600-GHz-band Terahertz Imaging Scanner System with Enhanced Focal Depth

Long focal depth property of lens/mirrors is of practical importance in terahertz (THz) imaging systems where the sample position is usually uncertain. A 600-GHz-band THz imaging scanner system using an integrated off-axis parabolic (OAP) mirror is presented for this requirement. Both simulation and experiment results show that a spatial resolution of ~2 mm can be achieved at a focal distance of 100 mm. Moreover, owing to the astigmatism of the proposed OAP mirror, a long focal depth of ~170 mm was validated with the imaging experiment. Finally, a real imaging experiment was provided for recognizing the hidden metal object, which can be potentially used for imaging targets at different distances.