The aim of the project is to develop a THz 2D-imaging device, centered around a femtosecond laser. Toshiba Research Europe Ltd. Below is a THz image obtained in Delft. With visible light, we cannot look inside the egg, but with THz radiation this is a piece of cake, excuse me, chocolate.
Dark shades mean strong absorption, lighter shades mean less absorption.
Below is the image of a yellow marker. Again, lighter shades means less absorption. Generally, many plastics are pretty transparent for THz radiation. The picture is of a screw in a 9 mm piece of wood. The screw was first screwed in and then partially screwed out again, leaving a hollow region underneath the screw.