Optical measurement method, optical measurement device, and storage medium storing program

Abstract

The present invention relates to an optical measurement method, an optical measurement device and an optical measurement program. The technical problem is to use a simple measurement mechanism to measure a spectral spectrum, determine the number of peaks or valleys included in the spectral spectrum and measure the accurate delay. The optical measurement method of the present invention includes: a step of measuring the spectral spectrum of a sample; a step of calculating the thickness of the sample at each wavelength represented by the peak or valley using a first wavelength dispersion formula, and a step of temporarily determining the coefficients included in the first wavelength dispersion formula under the condition that the evaluation value based on the calculated thickness is the largest; a step of setting the number of specific peaks under multiple conditions and calculating the second wavelength dispersion formula according to the set multiple conditions; a step of determining the number of specific peaks based on the first wavelength dispersion formula and the second wavelength dispersion formula including the temporarily determined coefficients, and a step of formally determining the coefficients based on the determined number and the second wavelength dispersion formula; a step of calculating the delay.

Description

Technical Field

[0001] The present invention relates to an optical measurement method, an optical measurement device and an optical measurement program. Background Art

[0002] Conventionally, an optical measuring device is known that measures the positional relationship between a sample, a polarizer, and an analyzer while rotating the sample in a plane direction to obtain the optical order and retardation (see Patent Documents 1 and 2 below). In addition, there is also a method for measuring retardation when either the birefringence index of a sample or the thickness of the sample is known (see Patent Document 3 below).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 11-211656

[0006] Patent Document 2: Japanese Patent Application Publication No. 2003-172691

[0007] Patent Document 3: Japanese Patent Application Publication No. 2003-240678

[0008] As described in Patent Documents 1 and 2, when the angle between the sample and the polarization optical system is changed to a variety of angles and measured, a driving mechanism that tilts the sample or the polarization optical system is required in the measuring device. In addition, particularly when the delay of the sample is high, it is difficult to determine the number of times and to measure the delay accurately. In the optical measurement method of Patent Document 3, if at least one of the birefringence of the sample or the thickness of the sample is not known, the wavelength dispersion of the delay cannot be measured. Summary of the invention

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to measure a spectral spectrum using a simple measuring mechanism, determine the number of peaks or valleys included in the spectral spectrum, and measure accurate delay.

[0010] Solutions for solving problems

[0011] In order to solve the above-mentioned technical problems, the optical measurement method of the present invention is characterized in that it includes: a step of measuring a spectral spectrum including multiple peaks and valleys of a sample within a specified wavelength region; a step of calculating the thickness of the sample at each wavelength represented by the peak or the valley using a first wavelength dispersion formula including coefficients set under multiple conditions, and temporarily determining the coefficients included in the first wavelength dispersion formula under the condition where the evaluation value of the calculated thickness is the largest; a step of setting the number of specific peaks included in the multiple peaks under multiple conditions, and calculating a second wavelength dispersion formula based on the numbers and wavelengths of the multiple peaks according to the set multiple conditions; a step of determining the number of the specific peak based on the first wavelength dispersion formula including the temporarily determined coefficients and the second wavelength dispersion formula, and formally determining the coefficients based on the determined number and the second wavelength dispersion formula; and a step of calculating the delay based on the second wavelength dispersion formula including the formally determined coefficients.

[0012] In addition, the optical measurement device of the present invention is characterized in that it includes: a measurement unit that measures a spectroscopic spectrum including a plurality of peaks and valleys in a specified wavelength region for a sample; a temporary determination unit that calculates the thickness of the sample at each wavelength represented by the peak or the valley using a first wavelength dispersion formula including coefficients set under a plurality of conditions, and temporarily determines the coefficients included in the first wavelength dispersion formula under the condition that an evaluation value based on the calculated thickness is the largest; a second wavelength dispersion formula calculation unit that sets the number of specific peaks included in the plurality of peaks under a plurality of conditions, and calculates a second wavelength dispersion formula based on the numbers and wavelengths of the plurality of peaks according to the set plurality of conditions; a formal determination unit that determines the number of the specific peak based on the first wavelength dispersion formula including the provisionally determined coefficients and the second wavelength dispersion formula, and formally determines the coefficients based on the determined number and the second wavelength dispersion formula; and a delay calculation unit that calculates a delay based on the second wavelength dispersion formula including the formally determined coefficients.

[0013] In addition, the optical measurement program of the present invention is executed by a computer used in an optical measurement device, and the optical measurement program is characterized in that the computer is caused to execute: a step of measuring a spectroscopic spectrum including a plurality of peaks and valleys within a specified wavelength region for a sample; a step of calculating the thickness of the sample at each wavelength represented by the peak or the valley using a first wavelength dispersion formula including coefficients set under a plurality of conditions, and provisionally determining the coefficients included in the first wavelength dispersion formula under the condition where an evaluation value based on the calculated thickness is maximum; a step of setting the number of specific peaks included in the plurality of peaks under a plurality of conditions, and calculating a second wavelength dispersion formula based on the numbers and wavelengths of the plurality of peaks according to the set plurality of conditions; a step of determining the number of the specific peak based on the first wavelength dispersion formula including the provisionally determined coefficients and the second wavelength dispersion formula, and formally determining the coefficients based on the determined number and the second wavelength dispersion formula; and a step of calculating a delay based on the second wavelength dispersion formula including the formally determined coefficients. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram showing a schematic configuration of an optical measurement device according to this embodiment.

[0015] Figure 2 This is a diagram showing an example of a schematic configuration of a measuring unit according to this embodiment.

[0016] Figure 3 This is a diagram showing an example of measured parallel Nicol spectra.

[0017] Figure 4 : is a flowchart showing the method of calculating delay according to the present embodiment.

[0018] Figure 5 This is a diagram showing an example of the wavelength dependency of thickness.

[0019] Figure 6 This is a diagram showing the first wavelength dispersion formula and the second wavelength dispersion formula in a graph.

[0020] Figure 7 This is a diagram showing an example of experimental results for verifying the effects of the present invention.

[0021] Figure 8 This is a diagram showing an example of experimental results for verifying the effects of the present invention.

[0022] Fig. 9 This is a diagram showing an example of experimental results for verifying the effects of the present invention.

[0023] Fig.10This is a diagram showing an example of experimental results for verifying the effects of the present invention.

[0024] Fig.11 Detailed description of the invention is a flowchart showing a method for calculating a thickness direction phase difference or a three-dimensional birefringence.

[0025] Fig.12 This is a diagram showing another example of the schematic configuration of the measuring unit according to the present embodiment.

[0026] Description of reference numerals:

[0027] 100 optical measurement device, 102 information processing unit, 104 measurement unit, 106 control unit, 108 storage unit, 110 display unit, 112 input / output unit, 114 data bus, 116 wavelength calculation unit, 120 temporary determination unit, 122 standardization unit, 124 second wavelength dispersion formula calculation unit, 126 formal determination unit, 128 delay calculation unit, 202 light source, 204 optical fiber, 206 condenser lens, 208 polarizer, 210 rotating sample stage, 212 sample, 214 analyzer, 216 multi-channel spectrometer, 1202 objective lens, 1204 semi-transparent and semi-reflective mirror, 1206 observation camera. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described using the drawings.

[0029] Figure 1 Schematic diagram showing the schematic structure of the optical measurement device 100 according to this embodiment. Figure 1 As shown, the optical measurement 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 in a manner that electrical signals can be exchanged with each other through a data bus 114.

[0030] The control unit 106 is a CPU (Central Processing Unit) serving as a processor. Specifically, the control unit 106 functionally includes a wavelength calculation unit 116, a temporary determination unit 120, a normalization unit 122, a second wavelength dispersion formula calculation unit 124, a formal determination unit 126, and a delay calculation unit 128, and each unit performs the calculations described below according to the program stored in the storage unit 108.

[0031] The storage unit 108 is a main storage device such as a RAM (Random Access Memory) and an auxiliary storage device such as a HDD (Hard Disk Drive) or a SSD (Solid State Drive) that can statically record information. In addition to the optical measurement program, the storage unit 108 also stores a program for controlling the operation of each unit included in the information processing unit 102.

[0032] The display unit 110 is a CRT (Cathode Ray Tube), a so-called flat panel display, etc. The display unit 110 displays an image to the user visually.

[0033] The input / output unit 112 is one or more devices such as a keyboard, a mouse, and a touch screen for a user to input information. The input / output unit 112 is one or more interfaces for the information processing unit 102 to exchange information with external devices such as the measuring unit 104. For example, the input / output unit 112 receives the results measured by the measuring unit 104. The input / output unit 112 may include various ports for wired connection and a controller for wireless connection. It should be noted that the configuration of the information processing unit 102 shown here is an example, and other configurations may also be used.

[0034] Figure 2 Schematic diagram showing the schematic structure of the measuring unit 104. Figure 2 As shown, the measuring 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 multi-channel spectrometer 216. It should be noted that: Figure 2 The measurement unit 104 shown is an example showing a case where a parallel Nicol spectrum is measured.

[0035] The light source 202 is, for example, a halogen lamp that emits white light. The light source 202 may be any other type of light source 202 as long as it emits light in the wavelength region to be measured. The light emitted by the light source 202 passes through the optical fiber 204 and is converted into parallel light by the condenser lens 206 .

[0036] The polarizer 208 is a linear polarizer and transmits only the component in the transmission axis direction of the parallel light converted by the condenser lens 206 .

[0037] The rotating sample stage 210 is provided with a sample 212. When the traveling direction of light passing through the polarizer 208 is set to the Z axis, the rotating sample stage 210 is configured to be able to change the angle between the surface of the sample 212 arranged on the rotating sample stage 210 and the Z axis. Figure 2In the figure, when the surface of the sample 212 is set as 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. In addition, the rotating sample stage 210 is formed of a material that transmits the component of the wavelength region to be measured in the light transmitted through the polarizer 208. It should be noted that the measuring unit 104 may not have a rotating sample stage 210.

[0038] The analyzer 214 is a linear polarizer, and its transmission axis is arranged to be parallel to the transmission axis of the polarizer 208. The light that has passed through the sample 212 has a phase difference between the X-axis component and the Y-axis component according to the wavelength. The analyzer 214 transmits only the component in the transmission axis direction of the light that has produced the phase difference. The transmitted light is condensed by the condenser lens 206 and input to the multi-channel spectrometer 216 via the optical fiber 204.

[0039] The multi-channel spectrometer 216 distinguishes and measures the intensity of the input light according to the wavelength. Specifically, for example, a multi-channel analyzer measures Figure 3 Parallel Nicol spectra shown. Figure 3 The vertical axis is the transmittance calculated from the intensity measured by the multi-channel analyzer, and the horizontal axis is the wavelength. The phase of the X-axis component and the Y-axis component of the light after passing through the sample 212 is different according to the wavelength, so Figure 3 As shown, the wavelength dependence of transmittance is wave-shaped.

[0040] Next, use Figure 4 The delay measurement method of this embodiment and the functions of each unit included in the control unit 106 are described in the flowchart shown in FIG. 1 . First, the measurement unit 104 measures a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region for the sample 212 (S402). Specifically, for example, the measurement unit 104 measures the spectral spectrum including a plurality of peaks and valleys in the predetermined wavelength region. Figure 3 In the wavelength region shown in FIG. 400 to 800 nm, a parallel Nicol spectrum including a plurality of peaks and valleys was measured.

[0041] Next, the wavelength calculation unit 116 calculates the wavelengths represented by the peaks and valleys included in the calculation wavelength region (S404). Specifically, for example, the wavelength calculation unit 116 sets the range of 500 nm to 750 nm as the calculation wavelength region. Figure 3 In the example of , the wavelength calculation unit 116 calculates the wavelengths represented by the seven peaks and seven valleys included in the calculation wavelength region. It should be noted that the calculation wavelength region can be set by the user inputting to the input / output unit 112.

[0042] Next, the provisional determination unit 120 uses the first wavelength dispersion formula including coefficients set under a plurality of conditions to calculate the thickness of the sample at each wavelength represented by the peak value or the valley value, and provisionally determines the coefficients included in the first wavelength dispersion formula under the condition that the evaluation value based on the calculated thickness is the largest (S406). Specifically, for example, the provisional determination unit 120 uses Formulas 1 to 4 to provisionally determine the wavelength dispersion coefficients A, B, and C. Formula 1 is a formula for calculating the wavelength dispersion coefficients A, B, and C as λ. C The formula for the thickness as a function of .

[0043] [Formula 1]

[0044]

[0045] In Formula 1, i is the index of the peak and valley. For example, among the wavelengths represented by the fourteen peaks and valleys calculated in S404, the index of the peak of the longest wavelength 740 nm is 0, and the index of the valley of the shortest wavelength 500 nm is 13. λ is the wavelength. C It is the middle wavelength of adjacent peaks or the middle wavelength of adjacent valleys, and is expressed by Formula 2.

[0046] [Formula 2]

[0047]

[0048] Δn(λ) is the birefringence at wavelength λ, and is calculated using the Cauchy wavelength dispersion formula shown in Formula 3 and the unknown wavelength dispersion coefficients A, B, and C, for example.

[0049] [Formula 3]

[0050]

[0051] The provisional determination unit 120 provisionally determines the wavelength dispersion coefficients A, B, and C included in the first wavelength dispersion formula in such a manner that the evaluation value based on the thickness calculated by Formula 1 is maximized. For example, the provisional determination unit 120 calculates the standard deviation σ using the thickness calculated from each peak or valley value using Formula 1 and Formula 4, and uses the reciprocal of the standard deviation σ as the evaluation value.

[0052] [Formula 4]

[0053]

[0054] In formula 4, d λC,iis the thickness of the sample 212 calculated according to the middle wavelength of the adjacent peak or the middle wavelength of the adjacent valley for each index i. max is the maximum value of the index in the operation wavelength region. In the above example, there are 14 peaks and valleys in the operation wavelength region, so the value of max is 13.

[0055] Specifically, the provisional determination unit 120 uses the reciprocal of the standard deviation σ as an evaluation value and uses the nonlinear least square method to calculate the chromatic dispersion coefficients A, B, and C. It should be noted that this algorithm is an example, and the chromatic dispersion coefficients A, B, and C may be provisionally determined using other algorithms as long as the chromatic dispersion coefficients A, B, and C under the condition where the evaluation value of the reciprocal of the standard deviation σ is the maximum can be determined.

[0056] Figure 5 : is a graph showing the relationship between the thickness d and the wavelength calculated under three conditions of the wavelength dispersion coefficients A, B and C that are repeatedly changed before the temporary determination unit 120 temporarily determines the wavelength dispersion coefficients A, B and C. Figure 5 In the example shown, the standard deviation of the thickness d is the smallest under the condition that the wavelength dispersion coefficient B is 13723. Therefore, the provisional determination unit 120 provisionally determines A, B, and C calculated under this condition as the wavelength dispersion coefficient.

[0057] It should be noted that the evaluation value can also be calculated by other methods. Specifically, the evaluation value can be set in such a way that the smaller the calculated wavelength correlation of the thickness is, the larger the value is. For example, the temporary decision unit 120 can calculate an approximate straight line of a first-order formula for the wavelength correlation of the thickness calculated under various conditions in S406. Then, the temporary decision unit 120 can temporarily determine A, B and C under the condition where the slope included in the approximate formula is the smallest as the wavelength dispersion coefficient. That is, the temporary decision unit 120 can temporarily determine A, B and C under the condition where the wavelength correlation of the thickness is the flattest as the wavelength dispersion coefficient.

[0058] Next, the normalizing unit 122 normalizes the first wavelength dispersion coefficient including the temporarily determined wavelength dispersion coefficients A, B, and C (S410). Specifically, the normalizing unit 122 uses Formula 5 to normalize the first wavelength dispersion coefficient using the delay at the specified wavelength λn as a reference. The specified wavelength λn can be set appropriately, but is set to 600nm here. It should be noted that A', B', and C' included in Formula 5 are the standardized wavelength dispersion coefficients.

[0059] [Formula 5]

[0060]

[0061] Next, the second wavelength dispersion formula calculation unit 124 calculates the second wavelength dispersion formula based on the number of peaks or valleys and the first wavelength dispersion formula according to the conditions that the number is set to multiple. Specifically, the second wavelength dispersion formula calculation unit 124 sets the number of specific peaks included in the multiple peaks under multiple conditions, and calculates the second wavelength dispersion formula based on the number of times and wavelengths of the multiple peaks according to the set multiple conditions. For example, the wavelength represented by the peak or valley with the longest wavelength among the peaks or valleys included in the operation wavelength region is set to λ0, and the number of the peak is set to m0. The second wavelength dispersion formula calculation unit 124 sets Figure 3 The measurement results shown include the conditions where the order m0 of the peak at a wavelength of 740 nm is 10, the condition where the order m0 is 11, and the condition where the order m0 is 12. The retardation Re.(λ i ) from equation 6 and equation 7.

[0062] [Formula 6]

[0063] Re.(λ i )=(m0+i)·λ i (λ i is the peak wavelength)

[0064] [Formula 7]

[0065] Re.(λ i )=(m0+i+1 / 2)·λ i (λ i is the valley wavelength)

[0066] For example, under the condition that the order of the peak at a wavelength of 740 nm is 10, the retardations of λ0, λ1, and λ2 are expressed by Formulas 8 to 10.

[0067] [Formula 8]

[0068] Re.(λ0)=(10+0)*740

[0069] [Formula 9]

[0070]

[0071] [Formula 10]

[0072] Re.(λ2)=(10+1)*690

[0073] Similarly, the delay of the wavelength represented by all the peaks and valleys included in the operation wavelength region is calculated using the above-mentioned formula 6 or formula 7. In addition, the second wavelength dispersion formula calculation unit 124 performs the same calculation under the condition that the order of the peak in the wavelength 740nm is 11 and under the condition that the order is 12.

[0074] Next, the second wavelength dispersion formula calculation unit 124 calculates the wavelength dispersion coefficient α m0 , β m0 and γ m0 And the second wavelength dispersion formula is represented by Formula 11. As shown in Formula 11, the second wavelength dispersion formula is the Cauchy wavelength dispersion formula like the first wavelength dispersion formula.

[0075] [Formula 11]

[0076]

[0077] The second wavelength dispersion formula calculation unit 124 calculates the wavelength dispersion coefficient α under each condition. m0 , β m0 and γ m0 , so that the residual between the value of each delay calculated using Formula 6 and Formula 7 and the value of each delay calculated using Formula 11 is minimized.

[0078] Then, the normalization unit 122 normalizes the wavelength dispersion coefficient α calculated under each condition based on the delay of the predetermined wavelength λn. m0 , β m0 and γ m0 The second wavelength dispersion formula after standardization is expressed by Formula 12. It should be noted that the specified wavelength λn is 600 nm used in S410.

[0079] [Formula 12]

[0080]

[0081] Here, α m0 ', β m0 ' and γ m0 ' is the wavelength dispersion coefficient included in the standardized second wavelength dispersion formula. Figure 6 1 is a diagram showing the normalized second chromatic dispersion formula calculated under the condition that the order m0 of the peak at a wavelength of 740 nm is 10, the condition that m0 is 11, and the condition that m0 is 12.

[0082] Next, the formal determination unit 126 determines the number of specific peaks based on the first wavelength dispersion formula including the temporarily determined coefficients and the second wavelength dispersion formula, and formally determines the coefficients based on the determined number and the second wavelength dispersion formula (S414). Specifically, the formal determination unit 126 compares each of the second wavelength dispersion formulas calculated and standardized in S412 with the first wavelength dispersion formula calculated in S410. Then, the formal determination unit 126 determines the number based on the condition of calculating the second wavelength dispersion formula that is most consistent with the first wavelength dispersion formula.

[0083] Figure 6 represents the standardized second wavelength dispersion formula calculated under each condition and the standardized first wavelength dispersion formula calculated in S410. Figure 6 As shown in FIG. 1 , the first wavelength dispersion formula calculated in S410 is most consistent with the second wavelength dispersion formula calculated under the condition that the number m0 of the peak at the wavelength 740 nm is 11. Therefore, the formal determination unit 126 determines that the number m0 of the peak at the wavelength 740 nm is 11. Furthermore, the formal determination unit 126 sets the α included in the second wavelength dispersion formula before normalization calculated under the condition that the number m0 is 11. m0 , β m0 and γ m0 Officially determined as the wavelength dispersion coefficient.

[0084] Next, the delay calculation unit 128 calculates the delay based on the second chromatic dispersion equation including the formally determined coefficients (S416). Specifically, the delay calculation unit 128 calculates the delay based on the second chromatic dispersion equation including the formally determined coefficients in S414. m0 , β m0 and γ m0 The delay at the wavelength desired by the user is calculated based on equation 11 and the wavelength input by the user into the input unit.

[0085] As described above, according to the present invention, a spectral spectrum can be measured using a simple measuring mechanism, the number of peaks or valleys included in the spectral spectrum can be determined, and accurate delay can be measured. The effects of the present invention will be described using actual measured data.

[0086] Figure 7 This is a diagram showing the spectral spectra (parallel Nicol spectra in this example) measured in step S402 for samples 212 (single-layer sample 1 and single-layer sample 2) which are two single-layer crystal plates having different retardation.

[0087] Figure 8 It means that Figure 7The sample 212 (overlapping sample) shown is made by overlapping two single-layer crystal plates, and is a graph of the spectral spectrum (parallel Nicol spectrum in this example) measured in step S402.

[0088] Fig. 9 It means use Figure 7 A graph showing the measurement results and the wavelength dependency of the delay calculated using the second wavelength dispersion formula calculated in steps S404 to S416. Fig.10 It means use Figure 8 The measurement results and the wavelength dependence of the delay calculated by the second wavelength dispersion formula calculated by steps S404 to S416 are shown. Fig.10 Will Fig. 9 The calculated value of adding the wavelength dependence of the retardation in the two single-layer crystal plates shown is also shown.

[0089] The total delay of the two single crystal plates should be consistent with the delay of the overlapped sample in theory. However, in steps S404 to S416, if the wavelength dispersion coefficient included in the second wavelength dispersion formula is not accurately calculated, the total delay of the two single crystal plates may be different from the delay of the overlapped sample. Fig.10 As shown in FIG. 1 , the calculated value and the measured value have a high degree of agreement. Therefore, it was confirmed that the present invention can measure accurate delay.

[0090] It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. Figure 4 The retardation calculated by the process shown is used to calculate the thickness direction phase difference or three-dimensional refractive index of the sample. Fig.11 This is a flow showing a method for calculating the thickness direction phase difference or three-dimensional refractive index of a sample.

[0091] First, the variable i is set to 0 (S1102). Next, the tilt angle of the rotating sample stage 210 is set to θ which is set in advance corresponding to each value of the variable i. i When the value of the variable i is 0, the tilt angle of the rotating sample stage 210 is set to θ0 degrees.

[0092] Then, the retardation is measured while maintaining the tilt angle of the rotating sample stage 210 (S1106). Specifically, as in step S402, the measuring unit 104 measures the parallel Nicol spectrum when the angle between the propagation direction of the light and the surface of the sample 212 is θ0 degrees. Then, the retardation is calculated based on the formal coefficients calculated in steps S404 to S416.

[0093] Next, it is determined whether the variable i is consistent with the prescribed constant n (S1108). If the variable i is consistent with the prescribed constant n, the process proceeds to S1112, and if not, the process proceeds to S1110. It should be noted that in order to calculate the thickness direction phase difference or the three-dimensional refractive index, the prescribed constant n is appropriately set by executing step S1106 a sufficient number of times.

[0094] When 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 the predetermined value θ corresponding to each value of the variable i. i Then, similarly to step S402, the measuring unit 104 sets the angle θ between the light traveling direction and the surface of the sample 212. i In the case of a degree, a parallel Nicol spectrum is measured. Then, the retardation is calculated based on the formal coefficients calculated in steps S404 to S416.

[0095] As described above, the step of changing the angle and the step of measuring the delay are repeated a predetermined number of times, thereby calculating a plurality of delays. Then, based on the calculated plurality of delays, the thickness direction phase difference or the three-dimensional refractive index of the sample is calculated (S1112). It should be noted that the inclination angle of the rotating sample stage 210 is the angle between the direction of travel of the light passing through the polarizer 208 and the surface of the sample, so the thickness direction phase difference or the three-dimensional refractive index of the sample can be calculated based on the delay measured while changing the angle. The calculation method is known, so a detailed description is omitted.

[0096] In addition, the measuring unit 104 of the present invention may include a microscopic optical system. Specifically, for example, the measuring unit 104 may be Fig.12 As shown in the figure. Figure 2 The same structure is omitted for explanation. Specifically, the measuring unit 104 has Figure 2 In addition to the structure of the optical system 1200, the optical system 1200 also includes an objective lens 1202, a semi-transparent mirror 1204, and an observation camera 1206. The objective lens 1202 guides the light of the micro region of the sample 212 as the measurement object to the analyzer 214. The semi-transparent mirror 1204 separates the light passing through the condenser lens 206. A part of the separated light is input to the multi-channel spectrometer 216, and the other part is input to the observation camera 1206. Thus, the delay of the micro region of the sample 212 as the measurement object can be measured, and the micro region can be observed by the observation camera 1206.

[0097] In the above, the case where the sample 212 is a crystal plate is described as an example of the experimental results, 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, so the cell gap of the liquid crystal panel can be measured.

[0098] In the above description, the spectral spectrum measured by the measuring unit 104 is a parallel Nicol spectrum, but the spectral spectrum is not limited to the parallel Nicol spectrum. The spectral spectrum may be a spectrum including spectral information obtained by a polarization optical system, and may be an orthogonal Nicol spectrum, for example.

[0099] In addition, in the above description, the case where the first wavelength dispersion formula and the second wavelength dispersion formula are the Cauchy wavelength dispersion formula is described, but the first wavelength dispersion formula and the second wavelength dispersion formula are not limited to the Cauchy wavelength dispersion formula. The first wavelength dispersion formula and the second wavelength dispersion formula can be polynomials that express the relationship between the birefringence and the wavelength, for example, they can also be the Sellmeier wavelength dispersion formula expressed by Formula 13.

[0100] [Formula 13]

[0101]

[0102] In addition, the method of calculating the delay is not limited to Figure 4 The method represented by the process shown. Specifically, first, the number of the longest wavelength peak included in the operation wavelength region is set to m0 (a prescribed integer). Then, under the condition that the number of the peak is m0, the delay is calculated for the wavelength represented by each peak and each valley value included in the operation wavelength region. Then, the delay in the wavelength represented by each peak and each valley value calculated is used to fit the Cauchy wavelength dispersion formula represented by Formula 3. The residual δm0 between the number calculated by fitting and the set number m0 is calculated. Next, the number of the longest wavelength peak included in the operation wavelength region is set to m0+1, and the residual δm0 of the number m0+1 is calculated in the same way. While changing the number of the longest wavelength peak included in the operation wavelength region from m0 to a prescribed value, the residual of the number is calculated for each number. The number under the condition that the residual is the smallest among the residuals calculated by the above steps is determined as the number of the longest wavelength peak included in the operation wavelength region. Moreover, based on the determined number, the delay is calculated for the wavelength represented by each peak and each valley value included in the operation wavelength region. The calculated delay is fitted to the Cauchy wavelength dispersion formula represented by Formula 3, thereby determining each coefficient included in the wavelength dispersion formula. Then, the delay at an arbitrary wavelength can be calculated using the wavelength dispersion formula with the determined coefficients.

Claims

1. An optical measurement method, characterized in that: include: The step of measuring a spectroscopic spectrum including a plurality of peaks and valleys within a specified wavelength region for the sample; A step of calculating the thickness of the sample at each wavelength represented by the peak value or the valley value using a first wavelength dispersion formula including a plurality of wavelength dispersion coefficients, and provisionally determining the wavelength dispersion coefficient calculated in such a manner that an evaluation value based on the calculated thickness is maximized as the wavelength dispersion coefficient included in the first wavelength dispersion formula; Assuming a plurality of values ​​as the number of a specific peak included in the plurality of peaks, and calculating a second wavelength dispersion formula based on the numbers and wavelengths of the plurality of peaks under the condition that the number of the specific peak is the assumed values; The step of determining the number of the specific peak based on the first wavelength dispersion formula including the provisionally determined wavelength dispersion coefficient and the second wavelength dispersion formula, and formally determining the wavelength dispersion coefficient based on the determined number and the second wavelength dispersion formula; as well as a step of calculating delay based on the second chromatic dispersion formula including the formally determined chromatic dispersion coefficient, The evaluation value is a value that is larger as the wavelength dependency of the calculated thickness is smaller, or the evaluation value is a value that is larger as the standard deviation of the calculated thickness is smaller.

2. The optical measurement method according to claim 1, characterized in that: The first wavelength dispersion formula and the second wavelength dispersion formula are Cauchy wavelength dispersion formulas.

3. The optical measurement method according to claim 1 or 2, characterized in that: The spectral spectrum is a parallel Nicol spectrum.

4. The optical measurement method according to claim 1, characterized in that: Also includes: The step of changing the angle between the direction of light travel and the surface of the sample; The step of measuring the spectral spectrum while maintaining the angle, and measuring the delay based on the second wavelength dispersion formula including the formally determined wavelength dispersion coefficient; as well as A step of calculating a thickness direction phase difference or a three-dimensional refractive index of the sample based on a plurality of retardations calculated by repeatedly performing the step of changing the angle and the step of measuring the retardation a predetermined number of times.

5. An optical measuring device, characterized in that: have: A measuring unit, which measures a spectroscopic spectrum including a plurality of peaks and valleys of the sample within a predetermined wavelength region; a provisional determination unit that calculates the thickness of the sample at each wavelength represented by the peak value or the valley value using a first wavelength dispersion formula including a plurality of wavelength dispersion coefficients, and provisionally determines the wavelength dispersion coefficient calculated in such a way that an evaluation value based on the calculated thickness is maximized as the wavelength dispersion coefficient included in the first wavelength dispersion formula; A second wavelength dispersion formula calculation unit, assuming a plurality of values ​​as the number of a specific peak included in the plurality of peaks, and calculating a second wavelength dispersion formula based on the numbers and wavelengths of the plurality of peaks under the condition that the number of the specific peak is the assumed values; a formal determination unit that determines the number of the specific peak based on the first wavelength dispersion formula including the provisionally determined wavelength dispersion coefficient and the second wavelength dispersion formula, and formally determines the wavelength dispersion coefficient based on the determined number and the second wavelength dispersion formula; as well as a delay calculation unit that calculates the delay based on the second chromatic dispersion equation including the formally determined chromatic dispersion coefficient, The evaluation value is a value that is larger as the wavelength dependency of the calculated thickness is smaller, or the evaluation value is a value that is larger as the standard deviation of the calculated thickness is smaller.

6. A storage medium storing an optical measurement program, wherein the optical measurement program is executed by a computer used in an optical measurement device, wherein: The optical measurement program causes the computer to execute: The step of measuring a spectroscopic spectrum including a plurality of peaks and valleys within a specified wavelength region for the sample; A step of calculating the thickness of the sample at each wavelength represented by the peak value or the valley value using a first wavelength dispersion formula including a plurality of wavelength dispersion coefficients, and provisionally determining the wavelength dispersion coefficient calculated in such a manner that an evaluation value based on the calculated thickness is maximized as the wavelength dispersion coefficient included in the first wavelength dispersion formula; Assuming a plurality of values ​​as the number of a specific peak included in the plurality of peaks, and calculating a second wavelength dispersion formula based on the numbers and wavelengths of the plurality of peaks under the condition that the number of the specific peak is the assumed values; The step of determining the number of the specific peak based on the first wavelength dispersion formula including the provisionally determined wavelength dispersion coefficient and the second wavelength dispersion formula, and formally determining the wavelength dispersion coefficient based on the determined number and the second wavelength dispersion formula; as well as a step of calculating delay based on the second chromatic dispersion formula including the formally determined chromatic dispersion coefficient, The evaluation value is a value that is larger as the wavelength dependency of the calculated thickness is smaller, or the evaluation value is a value that is larger as the standard deviation of the calculated thickness is smaller.

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