Wollaston prism

Beam path in a Wollaston prism

The Wollaston prism (after William Hyde Wollaston , 1820) is an optical device that polarizes light using a birefringent material (such as calcite ) (see polarizer ). The incident light is separated into two linearly polarized beams at right angles to one another, depending on the input polarization .

construction

The Wollaston prism consists of two birefringent calcite - prisms which are cemented together at the bottom (usually with Canada balsam form or another material having a low refractive index) to two right-angled triangles with perpendicular optical axes. The emitted light diverges from the prism in two polarized beams with an angle of deflection that is determined by the corners and edges of the prisms and the wavelength of the light. Commercial prisms are available with angles from 15 ° to 45 °.

Modifications

Similar prisms

Schematic beam path in the Rochon prism

Schematic beam path in the Sénarmont prism

By changing the prism arrangements, additional variants for the beam guidance in the birefringent prisms are obtained. Depending on the arrangement, other names for prisms based on the Wollaston principle have emerged, for example the Rochon prism ( Alexis-Marie de Rochon , 1801) and Sénarmont prism (1857). They differ in that the ordinary beam is not deflected and is achromatic . The extraordinary beam, on the other hand, is deflected laterally depending on the wavelength of the light. Sénarmont's arrangement differs from Rochons in terms of the orientation of the optical axis of the second partial prism. This allows easier production from the relatively expensive material (calcite, Icelandic spar).

Nomarski prism

Schematic beam path in the Nomarski prism

The Nomarski prism (after Georges Nomarski ) is a modified Wollaston prism that is often used in DIC microscopy . Similar to the Wollaston prism, the two optical axes are oriented perpendicular to one another, but one of the two optical axes is inclined to the on and the opposite cathetus of the corresponding triangular prism surface. This leads to a focus of the two beams outside of the prism, which makes it easier to focus a DIC microscope.

Areas of application

The Wollaston-Prima is not only used as a pure polarizer , but also in media technology and for special measuring devices, for example

for the MiniDiscs and the Magneto Optical Disk ,
general in laser technology ,
with the Babinet compensator ,
in the Danjon astrolabe for observing the coincidence of stars

literature

Jean M. Bennett: Polarizers . In: Michael Bass, Casimer Decusatis, Vasudevan Lakshminarayanan, Guifang Li, Carolyn MacDonald, Virendra Mahajan, Eric Van Stryland (eds.): Handbook of Optics, Volume I . 3. Edition. McGraw Hill Professional, 2009, ISBN 978-0-07-149889-0 , pp. 13.1 ff . (extensive compilation of all possible polarizing prisms).

Web links

Douglas B. Murphy, Jan Hinsch, Edward D. Salmon, Kenneth R. Spring, Matthew J. Parry-Hill, Robert T. Sutter, Michael W. Davidson: Wavefront Shear in Wollaston and Nomarski Prisms (Interactive Java Tutorials) . The Florida State University

Individual evidence

↑ Ludwig Bergmann, Clemens Schaefer: Textbook of Experimental Physics: Optics: Wave and Particle Optics . Walter de Gruyter, 2004, ISBN 978-3-11-017081-8 , p. 559 ( limited preview in Google Book search).
^ RD Allen, GB David, Georges Nomarski: The Zeiss-Nomarski differential interference equipment for transmitted-light microscopy. In: Journal for Scientific Microscopy and Microscopic Techniques . tape 69 , no. 4 , 1969, p. 193-221 .

[1] Ludwig Bergmann, Clemens Schaefer: Textbook of Experimental Physics: Optics: Wave and Particle Optics . Walter de Gruyter, 2004, ISBN 978-3-11-017081-8 , p. 559 ( limited preview in Google Book search).

[2] RD Allen, GB David, Georges Nomarski: The Zeiss-Nomarski differential interference equipment for transmitted-light microscopy. In: Journal for Scientific Microscopy and Microscopic Techniques . tape 69 , no. 4 , 1969, p. 193-221 .