A phase modulator for the modulation of the phase of circular polarised light which interacts with the phase modulator. The phase modulator has a first and a second substrate, an electrode arrangement and a liquid crystal layer with liquid crystal molecules. The first substrate is disposed adjacent to the second substrate. The liquid crystal layer is disposed between the two substrates. The first substrate has a first surface, and the second substrate has a second surface. The liquid crystal molecules situated next to the first surface are oriented substantially parallel to the first surface. The liquid crystal molecules situated next to the second surface are oriented substantially perpendicular to the second surface. An in-plane component of the liquid crystal molecule orientation can be set within an angular range of about 180°, e.g. between 90° and +90° related to a specifiable central orientation.