Abstract: The invention relates to a diaphragm assembly of an aperture diaphragm for delimiting the coating region which is operative in the deposition of a layer and to a sputtering device which uses the diaphragm assembly. The diaphragm assembly comprises a main part (13) which has a passage (14) delimited by a passage edge. The aim of the invention is to design the diaphragm opening to be temporally and geometrically variable in situ. This is achieved in that the diaphragm assembly has at least one diaphragm plate (17, 17?, 17?) which is assembled on the main part (13) so as to be movable in front of the passage (14) and back. The diaphragm assembly additionally comprises a movement device which is operatively connected to the diaphragm plate (17, 17?, 17?) in order to carry out the movement thereof.