## 5 Conclusions  
In this paper we characterize a THz-TDS system based on PCAs. We evaluate the performances of the system such as its spectral range emission and spatial resolution. Moreover, we reconstruct the 1D and 3D profiles of our THz beam, with two different methods: hole and knife edge. Both methods gave results that are in great accordance. Finally, we present a very simple and cheap resolution test that can be done with a linen pattern sample. We demonstrated that our system has the capability to spatially resolve objects with dimensions from \(\sim\)1.3 to \(\sim\)0.3 mm in the frequency range 0.5-2.5 THz, with a resolution of \(\sim\)0.7 mm at 1 THz. Finally, with the help of the experimental PSF, we show that the THz image quality can be considerably improved. The following are available online at [[https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)]([https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)) 7/11/2/562/s1, Figure S1: THz electric field vs. time, Figure S2: THz power spectrum vs. frequency, Figure S3: THz image background noise at 1.0 THz, Figure S4: THz image SNR vs. frequency, Figure S5: THz Linen Transmittance. Conceptualization, M.D.F., A.D. and S.L. ; formal analysis, M.D.F. and A.D.; writing--original draft preparation, M.D.F., A.D. and S.L. ; writing--review and editing, M.D.F., A.D., S.M., L.P., M.P. and S.L. ; supervision, S.L. ; project administration, S.L. ; funding acquisition, S.L. All authors have read and agreed to the published version of the manuscript. This research was funded by INFN, in the framework of Commissione V Call THz-ERA (TERA). The data presented in this study are available in \"Performance Evaluation of a THz Pulsed Imaging System: Point Spread Function, Broadband THz Beam Visualization and Image Reconstruction\" and in Supplementary Materials. Figure 10: Images used for deconvolution process. (**a**) Object image: 1.3 THz linen image, (**b**) PSF image: 200 μm pinhole at 1.3 THz, (**c**) Restored image: deconvolution of (**a**) and (**b**). The scale bar is 0.3 mm for (**a**) and (**c**) and 1 mm for (**b**). (**d**) Intensity profile of original (blue) and deconvolved (orange) images. (**e**) Derivative of original (blue) and deconvolved (orange) images. The selected regions for intensity profiles and derivatives are indicated with red boxes in (**a**) and (**c**). D\({}_{1}\) and D\({}_{2}\) in (**e**) indicate the differences between derivative maximum and minimum for original and deconvolved images. * _[PERSON] et al. (2018)_ [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON] Quality control and authentication of packaged integrated circuits using enhanced-spatial resolution terahertz time-domain spectroscopy and imaging. _Opt. Lasers Eng._**2018**, _104_, 274-284. [CrossRef]
* _[PERSON] et al. (2013)_ [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Imaging of broadband terahertz beams using an array of antenna-coupled microbolometers operating at room temperature. _Opt. Express_**2013**, _21_, 4817-4825. [CrossRef]
* _[PERSON] (2014)_ [PERSON]; [PERSON] Terahertz brightness at the extreme: Demonstration of a 5 GV/m, 17 T low frequency \(\uplambda\)3 terahertz bullet. _arXiv_**2014**, arXiv:1407.1656. * _[PERSON] et al. (2016)_ [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; et al. Strong spatial confinement of terahertz wave inside femtosecond laser filament. _ACS Photonics_**2016**, \(3\), 2338-2343. [CrossRef]
* _[PERSON] et al. (2013)_ [PERSON]; [PERSON]; [PERSON] Spatio-spectral characteristics of ultra-broadband THz emission from two-colour photoexcited gas plasmas and their impact for nonlinear spectroscopy. _New J. Phys._**2013**, _15_, 075023. [CrossRef]
* _[PERSON] (2007)_ [PERSON]; [PERSON] _Fundamentals of Photonics_; John Wiley and Sons: Hoboken, NJ, USA, 2007. * _[PERSON] (2014)_ [PERSON]; [PERSON] New opportunities for quality enhancing of images captured by passive THz camera.