
Phase Imaging Microscopy: Beyond Dark-Field, Phase Contrast, and Differential Interference Contrast Microscopy 503
(Liu et al. 2004). Although the Abel transform method assumes
that the object has at least one direction of rotational symmetry,
it has been demonstrated to measure refractive index proles
of optical ber. e SPI method uses as input two PS-DIC
images that have orthogonal shear directions. SPI is applicable
regardless of object symmetry and it has been demonstrated
to measure refractive index of polystyrene beads embedded in
optical cement (King et al. 2007, 2008).
e benet of using two DIC images with orthogonal ...