Practical dual-band terahertz imaging system.

This paper introduces a dual-band terahertz imaging system as a potential product for nondestructive testing using heterodyne detectors and continuous-wave sources. The operating frequencies of the system are 110.4 and 220.8 GHz. Multiband fusion technology combines the advantages of the greater spatial resolution of the high-frequency band and the enhanced sensitivity of the low-frequency band to improve the detection ability of the system. Additionally, the interference cancellation technology is used to obtain a superior image quality. The spatial resolution of this system was approximately 3 mm. The results show that the system can be used for bonding quality and embedded defect detection in radomes and foam materials adhered to metal plates in aircrafts.