LENS COUPLING EFFICIENCY - DERIVATION AND APPLICATION UNDER DIFFERINGGEOMETRICAL ASSUMPTIONS

The calculation of lens coupling efficiency is often performed in the design of lens coupled digital radiographic systems, now currently und er development. With these systems, an electronic camera is focused on to a planar scintillator such as a conventional intensifying screen. H istorically, this calculation has relied on certain assumptions concer ning the emission properties of the scintillator, and primarily this a ssumption is that the scintillator is either a Lambertian emitter (lig ht is emitted over all angles equally) or a point radiator. Because th ere now exists new classes of scintillators such as scintillating fibe r optic screens and pixelated intensifying screens, it is sometimes ne cessary to perform lens coupling calculations in the absence of the La mbertian and point source assumptions. In this paper we describe the n ecessary equations to accurately calculate lens coupling efficiency in the most general of cases. Graphical examples demonstrate the lens co upling efficiency for hypothetical Lambertian scintillating sources, f or a rare earth intensifying screen, and for a scintillating fiber opt ical screen. (C) 1997 American Association of Physicists in Medicine.