Enhancement in terahertz imaging of transparent objects using phase contrast methods in a 4f optical system.

In this study, the optical system designed to improve the visibility of transparent objects using terahertz radiation at a frequency of 260 GHz is presented. The setup employs the specific lens arrangement known as a 4f system. The imaging was performed using the positive and negative phase contrast methods, where dedicated phase filters introduced a phase delay in the central part of the Fourier plane. A significant improvement in contrast for the transparent samples was achieved, with contrast enhancement of 13.51 and 12.90, respectively.