Self-adaptive all-fiber laser ultrasonic measuring instrument

A self-adaptive all-fiber laser ultrasonic measuring instrument, comprising:

• a narrow-linewidth semiconductor fiber laser;
• a first fiber polarization controller;
• a first fiber polarization beam splitter;
• a first fiber circulator;
• a second fiber polarization controller;
• an interferometer;
• a wavelength division multiplexer;
• an indication laser;
• a fiber collimator;
• a biaxial scanning galvanometer;
• a light converging collector;
• a collimating lens;
• a second fiber circulator;
• and a third fiber polarization controller, wherein an output terminal of the narrow-linewidth semiconductor fiber laser is connected to an input terminal of the first fiber polarization controller and the first fiber polarization beam splitter, an output terminal of the first fiber polarization beam splitter is connected to a first port of the first fiber circulator, a second port of the first fiber circulator is connected to one end of the interferometer through the second fiber polarization controller, the other output terminal of the first fiber polarization beam splitter and the indication laser are jointly connected to two input terminals of the wavelength division multiplexer, an output terminal of the wavelength division multiplexer is connected to the fiber collimator, an output collimated beam of the fiber collimator is irradiated to a sample under test through the biaxial scanning galvanometer, the light converging collector is disposed above the sample under test, the light converging collector receives a scattered light from the sample under test and then enters the collimating lens, the collimating lens is connected to a first port of the second fiber circulator, and a second port of the second fiber circulator is connected to the other end of the interferometer through the third fiber polarization controller,
• wherein,
• the narrow-linewidth semiconductor fiber laser emits a continuous laser, which is polarized by the first fiber polarization controller to form orthogonally and linearly polarized light with p-polarization state and s-polarization state, and is split by the first fiber polarization beam splitter to form linearly polarized light with the p-polarization state and linearly polarized light with the s-polarization state,
• the linearly polarized light in the s-polarization state serves as a reference light, the reference light is incident into the second fiber polarization controller through the first fiber circulator, and is input into the interferometer after being polarized by the second fiber polarization controller,
• the linearly polarized light in the p-polarization state serves as a detection light, the detection light and a visible light output by the indication laser are jointly multiplexed by the wavelength division multiplexer and then input to the fiber collimator, the fiber collimator outputs a spatial free light, the spatial free light generates ultrasonic vibrations when being irradiated on the sample under test after passing through the biaxial scanning galvanometer, and scattered on a surface of the sample under test to generate a scattered light modulated by the ultrasonic vibrations, the scattered light is collected and converged by the light converging collector and then incident on the collimating lens, and becomes a signal light after passing through the collimating lens, the signal light is incident into the third fiber polarization controller through the second fiber circulator, and is input into the interferometer after being polarized by the third fiber polarization controller,
• both the reference light and the signal light are reflected and transmitted in the interferometer,
• the signal light transmitted by the interferometer and the reference light reflected by the interferometer are combined and incident into the first fiber circulator through the second fiber polarization controller, and are output from a third port of the first fiber circulator, and
• the reference light transmitted by the interferometer and the signal light reflected by the interferometer are combined and incident into the second fiber circulator through the third fiber polarization controller, and are output from a third port of the second fiber circulator.