Vector Wave Imagery with a Lens Masked by Polarizers

The optical transfer function (OTF) of an imaging system using polarization devices depends in general on the state of polarization of the input beam. In fact, the ‘amplitude point spread function’ (APSF) of such a system is different for different linearly polarized components of the input beam. This implies that the APSF of a system using polarizing devices behaves as a vector quantity. The nature of the final image is determined by the relative contribution of the two components of the vector APSF. The specific imaging system considered in the present study consists of a circularly symmetric polarization mask with linear polarizers having different orientations for the central circular and annular regions of an ideal lens aperture. If the light originating from an object point is in general elliptically polarized, the OTF of such a system with an analyser at the output is seen to have three additive components, which are, in fact, the Fourier coefficients of the OTF which varies periodically with the orientation of the analyser. It is also observed that the images produced by each additive component of the OTF can be separated—a fact that seems rewarding in view of potential applications.