Edge contrast in ionography.

The effect of Mylar foil thickness on the appearance of ionography images has been investigated. Approximate expressions for the depletion width of strips and halfplanes of charge are given with supporting experimental measurements. In microdensitometer traces of charged strips and halfplanes the density is shown to be proportional to the vertical field profile of the charge pattern near the Mylar. This work suggests a simple means of altering edge contrast for ionography by using different thicknesses of Mylar. Ionography images of a hand phantom illustrate this effect.