Abstract

A general analysis is given of the influence of stochastic amplifying and scattering mechanisms on the transfer of signal modulation and noise in imaging processes. A moment generating function approach allows us to obtain fundamental relationships for signal and noise that connect one stage of an imaging process to the next. In this way imaging systems of any complexity can be easily described by cascading the appropriate number of elementary stages. We have used this analysis to quantify the spatial-frequency dependence of signal and noise as they propagate through a multistage imaging system. It has been shown that although signal modulation to any stage of the system must pass through the modulation transfer function of that stage, uncorrelated input photon noise does not do so. Amplification of photon noise in one stage, however, can produce a noise structure that is correlated and thereby constitutes an effective signal spectrum to subsequent stages. Thus, in general, it is necessary to cascade these two components of the noise spectrum separately at each stage, and the formalism for doing so has been presented. As an example this formalism has been used to confirm previous physical arguments used in the derivation of an overall DQE model for a radiographic screen-film system.

© 1986 Optical Society of America