A theory is presented concerning the spatial light-energy fluctuation in a photographic emulsion placed in intimate contact with a fluorescent screen that is excited by x rays. For simplicity, the fluorescent screen is assumed to be irradiated with monoenergetic x rays. Formulas have been developed for the average light energy received by the emulsion, the autocorrelation function, and the Wiener spectral density associated with the fluctuation of light energy about the average value.
For a linear, time-invariant electrical network, the transfer function can be determined by means of a white-noise input. Theoretical considerations indicate that an analogous method is not valid for fluorescent-screen–film systems. This point is illustrated only analytically for a homogeneous fluorescent screen which consists of a thin, but large, macrocrystal of calcium tungstate.
The recording of the fluctuations of light energy as variations of optical density by the photographic film is discussed quantitatively.
© 1968 Optical Society of AmericaFull Article | PDF Article
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