An optical system (1) includes a first optical subsystem (3) with at least a first birefringent optical element (7), and further includes a second optical subsystem (5) with at least a second birefringent optical element (9). Between the first optical subsystem and the second optical subsystem, an optical retarding system (13) with at least a first optical retarding element (15) is arranged, which introduces a retardation of one-half of a wavelength between two mutually orthogonal states of polarization.