Orientation-independent differential interference contrast microscopy.
We describe a new technique for differential interference contrast (DIC) microscopy, which digitally generates phase gradient images independently of gradient orientation. To prove the principle we investigated specimens recorded at different orientations on a microscope equipped with a precision rotating stage and using regular DIC optics. The digitally generated images successfully displayed and measured phase gradients, independently of gradient orientation. One could also generate images showing distribution of optical path differences or enhanced, regular DIC images with any shear direction. Using special DIC prisms, one can switch the bias and shear directions rapidly without mechanically rotating the specimen or the prisms and orientation-independent DIC images are obtained in a fraction of a second.