Practice question

In differential interference contrast, contrast generation relies on interferometric mixing of two spatially separated polarized beams created by a Wollaston prism. After traversing slightly different paths through specimen, accumulated differential phase gradients arise from local differences in thickness and refractive index. A second prism recombines the beams, and interference converts phase differences into intensity variations when analyzed through crossed polarizer. Steep boundaries produce strong intensity changes giving relief-like appearance. Scattering, simple phase shift alone, or chemical staining are not responsible for this mechanism; interference of sheared wavefronts is central.