Indirect holographic imaging at 310 GHz

We present an indirect holographic imaging technique, which can be used, e.g., in airport check-in security. In this method, only amplitude detection is required - easing the challenges often encountered in active imagers requiring complex field measurement. The imaging is based on back-propagation of complex electric field reconstructed at a rectangular aperture of the imager. The complex field at the aperture is retrieved by applying a reference wave, which creates an interference pattern, a hologram, with the wave reflected from the target. The method presented also allows for use of reference wave other than a plane wave. We present a setup, with which details of size of 2 mm are discernable at a distance of 1.5 m from the aperture, indicating reasonably high cross-range resolution.