CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Phase application of PCT/JP2018/046266 filed Dec. 17, 2018, which claims priority to Japanese Patent Application No. 2018-006528, filed Jan. 18, 2018, the disclosures of these applications being incorporated herein by reference in their entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to a spectroscopic analysis apparatus, a spectroscopic analysis method, a steel strip production method, and a steel strip quality assurance method that are to be used for analyzing either or both of the composition and the composition ratio of the surface of a measurement target object.

BACKGROUND OF THE INVENTION

Patent Literature 1 describes a method for analyzing the composition of the surface of a measurement target object. Specifically, the method described in Patent Literature 1 measures, while p-polarized light polarized in parallel to an incident plane and s-polarized light polarized perpendicularly to the incident plane are caused to enter the surface of a measurement target object, the intensity ratio between reflection spectra from these beams of light. The method described in Patent Literature 1 then analyzes the composition of the surface of the measurement target object by dividing the measured intensity ratio by the intensity ratio previously measured with respect to a standard sample between the reflection spectra of p-polarized light and s-polarized light.

PATENT LITERATURE

Patent Literature 1: Japanese Patent No. 3637192

SUMMARY OF THE INVENTION

The method described in Patent Literature 1 assumes that the reflectance of s-polarized light at the incident plane is approximately 1 while using a gold mirror as a reference, and refers to table data to find the reflection spectrum intensity of s-polarized light. That is, the method, described in Patent Literature 1, calculates the intensity ratio substantially based on measurement of the reflection spectrum intensity of p-polarized light only. Therefore, the method described in Patent Literature 1 fails to calculate the intensity ratio with high accuracy when the reflection spectrum intensity of s-polarized light is changed by a disturbance. The method consequently fails to analyze the composition of the surface of a measurement target object with high accuracy. Here, examples of the disturbance are (1) a change in reflection intensity from a measurement target object caused by a change of liftoff or surface roughness, (2) a change of an atmosphere in optical path such as CO2or steam, (3) dirt on the mirror or a fluctuation of intensity of a light source, and (4) vibration or a shape defect of a measurement target object.

A measurement sequence considered applicable for measuring the reflection spectrum intensity of s-polarized light is to repeat alternately measuring the reflection spectrum intensity of s-polarized light and the reflection spectrum intensity of p-polarized light. However, this measurement sequence requires repeating measuring the reflection spectrum intensity of s-polarized light, switching polarizers, measuring the reflection spectrum intensity of p-polarized light, and switching the polarizers. In this measurement sequence, if a measurement target object is moving, it is also a disturbance because measurement on the same position is not possible. Additionally, it is not possible to eliminate a disturbance such as vibration of a measurement target object.

Furthermore, when the number of times of switching polarizers is increased, measurement cycles are limited by process time of switching the polarizers. As a result, an unmeasurable area where passed during the time of switching polarizers is increased.

Aspects of the present invention have been made in consideration of the above inconveniences, and one objective is to provide a spectroscopic analysis apparatus and a spectroscopic analysis method that enable either or both of the composition and the composition ratio of the surface of a measurement target object to be analyzed with high accuracy even when a disturbance is present. Another objective according to aspects of the present invention is to provide a steel strip production method that enables a steel strip having either or both of a desired surface composition and a desired surface composition ratio to be produced with a high yield. Still another objective according to aspects of the present invention is to provide a steel strip quality assurance method that enables a high-quality steel strip to be provided.

To solve the problem and achieve the object, a spectroscopic analysis apparatus according to aspects of the present invention includes: a light projecting unit configured to project infrared light to a measurement target object; a light receiving unit configured to receive, as reflected light, the infrared light reflected by a surface of the measurement target object; and an output unit configured to calculate either or both of a composition and a composition ratio of the surface of the measurement target object using the reflected light received by the light receiving unit, wherein the light receiving unit includes: a separator configured to separate the reflected light into s-polarized light and p-polarized light; a detector for s-polarized light configured to detect s-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the s-polarized light to the output unit; and a detector for p-polarized light configured to detect p-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the p-polarized light to the output unit; and the output unit is configured to: calculate an absorbance based on a ratio between the intensities of the s-polarized light and the p-polarized light using the electric signals output from the detector for s-polarized light and the detector for p-polarized light; and calculate either or both of the composition and the composition ratio of the surface of the measurement target object using an intensity of the absorbance at any desired wavenumber.

Moreover, the spectroscopic analysis apparatus according to aspects of the present invention further includes a distance measuring unit configured to measure a distance between a position irradiated with the infrared light on the measurement target object and a spectroscopic measurement apparatus, wherein the output unit corrects the absorbance in accordance with values measured by the distance measuring unit.

Moreover, a spectroscopic analysis method according to aspects of the present invention includes: a step of projecting infrared light to a measurement target object; a step of receiving, as reflected light, the infrared light reflected by a surface of the measurement target object; and a step of outputting that calculates either or both of a composition and a composition ratio of the surface of the measurement target object using the reflected light received at the step of receiving, wherein the step of receiving includes: a step of separating the reflected light into s-polarized light and p-polarized light; a step of detecting s-polarized light obtained through the step of separating, and outputting an electric signal that indicates an intensity of the detected s-polarized light; and a step of detecting p-polarized light obtained through the step of separating, and outputting an electric signal that indicates an intensity of the detected p-polarized light; and the step of outputting includes a step of: calculating an absorbance based on a ratio between the intensities of the s-polarized light and the p-polarized light using the electric signals output at the step of detecting s-polarized light and at the step of detecting p-polarized light; and calculating either or both of the composition and the composition ratio of the surface of the measurement target object using an intensity of the absorbance at any desired wavenumber.

Moreover, a steel strip production method according to aspects of the present invention includes: a step of producing a steel strip; and a step of analyzing either or both of a composition and a composition ratio of a surface of the steel strip produced at the step of producing using the spectroscopic analysis method according to aspects of the present invention.

Moreover, a method of assuring steel strip quality according to aspects of the present invention includes: a step of analyzing either or both of a composition and a composition ratio of a surface of a steel strip using the spectroscopic analysis method according to aspects of the present invention; and a step of conducting quality assurance of the steel strip based on an analysis result obtained at the step of analyzing.

The spectroscopic analysis apparatus and the spectroscopic analysis method according to aspects of the present invention enable either or both of the composition and the composition ratio of the surface of a measurement target object to be analyzed with high accuracy even when a disturbance is present. A steel strip production method according to aspects of the present invention enables a steel strip having either or both of a desired surface composition and a desired surface composition ratio to be produced with a high yield. A steel strip quality assurance method according to aspects of the present invention enables a high-quality steel strip to be provided.

