In this contribution. we present simulations and measurements of a reflector system that can rapidly scan a terahertz beam for a high-resolution standoff-imaging application, without compromising the beam quality. The antenna system utilizes a Gregorian confocal-reflector geometry, with a small mechanical rotating mirror. The system has been successfully fabricated and tested, with THz imagery of targets at a 25 m standoff range being obtained In five seconds. for the current configuration. We also describe how frame rates exceeding 2 Hz can be achieved using a heterodyne array of just a few elements, with or without a multiplexing technique.