Fig. 1
From: Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation
PA technologies for NDT/E. a: NDT/E with modulated CW laser for PA wave excitation (NDT/E with modulated CW laser for PA wave excitation section); (b): NDT/E with pulsed laser for PA wave excitation (NDT/E with pulsed laser for PA wave excitation section) (left) and illustration of the PA A-line signal (right). A flat or focused piezoelectric transducer can be used. (b.1): PA A-line and simple imaging; (b.2): PACT; and (b.3): AR-PAM (left) and OR-PAM (right). In (b), transmission mode is plotted for easy illustration. Note that OR-PAM in (b.3) can also be realized using a modulated CW laser; (c_: NDT/E with PA-generated US waves (NDT/E with PA-generated US waves section)