JP2007232550A - Optical characteristic measuring instrument and optical characteristic measuring method - Google Patents

Optical characteristic measuring instrument and optical characteristic measuring method Download PDF

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JP2007232550A
JP2007232550A JP2006054182A JP2006054182A JP2007232550A JP 2007232550 A JP2007232550 A JP 2007232550A JP 2006054182 A JP2006054182 A JP 2006054182A JP 2006054182 A JP2006054182 A JP 2006054182A JP 2007232550 A JP2007232550 A JP 2007232550A
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measurement
light
light intensity
optical
intensity information
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JP4947998B2 (en
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Mizue Ebisawa
Yukitoshi Otani
Yosuke Tsuji
幸利 大谷
瑞枝 海老澤
洋祐 辻
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Tokyo Univ Of Agriculture & Technology
国立大学法人東京農工大学
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical characteristic measuring instrument which reduces the restriction of a measuring target, can quantitatively detect the double refraction distribution of the measuring target and is suitable for analyzing a biosample or the like in a face state, and also to provide an optical characteristic measuring method. <P>SOLUTION: The optical characteristic measuring instrument includes an optical system 10, a light intensity data acquiring part 40 for acquiring the light intensity data of measuring light and an operational processing part 60. The optical system 10 is constituted so that the light emitted from a light source is thrown on a sample 100 through a polarizer 22, a first 1/2 wavelength plate 24, a 1/4 wavelength plate 26 and a second 1/2 wavelength plate 28 and also thrown on a light detection part 14 through an analyzer 30, and the first and second 1/2 wavelength plates and the analyzer are constituted in a rotatable manner. In the light intensity data acquiring part, the light intensity data of a plurality of measuring lights are acquired. In the operational processing part, at least one of the double diffraction phase difference and main axis azimuth of the sample is calculated on the basis of a theoretical formula of the intensity of measuring light and the light intensity data of measuring light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical characteristic measuring device and an optical characteristic measuring method.

  As a simple method for detecting the birefringence of a substance, a polarizing microscope is known in which a sample is sandwiched between two polarizers arranged orthogonally or in parallel and the birefringence is observed from the light and dark (Patent Document 1,). 2).

In addition, there is photoelasticity measurement in which the stress state of a resin product is observed with a measurement system in which two polarizers or a quarter wavelength plate is added to the polarizer as in a polarizing microscope (see Patent Document 3).
Furthermore, in order to measure birefringence quantitatively and accurately, polarization measurements such as a rotational analyzer method and a heterodyne interferometry are performed (see Patent Documents 4 and 5).
Japanese Patent Laid-Open No. 2005-3994 JP 2001-356276 A JP-A-7-77490 Japanese Patent Laid-Open No. 10-267831 Japanese translation of PCT publication No. 2002-504673

  However, each of the above techniques has the following problems.

  Since an image obtained from a polarizing microscope represents the amount of birefringence only in light and dark, there is a problem that quantitative birefringence information (birefringence phase difference and principal axis orientation) cannot be obtained.

  In measurement by photoelasticity, a sample having a birefringence phase difference of 180 degrees or more is a main measurement target. Therefore, there is a problem that it is difficult to measure the birefringence phase difference and the principal axis direction of a sample having minute anisotropy.

  According to polarization measurements such as the rotation analyzer method and the heterodyne interferometry, it is possible to measure minute birefringence with high accuracy. However, since this method has a large processing load, there is a problem that when the birefringence distribution in the sample is obtained, the number of measurement points increases and the measurement takes time.

  In birefringence measurement, it was common to use a Babinet Soleil compensator for phase modulation. However, in the Babinet Soleil compensator, a wedge-shaped crystal is moved with a micrometer to change the thickness and perform phase modulation. The work took time and automation was difficult. In particular, when measuring a biological sample, it is preferable to perform continuous sampling.

  The present invention has been made in view of these problems, and its purpose is to limit the number of measurement objects that can be measured, and to quantitatively detect the birefringence distribution of the measurement object. It is an object of the present invention to provide an optical characteristic measuring apparatus and an optical characteristic measuring method suitable for analyzing a sample having a spread and a state in which a state change occurs sequentially in a surface state.

(1) An optical property measuring apparatus according to the present invention is
A measuring device for measuring optical characteristics of a measurement object,
A light source that emits light of a predetermined wavelength, at least five optical elements, and a light receiving unit that receives measurement light obtained by modulating the light with the at least five optical elements and the measurement target, Including an optical system;
A light intensity information acquisition unit for acquiring light intensity information of the measurement light;
An arithmetic processing unit that performs arithmetic processing to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light; ,
Including
The at least five optical elements include first and second polarizers, first and second half-wave plates, and a quarter-wave plate,
The optical system converts light emitted from the light source into the first polarizer, the first half-wave plate, the quarter-wave plate, and the second half-wave plate. So that the light modulated by the measurement object is incident on the light receiving unit via the second polarizer, and
At least the first and second half-wave plates are configured to be rotatable,
In the light intensity information acquisition unit,
The first to Kth optical systems obtained by the optical system satisfying the first to Kth (K is an integer of 2 or more) principal axis azimuth conditions in which at least one of the principal axis directions of the first and second half-wave plates is different. Obtaining light intensity information of the measurement light of
In the arithmetic processing unit,
The first to Kth theoretical formulas of light intensity reflecting the principal axis directions of the at least five optical elements, including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables. Based on the light intensity information of the Kth measurement light, a calculation process is performed to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction.

  According to the present invention, the theoretical formula of the light intensity of the measurement light includes at least one of the birefringence phase difference and the principal axis direction of the measurement object as a variable. Further, the theoretical formula of the light intensity of the measurement light reflects the principal axis direction of the optical element. From this, if one piece of light intensity information acquired by the light intensity information acquisition unit and the principal axis orientation information of the optical element at that time are used, at least one of the birefringence phase difference and the principal axis orientation of the measurement target is included. One relational expression can be derived.

  Further, if the principal axis orientation of the optical element changes, the light intensity acquired and the coefficient included in the theoretical formula of the light intensity change, so that different relational expressions can be derived.

  If an optical element is appropriately set and a plurality of relational expressions are derived, the birefringence phase difference and the principal axis direction of the measurement target can be calculated by solving them together.

  In the present invention, the light intensity information acquisition unit acquires first to Kth (K is an integer of 2 or more) light intensity information, that is, K pieces of light intensity information. Here, the first to Kth light intensity information is the intensity information of the measurement light obtained by the optical system set to the first to Kth principal axis orientation conditions, respectively. The first to K-th principal axis orientation conditions differ from each other in at least one principal axis orientation of the optical element (first and second half-wave plates).

  For example, the first light intensity information is acquired using the optical system in which the first setting has been made first. Next, the second light intensity information is acquired using the optical system in which the second setting is made. By repeating this K times, K relational expressions including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables may be derived.

  According to the present invention, since the optical system can be configured using only a rotary optical element, the setting and changing of the optical system can be performed accurately in a short time. That is, according to the present invention, it is possible to provide an optical property measuring apparatus capable of efficiently performing measurement with high accuracy of optical properties.

(2) An optical property measuring apparatus according to the present invention is
A measuring device for measuring optical characteristics of a measurement object,
A light intensity information acquisition unit that acquires light intensity information of at least five optical elements included in the optical system and measurement light modulated by the measurement object;
An arithmetic processing unit that performs arithmetic processing to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light; ,
Including
The at least five optical elements include first and second polarizers, first and second half-wave plates, and quarter-wave plates, and at least the first and second optical plates. The half-wave plate is configured to be rotatable,
The measurement light includes light having a given wavelength emitted from a light source, the first polarizer, the first half-wave plate, the quarter-wave plate, and the second 1 / Light that is made incident on the measurement object via a two-wavelength plate, and that is obtained by making the light modulated by the measurement object incident on a light receiving unit via the second polarizer,
In the light intensity information acquisition unit,
The first to Kth optical systems obtained by the optical system satisfying the first to Kth (K is an integer of 2 or more) principal axis azimuth conditions in which at least one of the principal axis directions of the first and second half-wave plates is different. Obtaining light intensity information of the measurement light of
In the arithmetic processing unit,
The first to Kth theoretical formulas of light intensity reflecting the principal axis directions of the at least five optical elements, including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables. Based on the light intensity information of the Kth measurement light, a calculation process is performed to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction.

  According to the present invention, the theoretical formula of the light intensity of the measurement light includes at least one of the birefringence phase difference and the principal axis direction of the measurement object as a variable. Further, the theoretical formula of the light intensity of the measurement light reflects the principal axis direction of the optical element. From this, if one piece of light intensity information acquired by the light intensity information acquisition unit and the principal axis orientation information of the optical element at that time are used, at least one of the birefringence phase difference and the principal axis orientation of the measurement target is included. One relational expression can be derived.

  In addition, if optical systems having different principal axis orientations of optical elements are used, different relational expressions can be derived because the obtained light intensity and the coefficient included in the theoretical expression of the light intensity change.

  If an optical element is appropriately set and a plurality of relational expressions are derived, the birefringence phase difference and the principal axis direction of the measurement target can be calculated by solving them together.

  According to the present invention, since the optical system can be configured using only a rotary optical element, the setting and changing of the optical system can be performed accurately in a short time. That is, according to the present invention, it is possible to provide an optical property measuring apparatus capable of efficiently performing measurement with high accuracy of optical properties.

(3) In this optical characteristic measuring device,
The first polarizer, the first and second half-wave plates, and the quarter-wave plate constitute a phase modulation unit,
The first to K-th measurement lights may be measurement lights obtained by the optical system in which at least one of the birefringence phase difference and the principal axis direction of the phase modulation unit is different.

  That is, by using an optical system in which at least one of the birefringence phase difference and the principal axis direction of the phase modulation unit is different, a plurality of relational expressions suitable for analysis can be derived.

(4) In this optical characteristic measuring apparatus,
In each of the first to Kth measurement lights, the phase modulation unit has a birefringence phase difference value of any one of L (L is an integer of 2 or more) set values, and has the principal axis direction. The measurement light may be obtained by any one of L × M optical systems whose values are any of M (M is an integer of 2 or more) set values.

  At this time, K = L × M.

(5) In this optical characteristic measuring device,
L and M may be relatively prime.

(6) In this optical characteristic measuring device,
When the light intensity of the measurement light is I, and the birefringence phase difference and the principal axis direction of the phase modulation unit are δ and θ, respectively,
In the arithmetic processing unit,

The arithmetic processing may be performed based on the above.

  According to this, high-precision arithmetic processing (data analysis processing) can be performed efficiently. That is, highly accurate measurement can be performed efficiently.

(7) In this optical characteristic measuring device,
When the principal axis directions of the second half-wave plate and the analyzer are θ 2 and θ 3 respectively,
In the light intensity information acquisition unit,
θ 3 = 2θ 2 + 45 °
Light intensity information of the measurement light obtained by the optical system satisfying the above condition may be acquired.

However, the relationship between θ 2 and θ 3 is not limited to this. For example, measurement is possible even when θ 3 = 2θ 2 + (45 ° × H) (where H is an odd number).

(8) In this optical characteristic measuring apparatus,
In the light intensity information acquisition unit,
Light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are continuously rotated at a given rotation ratio may be acquired.

  According to this, optical characteristic measurement can be performed using light intensity information obtained by an optical system in which an optical element rotates continuously. Therefore, the measurement can be speeded up as compared with the case of using an optical element that repeats rotation and stationary.

(9) In this optical characteristic measuring apparatus,
In the light intensity information acquisition unit,
Light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are rotated at a rotation ratio of M: L may be acquired.

(10) In this measuring device,
First and second actuators for rotating the first and second half-wave plates;
First and second detectors for detecting principal axis orientations of the first and second half-wave plates;
A control signal generator for generating a control signal for controlling the operation of the first and second actuators;
Further including
The control signal generation unit may generate the control signal based on detection signals from the first and second detection units.

(11) An optical property measuring method according to the present invention includes:
A measurement method for measuring optical characteristics of a measurement object,
A light intensity information acquisition procedure for acquiring light intensity information of measurement light modulated by at least five optical elements included in the optical system and the measurement object;
An arithmetic processing procedure for performing arithmetic processing for calculating at least one of the birefringence phase difference of the measurement object and the main axis direction based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light; ,
Including
The at least five optical elements include first and second polarizers, first and second half-wave plates, and quarter-wave plates, and at least the first and second optical plates. The half-wave plate is configured to be rotatable,
The measurement light includes light having a given wavelength emitted from a light source, the first polarizer, the first half-wave plate, the quarter-wave plate, and the second 1 / Light that is made incident on the measurement object via a two-wavelength plate, and that is obtained by making the light modulated by the measurement object incident on a light receiving unit via the second polarizer,
In the light intensity information acquisition procedure,
The first to Kth optical systems obtained by the optical system satisfying the first to Kth (K is an integer of 2 or more) principal axis azimuth conditions in which at least one of the principal axis directions of the first and second half-wave plates is different. Obtaining light intensity information of the measurement light of
In the arithmetic processing procedure,
The first to Kth theoretical formulas of light intensity reflecting the principal axis directions of the at least five optical elements, including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables. Based on the light intensity information of the Kth measurement light, a calculation process is performed to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction.

  According to the present invention, the theoretical formula of the light intensity of the measurement light includes at least one of the birefringence phase difference and the principal axis direction of the measurement object as a variable. Further, the theoretical formula of the light intensity of the measurement light reflects the principal axis direction of the optical element. From this, if one piece of light intensity information acquired by the light intensity information acquisition unit and the principal axis orientation information of the optical element at that time are used, at least one of the birefringence phase difference and the principal axis orientation of the measurement target is included. One relational expression can be derived.

  In addition, if optical systems having different principal axis orientations of optical elements are used, different relational expressions can be derived because the obtained light intensity and the coefficient included in the theoretical expression of the light intensity change.

  If an optical element is appropriately set and a plurality of relational expressions are derived, the birefringence phase difference and the principal axis direction of the measurement target can be calculated by solving them together.

  In the present invention, first light intensity information is acquired using the optical system in which the first setting has been made. Next, the second light intensity information is acquired using the optical system in which the second setting is made. By repeating this K times, K relational expressions including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables may be derived.

  According to the present invention, since the optical system can be configured using only a rotary optical element, the setting and changing of the optical system can be performed accurately in a short time. That is, according to the present invention, it is possible to provide an optical property measurement method capable of efficiently performing measurement with high accuracy of optical properties.

(12) In this optical characteristic measurement method,
The first polarizer, the first and second half-wave plates, and the quarter-wave plate constitute a phase modulation unit,
The first to K-th measurement lights may be measurement lights obtained by the optical system in which at least one of the birefringence phase difference and the principal axis direction of the phase modulation unit is different.

  That is, by using an optical system in which at least one of the birefringence phase difference and the principal axis direction of the phase modulation unit is different, a plurality of relational expressions suitable for analysis can be derived.

(13) In this optical characteristic measurement method,
In each of the first to Kth measurement lights, the phase modulation unit has a birefringence phase difference value of any one of L (L is an integer of 2 or more) set values, and has the principal axis direction. The measurement light may be obtained by any one of L × M optical systems whose values are any of M (M is an integer of 2 or more) set values.

  At this time, K = L × M.

(14) In this optical characteristic measurement method,
L and M may be relatively prime.

(15) In this optical characteristic measurement method,
When the light intensity of the measurement light is I, and the birefringence phase difference and the principal axis direction of the phase modulation unit are δ and θ, respectively,
In the arithmetic processing procedure,
The arithmetic processing may be performed based on the above.

(16) In this optical characteristic measurement method,
When the principal axis directions of the second half-wave plate and the analyzer are θ 2 and θ 3 respectively,
In the light intensity information acquisition procedure,
θ 3 = 2θ 2 + 45 °
Light intensity information of the measurement light obtained by the optical system satisfying the above condition may be acquired.

However, the relationship between θ 2 and θ 3 is not limited to this. For example, measurement is possible even when θ 3 = 2θ 2 + (45 ° × H) (where H is an odd number).

(17) In this optical characteristic measurement method,
In the light intensity information acquisition procedure,
Light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are continuously rotated at a given rotation ratio may be acquired.

  According to this, optical characteristic measurement can be performed using light intensity information obtained by an optical system in which an optical element rotates continuously. Therefore, the measurement can be speeded up as compared with the case of using an optical element that repeats rotation and stationary.

(18) In this optical characteristic measurement method,
In the light intensity information acquisition procedure,
Light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are rotated at a rotation ratio of M: L may be acquired.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A measuring apparatus (optical characteristic measuring apparatus) according to an embodiment of the present invention measures an optical characteristic of a measurement target.

  Hereinafter, as a measurement apparatus (optical characteristic measurement apparatus) according to an embodiment to which the present invention is applied, a measurement apparatus 1 capable of measuring a birefringence phase difference and a principal axis direction of a sample 100 that is a measurement target will be described.

(1) Device Configuration FIGS. 1 and 2 are diagrams for explaining the device configuration of the measuring device 1. 1 is a schematic diagram of the optical system 10 (measuring device 1), and FIG. 2 is a block diagram of the measuring device 1.

  The measuring apparatus 1 according to the present embodiment is an apparatus that measures optical characteristics of a sample 100 that is a measurement target. The measurement apparatus 1 includes an optical system 10, a light intensity information acquisition unit 40, and an arithmetic processing unit 60. The light intensity information acquisition unit 40 acquires light intensity information of the measurement light modulated by the optical element included in the optical system 10 and the sample 100. The arithmetic processing unit 60 performs arithmetic processing for calculating the optical characteristics (birefringence phase difference and principal axis direction) of the sample 100 based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light. The sample 100 may be a substance that transmits light or a substance that reflects light.

  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 light receiving unit 14. The optical system 10 also includes a polarizer 22, a first ½ wavelength plate 24, a ¼ wavelength plate 26, and a second 1/1 provided on an optical path L connecting the light source 12 and the light receiving unit 14. A two-wave plate 28 and an analyzer 30 are included. These optical elements transmit light emitted from the light source 12 via a polarizer 22, a first half-wave plate 24, a quarter-wave plate 26, and a second half-wave plate 28. The light is incident on the sample 100 and the light modulated by the sample 100 is arranged to enter the light receiving unit 14 through the analyzer 30. Each will be described below.

  The light source 12 emits light having a given wavelength (wave number). That is, it can be said that the light source 12 is a light emitting device that emits monochromatic light. As the light source 12, a laser, an SLD, or the like may be used. The light source 12 may have a configuration capable of changing the wavelength (wave number) of the emitted light.

  The polarizer 22 is a polarizer on the incident side that is paired with the analyzer 30 and uses the light emitted from the light source 12 as linearly polarized light.

  The first and second half-wave plates 24 and 28 are optical elements that change the vibration direction of linearly polarized light. The quarter-wave plate 26 is an optical element that changes linearly polarized light into circularly polarized light (elliptical polarized light). The first and second wave plates 24 and 28 and the quarter wave plate 26 are selected corresponding to the wavelength of light emitted from the light source 12.

  In the optical system 10, the first and second half-wave plates 24 and 28 are configured to be rotatable. The first and second half-wave plates 24 and 28 can change the principal axis direction by rotating. In the optical system 10 (phase modulation unit 20), the linearly polarized light emitted from the polarizer 22 is arbitrarily phase-modulated by the rotation angles of the first and second half-wave plates 24 and 28.

  In the optical system 10, the polarizer 22, the first ½ wavelength plate 24, the ¼ wavelength plate 26, and the second ½ wavelength plate 28 constitute the phase modulation unit 20. The phase modulation unit 20 modulates incident light. That is, the phase modulation unit 20 has a function of changing the polarization state of incident light. The birefringence phase difference and the principal axis direction of the phase modulator 20 can be set by the rotation angles of the first and second half-wave plates 24 and 28. That is, the birefringence phase difference and the principal axis direction of the phase modulation unit 20 can be changed, and the values can be set by the first and second half-wave plates 24 and 28.

  In the optical system 10, the polarizer 22 and the quarter wavelength plate 26 may also be configured to be rotatable. Moreover, in the optical system 10, the polarizer 22 and the quarter wavelength plate 26 may be installed so that the angle difference of the principal axis directions is an odd multiple of 45 °.

  The analyzer 30 is an output-side polarizer that uses light modulated by the sample 100 as linearly polarized light. The analyzer 30 is paired with the polarizer 22. That is, the polarizer 22 may be referred to as a first polarizer, and the analyzer 30 may be referred to as a second polarizer. In the optical system 10, the analyzer 30 is configured to be rotatable. The analyzer 30 can change its principal axis direction by rotating.

  The light receiving unit 14 receives measurement light. The light intensity information acquisition unit 40 acquires light intensity information of measurement light incident on the light receiving unit 14. The light receiving unit 14 may include a plurality of light receiving elements 15. As shown in FIG. 3, the plurality of light receiving elements 15 may be arranged in a plane (two-dimensionally). At this time, the plurality of light receiving elements 15 may constitute a light receiving surface. Then, the light intensity information acquisition unit 40 may acquire the light intensity information of the incident measurement light for each light receiving element 15. For example, a CCD may be used as the light receiving unit 14.

  The optical system 10 may include a beam expander (not shown). The beam expander is an optical element (device) for increasing the beam diameter. The beam expander is disposed between the light source 12 and the sample 100. That is, the beam expander is disposed on the upstream side of the sample 100 in the optical path L. Thereby, light can be irradiated to a wide range of the sample 100. By using the light receiving unit 14 in which the light receiving elements 15 are two-dimensionally arranged corresponding to the beam expander, it is possible to measure optical characteristics over a wide range of the sample 100. That is, it is possible to efficiently perform optical characteristic measurement on the sample 100 having a spread. In other words, the sample 100 can be analyzed as a “surface” having a spread. However, an optical system having no beam expander may be used in the present invention.

  The optical system 10 may have a configuration including a reflection plate (mirror) (not shown). By using the reflecting plate, the optical system 10 can be configured to be able to arrange the sample 100 horizontally. That is, the optical system 10 may be configured as a microscope type by using a reflector.

  The optical system 10 may also be configured such that transmitted light that has passed through the sample 100 enters the analyzer 30 as shown in FIGS. 1 and 2. However, the optical system 10 may be configured such that the reflected light from the sample 100 enters the analyzer 30 (not shown).

1-2: Light intensity information acquisition unit 40
The light intensity information acquisition unit 40 acquires light intensity information of measurement light. That is, the light intensity information acquisition unit 40 acquires light intensity information of light (measurement light) modulated by the phase modulation unit 20, the sample 100, and the analyzer 30 and received by the light receiving unit 14. The light receiving unit 14 (spectrometer and light receiving element) may constitute a part of the light intensity information acquiring unit 40.

  In the measuring apparatus 1, the light intensity information acquisition unit 40 includes first to K-th main axes (K is an integer of 2 or more) in which at least one of the main axis directions of the first and second half-wave plates 24 and 28 is different. Light intensity information of the first to Kth measurement lights (a plurality of measurement lights) obtained by the optical system 10 set to the azimuth condition is acquired.

  Specifically, the light intensity information acquisition unit 40 acquires first to Kth (K is an integer of 2 or more) light intensity information, that is, K pieces of light intensity information. Here, the first to Kth light intensity information is the intensity information of the measurement light obtained by the optical system 10 set to the first to Kth principal axis orientation conditions, respectively. The first to Kth principal axis orientation conditions differ from each other in at least one principal axis orientation of the optical element (first and second half-wave plates 24 and 28).

  The plurality of light intensity information acquired by the light intensity information acquisition unit 40 may be stored in the storage device 50 of the control device 80. In the storage device 50, a plurality of pieces of light intensity information are stored in the setting conditions of the optical system 10 (polarizer 22, first and second half-wave plates 24 and 28, quarter-wave plate 26, and analyzer 30. May be stored in correspondence with the main axis direction). For example, the storage device 50 may store the first to Kth principal axis orientation conditions (main axis orientation information) and the first to Kth light intensity information in association with each other.

1-3: Arithmetic processing unit 60
The arithmetic processing unit 60 performs arithmetic processing for calculating the birefringence phase difference and the main axis direction of the measurement target (sample 100) based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light. As will be described in detail later, the theoretical formula of the light intensity of the measurement light includes the birefringence phase difference Δ and the main axis direction φ of the sample 100 as variables. Therefore, the birefringence phase difference Δ and the main axis direction φ of the sample 100 can be calculated by using the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light.

1-4: Drive / Detection Unit The measurement apparatus 1 further includes first and second drive / detection units 72 and 74. Here, the first driving / detecting unit 72 is a driving unit that rotates the first half-wave plate 24 and a detector that detects the principal axis direction of the first half-wave plate 24. is there. The second drive / detection unit 74 is a drive unit that rotates the second half-wave plate 28 and is a detection unit that detects the principal axis direction of the second half-wave plate 28. .

  In particular, in the measurement apparatus 1, the first and second drive / detection units 72 and 74 continuously rotate the first and second half-wave plates 24 and 28 at a predetermined rotation ratio, respectively. It may be configured.

  The measurement apparatus 1 may further include a third drive / detection unit 76. The third drive / detection unit 76 is a drive unit that rotates the analyzer 30 and is a detector that detects the main axis direction of the analyzer 30.

  The measurement apparatus 1 may further include a control signal generation unit 70 that controls the operations of the first to third drive / detection units 72, 74, and 76. For example, the control signal generation unit 70 may be configured to generate a control signal based on the detection signal from the detection unit and control the operation of the drive unit.

1-5: Control device 80
The measuring device 1 may include a control device 80. The control device 80 may have a function of comprehensively controlling the operation of the measurement device 1. That is, the control device 80 controls the first to third driving / detecting units 72, 74, and 76 to control the principal axes of the optical elements (the first and second half-wave plates 24 and 28 and the analyzer 30). The direction may be set, the light emission operation of the light source 12 may be controlled, and the operations of the light intensity information acquisition unit 40 and the arithmetic processing unit 60 may be controlled.

  The control device 80 may include a storage device 50 and an arithmetic processing unit 60. The storage device 50 has a function of temporarily storing various data. For example, the storage device 50 corresponds to the light intensity information of the measurement light with the main axis direction information (birefringence phase difference and main axis direction information of the phase modulator 20) of the first and second half-wave plates 24 and 28. You may add and memorize it.

  The control device 80 may also include a control signal generation unit 70. The control device 80 may further include a synchronization control unit. The synchronization controller is configured to synchronize the rotation of these optical elements when the first and second half-wave plates 24 and 28 and the analyzer 30 are continuously rotated to acquire light intensity information. Take control. The synchronization control unit is configured to generate a synchronization control signal based on the principal axis direction information of the first and second half-wave plates 24 and 28 and the analyzer 30, and to control the operation of the drive unit. Also good.

  The measuring device 1 can perform processing using a computer, particularly in the control device 80 (arithmetic processing unit 60). Here, the computer refers to a physical device (system) including a processor (processing unit: CPU or the like), a memory (storage unit), an input device, and an output device as basic components.

  In FIG. 4, an example of the functional block of the arithmetic processing system which comprises the measuring device 1 is shown.

  The processing unit 110 performs various processes of the present embodiment based on a program (data) stored in the information storage medium 130. That is, the information storage medium 130 stores a program for causing a computer to function as each unit of the present embodiment (a program for causing a computer to execute processing of each unit).

  The functions of the processing unit 110 can be realized by hardware such as various processors (CPU, DSP, etc.), ASIC (gate array, etc.), and programs.

  The storage unit 120 is a work area such as a processing unit, and its function can be realized by a RAM or the like.

  The information storage medium 130 (computer-readable medium) stores programs, data, and the like, and functions as an optical disk (CD, DVD), a magneto-optical disk (MO), a magnetic disk, a hard disk, and a magnetic tape. Alternatively, it can be realized by a memory (ROM).

  Based on the program stored in the information storage medium 130, the rotation ratio of the first and second half-wave plates 24 and 28 may be set, and the light emission operation of the light source 12 may be controlled.

  The display unit 140 may have a function of displaying information obtained by the measurement apparatus as an image. The display unit 140 may apply any known hardware.

(2) Optical characteristic measurement principle Next, the optical characteristic measurement principle employed by the light intensity characteristic measurement apparatus according to the present embodiment will be described.

2-1: Theoretical Expression of Light Intensity of Measurement Light The Stokes parameter of incident light incident on the phase modulation unit 20 is S 0, and the Stokes parameter of the modulated light obtained by modulating the incident light by the phase modulation unit 20 is S Then, the S can be expressed by the following equation.

Note that P 0 ° is a Mueller matrix of the polarizer 22 with the principal axis orientation set to 0 °. Also, H .theta.1 is the Mueller matrix of the first half-wave plate 24, theta 1 is its principal axis direction. Q 45 ° is a Mueller matrix of the quarter-wave plate 26 in which the principal axis direction is set to 45 °. H θ2 is the Mueller matrix of the second half-wave plate 28, and θ 2 is the principal axis direction. The polarizer 22 and the quarter-wave plate 26 may be installed so that the angle difference between the principal axis directions is an odd multiple of 45 °.

  The light (modulated light) given an arbitrary polarization state by the phase modulation unit 20 is further modulated by the sample 100 having an unknown birefringence phase difference Δ and a principal axis direction φ (transmitted through the sample 100 or reflected by the sample 100). ), Transmitted through the analyzer 30, and received by the light receiving unit 14 as measurement light. The Mueller matrix of the optical system 10 shown in FIG.

Here, S ′ is a Stokes parameter of the measurement light. When the intensity of the incident light is I 0 , the equation (2) is
It can be expressed as.

X Δ, φ is the Mueller matrix of the sample 100, and Δ, φ are the birefringence phase difference and the principal axis direction of the sample 100, respectively. Then, A .theta.3 is the Mueller matrix of the analyzer 30, theta 3 is its principal axis direction.

  When this is arranged with respect to the light intensity I,

It can be expressed as.

Here, when θ 3 = 2θ 2 + 45 °, the formula (A) is
It becomes.

Furthermore, when Δ << 1, the formula (A1) is
And can be transformed.

Here, using a trigonometric formula, the formula (A2) is
It becomes.

Here, since Δ << 1, Equation (A3) is
And can be transformed.

2-2: Calculation Principle of Birefringence Phase Difference Δ and Main Axis Direction φ of Sample 100 Looking at Expressions (A) to (B), the light intensity I of the measurement light is Δ, φ, and θ 1 , θ It can be seen that it can be expressed by a function of 23 ).

Incidentally, the value of the light intensity I can be known by the light intensity information acquisition unit 40. The values of θ 1 , θ 2 , and θ 3 can be set to known values by using a detection unit (drive / detection units 72, 74, and 76) or by preprogrammed information. . That is, the expressions (A) to (B) can be regarded as functions including Δ and φ as unknowns, respectively.

When the principal axis directions of the optical elements (the first and second half-wave plates 24 and 28 and the analyzer 30) constituting the optical system 10 are changed, the values of θ 1 , θ 2 , and θ 3 are changed. As a result, the value of the light intensity I also changes. That is, it can be said that the light intensity reflects the values of θ 1 , θ 2 , and θ 3 . Therefore, a plurality of relational expressions representing the relationship between Δ and φ can be derived by substituting the plurality of light intensity information and the principal axis orientation information of the corresponding optical element into the expression (A).

  Then, by solving a plurality of relational expressions representing the relation between Δ and φ and solving for Δ and φ, the birefringence phase difference Δ and the main axis direction φ of the sample 100 can be calculated. Note that only one of the birefringence phase difference Δ and the main axis direction φ may be calculated using these relational expressions.

In addition, by setting conditions for the optical system 10 and the sample, the theoretical formula of light intensity can be modified (simplified) as shown in the equations (A) to (B). Thereby, since it becomes possible to simplify the relational expression of Δ and φ, the arithmetic processing procedure can be simplified, and the arithmetic processing speed can be increased. For example, when measurement is performed using the formula (B), the measurement can be performed without using θ 3 . As a result, the parameters required for measurement can be reduced, and the processing speed can be increased.

(3) Optical characteristic measurement procedure Next, an optical characteristic measurement procedure by the optical characteristic measurement apparatus according to the present embodiment will be described.

  5 and 6 show operation flowcharts of the optical characteristic measuring apparatus according to the present embodiment.

3-1: Light Intensity Information Acquisition Procedure FIG. 5 is a flowchart of the light intensity information acquisition procedure.

  In the light intensity information acquisition procedure, first, the principal axis orientation of the optical elements constituting the optical system 10 is set (step S10).

  In this state, light is emitted from the light source 12, and measurement light modulated by the optical element and the sample 100 is received by the light receiving unit 14. Then, the light intensity information acquisition unit 40 acquires the light intensity information of the measurement light received by the light receiving unit 14 (step S12).

  It should be noted that a step of providing the sample 100 on the optical path L of the optical system 10 may be performed anywhere before step S12. This step may be performed either before or after the step of setting the principal axis orientation of the optical element.

  In these steps, the measurement apparatus 1 acquires the light intensity information of the first to K-th K measurement light beams. Here, the light intensity information of the first to K-th measurement lights is the measurement light obtained by the optical system 10 in which one of the principal axis directions of the first and second half-wave plates 24 and 28 is different. It is intensity information. That is, in the light intensity information acquisition procedure, the above steps S10 and S12 are performed a plurality of times while changing the principal axis orientation setting of the optical element (at least the first and second half-wave plates 24 and 28).

  Specifically, in the measuring apparatus 1, first, the optical system 10 (the principal axis direction of the optical element) is set to the first condition, and the first light intensity information is acquired. Then, the first condition (main axis direction information) and the first light intensity information are stored in the storage device 50 in association with each other. Subsequently, the optical system 10 is set (changed) to the second condition, the second light intensity information is acquired, and the storage device 50 associates the second condition with the second light intensity information. Store. Thereafter, this operation is repeated to acquire K principal axis direction information and K light intensity information, and store them in the storage device 50 in association with each other.

  In the measuring apparatus 1, K pieces of light intensity information are obtained using the optical system 10 in which the optical elements (the first and second half-wave plates 24 and 28 and the analyzer 30) are continuously rotated. You may get it.

  The principal axis direction of the optical element of the optical system 10 can be set (changed) by an actuator. Moreover, the principal axis direction information of the optical element of the optical system may be detected by a detection unit, or may be pre-programmed information.

3-2: Arithmetic Processing Procedure FIG. 6 is a flowchart of the arithmetic processing procedure. In the calculation processing procedure, the optical characteristics of the sample 100 are calculated based on the light intensity information of the measurement light acquired in the light intensity information acquisition procedure and the theoretical formula of the measurement light.

  In the arithmetic processing procedure, first, the light intensity information and the principal axis orientation information of the optical element are substituted into the theoretical formula (for example, the formula (A)) of the measurement light, and the optical characteristics of the sample 100 (birefringence phase difference Δ and principal axis). A relational expression representing the relationship between the direction (φ) and the light intensity of the measurement light is derived (step S20).

  One relational expression representing the relationship between the birefringence phase difference Δ and the main axis direction φ of the sample 100 can be derived from one light intensity information and one corresponding main axis direction information. That is, a plurality of relational expressions representing the relationship between the birefringence phase difference Δ and the main axis direction φ of the sample 100 can be derived by using K pieces of light intensity information and corresponding K pieces of main axis direction information. .

  Then, by solving a plurality of relational expressions, the optical characteristics (birefringence phase difference Δ and main axis direction φ) of the sample 100 are calculated (step S22).

(4) Specific Example of Calculation for Calculating Birefringence Phase Difference Δ and Main Axis Direction φ of Sample 100 Hereinafter, the birefringence phase difference Δ and main axis direction φ of sample 100, which can be applied to the measurement apparatus according to the present embodiment, are calculated. An example of the calculation to calculate is shown.

4-1: Theoretical Expression of Light Intensity Used in the Specific Example As described above, the theoretical expression of the light intensity of the measurement light received by the light receiving unit 14 is a condition of Δ << 1, θ 3 = 2θ 2 + 45 °. And can be expressed as the formula (B).

  When the birefringence phase difference and the principal axis direction of the phase modulation unit 20 are δ and θ, respectively, the equation (B) is an equivalent equation.

Can be converted to

In this specific example, the light intensity information I, the principal axis azimuth θ of the phase modulator 20 and the birefringence phase difference δ (first and second) are obtained using the equation (C) or the equation (B) equivalent thereto. The birefringence phase difference Δ and the main axis direction φ of the sample 100 are calculated based on the main axis direction information θ 1 , θ 2 ) of the half-wave plates 24 and 28. In this specific example, the birefringence phase difference Δ and the main axis direction φ of the sample 100 are calculated based on the light intensity information of the measurement light obtained by the optical system 10 that satisfies the condition of θ 3 = 2θ 2 + 45 °.

4-2: Consideration of Physical Meaning of Formula (B) and Conversion to Formula (C) In order to consider the physical meaning of the optical system 10, the Babinet Soleil compensator BSC shown in FIG. 7 is used. Contrast with the optical system 11 of the birefringence measurement.

In the optical system 11, the light having the light intensity I 0 emitted from the light source 12 passes through the polarizer P installed at 45 ° and becomes linearly polarized light at 45 °. Thereafter, the light that has been right-circularly polarized by the quarter-wave plate Q placed at 90 ° is given an arbitrary phase difference δ and elliptical principal axis direction θ by the Babinet-Soleil compensator BSC. Then, after passing through the sample and passing through the analyzer A installed at θ + 45 °, the light is received by the light receiving unit 14 and the light intensity is detected. When these relationships are calculated using the Mueller matrix, they can be expressed by the following equations.

  If Δ << 1 in the equation (4), the light intensity I of the light emitted from the analyzer A (the light intensity of the measurement light obtained by the optical system 11) is

It becomes.

  By the way, in the optical system 11, when the polarizer P, the quarter-wave plate Q, and the Babinet-Soleil compensator BSC are collectively regarded as the phase modulator 21, the phase modulator 21 has a birefringence phase difference of δ. It can be regarded as a phase modulator whose principal axis direction is θ.

  Therefore, when the birefringence phase difference of the phase modulation unit 20 of the optical system 10 is δ and the principal axis direction is θ, the optical system 10 is an equivalent optical system in which the phase modulator 21 of the optical system 11 is replaced with the phase modulation unit 20. It can be regarded as a system, and the equations (B) and (5) can also be regarded as equivalent equations.

Then, when the formula (B) and the formula (5) are compared, the birefringence phase difference δ and the principal axis direction θ of the phase modulator 20 and the rotation angles θ of the first and second half-wave plates 24 and 28 are compared. 1, between the theta 2, the following relationship is established.

Therefore, in the optical system 10, the birefringence phase difference δ and the principal axis direction θ of the phase modulation unit 20 are the same as those of the two half-wave plates (first and second half-wave plates 24 and 28). It can be seen that modulation can be performed independently by the rotation angles θ 1 and θ 2 .

  This can also be confirmed from FIGS. 11A and 11B showing measurement results described later.

4-3: Specific Calculation Processing Based on Formula (C) Hereinafter, specific calculation processing based on Formula (C) will be described. Here, a phase shift method is used as a method for detecting a phase change due to the polarization characteristic (birefringence) of the sample 100. The phase shift method is a method for obtaining the phase component (Φ) by changing the birefringence phase difference δ i given by the phase modulator 20 i times. However, the following calculation method is an example of calculation processing applicable to the measurement apparatus 1, and the present invention is not limited to this.

The above formula (C) is
Can be replaced.

  In addition, since the measured light intensity may include an amplitude and a bias component, an equation that takes this into account is introduced here.

In the conversion from the equation (C) to the equation (6), the phase Φ θ is
It was.

From Equation (6), the phase Φ θ is
It can be expressed as.

It is assumed that the phase difference δ i in the phase modulation unit 20 in Equation (6) is changed N times, and the measured value I ′ i including an error is approximated with the theoretical value I i in Equation (6), and a 0 , By determining a 1 and a 2 , the phase Φ θ is obtained. Here, by the method of least squares

Toki,
The a 0, a 1, a 2 satisfying, determined according to the following formulas.

Expression (11) can be expressed as follows using a matrix.
By obtaining the inverse matrix of Equation (12), a 1, a 2 are obtained as follows.

From the equations (8) and (13), the phase difference Φ θ is
It becomes.

Table 1 below shows an example of specific set values of the birefringence phase difference δ i (= 4θ 1 ) and the main axis azimuth θ (= 2θ 2 ), and the first and second for realizing this. An example of set values of the principal axis orientations θ 1 and θ 2 of the half-wave plates 24 and 28 is shown.

In Table 1, the birefringence phase difference δ i (= 4θ 1 ) takes one of five set values (0 °, 72 °, 144 °, 216 °, 288 °: L = 5), and the main axis The direction θ (= 2θ 2 ) takes one of four set values (0 °, 45 °, 90 °, 135 °: M = 4). The optical intensity information of L × M (= K) measurement beams is obtained using the optical system 10 set to L × M conditions combining the birefringence phase difference δ and the principal axis direction θ. To get.

Here, the light intensity obtained by the optical system 10 when the principal axis azimuth θ of the phase modulation unit 20 is fixed and the birefringence phase difference δ i is 0 °, 72 °, 144 °, 216 °, and 288 ° is shown. Assuming that I 0 , I 1 , I 2 , I 3 , and I 4 respectively, the values of I 0 to I 4 can be known as measured values.

If each value of I 0 to I 4 is substituted for I i in equation (6) and each value of 0 °, 72 °, 144 °, 216 °, and 288 ° is substituted for δ i , Φ θ and α , Β can be derived in a plurality of relational expressions. Then, by solving the plurality of relational expressions, it is possible to calculate the [Phi theta.

Each value of Φ 0 , Φ 45 , Φ 90 , Φ 135 is obtained by performing the above procedure by setting the main axis direction θ of the phase modulation unit 20 to values of 0 °, 45 °, 90 °, and 135 °. Can be calculated.

Next, a procedure for calculating the birefringence phase difference Δ and the main axis direction φ of the sample 100 using each value of Φ 0 , Φ 45 , Φ 90 , and Φ 135 will be described. Here, utilizing the fact phase [Phi theta is varying relative azimuth θ (= 2θ 2) of the phase modulation unit 20, obtains the birefringence phase difference Δ and principal axis direction φ contained in [Phi theta.

More and more
far.

Substituting 0 °, 45 °, 90 °, and 135 ° into θ in equation (16) (substituting 0 °, 22.5 °, 45 °, and 67.5 ° into θ 2 ), from equation (16),
Can be derived.

Incidentally, Φ '0, Φ' 45 , Φ '90, Φ' values of 135, Φ 0, Φ 45, Φ 90, each value of [Phi 135, and can be calculated from equation (15) (16) It is.

When Equation (17) is simultaneous,
Thus, the birefringence phase difference Δ and the main axis direction φ of the sample 100 can be calculated.

  Up to this point, the calculation method based on the 4-step phase shift method (M-step phase shift method), which is one of the phase shift methods, has been described. However, separately from this, the calculation process is performed based on the local sampling method. Also good.

For example, given the above [delta] of the setting for 36 ° of the initial phase (theta 1 with respect to 9 ° of the initial phase), δ = 36 °, 108 °, 180 °, 252 °, 324 ° , and the The birefringence phase difference δ is set at equal intervals around 180 °. Therefore, Σsinδ i becomes 0, and the equation (14) can be converted into the following simpler equation.

  For example, in sampling around 180 °, sampling can be performed as shown in FIG. 8 by changing δ = 36 °, 108 °, 180 °, 252 °, and 324 °.

  Here, the sine wave of the light intensity shown in the figure has a phase change due to the birefringence of the sample, the sampling point when θ = 0 ° is ○, the sampling point when θ = 45 ° is ●, Sampling points when θ = 90 ° are represented by □, and sampling points when θ = 135 ° are represented by ■.

Then, Φ 0 , Φ 45 , Φ 90 , and Φ 135 can be calculated by substituting each detected light intensity I ′ i into the equation (18).

After calculating Φ θ0 , Φ 45 , Φ 90 , Φ 135 ), the birefringence phase difference Δ and the main axis direction φ of the sample 100 can be obtained by the same procedure.

4-4: Conditions for data necessary to perform arithmetic processing based on equation (C) In order to perform accurate arithmetic processing (using the phase shift method) based on equation (C) described above, It is necessary to acquire light intensity information (data) that satisfies an appropriate condition. That is, according to the phase shift method, in order to calculate one phase Φ θ1 , the principal axis direction of the phase modulation unit 20 is θ 1 (constant), and the birefringence phase difference of the phase modulation unit 20 is δ 1 to. light intensity information of δ plurality of measurement light obtained by the optical system 10 set to each value of L (L pieces of measurement light) is required. Further, in order to calculate the phase [Phi .theta.2 is a principal axis direction is theta 2 of the phase modulating section 20, and an optical system birefringence phase difference of the phase modulation unit 20 is set to each value of δ 1L The light intensity information of the plurality of measurement lights (L measurement lights) obtained in 10 is required. From this, in order to calculate all the phases Φ 1 to Φ M , the phase modulation unit 20 has the principal axis directions θ 1 to θ M and the birefringence phase difference of the phase modulation unit 20 is It can be seen that light intensity information of L × M measurement lights obtained by the optical system 10 set to each value of δ 1 to δ L is necessary.

In summary, when L values of the birefringence phase difference δ of the phase modulation unit 20 are set and M values of the main axis direction θ of the phase modulation unit 20 are set, in order to calculate all Φ θ (In order to calculate the birefringence phase difference Δ and the main axis direction φ of the sample 100 using the phase shift method), the light intensity information of L × M pieces of measurement light is required. Each of the L × M measurement lights means that the phase modulation unit 20 has a birefringence phase difference δ of any one of L set values, and the main axis direction θ is any of the M set values. This is light obtained by the optical system 10.

  In order to acquire the light intensity information of the measurement light that satisfies this condition, for example, the birefringence phase difference is set to the first value to the Lth value while the principal axis direction of the phase modulation unit 20 is fixed to the first value. Until the light intensity information is obtained, and the birefringence phase difference is sequentially changed from the first value to the Lth value in a state where the principal axis direction of the phase modulation unit 20 is fixed to the second value. Get information. By repeating this operation until the principal axis direction of the phase modulation unit 20 reaches the Mth value, all the light intensity information necessary for the calculation by the phase shift method can be acquired.

  According to the optical system 10, the birefringence phase difference δ and the main axis direction θ of the phase modulator 20 change the main axis directions (rotation angles) of the first and second half-wave plates 24 and 28, respectively. Can be changed. Therefore, according to the measurement apparatus 1, the birefringence phase difference δ and the main axis azimuth θ of the phase modulation unit 20 can be easily set as compared with the case where a Babinet-Soleil compensator is used. Can be performed efficiently and at high speed.

4-5: Algorithm for performing measurement at higher speed As described above, the measurement apparatus 1 can perform measurement at higher speed than the conventional measurement apparatus, but according to the above procedure, the phase modulation unit The measurement is performed with a set value of 20 birefringence phase difference δ or main axis direction θ fixed for a fixed time. That is, at least one of the first and second half-wave plates 24 and 28 repeats rotation and stationary. On the other hand, if the measurement can be performed while continuously rotating the first and second half-wave plates 24 and 28, the measurement speed can be further greatly increased as compared with the above procedure. .

  By the way, when the first and second half-wave plates 24 and 28 are continuously rotated at the same rotation ratio (each speed), for example, as shown in Table 2, the birefringence phase difference δ and the main axis direction θ All the necessary data cannot be acquired because of the combination of.

  Further, when the first and second half-wave plates 24 and 28 are continuously rotated at a rotation ratio of 4: 6, for example, as shown in Table 3, the combination of phase differences is different only in two directions. Therefore, all necessary data cannot be acquired.

  In contrast, when the first and second half-wave plates 24 and 28 are continuously rotated at a rotation ratio of 4: 5, overlapping combinations do not appear as shown in Table 1. , You can get all the data you need.

  Alternatively, even when the first and second half-wave plates 24 and 28 are continuously rotated at a rotation ratio of 8: 3, overlapping combinations do not appear as shown in Table 4. , You can get all the data you need.

  When these are generalized, when the number L of the set values of the birefringence phase difference φ and the number M of the set values of the main axis azimuth θ are relatively prime integers, the first rotating continuously. The second half-wave plates 24 and 28 can acquire all necessary data.

  Then, assuming that the birefringence phase difference φ is a period of 360 °, the main axis azimuth θ is a 180 ° period, and the birefringence phase difference φ and the main axis azimuth θ are set at equal intervals, the phase modulation unit 20 performs the first and first phase modulation. If the two half-wave plates 24 and 28 are continuously rotated at a rotation ratio of M: L, the birefringence phase difference φ takes one of L values, and the principal axis direction θ is M values. The light intensity information of L × M measurement lights can be acquired.

  In other words, by rotating the first and second half-wave plates 24 and 28 at a prime integer ratio, the first and second half-wave plates 24 and 28 are continuously rotated. The system 10 can acquire all data (a plurality of light intensity information) suitable for analysis by the phase shift method.

When the analysis by the phase shift method is performed, as described above, the optical system 10 in which the principal axis orientation between the second half-wave plate 28 and the analyzer 30 satisfies the relationship of θ 3 = 2θ 2 + 45 °. Is used. Therefore, when the light intensity information is acquired by continuously rotating the first and second half-wave plates 24 and 28, the analyzer 30 is also rotated to satisfy the above relational expression ( That is, the light intensity information acquisition procedure is performed by rotating the analyzer 30 at a rotation ratio twice that of the second half-wave plate 28.

4-5: Synchronous control of first and second half-wave plates 24 and 28 and analyzer 30 As described above, first and second half-wave plates 24 and 28 rotate continuously. When the light intensity information is acquired by the optical system 10, it is necessary to synchronize the first and second half-wave plates 24 and 28 and the analyzer 30.

  In other words, the first and second half-wave plates 24 are arranged so that the principal axis orientation of the analyzer 30 is 45 ° when the principal axis orientations of the first and second half-wave plates 24 and 28 coincide. , 28 and analyzer 30 can be synchronized to obtain light intensity information suitable for analysis.

The method for performing these synchronization controls is not particularly limited. For example, the synchronization control may be performed based on the principal axis direction of the second half-wave plate 28. That is, the first and second half-wave plates 24 and 28 and the analyzer 30 are rotated at a predetermined rotation ratio, and the first and second driving / detecting units 72 and 74 are used to make the second When the main axis direction θ 2 of the half-wave plate 28 becomes 0 ° (when it coincides with the main axis direction of the polarizer 22), the main axis direction θ 1 of the first half-wave plate 24 is detected. Then, by applying a voltage corresponding to the detected difference to the first driving / detecting unit 72 (actuator), the main axis direction θ 1 of the first half-wave plate 24 is shifted, and the first 1/2 The wave plate 24 is synchronized with the second half-wave plate 28. Similarly, the main axis direction of the analyzer 30 when the main axis direction θ 2 of the second half-wave plate 28 becomes 0 ° by using the second and third drive / detection units 74 and 76. Detect θ 3 . Then, by applying a voltage corresponding to the detected difference to the third driving / detecting unit 76 (actuator), the main axis direction θ 3 of the analyzer 30 is shifted, and the analyzer 30 is moved to the second 1/2. It is synchronized with the wave plate 28.

  In FIG. 9, the flowchart figure for demonstrating the measurement procedure using the measuring device 1 including these synchronous controls is shown.

  First, the number of sampling points and the initial phase are determined (step S30). When the number of sampling points is determined, the rotation ratio of the motor (actuator) can be determined.

  Then, the motor is operated at the determined rotation ratio (step S32). That is, the motor is operated by applying a voltage according to the rotation ratio to the motor.

  Then, the motor is synchronized (step S34). This synchronizes the principal axis directions of the first and second half-wave plates 24 and 28 and the analyzer 30 (step S34).

  After the step of synchronizing the motor is completed, the sample 100 is placed in the optical path L (step S35), and the change characteristic element of the sample 100 is measured.

  That is, the sample 100 is installed on the optical path L (step S35), and light intensity information is acquired (step S36).

  Then, it is determined whether all data (light intensity information and spindle direction information) necessary for measurement have been acquired (step S38). If all the data is not complete (No in step S38), the light intensity information acquisition procedure is repeated. Then, when all the data are obtained (Yes in step S38), an arithmetic process for calculating the polarization characteristic element is performed (step S40).

  Then, it is determined whether or not to continue the measurement (step S42). When the measurement is continued, the same procedure is repeated from the light intensity information acquisition procedure (step S36). Note that the steps until the motors are synchronized (steps S30 to S34) need only be set once, and need not be repeated.

(5) Data Correction As described above, in the present embodiment, an approximation with Δ << 1 is used when the equation (B) is derived. Therefore, when a sample that does not satisfy Δ << 1 is measured, a situation in which a correct measurement result cannot be obtained may occur.

  However, by taking the arc tangent of Φ ′ used to determine the birefringence phase difference Δ and the main axis direction φ, and correcting the data, accurate measurement can be performed even for samples exceeding Δ << 1. Can do.

  FIG. 10 is a diagram illustrating measured values when data correction is not performed and when data correction is performed. As indicated by the circles in FIG. 10, when the data is not corrected, the difference between the measured value and the set value becomes large in the range where the birefringence phase difference Δ exceeds 60 ° (the range where Δ exceeds 1 rad). However, if the data is corrected by taking the arctangent, as shown by ● in FIG. 10, a measurement value equal to the set value can be obtained regardless of the range of the birefringence phase difference Δ. Therefore, by correcting the data, the conditions of the sample that can be measured can be relaxed, and the reliability of the measurement result can be improved.

  A biological sample usually has a birefringence phase difference of 30 ° or less. That is, in the case of a biological sample, a highly accurate measurement result can be obtained without performing data calibration (see FIG. 10). Therefore, when the optical property measuring apparatus according to the present invention is applied to measurement of a biological sample, calibration work is not necessary, and calculation processing can be performed in a shorter time.

(6) Calibration Next, apparatus calibration applicable when measurement is performed with an actual apparatus will be described.

  When actually measuring with an apparatus, the change of the polarization state by an optical element and the error at the time of optical axis adjustment arise. Therefore, the error caused by the birefringence of the experimental optical system is not compensated only by performing the above analysis. Therefore, calibration is performed to remove the birefringence of the apparatus and detect only the birefringence of the sample 100. Since the birefringence R is a vector quantity having a magnitude (birefringence phase difference Δ) and a direction (main axis azimuth φ), the birefringence of the sample and the birefringence of the apparatus do not match. As shown in the following equation, it is necessary to perform subtraction by a vector. Here, the subscript s is a sample value, m is a measured value, and n is a value only for the apparatus.

  In order to perform such calculation in consideration of the azimuth, it is necessary to perform correction at the stage of phase change including azimuth information, instead of simply subtracting the result of the birefringence phase difference and the principal axis azimuth.

First, by providing a phase difference in a state where nothing put sample, by detecting a change in light intensity, it is possible from the detected light intensities a differential phase shift [Phi theta. For example, phase changes Φ n0 , Φ n1 , Φ n2 , and Φ n3 are obtained by changing the orientation θ to 0, π / 4, π / 2, and 3π / 4. This is the phase in the null state. The null phase contains information on the birefringence magnitude and direction of the device. Next, the sample 100 is placed, and the phases Φ m0 , Φ m1 , Φ m2 , and Φ m3 are obtained in the same manner. This phase contains birefringence information for both the instrument and the sample. From these phases, phase changes Φ s0 , Φ s1 , Φ s2 , and Φ s3 due to the sample 100 alone are obtained. Specifically, as shown in the following equation, the phase change due to only the sample 100 can be calculated by subtracting the phase in each direction.

  By performing calibration by subtraction for each phase, the birefringence of the optical system and the birefringence of the sample are not handled as a quantity (scalar), but can be regarded as a vector in consideration of the direction. Therefore, even when the birefringence of the sample is small, highly accurate measurement is possible.

(7) Measurement Results FIGS. 11A to 12B show the measurement results of the optical characteristic measurement device according to this embodiment.

11A and 11B show a state in which the birefringence phase difference δ modulated by the rotary phase modulator (phase modulation unit 20) and the elliptical main axis direction θ are linearly deformed with respect to the rotation angle. Is shown. In FIG. 11, the horizontal axis represents the rotation angle of each element (first and second half-wave plates 24 and 28), and the vertical axis represents the measurement results of the birefringence phase difference δ and the elliptical main axis direction θ. Show. From FIG. 11A, it can be seen that the main axis azimuth θ changes linearly with respect to the rotation angle θ 1 of the first half-wave plate 24. 11B shows that the birefringence phase difference δ changes linearly with respect to the rotation angle of the second half-wave plate 28. FIG.

  12 (A) and 12 (B) show measurement results obtained by performing analysis using a high-speed birefringence algorithm using a rotary phase modulator (phase modulation unit 20). Here, a Babinet Soleil compensator was used as a sample to test the accuracy of the measuring device. FIG. 12A shows a measured value of the birefringence phase difference with respect to the calibration birefringence phase difference. FIG. 12B shows the measured value of the principal axis direction relative to the configuration direction. All of them changed linearly, and from the variation from the linearity, the measurement accuracy was 1.88 ° in the birefringence phase difference and 0.47 ° in the principal axis direction.

  And in FIG. 13 (A)-FIG. 14 (B), the analysis result obtained using this measuring device 1 is shown. Specifically, FIG. 13 (A) and FIG. 13 (B) show the birefringence phase difference and the principal axis orientation obtained by measuring the cross-section of the chicken deep pectoral muscle using the measuring device 1. FIGS. 14A and 14B show the birefringence phase difference and the main axis orientation obtained by measuring the cross section of the plastic disk using the measuring device 1, respectively. According to the measuring apparatus 1, as shown in FIGS. 13A to 14B, the result of analyzing the measurement object in units of planes can be obtained as visual data.

  In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation is possible. 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, the optical elements constituting the optical system 10 may be configured so that the principal axis direction can be changed manually. In this case, the principal axis direction information may be acquired by the detection unit, and various arithmetic processes may be performed.

  Since the present invention can visualize the orientation state and residual stress of polymers from birefringence distribution, product inspection of transparent bodies (optical elements such as lenses and glass substrates, molded products using plastics) such as glass and resin. Can be used.

  Moreover, the molecular orientation state and internal stress of a biological tissue can be observed by using a microscope type system. Since a specific site composed of oriented molecules can be detected without performing staining or enzyme treatment, it can be used in the medical analysis and cosmetic fields that handle various tissue fragments.

  Furthermore, by speeding up the measurement, it is possible to dynamically monitor the stress state during product processing and the internal stress state of the moving biological sample.

  In particular, according to the present invention, an optical characteristic element is measured using an optical system in which optical elements (first and second half-wave plates 24 and 28, analyzer 30) are continuously rotated. Can do. Therefore, the time required for the light intensity information acquisition procedure can be shortened. Therefore, according to the present invention, it is possible to provide a measuring apparatus capable of measuring in real time the state of a sample whose state is sequentially changed, such as a biological sample.

It is the schematic of an optical characteristic measuring device. It is a block diagram of an optical characteristic measuring device. It is a figure for demonstrating an optical characteristic measuring apparatus. It is a figure for demonstrating an optical characteristic measuring apparatus. It is a flowchart figure which shows a light intensity information acquisition procedure. It is a flowchart figure which shows an arithmetic processing procedure. It is a figure which shows an example of the conventional optical system. It is a figure which shows an example of light intensity. It is a flowchart figure which shows an optical characteristic measurement procedure. It is a figure for demonstrating correction | amendment of data. It is a figure which shows the result of an accuracy verification test. It is a figure which shows the result of an accuracy verification test. It is a figure which shows the measurement result by an optical characteristic measuring apparatus. It is a figure which shows the measurement result by an optical characteristic measuring apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Measuring apparatus, 10 ... Optical system, 11 ... Optical system, 12 ... Light source, 14 ... Light receiving part, 15 ... Light receiving element, 20 ... Phase modulation part, 21 ... Phase modulator, 22 ... Polarizer, 24 ... 1st 1/2 wavelength plate, 26 ... 1/4 wavelength plate, 28 ... 2nd 1/2 wavelength plate, 30 ... analyzer, 40 ... light intensity information acquisition unit, 50 ... storage device, 60 ... arithmetic processing unit, DESCRIPTION OF SYMBOLS 70 ... Control signal production | generation part, 72 ... 1st drive / detection part, 74 ... 2nd drive / detection part, 76 ... 3rd drive / detection part, 80 ... Control apparatus, 100 ... Sample, 110 ... Processing part 120: Storage unit 130: Information storage medium 140: Display unit

Claims (18)

  1. In an optical property measurement device that measures the optical properties of a measurement object,
    A light source that emits light of a predetermined wavelength, at least five optical elements, and a light receiving unit that receives measurement light obtained by modulating the light with the at least five optical elements and the measurement target, Including an optical system;
    A light intensity information acquisition unit for acquiring light intensity information of the measurement light;
    An arithmetic processing unit that performs arithmetic processing to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light; ,
    Including
    The at least five optical elements include first and second polarizers, first and second half-wave plates, and a quarter-wave plate,
    The optical system converts light emitted from the light source into the first polarizer, the first half-wave plate, the quarter-wave plate, and the second half-wave plate. So that the light modulated by the measurement object is incident on the light receiving unit via the second polarizer, and
    At least the first and second half-wave plates are configured to be rotatable,
    In the light intensity information acquisition unit,
    The first to Kth optical systems obtained by the optical system satisfying the first to Kth (K is an integer of 2 or more) principal axis azimuth conditions in which at least one of the principal axis directions of the first and second half-wave plates is different. Obtaining light intensity information of the measurement light of
    In the arithmetic processing unit,
    The first to Kth theoretical formulas of light intensity reflecting the principal axis directions of the at least five optical elements, including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables. An optical characteristic measurement apparatus that performs arithmetic processing for calculating at least one of the birefringence phase difference of the measurement target and the principal axis direction based on light intensity information of the Kth measurement light.
  2. In an optical property measurement device that measures the optical properties of a measurement object,
    A light intensity information acquisition unit that acquires light intensity information of at least five optical elements included in the optical system and measurement light modulated by the measurement object;
    An arithmetic processing unit that performs arithmetic processing to calculate at least one of the birefringence phase difference of the measurement target and the principal axis direction based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light; ,
    Including
    The at least five optical elements include first and second polarizers, first and second half-wave plates, and quarter-wave plates, and at least the first and second optical plates. The half-wave plate is configured to be rotatable,
    The measurement light includes light having a given wavelength emitted from a light source, the first polarizer, the first half-wave plate, the quarter-wave plate, and the second 1 / Light that is made incident on the measurement object via a two-wavelength plate, and that is obtained by making the light modulated by the measurement object incident on a light receiving unit via the second polarizer,
    In the light intensity information acquisition unit,
    The first to Kth optical systems obtained by the optical system satisfying the first to Kth (K is an integer of 2 or more) principal axis azimuth conditions in which at least one of the principal axis directions of the first and second half-wave plates is different. Obtaining light intensity information of the measurement light of
    In the arithmetic processing unit,
    The first to Kth theoretical formulas of light intensity reflecting the principal axis directions of the at least five optical elements, including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables. An optical characteristic measurement apparatus that performs arithmetic processing for calculating at least one of the birefringence phase difference of the measurement target and the principal axis direction based on light intensity information of the Kth measurement light.
  3. In the optical characteristic measuring device according to claim 1 or 2,
    The first polarizer, the first and second half-wave plates, and the quarter-wave plate constitute a phase modulation unit,
    The first to Kth measurement light is an optical characteristic measurement device that is measurement light obtained by the optical system in which at least one of a birefringence phase difference and a principal axis direction of the phase modulation unit is different.
  4. In the optical characteristic measuring device according to claim 3,
    In each of the first to Kth measurement lights, the phase modulation unit has a birefringence phase difference value of any one of L (L is an integer of 2 or more) set values, and has the principal axis direction. An optical characteristic measurement device which is measurement light obtained by one of L × M optical systems whose value is any one of M (M is an integer of 2 or more) set values.
  5. In the optical characteristic measuring device according to claim 4,
    The optical characteristic measuring apparatus in which L and M are prime.
  6. In the optical characteristic measuring device according to any one of claims 3 to 5,
    When the light intensity of the measurement light is I, and the birefringence phase difference and the principal axis direction of the phase modulation unit are δ and θ, respectively,
    In the arithmetic processing unit,
    An optical characteristic measuring device that performs the arithmetic processing based on the above.
  7. In the optical characteristic measuring device according to claim 6,
    When the principal axis directions of the second half-wave plate and the analyzer are θ 2 and θ 3 respectively,
    In the light intensity information acquisition unit,
    θ 3 = 2θ 2 + 45 °
    An optical characteristic measurement device that acquires light intensity information of the measurement light obtained by the optical system that satisfies the above.
  8. In the optical characteristic measuring device according to any one of claims 1 to 7,
    In the light intensity information acquisition unit,
    An optical characteristic measurement device that acquires light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are continuously rotated at a given rotation ratio.
  9. In the optical characteristic measuring device according to claim 8, which refers to any one of claims 4 to 7,
    In the light intensity information acquisition unit,
    An optical characteristic measurement device that acquires light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates rotate at an M: L rotation ratio.
  10. In the measuring device in any one of Claims 1-9,
    First and second actuators for rotating the first and second half-wave plates;
    First and second detectors for detecting principal axis orientations of the first and second half-wave plates;
    A control signal generator for generating a control signal for controlling the operation of the first and second actuators;
    Further including
    The control signal generation unit is a measurement device that generates the control signal based on detection signals from the first and second detection units.
  11. In the optical property measurement method for measuring the optical property of the measurement object,
    A light intensity information acquisition procedure for acquiring light intensity information of measurement light modulated by at least five optical elements included in the optical system and the measurement object;
    An arithmetic processing procedure for performing arithmetic processing for calculating at least one of the birefringence phase difference of the measurement object and the main axis direction based on the theoretical formula of the light intensity of the measurement light and the light intensity information of the measurement light; ,
    Including
    The at least five optical elements include first and second polarizers, first and second half-wave plates, and quarter-wave plates, and at least the first and second optical plates. The half-wave plate is configured to be rotatable,
    The measurement light includes light having a given wavelength emitted from a light source, the first polarizer, the first half-wave plate, the quarter-wave plate, and the second 1 / Light that is made incident on the measurement object via a two-wavelength plate, and that is obtained by making the light modulated by the measurement object incident on a light receiving unit via the second polarizer,
    In the light intensity information acquisition procedure,
    The first to Kth optical systems obtained by the optical system satisfying the first to Kth (K is an integer of 2 or more) principal axis azimuth conditions in which at least one of the principal axis directions of the first and second half-wave plates is different. Obtaining light intensity information of the measurement light of
    In the arithmetic processing procedure,
    The first to Kth theoretical formulas of light intensity reflecting the principal axis directions of the at least five optical elements, including at least one of the birefringence phase difference and the principal axis direction of the measurement object as variables. An optical characteristic measurement method for performing calculation processing for calculating at least one of the birefringence phase difference of the measurement target and the principal axis direction based on the light intensity information of the Kth measurement light.
  12. In the optical characteristic measuring method according to claim 11,
    The first polarizer, the first and second half-wave plates, and the quarter-wave plate constitute a phase modulation unit,
    The optical characteristic measurement method, wherein the first to Kth measurement lights are measurement lights obtained by the optical system in which at least one of a birefringence phase difference and a principal axis direction of the phase modulation unit is different.
  13. In the optical characteristic measuring method according to claim 12,
    In each of the first to Kth measurement lights, the phase modulation unit has a birefringence phase difference value of any one of L (L is an integer of 2 or more) set values, and has the principal axis direction. An optical characteristic measurement method which is measurement light obtained by one of L × M optical systems whose value is any one of M (M is an integer of 2 or more) set values.
  14. The optical property measuring method according to claim 13,
    The method for measuring optical characteristics, wherein L and M are prime to each other.
  15. In the optical characteristic measuring method according to any one of claims 12 to 14,
    When the light intensity of the measurement light is I, and the birefringence phase difference and the principal axis direction of the phase modulation unit are δ and θ, respectively,
    In the arithmetic processing procedure,
    An optical characteristic measuring method for performing the arithmetic processing based on the above.
  16. The optical property measuring method according to claim 15,
    When the principal axis directions of the second half-wave plate and the analyzer are θ 2 and θ 3 respectively,
    In the light intensity information acquisition procedure,
    θ 3 = 2θ 2 + 45 °
    An optical characteristic measurement method for acquiring light intensity information of the measurement light obtained by the optical system satisfying the above.
  17. The optical property measuring method according to any one of claims 11 to 16,
    In the light intensity information acquisition procedure,
    An optical characteristic measurement method for acquiring light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are continuously rotated at a given rotation ratio.
  18. The optical property measurement method according to claim 16, wherein any one of claims 13 to 16 is cited.
    In the light intensity information acquisition procedure,
    An optical characteristic measurement method for acquiring light intensity information of the measurement light obtained by the optical system in which the first and second half-wave plates are rotated at a rotation ratio of M: L.
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JP2012040224A (en) * 2010-08-20 2012-03-01 Fujifilm Corp Endoscope apparatus, and endoscopic diagnosis device
RU2474810C2 (en) * 2011-04-27 2013-02-10 Общество с ограниченной ответственностью "Поларлайт" Method of measuring polarisation state of light beam
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JP2012024146A (en) * 2010-07-20 2012-02-09 Fujifilm Corp Polarization image measurement display system
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