Nomarski prism

A Nomarski prism is a modification of the Wollaston prism, which is used in differential interference contrast microscopy. The Polish physicist Georges Nomarski contributed to the development of Differential Interference Contrast microscopy, by developing the Nomarski prism. Like the Wollaston prism, the Nomarski prism consists of two optical quartz or calcite wedges cemented together at the hypotenuse (e.g. with Canada balsam). One of the wedges is identical to a conventional Wollaston quartz wedge and has the optical axis oriented parallel to the surface of the prism. The second wedge of the prism is modified by cutting the quartz crystal in such a manner that the optical axis is oriented obliquely with respect to the flat surface of the prism. The Nomarski modification causes the light rays to come to a focal point outside the body of the prism, and so allows greater flexibility when setting up the microscope, the prism can be actively focused.