Optics 101

Wollaston Prism - Definition and Applications

Topics Covered

Introduction
Working Principle
Applications
References

Introduction

A Wollaston prism is an optical device which separates randomly polarized and unpolarized light into linearly polarized light beams. The prism was first invented by William Hyde Wollaston.

A Wollaston prism is essentially a polarizing beam splitter made of quartz or calcite. It provides the widest deviation angle of all beam-displacing polarizers.

Working Principle

A Wollaston prism polarizer consists of two orthogonal prisms fixed together at their base to form two triangular prisms with perpendicular optical axes. Light hitting the surface of the prism at right angles is disintegrated into an ordinary (O) and an extraordinary (E) ray. Double refraction does not take place as both the light rays travel along the same direction.

At the interface, the direction of O- and E- rays are interchanged as they approach a prism segment with optical axis orthogonal to the first segment. As a result, the light rays are bent in an opposite direction, due to refraction thereby diverging from the prism and producing two polarized light rays.

The angle of divergence of the light rays can be determined by the wedge angle of the prisms. The divergence angles of the commercially available prisms range from 15° to 45°.

Applications

Wollaston prisms find application in the following:

  • Nomarski microscopy, and polarization microscopy
  • Compact disk players
  • Rotation mounts

References

 

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