JP5905318B2 - Circular polarized light source system and circular dichroism measurement system - Google Patents

Description

  The present invention relates to a circularly polarized light source system and a circular dichroism measuring system including the circularly polarized light source system.

  Circular dichroism (CD) is a phenomenon caused by optical activity (chirality) of a molecule, and is defined as a difference in absorbance with respect to left and right circularly polarized light. Since this circular dichroism spectral information reflects the higher order structure of the molecule, it is often applied particularly to analysis of higher order structures of physiologically active substances.

  In order to measure circular dichroism, it is necessary to measure the difference in absorbance between right circularly polarized light and left circularly polarized light. Two types of circularly polarized light can be easily created by passing linearly polarized light through a quarter-wave plate. Specifically, for linearly polarized light in the X-axis direction, the optical axis is relative to the X-axis direction. By transmitting through a 1 / 4λ wave plate having an inclination of 45 °, left circularly polarized light is transmitted, and by transmitting a 1 / 4λ wave plate having an optical axis of −45 ° with respect to the X-axis direction. It can be right circularly polarized light.

  In the measurement of circular dichroism, measurement by a so-called modulation method is common. In the modulation method, an optical phase modulator such as a photoelastic modulator or a Pockel cell is used as a circular polarization modulator that generates circularly polarized light. However, it is known that a distortion component exists in the modulation of the circular polarization modulator (see, for example, Patent Document 1 and Non-Patent Document 1). In addition, it is known that the distortion component in this modulation becomes an artifact in the measurement of circular dichroism by coupling with the linear dichroism, linear polarization birefringence, circular polarization birefringence, etc. of the sample. ing. Due to the influence of this artifact, the modulation method has not been suitable for the measurement of circular dichroism of samples having macroscopic anisotropy such as solids, films, and liquid crystals (for example, non-patented). Reference 2).

  In contrast, various methods for measuring circular dichroism of solids, films, liquid crystals, and the like have been studied. For example, Patent Document 1 discloses a method of irradiating a sample with unpolarized light and causing the light transmitted through the sample to enter a circular polarization modulator and an analyzer (polarizing plate). Further, Patent Document 2 discloses a method of canceling an artifact component by acquiring the artifact components having different signs from each other by performing measurement when the sample is turned over, and adding them together.

Japanese Patent No. 3341828 Japanese Patent No. 4010760

Kamito, Spectroscopic Research, Vol. 34, No. 3, 153 (1985) Kamito, Spectroscopic Research, Vol.34, No.4, p.215 (1985)

  However, in the above method, the influence of the artifact derived from the circular polarization modulator cannot be sufficiently removed, and it is difficult to accurately measure the circular dichroism of the sample.

  The present invention has been made in view of the above, and a circularly polarized light source system capable of removing components derived from distortion and emitting more pure circularly polarized light, and a circular dichroism including the circularly polarized light source system An object is to provide a measurement system.

In order to achieve the above object, a circularly polarized light source system according to the present invention is a circularly polarized light source system that emits right circularly polarized light and left circularly polarized light, and a light source that emits linearly polarized light and the linearly polarized light from the light source. When the wavelength of the linearly polarized light is incident and λ, the maximum value δ ₀ of the phase difference between two polarization components having a vibration plane different from that of the linear polarization and orthogonal to each other is 1 / 4λ <δ. Included in the optical phase modulation means for periodically modulating the phase difference so as to be ₀ and emitting the light after the phase difference modulation, and the light subjected to the phase difference modulation by the optical phase modulator Control means for emitting circularly polarized light corresponding to the timing at which the output of the light of the horizontal polarization component becomes zero out of the light of the horizontal polarization component and the light of the circular polarization component.

According to the above circularly polarized light source system, in the optical phase modulation means, the maximum value δ ₀ of the phase difference between two polarization components having a vibration plane different from that of the linearly polarized light and orthogonal to each other is 1 / 4λ. By periodically modulating and emitting the phase difference so as to satisfy <δ ₀ , the output of the light of the horizontal polarization component that was not generated due to distortion according to the conventional circular polarization modulator is zero. The timing becomes. Therefore, the control means emits the circularly polarized light from the optical phase modulation means in response to the timing when the output of the horizontally polarized light becomes zero, thereby obtaining a purer circle from which the distortion-derived components have been removed. It becomes possible to emit polarized light.

  Here, as a configuration that effectively exhibits the above-described operation, specifically, a gate provided on an optical path of light emitted from the optical phase modulation means is further provided, and the control means opens and closes the gate by opening and closing the gate. There is a mode in which circularly polarized light is emitted corresponding to the timing when the output of the light of the horizontal polarization component becomes zero by switching between passage and blocking of light from the optical phase modulation means.

  As described above, by opening the gate provided on the optical path in response to the timing when the output of the light of the horizontal polarization component becomes zero, the light is allowed to pass through, so that more pure circularly polarized light can be obtained from the circularly polarized light source system. The light can be emitted.

  Further, as another configuration that effectively achieves the above-described operation, the light source is a pulse light source, and the control unit corresponds to the timing at which the output of the light of the horizontal polarization component becomes zero, from the pulse light source. A mode in which linearly polarized light is emitted can also be adopted.

  As described above, the light source is a pulsed light source, and the configuration in which linearly polarized light is incident on the optical phase modulation means in correspondence with the timing when the output of the light of the horizontal polarization component becomes zero, from the circularly polarized light source system, It becomes possible to emit more pure circularly polarized light.

  The control means detects the light emitted from the optical phase modulation means with a circularly polarized light detector, and determines the timing when the output of the horizontal polarization component becomes zero based on the detection result of the circularly polarized light detector. It can also be set as an aspect.

  When the above configuration is provided, the timing for emitting the circularly polarized light from the circularly polarized light source system is determined while detecting whether or not the light emitted from the optical phase modulation means is only the circularly polarized light component. Therefore, for example, it is not necessary to measure in advance the timing when the light output of the horizontal polarization component becomes zero, and it becomes possible to emit more appropriately pure circularly polarized light.

  The present invention can also be described as a circular dichroism measurement system including a circularly polarized light source system.

  That is, the circular dichroism measurement system according to the present invention emits right circularly polarized light and left circularly polarized light to the sample by modulating linearly polarized light, and the circularly polarized light source system. A light detecting means for detecting the light transmitted by the sample by converting it into an electric signal, a right circularly polarized image storing means for storing the right circular polarized light of the electric signal detected by the light detecting means, and a light Left circularly polarized image storage means for storing an electrical signal detected by the detection means by left circularly polarized light, an electrical signal by right circularly polarized light stored in the right circularly polarized image storage means, and a left circularly polarized image storage means Output means for obtaining a difference from the electrical signal of the left circularly polarized light stored in, and outputting the result as a circular dichroic image.

According to the above circular dichroism measurement system, the maximum value of the phase difference between two polarization components having a vibration plane different from the plane of vibration of the linearly polarized light in the optical phase modulation means of the circularly polarized light source system. More purely emitted in response to the timing when the output of the light of the horizontal polarization component obtained by periodically modulating and emitting the phase difference so that δ ₀ is 1 / 4λ <δ ₀ is emitted. Since circular dichroism is measured using circularly polarized light, more accurate circular dichroism can be measured.

  According to the present invention, there are provided a circularly polarized light source system capable of removing components derived from distortion and emitting more pure circularly polarized light, and a circular dichroism measuring system including the circularly polarized light source system.

It is a schematic block diagram explaining the structure of the circularly polarized light source system which concerns on 1st Embodiment. It is a figure explaining the time fluctuation of the light radiate | emitted from the conventional circular polarization modulator. It is a figure explaining the time fluctuation | variation of the light radiate | emitted from the circularly-polarized light modulator of the circularly-polarized light source system which concerns on 1st Embodiment. It is a schematic block diagram explaining the structure of the circular dichroism measuring system which concerns on 2nd Embodiment. It is a schematic block diagram explaining the structure of the circularly polarized light source system which concerns on 3rd Embodiment. It is a schematic block diagram explaining the structure of the circularly polarized light source system which concerns on 4th Embodiment. It is a schematic block diagram explaining the structure of the circularly polarized light detector contained in a circularly polarized light source system. It is a timing chart which put together the signal of each device in the case of emitting right circularly polarized light. It is a timing chart which put together the signal of each device in the case of emitting left circularly polarized light. It is a schematic block diagram explaining the structure of the circularly polarized light source system which concerns on 5th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is a schematic configuration diagram illustrating a configuration of a circularly polarized light source system 1 including a circularly polarized light modulator according to the first embodiment of the present invention. As shown in FIG. 1, the circularly polarized light source system 1 includes a light source 10, a monochromatic filter 20, a polarizing plate 30, a circularly polarized light modulator 40, a gate 60, and a gate driving device 81. In the circularly polarized light source system 1 of FIG. 1, for example, it is used as a part of an apparatus for capturing a circular dichroic image. In this case, right circularly polarized light and left circularly polarized light are emitted from the gate 60 and irradiated to a sample or the like disposed in the subsequent stage, whereby a right circularly polarized image and a left circularly polarized image related to the sample are captured, and Based on this, a circular dichroic image is formed. In the following embodiments, the configuration of each unit will be described on the assumption that the circularly polarized light source system 1 is used in a circular dichroic image capturing apparatus.

  The light source 10 emits light for irradiating the sample. The light emitted from the light source 10 is non-polarized light. For example, a deuterium lamp that emits light having a wavelength of 280 nm is used as the light source 10.

  The light emitted from the light source 10 passes through the monochromatic filter 20 and enters the polarizing plate 30. The monochromatic filter 20 is provided to remove wavelength components, noise components, and the like that are unnecessary for forming a circular dichroic image. In the circularly polarized light source system 1 of the present embodiment, the monochromatic filter 20 that transmits light having a wavelength of 280 nm is used. The polarizing plate 30 extracts linearly polarized light from the light emitted from the light source 10. For example, a Grand Taylor prism is used as the polarizing plate 30. Here, it is assumed that the polarizing plate 30 extracts linearly polarized light in the direction of 0 ° with respect to the X axis.

  The linearly polarized light extracted by the polarizing plate 30 is converted into right circularly polarized light or left circularly polarized light by the circular polarization modulator 40 and is emitted. The circular polarization modulator 40 includes an optical phase modulator 41 (optical phase modulation means) and a modulation signal oscillator 42 (control means). The optical phase modulator has an optical axis in a 45 ° direction with respect to the X axis. The modulation signal oscillator 42 uses a signal instructing conversion to right circularly polarized light and a signal instructing conversion to left circularly polarized light as modulation signals, and periodically oscillates these signals alternately. The modulation signal oscillator 42 oscillates a modulation signal having a period of 50 kHz, for example. Then, based on the modulation signal oscillated by the modulation signal oscillator 42, the phase difference between the two polarization components orthogonal to each other changes periodically with respect to the linearly polarized light incident on the optical phase modulator 41. By being modulated, the light is alternately converted into right circularly polarized light or left circularly polarized light and emitted. As specific elements of the optical phase modulator 41, for example, a photoelastic modulator, a Pockel cell, or the like is used.

  The modulation signal from the modulation signal oscillator 42 is sent from the modulation signal oscillator 42 to the gate driving device 81 (control means). The gate driving device 81 transmits an opening / closing signal to the gate 60 based on the modulation signal from the modulation signal oscillator 42. The gate 60 switches between passing and blocking of the light whose phase difference is modulated by the optical phase modulator 41 based on the opening / closing signal from the gate driving device 81.

Here, in the optical phase modulator 41, when the wavelength of the linearly polarized light from the light source 10 is λ, the phase difference between two polarization components that have a vibration surface different from the vibration surface of the linearly polarized light and are orthogonal to each other. When the maximum value (maximum delay amount) of δ is δ ₀ , modulation is periodically applied to the phase difference so that ¼λ <δ ₀ . In this regard, after describing the configuration of a general circular polarization modulator, the maximum delay amount in the circular polarization modulator 40 of the present embodiment will be described.

According to Patent Document 1 and Non-Patent Document 1, when a Mueller matrix representing an optical element is used, a circularly polarized light modulator having an optical axis in a 45 ° direction with respect to the X axis is expressed by the following formula (1). It is expressed as a matrix. Here, δ is a phase difference between the x and y axes of the circular polarization modulator, and α is a distortion component of the circular polarization modulator. δ is expressed as in Equation (2), t is time, ω is the angular velocity of modulation of the circular polarization modulator, δ ₀ is the maximum delay amount of the circular polarization modulator, and circular dichroism is measured. 1 / 4λ.

  When linearly polarized light in the X-axis direction is incident on the circular polarization modulator, the resulting Stokes vector of the transmitted light is calculated by Equation (3) as described in Non-Patent Document 1.

  According to Equation (3), the light emitted from the circular polarization modulator is represented by the circular polarization component represented by the third term [−sin (δ + α)] and the fourth term [cos (δ + α)]. Horizontal polarization component.

  Here, when α is 0, that is, when the circularly polarized light modulator is ideally operated without distortion, the time change between the circularly polarized light component and the horizontally polarized light component in the above equation is shown in FIG. . According to FIG. 2A, the horizontal polarization component becomes 0 at ωt = 0.5π and 1.5π. Therefore, the light emitted from the circular polarization modulator at this timing should be only the circular polarization component. The circularly polarized light component is −1 when ωt = 0.5π, that is, left circularly polarized light, and is 1 when ωt = 1.5π, that is, right circularly polarized light.

  However, since an actual circular polarization modulator has a distortion component α, the circular polarization component and the horizontal polarization component do not vary as shown in FIG. FIG. 2B shows the time change of each component when the distortion component α is included. Each element of the Stokes vector becomes a curve represented in FIG. 2B. As a result, although there is a timing when the horizontal polarization component is 0 and the circular polarization component is −1, that is, there is a timing when the left circular polarization is pure, There is no timing at which the horizontal polarization component is 0 and the circular polarization component is 1, that is, pure right circular polarization. Therefore, if the circular polarization modulator is distorted, there is a problem that pure left and right circular polarization cannot be modulated.

On the other hand, as in the present embodiment, the third and fourth terms of the Stokes vector in the light emitted from the circular polarization modulator 40 when the maximum delay amount δ ₀ of the optical phase modulator 41 is ½λ. That is, FIG. 3A shows temporal changes of the circularly polarized light component and the horizontally polarized light component. In FIG. 3A, both the circularly polarized light component and the horizontally polarized light component show different curves from the changes shown in FIG. Then, at the timing indicated by L in FIG. 3A, that is, when the circular polarization component is -1 and the horizontal polarization component is 0, the left circular polarization is 1, the circular polarization component indicated by R is 1, and the horizontal polarization component At the timing when becomes 0, the right circularly polarized light is emitted from the circular polarization modulator 40, respectively. Therefore, the gate drive device 81 adjusts the timing of the drive signal so that the gate 60 is opened at the timing of L or R shown in FIG. As a result, when the gate 60 is opened corresponding to the timing of L shown in FIG. 3A and the gate 60 is closed in other time zones, as a result, the left circularly polarized light from the circularly polarized light source system 1 is obtained. Is emitted. In this left circularly polarized light, the ratio of the horizontal polarized light component to the circularly polarized light component is low, so that the left circularly polarized light close to pure is emitted. Similarly, when the gate 60 is opened corresponding to the timing of R shown in FIG. 3A and the gate 60 is closed in other time zones, as a result, a right circle that is purely close to the circularly polarized light source system 1 is obtained. Polarized light is emitted.

In the circularly polarized light source system 1, at what timing the state indicated by L and R in FIG. 3A, that is, the state where the horizontal polarization component becomes 0 and the circular polarization component becomes −1 or 1 ( The timing at which the gate driving device 81 opens and closes the gate 60 varies depending on the value of the distortion α and the maximum delay amount δ _{0 in} the circular polarization modulator 40, and therefore measurement is separately performed using the circular polarization modulator 40. It is necessary to obtain the timing when the L and R states are obtained, and to obtain the opening / closing timing of the gate 60 based on this.

In addition, the time zone in which the gate 60 is opened is set to a predetermined time width centering on the timing of the R and L situations shown in FIG. By providing the time width, light in a region other than the timing in which the conditions of R and L are obtained is also emitted. Therefore, when the time width is widened, the horizontal polarization component is mixed into the circularly polarized light component. As shown in FIG. 3B, the mixing ratio varies depending on the maximum delay amount δ ₀ and the distortion α, and therefore it is necessary to set an appropriate value in each optical system. For example, when the circular polarization modulator 40 has the maximum delay amount δ ₀ = 1 / 2λ and distortion α = 0.5, the open time of the gate 60 is set to 0.00% in order to reduce the ratio of the horizontal polarization component to 5% or less. Set to 2 μs or less.

As described above, according to the circularly polarized light source system 1 according to the present embodiment, in the optical phase modulator 41, the phase difference between two polarization components orthogonal to each other having a vibration plane different from that of linearly polarized light is obtained. By modulating the phase difference so that the maximum value δ ₀ is ¼λ <δ ₀ and emitting the light subjected to the phase difference modulation, the light subjected to the phase difference modulation is emitted. The output of the light of the horizontal polarization component contained becomes zero, and the timing at which pure left circular polarization and right circular polarization are obtained, that is, the timings of L and R in FIG. The timing at which the output of the light of the horizontal polarization component becomes zero and pure left-handed circularly polarized light and right-handed circularly polarized light are obtained is due to distortion in the case of using a conventional circularly polarized light modulator. Accordingly, the gate 60 is opened and closed based on the transmission signal from the modulation signal oscillator 42, and light is allowed to pass according to the timing of R or L, so that a more pure left circle can be obtained from the circularly polarized light source system 1. Polarized light or right circularly polarized light can be emitted.

(Second Embodiment)
FIG. 4 is a schematic configuration diagram illustrating the configuration of a circular dichroism measurement system 1A according to the second embodiment of the present invention. A circular dichroism measurement system 1A according to the second embodiment is a circular dichroism measurement system 1A to which the circularly polarized light source system 1 according to the first embodiment is applied.

As shown in FIG. 4, the circular dichroism measuring system 1A includes a light source 10, a monochromatic filter 20, a polarizing plate 30, a circular polarization modulator 40, a gate 60, a gate driving device 81, a photodetector 100, and a signal switching device 110. , A right circular polarization image storage unit 111, a left circular polarization image storage unit 112, an image calculation unit 120, and an output unit 130. Among these, the light source 10, the monochromatic filter 20, the polarizing plate 30, the circular polarization modulator 40, the gate 60, and the gate drive device 81 have the same configuration as the circular polarization light source system 1 in the first embodiment. In other words, in the optical phase modulator 41 constituting the circular polarization modulator 40, the maximum value (maximum delay amount) δ between two polarization components having a vibration plane different from that of linearly polarized light and orthogonal to each other. _The point that ₀ satisfies the relationship of 1 / 4λ <δ ₀ is the same as in the first embodiment. The difference from the first embodiment is that a signal from the gate driving device 81 is transmitted to the signal switching device 110.

  The sample 50 is disposed between the circular polarization modulator 40 and the gate 60. That is, the light passing through the gate 60 is transmitted light that is emitted from the light source 10 and modulated by the circular polarization modulator 40 and then transmitted through the sample 50. The photodetector 100 has a function of converting the transmitted light that has passed through the gate 60 into an electrical signal. Then, the electrical signal converted by the photodetector 100 is stored by the signal switching device 110 separately into a right circularly polarized image storage unit 111 and a left circularly polarized image storage unit 112.

  In the circular dichroism measurement system 1A, when non-polarized light is emitted from the light source 1, light having a predetermined wavelength is selected by the monochromatic filter 20, and the polarizing plate 30 causes the light in the X-axis direction (0 °). Only linearly polarized light is extracted. This linearly polarized light reaches the sample 50 after passing through the circular polarization modulator 40 having the optical axis in the direction of 45 ° with respect to the X axis. The light that has passed through the sample 50 passes through the gate 60, enters the photodetector 100, and is converted into an electrical signal by the photodetector 100.

  Here, when the modulation signal from the modulation signal oscillator 42 of the circular polarization modulator 40 is transmitted to the gate drive device 81, the circularly polarized light emitted from the circular polarization modulator 40 does not include the light of the horizontal polarization component. The opening / closing of the gate 60 is adjusted so as to allow light to pass according to the time zone. That is, by turning the gate 60 open at the timings L and R shown in FIG. 3A and closing the gate 60 in other time zones, pure circularly polarized light with a very low proportion of the horizontal polarization component is gated. 60 passes through and enters the photodetector 100.

  Information relating to gate opening / closing by the gate driving device 81 is transmitted to the signal switching device 110. Accordingly, the signal switching device 110 determines whether the signal transmitted from the photodetector 100 is a signal related to right circular polarization or a signal related to left circular polarization, and the right circular polarization image storage unit 111 is determined according to the type of the signal. Alternatively, the information is stored in any of the left circularly polarized image storage unit 112.

  Further, the image calculation unit 120 has a function of obtaining a difference between signals stored in the right circular polarization image storage unit 111 and the left circular polarization image storage unit 112, respectively. The calculation result by the image calculation unit 120 is output from the output unit 130 as a circular dichroic image. The circular dichroic image is output to the outside from the output unit 130 by, for example, a method of displaying on a monitor or a method of outputting to a printer. Thereby, a circular dichroic image can be obtained.

As described above, according to the circular dichroism measurement system 1A according to the present embodiment, the maximum delay amount δ _{0 is set} to 1 / 4λ <δ _{0 in} the optical phase modulator 41, so that the conventional circular polarization modulator Therefore, the timing at which the output of the horizontal polarization component that has not occurred due to distortion becomes zero, that is, the timings of L and R in FIG. Therefore, the gate 60 is opened and closed on the basis of the transmission signal from the modulation signal oscillator 42, and light is allowed to pass in accordance with the timing of R or L so that the light detector 100 can detect this. A circular dichroic image using circularly polarized light can be obtained.

(Third embodiment)
Next, the circularly polarized light source system 2 according to the third embodiment will be described with reference to FIG. The circularly polarized light source system 2 is different from the circularly polarized light source system 1 according to the first embodiment in that the system of the first embodiment uses a gate 60 and a gate driving device 81 to pass and block light so that it is purely circularly polarized. In this case, pure circularly polarized light is extracted by controlling the light incident on the circular polarization modulator 40 instead of extracting the circularly polarized light.

In the circularly polarized light source system 2 according to the third embodiment, as shown in FIG. 5, the light source is a pulsed light source 12, and the pulsed light source 12 is adjusted by a light source drive timing adjuster 82 (control means). . The configuration of the circular polarization modulator 40 including the optical phase modulator 41 and the modulation signal oscillator 42 is the same as that of the first embodiment, and the optical phase modulator 41 has a vibration surface different from the vibration surface of linearly polarized light and the maximum value of the phase difference between two orthogonal polarization components (the maximum amount of delay) when the [delta] _0, satisfying the relation of 1 / 4λ <δ _0. The modulation signal from the modulation signal oscillator 42 is sent to the light source drive timing adjuster 82.

  The light source drive timing adjuster 82 outputs a voltage for driving the pulsed light source 12 to the pulsed light source 12 based on the modulation signal from the modulation signal oscillator 42. The timing for outputting the voltage is set so as to emit pulsed light corresponding to the timings of L and R shown in FIG. For example, when the pulsed light is emitted from the pulsed light source 12 at the timing L shown in FIG. 3a, the non-polarized light from the pulsed light source 12 is converted into light having a predetermined wavelength by the monochromatic filter 20. After being monochromatic and converted into linearly polarized light in the X-axis direction by the polarizing plate 30, the light is incident on the circularly polarized light modulator 40 and emitted as left circularly polarized light. When the pulsed light is emitted from the pulsed light source 12 at the timing R shown in FIG. 3A, the non-polarized light from the pulsed light source 12 is monochromatized into light of a predetermined wavelength by the monochromatic filter 20, After being converted into linearly polarized light in the X-axis direction by the polarizing plate 30, the light is incident on the circular polarization modulator 40 and emitted as right circularly polarized light.

In the circularly polarized light source system 1, at which timing the state indicated by L and R in FIG. 3A, that is, the state where the horizontal polarization component becomes 0 and the circular polarization component becomes −1 or 1 occurs (light source drive). The timing at which the timing adjuster 82 emits the pulsed light from the pulse light source 12 varies depending on the value of the distortion α and the maximum delay amount δ _{0 in} the circular polarization modulator 40. It is necessary to obtain the timing when the L and R states are obtained after performing the measurement, and to obtain the driving timing of the pulse light source 12 based on this.

Based on the above principle, according to the circularly polarized light source system 2 according to the present embodiment, in the optical phase modulator 41, the maximum value of the phase difference between two polarization components having a vibration plane different from that of linearly polarized light and orthogonal to each other. By setting the maximum delay amount δ ₀ to 1 / 4λ <δ ₀ , the timing at which the output of the horizontal polarization component that has not occurred due to distortion according to the conventional circular polarization modulator becomes zero, that is, FIG. A) L and R timings occur. Then, based on the transmission signal from the modulation signal oscillator 42, the timing for emitting the pulsed light from the pulsed light source 12 is adjusted, and the light is emitted in correspondence with the timings of L and R, so that the circularly polarized light source Pure right or left circularly polarized light can be emitted from the system 2.

(Fourth embodiment)
Next, the circularly polarized light source system 3 according to the fourth embodiment will be described with reference to FIG. The circularly polarized light source system 3 is different from the circularly polarized light source system 1 according to the first embodiment in that, in the system of the first embodiment, the timing at which purely circularly polarized light that does not include a horizontal component is emitted is measured in advance. However, in the circularly polarized light source system 3, the circularly polarized light detecting device 72 is separately provided, and the gate 60 is opened and closed based on the result while detecting the polarization state. Hereinafter, the difference will be mainly described.

  The configurations of the light source 10, the monochromatic filter 20, the polarizing plate 30, and the circular polarization modulator 40 are the same as those of the system according to the first embodiment. A beam splitter 71 is provided at the subsequent stage of the circular polarization modulator 40, and a part of the light from the circular polarization modulator 40 enters the circular polarization detection device 72.

The circularly polarized light detection device 72 has a function of determining whether or not the light from the circular polarization modulator 40 contains a horizontal polarization component. As shown in FIG. 3A, if the maximum delay amount δ ₀ of the optical phase modulator 41 is set to a value larger than 1 / 4λ, pure right circularly polarized light or left circularly polarized light is obtained during the modulation period. Timing, that is, L and R shown in FIG. The circularly polarized light detecting device 72 outputs a timing signal to the gate driving device 83 when the incident light is purely left or right circularly polarized light. The gate driving device 83 opens and closes the gate 60 based on the timing signal from the circularly polarized light detecting device 72.

  A specific device configuration of the circularly polarized light detecting device 72 is shown in FIG. The circularly polarized light detection device 72 includes a beam splitter 720, a Y-axis polarizer 721, an X-axis polarizer 722, a Y-axis photodetector 723, an X-axis photodetector 724, a calculation unit 725, a zero point detection unit 726, and a determination unit 727. It is comprised including.

  The beam splitter 720 bisects the light incident on the circularly polarized light detection device 72. Then, one of the divided lights is incident on the Y-axis polarizer 721. The linearly polarized light in the Y-axis direction extracted by the Y-axis polarizer 721 is incident on the Y-axis photodetector 723. On the other hand, the other of the bisected lights is incident on the X-axis polarizer 722. The X-axis direction linearly polarized light extracted by the X-axis polarizer 722 is incident on the X-axis photodetector 724. Thereafter, the difference between the lights detected by the Y-axis photodetector 723 and the X-axis photodetector 724 is calculated by the calculation unit 725, and after the zero point of the difference is detected by the zero point detection unit 726, the result is determined by the determination unit 727. The determination unit 727 determines left and right circularly polarized light based on the modulation signal from the modulation signal oscillator 42.

  Here, the Stokes vector of the light that has passed through the Y-axis polarizer 721 is expressed by the following formula (4). Here, it is known that the intensity of the light that passes through the Y-axis polarizer 721 and is detected by the Y-axis detector 723 is the first term of Equation (4).

  Further, the Stokes vector of the light that has passed through the X-axis polarizer 722 is represented by the following formula (5). Here, it is known that the intensity of the light that passes through the X-axis polarizer 722 and is detected by the X-axis detector 724 becomes the first term of Equation (5).

  Then, when the calculation unit 425 obtains the difference between the light intensity detected by the Y-axis detector 723 and the light intensity detected by the X-axis detector 724, Expression (6) is obtained.

  Here, L and R shown in FIG. 3A, that is, cos (δ + α) is zero at the timing when the horizontal polarization component is zero and pure circular polarization where the circular polarization component is −1 or 1 is obtained. It has become. Therefore, the point at which the value of Equation (6) becomes zero can be set as the timing at which pure circularly polarized light is obtained. However, in the actual measurement place, a certain time width is required for the measurement. Therefore, a predetermined time width including a timing at which the value of Equation (6) becomes zero is provided, and circularly polarized light is measured within the time width. This range is detected and determined by the zero point detection unit 726. The zero point detection unit 726 includes a window comparator circuit, and the absolute value of the difference between the light intensity detected by the Y axis detector 723 and the light intensity detected by the X axis detector 724 is smaller than a preset value. If it is small, the signal indicating the state is output only when it is small, so that it is within the time zone suitable for the measurement of circularly polarized light including the timing at which purely circularly polarized light is output. Show.

  Further, the discrimination between the right circularly polarized light and the left circularly polarized light is performed by the discriminating unit 727 with reference to the code of the modulation signal. When it is determined that the circularly polarized light is emitted from either the left or right, the timing signal is output. When the opposite circularly polarized light is emitted, the timing signal is not emitted. Thereby, an instruction to open the gate is given only in the circularly polarized light on the predetermined side.

  Here, the operation of each device will be described with reference to FIGS. 8 and 9, which are timing charts summarizing the signals of each device. FIG. 8 is a timing chart when left circularly polarized light is output (when a circular dichroism measurement system acquires an image of left circularly polarized light). FIG. 9 is a timing chart when right circularly polarized light is output (circular dichroism). 3 is a timing chart of a case where a right-circularly polarized image is acquired in the property measurement system.

  First, in the chart of FIG. 8, the modulation signal is set to H, and the timing signal is set to be output in a time zone before and after the timing indicated by L in FIG. As a result, the gate 60 opens in a time zone in which left circularly polarized light is emitted and the horizontal polarization component is close to zero. This makes it possible to emit pure left circularly polarized light.

  On the other hand, in the chart of FIG. 9, the modulation signal is L, and the timing signal is set to be output in a time zone before and after the timing indicated by R in FIG. As a result, the gate 60 opens in a time zone in which right circularly polarized light is emitted and the horizontal polarization component is close to zero. This makes it possible to emit pure right-handed circularly polarized light.

  As described above, according to the circularly polarized light source system 3 according to this embodiment, the open / close time of the gate 60 is set based on the detection result of the circularly polarized light detection device 72. Thereby, the gate 60 is opened in a predetermined time zone in which the circularly polarized light component is output and the horizontal polarized light component is close to zero. Therefore, it is possible to emit pure left and right circularly polarized light without having to measure the timing for opening the gate in advance.

(Fifth embodiment)
Next, the circularly polarized light source system 4 according to the fifth embodiment will be described with reference to FIG. The circularly polarized light source system 4 differs from the circularly polarized light source system 3 according to the fourth embodiment in the following points. In other words, the point of using the circularly polarized light detecting device 72 is the same, but the light source 10 is replaced with the pulsed light source 12 and the lighting control of the pulsed light source 12 by the pulsed light source driving device 84 is performed using the circularly polarized light detecting device 72. The point is different. Whether or not the circularly polarized light is detected by the circularly polarized light detection device 72 is determined by using the probe light source 11 provided in the front stage of the optical phase modulator 41.

  The light from the probe light source 11 is incident on the optical phase modulator 41 of the circular polarization modulator 40. Then, the modulated probe light from the circular polarization modulator 40 enters the circular polarization detection device 72. The circularly polarized light detection device 72 performs the same operation as in the fourth embodiment. That is, it determines whether the incident light is purely left or right, and outputs a timing signal to the pulse light source driving device 84 when it is either left or right circularly polarized light. The pulse light source driving device 84 turns on the pulse light source 12 based on this timing signal. As a result, the non-polarized light from the pulse light source 12 is monochromatic to a desired wavelength by the monochromatic filter 20, converted to linearly polarized light in the X-axis direction by the polarizing plate 30, and incident on the circularly polarized light modulator 40 and left and right. Either circularly polarized light.

As in the previous embodiments, in the optical phase modulator 41, the maximum value of the phase difference (maximum delay amount) between two polarization components having a vibration plane different from that of the linearly polarized light from the light source and orthogonal to each other. ) a when a δ _0, 1 / 4λ <so as to satisfy the relationship of [delta] _0, in addition to modulating the phase difference, with a configuration for emitting light phase difference modulation is performed, the modulation period Between them, there is a timing at which either right or left circularly polarized light is obtained, that is, R and L shown in FIG. Therefore, by operating the circularly polarized light detecting device 72 according to the timing charts shown in FIGS. 8 and 9, it is possible to output pure right circularly polarized light or left circularly polarized light with a low ratio of the horizontal polarization component.

  As described above, according to the circularly polarized light source system 4 according to the present embodiment, the emission timing of the pulsed light output from the pulsed light source 12 is set based on the detection result of the circularly polarized light detector 72, and based on this. The pulsed light is emitted from the pulsed light source 12 in a predetermined time zone in which the circularly polarized component is output and the horizontal polarized component is close to zero. Therefore, it is possible to emit pure left and right circularly polarized light without measuring the emission timing of the pulsed light in advance. Moreover, since the emission of the light of the horizontal polarization component is suppressed by adjusting the output timing of the pulse light source 12, there is an advantage that a high-speed optical gate is not necessary.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment,
Various changes can be made.

  For example, the gate 60 described in the first embodiment is provided at the subsequent stage of the optical phase modulator 41, but may be on the optical path of the light emitted from the light source 10, for example, at the previous stage of the optical phase modulator. Also good.

  In the above-described embodiment, the monochromatic filter 20 is provided in the subsequent stage of the sample 100. However, the monochromatic filter 20 may be provided in any place on the optical path of the light emitted from the light source 10.

  DESCRIPTION OF SYMBOLS 1-4 ... Circularly polarized light source system, 1A ... Circular dichroism measuring system, 10 ... Light source, 12 ... Pulse light source, 20 ... Monochromatic filter, 30 ... Polarizing plate, 40 ... Circularly polarized light modulator, 41 ... Optical phase modulator , 42 ... modulation signal oscillator, 50 ... sample, 60 ... gate, 71 ... beam splitter, 72 ... circularly polarized light detector, 81, 83 ... gate driver, 82 ... light source drive timing adjuster, 100 ... photodetector 110 ... Signal switching device, 120 ... Image calculation unit, 130 ... Output unit.

Claims (5)

A circularly polarized light source system that emits right and left circularly polarized light,
When a light source that emits linearly polarized light and the linearly polarized light from the light source are incident and the wavelength of the linearly polarized light is λ, two polarization components that have a vibration surface different from the vibration surface of the linearly polarized light and are orthogonal to each other. An optical phase modulation means for periodically modulating the phase difference so that the maximum value δ ₀ of the phase difference between them is 1 / 4λ <δ ₀ and emitting the light after the phase difference modulation;
Of the light of the horizontal polarization component and the light of the circular polarization component included in the light subjected to the phase difference modulation by the optical phase modulator, the circular polarization is corresponding to the timing when the output of the light of the horizontal polarization component becomes zero. Control means for emitting,
A circularly polarized light source system comprising: A gate provided on the optical path of the light emitted from the optical phase modulation means;
The control means switches between passing and blocking light from the optical phase modulation means by opening and closing the gate, and thereby circularly polarized light corresponding to the timing when the light output of the horizontal polarization component becomes zero. The circularly polarized light source system according to claim 1, wherein the light is emitted. The light source is a pulsed light source;
2. The circularly polarized light source system according to claim 1, wherein the control unit emits the linearly polarized light from the pulsed light source in correspondence with a timing when an output of the light of the horizontal polarization component becomes zero. The control means detects light emitted from the optical phase modulation means with a circularly polarized light detector, and determines the timing when the output of the horizontal polarization component becomes zero based on the detection result of the circularly polarized light detector. The circularly polarized light source system according to any one of claims 1 to 3. The circularly polarized light source system according to any one of claims 1 to 4, which emits right circularly polarized light and left circularly polarized light with respect to a sample;
A light detecting means for detecting transmitted light emitted from the circularly polarized light source system and transmitted by the sample by converting it into an electrical signal;
Right circularly polarized image storage means for storing right circularly polarized light among electrical signals detected by the light detection means;
A left circularly polarized image storing means for storing one of the electrical signals detected by the light detecting means by left circularly polarized light;
The difference between the electrical signal by the right circularly polarized light stored in the right circularly polarized image storage means and the electrical signal by the left circularly polarized light stored in the left circularly polarized image storage means is obtained, and the result is obtained as a circular dichroic image. Output means for outputting as
A circular dichroism measuring system comprising:

Images