Fig. 1. Schematic of terahertz imaging system

Fig. 2. Optical photo of the lacquer box

Fig. 3. Defect analysis of different interfaces. (a) Schematic of depth profiling by time domain imaging; (b) schematic of terahertz time-of-flight imaging

Fig. 4. Terahertz imaging analysis of lacquer box lid. (a) Surface reflection intensity on the surface of the lacquer box lid; (b) terahertz time domain waveform on the surface of the lacquer box lid