[Laser] Polarization Subtraction

[Glenn Thomas]

I'm not sure why the idea of sequential sampling was raised when the 
article spoke of parallel sampling. I'm not sure one can difference one 
polarization at one time with another polarization at a different time. 
The serial scheme would be very like trying do decode an FM stereo 
broadcast signal by sampling the L-R signal at one time and the L+R 
signal at another.

Am I missing something?

73 de Glenn wb6w

On 10/15/2012 11:31 AM, Tim Toast wrote:
> Hi All,
> Here's an article in Laser Focus World about a simple
> polarisation "trick" that brings out hidden detail in images.
>
> http://www.laserfocusworld.com/articles/print/volume-48/issue-10/world-news/novel-cameras-polarization-difference-imaging-camera-reveals-unseen-features.html
> or
> http://tinyurl.com/9ga4n4j
>
> In the example image on the website, you can see how well
> it cuts through fog to show the mountains in the distance.
>
> In a play on dual receivers or diversity reception, I think
> this might have some application for optical comms with their
> "single pixel" cameras. The idea apparently is to simultaneously
> capture two images of the same scene each having a different
> polarization (orthigonal or 90 degrees apart) and then subtract
> one from the other. This can be done either with two optics with
> two separate detectors or by splitting the image from a single
> optic into two images, each with its own polarization filter and
> detector. Either way, two detectors would be needed. Then with an
> op-amp, or other arangement, subtract one signal from the other.
>
> It is interesting to note that when two orthogonal polarizing
> filters are placed on top of each other, almost no light passes
> through.
>
> Several people over the years have thought of doing this but
> without polarisation filters, just for noise reduction. Having
> two detectors usually means more noise as well. The dual detector
> idea is used in microphone techniques to cancel noise but this
> is usually done when there is plenty of signal and not at the very
> weak signal levels in optical front ends.
>
> At any rate, i thought i'd bring this up to the groups in case
> there is something useful here that hasn't been tried before.
>
> Cheers!
> -toast
>
>
>
>
>
>
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