PROBLEM TO BE SOLVED: To reduce unnecessary exposure in a radiographic apparatus in which a radiation generator has a movable diaphragm unit.SOLUTION: A movable diaphragm unit is constituted so that, when a restriction blade 3 is moved in such a direction that the restriction blade 3 is separated from a perpendicular 2 hung down to a first virtual plane 14 including a detection surface from the center of a focus 1 of a radiation, a moving distance d1 to the center of the focus 1, of a cross line 17 between a second virtual plane 15 including the end face 4 of the restriction blade 3 and a third virtual plane 16 including the focus 1 becomes smaller than a moving distance d2 of the end face 4 to the perpendicular 2.COPYRIGHT: (C)2015,JPO&INPIT【課題】放射線発生装置が可動絞りユニットを有する放射線撮影装置において、不要被爆を低減する。【解決手段】放射線の焦点1の中心から検出面を含む第1の仮想平面14に垂らした垂線2に対して、制限羽根3を遠ざける方向に該制限羽根3を移動させた時、制限羽根3の端面4を含む第2の仮想平面15と焦点1を含む第3の仮想平面16との交差線17の焦点1の中心に対する移動距離d1が、端面4の垂線2に対する移動距離d2よりも小さくなるように可動絞りユニットを構成する。【選択図】図3
