抄録
Laser ultrasonic testing realizes non-contact and non-destructive inspection for various fields such as infrastructures and medicals.
A microchip laser is known as an ultra-compact solid-state laser with high power and single mode oscillation. Moreover, a self-optical
mixing interferometry is known as a new interference method using only a few optics. The self-optical mixing interferometry
combined with microchip laser makes an ultra-compact laser ultrasonic testing system possible. However, the microchip laser has
inherent noise depends on its crystal material, which overlaps ultrasonic signal. This noise occurs in a specific frequency band, and
it can be avoided by using a frequency filter and a frequency shifter. As a result, the ultrasonic signal can be extracted from the mess
signal containing the noise. In this article, we will introduce the mechanism of a laser ultrasonic measurement using a microchip
laser and a self-mixing interferometer, and how to control its inherent noise, using the ultrasonic measurement generated by a piezo
as an example.
