On the complex point spread function in interferometric cross-polarisation microscopy

The ability to characterize the Point Spread Function(PSF) is crucial in practical microscopy, but requires knowledge of the complex PSF for approaches that detect fields instead of intensities. Here we experimentally measure and theoretically model the volumetric amplitude and phase response of an Interferometric Cross-polarisation Microscope to demonstrate the technique's capability to provide confocal-like images of weakly birefringent structures in living cells. We find the axial FWHM of the amplitude PSF to be 0 : 70 +/- 0 : 01 mu m and 0 : 83 mu m for model and measurement, respectively, on par with confocal microscopy. Ultimately retaining both amplitude and phase information will however enable approaches for improved localisation of objects. (C) 2015 Optical Society of America