Intensity-only reconstruction algorithm for diffraction tomography

Several inversion algorithms for diffraction tomography have previously been provided in a wide range of situations where the first-order Born or Rytov approximation fails. These algorithms are based on the assumption of full field data so that it is assumed that both intensity and phase of the scattered field are measurable. However, it becomes difficult to measure the phase of the scattered field directly, if the frequency of the incident wave is beyond several tens of GHz. Therefore, some intensity-only reconstruction algorithms for the objects within the first-order Born or Rytov approximation were proposed. The present authors give an intensity-only reconstruction algorithm for the scatterers beyond the first-order Born approximation. This algorithm is based on the optimization method minimizing a functional which is the norm of the discrepancy between the measured intensity of the total field in the far-zone and the calculated one for an estimated object function. An outer boundary of the scatterer is used as a priori knowledge at each step of iteration. The proposed algorithm is an extension of Takenaka et al. (1993).