A polarizing beam splitter made of two birefringent crystal wedges cemented together. Unlike a standard Wollaston prism, one of the wedges in a Nomarski prism is cut so its optical axis is oblique to the flat surface. This shifts the focal plane of the split beams outside the prism body, allowing it to be placed outside the objective lens in a microscope.
Heard on the job
Make sure the Nomarski prism is properly aligned in the slider, or the DIC contrast will be completely washed out.