JP2017009338A - Measurement method of optical characteristic and measurement instrument of optical characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, when a measurement cell is used in a polarization characteristic measurement system, accurate measurement is difficult due to an incidence window and an exit window of the measurement cell, and the problem that accurate measurement of microscopic optical characteristics using an objective lens, optical characteristics of respective layers of a laminate film, and optical characteristics of a retina in medical applications is difficult.SOLUTION: A method for measuring optical characteristics by using probe light in accordance with this invention is characterized by comprising a step of disposing a plurality of measurement objects having polarization characteristics in a path of the probe light; a step of measuring a Mueller matrix of the plurality of measurement objects from polarized incident light and outgoing light obtained from the incident light through the plurality of measurement objects, a step of selecting respective polarization characteristic models of the plurality of measurement objects, and a step of setting up simultaneous equations in accordance with respective selected polarization characteristic models and solving them to obtain respective polarization characteristics of the plurality of measurement objects.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for accurately measuring optical characteristics of a plurality of measurement objects in a method for measuring optical characteristics of a plurality of measurement objects using Mueller matrix polarimetry.

  Light is an electromagnetic wave and has the property of a transverse wave. Assuming a three-axis (x, y, z) coordinate system orthogonal to each other and the light traveling direction is the z-axis direction, the vibration direction of the electric field vector (or magnetic field vector) of the light is along the xy plane. Can be divided into an x-axis component and a y-axis component. At that time, light in which the phase difference and amplitude ratio of the x-axis component and y-axis component change randomly with time is referred to as non-polarized light, and constant light without change is referred to as polarized light. The polarization state of light is related to the phase difference between the x-axis component and the y-axis component and the value of the amplitude ratio.

  When a transparent measurement object with optical anisotropy or the surface of the measurement object is irradiated with light in a certain polarization state and output light such as transmitted light or reflected light is obtained, the light is between the incident light and the output light. A change in the polarization state is observed. Obtaining information related to the anisotropy of the transparent measurement object or the optical properties of the surface of the measurement object from this change in polarization state is referred to as polarization measurement. The anisotropy of the measurement object is related to the anisotropy of the molecular structure, the presence of stress, and the optical characteristics of the measurement sample surface are related to the refractive index and the film thickness of the thin film.

  A polarization measurement method that measures changes in the polarization state of light caused by being transmitted through or reflected from a measurement object is called polarimetry. Since the polarization components in the orthogonal directions behave differently, the amplitude and phase of each of the orthogonal polarization components change greatly due to reflection and transmission from the measurement object. In polarimetry, values such as a birefringence phase difference δ representing a birefringence characteristic obtained from orthogonal polarization components of a transmitted wave and a reflected wave, a principal axis azimuth θ, an amplitude ratio ψ, and a phase difference Δ are determined.

  In recent years, optically transparent substances used for optical devices such as glass and polymer materials are required not to change optical properties due to temperature changes and external stress. It is also known that residual birefringence caused by stress generated during the manufacture of an optical device degrades optical characteristics, and there is a demand for reducing the residual stress. Accordingly, it has become important to measure the temperature dependence of the polarization property of a substance, the photoelastic effect due to stress, and the temperature dependence of the photoelastic effect.

  There are many types of ellipsometry principles, and many methods are known as birefringence measurement methods. For example, Patent Document 1 discloses a birefringence measuring apparatus including an optical system having an optical rotation means. However, it is assumed that there is one object to be measured in the optical path, and the parameters of the Jones matrix or Mueller matrix representing the polarization characteristics of the object to be measured are obtained. Therefore, when the measurement object is installed in a measurement cell such as a vacuum cell or a temperature control cell, and the measurement must be performed through the observation window of the cell, the birefringence characteristic of the measurement object is independent. An operation in which measurement cannot be performed and a measurement operation is performed in the absence of a measurement object in advance, then the measurement object is installed and measurement is performed, and a difference between the two (hereinafter referred to as “difference measurement”) is obtained. Had to be done.

  As an example of an ellipsometer, Patent Document 2 previously measures the polarization state of reflected light from a measurement object in the absence of a window, and then reflects the reflected light from the measurement object in a cell with a window. It is disclosed that the polarization state is measured, the photoelastic effect of the window is obtained, and window correction is performed. In this window correction formula, it is assumed that the birefringence amount due to the photoelastic effect of the entrance window and the exit window is the same in order to avoid complicated calculation. However, in practice, the amount of birefringence generated in the entrance window and the exit window is not always the same.

  In addition, the work to obtain such a difference must be based on the premise that the birefringence amount of the cell window does not change with time, and when the temperature condition or pressure condition inside the measurement cell is changed. Birefringence changes occur in the observation window.

  Although attempts have been made to improve the spatial resolution in measuring birefringence characteristics by placing objective lenses on both sides of the object to be measured instead of the observation window, the birefringence of objective lenses generally has a finite value. Therefore, the influence of the objective lens cannot be completely removed.

  Further, when the measurement object has a multilayer structure, it is considered that there are a plurality of layers of a substance having birefringence. Regarding the synthesis of birefringence characteristics in the case of having such a plurality of layers, it is known that analysis can be performed by the above difference measurement, but a system in which each layer exhibits independent changes due to temperature changes. No measurement method has been proposed so far.

  In the medical field, attempts have been made to measure the amount of birefringence resulting from the fiber structure of the retina as an early diagnosis technique for glaucoma, and a diagnostic apparatus using this method is commercially available. Birefringence is not only a characteristic of the retina, but also the cornea has a birefringence characteristic. In order to measure the fundus retina, it is necessary to remove the birefringence derived from the cornea. On the other hand, a commercially available diagnostic apparatus uses cornea-derived birefringence as a fixed value stored in the apparatus. For this reason, it has been reported that the diagnostic value varies greatly (= measurement error) depending on the posture of the head (= eyeball) and the right and left eyes being mixed during actual examination.

JP-A-8-327498 JP2012-52972

  As described above, the conventional measurement method has limitations, and there is a problem that sufficient measurement accuracy cannot be obtained.

  In order to solve the above problems, a method for measuring optical characteristics using probe light according to the present invention includes a step of arranging a plurality of measurement objects having polarization characteristics in a path of probe light, and polarized incident light. Measuring the Mueller matrix of the plurality of measurement objects from the incident light obtained by passing the incident light through the plurality of measurement objects; and selecting a polarization characteristic model of each of the plurality of measurement objects And a step of obtaining each polarization characteristic of the plurality of measurement objects by solving simultaneous equations in accordance with each selected polarization characteristic model.

  Further, the optical characteristic measuring apparatus according to the present invention is a measuring apparatus for optical characteristics of a plurality of measurement objects including a probe light source, a polarization generation system, a polarization detection system, and a photodetector, A calculation unit that calculates a Mueller matrix from the polarization characteristics of incident light irradiated from the polarization generation system and output light that enters the polarization detection system, and the calculation unit further includes the plurality of measurements from the Mueller matrix. It is characterized by calculating a model parameter of a polarization characteristic model of an object.

  According to the present invention, it is possible to measure optical characteristics with high accuracy by a single measurement operation.

These are the schematic diagrams of the measuring apparatus of the optical characteristic by this invention. These are figures which show the flow of the measuring method of the optical characteristic by this invention. These are figures which show the measuring apparatus of the optical characteristic provided with the measurement cell by Example 1 of this invention. These are figures which show the flow of the measuring method of the optical characteristic using the measuring apparatus of the optical characteristic provided with the measuring cell by Example 1 of this invention. These are figures which show the measuring apparatus of the optical property provided with the measurement cell by Example 1 of this invention, and also provided with the stress application apparatus and the temperature control apparatus. These are the optical characteristic measuring apparatuses provided with the heater by Example 1 of this invention, Comprising: It is a figure which shows a mode that compressive stress was added to the measuring object. These are the optical characteristic measuring apparatuses provided with the heater by Example 1 of this invention, Comprising: It is a figure which shows a mode that tensile stress was applied to the measuring object. These are figures which show the result of having measured by imitating the measuring device of the optical characteristic by Example 1 of the present invention. These are figures which show the measuring apparatus of the optical characteristic provided with the objective lens by Example 2 of this invention. These are figures which show the measurement of the optical characteristic at the time of setting the multilayer film by Example 3 of this invention as a measuring object. These are figures which show the measurement of the optical characteristic at the time of making the retina and cornea of the eyeball by Example 4 of this invention into a measuring object.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram of an optical characteristic measuring apparatus for carrying out the present invention. The measurement apparatus includes a light source 4 for emitting light, a polarization generation system 5 for controlling the polarization state of probe light that is received from the light source and is incident on a measurement object, and measurement is performed from the polarization generation system 5. A polarization detection system 6 for detecting the polarization state of outgoing light obtained through the objects 1 to 3 and a photodetector 7 for measuring the intensity of light are provided. An arithmetic unit 8 calculates a Mueller matrix from the polarization state of incident light and the polarization state of outgoing light. Here, the calculation unit may also serve as a control unit for the light source 4, the polarization generation system 5, the polarization detection system 6, and the photodetector 7. Reference numeral 9 denotes a probe light path.

  Here, the measurement objects 1 to 3 are arranged in series in the probe light path. Although the drawing shows a system in which all measurement objects transmit light, some of the measurement objects may be reflection systems.

  FIG. 2 is a diagram showing a flow of an optical characteristic measuring method for carrying out the present invention. A method for measuring optical characteristics according to the present invention will be described below.

  First, as shown in FIG. 1, it arrange | positions in the path | route of probe light so that a several measurement target object may become in series. In FIG. 1, a linear probe light path is shown. However, when the object to be measured is a reflection system, the path may be bent with a predetermined reflection angle.

  Next, the Mueller matrix of the system that combines the plurality of measurement objects is measured from the polarized incident light and the emitted light obtained by passing the incident light through the plurality of measurement objects. As the Mueller matrix polarimetry for measuring the Mueller matrix, there are a double rotation method and a 4-detector polarimeter method, and any method may be used.

  Next, a polarization characteristic model of each measurement object is selected. If the type of polarization characteristics of the measurement object is known, the model can be selected. However, if the type of polarization characteristics is unknown, it is calculated by assuming the prepared polarization characteristics model sequentially, and fitting, etc. The polarization characteristic model may be determined by selecting the most appropriate one by the above method.

There is a Mueller matrix as a notation of optical properties of a substance having a birefringence phase difference. The Mueller matrix has 4 × 4 = 16 parameters, and each parameter varies depending on the substance. In general, Mueller matrix

Is described.

  The following shows polarization characteristics models of materials having various birefringence characteristics.

Mueller matrix of polarization property model of material with linear birefringence property is

Δ represents the birefringence phase difference, and θ represents the principal axis orientation of linear birefringence.

The Mueller matrix of the polarization property model of a substance with optical rotatory birefringence is

And φ is a light application angle.

Mueller matrix of polarization property model of material with dichroic birefringence is

Β is the principal axis direction of linear dichroic birefringence, q is the transmittance of light oscillating in the β direction, and r is the transmittance of light oscillating in the direction perpendicular to β.

Mueller matrix of polarization property model for materials with circular dichroic birefringence is

S is the transmittance of counterclockwise circularly polarized light, and t is the transmittance of clockwise circularly polarized light.

Mueller matrix of polarization property model of material with reflective isotropic birefringence is

Ψ is an angle display of the amplitude ratio, and Δ is a phase difference.

Thus, the 16 matrix elements are not all independent, but the elements other than zero and 1 are functions of 1 to 3 parameters, which are quantities related to each other. If these parameters are determined, 16 matrix elements are determined. Also, it has symmetry or antisymmetry between non-diagonal elements. Therefore, the Mueller matrix indicating the polarization characteristics of each substance can be simply expressed by the following general formula.

Here, the signs + and − indicate symmetry and antisymmetry, and the left off-diagonal elements are not simultaneously + or −.

M ₁ each Mueller matrix here three measuring object represented in Figure 1,
When represented by M ₂ and M ₃ , the Mueller matrix M ₁₂₃ of the measurement object system obtained by combining the three is obtained by multiplying the three respective matrices.

That is, the entire system Mueller matrix is obtained by multiplying the matrix sequentially from the right in the order in which incident light passes. Here, since the multiplication of the matrix does not hold the exchange law, the order of the polarization element matrix of the equation (3) cannot be changed.

Each Mueller matrix M ₁ of the measurement object,
When expressed by M ₂ and M ₃ , the Mueller matrix M ₁₂₃ of a system in which three measurement objects are synthesized is

It becomes. Here, subscript numbers 1, 2, and 3 indicate matrix elements of measurement objects 1, 2, and 3, respectively.

  Equation (4) becomes a 16-element simultaneous equation. Finally, these simultaneous equations are solved to determine parameters (δ, θ) and the like of the object to be measured. As a method for solving simultaneous equations, a known addition / subtraction method, substitution method, Newton method, bisection method, or the like may be used. In the simultaneous equations of Equation (2), the numerator changes depending on the characteristics of the measurement object arranged in the optical path, and the sign also changes depending on specific matrix elements.

  By substituting the obtained parameters into the Mueller matrix of the measurement object and calculating, desired optical characteristics can be obtained.

  The following are specific examples of simultaneous equations, their genres, and characteristic parameters to be obtained depending on the number of objects to be measured and the type of polarization characteristic model.

<1-1. When there are three objects to be measured and all have linear birefringence characteristics>
From equation (1-2), AL in equation (4) becomes:

Therefore, Expression (4) becomes the following expression.

The matrix element m ₂₂ -m _{44 in the} equation (6) is a nine-way simultaneous equation including six unknown parameters (δ ₁ , δ ₂ , δ ₃ , θ ₁ , θ ₂ , θ ₃ ) of the _three measurement objects. . Since there are many simultaneous equations with unknown parameters, these simultaneous equations have a unique solution.

<1-2. When the birefringence phase difference [delta] is small and [delta] << 1 can be approximated>
Among the measurement objects 1, 2, and 3, when the birefringence phase difference δ between 1 and 3 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), each element of equation (5) is

Therefore, Equation (6) becomes

The matrix element m ₂₂ -m _{44 in the} equation (8) is a nine-element simultaneous equation including six unknown parameters (δ ₁ , δ ₂ , δ ₃ , θ ₁ , θ ₂ , θ ₃ ) of the _three measurement objects. . Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

  Even when the measurement objects 1 and 3 have a linear birefringence characteristic and the measurement object 2 has a characteristic other than the linear birefringence characteristic, parameters (δ, θ, φ, q, r, β, etc.) of each element can be established by establishing simultaneous equations. ) At the same time. Specific examples are shown below.

<2-1. When the measurement objects 1 and 3 have linear birefringence characteristics and the measurement object 2 has optical rotation birefringence characteristics>
AL in equation (4) becomes the following equation:


Therefore, Expression (4) becomes the following expression.

The matrix element m ₂₂ -m _{44 in the} equation (10) is a nine-element simultaneous equation including five unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , φ) of the _three measurement objects. Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

<2-2. When the birefringence phase difference [delta] is small and [delta] << 1 can be approximated>
Among the measurement objects 1, 2, and 3, when the birefringence phase difference δ between 1 and 3 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), Equation (7) Substituting for) gives

The matrix element m ₂₂ -m _{44 in the} equation (11) is a nine-element simultaneous equation including five unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , φ) of the _three measurement objects. Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

<3-1. When the measurement objects 1 and 3 have linear birefringence characteristics and the measurement object 2 has dichroic birefringence characteristics>
AL in equation (4) becomes the following equation:


Therefore, Equation (4) becomes

The matrix element m ₁₁ -m _{44 in the} equation (13) is a 16-way simultaneous equation including seven unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , q, r, β) of the three measurement objects. . Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

3-2. When birefringence phase difference δ is small and δ << 1 can be approximated>
Among the measurement objects 1, 2, and 3, when the birefringence phase difference δ between 1 and 3 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), Equation (5) Substituting for) gives

The matrix element m ₁₁ -m _{44 in the} equation (14) is a 14-element simultaneous equation including seven unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , q, r, β) of the three measurement objects. . Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

<4-1. Measurement objects 1 and 3 have linear birefringence characteristics, and measurement object 2 has circular dichroic birefringence characteristics>
AL in equation (4) becomes the following equation:


Therefore, Expression (4) becomes the following expression.

The matrix element m ₁₁ -m _{44 in the} equation (16) is a 16-element simultaneous equation including six unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , s, t) of the _three measurement objects. Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

<4-2. Case where birefringence phase difference δ is small and δ <<1>
Among the measurement objects 1, 2, and 3, when the birefringence phase difference δ between 1 and 3 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), Equation (15) Substituting for) gives

The matrix element m ₁₁ -m _{44 in the} equation (17) is a 15-element simultaneous equation including six unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , s, t) of the three measurement objects. Since there are many elements of simultaneous equations, this simultaneous equation also has a unique solution.

<5. Measurement objects 1 and 3 have linear birefringence characteristics and measurement object 2 has reflective isotropic birefringence characteristics>
Equation (4) becomes the following equation.

The matrix element m ₁₂ -m _{44 in the} equation (18) becomes a 15-way simultaneous equation including six unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ , Δ, ψ) of the _three measurement objects. . When the ELs of the measurement objects 1 and 3 are irrelevant parameters, the equation (18) is a 15-way simultaneous equation including 14 unknown parameters (E ₁ -L ₂ , E ₂ -L ₂ , Δ, Ψ). become. Since there are many elements of simultaneous equations for unknown parameters, these simultaneous equations also have a unique solution.

This method can also determine the polarization parameters when there are two objects to be measured. Specific examples are shown below. When measuring objects 1 and 2, A ₃ -L _{3 in} equation (4) becomes:

Therefore, Expression (4) becomes the following expression.

<6. When there are two objects to be measured and both have linear birefringence characteristics>
Equation (20) becomes the following equation.

The matrix element m _22- m _{44 in the} equation (21) is a nine-way simultaneous equation including four unknown parameters (δ ₁ , δ ₃ , θ ₁ , θ ₃ ) of the two measurement objects. Since there are many simultaneous equations with unknown parameters, these simultaneous equations have a unique solution.

<7-1. When the measurement object 1 has linearity and the measurement object 2 has optical rotatory birefringence>
Equation (20) becomes the following equation.

The matrix element m _22- m _{44 in the} equation (22) is a nine-way simultaneous equation including three unknown parameters (δ, θ, φ) of two measurement objects. Since there are many simultaneous equations with unknown parameters, these simultaneous equations have a unique solution.

<7-2. When measurement object 1 has optical rotation and measurement object 2 has linear birefringence characteristics>
Equation (20) becomes the following equation.

The matrix element m _22- m _{44 in the} equation (23) is a nine-element simultaneous equation including three unknown parameters (δ, θ, φ) of two measurement objects. Since there are many simultaneous equations with unknown parameters, these simultaneous equations have a unique solution.

<8-1. When the measuring object 1 has linearity and the measuring object 2 has linear dichroic birefringence characteristics>
Equation (20) becomes the following equation.

<8-2. When birefringence phase difference δ is small and δ << 1 can be approximated>
When the birefringence phase difference δ of the measurement object 1 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), the equation (20) becomes the following equation.

<8-3. When measurement object 1 has linear dichroism and measurement object 2 has linear birefringence characteristics>
Equation (20) becomes the following equation.

<8-4. When birefringence phase difference δ is small and δ << 1 can be approximated>
When the birefringence phase difference δ of the measurement object 2 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), the equation (20) becomes the following equation.

The matrix elements m _11- m _{44 in the} equation (24-27) are 15-way or 13-way simultaneous equations each including five unknown parameters (δ, θ, q, r, β) of two measurement objects.

<9-1. When the measurement object 1 has linearity and the measurement object 2 has birefringence characteristics of circular dichroism>
Equation (20) becomes the following equation.

<9-2. When birefringence phase difference δ is small and δ << 1 can be approximated>
When the birefringence phase difference δ of the measurement object 1 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), the equation (20) becomes the following equation.

<9-3. When measurement object 1 has circular dichroism and measurement object 2 has linear birefringence characteristics>
Equation (20) becomes the following equation.

<9-4. When birefringence phase difference δ is small and δ << 1 can be approximated>
When the birefringence phase difference δ of the measurement object 2 is small and can be approximated as δ << 1 (sin δ = δ, cos δ = 1), the equation (20) becomes the following equation.

The matrix elements m _11- m _{44 in the} equation (28-31) are 14-element or 11-element simultaneous equations each including four unknown parameters (δ, θ, s, t) of two measurement objects.

  Hereinafter, Example 1 of the present invention will be described in detail.

  FIG. 3 shows an apparatus for measuring the optical characteristics of the measurement object placed in the measurement cell according to this embodiment. A portion 10 surrounded by a broken line in the figure is a measurement cell. The measurement cell 10 includes an entrance window 1 and an exit window 3 made of a transparent material. The true measurement object 2 is arranged in the measurement cell. Similarly to FIG. 1, a white light source 4 for emitting light, a polarization generating system 5 for controlling the polarization state of probe light received from the light source and incident on the object to be measured, and this polarization generation A polarization detection system 6 for detecting the polarization state of the outgoing light obtained by passing through the entrance window 1, the true measurement object 2 and the outgoing window 3 from the system 5, and a photodetector 7 for measuring the light intensity are provided. . An arithmetic unit 8 calculates a Mueller matrix from the polarization state of incident light and the polarization state of outgoing light. Here, the calculation unit also serves as a control unit for the white light source 4, the polarization generation system 5, the polarization detection system 6, and the photodetector 7. Reference numeral 9 denotes a probe light path. Here, since the optical characteristics of the entrance window 1 and the exit window 3 are also unknown, the entrance window 1, the true measurement object 2 and the exit window 3 are the above-described measurement objects 1 to 3.

  FIG. 4 is a diagram showing the flow of the optical characteristic measuring method of this embodiment. A method for measuring optical characteristics according to the present invention will be described below. First, as shown in FIG. 3, the true measurement object 2 is placed inside the measurement cell 10 in the probe light path 9 between the entrance window 1 and the exit window 3. Next, the Mueller matrix of the system of the measurement object including the entrance window 1 and the exit window 3 is measured by a known method.

  Next, the polarization characteristic model is selected, and the entrance window 1 and the exit window 3 are treated as those for which the polarization characteristic model is already known. In this embodiment, since a window material having linear birefringence characteristics is used, a linear birefringence characteristic model is used. Although the optical property of the true measurement object 2 is unknown, a polarization property model that is considered appropriate is selected assuming a polarization property that can be estimated from the material. Next, a simultaneous equation corresponding to the selected model is established from the Mueller matrix of the system of the obtained measurement object, and a solution is obtained. Desired optical characteristics are calculated from the parameters of the true measurement object obtained.

  FIG. 5 shows an example in which the stress applying device 11 and the temperature control device 12 are provided inside the measurement cell. The stress applying device 11 holds the measurement object 2 and also measures the tensile stress, the compressive stress, the torsion, the shear stress, and the like by a calculation unit 8 that also serves as a control unit and a drive system such as a step motor and an actuator. Can be added to 2. Further, the temperature control device 12 can control the temperature inside the measurement cell by a heating element such as a heater or a cooling element such as a Peltier element by the calculation unit 8 that also serves as a control unit.

  Thus, it is possible to measure the photoelastic effect, which is the stress dependence of the polarization characteristics, the temperature dependence of the polarization characteristics, the temperature dependence of the photoelastic effect itself, and the like.

  6 and 7 specifically show the inside of a measurement cell equipped with a heater. FIG. 6 shows an example of measuring the temperature dependence of the photoelastic constant of a test sample by applying a compressive stress. It shows an example of measuring polarization characteristics when tensile stress is applied to a film as a test sample.

  FIGS. 8A and 8B show an example in which a phase film is used for the entrance window 1 and the exit window 3, and the optical characteristics are measured with a half-wave plate as the measurement object 2. (A) and (b) show δ and θ obtained using the linear birefringence characteristic model with the wavelength of the probe light on the horizontal axis. The “no window” line is a measurement of only a half-wave plate without the entrance window 1 and the exit window 3, and the “before window correction” line is a measurement result of the system including the entrance window 1 and the exit window 3. The “after window correction” line is the optical characteristic of only the half-wave plate obtained by the optical characteristic measuring method according to the present invention. From the figure, the case of no window and the characteristic after window correction are in good agreement over all wavelength ranges, indicating that the measurement method according to the present invention is effective.

  The second embodiment of the present invention will be described below.

  FIG. 9 shows an example in which the measurement objects 1 and 3 are objective lenses and a film is disposed as the measurement object 2. In order to measure the optical characteristics of the microscopic region, the diameter of the probe light is reduced by an objective lens arranged on both sides of the film, and local measurement is performed. It is necessary to align the optical axes of the respective lenses so that the probe light passes through the entrance and exit objective lenses.

  According to the present embodiment, it is possible to continuously change the measurement position of the film by scanning the measurement optical system including the objective lens, and an optical property map in the film plane can be obtained. It can be used for measuring the optical characteristics of a transparent electrode on which a pattern is formed, and for evaluating the uniformity of a film.

  Example 3 of the present invention will be described below.

  FIG. 10 shows a laminated film as an object to be measured. The figure shows a three-layer laminated film. Each layer is measured as measurement objects 1 to 3. In the figure, an example of three layers is shown, but two layers may be used.

  Moreover, although the embodiment shows only a calculation example with up to three measurement objects, the same calculation is performed on four or more measurement objects depending on the type of polarization characteristic model assumed. In some cases, it can be applied to a film having four or more layers. In addition, even when the parameters of each layer are known by some measurement, it may be applicable to a film having four or more layers depending on the number of unknown parameters and the number of simultaneous equations.

  The fourth embodiment of the present invention will be described below.

  FIG. 11 shows an example of measuring the birefringence characteristics of the retina of the eyeball. The probe light is incident from the pupil, passes through the cornea, the crystalline lens, and the vitreous body, then is reflected by the retina, and is emitted again following the same path as the incident path. Here, the measurement objects 1 and 3 are corneas having birefringence characteristics, and the measurement object 2 is a retina. Since the probe light is reflected in the retina, the reflection type isotropic characteristic is selected as the polarization characteristic model of the retina. According to the present embodiment, birefringence derived from the cornea can be removed, the optical characteristics of the fundus retina can be measured with high accuracy, and early diagnosis of glaucoma with high accuracy becomes possible.

  The optical characteristic measuring method and the optical characteristic measuring apparatus according to the present invention can accurately measure the measurement object in a state where the measurement object is arranged in the measurement cell provided with the optical window, and the measurement object is stressed in the measurement cell. Can be applied and the temperature can be controlled, so that the temperature dependence of the photoelastic effect and optical characteristics of the measurement object and the temperature dependence of the photoelastic effect itself can be measured. Therefore, in-situ observation in the manufacturing process such as film formation and etching is possible, and it can be used for manufacturing management and real-time measurement data collection in the manufacturing process of electronic devices such as semiconductor elements and display devices, and optical devices.

  In addition, since it is possible to measure the optical characteristics in the microscopic region using the objective lens, it is possible to obtain an optical characteristic map in the film plane, to measure the optical characteristics of the transparent electrode on which the pattern is formed, It can be used for evaluation of uniformity. In addition, the optical characteristics of each layer of the laminated film can be measured.

  Furthermore, in the medical field, the amount of birefringence resulting from the fiber structure of the retina can be measured by removing the birefringence derived from the cornea, and can be used for early diagnosis of glaucoma.

1 to 3 Measurement object 4 Light source 5 Polarization generation system 6 Polarization detection system 7 Photodetector 8 Calculation unit 9 Probe light path 10 Measurement cell 11 Stress application device 12 Temperature control device

Claims (18)

A method of measuring optical characteristics using probe light,
Arranging a plurality of measurement objects having polarization characteristics in the probe light path;
Measuring the Mueller matrix of the plurality of measurement objects from the polarized incident light and the outgoing light obtained by passing the incident light through the plurality of measurement objects;
Selecting a polarization property model for each of the plurality of measurement objects;
Obtaining a polarization characteristic of each of the plurality of measurement objects by solving a simultaneous equation according to each selected polarization characteristic model; and
A method for measuring optical characteristics, comprising:   The polarization characteristic model is selected from a linear birefringence characteristic model, an optical rotatory birefringence characteristic model, a dichroic birefringence characteristic model, a circular dichroic birefringence characteristic model, and a reflective isotropic birefringence characteristic model. 2. The method for measuring optical characteristics according to claim 1, wherein the optical characteristics are measured.   3. The optical system according to claim 2, wherein the polarization characteristic model is a linear birefringence characteristic model, and is a model when a birefringence phase difference δ can be approximated to δ << 1 among model parameters. How to measure characteristics.   4. The measurement object according to claim 2, wherein there are three measurement objects, and the polarization characteristic model of the measurement object closest to the light source and the farthest side is a linear birefringence characteristic model. Measuring method of optical properties.   Among the measurement objects, the polarization characteristic model of the measurement object closest to the light source is a linear birefringence characteristic model, an optical rotation birefringence characteristic model, a dichroic birefringence characteristic model, a circular dichroic birefringence characteristic model, 5. The optical characteristic measuring method according to claim 4, wherein the optical characteristic measuring model is one of a reflection type isotropic birefringence characteristic model.   4. The method for measuring optical characteristics according to claim 2, wherein the number of the measurement objects is two, and the polarization characteristic model of at least one measurement object is a linear birefringence characteristic model.   Among the measurement objects, the polarization characteristic model of the other measurement object is a linear birefringence characteristic model, an optical rotation birefringence characteristic model, a dichroic birefringence characteristic model, a circular dichroic birefringence characteristic model, a reflection type, etc. 7. The method for measuring optical characteristics according to claim 6, wherein the optical characteristics measurement model is one of anisotropic birefringence characteristic models.   The number of the measurement objects is three, and each measurement object is an incident window provided in the measurement cell, a measurement object, and an emission window provided in the measurement cell in order from the side closer to the light source. The method for measuring optical characteristics according to claim 1.   There are three measurement objects, and each measurement object is an incident light lens, a measurement object, and an output light lens for condensing probe light in order from the side closer to the light source. The method for measuring optical characteristics according to claim 1.   6. The method for measuring optical characteristics according to claim 1, wherein the object to be measured is each layer of a film having a multilayer structure.   There are three measurement objects, and each measurement object is, in order from the side closer to the incident light source, the cornea when the incident light is transmitted, the retina, and the cornea when the emitted light is transmitted. The method for measuring optical characteristics according to claim 1. A probe light source;
A polarization generating system;
A polarization detection system;
A photodetector;
A device for measuring the optical properties of a plurality of measurement objects comprising:
From the incident light irradiated from the polarization generation system and the polarization characteristics of the outgoing light entering the polarization detection system, comprising a calculation unit for calculating a Mueller matrix,
The optical characteristic measurement apparatus, wherein the calculation unit further calculates a model parameter of a polarization characteristic model of the plurality of measurement objects from the Mueller matrix. A measuring cell having an entrance window and an exit window for containing the measurement object inside is further provided.
The optical characteristic measuring apparatus according to claim 12, wherein the plurality of measurement objects include the entrance window and the exit window.   The optical characteristic measuring device according to claim 13, further comprising a temperature control device for controlling a temperature of the measurement object.   The optical characteristic measuring device according to claim 13 or 14, further comprising a stress applying device for controlling stress applied to the measurement object.   13. The apparatus according to claim 12, further comprising an incident light lens for condensing the probe light and irradiating the measurement object, and an outgoing light lens for receiving the probe light from the measurement object. Optical characteristic measuring device.   13. The optical property measuring apparatus according to claim 12, wherein the optical property of each layer is measured from the probe light that is incident on a multilayer film and transmitted through the multilayer film.   13. The optical characteristics of the retina are measured from the probe light that is incident on the eyes of an animal including a human, is transmitted through the cornea, is reflected at the bottom of the retina, and is transmitted through the cornea. The optical characteristic measuring device described in 1.