# US 10,309,767 B2 · Optical measurement apparatus and optical measurement method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,309,767 B2 - Document ID: US10309767B2 - Status: Granted - Kind: B2 - Application number: 15/996,970 - Filed: 2018-06-04 - Published: 2018-12-06 - Granted: 2019-06-04 - Earliest claimed: 2017-06-05 - Assignees: Otsuka Electronics Co., Ltd. - Applicants: Otsuka Electronics Co., Ltd. - Inventors: Nobuyuki Inoue; Kunikazu Taguchi - Web page: https://patentgrep.com/patent/US10309767B2 ## CPC - G01B 11/06: for measuring thickness {; e.g. of sheet material (thickness measurement by thermal means G01B21/085)} - G01B 9/02024: {Measuring in transmission, i.e. light traverses the object} - G01B 9/02041: {characterised by particular imaging or detection techniques} - G01B 9/02043: {Imaging of the Fourier or pupil or back focal plane, i.e. angle resolved imaging} - G01B 11/0625: {with measurement of absorption or reflection} - G01N 21/00: Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light (G01N3/00 - G01N19/00 take precedence) - G01N 21/45: using interferometric methods; using Schlieren methods - G01N 21/8422: {Investigating thin films, e.g. matrix isolation method} - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract An optical measurement method with an optical measurement apparatus including an irradiation optical system and a measurement optical system is provided. The optical measurement method includes obtaining a distribution of actually measured values when angles of incidence are different for the same sample, calculating a modification factor depending on an angle of incidence on the measurement optical system from each measurement point in association with a region in the two-dimensional image corresponding to each measurement point in the measurement target irradiated with the measurement light, and calculating optical characteristics including a refractive index of the sample based on a group of pixel values in one row or a plurality of rows along any one direction in the distribution of the actually measured values and a corresponding modification factor. ## Claims ### Claim 1 An optical measurement method with an optical measurement apparatus including an irradiation optical system and a measurement optical system, the irradiation optical system being configured to linearly irradiate a measurement target with measurement light having a certain wavelength range, the measurement optical system being configured to output a two-dimensional image by expanding linear measurement interference light in a wavelength direction orthogonal to a longitudinal direction of the measurement interference light, the measurement interference light being transmitted light or reflected light originating from the measurement target as a result of irradiation with the measurement light, the optical measurement method comprising: obtaining a distribution of actually measured values when angles of incidence are different for an identical sample; calculating a modification factor depending on an angle of incidence on the measurement optical system from each measurement point in association with a region in the two-dimensional image corresponding to each measurement point in the measurement target irradiated with the measurement light; and calculating optical characteristics including a refractive index of the sample based on a group of pixel values in one row or a plurality of rows along any one direction in the distribution of the actually measured values and corresponding modification factors. ### Claim 2 (depends on 1) The optical measurement method according to claim 1, wherein the calculating optical characteristics includes calculating film thicknesses at a plurality of positions in the distribution of the actually measured values based on a set refractive index, a modification factor corresponding to each position, and a group of pixel values in a wavelength direction at each position, calculating a film thickness dispersion which is a dispersion of the calculated film thicknesses, repeating the calculating film thicknesses and the calculating a film thickness dispersion, with the refractive index of the sample being set to a plurality of different values, and determining a refractive index of the sample based on the calculated film thickness dispersion. ### Claim 3 (depends on 2) The optical measurement method according to claim 2, wherein the determining a refractive index of the sample includes determining a refractive index at which the calculated film thickness dispersion becomes small as a refractive index of the sample. ### Claim 4 (depends on 2) The optical measurement method according to claim 2, wherein the determining a refractive index of the sample includes fitting a polynomial representing a predetermined film thickness dispersion to relation between a refractive index and a film thickness dispersion, and determining a refractive index of the sample based on a point at which the film thickness dispersion represented by the polynomial determined by fitting takes an extreme value. ### Claim 5 (depends on 2) The optical measurement method according to claim 2, wherein the determining a refractive index of the sample includes fitting a polynomial representing a predetermined squared residual value to relation between a refractive index and a squared residual value for the calculated film thicknesses, and determining a refractive index of the sample based on a point at which the squared residual value represented by the polynomial determined by fitting takes an extreme value. ### Claim 6 (depends on 2) The optical measurement method according to claim 2, wherein a refractive index of the sample is calculated in accordance with a prescribed wavelength dispersion formula, and the determining a refractive index of the sample includes applying a least squares method to any of relation between each coefficient defining the wavelength dispersion formula and a film thickness dispersion and relation between each coefficient defining the wavelength dispersion formula and a squared residual value, and determining a refractive index of the sample based on a set of coefficients when the film thickness dispersion or the squared residual value takes an extreme value. ### Claim 7 (depends on 1) The optical measurement method according to claim 1, wherein the calculating optical characteristics includes calculating a distribution of actually measured values exhibited by a group of pixel values in a position direction for any wavelength in the distribution of the actually measured values, calculating a distribution of theoretical values for the any wavelength based on a film thickness and a refractive index of the sample that are set in advance and a modification factor corresponding to each position, and determining a film thickness and a refractive index of the sample so as to decrease an error between the distribution of the theoretical values and the distribution of the actually measured values. ### Claim 8 (depends on 7) The optical measurement method according to claim 7, wherein the calculating optical characteristics includes determining a refractive index of the sample for each of a plurality of wavelengths in the distribution of the actually measured values. ### Claim 9 (depends on 7) The optical measurement method according to claim 7, wherein the calculating optical characteristics includes calculating film thicknesses of the sample for a plurality of wavelengths in the distribution of the actually measured values based on the error between the distribution of the theoretical values and the distribution of the actually measured values, and determining a more probable film thickness based on the calculated film thicknesses. ### Claim 10 (depends on 7) The optical measurement method according to claim 7, wherein the refractive index of the sample used for calculation of the distribution of the theoretical values is calculated in accordance with a prescribed wavelength dispersion formula, and the calculating optical characteristics includes fitting each coefficient defining the prescribed wavelength dispersion formula and the film thickness so as to decrease errors between the distribution of the theoretical values and the distribution of the actually measured values for a plurality of wavelengths in the distribution of the actually measured values. ### Claim 11 An optical measurement apparatus comprising: an irradiation optical system configured to linearly irradiate a measurement target with measurement light having a certain wavelength range; a measurement optical system configured to output a two-dimensional image by expanding linear measurement interference light in a wavelength direction orthogonal to a longitudinal direction of the measurement interference light, the measurement interference light being transmitted light or reflected light originating from the measurement target as a result of irradiation with the measurement light; and a processing device configured to obtain a distribution of actually measured values when angles of incidence are different for an identical sample, calculate a modification factor depending on an angle of incidence on the measurement optical system from each measurement point in association with a region in the two-dimensional image corresponding to each measurement point in the measurement target irradiated with the measurement light, and calculate optical characteristics including a refractive index of the sample based on a group of pixel values in one row or a plurality of rows along any one direction in the distribution of the actually measured values and corresponding modification factors.