Apparatus and methods for depositing variable interference filters

Apparatus for depositing one or more variable interference filters onto one or more substrates comprises a vacuum chamber, at least one magnetron sputtering device and at least one movable mount for supporting the one or more substrates within the vacuum chamber. The at least one magnetron sputtering device is configured to sputter material from a sputtering target towards the mount, thereby defining a sputtering zone within the vacuum chamber. At least one static sputtering mask is located between the sputtering target and the mount. The at least one static sputtering mask is configured such that, when each substrate is moved through the sputtering zone on the at least one movable mount, a layer of material having a non-uniform thickness is deposited on each said substrate.