Millimeter waves imaging systems have many applications in medicine, communications, homeland security, and space technology. The advantages of MMW includes high penetrates thru almost every dielectric materials and no known ionization hazard for biological tissue, and low atmospheric scattering compared to infrared and optical rays. The Glow Discharge Detector (GDD) is a low cost room temperature MMW detector based on a commercial neon indicator lamp. Previously the GDD was proven to be very sensitive and inexpensive MMW radiation detector capable of direct and heterodyne radiation detection. Focal Plane Arrays (FPA) of GDD pixels were constructed and experimentally tested. In those experiments, the change in the DC bias current of the GDD was measured as function of the incidence MMW radiation. In this work the up-conversion of MMW radiation to visual light is demonstrated. By using a CCD/CMOS camera and GDD FPA a faster, more sensitive, and very inexpensive MMW and THz imaging system can be implemented. Also it is shown that by using the up converting method a real time 2D and 3D images can be obtained. 3D imaging system can provide the topography of the object plane in addition to intensity reflected from the image. Preliminary experimental results of an imaging system based on a unique quasi optical system, an 8×8 GDD's focal plane array (FPA), and a CCD camera is demonstrated. Also it is shown that the MMW images can be obtained in Real time.