Analysis of Intensity Modulated Pulse Train Length for Laser Ultrasonic NDT
The use of modulated laser pulses to generate ultrasonic tonebursts has been demonstrated in recent years for improving the signal to noise ratio of laser generated ultrasound waves . Q-switched laser pulses generate broadband signals that can be difficult to measure because statistically, white noise is also broadband. If narrowband ultrasound can be generated then bandpass filters can be used to narrow the bandwidth of the ultrasonic reception system, the signal to noise ratio is inversely proportional to bandwidth, so signal enhancement can be achieved by using modulation. This is the primary motivation for modulating laser pulses in ultrasonic nondestructive testing.