Fig. 4.

(a) Boehler star target where each petal is filled by a different chemical powder, including $\alpha$ -lactose, HDPE, 3HBA, riboflavin, and PABA. The Boehler star is covered with a diffusive cloak with 0.3 $\text{g}/{\text{cm}}^3$ volume density. (b) $\epsilon$ of the chemicals measured without a scattering layer in the beam path. The black arrows mark the resonant frequencies. (c) $\beta$ of the images formed using $\epsilon$ (orange line) and the images formed using $\sum _{j=3}^6{\tilde{D}}_j$ (blue line). (d)-(h) Images formed using different combinations of ${\tilde{D}}_j(f)$ at the resonant frequencies, including $\sum _{j=3}^6{\tilde{D}}_j$ (0.53 THz) in (d), $\sum _{j=3}^6{\tilde{D}}_j$ (0.6 THz) in (e), ${\tilde{D}}_4$ (0.8 THz) in (f), ${\tilde{D}}_5$ (0.8 THz) in (g), and ${\tilde{D}}_6$ (1.03 THz) in (h).