JP7483423B2 - OPTICAL MEASUREMENT METHOD, OPTICAL MEASUREMENT DEVICE, AND OPTICAL MEASUREMENT PROGRAM - Google Patents

Description

The present invention relates to an optical measurement method, an optical measurement device, and an optical measurement program.

Conventionally, optical measurement devices are known that determine the optical order and retardation by performing measurements while rotating the positional relationship between the sample, polarizer, and analyzer in the plane direction of the sample (see Patent Documents 1 and 2 below). There is also a method for measuring retardation when either the birefringence of the sample or the thickness of the sample is known (see Patent Document 3 below).

Japanese Patent Application Laid-Open No. 11-211656 JP 2003-172691 A JP 2003-240678 A

When measuring by changing the angle between the sample and the polarizing optical system in multiple ways, as in Patent Documents 1 and 2, the measurement device needs a drive mechanism to tilt the sample or the polarizing optical system. In addition, when the retardation of the sample is particularly high, it is difficult to identify the order, and it is difficult to measure the retardation accurately. In the optical measurement method of Patent Document 3, the wavelength dispersion of retardation cannot be measured unless at least one of the birefringence of the sample or the thickness of the sample is known.

The present disclosure has been made in consideration of the above-mentioned circumstances, and its purpose is to measure a spectroscopic spectrum using a simple measurement mechanism, identify the order of a peak or valley contained in the spectroscopic spectrum, and measure accurate retardation.

In order to solve the above problem, the optical measurement method according to the present disclosure includes the steps of: measuring a spectrum including multiple peaks and valleys in a predetermined wavelength range for a sample; calculating the thickness of the sample for each wavelength represented by the peak or the valley using a first wavelength dispersion formula including coefficients set under multiple conditions, and provisionally determining the coefficients included in the first wavelength dispersion formula under the conditions in which the evaluation value based on the calculated thickness is the largest; setting the order of a specific peak included in the multiple peaks under multiple conditions, and calculating a second wavelength dispersion formula based on each order and wavelength of the multiple peaks under the multiple conditions set; identifying the order of the specific peak based on the first wavelength dispersion formula including the provisionally determined coefficients and the second wavelength dispersion formula, and finally determining the coefficient based on the identified order and the second wavelength dispersion formula; and calculating the retardation based on the second wavelength dispersion formula including the finally determined coefficients.

The optical measuring device according to the present disclosure also includes a measuring unit that measures a spectroscopic spectrum including multiple peaks and valleys in a predetermined wavelength range for a sample; a provisional determination unit that calculates the thickness of the sample for each wavelength represented by the peak or the valley using a first wavelength dispersion formula including coefficients set under multiple conditions, and provisionally determines the coefficients included in the first wavelength dispersion formula under the condition in which the evaluation value based on the calculated thickness is the largest; a second wavelength dispersion formula calculation unit that sets the order of a specific peak included in the multiple peaks under multiple conditions and calculates a second wavelength dispersion formula based on each order and wavelength of the multiple peaks under the multiple conditions that have been set; a final determination unit that identifies the order of the specific peak based on the first wavelength dispersion formula including the provisionally determined coefficients and the second wavelength dispersion formula, and finally determines the coefficient based on the identified order and the second wavelength dispersion formula; and a retardation calculation unit that calculates retardation based on the second wavelength dispersion formula including the finally determined coefficients.

The optical measurement program according to the present disclosure is an optical measurement program executed by a computer used in an optical measurement device, and is characterized in that the computer is caused to execute the following steps: measuring a spectrum including multiple peaks and valleys in a predetermined wavelength range for a sample; calculating the thickness of the sample for each wavelength represented by the peak or the valley using a first wavelength dispersion formula including coefficients set under multiple conditions, and provisionally determining the coefficients included in the first wavelength dispersion formula under the conditions in which the evaluation value based on the calculated thickness is the largest; setting the order of a specific peak included in the multiple peaks under multiple conditions, and calculating a second wavelength dispersion formula based on each order and wavelength of the multiple peaks under the multiple conditions that have been set; identifying the order of the specific peak based on the first wavelength dispersion formula including the provisionally determined coefficient and the second wavelength dispersion formula, and finally determining the coefficient based on the identified order and the second wavelength dispersion formula; and calculating the retardation based on the second wavelength dispersion formula including the finally determined coefficient.

FIG. 1 is a schematic diagram showing a schematic configuration of an optical measuring device according to this embodiment. FIG. 2 is a diagram showing an example of a schematic configuration of a measurement unit according to this embodiment. FIG. 3 is a diagram showing an example of a measured parallel Nicol spectrum. FIG. 4 is a flow chart showing a method for calculating retardation according to this embodiment. FIG. 5 is a diagram showing an example of the wavelength dependency of thickness. FIG. 6 is a graph showing the first wavelength dispersion equation and the second wavelength dispersion equation. FIG. 7 is a diagram showing an example of the results of an experiment for verifying the effect of the present invention. FIG. 8 is a diagram showing an example of the results of an experiment for verifying the effect of the present invention. FIG. 9 is a diagram showing an example of the results of an experiment for verifying the effect of the present invention. FIG. 10 is a diagram showing an example of the results of an experiment for verifying the effect of the present invention. FIG. 11 is a flow chart showing a method for calculating the thickness direction retardation or the three-dimensional birefringence. FIG. 12 is a diagram showing another example of the schematic configuration of the measurement unit according to the present embodiment.

Embodiments of this disclosure are described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the general configuration of an optical measuring device 100 of this embodiment. As shown in FIG. 1, the optical measuring device 100 of this embodiment includes an information processing unit 102 and a measurement unit 104. The information processing unit 102 includes a control unit 106, a storage unit 108, a display unit 110, and an input/output unit 112. The information processing unit 102 is, for example, a general computer. The control unit 106, the storage unit 108, the display unit 110, and the input/output unit 112 are connected to each other via a data bus 114 so that electrical signals can be exchanged between them.

The control unit 106 is a processor, a CPU (Central Processing Unit). Specifically, the control unit 106 functionally includes a wavelength calculation unit 116, a tentative determination unit 120, a normalization unit 122, a second wavelength dispersion equation calculation unit 124, a final determination unit 126, and a retardation calculation unit 128, and each unit performs calculations (described later) according to a program stored in the storage unit 108.

The storage unit 108 is a main storage device such as a RAM (Random Access Memory) and an auxiliary storage device that can statically record information, such as a HDD (Hard Disk Drive) or SSD (Solid State Drive). In addition to the optical measurement program, the storage unit 108 stores programs that control the operation of each part included in the information processing unit 102.

The display unit 110 is a CRT (Cathode Ray Tube) or a so-called flat panel display. The display unit 110 visually displays an image to the user.

The input/output unit 112 is one or more devices, such as a keyboard, mouse, or touch panel, through which the user inputs information. The input/output unit 112 is one or more interfaces through which the information processing unit 102 exchanges information with external devices such as the measurement unit 104. For example, the input/output unit 112 receives the results of measurements made by the measurement unit 104. The input/output unit 112 may include various ports for wired connections and a controller for wireless connections. Note that the configuration of the information processing unit 102 shown here is an example, and other configurations may also be used.

Figure 2 is a schematic diagram showing the general configuration of the measurement unit 104. As shown in Figure 2, the measurement unit 104 includes a light source 202, an optical fiber 204, a focusing lens 206, a polarizer 208, a rotating sample stage 210, an analyzer 214, and a multichannel spectrometer 216. Note that the measurement unit 104 shown in Figure 2 is an example showing the case where a parallel Nicol spectrum is measured.

The light source 202 is, for example, a halogen lamp that emits white light. The light source 202 may be of another type, so long as it emits light in the wavelength range that is the subject of measurement. The light emitted by the light source 202 passes through an optical fiber 204 and is converted into parallel light by a condenser lens 206.

The polarizer 208 is a linear polarizer. The polarizer 208 transmits only the component in the transmission axis direction of the parallel light converted by the focusing lens 206.

The rotating sample stage 210 has a sample 212 placed on it. When the light passing through the polarizer 208 travels in the Z-axis direction, the rotating sample stage 210 is configured to change the angle between the surface of the sample 212 placed on the rotating sample stage 210 and the Z-axis. In FIG. 2, when the surface of the sample 212 is the XY plane, the angle between the X-axis and the Z-axis and the angle between the Y-axis and the Z-axis are both 90 degrees. The rotating sample stage 210 is made of a material that transmits the components of the wavelength range to be measured out of the light that has passed through the polarizer 208. The measurement unit 104 may be configured without the rotating sample stage 210.

The analyzer 214 is a linear polarizer and is arranged so that its transmission axis is parallel to the polarizer 208. The light transmitted through the sample 212 has a phase difference between the X-axis component and the Y-axis component depending on the wavelength. The analyzer 214 transmits only the component of the light in the transmission axis direction that has the phase difference. The transmitted light is focused by the focusing lens 206 and input to the multichannel spectrometer 216 via the optical fiber 204.

The multichannel spectrometer 216 measures the intensity of the input light by distinguishing it according to wavelength. Specifically, for example, the multichannel analyzer measures a parallel Nicol spectrum as shown in FIG. 3. The vertical axis of FIG. 3 is the transmittance converted from the intensity measured by the multichannel analyzer, and the horizontal axis is the wavelength. After passing through the sample 212, the phase of the X-axis component and the Y-axis component differ depending on the wavelength, so the wavelength dependence of the transmittance is wavy, as shown in FIG. 3.

Next, the retardation measurement method according to this embodiment and the functions of each unit included in the control unit 106 will be described using the flow shown in FIG. 4. First, the measurement unit 104 measures an optical spectrum including multiple peaks and valleys in a predetermined wavelength range for the sample 212 (S402). Specifically, for example, the measurement unit 104 measures a parallel Nicol spectrum including multiple peaks and valleys in a wavelength range of 400 nm to 800 nm as shown in FIG. 3.

Next, the wavelength calculation unit 116 calculates the wavelengths represented by each peak and valley included in the calculation wavelength range (S404). Specifically, for example, the wavelength calculation unit 116 sets the range from 500 nm to 750 nm as the calculation wavelength range. In the example of FIG. 3, the wavelength calculation unit 116 calculates the wavelengths represented by each of the seven peaks and seven valleys included in the calculation wavelength range. The calculation wavelength range may be set by a user inputting it into the input/output unit 112.

Next, the tentative determination unit 120 calculates the thickness of the sample for each wavelength represented by the peak or valley using a first wavelength dispersion equation including coefficients set under multiple conditions, and tentatively determines the coefficients included in the first wavelength dispersion equation under the condition that maximizes the evaluation value based on the calculated thickness (S406). Specifically, for example, the tentative determination unit 120 tentatively determines the wavelength dispersion coefficients A, B, and C using Equations 1 to 4. Equation 1 is an equation for calculating the thickness, which is a function of _λC .

In the formula 1, i is the index of the peak and the valley. For example, among the wavelengths represented by the 14 peaks and the wavelengths represented by the valleys calculated in S404, the index of the peak with the longest wavelength of 740 nm is 0, and the index of the valley with the shortest wavelength of 500 nm is 13. λ is the wavelength. _{λ C} is the mid-wavelength of the adjacent peaks or the mid-wavelength of the adjacent valleys, and is expressed by the formula 2.

Δn(λ) is the birefringence at wavelength λ, and is calculated using Cauchy's wavelength dispersion formula and unknown wavelength dispersion coefficients A, B, and C, for example, as shown in Equation 3.

The tentative determination unit 120 tentatively determines the wavelength dispersion coefficients A, B, and C included in the first wavelength dispersion formula so as to maximize the evaluation value based on the thickness calculated by Equation 1. For example, the tentative determination unit 120 calculates the standard deviation σ using the thickness calculated at each peak or valley wavelength using Equation 1 and Equation 4, and sets the reciprocal of the standard deviation σ as the evaluation value.

In Equation 4, d _λC,i is the thickness of the sample 212 calculated for each index i at the mid-wavelength of the adjacent peak or the mid-wavelength of the adjacent valley. max is the maximum value of the index in the calculation wavelength range. In the above example, the calculation wavelength range includes a total of 14 peaks and valleys, so the value of max is 13.

Specifically, the tentative determination unit 120 uses the reciprocal of the standard deviation σ as the evaluation value and calculates the chromatic dispersion coefficients A, B, and C using the nonlinear least squares method. Note that this algorithm is only an example, and the chromatic dispersion coefficients A, B, and C may be tentatively determined using other algorithms as long as the chromatic dispersion coefficients A, B, and C under the conditions where the evaluation value, which is the reciprocal of the standard deviation σ, is maximized, can be identified.

Figure 5 shows the relationship between thickness d and wavelength calculated under three conditions for the wavelength dispersion coefficients A, B, and C that are repeatedly changed before the tentative determination unit 120 tentatively determines the wavelength dispersion coefficients A, B, and C. In the example shown in Figure 5, the condition where the wavelength dispersion coefficient B is 13723 has the smallest standard deviation of thickness d. Therefore, the tentative determination unit 120 tentatively determines A, B, and C calculated under this condition as the wavelength dispersion coefficients.

The evaluation value may be calculated by other methods. Specifically, the evaluation value may be set to a larger value as the calculated wavelength dependency of the thickness is smaller. For example, the tentative determination unit 120 may calculate an approximation line of a linear expression for the wavelength dependency of the thickness calculated under each condition in S406. Then, the tentative determination unit 120 may tentatively determine A, B, and C under the condition in which the slope included in the approximation formula is smallest as the wavelength dispersion coefficients. In other words, the tentative determination unit 120 may tentatively determine A, B, and C under the condition in which the wavelength dependency of the thickness is flattest as the wavelength dispersion coefficients.

Next, the normalization unit 122 normalizes the first wavelength dispersion formula including the provisionally determined wavelength dispersion coefficients A, B, and C (S410). Specifically, the normalization unit 122 normalizes the first wavelength dispersion coefficient using Equation 5 with the retardation at a predetermined wavelength λn as a reference. The predetermined wavelength λn may be set appropriately, but is assumed to be 600 nm here. Note that A', B', and C' included in Equation 5 are the wavelength dispersion coefficients after normalization.

Next, the second wavelength dispersion formula calculation unit 124 calculates the second wavelength dispersion formula based on the order of each peak or valley and the first wavelength dispersion formula under the condition where the order is set in a plurality of ways (S412). Specifically, the second wavelength dispersion formula calculation unit 124 sets the order of a specific peak included in the plurality of peaks under a plurality of conditions, and calculates the second wavelength dispersion formula based on each order and wavelength of the plurality of peaks under the plurality of conditions. For example, the wavelength represented by the peak or valley with the longest wavelength among the peaks or valleys included in the calculation wavelength range is set as λ ₀ , and the order of the peak is set as m _0. The second wavelength dispersion formula calculation unit 124 sets the condition that the order m ₀ of the peak at the wavelength of 740 nm included in the measurement result shown in FIG. 3 is 10, the condition that the order m ₀ is 11, and the condition that the order m ₀ is 12. The retardation Re.(λ _i ) at the wavelength represented by each peak and each valley is expressed by Equation 6 and Equation 7.

For example, under the condition that the order of the peak at a wavelength of 740 nm is 10, the retardations λ ₀ , λ ₁ and λ ₂ are expressed by the following equations (8) to (10).

Similarly, the retardation of the wavelengths represented by all peaks and valleys included in the calculation wavelength range is calculated using the above formula 6 or formula 7. In addition, the second wavelength dispersion equation calculation unit 124 performs a similar calculation under the condition that the order of the peak at a wavelength of 740 nm is 11 and the condition that it is 12.

Next, the second wavelength dispersion equation calculation unit 124 calculates a second wavelength dispersion equation including the wavelength dispersion coefficients α _m0 , β _m0 , and γ _m0 and expressed by Equation 11. As expressed by Equation 11, the second wavelength dispersion equation is the Cauchy wavelength dispersion equation, similar to the first wavelength dispersion equation.

The second wavelength dispersion equation calculation unit 124 calculates the wavelength dispersion coefficients α m0, β _m0 , and γ _m0 so that the residual between each retardation value calculated using equations 6 and 7 and each retardation value calculated using equation ₁₁ under each condition is minimized.

Furthermore, the normalization unit 122 normalizes the second wavelength dispersion equation including the wavelength dispersion coefficients α _m0 , β _m0 , and γ _m0 calculated under each condition, based on the retardation of a predetermined wavelength λn. The predetermined wavelength λn is 600 nm, which is used in S410. The normalized second wavelength dispersion equation is expressed by Equation 12.

Here, _αm0 ', _βm0 ', and _γm0 ' are chromatic dispersion coefficients included in the second chromatic dispersion formula after normalization. Fig. 6 is a diagram showing the second chromatic dispersion formula after normalization calculated under the condition that the order _m0 of the peak at the wavelength of 740 nm is 10, 11, and 12.

Next, the main determination unit 126 identifies the order of a specific peak based on the first wavelength dispersion equation including the provisionally determined coefficient and the second wavelength dispersion equation, and finally determines the coefficient based on the identified order and the second wavelength dispersion equation (S414). Specifically, the main determination unit 126 compares each of the second wavelength dispersion equations calculated and normalized in S412 with the first wavelength dispersion equation calculated in S410. The main determination unit 126 then identifies the order based on the conditions under which the second wavelength dispersion equation that most closely matches the first wavelength dispersion equation was calculated.

6 shows the first wavelength dispersion equation after normalization calculated in S410 together with the second wavelength dispersion equation after normalization calculated under each condition. As shown in FIG. 6, the first wavelength dispersion equation calculated in S410 has the highest degree of agreement with the second wavelength dispersion equation calculated under the condition that the order _m0 of the peak at a wavelength of 740 nm is 11. Therefore, the main determination unit 126 specifies that the order _m0 of the peak at a wavelength of 740 nm is 11. Furthermore, the main determination unit 126 finally determines α _m0 , β _m0 , and γ _m0 included in the second wavelength dispersion equation before normalization calculated under the condition that the order _m0 is 11 as the wavelength dispersion coefficient.

Next, the retardation calculation unit 128 calculates the retardation based on the second wavelength dispersion equation including the determined coefficients (S416). Specifically, the retardation calculation unit 128 calculates the retardation at the wavelength desired by the user based on Equation 11 including α _m0 , β _m0 , and γ _m0 determined in S414 and the wavelength input to the input unit by the user.

As described above, according to the present invention, it is possible to measure a spectrum using a simple measurement mechanism, identify the order of the peak or valley contained in the spectrum, and measure accurate retardation. The effects of the present invention will be explained using actual measurement data.

Figure 7 shows the optical spectra (parallel Nicol spectra in this example) measured in step S402 for sample 212 (single-layer sample 1 and single-layer sample 2), which are two single-layer quartz plates with different retardations.

Figure 8 shows the optical spectrum (parallel Nicol spectrum in this example) measured in step S402 for sample 212 (superimposed sample) created by superimposing two single-layer quartz plates shown in Figure 7.

Figure 9 shows the wavelength dependence of retardation calculated using the measurement results of Figure 7 and the second wavelength dispersion formula calculated in steps S404 to S416. Figure 10 shows the wavelength dependence of retardation calculated using the measurement results of Figure 8 and the second wavelength dispersion formula calculated in steps S404 to S416. Figure 10 also shows the calculated value obtained by adding up the wavelength dependence of retardation for the two single-layer quartz plates shown in Figure 9.

Theoretically, the sum of the retardation of the two single-layer quartz plates and the retardation of the stacked sample should match. However, if the wavelength dispersion coefficient included in the second wavelength dispersion formula is not calculated accurately in steps S404 to S416, the sum of the retardation of the two single-layer quartz plates and the retardation of the stacked sample may differ. According to the present invention, as shown in FIG. 10, there is a high degree of agreement between the calculated value and the measured value. Therefore, it has been confirmed that the present invention can measure accurate retardation.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, the present invention may calculate the thickness direction phase difference or the three-dimensional refractive index of a sample using the retardation calculated by the flow shown in FIG. 4. FIG. 11 is a flow diagram showing a method for calculating the thickness direction phase difference or the three-dimensional refractive index of a sample.

First, a variable i is set to 0 (S1102). Next, the tilt angle of the rotating sample stage 210 is set to θ _i degrees, which is set in advance in correspondence with each value of the variable i (S1104). When the value of the variable i is 0, the tilt angle of the rotating sample stage 210 is set to θ ₀ degrees.

Then, while the tilt angle of the rotating sample stage 210 is maintained, the retardation is measured (S1106). Specifically, similar to step S402, the measurement unit 104 measures the parallel Nicol spectrum when the angle between the light traveling direction and the surface of the sample 212 is θ ₀ degrees. Then, the retardation is calculated based on the main coefficient calculated in steps S404 to S416.

Next, it is determined whether the variable i matches a predetermined constant n (S1108). If the variable i matches the predetermined constant n, proceed to S1112, and if not, proceed to S1110. Note that the predetermined constant n is appropriately set so that step S1106 is executed a sufficient number of times to calculate the thickness direction retardation or the three-dimensional refractive index.

If the variable i does not match the predetermined constant n, the variable i is incremented (S1110). Then, the tilt angle of the rotating sample stage 210 is changed to θ _i degrees that is set in advance corresponding to each value of the variable i (S1104). Then, similar to step S402, the measurement unit 104 measures the parallel Nicol spectrum when the angle between the light traveling direction and the surface of the sample 212 is θ _i degrees. Furthermore, the retardation is calculated based on the main coefficient calculated in steps S404 to S416.

As described above, the step of changing the angle and the step of measuring the retardation are repeated a predetermined number of times to calculate multiple retardations. Then, based on the multiple calculated retardations, the thickness direction phase difference or the three-dimensional refractive index of the sample is calculated (S1112). Note that since the tilt angle of the rotating sample stage 210 is the angle between the traveling direction of the light transmitted through the polarizer 208 and the sample surface, the thickness direction phase difference or the three-dimensional refractive index of the sample can be calculated from the retardation measured while changing this angle. This calculation method is known, so a detailed description will be omitted.

The measurement unit 104 according to the present invention may also include a microscopic optical system. Specifically, for example, the measurement unit 104 may have the configuration shown in FIG. 12. The same configuration as that in FIG. 2 will not be described. Specifically, the measurement unit 104 includes an objective lens 1202, a half mirror 1204, and an observation camera 1206 in addition to the configuration in FIG. 2. The objective lens 1202 guides light that has passed through a minute region of the sample 212 to be measured to the analyzer 214. The half mirror 1204 separates the light that has passed through the condenser lens 206. A part of the separated light is input to the multichannel spectrometer 216, and the other part is input to the observation camera 1206. This makes it possible to measure the retardation of the minute region of the sample 212 to be measured, and to observe the minute region with the observation camera 1206.

In addition, in the above, an example of the experimental results was described in which the sample 212 was a quartz plate, but the sample 212 may also be a liquid crystal panel. According to the present invention, the thickness of the sample 212 can be calculated in step S406, and therefore the cell gap of the liquid crystal panel can be measured.

In the above description, the optical spectrum measured by the measuring unit 104 is a parallel Nicol spectrum, but the optical spectrum is not limited to a parallel Nicol spectrum. The optical spectrum may be any spectrum including spectral information obtained by a polarization optical system, and may be, for example, a crossed Nicol spectrum.

In the above description, the first and second wavelength dispersion formulas are Cauchy's wavelength dispersion formulas, but the first and second wavelength dispersion formulas are not limited to the Cauchy's wavelength dispersion formula. The first and second wavelength dispersion formulas may be polynomials expressing the relationship between birefringence and wavelength, and may be, for example, the Sellmeyer's wavelength dispersion formula expressed by Equation 13.

In addition, the method of calculating the retardation is not limited to the method shown in the flow shown in FIG. 4. Specifically, first, the order of the peak with the longest wavelength included in the calculation wavelength range is set to m ₀ (a predetermined integer). Next, under the condition that the order of the peak is m ₀ , the retardation is calculated for the wavelength represented by each peak and each valley included in the calculation wavelength range. Then, fitting is performed on the Cauchy wavelength dispersion formula represented by Equation 3 using the retardation at the wavelength represented by each peak and each valley calculated. The residual δm ₀ between the order calculated by fitting and the set order m ₀ is calculated. Next, the order of the peak with the longest wavelength included in the calculation wavelength range is set to m ₀ +1, and the residual δm ₀ of the order m ₀ +1 is similarly calculated. The residual of the order is calculated for each order while changing the order of the peak with the longest wavelength included in the calculation wavelength range from m ₀ to a predetermined value. The order under the condition where the residual calculated in the above steps is the smallest is identified as the order of the peak with the longest wavelength included in the calculation wavelength range. Furthermore, based on the identified order, the retardation is calculated for the wavelengths represented by each peak and each valley included in the calculation wavelength range. Each coefficient included in the wavelength dispersion formula is determined by fitting the calculated retardation to the Cauchy wavelength dispersion formula represented by Equation 3. Then, the retardation at any wavelength may be calculated using the wavelength dispersion formula with the determined coefficient.

100 Optical measuring device, 102 Information processing unit, 104 Measurement unit, 106 Control unit, 108 Memory unit, 110 Display unit, 112 Input/output unit, 114 Data bus, 116 Wavelength calculation unit, 120 Provisional determination unit, 122 Standardization unit, 124 Second wavelength dispersion formula calculation unit, 126 Final determination unit, 128 Retardation calculation unit, 202 Light source, 204 Optical fiber, 206 Condenser lens, 208 Polarizer, 210 Rotating sample stage, 212 Sample, 214 Analyzer, 216 Multichannel spectrometer, 1202 Objective lens, 1204 Half mirror, 1206 Observation camera.

Claims (6)

measuring a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength range for a sample;
A step of calculating the thickness of the sample for each wavelength represented by the peak or the valley using a first wavelength dispersion formula including a plurality of wavelength dispersion coefficients, and provisionally determining the wavelength dispersion coefficient calculated so that the evaluation value based on the calculated thickness is the largest as the wavelength dispersion coefficient used to identify each optical order of the plurality of peaks ;
A step of assuming a plurality of values as the optical order of a specific peak included in the plurality of peaks, and calculating a second wavelength dispersion formula based on each optical order and wavelength of the plurality of peaks under a condition that the optical order of the specific peak is each of the assumed values ;
specifying an optical order of the specific peak based on a first wavelength dispersion equation including the provisionally determined wavelength dispersion coefficient and the second wavelength dispersion equation, and finally determining the wavelength dispersion coefficient based on the specified optical order and the second wavelength dispersion equation;
Calculating the retardation based on the second wavelength dispersion equation including the determined wavelength dispersion coefficient;
Including,
An optical measurement method , characterized in that the evaluation value is larger as the wavelength dependency or standard deviation of the calculated thickness is smaller . The optical measurement method according to claim 1, characterized in that the first wavelength dispersion formula and the second wavelength dispersion formula are Cauchy's wavelength dispersion formula. The optical measurement method according to claim 1 or 2, characterized in that the optical spectrum is a parallel Nicol spectrum. changing an angle between a direction of light travel and a surface of the sample;
measuring the spectrum while the angle is maintained, and measuring retardation based on the second wavelength dispersion equation including the determined wavelength dispersion coefficient;
A step of calculating a phase difference in a thickness direction or a three-dimensional refractive index of the sample based on a plurality of retardations calculated by repeatedly executing the step of changing the angle and the step of measuring the retardation a predetermined number of times;
The optical measurement method according to any one of claims 1 to 3 , further comprising: A measurement unit that measures a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength range for a sample;
A provisional determination unit that calculates the thickness of the sample for each wavelength represented by the peak or the valley using a first wavelength dispersion formula including a plurality of wavelength dispersion coefficients, and provisionally determines the wavelength dispersion coefficient calculated so that the evaluation value based on the calculated thickness is the largest as the wavelength dispersion coefficient used to identify each optical order of the plurality of peaks ;
a second wavelength dispersion formula calculation unit that assumes a plurality of values as the optical order of a specific peak included in the plurality of peaks, and calculates a second wavelength dispersion formula based on each optical order and wavelength of the plurality of peaks under a condition that the optical order of the specific peak is each of the assumed values ;
a final determination unit that specifies an optical order of the specific peak based on a first wavelength dispersion equation including the provisionally determined wavelength dispersion coefficient and the second wavelength dispersion equation, and that finally determines the wavelength dispersion coefficient based on the specified optical order and the second wavelength dispersion equation;
A retardation calculation unit that calculates a retardation based on the second wavelength dispersion equation including the determined wavelength dispersion coefficient;
Including,
An optical measuring device according to claim 1, wherein the evaluation value is larger as the wavelength dependency or standard deviation of the calculated thickness is smaller. An optical measurement program executed by a computer used in an optical measurement device,
measuring a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength range for a sample;
A step of calculating the thickness of the sample for each wavelength represented by the peak or the valley using a first wavelength dispersion formula including a plurality of wavelength dispersion coefficients, and provisionally determining the wavelength dispersion coefficient calculated so that the evaluation value based on the calculated thickness is the largest as the wavelength dispersion coefficient used to identify each optical order of the plurality of peaks ;
A step of assuming a plurality of values as the optical order of a specific peak included in the plurality of peaks, and calculating a second wavelength dispersion formula based on each optical order and wavelength of the plurality of peaks under a condition that the optical order of the specific peak is each of the assumed values ;
specifying an optical order of the specific peak based on a first wavelength dispersion equation including the provisionally determined wavelength dispersion coefficient and the second wavelength dispersion equation, and finally determining the wavelength dispersion coefficient based on the specified optical order and the second wavelength dispersion equation;
Calculating the retardation based on the second wavelength dispersion equation including the determined wavelength dispersion coefficient;
causing the computer to execute
The optical measurement program according to claim 1, wherein the evaluation value is larger as the wavelength dependency or standard deviation of the calculated thickness is smaller.

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