Nomarski Prism is an optical component used in differential interference contrast (DIC) microscopy. It usually consists of two birefringent crystal wedges, such as quartz or calcite, glued together on their oblique sides with special optical cement. The optical axis of one wedge is parallel to the prism surface, while the optical axis of the other wedge is tilted relative to the prism surface.

Working Principle: When unpolarized light enters the Nomarski prism, it is split into an ordinary ray (o-ray) and an extraordinary ray (e-ray). These two beams experience different phase differences and path shifts during propagation in the prism. After passing through the prism, the two beams recombine. Since different parts of the prism produce different phase delays, an interference effect is generated, revealing sample details as variations in brightness or color and enhancing image contrast.

Optical Properties: Wide wavelength range, typically 180–3500 nm; high surface quality, e.g., S/D 40/20; surface flatness up to λ/4 @ 633 nm; extinction ratio approximately 1×10⁻⁵; deviation less than 30 arcseconds.

Applications: Widely used in biology, medicine, material science and other fields to observe the internal structure and subtle differences of transparent or translucent samples, such as cells, tissue sections, crystals, thin films, etc. It clearly reveals refractive index variations, stress distribution and other characteristics of the sample.