Some Complementary Results to the Granularity of Industrial

Abstract

Bundesanstalt für Materialprüfung, Unter den Eichen 87, D-100 Berlin 45. ABSTRACT Measurements of Wiener spectra and related quantities of industrial x-ray films were made by varying the parameters density, film-type, developer, energy of x-rays and light exposure. Relations derived for light exposure were found to be valid for x-rays and x-ray films too. There exists however a strong dependence of film granularity on the kind of developer, a fact, which in its consequences excludes film speed as a universal film measure. While the spectral distribution of a Wiener spectrum varies with the energy of the exposing x-rays, its integral value a² proves to be a constant for a given density and film at least in the investigated energy range between 10-400 keV. This rule is broken only for x-ray energies below 100 keV for sensitive film types by interference of their so called z-ampiification, which at higher energies however is dominated by the effects causing the spread function. As discrepancies between the MTF for a given x-ray energy and the shape of the corresponding Wiener spectrum, which is expected to vary with (MTF)², show, it is necessary to distinguish between the well known spread functions measured with slits and edges and a much narrower "hit-spread-function" suggested first in this paper. The last could be estimated from the difference between the Wiener spectra of a film exposed to x-rays and light respectively.

Finally the ratio γ/σ² is suggested as a quantity which can help to characterize a film independent of x-ray energy and density. A theoretical explanation and experimental evidence of this quantity is given.