I.I. とタンデムレンズを用いるシネ撮影におけるフィルム周辺部の露光量低下の原因

概要

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When the output image of the X-ray image intensifier (I.I.) is exposed on the film through tandem lens, vignetting on the film image can be seen. Vignetting means an exposure reduction on the periphery of film. We can then figure out the mechanism and quantity of this Vignetting as a parameter of the distance from the center of the film and the radious of iris diaphragm between two tandem lenses. The light beam from every luminous point on I.I. output is projected to the input lens and refracted. Because each refracted light beams pass the output lens through by a different path way, the light intensity projected output lens through iris diaphragm are all different from each other. Vignetting happens because of these differences. Vignetting is larger as the radious of iris diaphragm becomes larger. The distance from the center of the film also makes larger vignetting. You can see this vignetting with your eyes when the film is developed. Therefore, we can get a maximum radius of the iris diaphragm, with no vignetting seen on the film at all.
公益社団法人日本放射線技術学会の論文
1991-09-01