Fig. 6
From: Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation
Representative applications of other materials using PA technologies for NDT/E. (a): PA detection of underdrawings in paintings [40]. (i) Brightfield view of the painting (rural landscape), (ii) PA image of the underlying sketch of the painting over a region indicated by the white box in (i), (iii) NIR image of the underdrawing at 1200 nm, and (iv) Brightfield view of the original pencil sketch before overpainting. Scale bar = 1 cm; (b): SIR measurement of ultrasound transducers using PA method [51]. 2D acoustic intensity profile of a 93 MHz focused transducer on x-y plane at z = 6.2, 6.5, and 6.8 mm (top). Comparison of the PA-measured and calculated results (bottom), showing good agreement. The PA-measured results mean the acoustic intensity distribution measured by the PA method (denoted as “PA” in the legend); the calculated results mean the acoustic intensity distribution calculated by the angular spectrum approach (ASA) based on PA-measured SIR (denoted as “ASAPA” in the legend)