A solid-state harmonic generator sub-THz source based on a DRO with output power of 6 mW at 300 GHz and 3 mW at 150 GHz was used to mount a home made Terahertz imaging system. In general, the incoming THz radiation is modulated by a mechanical chopper between 0.233 to 5 kHz, collimated and focused by off-axis parabolic mirrors. A red LED (or laser) in combination with an indium tin oxide (ITO) mirror is used for the alignment of the THz beam.