Coherent reconstruction of a textile and a hidden object with terahertz radiation

Lorenzo Valzania, Peter Zolliker, Erwin Hack 

Optica Vol. 6,Issue 4,pp. 518-523, (2019)

https://doi.org/10.1364/OPTICA.6.000518

Abstract
 Imaging through scattering materials is of utmost importance, especially for security and biomedical imaging. Unlike the rest of the electromagnetic spectrum, terahertz radiation is a non-ionizing probe and allows imaging deep through non-conducting materials with sub-millimeter resolution. Here, we propose a coherent imaging technique reconstructing two objects, hidden one behind the other, from relative shifts between them. Experimental reconstructions at ??=96.5 μm of amplitude and phase objects hidden behind a glass fabric sample are presented. The hidden objects are retrieved with a lateral resolution of  ≈1.5λ and a depth resolution of ≈λ/10. Besides envisioning its use in non-invasive imaging, we anticipate that, in selected applications, the suggested approach can replace a similar phase retrieval technique, namely ptychography.