A laser ultrasonic measurement system and method suitable for samples with a wide film thickness range

Abstract

The invention belongs to the related technical field of laser ultrasonic detection, and specifically discloses a laser ultrasonic measurement system and method suitable for samples in a wide film thickness range. The system includes a pulse laser, a pump detection unit, a pulse width regulator, a detector and an industrial computer, wherein: the beam splitter in the pump detection unit divides the pulse laser into an excitation light beam and a detection light beam; the excitation light passes through the pulse The width adjuster irradiates the surface of the sample to be tested and excites an ultrasonic signal, which propagates in the sample to generate an echo signal; the detection light with a delay with the excitation light is reflected by the sample and then received by the detector; the industrial computer receives the electrical signal converted by the detector And extract the echo signal, when the intensity of the echo signal is less than the preset threshold, adjust the pulse width adjuster to the pulse stretching state; when the intensity of the echo signal is greater than or equal to the preset threshold, keep the pulse width adjuster in the compression state. Through the present invention, the film thickness range of the sample to which the laser ultrasonic measurement technique is applicable is enlarged.

Description

technical field [0001] The invention belongs to the technical field of laser ultrasonic detection, and more specifically relates to a laser ultrasonic measurement system and method suitable for samples with a wide film thickness range. Background technique [0002] Laser ultrasonic technology is a new type of ultrasonic testing technology that uses laser to excite and detect ultrasonic waves, and conduct research on ultrasonic propagation and sample characteristics. Since the frequency of the laser ultrasonic signal is inversely proportional to the pulse width of the excitation light, the laser ultrasonic signal with ultrashort pulse laser as the excitation source is usually in the frequency range of GHz to THz, corresponding to a high spatial resolution, especially suitable for micro Characterization and study of nanoscale thin film structures. Therefore, laser ultrasonic measurement technology is also widely used in the thickness measurement, defect detection, characteris...

AI Technical Summary

Problems solved by technology

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a laser ultrasonic measurement system and method suitable for samples with a wide film thickness range, and at the same time solves the problems in the time-domain signal curves existing in the laser ultrasonic measurement of thicker film thickness samples. The problem that the echo signal is difficult to distinguish from the noise, as well as the short interval between adjacent echo signals in the measurement of thinner film samples, which are easy to alias and difficult to distinguish, make the samples with thicker film thickness and thinner film thickness Can be measured uniformly, increasing the film thickness range of samples applicable to laser ultrasonic measurement technology

Images