The purpose of this article is to identify the polarity or consumer level LCD and LCoS projectors.  This information can be used to identify which projectors can be best used in dual projector 3D set-ups.

Generally speaking, LCoS projectors will have unified polarity at 0 degrees, LCD projectors will have R&B at 0 and G at 90.  DLP will be non polarized.  Panasonic LCD projectors also seem to be depolarized, probably due to the "smooth screen" filter.

Why is this useful?

Generally speaking, you'll lose at least 50% of your lumens when going from depolarized to polarized light.  However, with wave retarders, it's possible to "rotate" the polarity of already polarized light while losing very few lumens.  The PJs that deliver full colour, completely polarized light can be used with a wave retarder to deliver the desired polarity (such as 45/135) at a minimal loss of lumens to both the screen, and the eyes of the viewer(s).

PJs that are either depolarized or have different colours at different angles are subject to using polarizing filters that immediately cut your lumens at least by half- and are therefore less desirable for Polarity based Dual Projector 3D set-ups.

For LCDs with one colour 90 degrees offset from the other two, you can buy (rather expensive) SPAR filters that retard the one colour (usually green) 90 degrees more than the other 2, effectively bringing all 3 colours into a single polarized plane.  They are not quite as efficient (to be expected) as PJs that simply project all 3 colours in a unified plane to begin with, but they are an option for LCD projectors that don't sport enough light to immediately cut 50-60% out at the first polarized filter.

More Information:

http://www.avsforum.com/avs-vb/showthread.php?t=1280393