Material thickness measurement method and apparatus
View Patent ↗Longitudinal and shear ultrasonic waves are generated inside a material by irradiating a laser beam onto a first surface, e.g., incident surface, of the material. An ultrasonic longitudinal wave and a mode converted wave reflected by a second surface, e.g., a bottom surface, of the material are detected, and times of flight of the ultrasonic longitudinal wave and the mode converted wave are measured. A thickness of the material is measured based on the times of flight and a correlation, obtained in advance, between longitudinal and shear wave velocities of the material and temperature of the material.
1. A material thickness measuring apparatus, comprising:
a laser irradiating device that irradiates a laser beam onto a first surface of a material and thereby generates ultrasonic waves inside the material;
an ultrasonic wave detector that detects an ultrasonic longitudinal wave and a mode converted wave reflected by a second surface of the material, and outputs a detection signal;
a time of flight measuring device that measures times of flight, in the material, of the ultrasonic longitudinal wave and the mode converted wave based on the detection signal; and
a calculator that calculates a thickness of the material based on the times of flight and a correlation, which was obtained in advance, between longitudinal and shear wave velocities of the material and temperature of the material.
2. The material thickness measuring apparatus as set forth in claim 1 ,
wherein the ultrasonic wave detector comprises a laser oscillation device and an optical interferometer.
3. The material thickness measuring apparatus as set forth in claim 1 , wherein a position at which a laser beam is irradiated by the laser irradiation device and a position at which the ultrasonic wave detector performs ultrasonic wave detection are substantially the same position.
4. The material thickness measuring apparatus as set forth in claim 1 , wherein a position at which a laser beam is irradiated by the laser irradiation device and a position at which the ultrasonic wave detector performs ultrasonic wave detection are separated by a separation distance.
5. The material thickness measuring apparatus as set forth in claim 4 , wherein the separation distance is in a range of from about 1 mm to about 12 mm.
6. The material thickness measuring apparatus as set forth in claim 4 , wherein the separation distance is in a range of from about 2 mm to about 8 mm.
7. A metal manufacturing line having the material thickness measuring apparatus of claim 1 incorporated therein.
8. A method of measuring a material thickness, comprising:
generating ultrasonic waves inside a material by irradiating a laser beam onto a first surface of the material;
detecting an ultrasonic longitudinal wave and a mode converted wave reflected by a second surface of the material, and outputting a detection signal;
measuring times of flight, in the material, of the ultrasonic longitudinal wave and the mode converted wave based on the detection signal; and
calculating a thickness of the material based on the times of flight and a correlation, which was obtained in advance, between longitudinal and shear wave velocities of the material and temperature of the material.