A filter device is for a collimator of an irradiation device. In an embodiment, the filter device includes a plurality of filter disks, arranged on a disk that is rotatable around an axis. Each filter disk is mounted so as to be movable in a radial direction and is tensioned by way of a respective spring element radially away from the axis or toward the axis against a guide contour, effecting a radial movement of at least one filter disk.
