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Re: [OM] Identifying a filter and how to use it

Subject: Re: [OM] Identifying a filter and how to use it
From: Winsor Crosby <wincros@xxxxxxx>
Date: Thu, 16 Apr 1998 18:05:00 -0700
>? Kennedy wrote:
>
>> The circular polariser is really two specialist filters sandwiched into
>> one.  The first part is a normal linear polariser, and this works as you
>> expect on the light that passes through it.  The V on the filter shows
>> the orientation of the polarisation.  The second part of the sandwich is
>> a special filter called a quarter wave plate.  This splits the polarised
>> light from the first part into two parts and rotates one of them by
>> 90deg, like an X.
>
>Just being pedantic, but I think a more precise description would be:
>the quarter-wave plate splits the light into two components, each at
>45 degress to the original polarization axis.  One component is
>rotated in phase by 90 degrees (i.e. is retarded by one-quarter
>wavelength) with respect to the other, which gives light in which the
>polarization axis rotates -- i.e. circularly polarized light.
>
>Steve Schaffner
>sschaff@xxxxxxxxxxxxxxxxx
>
Thank you both. This is the first intelligible explanation of a circular
polarizer I have ever seen. Actually the name seems misleading, but I
suppose it is easier than something like a "rotated split phase polarizer".

Winsor Crosby
Long Beach, California
mailto:wincros@xxxxxxxxxxx





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