[Laser] Polarization Subtraction

[n5gui at cox.net]

When I first read this, I thought of a mechanically rotated polorizing filter and was going to suggest LCD technology that would electronically control the polarization in any desired sequence.  Frames would typically be set for either 0 or 90 degree, but could be set for any intermediate values if desired.  The mechanically rotated system would need synchronization and be limited by inertia.  Electronically controlled would still have some speed and settling limitations, but would be easier to change speed and sequencing, like 0,0,0,90,0,0,0,90, or maybe a pseudo-random pattern.

I now realize that you did not explicitly say a mechanical system.  While my comment may help clarify the concept of such a system for someone that is slow to catch on as I, I do not wish to imply that your idea was so limited as my first thought.

It is an interesting idea.  Might have some have some interesting applications.  I understand that there is a natural polarization to daylight.  Perhaps it would be worth some experimentation to see if it could be exploited to make LED or Laser communication, such as our amateur systems, easier to detect and / or more reliable in daylight.


Off topic, but perhaps related and interesting was an item in an old Boy Scout Signalling Merit Badge pamphlet about the use of polarizing filters on signal lights to send secret messages.  It did not seem to say how, but I suspect that they turned the sending filter by 90 degrees rather than bliniking the beam on and off to send Morse Code.  To someone without a filter on the receiving end, it would seem that the light was steady.


James
 n5gui

 
---- Tom Becker <GTBecker at RighTime.com> wrote: 
> Re: 
> http://www.laserfocusworld.com/articles/print/volume-48/issue-10/world-news/novel-cameras-polarization-difference-imaging-camera-reveals-unseen-features.html
> 
> Could not a frame-synchronized rotating polarizer produce 
> alternating-polarization video frames that could be subtracted and 
> normalized?  There might not be much detail among much noise, but the 
> difference should be visible, I expect.  Has that been done?
> 
> Tom
> 
> ______________________________________________________________
> Laser mailing list
> Home: http://mailman.qth.net/mailman/listinfo/laser
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Laser at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html