[Laser] Polarization modulation

[Tim Toast]

Hi Glenn and all,

I agree, a common LCD display may be the cheapest way to get good
polarization modulation. And they hardly use any power so they're 
battery friendly. From what I've read tonight, the only difference 
between the back-lit and reflective type LCD is the mirror backing. 
So once that is removed you'll have a back-lit type LCD. I think 
you will have to also remove the back polarizing filter or it will 
just be a light-gate and produce AM modulation. Changing the
polarization of the beam should not vary the brightness. I don't 
know if these things are linear or not, it may just jump from one
polarization to another when voltage is applied - experiment will 
tell :-)

One idea i had is for a simple tool to use when working with 
polarized light projects. A "polarized light detector". It might 
take the form of a simple light controlled oscillator, like the 
"audible s-meter" circuit by Clint. You would either spin a disk 
of polarizing material in front of the detector device, or, for a 
no moving parts version, use a modified modulated LCD pixel.
 
Normal unpolarized light would pass through the filter unaffected 
and produce a steady tone from the speaker. Polarized light would 
be attenuated periodically by the spinning filter or LCD and produce 
FM in the tone which should be clearly audible. Just a little gadget 
to let you hear the difference between pure light and varying 
degrees of polarized light. A small lens would give it a narrower 
well defined field of view for pointing at various objects and light
sources.

-toast