A Wollaston prism is an optical device. It separates randomly polarized or unpolarized light into two orthogonal (o光e光主平面重合，因为入射面是晶体主截面——光轴与发法线组成的平面), linearly polarized outgoing beams.

入射光为线偏振时：偏振光振动面垂直于主截面时： Io=1 , Ie=0  偏振光振动面平行于主截面时：Io=0, Ie=1

The Wollaston prism consists of two orthogonal calcite prisms, cemented together on their base (typically with Canada balsam) to form two right triangle prisms with perpendicular optic axes. Outgoing light beams diverge from the prism, giving two polarized rays, with the angle of divergence determined by the prisms' wedge angle and the wavelength of the light. Commercial prisms are available with divergence angles from 15° to about 45°.

 　（先入射到的那个棱镜的作用？）

 A Nomarski prism is a modification of the Wollaston prism, which is used in differential interference contrast microscopy. 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 (此时o光e光主平面才重合), and allows greater flexibility so that when setting up the microscope the prism can be actively focused.

 

 

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