[Laser] Polarization Subtraction

[bernieS]

Interesting tutorial on a 100kHz RTP Pockels cell Q-switch System, 
and similar systems:
http://www.leysop.com/100khz_rtp_q-switch.htm
http://www.leysop.com/pockels.htm

Unfortunately, these units cost over $1000:
http://www.leysop.com/prices.pdf

-Ed


At 02:06 PM 10/18/2012, Toast wrote:
>On 2012-10-18 12:02 PM, laser-request at mailman.qth.net wrote:
> > Date: Wed, 17 Oct 2012 21:02:38 -0700 (PDT)
> > From: Tim Toast <toasty256 at yahoo.com>
> > Subject: Re: [Laser] Polarization Subtraction
> > To: laser at mailman.qth.net
> > Message-ID:
> >       <1350532958.66967.YahooMailClassic at web161003.mail.bf1.yahoo.com>
> > Content-Type: text/plain; charset=iso-8859-1
> >
> > Thanks for all the responce to this,
> >
> > The two lens idea was mine and i tossed it in there with all
> > that. The article though mentions a single lens with a special
> > beam splitter. Yes, i think now the slight difference in angle
> > of a two lens capture would lead to a sort of non-simultaniousness
> > that is not intended by the article. Not to mention a totally 
> different, although similar, scene instead of "the same scene".
> > It sounds to me that they are using a single lens with a beam
> > splitter to get the two polarised images. Either a polarizing
> > prism type splitter that provides (I think) one polarized image
> > and one unpolarized one which would need a separate filter of its
> > own to provide the two orthogonal images -or- a plane beam
> > splitter that each image would need a polarizing filter.
> >
> > The key element is "at the same time" and not sequential though -
> > which negates my thought that two lenses might work or some sort
> > of alternate frame capture for a ccd.
>
>I had envisioned two CCDs driven from the same clock sources, such
>that their images would be read out simultaneously.  But, the CCD approach
>seems overly complex if all of the information could be supplied by two
>photocells.
>
> > You would think though that
> > any polarization changes going on would be slow ones at rates less
> > than say, 100 Hz but i don't know for sure things aren't
> > happening much quicker than that.
>
>If they're using a mechanical modulator, then the polarization change is
>probably reasonably slow.  But, if they're using something like a
>Pockels cell for the change of polarization modulation, then it may be
>VERY fast (few nS!):
>
>http://en.wikipedia.org/wiki/Pockels_cell#Applications_of_Pockels_cells
>
>Of course, there are other modulators:
>
>http://en.wikipedia.org/wiki/Kerr_effect
>http://en.wikipedia.org/wiki/Rapatronic_camera
>
>http://en.wikipedia.org/wiki/Magneto-optic_Kerr_effect
>
>http://en.wikipedia.org/wiki/Faraday_effect
>
> > Things aren't always as they
> > seem of course! We've learned that over and over :)
> >
> > -toast
>
>Dave
>WA4QAL
>
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