Optical measurement method, optical measurement apparatus, and optical measurement program

Abstract

[Assignment] Measure a spectroscopic spectrum using a simple measuring instrument, determine the order of the peaks or valleys included in the spectroscopic spectrum, and measure the accurate retardation. [Solution] An optical measurement method characterized by comprising: a step of measuring a spectroscopic spectrum for a sample; a step of calculating the thickness of the sample for each wavelength represented by a peak or valley using a first wavelength dispersion formula, and determining a coefficient included in the first wavelength dispersion formula under the condition where the evaluation value based on the calculated thickness is the largest; a step of setting the order of a specific peak as a plurality of conditions and calculating a second wavelength dispersion formula under the set plurality of conditions; a step of determining the order of a specific peak based on the first wavelength dispersion formula including the determined coefficient, and determining the coefficient based on the specified order and the second wavelength dispersion formula; and a step of calculating a retardation.

Description

Technology Field

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

[0002] Conventionally, an optical measuring device is known for determining optical order and retardation by performing measurements while rotating the positional relationship between a sample, a polarizer, and an analyzer in the plane direction of the sample (see Patent Documents 1 and 2 below). In addition, 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). Prior art literature

[0003] Japanese Patent Publication No. Hei 11-211656, Japanese Patent Publication No. 2003-172691, Japanese Patent Publication No. 2003-240678 The problem to be solved

[0004] As in Patent Documents 1 and 2, when measuring by changing the angle formed between the sample and the polarizing optical system as a plurality, a driving mechanism is required in the measuring device to tilt the sample or the polarizing optical system. Furthermore, particularly when the retardation of the sample is high, it is difficult to determine the order and difficult to perform accurate measurement of the retardation. In the optical measurement method of Patent Document 3, the wavelength dispersion of the retardation cannot be measured unless at least one of the birefringence of the sample or the thickness of the sample is known.

[0005] The present disclosure is made in light of the above circumstances, and its purpose is to measure a spectral spectrum using a simple measuring instrument, determine the order of the peaks or valleys included in the spectral spectrum, and measure accurate retardation. means of solving the problem

[0006] To solve the above problem, the optical measurement method according to the present disclosure comprises: a step of measuring a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region 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 coefficients set under a plurality of conditions, and determining the coefficients included in the first wavelength dispersion formula under the condition where the evaluation value based on the calculated thickness is the largest; a step of setting the order of a specific peak included in the plurality of peaks as a plurality of conditions, and calculating a second wavelength dispersion formula based on each order and wavelength of the plurality of peaks under the set plurality of conditions; a step of determining the order of the specific peak based on the first wavelength dispersion formula including the determined coefficients and the second wavelength dispersion formula, and determining the coefficients based on the determined order and the second wavelength dispersion formula; and a step of calculating retardation based on the second wavelength dispersion formula including the determined coefficients.

[0007] In addition, the optical measuring device according to the present disclosure comprises: a measuring unit that measures a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region for a sample; a determining unit that determines the coefficients included in the first wavelength dispersion formula by using a first wavelength dispersion formula including coefficients set under a plurality of conditions, and calculates the thickness of the sample for each wavelength represented by the peak or the valley, and in the condition where 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 plurality of peaks as a plurality of conditions, and calculates a second wavelength dispersion formula based on each order and wavelength of the plurality of peaks under the set plurality of conditions; a determining unit that determines the order of the specific peak based on the first wavelength dispersion formula including the determined coefficients and the second wavelength dispersion formula, and determines the coefficients based on the determined order and the second wavelength dispersion formula; and a retardation calculation unit that calculates retardation based on the second wavelength dispersion formula including the determined coefficients.

[0008] In addition, the optical measurement program according to the present disclosure is an optical measurement program executed on a computer used in an optical measurement device, and is characterized by executing on the computer the following steps: a step of measuring a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region 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 coefficients set under a plurality of conditions, and determining the coefficients included in the first wavelength dispersion formula under the condition where the evaluation value based on the calculated thickness is the largest; a step of setting the order of a specific peak included in the plurality of peaks as a plurality of conditions, and calculating a second wavelength dispersion formula based on each order and wavelength of the plurality of peaks under the set plurality of conditions; a step of determining the order of the specific peak based on the first wavelength dispersion formula including the determined coefficients and the second wavelength dispersion formula, and determining the coefficients based on the determined order and the second wavelength dispersion formula; and a step of calculating retardation based on the second wavelength dispersion formula including the determined coefficients. Brief explanation of the drawing

[0009] FIG. 1 is a schematic diagram illustrating the schematic configuration of an optical measuring device according to the present embodiment. FIG. 2 is a drawing illustrating an example of the schematic configuration of a measuring unit according to the present embodiment. Figure 3 is a diagram illustrating an example of a measured parallel Nicol spectrum. FIG. 4 is a flowchart illustrating a method for calculating retardation regarding the present embodiment. Figure 5 is a diagram illustrating an example of the wavelength dependence of thickness. Figure 6 is a graph showing the first wavelength dispersion formula and the second wavelength dispersion formula. FIG. 7 is a diagram illustrating an example of experimental results to verify the effects of the present invention. FIG. 8 is a diagram illustrating an example of experimental results to verify the effects of the present invention. FIG. 9 is a diagram illustrating an example of experimental results to verify the effects of the present invention. FIG. 10 is a drawing illustrating an example of experimental results to verify the effects of the present invention. Figure 11 is a flowchart illustrating a method for calculating the phase difference in the thickness direction or the three-dimensional birefringence. FIG. 12 is a drawing illustrating another example of the schematic configuration of a measuring unit according to the present embodiment. Specific details for implementing the invention

[0010] Embodiments of the present disclosure are described below with reference to the drawings.

[0011] FIG. 1 is a schematic diagram illustrating the general configuration of an optical measuring device (100) of the present embodiment. As shown in FIG. 1, the optical measuring device (100) of the present embodiment includes an information processing unit (102) and a measuring unit (104). The information processing unit (102) includes a control unit (106), a memory 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 memory unit (108), the display unit (110), and the input / output unit (112) are connected to each other via a data bus (114) so ​​as to be able to exchange electrical signals.

[0012] The control unit (106) is a CPU (Central Processing Unit) which is a processor. Specifically, the control unit (106) functionally includes a wavelength calculation unit (116), a decision unit (120), a normalization unit (122), a second wavelength dispersion formula calculation unit (124), a main decision unit (126), and a retardation calculation unit (128), and each unit performs the operations described below according to a program stored in the memory unit (108).

[0013] The memory unit (108) is a main memory device such as RAM (Random Access Memory) and an auxiliary memory device capable of statically recording information such as HDD (Hard Disk Drive) or SSD (Solid State Drive). In addition to the optical measurement program, the memory unit (108) stores a program that controls the operation of each unit included in the information processing unit (102).

[0014] 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.

[0015] The input / output unit (112) is one or more devices, such as a keyboard, mouse, or touch panel, 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 measurement unit (104). For example, the input / output unit (112) receives the results measured by the measurement unit (104). The input / output unit (112) may include various ports for wired connection and a controller for wireless connection. Furthermore, the configuration of the information processing unit (102) shown here is an example, and may have other configurations.

[0016] FIG. 2 is a schematic diagram illustrating the general configuration of a measuring unit (104). As shown in FIG. 2, the measuring unit (104) includes a light source (202), an optical fiber (204), a condensing lens (206), a polarizer (208), a rotating sample stage (210), an analyzer (214), and a multi-channel spectrometer (216). Additionally, the measuring unit (104) shown in FIG. 2 is an example illustrating the case of measuring a parallel Nicol spectrum.

[0017] 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 range of the object of measurement. The light emitted by the light source (202) is converted into parallel light by a condensing lens (206) via an optical fiber (204).

[0018] The polarizer (208) is a linear polarizer. The polarizer (208) transmits only the component in the direction of the transmission axis among the parallel light converted by the condensing lens (206).

[0019] A sample (212) is placed on a rotating sample stage (210). When the direction of propagation of light passing through the polarizer (208) is the Z-axis direction, the rotating sample stage (210) is configured to change the angle formed between the surface of the sample (212) placed on the rotating sample stage (210) and the Z-axis. FIG. 2 illustrates a case where the surface of the sample (212) is in the XY plane, and the angle formed between the X-axis and the Z-axis and the angle formed between the Y-axis and the Z-axis are both 90 degrees. Additionally, the rotating sample stage (210) is formed of a material that transmits the component of the wavelength region to be measured among the light transmitted through the polarizer (208). Furthermore, the measuring unit (104) may be configured not to have a rotating sample stage (210).

[0020] The analyzer (214) is a linear polarizer and is positioned so that its transmission axis is parallel to that of 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 in the direction of the transmission axis of the light with the phase difference. The transmitted light is concentrated by a condensing lens (206) and input to a multi-channel spectrometer (216) via an optical fiber (204).

[0021] The multi-channel spectrometer (216) measures the intensity of the input light by differentiating it for each wavelength. Specifically, for example, the multi-channel analyzer measures a parallel Nicol spectrum as shown in FIG. 3. The vertical axis of FIG. 3 is the transmittance calculated from the intensity measured by the multi-channel analyzer, and the horizontal axis is the wavelength. Since the phase of the X-axis component and the Y-axis component of the light after passing through the sample (212) differs depending on the wavelength, the wavelength dependence of the transmittance is wave-shaped as shown in FIG. 3.

[0022] Next, the measurement method of retardation according to the present embodiment and the functions of each part included in the control unit (106) will be explained using the flow shown in FIG. 4. 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 a parallel Nicol spectrum including a plurality of peaks and valleys in a wavelength region of 400 nm to 800 nm, as shown in FIG. 3.

[0023] Next, the wavelength calculation unit (116) calculates the wavelength represented by each peak and valley included in the calculation wavelength range (S404). Specifically, for example, the wavelength calculation unit (116) sets a range of 500 nm to 750 nm as the calculation wavelength range. In the example of FIG. 3, the wavelength calculation unit (116) calculates the wavelength represented by each of the seven peaks and seven valleys included in the calculation wavelength range. Additionally, the calculation wavelength range may be set by inputting to the input / output unit (112) by a user.

[0024] Next, the provisional determination unit (120) uses a first wavelength dispersion formula including coefficients set under a plurality of conditions to calculate the thickness of the sample for each wavelength indicated by a peak or valley, and provisionally determines the coefficients included in the first wavelength dispersion formula under the condition where the evaluation value based on the calculated thickness is the largest (S406). Specifically, for example, the provisional determination unit (120) provisionally determines wavelength dispersion coefficients A, B, and C using numbers 1 to 4. Number 1 is λ C This is a formula for calculating the thickness, which is a function of

[0025] <Number 1>

[0026]

[0027] In Number 1, i is the peak and valley indices. For example, among the wavelengths represented by the 14 peaks and valleys calculated from S404, the peak indices for the longest wavelength of 740 nm are 0, and the valley indices for the shortest wavelength of 500 nm are 13. λ is the wavelength. λ C is the mid-wavelength of an adjacent peak or the mid-wavelength of an adjacent valley, and is denoted by the number 2.

[0028] Number 2

[0029]

[0030] 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, as shown in Figure 3, for example.

[0031] Number 3

[0032]

[0033] The determining unit (120) determines the wavelength dispersion coefficients A, B, and C included in the first wavelength dispersion formula so that the evaluation value based on the thickness calculated in number 1 is maximized. For example, the determining unit (120) calculates the thickness calculated for each peak or valley wavelength using number 1, calculates the standard deviation σ using number 4, and takes the reciprocal of the standard deviation σ as the evaluation value.

[0034] Number 4

[0035]

[0036] In the number 4, d λC,i is the thickness of the sample (212) calculated for each index i at the intermediate wavelength of an adjacent peak or the intermediate wavelength of an adjacent valley. max is the maximum value of the index in the calculation wavelength range. In the above example, since there are 14 peaks and valleys in the calculation wavelength range, the value of max is 13.

[0037] Specifically, the provisional determination unit (120) takes the reciprocal of the standard deviation σ as the evaluation value and calculates wavelength dispersion coefficients A, B, and C using a non-linear least squares method. In addition, the said algorithm is an example, and if the wavelength dispersion coefficients A, B, and C can be determined under the condition where the evaluation value, which is the reciprocal of the standard deviation σ, is maximized, then other algorithms may be used to provisionally determine the wavelength dispersion coefficients A, B, and C.

[0038] FIG. 5 is a diagram showing the relationship between thickness d and wavelength calculated under three conditions among the repeatedly changed wavelength dispersion coefficients A, B, and C until the predetermining unit (120) predetermines the wavelength dispersion coefficients A, B, and C. In the example illustrated in FIG. 5, the condition where the wavelength dispersion coefficient B is 13723 has the smallest standard deviation of thickness d. Therefore, the predetermining unit (120) predetermines A, B, and C calculated under said condition as wavelength dispersion coefficients.

[0039] In addition, the evaluation value may be calculated by other methods. Specifically, the evaluation value may be set to be larger as the wavelength dependence of the calculated thickness decreases. For example, the provisional determination unit (120) may calculate an approximation straight line of a first-order equation for the wavelength dependence of the thickness calculated under each condition in S406. Furthermore, the provisional determination unit (120) may provisionally determine A, B, and C as wavelength dispersion coefficients under the condition where the slope included in the approximation equation is smallest. That is, the provisional determination unit (120) may provisionally determine A, B, and C as wavelength dispersion coefficients under the condition where the wavelength dependence of the thickness is flattest.

[0040] Next, the standardization unit (122) standardizes a first wavelength dispersion formula including the determined wavelength dispersion coefficients A, B, and C (S410). Specifically, the standardization unit (122) uses a number 5 to standardize the first wavelength dispersion coefficient based on the retardation at a predetermined wavelength λn. The predetermined wavelength λn can be set appropriately, but here it is set to 600 nm. Also, A', B', and C' included in the number 5 are the wavelength dispersion coefficients after standardization.

[0041] Number 5

[0042]

[0043] Next, the second wavelength dispersion calculation unit (124) calculates a second wavelength dispersion based on the order of each peak or valley and the first wavelength dispersion under the condition that the order is set as multiple (S412). Specifically, the second wavelength dispersion calculation unit (124) sets the order of a specific peak included in the multiple peaks under the condition that it is set as multiple, and calculates a second wavelength dispersion based on the order and wavelength of each of the multiple peaks under 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 calculation wavelength region is set to λ0, and the order of the corresponding peak is set to m0. The second wavelength dispersion calculation unit (124) sets the condition that the order m0 of the peak at a wavelength of 740 nm included in the measurement result shown in FIG. 3 is 10, the condition that the order m0 is 11, and the condition that the order m0 is 12. The retardation Re.(λ at the wavelength represented by each peak and each valley i ) is represented by numbers 6 and 7.

[0044] Number 6

[0045]

[0046] Number 7

[0047]

[0048] For example, under the condition that the order of the peak at a wavelength of 740 nm is 10, the retardation of λ0, λ1, and λ2 is expressed as numbers 8 to 10.

[0049] Number 8

[0050]

[0051] Number 9

[0052]

[0053] Number 10

[0054]

[0055] Likewise, the wavelength retardation represented by all peaks and valleys included in the calculation wavelength range is calculated using the number 6 or number 7. In addition, under conditions where the order of the peak at a wavelength of 740 nm is 11 and 12, the second wavelength dispersion formula calculation unit (124) performs the same calculation.

[0056] Next, the second wavelength dispersion formula calculation unit (124) calculates the wavelength dispersion coefficient α m0 , β m0 and γ m0 A second wavelength dispersion formula is derived, which includes and denotes by number 11. As denoted by number 11, the second wavelength dispersion formula is a Cauchy wavelength dispersion formula, just like the first wavelength dispersion formula.

[0057] Number 11

[0058]

[0059] The second wavelength dispersion formula calculation unit (124) calculates the wavelength dispersion coefficient α such that, under each condition, the residual between the value of each retardation calculated using numbers 6 and 7 and the value of each retardation calculated using number 11 is minimized. m0 , β m0 and γ m0 Produces.

[0060] In addition, the standardization unit (122) calculates the wavelength dispersion coefficient α under each condition based on the retardation of a predetermined wavelength λn. m0 , β m0 and γ m0 A second wavelength dispersion formula including is normalized. Also, a predetermined wavelength λn is 600 nm, which is used in S410. The normalized second wavelength dispersion formula is represented by the number 12.

[0061] Number 12

[0062]

[0063] Here, α m0 ', β m0 ' and γ m0' is a wavelength dispersion coefficient included in the second wavelength dispersion formula after normalization. FIG. 6 is a figure showing the second wavelength dispersion formula after normalization calculated under conditions where the order m0 of the peak at a wavelength of 740 nm is 10, 11, and 12.

[0064] Next, the determination unit (126) determines the order of a specific peak based on a first wavelength dispersion formula including a provisionally determined coefficient and a second wavelength dispersion formula, and determines the coefficient based on the determined order and the second wavelength dispersion formula (S414). Specifically, the determination unit (126) compares each second wavelength dispersion formula calculated and normalized in S412 with the first wavelength dispersion formula calculated in S410. Then, the determination unit (126) determines the order based on the conditions in which the second wavelength dispersion formula that most matches the first wavelength dispersion formula is calculated.

[0065] FIG. 6 shows the first wavelength dispersion formula after normalization calculated in S410, along with the second wavelength dispersion formula after normalization calculated under each condition. As shown in FIG. 6, the first wavelength dispersion formula calculated in S410 has the highest degree of agreement with the second wavelength dispersion formula calculated under the condition that the order m0 of the peak at a wavelength of 740 nm is 11. Therefore, the determination unit (126) specifies that the order m0 of the peak at a wavelength of 740 nm is 11. In addition, the determination unit (126) [includes] α in the second wavelength dispersion formula before normalization calculated under the condition that the order m0 is 11 m0 , β m0 and γ m0 It is determined as the wavelength dispersion coefficient.

[0066] Next, the retardation calculation unit (128) calculates the retardation based on a second wavelength dispersion formula including the determined coefficient (S416). Specifically, the retardation calculation unit (128) calculates the α determined in S414 m0 , β m0 and γ m0Based on the number 11 including and the wavelength input by the user to the input unit, the retardation at the wavelength desired by the user is calculated.

[0067] As described above, according to the present invention, a spectral spectrum can be measured using a simple measuring instrument, and the order of peaks or valleys included in the spectral spectrum can be determined, along with the accurate retardation. The effects of the present invention will be explained using data actually measured.

[0068] FIG. 7 is a diagram showing the spectroscopic spectra (parallel Nicol spectra in this example) measured at step S402 for each of the two monolayer modified plates (212) (monolayer sample 1 and monolayer sample 2) with different retardations.

[0069] FIG. 8 is a diagram showing the spectroscopic spectrum (parallel Nicol spectrum in this example) measured at step S402 for a sample (212) (overlapping sample) created by overlapping two single-layer modified plates shown in FIG. 7.

[0070] FIG. 9 is a diagram illustrating the wavelength dependence of retardation calculated using the measurement results of FIG. 7 and the second wavelength dispersion formula calculated in steps S404 to S416. FIG. 10 is a diagram illustrating the wavelength dependence of retardation calculated using the measurement results of FIG. 8 and the second wavelength dispersion formula calculated in steps S404 to S416. FIG. 10 also shows the calculated value of the sum of the wavelength dependence of retardation in the two monolayer modified plates shown in FIG. 9.

[0071] The sum of the retardation values ​​of two single-layer modified plates and the retardation of the superimposed sample will theoretically match. However, if the wavelength dispersion coefficient included in the second wavelength dispersion formula in steps S404 to S416 is not accurately calculated, there is a risk that the sum of the retardation values ​​of the two single-layer modified plates and the retardation of the superimposed sample will differ. According to the present invention, as shown in FIG. 10, the degree of agreement between the calculated value and the measured value is high. Therefore, it is confirmed that accurate retardation can be measured according to the present invention.

[0072] In addition, the present invention is not limited to the above embodiments and various modifications are possible. For example, the present invention may calculate the phase difference in the thickness direction or the three-dimensional refractive index of a sample using the retardation calculated in the flow shown in FIG. 4. FIG. 11 is a flow showing a method for calculating the phase difference in the thickness direction or the three-dimensional refractive index of a sample.

[0073] First, the variable i is set to 0 (S1102). Next, the inclination angle of the rotating sample stage (210) is θ, which is set in advance in correspondence with the angular value of the variable i. i The road is set (S1104). When the value of variable i is 0, the inclination angle of the rotating sample stage (210) is set to θ0 degrees.

[0074] Then, 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 a parallel Nicol spectrum when the angle formed between the direction of light propagation and the surface of the sample (212) is θ0 degrees. Then, retardation is calculated based on the coefficients calculated in steps S404 to S416.

[0075] Next, it is determined whether variable i matches a predetermined constant n (S1108). If variable i matches a predetermined constant n, proceed to S1112, and if it does not match, proceed to S1110. Additionally, a predetermined constant n is appropriately set so that a sufficient number of S1106 steps are executed to calculate the thickness direction phase difference or the three-dimensional refractive index.

[0076] If variable i does not match a predetermined constant n, variable i is incremented (S1110). Then, the inclination angle of the rotating sample stage (210) is θ, which is set in advance in correspondence with each value of variable i. i The road is changed (S1104). And, similar to the step of S402, the measuring unit (104) determines that the angle formed between the direction of light propagation and the surface of the sample (212) is θ i In the case of the parallel Nicol spectrum, the parallel Nicol spectrum is measured. In addition, retardation is calculated based on the coefficients calculated in steps S404 to S416.

[0077] As described above, a plurality of retardations are calculated by repeating the step of changing the angle and the step of measuring the retardation a predetermined number of times. Then, based on the calculated plurality of retardations, the phase difference in the thickness direction or the three-dimensional refractive index of the sample is calculated (S1112). In addition, since the tilt angle of the rotating sample stage (210) is the angle formed between the direction of propagation of light transmitted through the polarizer (208) and the sample surface, the phase difference in the thickness direction or the three-dimensional refractive index of the sample can be calculated by the retardation measured while changing the angle. Since the calculation method is known, a detailed description is omitted.

[0078] Additionally, the measuring unit (104) according to the present invention may include a micro-optical system. Specifically, for example, the measuring unit (104) may have the configuration shown in FIG. 12. A description of the configuration similar to FIG. 2 is omitted. Specifically, the measuring unit (104) includes, in addition to the configuration of FIG. 2, an objective lens (1202), a half mirror (1204), and an observation camera (1206). The objective lens (1202) guides light that has passed through a fine area of ​​the sample (212) to be measured to an analyzer (214). The half mirror (1204) separates the light that has passed through the condensing lens (206). A portion of the separated light is input to a multi-channel spectrometer (216), and another portion is input to an observation camera (1206). By doing so, the retardation of the fine area of ​​the sample (212) that is the subject of measurement can be measured, and the fine area can be observed with an observation camera (1206).

[0079] In addition, although the above description describes the case where the sample (212) is a modified plate as an example of an experimental result, the sample (212) may also be a liquid crystal panel. According to the present invention, since the thickness of the sample (212) can be calculated in step S406, the cell gap of the liquid crystal panel can be measured.

[0080] In addition, although the above description explains the case where the spectral spectrum measured by the measuring unit (104) is a parallel Nicol spectrum, the spectral spectrum is not limited to a parallel Nicol spectrum. The spectral spectrum may be any spectrum containing spectral information obtained from a polarizing optical system, and for example, it may be an orthogonal Nicol spectrum.

[0081] In addition, although the above description explains the case where the first wavelength dispersion formula and the second wavelength dispersion formula are Cauchy wavelength dispersion formulas, the first wavelength dispersion formula and the second wavelength dispersion formula are not limited to Cauchy wavelength dispersion formulas. The first wavelength dispersion formula and the second wavelength dispersion formula may be polynomials representing the relationship between birefringence and wavelength, and for example, they may be Selmeier wavelength dispersion formulas represented by number 13.

[0082] Number 13

[0083]

[0084] Furthermore, the method for calculating retardation is not limited to the method shown in the flowchart illustrated in FIG. 4. Specifically, first, the order of the longest wavelength peak included in the computational wavelength region is set to m0 (a predetermined integer). Next, under the condition that the order of the said peak is m0, retardation is calculated for the wavelengths represented by each peak and each valley included in the computational wavelength region. Then, using the calculated retardation for the wavelengths represented by each peak and each valley, fitting is performed on Cauchy's wavelength dispersion formula represented by Number 3. The order calculated by fitting and the residual δ of the set order m0 m0Calculate the order of the longest wavelength peak included in the operation wavelength region. Next, set the order of the longest wavelength peak included in the operation wavelength region to m0+1, and calculate the residual δm0 of the order m0+1. While varying the order of the longest wavelength peak included in the operation wavelength region from m0 to a predetermined value, calculate the residual for each order. Among the residuals calculated in the above steps, the order corresponding to the condition with the smallest residual is specified as the order of the longest wavelength peak included in the operation wavelength region. Furthermore, based on the specified order, calculate the retardation for the wavelength represented by each peak and each valley included in the operation wavelength region. By fitting the calculated retardation to the Cauchy wavelength dispersion formula represented by number 3, determine each coefficient included in the wavelength dispersion formula. Then, the retardation at any wavelength may be calculated using the wavelength dispersion formula with the determined coefficients. Explanation of the symbols

[0085] 100: Optical measuring device 102: Information Processing Unit 104: Measurement section 106: Control unit 108: Memory Department 110: Display unit 112: Input / Output Section 114: Data bus 116: Wavelength calculation unit 120: Provisional Decision 122: Standardization Department 124: Second wavelength dispersion formula calculation unit 126: This decision section 128: Retardation Calculation Unit 202: Light source 204: Optical fiber 206: Condensing lens 208: Polarizer 210: Rotary sample stage 212: Sample 214: Swordsman 216: Multichannel Spectrometer 1202: Objective lens 1204: Half Mirror 1206: Observation camera

Claims

Claim 1 A step of measuring a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region 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 determining a wavelength dispersion coefficient calculated such that the evaluation value based on the calculated thickness is maximized, as a wavelength dispersion coefficient used to specify each optical order of the plurality of peaks; a step of assuming a plurality of values ​​as optical orders of specific peaks included in the plurality of peaks, and calculating a second wavelength dispersion formula based on each optical order of the plurality of peaks and wavelengths under the condition that the optical order of the specific peak is each assumed value; a step of determining the wavelength dispersion coefficient based on the first wavelength dispersion formula including the determined wavelength dispersion coefficient and the second wavelength dispersion formula, while determining the optical order of the specific peak based on the determined optical order and the second wavelength dispersion formula; and a step of calculating retardation based on the second wavelength dispersion formula including the determined wavelength dispersion coefficient. An optical measurement method comprising, wherein the evaluation value is a larger value as the wavelength dependence or standard deviation of the calculated thickness is smaller. Claim 2 An 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. Claim 3 An optical measurement method according to claim 1 or 2, characterized in that the spectroscopic spectrum is a parallel Nicol spectrum. Claim 4 An optical measurement method according to claim 1 or 2, further comprising: a step of changing the angle formed between the direction of light propagation and the surface of the sample; a step of measuring the spectral spectrum while the angle is maintained and measuring the retardation based on the second wavelength dispersion formula including the determined wavelength dispersion coefficient; and a step of calculating the thickness direction phase difference or three-dimensional refractive index of the sample based on a plurality of retardations calculated by repeating the step of changing the angle and the step of measuring the retardation a predetermined number of times. Claim 5 A measuring unit for a sample, which measures a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region; a determining 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 determines the calculated wavelength dispersion coefficient as the wavelength dispersion coefficient used to determine each optical order of the plurality of peaks such that the evaluation value based on the calculated thickness is maximized; a second wavelength dispersion formula calculating unit that calculates a second wavelength dispersion formula based on each optical order of the plurality of peaks and wavelengths under the condition that the optical order of the specific peak included in the plurality of peaks is each of the assumed values; a determining unit that determines the wavelength dispersion coefficient based on the first wavelength dispersion formula including the determined wavelength dispersion coefficient and the second wavelength dispersion formula, and determines the optical order of the specific peak based on the determined optical order and the second wavelength dispersion formula; and based on the second wavelength dispersion formula including the determined wavelength dispersion coefficient, An optical measuring device comprising a retardation calculation unit for calculating retardation, wherein the evaluation value is a larger value as the wavelength dependence or standard deviation of the calculated thickness becomes smaller. Claim 6 A recording medium storing an optical measurement program executed on a computer used in an optical measurement device, comprising: a step of measuring a spectroscopic spectrum including a plurality of peaks and valleys in a predetermined wavelength region 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 determining a wavelength dispersion coefficient calculated such that the evaluation value based on the calculated thickness is maximized, as a wavelength dispersion coefficient used to specify 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 of the plurality of peaks and wavelengths under the condition that the optical order of the specific peak is each assumed value; a step of determining the wavelength dispersion coefficient based on the first wavelength dispersion formula including the determined wavelength dispersion coefficient and the second wavelength dispersion formula, while determining the optical order of the specific peak based on the determined optical order and the second wavelength dispersion formula; and the A recording medium storing an optical measurement program characterized by executing a step of calculating retardation based on a second wavelength dispersion formula on the computer, wherein the evaluation value is a larger value as the wavelength dependence or standard deviation of the calculated thickness becomes smaller. Claim 7 delete Claim 8 delete

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