Portability, low cost and fast acquisition rates are key features that a THz imaging system should satisfy for extended commercialized applications. With regards to these features, the source - detector association of a THz Quantum Cascade Laser (QCL) with an un-cooled micro-bolometer two-dimensional array looks promising for THz active imaging. QCLs performance is rapidly improving, with higher operating temperatures and output powers recently demonstrated. On the detector side, un-cooled micro-bolometer array opens the way to real-time video rate, with no raster scanning and potential low cost. In parallel to the development of room temperature micro-bolometer sensors specifically designed for the THz range, the authors have characterized experimentally the sensitivity of CEA-LETI standard amorphous Silicon infrared microbolometers illuminated by a 3THz QCL. The sensitivity of these existing sensors is then compared to the expected sensitivity of the CEA-LETI upcoming THz sensors.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.