US Patent 7965819 Device for limiting field on which radiation is irradiated

An irradiation field limiting device includes a plurality of aperture leaves arranged in a thickness direction, a flexible linear member secured to a thick portion of the aperture leaf, a driver section which drives the linear member a specific amount, and the like. One end of the linear member is secured to an aperture leaf through a connection section tangentially to the outer arc of the aperture leaf, and the other end is connected with a slider provided in a driver section. The slider is connected with a driving source through a connection portion and moves along an axial direction of a drive shaft inserted into a base accompanying rotation of the drive shaft. A load accompanying the movement of the slider is directly transmitted to the linear member, and the aperture leaf is driven a specific amount due to the load.