An optical device includes: a focusing optic that focuses a light beam in a focal plane; at least two phase filters for selectively focusing the light beam and effecting a phase shift of the light beam; and a filter wheel supporting the at least two phase filters which are individually introducible along an optical axis of the light beam, where the filter wheel is rotationally adjusted in relation to the optical axis by a stepper motor and linearly adjusted in an r-direction along a plane of the filter wheel by a linear adjustment mechanism.