| 摘要 |
PURPOSE:To level the output luminance distribution in an x-ray image tube so as to reduce variation in the distribution which is caused by change in the quality of x-rays by disposing a high density phosphor layer on the output side of a low density phosphor layer, and arranging the thickness of high density phosphor layer at the periphery of a fluorescent screen thicker than that at the central portion. CONSTITUTION:An input fluorescent screen 12 comprises low density and high density phosphor layers 13, 14. The high density phosphor layer 14 is disposed on the output side of the low density phosphor layer 13, and is arranged such that its film thickness at the periphery of the input fluorescent screen 12 is thicker than that at the central portion. On the other hand, the low density phosphor layer 13 is arranged such that its film thickness at the periphery of the input luminance screen 12 is thinner than that at the central portion thereof. In this manner, the output luminance distribution in an x-ray image tube can be made flat and variation in the distribution caused by change in the quality of x-rays can be omitted.
|
