In this paper, the imaging ability of terahertz wave in time-domain spectroscopy (THz-TDS) imaging system is assessed
by using the step-by-step scan imaging method to four small structures: thread, dots, round hole, and square on the focus
of the imaging system. We utilize THz-TDS energy imaging model to acquire the energy distribution of terahertz wave
passing through the different small structure, which can be use as a criterion of imaging ability. Theoretically, terahertz
imaging technology possesses highly spatial resolution because the size of spot is inversely proportional to the
frequency. Our experimental results also show that THz-TDS technology has a preferable spatial resolution on the
millimeter scale. In addition, a more delicate and smooth image can be obtained by means of the nearest neighbor
interpolation algorithm. A method to measure the size of target is provided. These results are important references for the
further terahertz spectroscopy imaging research.
Beam profile and spectral characteristic of terahertz (THz) wave in free space are presented in this paper. The beam
width of THz wave at the focus point of parabolic mirror is obtained by means of the narrow-slit measurement. By the
spectroscopic imaging, we present the transverse mode distribution of THz beam on the cross-section of focus point. Our
experimental results show that the centre wavelength of THz spectra has a distinguished red-shift when it is far away the
centre of THz focus point. The spectral range of THz wave far from the focus point is less than that of the centre. This
kind of spectral characteristic of THz wave is closely related to the diffraction effect of electromagnetic wave.