Back-focal plane Mueller matrix microscopy: Mueller conoscopy and Mueller diffractrometry

The common mode of observation in an imaging Mueller matrix polarimeter is orthoscopic observation, where the front focal plane of the objective is focused onto the camera sensor. Different points on the camera sensor correspond to different points on the sample. But for certain applications, valuable complementary information is obtained when the back focal plane of the objective is focused onto the camera sensor. This observation mode informs about the directions distribution of light so that different points on the camera sensor correspond to different directions of light propagation through the specimen. We distinguish between two types of illumination; the sample can be illuminated with a large numerical aperture, such that what is measured corresponds to usual transmission or specular reflection ellipsometry (Mueller conoscopy), or the sample may be illuminated with collimated light, and what is measured corresponds to scattering or diffraction of light (Mueller diffractometry). A polarimeter suitable for back-focal measurements is described and illustrative examples of Mueller conoscopy and Mueller diffractometry are presented.