Archived posting to the Leica Users Group, 1998/06/10

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Subject: Re: [Leica] The Polarizer Problem
From: Dan Cardish <dcardish@microtec.net>
Date: Wed, 10 Jun 1998 18:50:16 -0400

At 04:26 PM 10-06-98 -0700, you wrote:
>At 10:48 AM 6/10/98 , Frank Dernie wrote:
>heir swinging device? Also, on another tack what is a circular polariser?
>>If orhtogonality of polarised light is required for cancellation as I
>>understand it what is a circular polariser doing and how does it , for
>>example cancel a reflection?
>
>A circular polarised filter is simply a linear pol to filter
>the light based on the polarization, followed by a
>1/4 wave plate, which randomizes the polarization of
>the transmitted light.  [snip]

not quite.

The 1/4 wave plate delays one component of the electric field vector by
90=BA, so that the resulting E vector rotates in space as it travels forward=
,
looking like a corkscrew.  Recall (?) that the electric field vector (and
also the corresponding magnetic field vector B) are perpendicular to the
direction of the light ray.  Some substances like calcite have differing
indices of refraction (hence velocity of light) depending on which
direction a light wave travels through it.  This can be used to make the
1/4 wave plate which is placed after a regular polarizer (it is important
to use a circular polarozer in the proper orientation).

A very brief explanation, hope it makes sense!

Dan C.