Terahertz digital holographic imaging of visibly opaque printed dielectrics

Terahertz digital off-axis holography has been demonstrated as a non-destructive imaging tool for three-dimensional (3D) printed structures. Digital holographic reconstructions from two structures were used to measure the imager´s modulation transfer function and to show that terahertz digital holography can provide submillimeter resolution images of visually opaque printed structures and map their interior. As a demonstration we report on the detection of embedded air voids and material inclusions that differ from the host material in their complex refractive indices.