Practice question

Differential interference contrast depends critically on prisms that manipulate polarized light. A Nomarski prism, a modified Wollaston prism, splits plane-polarized illumination into two orthogonally polarized beams with slight lateral shear, typically less than resolution limit. After passing through specimen regions with different refractive indices, the beams acquire phase differences. A second Nomarski prism above objective recombines them, and analyzer converts phase gradients into intensity differences. This design yields high-contrast, pseudo-relief images highlighting membrane edges, nuclei and contractile vacuoles in live unstained protozoa and developing embryos.