An optical system is provided. The optical system comprises a first polarizing beamsplitter (PBS), a first reflecting image-forming device, and a first quarter-wave retarding element. An optical system is also provided that comprises an image-forming device, a reflective polarizing layer, at least a...http://www.google.com.au/patents/US7731366?utm_source=gb-gplus-sharePatent US7731366 - Stress birefringence compensation in polarizing beamsplitters and systems using same
