X線撮影系のレスポンス関数
(IV) 増感紙と写真フィルムの組み合わせ
1966 年 35 巻 8 号 p. 559-564
詳細
1966 年 35 巻 8 号 p. 559-564
A proposal is made to define the OTF (optical transfer function) of a screen-film combination which can be treated as linear, as the Fourier transform of a linear combination of effective exposure distributions of line images on each of two emulsion layers one over the other. This composite OTF is given as a product of OTFs of a single coated emulsion film optical scattering between film and screen, and two intensifying screens. The customary OTF which is somewhat ambiguous and non-linear is but an approximation of OTF of the new definition excepting the case of low contrast or low spatial frequency in which the two become the same. The OTFs obtained by experiment made on two different screen-film combinations differ considerably, but the OTFs of multiple scattering in these two combinations are almost the same, which justifies the theoretical presumption. The obtained value of OTF of multiple scattering calculated as a func-tion of film base thickness by using an approximate model corresponds well with the value found by experiment.
