94-GHz Imager With Extended Depth of Field

We describe a computational imaging technique to extend the depth-of-field of a 94-GHz imaging system. The technique uses a cubic phase element in the pupil plane of the system to render system operation relatively insensitive to object distance. However, the cubic phase element also introduces aberrations but, since these are fixed and known, we remove them using post-detection signal processing. We present experimental results that validate system performance and indicate a greater than four-fold increase in depth-of-field from 17” to greater than 68”.