The disclosure relates to a projector having an arrangement of polarizers and liquid crystal cells aligned on the axis of light in the order a first color polarizer colored in red, a first twisted nematic liquid crystal cell, a second twisted nematic liquid crystal cell, a second color polarizer colored...http://www.google.com.au/patents/US4838655?utm_source=gb-gplus-sharePatent US4838655 - Projector using guest-host liquid crystal cells for improved color purity
