment liquid crystal cells. In FIG. 8, illustration of the transparent electrode is omitted.

  In the example shown in FIG. 8, the first liquid crystal element 22 is constituted by two twist-aligned liquid crystal cells 27 having a twist angle of 10 °, and similarly the second liquid crystal element 24 has a twist angle of 10 °. Two twist alignment liquid crystal cells 28 are used. That is, the rubbing direction (alignment direction) of the alignment film AL of the two liquid crystal cells 27 constituting the first liquid crystal element 22 is set to 45 °, 55 °, 55 °, 65 ° in this order from the front side in the light traveling direction. The rubbing direction (alignment direction) of the alignment film AL of the two liquid crystal cells 28 constituting the second liquid crystal element 24 is set to 0 °, 10 °, 10 °, and 20 ° sequentially from the front side in the light traveling direction. That is, the twist angles of the first and second liquid crystal elements 22 and 24 shown in FIG. 8 are each 20 °, and the principal axis directions are 65 ° and 20 °, respectively.

Note that when each of the first and second liquid crystal elements is composed of n twist alignment liquid crystal cells, the Mueller matrix R _i of the i th (i = 1 to n) twist alignment liquid crystal cell is

It becomes. Here [delta] is the birefringence phase difference of the i-th liquid crystal cell, the birefringence phase difference of the first or second liquid crystal element and [delta] _R, it can be determined by δ = δ _{R /} n. Θ is the principal axis orientation of the i-th liquid crystal cell, and can be obtained by the following equation, where θ _R is the principal axis orientation of the first or second liquid crystal element and α is the twist angle.

  In the case where the first and second liquid crystal elements 22 and 24 are respectively composed of twist-aligned liquid crystal cells, the first and second liquid crystal elements 22 and 24 are formed using a Stokes polarimeter shown in FIG. The polarization state (Stokes parameter) of the emitted light from the first and second liquid crystal elements 22 and 24 (liquid crystal element 21) with respect to each voltage value to be applied is measured in advance, and based on the measurement result, shown in FIG. It is desirable to measure the optical rotation of the sample with the measuring device 1.

  It can be used not only for measuring the concentration of soft drinks and fruits, but also for analyzing molecular structures such as proteins, amino acids, and nucleic acids, and for quality control of chemicals. Moreover, it can utilize as a blood glucose level sensor which measures a blood glucose level.

The block diagram for demonstrating the structure of the measuring device of this embodiment. The figure which shows typically the liquid crystal element comprised from the 1st and 2nd liquid crystal element of this embodiment. The figure which shows the relationship between an applied voltage and a response speed about two liquid crystal cells from which a cell gap differs. The front view of the liquid crystal cell which comprises the 1st and 2nd liquid crystal element of this embodiment. The figure which shows typically the polarization modulation part of this embodiment. The figure for demonstrating a modification. The figure for demonstrating a modification. The figure for demonstrating a modification. The figure for demonstrating a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measuring apparatus, 10 Optical system, 12 Light source, 13 Collimate lens, 16 Interference filter, 18 Polarizer, 20 Polarization modulation part (polarization modulator), 21 Liquid crystal element, 22 1st liquid crystal element, 23 1st voltage control Unit, 24 second liquid crystal element, 25 second voltage control unit, 26 temperature control unit, 27 liquid crystal cell, 28 liquid crystal cell, 30 sample, 32 analyzer, 34 detection unit, 40 control unit, 50 arithmetic processing unit, 60 control signal generation unit, 70 storage unit

Claims (6)

A measuring device for measuring the optical rotation of a measurement object,
A first polarizer that transmits a predetermined polarization component of light including a predetermined band component;
A polarization modulation unit that modulates light transmitted through the first polarizer into arbitrary polarization;
A second polarizer that transmits a predetermined polarization component of the light transmitted through the measurement object via the polarization modulator;
A detector that detects the light transmitted through the second polarizer and converts it into an electrical signal;
The polarization modulator is
A first liquid crystal element and a second liquid crystal element having different principal axis directions;
A voltage control unit for controlling a voltage applied to the first liquid crystal element and the second liquid crystal element,
The measuring apparatus, wherein each of the first liquid crystal element and the second liquid crystal element includes a plurality of liquid crystal cells. In claim 1 ,
The measurement apparatus further comprising: an arithmetic processing unit that performs arithmetic processing for calculating the optical rotation of the measurement object based on the light intensity detected by the detection unit. In claim 1 or 2,
The measuring apparatus according to claim 1, wherein the first liquid crystal element and the second liquid crystal element have different principal axis directions due to different rubbing directions. In any one of Claims 1-3,
The liquid crystal cell is a parallel alignment liquid crystal cell. In any one of Claims 1-3,
The liquid crystal cell is a twist alignment liquid crystal cell. In any one of Claims 1-5,
The first liquid crystal element has a main axis direction inclined by an odd multiple of 45 ° with respect to the main axis direction of the first polarizer,
The measuring apparatus according to claim 2, wherein the second liquid crystal element has a main axis direction inclined at an even multiple of 45 ° with respect to the main axis direction of the first polarizer.