We present a terahertz (THz) imaging system with a Backward Wave Oscillator (BWO). BWO Continuous-Wave
THz imaging is a new approach to non-destructive testing. Many materials that are opaque to visible and infrared light
are transparent to THz radiation. THz wave image provides a higher spatial resolution than microwave image by having
much shorter wavelength. It also poses no known harm to living organisms, making it a safe and powerful imaging
technology. Unlike pulsed THz imaging, BWO THz imaging only yields intensity data without providing any depth,
frequency-domain or time-domain information about the subject. However, in most cases the energy plots are sufficient
for identification of targets. In exchange for the loss of depth, time-domain and frequency-domain information, BWO
imaging offers a simple, fast and relatively low-cost system. In this work we show a simple Terahertz (THz)
2-dimentional scanning imaging system utilizing a BWO source tunable from 0.52 to 0.71 THz and a pyroelectric sensor
detector operated in THz range. The sample is placed on an X-Z two-dimensional stage controlled by a computer. The
intensity information of the terahertz wave after passing sample is collected. Two-dimensional image of the sample is
obtained by raster scanning the sample in X and Z directions. A number of potential imaging applications are
demonstrated using the 0.71 THz radiation, including nondestructive real-time testing for campus debit card and various
articles contained in an envelop. And we present the digital image processing based on the result of the imaging system.
This work reveals that a BWO THz imaging system is very practical, effective and promising in nondestructive
identification and security inspections applications in future.