Wave field imaging for homeland security

We discuss two topics referring to homeland security: identifying concealed objects on persons and assessing the integrity of concrete buildings like bridges. For the first problem electromagnetic millimeter waves apply, and the second problem is tackled with ultrasonic elastic waves. Appropriate imaging algorithms rely on the principle of wave field back propagation of synthetic aperture data obtained from an FMCW sensor in the electromagnetic and from an impulsive excitation in the elastodynamic case; to process the data a Fourier domain diffraction tomographic version of the back propagation algorithm is applied. Results for a weapon concealed under clothing (ceramic knife and metallic pistol) as well as for tendon duct detection in concrete are presented.