DQE of imaging detectors in terms of spatial frequency

The most inclusive parameter describing the performance of an imaging detector may be considered detective quantum efficiency (DQE) expressed in function of the spatial frequencies. In this paper our effort is addressed to formulating a general and absolute expression of the DQE in the frequency domain, coherent with the condition DQE≤QE. The case of a flat-field input image and of integrating detectors is also considered.