Originally Posted by motorman45
your right in that if the green is offset at a different angle a single wave plate external would not fix things in an equal way. in the sxrd system the polarization is done right before the LCoS, if one could place the right wave plate after the green channel then you could orient it to match the others. but this would require getting inside the light engine.
This brings me back to the question I was asking a year ago, but never got a satisfactory answer.
Why is green's polarity offset in the first place?!?
Both LCD and LCoS tech's use 3 colour chips and use dichroic mirrors to separate the light into colours and a trichroic prism to recombine the colours. Both kinds of colour chips are polarizing.
When I talked to some trichroic prism manufacturers, they said that the trichroic prism would reflect green (instead of pass it) if it wasn't 90degrees off of the other two. But they also said that they sell trichroic prisms that don't require the green offset, but they were more expensive. Like $10 instead of $5.
And what exactly is creating the offset? The light is unpolarized before hitting the green LCD panel, and it is polarized when it exits (enters?) the prism. The LCD chip itself will polarize the light. Is the vertical polarization coming from the chip? If so, that means that R & B LCD chips are of one kind (Horizontal polarity) and G chips are of another kind. Seems like that's a lot of work to avoid a $5 price increase in your prism.
Summary: Putting a wave plate in your Green light channel inside your projector would probably cause green to not transmit through the prism. The SPAR filters rotate G to match R & B by targeting its wavelengths.