A detector model is proposed for the type of detection that occurs with phosphorescent screens or photocathode detection; that is, detection by means of absorption and secondary-emission amplification. The detective quantum efficiency for this type of detector is obtained in the case that the primary stream as well as the production of secondary events from each primary event can be approximated by Poisson distributions. If Q is the average number of secondary events produced from each incident photon, the detective quantum efficiency QD becomes QD=Q/(1+Q).
H. J. ZWEIG, "Detective Quantum Efficiency of Photodetectors with Some Amplification Mechanisms," J. Opt. Soc. Am. 55, 525-528 (1965)