ABSTRACT
In some imaging applications, one cannot measure the scattered field itself, for example at very high frequencies . Above ~1 THz we do not have detectors fast enough to measure the fluctuating field and all we acquire is a time averaged quantity . In electromagnetic problems we assume this is proportional to the magnitude squared of the (electric) field, |E|2 . As we shall see, the information required to solve the inverse problem and calculate an image of the object demands that we solve another problem, namely that of estimating from |E|, the function E = |E| exp(iϕ) or solve the so-called phase-retrieval problem (ϕ denotes phase) . This is also nontrivial and, without knowledge of the phase, the information we can recover about the object is severely limited and at best statistical in nature .
